path: root/src/codegen.ml

open Mips
open Typing

exception Very_bad_error of string

(* Environnement pour accéder aux variables *)
type whereis_var =
  | VGlobal
  | VStack of int (* position relative à $fp *)
  | VStackByRef of int

type cg_env = {
  c_penv : env;
  c_names : whereis_var Smap.t;
  c_ret_lbl : string;
  c_ret_ref : bool;
  c_fp_used : int;
}

let globals_env = ref Smap.empty

let strings = Hashtbl.create 12 (* string -> label *)

(* Identifiants uniques pour les machins - essentiellement labels *)
let id =
  let last = ref 0 in
  fun prefix -> (last := !last + 1; prefix ^ (string_of_int !last))


(* Génération de code des machins *)

let cr a = if a then lw a0 areg (0, a0) else nop (* conditionnally read *)

(* Convention : doit garder $sp invariant *)
let rec gen_expr env e = match e.te_desc with
  | TEInt(k) -> li a0 k, false
  | TENull -> move a0 zero, false
  | TEThis -> (* convention : this is always the last-pushed argument *)
    la a0 areg (8, fp), false
  | TEIdent(i) ->
    begin match Smap.find i env.c_names with
    | VGlobal -> la a0 alab i, true
    | VStack(i) -> la a0 areg (i, fp), true
    | VStackByRef(i) -> lw a0 areg (i, fp), true
    end
  | TEAssign(e1, e2) ->
    let t1, ae1 = gen_expr env e1 in
    assert ae1;
    let t2, ae2 = gen_expr env e2 in
    t1 ++ push a0 ++ t2 ++ cr ae2 ++ pop a1 ++ sw a0 areg (0, a1), false
  | TECallFun(id, args, b) ->
    let code = List.fold_left
      (fun code (arg, byref) ->
        let c, r = gen_expr env arg in
        assert (r || not byref);
        c ++ cr (r && not byref) ++ push a0 ++ code) nop args in
    code ++ jal id ++ popn (4 * (List.length args)), b
  | TECallVirtual(obj, ti, fi, args, b) ->
    let code = List.fold_left
      (fun code (arg, byref) ->
        let c, r = gen_expr env arg in
        assert (r || not byref);
        c ++ cr (r && not byref) ++ push a0 ++ code) nop args in
    let code2, a = gen_expr env obj in
    assert a;
    code ++ code2 ++ push a0 ++ lw a0 areg (ti, a0) ++ lw a0 areg (fi, a0)
      ++ jalr a0 ++ popn (4 * (1 + List.length args)), b
  | TEUnary (x, e) ->
    let t, a = gen_expr env e in
    begin match x with
    | Ast.Deref -> t ++ cr a, true
    | Ast.Ref -> assert a; t, false
    | Ast.Plus -> t, a
    | Ast.Minus -> t ++ cr a ++ sub a0 zero oreg a0, false
    | Ast.Not -> t ++ cr a ++ not_ a0 a0, false
    | Ast.PreIncr -> assert a; t ++ lw a1 areg (0, a0) ++ add a1 a1 oi 1 ++ sw a1 areg (0, a0), true
    | Ast.PreDecr -> assert a; t ++ lw a1 areg (0, a0) ++ sub a1 a1 oi 1 ++ sw a1 areg (0, a0), true
    | Ast.PostIncr -> assert a; t ++ move a1 a0 ++ lw a2 areg(0, a1) ++ move a0 a2 ++
          add a2 a2 oi 1 ++ sw a2 areg(0, a1), false
    | Ast.PostDecr -> assert a; t ++ move a1 a0 ++ lw a2 areg(0, a1) ++ move a0 a2 ++
          sub a2 a2 oi 1 ++ sw a2 areg(0, a1), false
    end
  | TEBinary(e1, op, e2) ->
    let t1, ae1 = gen_expr env e1 in
    let t2, ae2 = gen_expr env e2 in
    let t1 = t1 ++ cr ae1 in
    let t2 = t2 ++ cr ae2 in
    (
      match op with
      | Ast.Add -> t1 ++ push a0 ++ t2 ++ pop a1 ++ add a0 a1 oreg a0
      | Ast.Sub -> t1 ++ push a0 ++ t2 ++ pop a1 ++ sub a0 a1 oreg a0
      | Ast.Mul -> t1 ++ push a0 ++ t2 ++ pop a1 ++ mul a0 a1 oreg a0
      | Ast.Div -> t1 ++ push a0 ++ t2 ++ pop a1 ++ div a0 a1 oreg a0
      | Ast.Modulo -> t1 ++ push a0 ++ t2 ++ pop a1 ++ rem a0 a1 oreg a0
      | Ast.Equal -> t1 ++ push a0 ++ t2 ++ pop a1 ++ seq a0 a1 a0
      | Ast.NotEqual -> t1 ++ push a0 ++ t2 ++ pop a1 ++ sne a0 a1 a0
      | Ast.Lt -> t1 ++ push a0 ++ t2 ++ pop a1 ++ slt a0 a1 a0
      | Ast.Le -> t1 ++ push a0 ++ t2 ++ pop a1 ++ sle a0 a1 a0
      | Ast.Gt -> t1 ++ push a0 ++ t2 ++ pop a1 ++ sgt a0 a1 a0
      | Ast.Ge -> t1 ++ push a0 ++ t2 ++ pop a1 ++ sge a0 a1 a0
      | Ast.Land -> 
        let lazy_lbl = id "_lazy" in
        t1 ++ beqz a0 lazy_lbl ++ t2 ++ label lazy_lbl 
      | Ast.Lor -> 
        let lazy_lbl = id "_lazy" in
        t1 ++ bnez a0 lazy_lbl ++ t2 ++ label lazy_lbl
    ), false
  | TEMember(e, i) ->
    let c, a = gen_expr env e in
    if i <> 0 then begin
      assert a;
      c ++ la a0 areg (i, a0), true
    end else
      c, a
  | TENew(cls, constr, args) ->
    let alloc = 
      li v0 9 ++ li a0 cls.tc_size ++ syscall in
    begin match constr with
    | None -> alloc ++ (jal ("_c_" ^ cls.tc_name)), false
    | Some x ->
      let args_code = List.fold_left
        (fun code (arg, byref) ->
          let c, r = gen_expr env arg in
          assert (r || not byref);
          c ++ cr (r && not byref) ++ push a0 ++ code) nop args in
      let c = args_code ++ alloc ++ push v0 ++ jal x in
      c ++ pop a0 ++ popn (4 * List.length args), false
    end
    

let rec gen_stmt env = function
  | TSEmpty -> nop, nop, env
  | TSExpr(e) ->
    comment "expr" ++ (fst (gen_expr env e)), nop, env
  | TSIf(cond, s1, s2) ->
    let c, a = gen_expr env cond in
    let l_else = id "_cond" in
    let l_end = id "_cond" in
    let c_then, d_then, _ = gen_stmt env s1 in
    let c_else, d_else, _ = gen_stmt env s2 in
    comment "if" ++ c ++ cr a ++ beqz a0 l_else ++ c_then ++ b l_end ++
      label l_else ++ c_else ++ label l_end, d_then ++ d_else, env
  | TSWhile(cond, body) ->
    let c, a = gen_expr env cond in
    let l_begin = id "_while_begin" in
    let l_cond = id "_while_cond" in
    let c_body, d_body, _ = gen_stmt env body in
    comment "while" ++ b l_cond ++ label l_begin ++ c_body ++
      label l_cond ++ c ++ cr a ++ bnez a0 l_begin, d_body, env
  | TSFor(before, cond, after, body) ->
    let l_begin = id "_for_begin" in
    let l_cond = id "_for_cond" in
    let c_before = List.fold_left
      (fun code expr -> let c, _ = gen_expr env expr in code ++ c) nop before in
    let c_after = List.fold_left
      (fun code expr -> let c, _ = gen_expr env expr in code ++ c) nop after in
    let c_cond = match cond with
      | None -> b l_begin
      | Some x -> let c, a = gen_expr env x in
        c ++ cr a ++ bnez a0 l_begin in
    let c_body, d_body, _ = gen_stmt env body in
    comment "for" ++ c_before ++ b l_cond ++ label l_begin ++ c_body ++ c_after ++ label l_cond
      ++ c_cond, d_body, env
  | TSBlock(b) ->
    let c, d = gen_block env b in
    comment "block" ++ c, d, env
  | TSReturn (None) ->
    comment "return" ++ b env.c_ret_lbl, nop, env
  | TSReturn (Some e) ->
    let c, a = gen_expr env e in
    assert (a || not env.c_ret_ref);
    comment "return" ++ c ++ cr (not env.c_ret_ref && a) ++ b env.c_ret_lbl, nop, env
  | TSDeclare (ty, id) ->
    let s = type_size env.c_penv ty in
    let new_fp_used = env.c_fp_used + s in
    let pos = - new_fp_used in
    let code = match ty with
    | TClass(i) ->
      sub sp sp oi s ++
      la v0 areg (pos, fp) ++
      jal ("_c_" ^ i)
    | _ -> push zero
    in
    comment ("declare " ^ id) ++ code, nop, {
      c_penv = env.c_penv;
      c_names = Smap.add id (VStack pos) env.c_names;
      c_ret_lbl = env.c_ret_lbl;
      c_ret_ref = env.c_ret_ref;
      c_fp_used = new_fp_used }
  | TSDeclareAssignConstructor(cls, id, constr, args) ->
    let new_fp_used = env.c_fp_used + cls.tc_size in
    let pos = - new_fp_used in
    let code = match constr with
    | None -> sub sp sp oi cls.tc_size ++ move v0 sp ++ (jal ("_c_" ^ cls.tc_name))
    | Some x ->
      let args_code = List.fold_left
        (fun code (arg, byref) ->
          let c, r = gen_expr env arg in
          assert (r || not byref);
          c ++ cr (r && not byref) ++ push a0 ++ code) nop args in
      sub sp sp oi cls.tc_size ++ args_code ++ la a0 areg(pos, fp) ++ push a0 ++ jal x ++
          popn (4 * (List.length args + 1))
    in
    comment ("declare " ^ id) ++ code, nop, {
      c_penv = env.c_penv;
      c_names = Smap.add id (VStack pos) env.c_names;
      c_ret_lbl = env.c_ret_lbl;
      c_ret_ref = env.c_ret_ref;
      c_fp_used = new_fp_used; }
  | TSDeclareAssignExpr ((ty, r), id, e) ->
    let s = if r then 4 else type_size env.c_penv ty in
    assert (s = 4);
    let new_fp_used = env.c_fp_used + 4 in
    let pos = - new_fp_used in
    let code, a = gen_expr env e in
    assert (a || not r);
    comment ("declare " ^ id) ++ code ++ cr (a && not r) ++ push a0, nop, {
      c_penv = env.c_penv;
      c_names = Smap.add id (if r then VStackByRef pos else VStack pos) env.c_names;
      c_ret_lbl = env.c_ret_lbl;
      c_ret_ref = env.c_ret_ref;
      c_fp_used = new_fp_used }
  | TSWriteCout(sl) ->
    let text1, data1 = List.fold_left
      (fun (text, data) s ->
        match s with
        | TSEExpr(e) ->
          let t, a = gen_expr env e in
          text ++ t ++ cr a ++  li v0 1 ++ syscall, data
        | TSEStr(s) ->
          let l, d =
            if Hashtbl.mem strings s then
              Hashtbl.find strings s, nop
            else
              let l = id "_s" in Hashtbl.add strings s l;
              l, label l ++ asciiz s
          in
            text ++ la a0 alab l ++ li v0 4 ++ syscall, data ++ d) (nop, nop) sl in
    comment "cout<<..." ++ text1, data1, env
and gen_block env b =
  let text, data, fin_env =
    List.fold_left (fun (t, d, e) s ->
        let tt, dd, e = gen_stmt e s in
          t ++ tt, d ++ dd, e)
      (nop, nop, env) b
  in
    let n = (fin_env.c_fp_used - env.c_fp_used) in
    text ++ (if n = 0 then nop else popn n), data

let gen_decl tenv decl = match decl with
  | TDGlobal(ty, id) ->
    globals_env := Smap.add id VGlobal !globals_env;
    let bytes = type_size tenv ty in
    nop, (label id) ++ (dword (let rec a n = if n > 0 then 0::(a (n-4)) else [] in a bytes))
  | TDFunction(proto, block) ->
    let names, _ = List.fold_left 
            (fun (env, p) ((ty, r), id) -> 
              Smap.add id (if r then VStackByRef p else VStack p) env, p + (type_size tenv ty)) 
            (!globals_env, (match proto.tp_class with | None -> 8 | Some k -> 12)) proto.tp_args in
    let env = {
      c_penv = tenv;
      c_names = names;
      c_ret_lbl = id "_ret";
      c_ret_ref = (match proto.tp_ret_type with | None -> false | Some(_, r) -> r);
      c_fp_used = 0;
      } in
    let code_for_constructor = match proto.tp_ret_type with
      | Some _ -> nop
      | None -> let cls_name = (match proto.tp_class with | Some k -> k | None -> assert false) in
        la v0 areg (8, fp) ++ jal ("_c_" ^ cls_name)
    in
    let text, data = gen_block env block in 
    label proto.tp_unique_ident ++
    push fp ++ push ra ++ move fp sp ++ code_for_constructor ++
    text ++ label env.c_ret_lbl ++
    move sp fp ++ pop ra ++ pop fp ++ jr ra,
    data
  | TDClass(c) ->
    (* Build vtables and build constructor *)
    let rec mk_cls_code hh =
      let vtable_size = List.fold_left (fun k (p, _) -> max k (p+4)) 0 hh.h_vtable in
      let vtable_as_array = Array.make (vtable_size / 4) "_nothing" in
      List.iter (fun (p, s) -> vtable_as_array.(p/4) <- s.tp_unique_ident) hh.h_vtable;
      let vt_l = Array.to_list vtable_as_array in
      let vtable = label ("_vt_" ^ c.tc_name ^ "_as_" ^ hh.h_class) ++
        (if vt_l = [] then nop else address vt_l) in
      let constructor_code = la a0 alab ("_vt_" ^ c.tc_name ^ "_as_" ^ hh.h_class)
            ++ sw a0 areg (hh.h_pos, v0) in
      let c = get_c tenv hh.h_class in
      let init_code = Smap.fold
        (fun _ (ty, pos) code ->
          (match ty with
            | TClass(s) ->
              push ra ++ push v0 ++
                la v0 areg (pos + hh.h_pos, v0) ++
                jal ("_c_" ^ s) ++ pop v0 ++ pop ra
            | _ -> sw zero areg (pos + hh.h_pos, v0)
          ) ++ code) c.tc_members nop in
      List.fold_left
          (fun (vt, cc) sup ->
            let mvt, mcc = mk_cls_code sup in
            vt ++ mvt, cc ++ mcc)
          (vtable, constructor_code ++ init_code) hh.h_supers
    in
      let vt, cc = mk_cls_code c.tc_hier in
      label ("_c_" ^ c.tc_name) ++ cc ++ jr ra, vt


let generate p =
  try 
    let text, data = List.fold_left (fun (text, data) decl ->
        let more_text, more_data = gen_decl p.prog_env decl in
        text ++ more_text, data ++ more_data) (nop, nop) p.prog_decls in
    let text =
      label "main" ++ jal p.prog_main ++
      li v0 10 ++ syscall ++
      label "_nothing" ++ jr ra ++
      text in
    { text = text;
      data = data }
  with
  | Assert_failure (k, a, b) -> raise (Very_bad_error (
        "(unexpected) Assertion failure: "^k^" at "^(string_of_int a)^":"^(string_of_int b)))
  | Not_found -> raise (Very_bad_error ("(unexpected) Not found"))
  | Invalid_argument(k) -> raise (Very_bad_error ("(unexpected) Invalid argument: "^k))
  | Match_failure(k, a, b) -> raise (Very_bad_error (
      "(unexpected) Match failure: "^k^" at "^(string_of_int a)^":"^(string_of_int b)))
  | Stack_overflow -> raise (Very_bad_error ("(unexpected) Stack overflow"))
  | _ -> raise (Very_bad_error ("(unexpected) Other error"))