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.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. Create new one when needed. */
109 struct varpool_node
*
110 varpool_node (tree decl
)
112 struct varpool_node key
, *node
, **slot
;
114 gcc_assert (DECL_P (decl
) && TREE_CODE (decl
) != FUNCTION_DECL
);
117 varpool_hash
= htab_create_ggc (10, hash_varpool_node
,
118 eq_varpool_node
, NULL
);
120 slot
= (struct varpool_node
**)
121 htab_find_slot (varpool_hash
, &key
, INSERT
);
124 node
= GGC_CNEW (struct varpool_node
);
126 node
->order
= cgraph_order
++;
127 node
->next
= varpool_nodes
;
128 varpool_nodes
= node
;
133 /* Dump given cgraph node. */
135 dump_varpool_node (FILE *f
, struct varpool_node
*node
)
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
)]
142 if (DECL_INITIAL (node
->decl
))
143 fprintf (f
, " initialized");
145 fprintf (f
, " needed");
147 fprintf (f
, " analyzed");
149 fprintf (f
, " finalized");
151 fprintf (f
, " output");
152 if (node
->externally_visible
)
153 fprintf (f
, " externally_visible");
157 /* Dump the variable pool. */
159 dump_varpool (FILE *f
)
161 struct varpool_node
*node
;
163 fprintf (f
, "variable pool:\n\n");
164 for (node
= varpool_nodes
; node
; node
= node
->next
)
165 dump_varpool_node (f
, node
);
168 /* Dump the variable pool to stderr. */
173 dump_varpool (stderr
);
176 /* Given an assembler name, lookup node. */
177 struct varpool_node
*
178 varpool_node_for_asm (tree asmname
)
180 struct varpool_node
*node
;
182 for (node
= varpool_nodes
; node
; node
= node
->next
)
183 if (decl_assembler_name_equal (node
->decl
, asmname
))
189 /* Helper function for finalization code - add node into lists so it will
190 be analyzed and compiled. */
192 varpool_enqueue_needed_node (struct varpool_node
*node
)
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
);
205 /* Notify finalize_compilation_unit that given node is reachable
208 varpool_mark_needed_node (struct varpool_node
*node
)
210 if (node
->alias
&& node
->extra_name
)
211 node
= node
->extra_name
;
212 if (!node
->needed
&& node
->finalized
213 && !TREE_ASM_WRITTEN (node
->decl
))
214 varpool_enqueue_needed_node (node
);
218 /* Reset the queue of needed nodes. */
220 varpool_reset_queue (void)
222 varpool_last_needed_node
= NULL
;
223 varpool_nodes_queue
= NULL
;
224 varpool_first_unanalyzed_node
= NULL
;
227 /* Determine if variable DECL is needed. That is, visible to something
228 either outside this translation unit, something magic in the system
231 decide_is_variable_needed (struct varpool_node
*node
, tree decl
)
233 /* We do not track variable references at all and thus have no idea if the
234 variable was referenced in some other partition or not.
235 FIXME: We really need address taken edges in callgraph and varpool to
236 drive WPA and decide whether other partition might reference it or not. */
239 /* If the user told us it is used, then it must be so. */
240 if ((node
->externally_visible
&& !DECL_COMDAT (decl
))
241 || node
->force_output
)
244 /* ??? If the assembler name is set by hand, it is possible to assemble
245 the name later after finalizing the function and the fact is noticed
246 in assemble_name then. This is arguably a bug. */
247 if (DECL_ASSEMBLER_NAME_SET_P (decl
)
248 && TREE_SYMBOL_REFERENCED (DECL_ASSEMBLER_NAME (decl
)))
251 /* Externally visible variables must be output. The exception is
252 COMDAT variables that must be output only when they are needed. */
253 if (TREE_PUBLIC (decl
)
254 && !flag_whole_program
257 && !DECL_COMDAT (decl
)
258 && !DECL_EXTERNAL (decl
))
261 /* When emulating tls, we actually see references to the control
262 variable, rather than the user-level variable. */
263 if (!targetm
.have_tls
264 && TREE_CODE (decl
) == VAR_DECL
265 && DECL_THREAD_LOCAL_P (decl
))
267 tree control
= emutls_decl (decl
);
268 if (decide_is_variable_needed (varpool_node (control
), control
))
272 /* When not reordering top level variables, we have to assume that
273 we are going to keep everything. */
274 if (flag_toplevel_reorder
)
277 /* We want to emit COMDAT variables only when absolutely necessary. */
278 if (DECL_COMDAT (decl
))
283 /* Mark DECL as finalized. By finalizing the declaration, frontend instruct the
284 middle end to output the variable to asm file, if needed or externally
287 varpool_finalize_decl (tree decl
)
289 struct varpool_node
*node
= varpool_node (decl
);
291 /* FIXME: We don't really stream varpool datastructure and instead rebuild it
292 by varpool_finalize_decl. This is not quite correct since this way we can't
293 attach any info to varpool. Eventually we will want to stream varpool nodes
296 For the moment just prevent analysis of varpool nodes to happen again, so
297 we will re-try to compute "address_taken" flag of varpool that breaks
298 in presence of clones. */
300 node
->analyzed
= true;
302 /* The first declaration of a variable that comes through this function
303 decides whether it is global (in C, has external linkage)
304 or local (in C, has internal linkage). So do nothing more
305 if this function has already run. */
308 if (cgraph_global_info_ready
)
309 varpool_assemble_pending_decls ();
313 varpool_enqueue_needed_node (node
);
314 node
->finalized
= true;
316 if (decide_is_variable_needed (node
, decl
))
317 varpool_mark_needed_node (node
);
318 /* Since we reclaim unreachable nodes at the end of every language
319 level unit, we need to be conservative about possible entry points
321 else if (TREE_PUBLIC (decl
) && !DECL_COMDAT (decl
) && !DECL_EXTERNAL (decl
))
322 varpool_mark_needed_node (node
);
323 if (cgraph_global_info_ready
)
324 varpool_assemble_pending_decls ();
327 /* Return variable availability. See cgraph.h for description of individual
330 cgraph_variable_initializer_availability (struct varpool_node
*node
)
332 gcc_assert (cgraph_function_flags_ready
);
333 if (!node
->finalized
)
334 return AVAIL_NOT_AVAILABLE
;
335 if (!TREE_PUBLIC (node
->decl
))
336 return AVAIL_AVAILABLE
;
337 /* If the variable can be overwritten, return OVERWRITABLE. Takes
338 care of at least two notable extensions - the COMDAT variables
339 used to share template instantiations in C++. */
340 if (!(*targetm
.binds_local_p
) (node
->decl
) && !DECL_COMDAT (node
->decl
))
341 return AVAIL_OVERWRITABLE
;
342 return AVAIL_AVAILABLE
;
345 /* Walk the decls we marked as necessary and see if they reference new
346 variables or functions and add them into the worklists. */
348 varpool_analyze_pending_decls (void)
350 bool changed
= false;
351 timevar_push (TV_CGRAPH
);
353 while (varpool_first_unanalyzed_node
)
355 tree decl
= varpool_first_unanalyzed_node
->decl
;
356 bool analyzed
= varpool_first_unanalyzed_node
->analyzed
;
358 varpool_first_unanalyzed_node
->analyzed
= true;
360 varpool_first_unanalyzed_node
= varpool_first_unanalyzed_node
->next_needed
;
362 /* When reading back varpool at LTO time, we re-construct the queue in order
363 to have "needed" list right by inserting all needed nodes into varpool.
364 We however don't want to re-analyze already analyzed nodes. */
367 gcc_assert (!in_lto_p
);
368 /* Compute the alignment early so function body expanders are
369 already informed about increased alignment. */
370 align_variable (decl
, 0);
372 if (DECL_INITIAL (decl
))
373 record_references_in_initializer (decl
, analyzed
);
376 timevar_pop (TV_CGRAPH
);
380 /* Output one variable, if necessary. Return whether we output it. */
382 varpool_assemble_decl (struct varpool_node
*node
)
384 tree decl
= node
->decl
;
386 if (!TREE_ASM_WRITTEN (decl
)
388 && !DECL_EXTERNAL (decl
)
389 && (TREE_CODE (decl
) != VAR_DECL
|| !DECL_HAS_VALUE_EXPR_P (decl
)))
391 assemble_variable (decl
, 0, 1, 0);
392 if (TREE_ASM_WRITTEN (decl
))
394 struct varpool_node
*alias
;
396 node
->next_needed
= varpool_assembled_nodes_queue
;
397 varpool_assembled_nodes_queue
= node
;
400 /* Also emit any extra name aliases. */
401 for (alias
= node
->extra_name
; alias
; alias
= alias
->next
)
403 /* Update linkage fields in case they've changed. */
404 DECL_WEAK (alias
->decl
) = DECL_WEAK (decl
);
405 TREE_PUBLIC (alias
->decl
) = TREE_PUBLIC (decl
);
406 DECL_VISIBILITY (alias
->decl
) = DECL_VISIBILITY (decl
);
407 assemble_alias (alias
->decl
, DECL_ASSEMBLER_NAME (decl
));
417 /* Optimization of function bodies might've rendered some variables as
418 unnecessary so we want to avoid these from being compiled.
420 This is done by pruning the queue and keeping only the variables that
421 really appear needed (ie they are either externally visible or referenced
422 by compiled function). Re-doing the reachability analysis on variables
423 brings back the remaining variables referenced by these. */
425 varpool_remove_unreferenced_decls (void)
427 struct varpool_node
*next
, *node
= varpool_nodes_queue
;
429 varpool_reset_queue ();
431 if (errorcount
|| sorrycount
)
436 tree decl
= node
->decl
;
437 next
= node
->next_needed
;
441 && (decide_is_variable_needed (node
, decl
)
442 /* ??? Cgraph does not yet rule the world with an iron hand,
443 and does not control the emission of debug information.
444 After a variable has its DECL_RTL set, we must assume that
445 it may be referenced by the debug information, and we can
446 no longer elide it. */
447 || DECL_RTL_SET_P (decl
)))
448 varpool_mark_needed_node (node
);
452 /* Make sure we mark alias targets as used targets. */
454 varpool_analyze_pending_decls ();
457 /* Output all variables enqueued to be assembled. */
459 varpool_assemble_pending_decls (void)
461 bool changed
= false;
463 if (errorcount
|| sorrycount
)
466 /* EH might mark decls as needed during expansion. This should be safe since
467 we don't create references to new function, but it should not be used
469 varpool_analyze_pending_decls ();
471 while (varpool_nodes_queue
)
473 struct varpool_node
*node
= varpool_nodes_queue
;
475 varpool_nodes_queue
= varpool_nodes_queue
->next_needed
;
476 if (varpool_assemble_decl (node
))
479 node
->next_needed
= NULL
;
481 /* varpool_nodes_queue is now empty, clear the pointer to the last element
483 varpool_last_needed_node
= NULL
;
487 /* Remove all elements from the queue so we can re-use it for debug output. */
489 varpool_empty_needed_queue (void)
491 /* EH might mark decls as needed during expansion. This should be safe since
492 we don't create references to new function, but it should not be used
494 varpool_analyze_pending_decls ();
496 while (varpool_nodes_queue
)
498 struct varpool_node
*node
= varpool_nodes_queue
;
499 varpool_nodes_queue
= varpool_nodes_queue
->next_needed
;
500 node
->next_needed
= NULL
;
502 /* varpool_nodes_queue is now empty, clear the pointer to the last element
504 varpool_last_needed_node
= NULL
;
507 /* Create a new global variable of type TYPE. */
509 add_new_static_var (tree type
)
512 struct varpool_node
*new_node
;
514 new_decl
= create_tmp_var (type
, NULL
);
515 DECL_NAME (new_decl
) = create_tmp_var_name (NULL
);
516 TREE_READONLY (new_decl
) = 0;
517 TREE_STATIC (new_decl
) = 1;
518 TREE_USED (new_decl
) = 1;
519 DECL_CONTEXT (new_decl
) = NULL_TREE
;
520 DECL_ABSTRACT (new_decl
) = 0;
521 lang_hooks
.dup_lang_specific_decl (new_decl
);
522 create_var_ann (new_decl
);
523 new_node
= varpool_node (new_decl
);
524 varpool_mark_needed_node (new_node
);
525 add_referenced_var (new_decl
);
526 varpool_finalize_decl (new_decl
);
528 return new_node
->decl
;
531 /* Attempt to mark ALIAS as an alias to DECL. Return TRUE if successful.
532 Extra name aliases are output whenever DECL is output. */
535 varpool_extra_name_alias (tree alias
, tree decl
)
537 struct varpool_node key
, *alias_node
, *decl_node
, **slot
;
539 #ifndef ASM_OUTPUT_DEF
540 /* If aliases aren't supported by the assembler, fail. */
544 gcc_assert (TREE_CODE (decl
) == VAR_DECL
);
545 gcc_assert (TREE_CODE (alias
) == VAR_DECL
);
546 /* Make sure the hash table has been created. */
547 decl_node
= varpool_node (decl
);
551 slot
= (struct varpool_node
**) htab_find_slot (varpool_hash
, &key
, INSERT
);
553 /* If the varpool_node has been already created, fail. */
557 alias_node
= GGC_CNEW (struct varpool_node
);
558 alias_node
->decl
= alias
;
559 alias_node
->alias
= 1;
560 alias_node
->extra_name
= decl_node
;
561 alias_node
->next
= decl_node
->extra_name
;
562 decl_node
->extra_name
= alias_node
;
567 #include "gt-varpool.h"