Mercurial > hg > CbC > CbC_gcc

comparison gcc/tree-ssanames.c @ 0:a06113de4d67

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
first commit
author kent <kent@cr.ie.u-ryukyu.ac.jp>
date Fri, 17 Jul 2009 14:47:48 +0900
parents
children 77e2b8dfacca
comparison
equal deleted inserted replaced
-1:000000000000 0:a06113de4d67
1 /* Generic routines for manipulating SSA_NAME expressions
2 Copyright (C) 2003, 2004, 2005, 2007, 2008 Free Software Foundation, Inc.
3
4 This file is part of GCC.
5
6 GCC is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 3, or (at your option)
9 any later version.
10
11 GCC 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 General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
19
20 #include "config.h"
21 #include "system.h"
22 #include "coretypes.h"
23 #include "tm.h"
24 #include "tree.h"
25 #include "varray.h"
26 #include "ggc.h"
27 #include "tree-flow.h"
28 #include "tree-pass.h"
29
30 /* Rewriting a function into SSA form can create a huge number of SSA_NAMEs,
31 many of which may be thrown away shortly after their creation if jumps
32 were threaded through PHI nodes.
33
34 While our garbage collection mechanisms will handle this situation, it
35 is extremely wasteful to create nodes and throw them away, especially
36 when the nodes can be reused.
37
38 For PR 8361, we can significantly reduce the number of nodes allocated
39 and thus the total amount of memory allocated by managing SSA_NAMEs a
40 little. This additionally helps reduce the amount of work done by the
41 garbage collector. Similar results have been seen on a wider variety
42 of tests (such as the compiler itself).
43
44 Right now we maintain our free list on a per-function basis. It may
45 or may not make sense to maintain the free list for the duration of
46 a compilation unit.
47
48 External code should rely solely upon HIGHEST_SSA_VERSION and the
49 externally defined functions. External code should not know about
50 the details of the free list management.
51
52 External code should also not assume the version number on nodes is
53 monotonically increasing. We reuse the version number when we
54 reuse an SSA_NAME expression. This helps keep arrays and bitmaps
55 more compact.
56
57 We could also use a zone allocator for these objects since they have
58 a very well defined lifetime. If someone wants to experiment with that
59 this is the place to try it. */
60
61 /* Version numbers with special meanings. We start allocating new version
62 numbers after the special ones. */
63 #define UNUSED_NAME_VERSION 0
64
65 #ifdef GATHER_STATISTICS
66 unsigned int ssa_name_nodes_reused;
67 unsigned int ssa_name_nodes_created;
68 #endif
69
70 /* Initialize management of SSA_NAMEs to default SIZE. If SIZE is
71 zero use default. */
72
73 void
74 init_ssanames (struct function *fn, int size)
75 {
76 if (size < 50)
77 size = 50;
78
79 SSANAMES (fn) = VEC_alloc (tree, gc, size);
80
81 /* Version 0 is special, so reserve the first slot in the table. Though
82 currently unused, we may use version 0 in alias analysis as part of
83 the heuristics used to group aliases when the alias sets are too
84 large.
85
86 We use VEC_quick_push here because we know that SSA_NAMES has at
87 least 50 elements reserved in it. */
88 VEC_quick_push (tree, SSANAMES (fn), NULL_TREE);
89 FREE_SSANAMES (fn) = NULL;
90 }
91
92 /* Finalize management of SSA_NAMEs. */
93
94 void
95 fini_ssanames (void)
96 {
97 VEC_free (tree, gc, SSANAMES (cfun));
98 FREE_SSANAMES (cfun) = NULL;
99 }
100
101 /* Dump some simple statistics regarding the re-use of SSA_NAME nodes. */
102
103 #ifdef GATHER_STATISTICS
104 void
105 ssanames_print_statistics (void)
106 {
107 fprintf (stderr, "SSA_NAME nodes allocated: %u\n", ssa_name_nodes_created);
108 fprintf (stderr, "SSA_NAME nodes reused: %u\n", ssa_name_nodes_reused);
109 }
110 #endif
111
112 /* Return an SSA_NAME node for variable VAR defined in statement STMT
113 in function FN. STMT may be an empty statement for artificial
114 references (e.g., default definitions created when a variable is
115 used without a preceding definition). */
116
117 tree
118 make_ssa_name_fn (struct function *fn, tree var, gimple stmt)
119 {
120 tree t;
121 use_operand_p imm;
122
123 gcc_assert (DECL_P (var));
124
125 /* If our free list has an element, then use it. */
126 if (FREE_SSANAMES (fn))
127 {
128 t = FREE_SSANAMES (fn);
129 FREE_SSANAMES (fn) = TREE_CHAIN (FREE_SSANAMES (fn));
130 #ifdef GATHER_STATISTICS
131 ssa_name_nodes_reused++;
132 #endif
133
134 /* The node was cleared out when we put it on the free list, so
135 there is no need to do so again here. */
136 gcc_assert (ssa_name (SSA_NAME_VERSION (t)) == NULL);
137 VEC_replace (tree, SSANAMES (fn), SSA_NAME_VERSION (t), t);
138 }
139 else
140 {
141 t = make_node (SSA_NAME);
142 SSA_NAME_VERSION (t) = VEC_length (tree, SSANAMES (fn));
143 VEC_safe_push (tree, gc, SSANAMES (fn), t);
144 #ifdef GATHER_STATISTICS
145 ssa_name_nodes_created++;
146 #endif
147 }
148
149 TREE_TYPE (t) = TREE_TYPE (var);
150 SSA_NAME_VAR (t) = var;
151 SSA_NAME_DEF_STMT (t) = stmt;
152 SSA_NAME_PTR_INFO (t) = NULL;
153 SSA_NAME_IN_FREE_LIST (t) = 0;
154 SSA_NAME_IS_DEFAULT_DEF (t) = 0;
155 imm = &(SSA_NAME_IMM_USE_NODE (t));
156 imm->use = NULL;
157 imm->prev = imm;
158 imm->next = imm;
159 imm->loc.ssa_name = t;
160
161 return t;
162 }
163
164
165 /* We no longer need the SSA_NAME expression VAR, release it so that
166 it may be reused.
167
168 Note it is assumed that no calls to make_ssa_name will be made
169 until all uses of the ssa name are released and that the only
170 use of the SSA_NAME expression is to check its SSA_NAME_VAR. All
171 other fields must be assumed clobbered. */
172
173 void
174 release_ssa_name (tree var)
175 {
176 if (!var)
177 return;
178
179 /* Never release the default definition for a symbol. It's a
180 special SSA name that should always exist once it's created. */
181 if (SSA_NAME_IS_DEFAULT_DEF (var))
182 return;
183
184 /* If VAR has been registered for SSA updating, don't remove it.
185 After update_ssa has run, the name will be released. */
186 if (name_registered_for_update_p (var))
187 {
188 release_ssa_name_after_update_ssa (var);
189 return;
190 }
191
192 /* release_ssa_name can be called multiple times on a single SSA_NAME.
193 However, it should only end up on our free list one time. We
194 keep a status bit in the SSA_NAME node itself to indicate it has
195 been put on the free list.
196
197 Note that once on the freelist you can not reference the SSA_NAME's
198 defining statement. */
199 if (! SSA_NAME_IN_FREE_LIST (var))
200 {
201 tree saved_ssa_name_var = SSA_NAME_VAR (var);
202 int saved_ssa_name_version = SSA_NAME_VERSION (var);
203 use_operand_p imm = &(SSA_NAME_IMM_USE_NODE (var));
204
205 #ifdef ENABLE_CHECKING
206 verify_imm_links (stderr, var);
207 #endif
208 while (imm->next != imm)
209 delink_imm_use (imm->next);
210
211 VEC_replace (tree, SSANAMES (cfun),
212 SSA_NAME_VERSION (var), NULL_TREE);
213 memset (var, 0, tree_size (var));
214
215 imm->prev = imm;
216 imm->next = imm;
217 imm->loc.ssa_name = var;
218
219 /* First put back the right tree node so that the tree checking
220 macros do not complain. */
221 TREE_SET_CODE (var, SSA_NAME);
222
223 /* Restore the version number. */
224 SSA_NAME_VERSION (var) = saved_ssa_name_version;
225
226 /* Hopefully this can go away once we have the new incremental
227 SSA updating code installed. */
228 SSA_NAME_VAR (var) = saved_ssa_name_var;
229
230 /* Note this SSA_NAME is now in the first list. */
231 SSA_NAME_IN_FREE_LIST (var) = 1;
232
233 /* And finally link it into the free list. */
234 TREE_CHAIN (var) = FREE_SSANAMES (cfun);
235 FREE_SSANAMES (cfun) = var;
236 }
237 }
238
239 /* Creates a duplicate of a ssa name NAME defined in statement STMT. */
240
241 tree
242 duplicate_ssa_name (tree name, gimple stmt)
243 {
244 tree new_name = make_ssa_name (SSA_NAME_VAR (name), stmt);
245 struct ptr_info_def *old_ptr_info = SSA_NAME_PTR_INFO (name);
246
247 if (old_ptr_info)
248 duplicate_ssa_name_ptr_info (new_name, old_ptr_info);
249
250 return new_name;
251 }
252
253
254 /* Creates a duplicate of the ptr_info_def at PTR_INFO for use by
255 the SSA name NAME. */
256
257 void
258 duplicate_ssa_name_ptr_info (tree name, struct ptr_info_def *ptr_info)
259 {
260 struct ptr_info_def *new_ptr_info;
261
262 gcc_assert (POINTER_TYPE_P (TREE_TYPE (name)));
263 gcc_assert (!SSA_NAME_PTR_INFO (name));
264
265 if (!ptr_info)
266 return;
267
268 new_ptr_info = GGC_NEW (struct ptr_info_def);
269 *new_ptr_info = *ptr_info;
270
271 if (ptr_info->pt_vars)
272 {
273 new_ptr_info->pt_vars = BITMAP_GGC_ALLOC ();
274 bitmap_copy (new_ptr_info->pt_vars, ptr_info->pt_vars);
275 }
276
277 SSA_NAME_PTR_INFO (name) = new_ptr_info;
278 }
279
280
281 /* Release all the SSA_NAMEs created by STMT. */
282
283 void
284 release_defs (gimple stmt)
285 {
286 tree def;
287 ssa_op_iter iter;
288
289 /* Make sure that we are in SSA. Otherwise, operand cache may point
290 to garbage. */
291 gcc_assert (gimple_in_ssa_p (cfun));
292
293 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
294 if (TREE_CODE (def) == SSA_NAME)
295 release_ssa_name (def);
296 }
297
298
299 /* Replace the symbol associated with SSA_NAME with SYM. */
300
301 void
302 replace_ssa_name_symbol (tree ssa_name, tree sym)
303 {
304 SSA_NAME_VAR (ssa_name) = sym;
305 TREE_TYPE (ssa_name) = TREE_TYPE (sym);
306 }
307
308 /* Return SSA names that are unused to GGC memory. This is used to keep
309 footprint of compiler during interprocedural optimization.
310 As a side effect the SSA_NAME_VERSION number reuse is reduced
311 so this function should not be used too often. */
312 static unsigned int
313 release_dead_ssa_names (void)
314 {
315 tree t, next;
316 int n = 0;
317 referenced_var_iterator rvi;
318
319 /* Current defs point to various dead SSA names that in turn points to dead
320 statements so bunch of dead memory is held from releasing. */
321 FOR_EACH_REFERENCED_VAR (t, rvi)
322 set_current_def (t, NULL);
323 /* Now release the freelist. */
324 for (t = FREE_SSANAMES (cfun); t; t = next)
325 {
326 next = TREE_CHAIN (t);
327 /* Dangling pointers might make GGC to still see dead SSA names, so it is
328 important to unlink the list and avoid GGC from seeing all subsequent
329 SSA names. In longer run we want to have all dangling pointers here
330 removed (since they usually go through dead statements that consume
331 considerable amounts of memory). */
332 TREE_CHAIN (t) = NULL_TREE;
333 n++;
334 }
335 FREE_SSANAMES (cfun) = NULL;
336
337 /* Cgraph edges has been invalidated and point to dead statement. We need to
338 remove them now and will rebuild it before next IPA pass. */
339 cgraph_node_remove_callees (cgraph_node (current_function_decl));
340
341 if (dump_file)
342 fprintf (dump_file, "Released %i names, %.2f%%\n", n, n * 100.0 / num_ssa_names);
343 return 0;
344 }
345
346 struct gimple_opt_pass pass_release_ssa_names =
347 {
348 {
349 GIMPLE_PASS,
350 "release_ssa", /* name */
351 NULL, /* gate */
352 release_dead_ssa_names, /* execute */
353 NULL, /* sub */
354 NULL, /* next */
355 0, /* static_pass_number */
356 0, /* tv_id */
357 PROP_ssa, /* properties_required */
358 0, /* properties_provided */
359 0, /* properties_destroyed */
360 0, /* todo_flags_start */
361 TODO_dump_func /* todo_flags_finish */
362 }
363 };