[PATCH] D55780: [X86] Create PSUBUS from (add (umax X, C), -C)

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: RKSimon, spatel.

InstCombine seems to canonicalize or PSUB patter into a max with the cosntant and an add with an inverse of the constant.

This patch recognizes this pattern and turns it into PSUBUS.

Fixes PR40053


https://reviews.llvm.org/D55780

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/psubus.ll

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