1 /* Handling of fnspec attribute specifiers
2 Copyright (C) 2008-2023 Free Software Foundation, Inc.
3 Contributed by Richard Guenther <rguenther@suse.de>
4
5 This file is part of GCC.
6
7 GCC is free software; you can redistribute it and/or modify
8 under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
11
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
20
21 /* Parse string of attribute "fn spec". This is an internal attribute
22 describing side effects of a function as follows:
23
24 character 0 specifies properties of return values as follows:
25 '1'...'4' specifies number of argument function returns (as in memset)
26 'm' specifies that returned value is noalias (as in malloc)
27 '.' specifies that nothing is known.
28 character 1 specifies additional function properties
29 ' ' specifies that nothing is known
30 'p' or 'P' specifies that function is pure except for described side
31 effects.
32 'c' or 'C' specifies that function is const except for described side
33 effects.
34 The uppercase letter in addition specifies that function clobbers errno.
35
36 character 2+2i specifies properties of argument number i as follows:
37 'x' or 'X' specifies that parameter is unused.
38 'r' or 'R' specifies that the memory pointed to by the parameter is only
39 read and does not escape
40 'o' or 'O' specifies that the memory pointed to by the parameter is only
41 written and does not escape
42 'w' or 'W' specifies that the memory pointed to by the parameter does not
43 escape
44 '1'....'9' specifies that the memory pointed to by the parameter is
45 copied to memory pointed to by different parameter
46 (as in memcpy).
47 '.' specifies that nothing is known.
48 The uppercase letter in addition specifies that the memory pointed to
49 by the parameter is not dereferenced. For 'r' only read applies
50 transitively to pointers read from the pointed-to memory.
51
52 character 3+2i specifies additional properties of argument number i
53 as follows:
54 ' ' nothing is known
55 't' the size of value written/read corresponds to the size of
56 of the pointed-to type of the argument type
57 '1'...'9' specifies the size of value written/read is bound by the
58 specified argument
59 */
60
61 #ifndef ATTR_FNSPEC_H
62 #define ATTR_FNSPEC_H
63
64 class attr_fnspec
65 {
66 private:
67 /* fn spec attribute string. */
68 const char *str;
69 /* length of the fn spec string. */
70 const unsigned len;
71 /* Number of characters specifying return value. */
72 const unsigned int return_desc_size = 2;
73 /* Number of characters specifying size. */
74 const unsigned int arg_desc_size = 2;
75
76 /* Return start of specifier of arg i. */
77 unsigned int arg_idx (int i)
78 {
79 return return_desc_size + arg_desc_size * i;
80 }
81
82 public:
83 attr_fnspec (const char *str, unsigned len)
84 : str (str), len (len)
85 {
86 if (flag_checking)
87 verify ();
88 }
89 attr_fnspec (const char *str)
90 : str (str), len (strlen (str))
91 {
92 if (flag_checking)
93 verify ();
94 }
95 attr_fnspec (const_tree identifier)
96 : str (TREE_STRING_POINTER (identifier)),
97 len (TREE_STRING_LENGTH (identifier))
98 {
99 if (flag_checking)
100 verify ();
101 }
102 attr_fnspec ()
103 : str (NULL), len (0)
104 {
105 }
106
107 /* Return true if fn spec is known. */
108 bool
109 known_p ()
110 {
111 return len;
112 }
113
114 /* Return true if arg I is specified. */
115 bool
116 arg_specified_p (unsigned int i)
117 {
118 return len >= arg_idx (i + 1);
119 }
120
121 /* True if the argument is not dereferenced recursively, thus only
122 directly reachable memory is read or written. */
123 bool
124 arg_direct_p (unsigned int i)
125 {
126 unsigned int idx = arg_idx (i);
127 gcc_checking_assert (arg_specified_p (i));
128 return str[idx] == 'R' || str[idx] == 'O'
129 || str[idx] == 'W' || (str[idx] >= '1' && str[idx] <= '9');
130 }
131
132 /* True if argument is used. */
133 bool
134 arg_used_p (unsigned int i)
135 {
136 unsigned int idx = arg_idx (i);
137 gcc_checking_assert (arg_specified_p (i));
138 return str[idx] != 'x' && str[idx] != 'X';
139 }
140
141 /* True if memory reached by the argument is readonly (not clobbered). */
142 bool
143 arg_readonly_p (unsigned int i)
144 {
145 unsigned int idx = arg_idx (i);
146 gcc_checking_assert (arg_specified_p (i));
147 return str[idx] == 'r' || str[idx] == 'R' || (str[idx] >= '1' && str[idx] <= '9');
148 }
149
150 /* True if memory reached by the argument is read (directly or indirectly) */
151 bool
152 arg_maybe_read_p (unsigned int i)
153 {
154 unsigned int idx = arg_idx (i);
155 gcc_checking_assert (arg_specified_p (i));
156 return str[idx] != 'o' && str[idx] != 'O'
157 && str[idx] != 'x' && str[idx] != 'X';
158 }
159
160 /* True if memory reached by the argument is written.
161 (directly or indirectly) */
162 bool
163 arg_maybe_written_p (unsigned int i)
164 {
165 unsigned int idx = arg_idx (i);
166 gcc_checking_assert (arg_specified_p (i));
167 return str[idx] != 'r' && str[idx] != 'R'
168 && (str[idx] < '1' || str[idx] > '9')
169 && str[idx] != 'x' && str[idx] != 'X';
170 }
171
172 /* Return true if load of memory pointed to by argument I is bound
173 by another argument. In this case set ARG. */
174 bool
175 arg_max_access_size_given_by_arg_p (unsigned int i, unsigned int *arg)
176 {
177 unsigned int idx = arg_idx (i);
178 gcc_checking_assert (arg_specified_p (i));
179 if (str[idx + 1] >= '1' && str[idx + 1] <= '9')
180 {
181 *arg = str[idx + 1] - '1';
182 return true;
183 }
184 else
185 return false;
186 }
187
188 /* Return true if the pointed-to type of the argument correspond to the
189 size of the memory acccess. */
190 bool
191 arg_access_size_given_by_type_p (unsigned int i)
192 {
193 unsigned int idx = arg_idx (i);
194 gcc_checking_assert (arg_specified_p (i));
195 return str[idx + 1] == 't';
196 }
197
198 /* Return true if memory pointer to by argument is copied to a memory
199 pointed to by a different argument (as in memcpy).
200 In this case set ARG. */
201 bool
202 arg_copied_to_arg_p (unsigned int i, unsigned int *arg)
203 {
204 unsigned int idx = arg_idx (i);
205 gcc_checking_assert (arg_specified_p (i));
206 if (str[idx] < '1' || str[idx] > '9')
207 return false;
208 *arg = str[idx] - '1';
209 return true;
210 }
211
212
213 /* True if the argument does not escape. */
214 bool
215 arg_noescape_p (unsigned int i)
216 {
217 unsigned int idx = arg_idx (i);
218 gcc_checking_assert (arg_specified_p (i));
219 return str[idx] == 'w' || str[idx] == 'W'
220 || str[idx] == 'r' || str[idx] == 'R'
221 || str[idx] == 'o' || str[idx] == 'O';
222 }
223
224 /* Return true if function returns value of its parameter. If ARG_NO is
225 non-NULL return initialize it to the argument returned. */
226 bool
227 returns_arg (unsigned int *arg_no)
228 {
229 if (str[0] >= '1' && str[0] <= '4')
230 {
231 if (arg_no)
232 *arg_no = str[0] - '1';
233 return true;
234 }
235 return false;
236 }
237
238 /* Nonzero if the return value does not alias with anything. Functions
239 with the malloc attribute have this set on their return value. */
240 bool
241 returns_noalias_p ()
242 {
243 return str[0] == 'm';
244 }
245
246 /* Return true if all memory read by the function is specified by fnspec. */
247 bool
248 global_memory_read_p ()
249 {
250 return str[1] != 'c' && str[1] != 'C';
251 }
252
253 /* Return true if all memory written by the function
254 is specified by fnspec. */
255 bool
256 global_memory_written_p ()
257 {
258 return str[1] != 'c' && str[1] != 'C' && str[1] != 'p' && str[1] != 'P';
259 }
260
261 bool
262 errno_maybe_written_p ()
263 {
264 return str[1] == 'C' || str[1] == 'P';
265 }
266
267 /* Return EAF flags for arg I. */
268 int
269 arg_eaf_flags (unsigned int i)
270 {
271 int flags = 0;
272
273 if (!arg_specified_p (i))
274 ;
275 else if (!arg_used_p (i))
276 flags = EAF_UNUSED;
277 else
278 {
279 if (arg_direct_p (i))
280 flags |= EAF_NO_INDIRECT_READ | EAF_NO_INDIRECT_ESCAPE
281 | EAF_NOT_RETURNED_INDIRECTLY | EAF_NO_INDIRECT_CLOBBER;
282 if (arg_noescape_p (i))
283 flags |= EAF_NO_DIRECT_ESCAPE | EAF_NO_INDIRECT_ESCAPE;
284 if (arg_readonly_p (i))
285 flags |= EAF_NO_DIRECT_CLOBBER | EAF_NO_INDIRECT_CLOBBER;
286 }
287 return flags;
288 }
289
290 /* Check validity of the string. */
291 void verify ();
292
293 /* Return the fnspec string. */
294 const char *
295 get_str ()
296 {
297 return str;
298 }
299 };
300
301 extern attr_fnspec gimple_call_fnspec (const gcall *stmt);
302 extern attr_fnspec builtin_fnspec (tree);
303
304 #endif /* ATTR_FNSPEC_H */