[PATCH] D125321: [InstCombine] Freeze other uses of frozen value

[Nikita Popov via Phabricator via llvm-commits]

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If there is a `freeze %x`, we currently replace all other uses of `%x` with `freeze %x` -- as long as they are dominated by the freeze instruction. This patch extends this behavior to cases where we did not originally dominate the use by moving the freeze instruction to the nearest common dominator.

The motivation can be seen in test `@combine_and_after_freezing_uses`: Canonicalizing everything to `freeze %x` allows folds that are based on value identity (i.e. same operand occurring in two places) to trigger. This also covers the case from D125248 <https://reviews.llvm.org/D125248>.


https://reviews.llvm.org/D125321

Files:
  llvm/lib/Transforms/InstCombine/InstCombineInternal.h
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
  llvm/test/Transforms/InstCombine/freeze.ll
  llvm/test/Transforms/InstCombine/onehot_merge.ll

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