[PATCH] D46201: [DA] Use SCEV to conclude DVEntry::EQ in some cases.

[Florian Hahn via Phabricator via llvm-commits]

fhahn created this revision.
fhahn added reviewers: hfinkel, sebpop, grosser.
Herald added subscribers: javed.absar, mehdi_amini.

This is a very naive approach to conclude that both accesses to Arr1 in the
loop below access the same memory location.

  void foo(unsigned **Arr1) {
    for (int i = 0; i < 1024; ++i)
      for(int j = 0; j < 1024; ++j)
        Arr1[j][i] = Arr1[j][i] 10;
  }

By using SCEV, we can conclude that both accesses to Arr1 access the
same location in each loop iteration. I am probably missing something,
but this seems to work for loop variant accesses in the same loop.

It would be great if you could have a look and let me know what I am
missing :)

For SPEC2006 and the test-suite with LTO, this triggers in around 1100
cases. It also helps LoopInterchange to interchange a few more loops.


https://reviews.llvm.org/D46201

Files:
  lib/Analysis/DependenceAnalysis.cpp
  test/Analysis/DependenceAnalysis/AA.ll
  test/Analysis/DependenceAnalysis/Banerjee.ll
  test/Analysis/DependenceAnalysis/GCD.ll
  test/Analysis/DependenceAnalysis/Invariant.ll
  test/Analysis/DependenceAnalysis/NonCanonicalizedSubscript.ll
  test/Analysis/DependenceAnalysis/PR21585.ll
  test/Analysis/DependenceAnalysis/Preliminary.ll
  test/Analysis/DependenceAnalysis/Propagating.ll
  test/Analysis/DependenceAnalysis/Separability.ll
  test/Analysis/DependenceAnalysis/Symbolic.ll
  test/Analysis/DependenceAnalysis/SymbolicRDIV.ll
  test/Analysis/DependenceAnalysis/WeakZeroSrcSIV.ll
  test/Transforms/LoopInterchange/currentLimitation.ll
  test/Transforms/LoopInterchange/loop-interchange-optimization-remarks.ll

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