(* Pasted from Pottier's PP compiler *)

(* This module offers functions that count how many times each
   pseudo-register is used within a piece of [ERTL] code. This
   is used in [Coloring] to drive the spilling heuristics. *)

open ERTL

let lookup uses r =
  try
    Register.Map.find r uses
  with Not_found ->
    0

let count r uses = Register.Map.add r (lookup uses r + 1) uses

let examine_statement _ stmt uses =
  match stmt with
  | St_skip _
  | St_comment _
  | St_cost _
  | St_hdw_to_hdw _
  | St_newframe _
  | St_delframe _
  | St_clear_carry _
  | St_set_carry _
  | St_call_id _
  | St_return _ ->
    uses
  | St_get_hdw (r, _, _)
  | St_set_hdw (_, r, _)
  | St_framesize (r, _)
  | St_pop (r, _)
  | St_push (r, _)
  | St_int (r, _, _)
  | St_addrH (r, _, _)
  | St_addrL (r, _, _)
  | St_cond (r, _, _) ->
    count r uses
  | St_move (r1, r2, _)
  | St_op1 (_, r1, r2, _)
  | St_call_ptr (r1, r2, _, _) ->
    count r1 (count r2 uses)
  | St_opaccsA (_, r1, r2, r3, _)
  | St_opaccsB (_, r1, r2, r3, _)
  | St_op2 (_, r1, r2, r3, _)
  | St_load (r1, r2, r3, _)
  | St_store (r1, r2, r3, _) ->
    count r1 (count r2 (count r3 uses))

let examine_internal int_fun =
  let uses =
    Label.Map.fold examine_statement int_fun.f_graph Register.Map.empty
  in
  lookup uses