[PATCH] D117544: [AMDGPU] Fix missing waitcnt issue

[Jay Foad via Phabricator via llvm-commits]

foad added a comment.

As a bit of background, the `OldOutOfOrder` test was introduced by @nhaehnle in a large refactoring in D54231 <https://reviews.llvm.org/D54231>. I think it's just a performance optimisation: if the old state had events that completed out of order, then any use of the corresponding registers would have to be preceded by a "waitcnt 0", so there's no need to reprocess that block because the waitcnts are already as strict as they can be. But this goes wrong in the case where the merge introduces a wait on a particular register that had no wait in the old state (so no waitcnt would have been generated for it the last time the block was processed).


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D117544/new/

https://reviews.llvm.org/D117544