[PATCH] D70246: [InstCombine] remove identity shuffle simplification for mask with undefs

[Zhengyang Liu via Phabricator via llvm-commits]

liuz added a comment.

> Converting poison to undef is okay, but undef to poison is not. undef & 0 == undef, but poison & 0 == poison. If undef can be optimized to poison, this can cause miscompilation. See here: https://rise4fun.com/Alive/DFYf , https://rise4fun.com/Alive/OZU

Hi Juneyoung. Is that a typo? undef & 0 should be 0.


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  https://reviews.llvm.org/D70246/new/

https://reviews.llvm.org/D70246