1 /* LTO symbol table. 2 Copyright 2009, 2010 Free Software Foundation, Inc. 3 Contributed by CodeSourcery, Inc. 4 5 This file is part of GCC. 6 7 GCC is free software; you can redistribute it and/or modify it under 8 the terms of the GNU General Public License as published by the Free 9 Software Foundation; either version 3, or (at your option) any later 10 version. 11 12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY 13 WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 for more details. 16 17 You should have received a copy of the GNU General Public License 18 along with GCC; see the file COPYING3. If not see 19 <http://www.gnu.org/licenses/>. */ 20 21 #include "config.h" 22 #include "system.h" 23 #include "coretypes.h" 24 #include "diagnostic-core.h" 25 #include "tree.h" 26 #include "gimple.h" 27 #include "ggc.h" 28 #include "hashtab.h" 29 #include "plugin-api.h" 30 #include "lto-streamer.h" 31 32 /* Vector to keep track of external variables we've seen so far. */ 33 VEC(tree,gc) *lto_global_var_decls; 34 35 /* Symbol table entry. */ 36 37 struct GTY(()) lto_symtab_entry_def 38 { 39 /* The symbol table entry key, an IDENTIFIER. */ 40 tree id; 41 /* The symbol table entry, a DECL. */ 42 tree decl; 43 /* The cgraph node if decl is a function decl. Filled in during the 44 merging process. */ 45 struct cgraph_node *node; 46 /* The varpool node if decl is a variable decl. Filled in during the 47 merging process. */ 48 struct varpool_node *vnode; 49 /* LTO file-data and symbol resolution for this decl. */ 50 struct lto_file_decl_data * GTY((skip (""))) file_data; 51 enum ld_plugin_symbol_resolution resolution; 52 /* True when resolution was guessed and not read from the file. */ 53 bool guessed; 54 /* Pointer to the next entry with the same key. Before decl merging 55 this links all symbols from the different TUs. After decl merging 56 this links merged but incompatible decls, thus all prevailing ones 57 remaining. */ 58 struct lto_symtab_entry_def *next; 59 }; 60 typedef struct lto_symtab_entry_def *lto_symtab_entry_t; 61 62 /* A poor man's symbol table. This hashes identifier to prevailing DECL 63 if there is one. */ 64 65 static GTY ((if_marked ("lto_symtab_entry_marked_p"), 66 param_is (struct lto_symtab_entry_def))) 67 htab_t lto_symtab_identifiers; 68 69 /* Free symtab hashtable. */ 70 71 void 72 lto_symtab_free (void) 73 { 74 htab_delete (lto_symtab_identifiers); 75 lto_symtab_identifiers = NULL; 76 } 77 78 /* Return the hash value of an lto_symtab_entry_t object pointed to by P. */ 79 80 static hashval_t 81 lto_symtab_entry_hash (const void *p) 82 { 83 const struct lto_symtab_entry_def *base = 84 (const struct lto_symtab_entry_def *) p; 85 return IDENTIFIER_HASH_VALUE (base->id); 86 } 87 88 /* Return non-zero if P1 and P2 points to lto_symtab_entry_def structs 89 corresponding to the same symbol. */ 90 91 static int 92 lto_symtab_entry_eq (const void *p1, const void *p2) 93 { 94 const struct lto_symtab_entry_def *base1 = 95 (const struct lto_symtab_entry_def *) p1; 96 const struct lto_symtab_entry_def *base2 = 97 (const struct lto_symtab_entry_def *) p2; 98 return (base1->id == base2->id); 99 } 100 101 /* Returns non-zero if P points to an lto_symtab_entry_def struct that needs 102 to be marked for GC. */ 103 104 static int 105 lto_symtab_entry_marked_p (const void *p) 106 { 107 const struct lto_symtab_entry_def *base = 108 (const struct lto_symtab_entry_def *) p; 109 110 /* Keep this only if the common IDENTIFIER_NODE of the symtab chain 111 is marked which it will be if at least one of the DECLs in the 112 chain is marked. */ 113 return ggc_marked_p (base->id); 114 } 115 116 /* Lazily initialize resolution hash tables. */ 117 118 static void 119 lto_symtab_maybe_init_hash_table (void) 120 { 121 if (lto_symtab_identifiers) 122 return; 123 124 lto_symtab_identifiers = 125 htab_create_ggc (1021, lto_symtab_entry_hash, 126 lto_symtab_entry_eq, NULL); 127 } 128 129 /* Registers DECL with the LTO symbol table as having resolution RESOLUTION 130 and read from FILE_DATA. */ 131 132 void 133 lto_symtab_register_decl (tree decl, 134 ld_plugin_symbol_resolution_t resolution, 135 struct lto_file_decl_data *file_data) 136 { 137 lto_symtab_entry_t new_entry; 138 void **slot; 139 140 /* Check that declarations reaching this function do not have 141 properties inconsistent with having external linkage. If any of 142 these asertions fail, then the object file reader has failed to 143 detect these cases and issue appropriate error messages. */ 144 gcc_assert (decl 145 && TREE_PUBLIC (decl) 146 && (TREE_CODE (decl) == VAR_DECL 147 || TREE_CODE (decl) == FUNCTION_DECL) 148 && DECL_ASSEMBLER_NAME_SET_P (decl)); 149 if (TREE_CODE (decl) == VAR_DECL 150 && DECL_INITIAL (decl)) 151 gcc_assert (!DECL_EXTERNAL (decl) 152 || (TREE_STATIC (decl) && TREE_READONLY (decl))); 153 if (TREE_CODE (decl) == FUNCTION_DECL) 154 gcc_assert (!DECL_ABSTRACT (decl)); 155 156 new_entry = ggc_alloc_cleared_lto_symtab_entry_def (); 157 new_entry->id = (*targetm.asm_out.mangle_assembler_name) 158 (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl))); 159 new_entry->decl = decl; 160 new_entry->resolution = resolution; 161 new_entry->file_data = file_data; 162 163 lto_symtab_maybe_init_hash_table (); 164 slot = htab_find_slot (lto_symtab_identifiers, new_entry, INSERT); 165 new_entry->next = (lto_symtab_entry_t) *slot; 166 *slot = new_entry; 167 } 168 169 /* Get the lto_symtab_entry_def struct associated with ID 170 if there is one. */ 171 172 static lto_symtab_entry_t 173 lto_symtab_get (tree id) 174 { 175 struct lto_symtab_entry_def temp; 176 void **slot; 177 178 lto_symtab_maybe_init_hash_table (); 179 temp.id = id; 180 slot = htab_find_slot (lto_symtab_identifiers, &temp, NO_INSERT); 181 return slot ? (lto_symtab_entry_t) *slot : NULL; 182 } 183 184 /* Get the linker resolution for DECL. */ 185 186 enum ld_plugin_symbol_resolution 187 lto_symtab_get_resolution (tree decl) 188 { 189 lto_symtab_entry_t e; 190 191 gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl)); 192 193 e = lto_symtab_get ((*targetm.asm_out.mangle_assembler_name) 194 (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl)))); 195 while (e && e->decl != decl) 196 e = e->next; 197 if (!e) 198 return LDPR_UNKNOWN; 199 200 return e->resolution; 201 } 202 203 204 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging 205 all edges and removing the old node. */ 206 207 static void 208 lto_cgraph_replace_node (struct cgraph_node *node, 209 struct cgraph_node *prevailing_node) 210 { 211 struct cgraph_edge *e, *next; 212 bool compatible_p; 213 214 if (cgraph_dump_file) 215 { 216 fprintf (cgraph_dump_file, "Replacing cgraph node %s/%i by %s/%i" 217 " for symbol %s\n", 218 xstrdup (cgraph_node_name (node)), node->uid, 219 xstrdup (cgraph_node_name (prevailing_node)), 220 prevailing_node->uid, 221 IDENTIFIER_POINTER ((*targetm.asm_out.mangle_assembler_name) 222 (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (node->decl))))); 223 } 224 225 /* Merge node flags. */ 226 if (node->needed) 227 cgraph_mark_needed_node (prevailing_node); 228 if (node->reachable) 229 cgraph_mark_reachable_node (prevailing_node); 230 if (node->address_taken) 231 { 232 gcc_assert (!prevailing_node->global.inlined_to); 233 cgraph_mark_address_taken_node (prevailing_node); 234 } 235 236 /* Redirect all incoming edges. */ 237 compatible_p 238 = types_compatible_p (TREE_TYPE (TREE_TYPE (prevailing_node->decl)), 239 TREE_TYPE (TREE_TYPE (node->decl))); 240 for (e = node->callers; e; e = next) 241 { 242 next = e->next_caller; 243 cgraph_redirect_edge_callee (e, prevailing_node); 244 /* If there is a mismatch between the supposed callee return type and 245 the real one do not attempt to inline this function. 246 ??? We really need a way to match function signatures for ABI 247 compatibility and perform related promotions at inlining time. */ 248 if (!compatible_p) 249 e->call_stmt_cannot_inline_p = 1; 250 } 251 /* Redirect incomming references. */ 252 ipa_clone_refering (prevailing_node, NULL, &node->ref_list); 253 254 /* Finally remove the replaced node. */ 255 cgraph_remove_node (node); 256 } 257 258 /* Replace the cgraph node NODE with PREVAILING_NODE in the cgraph, merging 259 all edges and removing the old node. */ 260 261 static void 262 lto_varpool_replace_node (struct varpool_node *vnode, 263 struct varpool_node *prevailing_node) 264 { 265 /* Merge node flags. */ 266 if (vnode->needed) 267 { 268 gcc_assert (!vnode->analyzed || prevailing_node->analyzed); 269 varpool_mark_needed_node (prevailing_node); 270 } 271 gcc_assert (!vnode->finalized || prevailing_node->finalized); 272 gcc_assert (!vnode->analyzed || prevailing_node->analyzed); 273 274 ipa_clone_refering (NULL, prevailing_node, &vnode->ref_list); 275 276 /* Be sure we can garbage collect the initializer. */ 277 if (DECL_INITIAL (vnode->decl)) 278 DECL_INITIAL (vnode->decl) = error_mark_node; 279 /* Finally remove the replaced node. */ 280 varpool_remove_node (vnode); 281 } 282 283 /* Merge two variable or function symbol table entries PREVAILING and ENTRY. 284 Return false if the symbols are not fully compatible and a diagnostic 285 should be emitted. */ 286 287 static bool 288 lto_symtab_merge (lto_symtab_entry_t prevailing, lto_symtab_entry_t entry) 289 { 290 tree prevailing_decl = prevailing->decl; 291 tree decl = entry->decl; 292 tree prevailing_type, type; 293 294 /* Merge decl state in both directions, we may still end up using 295 the new decl. */ 296 TREE_ADDRESSABLE (prevailing_decl) |= TREE_ADDRESSABLE (decl); 297 TREE_ADDRESSABLE (decl) |= TREE_ADDRESSABLE (prevailing_decl); 298 299 /* The linker may ask us to combine two incompatible symbols. 300 Detect this case and notify the caller of required diagnostics. */ 301 302 if (TREE_CODE (decl) == FUNCTION_DECL) 303 { 304 if (!types_compatible_p (TREE_TYPE (prevailing_decl), 305 TREE_TYPE (decl))) 306 /* If we don't have a merged type yet...sigh. The linker 307 wouldn't complain if the types were mismatched, so we 308 probably shouldn't either. Just use the type from 309 whichever decl appears to be associated with the 310 definition. If for some odd reason neither decl is, the 311 older one wins. */ 312 (void) 0; 313 314 return true; 315 } 316 317 /* Now we exclusively deal with VAR_DECLs. */ 318 319 /* Sharing a global symbol is a strong hint that two types are 320 compatible. We could use this information to complete 321 incomplete pointed-to types more aggressively here, ignoring 322 mismatches in both field and tag names. It's difficult though 323 to guarantee that this does not have side-effects on merging 324 more compatible types from other translation units though. */ 325 326 /* We can tolerate differences in type qualification, the 327 qualification of the prevailing definition will prevail. 328 ??? In principle we might want to only warn for structurally 329 incompatible types here, but unless we have protective measures 330 for TBAA in place that would hide useful information. */ 331 prevailing_type = TYPE_MAIN_VARIANT (TREE_TYPE (prevailing_decl)); 332 type = TYPE_MAIN_VARIANT (TREE_TYPE (decl)); 333 334 if (!types_compatible_p (prevailing_type, type)) 335 { 336 if (COMPLETE_TYPE_P (type)) 337 return false; 338 339 /* If type is incomplete then avoid warnings in the cases 340 that TBAA handles just fine. */ 341 342 if (TREE_CODE (prevailing_type) != TREE_CODE (type)) 343 return false; 344 345 if (TREE_CODE (prevailing_type) == ARRAY_TYPE) 346 { 347 tree tem1 = TREE_TYPE (prevailing_type); 348 tree tem2 = TREE_TYPE (type); 349 while (TREE_CODE (tem1) == ARRAY_TYPE 350 && TREE_CODE (tem2) == ARRAY_TYPE) 351 { 352 tem1 = TREE_TYPE (tem1); 353 tem2 = TREE_TYPE (tem2); 354 } 355 356 if (TREE_CODE (tem1) != TREE_CODE (tem2)) 357 return false; 358 359 if (!types_compatible_p (tem1, tem2)) 360 return false; 361 } 362 363 /* Fallthru. Compatible enough. */ 364 } 365 366 /* ??? We might want to emit a warning here if type qualification 367 differences were spotted. Do not do this unconditionally though. */ 368 369 /* There is no point in comparing too many details of the decls here. 370 The type compatibility checks or the completing of types has properly 371 dealt with most issues. */ 372 373 /* The following should all not invoke fatal errors as in non-LTO 374 mode the linker wouldn't complain either. Just emit warnings. */ 375 376 /* Report a warning if user-specified alignments do not match. */ 377 if ((DECL_USER_ALIGN (prevailing_decl) && DECL_USER_ALIGN (decl)) 378 && DECL_ALIGN (prevailing_decl) < DECL_ALIGN (decl)) 379 return false; 380 381 return true; 382 } 383 384 /* Return true if the symtab entry E can be replaced by another symtab 385 entry. */ 386 387 static bool 388 lto_symtab_resolve_replaceable_p (lto_symtab_entry_t e) 389 { 390 if (DECL_EXTERNAL (e->decl) 391 || DECL_COMDAT (e->decl) 392 || DECL_ONE_ONLY (e->decl) 393 || DECL_WEAK (e->decl)) 394 return true; 395 396 if (TREE_CODE (e->decl) == VAR_DECL) 397 return (DECL_COMMON (e->decl) 398 || (!flag_no_common && !DECL_INITIAL (e->decl))); 399 400 return false; 401 } 402 403 /* Return true if the symtab entry E can be the prevailing one. */ 404 405 static bool 406 lto_symtab_resolve_can_prevail_p (lto_symtab_entry_t e) 407 { 408 /* The C++ frontend ends up neither setting TREE_STATIC nor 409 DECL_EXTERNAL on virtual methods but only TREE_PUBLIC. 410 So do not reject !TREE_STATIC here but only DECL_EXTERNAL. */ 411 if (DECL_EXTERNAL (e->decl)) 412 return false; 413 414 /* For functions we need a non-discarded body. */ 415 if (TREE_CODE (e->decl) == FUNCTION_DECL) 416 return (e->node && e->node->analyzed); 417 418 else if (TREE_CODE (e->decl) == VAR_DECL) 419 { 420 if (!e->vnode) 421 return false; 422 return e->vnode->finalized; 423 } 424 425 gcc_unreachable (); 426 } 427 428 /* Resolve the symbol with the candidates in the chain *SLOT and store 429 their resolutions. */ 430 431 static void 432 lto_symtab_resolve_symbols (void **slot) 433 { 434 lto_symtab_entry_t e; 435 lto_symtab_entry_t prevailing = NULL; 436 437 /* Always set e->node so that edges are updated to reflect decl merging. */ 438 for (e = (lto_symtab_entry_t) *slot; e; e = e->next) 439 { 440 if (TREE_CODE (e->decl) == FUNCTION_DECL) 441 e->node = cgraph_get_node (e->decl); 442 else if (TREE_CODE (e->decl) == VAR_DECL) 443 e->vnode = varpool_get_node (e->decl); 444 if (e->resolution == LDPR_PREVAILING_DEF_IRONLY 445 || e->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP 446 || e->resolution == LDPR_PREVAILING_DEF) 447 prevailing = e; 448 } 449 450 /* If the chain is already resolved there is nothing else to do. */ 451 if (prevailing) 452 return; 453 454 /* Find the single non-replaceable prevailing symbol and 455 diagnose ODR violations. */ 456 for (e = (lto_symtab_entry_t) *slot; e; e = e->next) 457 { 458 if (!lto_symtab_resolve_can_prevail_p (e)) 459 { 460 e->resolution = LDPR_RESOLVED_IR; 461 e->guessed = true; 462 continue; 463 } 464 465 /* Set a default resolution - the final prevailing one will get 466 adjusted later. */ 467 e->resolution = LDPR_PREEMPTED_IR; 468 e->guessed = true; 469 if (!lto_symtab_resolve_replaceable_p (e)) 470 { 471 if (prevailing) 472 { 473 error_at (DECL_SOURCE_LOCATION (e->decl), 474 "%qD has already been defined", e->decl); 475 inform (DECL_SOURCE_LOCATION (prevailing->decl), 476 "previously defined here"); 477 } 478 prevailing = e; 479 } 480 } 481 if (prevailing) 482 goto found; 483 484 /* Do a second round choosing one from the replaceable prevailing decls. */ 485 for (e = (lto_symtab_entry_t) *slot; e; e = e->next) 486 { 487 if (e->resolution != LDPR_PREEMPTED_IR) 488 continue; 489 490 /* Choose the first function that can prevail as prevailing. */ 491 if (TREE_CODE (e->decl) == FUNCTION_DECL) 492 { 493 prevailing = e; 494 break; 495 } 496 497 /* From variables that can prevail choose the largest one. */ 498 if (!prevailing 499 || tree_int_cst_lt (DECL_SIZE (prevailing->decl), 500 DECL_SIZE (e->decl))) 501 prevailing = e; 502 } 503 504 if (!prevailing) 505 return; 506 507 found: 508 /* If current lto files represent the whole program, 509 it is correct to use LDPR_PREVALING_DEF_IRONLY. 510 If current lto files are part of whole program, internal 511 resolver doesn't know if it is LDPR_PREVAILING_DEF 512 or LDPR_PREVAILING_DEF_IRONLY. Use IRONLY conforms to 513 using -fwhole-program. Otherwise, it doesn't 514 matter using either LDPR_PREVAILING_DEF or 515 LDPR_PREVAILING_DEF_IRONLY 516 517 FIXME: above workaround due to gold plugin makes some 518 variables IRONLY, which are indeed PREVAILING_DEF in 519 resolution file. These variables still need manual 520 externally_visible attribute. */ 521 prevailing->resolution = LDPR_PREVAILING_DEF_IRONLY; 522 prevailing->guessed = true; 523 } 524 525 /* Merge all decls in the symbol table chain to the prevailing decl and 526 issue diagnostics about type mismatches. If DIAGNOSED_P is true 527 do not issue further diagnostics.*/ 528 529 static void 530 lto_symtab_merge_decls_2 (void **slot, bool diagnosed_p) 531 { 532 lto_symtab_entry_t prevailing, e; 533 VEC(tree, heap) *mismatches = NULL; 534 unsigned i; 535 tree decl; 536 537 /* Nothing to do for a single entry. */ 538 prevailing = (lto_symtab_entry_t) *slot; 539 if (!prevailing->next) 540 return; 541 542 /* Try to merge each entry with the prevailing one. */ 543 for (e = prevailing->next; e; e = e->next) 544 { 545 if (!lto_symtab_merge (prevailing, e) 546 && !diagnosed_p) 547 VEC_safe_push (tree, heap, mismatches, e->decl); 548 } 549 if (VEC_empty (tree, mismatches)) 550 return; 551 552 /* Diagnose all mismatched re-declarations. */ 553 FOR_EACH_VEC_ELT (tree, mismatches, i, decl) 554 { 555 if (!types_compatible_p (TREE_TYPE (prevailing->decl), TREE_TYPE (decl))) 556 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0, 557 "type of %qD does not match original " 558 "declaration", decl); 559 560 else if ((DECL_USER_ALIGN (prevailing->decl) && DECL_USER_ALIGN (decl)) 561 && DECL_ALIGN (prevailing->decl) < DECL_ALIGN (decl)) 562 { 563 diagnosed_p |= warning_at (DECL_SOURCE_LOCATION (decl), 0, 564 "alignment of %qD is bigger than " 565 "original declaration", decl); 566 } 567 } 568 if (diagnosed_p) 569 inform (DECL_SOURCE_LOCATION (prevailing->decl), 570 "previously declared here"); 571 572 VEC_free (tree, heap, mismatches); 573 } 574 575 /* Helper to process the decl chain for the symbol table entry *SLOT. */ 576 577 static int 578 lto_symtab_merge_decls_1 (void **slot, void *data ATTRIBUTE_UNUSED) 579 { 580 lto_symtab_entry_t e, prevailing; 581 bool diagnosed_p = false; 582 583 /* Compute the symbol resolutions. This is a no-op when using the 584 linker plugin. */ 585 lto_symtab_resolve_symbols (slot); 586 587 /* Find the prevailing decl. */ 588 for (prevailing = (lto_symtab_entry_t) *slot; 589 prevailing 590 && prevailing->resolution != LDPR_PREVAILING_DEF_IRONLY 591 && prevailing->resolution != LDPR_PREVAILING_DEF_IRONLY_EXP 592 && prevailing->resolution != LDPR_PREVAILING_DEF; 593 prevailing = prevailing->next) 594 ; 595 596 /* Assert it's the only one. */ 597 if (prevailing) 598 for (e = prevailing->next; e; e = e->next) 599 { 600 if (e->resolution == LDPR_PREVAILING_DEF_IRONLY 601 || e->resolution == LDPR_PREVAILING_DEF_IRONLY_EXP 602 || e->resolution == LDPR_PREVAILING_DEF) 603 fatal_error ("multiple prevailing defs for %qE", 604 DECL_NAME (prevailing->decl)); 605 } 606 607 /* If there's not a prevailing symbol yet it's an external reference. 608 Happens a lot during ltrans. Choose the first symbol with a 609 cgraph or a varpool node. */ 610 if (!prevailing) 611 { 612 prevailing = (lto_symtab_entry_t) *slot; 613 /* For functions choose one with a cgraph node. */ 614 if (TREE_CODE (prevailing->decl) == FUNCTION_DECL) 615 while (!prevailing->node 616 && prevailing->next) 617 prevailing = prevailing->next; 618 /* For variables chose with a priority variant with vnode 619 attached (i.e. from unit where external declaration of 620 variable is actually used). 621 When there are multiple variants, chose one with size. 622 This is needed for C++ typeinfos, for example in 623 lto/20081204-1 there are typeifos in both units, just 624 one of them do have size. */ 625 if (TREE_CODE (prevailing->decl) == VAR_DECL) 626 { 627 for (e = prevailing->next; e; e = e->next) 628 if ((!prevailing->vnode && e->vnode) 629 || ((prevailing->vnode != NULL) == (e->vnode != NULL) 630 && !COMPLETE_TYPE_P (TREE_TYPE (prevailing->decl)) 631 && COMPLETE_TYPE_P (TREE_TYPE (e->decl)))) 632 prevailing = e; 633 } 634 } 635 636 /* Move it first in the list. */ 637 if ((lto_symtab_entry_t) *slot != prevailing) 638 { 639 for (e = (lto_symtab_entry_t) *slot; e->next != prevailing; e = e->next) 640 ; 641 e->next = prevailing->next; 642 prevailing->next = (lto_symtab_entry_t) *slot; 643 *slot = (void *) prevailing; 644 } 645 646 /* Record the prevailing variable. */ 647 if (TREE_CODE (prevailing->decl) == VAR_DECL) 648 VEC_safe_push (tree, gc, lto_global_var_decls, prevailing->decl); 649 650 /* Diagnose mismatched objects. */ 651 for (e = prevailing->next; e; e = e->next) 652 { 653 if (TREE_CODE (prevailing->decl) == TREE_CODE (e->decl)) 654 continue; 655 656 switch (TREE_CODE (prevailing->decl)) 657 { 658 case VAR_DECL: 659 gcc_assert (TREE_CODE (e->decl) == FUNCTION_DECL); 660 error_at (DECL_SOURCE_LOCATION (e->decl), 661 "variable %qD redeclared as function", prevailing->decl); 662 break; 663 664 case FUNCTION_DECL: 665 gcc_assert (TREE_CODE (e->decl) == VAR_DECL); 666 error_at (DECL_SOURCE_LOCATION (e->decl), 667 "function %qD redeclared as variable", prevailing->decl); 668 break; 669 670 default: 671 gcc_unreachable (); 672 } 673 674 diagnosed_p = true; 675 } 676 if (diagnosed_p) 677 inform (DECL_SOURCE_LOCATION (prevailing->decl), 678 "previously declared here"); 679 680 /* Merge the chain to the single prevailing decl and diagnose 681 mismatches. */ 682 lto_symtab_merge_decls_2 (slot, diagnosed_p); 683 684 /* Store resolution decision into the callgraph. 685 In LTRANS don't overwrite information we stored into callgraph at 686 WPA stage. 687 688 Do not bother to store guessed decisions. Generic code knows how 689 to handle UNKNOWN relocation well. 690 691 The problem with storing guessed decision is whether to use 692 PREVAILING_DEF, PREVAILING_DEF_IRONLY, PREVAILING_DEF_IRONLY_EXP. 693 First one would disable some whole program optimizations, while 694 ther second would imply to many whole program assumptions. */ 695 if (prevailing->node && !flag_ltrans && !prevailing->guessed) 696 prevailing->node->resolution = prevailing->resolution; 697 else if (prevailing->vnode && !flag_ltrans && !prevailing->guessed) 698 prevailing->vnode->resolution = prevailing->resolution; 699 return 1; 700 } 701 702 /* Resolve and merge all symbol table chains to a prevailing decl. */ 703 704 void 705 lto_symtab_merge_decls (void) 706 { 707 lto_symtab_maybe_init_hash_table (); 708 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_decls_1, NULL); 709 } 710 711 /* Helper to process the decl chain for the symbol table entry *SLOT. */ 712 713 static int 714 lto_symtab_merge_cgraph_nodes_1 (void **slot, void *data ATTRIBUTE_UNUSED) 715 { 716 lto_symtab_entry_t e, prevailing = (lto_symtab_entry_t) *slot; 717 718 if (!prevailing->next) 719 return 1; 720 721 /* Replace the cgraph node of each entry with the prevailing one. */ 722 for (e = prevailing->next; e; e = e->next) 723 { 724 if (e->node != NULL) 725 { 726 /* In case we prevail funcion by an alias, we can run into case 727 that the alias has no cgraph node attached, since it was 728 previously unused. Create the node. */ 729 if (!prevailing->node) 730 { 731 prevailing->node = cgraph_create_node (prevailing->decl); 732 prevailing->node->alias = true; 733 } 734 lto_cgraph_replace_node (e->node, prevailing->node); 735 } 736 if (e->vnode != NULL) 737 { 738 if (!prevailing->vnode) 739 { 740 prevailing->vnode = varpool_node (prevailing->decl); 741 prevailing->vnode->alias = true; 742 } 743 lto_varpool_replace_node (e->vnode, prevailing->vnode); 744 } 745 } 746 747 /* Drop all but the prevailing decl from the symtab. */ 748 prevailing->next = NULL; 749 750 return 1; 751 } 752 753 /* Merge cgraph nodes according to the symbol merging done by 754 lto_symtab_merge_decls. */ 755 756 void 757 lto_symtab_merge_cgraph_nodes (void) 758 { 759 struct cgraph_node *node; 760 struct varpool_node *vnode; 761 lto_symtab_maybe_init_hash_table (); 762 htab_traverse (lto_symtab_identifiers, lto_symtab_merge_cgraph_nodes_1, NULL); 763 764 for (node = cgraph_nodes; node; node = node->next) 765 if ((node->thunk.thunk_p || node->alias) 766 && node->thunk.alias) 767 node->thunk.alias = lto_symtab_prevailing_decl (node->thunk.alias); 768 for (vnode = varpool_nodes; vnode; vnode = vnode->next) 769 if (vnode->alias_of) 770 vnode->alias_of = lto_symtab_prevailing_decl (vnode->alias_of); 771 } 772 773 /* Given the decl DECL, return the prevailing decl with the same name. */ 774 775 tree 776 lto_symtab_prevailing_decl (tree decl) 777 { 778 lto_symtab_entry_t ret; 779 780 /* Builtins and local symbols are their own prevailing decl. */ 781 if (!TREE_PUBLIC (decl) || is_builtin_fn (decl)) 782 return decl; 783 784 /* DECL_ABSTRACTs are their own prevailng decl. */ 785 if (TREE_CODE (decl) == FUNCTION_DECL && DECL_ABSTRACT (decl)) 786 return decl; 787 788 /* Ensure DECL_ASSEMBLER_NAME will not set assembler name. */ 789 gcc_assert (DECL_ASSEMBLER_NAME_SET_P (decl)); 790 791 /* Walk through the list of candidates and return the one we merged to. */ 792 ret = lto_symtab_get ((*targetm.asm_out.mangle_assembler_name) 793 (IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (decl)))); 794 if (!ret) 795 return NULL_TREE; 796 797 return ret->decl; 798 } 799 800 #include "gt-lto-symtab.h" 801