[llvm] [ARM][TableGen][MC] Change the ARM mnemonic operands to be optional for ASM parsing (PR #83436)

[Sergei Barannikov via llvm-commits]

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@@ -4052,6 +4073,66 @@ static MCRegister MatchRegisterName(StringRef Name);
 
 /// }
 
+static bool isDataTypeToken(StringRef Tok) {
+  return Tok == ".8" || Tok == ".16" || Tok == ".32" || Tok == ".64" ||
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s-barannikov wrote:

Could be something like:
```C++
  static const DenseSet<StringRef> DataTypes{".8", ...};
  return DataTypes.contains(Tok);
```


https://github.com/llvm/llvm-project/pull/83436