DAG: Factor out helper function for odd vector sizes

[RKSimon]

LGTM

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

630

Pull out the repeated getVectorNumElements() calls?

[arsenm]

r341392

lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

for (unsigned i = 0; i < NumParts; i += StepSize) {
       }
     }
   }
 
   if (DAG.getDataLayout().isBigEndian())
     std::reverse(Parts, Parts + OrigNumParts);
 }
 
+static SDValue widenVectorToPartType(SelectionDAG &DAG,
+                                     SDValue Val, const SDLoc &DL, EVT PartVT) {
+  EVT ValueVT = Val.getValueType();
+  if (PartVT.isVector() &&
+      PartVT.getVectorElementType() == ValueVT.getVectorElementType() &&
+      PartVT.getVectorNumElements() > ValueVT.getVectorNumElements()) {
+    EVT ElementVT = PartVT.getVectorElementType();
+    // Vector widening case, e.g. <2 x float> -> <4 x float>.  Shuffle in
+    // undef elements.
+    SmallVector<SDValue, 16> Ops;
+    DAG.ExtractVectorElements(Val, Ops);
+    SDValue EltUndef = DAG.getUNDEF(ElementVT);
+    for (unsigned i = ValueVT.getVectorNumElements(),
+           e = PartVT.getVectorNumElements(); i != e; ++i)
+      Ops.push_back(EltUndef);
+
+    // FIXME: Use CONCAT for 2x -> 4x.
+    return DAG.getBuildVector(PartVT, DL, Ops);
+  }
+
+  return SDValue();
+}
+
 /// getCopyToPartsVector - Create a series of nodes that contain the specified
 /// value split into legal parts.
 static void getCopyToPartsVector(SelectionDAG &DAG, const SDLoc &DL,
                                  SDValue Val, SDValue *Parts, unsigned NumParts,
                                  MVT PartVT, const Value *V,
                                  Optional<CallingConv::ID> CallConv) {
   EVT ValueVT = Val.getValueType();
   assert(ValueVT.isVector() && "Not a vector");
   const TargetLowering &TLI = DAG.getTargetLoweringInfo();
   const bool IsABIRegCopy = CallConv.hasValue();
 
   if (NumParts == 1) {
     EVT PartEVT = PartVT;
     if (PartEVT == ValueVT) {
       // Nothing to do.
     } else if (PartVT.getSizeInBits() == ValueVT.getSizeInBits()) {
       // Bitconvert vector->vector case.
       Val = DAG.getNode(ISD::BITCAST, DL, PartVT, Val);
-    } else if (PartVT.isVector() &&
-               PartEVT.getVectorElementType() == ValueVT.getVectorElementType() &&
-               PartEVT.getVectorNumElements() > ValueVT.getVectorNumElements()) {
-      EVT ElementVT = PartVT.getVectorElementType();
-      // Vector widening case, e.g. <2 x float> -> <4 x float>.  Shuffle in
-      // undef elements.
-      SmallVector<SDValue, 16> Ops;
-      for (unsigned i = 0, e = ValueVT.getVectorNumElements(); i != e; ++i)
-        Ops.push_back(DAG.getNode(
-            ISD::EXTRACT_VECTOR_ELT, DL, ElementVT, Val,
-            DAG.getConstant(i, DL, TLI.getVectorIdxTy(DAG.getDataLayout()))));
-
-      for (unsigned i = ValueVT.getVectorNumElements(),
-           e = PartVT.getVectorNumElements(); i != e; ++i)
-        Ops.push_back(DAG.getUNDEF(ElementVT));
-
-      Val = DAG.getBuildVector(PartVT, DL, Ops);
-
-      // FIXME: Use CONCAT for 2x -> 4x.
-
-      //SDValue UndefElts = DAG.getUNDEF(VectorTy);
-      //Val = DAG.getNode(ISD::CONCAT_VECTORS, DL, PartVT, Val, UndefElts);
+    } else if (SDValue Widened = widenVectorToPartType(DAG, Val, DL, PartVT)) {
+      Val = Widened;
     } else if (PartVT.isVector() &&
                PartEVT.getVectorElementType().bitsGE(
                  ValueVT.getVectorElementType()) &&
                PartEVT.getVectorNumElements() == ValueVT.getVectorNumElements()) {
 
       // Promoted vector extract
       Val = DAG.getAnyExtOrTrunc(Val, DL, PartVT);
     } else {