Simon Pilgrim 844a30564e [X86][SSE] Improve combineLogicBlendIntoPBLENDV to use general masks.
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.).

Differential Revision: https://reviews.llvm.org/D32953

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@302424 91177308-0d34-0410-b5e6-96231b3b80d8
2017-05-08 14:16:39 +00:00
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