[X86] combineINSERT_SUBVECTOR - pull out common variables. NFC. (#133705)

Reduces diff for an updated version of #133083

Author: RKSimon

llvm/lib/Target/X86/X86ISelLowering.cpp

@@ -58823,6 +58823,8 @@ static SDValue combineINSERT_SUBVECTOR(SDNode *N, SelectionDAG &DAG,
 
   uint64_t IdxVal = N->getConstantOperandVal(2);
   MVT SubVecVT = SubVec.getSimpleValueType();
+  int VecNumElts = OpVT.getVectorNumElements();
+  int SubVecNumElts = SubVecVT.getVectorNumElements();
 
   if (Vec.isUndef() && SubVec.isUndef())
     return DAG.getUNDEF(OpVT);
@@ -58882,19 +58884,17 @@ static SDValue combineINSERT_SUBVECTOR(SDNode *N, SelectionDAG &DAG,
       SubVec.getOperand(0).getSimpleValueType() == OpVT &&
       (IdxVal != 0 ||
        !(Vec.isUndef() || ISD::isBuildVectorAllZeros(Vec.getNode())))) {
+    SDValue ExtSrc = SubVec.getOperand(0);
     int ExtIdxVal = SubVec.getConstantOperandVal(1);
     if (ExtIdxVal != 0) {
-      int VecNumElts = OpVT.getVectorNumElements();
-      int SubVecNumElts = SubVecVT.getVectorNumElements();
       SmallVector<int, 64> Mask(VecNumElts);
       // First create an identity shuffle mask.
       for (int i = 0; i != VecNumElts; ++i)
         Mask[i] = i;
       // Now insert the extracted portion.
       for (int i = 0; i != SubVecNumElts; ++i)
         Mask[i + IdxVal] = i + ExtIdxVal + VecNumElts;
-
-      return DAG.getVectorShuffle(OpVT, dl, Vec, SubVec.getOperand(0), Mask);
+      return DAG.getVectorShuffle(OpVT, dl, Vec, ExtSrc, Mask);
     }
   }
 
@@ -58942,7 +58942,7 @@ static SDValue combineINSERT_SUBVECTOR(SDNode *N, SelectionDAG &DAG,
   // If we're splatting the lower half subvector of a full vector load into the
   // upper half, attempt to create a subvector broadcast.
   // TODO: Drop hasOneUse checks.
-  if (IdxVal == (OpVT.getVectorNumElements() / 2) &&
+  if ((int)IdxVal == (VecNumElts / 2) &&
       Vec.getValueSizeInBits() == (2 * SubVec.getValueSizeInBits()) &&
       (Vec.hasOneUse() || SubVec.hasOneUse())) {
     auto *VecLd = dyn_cast<LoadSDNode>(Vec);