[X86][XOP] Added support for the lowering of 128-bit vector shifts to XOP shift instructions
The XOP shifts just have logical/arithmetic versions and the left/right shifts are controlled by whether the value is positive/negative. Because of this I've added new X86ISD nodes instead of trying to force them to use the existing shift nodes.
Additionally Excavator cores (bdver4) support XOP and AVX2 - meaning that it should use the AVX2 shifts when it can and fall back to XOP in other cases.
Differential Revision: http://reviews.llvm.org/D8690
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248878
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