[PATCH] [X86][SSE] pslldq/psrldq byte shifts/rotation for SSE2

[Chandler Carruth]

================
Comment at: lib/Target/X86/X86ISelLowering.cpp:7545
@@ +7544,3 @@
+  bool LoIsZero = ISD::isBuildVectorAllZeros(Lo.getNode());
+  bool HiIsZero = ISD::isBuildVectorAllZeros(Hi.getNode());
+
----------------
Please use the zeroable computation routine that the rest of the vector shuffle lowering uses. There are lots of other patterns that show up which this doesn't necessarily catch.

http://reviews.llvm.org/D5699