gcov(1)


NAME

   gcc - GNU project C and C++ compiler

SYNOPSIS

   gcc [-c|-S|-E] [-std=standard]
       [-g] [-pg] [-Olevel]
       [-Wwarn...] [-Wpedantic]
       [-Idir...] [-Ldir...]
       [-Dmacro[=defn]...] [-Umacro]
       [-foption...] [-mmachine-option...]
       [-o outfile] [@file] infile...

   Only the most useful options are listed here; see below for the
   remainder.  g++ accepts mostly the same options as gcc.

DESCRIPTION

   When you invoke GCC, it normally does preprocessing, compilation,
   assembly and linking.  The "overall options" allow you to stop this
   process at an intermediate stage.  For example, the -c option says not
   to run the linker.  Then the output consists of object files output by
   the assembler.

   Other options are passed on to one or more stages of processing.  Some
   options control the preprocessor and others the compiler itself.  Yet
   other options control the assembler and linker; most of these are not
   documented here, since you rarely need to use any of them.

   Most of the command-line options that you can use with GCC are useful
   for C programs; when an option is only useful with another language
   (usually C++), the explanation says so explicitly.  If the description
   for a particular option does not mention a source language, you can use
   that option with all supported languages.

   The usual way to run GCC is to run the executable called gcc, or
   machine-gcc when cross-compiling, or machine-gcc-version to run a
   specific version of GCC.  When you compile C++ programs, you should
   invoke GCC as g++ instead.

   The gcc program accepts options and file names as operands.  Many
   options have multi-letter names; therefore multiple single-letter
   options may not be grouped: -dv is very different from -d -v.

   You can mix options and other arguments.  For the most part, the order
   you use doesn't matter.  Order does matter when you use several options
   of the same kind; for example, if you specify -L more than once, the
   directories are searched in the order specified.  Also, the placement
   of the -l option is significant.

   Many options have long names starting with -f or with -W---for example,
   -fmove-loop-invariants, -Wformat and so on.  Most of these have both
   positive and negative forms; the negative form of -ffoo is -fno-foo.
   This manual documents only one of these two forms, whichever one is not
   the default.

OPTIONS

   Option Summary
   Here is a summary of all the options, grouped by type.  Explanations
   are in the following sections.

   Overall Options
       -c  -S  -E  -o file  -x language -v  -###  --help[=class[,...]]
       --target-help  --version -pass-exit-codes  -pipe  -specs=file
       -wrapper @file -fplugin=file -fplugin-arg-name=arg
       -fdump-ada-spec[-slim] -fada-spec-parent=unit -fdump-go-spec=file

   C Language Options
       -ansi  -std=standard  -fgnu89-inline -aux-info filename
       -fallow-parameterless-variadic-functions -fno-asm  -fno-builtin
       -fno-builtin-function -fhosted  -ffreestanding -fopenacc -fopenmp
       -fopenmp-simd -fms-extensions -fplan9-extensions
       -fsso-struct=endianness -fallow-single-precision  -fcond-mismatch
       -flax-vector-conversions -fsigned-bitfields  -fsigned-char
       -funsigned-bitfields  -funsigned-char -trigraphs -traditional
       -traditional-cpp

   C++ Language Options
       -fabi-version=n  -fno-access-control  -fcheck-new
       -fconstexpr-depth=n  -ffriend-injection -fno-elide-constructors
       -fno-enforce-eh-specs -ffor-scope  -fno-for-scope
       -fno-gnu-keywords -fno-implicit-templates
       -fno-implicit-inline-templates -fno-implement-inlines
       -fms-extensions -fno-nonansi-builtins  -fnothrow-opt
       -fno-operator-names -fno-optional-diags  -fpermissive
       -fno-pretty-templates -frepo  -fno-rtti -fsized-deallocation
       -ftemplate-backtrace-limit=n -ftemplate-depth=n
       -fno-threadsafe-statics  -fuse-cxa-atexit -fno-weak  -nostdinc++
       -fvisibility-inlines-hidden -fvisibility-ms-compat
       -fext-numeric-literals -Wabi=n  -Wabi-tag  -Wconversion-null
       -Wctor-dtor-privacy -Wdelete-non-virtual-dtor -Wliteral-suffix
       -Wmultiple-inheritance -Wnamespaces -Wnarrowing -Wnoexcept
       -Wnon-virtual-dtor  -Wreorder -Weffc++  -Wstrict-null-sentinel
       -Wtemplates -Wno-non-template-friend  -Wold-style-cast
       -Woverloaded-virtual  -Wno-pmf-conversions -Wsign-promo
       -Wvirtual-inheritance

   Objective-C and Objective-C++ Language Options
       -fconstant-string-class=class-name -fgnu-runtime  -fnext-runtime
       -fno-nil-receivers -fobjc-abi-version=n -fobjc-call-cxx-cdtors
       -fobjc-direct-dispatch -fobjc-exceptions -fobjc-gc -fobjc-nilcheck
       -fobjc-std=objc1 -fno-local-ivars
       -fivar-visibility=[public|protected|private|package]
       -freplace-objc-classes -fzero-link -gen-decls -Wassign-intercept
       -Wno-protocol  -Wselector -Wstrict-selector-match
       -Wundeclared-selector

   Diagnostic Message Formatting Options
       -fmessage-length=n -fdiagnostics-show-location=[once|every-line]
       -fdiagnostics-color=[auto|never|always]
       -fno-diagnostics-show-option -fno-diagnostics-show-caret

   Warning Options
       -fsyntax-only  -fmax-errors=n  -Wpedantic -pedantic-errors -w
       -Wextra  -Wall  -Waddress  -Waggregate-return
       -Wno-aggressive-loop-optimizations -Warray-bounds -Warray-bounds=n
       -Wno-attributes -Wbool-compare -Wno-builtin-macro-redefined
       -Wc90-c99-compat -Wc99-c11-compat -Wc++-compat -Wc++11-compat
       -Wc++14-compat -Wcast-align  -Wcast-qual -Wchar-subscripts
       -Wclobbered  -Wcomment -Wconditionally-supported -Wconversion
       -Wcoverage-mismatch -Wno-cpp -Wdate-time -Wdelete-incomplete
       -Wno-deprecated -Wno-deprecated-declarations -Wno-designated-init
       -Wdisabled-optimization -Wno-discarded-qualifiers
       -Wno-discarded-array-qualifiers -Wno-div-by-zero -Wdouble-promotion
       -Wduplicated-cond -Wempty-body  -Wenum-compare -Wno-endif-labels
       -Werror  -Werror=* -Wfatal-errors -Wfloat-equal  -Wformat
       -Wformat=2 -Wno-format-contains-nul -Wno-format-extra-args
       -Wformat-nonliteral -Wformat-security  -Wformat-signedness
       -Wformat-y2k -Wframe-address -Wframe-larger-than=len
       -Wno-free-nonheap-object -Wjump-misses-init -Wignored-qualifiers
       -Wignored-attributes  -Wincompatible-pointer-types -Wimplicit
       -Wimplicit-function-declaration  -Wimplicit-int -Winit-self
       -Winline  -Wno-int-conversion -Wno-int-to-pointer-cast
       -Winvalid-memory-model -Wno-invalid-offsetof -Winvalid-pch
       -Wlarger-than=len -Wlogical-op -Wlogical-not-parentheses
       -Wlong-long -Wmain -Wmaybe-uninitialized -Wmemset-transposed-args
       -Wmisleading-indentation -Wmissing-braces
       -Wmissing-field-initializers -Wmissing-include-dirs -Wno-multichar
       -Wnonnull -Wnonnull-compare -Wnormalized=[none|id|nfc|nfkc]
       -Wnull-dereference -Wodr  -Wno-overflow  -Wopenmp-simd
       -Woverride-init-side-effects -Woverlength-strings -Wpacked
       -Wpacked-bitfield-compat  -Wpadded -Wparentheses
       -Wno-pedantic-ms-format -Wplacement-new -Wplacement-new=n
       -Wpointer-arith  -Wno-pointer-to-int-cast -Wno-pragmas
       -Wredundant-decls  -Wno-return-local-addr -Wreturn-type
       -Wsequence-point  -Wshadow  -Wno-shadow-ivar -Wshift-overflow
       -Wshift-overflow=n -Wshift-count-negative -Wshift-count-overflow
       -Wshift-negative-value -Wsign-compare  -Wsign-conversion
       -Wfloat-conversion -Wno-scalar-storage-order
       -Wsizeof-pointer-memaccess  -Wsizeof-array-argument
       -Wstack-protector -Wstack-usage=len -Wstrict-aliasing
       -Wstrict-aliasing=n -Wstrict-overflow -Wstrict-overflow=n
       -Wsuggest-attribute=[pure|const|noreturn|format]
       -Wsuggest-final-types  -Wsuggest-final-methods -Wsuggest-override
       -Wmissing-format-attribute -Wsubobject-linkage -Wswitch
       -Wswitch-default  -Wswitch-enum -Wswitch-bool -Wsync-nand
       -Wsystem-headers  -Wtautological-compare  -Wtrampolines
       -Wtrigraphs -Wtype-limits  -Wundef -Wuninitialized
       -Wunknown-pragmas  -Wunsafe-loop-optimizations
       -Wunsuffixed-float-constants  -Wunused  -Wunused-function
       -Wunused-label  -Wunused-local-typedefs -Wunused-parameter
       -Wno-unused-result -Wunused-value  -Wunused-variable
       -Wunused-const-variable -Wunused-const-variable=n
       -Wunused-but-set-parameter -Wunused-but-set-variable -Wuseless-cast
       -Wvariadic-macros -Wvector-operation-performance -Wvla
       -Wvolatile-register-var  -Wwrite-strings
       -Wzero-as-null-pointer-constant -Whsa

   C and Objective-C-only Warning Options
       -Wbad-function-cast  -Wmissing-declarations
       -Wmissing-parameter-type  -Wmissing-prototypes  -Wnested-externs
       -Wold-style-declaration  -Wold-style-definition -Wstrict-prototypes
       -Wtraditional  -Wtraditional-conversion
       -Wdeclaration-after-statement -Wpointer-sign

   Debugging Options
       -g  -glevel  -gcoff  -gdwarf -gdwarf-version -ggdb
       -grecord-gcc-switches  -gno-record-gcc-switches -gstabs  -gstabs+
       -gstrict-dwarf  -gno-strict-dwarf -gvms  -gxcoff  -gxcoff+
       -gz[=type] -fdebug-prefix-map=old=new -fdebug-types-section
       -feliminate-dwarf2-dups -fno-eliminate-unused-debug-types
       -femit-struct-debug-baseonly -femit-struct-debug-reduced
       -femit-struct-debug-detailed[=spec-list]
       -feliminate-unused-debug-symbols -femit-class-debug-always
       -fno-merge-debug-strings -fno-dwarf2-cfi-asm -fvar-tracking
       -fvar-tracking-assignments

   Optimization Options
       -faggressive-loop-optimizations -falign-functions[=n]
       -falign-jumps[=n] -falign-labels[=n] -falign-loops[=n]
       -fassociative-math -fauto-profile -fauto-profile[=path]
       -fauto-inc-dec -fbranch-probabilities -fbranch-target-load-optimize
       -fbranch-target-load-optimize2 -fbtr-bb-exclusive -fcaller-saves
       -fcombine-stack-adjustments -fconserve-stack -fcompare-elim
       -fcprop-registers -fcrossjumping -fcse-follow-jumps
       -fcse-skip-blocks -fcx-fortran-rules -fcx-limited-range
       -fdata-sections -fdce -fdelayed-branch -fdelete-null-pointer-checks
       -fdevirtualize -fdevirtualize-speculatively
       -fdevirtualize-at-ltrans -fdse -fearly-inlining -fipa-sra
       -fexpensive-optimizations -ffat-lto-objects -ffast-math
       -ffinite-math-only -ffloat-store -fexcess-precision=style
       -fforward-propagate -ffp-contract=style -ffunction-sections -fgcse
       -fgcse-after-reload -fgcse-las -fgcse-lm -fgraphite-identity
       -fgcse-sm -fhoist-adjacent-loads -fif-conversion -fif-conversion2
       -findirect-inlining -finline-functions
       -finline-functions-called-once -finline-limit=n
       -finline-small-functions -fipa-cp -fipa-cp-clone -fipa-cp-alignment
       -fipa-pta -fipa-profile -fipa-pure-const -fipa-reference -fipa-icf
       -fira-algorithm=algorithm -fira-region=region -fira-hoist-pressure
       -fira-loop-pressure -fno-ira-share-save-slots
       -fno-ira-share-spill-slots -fisolate-erroneous-paths-dereference
       -fisolate-erroneous-paths-attribute -fivopts
       -fkeep-inline-functions -fkeep-static-functions
       -fkeep-static-consts -flive-range-shrinkage -floop-block
       -floop-interchange -floop-strip-mine -floop-unroll-and-jam
       -floop-nest-optimize -floop-parallelize-all -flra-remat -flto
       -flto-compression-level -flto-partition=alg -fmerge-all-constants
       -fmerge-constants -fmodulo-sched -fmodulo-sched-allow-regmoves
       -fmove-loop-invariants -fno-branch-count-reg -fno-defer-pop
       -fno-function-cse -fno-guess-branch-probability -fno-inline
       -fno-math-errno -fno-peephole -fno-peephole2 -fno-sched-interblock
       -fno-sched-spec -fno-signed-zeros -fno-toplevel-reorder
       -fno-trapping-math -fno-zero-initialized-in-bss
       -fomit-frame-pointer -foptimize-sibling-calls -fpartial-inlining
       -fpeel-loops -fpredictive-commoning -fprefetch-loop-arrays
       -fprofile-correction -fprofile-use -fprofile-use=path
       -fprofile-values -fprofile-reorder-functions -freciprocal-math
       -free -frename-registers -freorder-blocks
       -freorder-blocks-algorithm=algorithm -freorder-blocks-and-partition
       -freorder-functions -frerun-cse-after-loop
       -freschedule-modulo-scheduled-loops -frounding-math
       -fsched2-use-superblocks -fsched-pressure -fsched-spec-load
       -fsched-spec-load-dangerous -fsched-stalled-insns-dep[=n]
       -fsched-stalled-insns[=n] -fsched-group-heuristic
       -fsched-critical-path-heuristic -fsched-spec-insn-heuristic
       -fsched-rank-heuristic -fsched-last-insn-heuristic
       -fsched-dep-count-heuristic -fschedule-fusion -fschedule-insns
       -fschedule-insns2 -fsection-anchors -fselective-scheduling
       -fselective-scheduling2 -fsel-sched-pipelining
       -fsel-sched-pipelining-outer-loops -fsemantic-interposition
       -fshrink-wrap -fsignaling-nans -fsingle-precision-constant
       -fsplit-ivs-in-unroller -fsplit-paths -fsplit-wide-types
       -fssa-backprop -fssa-phiopt -fstdarg-opt -fstrict-aliasing
       -fstrict-overflow -fthread-jumps -ftracer -ftree-bit-ccp
       -ftree-builtin-call-dce -ftree-ccp -ftree-ch -ftree-coalesce-vars
       -ftree-copy-prop -ftree-dce -ftree-dominator-opts -ftree-dse
       -ftree-forwprop -ftree-fre -ftree-loop-if-convert
       -ftree-loop-if-convert-stores -ftree-loop-im -ftree-phiprop
       -ftree-loop-distribution -ftree-loop-distribute-patterns
       -ftree-loop-ivcanon -ftree-loop-linear -ftree-loop-optimize
       -ftree-loop-vectorize -ftree-parallelize-loops=n -ftree-pre
       -ftree-partial-pre -ftree-pta -ftree-reassoc -ftree-sink
       -ftree-slsr -ftree-sra -ftree-switch-conversion -ftree-tail-merge
       -ftree-ter -ftree-vectorize -ftree-vrp -funconstrained-commons
       -funit-at-a-time -funroll-all-loops -funroll-loops
       -funsafe-loop-optimizations -funsafe-math-optimizations
       -funswitch-loops -fipa-ra -fvariable-expansion-in-unroller
       -fvect-cost-model -fvpt -fweb -fwhole-program -fwpa
       -fuse-linker-plugin --param name=value -O  -O0  -O1  -O2  -O3  -Os
       -Ofast -Og

   Program Instrumentation Options
       -p  -pg  -fprofile-arcs --coverage -ftest-coverage
       -fprofile-dir=path -fprofile-generate -fprofile-generate=path
       -fsanitize=style -fsanitize-recover -fsanitize-recover=style
       -fasan-shadow-offset=number -fsanitize-sections=s1,s2,...
       -fsanitize-undefined-trap-on-error -fbounds-check
       -fcheck-pointer-bounds -fchkp-check-incomplete-type
       -fchkp-first-field-has-own-bounds -fchkp-narrow-bounds
       -fchkp-narrow-to-innermost-array -fchkp-optimize
       -fchkp-use-fast-string-functions -fchkp-use-nochk-string-functions
       -fchkp-use-static-bounds -fchkp-use-static-const-bounds
       -fchkp-treat-zero-dynamic-size-as-infinite -fchkp-check-read
       -fchkp-check-read -fchkp-check-write -fchkp-store-bounds
       -fchkp-instrument-calls -fchkp-instrument-marked-only
       -fchkp-use-wrappers -fstack-protector -fstack-protector-all
       -fstack-protector-strong -fstack-protector-explicit -fstack-check
       -fstack-limit-register=reg  -fstack-limit-symbol=sym
       -fno-stack-limit -fsplit-stack -fvtable-verify=[std|preinit|none]
       -fvtv-counts -fvtv-debug -finstrument-functions
       -finstrument-functions-exclude-function-list=sym,sym,...
       -finstrument-functions-exclude-file-list=file,file,...

   Preprocessor Options
       -Aquestion=answer -A-question[=answer] -C  -dD  -dI  -dM  -dN
       -Dmacro[=defn]  -E  -H -idirafter dir -include file  -imacros file
       -iprefix file  -iwithprefix dir -iwithprefixbefore dir  -isystem
       dir -imultilib dir -isysroot dir -M  -MM  -MF  -MG  -MP  -MQ  -MT
       -nostdinc -P  -fdebug-cpp -ftrack-macro-expansion
       -fworking-directory -remap -trigraphs  -undef  -Umacro -Wp,option
       -Xpreprocessor option -no-integrated-cpp

   Assembler Option
       -Wa,option  -Xassembler option

   Linker Options
       object-file-name  -fuse-ld=linker -llibrary -nostartfiles
       -nodefaultlibs  -nostdlib -pie -rdynamic -s  -static -static-libgcc
       -static-libstdc++ -static-libasan -static-libtsan -static-liblsan
       -static-libubsan -static-libmpx -static-libmpxwrappers -shared
       -shared-libgcc  -symbolic -T script  -Wl,option  -Xlinker option -u
       symbol -z keyword

   Directory Options
       -Bprefix -Idir -iplugindir=dir -iquotedir -Ldir
       -no-canonical-prefixes -I- --sysroot=dir --no-sysroot-suffix

   Code Generation Options
       -fcall-saved-reg  -fcall-used-reg -ffixed-reg  -fexceptions
       -fnon-call-exceptions  -fdelete-dead-exceptions  -funwind-tables
       -fasynchronous-unwind-tables -fno-gnu-unique
       -finhibit-size-directive  -fno-common  -fno-ident
       -fpcc-struct-return  -fpic  -fPIC -fpie -fPIE -fno-plt
       -fno-jump-tables -frecord-gcc-switches -freg-struct-return
       -fshort-enums  -fshort-wchar -fverbose-asm  -fpack-struct[=n]
       -fleading-underscore  -ftls-model=model -fstack-reuse=reuse_level
       -ftrapv  -fwrapv -fvisibility=[default|internal|hidden|protected]
       -fstrict-volatile-bitfields -fsync-libcalls

   Developer Options
       -dletters  -dumpspecs  -dumpmachine  -dumpversion -fchecking
       -fdbg-cnt-list -fdbg-cnt=counter-value-list -fdisable-ipa-pass_name
       -fdisable-rtl-pass_name -fdisable-rtl-pass-name=range-list
       -fdisable-tree-pass_name -fdisable-tree-pass-name=range-list
       -fdump-noaddr -fdump-unnumbered -fdump-unnumbered-links
       -fdump-translation-unit[-n] -fdump-class-hierarchy[-n]
       -fdump-ipa-all -fdump-ipa-cgraph -fdump-ipa-inline -fdump-passes
       -fdump-rtl-pass -fdump-rtl-pass=filename -fdump-statistics
       -fdump-tree-all -fdump-tree-original[-n] -fdump-tree-optimized[-n]
       -fdump-tree-cfg -fdump-tree-alias -fdump-tree-ch
       -fdump-tree-ssa[-n] -fdump-tree-pre[-n] -fdump-tree-ccp[-n]
       -fdump-tree-dce[-n] -fdump-tree-gimple[-raw] -fdump-tree-dom[-n]
       -fdump-tree-dse[-n] -fdump-tree-phiprop[-n] -fdump-tree-phiopt[-n]
       -fdump-tree-backprop[-n] -fdump-tree-forwprop[-n] -fdump-tree-nrv
       -fdump-tree-vect -fdump-tree-sink -fdump-tree-sra[-n]
       -fdump-tree-forwprop[-n] -fdump-tree-fre[-n]
       -fdump-tree-vtable-verify -fdump-tree-vrp[-n]
       -fdump-tree-split-paths[-n] -fdump-tree-storeccp[-n]
       -fdump-final-insns=file -fcompare-debug[=opts]
       -fcompare-debug-second -fenable-kind-pass -fenable-kind-pass=range-
       list -fira-verbose=n -flto-report -flto-report-wpa -fmem-report-wpa
       -fmem-report -fpre-ipa-mem-report -fpost-ipa-mem-report -fopt-info
       -fopt-info-options[=file] -fprofile-report -frandom-seed=string
       -fsched-verbose=n -fsel-sched-verbose -fsel-sched-dump-cfg
       -fsel-sched-pipelining-verbose -fstats  -fstack-usage
       -ftime-report -fvar-tracking-assignments-toggle -gtoggle
       -print-file-name=library  -print-libgcc-file-name
       -print-multi-directory  -print-multi-lib  -print-multi-os-directory
       -print-prog-name=program  -print-search-dirs  -Q -print-sysroot
       -print-sysroot-headers-suffix -save-temps -save-temps=cwd
       -save-temps=obj -time[=file]

   Machine-Dependent Options
       AArch64 Options -mabi=name  -mbig-endian  -mlittle-endian
       -mgeneral-regs-only -mcmodel=tiny  -mcmodel=small  -mcmodel=large
       -mstrict-align -momit-leaf-frame-pointer
       -mno-omit-leaf-frame-pointer -mtls-dialect=desc
       -mtls-dialect=traditional -mtls-size=size -mfix-cortex-a53-835769
       -mno-fix-cortex-a53-835769 -mfix-cortex-a53-843419
       -mno-fix-cortex-a53-843419 -mlow-precision-recip-sqrt
       -mno-low-precision-recip-sqrt -march=name  -mcpu=name  -mtune=name

       Adapteva Epiphany Options -mhalf-reg-file -mprefer-short-insn-regs
       -mbranch-cost=num -mcmove -mnops=num -msoft-cmpsf -msplit-lohi
       -mpost-inc -mpost-modify -mstack-offset=num -mround-nearest
       -mlong-calls -mshort-calls -msmall16 -mfp-mode=mode -mvect-double
       -max-vect-align=num -msplit-vecmove-early -m1reg-reg

       ARC Options -mbarrel-shifter -mcpu=cpu -mA6 -mARC600 -mA7 -mARC700
       -mdpfp -mdpfp-compact -mdpfp-fast -mno-dpfp-lrsr -mea -mno-mpy
       -mmul32x16 -mmul64 -matomic -mnorm -mspfp -mspfp-compact
       -mspfp-fast -msimd -msoft-float -mswap -mcrc -mdsp-packa -mdvbf
       -mlock -mmac-d16 -mmac-24 -mrtsc -mswape -mtelephony -mxy -misize
       -mannotate-align -marclinux -marclinux_prof -mlong-calls
       -mmedium-calls -msdata -mucb-mcount -mvolatile-cache -malign-call
       -mauto-modify-reg -mbbit-peephole -mno-brcc -mcase-vector-pcrel
       -mcompact-casesi -mno-cond-exec -mearly-cbranchsi -mexpand-adddi
       -mindexed-loads -mlra -mlra-priority-none -mlra-priority-compact
       mlra-priority-noncompact -mno-millicode -mmixed-code -mq-class
       -mRcq -mRcw -msize-level=level -mtune=cpu -mmultcost=num
       -munalign-prob-threshold=probability -mmpy-option=multo -mdiv-rem
       -mcode-density -mll64 -mfpu=fpu

       ARM Options -mapcs-frame  -mno-apcs-frame -mabi=name
       -mapcs-stack-check  -mno-apcs-stack-check -mapcs-float
       -mno-apcs-float -mapcs-reentrant  -mno-apcs-reentrant
       -msched-prolog  -mno-sched-prolog -mlittle-endian  -mbig-endian
       -mfloat-abi=name -mfp16-format=name -mthumb-interwork
       -mno-thumb-interwork -mcpu=name  -march=name  -mfpu=name
       -mtune=name -mprint-tune-info -mstructure-size-boundary=n
       -mabort-on-noreturn -mlong-calls  -mno-long-calls -msingle-pic-base
       -mno-single-pic-base -mpic-register=reg -mnop-fun-dllimport
       -mpoke-function-name -mthumb  -marm -mtpcs-frame  -mtpcs-leaf-frame
       -mcaller-super-interworking  -mcallee-super-interworking -mtp=name
       -mtls-dialect=dialect -mword-relocations -mfix-cortex-m3-ldrd
       -munaligned-access -mneon-for-64bits -mslow-flash-data
       -masm-syntax-unified -mrestrict-it

       AVR Options -mmcu=mcu -maccumulate-args -mbranch-cost=cost
       -mcall-prologues -mint8 -mn_flash=size -mno-interrupts -mrelax
       -mrmw -mstrict-X -mtiny-stack -nodevicelib -Waddr-space-convert

       Blackfin Options -mcpu=cpu[-sirevision] -msim
       -momit-leaf-frame-pointer  -mno-omit-leaf-frame-pointer
       -mspecld-anomaly  -mno-specld-anomaly  -mcsync-anomaly
       -mno-csync-anomaly -mlow-64k -mno-low64k  -mstack-check-l1
       -mid-shared-library -mno-id-shared-library  -mshared-library-id=n
       -mleaf-id-shared-library  -mno-leaf-id-shared-library -msep-data
       -mno-sep-data  -mlong-calls  -mno-long-calls -mfast-fp -minline-plt
       -mmulticore  -mcorea  -mcoreb  -msdram -micplb

       C6X Options -mbig-endian  -mlittle-endian -march=cpu -msim
       -msdata=sdata-type

       CRIS Options -mcpu=cpu  -march=cpu  -mtune=cpu -mmax-stack-frame=n
       -melinux-stacksize=n -metrax4  -metrax100  -mpdebug  -mcc-init
       -mno-side-effects -mstack-align  -mdata-align  -mconst-align
       -m32-bit  -m16-bit  -m8-bit  -mno-prologue-epilogue  -mno-gotplt
       -melf  -maout  -melinux  -mlinux  -sim  -sim2 -mmul-bug-workaround
       -mno-mul-bug-workaround

       CR16 Options -mmac -mcr16cplus -mcr16c -msim -mint32 -mbit-ops
       -mdata-model=model

       Darwin Options -all_load  -allowable_client  -arch
       -arch_errors_fatal -arch_only  -bind_at_load  -bundle
       -bundle_loader -client_name  -compatibility_version
       -current_version -dead_strip -dependency-file  -dylib_file
       -dylinker_install_name -dynamic  -dynamiclib
       -exported_symbols_list -filelist  -flat_namespace
       -force_cpusubtype_ALL -force_flat_namespace
       -headerpad_max_install_names -iframework -image_base  -init
       -install_name  -keep_private_externs -multi_module
       -multiply_defined  -multiply_defined_unused -noall_load
       -no_dead_strip_inits_and_terms -nofixprebinding -nomultidefs
       -noprebind  -noseglinkedit -pagezero_size  -prebind
       -prebind_all_twolevel_modules -private_bundle  -read_only_relocs
       -sectalign -sectobjectsymbols  -whyload  -seg1addr -sectcreate
       -sectobjectsymbols  -sectorder -segaddr -segs_read_only_addr
       -segs_read_write_addr -seg_addr_table  -seg_addr_table_filename
       -seglinkedit -segprot  -segs_read_only_addr  -segs_read_write_addr
       -single_module  -static  -sub_library  -sub_umbrella
       -twolevel_namespace  -umbrella  -undefined -unexported_symbols_list
       -weak_reference_mismatches -whatsloaded -F -gused -gfull
       -mmacosx-version-min=version -mkernel -mone-byte-bool

       DEC Alpha Options -mno-fp-regs  -msoft-float -mieee
       -mieee-with-inexact  -mieee-conformant -mfp-trap-mode=mode
       -mfp-rounding-mode=mode -mtrap-precision=mode  -mbuild-constants
       -mcpu=cpu-type  -mtune=cpu-type -mbwx  -mmax  -mfix  -mcix
       -mfloat-vax  -mfloat-ieee -mexplicit-relocs  -msmall-data
       -mlarge-data -msmall-text  -mlarge-text -mmemory-latency=time

       FR30 Options -msmall-model -mno-lsim

       FT32 Options -msim -mlra -mnodiv

       FRV Options -mgpr-32  -mgpr-64  -mfpr-32  -mfpr-64 -mhard-float
       -msoft-float -malloc-cc  -mfixed-cc  -mdword  -mno-dword -mdouble
       -mno-double -mmedia  -mno-media  -mmuladd  -mno-muladd -mfdpic
       -minline-plt -mgprel-ro  -multilib-library-pic -mlinked-fp
       -mlong-calls  -malign-labels -mlibrary-pic  -macc-4  -macc-8 -mpack
       -mno-pack  -mno-eflags  -mcond-move  -mno-cond-move
       -moptimize-membar -mno-optimize-membar -mscc  -mno-scc  -mcond-exec
       -mno-cond-exec -mvliw-branch  -mno-vliw-branch -mmulti-cond-exec
       -mno-multi-cond-exec  -mnested-cond-exec -mno-nested-cond-exec
       -mtomcat-stats -mTLS -mtls -mcpu=cpu

       GNU/Linux Options -mglibc -muclibc -mmusl -mbionic -mandroid
       -tno-android-cc -tno-android-ld

       H8/300 Options -mrelax  -mh  -ms  -mn  -mexr -mno-exr  -mint32
       -malign-300

       HPPA Options -march=architecture-type -mdisable-fpregs
       -mdisable-indexing -mfast-indirect-calls  -mgas  -mgnu-ld   -mhp-ld
       -mfixed-range=register-range -mjump-in-delay -mlinker-opt
       -mlong-calls -mlong-load-store  -mno-disable-fpregs
       -mno-disable-indexing  -mno-fast-indirect-calls  -mno-gas
       -mno-jump-in-delay  -mno-long-load-store -mno-portable-runtime
       -mno-soft-float -mno-space-regs  -msoft-float  -mpa-risc-1-0
       -mpa-risc-1-1  -mpa-risc-2-0  -mportable-runtime -mschedule=cpu-
       type  -mspace-regs  -msio  -mwsio -munix=unix-std  -nolibdld
       -static  -threads

       IA-64 Options -mbig-endian  -mlittle-endian  -mgnu-as  -mgnu-ld
       -mno-pic -mvolatile-asm-stop  -mregister-names  -msdata -mno-sdata
       -mconstant-gp  -mauto-pic  -mfused-madd
       -minline-float-divide-min-latency
       -minline-float-divide-max-throughput -mno-inline-float-divide
       -minline-int-divide-min-latency -minline-int-divide-max-throughput
       -mno-inline-int-divide -minline-sqrt-min-latency
       -minline-sqrt-max-throughput -mno-inline-sqrt -mdwarf2-asm
       -mearly-stop-bits -mfixed-range=register-range -mtls-size=tls-size
       -mtune=cpu-type -milp32 -mlp64 -msched-br-data-spec
       -msched-ar-data-spec -msched-control-spec -msched-br-in-data-spec
       -msched-ar-in-data-spec -msched-in-control-spec -msched-spec-ldc
       -msched-spec-control-ldc -msched-prefer-non-data-spec-insns
       -msched-prefer-non-control-spec-insns
       -msched-stop-bits-after-every-cycle
       -msched-count-spec-in-critical-path
       -msel-sched-dont-check-control-spec -msched-fp-mem-deps-zero-cost
       -msched-max-memory-insns-hard-limit -msched-max-memory-insns=max-
       insns

       LM32 Options -mbarrel-shift-enabled -mdivide-enabled
       -mmultiply-enabled -msign-extend-enabled -muser-enabled

       M32R/D Options -m32r2 -m32rx -m32r -mdebug -malign-loops
       -mno-align-loops -missue-rate=number -mbranch-cost=number
       -mmodel=code-size-model-type -msdata=sdata-type -mno-flush-func
       -mflush-func=name -mno-flush-trap -mflush-trap=number -G num

       M32C Options -mcpu=cpu -msim -memregs=number

       M680x0 Options -march=arch  -mcpu=cpu  -mtune=tune -m68000  -m68020
       -m68020-40  -m68020-60  -m68030  -m68040 -m68060  -mcpu32  -m5200
       -m5206e  -m528x  -m5307  -m5407 -mcfv4e  -mbitfield  -mno-bitfield
       -mc68000  -mc68020 -mnobitfield  -mrtd  -mno-rtd  -mdiv  -mno-div
       -mshort -mno-short  -mhard-float  -m68881  -msoft-float  -mpcrel
       -malign-int  -mstrict-align  -msep-data  -mno-sep-data
       -mshared-library-id=n  -mid-shared-library  -mno-id-shared-library
       -mxgot -mno-xgot

       MCore Options -mhardlit  -mno-hardlit  -mdiv  -mno-div
       -mrelax-immediates -mno-relax-immediates  -mwide-bitfields
       -mno-wide-bitfields -m4byte-functions  -mno-4byte-functions
       -mcallgraph-data -mno-callgraph-data  -mslow-bytes  -mno-slow-bytes
       -mno-lsim -mlittle-endian  -mbig-endian  -m210  -m340
       -mstack-increment

       MeP Options -mabsdiff -mall-opts -maverage -mbased=n -mbitops -mc=n
       -mclip -mconfig=name -mcop -mcop32 -mcop64 -mivc2 -mdc -mdiv -meb
       -mel -mio-volatile -ml -mleadz -mm -mminmax -mmult -mno-opts
       -mrepeat -ms -msatur -msdram -msim -msimnovec -mtf -mtiny=n

       MicroBlaze Options -msoft-float -mhard-float -msmall-divides
       -mcpu=cpu -mmemcpy -mxl-soft-mul -mxl-soft-div -mxl-barrel-shift
       -mxl-pattern-compare -mxl-stack-check -mxl-gp-opt -mno-clearbss
       -mxl-multiply-high -mxl-float-convert -mxl-float-sqrt -mbig-endian
       -mlittle-endian -mxl-reorder -mxl-mode-app-model

       MIPS Options -EL  -EB  -march=arch  -mtune=arch -mips1  -mips2
       -mips3  -mips4  -mips32  -mips32r2  -mips32r3  -mips32r5 -mips32r6
       -mips64  -mips64r2  -mips64r3  -mips64r5  -mips64r6 -mips16
       -mno-mips16  -mflip-mips16 -minterlink-compressed
       -mno-interlink-compressed -minterlink-mips16  -mno-interlink-mips16
       -mabi=abi  -mabicalls  -mno-abicalls -mshared  -mno-shared  -mplt
       -mno-plt  -mxgot  -mno-xgot -mgp32  -mgp64  -mfp32  -mfpxx  -mfp64
       -mhard-float  -msoft-float -mno-float  -msingle-float
       -mdouble-float -modd-spreg -mno-odd-spreg -mabs=mode
       -mnan=encoding -mdsp  -mno-dsp  -mdspr2  -mno-dspr2 -mmcu -mmno-mcu
       -meva -mno-eva -mvirt -mno-virt -mxpa -mno-xpa -mmicromips
       -mno-micromips -mfpu=fpu-type -msmartmips  -mno-smartmips
       -mpaired-single  -mno-paired-single  -mdmx  -mno-mdmx -mips3d
       -mno-mips3d  -mmt  -mno-mt  -mllsc  -mno-llsc -mlong64  -mlong32
       -msym32  -mno-sym32 -Gnum  -mlocal-sdata  -mno-local-sdata
       -mextern-sdata  -mno-extern-sdata  -mgpopt  -mno-gopt
       -membedded-data  -mno-embedded-data -muninit-const-in-rodata
       -mno-uninit-const-in-rodata -mcode-readable=setting
       -msplit-addresses  -mno-split-addresses -mexplicit-relocs
       -mno-explicit-relocs -mcheck-zero-division
       -mno-check-zero-division -mdivide-traps  -mdivide-breaks -mmemcpy
       -mno-memcpy  -mlong-calls  -mno-long-calls -mmad -mno-mad -mimadd
       -mno-imadd -mfused-madd  -mno-fused-madd  -nocpp -mfix-24k
       -mno-fix-24k -mfix-r4000  -mno-fix-r4000  -mfix-r4400
       -mno-fix-r4400 -mfix-r10000 -mno-fix-r10000  -mfix-rm7000
       -mno-fix-rm7000 -mfix-vr4120  -mno-fix-vr4120 -mfix-vr4130
       -mno-fix-vr4130  -mfix-sb1  -mno-fix-sb1 -mflush-func=func
       -mno-flush-func -mbranch-cost=num  -mbranch-likely
       -mno-branch-likely -mcompact-branches=policy -mfp-exceptions
       -mno-fp-exceptions -mvr4130-align -mno-vr4130-align -msynci
       -mno-synci -mrelax-pic-calls -mno-relax-pic-calls
       -mmcount-ra-address -mframe-header-opt -mno-frame-header-opt

       MMIX Options -mlibfuncs  -mno-libfuncs  -mepsilon  -mno-epsilon
       -mabi=gnu -mabi=mmixware  -mzero-extend  -mknuthdiv
       -mtoplevel-symbols -melf  -mbranch-predict  -mno-branch-predict
       -mbase-addresses -mno-base-addresses  -msingle-exit
       -mno-single-exit

       MN10300 Options -mmult-bug  -mno-mult-bug -mno-am33 -mam33 -mam33-2
       -mam34 -mtune=cpu-type -mreturn-pointer-on-d0 -mno-crt0  -mrelax
       -mliw -msetlb

       Moxie Options -meb -mel -mmul.x -mno-crt0

       MSP430 Options -msim -masm-hex -mmcu= -mcpu= -mlarge -msmall
       -mrelax -mwarn-mcu -mcode-region= -mdata-region= -msilicon-errata=
       -msilicon-errata-warn= -mhwmult= -minrt

       NDS32 Options -mbig-endian -mlittle-endian -mreduced-regs
       -mfull-regs -mcmov -mno-cmov -mperf-ext -mno-perf-ext -mv3push
       -mno-v3push -m16bit -mno-16bit -misr-vector-size=num
       -mcache-block-size=num -march=arch -mcmodel=code-model -mctor-dtor
       -mrelax

       Nios II Options -G num -mgpopt=option -mgpopt -mno-gpopt -mel -meb
       -mno-bypass-cache -mbypass-cache -mno-cache-volatile
       -mcache-volatile -mno-fast-sw-div -mfast-sw-div -mhw-mul
       -mno-hw-mul -mhw-mulx -mno-hw-mulx -mno-hw-div -mhw-div
       -mcustom-insn=N -mno-custom-insn -mcustom-fpu-cfg=name -mhal
       -msmallc -msys-crt0=name -msys-lib=name -march=arch -mbmx -mno-bmx
       -mcdx -mno-cdx

       Nvidia PTX Options -m32 -m64 -mmainkernel -moptimize

       PDP-11 Options -mfpu  -msoft-float  -mac0  -mno-ac0  -m40  -m45
       -m10 -mbcopy  -mbcopy-builtin  -mint32  -mno-int16 -mint16
       -mno-int32  -mfloat32  -mno-float64 -mfloat64  -mno-float32
       -mabshi  -mno-abshi -mbranch-expensive  -mbranch-cheap -munix-asm
       -mdec-asm

       picoChip Options -mae=ae_type -mvliw-lookahead=N
       -msymbol-as-address -mno-inefficient-warnings

       PowerPC Options See RS/6000 and PowerPC Options.

       RL78 Options -msim -mmul=none -mmul=g13 -mmul=g14 -mallregs
       -mcpu=g10 -mcpu=g13 -mcpu=g14 -mg10 -mg13 -mg14 -m64bit-doubles
       -m32bit-doubles

       RS/6000 and PowerPC Options -mcpu=cpu-type -mtune=cpu-type
       -mcmodel=code-model -mpowerpc64 -maltivec  -mno-altivec
       -mpowerpc-gpopt  -mno-powerpc-gpopt -mpowerpc-gfxopt
       -mno-powerpc-gfxopt -mmfcrf  -mno-mfcrf  -mpopcntb  -mno-popcntb
       -mpopcntd -mno-popcntd -mfprnd  -mno-fprnd -mcmpb -mno-cmpb
       -mmfpgpr -mno-mfpgpr -mhard-dfp -mno-hard-dfp -mfull-toc
       -mminimal-toc  -mno-fp-in-toc  -mno-sum-in-toc -m64  -m32
       -mxl-compat  -mno-xl-compat  -mpe -malign-power  -malign-natural
       -msoft-float  -mhard-float  -mmultiple  -mno-multiple
       -msingle-float -mdouble-float -msimple-fpu -mstring  -mno-string
       -mupdate  -mno-update -mavoid-indexed-addresses
       -mno-avoid-indexed-addresses -mfused-madd  -mno-fused-madd
       -mbit-align  -mno-bit-align -mstrict-align  -mno-strict-align
       -mrelocatable -mno-relocatable  -mrelocatable-lib
       -mno-relocatable-lib -mtoc  -mno-toc  -mlittle  -mlittle-endian
       -mbig  -mbig-endian -mdynamic-no-pic  -maltivec -mswdiv
       -msingle-pic-base -mprioritize-restricted-insns=priority
       -msched-costly-dep=dependence_type -minsert-sched-nops=scheme
       -mcall-sysv  -mcall-netbsd -maix-struct-return
       -msvr4-struct-return -mabi=abi-type -msecure-plt -mbss-plt
       -mblock-move-inline-limit=num -misel -mno-isel -misel=yes
       -misel=no -mspe -mno-spe -mspe=yes  -mspe=no -mpaired
       -mgen-cell-microcode -mwarn-cell-microcode -mvrsave -mno-vrsave
       -mmulhw -mno-mulhw -mdlmzb -mno-dlmzb -mfloat-gprs=yes
       -mfloat-gprs=no -mfloat-gprs=single -mfloat-gprs=double -mprototype
       -mno-prototype -msim  -mmvme  -mads  -myellowknife  -memb  -msdata
       -msdata=opt  -mvxworks  -G num  -pthread -mrecip -mrecip=opt
       -mno-recip -mrecip-precision -mno-recip-precision -mveclibabi=type
       -mfriz -mno-friz -mpointers-to-nested-functions
       -mno-pointers-to-nested-functions -msave-toc-indirect
       -mno-save-toc-indirect -mpower8-fusion -mno-mpower8-fusion
       -mpower8-vector -mno-power8-vector -mcrypto -mno-crypto -mhtm
       -mno-htm -mdirect-move -mno-direct-move -mquad-memory
       -mno-quad-memory -mquad-memory-atomic -mno-quad-memory-atomic
       -mcompat-align-parm -mno-compat-align-parm -mupper-regs-df
       -mno-upper-regs-df -mupper-regs-sf -mno-upper-regs-sf -mupper-regs
       -mno-upper-regs -mmodulo -mno-modulo -mfloat128 -mno-float128
       -mfloat128-hardware -mno-float128-hardware -mpower9-fusion
       -mno-mpower9-fusion -mpower9-vector -mno-power9-vector
       -mpower9-dform -mno-power9-dform -mlra -mno-lra

       RX Options -m64bit-doubles  -m32bit-doubles  -fpu  -nofpu -mcpu=
       -mbig-endian-data -mlittle-endian-data -msmall-data -msim  -mno-sim
       -mas100-syntax -mno-as100-syntax -mrelax -mmax-constant-size=
       -mint-register= -mpid -mallow-string-insns -mno-allow-string-insns
       -mjsr -mno-warn-multiple-fast-interrupts -msave-acc-in-interrupts

       S/390 and zSeries Options -mtune=cpu-type  -march=cpu-type
       -mhard-float  -msoft-float  -mhard-dfp -mno-hard-dfp
       -mlong-double-64 -mlong-double-128 -mbackchain  -mno-backchain
       -mpacked-stack  -mno-packed-stack -msmall-exec  -mno-small-exec
       -mmvcle -mno-mvcle -m64  -m31  -mdebug  -mno-debug  -mesa  -mzarch
       -mhtm -mvx -mzvector -mtpf-trace -mno-tpf-trace  -mfused-madd
       -mno-fused-madd -mwarn-framesize  -mwarn-dynamicstack  -mstack-size
       -mstack-guard -mhotpatch=halfwords,halfwords

       Score Options -meb -mel -mnhwloop -muls -mmac -mscore5 -mscore5u
       -mscore7 -mscore7d

       SH Options -m1  -m2  -m2e -m2a-nofpu -m2a-single-only -m2a-single
       -m2a -m3  -m3e -m4-nofpu  -m4-single-only  -m4-single  -m4
       -m4a-nofpu -m4a-single-only -m4a-single -m4a -m4al -mb  -ml
       -mdalign  -mrelax -mbigtable -mfmovd -mrenesas -mno-renesas
       -mnomacsave -mieee -mno-ieee -mbitops  -misize
       -minline-ic_invalidate -mpadstruct -mspace -mprefergot  -musermode
       -multcost=number -mdiv=strategy -mdivsi3_libfunc=name
       -mfixed-range=register-range -maccumulate-outgoing-args
       -matomic-model=atomic-model -mbranch-cost=num -mzdcbranch
       -mno-zdcbranch -mcbranch-force-delay-slot -mfused-madd
       -mno-fused-madd -mfsca -mno-fsca -mfsrra -mno-fsrra -mpretend-cmove
       -mtas

       Solaris 2 Options -mclear-hwcap -mno-clear-hwcap -mimpure-text
       -mno-impure-text -pthreads -pthread

       SPARC Options -mcpu=cpu-type -mtune=cpu-type -mcmodel=code-model
       -mmemory-model=mem-model -m32  -m64  -mapp-regs  -mno-app-regs
       -mfaster-structs  -mno-faster-structs  -mflat  -mno-flat -mfpu
       -mno-fpu  -mhard-float  -msoft-float -mhard-quad-float
       -msoft-quad-float -mstack-bias  -mno-stack-bias -mstd-struct-return
       -mno-std-struct-return -munaligned-doubles  -mno-unaligned-doubles
       -muser-mode  -mno-user-mode -mv8plus  -mno-v8plus  -mvis  -mno-vis
       -mvis2  -mno-vis2  -mvis3  -mno-vis3 -mcbcond -mno-cbcond -mfmaf
       -mno-fmaf  -mpopc  -mno-popc -mfix-at697f -mfix-ut699

       SPU Options -mwarn-reloc -merror-reloc -msafe-dma -munsafe-dma
       -mbranch-hints -msmall-mem -mlarge-mem -mstdmain
       -mfixed-range=register-range -mea32 -mea64
       -maddress-space-conversion -mno-address-space-conversion
       -mcache-size=cache-size -matomic-updates -mno-atomic-updates

       System V Options -Qy  -Qn  -YP,paths  -Ym,dir

       TILE-Gx Options -mcpu=CPU -m32 -m64 -mbig-endian -mlittle-endian
       -mcmodel=code-model

       TILEPro Options -mcpu=cpu -m32

       V850 Options -mlong-calls  -mno-long-calls  -mep  -mno-ep
       -mprolog-function  -mno-prolog-function  -mspace -mtda=n  -msda=n
       -mzda=n -mapp-regs  -mno-app-regs -mdisable-callt
       -mno-disable-callt -mv850e2v3 -mv850e2 -mv850e1 -mv850es -mv850e
       -mv850 -mv850e3v5 -mloop -mrelax -mlong-jumps -msoft-float
       -mhard-float -mgcc-abi -mrh850-abi -mbig-switch

       VAX Options -mg  -mgnu  -munix

       Visium Options -mdebug -msim -mfpu -mno-fpu -mhard-float
       -msoft-float -mcpu=cpu-type -mtune=cpu-type -msv-mode -muser-mode

       VMS Options -mvms-return-codes -mdebug-main=prefix -mmalloc64
       -mpointer-size=size

       VxWorks Options -mrtp  -non-static  -Bstatic  -Bdynamic -Xbind-lazy
       -Xbind-now

       x86 Options -mtune=cpu-type  -march=cpu-type -mtune-ctrl=feature-
       list -mdump-tune-features -mno-default -mfpmath=unit -masm=dialect
       -mno-fancy-math-387 -mno-fp-ret-in-387  -msoft-float
       -mno-wide-multiply  -mrtd  -malign-double
       -mpreferred-stack-boundary=num -mincoming-stack-boundary=num -mcld
       -mcx16 -msahf -mmovbe -mcrc32 -mrecip -mrecip=opt -mvzeroupper
       -mprefer-avx128 -mmmx  -msse  -msse2 -msse3 -mssse3 -msse4.1
       -msse4.2 -msse4 -mavx -mavx2 -mavx512f -mavx512pf -mavx512er
       -mavx512cd -mavx512vl -mavx512bw -mavx512dq -mavx512ifma
       -mavx512vbmi -msha -maes -mpclmul -mfsgsbase -mrdrnd -mf16c -mfma
       -mprefetchwt1 -mclflushopt -mxsavec -mxsaves -msse4a -m3dnow
       -mpopcnt -mabm -mbmi -mtbm -mfma4 -mxop -mlzcnt -mbmi2 -mfxsr
       -mxsave -mxsaveopt -mrtm -mlwp -mmpx -mmwaitx -mclzero -mpku
       -mthreads -mms-bitfields -mno-align-stringops
       -minline-all-stringops -minline-stringops-dynamically
       -mstringop-strategy=alg -mmemcpy-strategy=strategy
       -mmemset-strategy=strategy -mpush-args  -maccumulate-outgoing-args
       -m128bit-long-double -m96bit-long-double -mlong-double-64
       -mlong-double-80 -mlong-double-128 -mregparm=num  -msseregparm
       -mveclibabi=type -mvect8-ret-in-mem -mpc32 -mpc64 -mpc80
       -mstackrealign -momit-leaf-frame-pointer  -mno-red-zone
       -mno-tls-direct-seg-refs -mcmodel=code-model -mabi=name
       -maddress-mode=mode -m32 -m64 -mx32 -m16 -miamcu
       -mlarge-data-threshold=num -msse2avx -mfentry -mrecord-mcount
       -mnop-mcount -m8bit-idiv -mavx256-split-unaligned-load
       -mavx256-split-unaligned-store -malign-data=type
       -mstack-protector-guard=guard -mmitigate-rop

       x86 Windows Options -mconsole -mcygwin -mno-cygwin -mdll
       -mnop-fun-dllimport -mthread -municode -mwin32 -mwindows
       -fno-set-stack-executable

       Xstormy16 Options -msim

       Xtensa Options -mconst16 -mno-const16 -mfused-madd  -mno-fused-madd
       -mforce-no-pic -mserialize-volatile  -mno-serialize-volatile
       -mtext-section-literals  -mno-text-section-literals -mauto-litpools
       -mno-auto-litpools -mtarget-align  -mno-target-align -mlongcalls
       -mno-longcalls

       zSeries Options See S/390 and zSeries Options.

   Options Controlling the Kind of Output
   Compilation can involve up to four stages: preprocessing, compilation
   proper, assembly and linking, always in that order.  GCC is capable of
   preprocessing and compiling several files either into several assembler
   input files, or into one assembler input file; then each assembler
   input file produces an object file, and linking combines all the object
   files (those newly compiled, and those specified as input) into an
   executable file.

   For any given input file, the file name suffix determines what kind of
   compilation is done:

   file.c
       C source code that must be preprocessed.

   file.i
       C source code that should not be preprocessed.

   file.ii
       C++ source code that should not be preprocessed.

   file.m
       Objective-C source code.  Note that you must link with the libobjc
       library to make an Objective-C program work.

   file.mi
       Objective-C source code that should not be preprocessed.

   file.mm
   file.M
       Objective-C++ source code.  Note that you must link with the
       libobjc library to make an Objective-C++ program work.  Note that
       .M refers to a literal capital M.

   file.mii
       Objective-C++ source code that should not be preprocessed.

   file.h
       C, C++, Objective-C or Objective-C++ header file to be turned into
       a precompiled header (default), or C, C++ header file to be turned
       into an Ada spec (via the -fdump-ada-spec switch).

   file.cc
   file.cp
   file.cxx
   file.cpp
   file.CPP
   file.c++
   file.C
       C++ source code that must be preprocessed.  Note that in .cxx, the
       last two letters must both be literally x.  Likewise, .C refers to
       a literal capital C.

   file.mm
   file.M
       Objective-C++ source code that must be preprocessed.

   file.mii
       Objective-C++ source code that should not be preprocessed.

   file.hh
   file.H
   file.hp
   file.hxx
   file.hpp
   file.HPP
   file.h++
   file.tcc
       C++ header file to be turned into a precompiled header or Ada spec.

   file.f
   file.for
   file.ftn
       Fixed form Fortran source code that should not be preprocessed.

   file.F
   file.FOR
   file.fpp
   file.FPP
   file.FTN
       Fixed form Fortran source code that must be preprocessed (with the
       traditional preprocessor).

   file.f90
   file.f95
   file.f03
   file.f08
       Free form Fortran source code that should not be preprocessed.

   file.F90
   file.F95
   file.F03
   file.F08
       Free form Fortran source code that must be preprocessed (with the
       traditional preprocessor).

   file.go
       Go source code.

   file.ads
       Ada source code file that contains a library unit declaration (a
       declaration of a package, subprogram, or generic, or a generic
       instantiation), or a library unit renaming declaration (a package,
       generic, or subprogram renaming declaration).  Such files are also
       called specs.

   file.adb
       Ada source code file containing a library unit body (a subprogram
       or package body).  Such files are also called bodies.

   file.d
       D source code file.

   file.di
       D interface code file.

   file.dd
       D documentation code file.

   file.s
       Assembler code.

   file.S
   file.sx
       Assembler code that must be preprocessed.

   other
       An object file to be fed straight into linking.  Any file name with
       no recognized suffix is treated this way.

   You can specify the input language explicitly with the -x option:

   -x language
       Specify explicitly the language for the following input files
       (rather than letting the compiler choose a default based on the
       file name suffix).  This option applies to all following input
       files until the next -x option.  Possible values for language are:

               c  c-header  cpp-output
               c++  c++-header  c++-cpp-output
               objective-c  objective-c-header  objective-c-cpp-output
               objective-c++ objective-c++-header objective-c++-cpp-output
               assembler  assembler-with-cpp
               ada
               d
               f77  f77-cpp-input f95  f95-cpp-input
               go
               java

   -x none
       Turn off any specification of a language, so that subsequent files
       are handled according to their file name suffixes (as they are if
       -x has not been used at all).

   If you only want some of the stages of compilation, you can use -x (or
   filename suffixes) to tell gcc where to start, and one of the options
   -c, -S, or -E to say where gcc is to stop.  Note that some combinations
   (for example, -x cpp-output -E) instruct gcc to do nothing at all.

   -c  Compile or assemble the source files, but do not link.  The linking
       stage simply is not done.  The ultimate output is in the form of an
       object file for each source file.

       By default, the object file name for a source file is made by
       replacing the suffix .c, .i, .s, etc., with .o.

       Unrecognized input files, not requiring compilation or assembly,
       are ignored.

   -S  Stop after the stage of compilation proper; do not assemble.  The
       output is in the form of an assembler code file for each non-
       assembler input file specified.

       By default, the assembler file name for a source file is made by
       replacing the suffix .c, .i, etc., with .s.

       Input files that don't require compilation are ignored.

   -E  Stop after the preprocessing stage; do not run the compiler proper.
       The output is in the form of preprocessed source code, which is
       sent to the standard output.

       Input files that don't require preprocessing are ignored.

   -o file
       Place output in file file.  This applies to whatever sort of output
       is being produced, whether it be an executable file, an object
       file, an assembler file or preprocessed C code.

       If -o is not specified, the default is to put an executable file in
       a.out, the object file for source.suffix in source.o, its assembler
       file in source.s, a precompiled header file in source.suffix.gch,
       and all preprocessed C source on standard output.

   -v  Print (on standard error output) the commands executed to run the
       stages of compilation.  Also print the version number of the
       compiler driver program and of the preprocessor and the compiler
       proper.

   -###
       Like -v except the commands are not executed and arguments are
       quoted unless they contain only alphanumeric characters or "./-_".
       This is useful for shell scripts to capture the driver-generated
       command lines.

   --help
       Print (on the standard output) a description of the command-line
       options understood by gcc.  If the -v option is also specified then
       --help is also passed on to the various processes invoked by gcc,
       so that they can display the command-line options they accept.  If
       the -Wextra option has also been specified (prior to the --help
       option), then command-line options that have no documentation
       associated with them are also displayed.

   --target-help
       Print (on the standard output) a description of target-specific
       command-line options for each tool.  For some targets extra target-
       specific information may also be printed.

   --help={class|[^]qualifier}[,...]
       Print (on the standard output) a description of the command-line
       options understood by the compiler that fit into all specified
       classes and qualifiers.  These are the supported classes:

       optimizers
           Display all of the optimization options supported by the
           compiler.

       warnings
           Display all of the options controlling warning messages
           produced by the compiler.

       target
           Display target-specific options.  Unlike the --target-help
           option however, target-specific options of the linker and
           assembler are not displayed.  This is because those tools do
           not currently support the extended --help= syntax.

       params
           Display the values recognized by the --param option.

       language
           Display the options supported for language, where language is
           the name of one of the languages supported in this version of
           GCC.

       common
           Display the options that are common to all languages.

       These are the supported qualifiers:

       undocumented
           Display only those options that are undocumented.

       joined
           Display options taking an argument that appears after an equal
           sign in the same continuous piece of text, such as:
           --help=target.

       separate
           Display options taking an argument that appears as a separate
           word following the original option, such as: -o output-file.

       Thus for example to display all the undocumented target-specific
       switches supported by the compiler, use:

               --help=target,undocumented

       The sense of a qualifier can be inverted by prefixing it with the ^
       character, so for example to display all binary warning options
       (i.e., ones that are either on or off and that do not take an
       argument) that have a description, use:

               --help=warnings,^joined,^undocumented

       The argument to --help= should not consist solely of inverted
       qualifiers.

       Combining several classes is possible, although this usually
       restricts the output so much that there is nothing to display.  One
       case where it does work, however, is when one of the classes is
       target.  For example, to display all the target-specific
       optimization options, use:

               --help=target,optimizers

       The --help= option can be repeated on the command line.  Each
       successive use displays its requested class of options, skipping
       those that have already been displayed.

       If the -Q option appears on the command line before the --help=
       option, then the descriptive text displayed by --help= is changed.
       Instead of describing the displayed options, an indication is given
       as to whether the option is enabled, disabled or set to a specific
       value (assuming that the compiler knows this at the point where the
       --help= option is used).

       Here is a truncated example from the ARM port of gcc:

                 % gcc -Q -mabi=2 --help=target -c
                 The following options are target specific:
                 -mabi=                                2
                 -mabort-on-noreturn                   [disabled]
                 -mapcs                                [disabled]

       The output is sensitive to the effects of previous command-line
       options, so for example it is possible to find out which
       optimizations are enabled at -O2 by using:

               -Q -O2 --help=optimizers

       Alternatively you can discover which binary optimizations are
       enabled by -O3 by using:

               gcc -c -Q -O3 --help=optimizers > /tmp/O3-opts
               gcc -c -Q -O2 --help=optimizers > /tmp/O2-opts
               diff /tmp/O2-opts /tmp/O3-opts | grep enabled

   --version
       Display the version number and copyrights of the invoked GCC.

   -pass-exit-codes
       Normally the gcc program exits with the code of 1 if any phase of
       the compiler returns a non-success return code.  If you specify
       -pass-exit-codes, the gcc program instead returns with the
       numerically highest error produced by any phase returning an error
       indication.  The C, C++, and Fortran front ends return 4 if an
       internal compiler error is encountered.

   -pipe
       Use pipes rather than temporary files for communication between the
       various stages of compilation.  This fails to work on some systems
       where the assembler is unable to read from a pipe; but the GNU
       assembler has no trouble.

   -specs=file
       Process file after the compiler reads in the standard specs file,
       in order to override the defaults which the gcc driver program uses
       when determining what switches to pass to cc1, cc1plus, as, ld,
       etc.  More than one -specs=file can be specified on the command
       line, and they are processed in order, from left to right.

   -wrapper
       Invoke all subcommands under a wrapper program.  The name of the
       wrapper program and its parameters are passed as a comma separated
       list.

               gcc -c t.c -wrapper gdb,--args

       This invokes all subprograms of gcc under gdb --args, thus the
       invocation of cc1 is gdb --args cc1 ....

   -fplugin=name.so
       Load the plugin code in file name.so, assumed to be a shared object
       to be dlopen'd by the compiler.  The base name of the shared object
       file is used to identify the plugin for the purposes of argument
       parsing (See -fplugin-arg-name-key=value below).  Each plugin
       should define the callback functions specified in the Plugins API.

   -fplugin-arg-name-key=value
       Define an argument called key with a value of value for the plugin
       called name.

   -fdump-ada-spec[-slim]
       For C and C++ source and include files, generate corresponding Ada
       specs.

   -fada-spec-parent=unit
       In conjunction with -fdump-ada-spec[-slim] above, generate Ada
       specs as child units of parent unit.

   -fdump-go-spec=file
       For input files in any language, generate corresponding Go
       declarations in file.  This generates Go "const", "type", "var",
       and "func" declarations which may be a useful way to start writing
       a Go interface to code written in some other language.

   @file
       Read command-line options from file.  The options read are inserted
       in place of the original @file option.  If file does not exist, or
       cannot be read, then the option will be treated literally, and not
       removed.

       Options in file are separated by whitespace.  A whitespace
       character may be included in an option by surrounding the entire
       option in either single or double quotes.  Any character (including
       a backslash) may be included by prefixing the character to be
       included with a backslash.  The file may itself contain additional
       @file options; any such options will be processed recursively.

   Compiling C++ Programs
   C++ source files conventionally use one of the suffixes .C, .cc, .cpp,
   .CPP, .c++, .cp, or .cxx; C++ header files often use .hh, .hpp, .H, or
   (for shared template code) .tcc; and preprocessed C++ files use the
   suffix .ii.  GCC recognizes files with these names and compiles them as
   C++ programs even if you call the compiler the same way as for
   compiling C programs (usually with the name gcc).

   However, the use of gcc does not add the C++ library.  g++ is a program
   that calls GCC and automatically specifies linking against the C++
   library.  It treats .c, .h and .i files as C++ source files instead of
   C source files unless -x is used.  This program is also useful when
   precompiling a C header file with a .h extension for use in C++
   compilations.  On many systems, g++ is also installed with the name
   c++.

   When you compile C++ programs, you may specify many of the same
   command-line options that you use for compiling programs in any
   language; or command-line options meaningful for C and related
   languages; or options that are meaningful only for C++ programs.

   Options Controlling C Dialect
   The following options control the dialect of C (or languages derived
   from C, such as C++, Objective-C and Objective-C++) that the compiler
   accepts:

   -ansi
       In C mode, this is equivalent to -std=c90. In C++ mode, it is
       equivalent to -std=c++98.

       This turns off certain features of GCC that are incompatible with
       ISO C90 (when compiling C code), or of standard C++ (when compiling
       C++ code), such as the "asm" and "typeof" keywords, and predefined
       macros such as "unix" and "vax" that identify the type of system
       you are using.  It also enables the undesirable and rarely used ISO
       trigraph feature.  For the C compiler, it disables recognition of
       C++ style // comments as well as the "inline" keyword.

       The alternate keywords "__asm__", "__extension__", "__inline__" and
       "__typeof__" continue to work despite -ansi.  You would not want to
       use them in an ISO C program, of course, but it is useful to put
       them in header files that might be included in compilations done
       with -ansi.  Alternate predefined macros such as "__unix__" and
       "__vax__" are also available, with or without -ansi.

       The -ansi option does not cause non-ISO programs to be rejected
       gratuitously.  For that, -Wpedantic is required in addition to
       -ansi.

       The macro "__STRICT_ANSI__" is predefined when the -ansi option is
       used.  Some header files may notice this macro and refrain from
       declaring certain functions or defining certain macros that the ISO
       standard doesn't call for; this is to avoid interfering with any
       programs that might use these names for other things.

       Functions that are normally built in but do not have semantics
       defined by ISO C (such as "alloca" and "ffs") are not built-in
       functions when -ansi is used.

   -std=
       Determine the language standard.   This option is currently only
       supported when compiling C or C++.

       The compiler can accept several base standards, such as c90 or
       c++98, and GNU dialects of those standards, such as gnu90 or
       gnu++98.  When a base standard is specified, the compiler accepts
       all programs following that standard plus those using GNU
       extensions that do not contradict it.  For example, -std=c90 turns
       off certain features of GCC that are incompatible with ISO C90,
       such as the "asm" and "typeof" keywords, but not other GNU
       extensions that do not have a meaning in ISO C90, such as omitting
       the middle term of a "?:" expression. On the other hand, when a GNU
       dialect of a standard is specified, all features supported by the
       compiler are enabled, even when those features change the meaning
       of the base standard.  As a result, some strict-conforming programs
       may be rejected.  The particular standard is used by -Wpedantic to
       identify which features are GNU extensions given that version of
       the standard. For example -std=gnu90 -Wpedantic warns about C++
       style // comments, while -std=gnu99 -Wpedantic does not.

       A value for this option must be provided; possible values are

       c90
       c89
       iso9899:1990
           Support all ISO C90 programs (certain GNU extensions that
           conflict with ISO C90 are disabled). Same as -ansi for C code.

       iso9899:199409
           ISO C90 as modified in amendment 1.

       c99
       c9x
       iso9899:1999
       iso9899:199x
           ISO C99.  This standard is substantially completely supported,
           modulo bugs and floating-point issues (mainly but not entirely
           relating to optional C99 features from Annexes F and G).  See
           <http://gcc.gnu.org/c99status.html> for more information.  The
           names c9x and iso9899:199x are deprecated.

       c11
       c1x
       iso9899:2011
           ISO C11, the 2011 revision of the ISO C standard.  This
           standard is substantially completely supported, modulo bugs,
           floating-point issues (mainly but not entirely relating to
           optional C11 features from Annexes F and G) and the optional
           Annexes K (Bounds-checking interfaces) and L (Analyzability).
           The name c1x is deprecated.

       gnu90
       gnu89
           GNU dialect of ISO C90 (including some C99 features).

       gnu99
       gnu9x
           GNU dialect of ISO C99.  The name gnu9x is deprecated.

       gnu11
       gnu1x
           GNU dialect of ISO C11.  This is the default for C code.  The
           name gnu1x is deprecated.

       c++98
       c++03
           The 1998 ISO C++ standard plus the 2003 technical corrigendum
           and some additional defect reports. Same as -ansi for C++ code.

       gnu++98
       gnu++03
           GNU dialect of -std=c++98.

       c++11
       c++0x
           The 2011 ISO C++ standard plus amendments.  The name c++0x is
           deprecated.

       gnu++11
       gnu++0x
           GNU dialect of -std=c++11.  The name gnu++0x is deprecated.

       c++14
       c++1y
           The 2014 ISO C++ standard plus amendments.  The name c++1y is
           deprecated.

       gnu++14
       gnu++1y
           GNU dialect of -std=c++14.  This is the default for C++ code.
           The name gnu++1y is deprecated.

       c++1z
           The next revision of the ISO C++ standard, tentatively planned
           for 2017.  Support is highly experimental, and will almost
           certainly change in incompatible ways in future releases.

       gnu++1z
           GNU dialect of -std=c++1z.  Support is highly experimental, and
           will almost certainly change in incompatible ways in future
           releases.

   -fgnu89-inline
       The option -fgnu89-inline tells GCC to use the traditional GNU
       semantics for "inline" functions when in C99 mode.

       Using this option is roughly equivalent to adding the "gnu_inline"
       function attribute to all inline functions.

       The option -fno-gnu89-inline explicitly tells GCC to use the C99
       semantics for "inline" when in C99 or gnu99 mode (i.e., it
       specifies the default behavior).  This option is not supported in
       -std=c90 or -std=gnu90 mode.

       The preprocessor macros "__GNUC_GNU_INLINE__" and
       "__GNUC_STDC_INLINE__" may be used to check which semantics are in
       effect for "inline" functions.

   -aux-info filename
       Output to the given filename prototyped declarations for all
       functions declared and/or defined in a translation unit, including
       those in header files.  This option is silently ignored in any
       language other than C.

       Besides declarations, the file indicates, in comments, the origin
       of each declaration (source file and line), whether the declaration
       was implicit, prototyped or unprototyped (I, N for new or O for
       old, respectively, in the first character after the line number and
       the colon), and whether it came from a declaration or a definition
       (C or F, respectively, in the following character).  In the case of
       function definitions, a K&R-style list of arguments followed by
       their declarations is also provided, inside comments, after the
       declaration.

   -fallow-parameterless-variadic-functions
       Accept variadic functions without named parameters.

       Although it is possible to define such a function, this is not very
       useful as it is not possible to read the arguments.  This is only
       supported for C as this construct is allowed by C++.

   -fno-asm
       Do not recognize "asm", "inline" or "typeof" as a keyword, so that
       code can use these words as identifiers.  You can use the keywords
       "__asm__", "__inline__" and "__typeof__" instead.  -ansi implies
       -fno-asm.

       In C++, this switch only affects the "typeof" keyword, since "asm"
       and "inline" are standard keywords.  You may want to use the
       -fno-gnu-keywords flag instead, which has the same effect.  In C99
       mode (-std=c99 or -std=gnu99), this switch only affects the "asm"
       and "typeof" keywords, since "inline" is a standard keyword in ISO
       C99.

   -fno-builtin
   -fno-builtin-function
       Don't recognize built-in functions that do not begin with
       __builtin_ as prefix.

       GCC normally generates special code to handle certain built-in
       functions more efficiently; for instance, calls to "alloca" may
       become single instructions which adjust the stack directly, and
       calls to "memcpy" may become inline copy loops.  The resulting code
       is often both smaller and faster, but since the function calls no
       longer appear as such, you cannot set a breakpoint on those calls,
       nor can you change the behavior of the functions by linking with a
       different library.  In addition, when a function is recognized as a
       built-in function, GCC may use information about that function to
       warn about problems with calls to that function, or to generate
       more efficient code, even if the resulting code still contains
       calls to that function.  For example, warnings are given with
       -Wformat for bad calls to "printf" when "printf" is built in and
       "strlen" is known not to modify global memory.

       With the -fno-builtin-function option only the built-in function
       function is disabled.  function must not begin with __builtin_.  If
       a function is named that is not built-in in this version of GCC,
       this option is ignored.  There is no corresponding
       -fbuiltin-function option; if you wish to enable built-in functions
       selectively when using -fno-builtin or -ffreestanding, you may
       define macros such as:

               #define abs(n)          __builtin_abs ((n))
               #define strcpy(d, s)    __builtin_strcpy ((d), (s))

   -fhosted
       Assert that compilation targets a hosted environment.  This implies
       -fbuiltin.  A hosted environment is one in which the entire
       standard library is available, and in which "main" has a return
       type of "int".  Examples are nearly everything except a kernel.
       This is equivalent to -fno-freestanding.

   -ffreestanding
       Assert that compilation targets a freestanding environment.  This
       implies -fno-builtin.  A freestanding environment is one in which
       the standard library may not exist, and program startup may not
       necessarily be at "main".  The most obvious example is an OS
       kernel.  This is equivalent to -fno-hosted.

   -fopenacc
       Enable handling of OpenACC directives "#pragma acc" in C/C++ and
       "!$acc" in Fortran.  When -fopenacc is specified, the compiler
       generates accelerated code according to the OpenACC Application
       Programming Interface v2.0 <http://www.openacc.org/>.  This option
       implies -pthread, and thus is only supported on targets that have
       support for -pthread.

   -fopenacc-dim=geom
       Specify default compute dimensions for parallel offload regions
       that do not explicitly specify.  The geom value is a triple of
       ':'-separated sizes, in order 'gang', 'worker' and, 'vector'.  A
       size can be omitted, to use a target-specific default value.

   -fopenmp
       Enable handling of OpenMP directives "#pragma omp" in C/C++ and
       "!$omp" in Fortran.  When -fopenmp is specified, the compiler
       generates parallel code according to the OpenMP Application Program
       Interface v4.0 <http://www.openmp.org/>.  This option implies
       -pthread, and thus is only supported on targets that have support
       for -pthread. -fopenmp implies -fopenmp-simd.

   -fopenmp-simd
       Enable handling of OpenMP's SIMD directives with "#pragma omp" in
       C/C++ and "!$omp" in Fortran. Other OpenMP directives are ignored.

   -fcilkplus
       Enable the usage of Cilk Plus language extension features for
       C/C++.  When the option -fcilkplus is specified, enable the usage
       of the Cilk Plus Language extension features for C/C++.  The
       present implementation follows ABI version 1.2.  This is an
       experimental feature that is only partially complete, and whose
       interface may change in future versions of GCC as the official
       specification changes.  Currently, all features but "_Cilk_for"
       have been implemented.

   -fgnu-tm
       When the option -fgnu-tm is specified, the compiler generates code
       for the Linux variant of Intel's current Transactional Memory ABI
       specification document (Revision 1.1, May 6 2009).  This is an
       experimental feature whose interface may change in future versions
       of GCC, as the official specification changes.  Please note that
       not all architectures are supported for this feature.

       For more information on GCC's support for transactional memory,

       Note that the transactional memory feature is not supported with
       non-call exceptions (-fnon-call-exceptions).

   -fms-extensions
       Accept some non-standard constructs used in Microsoft header files.

       In C++ code, this allows member names in structures to be similar
       to previous types declarations.

               typedef int UOW;
               struct ABC {
                 UOW UOW;
               };

       Some cases of unnamed fields in structures and unions are only
       accepted with this option.

       Note that this option is off for all targets but x86 targets using
       ms-abi.

   -fplan9-extensions
       Accept some non-standard constructs used in Plan 9 code.

       This enables -fms-extensions, permits passing pointers to
       structures with anonymous fields to functions that expect pointers
       to elements of the type of the field, and permits referring to
       anonymous fields declared using a typedef.    This is only
       supported for C, not C++.

   -trigraphs
       Support ISO C trigraphs.  The -ansi option (and -std options for
       strict ISO C conformance) implies -trigraphs.

   -traditional
   -traditional-cpp
       Formerly, these options caused GCC to attempt to emulate a pre-
       standard C compiler.  They are now only supported with the -E
       switch.  The preprocessor continues to support a pre-standard mode.
       See the GNU CPP manual for details.

   -fcond-mismatch
       Allow conditional expressions with mismatched types in the second
       and third arguments.  The value of such an expression is void.
       This option is not supported for C++.

   -flax-vector-conversions
       Allow implicit conversions between vectors with differing numbers
       of elements and/or incompatible element types.  This option should
       not be used for new code.

   -funsigned-char
       Let the type "char" be unsigned, like "unsigned char".

       Each kind of machine has a default for what "char" should be.  It
       is either like "unsigned char" by default or like "signed char" by
       default.

       Ideally, a portable program should always use "signed char" or
       "unsigned char" when it depends on the signedness of an object.
       But many programs have been written to use plain "char" and expect
       it to be signed, or expect it to be unsigned, depending on the
       machines they were written for.  This option, and its inverse, let
       you make such a program work with the opposite default.

       The type "char" is always a distinct type from each of "signed
       char" or "unsigned char", even though its behavior is always just
       like one of those two.

   -fsigned-char
       Let the type "char" be signed, like "signed char".

       Note that this is equivalent to -fno-unsigned-char, which is the
       negative form of -funsigned-char.  Likewise, the option
       -fno-signed-char is equivalent to -funsigned-char.

   -fsigned-bitfields
   -funsigned-bitfields
   -fno-signed-bitfields
   -fno-unsigned-bitfields
       These options control whether a bit-field is signed or unsigned,
       when the declaration does not use either "signed" or "unsigned".
       By default, such a bit-field is signed, because this is consistent:
       the basic integer types such as "int" are signed types.

   -fsso-struct=endianness
       Set the default scalar storage order of structures and unions to
       the specified endianness.  The accepted values are big-endian and
       little-endian.  If the option is not passed, the compiler uses the
       native endianness of the target.  This option is not supported for
       C++.

       Warning: the -fsso-struct switch causes GCC to generate code that
       is not binary compatible with code generated without it if the
       specified endianness is not the native endianness of the target.

   Options Controlling C++ Dialect
   This section describes the command-line options that are only
   meaningful for C++ programs.  You can also use most of the GNU compiler
   options regardless of what language your program is in.  For example,
   you might compile a file firstClass.C like this:

           g++ -g -fstrict-enums -O -c firstClass.C

   In this example, only -fstrict-enums is an option meant only for C++
   programs; you can use the other options with any language supported by
   GCC.

   Some options for compiling C programs, such as -std, are also relevant
   for C++ programs.

   Here is a list of options that are only for compiling C++ programs:

   -fabi-version=n
       Use version n of the C++ ABI.  The default is version 0.

       Version 0 refers to the version conforming most closely to the C++
       ABI specification.  Therefore, the ABI obtained using version 0
       will change in different versions of G++ as ABI bugs are fixed.

       Version 1 is the version of the C++ ABI that first appeared in G++
       3.2.

       Version 2 is the version of the C++ ABI that first appeared in G++
       3.4, and was the default through G++ 4.9.

       Version 3 corrects an error in mangling a constant address as a
       template argument.

       Version 4, which first appeared in G++ 4.5, implements a standard
       mangling for vector types.

       Version 5, which first appeared in G++ 4.6, corrects the mangling
       of attribute const/volatile on function pointer types, decltype of
       a plain decl, and use of a function parameter in the declaration of
       another parameter.

       Version 6, which first appeared in G++ 4.7, corrects the promotion
       behavior of C++11 scoped enums and the mangling of template
       argument packs, const/static_cast, prefix ++ and --, and a class
       scope function used as a template argument.

       Version 7, which first appeared in G++ 4.8, that treats nullptr_t
       as a builtin type and corrects the mangling of lambdas in default
       argument scope.

       Version 8, which first appeared in G++ 4.9, corrects the
       substitution behavior of function types with function-cv-
       qualifiers.

       Version 9, which first appeared in G++ 5.2, corrects the alignment
       of "nullptr_t".

       Version 10, which first appeared in G++ 6.1, adds mangling of
       attributes that affect type identity, such as ia32 calling
       convention attributes (e.g. stdcall).

       See also -Wabi.

   -fabi-compat-version=n
       On targets that support strong aliases, G++ works around mangling
       changes by creating an alias with the correct mangled name when
       defining a symbol with an incorrect mangled name.  This switch
       specifies which ABI version to use for the alias.

       With -fabi-version=0 (the default), this defaults to 8 (GCC 5
       compatibility).  If another ABI version is explicitly selected,
       this defaults to 0.  For compatibility with GCC versions 3.2
       through 4.9, use -fabi-compat-version=2.

       If this option is not provided but -Wabi=n is, that version is used
       for compatibility aliases.  If this option is provided along with
       -Wabi (without the version), the version from this option is used
       for the warning.

   -fno-access-control
       Turn off all access checking.  This switch is mainly useful for
       working around bugs in the access control code.

   -fcheck-new
       Check that the pointer returned by "operator new" is non-null
       before attempting to modify the storage allocated.  This check is
       normally unnecessary because the C++ standard specifies that
       "operator new" only returns 0 if it is declared "throw()", in which
       case the compiler always checks the return value even without this
       option.  In all other cases, when "operator new" has a non-empty
       exception specification, memory exhaustion is signalled by throwing
       "std::bad_alloc".  See also new (nothrow).

   -fconcepts
       Enable support for the C++ Extensions for Concepts Technical
       Specification, ISO 19217 (2015), which allows code like

               template <class T> concept bool Addable = requires (T t) { t + t; };
               template <Addable T> T add (T a, T b) { return a + b; }

   -fconstexpr-depth=n
       Set the maximum nested evaluation depth for C++11 constexpr
       functions to n.  A limit is needed to detect endless recursion
       during constant expression evaluation.  The minimum specified by
       the standard is 512.

   -fdeduce-init-list
       Enable deduction of a template type parameter as
       "std::initializer_list" from a brace-enclosed initializer list,
       i.e.

               template <class T> auto forward(T t) -> decltype (realfn (t))
               {
                 return realfn (t);
               }

               void f()
               {
                 forward({1,2}); // call forward<std::initializer_list<int>>
               }

       This deduction was implemented as a possible extension to the
       originally proposed semantics for the C++11 standard, but was not
       part of the final standard, so it is disabled by default.  This
       option is deprecated, and may be removed in a future version of
       G++.

   -ffriend-injection
       Inject friend functions into the enclosing namespace, so that they
       are visible outside the scope of the class in which they are
       declared.  Friend functions were documented to work this way in the
       old Annotated C++ Reference Manual.  However, in ISO C++ a friend
       function that is not declared in an enclosing scope can only be
       found using argument dependent lookup.  GCC defaults to the
       standard behavior.

       This option is for compatibility, and may be removed in a future
       release of G++.

   -fno-elide-constructors
       The C++ standard allows an implementation to omit creating a
       temporary that is only used to initialize another object of the
       same type.  Specifying this option disables that optimization, and
       forces G++ to call the copy constructor in all cases.

   -fno-enforce-eh-specs
       Don't generate code to check for violation of exception
       specifications at run time.  This option violates the C++ standard,
       but may be useful for reducing code size in production builds, much
       like defining "NDEBUG".  This does not give user code permission to
       throw exceptions in violation of the exception specifications; the
       compiler still optimizes based on the specifications, so throwing
       an unexpected exception results in undefined behavior at run time.

   -fextern-tls-init
   -fno-extern-tls-init
       The C++11 and OpenMP standards allow "thread_local" and
       "threadprivate" variables to have dynamic (runtime) initialization.
       To support this, any use of such a variable goes through a wrapper
       function that performs any necessary initialization.  When the use
       and definition of the variable are in the same translation unit,
       this overhead can be optimized away, but when the use is in a
       different translation unit there is significant overhead even if
       the variable doesn't actually need dynamic initialization.  If the
       programmer can be sure that no use of the variable in a non-
       defining TU needs to trigger dynamic initialization (either because
       the variable is statically initialized, or a use of the variable in
       the defining TU will be executed before any uses in another TU),
       they can avoid this overhead with the -fno-extern-tls-init option.

       On targets that support symbol aliases, the default is
       -fextern-tls-init.  On targets that do not support symbol aliases,
       the default is -fno-extern-tls-init.

   -ffor-scope
   -fno-for-scope
       If -ffor-scope is specified, the scope of variables declared in a
       for-init-statement is limited to the "for" loop itself, as
       specified by the C++ standard.  If -fno-for-scope is specified, the
       scope of variables declared in a for-init-statement extends to the
       end of the enclosing scope, as was the case in old versions of G++,
       and other (traditional) implementations of C++.

       If neither flag is given, the default is to follow the standard,
       but to allow and give a warning for old-style code that would
       otherwise be invalid, or have different behavior.

   -fno-gnu-keywords
       Do not recognize "typeof" as a keyword, so that code can use this
       word as an identifier.  You can use the keyword "__typeof__"
       instead.  This option is implied by the strict ISO C++ dialects:
       -ansi, -std=c++98, -std=c++11, etc.

   -fno-implicit-templates
       Never emit code for non-inline templates that are instantiated
       implicitly (i.e. by use); only emit code for explicit
       instantiations.

   -fno-implicit-inline-templates
       Don't emit code for implicit instantiations of inline templates,
       either.  The default is to handle inlines differently so that
       compiles with and without optimization need the same set of
       explicit instantiations.

   -fno-implement-inlines
       To save space, do not emit out-of-line copies of inline functions
       controlled by "#pragma implementation".  This causes linker errors
       if these functions are not inlined everywhere they are called.

   -fms-extensions
       Disable Wpedantic warnings about constructs used in MFC, such as
       implicit int and getting a pointer to member function via non-
       standard syntax.

   -fno-nonansi-builtins
       Disable built-in declarations of functions that are not mandated by
       ANSI/ISO C.  These include "ffs", "alloca", "_exit", "index",
       "bzero", "conjf", and other related functions.

   -fnothrow-opt
       Treat a "throw()" exception specification as if it were a
       "noexcept" specification to reduce or eliminate the text size
       overhead relative to a function with no exception specification.
       If the function has local variables of types with non-trivial
       destructors, the exception specification actually makes the
       function smaller because the EH cleanups for those variables can be
       optimized away.  The semantic effect is that an exception thrown
       out of a function with such an exception specification results in a
       call to "terminate" rather than "unexpected".

   -fno-operator-names
       Do not treat the operator name keywords "and", "bitand", "bitor",
       "compl", "not", "or" and "xor" as synonyms as keywords.

   -fno-optional-diags
       Disable diagnostics that the standard says a compiler does not need
       to issue.  Currently, the only such diagnostic issued by G++ is the
       one for a name having multiple meanings within a class.

   -fpermissive
       Downgrade some diagnostics about nonconformant code from errors to
       warnings.  Thus, using -fpermissive allows some nonconforming code
       to compile.

   -fno-pretty-templates
       When an error message refers to a specialization of a function
       template, the compiler normally prints the signature of the
       template followed by the template arguments and any typedefs or
       typenames in the signature (e.g. "void f(T) [with T = int]" rather
       than "void f(int)") so that it's clear which template is involved.
       When an error message refers to a specialization of a class
       template, the compiler omits any template arguments that match the
       default template arguments for that template.  If either of these
       behaviors make it harder to understand the error message rather
       than easier, you can use -fno-pretty-templates to disable them.

   -frepo
       Enable automatic template instantiation at link time.  This option
       also implies -fno-implicit-templates.

   -fno-rtti
       Disable generation of information about every class with virtual
       functions for use by the C++ run-time type identification features
       ("dynamic_cast" and "typeid").  If you don't use those parts of the
       language, you can save some space by using this flag.  Note that
       exception handling uses the same information, but G++ generates it
       as needed. The "dynamic_cast" operator can still be used for casts
       that do not require run-time type information, i.e. casts to "void
       *" or to unambiguous base classes.

   -fsized-deallocation
       Enable the built-in global declarations

               void operator delete (void *, std::size_t) noexcept;
               void operator delete[] (void *, std::size_t) noexcept;

       as introduced in C++14.  This is useful for user-defined
       replacement deallocation functions that, for example, use the size
       of the object to make deallocation faster.  Enabled by default
       under -std=c++14 and above.  The flag -Wsized-deallocation warns
       about places that might want to add a definition.

   -fstrict-enums
       Allow the compiler to optimize using the assumption that a value of
       enumerated type can only be one of the values of the enumeration
       (as defined in the C++ standard; basically, a value that can be
       represented in the minimum number of bits needed to represent all
       the enumerators).  This assumption may not be valid if the program
       uses a cast to convert an arbitrary integer value to the enumerated
       type.

   -ftemplate-backtrace-limit=n
       Set the maximum number of template instantiation notes for a single
       warning or error to n.  The default value is 10.

   -ftemplate-depth=n
       Set the maximum instantiation depth for template classes to n.  A
       limit on the template instantiation depth is needed to detect
       endless recursions during template class instantiation.  ANSI/ISO
       C++ conforming programs must not rely on a maximum depth greater
       than 17 (changed to 1024 in C++11).  The default value is 900, as
       the compiler can run out of stack space before hitting 1024 in some
       situations.

   -fno-threadsafe-statics
       Do not emit the extra code to use the routines specified in the C++
       ABI for thread-safe initialization of local statics.  You can use
       this option to reduce code size slightly in code that doesn't need
       to be thread-safe.

   -fuse-cxa-atexit
       Register destructors for objects with static storage duration with
       the "__cxa_atexit" function rather than the "atexit" function.
       This option is required for fully standards-compliant handling of
       static destructors, but only works if your C library supports
       "__cxa_atexit".

   -fno-use-cxa-get-exception-ptr
       Don't use the "__cxa_get_exception_ptr" runtime routine.  This
       causes "std::uncaught_exception" to be incorrect, but is necessary
       if the runtime routine is not available.

   -fvisibility-inlines-hidden
       This switch declares that the user does not attempt to compare
       pointers to inline functions or methods where the addresses of the
       two functions are taken in different shared objects.

       The effect of this is that GCC may, effectively, mark inline
       methods with "__attribute__ ((visibility ("hidden")))" so that they
       do not appear in the export table of a DSO and do not require a PLT
       indirection when used within the DSO.  Enabling this option can
       have a dramatic effect on load and link times of a DSO as it
       massively reduces the size of the dynamic export table when the
       library makes heavy use of templates.

       The behavior of this switch is not quite the same as marking the
       methods as hidden directly, because it does not affect static
       variables local to the function or cause the compiler to deduce
       that the function is defined in only one shared object.

       You may mark a method as having a visibility explicitly to negate
       the effect of the switch for that method.  For example, if you do
       want to compare pointers to a particular inline method, you might
       mark it as having default visibility.  Marking the enclosing class
       with explicit visibility has no effect.

       Explicitly instantiated inline methods are unaffected by this
       option as their linkage might otherwise cross a shared library
       boundary.

   -fvisibility-ms-compat
       This flag attempts to use visibility settings to make GCC's C++
       linkage model compatible with that of Microsoft Visual Studio.

       The flag makes these changes to GCC's linkage model:

       1.  It sets the default visibility to "hidden", like
           -fvisibility=hidden.

       2.  Types, but not their members, are not hidden by default.

       3.  The One Definition Rule is relaxed for types without explicit
           visibility specifications that are defined in more than one
           shared object: those declarations are permitted if they are
           permitted when this option is not used.

       In new code it is better to use -fvisibility=hidden and export
       those classes that are intended to be externally visible.
       Unfortunately it is possible for code to rely, perhaps
       accidentally, on the Visual Studio behavior.

       Among the consequences of these changes are that static data
       members of the same type with the same name but defined in
       different shared objects are different, so changing one does not
       change the other; and that pointers to function members defined in
       different shared objects may not compare equal.  When this flag is
       given, it is a violation of the ODR to define types with the same
       name differently.

   -fno-weak
       Do not use weak symbol support, even if it is provided by the
       linker.  By default, G++ uses weak symbols if they are available.
       This option exists only for testing, and should not be used by end-
       users; it results in inferior code and has no benefits.  This
       option may be removed in a future release of G++.

   -nostdinc++
       Do not search for header files in the standard directories specific
       to C++, but do still search the other standard directories.  (This
       option is used when building the C++ library.)

   In addition, these optimization, warning, and code generation options
   have meanings only for C++ programs:

   -Wabi (C, Objective-C, C++ and Objective-C++ only)
       Warn when G++ it generates code that is probably not compatible
       with the vendor-neutral C++ ABI.  Since G++ now defaults to
       updating the ABI with each major release, normally -Wabi will warn
       only if there is a check added later in a release series for an ABI
       issue discovered since the initial release.  -Wabi will warn about
       more things if an older ABI version is selected (with
       -fabi-version=n).

       -Wabi can also be used with an explicit version number to warn
       about compatibility with a particular -fabi-version level, e.g.
       -Wabi=2 to warn about changes relative to -fabi-version=2.

       If an explicit version number is provided and -fabi-compat-version
       is not specified, the version number from this option is used for
       compatibility aliases.  If no explicit version number is provided
       with this option, but -fabi-compat-version is specified, that
       version number is used for ABI warnings.

       Although an effort has been made to warn about all such cases,
       there are probably some cases that are not warned about, even
       though G++ is generating incompatible code.  There may also be
       cases where warnings are emitted even though the code that is
       generated is compatible.

       You should rewrite your code to avoid these warnings if you are
       concerned about the fact that code generated by G++ may not be
       binary compatible with code generated by other compilers.

       Known incompatibilities in -fabi-version=2 (which was the default
       from GCC 3.4 to 4.9) include:

       *   A template with a non-type template parameter of reference type
           was mangled incorrectly:

                   extern int N;
                   template <int &> struct S {};
                   void n (S<N>) {2}

           This was fixed in -fabi-version=3.

       *   SIMD vector types declared using "__attribute ((vector_size))"
           were mangled in a non-standard way that does not allow for
           overloading of functions taking vectors of different sizes.

           The mangling was changed in -fabi-version=4.

       *   "__attribute ((const))" and "noreturn" were mangled as type
           qualifiers, and "decltype" of a plain declaration was folded
           away.

           These mangling issues were fixed in -fabi-version=5.

       *   Scoped enumerators passed as arguments to a variadic function
           are promoted like unscoped enumerators, causing "va_arg" to
           complain.  On most targets this does not actually affect the
           parameter passing ABI, as there is no way to pass an argument
           smaller than "int".

           Also, the ABI changed the mangling of template argument packs,
           "const_cast", "static_cast", prefix increment/decrement, and a
           class scope function used as a template argument.

           These issues were corrected in -fabi-version=6.

       *   Lambdas in default argument scope were mangled incorrectly, and
           the ABI changed the mangling of "nullptr_t".

           These issues were corrected in -fabi-version=7.

       *   When mangling a function type with function-cv-qualifiers, the
           un-qualified function type was incorrectly treated as a
           substitution candidate.

           This was fixed in -fabi-version=8, the default for GCC 5.1.

       *   "decltype(nullptr)" incorrectly had an alignment of 1, leading
           to unaligned accesses.  Note that this did not affect the ABI
           of a function with a "nullptr_t" parameter, as parameters have
           a minimum alignment.

           This was fixed in -fabi-version=9, the default for GCC 5.2.

       *   Target-specific attributes that affect the identity of a type,
           such as ia32 calling conventions on a function type (stdcall,
           regparm, etc.), did not affect the mangled name, leading to
           name collisions when function pointers were used as template
           arguments.

           This was fixed in -fabi-version=10, the default for GCC 6.1.

       It also warns about psABI-related changes.  The known psABI changes
       at this point include:

       *   For SysV/x86-64, unions with "long double" members are passed
           in memory as specified in psABI.  For example:

                   union U {
                     long double ld;
                     int i;
                   };

           "union U" is always passed in memory.

   -Wabi-tag (C++ and Objective-C++ only)
       Warn when a type with an ABI tag is used in a context that does not
       have that ABI tag.  See C++ Attributes for more information about
       ABI tags.

   -Wctor-dtor-privacy (C++ and Objective-C++ only)
       Warn when a class seems unusable because all the constructors or
       destructors in that class are private, and it has neither friends
       nor public static member functions.  Also warn if there are no non-
       private methods, and there's at least one private member function
       that isn't a constructor or destructor.

   -Wdelete-non-virtual-dtor (C++ and Objective-C++ only)
       Warn when "delete" is used to destroy an instance of a class that
       has virtual functions and non-virtual destructor. It is unsafe to
       delete an instance of a derived class through a pointer to a base
       class if the base class does not have a virtual destructor.  This
       warning is enabled by -Wall.

   -Wliteral-suffix (C++ and Objective-C++ only)
       Warn when a string or character literal is followed by a ud-suffix
       which does not begin with an underscore.  As a conforming
       extension, GCC treats such suffixes as separate preprocessing
       tokens in order to maintain backwards compatibility with code that
       uses formatting macros from "<inttypes.h>".  For example:

               #define __STDC_FORMAT_MACROS
               #include <inttypes.h>
               #include <stdio.h>

               int main() {
                 int64_t i64 = 123;
                 printf("My int64: %" PRId64"\n", i64);
               }

       In this case, "PRId64" is treated as a separate preprocessing
       token.

       This warning is enabled by default.

   -Wlto-type-mismatch
       During the link-time optimization warn about type mismatches in
       global declarations from different compilation units.  Requires
       -flto to be enabled.  Enabled by default.

   -Wnarrowing (C++ and Objective-C++ only)
       With -std=gnu++98 or -std=c++98, warn when a narrowing conversion
       prohibited by C++11 occurs within { }, e.g.

               int i = { 2.2 }; // error: narrowing from double to int

       This flag is included in -Wall and -Wc++11-compat.

       When a later standard is in effect, e.g. when using -std=c++11,
       narrowing conversions are diagnosed by default, as required by the
       standard.  A narrowing conversion from a constant produces an
       error, and a narrowing conversion from a non-constant produces a
       warning, but -Wno-narrowing suppresses the diagnostic.  Note that
       this does not affect the meaning of well-formed code; narrowing
       conversions are still considered ill-formed in SFINAE contexts.

   -Wnoexcept (C++ and Objective-C++ only)
       Warn when a noexcept-expression evaluates to false because of a
       call to a function that does not have a non-throwing exception
       specification (i.e. "throw()" or "noexcept") but is known by the
       compiler to never throw an exception.

   -Wnon-virtual-dtor (C++ and Objective-C++ only)
       Warn when a class has virtual functions and an accessible non-
       virtual destructor itself or in an accessible polymorphic base
       class, in which case it is possible but unsafe to delete an
       instance of a derived class through a pointer to the class itself
       or base class.  This warning is automatically enabled if -Weffc++
       is specified.

   -Wreorder (C++ and Objective-C++ only)
       Warn when the order of member initializers given in the code does
       not match the order in which they must be executed.  For instance:

               struct A {
                 int i;
                 int j;
                 A(): j (0), i (1) { }
               };

       The compiler rearranges the member initializers for "i" and "j" to
       match the declaration order of the members, emitting a warning to
       that effect.  This warning is enabled by -Wall.

   -fext-numeric-literals (C++ and Objective-C++ only)
       Accept imaginary, fixed-point, or machine-defined literal number
       suffixes as GNU extensions.  When this option is turned off these
       suffixes are treated as C++11 user-defined literal numeric
       suffixes.  This is on by default for all pre-C++11 dialects and all
       GNU dialects: -std=c++98, -std=gnu++98, -std=gnu++11, -std=gnu++14.
       This option is off by default for ISO C++11 onwards (-std=c++11,
       ...).

   The following -W... options are not affected by -Wall.

   -Weffc++ (C++ and Objective-C++ only)
       Warn about violations of the following style guidelines from Scott
       Meyers' Effective C++ series of books:

       *   Define a copy constructor and an assignment operator for
           classes with dynamically-allocated memory.

       *   Prefer initialization to assignment in constructors.

       *   Have "operator=" return a reference to *this.

       *   Don't try to return a reference when you must return an object.

       *   Distinguish between prefix and postfix forms of increment and
           decrement operators.

       *   Never overload "&&", "||", or ",".

       This option also enables -Wnon-virtual-dtor, which is also one of
       the effective C++ recommendations.  However, the check is extended
       to warn about the lack of virtual destructor in accessible non-
       polymorphic bases classes too.

       When selecting this option, be aware that the standard library
       headers do not obey all of these guidelines; use grep -v to filter
       out those warnings.

   -Wstrict-null-sentinel (C++ and Objective-C++ only)
       Warn about the use of an uncasted "NULL" as sentinel.  When
       compiling only with GCC this is a valid sentinel, as "NULL" is
       defined to "__null".  Although it is a null pointer constant rather
       than a null pointer, it is guaranteed to be of the same size as a
       pointer.  But this use is not portable across different compilers.

   -Wno-non-template-friend (C++ and Objective-C++ only)
       Disable warnings when non-templatized friend functions are declared
       within a template.  Since the advent of explicit template
       specification support in G++, if the name of the friend is an
       unqualified-id (i.e., friend foo(int)), the C++ language
       specification demands that the friend declare or define an
       ordinary, nontemplate function.  (Section 14.5.3).  Before G++
       implemented explicit specification, unqualified-ids could be
       interpreted as a particular specialization of a templatized
       function.  Because this non-conforming behavior is no longer the
       default behavior for G++, -Wnon-template-friend allows the compiler
       to check existing code for potential trouble spots and is on by
       default.  This new compiler behavior can be turned off with
       -Wno-non-template-friend, which keeps the conformant compiler code
       but disables the helpful warning.

   -Wold-style-cast (C++ and Objective-C++ only)
       Warn if an old-style (C-style) cast to a non-void type is used
       within a C++ program.  The new-style casts ("dynamic_cast",
       "static_cast", "reinterpret_cast", and "const_cast") are less
       vulnerable to unintended effects and much easier to search for.

   -Woverloaded-virtual (C++ and Objective-C++ only)
       Warn when a function declaration hides virtual functions from a
       base class.  For example, in:

               struct A {
                 virtual void f();
               };

               struct B: public A {
                 void f(int);
               };

       the "A" class version of "f" is hidden in "B", and code like:

               B* b;
               b->f();

       fails to compile.

   -Wno-pmf-conversions (C++ and Objective-C++ only)
       Disable the diagnostic for converting a bound pointer to member
       function to a plain pointer.

   -Wsign-promo (C++ and Objective-C++ only)
       Warn when overload resolution chooses a promotion from unsigned or
       enumerated type to a signed type, over a conversion to an unsigned
       type of the same size.  Previous versions of G++ tried to preserve
       unsignedness, but the standard mandates the current behavior.

   -Wtemplates (C++ and Objective-C++ only)
       Warn when a primary template declaration is encountered.  Some
       coding rules disallow templates, and this may be used to enforce
       that rule.  The warning is inactive inside a system header file,
       such as the STL, so one can still use the STL.  One may also
       instantiate or specialize templates.

   -Wmultiple-inheritance (C++ and Objective-C++ only)
       Warn when a class is defined with multiple direct base classes.
       Some coding rules disallow multiple inheritance, and this may be
       used to enforce that rule.  The warning is inactive inside a system
       header file, such as the STL, so one can still use the STL.  One
       may also define classes that indirectly use multiple inheritance.

   -Wvirtual-inheritance
       Warn when a class is defined with a virtual direct base classe.
       Some coding rules disallow multiple inheritance, and this may be
       used to enforce that rule.  The warning is inactive inside a system
       header file, such as the STL, so one can still use the STL.  One
       may also define classes that indirectly use virtual inheritance.

   -Wnamespaces
       Warn when a namespace definition is opened.  Some coding rules
       disallow namespaces, and this may be used to enforce that rule.
       The warning is inactive inside a system header file, such as the
       STL, so one can still use the STL.  One may also use using
       directives and qualified names.

   -Wno-terminate (C++ and Objective-C++ only)
       Disable the warning about a throw-expression that will immediately
       result in a call to "terminate".

   Options Controlling Objective-C and Objective-C++ Dialects
   (NOTE: This manual does not describe the Objective-C and Objective-C++
   languages themselves.

   This section describes the command-line options that are only
   meaningful for Objective-C and Objective-C++ programs.  You can also
   use most of the language-independent GNU compiler options.  For
   example, you might compile a file some_class.m like this:

           gcc -g -fgnu-runtime -O -c some_class.m

   In this example, -fgnu-runtime is an option meant only for Objective-C
   and Objective-C++ programs; you can use the other options with any
   language supported by GCC.

   Note that since Objective-C is an extension of the C language,
   Objective-C compilations may also use options specific to the C front-
   end (e.g., -Wtraditional).  Similarly, Objective-C++ compilations may
   use C++-specific options (e.g., -Wabi).

   Here is a list of options that are only for compiling Objective-C and
   Objective-C++ programs:

   -fconstant-string-class=class-name
       Use class-name as the name of the class to instantiate for each
       literal string specified with the syntax "@"..."".  The default
       class name is "NXConstantString" if the GNU runtime is being used,
       and "NSConstantString" if the NeXT runtime is being used (see
       below).  The -fconstant-cfstrings option, if also present,
       overrides the -fconstant-string-class setting and cause "@"...""
       literals to be laid out as constant CoreFoundation strings.

   -fgnu-runtime
       Generate object code compatible with the standard GNU Objective-C
       runtime.  This is the default for most types of systems.

   -fnext-runtime
       Generate output compatible with the NeXT runtime.  This is the
       default for NeXT-based systems, including Darwin and Mac OS X.  The
       macro "__NEXT_RUNTIME__" is predefined if (and only if) this option
       is used.

   -fno-nil-receivers
       Assume that all Objective-C message dispatches ("[receiver
       message:arg]") in this translation unit ensure that the receiver is
       not "nil".  This allows for more efficient entry points in the
       runtime to be used.  This option is only available in conjunction
       with the NeXT runtime and ABI version 0 or 1.

   -fobjc-abi-version=n
       Use version n of the Objective-C ABI for the selected runtime.
       This option is currently supported only for the NeXT runtime.  In
       that case, Version 0 is the traditional (32-bit) ABI without
       support for properties and other Objective-C 2.0 additions.
       Version 1 is the traditional (32-bit) ABI with support for
       properties and other Objective-C 2.0 additions.  Version 2 is the
       modern (64-bit) ABI.  If nothing is specified, the default is
       Version 0 on 32-bit target machines, and Version 2 on 64-bit target
       machines.

   -fobjc-call-cxx-cdtors
       For each Objective-C class, check if any of its instance variables
       is a C++ object with a non-trivial default constructor.  If so,
       synthesize a special "- (id) .cxx_construct" instance method which
       runs non-trivial default constructors on any such instance
       variables, in order, and then return "self".  Similarly, check if
       any instance variable is a C++ object with a non-trivial
       destructor, and if so, synthesize a special "- (void)
       .cxx_destruct" method which runs all such default destructors, in
       reverse order.

       The "- (id) .cxx_construct" and "- (void) .cxx_destruct" methods
       thusly generated only operate on instance variables declared in the
       current Objective-C class, and not those inherited from
       superclasses.  It is the responsibility of the Objective-C runtime
       to invoke all such methods in an object's inheritance hierarchy.
       The "- (id) .cxx_construct" methods are invoked by the runtime
       immediately after a new object instance is allocated; the "- (void)
       .cxx_destruct" methods are invoked immediately before the runtime
       deallocates an object instance.

       As of this writing, only the NeXT runtime on Mac OS X 10.4 and
       later has support for invoking the "- (id) .cxx_construct" and "-
       (void) .cxx_destruct" methods.

   -fobjc-direct-dispatch
       Allow fast jumps to the message dispatcher.  On Darwin this is
       accomplished via the comm page.

   -fobjc-exceptions
       Enable syntactic support for structured exception handling in
       Objective-C, similar to what is offered by C++ and Java.  This
       option is required to use the Objective-C keywords @try, @throw,
       @catch, @finally and @synchronized.  This option is available with
       both the GNU runtime and the NeXT runtime (but not available in
       conjunction with the NeXT runtime on Mac OS X 10.2 and earlier).

   -fobjc-gc
       Enable garbage collection (GC) in Objective-C and Objective-C++
       programs.  This option is only available with the NeXT runtime; the
       GNU runtime has a different garbage collection implementation that
       does not require special compiler flags.

   -fobjc-nilcheck
       For the NeXT runtime with version 2 of the ABI, check for a nil
       receiver in method invocations before doing the actual method call.
       This is the default and can be disabled using -fno-objc-nilcheck.
       Class methods and super calls are never checked for nil in this way
       no matter what this flag is set to.  Currently this flag does
       nothing when the GNU runtime, or an older version of the NeXT
       runtime ABI, is used.

   -fobjc-std=objc1
       Conform to the language syntax of Objective-C 1.0, the language
       recognized by GCC 4.0.  This only affects the Objective-C additions
       to the C/C++ language; it does not affect conformance to C/C++
       standards, which is controlled by the separate C/C++ dialect option
       flags.  When this option is used with the Objective-C or
       Objective-C++ compiler, any Objective-C syntax that is not
       recognized by GCC 4.0 is rejected.  This is useful if you need to
       make sure that your Objective-C code can be compiled with older
       versions of GCC.

   -freplace-objc-classes
       Emit a special marker instructing ld(1) not to statically link in
       the resulting object file, and allow dyld(1) to load it in at run
       time instead.  This is used in conjunction with the Fix-and-
       Continue debugging mode, where the object file in question may be
       recompiled and dynamically reloaded in the course of program
       execution, without the need to restart the program itself.
       Currently, Fix-and-Continue functionality is only available in
       conjunction with the NeXT runtime on Mac OS X 10.3 and later.

   -fzero-link
       When compiling for the NeXT runtime, the compiler ordinarily
       replaces calls to "objc_getClass("...")" (when the name of the
       class is known at compile time) with static class references that
       get initialized at load time, which improves run-time performance.
       Specifying the -fzero-link flag suppresses this behavior and causes
       calls to "objc_getClass("...")"  to be retained.  This is useful in
       Zero-Link debugging mode, since it allows for individual class
       implementations to be modified during program execution.  The GNU
       runtime currently always retains calls to "objc_get_class("...")"
       regardless of command-line options.

   -fno-local-ivars
       By default instance variables in Objective-C can be accessed as if
       they were local variables from within the methods of the class
       they're declared in.  This can lead to shadowing between instance
       variables and other variables declared either locally inside a
       class method or globally with the same name.  Specifying the
       -fno-local-ivars flag disables this behavior thus avoiding variable
       shadowing issues.

   -fivar-visibility=[public|protected|private|package]
       Set the default instance variable visibility to the specified
       option so that instance variables declared outside the scope of any
       access modifier directives default to the specified visibility.

   -gen-decls
       Dump interface declarations for all classes seen in the source file
       to a file named sourcename.decl.

   -Wassign-intercept (Objective-C and Objective-C++ only)
       Warn whenever an Objective-C assignment is being intercepted by the
       garbage collector.

   -Wno-protocol (Objective-C and Objective-C++ only)
       If a class is declared to implement a protocol, a warning is issued
       for every method in the protocol that is not implemented by the
       class.  The default behavior is to issue a warning for every method
       not explicitly implemented in the class, even if a method
       implementation is inherited from the superclass.  If you use the
       -Wno-protocol option, then methods inherited from the superclass
       are considered to be implemented, and no warning is issued for
       them.

   -Wselector (Objective-C and Objective-C++ only)
       Warn if multiple methods of different types for the same selector
       are found during compilation.  The check is performed on the list
       of methods in the final stage of compilation.  Additionally, a
       check is performed for each selector appearing in a
       "@selector(...)"  expression, and a corresponding method for that
       selector has been found during compilation.  Because these checks
       scan the method table only at the end of compilation, these
       warnings are not produced if the final stage of compilation is not
       reached, for example because an error is found during compilation,
       or because the -fsyntax-only option is being used.

   -Wstrict-selector-match (Objective-C and Objective-C++ only)
       Warn if multiple methods with differing argument and/or return
       types are found for a given selector when attempting to send a
       message using this selector to a receiver of type "id" or "Class".
       When this flag is off (which is the default behavior), the compiler
       omits such warnings if any differences found are confined to types
       that share the same size and alignment.

   -Wundeclared-selector (Objective-C and Objective-C++ only)
       Warn if a "@selector(...)" expression referring to an undeclared
       selector is found.  A selector is considered undeclared if no
       method with that name has been declared before the "@selector(...)"
       expression, either explicitly in an @interface or @protocol
       declaration, or implicitly in an @implementation section.  This
       option always performs its checks as soon as a "@selector(...)"
       expression is found, while -Wselector only performs its checks in
       the final stage of compilation.  This also enforces the coding
       style convention that methods and selectors must be declared before
       being used.

   -print-objc-runtime-info
       Generate C header describing the largest structure that is passed
       by value, if any.

   Options to Control Diagnostic Messages Formatting
   Traditionally, diagnostic messages have been formatted irrespective of
   the output device's aspect (e.g. its width, ...).  You can use the
   options described below to control the formatting algorithm for
   diagnostic messages, e.g. how many characters per line, how often
   source location information should be reported.  Note that some
   language front ends may not honor these options.

   -fmessage-length=n
       Try to format error messages so that they fit on lines of about n
       characters.  If n is zero, then no line-wrapping is done; each
       error message appears on a single line.  This is the default for
       all front ends.

   -fdiagnostics-show-location=once
       Only meaningful in line-wrapping mode.  Instructs the diagnostic
       messages reporter to emit source location information once; that
       is, in case the message is too long to fit on a single physical
       line and has to be wrapped, the source location won't be emitted
       (as prefix) again, over and over, in subsequent continuation lines.
       This is the default behavior.

   -fdiagnostics-show-location=every-line
       Only meaningful in line-wrapping mode.  Instructs the diagnostic
       messages reporter to emit the same source location information (as
       prefix) for physical lines that result from the process of breaking
       a message which is too long to fit on a single line.

   -fdiagnostics-color[=WHEN]
   -fno-diagnostics-color
       Use color in diagnostics.  WHEN is never, always, or auto.  The
       default depends on how the compiler has been configured, it can be
       any of the above WHEN options or also never if GCC_COLORS
       environment variable isn't present in the environment, and auto
       otherwise.  auto means to use color only when the standard error is
       a terminal.  The forms -fdiagnostics-color and
       -fno-diagnostics-color are aliases for -fdiagnostics-color=always
       and -fdiagnostics-color=never, respectively.

       The colors are defined by the environment variable GCC_COLORS.  Its
       value is a colon-separated list of capabilities and Select Graphic
       Rendition (SGR) substrings. SGR commands are interpreted by the
       terminal or terminal emulator.  (See the section in the
       documentation of your text terminal for permitted values and their
       meanings as character attributes.)  These substring values are
       integers in decimal representation and can be concatenated with
       semicolons.  Common values to concatenate include 1 for bold, 4 for
       underline, 5 for blink, 7 for inverse, 39 for default foreground
       color, 30 to 37 for foreground colors, 90 to 97 for 16-color mode
       foreground colors, 38;5;0 to 38;5;255 for 88-color and 256-color
       modes foreground colors, 49 for default background color, 40 to 47
       for background colors, 100 to 107 for 16-color mode background
       colors, and 48;5;0 to 48;5;255 for 88-color and 256-color modes
       background colors.

       The default GCC_COLORS is

               error=01;31:warning=01;35:note=01;36:caret=01;32:locus=01:quote=01

       where 01;31 is bold red, 01;35 is bold magenta, 01;36 is bold cyan,
       01;32 is bold green and 01 is bold. Setting GCC_COLORS to the empty
       string disables colors.  Supported capabilities are as follows.

       "error="
           SGR substring for error: markers.

       "warning="
           SGR substring for warning: markers.

       "note="
           SGR substring for note: markers.

       "caret="
           SGR substring for caret line.

       "locus="
           SGR substring for location information, file:line or
           file:line:column etc.

       "quote="
           SGR substring for information printed within quotes.

   -fno-diagnostics-show-option
       By default, each diagnostic emitted includes text indicating the
       command-line option that directly controls the diagnostic (if such
       an option is known to the diagnostic machinery).  Specifying the
       -fno-diagnostics-show-option flag suppresses that behavior.

   -fno-diagnostics-show-caret
       By default, each diagnostic emitted includes the original source
       line and a caret ^ indicating the column.  This option suppresses
       this information.  The source line is truncated to n characters, if
       the -fmessage-length=n option is given.  When the output is done to
       the terminal, the width is limited to the width given by the
       COLUMNS environment variable or, if not set, to the terminal width.

   Options to Request or Suppress Warnings
   Warnings are diagnostic messages that report constructions that are not
   inherently erroneous but that are risky or suggest there may have been
   an error.

   The following language-independent options do not enable specific
   warnings but control the kinds of diagnostics produced by GCC.

   -fsyntax-only
       Check the code for syntax errors, but don't do anything beyond
       that.

   -fmax-errors=n
       Limits the maximum number of error messages to n, at which point
       GCC bails out rather than attempting to continue processing the
       source code.  If n is 0 (the default), there is no limit on the
       number of error messages produced.  If -Wfatal-errors is also
       specified, then -Wfatal-errors takes precedence over this option.

   -w  Inhibit all warning messages.

   -Werror
       Make all warnings into errors.

   -Werror=
       Make the specified warning into an error.  The specifier for a
       warning is appended; for example -Werror=switch turns the warnings
       controlled by -Wswitch into errors.  This switch takes a negative
       form, to be used to negate -Werror for specific warnings; for
       example -Wno-error=switch makes -Wswitch warnings not be errors,
       even when -Werror is in effect.

       The warning message for each controllable warning includes the
       option that controls the warning.  That option can then be used
       with -Werror= and -Wno-error= as described above.  (Printing of the
       option in the warning message can be disabled using the
       -fno-diagnostics-show-option flag.)

       Note that specifying -Werror=foo automatically implies -Wfoo.
       However, -Wno-error=foo does not imply anything.

   -Wfatal-errors
       This option causes the compiler to abort compilation on the first
       error occurred rather than trying to keep going and printing
       further error messages.

   You can request many specific warnings with options beginning with -W,
   for example -Wimplicit to request warnings on implicit declarations.
   Each of these specific warning options also has a negative form
   beginning -Wno- to turn off warnings; for example, -Wno-implicit.  This
   manual lists only one of the two forms, whichever is not the default.
   For further language-specific options also refer to C++ Dialect Options
   and Objective-C and Objective-C++ Dialect Options.

   Some options, such as -Wall and -Wextra, turn on other options, such as
   -Wunused, which may turn on further options, such as -Wunused-value.
   The combined effect of positive and negative forms is that more
   specific options have priority over less specific ones, independently
   of their position in the command-line. For options of the same
   specificity, the last one takes effect. Options enabled or disabled via
   pragmas take effect as if they appeared at the end of the command-line.

   When an unrecognized warning option is requested (e.g.,
   -Wunknown-warning), GCC emits a diagnostic stating that the option is
   not recognized.  However, if the -Wno- form is used, the behavior is
   slightly different: no diagnostic is produced for -Wno-unknown-warning
   unless other diagnostics are being produced.  This allows the use of
   new -Wno- options with old compilers, but if something goes wrong, the
   compiler warns that an unrecognized option is present.

   -Wpedantic
   -pedantic
       Issue all the warnings demanded by strict ISO C and ISO C++; reject
       all programs that use forbidden extensions, and some other programs
       that do not follow ISO C and ISO C++.  For ISO C, follows the
       version of the ISO C standard specified by any -std option used.

       Valid ISO C and ISO C++ programs should compile properly with or
       without this option (though a rare few require -ansi or a -std
       option specifying the required version of ISO C).  However, without
       this option, certain GNU extensions and traditional C and C++
       features are supported as well.  With this option, they are
       rejected.

       -Wpedantic does not cause warning messages for use of the alternate
       keywords whose names begin and end with __.  Pedantic warnings are
       also disabled in the expression that follows "__extension__".
       However, only system header files should use these escape routes;
       application programs should avoid them.

       Some users try to use -Wpedantic to check programs for strict ISO C
       conformance.  They soon find that it does not do quite what they
       want: it finds some non-ISO practices, but not all---only those for
       which ISO C requires a diagnostic, and some others for which
       diagnostics have been added.

       A feature to report any failure to conform to ISO C might be useful
       in some instances, but would require considerable additional work
       and would be quite different from -Wpedantic.  We don't have plans
       to support such a feature in the near future.

       Where the standard specified with -std represents a GNU extended
       dialect of C, such as gnu90 or gnu99, there is a corresponding base
       standard, the version of ISO C on which the GNU extended dialect is
       based.  Warnings from -Wpedantic are given where they are required
       by the base standard.  (It does not make sense for such warnings to
       be given only for features not in the specified GNU C dialect,
       since by definition the GNU dialects of C include all features the
       compiler supports with the given option, and there would be nothing
       to warn about.)

   -pedantic-errors
       Give an error whenever the base standard (see -Wpedantic) requires
       a diagnostic, in some cases where there is undefined behavior at
       compile-time and in some other cases that do not prevent
       compilation of programs that are valid according to the standard.
       This is not equivalent to -Werror=pedantic, since there are errors
       enabled by this option and not enabled by the latter and vice
       versa.

   -Wall
       This enables all the warnings about constructions that some users
       consider questionable, and that are easy to avoid (or modify to
       prevent the warning), even in conjunction with macros.  This also
       enables some language-specific warnings described in C++ Dialect
       Options and Objective-C and Objective-C++ Dialect Options.

       -Wall turns on the following warning flags:

       -Waddress -Warray-bounds=1 (only with -O2) -Wbool-compare
       -Wc++11-compat  -Wc++14-compat -Wchar-subscripts -Wcomment
       -Wenum-compare (in C/ObjC; this is on by default in C++) -Wformat
       -Wimplicit (C and Objective-C only) -Wimplicit-int (C and
       Objective-C only) -Wimplicit-function-declaration (C and Objective-
       C only) -Winit-self (only for C++) -Wlogical-not-parentheses -Wmain
       (only for C/ObjC and unless -ffreestanding) -Wmaybe-uninitialized
       -Wmemset-transposed-args -Wmisleading-indentation (only for C/C++)
       -Wmissing-braces (only for C/ObjC) -Wnarrowing (only for C++)
       -Wnonnull -Wnonnull-compare -Wopenmp-simd -Wparentheses
       -Wpointer-sign -Wreorder -Wreturn-type -Wsequence-point
       -Wsign-compare (only in C++) -Wsizeof-pointer-memaccess
       -Wstrict-aliasing -Wstrict-overflow=1 -Wswitch
       -Wtautological-compare -Wtrigraphs -Wuninitialized
       -Wunknown-pragmas -Wunused-function -Wunused-label -Wunused-value
       -Wunused-variable -Wvolatile-register-var

       Note that some warning flags are not implied by -Wall.  Some of
       them warn about constructions that users generally do not consider
       questionable, but which occasionally you might wish to check for;
       others warn about constructions that are necessary or hard to avoid
       in some cases, and there is no simple way to modify the code to
       suppress the warning. Some of them are enabled by -Wextra but many
       of them must be enabled individually.

   -Wextra
       This enables some extra warning flags that are not enabled by
       -Wall. (This option used to be called -W.  The older name is still
       supported, but the newer name is more descriptive.)

       -Wclobbered -Wempty-body -Wignored-qualifiers
       -Wmissing-field-initializers -Wmissing-parameter-type (C only)
       -Wold-style-declaration (C only) -Woverride-init -Wsign-compare (C
       only) -Wtype-limits -Wuninitialized -Wshift-negative-value (in
       C++03 and in C99 and newer) -Wunused-parameter (only with -Wunused
       or -Wall) -Wunused-but-set-parameter (only with -Wunused or -Wall)

       The option -Wextra also prints warning messages for the following
       cases:

       *   A pointer is compared against integer zero with "<", "<=", ">",
           or ">=".

       *   (C++ only) An enumerator and a non-enumerator both appear in a
           conditional expression.

       *   (C++ only) Ambiguous virtual bases.

       *   (C++ only) Subscripting an array that has been declared
           "register".

       *   (C++ only) Taking the address of a variable that has been
           declared "register".

       *   (C++ only) A base class is not initialized in a derived class's
           copy constructor.

   -Wchar-subscripts
       Warn if an array subscript has type "char".  This is a common cause
       of error, as programmers often forget that this type is signed on
       some machines.  This warning is enabled by -Wall.

   -Wcomment
       Warn whenever a comment-start sequence /* appears in a /* comment,
       or whenever a Backslash-Newline appears in a // comment.  This
       warning is enabled by -Wall.

   -Wno-coverage-mismatch
       Warn if feedback profiles do not match when using the -fprofile-use
       option.  If a source file is changed between compiling with
       -fprofile-gen and with -fprofile-use, the files with the profile
       feedback can fail to match the source file and GCC cannot use the
       profile feedback information.  By default, this warning is enabled
       and is treated as an error.  -Wno-coverage-mismatch can be used to
       disable the warning or -Wno-error=coverage-mismatch can be used to
       disable the error.  Disabling the error for this warning can result
       in poorly optimized code and is useful only in the case of very
       minor changes such as bug fixes to an existing code-base.
       Completely disabling the warning is not recommended.

   -Wno-cpp
       (C, Objective-C, C++, Objective-C++ and Fortran only)

       Suppress warning messages emitted by "#warning" directives.

   -Wdouble-promotion (C, C++, Objective-C and Objective-C++ only)
       Give a warning when a value of type "float" is implicitly promoted
       to "double".  CPUs with a 32-bit "single-precision" floating-point
       unit implement "float" in hardware, but emulate "double" in
       software.  On such a machine, doing computations using "double"
       values is much more expensive because of the overhead required for
       software emulation.

       It is easy to accidentally do computations with "double" because
       floating-point literals are implicitly of type "double".  For
       example, in:

               float area(float radius)
               {
                  return 3.14159 * radius * radius;
               }

       the compiler performs the entire computation with "double" because
       the floating-point literal is a "double".

   -Wformat
   -Wformat=n
       Check calls to "printf" and "scanf", etc., to make sure that the
       arguments supplied have types appropriate to the format string
       specified, and that the conversions specified in the format string
       make sense.  This includes standard functions, and others specified
       by format attributes, in the "printf", "scanf", "strftime" and
       "strfmon" (an X/Open extension, not in the C standard) families (or
       other target-specific families).  Which functions are checked
       without format attributes having been specified depends on the
       standard version selected, and such checks of functions without the
       attribute specified are disabled by -ffreestanding or -fno-builtin.

       The formats are checked against the format features supported by
       GNU libc version 2.2.  These include all ISO C90 and C99 features,
       as well as features from the Single Unix Specification and some BSD
       and GNU extensions.  Other library implementations may not support
       all these features; GCC does not support warning about features
       that go beyond a particular library's limitations.  However, if
       -Wpedantic is used with -Wformat, warnings are given about format
       features not in the selected standard version (but not for
       "strfmon" formats, since those are not in any version of the C
       standard).

       -Wformat=1
       -Wformat
           Option -Wformat is equivalent to -Wformat=1, and -Wno-format is
           equivalent to -Wformat=0.  Since -Wformat also checks for null
           format arguments for several functions, -Wformat also implies
           -Wnonnull.  Some aspects of this level of format checking can
           be disabled by the options: -Wno-format-contains-nul,
           -Wno-format-extra-args, and -Wno-format-zero-length.  -Wformat
           is enabled by -Wall.

       -Wno-format-contains-nul
           If -Wformat is specified, do not warn about format strings that
           contain NUL bytes.

       -Wno-format-extra-args
           If -Wformat is specified, do not warn about excess arguments to
           a "printf" or "scanf" format function.  The C standard
           specifies that such arguments are ignored.

           Where the unused arguments lie between used arguments that are
           specified with $ operand number specifications, normally
           warnings are still given, since the implementation could not
           know what type to pass to "va_arg" to skip the unused
           arguments.  However, in the case of "scanf" formats, this
           option suppresses the warning if the unused arguments are all
           pointers, since the Single Unix Specification says that such
           unused arguments are allowed.

       -Wno-format-zero-length
           If -Wformat is specified, do not warn about zero-length
           formats.  The C standard specifies that zero-length formats are
           allowed.

       -Wformat=2
           Enable -Wformat plus additional format checks.  Currently
           equivalent to -Wformat -Wformat-nonliteral -Wformat-security
           -Wformat-y2k.

       -Wformat-nonliteral
           If -Wformat is specified, also warn if the format string is not
           a string literal and so cannot be checked, unless the format
           function takes its format arguments as a "va_list".

       -Wformat-security
           If -Wformat is specified, also warn about uses of format
           functions that represent possible security problems.  At
           present, this warns about calls to "printf" and "scanf"
           functions where the format string is not a string literal and
           there are no format arguments, as in "printf (foo);".  This may
           be a security hole if the format string came from untrusted
           input and contains %n.  (This is currently a subset of what
           -Wformat-nonliteral warns about, but in future warnings may be
           added to -Wformat-security that are not included in
           -Wformat-nonliteral.)

       -Wformat-signedness
           If -Wformat is specified, also warn if the format string
           requires an unsigned argument and the argument is signed and
           vice versa.

           NOTE: In Ubuntu 8.10 and later versions this option is enabled
           by default for C, C++, ObjC, ObjC++.  To disable, use
           -Wno-format-security, or disable all format warnings with
           -Wformat=0.  To make format security warnings fatal, specify
           -Werror=format-security.

       -Wformat-y2k
           If -Wformat is specified, also warn about "strftime" formats
           that may yield only a two-digit year.

   -Wnonnull
       Warn about passing a null pointer for arguments marked as requiring
       a non-null value by the "nonnull" function attribute.

       -Wnonnull is included in -Wall and -Wformat.  It can be disabled
       with the -Wno-nonnull option.

   -Wnonnull-compare
       Warn when comparing an argument marked with the "nonnull" function
       attribute against null inside the function.

       -Wnonnull-compare is included in -Wall.  It can be disabled with
       the -Wno-nonnull-compare option.

   -Wnull-dereference
       Warn if the compiler detects paths that trigger erroneous or
       undefined behavior due to dereferencing a null pointer.  This
       option is only active when -fdelete-null-pointer-checks is active,
       which is enabled by optimizations in most targets.  The precision
       of the warnings depends on the optimization options used.

   -Winit-self (C, C++, Objective-C and Objective-C++ only)
       Warn about uninitialized variables that are initialized with
       themselves.  Note this option can only be used with the
       -Wuninitialized option.

       For example, GCC warns about "i" being uninitialized in the
       following snippet only when -Winit-self has been specified:

               int f()
               {
                 int i = i;
                 return i;
               }

       This warning is enabled by -Wall in C++.

   -Wimplicit-int (C and Objective-C only)
       Warn when a declaration does not specify a type.  This warning is
       enabled by -Wall.

   -Wimplicit-function-declaration (C and Objective-C only)
       Give a warning whenever a function is used before being declared.
       In C99 mode (-std=c99 or -std=gnu99), this warning is enabled by
       default and it is made into an error by -pedantic-errors. This
       warning is also enabled by -Wall.

   -Wimplicit (C and Objective-C only)
       Same as -Wimplicit-int and -Wimplicit-function-declaration.  This
       warning is enabled by -Wall.

   -Wignored-qualifiers (C and C++ only)
       Warn if the return type of a function has a type qualifier such as
       "const".  For ISO C such a type qualifier has no effect, since the
       value returned by a function is not an lvalue.  For C++, the
       warning is only emitted for scalar types or "void".  ISO C
       prohibits qualified "void" return types on function definitions, so
       such return types always receive a warning even without this
       option.

       This warning is also enabled by -Wextra.

   -Wignored-attributes (C and C++ only)
       Warn when an attribute is ignored.  This is different from the
       -Wattributes option in that it warns whenever the compiler decides
       to drop an attribute, not that the attribute is either unknown,
       used in a wrong place, etc.  This warning is enabled by default.

   -Wmain
       Warn if the type of "main" is suspicious.  "main" should be a
       function with external linkage, returning int, taking either zero
       arguments, two, or three arguments of appropriate types.  This
       warning is enabled by default in C++ and is enabled by either -Wall
       or -Wpedantic.

   -Wmisleading-indentation (C and C++ only)
       Warn when the indentation of the code does not reflect the block
       structure.  Specifically, a warning is issued for "if", "else",
       "while", and "for" clauses with a guarded statement that does not
       use braces, followed by an unguarded statement with the same
       indentation.

       In the following example, the call to "bar" is misleadingly
       indented as if it were guarded by the "if" conditional.

                 if (some_condition ())
                   foo ();
                   bar ();  /* Gotcha: this is not guarded by the "if".  */

       In the case of mixed tabs and spaces, the warning uses the
       -ftabstop= option to determine if the statements line up
       (defaulting to 8).

       The warning is not issued for code involving multiline preprocessor
       logic such as the following example.

                 if (flagA)
                   foo (0);
               #if SOME_CONDITION_THAT_DOES_NOT_HOLD
                 if (flagB)
               #endif
                   foo (1);

       The warning is not issued after a "#line" directive, since this
       typically indicates autogenerated code, and no assumptions can be
       made about the layout of the file that the directive references.

       This warning is enabled by -Wall in C and C++.

   -Wmissing-braces
       Warn if an aggregate or union initializer is not fully bracketed.
       In the following example, the initializer for "a" is not fully
       bracketed, but that for "b" is fully bracketed.  This warning is
       enabled by -Wall in C.

               int a[2][2] = { 0, 1, 2, 3 };
               int b[2][2] = { { 0, 1 }, { 2, 3 } };

       This warning is enabled by -Wall.

   -Wmissing-include-dirs (C, C++, Objective-C and Objective-C++ only)
       Warn if a user-supplied include directory does not exist.

   -Wparentheses
       Warn if parentheses are omitted in certain contexts, such as when
       there is an assignment in a context where a truth value is
       expected, or when operators are nested whose precedence people
       often get confused about.

       Also warn if a comparison like "x<=y<=z" appears; this is
       equivalent to "(x<=y ? 1 : 0) <= z", which is a different
       interpretation from that of ordinary mathematical notation.

       Also warn about constructions where there may be confusion to which
       "if" statement an "else" branch belongs.  Here is an example of
       such a case:

               {
                 if (a)
                   if (b)
                     foo ();
                 else
                   bar ();
               }

       In C/C++, every "else" branch belongs to the innermost possible
       "if" statement, which in this example is "if (b)".  This is often
       not what the programmer expected, as illustrated in the above
       example by indentation the programmer chose.  When there is the
       potential for this confusion, GCC issues a warning when this flag
       is specified.  To eliminate the warning, add explicit braces around
       the innermost "if" statement so there is no way the "else" can
       belong to the enclosing "if".  The resulting code looks like this:

               {
                 if (a)
                   {
                     if (b)
                       foo ();
                     else
                       bar ();
                   }
               }

       Also warn for dangerous uses of the GNU extension to "?:" with
       omitted middle operand. When the condition in the "?": operator is
       a boolean expression, the omitted value is always 1.  Often
       programmers expect it to be a value computed inside the conditional
       expression instead.

       This warning is enabled by -Wall.

   -Wsequence-point
       Warn about code that may have undefined semantics because of
       violations of sequence point rules in the C and C++ standards.

       The C and C++ standards define the order in which expressions in a
       C/C++ program are evaluated in terms of sequence points, which
       represent a partial ordering between the execution of parts of the
       program: those executed before the sequence point, and those
       executed after it.  These occur after the evaluation of a full
       expression (one which is not part of a larger expression), after
       the evaluation of the first operand of a "&&", "||", "? :" or ","
       (comma) operator, before a function is called (but after the
       evaluation of its arguments and the expression denoting the called
       function), and in certain other places.  Other than as expressed by
       the sequence point rules, the order of evaluation of subexpressions
       of an expression is not specified.  All these rules describe only a
       partial order rather than a total order, since, for example, if two
       functions are called within one expression with no sequence point
       between them, the order in which the functions are called is not
       specified.  However, the standards committee have ruled that
       function calls do not overlap.

       It is not specified when between sequence points modifications to
       the values of objects take effect.  Programs whose behavior depends
       on this have undefined behavior; the C and C++ standards specify
       that "Between the previous and next sequence point an object shall
       have its stored value modified at most once by the evaluation of an
       expression.  Furthermore, the prior value shall be read only to
       determine the value to be stored.".  If a program breaks these
       rules, the results on any particular implementation are entirely
       unpredictable.

       Examples of code with undefined behavior are "a = a++;", "a[n] =
       b[n++]" and "a[i++] = i;".  Some more complicated cases are not
       diagnosed by this option, and it may give an occasional false
       positive result, but in general it has been found fairly effective
       at detecting this sort of problem in programs.

       The standard is worded confusingly, therefore there is some debate
       over the precise meaning of the sequence point rules in subtle
       cases.  Links to discussions of the problem, including proposed
       formal definitions, may be found on the GCC readings page, at
       <http://gcc.gnu.org/readings.html>.

       This warning is enabled by -Wall for C and C++.

   -Wno-return-local-addr
       Do not warn about returning a pointer (or in C++, a reference) to a
       variable that goes out of scope after the function returns.

   -Wreturn-type
       Warn whenever a function is defined with a return type that
       defaults to "int".  Also warn about any "return" statement with no
       return value in a function whose return type is not "void" (falling
       off the end of the function body is considered returning without a
       value), and about a "return" statement with an expression in a
       function whose return type is "void".

       For C++, a function without return type always produces a
       diagnostic message, even when -Wno-return-type is specified.  The
       only exceptions are "main" and functions defined in system headers.

       This warning is enabled by -Wall.

   -Wshift-count-negative
       Warn if shift count is negative. This warning is enabled by
       default.

   -Wshift-count-overflow
       Warn if shift count >= width of type. This warning is enabled by
       default.

   -Wshift-negative-value
       Warn if left shifting a negative value.  This warning is enabled by
       -Wextra in C99 and C++11 modes (and newer).

   -Wshift-overflow
   -Wshift-overflow=n
       Warn about left shift overflows.  This warning is enabled by
       default in C99 and C++11 modes (and newer).

       -Wshift-overflow=1
           This is the warning level of -Wshift-overflow and is enabled by
           default in C99 and C++11 modes (and newer).  This warning level
           does not warn about left-shifting 1 into the sign bit.
           (However, in C, such an overflow is still rejected in contexts
           where an integer constant expression is required.)

       -Wshift-overflow=2
           This warning level also warns about left-shifting 1 into the
           sign bit, unless C++14 mode is active.

   -Wswitch
       Warn whenever a "switch" statement has an index of enumerated type
       and lacks a "case" for one or more of the named codes of that
       enumeration.  (The presence of a "default" label prevents this
       warning.)  "case" labels outside the enumeration range also provoke
       warnings when this option is used (even if there is a "default"
       label).  This warning is enabled by -Wall.

   -Wswitch-default
       Warn whenever a "switch" statement does not have a "default" case.

   -Wswitch-enum
       Warn whenever a "switch" statement has an index of enumerated type
       and lacks a "case" for one or more of the named codes of that
       enumeration.  "case" labels outside the enumeration range also
       provoke warnings when this option is used.  The only difference
       between -Wswitch and this option is that this option gives a
       warning about an omitted enumeration code even if there is a
       "default" label.

   -Wswitch-bool
       Warn whenever a "switch" statement has an index of boolean type and
       the case values are outside the range of a boolean type.  It is
       possible to suppress this warning by casting the controlling
       expression to a type other than "bool".  For example:

               switch ((int) (a == 4))
                 {
                 ...
                 }

       This warning is enabled by default for C and C++ programs.

   -Wsync-nand (C and C++ only)
       Warn when "__sync_fetch_and_nand" and "__sync_nand_and_fetch"
       built-in functions are used.  These functions changed semantics in
       GCC 4.4.

   -Wtrigraphs
       Warn if any trigraphs are encountered that might change the meaning
       of the program (trigraphs within comments are not warned about).
       This warning is enabled by -Wall.

   -Wunused-but-set-parameter
       Warn whenever a function parameter is assigned to, but otherwise
       unused (aside from its declaration).

       To suppress this warning use the "unused" attribute.

       This warning is also enabled by -Wunused together with -Wextra.

   -Wunused-but-set-variable
       Warn whenever a local variable is assigned to, but otherwise unused
       (aside from its declaration).  This warning is enabled by -Wall.

       To suppress this warning use the "unused" attribute.

       This warning is also enabled by -Wunused, which is enabled by
       -Wall.

   -Wunused-function
       Warn whenever a static function is declared but not defined or a
       non-inline static function is unused.  This warning is enabled by
       -Wall.

   -Wunused-label
       Warn whenever a label is declared but not used.  This warning is
       enabled by -Wall.

       To suppress this warning use the "unused" attribute.

   -Wunused-local-typedefs (C, Objective-C, C++ and Objective-C++ only)
       Warn when a typedef locally defined in a function is not used.
       This warning is enabled by -Wall.

   -Wunused-parameter
       Warn whenever a function parameter is unused aside from its
       declaration.

       To suppress this warning use the "unused" attribute.

   -Wno-unused-result
       Do not warn if a caller of a function marked with attribute
       "warn_unused_result" does not use its return value. The default is
       -Wunused-result.

   -Wunused-variable
       Warn whenever a local or static variable is unused aside from its
       declaration. This option implies -Wunused-const-variable=1 for C,
       but not for C++. This warning is enabled by -Wall.

       To suppress this warning use the "unused" attribute.

   -Wunused-const-variable
   -Wunused-const-variable=n
       Warn whenever a constant static variable is unused aside from its
       declaration.  -Wunused-const-variable=1 is enabled by
       -Wunused-variable for C, but not for C++. In C this declares
       variable storage, but in C++ this is not an error since const
       variables take the place of "#define"s.

       To suppress this warning use the "unused" attribute.

       -Wunused-const-variable=1
           This is the warning level that is enabled by -Wunused-variable
           for C.  It warns only about unused static const variables
           defined in the main compilation unit, but not about static
           const variables declared in any header included.

       -Wunused-const-variable=2
           This warning level also warns for unused constant static
           variables in headers (excluding system headers).  This is the
           warning level of -Wunused-const-variable and must be explicitly
           requested since in C++ this isn't an error and in C it might be
           harder to clean up all headers included.

   -Wunused-value
       Warn whenever a statement computes a result that is explicitly not
       used. To suppress this warning cast the unused expression to
       "void". This includes an expression-statement or the left-hand side
       of a comma expression that contains no side effects. For example,
       an expression such as "x[i,j]" causes a warning, while
       "x[(void)i,j]" does not.

       This warning is enabled by -Wall.

   -Wunused
       All the above -Wunused options combined.

       In order to get a warning about an unused function parameter, you
       must either specify -Wextra -Wunused (note that -Wall implies
       -Wunused), or separately specify -Wunused-parameter.

   -Wuninitialized
       Warn if an automatic variable is used without first being
       initialized or if a variable may be clobbered by a "setjmp" call.
       In C++, warn if a non-static reference or non-static "const" member
       appears in a class without constructors.

       If you want to warn about code that uses the uninitialized value of
       the variable in its own initializer, use the -Winit-self option.

       These warnings occur for individual uninitialized or clobbered
       elements of structure, union or array variables as well as for
       variables that are uninitialized or clobbered as a whole.  They do
       not occur for variables or elements declared "volatile".  Because
       these warnings depend on optimization, the exact variables or
       elements for which there are warnings depends on the precise
       optimization options and version of GCC used.

       Note that there may be no warning about a variable that is used
       only to compute a value that itself is never used, because such
       computations may be deleted by data flow analysis before the
       warnings are printed.

   -Winvalid-memory-model
       Warn for invocations of __atomic Builtins, __sync Builtins, and the
       C11 atomic generic functions with a memory consistency argument
       that is either invalid for the operation or outside the range of
       values of the "memory_order" enumeration.  For example, since the
       "__atomic_store" and "__atomic_store_n" built-ins are only defined
       for the relaxed, release, and sequentially consistent memory orders
       the following code is diagnosed:

               void store (int *i)
               {
                 __atomic_store_n (i, 0, memory_order_consume);
               }

       -Winvalid-memory-model is enabled by default.

   -Wmaybe-uninitialized
       For an automatic variable, if there exists a path from the function
       entry to a use of the variable that is initialized, but there exist
       some other paths for which the variable is not initialized, the
       compiler emits a warning if it cannot prove the uninitialized paths
       are not executed at run time. These warnings are made optional
       because GCC is not smart enough to see all the reasons why the code
       might be correct in spite of appearing to have an error.  Here is
       one example of how this can happen:

               {
                 int x;
                 switch (y)
                   {
                   case 1: x = 1;
                     break;
                   case 2: x = 4;
                     break;
                   case 3: x = 5;
                   }
                 foo (x);
               }

       If the value of "y" is always 1, 2 or 3, then "x" is always
       initialized, but GCC doesn't know this. To suppress the warning,
       you need to provide a default case with assert(0) or similar code.

       This option also warns when a non-volatile automatic variable might
       be changed by a call to "longjmp".  These warnings as well are
       possible only in optimizing compilation.

       The compiler sees only the calls to "setjmp".  It cannot know where
       "longjmp" will be called; in fact, a signal handler could call it
       at any point in the code.  As a result, you may get a warning even
       when there is in fact no problem because "longjmp" cannot in fact
       be called at the place that would cause a problem.

       Some spurious warnings can be avoided if you declare all the
       functions you use that never return as "noreturn".

       This warning is enabled by -Wall or -Wextra.

   -Wunknown-pragmas
       Warn when a "#pragma" directive is encountered that is not
       understood by GCC.  If this command-line option is used, warnings
       are even issued for unknown pragmas in system header files.  This
       is not the case if the warnings are only enabled by the -Wall
       command-line option.

   -Wno-pragmas
       Do not warn about misuses of pragmas, such as incorrect parameters,
       invalid syntax, or conflicts between pragmas.  See also
       -Wunknown-pragmas.

   -Wstrict-aliasing
       This option is only active when -fstrict-aliasing is active.  It
       warns about code that might break the strict aliasing rules that
       the compiler is using for optimization.  The warning does not catch
       all cases, but does attempt to catch the more common pitfalls.  It
       is included in -Wall.  It is equivalent to -Wstrict-aliasing=3

   -Wstrict-aliasing=n
       This option is only active when -fstrict-aliasing is active.  It
       warns about code that might break the strict aliasing rules that
       the compiler is using for optimization.  Higher levels correspond
       to higher accuracy (fewer false positives).  Higher levels also
       correspond to more effort, similar to the way -O works.
       -Wstrict-aliasing is equivalent to -Wstrict-aliasing=3.

       Level 1: Most aggressive, quick, least accurate.  Possibly useful
       when higher levels do not warn but -fstrict-aliasing still breaks
       the code, as it has very few false negatives.  However, it has many
       false positives.  Warns for all pointer conversions between
       possibly incompatible types, even if never dereferenced.  Runs in
       the front end only.

       Level 2: Aggressive, quick, not too precise.  May still have many
       false positives (not as many as level 1 though), and few false
       negatives (but possibly more than level 1).  Unlike level 1, it
       only warns when an address is taken.  Warns about incomplete types.
       Runs in the front end only.

       Level 3 (default for -Wstrict-aliasing): Should have very few false
       positives and few false negatives.  Slightly slower than levels 1
       or 2 when optimization is enabled.  Takes care of the common
       pun+dereference pattern in the front end: "*(int*)&some_float".  If
       optimization is enabled, it also runs in the back end, where it
       deals with multiple statement cases using flow-sensitive points-to
       information.  Only warns when the converted pointer is
       dereferenced.  Does not warn about incomplete types.

   -Wstrict-overflow
   -Wstrict-overflow=n
       This option is only active when -fstrict-overflow is active.  It
       warns about cases where the compiler optimizes based on the
       assumption that signed overflow does not occur.  Note that it does
       not warn about all cases where the code might overflow: it only
       warns about cases where the compiler implements some optimization.
       Thus this warning depends on the optimization level.

       An optimization that assumes that signed overflow does not occur is
       perfectly safe if the values of the variables involved are such
       that overflow never does, in fact, occur.  Therefore this warning
       can easily give a false positive: a warning about code that is not
       actually a problem.  To help focus on important issues, several
       warning levels are defined.  No warnings are issued for the use of
       undefined signed overflow when estimating how many iterations a
       loop requires, in particular when determining whether a loop will
       be executed at all.

       -Wstrict-overflow=1
           Warn about cases that are both questionable and easy to avoid.
           For example,  with -fstrict-overflow, the compiler simplifies
           "x + 1 > x" to 1.  This level of -Wstrict-overflow is enabled
           by -Wall; higher levels are not, and must be explicitly
           requested.

       -Wstrict-overflow=2
           Also warn about other cases where a comparison is simplified to
           a constant.  For example: "abs (x) >= 0".  This can only be
           simplified when -fstrict-overflow is in effect, because "abs
           (INT_MIN)" overflows to "INT_MIN", which is less than zero.
           -Wstrict-overflow (with no level) is the same as
           -Wstrict-overflow=2.

       -Wstrict-overflow=3
           Also warn about other cases where a comparison is simplified.
           For example: "x + 1 > 1" is simplified to "x > 0".

       -Wstrict-overflow=4
           Also warn about other simplifications not covered by the above
           cases.  For example: "(x * 10) / 5" is simplified to "x * 2".

       -Wstrict-overflow=5
           Also warn about cases where the compiler reduces the magnitude
           of a constant involved in a comparison.  For example: "x + 2 >
           y" is simplified to "x + 1 >= y".  This is reported only at the
           highest warning level because this simplification applies to
           many comparisons, so this warning level gives a very large
           number of false positives.

   -Wsuggest-attribute=[pure|const|noreturn|format]
       Warn for cases where adding an attribute may be beneficial. The
       attributes currently supported are listed below.

       -Wsuggest-attribute=pure
       -Wsuggest-attribute=const
       -Wsuggest-attribute=noreturn
           Warn about functions that might be candidates for attributes
           "pure", "const" or "noreturn".  The compiler only warns for
           functions visible in other compilation units or (in the case of
           "pure" and "const") if it cannot prove that the function
           returns normally. A function returns normally if it doesn't
           contain an infinite loop or return abnormally by throwing,
           calling "abort" or trapping.  This analysis requires option
           -fipa-pure-const, which is enabled by default at -O and higher.
           Higher optimization levels improve the accuracy of the
           analysis.

       -Wsuggest-attribute=format
       -Wmissing-format-attribute
           Warn about function pointers that might be candidates for
           "format" attributes.  Note these are only possible candidates,
           not absolute ones.  GCC guesses that function pointers with
           "format" attributes that are used in assignment,
           initialization, parameter passing or return statements should
           have a corresponding "format" attribute in the resulting type.
           I.e. the left-hand side of the assignment or initialization,
           the type of the parameter variable, or the return type of the
           containing function respectively should also have a "format"
           attribute to avoid the warning.

           GCC also warns about function definitions that might be
           candidates for "format" attributes.  Again, these are only
           possible candidates.  GCC guesses that "format" attributes
           might be appropriate for any function that calls a function
           like "vprintf" or "vscanf", but this might not always be the
           case, and some functions for which "format" attributes are
           appropriate may not be detected.

   -Wsuggest-final-types
       Warn about types with virtual methods where code quality would be
       improved if the type were declared with the C++11 "final"
       specifier, or, if possible, declared in an anonymous namespace.
       This allows GCC to more aggressively devirtualize the polymorphic
       calls. This warning is more effective with link time optimization,
       where the information about the class hierarchy graph is more
       complete.

   -Wsuggest-final-methods
       Warn about virtual methods where code quality would be improved if
       the method were declared with the C++11 "final" specifier, or, if
       possible, its type were declared in an anonymous namespace or with
       the "final" specifier.  This warning is more effective with link
       time optimization, where the information about the class hierarchy
       graph is more complete. It is recommended to first consider
       suggestions of -Wsuggest-final-types and then rebuild with new
       annotations.

   -Wsuggest-override
       Warn about overriding virtual functions that are not marked with
       the override keyword.

   -Warray-bounds
   -Warray-bounds=n
       This option is only active when -ftree-vrp is active (default for
       -O2 and above). It warns about subscripts to arrays that are always
       out of bounds. This warning is enabled by -Wall.

       -Warray-bounds=1
           This is the warning level of -Warray-bounds and is enabled by
           -Wall; higher levels are not, and must be explicitly requested.

       -Warray-bounds=2
           This warning level also warns about out of bounds access for
           arrays at the end of a struct and for arrays accessed through
           pointers. This warning level may give a larger number of false
           positives and is deactivated by default.

   -Wbool-compare
       Warn about boolean expression compared with an integer value
       different from "true"/"false".  For instance, the following
       comparison is always false:

               int n = 5;
               ...
               if ((n > 1) == 2) { ... }

       This warning is enabled by -Wall.

   -Wduplicated-cond
       Warn about duplicated conditions in an if-else-if chain.  For
       instance, warn for the following code:

               if (p->q != NULL) { ... }
               else if (p->q != NULL) { ... }

   -Wframe-address
       Warn when the __builtin_frame_address or __builtin_return_address
       is called with an argument greater than 0.  Such calls may return
       indeterminate values or crash the program.  The warning is included
       in -Wall.

   -Wno-discarded-qualifiers (C and Objective-C only)
       Do not warn if type qualifiers on pointers are being discarded.
       Typically, the compiler warns if a "const char *" variable is
       passed to a function that takes a "char *" parameter.  This option
       can be used to suppress such a warning.

   -Wno-discarded-array-qualifiers (C and Objective-C only)
       Do not warn if type qualifiers on arrays which are pointer targets
       are being discarded. Typically, the compiler warns if a "const int
       (*)[]" variable is passed to a function that takes a "int (*)[]"
       parameter.  This option can be used to suppress such a warning.

   -Wno-incompatible-pointer-types (C and Objective-C only)
       Do not warn when there is a conversion between pointers that have
       incompatible types.  This warning is for cases not covered by
       -Wno-pointer-sign, which warns for pointer argument passing or
       assignment with different signedness.

   -Wno-int-conversion (C and Objective-C only)
       Do not warn about incompatible integer to pointer and pointer to
       integer conversions.  This warning is about implicit conversions;
       for explicit conversions the warnings -Wno-int-to-pointer-cast and
       -Wno-pointer-to-int-cast may be used.

   -Wno-div-by-zero
       Do not warn about compile-time integer division by zero.  Floating-
       point division by zero is not warned about, as it can be a
       legitimate way of obtaining infinities and NaNs.

   -Wsystem-headers
       Print warning messages for constructs found in system header files.
       Warnings from system headers are normally suppressed, on the
       assumption that they usually do not indicate real problems and
       would only make the compiler output harder to read.  Using this
       command-line option tells GCC to emit warnings from system headers
       as if they occurred in user code.  However, note that using -Wall
       in conjunction with this option does not warn about unknown pragmas
       in system headers---for that, -Wunknown-pragmas must also be used.

   -Wtautological-compare
       Warn if a self-comparison always evaluates to true or false.  This
       warning detects various mistakes such as:

               int i = 1;
               ...
               if (i > i) { ... }

       This warning is enabled by -Wall.

   -Wtrampolines
       Warn about trampolines generated for pointers to nested functions.
       A trampoline is a small piece of data or code that is created at
       run time on the stack when the address of a nested function is
       taken, and is used to call the nested function indirectly.  For
       some targets, it is made up of data only and thus requires no
       special treatment.  But, for most targets, it is made up of code
       and thus requires the stack to be made executable in order for the
       program to work properly.

   -Wfloat-equal
       Warn if floating-point values are used in equality comparisons.

       The idea behind this is that sometimes it is convenient (for the
       programmer) to consider floating-point values as approximations to
       infinitely precise real numbers.  If you are doing this, then you
       need to compute (by analyzing the code, or in some other way) the
       maximum or likely maximum error that the computation introduces,
       and allow for it when performing comparisons (and when producing
       output, but that's a different problem).  In particular, instead of
       testing for equality, you should check to see whether the two
       values have ranges that overlap; and this is done with the
       relational operators, so equality comparisons are probably
       mistaken.

   -Wtraditional (C and Objective-C only)
       Warn about certain constructs that behave differently in
       traditional and ISO C.  Also warn about ISO C constructs that have
       no traditional C equivalent, and/or problematic constructs that
       should be avoided.

       *   Macro parameters that appear within string literals in the
           macro body.  In traditional C macro replacement takes place
           within string literals, but in ISO C it does not.

       *   In traditional C, some preprocessor directives did not exist.
           Traditional preprocessors only considered a line to be a
           directive if the # appeared in column 1 on the line.  Therefore
           -Wtraditional warns about directives that traditional C
           understands but ignores because the # does not appear as the
           first character on the line.  It also suggests you hide
           directives like "#pragma" not understood by traditional C by
           indenting them.  Some traditional implementations do not
           recognize "#elif", so this option suggests avoiding it
           altogether.

       *   A function-like macro that appears without arguments.

       *   The unary plus operator.

       *   The U integer constant suffix, or the F or L floating-point
           constant suffixes.  (Traditional C does support the L suffix on
           integer constants.)  Note, these suffixes appear in macros
           defined in the system headers of most modern systems, e.g. the
           _MIN/_MAX macros in "<limits.h>".  Use of these macros in user
           code might normally lead to spurious warnings, however GCC's
           integrated preprocessor has enough context to avoid warning in
           these cases.

       *   A function declared external in one block and then used after
           the end of the block.

       *   A "switch" statement has an operand of type "long".

       *   A non-"static" function declaration follows a "static" one.
           This construct is not accepted by some traditional C compilers.

       *   The ISO type of an integer constant has a different width or
           signedness from its traditional type.  This warning is only
           issued if the base of the constant is ten.  I.e. hexadecimal or
           octal values, which typically represent bit patterns, are not
           warned about.

       *   Usage of ISO string concatenation is detected.

       *   Initialization of automatic aggregates.

       *   Identifier conflicts with labels.  Traditional C lacks a
           separate namespace for labels.

       *   Initialization of unions.  If the initializer is zero, the
           warning is omitted.  This is done under the assumption that the
           zero initializer in user code appears conditioned on e.g.
           "__STDC__" to avoid missing initializer warnings and relies on
           default initialization to zero in the traditional C case.

       *   Conversions by prototypes between fixed/floating-point values
           and vice versa.  The absence of these prototypes when compiling
           with traditional C causes serious problems.  This is a subset
           of the possible conversion warnings; for the full set use
           -Wtraditional-conversion.

       *   Use of ISO C style function definitions.  This warning
           intentionally is not issued for prototype declarations or
           variadic functions because these ISO C features appear in your
           code when using libiberty's traditional C compatibility macros,
           "PARAMS" and "VPARAMS".  This warning is also bypassed for
           nested functions because that feature is already a GCC
           extension and thus not relevant to traditional C compatibility.

   -Wtraditional-conversion (C and Objective-C only)
       Warn if a prototype causes a type conversion that is different from
       what would happen to the same argument in the absence of a
       prototype.  This includes conversions of fixed point to floating
       and vice versa, and conversions changing the width or signedness of
       a fixed-point argument except when the same as the default
       promotion.

   -Wdeclaration-after-statement (C and Objective-C only)
       Warn when a declaration is found after a statement in a block.
       This construct, known from C++, was introduced with ISO C99 and is
       by default allowed in GCC.  It is not supported by ISO C90.

   -Wundef
       Warn if an undefined identifier is evaluated in an "#if" directive.

   -Wno-endif-labels
       Do not warn whenever an "#else" or an "#endif" are followed by
       text.

   -Wshadow
       Warn whenever a local variable or type declaration shadows another
       variable, parameter, type, class member (in C++), or instance
       variable (in Objective-C) or whenever a built-in function is
       shadowed. Note that in C++, the compiler warns if a local variable
       shadows an explicit typedef, but not if it shadows a
       struct/class/enum.

   -Wno-shadow-ivar (Objective-C only)
       Do not warn whenever a local variable shadows an instance variable
       in an Objective-C method.

   -Wlarger-than=len
       Warn whenever an object of larger than len bytes is defined.

   -Wframe-larger-than=len
       Warn if the size of a function frame is larger than len bytes.  The
       computation done to determine the stack frame size is approximate
       and not conservative.  The actual requirements may be somewhat
       greater than len even if you do not get a warning.  In addition,
       any space allocated via "alloca", variable-length arrays, or
       related constructs is not included by the compiler when determining
       whether or not to issue a warning.

   -Wno-free-nonheap-object
       Do not warn when attempting to free an object that was not
       allocated on the heap.

   -Wstack-usage=len
       Warn if the stack usage of a function might be larger than len
       bytes.  The computation done to determine the stack usage is
       conservative.  Any space allocated via "alloca", variable-length
       arrays, or related constructs is included by the compiler when
       determining whether or not to issue a warning.

       The message is in keeping with the output of -fstack-usage.

       *   If the stack usage is fully static but exceeds the specified
           amount, it's:

                     warning: stack usage is 1120 bytes

       *   If the stack usage is (partly) dynamic but bounded, it's:

                     warning: stack usage might be 1648 bytes

       *   If the stack usage is (partly) dynamic and not bounded, it's:

                     warning: stack usage might be unbounded

   -Wunsafe-loop-optimizations
       Warn if the loop cannot be optimized because the compiler cannot
       assume anything on the bounds of the loop indices.  With
       -funsafe-loop-optimizations warn if the compiler makes such
       assumptions.

   -Wno-pedantic-ms-format (MinGW targets only)
       When used in combination with -Wformat and -pedantic without GNU
       extensions, this option disables the warnings about non-ISO
       "printf" / "scanf" format width specifiers "I32", "I64", and "I"
       used on Windows targets, which depend on the MS runtime.

   -Wplacement-new
   -Wplacement-new=n
       Warn about placement new expressions with undefined behavior, such
       as constructing an object in a buffer that is smaller than the type
       of the object.  For example, the placement new expression below is
       diagnosed because it attempts to construct an array of 64 integers
       in a buffer only 64 bytes large.

               char buf [64];
               new (buf) int[64];

       This warning is enabled by default.

       -Wplacement-new=1
           This is the default warning level of -Wplacement-new.  At this
           level the warning is not issued for some strictly undefined
           constructs that GCC allows as extensions for compatibility with
           legacy code.  For example, the following "new" expression is
           not diagnosed at this level even though it has undefined
           behavior according to the C++ standard because it writes past
           the end of the one-element array.

                   struct S { int n, a[1]; };
                   S *s = (S *)malloc (sizeof *s + 31 * sizeof s->a[0]);
                   new (s->a)int [32]();

       -Wplacement-new=2
           At this level, in addition to diagnosing all the same
           constructs as at level 1, a diagnostic is also issued for
           placement new expressions that construct an object in the last
           member of structure whose type is an array of a single element
           and whose size is less than the size of the object being
           constructed.  While the previous example would be diagnosed,
           the following construct makes use of the flexible member array
           extension to avoid the warning at level 2.

                   struct S { int n, a[]; };
                   S *s = (S *)malloc (sizeof *s + 32 * sizeof s->a[0]);
                   new (s->a)int [32]();

   -Wpointer-arith
       Warn about anything that depends on the "size of" a function type
       or of "void".  GNU C assigns these types a size of 1, for
       convenience in calculations with "void *" pointers and pointers to
       functions.  In C++, warn also when an arithmetic operation involves
       "NULL".  This warning is also enabled by -Wpedantic.

   -Wtype-limits
       Warn if a comparison is always true or always false due to the
       limited range of the data type, but do not warn for constant
       expressions.  For example, warn if an unsigned variable is compared
       against zero with "<" or ">=".  This warning is also enabled by
       -Wextra.

   -Wbad-function-cast (C and Objective-C only)
       Warn when a function call is cast to a non-matching type.  For
       example, warn if a call to a function returning an integer type is
       cast to a pointer type.

   -Wc90-c99-compat (C and Objective-C only)
       Warn about features not present in ISO C90, but present in ISO C99.
       For instance, warn about use of variable length arrays, "long long"
       type, "bool" type, compound literals, designated initializers, and
       so on.  This option is independent of the standards mode.  Warnings
       are disabled in the expression that follows "__extension__".

   -Wc99-c11-compat (C and Objective-C only)
       Warn about features not present in ISO C99, but present in ISO C11.
       For instance, warn about use of anonymous structures and unions,
       "_Atomic" type qualifier, "_Thread_local" storage-class specifier,
       "_Alignas" specifier, "Alignof" operator, "_Generic" keyword, and
       so on.  This option is independent of the standards mode.  Warnings
       are disabled in the expression that follows "__extension__".

   -Wc++-compat (C and Objective-C only)
       Warn about ISO C constructs that are outside of the common subset
       of ISO C and ISO C++, e.g. request for implicit conversion from
       "void *" to a pointer to non-"void" type.

   -Wc++11-compat (C++ and Objective-C++ only)
       Warn about C++ constructs whose meaning differs between ISO C++
       1998 and ISO C++ 2011, e.g., identifiers in ISO C++ 1998 that are
       keywords in ISO C++ 2011.  This warning turns on -Wnarrowing and is
       enabled by -Wall.

   -Wc++14-compat (C++ and Objective-C++ only)
       Warn about C++ constructs whose meaning differs between ISO C++
       2011 and ISO C++ 2014.  This warning is enabled by -Wall.

   -Wcast-qual
       Warn whenever a pointer is cast so as to remove a type qualifier
       from the target type.  For example, warn if a "const char *" is
       cast to an ordinary "char *".

       Also warn when making a cast that introduces a type qualifier in an
       unsafe way.  For example, casting "char **" to "const char **" is
       unsafe, as in this example:

                 /* p is char ** value.  */
                 const char **q = (const char **) p;
                 /* Assignment of readonly string to const char * is OK.  */
                 *q = "string";
                 /* Now char** pointer points to read-only memory.  */
                 **p = 'b';

   -Wcast-align
       Warn whenever a pointer is cast such that the required alignment of
       the target is increased.  For example, warn if a "char *" is cast
       to an "int *" on machines where integers can only be accessed at
       two- or four-byte boundaries.

   -Wwrite-strings
       When compiling C, give string constants the type "const
       char[length]" so that copying the address of one into a non-"const"
       "char *" pointer produces a warning.  These warnings help you find
       at compile time code that can try to write into a string constant,
       but only if you have been very careful about using "const" in
       declarations and prototypes.  Otherwise, it is just a nuisance.
       This is why we did not make -Wall request these warnings.

       When compiling C++, warn about the deprecated conversion from
       string literals to "char *".  This warning is enabled by default
       for C++ programs.

   -Wclobbered
       Warn for variables that might be changed by "longjmp" or "vfork".
       This warning is also enabled by -Wextra.

   -Wconditionally-supported (C++ and Objective-C++ only)
       Warn for conditionally-supported (C++11 [intro.defs]) constructs.

   -Wconversion
       Warn for implicit conversions that may alter a value. This includes
       conversions between real and integer, like "abs (x)" when "x" is
       "double"; conversions between signed and unsigned, like "unsigned
       ui = -1"; and conversions to smaller types, like "sqrtf (M_PI)". Do
       not warn for explicit casts like "abs ((int) x)" and "ui =
       (unsigned) -1", or if the value is not changed by the conversion
       like in "abs (2.0)".  Warnings about conversions between signed and
       unsigned integers can be disabled by using -Wno-sign-conversion.

       For C++, also warn for confusing overload resolution for user-
       defined conversions; and conversions that never use a type
       conversion operator: conversions to "void", the same type, a base
       class or a reference to them. Warnings about conversions between
       signed and unsigned integers are disabled by default in C++ unless
       -Wsign-conversion is explicitly enabled.

   -Wno-conversion-null (C++ and Objective-C++ only)
       Do not warn for conversions between "NULL" and non-pointer types.
       -Wconversion-null is enabled by default.

   -Wzero-as-null-pointer-constant (C++ and Objective-C++ only)
       Warn when a literal 0 is used as null pointer constant.  This can
       be useful to facilitate the conversion to "nullptr" in C++11.

   -Wsubobject-linkage (C++ and Objective-C++ only)
       Warn if a class type has a base or a field whose type uses the
       anonymous namespace or depends on a type with no linkage.  If a
       type A depends on a type B with no or internal linkage, defining it
       in multiple translation units would be an ODR violation because the
       meaning of B is different in each translation unit.  If A only
       appears in a single translation unit, the best way to silence the
       warning is to give it internal linkage by putting it in an
       anonymous namespace as well.  The compiler doesn't give this
       warning for types defined in the main .C file, as those are
       unlikely to have multiple definitions.  -Wsubobject-linkage is
       enabled by default.

   -Wdate-time
       Warn when macros "__TIME__", "__DATE__" or "__TIMESTAMP__" are
       encountered as they might prevent bit-wise-identical reproducible
       compilations.

   -Wdelete-incomplete (C++ and Objective-C++ only)
       Warn when deleting a pointer to incomplete type, which may cause
       undefined behavior at runtime.  This warning is enabled by default.

   -Wuseless-cast (C++ and Objective-C++ only)
       Warn when an expression is casted to its own type.

   -Wempty-body
       Warn if an empty body occurs in an "if", "else" or "do while"
       statement.  This warning is also enabled by -Wextra.

   -Wenum-compare
       Warn about a comparison between values of different enumerated
       types.  In C++ enumeral mismatches in conditional expressions are
       also diagnosed and the warning is enabled by default.  In C this
       warning is enabled by -Wall.

   -Wjump-misses-init (C, Objective-C only)
       Warn if a "goto" statement or a "switch" statement jumps forward
       across the initialization of a variable, or jumps backward to a
       label after the variable has been initialized.  This only warns
       about variables that are initialized when they are declared.  This
       warning is only supported for C and Objective-C; in C++ this sort
       of branch is an error in any case.

       -Wjump-misses-init is included in -Wc++-compat.  It can be disabled
       with the -Wno-jump-misses-init option.

   -Wsign-compare
       Warn when a comparison between signed and unsigned values could
       produce an incorrect result when the signed value is converted to
       unsigned.  In C++, this warning is also enabled by -Wall.  In C, it
       is also enabled by -Wextra.

   -Wsign-conversion
       Warn for implicit conversions that may change the sign of an
       integer value, like assigning a signed integer expression to an
       unsigned integer variable. An explicit cast silences the warning.
       In C, this option is enabled also by -Wconversion.

   -Wfloat-conversion
       Warn for implicit conversions that reduce the precision of a real
       value.  This includes conversions from real to integer, and from
       higher precision real to lower precision real values.  This option
       is also enabled by -Wconversion.

   -Wno-scalar-storage-order
       Do not warn on suspicious constructs involving reverse scalar
       storage order.

   -Wsized-deallocation (C++ and Objective-C++ only)
       Warn about a definition of an unsized deallocation function

               void operator delete (void *) noexcept;
               void operator delete[] (void *) noexcept;

       without a definition of the corresponding sized deallocation
       function

               void operator delete (void *, std::size_t) noexcept;
               void operator delete[] (void *, std::size_t) noexcept;

       or vice versa.  Enabled by -Wextra along with -fsized-deallocation.

   -Wsizeof-pointer-memaccess
       Warn for suspicious length parameters to certain string and memory
       built-in functions if the argument uses "sizeof".  This warning
       warns e.g.  about "memset (ptr, 0, sizeof (ptr));" if "ptr" is not
       an array, but a pointer, and suggests a possible fix, or about
       "memcpy (&foo, ptr, sizeof (&foo));".  This warning is enabled by
       -Wall.

   -Wsizeof-array-argument
       Warn when the "sizeof" operator is applied to a parameter that is
       declared as an array in a function definition.  This warning is
       enabled by default for C and C++ programs.

   -Wmemset-transposed-args
       Warn for suspicious calls to the "memset" built-in function, if the
       second argument is not zero and the third argument is zero.  This
       warns e.g.@ about "memset (buf, sizeof buf, 0)" where most probably
       "memset (buf, 0, sizeof buf)" was meant instead.  The diagnostics
       is only emitted if the third argument is literal zero.  If it is
       some expression that is folded to zero, a cast of zero to some
       type, etc., it is far less likely that the user has mistakenly
       exchanged the arguments and no warning is emitted.  This warning is
       enabled by -Wall.

   -Waddress
       Warn about suspicious uses of memory addresses. These include using
       the address of a function in a conditional expression, such as
       "void func(void); if (func)", and comparisons against the memory
       address of a string literal, such as "if (x == "abc")".  Such uses
       typically indicate a programmer error: the address of a function
       always evaluates to true, so their use in a conditional usually
       indicate that the programmer forgot the parentheses in a function
       call; and comparisons against string literals result in unspecified
       behavior and are not portable in C, so they usually indicate that
       the programmer intended to use "strcmp".  This warning is enabled
       by -Wall.

   -Wlogical-op
       Warn about suspicious uses of logical operators in expressions.
       This includes using logical operators in contexts where a bit-wise
       operator is likely to be expected.  Also warns when the operands of
       a logical operator are the same:

               extern int a;
               if (a < 0 && a < 0) { ... }

   -Wlogical-not-parentheses
       Warn about logical not used on the left hand side operand of a
       comparison.  This option does not warn if the RHS operand is of a
       boolean type.  Its purpose is to detect suspicious code like the
       following:

               int a;
               ...
               if (!a > 1) { ... }

       It is possible to suppress the warning by wrapping the LHS into
       parentheses:

               if ((!a) > 1) { ... }

       This warning is enabled by -Wall.

   -Waggregate-return
       Warn if any functions that return structures or unions are defined
       or called.  (In languages where you can return an array, this also
       elicits a warning.)

   -Wno-aggressive-loop-optimizations
       Warn if in a loop with constant number of iterations the compiler
       detects undefined behavior in some statement during one or more of
       the iterations.

   -Wno-attributes
       Do not warn if an unexpected "__attribute__" is used, such as
       unrecognized attributes, function attributes applied to variables,
       etc.  This does not stop errors for incorrect use of supported
       attributes.

   -Wno-builtin-macro-redefined
       Do not warn if certain built-in macros are redefined.  This
       suppresses warnings for redefinition of "__TIMESTAMP__",
       "__TIME__", "__DATE__", "__FILE__", and "__BASE_FILE__".

   -Wstrict-prototypes (C and Objective-C only)
       Warn if a function is declared or defined without specifying the
       argument types.  (An old-style function definition is permitted
       without a warning if preceded by a declaration that specifies the
       argument types.)

   -Wold-style-declaration (C and Objective-C only)
       Warn for obsolescent usages, according to the C Standard, in a
       declaration. For example, warn if storage-class specifiers like
       "static" are not the first things in a declaration.  This warning
       is also enabled by -Wextra.

   -Wold-style-definition (C and Objective-C only)
       Warn if an old-style function definition is used.  A warning is
       given even if there is a previous prototype.

   -Wmissing-parameter-type (C and Objective-C only)
       A function parameter is declared without a type specifier in
       K&R-style functions:

               void foo(bar) { }

       This warning is also enabled by -Wextra.

   -Wmissing-prototypes (C and Objective-C only)
       Warn if a global function is defined without a previous prototype
       declaration.  This warning is issued even if the definition itself
       provides a prototype.  Use this option to detect global functions
       that do not have a matching prototype declaration in a header file.
       This option is not valid for C++ because all function declarations
       provide prototypes and a non-matching declaration declares an
       overload rather than conflict with an earlier declaration.  Use
       -Wmissing-declarations to detect missing declarations in C++.

   -Wmissing-declarations
       Warn if a global function is defined without a previous
       declaration.  Do so even if the definition itself provides a
       prototype.  Use this option to detect global functions that are not
       declared in header files.  In C, no warnings are issued for
       functions with previous non-prototype declarations; use
       -Wmissing-prototypes to detect missing prototypes.  In C++, no
       warnings are issued for function templates, or for inline
       functions, or for functions in anonymous namespaces.

   -Wmissing-field-initializers
       Warn if a structure's initializer has some fields missing.  For
       example, the following code causes such a warning, because "x.h" is
       implicitly zero:

               struct s { int f, g, h; };
               struct s x = { 3, 4 };

       This option does not warn about designated initializers, so the
       following modification does not trigger a warning:

               struct s { int f, g, h; };
               struct s x = { .f = 3, .g = 4 };

       In C++ this option does not warn either about the empty { }
       initializer, for example:

               struct s { int f, g, h; };
               s x = { };

       This warning is included in -Wextra.  To get other -Wextra warnings
       without this one, use -Wextra -Wno-missing-field-initializers.

   -Wno-multichar
       Do not warn if a multicharacter constant ('FOOF') is used.  Usually
       they indicate a typo in the user's code, as they have
       implementation-defined values, and should not be used in portable
       code.

   -Wnormalized[=<none|id|nfc|nfkc>]
       In ISO C and ISO C++, two identifiers are different if they are
       different sequences of characters.  However, sometimes when
       characters outside the basic ASCII character set are used, you can
       have two different character sequences that look the same.  To
       avoid confusion, the ISO 10646 standard sets out some normalization
       rules which when applied ensure that two sequences that look the
       same are turned into the same sequence.  GCC can warn you if you
       are using identifiers that have not been normalized; this option
       controls that warning.

       There are four levels of warning supported by GCC.  The default is
       -Wnormalized=nfc, which warns about any identifier that is not in
       the ISO 10646 "C" normalized form, NFC.  NFC is the recommended
       form for most uses.  It is equivalent to -Wnormalized.

       Unfortunately, there are some characters allowed in identifiers by
       ISO C and ISO C++ that, when turned into NFC, are not allowed in
       identifiers.  That is, there's no way to use these symbols in
       portable ISO C or C++ and have all your identifiers in NFC.
       -Wnormalized=id suppresses the warning for these characters.  It is
       hoped that future versions of the standards involved will correct
       this, which is why this option is not the default.

       You can switch the warning off for all characters by writing
       -Wnormalized=none or -Wno-normalized.  You should only do this if
       you are using some other normalization scheme (like "D"), because
       otherwise you can easily create bugs that are literally impossible
       to see.

       Some characters in ISO 10646 have distinct meanings but look
       identical in some fonts or display methodologies, especially once
       formatting has been applied.  For instance "\u207F", "SUPERSCRIPT
       LATIN SMALL LETTER N", displays just like a regular "n" that has
       been placed in a superscript.  ISO 10646 defines the NFKC
       normalization scheme to convert all these into a standard form as
       well, and GCC warns if your code is not in NFKC if you use
       -Wnormalized=nfkc.  This warning is comparable to warning about
       every identifier that contains the letter O because it might be
       confused with the digit 0, and so is not the default, but may be
       useful as a local coding convention if the programming environment
       cannot be fixed to display these characters distinctly.

   -Wno-deprecated
       Do not warn about usage of deprecated features.

   -Wno-deprecated-declarations
       Do not warn about uses of functions, variables, and types marked as
       deprecated by using the "deprecated" attribute.

   -Wno-overflow
       Do not warn about compile-time overflow in constant expressions.

   -Wno-odr
       Warn about One Definition Rule violations during link-time
       optimization.  Requires -flto-odr-type-merging to be enabled.
       Enabled by default.

   -Wopenmp-simd
       Warn if the vectorizer cost model overrides the OpenMP or the Cilk
       Plus simd directive set by user.  The -fsimd-cost-model=unlimited
       option can be used to relax the cost model.

   -Woverride-init (C and Objective-C only)
       Warn if an initialized field without side effects is overridden
       when using designated initializers.

       This warning is included in -Wextra.  To get other -Wextra warnings
       without this one, use -Wextra -Wno-override-init.

   -Woverride-init-side-effects (C and Objective-C only)
       Warn if an initialized field with side effects is overridden when
       using designated initializers.  This warning is enabled by default.

   -Wpacked
       Warn if a structure is given the packed attribute, but the packed
       attribute has no effect on the layout or size of the structure.
       Such structures may be mis-aligned for little benefit.  For
       instance, in this code, the variable "f.x" in "struct bar" is
       misaligned even though "struct bar" does not itself have the packed
       attribute:

               struct foo {
                 int x;
                 char a, b, c, d;
               } __attribute__((packed));
               struct bar {
                 char z;
                 struct foo f;
               };

   -Wpacked-bitfield-compat
       The 4.1, 4.2 and 4.3 series of GCC ignore the "packed" attribute on
       bit-fields of type "char".  This has been fixed in GCC 4.4 but the
       change can lead to differences in the structure layout.  GCC
       informs you when the offset of such a field has changed in GCC 4.4.
       For example there is no longer a 4-bit padding between field "a"
       and "b" in this structure:

               struct foo
               {
                 char a:4;
                 char b:8;
               } __attribute__ ((packed));

       This warning is enabled by default.  Use
       -Wno-packed-bitfield-compat to disable this warning.

   -Wpadded
       Warn if padding is included in a structure, either to align an
       element of the structure or to align the whole structure.
       Sometimes when this happens it is possible to rearrange the fields
       of the structure to reduce the padding and so make the structure
       smaller.

   -Wredundant-decls
       Warn if anything is declared more than once in the same scope, even
       in cases where multiple declaration is valid and changes nothing.

   -Wnested-externs (C and Objective-C only)
       Warn if an "extern" declaration is encountered within a function.

   -Wno-inherited-variadic-ctor
       Suppress warnings about use of C++11 inheriting constructors when
       the base class inherited from has a C variadic constructor; the
       warning is on by default because the ellipsis is not inherited.

   -Winline
       Warn if a function that is declared as inline cannot be inlined.
       Even with this option, the compiler does not warn about failures to
       inline functions declared in system headers.

       The compiler uses a variety of heuristics to determine whether or
       not to inline a function.  For example, the compiler takes into
       account the size of the function being inlined and the amount of
       inlining that has already been done in the current function.
       Therefore, seemingly insignificant changes in the source program
       can cause the warnings produced by -Winline to appear or disappear.

   -Wno-invalid-offsetof (C++ and Objective-C++ only)
       Suppress warnings from applying the "offsetof" macro to a non-POD
       type.  According to the 2014 ISO C++ standard, applying "offsetof"
       to a non-standard-layout type is undefined.  In existing C++
       implementations, however, "offsetof" typically gives meaningful
       results.  This flag is for users who are aware that they are
       writing nonportable code and who have deliberately chosen to ignore
       the warning about it.

       The restrictions on "offsetof" may be relaxed in a future version
       of the C++ standard.

   -Wno-int-to-pointer-cast
       Suppress warnings from casts to pointer type of an integer of a
       different size. In C++, casting to a pointer type of smaller size
       is an error. Wint-to-pointer-cast is enabled by default.

   -Wno-pointer-to-int-cast (C and Objective-C only)
       Suppress warnings from casts from a pointer to an integer type of a
       different size.

   -Winvalid-pch
       Warn if a precompiled header is found in the search path but can't
       be used.

   -Wlong-long
       Warn if "long long" type is used.  This is enabled by either
       -Wpedantic or -Wtraditional in ISO C90 and C++98 modes.  To inhibit
       the warning messages, use -Wno-long-long.

   -Wvariadic-macros
       Warn if variadic macros are used in ISO C90 mode, or if the GNU
       alternate syntax is used in ISO C99 mode.  This is enabled by
       either -Wpedantic or -Wtraditional.  To inhibit the warning
       messages, use -Wno-variadic-macros.

   -Wvarargs
       Warn upon questionable usage of the macros used to handle variable
       arguments like "va_start".  This is default.  To inhibit the
       warning messages, use -Wno-varargs.

   -Wvector-operation-performance
       Warn if vector operation is not implemented via SIMD capabilities
       of the architecture.  Mainly useful for the performance tuning.
       Vector operation can be implemented "piecewise", which means that
       the scalar operation is performed on every vector element; "in
       parallel", which means that the vector operation is implemented
       using scalars of wider type, which normally is more performance
       efficient; and "as a single scalar", which means that vector fits
       into a scalar type.

   -Wno-virtual-move-assign
       Suppress warnings about inheriting from a virtual base with a non-
       trivial C++11 move assignment operator.  This is dangerous because
       if the virtual base is reachable along more than one path, it is
       moved multiple times, which can mean both objects end up in the
       moved-from state.  If the move assignment operator is written to
       avoid moving from a moved-from object, this warning can be
       disabled.

   -Wvla
       Warn if variable length array is used in the code.  -Wno-vla
       prevents the -Wpedantic warning of the variable length array.

   -Wvolatile-register-var
       Warn if a register variable is declared volatile.  The volatile
       modifier does not inhibit all optimizations that may eliminate
       reads and/or writes to register variables.  This warning is enabled
       by -Wall.

   -Wdisabled-optimization
       Warn if a requested optimization pass is disabled.  This warning
       does not generally indicate that there is anything wrong with your
       code; it merely indicates that GCC's optimizers are unable to
       handle the code effectively.  Often, the problem is that your code
       is too big or too complex; GCC refuses to optimize programs when
       the optimization itself is likely to take inordinate amounts of
       time.

   -Wpointer-sign (C and Objective-C only)
       Warn for pointer argument passing or assignment with different
       signedness.  This option is only supported for C and Objective-C.
       It is implied by -Wall and by -Wpedantic, which can be disabled
       with -Wno-pointer-sign.

   -Wstack-protector
       This option is only active when -fstack-protector is active.  It
       warns about functions that are not protected against stack
       smashing.

   -Woverlength-strings
       Warn about string constants that are longer than the "minimum
       maximum" length specified in the C standard.  Modern compilers
       generally allow string constants that are much longer than the
       standard's minimum limit, but very portable programs should avoid
       using longer strings.

       The limit applies after string constant concatenation, and does not
       count the trailing NUL.  In C90, the limit was 509 characters; in
       C99, it was raised to 4095.  C++98 does not specify a normative
       minimum maximum, so we do not diagnose overlength strings in C++.

       This option is implied by -Wpedantic, and can be disabled with
       -Wno-overlength-strings.

   -Wunsuffixed-float-constants (C and Objective-C only)
       Issue a warning for any floating constant that does not have a
       suffix.  When used together with -Wsystem-headers it warns about
       such constants in system header files.  This can be useful when
       preparing code to use with the "FLOAT_CONST_DECIMAL64" pragma from
       the decimal floating-point extension to C99.

   -Wno-designated-init (C and Objective-C only)
       Suppress warnings when a positional initializer is used to
       initialize a structure that has been marked with the
       "designated_init" attribute.

   -Whsa
       Issue a warning when HSAIL cannot be emitted for the compiled
       function or OpenMP construct.

   Options for Debugging Your Program
   To tell GCC to emit extra information for use by a debugger, in almost
   all cases you need only to add -g to your other options.

   GCC allows you to use -g with -O.  The shortcuts taken by optimized
   code may occasionally be surprising: some variables you declared may
   not exist at all; flow of control may briefly move where you did not
   expect it; some statements may not be executed because they compute
   constant results or their values are already at hand; some statements
   may execute in different places because they have been moved out of
   loops.  Nevertheless it is possible to debug optimized output.  This
   makes it reasonable to use the optimizer for programs that might have
   bugs.

   If you are not using some other optimization option, consider using -Og
   with -g.  With no -O option at all, some compiler passes that collect
   information useful for debugging do not run at all, so that -Og may
   result in a better debugging experience.

   -g  Produce debugging information in the operating system's native
       format (stabs, COFF, XCOFF, or DWARF).  GDB can work with this
       debugging information.

       On most systems that use stabs format, -g enables use of extra
       debugging information that only GDB can use; this extra information
       makes debugging work better in GDB but probably makes other
       debuggers crash or refuse to read the program.  If you want to
       control for certain whether to generate the extra information, use
       -gstabs+, -gstabs, -gxcoff+, -gxcoff, or -gvms (see below).

   -ggdb
       Produce debugging information for use by GDB.  This means to use
       the most expressive format available (DWARF, stabs, or the native
       format if neither of those are supported), including GDB extensions
       if at all possible.

   -gdwarf
   -gdwarf-version
       Produce debugging information in DWARF format (if that is
       supported).  The value of version may be either 2, 3, 4 or 5; the
       default version for most targets is 4.  DWARF Version 5 is only
       experimental.

       Note that with DWARF Version 2, some ports require and always use
       some non-conflicting DWARF 3 extensions in the unwind tables.

       Version 4 may require GDB 7.0 and -fvar-tracking-assignments for
       maximum benefit.

       GCC no longer supports DWARF Version 1, which is substantially
       different than Version 2 and later.  For historical reasons, some
       other DWARF-related options (including -feliminate-dwarf2-dups and
       -fno-dwarf2-cfi-asm) retain a reference to DWARF Version 2 in their
       names, but apply to all currently-supported versions of DWARF.

   -gstabs
       Produce debugging information in stabs format (if that is
       supported), without GDB extensions.  This is the format used by DBX
       on most BSD systems.  On MIPS, Alpha and System V Release 4 systems
       this option produces stabs debugging output that is not understood
       by DBX or SDB.  On System V Release 4 systems this option requires
       the GNU assembler.

   -gstabs+
       Produce debugging information in stabs format (if that is
       supported), using GNU extensions understood only by the GNU
       debugger (GDB).  The use of these extensions is likely to make
       other debuggers crash or refuse to read the program.

   -gcoff
       Produce debugging information in COFF format (if that is
       supported).  This is the format used by SDB on most System V
       systems prior to System V Release 4.

   -gxcoff
       Produce debugging information in XCOFF format (if that is
       supported).  This is the format used by the DBX debugger on IBM
       RS/6000 systems.

   -gxcoff+
       Produce debugging information in XCOFF format (if that is
       supported), using GNU extensions understood only by the GNU
       debugger (GDB).  The use of these extensions is likely to make
       other debuggers crash or refuse to read the program, and may cause
       assemblers other than the GNU assembler (GAS) to fail with an
       error.

   -gvms
       Produce debugging information in Alpha/VMS debug format (if that is
       supported).  This is the format used by DEBUG on Alpha/VMS systems.

   -glevel
   -ggdblevel
   -gstabslevel
   -gcofflevel
   -gxcofflevel
   -gvmslevel
       Request debugging information and also use level to specify how
       much information.  The default level is 2.

       Level 0 produces no debug information at all.  Thus, -g0 negates
       -g.

       Level 1 produces minimal information, enough for making backtraces
       in parts of the program that you don't plan to debug.  This
       includes descriptions of functions and external variables, and line
       number tables, but no information about local variables.

       Level 3 includes extra information, such as all the macro
       definitions present in the program.  Some debuggers support macro
       expansion when you use -g3.

       -gdwarf does not accept a concatenated debug level, to avoid
       confusion with -gdwarf-level.  Instead use an additional -glevel
       option to change the debug level for DWARF.

   -feliminate-unused-debug-symbols
       Produce debugging information in stabs format (if that is
       supported), for only symbols that are actually used.

   -femit-class-debug-always
       Instead of emitting debugging information for a C++ class in only
       one object file, emit it in all object files using the class.  This
       option should be used only with debuggers that are unable to handle
       the way GCC normally emits debugging information for classes
       because using this option increases the size of debugging
       information by as much as a factor of two.

   -fno-merge-debug-strings
       Direct the linker to not merge together strings in the debugging
       information that are identical in different object files.  Merging
       is not supported by all assemblers or linkers.  Merging decreases
       the size of the debug information in the output file at the cost of
       increasing link processing time.  Merging is enabled by default.

   -fdebug-prefix-map=old=new
       When compiling files in directory old, record debugging information
       describing them as in new instead.

   -fvar-tracking
       Run variable tracking pass.  It computes where variables are stored
       at each position in code.  Better debugging information is then
       generated (if the debugging information format supports this
       information).

       It is enabled by default when compiling with optimization (-Os, -O,
       -O2, ...), debugging information (-g) and the debug info format
       supports it.

   -fvar-tracking-assignments
       Annotate assignments to user variables early in the compilation and
       attempt to carry the annotations over throughout the compilation
       all the way to the end, in an attempt to improve debug information
       while optimizing.  Use of -gdwarf-4 is recommended along with it.

       It can be enabled even if var-tracking is disabled, in which case
       annotations are created and maintained, but discarded at the end.
       By default, this flag is enabled together with -fvar-tracking,
       except when selective scheduling is enabled.

   -gsplit-dwarf
       Separate as much DWARF debugging information as possible into a
       separate output file with the extension .dwo.  This option allows
       the build system to avoid linking files with debug information.  To
       be useful, this option requires a debugger capable of reading .dwo
       files.

   -gpubnames
       Generate DWARF ".debug_pubnames" and ".debug_pubtypes" sections.

   -ggnu-pubnames
       Generate ".debug_pubnames" and ".debug_pubtypes" sections in a
       format suitable for conversion into a GDB index.  This option is
       only useful with a linker that can produce GDB index version 7.

   -fdebug-types-section
       When using DWARF Version 4 or higher, type DIEs can be put into
       their own ".debug_types" section instead of making them part of the
       ".debug_info" section.  It is more efficient to put them in a
       separate comdat sections since the linker can then remove
       duplicates.  But not all DWARF consumers support ".debug_types"
       sections yet and on some objects ".debug_types" produces larger
       instead of smaller debugging information.

   -grecord-gcc-switches
   -gno-record-gcc-switches
       This switch causes the command-line options used to invoke the
       compiler that may affect code generation to be appended to the
       DW_AT_producer attribute in DWARF debugging information.  The
       options are concatenated with spaces separating them from each
       other and from the compiler version.  It is enabled by default.
       See also -frecord-gcc-switches for another way of storing compiler
       options into the object file.

   -gstrict-dwarf
       Disallow using extensions of later DWARF standard version than
       selected with -gdwarf-version.  On most targets using non-
       conflicting DWARF extensions from later standard versions is
       allowed.

   -gno-strict-dwarf
       Allow using extensions of later DWARF standard version than
       selected with -gdwarf-version.

   -gz[=type]
       Produce compressed debug sections in DWARF format, if that is
       supported.  If type is not given, the default type depends on the
       capabilities of the assembler and linker used.  type may be one of
       none (don't compress debug sections), zlib (use zlib compression in
       ELF gABI format), or zlib-gnu (use zlib compression in traditional
       GNU format).  If the linker doesn't support writing compressed
       debug sections, the option is rejected.  Otherwise, if the
       assembler does not support them, -gz is silently ignored when
       producing object files.

   -feliminate-dwarf2-dups
       Compress DWARF debugging information by eliminating duplicated
       information about each symbol.  This option only makes sense when
       generating DWARF debugging information.

   -femit-struct-debug-baseonly
       Emit debug information for struct-like types only when the base
       name of the compilation source file matches the base name of file
       in which the struct is defined.

       This option substantially reduces the size of debugging
       information, but at significant potential loss in type information
       to the debugger.  See -femit-struct-debug-reduced for a less
       aggressive option.  See -femit-struct-debug-detailed for more
       detailed control.

       This option works only with DWARF debug output.

   -femit-struct-debug-reduced
       Emit debug information for struct-like types only when the base
       name of the compilation source file matches the base name of file
       in which the type is defined, unless the struct is a template or
       defined in a system header.

       This option significantly reduces the size of debugging
       information, with some potential loss in type information to the
       debugger.  See -femit-struct-debug-baseonly for a more aggressive
       option.  See -femit-struct-debug-detailed for more detailed
       control.

       This option works only with DWARF debug output.

   -femit-struct-debug-detailed[=spec-list]
       Specify the struct-like types for which the compiler generates
       debug information.  The intent is to reduce duplicate struct debug
       information between different object files within the same program.

       This option is a detailed version of -femit-struct-debug-reduced
       and -femit-struct-debug-baseonly, which serves for most needs.

       A specification has the
       syntax[dir:|ind:][ord:|gen:](any|sys|base|none)

       The optional first word limits the specification to structs that
       are used directly (dir:) or used indirectly (ind:).  A struct type
       is used directly when it is the type of a variable, member.
       Indirect uses arise through pointers to structs.  That is, when use
       of an incomplete struct is valid, the use is indirect.  An example
       is struct one direct; struct two * indirect;.

       The optional second word limits the specification to ordinary
       structs (ord:) or generic structs (gen:).  Generic structs are a
       bit complicated to explain.  For C++, these are non-explicit
       specializations of template classes, or non-template classes within
       the above.  Other programming languages have generics, but
       -femit-struct-debug-detailed does not yet implement them.

       The third word specifies the source files for those structs for
       which the compiler should emit debug information.  The values none
       and any have the normal meaning.  The value base means that the
       base of name of the file in which the type declaration appears must
       match the base of the name of the main compilation file.  In
       practice, this means that when compiling foo.c, debug information
       is generated for types declared in that file and foo.h, but not
       other header files.  The value sys means those types satisfying
       base or declared in system or compiler headers.

       You may need to experiment to determine the best settings for your
       application.

       The default is -femit-struct-debug-detailed=all.

       This option works only with DWARF debug output.

   -fno-dwarf2-cfi-asm
       Emit DWARF unwind info as compiler generated ".eh_frame" section
       instead of using GAS ".cfi_*" directives.

   -fno-eliminate-unused-debug-types
       Normally, when producing DWARF output, GCC avoids producing debug
       symbol output for types that are nowhere used in the source file
       being compiled.  Sometimes it is useful to have GCC emit debugging
       information for all types declared in a compilation unit,
       regardless of whether or not they are actually used in that
       compilation unit, for example if, in the debugger, you want to cast
       a value to a type that is not actually used in your program (but is
       declared).  More often, however, this results in a significant
       amount of wasted space.

   Options That Control Optimization
   These options control various sorts of optimizations.

   Without any optimization option, the compiler's goal is to reduce the
   cost of compilation and to make debugging produce the expected results.
   Statements are independent: if you stop the program with a breakpoint
   between statements, you can then assign a new value to any variable or
   change the program counter to any other statement in the function and
   get exactly the results you expect from the source code.

   Turning on optimization flags makes the compiler attempt to improve the
   performance and/or code size at the expense of compilation time and
   possibly the ability to debug the program.

   The compiler performs optimization based on the knowledge it has of the
   program.  Compiling multiple files at once to a single output file mode
   allows the compiler to use information gained from all of the files
   when compiling each of them.

   Not all optimizations are controlled directly by a flag.  Only
   optimizations that have a flag are listed in this section.

   Most optimizations are only enabled if an -O level is set on the
   command line.  Otherwise they are disabled, even if individual
   optimization flags are specified.

   Depending on the target and how GCC was configured, a slightly
   different set of optimizations may be enabled at each -O level than
   those listed here.  You can invoke GCC with -Q --help=optimizers to
   find out the exact set of optimizations that are enabled at each level.

   -O
   -O1 Optimize.  Optimizing compilation takes somewhat more time, and a
       lot more memory for a large function.

       With -O, the compiler tries to reduce code size and execution time,
       without performing any optimizations that take a great deal of
       compilation time.

       -O turns on the following optimization flags:

       -fauto-inc-dec -fbranch-count-reg -fcombine-stack-adjustments
       -fcompare-elim -fcprop-registers -fdce -fdefer-pop -fdelayed-branch
       -fdse -fforward-propagate -fguess-branch-probability
       -fif-conversion2 -fif-conversion -finline-functions-called-once
       -fipa-pure-const -fipa-profile -fipa-reference -fmerge-constants
       -fmove-loop-invariants -freorder-blocks -fshrink-wrap
       -fsplit-wide-types -fssa-backprop -fssa-phiopt -ftree-bit-ccp
       -ftree-ccp -ftree-ch -ftree-coalesce-vars -ftree-copy-prop
       -ftree-dce -ftree-dominator-opts -ftree-dse -ftree-forwprop
       -ftree-fre -ftree-phiprop -ftree-sink -ftree-slsr -ftree-sra
       -ftree-pta -ftree-ter -funit-at-a-time

       -O also turns on -fomit-frame-pointer on machines where doing so
       does not interfere with debugging.

   -O2 Optimize even more.  GCC performs nearly all supported
       optimizations that do not involve a space-speed tradeoff.  As
       compared to -O, this option increases both compilation time and the
       performance of the generated code.

       -O2 turns on all optimization flags specified by -O.  It also turns
       on the following optimization flags: -fthread-jumps
       -falign-functions  -falign-jumps -falign-loops  -falign-labels
       -fcaller-saves -fcrossjumping -fcse-follow-jumps  -fcse-skip-blocks
       -fdelete-null-pointer-checks -fdevirtualize
       -fdevirtualize-speculatively -fexpensive-optimizations -fgcse
       -fgcse-lm -fhoist-adjacent-loads -finline-small-functions
       -findirect-inlining -fipa-cp -fipa-cp-alignment -fipa-sra -fipa-icf
       -fisolate-erroneous-paths-dereference -flra-remat
       -foptimize-sibling-calls -foptimize-strlen -fpartial-inlining
       -fpeephole2 -freorder-blocks-algorithm=stc
       -freorder-blocks-and-partition -freorder-functions
       -frerun-cse-after-loop -fsched-interblock  -fsched-spec
       -fschedule-insns  -fschedule-insns2 -fstrict-aliasing
       -fstrict-overflow -ftree-builtin-call-dce -ftree-switch-conversion
       -ftree-tail-merge -ftree-pre -ftree-vrp -fipa-ra

       Please note the warning under -fgcse about invoking -O2 on programs
       that use computed gotos.

       NOTE: In Ubuntu 8.10 and later versions, -D_FORTIFY_SOURCE=2 is set
       by default, and is activated when -O is set to 2 or higher.  This
       enables additional compile-time and run-time checks for several
       libc functions.  To disable, specify either -U_FORTIFY_SOURCE or
       -D_FORTIFY_SOURCE=0.

   -O3 Optimize yet more.  -O3 turns on all optimizations specified by -O2
       and also turns on the -finline-functions, -funswitch-loops,
       -fpredictive-commoning, -fgcse-after-reload, -ftree-loop-vectorize,
       -ftree-loop-distribute-patterns, -fsplit-paths
       -ftree-slp-vectorize, -fvect-cost-model, -ftree-partial-pre and
       -fipa-cp-clone options.

   -O0 Reduce compilation time and make debugging produce the expected
       results.  This is the default.

   -Os Optimize for size.  -Os enables all -O2 optimizations that do not
       typically increase code size.  It also performs further
       optimizations designed to reduce code size.

       -Os disables the following optimization flags: -falign-functions
       -falign-jumps  -falign-loops -falign-labels  -freorder-blocks
       -freorder-blocks-algorithm=stc -freorder-blocks-and-partition
       -fprefetch-loop-arrays

   -Ofast
       Disregard strict standards compliance.  -Ofast enables all -O3
       optimizations.  It also enables optimizations that are not valid
       for all standard-compliant programs.  It turns on -ffast-math and
       the Fortran-specific -fno-protect-parens and -fstack-arrays.

   -Og Optimize debugging experience.  -Og enables optimizations that do
       not interfere with debugging. It should be the optimization level
       of choice for the standard edit-compile-debug cycle, offering a
       reasonable level of optimization while maintaining fast compilation
       and a good debugging experience.

   If you use multiple -O options, with or without level numbers, the last
   such option is the one that is effective.

   Options of the form -fflag specify machine-independent flags.  Most
   flags have both positive and negative forms; the negative form of -ffoo
   is -fno-foo.  In the table below, only one of the forms is listed---the
   one you typically use.  You can figure out the other form by either
   removing no- or adding it.

   The following options control specific optimizations.  They are either
   activated by -O options or are related to ones that are.  You can use
   the following flags in the rare cases when "fine-tuning" of
   optimizations to be performed is desired.

   -fno-defer-pop
       Always pop the arguments to each function call as soon as that
       function returns.  For machines that must pop arguments after a
       function call, the compiler normally lets arguments accumulate on
       the stack for several function calls and pops them all at once.

       Disabled at levels -O, -O2, -O3, -Os.

   -fforward-propagate
       Perform a forward propagation pass on RTL.  The pass tries to
       combine two instructions and checks if the result can be
       simplified.  If loop unrolling is active, two passes are performed
       and the second is scheduled after loop unrolling.

       This option is enabled by default at optimization levels -O, -O2,
       -O3, -Os.

   -ffp-contract=style
       -ffp-contract=off disables floating-point expression contraction.
       -ffp-contract=fast enables floating-point expression contraction
       such as forming of fused multiply-add operations if the target has
       native support for them.  -ffp-contract=on enables floating-point
       expression contraction if allowed by the language standard.  This
       is currently not implemented and treated equal to
       -ffp-contract=off.

       The default is -ffp-contract=fast.

   -fomit-frame-pointer
       Don't keep the frame pointer in a register for functions that don't
       need one.  This avoids the instructions to save, set up and restore
       frame pointers; it also makes an extra register available in many
       functions.  It also makes debugging impossible on some machines.

       On some machines, such as the VAX, this flag has no effect, because
       the standard calling sequence automatically handles the frame
       pointer and nothing is saved by pretending it doesn't exist.  The
       machine-description macro "FRAME_POINTER_REQUIRED" controls whether
       a target machine supports this flag.

       The default setting (when not optimizing for size) for 32-bit
       GNU/Linux x86 and 32-bit Darwin x86 targets is
       -fomit-frame-pointer.  You can configure GCC with the
       --enable-frame-pointer configure option to change the default.

       Enabled at levels -O, -O2, -O3, -Os.

   -foptimize-sibling-calls
       Optimize sibling and tail recursive calls.

       Enabled at levels -O2, -O3, -Os.

   -foptimize-strlen
       Optimize various standard C string functions (e.g. "strlen",
       "strchr" or "strcpy") and their "_FORTIFY_SOURCE" counterparts into
       faster alternatives.

       Enabled at levels -O2, -O3.

   -fno-inline
       Do not expand any functions inline apart from those marked with the
       "always_inline" attribute.  This is the default when not
       optimizing.

       Single functions can be exempted from inlining by marking them with
       the "noinline" attribute.

   -finline-small-functions
       Integrate functions into their callers when their body is smaller
       than expected function call code (so overall size of program gets
       smaller).  The compiler heuristically decides which functions are
       simple enough to be worth integrating in this way.  This inlining
       applies to all functions, even those not declared inline.

       Enabled at level -O2.

   -findirect-inlining
       Inline also indirect calls that are discovered to be known at
       compile time thanks to previous inlining.  This option has any
       effect only when inlining itself is turned on by the
       -finline-functions or -finline-small-functions options.

       Enabled at level -O2.

   -finline-functions
       Consider all functions for inlining, even if they are not declared
       inline.  The compiler heuristically decides which functions are
       worth integrating in this way.

       If all calls to a given function are integrated, and the function
       is declared "static", then the function is normally not output as
       assembler code in its own right.

       Enabled at level -O3.

   -finline-functions-called-once
       Consider all "static" functions called once for inlining into their
       caller even if they are not marked "inline".  If a call to a given
       function is integrated, then the function is not output as
       assembler code in its own right.

       Enabled at levels -O1, -O2, -O3 and -Os.

   -fearly-inlining
       Inline functions marked by "always_inline" and functions whose body
       seems smaller than the function call overhead early before doing
       -fprofile-generate instrumentation and real inlining pass.  Doing
       so makes profiling significantly cheaper and usually inlining
       faster on programs having large chains of nested wrapper functions.

       Enabled by default.

   -fipa-sra
       Perform interprocedural scalar replacement of aggregates, removal
       of unused parameters and replacement of parameters passed by
       reference by parameters passed by value.

       Enabled at levels -O2, -O3 and -Os.

   -finline-limit=n
       By default, GCC limits the size of functions that can be inlined.
       This flag allows coarse control of this limit.  n is the size of
       functions that can be inlined in number of pseudo instructions.

       Inlining is actually controlled by a number of parameters, which
       may be specified individually by using --param name=value.  The
       -finline-limit=n option sets some of these parameters as follows:

       max-inline-insns-single
           is set to n/2.

       max-inline-insns-auto
           is set to n/2.

       See below for a documentation of the individual parameters
       controlling inlining and for the defaults of these parameters.

       Note: there may be no value to -finline-limit that results in
       default behavior.

       Note: pseudo instruction represents, in this particular context, an
       abstract measurement of function's size.  In no way does it
       represent a count of assembly instructions and as such its exact
       meaning might change from one release to an another.

   -fno-keep-inline-dllexport
       This is a more fine-grained version of -fkeep-inline-functions,
       which applies only to functions that are declared using the
       "dllexport" attribute or declspec

   -fkeep-inline-functions
       In C, emit "static" functions that are declared "inline" into the
       object file, even if the function has been inlined into all of its
       callers.  This switch does not affect functions using the "extern
       inline" extension in GNU C90.  In C++, emit any and all inline
       functions into the object file.

   -fkeep-static-functions
       Emit "static" functions into the object file, even if the function
       is never used.

   -fkeep-static-consts
       Emit variables declared "static const" when optimization isn't
       turned on, even if the variables aren't referenced.

       GCC enables this option by default.  If you want to force the
       compiler to check if a variable is referenced, regardless of
       whether or not optimization is turned on, use the
       -fno-keep-static-consts option.

   -fmerge-constants
       Attempt to merge identical constants (string constants and
       floating-point constants) across compilation units.

       This option is the default for optimized compilation if the
       assembler and linker support it.  Use -fno-merge-constants to
       inhibit this behavior.

       Enabled at levels -O, -O2, -O3, -Os.

   -fmerge-all-constants
       Attempt to merge identical constants and identical variables.

       This option implies -fmerge-constants.  In addition to
       -fmerge-constants this considers e.g. even constant initialized
       arrays or initialized constant variables with integral or floating-
       point types.  Languages like C or C++ require each variable,
       including multiple instances of the same variable in recursive
       calls, to have distinct locations, so using this option results in
       non-conforming behavior.

   -fmodulo-sched
       Perform swing modulo scheduling immediately before the first
       scheduling pass.  This pass looks at innermost loops and reorders
       their instructions by overlapping different iterations.

   -fmodulo-sched-allow-regmoves
       Perform more aggressive SMS-based modulo scheduling with register
       moves allowed.  By setting this flag certain anti-dependences edges
       are deleted, which triggers the generation of reg-moves based on
       the life-range analysis.  This option is effective only with
       -fmodulo-sched enabled.

   -fno-branch-count-reg
       Avoid running a pass scanning for opportunities to use "decrement
       and branch" instructions on a count register instead of generating
       sequences of instructions that decrement a register, compare it
       against zero, and then branch based upon the result.  This option
       is only meaningful on architectures that support such instructions,
       which include x86, PowerPC, IA-64 and S/390.  Note that the
       -fno-branch-count-reg option doesn't remove the decrement and
       branch instructions from the generated instruction stream
       introduced by other optimization passes.

       Enabled by default at -O1 and higher.

       The default is -fbranch-count-reg.

   -fno-function-cse
       Do not put function addresses in registers; make each instruction
       that calls a constant function contain the function's address
       explicitly.

       This option results in less efficient code, but some strange hacks
       that alter the assembler output may be confused by the
       optimizations performed when this option is not used.

       The default is -ffunction-cse

   -fno-zero-initialized-in-bss
       If the target supports a BSS section, GCC by default puts variables
       that are initialized to zero into BSS.  This can save space in the
       resulting code.

       This option turns off this behavior because some programs
       explicitly rely on variables going to the data section---e.g., so
       that the resulting executable can find the beginning of that
       section and/or make assumptions based on that.

       The default is -fzero-initialized-in-bss.

   -fthread-jumps
       Perform optimizations that check to see if a jump branches to a
       location where another comparison subsumed by the first is found.
       If so, the first branch is redirected to either the destination of
       the second branch or a point immediately following it, depending on
       whether the condition is known to be true or false.

       Enabled at levels -O2, -O3, -Os.

   -fsplit-wide-types
       When using a type that occupies multiple registers, such as "long
       long" on a 32-bit system, split the registers apart and allocate
       them independently.  This normally generates better code for those
       types, but may make debugging more difficult.

       Enabled at levels -O, -O2, -O3, -Os.

   -fcse-follow-jumps
       In common subexpression elimination (CSE), scan through jump
       instructions when the target of the jump is not reached by any
       other path.  For example, when CSE encounters an "if" statement
       with an "else" clause, CSE follows the jump when the condition
       tested is false.

       Enabled at levels -O2, -O3, -Os.

   -fcse-skip-blocks
       This is similar to -fcse-follow-jumps, but causes CSE to follow
       jumps that conditionally skip over blocks.  When CSE encounters a
       simple "if" statement with no else clause, -fcse-skip-blocks causes
       CSE to follow the jump around the body of the "if".

       Enabled at levels -O2, -O3, -Os.

   -frerun-cse-after-loop
       Re-run common subexpression elimination after loop optimizations
       are performed.

       Enabled at levels -O2, -O3, -Os.

   -fgcse
       Perform a global common subexpression elimination pass.  This pass
       also performs global constant and copy propagation.

       Note: When compiling a program using computed gotos, a GCC
       extension, you may get better run-time performance if you disable
       the global common subexpression elimination pass by adding
       -fno-gcse to the command line.

       Enabled at levels -O2, -O3, -Os.

   -fgcse-lm
       When -fgcse-lm is enabled, global common subexpression elimination
       attempts to move loads that are only killed by stores into
       themselves.  This allows a loop containing a load/store sequence to
       be changed to a load outside the loop, and a copy/store within the
       loop.

       Enabled by default when -fgcse is enabled.

   -fgcse-sm
       When -fgcse-sm is enabled, a store motion pass is run after global
       common subexpression elimination.  This pass attempts to move
       stores out of loops.  When used in conjunction with -fgcse-lm,
       loops containing a load/store sequence can be changed to a load
       before the loop and a store after the loop.

       Not enabled at any optimization level.

   -fgcse-las
       When -fgcse-las is enabled, the global common subexpression
       elimination pass eliminates redundant loads that come after stores
       to the same memory location (both partial and full redundancies).

       Not enabled at any optimization level.

   -fgcse-after-reload
       When -fgcse-after-reload is enabled, a redundant load elimination
       pass is performed after reload.  The purpose of this pass is to
       clean up redundant spilling.

   -faggressive-loop-optimizations
       This option tells the loop optimizer to use language constraints to
       derive bounds for the number of iterations of a loop.  This assumes
       that loop code does not invoke undefined behavior by for example
       causing signed integer overflows or out-of-bound array accesses.
       The bounds for the number of iterations of a loop are used to guide
       loop unrolling and peeling and loop exit test optimizations.  This
       option is enabled by default.

   -funsafe-loop-optimizations
       This option tells the loop optimizer to assume that loop indices do
       not overflow, and that loops with nontrivial exit condition are not
       infinite.  This enables a wider range of loop optimizations even if
       the loop optimizer itself cannot prove that these assumptions are
       valid.  If you use -Wunsafe-loop-optimizations, the compiler warns
       you if it finds this kind of loop.

   -funconstrained-commons
       This option tells the compiler that variables declared in common
       blocks (e.g. Fortran) may later be overridden with longer trailing
       arrays. This prevents certain optimizations that depend on knowing
       the array bounds.

   -fcrossjumping
       Perform cross-jumping transformation.  This transformation unifies
       equivalent code and saves code size.  The resulting code may or may
       not perform better than without cross-jumping.

       Enabled at levels -O2, -O3, -Os.

   -fauto-inc-dec
       Combine increments or decrements of addresses with memory accesses.
       This pass is always skipped on architectures that do not have
       instructions to support this.  Enabled by default at -O and higher
       on architectures that support this.

   -fdce
       Perform dead code elimination (DCE) on RTL.  Enabled by default at
       -O and higher.

   -fdse
       Perform dead store elimination (DSE) on RTL.  Enabled by default at
       -O and higher.

   -fif-conversion
       Attempt to transform conditional jumps into branch-less
       equivalents.  This includes use of conditional moves, min, max, set
       flags and abs instructions, and some tricks doable by standard
       arithmetics.  The use of conditional execution on chips where it is
       available is controlled by -fif-conversion2.

       Enabled at levels -O, -O2, -O3, -Os.

   -fif-conversion2
       Use conditional execution (where available) to transform
       conditional jumps into branch-less equivalents.

       Enabled at levels -O, -O2, -O3, -Os.

   -fdeclone-ctor-dtor
       The C++ ABI requires multiple entry points for constructors and
       destructors: one for a base subobject, one for a complete object,
       and one for a virtual destructor that calls operator delete
       afterwards.  For a hierarchy with virtual bases, the base and
       complete variants are clones, which means two copies of the
       function.  With this option, the base and complete variants are
       changed to be thunks that call a common implementation.

       Enabled by -Os.

   -fdelete-null-pointer-checks
       Assume that programs cannot safely dereference null pointers, and
       that no code or data element resides at address zero.  This option
       enables simple constant folding optimizations at all optimization
       levels.  In addition, other optimization passes in GCC use this
       flag to control global dataflow analyses that eliminate useless
       checks for null pointers; these assume that a memory access to
       address zero always results in a trap, so that if a pointer is
       checked after it has already been dereferenced, it cannot be null.

       Note however that in some environments this assumption is not true.
       Use -fno-delete-null-pointer-checks to disable this optimization
       for programs that depend on that behavior.

       This option is enabled by default on most targets.  On Nios II ELF,
       it defaults to off.  On AVR and CR16, this option is completely
       disabled.

       Passes that use the dataflow information are enabled independently
       at different optimization levels.

   -fdevirtualize
       Attempt to convert calls to virtual functions to direct calls.
       This is done both within a procedure and interprocedurally as part
       of indirect inlining (-findirect-inlining) and interprocedural
       constant propagation (-fipa-cp).  Enabled at levels -O2, -O3, -Os.

   -fdevirtualize-speculatively
       Attempt to convert calls to virtual functions to speculative direct
       calls.  Based on the analysis of the type inheritance graph,
       determine for a given call the set of likely targets. If the set is
       small, preferably of size 1, change the call into a conditional
       deciding between direct and indirect calls.  The speculative calls
       enable more optimizations, such as inlining.  When they seem
       useless after further optimization, they are converted back into
       original form.

   -fdevirtualize-at-ltrans
       Stream extra information needed for aggressive devirtualization
       when running the link-time optimizer in local transformation mode.
       This option enables more devirtualization but significantly
       increases the size of streamed data. For this reason it is disabled
       by default.

   -fexpensive-optimizations
       Perform a number of minor optimizations that are relatively
       expensive.

       Enabled at levels -O2, -O3, -Os.

   -free
       Attempt to remove redundant extension instructions.  This is
       especially helpful for the x86-64 architecture, which implicitly
       zero-extends in 64-bit registers after writing to their lower
       32-bit half.

       Enabled for Alpha, AArch64 and x86 at levels -O2, -O3, -Os.

   -fno-lifetime-dse
       In C++ the value of an object is only affected by changes within
       its lifetime: when the constructor begins, the object has an
       indeterminate value, and any changes during the lifetime of the
       object are dead when the object is destroyed.  Normally dead store
       elimination will take advantage of this; if your code relies on the
       value of the object storage persisting beyond the lifetime of the
       object, you can use this flag to disable this optimization.  To
       preserve stores before the constructor starts (e.g. because your
       operator new clears the object storage) but still treat the object
       as dead after the destructor you, can use -flifetime-dse=1.  The
       default behavior can be explicitly selected with -flifetime-dse=2.
       -flifetime-dse=0 is equivalent to -fno-lifetime-dse.

   -flive-range-shrinkage
       Attempt to decrease register pressure through register live range
       shrinkage.  This is helpful for fast processors with small or
       moderate size register sets.

   -fira-algorithm=algorithm
       Use the specified coloring algorithm for the integrated register
       allocator.  The algorithm argument can be priority, which specifies
       Chow's priority coloring, or CB, which specifies Chaitin-Briggs
       coloring.  Chaitin-Briggs coloring is not implemented for all
       architectures, but for those targets that do support it, it is the
       default because it generates better code.

   -fira-region=region
       Use specified regions for the integrated register allocator.  The
       region argument should be one of the following:

       all Use all loops as register allocation regions.  This can give
           the best results for machines with a small and/or irregular
           register set.

       mixed
           Use all loops except for loops with small register pressure as
           the regions.  This value usually gives the best results in most
           cases and for most architectures, and is enabled by default
           when compiling with optimization for speed (-O, -O2, ...).

       one Use all functions as a single region.  This typically results
           in the smallest code size, and is enabled by default for -Os or
           -O0.

   -fira-hoist-pressure
       Use IRA to evaluate register pressure in the code hoisting pass for
       decisions to hoist expressions.  This option usually results in
       smaller code, but it can slow the compiler down.

       This option is enabled at level -Os for all targets.

   -fira-loop-pressure
       Use IRA to evaluate register pressure in loops for decisions to
       move loop invariants.  This option usually results in generation of
       faster and smaller code on machines with large register files (>=
       32 registers), but it can slow the compiler down.

       This option is enabled at level -O3 for some targets.

   -fno-ira-share-save-slots
       Disable sharing of stack slots used for saving call-used hard
       registers living through a call.  Each hard register gets a
       separate stack slot, and as a result function stack frames are
       larger.

   -fno-ira-share-spill-slots
       Disable sharing of stack slots allocated for pseudo-registers.
       Each pseudo-register that does not get a hard register gets a
       separate stack slot, and as a result function stack frames are
       larger.

   -flra-remat
       Enable CFG-sensitive rematerialization in LRA.  Instead of loading
       values of spilled pseudos, LRA tries to rematerialize (recalculate)
       values if it is profitable.

       Enabled at levels -O2, -O3, -Os.

   -fdelayed-branch
       If supported for the target machine, attempt to reorder
       instructions to exploit instruction slots available after delayed
       branch instructions.

       Enabled at levels -O, -O2, -O3, -Os.

   -fschedule-insns
       If supported for the target machine, attempt to reorder
       instructions to eliminate execution stalls due to required data
       being unavailable.  This helps machines that have slow floating
       point or memory load instructions by allowing other instructions to
       be issued until the result of the load or floating-point
       instruction is required.

       Enabled at levels -O2, -O3.

   -fschedule-insns2
       Similar to -fschedule-insns, but requests an additional pass of
       instruction scheduling after register allocation has been done.
       This is especially useful on machines with a relatively small
       number of registers and where memory load instructions take more
       than one cycle.

       Enabled at levels -O2, -O3, -Os.

   -fno-sched-interblock
       Don't schedule instructions across basic blocks.  This is normally
       enabled by default when scheduling before register allocation, i.e.
       with -fschedule-insns or at -O2 or higher.

   -fno-sched-spec
       Don't allow speculative motion of non-load instructions.  This is
       normally enabled by default when scheduling before register
       allocation, i.e.  with -fschedule-insns or at -O2 or higher.

   -fsched-pressure
       Enable register pressure sensitive insn scheduling before register
       allocation.  This only makes sense when scheduling before register
       allocation is enabled, i.e. with -fschedule-insns or at -O2 or
       higher.  Usage of this option can improve the generated code and
       decrease its size by preventing register pressure increase above
       the number of available hard registers and subsequent spills in
       register allocation.

   -fsched-spec-load
       Allow speculative motion of some load instructions.  This only
       makes sense when scheduling before register allocation, i.e. with
       -fschedule-insns or at -O2 or higher.

   -fsched-spec-load-dangerous
       Allow speculative motion of more load instructions.  This only
       makes sense when scheduling before register allocation, i.e. with
       -fschedule-insns or at -O2 or higher.

   -fsched-stalled-insns
   -fsched-stalled-insns=n
       Define how many insns (if any) can be moved prematurely from the
       queue of stalled insns into the ready list during the second
       scheduling pass.  -fno-sched-stalled-insns means that no insns are
       moved prematurely, -fsched-stalled-insns=0 means there is no limit
       on how many queued insns can be moved prematurely.
       -fsched-stalled-insns without a value is equivalent to
       -fsched-stalled-insns=1.

   -fsched-stalled-insns-dep
   -fsched-stalled-insns-dep=n
       Define how many insn groups (cycles) are examined for a dependency
       on a stalled insn that is a candidate for premature removal from
       the queue of stalled insns.  This has an effect only during the
       second scheduling pass, and only if -fsched-stalled-insns is used.
       -fno-sched-stalled-insns-dep is equivalent to
       -fsched-stalled-insns-dep=0.  -fsched-stalled-insns-dep without a
       value is equivalent to -fsched-stalled-insns-dep=1.

   -fsched2-use-superblocks
       When scheduling after register allocation, use superblock
       scheduling.  This allows motion across basic block boundaries,
       resulting in faster schedules.  This option is experimental, as not
       all machine descriptions used by GCC model the CPU closely enough
       to avoid unreliable results from the algorithm.

       This only makes sense when scheduling after register allocation,
       i.e. with -fschedule-insns2 or at -O2 or higher.

   -fsched-group-heuristic
       Enable the group heuristic in the scheduler.  This heuristic favors
       the instruction that belongs to a schedule group.  This is enabled
       by default when scheduling is enabled, i.e. with -fschedule-insns
       or -fschedule-insns2 or at -O2 or higher.

   -fsched-critical-path-heuristic
       Enable the critical-path heuristic in the scheduler.  This
       heuristic favors instructions on the critical path.  This is
       enabled by default when scheduling is enabled, i.e. with
       -fschedule-insns or -fschedule-insns2 or at -O2 or higher.

   -fsched-spec-insn-heuristic
       Enable the speculative instruction heuristic in the scheduler.
       This heuristic favors speculative instructions with greater
       dependency weakness.  This is enabled by default when scheduling is
       enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2
       or higher.

   -fsched-rank-heuristic
       Enable the rank heuristic in the scheduler.  This heuristic favors
       the instruction belonging to a basic block with greater size or
       frequency.  This is enabled by default when scheduling is enabled,
       i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2 or
       higher.

   -fsched-last-insn-heuristic
       Enable the last-instruction heuristic in the scheduler.  This
       heuristic favors the instruction that is less dependent on the last
       instruction scheduled.  This is enabled by default when scheduling
       is enabled, i.e. with -fschedule-insns or -fschedule-insns2 or at
       -O2 or higher.

   -fsched-dep-count-heuristic
       Enable the dependent-count heuristic in the scheduler.  This
       heuristic favors the instruction that has more instructions
       depending on it.  This is enabled by default when scheduling is
       enabled, i.e.  with -fschedule-insns or -fschedule-insns2 or at -O2
       or higher.

   -freschedule-modulo-scheduled-loops
       Modulo scheduling is performed before traditional scheduling.  If a
       loop is modulo scheduled, later scheduling passes may change its
       schedule.  Use this option to control that behavior.

   -fselective-scheduling
       Schedule instructions using selective scheduling algorithm.
       Selective scheduling runs instead of the first scheduler pass.

   -fselective-scheduling2
       Schedule instructions using selective scheduling algorithm.
       Selective scheduling runs instead of the second scheduler pass.

   -fsel-sched-pipelining
       Enable software pipelining of innermost loops during selective
       scheduling.  This option has no effect unless one of
       -fselective-scheduling or -fselective-scheduling2 is turned on.

   -fsel-sched-pipelining-outer-loops
       When pipelining loops during selective scheduling, also pipeline
       outer loops.  This option has no effect unless
       -fsel-sched-pipelining is turned on.

   -fsemantic-interposition
       Some object formats, like ELF, allow interposing of symbols by the
       dynamic linker.  This means that for symbols exported from the DSO,
       the compiler cannot perform interprocedural propagation, inlining
       and other optimizations in anticipation that the function or
       variable in question may change. While this feature is useful, for
       example, to rewrite memory allocation functions by a debugging
       implementation, it is expensive in the terms of code quality.  With
       -fno-semantic-interposition the compiler assumes that if
       interposition happens for functions the overwriting function will
       have precisely the same semantics (and side effects).  Similarly if
       interposition happens for variables, the constructor of the
       variable will be the same. The flag has no effect for functions
       explicitly declared inline (where it is never allowed for
       interposition to change semantics) and for symbols explicitly
       declared weak.

   -fshrink-wrap
       Emit function prologues only before parts of the function that need
       it, rather than at the top of the function.  This flag is enabled
       by default at -O and higher.

   -fcaller-saves
       Enable allocation of values to registers that are clobbered by
       function calls, by emitting extra instructions to save and restore
       the registers around such calls.  Such allocation is done only when
       it seems to result in better code.

       This option is always enabled by default on certain machines,
       usually those which have no call-preserved registers to use
       instead.

       Enabled at levels -O2, -O3, -Os.

   -fcombine-stack-adjustments
       Tracks stack adjustments (pushes and pops) and stack memory
       references and then tries to find ways to combine them.

       Enabled by default at -O1 and higher.

   -fipa-ra
       Use caller save registers for allocation if those registers are not
       used by any called function.  In that case it is not necessary to
       save and restore them around calls.  This is only possible if
       called functions are part of same compilation unit as current
       function and they are compiled before it.

       Enabled at levels -O2, -O3, -Os.

   -fconserve-stack
       Attempt to minimize stack usage.  The compiler attempts to use less
       stack space, even if that makes the program slower.  This option
       implies setting the large-stack-frame parameter to 100 and the
       large-stack-frame-growth parameter to 400.

   -ftree-reassoc
       Perform reassociation on trees.  This flag is enabled by default at
       -O and higher.

   -ftree-pre
       Perform partial redundancy elimination (PRE) on trees.  This flag
       is enabled by default at -O2 and -O3.

   -ftree-partial-pre
       Make partial redundancy elimination (PRE) more aggressive.  This
       flag is enabled by default at -O3.

   -ftree-forwprop
       Perform forward propagation on trees.  This flag is enabled by
       default at -O and higher.

   -ftree-fre
       Perform full redundancy elimination (FRE) on trees.  The difference
       between FRE and PRE is that FRE only considers expressions that are
       computed on all paths leading to the redundant computation.  This
       analysis is faster than PRE, though it exposes fewer redundancies.
       This flag is enabled by default at -O and higher.

   -ftree-phiprop
       Perform hoisting of loads from conditional pointers on trees.  This
       pass is enabled by default at -O and higher.

   -fhoist-adjacent-loads
       Speculatively hoist loads from both branches of an if-then-else if
       the loads are from adjacent locations in the same structure and the
       target architecture has a conditional move instruction.  This flag
       is enabled by default at -O2 and higher.

   -ftree-copy-prop
       Perform copy propagation on trees.  This pass eliminates
       unnecessary copy operations.  This flag is enabled by default at -O
       and higher.

   -fipa-pure-const
       Discover which functions are pure or constant.  Enabled by default
       at -O and higher.

   -fipa-reference
       Discover which static variables do not escape the compilation unit.
       Enabled by default at -O and higher.

   -fipa-pta
       Perform interprocedural pointer analysis and interprocedural
       modification and reference analysis.  This option can cause
       excessive memory and compile-time usage on large compilation units.
       It is not enabled by default at any optimization level.

   -fipa-profile
       Perform interprocedural profile propagation.  The functions called
       only from cold functions are marked as cold. Also functions
       executed once (such as "cold", "noreturn", static constructors or
       destructors) are identified. Cold functions and loop less parts of
       functions executed once are then optimized for size.  Enabled by
       default at -O and higher.

   -fipa-cp
       Perform interprocedural constant propagation.  This optimization
       analyzes the program to determine when values passed to functions
       are constants and then optimizes accordingly.  This optimization
       can substantially increase performance if the application has
       constants passed to functions.  This flag is enabled by default at
       -O2, -Os and -O3.

   -fipa-cp-clone
       Perform function cloning to make interprocedural constant
       propagation stronger.  When enabled, interprocedural constant
       propagation performs function cloning when externally visible
       function can be called with constant arguments.  Because this
       optimization can create multiple copies of functions, it may
       significantly increase code size (see --param
       ipcp-unit-growth=value).  This flag is enabled by default at -O3.

   -fipa-cp-alignment
       When enabled, this optimization propagates alignment of function
       parameters to support better vectorization and string operations.

       This flag is enabled by default at -O2 and -Os.  It requires that
       -fipa-cp is enabled.

   -fipa-icf
       Perform Identical Code Folding for functions and read-only
       variables.  The optimization reduces code size and may disturb
       unwind stacks by replacing a function by equivalent one with a
       different name. The optimization works more effectively with link
       time optimization enabled.

       Nevertheless the behavior is similar to Gold Linker ICF
       optimization, GCC ICF works on different levels and thus the
       optimizations are not same - there are equivalences that are found
       only by GCC and equivalences found only by Gold.

       This flag is enabled by default at -O2 and -Os.

   -fisolate-erroneous-paths-dereference
       Detect paths that trigger erroneous or undefined behavior due to
       dereferencing a null pointer.  Isolate those paths from the main
       control flow and turn the statement with erroneous or undefined
       behavior into a trap.  This flag is enabled by default at -O2 and
       higher and depends on -fdelete-null-pointer-checks also being
       enabled.

   -fisolate-erroneous-paths-attribute
       Detect paths that trigger erroneous or undefined behavior due a
       null value being used in a way forbidden by a "returns_nonnull" or
       "nonnull" attribute.  Isolate those paths from the main control
       flow and turn the statement with erroneous or undefined behavior
       into a trap.  This is not currently enabled, but may be enabled by
       -O2 in the future.

   -ftree-sink
       Perform forward store motion on trees.  This flag is enabled by
       default at -O and higher.

   -ftree-bit-ccp
       Perform sparse conditional bit constant propagation on trees and
       propagate pointer alignment information.  This pass only operates
       on local scalar variables and is enabled by default at -O and
       higher.  It requires that -ftree-ccp is enabled.

   -ftree-ccp
       Perform sparse conditional constant propagation (CCP) on trees.
       This pass only operates on local scalar variables and is enabled by
       default at -O and higher.

   -fssa-backprop
       Propagate information about uses of a value up the definition chain
       in order to simplify the definitions.  For example, this pass
       strips sign operations if the sign of a value never matters.  The
       flag is enabled by default at -O and higher.

   -fssa-phiopt
       Perform pattern matching on SSA PHI nodes to optimize conditional
       code.  This pass is enabled by default at -O and higher.

   -ftree-switch-conversion
       Perform conversion of simple initializations in a switch to
       initializations from a scalar array.  This flag is enabled by
       default at -O2 and higher.

   -ftree-tail-merge
       Look for identical code sequences.  When found, replace one with a
       jump to the other.  This optimization is known as tail merging or
       cross jumping.  This flag is enabled by default at -O2 and higher.
       The compilation time in this pass can be limited using max-tail-
       merge-comparisons parameter and max-tail-merge-iterations
       parameter.

   -ftree-dce
       Perform dead code elimination (DCE) on trees.  This flag is enabled
       by default at -O and higher.

   -ftree-builtin-call-dce
       Perform conditional dead code elimination (DCE) for calls to built-
       in functions that may set "errno" but are otherwise side-effect
       free.  This flag is enabled by default at -O2 and higher if -Os is
       not also specified.

   -ftree-dominator-opts
       Perform a variety of simple scalar cleanups (constant/copy
       propagation, redundancy elimination, range propagation and
       expression simplification) based on a dominator tree traversal.
       This also performs jump threading (to reduce jumps to jumps). This
       flag is enabled by default at -O and higher.

   -ftree-dse
       Perform dead store elimination (DSE) on trees.  A dead store is a
       store into a memory location that is later overwritten by another
       store without any intervening loads.  In this case the earlier
       store can be deleted.  This flag is enabled by default at -O and
       higher.

   -ftree-ch
       Perform loop header copying on trees.  This is beneficial since it
       increases effectiveness of code motion optimizations.  It also
       saves one jump.  This flag is enabled by default at -O and higher.
       It is not enabled for -Os, since it usually increases code size.

   -ftree-loop-optimize
       Perform loop optimizations on trees.  This flag is enabled by
       default at -O and higher.

   -ftree-loop-linear
   -floop-interchange
   -floop-strip-mine
   -floop-block
   -floop-unroll-and-jam
       Perform loop nest optimizations.  Same as -floop-nest-optimize.  To
       use this code transformation, GCC has to be configured with
       --with-isl to enable the Graphite loop transformation
       infrastructure.

   -fgraphite-identity
       Enable the identity transformation for graphite.  For every SCoP we
       generate the polyhedral representation and transform it back to
       gimple.  Using -fgraphite-identity we can check the costs or
       benefits of the GIMPLE -> GRAPHITE -> GIMPLE transformation.  Some
       minimal optimizations are also performed by the code generator isl,
       like index splitting and dead code elimination in loops.

   -floop-nest-optimize
       Enable the isl based loop nest optimizer.  This is a generic loop
       nest optimizer based on the Pluto optimization algorithms.  It
       calculates a loop structure optimized for data-locality and
       parallelism.  This option is experimental.

   -floop-parallelize-all
       Use the Graphite data dependence analysis to identify loops that
       can be parallelized.  Parallelize all the loops that can be
       analyzed to not contain loop carried dependences without checking
       that it is profitable to parallelize the loops.

   -ftree-coalesce-vars
       While transforming the program out of the SSA representation,
       attempt to reduce copying by coalescing versions of different user-
       defined variables, instead of just compiler temporaries.  This may
       severely limit the ability to debug an optimized program compiled
       with -fno-var-tracking-assignments.  In the negated form, this flag
       prevents SSA coalescing of user variables.  This option is enabled
       by default if optimization is enabled, and it does very little
       otherwise.

   -ftree-loop-if-convert
       Attempt to transform conditional jumps in the innermost loops to
       branch-less equivalents.  The intent is to remove control-flow from
       the innermost loops in order to improve the ability of the
       vectorization pass to handle these loops.  This is enabled by
       default if vectorization is enabled.

   -ftree-loop-if-convert-stores
       Attempt to also if-convert conditional jumps containing memory
       writes.  This transformation can be unsafe for multi-threaded
       programs as it transforms conditional memory writes into
       unconditional memory writes.  For example,

               for (i = 0; i < N; i++)
                 if (cond)
                   A[i] = expr;

       is transformed to

               for (i = 0; i < N; i++)
                 A[i] = cond ? expr : A[i];

       potentially producing data races.

   -ftree-loop-distribution
       Perform loop distribution.  This flag can improve cache performance
       on big loop bodies and allow further loop optimizations, like
       parallelization or vectorization, to take place.  For example, the
       loop

               DO I = 1, N
                 A(I) = B(I) + C
                 D(I) = E(I) * F
               ENDDO

       is transformed to

               DO I = 1, N
                  A(I) = B(I) + C
               ENDDO
               DO I = 1, N
                  D(I) = E(I) * F
               ENDDO

   -ftree-loop-distribute-patterns
       Perform loop distribution of patterns that can be code generated
       with calls to a library.  This flag is enabled by default at -O3.

       This pass distributes the initialization loops and generates a call
       to memset zero.  For example, the loop

               DO I = 1, N
                 A(I) = 0
                 B(I) = A(I) + I
               ENDDO

       is transformed to

               DO I = 1, N
                  A(I) = 0
               ENDDO
               DO I = 1, N
                  B(I) = A(I) + I
               ENDDO

       and the initialization loop is transformed into a call to memset
       zero.

   -ftree-loop-im
       Perform loop invariant motion on trees.  This pass moves only
       invariants that are hard to handle at RTL level (function calls,
       operations that expand to nontrivial sequences of insns).  With
       -funswitch-loops it also moves operands of conditions that are
       invariant out of the loop, so that we can use just trivial
       invariantness analysis in loop unswitching.  The pass also includes
       store motion.

   -ftree-loop-ivcanon
       Create a canonical counter for number of iterations in loops for
       which determining number of iterations requires complicated
       analysis.  Later optimizations then may determine the number
       easily.  Useful especially in connection with unrolling.

   -fivopts
       Perform induction variable optimizations (strength reduction,
       induction variable merging and induction variable elimination) on
       trees.

   -ftree-parallelize-loops=n
       Parallelize loops, i.e., split their iteration space to run in n
       threads.  This is only possible for loops whose iterations are
       independent and can be arbitrarily reordered.  The optimization is
       only profitable on multiprocessor machines, for loops that are CPU-
       intensive, rather than constrained e.g. by memory bandwidth.  This
       option implies -pthread, and thus is only supported on targets that
       have support for -pthread.

   -ftree-pta
       Perform function-local points-to analysis on trees.  This flag is
       enabled by default at -O and higher.

   -ftree-sra
       Perform scalar replacement of aggregates.  This pass replaces
       structure references with scalars to prevent committing structures
       to memory too early.  This flag is enabled by default at -O and
       higher.

   -ftree-ter
       Perform temporary expression replacement during the SSA->normal
       phase.  Single use/single def temporaries are replaced at their use
       location with their defining expression.  This results in non-
       GIMPLE code, but gives the expanders much more complex trees to
       work on resulting in better RTL generation.  This is enabled by
       default at -O and higher.

   -ftree-slsr
       Perform straight-line strength reduction on trees.  This recognizes
       related expressions involving multiplications and replaces them by
       less expensive calculations when possible.  This is enabled by
       default at -O and higher.

   -ftree-vectorize
       Perform vectorization on trees. This flag enables
       -ftree-loop-vectorize and -ftree-slp-vectorize if not explicitly
       specified.

   -ftree-loop-vectorize
       Perform loop vectorization on trees. This flag is enabled by
       default at -O3 and when -ftree-vectorize is enabled.

   -ftree-slp-vectorize
       Perform basic block vectorization on trees. This flag is enabled by
       default at -O3 and when -ftree-vectorize is enabled.

   -fvect-cost-model=model
       Alter the cost model used for vectorization.  The model argument
       should be one of unlimited, dynamic or cheap.  With the unlimited
       model the vectorized code-path is assumed to be profitable while
       with the dynamic model a runtime check guards the vectorized code-
       path to enable it only for iteration counts that will likely
       execute faster than when executing the original scalar loop.  The
       cheap model disables vectorization of loops where doing so would be
       cost prohibitive for example due to required runtime checks for
       data dependence or alignment but otherwise is equal to the dynamic
       model.  The default cost model depends on other optimization flags
       and is either dynamic or cheap.

   -fsimd-cost-model=model
       Alter the cost model used for vectorization of loops marked with
       the OpenMP or Cilk Plus simd directive.  The model argument should
       be one of unlimited, dynamic, cheap.  All values of model have the
       same meaning as described in -fvect-cost-model and by default a
       cost model defined with -fvect-cost-model is used.

   -ftree-vrp
       Perform Value Range Propagation on trees.  This is similar to the
       constant propagation pass, but instead of values, ranges of values
       are propagated.  This allows the optimizers to remove unnecessary
       range checks like array bound checks and null pointer checks.  This
       is enabled by default at -O2 and higher.  Null pointer check
       elimination is only done if -fdelete-null-pointer-checks is
       enabled.

   -fsplit-paths
       Split paths leading to loop backedges.  This can improve dead code
       elimination and common subexpression elimination.  This is enabled
       by default at -O2 and above.

   -fsplit-ivs-in-unroller
       Enables expression of values of induction variables in later
       iterations of the unrolled loop using the value in the first
       iteration.  This breaks long dependency chains, thus improving
       efficiency of the scheduling passes.

       A combination of -fweb and CSE is often sufficient to obtain the
       same effect.  However, that is not reliable in cases where the loop
       body is more complicated than a single basic block.  It also does
       not work at all on some architectures due to restrictions in the
       CSE pass.

       This optimization is enabled by default.

   -fvariable-expansion-in-unroller
       With this option, the compiler creates multiple copies of some
       local variables when unrolling a loop, which can result in superior
       code.

   -fpartial-inlining
       Inline parts of functions.  This option has any effect only when
       inlining itself is turned on by the -finline-functions or
       -finline-small-functions options.

       Enabled at level -O2.

   -fpredictive-commoning
       Perform predictive commoning optimization, i.e., reusing
       computations (especially memory loads and stores) performed in
       previous iterations of loops.

       This option is enabled at level -O3.

   -fprefetch-loop-arrays
       If supported by the target machine, generate instructions to
       prefetch memory to improve the performance of loops that access
       large arrays.

       This option may generate better or worse code; results are highly
       dependent on the structure of loops within the source code.

       Disabled at level -Os.

   -fno-peephole
   -fno-peephole2
       Disable any machine-specific peephole optimizations.  The
       difference between -fno-peephole and -fno-peephole2 is in how they
       are implemented in the compiler; some targets use one, some use the
       other, a few use both.

       -fpeephole is enabled by default.  -fpeephole2 enabled at levels
       -O2, -O3, -Os.

   -fno-guess-branch-probability
       Do not guess branch probabilities using heuristics.

       GCC uses heuristics to guess branch probabilities if they are not
       provided by profiling feedback (-fprofile-arcs).  These heuristics
       are based on the control flow graph.  If some branch probabilities
       are specified by "__builtin_expect", then the heuristics are used
       to guess branch probabilities for the rest of the control flow
       graph, taking the "__builtin_expect" info into account.  The
       interactions between the heuristics and "__builtin_expect" can be
       complex, and in some cases, it may be useful to disable the
       heuristics so that the effects of "__builtin_expect" are easier to
       understand.

       The default is -fguess-branch-probability at levels -O, -O2, -O3,
       -Os.

   -freorder-blocks
       Reorder basic blocks in the compiled function in order to reduce
       number of taken branches and improve code locality.

       Enabled at levels -O, -O2, -O3, -Os.

   -freorder-blocks-algorithm=algorithm
       Use the specified algorithm for basic block reordering.  The
       algorithm argument can be simple, which does not increase code size
       (except sometimes due to secondary effects like alignment), or stc,
       the "software trace cache" algorithm, which tries to put all often
       executed code together, minimizing the number of branches executed
       by making extra copies of code.

       The default is simple at levels -O, -Os, and stc at levels -O2,
       -O3.

   -freorder-blocks-and-partition
       In addition to reordering basic blocks in the compiled function, in
       order to reduce number of taken branches, partitions hot and cold
       basic blocks into separate sections of the assembly and .o files,
       to improve paging and cache locality performance.

       This optimization is automatically turned off in the presence of
       exception handling, for linkonce sections, for functions with a
       user-defined section attribute and on any architecture that does
       not support named sections.

       Enabled for x86 at levels -O2, -O3.

   -freorder-functions
       Reorder functions in the object file in order to improve code
       locality.  This is implemented by using special subsections
       ".text.hot" for most frequently executed functions and
       ".text.unlikely" for unlikely executed functions.  Reordering is
       done by the linker so object file format must support named
       sections and linker must place them in a reasonable way.

       Also profile feedback must be available to make this option
       effective.  See -fprofile-arcs for details.

       Enabled at levels -O2, -O3, -Os.

   -fstrict-aliasing
       Allow the compiler to assume the strictest aliasing rules
       applicable to the language being compiled.  For C (and C++), this
       activates optimizations based on the type of expressions.  In
       particular, an object of one type is assumed never to reside at the
       same address as an object of a different type, unless the types are
       almost the same.  For example, an "unsigned int" can alias an
       "int", but not a "void*" or a "double".  A character type may alias
       any other type.

       Pay special attention to code like this:

               union a_union {
                 int i;
                 double d;
               };

               int f() {
                 union a_union t;
                 t.d = 3.0;
                 return t.i;
               }

       The practice of reading from a different union member than the one
       most recently written to (called "type-punning") is common.  Even
       with -fstrict-aliasing, type-punning is allowed, provided the
       memory is accessed through the union type.  So, the code above
       works as expected.    However, this code might not:

               int f() {
                 union a_union t;
                 int* ip;
                 t.d = 3.0;
                 ip = &t.i;
                 return *ip;
               }

       Similarly, access by taking the address, casting the resulting
       pointer and dereferencing the result has undefined behavior, even
       if the cast uses a union type, e.g.:

               int f() {
                 double d = 3.0;
                 return ((union a_union *) &d)->i;
               }

       The -fstrict-aliasing option is enabled at levels -O2, -O3, -Os.

   -fstrict-overflow
       Allow the compiler to assume strict signed overflow rules,
       depending on the language being compiled.  For C (and C++) this
       means that overflow when doing arithmetic with signed numbers is
       undefined, which means that the compiler may assume that it does
       not happen.  This permits various optimizations.  For example, the
       compiler assumes that an expression like "i + 10 > i" is always
       true for signed "i".  This assumption is only valid if signed
       overflow is undefined, as the expression is false if "i + 10"
       overflows when using twos complement arithmetic.  When this option
       is in effect any attempt to determine whether an operation on
       signed numbers overflows must be written carefully to not actually
       involve overflow.

       This option also allows the compiler to assume strict pointer
       semantics: given a pointer to an object, if adding an offset to
       that pointer does not produce a pointer to the same object, the
       addition is undefined.  This permits the compiler to conclude that
       "p + u > p" is always true for a pointer "p" and unsigned integer
       "u".  This assumption is only valid because pointer wraparound is
       undefined, as the expression is false if "p + u" overflows using
       twos complement arithmetic.

       See also the -fwrapv option.  Using -fwrapv means that integer
       signed overflow is fully defined: it wraps.  When -fwrapv is used,
       there is no difference between -fstrict-overflow and
       -fno-strict-overflow for integers.  With -fwrapv certain types of
       overflow are permitted.  For example, if the compiler gets an
       overflow when doing arithmetic on constants, the overflowed value
       can still be used with -fwrapv, but not otherwise.

       The -fstrict-overflow option is enabled at levels -O2, -O3, -Os.

   -falign-functions
   -falign-functions=n
       Align the start of functions to the next power-of-two greater than
       n, skipping up to n bytes.  For instance, -falign-functions=32
       aligns functions to the next 32-byte boundary, but
       -falign-functions=24 aligns to the next 32-byte boundary only if
       this can be done by skipping 23 bytes or less.

       -fno-align-functions and -falign-functions=1 are equivalent and
       mean that functions are not aligned.

       Some assemblers only support this flag when n is a power of two; in
       that case, it is rounded up.

       If n is not specified or is zero, use a machine-dependent default.

       Enabled at levels -O2, -O3.

   -falign-labels
   -falign-labels=n
       Align all branch targets to a power-of-two boundary, skipping up to
       n bytes like -falign-functions.  This option can easily make code
       slower, because it must insert dummy operations for when the branch
       target is reached in the usual flow of the code.

       -fno-align-labels and -falign-labels=1 are equivalent and mean that
       labels are not aligned.

       If -falign-loops or -falign-jumps are applicable and are greater
       than this value, then their values are used instead.

       If n is not specified or is zero, use a machine-dependent default
       which is very likely to be 1, meaning no alignment.

       Enabled at levels -O2, -O3.

   -falign-loops
   -falign-loops=n
       Align loops to a power-of-two boundary, skipping up to n bytes like
       -falign-functions.  If the loops are executed many times, this
       makes up for any execution of the dummy operations.

       -fno-align-loops and -falign-loops=1 are equivalent and mean that
       loops are not aligned.

       If n is not specified or is zero, use a machine-dependent default.

       Enabled at levels -O2, -O3.

   -falign-jumps
   -falign-jumps=n
       Align branch targets to a power-of-two boundary, for branch targets
       where the targets can only be reached by jumping, skipping up to n
       bytes like -falign-functions.  In this case, no dummy operations
       need be executed.

       -fno-align-jumps and -falign-jumps=1 are equivalent and mean that
       loops are not aligned.

       If n is not specified or is zero, use a machine-dependent default.

       Enabled at levels -O2, -O3.

   -funit-at-a-time
       This option is left for compatibility reasons. -funit-at-a-time has
       no effect, while -fno-unit-at-a-time implies -fno-toplevel-reorder
       and -fno-section-anchors.

       Enabled by default.

   -fno-toplevel-reorder
       Do not reorder top-level functions, variables, and "asm"
       statements.  Output them in the same order that they appear in the
       input file.  When this option is used, unreferenced static
       variables are not removed.  This option is intended to support
       existing code that relies on a particular ordering.  For new code,
       it is better to use attributes when possible.

       Enabled at level -O0.  When disabled explicitly, it also implies
       -fno-section-anchors, which is otherwise enabled at -O0 on some
       targets.

   -fweb
       Constructs webs as commonly used for register allocation purposes
       and assign each web individual pseudo register.  This allows the
       register allocation pass to operate on pseudos directly, but also
       strengthens several other optimization passes, such as CSE, loop
       optimizer and trivial dead code remover.  It can, however, make
       debugging impossible, since variables no longer stay in a "home
       register".

       Enabled by default with -funroll-loops.

   -fwhole-program
       Assume that the current compilation unit represents the whole
       program being compiled.  All public functions and variables with
       the exception of "main" and those merged by attribute
       "externally_visible" become static functions and in effect are
       optimized more aggressively by interprocedural optimizers.

       This option should not be used in combination with -flto.  Instead
       relying on a linker plugin should provide safer and more precise
       information.

   -flto[=n]
       This option runs the standard link-time optimizer.  When invoked
       with source code, it generates GIMPLE (one of GCC's internal
       representations) and writes it to special ELF sections in the
       object file.  When the object files are linked together, all the
       function bodies are read from these ELF sections and instantiated
       as if they had been part of the same translation unit.

       To use the link-time optimizer, -flto and optimization options
       should be specified at compile time and during the final link.  It
       is recommended that you compile all the files participating in the
       same link with the same options and also specify those options at
       link time.  For example:

               gcc -c -O2 -flto foo.c
               gcc -c -O2 -flto bar.c
               gcc -o myprog -flto -O2 foo.o bar.o

       The first two invocations to GCC save a bytecode representation of
       GIMPLE into special ELF sections inside foo.o and bar.o.  The final
       invocation reads the GIMPLE bytecode from foo.o and bar.o, merges
       the two files into a single internal image, and compiles the result
       as usual.  Since both foo.o and bar.o are merged into a single
       image, this causes all the interprocedural analyses and
       optimizations in GCC to work across the two files as if they were a
       single one.  This means, for example, that the inliner is able to
       inline functions in bar.o into functions in foo.o and vice-versa.

       Another (simpler) way to enable link-time optimization is:

               gcc -o myprog -flto -O2 foo.c bar.c

       The above generates bytecode for foo.c and bar.c, merges them
       together into a single GIMPLE representation and optimizes them as
       usual to produce myprog.

       The only important thing to keep in mind is that to enable link-
       time optimizations you need to use the GCC driver to perform the
       link step.  GCC then automatically performs link-time optimization
       if any of the objects involved were compiled with the -flto
       command-line option.  You generally should specify the optimization
       options to be used for link-time optimization though GCC tries to
       be clever at guessing an optimization level to use from the options
       used at compile time if you fail to specify one at link time.  You
       can always override the automatic decision to do link-time
       optimization at link time by passing -fno-lto to the link command.

       To make whole program optimization effective, it is necessary to
       make certain whole program assumptions.  The compiler needs to know
       what functions and variables can be accessed by libraries and
       runtime outside of the link-time optimized unit.  When supported by
       the linker, the linker plugin (see -fuse-linker-plugin) passes
       information to the compiler about used and externally visible
       symbols.  When the linker plugin is not available, -fwhole-program
       should be used to allow the compiler to make these assumptions,
       which leads to more aggressive optimization decisions.

       When -fuse-linker-plugin is not enabled, when a file is compiled
       with -flto, the generated object file is larger than a regular
       object file because it contains GIMPLE bytecodes and the usual
       final code (see -ffat-lto-objects.  This means that object files
       with LTO information can be linked as normal object files; if
       -fno-lto is passed to the linker, no interprocedural optimizations
       are applied.  Note that when -fno-fat-lto-objects is enabled the
       compile stage is faster but you cannot perform a regular, non-LTO
       link on them.

       Additionally, the optimization flags used to compile individual
       files are not necessarily related to those used at link time.  For
       instance,

               gcc -c -O0 -ffat-lto-objects -flto foo.c
               gcc -c -O0 -ffat-lto-objects -flto bar.c
               gcc -o myprog -O3 foo.o bar.o

       This produces individual object files with unoptimized assembler
       code, but the resulting binary myprog is optimized at -O3.  If,
       instead, the final binary is generated with -fno-lto, then myprog
       is not optimized.

       When producing the final binary, GCC only applies link-time
       optimizations to those files that contain bytecode.  Therefore, you
       can mix and match object files and libraries with GIMPLE bytecodes
       and final object code.  GCC automatically selects which files to
       optimize in LTO mode and which files to link without further
       processing.

       There are some code generation flags preserved by GCC when
       generating bytecodes, as they need to be used during the final link
       stage.  Generally options specified at link time override those
       specified at compile time.

       If you do not specify an optimization level option -O at link time,
       then GCC uses the highest optimization level used when compiling
       the object files.

       Currently, the following options and their settings are taken from
       the first object file that explicitly specifies them: -fPIC, -fpic,
       -fpie, -fcommon, -fexceptions, -fnon-call-exceptions, -fgnu-tm and
       all the -m target flags.

       Certain ABI-changing flags are required to match in all compilation
       units, and trying to override this at link time with a conflicting
       value is ignored.  This includes options such as
       -freg-struct-return and -fpcc-struct-return.

       Other options such as -ffp-contract, -fno-strict-overflow, -fwrapv,
       -fno-trapv or -fno-strict-aliasing are passed through to the link
       stage and merged conservatively for conflicting translation units.
       Specifically -fno-strict-overflow, -fwrapv and -fno-trapv take
       precedence; and for example -ffp-contract=off takes precedence over
       -ffp-contract=fast.  You can override them at link time.

       If LTO encounters objects with C linkage declared with incompatible
       types in separate translation units to be linked together
       (undefined behavior according to ISO C99 6.2.7), a non-fatal
       diagnostic may be issued.  The behavior is still undefined at run
       time.  Similar diagnostics may be raised for other languages.

       Another feature of LTO is that it is possible to apply
       interprocedural optimizations on files written in different
       languages:

               gcc -c -flto foo.c
               g++ -c -flto bar.cc
               gfortran -c -flto baz.f90
               g++ -o myprog -flto -O3 foo.o bar.o baz.o -lgfortran

       Notice that the final link is done with g++ to get the C++ runtime
       libraries and -lgfortran is added to get the Fortran runtime
       libraries.  In general, when mixing languages in LTO mode, you
       should use the same link command options as when mixing languages
       in a regular (non-LTO) compilation.

       If object files containing GIMPLE bytecode are stored in a library
       archive, say libfoo.a, it is possible to extract and use them in an
       LTO link if you are using a linker with plugin support.  To create
       static libraries suitable for LTO, use gcc-ar and gcc-ranlib
       instead of ar and ranlib; to show the symbols of object files with
       GIMPLE bytecode, use gcc-nm.  Those commands require that ar,
       ranlib and nm have been compiled with plugin support.  At link
       time, use the the flag -fuse-linker-plugin to ensure that the
       library participates in the LTO optimization process:

               gcc -o myprog -O2 -flto -fuse-linker-plugin a.o b.o -lfoo

       With the linker plugin enabled, the linker extracts the needed
       GIMPLE files from libfoo.a and passes them on to the running GCC to
       make them part of the aggregated GIMPLE image to be optimized.

       If you are not using a linker with plugin support and/or do not
       enable the linker plugin, then the objects inside libfoo.a are
       extracted and linked as usual, but they do not participate in the
       LTO optimization process.  In order to make a static library
       suitable for both LTO optimization and usual linkage, compile its
       object files with -flto -ffat-lto-objects.

       Link-time optimizations do not require the presence of the whole
       program to operate.  If the program does not require any symbols to
       be exported, it is possible to combine -flto and -fwhole-program to
       allow the interprocedural optimizers to use more aggressive
       assumptions which may lead to improved optimization opportunities.
       Use of -fwhole-program is not needed when linker plugin is active
       (see -fuse-linker-plugin).

       The current implementation of LTO makes no attempt to generate
       bytecode that is portable between different types of hosts.  The
       bytecode files are versioned and there is a strict version check,
       so bytecode files generated in one version of GCC do not work with
       an older or newer version of GCC.

       Link-time optimization does not work well with generation of
       debugging information.  Combining -flto with -g is currently
       experimental and expected to produce unexpected results.

       If you specify the optional n, the optimization and code generation
       done at link time is executed in parallel using n parallel jobs by
       utilizing an installed make program.  The environment variable MAKE
       may be used to override the program used.  The default value for n
       is 1.

       You can also specify -flto=jobserver to use GNU make's job server
       mode to determine the number of parallel jobs. This is useful when
       the Makefile calling GCC is already executing in parallel.  You
       must prepend a + to the command recipe in the parent Makefile for
       this to work.  This option likely only works if MAKE is GNU make.

   -flto-partition=alg
       Specify the partitioning algorithm used by the link-time optimizer.
       The value is either 1to1 to specify a partitioning mirroring the
       original source files or balanced to specify partitioning into
       equally sized chunks (whenever possible) or max to create new
       partition for every symbol where possible.  Specifying none as an
       algorithm disables partitioning and streaming completely.  The
       default value is balanced. While 1to1 can be used as an workaround
       for various code ordering issues, the max partitioning is intended
       for internal testing only.  The value one specifies that exactly
       one partition should be used while the value none bypasses
       partitioning and executes the link-time optimization step directly
       from the WPA phase.

   -flto-odr-type-merging
       Enable streaming of mangled types names of C++ types and their
       unification at link time.  This increases size of LTO object files,
       but enables diagnostics about One Definition Rule violations.

   -flto-compression-level=n
       This option specifies the level of compression used for
       intermediate language written to LTO object files, and is only
       meaningful in conjunction with LTO mode (-flto).  Valid values are
       0 (no compression) to 9 (maximum compression).  Values outside this
       range are clamped to either 0 or 9.  If the option is not given, a
       default balanced compression setting is used.

   -fuse-linker-plugin
       Enables the use of a linker plugin during link-time optimization.
       This option relies on plugin support in the linker, which is
       available in gold or in GNU ld 2.21 or newer.

       This option enables the extraction of object files with GIMPLE
       bytecode out of library archives. This improves the quality of
       optimization by exposing more code to the link-time optimizer.
       This information specifies what symbols can be accessed externally
       (by non-LTO object or during dynamic linking).  Resulting code
       quality improvements on binaries (and shared libraries that use
       hidden visibility) are similar to -fwhole-program.  See -flto for a
       description of the effect of this flag and how to use it.

       This option is enabled by default when LTO support in GCC is
       enabled and GCC was configured for use with a linker supporting
       plugins (GNU ld 2.21 or newer or gold).

   -ffat-lto-objects
       Fat LTO objects are object files that contain both the intermediate
       language and the object code. This makes them usable for both LTO
       linking and normal linking. This option is effective only when
       compiling with -flto and is ignored at link time.

       -fno-fat-lto-objects improves compilation time over plain LTO, but
       requires the complete toolchain to be aware of LTO. It requires a
       linker with linker plugin support for basic functionality.
       Additionally, nm, ar and ranlib need to support linker plugins to
       allow a full-featured build environment (capable of building static
       libraries etc).  GCC provides the gcc-ar, gcc-nm, gcc-ranlib
       wrappers to pass the right options to these tools. With non fat LTO
       makefiles need to be modified to use them.

       The default is -fno-fat-lto-objects on targets with linker plugin
       support.

   -fcompare-elim
       After register allocation and post-register allocation instruction
       splitting, identify arithmetic instructions that compute processor
       flags similar to a comparison operation based on that arithmetic.
       If possible, eliminate the explicit comparison operation.

       This pass only applies to certain targets that cannot explicitly
       represent the comparison operation before register allocation is
       complete.

       Enabled at levels -O, -O2, -O3, -Os.

   -fcprop-registers
       After register allocation and post-register allocation instruction
       splitting, perform a copy-propagation pass to try to reduce
       scheduling dependencies and occasionally eliminate the copy.

       Enabled at levels -O, -O2, -O3, -Os.

   -fprofile-correction
       Profiles collected using an instrumented binary for multi-threaded
       programs may be inconsistent due to missed counter updates. When
       this option is specified, GCC uses heuristics to correct or smooth
       out such inconsistencies. By default, GCC emits an error message
       when an inconsistent profile is detected.

   -fprofile-use
   -fprofile-use=path
       Enable profile feedback-directed optimizations, and the following
       optimizations which are generally profitable only with profile
       feedback available: -fbranch-probabilities, -fvpt, -funroll-loops,
       -fpeel-loops, -ftracer, -ftree-vectorize, and ftree-loop-
       distribute-patterns.

       Before you can use this option, you must first generate profiling
       information.

       By default, GCC emits an error message if the feedback profiles do
       not match the source code.  This error can be turned into a warning
       by using -Wcoverage-mismatch.  Note this may result in poorly
       optimized code.

       If path is specified, GCC looks at the path to find the profile
       feedback data files. See -fprofile-dir.

   -fauto-profile
   -fauto-profile=path
       Enable sampling-based feedback-directed optimizations, and the
       following optimizations which are generally profitable only with
       profile feedback available: -fbranch-probabilities, -fvpt,
       -funroll-loops, -fpeel-loops, -ftracer, -ftree-vectorize,
       -finline-functions, -fipa-cp, -fipa-cp-clone,
       -fpredictive-commoning, -funswitch-loops, -fgcse-after-reload, and
       -ftree-loop-distribute-patterns.

       path is the name of a file containing AutoFDO profile information.
       If omitted, it defaults to fbdata.afdo in the current directory.

       Producing an AutoFDO profile data file requires running your
       program with the perf utility on a supported GNU/Linux target
       system.  For more information, see <https://perf.wiki.kernel.org/>.

       E.g.

               perf record -e br_inst_retired:near_taken -b -o perf.data \
                   -- your_program

       Then use the create_gcov tool to convert the raw profile data to a
       format that can be used by GCC.  You must also supply the
       unstripped binary for your program to this tool.  See
       <https://github.com/google/autofdo>.

       E.g.

               create_gcov --binary=your_program.unstripped --profile=perf.data \
                   --gcov=profile.afdo

   The following options control compiler behavior regarding floating-
   point arithmetic.  These options trade off between speed and
   correctness.  All must be specifically enabled.

   -ffloat-store
       Do not store floating-point variables in registers, and inhibit
       other options that might change whether a floating-point value is
       taken from a register or memory.

       This option prevents undesirable excess precision on machines such
       as the 68000 where the floating registers (of the 68881) keep more
       precision than a "double" is supposed to have.  Similarly for the
       x86 architecture.  For most programs, the excess precision does
       only good, but a few programs rely on the precise definition of
       IEEE floating point.  Use -ffloat-store for such programs, after
       modifying them to store all pertinent intermediate computations
       into variables.

   -fexcess-precision=style
       This option allows further control over excess precision on
       machines where floating-point registers have more precision than
       the IEEE "float" and "double" types and the processor does not
       support operations rounding to those types.  By default,
       -fexcess-precision=fast is in effect; this means that operations
       are carried out in the precision of the registers and that it is
       unpredictable when rounding to the types specified in the source
       code takes place.  When compiling C, if -fexcess-precision=standard
       is specified then excess precision follows the rules specified in
       ISO C99; in particular, both casts and assignments cause values to
       be rounded to their semantic types (whereas -ffloat-store only
       affects assignments).  This option is enabled by default for C if a
       strict conformance option such as -std=c99 is used.

       -fexcess-precision=standard is not implemented for languages other
       than C, and has no effect if -funsafe-math-optimizations or
       -ffast-math is specified.  On the x86, it also has no effect if
       -mfpmath=sse or -mfpmath=sse+387 is specified; in the former case,
       IEEE semantics apply without excess precision, and in the latter,
       rounding is unpredictable.

   -ffast-math
       Sets the options -fno-math-errno, -funsafe-math-optimizations,
       -ffinite-math-only, -fno-rounding-math, -fno-signaling-nans and
       -fcx-limited-range.

       This option causes the preprocessor macro "__FAST_MATH__" to be
       defined.

       This option is not turned on by any -O option besides -Ofast since
       it can result in incorrect output for programs that depend on an
       exact implementation of IEEE or ISO rules/specifications for math
       functions. It may, however, yield faster code for programs that do
       not require the guarantees of these specifications.

   -fno-math-errno
       Do not set "errno" after calling math functions that are executed
       with a single instruction, e.g., "sqrt".  A program that relies on
       IEEE exceptions for math error handling may want to use this flag
       for speed while maintaining IEEE arithmetic compatibility.

       This option is not turned on by any -O option since it can result
       in incorrect output for programs that depend on an exact
       implementation of IEEE or ISO rules/specifications for math
       functions. It may, however, yield faster code for programs that do
       not require the guarantees of these specifications.

       The default is -fmath-errno.

       On Darwin systems, the math library never sets "errno".  There is
       therefore no reason for the compiler to consider the possibility
       that it might, and -fno-math-errno is the default.

   -funsafe-math-optimizations
       Allow optimizations for floating-point arithmetic that (a) assume
       that arguments and results are valid and (b) may violate IEEE or
       ANSI standards.  When used at link time, it may include libraries
       or startup files that change the default FPU control word or other
       similar optimizations.

       This option is not turned on by any -O option since it can result
       in incorrect output for programs that depend on an exact
       implementation of IEEE or ISO rules/specifications for math
       functions. It may, however, yield faster code for programs that do
       not require the guarantees of these specifications.  Enables
       -fno-signed-zeros, -fno-trapping-math, -fassociative-math and
       -freciprocal-math.

       The default is -fno-unsafe-math-optimizations.

   -fassociative-math
       Allow re-association of operands in series of floating-point
       operations.  This violates the ISO C and C++ language standard by
       possibly changing computation result.  NOTE: re-ordering may change
       the sign of zero as well as ignore NaNs and inhibit or create
       underflow or overflow (and thus cannot be used on code that relies
       on rounding behavior like "(x + 2**52) - 2**52".  May also reorder
       floating-point comparisons and thus may not be used when ordered
       comparisons are required.  This option requires that both
       -fno-signed-zeros and -fno-trapping-math be in effect.  Moreover,
       it doesn't make much sense with -frounding-math. For Fortran the
       option is automatically enabled when both -fno-signed-zeros and
       -fno-trapping-math are in effect.

       The default is -fno-associative-math.

   -freciprocal-math
       Allow the reciprocal of a value to be used instead of dividing by
       the value if this enables optimizations.  For example "x / y" can
       be replaced with "x * (1/y)", which is useful if "(1/y)" is subject
       to common subexpression elimination.  Note that this loses
       precision and increases the number of flops operating on the value.

       The default is -fno-reciprocal-math.

   -ffinite-math-only
       Allow optimizations for floating-point arithmetic that assume that
       arguments and results are not NaNs or +-Infs.

       This option is not turned on by any -O option since it can result
       in incorrect output for programs that depend on an exact
       implementation of IEEE or ISO rules/specifications for math
       functions. It may, however, yield faster code for programs that do
       not require the guarantees of these specifications.

       The default is -fno-finite-math-only.

   -fno-signed-zeros
       Allow optimizations for floating-point arithmetic that ignore the
       signedness of zero.  IEEE arithmetic specifies the behavior of
       distinct +0.0 and -0.0 values, which then prohibits simplification
       of expressions such as x+0.0 or 0.0*x (even with
       -ffinite-math-only).  This option implies that the sign of a zero
       result isn't significant.

       The default is -fsigned-zeros.

   -fno-trapping-math
       Compile code assuming that floating-point operations cannot
       generate user-visible traps.  These traps include division by zero,
       overflow, underflow, inexact result and invalid operation.  This
       option requires that -fno-signaling-nans be in effect.  Setting
       this option may allow faster code if one relies on "non-stop" IEEE
       arithmetic, for example.

       This option should never be turned on by any -O option since it can
       result in incorrect output for programs that depend on an exact
       implementation of IEEE or ISO rules/specifications for math
       functions.

       The default is -ftrapping-math.

   -frounding-math
       Disable transformations and optimizations that assume default
       floating-point rounding behavior.  This is round-to-zero for all
       floating point to integer conversions, and round-to-nearest for all
       other arithmetic truncations.  This option should be specified for
       programs that change the FP rounding mode dynamically, or that may
       be executed with a non-default rounding mode.  This option disables
       constant folding of floating-point expressions at compile time
       (which may be affected by rounding mode) and arithmetic
       transformations that are unsafe in the presence of sign-dependent
       rounding modes.

       The default is -fno-rounding-math.

       This option is experimental and does not currently guarantee to
       disable all GCC optimizations that are affected by rounding mode.
       Future versions of GCC may provide finer control of this setting
       using C99's "FENV_ACCESS" pragma.  This command-line option will be
       used to specify the default state for "FENV_ACCESS".

   -fsignaling-nans
       Compile code assuming that IEEE signaling NaNs may generate user-
       visible traps during floating-point operations.  Setting this
       option disables optimizations that may change the number of
       exceptions visible with signaling NaNs.  This option implies
       -ftrapping-math.

       This option causes the preprocessor macro "__SUPPORT_SNAN__" to be
       defined.

       The default is -fno-signaling-nans.

       This option is experimental and does not currently guarantee to
       disable all GCC optimizations that affect signaling NaN behavior.

   -fsingle-precision-constant
       Treat floating-point constants as single precision instead of
       implicitly converting them to double-precision constants.

   -fcx-limited-range
       When enabled, this option states that a range reduction step is not
       needed when performing complex division.  Also, there is no
       checking whether the result of a complex multiplication or division
       is "NaN + I*NaN", with an attempt to rescue the situation in that
       case.  The default is -fno-cx-limited-range, but is enabled by
       -ffast-math.

       This option controls the default setting of the ISO C99
       "CX_LIMITED_RANGE" pragma.  Nevertheless, the option applies to all
       languages.

   -fcx-fortran-rules
       Complex multiplication and division follow Fortran rules.  Range
       reduction is done as part of complex division, but there is no
       checking whether the result of a complex multiplication or division
       is "NaN + I*NaN", with an attempt to rescue the situation in that
       case.

       The default is -fno-cx-fortran-rules.

   The following options control optimizations that may improve
   performance, but are not enabled by any -O options.  This section
   includes experimental options that may produce broken code.

   -fbranch-probabilities
       After running a program compiled with -fprofile-arcs, you can
       compile it a second time using -fbranch-probabilities, to improve
       optimizations based on the number of times each branch was taken.
       When a program compiled with -fprofile-arcs exits, it saves arc
       execution counts to a file called sourcename.gcda for each source
       file.  The information in this data file is very dependent on the
       structure of the generated code, so you must use the same source
       code and the same optimization options for both compilations.

       With -fbranch-probabilities, GCC puts a REG_BR_PROB note on each
       JUMP_INSN and CALL_INSN.  These can be used to improve
       optimization.  Currently, they are only used in one place: in
       reorg.c, instead of guessing which path a branch is most likely to
       take, the REG_BR_PROB values are used to exactly determine which
       path is taken more often.

   -fprofile-values
       If combined with -fprofile-arcs, it adds code so that some data
       about values of expressions in the program is gathered.

       With -fbranch-probabilities, it reads back the data gathered from
       profiling values of expressions for usage in optimizations.

       Enabled with -fprofile-generate and -fprofile-use.

   -fprofile-reorder-functions
       Function reordering based on profile instrumentation collects first
       time of execution of a function and orders these functions in
       ascending order.

       Enabled with -fprofile-use.

   -fvpt
       If combined with -fprofile-arcs, this option instructs the compiler
       to add code to gather information about values of expressions.

       With -fbranch-probabilities, it reads back the data gathered and
       actually performs the optimizations based on them.  Currently the
       optimizations include specialization of division operations using
       the knowledge about the value of the denominator.

   -frename-registers
       Attempt to avoid false dependencies in scheduled code by making use
       of registers left over after register allocation.  This
       optimization most benefits processors with lots of registers.
       Depending on the debug information format adopted by the target,
       however, it can make debugging impossible, since variables no
       longer stay in a "home register".

       Enabled by default with -funroll-loops and -fpeel-loops.

   -fschedule-fusion
       Performs a target dependent pass over the instruction stream to
       schedule instructions of same type together because target machine
       can execute them more efficiently if they are adjacent to each
       other in the instruction flow.

       Enabled at levels -O2, -O3, -Os.

   -ftracer
       Perform tail duplication to enlarge superblock size.  This
       transformation simplifies the control flow of the function allowing
       other optimizations to do a better job.

       Enabled with -fprofile-use.

   -funroll-loops
       Unroll loops whose number of iterations can be determined at
       compile time or upon entry to the loop.  -funroll-loops implies
       -frerun-cse-after-loop, -fweb and -frename-registers.  It also
       turns on complete loop peeling (i.e. complete removal of loops with
       a small constant number of iterations).  This option makes code
       larger, and may or may not make it run faster.

       Enabled with -fprofile-use.

   -funroll-all-loops
       Unroll all loops, even if their number of iterations is uncertain
       when the loop is entered.  This usually makes programs run more
       slowly.  -funroll-all-loops implies the same options as
       -funroll-loops.

   -fpeel-loops
       Peels loops for which there is enough information that they do not
       roll much (from profile feedback).  It also turns on complete loop
       peeling (i.e. complete removal of loops with small constant number
       of iterations).

       Enabled with -fprofile-use.

   -fmove-loop-invariants
       Enables the loop invariant motion pass in the RTL loop optimizer.
       Enabled at level -O1

   -funswitch-loops
       Move branches with loop invariant conditions out of the loop, with
       duplicates of the loop on both branches (modified according to
       result of the condition).

   -ffunction-sections
   -fdata-sections
       Place each function or data item into its own section in the output
       file if the target supports arbitrary sections.  The name of the
       function or the name of the data item determines the section's name
       in the output file.

       Use these options on systems where the linker can perform
       optimizations to improve locality of reference in the instruction
       space.  Most systems using the ELF object format and SPARC
       processors running Solaris 2 have linkers with such optimizations.
       AIX may have these optimizations in the future.

       Only use these options when there are significant benefits from
       doing so.  When you specify these options, the assembler and linker
       create larger object and executable files and are also slower.  You
       cannot use gprof on all systems if you specify this option, and you
       may have problems with debugging if you specify both this option
       and -g.

   -fbranch-target-load-optimize
       Perform branch target register load optimization before prologue /
       epilogue threading.  The use of target registers can typically be
       exposed only during reload, thus hoisting loads out of loops and
       doing inter-block scheduling needs a separate optimization pass.

   -fbranch-target-load-optimize2
       Perform branch target register load optimization after prologue /
       epilogue threading.

   -fbtr-bb-exclusive
       When performing branch target register load optimization, don't
       reuse branch target registers within any basic block.

   -fstdarg-opt
       Optimize the prologue of variadic argument functions with respect
       to usage of those arguments.

       NOTE: In Ubuntu 14.10 and later versions, -fstack-protector-strong
       is enabled by default for C, C++, ObjC, ObjC++, if none of
       -fno-stack-protector, -nostdlib, nor -ffreestanding are found.

   -fsection-anchors
       Try to reduce the number of symbolic address calculations by using
       shared "anchor" symbols to address nearby objects.  This
       transformation can help to reduce the number of GOT entries and GOT
       accesses on some targets.

       For example, the implementation of the following function "foo":

               static int a, b, c;
               int foo (void) { return a + b + c; }

       usually calculates the addresses of all three variables, but if you
       compile it with -fsection-anchors, it accesses the variables from a
       common anchor point instead.  The effect is similar to the
       following pseudocode (which isn't valid C):

               int foo (void)
               {
                 register int *xr = &x;
                 return xr[&a - &x] + xr[&b - &x] + xr[&c - &x];
               }

       Not all targets support this option.

   --param name=value
       In some places, GCC uses various constants to control the amount of
       optimization that is done.  For example, GCC does not inline
       functions that contain more than a certain number of instructions.
       You can control some of these constants on the command line using
       the --param option.

       The names of specific parameters, and the meaning of the values,
       are tied to the internals of the compiler, and are subject to
       change without notice in future releases.

       In each case, the value is an integer.  The allowable choices for
       name are:

       predictable-branch-outcome
           When branch is predicted to be taken with probability lower
           than this threshold (in percent), then it is considered well
           predictable. The default is 10.

       max-rtl-if-conversion-insns
           RTL if-conversion tries to remove conditional branches around a
           block and replace them with conditionally executed
           instructions.  This parameter gives the maximum number of
           instructions in a block which should be considered for if-
           conversion.  The default is 10, though the compiler will also
           use other heuristics to decide whether if-conversion is likely
           to be profitable.

       max-crossjump-edges
           The maximum number of incoming edges to consider for cross-
           jumping.  The algorithm used by -fcrossjumping is O(N^2) in the
           number of edges incoming to each block.  Increasing values mean
           more aggressive optimization, making the compilation time
           increase with probably small improvement in executable size.

       min-crossjump-insns
           The minimum number of instructions that must be matched at the
           end of two blocks before cross-jumping is performed on them.
           This value is ignored in the case where all instructions in the
           block being cross-jumped from are matched.  The default value
           is 5.

       max-grow-copy-bb-insns
           The maximum code size expansion factor when copying basic
           blocks instead of jumping.  The expansion is relative to a jump
           instruction.  The default value is 8.

       max-goto-duplication-insns
           The maximum number of instructions to duplicate to a block that
           jumps to a computed goto.  To avoid O(N^2) behavior in a number
           of passes, GCC factors computed gotos early in the compilation
           process, and unfactors them as late as possible.  Only computed
           jumps at the end of a basic blocks with no more than max-goto-
           duplication-insns are unfactored.  The default value is 8.

       max-delay-slot-insn-search
           The maximum number of instructions to consider when looking for
           an instruction to fill a delay slot.  If more than this
           arbitrary number of instructions are searched, the time savings
           from filling the delay slot are minimal, so stop searching.
           Increasing values mean more aggressive optimization, making the
           compilation time increase with probably small improvement in
           execution time.

       max-delay-slot-live-search
           When trying to fill delay slots, the maximum number of
           instructions to consider when searching for a block with valid
           live register information.  Increasing this arbitrarily chosen
           value means more aggressive optimization, increasing the
           compilation time.  This parameter should be removed when the
           delay slot code is rewritten to maintain the control-flow
           graph.

       max-gcse-memory
           The approximate maximum amount of memory that can be allocated
           in order to perform the global common subexpression elimination
           optimization.  If more memory than specified is required, the
           optimization is not done.

       max-gcse-insertion-ratio
           If the ratio of expression insertions to deletions is larger
           than this value for any expression, then RTL PRE inserts or
           removes the expression and thus leaves partially redundant
           computations in the instruction stream.  The default value is
           20.

       max-pending-list-length
           The maximum number of pending dependencies scheduling allows
           before flushing the current state and starting over.  Large
           functions with few branches or calls can create excessively
           large lists which needlessly consume memory and resources.

       max-modulo-backtrack-attempts
           The maximum number of backtrack attempts the scheduler should
           make when modulo scheduling a loop.  Larger values can
           exponentially increase compilation time.

       max-inline-insns-single
           Several parameters control the tree inliner used in GCC.  This
           number sets the maximum number of instructions (counted in
           GCC's internal representation) in a single function that the
           tree inliner considers for inlining.  This only affects
           functions declared inline and methods implemented in a class
           declaration (C++).  The default value is 400.

       max-inline-insns-auto
           When you use -finline-functions (included in -O3), a lot of
           functions that would otherwise not be considered for inlining
           by the compiler are investigated.  To those functions, a
           different (more restrictive) limit compared to functions
           declared inline can be applied.  The default value is 40.

       inline-min-speedup
           When estimated performance improvement of caller + callee
           runtime exceeds this threshold (in precent), the function can
           be inlined regardless the limit on --param max-inline-insns-
           single and --param max-inline-insns-auto.

       large-function-insns
           The limit specifying really large functions.  For functions
           larger than this limit after inlining, inlining is constrained
           by --param large-function-growth.  This parameter is useful
           primarily to avoid extreme compilation time caused by non-
           linear algorithms used by the back end.  The default value is
           2700.

       large-function-growth
           Specifies maximal growth of large function caused by inlining
           in percents.  The default value is 100 which limits large
           function growth to 2.0 times the original size.

       large-unit-insns
           The limit specifying large translation unit.  Growth caused by
           inlining of units larger than this limit is limited by --param
           inline-unit-growth.  For small units this might be too tight.
           For example, consider a unit consisting of function A that is
           inline and B that just calls A three times.  If B is small
           relative to A, the growth of unit is 300\% and yet such
           inlining is very sane.  For very large units consisting of
           small inlineable functions, however, the overall unit growth
           limit is needed to avoid exponential explosion of code size.
           Thus for smaller units, the size is increased to --param large-
           unit-insns before applying --param inline-unit-growth.  The
           default is 10000.

       inline-unit-growth
           Specifies maximal overall growth of the compilation unit caused
           by inlining.  The default value is 20 which limits unit growth
           to 1.2 times the original size. Cold functions (either marked
           cold via an attribute or by profile feedback) are not accounted
           into the unit size.

       ipcp-unit-growth
           Specifies maximal overall growth of the compilation unit caused
           by interprocedural constant propagation.  The default value is
           10 which limits unit growth to 1.1 times the original size.

       large-stack-frame
           The limit specifying large stack frames.  While inlining the
           algorithm is trying to not grow past this limit too much.  The
           default value is 256 bytes.

       large-stack-frame-growth
           Specifies maximal growth of large stack frames caused by
           inlining in percents.  The default value is 1000 which limits
           large stack frame growth to 11 times the original size.

       max-inline-insns-recursive
       max-inline-insns-recursive-auto
           Specifies the maximum number of instructions an out-of-line
           copy of a self-recursive inline function can grow into by
           performing recursive inlining.

           --param max-inline-insns-recursive applies to functions
           declared inline.  For functions not declared inline, recursive
           inlining happens only when -finline-functions (included in -O3)
           is enabled; --param max-inline-insns-recursive-auto applies
           instead.  The default value is 450.

       max-inline-recursive-depth
       max-inline-recursive-depth-auto
           Specifies the maximum recursion depth used for recursive
           inlining.

           --param max-inline-recursive-depth applies to functions
           declared inline.  For functions not declared inline, recursive
           inlining happens only when -finline-functions (included in -O3)
           is enabled; --param max-inline-recursive-depth-auto applies
           instead.  The default value is 8.

       min-inline-recursive-probability
           Recursive inlining is profitable only for function having deep
           recursion in average and can hurt for function having little
           recursion depth by increasing the prologue size or complexity
           of function body to other optimizers.

           When profile feedback is available (see -fprofile-generate) the
           actual recursion depth can be guessed from probability that
           function recurses via a given call expression.  This parameter
           limits inlining only to call expressions whose probability
           exceeds the given threshold (in percents).  The default value
           is 10.

       early-inlining-insns
           Specify growth that the early inliner can make.  In effect it
           increases the amount of inlining for code having a large
           abstraction penalty.  The default value is 14.

       max-early-inliner-iterations
           Limit of iterations of the early inliner.  This basically
           bounds the number of nested indirect calls the early inliner
           can resolve.  Deeper chains are still handled by late inlining.

       comdat-sharing-probability
           Probability (in percent) that C++ inline function with comdat
           visibility are shared across multiple compilation units.  The
           default value is 20.

       profile-func-internal-id
           A parameter to control whether to use function internal id in
           profile database lookup. If the value is 0, the compiler uses
           an id that is based on function assembler name and filename,
           which makes old profile data more tolerant to source changes
           such as function reordering etc.  The default value is 0.

       min-vect-loop-bound
           The minimum number of iterations under which loops are not
           vectorized when -ftree-vectorize is used.  The number of
           iterations after vectorization needs to be greater than the
           value specified by this option to allow vectorization.  The
           default value is 0.

       gcse-cost-distance-ratio
           Scaling factor in calculation of maximum distance an expression
           can be moved by GCSE optimizations.  This is currently
           supported only in the code hoisting pass.  The bigger the
           ratio, the more aggressive code hoisting is with simple
           expressions, i.e., the expressions that have cost less than
           gcse-unrestricted-cost.  Specifying 0 disables hoisting of
           simple expressions.  The default value is 10.

       gcse-unrestricted-cost
           Cost, roughly measured as the cost of a single typical machine
           instruction, at which GCSE optimizations do not constrain the
           distance an expression can travel.  This is currently supported
           only in the code hoisting pass.  The lesser the cost, the more
           aggressive code hoisting is.  Specifying 0 allows all
           expressions to travel unrestricted distances.  The default
           value is 3.

       max-hoist-depth
           The depth of search in the dominator tree for expressions to
           hoist.  This is used to avoid quadratic behavior in hoisting
           algorithm.  The value of 0 does not limit on the search, but
           may slow down compilation of huge functions.  The default value
           is 30.

       max-tail-merge-comparisons
           The maximum amount of similar bbs to compare a bb with.  This
           is used to avoid quadratic behavior in tree tail merging.  The
           default value is 10.

       max-tail-merge-iterations
           The maximum amount of iterations of the pass over the function.
           This is used to limit compilation time in tree tail merging.
           The default value is 2.

       max-unrolled-insns
           The maximum number of instructions that a loop may have to be
           unrolled.  If a loop is unrolled, this parameter also
           determines how many times the loop code is unrolled.

       max-average-unrolled-insns
           The maximum number of instructions biased by probabilities of
           their execution that a loop may have to be unrolled.  If a loop
           is unrolled, this parameter also determines how many times the
           loop code is unrolled.

       max-unroll-times
           The maximum number of unrollings of a single loop.

       max-peeled-insns
           The maximum number of instructions that a loop may have to be
           peeled.  If a loop is peeled, this parameter also determines
           how many times the loop code is peeled.

       max-peel-times
           The maximum number of peelings of a single loop.

       max-peel-branches
           The maximum number of branches on the hot path through the
           peeled sequence.

       max-completely-peeled-insns
           The maximum number of insns of a completely peeled loop.

       max-completely-peel-times
           The maximum number of iterations of a loop to be suitable for
           complete peeling.

       max-completely-peel-loop-nest-depth
           The maximum depth of a loop nest suitable for complete peeling.

       max-unswitch-insns
           The maximum number of insns of an unswitched loop.

       max-unswitch-level
           The maximum number of branches unswitched in a single loop.

       lim-expensive
           The minimum cost of an expensive expression in the loop
           invariant motion.

       iv-consider-all-candidates-bound
           Bound on number of candidates for induction variables, below
           which all candidates are considered for each use in induction
           variable optimizations.  If there are more candidates than
           this, only the most relevant ones are considered to avoid
           quadratic time complexity.

       iv-max-considered-uses
           The induction variable optimizations give up on loops that
           contain more induction variable uses.

       iv-always-prune-cand-set-bound
           If the number of candidates in the set is smaller than this
           value, always try to remove unnecessary ivs from the set when
           adding a new one.

       scev-max-expr-size
           Bound on size of expressions used in the scalar evolutions
           analyzer.  Large expressions slow the analyzer.

       scev-max-expr-complexity
           Bound on the complexity of the expressions in the scalar
           evolutions analyzer.  Complex expressions slow the analyzer.

       vect-max-version-for-alignment-checks
           The maximum number of run-time checks that can be performed
           when doing loop versioning for alignment in the vectorizer.

       vect-max-version-for-alias-checks
           The maximum number of run-time checks that can be performed
           when doing loop versioning for alias in the vectorizer.

       vect-max-peeling-for-alignment
           The maximum number of loop peels to enhance access alignment
           for vectorizer. Value -1 means no limit.

       max-iterations-to-track
           The maximum number of iterations of a loop the brute-force
           algorithm for analysis of the number of iterations of the loop
           tries to evaluate.

       hot-bb-count-ws-permille
           A basic block profile count is considered hot if it contributes
           to the given permillage (i.e. 0...1000) of the entire profiled
           execution.

       hot-bb-frequency-fraction
           Select fraction of the entry block frequency of executions of
           basic block in function given basic block needs to have to be
           considered hot.

       max-predicted-iterations
           The maximum number of loop iterations we predict statically.
           This is useful in cases where a function contains a single loop
           with known bound and another loop with unknown bound.  The
           known number of iterations is predicted correctly, while the
           unknown number of iterations average to roughly 10.  This means
           that the loop without bounds appears artificially cold relative
           to the other one.

       builtin-expect-probability
           Control the probability of the expression having the specified
           value. This parameter takes a percentage (i.e. 0 ... 100) as
           input.  The default probability of 90 is obtained empirically.

       align-threshold
           Select fraction of the maximal frequency of executions of a
           basic block in a function to align the basic block.

       align-loop-iterations
           A loop expected to iterate at least the selected number of
           iterations is aligned.

       tracer-dynamic-coverage
       tracer-dynamic-coverage-feedback
           This value is used to limit superblock formation once the given
           percentage of executed instructions is covered.  This limits
           unnecessary code size expansion.

           The tracer-dynamic-coverage-feedback parameter is used only
           when profile feedback is available.  The real profiles (as
           opposed to statically estimated ones) are much less balanced
           allowing the threshold to be larger value.

       tracer-max-code-growth
           Stop tail duplication once code growth has reached given
           percentage.  This is a rather artificial limit, as most of the
           duplicates are eliminated later in cross jumping, so it may be
           set to much higher values than is the desired code growth.

       tracer-min-branch-ratio
           Stop reverse growth when the reverse probability of best edge
           is less than this threshold (in percent).

       tracer-min-branch-probability
       tracer-min-branch-probability-feedback
           Stop forward growth if the best edge has probability lower than
           this threshold.

           Similarly to tracer-dynamic-coverage two parameters are
           provided.  tracer-min-branch-probability-feedback is used for
           compilation with profile feedback and tracer-min-branch-
           probability compilation without.  The value for compilation
           with profile feedback needs to be more conservative (higher) in
           order to make tracer effective.

       max-cse-path-length
           The maximum number of basic blocks on path that CSE considers.
           The default is 10.

       max-cse-insns
           The maximum number of instructions CSE processes before
           flushing.  The default is 1000.

       ggc-min-expand
           GCC uses a garbage collector to manage its own memory
           allocation.  This parameter specifies the minimum percentage by
           which the garbage collector's heap should be allowed to expand
           between collections.  Tuning this may improve compilation
           speed; it has no effect on code generation.

           The default is 30% + 70% * (RAM/1GB) with an upper bound of
           100% when RAM >= 1GB.  If "getrlimit" is available, the notion
           of "RAM" is the smallest of actual RAM and "RLIMIT_DATA" or
           "RLIMIT_AS".  If GCC is not able to calculate RAM on a
           particular platform, the lower bound of 30% is used.  Setting
           this parameter and ggc-min-heapsize to zero causes a full
           collection to occur at every opportunity.  This is extremely
           slow, but can be useful for debugging.

       ggc-min-heapsize
           Minimum size of the garbage collector's heap before it begins
           bothering to collect garbage.  The first collection occurs
           after the heap expands by ggc-min-expand% beyond ggc-min-
           heapsize.  Again, tuning this may improve compilation speed,
           and has no effect on code generation.

           The default is the smaller of RAM/8, RLIMIT_RSS, or a limit
           that tries to ensure that RLIMIT_DATA or RLIMIT_AS are not
           exceeded, but with a lower bound of 4096 (four megabytes) and
           an upper bound of 131072 (128 megabytes).  If GCC is not able
           to calculate RAM on a particular platform, the lower bound is
           used.  Setting this parameter very large effectively disables
           garbage collection.  Setting this parameter and ggc-min-expand
           to zero causes a full collection to occur at every opportunity.

       max-reload-search-insns
           The maximum number of instruction reload should look backward
           for equivalent register.  Increasing values mean more
           aggressive optimization, making the compilation time increase
           with probably slightly better performance.  The default value
           is 100.

       max-cselib-memory-locations
           The maximum number of memory locations cselib should take into
           account.  Increasing values mean more aggressive optimization,
           making the compilation time increase with probably slightly
           better performance.  The default value is 500.

       max-sched-ready-insns
           The maximum number of instructions ready to be issued the
           scheduler should consider at any given time during the first
           scheduling pass.  Increasing values mean more thorough
           searches, making the compilation time increase with probably
           little benefit.  The default value is 100.

       max-sched-region-blocks
           The maximum number of blocks in a region to be considered for
           interblock scheduling.  The default value is 10.

       max-pipeline-region-blocks
           The maximum number of blocks in a region to be considered for
           pipelining in the selective scheduler.  The default value is
           15.

       max-sched-region-insns
           The maximum number of insns in a region to be considered for
           interblock scheduling.  The default value is 100.

       max-pipeline-region-insns
           The maximum number of insns in a region to be considered for
           pipelining in the selective scheduler.  The default value is
           200.

       min-spec-prob
           The minimum probability (in percents) of reaching a source
           block for interblock speculative scheduling.  The default value
           is 40.

       max-sched-extend-regions-iters
           The maximum number of iterations through CFG to extend regions.
           A value of 0 (the default) disables region extensions.

       max-sched-insn-conflict-delay
           The maximum conflict delay for an insn to be considered for
           speculative motion.  The default value is 3.

       sched-spec-prob-cutoff
           The minimal probability of speculation success (in percents),
           so that speculative insns are scheduled.  The default value is
           40.

       sched-state-edge-prob-cutoff
           The minimum probability an edge must have for the scheduler to
           save its state across it.  The default value is 10.

       sched-mem-true-dep-cost
           Minimal distance (in CPU cycles) between store and load
           targeting same memory locations.  The default value is 1.

       selsched-max-lookahead
           The maximum size of the lookahead window of selective
           scheduling.  It is a depth of search for available
           instructions.  The default value is 50.

       selsched-max-sched-times
           The maximum number of times that an instruction is scheduled
           during selective scheduling.  This is the limit on the number
           of iterations through which the instruction may be pipelined.
           The default value is 2.

       selsched-insns-to-rename
           The maximum number of best instructions in the ready list that
           are considered for renaming in the selective scheduler.  The
           default value is 2.

       sms-min-sc
           The minimum value of stage count that swing modulo scheduler
           generates.  The default value is 2.

       max-last-value-rtl
           The maximum size measured as number of RTLs that can be
           recorded in an expression in combiner for a pseudo register as
           last known value of that register.  The default is 10000.

       max-combine-insns
           The maximum number of instructions the RTL combiner tries to
           combine.  The default value is 2 at -Og and 4 otherwise.

       integer-share-limit
           Small integer constants can use a shared data structure,
           reducing the compiler's memory usage and increasing its speed.
           This sets the maximum value of a shared integer constant.  The
           default value is 256.

       ssp-buffer-size
           The minimum size of buffers (i.e. arrays) that receive stack
           smashing protection when -fstack-protection is used.

           This default before Ubuntu 10.10 was "8". Currently it is "4",
           to increase the number of functions protected by the stack
           protector.

       min-size-for-stack-sharing
           The minimum size of variables taking part in stack slot sharing
           when not optimizing. The default value is 32.

       max-jump-thread-duplication-stmts
           Maximum number of statements allowed in a block that needs to
           be duplicated when threading jumps.

       max-fields-for-field-sensitive
           Maximum number of fields in a structure treated in a field
           sensitive manner during pointer analysis.  The default is zero
           for -O0 and -O1, and 100 for -Os, -O2, and -O3.

       prefetch-latency
           Estimate on average number of instructions that are executed
           before prefetch finishes.  The distance prefetched ahead is
           proportional to this constant.  Increasing this number may also
           lead to less streams being prefetched (see simultaneous-
           prefetches).

       simultaneous-prefetches
           Maximum number of prefetches that can run at the same time.

       l1-cache-line-size
           The size of cache line in L1 cache, in bytes.

       l1-cache-size
           The size of L1 cache, in kilobytes.

       l2-cache-size
           The size of L2 cache, in kilobytes.

       min-insn-to-prefetch-ratio
           The minimum ratio between the number of instructions and the
           number of prefetches to enable prefetching in a loop.

       prefetch-min-insn-to-mem-ratio
           The minimum ratio between the number of instructions and the
           number of memory references to enable prefetching in a loop.

       use-canonical-types
           Whether the compiler should use the "canonical" type system.
           By default, this should always be 1, which uses a more
           efficient internal mechanism for comparing types in C++ and
           Objective-C++.  However, if bugs in the canonical type system
           are causing compilation failures, set this value to 0 to
           disable canonical types.

       switch-conversion-max-branch-ratio
           Switch initialization conversion refuses to create arrays that
           are bigger than switch-conversion-max-branch-ratio times the
           number of branches in the switch.

       max-partial-antic-length
           Maximum length of the partial antic set computed during the
           tree partial redundancy elimination optimization (-ftree-pre)
           when optimizing at -O3 and above.  For some sorts of source
           code the enhanced partial redundancy elimination optimization
           can run away, consuming all of the memory available on the host
           machine.  This parameter sets a limit on the length of the sets
           that are computed, which prevents the runaway behavior.
           Setting a value of 0 for this parameter allows an unlimited set
           length.

       sccvn-max-scc-size
           Maximum size of a strongly connected component (SCC) during
           SCCVN processing.  If this limit is hit, SCCVN processing for
           the whole function is not done and optimizations depending on
           it are disabled.  The default maximum SCC size is 10000.

       sccvn-max-alias-queries-per-access
           Maximum number of alias-oracle queries we perform when looking
           for redundancies for loads and stores.  If this limit is hit
           the search is aborted and the load or store is not considered
           redundant.  The number of queries is algorithmically limited to
           the number of stores on all paths from the load to the function
           entry.  The default maximum number of queries is 1000.

       ira-max-loops-num
           IRA uses regional register allocation by default.  If a
           function contains more loops than the number given by this
           parameter, only at most the given number of the most
           frequently-executed loops form regions for regional register
           allocation.  The default value of the parameter is 100.

       ira-max-conflict-table-size
           Although IRA uses a sophisticated algorithm to compress the
           conflict table, the table can still require excessive amounts
           of memory for huge functions.  If the conflict table for a
           function could be more than the size in MB given by this
           parameter, the register allocator instead uses a faster,
           simpler, and lower-quality algorithm that does not require
           building a pseudo-register conflict table.  The default value
           of the parameter is 2000.

       ira-loop-reserved-regs
           IRA can be used to evaluate more accurate register pressure in
           loops for decisions to move loop invariants (see -O3).  The
           number of available registers reserved for some other purposes
           is given by this parameter.  The default value of the parameter
           is 2, which is the minimal number of registers needed by
           typical instructions.  This value is the best found from
           numerous experiments.

       lra-inheritance-ebb-probability-cutoff
           LRA tries to reuse values reloaded in registers in subsequent
           insns.  This optimization is called inheritance.  EBB is used
           as a region to do this optimization.  The parameter defines a
           minimal fall-through edge probability in percentage used to add
           BB to inheritance EBB in LRA.  The default value of the
           parameter is 40.  The value was chosen from numerous runs of
           SPEC2000 on x86-64.

       loop-invariant-max-bbs-in-loop
           Loop invariant motion can be very expensive, both in
           compilation time and in amount of needed compile-time memory,
           with very large loops.  Loops with more basic blocks than this
           parameter won't have loop invariant motion optimization
           performed on them.  The default value of the parameter is 1000
           for -O1 and 10000 for -O2 and above.

       loop-max-datarefs-for-datadeps
           Building data dependencies is expensive for very large loops.
           This parameter limits the number of data references in loops
           that are considered for data dependence analysis.  These large
           loops are no handled by the optimizations using loop data
           dependencies.  The default value is 1000.

       max-vartrack-size
           Sets a maximum number of hash table slots to use during
           variable tracking dataflow analysis of any function.  If this
           limit is exceeded with variable tracking at assignments
           enabled, analysis for that function is retried without it,
           after removing all debug insns from the function.  If the limit
           is exceeded even without debug insns, var tracking analysis is
           completely disabled for the function.  Setting the parameter to
           zero makes it unlimited.

       max-vartrack-expr-depth
           Sets a maximum number of recursion levels when attempting to
           map variable names or debug temporaries to value expressions.
           This trades compilation time for more complete debug
           information.  If this is set too low, value expressions that
           are available and could be represented in debug information may
           end up not being used; setting this higher may enable the
           compiler to find more complex debug expressions, but compile
           time and memory use may grow.  The default is 12.

       min-nondebug-insn-uid
           Use uids starting at this parameter for nondebug insns.  The
           range below the parameter is reserved exclusively for debug
           insns created by -fvar-tracking-assignments, but debug insns
           may get (non-overlapping) uids above it if the reserved range
           is exhausted.

       ipa-sra-ptr-growth-factor
           IPA-SRA replaces a pointer to an aggregate with one or more new
           parameters only when their cumulative size is less or equal to
           ipa-sra-ptr-growth-factor times the size of the original
           pointer parameter.

       sra-max-scalarization-size-Ospeed
       sra-max-scalarization-size-Osize
           The two Scalar Reduction of Aggregates passes (SRA and IPA-SRA)
           aim to replace scalar parts of aggregates with uses of
           independent scalar variables.  These parameters control the
           maximum size, in storage units, of aggregate which is
           considered for replacement when compiling for speed (sra-max-
           scalarization-size-Ospeed) or size (sra-max-scalarization-size-
           Osize) respectively.

       tm-max-aggregate-size
           When making copies of thread-local variables in a transaction,
           this parameter specifies the size in bytes after which
           variables are saved with the logging functions as opposed to
           save/restore code sequence pairs.  This option only applies
           when using -fgnu-tm.

       graphite-max-nb-scop-params
           To avoid exponential effects in the Graphite loop transforms,
           the number of parameters in a Static Control Part (SCoP) is
           bounded.  The default value is 10 parameters.  A variable whose
           value is unknown at compilation time and defined outside a SCoP
           is a parameter of the SCoP.

       graphite-max-bbs-per-function
           To avoid exponential effects in the detection of SCoPs, the
           size of the functions analyzed by Graphite is bounded.  The
           default value is 100 basic blocks.

       loop-block-tile-size
           Loop blocking or strip mining transforms, enabled with
           -floop-block or -floop-strip-mine, strip mine each loop in the
           loop nest by a given number of iterations.  The strip length
           can be changed using the loop-block-tile-size parameter.  The
           default value is 51 iterations.

       loop-unroll-jam-size
           Specify the unroll factor for the -floop-unroll-and-jam option.
           The default value is 4.

       loop-unroll-jam-depth
           Specify the dimension to be unrolled (counting from the most
           inner loop) for the  -floop-unroll-and-jam.  The default value
           is 2.

       ipa-cp-value-list-size
           IPA-CP attempts to track all possible values and types passed
           to a function's parameter in order to propagate them and
           perform devirtualization.  ipa-cp-value-list-size is the
           maximum number of values and types it stores per one formal
           parameter of a function.

       ipa-cp-eval-threshold
           IPA-CP calculates its own score of cloning profitability
           heuristics and performs those cloning opportunities with scores
           that exceed ipa-cp-eval-threshold.

       ipa-cp-recursion-penalty
           Percentage penalty the recursive functions will receive when
           they are evaluated for cloning.

       ipa-cp-single-call-penalty
           Percentage penalty functions containg a single call to another
           function will receive when they are evaluated for cloning.

       ipa-max-agg-items
           IPA-CP is also capable to propagate a number of scalar values
           passed in an aggregate. ipa-max-agg-items controls the maximum
           number of such values per one parameter.

       ipa-cp-loop-hint-bonus
           When IPA-CP determines that a cloning candidate would make the
           number of iterations of a loop known, it adds a bonus of ipa-
           cp-loop-hint-bonus to the profitability score of the candidate.

       ipa-cp-array-index-hint-bonus
           When IPA-CP determines that a cloning candidate would make the
           index of an array access known, it adds a bonus of ipa-cp-
           array-index-hint-bonus to the profitability score of the
           candidate.

       ipa-max-aa-steps
           During its analysis of function bodies, IPA-CP employs alias
           analysis in order to track values pointed to by function
           parameters.  In order not spend too much time analyzing huge
           functions, it gives up and consider all memory clobbered after
           examining ipa-max-aa-steps statements modifying memory.

       lto-partitions
           Specify desired number of partitions produced during WHOPR
           compilation.  The number of partitions should exceed the number
           of CPUs used for compilation.  The default value is 32.

       lto-min-partition
           Size of minimal partition for WHOPR (in estimated
           instructions).  This prevents expenses of splitting very small
           programs into too many partitions.

       cxx-max-namespaces-for-diagnostic-help
           The maximum number of namespaces to consult for suggestions
           when C++ name lookup fails for an identifier.  The default is
           1000.

       sink-frequency-threshold
           The maximum relative execution frequency (in percents) of the
           target block relative to a statement's original block to allow
           statement sinking of a statement.  Larger numbers result in
           more aggressive statement sinking.  The default value is 75.  A
           small positive adjustment is applied for statements with memory
           operands as those are even more profitable so sink.

       max-stores-to-sink
           The maximum number of conditional store pairs that can be sunk.
           Set to 0 if either vectorization (-ftree-vectorize) or if-
           conversion (-ftree-loop-if-convert) is disabled.  The default
           is 2.

       allow-store-data-races
           Allow optimizers to introduce new data races on stores.  Set to
           1 to allow, otherwise to 0.  This option is enabled by default
           at optimization level -Ofast.

       case-values-threshold
           The smallest number of different values for which it is best to
           use a jump-table instead of a tree of conditional branches.  If
           the value is 0, use the default for the machine.  The default
           is 0.

       tree-reassoc-width
           Set the maximum number of instructions executed in parallel in
           reassociated tree. This parameter overrides target dependent
           heuristics used by default if has non zero value.

       sched-pressure-algorithm
           Choose between the two available implementations of
           -fsched-pressure.  Algorithm 1 is the original implementation
           and is the more likely to prevent instructions from being
           reordered.  Algorithm 2 was designed to be a compromise between
           the relatively conservative approach taken by algorithm 1 and
           the rather aggressive approach taken by the default scheduler.
           It relies more heavily on having a regular register file and
           accurate register pressure classes.  See haifa-sched.c in the
           GCC sources for more details.

           The default choice depends on the target.

       max-slsr-cand-scan
           Set the maximum number of existing candidates that are
           considered when seeking a basis for a new straight-line
           strength reduction candidate.

       asan-globals
           Enable buffer overflow detection for global objects.  This kind
           of protection is enabled by default if you are using
           -fsanitize=address option.  To disable global objects
           protection use --param asan-globals=0.

       asan-stack
           Enable buffer overflow detection for stack objects.  This kind
           of protection is enabled by default when using
           -fsanitize=address.  To disable stack protection use --param
           asan-stack=0 option.

       asan-instrument-reads
           Enable buffer overflow detection for memory reads.  This kind
           of protection is enabled by default when using
           -fsanitize=address.  To disable memory reads protection use
           --param asan-instrument-reads=0.

       asan-instrument-writes
           Enable buffer overflow detection for memory writes.  This kind
           of protection is enabled by default when using
           -fsanitize=address.  To disable memory writes protection use
           --param asan-instrument-writes=0 option.

       asan-memintrin
           Enable detection for built-in functions.  This kind of
           protection is enabled by default when using -fsanitize=address.
           To disable built-in functions protection use --param
           asan-memintrin=0.

       asan-use-after-return
           Enable detection of use-after-return.  This kind of protection
           is enabled by default when using -fsanitize=address option.  To
           disable use-after-return detection use --param
           asan-use-after-return=0.

       asan-instrumentation-with-call-threshold
           If number of memory accesses in function being instrumented is
           greater or equal to this number, use callbacks instead of
           inline checks.  E.g. to disable inline code use --param
           asan-instrumentation-with-call-threshold=0.

       chkp-max-ctor-size
           Static constructors generated by Pointer Bounds Checker may
           become very large and significantly increase compile time at
           optimization level -O1 and higher.  This parameter is a maximum
           nubmer of statements in a single generated constructor.
           Default value is 5000.

       max-fsm-thread-path-insns
           Maximum number of instructions to copy when duplicating blocks
           on a finite state automaton jump thread path.  The default is
           100.

       max-fsm-thread-length
           Maximum number of basic blocks on a finite state automaton jump
           thread path.  The default is 10.

       max-fsm-thread-paths
           Maximum number of new jump thread paths to create for a finite
           state automaton.  The default is 50.

       parloops-chunk-size
           Chunk size of omp schedule for loops parallelized by parloops.
           The default is 0.

       parloops-schedule
           Schedule type of omp schedule for loops parallelized by
           parloops (static, dynamic, guided, auto, runtime).  The default
           is static.

       max-ssa-name-query-depth
           Maximum depth of recursion when querying properties of SSA
           names in things like fold routines.  One level of recursion
           corresponds to following a use-def chain.

       hsa-gen-debug-stores
           Enable emission of special debug stores within HSA kernels
           which are then read and reported by libgomp plugin.  Generation
           of these stores is disabled by default, use --param
           hsa-gen-debug-stores=1 to enable it.

       max-speculative-devirt-maydefs
           The maximum number of may-defs we analyze when looking for a
           must-def specifying the dynamic type of an object that invokes
           a virtual call we may be able to devirtualize speculatively.

   Program Instrumentation Options
   GCC supports a number of command-line options that control adding run-
   time instrumentation to the code it normally generates.  For example,
   one purpose of instrumentation is collect profiling statistics for use
   in finding program hot spots, code coverage analysis, or profile-guided
   optimizations.  Another class of program instrumentation is adding run-
   time checking to detect programming errors like invalid pointer
   dereferences or out-of-bounds array accesses, as well as deliberately
   hostile attacks such as stack smashing or C++ vtable hijacking.  There
   is also a general hook which can be used to implement other forms of
   tracing or function-level instrumentation for debug or program analysis
   purposes.

   -p  Generate extra code to write profile information suitable for the
       analysis program prof.  You must use this option when compiling the
       source files you want data about, and you must also use it when
       linking.

   -pg Generate extra code to write profile information suitable for the
       analysis program gprof.  You must use this option when compiling
       the source files you want data about, and you must also use it when
       linking.

   -fprofile-arcs
       Add code so that program flow arcs are instrumented.  During
       execution the program records how many times each branch and call
       is executed and how many times it is taken or returns.  When the
       compiled program exits it saves this data to a file called
       auxname.gcda for each source file.  The data may be used for
       profile-directed optimizations (-fbranch-probabilities), or for
       test coverage analysis (-ftest-coverage).  Each object file's
       auxname is generated from the name of the output file, if
       explicitly specified and it is not the final executable, otherwise
       it is the basename of the source file.  In both cases any suffix is
       removed (e.g. foo.gcda for input file dir/foo.c, or dir/foo.gcda
       for output file specified as -o dir/foo.o).

   --coverage
       This option is used to compile and link code instrumented for
       coverage analysis.  The option is a synonym for -fprofile-arcs
       -ftest-coverage (when compiling) and -lgcov (when linking).  See
       the documentation for those options for more details.

       *   Compile the source files with -fprofile-arcs plus optimization
           and code generation options.  For test coverage analysis, use
           the additional -ftest-coverage option.  You do not need to
           profile every source file in a program.

       *   Link your object files with -lgcov or -fprofile-arcs (the
           latter implies the former).

       *   Run the program on a representative workload to generate the
           arc profile information.  This may be repeated any number of
           times.  You can run concurrent instances of your program, and
           provided that the file system supports locking, the data files
           will be correctly updated.  Also "fork" calls are detected and
           correctly handled (double counting will not happen).

       *   For profile-directed optimizations, compile the source files
           again with the same optimization and code generation options
           plus -fbranch-probabilities.

       *   For test coverage analysis, use gcov to produce human readable
           information from the .gcno and .gcda files.  Refer to the gcov
           documentation for further information.

       With -fprofile-arcs, for each function of your program GCC creates
       a program flow graph, then finds a spanning tree for the graph.
       Only arcs that are not on the spanning tree have to be
       instrumented: the compiler adds code to count the number of times
       that these arcs are executed.  When an arc is the only exit or only
       entrance to a block, the instrumentation code can be added to the
       block; otherwise, a new basic block must be created to hold the
       instrumentation code.

   -ftest-coverage
       Produce a notes file that the gcov code-coverage utility can use to
       show program coverage.  Each source file's note file is called
       auxname.gcno.  Refer to the -fprofile-arcs option above for a
       description of auxname and instructions on how to generate test
       coverage data.  Coverage data matches the source files more closely
       if you do not optimize.

   -fprofile-dir=path
       Set the directory to search for the profile data files in to path.
       This option affects only the profile data generated by
       -fprofile-generate, -ftest-coverage, -fprofile-arcs and used by
       -fprofile-use and -fbranch-probabilities and its related options.
       Both absolute and relative paths can be used.  By default, GCC uses
       the current directory as path, thus the profile data file appears
       in the same directory as the object file.

   -fprofile-generate
   -fprofile-generate=path
       Enable options usually used for instrumenting application to
       produce profile useful for later recompilation with profile
       feedback based optimization.  You must use -fprofile-generate both
       when compiling and when linking your program.

       The following options are enabled: -fprofile-arcs,
       -fprofile-values, -fvpt.

       If path is specified, GCC looks at the path to find the profile
       feedback data files. See -fprofile-dir.

       To optimize the program based on the collected profile information,
       use -fprofile-use.

   -fsanitize=address
       Enable AddressSanitizer, a fast memory error detector.  Memory
       access instructions are instrumented to detect out-of-bounds and
       use-after-free bugs.  See
       <https://github.com/google/sanitizers/wiki/AddressSanitizer> for
       more details.  The run-time behavior can be influenced using the
       ASAN_OPTIONS environment variable.  When set to "help=1", the
       available options are shown at startup of the instrumented program.
       See
       <https://github.com/google/sanitizers/wiki/AddressSanitizerFlags#run-time-flags>
       for a list of supported options.

   -fsanitize=kernel-address
       Enable AddressSanitizer for Linux kernel.  See
       <https://github.com/google/kasan/wiki> for more details.

   -fsanitize=thread
       Enable ThreadSanitizer, a fast data race detector.  Memory access
       instructions are instrumented to detect data race bugs.  See
       <https://github.com/google/sanitizers/wiki#threadsanitizer> for
       more details. The run-time behavior can be influenced using the
       TSAN_OPTIONS environment variable; see
       <https://github.com/google/sanitizers/wiki/ThreadSanitizerFlags>
       for a list of supported options.

   -fsanitize=leak
       Enable LeakSanitizer, a memory leak detector.  This option only
       matters for linking of executables and if neither
       -fsanitize=address nor -fsanitize=thread is used.  In that case the
       executable is linked against a library that overrides "malloc" and
       other allocator functions.  See
       <https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer>
       for more details.  The run-time behavior can be influenced using
       the LSAN_OPTIONS environment variable.

   -fsanitize=undefined
       Enable UndefinedBehaviorSanitizer, a fast undefined behavior
       detector.  Various computations are instrumented to detect
       undefined behavior at runtime.  Current suboptions are:

       -fsanitize=shift
           This option enables checking that the result of a shift
           operation is not undefined.  Note that what exactly is
           considered undefined differs slightly between C and C++, as
           well as between ISO C90 and C99, etc.

       -fsanitize=integer-divide-by-zero
           Detect integer division by zero as well as "INT_MIN / -1"
           division.

       -fsanitize=unreachable
           With this option, the compiler turns the
           "__builtin_unreachable" call into a diagnostics message call
           instead.  When reaching the "__builtin_unreachable" call, the
           behavior is undefined.

       -fsanitize=vla-bound
           This option instructs the compiler to check that the size of a
           variable length array is positive.

       -fsanitize=null
           This option enables pointer checking.  Particularly, the
           application built with this option turned on will issue an
           error message when it tries to dereference a NULL pointer, or
           if a reference (possibly an rvalue reference) is bound to a
           NULL pointer, or if a method is invoked on an object pointed by
           a NULL pointer.

       -fsanitize=return
           This option enables return statement checking.  Programs built
           with this option turned on will issue an error message when the
           end of a non-void function is reached without actually
           returning a value.  This option works in C++ only.

       -fsanitize=signed-integer-overflow
           This option enables signed integer overflow checking.  We check
           that the result of "+", "*", and both unary and binary "-" does
           not overflow in the signed arithmetics.  Note, integer
           promotion rules must be taken into account.  That is, the
           following is not an overflow:

                   signed char a = SCHAR_MAX;
                   a++;

       -fsanitize=bounds
           This option enables instrumentation of array bounds.  Various
           out of bounds accesses are detected.  Flexible array members,
           flexible array member-like arrays, and initializers of
           variables with static storage are not instrumented.

       -fsanitize=bounds-strict
           This option enables strict instrumentation of array bounds.
           Most out of bounds accesses are detected, including flexible
           array members and flexible array member-like arrays.
           Initializers of variables with static storage are not
           instrumented.

       -fsanitize=alignment
           This option enables checking of alignment of pointers when they
           are dereferenced, or when a reference is bound to
           insufficiently aligned target, or when a method or constructor
           is invoked on insufficiently aligned object.

       -fsanitize=object-size
           This option enables instrumentation of memory references using
           the "__builtin_object_size" function.  Various out of bounds
           pointer accesses are detected.

       -fsanitize=float-divide-by-zero
           Detect floating-point division by zero.  Unlike other similar
           options, -fsanitize=float-divide-by-zero is not enabled by
           -fsanitize=undefined, since floating-point division by zero can
           be a legitimate way of obtaining infinities and NaNs.

       -fsanitize=float-cast-overflow
           This option enables floating-point type to integer conversion
           checking.  We check that the result of the conversion does not
           overflow.  Unlike other similar options,
           -fsanitize=float-cast-overflow is not enabled by
           -fsanitize=undefined.  This option does not work well with
           "FE_INVALID" exceptions enabled.

       -fsanitize=nonnull-attribute
           This option enables instrumentation of calls, checking whether
           null values are not passed to arguments marked as requiring a
           non-null value by the "nonnull" function attribute.

       -fsanitize=returns-nonnull-attribute
           This option enables instrumentation of return statements in
           functions marked with "returns_nonnull" function attribute, to
           detect returning of null values from such functions.

       -fsanitize=bool
           This option enables instrumentation of loads from bool.  If a
           value other than 0/1 is loaded, a run-time error is issued.

       -fsanitize=enum
           This option enables instrumentation of loads from an enum type.
           If a value outside the range of values for the enum type is
           loaded, a run-time error is issued.

       -fsanitize=vptr
           This option enables instrumentation of C++ member function
           calls, member accesses and some conversions between pointers to
           base and derived classes, to verify the referenced object has
           the correct dynamic type.

       While -ftrapv causes traps for signed overflows to be emitted,
       -fsanitize=undefined gives a diagnostic message.  This currently
       works only for the C family of languages.

   -fno-sanitize=all
       This option disables all previously enabled sanitizers.
       -fsanitize=all is not allowed, as some sanitizers cannot be used
       together.

   -fasan-shadow-offset=number
       This option forces GCC to use custom shadow offset in
       AddressSanitizer checks.  It is useful for experimenting with
       different shadow memory layouts in Kernel AddressSanitizer.

   -fsanitize-sections=s1,s2,...
       Sanitize global variables in selected user-defined sections.  si
       may contain wildcards.

   -fsanitize-recover[=opts]
       -fsanitize-recover= controls error recovery mode for sanitizers
       mentioned in comma-separated list of opts.  Enabling this option
       for a sanitizer component causes it to attempt to continue running
       the program as if no error happened.  This means multiple runtime
       errors can be reported in a single program run, and the exit code
       of the program may indicate success even when errors have been
       reported.  The -fno-sanitize-recover= option can be used to alter
       this behavior: only the first detected error is reported and
       program then exits with a non-zero exit code.

       Currently this feature only works for -fsanitize=undefined (and its
       suboptions except for -fsanitize=unreachable and
       -fsanitize=return), -fsanitize=float-cast-overflow,
       -fsanitize=float-divide-by-zero, -fsanitize=kernel-address and
       -fsanitize=address.  For these sanitizers error recovery is turned
       on by default, except -fsanitize=address, for which this feature is
       experimental.  -fsanitize-recover=all and -fno-sanitize-recover=all
       is also accepted, the former enables recovery for all sanitizers
       that support it, the latter disables recovery for all sanitizers
       that support it.

       Syntax without explicit opts parameter is deprecated.  It is
       equivalent to

               -fsanitize-recover=undefined,float-cast-overflow,float-divide-by-zero

       Similarly -fno-sanitize-recover is equivalent to

               -fno-sanitize-recover=undefined,float-cast-overflow,float-divide-by-zero

   -fsanitize-undefined-trap-on-error
       The -fsanitize-undefined-trap-on-error option instructs the
       compiler to report undefined behavior using "__builtin_trap" rather
       than a "libubsan" library routine.  The advantage of this is that
       the "libubsan" library is not needed and is not linked in, so this
       is usable even in freestanding environments.

   -fsanitize-coverage=trace-pc
       Enable coverage-guided fuzzing code instrumentation.  Inserts a
       call to "__sanitizer_cov_trace_pc" into every basic block.

   -fbounds-check
       For front ends that support it, generate additional code to check
       that indices used to access arrays are within the declared range.
       This is currently only supported by the Java and Fortran front
       ends, where this option defaults to true and false respectively.

   -fcheck-pointer-bounds
       Enable Pointer Bounds Checker instrumentation.  Each memory
       reference is instrumented with checks of the pointer used for
       memory access against bounds associated with that pointer.

       Currently there is only an implementation for Intel MPX available,
       thus x86 GNU/Linux target and -mmpx are required to enable this
       feature.  MPX-based instrumentation requires a runtime library to
       enable MPX in hardware and handle bounds violation signals.  By
       default when -fcheck-pointer-bounds and -mmpx options are used to
       link a program, the GCC driver links against the libmpx and
       libmpxwrappers libraries.  Bounds checking on calls to dynamic
       libraries requires a linker with -z bndplt support; if GCC was
       configured with a linker without support for this option (including
       the Gold linker and older versions of ld), a warning is given if
       you link with -mmpx without also specifying -static, since the
       overall effectiveness of the bounds checking protection is reduced.
       See also -static-libmpxwrappers.

       MPX-based instrumentation may be used for debugging and also may be
       included in production code to increase program security.
       Depending on usage, you may have different requirements for the
       runtime library.  The current version of the MPX runtime library is
       more oriented for use as a debugging tool.  MPX runtime library
       usage implies -lpthread.  See also -static-libmpx.  The runtime
       library  behavior can be influenced using various CHKP_RT_*
       environment variables.  See
       <https://gcc.gnu.org/wiki/Intel%20MPX%20support%20in%20the%20GCC%20compiler>
       for more details.

       Generated instrumentation may be controlled by various -fchkp-*
       options and by the "bnd_variable_size" structure field attribute
       and "bnd_legacy", and "bnd_instrument" function attributes.  GCC
       also provides a number of built-in functions for controlling the
       Pointer Bounds Checker.

   -fchkp-check-incomplete-type
       Generate pointer bounds checks for variables with incomplete type.
       Enabled by default.

   -fchkp-narrow-bounds
       Controls bounds used by Pointer Bounds Checker for pointers to
       object fields.  If narrowing is enabled then field bounds are used.
       Otherwise object bounds are used.  See also
       -fchkp-narrow-to-innermost-array and
       -fchkp-first-field-has-own-bounds.  Enabled by default.

   -fchkp-first-field-has-own-bounds
       Forces Pointer Bounds Checker to use narrowed bounds for the
       address of the first field in the structure.  By default a pointer
       to the first field has the same bounds as a pointer to the whole
       structure.

   -fchkp-narrow-to-innermost-array
       Forces Pointer Bounds Checker to use bounds of the innermost arrays
       in case of nested static array access.  By default this option is
       disabled and bounds of the outermost array are used.

   -fchkp-optimize
       Enables Pointer Bounds Checker optimizations.  Enabled by default
       at optimization levels -O, -O2, -O3.

   -fchkp-use-fast-string-functions
       Enables use of *_nobnd versions of string functions (not copying
       bounds) by Pointer Bounds Checker.  Disabled by default.

   -fchkp-use-nochk-string-functions
       Enables use of *_nochk versions of string functions (not checking
       bounds) by Pointer Bounds Checker.  Disabled by default.

   -fchkp-use-static-bounds
       Allow Pointer Bounds Checker to generate static bounds holding
       bounds of static variables.  Enabled by default.

   -fchkp-use-static-const-bounds
       Use statically-initialized bounds for constant bounds instead of
       generating them each time they are required.  By default enabled
       when -fchkp-use-static-bounds is enabled.

   -fchkp-treat-zero-dynamic-size-as-infinite
       With this option, objects with incomplete type whose dynamically-
       obtained size is zero are treated as having infinite size instead
       by Pointer Bounds Checker.  This option may be helpful if a program
       is linked with a library missing size information for some symbols.
       Disabled by default.

   -fchkp-check-read
       Instructs Pointer Bounds Checker to generate checks for all read
       accesses to memory.  Enabled by default.

   -fchkp-check-write
       Instructs Pointer Bounds Checker to generate checks for all write
       accesses to memory.  Enabled by default.

   -fchkp-store-bounds
       Instructs Pointer Bounds Checker to generate bounds stores for
       pointer writes.  Enabled by default.

   -fchkp-instrument-calls
       Instructs Pointer Bounds Checker to pass pointer bounds to calls.
       Enabled by default.

   -fchkp-instrument-marked-only
       Instructs Pointer Bounds Checker to instrument only functions
       marked with the "bnd_instrument" attribute.  Disabled by default.

   -fchkp-use-wrappers
       Allows Pointer Bounds Checker to replace calls to built-in
       functions with calls to wrapper functions.  When
       -fchkp-use-wrappers is used to link a program, the GCC driver
       automatically links against libmpxwrappers.  See also
       -static-libmpxwrappers.  Enabled by default.

   -fstack-protector
       Emit extra code to check for buffer overflows, such as stack
       smashing attacks.  This is done by adding a guard variable to
       functions with vulnerable objects.  This includes functions that
       call "alloca", and functions with buffers larger than 8 bytes.  The
       guards are initialized when a function is entered and then checked
       when the function exits.  If a guard check fails, an error message
       is printed and the program exits.

   -fstack-protector-all
       Like -fstack-protector except that all functions are protected.

   -fstack-protector-strong
       Like -fstack-protector but includes additional functions to be
       protected --- those that have local array definitions, or have
       references to local frame addresses.

   -fstack-protector-explicit
       Like -fstack-protector but only protects those functions which have
       the "stack_protect" attribute.

   -fstack-check
       Generate code to verify that you do not go beyond the boundary of
       the stack.  You should specify this flag if you are running in an
       environment with multiple threads, but you only rarely need to
       specify it in a single-threaded environment since stack overflow is
       automatically detected on nearly all systems if there is only one
       stack.

       Note that this switch does not actually cause checking to be done;
       the operating system or the language runtime must do that.  The
       switch causes generation of code to ensure that they see the stack
       being extended.

       You can additionally specify a string parameter: no means no
       checking, generic means force the use of old-style checking,
       specific means use the best checking method and is equivalent to
       bare -fstack-check.

       Old-style checking is a generic mechanism that requires no specific
       target support in the compiler but comes with the following
       drawbacks:

       1.  Modified allocation strategy for large objects: they are always
           allocated dynamically if their size exceeds a fixed threshold.

       2.  Fixed limit on the size of the static frame of functions: when
           it is topped by a particular function, stack checking is not
           reliable and a warning is issued by the compiler.

       3.  Inefficiency: because of both the modified allocation strategy
           and the generic implementation, code performance is hampered.

       Note that old-style stack checking is also the fallback method for
       specific if no target support has been added in the compiler.

   -fstack-limit-register=reg
   -fstack-limit-symbol=sym
   -fno-stack-limit
       Generate code to ensure that the stack does not grow beyond a
       certain value, either the value of a register or the address of a
       symbol.  If a larger stack is required, a signal is raised at run
       time.  For most targets, the signal is raised before the stack
       overruns the boundary, so it is possible to catch the signal
       without taking special precautions.

       For instance, if the stack starts at absolute address 0x80000000
       and grows downwards, you can use the flags
       -fstack-limit-symbol=__stack_limit and
       -Wl,--defsym,__stack_limit=0x7ffe0000 to enforce a stack limit of
       128KB.  Note that this may only work with the GNU linker.

       You can locally override stack limit checking by using the
       "no_stack_limit" function attribute.

   -fsplit-stack
       Generate code to automatically split the stack before it overflows.
       The resulting program has a discontiguous stack which can only
       overflow if the program is unable to allocate any more memory.
       This is most useful when running threaded programs, as it is no
       longer necessary to calculate a good stack size to use for each
       thread.  This is currently only implemented for the x86 targets
       running GNU/Linux.

       When code compiled with -fsplit-stack calls code compiled without
       -fsplit-stack, there may not be much stack space available for the
       latter code to run.  If compiling all code, including library code,
       with -fsplit-stack is not an option, then the linker can fix up
       these calls so that the code compiled without -fsplit-stack always
       has a large stack.  Support for this is implemented in the gold
       linker in GNU binutils release 2.21 and later.

   -fvtable-verify=[std|preinit|none]
       This option is only available when compiling C++ code.  It turns on
       (or off, if using -fvtable-verify=none) the security feature that
       verifies at run time, for every virtual call, that the vtable
       pointer through which the call is made is valid for the type of the
       object, and has not been corrupted or overwritten.  If an invalid
       vtable pointer is detected at run time, an error is reported and
       execution of the program is immediately halted.

       This option causes run-time data structures to be built at program
       startup, which are used for verifying the vtable pointers.  The
       options std and preinit control the timing of when these data
       structures are built.  In both cases the data structures are built
       before execution reaches "main".  Using -fvtable-verify=std causes
       the data structures to be built after shared libraries have been
       loaded and initialized.  -fvtable-verify=preinit causes them to be
       built before shared libraries have been loaded and initialized.

       If this option appears multiple times in the command line with
       different values specified, none takes highest priority over both
       std and preinit; preinit takes priority over std.

   -fvtv-debug
       When used in conjunction with -fvtable-verify=std or
       -fvtable-verify=preinit, causes debug versions of the runtime
       functions for the vtable verification feature to be called.  This
       flag also causes the compiler to log information about which vtable
       pointers it finds for each class.  This information is written to a
       file named vtv_set_ptr_data.log in the directory named by the
       environment variable VTV_LOGS_DIR if that is defined or the current
       working directory otherwise.

       Note:  This feature appends data to the log file. If you want a
       fresh log file, be sure to delete any existing one.

   -fvtv-counts
       This is a debugging flag.  When used in conjunction with
       -fvtable-verify=std or -fvtable-verify=preinit, this causes the
       compiler to keep track of the total number of virtual calls it
       encounters and the number of verifications it inserts.  It also
       counts the number of calls to certain run-time library functions
       that it inserts and logs this information for each compilation
       unit.  The compiler writes this information to a file named
       vtv_count_data.log in the directory named by the environment
       variable VTV_LOGS_DIR if that is defined or the current working
       directory otherwise.  It also counts the size of the vtable pointer
       sets for each class, and writes this information to
       vtv_class_set_sizes.log in the same directory.

       Note:  This feature appends data to the log files.  To get fresh
       log files, be sure to delete any existing ones.

   -finstrument-functions
       Generate instrumentation calls for entry and exit to functions.
       Just after function entry and just before function exit, the
       following profiling functions are called with the address of the
       current function and its call site.  (On some platforms,
       "__builtin_return_address" does not work beyond the current
       function, so the call site information may not be available to the
       profiling functions otherwise.)

               void __cyg_profile_func_enter (void *this_fn,
                                              void *call_site);
               void __cyg_profile_func_exit  (void *this_fn,
                                              void *call_site);

       The first argument is the address of the start of the current
       function, which may be looked up exactly in the symbol table.

       This instrumentation is also done for functions expanded inline in
       other functions.  The profiling calls indicate where, conceptually,
       the inline function is entered and exited.  This means that
       addressable versions of such functions must be available.  If all
       your uses of a function are expanded inline, this may mean an
       additional expansion of code size.  If you use "extern inline" in
       your C code, an addressable version of such functions must be
       provided.  (This is normally the case anyway, but if you get lucky
       and the optimizer always expands the functions inline, you might
       have gotten away without providing static copies.)

       A function may be given the attribute "no_instrument_function", in
       which case this instrumentation is not done.  This can be used, for
       example, for the profiling functions listed above, high-priority
       interrupt routines, and any functions from which the profiling
       functions cannot safely be called (perhaps signal handlers, if the
       profiling routines generate output or allocate memory).

   -finstrument-functions-exclude-file-list=file,file,...
       Set the list of functions that are excluded from instrumentation
       (see the description of -finstrument-functions).  If the file that
       contains a function definition matches with one of file, then that
       function is not instrumented.  The match is done on substrings: if
       the file parameter is a substring of the file name, it is
       considered to be a match.

       For example:

               -finstrument-functions-exclude-file-list=/bits/stl,include/sys

       excludes any inline function defined in files whose pathnames
       contain /bits/stl or include/sys.

       If, for some reason, you want to include letter , in one of sym,
       write ,. For example,
       -finstrument-functions-exclude-file-list=',,tmp' (note the single
       quote surrounding the option).

   -finstrument-functions-exclude-function-list=sym,sym,...
       This is similar to -finstrument-functions-exclude-file-list, but
       this option sets the list of function names to be excluded from
       instrumentation.  The function name to be matched is its user-
       visible name, such as "vector<int> blah(const vector<int> &)", not
       the internal mangled name (e.g., "_Z4blahRSt6vectorIiSaIiEE").  The
       match is done on substrings: if the sym parameter is a substring of
       the function name, it is considered to be a match.  For C99 and C++
       extended identifiers, the function name must be given in UTF-8, not
       using universal character names.

   Options Controlling the Preprocessor
   These options control the C preprocessor, which is run on each C source
   file before actual compilation.

   If you use the -E option, nothing is done except preprocessing.  Some
   of these options make sense only together with -E because they cause
   the preprocessor output to be unsuitable for actual compilation.

   -Wp,option
       You can use -Wp,option to bypass the compiler driver and pass
       option directly through to the preprocessor.  If option contains
       commas, it is split into multiple options at the commas.  However,
       many options are modified, translated or interpreted by the
       compiler driver before being passed to the preprocessor, and -Wp
       forcibly bypasses this phase.  The preprocessor's direct interface
       is undocumented and subject to change, so whenever possible you
       should avoid using -Wp and let the driver handle the options
       instead.

   -Xpreprocessor option
       Pass option as an option to the preprocessor.  You can use this to
       supply system-specific preprocessor options that GCC does not
       recognize.

       If you want to pass an option that takes an argument, you must use
       -Xpreprocessor twice, once for the option and once for the
       argument.

   -no-integrated-cpp
       Perform preprocessing as a separate pass before compilation.  By
       default, GCC performs preprocessing as an integrated part of input
       tokenization and parsing.  If this option is provided, the
       appropriate language front end (cc1, cc1plus, or cc1obj for C, C++,
       and Objective-C, respectively) is instead invoked twice, once for
       preprocessing only and once for actual compilation of the
       preprocessed input.  This option may be useful in conjunction with
       the -B or -wrapper options to specify an alternate preprocessor or
       perform additional processing of the program source between normal
       preprocessing and compilation.

   -D name
       Predefine name as a macro, with definition 1.

   -D name=definition
       The contents of definition are tokenized and processed as if they
       appeared during translation phase three in a #define directive.  In
       particular, the definition will be truncated by embedded newline
       characters.

       If you are invoking the preprocessor from a shell or shell-like
       program you may need to use the shell's quoting syntax to protect
       characters such as spaces that have a meaning in the shell syntax.

       If you wish to define a function-like macro on the command line,
       write its argument list with surrounding parentheses before the
       equals sign (if any).  Parentheses are meaningful to most shells,
       so you will need to quote the option.  With sh and csh,
       -D'name(args...)=definition' works.

       -D and -U options are processed in the order they are given on the
       command line.  All -imacros file and -include file options are
       processed after all -D and -U options.

   -U name
       Cancel any previous definition of name, either built in or provided
       with a -D option.

   -undef
       Do not predefine any system-specific or GCC-specific macros.  The
       standard predefined macros remain defined.

   -I dir
       Add the directory dir to the list of directories to be searched for
       header files.  Directories named by -I are searched before the
       standard system include directories.  If the directory dir is a
       standard system include directory, the option is ignored to ensure
       that the default search order for system directories and the
       special treatment of system headers are not defeated .  If dir
       begins with "=", then the "=" will be replaced by the sysroot
       prefix; see --sysroot and -isysroot.

   -o file
       Write output to file.  This is the same as specifying file as the
       second non-option argument to cpp.  gcc has a different
       interpretation of a second non-option argument, so you must use -o
       to specify the output file.

   -Wall
       Turns on all optional warnings which are desirable for normal code.
       At present this is -Wcomment, -Wtrigraphs, -Wmultichar and a
       warning about integer promotion causing a change of sign in "#if"
       expressions.  Note that many of the preprocessor's warnings are on
       by default and have no options to control them.

   -Wcomment
   -Wcomments
       Warn whenever a comment-start sequence /* appears in a /* comment,
       or whenever a backslash-newline appears in a // comment.  (Both
       forms have the same effect.)

   -Wtrigraphs
       Most trigraphs in comments cannot affect the meaning of the
       program.  However, a trigraph that would form an escaped newline
       (??/ at the end of a line) can, by changing where the comment
       begins or ends.  Therefore, only trigraphs that would form escaped
       newlines produce warnings inside a comment.

       This option is implied by -Wall.  If -Wall is not given, this
       option is still enabled unless trigraphs are enabled.  To get
       trigraph conversion without warnings, but get the other -Wall
       warnings, use -trigraphs -Wall -Wno-trigraphs.

   -Wtraditional
       Warn about certain constructs that behave differently in
       traditional and ISO C.  Also warn about ISO C constructs that have
       no traditional C equivalent, and problematic constructs which
       should be avoided.

   -Wundef
       Warn whenever an identifier which is not a macro is encountered in
       an #if directive, outside of defined.  Such identifiers are
       replaced with zero.

   -Wunused-macros
       Warn about macros defined in the main file that are unused.  A
       macro is used if it is expanded or tested for existence at least
       once.  The preprocessor will also warn if the macro has not been
       used at the time it is redefined or undefined.

       Built-in macros, macros defined on the command line, and macros
       defined in include files are not warned about.

       Note: If a macro is actually used, but only used in skipped
       conditional blocks, then CPP will report it as unused.  To avoid
       the warning in such a case, you might improve the scope of the
       macro's definition by, for example, moving it into the first
       skipped block.  Alternatively, you could provide a dummy use with
       something like:

               #if defined the_macro_causing_the_warning
               #endif

   -Wendif-labels
       Warn whenever an #else or an #endif are followed by text.  This
       usually happens in code of the form

               #if FOO
               ...
               #else FOO
               ...
               #endif FOO

       The second and third "FOO" should be in comments, but often are not
       in older programs.  This warning is on by default.

   -Werror
       Make all warnings into hard errors.  Source code which triggers
       warnings will be rejected.

   -Wsystem-headers
       Issue warnings for code in system headers.  These are normally
       unhelpful in finding bugs in your own code, therefore suppressed.
       If you are responsible for the system library, you may want to see
       them.

   -w  Suppress all warnings, including those which GNU CPP issues by
       default.

   -pedantic
       Issue all the mandatory diagnostics listed in the C standard.  Some
       of them are left out by default, since they trigger frequently on
       harmless code.

   -pedantic-errors
       Issue all the mandatory diagnostics, and make all mandatory
       diagnostics into errors.  This includes mandatory diagnostics that
       GCC issues without -pedantic but treats as warnings.

   -M  Instead of outputting the result of preprocessing, output a rule
       suitable for make describing the dependencies of the main source
       file.  The preprocessor outputs one make rule containing the object
       file name for that source file, a colon, and the names of all the
       included files, including those coming from -include or -imacros
       command-line options.

       Unless specified explicitly (with -MT or -MQ), the object file name
       consists of the name of the source file with any suffix replaced
       with object file suffix and with any leading directory parts
       removed.  If there are many included files then the rule is split
       into several lines using \-newline.  The rule has no commands.

       This option does not suppress the preprocessor's debug output, such
       as -dM.  To avoid mixing such debug output with the dependency
       rules you should explicitly specify the dependency output file with
       -MF, or use an environment variable like DEPENDENCIES_OUTPUT.
       Debug output will still be sent to the regular output stream as
       normal.

       Passing -M to the driver implies -E, and suppresses warnings with
       an implicit -w.

   -MM Like -M but do not mention header files that are found in system
       header directories, nor header files that are included, directly or
       indirectly, from such a header.

       This implies that the choice of angle brackets or double quotes in
       an #include directive does not in itself determine whether that
       header will appear in -MM dependency output.  This is a slight
       change in semantics from GCC versions 3.0 and earlier.

   -MF file
       When used with -M or -MM, specifies a file to write the
       dependencies to.  If no -MF switch is given the preprocessor sends
       the rules to the same place it would have sent preprocessed output.

       When used with the driver options -MD or -MMD, -MF overrides the
       default dependency output file.

   -MG In conjunction with an option such as -M requesting dependency
       generation, -MG assumes missing header files are generated files
       and adds them to the dependency list without raising an error.  The
       dependency filename is taken directly from the "#include" directive
       without prepending any path.  -MG also suppresses preprocessed
       output, as a missing header file renders this useless.

       This feature is used in automatic updating of makefiles.

   -MP This option instructs CPP to add a phony target for each dependency
       other than the main file, causing each to depend on nothing.  These
       dummy rules work around errors make gives if you remove header
       files without updating the Makefile to match.

       This is typical output:

               test.o: test.c test.h

               test.h:

   -MT target
       Change the target of the rule emitted by dependency generation.  By
       default CPP takes the name of the main input file, deletes any
       directory components and any file suffix such as .c, and appends
       the platform's usual object suffix.  The result is the target.

       An -MT option will set the target to be exactly the string you
       specify.  If you want multiple targets, you can specify them as a
       single argument to -MT, or use multiple -MT options.

       For example, -MT '$(objpfx)foo.o' might give

               $(objpfx)foo.o: foo.c

   -MQ target
       Same as -MT, but it quotes any characters which are special to
       Make.  -MQ '$(objpfx)foo.o' gives

               $$(objpfx)foo.o: foo.c

       The default target is automatically quoted, as if it were given
       with -MQ.

   -MD -MD is equivalent to -M -MF file, except that -E is not implied.
       The driver determines file based on whether an -o option is given.
       If it is, the driver uses its argument but with a suffix of .d,
       otherwise it takes the name of the input file, removes any
       directory components and suffix, and applies a .d suffix.

       If -MD is used in conjunction with -E, any -o switch is understood
       to specify the dependency output file, but if used without -E, each
       -o is understood to specify a target object file.

       Since -E is not implied, -MD can be used to generate a dependency
       output file as a side-effect of the compilation process.

   -MMD
       Like -MD except mention only user header files, not system header
       files.

   -fpch-deps
       When using precompiled headers, this flag will cause the
       dependency-output flags to also list the files from the precompiled
       header's dependencies.  If not specified only the precompiled
       header would be listed and not the files that were used to create
       it because those files are not consulted when a precompiled header
       is used.

   -fpch-preprocess
       This option allows use of a precompiled header together with -E.
       It inserts a special "#pragma", "#pragma GCC pch_preprocess
       "filename"" in the output to mark the place where the precompiled
       header was found, and its filename.  When -fpreprocessed is in use,
       GCC recognizes this "#pragma" and loads the PCH.

       This option is off by default, because the resulting preprocessed
       output is only really suitable as input to GCC.  It is switched on
       by -save-temps.

       You should not write this "#pragma" in your own code, but it is
       safe to edit the filename if the PCH file is available in a
       different location.  The filename may be absolute or it may be
       relative to GCC's current directory.

   -x c
   -x c++
   -x objective-c
   -x assembler-with-cpp
       Specify the source language: C, C++, Objective-C, or assembly.
       This has nothing to do with standards conformance or extensions; it
       merely selects which base syntax to expect.  If you give none of
       these options, cpp will deduce the language from the extension of
       the source file: .c, .cc, .m, or .S.  Some other common extensions
       for C++ and assembly are also recognized.  If cpp does not
       recognize the extension, it will treat the file as C; this is the
       most generic mode.

       Note: Previous versions of cpp accepted a -lang option which
       selected both the language and the standards conformance level.
       This option has been removed, because it conflicts with the -l
       option.

   -std=standard
   -ansi
       Specify the standard to which the code should conform.  Currently
       CPP knows about C and C++ standards; others may be added in the
       future.

       standard may be one of:

       "c90"
       "c89"
       "iso9899:1990"
           The ISO C standard from 1990.  c90 is the customary shorthand
           for this version of the standard.

           The -ansi option is equivalent to -std=c90.

       "iso9899:199409"
           The 1990 C standard, as amended in 1994.

       "iso9899:1999"
       "c99"
       "iso9899:199x"
       "c9x"
           The revised ISO C standard, published in December 1999.  Before
           publication, this was known as C9X.

       "iso9899:2011"
       "c11"
       "c1x"
           The revised ISO C standard, published in December 2011.  Before
           publication, this was known as C1X.

       "gnu90"
       "gnu89"
           The 1990 C standard plus GNU extensions.  This is the default.

       "gnu99"
       "gnu9x"
           The 1999 C standard plus GNU extensions.

       "gnu11"
       "gnu1x"
           The 2011 C standard plus GNU extensions.

       "c++98"
           The 1998 ISO C++ standard plus amendments.

       "gnu++98"
           The same as -std=c++98 plus GNU extensions.  This is the
           default for C++ code.

   -I- Split the include path.  Any directories specified with -I options
       before -I- are searched only for headers requested with
       "#include "file""; they are not searched for "#include <file>".  If
       additional directories are specified with -I options after the -I-,
       those directories are searched for all #include directives.

       In addition, -I- inhibits the use of the directory of the current
       file directory as the first search directory for "#include "file"".
       This option has been deprecated.

   -nostdinc
       Do not search the standard system directories for header files.
       Only the directories you have specified with -I options (and the
       directory of the current file, if appropriate) are searched.

   -nostdinc++
       Do not search for header files in the C++-specific standard
       directories, but do still search the other standard directories.
       (This option is used when building the C++ library.)

   -include file
       Process file as if "#include "file"" appeared as the first line of
       the primary source file.  However, the first directory searched for
       file is the preprocessor's working directory instead of the
       directory containing the main source file.  If not found there, it
       is searched for in the remainder of the "#include "..."" search
       chain as normal.

       If multiple -include options are given, the files are included in
       the order they appear on the command line.

   -imacros file
       Exactly like -include, except that any output produced by scanning
       file is thrown away.  Macros it defines remain defined.  This
       allows you to acquire all the macros from a header without also
       processing its declarations.

       All files specified by -imacros are processed before all files
       specified by -include.

   -idirafter dir
       Search dir for header files, but do it after all directories
       specified with -I and the standard system directories have been
       exhausted.  dir is treated as a system include directory.  If dir
       begins with "=", then the "=" will be replaced by the sysroot
       prefix; see --sysroot and -isysroot.

   -iprefix prefix
       Specify prefix as the prefix for subsequent -iwithprefix options.
       If the prefix represents a directory, you should include the final
       /.

   -iwithprefix dir
   -iwithprefixbefore dir
       Append dir to the prefix specified previously with -iprefix, and
       add the resulting directory to the include search path.
       -iwithprefixbefore puts it in the same place -I would; -iwithprefix
       puts it where -idirafter would.

   -isysroot dir
       This option is like the --sysroot option, but applies only to
       header files (except for Darwin targets, where it applies to both
       header files and libraries).  See the --sysroot option for more
       information.

   -imultilib dir
       Use dir as a subdirectory of the directory containing target-
       specific C++ headers.

   -isystem dir
       Search dir for header files, after all directories specified by -I
       but before the standard system directories.  Mark it as a system
       directory, so that it gets the same special treatment as is applied
       to the standard system directories.  If dir begins with "=", then
       the "=" will be replaced by the sysroot prefix; see --sysroot and
       -isysroot.

   -iquote dir
       Search dir only for header files requested with "#include "file"";
       they are not searched for "#include <file>", before all directories
       specified by -I and before the standard system directories.  If dir
       begins with "=", then the "=" will be replaced by the sysroot
       prefix; see --sysroot and -isysroot.

   -fdirectives-only
       When preprocessing, handle directives, but do not expand macros.

       The option's behavior depends on the -E and -fpreprocessed options.

       With -E, preprocessing is limited to the handling of directives
       such as "#define", "#ifdef", and "#error".  Other preprocessor
       operations, such as macro expansion and trigraph conversion are not
       performed.  In addition, the -dD option is implicitly enabled.

       With -fpreprocessed, predefinition of command line and most builtin
       macros is disabled.  Macros such as "__LINE__", which are
       contextually dependent, are handled normally.  This enables
       compilation of files previously preprocessed with "-E
       -fdirectives-only".

       With both -E and -fpreprocessed, the rules for -fpreprocessed take
       precedence.  This enables full preprocessing of files previously
       preprocessed with "-E -fdirectives-only".

   -fdollars-in-identifiers
       Accept $ in identifiers.

   -fextended-identifiers
       Accept universal character names in identifiers.  This option is
       enabled by default for C99 (and later C standard versions) and C++.

   -fno-canonical-system-headers
       When preprocessing, do not shorten system header paths with
       canonicalization.

   -fpreprocessed
       Indicate to the preprocessor that the input file has already been
       preprocessed.  This suppresses things like macro expansion,
       trigraph conversion, escaped newline splicing, and processing of
       most directives.  The preprocessor still recognizes and removes
       comments, so that you can pass a file preprocessed with -C to the
       compiler without problems.  In this mode the integrated
       preprocessor is little more than a tokenizer for the front ends.

       -fpreprocessed is implicit if the input file has one of the
       extensions .i, .ii or .mi.  These are the extensions that GCC uses
       for preprocessed files created by -save-temps.

   -ftabstop=width
       Set the distance between tab stops.  This helps the preprocessor
       report correct column numbers in warnings or errors, even if tabs
       appear on the line.  If the value is less than 1 or greater than
       100, the option is ignored.  The default is 8.

   -fdebug-cpp
       This option is only useful for debugging GCC.  When used with -E,
       dumps debugging information about location maps.  Every token in
       the output is preceded by the dump of the map its location belongs
       to.  The dump of the map holding the location of a token would be:

               {"P":F</file/path>;"F":F</includer/path>;"L":<line_num>;"C":<col_num>;"S":<system_header_p>;"M":<map_address>;"E":<macro_expansion_p>,"loc":<location>}

       When used without -E, this option has no effect.

   -ftrack-macro-expansion[=level]
       Track locations of tokens across macro expansions. This allows the
       compiler to emit diagnostic about the current macro expansion stack
       when a compilation error occurs in a macro expansion. Using this
       option makes the preprocessor and the compiler consume more memory.
       The level parameter can be used to choose the level of precision of
       token location tracking thus decreasing the memory consumption if
       necessary. Value 0 of level de-activates this option just as if no
       -ftrack-macro-expansion was present on the command line. Value 1
       tracks tokens locations in a degraded mode for the sake of minimal
       memory overhead. In this mode all tokens resulting from the
       expansion of an argument of a function-like macro have the same
       location. Value 2 tracks tokens locations completely. This value is
       the most memory hungry.  When this option is given no argument, the
       default parameter value is 2.

       Note that "-ftrack-macro-expansion=2" is activated by default.

   -fexec-charset=charset
       Set the execution character set, used for string and character
       constants.  The default is UTF-8.  charset can be any encoding
       supported by the system's "iconv" library routine.

   -fwide-exec-charset=charset
       Set the wide execution character set, used for wide string and
       character constants.  The default is UTF-32 or UTF-16, whichever
       corresponds to the width of "wchar_t".  As with -fexec-charset,
       charset can be any encoding supported by the system's "iconv"
       library routine; however, you will have problems with encodings
       that do not fit exactly in "wchar_t".

   -finput-charset=charset
       Set the input character set, used for translation from the
       character set of the input file to the source character set used by
       GCC.  If the locale does not specify, or GCC cannot get this
       information from the locale, the default is UTF-8.  This can be
       overridden by either the locale or this command-line option.
       Currently the command-line option takes precedence if there's a
       conflict.  charset can be any encoding supported by the system's
       "iconv" library routine.

   -fworking-directory
       Enable generation of linemarkers in the preprocessor output that
       will let the compiler know the current working directory at the
       time of preprocessing.  When this option is enabled, the
       preprocessor will emit, after the initial linemarker, a second
       linemarker with the current working directory followed by two
       slashes.  GCC will use this directory, when it's present in the
       preprocessed input, as the directory emitted as the current working
       directory in some debugging information formats.  This option is
       implicitly enabled if debugging information is enabled, but this
       can be inhibited with the negated form -fno-working-directory.  If
       the -P flag is present in the command line, this option has no
       effect, since no "#line" directives are emitted whatsoever.

   -fno-show-column
       Do not print column numbers in diagnostics.  This may be necessary
       if diagnostics are being scanned by a program that does not
       understand the column numbers, such as dejagnu.

   -A predicate=answer
       Make an assertion with the predicate predicate and answer answer.
       This form is preferred to the older form -A predicate(answer),
       which is still supported, because it does not use shell special
       characters.

   -A -predicate=answer
       Cancel an assertion with the predicate predicate and answer answer.

   -dCHARS
       CHARS is a sequence of one or more of the following characters, and
       must not be preceded by a space.  Other characters are interpreted
       by the compiler proper, or reserved for future versions of GCC, and
       so are silently ignored.  If you specify characters whose behavior
       conflicts, the result is undefined.

       M   Instead of the normal output, generate a list of #define
           directives for all the macros defined during the execution of
           the preprocessor, including predefined macros.  This gives you
           a way of finding out what is predefined in your version of the
           preprocessor.  Assuming you have no file foo.h, the command

                   touch foo.h; cpp -dM foo.h

           will show all the predefined macros.

           If you use -dM without the -E option, -dM is interpreted as a
           synonym for -fdump-rtl-mach.

       D   Like M except in two respects: it does not include the
           predefined macros, and it outputs both the #define directives
           and the result of preprocessing.  Both kinds of output go to
           the standard output file.

       N   Like D, but emit only the macro names, not their expansions.

       I   Output #include directives in addition to the result of
           preprocessing.

       U   Like D except that only macros that are expanded, or whose
           definedness is tested in preprocessor directives, are output;
           the output is delayed until the use or test of the macro; and
           #undef directives are also output for macros tested but
           undefined at the time.

   -P  Inhibit generation of linemarkers in the output from the
       preprocessor.  This might be useful when running the preprocessor
       on something that is not C code, and will be sent to a program
       which might be confused by the linemarkers.

   -C  Do not discard comments.  All comments are passed through to the
       output file, except for comments in processed directives, which are
       deleted along with the directive.

       You should be prepared for side effects when using -C; it causes
       the preprocessor to treat comments as tokens in their own right.
       For example, comments appearing at the start of what would be a
       directive line have the effect of turning that line into an
       ordinary source line, since the first token on the line is no
       longer a #.

   -CC Do not discard comments, including during macro expansion.  This is
       like -C, except that comments contained within macros are also
       passed through to the output file where the macro is expanded.

       In addition to the side-effects of the -C option, the -CC option
       causes all C++-style comments inside a macro to be converted to
       C-style comments.  This is to prevent later use of that macro from
       inadvertently commenting out the remainder of the source line.

       The -CC option is generally used to support lint comments.

   -traditional-cpp
       Try to imitate the behavior of old-fashioned C preprocessors, as
       opposed to ISO C preprocessors.

   -trigraphs
       Process trigraph sequences.  These are three-character sequences,
       all starting with ??, that are defined by ISO C to stand for single
       characters.  For example, ??/ stands for \, so '??/n' is a
       character constant for a newline.  By default, GCC ignores
       trigraphs, but in standard-conforming modes it converts them.  See
       the -std and -ansi options.

       The nine trigraphs and their replacements are

               Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-
               Replacement:      [    ]    {    }    #    \    ^    |    ~

   -remap
       Enable special code to work around file systems which only permit
       very short file names, such as MS-DOS.

   --help
   --target-help
       Print text describing all the command-line options instead of
       preprocessing anything.

   -v  Verbose mode.  Print out GNU CPP's version number at the beginning
       of execution, and report the final form of the include path.

   -H  Print the name of each header file used, in addition to other
       normal activities.  Each name is indented to show how deep in the
       #include stack it is.  Precompiled header files are also printed,
       even if they are found to be invalid; an invalid precompiled header
       file is printed with ...x and a valid one with ...! .

   -version
   --version
       Print out GNU CPP's version number.  With one dash, proceed to
       preprocess as normal.  With two dashes, exit immediately.

   Passing Options to the Assembler
   You can pass options to the assembler.

   -Wa,option
       Pass option as an option to the assembler.  If option contains
       commas, it is split into multiple options at the commas.

   -Xassembler option
       Pass option as an option to the assembler.  You can use this to
       supply system-specific assembler options that GCC does not
       recognize.

       If you want to pass an option that takes an argument, you must use
       -Xassembler twice, once for the option and once for the argument.

   Options for Linking
   These options come into play when the compiler links object files into
   an executable output file.  They are meaningless if the compiler is not
   doing a link step.

   object-file-name
       A file name that does not end in a special recognized suffix is
       considered to name an object file or library.  (Object files are
       distinguished from libraries by the linker according to the file
       contents.)  If linking is done, these object files are used as
       input to the linker.

   -c
   -S
   -E  If any of these options is used, then the linker is not run, and
       object file names should not be used as arguments.

   -fuse-ld=bfd
       Use the bfd linker instead of the default linker.

   -fuse-ld=gold
       Use the gold linker instead of the default linker.

   -llibrary
   -l library
       Search the library named library when linking.  (The second
       alternative with the library as a separate argument is only for
       POSIX compliance and is not recommended.)

       It makes a difference where in the command you write this option;
       the linker searches and processes libraries and object files in the
       order they are specified.  Thus, foo.o -lz bar.o searches library z
       after file foo.o but before bar.o.  If bar.o refers to functions in
       z, those functions may not be loaded.

       The linker searches a standard list of directories for the library,
       which is actually a file named liblibrary.a.  The linker then uses
       this file as if it had been specified precisely by name.

       The directories searched include several standard system
       directories plus any that you specify with -L.

       Normally the files found this way are library files---archive files
       whose members are object files.  The linker handles an archive file
       by scanning through it for members which define symbols that have
       so far been referenced but not defined.  But if the file that is
       found is an ordinary object file, it is linked in the usual
       fashion.  The only difference between using an -l option and
       specifying a file name is that -l surrounds library with lib and .a
       and searches several directories.

   -lobjc
       You need this special case of the -l option in order to link an
       Objective-C or Objective-C++ program.

   -nostartfiles
       Do not use the standard system startup files when linking.  The
       standard system libraries are used normally, unless -nostdlib or
       -nodefaultlibs is used.

   -nodefaultlibs
       Do not use the standard system libraries when linking.  Only the
       libraries you specify are passed to the linker, and options
       specifying linkage of the system libraries, such as -static-libgcc
       or -shared-libgcc, are ignored.  The standard startup files are
       used normally, unless -nostartfiles is used.

       The compiler may generate calls to "memcmp", "memset", "memcpy" and
       "memmove".  These entries are usually resolved by entries in libc.
       These entry points should be supplied through some other mechanism
       when this option is specified.

   -nostdlib
       Do not use the standard system startup files or libraries when
       linking.  No startup files and only the libraries you specify are
       passed to the linker, and options specifying linkage of the system
       libraries, such as -static-libgcc or -shared-libgcc, are ignored.

       The compiler may generate calls to "memcmp", "memset", "memcpy" and
       "memmove".  These entries are usually resolved by entries in libc.
       These entry points should be supplied through some other mechanism
       when this option is specified.

       One of the standard libraries bypassed by -nostdlib and
       -nodefaultlibs is libgcc.a, a library of internal subroutines which
       GCC uses to overcome shortcomings of particular machines, or
       special needs for some languages.

       In most cases, you need libgcc.a even when you want to avoid other
       standard libraries.  In other words, when you specify -nostdlib or
       -nodefaultlibs you should usually specify -lgcc as well.  This
       ensures that you have no unresolved references to internal GCC
       library subroutines.  (An example of such an internal subroutine is
       "__main", used to ensure C++ constructors are called.)

   -pie
       Produce a position independent executable on targets that support
       it.  For predictable results, you must also specify the same set of
       options used for compilation (-fpie, -fPIE, or model suboptions)
       when you specify this linker option.

   -no-pie
       Don't produce a position independent executable.

   -rdynamic
       Pass the flag -export-dynamic to the ELF linker, on targets that
       support it. This instructs the linker to add all symbols, not only
       used ones, to the dynamic symbol table. This option is needed for
       some uses of "dlopen" or to allow obtaining backtraces from within
       a program.

   -s  Remove all symbol table and relocation information from the
       executable.

   -static
       On systems that support dynamic linking, this prevents linking with
       the shared libraries.  On other systems, this option has no effect.

   -shared
       Produce a shared object which can then be linked with other objects
       to form an executable.  Not all systems support this option.  For
       predictable results, you must also specify the same set of options
       used for compilation (-fpic, -fPIC, or model suboptions) when you
       specify this linker option.[1]

   -shared-libgcc
   -static-libgcc
       On systems that provide libgcc as a shared library, these options
       force the use of either the shared or static version, respectively.
       If no shared version of libgcc was built when the compiler was
       configured, these options have no effect.

       There are several situations in which an application should use the
       shared libgcc instead of the static version.  The most common of
       these is when the application wishes to throw and catch exceptions
       across different shared libraries.  In that case, each of the
       libraries as well as the application itself should use the shared
       libgcc.

       Therefore, the G++ and GCJ drivers automatically add -shared-libgcc
       whenever you build a shared library or a main executable, because
       C++ and Java programs typically use exceptions, so this is the
       right thing to do.

       If, instead, you use the GCC driver to create shared libraries, you
       may find that they are not always linked with the shared libgcc.
       If GCC finds, at its configuration time, that you have a non-GNU
       linker or a GNU linker that does not support option --eh-frame-hdr,
       it links the shared version of libgcc into shared libraries by
       default.  Otherwise, it takes advantage of the linker and optimizes
       away the linking with the shared version of libgcc, linking with
       the static version of libgcc by default.  This allows exceptions to
       propagate through such shared libraries, without incurring
       relocation costs at library load time.

       However, if a library or main executable is supposed to throw or
       catch exceptions, you must link it using the G++ or GCJ driver, as
       appropriate for the languages used in the program, or using the
       option -shared-libgcc, such that it is linked with the shared
       libgcc.

   -static-libasan
       When the -fsanitize=address option is used to link a program, the
       GCC driver automatically links against libasan.  If libasan is
       available as a shared library, and the -static option is not used,
       then this links against the shared version of libasan.  The
       -static-libasan option directs the GCC driver to link libasan
       statically, without necessarily linking other libraries statically.

   -static-libtsan
       When the -fsanitize=thread option is used to link a program, the
       GCC driver automatically links against libtsan.  If libtsan is
       available as a shared library, and the -static option is not used,
       then this links against the shared version of libtsan.  The
       -static-libtsan option directs the GCC driver to link libtsan
       statically, without necessarily linking other libraries statically.

   -static-liblsan
       When the -fsanitize=leak option is used to link a program, the GCC
       driver automatically links against liblsan.  If liblsan is
       available as a shared library, and the -static option is not used,
       then this links against the shared version of liblsan.  The
       -static-liblsan option directs the GCC driver to link liblsan
       statically, without necessarily linking other libraries statically.

   -static-libubsan
       When the -fsanitize=undefined option is used to link a program, the
       GCC driver automatically links against libubsan.  If libubsan is
       available as a shared library, and the -static option is not used,
       then this links against the shared version of libubsan.  The
       -static-libubsan option directs the GCC driver to link libubsan
       statically, without necessarily linking other libraries statically.

   -static-libmpx
       When the -fcheck-pointer bounds and -mmpx options are used to link
       a program, the GCC driver automatically links against libmpx.  If
       libmpx is available as a shared library, and the -static option is
       not used, then this links against the shared version of libmpx.
       The -static-libmpx option directs the GCC driver to link libmpx
       statically, without necessarily linking other libraries statically.

   -static-libmpxwrappers
       When the -fcheck-pointer bounds and -mmpx options are used to link
       a program without also using -fno-chkp-use-wrappers, the GCC driver
       automatically links against libmpxwrappers.  If libmpxwrappers is
       available as a shared library, and the -static option is not used,
       then this links against the shared version of libmpxwrappers.  The
       -static-libmpxwrappers option directs the GCC driver to link
       libmpxwrappers statically, without necessarily linking other
       libraries statically.

   -static-libstdc++
       When the g++ program is used to link a C++ program, it normally
       automatically links against libstdc++.  If libstdc++ is available
       as a shared library, and the -static option is not used, then this
       links against the shared version of libstdc++.  That is normally
       fine.  However, it is sometimes useful to freeze the version of
       libstdc++ used by the program without going all the way to a fully
       static link.  The -static-libstdc++ option directs the g++ driver
       to link libstdc++ statically, without necessarily linking other
       libraries statically.

   -symbolic
       Bind references to global symbols when building a shared object.
       Warn about any unresolved references (unless overridden by the link
       editor option -Xlinker -z -Xlinker defs).  Only a few systems
       support this option.

   -T script
       Use script as the linker script.  This option is supported by most
       systems using the GNU linker.  On some targets, such as bare-board
       targets without an operating system, the -T option may be required
       when linking to avoid references to undefined symbols.

   -Xlinker option
       Pass option as an option to the linker.  You can use this to supply
       system-specific linker options that GCC does not recognize.

       If you want to pass an option that takes a separate argument, you
       must use -Xlinker twice, once for the option and once for the
       argument.  For example, to pass -assert definitions, you must write
       -Xlinker -assert -Xlinker definitions.  It does not work to write
       -Xlinker "-assert definitions", because this passes the entire
       string as a single argument, which is not what the linker expects.

       When using the GNU linker, it is usually more convenient to pass
       arguments to linker options using the option=value syntax than as
       separate arguments.  For example, you can specify -Xlinker
       -Map=output.map rather than -Xlinker -Map -Xlinker output.map.
       Other linkers may not support this syntax for command-line options.

   -Wl,option
       Pass option as an option to the linker.  If option contains commas,
       it is split into multiple options at the commas.  You can use this
       syntax to pass an argument to the option.  For example,
       -Wl,-Map,output.map passes -Map output.map to the linker.  When
       using the GNU linker, you can also get the same effect with
       -Wl,-Map=output.map.

       NOTE: In Ubuntu 8.10 and later versions, for LDFLAGS, the option
       -Wl,-z,relro is used.  To disable, use -Wl,-z,norelro.

   -u symbol
       Pretend the symbol symbol is undefined, to force linking of library
       modules to define it.  You can use -u multiple times with different
       symbols to force loading of additional library modules.

   -z keyword
       -z is passed directly on to the linker along with the keyword
       keyword. See the section in the documentation of your linker for
       permitted values and their meanings.

   Options for Directory Search
   These options specify directories to search for header files, for
   libraries and for parts of the compiler:

   -Idir
       Add the directory dir to the head of the list of directories to be
       searched for header files.  This can be used to override a system
       header file, substituting your own version, since these directories
       are searched before the system header file directories.  However,
       you should not use this option to add directories that contain
       vendor-supplied system header files (use -isystem for that).  If
       you use more than one -I option, the directories are scanned in
       left-to-right order; the standard system directories come after.

       If a standard system include directory, or a directory specified
       with -isystem, is also specified with -I, the -I option is ignored.
       The directory is still searched but as a system directory at its
       normal position in the system include chain.  This is to ensure
       that GCC's procedure to fix buggy system headers and the ordering
       for the "include_next" directive are not inadvertently changed.  If
       you really need to change the search order for system directories,
       use the -nostdinc and/or -isystem options.

   -iplugindir=dir
       Set the directory to search for plugins that are passed by
       -fplugin=name instead of -fplugin=path/name.so.  This option is not
       meant to be used by the user, but only passed by the driver.

   -iquotedir
       Add the directory dir to the head of the list of directories to be
       searched for header files only for the case of "#include "file"";
       they are not searched for "#include <file>", otherwise just like
       -I.

   -Ldir
       Add directory dir to the list of directories to be searched for -l.

   -Bprefix
       This option specifies where to find the executables, libraries,
       include files, and data files of the compiler itself.

       The compiler driver program runs one or more of the subprograms
       cpp, cc1, as and ld.  It tries prefix as a prefix for each program
       it tries to run, both with and without machine/version/ for the
       corresponding target machine and compiler version.

       For each subprogram to be run, the compiler driver first tries the
       -B prefix, if any.  If that name is not found, or if -B is not
       specified, the driver tries two standard prefixes, /usr/lib/gcc/
       and /usr/local/lib/gcc/.  If neither of those results in a file
       name that is found, the unmodified program name is searched for
       using the directories specified in your PATH environment variable.

       The compiler checks to see if the path provided by -B refers to a
       directory, and if necessary it adds a directory separator character
       at the end of the path.

       -B prefixes that effectively specify directory names also apply to
       libraries in the linker, because the compiler translates these
       options into -L options for the linker.  They also apply to include
       files in the preprocessor, because the compiler translates these
       options into -isystem options for the preprocessor.  In this case,
       the compiler appends include to the prefix.

       The runtime support file libgcc.a can also be searched for using
       the -B prefix, if needed.  If it is not found there, the two
       standard prefixes above are tried, and that is all.  The file is
       left out of the link if it is not found by those means.

       Another way to specify a prefix much like the -B prefix is to use
       the environment variable GCC_EXEC_PREFIX.

       As a special kludge, if the path provided by -B is [dir/]stageN/,
       where N is a number in the range 0 to 9, then it is replaced by
       [dir/]include.  This is to help with boot-strapping the compiler.

   -no-canonical-prefixes
       Do not expand any symbolic links, resolve references to /../ or
       /./, or make the path absolute when generating a relative prefix.

   --sysroot=dir
       Use dir as the logical root directory for headers and libraries.
       For example, if the compiler normally searches for headers in
       /usr/include and libraries in /usr/lib, it instead searches
       dir/usr/include and dir/usr/lib.

       If you use both this option and the -isysroot option, then the
       --sysroot option applies to libraries, but the -isysroot option
       applies to header files.

       The GNU linker (beginning with version 2.16) has the necessary
       support for this option.  If your linker does not support this
       option, the header file aspect of --sysroot still works, but the
       library aspect does not.

   --no-sysroot-suffix
       For some targets, a suffix is added to the root directory specified
       with --sysroot, depending on the other options used, so that
       headers may for example be found in dir/suffix/usr/include instead
       of dir/usr/include.  This option disables the addition of such a
       suffix.

   -I- This option has been deprecated.  Please use -iquote instead for -I
       directories before the -I- and remove the -I- option.  Any
       directories you specify with -I options before the -I- option are
       searched only for the case of "#include "file""; they are not
       searched for "#include <file>".

       If additional directories are specified with -I options after the
       -I- option, these directories are searched for all "#include"
       directives.  (Ordinarily all -I directories are used this way.)

       In addition, the -I- option inhibits the use of the current
       directory (where the current input file came from) as the first
       search directory for "#include "file"".  There is no way to
       override this effect of -I-.  With -I. you can specify searching
       the directory that is current when the compiler is invoked.  That
       is not exactly the same as what the preprocessor does by default,
       but it is often satisfactory.

       -I- does not inhibit the use of the standard system directories for
       header files.  Thus, -I- and -nostdinc are independent.

   Options for Code Generation Conventions
   These machine-independent options control the interface conventions
   used in code generation.

   Most of them have both positive and negative forms; the negative form
   of -ffoo is -fno-foo.  In the table below, only one of the forms is
   listed---the one that is not the default.  You can figure out the other
   form by either removing no- or adding it.

   -fstack-reuse=reuse-level
       This option controls stack space reuse for user declared local/auto
       variables and compiler generated temporaries.  reuse_level can be
       all, named_vars, or none. all enables stack reuse for all local
       variables and temporaries, named_vars enables the reuse only for
       user defined local variables with names, and none disables stack
       reuse completely. The default value is all. The option is needed
       when the program extends the lifetime of a scoped local variable or
       a compiler generated temporary beyond the end point defined by the
       language.  When a lifetime of a variable ends, and if the variable
       lives in memory, the optimizing compiler has the freedom to reuse
       its stack space with other temporaries or scoped local variables
       whose live range does not overlap with it. Legacy code extending
       local lifetime is likely to break with the stack reuse
       optimization.

       For example,

                  int *p;
                  {
                    int local1;

                    p = &local1;
                    local1 = 10;
                    ....
                  }
                  {
                     int local2;
                     local2 = 20;
                     ...
                  }

                  if (*p == 10)  // out of scope use of local1
                    {

                    }

       Another example:

                  struct A
                  {
                      A(int k) : i(k), j(k) { }
                      int i;
                      int j;
                  };

                  A *ap;

                  void foo(const A& ar)
                  {
                     ap = &ar;
                  }

                  void bar()
                  {
                     foo(A(10)); // temp object's lifetime ends when foo returns

                     {
                       A a(20);
                       ....
                     }
                     ap->i+= 10;  // ap references out of scope temp whose space
                                  // is reused with a. What is the value of ap->i?
                  }

       The lifetime of a compiler generated temporary is well defined by
       the C++ standard. When a lifetime of a temporary ends, and if the
       temporary lives in memory, the optimizing compiler has the freedom
       to reuse its stack space with other temporaries or scoped local
       variables whose live range does not overlap with it. However some
       of the legacy code relies on the behavior of older compilers in
       which temporaries' stack space is not reused, the aggressive stack
       reuse can lead to runtime errors. This option is used to control
       the temporary stack reuse optimization.

   -ftrapv
       This option generates traps for signed overflow on addition,
       subtraction, multiplication operations.  The options -ftrapv and
       -fwrapv override each other, so using -ftrapv -fwrapv on the
       command-line results in -fwrapv being effective.  Note that only
       active options override, so using -ftrapv -fwrapv -fno-wrapv on the
       command-line results in -ftrapv being effective.

   -fwrapv
       This option instructs the compiler to assume that signed arithmetic
       overflow of addition, subtraction and multiplication wraps around
       using twos-complement representation.  This flag enables some
       optimizations and disables others.  This option is enabled by
       default for the Java front end, as required by the Java language
       specification.  The options -ftrapv and -fwrapv override each
       other, so using -ftrapv -fwrapv on the command-line results in
       -fwrapv being effective.  Note that only active options override,
       so using -ftrapv -fwrapv -fno-wrapv on the command-line results in
       -ftrapv being effective.

   -fexceptions
       Enable exception handling.  Generates extra code needed to
       propagate exceptions.  For some targets, this implies GCC generates
       frame unwind information for all functions, which can produce
       significant data size overhead, although it does not affect
       execution.  If you do not specify this option, GCC enables it by
       default for languages like C++ that normally require exception
       handling, and disables it for languages like C that do not normally
       require it.  However, you may need to enable this option when
       compiling C code that needs to interoperate properly with exception
       handlers written in C++.  You may also wish to disable this option
       if you are compiling older C++ programs that don't use exception
       handling.

   -fnon-call-exceptions
       Generate code that allows trapping instructions to throw
       exceptions.  Note that this requires platform-specific runtime
       support that does not exist everywhere.  Moreover, it only allows
       trapping instructions to throw exceptions, i.e. memory references
       or floating-point instructions.  It does not allow exceptions to be
       thrown from arbitrary signal handlers such as "SIGALRM".

   -fdelete-dead-exceptions
       Consider that instructions that may throw exceptions but don't
       otherwise contribute to the execution of the program can be
       optimized away.  This option is enabled by default for the Ada
       front end, as permitted by the Ada language specification.
       Optimization passes that cause dead exceptions to be removed are
       enabled independently at different optimization levels.

   -funwind-tables
       Similar to -fexceptions, except that it just generates any needed
       static data, but does not affect the generated code in any other
       way.  You normally do not need to enable this option; instead, a
       language processor that needs this handling enables it on your
       behalf.

   -fasynchronous-unwind-tables
       Generate unwind table in DWARF format, if supported by target
       machine.  The table is exact at each instruction boundary, so it
       can be used for stack unwinding from asynchronous events (such as
       debugger or garbage collector).

   -fno-gnu-unique
       On systems with recent GNU assembler and C library, the C++
       compiler uses the "STB_GNU_UNIQUE" binding to make sure that
       definitions of template static data members and static local
       variables in inline functions are unique even in the presence of
       "RTLD_LOCAL"; this is necessary to avoid problems with a library
       used by two different "RTLD_LOCAL" plugins depending on a
       definition in one of them and therefore disagreeing with the other
       one about the binding of the symbol.  But this causes "dlclose" to
       be ignored for affected DSOs; if your program relies on
       reinitialization of a DSO via "dlclose" and "dlopen", you can use
       -fno-gnu-unique.

   -fpcc-struct-return
       Return "short" "struct" and "union" values in memory like longer
       ones, rather than in registers.  This convention is less efficient,
       but it has the advantage of allowing intercallability between GCC-
       compiled files and files compiled with other compilers,
       particularly the Portable C Compiler (pcc).

       The precise convention for returning structures in memory depends
       on the target configuration macros.

       Short structures and unions are those whose size and alignment
       match that of some integer type.

       Warning: code compiled with the -fpcc-struct-return switch is not
       binary compatible with code compiled with the -freg-struct-return
       switch.  Use it to conform to a non-default application binary
       interface.

   -freg-struct-return
       Return "struct" and "union" values in registers when possible.
       This is more efficient for small structures than
       -fpcc-struct-return.

       If you specify neither -fpcc-struct-return nor -freg-struct-return,
       GCC defaults to whichever convention is standard for the target.
       If there is no standard convention, GCC defaults to
       -fpcc-struct-return, except on targets where GCC is the principal
       compiler.  In those cases, we can choose the standard, and we chose
       the more efficient register return alternative.

       Warning: code compiled with the -freg-struct-return switch is not
       binary compatible with code compiled with the -fpcc-struct-return
       switch.  Use it to conform to a non-default application binary
       interface.

   -fshort-enums
       Allocate to an "enum" type only as many bytes as it needs for the
       declared range of possible values.  Specifically, the "enum" type
       is equivalent to the smallest integer type that has enough room.

       Warning: the -fshort-enums switch causes GCC to generate code that
       is not binary compatible with code generated without that switch.
       Use it to conform to a non-default application binary interface.

   -fshort-wchar
       Override the underlying type for "wchar_t" to be "short unsigned
       int" instead of the default for the target.  This option is useful
       for building programs to run under WINE.

       Warning: the -fshort-wchar switch causes GCC to generate code that
       is not binary compatible with code generated without that switch.
       Use it to conform to a non-default application binary interface.

   -fno-common
       In C code, controls the placement of uninitialized global
       variables.  Unix C compilers have traditionally permitted multiple
       definitions of such variables in different compilation units by
       placing the variables in a common block.  This is the behavior
       specified by -fcommon, and is the default for GCC on most targets.
       On the other hand, this behavior is not required by ISO C, and on
       some targets may carry a speed or code size penalty on variable
       references.  The -fno-common option specifies that the compiler
       should place uninitialized global variables in the data section of
       the object file, rather than generating them as common blocks.
       This has the effect that if the same variable is declared (without
       "extern") in two different compilations, you get a multiple-
       definition error when you link them.  In this case, you must
       compile with -fcommon instead.  Compiling with -fno-common is
       useful on targets for which it provides better performance, or if
       you wish to verify that the program will work on other systems that
       always treat uninitialized variable declarations this way.

   -fno-ident
       Ignore the "#ident" directive.

   -finhibit-size-directive
       Don't output a ".size" assembler directive, or anything else that
       would cause trouble if the function is split in the middle, and the
       two halves are placed at locations far apart in memory.  This
       option is used when compiling crtstuff.c; you should not need to
       use it for anything else.

   -fverbose-asm
       Put extra commentary information in the generated assembly code to
       make it more readable.  This option is generally only of use to
       those who actually need to read the generated assembly code
       (perhaps while debugging the compiler itself).

       -fno-verbose-asm, the default, causes the extra information to be
       omitted and is useful when comparing two assembler files.

   -frecord-gcc-switches
       This switch causes the command line used to invoke the compiler to
       be recorded into the object file that is being created.  This
       switch is only implemented on some targets and the exact format of
       the recording is target and binary file format dependent, but it
       usually takes the form of a section containing ASCII text.  This
       switch is related to the -fverbose-asm switch, but that switch only
       records information in the assembler output file as comments, so it
       never reaches the object file.  See also -grecord-gcc-switches for
       another way of storing compiler options into the object file.

   -fpic
       Generate position-independent code (PIC) suitable for use in a
       shared library, if supported for the target machine.  Such code
       accesses all constant addresses through a global offset table
       (GOT).  The dynamic loader resolves the GOT entries when the
       program starts (the dynamic loader is not part of GCC; it is part
       of the operating system).  If the GOT size for the linked
       executable exceeds a machine-specific maximum size, you get an
       error message from the linker indicating that -fpic does not work;
       in that case, recompile with -fPIC instead.  (These maximums are 8k
       on the SPARC, 28k on AArch64 and 32k on the m68k and RS/6000.  The
       x86 has no such limit.)

       Position-independent code requires special support, and therefore
       works only on certain machines.  For the x86, GCC supports PIC for
       System V but not for the Sun 386i.  Code generated for the IBM
       RS/6000 is always position-independent.

       When this flag is set, the macros "__pic__" and "__PIC__" are
       defined to 1.

   -fPIC
       If supported for the target machine, emit position-independent
       code, suitable for dynamic linking and avoiding any limit on the
       size of the global offset table.  This option makes a difference on
       AArch64, m68k, PowerPC and SPARC.

       Position-independent code requires special support, and therefore
       works only on certain machines.

       When this flag is set, the macros "__pic__" and "__PIC__" are
       defined to 2.

   -fpie
   -fPIE
       These options are similar to -fpic and -fPIC, but generated
       position independent code can be only linked into executables.
       Usually these options are used when -pie GCC option is used during
       linking.

       -fpie and -fPIE both define the macros "__pie__" and "__PIE__".
       The macros have the value 1 for -fpie and 2 for -fPIE.

   -fno-plt
       Do not use the PLT for external function calls in position-
       independent code.  Instead, load the callee address at call sites
       from the GOT and branch to it.  This leads to more efficient code
       by eliminating PLT stubs and exposing GOT loads to optimizations.
       On architectures such as 32-bit x86 where PLT stubs expect the GOT
       pointer in a specific register, this gives more register allocation
       freedom to the compiler.  Lazy binding requires use of the PLT;
       with -fno-plt all external symbols are resolved at load time.

       Alternatively, the function attribute "noplt" can be used to avoid
       calls through the PLT for specific external functions.

       In position-dependent code, a few targets also convert calls to
       functions that are marked to not use the PLT to use the GOT
       instead.

   -fno-jump-tables
       Do not use jump tables for switch statements even where it would be
       more efficient than other code generation strategies.  This option
       is of use in conjunction with -fpic or -fPIC for building code that
       forms part of a dynamic linker and cannot reference the address of
       a jump table.  On some targets, jump tables do not require a GOT
       and this option is not needed.

   -ffixed-reg
       Treat the register named reg as a fixed register; generated code
       should never refer to it (except perhaps as a stack pointer, frame
       pointer or in some other fixed role).

       reg must be the name of a register.  The register names accepted
       are machine-specific and are defined in the "REGISTER_NAMES" macro
       in the machine description macro file.

       This flag does not have a negative form, because it specifies a
       three-way choice.

   -fcall-used-reg
       Treat the register named reg as an allocable register that is
       clobbered by function calls.  It may be allocated for temporaries
       or variables that do not live across a call.  Functions compiled
       this way do not save and restore the register reg.

       It is an error to use this flag with the frame pointer or stack
       pointer.  Use of this flag for other registers that have fixed
       pervasive roles in the machine's execution model produces
       disastrous results.

       This flag does not have a negative form, because it specifies a
       three-way choice.

   -fcall-saved-reg
       Treat the register named reg as an allocable register saved by
       functions.  It may be allocated even for temporaries or variables
       that live across a call.  Functions compiled this way save and
       restore the register reg if they use it.

       It is an error to use this flag with the frame pointer or stack
       pointer.  Use of this flag for other registers that have fixed
       pervasive roles in the machine's execution model produces
       disastrous results.

       A different sort of disaster results from the use of this flag for
       a register in which function values may be returned.

       This flag does not have a negative form, because it specifies a
       three-way choice.

   -fpack-struct[=n]
       Without a value specified, pack all structure members together
       without holes.  When a value is specified (which must be a small
       power of two), pack structure members according to this value,
       representing the maximum alignment (that is, objects with default
       alignment requirements larger than this are output potentially
       unaligned at the next fitting location.

       Warning: the -fpack-struct switch causes GCC to generate code that
       is not binary compatible with code generated without that switch.
       Additionally, it makes the code suboptimal.  Use it to conform to a
       non-default application binary interface.

   -fleading-underscore
       This option and its counterpart, -fno-leading-underscore, forcibly
       change the way C symbols are represented in the object file.  One
       use is to help link with legacy assembly code.

       Warning: the -fleading-underscore switch causes GCC to generate
       code that is not binary compatible with code generated without that
       switch.  Use it to conform to a non-default application binary
       interface.  Not all targets provide complete support for this
       switch.

   -ftls-model=model
       Alter the thread-local storage model to be used.  The model
       argument should be one of global-dynamic, local-dynamic, initial-
       exec or local-exec.  Note that the choice is subject to
       optimization: the compiler may use a more efficient model for
       symbols not visible outside of the translation unit, or if -fpic is
       not given on the command line.

       The default without -fpic is initial-exec; with -fpic the default
       is global-dynamic.

   -fvisibility=[default|internal|hidden|protected]
       Set the default ELF image symbol visibility to the specified
       option---all symbols are marked with this unless overridden within
       the code.  Using this feature can very substantially improve
       linking and load times of shared object libraries, produce more
       optimized code, provide near-perfect API export and prevent symbol
       clashes.  It is strongly recommended that you use this in any
       shared objects you distribute.

       Despite the nomenclature, default always means public; i.e.,
       available to be linked against from outside the shared object.
       protected and internal are pretty useless in real-world usage so
       the only other commonly used option is hidden.  The default if
       -fvisibility isn't specified is default, i.e., make every symbol
       public.

       A good explanation of the benefits offered by ensuring ELF symbols
       have the correct visibility is given by "How To Write Shared
       Libraries" by Ulrich Drepper (which can be found at
       <http://www.akkadia.org/drepper/>)---however a superior solution
       made possible by this option to marking things hidden when the
       default is public is to make the default hidden and mark things
       public.  This is the norm with DLLs on Windows and with
       -fvisibility=hidden and "__attribute__ ((visibility("default")))"
       instead of "__declspec(dllexport)" you get almost identical
       semantics with identical syntax.  This is a great boon to those
       working with cross-platform projects.

       For those adding visibility support to existing code, you may find
       "#pragma GCC visibility" of use.  This works by you enclosing the
       declarations you wish to set visibility for with (for example)
       "#pragma GCC visibility push(hidden)" and "#pragma GCC visibility
       pop".  Bear in mind that symbol visibility should be viewed as part
       of the API interface contract and thus all new code should always
       specify visibility when it is not the default; i.e., declarations
       only for use within the local DSO should always be marked
       explicitly as hidden as so to avoid PLT indirection
       overheads---making this abundantly clear also aids readability and
       self-documentation of the code.  Note that due to ISO C++
       specification requirements, "operator new" and "operator delete"
       must always be of default visibility.

       Be aware that headers from outside your project, in particular
       system headers and headers from any other library you use, may not
       be expecting to be compiled with visibility other than the default.
       You may need to explicitly say "#pragma GCC visibility
       push(default)" before including any such headers.

       "extern" declarations are not affected by -fvisibility, so a lot of
       code can be recompiled with -fvisibility=hidden with no
       modifications.  However, this means that calls to "extern"
       functions with no explicit visibility use the PLT, so it is more
       effective to use "__attribute ((visibility))" and/or "#pragma GCC
       visibility" to tell the compiler which "extern" declarations should
       be treated as hidden.

       Note that -fvisibility does affect C++ vague linkage entities. This
       means that, for instance, an exception class that is be thrown
       between DSOs must be explicitly marked with default visibility so
       that the type_info nodes are unified between the DSOs.

       An overview of these techniques, their benefits and how to use them
       is at <http://gcc.gnu.org/wiki/Visibility>.

   -fstrict-volatile-bitfields
       This option should be used if accesses to volatile bit-fields (or
       other structure fields, although the compiler usually honors those
       types anyway) should use a single access of the width of the
       field's type, aligned to a natural alignment if possible.  For
       example, targets with memory-mapped peripheral registers might
       require all such accesses to be 16 bits wide; with this flag you
       can declare all peripheral bit-fields as "unsigned short" (assuming
       short is 16 bits on these targets) to force GCC to use 16-bit
       accesses instead of, perhaps, a more efficient 32-bit access.

       If this option is disabled, the compiler uses the most efficient
       instruction.  In the previous example, that might be a 32-bit load
       instruction, even though that accesses bytes that do not contain
       any portion of the bit-field, or memory-mapped registers unrelated
       to the one being updated.

       In some cases, such as when the "packed" attribute is applied to a
       structure field, it may not be possible to access the field with a
       single read or write that is correctly aligned for the target
       machine.  In this case GCC falls back to generating multiple
       accesses rather than code that will fault or truncate the result at
       run time.

       Note:  Due to restrictions of the C/C++11 memory model, write
       accesses are not allowed to touch non bit-field members.  It is
       therefore recommended to define all bits of the field's type as
       bit-field members.

       The default value of this option is determined by the application
       binary interface for the target processor.

   -fsync-libcalls
       This option controls whether any out-of-line instance of the
       "__sync" family of functions may be used to implement the C++11
       "__atomic" family of functions.

       The default value of this option is enabled, thus the only useful
       form of the option is -fno-sync-libcalls.  This option is used in
       the implementation of the libatomic runtime library.

   GCC Developer Options
   This section describes command-line options that are primarily of
   interest to GCC developers, including options to support compiler
   testing and investigation of compiler bugs and compile-time performance
   problems.  This includes options that produce debug dumps at various
   points in the compilation; that print statistics such as memory use and
   execution time; and that print information about GCC's configuration,
   such as where it searches for libraries.  You should rarely need to use
   any of these options for ordinary compilation and linking tasks.

   -dletters
   -fdump-rtl-pass
   -fdump-rtl-pass=filename
       Says to make debugging dumps during compilation at times specified
       by letters.  This is used for debugging the RTL-based passes of the
       compiler.  The file names for most of the dumps are made by
       appending a pass number and a word to the dumpname, and the files
       are created in the directory of the output file.  In case of
       =filename option, the dump is output on the given file instead of
       the pass numbered dump files.  Note that the pass number is
       assigned as passes are registered into the pass manager.  Most
       passes are registered in the order that they will execute and for
       these passes the number corresponds to the pass execution order.
       However, passes registered by plugins, passes specific to
       compilation targets, or passes that are otherwise registered after
       all the other passes are numbered higher than a pass named "final",
       even if they are executed earlier.  dumpname is generated from the
       name of the output file if explicitly specified and not an
       executable, otherwise it is the basename of the source file.  These
       switches may have different effects when -E is used for
       preprocessing.

       Debug dumps can be enabled with a -fdump-rtl switch or some -d
       option letters.  Here are the possible letters for use in pass and
       letters, and their meanings:

       -fdump-rtl-alignments
           Dump after branch alignments have been computed.

       -fdump-rtl-asmcons
           Dump after fixing rtl statements that have unsatisfied in/out
           constraints.

       -fdump-rtl-auto_inc_dec
           Dump after auto-inc-dec discovery.  This pass is only run on
           architectures that have auto inc or auto dec instructions.

       -fdump-rtl-barriers
           Dump after cleaning up the barrier instructions.

       -fdump-rtl-bbpart
           Dump after partitioning hot and cold basic blocks.

       -fdump-rtl-bbro
           Dump after block reordering.

       -fdump-rtl-btl1
       -fdump-rtl-btl2
           -fdump-rtl-btl1 and -fdump-rtl-btl2 enable dumping after the
           two branch target load optimization passes.

       -fdump-rtl-bypass
           Dump after jump bypassing and control flow optimizations.

       -fdump-rtl-combine
           Dump after the RTL instruction combination pass.

       -fdump-rtl-compgotos
           Dump after duplicating the computed gotos.

       -fdump-rtl-ce1
       -fdump-rtl-ce2
       -fdump-rtl-ce3
           -fdump-rtl-ce1, -fdump-rtl-ce2, and -fdump-rtl-ce3 enable
           dumping after the three if conversion passes.

       -fdump-rtl-cprop_hardreg
           Dump after hard register copy propagation.

       -fdump-rtl-csa
           Dump after combining stack adjustments.

       -fdump-rtl-cse1
       -fdump-rtl-cse2
           -fdump-rtl-cse1 and -fdump-rtl-cse2 enable dumping after the
           two common subexpression elimination passes.

       -fdump-rtl-dce
           Dump after the standalone dead code elimination passes.

       -fdump-rtl-dbr
           Dump after delayed branch scheduling.

       -fdump-rtl-dce1
       -fdump-rtl-dce2
           -fdump-rtl-dce1 and -fdump-rtl-dce2 enable dumping after the
           two dead store elimination passes.

       -fdump-rtl-eh
           Dump after finalization of EH handling code.

       -fdump-rtl-eh_ranges
           Dump after conversion of EH handling range regions.

       -fdump-rtl-expand
           Dump after RTL generation.

       -fdump-rtl-fwprop1
       -fdump-rtl-fwprop2
           -fdump-rtl-fwprop1 and -fdump-rtl-fwprop2 enable dumping after
           the two forward propagation passes.

       -fdump-rtl-gcse1
       -fdump-rtl-gcse2
           -fdump-rtl-gcse1 and -fdump-rtl-gcse2 enable dumping after
           global common subexpression elimination.

       -fdump-rtl-init-regs
           Dump after the initialization of the registers.

       -fdump-rtl-initvals
           Dump after the computation of the initial value sets.

       -fdump-rtl-into_cfglayout
           Dump after converting to cfglayout mode.

       -fdump-rtl-ira
           Dump after iterated register allocation.

       -fdump-rtl-jump
           Dump after the second jump optimization.

       -fdump-rtl-loop2
           -fdump-rtl-loop2 enables dumping after the rtl loop
           optimization passes.

       -fdump-rtl-mach
           Dump after performing the machine dependent reorganization
           pass, if that pass exists.

       -fdump-rtl-mode_sw
           Dump after removing redundant mode switches.

       -fdump-rtl-rnreg
           Dump after register renumbering.

       -fdump-rtl-outof_cfglayout
           Dump after converting from cfglayout mode.

       -fdump-rtl-peephole2
           Dump after the peephole pass.

       -fdump-rtl-postreload
           Dump after post-reload optimizations.

       -fdump-rtl-pro_and_epilogue
           Dump after generating the function prologues and epilogues.

       -fdump-rtl-sched1
       -fdump-rtl-sched2
           -fdump-rtl-sched1 and -fdump-rtl-sched2 enable dumping after
           the basic block scheduling passes.

       -fdump-rtl-ree
           Dump after sign/zero extension elimination.

       -fdump-rtl-seqabstr
           Dump after common sequence discovery.

       -fdump-rtl-shorten
           Dump after shortening branches.

       -fdump-rtl-sibling
           Dump after sibling call optimizations.

       -fdump-rtl-split1
       -fdump-rtl-split2
       -fdump-rtl-split3
       -fdump-rtl-split4
       -fdump-rtl-split5
           These options enable dumping after five rounds of instruction
           splitting.

       -fdump-rtl-sms
           Dump after modulo scheduling.  This pass is only run on some
           architectures.

       -fdump-rtl-stack
           Dump after conversion from GCC's "flat register file" registers
           to the x87's stack-like registers.  This pass is only run on
           x86 variants.

       -fdump-rtl-subreg1
       -fdump-rtl-subreg2
           -fdump-rtl-subreg1 and -fdump-rtl-subreg2 enable dumping after
           the two subreg expansion passes.

       -fdump-rtl-unshare
           Dump after all rtl has been unshared.

       -fdump-rtl-vartrack
           Dump after variable tracking.

       -fdump-rtl-vregs
           Dump after converting virtual registers to hard registers.

       -fdump-rtl-web
           Dump after live range splitting.

       -fdump-rtl-regclass
       -fdump-rtl-subregs_of_mode_init
       -fdump-rtl-subregs_of_mode_finish
       -fdump-rtl-dfinit
       -fdump-rtl-dfinish
           These dumps are defined but always produce empty files.

       -da
       -fdump-rtl-all
           Produce all the dumps listed above.

       -dA Annotate the assembler output with miscellaneous debugging
           information.

       -dD Dump all macro definitions, at the end of preprocessing, in
           addition to normal output.

       -dH Produce a core dump whenever an error occurs.

       -dp Annotate the assembler output with a comment indicating which
           pattern and alternative is used.  The length of each
           instruction is also printed.

       -dP Dump the RTL in the assembler output as a comment before each
           instruction.  Also turns on -dp annotation.

       -dx Just generate RTL for a function instead of compiling it.
           Usually used with -fdump-rtl-expand.

   -fdump-noaddr
       When doing debugging dumps, suppress address output.  This makes it
       more feasible to use diff on debugging dumps for compiler
       invocations with different compiler binaries and/or different text
       / bss / data / heap / stack / dso start locations.

   -freport-bug
       Collect and dump debug information into a temporary file if an
       internal compiler error (ICE) occurs.

   -fdump-unnumbered
       When doing debugging dumps, suppress instruction numbers and
       address output.  This makes it more feasible to use diff on
       debugging dumps for compiler invocations with different options, in
       particular with and without -g.

   -fdump-unnumbered-links
       When doing debugging dumps (see -d option above), suppress
       instruction numbers for the links to the previous and next
       instructions in a sequence.

   -fdump-translation-unit (C++ only)
   -fdump-translation-unit-options (C++ only)
       Dump a representation of the tree structure for the entire
       translation unit to a file.  The file name is made by appending .tu
       to the source file name, and the file is created in the same
       directory as the output file.  If the -options form is used,
       options controls the details of the dump as described for the
       -fdump-tree options.

   -fdump-class-hierarchy (C++ only)
   -fdump-class-hierarchy-options (C++ only)
       Dump a representation of each class's hierarchy and virtual
       function table layout to a file.  The file name is made by
       appending .class to the source file name, and the file is created
       in the same directory as the output file.  If the -options form is
       used, options controls the details of the dump as described for the
       -fdump-tree options.

   -fdump-ipa-switch
       Control the dumping at various stages of inter-procedural analysis
       language tree to a file.  The file name is generated by appending a
       switch specific suffix to the source file name, and the file is
       created in the same directory as the output file.  The following
       dumps are possible:

       all Enables all inter-procedural analysis dumps.

       cgraph
           Dumps information about call-graph optimization, unused
           function removal, and inlining decisions.

       inline
           Dump after function inlining.

   -fdump-passes
       Dump the list of optimization passes that are turned on and off by
       the current command-line options.

   -fdump-statistics-option
       Enable and control dumping of pass statistics in a separate file.
       The file name is generated by appending a suffix ending in
       .statistics to the source file name, and the file is created in the
       same directory as the output file.  If the -option form is used,
       -stats causes counters to be summed over the whole compilation unit
       while -details dumps every event as the passes generate them.  The
       default with no option is to sum counters for each function
       compiled.

   -fdump-tree-switch
   -fdump-tree-switch-options
   -fdump-tree-switch-options=filename
       Control the dumping at various stages of processing the
       intermediate language tree to a file.  The file name is generated
       by appending a switch-specific suffix to the source file name, and
       the file is created in the same directory as the output file. In
       case of =filename option, the dump is output on the given file
       instead of the auto named dump files.  If the -options form is
       used, options is a list of - separated options which control the
       details of the dump.  Not all options are applicable to all dumps;
       those that are not meaningful are ignored.  The following options
       are available

       address
           Print the address of each node.  Usually this is not meaningful
           as it changes according to the environment and source file.
           Its primary use is for tying up a dump file with a debug
           environment.

       asmname
           If "DECL_ASSEMBLER_NAME" has been set for a given decl, use
           that in the dump instead of "DECL_NAME".  Its primary use is
           ease of use working backward from mangled names in the assembly
           file.

       slim
           When dumping front-end intermediate representations, inhibit
           dumping of members of a scope or body of a function merely
           because that scope has been reached.  Only dump such items when
           they are directly reachable by some other path.

           When dumping pretty-printed trees, this option inhibits dumping
           the bodies of control structures.

           When dumping RTL, print the RTL in slim (condensed) form
           instead of the default LISP-like representation.

       raw Print a raw representation of the tree.  By default, trees are
           pretty-printed into a C-like representation.

       details
           Enable more detailed dumps (not honored by every dump option).
           Also include information from the optimization passes.

       stats
           Enable dumping various statistics about the pass (not honored
           by every dump option).

       blocks
           Enable showing basic block boundaries (disabled in raw dumps).

       graph
           For each of the other indicated dump files (-fdump-rtl-pass),
           dump a representation of the control flow graph suitable for
           viewing with GraphViz to file.passid.pass.dot.  Each function
           in the file is pretty-printed as a subgraph, so that GraphViz
           can render them all in a single plot.

           This option currently only works for RTL dumps, and the RTL is
           always dumped in slim form.

       vops
           Enable showing virtual operands for every statement.

       lineno
           Enable showing line numbers for statements.

       uid Enable showing the unique ID ("DECL_UID") for each variable.

       verbose
           Enable showing the tree dump for each statement.

       eh  Enable showing the EH region number holding each statement.

       scev
           Enable showing scalar evolution analysis details.

       optimized
           Enable showing optimization information (only available in
           certain passes).

       missed
           Enable showing missed optimization information (only available
           in certain passes).

       note
           Enable other detailed optimization information (only available
           in certain passes).

       =filename
           Instead of an auto named dump file, output into the given file
           name. The file names stdout and stderr are treated specially
           and are considered already open standard streams. For example,

                   gcc -O2 -ftree-vectorize -fdump-tree-vect-blocks=foo.dump
                        -fdump-tree-pre=stderr file.c

           outputs vectorizer dump into foo.dump, while the PRE dump is
           output on to stderr. If two conflicting dump filenames are
           given for the same pass, then the latter option overrides the
           earlier one.

       split-paths
           Dump each function after splitting paths to loop backedges.
           The file name is made by appending .split-paths to the source
           file name.

       all Turn on all options, except raw, slim, verbose and lineno.

       optall
           Turn on all optimization options, i.e., optimized, missed, and
           note.

       The following tree dumps are possible:

       original
           Dump before any tree based optimization, to file.original.

       optimized
           Dump after all tree based optimization, to file.optimized.

       gimple
           Dump each function before and after the gimplification pass to
           a file.  The file name is made by appending .gimple to the
           source file name.

       cfg Dump the control flow graph of each function to a file.  The
           file name is made by appending .cfg to the source file name.

       ch  Dump each function after copying loop headers.  The file name
           is made by appending .ch to the source file name.

       ssa Dump SSA related information to a file.  The file name is made
           by appending .ssa to the source file name.

       alias
           Dump aliasing information for each function.  The file name is
           made by appending .alias to the source file name.

       ccp Dump each function after CCP.  The file name is made by
           appending .ccp to the source file name.

       storeccp
           Dump each function after STORE-CCP.  The file name is made by
           appending .storeccp to the source file name.

       pre Dump trees after partial redundancy elimination.  The file name
           is made by appending .pre to the source file name.

       fre Dump trees after full redundancy elimination.  The file name is
           made by appending .fre to the source file name.

       copyprop
           Dump trees after copy propagation.  The file name is made by
           appending .copyprop to the source file name.

       store_copyprop
           Dump trees after store copy-propagation.  The file name is made
           by appending .store_copyprop to the source file name.

       dce Dump each function after dead code elimination.  The file name
           is made by appending .dce to the source file name.

       sra Dump each function after performing scalar replacement of
           aggregates.  The file name is made by appending .sra to the
           source file name.

       sink
           Dump each function after performing code sinking.  The file
           name is made by appending .sink to the source file name.

       dom Dump each function after applying dominator tree optimizations.
           The file name is made by appending .dom to the source file
           name.

       dse Dump each function after applying dead store elimination.  The
           file name is made by appending .dse to the source file name.

       phiopt
           Dump each function after optimizing PHI nodes into straightline
           code.  The file name is made by appending .phiopt to the source
           file name.

       backprop
           Dump each function after back-propagating use information up
           the definition chain.  The file name is made by appending
           .backprop to the source file name.

       forwprop
           Dump each function after forward propagating single use
           variables.  The file name is made by appending .forwprop to the
           source file name.

       nrv Dump each function after applying the named return value
           optimization on generic trees.  The file name is made by
           appending .nrv to the source file name.

       vect
           Dump each function after applying vectorization of loops.  The
           file name is made by appending .vect to the source file name.

       slp Dump each function after applying vectorization of basic
           blocks.  The file name is made by appending .slp to the source
           file name.

       vrp Dump each function after Value Range Propagation (VRP).  The
           file name is made by appending .vrp to the source file name.

       oaccdevlow
           Dump each function after applying device-specific OpenACC
           transformations.  The file name is made by appending
           .oaccdevlow to the source file name.

       all Enable all the available tree dumps with the flags provided in
           this option.

   -fopt-info
   -fopt-info-options
   -fopt-info-options=filename
       Controls optimization dumps from various optimization passes. If
       the -options form is used, options is a list of - separated option
       keywords to select the dump details and optimizations.

       The options can be divided into two groups: options describing the
       verbosity of the dump, and options describing which optimizations
       should be included. The options from both the groups can be freely
       mixed as they are non-overlapping. However, in case of any
       conflicts, the later options override the earlier options on the
       command line.

       The following options control the dump verbosity:

       optimized
           Print information when an optimization is successfully applied.
           It is up to a pass to decide which information is relevant. For
           example, the vectorizer passes print the source location of
           loops which are successfully vectorized.

       missed
           Print information about missed optimizations. Individual passes
           control which information to include in the output.

       note
           Print verbose information about optimizations, such as certain
           transformations, more detailed messages about decisions etc.

       all Print detailed optimization information. This includes
           optimized, missed, and note.

       One or more of the following option keywords can be used to
       describe a group of optimizations:

       ipa Enable dumps from all interprocedural optimizations.

       loop
           Enable dumps from all loop optimizations.

       inline
           Enable dumps from all inlining optimizations.

       vec Enable dumps from all vectorization optimizations.

       optall
           Enable dumps from all optimizations. This is a superset of the
           optimization groups listed above.

       If options is omitted, it defaults to optimized-optall, which means
       to dump all info about successful optimizations from all the
       passes.

       If the filename is provided, then the dumps from all the applicable
       optimizations are concatenated into the filename.  Otherwise the
       dump is output onto stderr. Though multiple -fopt-info options are
       accepted, only one of them can include a filename. If other
       filenames are provided then all but the first such option are
       ignored.

       Note that the output filename is overwritten in case of multiple
       translation units. If a combined output from multiple translation
       units is desired, stderr should be used instead.

       In the following example, the optimization info is output to
       stderr:

               gcc -O3 -fopt-info

       This example:

               gcc -O3 -fopt-info-missed=missed.all

       outputs missed optimization report from all the passes into
       missed.all, and this one:

               gcc -O2 -ftree-vectorize -fopt-info-vec-missed

       prints information about missed optimization opportunities from
       vectorization passes on stderr.  Note that -fopt-info-vec-missed is
       equivalent to -fopt-info-missed-vec.

       As another example,

               gcc -O3 -fopt-info-inline-optimized-missed=inline.txt

       outputs information about missed optimizations as well as optimized
       locations from all the inlining passes into inline.txt.

       Finally, consider:

               gcc -fopt-info-vec-missed=vec.miss -fopt-info-loop-optimized=loop.opt

       Here the two output filenames vec.miss and loop.opt are in conflict
       since only one output file is allowed. In this case, only the first
       option takes effect and the subsequent options are ignored. Thus
       only vec.miss is produced which contains dumps from the vectorizer
       about missed opportunities.

   -fsched-verbose=n
       On targets that use instruction scheduling, this option controls
       the amount of debugging output the scheduler prints to the dump
       files.

       For n greater than zero, -fsched-verbose outputs the same
       information as -fdump-rtl-sched1 and -fdump-rtl-sched2.  For n
       greater than one, it also output basic block probabilities,
       detailed ready list information and unit/insn info.  For n greater
       than two, it includes RTL at abort point, control-flow and regions
       info.  And for n over four, -fsched-verbose also includes
       dependence info.

   -fenable-kind-pass
   -fdisable-kind-pass=range-list
       This is a set of options that are used to explicitly disable/enable
       optimization passes.  These options are intended for use for
       debugging GCC.  Compiler users should use regular options for
       enabling/disabling passes instead.

       -fdisable-ipa-pass
           Disable IPA pass pass. pass is the pass name.  If the same pass
           is statically invoked in the compiler multiple times, the pass
           name should be appended with a sequential number starting from
           1.

       -fdisable-rtl-pass
       -fdisable-rtl-pass=range-list
           Disable RTL pass pass.  pass is the pass name.  If the same
           pass is statically invoked in the compiler multiple times, the
           pass name should be appended with a sequential number starting
           from 1.  range-list is a comma-separated list of function
           ranges or assembler names.  Each range is a number pair
           separated by a colon.  The range is inclusive in both ends.  If
           the range is trivial, the number pair can be simplified as a
           single number.  If the function's call graph node's uid falls
           within one of the specified ranges, the pass is disabled for
           that function.  The uid is shown in the function header of a
           dump file, and the pass names can be dumped by using option
           -fdump-passes.

       -fdisable-tree-pass
       -fdisable-tree-pass=range-list
           Disable tree pass pass.  See -fdisable-rtl for the description
           of option arguments.

       -fenable-ipa-pass
           Enable IPA pass pass.  pass is the pass name.  If the same pass
           is statically invoked in the compiler multiple times, the pass
           name should be appended with a sequential number starting from
           1.

       -fenable-rtl-pass
       -fenable-rtl-pass=range-list
           Enable RTL pass pass.  See -fdisable-rtl for option argument
           description and examples.

       -fenable-tree-pass
       -fenable-tree-pass=range-list
           Enable tree pass pass.  See -fdisable-rtl for the description
           of option arguments.

       Here are some examples showing uses of these options.

               # disable ccp1 for all functions
                  -fdisable-tree-ccp1
               # disable complete unroll for function whose cgraph node uid is 1
                  -fenable-tree-cunroll=1
               # disable gcse2 for functions at the following ranges [1,1],
               # [300,400], and [400,1000]
               # disable gcse2 for functions foo and foo2
                  -fdisable-rtl-gcse2=foo,foo2
               # disable early inlining
                  -fdisable-tree-einline
               # disable ipa inlining
                  -fdisable-ipa-inline
               # enable tree full unroll
                  -fenable-tree-unroll

   -fchecking
       Enable internal consistency checking.  The default depends on the
       compiler configuration.

   -frandom-seed=string
       This option provides a seed that GCC uses in place of random
       numbers in generating certain symbol names that have to be
       different in every compiled file.  It is also used to place unique
       stamps in coverage data files and the object files that produce
       them.  You can use the -frandom-seed option to produce reproducibly
       identical object files.

       The string can either be a number (decimal, octal or hex) or an
       arbitrary string (in which case it's converted to a number by
       computing CRC32).

       The string should be different for every file you compile.

   -save-temps
   -save-temps=cwd
       Store the usual "temporary" intermediate files permanently; place
       them in the current directory and name them based on the source
       file.  Thus, compiling foo.c with -c -save-temps produces files
       foo.i and foo.s, as well as foo.o.  This creates a preprocessed
       foo.i output file even though the compiler now normally uses an
       integrated preprocessor.

       When used in combination with the -x command-line option,
       -save-temps is sensible enough to avoid over writing an input
       source file with the same extension as an intermediate file.  The
       corresponding intermediate file may be obtained by renaming the
       source file before using -save-temps.

       If you invoke GCC in parallel, compiling several different source
       files that share a common base name in different subdirectories or
       the same source file compiled for multiple output destinations, it
       is likely that the different parallel compilers will interfere with
       each other, and overwrite the temporary files.  For instance:

               gcc -save-temps -o outdir1/foo.o indir1/foo.c&
               gcc -save-temps -o outdir2/foo.o indir2/foo.c&

       may result in foo.i and foo.o being written to simultaneously by
       both compilers.

   -save-temps=obj
       Store the usual "temporary" intermediate files permanently.  If the
       -o option is used, the temporary files are based on the object
       file.  If the -o option is not used, the -save-temps=obj switch
       behaves like -save-temps.

       For example:

               gcc -save-temps=obj -c foo.c
               gcc -save-temps=obj -c bar.c -o dir/xbar.o
               gcc -save-temps=obj foobar.c -o dir2/yfoobar

       creates foo.i, foo.s, dir/xbar.i, dir/xbar.s, dir2/yfoobar.i,
       dir2/yfoobar.s, and dir2/yfoobar.o.

   -time[=file]
       Report the CPU time taken by each subprocess in the compilation
       sequence.  For C source files, this is the compiler proper and
       assembler (plus the linker if linking is done).

       Without the specification of an output file, the output looks like
       this:

               # cc1 0.12 0.01
               # as 0.00 0.01

       The first number on each line is the "user time", that is time
       spent executing the program itself.  The second number is "system
       time", time spent executing operating system routines on behalf of
       the program.  Both numbers are in seconds.

       With the specification of an output file, the output is appended to
       the named file, and it looks like this:

               0.12 0.01 cc1 <options>
               0.00 0.01 as <options>

       The "user time" and the "system time" are moved before the program
       name, and the options passed to the program are displayed, so that
       one can later tell what file was being compiled, and with which
       options.

   -fdump-final-insns[=file]
       Dump the final internal representation (RTL) to file.  If the
       optional argument is omitted (or if file is "."), the name of the
       dump file is determined by appending ".gkd" to the compilation
       output file name.

   -fcompare-debug[=opts]
       If no error occurs during compilation, run the compiler a second
       time, adding opts and -fcompare-debug-second to the arguments
       passed to the second compilation.  Dump the final internal
       representation in both compilations, and print an error if they
       differ.

       If the equal sign is omitted, the default -gtoggle is used.

       The environment variable GCC_COMPARE_DEBUG, if defined, non-empty
       and nonzero, implicitly enables -fcompare-debug.  If
       GCC_COMPARE_DEBUG is defined to a string starting with a dash, then
       it is used for opts, otherwise the default -gtoggle is used.

       -fcompare-debug=, with the equal sign but without opts, is
       equivalent to -fno-compare-debug, which disables the dumping of the
       final representation and the second compilation, preventing even
       GCC_COMPARE_DEBUG from taking effect.

       To verify full coverage during -fcompare-debug testing, set
       GCC_COMPARE_DEBUG to say -fcompare-debug-not-overridden, which GCC
       rejects as an invalid option in any actual compilation (rather than
       preprocessing, assembly or linking).  To get just a warning,
       setting GCC_COMPARE_DEBUG to -w%n-fcompare-debug not overridden
       will do.

   -fcompare-debug-second
       This option is implicitly passed to the compiler for the second
       compilation requested by -fcompare-debug, along with options to
       silence warnings, and omitting other options that would cause side-
       effect compiler outputs to files or to the standard output.  Dump
       files and preserved temporary files are renamed so as to contain
       the ".gk" additional extension during the second compilation, to
       avoid overwriting those generated by the first.

       When this option is passed to the compiler driver, it causes the
       first compilation to be skipped, which makes it useful for little
       other than debugging the compiler proper.

   -gtoggle
       Turn off generation of debug info, if leaving out this option
       generates it, or turn it on at level 2 otherwise.  The position of
       this argument in the command line does not matter; it takes effect
       after all other options are processed, and it does so only once, no
       matter how many times it is given.  This is mainly intended to be
       used with -fcompare-debug.

   -fvar-tracking-assignments-toggle
       Toggle -fvar-tracking-assignments, in the same way that -gtoggle
       toggles -g.

   -Q  Makes the compiler print out each function name as it is compiled,
       and print some statistics about each pass when it finishes.

   -ftime-report
       Makes the compiler print some statistics about the time consumed by
       each pass when it finishes.

   -fira-verbose=n
       Control the verbosity of the dump file for the integrated register
       allocator.  The default value is 5.  If the value n is greater or
       equal to 10, the dump output is sent to stderr using the same
       format as n minus 10.

   -flto-report
       Prints a report with internal details on the workings of the link-
       time optimizer.  The contents of this report vary from version to
       version.  It is meant to be useful to GCC developers when
       processing object files in LTO mode (via -flto).

       Disabled by default.

   -flto-report-wpa
       Like -flto-report, but only print for the WPA phase of Link Time
       Optimization.

   -fmem-report
       Makes the compiler print some statistics about permanent memory
       allocation when it finishes.

   -fmem-report-wpa
       Makes the compiler print some statistics about permanent memory
       allocation for the WPA phase only.

   -fpre-ipa-mem-report
   -fpost-ipa-mem-report
       Makes the compiler print some statistics about permanent memory
       allocation before or after interprocedural optimization.

   -fprofile-report
       Makes the compiler print some statistics about consistency of the
       (estimated) profile and effect of individual passes.

   -fstack-usage
       Makes the compiler output stack usage information for the program,
       on a per-function basis.  The filename for the dump is made by
       appending .su to the auxname.  auxname is generated from the name
       of the output file, if explicitly specified and it is not an
       executable, otherwise it is the basename of the source file.  An
       entry is made up of three fields:

       *   The name of the function.

       *   A number of bytes.

       *   One or more qualifiers: "static", "dynamic", "bounded".

       The qualifier "static" means that the function manipulates the
       stack statically: a fixed number of bytes are allocated for the
       frame on function entry and released on function exit; no stack
       adjustments are otherwise made in the function.  The second field
       is this fixed number of bytes.

       The qualifier "dynamic" means that the function manipulates the
       stack dynamically: in addition to the static allocation described
       above, stack adjustments are made in the body of the function, for
       example to push/pop arguments around function calls.  If the
       qualifier "bounded" is also present, the amount of these
       adjustments is bounded at compile time and the second field is an
       upper bound of the total amount of stack used by the function.  If
       it is not present, the amount of these adjustments is not bounded
       at compile time and the second field only represents the bounded
       part.

   -fstats
       Emit statistics about front-end processing at the end of the
       compilation.  This option is supported only by the C++ front end,
       and the information is generally only useful to the G++ development
       team.

   -fdbg-cnt-list
       Print the name and the counter upper bound for all debug counters.

   -fdbg-cnt=counter-value-list
       Set the internal debug counter upper bound.  counter-value-list is
       a comma-separated list of name:value pairs which sets the upper
       bound of each debug counter name to value.  All debug counters have
       the initial upper bound of "UINT_MAX"; thus "dbg_cnt" returns true
       always unless the upper bound is set by this option.  For example,
       with -fdbg-cnt=dce:10,tail_call:0, "dbg_cnt(dce)" returns true only
       for first 10 invocations.

   -print-file-name=library
       Print the full absolute name of the library file library that would
       be used when linking---and don't do anything else.  With this
       option, GCC does not compile or link anything; it just prints the
       file name.

   -print-multi-directory
       Print the directory name corresponding to the multilib selected by
       any other switches present in the command line.  This directory is
       supposed to exist in GCC_EXEC_PREFIX.

   -print-multi-lib
       Print the mapping from multilib directory names to compiler
       switches that enable them.  The directory name is separated from
       the switches by ;, and each switch starts with an @ instead of the
       -, without spaces between multiple switches.  This is supposed to
       ease shell processing.

   -print-multi-os-directory
       Print the path to OS libraries for the selected multilib, relative
       to some lib subdirectory.  If OS libraries are present in the lib
       subdirectory and no multilibs are used, this is usually just ., if
       OS libraries are present in libsuffix sibling directories this
       prints e.g. ../lib64, ../lib or ../lib32, or if OS libraries are
       present in lib/subdir subdirectories it prints e.g. amd64, sparcv9
       or ev6.

   -print-multiarch
       Print the path to OS libraries for the selected multiarch, relative
       to some lib subdirectory.

   -print-prog-name=program
       Like -print-file-name, but searches for a program such as cpp.

   -print-libgcc-file-name
       Same as -print-file-name=libgcc.a.

       This is useful when you use -nostdlib or -nodefaultlibs but you do
       want to link with libgcc.a.  You can do:

               gcc -nostdlib <files>... `gcc -print-libgcc-file-name`

   -print-search-dirs
       Print the name of the configured installation directory and a list
       of program and library directories gcc searches---and don't do
       anything else.

       This is useful when gcc prints the error message installation
       problem, cannot exec cpp0: No such file or directory.  To resolve
       this you either need to put cpp0 and the other compiler components
       where gcc expects to find them, or you can set the environment
       variable GCC_EXEC_PREFIX to the directory where you installed them.
       Don't forget the trailing /.

   -print-sysroot
       Print the target sysroot directory that is used during compilation.
       This is the target sysroot specified either at configure time or
       using the --sysroot option, possibly with an extra suffix that
       depends on compilation options.  If no target sysroot is specified,
       the option prints nothing.

   -print-sysroot-headers-suffix
       Print the suffix added to the target sysroot when searching for
       headers, or give an error if the compiler is not configured with
       such a suffix---and don't do anything else.

   -dumpmachine
       Print the compiler's target machine (for example,
       i686-pc-linux-gnu)---and don't do anything else.

   -dumpversion
       Print the compiler version (for example, 3.0)---and don't do
       anything else.

   -dumpspecs
       Print the compiler's built-in specs---and don't do anything else.
       (This is used when GCC itself is being built.)

   Machine-Dependent Options
   Each target machine supported by GCC can have its own options---for
   example, to allow you to compile for a particular processor variant or
   ABI, or to control optimizations specific to that machine.  By
   convention, the names of machine-specific options start with -m.

   Some configurations of the compiler also support additional target-
   specific options, usually for compatibility with other compilers on the
   same platform.

   AArch64 Options

   These options are defined for AArch64 implementations:

   -mabi=name
       Generate code for the specified data model.  Permissible values are
       ilp32 for SysV-like data model where int, long int and pointer are
       32-bit, and lp64 for SysV-like data model where int is 32-bit, but
       long int and pointer are 64-bit.

       The default depends on the specific target configuration.  Note
       that the LP64 and ILP32 ABIs are not link-compatible; you must
       compile your entire program with the same ABI, and link with a
       compatible set of libraries.

   -mbig-endian
       Generate big-endian code.  This is the default when GCC is
       configured for an aarch64_be-*-* target.

   -mgeneral-regs-only
       Generate code which uses only the general-purpose registers.  This
       will prevent the compiler from using floating-point and Advanced
       SIMD registers but will not impose any restrictions on the
       assembler.

   -mlittle-endian
       Generate little-endian code.  This is the default when GCC is
       configured for an aarch64-*-* but not an aarch64_be-*-* target.

   -mcmodel=tiny
       Generate code for the tiny code model.  The program and its
       statically defined symbols must be within 1GB of each other.
       Pointers are 64 bits.  Programs can be statically or dynamically
       linked.  This model is not fully implemented and mostly treated as
       small.

   -mcmodel=small
       Generate code for the small code model.  The program and its
       statically defined symbols must be within 4GB of each other.
       Pointers are 64 bits.  Programs can be statically or dynamically
       linked.  This is the default code model.

   -mcmodel=large
       Generate code for the large code model.  This makes no assumptions
       about addresses and sizes of sections.  Pointers are 64 bits.
       Programs can be statically linked only.

   -mstrict-align
       Do not assume that unaligned memory references are handled by the
       system.

   -momit-leaf-frame-pointer
   -mno-omit-leaf-frame-pointer
       Omit or keep the frame pointer in leaf functions.  The former
       behavior is the default.

   -mtls-dialect=desc
       Use TLS descriptors as the thread-local storage mechanism for
       dynamic accesses of TLS variables.  This is the default.

   -mtls-dialect=traditional
       Use traditional TLS as the thread-local storage mechanism for
       dynamic accesses of TLS variables.

   -mtls-size=size
       Specify bit size of immediate TLS offsets.  Valid values are 12,
       24, 32, 48.  This option depends on binutils higher than 2.25.

   -mfix-cortex-a53-835769
   -mno-fix-cortex-a53-835769
       Enable or disable the workaround for the ARM Cortex-A53 erratum
       number 835769.  This involves inserting a NOP instruction between
       memory instructions and 64-bit integer multiply-accumulate
       instructions.

   -mfix-cortex-a53-843419
   -mno-fix-cortex-a53-843419
       Enable or disable the workaround for the ARM Cortex-A53 erratum
       number 843419.  This erratum workaround is made at link time and
       this will only pass the corresponding flag to the linker.

   -mlow-precision-recip-sqrt
   -mno-low-precision-recip-sqrt
       When calculating the reciprocal square root approximation, uses one
       less step than otherwise, thus reducing latency and precision.
       This is only relevant if -ffast-math enables the reciprocal square
       root approximation, which in turn depends on the target processor.

   -march=name
       Specify the name of the target architecture and, optionally, one or
       more feature modifiers.  This option has the form
       -march=arch{+[no]feature}*.

       The permissible values for arch are armv8-a, armv8.1-a or native.

       The value armv8.1-a implies armv8-a and enables compiler support
       for the ARMv8.1 architecture extension.  In particular, it enables
       the +crc and +lse features.

       The value native is available on native AArch64 GNU/Linux and
       causes the compiler to pick the architecture of the host system.
       This option has no effect if the compiler is unable to recognize
       the architecture of the host system,

       The permissible values for feature are listed in the sub-section on
       aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers.
       Where conflicting feature modifiers are specified, the right-most
       feature is used.

       GCC uses name to determine what kind of instructions it can emit
       when generating assembly code.  If -march is specified without
       either of -mtune or -mcpu also being specified, the code is tuned
       to perform well across a range of target processors implementing
       the target architecture.

   -mtune=name
       Specify the name of the target processor for which GCC should tune
       the performance of the code.  Permissible values for this option
       are: generic, cortex-a35, cortex-a53, cortex-a57, cortex-a72,
       exynos-m1, qdf24xx, thunderx, vulcan, xgene1.

       Additionally, this option can specify that GCC should tune the
       performance of the code for a big.LITTLE system.  Permissible
       values for this option are: cortex-a57.cortex-a53,
       cortex-a72.cortex-a53.

       Additionally on native AArch64 GNU/Linux systems the value native
       is available.  This option causes the compiler to pick the
       architecture of and tune the performance of the code for the
       processor of the host system.  This option has no effect if the
       compiler is unable to recognize the architecture of the host
       system.

       Where none of -mtune=, -mcpu= or -march= are specified, the code is
       tuned to perform well across a range of target processors.

       This option cannot be suffixed by feature modifiers.

   -mcpu=name
       Specify the name of the target processor, optionally suffixed by
       one or more feature modifiers.  This option has the form
       -mcpu=cpu{+[no]feature}*, where the permissible values for cpu are
       the same as those available for -mtune.  The permissible values for
       feature are documented in the sub-section on
       aarch64-feature-modifiers,,-march and -mcpu Feature Modifiers.
       Where conflicting feature modifiers are specified, the right-most
       feature is used.

       Additionally on native AArch64 GNU/Linux systems the value native
       is available.  This option causes the compiler to tune the
       performance of the code for the processor of the host system.  This
       option has no effect if the compiler is unable to recognize the
       architecture of the host system.

       GCC uses name to determine what kind of instructions it can emit
       when generating assembly code (as if by -march) and to determine
       the target processor for which to tune for performance (as if by
       -mtune).  Where this option is used in conjunction with -march or
       -mtune, those options take precedence over the appropriate part of
       this option.

   -moverride=string
       Override tuning decisions made by the back-end in response to a
       -mtune= switch.  The syntax, semantics, and accepted values for
       string in this option are not guaranteed to be consistent across
       releases.

       This option is only intended to be useful when developing GCC.

   -mpc-relative-literal-loads
       Enable PC relative literal loads. If this option is used, literal
       pools are assumed to have a range of up to 1MiB and an appropriate
       instruction sequence is used. This option has no impact when used
       with -mcmodel=tiny.

   -march and -mcpu Feature Modifiers

   Feature modifiers used with -march and -mcpu can be any of the
   following and their inverses nofeature:

   crc Enable CRC extension.  This is on by default for -march=armv8.1-a.

   crypto
       Enable Crypto extension.  This also enables Advanced SIMD and
       floating-point instructions.

   fp  Enable floating-point instructions.  This is on by default for all
       possible values for options -march and -mcpu.

   simd
       Enable Advanced SIMD instructions.  This also enables floating-
       point instructions.  This is on by default for all possible values
       for options -march and -mcpu.

   lse Enable Large System Extension instructions.  This is on by default
       for -march=armv8.1-a.

   That is, crypto implies simd implies fp.  Conversely, nofp (or
   equivalently, -mgeneral-regs-only) implies nosimd implies nocrypto.

   Adapteva Epiphany Options

   These -m options are defined for Adapteva Epiphany:

   -mhalf-reg-file
       Don't allocate any register in the range "r32"..."r63".  That
       allows code to run on hardware variants that lack these registers.

   -mprefer-short-insn-regs
       Preferentially allocate registers that allow short instruction
       generation.  This can result in increased instruction count, so
       this may either reduce or increase overall code size.

   -mbranch-cost=num
       Set the cost of branches to roughly num "simple" instructions.
       This cost is only a heuristic and is not guaranteed to produce
       consistent results across releases.

   -mcmove
       Enable the generation of conditional moves.

   -mnops=num
       Emit num NOPs before every other generated instruction.

   -mno-soft-cmpsf
       For single-precision floating-point comparisons, emit an "fsub"
       instruction and test the flags.  This is faster than a software
       comparison, but can get incorrect results in the presence of NaNs,
       or when two different small numbers are compared such that their
       difference is calculated as zero.  The default is -msoft-cmpsf,
       which uses slower, but IEEE-compliant, software comparisons.

   -mstack-offset=num
       Set the offset between the top of the stack and the stack pointer.
       E.g., a value of 8 means that the eight bytes in the range
       "sp+0...sp+7" can be used by leaf functions without stack
       allocation.  Values other than 8 or 16 are untested and unlikely to
       work.  Note also that this option changes the ABI; compiling a
       program with a different stack offset than the libraries have been
       compiled with generally does not work.  This option can be useful
       if you want to evaluate if a different stack offset would give you
       better code, but to actually use a different stack offset to build
       working programs, it is recommended to configure the toolchain with
       the appropriate --with-stack-offset=num option.

   -mno-round-nearest
       Make the scheduler assume that the rounding mode has been set to
       truncating.  The default is -mround-nearest.

   -mlong-calls
       If not otherwise specified by an attribute, assume all calls might
       be beyond the offset range of the "b" / "bl" instructions, and
       therefore load the function address into a register before
       performing a (otherwise direct) call.  This is the default.

   -mshort-calls
       If not otherwise specified by an attribute, assume all direct calls
       are in the range of the "b" / "bl" instructions, so use these
       instructions for direct calls.  The default is -mlong-calls.

   -msmall16
       Assume addresses can be loaded as 16-bit unsigned values.  This
       does not apply to function addresses for which -mlong-calls
       semantics are in effect.

   -mfp-mode=mode
       Set the prevailing mode of the floating-point unit.  This
       determines the floating-point mode that is provided and expected at
       function call and return time.  Making this mode match the mode you
       predominantly need at function start can make your programs smaller
       and faster by avoiding unnecessary mode switches.

       mode can be set to one the following values:

       caller
           Any mode at function entry is valid, and retained or restored
           when the function returns, and when it calls other functions.
           This mode is useful for compiling libraries or other
           compilation units you might want to incorporate into different
           programs with different prevailing FPU modes, and the
           convenience of being able to use a single object file outweighs
           the size and speed overhead for any extra mode switching that
           might be needed, compared with what would be needed with a more
           specific choice of prevailing FPU mode.

       truncate
           This is the mode used for floating-point calculations with
           truncating (i.e. round towards zero) rounding mode.  That
           includes conversion from floating point to integer.

       round-nearest
           This is the mode used for floating-point calculations with
           round-to-nearest-or-even rounding mode.

       int This is the mode used to perform integer calculations in the
           FPU, e.g.  integer multiply, or integer multiply-and-
           accumulate.

       The default is -mfp-mode=caller

   -mnosplit-lohi
   -mno-postinc
   -mno-postmodify
       Code generation tweaks that disable, respectively, splitting of
       32-bit loads, generation of post-increment addresses, and
       generation of post-modify addresses.  The defaults are msplit-lohi,
       -mpost-inc, and -mpost-modify.

   -mnovect-double
       Change the preferred SIMD mode to SImode.  The default is
       -mvect-double, which uses DImode as preferred SIMD mode.

   -max-vect-align=num
       The maximum alignment for SIMD vector mode types.  num may be 4 or
       8.  The default is 8.  Note that this is an ABI change, even though
       many library function interfaces are unaffected if they don't use
       SIMD vector modes in places that affect size and/or alignment of
       relevant types.

   -msplit-vecmove-early
       Split vector moves into single word moves before reload.  In theory
       this can give better register allocation, but so far the reverse
       seems to be generally the case.

   -m1reg-reg
       Specify a register to hold the constant -1, which makes loading
       small negative constants and certain bitmasks faster.  Allowable
       values for reg are r43 and r63, which specify use of that register
       as a fixed register, and none, which means that no register is used
       for this purpose.  The default is -m1reg-none.

   ARC Options

   The following options control the architecture variant for which code
   is being compiled:

   -mbarrel-shifter
       Generate instructions supported by barrel shifter.  This is the
       default unless -mcpu=ARC601 or -mcpu=ARCEM is in effect.

   -mcpu=cpu
       Set architecture type, register usage, and instruction scheduling
       parameters for cpu.  There are also shortcut alias options
       available for backward compatibility and convenience.  Supported
       values for cpu are

       ARC600
       arc600
           Compile for ARC600.  Aliases: -mA6, -mARC600.

       ARC601
       arc601
           Compile for ARC601.  Alias: -mARC601.

       ARC700
       arc700
           Compile for ARC700.  Aliases: -mA7, -mARC700.  This is the
           default when configured with --with-cpu=arc700.

       ARCEM
       arcem
           Compile for ARC EM.

       ARCHS
       archs
           Compile for ARC HS.

   -mdpfp
   -mdpfp-compact
       FPX: Generate Double Precision FPX instructions, tuned for the
       compact implementation.

   -mdpfp-fast
       FPX: Generate Double Precision FPX instructions, tuned for the fast
       implementation.

   -mno-dpfp-lrsr
       Disable LR and SR instructions from using FPX extension aux
       registers.

   -mea
       Generate Extended arithmetic instructions.  Currently only "divaw",
       "adds", "subs", and "sat16" are supported.  This is always enabled
       for -mcpu=ARC700.

   -mno-mpy
       Do not generate mpy instructions for ARC700.

   -mmul32x16
       Generate 32x16 bit multiply and mac instructions.

   -mmul64
       Generate mul64 and mulu64 instructions.  Only valid for
       -mcpu=ARC600.

   -mnorm
       Generate norm instruction.  This is the default if -mcpu=ARC700 is
       in effect.

   -mspfp
   -mspfp-compact
       FPX: Generate Single Precision FPX instructions, tuned for the
       compact implementation.

   -mspfp-fast
       FPX: Generate Single Precision FPX instructions, tuned for the fast
       implementation.

   -msimd
       Enable generation of ARC SIMD instructions via target-specific
       builtins.  Only valid for -mcpu=ARC700.

   -msoft-float
       This option ignored; it is provided for compatibility purposes
       only.  Software floating point code is emitted by default, and this
       default can overridden by FPX options; mspfp, mspfp-compact, or
       mspfp-fast for single precision, and mdpfp, mdpfp-compact, or
       mdpfp-fast for double precision.

   -mswap
       Generate swap instructions.

   -matomic
       This enables Locked Load/Store Conditional extension to implement
       atomic memopry built-in functions.  Not available for ARC 6xx or
       ARC EM cores.

   -mdiv-rem
       Enable DIV/REM instructions for ARCv2 cores.

   -mcode-density
       Enable code density instructions for ARC EM, default on for ARC HS.

   -mll64
       Enable double load/store operations for ARC HS cores.

   -mmpy-option=multo
       Compile ARCv2 code with a multiplier design option.  wlh1 is the
       default value.  The recognized values for multo are:

       0   No multiplier available.

       1   The multiply option is set to w: 16x16 multiplier, fully
           pipelined.  The following instructions are enabled: MPYW, and
           MPYUW.

       2   The multiply option is set to wlh1: 32x32 multiplier, fully
           pipelined (1 stage).  The following instructions are
           additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

       3   The multiply option is set to wlh2: 32x32 multiplier, fully
           pipelined (2 stages).  The following instructions are
           additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

       4   The multiply option is set to wlh3: Two 16x16 multiplier,
           blocking, sequential.  The following instructions are
           additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

       5   The multiply option is set to wlh4: One 16x16 multiplier,
           blocking, sequential.  The following instructions are
           additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

       6   The multiply option is set to wlh5: One 32x4 multiplier,
           blocking, sequential.  The following instructions are
           additionally enabled: MPY, MPYU, MPYM, MPYMU, and MPY_S.

       This option is only available for ARCv2 cores.

   -mfpu=fpu
       Enables specific floating-point hardware extension for ARCv2 core.
       Supported values for fpu are:

       fpus
           Enables support for single precision floating point hardware
           extensions.

       fpud
           Enables support for double precision floating point hardware
           extensions.  The single precision floating point extension is
           also enabled.  Not available for ARC EM.

       fpuda
           Enables support for double precision floating point hardware
           extensions using double precision assist instructions.  The
           single precision floating point extension is also enabled.
           This option is only available for ARC EM.

       fpuda_div
           Enables support for double precision floating point hardware
           extensions using double precision assist instructions, and
           simple precision square-root and divide hardware extensions.
           The single precision floating point extension is also enabled.
           This option is only available for ARC EM.

       fpuda_fma
           Enables support for double precision floating point hardware
           extensions using double precision assist instructions, and
           simple precision fused multiple and add hardware extension.
           The single precision floating point extension is also enabled.
           This option is only available for ARC EM.

       fpuda_all
           Enables support for double precision floating point hardware
           extensions using double precision assist instructions, and all
           simple precision hardware extensions.  The single precision
           floating point extension is also enabled.  This option is only
           available for ARC EM.

       fpus_div
           Enables support for single precision floating point, and single
           precision square-root and divide hardware extensions.

       fpud_div
           Enables support for double precision floating point, and double
           precision square-root and divide hardware extensions.  This
           option includes option fpus_div. Not available for ARC EM.

       fpus_fma
           Enables support for single precision floating point, and single
           precision fused multiple and add hardware extensions.

       fpud_fma
           Enables support for double precision floating point, and double
           precision fused multiple and add hardware extensions.  This
           option includes option fpus_fma.  Not available for ARC EM.

       fpus_all
           Enables support for all single precision floating point
           hardware extensions.

       fpud_all
           Enables support for all single and double precision floating
           point hardware extensions.  Not available for ARC EM.

   The following options are passed through to the assembler, and also
   define preprocessor macro symbols.

   -mdsp-packa
       Passed down to the assembler to enable the DSP Pack A extensions.
       Also sets the preprocessor symbol "__Xdsp_packa".

   -mdvbf
       Passed down to the assembler to enable the dual viterbi butterfly
       extension.  Also sets the preprocessor symbol "__Xdvbf".

   -mlock
       Passed down to the assembler to enable the Locked Load/Store
       Conditional extension.  Also sets the preprocessor symbol
       "__Xlock".

   -mmac-d16
       Passed down to the assembler.  Also sets the preprocessor symbol
       "__Xxmac_d16".

   -mmac-24
       Passed down to the assembler.  Also sets the preprocessor symbol
       "__Xxmac_24".

   -mrtsc
       Passed down to the assembler to enable the 64-bit Time-Stamp
       Counter extension instruction.  Also sets the preprocessor symbol
       "__Xrtsc".

   -mswape
       Passed down to the assembler to enable the swap byte ordering
       extension instruction.  Also sets the preprocessor symbol
       "__Xswape".

   -mtelephony
       Passed down to the assembler to enable dual and single operand
       instructions for telephony.  Also sets the preprocessor symbol
       "__Xtelephony".

   -mxy
       Passed down to the assembler to enable the XY Memory extension.
       Also sets the preprocessor symbol "__Xxy".

   The following options control how the assembly code is annotated:

   -misize
       Annotate assembler instructions with estimated addresses.

   -mannotate-align
       Explain what alignment considerations lead to the decision to make
       an instruction short or long.

   The following options are passed through to the linker:

   -marclinux
       Passed through to the linker, to specify use of the "arclinux"
       emulation.  This option is enabled by default in tool chains built
       for "arc-linux-uclibc" and "arceb-linux-uclibc" targets when
       profiling is not requested.

   -marclinux_prof
       Passed through to the linker, to specify use of the "arclinux_prof"
       emulation.  This option is enabled by default in tool chains built
       for "arc-linux-uclibc" and "arceb-linux-uclibc" targets when
       profiling is requested.

   The following options control the semantics of generated code:

   -mlong-calls
       Generate call insns as register indirect calls, thus providing
       access to the full 32-bit address range.

   -mmedium-calls
       Don't use less than 25 bit addressing range for calls, which is the
       offset available for an unconditional branch-and-link instruction.
       Conditional execution of function calls is suppressed, to allow use
       of the 25-bit range, rather than the 21-bit range with conditional
       branch-and-link.  This is the default for tool chains built for
       "arc-linux-uclibc" and "arceb-linux-uclibc" targets.

   -mno-sdata
       Do not generate sdata references.  This is the default for tool
       chains built for "arc-linux-uclibc" and "arceb-linux-uclibc"
       targets.

   -mucb-mcount
       Instrument with mcount calls as used in UCB code.  I.e. do the
       counting in the callee, not the caller.  By default ARC
       instrumentation counts in the caller.

   -mvolatile-cache
       Use ordinarily cached memory accesses for volatile references.
       This is the default.

   -mno-volatile-cache
       Enable cache bypass for volatile references.

   The following options fine tune code generation:

   -malign-call
       Do alignment optimizations for call instructions.

   -mauto-modify-reg
       Enable the use of pre/post modify with register displacement.

   -mbbit-peephole
       Enable bbit peephole2.

   -mno-brcc
       This option disables a target-specific pass in arc_reorg to
       generate "BRcc" instructions.  It has no effect on "BRcc"
       generation driven by the combiner pass.

   -mcase-vector-pcrel
       Use pc-relative switch case tables - this enables case table
       shortening.  This is the default for -Os.

   -mcompact-casesi
       Enable compact casesi pattern.  This is the default for -Os.

   -mno-cond-exec
       Disable ARCompact specific pass to generate conditional execution
       instructions.  Due to delay slot scheduling and interactions
       between operand numbers, literal sizes, instruction lengths, and
       the support for conditional execution, the target-independent pass
       to generate conditional execution is often lacking, so the ARC port
       has kept a special pass around that tries to find more conditional
       execution generating opportunities after register allocation,
       branch shortening, and delay slot scheduling have been done.  This
       pass generally, but not always, improves performance and code size,
       at the cost of extra compilation time, which is why there is an
       option to switch it off.  If you have a problem with call
       instructions exceeding their allowable offset range because they
       are conditionalized, you should consider using -mmedium-calls
       instead.

   -mearly-cbranchsi
       Enable pre-reload use of the cbranchsi pattern.

   -mexpand-adddi
       Expand "adddi3" and "subdi3" at rtl generation time into "add.f",
       "adc" etc.

   -mindexed-loads
       Enable the use of indexed loads.  This can be problematic because
       some optimizers then assume that indexed stores exist, which is not
       the case.

       Enable Local Register Allocation.  This is still experimental for
       ARC, so by default the compiler uses standard reload (i.e.
       -mno-lra).

   -mlra-priority-none
       Don't indicate any priority for target registers.

   -mlra-priority-compact
       Indicate target register priority for r0..r3 / r12..r15.

   -mlra-priority-noncompact
       Reduce target register priority for r0..r3 / r12..r15.

   -mno-millicode
       When optimizing for size (using -Os), prologues and epilogues that
       have to save or restore a large number of registers are often
       shortened by using call to a special function in libgcc; this is
       referred to as a millicode call.  As these calls can pose
       performance issues, and/or cause linking issues when linking in a
       nonstandard way, this option is provided to turn off millicode call
       generation.

   -mmixed-code
       Tweak register allocation to help 16-bit instruction generation.
       This generally has the effect of decreasing the average instruction
       size while increasing the instruction count.

   -mq-class
       Enable 'q' instruction alternatives.  This is the default for -Os.

   -mRcq
       Enable Rcq constraint handling - most short code generation depends
       on this.  This is the default.

   -mRcw
       Enable Rcw constraint handling - ccfsm condexec mostly depends on
       this.  This is the default.

   -msize-level=level
       Fine-tune size optimization with regards to instruction lengths and
       alignment.  The recognized values for level are:

       0   No size optimization.  This level is deprecated and treated
           like 1.

       1   Short instructions are used opportunistically.

       2   In addition, alignment of loops and of code after barriers are
           dropped.

       3   In addition, optional data alignment is dropped, and the option
           Os is enabled.

       This defaults to 3 when -Os is in effect.  Otherwise, the behavior
       when this is not set is equivalent to level 1.

   -mtune=cpu
       Set instruction scheduling parameters for cpu, overriding any
       implied by -mcpu=.

       Supported values for cpu are

       ARC600
           Tune for ARC600 cpu.

       ARC601
           Tune for ARC601 cpu.

       ARC700
           Tune for ARC700 cpu with standard multiplier block.

       ARC700-xmac
           Tune for ARC700 cpu with XMAC block.

       ARC725D
           Tune for ARC725D cpu.

       ARC750D
           Tune for ARC750D cpu.

   -mmultcost=num
       Cost to assume for a multiply instruction, with 4 being equal to a
       normal instruction.

   -munalign-prob-threshold=probability
       Set probability threshold for unaligning branches.  When tuning for
       ARC700 and optimizing for speed, branches without filled delay slot
       are preferably emitted unaligned and long, unless profiling
       indicates that the probability for the branch to be taken is below
       probability.  The default is (REG_BR_PROB_BASE/2), i.e. 5000.

   The following options are maintained for backward compatibility, but
   are now deprecated and will be removed in a future release:

   -margonaut
       Obsolete FPX.

   -mbig-endian
   -EB Compile code for big endian targets.  Use of these options is now
       deprecated.  Users wanting big-endian code, should use the
       "arceb-elf32" and "arceb-linux-uclibc" targets when building the
       tool chain, for which big-endian is the default.

   -mlittle-endian
   -EL Compile code for little endian targets.  Use of these options is
       now deprecated.  Users wanting little-endian code should use the
       "arc-elf32" and "arc-linux-uclibc" targets when building the tool
       chain, for which little-endian is the default.

   -mbarrel_shifter
       Replaced by -mbarrel-shifter.

   -mdpfp_compact
       Replaced by -mdpfp-compact.

   -mdpfp_fast
       Replaced by -mdpfp-fast.

   -mdsp_packa
       Replaced by -mdsp-packa.

   -mEA
       Replaced by -mea.

   -mmac_24
       Replaced by -mmac-24.

   -mmac_d16
       Replaced by -mmac-d16.

   -mspfp_compact
       Replaced by -mspfp-compact.

   -mspfp_fast
       Replaced by -mspfp-fast.

   -mtune=cpu
       Values arc600, arc601, arc700 and arc700-xmac for cpu are replaced
       by ARC600, ARC601, ARC700 and ARC700-xmac respectively

   -multcost=num
       Replaced by -mmultcost.

   ARM Options

   These -m options are defined for the ARM port:

   -mabi=name
       Generate code for the specified ABI.  Permissible values are: apcs-
       gnu, atpcs, aapcs, aapcs-linux and iwmmxt.

   -mapcs-frame
       Generate a stack frame that is compliant with the ARM Procedure
       Call Standard for all functions, even if this is not strictly
       necessary for correct execution of the code.  Specifying
       -fomit-frame-pointer with this option causes the stack frames not
       to be generated for leaf functions.  The default is
       -mno-apcs-frame.  This option is deprecated.

   -mapcs
       This is a synonym for -mapcs-frame and is deprecated.

   -mthumb-interwork
       Generate code that supports calling between the ARM and Thumb
       instruction sets.  Without this option, on pre-v5 architectures,
       the two instruction sets cannot be reliably used inside one
       program.  The default is -mno-thumb-interwork, since slightly
       larger code is generated when -mthumb-interwork is specified.  In
       AAPCS configurations this option is meaningless.

   -mno-sched-prolog
       Prevent the reordering of instructions in the function prologue, or
       the merging of those instruction with the instructions in the
       function's body.  This means that all functions start with a
       recognizable set of instructions (or in fact one of a choice from a
       small set of different function prologues), and this information
       can be used to locate the start of functions inside an executable
       piece of code.  The default is -msched-prolog.

   -mfloat-abi=name
       Specifies which floating-point ABI to use.  Permissible values are:
       soft, softfp and hard.

       Specifying soft causes GCC to generate output containing library
       calls for floating-point operations.  softfp allows the generation
       of code using hardware floating-point instructions, but still uses
       the soft-float calling conventions.  hard allows generation of
       floating-point instructions and uses FPU-specific calling
       conventions.

       The default depends on the specific target configuration.  Note
       that the hard-float and soft-float ABIs are not link-compatible;
       you must compile your entire program with the same ABI, and link
       with a compatible set of libraries.

   -mlittle-endian
       Generate code for a processor running in little-endian mode.  This
       is the default for all standard configurations.

   -mbig-endian
       Generate code for a processor running in big-endian mode; the
       default is to compile code for a little-endian processor.

   -march=name
       This specifies the name of the target ARM architecture.  GCC uses
       this name to determine what kind of instructions it can emit when
       generating assembly code.  This option can be used in conjunction
       with or instead of the -mcpu= option.  Permissible names are:
       armv2, armv2a, armv3, armv3m, armv4, armv4t, armv5, armv5t, armv5e,
       armv5te, armv6, armv6j, armv6t2, armv6z, armv6kz, armv6-m, armv7,
       armv7-a, armv7-r, armv7-m, armv7e-m, armv7ve, armv8-a, armv8-a+crc,
       armv8.1-a, armv8.1-a+crc, iwmmxt, iwmmxt2, ep9312.

       Architecture revisions older than armv4t are deprecated.

       -march=armv7ve is the armv7-a architecture with virtualization
       extensions.

       -march=armv8-a+crc enables code generation for the ARMv8-A
       architecture together with the optional CRC32 extensions.

       -march=native causes the compiler to auto-detect the architecture
       of the build computer.  At present, this feature is only supported
       on GNU/Linux, and not all architectures are recognized.  If the
       auto-detect is unsuccessful the option has no effect.

   -mtune=name
       This option specifies the name of the target ARM processor for
       which GCC should tune the performance of the code.  For some ARM
       implementations better performance can be obtained by using this
       option.  Permissible names are: arm2, arm250, arm3, arm6, arm60,
       arm600, arm610, arm620, arm7, arm7m, arm7d, arm7dm, arm7di,
       arm7dmi, arm70, arm700, arm700i, arm710, arm710c, arm7100, arm720,
       arm7500, arm7500fe, arm7tdmi, arm7tdmi-s, arm710t, arm720t,
       arm740t, strongarm, strongarm110, strongarm1100, strongarm1110,
       arm8, arm810, arm9, arm9e, arm920, arm920t, arm922t, arm946e-s,
       arm966e-s, arm968e-s, arm926ej-s, arm940t, arm9tdmi, arm10tdmi,
       arm1020t, arm1026ej-s, arm10e, arm1020e, arm1022e, arm1136j-s,
       arm1136jf-s, mpcore, mpcorenovfp, arm1156t2-s, arm1156t2f-s,
       arm1176jz-s, arm1176jzf-s, generic-armv7-a, cortex-a5, cortex-a7,
       cortex-a8, cortex-a9, cortex-a12, cortex-a15, cortex-a17,
       cortex-a32, cortex-a35, cortex-a53, cortex-a57, cortex-a72,
       cortex-r4, cortex-r4f, cortex-r5, cortex-r7, cortex-r8, cortex-m7,
       cortex-m4, cortex-m3, cortex-m1, cortex-m0, cortex-m0plus,
       cortex-m1.small-multiply, cortex-m0.small-multiply,
       cortex-m0plus.small-multiply, exynos-m1, qdf24xx, marvell-pj4,
       xscale, iwmmxt, iwmmxt2, ep9312, fa526, fa626, fa606te, fa626te,
       fmp626, fa726te, xgene1.

       Additionally, this option can specify that GCC should tune the
       performance of the code for a big.LITTLE system.  Permissible names
       are: cortex-a15.cortex-a7, cortex-a17.cortex-a7,
       cortex-a57.cortex-a53, cortex-a72.cortex-a53.

       -mtune=generic-arch specifies that GCC should tune the performance
       for a blend of processors within architecture arch.  The aim is to
       generate code that run well on the current most popular processors,
       balancing between optimizations that benefit some CPUs in the
       range, and avoiding performance pitfalls of other CPUs.  The
       effects of this option may change in future GCC versions as CPU
       models come and go.

       -mtune=native causes the compiler to auto-detect the CPU of the
       build computer.  At present, this feature is only supported on
       GNU/Linux, and not all architectures are recognized.  If the auto-
       detect is unsuccessful the option has no effect.

   -mcpu=name
       This specifies the name of the target ARM processor.  GCC uses this
       name to derive the name of the target ARM architecture (as if
       specified by -march) and the ARM processor type for which to tune
       for performance (as if specified by -mtune).  Where this option is
       used in conjunction with -march or -mtune, those options take
       precedence over the appropriate part of this option.

       Permissible names for this option are the same as those for -mtune.

       -mcpu=generic-arch is also permissible, and is equivalent to
       -march=arch -mtune=generic-arch.  See -mtune for more information.

       -mcpu=native causes the compiler to auto-detect the CPU of the
       build computer.  At present, this feature is only supported on
       GNU/Linux, and not all architectures are recognized.  If the auto-
       detect is unsuccessful the option has no effect.

   -mfpu=name
       This specifies what floating-point hardware (or hardware emulation)
       is available on the target.  Permissible names are: vfp, vfpv3,
       vfpv3-fp16, vfpv3-d16, vfpv3-d16-fp16, vfpv3xd, vfpv3xd-fp16, neon,
       neon-fp16, vfpv4, vfpv4-d16, fpv4-sp-d16, neon-vfpv4, fpv5-d16,
       fpv5-sp-d16, fp-armv8, neon-fp-armv8 and crypto-neon-fp-armv8.

       If -msoft-float is specified this specifies the format of floating-
       point values.

       If the selected floating-point hardware includes the NEON extension
       (e.g. -mfpu=neon), note that floating-point operations are not
       generated by GCC's auto-vectorization pass unless
       -funsafe-math-optimizations is also specified.  This is because
       NEON hardware does not fully implement the IEEE 754 standard for
       floating-point arithmetic (in particular denormal values are
       treated as zero), so the use of NEON instructions may lead to a
       loss of precision.

       You can also set the fpu name at function level by using the
       "target("fpu=")" function attributes or pragmas.

   -mfp16-format=name
       Specify the format of the "__fp16" half-precision floating-point
       type.  Permissible names are none, ieee, and alternative; the
       default is none, in which case the "__fp16" type is not defined.

   -mstructure-size-boundary=n
       The sizes of all structures and unions are rounded up to a multiple
       of the number of bits set by this option.  Permissible values are
       8, 32 and 64.  The default value varies for different toolchains.
       For the COFF targeted toolchain the default value is 8.  A value of
       64 is only allowed if the underlying ABI supports it.

       Specifying a larger number can produce faster, more efficient code,
       but can also increase the size of the program.  Different values
       are potentially incompatible.  Code compiled with one value cannot
       necessarily expect to work with code or libraries compiled with
       another value, if they exchange information using structures or
       unions.

   -mabort-on-noreturn
       Generate a call to the function "abort" at the end of a "noreturn"
       function.  It is executed if the function tries to return.

   -mlong-calls
   -mno-long-calls
       Tells the compiler to perform function calls by first loading the
       address of the function into a register and then performing a
       subroutine call on this register.  This switch is needed if the
       target function lies outside of the 64-megabyte addressing range of
       the offset-based version of subroutine call instruction.

       Even if this switch is enabled, not all function calls are turned
       into long calls.  The heuristic is that static functions, functions
       that have the "short_call" attribute, functions that are inside the
       scope of a "#pragma no_long_calls" directive, and functions whose
       definitions have already been compiled within the current
       compilation unit are not turned into long calls.  The exceptions to
       this rule are that weak function definitions, functions with the
       "long_call" attribute or the "section" attribute, and functions
       that are within the scope of a "#pragma long_calls" directive are
       always turned into long calls.

       This feature is not enabled by default.  Specifying -mno-long-calls
       restores the default behavior, as does placing the function calls
       within the scope of a "#pragma long_calls_off" directive.  Note
       these switches have no effect on how the compiler generates code to
       handle function calls via function pointers.

   -msingle-pic-base
       Treat the register used for PIC addressing as read-only, rather
       than loading it in the prologue for each function.  The runtime
       system is responsible for initializing this register with an
       appropriate value before execution begins.

   -mpic-register=reg
       Specify the register to be used for PIC addressing.  For standard
       PIC base case, the default is any suitable register determined by
       compiler.  For single PIC base case, the default is R9 if target is
       EABI based or stack-checking is enabled, otherwise the default is
       R10.

   -mpic-data-is-text-relative
       Assume that each data segments are relative to text segment at load
       time.  Therefore, it permits addressing data using PC-relative
       operations.  This option is on by default for targets other than
       VxWorks RTP.

   -mpoke-function-name
       Write the name of each function into the text section, directly
       preceding the function prologue.  The generated code is similar to
       this:

                    t0
                        .ascii "arm_poke_function_name", 0
                        .align
                    t1
                        .word 0xff000000 + (t1 - t0)
                    arm_poke_function_name
                        mov     ip, sp
                        stmfd   sp!, {fp, ip, lr, pc}
                        sub     fp, ip, #4

       When performing a stack backtrace, code can inspect the value of
       "pc" stored at "fp + 0".  If the trace function then looks at
       location "pc - 12" and the top 8 bits are set, then we know that
       there is a function name embedded immediately preceding this
       location and has length "((pc[-3]) & 0xff000000)".

   -mthumb
   -marm
       Select between generating code that executes in ARM and Thumb
       states.  The default for most configurations is to generate code
       that executes in ARM state, but the default can be changed by
       configuring GCC with the --with-mode=state configure option.

       You can also override the ARM and Thumb mode for each function by
       using the "target("thumb")" and "target("arm")" function attributes
       or pragmas.

   -mtpcs-frame
       Generate a stack frame that is compliant with the Thumb Procedure
       Call Standard for all non-leaf functions.  (A leaf function is one
       that does not call any other functions.)  The default is
       -mno-tpcs-frame.

   -mtpcs-leaf-frame
       Generate a stack frame that is compliant with the Thumb Procedure
       Call Standard for all leaf functions.  (A leaf function is one that
       does not call any other functions.)  The default is
       -mno-apcs-leaf-frame.

   -mcallee-super-interworking
       Gives all externally visible functions in the file being compiled
       an ARM instruction set header which switches to Thumb mode before
       executing the rest of the function.  This allows these functions to
       be called from non-interworking code.  This option is not valid in
       AAPCS configurations because interworking is enabled by default.

   -mcaller-super-interworking
       Allows calls via function pointers (including virtual functions) to
       execute correctly regardless of whether the target code has been
       compiled for interworking or not.  There is a small overhead in the
       cost of executing a function pointer if this option is enabled.
       This option is not valid in AAPCS configurations because
       interworking is enabled by default.

   -mtp=name
       Specify the access model for the thread local storage pointer.  The
       valid models are soft, which generates calls to "__aeabi_read_tp",
       cp15, which fetches the thread pointer from "cp15" directly
       (supported in the arm6k architecture), and auto, which uses the
       best available method for the selected processor.  The default
       setting is auto.

   -mtls-dialect=dialect
       Specify the dialect to use for accessing thread local storage.  Two
       dialects are supported---gnu and gnu2.  The gnu dialect selects the
       original GNU scheme for supporting local and global dynamic TLS
       models.  The gnu2 dialect selects the GNU descriptor scheme, which
       provides better performance for shared libraries.  The GNU
       descriptor scheme is compatible with the original scheme, but does
       require new assembler, linker and library support.  Initial and
       local exec TLS models are unaffected by this option and always use
       the original scheme.

   -mword-relocations
       Only generate absolute relocations on word-sized values (i.e.
       R_ARM_ABS32).  This is enabled by default on targets (uClinux,
       SymbianOS) where the runtime loader imposes this restriction, and
       when -fpic or -fPIC is specified.

   -mfix-cortex-m3-ldrd
       Some Cortex-M3 cores can cause data corruption when "ldrd"
       instructions with overlapping destination and base registers are
       used.  This option avoids generating these instructions.  This
       option is enabled by default when -mcpu=cortex-m3 is specified.

   -munaligned-access
   -mno-unaligned-access
       Enables (or disables) reading and writing of 16- and 32- bit values
       from addresses that are not 16- or 32- bit aligned.  By default
       unaligned access is disabled for all pre-ARMv6 and all ARMv6-M
       architectures, and enabled for all other architectures.  If
       unaligned access is not enabled then words in packed data
       structures are accessed a byte at a time.

       The ARM attribute "Tag_CPU_unaligned_access" is set in the
       generated object file to either true or false, depending upon the
       setting of this option.  If unaligned access is enabled then the
       preprocessor symbol "__ARM_FEATURE_UNALIGNED" is also defined.

   -mneon-for-64bits
       Enables using Neon to handle scalar 64-bits operations. This is
       disabled by default since the cost of moving data from core
       registers to Neon is high.

   -mslow-flash-data
       Assume loading data from flash is slower than fetching instruction.
       Therefore literal load is minimized for better performance.  This
       option is only supported when compiling for ARMv7 M-profile and off
       by default.

   -masm-syntax-unified
       Assume inline assembler is using unified asm syntax.  The default
       is currently off which implies divided syntax.  This option has no
       impact on Thumb2. However, this may change in future releases of
       GCC.  Divided syntax should be considered deprecated.

   -mrestrict-it
       Restricts generation of IT blocks to conform to the rules of ARMv8.
       IT blocks can only contain a single 16-bit instruction from a
       select set of instructions. This option is on by default for ARMv8
       Thumb mode.

   -mprint-tune-info
       Print CPU tuning information as comment in assembler file.  This is
       an option used only for regression testing of the compiler and not
       intended for ordinary use in compiling code.  This option is
       disabled by default.

   AVR Options

   These options are defined for AVR implementations:

   -mmcu=mcu
       Specify Atmel AVR instruction set architectures (ISA) or MCU type.

       The default for this option is@tie{}avr2.

       GCC supports the following AVR devices and ISAs:

       "avr2"
           "Classic" devices with up to 8@tie{}KiB of program memory.
           mcu@tie{}= "attiny22", "attiny26", "at90c8534", "at90s2313",
           "at90s2323", "at90s2333", "at90s2343", "at90s4414",
           "at90s4433", "at90s4434", "at90s8515", "at90s8535".

       "avr25"
           "Classic" devices with up to 8@tie{}KiB of program memory and
           with the "MOVW" instruction.  mcu@tie{}= "ata5272", "ata6616c",
           "attiny13", "attiny13a", "attiny2313", "attiny2313a",
           "attiny24", "attiny24a", "attiny25", "attiny261", "attiny261a",
           "attiny43u", "attiny4313", "attiny44", "attiny44a",
           "attiny441", "attiny45", "attiny461", "attiny461a", "attiny48",
           "attiny828", "attiny84", "attiny84a", "attiny841", "attiny85",
           "attiny861", "attiny861a", "attiny87", "attiny88", "at86rf401".

       "avr3"
           "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB of
           program memory.  mcu@tie{}= "at43usb355", "at76c711".

       "avr31"
           "Classic" devices with 128@tie{}KiB of program memory.
           mcu@tie{}= "atmega103", "at43usb320".

       "avr35"
           "Classic" devices with 16@tie{}KiB up to 64@tie{}KiB of program
           memory and with the "MOVW" instruction.  mcu@tie{}= "ata5505",
           "ata6617c", "ata664251", "atmega16u2", "atmega32u2",
           "atmega8u2", "attiny1634", "attiny167", "at90usb162",
           "at90usb82".

       "avr4"
           "Enhanced" devices with up to 8@tie{}KiB of program memory.
           mcu@tie{}= "ata6285", "ata6286", "ata6289", "ata6612c",
           "atmega48", "atmega48a", "atmega48p", "atmega48pa",
           "atmega48pb", "atmega8", "atmega8a", "atmega8hva",
           "atmega8515", "atmega8535", "atmega88", "atmega88a",
           "atmega88p", "atmega88pa", "atmega88pb", "at90pwm1",
           "at90pwm2", "at90pwm2b", "at90pwm3", "at90pwm3b", "at90pwm81".

       "avr5"
           "Enhanced" devices with 16@tie{}KiB up to 64@tie{}KiB of
           program memory.  mcu@tie{}= "ata5702m322", "ata5782",
           "ata5790", "ata5790n", "ata5791", "ata5795", "ata5831",
           "ata6613c", "ata6614q", "ata8210", "ata8510", "atmega16",
           "atmega16a", "atmega16hva", "atmega16hva2", "atmega16hvb",
           "atmega16hvbrevb", "atmega16m1", "atmega16u4", "atmega161",
           "atmega162", "atmega163", "atmega164a", "atmega164p",
           "atmega164pa", "atmega165", "atmega165a", "atmega165p",
           "atmega165pa", "atmega168", "atmega168a", "atmega168p",
           "atmega168pa", "atmega168pb", "atmega169", "atmega169a",
           "atmega169p", "atmega169pa", "atmega32", "atmega32a",
           "atmega32c1", "atmega32hvb", "atmega32hvbrevb", "atmega32m1",
           "atmega32u4", "atmega32u6", "atmega323", "atmega324a",
           "atmega324p", "atmega324pa", "atmega325", "atmega325a",
           "atmega325p", "atmega325pa", "atmega3250", "atmega3250a",
           "atmega3250p", "atmega3250pa", "atmega328", "atmega328p",
           "atmega328pb", "atmega329", "atmega329a", "atmega329p",
           "atmega329pa", "atmega3290", "atmega3290a", "atmega3290p",
           "atmega3290pa", "atmega406", "atmega64", "atmega64a",
           "atmega64c1", "atmega64hve", "atmega64hve2", "atmega64m1",
           "atmega64rfr2", "atmega640", "atmega644", "atmega644a",
           "atmega644p", "atmega644pa", "atmega644rfr2", "atmega645",
           "atmega645a", "atmega645p", "atmega6450", "atmega6450a",
           "atmega6450p", "atmega649", "atmega649a", "atmega649p",
           "atmega6490", "atmega6490a", "atmega6490p", "at90can32",
           "at90can64", "at90pwm161", "at90pwm216", "at90pwm316",
           "at90scr100", "at90usb646", "at90usb647", "at94k", "m3000".

       "avr51"
           "Enhanced" devices with 128@tie{}KiB of program memory.
           mcu@tie{}= "atmega128", "atmega128a", "atmega128rfa1",
           "atmega128rfr2", "atmega1280", "atmega1281", "atmega1284",
           "atmega1284p", "atmega1284rfr2", "at90can128", "at90usb1286",
           "at90usb1287".

       "avr6"
           "Enhanced" devices with 3-byte PC, i.e. with more than
           128@tie{}KiB of program memory.  mcu@tie{}= "atmega256rfr2",
           "atmega2560", "atmega2561", "atmega2564rfr2".

       "avrxmega2"
           "XMEGA" devices with more than 8@tie{}KiB and up to 64@tie{}KiB
           of program memory.  mcu@tie{}= "atxmega16a4", "atxmega16a4u",
           "atxmega16c4", "atxmega16d4", "atxmega16e5", "atxmega32a4",
           "atxmega32a4u", "atxmega32c3", "atxmega32c4", "atxmega32d3",
           "atxmega32d4", "atxmega32e5", "atxmega8e5".

       "avrxmega4"
           "XMEGA" devices with more than 64@tie{}KiB and up to
           128@tie{}KiB of program memory.  mcu@tie{}= "atxmega64a3",
           "atxmega64a3u", "atxmega64a4u", "atxmega64b1", "atxmega64b3",
           "atxmega64c3", "atxmega64d3", "atxmega64d4".

       "avrxmega5"
           "XMEGA" devices with more than 64@tie{}KiB and up to
           128@tie{}KiB of program memory and more than 64@tie{}KiB of
           RAM.  mcu@tie{}= "atxmega64a1", "atxmega64a1u".

       "avrxmega6"
           "XMEGA" devices with more than 128@tie{}KiB of program memory.
           mcu@tie{}= "atxmega128a3", "atxmega128a3u", "atxmega128b1",
           "atxmega128b3", "atxmega128c3", "atxmega128d3", "atxmega128d4",
           "atxmega192a3", "atxmega192a3u", "atxmega192c3",
           "atxmega192d3", "atxmega256a3", "atxmega256a3b",
           "atxmega256a3bu", "atxmega256a3u", "atxmega256c3",
           "atxmega256d3", "atxmega384c3", "atxmega384d3".

       "avrxmega7"
           "XMEGA" devices with more than 128@tie{}KiB of program memory
           and more than 64@tie{}KiB of RAM.  mcu@tie{}= "atxmega128a1",
           "atxmega128a1u", "atxmega128a4u".

       "avrtiny"
           "TINY" Tiny core devices with 512@tie{}B up to 4@tie{}KiB of
           program memory.  mcu@tie{}= "attiny10", "attiny20", "attiny4",
           "attiny40", "attiny5", "attiny9".

       "avr1"
           This ISA is implemented by the minimal AVR core and supported
           for assembler only.  mcu@tie{}= "attiny11", "attiny12",
           "attiny15", "attiny28", "at90s1200".

   -maccumulate-args
       Accumulate outgoing function arguments and acquire/release the
       needed stack space for outgoing function arguments once in function
       prologue/epilogue.  Without this option, outgoing arguments are
       pushed before calling a function and popped afterwards.

       Popping the arguments after the function call can be expensive on
       AVR so that accumulating the stack space might lead to smaller
       executables because arguments need not to be removed from the stack
       after such a function call.

       This option can lead to reduced code size for functions that
       perform several calls to functions that get their arguments on the
       stack like calls to printf-like functions.

   -mbranch-cost=cost
       Set the branch costs for conditional branch instructions to cost.
       Reasonable values for cost are small, non-negative integers. The
       default branch cost is 0.

   -mcall-prologues
       Functions prologues/epilogues are expanded as calls to appropriate
       subroutines.  Code size is smaller.

   -mint8
       Assume "int" to be 8-bit integer.  This affects the sizes of all
       types: a "char" is 1 byte, an "int" is 1 byte, a "long" is 2 bytes,
       and "long long" is 4 bytes.  Please note that this option does not
       conform to the C standards, but it results in smaller code size.

   -mn-flash=num
       Assume that the flash memory has a size of num times 64@tie{}KiB.

   -mno-interrupts
       Generated code is not compatible with hardware interrupts.  Code
       size is smaller.

   -mrelax
       Try to replace "CALL" resp. "JMP" instruction by the shorter
       "RCALL" resp. "RJMP" instruction if applicable.  Setting -mrelax
       just adds the --mlink-relax option to the assembler's command line
       and the --relax option to the linker's command line.

       Jump relaxing is performed by the linker because jump offsets are
       not known before code is located. Therefore, the assembler code
       generated by the compiler is the same, but the instructions in the
       executable may differ from instructions in the assembler code.

       Relaxing must be turned on if linker stubs are needed, see the
       section on "EIND" and linker stubs below.

   -mrmw
       Assume that the device supports the Read-Modify-Write instructions
       "XCH", "LAC", "LAS" and "LAT".

   -msp8
       Treat the stack pointer register as an 8-bit register, i.e. assume
       the high byte of the stack pointer is zero.  In general, you don't
       need to set this option by hand.

       This option is used internally by the compiler to select and build
       multilibs for architectures "avr2" and "avr25".  These
       architectures mix devices with and without "SPH".  For any setting
       other than -mmcu=avr2 or -mmcu=avr25 the compiler driver adds or
       removes this option from the compiler proper's command line,
       because the compiler then knows if the device or architecture has
       an 8-bit stack pointer and thus no "SPH" register or not.

   -mstrict-X
       Use address register "X" in a way proposed by the hardware.  This
       means that "X" is only used in indirect, post-increment or pre-
       decrement addressing.

       Without this option, the "X" register may be used in the same way
       as "Y" or "Z" which then is emulated by additional instructions.
       For example, loading a value with "X+const" addressing with a small
       non-negative "const < 64" to a register Rn is performed as

               adiw r26, const   ; X += const
               ld   <Rn>, X        ; <Rn> = *X
               sbiw r26, const   ; X -= const

   -mtiny-stack
       Only change the lower 8@tie{}bits of the stack pointer.

   -nodevicelib
       Don't link against AVR-LibC's device specific library "libdev.a".

   -Waddr-space-convert
       Warn about conversions between address spaces in the case where the
       resulting address space is not contained in the incoming address
       space.

   "EIND" and Devices with More Than 128 Ki Bytes of Flash

   Pointers in the implementation are 16@tie{}bits wide.  The address of a
   function or label is represented as word address so that indirect jumps
   and calls can target any code address in the range of 64@tie{}Ki words.

   In order to facilitate indirect jump on devices with more than
   128@tie{}Ki bytes of program memory space, there is a special function
   register called "EIND" that serves as most significant part of the
   target address when "EICALL" or "EIJMP" instructions are used.

   Indirect jumps and calls on these devices are handled as follows by the
   compiler and are subject to some limitations:

   *   The compiler never sets "EIND".

   *   The compiler uses "EIND" implicitly in "EICALL"/"EIJMP"
       instructions or might read "EIND" directly in order to emulate an
       indirect call/jump by means of a "RET" instruction.

   *   The compiler assumes that "EIND" never changes during the startup
       code or during the application. In particular, "EIND" is not
       saved/restored in function or interrupt service routine
       prologue/epilogue.

   *   For indirect calls to functions and computed goto, the linker
       generates stubs. Stubs are jump pads sometimes also called
       trampolines. Thus, the indirect call/jump jumps to such a stub.
       The stub contains a direct jump to the desired address.

   *   Linker relaxation must be turned on so that the linker generates
       the stubs correctly in all situations. See the compiler option
       -mrelax and the linker option --relax.  There are corner cases
       where the linker is supposed to generate stubs but aborts without
       relaxation and without a helpful error message.

   *   The default linker script is arranged for code with "EIND = 0".  If
       code is supposed to work for a setup with "EIND != 0", a custom
       linker script has to be used in order to place the sections whose
       name start with ".trampolines" into the segment where "EIND" points
       to.

   *   The startup code from libgcc never sets "EIND".  Notice that
       startup code is a blend of code from libgcc and AVR-LibC.  For the
       impact of AVR-LibC on "EIND", see the AVR-LibC user manual
       ("http://nongnu.org/avr-libc/user-manual/").

   *   It is legitimate for user-specific startup code to set up "EIND"
       early, for example by means of initialization code located in
       section ".init3". Such code runs prior to general startup code that
       initializes RAM and calls constructors, but after the bit of
       startup code from AVR-LibC that sets "EIND" to the segment where
       the vector table is located.

               #include <avr/io.h>

               static void
               __attribute__((section(".init3"),naked,used,no_instrument_function))
               init3_set_eind (void)
               {
                 __asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
                                 "out %i0,r24" :: "n" (&EIND) : "r24","memory");
               }

       The "__trampolines_start" symbol is defined in the linker script.

   *   Stubs are generated automatically by the linker if the following
       two conditions are met:

       -<The address of a label is taken by means of the "gs" modifier>
           (short for generate stubs) like so:

                   LDI r24, lo8(gs(<func>))
                   LDI r25, hi8(gs(<func>))

       -<The final location of that label is in a code segment>
           outside the segment where the stubs are located.

   *   The compiler emits such "gs" modifiers for code labels in the
       following situations:

       -<Taking address of a function or code label.>
       -<Computed goto.>
       -<If prologue-save function is used, see -mcall-prologues>
           command-line option.

       -<Switch/case dispatch tables. If you do not want such dispatch>
           tables you can specify the -fno-jump-tables command-line
           option.

       -<C and C++ constructors/destructors called during
       startup/shutdown.>
       -<If the tools hit a "gs()" modifier explained above.>
   *   Jumping to non-symbolic addresses like so is not supported:

               int main (void)
               {
                   /* Call function at word address 0x2 */
                   return ((int(*)(void)) 0x2)();
               }

       Instead, a stub has to be set up, i.e. the function has to be
       called through a symbol ("func_4" in the example):

               int main (void)
               {
                   extern int func_4 (void);

                   /* Call function at byte address 0x4 */
                   return func_4();
               }

       and the application be linked with -Wl,--defsym,func_4=0x4.
       Alternatively, "func_4" can be defined in the linker script.

   Handling of the "RAMPD", "RAMPX", "RAMPY" and "RAMPZ" Special Function
   Registers

   Some AVR devices support memories larger than the 64@tie{}KiB range
   that can be accessed with 16-bit pointers.  To access memory locations
   outside this 64@tie{}KiB range, the contentent of a "RAMP" register is
   used as high part of the address: The "X", "Y", "Z" address register is
   concatenated with the "RAMPX", "RAMPY", "RAMPZ" special function
   register, respectively, to get a wide address. Similarly, "RAMPD" is
   used together with direct addressing.

   *   The startup code initializes the "RAMP" special function registers
       with zero.

   *   If a AVR Named Address Spaces,named address space other than
       generic or "__flash" is used, then "RAMPZ" is set as needed before
       the operation.

   *   If the device supports RAM larger than 64@tie{}KiB and the compiler
       needs to change "RAMPZ" to accomplish an operation, "RAMPZ" is
       reset to zero after the operation.

   *   If the device comes with a specific "RAMP" register, the ISR
       prologue/epilogue saves/restores that SFR and initializes it with
       zero in case the ISR code might (implicitly) use it.

   *   RAM larger than 64@tie{}KiB is not supported by GCC for AVR
       targets.  If you use inline assembler to read from locations
       outside the 16-bit address range and change one of the "RAMP"
       registers, you must reset it to zero after the access.

   AVR Built-in Macros

   GCC defines several built-in macros so that the user code can test for
   the presence or absence of features.  Almost any of the following
   built-in macros are deduced from device capabilities and thus triggered
   by the -mmcu= command-line option.

   For even more AVR-specific built-in macros see AVR Named Address Spaces
   and AVR Built-in Functions.

   "__AVR_ARCH__"
       Build-in macro that resolves to a decimal number that identifies
       the architecture and depends on the -mmcu=mcu option.  Possible
       values are:

       2, 25, 3, 31, 35, 4, 5, 51, 6

       for mcu="avr2", "avr25", "avr3", "avr31", "avr35", "avr4", "avr5",
       "avr51", "avr6",

       respectively and

       100, 102, 104, 105, 106, 107

       for mcu="avrtiny", "avrxmega2", "avrxmega4", "avrxmega5",
       "avrxmega6", "avrxmega7", respectively.  If mcu specifies a device,
       this built-in macro is set accordingly. For example, with
       -mmcu=atmega8 the macro is defined to 4.

   "__AVR_Device__"
       Setting -mmcu=device defines this built-in macro which reflects the
       device's name. For example, -mmcu=atmega8 defines the built-in
       macro "__AVR_ATmega8__", -mmcu=attiny261a defines
       "__AVR_ATtiny261A__", etc.

       The built-in macros' names follow the scheme "__AVR_Device__" where
       Device is the device name as from the AVR user manual. The
       difference between Device in the built-in macro and device in
       -mmcu=device is that the latter is always lowercase.

       If device is not a device but only a core architecture like avr51,
       this macro is not defined.

   "__AVR_DEVICE_NAME__"
       Setting -mmcu=device defines this built-in macro to the device's
       name. For example, with -mmcu=atmega8 the macro is defined to
       "atmega8".

       If device is not a device but only a core architecture like avr51,
       this macro is not defined.

   "__AVR_XMEGA__"
       The device / architecture belongs to the XMEGA family of devices.

   "__AVR_HAVE_ELPM__"
       The device has the "ELPM" instruction.

   "__AVR_HAVE_ELPMX__"
       The device has the "ELPM Rn,Z" and "ELPM Rn,Z+" instructions.

   "__AVR_HAVE_MOVW__"
       The device has the "MOVW" instruction to perform 16-bit register-
       register moves.

   "__AVR_HAVE_LPMX__"
       The device has the "LPM Rn,Z" and "LPM Rn,Z+" instructions.

   "__AVR_HAVE_MUL__"
       The device has a hardware multiplier.

   "__AVR_HAVE_JMP_CALL__"
       The device has the "JMP" and "CALL" instructions.  This is the case
       for devices with at least 16@tie{}KiB of program memory.

   "__AVR_HAVE_EIJMP_EICALL__"
   "__AVR_3_BYTE_PC__"
       The device has the "EIJMP" and "EICALL" instructions.  This is the
       case for devices with more than 128@tie{}KiB of program memory.
       This also means that the program counter (PC) is 3@tie{}bytes wide.

   "__AVR_2_BYTE_PC__"
       The program counter (PC) is 2@tie{}bytes wide. This is the case for
       devices with up to 128@tie{}KiB of program memory.

   "__AVR_HAVE_8BIT_SP__"
   "__AVR_HAVE_16BIT_SP__"
       The stack pointer (SP) register is treated as 8-bit respectively
       16-bit register by the compiler.  The definition of these macros is
       affected by -mtiny-stack.

   "__AVR_HAVE_SPH__"
   "__AVR_SP8__"
       The device has the SPH (high part of stack pointer) special
       function register or has an 8-bit stack pointer, respectively.  The
       definition of these macros is affected by -mmcu= and in the cases
       of -mmcu=avr2 and -mmcu=avr25 also by -msp8.

   "__AVR_HAVE_RAMPD__"
   "__AVR_HAVE_RAMPX__"
   "__AVR_HAVE_RAMPY__"
   "__AVR_HAVE_RAMPZ__"
       The device has the "RAMPD", "RAMPX", "RAMPY", "RAMPZ" special
       function register, respectively.

   "__NO_INTERRUPTS__"
       This macro reflects the -mno-interrupts command-line option.

   "__AVR_ERRATA_SKIP__"
   "__AVR_ERRATA_SKIP_JMP_CALL__"
       Some AVR devices (AT90S8515, ATmega103) must not skip 32-bit
       instructions because of a hardware erratum.  Skip instructions are
       "SBRS", "SBRC", "SBIS", "SBIC" and "CPSE".  The second macro is
       only defined if "__AVR_HAVE_JMP_CALL__" is also set.

   "__AVR_ISA_RMW__"
       The device has Read-Modify-Write instructions (XCH, LAC, LAS and
       LAT).

   "__AVR_SFR_OFFSET__=offset"
       Instructions that can address I/O special function registers
       directly like "IN", "OUT", "SBI", etc. may use a different address
       as if addressed by an instruction to access RAM like "LD" or "STS".
       This offset depends on the device architecture and has to be
       subtracted from the RAM address in order to get the respective
       I/O@tie{}address.

   "__WITH_AVRLIBC__"
       The compiler is configured to be used together with AVR-Libc.  See
       the --with-avrlibc configure option.

   Blackfin Options

   -mcpu=cpu[-sirevision]
       Specifies the name of the target Blackfin processor.  Currently,
       cpu can be one of bf512, bf514, bf516, bf518, bf522, bf523, bf524,
       bf525, bf526, bf527, bf531, bf532, bf533, bf534, bf536, bf537,
       bf538, bf539, bf542, bf544, bf547, bf548, bf549, bf542m, bf544m,
       bf547m, bf548m, bf549m, bf561, bf592.

       The optional sirevision specifies the silicon revision of the
       target Blackfin processor.  Any workarounds available for the
       targeted silicon revision are enabled.  If sirevision is none, no
       workarounds are enabled.  If sirevision is any, all workarounds for
       the targeted processor are enabled.  The "__SILICON_REVISION__"
       macro is defined to two hexadecimal digits representing the major
       and minor numbers in the silicon revision.  If sirevision is none,
       the "__SILICON_REVISION__" is not defined.  If sirevision is any,
       the "__SILICON_REVISION__" is defined to be 0xffff.  If this
       optional sirevision is not used, GCC assumes the latest known
       silicon revision of the targeted Blackfin processor.

       GCC defines a preprocessor macro for the specified cpu.  For the
       bfin-elf toolchain, this option causes the hardware BSP provided by
       libgloss to be linked in if -msim is not given.

       Without this option, bf532 is used as the processor by default.

       Note that support for bf561 is incomplete.  For bf561, only the
       preprocessor macro is defined.

   -msim
       Specifies that the program will be run on the simulator.  This
       causes the simulator BSP provided by libgloss to be linked in.
       This option has effect only for bfin-elf toolchain.  Certain other
       options, such as -mid-shared-library and -mfdpic, imply -msim.

   -momit-leaf-frame-pointer
       Don't keep the frame pointer in a register for leaf functions.
       This avoids the instructions to save, set up and restore frame
       pointers and makes an extra register available in leaf functions.
       The option -fomit-frame-pointer removes the frame pointer for all
       functions, which might make debugging harder.

   -mspecld-anomaly
       When enabled, the compiler ensures that the generated code does not
       contain speculative loads after jump instructions. If this option
       is used, "__WORKAROUND_SPECULATIVE_LOADS" is defined.

   -mno-specld-anomaly
       Don't generate extra code to prevent speculative loads from
       occurring.

   -mcsync-anomaly
       When enabled, the compiler ensures that the generated code does not
       contain CSYNC or SSYNC instructions too soon after conditional
       branches.  If this option is used, "__WORKAROUND_SPECULATIVE_SYNCS"
       is defined.

   -mno-csync-anomaly
       Don't generate extra code to prevent CSYNC or SSYNC instructions
       from occurring too soon after a conditional branch.

   -mlow-64k
       When enabled, the compiler is free to take advantage of the
       knowledge that the entire program fits into the low 64k of memory.

   -mno-low-64k
       Assume that the program is arbitrarily large.  This is the default.

   -mstack-check-l1
       Do stack checking using information placed into L1 scratchpad
       memory by the uClinux kernel.

   -mid-shared-library
       Generate code that supports shared libraries via the library ID
       method.  This allows for execute in place and shared libraries in
       an environment without virtual memory management.  This option
       implies -fPIC.  With a bfin-elf target, this option implies -msim.

   -mno-id-shared-library
       Generate code that doesn't assume ID-based shared libraries are
       being used.  This is the default.

   -mleaf-id-shared-library
       Generate code that supports shared libraries via the library ID
       method, but assumes that this library or executable won't link
       against any other ID shared libraries.  That allows the compiler to
       use faster code for jumps and calls.

   -mno-leaf-id-shared-library
       Do not assume that the code being compiled won't link against any
       ID shared libraries.  Slower code is generated for jump and call
       insns.

   -mshared-library-id=n
       Specifies the identification number of the ID-based shared library
       being compiled.  Specifying a value of 0 generates more compact
       code; specifying other values forces the allocation of that number
       to the current library but is no more space- or time-efficient than
       omitting this option.

   -msep-data
       Generate code that allows the data segment to be located in a
       different area of memory from the text segment.  This allows for
       execute in place in an environment without virtual memory
       management by eliminating relocations against the text section.

   -mno-sep-data
       Generate code that assumes that the data segment follows the text
       segment.  This is the default.

   -mlong-calls
   -mno-long-calls
       Tells the compiler to perform function calls by first loading the
       address of the function into a register and then performing a
       subroutine call on this register.  This switch is needed if the
       target function lies outside of the 24-bit addressing range of the
       offset-based version of subroutine call instruction.

       This feature is not enabled by default.  Specifying -mno-long-calls
       restores the default behavior.  Note these switches have no effect
       on how the compiler generates code to handle function calls via
       function pointers.

   -mfast-fp
       Link with the fast floating-point library. This library relaxes
       some of the IEEE floating-point standard's rules for checking
       inputs against Not-a-Number (NAN), in the interest of performance.

   -minline-plt
       Enable inlining of PLT entries in function calls to functions that
       are not known to bind locally.  It has no effect without -mfdpic.

   -mmulticore
       Build a standalone application for multicore Blackfin processors.
       This option causes proper start files and link scripts supporting
       multicore to be used, and defines the macro "__BFIN_MULTICORE".  It
       can only be used with -mcpu=bf561[-sirevision].

       This option can be used with -mcorea or -mcoreb, which selects the
       one-application-per-core programming model.  Without -mcorea or
       -mcoreb, the single-application/dual-core programming model is
       used. In this model, the main function of Core B should be named as
       "coreb_main".

       If this option is not used, the single-core application programming
       model is used.

   -mcorea
       Build a standalone application for Core A of BF561 when using the
       one-application-per-core programming model. Proper start files and
       link scripts are used to support Core A, and the macro
       "__BFIN_COREA" is defined.  This option can only be used in
       conjunction with -mmulticore.

   -mcoreb
       Build a standalone application for Core B of BF561 when using the
       one-application-per-core programming model. Proper start files and
       link scripts are used to support Core B, and the macro
       "__BFIN_COREB" is defined. When this option is used, "coreb_main"
       should be used instead of "main".  This option can only be used in
       conjunction with -mmulticore.

   -msdram
       Build a standalone application for SDRAM. Proper start files and
       link scripts are used to put the application into SDRAM, and the
       macro "__BFIN_SDRAM" is defined.  The loader should initialize
       SDRAM before loading the application.

   -micplb
       Assume that ICPLBs are enabled at run time.  This has an effect on
       certain anomaly workarounds.  For Linux targets, the default is to
       assume ICPLBs are enabled; for standalone applications the default
       is off.

   C6X Options

   -march=name
       This specifies the name of the target architecture.  GCC uses this
       name to determine what kind of instructions it can emit when
       generating assembly code.  Permissible names are: c62x, c64x,
       c64x+, c67x, c67x+, c674x.

   -mbig-endian
       Generate code for a big-endian target.

   -mlittle-endian
       Generate code for a little-endian target.  This is the default.

   -msim
       Choose startup files and linker script suitable for the simulator.

   -msdata=default
       Put small global and static data in the ".neardata" section, which
       is pointed to by register "B14".  Put small uninitialized global
       and static data in the ".bss" section, which is adjacent to the
       ".neardata" section.  Put small read-only data into the ".rodata"
       section.  The corresponding sections used for large pieces of data
       are ".fardata", ".far" and ".const".

   -msdata=all
       Put all data, not just small objects, into the sections reserved
       for small data, and use addressing relative to the "B14" register
       to access them.

   -msdata=none
       Make no use of the sections reserved for small data, and use
       absolute addresses to access all data.  Put all initialized global
       and static data in the ".fardata" section, and all uninitialized
       data in the ".far" section.  Put all constant data into the
       ".const" section.

   CRIS Options

   These options are defined specifically for the CRIS ports.

   -march=architecture-type
   -mcpu=architecture-type
       Generate code for the specified architecture.  The choices for
       architecture-type are v3, v8 and v10 for respectively ETRAX 4,
       ETRAX 100, and ETRAX 100 LX.  Default is v0 except for cris-axis-
       linux-gnu, where the default is v10.

   -mtune=architecture-type
       Tune to architecture-type everything applicable about the generated
       code, except for the ABI and the set of available instructions.
       The choices for architecture-type are the same as for
       -march=architecture-type.

   -mmax-stack-frame=n
       Warn when the stack frame of a function exceeds n bytes.

   -metrax4
   -metrax100
       The options -metrax4 and -metrax100 are synonyms for -march=v3 and
       -march=v8 respectively.

   -mmul-bug-workaround
   -mno-mul-bug-workaround
       Work around a bug in the "muls" and "mulu" instructions for CPU
       models where it applies.  This option is active by default.

   -mpdebug
       Enable CRIS-specific verbose debug-related information in the
       assembly code.  This option also has the effect of turning off the
       #NO_APP formatted-code indicator to the assembler at the beginning
       of the assembly file.

   -mcc-init
       Do not use condition-code results from previous instruction; always
       emit compare and test instructions before use of condition codes.

   -mno-side-effects
       Do not emit instructions with side effects in addressing modes
       other than post-increment.

   -mstack-align
   -mno-stack-align
   -mdata-align
   -mno-data-align
   -mconst-align
   -mno-const-align
       These options (no- options) arrange (eliminate arrangements) for
       the stack frame, individual data and constants to be aligned for
       the maximum single data access size for the chosen CPU model.  The
       default is to arrange for 32-bit alignment.  ABI details such as
       structure layout are not affected by these options.

   -m32-bit
   -m16-bit
   -m8-bit
       Similar to the stack- data- and const-align options above, these
       options arrange for stack frame, writable data and constants to all
       be 32-bit, 16-bit or 8-bit aligned.  The default is 32-bit
       alignment.

   -mno-prologue-epilogue
   -mprologue-epilogue
       With -mno-prologue-epilogue, the normal function prologue and
       epilogue which set up the stack frame are omitted and no return
       instructions or return sequences are generated in the code.  Use
       this option only together with visual inspection of the compiled
       code: no warnings or errors are generated when call-saved registers
       must be saved, or storage for local variables needs to be
       allocated.

   -mno-gotplt
   -mgotplt
       With -fpic and -fPIC, don't generate (do generate) instruction
       sequences that load addresses for functions from the PLT part of
       the GOT rather than (traditional on other architectures) calls to
       the PLT.  The default is -mgotplt.

   -melf
       Legacy no-op option only recognized with the cris-axis-elf and
       cris-axis-linux-gnu targets.

   -mlinux
       Legacy no-op option only recognized with the cris-axis-linux-gnu
       target.

   -sim
       This option, recognized for the cris-axis-elf, arranges to link
       with input-output functions from a simulator library.  Code,
       initialized data and zero-initialized data are allocated
       consecutively.

   -sim2
       Like -sim, but pass linker options to locate initialized data at
       0x40000000 and zero-initialized data at 0x80000000.

   CR16 Options

   These options are defined specifically for the CR16 ports.

   -mmac
       Enable the use of multiply-accumulate instructions. Disabled by
       default.

   -mcr16cplus
   -mcr16c
       Generate code for CR16C or CR16C+ architecture. CR16C+ architecture
       is default.

   -msim
       Links the library libsim.a which is in compatible with simulator.
       Applicable to ELF compiler only.

   -mint32
       Choose integer type as 32-bit wide.

   -mbit-ops
       Generates "sbit"/"cbit" instructions for bit manipulations.

   -mdata-model=model
       Choose a data model. The choices for model are near, far or medium.
       medium is default.  However, far is not valid with -mcr16c, as the
       CR16C architecture does not support the far data model.

   Darwin Options

   These options are defined for all architectures running the Darwin
   operating system.

   FSF GCC on Darwin does not create "fat" object files; it creates an
   object file for the single architecture that GCC was built to target.
   Apple's GCC on Darwin does create "fat" files if multiple -arch options
   are used; it does so by running the compiler or linker multiple times
   and joining the results together with lipo.

   The subtype of the file created (like ppc7400 or ppc970 or i686) is
   determined by the flags that specify the ISA that GCC is targeting,
   like -mcpu or -march.  The -force_cpusubtype_ALL option can be used to
   override this.

   The Darwin tools vary in their behavior when presented with an ISA
   mismatch.  The assembler, as, only permits instructions to be used that
   are valid for the subtype of the file it is generating, so you cannot
   put 64-bit instructions in a ppc750 object file.  The linker for shared
   libraries, /usr/bin/libtool, fails and prints an error if asked to
   create a shared library with a less restrictive subtype than its input
   files (for instance, trying to put a ppc970 object file in a ppc7400
   library).  The linker for executables, ld, quietly gives the executable
   the most restrictive subtype of any of its input files.

   -Fdir
       Add the framework directory dir to the head of the list of
       directories to be searched for header files.  These directories are
       interleaved with those specified by -I options and are scanned in a
       left-to-right order.

       A framework directory is a directory with frameworks in it.  A
       framework is a directory with a Headers and/or PrivateHeaders
       directory contained directly in it that ends in .framework.  The
       name of a framework is the name of this directory excluding the
       .framework.  Headers associated with the framework are found in one
       of those two directories, with Headers being searched first.  A
       subframework is a framework directory that is in a framework's
       Frameworks directory.  Includes of subframework headers can only
       appear in a header of a framework that contains the subframework,
       or in a sibling subframework header.  Two subframeworks are
       siblings if they occur in the same framework.  A subframework
       should not have the same name as a framework; a warning is issued
       if this is violated.  Currently a subframework cannot have
       subframeworks; in the future, the mechanism may be extended to
       support this.  The standard frameworks can be found in
       /System/Library/Frameworks and /Library/Frameworks.  An example
       include looks like "#include <Framework/header.h>", where Framework
       denotes the name of the framework and header.h is found in the
       PrivateHeaders or Headers directory.

   -iframeworkdir
       Like -F except the directory is a treated as a system directory.
       The main difference between this -iframework and -F is that with
       -iframework the compiler does not warn about constructs contained
       within header files found via dir.  This option is valid only for
       the C family of languages.

   -gused
       Emit debugging information for symbols that are used.  For stabs
       debugging format, this enables -feliminate-unused-debug-symbols.
       This is by default ON.

   -gfull
       Emit debugging information for all symbols and types.

   -mmacosx-version-min=version
       The earliest version of MacOS X that this executable will run on is
       version.  Typical values of version include 10.1, 10.2, and 10.3.9.

       If the compiler was built to use the system's headers by default,
       then the default for this option is the system version on which the
       compiler is running, otherwise the default is to make choices that
       are compatible with as many systems and code bases as possible.

   -mkernel
       Enable kernel development mode.  The -mkernel option sets -static,
       -fno-common, -fno-use-cxa-atexit, -fno-exceptions,
       -fno-non-call-exceptions, -fapple-kext, -fno-weak and -fno-rtti
       where applicable.  This mode also sets -mno-altivec, -msoft-float,
       -fno-builtin and -mlong-branch for PowerPC targets.

   -mone-byte-bool
       Override the defaults for "bool" so that "sizeof(bool)==1".  By
       default "sizeof(bool)" is 4 when compiling for Darwin/PowerPC and 1
       when compiling for Darwin/x86, so this option has no effect on x86.

       Warning: The -mone-byte-bool switch causes GCC to generate code
       that is not binary compatible with code generated without that
       switch.  Using this switch may require recompiling all other
       modules in a program, including system libraries.  Use this switch
       to conform to a non-default data model.

   -mfix-and-continue
   -ffix-and-continue
   -findirect-data
       Generate code suitable for fast turnaround development, such as to
       allow GDB to dynamically load .o files into already-running
       programs.  -findirect-data and -ffix-and-continue are provided for
       backwards compatibility.

   -all_load
       Loads all members of static archive libraries.  See man ld(1) for
       more information.

   -arch_errors_fatal
       Cause the errors having to do with files that have the wrong
       architecture to be fatal.

   -bind_at_load
       Causes the output file to be marked such that the dynamic linker
       will bind all undefined references when the file is loaded or
       launched.

   -bundle
       Produce a Mach-o bundle format file.  See man ld(1) for more
       information.

   -bundle_loader executable
       This option specifies the executable that will load the build
       output file being linked.  See man ld(1) for more information.

   -dynamiclib
       When passed this option, GCC produces a dynamic library instead of
       an executable when linking, using the Darwin libtool command.

   -force_cpusubtype_ALL
       This causes GCC's output file to have the ALL subtype, instead of
       one controlled by the -mcpu or -march option.

   -allowable_client  client_name
   -client_name
   -compatibility_version
   -current_version
   -dead_strip
   -dependency-file
   -dylib_file
   -dylinker_install_name
   -dynamic
   -exported_symbols_list
   -filelist
   -flat_namespace
   -force_flat_namespace
   -headerpad_max_install_names
   -image_base
   -init
   -install_name
   -keep_private_externs
   -multi_module
   -multiply_defined
   -multiply_defined_unused
   -noall_load
   -no_dead_strip_inits_and_terms
   -nofixprebinding
   -nomultidefs
   -noprebind
   -noseglinkedit
   -pagezero_size
   -prebind
   -prebind_all_twolevel_modules
   -private_bundle
   -read_only_relocs
   -sectalign
   -sectobjectsymbols
   -whyload
   -seg1addr
   -sectcreate
   -sectobjectsymbols
   -sectorder
   -segaddr
   -segs_read_only_addr
   -segs_read_write_addr
   -seg_addr_table
   -seg_addr_table_filename
   -seglinkedit
   -segprot
   -segs_read_only_addr
   -segs_read_write_addr
   -single_module
   -static
   -sub_library
   -sub_umbrella
   -twolevel_namespace
   -umbrella
   -undefined
   -unexported_symbols_list
   -weak_reference_mismatches
   -whatsloaded
       These options are passed to the Darwin linker.  The Darwin linker
       man page describes them in detail.

   DEC Alpha Options

   These -m options are defined for the DEC Alpha implementations:

   -mno-soft-float
   -msoft-float
       Use (do not use) the hardware floating-point instructions for
       floating-point operations.  When -msoft-float is specified,
       functions in libgcc.a are used to perform floating-point
       operations.  Unless they are replaced by routines that emulate the
       floating-point operations, or compiled in such a way as to call
       such emulations routines, these routines issue floating-point
       operations.   If you are compiling for an Alpha without floating-
       point operations, you must ensure that the library is built so as
       not to call them.

       Note that Alpha implementations without floating-point operations
       are required to have floating-point registers.

   -mfp-reg
   -mno-fp-regs
       Generate code that uses (does not use) the floating-point register
       set.  -mno-fp-regs implies -msoft-float.  If the floating-point
       register set is not used, floating-point operands are passed in
       integer registers as if they were integers and floating-point
       results are passed in $0 instead of $f0.  This is a non-standard
       calling sequence, so any function with a floating-point argument or
       return value called by code compiled with -mno-fp-regs must also be
       compiled with that option.

       A typical use of this option is building a kernel that does not
       use, and hence need not save and restore, any floating-point
       registers.

   -mieee
       The Alpha architecture implements floating-point hardware optimized
       for maximum performance.  It is mostly compliant with the IEEE
       floating-point standard.  However, for full compliance, software
       assistance is required.  This option generates code fully IEEE-
       compliant code except that the inexact-flag is not maintained (see
       below).  If this option is turned on, the preprocessor macro
       "_IEEE_FP" is defined during compilation.  The resulting code is
       less efficient but is able to correctly support denormalized
       numbers and exceptional IEEE values such as not-a-number and
       plus/minus infinity.  Other Alpha compilers call this option
       -ieee_with_no_inexact.

   -mieee-with-inexact
       This is like -mieee except the generated code also maintains the
       IEEE inexact-flag.  Turning on this option causes the generated
       code to implement fully-compliant IEEE math.  In addition to
       "_IEEE_FP", "_IEEE_FP_EXACT" is defined as a preprocessor macro.
       On some Alpha implementations the resulting code may execute
       significantly slower than the code generated by default.  Since
       there is very little code that depends on the inexact-flag, you
       should normally not specify this option.  Other Alpha compilers
       call this option -ieee_with_inexact.

   -mfp-trap-mode=trap-mode
       This option controls what floating-point related traps are enabled.
       Other Alpha compilers call this option -fptm trap-mode.  The trap
       mode can be set to one of four values:

       n   This is the default (normal) setting.  The only traps that are
           enabled are the ones that cannot be disabled in software (e.g.,
           division by zero trap).

       u   In addition to the traps enabled by n, underflow traps are
           enabled as well.

       su  Like u, but the instructions are marked to be safe for software
           completion (see Alpha architecture manual for details).

       sui Like su, but inexact traps are enabled as well.

   -mfp-rounding-mode=rounding-mode
       Selects the IEEE rounding mode.  Other Alpha compilers call this
       option -fprm rounding-mode.  The rounding-mode can be one of:

       n   Normal IEEE rounding mode.  Floating-point numbers are rounded
           towards the nearest machine number or towards the even machine
           number in case of a tie.

       m   Round towards minus infinity.

       c   Chopped rounding mode.  Floating-point numbers are rounded
           towards zero.

       d   Dynamic rounding mode.  A field in the floating-point control
           register (fpcr, see Alpha architecture reference manual)
           controls the rounding mode in effect.  The C library
           initializes this register for rounding towards plus infinity.
           Thus, unless your program modifies the fpcr, d corresponds to
           round towards plus infinity.

   -mtrap-precision=trap-precision
       In the Alpha architecture, floating-point traps are imprecise.
       This means without software assistance it is impossible to recover
       from a floating trap and program execution normally needs to be
       terminated.  GCC can generate code that can assist operating system
       trap handlers in determining the exact location that caused a
       floating-point trap.  Depending on the requirements of an
       application, different levels of precisions can be selected:

       p   Program precision.  This option is the default and means a trap
           handler can only identify which program caused a floating-point
           exception.

       f   Function precision.  The trap handler can determine the
           function that caused a floating-point exception.

       i   Instruction precision.  The trap handler can determine the
           exact instruction that caused a floating-point exception.

       Other Alpha compilers provide the equivalent options called
       -scope_safe and -resumption_safe.

   -mieee-conformant
       This option marks the generated code as IEEE conformant.  You must
       not use this option unless you also specify -mtrap-precision=i and
       either -mfp-trap-mode=su or -mfp-trap-mode=sui.  Its only effect is
       to emit the line .eflag 48 in the function prologue of the
       generated assembly file.

   -mbuild-constants
       Normally GCC examines a 32- or 64-bit integer constant to see if it
       can construct it from smaller constants in two or three
       instructions.  If it cannot, it outputs the constant as a literal
       and generates code to load it from the data segment at run time.

       Use this option to require GCC to construct all integer constants
       using code, even if it takes more instructions (the maximum is
       six).

       You typically use this option to build a shared library dynamic
       loader.  Itself a shared library, it must relocate itself in memory
       before it can find the variables and constants in its own data
       segment.

   -mbwx
   -mno-bwx
   -mcix
   -mno-cix
   -mfix
   -mno-fix
   -mmax
   -mno-max
       Indicate whether GCC should generate code to use the optional BWX,
       CIX, FIX and MAX instruction sets.  The default is to use the
       instruction sets supported by the CPU type specified via -mcpu=
       option or that of the CPU on which GCC was built if none is
       specified.

   -mfloat-vax
   -mfloat-ieee
       Generate code that uses (does not use) VAX F and G floating-point
       arithmetic instead of IEEE single and double precision.

   -mexplicit-relocs
   -mno-explicit-relocs
       Older Alpha assemblers provided no way to generate symbol
       relocations except via assembler macros.  Use of these macros does
       not allow optimal instruction scheduling.  GNU binutils as of
       version 2.12 supports a new syntax that allows the compiler to
       explicitly mark which relocations should apply to which
       instructions.  This option is mostly useful for debugging, as GCC
       detects the capabilities of the assembler when it is built and sets
       the default accordingly.

   -msmall-data
   -mlarge-data
       When -mexplicit-relocs is in effect, static data is accessed via
       gp-relative relocations.  When -msmall-data is used, objects 8
       bytes long or smaller are placed in a small data area (the ".sdata"
       and ".sbss" sections) and are accessed via 16-bit relocations off
       of the $gp register.  This limits the size of the small data area
       to 64KB, but allows the variables to be directly accessed via a
       single instruction.

       The default is -mlarge-data.  With this option the data area is
       limited to just below 2GB.  Programs that require more than 2GB of
       data must use "malloc" or "mmap" to allocate the data in the heap
       instead of in the program's data segment.

       When generating code for shared libraries, -fpic implies
       -msmall-data and -fPIC implies -mlarge-data.

   -msmall-text
   -mlarge-text
       When -msmall-text is used, the compiler assumes that the code of
       the entire program (or shared library) fits in 4MB, and is thus
       reachable with a branch instruction.  When -msmall-data is used,
       the compiler can assume that all local symbols share the same $gp
       value, and thus reduce the number of instructions required for a
       function call from 4 to 1.

       The default is -mlarge-text.

   -mcpu=cpu_type
       Set the instruction set and instruction scheduling parameters for
       machine type cpu_type.  You can specify either the EV style name or
       the corresponding chip number.  GCC supports scheduling parameters
       for the EV4, EV5 and EV6 family of processors and chooses the
       default values for the instruction set from the processor you
       specify.  If you do not specify a processor type, GCC defaults to
       the processor on which the compiler was built.

       Supported values for cpu_type are

       ev4
       ev45
       21064
           Schedules as an EV4 and has no instruction set extensions.

       ev5
       21164
           Schedules as an EV5 and has no instruction set extensions.

       ev56
       21164a
           Schedules as an EV5 and supports the BWX extension.

       pca56
       21164pc
       21164PC
           Schedules as an EV5 and supports the BWX and MAX extensions.

       ev6
       21264
           Schedules as an EV6 and supports the BWX, FIX, and MAX
           extensions.

       ev67
       21264a
           Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX
           extensions.

       Native toolchains also support the value native, which selects the
       best architecture option for the host processor.  -mcpu=native has
       no effect if GCC does not recognize the processor.

   -mtune=cpu_type
       Set only the instruction scheduling parameters for machine type
       cpu_type.  The instruction set is not changed.

       Native toolchains also support the value native, which selects the
       best architecture option for the host processor.  -mtune=native has
       no effect if GCC does not recognize the processor.

   -mmemory-latency=time
       Sets the latency the scheduler should assume for typical memory
       references as seen by the application.  This number is highly
       dependent on the memory access patterns used by the application and
       the size of the external cache on the machine.

       Valid options for time are

       number
           A decimal number representing clock cycles.

       L1
       L2
       L3
       main
           The compiler contains estimates of the number of clock cycles
           for "typical" EV4 & EV5 hardware for the Level 1, 2 & 3 caches
           (also called Dcache, Scache, and Bcache), as well as to main
           memory.  Note that L3 is only valid for EV5.

   FR30 Options

   These options are defined specifically for the FR30 port.

   -msmall-model
       Use the small address space model.  This can produce smaller code,
       but it does assume that all symbolic values and addresses fit into
       a 20-bit range.

   -mno-lsim
       Assume that runtime support has been provided and so there is no
       need to include the simulator library (libsim.a) on the linker
       command line.

   FT32 Options

   These options are defined specifically for the FT32 port.

   -msim
       Specifies that the program will be run on the simulator.  This
       causes an alternate runtime startup and library to be linked.  You
       must not use this option when generating programs that will run on
       real hardware; you must provide your own runtime library for
       whatever I/O functions are needed.

   -mlra
       Enable Local Register Allocation.  This is still experimental for
       FT32, so by default the compiler uses standard reload.

   -mnodiv
       Do not use div and mod instructions.

   FRV Options

   -mgpr-32
       Only use the first 32 general-purpose registers.

   -mgpr-64
       Use all 64 general-purpose registers.

   -mfpr-32
       Use only the first 32 floating-point registers.

   -mfpr-64
       Use all 64 floating-point registers.

   -mhard-float
       Use hardware instructions for floating-point operations.

   -msoft-float
       Use library routines for floating-point operations.

   -malloc-cc
       Dynamically allocate condition code registers.

   -mfixed-cc
       Do not try to dynamically allocate condition code registers, only
       use "icc0" and "fcc0".

   -mdword
       Change ABI to use double word insns.

   -mno-dword
       Do not use double word instructions.

   -mdouble
       Use floating-point double instructions.

   -mno-double
       Do not use floating-point double instructions.

   -mmedia
       Use media instructions.

   -mno-media
       Do not use media instructions.

   -mmuladd
       Use multiply and add/subtract instructions.

   -mno-muladd
       Do not use multiply and add/subtract instructions.

   -mfdpic
       Select the FDPIC ABI, which uses function descriptors to represent
       pointers to functions.  Without any PIC/PIE-related options, it
       implies -fPIE.  With -fpic or -fpie, it assumes GOT entries and
       small data are within a 12-bit range from the GOT base address;
       with -fPIC or -fPIE, GOT offsets are computed with 32 bits.  With a
       bfin-elf target, this option implies -msim.

   -minline-plt
       Enable inlining of PLT entries in function calls to functions that
       are not known to bind locally.  It has no effect without -mfdpic.
       It's enabled by default if optimizing for speed and compiling for
       shared libraries (i.e., -fPIC or -fpic), or when an optimization
       option such as -O3 or above is present in the command line.

   -mTLS
       Assume a large TLS segment when generating thread-local code.

   -mtls
       Do not assume a large TLS segment when generating thread-local
       code.

   -mgprel-ro
       Enable the use of "GPREL" relocations in the FDPIC ABI for data
       that is known to be in read-only sections.  It's enabled by
       default, except for -fpic or -fpie: even though it may help make
       the global offset table smaller, it trades 1 instruction for 4.
       With -fPIC or -fPIE, it trades 3 instructions for 4, one of which
       may be shared by multiple symbols, and it avoids the need for a GOT
       entry for the referenced symbol, so it's more likely to be a win.
       If it is not, -mno-gprel-ro can be used to disable it.

   -multilib-library-pic
       Link with the (library, not FD) pic libraries.  It's implied by
       -mlibrary-pic, as well as by -fPIC and -fpic without -mfdpic.  You
       should never have to use it explicitly.

   -mlinked-fp
       Follow the EABI requirement of always creating a frame pointer
       whenever a stack frame is allocated.  This option is enabled by
       default and can be disabled with -mno-linked-fp.

   -mlong-calls
       Use indirect addressing to call functions outside the current
       compilation unit.  This allows the functions to be placed anywhere
       within the 32-bit address space.

   -malign-labels
       Try to align labels to an 8-byte boundary by inserting NOPs into
       the previous packet.  This option only has an effect when VLIW
       packing is enabled.  It doesn't create new packets; it merely adds
       NOPs to existing ones.

   -mlibrary-pic
       Generate position-independent EABI code.

   -macc-4
       Use only the first four media accumulator registers.

   -macc-8
       Use all eight media accumulator registers.

   -mpack
       Pack VLIW instructions.

   -mno-pack
       Do not pack VLIW instructions.

   -mno-eflags
       Do not mark ABI switches in e_flags.

   -mcond-move
       Enable the use of conditional-move instructions (default).

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mno-cond-move
       Disable the use of conditional-move instructions.

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mscc
       Enable the use of conditional set instructions (default).

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mno-scc
       Disable the use of conditional set instructions.

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mcond-exec
       Enable the use of conditional execution (default).

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mno-cond-exec
       Disable the use of conditional execution.

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mvliw-branch
       Run a pass to pack branches into VLIW instructions (default).

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mno-vliw-branch
       Do not run a pass to pack branches into VLIW instructions.

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mmulti-cond-exec
       Enable optimization of "&&" and "||" in conditional execution
       (default).

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mno-multi-cond-exec
       Disable optimization of "&&" and "||" in conditional execution.

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mnested-cond-exec
       Enable nested conditional execution optimizations (default).

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -mno-nested-cond-exec
       Disable nested conditional execution optimizations.

       This switch is mainly for debugging the compiler and will likely be
       removed in a future version.

   -moptimize-membar
       This switch removes redundant "membar" instructions from the
       compiler-generated code.  It is enabled by default.

   -mno-optimize-membar
       This switch disables the automatic removal of redundant "membar"
       instructions from the generated code.

   -mtomcat-stats
       Cause gas to print out tomcat statistics.

   -mcpu=cpu
       Select the processor type for which to generate code.  Possible
       values are frv, fr550, tomcat, fr500, fr450, fr405, fr400, fr300
       and simple.

   GNU/Linux Options

   These -m options are defined for GNU/Linux targets:

   -mglibc
       Use the GNU C library.  This is the default except on
       *-*-linux-*uclibc*, *-*-linux-*musl* and *-*-linux-*android*
       targets.

   -muclibc
       Use uClibc C library.  This is the default on *-*-linux-*uclibc*
       targets.

   -mmusl
       Use the musl C library.  This is the default on *-*-linux-*musl*
       targets.

   -mbionic
       Use Bionic C library.  This is the default on *-*-linux-*android*
       targets.

   -mandroid
       Compile code compatible with Android platform.  This is the default
       on *-*-linux-*android* targets.

       When compiling, this option enables -mbionic, -fPIC,
       -fno-exceptions and -fno-rtti by default.  When linking, this
       option makes the GCC driver pass Android-specific options to the
       linker.  Finally, this option causes the preprocessor macro
       "__ANDROID__" to be defined.

   -tno-android-cc
       Disable compilation effects of -mandroid, i.e., do not enable
       -mbionic, -fPIC, -fno-exceptions and -fno-rtti by default.

   -tno-android-ld
       Disable linking effects of -mandroid, i.e., pass standard Linux
       linking options to the linker.

   H8/300 Options

   These -m options are defined for the H8/300 implementations:

   -mrelax
       Shorten some address references at link time, when possible; uses
       the linker option -relax.

   -mh Generate code for the H8/300H.

   -ms Generate code for the H8S.

   -mn Generate code for the H8S and H8/300H in the normal mode.  This
       switch must be used either with -mh or -ms.

   -ms2600
       Generate code for the H8S/2600.  This switch must be used with -ms.

   -mexr
       Extended registers are stored on stack before execution of function
       with monitor attribute. Default option is -mexr.  This option is
       valid only for H8S targets.

   -mno-exr
       Extended registers are not stored on stack before execution of
       function with monitor attribute. Default option is -mno-exr.  This
       option is valid only for H8S targets.

   -mint32
       Make "int" data 32 bits by default.

   -malign-300
       On the H8/300H and H8S, use the same alignment rules as for the
       H8/300.  The default for the H8/300H and H8S is to align longs and
       floats on 4-byte boundaries.  -malign-300 causes them to be aligned
       on 2-byte boundaries.  This option has no effect on the H8/300.

   HPPA Options

   These -m options are defined for the HPPA family of computers:

   -march=architecture-type
       Generate code for the specified architecture.  The choices for
       architecture-type are 1.0 for PA 1.0, 1.1 for PA 1.1, and 2.0 for
       PA 2.0 processors.  Refer to /usr/lib/sched.models on an HP-UX
       system to determine the proper architecture option for your
       machine.  Code compiled for lower numbered architectures runs on
       higher numbered architectures, but not the other way around.

   -mpa-risc-1-0
   -mpa-risc-1-1
   -mpa-risc-2-0
       Synonyms for -march=1.0, -march=1.1, and -march=2.0 respectively.

   -mjump-in-delay
       This option is ignored and provided for compatibility purposes
       only.

   -mdisable-fpregs
       Prevent floating-point registers from being used in any manner.
       This is necessary for compiling kernels that perform lazy context
       switching of floating-point registers.  If you use this option and
       attempt to perform floating-point operations, the compiler aborts.

   -mdisable-indexing
       Prevent the compiler from using indexing address modes.  This
       avoids some rather obscure problems when compiling MIG generated
       code under MACH.

   -mno-space-regs
       Generate code that assumes the target has no space registers.  This
       allows GCC to generate faster indirect calls and use unscaled index
       address modes.

       Such code is suitable for level 0 PA systems and kernels.

   -mfast-indirect-calls
       Generate code that assumes calls never cross space boundaries.
       This allows GCC to emit code that performs faster indirect calls.

       This option does not work in the presence of shared libraries or
       nested functions.

   -mfixed-range=register-range
       Generate code treating the given register range as fixed registers.
       A fixed register is one that the register allocator cannot use.
       This is useful when compiling kernel code.  A register range is
       specified as two registers separated by a dash.  Multiple register
       ranges can be specified separated by a comma.

   -mlong-load-store
       Generate 3-instruction load and store sequences as sometimes
       required by the HP-UX 10 linker.  This is equivalent to the +k
       option to the HP compilers.

   -mportable-runtime
       Use the portable calling conventions proposed by HP for ELF
       systems.

   -mgas
       Enable the use of assembler directives only GAS understands.

   -mschedule=cpu-type
       Schedule code according to the constraints for the machine type
       cpu-type.  The choices for cpu-type are 700 7100, 7100LC, 7200,
       7300 and 8000.  Refer to /usr/lib/sched.models on an HP-UX system
       to determine the proper scheduling option for your machine.  The
       default scheduling is 8000.

   -mlinker-opt
       Enable the optimization pass in the HP-UX linker.  Note this makes
       symbolic debugging impossible.  It also triggers a bug in the HP-UX
       8 and HP-UX 9 linkers in which they give bogus error messages when
       linking some programs.

   -msoft-float
       Generate output containing library calls for floating point.
       Warning: the requisite libraries are not available for all HPPA
       targets.  Normally the facilities of the machine's usual C compiler
       are used, but this cannot be done directly in cross-compilation.
       You must make your own arrangements to provide suitable library
       functions for cross-compilation.

       -msoft-float changes the calling convention in the output file;
       therefore, it is only useful if you compile all of a program with
       this option.  In particular, you need to compile libgcc.a, the
       library that comes with GCC, with -msoft-float in order for this to
       work.

   -msio
       Generate the predefine, "_SIO", for server IO.  The default is
       -mwsio.  This generates the predefines, "__hp9000s700",
       "__hp9000s700__" and "_WSIO", for workstation IO.  These options
       are available under HP-UX and HI-UX.

   -mgnu-ld
       Use options specific to GNU ld.  This passes -shared to ld when
       building a shared library.  It is the default when GCC is
       configured, explicitly or implicitly, with the GNU linker.  This
       option does not affect which ld is called; it only changes what
       parameters are passed to that ld.  The ld that is called is
       determined by the --with-ld configure option, GCC's program search
       path, and finally by the user's PATH.  The linker used by GCC can
       be printed using which `gcc -print-prog-name=ld`.  This option is
       only available on the 64-bit HP-UX GCC, i.e. configured with
       hppa*64*-*-hpux*.

   -mhp-ld
       Use options specific to HP ld.  This passes -b to ld when building
       a shared library and passes +Accept TypeMismatch to ld on all
       links.  It is the default when GCC is configured, explicitly or
       implicitly, with the HP linker.  This option does not affect which
       ld is called; it only changes what parameters are passed to that
       ld.  The ld that is called is determined by the --with-ld configure
       option, GCC's program search path, and finally by the user's PATH.
       The linker used by GCC can be printed using which `gcc
       -print-prog-name=ld`.  This option is only available on the 64-bit
       HP-UX GCC, i.e. configured with hppa*64*-*-hpux*.

   -mlong-calls
       Generate code that uses long call sequences.  This ensures that a
       call is always able to reach linker generated stubs.  The default
       is to generate long calls only when the distance from the call site
       to the beginning of the function or translation unit, as the case
       may be, exceeds a predefined limit set by the branch type being
       used.  The limits for normal calls are 7,600,000 and 240,000 bytes,
       respectively for the PA 2.0 and PA 1.X architectures.  Sibcalls are
       always limited at 240,000 bytes.

       Distances are measured from the beginning of functions when using
       the -ffunction-sections option, or when using the -mgas and
       -mno-portable-runtime options together under HP-UX with the SOM
       linker.

       It is normally not desirable to use this option as it degrades
       performance.  However, it may be useful in large applications,
       particularly when partial linking is used to build the application.

       The types of long calls used depends on the capabilities of the
       assembler and linker, and the type of code being generated.  The
       impact on systems that support long absolute calls, and long pic
       symbol-difference or pc-relative calls should be relatively small.
       However, an indirect call is used on 32-bit ELF systems in pic code
       and it is quite long.

   -munix=unix-std
       Generate compiler predefines and select a startfile for the
       specified UNIX standard.  The choices for unix-std are 93, 95 and
       98.  93 is supported on all HP-UX versions.  95 is available on HP-
       UX 10.10 and later.  98 is available on HP-UX 11.11 and later.  The
       default values are 93 for HP-UX 10.00, 95 for HP-UX 10.10 though to
       11.00, and 98 for HP-UX 11.11 and later.

       -munix=93 provides the same predefines as GCC 3.3 and 3.4.
       -munix=95 provides additional predefines for "XOPEN_UNIX" and
       "_XOPEN_SOURCE_EXTENDED", and the startfile unix95.o.  -munix=98
       provides additional predefines for "_XOPEN_UNIX",
       "_XOPEN_SOURCE_EXTENDED", "_INCLUDE__STDC_A1_SOURCE" and
       "_INCLUDE_XOPEN_SOURCE_500", and the startfile unix98.o.

       It is important to note that this option changes the interfaces for
       various library routines.  It also affects the operational behavior
       of the C library.  Thus, extreme care is needed in using this
       option.

       Library code that is intended to operate with more than one UNIX
       standard must test, set and restore the variable
       "__xpg4_extended_mask" as appropriate.  Most GNU software doesn't
       provide this capability.

   -nolibdld
       Suppress the generation of link options to search libdld.sl when
       the -static option is specified on HP-UX 10 and later.

   -static
       The HP-UX implementation of setlocale in libc has a dependency on
       libdld.sl.  There isn't an archive version of libdld.sl.  Thus,
       when the -static option is specified, special link options are
       needed to resolve this dependency.

       On HP-UX 10 and later, the GCC driver adds the necessary options to
       link with libdld.sl when the -static option is specified.  This
       causes the resulting binary to be dynamic.  On the 64-bit port, the
       linkers generate dynamic binaries by default in any case.  The
       -nolibdld option can be used to prevent the GCC driver from adding
       these link options.

   -threads
       Add support for multithreading with the dce thread library under
       HP-UX.  This option sets flags for both the preprocessor and
       linker.

   IA-64 Options

   These are the -m options defined for the Intel IA-64 architecture.

   -mbig-endian
       Generate code for a big-endian target.  This is the default for HP-
       UX.

   -mlittle-endian
       Generate code for a little-endian target.  This is the default for
       AIX5 and GNU/Linux.

   -mgnu-as
   -mno-gnu-as
       Generate (or don't) code for the GNU assembler.  This is the
       default.

   -mgnu-ld
   -mno-gnu-ld
       Generate (or don't) code for the GNU linker.  This is the default.

   -mno-pic
       Generate code that does not use a global pointer register.  The
       result is not position independent code, and violates the IA-64
       ABI.

   -mvolatile-asm-stop
   -mno-volatile-asm-stop
       Generate (or don't) a stop bit immediately before and after
       volatile asm statements.

   -mregister-names
   -mno-register-names
       Generate (or don't) in, loc, and out register names for the stacked
       registers.  This may make assembler output more readable.

   -mno-sdata
   -msdata
       Disable (or enable) optimizations that use the small data section.
       This may be useful for working around optimizer bugs.

   -mconstant-gp
       Generate code that uses a single constant global pointer value.
       This is useful when compiling kernel code.

   -mauto-pic
       Generate code that is self-relocatable.  This implies
       -mconstant-gp.  This is useful when compiling firmware code.

   -minline-float-divide-min-latency
       Generate code for inline divides of floating-point values using the
       minimum latency algorithm.

   -minline-float-divide-max-throughput
       Generate code for inline divides of floating-point values using the
       maximum throughput algorithm.

   -mno-inline-float-divide
       Do not generate inline code for divides of floating-point values.

   -minline-int-divide-min-latency
       Generate code for inline divides of integer values using the
       minimum latency algorithm.

   -minline-int-divide-max-throughput
       Generate code for inline divides of integer values using the
       maximum throughput algorithm.

   -mno-inline-int-divide
       Do not generate inline code for divides of integer values.

   -minline-sqrt-min-latency
       Generate code for inline square roots using the minimum latency
       algorithm.

   -minline-sqrt-max-throughput
       Generate code for inline square roots using the maximum throughput
       algorithm.

   -mno-inline-sqrt
       Do not generate inline code for "sqrt".

   -mfused-madd
   -mno-fused-madd
       Do (don't) generate code that uses the fused multiply/add or
       multiply/subtract instructions.  The default is to use these
       instructions.

   -mno-dwarf2-asm
   -mdwarf2-asm
       Don't (or do) generate assembler code for the DWARF line number
       debugging info.  This may be useful when not using the GNU
       assembler.

   -mearly-stop-bits
   -mno-early-stop-bits
       Allow stop bits to be placed earlier than immediately preceding the
       instruction that triggered the stop bit.  This can improve
       instruction scheduling, but does not always do so.

   -mfixed-range=register-range
       Generate code treating the given register range as fixed registers.
       A fixed register is one that the register allocator cannot use.
       This is useful when compiling kernel code.  A register range is
       specified as two registers separated by a dash.  Multiple register
       ranges can be specified separated by a comma.

   -mtls-size=tls-size
       Specify bit size of immediate TLS offsets.  Valid values are 14,
       22, and 64.

   -mtune=cpu-type
       Tune the instruction scheduling for a particular CPU, Valid values
       are itanium, itanium1, merced, itanium2, and mckinley.

   -milp32
   -mlp64
       Generate code for a 32-bit or 64-bit environment.  The 32-bit
       environment sets int, long and pointer to 32 bits.  The 64-bit
       environment sets int to 32 bits and long and pointer to 64 bits.
       These are HP-UX specific flags.

   -mno-sched-br-data-spec
   -msched-br-data-spec
       (Dis/En)able data speculative scheduling before reload.  This
       results in generation of "ld.a" instructions and the corresponding
       check instructions ("ld.c" / "chk.a").  The default setting is
       disabled.

   -msched-ar-data-spec
   -mno-sched-ar-data-spec
       (En/Dis)able data speculative scheduling after reload.  This
       results in generation of "ld.a" instructions and the corresponding
       check instructions ("ld.c" / "chk.a").  The default setting is
       enabled.

   -mno-sched-control-spec
   -msched-control-spec
       (Dis/En)able control speculative scheduling.  This feature is
       available only during region scheduling (i.e. before reload).  This
       results in generation of the "ld.s" instructions and the
       corresponding check instructions "chk.s".  The default setting is
       disabled.

   -msched-br-in-data-spec
   -mno-sched-br-in-data-spec
       (En/Dis)able speculative scheduling of the instructions that are
       dependent on the data speculative loads before reload.  This is
       effective only with -msched-br-data-spec enabled.  The default
       setting is enabled.

   -msched-ar-in-data-spec
   -mno-sched-ar-in-data-spec
       (En/Dis)able speculative scheduling of the instructions that are
       dependent on the data speculative loads after reload.  This is
       effective only with -msched-ar-data-spec enabled.  The default
       setting is enabled.

   -msched-in-control-spec
   -mno-sched-in-control-spec
       (En/Dis)able speculative scheduling of the instructions that are
       dependent on the control speculative loads.  This is effective only
       with -msched-control-spec enabled.  The default setting is enabled.

   -mno-sched-prefer-non-data-spec-insns
   -msched-prefer-non-data-spec-insns
       If enabled, data-speculative instructions are chosen for schedule
       only if there are no other choices at the moment.  This makes the
       use of the data speculation much more conservative.  The default
       setting is disabled.

   -mno-sched-prefer-non-control-spec-insns
   -msched-prefer-non-control-spec-insns
       If enabled, control-speculative instructions are chosen for
       schedule only if there are no other choices at the moment.  This
       makes the use of the control speculation much more conservative.
       The default setting is disabled.

   -mno-sched-count-spec-in-critical-path
   -msched-count-spec-in-critical-path
       If enabled, speculative dependencies are considered during
       computation of the instructions priorities.  This makes the use of
       the speculation a bit more conservative.  The default setting is
       disabled.

   -msched-spec-ldc
       Use a simple data speculation check.  This option is on by default.

   -msched-control-spec-ldc
       Use a simple check for control speculation.  This option is on by
       default.

   -msched-stop-bits-after-every-cycle
       Place a stop bit after every cycle when scheduling.  This option is
       on by default.

   -msched-fp-mem-deps-zero-cost
       Assume that floating-point stores and loads are not likely to cause
       a conflict when placed into the same instruction group.  This
       option is disabled by default.

   -msel-sched-dont-check-control-spec
       Generate checks for control speculation in selective scheduling.
       This flag is disabled by default.

   -msched-max-memory-insns=max-insns
       Limit on the number of memory insns per instruction group, giving
       lower priority to subsequent memory insns attempting to schedule in
       the same instruction group. Frequently useful to prevent cache bank
       conflicts.  The default value is 1.

   -msched-max-memory-insns-hard-limit
       Makes the limit specified by msched-max-memory-insns a hard limit,
       disallowing more than that number in an instruction group.
       Otherwise, the limit is "soft", meaning that non-memory operations
       are preferred when the limit is reached, but memory operations may
       still be scheduled.

   LM32 Options

   These -m options are defined for the LatticeMico32 architecture:

   -mbarrel-shift-enabled
       Enable barrel-shift instructions.

   -mdivide-enabled
       Enable divide and modulus instructions.

   -mmultiply-enabled
       Enable multiply instructions.

   -msign-extend-enabled
       Enable sign extend instructions.

   -muser-enabled
       Enable user-defined instructions.

   M32C Options

   -mcpu=name
       Select the CPU for which code is generated.  name may be one of r8c
       for the R8C/Tiny series, m16c for the M16C (up to /60) series,
       m32cm for the M16C/80 series, or m32c for the M32C/80 series.

   -msim
       Specifies that the program will be run on the simulator.  This
       causes an alternate runtime library to be linked in which supports,
       for example, file I/O.  You must not use this option when
       generating programs that will run on real hardware; you must
       provide your own runtime library for whatever I/O functions are
       needed.

   -memregs=number
       Specifies the number of memory-based pseudo-registers GCC uses
       during code generation.  These pseudo-registers are used like real
       registers, so there is a tradeoff between GCC's ability to fit the
       code into available registers, and the performance penalty of using
       memory instead of registers.  Note that all modules in a program
       must be compiled with the same value for this option.  Because of
       that, you must not use this option with GCC's default runtime
       libraries.

   M32R/D Options

   These -m options are defined for Renesas M32R/D architectures:

   -m32r2
       Generate code for the M32R/2.

   -m32rx
       Generate code for the M32R/X.

   -m32r
       Generate code for the M32R.  This is the default.

   -mmodel=small
       Assume all objects live in the lower 16MB of memory (so that their
       addresses can be loaded with the "ld24" instruction), and assume
       all subroutines are reachable with the "bl" instruction.  This is
       the default.

       The addressability of a particular object can be set with the
       "model" attribute.

   -mmodel=medium
       Assume objects may be anywhere in the 32-bit address space (the
       compiler generates "seth/add3" instructions to load their
       addresses), and assume all subroutines are reachable with the "bl"
       instruction.

   -mmodel=large
       Assume objects may be anywhere in the 32-bit address space (the
       compiler generates "seth/add3" instructions to load their
       addresses), and assume subroutines may not be reachable with the
       "bl" instruction (the compiler generates the much slower
       "seth/add3/jl" instruction sequence).

   -msdata=none
       Disable use of the small data area.  Variables are put into one of
       ".data", ".bss", or ".rodata" (unless the "section" attribute has
       been specified).  This is the default.

       The small data area consists of sections ".sdata" and ".sbss".
       Objects may be explicitly put in the small data area with the
       "section" attribute using one of these sections.

   -msdata=sdata
       Put small global and static data in the small data area, but do not
       generate special code to reference them.

   -msdata=use
       Put small global and static data in the small data area, and
       generate special instructions to reference them.

   -G num
       Put global and static objects less than or equal to num bytes into
       the small data or BSS sections instead of the normal data or BSS
       sections.  The default value of num is 8.  The -msdata option must
       be set to one of sdata or use for this option to have any effect.

       All modules should be compiled with the same -G num value.
       Compiling with different values of num may or may not work; if it
       doesn't the linker gives an error message---incorrect code is not
       generated.

   -mdebug
       Makes the M32R-specific code in the compiler display some
       statistics that might help in debugging programs.

   -malign-loops
       Align all loops to a 32-byte boundary.

   -mno-align-loops
       Do not enforce a 32-byte alignment for loops.  This is the default.

   -missue-rate=number
       Issue number instructions per cycle.  number can only be 1 or 2.

   -mbranch-cost=number
       number can only be 1 or 2.  If it is 1 then branches are preferred
       over conditional code, if it is 2, then the opposite applies.

   -mflush-trap=number
       Specifies the trap number to use to flush the cache.  The default
       is 12.  Valid numbers are between 0 and 15 inclusive.

   -mno-flush-trap
       Specifies that the cache cannot be flushed by using a trap.

   -mflush-func=name
       Specifies the name of the operating system function to call to
       flush the cache.  The default is _flush_cache, but a function call
       is only used if a trap is not available.

   -mno-flush-func
       Indicates that there is no OS function for flushing the cache.

   M680x0 Options

   These are the -m options defined for M680x0 and ColdFire processors.
   The default settings depend on which architecture was selected when the
   compiler was configured; the defaults for the most common choices are
   given below.

   -march=arch
       Generate code for a specific M680x0 or ColdFire instruction set
       architecture.  Permissible values of arch for M680x0 architectures
       are: 68000, 68010, 68020, 68030, 68040, 68060 and cpu32.  ColdFire
       architectures are selected according to Freescale's ISA
       classification and the permissible values are: isaa, isaaplus, isab
       and isac.

       GCC defines a macro "__mcfarch__" whenever it is generating code
       for a ColdFire target.  The arch in this macro is one of the -march
       arguments given above.

       When used together, -march and -mtune select code that runs on a
       family of similar processors but that is optimized for a particular
       microarchitecture.

   -mcpu=cpu
       Generate code for a specific M680x0 or ColdFire processor.  The
       M680x0 cpus are: 68000, 68010, 68020, 68030, 68040, 68060, 68302,
       68332 and cpu32.  The ColdFire cpus are given by the table below,
       which also classifies the CPUs into families:

       Family : -mcpu arguments
       51 : 51 51ac 51ag 51cn 51em 51je 51jf 51jg 51jm 51mm 51qe 51qm
       5206 : 5202 5204 5206
       5206e : 5206e
       5208 : 5207 5208
       5211a : 5210a 5211a
       5213 : 5211 5212 5213
       5216 : 5214 5216
       52235 : 52230 52231 52232 52233 52234 52235
       5225 : 5224 5225
       52259 : 52252 52254 52255 52256 52258 52259
       5235 : 5232 5233 5234 5235 523x
       5249 : 5249
       5250 : 5250
       5271 : 5270 5271
       5272 : 5272
       5275 : 5274 5275
       5282 : 5280 5281 5282 528x
       53017 : 53011 53012 53013 53014 53015 53016 53017
       5307 : 5307
       5329 : 5327 5328 5329 532x
       5373 : 5372 5373 537x
       5407 : 5407
       5475 : 5470 5471 5472 5473 5474 5475 547x 5480 5481 5482 5483 5484
       5485

       -mcpu=cpu overrides -march=arch if arch is compatible with cpu.
       Other combinations of -mcpu and -march are rejected.

       GCC defines the macro "__mcf_cpu_cpu" when ColdFire target cpu is
       selected.  It also defines "__mcf_family_family", where the value
       of family is given by the table above.

   -mtune=tune
       Tune the code for a particular microarchitecture within the
       constraints set by -march and -mcpu.  The M680x0 microarchitectures
       are: 68000, 68010, 68020, 68030, 68040, 68060 and cpu32.  The
       ColdFire microarchitectures are: cfv1, cfv2, cfv3, cfv4 and cfv4e.

       You can also use -mtune=68020-40 for code that needs to run
       relatively well on 68020, 68030 and 68040 targets.  -mtune=68020-60
       is similar but includes 68060 targets as well.  These two options
       select the same tuning decisions as -m68020-40 and -m68020-60
       respectively.

       GCC defines the macros "__mcarch" and "__mcarch__" when tuning for
       680x0 architecture arch.  It also defines "mcarch" unless either
       -ansi or a non-GNU -std option is used.  If GCC is tuning for a
       range of architectures, as selected by -mtune=68020-40 or
       -mtune=68020-60, it defines the macros for every architecture in
       the range.

       GCC also defines the macro "__muarch__" when tuning for ColdFire
       microarchitecture uarch, where uarch is one of the arguments given
       above.

   -m68000
   -mc68000
       Generate output for a 68000.  This is the default when the compiler
       is configured for 68000-based systems.  It is equivalent to
       -march=68000.

       Use this option for microcontrollers with a 68000 or EC000 core,
       including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356.

   -m68010
       Generate output for a 68010.  This is the default when the compiler
       is configured for 68010-based systems.  It is equivalent to
       -march=68010.

   -m68020
   -mc68020
       Generate output for a 68020.  This is the default when the compiler
       is configured for 68020-based systems.  It is equivalent to
       -march=68020.

   -m68030
       Generate output for a 68030.  This is the default when the compiler
       is configured for 68030-based systems.  It is equivalent to
       -march=68030.

   -m68040
       Generate output for a 68040.  This is the default when the compiler
       is configured for 68040-based systems.  It is equivalent to
       -march=68040.

       This option inhibits the use of 68881/68882 instructions that have
       to be emulated by software on the 68040.  Use this option if your
       68040 does not have code to emulate those instructions.

   -m68060
       Generate output for a 68060.  This is the default when the compiler
       is configured for 68060-based systems.  It is equivalent to
       -march=68060.

       This option inhibits the use of 68020 and 68881/68882 instructions
       that have to be emulated by software on the 68060.  Use this option
       if your 68060 does not have code to emulate those instructions.

   -mcpu32
       Generate output for a CPU32.  This is the default when the compiler
       is configured for CPU32-based systems.  It is equivalent to
       -march=cpu32.

       Use this option for microcontrollers with a CPU32 or CPU32+ core,
       including the 68330, 68331, 68332, 68333, 68334, 68336, 68340,
       68341, 68349 and 68360.

   -m5200
       Generate output for a 520X ColdFire CPU.  This is the default when
       the compiler is configured for 520X-based systems.  It is
       equivalent to -mcpu=5206, and is now deprecated in favor of that
       option.

       Use this option for microcontroller with a 5200 core, including the
       MCF5202, MCF5203, MCF5204 and MCF5206.

   -m5206e
       Generate output for a 5206e ColdFire CPU.  The option is now
       deprecated in favor of the equivalent -mcpu=5206e.

   -m528x
       Generate output for a member of the ColdFire 528X family.  The
       option is now deprecated in favor of the equivalent -mcpu=528x.

   -m5307
       Generate output for a ColdFire 5307 CPU.  The option is now
       deprecated in favor of the equivalent -mcpu=5307.

   -m5407
       Generate output for a ColdFire 5407 CPU.  The option is now
       deprecated in favor of the equivalent -mcpu=5407.

   -mcfv4e
       Generate output for a ColdFire V4e family CPU (e.g. 547x/548x).
       This includes use of hardware floating-point instructions.  The
       option is equivalent to -mcpu=547x, and is now deprecated in favor
       of that option.

   -m68020-40
       Generate output for a 68040, without using any of the new
       instructions.  This results in code that can run relatively
       efficiently on either a 68020/68881 or a 68030 or a 68040.  The
       generated code does use the 68881 instructions that are emulated on
       the 68040.

       The option is equivalent to -march=68020 -mtune=68020-40.

   -m68020-60
       Generate output for a 68060, without using any of the new
       instructions.  This results in code that can run relatively
       efficiently on either a 68020/68881 or a 68030 or a 68040.  The
       generated code does use the 68881 instructions that are emulated on
       the 68060.

       The option is equivalent to -march=68020 -mtune=68020-60.

   -mhard-float
   -m68881
       Generate floating-point instructions.  This is the default for
       68020 and above, and for ColdFire devices that have an FPU.  It
       defines the macro "__HAVE_68881__" on M680x0 targets and
       "__mcffpu__" on ColdFire targets.

   -msoft-float
       Do not generate floating-point instructions; use library calls
       instead.  This is the default for 68000, 68010, and 68832 targets.
       It is also the default for ColdFire devices that have no FPU.

   -mdiv
   -mno-div
       Generate (do not generate) ColdFire hardware divide and remainder
       instructions.  If -march is used without -mcpu, the default is "on"
       for ColdFire architectures and "off" for M680x0 architectures.
       Otherwise, the default is taken from the target CPU (either the
       default CPU, or the one specified by -mcpu).  For example, the
       default is "off" for -mcpu=5206 and "on" for -mcpu=5206e.

       GCC defines the macro "__mcfhwdiv__" when this option is enabled.

   -mshort
       Consider type "int" to be 16 bits wide, like "short int".
       Additionally, parameters passed on the stack are also aligned to a
       16-bit boundary even on targets whose API mandates promotion to
       32-bit.

   -mno-short
       Do not consider type "int" to be 16 bits wide.  This is the
       default.

   -mnobitfield
   -mno-bitfield
       Do not use the bit-field instructions.  The -m68000, -mcpu32 and
       -m5200 options imply -mnobitfield.

   -mbitfield
       Do use the bit-field instructions.  The -m68020 option implies
       -mbitfield.  This is the default if you use a configuration
       designed for a 68020.

   -mrtd
       Use a different function-calling convention, in which functions
       that take a fixed number of arguments return with the "rtd"
       instruction, which pops their arguments while returning.  This
       saves one instruction in the caller since there is no need to pop
       the arguments there.

       This calling convention is incompatible with the one normally used
       on Unix, so you cannot use it if you need to call libraries
       compiled with the Unix compiler.

       Also, you must provide function prototypes for all functions that
       take variable numbers of arguments (including "printf"); otherwise
       incorrect code is generated for calls to those functions.

       In addition, seriously incorrect code results if you call a
       function with too many arguments.  (Normally, extra arguments are
       harmlessly ignored.)

       The "rtd" instruction is supported by the 68010, 68020, 68030,
       68040, 68060 and CPU32 processors, but not by the 68000 or 5200.

   -mno-rtd
       Do not use the calling conventions selected by -mrtd.  This is the
       default.

   -malign-int
   -mno-align-int
       Control whether GCC aligns "int", "long", "long long", "float",
       "double", and "long double" variables on a 32-bit boundary
       (-malign-int) or a 16-bit boundary (-mno-align-int).  Aligning
       variables on 32-bit boundaries produces code that runs somewhat
       faster on processors with 32-bit busses at the expense of more
       memory.

       Warning: if you use the -malign-int switch, GCC aligns structures
       containing the above types differently than most published
       application binary interface specifications for the m68k.

   -mpcrel
       Use the pc-relative addressing mode of the 68000 directly, instead
       of using a global offset table.  At present, this option implies
       -fpic, allowing at most a 16-bit offset for pc-relative addressing.
       -fPIC is not presently supported with -mpcrel, though this could be
       supported for 68020 and higher processors.

   -mno-strict-align
   -mstrict-align
       Do not (do) assume that unaligned memory references are handled by
       the system.

   -msep-data
       Generate code that allows the data segment to be located in a
       different area of memory from the text segment.  This allows for
       execute-in-place in an environment without virtual memory
       management.  This option implies -fPIC.

   -mno-sep-data
       Generate code that assumes that the data segment follows the text
       segment.  This is the default.

   -mid-shared-library
       Generate code that supports shared libraries via the library ID
       method.  This allows for execute-in-place and shared libraries in
       an environment without virtual memory management.  This option
       implies -fPIC.

   -mno-id-shared-library
       Generate code that doesn't assume ID-based shared libraries are
       being used.  This is the default.

   -mshared-library-id=n
       Specifies the identification number of the ID-based shared library
       being compiled.  Specifying a value of 0 generates more compact
       code; specifying other values forces the allocation of that number
       to the current library, but is no more space- or time-efficient
       than omitting this option.

   -mxgot
   -mno-xgot
       When generating position-independent code for ColdFire, generate
       code that works if the GOT has more than 8192 entries.  This code
       is larger and slower than code generated without this option.  On
       M680x0 processors, this option is not needed; -fPIC suffices.

       GCC normally uses a single instruction to load values from the GOT.
       While this is relatively efficient, it only works if the GOT is
       smaller than about 64k.  Anything larger causes the linker to
       report an error such as:

               relocation truncated to fit: R_68K_GOT16O foobar

       If this happens, you should recompile your code with -mxgot.  It
       should then work with very large GOTs.  However, code generated
       with -mxgot is less efficient, since it takes 4 instructions to
       fetch the value of a global symbol.

       Note that some linkers, including newer versions of the GNU linker,
       can create multiple GOTs and sort GOT entries.  If you have such a
       linker, you should only need to use -mxgot when compiling a single
       object file that accesses more than 8192 GOT entries.  Very few do.

       These options have no effect unless GCC is generating position-
       independent code.

   MCore Options

   These are the -m options defined for the Motorola M*Core processors.

   -mhardlit
   -mno-hardlit
       Inline constants into the code stream if it can be done in two
       instructions or less.

   -mdiv
   -mno-div
       Use the divide instruction.  (Enabled by default).

   -mrelax-immediate
   -mno-relax-immediate
       Allow arbitrary-sized immediates in bit operations.

   -mwide-bitfields
   -mno-wide-bitfields
       Always treat bit-fields as "int"-sized.

   -m4byte-functions
   -mno-4byte-functions
       Force all functions to be aligned to a 4-byte boundary.

   -mcallgraph-data
   -mno-callgraph-data
       Emit callgraph information.

   -mslow-bytes
   -mno-slow-bytes
       Prefer word access when reading byte quantities.

   -mlittle-endian
   -mbig-endian
       Generate code for a little-endian target.

   -m210
   -m340
       Generate code for the 210 processor.

   -mno-lsim
       Assume that runtime support has been provided and so omit the
       simulator library (libsim.a) from the linker command line.

   -mstack-increment=size
       Set the maximum amount for a single stack increment operation.
       Large values can increase the speed of programs that contain
       functions that need a large amount of stack space, but they can
       also trigger a segmentation fault if the stack is extended too
       much.  The default value is 0x1000.

   MeP Options

   -mabsdiff
       Enables the "abs" instruction, which is the absolute difference
       between two registers.

   -mall-opts
       Enables all the optional instructions---average, multiply, divide,
       bit operations, leading zero, absolute difference, min/max, clip,
       and saturation.

   -maverage
       Enables the "ave" instruction, which computes the average of two
       registers.

   -mbased=n
       Variables of size n bytes or smaller are placed in the ".based"
       section by default.  Based variables use the $tp register as a base
       register, and there is a 128-byte limit to the ".based" section.

   -mbitops
       Enables the bit operation instructions---bit test ("btstm"), set
       ("bsetm"), clear ("bclrm"), invert ("bnotm"), and test-and-set
       ("tas").

   -mc=name
       Selects which section constant data is placed in.  name may be
       tiny, near, or far.

   -mclip
       Enables the "clip" instruction.  Note that -mclip is not useful
       unless you also provide -mminmax.

   -mconfig=name
       Selects one of the built-in core configurations.  Each MeP chip has
       one or more modules in it; each module has a core CPU and a variety
       of coprocessors, optional instructions, and peripherals.  The
       "MeP-Integrator" tool, not part of GCC, provides these
       configurations through this option; using this option is the same
       as using all the corresponding command-line options.  The default
       configuration is default.

   -mcop
       Enables the coprocessor instructions.  By default, this is a 32-bit
       coprocessor.  Note that the coprocessor is normally enabled via the
       -mconfig= option.

   -mcop32
       Enables the 32-bit coprocessor's instructions.

   -mcop64
       Enables the 64-bit coprocessor's instructions.

   -mivc2
       Enables IVC2 scheduling.  IVC2 is a 64-bit VLIW coprocessor.

   -mdc
       Causes constant variables to be placed in the ".near" section.

   -mdiv
       Enables the "div" and "divu" instructions.

   -meb
       Generate big-endian code.

   -mel
       Generate little-endian code.

   -mio-volatile
       Tells the compiler that any variable marked with the "io" attribute
       is to be considered volatile.

   -ml Causes variables to be assigned to the ".far" section by default.

   -mleadz
       Enables the "leadz" (leading zero) instruction.

   -mm Causes variables to be assigned to the ".near" section by default.

   -mminmax
       Enables the "min" and "max" instructions.

   -mmult
       Enables the multiplication and multiply-accumulate instructions.

   -mno-opts
       Disables all the optional instructions enabled by -mall-opts.

   -mrepeat
       Enables the "repeat" and "erepeat" instructions, used for low-
       overhead looping.

   -ms Causes all variables to default to the ".tiny" section.  Note that
       there is a 65536-byte limit to this section.  Accesses to these
       variables use the %gp base register.

   -msatur
       Enables the saturation instructions.  Note that the compiler does
       not currently generate these itself, but this option is included
       for compatibility with other tools, like "as".

   -msdram
       Link the SDRAM-based runtime instead of the default ROM-based
       runtime.

   -msim
       Link the simulator run-time libraries.

   -msimnovec
       Link the simulator runtime libraries, excluding built-in support
       for reset and exception vectors and tables.

   -mtf
       Causes all functions to default to the ".far" section.  Without
       this option, functions default to the ".near" section.

   -mtiny=n
       Variables that are n bytes or smaller are allocated to the ".tiny"
       section.  These variables use the $gp base register.  The default
       for this option is 4, but note that there's a 65536-byte limit to
       the ".tiny" section.

   MicroBlaze Options

   -msoft-float
       Use software emulation for floating point (default).

   -mhard-float
       Use hardware floating-point instructions.

   -mmemcpy
       Do not optimize block moves, use "memcpy".

   -mno-clearbss
       This option is deprecated.  Use -fno-zero-initialized-in-bss
       instead.

   -mcpu=cpu-type
       Use features of, and schedule code for, the given CPU.  Supported
       values are in the format vX.YY.Z, where X is a major version, YY is
       the minor version, and Z is compatibility code.  Example values are
       v3.00.a, v4.00.b, v5.00.a, v5.00.b, v5.00.b, v6.00.a.

   -mxl-soft-mul
       Use software multiply emulation (default).

   -mxl-soft-div
       Use software emulation for divides (default).

   -mxl-barrel-shift
       Use the hardware barrel shifter.

   -mxl-pattern-compare
       Use pattern compare instructions.

   -msmall-divides
       Use table lookup optimization for small signed integer divisions.

   -mxl-stack-check
       This option is deprecated.  Use -fstack-check instead.

   -mxl-gp-opt
       Use GP-relative ".sdata"/".sbss" sections.

   -mxl-multiply-high
       Use multiply high instructions for high part of 32x32 multiply.

   -mxl-float-convert
       Use hardware floating-point conversion instructions.

   -mxl-float-sqrt
       Use hardware floating-point square root instruction.

   -mbig-endian
       Generate code for a big-endian target.

   -mlittle-endian
       Generate code for a little-endian target.

   -mxl-reorder
       Use reorder instructions (swap and byte reversed load/store).

   -mxl-mode-app-model
       Select application model app-model.  Valid models are

       executable
           normal executable (default), uses startup code crt0.o.

       xmdstub
           for use with Xilinx Microprocessor Debugger (XMD) based
           software intrusive debug agent called xmdstub. This uses
           startup file crt1.o and sets the start address of the program
           to 0x800.

       bootstrap
           for applications that are loaded using a bootloader.  This
           model uses startup file crt2.o which does not contain a
           processor reset vector handler. This is suitable for
           transferring control on a processor reset to the bootloader
           rather than the application.

       novectors
           for applications that do not require any of the MicroBlaze
           vectors. This option may be useful for applications running
           within a monitoring application. This model uses crt3.o as a
           startup file.

       Option -xl-mode-app-model is a deprecated alias for -mxl-mode-app-
       model.

   MIPS Options

   -EB Generate big-endian code.

   -EL Generate little-endian code.  This is the default for mips*el-*-*
       configurations.

   -march=arch
       Generate code that runs on arch, which can be the name of a generic
       MIPS ISA, or the name of a particular processor.  The ISA names
       are: mips1, mips2, mips3, mips4, mips32, mips32r2, mips32r3,
       mips32r5, mips32r6, mips64, mips64r2, mips64r3, mips64r5 and
       mips64r6.  The processor names are: 4kc, 4km, 4kp, 4ksc, 4kec,
       4kem, 4kep, 4ksd, 5kc, 5kf, 20kc, 24kc, 24kf2_1, 24kf1_1, 24kec,
       24kef2_1, 24kef1_1, 34kc, 34kf2_1, 34kf1_1, 34kn, 74kc, 74kf2_1,
       74kf1_1, 74kf3_2, 1004kc, 1004kf2_1, 1004kf1_1, i6400, interaptiv,
       loongson2e, loongson2f, loongson3a, m4k, m14k, m14kc, m14ke,
       m14kec, m5100, m5101, octeon, octeon+, octeon2, octeon3, orion,
       p5600, r2000, r3000, r3900, r4000, r4400, r4600, r4650, r4700,
       r6000, r8000, rm7000, rm9000, r10000, r12000, r14000, r16000, sb1,
       sr71000, vr4100, vr4111, vr4120, vr4130, vr4300, vr5000, vr5400,
       vr5500, xlr and xlp.  The special value from-abi selects the most
       compatible architecture for the selected ABI (that is, mips1 for
       32-bit ABIs and mips3 for 64-bit ABIs).

       The native Linux/GNU toolchain also supports the value native,
       which selects the best architecture option for the host processor.
       -march=native has no effect if GCC does not recognize the
       processor.

       In processor names, a final 000 can be abbreviated as k (for
       example, -march=r2k).  Prefixes are optional, and vr may be written
       r.

       Names of the form nf2_1 refer to processors with FPUs clocked at
       half the rate of the core, names of the form nf1_1 refer to
       processors with FPUs clocked at the same rate as the core, and
       names of the form nf3_2 refer to processors with FPUs clocked a
       ratio of 3:2 with respect to the core.  For compatibility reasons,
       nf is accepted as a synonym for nf2_1 while nx and bfx are accepted
       as synonyms for nf1_1.

       GCC defines two macros based on the value of this option.  The
       first is "_MIPS_ARCH", which gives the name of target architecture,
       as a string.  The second has the form "_MIPS_ARCH_foo", where foo
       is the capitalized value of "_MIPS_ARCH".  For example,
       -march=r2000 sets "_MIPS_ARCH" to "r2000" and defines the macro
       "_MIPS_ARCH_R2000".

       Note that the "_MIPS_ARCH" macro uses the processor names given
       above.  In other words, it has the full prefix and does not
       abbreviate 000 as k.  In the case of from-abi, the macro names the
       resolved architecture (either "mips1" or "mips3").  It names the
       default architecture when no -march option is given.

   -mtune=arch
       Optimize for arch.  Among other things, this option controls the
       way instructions are scheduled, and the perceived cost of
       arithmetic operations.  The list of arch values is the same as for
       -march.

       When this option is not used, GCC optimizes for the processor
       specified by -march.  By using -march and -mtune together, it is
       possible to generate code that runs on a family of processors, but
       optimize the code for one particular member of that family.

       -mtune defines the macros "_MIPS_TUNE" and "_MIPS_TUNE_foo", which
       work in the same way as the -march ones described above.

   -mips1
       Equivalent to -march=mips1.

   -mips2
       Equivalent to -march=mips2.

   -mips3
       Equivalent to -march=mips3.

   -mips4
       Equivalent to -march=mips4.

   -mips32
       Equivalent to -march=mips32.

   -mips32r3
       Equivalent to -march=mips32r3.

   -mips32r5
       Equivalent to -march=mips32r5.

   -mips32r6
       Equivalent to -march=mips32r6.

   -mips64
       Equivalent to -march=mips64.

   -mips64r2
       Equivalent to -march=mips64r2.

   -mips64r3
       Equivalent to -march=mips64r3.

   -mips64r5
       Equivalent to -march=mips64r5.

   -mips64r6
       Equivalent to -march=mips64r6.

   -mips16
   -mno-mips16
       Generate (do not generate) MIPS16 code.  If GCC is targeting a
       MIPS32 or MIPS64 architecture, it makes use of the MIPS16e ASE.

       MIPS16 code generation can also be controlled on a per-function
       basis by means of "mips16" and "nomips16" attributes.

   -mflip-mips16
       Generate MIPS16 code on alternating functions.  This option is
       provided for regression testing of mixed MIPS16/non-MIPS16 code
       generation, and is not intended for ordinary use in compiling user
       code.

   -minterlink-compressed
   -mno-interlink-compressed
       Require (do not require) that code using the standard
       (uncompressed) MIPS ISA be link-compatible with MIPS16 and
       microMIPS code, and vice versa.

       For example, code using the standard ISA encoding cannot jump
       directly to MIPS16 or microMIPS code; it must either use a call or
       an indirect jump.  -minterlink-compressed therefore disables direct
       jumps unless GCC knows that the target of the jump is not
       compressed.

   -minterlink-mips16
   -mno-interlink-mips16
       Aliases of -minterlink-compressed and -mno-interlink-compressed.
       These options predate the microMIPS ASE and are retained for
       backwards compatibility.

   -mabi=32
   -mabi=o64
   -mabi=n32
   -mabi=64
   -mabi=eabi
       Generate code for the given ABI.

       Note that the EABI has a 32-bit and a 64-bit variant.  GCC normally
       generates 64-bit code when you select a 64-bit architecture, but
       you can use -mgp32 to get 32-bit code instead.

       For information about the O64 ABI, see
       <http://gcc.gnu.org/projects/mipso64-abi.html>.

       GCC supports a variant of the o32 ABI in which floating-point
       registers are 64 rather than 32 bits wide.  You can select this
       combination with -mabi=32 -mfp64.  This ABI relies on the "mthc1"
       and "mfhc1" instructions and is therefore only supported for
       MIPS32R2, MIPS32R3 and MIPS32R5 processors.

       The register assignments for arguments and return values remain the
       same, but each scalar value is passed in a single 64-bit register
       rather than a pair of 32-bit registers.  For example, scalar
       floating-point values are returned in $f0 only, not a $f0/$f1 pair.
       The set of call-saved registers also remains the same in that the
       even-numbered double-precision registers are saved.

       Two additional variants of the o32 ABI are supported to enable a
       transition from 32-bit to 64-bit registers.  These are FPXX
       (-mfpxx) and FP64A (-mfp64 -mno-odd-spreg).  The FPXX extension
       mandates that all code must execute correctly when run using 32-bit
       or 64-bit registers.  The code can be interlinked with either FP32
       or FP64, but not both.  The FP64A extension is similar to the FP64
       extension but forbids the use of odd-numbered single-precision
       registers.  This can be used in conjunction with the "FRE" mode of
       FPUs in MIPS32R5 processors and allows both FP32 and FP64A code to
       interlink and run in the same process without changing FPU modes.

   -mabicalls
   -mno-abicalls
       Generate (do not generate) code that is suitable for SVR4-style
       dynamic objects.  -mabicalls is the default for SVR4-based systems.

   -mshared
   -mno-shared
       Generate (do not generate) code that is fully position-independent,
       and that can therefore be linked into shared libraries.  This
       option only affects -mabicalls.

       All -mabicalls code has traditionally been position-independent,
       regardless of options like -fPIC and -fpic.  However, as an
       extension, the GNU toolchain allows executables to use absolute
       accesses for locally-binding symbols.  It can also use shorter GP
       initialization sequences and generate direct calls to locally-
       defined functions.  This mode is selected by -mno-shared.

       -mno-shared depends on binutils 2.16 or higher and generates
       objects that can only be linked by the GNU linker.  However, the
       option does not affect the ABI of the final executable; it only
       affects the ABI of relocatable objects.  Using -mno-shared
       generally makes executables both smaller and quicker.

       -mshared is the default.

   -mplt
   -mno-plt
       Assume (do not assume) that the static and dynamic linkers support
       PLTs and copy relocations.  This option only affects -mno-shared
       -mabicalls.  For the n64 ABI, this option has no effect without
       -msym32.

       You can make -mplt the default by configuring GCC with
       --with-mips-plt.  The default is -mno-plt otherwise.

   -mxgot
   -mno-xgot
       Lift (do not lift) the usual restrictions on the size of the global
       offset table.

       GCC normally uses a single instruction to load values from the GOT.
       While this is relatively efficient, it only works if the GOT is
       smaller than about 64k.  Anything larger causes the linker to
       report an error such as:

               relocation truncated to fit: R_MIPS_GOT16 foobar

       If this happens, you should recompile your code with -mxgot.  This
       works with very large GOTs, although the code is also less
       efficient, since it takes three instructions to fetch the value of
       a global symbol.

       Note that some linkers can create multiple GOTs.  If you have such
       a linker, you should only need to use -mxgot when a single object
       file accesses more than 64k's worth of GOT entries.  Very few do.

       These options have no effect unless GCC is generating position
       independent code.

   -mgp32
       Assume that general-purpose registers are 32 bits wide.

   -mgp64
       Assume that general-purpose registers are 64 bits wide.

   -mfp32
       Assume that floating-point registers are 32 bits wide.

   -mfp64
       Assume that floating-point registers are 64 bits wide.

   -mfpxx
       Do not assume the width of floating-point registers.

   -mhard-float
       Use floating-point coprocessor instructions.

   -msoft-float
       Do not use floating-point coprocessor instructions.  Implement
       floating-point calculations using library calls instead.

   -mno-float
       Equivalent to -msoft-float, but additionally asserts that the
       program being compiled does not perform any floating-point
       operations.  This option is presently supported only by some bare-
       metal MIPS configurations, where it may select a special set of
       libraries that lack all floating-point support (including, for
       example, the floating-point "printf" formats).  If code compiled
       with -mno-float accidentally contains floating-point operations, it
       is likely to suffer a link-time or run-time failure.

   -msingle-float
       Assume that the floating-point coprocessor only supports single-
       precision operations.

   -mdouble-float
       Assume that the floating-point coprocessor supports double-
       precision operations.  This is the default.

   -modd-spreg
   -mno-odd-spreg
       Enable the use of odd-numbered single-precision floating-point
       registers for the o32 ABI.  This is the default for processors that
       are known to support these registers.  When using the o32 FPXX ABI,
       -mno-odd-spreg is set by default.

   -mabs=2008
   -mabs=legacy
       These options control the treatment of the special not-a-number
       (NaN) IEEE 754 floating-point data with the "abs.fmt" and "neg.fmt"
       machine instructions.

       By default or when -mabs=legacy is used the legacy treatment is
       selected.  In this case these instructions are considered
       arithmetic and avoided where correct operation is required and the
       input operand might be a NaN.  A longer sequence of instructions
       that manipulate the sign bit of floating-point datum manually is
       used instead unless the -ffinite-math-only option has also been
       specified.

       The -mabs=2008 option selects the IEEE 754-2008 treatment.  In this
       case these instructions are considered non-arithmetic and therefore
       operating correctly in all cases, including in particular where the
       input operand is a NaN.  These instructions are therefore always
       used for the respective operations.

   -mnan=2008
   -mnan=legacy
       These options control the encoding of the special not-a-number
       (NaN) IEEE 754 floating-point data.

       The -mnan=legacy option selects the legacy encoding.  In this case
       quiet NaNs (qNaNs) are denoted by the first bit of their trailing
       significand field being 0, whereas signalling NaNs (sNaNs) are
       denoted by the first bit of their trailing significand field being
       1.

       The -mnan=2008 option selects the IEEE 754-2008 encoding.  In this
       case qNaNs are denoted by the first bit of their trailing
       significand field being 1, whereas sNaNs are denoted by the first
       bit of their trailing significand field being 0.

       The default is -mnan=legacy unless GCC has been configured with
       --with-nan=2008.

   -mllsc
   -mno-llsc
       Use (do not use) ll, sc, and sync instructions to implement atomic
       memory built-in functions.  When neither option is specified, GCC
       uses the instructions if the target architecture supports them.

       -mllsc is useful if the runtime environment can emulate the
       instructions and -mno-llsc can be useful when compiling for
       nonstandard ISAs.  You can make either option the default by
       configuring GCC with --with-llsc and --without-llsc respectively.
       --with-llsc is the default for some configurations; see the
       installation documentation for details.

   -mdsp
   -mno-dsp
       Use (do not use) revision 1 of the MIPS DSP ASE.
         This option defines the preprocessor macro "__mips_dsp".  It also
       defines "__mips_dsp_rev" to 1.

   -mdspr2
   -mno-dspr2
       Use (do not use) revision 2 of the MIPS DSP ASE.
         This option defines the preprocessor macros "__mips_dsp" and
       "__mips_dspr2".  It also defines "__mips_dsp_rev" to 2.

   -msmartmips
   -mno-smartmips
       Use (do not use) the MIPS SmartMIPS ASE.

   -mpaired-single
   -mno-paired-single
       Use (do not use) paired-single floating-point instructions.
         This option requires hardware floating-point support to be
       enabled.

   -mdmx
   -mno-mdmx
       Use (do not use) MIPS Digital Media Extension instructions.  This
       option can only be used when generating 64-bit code and requires
       hardware floating-point support to be enabled.

   -mips3d
   -mno-mips3d
       Use (do not use) the MIPS-3D ASE.  The option -mips3d implies
       -mpaired-single.

   -mmicromips
   -mno-micromips
       Generate (do not generate) microMIPS code.

       MicroMIPS code generation can also be controlled on a per-function
       basis by means of "micromips" and "nomicromips" attributes.

   -mmt
   -mno-mt
       Use (do not use) MT Multithreading instructions.

   -mmcu
   -mno-mcu
       Use (do not use) the MIPS MCU ASE instructions.

   -meva
   -mno-eva
       Use (do not use) the MIPS Enhanced Virtual Addressing instructions.

   -mvirt
   -mno-virt
       Use (do not use) the MIPS Virtualization Application Specific
       instructions.

   -mxpa
   -mno-xpa
       Use (do not use) the MIPS eXtended Physical Address (XPA)
       instructions.

   -mlong64
       Force "long" types to be 64 bits wide.  See -mlong32 for an
       explanation of the default and the way that the pointer size is
       determined.

   -mlong32
       Force "long", "int", and pointer types to be 32 bits wide.

       The default size of "int"s, "long"s and pointers depends on the
       ABI.  All the supported ABIs use 32-bit "int"s.  The n64 ABI uses
       64-bit "long"s, as does the 64-bit EABI; the others use 32-bit
       "long"s.  Pointers are the same size as "long"s, or the same size
       as integer registers, whichever is smaller.

   -msym32
   -mno-sym32
       Assume (do not assume) that all symbols have 32-bit values,
       regardless of the selected ABI.  This option is useful in
       combination with -mabi=64 and -mno-abicalls because it allows GCC
       to generate shorter and faster references to symbolic addresses.

   -G num
       Put definitions of externally-visible data in a small data section
       if that data is no bigger than num bytes.  GCC can then generate
       more efficient accesses to the data; see -mgpopt for details.

       The default -G option depends on the configuration.

   -mlocal-sdata
   -mno-local-sdata
       Extend (do not extend) the -G behavior to local data too, such as
       to static variables in C.  -mlocal-sdata is the default for all
       configurations.

       If the linker complains that an application is using too much small
       data, you might want to try rebuilding the less performance-
       critical parts with -mno-local-sdata.  You might also want to build
       large libraries with -mno-local-sdata, so that the libraries leave
       more room for the main program.

   -mextern-sdata
   -mno-extern-sdata
       Assume (do not assume) that externally-defined data is in a small
       data section if the size of that data is within the -G limit.
       -mextern-sdata is the default for all configurations.

       If you compile a module Mod with -mextern-sdata -G num -mgpopt, and
       Mod references a variable Var that is no bigger than num bytes, you
       must make sure that Var is placed in a small data section.  If Var
       is defined by another module, you must either compile that module
       with a high-enough -G setting or attach a "section" attribute to
       Var's definition.  If Var is common, you must link the application
       with a high-enough -G setting.

       The easiest way of satisfying these restrictions is to compile and
       link every module with the same -G option.  However, you may wish
       to build a library that supports several different small data
       limits.  You can do this by compiling the library with the highest
       supported -G setting and additionally using -mno-extern-sdata to
       stop the library from making assumptions about externally-defined
       data.

   -mgpopt
   -mno-gpopt
       Use (do not use) GP-relative accesses for symbols that are known to
       be in a small data section; see -G, -mlocal-sdata and
       -mextern-sdata.  -mgpopt is the default for all configurations.

       -mno-gpopt is useful for cases where the $gp register might not
       hold the value of "_gp".  For example, if the code is part of a
       library that might be used in a boot monitor, programs that call
       boot monitor routines pass an unknown value in $gp.  (In such
       situations, the boot monitor itself is usually compiled with -G0.)

       -mno-gpopt implies -mno-local-sdata and -mno-extern-sdata.

   -membedded-data
   -mno-embedded-data
       Allocate variables to the read-only data section first if possible,
       then next in the small data section if possible, otherwise in data.
       This gives slightly slower code than the default, but reduces the
       amount of RAM required when executing, and thus may be preferred
       for some embedded systems.

   -muninit-const-in-rodata
   -mno-uninit-const-in-rodata
       Put uninitialized "const" variables in the read-only data section.
       This option is only meaningful in conjunction with -membedded-data.

   -mcode-readable=setting
       Specify whether GCC may generate code that reads from executable
       sections.  There are three possible settings:

       -mcode-readable=yes
           Instructions may freely access executable sections.  This is
           the default setting.

       -mcode-readable=pcrel
           MIPS16 PC-relative load instructions can access executable
           sections, but other instructions must not do so.  This option
           is useful on 4KSc and 4KSd processors when the code TLBs have
           the Read Inhibit bit set.  It is also useful on processors that
           can be configured to have a dual instruction/data SRAM
           interface and that, like the M4K, automatically redirect PC-
           relative loads to the instruction RAM.

       -mcode-readable=no
           Instructions must not access executable sections.  This option
           can be useful on targets that are configured to have a dual
           instruction/data SRAM interface but that (unlike the M4K) do
           not automatically redirect PC-relative loads to the instruction
           RAM.

   -msplit-addresses
   -mno-split-addresses
       Enable (disable) use of the "%hi()" and "%lo()" assembler
       relocation operators.  This option has been superseded by
       -mexplicit-relocs but is retained for backwards compatibility.

   -mexplicit-relocs
   -mno-explicit-relocs
       Use (do not use) assembler relocation operators when dealing with
       symbolic addresses.  The alternative, selected by
       -mno-explicit-relocs, is to use assembler macros instead.

       -mexplicit-relocs is the default if GCC was configured to use an
       assembler that supports relocation operators.

   -mcheck-zero-division
   -mno-check-zero-division
       Trap (do not trap) on integer division by zero.

       The default is -mcheck-zero-division.

   -mdivide-traps
   -mdivide-breaks
       MIPS systems check for division by zero by generating either a
       conditional trap or a break instruction.  Using traps results in
       smaller code, but is only supported on MIPS II and later.  Also,
       some versions of the Linux kernel have a bug that prevents trap
       from generating the proper signal ("SIGFPE").  Use -mdivide-traps
       to allow conditional traps on architectures that support them and
       -mdivide-breaks to force the use of breaks.

       The default is usually -mdivide-traps, but this can be overridden
       at configure time using --with-divide=breaks.  Divide-by-zero
       checks can be completely disabled using -mno-check-zero-division.

   -mmemcpy
   -mno-memcpy
       Force (do not force) the use of "memcpy" for non-trivial block
       moves.  The default is -mno-memcpy, which allows GCC to inline most
       constant-sized copies.

   -mlong-calls
   -mno-long-calls
       Disable (do not disable) use of the "jal" instruction.  Calling
       functions using "jal" is more efficient but requires the caller and
       callee to be in the same 256 megabyte segment.

       This option has no effect on abicalls code.  The default is
       -mno-long-calls.

   -mmad
   -mno-mad
       Enable (disable) use of the "mad", "madu" and "mul" instructions,
       as provided by the R4650 ISA.

   -mimadd
   -mno-imadd
       Enable (disable) use of the "madd" and "msub" integer instructions.
       The default is -mimadd on architectures that support "madd" and
       "msub" except for the 74k architecture where it was found to
       generate slower code.

   -mfused-madd
   -mno-fused-madd
       Enable (disable) use of the floating-point multiply-accumulate
       instructions, when they are available.  The default is
       -mfused-madd.

       On the R8000 CPU when multiply-accumulate instructions are used,
       the intermediate product is calculated to infinite precision and is
       not subject to the FCSR Flush to Zero bit.  This may be undesirable
       in some circumstances.  On other processors the result is
       numerically identical to the equivalent computation using separate
       multiply, add, subtract and negate instructions.

   -nocpp
       Tell the MIPS assembler to not run its preprocessor over user
       assembler files (with a .s suffix) when assembling them.

   -mfix-24k
   -mno-fix-24k
       Work around the 24K E48 (lost data on stores during refill) errata.
       The workarounds are implemented by the assembler rather than by
       GCC.

   -mfix-r4000
   -mno-fix-r4000
       Work around certain R4000 CPU errata:

       -   A double-word or a variable shift may give an incorrect result
           if executed immediately after starting an integer division.

       -   A double-word or a variable shift may give an incorrect result
           if executed while an integer multiplication is in progress.

       -   An integer division may give an incorrect result if started in
           a delay slot of a taken branch or a jump.

   -mfix-r4400
   -mno-fix-r4400
       Work around certain R4400 CPU errata:

       -   A double-word or a variable shift may give an incorrect result
           if executed immediately after starting an integer division.

   -mfix-r10000
   -mno-fix-r10000
       Work around certain R10000 errata:

       -   "ll"/"sc" sequences may not behave atomically on revisions
           prior to 3.0.  They may deadlock on revisions 2.6 and earlier.

       This option can only be used if the target architecture supports
       branch-likely instructions.  -mfix-r10000 is the default when
       -march=r10000 is used; -mno-fix-r10000 is the default otherwise.

   -mfix-rm7000
   -mno-fix-rm7000
       Work around the RM7000 "dmult"/"dmultu" errata.  The workarounds
       are implemented by the assembler rather than by GCC.

   -mfix-vr4120
   -mno-fix-vr4120
       Work around certain VR4120 errata:

       -   "dmultu" does not always produce the correct result.

       -   "div" and "ddiv" do not always produce the correct result if
           one of the operands is negative.

       The workarounds for the division errata rely on special functions
       in libgcc.a.  At present, these functions are only provided by the
       "mips64vr*-elf" configurations.

       Other VR4120 errata require a NOP to be inserted between certain
       pairs of instructions.  These errata are handled by the assembler,
       not by GCC itself.

   -mfix-vr4130
       Work around the VR4130 "mflo"/"mfhi" errata.  The workarounds are
       implemented by the assembler rather than by GCC, although GCC
       avoids using "mflo" and "mfhi" if the VR4130 "macc", "macchi",
       "dmacc" and "dmacchi" instructions are available instead.

   -mfix-sb1
   -mno-fix-sb1
       Work around certain SB-1 CPU core errata.  (This flag currently
       works around the SB-1 revision 2 "F1" and "F2" floating-point
       errata.)

   -mr10k-cache-barrier=setting
       Specify whether GCC should insert cache barriers to avoid the side-
       effects of speculation on R10K processors.

       In common with many processors, the R10K tries to predict the
       outcome of a conditional branch and speculatively executes
       instructions from the "taken" branch.  It later aborts these
       instructions if the predicted outcome is wrong.  However, on the
       R10K, even aborted instructions can have side effects.

       This problem only affects kernel stores and, depending on the
       system, kernel loads.  As an example, a speculatively-executed
       store may load the target memory into cache and mark the cache line
       as dirty, even if the store itself is later aborted.  If a DMA
       operation writes to the same area of memory before the "dirty" line
       is flushed, the cached data overwrites the DMA-ed data.  See the
       R10K processor manual for a full description, including other
       potential problems.

       One workaround is to insert cache barrier instructions before every
       memory access that might be speculatively executed and that might
       have side effects even if aborted.  -mr10k-cache-barrier=setting
       controls GCC's implementation of this workaround.  It assumes that
       aborted accesses to any byte in the following regions does not have
       side effects:

       1.  the memory occupied by the current function's stack frame;

       2.  the memory occupied by an incoming stack argument;

       3.  the memory occupied by an object with a link-time-constant
           address.

       It is the kernel's responsibility to ensure that speculative
       accesses to these regions are indeed safe.

       If the input program contains a function declaration such as:

               void foo (void);

       then the implementation of "foo" must allow "j foo" and "jal foo"
       to be executed speculatively.  GCC honors this restriction for
       functions it compiles itself.  It expects non-GCC functions (such
       as hand-written assembly code) to do the same.

       The option has three forms:

       -mr10k-cache-barrier=load-store
           Insert a cache barrier before a load or store that might be
           speculatively executed and that might have side effects even if
           aborted.

       -mr10k-cache-barrier=store
           Insert a cache barrier before a store that might be
           speculatively executed and that might have side effects even if
           aborted.

       -mr10k-cache-barrier=none
           Disable the insertion of cache barriers.  This is the default
           setting.

   -mflush-func=func
   -mno-flush-func
       Specifies the function to call to flush the I and D caches, or to
       not call any such function.  If called, the function must take the
       same arguments as the common "_flush_func", that is, the address of
       the memory range for which the cache is being flushed, the size of
       the memory range, and the number 3 (to flush both caches).  The
       default depends on the target GCC was configured for, but commonly
       is either "_flush_func" or "__cpu_flush".

   mbranch-cost=num
       Set the cost of branches to roughly num "simple" instructions.
       This cost is only a heuristic and is not guaranteed to produce
       consistent results across releases.  A zero cost redundantly
       selects the default, which is based on the -mtune setting.

   -mbranch-likely
   -mno-branch-likely
       Enable or disable use of Branch Likely instructions, regardless of
       the default for the selected architecture.  By default, Branch
       Likely instructions may be generated if they are supported by the
       selected architecture.  An exception is for the MIPS32 and MIPS64
       architectures and processors that implement those architectures;
       for those, Branch Likely instructions are not be generated by
       default because the MIPS32 and MIPS64 architectures specifically
       deprecate their use.

   -mcompact-branches=never
   -mcompact-branches=optimal
   -mcompact-branches=always
       These options control which form of branches will be generated.
       The default is -mcompact-branches=optimal.

       The -mcompact-branches=never option ensures that compact branch
       instructions will never be generated.

       The -mcompact-branches=always option ensures that a compact branch
       instruction will be generated if available.  If a compact branch
       instruction is not available, a delay slot form of the branch will
       be used instead.

       This option is supported from MIPS Release 6 onwards.

       The -mcompact-branches=optimal option will cause a delay slot
       branch to be used if one is available in the current ISA and the
       delay slot is successfully filled.  If the delay slot is not
       filled, a compact branch will be chosen if one is available.

   -mfp-exceptions
   -mno-fp-exceptions
       Specifies whether FP exceptions are enabled.  This affects how FP
       instructions are scheduled for some processors.  The default is
       that FP exceptions are enabled.

       For instance, on the SB-1, if FP exceptions are disabled, and we
       are emitting 64-bit code, then we can use both FP pipes.
       Otherwise, we can only use one FP pipe.

   -mvr4130-align
   -mno-vr4130-align
       The VR4130 pipeline is two-way superscalar, but can only issue two
       instructions together if the first one is 8-byte aligned.  When
       this option is enabled, GCC aligns pairs of instructions that it
       thinks should execute in parallel.

       This option only has an effect when optimizing for the VR4130.  It
       normally makes code faster, but at the expense of making it bigger.
       It is enabled by default at optimization level -O3.

   -msynci
   -mno-synci
       Enable (disable) generation of "synci" instructions on
       architectures that support it.  The "synci" instructions (if
       enabled) are generated when "__builtin___clear_cache" is compiled.

       This option defaults to -mno-synci, but the default can be
       overridden by configuring GCC with --with-synci.

       When compiling code for single processor systems, it is generally
       safe to use "synci".  However, on many multi-core (SMP) systems, it
       does not invalidate the instruction caches on all cores and may
       lead to undefined behavior.

   -mrelax-pic-calls
   -mno-relax-pic-calls
       Try to turn PIC calls that are normally dispatched via register $25
       into direct calls.  This is only possible if the linker can resolve
       the destination at link time and if the destination is within range
       for a direct call.

       -mrelax-pic-calls is the default if GCC was configured to use an
       assembler and a linker that support the ".reloc" assembly directive
       and -mexplicit-relocs is in effect.  With -mno-explicit-relocs,
       this optimization can be performed by the assembler and the linker
       alone without help from the compiler.

   -mmcount-ra-address
   -mno-mcount-ra-address
       Emit (do not emit) code that allows "_mcount" to modify the calling
       function's return address.  When enabled, this option extends the
       usual "_mcount" interface with a new ra-address parameter, which
       has type "intptr_t *" and is passed in register $12.  "_mcount" can
       then modify the return address by doing both of the following:

       *   Returning the new address in register $31.

       *   Storing the new address in "*ra-address", if ra-address is
           nonnull.

       The default is -mno-mcount-ra-address.

   -mframe-header-opt
   -mno-frame-header-opt
       Enable (disable) frame header optimization in the o32 ABI.  When
       using the o32 ABI, calling functions will allocate 16 bytes on the
       stack for the called function to write out register arguments.
       When enabled, this optimization will suppress the allocation of the
       frame header if it can be determined that it is unused.

       This optimization is off by default at all optimization levels.

   MMIX Options

   These options are defined for the MMIX:

   -mlibfuncs
   -mno-libfuncs
       Specify that intrinsic library functions are being compiled,
       passing all values in registers, no matter the size.

   -mepsilon
   -mno-epsilon
       Generate floating-point comparison instructions that compare with
       respect to the "rE" epsilon register.

   -mabi=mmixware
   -mabi=gnu
       Generate code that passes function parameters and return values
       that (in the called function) are seen as registers $0 and up, as
       opposed to the GNU ABI which uses global registers $231 and up.

   -mzero-extend
   -mno-zero-extend
       When reading data from memory in sizes shorter than 64 bits, use
       (do not use) zero-extending load instructions by default, rather
       than sign-extending ones.

   -mknuthdiv
   -mno-knuthdiv
       Make the result of a division yielding a remainder have the same
       sign as the divisor.  With the default, -mno-knuthdiv, the sign of
       the remainder follows the sign of the dividend.  Both methods are
       arithmetically valid, the latter being almost exclusively used.

   -mtoplevel-symbols
   -mno-toplevel-symbols
       Prepend (do not prepend) a : to all global symbols, so the assembly
       code can be used with the "PREFIX" assembly directive.

   -melf
       Generate an executable in the ELF format, rather than the default
       mmo format used by the mmix simulator.

   -mbranch-predict
   -mno-branch-predict
       Use (do not use) the probable-branch instructions, when static
       branch prediction indicates a probable branch.

   -mbase-addresses
   -mno-base-addresses
       Generate (do not generate) code that uses base addresses.  Using a
       base address automatically generates a request (handled by the
       assembler and the linker) for a constant to be set up in a global
       register.  The register is used for one or more base address
       requests within the range 0 to 255 from the value held in the
       register.  The generally leads to short and fast code, but the
       number of different data items that can be addressed is limited.
       This means that a program that uses lots of static data may require
       -mno-base-addresses.

   -msingle-exit
   -mno-single-exit
       Force (do not force) generated code to have a single exit point in
       each function.

   MN10300 Options

   These -m options are defined for Matsushita MN10300 architectures:

   -mmult-bug
       Generate code to avoid bugs in the multiply instructions for the
       MN10300 processors.  This is the default.

   -mno-mult-bug
       Do not generate code to avoid bugs in the multiply instructions for
       the MN10300 processors.

   -mam33
       Generate code using features specific to the AM33 processor.

   -mno-am33
       Do not generate code using features specific to the AM33 processor.
       This is the default.

   -mam33-2
       Generate code using features specific to the AM33/2.0 processor.

   -mam34
       Generate code using features specific to the AM34 processor.

   -mtune=cpu-type
       Use the timing characteristics of the indicated CPU type when
       scheduling instructions.  This does not change the targeted
       processor type.  The CPU type must be one of mn10300, am33, am33-2
       or am34.

   -mreturn-pointer-on-d0
       When generating a function that returns a pointer, return the
       pointer in both "a0" and "d0".  Otherwise, the pointer is returned
       only in "a0", and attempts to call such functions without a
       prototype result in errors.  Note that this option is on by
       default; use -mno-return-pointer-on-d0 to disable it.

   -mno-crt0
       Do not link in the C run-time initialization object file.

   -mrelax
       Indicate to the linker that it should perform a relaxation
       optimization pass to shorten branches, calls and absolute memory
       addresses.  This option only has an effect when used on the command
       line for the final link step.

       This option makes symbolic debugging impossible.

   -mliw
       Allow the compiler to generate Long Instruction Word instructions
       if the target is the AM33 or later.  This is the default.  This
       option defines the preprocessor macro "__LIW__".

   -mnoliw
       Do not allow the compiler to generate Long Instruction Word
       instructions.  This option defines the preprocessor macro
       "__NO_LIW__".

   -msetlb
       Allow the compiler to generate the SETLB and Lcc instructions if
       the target is the AM33 or later.  This is the default.  This option
       defines the preprocessor macro "__SETLB__".

   -mnosetlb
       Do not allow the compiler to generate SETLB or Lcc instructions.
       This option defines the preprocessor macro "__NO_SETLB__".

   Moxie Options

   -meb
       Generate big-endian code.  This is the default for moxie-*-*
       configurations.

   -mel
       Generate little-endian code.

   -mmul.x
       Generate mul.x and umul.x instructions.  This is the default for
       moxiebox-*-* configurations.

   -mno-crt0
       Do not link in the C run-time initialization object file.

   MSP430 Options

   These options are defined for the MSP430:

   -masm-hex
       Force assembly output to always use hex constants.  Normally such
       constants are signed decimals, but this option is available for
       testsuite and/or aesthetic purposes.

   -mmcu=
       Select the MCU to target.  This is used to create a C preprocessor
       symbol based upon the MCU name, converted to upper case and pre-
       and post-fixed with __.  This in turn is used by the msp430.h
       header file to select an MCU-specific supplementary header file.

       The option also sets the ISA to use.  If the MCU name is one that
       is known to only support the 430 ISA then that is selected,
       otherwise the 430X ISA is selected.  A generic MCU name of msp430
       can also be used to select the 430 ISA.  Similarly the generic
       msp430x MCU name selects the 430X ISA.

       In addition an MCU-specific linker script is added to the linker
       command line.  The script's name is the name of the MCU with .ld
       appended.  Thus specifying -mmcu=xxx on the gcc command line
       defines the C preprocessor symbol "__XXX__" and cause the linker to
       search for a script called xxx.ld.

       This option is also passed on to the assembler.

   -mwarn-mcu
   -mno-warn-mcu
       This option enables or disables warnings about conflicts between
       the MCU name specified by the -mmcu option and the ISA set by the
       -mcpu option and/or the hardware multiply support set by the
       -mhwmult option.  It also toggles warnings about unrecognized MCU
       names.  This option is on by default.

   -mcpu=
       Specifies the ISA to use.  Accepted values are msp430, msp430x and
       msp430xv2.  This option is deprecated.  The -mmcu= option should be
       used to select the ISA.

   -msim
       Link to the simulator runtime libraries and linker script.
       Overrides any scripts that would be selected by the -mmcu= option.

   -mlarge
       Use large-model addressing (20-bit pointers, 32-bit "size_t").

   -msmall
       Use small-model addressing (16-bit pointers, 16-bit "size_t").

   -mrelax
       This option is passed to the assembler and linker, and allows the
       linker to perform certain optimizations that cannot be done until
       the final link.

   mhwmult=
       Describes the type of hardware multiply supported by the target.
       Accepted values are none for no hardware multiply, 16bit for the
       original 16-bit-only multiply supported by early MCUs.  32bit for
       the 16/32-bit multiply supported by later MCUs and f5series for the
       16/32-bit multiply supported by F5-series MCUs.  A value of auto
       can also be given.  This tells GCC to deduce the hardware multiply
       support based upon the MCU name provided by the -mmcu option.  If
       no -mmcu option is specified or if the MCU name is not recognized
       then no hardware multiply support is assumed.  "auto" is the
       default setting.

       Hardware multiplies are normally performed by calling a library
       routine.  This saves space in the generated code.  When compiling
       at -O3 or higher however the hardware multiplier is invoked inline.
       This makes for bigger, but faster code.

       The hardware multiply routines disable interrupts whilst running
       and restore the previous interrupt state when they finish.  This
       makes them safe to use inside interrupt handlers as well as in
       normal code.

   -minrt
       Enable the use of a minimum runtime environment - no static
       initializers or constructors.  This is intended for memory-
       constrained devices.  The compiler includes special symbols in some
       objects that tell the linker and runtime which code fragments are
       required.

   -mcode-region=
   -mdata-region=
       These options tell the compiler where to place functions and data
       that do not have one of the "lower", "upper", "either" or "section"
       attributes.  Possible values are "lower", "upper", "either" or
       "any".  The first three behave like the corresponding attribute.
       The fourth possible value - "any" - is the default.  It leaves
       placement entirely up to the linker script and how it assigns the
       standard sections (".text", ".data", etc) to the memory regions.

   -msilicon-errata=
       This option passes on a request to assembler to enable the fixes
       for the named silicon errata.

   -msilicon-errata-warn=
       This option passes on a request to the assembler to enable warning
       messages when a silicon errata might need to be applied.

   NDS32 Options

   These options are defined for NDS32 implementations:

   -mbig-endian
       Generate code in big-endian mode.

   -mlittle-endian
       Generate code in little-endian mode.

   -mreduced-regs
       Use reduced-set registers for register allocation.

   -mfull-regs
       Use full-set registers for register allocation.

   -mcmov
       Generate conditional move instructions.

   -mno-cmov
       Do not generate conditional move instructions.

   -mperf-ext
       Generate performance extension instructions.

   -mno-perf-ext
       Do not generate performance extension instructions.

   -mv3push
       Generate v3 push25/pop25 instructions.

   -mno-v3push
       Do not generate v3 push25/pop25 instructions.

   -m16-bit
       Generate 16-bit instructions.

   -mno-16-bit
       Do not generate 16-bit instructions.

   -misr-vector-size=num
       Specify the size of each interrupt vector, which must be 4 or 16.

   -mcache-block-size=num
       Specify the size of each cache block, which must be a power of 2
       between 4 and 512.

   -march=arch
       Specify the name of the target architecture.

   -mcmodel=code-model
       Set the code model to one of

       small
           All the data and read-only data segments must be within 512KB
           addressing space.  The text segment must be within 16MB
           addressing space.

       medium
           The data segment must be within 512KB while the read-only data
           segment can be within 4GB addressing space.  The text segment
           should be still within 16MB addressing space.

       large
           All the text and data segments can be within 4GB addressing
           space.

   -mctor-dtor
       Enable constructor/destructor feature.

   -mrelax
       Guide linker to relax instructions.

   Nios II Options

   These are the options defined for the Altera Nios II processor.

   -G num
       Put global and static objects less than or equal to num bytes into
       the small data or BSS sections instead of the normal data or BSS
       sections.  The default value of num is 8.

   -mgpopt=option
   -mgpopt
   -mno-gpopt
       Generate (do not generate) GP-relative accesses.  The following
       option names are recognized:

       none
           Do not generate GP-relative accesses.

       local
           Generate GP-relative accesses for small data objects that are
           not external, weak, or uninitialized common symbols.  Also use
           GP-relative addressing for objects that have been explicitly
           placed in a small data section via a "section" attribute.

       global
           As for local, but also generate GP-relative accesses for small
           data objects that are external, weak, or common.  If you use
           this option, you must ensure that all parts of your program
           (including libraries) are compiled with the same -G setting.

       data
           Generate GP-relative accesses for all data objects in the
           program.  If you use this option, the entire data and BSS
           segments of your program must fit in 64K of memory and you must
           use an appropriate linker script to allocate them within the
           addressable range of the global pointer.

       all Generate GP-relative addresses for function pointers as well as
           data pointers.  If you use this option, the entire text, data,
           and BSS segments of your program must fit in 64K of memory and
           you must use an appropriate linker script to allocate them
           within the addressable range of the global pointer.

       -mgpopt is equivalent to -mgpopt=local, and -mno-gpopt is
       equivalent to -mgpopt=none.

       The default is -mgpopt except when -fpic or -fPIC is specified to
       generate position-independent code.  Note that the Nios II ABI does
       not permit GP-relative accesses from shared libraries.

       You may need to specify -mno-gpopt explicitly when building
       programs that include large amounts of small data, including large
       GOT data sections.  In this case, the 16-bit offset for GP-relative
       addressing may not be large enough to allow access to the entire
       small data section.

   -mel
   -meb
       Generate little-endian (default) or big-endian (experimental) code,
       respectively.

   -march=arch
       This specifies the name of the target Nios II architecture.  GCC
       uses this name to determine what kind of instructions it can emit
       when generating assembly code.  Permissible names are: r1, r2.

       The preprocessor macro "__nios2_arch__" is available to programs,
       with value 1 or 2, indicating the targeted ISA level.

   -mbypass-cache
   -mno-bypass-cache
       Force all load and store instructions to always bypass cache by
       using I/O variants of the instructions. The default is not to
       bypass the cache.

   -mno-cache-volatile
   -mcache-volatile
       Volatile memory access bypass the cache using the I/O variants of
       the load and store instructions. The default is not to bypass the
       cache.

   -mno-fast-sw-div
   -mfast-sw-div
       Do not use table-based fast divide for small numbers. The default
       is to use the fast divide at -O3 and above.

   -mno-hw-mul
   -mhw-mul
   -mno-hw-mulx
   -mhw-mulx
   -mno-hw-div
   -mhw-div
       Enable or disable emitting "mul", "mulx" and "div" family of
       instructions by the compiler. The default is to emit "mul" and not
       emit "div" and "mulx".

   -mbmx
   -mno-bmx
   -mcdx
   -mno-cdx
       Enable or disable generation of Nios II R2 BMX (bit manipulation)
       and CDX (code density) instructions.  Enabling these instructions
       also requires -march=r2.  Since these instructions are optional
       extensions to the R2 architecture, the default is not to emit them.

   -mcustom-insn=N
   -mno-custom-insn
       Each -mcustom-insn=N option enables use of a custom instruction
       with encoding N when generating code that uses insn.  For example,
       -mcustom-fadds=253 generates custom instruction 253 for single-
       precision floating-point add operations instead of the default
       behavior of using a library call.

       The following values of insn are supported.  Except as otherwise
       noted, floating-point operations are expected to be implemented
       with normal IEEE 754 semantics and correspond directly to the C
       operators or the equivalent GCC built-in functions.

       Single-precision floating point:

       fadds, fsubs, fdivs, fmuls
           Binary arithmetic operations.

       fnegs
           Unary negation.

       fabss
           Unary absolute value.

       fcmpeqs, fcmpges, fcmpgts, fcmples, fcmplts, fcmpnes
           Comparison operations.

       fmins, fmaxs
           Floating-point minimum and maximum.  These instructions are
           only generated if -ffinite-math-only is specified.

       fsqrts
           Unary square root operation.

       fcoss, fsins, ftans, fatans, fexps, flogs
           Floating-point trigonometric and exponential functions.  These
           instructions are only generated if -funsafe-math-optimizations
           is also specified.

       Double-precision floating point:

       faddd, fsubd, fdivd, fmuld
           Binary arithmetic operations.

       fnegd
           Unary negation.

       fabsd
           Unary absolute value.

       fcmpeqd, fcmpged, fcmpgtd, fcmpled, fcmpltd, fcmpned
           Comparison operations.

       fmind, fmaxd
           Double-precision minimum and maximum.  These instructions are
           only generated if -ffinite-math-only is specified.

       fsqrtd
           Unary square root operation.

       fcosd, fsind, ftand, fatand, fexpd, flogd
           Double-precision trigonometric and exponential functions.
           These instructions are only generated if
           -funsafe-math-optimizations is also specified.

       Conversions:

       fextsd
           Conversion from single precision to double precision.

       ftruncds
           Conversion from double precision to single precision.

       fixsi, fixsu, fixdi, fixdu
           Conversion from floating point to signed or unsigned integer
           types, with truncation towards zero.

       round
           Conversion from single-precision floating point to signed
           integer, rounding to the nearest integer and ties away from
           zero.  This corresponds to the "__builtin_lroundf" function
           when -fno-math-errno is used.

       floatis, floatus, floatid, floatud
           Conversion from signed or unsigned integer types to floating-
           point types.

       In addition, all of the following transfer instructions for
       internal registers X and Y must be provided to use any of the
       double-precision floating-point instructions.  Custom instructions
       taking two double-precision source operands expect the first
       operand in the 64-bit register X.  The other operand (or only
       operand of a unary operation) is given to the custom arithmetic
       instruction with the least significant half in source register src1
       and the most significant half in src2.  A custom instruction that
       returns a double-precision result returns the most significant 32
       bits in the destination register and the other half in 32-bit
       register Y.  GCC automatically generates the necessary code
       sequences to write register X and/or read register Y when double-
       precision floating-point instructions are used.

       fwrx
           Write src1 into the least significant half of X and src2 into
           the most significant half of X.

       fwry
           Write src1 into Y.

       frdxhi, frdxlo
           Read the most or least (respectively) significant half of X and
           store it in dest.

       frdy
           Read the value of Y and store it into dest.

       Note that you can gain more local control over generation of Nios
       II custom instructions by using the "target("custom-insn=N")" and
       "target("no-custom-insn")" function attributes or pragmas.

   -mcustom-fpu-cfg=name
       This option enables a predefined, named set of custom instruction
       encodings (see -mcustom-insn above).  Currently, the following sets
       are defined:

       -mcustom-fpu-cfg=60-1 is equivalent to: -mcustom-fmuls=252
       -mcustom-fadds=253 -mcustom-fsubs=254 -fsingle-precision-constant

       -mcustom-fpu-cfg=60-2 is equivalent to: -mcustom-fmuls=252
       -mcustom-fadds=253 -mcustom-fsubs=254 -mcustom-fdivs=255
       -fsingle-precision-constant

       -mcustom-fpu-cfg=72-3 is equivalent to: -mcustom-floatus=243
       -mcustom-fixsi=244 -mcustom-floatis=245 -mcustom-fcmpgts=246
       -mcustom-fcmples=249 -mcustom-fcmpeqs=250 -mcustom-fcmpnes=251
       -mcustom-fmuls=252 -mcustom-fadds=253 -mcustom-fsubs=254
       -mcustom-fdivs=255 -fsingle-precision-constant

       Custom instruction assignments given by individual -mcustom-insn=
       options override those given by -mcustom-fpu-cfg=, regardless of
       the order of the options on the command line.

       Note that you can gain more local control over selection of a FPU
       configuration by using the "target("custom-fpu-cfg=name")" function
       attribute or pragma.

   These additional -m options are available for the Altera Nios II ELF
   (bare-metal) target:

   -mhal
       Link with HAL BSP.  This suppresses linking with the GCC-provided C
       runtime startup and termination code, and is typically used in
       conjunction with -msys-crt0= to specify the location of the
       alternate startup code provided by the HAL BSP.

   -msmallc
       Link with a limited version of the C library, -lsmallc, rather than
       Newlib.

   -msys-crt0=startfile
       startfile is the file name of the startfile (crt0) to use when
       linking.  This option is only useful in conjunction with -mhal.

   -msys-lib=systemlib
       systemlib is the library name of the library that provides low-
       level system calls required by the C library, e.g. "read" and
       "write".  This option is typically used to link with a library
       provided by a HAL BSP.

   Nvidia PTX Options

   These options are defined for Nvidia PTX:

   -m32
   -m64
       Generate code for 32-bit or 64-bit ABI.

   -mmainkernel
       Link in code for a __main kernel.  This is for stand-alone instead
       of offloading execution.

   -moptimize
       Apply partitioned execution optimizations.  This is the default
       when any level of optimization is selected.

   PDP-11 Options

   These options are defined for the PDP-11:

   -mfpu
       Use hardware FPP floating point.  This is the default.  (FIS
       floating point on the PDP-11/40 is not supported.)

   -msoft-float
       Do not use hardware floating point.

   -mac0
       Return floating-point results in ac0 (fr0 in Unix assembler
       syntax).

   -mno-ac0
       Return floating-point results in memory.  This is the default.

   -m40
       Generate code for a PDP-11/40.

   -m45
       Generate code for a PDP-11/45.  This is the default.

   -m10
       Generate code for a PDP-11/10.

   -mbcopy-builtin
       Use inline "movmemhi" patterns for copying memory.  This is the
       default.

   -mbcopy
       Do not use inline "movmemhi" patterns for copying memory.

   -mint16
   -mno-int32
       Use 16-bit "int".  This is the default.

   -mint32
   -mno-int16
       Use 32-bit "int".

   -mfloat64
   -mno-float32
       Use 64-bit "float".  This is the default.

   -mfloat32
   -mno-float64
       Use 32-bit "float".

   -mabshi
       Use "abshi2" pattern.  This is the default.

   -mno-abshi
       Do not use "abshi2" pattern.

   -mbranch-expensive
       Pretend that branches are expensive.  This is for experimenting
       with code generation only.

   -mbranch-cheap
       Do not pretend that branches are expensive.  This is the default.

   -munix-asm
       Use Unix assembler syntax.  This is the default when configured for
       pdp11-*-bsd.

   -mdec-asm
       Use DEC assembler syntax.  This is the default when configured for
       any PDP-11 target other than pdp11-*-bsd.

   picoChip Options

   These -m options are defined for picoChip implementations:

   -mae=ae_type
       Set the instruction set, register set, and instruction scheduling
       parameters for array element type ae_type.  Supported values for
       ae_type are ANY, MUL, and MAC.

       -mae=ANY selects a completely generic AE type.  Code generated with
       this option runs on any of the other AE types.  The code is not as
       efficient as it would be if compiled for a specific AE type, and
       some types of operation (e.g., multiplication) do not work properly
       on all types of AE.

       -mae=MUL selects a MUL AE type.  This is the most useful AE type
       for compiled code, and is the default.

       -mae=MAC selects a DSP-style MAC AE.  Code compiled with this
       option may suffer from poor performance of byte (char)
       manipulation, since the DSP AE does not provide hardware support
       for byte load/stores.

   -msymbol-as-address
       Enable the compiler to directly use a symbol name as an address in
       a load/store instruction, without first loading it into a register.
       Typically, the use of this option generates larger programs, which
       run faster than when the option isn't used.  However, the results
       vary from program to program, so it is left as a user option,
       rather than being permanently enabled.

   -mno-inefficient-warnings
       Disables warnings about the generation of inefficient code.  These
       warnings can be generated, for example, when compiling code that
       performs byte-level memory operations on the MAC AE type.  The MAC
       AE has no hardware support for byte-level memory operations, so all
       byte load/stores must be synthesized from word load/store
       operations.  This is inefficient and a warning is generated to
       indicate that you should rewrite the code to avoid byte operations,
       or to target an AE type that has the necessary hardware support.
       This option disables these warnings.

   PowerPC Options

   These are listed under

   RL78 Options

   -msim
       Links in additional target libraries to support operation within a
       simulator.

   -mmul=none
   -mmul=g10
   -mmul=g13
   -mmul=g14
   -mmul=rl78
       Specifies the type of hardware multiplication and division support
       to be used.  The simplest is "none", which uses software for both
       multiplication and division.  This is the default.  The "g13" value
       is for the hardware multiply/divide peripheral found on the
       RL78/G13 (S2 core) targets.  The "g14" value selects the use of the
       multiplication and division instructions supported by the RL78/G14
       (S3 core) parts.  The value "rl78" is an alias for "g14" and the
       value "mg10" is an alias for "none".

       In addition a C preprocessor macro is defined, based upon the
       setting of this option.  Possible values are: "__RL78_MUL_NONE__",
       "__RL78_MUL_G13__" or "__RL78_MUL_G14__".

   -mcpu=g10
   -mcpu=g13
   -mcpu=g14
   -mcpu=rl78
       Specifies the RL78 core to target.  The default is the G14 core,
       also known as an S3 core or just RL78.  The G13 or S2 core does not
       have multiply or divide instructions, instead it uses a hardware
       peripheral for these operations.  The G10 or S1 core does not have
       register banks, so it uses a different calling convention.

       If this option is set it also selects the type of hardware multiply
       support to use, unless this is overridden by an explicit -mmul=none
       option on the command line.  Thus specifying -mcpu=g13 enables the
       use of the G13 hardware multiply peripheral and specifying
       -mcpu=g10 disables the use of hardware multiplications altogether.

       Note, although the RL78/G14 core is the default target, specifying
       -mcpu=g14 or -mcpu=rl78 on the command line does change the
       behavior of the toolchain since it also enables G14 hardware
       multiply support.  If these options are not specified on the
       command line then software multiplication routines will be used
       even though the code targets the RL78 core.  This is for backwards
       compatibility with older toolchains which did not have hardware
       multiply and divide support.

       In addition a C preprocessor macro is defined, based upon the
       setting of this option.  Possible values are: "__RL78_G10__",
       "__RL78_G13__" or "__RL78_G14__".

   -mg10
   -mg13
   -mg14
   -mrl78
       These are aliases for the corresponding -mcpu= option.  They are
       provided for backwards compatibility.

   -mallregs
       Allow the compiler to use all of the available registers.  By
       default registers "r24..r31" are reserved for use in interrupt
       handlers.  With this option enabled these registers can be used in
       ordinary functions as well.

   -m64bit-doubles
   -m32bit-doubles
       Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits
       (-m32bit-doubles) in size.  The default is -m32bit-doubles.

   IBM RS/6000 and PowerPC Options

   These -m options are defined for the IBM RS/6000 and PowerPC:

   -mpowerpc-gpopt
   -mno-powerpc-gpopt
   -mpowerpc-gfxopt
   -mno-powerpc-gfxopt
   -mpowerpc64
   -mno-powerpc64
   -mmfcrf
   -mno-mfcrf
   -mpopcntb
   -mno-popcntb
   -mpopcntd
   -mno-popcntd
   -mfprnd
   -mno-fprnd
   -mcmpb
   -mno-cmpb
   -mmfpgpr
   -mno-mfpgpr
   -mhard-dfp
   -mno-hard-dfp
       You use these options to specify which instructions are available
       on the processor you are using.  The default value of these options
       is determined when configuring GCC.  Specifying the -mcpu=cpu_type
       overrides the specification of these options.  We recommend you use
       the -mcpu=cpu_type option rather than the options listed above.

       Specifying -mpowerpc-gpopt allows GCC to use the optional PowerPC
       architecture instructions in the General Purpose group, including
       floating-point square root.  Specifying -mpowerpc-gfxopt allows GCC
       to use the optional PowerPC architecture instructions in the
       Graphics group, including floating-point select.

       The -mmfcrf option allows GCC to generate the move from condition
       register field instruction implemented on the POWER4 processor and
       other processors that support the PowerPC V2.01 architecture.  The
       -mpopcntb option allows GCC to generate the popcount and double-
       precision FP reciprocal estimate instruction implemented on the
       POWER5 processor and other processors that support the PowerPC
       V2.02 architecture.  The -mpopcntd option allows GCC to generate
       the popcount instruction implemented on the POWER7 processor and
       other processors that support the PowerPC V2.06 architecture.  The
       -mfprnd option allows GCC to generate the FP round to integer
       instructions implemented on the POWER5+ processor and other
       processors that support the PowerPC V2.03 architecture.  The -mcmpb
       option allows GCC to generate the compare bytes instruction
       implemented on the POWER6 processor and other processors that
       support the PowerPC V2.05 architecture.  The -mmfpgpr option allows
       GCC to generate the FP move to/from general-purpose register
       instructions implemented on the POWER6X processor and other
       processors that support the extended PowerPC V2.05 architecture.
       The -mhard-dfp option allows GCC to generate the decimal floating-
       point instructions implemented on some POWER processors.

       The -mpowerpc64 option allows GCC to generate the additional 64-bit
       instructions that are found in the full PowerPC64 architecture and
       to treat GPRs as 64-bit, doubleword quantities.  GCC defaults to
       -mno-powerpc64.

   -mcpu=cpu_type
       Set architecture type, register usage, and instruction scheduling
       parameters for machine type cpu_type.  Supported values for
       cpu_type are 401, 403, 405, 405fp, 440, 440fp, 464, 464fp, 476,
       476fp, 505, 601, 602, 603, 603e, 604, 604e, 620, 630, 740, 7400,
       7450, 750, 801, 821, 823, 860, 970, 8540, a2, e300c2, e300c3,
       e500mc, e500mc64, e5500, e6500, ec603e, G3, G4, G5, titan, power3,
       power4, power5, power5+, power6, power6x, power7, power8, power9,
       powerpc, powerpc64, powerpc64le, and rs64.

       -mcpu=powerpc, -mcpu=powerpc64, and -mcpu=powerpc64le specify pure
       32-bit PowerPC (either endian), 64-bit big endian PowerPC and
       64-bit little endian PowerPC architecture machine types, with an
       appropriate, generic processor model assumed for scheduling
       purposes.

       The other options specify a specific processor.  Code generated
       under those options runs best on that processor, and may not run at
       all on others.

       The -mcpu options automatically enable or disable the following
       options:

       -maltivec  -mfprnd  -mhard-float  -mmfcrf  -mmultiple -mpopcntb
       -mpopcntd  -mpowerpc64 -mpowerpc-gpopt  -mpowerpc-gfxopt
       -msingle-float -mdouble-float -msimple-fpu -mstring  -mmulhw
       -mdlmzb  -mmfpgpr -mvsx -mcrypto -mdirect-move -mhtm
       -mpower8-fusion -mpower8-vector -mquad-memory -mquad-memory-atomic
       -mmodulo -mfloat128 -mfloat128-hardware -mpower9-fusion
       -mpower9-vector -mpower9-dform

       The particular options set for any particular CPU varies between
       compiler versions, depending on what setting seems to produce
       optimal code for that CPU; it doesn't necessarily reflect the
       actual hardware's capabilities.  If you wish to set an individual
       option to a particular value, you may specify it after the -mcpu
       option, like -mcpu=970 -mno-altivec.

       On AIX, the -maltivec and -mpowerpc64 options are not enabled or
       disabled by the -mcpu option at present because AIX does not have
       full support for these options.  You may still enable or disable
       them individually if you're sure it'll work in your environment.

   -mtune=cpu_type
       Set the instruction scheduling parameters for machine type
       cpu_type, but do not set the architecture type or register usage,
       as -mcpu=cpu_type does.  The same values for cpu_type are used for
       -mtune as for -mcpu.  If both are specified, the code generated
       uses the architecture and registers set by -mcpu, but the
       scheduling parameters set by -mtune.

   -mcmodel=small
       Generate PowerPC64 code for the small model: The TOC is limited to
       64k.

   -mcmodel=medium
       Generate PowerPC64 code for the medium model: The TOC and other
       static data may be up to a total of 4G in size.

   -mcmodel=large
       Generate PowerPC64 code for the large model: The TOC may be up to
       4G in size.  Other data and code is only limited by the 64-bit
       address space.

   -maltivec
   -mno-altivec
       Generate code that uses (does not use) AltiVec instructions, and
       also enable the use of built-in functions that allow more direct
       access to the AltiVec instruction set.  You may also need to set
       -mabi=altivec to adjust the current ABI with AltiVec ABI
       enhancements.

       When -maltivec is used, rather than -maltivec=le or -maltivec=be,
       the element order for AltiVec intrinsics such as "vec_splat",
       "vec_extract", and "vec_insert" match array element order
       corresponding to the endianness of the target.  That is, element
       zero identifies the leftmost element in a vector register when
       targeting a big-endian platform, and identifies the rightmost
       element in a vector register when targeting a little-endian
       platform.

   -maltivec=be
       Generate AltiVec instructions using big-endian element order,
       regardless of whether the target is big- or little-endian.  This is
       the default when targeting a big-endian platform.

       The element order is used to interpret element numbers in AltiVec
       intrinsics such as "vec_splat", "vec_extract", and "vec_insert".
       By default, these match array element order corresponding to the
       endianness for the target.

   -maltivec=le
       Generate AltiVec instructions using little-endian element order,
       regardless of whether the target is big- or little-endian.  This is
       the default when targeting a little-endian platform.  This option
       is currently ignored when targeting a big-endian platform.

       The element order is used to interpret element numbers in AltiVec
       intrinsics such as "vec_splat", "vec_extract", and "vec_insert".
       By default, these match array element order corresponding to the
       endianness for the target.

   -mvrsave
   -mno-vrsave
       Generate VRSAVE instructions when generating AltiVec code.

   -mgen-cell-microcode
       Generate Cell microcode instructions.

   -mwarn-cell-microcode
       Warn when a Cell microcode instruction is emitted.  An example of a
       Cell microcode instruction is a variable shift.

   -msecure-plt
       Generate code that allows ld and ld.so to build executables and
       shared libraries with non-executable ".plt" and ".got" sections.
       This is a PowerPC 32-bit SYSV ABI option.

   -mbss-plt
       Generate code that uses a BSS ".plt" section that ld.so fills in,
       and requires ".plt" and ".got" sections that are both writable and
       executable.  This is a PowerPC 32-bit SYSV ABI option.

   -misel
   -mno-isel
       This switch enables or disables the generation of ISEL
       instructions.

   -misel=yes/no
       This switch has been deprecated.  Use -misel and -mno-isel instead.

   -mlra
       Enable Local Register Allocation.  This is still experimental for
       PowerPC, so by default the compiler uses standard reload (i.e.
       -mno-lra).

   -mspe
   -mno-spe
       This switch enables or disables the generation of SPE simd
       instructions.

   -mpaired
   -mno-paired
       This switch enables or disables the generation of PAIRED simd
       instructions.

   -mspe=yes/no
       This option has been deprecated.  Use -mspe and -mno-spe instead.

   -mvsx
   -mno-vsx
       Generate code that uses (does not use) vector/scalar (VSX)
       instructions, and also enable the use of built-in functions that
       allow more direct access to the VSX instruction set.

   -mcrypto
   -mno-crypto
       Enable the use (disable) of the built-in functions that allow
       direct access to the cryptographic instructions that were added in
       version 2.07 of the PowerPC ISA.

   -mdirect-move
   -mno-direct-move
       Generate code that uses (does not use) the instructions to move
       data between the general purpose registers and the vector/scalar
       (VSX) registers that were added in version 2.07 of the PowerPC ISA.

   -mhtm
   -mno-htm
       Enable (disable) the use of the built-in functions that allow
       direct access to the Hardware Transactional Memory (HTM)
       instructions that were added in version 2.07 of the PowerPC ISA.

   -mpower8-fusion
   -mno-power8-fusion
       Generate code that keeps (does not keeps) some integer operations
       adjacent so that the instructions can be fused together on power8
       and later processors.

   -mpower8-vector
   -mno-power8-vector
       Generate code that uses (does not use) the vector and scalar
       instructions that were added in version 2.07 of the PowerPC ISA.
       Also enable the use of built-in functions that allow more direct
       access to the vector instructions.

   -mquad-memory
   -mno-quad-memory
       Generate code that uses (does not use) the non-atomic quad word
       memory instructions.  The -mquad-memory option requires use of
       64-bit mode.

   -mquad-memory-atomic
   -mno-quad-memory-atomic
       Generate code that uses (does not use) the atomic quad word memory
       instructions.  The -mquad-memory-atomic option requires use of
       64-bit mode.

   -mupper-regs-df
   -mno-upper-regs-df
       Generate code that uses (does not use) the scalar double precision
       instructions that target all 64 registers in the vector/scalar
       floating point register set that were added in version 2.06 of the
       PowerPC ISA.  -mupper-regs-df is turned on by default if you use
       any of the -mcpu=power7, -mcpu=power8, or -mvsx options.

   -mupper-regs-sf
   -mno-upper-regs-sf
       Generate code that uses (does not use) the scalar single precision
       instructions that target all 64 registers in the vector/scalar
       floating point register set that were added in version 2.07 of the
       PowerPC ISA.  -mupper-regs-sf is turned on by default if you use
       either of the -mcpu=power8 or -mpower8-vector options.

   -mupper-regs
   -mno-upper-regs
       Generate code that uses (does not use) the scalar instructions that
       target all 64 registers in the vector/scalar floating point
       register set, depending on the model of the machine.

       If the -mno-upper-regs option is used, it turns off both
       -mupper-regs-sf and -mupper-regs-df options.

   -mfloat128
   -mno-float128
       Enable/disable the __float128 keyword for IEEE 128-bit floating
       point and use either software emulation for IEEE 128-bit floating
       point or hardware instructions.

       The VSX instruction set (-mvsx, -mcpu=power7, or -mcpu=power8) must
       be enabled to use the -mfloat128 option.  The -mfloat128 option
       only works on PowerPC 64-bit Linux systems.

       If you use the ISA 3.0 instruction set (-mcpu=power9), the
       -mfloat128 option will also enable the generation of ISA 3.0 IEEE
       128-bit floating point instructions.  Otherwise, IEEE 128-bit
       floating point will be done with software emulation.

   -mfloat128-hardware
   -mno-float128-hardware
       Enable/disable using ISA 3.0 hardware instructions to support the
       __float128 data type.

       If you use -mfloat128-hardware, it will enable the option
       -mfloat128 as well.

       If you select ISA 3.0 instructions with -mcpu=power9, but do not
       use either -mfloat128 or -mfloat128-hardware, the IEEE 128-bit
       floating point support will not be enabled.

   -mmodulo
   -mno-modulo
       Generate code that uses (does not use) the ISA 3.0 integer modulo
       instructions.  The -mmodulo option is enabled by default with the
       -mcpu=power9 option.

   -mpower9-fusion
   -mno-power9-fusion
       Generate code that keeps (does not keeps) some operations adjacent
       so that the instructions can be fused together on power9 and later
       processors.

   -mpower9-vector
   -mno-power9-vector
       Generate code that uses (does not use) the vector and scalar
       instructions that were added in version 3.0 of the PowerPC ISA.
       Also enable the use of built-in functions that allow more direct
       access to the vector instructions.

   -mpower9-dform
   -mno-power9-dform
       Enable (disable) scalar d-form (register + offset) memory
       instructions to load/store traditional Altivec registers. If the
       LRA register allocator is enabled, also enable (disable) vector
       d-form memory instructions.

   -mfloat-gprs=yes/single/double/no
   -mfloat-gprs
       This switch enables or disables the generation of floating-point
       operations on the general-purpose registers for architectures that
       support it.

       The argument yes or single enables the use of single-precision
       floating-point operations.

       The argument double enables the use of single and double-precision
       floating-point operations.

       The argument no disables floating-point operations on the general-
       purpose registers.

       This option is currently only available on the MPC854x.

   -m32
   -m64
       Generate code for 32-bit or 64-bit environments of Darwin and SVR4
       targets (including GNU/Linux).  The 32-bit environment sets int,
       long and pointer to 32 bits and generates code that runs on any
       PowerPC variant.  The 64-bit environment sets int to 32 bits and
       long and pointer to 64 bits, and generates code for PowerPC64, as
       for -mpowerpc64.

   -mfull-toc
   -mno-fp-in-toc
   -mno-sum-in-toc
   -mminimal-toc
       Modify generation of the TOC (Table Of Contents), which is created
       for every executable file.  The -mfull-toc option is selected by
       default.  In that case, GCC allocates at least one TOC entry for
       each unique non-automatic variable reference in your program.  GCC
       also places floating-point constants in the TOC.  However, only
       16,384 entries are available in the TOC.

       If you receive a linker error message that saying you have
       overflowed the available TOC space, you can reduce the amount of
       TOC space used with the -mno-fp-in-toc and -mno-sum-in-toc options.
       -mno-fp-in-toc prevents GCC from putting floating-point constants
       in the TOC and -mno-sum-in-toc forces GCC to generate code to
       calculate the sum of an address and a constant at run time instead
       of putting that sum into the TOC.  You may specify one or both of
       these options.  Each causes GCC to produce very slightly slower and
       larger code at the expense of conserving TOC space.

       If you still run out of space in the TOC even when you specify both
       of these options, specify -mminimal-toc instead.  This option
       causes GCC to make only one TOC entry for every file.  When you
       specify this option, GCC produces code that is slower and larger
       but which uses extremely little TOC space.  You may wish to use
       this option only on files that contain less frequently-executed
       code.

   -maix64
   -maix32
       Enable 64-bit AIX ABI and calling convention: 64-bit pointers,
       64-bit "long" type, and the infrastructure needed to support them.
       Specifying -maix64 implies -mpowerpc64, while -maix32 disables the
       64-bit ABI and implies -mno-powerpc64.  GCC defaults to -maix32.

   -mxl-compat
   -mno-xl-compat
       Produce code that conforms more closely to IBM XL compiler
       semantics when using AIX-compatible ABI.  Pass floating-point
       arguments to prototyped functions beyond the register save area
       (RSA) on the stack in addition to argument FPRs.  Do not assume
       that most significant double in 128-bit long double value is
       properly rounded when comparing values and converting to double.
       Use XL symbol names for long double support routines.

       The AIX calling convention was extended but not initially
       documented to handle an obscure K&R C case of calling a function
       that takes the address of its arguments with fewer arguments than
       declared.  IBM XL compilers access floating-point arguments that do
       not fit in the RSA from the stack when a subroutine is compiled
       without optimization.  Because always storing floating-point
       arguments on the stack is inefficient and rarely needed, this
       option is not enabled by default and only is necessary when calling
       subroutines compiled by IBM XL compilers without optimization.

   -mpe
       Support IBM RS/6000 SP Parallel Environment (PE).  Link an
       application written to use message passing with special startup
       code to enable the application to run.  The system must have PE
       installed in the standard location (/usr/lpp/ppe.poe/), or the
       specs file must be overridden with the -specs= option to specify
       the appropriate directory location.  The Parallel Environment does
       not support threads, so the -mpe option and the -pthread option are
       incompatible.

   -malign-natural
   -malign-power
       On AIX, 32-bit Darwin, and 64-bit PowerPC GNU/Linux, the option
       -malign-natural overrides the ABI-defined alignment of larger
       types, such as floating-point doubles, on their natural size-based
       boundary.  The option -malign-power instructs GCC to follow the
       ABI-specified alignment rules.  GCC defaults to the standard
       alignment defined in the ABI.

       On 64-bit Darwin, natural alignment is the default, and
       -malign-power is not supported.

   -msoft-float
   -mhard-float
       Generate code that does not use (uses) the floating-point register
       set.  Software floating-point emulation is provided if you use the
       -msoft-float option, and pass the option to GCC when linking.

   -msingle-float
   -mdouble-float
       Generate code for single- or double-precision floating-point
       operations.  -mdouble-float implies -msingle-float.

   -msimple-fpu
       Do not generate "sqrt" and "div" instructions for hardware
       floating-point unit.

   -mfpu=name
       Specify type of floating-point unit.  Valid values for name are
       sp_lite (equivalent to -msingle-float -msimple-fpu), dp_lite
       (equivalent to -mdouble-float -msimple-fpu), sp_full (equivalent to
       -msingle-float), and dp_full (equivalent to -mdouble-float).

   -mxilinx-fpu
       Perform optimizations for the floating-point unit on Xilinx PPC
       405/440.

   -mmultiple
   -mno-multiple
       Generate code that uses (does not use) the load multiple word
       instructions and the store multiple word instructions.  These
       instructions are generated by default on POWER systems, and not
       generated on PowerPC systems.  Do not use -mmultiple on little-
       endian PowerPC systems, since those instructions do not work when
       the processor is in little-endian mode.  The exceptions are PPC740
       and PPC750 which permit these instructions in little-endian mode.

   -mstring
   -mno-string
       Generate code that uses (does not use) the load string instructions
       and the store string word instructions to save multiple registers
       and do small block moves.  These instructions are generated by
       default on POWER systems, and not generated on PowerPC systems.  Do
       not use -mstring on little-endian PowerPC systems, since those
       instructions do not work when the processor is in little-endian
       mode.  The exceptions are PPC740 and PPC750 which permit these
       instructions in little-endian mode.

   -mupdate
   -mno-update
       Generate code that uses (does not use) the load or store
       instructions that update the base register to the address of the
       calculated memory location.  These instructions are generated by
       default.  If you use -mno-update, there is a small window between
       the time that the stack pointer is updated and the address of the
       previous frame is stored, which means code that walks the stack
       frame across interrupts or signals may get corrupted data.

   -mavoid-indexed-addresses
   -mno-avoid-indexed-addresses
       Generate code that tries to avoid (not avoid) the use of indexed
       load or store instructions. These instructions can incur a
       performance penalty on Power6 processors in certain situations,
       such as when stepping through large arrays that cross a 16M
       boundary.  This option is enabled by default when targeting Power6
       and disabled otherwise.

   -mfused-madd
   -mno-fused-madd
       Generate code that uses (does not use) the floating-point multiply
       and accumulate instructions.  These instructions are generated by
       default if hardware floating point is used.  The machine-dependent
       -mfused-madd option is now mapped to the machine-independent
       -ffp-contract=fast option, and -mno-fused-madd is mapped to
       -ffp-contract=off.

   -mmulhw
   -mno-mulhw
       Generate code that uses (does not use) the half-word multiply and
       multiply-accumulate instructions on the IBM 405, 440, 464 and 476
       processors.  These instructions are generated by default when
       targeting those processors.

   -mdlmzb
   -mno-dlmzb
       Generate code that uses (does not use) the string-search dlmzb
       instruction on the IBM 405, 440, 464 and 476 processors.  This
       instruction is generated by default when targeting those
       processors.

   -mno-bit-align
   -mbit-align
       On System V.4 and embedded PowerPC systems do not (do) force
       structures and unions that contain bit-fields to be aligned to the
       base type of the bit-field.

       For example, by default a structure containing nothing but 8
       "unsigned" bit-fields of length 1 is aligned to a 4-byte boundary
       and has a size of 4 bytes.  By using -mno-bit-align, the structure
       is aligned to a 1-byte boundary and is 1 byte in size.

   -mno-strict-align
   -mstrict-align
       On System V.4 and embedded PowerPC systems do not (do) assume that
       unaligned memory references are handled by the system.

   -mrelocatable
   -mno-relocatable
       Generate code that allows (does not allow) a static executable to
       be relocated to a different address at run time.  A simple embedded
       PowerPC system loader should relocate the entire contents of
       ".got2" and 4-byte locations listed in the ".fixup" section, a
       table of 32-bit addresses generated by this option.  For this to
       work, all objects linked together must be compiled with
       -mrelocatable or -mrelocatable-lib.  -mrelocatable code aligns the
       stack to an 8-byte boundary.

   -mrelocatable-lib
   -mno-relocatable-lib
       Like -mrelocatable, -mrelocatable-lib generates a ".fixup" section
       to allow static executables to be relocated at run time, but
       -mrelocatable-lib does not use the smaller stack alignment of
       -mrelocatable.  Objects compiled with -mrelocatable-lib may be
       linked with objects compiled with any combination of the
       -mrelocatable options.

   -mno-toc
   -mtoc
       On System V.4 and embedded PowerPC systems do not (do) assume that
       register 2 contains a pointer to a global area pointing to the
       addresses used in the program.

   -mlittle
   -mlittle-endian
       On System V.4 and embedded PowerPC systems compile code for the
       processor in little-endian mode.  The -mlittle-endian option is the
       same as -mlittle.

   -mbig
   -mbig-endian
       On System V.4 and embedded PowerPC systems compile code for the
       processor in big-endian mode.  The -mbig-endian option is the same
       as -mbig.

   -mdynamic-no-pic
       On Darwin and Mac OS X systems, compile code so that it is not
       relocatable, but that its external references are relocatable.  The
       resulting code is suitable for applications, but not shared
       libraries.

   -msingle-pic-base
       Treat the register used for PIC addressing as read-only, rather
       than loading it in the prologue for each function.  The runtime
       system is responsible for initializing this register with an
       appropriate value before execution begins.

   -mprioritize-restricted-insns=priority
       This option controls the priority that is assigned to dispatch-slot
       restricted instructions during the second scheduling pass.  The
       argument priority takes the value 0, 1, or 2 to assign no, highest,
       or second-highest (respectively) priority to dispatch-slot
       restricted instructions.

   -msched-costly-dep=dependence_type
       This option controls which dependences are considered costly by the
       target during instruction scheduling.  The argument dependence_type
       takes one of the following values:

       no  No dependence is costly.

       all All dependences are costly.

       true_store_to_load
           A true dependence from store to load is costly.

       store_to_load
           Any dependence from store to load is costly.

       number
           Any dependence for which the latency is greater than or equal
           to number is costly.

   -minsert-sched-nops=scheme
       This option controls which NOP insertion scheme is used during the
       second scheduling pass.  The argument scheme takes one of the
       following values:

       no  Don't insert NOPs.

       pad Pad with NOPs any dispatch group that has vacant issue slots,
           according to the scheduler's grouping.

       regroup_exact
           Insert NOPs to force costly dependent insns into separate
           groups.  Insert exactly as many NOPs as needed to force an insn
           to a new group, according to the estimated processor grouping.

       number
           Insert NOPs to force costly dependent insns into separate
           groups.  Insert number NOPs to force an insn to a new group.

   -mcall-sysv
       On System V.4 and embedded PowerPC systems compile code using
       calling conventions that adhere to the March 1995 draft of the
       System V Application Binary Interface, PowerPC processor
       supplement.  This is the default unless you configured GCC using
       powerpc-*-eabiaix.

   -mcall-sysv-eabi
   -mcall-eabi
       Specify both -mcall-sysv and -meabi options.

   -mcall-sysv-noeabi
       Specify both -mcall-sysv and -mno-eabi options.

   -mcall-aixdesc
       On System V.4 and embedded PowerPC systems compile code for the AIX
       operating system.

   -mcall-linux
       On System V.4 and embedded PowerPC systems compile code for the
       Linux-based GNU system.

   -mcall-freebsd
       On System V.4 and embedded PowerPC systems compile code for the
       FreeBSD operating system.

   -mcall-netbsd
       On System V.4 and embedded PowerPC systems compile code for the
       NetBSD operating system.

   -mcall-openbsd
       On System V.4 and embedded PowerPC systems compile code for the
       OpenBSD operating system.

   -maix-struct-return
       Return all structures in memory (as specified by the AIX ABI).

   -msvr4-struct-return
       Return structures smaller than 8 bytes in registers (as specified
       by the SVR4 ABI).

   -mabi=abi-type
       Extend the current ABI with a particular extension, or remove such
       extension.  Valid values are altivec, no-altivec, spe, no-spe,
       ibmlongdouble, ieeelongdouble, elfv1, elfv2.

   -mabi=spe
       Extend the current ABI with SPE ABI extensions.  This does not
       change the default ABI, instead it adds the SPE ABI extensions to
       the current ABI.

   -mabi=no-spe
       Disable Book-E SPE ABI extensions for the current ABI.

   -mabi=ibmlongdouble
       Change the current ABI to use IBM extended-precision long double.
       This is a PowerPC 32-bit SYSV ABI option.

   -mabi=ieeelongdouble
       Change the current ABI to use IEEE extended-precision long double.
       This is a PowerPC 32-bit Linux ABI option.

   -mabi=elfv1
       Change the current ABI to use the ELFv1 ABI.  This is the default
       ABI for big-endian PowerPC 64-bit Linux.  Overriding the default
       ABI requires special system support and is likely to fail in
       spectacular ways.

   -mabi=elfv2
       Change the current ABI to use the ELFv2 ABI.  This is the default
       ABI for little-endian PowerPC 64-bit Linux.  Overriding the default
       ABI requires special system support and is likely to fail in
       spectacular ways.

   -mprototype
   -mno-prototype
       On System V.4 and embedded PowerPC systems assume that all calls to
       variable argument functions are properly prototyped.  Otherwise,
       the compiler must insert an instruction before every non-prototyped
       call to set or clear bit 6 of the condition code register ("CR") to
       indicate whether floating-point values are passed in the floating-
       point registers in case the function takes variable arguments.
       With -mprototype, only calls to prototyped variable argument
       functions set or clear the bit.

   -msim
       On embedded PowerPC systems, assume that the startup module is
       called sim-crt0.o and that the standard C libraries are libsim.a
       and libc.a.  This is the default for powerpc-*-eabisim
       configurations.

   -mmvme
       On embedded PowerPC systems, assume that the startup module is
       called crt0.o and the standard C libraries are libmvme.a and
       libc.a.

   -mads
       On embedded PowerPC systems, assume that the startup module is
       called crt0.o and the standard C libraries are libads.a and libc.a.

   -myellowknife
       On embedded PowerPC systems, assume that the startup module is
       called crt0.o and the standard C libraries are libyk.a and libc.a.

   -mvxworks
       On System V.4 and embedded PowerPC systems, specify that you are
       compiling for a VxWorks system.

   -memb
       On embedded PowerPC systems, set the "PPC_EMB" bit in the ELF flags
       header to indicate that eabi extended relocations are used.

   -meabi
   -mno-eabi
       On System V.4 and embedded PowerPC systems do (do not) adhere to
       the Embedded Applications Binary Interface (EABI), which is a set
       of modifications to the System V.4 specifications.  Selecting
       -meabi means that the stack is aligned to an 8-byte boundary, a
       function "__eabi" is called from "main" to set up the EABI
       environment, and the -msdata option can use both "r2" and "r13" to
       point to two separate small data areas.  Selecting -mno-eabi means
       that the stack is aligned to a 16-byte boundary, no EABI
       initialization function is called from "main", and the -msdata
       option only uses "r13" to point to a single small data area.  The
       -meabi option is on by default if you configured GCC using one of
       the powerpc*-*-eabi* options.

   -msdata=eabi
       On System V.4 and embedded PowerPC systems, put small initialized
       "const" global and static data in the ".sdata2" section, which is
       pointed to by register "r2".  Put small initialized non-"const"
       global and static data in the ".sdata" section, which is pointed to
       by register "r13".  Put small uninitialized global and static data
       in the ".sbss" section, which is adjacent to the ".sdata" section.
       The -msdata=eabi option is incompatible with the -mrelocatable
       option.  The -msdata=eabi option also sets the -memb option.

   -msdata=sysv
       On System V.4 and embedded PowerPC systems, put small global and
       static data in the ".sdata" section, which is pointed to by
       register "r13".  Put small uninitialized global and static data in
       the ".sbss" section, which is adjacent to the ".sdata" section.
       The -msdata=sysv option is incompatible with the -mrelocatable
       option.

   -msdata=default
   -msdata
       On System V.4 and embedded PowerPC systems, if -meabi is used,
       compile code the same as -msdata=eabi, otherwise compile code the
       same as -msdata=sysv.

   -msdata=data
       On System V.4 and embedded PowerPC systems, put small global data
       in the ".sdata" section.  Put small uninitialized global data in
       the ".sbss" section.  Do not use register "r13" to address small
       data however.  This is the default behavior unless other -msdata
       options are used.

   -msdata=none
   -mno-sdata
       On embedded PowerPC systems, put all initialized global and static
       data in the ".data" section, and all uninitialized data in the
       ".bss" section.

   -mblock-move-inline-limit=num
       Inline all block moves (such as calls to "memcpy" or structure
       copies) less than or equal to num bytes.  The minimum value for num
       is 32 bytes on 32-bit targets and 64 bytes on 64-bit targets.  The
       default value is target-specific.

   -G num
       On embedded PowerPC systems, put global and static items less than
       or equal to num bytes into the small data or BSS sections instead
       of the normal data or BSS section.  By default, num is 8.  The -G
       num switch is also passed to the linker.  All modules should be
       compiled with the same -G num value.

   -mregnames
   -mno-regnames
       On System V.4 and embedded PowerPC systems do (do not) emit
       register names in the assembly language output using symbolic
       forms.

   -mlongcall
   -mno-longcall
       By default assume that all calls are far away so that a longer and
       more expensive calling sequence is required.  This is required for
       calls farther than 32 megabytes (33,554,432 bytes) from the current
       location.  A short call is generated if the compiler knows the call
       cannot be that far away.  This setting can be overridden by the
       "shortcall" function attribute, or by "#pragma longcall(0)".

       Some linkers are capable of detecting out-of-range calls and
       generating glue code on the fly.  On these systems, long calls are
       unnecessary and generate slower code.  As of this writing, the AIX
       linker can do this, as can the GNU linker for PowerPC/64.  It is
       planned to add this feature to the GNU linker for 32-bit PowerPC
       systems as well.

       On Darwin/PPC systems, "#pragma longcall" generates "jbsr callee,
       L42", plus a branch island (glue code).  The two target addresses
       represent the callee and the branch island.  The Darwin/PPC linker
       prefers the first address and generates a "bl callee" if the PPC
       "bl" instruction reaches the callee directly; otherwise, the linker
       generates "bl L42" to call the branch island.  The branch island is
       appended to the body of the calling function; it computes the full
       32-bit address of the callee and jumps to it.

       On Mach-O (Darwin) systems, this option directs the compiler emit
       to the glue for every direct call, and the Darwin linker decides
       whether to use or discard it.

       In the future, GCC may ignore all longcall specifications when the
       linker is known to generate glue.

   -mtls-markers
   -mno-tls-markers
       Mark (do not mark) calls to "__tls_get_addr" with a relocation
       specifying the function argument.  The relocation allows the linker
       to reliably associate function call with argument setup
       instructions for TLS optimization, which in turn allows GCC to
       better schedule the sequence.

   -pthread
       Adds support for multithreading with the pthreads library.  This
       option sets flags for both the preprocessor and linker.

   -mrecip
   -mno-recip
       This option enables use of the reciprocal estimate and reciprocal
       square root estimate instructions with additional Newton-Raphson
       steps to increase precision instead of doing a divide or square
       root and divide for floating-point arguments.  You should use the
       -ffast-math option when using -mrecip (or at least
       -funsafe-math-optimizations, -ffinite-math-only, -freciprocal-math
       and -fno-trapping-math).  Note that while the throughput of the
       sequence is generally higher than the throughput of the non-
       reciprocal instruction, the precision of the sequence can be
       decreased by up to 2 ulp (i.e. the inverse of 1.0 equals
       0.99999994) for reciprocal square roots.

   -mrecip=opt
       This option controls which reciprocal estimate instructions may be
       used.  opt is a comma-separated list of options, which may be
       preceded by a "!" to invert the option:

       all Enable all estimate instructions.

       default
           Enable the default instructions, equivalent to -mrecip.

       none
           Disable all estimate instructions, equivalent to -mno-recip.

       div Enable the reciprocal approximation instructions for both
           single and double precision.

       divf
           Enable the single-precision reciprocal approximation
           instructions.

       divd
           Enable the double-precision reciprocal approximation
           instructions.

       rsqrt
           Enable the reciprocal square root approximation instructions
           for both single and double precision.

       rsqrtf
           Enable the single-precision reciprocal square root
           approximation instructions.

       rsqrtd
           Enable the double-precision reciprocal square root
           approximation instructions.

       So, for example, -mrecip=all,!rsqrtd enables all of the reciprocal
       estimate instructions, except for the "FRSQRTE", "XSRSQRTEDP", and
       "XVRSQRTEDP" instructions which handle the double-precision
       reciprocal square root calculations.

   -mrecip-precision
   -mno-recip-precision
       Assume (do not assume) that the reciprocal estimate instructions
       provide higher-precision estimates than is mandated by the PowerPC
       ABI.  Selecting -mcpu=power6, -mcpu=power7 or -mcpu=power8
       automatically selects -mrecip-precision.  The double-precision
       square root estimate instructions are not generated by default on
       low-precision machines, since they do not provide an estimate that
       converges after three steps.

   -mveclibabi=type
       Specifies the ABI type to use for vectorizing intrinsics using an
       external library.  The only type supported at present is mass,
       which specifies to use IBM's Mathematical Acceleration Subsystem
       (MASS) libraries for vectorizing intrinsics using external
       libraries.  GCC currently emits calls to "acosd2", "acosf4",
       "acoshd2", "acoshf4", "asind2", "asinf4", "asinhd2", "asinhf4",
       "atan2d2", "atan2f4", "atand2", "atanf4", "atanhd2", "atanhf4",
       "cbrtd2", "cbrtf4", "cosd2", "cosf4", "coshd2", "coshf4", "erfcd2",
       "erfcf4", "erfd2", "erff4", "exp2d2", "exp2f4", "expd2", "expf4",
       "expm1d2", "expm1f4", "hypotd2", "hypotf4", "lgammad2", "lgammaf4",
       "log10d2", "log10f4", "log1pd2", "log1pf4", "log2d2", "log2f4",
       "logd2", "logf4", "powd2", "powf4", "sind2", "sinf4", "sinhd2",
       "sinhf4", "sqrtd2", "sqrtf4", "tand2", "tanf4", "tanhd2", and
       "tanhf4" when generating code for power7.  Both -ftree-vectorize
       and -funsafe-math-optimizations must also be enabled.  The MASS
       libraries must be specified at link time.

   -mfriz
   -mno-friz
       Generate (do not generate) the "friz" instruction when the
       -funsafe-math-optimizations option is used to optimize rounding of
       floating-point values to 64-bit integer and back to floating point.
       The "friz" instruction does not return the same value if the
       floating-point number is too large to fit in an integer.

   -mpointers-to-nested-functions
   -mno-pointers-to-nested-functions
       Generate (do not generate) code to load up the static chain
       register ("r11") when calling through a pointer on AIX and 64-bit
       Linux systems where a function pointer points to a 3-word
       descriptor giving the function address, TOC value to be loaded in
       register "r2", and static chain value to be loaded in register
       "r11".  The -mpointers-to-nested-functions is on by default.  You
       cannot call through pointers to nested functions or pointers to
       functions compiled in other languages that use the static chain if
       you use -mno-pointers-to-nested-functions.

   -msave-toc-indirect
   -mno-save-toc-indirect
       Generate (do not generate) code to save the TOC value in the
       reserved stack location in the function prologue if the function
       calls through a pointer on AIX and 64-bit Linux systems.  If the
       TOC value is not saved in the prologue, it is saved just before the
       call through the pointer.  The -mno-save-toc-indirect option is the
       default.

   -mcompat-align-parm
   -mno-compat-align-parm
       Generate (do not generate) code to pass structure parameters with a
       maximum alignment of 64 bits, for compatibility with older versions
       of GCC.

       Older versions of GCC (prior to 4.9.0) incorrectly did not align a
       structure parameter on a 128-bit boundary when that structure
       contained a member requiring 128-bit alignment.  This is corrected
       in more recent versions of GCC.  This option may be used to
       generate code that is compatible with functions compiled with older
       versions of GCC.

       The -mno-compat-align-parm option is the default.

   RX Options

   These command-line options are defined for RX targets:

   -m64bit-doubles
   -m32bit-doubles
       Make the "double" data type be 64 bits (-m64bit-doubles) or 32 bits
       (-m32bit-doubles) in size.  The default is -m32bit-doubles.  Note
       RX floating-point hardware only works on 32-bit values, which is
       why the default is -m32bit-doubles.

   -fpu
   -nofpu
       Enables (-fpu) or disables (-nofpu) the use of RX floating-point
       hardware.  The default is enabled for the RX600 series and disabled
       for the RX200 series.

       Floating-point instructions are only generated for 32-bit floating-
       point values, however, so the FPU hardware is not used for doubles
       if the -m64bit-doubles option is used.

       Note If the -fpu option is enabled then -funsafe-math-optimizations
       is also enabled automatically.  This is because the RX FPU
       instructions are themselves unsafe.

   -mcpu=name
       Selects the type of RX CPU to be targeted.  Currently three types
       are supported, the generic RX600 and RX200 series hardware and the
       specific RX610 CPU.  The default is RX600.

       The only difference between RX600 and RX610 is that the RX610 does
       not support the "MVTIPL" instruction.

       The RX200 series does not have a hardware floating-point unit and
       so -nofpu is enabled by default when this type is selected.

   -mbig-endian-data
   -mlittle-endian-data
       Store data (but not code) in the big-endian format.  The default is
       -mlittle-endian-data, i.e. to store data in the little-endian
       format.

   -msmall-data-limit=N
       Specifies the maximum size in bytes of global and static variables
       which can be placed into the small data area.  Using the small data
       area can lead to smaller and faster code, but the size of area is
       limited and it is up to the programmer to ensure that the area does
       not overflow.  Also when the small data area is used one of the
       RX's registers (usually "r13") is reserved for use pointing to this
       area, so it is no longer available for use by the compiler.  This
       could result in slower and/or larger code if variables are pushed
       onto the stack instead of being held in this register.

       Note, common variables (variables that have not been initialized)
       and constants are not placed into the small data area as they are
       assigned to other sections in the output executable.

       The default value is zero, which disables this feature.  Note, this
       feature is not enabled by default with higher optimization levels
       (-O2 etc) because of the potentially detrimental effects of
       reserving a register.  It is up to the programmer to experiment and
       discover whether this feature is of benefit to their program.  See
       the description of the -mpid option for a description of how the
       actual register to hold the small data area pointer is chosen.

   -msim
   -mno-sim
       Use the simulator runtime.  The default is to use the libgloss
       board-specific runtime.

   -mas100-syntax
   -mno-as100-syntax
       When generating assembler output use a syntax that is compatible
       with Renesas's AS100 assembler.  This syntax can also be handled by
       the GAS assembler, but it has some restrictions so it is not
       generated by default.

   -mmax-constant-size=N
       Specifies the maximum size, in bytes, of a constant that can be
       used as an operand in a RX instruction.  Although the RX
       instruction set does allow constants of up to 4 bytes in length to
       be used in instructions, a longer value equates to a longer
       instruction.  Thus in some circumstances it can be beneficial to
       restrict the size of constants that are used in instructions.
       Constants that are too big are instead placed into a constant pool
       and referenced via register indirection.

       The value N can be between 0 and 4.  A value of 0 (the default) or
       4 means that constants of any size are allowed.

   -mrelax
       Enable linker relaxation.  Linker relaxation is a process whereby
       the linker attempts to reduce the size of a program by finding
       shorter versions of various instructions.  Disabled by default.

   -mint-register=N
       Specify the number of registers to reserve for fast interrupt
       handler functions.  The value N can be between 0 and 4.  A value of
       1 means that register "r13" is reserved for the exclusive use of
       fast interrupt handlers.  A value of 2 reserves "r13" and "r12".  A
       value of 3 reserves "r13", "r12" and "r11", and a value of 4
       reserves "r13" through "r10".  A value of 0, the default, does not
       reserve any registers.

   -msave-acc-in-interrupts
       Specifies that interrupt handler functions should preserve the
       accumulator register.  This is only necessary if normal code might
       use the accumulator register, for example because it performs
       64-bit multiplications.  The default is to ignore the accumulator
       as this makes the interrupt handlers faster.

   -mpid
   -mno-pid
       Enables the generation of position independent data.  When enabled
       any access to constant data is done via an offset from a base
       address held in a register.  This allows the location of constant
       data to be determined at run time without requiring the executable
       to be relocated, which is a benefit to embedded applications with
       tight memory constraints.  Data that can be modified is not
       affected by this option.

       Note, using this feature reserves a register, usually "r13", for
       the constant data base address.  This can result in slower and/or
       larger code, especially in complicated functions.

       The actual register chosen to hold the constant data base address
       depends upon whether the -msmall-data-limit and/or the
       -mint-register command-line options are enabled.  Starting with
       register "r13" and proceeding downwards, registers are allocated
       first to satisfy the requirements of -mint-register, then -mpid and
       finally -msmall-data-limit.  Thus it is possible for the small data
       area register to be "r8" if both -mint-register=4 and -mpid are
       specified on the command line.

       By default this feature is not enabled.  The default can be
       restored via the -mno-pid command-line option.

   -mno-warn-multiple-fast-interrupts
   -mwarn-multiple-fast-interrupts
       Prevents GCC from issuing a warning message if it finds more than
       one fast interrupt handler when it is compiling a file.  The
       default is to issue a warning for each extra fast interrupt handler
       found, as the RX only supports one such interrupt.

   -mallow-string-insns
   -mno-allow-string-insns
       Enables or disables the use of the string manipulation instructions
       "SMOVF", "SCMPU", "SMOVB", "SMOVU", "SUNTIL" "SWHILE" and also the
       "RMPA" instruction.  These instructions may prefetch data, which is
       not safe to do if accessing an I/O register.  (See section 12.2.7
       of the RX62N Group User's Manual for more information).

       The default is to allow these instructions, but it is not possible
       for GCC to reliably detect all circumstances where a string
       instruction might be used to access an I/O register, so their use
       cannot be disabled automatically.  Instead it is reliant upon the
       programmer to use the -mno-allow-string-insns option if their
       program accesses I/O space.

       When the instructions are enabled GCC defines the C preprocessor
       symbol "__RX_ALLOW_STRING_INSNS__", otherwise it defines the symbol
       "__RX_DISALLOW_STRING_INSNS__".

   -mjsr
   -mno-jsr
       Use only (or not only) "JSR" instructions to access functions.
       This option can be used when code size exceeds the range of "BSR"
       instructions.  Note that -mno-jsr does not mean to not use "JSR"
       but instead means that any type of branch may be used.

   Note: The generic GCC command-line option -ffixed-reg has special
   significance to the RX port when used with the "interrupt" function
   attribute.  This attribute indicates a function intended to process
   fast interrupts.  GCC ensures that it only uses the registers "r10",
   "r11", "r12" and/or "r13" and only provided that the normal use of the
   corresponding registers have been restricted via the -ffixed-reg or
   -mint-register command-line options.

   S/390 and zSeries Options

   These are the -m options defined for the S/390 and zSeries
   architecture.

   -mhard-float
   -msoft-float
       Use (do not use) the hardware floating-point instructions and
       registers for floating-point operations.  When -msoft-float is
       specified, functions in libgcc.a are used to perform floating-point
       operations.  When -mhard-float is specified, the compiler generates
       IEEE floating-point instructions.  This is the default.

   -mhard-dfp
   -mno-hard-dfp
       Use (do not use) the hardware decimal-floating-point instructions
       for decimal-floating-point operations.  When -mno-hard-dfp is
       specified, functions in libgcc.a are used to perform decimal-
       floating-point operations.  When -mhard-dfp is specified, the
       compiler generates decimal-floating-point hardware instructions.
       This is the default for -march=z9-ec or higher.

   -mlong-double-64
   -mlong-double-128
       These switches control the size of "long double" type. A size of 64
       bits makes the "long double" type equivalent to the "double" type.
       This is the default.

   -mbackchain
   -mno-backchain
       Store (do not store) the address of the caller's frame as backchain
       pointer into the callee's stack frame.  A backchain may be needed
       to allow debugging using tools that do not understand DWARF call
       frame information.  When -mno-packed-stack is in effect, the
       backchain pointer is stored at the bottom of the stack frame; when
       -mpacked-stack is in effect, the backchain is placed into the
       topmost word of the 96/160 byte register save area.

       In general, code compiled with -mbackchain is call-compatible with
       code compiled with -mmo-backchain; however, use of the backchain
       for debugging purposes usually requires that the whole binary is
       built with -mbackchain.  Note that the combination of -mbackchain,
       -mpacked-stack and -mhard-float is not supported.  In order to
       build a linux kernel use -msoft-float.

       The default is to not maintain the backchain.

   -mpacked-stack
   -mno-packed-stack
       Use (do not use) the packed stack layout.  When -mno-packed-stack
       is specified, the compiler uses the all fields of the 96/160 byte
       register save area only for their default purpose; unused fields
       still take up stack space.  When -mpacked-stack is specified,
       register save slots are densely packed at the top of the register
       save area; unused space is reused for other purposes, allowing for
       more efficient use of the available stack space.  However, when
       -mbackchain is also in effect, the topmost word of the save area is
       always used to store the backchain, and the return address register
       is always saved two words below the backchain.

       As long as the stack frame backchain is not used, code generated
       with -mpacked-stack is call-compatible with code generated with
       -mno-packed-stack.  Note that some non-FSF releases of GCC 2.95 for
       S/390 or zSeries generated code that uses the stack frame backchain
       at run time, not just for debugging purposes.  Such code is not
       call-compatible with code compiled with -mpacked-stack.  Also, note
       that the combination of -mbackchain, -mpacked-stack and
       -mhard-float is not supported.  In order to build a linux kernel
       use -msoft-float.

       The default is to not use the packed stack layout.

   -msmall-exec
   -mno-small-exec
       Generate (or do not generate) code using the "bras" instruction to
       do subroutine calls.  This only works reliably if the total
       executable size does not exceed 64k.  The default is to use the
       "basr" instruction instead, which does not have this limitation.

   -m64
   -m31
       When -m31 is specified, generate code compliant to the GNU/Linux
       for S/390 ABI.  When -m64 is specified, generate code compliant to
       the GNU/Linux for zSeries ABI.  This allows GCC in particular to
       generate 64-bit instructions.  For the s390 targets, the default is
       -m31, while the s390x targets default to -m64.

   -mzarch
   -mesa
       When -mzarch is specified, generate code using the instructions
       available on z/Architecture.  When -mesa is specified, generate
       code using the instructions available on ESA/390.  Note that -mesa
       is not possible with -m64.  When generating code compliant to the
       GNU/Linux for S/390 ABI, the default is -mesa.  When generating
       code compliant to the GNU/Linux for zSeries ABI, the default is
       -mzarch.

   -mhtm
   -mno-htm
       The -mhtm option enables a set of builtins making use of
       instructions available with the transactional execution facility
       introduced with the IBM zEnterprise EC12 machine generation S/390
       System z Built-in Functions.  -mhtm is enabled by default when
       using -march=zEC12.

   -mvx
   -mno-vx
       When -mvx is specified, generate code using the instructions
       available with the vector extension facility introduced with the
       IBM z13 machine generation.  This option changes the ABI for some
       vector type values with regard to alignment and calling
       conventions.  In case vector type values are being used in an ABI-
       relevant context a GAS .gnu_attribute command will be added to mark
       the resulting binary with the ABI used.  -mvx is enabled by default
       when using -march=z13.

   -mzvector
   -mno-zvector
       The -mzvector option enables vector language extensions and
       builtins using instructions available with the vector extension
       facility introduced with the IBM z13 machine generation.  This
       option adds support for vector to be used as a keyword to define
       vector type variables and arguments.  vector is only available when
       GNU extensions are enabled.  It will not be expanded when
       requesting strict standard compliance e.g. with -std=c99.  In
       addition to the GCC low-level builtins -mzvector enables a set of
       builtins added for compatibility with AltiVec-style implementations
       like Power and Cell.  In order to make use of these builtins the
       header file vecintrin.h needs to be included.  -mzvector is
       disabled by default.

   -mmvcle
   -mno-mvcle
       Generate (or do not generate) code using the "mvcle" instruction to
       perform block moves.  When -mno-mvcle is specified, use a "mvc"
       loop instead.  This is the default unless optimizing for size.

   -mdebug
   -mno-debug
       Print (or do not print) additional debug information when
       compiling.  The default is to not print debug information.

   -march=cpu-type
       Generate code that runs on cpu-type, which is the name of a system
       representing a certain processor type.  Possible values for cpu-
       type are z900, z990, z9-109, z9-ec, z10, z196, zEC12, and z13.  The
       default is -march=z900.  g5 and g6 are deprecated and will be
       removed with future releases.

   -mtune=cpu-type
       Tune to cpu-type everything applicable about the generated code,
       except for the ABI and the set of available instructions.  The list
       of cpu-type values is the same as for -march.  The default is the
       value used for -march.

   -mtpf-trace
   -mno-tpf-trace
       Generate code that adds (does not add) in TPF OS specific branches
       to trace routines in the operating system.  This option is off by
       default, even when compiling for the TPF OS.

   -mfused-madd
   -mno-fused-madd
       Generate code that uses (does not use) the floating-point multiply
       and accumulate instructions.  These instructions are generated by
       default if hardware floating point is used.

   -mwarn-framesize=framesize
       Emit a warning if the current function exceeds the given frame
       size.  Because this is a compile-time check it doesn't need to be a
       real problem when the program runs.  It is intended to identify
       functions that most probably cause a stack overflow.  It is useful
       to be used in an environment with limited stack size e.g. the linux
       kernel.

   -mwarn-dynamicstack
       Emit a warning if the function calls "alloca" or uses dynamically-
       sized arrays.  This is generally a bad idea with a limited stack
       size.

   -mstack-guard=stack-guard
   -mstack-size=stack-size
       If these options are provided the S/390 back end emits additional
       instructions in the function prologue that trigger a trap if the
       stack size is stack-guard bytes above the stack-size (remember that
       the stack on S/390 grows downward).  If the stack-guard option is
       omitted the smallest power of 2 larger than the frame size of the
       compiled function is chosen.  These options are intended to be used
       to help debugging stack overflow problems.  The additionally
       emitted code causes only little overhead and hence can also be used
       in production-like systems without greater performance degradation.
       The given values have to be exact powers of 2 and stack-size has to
       be greater than stack-guard without exceeding 64k.  In order to be
       efficient the extra code makes the assumption that the stack starts
       at an address aligned to the value given by stack-size.  The stack-
       guard option can only be used in conjunction with stack-size.

   -mhotpatch=pre-halfwords,post-halfwords
       If the hotpatch option is enabled, a "hot-patching" function
       prologue is generated for all functions in the compilation unit.
       The funtion label is prepended with the given number of two-byte
       NOP instructions (pre-halfwords, maximum 1000000).  After the
       label, 2 * post-halfwords bytes are appended, using the largest NOP
       like instructions the architecture allows (maximum 1000000).

       If both arguments are zero, hotpatching is disabled.

       This option can be overridden for individual functions with the
       "hotpatch" attribute.

   Score Options

   These options are defined for Score implementations:

   -meb
       Compile code for big-endian mode.  This is the default.

   -mel
       Compile code for little-endian mode.

   -mnhwloop
       Disable generation of "bcnz" instructions.

   -muls
       Enable generation of unaligned load and store instructions.

   -mmac
       Enable the use of multiply-accumulate instructions. Disabled by
       default.

   -mscore5
       Specify the SCORE5 as the target architecture.

   -mscore5u
       Specify the SCORE5U of the target architecture.

   -mscore7
       Specify the SCORE7 as the target architecture. This is the default.

   -mscore7d
       Specify the SCORE7D as the target architecture.

   SH Options

   These -m options are defined for the SH implementations:

   -m1 Generate code for the SH1.

   -m2 Generate code for the SH2.

   -m2e
       Generate code for the SH2e.

   -m2a-nofpu
       Generate code for the SH2a without FPU, or for a SH2a-FPU in such a
       way that the floating-point unit is not used.

   -m2a-single-only
       Generate code for the SH2a-FPU, in such a way that no double-
       precision floating-point operations are used.

   -m2a-single
       Generate code for the SH2a-FPU assuming the floating-point unit is
       in single-precision mode by default.

   -m2a
       Generate code for the SH2a-FPU assuming the floating-point unit is
       in double-precision mode by default.

   -m3 Generate code for the SH3.

   -m3e
       Generate code for the SH3e.

   -m4-nofpu
       Generate code for the SH4 without a floating-point unit.

   -m4-single-only
       Generate code for the SH4 with a floating-point unit that only
       supports single-precision arithmetic.

   -m4-single
       Generate code for the SH4 assuming the floating-point unit is in
       single-precision mode by default.

   -m4 Generate code for the SH4.

   -m4-100
       Generate code for SH4-100.

   -m4-100-nofpu
       Generate code for SH4-100 in such a way that the floating-point
       unit is not used.

   -m4-100-single
       Generate code for SH4-100 assuming the floating-point unit is in
       single-precision mode by default.

   -m4-100-single-only
       Generate code for SH4-100 in such a way that no double-precision
       floating-point operations are used.

   -m4-200
       Generate code for SH4-200.

   -m4-200-nofpu
       Generate code for SH4-200 without in such a way that the floating-
       point unit is not used.

   -m4-200-single
       Generate code for SH4-200 assuming the floating-point unit is in
       single-precision mode by default.

   -m4-200-single-only
       Generate code for SH4-200 in such a way that no double-precision
       floating-point operations are used.

   -m4-300
       Generate code for SH4-300.

   -m4-300-nofpu
       Generate code for SH4-300 without in such a way that the floating-
       point unit is not used.

   -m4-300-single
       Generate code for SH4-300 in such a way that no double-precision
       floating-point operations are used.

   -m4-300-single-only
       Generate code for SH4-300 in such a way that no double-precision
       floating-point operations are used.

   -m4-340
       Generate code for SH4-340 (no MMU, no FPU).

   -m4-500
       Generate code for SH4-500 (no FPU).  Passes -isa=sh4-nofpu to the
       assembler.

   -m4a-nofpu
       Generate code for the SH4al-dsp, or for a SH4a in such a way that
       the floating-point unit is not used.

   -m4a-single-only
       Generate code for the SH4a, in such a way that no double-precision
       floating-point operations are used.

   -m4a-single
       Generate code for the SH4a assuming the floating-point unit is in
       single-precision mode by default.

   -m4a
       Generate code for the SH4a.

   -m4al
       Same as -m4a-nofpu, except that it implicitly passes -dsp to the
       assembler.  GCC doesn't generate any DSP instructions at the
       moment.

   -mb Compile code for the processor in big-endian mode.

   -ml Compile code for the processor in little-endian mode.

   -mdalign
       Align doubles at 64-bit boundaries.  Note that this changes the
       calling conventions, and thus some functions from the standard C
       library do not work unless you recompile it first with -mdalign.

   -mrelax
       Shorten some address references at link time, when possible; uses
       the linker option -relax.

   -mbigtable
       Use 32-bit offsets in "switch" tables.  The default is to use
       16-bit offsets.

   -mbitops
       Enable the use of bit manipulation instructions on SH2A.

   -mfmovd
       Enable the use of the instruction "fmovd".  Check -mdalign for
       alignment constraints.

   -mrenesas
       Comply with the calling conventions defined by Renesas.

   -mno-renesas
       Comply with the calling conventions defined for GCC before the
       Renesas conventions were available.  This option is the default for
       all targets of the SH toolchain.

   -mnomacsave
       Mark the "MAC" register as call-clobbered, even if -mrenesas is
       given.

   -mieee
   -mno-ieee
       Control the IEEE compliance of floating-point comparisons, which
       affects the handling of cases where the result of a comparison is
       unordered.  By default -mieee is implicitly enabled.  If
       -ffinite-math-only is enabled -mno-ieee is implicitly set, which
       results in faster floating-point greater-equal and less-equal
       comparisons.  The implicit settings can be overridden by specifying
       either -mieee or -mno-ieee.

   -minline-ic_invalidate
       Inline code to invalidate instruction cache entries after setting
       up nested function trampolines.  This option has no effect if
       -musermode is in effect and the selected code generation option
       (e.g. -m4) does not allow the use of the "icbi" instruction.  If
       the selected code generation option does not allow the use of the
       "icbi" instruction, and -musermode is not in effect, the inlined
       code manipulates the instruction cache address array directly with
       an associative write.  This not only requires privileged mode at
       run time, but it also fails if the cache line had been mapped via
       the TLB and has become unmapped.

   -misize
       Dump instruction size and location in the assembly code.

   -mpadstruct
       This option is deprecated.  It pads structures to multiple of 4
       bytes, which is incompatible with the SH ABI.

   -matomic-model=model
       Sets the model of atomic operations and additional parameters as a
       comma separated list.  For details on the atomic built-in functions
       see __atomic Builtins.  The following models and parameters are
       supported:

       none
           Disable compiler generated atomic sequences and emit library
           calls for atomic operations.  This is the default if the target
           is not "sh*-*-linux*".

       soft-gusa
           Generate GNU/Linux compatible gUSA software atomic sequences
           for the atomic built-in functions.  The generated atomic
           sequences require additional support from the
           interrupt/exception handling code of the system and are only
           suitable for SH3* and SH4* single-core systems.  This option is
           enabled by default when the target is "sh*-*-linux*" and SH3*
           or SH4*.  When the target is SH4A, this option also partially
           utilizes the hardware atomic instructions "movli.l" and
           "movco.l" to create more efficient code, unless strict is
           specified.

       soft-tcb
           Generate software atomic sequences that use a variable in the
           thread control block.  This is a variation of the gUSA
           sequences which can also be used on SH1* and SH2* targets.  The
           generated atomic sequences require additional support from the
           interrupt/exception handling code of the system and are only
           suitable for single-core systems.  When using this model, the
           gbr-offset= parameter has to be specified as well.

       soft-imask
           Generate software atomic sequences that temporarily disable
           interrupts by setting "SR.IMASK = 1111".  This model works only
           when the program runs in privileged mode and is only suitable
           for single-core systems.  Additional support from the
           interrupt/exception handling code of the system is not
           required.  This model is enabled by default when the target is
           "sh*-*-linux*" and SH1* or SH2*.

       hard-llcs
           Generate hardware atomic sequences using the "movli.l" and
           "movco.l" instructions only.  This is only available on SH4A
           and is suitable for multi-core systems.  Since the hardware
           instructions support only 32 bit atomic variables access to 8
           or 16 bit variables is emulated with 32 bit accesses.  Code
           compiled with this option is also compatible with other
           software atomic model interrupt/exception handling systems if
           executed on an SH4A system.  Additional support from the
           interrupt/exception handling code of the system is not required
           for this model.

       gbr-offset=
           This parameter specifies the offset in bytes of the variable in
           the thread control block structure that should be used by the
           generated atomic sequences when the soft-tcb model has been
           selected.  For other models this parameter is ignored.  The
           specified value must be an integer multiple of four and in the
           range 0-1020.

       strict
           This parameter prevents mixed usage of multiple atomic models,
           even if they are compatible, and makes the compiler generate
           atomic sequences of the specified model only.

   -mtas
       Generate the "tas.b" opcode for "__atomic_test_and_set".  Notice
       that depending on the particular hardware and software
       configuration this can degrade overall performance due to the
       operand cache line flushes that are implied by the "tas.b"
       instruction.  On multi-core SH4A processors the "tas.b" instruction
       must be used with caution since it can result in data corruption
       for certain cache configurations.

   -mprefergot
       When generating position-independent code, emit function calls
       using the Global Offset Table instead of the Procedure Linkage
       Table.

   -musermode
   -mno-usermode
       Don't allow (allow) the compiler generating privileged mode code.
       Specifying -musermode also implies -mno-inline-ic_invalidate if the
       inlined code would not work in user mode.  -musermode is the
       default when the target is "sh*-*-linux*".  If the target is SH1*
       or SH2* -musermode has no effect, since there is no user mode.

   -multcost=number
       Set the cost to assume for a multiply insn.

   -mdiv=strategy
       Set the division strategy to be used for integer division
       operations.  strategy can be one of:

       call-div1
           Calls a library function that uses the single-step division
           instruction "div1" to perform the operation.  Division by zero
           calculates an unspecified result and does not trap.  This is
           the default except for SH4, SH2A and SHcompact.

       call-fp
           Calls a library function that performs the operation in double
           precision floating point.  Division by zero causes a floating-
           point exception.  This is the default for SHcompact with FPU.
           Specifying this for targets that do not have a double precision
           FPU defaults to "call-div1".

       call-table
           Calls a library function that uses a lookup table for small
           divisors and the "div1" instruction with case distinction for
           larger divisors.  Division by zero calculates an unspecified
           result and does not trap.  This is the default for SH4.
           Specifying this for targets that do not have dynamic shift
           instructions defaults to "call-div1".

       When a division strategy has not been specified the default
       strategy is selected based on the current target.  For SH2A the
       default strategy is to use the "divs" and "divu" instructions
       instead of library function calls.

   -maccumulate-outgoing-args
       Reserve space once for outgoing arguments in the function prologue
       rather than around each call.  Generally beneficial for performance
       and size.  Also needed for unwinding to avoid changing the stack
       frame around conditional code.

   -mdivsi3_libfunc=name
       Set the name of the library function used for 32-bit signed
       division to name.  This only affects the name used in the call
       division strategies, and the compiler still expects the same sets
       of input/output/clobbered registers as if this option were not
       present.

   -mfixed-range=register-range
       Generate code treating the given register range as fixed registers.
       A fixed register is one that the register allocator can not use.
       This is useful when compiling kernel code.  A register range is
       specified as two registers separated by a dash.  Multiple register
       ranges can be specified separated by a comma.

   -mbranch-cost=num
       Assume num to be the cost for a branch instruction.  Higher numbers
       make the compiler try to generate more branch-free code if
       possible.  If not specified the value is selected depending on the
       processor type that is being compiled for.

   -mzdcbranch
   -mno-zdcbranch
       Assume (do not assume) that zero displacement conditional branch
       instructions "bt" and "bf" are fast.  If -mzdcbranch is specified,
       the compiler prefers zero displacement branch code sequences.  This
       is enabled by default when generating code for SH4 and SH4A.  It
       can be explicitly disabled by specifying -mno-zdcbranch.

   -mcbranch-force-delay-slot
       Force the usage of delay slots for conditional branches, which
       stuffs the delay slot with a "nop" if a suitable instruction can't
       be found.  By default this option is disabled.  It can be enabled
       to work around hardware bugs as found in the original SH7055.

   -mfused-madd
   -mno-fused-madd
       Generate code that uses (does not use) the floating-point multiply
       and accumulate instructions.  These instructions are generated by
       default if hardware floating point is used.  The machine-dependent
       -mfused-madd option is now mapped to the machine-independent
       -ffp-contract=fast option, and -mno-fused-madd is mapped to
       -ffp-contract=off.

   -mfsca
   -mno-fsca
       Allow or disallow the compiler to emit the "fsca" instruction for
       sine and cosine approximations.  The option -mfsca must be used in
       combination with -funsafe-math-optimizations.  It is enabled by
       default when generating code for SH4A.  Using -mno-fsca disables
       sine and cosine approximations even if -funsafe-math-optimizations
       is in effect.

   -mfsrra
   -mno-fsrra
       Allow or disallow the compiler to emit the "fsrra" instruction for
       reciprocal square root approximations.  The option -mfsrra must be
       used in combination with -funsafe-math-optimizations and
       -ffinite-math-only.  It is enabled by default when generating code
       for SH4A.  Using -mno-fsrra disables reciprocal square root
       approximations even if -funsafe-math-optimizations and
       -ffinite-math-only are in effect.

   -mpretend-cmove
       Prefer zero-displacement conditional branches for conditional move
       instruction patterns.  This can result in faster code on the SH4
       processor.

   -mfdpic
       Generate code using the FDPIC ABI.

   Solaris 2 Options

   These -m options are supported on Solaris 2:

   -mclear-hwcap
       -mclear-hwcap tells the compiler to remove the hardware
       capabilities generated by the Solaris assembler.  This is only
       necessary when object files use ISA extensions not supported by the
       current machine, but check at runtime whether or not to use them.

   -mimpure-text
       -mimpure-text, used in addition to -shared, tells the compiler to
       not pass -z text to the linker when linking a shared object.  Using
       this option, you can link position-dependent code into a shared
       object.

       -mimpure-text suppresses the "relocations remain against
       allocatable but non-writable sections" linker error message.
       However, the necessary relocations trigger copy-on-write, and the
       shared object is not actually shared across processes.  Instead of
       using -mimpure-text, you should compile all source code with -fpic
       or -fPIC.

   These switches are supported in addition to the above on Solaris 2:

   -pthreads
       Add support for multithreading using the POSIX threads library.
       This option sets flags for both the preprocessor and linker.  This
       option does not affect the thread safety of object code produced
       by the compiler or that of libraries supplied with it.

   -pthread
       This is a synonym for -pthreads.

   SPARC Options

   These -m options are supported on the SPARC:

   -mno-app-regs
   -mapp-regs
       Specify -mapp-regs to generate output using the global registers 2
       through 4, which the SPARC SVR4 ABI reserves for applications.
       Like the global register 1, each global register 2 through 4 is
       then treated as an allocable register that is clobbered by function
       calls.  This is the default.

       To be fully SVR4 ABI-compliant at the cost of some performance
       loss, specify -mno-app-regs.  You should compile libraries and
       system software with this option.

   -mflat
   -mno-flat
       With -mflat, the compiler does not generate save/restore
       instructions and uses a "flat" or single register window model.
       This model is compatible with the regular register window model.
       The local registers and the input registers (0--5) are still
       treated as "call-saved" registers and are saved on the stack as
       needed.

       With -mno-flat (the default), the compiler generates save/restore
       instructions (except for leaf functions).  This is the normal
       operating mode.

   -mfpu
   -mhard-float
       Generate output containing floating-point instructions.  This is
       the default.

   -mno-fpu
   -msoft-float
       Generate output containing library calls for floating point.
       Warning: the requisite libraries are not available for all SPARC
       targets.  Normally the facilities of the machine's usual C compiler
       are used, but this cannot be done directly in cross-compilation.
       You must make your own arrangements to provide suitable library
       functions for cross-compilation.  The embedded targets sparc-*-aout
       and sparclite-*-* do provide software floating-point support.

       -msoft-float changes the calling convention in the output file;
       therefore, it is only useful if you compile all of a program with
       this option.  In particular, you need to compile libgcc.a, the
       library that comes with GCC, with -msoft-float in order for this to
       work.

   -mhard-quad-float
       Generate output containing quad-word (long double) floating-point
       instructions.

   -msoft-quad-float
       Generate output containing library calls for quad-word (long
       double) floating-point instructions.  The functions called are
       those specified in the SPARC ABI.  This is the default.

       As of this writing, there are no SPARC implementations that have
       hardware support for the quad-word floating-point instructions.
       They all invoke a trap handler for one of these instructions, and
       then the trap handler emulates the effect of the instruction.
       Because of the trap handler overhead, this is much slower than
       calling the ABI library routines.  Thus the -msoft-quad-float
       option is the default.

   -mno-unaligned-doubles
   -munaligned-doubles
       Assume that doubles have 8-byte alignment.  This is the default.

       With -munaligned-doubles, GCC assumes that doubles have 8-byte
       alignment only if they are contained in another type, or if they
       have an absolute address.  Otherwise, it assumes they have 4-byte
       alignment.  Specifying this option avoids some rare compatibility
       problems with code generated by other compilers.  It is not the
       default because it results in a performance loss, especially for
       floating-point code.

   -muser-mode
   -mno-user-mode
       Do not generate code that can only run in supervisor mode.  This is
       relevant only for the "casa" instruction emitted for the LEON3
       processor.  This is the default.

   -mfaster-structs
   -mno-faster-structs
       With -mfaster-structs, the compiler assumes that structures should
       have 8-byte alignment.  This enables the use of pairs of "ldd" and
       "std" instructions for copies in structure assignment, in place of
       twice as many "ld" and "st" pairs.  However, the use of this
       changed alignment directly violates the SPARC ABI.  Thus, it's
       intended only for use on targets where the developer acknowledges
       that their resulting code is not directly in line with the rules of
       the ABI.

   -mstd-struct-return
   -mno-std-struct-return
       With -mstd-struct-return, the compiler generates checking code in
       functions returning structures or unions to detect size mismatches
       between the two sides of function calls, as per the 32-bit ABI.

       The default is -mno-std-struct-return.  This option has no effect
       in 64-bit mode.

   -mcpu=cpu_type
       Set the instruction set, register set, and instruction scheduling
       parameters for machine type cpu_type.  Supported values for
       cpu_type are v7, cypress, v8, supersparc, hypersparc, leon, leon3,
       leon3v7, sparclite, f930, f934, sparclite86x, sparclet, tsc701, v9,
       ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4 and
       niagara7.

       Native Solaris and GNU/Linux toolchains also support the value
       native, which selects the best architecture option for the host
       processor.  -mcpu=native has no effect if GCC does not recognize
       the processor.

       Default instruction scheduling parameters are used for values that
       select an architecture and not an implementation.  These are v7,
       v8, sparclite, sparclet, v9.

       Here is a list of each supported architecture and their supported
       implementations.

       v7  cypress, leon3v7

       v8  supersparc, hypersparc, leon, leon3

       sparclite
           f930, f934, sparclite86x

       sparclet
           tsc701

       v9  ultrasparc, ultrasparc3, niagara, niagara2, niagara3, niagara4,
           niagara7

       By default (unless configured otherwise), GCC generates code for
       the V7 variant of the SPARC architecture.  With -mcpu=cypress, the
       compiler additionally optimizes it for the Cypress CY7C602 chip, as
       used in the SPARCStation/SPARCServer 3xx series.  This is also
       appropriate for the older SPARCStation 1, 2, IPX etc.

       With -mcpu=v8, GCC generates code for the V8 variant of the SPARC
       architecture.  The only difference from V7 code is that the
       compiler emits the integer multiply and integer divide instructions
       which exist in SPARC-V8 but not in SPARC-V7.  With
       -mcpu=supersparc, the compiler additionally optimizes it for the
       SuperSPARC chip, as used in the SPARCStation 10, 1000 and 2000
       series.

       With -mcpu=sparclite, GCC generates code for the SPARClite variant
       of the SPARC architecture.  This adds the integer multiply, integer
       divide step and scan ("ffs") instructions which exist in SPARClite
       but not in SPARC-V7.  With -mcpu=f930, the compiler additionally
       optimizes it for the Fujitsu MB86930 chip, which is the original
       SPARClite, with no FPU.  With -mcpu=f934, the compiler additionally
       optimizes it for the Fujitsu MB86934 chip, which is the more recent
       SPARClite with FPU.

       With -mcpu=sparclet, GCC generates code for the SPARClet variant of
       the SPARC architecture.  This adds the integer multiply,
       multiply/accumulate, integer divide step and scan ("ffs")
       instructions which exist in SPARClet but not in SPARC-V7.  With
       -mcpu=tsc701, the compiler additionally optimizes it for the TEMIC
       SPARClet chip.

       With -mcpu=v9, GCC generates code for the V9 variant of the SPARC
       architecture.  This adds 64-bit integer and floating-point move
       instructions, 3 additional floating-point condition code registers
       and conditional move instructions.  With -mcpu=ultrasparc, the
       compiler additionally optimizes it for the Sun UltraSPARC I/II/IIi
       chips.  With -mcpu=ultrasparc3, the compiler additionally optimizes
       it for the Sun UltraSPARC III/III+/IIIi/IIIi+/IV/IV+ chips.  With
       -mcpu=niagara, the compiler additionally optimizes it for Sun
       UltraSPARC T1 chips.  With -mcpu=niagara2, the compiler
       additionally optimizes it for Sun UltraSPARC T2 chips. With
       -mcpu=niagara3, the compiler additionally optimizes it for Sun
       UltraSPARC T3 chips.  With -mcpu=niagara4, the compiler
       additionally optimizes it for Sun UltraSPARC T4 chips.  With
       -mcpu=niagara7, the compiler additionally optimizes it for Oracle
       SPARC M7 chips.

   -mtune=cpu_type
       Set the instruction scheduling parameters for machine type
       cpu_type, but do not set the instruction set or register set that
       the option -mcpu=cpu_type does.

       The same values for -mcpu=cpu_type can be used for -mtune=cpu_type,
       but the only useful values are those that select a particular CPU
       implementation.  Those are cypress, supersparc, hypersparc, leon,
       leon3, leon3v7, f930, f934, sparclite86x, tsc701, ultrasparc,
       ultrasparc3, niagara, niagara2, niagara3, niagara4 and niagara7.
       With native Solaris and GNU/Linux toolchains, native can also be
       used.

   -mv8plus
   -mno-v8plus
       With -mv8plus, GCC generates code for the SPARC-V8+ ABI.  The
       difference from the V8 ABI is that the global and out registers are
       considered 64 bits wide.  This is enabled by default on Solaris in
       32-bit mode for all SPARC-V9 processors.

   -mvis
   -mno-vis
       With -mvis, GCC generates code that takes advantage of the
       UltraSPARC Visual Instruction Set extensions.  The default is
       -mno-vis.

   -mvis2
   -mno-vis2
       With -mvis2, GCC generates code that takes advantage of version 2.0
       of the UltraSPARC Visual Instruction Set extensions.  The default
       is -mvis2 when targeting a cpu that supports such instructions,
       such as UltraSPARC-III and later.  Setting -mvis2 also sets -mvis.

   -mvis3
   -mno-vis3
       With -mvis3, GCC generates code that takes advantage of version 3.0
       of the UltraSPARC Visual Instruction Set extensions.  The default
       is -mvis3 when targeting a cpu that supports such instructions,
       such as niagara-3 and later.  Setting -mvis3 also sets -mvis2 and
       -mvis.

   -mvis4
   -mno-vis4
       With -mvis4, GCC generates code that takes advantage of version 4.0
       of the UltraSPARC Visual Instruction Set extensions.  The default
       is -mvis4 when targeting a cpu that supports such instructions,
       such as niagara-7 and later.  Setting -mvis4 also sets -mvis3,
       -mvis2 and -mvis.

   -mcbcond
   -mno-cbcond
       With -mcbcond, GCC generates code that takes advantage of compare-
       and-branch instructions, as defined in the Sparc Architecture 2011.
       The default is -mcbcond when targeting a cpu that supports such
       instructions, such as niagara-4 and later.

   -mpopc
   -mno-popc
       With -mpopc, GCC generates code that takes advantage of the
       UltraSPARC population count instruction.  The default is -mpopc
       when targeting a cpu that supports such instructions, such as
       Niagara-2 and later.

   -mfmaf
   -mno-fmaf
       With -mfmaf, GCC generates code that takes advantage of the
       UltraSPARC Fused Multiply-Add Floating-point extensions.  The
       default is -mfmaf when targeting a cpu that supports such
       instructions, such as Niagara-3 and later.

   -mfix-at697f
       Enable the documented workaround for the single erratum of the
       Atmel AT697F processor (which corresponds to erratum #13 of the
       AT697E processor).

   -mfix-ut699
       Enable the documented workarounds for the floating-point errata and
       the data cache nullify errata of the UT699 processor.

   These -m options are supported in addition to the above on SPARC-V9
   processors in 64-bit environments:

   -m32
   -m64
       Generate code for a 32-bit or 64-bit environment.  The 32-bit
       environment sets int, long and pointer to 32 bits.  The 64-bit
       environment sets int to 32 bits and long and pointer to 64 bits.

   -mcmodel=which
       Set the code model to one of

       medlow
           The Medium/Low code model: 64-bit addresses, programs must be
           linked in the low 32 bits of memory.  Programs can be
           statically or dynamically linked.

       medmid
           The Medium/Middle code model: 64-bit addresses, programs must
           be linked in the low 44 bits of memory, the text and data
           segments must be less than 2GB in size and the data segment
           must be located within 2GB of the text segment.

       medany
           The Medium/Anywhere code model: 64-bit addresses, programs may
           be linked anywhere in memory, the text and data segments must
           be less than 2GB in size and the data segment must be located
           within 2GB of the text segment.

       embmedany
           The Medium/Anywhere code model for embedded systems: 64-bit
           addresses, the text and data segments must be less than 2GB in
           size, both starting anywhere in memory (determined at link
           time).  The global register %g4 points to the base of the data
           segment.  Programs are statically linked and PIC is not
           supported.

   -mmemory-model=mem-model
       Set the memory model in force on the processor to one of

       default
           The default memory model for the processor and operating
           system.

       rmo Relaxed Memory Order

       pso Partial Store Order

       tso Total Store Order

       sc  Sequential Consistency

       These memory models are formally defined in Appendix D of the Sparc
       V9 architecture manual, as set in the processor's "PSTATE.MM"
       field.

   -mstack-bias
   -mno-stack-bias
       With -mstack-bias, GCC assumes that the stack pointer, and frame
       pointer if present, are offset by -2047 which must be added back
       when making stack frame references.  This is the default in 64-bit
       mode.  Otherwise, assume no such offset is present.

   SPU Options

   These -m options are supported on the SPU:

   -mwarn-reloc
   -merror-reloc
       The loader for SPU does not handle dynamic relocations.  By
       default, GCC gives an error when it generates code that requires a
       dynamic relocation.  -mno-error-reloc disables the error,
       -mwarn-reloc generates a warning instead.

   -msafe-dma
   -munsafe-dma
       Instructions that initiate or test completion of DMA must not be
       reordered with respect to loads and stores of the memory that is
       being accessed.  With -munsafe-dma you must use the "volatile"
       keyword to protect memory accesses, but that can lead to
       inefficient code in places where the memory is known to not change.
       Rather than mark the memory as volatile, you can use -msafe-dma to
       tell the compiler to treat the DMA instructions as potentially
       affecting all memory.

   -mbranch-hints
       By default, GCC generates a branch hint instruction to avoid
       pipeline stalls for always-taken or probably-taken branches.  A
       hint is not generated closer than 8 instructions away from its
       branch.  There is little reason to disable them, except for
       debugging purposes, or to make an object a little bit smaller.

   -msmall-mem
   -mlarge-mem
       By default, GCC generates code assuming that addresses are never
       larger than 18 bits.  With -mlarge-mem code is generated that
       assumes a full 32-bit address.

   -mstdmain
       By default, GCC links against startup code that assumes the SPU-
       style main function interface (which has an unconventional
       parameter list).  With -mstdmain, GCC links your program against
       startup code that assumes a C99-style interface to "main",
       including a local copy of "argv" strings.

   -mfixed-range=register-range
       Generate code treating the given register range as fixed registers.
       A fixed register is one that the register allocator cannot use.
       This is useful when compiling kernel code.  A register range is
       specified as two registers separated by a dash.  Multiple register
       ranges can be specified separated by a comma.

   -mea32
   -mea64
       Compile code assuming that pointers to the PPU address space
       accessed via the "__ea" named address space qualifier are either 32
       or 64 bits wide.  The default is 32 bits.  As this is an ABI-
       changing option, all object code in an executable must be compiled
       with the same setting.

   -maddress-space-conversion
   -mno-address-space-conversion
       Allow/disallow treating the "__ea" address space as superset of the
       generic address space.  This enables explicit type casts between
       "__ea" and generic pointer as well as implicit conversions of
       generic pointers to "__ea" pointers.  The default is to allow
       address space pointer conversions.

   -mcache-size=cache-size
       This option controls the version of libgcc that the compiler links
       to an executable and selects a software-managed cache for accessing
       variables in the "__ea" address space with a particular cache size.
       Possible options for cache-size are 8, 16, 32, 64 and 128.  The
       default cache size is 64KB.

   -matomic-updates
   -mno-atomic-updates
       This option controls the version of libgcc that the compiler links
       to an executable and selects whether atomic updates to the
       software-managed cache of PPU-side variables are used.  If you use
       atomic updates, changes to a PPU variable from SPU code using the
       "__ea" named address space qualifier do not interfere with changes
       to other PPU variables residing in the same cache line from PPU
       code.  If you do not use atomic updates, such interference may
       occur; however, writing back cache lines is more efficient.  The
       default behavior is to use atomic updates.

   -mdual-nops
   -mdual-nops=n
       By default, GCC inserts nops to increase dual issue when it expects
       it to increase performance.  n can be a value from 0 to 10.  A
       smaller n inserts fewer nops.  10 is the default, 0 is the same as
       -mno-dual-nops.  Disabled with -Os.

   -mhint-max-nops=n
       Maximum number of nops to insert for a branch hint.  A branch hint
       must be at least 8 instructions away from the branch it is
       affecting.  GCC inserts up to n nops to enforce this, otherwise it
       does not generate the branch hint.

   -mhint-max-distance=n
       The encoding of the branch hint instruction limits the hint to be
       within 256 instructions of the branch it is affecting.  By default,
       GCC makes sure it is within 125.

   -msafe-hints
       Work around a hardware bug that causes the SPU to stall
       indefinitely.  By default, GCC inserts the "hbrp" instruction to
       make sure this stall won't happen.

   Options for System V

   These additional options are available on System V Release 4 for
   compatibility with other compilers on those systems:

   -G  Create a shared object.  It is recommended that -symbolic or
       -shared be used instead.

   -Qy Identify the versions of each tool used by the compiler, in a
       ".ident" assembler directive in the output.

   -Qn Refrain from adding ".ident" directives to the output file (this is
       the default).

   -YP,dirs
       Search the directories dirs, and no others, for libraries specified
       with -l.

   -Ym,dir
       Look in the directory dir to find the M4 preprocessor.  The
       assembler uses this option.

   TILE-Gx Options

   These -m options are supported on the TILE-Gx:

   -mcmodel=small
       Generate code for the small model.  The distance for direct calls
       is limited to 500M in either direction.  PC-relative addresses are
       32 bits.  Absolute addresses support the full address range.

   -mcmodel=large
       Generate code for the large model.  There is no limitation on call
       distance, pc-relative addresses, or absolute addresses.

   -mcpu=name
       Selects the type of CPU to be targeted.  Currently the only
       supported type is tilegx.

   -m32
   -m64
       Generate code for a 32-bit or 64-bit environment.  The 32-bit
       environment sets int, long, and pointer to 32 bits.  The 64-bit
       environment sets int to 32 bits and long and pointer to 64 bits.

   -mbig-endian
   -mlittle-endian
       Generate code in big/little endian mode, respectively.

   TILEPro Options

   These -m options are supported on the TILEPro:

   -mcpu=name
       Selects the type of CPU to be targeted.  Currently the only
       supported type is tilepro.

   -m32
       Generate code for a 32-bit environment, which sets int, long, and
       pointer to 32 bits.  This is the only supported behavior so the
       flag is essentially ignored.

   V850 Options

   These -m options are defined for V850 implementations:

   -mlong-calls
   -mno-long-calls
       Treat all calls as being far away (near).  If calls are assumed to
       be far away, the compiler always loads the function's address into
       a register, and calls indirect through the pointer.

   -mno-ep
   -mep
       Do not optimize (do optimize) basic blocks that use the same index
       pointer 4 or more times to copy pointer into the "ep" register, and
       use the shorter "sld" and "sst" instructions.  The -mep option is
       on by default if you optimize.

   -mno-prolog-function
   -mprolog-function
       Do not use (do use) external functions to save and restore
       registers at the prologue and epilogue of a function.  The external
       functions are slower, but use less code space if more than one
       function saves the same number of registers.  The -mprolog-function
       option is on by default if you optimize.

   -mspace
       Try to make the code as small as possible.  At present, this just
       turns on the -mep and -mprolog-function options.

   -mtda=n
       Put static or global variables whose size is n bytes or less into
       the tiny data area that register "ep" points to.  The tiny data
       area can hold up to 256 bytes in total (128 bytes for byte
       references).

   -msda=n
       Put static or global variables whose size is n bytes or less into
       the small data area that register "gp" points to.  The small data
       area can hold up to 64 kilobytes.

   -mzda=n
       Put static or global variables whose size is n bytes or less into
       the first 32 kilobytes of memory.

   -mv850
       Specify that the target processor is the V850.

   -mv850e3v5
       Specify that the target processor is the V850E3V5.  The
       preprocessor constant "__v850e3v5__" is defined if this option is
       used.

   -mv850e2v4
       Specify that the target processor is the V850E3V5.  This is an
       alias for the -mv850e3v5 option.

   -mv850e2v3
       Specify that the target processor is the V850E2V3.  The
       preprocessor constant "__v850e2v3__" is defined if this option is
       used.

   -mv850e2
       Specify that the target processor is the V850E2.  The preprocessor
       constant "__v850e2__" is defined if this option is used.

   -mv850e1
       Specify that the target processor is the V850E1.  The preprocessor
       constants "__v850e1__" and "__v850e__" are defined if this option
       is used.

   -mv850es
       Specify that the target processor is the V850ES.  This is an alias
       for the -mv850e1 option.

   -mv850e
       Specify that the target processor is the V850E.  The preprocessor
       constant "__v850e__" is defined if this option is used.

       If neither -mv850 nor -mv850e nor -mv850e1 nor -mv850e2 nor
       -mv850e2v3 nor -mv850e3v5 are defined then a default target
       processor is chosen and the relevant __v850*__ preprocessor
       constant is defined.

       The preprocessor constants "__v850" and "__v851__" are always
       defined, regardless of which processor variant is the target.

   -mdisable-callt
   -mno-disable-callt
       This option suppresses generation of the "CALLT" instruction for
       the v850e, v850e1, v850e2, v850e2v3 and v850e3v5 flavors of the
       v850 architecture.

       This option is enabled by default when the RH850 ABI is in use (see
       -mrh850-abi), and disabled by default when the GCC ABI is in use.
       If "CALLT" instructions are being generated then the C preprocessor
       symbol "__V850_CALLT__" is defined.

   -mrelax
   -mno-relax
       Pass on (or do not pass on) the -mrelax command-line option to the
       assembler.

   -mlong-jumps
   -mno-long-jumps
       Disable (or re-enable) the generation of PC-relative jump
       instructions.

   -msoft-float
   -mhard-float
       Disable (or re-enable) the generation of hardware floating point
       instructions.  This option is only significant when the target
       architecture is V850E2V3 or higher.  If hardware floating point
       instructions are being generated then the C preprocessor symbol
       "__FPU_OK__" is defined, otherwise the symbol "__NO_FPU__" is
       defined.

   -mloop
       Enables the use of the e3v5 LOOP instruction.  The use of this
       instruction is not enabled by default when the e3v5 architecture is
       selected because its use is still experimental.

   -mrh850-abi
   -mghs
       Enables support for the RH850 version of the V850 ABI.  This is the
       default.  With this version of the ABI the following rules apply:

       *   Integer sized structures and unions are returned via a memory
           pointer rather than a register.

       *   Large structures and unions (more than 8 bytes in size) are
           passed by value.

       *   Functions are aligned to 16-bit boundaries.

       *   The -m8byte-align command-line option is supported.

       *   The -mdisable-callt command-line option is enabled by default.
           The -mno-disable-callt command-line option is not supported.

       When this version of the ABI is enabled the C preprocessor symbol
       "__V850_RH850_ABI__" is defined.

   -mgcc-abi
       Enables support for the old GCC version of the V850 ABI.  With this
       version of the ABI the following rules apply:

       *   Integer sized structures and unions are returned in register
           "r10".

       *   Large structures and unions (more than 8 bytes in size) are
           passed by reference.

       *   Functions are aligned to 32-bit boundaries, unless optimizing
           for size.

       *   The -m8byte-align command-line option is not supported.

       *   The -mdisable-callt command-line option is supported but not
           enabled by default.

       When this version of the ABI is enabled the C preprocessor symbol
       "__V850_GCC_ABI__" is defined.

   -m8byte-align
   -mno-8byte-align
       Enables support for "double" and "long long" types to be aligned on
       8-byte boundaries.  The default is to restrict the alignment of all
       objects to at most 4-bytes.  When -m8byte-align is in effect the C
       preprocessor symbol "__V850_8BYTE_ALIGN__" is defined.

   -mbig-switch
       Generate code suitable for big switch tables.  Use this option only
       if the assembler/linker complain about out of range branches within
       a switch table.

   -mapp-regs
       This option causes r2 and r5 to be used in the code generated by
       the compiler.  This setting is the default.

   -mno-app-regs
       This option causes r2 and r5 to be treated as fixed registers.

   VAX Options

   These -m options are defined for the VAX:

   -munix
       Do not output certain jump instructions ("aobleq" and so on) that
       the Unix assembler for the VAX cannot handle across long ranges.

   -mgnu
       Do output those jump instructions, on the assumption that the GNU
       assembler is being used.

   -mg Output code for G-format floating-point numbers instead of
       D-format.

   Visium Options

   -mdebug
       A program which performs file I/O and is destined to run on an MCM
       target should be linked with this option.  It causes the libraries
       libc.a and libdebug.a to be linked.  The program should be run on
       the target under the control of the GDB remote debugging stub.

   -msim
       A program which performs file I/O and is destined to run on the
       simulator should be linked with option.  This causes libraries
       libc.a and libsim.a to be linked.

   -mfpu
   -mhard-float
       Generate code containing floating-point instructions.  This is the
       default.

   -mno-fpu
   -msoft-float
       Generate code containing library calls for floating-point.

       -msoft-float changes the calling convention in the output file;
       therefore, it is only useful if you compile all of a program with
       this option.  In particular, you need to compile libgcc.a, the
       library that comes with GCC, with -msoft-float in order for this to
       work.

   -mcpu=cpu_type
       Set the instruction set, register set, and instruction scheduling
       parameters for machine type cpu_type.  Supported values for
       cpu_type are mcm, gr5 and gr6.

       mcm is a synonym of gr5 present for backward compatibility.

       By default (unless configured otherwise), GCC generates code for
       the GR5 variant of the Visium architecture.

       With -mcpu=gr6, GCC generates code for the GR6 variant of the
       Visium architecture.  The only difference from GR5 code is that the
       compiler will generate block move instructions.

   -mtune=cpu_type
       Set the instruction scheduling parameters for machine type
       cpu_type, but do not set the instruction set or register set that
       the option -mcpu=cpu_type would.

   -msv-mode
       Generate code for the supervisor mode, where there are no
       restrictions on the access to general registers.  This is the
       default.

   -muser-mode
       Generate code for the user mode, where the access to some general
       registers is forbidden: on the GR5, registers r24 to r31 cannot be
       accessed in this mode; on the GR6, only registers r29 to r31 are
       affected.

   VMS Options

   These -m options are defined for the VMS implementations:

   -mvms-return-codes
       Return VMS condition codes from "main". The default is to return
       POSIX-style condition (e.g. error) codes.

   -mdebug-main=prefix
       Flag the first routine whose name starts with prefix as the main
       routine for the debugger.

   -mmalloc64
       Default to 64-bit memory allocation routines.

   -mpointer-size=size
       Set the default size of pointers. Possible options for size are 32
       or short for 32 bit pointers, 64 or long for 64 bit pointers, and
       no for supporting only 32 bit pointers.  The later option disables
       "pragma pointer_size".

   VxWorks Options

   The options in this section are defined for all VxWorks targets.
   Options specific to the target hardware are listed with the other
   options for that target.

   -mrtp
       GCC can generate code for both VxWorks kernels and real time
       processes (RTPs).  This option switches from the former to the
       latter.  It also defines the preprocessor macro "__RTP__".

   -non-static
       Link an RTP executable against shared libraries rather than static
       libraries.  The options -static and -shared can also be used for
       RTPs; -static is the default.

   -Bstatic
   -Bdynamic
       These options are passed down to the linker.  They are defined for
       compatibility with Diab.

   -Xbind-lazy
       Enable lazy binding of function calls.  This option is equivalent
       to -Wl,-z,now and is defined for compatibility with Diab.

   -Xbind-now
       Disable lazy binding of function calls.  This option is the default
       and is defined for compatibility with Diab.

   x86 Options

   These -m options are defined for the x86 family of computers.

   -march=cpu-type
       Generate instructions for the machine type cpu-type.  In contrast
       to -mtune=cpu-type, which merely tunes the generated code for the
       specified cpu-type, -march=cpu-type allows GCC to generate code
       that may not run at all on processors other than the one indicated.
       Specifying -march=cpu-type implies -mtune=cpu-type.

       The choices for cpu-type are:

       native
           This selects the CPU to generate code for at compilation time
           by determining the processor type of the compiling machine.
           Using -march=native enables all instruction subsets supported
           by the local machine (hence the result might not run on
           different machines).  Using -mtune=native produces code
           optimized for the local machine under the constraints of the
           selected instruction set.

       i386
           Original Intel i386 CPU.

       i486
           Intel i486 CPU.  (No scheduling is implemented for this chip.)

       i586
       pentium
           Intel Pentium CPU with no MMX support.

       lakemont
           Intel Lakemont MCU, based on Intel Pentium CPU.

       pentium-mmx
           Intel Pentium MMX CPU, based on Pentium core with MMX
           instruction set support.

       pentiumpro
           Intel Pentium Pro CPU.

       i686
           When used with -march, the Pentium Pro instruction set is used,
           so the code runs on all i686 family chips.  When used with
           -mtune, it has the same meaning as generic.

       pentium2
           Intel Pentium II CPU, based on Pentium Pro core with MMX
           instruction set support.

       pentium3
       pentium3m
           Intel Pentium III CPU, based on Pentium Pro core with MMX and
           SSE instruction set support.

       pentium-m
           Intel Pentium M; low-power version of Intel Pentium III CPU
           with MMX, SSE and SSE2 instruction set support.  Used by
           Centrino notebooks.

       pentium4
       pentium4m
           Intel Pentium 4 CPU with MMX, SSE and SSE2 instruction set
           support.

       prescott
           Improved version of Intel Pentium 4 CPU with MMX, SSE, SSE2 and
           SSE3 instruction set support.

       nocona
           Improved version of Intel Pentium 4 CPU with 64-bit extensions,
           MMX, SSE, SSE2 and SSE3 instruction set support.

       core2
           Intel Core 2 CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3
           and SSSE3 instruction set support.

       nehalem
           Intel Nehalem CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3,
           SSSE3, SSE4.1, SSE4.2 and POPCNT instruction set support.

       westmere
           Intel Westmere CPU with 64-bit extensions, MMX, SSE, SSE2,
           SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES and PCLMUL instruction
           set support.

       sandybridge
           Intel Sandy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2,
           SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AES and PCLMUL
           instruction set support.

       ivybridge
           Intel Ivy Bridge CPU with 64-bit extensions, MMX, SSE, SSE2,
           SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AES, PCLMUL,
           FSGSBASE, RDRND and F16C instruction set support.

       haswell
           Intel Haswell CPU with 64-bit extensions, MOVBE, MMX, SSE,
           SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
           PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2 and F16C instruction
           set support.

       broadwell
           Intel Broadwell CPU with 64-bit extensions, MOVBE, MMX, SSE,
           SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
           PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C, RDSEED, ADCX and
           PREFETCHW instruction set support.

       skylake
           Intel Skylake CPU with 64-bit extensions, MOVBE, MMX, SSE,
           SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
           PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C, RDSEED, ADCX,
           PREFETCHW, CLFLUSHOPT, XSAVEC and XSAVES instruction set
           support.

       bonnell
           Intel Bonnell CPU with 64-bit extensions, MOVBE, MMX, SSE,
           SSE2, SSE3 and SSSE3 instruction set support.

       silvermont
           Intel Silvermont CPU with 64-bit extensions, MOVBE, MMX, SSE,
           SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AES, PCLMUL and
           RDRND instruction set support.

       knl Intel Knight's Landing CPU with 64-bit extensions, MOVBE, MMX,
           SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, AVX, AVX2, AES,
           PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C, RDSEED, ADCX,
           PREFETCHW, AVX512F, AVX512PF, AVX512ER and AVX512CD instruction
           set support.

       skylake-avx512
           Intel Skylake Server CPU with 64-bit extensions, MOVBE, MMX,
           SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, POPCNT, PKU, AVX, AVX2,
           AES, PCLMUL, FSGSBASE, RDRND, FMA, BMI, BMI2, F16C, RDSEED,
           ADCX, PREFETCHW, CLFLUSHOPT, XSAVEC, XSAVES, AVX512F, AVX512VL,
           AVX512BW, AVX512DQ and AVX512CD instruction set support.

       k6  AMD K6 CPU with MMX instruction set support.

       k6-2
       k6-3
           Improved versions of AMD K6 CPU with MMX and 3DNow! instruction
           set support.

       athlon
       athlon-tbird
           AMD Athlon CPU with MMX, 3dNOW!, enhanced 3DNow! and SSE
           prefetch instructions support.

       athlon-4
       athlon-xp
       athlon-mp
           Improved AMD Athlon CPU with MMX, 3DNow!, enhanced 3DNow! and
           full SSE instruction set support.

       k8
       opteron
       athlon64
       athlon-fx
           Processors based on the AMD K8 core with x86-64 instruction set
           support, including the AMD Opteron, Athlon 64, and Athlon 64 FX
           processors.  (This supersets MMX, SSE, SSE2, 3DNow!, enhanced
           3DNow! and 64-bit instruction set extensions.)

       k8-sse3
       opteron-sse3
       athlon64-sse3
           Improved versions of AMD K8 cores with SSE3 instruction set
           support.

       amdfam10
       barcelona
           CPUs based on AMD Family 10h cores with x86-64 instruction set
           support.  (This supersets MMX, SSE, SSE2, SSE3, SSE4A, 3DNow!,
           enhanced 3DNow!, ABM and 64-bit instruction set extensions.)

       bdver1
           CPUs based on AMD Family 15h cores with x86-64 instruction set
           support.  (This supersets FMA4, AVX, XOP, LWP, AES, PCL_MUL,
           CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM
           and 64-bit instruction set extensions.)

       bdver2
           AMD Family 15h core based CPUs with x86-64 instruction set
           support.  (This supersets BMI, TBM, F16C, FMA, FMA4, AVX, XOP,
           LWP, AES, PCL_MUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3,
           SSE4.1, SSE4.2, ABM and 64-bit instruction set extensions.)

       bdver3
           AMD Family 15h core based CPUs with x86-64 instruction set
           support.  (This supersets BMI, TBM, F16C, FMA, FMA4, FSGSBASE,
           AVX, XOP, LWP, AES, PCL_MUL, CX16, MMX, SSE, SSE2, SSE3, SSE4A,
           SSSE3, SSE4.1, SSE4.2, ABM and 64-bit instruction set
           extensions.

       bdver4
           AMD Family 15h core based CPUs with x86-64 instruction set
           support.  (This supersets BMI, BMI2, TBM, F16C, FMA, FMA4,
           FSGSBASE, AVX, AVX2, XOP, LWP, AES, PCL_MUL, CX16, MOVBE, MMX,
           SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM and 64-bit
           instruction set extensions.

       znver1
           AMD Family 17h core based CPUs with x86-64 instruction set
           support.  (This supersets BMI, BMI2, F16C, FMA, FSGSBASE, AVX,
           AVX2, ADCX, RDSEED, MWAITX, SHA, CLZERO, AES, PCL_MUL, CX16,
           MOVBE, MMX, SSE, SSE2, SSE3, SSE4A, SSSE3, SSE4.1, SSE4.2, ABM,
           XSAVEC, XSAVES, CLFLUSHOPT, POPCNT, and 64-bit instruction set
           extensions.

       btver1
           CPUs based on AMD Family 14h cores with x86-64 instruction set
           support.  (This supersets MMX, SSE, SSE2, SSE3, SSSE3, SSE4A,
           CX16, ABM and 64-bit instruction set extensions.)

       btver2
           CPUs based on AMD Family 16h cores with x86-64 instruction set
           support. This includes MOVBE, F16C, BMI, AVX, PCL_MUL, AES,
           SSE4.2, SSE4.1, CX16, ABM, SSE4A, SSSE3, SSE3, SSE2, SSE, MMX
           and 64-bit instruction set extensions.

       winchip-c6
           IDT WinChip C6 CPU, dealt in same way as i486 with additional
           MMX instruction set support.

       winchip2
           IDT WinChip 2 CPU, dealt in same way as i486 with additional
           MMX and 3DNow!  instruction set support.

       c3  VIA C3 CPU with MMX and 3DNow! instruction set support.  (No
           scheduling is implemented for this chip.)

       c3-2
           VIA C3-2 (Nehemiah/C5XL) CPU with MMX and SSE instruction set
           support.  (No scheduling is implemented for this chip.)

       geode
           AMD Geode embedded processor with MMX and 3DNow! instruction
           set support.

   -mtune=cpu-type
       Tune to cpu-type everything applicable about the generated code,
       except for the ABI and the set of available instructions.  While
       picking a specific cpu-type schedules things appropriately for that
       particular chip, the compiler does not generate any code that
       cannot run on the default machine type unless you use a -march=cpu-
       type option.  For example, if GCC is configured for
       i686-pc-linux-gnu then -mtune=pentium4 generates code that is tuned
       for Pentium 4 but still runs on i686 machines.

       The choices for cpu-type are the same as for -march.  In addition,
       -mtune supports 2 extra choices for cpu-type:

       generic
           Produce code optimized for the most common IA32/AMD64/EM64T
           processors.  If you know the CPU on which your code will run,
           then you should use the corresponding -mtune or -march option
           instead of -mtune=generic.  But, if you do not know exactly
           what CPU users of your application will have, then you should
           use this option.

           As new processors are deployed in the marketplace, the behavior
           of this option will change.  Therefore, if you upgrade to a
           newer version of GCC, code generation controlled by this option
           will change to reflect the processors that are most common at
           the time that version of GCC is released.

           There is no -march=generic option because -march indicates the
           instruction set the compiler can use, and there is no generic
           instruction set applicable to all processors.  In contrast,
           -mtune indicates the processor (or, in this case, collection of
           processors) for which the code is optimized.

       intel
           Produce code optimized for the most current Intel processors,
           which are Haswell and Silvermont for this version of GCC.  If
           you know the CPU on which your code will run, then you should
           use the corresponding -mtune or -march option instead of
           -mtune=intel.  But, if you want your application performs
           better on both Haswell and Silvermont, then you should use this
           option.

           As new Intel processors are deployed in the marketplace, the
           behavior of this option will change.  Therefore, if you upgrade
           to a newer version of GCC, code generation controlled by this
           option will change to reflect the most current Intel processors
           at the time that version of GCC is released.

           There is no -march=intel option because -march indicates the
           instruction set the compiler can use, and there is no common
           instruction set applicable to all processors.  In contrast,
           -mtune indicates the processor (or, in this case, collection of
           processors) for which the code is optimized.

   -mcpu=cpu-type
       A deprecated synonym for -mtune.

   -mfpmath=unit
       Generate floating-point arithmetic for selected unit unit.  The
       choices for unit are:

       387 Use the standard 387 floating-point coprocessor present on the
           majority of chips and emulated otherwise.  Code compiled with
           this option runs almost everywhere.  The temporary results are
           computed in 80-bit precision instead of the precision specified
           by the type, resulting in slightly different results compared
           to most of other chips.  See -ffloat-store for more detailed
           description.

           This is the default choice for x86-32 targets.

       sse Use scalar floating-point instructions present in the SSE
           instruction set.  This instruction set is supported by Pentium
           III and newer chips, and in the AMD line by Athlon-4, Athlon XP
           and Athlon MP chips.  The earlier version of the SSE
           instruction set supports only single-precision arithmetic, thus
           the double and extended-precision arithmetic are still done
           using 387.  A later version, present only in Pentium 4 and AMD
           x86-64 chips, supports double-precision arithmetic too.

           For the x86-32 compiler, you must use -march=cpu-type, -msse or
           -msse2 switches to enable SSE extensions and make this option
           effective.  For the x86-64 compiler, these extensions are
           enabled by default.

           The resulting code should be considerably faster in the
           majority of cases and avoid the numerical instability problems
           of 387 code, but may break some existing code that expects
           temporaries to be 80 bits.

           This is the default choice for the x86-64 compiler.

       sse,387
       sse+387
       both
           Attempt to utilize both instruction sets at once.  This
           effectively doubles the amount of available registers, and on
           chips with separate execution units for 387 and SSE the
           execution resources too.  Use this option with care, as it is
           still experimental, because the GCC register allocator does not
           model separate functional units well, resulting in unstable
           performance.

   -masm=dialect
       Output assembly instructions using selected dialect.  Also affects
       which dialect is used for basic "asm" and extended "asm". Supported
       choices (in dialect order) are att or intel. The default is att.
       Darwin does not support intel.

   -mieee-fp
   -mno-ieee-fp
       Control whether or not the compiler uses IEEE floating-point
       comparisons.  These correctly handle the case where the result of a
       comparison is unordered.

   -msoft-float
       Generate output containing library calls for floating point.

       Warning: the requisite libraries are not part of GCC.  Normally the
       facilities of the machine's usual C compiler are used, but this
       can't be done directly in cross-compilation.  You must make your
       own arrangements to provide suitable library functions for cross-
       compilation.

       On machines where a function returns floating-point results in the
       80387 register stack, some floating-point opcodes may be emitted
       even if -msoft-float is used.

   -mno-fp-ret-in-387
       Do not use the FPU registers for return values of functions.

       The usual calling convention has functions return values of types
       "float" and "double" in an FPU register, even if there is no FPU.
       The idea is that the operating system should emulate an FPU.

       The option -mno-fp-ret-in-387 causes such values to be returned in
       ordinary CPU registers instead.

   -mno-fancy-math-387
       Some 387 emulators do not support the "sin", "cos" and "sqrt"
       instructions for the 387.  Specify this option to avoid generating
       those instructions.  This option is the default on OpenBSD and
       NetBSD.  This option is overridden when -march indicates that the
       target CPU always has an FPU and so the instruction does not need
       emulation.  These instructions are not generated unless you also
       use the -funsafe-math-optimizations switch.

   -malign-double
   -mno-align-double
       Control whether GCC aligns "double", "long double", and "long long"
       variables on a two-word boundary or a one-word boundary.  Aligning
       "double" variables on a two-word boundary produces code that runs
       somewhat faster on a Pentium at the expense of more memory.

       On x86-64, -malign-double is enabled by default.

       Warning: if you use the -malign-double switch, structures
       containing the above types are aligned differently than the
       published application binary interface specifications for the
       x86-32 and are not binary compatible with structures in code
       compiled without that switch.

   -m96bit-long-double
   -m128bit-long-double
       These switches control the size of "long double" type.  The x86-32
       application binary interface specifies the size to be 96 bits, so
       -m96bit-long-double is the default in 32-bit mode.

       Modern architectures (Pentium and newer) prefer "long double" to be
       aligned to an 8- or 16-byte boundary.  In arrays or structures
       conforming to the ABI, this is not possible.  So specifying
       -m128bit-long-double aligns "long double" to a 16-byte boundary by
       padding the "long double" with an additional 32-bit zero.

       In the x86-64 compiler, -m128bit-long-double is the default choice
       as its ABI specifies that "long double" is aligned on 16-byte
       boundary.

       Notice that neither of these options enable any extra precision
       over the x87 standard of 80 bits for a "long double".

       Warning: if you override the default value for your target ABI,
       this changes the size of structures and arrays containing "long
       double" variables, as well as modifying the function calling
       convention for functions taking "long double".  Hence they are not
       binary-compatible with code compiled without that switch.

   -mlong-double-64
   -mlong-double-80
   -mlong-double-128
       These switches control the size of "long double" type. A size of 64
       bits makes the "long double" type equivalent to the "double" type.
       This is the default for 32-bit Bionic C library.  A size of 128
       bits makes the "long double" type equivalent to the "__float128"
       type. This is the default for 64-bit Bionic C library.

       Warning: if you override the default value for your target ABI,
       this changes the size of structures and arrays containing "long
       double" variables, as well as modifying the function calling
       convention for functions taking "long double".  Hence they are not
       binary-compatible with code compiled without that switch.

   -malign-data=type
       Control how GCC aligns variables.  Supported values for type are
       compat uses increased alignment value compatible uses GCC 4.8 and
       earlier, abi uses alignment value as specified by the psABI, and
       cacheline uses increased alignment value to match the cache line
       size.  compat is the default.

   -mlarge-data-threshold=threshold
       When -mcmodel=medium is specified, data objects larger than
       threshold are placed in the large data section.  This value must be
       the same across all objects linked into the binary, and defaults to
       65535.

   -mrtd
       Use a different function-calling convention, in which functions
       that take a fixed number of arguments return with the "ret num"
       instruction, which pops their arguments while returning.  This
       saves one instruction in the caller since there is no need to pop
       the arguments there.

       You can specify that an individual function is called with this
       calling sequence with the function attribute "stdcall".  You can
       also override the -mrtd option by using the function attribute
       "cdecl".

       Warning: this calling convention is incompatible with the one
       normally used on Unix, so you cannot use it if you need to call
       libraries compiled with the Unix compiler.

       Also, you must provide function prototypes for all functions that
       take variable numbers of arguments (including "printf"); otherwise
       incorrect code is generated for calls to those functions.

       In addition, seriously incorrect code results if you call a
       function with too many arguments.  (Normally, extra arguments are
       harmlessly ignored.)

   -mregparm=num
       Control how many registers are used to pass integer arguments.  By
       default, no registers are used to pass arguments, and at most 3
       registers can be used.  You can control this behavior for a
       specific function by using the function attribute "regparm".

       Warning: if you use this switch, and num is nonzero, then you must
       build all modules with the same value, including any libraries.
       This includes the system libraries and startup modules.

   -msseregparm
       Use SSE register passing conventions for float and double arguments
       and return values.  You can control this behavior for a specific
       function by using the function attribute "sseregparm".

       Warning: if you use this switch then you must build all modules
       with the same value, including any libraries.  This includes the
       system libraries and startup modules.

   -mvect8-ret-in-mem
       Return 8-byte vectors in memory instead of MMX registers.  This is
       the default on Solaris@tie{}8 and 9 and VxWorks to match the ABI of
       the Sun Studio compilers until version 12.  Later compiler versions
       (starting with Studio 12 Update@tie{}1) follow the ABI used by
       other x86 targets, which is the default on Solaris@tie{}10 and
       later.  Only use this option if you need to remain compatible with
       existing code produced by those previous compiler versions or older
       versions of GCC.

   -mpc32
   -mpc64
   -mpc80
       Set 80387 floating-point precision to 32, 64 or 80 bits.  When
       -mpc32 is specified, the significands of results of floating-point
       operations are rounded to 24 bits (single precision); -mpc64 rounds
       the significands of results of floating-point operations to 53 bits
       (double precision) and -mpc80 rounds the significands of results of
       floating-point operations to 64 bits (extended double precision),
       which is the default.  When this option is used, floating-point
       operations in higher precisions are not available to the programmer
       without setting the FPU control word explicitly.

       Setting the rounding of floating-point operations to less than the
       default 80 bits can speed some programs by 2% or more.  Note that
       some mathematical libraries assume that extended-precision (80-bit)
       floating-point operations are enabled by default; routines in such
       libraries could suffer significant loss of accuracy, typically
       through so-called "catastrophic cancellation", when this option is
       used to set the precision to less than extended precision.

   -mstackrealign
       Realign the stack at entry.  On the x86, the -mstackrealign option
       generates an alternate prologue and epilogue that realigns the run-
       time stack if necessary.  This supports mixing legacy codes that
       keep 4-byte stack alignment with modern codes that keep 16-byte
       stack alignment for SSE compatibility.  See also the attribute
       "force_align_arg_pointer", applicable to individual functions.

   -mpreferred-stack-boundary=num
       Attempt to keep the stack boundary aligned to a 2 raised to num
       byte boundary.  If -mpreferred-stack-boundary is not specified, the
       default is 4 (16 bytes or 128 bits).

       Warning: When generating code for the x86-64 architecture with SSE
       extensions disabled, -mpreferred-stack-boundary=3 can be used to
       keep the stack boundary aligned to 8 byte boundary.  Since x86-64
       ABI require 16 byte stack alignment, this is ABI incompatible and
       intended to be used in controlled environment where stack space is
       important limitation.  This option leads to wrong code when
       functions compiled with 16 byte stack alignment (such as functions
       from a standard library) are called with misaligned stack.  In this
       case, SSE instructions may lead to misaligned memory access traps.
       In addition, variable arguments are handled incorrectly for 16 byte
       aligned objects (including x87 long double and __int128), leading
       to wrong results.  You must build all modules with
       -mpreferred-stack-boundary=3, including any libraries.  This
       includes the system libraries and startup modules.

   -mincoming-stack-boundary=num
       Assume the incoming stack is aligned to a 2 raised to num byte
       boundary.  If -mincoming-stack-boundary is not specified, the one
       specified by -mpreferred-stack-boundary is used.

       On Pentium and Pentium Pro, "double" and "long double" values
       should be aligned to an 8-byte boundary (see -malign-double) or
       suffer significant run time performance penalties.  On Pentium III,
       the Streaming SIMD Extension (SSE) data type "__m128" may not work
       properly if it is not 16-byte aligned.

       To ensure proper alignment of this values on the stack, the stack
       boundary must be as aligned as that required by any value stored on
       the stack.  Further, every function must be generated such that it
       keeps the stack aligned.  Thus calling a function compiled with a
       higher preferred stack boundary from a function compiled with a
       lower preferred stack boundary most likely misaligns the stack.  It
       is recommended that libraries that use callbacks always use the
       default setting.

       This extra alignment does consume extra stack space, and generally
       increases code size.  Code that is sensitive to stack space usage,
       such as embedded systems and operating system kernels, may want to
       reduce the preferred alignment to -mpreferred-stack-boundary=2.

   -mmmx
   -msse
   -msse2
   -msse3
   -mssse3
   -msse4
   -msse4a
   -msse4.1
   -msse4.2
   -mavx
   -mavx2
   -mavx512f
   -mavx512pf
   -mavx512er
   -mavx512cd
   -mavx512vl
   -mavx512bw
   -mavx512dq
   -mavx512ifma
   -mavx512vbmi
   -msha
   -maes
   -mpclmul
   -mclfushopt
   -mfsgsbase
   -mrdrnd
   -mf16c
   -mfma
   -mfma4
   -mprefetchwt1
   -mxop
   -mlwp
   -m3dnow
   -mpopcnt
   -mabm
   -mbmi
   -mbmi2
   -mlzcnt
   -mfxsr
   -mxsave
   -mxsaveopt
   -mxsavec
   -mxsaves
   -mrtm
   -mtbm
   -mmpx
   -mmwaitx
   -mclzero
   -mpku
       These switches enable the use of instructions in the MMX, SSE,
       SSE2, SSE3, SSSE3, SSE4.1, AVX, AVX2, AVX512F, AVX512PF, AVX512ER,
       AVX512CD, SHA, AES, PCLMUL, FSGSBASE, RDRND, F16C, FMA, SSE4A,
       FMA4, XOP, LWP, ABM, AVX512VL, AVX512BW, AVX512DQ, AVX512IFMA
       AVX512VBMI, BMI, BMI2, FXSR, XSAVE, XSAVEOPT, LZCNT, RTM, MPX,
       MWAITX, PKU or 3DNow!  extended instruction sets.  Each has a
       corresponding -mno- option to disable use of these instructions.

       These extensions are also available as built-in functions: see x86
       Built-in Functions, for details of the functions enabled and
       disabled by these switches.

       To generate SSE/SSE2 instructions automatically from floating-point
       code (as opposed to 387 instructions), see -mfpmath=sse.

       GCC depresses SSEx instructions when -mavx is used. Instead, it
       generates new AVX instructions or AVX equivalence for all SSEx
       instructions when needed.

       These options enable GCC to use these extended instructions in
       generated code, even without -mfpmath=sse.  Applications that
       perform run-time CPU detection must compile separate files for each
       supported architecture, using the appropriate flags.  In
       particular, the file containing the CPU detection code should be
       compiled without these options.

   -mdump-tune-features
       This option instructs GCC to dump the names of the x86 performance
       tuning features and default settings. The names can be used in
       -mtune-ctrl=feature-list.

   -mtune-ctrl=feature-list
       This option is used to do fine grain control of x86 code generation
       features.  feature-list is a comma separated list of feature names.
       See also -mdump-tune-features. When specified, the feature is
       turned on if it is not preceded with ^, otherwise, it is turned
       off.  -mtune-ctrl=feature-list is intended to be used by GCC
       developers. Using it may lead to code paths not covered by testing
       and can potentially result in compiler ICEs or runtime errors.

   -mno-default
       This option instructs GCC to turn off all tunable features. See
       also -mtune-ctrl=feature-list and -mdump-tune-features.

   -mcld
       This option instructs GCC to emit a "cld" instruction in the
       prologue of functions that use string instructions.  String
       instructions depend on the DF flag to select between autoincrement
       or autodecrement mode.  While the ABI specifies the DF flag to be
       cleared on function entry, some operating systems violate this
       specification by not clearing the DF flag in their exception
       dispatchers.  The exception handler can be invoked with the DF flag
       set, which leads to wrong direction mode when string instructions
       are used.  This option can be enabled by default on 32-bit x86
       targets by configuring GCC with the --enable-cld configure option.
       Generation of "cld" instructions can be suppressed with the
       -mno-cld compiler option in this case.

   -mvzeroupper
       This option instructs GCC to emit a "vzeroupper" instruction before
       a transfer of control flow out of the function to minimize the AVX
       to SSE transition penalty as well as remove unnecessary "zeroupper"
       intrinsics.

   -mprefer-avx128
       This option instructs GCC to use 128-bit AVX instructions instead
       of 256-bit AVX instructions in the auto-vectorizer.

   -mcx16
       This option enables GCC to generate "CMPXCHG16B" instructions.
       "CMPXCHG16B" allows for atomic operations on 128-bit double
       quadword (or oword) data types.  This is useful for high-resolution
       counters that can be updated by multiple processors (or cores).
       This instruction is generated as part of atomic built-in functions:
       see __sync Builtins or __atomic Builtins for details.

   -msahf
       This option enables generation of "SAHF" instructions in 64-bit
       code.  Early Intel Pentium 4 CPUs with Intel 64 support, prior to
       the introduction of Pentium 4 G1 step in December 2005, lacked the
       "LAHF" and "SAHF" instructions which are supported by AMD64.  These
       are load and store instructions, respectively, for certain status
       flags.  In 64-bit mode, the "SAHF" instruction is used to optimize
       "fmod", "drem", and "remainder" built-in functions; see Other
       Builtins for details.

   -mmovbe
       This option enables use of the "movbe" instruction to implement
       "__builtin_bswap32" and "__builtin_bswap64".

   -mcrc32
       This option enables built-in functions "__builtin_ia32_crc32qi",
       "__builtin_ia32_crc32hi", "__builtin_ia32_crc32si" and
       "__builtin_ia32_crc32di" to generate the "crc32" machine
       instruction.

   -mrecip
       This option enables use of "RCPSS" and "RSQRTSS" instructions (and
       their vectorized variants "RCPPS" and "RSQRTPS") with an additional
       Newton-Raphson step to increase precision instead of "DIVSS" and
       "SQRTSS" (and their vectorized variants) for single-precision
       floating-point arguments.  These instructions are generated only
       when -funsafe-math-optimizations is enabled together with
       -ffinite-math-only and -fno-trapping-math.  Note that while the
       throughput of the sequence is higher than the throughput of the
       non-reciprocal instruction, the precision of the sequence can be
       decreased by up to 2 ulp (i.e. the inverse of 1.0 equals
       0.99999994).

       Note that GCC implements "1.0f/sqrtf(x)" in terms of "RSQRTSS" (or
       "RSQRTPS") already with -ffast-math (or the above option
       combination), and doesn't need -mrecip.

       Also note that GCC emits the above sequence with additional Newton-
       Raphson step for vectorized single-float division and vectorized
       "sqrtf(x)" already with -ffast-math (or the above option
       combination), and doesn't need -mrecip.

   -mrecip=opt
       This option controls which reciprocal estimate instructions may be
       used.  opt is a comma-separated list of options, which may be
       preceded by a ! to invert the option:

       all Enable all estimate instructions.

       default
           Enable the default instructions, equivalent to -mrecip.

       none
           Disable all estimate instructions, equivalent to -mno-recip.

       div Enable the approximation for scalar division.

       vec-div
           Enable the approximation for vectorized division.

       sqrt
           Enable the approximation for scalar square root.

       vec-sqrt
           Enable the approximation for vectorized square root.

       So, for example, -mrecip=all,!sqrt enables all of the reciprocal
       approximations, except for square root.

   -mveclibabi=type
       Specifies the ABI type to use for vectorizing intrinsics using an
       external library.  Supported values for type are svml for the Intel
       short vector math library and acml for the AMD math core library.
       To use this option, both -ftree-vectorize and
       -funsafe-math-optimizations have to be enabled, and an SVML or ACML
       ABI-compatible library must be specified at link time.

       GCC currently emits calls to "vmldExp2", "vmldLn2", "vmldLog102",
       "vmldLog102", "vmldPow2", "vmldTanh2", "vmldTan2", "vmldAtan2",
       "vmldAtanh2", "vmldCbrt2", "vmldSinh2", "vmldSin2", "vmldAsinh2",
       "vmldAsin2", "vmldCosh2", "vmldCos2", "vmldAcosh2", "vmldAcos2",
       "vmlsExp4", "vmlsLn4", "vmlsLog104", "vmlsLog104", "vmlsPow4",
       "vmlsTanh4", "vmlsTan4", "vmlsAtan4", "vmlsAtanh4", "vmlsCbrt4",
       "vmlsSinh4", "vmlsSin4", "vmlsAsinh4", "vmlsAsin4", "vmlsCosh4",
       "vmlsCos4", "vmlsAcosh4" and "vmlsAcos4" for corresponding function
       type when -mveclibabi=svml is used, and "__vrd2_sin", "__vrd2_cos",
       "__vrd2_exp", "__vrd2_log", "__vrd2_log2", "__vrd2_log10",
       "__vrs4_sinf", "__vrs4_cosf", "__vrs4_expf", "__vrs4_logf",
       "__vrs4_log2f", "__vrs4_log10f" and "__vrs4_powf" for the
       corresponding function type when -mveclibabi=acml is used.

   -mabi=name
       Generate code for the specified calling convention.  Permissible
       values are sysv for the ABI used on GNU/Linux and other systems,
       and ms for the Microsoft ABI.  The default is to use the Microsoft
       ABI when targeting Microsoft Windows and the SysV ABI on all other
       systems.  You can control this behavior for specific functions by
       using the function attributes "ms_abi" and "sysv_abi".

   -mtls-dialect=type
       Generate code to access thread-local storage using the gnu or gnu2
       conventions.  gnu is the conservative default; gnu2 is more
       efficient, but it may add compile- and run-time requirements that
       cannot be satisfied on all systems.

   -mpush-args
   -mno-push-args
       Use PUSH operations to store outgoing parameters.  This method is
       shorter and usually equally fast as method using SUB/MOV operations
       and is enabled by default.  In some cases disabling it may improve
       performance because of improved scheduling and reduced
       dependencies.

   -maccumulate-outgoing-args
       If enabled, the maximum amount of space required for outgoing
       arguments is computed in the function prologue.  This is faster on
       most modern CPUs because of reduced dependencies, improved
       scheduling and reduced stack usage when the preferred stack
       boundary is not equal to 2.  The drawback is a notable increase in
       code size.  This switch implies -mno-push-args.

   -mthreads
       Support thread-safe exception handling on MinGW.  Programs that
       rely on thread-safe exception handling must compile and link all
       code with the -mthreads option.  When compiling, -mthreads defines
       -D_MT; when linking, it links in a special thread helper library
       -lmingwthrd which cleans up per-thread exception-handling data.

   -mms-bitfields
   -mno-ms-bitfields
       Enable/disable bit-field layout compatible with the native
       Microsoft Windows compiler.

       If "packed" is used on a structure, or if bit-fields are used, it
       may be that the Microsoft ABI lays out the structure differently
       than the way GCC normally does.  Particularly when moving packed
       data between functions compiled with GCC and the native Microsoft
       compiler (either via function call or as data in a file), it may be
       necessary to access either format.

       This option is enabled by default for Microsoft Windows targets.
       This behavior can also be controlled locally by use of variable or
       type attributes.  For more information, see x86 Variable Attributes
       and x86 Type Attributes.

       The Microsoft structure layout algorithm is fairly simple with the
       exception of the bit-field packing.  The padding and alignment of
       members of structures and whether a bit-field can straddle a
       storage-unit boundary are determine by these rules:

       1. Structure members are stored sequentially in the order in which
       they are
           declared: the first member has the lowest memory address and
           the last member the highest.

       2. Every data object has an alignment requirement.  The alignment
       requirement
           for all data except structures, unions, and arrays is either
           the size of the object or the current packing size (specified
           with either the "aligned" attribute or the "pack" pragma),
           whichever is less.  For structures, unions, and arrays, the
           alignment requirement is the largest alignment requirement of
           its members.  Every object is allocated an offset so that:

                   offset % alignment_requirement == 0

       3. Adjacent bit-fields are packed into the same 1-, 2-, or 4-byte
       allocation
           unit if the integral types are the same size and if the next
           bit-field fits into the current allocation unit without
           crossing the boundary imposed by the common alignment
           requirements of the bit-fields.

       MSVC interprets zero-length bit-fields in the following ways:

       1. If a zero-length bit-field is inserted between two bit-fields
       that
           are normally coalesced, the bit-fields are not coalesced.

           For example:

                   struct
                    {
                      unsigned long bf_1 : 12;
                      unsigned long : 0;
                      unsigned long bf_2 : 12;
                    } t1;

           The size of "t1" is 8 bytes with the zero-length bit-field.  If
           the zero-length bit-field were removed, "t1"'s size would be 4
           bytes.

       2. If a zero-length bit-field is inserted after a bit-field, "foo",
       and the
           alignment of the zero-length bit-field is greater than the
           member that follows it, "bar", "bar" is aligned as the type of
           the zero-length bit-field.

           For example:

                   struct
                    {
                      char foo : 4;
                      short : 0;
                      char bar;
                    } t2;

                   struct
                    {
                      char foo : 4;
                      short : 0;
                      double bar;
                    } t3;

           For "t2", "bar" is placed at offset 2, rather than offset 1.
           Accordingly, the size of "t2" is 4.  For "t3", the zero-length
           bit-field does not affect the alignment of "bar" or, as a
           result, the size of the structure.

           Taking this into account, it is important to note the
           following:

           1. If a zero-length bit-field follows a normal bit-field, the
           type of the
               zero-length bit-field may affect the alignment of the
               structure as whole. For example, "t2" has a size of 4
               bytes, since the zero-length bit-field follows a normal
               bit-field, and is of type short.

           2. Even if a zero-length bit-field is not followed by a normal
           bit-field, it may
               still affect the alignment of the structure:

                       struct
                        {
                          char foo : 6;
                          long : 0;
                        } t4;

               Here, "t4" takes up 4 bytes.

       3. Zero-length bit-fields following non-bit-field members are
       ignored:
                   struct
                    {
                      char foo;
                      long : 0;
                      char bar;
                    } t5;

           Here, "t5" takes up 2 bytes.

   -mno-align-stringops
       Do not align the destination of inlined string operations.  This
       switch reduces code size and improves performance in case the
       destination is already aligned, but GCC doesn't know about it.

   -minline-all-stringops
       By default GCC inlines string operations only when the destination
       is known to be aligned to least a 4-byte boundary.  This enables
       more inlining and increases code size, but may improve performance
       of code that depends on fast "memcpy", "strlen", and "memset" for
       short lengths.

   -minline-stringops-dynamically
       For string operations of unknown size, use run-time checks with
       inline code for small blocks and a library call for large blocks.

   -mstringop-strategy=alg
       Override the internal decision heuristic for the particular
       algorithm to use for inlining string operations.  The allowed
       values for alg are:

       rep_byte
       rep_4byte
       rep_8byte
           Expand using i386 "rep" prefix of the specified size.

       byte_loop
       loop
       unrolled_loop
           Expand into an inline loop.

       libcall
           Always use a library call.

   -mmemcpy-strategy=strategy
       Override the internal decision heuristic to decide if
       "__builtin_memcpy" should be inlined and what inline algorithm to
       use when the expected size of the copy operation is known. strategy
       is a comma-separated list of alg:max_size:dest_align triplets.  alg
       is specified in -mstringop-strategy, max_size specifies the max
       byte size with which inline algorithm alg is allowed.  For the last
       triplet, the max_size must be "-1". The max_size of the triplets in
       the list must be specified in increasing order.  The minimal byte
       size for alg is 0 for the first triplet and "max_size + 1" of the
       preceding range.

   -mmemset-strategy=strategy
       The option is similar to -mmemcpy-strategy= except that it is to
       control "__builtin_memset" expansion.

   -momit-leaf-frame-pointer
       Don't keep the frame pointer in a register for leaf functions.
       This avoids the instructions to save, set up, and restore frame
       pointers and makes an extra register available in leaf functions.
       The option -fomit-leaf-frame-pointer removes the frame pointer for
       leaf functions, which might make debugging harder.

   -mtls-direct-seg-refs
   -mno-tls-direct-seg-refs
       Controls whether TLS variables may be accessed with offsets from
       the TLS segment register (%gs for 32-bit, %fs for 64-bit), or
       whether the thread base pointer must be added.  Whether or not this
       is valid depends on the operating system, and whether it maps the
       segment to cover the entire TLS area.

       For systems that use the GNU C Library, the default is on.

   -msse2avx
   -mno-sse2avx
       Specify that the assembler should encode SSE instructions with VEX
       prefix.  The option -mavx turns this on by default.

   -mfentry
   -mno-fentry
       If profiling is active (-pg), put the profiling counter call before
       the prologue.  Note: On x86 architectures the attribute
       "ms_hook_prologue" isn't possible at the moment for -mfentry and
       -pg.

   -mrecord-mcount
   -mno-record-mcount
       If profiling is active (-pg), generate a __mcount_loc section that
       contains pointers to each profiling call. This is useful for
       automatically patching and out calls.

   -mnop-mcount
   -mno-nop-mcount
       If profiling is active (-pg), generate the calls to the profiling
       functions as nops. This is useful when they should be patched in
       later dynamically. This is likely only useful together with
       -mrecord-mcount.

   -mskip-rax-setup
   -mno-skip-rax-setup
       When generating code for the x86-64 architecture with SSE
       extensions disabled, -mskip-rax-setup can be used to skip setting
       up RAX register when there are no variable arguments passed in
       vector registers.

       Warning: Since RAX register is used to avoid unnecessarily saving
       vector registers on stack when passing variable arguments, the
       impacts of this option are callees may waste some stack space,
       misbehave or jump to a random location.  GCC 4.4 or newer don't
       have those issues, regardless the RAX register value.

   -m8bit-idiv
   -mno-8bit-idiv
       On some processors, like Intel Atom, 8-bit unsigned integer divide
       is much faster than 32-bit/64-bit integer divide.  This option
       generates a run-time check.  If both dividend and divisor are
       within range of 0 to 255, 8-bit unsigned integer divide is used
       instead of 32-bit/64-bit integer divide.

   -mavx256-split-unaligned-load
   -mavx256-split-unaligned-store
       Split 32-byte AVX unaligned load and store.

   -mstack-protector-guard=guard
       Generate stack protection code using canary at guard.  Supported
       locations are global for global canary or tls for per-thread canary
       in the TLS block (the default).  This option has effect only when
       -fstack-protector or -fstack-protector-all is specified.

   -mmitigate-rop
       Try to avoid generating code sequences that contain unintended
       return opcodes, to mitigate against certain forms of attack. At the
       moment, this option is limited in what it can do and should not be
       relied on to provide serious protection.

   These -m switches are supported in addition to the above on x86-64
   processors in 64-bit environments.

   -m32
   -m64
   -mx32
   -m16
   -miamcu
       Generate code for a 16-bit, 32-bit or 64-bit environment.  The -m32
       option sets "int", "long", and pointer types to 32 bits, and
       generates code that runs on any i386 system.

       The -m64 option sets "int" to 32 bits and "long" and pointer types
       to 64 bits, and generates code for the x86-64 architecture.  For
       Darwin only the -m64 option also turns off the -fno-pic and
       -mdynamic-no-pic options.

       The -mx32 option sets "int", "long", and pointer types to 32 bits,
       and generates code for the x86-64 architecture.

       The -m16 option is the same as -m32, except for that it outputs the
       ".code16gcc" assembly directive at the beginning of the assembly
       output so that the binary can run in 16-bit mode.

       The -miamcu option generates code which conforms to Intel MCU
       psABI.  It requires the -m32 option to be turned on.

   -mno-red-zone
       Do not use a so-called "red zone" for x86-64 code.  The red zone is
       mandated by the x86-64 ABI; it is a 128-byte area beyond the
       location of the stack pointer that is not modified by signal or
       interrupt handlers and therefore can be used for temporary data
       without adjusting the stack pointer.  The flag -mno-red-zone
       disables this red zone.

   -mcmodel=small
       Generate code for the small code model: the program and its symbols
       must be linked in the lower 2 GB of the address space.  Pointers
       are 64 bits.  Programs can be statically or dynamically linked.
       This is the default code model.

   -mcmodel=kernel
       Generate code for the kernel code model.  The kernel runs in the
       negative 2 GB of the address space.  This model has to be used for
       Linux kernel code.

   -mcmodel=medium
       Generate code for the medium model: the program is linked in the
       lower 2 GB of the address space.  Small symbols are also placed
       there.  Symbols with sizes larger than -mlarge-data-threshold are
       put into large data or BSS sections and can be located above 2GB.
       Programs can be statically or dynamically linked.

   -mcmodel=large
       Generate code for the large model.  This model makes no assumptions
       about addresses and sizes of sections.

   -maddress-mode=long
       Generate code for long address mode.  This is only supported for
       64-bit and x32 environments.  It is the default address mode for
       64-bit environments.

   -maddress-mode=short
       Generate code for short address mode.  This is only supported for
       32-bit and x32 environments.  It is the default address mode for
       32-bit and x32 environments.

   x86 Windows Options

   These additional options are available for Microsoft Windows targets:

   -mconsole
       This option specifies that a console application is to be
       generated, by instructing the linker to set the PE header subsystem
       type required for console applications.  This option is available
       for Cygwin and MinGW targets and is enabled by default on those
       targets.

   -mdll
       This option is available for Cygwin and MinGW targets.  It
       specifies that a DLL---a dynamic link library---is to be generated,
       enabling the selection of the required runtime startup object and
       entry point.

   -mnop-fun-dllimport
       This option is available for Cygwin and MinGW targets.  It
       specifies that the "dllimport" attribute should be ignored.

   -mthread
       This option is available for MinGW targets. It specifies that
       MinGW-specific thread support is to be used.

   -municode
       This option is available for MinGW-w64 targets.  It causes the
       "UNICODE" preprocessor macro to be predefined, and chooses Unicode-
       capable runtime startup code.

   -mwin32
       This option is available for Cygwin and MinGW targets.  It
       specifies that the typical Microsoft Windows predefined macros are
       to be set in the pre-processor, but does not influence the choice
       of runtime library/startup code.

   -mwindows
       This option is available for Cygwin and MinGW targets.  It
       specifies that a GUI application is to be generated by instructing
       the linker to set the PE header subsystem type appropriately.

   -fno-set-stack-executable
       This option is available for MinGW targets. It specifies that the
       executable flag for the stack used by nested functions isn't set.
       This is necessary for binaries running in kernel mode of Microsoft
       Windows, as there the User32 API, which is used to set executable
       privileges, isn't available.

   -fwritable-relocated-rdata
       This option is available for MinGW and Cygwin targets.  It
       specifies that relocated-data in read-only section is put into the
       ".data" section.  This is a necessary for older runtimes not
       supporting modification of ".rdata" sections for pseudo-relocation.

   -mpe-aligned-commons
       This option is available for Cygwin and MinGW targets.  It
       specifies that the GNU extension to the PE file format that permits
       the correct alignment of COMMON variables should be used when
       generating code.  It is enabled by default if GCC detects that the
       target assembler found during configuration supports the feature.

   See also under x86 Options for standard options.

   Xstormy16 Options

   These options are defined for Xstormy16:

   -msim
       Choose startup files and linker script suitable for the simulator.

   Xtensa Options

   These options are supported for Xtensa targets:

   -mconst16
   -mno-const16
       Enable or disable use of "CONST16" instructions for loading
       constant values.  The "CONST16" instruction is currently not a
       standard option from Tensilica.  When enabled, "CONST16"
       instructions are always used in place of the standard "L32R"
       instructions.  The use of "CONST16" is enabled by default only if
       the "L32R" instruction is not available.

   -mfused-madd
   -mno-fused-madd
       Enable or disable use of fused multiply/add and multiply/subtract
       instructions in the floating-point option.  This has no effect if
       the floating-point option is not also enabled.  Disabling fused
       multiply/add and multiply/subtract instructions forces the compiler
       to use separate instructions for the multiply and add/subtract
       operations.  This may be desirable in some cases where strict IEEE
       754-compliant results are required: the fused multiply add/subtract
       instructions do not round the intermediate result, thereby
       producing results with more bits of precision than specified by the
       IEEE standard.  Disabling fused multiply add/subtract instructions
       also ensures that the program output is not sensitive to the
       compiler's ability to combine multiply and add/subtract operations.

   -mserialize-volatile
   -mno-serialize-volatile
       When this option is enabled, GCC inserts "MEMW" instructions before
       "volatile" memory references to guarantee sequential consistency.
       The default is -mserialize-volatile.  Use -mno-serialize-volatile
       to omit the "MEMW" instructions.

   -mforce-no-pic
       For targets, like GNU/Linux, where all user-mode Xtensa code must
       be position-independent code (PIC), this option disables PIC for
       compiling kernel code.

   -mtext-section-literals
   -mno-text-section-literals
       These options control the treatment of literal pools.  The default
       is -mno-text-section-literals, which places literals in a separate
       section in the output file.  This allows the literal pool to be
       placed in a data RAM/ROM, and it also allows the linker to combine
       literal pools from separate object files to remove redundant
       literals and improve code size.  With -mtext-section-literals, the
       literals are interspersed in the text section in order to keep them
       as close as possible to their references.  This may be necessary
       for large assembly files.  Literals for each function are placed
       right before that function.

   -mauto-litpools
   -mno-auto-litpools
       These options control the treatment of literal pools.  The default
       is -mno-auto-litpools, which places literals in a separate section
       in the output file unless -mtext-section-literals is used.  With
       -mauto-litpools the literals are interspersed in the text section
       by the assembler.  Compiler does not produce explicit ".literal"
       directives and loads literals into registers with "MOVI"
       instructions instead of "L32R" to let the assembler do relaxation
       and place literals as necessary.  This option allows assembler to
       create several literal pools per function and assemble very big
       functions, which may not be possible with -mtext-section-literals.

   -mtarget-align
   -mno-target-align
       When this option is enabled, GCC instructs the assembler to
       automatically align instructions to reduce branch penalties at the
       expense of some code density.  The assembler attempts to widen
       density instructions to align branch targets and the instructions
       following call instructions.  If there are not enough preceding
       safe density instructions to align a target, no widening is
       performed.  The default is -mtarget-align.  These options do not
       affect the treatment of auto-aligned instructions like "LOOP",
       which the assembler always aligns, either by widening density
       instructions or by inserting NOP instructions.

   -mlongcalls
   -mno-longcalls
       When this option is enabled, GCC instructs the assembler to
       translate direct calls to indirect calls unless it can determine
       that the target of a direct call is in the range allowed by the
       call instruction.  This translation typically occurs for calls to
       functions in other source files.  Specifically, the assembler
       translates a direct "CALL" instruction into an "L32R" followed by a
       "CALLX" instruction.  The default is -mno-longcalls.  This option
       should be used in programs where the call target can potentially be
       out of range.  This option is implemented in the assembler, not the
       compiler, so the assembly code generated by GCC still shows direct
       call instructions---look at the disassembled object code to see the
       actual instructions.  Note that the assembler uses an indirect call
       for every cross-file call, not just those that really are out of
       range.

   zSeries Options

   These are listed under

ENVIRONMENT

   This section describes several environment variables that affect how
   GCC operates.  Some of them work by specifying directories or prefixes
   to use when searching for various kinds of files.  Some are used to
   specify other aspects of the compilation environment.

   Note that you can also specify places to search using options such as
   -B, -I and -L.  These take precedence over places specified using
   environment variables, which in turn take precedence over those
   specified by the configuration of GCC.

   LANG
   LC_CTYPE
   LC_MESSAGES
   LC_ALL
       These environment variables control the way that GCC uses
       localization information which allows GCC to work with different
       national conventions.  GCC inspects the locale categories LC_CTYPE
       and LC_MESSAGES if it has been configured to do so.  These locale
       categories can be set to any value supported by your installation.
       A typical value is en_GB.UTF-8 for English in the United Kingdom
       encoded in UTF-8.

       The LC_CTYPE environment variable specifies character
       classification.  GCC uses it to determine the character boundaries
       in a string; this is needed for some multibyte encodings that
       contain quote and escape characters that are otherwise interpreted
       as a string end or escape.

       The LC_MESSAGES environment variable specifies the language to use
       in diagnostic messages.

       If the LC_ALL environment variable is set, it overrides the value
       of LC_CTYPE and LC_MESSAGES; otherwise, LC_CTYPE and LC_MESSAGES
       default to the value of the LANG environment variable.  If none of
       these variables are set, GCC defaults to traditional C English
       behavior.

   TMPDIR
       If TMPDIR is set, it specifies the directory to use for temporary
       files.  GCC uses temporary files to hold the output of one stage of
       compilation which is to be used as input to the next stage: for
       example, the output of the preprocessor, which is the input to the
       compiler proper.

   GCC_COMPARE_DEBUG
       Setting GCC_COMPARE_DEBUG is nearly equivalent to passing
       -fcompare-debug to the compiler driver.  See the documentation of
       this option for more details.

   GCC_EXEC_PREFIX
       If GCC_EXEC_PREFIX is set, it specifies a prefix to use in the
       names of the subprograms executed by the compiler.  No slash is
       added when this prefix is combined with the name of a subprogram,
       but you can specify a prefix that ends with a slash if you wish.

       If GCC_EXEC_PREFIX is not set, GCC attempts to figure out an
       appropriate prefix to use based on the pathname it is invoked with.

       If GCC cannot find the subprogram using the specified prefix, it
       tries looking in the usual places for the subprogram.

       The default value of GCC_EXEC_PREFIX is prefix/lib/gcc/ where
       prefix is the prefix to the installed compiler. In many cases
       prefix is the value of "prefix" when you ran the configure script.

       Other prefixes specified with -B take precedence over this prefix.

       This prefix is also used for finding files such as crt0.o that are
       used for linking.

       In addition, the prefix is used in an unusual way in finding the
       directories to search for header files.  For each of the standard
       directories whose name normally begins with /usr/local/lib/gcc
       (more precisely, with the value of GCC_INCLUDE_DIR), GCC tries
       replacing that beginning with the specified prefix to produce an
       alternate directory name.  Thus, with -Bfoo/, GCC searches foo/bar
       just before it searches the standard directory /usr/local/lib/bar.
       If a standard directory begins with the configured prefix then the
       value of prefix is replaced by GCC_EXEC_PREFIX when looking for
       header files.

   COMPILER_PATH
       The value of COMPILER_PATH is a colon-separated list of
       directories, much like PATH.  GCC tries the directories thus
       specified when searching for subprograms, if it can't find the
       subprograms using GCC_EXEC_PREFIX.

   LIBRARY_PATH
       The value of LIBRARY_PATH is a colon-separated list of directories,
       much like PATH.  When configured as a native compiler, GCC tries
       the directories thus specified when searching for special linker
       files, if it can't find them using GCC_EXEC_PREFIX.  Linking using
       GCC also uses these directories when searching for ordinary
       libraries for the -l option (but directories specified with -L come
       first).

   LANG
       This variable is used to pass locale information to the compiler.
       One way in which this information is used is to determine the
       character set to be used when character literals, string literals
       and comments are parsed in C and C++.  When the compiler is
       configured to allow multibyte characters, the following values for
       LANG are recognized:

       C-JIS
           Recognize JIS characters.

       C-SJIS
           Recognize SJIS characters.

       C-EUCJP
           Recognize EUCJP characters.

       If LANG is not defined, or if it has some other value, then the
       compiler uses "mblen" and "mbtowc" as defined by the default locale
       to recognize and translate multibyte characters.

   Some additional environment variables affect the behavior of the
   preprocessor.

   CPATH
   C_INCLUDE_PATH
   CPLUS_INCLUDE_PATH
   OBJC_INCLUDE_PATH
       Each variable's value is a list of directories separated by a
       special character, much like PATH, in which to look for header
       files.  The special character, "PATH_SEPARATOR", is target-
       dependent and determined at GCC build time.  For Microsoft Windows-
       based targets it is a semicolon, and for almost all other targets
       it is a colon.

       CPATH specifies a list of directories to be searched as if
       specified with -I, but after any paths given with -I options on the
       command line.  This environment variable is used regardless of
       which language is being preprocessed.

       The remaining environment variables apply only when preprocessing
       the particular language indicated.  Each specifies a list of
       directories to be searched as if specified with -isystem, but after
       any paths given with -isystem options on the command line.

       In all these variables, an empty element instructs the compiler to
       search its current working directory.  Empty elements can appear at
       the beginning or end of a path.  For instance, if the value of
       CPATH is ":/special/include", that has the same effect as
       -I. -I/special/include.

   DEPENDENCIES_OUTPUT
       If this variable is set, its value specifies how to output
       dependencies for Make based on the non-system header files
       processed by the compiler.  System header files are ignored in the
       dependency output.

       The value of DEPENDENCIES_OUTPUT can be just a file name, in which
       case the Make rules are written to that file, guessing the target
       name from the source file name.  Or the value can have the form
       file target, in which case the rules are written to file file using
       target as the target name.

       In other words, this environment variable is equivalent to
       combining the options -MM and -MF, with an optional -MT switch too.

   SUNPRO_DEPENDENCIES
       This variable is the same as DEPENDENCIES_OUTPUT (see above),
       except that system header files are not ignored, so it implies -M
       rather than -MM.  However, the dependence on the main input file is
       omitted.

   SOURCE_DATE_EPOCH
       If this variable is set, its value specifies a UNIX timestamp to be
       used in replacement of the current date and time in the "__DATE__"
       and "__TIME__" macros, so that the embedded timestamps become
       reproducible.

       The value of SOURCE_DATE_EPOCH must be a UNIX timestamp, defined as
       the number of seconds (excluding leap seconds) since 01 Jan 1970
       00:00:00 represented in ASCII; identical to the output of
       @command{date +%s} on GNU/Linux and other systems that support the
       %s extension in the "date" command.

       The value should be a known timestamp such as the last modification
       time of the source or package and it should be set by the build
       process.

BUGS

   For instructions on reporting bugs, see
   <file:///usr/share/doc/gcc-6/README.Bugs>.

FOOTNOTES

   1.  On some systems, gcc -shared needs to build supplementary stub code
       for constructors to work.  On multi-libbed systems, gcc -shared
       must select the correct support libraries to link against.  Failing
       to supply the correct flags may lead to subtle defects.  Supplying
       them in cases where they are not necessary is innocuous.

SEE ALSO

   gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), as(1), ld(1), gdb(1),
   adb(1), dbx(1), sdb(1) and the Info entries for gcc, cpp, as, ld,
   binutils and gdb.

AUTHOR

   See the Info entry for gcc, or
   <http://gcc.gnu.org/onlinedocs/gcc/Contributors.html>, for contributors
   to GCC.

COPYRIGHT

   Copyright (c) 1988-2016 Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
   under the terms of the GNU Free Documentation License, Version 1.3 or
   any later version published by the Free Software Foundation; with the
   Invariant Sections being "GNU General Public License" and "Funding Free
   Software", the Front-Cover texts being (a) (see below), and with the
   Back-Cover Texts being (b) (see below).  A copy of the license is
   included in the gfdl(7) man page.

   (a) The FSF's Front-Cover Text is:

        A GNU Manual

   (b) The FSF's Back-Cover Text is:

        You have freedom to copy and modify this GNU Manual, like GNU
        software.  Copies published by the Free Software Foundation raise
        funds for GNU development.





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