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 DECL is constant and its initial value is known (so we can do
363 constant folding using DECL_INITIAL (decl)). */
366 const_value_known_p (tree decl)
368 struct varpool_node *vnode;
370 if (TREE_CODE (decl) == PARM_DECL
371 || TREE_CODE (decl) == RESULT_DECL)
374 if (TREE_CODE (decl) == CONST_DECL
375 || DECL_IN_CONSTANT_POOL (decl))
378 gcc_assert (TREE_CODE (decl) == VAR_DECL);
380 if (!TREE_READONLY (decl))
383 /* Gimplifier takes away constructors of local vars */
384 if (!TREE_STATIC (decl) && !DECL_EXTERNAL (decl))
385 return DECL_INITIAL (decl) != NULL;
387 gcc_assert (TREE_STATIC (decl) || DECL_EXTERNAL (decl));
389 /* In WHOPR mode we can put variable into one partition
390 and make it external in the other partition. In this
391 case we still know the value, but it can't be determined
392 from DECL flags. For this reason we keep const_value_known
393 flag in varpool nodes. */
394 if ((vnode = varpool_get_node (decl))
395 && vnode->const_value_known)
398 /* Variables declared 'const' without an initializer
399 have zero as the initializer if they may not be
400 overridden at link or run time. */
401 if (!DECL_INITIAL (decl)
402 && (DECL_EXTERNAL (decl)
403 || DECL_REPLACEABLE_P (decl)))
406 /* Variables declared `const' with an initializer are considered
407 to not be overwritable with different initializer by default.
409 ??? Previously we behaved so for scalar variables but not for array
414 /* Mark DECL as finalized. By finalizing the declaration, frontend instruct the
415 middle end to output the variable to asm file, if needed or externally
418 varpool_finalize_decl (tree decl)
420 struct varpool_node *node = varpool_node (decl);
422 gcc_assert (TREE_STATIC (decl));
424 /* The first declaration of a variable that comes through this function
425 decides whether it is global (in C, has external linkage)
426 or local (in C, has internal linkage). So do nothing more
427 if this function has already run. */
430 if (cgraph_global_info_ready)
431 varpool_assemble_pending_decls ();
435 varpool_enqueue_needed_node (node);
436 node->finalized = true;
437 if (TREE_THIS_VOLATILE (decl) || DECL_PRESERVE_P (decl))
438 node->force_output = true;
440 if (decide_is_variable_needed (node, decl))
441 varpool_mark_needed_node (node);
442 /* Since we reclaim unreachable nodes at the end of every language
443 level unit, we need to be conservative about possible entry points
445 else if (TREE_PUBLIC (decl) && !DECL_COMDAT (decl) && !DECL_EXTERNAL (decl))
446 varpool_mark_needed_node (node);
447 node->const_value_known |= const_value_known_p (node->decl);
448 if (cgraph_global_info_ready)
449 varpool_assemble_pending_decls ();
452 /* Return variable availability. See cgraph.h for description of individual
455 cgraph_variable_initializer_availability (struct varpool_node *node)
457 gcc_assert (cgraph_function_flags_ready);
458 if (!node->finalized)
459 return AVAIL_NOT_AVAILABLE;
460 if (!TREE_PUBLIC (node->decl))
461 return AVAIL_AVAILABLE;
462 /* If the variable can be overwritten, return OVERWRITABLE. Takes
463 care of at least two notable extensions - the COMDAT variables
464 used to share template instantiations in C++. */
465 if (!(*targetm.binds_local_p) (node->decl) && !DECL_COMDAT (node->decl))
466 return AVAIL_OVERWRITABLE;
467 return AVAIL_AVAILABLE;
470 /* Walk the decls we marked as necessary and see if they reference new
471 variables or functions and add them into the worklists. */
473 varpool_analyze_pending_decls (void)
475 bool changed = false;
477 timevar_push (TV_VARPOOL);
478 while (varpool_first_unanalyzed_node)
480 struct varpool_node *node = varpool_first_unanalyzed_node, *next;
481 tree decl = node->decl;
482 bool analyzed = node->analyzed;
484 varpool_first_unanalyzed_node->analyzed = true;
486 varpool_first_unanalyzed_node = varpool_first_unanalyzed_node->next_needed;
488 /* When reading back varpool at LTO time, we re-construct the queue in order
489 to have "needed" list right by inserting all needed nodes into varpool.
490 We however don't want to re-analyze already analyzed nodes. */
493 gcc_assert (!in_lto_p || cgraph_function_flags_ready);
494 /* Compute the alignment early so function body expanders are
495 already informed about increased alignment. */
496 align_variable (decl, 0);
498 if (DECL_INITIAL (decl))
499 record_references_in_initializer (decl, analyzed);
500 if (node->same_comdat_group)
502 for (next = node->same_comdat_group;
504 next = next->same_comdat_group)
505 varpool_mark_needed_node (next);
509 timevar_pop (TV_VARPOOL);
513 /* Output one variable, if necessary. Return whether we output it. */
515 varpool_assemble_decl (struct varpool_node *node)
517 tree decl = node->decl;
519 if (!TREE_ASM_WRITTEN (decl)
521 && !node->in_other_partition
522 && !DECL_EXTERNAL (decl)
523 && (TREE_CODE (decl) != VAR_DECL || !DECL_HAS_VALUE_EXPR_P (decl)))
525 assemble_variable (decl, 0, 1, 0);
526 if (TREE_ASM_WRITTEN (decl))
528 struct varpool_node *alias;
530 node->next_needed = varpool_assembled_nodes_queue;
531 node->prev_needed = NULL;
532 if (varpool_assembled_nodes_queue)
533 varpool_assembled_nodes_queue->prev_needed = node;
534 varpool_assembled_nodes_queue = node;
537 /* Also emit any extra name aliases. */
538 for (alias = node->extra_name; alias; alias = alias->next)
540 /* Update linkage fields in case they've changed. */
541 DECL_WEAK (alias->decl) = DECL_WEAK (decl);
542 TREE_PUBLIC (alias->decl) = TREE_PUBLIC (decl);
543 DECL_VISIBILITY (alias->decl) = DECL_VISIBILITY (decl);
544 assemble_alias (alias->decl, DECL_ASSEMBLER_NAME (decl));
554 /* Optimization of function bodies might've rendered some variables as
555 unnecessary so we want to avoid these from being compiled.
557 This is done by pruning the queue and keeping only the variables that
558 really appear needed (ie they are either externally visible or referenced
559 by compiled function). Re-doing the reachability analysis on variables
560 brings back the remaining variables referenced by these. */
562 varpool_remove_unreferenced_decls (void)
564 struct varpool_node *next, *node = varpool_nodes_queue;
566 varpool_reset_queue ();
573 tree decl = node->decl;
574 next = node->next_needed;
578 && (decide_is_variable_needed (node, decl)
579 /* ??? Cgraph does not yet rule the world with an iron hand,
580 and does not control the emission of debug information.
581 After a variable has its DECL_RTL set, we must assume that
582 it may be referenced by the debug information, and we can
583 no longer elide it. */
584 || DECL_RTL_SET_P (decl)))
585 varpool_mark_needed_node (node);
589 /* Make sure we mark alias targets as used targets. */
591 varpool_analyze_pending_decls ();
594 /* Output all variables enqueued to be assembled. */
596 varpool_assemble_pending_decls (void)
598 bool changed = false;
603 timevar_push (TV_VAROUT);
604 /* EH might mark decls as needed during expansion. This should be safe since
605 we don't create references to new function, but it should not be used
607 varpool_analyze_pending_decls ();
609 while (varpool_nodes_queue)
611 struct varpool_node *node = varpool_nodes_queue;
613 varpool_nodes_queue = varpool_nodes_queue->next_needed;
614 if (varpool_assemble_decl (node))
618 node->prev_needed = NULL;
619 node->next_needed = NULL;
622 /* varpool_nodes_queue is now empty, clear the pointer to the last element
624 varpool_last_needed_node = NULL;
625 timevar_pop (TV_VAROUT);
629 /* Remove all elements from the queue so we can re-use it for debug output. */
631 varpool_empty_needed_queue (void)
633 /* EH might mark decls as needed during expansion. This should be safe since
634 we don't create references to new function, but it should not be used
636 varpool_analyze_pending_decls ();
638 while (varpool_nodes_queue)
640 struct varpool_node *node = varpool_nodes_queue;
641 varpool_nodes_queue = varpool_nodes_queue->next_needed;
642 node->next_needed = NULL;
643 node->prev_needed = NULL;
645 /* varpool_nodes_queue is now empty, clear the pointer to the last element
647 varpool_last_needed_node = NULL;
650 /* Create a new global variable of type TYPE. */
652 add_new_static_var (tree type)
655 struct varpool_node *new_node;
657 new_decl = create_tmp_var (type, NULL);
658 DECL_NAME (new_decl) = create_tmp_var_name (NULL);
659 TREE_READONLY (new_decl) = 0;
660 TREE_STATIC (new_decl) = 1;
661 TREE_USED (new_decl) = 1;
662 DECL_CONTEXT (new_decl) = NULL_TREE;
663 DECL_ABSTRACT (new_decl) = 0;
664 lang_hooks.dup_lang_specific_decl (new_decl);
665 create_var_ann (new_decl);
666 new_node = varpool_node (new_decl);
667 varpool_mark_needed_node (new_node);
668 add_referenced_var (new_decl);
669 varpool_finalize_decl (new_decl);
671 return new_node->decl;
674 /* Attempt to mark ALIAS as an alias to DECL. Return TRUE if successful.
675 Extra name aliases are output whenever DECL is output. */
678 varpool_extra_name_alias (tree alias, tree decl)
680 struct varpool_node key, *alias_node, *decl_node, **slot;
682 #ifndef ASM_OUTPUT_DEF
683 /* If aliases aren't supported by the assembler, fail. */
687 gcc_assert (TREE_CODE (decl) == VAR_DECL);
688 gcc_assert (TREE_CODE (alias) == VAR_DECL);
689 /* Make sure the hash table has been created. */
690 decl_node = varpool_node (decl);
694 slot = (struct varpool_node **) htab_find_slot (varpool_hash, &key, INSERT);
696 /* If the varpool_node has been already created, fail. */
700 alias_node = ggc_alloc_cleared_varpool_node ();
701 alias_node->decl = alias;
702 alias_node->alias = 1;
703 alias_node->extra_name = decl_node;
704 alias_node->next = decl_node->extra_name;
705 ipa_empty_ref_list (&alias_node->ref_list);
706 if (decl_node->extra_name)
707 decl_node->extra_name->prev = alias_node;
708 decl_node->extra_name = alias_node;
713 #include "gt-varpool.h"