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
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
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/>. */
24 #include "coretypes.h"
28 #include "langhooks.h"
29 #include "diagnostic-core.h"
37 #include "tree-flow.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
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
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
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. */
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. */
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. */
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 (TREE_CODE (decl) == VAR_DECL
115 && (TREE_STATIC (decl) || DECL_EXTERNAL (decl)));
120 slot = (struct varpool_node **)
121 htab_find_slot (varpool_hash, &key, NO_INSERT);
127 /* Return varpool node assigned to DECL. Create new one when needed. */
128 struct varpool_node *
129 varpool_node (tree decl)
131 struct varpool_node key, *node, **slot;
133 gcc_assert (TREE_CODE (decl) == VAR_DECL
134 && (TREE_STATIC (decl) || DECL_EXTERNAL (decl)));
137 varpool_hash = htab_create_ggc (10, hash_varpool_node,
138 eq_varpool_node, NULL);
140 slot = (struct varpool_node **)
141 htab_find_slot (varpool_hash, &key, INSERT);
144 node = ggc_alloc_cleared_varpool_node ();
146 node->order = cgraph_order++;
147 node->next = varpool_nodes;
148 ipa_empty_ref_list (&node->ref_list);
150 varpool_nodes->prev = node;
151 varpool_nodes = node;
156 /* Remove node from the varpool. */
158 varpool_remove_node (struct varpool_node *node)
161 slot = htab_find_slot (varpool_hash, node, NO_INSERT);
162 gcc_assert (*slot == node);
163 htab_clear_slot (varpool_hash, slot);
164 gcc_assert (!varpool_assembled_nodes_queue);
166 while (node->extra_name)
167 varpool_remove_node (node->extra_name);
169 node->next->prev = node->prev;
171 node->prev->next = node->next;
174 if (node->alias && node->extra_name)
176 gcc_assert (node->extra_name->extra_name == node);
177 node->extra_name->extra_name = node->next;
181 gcc_assert (varpool_nodes == node);
182 varpool_nodes = node->next;
185 if (varpool_first_unanalyzed_node == node)
186 varpool_first_unanalyzed_node = node->next_needed;
187 if (node->next_needed)
188 node->next_needed->prev_needed = node->prev_needed;
189 else if (node->prev_needed)
191 gcc_assert (varpool_last_needed_node);
192 varpool_last_needed_node = node->prev_needed;
194 if (node->prev_needed)
195 node->prev_needed->next_needed = node->next_needed;
196 else if (node->next_needed)
198 gcc_assert (varpool_nodes_queue == node);
199 varpool_nodes_queue = node->next_needed;
201 if (node->same_comdat_group)
203 struct varpool_node *prev;
204 for (prev = node->same_comdat_group;
205 prev->same_comdat_group != node;
206 prev = prev->same_comdat_group)
208 if (node->same_comdat_group == prev)
209 prev->same_comdat_group = NULL;
211 prev->same_comdat_group = node->same_comdat_group;
212 node->same_comdat_group = NULL;
214 ipa_remove_all_references (&node->ref_list);
215 ipa_remove_all_refering (&node->ref_list);
219 /* Dump given cgraph node. */
221 dump_varpool_node (FILE *f, struct varpool_node *node)
223 fprintf (f, "%s:", varpool_node_name (node));
224 fprintf (f, " availability:%s",
225 cgraph_function_flags_ready
226 ? cgraph_availability_names[cgraph_variable_initializer_availability (node)]
228 if (DECL_ASSEMBLER_NAME_SET_P (node->decl))
229 fprintf (f, " (asm: %s)", IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (node->decl)));
230 if (DECL_INITIAL (node->decl))
231 fprintf (f, " initialized");
232 if (TREE_ASM_WRITTEN (node->decl))
233 fprintf (f, " (asm written)");
235 fprintf (f, " needed");
237 fprintf (f, " analyzed");
239 fprintf (f, " finalized");
241 fprintf (f, " output");
242 if (node->externally_visible)
243 fprintf (f, " externally_visible");
244 if (node->in_other_partition)
245 fprintf (f, " in_other_partition");
246 else if (node->used_from_other_partition)
247 fprintf (f, " used_from_other_partition");
249 fprintf (f, " References: ");
250 ipa_dump_references (f, &node->ref_list);
251 fprintf (f, " Refering this var: ");
252 ipa_dump_refering (f, &node->ref_list);
255 /* Dump the variable pool. */
257 dump_varpool (FILE *f)
259 struct varpool_node *node;
261 fprintf (f, "variable pool:\n\n");
262 for (node = varpool_nodes; node; node = node->next)
263 dump_varpool_node (f, node);
266 /* Dump the variable pool to stderr. */
271 dump_varpool (stderr);
274 /* Given an assembler name, lookup node. */
275 struct varpool_node *
276 varpool_node_for_asm (tree asmname)
278 struct varpool_node *node;
280 for (node = varpool_nodes; node ; node = node->next)
281 if (decl_assembler_name_equal (node->decl, asmname))
287 /* Helper function for finalization code - add node into lists so it will
288 be analyzed and compiled. */
290 varpool_enqueue_needed_node (struct varpool_node *node)
292 if (varpool_last_needed_node)
294 varpool_last_needed_node->next_needed = node;
295 node->prev_needed = varpool_last_needed_node;
297 varpool_last_needed_node = node;
298 node->next_needed = NULL;
299 if (!varpool_nodes_queue)
300 varpool_nodes_queue = node;
301 if (!varpool_first_unanalyzed_node)
302 varpool_first_unanalyzed_node = node;
303 notice_global_symbol (node->decl);
306 /* Notify finalize_compilation_unit that given node is reachable
309 varpool_mark_needed_node (struct varpool_node *node)
311 if (node->alias && node->extra_name)
312 node = node->extra_name;
313 if (!node->needed && node->finalized
314 && !TREE_ASM_WRITTEN (node->decl))
315 varpool_enqueue_needed_node (node);
319 /* Reset the queue of needed nodes. */
321 varpool_reset_queue (void)
323 varpool_last_needed_node = NULL;
324 varpool_nodes_queue = NULL;
325 varpool_first_unanalyzed_node = NULL;
328 /* Determine if variable DECL is needed. That is, visible to something
329 either outside this translation unit, something magic in the system
332 decide_is_variable_needed (struct varpool_node *node, tree decl)
334 if (node->used_from_other_partition)
336 /* If the user told us it is used, then it must be so. */
337 if ((node->externally_visible && !DECL_COMDAT (decl))
338 || node->force_output)
341 /* Externally visible variables must be output. The exception is
342 COMDAT variables that must be output only when they are needed. */
343 if (TREE_PUBLIC (decl)
344 && !flag_whole_program
347 && !DECL_COMDAT (decl)
348 && !DECL_EXTERNAL (decl))
351 /* When not reordering top level variables, we have to assume that
352 we are going to keep everything. */
353 if (flag_toplevel_reorder)
356 /* We want to emit COMDAT variables only when absolutely necessary. */
357 if (DECL_COMDAT (decl))
362 /* Return if NODE is constant and its initial value is known (so we can do
363 constant folding). The decision depends on whole program decisions
364 and can not be recomputed at ltrans stage for variables from other
365 partitions. For this reason the new value should be always combined
366 with the previous knowledge. */
369 varpool_decide_const_value_known (struct varpool_node *node)
371 tree decl = node->decl;
373 gcc_assert (TREE_STATIC (decl) || DECL_EXTERNAL (decl));
374 gcc_assert (TREE_CODE (decl) == VAR_DECL);
375 if (!TREE_READONLY (decl))
377 /* Variables declared 'const' without an initializer
378 have zero as the initializer if they may not be
379 overridden at link or run time. */
380 if (!DECL_INITIAL (decl)
381 && (DECL_EXTERNAL (decl)
382 || DECL_REPLACEABLE_P (decl)))
385 /* Variables declared `const' with an initializer are considered
386 to not be overwritable with different initializer by default.
388 ??? Previously we behaved so for scalar variables but not for array
393 /* Mark DECL as finalized. By finalizing the declaration, frontend instruct the
394 middle end to output the variable to asm file, if needed or externally
397 varpool_finalize_decl (tree decl)
399 struct varpool_node *node = varpool_node (decl);
401 gcc_assert (TREE_STATIC (decl));
403 /* The first declaration of a variable that comes through this function
404 decides whether it is global (in C, has external linkage)
405 or local (in C, has internal linkage). So do nothing more
406 if this function has already run. */
409 if (cgraph_global_info_ready)
410 varpool_assemble_pending_decls ();
414 varpool_enqueue_needed_node (node);
415 node->finalized = true;
416 if (TREE_THIS_VOLATILE (decl) || DECL_PRESERVE_P (decl))
417 node->force_output = true;
419 if (decide_is_variable_needed (node, decl))
420 varpool_mark_needed_node (node);
421 /* Since we reclaim unreachable nodes at the end of every language
422 level unit, we need to be conservative about possible entry points
424 else if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
425 varpool_mark_needed_node (node);
426 if (cgraph_global_info_ready)
427 varpool_assemble_pending_decls ();
430 /* Return variable availability. See cgraph.h for description of individual
433 cgraph_variable_initializer_availability (struct varpool_node *node)
435 gcc_assert (cgraph_function_flags_ready);
436 if (!node->finalized)
437 return AVAIL_NOT_AVAILABLE;
438 if (!TREE_PUBLIC (node->decl))
439 return AVAIL_AVAILABLE;
440 /* If the variable can be overwritten, return OVERWRITABLE. Takes
441 care of at least two notable extensions - the COMDAT variables
442 used to share template instantiations in C++. */
443 if (!(*targetm.binds_local_p) (node->decl) && !DECL_COMDAT (node->decl))
444 return AVAIL_OVERWRITABLE;
445 return AVAIL_AVAILABLE;
448 /* Walk the decls we marked as necessary and see if they reference new
449 variables or functions and add them into the worklists. */
451 varpool_analyze_pending_decls (void)
453 bool changed = false;
455 timevar_push (TV_VARPOOL);
456 while (varpool_first_unanalyzed_node)
458 struct varpool_node *node = varpool_first_unanalyzed_node, *next;
459 tree decl = node->decl;
460 bool analyzed = node->analyzed;
462 varpool_first_unanalyzed_node->analyzed = true;
464 varpool_first_unanalyzed_node = varpool_first_unanalyzed_node->next_needed;
466 /* When reading back varpool at LTO time, we re-construct the queue in order
467 to have "needed" list right by inserting all needed nodes into varpool.
468 We however don't want to re-analyze already analyzed nodes. */
471 gcc_assert (!in_lto_p || cgraph_function_flags_ready);
472 /* Compute the alignment early so function body expanders are
473 already informed about increased alignment. */
474 align_variable (decl, 0);
476 if (DECL_INITIAL (decl))
477 record_references_in_initializer (decl, analyzed);
478 if (node->same_comdat_group)
480 for (next = node->same_comdat_group;
482 next = next->same_comdat_group)
483 varpool_mark_needed_node (next);
487 timevar_pop (TV_VARPOOL);
491 /* Output one variable, if necessary. Return whether we output it. */
493 varpool_assemble_decl (struct varpool_node *node)
495 tree decl = node->decl;
497 if (!TREE_ASM_WRITTEN (decl)
499 && !node->in_other_partition
500 && !DECL_EXTERNAL (decl)
501 && (TREE_CODE (decl) != VAR_DECL || !DECL_HAS_VALUE_EXPR_P (decl)))
503 assemble_variable (decl, 0, 1, 0);
504 if (TREE_ASM_WRITTEN (decl))
506 struct varpool_node *alias;
508 node->next_needed = varpool_assembled_nodes_queue;
509 node->prev_needed = NULL;
510 if (varpool_assembled_nodes_queue)
511 varpool_assembled_nodes_queue->prev_needed = node;
512 varpool_assembled_nodes_queue = node;
515 /* Also emit any extra name aliases. */
516 for (alias = node->extra_name; alias; alias = alias->next)
518 /* Update linkage fields in case they've changed. */
519 DECL_WEAK (alias->decl) = DECL_WEAK (decl);
520 TREE_PUBLIC (alias->decl) = TREE_PUBLIC (decl);
521 DECL_VISIBILITY (alias->decl) = DECL_VISIBILITY (decl);
522 assemble_alias (alias->decl, DECL_ASSEMBLER_NAME (decl));
532 /* Optimization of function bodies might've rendered some variables as
533 unnecessary so we want to avoid these from being compiled.
535 This is done by pruning the queue and keeping only the variables that
536 really appear needed (ie they are either externally visible or referenced
537 by compiled function). Re-doing the reachability analysis on variables
538 brings back the remaining variables referenced by these. */
540 varpool_remove_unreferenced_decls (void)
542 struct varpool_node *next, *node = varpool_nodes_queue;
544 varpool_reset_queue ();
551 tree decl = node->decl;
552 next = node->next_needed;
556 && (decide_is_variable_needed (node, decl)
557 /* ??? Cgraph does not yet rule the world with an iron hand,
558 and does not control the emission of debug information.
559 After a variable has its DECL_RTL set, we must assume that
560 it may be referenced by the debug information, and we can
561 no longer elide it. */
562 || DECL_RTL_SET_P (decl)))
563 varpool_mark_needed_node (node);
567 /* Make sure we mark alias targets as used targets. */
569 varpool_analyze_pending_decls ();
572 /* Output all variables enqueued to be assembled. */
574 varpool_assemble_pending_decls (void)
576 bool changed = false;
581 timevar_push (TV_VAROUT);
582 /* EH might mark decls as needed during expansion. This should be safe since
583 we don't create references to new function, but it should not be used
585 varpool_analyze_pending_decls ();
587 while (varpool_nodes_queue)
589 struct varpool_node *node = varpool_nodes_queue;
591 varpool_nodes_queue = varpool_nodes_queue->next_needed;
592 if (varpool_assemble_decl (node))
596 node->prev_needed = NULL;
597 node->next_needed = NULL;
600 /* varpool_nodes_queue is now empty, clear the pointer to the last element
602 varpool_last_needed_node = NULL;
603 timevar_pop (TV_VAROUT);
607 /* Remove all elements from the queue so we can re-use it for debug output. */
609 varpool_empty_needed_queue (void)
611 /* EH might mark decls as needed during expansion. This should be safe since
612 we don't create references to new function, but it should not be used
614 varpool_analyze_pending_decls ();
616 while (varpool_nodes_queue)
618 struct varpool_node *node = varpool_nodes_queue;
619 varpool_nodes_queue = varpool_nodes_queue->next_needed;
620 node->next_needed = NULL;
621 node->prev_needed = NULL;
623 /* varpool_nodes_queue is now empty, clear the pointer to the last element
625 varpool_last_needed_node = NULL;
628 /* Create a new global variable of type TYPE. */
630 add_new_static_var (tree type)
633 struct varpool_node *new_node;
635 new_decl = create_tmp_var (type, NULL);
636 DECL_NAME (new_decl) = create_tmp_var_name (NULL);
637 TREE_READONLY (new_decl) = 0;
638 TREE_STATIC (new_decl) = 1;
639 TREE_USED (new_decl) = 1;
640 DECL_CONTEXT (new_decl) = NULL_TREE;
641 DECL_ABSTRACT (new_decl) = 0;
642 lang_hooks.dup_lang_specific_decl (new_decl);
643 create_var_ann (new_decl);
644 new_node = varpool_node (new_decl);
645 varpool_mark_needed_node (new_node);
646 add_referenced_var (new_decl);
647 varpool_finalize_decl (new_decl);
649 return new_node->decl;
652 /* Attempt to mark ALIAS as an alias to DECL. Return TRUE if successful.
653 Extra name aliases are output whenever DECL is output. */
656 varpool_extra_name_alias (tree alias, tree decl)
658 struct varpool_node key, *alias_node, *decl_node, **slot;
660 #ifndef ASM_OUTPUT_DEF
661 /* If aliases aren't supported by the assembler, fail. */
665 gcc_assert (TREE_CODE (decl) == VAR_DECL);
666 gcc_assert (TREE_CODE (alias) == VAR_DECL);
667 /* Make sure the hash table has been created. */
668 decl_node = varpool_node (decl);
672 slot = (struct varpool_node **) htab_find_slot (varpool_hash, &key, INSERT);
674 /* If the varpool_node has been already created, fail. */
678 alias_node = ggc_alloc_cleared_varpool_node ();
679 alias_node->decl = alias;
680 alias_node->alias = 1;
681 alias_node->extra_name = decl_node;
682 alias_node->next = decl_node->extra_name;
683 ipa_empty_ref_list (&alias_node->ref_list);
684 if (decl_node->extra_name)
685 decl_node->extra_name->prev = alias_node;
686 decl_node->extra_name = alias_node;
691 #include "gt-varpool.h"