aboutsummaryrefslogtreecommitdiffstats
path: root/lib/compiler/src/beam_clean.erl
blob: 72996544760cf981d315fc46f0ec05d0ae8c5a50 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
%%
%% %CopyrightBegin%
%% 
%% Copyright Ericsson AB 2000-2018. All Rights Reserved.
%% 
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%%     http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%% 
%% %CopyrightEnd%
%%
%% Purpose : Clean up, such as removing unused labels and unused functions.

-module(beam_clean).

-export([module/2]).
-export([clean_labels/1]).

-spec module(beam_utils:module_code(), [compile:option()]) ->
                    {'ok',beam_utils:module_code()}.

module({Mod,Exp,Attr,Fs0,_}, Opts) ->
    Order = [Lbl || {function,_,_,Lbl,_} <- Fs0],
    All = maps:from_list([{Lbl,Func} || {function,_,_,Lbl,_}=Func <- Fs0]),
    WorkList = rootset(Fs0, Exp, Attr),
    Used = find_all_used(WorkList, All, cerl_sets:from_list(WorkList)),
    Fs1 = remove_unused(Order, Used, All),
    {Fs2,Lc} = clean_labels(Fs1),
    Fs = maybe_remove_lines(Fs2, Opts),
    {ok,{Mod,Exp,Attr,Fs,Lc}}.

%% Determine the rootset, i.e. exported functions and
%% the on_load function (if any).

rootset(Fs, Root0, Attr) ->
    Root1 = case proplists:get_value(on_load, Attr) of
		undefined -> Root0;
		[OnLoad] -> [OnLoad|Root0]
	   end,
    Root = sofs:set(Root1, [function]),
    Map0 = [{{Name,Arity},Lbl} || {function,Name,Arity,Lbl,_} <- Fs],
    Map = sofs:relation(Map0, [{function,label}]),
    sofs:to_external(sofs:image(Map, Root)).

%% Remove the unused functions.

remove_unused([F|Fs], Used, All) ->
    case cerl_sets:is_element(F, Used) of
	false -> remove_unused(Fs, Used, All);
	true -> [map_get(F, All)|remove_unused(Fs, Used, All)]
    end;
remove_unused([], _, _) -> [].

%% Find all used functions.

find_all_used([F|Fs0], All, Used0) ->
    {function,_,_,_,Code} = map_get(F, All),
    {Fs,Used} = update_work_list(Code, {Fs0,Used0}),
    find_all_used(Fs, All, Used);
find_all_used([], _All, Used) -> Used.

update_work_list([{call,_,{f,L}}|Is], Sets) ->
    update_work_list(Is, add_to_work_list(L, Sets));
update_work_list([{make_fun2,{f,L},_,_,_}|Is], Sets) ->
    update_work_list(Is, add_to_work_list(L, Sets));
update_work_list([_|Is], Sets) ->
    update_work_list(Is, Sets);
update_work_list([], Sets) -> Sets.

add_to_work_list(F, {Fs,Used}=Sets) ->
    case cerl_sets:is_element(F, Used) of
	true -> Sets;
	false -> {[F|Fs],cerl_sets:add_element(F, Used)}
    end.


%%%
%%% Coalesce adjacent labels. Renumber all labels to eliminate gaps.
%%% This cleanup will slightly reduce file size and slightly speed up
%%% loading.
%%%

-type label() :: beam_asm:label().

-record(st, {lmap :: [{label(),label()}], %Translation tables for labels.
	     entry :: beam_asm:label(),   %Number of entry label.
	     lc :: non_neg_integer()      %Label counter
	     }).

-spec clean_labels([beam_utils:instruction()]) ->
                          {[beam_utils:instruction()],pos_integer()}.

clean_labels(Fs0) ->
    St0 = #st{lmap=[],entry=1,lc=1},
    {Fs1,#st{lmap=Lmap0,lc=Lc}} = function_renumber(Fs0, St0, []),
    Lmap = maps:from_list(Lmap0),
    Fs = function_replace(Fs1, Lmap, []),
    {Fs,Lc}.

function_renumber([{function,Name,Arity,_Entry,Asm0}|Fs], St0, Acc) ->
    {Asm,St} = renumber_labels(Asm0, [], St0),
    function_renumber(Fs, St, [{function,Name,Arity,St#st.entry,Asm}|Acc]);
function_renumber([], St, Acc) -> {Acc,St}.

renumber_labels([{label,Old}|Is], [{label,New}|_]=Acc, #st{lmap=D0}=St) ->
    D = [{Old,New}|D0],
    renumber_labels(Is, Acc, St#st{lmap=D});
renumber_labels([{label,Old}|Is], Acc, St0) ->
    New = St0#st.lc,
    D = [{Old,New}|St0#st.lmap],
    renumber_labels(Is, [{label,New}|Acc], St0#st{lmap=D,lc=New+1});
renumber_labels([{func_info,_,_,_}=Fi|Is], Acc, St0) ->
    renumber_labels(Is, [Fi|Acc], St0#st{entry=St0#st.lc});
renumber_labels([I|Is], Acc, St0) ->
    renumber_labels(Is, [I|Acc], St0);
renumber_labels([], Acc, St) -> {Acc,St}.

function_replace([{function,Name,Arity,Entry,Asm0}|Fs], Dict, Acc) ->
    Asm = try
              Fb = fun(Old) -> throw({error,{undefined_label,Old}}) end,
              beam_utils:replace_labels(Asm0, [], Dict, Fb)
	  catch
	      throw:{error,{undefined_label,Lbl}=Reason} ->
		  io:format("Function ~s/~w refers to undefined label ~w\n",
			    [Name,Arity,Lbl]),
		  exit(Reason)
	  end,
    function_replace(Fs, Dict, [{function,Name,Arity,Entry,Asm}|Acc]);
function_replace([], _, Acc) -> Acc.

%%%
%%% Remove line instructions if requested.
%%%

maybe_remove_lines(Fs, Opts) ->
    case proplists:get_bool(no_line_info, Opts) of
	false -> Fs;
	true -> remove_lines(Fs)
    end.

remove_lines([{function,N,A,Lbl,Is0}|T]) ->
    Is = remove_lines_fun(Is0),
    [{function,N,A,Lbl,Is}|remove_lines(T)];
remove_lines([]) -> [].

remove_lines_fun([{line,_}|Is]) ->
    remove_lines_fun(Is);
remove_lines_fun([{block,Bl0}|Is]) ->
    Bl = remove_lines_block(Bl0),
    [{block,Bl}|remove_lines_fun(Is)];
remove_lines_fun([I|Is]) ->
    [I|remove_lines_fun(Is)];
remove_lines_fun([]) -> [].

remove_lines_block([{set,_,_,{line,_}}|Is]) ->
    remove_lines_block(Is);
remove_lines_block([I|Is]) ->
    [I|remove_lines_block(Is)];
remove_lines_block([]) -> [].