compiler/src/lib/tiger/tiger_mips_frame.ml

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