1 /* IPA visibility pass 2 Copyright (C) 2003-2018 Free Software Foundation, Inc. 3 4 This file is part of GCC. 5 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 9 version. 10 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 14 for more details. 15 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/>. */ 19 20 /* This file implements two related passes: 21 22 - pass_data_ipa_function_and_variable_visibility run just after 23 symbol table, references and callgraph are built 24 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. 28 29 Purpose of both passes is to set correctly visibility properties 30 of all symbols. This includes: 31 32 - Symbol privatization: 33 34 Some symbols that are declared public by frontend may be 35 turned local (either by -fwhole-program flag, by linker plugin feedback 36 or by other reasons) 37 38 - Discovery of local functions: 39 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. 44 45 externally_visible flag is set for symbols that can not be privatized. 46 For privatized symbols we clear TREE_PUBLIC flag and dismantle comdat 47 group. 48 49 - Dismantling of comdat groups: 50 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. 58 59 - Local aliases: 60 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 66 calls to it. 67 68 TODO: This should be done for references, too. 69 70 - Removal of static ocnstructors and destructors that have no side effects. 71 72 - Regularization of several oddities introduced by frontends that may 73 be impractical later in the optimization queue. */ 74 75 #include "config.h" 76 #include "system.h" 77 #include "coretypes.h" 78 #include "tm.h" 79 #include "function.h" 80 #include "tree.h" 81 #include "gimple-expr.h" 82 #include "tree-pass.h" 83 #include "cgraph.h" 84 #include "calls.h" 85 #include "varasm.h" 86 #include "ipa-utils.h" 87 #include "stringpool.h" 88 #include "attribs.h" 89 90 /* Return true when NODE can not be local. Worker for cgraph_local_node_p. */ 91 92 static bool 93 non_local_p (struct cgraph_node *node, void *data ATTRIBUTE_UNUSED) 94 { 95 return !(node->only_called_directly_or_aliased_p () 96 /* i386 would need update to output thunk with local calling 97 conventions. */ 98 && !node->thunk.thunk_p 99 && node->definition 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); 106 } 107 108 /* Return true when function can be marked local. */ 109 110 bool 111 cgraph_node::local_p (void) 112 { 113 cgraph_node *n = ultimate_alias_target (); 114 115 if (n->thunk.thunk_p) 116 return n->callees->callee->local_p (); 117 return !n->call_for_symbol_thunks_and_aliases (non_local_p, 118 NULL, true); 119 120 } 121 122 /* A helper for comdat_can_be_unshared_p. */ 123 124 static bool 125 comdat_can_be_unshared_p_1 (symtab_node *node) 126 { 127 if (!node->externally_visible) 128 return true; 129 if (node->address_can_be_compared_p ()) 130 { 131 struct ipa_ref *ref; 132 133 for (unsigned int i = 0; node->iterate_referring (i, ref); i++) 134 if (ref->address_matters_p ()) 135 return false; 136 } 137 138 /* If the symbol is used in some weird way, better to not touch it. */ 139 if (node->force_output) 140 return false; 141 142 /* Explicit instantiations needs to be output when possibly 143 used externally. */ 144 if (node->forced_by_abi 145 && TREE_PUBLIC (node->decl) 146 && (node->resolution != LDPR_PREVAILING_DEF_IRONLY 147 && !flag_whole_program)) 148 return false; 149 150 /* Non-readonly and volatile variables can not be duplicated. */ 151 if (is_a <varpool_node *> (node) 152 && (!TREE_READONLY (node->decl) 153 || TREE_THIS_VOLATILE (node->decl))) 154 return false; 155 return true; 156 } 157 158 /* COMDAT functions must be shared only if they have address taken, 159 otherwise we can produce our own private implementation with 160 -fwhole-program. 161 Return true when turning COMDAT function static can not lead to wrong 162 code when the resulting object links with a library defining same COMDAT. 163 164 Virtual functions do have their addresses taken from the vtables, 165 but in C++ there is no way to compare their addresses for equality. */ 166 167 static bool 168 comdat_can_be_unshared_p (symtab_node *node) 169 { 170 if (!comdat_can_be_unshared_p_1 (node)) 171 return false; 172 if (node->same_comdat_group) 173 { 174 symtab_node *next; 175 176 /* 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 178 address taken. */ 179 for (next = node->same_comdat_group; 180 next != node; next = next->same_comdat_group) 181 if (!comdat_can_be_unshared_p_1 (next)) 182 return false; 183 } 184 return true; 185 } 186 187 /* Return true when function NODE should be considered externally visible. */ 188 189 static bool 190 cgraph_externally_visible_p (struct cgraph_node *node, 191 bool whole_program) 192 { 193 while (node->transparent_alias && node->definition) 194 node = node->get_alias_target (); 195 if (!node->definition) 196 return false; 197 if (!TREE_PUBLIC (node->decl) 198 || DECL_EXTERNAL (node->decl)) 199 return false; 200 201 /* 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 (DECL_BUILT_IN (node->decl)) 207 return true; 208 209 /* If linker counts on us, we must preserve the function. */ 210 if (node->used_from_object_file_p ()) 211 return true; 212 if (DECL_PRESERVE_P (node->decl)) 213 return true; 214 if (lookup_attribute ("externally_visible", 215 DECL_ATTRIBUTES (node->decl))) 216 return true; 217 if (lookup_attribute ("noipa", DECL_ATTRIBUTES (node->decl))) 218 return true; 219 if (TARGET_DLLIMPORT_DECL_ATTRIBUTES 220 && lookup_attribute ("dllexport", 221 DECL_ATTRIBUTES (node->decl))) 222 return true; 223 if (node->resolution == LDPR_PREVAILING_DEF_IRONLY) 224 return false; 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)) 232 return false; 233 234 /* 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. */ 240 && node->definition) 241 ; 242 else if (!whole_program) 243 return true; 244 245 if (MAIN_NAME_P (DECL_NAME (node->decl))) 246 return true; 247 248 if (node->instrumentation_clone 249 && MAIN_NAME_P (DECL_NAME (node->orig_decl))) 250 return true; 251 252 return false; 253 } 254 255 /* Return true when variable should be considered externally visible. */ 256 257 bool 258 varpool_node::externally_visible_p (void) 259 { 260 while (transparent_alias && definition) 261 return get_alias_target ()->externally_visible_p (); 262 if (DECL_EXTERNAL (decl)) 263 return true; 264 265 if (!TREE_PUBLIC (decl)) 266 return false; 267 268 /* If linker counts on us, we must preserve the function. */ 269 if (used_from_object_file_p ()) 270 return true; 271 272 /* Bringing TLS variables local may cause dynamic linker failures 273 on limits of static TLS vars. */ 274 if (DECL_THREAD_LOCAL_P (decl) 275 && (DECL_TLS_MODEL (decl) != TLS_MODEL_EMULATED 276 && DECL_TLS_MODEL (decl) != TLS_MODEL_INITIAL_EXEC)) 277 return true; 278 279 if (DECL_HARD_REGISTER (decl)) 280 return true; 281 if (DECL_PRESERVE_P (decl)) 282 return true; 283 if (lookup_attribute ("externally_visible", 284 DECL_ATTRIBUTES (decl))) 285 return true; 286 if (TARGET_DLLIMPORT_DECL_ATTRIBUTES 287 && lookup_attribute ("dllexport", 288 DECL_ATTRIBUTES (decl))) 289 return true; 290 291 /* See if we have linker information about symbol not being used or 292 if we need to make guess based on the declaration. 293 294 Even if the linker clams the symbol is unused, never bring internal 295 symbols that are declared by user as used or externally visible. 296 This is needed for i.e. references from asm statements. */ 297 if (used_from_object_file_p ()) 298 return true; 299 if (resolution == LDPR_PREVAILING_DEF_IRONLY) 300 return false; 301 302 /* As a special case, the COMDAT virtual tables can be unshared. 303 In LTO mode turn vtables into static variables. The variable is readonly, 304 so this does not enable more optimization, but referring static var 305 is faster for dynamic linking. Also this match logic hidding vtables 306 from LTO symbol tables. */ 307 if (((in_lto_p || flag_whole_program) && !flag_incremental_link) 308 && DECL_COMDAT (decl) 309 && comdat_can_be_unshared_p (this)) 310 return false; 311 312 /* When doing link time optimizations, hidden symbols become local. */ 313 if (in_lto_p && !flag_incremental_link 314 && (DECL_VISIBILITY (decl) == VISIBILITY_HIDDEN 315 || DECL_VISIBILITY (decl) == VISIBILITY_INTERNAL) 316 /* Be sure that node is defined in IR file, not in other object 317 file. In that case we don't set used_from_other_object_file. */ 318 && definition) 319 ; 320 else if (!flag_whole_program) 321 return true; 322 323 /* Do not attempt to privatize COMDATS by default. 324 This would break linking with C++ libraries sharing 325 inline definitions. 326 327 FIXME: We can do so for readonly vars with no address taken and 328 possibly also for vtables since no direct pointer comparsion is done. 329 It might be interesting to do so to reduce linking overhead. */ 330 if (DECL_COMDAT (decl) || DECL_WEAK (decl)) 331 return true; 332 return false; 333 } 334 335 /* Return true if reference to NODE can be replaced by a local alias. 336 Local aliases save dynamic linking overhead and enable more optimizations. 337 */ 338 339 static bool 340 can_replace_by_local_alias (symtab_node *node) 341 { 342 /* If aliases aren't supported, we can't do replacement. */ 343 if (!TARGET_SUPPORTS_ALIASES) 344 return false; 345 346 /* Weakrefs have a reason to be non-local. Be sure we do not replace 347 them. */ 348 while (node->transparent_alias && node->definition && !node->weakref) 349 node = node->get_alias_target (); 350 if (node->weakref) 351 return false; 352 353 return (node->get_availability () > AVAIL_INTERPOSABLE 354 && !decl_binds_to_current_def_p (node->decl) 355 && !node->can_be_discarded_p ()); 356 } 357 358 /* Return true if we can replace reference to NODE by local alias 359 within a virtual table. Generally we can replace function pointers 360 and virtual table pointers. */ 361 362 static bool 363 can_replace_by_local_alias_in_vtable (symtab_node *node) 364 { 365 if (is_a <varpool_node *> (node) 366 && !DECL_VIRTUAL_P (node->decl)) 367 return false; 368 return can_replace_by_local_alias (node); 369 } 370 371 /* walk_tree callback that rewrites initializer references. */ 372 373 static tree 374 update_vtable_references (tree *tp, int *walk_subtrees, 375 void *data ATTRIBUTE_UNUSED) 376 { 377 if (VAR_OR_FUNCTION_DECL_P (*tp)) 378 { 379 if (can_replace_by_local_alias_in_vtable (symtab_node::get (*tp))) 380 *tp = symtab_node::get (*tp)->noninterposable_alias ()->decl; 381 *walk_subtrees = 0; 382 } 383 else if (IS_TYPE_OR_DECL_P (*tp)) 384 *walk_subtrees = 0; 385 return NULL; 386 } 387 388 /* In LTO we can remove COMDAT groups and weak symbols. 389 Either turn them into normal symbols or external symbol depending on 390 resolution info. */ 391 392 static void 393 update_visibility_by_resolution_info (symtab_node * node) 394 { 395 bool define; 396 397 if (!node->externally_visible 398 || (!DECL_WEAK (node->decl) && !DECL_ONE_ONLY (node->decl)) 399 || node->resolution == LDPR_UNKNOWN) 400 return; 401 402 define = (node->resolution == LDPR_PREVAILING_DEF_IRONLY 403 || node->resolution == LDPR_PREVAILING_DEF 404 || node->resolution == LDPR_UNDEF 405 || node->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP); 406 407 /* The linker decisions ought to agree in the whole group. */ 408 if (node->same_comdat_group) 409 for (symtab_node *next = node->same_comdat_group; 410 next != node; next = next->same_comdat_group) 411 { 412 if (!next->externally_visible || next->transparent_alias) 413 continue; 414 415 bool same_def 416 = define == (next->resolution == LDPR_PREVAILING_DEF_IRONLY 417 || next->resolution == LDPR_PREVAILING_DEF 418 || next->resolution == LDPR_UNDEF 419 || next->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP); 420 gcc_assert (in_lto_p || same_def); 421 if (!same_def) 422 return; 423 } 424 425 if (node->same_comdat_group) 426 for (symtab_node *next = node->same_comdat_group; 427 next != node; next = next->same_comdat_group) 428 { 429 /* During incremental linking we need to keep symbol weak for future 430 linking. We can still drop definition if we know non-LTO world 431 prevails. */ 432 if (!flag_incremental_link) 433 { 434 DECL_WEAK (next->decl) = false; 435 next->set_comdat_group (NULL); 436 } 437 if (!define) 438 { 439 if (next->externally_visible) 440 DECL_EXTERNAL (next->decl) = true; 441 next->set_comdat_group (NULL); 442 } 443 } 444 445 /* During incremental linking we need to keep symbol weak for future 446 linking. We can still drop definition if we know non-LTO world prevails. */ 447 if (!flag_incremental_link) 448 { 449 DECL_WEAK (node->decl) = false; 450 node->set_comdat_group (NULL); 451 node->dissolve_same_comdat_group_list (); 452 } 453 if (!define) 454 { 455 DECL_EXTERNAL (node->decl) = true; 456 node->set_comdat_group (NULL); 457 node->dissolve_same_comdat_group_list (); 458 } 459 } 460 461 /* Try to get rid of weakref. */ 462 463 static void 464 optimize_weakref (symtab_node *node) 465 { 466 bool strip_weakref = false; 467 bool static_alias = false; 468 469 gcc_assert (node->weakref); 470 471 /* Weakrefs with no target defined can not be optimized. */ 472 if (!node->analyzed) 473 return; 474 symtab_node *target = node->get_alias_target (); 475 476 /* Weakrefs to weakrefs can be optimized only if target can be. */ 477 if (target->weakref) 478 optimize_weakref (target); 479 if (target->weakref) 480 return; 481 482 /* If we have definition of weakref's target and we know it binds locally, 483 we can turn weakref to static alias. */ 484 if (TARGET_SUPPORTS_ALIASES 485 && target->definition && decl_binds_to_current_def_p (target->decl)) 486 strip_weakref = static_alias = true; 487 /* Otherwise we can turn weakref into transparent alias. This transformation 488 may break asm statements which directly refers to symbol name and expect 489 GNU as to translate it via .weakref directive. So do not optimize when 490 DECL_PRESERVED is set and .weakref is supported. */ 491 else if ((!DECL_PRESERVE_P (target->decl) 492 || IDENTIFIER_TRANSPARENT_ALIAS (DECL_ASSEMBLER_NAME (node->decl))) 493 && !DECL_WEAK (target->decl) 494 && !DECL_EXTERNAL (target->decl) 495 && ((target->definition && !target->can_be_discarded_p ()) 496 || target->resolution != LDPR_UNDEF)) 497 strip_weakref = true; 498 if (!strip_weakref) 499 return; 500 node->weakref = false; 501 IDENTIFIER_TRANSPARENT_ALIAS (DECL_ASSEMBLER_NAME (node->decl)) = 0; 502 TREE_CHAIN (DECL_ASSEMBLER_NAME (node->decl)) = NULL_TREE; 503 DECL_ATTRIBUTES (node->decl) = remove_attribute ("weakref", 504 DECL_ATTRIBUTES 505 (node->decl)); 506 507 if (dump_file) 508 fprintf (dump_file, "Optimizing weakref %s %s\n", 509 node->name(), 510 static_alias ? "as static alias" : "as transparent alias"); 511 512 if (static_alias) 513 { 514 /* make_decl_local will shortcircuit if it doesn't see TREE_PUBLIC. 515 be sure it really clears the WEAK flag. */ 516 TREE_PUBLIC (node->decl) = true; 517 node->make_decl_local (); 518 node->forced_by_abi = false; 519 node->resolution = LDPR_PREVAILING_DEF_IRONLY; 520 node->externally_visible = false; 521 gcc_assert (!DECL_WEAK (node->decl)); 522 node->transparent_alias = false; 523 } 524 else 525 { 526 symtab->change_decl_assembler_name 527 (node->decl, DECL_ASSEMBLER_NAME (node->get_alias_target ()->decl)); 528 node->transparent_alias = true; 529 node->copy_visibility_from (target); 530 } 531 gcc_assert (node->alias); 532 } 533 534 /* NODE is an externally visible definition, which we've discovered is 535 not needed externally. Make it local to this compilation. */ 536 537 static void 538 localize_node (bool whole_program, symtab_node *node) 539 { 540 gcc_assert (whole_program || in_lto_p || !TREE_PUBLIC (node->decl)); 541 542 /* It is possible that one comdat group contains both hidden and non-hidden 543 symbols. In this case we can privatize all hidden symbol but we need 544 to keep non-hidden exported. */ 545 if (node->same_comdat_group 546 && node->resolution == LDPR_PREVAILING_DEF_IRONLY) 547 { 548 symtab_node *next; 549 for (next = node->same_comdat_group; 550 next != node; next = next->same_comdat_group) 551 if (next->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP 552 || next->resolution == LDPR_PREVAILING_DEF) 553 break; 554 if (node != next) 555 { 556 if (!node->transparent_alias) 557 { 558 node->resolution = LDPR_PREVAILING_DEF_IRONLY; 559 node->make_decl_local (); 560 if (!flag_incremental_link) 561 node->unique_name |= true; 562 return; 563 } 564 } 565 } 566 /* For similar reason do not privatize whole comdat when seeing comdat 567 local. Wait for non-comdat symbol to be privatized first. */ 568 if (node->comdat_local_p ()) 569 return; 570 571 if (node->same_comdat_group && TREE_PUBLIC (node->decl)) 572 { 573 for (symtab_node *next = node->same_comdat_group; 574 next != node; next = next->same_comdat_group) 575 { 576 next->set_comdat_group (NULL); 577 if (!next->alias) 578 next->set_section (NULL); 579 if (!next->transparent_alias) 580 next->make_decl_local (); 581 next->unique_name 582 |= ((next->resolution == LDPR_PREVAILING_DEF_IRONLY 583 || next->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP) 584 && TREE_PUBLIC (next->decl) 585 && !flag_incremental_link); 586 } 587 588 /* Now everything's localized, the grouping has no meaning, and 589 will cause crashes if we keep it around. */ 590 node->dissolve_same_comdat_group_list (); 591 } 592 593 node->unique_name 594 |= ((node->resolution == LDPR_PREVAILING_DEF_IRONLY 595 || node->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP) 596 && TREE_PUBLIC (node->decl) 597 && !flag_incremental_link); 598 599 if (TREE_PUBLIC (node->decl)) 600 node->set_comdat_group (NULL); 601 if (DECL_COMDAT (node->decl) && !node->alias) 602 node->set_section (NULL); 603 if (!node->transparent_alias) 604 { 605 node->resolution = LDPR_PREVAILING_DEF_IRONLY; 606 node->make_decl_local (); 607 } 608 } 609 610 /* Decide on visibility of all symbols. */ 611 612 static unsigned int 613 function_and_variable_visibility (bool whole_program) 614 { 615 struct cgraph_node *node; 616 varpool_node *vnode; 617 618 /* All aliases should be processed at this point. */ 619 gcc_checking_assert (!alias_pairs || !alias_pairs->length ()); 620 621 #ifdef ASM_OUTPUT_DEF 622 FOR_EACH_DEFINED_FUNCTION (node) 623 { 624 if (node->get_availability () != AVAIL_INTERPOSABLE 625 || DECL_EXTERNAL (node->decl) 626 || node->has_aliases_p () 627 || lookup_attribute ("noipa", DECL_ATTRIBUTES (node->decl))) 628 continue; 629 630 cgraph_node *alias = 0; 631 for (cgraph_edge *e = node->callees; e; e = e->next_callee) 632 { 633 /* Recursive function calls usually can't be interposed. */ 634 635 if (!e->recursive_p ()) 636 continue; 637 638 if (!alias) 639 { 640 alias = dyn_cast<cgraph_node *> (node->noninterposable_alias ()); 641 gcc_assert (alias && alias != node); 642 } 643 644 e->redirect_callee (alias); 645 if (gimple_has_body_p (e->caller->decl)) 646 { 647 push_cfun (DECL_STRUCT_FUNCTION (e->caller->decl)); 648 e->redirect_call_stmt_to_callee (); 649 pop_cfun (); 650 } 651 } 652 } 653 #endif 654 655 FOR_EACH_FUNCTION (node) 656 { 657 int flags = flags_from_decl_or_type (node->decl); 658 659 /* Optimize away PURE and CONST constructors and destructors. */ 660 if (node->analyzed 661 && (DECL_STATIC_CONSTRUCTOR (node->decl) 662 || DECL_STATIC_DESTRUCTOR (node->decl)) 663 && (flags & (ECF_CONST | ECF_PURE)) 664 && !(flags & ECF_LOOPING_CONST_OR_PURE) 665 && opt_for_fn (node->decl, optimize)) 666 { 667 DECL_STATIC_CONSTRUCTOR (node->decl) = 0; 668 DECL_STATIC_DESTRUCTOR (node->decl) = 0; 669 } 670 671 /* Frontends and alias code marks nodes as needed before parsing 672 is finished. We may end up marking as node external nodes 673 where this flag is meaningless strip it. */ 674 if (DECL_EXTERNAL (node->decl) || !node->definition) 675 { 676 node->force_output = 0; 677 node->forced_by_abi = 0; 678 } 679 680 /* C++ FE on lack of COMDAT support create local COMDAT functions 681 (that ought to be shared but can not due to object format 682 limitations). It is necessary to keep the flag to make rest of C++ FE 683 happy. Clear the flag here to avoid confusion in middle-end. */ 684 if (DECL_COMDAT (node->decl) && !TREE_PUBLIC (node->decl)) 685 DECL_COMDAT (node->decl) = 0; 686 687 /* For external decls stop tracking same_comdat_group. It doesn't matter 688 what comdat group they are in when they won't be emitted in this TU. 689 690 An exception is LTO where we may end up with both external 691 and non-external declarations in the same comdat group in 692 the case declarations was not merged. */ 693 if (node->same_comdat_group && DECL_EXTERNAL (node->decl) && !in_lto_p) 694 { 695 if (flag_checking) 696 { 697 for (symtab_node *n = node->same_comdat_group; 698 n != node; 699 n = n->same_comdat_group) 700 /* If at least one of same comdat group functions is external, 701 all of them have to be, otherwise it is a front-end bug. */ 702 gcc_assert (DECL_EXTERNAL (n->decl)); 703 } 704 node->dissolve_same_comdat_group_list (); 705 } 706 gcc_assert ((!DECL_WEAK (node->decl) 707 && !DECL_COMDAT (node->decl)) 708 || TREE_PUBLIC (node->decl) 709 || node->weakref 710 || DECL_EXTERNAL (node->decl)); 711 if (cgraph_externally_visible_p (node, whole_program)) 712 { 713 gcc_assert (!node->global.inlined_to); 714 node->externally_visible = true; 715 } 716 else 717 { 718 node->externally_visible = false; 719 node->forced_by_abi = false; 720 } 721 if (!node->externally_visible 722 && node->definition && !node->weakref 723 && !DECL_EXTERNAL (node->decl)) 724 localize_node (whole_program, node); 725 726 if (node->thunk.thunk_p 727 && !node->thunk.add_pointer_bounds_args 728 && TREE_PUBLIC (node->decl)) 729 { 730 struct cgraph_node *decl_node = node; 731 732 decl_node = decl_node->callees->callee->function_symbol (); 733 734 /* Thunks have the same visibility as function they are attached to. 735 Make sure the C++ front end set this up properly. */ 736 if (DECL_ONE_ONLY (decl_node->decl)) 737 { 738 gcc_checking_assert (DECL_COMDAT (node->decl) 739 == DECL_COMDAT (decl_node->decl)); 740 gcc_checking_assert (node->in_same_comdat_group_p (decl_node)); 741 gcc_checking_assert (node->same_comdat_group); 742 } 743 node->forced_by_abi = decl_node->forced_by_abi; 744 if (DECL_EXTERNAL (decl_node->decl)) 745 DECL_EXTERNAL (node->decl) = 1; 746 } 747 748 update_visibility_by_resolution_info (node); 749 if (node->weakref) 750 optimize_weakref (node); 751 } 752 FOR_EACH_DEFINED_FUNCTION (node) 753 { 754 if (!node->local.local) 755 node->local.local |= node->local_p (); 756 757 /* If we know that function can not be overwritten by a 758 different semantics and moreover its section can not be 759 discarded, replace all direct calls by calls to an 760 noninterposable alias. This make dynamic linking cheaper and 761 enable more optimization. 762 763 TODO: We can also update virtual tables. */ 764 if (node->callers 765 && can_replace_by_local_alias (node)) 766 { 767 cgraph_node *alias = dyn_cast<cgraph_node *> 768 (node->noninterposable_alias ()); 769 770 if (alias && alias != node) 771 { 772 while (node->callers) 773 { 774 struct cgraph_edge *e = node->callers; 775 776 e->redirect_callee (alias); 777 if (gimple_has_body_p (e->caller->decl)) 778 { 779 push_cfun (DECL_STRUCT_FUNCTION (e->caller->decl)); 780 e->redirect_call_stmt_to_callee (); 781 pop_cfun (); 782 } 783 } 784 } 785 } 786 } 787 FOR_EACH_VARIABLE (vnode) 788 { 789 /* weak flag makes no sense on local variables. */ 790 gcc_assert (!DECL_WEAK (vnode->decl) 791 || vnode->weakref 792 || TREE_PUBLIC (vnode->decl) 793 || DECL_EXTERNAL (vnode->decl)); 794 /* In several cases declarations can not be common: 795 796 - when declaration has initializer 797 - when it is in weak 798 - when it has specific section 799 - when it resides in non-generic address space. 800 - if declaration is local, it will get into .local common section 801 so common flag is not needed. Frontends still produce these in 802 certain cases, such as for: 803 804 static int a __attribute__ ((common)) 805 806 Canonicalize things here and clear the redundant flag. */ 807 if (DECL_COMMON (vnode->decl) 808 && (!(TREE_PUBLIC (vnode->decl) 809 || DECL_EXTERNAL (vnode->decl)) 810 || (DECL_INITIAL (vnode->decl) 811 && DECL_INITIAL (vnode->decl) != error_mark_node) 812 || DECL_WEAK (vnode->decl) 813 || DECL_SECTION_NAME (vnode->decl) != NULL 814 || ! (ADDR_SPACE_GENERIC_P 815 (TYPE_ADDR_SPACE (TREE_TYPE (vnode->decl)))))) 816 DECL_COMMON (vnode->decl) = 0; 817 if (vnode->weakref) 818 optimize_weakref (vnode); 819 } 820 FOR_EACH_DEFINED_VARIABLE (vnode) 821 { 822 if (!vnode->definition) 823 continue; 824 if (vnode->externally_visible_p ()) 825 vnode->externally_visible = true; 826 else 827 { 828 vnode->externally_visible = false; 829 vnode->forced_by_abi = false; 830 } 831 if (lookup_attribute ("no_reorder", 832 DECL_ATTRIBUTES (vnode->decl))) 833 vnode->no_reorder = 1; 834 835 if (!vnode->externally_visible 836 && !vnode->transparent_alias 837 && !DECL_EXTERNAL (vnode->decl)) 838 localize_node (whole_program, vnode); 839 840 update_visibility_by_resolution_info (vnode); 841 842 /* Update virtual tables to point to local aliases where possible. */ 843 if (DECL_VIRTUAL_P (vnode->decl) 844 && !DECL_EXTERNAL (vnode->decl)) 845 { 846 int i; 847 struct ipa_ref *ref; 848 bool found = false; 849 850 /* See if there is something to update. */ 851 for (i = 0; vnode->iterate_reference (i, ref); i++) 852 if (ref->use == IPA_REF_ADDR 853 && can_replace_by_local_alias_in_vtable (ref->referred)) 854 { 855 found = true; 856 break; 857 } 858 if (found) 859 { 860 hash_set<tree> visited_nodes; 861 862 vnode->get_constructor (); 863 walk_tree (&DECL_INITIAL (vnode->decl), 864 update_vtable_references, NULL, &visited_nodes); 865 vnode->remove_all_references (); 866 record_references_in_initializer (vnode->decl, false); 867 } 868 } 869 } 870 871 if (dump_file) 872 { 873 fprintf (dump_file, "\nMarking local functions:"); 874 FOR_EACH_DEFINED_FUNCTION (node) 875 if (node->local.local) 876 fprintf (dump_file, " %s", node->name ()); 877 fprintf (dump_file, "\n\n"); 878 fprintf (dump_file, "\nMarking externally visible functions:"); 879 FOR_EACH_DEFINED_FUNCTION (node) 880 if (node->externally_visible) 881 fprintf (dump_file, " %s", node->name ()); 882 fprintf (dump_file, "\n\n"); 883 fprintf (dump_file, "\nMarking externally visible variables:"); 884 FOR_EACH_DEFINED_VARIABLE (vnode) 885 if (vnode->externally_visible) 886 fprintf (dump_file, " %s", vnode->name ()); 887 fprintf (dump_file, "\n\n"); 888 } 889 symtab->function_flags_ready = true; 890 return 0; 891 } 892 893 /* Local function pass handling visibilities. This happens before LTO streaming 894 so in particular -fwhole-program should be ignored at this level. */ 895 896 namespace { 897 898 const pass_data pass_data_ipa_function_and_variable_visibility = 899 { 900 SIMPLE_IPA_PASS, /* type */ 901 "visibility", /* name */ 902 OPTGROUP_NONE, /* optinfo_flags */ 903 TV_CGRAPHOPT, /* tv_id */ 904 0, /* properties_required */ 905 0, /* properties_provided */ 906 0, /* properties_destroyed */ 907 0, /* todo_flags_start */ 908 ( TODO_remove_functions | TODO_dump_symtab ), /* todo_flags_finish */ 909 }; 910 911 /* Bring functions local at LTO time with -fwhole-program. */ 912 913 static unsigned int 914 whole_program_function_and_variable_visibility (void) 915 { 916 function_and_variable_visibility (flag_whole_program); 917 if (optimize || in_lto_p) 918 ipa_discover_readonly_nonaddressable_vars (); 919 return 0; 920 } 921 922 } // anon namespace 923 924 namespace { 925 926 const pass_data pass_data_ipa_whole_program_visibility = 927 { 928 IPA_PASS, /* type */ 929 "whole-program", /* name */ 930 OPTGROUP_NONE, /* optinfo_flags */ 931 TV_CGRAPHOPT, /* tv_id */ 932 0, /* properties_required */ 933 0, /* properties_provided */ 934 0, /* properties_destroyed */ 935 0, /* todo_flags_start */ 936 ( TODO_remove_functions | TODO_dump_symtab ), /* todo_flags_finish */ 937 }; 938 939 class pass_ipa_whole_program_visibility : public ipa_opt_pass_d 940 { 941 public: 942 pass_ipa_whole_program_visibility (gcc::context *ctxt) 943 : ipa_opt_pass_d (pass_data_ipa_whole_program_visibility, ctxt, 944 NULL, /* generate_summary */ 945 NULL, /* write_summary */ 946 NULL, /* read_summary */ 947 NULL, /* write_optimization_summary */ 948 NULL, /* read_optimization_summary */ 949 NULL, /* stmt_fixup */ 950 0, /* function_transform_todo_flags_start */ 951 NULL, /* function_transform */ 952 NULL) /* variable_transform */ 953 {} 954 955 /* opt_pass methods: */ 956 957 virtual bool gate (function *) 958 { 959 /* Do not re-run on ltrans stage. */ 960 return !flag_ltrans; 961 } 962 virtual unsigned int execute (function *) 963 { 964 return whole_program_function_and_variable_visibility (); 965 } 966 967 }; // class pass_ipa_whole_program_visibility 968 969 } // anon namespace 970 971 ipa_opt_pass_d * 972 make_pass_ipa_whole_program_visibility (gcc::context *ctxt) 973 { 974 return new pass_ipa_whole_program_visibility (ctxt); 975 } 976 977 class pass_ipa_function_and_variable_visibility : public simple_ipa_opt_pass 978 { 979 public: 980 pass_ipa_function_and_variable_visibility (gcc::context *ctxt) 981 : simple_ipa_opt_pass (pass_data_ipa_function_and_variable_visibility, 982 ctxt) 983 {} 984 985 /* opt_pass methods: */ 986 virtual unsigned int execute (function *) 987 { 988 return function_and_variable_visibility (flag_whole_program && !flag_lto); 989 } 990 991 }; // class pass_ipa_function_and_variable_visibility 992 993 simple_ipa_opt_pass * 994 make_pass_ipa_function_and_variable_visibility (gcc::context *ctxt) 995 { 996 return new pass_ipa_function_and_variable_visibility (ctxt); 997 } 998