[all-commits] [llvm/llvm-project] 339795: [LV] Fix FindLastIV reduction for epilogue vectori...

[Mel Chen via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 3397950f2d21426c7520d114a12588128906a897
      https://github.com/llvm/llvm-project/commit/3397950f2d21426c7520d114a12588128906a897
  Author: Mel Chen <mel.chen at sifive.com>
  Date:   2025-01-13 (Mon, 13 Jan 2025)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    M llvm/test/Transforms/LoopVectorize/epilog-iv-select-cmp.ll

  Log Message:
  -----------
  [LV] Fix FindLastIV reduction for epilogue vectorization. (#120395)

Following 0e528ac404e13ed2d952a2d83aaf8383293c851e, this patch adjusts
the resume value of VPReductionPHIRecipe for FindLastIV reductions.
Replacing the resume value with:

  ResumeValue = ResumeValue == StartValue ? SentinelValue : ResumeValue;

This addressed the correctness issue when the start value might not be
less than the minimum value of a monotonically increasing induction
variable.

Thanks Florian Hahn for the help.

---------

Co-authored-by: Florian Hahn <flo at fhahn.com>



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