[all-commits] [llvm/llvm-project] b82f80: [DSE] Use walker to skip noalias stores between cu...

[Florian Hahn via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: b82f80057d69564a889f1439a683c3544d30b7fa
      https://github.com/llvm/llvm-project/commit/b82f80057d69564a889f1439a683c3544d30b7fa
  Author: Florian Hahn <flo at fhahn.com>
  Date:   2020-10-28 (Wed, 28 Oct 2020)

  Changed paths:
    M llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp
    M llvm/test/Transforms/DeadStoreElimination/MSSA/noop-stores.ll

  Log Message:
  -----------
  [DSE] Use walker to skip noalias stores between current & clobber def.

Instead of getting the defining access we should be able to use
getClobberingMemoryAccess to skip non-aliasing MemoryDefs. No additional
checks should be needed, because we only remove the starting def if it
matches the defining access of the load. All we need to worry about is
that there are no (may)alias stores between the starting def and the
load and getClobberingMemoryAccess should guarantee that.

Partly fixes PR47887.

This improves the number of redundant stores removed in some cases
(numbers below for MultiSource, SPEC2000, SPEC2006 on X86 with -flto
-O3).

Same hash: 226 (filtered out)
Remaining: 11
Metric: dse.NumRedundantStores

Program                                        base   patch1 diff
 test-suite...:: External/Povray/povray.test     1.00   5.00 400.0%
 test-suite...chmarks/MallocBench/gs/gs.test     1.00   3.00 200.0%
 test-suite...0/253.perlbmk/253.perlbmk.test    21.00  37.00 76.2%
 test-suite...0.perlbench/400.perlbench.test    24.00  37.00 54.2%
 test-suite.../Applications/SPASS/SPASS.test     3.00   4.00 33.3%
 test-suite...006/453.povray/453.povray.test    15.00  18.00 20.0%
 test-suite...T2006/445.gobmk/445.gobmk.test    27.00  29.00  7.4%
 test-suite.../CINT2006/403.gcc/403.gcc.test   136.00 137.00  0.7%
 test-suite.../CINT2000/176.gcc/176.gcc.test     6.00   6.00  0.0%
 test-suite.../Benchmarks/Bullet/bullet.test    NaN     3.00  nan%
 test-suite.../Benchmarks/Ptrdist/bc/bc.test    NaN     1.00  nan%

Reviewed By: asbirlea

Differential Revision: https://reviews.llvm.org/D89647