[PATCH] D99674: [InstCombine] Conditionally fold select i1 into and/or

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune created this revision.
aqjune added reviewers: nikic, lebedev.ri, spatel.
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This patch fixes llvm.org/pr49688 by conditionally folding select i1 into and/or:

  select cond, cond2, false
  ->
  and cond, cond2

This is not safe if cond2 is poison whereas cond isn’t.

Unconditionally disabling this transformation affects later pipelines that depend on and/or i1s.
To minimize its impact, this patch conservatively checks whether cond2 is an instruction that
creates a poison or its operand creates a poison.
This approach is similar to what InstSimplify's SimplifyWithOpReplaced is doing.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D99674

Files:
  llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
  llvm/test/Transforms/InstCombine/and-fcmp.ll
  llvm/test/Transforms/InstCombine/onehot_merge.ll
  llvm/test/Transforms/InstCombine/pr49668.ll
  llvm/test/Transforms/InstCombine/signed-truncation-check.ll
  llvm/test/Transforms/InstCombine/widenable-conditions.ll
  llvm/test/Transforms/PhaseOrdering/unsigned-multiply-overflow-check.ll

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