[all-commits] [llvm/llvm-project] 94d8f1: [InstCombine] Fix infinite loop in select equivale...

[Nikita Popov via All-commits]

  Branch: refs/heads/release/18.x
  Home:   https://github.com/llvm/llvm-project
  Commit: 94d8f150ed8b6afb83ba47f68116a0247a23cb52
      https://github.com/llvm/llvm-project/commit/94d8f150ed8b6afb83ba47f68116a0247a23cb52
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2024-03-11 (Mon, 11 Mar 2024)

  Changed paths:
    M llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
    M llvm/test/Transforms/InstCombine/select.ll

  Log Message:
  -----------
  [InstCombine] Fix infinite loop in select equivalence fold (#84036)

When replacing with a non-constant, it's possible that the result of the
simplification is actually more complicated than the original, and may
result in an infinite combine loop.

Mitigate the issue by requiring that either the replacement or
simplification result is constant, which should ensure that it's
simpler. While this check is crude, it does not appear to cause
optimization regressions in real-world code in practice.

Fixes https://github.com/llvm/llvm-project/issues/83127.

(cherry picked from commit 9f45c5e1a65a1abf4920b617d36ed05e73c04bea)



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