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 (const_tree decl)
112 struct varpool_node key, **slot;
114 gcc_assert (TREE_CODE (decl) == VAR_DECL
115 && (TREE_STATIC (decl) || DECL_EXTERNAL (decl)));
119 key.decl = CONST_CAST2 (tree, const_tree, 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
346 && !DECL_COMDAT (decl)
347 && !DECL_EXTERNAL (decl))
350 /* When not reordering top level variables, we have to assume that
351 we are going to keep everything. */
352 if (flag_toplevel_reorder)
355 /* We want to emit COMDAT variables only when absolutely necessary. */
356 if (DECL_COMDAT (decl))
361 /* Return if DECL is constant and its initial value is known (so we can do
362 constant folding using DECL_INITIAL (decl)). */
365 const_value_known_p (tree decl)
367 if (TREE_CODE (decl) != VAR_DECL
368 &&TREE_CODE (decl) != CONST_DECL)
371 if (TREE_CODE (decl) == CONST_DECL
372 || DECL_IN_CONSTANT_POOL (decl))
375 gcc_assert (TREE_CODE (decl) == VAR_DECL);
377 if (!TREE_READONLY (decl))
380 /* Gimplifier takes away constructors of local vars */
381 if (!TREE_STATIC (decl) && !DECL_EXTERNAL (decl))
382 return DECL_INITIAL (decl) != NULL;
384 gcc_assert (TREE_STATIC (decl) || DECL_EXTERNAL (decl));
386 /* Variables declared 'const' without an initializer
387 have zero as the initializer if they may not be
388 overridden at link or run time. */
389 if (!DECL_INITIAL (decl)
390 && (DECL_EXTERNAL (decl)
391 || decl_replaceable_p (decl)))
394 /* Variables declared `const' with an initializer are considered
395 to not be overwritable with different initializer by default.
397 ??? Previously we behaved so for scalar variables but not for array
402 /* Mark DECL as finalized. By finalizing the declaration, frontend instruct the
403 middle end to output the variable to asm file, if needed or externally
406 varpool_finalize_decl (tree decl)
408 struct varpool_node *node = varpool_node (decl);
410 gcc_assert (TREE_STATIC (decl));
412 /* The first declaration of a variable that comes through this function
413 decides whether it is global (in C, has external linkage)
414 or local (in C, has internal linkage). So do nothing more
415 if this function has already run. */
418 if (cgraph_global_info_ready)
419 varpool_assemble_pending_decls ();
423 varpool_enqueue_needed_node (node);
424 node->finalized = true;
425 if (TREE_THIS_VOLATILE (decl) || DECL_PRESERVE_P (decl))
426 node->force_output = true;
428 if (decide_is_variable_needed (node, decl))
429 varpool_mark_needed_node (node);
430 /* Since we reclaim unreachable nodes at the end of every language
431 level unit, we need to be conservative about possible entry points
433 else if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
434 varpool_mark_needed_node (node);
435 if (cgraph_global_info_ready)
436 varpool_assemble_pending_decls ();
439 /* Return variable availability. See cgraph.h for description of individual
442 cgraph_variable_initializer_availability (struct varpool_node *node)
444 gcc_assert (cgraph_function_flags_ready);
445 if (!node->finalized)
446 return AVAIL_NOT_AVAILABLE;
447 if (!TREE_PUBLIC (node->decl))
448 return AVAIL_AVAILABLE;
449 /* If the variable can be overwritten, return OVERWRITABLE. Takes
450 care of at least two notable extensions - the COMDAT variables
451 used to share template instantiations in C++. */
452 if (!decl_replaceable_p (node->decl))
453 return AVAIL_OVERWRITABLE;
454 return AVAIL_AVAILABLE;
457 /* Walk the decls we marked as necessary and see if they reference new
458 variables or functions and add them into the worklists. */
460 varpool_analyze_pending_decls (void)
462 bool changed = false;
464 timevar_push (TV_VARPOOL);
465 while (varpool_first_unanalyzed_node)
467 struct varpool_node *node = varpool_first_unanalyzed_node, *next;
468 tree decl = node->decl;
469 bool analyzed = node->analyzed;
471 varpool_first_unanalyzed_node->analyzed = true;
473 varpool_first_unanalyzed_node = varpool_first_unanalyzed_node->next_needed;
475 /* When reading back varpool at LTO time, we re-construct the queue in order
476 to have "needed" list right by inserting all needed nodes into varpool.
477 We however don't want to re-analyze already analyzed nodes. */
480 gcc_assert (!in_lto_p || cgraph_function_flags_ready);
481 /* Compute the alignment early so function body expanders are
482 already informed about increased alignment. */
483 align_variable (decl, 0);
485 if (DECL_INITIAL (decl))
486 record_references_in_initializer (decl, analyzed);
487 if (node->same_comdat_group)
489 for (next = node->same_comdat_group;
491 next = next->same_comdat_group)
492 varpool_mark_needed_node (next);
496 timevar_pop (TV_VARPOOL);
500 /* Output one variable, if necessary. Return whether we output it. */
502 varpool_assemble_decl (struct varpool_node *node)
504 tree decl = node->decl;
506 if (!TREE_ASM_WRITTEN (decl)
508 && !node->in_other_partition
509 && !DECL_EXTERNAL (decl)
510 && (TREE_CODE (decl) != VAR_DECL || !DECL_HAS_VALUE_EXPR_P (decl)))
512 assemble_variable (decl, 0, 1, 0);
513 if (TREE_ASM_WRITTEN (decl))
515 struct varpool_node *alias;
517 node->next_needed = varpool_assembled_nodes_queue;
518 node->prev_needed = NULL;
519 if (varpool_assembled_nodes_queue)
520 varpool_assembled_nodes_queue->prev_needed = node;
521 varpool_assembled_nodes_queue = node;
524 /* Also emit any extra name aliases. */
525 for (alias = node->extra_name; alias; alias = alias->next)
527 /* Update linkage fields in case they've changed. */
528 DECL_WEAK (alias->decl) = DECL_WEAK (decl);
529 TREE_PUBLIC (alias->decl) = TREE_PUBLIC (decl);
530 DECL_VISIBILITY (alias->decl) = DECL_VISIBILITY (decl);
531 assemble_alias (alias->decl, DECL_ASSEMBLER_NAME (decl));
541 /* Optimization of function bodies might've rendered some variables as
542 unnecessary so we want to avoid these from being compiled.
544 This is done by pruning the queue and keeping only the variables that
545 really appear needed (ie they are either externally visible or referenced
546 by compiled function). Re-doing the reachability analysis on variables
547 brings back the remaining variables referenced by these. */
549 varpool_remove_unreferenced_decls (void)
551 struct varpool_node *next, *node = varpool_nodes_queue;
553 varpool_reset_queue ();
560 tree decl = node->decl;
561 next = node->next_needed;
565 && (decide_is_variable_needed (node, decl)
566 /* ??? Cgraph does not yet rule the world with an iron hand,
567 and does not control the emission of debug information.
568 After a variable has its DECL_RTL set, we must assume that
569 it may be referenced by the debug information, and we can
570 no longer elide it. */
571 || DECL_RTL_SET_P (decl)))
572 varpool_mark_needed_node (node);
576 /* Make sure we mark alias targets as used targets. */
578 varpool_analyze_pending_decls ();
581 /* Output all variables enqueued to be assembled. */
583 varpool_assemble_pending_decls (void)
585 bool changed = false;
590 timevar_push (TV_VAROUT);
591 /* EH might mark decls as needed during expansion. This should be safe since
592 we don't create references to new function, but it should not be used
594 varpool_analyze_pending_decls ();
596 while (varpool_nodes_queue)
598 struct varpool_node *node = varpool_nodes_queue;
600 varpool_nodes_queue = varpool_nodes_queue->next_needed;
601 if (varpool_assemble_decl (node))
605 node->prev_needed = NULL;
606 node->next_needed = NULL;
609 /* varpool_nodes_queue is now empty, clear the pointer to the last element
611 varpool_last_needed_node = NULL;
612 timevar_pop (TV_VAROUT);
616 /* Remove all elements from the queue so we can re-use it for debug output. */
618 varpool_empty_needed_queue (void)
620 /* EH might mark decls as needed during expansion. This should be safe since
621 we don't create references to new function, but it should not be used
623 varpool_analyze_pending_decls ();
625 while (varpool_nodes_queue)
627 struct varpool_node *node = varpool_nodes_queue;
628 varpool_nodes_queue = varpool_nodes_queue->next_needed;
629 node->next_needed = NULL;
630 node->prev_needed = NULL;
632 /* varpool_nodes_queue is now empty, clear the pointer to the last element
634 varpool_last_needed_node = NULL;
637 /* Create a new global variable of type TYPE. */
639 add_new_static_var (tree type)
642 struct varpool_node *new_node;
644 new_decl = create_tmp_var (type, NULL);
645 DECL_NAME (new_decl) = create_tmp_var_name (NULL);
646 TREE_READONLY (new_decl) = 0;
647 TREE_STATIC (new_decl) = 1;
648 TREE_USED (new_decl) = 1;
649 DECL_CONTEXT (new_decl) = NULL_TREE;
650 DECL_ABSTRACT (new_decl) = 0;
651 lang_hooks.dup_lang_specific_decl (new_decl);
652 create_var_ann (new_decl);
653 new_node = varpool_node (new_decl);
654 varpool_mark_needed_node (new_node);
655 add_referenced_var (new_decl);
656 varpool_finalize_decl (new_decl);
658 return new_node->decl;
661 /* Attempt to mark ALIAS as an alias to DECL. Return TRUE if successful.
662 Extra name aliases are output whenever DECL is output. */
664 struct varpool_node *
665 varpool_extra_name_alias (tree alias, tree decl)
667 struct varpool_node key, *alias_node, *decl_node, **slot;
669 #ifndef ASM_OUTPUT_DEF
670 /* If aliases aren't supported by the assembler, fail. */
674 gcc_assert (TREE_CODE (decl) == VAR_DECL);
675 gcc_assert (TREE_CODE (alias) == VAR_DECL);
676 /* Make sure the hash table has been created. */
677 decl_node = varpool_node (decl);
681 slot = (struct varpool_node **) htab_find_slot (varpool_hash, &key, INSERT);
683 /* If the varpool_node has been already created, fail. */
687 alias_node = ggc_alloc_cleared_varpool_node ();
688 alias_node->decl = alias;
689 alias_node->alias = 1;
690 alias_node->extra_name = decl_node;
691 alias_node->next = decl_node->extra_name;
692 ipa_empty_ref_list (&alias_node->ref_list);
693 if (decl_node->extra_name)
694 decl_node->extra_name->prev = alias_node;
695 decl_node->extra_name = alias_node;
700 /* Return true when NODE is known to be used from other (non-LTO) object file.
701 Known only when doing LTO via linker plugin. */
704 varpool_used_from_object_file_p (struct varpool_node *node)
706 struct varpool_node *alias;
708 if (!TREE_PUBLIC (node->decl))
710 if (resolution_used_from_other_file_p (node->resolution))
712 for (alias = node->extra_name; alias; alias = alias->next)
713 if (TREE_PUBLIC (alias->decl)
714 && resolution_used_from_other_file_p (alias->resolution))
719 #include "gt-varpool.h"