compiler/src/lib/tiger/tiger_mips_frame.ml

   1 module List = ListLabels
   2
   3 module Temp = Tiger_temp
   4 module T    = Tiger_tree
   5
   6 type access =
   7   | InFrame of {offset_from_frame_pointer : int}
   8   | InReg of {register : Temp.Temp.t}
   9
  10 type t =
  11 (* p.136 Frame.t is a data structure holding:
  12  * - the locations of all the formals
  13  * - instructions required to implement the "view shift"
  14  * - the number of locals allocated so far
  15  * - the `label` at which the function's machine code is to begin (see p.140)
  16  * *)
  17   { name         : Temp.Label.t
  18   ; formals      : access list
  19   ; locals_count : int
  20   ; instructions : unit  (* TODO: instructions for view shift *)
  21   }
  22
  23 let pointer = Temp.Temp.gen ()
  24
  25 let word_size_bits  = 32
  26 let word_size_bytes = word_size_bits / 8
  27 let word_size       = word_size_bytes
  28
  29 let name {name; _} =
  30   name
  31
  32 let formals {formals; _} =
  33   formals
  34
  35 let alloc offset_from_frame_pointer ~escapes =
  36   if escapes then
  37     InFrame {offset_from_frame_pointer}
  38   else
  39     InReg {register = Temp.Temp.gen ()}
  40
  41 let alloc_local _ ~escapes =
  42     (* FIXME: offset_from_frame_pointer. With neither mutation nor new frame? *)
  43     let offset_from_frame_pointer = 0 in
  44     alloc offset_from_frame_pointer ~escapes
  45
  46 let make ~name ~formals =
  47   (* p.136: For each formal parameter, "newFrame" must calculate two things:
  48    * - How the parameter will be seen from inside the function
  49    *   (in a register, or in a frame location);
  50    * - What instructions must be produced to implement the "view shift"
  51    * *)
  52   let formals, locals_count =
  53    (* TODO: What should offset increment be? Word? *)
  54     List.fold_left formals ~init:([], 0) ~f:(fun (formals, offset) escapes ->
  55       ((alloc offset ~escapes) :: formals, succ offset)
  56     )
  57   in
  58   { name
  59   ; formals
  60   ; locals_count
  61   ; instructions = ()  (* TODO: instructions for view shift *)
  62   }
  63
  64 (*failwith ("NOT IMPLEMENTED: " ^ __MODULE__ ^ ".exp")*)
  65
  66 let exp ~access ~pointer =
  67   match access with
  68   | InReg {register} ->
  69       T.TEMP register
  70   | InFrame {offset_from_frame_pointer} ->
  71       T.MEM (T.BINOP (T.PLUS, pointer, T.CONST offset_from_frame_pointer))