[PATCH] D133840: AMDGPU: Add a pass to rewrite certain undef in PHI

[Sameer Sahasrabuddhe via Phabricator via llvm-commits]

sameerds added a comment.

In D133840#3791418 <https://reviews.llvm.org/D133840#3791418>, @ruiling wrote:

> Move the pass after SIAnnotateControlFlow.
> Simplify the backedge undef logic since joining divergent threads at loop header has been handled by SIAnnotateControlFlow.

Is there an advantage in making this assumption that it always runs after SIAnnotateControlFlow? It makes the pass less useful for anything other than the current AMDGPU. If there is no harm in keeping the backedge logic, then the pass will remain useful for any future use where such loops do occur.


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  https://reviews.llvm.org/D133840/new/

https://reviews.llvm.org/D133840