[PATCH] D42772: [X86] Allow KTEST instruction to be used for testing if a mask is all ones

[Craig Topper via Phabricator via llvm-commits]

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

The KTEST instruction sets the C flag if the result of anding both operands together is all 1s. We can use this to lower (icmp eq/ne (bitcast (vXi1 X), -1)


https://reviews.llvm.org/D42772

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/avx512-mask-op.ll

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