[PATCH] D124247: [Trivial Dead] Consider any non volatile load as trivially dead independent on ordering

[Serguei Katkov via Phabricator via llvm-commits]

skatkov created this revision.
skatkov added reviewers: reames, fhahn, nikic, rampitec, efriedma, timshen.
Herald added subscribers: kerbowa, hiraditya, jvesely, nemanjai.
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skatkov requested review of this revision.
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None volatile load can be considered as trivial dead independent on atomic
semantic. This is based on the fact that release-acquire synchronization
happens only if load reads the value written by store-release operation.
As soone as load instruction does not have uses, so no one will check what
actually value has been read. So optimizer may suggest that load reads the
value was before store release happened and so no synchronization happened.
This allows us simply to remove this load.


https://reviews.llvm.org/D124247

Files:
  llvm/lib/Transforms/Utils/Local.cpp
  llvm/test/CodeGen/AMDGPU/noclobber-barrier.ll
  llvm/test/CodeGen/PowerPC/atomics-constant.ll
  llvm/test/Transforms/EarlyCSE/atomics.ll
  llvm/test/Transforms/EarlyCSE/basic.ll
  llvm/test/Transforms/InstCombine/atomic.ll
  llvm/test/Transforms/InstCombine/store.ll

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