type reg = V0
type label = string
type instr = Li of reg * int
type directive = Asciiz of string
type decl = label * directive

type asm =
  { text : instr list
  ; data : decl list
  }

let ps = Printf.sprintf (* alias raccourci *)

let fmt_reg = function
  | V0 -> "$v0"
;;

let fmt_instr = function
  | Li (r, i) -> ps "  li %s, %d" (fmt_reg r) i
;;

let fmt_dir = function
  | Asciiz s -> ps ".asciiz \"%s\"" s
;;

let emit oc asm =
  Printf.fprintf oc ".text\n.globl main\nmain:\n";
  List.iter (fun i -> Printf.fprintf oc "%s\n" (fmt_instr i)) asm.text;
  Printf.fprintf oc "  move $a0, $v0\n  li $v0, 1\n  syscall\n  jr $ra\n";
  Printf.fprintf oc "\n.data\n";
  List.iter (fun (l, d) -> Printf.fprintf oc "%s: %s\n" l (fmt_dir d)) asm.data
;;