[LegalizeVectorTypes] When widening the result of a bitcast from a scalar type, use a scalar_to_vector to turn the scalar into a vector intead of a build vector full of mostly undefs.

This is more consistent with what we usually do and matches some code X86 custom emits in some cases that I think I can cleanup.

The MIPS test change just looks to be an instruction ordering change.

llvm-svn: 344422

1 files changed, 12 insertions, 14 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
index 310f5ef5dc7..f4cad796863 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeVectorTypes.cpp
@@ -3022,22 +3022,20 @@ SDValue DAGTypeLegalizer::WidenVecRes_BITCAST(SDNode *N) {
     }
 
     if (TLI.isTypeLegal(NewInVT)) {
-      // Because the result and the input are different vector types, widening
-      // the result could create a legal type but widening the input might make
-      // it an illegal type that might lead to repeatedly splitting the input
-      // and then widening it. To avoid this, we widen the input only if
-      // it results in a legal type.
-      SmallVector<SDValue, 16> Ops(NewNumElts);
-      SDValue UndefVal = DAG.getUNDEF(InVT);
-      Ops[0] = InOp;
-      for (unsigned i = 1; i < NewNumElts; ++i)
-        Ops[i] = UndefVal;
-
       SDValue NewVec;
-      if (InVT.isVector())
+      if (InVT.isVector()) {
+        // Because the result and the input are different vector types, widening
+        // the result could create a legal type but widening the input might make
+        // it an illegal type that might lead to repeatedly splitting the input
+        // and then widening it. To avoid this, we widen the input only if
+        // it results in a legal type.
+        SmallVector<SDValue, 16> Ops(NewNumElts, DAG.getUNDEF(InVT));
+        Ops[0] = InOp;
+
         NewVec = DAG.getNode(ISD::CONCAT_VECTORS, dl, NewInVT, Ops);
-      else
-        NewVec = DAG.getBuildVector(NewInVT, dl, Ops);
+      } else {
+        NewVec = DAG.getNode(ISD::SCALAR_TO_VECTOR, dl, NewInVT, InOp);
+      }
       return DAG.getNode(ISD::BITCAST, dl, WidenVT, NewVec);
     }
   }