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

[via llvm-commits]

gonzalobg wrote:

>  For each of these suggestions, if the user used, for instance, GCC, which does not support this backend feature in its AMDGPU backend, would your suggested directive be ignored, or would the user encounter a compiler error?

I'd expect the C++ attributes to warn and be ignored by GCC unless `-Werror`, and the asm clobber/operand options to error, until GCC adds support for these features. I'd also expect SW that wants to be portable to both compilers to use macros to detect the compiler and only use features supported on each compiler.

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