I'm interesting in founding a way (if any) to guaranty that I'll ask for a specific register and that I'll get it. I want the compiler to ignore this register and not use it for the rest of the program (or scope). I know about the "register" keyword but from what I heard, it does "hint" the compiler but doesn't for it to give you a register. I want something that will guarentty that I'll get a specific register and that I'll be able to safely using it (where "safely" means that the compiler will not modify its value).
For anyone that will ask why to do that. I know that the compiler already does the best job using registers but I want to use TCC (which doesn't) as a backend for my code generation and write inline assembly instead of output assembly and then using "GAS" and "LD" to link. And why I want to do that? Well because TCC compiles 2-3 times faster than the time needed for "GAS" + "LD".