cheat sheet of c calling conventions

cdecl-cheatsheet.s

; Only need to save reg if we use them after

; caller rules:
; 1. save caller-saved reg r10, r11
;    /!\ all param reg
; 2. pass param with regs rdi, rsi, rdx, rcx, r8, r9
;    if there is more pass them onto the stack in reverse order
; 3. use call
; 4. restore stack state by removing passed on the stack param
; 5. return value of callee in rax
; 6. restore the caller-saved register and saved passed params
; We can assume that no other register has been altered.


; callee rules:
; 1. allocate local variables by sub sum of sizes of thoses var to rsp
;    the stack grows downward so we will access those local by adding to rsp.
; 2. push callee-saved reg onto the stack: rbx, rbp, r12, r13, r14, r15.
;
; >>> function body <<<
;
; 3. place return value in rax
; 4. restore callee-saved registers
; 5. remove local var, add to the stack the previoulsy subtracted amount.
; 6. use ret