2 Copyright (C) 2003-2019 Free Software Foundation, Inc.
4 This file is part of GCC.
6 GCC is free software; you can redistribute it and/or modify it under
7 the terms of the GNU General Public License as published by the Free
8 Software Foundation; either version 3, or (at your option) any later
11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12 WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 You should have received a copy of the GNU General Public License
17 along with GCC; see the file COPYING3. If not see
18 <http://www.gnu.org/licenses/>. */
20 /* This file implements two related passes:
22 - pass_data_ipa_function_and_variable_visibility run just after
23 symbol table, references and callgraph are built
25 - pass_data_ipa_function_and_variable_visibility run as first
26 proper IPA pass (that is after early optimization, or, (with LTO)
27 as a first pass done at link-time.
29 Purpose of both passes is to set correctly visibility properties
30 of all symbols. This includes:
32 - Symbol privatization:
34 Some symbols that are declared public by frontend may be
35 turned local (either by -fwhole-program flag, by linker plugin feedback
38 - Discovery of local functions:
40 A local function is one whose calls can occur only in the current
41 compilation unit and all its calls are explicit, so we can change
42 its calling convention. We simply mark all static functions whose
43 address is not taken as local.
45 externally_visible flag is set for symbols that cannot be privatized.
46 For privatized symbols we clear TREE_PUBLIC flag and dismantle comdat
49 - Dismantling of comdat groups:
51 Comdat group represent a section that may be replaced by linker by
52 a different copy of the same section from other unit.
53 If we have resolution information (from linker plugin) and we know that
54 a given comdat gorup is prevailing, we can dismantle it and turn symbols
55 into normal symbols. If the resolution information says that the
56 section was previaled by copy from non-LTO code, we can also dismantle
57 it and turn all symbols into external.
61 Some symbols can be interposed by dynamic linker. Refering to these
62 symbols is expensive, since it needs to be overwritable by the dynamic
63 linker. In some cases we know that the interposition does not change
64 semantic and we can always refer to a local copy (as in the case of
65 inline function). In this case we produce a local alias and redirect
68 TODO: This should be done for references, too.
70 - Removal of static ocnstructors and destructors that have no side effects.
72 - Regularization of several oddities introduced by frontends that may
73 be impractical later in the optimization queue. */
77 #include "coretypes.h"
81 #include "gimple-expr.h"
82 #include "tree-pass.h"
86 #include "ipa-utils.h"
87 #include "stringpool.h"
90 /* Return true when NODE cannot be local. Worker for cgraph_local_node_p. */
93 non_local_p (struct cgraph_node
*node
, void *data ATTRIBUTE_UNUSED
)
95 return !(node
->only_called_directly_or_aliased_p ()
96 /* i386 would need update to output thunk with local calling
98 && !node
->thunk
.thunk_p
100 && !DECL_EXTERNAL (node
->decl
)
101 && !lookup_attribute ("noipa", DECL_ATTRIBUTES (node
->decl
))
102 && !node
->externally_visible
103 && !node
->used_from_other_partition
104 && !node
->in_other_partition
105 && node
->get_availability () >= AVAIL_AVAILABLE
);
108 /* Return true when function can be marked local. */
111 cgraph_node::local_p (void)
113 cgraph_node
*n
= ultimate_alias_target ();
115 if (n
->thunk
.thunk_p
)
116 return n
->callees
->callee
->local_p ();
117 return !n
->call_for_symbol_thunks_and_aliases (non_local_p
,
122 /* A helper for comdat_can_be_unshared_p. */
125 comdat_can_be_unshared_p_1 (symtab_node
*node
)
127 if (!node
->externally_visible
)
129 if (node
->address_can_be_compared_p ())
133 for (unsigned int i
= 0; node
->iterate_referring (i
, ref
); i
++)
134 if (ref
->address_matters_p ())
138 /* If the symbol is used in some weird way, better to not touch it. */
139 if (node
->force_output
)
142 /* Explicit instantiations needs to be output when possibly
144 if (node
->forced_by_abi
145 && TREE_PUBLIC (node
->decl
)
146 && (node
->resolution
!= LDPR_PREVAILING_DEF_IRONLY
147 && !flag_whole_program
))
150 /* Non-readonly and volatile variables cannot be duplicated. */
151 if (is_a
<varpool_node
*> (node
)
152 && (!TREE_READONLY (node
->decl
)
153 || TREE_THIS_VOLATILE (node
->decl
)))
158 /* COMDAT functions must be shared only if they have address taken,
159 otherwise we can produce our own private implementation with
161 Return true when turning COMDAT function static cannot lead to wrong
162 code when the resulting object links with a library defining same COMDAT.
164 Virtual functions do have their addresses taken from the vtables,
165 but in C++ there is no way to compare their addresses for equality. */
168 comdat_can_be_unshared_p (symtab_node
*node
)
170 if (!comdat_can_be_unshared_p_1 (node
))
172 if (node
->same_comdat_group
)
176 /* If more than one function is in the same COMDAT group, it must
177 be shared even if just one function in the comdat group has
179 for (next
= node
->same_comdat_group
;
180 next
!= node
; next
= next
->same_comdat_group
)
181 if (!comdat_can_be_unshared_p_1 (next
))
187 /* Return true when function NODE should be considered externally visible. */
190 cgraph_externally_visible_p (struct cgraph_node
*node
,
193 while (node
->transparent_alias
&& node
->definition
)
194 node
= node
->get_alias_target ();
195 if (!node
->definition
)
197 if (!TREE_PUBLIC (node
->decl
)
198 || DECL_EXTERNAL (node
->decl
))
201 /* Do not try to localize built-in functions yet. One of problems is that we
202 end up mangling their asm for WHOPR that makes it impossible to call them
203 using the implicit built-in declarations anymore. Similarly this enables
204 us to remove them as unreachable before actual calls may appear during
205 expansion or folding. */
206 if (fndecl_built_in_p (node
->decl
))
209 /* If linker counts on us, we must preserve the function. */
210 if (node
->used_from_object_file_p ())
212 if (DECL_PRESERVE_P (node
->decl
))
214 if (lookup_attribute ("externally_visible",
215 DECL_ATTRIBUTES (node
->decl
)))
217 if (lookup_attribute ("noipa", DECL_ATTRIBUTES (node
->decl
)))
219 if (TARGET_DLLIMPORT_DECL_ATTRIBUTES
220 && lookup_attribute ("dllexport",
221 DECL_ATTRIBUTES (node
->decl
)))
223 if (node
->resolution
== LDPR_PREVAILING_DEF_IRONLY
)
225 /* When doing LTO or whole program, we can bring COMDAT functoins static.
226 This improves code quality and we know we will duplicate them at most twice
227 (in the case that we are not using plugin and link with object file
228 implementing same COMDAT) */
229 if (((in_lto_p
|| whole_program
) && !flag_incremental_link
)
230 && DECL_COMDAT (node
->decl
)
231 && comdat_can_be_unshared_p (node
))
234 /* When doing link time optimizations, hidden symbols become local. */
235 if ((in_lto_p
&& !flag_incremental_link
)
236 && (DECL_VISIBILITY (node
->decl
) == VISIBILITY_HIDDEN
237 || DECL_VISIBILITY (node
->decl
) == VISIBILITY_INTERNAL
)
238 /* Be sure that node is defined in IR file, not in other object
239 file. In that case we don't set used_from_other_object_file. */
242 else if (!whole_program
)
245 if (MAIN_NAME_P (DECL_NAME (node
->decl
)))
251 /* Return true when variable should be considered externally visible. */
254 varpool_node::externally_visible_p (void)
256 while (transparent_alias
&& definition
)
257 return get_alias_target ()->externally_visible_p ();
258 if (DECL_EXTERNAL (decl
))
261 if (!TREE_PUBLIC (decl
))
264 /* If linker counts on us, we must preserve the function. */
265 if (used_from_object_file_p ())
268 /* Bringing TLS variables local may cause dynamic linker failures
269 on limits of static TLS vars. */
270 if (DECL_THREAD_LOCAL_P (decl
)
271 && (DECL_TLS_MODEL (decl
) != TLS_MODEL_EMULATED
272 && DECL_TLS_MODEL (decl
) != TLS_MODEL_INITIAL_EXEC
))
275 if (DECL_HARD_REGISTER (decl
))
277 if (DECL_PRESERVE_P (decl
))
279 if (lookup_attribute ("externally_visible",
280 DECL_ATTRIBUTES (decl
)))
282 if (TARGET_DLLIMPORT_DECL_ATTRIBUTES
283 && lookup_attribute ("dllexport",
284 DECL_ATTRIBUTES (decl
)))
287 /* See if we have linker information about symbol not being used or
288 if we need to make guess based on the declaration.
290 Even if the linker clams the symbol is unused, never bring internal
291 symbols that are declared by user as used or externally visible.
292 This is needed for i.e. references from asm statements. */
293 if (used_from_object_file_p ())
295 if (resolution
== LDPR_PREVAILING_DEF_IRONLY
)
298 /* As a special case, the COMDAT virtual tables can be unshared.
299 In LTO mode turn vtables into static variables. The variable is readonly,
300 so this does not enable more optimization, but referring static var
301 is faster for dynamic linking. Also this match logic hidding vtables
302 from LTO symbol tables. */
303 if (((in_lto_p
|| flag_whole_program
) && !flag_incremental_link
)
304 && DECL_COMDAT (decl
)
305 && comdat_can_be_unshared_p (this))
308 /* When doing link time optimizations, hidden symbols become local. */
309 if (in_lto_p
&& !flag_incremental_link
310 && (DECL_VISIBILITY (decl
) == VISIBILITY_HIDDEN
311 || DECL_VISIBILITY (decl
) == VISIBILITY_INTERNAL
)
312 /* Be sure that node is defined in IR file, not in other object
313 file. In that case we don't set used_from_other_object_file. */
316 else if (!flag_whole_program
)
319 /* Do not attempt to privatize COMDATS by default.
320 This would break linking with C++ libraries sharing
323 FIXME: We can do so for readonly vars with no address taken and
324 possibly also for vtables since no direct pointer comparsion is done.
325 It might be interesting to do so to reduce linking overhead. */
326 if (DECL_COMDAT (decl
) || DECL_WEAK (decl
))
331 /* Return true if reference to NODE can be replaced by a local alias.
332 Local aliases save dynamic linking overhead and enable more optimizations.
336 can_replace_by_local_alias (symtab_node
*node
)
338 /* If aliases aren't supported, we can't do replacement. */
339 if (!TARGET_SUPPORTS_ALIASES
)
342 /* Weakrefs have a reason to be non-local. Be sure we do not replace
344 while (node
->transparent_alias
&& node
->definition
&& !node
->weakref
)
345 node
= node
->get_alias_target ();
349 return (node
->get_availability () > AVAIL_INTERPOSABLE
350 && !decl_binds_to_current_def_p (node
->decl
)
351 && !node
->can_be_discarded_p ());
354 /* Return true if we can replace reference to NODE by local alias
355 within a virtual table. Generally we can replace function pointers
356 and virtual table pointers. */
359 can_replace_by_local_alias_in_vtable (symtab_node
*node
)
361 if (is_a
<varpool_node
*> (node
)
362 && !DECL_VIRTUAL_P (node
->decl
))
364 return can_replace_by_local_alias (node
);
367 /* walk_tree callback that rewrites initializer references. */
370 update_vtable_references (tree
*tp
, int *walk_subtrees
,
371 void *data ATTRIBUTE_UNUSED
)
373 if (VAR_OR_FUNCTION_DECL_P (*tp
))
375 if (can_replace_by_local_alias_in_vtable (symtab_node::get (*tp
)))
376 *tp
= symtab_node::get (*tp
)->noninterposable_alias ()->decl
;
379 else if (IS_TYPE_OR_DECL_P (*tp
))
384 /* In LTO we can remove COMDAT groups and weak symbols.
385 Either turn them into normal symbols or external symbol depending on
389 update_visibility_by_resolution_info (symtab_node
* node
)
393 if (!node
->externally_visible
394 || (!DECL_WEAK (node
->decl
) && !DECL_ONE_ONLY (node
->decl
))
395 || node
->resolution
== LDPR_UNKNOWN
)
398 define
= (node
->resolution
== LDPR_PREVAILING_DEF_IRONLY
399 || node
->resolution
== LDPR_PREVAILING_DEF
400 || node
->resolution
== LDPR_UNDEF
401 || node
->resolution
== LDPR_PREVAILING_DEF_IRONLY_EXP
);
403 /* The linker decisions ought to agree in the whole group. */
404 if (node
->same_comdat_group
)
405 for (symtab_node
*next
= node
->same_comdat_group
;
406 next
!= node
; next
= next
->same_comdat_group
)
408 if (!next
->externally_visible
|| next
->transparent_alias
)
412 = define
== (next
->resolution
== LDPR_PREVAILING_DEF_IRONLY
413 || next
->resolution
== LDPR_PREVAILING_DEF
414 || next
->resolution
== LDPR_UNDEF
415 || next
->resolution
== LDPR_PREVAILING_DEF_IRONLY_EXP
);
416 gcc_assert (in_lto_p
|| same_def
);
421 if (node
->same_comdat_group
)
422 for (symtab_node
*next
= node
->same_comdat_group
;
423 next
!= node
; next
= next
->same_comdat_group
)
425 /* During incremental linking we need to keep symbol weak for future
426 linking. We can still drop definition if we know non-LTO world
428 if (!flag_incremental_link
)
430 DECL_WEAK (next
->decl
) = false;
431 next
->set_comdat_group (NULL
);
435 if (next
->externally_visible
)
436 DECL_EXTERNAL (next
->decl
) = true;
437 next
->set_comdat_group (NULL
);
441 /* During incremental linking we need to keep symbol weak for future
442 linking. We can still drop definition if we know non-LTO world prevails. */
443 if (!flag_incremental_link
)
445 DECL_WEAK (node
->decl
) = false;
446 node
->set_comdat_group (NULL
);
447 node
->dissolve_same_comdat_group_list ();
451 DECL_EXTERNAL (node
->decl
) = true;
452 node
->set_comdat_group (NULL
);
453 node
->dissolve_same_comdat_group_list ();
457 /* Try to get rid of weakref. */
460 optimize_weakref (symtab_node
*node
)
462 bool strip_weakref
= false;
463 bool static_alias
= false;
465 gcc_assert (node
->weakref
);
467 /* Weakrefs with no target defined cannot be optimized. */
470 symtab_node
*target
= node
->get_alias_target ();
472 /* Weakrefs to weakrefs can be optimized only if target can be. */
474 optimize_weakref (target
);
478 /* If we have definition of weakref's target and we know it binds locally,
479 we can turn weakref to static alias. */
480 if (TARGET_SUPPORTS_ALIASES
481 && target
->definition
&& decl_binds_to_current_def_p (target
->decl
))
482 strip_weakref
= static_alias
= true;
483 /* Otherwise we can turn weakref into transparent alias. This transformation
484 may break asm statements which directly refers to symbol name and expect
485 GNU as to translate it via .weakref directive. So do not optimize when
486 DECL_PRESERVED is set and .weakref is supported. */
487 else if ((!DECL_PRESERVE_P (target
->decl
)
488 || IDENTIFIER_TRANSPARENT_ALIAS (DECL_ASSEMBLER_NAME (node
->decl
)))
489 && !DECL_WEAK (target
->decl
)
490 && !DECL_EXTERNAL (target
->decl
)
491 && ((target
->definition
&& !target
->can_be_discarded_p ())
492 || target
->resolution
!= LDPR_UNDEF
))
493 strip_weakref
= true;
496 node
->weakref
= false;
497 IDENTIFIER_TRANSPARENT_ALIAS (DECL_ASSEMBLER_NAME (node
->decl
)) = 0;
498 TREE_CHAIN (DECL_ASSEMBLER_NAME (node
->decl
)) = NULL_TREE
;
499 DECL_ATTRIBUTES (node
->decl
) = remove_attribute ("weakref",
504 fprintf (dump_file
, "Optimizing weakref %s %s\n",
506 static_alias
? "as static alias" : "as transparent alias");
510 /* make_decl_local will shortcircuit if it doesn't see TREE_PUBLIC.
511 be sure it really clears the WEAK flag. */
512 TREE_PUBLIC (node
->decl
) = true;
513 node
->make_decl_local ();
514 node
->forced_by_abi
= false;
515 node
->resolution
= LDPR_PREVAILING_DEF_IRONLY
;
516 node
->externally_visible
= false;
517 gcc_assert (!DECL_WEAK (node
->decl
));
518 node
->transparent_alias
= false;
522 symtab
->change_decl_assembler_name
523 (node
->decl
, DECL_ASSEMBLER_NAME (node
->get_alias_target ()->decl
));
524 node
->transparent_alias
= true;
525 node
->copy_visibility_from (target
);
527 gcc_assert (node
->alias
);
530 /* NODE is an externally visible definition, which we've discovered is
531 not needed externally. Make it local to this compilation. */
534 localize_node (bool whole_program
, symtab_node
*node
)
536 gcc_assert (whole_program
|| in_lto_p
|| !TREE_PUBLIC (node
->decl
));
538 /* It is possible that one comdat group contains both hidden and non-hidden
539 symbols. In this case we can privatize all hidden symbol but we need
540 to keep non-hidden exported. */
541 if (node
->same_comdat_group
542 && (node
->resolution
== LDPR_PREVAILING_DEF_IRONLY
543 || node
->resolution
== LDPR_PREVAILING_DEF_IRONLY_EXP
))
546 for (next
= node
->same_comdat_group
;
547 next
!= node
; next
= next
->same_comdat_group
)
548 if (next
->resolution
== LDPR_PREVAILING_DEF_IRONLY_EXP
549 || next
->resolution
== LDPR_PREVAILING_DEF
)
553 if (!node
->transparent_alias
)
555 node
->resolution
= LDPR_PREVAILING_DEF_IRONLY
;
556 node
->make_decl_local ();
557 if (!flag_incremental_link
)
558 node
->unique_name
|= true;
563 /* For similar reason do not privatize whole comdat when seeing comdat
564 local. Wait for non-comdat symbol to be privatized first. */
565 if (node
->comdat_local_p ())
568 if (node
->same_comdat_group
&& TREE_PUBLIC (node
->decl
))
570 for (symtab_node
*next
= node
->same_comdat_group
;
571 next
!= node
; next
= next
->same_comdat_group
)
573 next
->set_comdat_group (NULL
);
575 next
->set_section (NULL
);
576 if (!next
->transparent_alias
)
577 next
->make_decl_local ();
579 |= ((next
->resolution
== LDPR_PREVAILING_DEF_IRONLY
580 || next
->resolution
== LDPR_PREVAILING_DEF_IRONLY_EXP
)
581 && TREE_PUBLIC (next
->decl
)
582 && !flag_incremental_link
);
585 /* Now everything's localized, the grouping has no meaning, and
586 will cause crashes if we keep it around. */
587 node
->dissolve_same_comdat_group_list ();
591 |= ((node
->resolution
== LDPR_PREVAILING_DEF_IRONLY
592 || node
->resolution
== LDPR_PREVAILING_DEF_IRONLY_EXP
)
593 && TREE_PUBLIC (node
->decl
)
594 && !flag_incremental_link
);
596 if (TREE_PUBLIC (node
->decl
))
597 node
->set_comdat_group (NULL
);
598 if (DECL_COMDAT (node
->decl
) && !node
->alias
)
599 node
->set_section (NULL
);
600 if (!node
->transparent_alias
)
602 node
->resolution
= LDPR_PREVAILING_DEF_IRONLY
;
603 node
->make_decl_local ();
607 /* Decide on visibility of all symbols. */
610 function_and_variable_visibility (bool whole_program
)
612 struct cgraph_node
*node
;
615 /* All aliases should be processed at this point. */
616 gcc_checking_assert (!alias_pairs
|| !alias_pairs
->length ());
618 #ifdef ASM_OUTPUT_DEF
619 FOR_EACH_DEFINED_FUNCTION (node
)
621 if (node
->get_availability () != AVAIL_INTERPOSABLE
622 || DECL_EXTERNAL (node
->decl
)
623 || node
->has_aliases_p ()
624 || lookup_attribute ("noipa", DECL_ATTRIBUTES (node
->decl
)))
627 cgraph_node
*alias
= 0;
628 for (cgraph_edge
*e
= node
->callees
; e
; e
= e
->next_callee
)
630 /* Recursive function calls usually can't be interposed. */
632 if (!e
->recursive_p ())
637 alias
= dyn_cast
<cgraph_node
*> (node
->noninterposable_alias ());
638 gcc_assert (alias
&& alias
!= node
);
641 e
->redirect_callee (alias
);
642 if (gimple_has_body_p (e
->caller
->decl
))
644 push_cfun (DECL_STRUCT_FUNCTION (e
->caller
->decl
));
645 e
->redirect_call_stmt_to_callee ();
652 FOR_EACH_FUNCTION (node
)
654 int flags
= flags_from_decl_or_type (node
->decl
);
656 /* Optimize away PURE and CONST constructors and destructors. */
658 && (DECL_STATIC_CONSTRUCTOR (node
->decl
)
659 || DECL_STATIC_DESTRUCTOR (node
->decl
))
660 && (flags
& (ECF_CONST
| ECF_PURE
))
661 && !(flags
& ECF_LOOPING_CONST_OR_PURE
)
662 && opt_for_fn (node
->decl
, optimize
))
664 DECL_STATIC_CONSTRUCTOR (node
->decl
) = 0;
665 DECL_STATIC_DESTRUCTOR (node
->decl
) = 0;
668 /* Frontends and alias code marks nodes as needed before parsing
669 is finished. We may end up marking as node external nodes
670 where this flag is meaningless strip it. */
671 if (DECL_EXTERNAL (node
->decl
) || !node
->definition
)
673 node
->force_output
= 0;
674 node
->forced_by_abi
= 0;
677 /* C++ FE on lack of COMDAT support create local COMDAT functions
678 (that ought to be shared but cannot due to object format
679 limitations). It is necessary to keep the flag to make rest of C++ FE
680 happy. Clear the flag here to avoid confusion in middle-end. */
681 if (DECL_COMDAT (node
->decl
) && !TREE_PUBLIC (node
->decl
))
682 DECL_COMDAT (node
->decl
) = 0;
684 /* For external decls stop tracking same_comdat_group. It doesn't matter
685 what comdat group they are in when they won't be emitted in this TU.
687 An exception is LTO where we may end up with both external
688 and non-external declarations in the same comdat group in
689 the case declarations was not merged. */
690 if (node
->same_comdat_group
&& DECL_EXTERNAL (node
->decl
) && !in_lto_p
)
694 for (symtab_node
*n
= node
->same_comdat_group
;
696 n
= n
->same_comdat_group
)
697 /* If at least one of same comdat group functions is external,
698 all of them have to be, otherwise it is a front-end bug. */
699 gcc_assert (DECL_EXTERNAL (n
->decl
));
701 node
->dissolve_same_comdat_group_list ();
703 gcc_assert ((!DECL_WEAK (node
->decl
)
704 && !DECL_COMDAT (node
->decl
))
705 || TREE_PUBLIC (node
->decl
)
707 || DECL_EXTERNAL (node
->decl
));
708 if (cgraph_externally_visible_p (node
, whole_program
))
710 gcc_assert (!node
->inlined_to
);
711 node
->externally_visible
= true;
715 node
->externally_visible
= false;
716 node
->forced_by_abi
= false;
718 if (!node
->externally_visible
719 && node
->definition
&& !node
->weakref
720 && !DECL_EXTERNAL (node
->decl
))
721 localize_node (whole_program
, node
);
723 if (node
->thunk
.thunk_p
724 && TREE_PUBLIC (node
->decl
))
726 struct cgraph_node
*decl_node
= node
;
728 decl_node
= decl_node
->callees
->callee
->function_symbol ();
730 /* Thunks have the same visibility as function they are attached to.
731 Make sure the C++ front end set this up properly. */
732 if (DECL_ONE_ONLY (decl_node
->decl
))
734 gcc_checking_assert (DECL_COMDAT (node
->decl
)
735 == DECL_COMDAT (decl_node
->decl
));
736 gcc_checking_assert (node
->in_same_comdat_group_p (decl_node
));
737 gcc_checking_assert (node
->same_comdat_group
);
739 node
->forced_by_abi
= decl_node
->forced_by_abi
;
740 if (DECL_EXTERNAL (decl_node
->decl
))
741 DECL_EXTERNAL (node
->decl
) = 1;
744 update_visibility_by_resolution_info (node
);
746 optimize_weakref (node
);
748 FOR_EACH_DEFINED_FUNCTION (node
)
751 node
->local
|= node
->local_p ();
753 /* If we know that function cannot be overwritten by a
754 different semantics and moreover its section cannot be
755 discarded, replace all direct calls by calls to an
756 noninterposable alias. This make dynamic linking cheaper and
757 enable more optimization.
759 TODO: We can also update virtual tables. */
761 && can_replace_by_local_alias (node
))
763 cgraph_node
*alias
= dyn_cast
<cgraph_node
*>
764 (node
->noninterposable_alias ());
766 if (alias
&& alias
!= node
)
768 while (node
->callers
)
770 struct cgraph_edge
*e
= node
->callers
;
772 e
->redirect_callee (alias
);
773 if (gimple_has_body_p (e
->caller
->decl
))
775 push_cfun (DECL_STRUCT_FUNCTION (e
->caller
->decl
));
776 e
->redirect_call_stmt_to_callee ();
783 FOR_EACH_VARIABLE (vnode
)
785 /* weak flag makes no sense on local variables. */
786 gcc_assert (!DECL_WEAK (vnode
->decl
)
788 || TREE_PUBLIC (vnode
->decl
)
789 || DECL_EXTERNAL (vnode
->decl
));
790 /* In several cases declarations cannot be common:
792 - when declaration has initializer
794 - when it has specific section
795 - when it resides in non-generic address space.
796 - if declaration is local, it will get into .local common section
797 so common flag is not needed. Frontends still produce these in
798 certain cases, such as for:
800 static int a __attribute__ ((common))
802 Canonicalize things here and clear the redundant flag. */
803 if (DECL_COMMON (vnode
->decl
)
804 && (!(TREE_PUBLIC (vnode
->decl
)
805 || DECL_EXTERNAL (vnode
->decl
))
806 || (DECL_INITIAL (vnode
->decl
)
807 && DECL_INITIAL (vnode
->decl
) != error_mark_node
)
808 || DECL_WEAK (vnode
->decl
)
809 || DECL_SECTION_NAME (vnode
->decl
) != NULL
810 || ! (ADDR_SPACE_GENERIC_P
811 (TYPE_ADDR_SPACE (TREE_TYPE (vnode
->decl
))))))
812 DECL_COMMON (vnode
->decl
) = 0;
814 optimize_weakref (vnode
);
816 FOR_EACH_DEFINED_VARIABLE (vnode
)
818 if (!vnode
->definition
)
820 if (vnode
->externally_visible_p ())
821 vnode
->externally_visible
= true;
824 vnode
->externally_visible
= false;
825 vnode
->forced_by_abi
= false;
827 if (lookup_attribute ("no_reorder",
828 DECL_ATTRIBUTES (vnode
->decl
)))
829 vnode
->no_reorder
= 1;
831 if (!vnode
->externally_visible
832 && !vnode
->transparent_alias
833 && !DECL_EXTERNAL (vnode
->decl
))
834 localize_node (whole_program
, vnode
);
836 update_visibility_by_resolution_info (vnode
);
838 /* Update virtual tables to point to local aliases where possible. */
839 if (DECL_VIRTUAL_P (vnode
->decl
)
840 && !DECL_EXTERNAL (vnode
->decl
))
846 /* See if there is something to update. */
847 for (i
= 0; vnode
->iterate_reference (i
, ref
); i
++)
848 if (ref
->use
== IPA_REF_ADDR
849 && can_replace_by_local_alias_in_vtable (ref
->referred
))
856 hash_set
<tree
> visited_nodes
;
858 vnode
->get_constructor ();
859 walk_tree (&DECL_INITIAL (vnode
->decl
),
860 update_vtable_references
, NULL
, &visited_nodes
);
861 vnode
->remove_all_references ();
862 record_references_in_initializer (vnode
->decl
, false);
869 fprintf (dump_file
, "\nMarking local functions:");
870 FOR_EACH_DEFINED_FUNCTION (node
)
872 fprintf (dump_file
, " %s", node
->name ());
873 fprintf (dump_file
, "\n\n");
874 fprintf (dump_file
, "\nMarking externally visible functions:");
875 FOR_EACH_DEFINED_FUNCTION (node
)
876 if (node
->externally_visible
)
877 fprintf (dump_file
, " %s", node
->name ());
878 fprintf (dump_file
, "\n\n");
879 fprintf (dump_file
, "\nMarking externally visible variables:");
880 FOR_EACH_DEFINED_VARIABLE (vnode
)
881 if (vnode
->externally_visible
)
882 fprintf (dump_file
, " %s", vnode
->name ());
883 fprintf (dump_file
, "\n\n");
885 symtab
->function_flags_ready
= true;
889 /* Local function pass handling visibilities. This happens before LTO streaming
890 so in particular -fwhole-program should be ignored at this level. */
894 const pass_data pass_data_ipa_function_and_variable_visibility
=
896 SIMPLE_IPA_PASS
, /* type */
897 "visibility", /* name */
898 OPTGROUP_NONE
, /* optinfo_flags */
899 TV_CGRAPHOPT
, /* tv_id */
900 0, /* properties_required */
901 0, /* properties_provided */
902 0, /* properties_destroyed */
903 0, /* todo_flags_start */
904 ( TODO_remove_functions
| TODO_dump_symtab
), /* todo_flags_finish */
907 /* Bring functions local at LTO time with -fwhole-program. */
910 whole_program_function_and_variable_visibility (void)
912 function_and_variable_visibility (flag_whole_program
);
913 if (optimize
|| in_lto_p
)
914 ipa_discover_variable_flags ();
922 const pass_data pass_data_ipa_whole_program_visibility
=
925 "whole-program", /* name */
926 OPTGROUP_NONE
, /* optinfo_flags */
927 TV_CGRAPHOPT
, /* tv_id */
928 0, /* properties_required */
929 0, /* properties_provided */
930 0, /* properties_destroyed */
931 0, /* todo_flags_start */
932 ( TODO_remove_functions
| TODO_dump_symtab
), /* todo_flags_finish */
935 class pass_ipa_whole_program_visibility
: public ipa_opt_pass_d
938 pass_ipa_whole_program_visibility (gcc::context
*ctxt
)
939 : ipa_opt_pass_d (pass_data_ipa_whole_program_visibility
, ctxt
,
940 NULL
, /* generate_summary */
941 NULL
, /* write_summary */
942 NULL
, /* read_summary */
943 NULL
, /* write_optimization_summary */
944 NULL
, /* read_optimization_summary */
945 NULL
, /* stmt_fixup */
946 0, /* function_transform_todo_flags_start */
947 NULL
, /* function_transform */
948 NULL
) /* variable_transform */
951 /* opt_pass methods: */
953 virtual bool gate (function
*)
955 /* Do not re-run on ltrans stage. */
958 virtual unsigned int execute (function
*)
960 return whole_program_function_and_variable_visibility ();
963 }; // class pass_ipa_whole_program_visibility
968 make_pass_ipa_whole_program_visibility (gcc::context
*ctxt
)
970 return new pass_ipa_whole_program_visibility (ctxt
);
973 class pass_ipa_function_and_variable_visibility
: public simple_ipa_opt_pass
976 pass_ipa_function_and_variable_visibility (gcc::context
*ctxt
)
977 : simple_ipa_opt_pass (pass_data_ipa_function_and_variable_visibility
,
981 /* opt_pass methods: */
982 virtual unsigned int execute (function
*)
984 return function_and_variable_visibility (flag_whole_program
&& !flag_lto
);
987 }; // class pass_ipa_function_and_variable_visibility
989 simple_ipa_opt_pass
*
990 make_pass_ipa_function_and_variable_visibility (gcc::context
*ctxt
)
992 return new pass_ipa_function_and_variable_visibility (ctxt
);