[LegalizeTypes][NFC] Use getConstantOperandAPInt instead of cast constant getAPInt

[Jimerlife]

Summary

Use getConstantOperandAPInt(Num) instead of cast<ConstantSDNode>(N->getOperand(Num))->getAPIntValue()

[RKSimon]

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

1558

const APInt &

5355

const APInt &

[RKSimon]

LGTM - cheers

llvm/lib/CodeGen/SelectionDAG/LegalizeIntegerTypes.cpp

 SDValue DAGTypeLegalizer::PromoteIntRes_UNDEF(SDNode *N) {
   return DAG.getUNDEF(TLI.getTypeToTransformTo(*DAG.getContext(),
                                                N->getValueType(0)));
 }
 
 SDValue DAGTypeLegalizer::PromoteIntRes_VSCALE(SDNode *N) {
   EVT VT = TLI.getTypeToTransformTo(*DAG.getContext(), N->getValueType(0));
 
-  APInt MulImm = cast<ConstantSDNode>(N->getOperand(0))->getAPIntValue();
+  const APInt &MulImm = N->getConstantOperandAPInt(0);
   return DAG.getVScale(SDLoc(N), VT, MulImm.sext(VT.getSizeInBits()));
 }
 
 SDValue DAGTypeLegalizer::PromoteIntRes_VAARG(SDNode *N) {
   SDValue Chain = N->getOperand(0); // Get the chain.
   SDValue Ptr = N->getOperand(1); // Get the pointer.
   EVT VT = N->getValueType(0);
   SDLoc dl(N);

 }
 
 SDValue DAGTypeLegalizer::PromoteIntRes_STEP_VECTOR(SDNode *N) {
   SDLoc dl(N);
   EVT OutVT = N->getValueType(0);
   EVT NOutVT = TLI.getTypeToTransformTo(*DAG.getContext(), OutVT);
   assert(NOutVT.isScalableVector() &&
          "Type must be promoted to a scalable vector type");
-  APInt StepVal = cast<ConstantSDNode>(N->getOperand(0))->getAPIntValue();
+  const APInt &StepVal = N->getConstantOperandAPInt(0);
   return DAG.getStepVector(dl, NOutVT,
                            StepVal.sext(NOutVT.getScalarSizeInBits()));
 }
 
 SDValue DAGTypeLegalizer::PromoteIntRes_CONCAT_VECTORS(SDNode *N) {
   SDLoc dl(N);
 
   EVT OutVT = N->getValueType(0);