[all-commits] [llvm/llvm-project] a1a590: [InstCombine] Fix miscompilation in PR83947 (#83993)

[Yingwei Zheng via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: a1a590ef120c273b5c278f2412c4c4eac5280f23
      https://github.com/llvm/llvm-project/commit/a1a590ef120c273b5c278f2412c4c4eac5280f23
  Author: Yingwei Zheng <dtcxzyw2333 at gmail.com>
  Date:   2024-03-05 (Tue, 05 Mar 2024)

  Changed paths:
    M llvm/include/llvm/Analysis/VectorUtils.h
    M llvm/lib/Analysis/VectorUtils.cpp
    M llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
    A llvm/test/Transforms/InstCombine/pr83947.ll

  Log Message:
  -----------
  [InstCombine] Fix miscompilation in PR83947 (#83993)

https://github.com/llvm/llvm-project/blob/762f762504967efbe159db5c737154b989afc9bb/llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp#L394-L407

Comment from @topperc:
> This transforms assumes the mask is a non-zero splat. We only know its
a splat and not provably all 0s. The mask is a constexpr that includes
the address of the global variable. We can't resolve the constant
expression to an exact value.

Fixes #83947.



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