[PATCH] D52121: [X86] Fold (movmsk (setne (and X, (1 << C)), 0)) -> (movmsk (X << C))

[Craig Topper via Phabricator via llvm-commits]

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

MOVMSK only care about the sign bit so we don't need the setcc to fill the whole element with 0s/1s. We can just shift the bit we're looking for into the sign bit. This saves a constant pool load.

Inspired by PR38840.


https://reviews.llvm.org/D52121

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/movmsk-cmp.ll

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