[llvm] [LangRef] inline asm: the instructions are treated opaquely (PR #157080)

[via llvm-commits]

gonzalobg wrote:

> using just [standard C++11](https://en.cppreference.com/w/cpp/language/asm.html):

Or via a new backend-specific clobber:

```c++
asm ("instructions_like_normal" : : : "sgmask(...)" );
```

or backend-specific operand

```c++
asm (
  "instruction0;\n"   // doesn't get the property
  "instruction1 %0;" // gets the property
  : : "sgmask"(0) 
);
```

The rules of the clobber or operand then say what the effect of this new option is (e.g. it inserts a hint so that the assembler can do X).


https://github.com/llvm/llvm-project/pull/157080