[PATCH] D115113: [InstCombine] Do not combine atomic and non-atomic loads.

[Ricky Zhou via Phabricator via llvm-commits]

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Before this change, InstCombine was willing to fold atomic and
non-atomic loads through a PHI node as long as the first PHI argument
is not an atomic load. The combined load would be non-atomic, which is
incorrect.

Fix this by only combining the loads in a PHI node when all of the
arguments are non-atomic loads.

Thanks to Eli Friedman for pointing out the bug at
https://bugs.llvm.org/show_bug.cgi?id=51435#c3!

Fixes PR51435.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D115113

Files:
  llvm/lib/Transforms/InstCombine/InstCombinePHI.cpp
  llvm/test/Transforms/InstCombine/pr51435.ll

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