[X86][AVX] Fix failed broadcast fold

Strip excess BITCASTs from EXTRACT_SUBVECTOR input

llvm-svn: 320930

1 files changed, 7 insertions, 3 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index 3cd1704c9c6..01636128df0 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -10483,9 +10483,13 @@ static SDValue lowerVectorShuffleAsBroadcast(const SDLoc &DL, MVT VT,
 
   // We only support broadcasting from 128-bit vectors to minimize the
   // number of patterns we need to deal with in isel. So extract down to
-  // 128-bits.
-  if (SrcVT.getSizeInBits() > 128)
-    V = extract128BitVector(V, 0, DAG, DL);
+  // 128-bits, removing as many bitcasts as possible.
+  if (SrcVT.getSizeInBits() > 128) {
+    MVT ExtVT = MVT::getVectorVT(SrcVT.getScalarType(),
+                                 128 / SrcVT.getScalarSizeInBits());
+    V = extract128BitVector(peekThroughBitcasts(V), 0, DAG, DL);
+    V = DAG.getBitcast(ExtVT, V);
+  }
 
   return DAG.getBitcast(VT, DAG.getNode(Opcode, DL, BroadcastVT, V));
 }