[RISCV] Use getNegative instead of subtracting from zero. NFC (#162313)

Author: svs-quic

llvm/lib/Target/RISCV/RISCVISelLowering.cpp

@@ -15721,8 +15721,7 @@ static SDValue combineAddOfBooleanXor(SDNode *N, SelectionDAG &DAG) {
     return SDValue();
 
   // Emit a negate of the setcc.
-  return DAG.getNode(ISD::SUB, DL, VT, DAG.getConstant(0, DL, VT),
-                     N0.getOperand(0));
+  return DAG.getNegative(N0.getOperand(0), DL, VT);
 }
 
 static SDValue performADDCombine(SDNode *N,
@@ -16974,7 +16973,7 @@ performSIGN_EXTEND_INREGCombine(SDNode *N, TargetLowering::DAGCombinerInfo &DCI,
 
   // Fold (sext_inreg (setcc), i1) -> (sub 0, (setcc))
   if (Opc == ISD::SETCC && SrcVT == MVT::i1 && DCI.isAfterLegalizeDAG())
-    return DAG.getNode(ISD::SUB, DL, VT, DAG.getConstant(0, DL, VT), Src);
+    return DAG.getNegative(Src, DL, VT);
 
   // Fold (sext_inreg (xor (setcc), -1), i1) -> (add (setcc), -1)
   if (Opc == ISD::XOR && SrcVT == MVT::i1 &&