[all-commits] [llvm/llvm-project] ff4de8: [DSE, MSSA] Treat `store 0` after calloc as noop st...

[Florian Hahn via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: ff4de8683ad1802dbf20d0286861bd98462e92e2
      https://github.com/llvm/llvm-project/commit/ff4de8683ad1802dbf20d0286861bd98462e92e2
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2020-06-23 (Tue, 23 Jun 2020)

  Changed paths:
    M llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
    M llvm/test/Transforms/DeadStoreElimination/MSSA/calloc-store.ll
    M llvm/test/Transforms/DeadStoreElimination/MSSA/simple-todo.ll
    M llvm/test/Transforms/DeadStoreElimination/MSSA/simple.ll

  Log Message:
  -----------
  [DSE,MSSA] Treat `store 0` after calloc as noop stores.

This patch extends storeIsNoop to also detect stores of 0 to an calloced
object. This basically ports the logic from legacy DSE to the MemorySSA
backed version.

It triggers in a few cases on MultiSource, SPEC2000, SPEC2006 with -O3
LTO:

Same hash: 218 (filtered out)
Remaining: 19
Metric: dse.NumNoopStores

Program                                        base   patch2 diff
 test-suite...CFP2000/177.mesa/177.mesa.test     1.00  15.00 1400.0%
 test-suite...6/482.sphinx3/482.sphinx3.test     1.00  14.00 1300.0%
 test-suite...lications/ClamAV/clamscan.test     2.00  28.00 1300.0%
 test-suite...CFP2006/433.milc/433.milc.test     1.00   8.00 700.0%
 test-suite...pplications/oggenc/oggenc.test     2.00   9.00 350.0%
 test-suite.../CINT2000/176.gcc/176.gcc.test     6.00   6.00  0.0%
 test-suite.../CINT2006/403.gcc/403.gcc.test    NaN   137.00  nan%
 test-suite...libquantum/462.libquantum.test    NaN     3.00  nan%
 test-suite...6/464.h264ref/464.h264ref.test    NaN     7.00  nan%
 test-suite...decode/alacconvert-decode.test    NaN     2.00  nan%
 test-suite...encode/alacconvert-encode.test    NaN     2.00  nan%
 test-suite...ications/JM/ldecod/ldecod.test    NaN     9.00  nan%
 test-suite...ications/JM/lencod/lencod.test    NaN    39.00  nan%
 test-suite.../Applications/lemon/lemon.test    NaN     2.00  nan%
 test-suite...pplications/treecc/treecc.test    NaN     4.00  nan%
 test-suite...hmarks/McCat/08-main/main.test    NaN     4.00  nan%
 test-suite...nsumer-lame/consumer-lame.test    NaN     3.00  nan%
 test-suite.../Prolangs-C/bison/mybison.test    NaN     1.00  nan%
 test-suite...arks/mafft/pairlocalalign.test    NaN    30.00  nan%

Reviewers: efriedma, zoecarver, asbirlea

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D82204