[llvm] [AArch64] Handle XAR with v1i64 operand types (PR #141754)

[Cullen Rhodes via llvm-commits]

================
@@ -4637,15 +4637,39 @@ bool AArch64DAGToDAGISel::trySelectXAR(SDNode *N) {
 
   if (!IsXOROperand) {
     SDValue Zero = CurDAG->getTargetConstant(0, DL, MVT::i64);
-    SDNode *MOV = CurDAG->getMachineNode(AArch64::MOVIv2d_ns, DL, VT, Zero);
+    SDNode *MOV =
+        CurDAG->getMachineNode(AArch64::MOVIv2d_ns, DL, MVT::v2i64, Zero);
     SDValue MOVIV = SDValue(MOV, 0);
     R1 = N1->getOperand(0);
     R2 = MOVIV;
   }
 
+  // If the input is a v1i64, widen to a v2i64 to use XAR.
+  assert((VT == MVT::v1i64 || VT == MVT::v2i64) && "Unexpected XAR type!");
+  if (VT == MVT::v1i64) {
+    EVT SVT = MVT::v2i64;
+    SDValue Undef =
+        SDValue(CurDAG->getMachineNode(AArch64::IMPLICIT_DEF, DL, SVT), 0);
+    SDValue DSub = CurDAG->getTargetConstant(AArch64::dsub, DL, MVT::i32);
+    R1 = SDValue(CurDAG->getMachineNode(AArch64::INSERT_SUBREG, DL, SVT, Undef,
+                                        R1, DSub),
+                 0);
+    if (R2.getValueType() == MVT::v1i64)
+      R2 = SDValue(CurDAG->getMachineNode(AArch64::INSERT_SUBREG, DL, SVT,
+                                          Undef, R2, DSub),
+                   0);
+  }
+
   SDValue Ops[] = {R1, R2, Imm};
-  CurDAG->SelectNodeTo(N, AArch64::XAR, N0.getValueType(), Ops);
+  SDNode *XAR =
+      CurDAG->getMachineNode(AArch64::XAR, DL, R1.getValueType(), Ops);
----------------
c-rhodes wrote:

nit: if it can only be this value type personally I'd find it clearer if it just used it to save me the uncertainty
```suggestion
      CurDAG->getMachineNode(AArch64::XAR, DL, MVT::v2i64, Ops);
```

https://github.com/llvm/llvm-project/pull/141754