[PATCH] D47076: [InstCombine] choose 1 form of abs and nabs as canonical

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
spatel added reviewers: craig.topper, dmgreen, efriedma.
Herald added a subscriber: mcrosier.

We already do this for min/max (see the blob above the diff), so we should do the same for abs/nabs.
Compare with 0 and having the original argument as the true value of the select feels the most natural to me, but if someone prefers a different flavor, we could do that too.

This might solve the motivating cases for https://reviews.llvm.org/D47037 and https://reviews.llvm.org/D47041, but I think those patches still make sense. We can't guarantee this canonicalization if the icmp has more than one use.

I adjusted the shifty abs transform to the pattern here to make that transform more efficient.


https://reviews.llvm.org/D47076

Files:
  lib/Transforms/InstCombine/InstCombineAndOrXor.cpp
  lib/Transforms/InstCombine/InstCombineSelect.cpp
  test/Transforms/InstCombine/abs-1.ll
  test/Transforms/InstCombine/abs_abs.ll
  test/Transforms/InstCombine/icmp.ll
  test/Transforms/InstCombine/max-of-nots.ll
  test/Transforms/InstCombine/select_meta.ll
  test/Transforms/InstSimplify/call-callconv.ll

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