Thread: Is there a way to ask for a register and GUARANTY that I'll get it?

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".

Originally Posted by Salem

Also, just excluding a register in your compiled code says nothing about whether any libraries you link with, which would be free to use that same register.

........! I didn't thought about that! Then I'm back into learning Assembly and Machine language (and ELF of course). Tbh, after I posted this, I found some articles and a great repo on Github that helped my understand the program header and the segments and I'm able to move on. Thanks a lot however! It seems to me that I have decided that I want to do it this way and I thought bad about giving up and trying something else. So yeah, thanks for your time!