[PATCH] D63489: [InstSimplify] LCSSA PHIs should not be simplified away

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

> This causes generation of incorrect code in AMDGPU backend.

This sounds like some other check is missing elsewhere?
What happens if you feed it such an ir as-if after this transform, but manually written?
("that will result in broken asm/crashes" is hopefully not the answer)

That being said, why is `LCSSAPass` not sufficient?
It's already supposed to undo transforms like this.


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  https://reviews.llvm.org/D63489/new/

https://reviews.llvm.org/D63489