[PATCH] D50878: [X86] Teach combineTruncatedArithmetic to handle some cases of ISD::SUB

[Craig Topper via Phabricator via llvm-commits]

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

We can safely avoid interfering with the subus combine if both inputs are freely truncatable. Either both extends, or an extend and a constant vector.


https://reviews.llvm.org/D50878

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/vector-trunc-math.ll

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