[x86] Teach the x86 DAG combiner to form MOVSLDUP and MOVSHDUP

instructions when it finds an appropriate pattern.

These are lovely instructions, and its a shame to not use them. =] They
are fast, and can hand loads folded into their operands, etc.

I've also plumbed the comment shuffle decoding through the various
layers so that the test cases are printed nicely.

llvm-svn: 217758

1 files changed, 16 insertions, 0 deletions

diff --git a/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp b/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp
index 5da63bef4d7..51d251e551c 100644
--- a/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp
+++ b/llvm/lib/Target/X86/Utils/X86ShuffleDecode.cpp
@@ -63,6 +63,22 @@ void DecodeMOVLHPSMask(unsigned NElts, SmallVectorImpl<int> &ShuffleMask) {
     ShuffleMask.push_back(NElts+i);
 }
 
+void DecodeMOVSLDUPMask(MVT VT, SmallVectorImpl<int> &ShuffleMask) {
+  unsigned NumElts = VT.getVectorNumElements();
+  for (int i = 0, e = NumElts / 2; i < e; ++i) {
+    ShuffleMask.push_back(2 * i);
+    ShuffleMask.push_back(2 * i);
+  }
+}
+
+void DecodeMOVSHDUPMask(MVT VT, SmallVectorImpl<int> &ShuffleMask) {
+  unsigned NumElts = VT.getVectorNumElements();
+  for (int i = 0, e = NumElts / 2; i < e; ++i) {
+    ShuffleMask.push_back(2 * i + 1);
+    ShuffleMask.push_back(2 * i + 1);
+  }
+}
+
 void DecodePALIGNRMask(MVT VT, unsigned Imm,
                        SmallVectorImpl<int> &ShuffleMask) {
   unsigned NumElts = VT.getVectorNumElements();