[llvm] [llvm][AArch64][Assembly]: Add LUT assembly/disassembly. (PR #70802)

[via llvm-commits]

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@@ -4546,14 +4548,18 @@ ParseStatus AArch64AsmParser::tryParseZTOperand(OperandVector &Operands) {
     if (getParser().parseExpression(ImmVal))
       return ParseStatus::NoMatch;
     const MCConstantExpr *MCE = dyn_cast<MCConstantExpr>(ImmVal);
+    Operands.push_back(AArch64Operand::CreateImm(
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CarolineConcatto wrote:

Can you change the order between the tests and the Operand push
```
   if (!MCE)
      return TokError("immediate value expected for vector index");
    Operands.push_back(AArch64Operand::CreateImm( ...);
```
It makes more sense because we are using MCE->getValue() when getting the value, if MCE does not exists it will fail

https://github.com/llvm/llvm-project/pull/70802