[PATCH] D69157: [X86] Prefer KORTEST on Knights Landing or later for memcmp()

Thu Oct 17 21:24:18 PDT 2019

davezarzycki created this revision.
davezarzycki added reviewers: craig.topper, RKSimon, spatel.
davezarzycki added a project: LLVM.

PTEST and especially the MOVMSK instructions are slow on Knights Landing or later. As a bonus, this patch increases instruction parallelism by emitting.

  KORTEST(PCMPNEQ(a, b), PCMPNEQ(c, d)) == 0

Instead of:

  KORTEST(AND(PCMPEQ(a, b), PCMPEQ(c, d))) == ~0

Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D69157

Files:
  lib/Target/X86/X86.td
  lib/Target/X86/X86ISelLowering.cpp
  lib/Target/X86/X86Subtarget.h
  lib/Target/X86/X86TargetTransformInfo.h
  test/CodeGen/X86/memcmp.ll
  test/CodeGen/X86/setcc-wide-types.ll

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