Clang 최적화 수준

Clang 최적화 수준

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GCC에서 매뉴얼이 무엇인지 설명하고 -O3, -Os등 특정 최적화 인수의 관점에서로 번역 ( -funswitch-loops, -fcompare-elim, 등)

clang에 대한 동일한 정보를 찾고 있습니다.

내가 검토 한 온라인 및에 man clang있는 전용 (일반 정보를 제공합니다 -O2개를 최적화를 -O1, -Os속도 최적화, ...) 또한 스택 오버플로 여기에보고 발견 이 ,하지만 난 인용 된 소스 파일의 관련 아무것도 발견하지 않았습니다.

편집 : 답을 찾았지만 모든 최적화 패스와에서 선택한 패스를 문서화하는 사용자 설명서에 대한 링크가있는 사람이 있다면 여전히 관심 이 있습니다. 현재 난 그냥 발견 이 최적화 레벨을 뚫고 목록,하지만 아무것도.-Ox

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이 관련 질문을 찾았습니다 .

요약하면 컴파일러 최적화 단계에 대해 알아 보려면 다음을 수행하십시오.

llvm-as < /dev/null | opt -O3 -disable-output -debug-pass=Arguments

Geoff Nixon 의 답변 (+1) 에서 지적했듯이 clang추가로 몇 가지 더 높은 수준의 최적화를 실행하며 다음을 사용하여 검색 할 수 있습니다.

echo 'int;' | clang -xc -O3 - -o /dev/null -\#\#\#

개별 패스에 대한 문서는 여기에서 볼 수 있습니다 .

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으로 버전 6.0 출입증은 다음과 같습니다 :

• 기준선 ( -O0) :

  • opt세트 : -tti -verify -ee-instrument -targetlibinfo -assumption-cache-tracker -profile-summary-info -forceattrs -basiccg -always-inline -barrier
  • clang추가 : -mdisable-fp-elim -mrelax-all

• -O1 기반 -O0

  • opt 추가:-targetlibinfo -tti -tbaa -scoped-noalias -assumption-cache-tracker -profile-summary-info -forceattrs -inferattrs -ipsccp-called-value-propagation -globalopt -domtree -mem2reg -deadargelim -basicaa -aa -loops -lazy -branch-prob -lazy-block-freq -opt-remark-emitter -instcombine -simplifycfg -basiccg -globals-aa -prune-eh -always-inline -functionattrs -sroa -memoryssa -early-cse-memssa-예측 실행 -lazy-value-info -jump-threading -correlated-propagation -libcalls-shrinkwrap -branch-prob -block-freq -pgo-memop-opt -tailcallelim -reassociate -loop-simplify -lcssa-verification -lcssa -scalar-evolution -loop-rotate -licm -loop-unswitch -indvars -loop-idiom -loop-deletion -loop-unroll -memdep -memcpyopt -sccp -demanded-bits -bdce -dse -postdomtree -adce -barrier -rpo-functionattrs -globaldce -float2int -loop-accesses -loop-distribute-loop-vectorize -loop-load-elim-가정에서 정렬 -strip-dead-prototypes -loop-sink -instsimplify -div-rem-pairs -verify -ee-instrument -early-cse -lower-expect
  • clang추가 : -momit-leaf-frame-pointer
  • clang상품 : -mdisable-fp-elim -mrelax-all

• -O2 기반 -O1

  • opt추가 : -inline -mldst-motion -gvn -elim-avail-extern -slp-vectorizer -constmerge
  • opt상품 :-항상 인라인
  • clang추가 : -vectorize-loops -vectorize-slp

• -O3 기반 -O2

  • opt추가 : -callsite-splitting -argpromotion

• -Ofast을 (를) 기반으로 -O3하고 유효 clang하지만 유효 하지는 않습니다.opt

  • clang추가 : -fno-signed-zeros -freciprocal-math -ffp-contract = fast -menable-unsafe-fp-math -menable-no-nans -menable-no-infs -mreassociate -fno-trapping-math -ffast-math -ffinite-math-only

• -Os 비슷하다 -O2

  • optdrops : -libcalls-shrinkwrap 및 -pgo-memopt-opt

• -Oz 기반 -Os

  • opt방울 : -slp-vectorizer

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With version 3.8 the passes are as follow:

• baseline (-O0):

  • opt sets : -targetlibinfo -tti -verify
  • clang adds : -mdisable-fp-elim -mrelax-all

• -O1 is based on -O0

  • opt adds: -globalopt -demanded-bits -branch-prob -inferattrs -ipsccp -dse -loop-simplify -scoped-noalias -barrier -adce -deadargelim -memdep -licm -globals-aa -rpo-functionattrs -basiccg -loop-idiom -forceattrs -mem2reg -simplifycfg -early-cse -instcombine -sccp -loop-unswitch -loop-vectorize -tailcallelim -functionattrs -loop-accesses -memcpyopt -loop-deletion -reassociate -strip-dead-prototypes -loops -basicaa -correlated-propagation -lcssa -domtree -always-inline -aa -block-freq -float2int -lower-expect -sroa -loop-unroll -alignment-from-assumptions -lazy-value-info -prune-eh -jump-threading -loop-rotate -indvars -bdce -scalar-evolution -tbaa -assumption-cache-tracker
  • clang adds : -momit-leaf-frame-pointer
  • clang drops : -mdisable-fp-elim -mrelax-all

• -O2 is based on -O1

  • opt adds: -elim-avail-extern -mldst-motion -slp-vectorizer -gvn -inline -globaldce -constmerge
  • opt drops: -always-inline
  • clang adds: -vectorize-loops -vectorize-slp

• -O3 is based on -O2

  • opt adds: -argpromotion

• -Ofast is based on -O3, valid in clang but not in opt

  • clang adds: -fno-signed-zeros -freciprocal-math -ffp-contract=fast -menable-unsafe-fp-math -menable-no-nans -menable-no-infs

• -Os is the same as -O2

• -Oz is based on -Os

  • opt drops: -slp-vectorizer
  • clang drops: -vectorize-loops

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With version 3.7 the passes are as follow (parsed output of the command above):

• default (-O0): -targetlibinfo -verify -tti

• -O1 is based on -O0

  • adds: -sccp -loop-simplify -float2int -lazy-value-info -correlated-propagation -bdce -lcssa -deadargelim -loop-unroll -loop-vectorize -barrier -memcpyopt -loop-accesses -assumption-cache-tracker -reassociate -loop-deletion -branch-prob -jump-threading -domtree -dse -loop-rotate -ipsccp -instcombine -scoped-noalias -licm -prune-eh -loop-unswitch -alignment-from-assumptions -early-cse -inline-cost -simplifycfg -strip-dead-prototypes -tbaa -sroa -no-aa -adce -functionattrs -lower-expect -basiccg -loops -loop-idiom -tailcallelim -basicaa -indvars -globalopt -block-freq -scalar-evolution -memdep -always-inline

• -O2 is based on -01

  • adds: -elim-avail-extern -globaldce -inline -constmerge -mldst-motion -gvn -slp-vectorizer
  • removes: -always-inline

• -O3 is based on -O2

  • adds: -argpromotion -verif

• -Os is identical to -O2

• -Oz is based on -Os

  • removes: -slp-vectorizer

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For version 3.6 the passes are as documented in GYUNGMIN KIM's post.

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With version 3.5 the passes are as follow (parsed output of the command above):

• default (-O0): -targetlibinfo -verify -verify-di

• -O1 is based on -O0

  • adds: -correlated-propagation -basiccg -simplifycfg -no-aa -jump-threading -sroa -loop-unswitch -ipsccp -instcombine -memdep -memcpyopt -barrier -block-freq -loop-simplify -loop-vectorize -inline-cost -branch-prob -early-cse -lazy-value-info -loop-rotate -strip-dead-prototypes -loop-deletion -tbaa -prune-eh -indvars -loop-unroll -reassociate -loops -sccp -always-inline -basicaa -dse -globalopt -tailcallelim -functionattrs -deadargelim -notti -scalar-evolution -lower-expect -licm -loop-idiom -adce -domtree -lcssa

• -O2 is based on -01

  • adds: -gvn -constmerge -globaldce -slp-vectorizer -mldst-motion -inline
  • removes: -always-inline

• -O3 is based on -O2

  • adds: -argpromotion

• -Os is identical to -O2

• -Oz is based on -Os

  • removes: -slp-vectorizer

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With version 3.4 the passes are as follow (parsed output of the command above):

• -O0: -targetlibinfo -preverify -domtree -verify

• -O1 is based on -O0

  • adds: -adce -always-inline -basicaa -basiccg -correlated-propagation -deadargelim -dse -early-cse -functionattrs -globalopt -indvars -inline-cost -instcombine -ipsccp -jump-threading -lazy-value-info -lcssa -licm -loop-deletion -loop-idiom -loop-rotate -loop-simplify -loop-unroll -loop-unswitch -loops -lower-expect -memcpyopt -memdep -no-aa -notti -prune-eh -reassociate -scalar-evolution -sccp -simplifycfg -sroa -strip-dead-prototypes -tailcallelim -tbaa

• -O2 is based on -01

  • adds: -barrier -constmerge -domtree -globaldce -gvn -inline -loop-vectorize -preverify -slp-vectorizer -targetlibinfo -verify
  • removes: -always-inline

• -O3 is based on -O2

  • adds: -argpromotion

• -Os is identical to -O2

• -Oz is based on -O2

  • removes: -barrier -loop-vectorize -slp-vectorizer

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With version 3.2 the passes are as follow (parsed output of the command above):

• -O0: -targetlibinfo -preverify -domtree -verify

• -O1 is based on -O0

  • adds: -sroa -early-cse -lower-expect -no-aa -tbaa -basicaa -globalopt -ipsccp -deadargelim -instcombine -simplifycfg -basiccg -prune-eh -always-inline -functionattrs -simplify-libcalls -lazy-value-info -jump-threading -correlated-propagation -tailcallelim -reassociate -loops -loop-simplify -lcssa -loop-rotate -licm -loop-unswitch -scalar-evolution -indvars -loop-idiom -loop-deletion -loop-unroll -memdep -memcpyopt -sccp -dse -adce -strip-dead-prototypes

• -O2 is based on -01

  • adds: -inline -globaldce -constmerge
  • removes: -always-inline

• -O3 is based on -O2

  • adds: -argpromotion

• -Os is identical to -O2

• -Oz is identical to -Os

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Edit [march 2014] removed duplicates from lists.

Edit [april 2014] added documentation link + options for 3.4

Edit [september 2014] added options for 3.5

Edit [december 2015] added options for 3.7 and mention existing answer for 3.6

Edit [may 2016] added options for 3.8, for both opt and clang and mention existing answer for clang (versus opt)

Edit [nov 2018] add options for 6.0

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@Antoine's answer (and the other question linked) accurately describe the LLVM optimizations that are enabled, but there are a few other Clang-specific options (i.e., those that affect lowering to the AST) that affected by the -O[0|1|2|3|fast] flags.

You can take a look at these with:

echo 'int;' | clang -xc -O0 - -o /dev/null -\#\#\#

echo 'int;' | clang -xc -O1 - -o /dev/null -\#\#\#

echo 'int;' | clang -xc -O2 - -o /dev/null -\#\#\#

echo 'int;' | clang -xc -O3 - -o /dev/null -\#\#\#

echo 'int;' | clang -xc -Ofast - -o /dev/null -\#\#\#

For example, -O0 enables -mrelax-all, -O1 enables -vectorize-loops and -vectorize-slp, and -Ofast enables -menable-no-infs, -menable-no-nans, -menable-unsafe-fp-math, -ffp-contract=fast and -ffast-math.

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@Techogrebo:

Yes, no don't necessarily need the other LLVM tools. Try:

echo 'int;' | clang -xc - -o /dev/null -mllvm -print-all-options

Also, there are a lot more detailed options you can examine/modify with Clang alone... you just need to know how to get to them!

Try a few of:

clang -help

clang -cc1 -help

clang -cc1 -mllvm -help

clang -cc1 -mllvm -help-list-hidden

clang -cc1as -help

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LLVM 3.6 -O1

Pass Arguments: -targetlibinfo -no-aa -tbaa -scoped-noalias -assumption-cache-tracker -basicaa -notti -verify-di -ipsccp -globalopt -deadargelim -domtree -instcombine -simplifycfg -basiccg -prune-eh -inline-cost -always-inline -functionattrs -sroa -domtree -early-cse -lazy-value-info -jump-threading -correlated-propagation -simplifycfg -domtree -instcombine -tailcallelim -simplifycfg -reassociate -domtree -loops -loop-simplify -lcssa -loop-rotate -licm -loop-unswitch -instcombine -scalar-evolution -loop-simplify -lcssa -indvars -loop-idiom -loop-deletion -function_tti -loop-unroll -memdep -memcpyopt -sccp -domtree -instcombine -lazy-value-info -jump-threading -correlated-propagation -domtree -memdep -dse -adce -simplifycfg -domtree -instcombine -barrier -domtree -loops -loop-simplify -lcssa -branch-prob -block-freq -scalar-evolution -loop-vectorize -instcombine -simplifycfg -domtree -instcombine -loops -loop-simplify -lcssa -scalar-evolution -function_tti -loop-unroll -alignment-from-assumptions -strip-dead-prototypes -verify -verify-di

-O2 base on -O1

add : -inline -mldst-motion -domtree -memdep -gvn -memdep -scalar-evolution -slp-vectorizer -globaldce -constmerge

and removes: -always-inline

-O3 based on -O2

add: -argpromotion

참고URL : https://stackoverflow.com/questions/15548023/clang-optimization-levels