[llvm] [AArch64] Add lowering for NEON saturating shift intrinsics (PR #171485)

[Kerry McLaughlin via llvm-commits]

================
@@ -4570,11 +4571,18 @@ static SDValue lowerIntNeonIntrinsic(SDValue Op, unsigned Opcode,
   auto bitcastToFloat = [&](SDValue Val) {
     return DAG.getBitcast(getFloatVT(Val.getValueType()), Val);
   };
+
+  const unsigned NumOps = Op.getNumOperands();
+  const unsigned LastOpIdx = NumOps - 1;
   SmallVector<SDValue, 2> NewOps;
-  NewOps.reserve(Op.getNumOperands() - 1);
+  NewOps.reserve(NumOps - 1);
----------------
kmclaughlin-arm wrote:

```suggestion
  NewOps.reserve(LastOpIdx);
```

https://github.com/llvm/llvm-project/pull/171485