[clang] [llvm] [SelectionDAG] Fix assertion failure on inline asm register type mismatch (PR #166615)

[Ahmed Nour via llvm-commits]

ahmednoursphinx wrote:

> This is not what I expected. We should do the check as early as in the front end. I assume we just need to add back
> 
> ```
>   bool IsMMXCons = llvm::StringSwitch<bool>(Constraint)
>                      .Cases("y", "&y", "^Ym", true)
>                      .Default(false);
>   if (IsMMXCons && Ty->isVectorTy()) {
>     if (cast<llvm::VectorType>(Ty)->getPrimitiveSizeInBits().getFixedValue() !=
>         64) {
>       // Invalid MMX constraint
>       return nullptr;
>     }
>   }
> ```
> 
> in X86AdjustInlineAsmType which was removed in [e59a619](https://github.com/llvm/llvm-project/commit/e59a619acf0b829f34a1c63aab0ad829ca0defc9)

Thanks @phoebewang  i have reverted the frontend check , please check when you have time

https://github.com/llvm/llvm-project/pull/166615