Allow lowering for palignr instructions for mmx sized vectors.  Add
patterns to handle the lowering.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@101331 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 6e6d2f5..b33fd82 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -7949,9 +7949,9 @@
 bool
 X86TargetLowering::isShuffleMaskLegal(const SmallVectorImpl<int> &M,
                                       EVT VT) const {
-  // Only do shuffles on 128-bit vector types for now.
+  // Very little shuffling can be done for 64-bit vectors right now.
   if (VT.getSizeInBits() == 64)
-    return false;
+    return isPALIGNRMask(M, VT, Subtarget->hasSSSE3());
 
   // FIXME: pshufb, blends, shifts.
   return (VT.getVectorNumElements() == 2 ||