[PATCH] D145073: [InstCombine] fold signed absolute diff patterns

[Sanjay Patel via Phabricator via llvm-commits]

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This overlaps partially with the codegen patch D144789 <https://reviews.llvm.org/D144789>. This needs nsw for correctness, and I'm not sure if there's an unsigned equivalent:
https://alive2.llvm.org/ce/z/ErmQ-9

This is obviously an improvement in IR, and it looks like a codegen win for all targets and data types that I sampled.

The 'nabs' case is not as clean because I think it would require clearing nsw from the subtract to be correct, so that's left as a potential follow-up (and seems less likely to occur in real code).


https://reviews.llvm.org/D145073

Files:
  llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
  llvm/test/Transforms/InstCombine/abs-1.ll

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