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1d416bd7 | 1 | /* Callgraph handling code. |
cfaf579d | 2 | Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 |
3 | Free Software Foundation, Inc. | |
1d416bd7 | 4 | Contributed by Jan Hubicka |
5 | ||
6 | This file is part of GCC. | |
7 | ||
8 | GCC is free software; you can redistribute it and/or modify it under | |
9 | the terms of the GNU General Public License as published by the Free | |
8c4c00c1 | 10 | Software Foundation; either version 3, or (at your option) any later |
1d416bd7 | 11 | version. |
12 | ||
13 | GCC is distributed in the hope that it will be useful, but WITHOUT ANY | |
14 | WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
15 | FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
16 | for more details. | |
17 | ||
18 | You should have received a copy of the GNU General Public License | |
8c4c00c1 | 19 | along with GCC; see the file COPYING3. If not see |
20 | <http://www.gnu.org/licenses/>. */ | |
1d416bd7 | 21 | |
22 | #include "config.h" | |
23 | #include "system.h" | |
24 | #include "coretypes.h" | |
25 | #include "tm.h" | |
26 | #include "tree.h" | |
27 | #include "cgraph.h" | |
28 | #include "langhooks.h" | |
29 | #include "diagnostic.h" | |
30 | #include "hashtab.h" | |
31 | #include "ggc.h" | |
32 | #include "timevar.h" | |
33 | #include "debug.h" | |
34 | #include "target.h" | |
35 | #include "output.h" | |
75a70cf9 | 36 | #include "gimple.h" |
604cde73 | 37 | #include "tree-flow.h" |
59dd4830 | 38 | #include "flags.h" |
1d416bd7 | 39 | |
40 | /* This file contains basic routines manipulating variable pool. | |
41 | ||
42 | Varpool acts as interface in between the front-end and middle-end | |
43 | and drives the decision process on what variables and when are | |
44 | going to be compiled. | |
45 | ||
7920eed5 | 46 | The varpool nodes are allocated lazily for declarations |
1d416bd7 | 47 | either by frontend or at callgraph construction time. |
48 | All variables supposed to be output into final file needs to be | |
ccd2f3d1 | 49 | explicitly marked by frontend via VARPOOL_FINALIZE_DECL function. */ |
1d416bd7 | 50 | |
51 | /* Hash table used to convert declarations into nodes. */ | |
52 | static GTY((param_is (struct varpool_node))) htab_t varpool_hash; | |
53 | ||
54 | /* The linked list of cgraph varpool nodes. | |
55 | Linked via node->next pointer. */ | |
56 | struct varpool_node *varpool_nodes; | |
57 | ||
58 | /* Queue of cgraph nodes scheduled to be lowered and output. | |
59 | The queue is maintained via mark_needed_node, linked via node->next_needed | |
60 | pointer. | |
61 | ||
b1a2195b | 62 | LAST_NEEDED_NODE points to the end of queue, so it can be |
dd603549 | 63 | maintained in forward order. GTY is needed to make it friendly to |
b1a2195b | 64 | PCH. |
1d416bd7 | 65 | |
6329636b | 66 | During compilation we construct the queue of needed variables |
1d416bd7 | 67 | twice: first time it is during cgraph construction, second time it is at the |
68 | end of compilation in VARPOOL_REMOVE_UNREFERENCED_DECLS so we can avoid | |
69 | optimized out variables being output. | |
70 | ||
71 | Each variable is thus first analyzed and then later possibly output. | |
72 | FIRST_UNANALYZED_NODE points to first node in queue that was not analyzed | |
73 | yet and is moved via VARPOOL_ANALYZE_PENDING_DECLS. */ | |
74 | ||
75 | struct varpool_node *varpool_nodes_queue; | |
76 | static GTY(()) struct varpool_node *varpool_last_needed_node; | |
77 | static GTY(()) struct varpool_node *varpool_first_unanalyzed_node; | |
78 | ||
79 | /* Lists all assembled variables to be sent to debugger output later on. */ | |
80 | static GTY(()) struct varpool_node *varpool_assembled_nodes_queue; | |
81 | ||
82 | /* Return name of the node used in debug output. */ | |
83 | static const char * | |
84 | varpool_node_name (struct varpool_node *node) | |
85 | { | |
86 | return lang_hooks.decl_printable_name (node->decl, 2); | |
87 | } | |
88 | ||
89 | /* Returns a hash code for P. */ | |
90 | static hashval_t | |
91 | hash_varpool_node (const void *p) | |
92 | { | |
93 | const struct varpool_node *n = (const struct varpool_node *) p; | |
94 | return (hashval_t) DECL_UID (n->decl); | |
95 | } | |
96 | ||
97 | /* Returns nonzero if P1 and P2 are equal. */ | |
98 | static int | |
99 | eq_varpool_node (const void *p1, const void *p2) | |
100 | { | |
101 | const struct varpool_node *n1 = | |
102 | (const struct varpool_node *) p1; | |
103 | const struct varpool_node *n2 = | |
104 | (const struct varpool_node *) p2; | |
105 | return DECL_UID (n1->decl) == DECL_UID (n2->decl); | |
106 | } | |
107 | ||
108 | /* Return varpool node assigned to DECL. Create new one when needed. */ | |
109 | struct varpool_node * | |
110 | varpool_node (tree decl) | |
111 | { | |
112 | struct varpool_node key, *node, **slot; | |
113 | ||
114 | gcc_assert (DECL_P (decl) && TREE_CODE (decl) != FUNCTION_DECL); | |
115 | ||
116 | if (!varpool_hash) | |
117 | varpool_hash = htab_create_ggc (10, hash_varpool_node, | |
118 | eq_varpool_node, NULL); | |
119 | key.decl = decl; | |
120 | slot = (struct varpool_node **) | |
121 | htab_find_slot (varpool_hash, &key, INSERT); | |
122 | if (*slot) | |
123 | return *slot; | |
124 | node = GGC_CNEW (struct varpool_node); | |
125 | node->decl = decl; | |
126 | node->order = cgraph_order++; | |
127 | node->next = varpool_nodes; | |
128 | varpool_nodes = node; | |
129 | *slot = node; | |
130 | return node; | |
131 | } | |
132 | ||
133 | /* Dump given cgraph node. */ | |
134 | void | |
135 | dump_varpool_node (FILE *f, struct varpool_node *node) | |
136 | { | |
137 | fprintf (f, "%s:", varpool_node_name (node)); | |
138 | fprintf (f, " availability:%s", | |
139 | cgraph_function_flags_ready | |
140 | ? cgraph_availability_names[cgraph_variable_initializer_availability (node)] | |
141 | : "not-ready"); | |
142 | if (DECL_INITIAL (node->decl)) | |
143 | fprintf (f, " initialized"); | |
144 | if (node->needed) | |
145 | fprintf (f, " needed"); | |
146 | if (node->analyzed) | |
147 | fprintf (f, " analyzed"); | |
148 | if (node->finalized) | |
149 | fprintf (f, " finalized"); | |
150 | if (node->output) | |
151 | fprintf (f, " output"); | |
152 | if (node->externally_visible) | |
153 | fprintf (f, " externally_visible"); | |
154 | fprintf (f, "\n"); | |
155 | } | |
156 | ||
157 | /* Dump the variable pool. */ | |
158 | void | |
159 | dump_varpool (FILE *f) | |
160 | { | |
161 | struct varpool_node *node; | |
162 | ||
163 | fprintf (f, "variable pool:\n\n"); | |
dd603549 | 164 | for (node = varpool_nodes; node; node = node->next) |
1d416bd7 | 165 | dump_varpool_node (f, node); |
166 | } | |
167 | ||
64f3398b | 168 | /* Dump the variable pool to stderr. */ |
169 | ||
170 | void | |
171 | debug_varpool (void) | |
172 | { | |
173 | dump_varpool (stderr); | |
174 | } | |
175 | ||
1d416bd7 | 176 | /* Given an assembler name, lookup node. */ |
177 | struct varpool_node * | |
178 | varpool_node_for_asm (tree asmname) | |
179 | { | |
180 | struct varpool_node *node; | |
181 | ||
182 | for (node = varpool_nodes; node ; node = node->next) | |
183 | if (decl_assembler_name_equal (node->decl, asmname)) | |
184 | return node; | |
185 | ||
186 | return NULL; | |
187 | } | |
188 | ||
189 | /* Helper function for finalization code - add node into lists so it will | |
190 | be analyzed and compiled. */ | |
191 | static void | |
192 | varpool_enqueue_needed_node (struct varpool_node *node) | |
193 | { | |
194 | if (varpool_last_needed_node) | |
195 | varpool_last_needed_node->next_needed = node; | |
196 | varpool_last_needed_node = node; | |
197 | node->next_needed = NULL; | |
198 | if (!varpool_nodes_queue) | |
199 | varpool_nodes_queue = node; | |
200 | if (!varpool_first_unanalyzed_node) | |
201 | varpool_first_unanalyzed_node = node; | |
202 | notice_global_symbol (node->decl); | |
203 | } | |
204 | ||
205 | /* Notify finalize_compilation_unit that given node is reachable | |
206 | or needed. */ | |
207 | void | |
208 | varpool_mark_needed_node (struct varpool_node *node) | |
209 | { | |
210 | if (!node->needed && node->finalized | |
211 | && !TREE_ASM_WRITTEN (node->decl)) | |
212 | varpool_enqueue_needed_node (node); | |
213 | node->needed = 1; | |
214 | } | |
215 | ||
216 | /* Reset the queue of needed nodes. */ | |
217 | static void | |
218 | varpool_reset_queue (void) | |
219 | { | |
220 | varpool_last_needed_node = NULL; | |
221 | varpool_nodes_queue = NULL; | |
222 | varpool_first_unanalyzed_node = NULL; | |
223 | } | |
224 | ||
225 | /* Determine if variable DECL is needed. That is, visible to something | |
226 | either outside this translation unit, something magic in the system | |
6329636b | 227 | configury */ |
1d416bd7 | 228 | bool |
229 | decide_is_variable_needed (struct varpool_node *node, tree decl) | |
230 | { | |
231 | /* If the user told us it is used, then it must be so. */ | |
9dda1f80 | 232 | if (node->externally_visible || node->force_output) |
1d416bd7 | 233 | return true; |
1d416bd7 | 234 | |
235 | /* ??? If the assembler name is set by hand, it is possible to assemble | |
236 | the name later after finalizing the function and the fact is noticed | |
237 | in assemble_name then. This is arguably a bug. */ | |
238 | if (DECL_ASSEMBLER_NAME_SET_P (decl) | |
239 | && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl))) | |
240 | return true; | |
241 | ||
242 | /* If we decided it was needed before, but at the time we didn't have | |
243 | the definition available, then it's still needed. */ | |
244 | if (node->needed) | |
245 | return true; | |
246 | ||
247 | /* Externally visible variables must be output. The exception is | |
248 | COMDAT variables that must be output only when they are needed. */ | |
59dd4830 | 249 | if (TREE_PUBLIC (decl) |
250 | && !flag_whole_program | |
251 | && !flag_lto | |
252 | && !flag_whopr | |
253 | && !DECL_COMDAT (decl) | |
1d416bd7 | 254 | && !DECL_EXTERNAL (decl)) |
255 | return true; | |
256 | ||
9dda1f80 | 257 | /* When emulating tls, we actually see references to the control |
258 | variable, rather than the user-level variable. */ | |
259 | if (!targetm.have_tls | |
260 | && TREE_CODE (decl) == VAR_DECL | |
261 | && DECL_THREAD_LOCAL_P (decl)) | |
262 | { | |
263 | tree control = emutls_decl (decl); | |
264 | if (decide_is_variable_needed (varpool_node (control), control)) | |
265 | return true; | |
266 | } | |
267 | ||
1d416bd7 | 268 | /* When not reordering top level variables, we have to assume that |
269 | we are going to keep everything. */ | |
6329636b | 270 | if (flag_toplevel_reorder) |
1d416bd7 | 271 | return false; |
272 | ||
273 | /* We want to emit COMDAT variables only when absolutely necessary. */ | |
274 | if (DECL_COMDAT (decl)) | |
275 | return false; | |
276 | return true; | |
277 | } | |
278 | ||
279 | /* Mark DECL as finalized. By finalizing the declaration, frontend instruct the | |
280 | middle end to output the variable to asm file, if needed or externally | |
281 | visible. */ | |
282 | void | |
283 | varpool_finalize_decl (tree decl) | |
284 | { | |
285 | struct varpool_node *node = varpool_node (decl); | |
286 | ||
59dd4830 | 287 | /* FIXME: We don't really stream varpool datastructure and instead rebuild it |
288 | by varpool_finalize_decl. This is not quite correct since this way we can't | |
289 | attach any info to varpool. Eventually we will want to stream varpool nodes | |
290 | and the flags. | |
291 | ||
292 | For the moment just prevent analysis of varpool nodes to happen again, so | |
293 | we will re-try to compute "address_taken" flag of varpool that breaks | |
294 | in presence of clones. */ | |
295 | if (in_lto_p) | |
296 | node->analyzed = true; | |
297 | ||
1d416bd7 | 298 | /* The first declaration of a variable that comes through this function |
299 | decides whether it is global (in C, has external linkage) | |
300 | or local (in C, has internal linkage). So do nothing more | |
301 | if this function has already run. */ | |
302 | if (node->finalized) | |
303 | { | |
6329636b | 304 | if (cgraph_global_info_ready) |
1d416bd7 | 305 | varpool_assemble_pending_decls (); |
306 | return; | |
307 | } | |
308 | if (node->needed) | |
309 | varpool_enqueue_needed_node (node); | |
310 | node->finalized = true; | |
311 | ||
312 | if (decide_is_variable_needed (node, decl)) | |
313 | varpool_mark_needed_node (node); | |
314 | /* Since we reclaim unreachable nodes at the end of every language | |
315 | level unit, we need to be conservative about possible entry points | |
316 | there. */ | |
317 | else if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl)) | |
318 | varpool_mark_needed_node (node); | |
6329636b | 319 | if (cgraph_global_info_ready) |
1d416bd7 | 320 | varpool_assemble_pending_decls (); |
321 | } | |
322 | ||
323 | /* Return variable availability. See cgraph.h for description of individual | |
324 | return values. */ | |
325 | enum availability | |
326 | cgraph_variable_initializer_availability (struct varpool_node *node) | |
327 | { | |
328 | gcc_assert (cgraph_function_flags_ready); | |
329 | if (!node->finalized) | |
330 | return AVAIL_NOT_AVAILABLE; | |
331 | if (!TREE_PUBLIC (node->decl)) | |
332 | return AVAIL_AVAILABLE; | |
333 | /* If the variable can be overwritten, return OVERWRITABLE. Takes | |
334 | care of at least two notable extensions - the COMDAT variables | |
335 | used to share template instantiations in C++. */ | |
336 | if (!(*targetm.binds_local_p) (node->decl) && !DECL_COMDAT (node->decl)) | |
337 | return AVAIL_OVERWRITABLE; | |
338 | return AVAIL_AVAILABLE; | |
339 | } | |
340 | ||
341 | /* Walk the decls we marked as necessary and see if they reference new | |
342 | variables or functions and add them into the worklists. */ | |
343 | bool | |
344 | varpool_analyze_pending_decls (void) | |
345 | { | |
346 | bool changed = false; | |
347 | timevar_push (TV_CGRAPH); | |
348 | ||
349 | while (varpool_first_unanalyzed_node) | |
350 | { | |
351 | tree decl = varpool_first_unanalyzed_node->decl; | |
59dd4830 | 352 | bool analyzed = varpool_first_unanalyzed_node->analyzed; |
1d416bd7 | 353 | |
354 | varpool_first_unanalyzed_node->analyzed = true; | |
355 | ||
356 | varpool_first_unanalyzed_node = varpool_first_unanalyzed_node->next_needed; | |
357 | ||
59dd4830 | 358 | /* When reading back varpool at LTO time, we re-construct the queue in order |
359 | to have "needed" list right by inserting all needed nodes into varpool. | |
360 | We however don't want to re-analyze already analyzed nodes. */ | |
361 | if (!analyzed) | |
362 | { | |
363 | gcc_assert (!in_lto_p); | |
364 | /* Compute the alignment early so function body expanders are | |
365 | already informed about increased alignment. */ | |
366 | align_variable (decl, 0); | |
1d416bd7 | 367 | |
59dd4830 | 368 | if (DECL_INITIAL (decl)) |
369 | record_references_in_initializer (decl); | |
370 | } | |
1d416bd7 | 371 | changed = true; |
372 | } | |
373 | timevar_pop (TV_CGRAPH); | |
374 | return changed; | |
375 | } | |
376 | ||
377 | /* Output one variable, if necessary. Return whether we output it. */ | |
378 | bool | |
379 | varpool_assemble_decl (struct varpool_node *node) | |
380 | { | |
381 | tree decl = node->decl; | |
382 | ||
383 | if (!TREE_ASM_WRITTEN (decl) | |
384 | && !node->alias | |
385 | && !DECL_EXTERNAL (decl) | |
386 | && (TREE_CODE (decl) != VAR_DECL || !DECL_HAS_VALUE_EXPR_P (decl))) | |
387 | { | |
388 | assemble_variable (decl, 0, 1, 0); | |
304e5318 | 389 | if (TREE_ASM_WRITTEN (decl)) |
390 | { | |
391 | node->next_needed = varpool_assembled_nodes_queue; | |
392 | varpool_assembled_nodes_queue = node; | |
393 | node->finalized = 1; | |
394 | return true; | |
395 | } | |
1d416bd7 | 396 | } |
397 | ||
398 | return false; | |
399 | } | |
400 | ||
401 | /* Optimization of function bodies might've rendered some variables as | |
402 | unnecessary so we want to avoid these from being compiled. | |
403 | ||
404 | This is done by pruning the queue and keeping only the variables that | |
405 | really appear needed (ie they are either externally visible or referenced | |
406 | by compiled function). Re-doing the reachability analysis on variables | |
407 | brings back the remaining variables referenced by these. */ | |
408 | void | |
409 | varpool_remove_unreferenced_decls (void) | |
410 | { | |
411 | struct varpool_node *next, *node = varpool_nodes_queue; | |
412 | ||
413 | varpool_reset_queue (); | |
414 | ||
415 | if (errorcount || sorrycount) | |
416 | return; | |
417 | ||
418 | while (node) | |
419 | { | |
420 | tree decl = node->decl; | |
421 | next = node->next_needed; | |
422 | node->needed = 0; | |
423 | ||
424 | if (node->finalized | |
9dda1f80 | 425 | && (decide_is_variable_needed (node, decl) |
1d416bd7 | 426 | /* ??? Cgraph does not yet rule the world with an iron hand, |
427 | and does not control the emission of debug information. | |
428 | After a variable has its DECL_RTL set, we must assume that | |
429 | it may be referenced by the debug information, and we can | |
430 | no longer elide it. */ | |
431 | || DECL_RTL_SET_P (decl))) | |
432 | varpool_mark_needed_node (node); | |
433 | ||
434 | node = next; | |
435 | } | |
436 | /* Make sure we mark alias targets as used targets. */ | |
437 | finish_aliases_1 (); | |
438 | varpool_analyze_pending_decls (); | |
439 | } | |
440 | ||
441 | /* Output all variables enqueued to be assembled. */ | |
442 | bool | |
443 | varpool_assemble_pending_decls (void) | |
444 | { | |
445 | bool changed = false; | |
446 | ||
447 | if (errorcount || sorrycount) | |
448 | return false; | |
449 | ||
450 | /* EH might mark decls as needed during expansion. This should be safe since | |
451 | we don't create references to new function, but it should not be used | |
452 | elsewhere. */ | |
453 | varpool_analyze_pending_decls (); | |
454 | ||
455 | while (varpool_nodes_queue) | |
456 | { | |
457 | struct varpool_node *node = varpool_nodes_queue; | |
458 | ||
459 | varpool_nodes_queue = varpool_nodes_queue->next_needed; | |
460 | if (varpool_assemble_decl (node)) | |
304e5318 | 461 | changed = true; |
1d416bd7 | 462 | else |
463 | node->next_needed = NULL; | |
464 | } | |
11cc227f | 465 | /* varpool_nodes_queue is now empty, clear the pointer to the last element |
466 | in the queue. */ | |
467 | varpool_last_needed_node = NULL; | |
1d416bd7 | 468 | return changed; |
469 | } | |
470 | ||
304e5318 | 471 | /* Remove all elements from the queue so we can re-use it for debug output. */ |
472 | void | |
473 | varpool_empty_needed_queue (void) | |
474 | { | |
475 | /* EH might mark decls as needed during expansion. This should be safe since | |
476 | we don't create references to new function, but it should not be used | |
477 | elsewhere. */ | |
478 | varpool_analyze_pending_decls (); | |
479 | ||
480 | while (varpool_nodes_queue) | |
481 | { | |
482 | struct varpool_node *node = varpool_nodes_queue; | |
483 | varpool_nodes_queue = varpool_nodes_queue->next_needed; | |
484 | node->next_needed = NULL; | |
485 | } | |
486 | /* varpool_nodes_queue is now empty, clear the pointer to the last element | |
487 | in the queue. */ | |
488 | varpool_last_needed_node = NULL; | |
489 | } | |
490 | ||
604cde73 | 491 | /* Create a new global variable of type TYPE. */ |
492 | tree | |
493 | add_new_static_var (tree type) | |
494 | { | |
495 | tree new_decl; | |
496 | struct varpool_node *new_node; | |
497 | ||
498 | new_decl = create_tmp_var (type, NULL); | |
499 | DECL_NAME (new_decl) = create_tmp_var_name (NULL); | |
500 | TREE_READONLY (new_decl) = 0; | |
501 | TREE_STATIC (new_decl) = 1; | |
502 | TREE_USED (new_decl) = 1; | |
503 | DECL_CONTEXT (new_decl) = NULL_TREE; | |
504 | DECL_ABSTRACT (new_decl) = 0; | |
505 | lang_hooks.dup_lang_specific_decl (new_decl); | |
506 | create_var_ann (new_decl); | |
507 | new_node = varpool_node (new_decl); | |
508 | varpool_mark_needed_node (new_node); | |
509 | add_referenced_var (new_decl); | |
510 | varpool_finalize_decl (new_decl); | |
511 | ||
512 | return new_node->decl; | |
513 | } | |
514 | ||
1d416bd7 | 515 | #include "gt-varpool.h" |