/tryocaml/js_of_ocaml-patched/compiler/pure_fun.ml

 1(* Js_of_ocaml compiler
 2 * http://www.ocsigen.org/js_of_ocaml/
 3 * Copyright (C) 2010 Jérôme Vouillon
 4 * Laboratoire PPS - CNRS Université Paris Diderot
 5 *
 6 * This program is free software; you can redistribute it and/or modify
 7 * it under the terms of the GNU Lesser General Public License as published by
 8 * the Free Software Foundation, with linking exception;
 9 * either version 2.1 of the License, or (at your option) any later version.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14 * GNU Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
19 *)
20
21open Code
22
23(****)
24
25let pure_expr pure_funs e =
26  match e with
27    Const _  | Block _ | Field _ | Closure _ | Constant _ ->
28      true
29  | Apply (f, l, n) ->
30      begin match n with
31        Some n -> let m = List.length l in
32                  m < n || (m = n && VarSet.mem f pure_funs)
33      | None   -> false
34      end
35  | Prim (p, l) ->
36      match p with
37        Extern f -> Primitive.is_pure f
38      | _        -> true
39
40let pure_instr pure_funs i =
41  match i with
42    Let (_, e) ->
43      pure_expr pure_funs e
44  | Set_field _ | Offset_ref _ | Array_set _ ->
45      false
46
47(****)
48
49let rec traverse blocks pc visited funs =
50  try
51    (AddrMap.find pc visited, visited, funs)
52  with Not_found ->
53    let visited = AddrMap.add pc false visited in
54    let (pure, visited, funs) =
55      fold_children blocks pc
56        (fun pc (pure, visited, funs) ->
57           let (pure', visited, funs) = traverse blocks pc visited funs in
58           (pure && pure', visited, funs))
59        (true, visited, funs)
60    in
61    let (pure, visited, funs) = block blocks pc pure visited funs in
62    (pure, AddrMap.add pc pure visited, funs)
63
64and block blocks pc pure visited funs =
65  let b = AddrMap.find pc blocks in
66  let pure = match b.branch with Raise _ -> false | _ -> pure in
67  List.fold_left
68    (fun (pure, visited, funs) i ->
69       let (visited, funs) =
70         match i with
71           Let (x, Closure (_, (pc, _))) ->
72             let (pure, visited, funs) = traverse blocks pc visited funs in
73             (visited, if pure then VarSet.add x funs else funs)
74         | _ ->
75             (visited, funs)
76       in
77       (pure && pure_instr funs i, visited, funs))
78    (pure, visited, funs) b.body
79
80let f (pc, blocks, _) =
81  let (_, _, funs) = traverse blocks pc AddrMap.empty VarSet.empty in
82  funs