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

This patch builds on http://reviews.llvm.org/D5598 to perform byte rotation shuffles (lowerVectorShuffleAsByteRotate) on pre-SSSE3 (palignr) targets - pre-SSSE3 is only enabled on i8 and i16 vector targets where it is a more definite performance gain.

I've also added a separate byte shift shuffle (lowerVectorShuffleAsByteShift) that makes use of the ability of the SLLDQ/SRLDQ instructions to implicitly shift in zero bytes to avoid the need to create a zero register if we had used palignr.

Differential Revision: http://reviews.llvm.org/D5699

llvm-svn: 222340

1 files changed, 2 insertions, 2 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
index adaa12ea426..7961e66d8c8 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp
@@ -96,7 +96,7 @@ bool ConstantFPSDNode::isValueValidForType(EVT VT,
 /// BUILD_VECTOR where all of the elements are ~0 or undef.
 bool ISD::isBuildVectorAllOnes(const SDNode *N) {
   // Look through a bit convert.
-  if (N->getOpcode() == ISD::BITCAST)
+  while (N->getOpcode() == ISD::BITCAST)
     N = N->getOperand(0).getNode();
 
   if (N->getOpcode() != ISD::BUILD_VECTOR) return false;
@@ -144,7 +144,7 @@ bool ISD::isBuildVectorAllOnes(const SDNode *N) {
 /// BUILD_VECTOR where all of the elements are 0 or undef.
 bool ISD::isBuildVectorAllZeros(const SDNode *N) {
   // Look through a bit convert.
-  if (N->getOpcode() == ISD::BITCAST)
+  while (N->getOpcode() == ISD::BITCAST)
     N = N->getOperand(0).getNode();
 
   if (N->getOpcode() != ISD::BUILD_VECTOR) return false;