;;; scratch.s -- ideas for how code generation will work | |
;; (defun lisp-function (A B) | |
;; (let ((local-var (whatever))) | |
;; (whatever local-var (something-else 4)))) | |
;; | |
;; This means the stack looks like this: | |
;; B_value | |
;; B_tag | |
;; A_value | |
;; A_tag | |
;; result pointer | |
;; return pointer <---- esp | |
lisp_function: | |
push ebp ; Now ebp can be used as an offset | |
mov ebp, esp | |
sub esp, 16 ; 1 var, 1 temporary | |
;; Now, call `whatever' with no arguments | |
;; For now we will do no register allocation, so don't even | |
;; bother saving anything. | |
lea eax, [ebp - 8] | |
push eax ; Return address | |
call whatever | |
;; Now we need to evaluate (something-else 4) and store it in a | |
;; temporary variable. | |
;; First set up the literal 4 | |
push 4 ; The value | |
push 0x20000000 ; Type tag and length | |
;; Then set up the return address | |
lea eax, [ebp - 16] | |
push eax | |
call something_else ; Result stored in temporary | |
;; Next function: `whatever' | |
push [ebp - 12] ; The temporary | |
push [ebp - 16] | |
push [ebp - 8] ; The variable | |
push [ebp - 4] | |
push [ebp + 4] ; The function's return address | |
call whatever | |
ret |