[X86] Use vmovss to handle inserting an element into index 0 of a v8f32 vector of zeros.

llvm-svn: 231354

1 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index e5af7293b0e..e51149210bf 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -5634,12 +5634,13 @@ X86TargetLowering::LowerBUILD_VECTOR(SDValue Op, SelectionDAG &DAG) const {
 
       if (ExtVT == MVT::i32 || ExtVT == MVT::f32 || ExtVT == MVT::f64 ||
           (ExtVT == MVT::i64 && Subtarget->is64Bit())) {
-        if (VT.is256BitVector() || VT.is512BitVector()) {
+        if (VT.is512BitVector()) {
           SDValue ZeroVec = getZeroVector(VT, Subtarget, DAG, dl);
           return DAG.getNode(ISD::INSERT_VECTOR_ELT, dl, VT, ZeroVec,
                              Item, DAG.getIntPtrConstant(0));
         }
-        assert(VT.is128BitVector() && "Expected an SSE value type!");
+        assert((VT.is128BitVector() || VT.is256BitVector()) &&
+               "Expected an SSE value type!");
         Item = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, VT, Item);
         // Turn it into a MOVL (i.e. movss, movsd, or movd) to a zero vector.
         return getShuffleVectorZeroOrUndef(Item, 0, true, Subtarget, DAG);
@@ -9333,6 +9334,15 @@ static SDValue lowerV8F32VectorShuffle(SDValue Op, SDValue V1, SDValue V2,
   ArrayRef<int> Mask = SVOp->getMask();
   assert(Mask.size() == 8 && "Unexpected mask size for v8 shuffle!");
 
+  // If we have a single input to the zero element, insert that into V1 if we
+  // can do so cheaply.
+  int NumV2Elements =
+      std::count_if(Mask.begin(), Mask.end(), [](int M) { return M >= 8; });
+  if (NumV2Elements == 1 && Mask[0] >= 8)
+    if (SDValue Insertion = lowerVectorShuffleAsElementInsertion(
+            DL, MVT::v8f32, V1, V2, Mask, Subtarget, DAG))
+      return Insertion;
+
   if (SDValue Blend = lowerVectorShuffleAsBlend(DL, MVT::v8f32, V1, V2, Mask,
                                                 Subtarget, DAG))
     return Blend;