[PATCH] D32953: [X86][SSE] Improve combineLogicBlendIntoPBLENDV to use general masks.

[Simon Pilgrim via Phabricator via llvm-commits]

RKSimon created this revision.

Currently combineLogicBlendIntoPBLENDV can only match ASHR to detect sign splatting of a bit mask, this patch generalises this to use computeNumSignBits instead.

This is a first step in several things we can do to improve PBLENDV support:

- Better matching of X86ISD::ANDNP patterns.
- Handle floating point cases.
- Better vector and bitcast support in computeNumSignBits.
- Recognise that PBLENDV only uses the sign bit of the mask, we should be able strip away sign splats (ASHR, PCMPGT isNeg tests etc.).


Repository:
  rL LLVM

https://reviews.llvm.org/D32953

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/cast-vsel.ll
  test/CodeGen/X86/pr32907.ll
  test/CodeGen/X86/vselect-pcmp.ll

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