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

[Ralf Jung via llvm-commits]

RalfJung wrote:

Changing the code to write a different value to the register is *not* in violation of the operand constraint. So no, your wording simply doesn't constrain the compiler enough. No information about what the inline asm block does must be used to optimize the surrounding code.

I have no idea what you mean by "operand constraints must be treated opaquely"; the entire point of those constraints is for the compiler to analyze them so they are not opaque. It's the actually asm template string that must be opaque.

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