Actually, why don't you try to use just the normal tcc function parser?
It knows how to type-check arguments, it knows how to assign the correct
return type, it knows how to call functions according to ABI conventions
on Linux and Windows as well, and it knows how to pass small structs in
registers.
Can this be apted to case where we dynamically determine the type of the function to be called, and when the same function can be called with actually different (though binary compatible) arguments? I haven't find the code which fits my needs; if there's one, I'm OK with adopting it.
All what you're trying to reinvent, for what reason?
Please share a concrete example where tcc parses a generic function, like it has to be done with atomics.