[PATCH] D150246: AMDGPU: remove an illegal transform for shl(or)

[Ruiling, Song via Phabricator via llvm-commits]

ruiling added a comment.

> It should help because `SelectionDAG::isBaseWithConstantOffset` knows how to match OR (if the known bits do not overlap) as well as ADD.

Do you mean we can optimize for `shl(or)` with the help of knownbits? I think I agree with you. But I am not sure whether it is really helpful in practical cases. The `isBaseWithConstantOffset` you mentioned specifically designed to work on stack slot access. I am not sure if such patterns can also be observed more broadly. And I think such kind of optimization should be done separately, maybe it should be added in the common LLVM code. And the lit-test should also be redesigned. I would rather fix the problematic transformation first. sounds ok to you?


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  https://reviews.llvm.org/D150246/new/

https://reviews.llvm.org/D150246