[PATCH] D110867: X86InstrInfo: Support immediates that are +1/-1 different in optimizeCompareInstr

Wed Nov 3 11:09:55 PDT 2021

rupprecht added a comment.

In D110867#3106660 <https://reviews.llvm.org/D110867#3106660>, @MatzeB wrote:

>> I've reverted back to green in https://github.com/llvm/llvm-project/commit/a2a58d91e82db38fbdf88cc317dcb3753d79d492 until this can be fixed.
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>> FWIW, we also saw a non-determinism issue as a result of this patch in a stage2 PGO'd build of clang.
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> I believe the new version of this diff fixes the reported issue. Do you have a way to confirm?

In theory you should be able to reproduce the non-determinism issue, as it's just clang (nothing internal), but it may depend on some particular workflow we do internally. I'll patch it and report back.

I don't have a way to verify the miscompile Hans is talking about.

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D110867/new/

https://reviews.llvm.org/D110867