1 /* Rewrite a program in Normal form into SSA. 2 Copyright (C) 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010 3 Free Software Foundation, Inc. 4 Contributed by Diego Novillo <dnovillo@redhat.com> 5 6 This file is part of GCC. 7 8 GCC is free software; you can redistribute it and/or modify 9 it under the terms of the GNU General Public License as published by 10 the Free Software Foundation; either version 3, or (at your option) 11 any later version. 12 13 GCC is distributed in the hope that it will be useful, 14 but WITHOUT ANY WARRANTY; without even the implied warranty of 15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 GNU General Public License for more details. 17 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/>. */ 21 22 #include "config.h" 23 #include "system.h" 24 #include "coretypes.h" 25 #include "tm.h" 26 #include "tree.h" 27 #include "flags.h" 28 #include "rtl.h" 29 #include "tm_p.h" 30 #include "langhooks.h" 31 #include "hard-reg-set.h" 32 #include "basic-block.h" 33 #include "output.h" 34 #include "expr.h" 35 #include "function.h" 36 #include "diagnostic.h" 37 #include "bitmap.h" 38 #include "tree-flow.h" 39 #include "gimple.h" 40 #include "tree-inline.h" 41 #include "varray.h" 42 #include "timevar.h" 43 #include "hashtab.h" 44 #include "tree-dump.h" 45 #include "tree-pass.h" 46 #include "cfgloop.h" 47 #include "domwalk.h" 48 #include "ggc.h" 49 #include "params.h" 50 #include "vecprim.h" 51 52 53 /* This file builds the SSA form for a function as described in: 54 R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently 55 Computing Static Single Assignment Form and the Control Dependence 56 Graph. ACM Transactions on Programming Languages and Systems, 57 13(4):451-490, October 1991. */ 58 59 /* Structure to map a variable VAR to the set of blocks that contain 60 definitions for VAR. */ 61 struct def_blocks_d 62 { 63 /* The variable. */ 64 tree var; 65 66 /* Blocks that contain definitions of VAR. Bit I will be set if the 67 Ith block contains a definition of VAR. */ 68 bitmap def_blocks; 69 70 /* Blocks that contain a PHI node for VAR. */ 71 bitmap phi_blocks; 72 73 /* Blocks where VAR is live-on-entry. Similar semantics as 74 DEF_BLOCKS. */ 75 bitmap livein_blocks; 76 }; 77 78 79 /* Each entry in DEF_BLOCKS contains an element of type STRUCT 80 DEF_BLOCKS_D, mapping a variable VAR to a bitmap describing all the 81 basic blocks where VAR is defined (assigned a new value). It also 82 contains a bitmap of all the blocks where VAR is live-on-entry 83 (i.e., there is a use of VAR in block B without a preceding 84 definition in B). The live-on-entry information is used when 85 computing PHI pruning heuristics. */ 86 static htab_t def_blocks; 87 88 /* Stack of trees used to restore the global currdefs to its original 89 state after completing rewriting of a block and its dominator 90 children. Its elements have the following properties: 91 92 - An SSA_NAME (N) indicates that the current definition of the 93 underlying variable should be set to the given SSA_NAME. If the 94 symbol associated with the SSA_NAME is not a GIMPLE register, the 95 next slot in the stack must be a _DECL node (SYM). In this case, 96 the name N in the previous slot is the current reaching 97 definition for SYM. 98 99 - A _DECL node indicates that the underlying variable has no 100 current definition. 101 102 - A NULL node at the top entry is used to mark the last slot 103 associated with the current block. */ 104 static VEC(tree,heap) *block_defs_stack; 105 106 107 /* Set of existing SSA names being replaced by update_ssa. */ 108 static sbitmap old_ssa_names; 109 110 /* Set of new SSA names being added by update_ssa. Note that both 111 NEW_SSA_NAMES and OLD_SSA_NAMES are dense bitmaps because most of 112 the operations done on them are presence tests. */ 113 static sbitmap new_ssa_names; 114 115 sbitmap interesting_blocks; 116 117 /* Set of SSA names that have been marked to be released after they 118 were registered in the replacement table. They will be finally 119 released after we finish updating the SSA web. */ 120 static bitmap names_to_release; 121 122 static VEC(gimple_vec, heap) *phis_to_rewrite; 123 124 /* The bitmap of non-NULL elements of PHIS_TO_REWRITE. */ 125 static bitmap blocks_with_phis_to_rewrite; 126 127 /* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need 128 to grow as the callers to register_new_name_mapping will typically 129 create new names on the fly. FIXME. Currently set to 1/3 to avoid 130 frequent reallocations but still need to find a reasonable growth 131 strategy. */ 132 #define NAME_SETS_GROWTH_FACTOR (MAX (3, num_ssa_names / 3)) 133 134 /* Tuple used to represent replacement mappings. */ 135 struct repl_map_d 136 { 137 tree name; 138 bitmap set; 139 }; 140 141 142 /* NEW -> OLD_SET replacement table. If we are replacing several 143 existing SSA names O_1, O_2, ..., O_j with a new name N_i, 144 then REPL_TBL[N_i] = { O_1, O_2, ..., O_j }. */ 145 static htab_t repl_tbl; 146 147 /* The function the SSA updating data structures have been initialized for. 148 NULL if they need to be initialized by register_new_name_mapping. */ 149 static struct function *update_ssa_initialized_fn = NULL; 150 151 /* Statistics kept by update_ssa to use in the virtual mapping 152 heuristic. If the number of virtual mappings is beyond certain 153 threshold, the updater will switch from using the mappings into 154 renaming the virtual symbols from scratch. In some cases, the 155 large number of name mappings for virtual names causes significant 156 slowdowns in the PHI insertion code. */ 157 struct update_ssa_stats_d 158 { 159 unsigned num_virtual_mappings; 160 unsigned num_total_mappings; 161 bitmap virtual_symbols; 162 unsigned num_virtual_symbols; 163 }; 164 static struct update_ssa_stats_d update_ssa_stats; 165 166 /* Global data to attach to the main dominator walk structure. */ 167 struct mark_def_sites_global_data 168 { 169 /* This bitmap contains the variables which are set before they 170 are used in a basic block. */ 171 bitmap kills; 172 }; 173 174 175 /* Information stored for SSA names. */ 176 struct ssa_name_info 177 { 178 /* The current reaching definition replacing this SSA name. */ 179 tree current_def; 180 181 /* This field indicates whether or not the variable may need PHI nodes. 182 See the enum's definition for more detailed information about the 183 states. */ 184 ENUM_BITFIELD (need_phi_state) need_phi_state : 2; 185 186 /* Age of this record (so that info_for_ssa_name table can be cleared 187 quickly); if AGE < CURRENT_INFO_FOR_SSA_NAME_AGE, then the fields 188 are assumed to be null. */ 189 unsigned age; 190 }; 191 192 /* The information associated with names. */ 193 typedef struct ssa_name_info *ssa_name_info_p; 194 DEF_VEC_P (ssa_name_info_p); 195 DEF_VEC_ALLOC_P (ssa_name_info_p, heap); 196 197 static VEC(ssa_name_info_p, heap) *info_for_ssa_name; 198 static unsigned current_info_for_ssa_name_age; 199 200 /* The set of blocks affected by update_ssa. */ 201 static bitmap blocks_to_update; 202 203 /* The main entry point to the SSA renamer (rewrite_blocks) may be 204 called several times to do different, but related, tasks. 205 Initially, we need it to rename the whole program into SSA form. 206 At other times, we may need it to only rename into SSA newly 207 exposed symbols. Finally, we can also call it to incrementally fix 208 an already built SSA web. */ 209 enum rewrite_mode { 210 /* Convert the whole function into SSA form. */ 211 REWRITE_ALL, 212 213 /* Incrementally update the SSA web by replacing existing SSA 214 names with new ones. See update_ssa for details. */ 215 REWRITE_UPDATE 216 }; 217 218 219 220 221 /* Prototypes for debugging functions. */ 222 extern void dump_tree_ssa (FILE *); 223 extern void debug_tree_ssa (void); 224 extern void debug_def_blocks (void); 225 extern void dump_tree_ssa_stats (FILE *); 226 extern void debug_tree_ssa_stats (void); 227 extern void dump_update_ssa (FILE *); 228 extern void debug_update_ssa (void); 229 extern void dump_names_replaced_by (FILE *, tree); 230 extern void debug_names_replaced_by (tree); 231 extern void dump_def_blocks (FILE *); 232 extern void debug_def_blocks (void); 233 extern void dump_defs_stack (FILE *, int); 234 extern void debug_defs_stack (int); 235 extern void dump_currdefs (FILE *); 236 extern void debug_currdefs (void); 237 238 /* Return true if STMT needs to be rewritten. When renaming a subset 239 of the variables, not all statements will be processed. This is 240 decided in mark_def_sites. */ 241 242 static inline bool 243 rewrite_uses_p (gimple stmt) 244 { 245 return gimple_visited_p (stmt); 246 } 247 248 249 /* Set the rewrite marker on STMT to the value given by REWRITE_P. */ 250 251 static inline void 252 set_rewrite_uses (gimple stmt, bool rewrite_p) 253 { 254 gimple_set_visited (stmt, rewrite_p); 255 } 256 257 258 /* Return true if the DEFs created by statement STMT should be 259 registered when marking new definition sites. This is slightly 260 different than rewrite_uses_p: it's used by update_ssa to 261 distinguish statements that need to have both uses and defs 262 processed from those that only need to have their defs processed. 263 Statements that define new SSA names only need to have their defs 264 registered, but they don't need to have their uses renamed. */ 265 266 static inline bool 267 register_defs_p (gimple stmt) 268 { 269 return gimple_plf (stmt, GF_PLF_1) != 0; 270 } 271 272 273 /* If REGISTER_DEFS_P is true, mark STMT to have its DEFs registered. */ 274 275 static inline void 276 set_register_defs (gimple stmt, bool register_defs_p) 277 { 278 gimple_set_plf (stmt, GF_PLF_1, register_defs_p); 279 } 280 281 282 /* Get the information associated with NAME. */ 283 284 static inline ssa_name_info_p 285 get_ssa_name_ann (tree name) 286 { 287 unsigned ver = SSA_NAME_VERSION (name); 288 unsigned len = VEC_length (ssa_name_info_p, info_for_ssa_name); 289 struct ssa_name_info *info; 290 291 if (ver >= len) 292 { 293 unsigned new_len = num_ssa_names; 294 295 VEC_reserve (ssa_name_info_p, heap, info_for_ssa_name, new_len); 296 while (len++ < new_len) 297 { 298 struct ssa_name_info *info = XCNEW (struct ssa_name_info); 299 info->age = current_info_for_ssa_name_age; 300 VEC_quick_push (ssa_name_info_p, info_for_ssa_name, info); 301 } 302 } 303 304 info = VEC_index (ssa_name_info_p, info_for_ssa_name, ver); 305 if (info->age < current_info_for_ssa_name_age) 306 { 307 info->need_phi_state = NEED_PHI_STATE_UNKNOWN; 308 info->current_def = NULL_TREE; 309 info->age = current_info_for_ssa_name_age; 310 } 311 312 return info; 313 } 314 315 316 /* Clears info for SSA names. */ 317 318 static void 319 clear_ssa_name_info (void) 320 { 321 current_info_for_ssa_name_age++; 322 } 323 324 325 /* Get phi_state field for VAR. */ 326 327 static inline enum need_phi_state 328 get_phi_state (tree var) 329 { 330 if (TREE_CODE (var) == SSA_NAME) 331 return get_ssa_name_ann (var)->need_phi_state; 332 else 333 return var_ann (var)->need_phi_state; 334 } 335 336 337 /* Sets phi_state field for VAR to STATE. */ 338 339 static inline void 340 set_phi_state (tree var, enum need_phi_state state) 341 { 342 if (TREE_CODE (var) == SSA_NAME) 343 get_ssa_name_ann (var)->need_phi_state = state; 344 else 345 var_ann (var)->need_phi_state = state; 346 } 347 348 349 /* Return the current definition for VAR. */ 350 351 tree 352 get_current_def (tree var) 353 { 354 if (TREE_CODE (var) == SSA_NAME) 355 return get_ssa_name_ann (var)->current_def; 356 else 357 return var_ann (var)->current_def; 358 } 359 360 361 /* Sets current definition of VAR to DEF. */ 362 363 void 364 set_current_def (tree var, tree def) 365 { 366 if (TREE_CODE (var) == SSA_NAME) 367 get_ssa_name_ann (var)->current_def = def; 368 else 369 var_ann (var)->current_def = def; 370 } 371 372 373 /* Compute global livein information given the set of blocks where 374 an object is locally live at the start of the block (LIVEIN) 375 and the set of blocks where the object is defined (DEF_BLOCKS). 376 377 Note: This routine augments the existing local livein information 378 to include global livein (i.e., it modifies the underlying bitmap 379 for LIVEIN). */ 380 381 void 382 compute_global_livein (bitmap livein ATTRIBUTE_UNUSED, bitmap def_blocks ATTRIBUTE_UNUSED) 383 { 384 basic_block bb, *worklist, *tos; 385 unsigned i; 386 bitmap_iterator bi; 387 388 tos = worklist 389 = (basic_block *) xmalloc (sizeof (basic_block) * (last_basic_block + 1)); 390 391 EXECUTE_IF_SET_IN_BITMAP (livein, 0, i, bi) 392 *tos++ = BASIC_BLOCK (i); 393 394 /* Iterate until the worklist is empty. */ 395 while (tos != worklist) 396 { 397 edge e; 398 edge_iterator ei; 399 400 /* Pull a block off the worklist. */ 401 bb = *--tos; 402 403 /* For each predecessor block. */ 404 FOR_EACH_EDGE (e, ei, bb->preds) 405 { 406 basic_block pred = e->src; 407 int pred_index = pred->index; 408 409 /* None of this is necessary for the entry block. */ 410 if (pred != ENTRY_BLOCK_PTR 411 && ! bitmap_bit_p (livein, pred_index) 412 && ! bitmap_bit_p (def_blocks, pred_index)) 413 { 414 *tos++ = pred; 415 bitmap_set_bit (livein, pred_index); 416 } 417 } 418 } 419 420 free (worklist); 421 } 422 423 424 /* Cleans up the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags for 425 all statements in basic block BB. */ 426 427 static void 428 initialize_flags_in_bb (basic_block bb) 429 { 430 gimple stmt; 431 gimple_stmt_iterator gsi; 432 433 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) 434 { 435 gimple phi = gsi_stmt (gsi); 436 set_rewrite_uses (phi, false); 437 set_register_defs (phi, false); 438 } 439 440 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) 441 { 442 stmt = gsi_stmt (gsi); 443 444 /* We are going to use the operand cache API, such as 445 SET_USE, SET_DEF, and FOR_EACH_IMM_USE_FAST. The operand 446 cache for each statement should be up-to-date. */ 447 gcc_assert (!gimple_modified_p (stmt)); 448 set_rewrite_uses (stmt, false); 449 set_register_defs (stmt, false); 450 } 451 } 452 453 /* Mark block BB as interesting for update_ssa. */ 454 455 static void 456 mark_block_for_update (basic_block bb) 457 { 458 gcc_assert (blocks_to_update != NULL); 459 if (bitmap_bit_p (blocks_to_update, bb->index)) 460 return; 461 bitmap_set_bit (blocks_to_update, bb->index); 462 initialize_flags_in_bb (bb); 463 } 464 465 /* Return the set of blocks where variable VAR is defined and the blocks 466 where VAR is live on entry (livein). If no entry is found in 467 DEF_BLOCKS, a new one is created and returned. */ 468 469 static inline struct def_blocks_d * 470 get_def_blocks_for (tree var) 471 { 472 struct def_blocks_d db, *db_p; 473 void **slot; 474 475 db.var = var; 476 slot = htab_find_slot (def_blocks, (void *) &db, INSERT); 477 if (*slot == NULL) 478 { 479 db_p = XNEW (struct def_blocks_d); 480 db_p->var = var; 481 db_p->def_blocks = BITMAP_ALLOC (NULL); 482 db_p->phi_blocks = BITMAP_ALLOC (NULL); 483 db_p->livein_blocks = BITMAP_ALLOC (NULL); 484 *slot = (void *) db_p; 485 } 486 else 487 db_p = (struct def_blocks_d *) *slot; 488 489 return db_p; 490 } 491 492 493 /* Mark block BB as the definition site for variable VAR. PHI_P is true if 494 VAR is defined by a PHI node. */ 495 496 static void 497 set_def_block (tree var, basic_block bb, bool phi_p) 498 { 499 struct def_blocks_d *db_p; 500 enum need_phi_state state; 501 502 state = get_phi_state (var); 503 db_p = get_def_blocks_for (var); 504 505 /* Set the bit corresponding to the block where VAR is defined. */ 506 bitmap_set_bit (db_p->def_blocks, bb->index); 507 if (phi_p) 508 bitmap_set_bit (db_p->phi_blocks, bb->index); 509 510 /* Keep track of whether or not we may need to insert PHI nodes. 511 512 If we are in the UNKNOWN state, then this is the first definition 513 of VAR. Additionally, we have not seen any uses of VAR yet, so 514 we do not need a PHI node for this variable at this time (i.e., 515 transition to NEED_PHI_STATE_NO). 516 517 If we are in any other state, then we either have multiple definitions 518 of this variable occurring in different blocks or we saw a use of the 519 variable which was not dominated by the block containing the 520 definition(s). In this case we may need a PHI node, so enter 521 state NEED_PHI_STATE_MAYBE. */ 522 if (state == NEED_PHI_STATE_UNKNOWN) 523 set_phi_state (var, NEED_PHI_STATE_NO); 524 else 525 set_phi_state (var, NEED_PHI_STATE_MAYBE); 526 } 527 528 529 /* Mark block BB as having VAR live at the entry to BB. */ 530 531 static void 532 set_livein_block (tree var, basic_block bb) 533 { 534 struct def_blocks_d *db_p; 535 enum need_phi_state state = get_phi_state (var); 536 537 db_p = get_def_blocks_for (var); 538 539 /* Set the bit corresponding to the block where VAR is live in. */ 540 bitmap_set_bit (db_p->livein_blocks, bb->index); 541 542 /* Keep track of whether or not we may need to insert PHI nodes. 543 544 If we reach here in NEED_PHI_STATE_NO, see if this use is dominated 545 by the single block containing the definition(s) of this variable. If 546 it is, then we remain in NEED_PHI_STATE_NO, otherwise we transition to 547 NEED_PHI_STATE_MAYBE. */ 548 if (state == NEED_PHI_STATE_NO) 549 { 550 int def_block_index = bitmap_first_set_bit (db_p->def_blocks); 551 552 if (def_block_index == -1 553 || ! dominated_by_p (CDI_DOMINATORS, bb, 554 BASIC_BLOCK (def_block_index))) 555 set_phi_state (var, NEED_PHI_STATE_MAYBE); 556 } 557 else 558 set_phi_state (var, NEED_PHI_STATE_MAYBE); 559 } 560 561 562 /* Return true if symbol SYM is marked for renaming. */ 563 564 static inline bool 565 symbol_marked_for_renaming (tree sym) 566 { 567 return bitmap_bit_p (SYMS_TO_RENAME (cfun), DECL_UID (sym)); 568 } 569 570 571 /* Return true if NAME is in OLD_SSA_NAMES. */ 572 573 static inline bool 574 is_old_name (tree name) 575 { 576 unsigned ver = SSA_NAME_VERSION (name); 577 if (!new_ssa_names) 578 return false; 579 return ver < new_ssa_names->n_bits && TEST_BIT (old_ssa_names, ver); 580 } 581 582 583 /* Return true if NAME is in NEW_SSA_NAMES. */ 584 585 static inline bool 586 is_new_name (tree name) 587 { 588 unsigned ver = SSA_NAME_VERSION (name); 589 if (!new_ssa_names) 590 return false; 591 return ver < new_ssa_names->n_bits && TEST_BIT (new_ssa_names, ver); 592 } 593 594 595 /* Hashing and equality functions for REPL_TBL. */ 596 597 static hashval_t 598 repl_map_hash (const void *p) 599 { 600 return htab_hash_pointer ((const void *)((const struct repl_map_d *)p)->name); 601 } 602 603 static int 604 repl_map_eq (const void *p1, const void *p2) 605 { 606 return ((const struct repl_map_d *)p1)->name 607 == ((const struct repl_map_d *)p2)->name; 608 } 609 610 static void 611 repl_map_free (void *p) 612 { 613 BITMAP_FREE (((struct repl_map_d *)p)->set); 614 free (p); 615 } 616 617 618 /* Return the names replaced by NEW_TREE (i.e., REPL_TBL[NEW_TREE].SET). */ 619 620 static inline bitmap 621 names_replaced_by (tree new_tree) 622 { 623 struct repl_map_d m; 624 void **slot; 625 626 m.name = new_tree; 627 slot = htab_find_slot (repl_tbl, (void *) &m, NO_INSERT); 628 629 /* If N was not registered in the replacement table, return NULL. */ 630 if (slot == NULL || *slot == NULL) 631 return NULL; 632 633 return ((struct repl_map_d *) *slot)->set; 634 } 635 636 637 /* Add OLD to REPL_TBL[NEW_TREE].SET. */ 638 639 static inline void 640 add_to_repl_tbl (tree new_tree, tree old) 641 { 642 struct repl_map_d m, *mp; 643 void **slot; 644 645 m.name = new_tree; 646 slot = htab_find_slot (repl_tbl, (void *) &m, INSERT); 647 if (*slot == NULL) 648 { 649 mp = XNEW (struct repl_map_d); 650 mp->name = new_tree; 651 mp->set = BITMAP_ALLOC (NULL); 652 *slot = (void *) mp; 653 } 654 else 655 mp = (struct repl_map_d *) *slot; 656 657 bitmap_set_bit (mp->set, SSA_NAME_VERSION (old)); 658 } 659 660 661 /* Add a new mapping NEW_TREE -> OLD REPL_TBL. Every entry N_i in REPL_TBL 662 represents the set of names O_1 ... O_j replaced by N_i. This is 663 used by update_ssa and its helpers to introduce new SSA names in an 664 already formed SSA web. */ 665 666 static void 667 add_new_name_mapping (tree new_tree, tree old) 668 { 669 timevar_push (TV_TREE_SSA_INCREMENTAL); 670 671 /* OLD and NEW_TREE must be different SSA names for the same symbol. */ 672 gcc_assert (new_tree != old && SSA_NAME_VAR (new_tree) == SSA_NAME_VAR (old)); 673 674 /* If this mapping is for virtual names, we will need to update 675 virtual operands. If this is a mapping for .MEM, then we gather 676 the symbols associated with each name. */ 677 if (!is_gimple_reg (new_tree)) 678 { 679 tree sym; 680 681 update_ssa_stats.num_virtual_mappings++; 682 update_ssa_stats.num_virtual_symbols++; 683 684 /* Keep counts of virtual mappings and symbols to use in the 685 virtual mapping heuristic. If we have large numbers of 686 virtual mappings for a relatively low number of symbols, it 687 will make more sense to rename the symbols from scratch. 688 Otherwise, the insertion of PHI nodes for each of the old 689 names in these mappings will be very slow. */ 690 sym = SSA_NAME_VAR (new_tree); 691 bitmap_set_bit (update_ssa_stats.virtual_symbols, DECL_UID (sym)); 692 } 693 694 /* We may need to grow NEW_SSA_NAMES and OLD_SSA_NAMES because our 695 caller may have created new names since the set was created. */ 696 if (new_ssa_names->n_bits <= num_ssa_names - 1) 697 { 698 unsigned int new_sz = num_ssa_names + NAME_SETS_GROWTH_FACTOR; 699 new_ssa_names = sbitmap_resize (new_ssa_names, new_sz, 0); 700 old_ssa_names = sbitmap_resize (old_ssa_names, new_sz, 0); 701 } 702 703 /* Update the REPL_TBL table. */ 704 add_to_repl_tbl (new_tree, old); 705 706 /* If OLD had already been registered as a new name, then all the 707 names that OLD replaces should also be replaced by NEW_TREE. */ 708 if (is_new_name (old)) 709 bitmap_ior_into (names_replaced_by (new_tree), names_replaced_by (old)); 710 711 /* Register NEW_TREE and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES, 712 respectively. */ 713 SET_BIT (new_ssa_names, SSA_NAME_VERSION (new_tree)); 714 SET_BIT (old_ssa_names, SSA_NAME_VERSION (old)); 715 716 /* Update mapping counter to use in the virtual mapping heuristic. */ 717 update_ssa_stats.num_total_mappings++; 718 719 timevar_pop (TV_TREE_SSA_INCREMENTAL); 720 } 721 722 723 /* Call back for walk_dominator_tree used to collect definition sites 724 for every variable in the function. For every statement S in block 725 BB: 726 727 1- Variables defined by S in the DEFS of S are marked in the bitmap 728 KILLS. 729 730 2- If S uses a variable VAR and there is no preceding kill of VAR, 731 then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR. 732 733 This information is used to determine which variables are live 734 across block boundaries to reduce the number of PHI nodes 735 we create. */ 736 737 static void 738 mark_def_sites (basic_block bb, gimple stmt, bitmap kills) 739 { 740 tree def; 741 use_operand_p use_p; 742 ssa_op_iter iter; 743 744 /* Since this is the first time that we rewrite the program into SSA 745 form, force an operand scan on every statement. */ 746 update_stmt (stmt); 747 748 gcc_assert (blocks_to_update == NULL); 749 set_register_defs (stmt, false); 750 set_rewrite_uses (stmt, false); 751 752 if (is_gimple_debug (stmt)) 753 return; 754 755 /* If a variable is used before being set, then the variable is live 756 across a block boundary, so mark it live-on-entry to BB. */ 757 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE) 758 { 759 tree sym = USE_FROM_PTR (use_p); 760 gcc_assert (DECL_P (sym)); 761 if (!bitmap_bit_p (kills, DECL_UID (sym))) 762 set_livein_block (sym, bb); 763 set_rewrite_uses (stmt, true); 764 } 765 766 /* Now process the defs. Mark BB as the definition block and add 767 each def to the set of killed symbols. */ 768 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF) 769 { 770 gcc_assert (DECL_P (def)); 771 set_def_block (def, bb, false); 772 bitmap_set_bit (kills, DECL_UID (def)); 773 set_register_defs (stmt, true); 774 } 775 776 /* If we found the statement interesting then also mark the block BB 777 as interesting. */ 778 if (rewrite_uses_p (stmt) || register_defs_p (stmt)) 779 SET_BIT (interesting_blocks, bb->index); 780 } 781 782 /* Structure used by prune_unused_phi_nodes to record bounds of the intervals 783 in the dfs numbering of the dominance tree. */ 784 785 struct dom_dfsnum 786 { 787 /* Basic block whose index this entry corresponds to. */ 788 unsigned bb_index; 789 790 /* The dfs number of this node. */ 791 unsigned dfs_num; 792 }; 793 794 /* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback 795 for qsort. */ 796 797 static int 798 cmp_dfsnum (const void *a, const void *b) 799 { 800 const struct dom_dfsnum *const da = (const struct dom_dfsnum *) a; 801 const struct dom_dfsnum *const db = (const struct dom_dfsnum *) b; 802 803 return (int) da->dfs_num - (int) db->dfs_num; 804 } 805 806 /* Among the intervals starting at the N points specified in DEFS, find 807 the one that contains S, and return its bb_index. */ 808 809 static unsigned 810 find_dfsnum_interval (struct dom_dfsnum *defs, unsigned n, unsigned s) 811 { 812 unsigned f = 0, t = n, m; 813 814 while (t > f + 1) 815 { 816 m = (f + t) / 2; 817 if (defs[m].dfs_num <= s) 818 f = m; 819 else 820 t = m; 821 } 822 823 return defs[f].bb_index; 824 } 825 826 /* Clean bits from PHIS for phi nodes whose value cannot be used in USES. 827 KILLS is a bitmap of blocks where the value is defined before any use. */ 828 829 static void 830 prune_unused_phi_nodes (bitmap phis, bitmap kills, bitmap uses) 831 { 832 VEC(int, heap) *worklist; 833 bitmap_iterator bi; 834 unsigned i, b, p, u, top; 835 bitmap live_phis; 836 basic_block def_bb, use_bb; 837 edge e; 838 edge_iterator ei; 839 bitmap to_remove; 840 struct dom_dfsnum *defs; 841 unsigned n_defs, adef; 842 843 if (bitmap_empty_p (uses)) 844 { 845 bitmap_clear (phis); 846 return; 847 } 848 849 /* The phi must dominate a use, or an argument of a live phi. Also, we 850 do not create any phi nodes in def blocks, unless they are also livein. */ 851 to_remove = BITMAP_ALLOC (NULL); 852 bitmap_and_compl (to_remove, kills, uses); 853 bitmap_and_compl_into (phis, to_remove); 854 if (bitmap_empty_p (phis)) 855 { 856 BITMAP_FREE (to_remove); 857 return; 858 } 859 860 /* We want to remove the unnecessary phi nodes, but we do not want to compute 861 liveness information, as that may be linear in the size of CFG, and if 862 there are lot of different variables to rewrite, this may lead to quadratic 863 behavior. 864 865 Instead, we basically emulate standard dce. We put all uses to worklist, 866 then for each of them find the nearest def that dominates them. If this 867 def is a phi node, we mark it live, and if it was not live before, we 868 add the predecessors of its basic block to the worklist. 869 870 To quickly locate the nearest def that dominates use, we use dfs numbering 871 of the dominance tree (that is already available in order to speed up 872 queries). For each def, we have the interval given by the dfs number on 873 entry to and on exit from the corresponding subtree in the dominance tree. 874 The nearest dominator for a given use is the smallest of these intervals 875 that contains entry and exit dfs numbers for the basic block with the use. 876 If we store the bounds for all the uses to an array and sort it, we can 877 locate the nearest dominating def in logarithmic time by binary search.*/ 878 bitmap_ior (to_remove, kills, phis); 879 n_defs = bitmap_count_bits (to_remove); 880 defs = XNEWVEC (struct dom_dfsnum, 2 * n_defs + 1); 881 defs[0].bb_index = 1; 882 defs[0].dfs_num = 0; 883 adef = 1; 884 EXECUTE_IF_SET_IN_BITMAP (to_remove, 0, i, bi) 885 { 886 def_bb = BASIC_BLOCK (i); 887 defs[adef].bb_index = i; 888 defs[adef].dfs_num = bb_dom_dfs_in (CDI_DOMINATORS, def_bb); 889 defs[adef + 1].bb_index = i; 890 defs[adef + 1].dfs_num = bb_dom_dfs_out (CDI_DOMINATORS, def_bb); 891 adef += 2; 892 } 893 BITMAP_FREE (to_remove); 894 gcc_assert (adef == 2 * n_defs + 1); 895 qsort (defs, adef, sizeof (struct dom_dfsnum), cmp_dfsnum); 896 gcc_assert (defs[0].bb_index == 1); 897 898 /* Now each DEFS entry contains the number of the basic block to that the 899 dfs number corresponds. Change them to the number of basic block that 900 corresponds to the interval following the dfs number. Also, for the 901 dfs_out numbers, increase the dfs number by one (so that it corresponds 902 to the start of the following interval, not to the end of the current 903 one). We use WORKLIST as a stack. */ 904 worklist = VEC_alloc (int, heap, n_defs + 1); 905 VEC_quick_push (int, worklist, 1); 906 top = 1; 907 n_defs = 1; 908 for (i = 1; i < adef; i++) 909 { 910 b = defs[i].bb_index; 911 if (b == top) 912 { 913 /* This is a closing element. Interval corresponding to the top 914 of the stack after removing it follows. */ 915 VEC_pop (int, worklist); 916 top = VEC_index (int, worklist, VEC_length (int, worklist) - 1); 917 defs[n_defs].bb_index = top; 918 defs[n_defs].dfs_num = defs[i].dfs_num + 1; 919 } 920 else 921 { 922 /* Opening element. Nothing to do, just push it to the stack and move 923 it to the correct position. */ 924 defs[n_defs].bb_index = defs[i].bb_index; 925 defs[n_defs].dfs_num = defs[i].dfs_num; 926 VEC_quick_push (int, worklist, b); 927 top = b; 928 } 929 930 /* If this interval starts at the same point as the previous one, cancel 931 the previous one. */ 932 if (defs[n_defs].dfs_num == defs[n_defs - 1].dfs_num) 933 defs[n_defs - 1].bb_index = defs[n_defs].bb_index; 934 else 935 n_defs++; 936 } 937 VEC_pop (int, worklist); 938 gcc_assert (VEC_empty (int, worklist)); 939 940 /* Now process the uses. */ 941 live_phis = BITMAP_ALLOC (NULL); 942 EXECUTE_IF_SET_IN_BITMAP (uses, 0, i, bi) 943 { 944 VEC_safe_push (int, heap, worklist, i); 945 } 946 947 while (!VEC_empty (int, worklist)) 948 { 949 b = VEC_pop (int, worklist); 950 if (b == ENTRY_BLOCK) 951 continue; 952 953 /* If there is a phi node in USE_BB, it is made live. Otherwise, 954 find the def that dominates the immediate dominator of USE_BB 955 (the kill in USE_BB does not dominate the use). */ 956 if (bitmap_bit_p (phis, b)) 957 p = b; 958 else 959 { 960 use_bb = get_immediate_dominator (CDI_DOMINATORS, BASIC_BLOCK (b)); 961 p = find_dfsnum_interval (defs, n_defs, 962 bb_dom_dfs_in (CDI_DOMINATORS, use_bb)); 963 if (!bitmap_bit_p (phis, p)) 964 continue; 965 } 966 967 /* If the phi node is already live, there is nothing to do. */ 968 if (bitmap_bit_p (live_phis, p)) 969 continue; 970 971 /* Mark the phi as live, and add the new uses to the worklist. */ 972 bitmap_set_bit (live_phis, p); 973 def_bb = BASIC_BLOCK (p); 974 FOR_EACH_EDGE (e, ei, def_bb->preds) 975 { 976 u = e->src->index; 977 if (bitmap_bit_p (uses, u)) 978 continue; 979 980 /* In case there is a kill directly in the use block, do not record 981 the use (this is also necessary for correctness, as we assume that 982 uses dominated by a def directly in their block have been filtered 983 out before). */ 984 if (bitmap_bit_p (kills, u)) 985 continue; 986 987 bitmap_set_bit (uses, u); 988 VEC_safe_push (int, heap, worklist, u); 989 } 990 } 991 992 VEC_free (int, heap, worklist); 993 bitmap_copy (phis, live_phis); 994 BITMAP_FREE (live_phis); 995 free (defs); 996 } 997 998 /* Return the set of blocks where variable VAR is defined and the blocks 999 where VAR is live on entry (livein). Return NULL, if no entry is 1000 found in DEF_BLOCKS. */ 1001 1002 static inline struct def_blocks_d * 1003 find_def_blocks_for (tree var) 1004 { 1005 struct def_blocks_d dm; 1006 dm.var = var; 1007 return (struct def_blocks_d *) htab_find (def_blocks, &dm); 1008 } 1009 1010 1011 /* Retrieve or create a default definition for symbol SYM. */ 1012 1013 static inline tree 1014 get_default_def_for (tree sym) 1015 { 1016 tree ddef = gimple_default_def (cfun, sym); 1017 1018 if (ddef == NULL_TREE) 1019 { 1020 ddef = make_ssa_name (sym, gimple_build_nop ()); 1021 set_default_def (sym, ddef); 1022 } 1023 1024 return ddef; 1025 } 1026 1027 1028 /* Marks phi node PHI in basic block BB for rewrite. */ 1029 1030 static void 1031 mark_phi_for_rewrite (basic_block bb, gimple phi) 1032 { 1033 gimple_vec phis; 1034 unsigned i, idx = bb->index; 1035 1036 if (rewrite_uses_p (phi)) 1037 return; 1038 1039 set_rewrite_uses (phi, true); 1040 1041 if (!blocks_with_phis_to_rewrite) 1042 return; 1043 1044 bitmap_set_bit (blocks_with_phis_to_rewrite, idx); 1045 VEC_reserve (gimple_vec, heap, phis_to_rewrite, last_basic_block + 1); 1046 for (i = VEC_length (gimple_vec, phis_to_rewrite); i <= idx; i++) 1047 VEC_quick_push (gimple_vec, phis_to_rewrite, NULL); 1048 1049 phis = VEC_index (gimple_vec, phis_to_rewrite, idx); 1050 if (!phis) 1051 phis = VEC_alloc (gimple, heap, 10); 1052 1053 VEC_safe_push (gimple, heap, phis, phi); 1054 VEC_replace (gimple_vec, phis_to_rewrite, idx, phis); 1055 } 1056 1057 /* Insert PHI nodes for variable VAR using the iterated dominance 1058 frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this 1059 function assumes that the caller is incrementally updating the 1060 existing SSA form, in which case VAR may be an SSA name instead of 1061 a symbol. 1062 1063 PHI_INSERTION_POINTS is updated to reflect nodes that already had a 1064 PHI node for VAR. On exit, only the nodes that received a PHI node 1065 for VAR will be present in PHI_INSERTION_POINTS. */ 1066 1067 static void 1068 insert_phi_nodes_for (tree var, bitmap phi_insertion_points, bool update_p) 1069 { 1070 unsigned bb_index; 1071 edge e; 1072 gimple phi; 1073 basic_block bb; 1074 bitmap_iterator bi; 1075 struct def_blocks_d *def_map; 1076 1077 def_map = find_def_blocks_for (var); 1078 gcc_assert (def_map); 1079 1080 /* Remove the blocks where we already have PHI nodes for VAR. */ 1081 bitmap_and_compl_into (phi_insertion_points, def_map->phi_blocks); 1082 1083 /* Remove obviously useless phi nodes. */ 1084 prune_unused_phi_nodes (phi_insertion_points, def_map->def_blocks, 1085 def_map->livein_blocks); 1086 1087 /* And insert the PHI nodes. */ 1088 EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points, 0, bb_index, bi) 1089 { 1090 bb = BASIC_BLOCK (bb_index); 1091 if (update_p) 1092 mark_block_for_update (bb); 1093 1094 phi = NULL; 1095 1096 if (TREE_CODE (var) == SSA_NAME) 1097 { 1098 /* If we are rewriting SSA names, create the LHS of the PHI 1099 node by duplicating VAR. This is useful in the case of 1100 pointers, to also duplicate pointer attributes (alias 1101 information, in particular). */ 1102 edge_iterator ei; 1103 tree new_lhs; 1104 1105 gcc_assert (update_p); 1106 phi = create_phi_node (var, bb); 1107 1108 new_lhs = duplicate_ssa_name (var, phi); 1109 gimple_phi_set_result (phi, new_lhs); 1110 add_new_name_mapping (new_lhs, var); 1111 1112 /* Add VAR to every argument slot of PHI. We need VAR in 1113 every argument so that rewrite_update_phi_arguments knows 1114 which name is this PHI node replacing. If VAR is a 1115 symbol marked for renaming, this is not necessary, the 1116 renamer will use the symbol on the LHS to get its 1117 reaching definition. */ 1118 FOR_EACH_EDGE (e, ei, bb->preds) 1119 add_phi_arg (phi, var, e, UNKNOWN_LOCATION); 1120 } 1121 else 1122 { 1123 tree tracked_var; 1124 1125 gcc_assert (DECL_P (var)); 1126 phi = create_phi_node (var, bb); 1127 1128 tracked_var = target_for_debug_bind (var); 1129 if (tracked_var) 1130 { 1131 gimple note = gimple_build_debug_bind (tracked_var, 1132 PHI_RESULT (phi), 1133 phi); 1134 gimple_stmt_iterator si = gsi_after_labels (bb); 1135 gsi_insert_before (&si, note, GSI_SAME_STMT); 1136 } 1137 } 1138 1139 /* Mark this PHI node as interesting for update_ssa. */ 1140 set_register_defs (phi, true); 1141 mark_phi_for_rewrite (bb, phi); 1142 } 1143 } 1144 1145 1146 /* Insert PHI nodes at the dominance frontier of blocks with variable 1147 definitions. DFS contains the dominance frontier information for 1148 the flowgraph. */ 1149 1150 static void 1151 insert_phi_nodes (bitmap *dfs) 1152 { 1153 referenced_var_iterator rvi; 1154 bitmap_iterator bi; 1155 tree var; 1156 bitmap vars; 1157 unsigned uid; 1158 1159 timevar_push (TV_TREE_INSERT_PHI_NODES); 1160 1161 /* Do two stages to avoid code generation differences for UID 1162 differences but no UID ordering differences. */ 1163 1164 vars = BITMAP_ALLOC (NULL); 1165 FOR_EACH_REFERENCED_VAR (var, rvi) 1166 { 1167 struct def_blocks_d *def_map; 1168 1169 def_map = find_def_blocks_for (var); 1170 if (def_map == NULL) 1171 continue; 1172 1173 if (get_phi_state (var) != NEED_PHI_STATE_NO) 1174 bitmap_set_bit (vars, DECL_UID (var)); 1175 } 1176 1177 EXECUTE_IF_SET_IN_BITMAP (vars, 0, uid, bi) 1178 { 1179 tree var = referenced_var (uid); 1180 struct def_blocks_d *def_map; 1181 bitmap idf; 1182 1183 def_map = find_def_blocks_for (var); 1184 idf = compute_idf (def_map->def_blocks, dfs); 1185 insert_phi_nodes_for (var, idf, false); 1186 BITMAP_FREE (idf); 1187 } 1188 1189 BITMAP_FREE (vars); 1190 1191 timevar_pop (TV_TREE_INSERT_PHI_NODES); 1192 } 1193 1194 1195 /* Push SYM's current reaching definition into BLOCK_DEFS_STACK and 1196 register DEF (an SSA_NAME) to be a new definition for SYM. */ 1197 1198 static void 1199 register_new_def (tree def, tree sym) 1200 { 1201 tree currdef; 1202 1203 /* If this variable is set in a single basic block and all uses are 1204 dominated by the set(s) in that single basic block, then there is 1205 no reason to record anything for this variable in the block local 1206 definition stacks. Doing so just wastes time and memory. 1207 1208 This is the same test to prune the set of variables which may 1209 need PHI nodes. So we just use that information since it's already 1210 computed and available for us to use. */ 1211 if (get_phi_state (sym) == NEED_PHI_STATE_NO) 1212 { 1213 set_current_def (sym, def); 1214 return; 1215 } 1216 1217 currdef = get_current_def (sym); 1218 1219 /* If SYM is not a GIMPLE register, then CURRDEF may be a name whose 1220 SSA_NAME_VAR is not necessarily SYM. In this case, also push SYM 1221 in the stack so that we know which symbol is being defined by 1222 this SSA name when we unwind the stack. */ 1223 if (currdef && !is_gimple_reg (sym)) 1224 VEC_safe_push (tree, heap, block_defs_stack, sym); 1225 1226 /* Push the current reaching definition into BLOCK_DEFS_STACK. This 1227 stack is later used by the dominator tree callbacks to restore 1228 the reaching definitions for all the variables defined in the 1229 block after a recursive visit to all its immediately dominated 1230 blocks. If there is no current reaching definition, then just 1231 record the underlying _DECL node. */ 1232 VEC_safe_push (tree, heap, block_defs_stack, currdef ? currdef : sym); 1233 1234 /* Set the current reaching definition for SYM to be DEF. */ 1235 set_current_def (sym, def); 1236 } 1237 1238 1239 /* Perform a depth-first traversal of the dominator tree looking for 1240 variables to rename. BB is the block where to start searching. 1241 Renaming is a five step process: 1242 1243 1- Every definition made by PHI nodes at the start of the blocks is 1244 registered as the current definition for the corresponding variable. 1245 1246 2- Every statement in BB is rewritten. USE and VUSE operands are 1247 rewritten with their corresponding reaching definition. DEF and 1248 VDEF targets are registered as new definitions. 1249 1250 3- All the PHI nodes in successor blocks of BB are visited. The 1251 argument corresponding to BB is replaced with its current reaching 1252 definition. 1253 1254 4- Recursively rewrite every dominator child block of BB. 1255 1256 5- Restore (in reverse order) the current reaching definition for every 1257 new definition introduced in this block. This is done so that when 1258 we return from the recursive call, all the current reaching 1259 definitions are restored to the names that were valid in the 1260 dominator parent of BB. */ 1261 1262 /* Return the current definition for variable VAR. If none is found, 1263 create a new SSA name to act as the zeroth definition for VAR. */ 1264 1265 static tree 1266 get_reaching_def (tree var) 1267 { 1268 tree currdef; 1269 1270 /* Lookup the current reaching definition for VAR. */ 1271 currdef = get_current_def (var); 1272 1273 /* If there is no reaching definition for VAR, create and register a 1274 default definition for it (if needed). */ 1275 if (currdef == NULL_TREE) 1276 { 1277 tree sym = DECL_P (var) ? var : SSA_NAME_VAR (var); 1278 currdef = get_default_def_for (sym); 1279 set_current_def (var, currdef); 1280 } 1281 1282 /* Return the current reaching definition for VAR, or the default 1283 definition, if we had to create one. */ 1284 return currdef; 1285 } 1286 1287 1288 /* SSA Rewriting Step 2. Rewrite every variable used in each statement in 1289 the block with its immediate reaching definitions. Update the current 1290 definition of a variable when a new real or virtual definition is found. */ 1291 1292 static void 1293 rewrite_stmt (gimple_stmt_iterator si) 1294 { 1295 use_operand_p use_p; 1296 def_operand_p def_p; 1297 ssa_op_iter iter; 1298 gimple stmt = gsi_stmt (si); 1299 1300 /* If mark_def_sites decided that we don't need to rewrite this 1301 statement, ignore it. */ 1302 gcc_assert (blocks_to_update == NULL); 1303 if (!rewrite_uses_p (stmt) && !register_defs_p (stmt)) 1304 return; 1305 1306 if (dump_file && (dump_flags & TDF_DETAILS)) 1307 { 1308 fprintf (dump_file, "Renaming statement "); 1309 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); 1310 fprintf (dump_file, "\n"); 1311 } 1312 1313 /* Step 1. Rewrite USES in the statement. */ 1314 if (rewrite_uses_p (stmt)) 1315 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE) 1316 { 1317 tree var = USE_FROM_PTR (use_p); 1318 gcc_assert (DECL_P (var)); 1319 SET_USE (use_p, get_reaching_def (var)); 1320 } 1321 1322 /* Step 2. Register the statement's DEF operands. */ 1323 if (register_defs_p (stmt)) 1324 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_DEF) 1325 { 1326 tree var = DEF_FROM_PTR (def_p); 1327 tree name = make_ssa_name (var, stmt); 1328 tree tracked_var; 1329 gcc_assert (DECL_P (var)); 1330 SET_DEF (def_p, name); 1331 register_new_def (DEF_FROM_PTR (def_p), var); 1332 1333 tracked_var = target_for_debug_bind (var); 1334 if (tracked_var) 1335 { 1336 gimple note = gimple_build_debug_bind (tracked_var, name, stmt); 1337 gsi_insert_after (&si, note, GSI_SAME_STMT); 1338 } 1339 } 1340 } 1341 1342 1343 /* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for 1344 PHI nodes. For every PHI node found, add a new argument containing the 1345 current reaching definition for the variable and the edge through which 1346 that definition is reaching the PHI node. */ 1347 1348 static void 1349 rewrite_add_phi_arguments (basic_block bb) 1350 { 1351 edge e; 1352 edge_iterator ei; 1353 1354 FOR_EACH_EDGE (e, ei, bb->succs) 1355 { 1356 gimple phi; 1357 gimple_stmt_iterator gsi; 1358 1359 for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi); 1360 gsi_next (&gsi)) 1361 { 1362 tree currdef; 1363 gimple stmt; 1364 1365 phi = gsi_stmt (gsi); 1366 currdef = get_reaching_def (SSA_NAME_VAR (gimple_phi_result (phi))); 1367 stmt = SSA_NAME_DEF_STMT (currdef); 1368 add_phi_arg (phi, currdef, e, gimple_location (stmt)); 1369 } 1370 } 1371 } 1372 1373 /* SSA Rewriting Step 1. Initialization, create a block local stack 1374 of reaching definitions for new SSA names produced in this block 1375 (BLOCK_DEFS). Register new definitions for every PHI node in the 1376 block. */ 1377 1378 static void 1379 rewrite_enter_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, 1380 basic_block bb) 1381 { 1382 gimple phi; 1383 gimple_stmt_iterator gsi; 1384 1385 if (dump_file && (dump_flags & TDF_DETAILS)) 1386 fprintf (dump_file, "\n\nRenaming block #%d\n\n", bb->index); 1387 1388 /* Mark the unwind point for this block. */ 1389 VEC_safe_push (tree, heap, block_defs_stack, NULL_TREE); 1390 1391 /* Step 1. Register new definitions for every PHI node in the block. 1392 Conceptually, all the PHI nodes are executed in parallel and each PHI 1393 node introduces a new version for the associated variable. */ 1394 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) 1395 { 1396 tree result; 1397 1398 phi = gsi_stmt (gsi); 1399 result = gimple_phi_result (phi); 1400 gcc_assert (is_gimple_reg (result)); 1401 register_new_def (result, SSA_NAME_VAR (result)); 1402 } 1403 1404 /* Step 2. Rewrite every variable used in each statement in the block 1405 with its immediate reaching definitions. Update the current definition 1406 of a variable when a new real or virtual definition is found. */ 1407 if (TEST_BIT (interesting_blocks, bb->index)) 1408 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) 1409 rewrite_stmt (gsi); 1410 1411 /* Step 3. Visit all the successor blocks of BB looking for PHI nodes. 1412 For every PHI node found, add a new argument containing the current 1413 reaching definition for the variable and the edge through which that 1414 definition is reaching the PHI node. */ 1415 rewrite_add_phi_arguments (bb); 1416 } 1417 1418 1419 1420 /* Called after visiting all the statements in basic block BB and all 1421 of its dominator children. Restore CURRDEFS to its original value. */ 1422 1423 static void 1424 rewrite_leave_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, 1425 basic_block bb ATTRIBUTE_UNUSED) 1426 { 1427 /* Restore CURRDEFS to its original state. */ 1428 while (VEC_length (tree, block_defs_stack) > 0) 1429 { 1430 tree tmp = VEC_pop (tree, block_defs_stack); 1431 tree saved_def, var; 1432 1433 if (tmp == NULL_TREE) 1434 break; 1435 1436 if (TREE_CODE (tmp) == SSA_NAME) 1437 { 1438 /* If we recorded an SSA_NAME, then make the SSA_NAME the 1439 current definition of its underlying variable. Note that 1440 if the SSA_NAME is not for a GIMPLE register, the symbol 1441 being defined is stored in the next slot in the stack. 1442 This mechanism is needed because an SSA name for a 1443 non-register symbol may be the definition for more than 1444 one symbol (e.g., SFTs, aliased variables, etc). */ 1445 saved_def = tmp; 1446 var = SSA_NAME_VAR (saved_def); 1447 if (!is_gimple_reg (var)) 1448 var = VEC_pop (tree, block_defs_stack); 1449 } 1450 else 1451 { 1452 /* If we recorded anything else, it must have been a _DECL 1453 node and its current reaching definition must have been 1454 NULL. */ 1455 saved_def = NULL; 1456 var = tmp; 1457 } 1458 1459 set_current_def (var, saved_def); 1460 } 1461 } 1462 1463 1464 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */ 1465 1466 void 1467 dump_decl_set (FILE *file, bitmap set) 1468 { 1469 if (set) 1470 { 1471 bitmap_iterator bi; 1472 unsigned i; 1473 1474 fprintf (file, "{ "); 1475 1476 EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi) 1477 { 1478 print_generic_expr (file, referenced_var (i), 0); 1479 fprintf (file, " "); 1480 } 1481 1482 fprintf (file, "}"); 1483 } 1484 else 1485 fprintf (file, "NIL"); 1486 } 1487 1488 1489 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */ 1490 1491 void 1492 debug_decl_set (bitmap set) 1493 { 1494 dump_decl_set (stderr, set); 1495 fprintf (stderr, "\n"); 1496 } 1497 1498 1499 /* Dump the renaming stack (block_defs_stack) to FILE. Traverse the 1500 stack up to a maximum of N levels. If N is -1, the whole stack is 1501 dumped. New levels are created when the dominator tree traversal 1502 used for renaming enters a new sub-tree. */ 1503 1504 void 1505 dump_defs_stack (FILE *file, int n) 1506 { 1507 int i, j; 1508 1509 fprintf (file, "\n\nRenaming stack"); 1510 if (n > 0) 1511 fprintf (file, " (up to %d levels)", n); 1512 fprintf (file, "\n\n"); 1513 1514 i = 1; 1515 fprintf (file, "Level %d (current level)\n", i); 1516 for (j = (int) VEC_length (tree, block_defs_stack) - 1; j >= 0; j--) 1517 { 1518 tree name, var; 1519 1520 name = VEC_index (tree, block_defs_stack, j); 1521 if (name == NULL_TREE) 1522 { 1523 i++; 1524 if (n > 0 && i > n) 1525 break; 1526 fprintf (file, "\nLevel %d\n", i); 1527 continue; 1528 } 1529 1530 if (DECL_P (name)) 1531 { 1532 var = name; 1533 name = NULL_TREE; 1534 } 1535 else 1536 { 1537 var = SSA_NAME_VAR (name); 1538 if (!is_gimple_reg (var)) 1539 { 1540 j--; 1541 var = VEC_index (tree, block_defs_stack, j); 1542 } 1543 } 1544 1545 fprintf (file, " Previous CURRDEF ("); 1546 print_generic_expr (file, var, 0); 1547 fprintf (file, ") = "); 1548 if (name) 1549 print_generic_expr (file, name, 0); 1550 else 1551 fprintf (file, "<NIL>"); 1552 fprintf (file, "\n"); 1553 } 1554 } 1555 1556 1557 /* Dump the renaming stack (block_defs_stack) to stderr. Traverse the 1558 stack up to a maximum of N levels. If N is -1, the whole stack is 1559 dumped. New levels are created when the dominator tree traversal 1560 used for renaming enters a new sub-tree. */ 1561 1562 void 1563 debug_defs_stack (int n) 1564 { 1565 dump_defs_stack (stderr, n); 1566 } 1567 1568 1569 /* Dump the current reaching definition of every symbol to FILE. */ 1570 1571 void 1572 dump_currdefs (FILE *file) 1573 { 1574 referenced_var_iterator i; 1575 tree var; 1576 1577 fprintf (file, "\n\nCurrent reaching definitions\n\n"); 1578 FOR_EACH_REFERENCED_VAR (var, i) 1579 if (SYMS_TO_RENAME (cfun) == NULL 1580 || bitmap_bit_p (SYMS_TO_RENAME (cfun), DECL_UID (var))) 1581 { 1582 fprintf (file, "CURRDEF ("); 1583 print_generic_expr (file, var, 0); 1584 fprintf (file, ") = "); 1585 if (get_current_def (var)) 1586 print_generic_expr (file, get_current_def (var), 0); 1587 else 1588 fprintf (file, "<NIL>"); 1589 fprintf (file, "\n"); 1590 } 1591 } 1592 1593 1594 /* Dump the current reaching definition of every symbol to stderr. */ 1595 1596 void 1597 debug_currdefs (void) 1598 { 1599 dump_currdefs (stderr); 1600 } 1601 1602 1603 /* Dump SSA information to FILE. */ 1604 1605 void 1606 dump_tree_ssa (FILE *file) 1607 { 1608 const char *funcname 1609 = lang_hooks.decl_printable_name (current_function_decl, 2); 1610 1611 fprintf (file, "SSA renaming information for %s\n\n", funcname); 1612 1613 dump_def_blocks (file); 1614 dump_defs_stack (file, -1); 1615 dump_currdefs (file); 1616 dump_tree_ssa_stats (file); 1617 } 1618 1619 1620 /* Dump SSA information to stderr. */ 1621 1622 void 1623 debug_tree_ssa (void) 1624 { 1625 dump_tree_ssa (stderr); 1626 } 1627 1628 1629 /* Dump statistics for the hash table HTAB. */ 1630 1631 static void 1632 htab_statistics (FILE *file, htab_t htab) 1633 { 1634 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n", 1635 (long) htab_size (htab), 1636 (long) htab_elements (htab), 1637 htab_collisions (htab)); 1638 } 1639 1640 1641 /* Dump SSA statistics on FILE. */ 1642 1643 void 1644 dump_tree_ssa_stats (FILE *file) 1645 { 1646 if (def_blocks || repl_tbl) 1647 fprintf (file, "\nHash table statistics:\n"); 1648 1649 if (def_blocks) 1650 { 1651 fprintf (file, " def_blocks: "); 1652 htab_statistics (file, def_blocks); 1653 } 1654 1655 if (repl_tbl) 1656 { 1657 fprintf (file, " repl_tbl: "); 1658 htab_statistics (file, repl_tbl); 1659 } 1660 1661 if (def_blocks || repl_tbl) 1662 fprintf (file, "\n"); 1663 } 1664 1665 1666 /* Dump SSA statistics on stderr. */ 1667 1668 void 1669 debug_tree_ssa_stats (void) 1670 { 1671 dump_tree_ssa_stats (stderr); 1672 } 1673 1674 1675 /* Hashing and equality functions for DEF_BLOCKS. */ 1676 1677 static hashval_t 1678 def_blocks_hash (const void *p) 1679 { 1680 return htab_hash_pointer 1681 ((const void *)((const struct def_blocks_d *)p)->var); 1682 } 1683 1684 static int 1685 def_blocks_eq (const void *p1, const void *p2) 1686 { 1687 return ((const struct def_blocks_d *)p1)->var 1688 == ((const struct def_blocks_d *)p2)->var; 1689 } 1690 1691 1692 /* Free memory allocated by one entry in DEF_BLOCKS. */ 1693 1694 static void 1695 def_blocks_free (void *p) 1696 { 1697 struct def_blocks_d *entry = (struct def_blocks_d *) p; 1698 BITMAP_FREE (entry->def_blocks); 1699 BITMAP_FREE (entry->phi_blocks); 1700 BITMAP_FREE (entry->livein_blocks); 1701 free (entry); 1702 } 1703 1704 1705 /* Callback for htab_traverse to dump the DEF_BLOCKS hash table. */ 1706 1707 static int 1708 debug_def_blocks_r (void **slot, void *data) 1709 { 1710 FILE *file = (FILE *) data; 1711 struct def_blocks_d *db_p = (struct def_blocks_d *) *slot; 1712 1713 fprintf (file, "VAR: "); 1714 print_generic_expr (file, db_p->var, dump_flags); 1715 bitmap_print (file, db_p->def_blocks, ", DEF_BLOCKS: { ", "}"); 1716 bitmap_print (file, db_p->livein_blocks, ", LIVEIN_BLOCKS: { ", "}"); 1717 bitmap_print (file, db_p->phi_blocks, ", PHI_BLOCKS: { ", "}\n"); 1718 1719 return 1; 1720 } 1721 1722 1723 /* Dump the DEF_BLOCKS hash table on FILE. */ 1724 1725 void 1726 dump_def_blocks (FILE *file) 1727 { 1728 fprintf (file, "\n\nDefinition and live-in blocks:\n\n"); 1729 if (def_blocks) 1730 htab_traverse (def_blocks, debug_def_blocks_r, file); 1731 } 1732 1733 1734 /* Dump the DEF_BLOCKS hash table on stderr. */ 1735 1736 void 1737 debug_def_blocks (void) 1738 { 1739 dump_def_blocks (stderr); 1740 } 1741 1742 1743 /* Register NEW_NAME to be the new reaching definition for OLD_NAME. */ 1744 1745 static inline void 1746 register_new_update_single (tree new_name, tree old_name) 1747 { 1748 tree currdef = get_current_def (old_name); 1749 1750 /* Push the current reaching definition into BLOCK_DEFS_STACK. 1751 This stack is later used by the dominator tree callbacks to 1752 restore the reaching definitions for all the variables 1753 defined in the block after a recursive visit to all its 1754 immediately dominated blocks. */ 1755 VEC_reserve (tree, heap, block_defs_stack, 2); 1756 VEC_quick_push (tree, block_defs_stack, currdef); 1757 VEC_quick_push (tree, block_defs_stack, old_name); 1758 1759 /* Set the current reaching definition for OLD_NAME to be 1760 NEW_NAME. */ 1761 set_current_def (old_name, new_name); 1762 } 1763 1764 1765 /* Register NEW_NAME to be the new reaching definition for all the 1766 names in OLD_NAMES. Used by the incremental SSA update routines to 1767 replace old SSA names with new ones. */ 1768 1769 static inline void 1770 register_new_update_set (tree new_name, bitmap old_names) 1771 { 1772 bitmap_iterator bi; 1773 unsigned i; 1774 1775 EXECUTE_IF_SET_IN_BITMAP (old_names, 0, i, bi) 1776 register_new_update_single (new_name, ssa_name (i)); 1777 } 1778 1779 1780 1781 /* If the operand pointed to by USE_P is a name in OLD_SSA_NAMES or 1782 it is a symbol marked for renaming, replace it with USE_P's current 1783 reaching definition. */ 1784 1785 static inline void 1786 maybe_replace_use (use_operand_p use_p) 1787 { 1788 tree rdef = NULL_TREE; 1789 tree use = USE_FROM_PTR (use_p); 1790 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use); 1791 1792 if (symbol_marked_for_renaming (sym)) 1793 rdef = get_reaching_def (sym); 1794 else if (is_old_name (use)) 1795 rdef = get_reaching_def (use); 1796 1797 if (rdef && rdef != use) 1798 SET_USE (use_p, rdef); 1799 } 1800 1801 1802 /* Same as maybe_replace_use, but without introducing default stmts, 1803 returning false to indicate a need to do so. */ 1804 1805 static inline bool 1806 maybe_replace_use_in_debug_stmt (use_operand_p use_p) 1807 { 1808 tree rdef = NULL_TREE; 1809 tree use = USE_FROM_PTR (use_p); 1810 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use); 1811 1812 if (symbol_marked_for_renaming (sym)) 1813 rdef = get_current_def (sym); 1814 else if (is_old_name (use)) 1815 { 1816 rdef = get_current_def (use); 1817 /* We can't assume that, if there's no current definition, the 1818 default one should be used. It could be the case that we've 1819 rearranged blocks so that the earlier definition no longer 1820 dominates the use. */ 1821 if (!rdef && SSA_NAME_IS_DEFAULT_DEF (use)) 1822 rdef = use; 1823 } 1824 else 1825 rdef = use; 1826 1827 if (rdef && rdef != use) 1828 SET_USE (use_p, rdef); 1829 1830 return rdef != NULL_TREE; 1831 } 1832 1833 1834 /* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES 1835 or OLD_SSA_NAMES, or if it is a symbol marked for renaming, 1836 register it as the current definition for the names replaced by 1837 DEF_P. */ 1838 1839 static inline void 1840 maybe_register_def (def_operand_p def_p, gimple stmt, 1841 gimple_stmt_iterator gsi) 1842 { 1843 tree def = DEF_FROM_PTR (def_p); 1844 tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def); 1845 1846 /* If DEF is a naked symbol that needs renaming, create a new 1847 name for it. */ 1848 if (symbol_marked_for_renaming (sym)) 1849 { 1850 if (DECL_P (def)) 1851 { 1852 tree tracked_var; 1853 1854 def = make_ssa_name (def, stmt); 1855 SET_DEF (def_p, def); 1856 1857 tracked_var = target_for_debug_bind (sym); 1858 if (tracked_var) 1859 { 1860 gimple note = gimple_build_debug_bind (tracked_var, def, stmt); 1861 /* If stmt ends the bb, insert the debug stmt on the single 1862 non-EH edge from the stmt. */ 1863 if (gsi_one_before_end_p (gsi) && stmt_ends_bb_p (stmt)) 1864 { 1865 basic_block bb = gsi_bb (gsi); 1866 edge_iterator ei; 1867 edge e, ef = NULL; 1868 FOR_EACH_EDGE (e, ei, bb->succs) 1869 if (!(e->flags & EDGE_EH)) 1870 { 1871 gcc_assert (!ef); 1872 ef = e; 1873 } 1874 gcc_assert (ef 1875 && single_pred_p (ef->dest) 1876 && !phi_nodes (ef->dest) 1877 && ef->dest != EXIT_BLOCK_PTR); 1878 gsi_insert_on_edge_immediate (ef, note); 1879 } 1880 else 1881 gsi_insert_after (&gsi, note, GSI_SAME_STMT); 1882 } 1883 } 1884 1885 register_new_update_single (def, sym); 1886 } 1887 else 1888 { 1889 /* If DEF is a new name, register it as a new definition 1890 for all the names replaced by DEF. */ 1891 if (is_new_name (def)) 1892 register_new_update_set (def, names_replaced_by (def)); 1893 1894 /* If DEF is an old name, register DEF as a new 1895 definition for itself. */ 1896 if (is_old_name (def)) 1897 register_new_update_single (def, def); 1898 } 1899 } 1900 1901 1902 /* Update every variable used in the statement pointed-to by SI. The 1903 statement is assumed to be in SSA form already. Names in 1904 OLD_SSA_NAMES used by SI will be updated to their current reaching 1905 definition. Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI 1906 will be registered as a new definition for their corresponding name 1907 in OLD_SSA_NAMES. */ 1908 1909 static void 1910 rewrite_update_stmt (gimple stmt, gimple_stmt_iterator gsi) 1911 { 1912 use_operand_p use_p; 1913 def_operand_p def_p; 1914 ssa_op_iter iter; 1915 1916 /* Only update marked statements. */ 1917 if (!rewrite_uses_p (stmt) && !register_defs_p (stmt)) 1918 return; 1919 1920 if (dump_file && (dump_flags & TDF_DETAILS)) 1921 { 1922 fprintf (dump_file, "Updating SSA information for statement "); 1923 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM); 1924 fprintf (dump_file, "\n"); 1925 } 1926 1927 /* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying 1928 symbol is marked for renaming. */ 1929 if (rewrite_uses_p (stmt)) 1930 { 1931 if (is_gimple_debug (stmt)) 1932 { 1933 bool failed = false; 1934 1935 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE) 1936 if (!maybe_replace_use_in_debug_stmt (use_p)) 1937 { 1938 failed = true; 1939 break; 1940 } 1941 1942 if (failed) 1943 { 1944 /* DOM sometimes threads jumps in such a way that a 1945 debug stmt ends up referencing a SSA variable that no 1946 longer dominates the debug stmt, but such that all 1947 incoming definitions refer to the same definition in 1948 an earlier dominator. We could try to recover that 1949 definition somehow, but this will have to do for now. 1950 1951 Introducing a default definition, which is what 1952 maybe_replace_use() would do in such cases, may 1953 modify code generation, for the otherwise-unused 1954 default definition would never go away, modifying SSA 1955 version numbers all over. */ 1956 gimple_debug_bind_reset_value (stmt); 1957 update_stmt (stmt); 1958 } 1959 } 1960 else 1961 { 1962 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES) 1963 maybe_replace_use (use_p); 1964 } 1965 } 1966 1967 /* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES. 1968 Also register definitions for names whose underlying symbol is 1969 marked for renaming. */ 1970 if (register_defs_p (stmt)) 1971 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS) 1972 maybe_register_def (def_p, stmt, gsi); 1973 } 1974 1975 1976 /* Visit all the successor blocks of BB looking for PHI nodes. For 1977 every PHI node found, check if any of its arguments is in 1978 OLD_SSA_NAMES. If so, and if the argument has a current reaching 1979 definition, replace it. */ 1980 1981 static void 1982 rewrite_update_phi_arguments (basic_block bb) 1983 { 1984 edge e; 1985 edge_iterator ei; 1986 unsigned i; 1987 1988 FOR_EACH_EDGE (e, ei, bb->succs) 1989 { 1990 gimple phi; 1991 gimple_vec phis; 1992 1993 if (!bitmap_bit_p (blocks_with_phis_to_rewrite, e->dest->index)) 1994 continue; 1995 1996 phis = VEC_index (gimple_vec, phis_to_rewrite, e->dest->index); 1997 for (i = 0; VEC_iterate (gimple, phis, i, phi); i++) 1998 { 1999 tree arg, lhs_sym, reaching_def = NULL; 2000 use_operand_p arg_p; 2001 2002 gcc_assert (rewrite_uses_p (phi)); 2003 2004 arg_p = PHI_ARG_DEF_PTR_FROM_EDGE (phi, e); 2005 arg = USE_FROM_PTR (arg_p); 2006 2007 if (arg && !DECL_P (arg) && TREE_CODE (arg) != SSA_NAME) 2008 continue; 2009 2010 lhs_sym = SSA_NAME_VAR (gimple_phi_result (phi)); 2011 2012 if (arg == NULL_TREE) 2013 { 2014 /* When updating a PHI node for a recently introduced 2015 symbol we may find NULL arguments. That's why we 2016 take the symbol from the LHS of the PHI node. */ 2017 reaching_def = get_reaching_def (lhs_sym); 2018 2019 } 2020 else 2021 { 2022 tree sym = DECL_P (arg) ? arg : SSA_NAME_VAR (arg); 2023 2024 if (symbol_marked_for_renaming (sym)) 2025 reaching_def = get_reaching_def (sym); 2026 else if (is_old_name (arg)) 2027 reaching_def = get_reaching_def (arg); 2028 } 2029 2030 /* Update the argument if there is a reaching def. */ 2031 if (reaching_def) 2032 { 2033 gimple stmt; 2034 source_location locus; 2035 int arg_i = PHI_ARG_INDEX_FROM_USE (arg_p); 2036 2037 SET_USE (arg_p, reaching_def); 2038 stmt = SSA_NAME_DEF_STMT (reaching_def); 2039 2040 /* Single element PHI nodes behave like copies, so get the 2041 location from the phi argument. */ 2042 if (gimple_code (stmt) == GIMPLE_PHI && 2043 gimple_phi_num_args (stmt) == 1) 2044 locus = gimple_phi_arg_location (stmt, 0); 2045 else 2046 locus = gimple_location (stmt); 2047 2048 gimple_phi_arg_set_location (phi, arg_i, locus); 2049 } 2050 2051 2052 if (e->flags & EDGE_ABNORMAL) 2053 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p)) = 1; 2054 } 2055 } 2056 } 2057 2058 2059 /* Initialization of block data structures for the incremental SSA 2060 update pass. Create a block local stack of reaching definitions 2061 for new SSA names produced in this block (BLOCK_DEFS). Register 2062 new definitions for every PHI node in the block. */ 2063 2064 static void 2065 rewrite_update_enter_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, 2066 basic_block bb) 2067 { 2068 edge e; 2069 edge_iterator ei; 2070 bool is_abnormal_phi; 2071 gimple_stmt_iterator gsi; 2072 2073 if (dump_file && (dump_flags & TDF_DETAILS)) 2074 fprintf (dump_file, "\n\nRegistering new PHI nodes in block #%d\n\n", 2075 bb->index); 2076 2077 /* Mark the unwind point for this block. */ 2078 VEC_safe_push (tree, heap, block_defs_stack, NULL_TREE); 2079 2080 if (!bitmap_bit_p (blocks_to_update, bb->index)) 2081 return; 2082 2083 /* Mark the LHS if any of the arguments flows through an abnormal 2084 edge. */ 2085 is_abnormal_phi = false; 2086 FOR_EACH_EDGE (e, ei, bb->preds) 2087 if (e->flags & EDGE_ABNORMAL) 2088 { 2089 is_abnormal_phi = true; 2090 break; 2091 } 2092 2093 /* If any of the PHI nodes is a replacement for a name in 2094 OLD_SSA_NAMES or it's one of the names in NEW_SSA_NAMES, then 2095 register it as a new definition for its corresponding name. Also 2096 register definitions for names whose underlying symbols are 2097 marked for renaming. */ 2098 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi)) 2099 { 2100 tree lhs, lhs_sym; 2101 gimple phi = gsi_stmt (gsi); 2102 2103 if (!register_defs_p (phi)) 2104 continue; 2105 2106 lhs = gimple_phi_result (phi); 2107 lhs_sym = SSA_NAME_VAR (lhs); 2108 2109 if (symbol_marked_for_renaming (lhs_sym)) 2110 register_new_update_single (lhs, lhs_sym); 2111 else 2112 { 2113 2114 /* If LHS is a new name, register a new definition for all 2115 the names replaced by LHS. */ 2116 if (is_new_name (lhs)) 2117 register_new_update_set (lhs, names_replaced_by (lhs)); 2118 2119 /* If LHS is an OLD name, register it as a new definition 2120 for itself. */ 2121 if (is_old_name (lhs)) 2122 register_new_update_single (lhs, lhs); 2123 } 2124 2125 if (is_abnormal_phi) 2126 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs) = 1; 2127 } 2128 2129 /* Step 2. Rewrite every variable used in each statement in the block. */ 2130 if (TEST_BIT (interesting_blocks, bb->index)) 2131 { 2132 gcc_assert (bitmap_bit_p (blocks_to_update, bb->index)); 2133 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) 2134 rewrite_update_stmt (gsi_stmt (gsi), gsi); 2135 } 2136 2137 /* Step 3. Update PHI nodes. */ 2138 rewrite_update_phi_arguments (bb); 2139 } 2140 2141 /* Called after visiting block BB. Unwind BLOCK_DEFS_STACK to restore 2142 the current reaching definition of every name re-written in BB to 2143 the original reaching definition before visiting BB. This 2144 unwinding must be done in the opposite order to what is done in 2145 register_new_update_set. */ 2146 2147 static void 2148 rewrite_update_leave_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED, 2149 basic_block bb ATTRIBUTE_UNUSED) 2150 { 2151 while (VEC_length (tree, block_defs_stack) > 0) 2152 { 2153 tree var = VEC_pop (tree, block_defs_stack); 2154 tree saved_def; 2155 2156 /* NULL indicates the unwind stop point for this block (see 2157 rewrite_update_enter_block). */ 2158 if (var == NULL) 2159 return; 2160 2161 saved_def = VEC_pop (tree, block_defs_stack); 2162 set_current_def (var, saved_def); 2163 } 2164 } 2165 2166 2167 /* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA 2168 form. 2169 2170 ENTRY indicates the block where to start. Every block dominated by 2171 ENTRY will be rewritten. 2172 2173 WHAT indicates what actions will be taken by the renamer (see enum 2174 rewrite_mode). 2175 2176 BLOCKS are the set of interesting blocks for the dominator walker 2177 to process. If this set is NULL, then all the nodes dominated 2178 by ENTRY are walked. Otherwise, blocks dominated by ENTRY that 2179 are not present in BLOCKS are ignored. */ 2180 2181 static void 2182 rewrite_blocks (basic_block entry, enum rewrite_mode what) 2183 { 2184 struct dom_walk_data walk_data; 2185 2186 /* Rewrite all the basic blocks in the program. */ 2187 timevar_push (TV_TREE_SSA_REWRITE_BLOCKS); 2188 2189 /* Setup callbacks for the generic dominator tree walker. */ 2190 memset (&walk_data, 0, sizeof (walk_data)); 2191 2192 walk_data.dom_direction = CDI_DOMINATORS; 2193 2194 if (what == REWRITE_ALL) 2195 { 2196 walk_data.before_dom_children = rewrite_enter_block; 2197 walk_data.after_dom_children = rewrite_leave_block; 2198 } 2199 else if (what == REWRITE_UPDATE) 2200 { 2201 walk_data.before_dom_children = rewrite_update_enter_block; 2202 walk_data.after_dom_children = rewrite_update_leave_block; 2203 } 2204 else 2205 gcc_unreachable (); 2206 2207 block_defs_stack = VEC_alloc (tree, heap, 10); 2208 2209 /* Initialize the dominator walker. */ 2210 init_walk_dominator_tree (&walk_data); 2211 2212 /* Recursively walk the dominator tree rewriting each statement in 2213 each basic block. */ 2214 walk_dominator_tree (&walk_data, entry); 2215 2216 /* Finalize the dominator walker. */ 2217 fini_walk_dominator_tree (&walk_data); 2218 2219 /* Debugging dumps. */ 2220 if (dump_file && (dump_flags & TDF_STATS)) 2221 { 2222 dump_dfa_stats (dump_file); 2223 if (def_blocks) 2224 dump_tree_ssa_stats (dump_file); 2225 } 2226 2227 VEC_free (tree, heap, block_defs_stack); 2228 2229 timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS); 2230 } 2231 2232 2233 /* Block processing routine for mark_def_sites. Clear the KILLS bitmap 2234 at the start of each block, and call mark_def_sites for each statement. */ 2235 2236 static void 2237 mark_def_sites_block (struct dom_walk_data *walk_data, basic_block bb) 2238 { 2239 struct mark_def_sites_global_data *gd; 2240 bitmap kills; 2241 gimple_stmt_iterator gsi; 2242 2243 gd = (struct mark_def_sites_global_data *) walk_data->global_data; 2244 kills = gd->kills; 2245 2246 bitmap_clear (kills); 2247 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi)) 2248 mark_def_sites (bb, gsi_stmt (gsi), kills); 2249 } 2250 2251 2252 /* Mark the definition site blocks for each variable, so that we know 2253 where the variable is actually live. 2254 2255 The INTERESTING_BLOCKS global will be filled in with all the blocks 2256 that should be processed by the renamer. It is assumed that the 2257 caller has already initialized and zeroed it. */ 2258 2259 static void 2260 mark_def_site_blocks (void) 2261 { 2262 struct dom_walk_data walk_data; 2263 struct mark_def_sites_global_data mark_def_sites_global_data; 2264 2265 /* Setup callbacks for the generic dominator tree walker to find and 2266 mark definition sites. */ 2267 walk_data.dom_direction = CDI_DOMINATORS; 2268 walk_data.initialize_block_local_data = NULL; 2269 walk_data.before_dom_children = mark_def_sites_block; 2270 walk_data.after_dom_children = NULL; 2271 2272 /* Notice that this bitmap is indexed using variable UIDs, so it must be 2273 large enough to accommodate all the variables referenced in the 2274 function, not just the ones we are renaming. */ 2275 mark_def_sites_global_data.kills = BITMAP_ALLOC (NULL); 2276 walk_data.global_data = &mark_def_sites_global_data; 2277 2278 /* We do not have any local data. */ 2279 walk_data.block_local_data_size = 0; 2280 2281 /* Initialize the dominator walker. */ 2282 init_walk_dominator_tree (&walk_data); 2283 2284 /* Recursively walk the dominator tree. */ 2285 walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR); 2286 2287 /* Finalize the dominator walker. */ 2288 fini_walk_dominator_tree (&walk_data); 2289 2290 /* We no longer need this bitmap, clear and free it. */ 2291 BITMAP_FREE (mark_def_sites_global_data.kills); 2292 } 2293 2294 2295 /* Initialize internal data needed during renaming. */ 2296 2297 static void 2298 init_ssa_renamer (void) 2299 { 2300 tree var; 2301 referenced_var_iterator rvi; 2302 2303 cfun->gimple_df->in_ssa_p = false; 2304 2305 /* Allocate memory for the DEF_BLOCKS hash table. */ 2306 gcc_assert (def_blocks == NULL); 2307 def_blocks = htab_create (num_referenced_vars, def_blocks_hash, 2308 def_blocks_eq, def_blocks_free); 2309 2310 FOR_EACH_REFERENCED_VAR(var, rvi) 2311 set_current_def (var, NULL_TREE); 2312 } 2313 2314 2315 /* Deallocate internal data structures used by the renamer. */ 2316 2317 static void 2318 fini_ssa_renamer (void) 2319 { 2320 if (def_blocks) 2321 { 2322 htab_delete (def_blocks); 2323 def_blocks = NULL; 2324 } 2325 2326 cfun->gimple_df->in_ssa_p = true; 2327 } 2328 2329 /* Main entry point into the SSA builder. The renaming process 2330 proceeds in four main phases: 2331 2332 1- Compute dominance frontier and immediate dominators, needed to 2333 insert PHI nodes and rename the function in dominator tree 2334 order. 2335 2336 2- Find and mark all the blocks that define variables 2337 (mark_def_site_blocks). 2338 2339 3- Insert PHI nodes at dominance frontiers (insert_phi_nodes). 2340 2341 4- Rename all the blocks (rewrite_blocks) and statements in the program. 2342 2343 Steps 3 and 4 are done using the dominator tree walker 2344 (walk_dominator_tree). */ 2345 2346 static unsigned int 2347 rewrite_into_ssa (void) 2348 { 2349 bitmap *dfs; 2350 basic_block bb; 2351 2352 timevar_push (TV_TREE_SSA_OTHER); 2353 2354 /* Initialize operand data structures. */ 2355 init_ssa_operands (); 2356 2357 /* Initialize internal data needed by the renamer. */ 2358 init_ssa_renamer (); 2359 2360 /* Initialize the set of interesting blocks. The callback 2361 mark_def_sites will add to this set those blocks that the renamer 2362 should process. */ 2363 interesting_blocks = sbitmap_alloc (last_basic_block); 2364 sbitmap_zero (interesting_blocks); 2365 2366 /* Initialize dominance frontier. */ 2367 dfs = XNEWVEC (bitmap, last_basic_block); 2368 FOR_EACH_BB (bb) 2369 dfs[bb->index] = BITMAP_ALLOC (NULL); 2370 2371 /* 1- Compute dominance frontiers. */ 2372 calculate_dominance_info (CDI_DOMINATORS); 2373 compute_dominance_frontiers (dfs); 2374 2375 /* 2- Find and mark definition sites. */ 2376 mark_def_site_blocks (); 2377 2378 /* 3- Insert PHI nodes at dominance frontiers of definition blocks. */ 2379 insert_phi_nodes (dfs); 2380 2381 /* 4- Rename all the blocks. */ 2382 rewrite_blocks (ENTRY_BLOCK_PTR, REWRITE_ALL); 2383 2384 /* Free allocated memory. */ 2385 FOR_EACH_BB (bb) 2386 BITMAP_FREE (dfs[bb->index]); 2387 free (dfs); 2388 2389 sbitmap_free (interesting_blocks); 2390 2391 fini_ssa_renamer (); 2392 2393 timevar_pop (TV_TREE_SSA_OTHER); 2394 return 0; 2395 } 2396 2397 2398 struct gimple_opt_pass pass_build_ssa = 2399 { 2400 { 2401 GIMPLE_PASS, 2402 "ssa", /* name */ 2403 NULL, /* gate */ 2404 rewrite_into_ssa, /* execute */ 2405 NULL, /* sub */ 2406 NULL, /* next */ 2407 0, /* static_pass_number */ 2408 TV_NONE, /* tv_id */ 2409 PROP_cfg | PROP_referenced_vars, /* properties_required */ 2410 PROP_ssa, /* properties_provided */ 2411 0, /* properties_destroyed */ 2412 0, /* todo_flags_start */ 2413 TODO_dump_func 2414 | TODO_update_ssa_only_virtuals 2415 | TODO_verify_ssa 2416 | TODO_remove_unused_locals /* todo_flags_finish */ 2417 } 2418 }; 2419 2420 2421 /* Mark the definition of VAR at STMT and BB as interesting for the 2422 renamer. BLOCKS is the set of blocks that need updating. */ 2423 2424 static void 2425 mark_def_interesting (tree var, gimple stmt, basic_block bb, bool insert_phi_p) 2426 { 2427 gcc_assert (bitmap_bit_p (blocks_to_update, bb->index)); 2428 set_register_defs (stmt, true); 2429 2430 if (insert_phi_p) 2431 { 2432 bool is_phi_p = gimple_code (stmt) == GIMPLE_PHI; 2433 2434 set_def_block (var, bb, is_phi_p); 2435 2436 /* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition 2437 site for both itself and all the old names replaced by it. */ 2438 if (TREE_CODE (var) == SSA_NAME && is_new_name (var)) 2439 { 2440 bitmap_iterator bi; 2441 unsigned i; 2442 bitmap set = names_replaced_by (var); 2443 if (set) 2444 EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi) 2445 set_def_block (ssa_name (i), bb, is_phi_p); 2446 } 2447 } 2448 } 2449 2450 2451 /* Mark the use of VAR at STMT and BB as interesting for the 2452 renamer. INSERT_PHI_P is true if we are going to insert new PHI 2453 nodes. */ 2454 2455 static inline void 2456 mark_use_interesting (tree var, gimple stmt, basic_block bb, bool insert_phi_p) 2457 { 2458 basic_block def_bb = gimple_bb (stmt); 2459 2460 mark_block_for_update (def_bb); 2461 mark_block_for_update (bb); 2462 2463 if (gimple_code (stmt) == GIMPLE_PHI) 2464 mark_phi_for_rewrite (def_bb, stmt); 2465 else 2466 { 2467 set_rewrite_uses (stmt, true); 2468 2469 if (is_gimple_debug (stmt)) 2470 return; 2471 } 2472 2473 /* If VAR has not been defined in BB, then it is live-on-entry 2474 to BB. Note that we cannot just use the block holding VAR's 2475 definition because if VAR is one of the names in OLD_SSA_NAMES, 2476 it will have several definitions (itself and all the names that 2477 replace it). */ 2478 if (insert_phi_p) 2479 { 2480 struct def_blocks_d *db_p = get_def_blocks_for (var); 2481 if (!bitmap_bit_p (db_p->def_blocks, bb->index)) 2482 set_livein_block (var, bb); 2483 } 2484 } 2485 2486 2487 /* Do a dominator walk starting at BB processing statements that 2488 reference symbols in SYMS_TO_RENAME. This is very similar to 2489 mark_def_sites, but the scan handles statements whose operands may 2490 already be SSA names. 2491 2492 If INSERT_PHI_P is true, mark those uses as live in the 2493 corresponding block. This is later used by the PHI placement 2494 algorithm to make PHI pruning decisions. 2495 2496 FIXME. Most of this would be unnecessary if we could associate a 2497 symbol to all the SSA names that reference it. But that 2498 sounds like it would be expensive to maintain. Still, it 2499 would be interesting to see if it makes better sense to do 2500 that. */ 2501 2502 static void 2503 prepare_block_for_update (basic_block bb, bool insert_phi_p) 2504 { 2505 basic_block son; 2506 gimple_stmt_iterator si; 2507 edge e; 2508 edge_iterator ei; 2509 2510 mark_block_for_update (bb); 2511 2512 /* Process PHI nodes marking interesting those that define or use 2513 the symbols that we are interested in. */ 2514 for (si = gsi_start_phis (bb); !gsi_end_p (si); gsi_next (&si)) 2515 { 2516 gimple phi = gsi_stmt (si); 2517 tree lhs_sym, lhs = gimple_phi_result (phi); 2518 2519 lhs_sym = DECL_P (lhs) ? lhs : SSA_NAME_VAR (lhs); 2520 2521 if (!symbol_marked_for_renaming (lhs_sym)) 2522 continue; 2523 2524 mark_def_interesting (lhs_sym, phi, bb, insert_phi_p); 2525 2526 /* Mark the uses in phi nodes as interesting. It would be more correct 2527 to process the arguments of the phi nodes of the successor edges of 2528 BB at the end of prepare_block_for_update, however, that turns out 2529 to be significantly more expensive. Doing it here is conservatively 2530 correct -- it may only cause us to believe a value to be live in a 2531 block that also contains its definition, and thus insert a few more 2532 phi nodes for it. */ 2533 FOR_EACH_EDGE (e, ei, bb->preds) 2534 mark_use_interesting (lhs_sym, phi, e->src, insert_phi_p); 2535 } 2536 2537 /* Process the statements. */ 2538 for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si)) 2539 { 2540 gimple stmt; 2541 ssa_op_iter i; 2542 use_operand_p use_p; 2543 def_operand_p def_p; 2544 2545 stmt = gsi_stmt (si); 2546 2547 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, i, SSA_OP_ALL_USES) 2548 { 2549 tree use = USE_FROM_PTR (use_p); 2550 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use); 2551 if (symbol_marked_for_renaming (sym)) 2552 mark_use_interesting (sym, stmt, bb, insert_phi_p); 2553 } 2554 2555 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, i, SSA_OP_ALL_DEFS) 2556 { 2557 tree def = DEF_FROM_PTR (def_p); 2558 tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def); 2559 if (symbol_marked_for_renaming (sym)) 2560 mark_def_interesting (sym, stmt, bb, insert_phi_p); 2561 } 2562 } 2563 2564 /* Now visit all the blocks dominated by BB. */ 2565 for (son = first_dom_son (CDI_DOMINATORS, bb); 2566 son; 2567 son = next_dom_son (CDI_DOMINATORS, son)) 2568 prepare_block_for_update (son, insert_phi_p); 2569 } 2570 2571 2572 /* Helper for prepare_names_to_update. Mark all the use sites for 2573 NAME as interesting. BLOCKS and INSERT_PHI_P are as in 2574 prepare_names_to_update. */ 2575 2576 static void 2577 prepare_use_sites_for (tree name, bool insert_phi_p) 2578 { 2579 use_operand_p use_p; 2580 imm_use_iterator iter; 2581 2582 FOR_EACH_IMM_USE_FAST (use_p, iter, name) 2583 { 2584 gimple stmt = USE_STMT (use_p); 2585 basic_block bb = gimple_bb (stmt); 2586 2587 if (gimple_code (stmt) == GIMPLE_PHI) 2588 { 2589 int ix = PHI_ARG_INDEX_FROM_USE (use_p); 2590 edge e = gimple_phi_arg_edge (stmt, ix); 2591 mark_use_interesting (name, stmt, e->src, insert_phi_p); 2592 } 2593 else 2594 { 2595 /* For regular statements, mark this as an interesting use 2596 for NAME. */ 2597 mark_use_interesting (name, stmt, bb, insert_phi_p); 2598 } 2599 } 2600 } 2601 2602 2603 /* Helper for prepare_names_to_update. Mark the definition site for 2604 NAME as interesting. BLOCKS and INSERT_PHI_P are as in 2605 prepare_names_to_update. */ 2606 2607 static void 2608 prepare_def_site_for (tree name, bool insert_phi_p) 2609 { 2610 gimple stmt; 2611 basic_block bb; 2612 2613 gcc_assert (names_to_release == NULL 2614 || !bitmap_bit_p (names_to_release, SSA_NAME_VERSION (name))); 2615 2616 stmt = SSA_NAME_DEF_STMT (name); 2617 bb = gimple_bb (stmt); 2618 if (bb) 2619 { 2620 gcc_assert (bb->index < last_basic_block); 2621 mark_block_for_update (bb); 2622 mark_def_interesting (name, stmt, bb, insert_phi_p); 2623 } 2624 } 2625 2626 2627 /* Mark definition and use sites of names in NEW_SSA_NAMES and 2628 OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert 2629 PHI nodes for newly created names. */ 2630 2631 static void 2632 prepare_names_to_update (bool insert_phi_p) 2633 { 2634 unsigned i = 0; 2635 bitmap_iterator bi; 2636 sbitmap_iterator sbi; 2637 2638 /* If a name N from NEW_SSA_NAMES is also marked to be released, 2639 remove it from NEW_SSA_NAMES so that we don't try to visit its 2640 defining basic block (which most likely doesn't exist). Notice 2641 that we cannot do the same with names in OLD_SSA_NAMES because we 2642 want to replace existing instances. */ 2643 if (names_to_release) 2644 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi) 2645 RESET_BIT (new_ssa_names, i); 2646 2647 /* First process names in NEW_SSA_NAMES. Otherwise, uses of old 2648 names may be considered to be live-in on blocks that contain 2649 definitions for their replacements. */ 2650 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names, 0, i, sbi) 2651 prepare_def_site_for (ssa_name (i), insert_phi_p); 2652 2653 /* If an old name is in NAMES_TO_RELEASE, we cannot remove it from 2654 OLD_SSA_NAMES, but we have to ignore its definition site. */ 2655 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi) 2656 { 2657 if (names_to_release == NULL || !bitmap_bit_p (names_to_release, i)) 2658 prepare_def_site_for (ssa_name (i), insert_phi_p); 2659 prepare_use_sites_for (ssa_name (i), insert_phi_p); 2660 } 2661 } 2662 2663 2664 /* Dump all the names replaced by NAME to FILE. */ 2665 2666 void 2667 dump_names_replaced_by (FILE *file, tree name) 2668 { 2669 unsigned i; 2670 bitmap old_set; 2671 bitmap_iterator bi; 2672 2673 print_generic_expr (file, name, 0); 2674 fprintf (file, " -> { "); 2675 2676 old_set = names_replaced_by (name); 2677 EXECUTE_IF_SET_IN_BITMAP (old_set, 0, i, bi) 2678 { 2679 print_generic_expr (file, ssa_name (i), 0); 2680 fprintf (file, " "); 2681 } 2682 2683 fprintf (file, "}\n"); 2684 } 2685 2686 2687 /* Dump all the names replaced by NAME to stderr. */ 2688 2689 void 2690 debug_names_replaced_by (tree name) 2691 { 2692 dump_names_replaced_by (stderr, name); 2693 } 2694 2695 2696 /* Dump SSA update information to FILE. */ 2697 2698 void 2699 dump_update_ssa (FILE *file) 2700 { 2701 unsigned i = 0; 2702 bitmap_iterator bi; 2703 2704 if (!need_ssa_update_p (cfun)) 2705 return; 2706 2707 if (new_ssa_names && sbitmap_first_set_bit (new_ssa_names) >= 0) 2708 { 2709 sbitmap_iterator sbi; 2710 2711 fprintf (file, "\nSSA replacement table\n"); 2712 fprintf (file, "N_i -> { O_1 ... O_j } means that N_i replaces " 2713 "O_1, ..., O_j\n\n"); 2714 2715 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names, 0, i, sbi) 2716 dump_names_replaced_by (file, ssa_name (i)); 2717 2718 fprintf (file, "\n"); 2719 fprintf (file, "Number of virtual NEW -> OLD mappings: %7u\n", 2720 update_ssa_stats.num_virtual_mappings); 2721 fprintf (file, "Number of real NEW -> OLD mappings: %7u\n", 2722 update_ssa_stats.num_total_mappings 2723 - update_ssa_stats.num_virtual_mappings); 2724 fprintf (file, "Number of total NEW -> OLD mappings: %7u\n", 2725 update_ssa_stats.num_total_mappings); 2726 2727 fprintf (file, "\nNumber of virtual symbols: %u\n", 2728 update_ssa_stats.num_virtual_symbols); 2729 } 2730 2731 if (!bitmap_empty_p (SYMS_TO_RENAME (cfun))) 2732 { 2733 fprintf (file, "\n\nSymbols to be put in SSA form\n\n"); 2734 dump_decl_set (file, SYMS_TO_RENAME (cfun)); 2735 fprintf (file, "\n"); 2736 } 2737 2738 if (names_to_release && !bitmap_empty_p (names_to_release)) 2739 { 2740 fprintf (file, "\n\nSSA names to release after updating the SSA web\n\n"); 2741 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi) 2742 { 2743 print_generic_expr (file, ssa_name (i), 0); 2744 fprintf (file, " "); 2745 } 2746 } 2747 2748 fprintf (file, "\n\n"); 2749 } 2750 2751 2752 /* Dump SSA update information to stderr. */ 2753 2754 void 2755 debug_update_ssa (void) 2756 { 2757 dump_update_ssa (stderr); 2758 } 2759 2760 2761 /* Initialize data structures used for incremental SSA updates. */ 2762 2763 static void 2764 init_update_ssa (struct function *fn) 2765 { 2766 /* Reserve more space than the current number of names. The calls to 2767 add_new_name_mapping are typically done after creating new SSA 2768 names, so we'll need to reallocate these arrays. */ 2769 old_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR); 2770 sbitmap_zero (old_ssa_names); 2771 2772 new_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR); 2773 sbitmap_zero (new_ssa_names); 2774 2775 repl_tbl = htab_create (20, repl_map_hash, repl_map_eq, repl_map_free); 2776 names_to_release = NULL; 2777 memset (&update_ssa_stats, 0, sizeof (update_ssa_stats)); 2778 update_ssa_stats.virtual_symbols = BITMAP_ALLOC (NULL); 2779 update_ssa_initialized_fn = fn; 2780 } 2781 2782 2783 /* Deallocate data structures used for incremental SSA updates. */ 2784 2785 void 2786 delete_update_ssa (void) 2787 { 2788 unsigned i; 2789 bitmap_iterator bi; 2790 2791 sbitmap_free (old_ssa_names); 2792 old_ssa_names = NULL; 2793 2794 sbitmap_free (new_ssa_names); 2795 new_ssa_names = NULL; 2796 2797 htab_delete (repl_tbl); 2798 repl_tbl = NULL; 2799 2800 bitmap_clear (SYMS_TO_RENAME (update_ssa_initialized_fn)); 2801 BITMAP_FREE (update_ssa_stats.virtual_symbols); 2802 2803 if (names_to_release) 2804 { 2805 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi) 2806 release_ssa_name (ssa_name (i)); 2807 BITMAP_FREE (names_to_release); 2808 } 2809 2810 clear_ssa_name_info (); 2811 2812 fini_ssa_renamer (); 2813 2814 if (blocks_with_phis_to_rewrite) 2815 EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite, 0, i, bi) 2816 { 2817 gimple_vec phis = VEC_index (gimple_vec, phis_to_rewrite, i); 2818 2819 VEC_free (gimple, heap, phis); 2820 VEC_replace (gimple_vec, phis_to_rewrite, i, NULL); 2821 } 2822 2823 BITMAP_FREE (blocks_with_phis_to_rewrite); 2824 BITMAP_FREE (blocks_to_update); 2825 update_ssa_initialized_fn = NULL; 2826 } 2827 2828 2829 /* Create a new name for OLD_NAME in statement STMT and replace the 2830 operand pointed to by DEF_P with the newly created name. Return 2831 the new name and register the replacement mapping <NEW, OLD> in 2832 update_ssa's tables. */ 2833 2834 tree 2835 create_new_def_for (tree old_name, gimple stmt, def_operand_p def) 2836 { 2837 tree new_name = duplicate_ssa_name (old_name, stmt); 2838 2839 SET_DEF (def, new_name); 2840 2841 if (gimple_code (stmt) == GIMPLE_PHI) 2842 { 2843 edge e; 2844 edge_iterator ei; 2845 basic_block bb = gimple_bb (stmt); 2846 2847 /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */ 2848 FOR_EACH_EDGE (e, ei, bb->preds) 2849 if (e->flags & EDGE_ABNORMAL) 2850 { 2851 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name) = 1; 2852 break; 2853 } 2854 } 2855 2856 register_new_name_mapping (new_name, old_name); 2857 2858 /* For the benefit of passes that will be updating the SSA form on 2859 their own, set the current reaching definition of OLD_NAME to be 2860 NEW_NAME. */ 2861 set_current_def (old_name, new_name); 2862 2863 return new_name; 2864 } 2865 2866 2867 /* Register name NEW to be a replacement for name OLD. This function 2868 must be called for every replacement that should be performed by 2869 update_ssa. */ 2870 2871 void 2872 register_new_name_mapping (tree new_tree, tree old) 2873 { 2874 if (!update_ssa_initialized_fn) 2875 init_update_ssa (cfun); 2876 2877 gcc_assert (update_ssa_initialized_fn == cfun); 2878 2879 add_new_name_mapping (new_tree, old); 2880 } 2881 2882 2883 /* Register symbol SYM to be renamed by update_ssa. */ 2884 2885 void 2886 mark_sym_for_renaming (tree sym) 2887 { 2888 bitmap_set_bit (SYMS_TO_RENAME (cfun), DECL_UID (sym)); 2889 } 2890 2891 2892 /* Register all the symbols in SET to be renamed by update_ssa. */ 2893 2894 void 2895 mark_set_for_renaming (bitmap set) 2896 { 2897 bitmap_iterator bi; 2898 unsigned i; 2899 2900 if (set == NULL || bitmap_empty_p (set)) 2901 return; 2902 2903 EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi) 2904 mark_sym_for_renaming (referenced_var (i)); 2905 } 2906 2907 2908 /* Return true if there is any work to be done by update_ssa 2909 for function FN. */ 2910 2911 bool 2912 need_ssa_update_p (struct function *fn) 2913 { 2914 gcc_assert (fn != NULL); 2915 return (update_ssa_initialized_fn == fn 2916 || (fn->gimple_df 2917 && !bitmap_empty_p (SYMS_TO_RENAME (fn)))); 2918 } 2919 2920 /* Return true if SSA name mappings have been registered for SSA updating. */ 2921 2922 bool 2923 name_mappings_registered_p (void) 2924 { 2925 if (!update_ssa_initialized_fn) 2926 return false; 2927 2928 gcc_assert (update_ssa_initialized_fn == cfun); 2929 2930 return repl_tbl && htab_elements (repl_tbl) > 0; 2931 } 2932 2933 /* Return true if name N has been registered in the replacement table. */ 2934 2935 bool 2936 name_registered_for_update_p (tree n ATTRIBUTE_UNUSED) 2937 { 2938 if (!update_ssa_initialized_fn) 2939 return false; 2940 2941 gcc_assert (update_ssa_initialized_fn == cfun); 2942 2943 return is_new_name (n) || is_old_name (n); 2944 } 2945 2946 2947 /* Return the set of all the SSA names marked to be replaced. */ 2948 2949 bitmap 2950 ssa_names_to_replace (void) 2951 { 2952 unsigned i = 0; 2953 bitmap ret; 2954 sbitmap_iterator sbi; 2955 2956 gcc_assert (update_ssa_initialized_fn == NULL 2957 || update_ssa_initialized_fn == cfun); 2958 2959 ret = BITMAP_ALLOC (NULL); 2960 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi) 2961 bitmap_set_bit (ret, i); 2962 2963 return ret; 2964 } 2965 2966 2967 /* Mark NAME to be released after update_ssa has finished. */ 2968 2969 void 2970 release_ssa_name_after_update_ssa (tree name) 2971 { 2972 gcc_assert (cfun && update_ssa_initialized_fn == cfun); 2973 2974 if (names_to_release == NULL) 2975 names_to_release = BITMAP_ALLOC (NULL); 2976 2977 bitmap_set_bit (names_to_release, SSA_NAME_VERSION (name)); 2978 } 2979 2980 2981 /* Insert new PHI nodes to replace VAR. DFS contains dominance 2982 frontier information. BLOCKS is the set of blocks to be updated. 2983 2984 This is slightly different than the regular PHI insertion 2985 algorithm. The value of UPDATE_FLAGS controls how PHI nodes for 2986 real names (i.e., GIMPLE registers) are inserted: 2987 2988 - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI 2989 nodes inside the region affected by the block that defines VAR 2990 and the blocks that define all its replacements. All these 2991 definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS. 2992 2993 First, we compute the entry point to the region (ENTRY). This is 2994 given by the nearest common dominator to all the definition 2995 blocks. When computing the iterated dominance frontier (IDF), any 2996 block not strictly dominated by ENTRY is ignored. 2997 2998 We then call the standard PHI insertion algorithm with the pruned 2999 IDF. 3000 3001 - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real 3002 names is not pruned. PHI nodes are inserted at every IDF block. */ 3003 3004 static void 3005 insert_updated_phi_nodes_for (tree var, bitmap *dfs, bitmap blocks, 3006 unsigned update_flags) 3007 { 3008 basic_block entry; 3009 struct def_blocks_d *db; 3010 bitmap idf, pruned_idf; 3011 bitmap_iterator bi; 3012 unsigned i; 3013 3014 #if defined ENABLE_CHECKING 3015 if (TREE_CODE (var) == SSA_NAME) 3016 gcc_assert (is_old_name (var)); 3017 else 3018 gcc_assert (symbol_marked_for_renaming (var)); 3019 #endif 3020 3021 /* Get all the definition sites for VAR. */ 3022 db = find_def_blocks_for (var); 3023 3024 /* No need to do anything if there were no definitions to VAR. */ 3025 if (db == NULL || bitmap_empty_p (db->def_blocks)) 3026 return; 3027 3028 /* Compute the initial iterated dominance frontier. */ 3029 idf = compute_idf (db->def_blocks, dfs); 3030 pruned_idf = BITMAP_ALLOC (NULL); 3031 3032 if (TREE_CODE (var) == SSA_NAME) 3033 { 3034 if (update_flags == TODO_update_ssa) 3035 { 3036 /* If doing regular SSA updates for GIMPLE registers, we are 3037 only interested in IDF blocks dominated by the nearest 3038 common dominator of all the definition blocks. */ 3039 entry = nearest_common_dominator_for_set (CDI_DOMINATORS, 3040 db->def_blocks); 3041 if (entry != ENTRY_BLOCK_PTR) 3042 EXECUTE_IF_SET_IN_BITMAP (idf, 0, i, bi) 3043 if (BASIC_BLOCK (i) != entry 3044 && dominated_by_p (CDI_DOMINATORS, BASIC_BLOCK (i), entry)) 3045 bitmap_set_bit (pruned_idf, i); 3046 } 3047 else 3048 { 3049 /* Otherwise, do not prune the IDF for VAR. */ 3050 gcc_assert (update_flags == TODO_update_ssa_full_phi); 3051 bitmap_copy (pruned_idf, idf); 3052 } 3053 } 3054 else 3055 { 3056 /* Otherwise, VAR is a symbol that needs to be put into SSA form 3057 for the first time, so we need to compute the full IDF for 3058 it. */ 3059 bitmap_copy (pruned_idf, idf); 3060 } 3061 3062 if (!bitmap_empty_p (pruned_idf)) 3063 { 3064 /* Make sure that PRUNED_IDF blocks and all their feeding blocks 3065 are included in the region to be updated. The feeding blocks 3066 are important to guarantee that the PHI arguments are renamed 3067 properly. */ 3068 3069 /* FIXME, this is not needed if we are updating symbols. We are 3070 already starting at the ENTRY block anyway. */ 3071 bitmap_ior_into (blocks, pruned_idf); 3072 EXECUTE_IF_SET_IN_BITMAP (pruned_idf, 0, i, bi) 3073 { 3074 edge e; 3075 edge_iterator ei; 3076 basic_block bb = BASIC_BLOCK (i); 3077 3078 FOR_EACH_EDGE (e, ei, bb->preds) 3079 if (e->src->index >= 0) 3080 bitmap_set_bit (blocks, e->src->index); 3081 } 3082 3083 insert_phi_nodes_for (var, pruned_idf, true); 3084 } 3085 3086 BITMAP_FREE (pruned_idf); 3087 BITMAP_FREE (idf); 3088 } 3089 3090 3091 /* Heuristic to determine whether SSA name mappings for virtual names 3092 should be discarded and their symbols rewritten from scratch. When 3093 there is a large number of mappings for virtual names, the 3094 insertion of PHI nodes for the old names in the mappings takes 3095 considerable more time than if we inserted PHI nodes for the 3096 symbols instead. 3097 3098 Currently the heuristic takes these stats into account: 3099 3100 - Number of mappings for virtual SSA names. 3101 - Number of distinct virtual symbols involved in those mappings. 3102 3103 If the number of virtual mappings is much larger than the number of 3104 virtual symbols, then it will be faster to compute PHI insertion 3105 spots for the symbols. Even if this involves traversing the whole 3106 CFG, which is what happens when symbols are renamed from scratch. */ 3107 3108 static bool 3109 switch_virtuals_to_full_rewrite_p (void) 3110 { 3111 if (update_ssa_stats.num_virtual_mappings < (unsigned) MIN_VIRTUAL_MAPPINGS) 3112 return false; 3113 3114 if (update_ssa_stats.num_virtual_mappings 3115 > (unsigned) VIRTUAL_MAPPINGS_TO_SYMS_RATIO 3116 * update_ssa_stats.num_virtual_symbols) 3117 return true; 3118 3119 return false; 3120 } 3121 3122 3123 /* Remove every virtual mapping and mark all the affected virtual 3124 symbols for renaming. */ 3125 3126 static void 3127 switch_virtuals_to_full_rewrite (void) 3128 { 3129 unsigned i = 0; 3130 sbitmap_iterator sbi; 3131 3132 if (dump_file) 3133 { 3134 fprintf (dump_file, "\nEnabled virtual name mapping heuristic.\n"); 3135 fprintf (dump_file, "\tNumber of virtual mappings: %7u\n", 3136 update_ssa_stats.num_virtual_mappings); 3137 fprintf (dump_file, "\tNumber of unique virtual symbols: %7u\n", 3138 update_ssa_stats.num_virtual_symbols); 3139 fprintf (dump_file, "Updating FUD-chains from top of CFG will be " 3140 "faster than processing\nthe name mappings.\n\n"); 3141 } 3142 3143 /* Remove all virtual names from NEW_SSA_NAMES and OLD_SSA_NAMES. 3144 Note that it is not really necessary to remove the mappings from 3145 REPL_TBL, that would only waste time. */ 3146 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names, 0, i, sbi) 3147 if (!is_gimple_reg (ssa_name (i))) 3148 RESET_BIT (new_ssa_names, i); 3149 3150 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi) 3151 if (!is_gimple_reg (ssa_name (i))) 3152 RESET_BIT (old_ssa_names, i); 3153 3154 mark_set_for_renaming (update_ssa_stats.virtual_symbols); 3155 } 3156 3157 3158 /* Given a set of newly created SSA names (NEW_SSA_NAMES) and a set of 3159 existing SSA names (OLD_SSA_NAMES), update the SSA form so that: 3160 3161 1- The names in OLD_SSA_NAMES dominated by the definitions of 3162 NEW_SSA_NAMES are all re-written to be reached by the 3163 appropriate definition from NEW_SSA_NAMES. 3164 3165 2- If needed, new PHI nodes are added to the iterated dominance 3166 frontier of the blocks where each of NEW_SSA_NAMES are defined. 3167 3168 The mapping between OLD_SSA_NAMES and NEW_SSA_NAMES is setup by 3169 calling register_new_name_mapping for every pair of names that the 3170 caller wants to replace. 3171 3172 The caller identifies the new names that have been inserted and the 3173 names that need to be replaced by calling register_new_name_mapping 3174 for every pair <NEW, OLD>. Note that the function assumes that the 3175 new names have already been inserted in the IL. 3176 3177 For instance, given the following code: 3178 3179 1 L0: 3180 2 x_1 = PHI (0, x_5) 3181 3 if (x_1 < 10) 3182 4 if (x_1 > 7) 3183 5 y_2 = 0 3184 6 else 3185 7 y_3 = x_1 + x_7 3186 8 endif 3187 9 x_5 = x_1 + 1 3188 10 goto L0; 3189 11 endif 3190 3191 Suppose that we insert new names x_10 and x_11 (lines 4 and 8). 3192 3193 1 L0: 3194 2 x_1 = PHI (0, x_5) 3195 3 if (x_1 < 10) 3196 4 x_10 = ... 3197 5 if (x_1 > 7) 3198 6 y_2 = 0 3199 7 else 3200 8 x_11 = ... 3201 9 y_3 = x_1 + x_7 3202 10 endif 3203 11 x_5 = x_1 + 1 3204 12 goto L0; 3205 13 endif 3206 3207 We want to replace all the uses of x_1 with the new definitions of 3208 x_10 and x_11. Note that the only uses that should be replaced are 3209 those at lines 5, 9 and 11. Also, the use of x_7 at line 9 should 3210 *not* be replaced (this is why we cannot just mark symbol 'x' for 3211 renaming). 3212 3213 Additionally, we may need to insert a PHI node at line 11 because 3214 that is a merge point for x_10 and x_11. So the use of x_1 at line 3215 11 will be replaced with the new PHI node. The insertion of PHI 3216 nodes is optional. They are not strictly necessary to preserve the 3217 SSA form, and depending on what the caller inserted, they may not 3218 even be useful for the optimizers. UPDATE_FLAGS controls various 3219 aspects of how update_ssa operates, see the documentation for 3220 TODO_update_ssa*. */ 3221 3222 void 3223 update_ssa (unsigned update_flags) 3224 { 3225 basic_block bb, start_bb; 3226 bitmap_iterator bi; 3227 unsigned i = 0; 3228 bool insert_phi_p; 3229 sbitmap_iterator sbi; 3230 3231 if (!need_ssa_update_p (cfun)) 3232 return; 3233 3234 timevar_push (TV_TREE_SSA_INCREMENTAL); 3235 3236 if (!update_ssa_initialized_fn) 3237 init_update_ssa (cfun); 3238 gcc_assert (update_ssa_initialized_fn == cfun); 3239 3240 blocks_with_phis_to_rewrite = BITMAP_ALLOC (NULL); 3241 if (!phis_to_rewrite) 3242 phis_to_rewrite = VEC_alloc (gimple_vec, heap, last_basic_block); 3243 blocks_to_update = BITMAP_ALLOC (NULL); 3244 3245 /* Ensure that the dominance information is up-to-date. */ 3246 calculate_dominance_info (CDI_DOMINATORS); 3247 3248 /* Only one update flag should be set. */ 3249 gcc_assert (update_flags == TODO_update_ssa 3250 || update_flags == TODO_update_ssa_no_phi 3251 || update_flags == TODO_update_ssa_full_phi 3252 || update_flags == TODO_update_ssa_only_virtuals); 3253 3254 /* If we only need to update virtuals, remove all the mappings for 3255 real names before proceeding. The caller is responsible for 3256 having dealt with the name mappings before calling update_ssa. */ 3257 if (update_flags == TODO_update_ssa_only_virtuals) 3258 { 3259 sbitmap_zero (old_ssa_names); 3260 sbitmap_zero (new_ssa_names); 3261 htab_empty (repl_tbl); 3262 } 3263 3264 insert_phi_p = (update_flags != TODO_update_ssa_no_phi); 3265 3266 if (insert_phi_p) 3267 { 3268 /* If the caller requested PHI nodes to be added, initialize 3269 live-in information data structures (DEF_BLOCKS). */ 3270 3271 /* For each SSA name N, the DEF_BLOCKS table describes where the 3272 name is defined, which blocks have PHI nodes for N, and which 3273 blocks have uses of N (i.e., N is live-on-entry in those 3274 blocks). */ 3275 def_blocks = htab_create (num_ssa_names, def_blocks_hash, 3276 def_blocks_eq, def_blocks_free); 3277 } 3278 else 3279 { 3280 def_blocks = NULL; 3281 } 3282 3283 /* Heuristic to avoid massive slow downs when the replacement 3284 mappings include lots of virtual names. */ 3285 if (insert_phi_p && switch_virtuals_to_full_rewrite_p ()) 3286 switch_virtuals_to_full_rewrite (); 3287 3288 /* If there are names defined in the replacement table, prepare 3289 definition and use sites for all the names in NEW_SSA_NAMES and 3290 OLD_SSA_NAMES. */ 3291 if (sbitmap_first_set_bit (new_ssa_names) >= 0) 3292 { 3293 prepare_names_to_update (insert_phi_p); 3294 3295 /* If all the names in NEW_SSA_NAMES had been marked for 3296 removal, and there are no symbols to rename, then there's 3297 nothing else to do. */ 3298 if (sbitmap_first_set_bit (new_ssa_names) < 0 3299 && bitmap_empty_p (SYMS_TO_RENAME (cfun))) 3300 goto done; 3301 } 3302 3303 /* Next, determine the block at which to start the renaming process. */ 3304 if (!bitmap_empty_p (SYMS_TO_RENAME (cfun))) 3305 { 3306 /* If we have to rename some symbols from scratch, we need to 3307 start the process at the root of the CFG. FIXME, it should 3308 be possible to determine the nearest block that had a 3309 definition for each of the symbols that are marked for 3310 updating. For now this seems more work than it's worth. */ 3311 start_bb = ENTRY_BLOCK_PTR; 3312 3313 /* Traverse the CFG looking for existing definitions and uses of 3314 symbols in SYMS_TO_RENAME. Mark interesting blocks and 3315 statements and set local live-in information for the PHI 3316 placement heuristics. */ 3317 prepare_block_for_update (start_bb, insert_phi_p); 3318 } 3319 else 3320 { 3321 /* Otherwise, the entry block to the region is the nearest 3322 common dominator for the blocks in BLOCKS. */ 3323 start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS, 3324 blocks_to_update); 3325 } 3326 3327 /* If requested, insert PHI nodes at the iterated dominance frontier 3328 of every block, creating new definitions for names in OLD_SSA_NAMES 3329 and for symbols in SYMS_TO_RENAME. */ 3330 if (insert_phi_p) 3331 { 3332 bitmap *dfs; 3333 3334 /* If the caller requested PHI nodes to be added, compute 3335 dominance frontiers. */ 3336 dfs = XNEWVEC (bitmap, last_basic_block); 3337 FOR_EACH_BB (bb) 3338 dfs[bb->index] = BITMAP_ALLOC (NULL); 3339 compute_dominance_frontiers (dfs); 3340 3341 if (sbitmap_first_set_bit (old_ssa_names) >= 0) 3342 { 3343 sbitmap_iterator sbi; 3344 3345 /* insert_update_phi_nodes_for will call add_new_name_mapping 3346 when inserting new PHI nodes, so the set OLD_SSA_NAMES 3347 will grow while we are traversing it (but it will not 3348 gain any new members). Copy OLD_SSA_NAMES to a temporary 3349 for traversal. */ 3350 sbitmap tmp = sbitmap_alloc (old_ssa_names->n_bits); 3351 sbitmap_copy (tmp, old_ssa_names); 3352 EXECUTE_IF_SET_IN_SBITMAP (tmp, 0, i, sbi) 3353 insert_updated_phi_nodes_for (ssa_name (i), dfs, blocks_to_update, 3354 update_flags); 3355 sbitmap_free (tmp); 3356 } 3357 3358 EXECUTE_IF_SET_IN_BITMAP (SYMS_TO_RENAME (cfun), 0, i, bi) 3359 insert_updated_phi_nodes_for (referenced_var (i), dfs, blocks_to_update, 3360 update_flags); 3361 3362 FOR_EACH_BB (bb) 3363 BITMAP_FREE (dfs[bb->index]); 3364 free (dfs); 3365 3366 /* Insertion of PHI nodes may have added blocks to the region. 3367 We need to re-compute START_BB to include the newly added 3368 blocks. */ 3369 if (start_bb != ENTRY_BLOCK_PTR) 3370 start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS, 3371 blocks_to_update); 3372 } 3373 3374 /* Reset the current definition for name and symbol before renaming 3375 the sub-graph. */ 3376 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi) 3377 set_current_def (ssa_name (i), NULL_TREE); 3378 3379 EXECUTE_IF_SET_IN_BITMAP (SYMS_TO_RENAME (cfun), 0, i, bi) 3380 set_current_def (referenced_var (i), NULL_TREE); 3381 3382 /* Now start the renaming process at START_BB. */ 3383 interesting_blocks = sbitmap_alloc (last_basic_block); 3384 sbitmap_zero (interesting_blocks); 3385 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi) 3386 SET_BIT (interesting_blocks, i); 3387 3388 rewrite_blocks (start_bb, REWRITE_UPDATE); 3389 3390 sbitmap_free (interesting_blocks); 3391 3392 /* Debugging dumps. */ 3393 if (dump_file) 3394 { 3395 int c; 3396 unsigned i; 3397 3398 dump_update_ssa (dump_file); 3399 3400 fprintf (dump_file, "Incremental SSA update started at block: %d\n\n", 3401 start_bb->index); 3402 3403 c = 0; 3404 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi) 3405 c++; 3406 fprintf (dump_file, "Number of blocks in CFG: %d\n", last_basic_block); 3407 fprintf (dump_file, "Number of blocks to update: %d (%3.0f%%)\n\n", 3408 c, PERCENT (c, last_basic_block)); 3409 3410 if (dump_flags & TDF_DETAILS) 3411 { 3412 fprintf (dump_file, "Affected blocks: "); 3413 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi) 3414 fprintf (dump_file, "%u ", i); 3415 fprintf (dump_file, "\n"); 3416 } 3417 3418 fprintf (dump_file, "\n\n"); 3419 } 3420 3421 /* Free allocated memory. */ 3422 done: 3423 delete_update_ssa (); 3424 3425 timevar_pop (TV_TREE_SSA_INCREMENTAL); 3426 } 3427