[PATCH] D125378: [Attribute] Introduce shuffle attribute to be used for __shfl_sync like cross-lane APIs

[Nicolai Hähnle via Phabricator via llvm-commits]

nhaehnle requested changes to this revision.
nhaehnle added a comment.

I'm sorry to say that this patch seems confused about semantics. It lacks clear definitions, and in particular for the `shuffle` attribute in LLVM IR, you almost certainly just want the already existing `convergent` instead.

If, separately from that, you still find a need to prevent Clang from labeling certain function arguments or return values as `noundef`, then presumably that should be done with an explicit "maybe undef" attribute instead, as @jdoerfert suggests.


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  https://reviews.llvm.org/D125378/new/

https://reviews.llvm.org/D125378