[PATCH] D144760: [InstCombine] use demanded vector elements to eliminate partially redundant instructions

[Sanjay Patel via Phabricator via llvm-commits]

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In issue #60632 <https://github.com/llvm/llvm-project/issues/60632>, we have vector math ops that differ because an operand is shuffled, but the math has limited demanded elements, so it can be replaced by another instruction:
https://alive2.llvm.org/ce/z/TKqq7H

I don't think we have anything like this yet - it's like a CSE/GVN fold, but driven by demanded elements of a vector op.
This is limited to splat-0 as a first step to keep it simple and to save time in case it would be better to try this somewhere else.


https://reviews.llvm.org/D144760

Files:
  llvm/lib/Transforms/InstCombine/InstCombineSimplifyDemanded.cpp
  llvm/test/Transforms/InstCombine/vec_demanded_elts.ll

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