[SelectionDAG] ISD::XOR has the same non-zero detection as ISD::SUB

If X - Y != 0, then X ^ Y != 0

Author: AZero13

llvm/lib/CodeGen/SelectionDAG/SelectionDAG.cpp

@@ -6016,6 +6016,9 @@ bool SelectionDAG::isKnownNeverZero(SDValue Op, unsigned Depth) const {
         return true;
     // TODO: There are a lot more cases we can prove for add.
     break;
+
+  // If X - Y != 0, then X ^ Y != 0
+  case ISD::XOR:
   case ISD::SUB: {
     if (isNullConstant(Op.getOperand(0)))
       return isKnownNeverZero(Op.getOperand(1), Depth + 1);