[PATCH] D132365: [DSE] Support looking through memory phis at end of function.

Mon Aug 22 03:06:58 PDT 2022

fhahn created this revision.
fhahn added reviewers: aeubanks, nikic, asbirlea.
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Update isWriteAtEndOfFunction to look through MemoryPhis. The reason
MemoryPhis were skipped so far was the known AliasAnalysis issue with it
missing loop-carried dependences.

This problem is already addressed in other parts of the code by skipping
MemoryDefs that may be in difference loops. I think the same logic can
be applied here.

This can have a substantial impact on the number of stores removed in
some cases. For MultiSource/SPEC2006/SPEC2017 with -O3:

Metric: dse.NumFastStores

Program                                       dse.NumFastStores

  base              patch   diff

External/S...CINT2017rate/557.xz_r/557.xz_r     14.00             45.00 221.4%
External/S...te/538.imagick_r/538.imagick_r    439.00           1267.00 188.6%
MultiSourc...e/Applications/SIBsim4/SIBsim4      6.00             15.00 150.0%
MultiSourc...Prolangs-C/simulator/simulator      3.00              7.00 133.3%
MultiSource/Applications/siod/siod               3.00              7.00 133.3%
MultiSourc...arks/FreeBench/distray/distray      6.00              9.00  50.0%
MultiSourc...e/Applications/obsequi/Obsequi     22.00             30.00  36.4%
MultiSource/Benchmarks/Ptrdist/bc/bc            23.00             28.00  21.7%
External/S...NT2017rate/502.gcc_r/502.gcc_r   1258.00           1512.00  20.2%
External/S...te/520.omnetpp_r/520.omnetpp_r    954.00           1143.00  19.8%
External/S...rate/510.parest_r/510.parest_r   5961.00           7122.00  19.5%
External/S...C/CINT2006/445.gobmk/445.gobmk     47.00             56.00  19.1%
External/S...00.perlbench_r/500.perlbench_r    241.00            286.00  18.7%
External/S...NT2006/471.omnetpp/471.omnetpp     36.00             42.00  16.7%
External/S...06/400.perlbench/400.perlbench    183.00            210.00  14.8%
MultiSource/Applications/SPASS/SPASS            72.00             81.00  12.5%
External/S...17rate/541.leela_r/541.leela_r     72.00             80.00  11.1%
External/SPEC/CINT2006/403.gcc/403.gcc         585.00            642.00   9.7%
MultiSourc...e/Applications/sqlite3/sqlite3    120.00            131.00   9.2%
MultiSourc...Applications/hexxagon/hexxagon     11.00             12.00   9.1%
External/S.../CFP2006/453.povray/453.povray    566.00            615.00   8.7%
External/S...rate/511.povray_r/511.povray_r    578.00            627.00   8.5%
External/S...FP2006/482.sphinx3/482.sphinx3     12.00             13.00   8.3%
MultiSource/Applications/oggenc/oggenc         130.00            140.00   7.7%
MultiSourc...e/Applications/ClamAV/clamscan    250.00            268.00   7.2%
MultiSourc.../mediabench/jpeg/jpeg-6a/cjpeg     19.00             20.00   5.3%
MultiSourc...ch/consumer-jpeg/consumer-jpeg     19.00             20.00   5.3%
External/S...te/526.blender_r/526.blender_r   3747.00           3928.00   4.8%
MultiSourc...OE-ProxyApps-C++/miniFE/miniFE    104.00            108.00   3.8%
MultiSourc...ch/consumer-lame/consumer-lame     54.00             56.00   3.7%
MultiSource/Benchmarks/Bullet/bullet          1222.00           1264.00   3.4%
MultiSourc...nchmarks/tramp3d-v4/tramp3d-v4    973.00           1005.00   3.3%
External/S.../CFP2006/447.dealII/447.dealII   2699.00           2780.00   3.0%
External/S...06/483.xalancbmk/483.xalancbmk    788.00            810.00   2.8%
External/S.../CFP2006/450.soplex/450.soplex    180.00            185.00   2.8%
MultiSourc.../DOE-ProxyApps-C++/CLAMR/CLAMR    338.00            345.00   2.1%
MultiSourc...Benchmarks/7zip/7zip-benchmark    685.00            699.00   2.0%
External/S...FP2017rate/544.nab_r/544.nab_r    158.00            160.00   1.3%
MultiSourc...sumer-typeset/consumer-typeset    772.00            781.00   1.2%
External/S...2017rate/525.x264_r/525.x264_r    410.00            414.00   1.0%
External/S...23.xalancbmk_r/523.xalancbmk_r    998.00           1002.00   0.4%

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D132365

Files:
  llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
  llvm/test/Transforms/DeadStoreElimination/multiblock-loop-carried-dependence.ll
  llvm/test/Transforms/DeadStoreElimination/multiblock-malloc-free.ll
  llvm/test/Transforms/DeadStoreElimination/multiblock-memintrinsics.ll
  llvm/test/Transforms/DeadStoreElimination/phi-translation.ll

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