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
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
|
/**
* mds — A micro-display server
* Copyright © 2014, 2015, 2016, 2017 Mattias Andrée (m@maandree.se)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "eliminate-dead-code.h"
#include "include-stack.h"
#include <stdlib.h>
#include <errno.h>
/**
* Tree type constant shortener
*/
#define C(TYPE) MDS_KBDC_TREE_TYPE_##TYPE
/**
* Add an error with “included from here”-notes to the error list
*
* @param NODE:const mds_kbdc_tree_t* The node the triggered the error
* @param PTR:size_t The number of “included from here”-notes
* @param SEVERITY:identifier * in `MDS_KBDC_PARSE_ERROR_*` to indicate severity
* @param ...:const char*, ... Error description format string and arguments
* @scope error:mds_kbdc_parse_error_t* Variable where the new error will be stored
*/
#define NEW_ERROR(NODE, PTR, SEVERITY, ...)\
NEW_ERROR_WITH_INCLUDES(NODE, PTR, SEVERITY, __VA_ARGS__)
/**
* Variable whether the latest created error is stored
*/
static mds_kbdc_parse_error_t *error;
/**
* The parameter of `eliminate_dead_code`
*/
static mds_kbdc_parsed_t *restrict result;
/**
* 2: Eliminating because of a return-statement
* 1: Eliminating because of a break- or continue-statement
* 0: Not eliminating
*/
static int elimination_level = 0;
/**
* Eliminate dead code in a subtree
*
* @param tree The tree to reduce
* @return Zero on success, -1 on error
*/
static int eliminate_subtree(mds_kbdc_tree_t *restrict tree);
/**
* Eliminate dead code in an include-statement
*
* @param tree The tree to reduce
* @return Zero on success, -1 on error
*/
static int
eliminate_include(mds_kbdc_tree_include_t *restrict tree)
{
void *data;
int r;
fail_if (mds_kbdc_include_stack_push(tree, &data));
r = eliminate_subtree(tree->inner);
mds_kbdc_include_stack_pop(data);
fail_if (r);
return 0;
fail:
return -1;
}
/**
* Eliminate dead code in an if-statement
*
* @param tree The tree to reduce
* @return Zero on success, -1 on error
*/
static int
eliminate_if(mds_kbdc_tree_if_t *restrict tree)
{
int elimination;
fail_if (eliminate_subtree(tree->inner));
elimination = elimination_level, elimination_level = 0;
fail_if (eliminate_subtree(tree->otherwise));
if (elimination > elimination_level)
elimination = elimination_level;
return 0;
fail:
return -1;
}
/**
* Eliminate dead code in a subtree
*
* @param tree The tree to reduce
* @return Zero on success, -1 on error
*/
static int
eliminate_subtree(mds_kbdc_tree_t *restrict tree)
{
#define e(type) fail_if (eliminate_##type(&tree->type))
#define E(type) fail_if (eliminate_##type(&tree->type##_))
again:
if (!tree)
return 0;
switch (tree->type) {
case C(INCLUDE):
e(include);
break;
case C(IF):
E(if);
break;
case C(INFORMATION):
case C(FUNCTION):
case C(MACRO):
case C(ASSUMPTION):
case C(FOR):
fail_if (eliminate_subtree(tree->information.inner));
if (tree->type == C(FUNCTION) || tree->type == C(MACRO))
elimination_level = 0;
else if (tree->type == C(FOR) && elimination_level == 1)
elimination_level = 0;
break;
case C(RETURN):
case C(BREAK):
case C(CONTINUE):
elimination_level = tree->type == C(RETURN) ? 2 : 1;
break;
default:
break;
}
if (tree->next && elimination_level) {
NEW_ERROR(tree->next, includes_ptr, WARNING, "statement is unreachable");
mds_kbdc_tree_free(tree->next), tree->next = NULL;
}
tree = tree->next;
goto again;
fail:
return -1;
#undef E
#undef e
}
/**
* Eliminate and warn about dead code
*
* @param result_ `result` from `validate_tree`, will be updated
* @return -1 if an error occursed that cannot be stored in `result`, zero otherwise
*/
int
eliminate_dead_code(mds_kbdc_parsed_t *restrict result_)
{
int r;
mds_kbdc_include_stack_begin(result = result_);
r = eliminate_subtree(result_->tree);
mds_kbdc_include_stack_end();
fail_if (r);
return 0;
fail:
return -1;
}
#undef NEW_ERROR
#undef C
|
