[AArch64] Use getNegative instead of manually sub with 0 (NFC)

Author: AZero13

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -7312,8 +7312,8 @@ SDValue AArch64TargetLowering::LowerABS(SDValue Op, SelectionDAG &DAG) const {
     return LowerToPredicatedOp(Op, DAG, AArch64ISD::ABS_MERGE_PASSTHRU);
 
   SDLoc DL(Op);
-  SDValue Neg = DAG.getNode(ISD::SUB, DL, VT, DAG.getConstant(0, DL, VT),
-                            Op.getOperand(0));
+  SDValue Neg = DAG.getNegative(Op.getOperand(0), DL, VT);
+
   // Generate SUBS & CSEL.
   SDValue Cmp = DAG.getNode(AArch64ISD::SUBS, DL, DAG.getVTList(VT, FlagsVT),
                             Op.getOperand(0), DAG.getConstant(0, DL, VT));