Merged r158704 through r158906 into branch.
[official-gcc.git] / gcc / varpool.c
blob77f52c3dee651075a1e0b53af0a007cbcc05a858
1 /* Callgraph handling code.
2 Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2010
3 Free Software Foundation, Inc.
4 Contributed by Jan Hubicka
6 This file is part of GCC.
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
10 Software Foundation; either version 3, or (at your option) any later
11 version.
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.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
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"
36 #include "gimple.h"
37 #include "tree-flow.h"
38 #include "flags.h"
40 /* This file contains basic routines manipulating variable pool.
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.
46 The varpool nodes are allocated lazily for declarations
47 either by frontend or at callgraph construction time.
48 All variables supposed to be output into final file needs to be
49 explicitly marked by frontend via VARPOOL_FINALIZE_DECL function. */
51 /* Hash table used to convert declarations into nodes. */
52 static GTY((param_is (struct varpool_node))) htab_t varpool_hash;
54 /* The linked list of cgraph varpool nodes.
55 Linked via node->next pointer. */
56 struct varpool_node *varpool_nodes;
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.
62 LAST_NEEDED_NODE points to the end of queue, so it can be
63 maintained in forward order. GTY is needed to make it friendly to
64 PCH.
66 During compilation we construct the queue of needed variables
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.
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. */
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;
79 /* Lists all assembled variables to be sent to debugger output later on. */
80 static GTY(()) struct varpool_node *varpool_assembled_nodes_queue;
82 /* Return name of the node used in debug output. */
83 const char *
84 varpool_node_name (struct varpool_node *node)
86 return lang_hooks.decl_printable_name (node->decl, 2);
89 /* Returns a hash code for P. */
90 static hashval_t
91 hash_varpool_node (const void *p)
93 const struct varpool_node *n = (const struct varpool_node *) p;
94 return (hashval_t) DECL_UID (n->decl);
97 /* Returns nonzero if P1 and P2 are equal. */
98 static int
99 eq_varpool_node (const void *p1, const void *p2)
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);
108 /* Return varpool node assigned to DECL without creating new one. */
109 struct varpool_node *
110 varpool_get_node (tree decl)
112 struct varpool_node key, **slot;
114 gcc_assert (DECL_P (decl) && TREE_CODE (decl) != FUNCTION_DECL);
116 if (!varpool_hash)
117 return NULL;
118 key.decl = decl;
119 slot = (struct varpool_node **)
120 htab_find_slot (varpool_hash, &key, INSERT);
121 return *slot;
124 /* Return varpool node assigned to DECL. Create new one when needed. */
125 struct varpool_node *
126 varpool_node (tree decl)
128 struct varpool_node key, *node, **slot;
130 gcc_assert (DECL_P (decl) && TREE_CODE (decl) != FUNCTION_DECL);
132 if (!varpool_hash)
133 varpool_hash = htab_create_ggc (10, hash_varpool_node,
134 eq_varpool_node, NULL);
135 key.decl = decl;
136 slot = (struct varpool_node **)
137 htab_find_slot (varpool_hash, &key, INSERT);
138 if (*slot)
139 return *slot;
140 node = GGC_CNEW (struct varpool_node);
141 node->decl = decl;
142 node->order = cgraph_order++;
143 node->next = varpool_nodes;
144 if (varpool_nodes)
145 varpool_nodes->prev = node;
146 varpool_nodes = node;
147 *slot = node;
148 return node;
151 /* Remove node from the varpool. */
152 void
153 varpool_remove_node (struct varpool_node *node)
155 void **slot;
156 slot = htab_find_slot (varpool_hash, node, NO_INSERT);
157 gcc_assert (*slot == node);
158 htab_clear_slot (varpool_hash, slot);
159 gcc_assert (!varpool_assembled_nodes_queue);
160 if (node->next)
161 node->next->prev = node->prev;
162 if (node->prev)
163 node->prev->next = node->next;
164 else if (node->next)
166 gcc_assert (varpool_nodes == node);
167 varpool_nodes = node->next;
169 if (varpool_first_unanalyzed_node == node)
170 varpool_first_unanalyzed_node = node->next_needed;
171 if (node->next_needed)
172 node->next_needed->prev_needed = node->prev_needed;
173 else if (node->prev_needed)
175 gcc_assert (varpool_last_needed_node);
176 varpool_last_needed_node = node->prev_needed;
178 if (node->prev_needed)
179 node->prev_needed->next_needed = node->next_needed;
180 else if (node->next_needed)
182 gcc_assert (varpool_nodes_queue == node);
183 varpool_nodes_queue = node->next_needed;
185 node->decl = NULL;
188 /* Dump given cgraph node. */
189 void
190 dump_varpool_node (FILE *f, struct varpool_node *node)
192 fprintf (f, "%s:", varpool_node_name (node));
193 fprintf (f, " availability:%s",
194 cgraph_function_flags_ready
195 ? cgraph_availability_names[cgraph_variable_initializer_availability (node)]
196 : "not-ready");
197 if (DECL_ASSEMBLER_NAME_SET_P (node->decl))
198 fprintf (f, " (asm: %s)", IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (node->decl)));
199 if (DECL_INITIAL (node->decl))
200 fprintf (f, " initialized");
201 if (TREE_ASM_WRITTEN (node->decl))
202 fprintf (f, " (asm written)");
203 if (node->needed)
204 fprintf (f, " needed");
205 if (node->analyzed)
206 fprintf (f, " analyzed");
207 if (node->finalized)
208 fprintf (f, " finalized");
209 if (node->output)
210 fprintf (f, " output");
211 if (node->externally_visible)
212 fprintf (f, " externally_visible");
213 if (node->in_other_partition)
214 fprintf (f, " in_other_partition");
215 else if (node->used_from_other_partition)
216 fprintf (f, " used_from_other_partition");
217 fprintf (f, "\n");
220 /* Dump the variable pool. */
221 void
222 dump_varpool (FILE *f)
224 struct varpool_node *node;
226 fprintf (f, "variable pool:\n\n");
227 for (node = varpool_nodes; node; node = node->next)
228 dump_varpool_node (f, node);
231 /* Dump the variable pool to stderr. */
233 void
234 debug_varpool (void)
236 dump_varpool (stderr);
239 /* Given an assembler name, lookup node. */
240 struct varpool_node *
241 varpool_node_for_asm (tree asmname)
243 struct varpool_node *node;
245 for (node = varpool_nodes; node ; node = node->next)
246 if (decl_assembler_name_equal (node->decl, asmname))
247 return node;
249 return NULL;
252 /* Helper function for finalization code - add node into lists so it will
253 be analyzed and compiled. */
254 static void
255 varpool_enqueue_needed_node (struct varpool_node *node)
257 if (varpool_last_needed_node)
259 varpool_last_needed_node->next_needed = node;
260 node->prev_needed = varpool_last_needed_node;
262 varpool_last_needed_node = node;
263 node->next_needed = NULL;
264 if (!varpool_nodes_queue)
265 varpool_nodes_queue = node;
266 if (!varpool_first_unanalyzed_node)
267 varpool_first_unanalyzed_node = node;
268 notice_global_symbol (node->decl);
271 /* Notify finalize_compilation_unit that given node is reachable
272 or needed. */
273 void
274 varpool_mark_needed_node (struct varpool_node *node)
276 if (node->alias && node->extra_name)
277 node = node->extra_name;
278 if (!node->needed && node->finalized
279 && !TREE_ASM_WRITTEN (node->decl))
280 varpool_enqueue_needed_node (node);
281 node->needed = 1;
284 /* Reset the queue of needed nodes. */
285 static void
286 varpool_reset_queue (void)
288 varpool_last_needed_node = NULL;
289 varpool_nodes_queue = NULL;
290 varpool_first_unanalyzed_node = NULL;
293 /* Determine if variable DECL is needed. That is, visible to something
294 either outside this translation unit, something magic in the system
295 configury */
296 bool
297 decide_is_variable_needed (struct varpool_node *node, tree decl)
299 if (node->used_from_other_partition)
300 return true;
301 /* If the user told us it is used, then it must be so. */
302 if ((node->externally_visible && !DECL_COMDAT (decl))
303 || node->force_output)
304 return true;
306 /* ??? If the assembler name is set by hand, it is possible to assemble
307 the name later after finalizing the function and the fact is noticed
308 in assemble_name then. This is arguably a bug. */
309 if (DECL_ASSEMBLER_NAME_SET_P (decl)
310 && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl)))
311 return true;
313 /* Externally visible variables must be output. The exception is
314 COMDAT variables that must be output only when they are needed. */
315 if (TREE_PUBLIC (decl)
316 && !flag_whole_program
317 && !flag_lto
318 && !flag_whopr
319 && !DECL_COMDAT (decl)
320 && !DECL_EXTERNAL (decl))
321 return true;
323 /* When emulating tls, we actually see references to the control
324 variable, rather than the user-level variable. */
325 if (!targetm.have_tls
326 && TREE_CODE (decl) == VAR_DECL
327 && DECL_THREAD_LOCAL_P (decl))
329 tree control = emutls_decl (decl);
330 if (decide_is_variable_needed (varpool_node (control), control))
331 return true;
334 /* When not reordering top level variables, we have to assume that
335 we are going to keep everything. */
336 if (flag_toplevel_reorder)
337 return false;
339 /* We want to emit COMDAT variables only when absolutely necessary. */
340 if (DECL_COMDAT (decl))
341 return false;
342 return true;
345 /* Mark DECL as finalized. By finalizing the declaration, frontend instruct the
346 middle end to output the variable to asm file, if needed or externally
347 visible. */
348 void
349 varpool_finalize_decl (tree decl)
351 struct varpool_node *node = varpool_node (decl);
353 /* The first declaration of a variable that comes through this function
354 decides whether it is global (in C, has external linkage)
355 or local (in C, has internal linkage). So do nothing more
356 if this function has already run. */
357 if (node->finalized)
359 if (cgraph_global_info_ready)
360 varpool_assemble_pending_decls ();
361 return;
363 if (node->needed)
364 varpool_enqueue_needed_node (node);
365 node->finalized = true;
367 if (decide_is_variable_needed (node, decl))
368 varpool_mark_needed_node (node);
369 /* Since we reclaim unreachable nodes at the end of every language
370 level unit, we need to be conservative about possible entry points
371 there. */
372 else if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
373 varpool_mark_needed_node (node);
374 if (cgraph_global_info_ready)
375 varpool_assemble_pending_decls ();
378 /* Return variable availability. See cgraph.h for description of individual
379 return values. */
380 enum availability
381 cgraph_variable_initializer_availability (struct varpool_node *node)
383 gcc_assert (cgraph_function_flags_ready);
384 if (!node->finalized)
385 return AVAIL_NOT_AVAILABLE;
386 if (!TREE_PUBLIC (node->decl))
387 return AVAIL_AVAILABLE;
388 /* If the variable can be overwritten, return OVERWRITABLE. Takes
389 care of at least two notable extensions - the COMDAT variables
390 used to share template instantiations in C++. */
391 if (!(*targetm.binds_local_p) (node->decl) && !DECL_COMDAT (node->decl))
392 return AVAIL_OVERWRITABLE;
393 return AVAIL_AVAILABLE;
396 /* Walk the decls we marked as necessary and see if they reference new
397 variables or functions and add them into the worklists. */
398 bool
399 varpool_analyze_pending_decls (void)
401 bool changed = false;
402 timevar_push (TV_CGRAPH);
404 while (varpool_first_unanalyzed_node)
406 tree decl = varpool_first_unanalyzed_node->decl;
407 bool analyzed = varpool_first_unanalyzed_node->analyzed;
409 varpool_first_unanalyzed_node->analyzed = true;
411 varpool_first_unanalyzed_node = varpool_first_unanalyzed_node->next_needed;
413 /* When reading back varpool at LTO time, we re-construct the queue in order
414 to have "needed" list right by inserting all needed nodes into varpool.
415 We however don't want to re-analyze already analyzed nodes. */
416 if (!analyzed)
418 gcc_assert (!in_lto_p || cgraph_function_flags_ready);
419 /* Compute the alignment early so function body expanders are
420 already informed about increased alignment. */
421 align_variable (decl, 0);
423 if (DECL_INITIAL (decl))
424 record_references_in_initializer (decl, analyzed);
425 changed = true;
427 timevar_pop (TV_CGRAPH);
428 return changed;
431 /* Output one variable, if necessary. Return whether we output it. */
432 bool
433 varpool_assemble_decl (struct varpool_node *node)
435 tree decl = node->decl;
437 if (!TREE_ASM_WRITTEN (decl)
438 && !node->alias
439 && !node->in_other_partition
440 && !DECL_EXTERNAL (decl)
441 && (TREE_CODE (decl) != VAR_DECL || !DECL_HAS_VALUE_EXPR_P (decl)))
443 assemble_variable (decl, 0, 1, 0);
444 if (TREE_ASM_WRITTEN (decl))
446 struct varpool_node *alias;
448 node->next_needed = varpool_assembled_nodes_queue;
449 node->prev_needed = NULL;
450 if (varpool_assembled_nodes_queue)
451 varpool_assembled_nodes_queue->prev_needed = node;
452 varpool_assembled_nodes_queue = node;
453 node->finalized = 1;
455 /* Also emit any extra name aliases. */
456 for (alias = node->extra_name; alias; alias = alias->next)
458 /* Update linkage fields in case they've changed. */
459 DECL_WEAK (alias->decl) = DECL_WEAK (decl);
460 TREE_PUBLIC (alias->decl) = TREE_PUBLIC (decl);
461 DECL_VISIBILITY (alias->decl) = DECL_VISIBILITY (decl);
462 assemble_alias (alias->decl, DECL_ASSEMBLER_NAME (decl));
465 return true;
469 return false;
472 /* Optimization of function bodies might've rendered some variables as
473 unnecessary so we want to avoid these from being compiled.
475 This is done by pruning the queue and keeping only the variables that
476 really appear needed (ie they are either externally visible or referenced
477 by compiled function). Re-doing the reachability analysis on variables
478 brings back the remaining variables referenced by these. */
479 void
480 varpool_remove_unreferenced_decls (void)
482 struct varpool_node *next, *node = varpool_nodes_queue;
484 varpool_reset_queue ();
486 if (errorcount || sorrycount)
487 return;
489 while (node)
491 tree decl = node->decl;
492 next = node->next_needed;
493 node->needed = 0;
495 if (node->finalized
496 && (decide_is_variable_needed (node, decl)
497 /* ??? Cgraph does not yet rule the world with an iron hand,
498 and does not control the emission of debug information.
499 After a variable has its DECL_RTL set, we must assume that
500 it may be referenced by the debug information, and we can
501 no longer elide it. */
502 || DECL_RTL_SET_P (decl)))
503 varpool_mark_needed_node (node);
505 node = next;
507 /* Make sure we mark alias targets as used targets. */
508 finish_aliases_1 ();
509 varpool_analyze_pending_decls ();
512 /* Output all variables enqueued to be assembled. */
513 bool
514 varpool_assemble_pending_decls (void)
516 bool changed = false;
518 if (errorcount || sorrycount)
519 return false;
521 /* EH might mark decls as needed during expansion. This should be safe since
522 we don't create references to new function, but it should not be used
523 elsewhere. */
524 varpool_analyze_pending_decls ();
526 while (varpool_nodes_queue)
528 struct varpool_node *node = varpool_nodes_queue;
530 varpool_nodes_queue = varpool_nodes_queue->next_needed;
531 if (varpool_assemble_decl (node))
532 changed = true;
533 else
535 node->prev_needed = NULL;
536 node->next_needed = NULL;
539 /* varpool_nodes_queue is now empty, clear the pointer to the last element
540 in the queue. */
541 varpool_last_needed_node = NULL;
542 return changed;
545 /* Remove all elements from the queue so we can re-use it for debug output. */
546 void
547 varpool_empty_needed_queue (void)
549 /* EH might mark decls as needed during expansion. This should be safe since
550 we don't create references to new function, but it should not be used
551 elsewhere. */
552 varpool_analyze_pending_decls ();
554 while (varpool_nodes_queue)
556 struct varpool_node *node = varpool_nodes_queue;
557 varpool_nodes_queue = varpool_nodes_queue->next_needed;
558 node->next_needed = NULL;
559 node->prev_needed = NULL;
561 /* varpool_nodes_queue is now empty, clear the pointer to the last element
562 in the queue. */
563 varpool_last_needed_node = NULL;
566 /* Create a new global variable of type TYPE. */
567 tree
568 add_new_static_var (tree type)
570 tree new_decl;
571 struct varpool_node *new_node;
573 new_decl = create_tmp_var (type, NULL);
574 DECL_NAME (new_decl) = create_tmp_var_name (NULL);
575 TREE_READONLY (new_decl) = 0;
576 TREE_STATIC (new_decl) = 1;
577 TREE_USED (new_decl) = 1;
578 DECL_CONTEXT (new_decl) = NULL_TREE;
579 DECL_ABSTRACT (new_decl) = 0;
580 lang_hooks.dup_lang_specific_decl (new_decl);
581 create_var_ann (new_decl);
582 new_node = varpool_node (new_decl);
583 varpool_mark_needed_node (new_node);
584 add_referenced_var (new_decl);
585 varpool_finalize_decl (new_decl);
587 return new_node->decl;
590 /* Attempt to mark ALIAS as an alias to DECL. Return TRUE if successful.
591 Extra name aliases are output whenever DECL is output. */
593 bool
594 varpool_extra_name_alias (tree alias, tree decl)
596 struct varpool_node key, *alias_node, *decl_node, **slot;
598 #ifndef ASM_OUTPUT_DEF
599 /* If aliases aren't supported by the assembler, fail. */
600 return false;
601 #endif
603 gcc_assert (TREE_CODE (decl) == VAR_DECL);
604 gcc_assert (TREE_CODE (alias) == VAR_DECL);
605 /* Make sure the hash table has been created. */
606 decl_node = varpool_node (decl);
608 key.decl = alias;
610 slot = (struct varpool_node **) htab_find_slot (varpool_hash, &key, INSERT);
612 /* If the varpool_node has been already created, fail. */
613 if (*slot)
614 return false;
616 alias_node = GGC_CNEW (struct varpool_node);
617 alias_node->decl = alias;
618 alias_node->alias = 1;
619 alias_node->extra_name = decl_node;
620 alias_node->next = decl_node->extra_name;
621 if (decl_node->extra_name)
622 decl_node->extra_name->prev = alias_node;
623 decl_node->extra_name = alias_node;
624 *slot = alias_node;
625 return true;
628 #include "gt-varpool.h"