[PATCH] D95235: [InstCombine] narrow abs with sign-extended input

[Sanjay Patel via Phabricator via llvm-commits]

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In the motivating cases from https://llvm.org/PR48816 , we have a trailing `trunc`. But that is not required to reduce the abs width:
https://alive2.llvm.org/ce/z/ECaz-p
...as long as we clear the int-min-is-poison bit (`nsw`).

We have some existing tests that are affected, and I'm not sure what the overall implications are, but in general I think we favor narrowing operations over preserving nsw/nuw. If not, we could restrict this transform based on type (shouldChangeType() and/or vector vs. scalar).


https://reviews.llvm.org/D95235

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

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