[all-commits] [llvm/llvm-project] 28fe6d: [InstCombine] Remove AllOnes fallbacks in getMaske...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 28fe6ddd9b9af0167d355ceb5b9eace53c7f162b
      https://github.com/llvm/llvm-project/commit/28fe6ddd9b9af0167d355ceb5b9eace53c7f162b
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2024-08-26 (Mon, 26 Aug 2024)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
    M llvm/test/Transforms/InstCombine/bit-checks.ll

  Log Message:
  -----------
  [InstCombine] Remove AllOnes fallbacks in getMaskedTypeForICmpPair() (#104941)

getMaskedTypeForICmpPair() tries to model non-and operands as x & -1.
However, this can end up confusing the matching logic, by picking the -1
operand as the "common" operand, resulting in a successful, but useless,
match. This is what causes commutation failures for some of the
optimizations driven by this function.

Fix this by treating a match against -1 as a non-match.



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