[llvm] [AArch64] Add @llvm.experimental.vector.match (PR #101974)

[Paul Walker via llvm-commits]

================
@@ -8156,6 +8156,37 @@ void SelectionDAGBuilder::visitIntrinsicCall(const CallInst &I,
              DAG.getNode(ISD::EXTRACT_SUBVECTOR, sdl, ResultVT, Vec, Index));
     return;
   }
+  case Intrinsic::experimental_vector_match: {
+    SDValue Op1 = getValue(I.getOperand(0));
+    SDValue Op2 = getValue(I.getOperand(1));
+    SDValue Mask = getValue(I.getOperand(2));
+    EVT Op1VT = Op1.getValueType();
+    EVT Op2VT = Op2.getValueType();
+    EVT ResVT = Mask.getValueType();
+    unsigned SearchSize = Op2VT.getVectorNumElements();
+
+    // If the target has native support for this vector match operation, lower
+    // the intrinsic directly; otherwise, lower it below.
+    if (!TLI.shouldExpandVectorMatch(Op1VT, SearchSize)) {
+      visitTargetIntrinsic(I, Intrinsic);
+      return;
+    }
+
+    SDValue Ret = DAG.getNode(ISD::SPLAT_VECTOR, sdl, ResVT,
+                              DAG.getConstant(0, sdl, MVT::i1));
----------------
paulwalker-arm wrote:

```suggestion
    SDValue Ret = DAG.getConstant(0, sdl, ResVT));
```

https://github.com/llvm/llvm-project/pull/101974