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[official-gcc.git] / gcc / tree-into-ssa.c
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1 /* Rewrite a program in Normal form into SSA.
2 Copyright (C) 2001-2021 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
10 any later version.
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
21 #include "config.h"
22 #include "system.h"
23 #include "coretypes.h"
24 #include "backend.h"
25 #include "rtl.h"
26 #include "tree.h"
27 #include "gimple.h"
28 #include "tree-pass.h"
29 #include "ssa.h"
30 #include "gimple-pretty-print.h"
31 #include "diagnostic-core.h"
32 #include "langhooks.h"
33 #include "cfganal.h"
34 #include "gimple-iterator.h"
35 #include "tree-cfg.h"
36 #include "tree-into-ssa.h"
37 #include "tree-dfa.h"
38 #include "tree-ssa.h"
39 #include "domwalk.h"
40 #include "statistics.h"
41 #include "stringpool.h"
42 #include "attribs.h"
43 #include "asan.h"
44 #include "attr-fnspec.h"
46 #define PERCENT(x,y) ((float)(x) * 100.0 / (float)(y))
48 /* This file builds the SSA form for a function as described in:
49 R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently
50 Computing Static Single Assignment Form and the Control Dependence
51 Graph. ACM Transactions on Programming Languages and Systems,
52 13(4):451-490, October 1991. */
54 /* Structure to map a variable VAR to the set of blocks that contain
55 definitions for VAR. */
56 struct def_blocks
58 /* Blocks that contain definitions of VAR. Bit I will be set if the
59 Ith block contains a definition of VAR. */
60 bitmap def_blocks;
62 /* Blocks that contain a PHI node for VAR. */
63 bitmap phi_blocks;
65 /* Blocks where VAR is live-on-entry. Similar semantics as
66 DEF_BLOCKS. */
67 bitmap livein_blocks;
70 /* Stack of trees used to restore the global currdefs to its original
71 state after completing rewriting of a block and its dominator
72 children. Its elements have the following properties:
74 - An SSA_NAME (N) indicates that the current definition of the
75 underlying variable should be set to the given SSA_NAME. If the
76 symbol associated with the SSA_NAME is not a GIMPLE register, the
77 next slot in the stack must be a _DECL node (SYM). In this case,
78 the name N in the previous slot is the current reaching
79 definition for SYM.
81 - A _DECL node indicates that the underlying variable has no
82 current definition.
84 - A NULL node at the top entry is used to mark the last slot
85 associated with the current block. */
86 static vec<tree> block_defs_stack;
89 /* Set of existing SSA names being replaced by update_ssa. */
90 static sbitmap old_ssa_names;
92 /* Set of new SSA names being added by update_ssa. Note that both
93 NEW_SSA_NAMES and OLD_SSA_NAMES are dense bitmaps because most of
94 the operations done on them are presence tests. */
95 static sbitmap new_ssa_names;
97 static sbitmap interesting_blocks;
99 /* Set of SSA names that have been marked to be released after they
100 were registered in the replacement table. They will be finally
101 released after we finish updating the SSA web. */
102 bitmap names_to_release;
104 /* vec of vec of PHIs to rewrite in a basic block. Element I corresponds
105 the to basic block with index I. Allocated once per compilation, *not*
106 released between different functions. */
107 static vec< vec<gphi *> > phis_to_rewrite;
109 /* The bitmap of non-NULL elements of PHIS_TO_REWRITE. */
110 static bitmap blocks_with_phis_to_rewrite;
112 /* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need
113 to grow as the callers to create_new_def_for will create new names on
114 the fly.
115 FIXME. Currently set to 1/3 to avoid frequent reallocations but still
116 need to find a reasonable growth strategy. */
117 #define NAME_SETS_GROWTH_FACTOR (MAX (3, num_ssa_names / 3))
120 /* The function the SSA updating data structures have been initialized for.
121 NULL if they need to be initialized by create_new_def_for. */
122 static struct function *update_ssa_initialized_fn = NULL;
124 /* Global data to attach to the main dominator walk structure. */
125 struct mark_def_sites_global_data
127 /* This bitmap contains the variables which are set before they
128 are used in a basic block. */
129 bitmap kills;
132 /* It is advantageous to avoid things like life analysis for variables which
133 do not need PHI nodes. This enum describes whether or not a particular
134 variable may need a PHI node. */
136 enum need_phi_state {
137 /* This is the default. If we are still in this state after finding
138 all the definition and use sites, then we will assume the variable
139 needs PHI nodes. This is probably an overly conservative assumption. */
140 NEED_PHI_STATE_UNKNOWN,
142 /* This state indicates that we have seen one or more sets of the
143 variable in a single basic block and that the sets dominate all
144 uses seen so far. If after finding all definition and use sites
145 we are still in this state, then the variable does not need any
146 PHI nodes. */
147 NEED_PHI_STATE_NO,
149 /* This state indicates that we have either seen multiple definitions of
150 the variable in multiple blocks, or that we encountered a use in a
151 block that was not dominated by the block containing the set(s) of
152 this variable. This variable is assumed to need PHI nodes. */
153 NEED_PHI_STATE_MAYBE
156 /* Information stored for both SSA names and decls. */
157 struct common_info
159 /* This field indicates whether or not the variable may need PHI nodes.
160 See the enum's definition for more detailed information about the
161 states. */
162 ENUM_BITFIELD (need_phi_state) need_phi_state : 2;
164 /* The current reaching definition replacing this var. */
165 tree current_def;
167 /* Definitions for this var. */
168 struct def_blocks def_blocks;
171 /* Information stored for decls. */
172 struct var_info
174 /* The variable. */
175 tree var;
177 /* Information stored for both SSA names and decls. */
178 common_info info;
182 /* VAR_INFOS hashtable helpers. */
184 struct var_info_hasher : free_ptr_hash <var_info>
186 static inline hashval_t hash (const value_type &);
187 static inline bool equal (const value_type &, const compare_type &);
190 inline hashval_t
191 var_info_hasher::hash (const value_type &p)
193 return DECL_UID (p->var);
196 inline bool
197 var_info_hasher::equal (const value_type &p1, const compare_type &p2)
199 return p1->var == p2->var;
203 /* Each entry in VAR_INFOS contains an element of type STRUCT
204 VAR_INFO_D. */
205 static hash_table<var_info_hasher> *var_infos;
208 /* Information stored for SSA names. */
209 struct ssa_name_info
211 /* Age of this record (so that info_for_ssa_name table can be cleared
212 quickly); if AGE < CURRENT_INFO_FOR_SSA_NAME_AGE, then the fields
213 are assumed to be null. */
214 unsigned age;
216 /* Replacement mappings, allocated from update_ssa_obstack. */
217 bitmap repl_set;
219 /* Information stored for both SSA names and decls. */
220 common_info info;
223 static vec<ssa_name_info *> info_for_ssa_name;
224 static unsigned current_info_for_ssa_name_age;
226 static bitmap_obstack update_ssa_obstack;
228 /* The set of blocks affected by update_ssa. */
229 static bitmap blocks_to_update;
231 /* The main entry point to the SSA renamer (rewrite_blocks) may be
232 called several times to do different, but related, tasks.
233 Initially, we need it to rename the whole program into SSA form.
234 At other times, we may need it to only rename into SSA newly
235 exposed symbols. Finally, we can also call it to incrementally fix
236 an already built SSA web. */
237 enum rewrite_mode {
238 /* Convert the whole function into SSA form. */
239 REWRITE_ALL,
241 /* Incrementally update the SSA web by replacing existing SSA
242 names with new ones. See update_ssa for details. */
243 REWRITE_UPDATE
246 /* The set of symbols we ought to re-write into SSA form in update_ssa. */
247 static bitmap symbols_to_rename_set;
248 static vec<tree> symbols_to_rename;
250 /* Mark SYM for renaming. */
252 static void
253 mark_for_renaming (tree sym)
255 if (!symbols_to_rename_set)
256 symbols_to_rename_set = BITMAP_ALLOC (NULL);
257 if (bitmap_set_bit (symbols_to_rename_set, DECL_UID (sym)))
258 symbols_to_rename.safe_push (sym);
261 /* Return true if SYM is marked for renaming. */
263 static bool
264 marked_for_renaming (tree sym)
266 if (!symbols_to_rename_set || sym == NULL_TREE)
267 return false;
268 return bitmap_bit_p (symbols_to_rename_set, DECL_UID (sym));
272 /* Return true if STMT needs to be rewritten. When renaming a subset
273 of the variables, not all statements will be processed. This is
274 decided in mark_def_sites. */
276 static inline bool
277 rewrite_uses_p (gimple *stmt)
279 return gimple_visited_p (stmt);
283 /* Set the rewrite marker on STMT to the value given by REWRITE_P. */
285 static inline void
286 set_rewrite_uses (gimple *stmt, bool rewrite_p)
288 gimple_set_visited (stmt, rewrite_p);
292 /* Return true if the DEFs created by statement STMT should be
293 registered when marking new definition sites. This is slightly
294 different than rewrite_uses_p: it's used by update_ssa to
295 distinguish statements that need to have both uses and defs
296 processed from those that only need to have their defs processed.
297 Statements that define new SSA names only need to have their defs
298 registered, but they don't need to have their uses renamed. */
300 static inline bool
301 register_defs_p (gimple *stmt)
303 return gimple_plf (stmt, GF_PLF_1) != 0;
307 /* If REGISTER_DEFS_P is true, mark STMT to have its DEFs registered. */
309 static inline void
310 set_register_defs (gimple *stmt, bool register_defs_p)
312 gimple_set_plf (stmt, GF_PLF_1, register_defs_p);
316 /* Get the information associated with NAME. */
318 static inline ssa_name_info *
319 get_ssa_name_ann (tree name)
321 unsigned ver = SSA_NAME_VERSION (name);
322 unsigned len = info_for_ssa_name.length ();
323 struct ssa_name_info *info;
325 /* Re-allocate the vector at most once per update/into-SSA. */
326 if (ver >= len)
327 info_for_ssa_name.safe_grow_cleared (num_ssa_names, true);
329 /* But allocate infos lazily. */
330 info = info_for_ssa_name[ver];
331 if (!info)
333 info = XCNEW (struct ssa_name_info);
334 info->age = current_info_for_ssa_name_age;
335 info->info.need_phi_state = NEED_PHI_STATE_UNKNOWN;
336 info_for_ssa_name[ver] = info;
339 if (info->age < current_info_for_ssa_name_age)
341 info->age = current_info_for_ssa_name_age;
342 info->repl_set = NULL;
343 info->info.need_phi_state = NEED_PHI_STATE_UNKNOWN;
344 info->info.current_def = NULL_TREE;
345 info->info.def_blocks.def_blocks = NULL;
346 info->info.def_blocks.phi_blocks = NULL;
347 info->info.def_blocks.livein_blocks = NULL;
350 return info;
353 /* Return and allocate the auxiliar information for DECL. */
355 static inline var_info *
356 get_var_info (tree decl)
358 var_info vi;
359 var_info **slot;
360 vi.var = decl;
361 slot = var_infos->find_slot_with_hash (&vi, DECL_UID (decl), INSERT);
362 if (*slot == NULL)
364 var_info *v = XCNEW (var_info);
365 v->var = decl;
366 *slot = v;
367 return v;
369 return *slot;
373 /* Clears info for SSA names. */
375 static void
376 clear_ssa_name_info (void)
378 current_info_for_ssa_name_age++;
380 /* If current_info_for_ssa_name_age wraps we use stale information.
381 Asser that this does not happen. */
382 gcc_assert (current_info_for_ssa_name_age != 0);
386 /* Get access to the auxiliar information stored per SSA name or decl. */
388 static inline common_info *
389 get_common_info (tree var)
391 if (TREE_CODE (var) == SSA_NAME)
392 return &get_ssa_name_ann (var)->info;
393 else
394 return &get_var_info (var)->info;
398 /* Return the current definition for VAR. */
400 tree
401 get_current_def (tree var)
403 return get_common_info (var)->current_def;
407 /* Sets current definition of VAR to DEF. */
409 void
410 set_current_def (tree var, tree def)
412 get_common_info (var)->current_def = def;
415 /* Cleans up the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags for
416 all statements in basic block BB. */
418 static void
419 initialize_flags_in_bb (basic_block bb)
421 gimple *stmt;
422 gimple_stmt_iterator gsi;
424 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
426 gimple *phi = gsi_stmt (gsi);
427 set_rewrite_uses (phi, false);
428 set_register_defs (phi, false);
431 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
433 stmt = gsi_stmt (gsi);
435 /* We are going to use the operand cache API, such as
436 SET_USE, SET_DEF, and FOR_EACH_IMM_USE_FAST. The operand
437 cache for each statement should be up-to-date. */
438 gcc_checking_assert (!gimple_modified_p (stmt));
439 set_rewrite_uses (stmt, false);
440 set_register_defs (stmt, false);
444 /* Mark block BB as interesting for update_ssa. */
446 static void
447 mark_block_for_update (basic_block bb)
449 gcc_checking_assert (blocks_to_update != NULL);
450 if (!bitmap_set_bit (blocks_to_update, bb->index))
451 return;
452 initialize_flags_in_bb (bb);
455 /* Return the set of blocks where variable VAR is defined and the blocks
456 where VAR is live on entry (livein). If no entry is found in
457 DEF_BLOCKS, a new one is created and returned. */
459 static inline def_blocks *
460 get_def_blocks_for (common_info *info)
462 def_blocks *db_p = &info->def_blocks;
463 if (!db_p->def_blocks)
465 db_p->def_blocks = BITMAP_ALLOC (&update_ssa_obstack);
466 db_p->phi_blocks = BITMAP_ALLOC (&update_ssa_obstack);
467 db_p->livein_blocks = BITMAP_ALLOC (&update_ssa_obstack);
470 return db_p;
474 /* Mark block BB as the definition site for variable VAR. PHI_P is true if
475 VAR is defined by a PHI node. */
477 static void
478 set_def_block (tree var, basic_block bb, bool phi_p)
480 def_blocks *db_p;
481 common_info *info;
483 info = get_common_info (var);
484 db_p = get_def_blocks_for (info);
486 /* Set the bit corresponding to the block where VAR is defined. */
487 bitmap_set_bit (db_p->def_blocks, bb->index);
488 if (phi_p)
489 bitmap_set_bit (db_p->phi_blocks, bb->index);
491 /* Keep track of whether or not we may need to insert PHI nodes.
493 If we are in the UNKNOWN state, then this is the first definition
494 of VAR. Additionally, we have not seen any uses of VAR yet, so
495 we do not need a PHI node for this variable at this time (i.e.,
496 transition to NEED_PHI_STATE_NO).
498 If we are in any other state, then we either have multiple definitions
499 of this variable occurring in different blocks or we saw a use of the
500 variable which was not dominated by the block containing the
501 definition(s). In this case we may need a PHI node, so enter
502 state NEED_PHI_STATE_MAYBE. */
503 if (info->need_phi_state == NEED_PHI_STATE_UNKNOWN)
504 info->need_phi_state = NEED_PHI_STATE_NO;
505 else
506 info->need_phi_state = NEED_PHI_STATE_MAYBE;
510 /* Mark block BB as having VAR live at the entry to BB. */
512 static void
513 set_livein_block (tree var, basic_block bb)
515 common_info *info;
516 def_blocks *db_p;
518 info = get_common_info (var);
519 db_p = get_def_blocks_for (info);
521 /* Set the bit corresponding to the block where VAR is live in. */
522 bitmap_set_bit (db_p->livein_blocks, bb->index);
524 /* Keep track of whether or not we may need to insert PHI nodes.
526 If we reach here in NEED_PHI_STATE_NO, see if this use is dominated
527 by the single block containing the definition(s) of this variable. If
528 it is, then we remain in NEED_PHI_STATE_NO, otherwise we transition to
529 NEED_PHI_STATE_MAYBE. */
530 if (info->need_phi_state == NEED_PHI_STATE_NO)
532 int def_block_index = bitmap_first_set_bit (db_p->def_blocks);
534 if (def_block_index == -1
535 || ! dominated_by_p (CDI_DOMINATORS, bb,
536 BASIC_BLOCK_FOR_FN (cfun, def_block_index)))
537 info->need_phi_state = NEED_PHI_STATE_MAYBE;
539 else
540 info->need_phi_state = NEED_PHI_STATE_MAYBE;
544 /* Return true if NAME is in OLD_SSA_NAMES. */
546 static inline bool
547 is_old_name (tree name)
549 unsigned ver = SSA_NAME_VERSION (name);
550 if (!old_ssa_names)
551 return false;
552 return (ver < SBITMAP_SIZE (old_ssa_names)
553 && bitmap_bit_p (old_ssa_names, ver));
557 /* Return true if NAME is in NEW_SSA_NAMES. */
559 static inline bool
560 is_new_name (tree name)
562 unsigned ver = SSA_NAME_VERSION (name);
563 if (!new_ssa_names)
564 return false;
565 return (ver < SBITMAP_SIZE (new_ssa_names)
566 && bitmap_bit_p (new_ssa_names, ver));
570 /* Return the names replaced by NEW_TREE (i.e., REPL_TBL[NEW_TREE].SET). */
572 static inline bitmap
573 names_replaced_by (tree new_tree)
575 return get_ssa_name_ann (new_tree)->repl_set;
579 /* Add OLD to REPL_TBL[NEW_TREE].SET. */
581 static inline void
582 add_to_repl_tbl (tree new_tree, tree old)
584 bitmap *set = &get_ssa_name_ann (new_tree)->repl_set;
585 if (!*set)
586 *set = BITMAP_ALLOC (&update_ssa_obstack);
587 bitmap_set_bit (*set, SSA_NAME_VERSION (old));
591 /* Add a new mapping NEW_TREE -> OLD REPL_TBL. Every entry N_i in REPL_TBL
592 represents the set of names O_1 ... O_j replaced by N_i. This is
593 used by update_ssa and its helpers to introduce new SSA names in an
594 already formed SSA web. */
596 static void
597 add_new_name_mapping (tree new_tree, tree old)
599 /* OLD and NEW_TREE must be different SSA names for the same symbol. */
600 gcc_checking_assert (new_tree != old
601 && SSA_NAME_VAR (new_tree) == SSA_NAME_VAR (old));
603 /* We may need to grow NEW_SSA_NAMES and OLD_SSA_NAMES because our
604 caller may have created new names since the set was created. */
605 if (SBITMAP_SIZE (new_ssa_names) <= num_ssa_names - 1)
607 unsigned int new_sz = num_ssa_names + NAME_SETS_GROWTH_FACTOR;
608 new_ssa_names = sbitmap_resize (new_ssa_names, new_sz, 0);
609 old_ssa_names = sbitmap_resize (old_ssa_names, new_sz, 0);
612 /* Update the REPL_TBL table. */
613 add_to_repl_tbl (new_tree, old);
615 /* If OLD had already been registered as a new name, then all the
616 names that OLD replaces should also be replaced by NEW_TREE. */
617 if (is_new_name (old))
618 bitmap_ior_into (names_replaced_by (new_tree), names_replaced_by (old));
620 /* Register NEW_TREE and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES,
621 respectively. */
622 bitmap_set_bit (new_ssa_names, SSA_NAME_VERSION (new_tree));
623 bitmap_set_bit (old_ssa_names, SSA_NAME_VERSION (old));
627 /* Call back for walk_dominator_tree used to collect definition sites
628 for every variable in the function. For every statement S in block
631 1- Variables defined by S in the DEFS of S are marked in the bitmap
632 KILLS.
634 2- If S uses a variable VAR and there is no preceding kill of VAR,
635 then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR.
637 This information is used to determine which variables are live
638 across block boundaries to reduce the number of PHI nodes
639 we create. */
641 static void
642 mark_def_sites (basic_block bb, gimple *stmt, bitmap kills)
644 tree def;
645 use_operand_p use_p;
646 ssa_op_iter iter;
648 /* Since this is the first time that we rewrite the program into SSA
649 form, force an operand scan on every statement. */
650 update_stmt (stmt);
652 gcc_checking_assert (blocks_to_update == NULL);
653 set_register_defs (stmt, false);
654 set_rewrite_uses (stmt, false);
656 if (is_gimple_debug (stmt))
658 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
660 tree sym = USE_FROM_PTR (use_p);
661 gcc_checking_assert (DECL_P (sym));
662 set_rewrite_uses (stmt, true);
664 if (rewrite_uses_p (stmt))
665 bitmap_set_bit (interesting_blocks, bb->index);
666 return;
669 /* If a variable is used before being set, then the variable is live
670 across a block boundary, so mark it live-on-entry to BB. */
671 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
673 tree sym = USE_FROM_PTR (use_p);
674 if (TREE_CODE (sym) == SSA_NAME)
675 continue;
676 gcc_checking_assert (DECL_P (sym));
677 if (!bitmap_bit_p (kills, DECL_UID (sym)))
678 set_livein_block (sym, bb);
679 set_rewrite_uses (stmt, true);
682 /* Now process the defs. Mark BB as the definition block and add
683 each def to the set of killed symbols. */
684 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
686 if (TREE_CODE (def) == SSA_NAME)
687 continue;
688 gcc_checking_assert (DECL_P (def));
689 set_def_block (def, bb, false);
690 bitmap_set_bit (kills, DECL_UID (def));
691 set_register_defs (stmt, true);
694 /* If we found the statement interesting then also mark the block BB
695 as interesting. */
696 if (rewrite_uses_p (stmt) || register_defs_p (stmt))
697 bitmap_set_bit (interesting_blocks, bb->index);
700 /* Structure used by prune_unused_phi_nodes to record bounds of the intervals
701 in the dfs numbering of the dominance tree. */
703 struct dom_dfsnum
705 /* Basic block whose index this entry corresponds to. */
706 unsigned bb_index;
708 /* The dfs number of this node. */
709 unsigned dfs_num;
712 /* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback
713 for qsort. */
715 static int
716 cmp_dfsnum (const void *a, const void *b)
718 const struct dom_dfsnum *const da = (const struct dom_dfsnum *) a;
719 const struct dom_dfsnum *const db = (const struct dom_dfsnum *) b;
721 return (int) da->dfs_num - (int) db->dfs_num;
724 /* Among the intervals starting at the N points specified in DEFS, find
725 the one that contains S, and return its bb_index. */
727 static unsigned
728 find_dfsnum_interval (struct dom_dfsnum *defs, unsigned n, unsigned s)
730 unsigned f = 0, t = n, m;
732 while (t > f + 1)
734 m = (f + t) / 2;
735 if (defs[m].dfs_num <= s)
736 f = m;
737 else
738 t = m;
741 return defs[f].bb_index;
744 /* Clean bits from PHIS for phi nodes whose value cannot be used in USES.
745 KILLS is a bitmap of blocks where the value is defined before any use. */
747 static void
748 prune_unused_phi_nodes (bitmap phis, bitmap kills, bitmap uses)
750 bitmap_iterator bi;
751 unsigned i, b, p, u, top;
752 bitmap live_phis;
753 basic_block def_bb, use_bb;
754 edge e;
755 edge_iterator ei;
756 bitmap to_remove;
757 struct dom_dfsnum *defs;
758 unsigned n_defs, adef;
760 if (bitmap_empty_p (uses))
762 bitmap_clear (phis);
763 return;
766 /* The phi must dominate a use, or an argument of a live phi. Also, we
767 do not create any phi nodes in def blocks, unless they are also livein. */
768 to_remove = BITMAP_ALLOC (NULL);
769 bitmap_and_compl (to_remove, kills, uses);
770 bitmap_and_compl_into (phis, to_remove);
771 if (bitmap_empty_p (phis))
773 BITMAP_FREE (to_remove);
774 return;
777 /* We want to remove the unnecessary phi nodes, but we do not want to compute
778 liveness information, as that may be linear in the size of CFG, and if
779 there are lot of different variables to rewrite, this may lead to quadratic
780 behavior.
782 Instead, we basically emulate standard dce. We put all uses to worklist,
783 then for each of them find the nearest def that dominates them. If this
784 def is a phi node, we mark it live, and if it was not live before, we
785 add the predecessors of its basic block to the worklist.
787 To quickly locate the nearest def that dominates use, we use dfs numbering
788 of the dominance tree (that is already available in order to speed up
789 queries). For each def, we have the interval given by the dfs number on
790 entry to and on exit from the corresponding subtree in the dominance tree.
791 The nearest dominator for a given use is the smallest of these intervals
792 that contains entry and exit dfs numbers for the basic block with the use.
793 If we store the bounds for all the uses to an array and sort it, we can
794 locate the nearest dominating def in logarithmic time by binary search.*/
795 bitmap_ior (to_remove, kills, phis);
796 n_defs = bitmap_count_bits (to_remove);
797 defs = XNEWVEC (struct dom_dfsnum, 2 * n_defs + 1);
798 defs[0].bb_index = 1;
799 defs[0].dfs_num = 0;
800 adef = 1;
801 EXECUTE_IF_SET_IN_BITMAP (to_remove, 0, i, bi)
803 def_bb = BASIC_BLOCK_FOR_FN (cfun, i);
804 defs[adef].bb_index = i;
805 defs[adef].dfs_num = bb_dom_dfs_in (CDI_DOMINATORS, def_bb);
806 defs[adef + 1].bb_index = i;
807 defs[adef + 1].dfs_num = bb_dom_dfs_out (CDI_DOMINATORS, def_bb);
808 adef += 2;
810 BITMAP_FREE (to_remove);
811 gcc_assert (adef == 2 * n_defs + 1);
812 qsort (defs, adef, sizeof (struct dom_dfsnum), cmp_dfsnum);
813 gcc_assert (defs[0].bb_index == 1);
815 /* Now each DEFS entry contains the number of the basic block to that the
816 dfs number corresponds. Change them to the number of basic block that
817 corresponds to the interval following the dfs number. Also, for the
818 dfs_out numbers, increase the dfs number by one (so that it corresponds
819 to the start of the following interval, not to the end of the current
820 one). We use WORKLIST as a stack. */
821 auto_vec<int> worklist (n_defs + 1);
822 worklist.quick_push (1);
823 top = 1;
824 n_defs = 1;
825 for (i = 1; i < adef; i++)
827 b = defs[i].bb_index;
828 if (b == top)
830 /* This is a closing element. Interval corresponding to the top
831 of the stack after removing it follows. */
832 worklist.pop ();
833 top = worklist[worklist.length () - 1];
834 defs[n_defs].bb_index = top;
835 defs[n_defs].dfs_num = defs[i].dfs_num + 1;
837 else
839 /* Opening element. Nothing to do, just push it to the stack and move
840 it to the correct position. */
841 defs[n_defs].bb_index = defs[i].bb_index;
842 defs[n_defs].dfs_num = defs[i].dfs_num;
843 worklist.quick_push (b);
844 top = b;
847 /* If this interval starts at the same point as the previous one, cancel
848 the previous one. */
849 if (defs[n_defs].dfs_num == defs[n_defs - 1].dfs_num)
850 defs[n_defs - 1].bb_index = defs[n_defs].bb_index;
851 else
852 n_defs++;
854 worklist.pop ();
855 gcc_assert (worklist.is_empty ());
857 /* Now process the uses. */
858 live_phis = BITMAP_ALLOC (NULL);
859 EXECUTE_IF_SET_IN_BITMAP (uses, 0, i, bi)
861 worklist.safe_push (i);
864 while (!worklist.is_empty ())
866 b = worklist.pop ();
867 if (b == ENTRY_BLOCK)
868 continue;
870 /* If there is a phi node in USE_BB, it is made live. Otherwise,
871 find the def that dominates the immediate dominator of USE_BB
872 (the kill in USE_BB does not dominate the use). */
873 if (bitmap_bit_p (phis, b))
874 p = b;
875 else
877 use_bb = get_immediate_dominator (CDI_DOMINATORS,
878 BASIC_BLOCK_FOR_FN (cfun, b));
879 p = find_dfsnum_interval (defs, n_defs,
880 bb_dom_dfs_in (CDI_DOMINATORS, use_bb));
881 if (!bitmap_bit_p (phis, p))
882 continue;
885 /* If the phi node is already live, there is nothing to do. */
886 if (!bitmap_set_bit (live_phis, p))
887 continue;
889 /* Add the new uses to the worklist. */
890 def_bb = BASIC_BLOCK_FOR_FN (cfun, p);
891 FOR_EACH_EDGE (e, ei, def_bb->preds)
893 u = e->src->index;
894 if (bitmap_bit_p (uses, u))
895 continue;
897 /* In case there is a kill directly in the use block, do not record
898 the use (this is also necessary for correctness, as we assume that
899 uses dominated by a def directly in their block have been filtered
900 out before). */
901 if (bitmap_bit_p (kills, u))
902 continue;
904 bitmap_set_bit (uses, u);
905 worklist.safe_push (u);
909 bitmap_copy (phis, live_phis);
910 BITMAP_FREE (live_phis);
911 free (defs);
914 /* Return the set of blocks where variable VAR is defined and the blocks
915 where VAR is live on entry (livein). Return NULL, if no entry is
916 found in DEF_BLOCKS. */
918 static inline def_blocks *
919 find_def_blocks_for (tree var)
921 def_blocks *p = &get_common_info (var)->def_blocks;
922 if (!p->def_blocks)
923 return NULL;
924 return p;
928 /* Marks phi node PHI in basic block BB for rewrite. */
930 static void
931 mark_phi_for_rewrite (basic_block bb, gphi *phi)
933 vec<gphi *> phis;
934 unsigned n, idx = bb->index;
936 if (rewrite_uses_p (phi))
937 return;
939 set_rewrite_uses (phi, true);
941 if (!blocks_with_phis_to_rewrite)
942 return;
944 if (bitmap_set_bit (blocks_with_phis_to_rewrite, idx))
946 n = (unsigned) last_basic_block_for_fn (cfun) + 1;
947 if (phis_to_rewrite.length () < n)
948 phis_to_rewrite.safe_grow_cleared (n, true);
950 phis = phis_to_rewrite[idx];
951 gcc_assert (!phis.exists ());
952 phis.create (10);
954 else
955 phis = phis_to_rewrite[idx];
957 phis.safe_push (phi);
958 phis_to_rewrite[idx] = phis;
961 /* Insert PHI nodes for variable VAR using the iterated dominance
962 frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
963 function assumes that the caller is incrementally updating the
964 existing SSA form, in which case VAR may be an SSA name instead of
965 a symbol.
967 PHI_INSERTION_POINTS is updated to reflect nodes that already had a
968 PHI node for VAR. On exit, only the nodes that received a PHI node
969 for VAR will be present in PHI_INSERTION_POINTS. */
971 static void
972 insert_phi_nodes_for (tree var, bitmap phi_insertion_points, bool update_p)
974 unsigned bb_index;
975 edge e;
976 gphi *phi;
977 basic_block bb;
978 bitmap_iterator bi;
979 def_blocks *def_map = find_def_blocks_for (var);
981 /* Remove the blocks where we already have PHI nodes for VAR. */
982 bitmap_and_compl_into (phi_insertion_points, def_map->phi_blocks);
984 /* Remove obviously useless phi nodes. */
985 prune_unused_phi_nodes (phi_insertion_points, def_map->def_blocks,
986 def_map->livein_blocks);
988 /* And insert the PHI nodes. */
989 EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points, 0, bb_index, bi)
991 bb = BASIC_BLOCK_FOR_FN (cfun, bb_index);
992 if (update_p)
993 mark_block_for_update (bb);
995 if (dump_file && (dump_flags & TDF_DETAILS))
997 fprintf (dump_file, "creating PHI node in block #%d for ", bb_index);
998 print_generic_expr (dump_file, var, TDF_SLIM);
999 fprintf (dump_file, "\n");
1001 phi = NULL;
1003 if (TREE_CODE (var) == SSA_NAME)
1005 /* If we are rewriting SSA names, create the LHS of the PHI
1006 node by duplicating VAR. This is useful in the case of
1007 pointers, to also duplicate pointer attributes (alias
1008 information, in particular). */
1009 edge_iterator ei;
1010 tree new_lhs;
1012 gcc_checking_assert (update_p);
1013 new_lhs = duplicate_ssa_name (var, NULL);
1014 phi = create_phi_node (new_lhs, bb);
1015 add_new_name_mapping (new_lhs, var);
1017 /* Add VAR to every argument slot of PHI. We need VAR in
1018 every argument so that rewrite_update_phi_arguments knows
1019 which name is this PHI node replacing. If VAR is a
1020 symbol marked for renaming, this is not necessary, the
1021 renamer will use the symbol on the LHS to get its
1022 reaching definition. */
1023 FOR_EACH_EDGE (e, ei, bb->preds)
1024 add_phi_arg (phi, var, e, UNKNOWN_LOCATION);
1026 else
1028 tree tracked_var;
1030 gcc_checking_assert (DECL_P (var));
1031 phi = create_phi_node (var, bb);
1033 tracked_var = target_for_debug_bind (var);
1034 if (tracked_var)
1036 gimple *note = gimple_build_debug_bind (tracked_var,
1037 PHI_RESULT (phi),
1038 phi);
1039 gimple_stmt_iterator si = gsi_after_labels (bb);
1040 gsi_insert_before (&si, note, GSI_SAME_STMT);
1044 /* Mark this PHI node as interesting for update_ssa. */
1045 set_register_defs (phi, true);
1046 mark_phi_for_rewrite (bb, phi);
1050 /* Sort var_infos after DECL_UID of their var. */
1052 static int
1053 insert_phi_nodes_compare_var_infos (const void *a, const void *b)
1055 const var_info *defa = *(var_info * const *)a;
1056 const var_info *defb = *(var_info * const *)b;
1057 if (DECL_UID (defa->var) < DECL_UID (defb->var))
1058 return -1;
1059 else
1060 return 1;
1063 /* Insert PHI nodes at the dominance frontier of blocks with variable
1064 definitions. DFS contains the dominance frontier information for
1065 the flowgraph. */
1067 static void
1068 insert_phi_nodes (bitmap_head *dfs)
1070 hash_table<var_info_hasher>::iterator hi;
1071 unsigned i;
1072 var_info *info;
1074 /* When the gimplifier introduces SSA names it cannot easily avoid
1075 situations where abnormal edges added by CFG construction break
1076 the use-def dominance requirement. For this case rewrite SSA
1077 names with broken use-def dominance out-of-SSA and register them
1078 for PHI insertion. We only need to do this if abnormal edges
1079 can appear in the function. */
1080 tree name;
1081 if (cfun->calls_setjmp
1082 || cfun->has_nonlocal_label)
1083 FOR_EACH_SSA_NAME (i, name, cfun)
1085 gimple *def_stmt = SSA_NAME_DEF_STMT (name);
1086 if (SSA_NAME_IS_DEFAULT_DEF (name))
1087 continue;
1089 basic_block def_bb = gimple_bb (def_stmt);
1090 imm_use_iterator it;
1091 gimple *use_stmt;
1092 bool need_phis = false;
1093 FOR_EACH_IMM_USE_STMT (use_stmt, it, name)
1095 basic_block use_bb = gimple_bb (use_stmt);
1096 if (use_bb != def_bb
1097 && ! dominated_by_p (CDI_DOMINATORS, use_bb, def_bb))
1098 need_phis = true;
1100 if (need_phis)
1102 tree var = create_tmp_reg (TREE_TYPE (name));
1103 use_operand_p use_p;
1104 FOR_EACH_IMM_USE_STMT (use_stmt, it, name)
1106 basic_block use_bb = gimple_bb (use_stmt);
1107 FOR_EACH_IMM_USE_ON_STMT (use_p, it)
1108 SET_USE (use_p, var);
1109 update_stmt (use_stmt);
1110 set_livein_block (var, use_bb);
1111 set_rewrite_uses (use_stmt, true);
1112 bitmap_set_bit (interesting_blocks, use_bb->index);
1114 def_operand_p def_p;
1115 ssa_op_iter dit;
1116 FOR_EACH_SSA_DEF_OPERAND (def_p, def_stmt, dit, SSA_OP_DEF)
1117 if (DEF_FROM_PTR (def_p) == name)
1118 SET_DEF (def_p, var);
1119 update_stmt (def_stmt);
1120 set_def_block (var, def_bb, false);
1121 set_register_defs (def_stmt, true);
1122 bitmap_set_bit (interesting_blocks, def_bb->index);
1123 release_ssa_name (name);
1127 auto_vec<var_info *> vars (var_infos->elements ());
1128 FOR_EACH_HASH_TABLE_ELEMENT (*var_infos, info, var_info_p, hi)
1129 if (info->info.need_phi_state != NEED_PHI_STATE_NO)
1130 vars.quick_push (info);
1132 /* Do two stages to avoid code generation differences for UID
1133 differences but no UID ordering differences. */
1134 vars.qsort (insert_phi_nodes_compare_var_infos);
1136 FOR_EACH_VEC_ELT (vars, i, info)
1138 bitmap idf = compute_idf (info->info.def_blocks.def_blocks, dfs);
1139 insert_phi_nodes_for (info->var, idf, false);
1140 BITMAP_FREE (idf);
1145 /* Push SYM's current reaching definition into BLOCK_DEFS_STACK and
1146 register DEF (an SSA_NAME) to be a new definition for SYM. */
1148 static void
1149 register_new_def (tree def, tree sym)
1151 common_info *info = get_common_info (sym);
1152 tree currdef;
1154 /* If this variable is set in a single basic block and all uses are
1155 dominated by the set(s) in that single basic block, then there is
1156 no reason to record anything for this variable in the block local
1157 definition stacks. Doing so just wastes time and memory.
1159 This is the same test to prune the set of variables which may
1160 need PHI nodes. So we just use that information since it's already
1161 computed and available for us to use. */
1162 if (info->need_phi_state == NEED_PHI_STATE_NO)
1164 info->current_def = def;
1165 return;
1168 currdef = info->current_def;
1170 /* If SYM is not a GIMPLE register, then CURRDEF may be a name whose
1171 SSA_NAME_VAR is not necessarily SYM. In this case, also push SYM
1172 in the stack so that we know which symbol is being defined by
1173 this SSA name when we unwind the stack. */
1174 if (currdef && !is_gimple_reg (sym))
1175 block_defs_stack.safe_push (sym);
1177 /* Push the current reaching definition into BLOCK_DEFS_STACK. This
1178 stack is later used by the dominator tree callbacks to restore
1179 the reaching definitions for all the variables defined in the
1180 block after a recursive visit to all its immediately dominated
1181 blocks. If there is no current reaching definition, then just
1182 record the underlying _DECL node. */
1183 block_defs_stack.safe_push (currdef ? currdef : sym);
1185 /* Set the current reaching definition for SYM to be DEF. */
1186 info->current_def = def;
1190 /* Perform a depth-first traversal of the dominator tree looking for
1191 variables to rename. BB is the block where to start searching.
1192 Renaming is a five step process:
1194 1- Every definition made by PHI nodes at the start of the blocks is
1195 registered as the current definition for the corresponding variable.
1197 2- Every statement in BB is rewritten. USE and VUSE operands are
1198 rewritten with their corresponding reaching definition. DEF and
1199 VDEF targets are registered as new definitions.
1201 3- All the PHI nodes in successor blocks of BB are visited. The
1202 argument corresponding to BB is replaced with its current reaching
1203 definition.
1205 4- Recursively rewrite every dominator child block of BB.
1207 5- Restore (in reverse order) the current reaching definition for every
1208 new definition introduced in this block. This is done so that when
1209 we return from the recursive call, all the current reaching
1210 definitions are restored to the names that were valid in the
1211 dominator parent of BB. */
1213 /* Return the current definition for variable VAR. If none is found,
1214 create a new SSA name to act as the zeroth definition for VAR. */
1216 static tree
1217 get_reaching_def (tree var)
1219 common_info *info = get_common_info (var);
1220 tree currdef;
1222 /* Lookup the current reaching definition for VAR. */
1223 currdef = info->current_def;
1225 /* If there is no reaching definition for VAR, create and register a
1226 default definition for it (if needed). */
1227 if (currdef == NULL_TREE)
1229 tree sym = DECL_P (var) ? var : SSA_NAME_VAR (var);
1230 if (! sym)
1231 sym = create_tmp_reg (TREE_TYPE (var));
1232 currdef = get_or_create_ssa_default_def (cfun, sym);
1235 /* Return the current reaching definition for VAR, or the default
1236 definition, if we had to create one. */
1237 return currdef;
1241 /* Helper function for rewrite_stmt. Rewrite uses in a debug stmt. */
1243 static void
1244 rewrite_debug_stmt_uses (gimple *stmt)
1246 use_operand_p use_p;
1247 ssa_op_iter iter;
1248 bool update = false;
1250 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
1252 tree var = USE_FROM_PTR (use_p), def;
1253 common_info *info = get_common_info (var);
1254 gcc_checking_assert (DECL_P (var));
1255 def = info->current_def;
1256 if (!def)
1258 if (TREE_CODE (var) == PARM_DECL
1259 && single_succ_p (ENTRY_BLOCK_PTR_FOR_FN (cfun)))
1261 gimple_stmt_iterator gsi
1263 gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
1264 int lim;
1265 /* Search a few source bind stmts at the start of first bb to
1266 see if a DEBUG_EXPR_DECL can't be reused. */
1267 for (lim = 32;
1268 !gsi_end_p (gsi) && lim > 0;
1269 gsi_next (&gsi), lim--)
1271 gimple *gstmt = gsi_stmt (gsi);
1272 if (!gimple_debug_source_bind_p (gstmt))
1273 break;
1274 if (gimple_debug_source_bind_get_value (gstmt) == var)
1276 def = gimple_debug_source_bind_get_var (gstmt);
1277 if (TREE_CODE (def) == DEBUG_EXPR_DECL)
1278 break;
1279 else
1280 def = NULL_TREE;
1283 /* If not, add a new source bind stmt. */
1284 if (def == NULL_TREE)
1286 gimple *def_temp;
1287 def = make_node (DEBUG_EXPR_DECL);
1288 def_temp = gimple_build_debug_source_bind (def, var, NULL);
1289 DECL_ARTIFICIAL (def) = 1;
1290 TREE_TYPE (def) = TREE_TYPE (var);
1291 SET_DECL_MODE (def, DECL_MODE (var));
1292 gsi =
1293 gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
1294 gsi_insert_before (&gsi, def_temp, GSI_SAME_STMT);
1296 update = true;
1299 else
1301 /* Check if info->current_def can be trusted. */
1302 basic_block bb = gimple_bb (stmt);
1303 basic_block def_bb
1304 = SSA_NAME_IS_DEFAULT_DEF (def)
1305 ? NULL : gimple_bb (SSA_NAME_DEF_STMT (def));
1307 /* If definition is in current bb, it is fine. */
1308 if (bb == def_bb)
1310 /* If definition bb doesn't dominate the current bb,
1311 it can't be used. */
1312 else if (def_bb && !dominated_by_p (CDI_DOMINATORS, bb, def_bb))
1313 def = NULL;
1314 /* If there is just one definition and dominates the current
1315 bb, it is fine. */
1316 else if (info->need_phi_state == NEED_PHI_STATE_NO)
1318 else
1320 def_blocks *db_p = get_def_blocks_for (info);
1322 /* If there are some non-debug uses in the current bb,
1323 it is fine. */
1324 if (bitmap_bit_p (db_p->livein_blocks, bb->index))
1326 /* Otherwise give up for now. */
1327 else
1328 def = NULL;
1331 if (def == NULL)
1333 gimple_debug_bind_reset_value (stmt);
1334 update_stmt (stmt);
1335 return;
1337 SET_USE (use_p, def);
1339 if (update)
1340 update_stmt (stmt);
1343 /* SSA Rewriting Step 2. Rewrite every variable used in each statement in
1344 the block with its immediate reaching definitions. Update the current
1345 definition of a variable when a new real or virtual definition is found. */
1347 static void
1348 rewrite_stmt (gimple_stmt_iterator *si)
1350 use_operand_p use_p;
1351 def_operand_p def_p;
1352 ssa_op_iter iter;
1353 gimple *stmt = gsi_stmt (*si);
1355 /* If mark_def_sites decided that we don't need to rewrite this
1356 statement, ignore it. */
1357 gcc_assert (blocks_to_update == NULL);
1358 if (!rewrite_uses_p (stmt) && !register_defs_p (stmt))
1359 return;
1361 if (dump_file && (dump_flags & TDF_DETAILS))
1363 fprintf (dump_file, "Renaming statement ");
1364 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
1365 fprintf (dump_file, "\n");
1368 /* Step 1. Rewrite USES in the statement. */
1369 if (rewrite_uses_p (stmt))
1371 if (is_gimple_debug (stmt))
1372 rewrite_debug_stmt_uses (stmt);
1373 else
1374 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
1376 tree var = USE_FROM_PTR (use_p);
1377 if (TREE_CODE (var) == SSA_NAME)
1378 continue;
1379 gcc_checking_assert (DECL_P (var));
1380 SET_USE (use_p, get_reaching_def (var));
1384 /* Step 2. Register the statement's DEF operands. */
1385 if (register_defs_p (stmt))
1386 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
1388 tree var = DEF_FROM_PTR (def_p);
1389 tree name;
1390 tree tracked_var;
1392 if (TREE_CODE (var) == SSA_NAME)
1393 continue;
1394 gcc_checking_assert (DECL_P (var));
1396 if (gimple_clobber_p (stmt)
1397 && is_gimple_reg (var))
1399 /* If we rewrite a DECL into SSA form then drop its
1400 clobber stmts and replace uses with a new default def. */
1401 gcc_checking_assert (VAR_P (var) && !gimple_vdef (stmt));
1402 gsi_replace (si, gimple_build_nop (), true);
1403 register_new_def (get_or_create_ssa_default_def (cfun, var), var);
1404 break;
1407 name = make_ssa_name (var, stmt);
1408 SET_DEF (def_p, name);
1409 register_new_def (DEF_FROM_PTR (def_p), var);
1411 /* Do not insert debug stmts if the stmt ends the BB. */
1412 if (stmt_ends_bb_p (stmt))
1413 continue;
1415 tracked_var = target_for_debug_bind (var);
1416 if (tracked_var)
1418 gimple *note = gimple_build_debug_bind (tracked_var, name, stmt);
1419 gsi_insert_after (si, note, GSI_SAME_STMT);
1425 /* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for
1426 PHI nodes. For every PHI node found, add a new argument containing the
1427 current reaching definition for the variable and the edge through which
1428 that definition is reaching the PHI node. */
1430 static void
1431 rewrite_add_phi_arguments (basic_block bb)
1433 edge e;
1434 edge_iterator ei;
1436 FOR_EACH_EDGE (e, ei, bb->succs)
1438 gphi *phi;
1439 gphi_iterator gsi;
1441 for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi);
1442 gsi_next (&gsi))
1444 tree currdef, res;
1445 location_t loc;
1447 phi = gsi.phi ();
1448 res = gimple_phi_result (phi);
1449 currdef = get_reaching_def (SSA_NAME_VAR (res));
1450 /* Virtual operand PHI args do not need a location. */
1451 if (virtual_operand_p (res))
1452 loc = UNKNOWN_LOCATION;
1453 else
1454 loc = gimple_location (SSA_NAME_DEF_STMT (currdef));
1455 add_phi_arg (phi, currdef, e, loc);
1460 class rewrite_dom_walker : public dom_walker
1462 public:
1463 rewrite_dom_walker (cdi_direction direction)
1464 : dom_walker (direction, ALL_BLOCKS, NULL) {}
1466 virtual edge before_dom_children (basic_block);
1467 virtual void after_dom_children (basic_block);
1470 /* SSA Rewriting Step 1. Initialization, create a block local stack
1471 of reaching definitions for new SSA names produced in this block
1472 (BLOCK_DEFS). Register new definitions for every PHI node in the
1473 block. */
1475 edge
1476 rewrite_dom_walker::before_dom_children (basic_block bb)
1478 if (dump_file && (dump_flags & TDF_DETAILS))
1479 fprintf (dump_file, "\n\nRenaming block #%d\n\n", bb->index);
1481 /* Mark the unwind point for this block. */
1482 block_defs_stack.safe_push (NULL_TREE);
1484 /* Step 1. Register new definitions for every PHI node in the block.
1485 Conceptually, all the PHI nodes are executed in parallel and each PHI
1486 node introduces a new version for the associated variable. */
1487 for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
1488 gsi_next (&gsi))
1490 tree result = gimple_phi_result (gsi_stmt (gsi));
1491 register_new_def (result, SSA_NAME_VAR (result));
1494 /* Step 2. Rewrite every variable used in each statement in the block
1495 with its immediate reaching definitions. Update the current definition
1496 of a variable when a new real or virtual definition is found. */
1497 if (bitmap_bit_p (interesting_blocks, bb->index))
1498 for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi);
1499 gsi_next (&gsi))
1500 rewrite_stmt (&gsi);
1502 /* Step 3. Visit all the successor blocks of BB looking for PHI nodes.
1503 For every PHI node found, add a new argument containing the current
1504 reaching definition for the variable and the edge through which that
1505 definition is reaching the PHI node. */
1506 rewrite_add_phi_arguments (bb);
1508 return NULL;
1513 /* Called after visiting all the statements in basic block BB and all
1514 of its dominator children. Restore CURRDEFS to its original value. */
1516 void
1517 rewrite_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED)
1519 /* Restore CURRDEFS to its original state. */
1520 while (block_defs_stack.length () > 0)
1522 tree tmp = block_defs_stack.pop ();
1523 tree saved_def, var;
1525 if (tmp == NULL_TREE)
1526 break;
1528 if (TREE_CODE (tmp) == SSA_NAME)
1530 /* If we recorded an SSA_NAME, then make the SSA_NAME the
1531 current definition of its underlying variable. Note that
1532 if the SSA_NAME is not for a GIMPLE register, the symbol
1533 being defined is stored in the next slot in the stack.
1534 This mechanism is needed because an SSA name for a
1535 non-register symbol may be the definition for more than
1536 one symbol (e.g., SFTs, aliased variables, etc). */
1537 saved_def = tmp;
1538 var = SSA_NAME_VAR (saved_def);
1539 if (!is_gimple_reg (var))
1540 var = block_defs_stack.pop ();
1542 else
1544 /* If we recorded anything else, it must have been a _DECL
1545 node and its current reaching definition must have been
1546 NULL. */
1547 saved_def = NULL;
1548 var = tmp;
1551 get_common_info (var)->current_def = saved_def;
1556 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1558 DEBUG_FUNCTION void
1559 debug_decl_set (bitmap set)
1561 dump_decl_set (stderr, set);
1562 fprintf (stderr, "\n");
1566 /* Dump the renaming stack (block_defs_stack) to FILE. Traverse the
1567 stack up to a maximum of N levels. If N is -1, the whole stack is
1568 dumped. New levels are created when the dominator tree traversal
1569 used for renaming enters a new sub-tree. */
1571 void
1572 dump_defs_stack (FILE *file, int n)
1574 int i, j;
1576 fprintf (file, "\n\nRenaming stack");
1577 if (n > 0)
1578 fprintf (file, " (up to %d levels)", n);
1579 fprintf (file, "\n\n");
1581 i = 1;
1582 fprintf (file, "Level %d (current level)\n", i);
1583 for (j = (int) block_defs_stack.length () - 1; j >= 0; j--)
1585 tree name, var;
1587 name = block_defs_stack[j];
1588 if (name == NULL_TREE)
1590 i++;
1591 if (n > 0 && i > n)
1592 break;
1593 fprintf (file, "\nLevel %d\n", i);
1594 continue;
1597 if (DECL_P (name))
1599 var = name;
1600 name = NULL_TREE;
1602 else
1604 var = SSA_NAME_VAR (name);
1605 if (!is_gimple_reg (var))
1607 j--;
1608 var = block_defs_stack[j];
1612 fprintf (file, " Previous CURRDEF (");
1613 print_generic_expr (file, var);
1614 fprintf (file, ") = ");
1615 if (name)
1616 print_generic_expr (file, name);
1617 else
1618 fprintf (file, "<NIL>");
1619 fprintf (file, "\n");
1624 /* Dump the renaming stack (block_defs_stack) to stderr. Traverse the
1625 stack up to a maximum of N levels. If N is -1, the whole stack is
1626 dumped. New levels are created when the dominator tree traversal
1627 used for renaming enters a new sub-tree. */
1629 DEBUG_FUNCTION void
1630 debug_defs_stack (int n)
1632 dump_defs_stack (stderr, n);
1636 /* Dump the current reaching definition of every symbol to FILE. */
1638 void
1639 dump_currdefs (FILE *file)
1641 if (symbols_to_rename.is_empty ())
1642 return;
1644 fprintf (file, "\n\nCurrent reaching definitions\n\n");
1645 for (tree var : symbols_to_rename)
1647 common_info *info = get_common_info (var);
1648 fprintf (file, "CURRDEF (");
1649 print_generic_expr (file, var);
1650 fprintf (file, ") = ");
1651 if (info->current_def)
1652 print_generic_expr (file, info->current_def);
1653 else
1654 fprintf (file, "<NIL>");
1655 fprintf (file, "\n");
1660 /* Dump the current reaching definition of every symbol to stderr. */
1662 DEBUG_FUNCTION void
1663 debug_currdefs (void)
1665 dump_currdefs (stderr);
1669 /* Dump SSA information to FILE. */
1671 void
1672 dump_tree_ssa (FILE *file)
1674 const char *funcname
1675 = lang_hooks.decl_printable_name (current_function_decl, 2);
1677 fprintf (file, "SSA renaming information for %s\n\n", funcname);
1679 dump_var_infos (file);
1680 dump_defs_stack (file, -1);
1681 dump_currdefs (file);
1682 dump_tree_ssa_stats (file);
1686 /* Dump SSA information to stderr. */
1688 DEBUG_FUNCTION void
1689 debug_tree_ssa (void)
1691 dump_tree_ssa (stderr);
1695 /* Dump statistics for the hash table HTAB. */
1697 static void
1698 htab_statistics (FILE *file, const hash_table<var_info_hasher> &htab)
1700 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1701 (long) htab.size (),
1702 (long) htab.elements (),
1703 htab.collisions ());
1707 /* Dump SSA statistics on FILE. */
1709 void
1710 dump_tree_ssa_stats (FILE *file)
1712 if (var_infos)
1714 fprintf (file, "\nHash table statistics:\n");
1715 fprintf (file, " var_infos: ");
1716 htab_statistics (file, *var_infos);
1717 fprintf (file, "\n");
1722 /* Dump SSA statistics on stderr. */
1724 DEBUG_FUNCTION void
1725 debug_tree_ssa_stats (void)
1727 dump_tree_ssa_stats (stderr);
1731 /* Callback for htab_traverse to dump the VAR_INFOS hash table. */
1734 debug_var_infos_r (var_info **slot, FILE *file)
1736 var_info *info = *slot;
1738 fprintf (file, "VAR: ");
1739 print_generic_expr (file, info->var, dump_flags);
1740 bitmap_print (file, info->info.def_blocks.def_blocks,
1741 ", DEF_BLOCKS: { ", "}");
1742 bitmap_print (file, info->info.def_blocks.livein_blocks,
1743 ", LIVEIN_BLOCKS: { ", "}");
1744 bitmap_print (file, info->info.def_blocks.phi_blocks,
1745 ", PHI_BLOCKS: { ", "}\n");
1747 return 1;
1751 /* Dump the VAR_INFOS hash table on FILE. */
1753 void
1754 dump_var_infos (FILE *file)
1756 fprintf (file, "\n\nDefinition and live-in blocks:\n\n");
1757 if (var_infos)
1758 var_infos->traverse <FILE *, debug_var_infos_r> (file);
1762 /* Dump the VAR_INFOS hash table on stderr. */
1764 DEBUG_FUNCTION void
1765 debug_var_infos (void)
1767 dump_var_infos (stderr);
1771 /* Register NEW_NAME to be the new reaching definition for OLD_NAME. */
1773 static inline void
1774 register_new_update_single (tree new_name, tree old_name)
1776 common_info *info = get_common_info (old_name);
1777 tree currdef = info->current_def;
1779 /* Push the current reaching definition into BLOCK_DEFS_STACK.
1780 This stack is later used by the dominator tree callbacks to
1781 restore the reaching definitions for all the variables
1782 defined in the block after a recursive visit to all its
1783 immediately dominated blocks. */
1784 block_defs_stack.reserve (2);
1785 block_defs_stack.quick_push (currdef);
1786 block_defs_stack.quick_push (old_name);
1788 /* Set the current reaching definition for OLD_NAME to be
1789 NEW_NAME. */
1790 info->current_def = new_name;
1794 /* Register NEW_NAME to be the new reaching definition for all the
1795 names in OLD_NAMES. Used by the incremental SSA update routines to
1796 replace old SSA names with new ones. */
1798 static inline void
1799 register_new_update_set (tree new_name, bitmap old_names)
1801 bitmap_iterator bi;
1802 unsigned i;
1804 EXECUTE_IF_SET_IN_BITMAP (old_names, 0, i, bi)
1805 register_new_update_single (new_name, ssa_name (i));
1810 /* If the operand pointed to by USE_P is a name in OLD_SSA_NAMES or
1811 it is a symbol marked for renaming, replace it with USE_P's current
1812 reaching definition. */
1814 static inline void
1815 maybe_replace_use (use_operand_p use_p)
1817 tree rdef = NULL_TREE;
1818 tree use = USE_FROM_PTR (use_p);
1819 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
1821 if (marked_for_renaming (sym))
1822 rdef = get_reaching_def (sym);
1823 else if (is_old_name (use))
1824 rdef = get_reaching_def (use);
1826 if (rdef && rdef != use)
1827 SET_USE (use_p, rdef);
1831 /* Same as maybe_replace_use, but without introducing default stmts,
1832 returning false to indicate a need to do so. */
1834 static inline bool
1835 maybe_replace_use_in_debug_stmt (use_operand_p use_p)
1837 tree rdef = NULL_TREE;
1838 tree use = USE_FROM_PTR (use_p);
1839 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
1841 if (marked_for_renaming (sym))
1842 rdef = get_var_info (sym)->info.current_def;
1843 else if (is_old_name (use))
1845 rdef = get_ssa_name_ann (use)->info.current_def;
1846 /* We can't assume that, if there's no current definition, the
1847 default one should be used. It could be the case that we've
1848 rearranged blocks so that the earlier definition no longer
1849 dominates the use. */
1850 if (!rdef && SSA_NAME_IS_DEFAULT_DEF (use))
1851 rdef = use;
1853 else
1854 rdef = use;
1856 if (rdef && rdef != use)
1857 SET_USE (use_p, rdef);
1859 return rdef != NULL_TREE;
1863 /* If DEF has x_5 = ASAN_POISON () as its current def, add
1864 ASAN_POISON_USE (x_5) stmt before GSI to denote the stmt writes into
1865 a poisoned (out of scope) variable. */
1867 static void
1868 maybe_add_asan_poison_write (tree def, gimple_stmt_iterator *gsi)
1870 tree cdef = get_current_def (def);
1871 if (cdef != NULL
1872 && TREE_CODE (cdef) == SSA_NAME
1873 && gimple_call_internal_p (SSA_NAME_DEF_STMT (cdef), IFN_ASAN_POISON))
1875 gcall *call
1876 = gimple_build_call_internal (IFN_ASAN_POISON_USE, 1, cdef);
1877 gimple_set_location (call, gimple_location (gsi_stmt (*gsi)));
1878 gsi_insert_before (gsi, call, GSI_SAME_STMT);
1883 /* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
1884 or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
1885 register it as the current definition for the names replaced by
1886 DEF_P. Returns whether the statement should be removed. */
1888 static inline bool
1889 maybe_register_def (def_operand_p def_p, gimple *stmt,
1890 gimple_stmt_iterator gsi)
1892 tree def = DEF_FROM_PTR (def_p);
1893 tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
1894 bool to_delete = false;
1896 /* If DEF is a naked symbol that needs renaming, create a new
1897 name for it. */
1898 if (marked_for_renaming (sym))
1900 if (DECL_P (def))
1902 if (gimple_clobber_p (stmt) && is_gimple_reg (sym))
1904 gcc_checking_assert (VAR_P (sym));
1905 /* Replace clobber stmts with a default def. This new use of a
1906 default definition may make it look like SSA_NAMEs have
1907 conflicting lifetimes, so we need special code to let them
1908 coalesce properly. */
1909 to_delete = true;
1910 def = get_or_create_ssa_default_def (cfun, sym);
1912 else
1914 if (asan_sanitize_use_after_scope ())
1915 maybe_add_asan_poison_write (def, &gsi);
1916 def = make_ssa_name (def, stmt);
1918 SET_DEF (def_p, def);
1920 tree tracked_var = target_for_debug_bind (sym);
1921 if (tracked_var)
1923 gimple *note = gimple_build_debug_bind (tracked_var, def, stmt);
1924 /* If stmt ends the bb, insert the debug stmt on the single
1925 non-EH edge from the stmt. */
1926 if (gsi_one_before_end_p (gsi) && stmt_ends_bb_p (stmt))
1928 basic_block bb = gsi_bb (gsi);
1929 edge_iterator ei;
1930 edge e, ef = NULL;
1931 FOR_EACH_EDGE (e, ei, bb->succs)
1932 if (!(e->flags & EDGE_EH))
1934 gcc_checking_assert (!ef);
1935 ef = e;
1937 /* If there are other predecessors to ef->dest, then
1938 there must be PHI nodes for the modified
1939 variable, and therefore there will be debug bind
1940 stmts after the PHI nodes. The debug bind notes
1941 we'd insert would force the creation of a new
1942 block (diverging codegen) and be redundant with
1943 the post-PHI bind stmts, so don't add them.
1945 As for the exit edge, there wouldn't be redundant
1946 bind stmts, but there wouldn't be a PC to bind
1947 them to either, so avoid diverging the CFG. */
1948 if (ef && single_pred_p (ef->dest)
1949 && ef->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
1951 /* If there were PHI nodes in the node, we'd
1952 have to make sure the value we're binding
1953 doesn't need rewriting. But there shouldn't
1954 be PHI nodes in a single-predecessor block,
1955 so we just add the note. */
1956 gsi_insert_on_edge_immediate (ef, note);
1959 else
1960 gsi_insert_after (&gsi, note, GSI_SAME_STMT);
1964 register_new_update_single (def, sym);
1966 else
1968 /* If DEF is a new name, register it as a new definition
1969 for all the names replaced by DEF. */
1970 if (is_new_name (def))
1971 register_new_update_set (def, names_replaced_by (def));
1973 /* If DEF is an old name, register DEF as a new
1974 definition for itself. */
1975 if (is_old_name (def))
1976 register_new_update_single (def, def);
1979 return to_delete;
1983 /* Update every variable used in the statement pointed-to by SI. The
1984 statement is assumed to be in SSA form already. Names in
1985 OLD_SSA_NAMES used by SI will be updated to their current reaching
1986 definition. Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI
1987 will be registered as a new definition for their corresponding name
1988 in OLD_SSA_NAMES. Returns whether STMT should be removed. */
1990 static bool
1991 rewrite_update_stmt (gimple *stmt, gimple_stmt_iterator gsi)
1993 use_operand_p use_p;
1994 def_operand_p def_p;
1995 ssa_op_iter iter;
1997 /* Only update marked statements. */
1998 if (!rewrite_uses_p (stmt) && !register_defs_p (stmt))
1999 return false;
2001 if (dump_file && (dump_flags & TDF_DETAILS))
2003 fprintf (dump_file, "Updating SSA information for statement ");
2004 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
2007 /* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying
2008 symbol is marked for renaming. */
2009 if (rewrite_uses_p (stmt))
2011 if (is_gimple_debug (stmt))
2013 bool failed = false;
2015 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
2016 if (!maybe_replace_use_in_debug_stmt (use_p))
2018 failed = true;
2019 break;
2022 if (failed)
2024 /* DOM sometimes threads jumps in such a way that a
2025 debug stmt ends up referencing a SSA variable that no
2026 longer dominates the debug stmt, but such that all
2027 incoming definitions refer to the same definition in
2028 an earlier dominator. We could try to recover that
2029 definition somehow, but this will have to do for now.
2031 Introducing a default definition, which is what
2032 maybe_replace_use() would do in such cases, may
2033 modify code generation, for the otherwise-unused
2034 default definition would never go away, modifying SSA
2035 version numbers all over. */
2036 gimple_debug_bind_reset_value (stmt);
2037 update_stmt (stmt);
2040 else
2042 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
2043 maybe_replace_use (use_p);
2047 /* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES.
2048 Also register definitions for names whose underlying symbol is
2049 marked for renaming. */
2050 bool to_delete = false;
2051 if (register_defs_p (stmt))
2052 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
2053 to_delete |= maybe_register_def (def_p, stmt, gsi);
2055 return to_delete;
2059 /* Visit all the successor blocks of BB looking for PHI nodes. For
2060 every PHI node found, check if any of its arguments is in
2061 OLD_SSA_NAMES. If so, and if the argument has a current reaching
2062 definition, replace it. */
2064 static void
2065 rewrite_update_phi_arguments (basic_block bb)
2067 edge e;
2068 edge_iterator ei;
2070 FOR_EACH_EDGE (e, ei, bb->succs)
2072 vec<gphi *> phis;
2074 if (!bitmap_bit_p (blocks_with_phis_to_rewrite, e->dest->index))
2075 continue;
2077 phis = phis_to_rewrite[e->dest->index];
2078 for (gphi *phi : phis)
2080 tree arg, lhs_sym, reaching_def = NULL;
2081 use_operand_p arg_p;
2083 gcc_checking_assert (rewrite_uses_p (phi));
2085 arg_p = PHI_ARG_DEF_PTR_FROM_EDGE (phi, e);
2086 arg = USE_FROM_PTR (arg_p);
2088 if (arg && !DECL_P (arg) && TREE_CODE (arg) != SSA_NAME)
2089 continue;
2091 lhs_sym = SSA_NAME_VAR (gimple_phi_result (phi));
2093 if (arg == NULL_TREE)
2095 /* When updating a PHI node for a recently introduced
2096 symbol we may find NULL arguments. That's why we
2097 take the symbol from the LHS of the PHI node. */
2098 reaching_def = get_reaching_def (lhs_sym);
2101 else
2103 tree sym = DECL_P (arg) ? arg : SSA_NAME_VAR (arg);
2105 if (marked_for_renaming (sym))
2106 reaching_def = get_reaching_def (sym);
2107 else if (is_old_name (arg))
2108 reaching_def = get_reaching_def (arg);
2111 /* Update the argument if there is a reaching def. */
2112 if (reaching_def)
2114 location_t locus;
2115 int arg_i = PHI_ARG_INDEX_FROM_USE (arg_p);
2117 SET_USE (arg_p, reaching_def);
2119 /* Virtual operands do not need a location. */
2120 if (virtual_operand_p (reaching_def))
2121 locus = UNKNOWN_LOCATION;
2122 else
2124 gimple *stmt = SSA_NAME_DEF_STMT (reaching_def);
2125 gphi *other_phi = dyn_cast <gphi *> (stmt);
2127 /* Single element PHI nodes behave like copies, so get the
2128 location from the phi argument. */
2129 if (other_phi
2130 && gimple_phi_num_args (other_phi) == 1)
2131 locus = gimple_phi_arg_location (other_phi, 0);
2132 else
2133 locus = gimple_location (stmt);
2136 gimple_phi_arg_set_location (phi, arg_i, locus);
2140 if (e->flags & EDGE_ABNORMAL)
2141 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p)) = 1;
2146 class rewrite_update_dom_walker : public dom_walker
2148 public:
2149 rewrite_update_dom_walker (cdi_direction direction)
2150 : dom_walker (direction, ALL_BLOCKS, NULL) {}
2152 virtual edge before_dom_children (basic_block);
2153 virtual void after_dom_children (basic_block);
2156 /* Initialization of block data structures for the incremental SSA
2157 update pass. Create a block local stack of reaching definitions
2158 for new SSA names produced in this block (BLOCK_DEFS). Register
2159 new definitions for every PHI node in the block. */
2161 edge
2162 rewrite_update_dom_walker::before_dom_children (basic_block bb)
2164 bool is_abnormal_phi;
2166 if (dump_file && (dump_flags & TDF_DETAILS))
2167 fprintf (dump_file, "Registering new PHI nodes in block #%d\n",
2168 bb->index);
2170 /* Mark the unwind point for this block. */
2171 block_defs_stack.safe_push (NULL_TREE);
2173 if (!bitmap_bit_p (blocks_to_update, bb->index))
2174 return NULL;
2176 /* Mark the LHS if any of the arguments flows through an abnormal
2177 edge. */
2178 is_abnormal_phi = bb_has_abnormal_pred (bb);
2180 /* If any of the PHI nodes is a replacement for a name in
2181 OLD_SSA_NAMES or it's one of the names in NEW_SSA_NAMES, then
2182 register it as a new definition for its corresponding name. Also
2183 register definitions for names whose underlying symbols are
2184 marked for renaming. */
2185 for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
2186 gsi_next (&gsi))
2188 tree lhs, lhs_sym;
2189 gphi *phi = gsi.phi ();
2191 if (!register_defs_p (phi))
2192 continue;
2194 lhs = gimple_phi_result (phi);
2195 lhs_sym = SSA_NAME_VAR (lhs);
2197 if (marked_for_renaming (lhs_sym))
2198 register_new_update_single (lhs, lhs_sym);
2199 else
2202 /* If LHS is a new name, register a new definition for all
2203 the names replaced by LHS. */
2204 if (is_new_name (lhs))
2205 register_new_update_set (lhs, names_replaced_by (lhs));
2207 /* If LHS is an OLD name, register it as a new definition
2208 for itself. */
2209 if (is_old_name (lhs))
2210 register_new_update_single (lhs, lhs);
2213 if (is_abnormal_phi)
2214 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs) = 1;
2217 /* Step 2. Rewrite every variable used in each statement in the block. */
2218 if (bitmap_bit_p (interesting_blocks, bb->index))
2220 gcc_checking_assert (bitmap_bit_p (blocks_to_update, bb->index));
2221 for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
2222 if (rewrite_update_stmt (gsi_stmt (gsi), gsi))
2223 gsi_remove (&gsi, true);
2224 else
2225 gsi_next (&gsi);
2228 /* Step 3. Update PHI nodes. */
2229 rewrite_update_phi_arguments (bb);
2231 return NULL;
2234 /* Called after visiting block BB. Unwind BLOCK_DEFS_STACK to restore
2235 the current reaching definition of every name re-written in BB to
2236 the original reaching definition before visiting BB. This
2237 unwinding must be done in the opposite order to what is done in
2238 register_new_update_set. */
2240 void
2241 rewrite_update_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED)
2243 while (block_defs_stack.length () > 0)
2245 tree var = block_defs_stack.pop ();
2246 tree saved_def;
2248 /* NULL indicates the unwind stop point for this block (see
2249 rewrite_update_enter_block). */
2250 if (var == NULL)
2251 return;
2253 saved_def = block_defs_stack.pop ();
2254 get_common_info (var)->current_def = saved_def;
2259 /* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
2260 form.
2262 ENTRY indicates the block where to start. Every block dominated by
2263 ENTRY will be rewritten.
2265 WHAT indicates what actions will be taken by the renamer (see enum
2266 rewrite_mode).
2268 BLOCKS are the set of interesting blocks for the dominator walker
2269 to process. If this set is NULL, then all the nodes dominated
2270 by ENTRY are walked. Otherwise, blocks dominated by ENTRY that
2271 are not present in BLOCKS are ignored. */
2273 static void
2274 rewrite_blocks (basic_block entry, enum rewrite_mode what)
2276 block_defs_stack.create (10);
2278 /* Recursively walk the dominator tree rewriting each statement in
2279 each basic block. */
2280 if (what == REWRITE_ALL)
2281 rewrite_dom_walker (CDI_DOMINATORS).walk (entry);
2282 else if (what == REWRITE_UPDATE)
2283 rewrite_update_dom_walker (CDI_DOMINATORS).walk (entry);
2284 else
2285 gcc_unreachable ();
2287 /* Debugging dumps. */
2288 if (dump_file && (dump_flags & TDF_STATS))
2290 dump_dfa_stats (dump_file);
2291 if (var_infos)
2292 dump_tree_ssa_stats (dump_file);
2295 block_defs_stack.release ();
2298 class mark_def_dom_walker : public dom_walker
2300 public:
2301 mark_def_dom_walker (cdi_direction direction);
2302 ~mark_def_dom_walker ();
2304 virtual edge before_dom_children (basic_block);
2306 private:
2307 /* Notice that this bitmap is indexed using variable UIDs, so it must be
2308 large enough to accommodate all the variables referenced in the
2309 function, not just the ones we are renaming. */
2310 bitmap m_kills;
2313 mark_def_dom_walker::mark_def_dom_walker (cdi_direction direction)
2314 : dom_walker (direction, ALL_BLOCKS, NULL), m_kills (BITMAP_ALLOC (NULL))
2318 mark_def_dom_walker::~mark_def_dom_walker ()
2320 BITMAP_FREE (m_kills);
2323 /* Block processing routine for mark_def_sites. Clear the KILLS bitmap
2324 at the start of each block, and call mark_def_sites for each statement. */
2326 edge
2327 mark_def_dom_walker::before_dom_children (basic_block bb)
2329 gimple_stmt_iterator gsi;
2331 bitmap_clear (m_kills);
2332 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
2333 mark_def_sites (bb, gsi_stmt (gsi), m_kills);
2334 return NULL;
2337 /* Initialize internal data needed during renaming. */
2339 static void
2340 init_ssa_renamer (void)
2342 cfun->gimple_df->in_ssa_p = false;
2344 /* Allocate memory for the DEF_BLOCKS hash table. */
2345 gcc_assert (!var_infos);
2346 var_infos = new hash_table<var_info_hasher>
2347 (vec_safe_length (cfun->local_decls));
2349 bitmap_obstack_initialize (&update_ssa_obstack);
2353 /* Deallocate internal data structures used by the renamer. */
2355 static void
2356 fini_ssa_renamer (void)
2358 delete var_infos;
2359 var_infos = NULL;
2361 bitmap_obstack_release (&update_ssa_obstack);
2363 cfun->gimple_df->ssa_renaming_needed = 0;
2364 cfun->gimple_df->rename_vops = 0;
2365 cfun->gimple_df->in_ssa_p = true;
2368 /* Main entry point into the SSA builder. The renaming process
2369 proceeds in four main phases:
2371 1- Compute dominance frontier and immediate dominators, needed to
2372 insert PHI nodes and rename the function in dominator tree
2373 order.
2375 2- Find and mark all the blocks that define variables.
2377 3- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
2379 4- Rename all the blocks (rewrite_blocks) and statements in the program.
2381 Steps 3 and 4 are done using the dominator tree walker
2382 (walk_dominator_tree). */
2384 namespace {
2386 const pass_data pass_data_build_ssa =
2388 GIMPLE_PASS, /* type */
2389 "ssa", /* name */
2390 OPTGROUP_NONE, /* optinfo_flags */
2391 TV_TREE_INTO_SSA, /* tv_id */
2392 PROP_cfg, /* properties_required */
2393 PROP_ssa, /* properties_provided */
2394 0, /* properties_destroyed */
2395 0, /* todo_flags_start */
2396 TODO_remove_unused_locals, /* todo_flags_finish */
2399 class pass_build_ssa : public gimple_opt_pass
2401 public:
2402 pass_build_ssa (gcc::context *ctxt)
2403 : gimple_opt_pass (pass_data_build_ssa, ctxt)
2406 /* opt_pass methods: */
2407 virtual bool gate (function *fun)
2409 /* Do nothing for funcions that was produced already in SSA form. */
2410 return !(fun->curr_properties & PROP_ssa);
2413 virtual unsigned int execute (function *);
2415 }; // class pass_build_ssa
2417 unsigned int
2418 pass_build_ssa::execute (function *fun)
2420 bitmap_head *dfs;
2421 basic_block bb;
2423 /* Increase the set of variables we can rewrite into SSA form
2424 by clearing TREE_ADDRESSABLE and transform the IL to support this. */
2425 if (optimize)
2426 execute_update_addresses_taken ();
2428 /* Initialize operand data structures. */
2429 init_ssa_operands (fun);
2431 /* Initialize internal data needed by the renamer. */
2432 init_ssa_renamer ();
2434 /* Initialize the set of interesting blocks. The callback
2435 mark_def_sites will add to this set those blocks that the renamer
2436 should process. */
2437 interesting_blocks = sbitmap_alloc (last_basic_block_for_fn (fun));
2438 bitmap_clear (interesting_blocks);
2440 /* Initialize dominance frontier. */
2441 dfs = XNEWVEC (bitmap_head, last_basic_block_for_fn (fun));
2442 FOR_EACH_BB_FN (bb, fun)
2443 bitmap_initialize (&dfs[bb->index], &bitmap_default_obstack);
2445 /* 1- Compute dominance frontiers. */
2446 calculate_dominance_info (CDI_DOMINATORS);
2447 compute_dominance_frontiers (dfs);
2449 /* 2- Find and mark definition sites. */
2450 mark_def_dom_walker (CDI_DOMINATORS).walk (fun->cfg->x_entry_block_ptr);
2452 /* 3- Insert PHI nodes at dominance frontiers of definition blocks. */
2453 insert_phi_nodes (dfs);
2455 /* 4- Rename all the blocks. */
2456 rewrite_blocks (ENTRY_BLOCK_PTR_FOR_FN (fun), REWRITE_ALL);
2458 /* Free allocated memory. */
2459 FOR_EACH_BB_FN (bb, fun)
2460 bitmap_clear (&dfs[bb->index]);
2461 free (dfs);
2463 sbitmap_free (interesting_blocks);
2465 fini_ssa_renamer ();
2467 /* Try to get rid of all gimplifier generated temporaries by making
2468 its SSA names anonymous. This way we can garbage collect them
2469 all after removing unused locals which we do in our TODO. */
2470 unsigned i;
2471 tree name;
2473 FOR_EACH_SSA_NAME (i, name, cfun)
2475 if (SSA_NAME_IS_DEFAULT_DEF (name))
2476 continue;
2477 tree decl = SSA_NAME_VAR (name);
2478 if (decl
2479 && VAR_P (decl)
2480 && !VAR_DECL_IS_VIRTUAL_OPERAND (decl)
2481 && DECL_IGNORED_P (decl))
2482 SET_SSA_NAME_VAR_OR_IDENTIFIER (name, DECL_NAME (decl));
2485 /* Initialize SSA_NAME_POINTS_TO_READONLY_MEMORY. */
2486 tree fnspec_tree
2487 = lookup_attribute ("fn spec",
2488 TYPE_ATTRIBUTES (TREE_TYPE (fun->decl)));
2489 if (fnspec_tree)
2491 attr_fnspec fnspec (TREE_VALUE (TREE_VALUE (fnspec_tree)));
2492 unsigned i = 0;
2493 for (tree arg = DECL_ARGUMENTS (cfun->decl);
2494 arg; arg = DECL_CHAIN (arg), ++i)
2496 if (!fnspec.arg_specified_p (i))
2497 break;
2498 if (fnspec.arg_readonly_p (i))
2500 tree name = ssa_default_def (fun, arg);
2501 if (name)
2502 SSA_NAME_POINTS_TO_READONLY_MEMORY (name) = 1;
2507 return 0;
2510 } // anon namespace
2512 gimple_opt_pass *
2513 make_pass_build_ssa (gcc::context *ctxt)
2515 return new pass_build_ssa (ctxt);
2519 /* Mark the definition of VAR at STMT and BB as interesting for the
2520 renamer. BLOCKS is the set of blocks that need updating. */
2522 static void
2523 mark_def_interesting (tree var, gimple *stmt, basic_block bb,
2524 bool insert_phi_p)
2526 gcc_checking_assert (bitmap_bit_p (blocks_to_update, bb->index));
2527 set_register_defs (stmt, true);
2529 if (insert_phi_p)
2531 bool is_phi_p = gimple_code (stmt) == GIMPLE_PHI;
2533 set_def_block (var, bb, is_phi_p);
2535 /* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition
2536 site for both itself and all the old names replaced by it. */
2537 if (TREE_CODE (var) == SSA_NAME && is_new_name (var))
2539 bitmap_iterator bi;
2540 unsigned i;
2541 bitmap set = names_replaced_by (var);
2542 if (set)
2543 EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
2544 set_def_block (ssa_name (i), bb, is_phi_p);
2550 /* Mark the use of VAR at STMT and BB as interesting for the
2551 renamer. INSERT_PHI_P is true if we are going to insert new PHI
2552 nodes. */
2554 static inline void
2555 mark_use_interesting (tree var, gimple *stmt, basic_block bb,
2556 bool insert_phi_p)
2558 basic_block def_bb = gimple_bb (stmt);
2560 mark_block_for_update (def_bb);
2561 mark_block_for_update (bb);
2563 if (gimple_code (stmt) == GIMPLE_PHI)
2564 mark_phi_for_rewrite (def_bb, as_a <gphi *> (stmt));
2565 else
2567 set_rewrite_uses (stmt, true);
2569 if (is_gimple_debug (stmt))
2570 return;
2573 /* If VAR has not been defined in BB, then it is live-on-entry
2574 to BB. Note that we cannot just use the block holding VAR's
2575 definition because if VAR is one of the names in OLD_SSA_NAMES,
2576 it will have several definitions (itself and all the names that
2577 replace it). */
2578 if (insert_phi_p)
2580 def_blocks *db_p = get_def_blocks_for (get_common_info (var));
2581 if (!bitmap_bit_p (db_p->def_blocks, bb->index))
2582 set_livein_block (var, bb);
2586 /* Processing statements in BB that reference symbols in SSA operands.
2587 This is very similar to mark_def_sites, but the scan handles
2588 statements whose operands may already be SSA names.
2590 If INSERT_PHI_P is true, mark those uses as live in the
2591 corresponding block. This is later used by the PHI placement
2592 algorithm to make PHI pruning decisions.
2594 FIXME. Most of this would be unnecessary if we could associate a
2595 symbol to all the SSA names that reference it. But that
2596 sounds like it would be expensive to maintain. Still, it
2597 would be interesting to see if it makes better sense to do
2598 that. */
2600 static void
2601 prepare_block_for_update_1 (basic_block bb, bool insert_phi_p)
2603 edge e;
2604 edge_iterator ei;
2606 mark_block_for_update (bb);
2608 /* Process PHI nodes marking interesting those that define or use
2609 the symbols that we are interested in. */
2610 for (gphi_iterator si = gsi_start_phis (bb); !gsi_end_p (si);
2611 gsi_next (&si))
2613 gphi *phi = si.phi ();
2614 tree lhs_sym, lhs = gimple_phi_result (phi);
2616 if (TREE_CODE (lhs) == SSA_NAME
2617 && (! virtual_operand_p (lhs)
2618 || ! cfun->gimple_df->rename_vops))
2619 continue;
2621 lhs_sym = DECL_P (lhs) ? lhs : SSA_NAME_VAR (lhs);
2622 mark_for_renaming (lhs_sym);
2623 mark_def_interesting (lhs_sym, phi, bb, insert_phi_p);
2625 /* Mark the uses in phi nodes as interesting. It would be more correct
2626 to process the arguments of the phi nodes of the successor edges of
2627 BB at the end of prepare_block_for_update, however, that turns out
2628 to be significantly more expensive. Doing it here is conservatively
2629 correct -- it may only cause us to believe a value to be live in a
2630 block that also contains its definition, and thus insert a few more
2631 phi nodes for it. */
2632 FOR_EACH_EDGE (e, ei, bb->preds)
2633 mark_use_interesting (lhs_sym, phi, e->src, insert_phi_p);
2636 /* Process the statements. */
2637 for (gimple_stmt_iterator si = gsi_start_bb (bb); !gsi_end_p (si);
2638 gsi_next (&si))
2640 gimple *stmt;
2641 ssa_op_iter i;
2642 use_operand_p use_p;
2643 def_operand_p def_p;
2645 stmt = gsi_stmt (si);
2647 if (cfun->gimple_df->rename_vops
2648 && gimple_vuse (stmt))
2650 tree use = gimple_vuse (stmt);
2651 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
2652 mark_for_renaming (sym);
2653 mark_use_interesting (sym, stmt, bb, insert_phi_p);
2656 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, i, SSA_OP_USE)
2658 tree use = USE_FROM_PTR (use_p);
2659 if (!DECL_P (use))
2660 continue;
2661 mark_for_renaming (use);
2662 mark_use_interesting (use, stmt, bb, insert_phi_p);
2665 if (cfun->gimple_df->rename_vops
2666 && gimple_vdef (stmt))
2668 tree def = gimple_vdef (stmt);
2669 tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
2670 mark_for_renaming (sym);
2671 mark_def_interesting (sym, stmt, bb, insert_phi_p);
2674 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, i, SSA_OP_DEF)
2676 tree def = DEF_FROM_PTR (def_p);
2677 if (!DECL_P (def))
2678 continue;
2679 mark_for_renaming (def);
2680 mark_def_interesting (def, stmt, bb, insert_phi_p);
2686 /* Do a dominator walk starting at BB processing statements that
2687 reference symbols in SSA operands. This is very similar to
2688 mark_def_sites, but the scan handles statements whose operands may
2689 already be SSA names.
2691 If INSERT_PHI_P is true, mark those uses as live in the
2692 corresponding block. This is later used by the PHI placement
2693 algorithm to make PHI pruning decisions.
2695 FIXME. Most of this would be unnecessary if we could associate a
2696 symbol to all the SSA names that reference it. But that
2697 sounds like it would be expensive to maintain. Still, it
2698 would be interesting to see if it makes better sense to do
2699 that. */
2700 static void
2701 prepare_block_for_update (basic_block bb, bool insert_phi_p)
2703 size_t sp = 0;
2704 basic_block *worklist;
2706 /* Allocate the worklist. */
2707 worklist = XNEWVEC (basic_block, n_basic_blocks_for_fn (cfun));
2708 /* Add the BB to the worklist. */
2709 worklist[sp++] = bb;
2711 while (sp)
2713 basic_block bb;
2714 basic_block son;
2716 /* Pick a block from the worklist. */
2717 bb = worklist[--sp];
2719 prepare_block_for_update_1 (bb, insert_phi_p);
2721 /* Now add all the blocks dominated by BB to the worklist. */
2722 for (son = first_dom_son (CDI_DOMINATORS, bb);
2723 son;
2724 son = next_dom_son (CDI_DOMINATORS, son))
2725 worklist[sp++] = son;
2727 free (worklist);
2730 /* Helper for prepare_names_to_update. Mark all the use sites for
2731 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2732 prepare_names_to_update. */
2734 static void
2735 prepare_use_sites_for (tree name, bool insert_phi_p)
2737 use_operand_p use_p;
2738 imm_use_iterator iter;
2740 /* If we rename virtual operands do not update them. */
2741 if (virtual_operand_p (name)
2742 && cfun->gimple_df->rename_vops)
2743 return;
2745 FOR_EACH_IMM_USE_FAST (use_p, iter, name)
2747 gimple *stmt = USE_STMT (use_p);
2748 basic_block bb = gimple_bb (stmt);
2750 if (gimple_code (stmt) == GIMPLE_PHI)
2752 int ix = PHI_ARG_INDEX_FROM_USE (use_p);
2753 edge e = gimple_phi_arg_edge (as_a <gphi *> (stmt), ix);
2754 mark_use_interesting (name, stmt, e->src, insert_phi_p);
2756 else
2758 /* For regular statements, mark this as an interesting use
2759 for NAME. */
2760 mark_use_interesting (name, stmt, bb, insert_phi_p);
2766 /* Helper for prepare_names_to_update. Mark the definition site for
2767 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2768 prepare_names_to_update. */
2770 static void
2771 prepare_def_site_for (tree name, bool insert_phi_p)
2773 gimple *stmt;
2774 basic_block bb;
2776 gcc_checking_assert (names_to_release == NULL
2777 || !bitmap_bit_p (names_to_release,
2778 SSA_NAME_VERSION (name)));
2780 /* If we rename virtual operands do not update them. */
2781 if (virtual_operand_p (name)
2782 && cfun->gimple_df->rename_vops)
2783 return;
2785 stmt = SSA_NAME_DEF_STMT (name);
2786 bb = gimple_bb (stmt);
2787 if (bb)
2789 gcc_checking_assert (bb->index < last_basic_block_for_fn (cfun));
2790 mark_block_for_update (bb);
2791 mark_def_interesting (name, stmt, bb, insert_phi_p);
2796 /* Mark definition and use sites of names in NEW_SSA_NAMES and
2797 OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert
2798 PHI nodes for newly created names. */
2800 static void
2801 prepare_names_to_update (bool insert_phi_p)
2803 unsigned i = 0;
2804 bitmap_iterator bi;
2805 sbitmap_iterator sbi;
2807 /* If a name N from NEW_SSA_NAMES is also marked to be released,
2808 remove it from NEW_SSA_NAMES so that we don't try to visit its
2809 defining basic block (which most likely doesn't exist). Notice
2810 that we cannot do the same with names in OLD_SSA_NAMES because we
2811 want to replace existing instances. */
2812 if (names_to_release)
2813 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
2814 bitmap_clear_bit (new_ssa_names, i);
2816 /* First process names in NEW_SSA_NAMES. Otherwise, uses of old
2817 names may be considered to be live-in on blocks that contain
2818 definitions for their replacements. */
2819 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names, 0, i, sbi)
2820 prepare_def_site_for (ssa_name (i), insert_phi_p);
2822 /* If an old name is in NAMES_TO_RELEASE, we cannot remove it from
2823 OLD_SSA_NAMES, but we have to ignore its definition site. */
2824 EXECUTE_IF_SET_IN_BITMAP (old_ssa_names, 0, i, sbi)
2826 if (names_to_release == NULL || !bitmap_bit_p (names_to_release, i))
2827 prepare_def_site_for (ssa_name (i), insert_phi_p);
2828 prepare_use_sites_for (ssa_name (i), insert_phi_p);
2833 /* Dump all the names replaced by NAME to FILE. */
2835 void
2836 dump_names_replaced_by (FILE *file, tree name)
2838 unsigned i;
2839 bitmap old_set;
2840 bitmap_iterator bi;
2842 print_generic_expr (file, name);
2843 fprintf (file, " -> { ");
2845 old_set = names_replaced_by (name);
2846 EXECUTE_IF_SET_IN_BITMAP (old_set, 0, i, bi)
2848 print_generic_expr (file, ssa_name (i));
2849 fprintf (file, " ");
2852 fprintf (file, "}\n");
2856 /* Dump all the names replaced by NAME to stderr. */
2858 DEBUG_FUNCTION void
2859 debug_names_replaced_by (tree name)
2861 dump_names_replaced_by (stderr, name);
2865 /* Dump SSA update information to FILE. */
2867 void
2868 dump_update_ssa (FILE *file)
2870 unsigned i = 0;
2871 bitmap_iterator bi;
2873 if (!need_ssa_update_p (cfun))
2874 return;
2876 if (new_ssa_names && bitmap_first_set_bit (new_ssa_names) >= 0)
2878 sbitmap_iterator sbi;
2880 fprintf (file, "\nSSA replacement table\n");
2881 fprintf (file, "N_i -> { O_1 ... O_j } means that N_i replaces "
2882 "O_1, ..., O_j\n\n");
2884 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names, 0, i, sbi)
2885 dump_names_replaced_by (file, ssa_name (i));
2888 if (symbols_to_rename_set && !bitmap_empty_p (symbols_to_rename_set))
2890 fprintf (file, "\nSymbols to be put in SSA form\n");
2891 dump_decl_set (file, symbols_to_rename_set);
2892 fprintf (file, "\n");
2895 if (names_to_release && !bitmap_empty_p (names_to_release))
2897 fprintf (file, "\nSSA names to release after updating the SSA web\n\n");
2898 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
2900 print_generic_expr (file, ssa_name (i));
2901 fprintf (file, " ");
2903 fprintf (file, "\n");
2908 /* Dump SSA update information to stderr. */
2910 DEBUG_FUNCTION void
2911 debug_update_ssa (void)
2913 dump_update_ssa (stderr);
2917 /* Initialize data structures used for incremental SSA updates. */
2919 static void
2920 init_update_ssa (struct function *fn)
2922 /* Reserve more space than the current number of names. The calls to
2923 add_new_name_mapping are typically done after creating new SSA
2924 names, so we'll need to reallocate these arrays. */
2925 old_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR);
2926 bitmap_clear (old_ssa_names);
2928 new_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR);
2929 bitmap_clear (new_ssa_names);
2931 bitmap_obstack_initialize (&update_ssa_obstack);
2933 names_to_release = NULL;
2934 update_ssa_initialized_fn = fn;
2938 /* Deallocate data structures used for incremental SSA updates. */
2940 void
2941 delete_update_ssa (void)
2943 unsigned i;
2944 bitmap_iterator bi;
2946 sbitmap_free (old_ssa_names);
2947 old_ssa_names = NULL;
2949 sbitmap_free (new_ssa_names);
2950 new_ssa_names = NULL;
2952 BITMAP_FREE (symbols_to_rename_set);
2953 symbols_to_rename_set = NULL;
2954 symbols_to_rename.release ();
2956 if (names_to_release)
2958 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
2959 release_ssa_name (ssa_name (i));
2960 BITMAP_FREE (names_to_release);
2963 clear_ssa_name_info ();
2965 fini_ssa_renamer ();
2967 if (blocks_with_phis_to_rewrite)
2968 EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite, 0, i, bi)
2969 phis_to_rewrite[i].release ();
2971 BITMAP_FREE (blocks_with_phis_to_rewrite);
2972 BITMAP_FREE (blocks_to_update);
2974 update_ssa_initialized_fn = NULL;
2978 /* Create a new name for OLD_NAME in statement STMT and replace the
2979 operand pointed to by DEF_P with the newly created name. If DEF_P
2980 is NULL then STMT should be a GIMPLE assignment.
2981 Return the new name and register the replacement mapping <NEW, OLD> in
2982 update_ssa's tables. */
2984 tree
2985 create_new_def_for (tree old_name, gimple *stmt, def_operand_p def)
2987 tree new_name;
2989 timevar_push (TV_TREE_SSA_INCREMENTAL);
2991 if (!update_ssa_initialized_fn)
2992 init_update_ssa (cfun);
2994 gcc_assert (update_ssa_initialized_fn == cfun);
2996 new_name = duplicate_ssa_name (old_name, stmt);
2997 if (def)
2998 SET_DEF (def, new_name);
2999 else
3000 gimple_assign_set_lhs (stmt, new_name);
3002 if (gimple_code (stmt) == GIMPLE_PHI)
3004 basic_block bb = gimple_bb (stmt);
3006 /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
3007 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name) = bb_has_abnormal_pred (bb);
3010 add_new_name_mapping (new_name, old_name);
3012 /* For the benefit of passes that will be updating the SSA form on
3013 their own, set the current reaching definition of OLD_NAME to be
3014 NEW_NAME. */
3015 get_ssa_name_ann (old_name)->info.current_def = new_name;
3017 timevar_pop (TV_TREE_SSA_INCREMENTAL);
3019 return new_name;
3023 /* Mark virtual operands of FN for renaming by update_ssa. */
3025 void
3026 mark_virtual_operands_for_renaming (struct function *fn)
3028 fn->gimple_df->ssa_renaming_needed = 1;
3029 fn->gimple_df->rename_vops = 1;
3032 /* Replace all uses of NAME by underlying variable and mark it
3033 for renaming. This assumes the defining statement of NAME is
3034 going to be removed. */
3036 void
3037 mark_virtual_operand_for_renaming (tree name)
3039 tree name_var = SSA_NAME_VAR (name);
3040 bool used = false;
3041 imm_use_iterator iter;
3042 use_operand_p use_p;
3043 gimple *stmt;
3045 gcc_assert (VAR_DECL_IS_VIRTUAL_OPERAND (name_var));
3046 FOR_EACH_IMM_USE_STMT (stmt, iter, name)
3048 FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
3049 SET_USE (use_p, name_var);
3050 used = true;
3052 if (used)
3053 mark_virtual_operands_for_renaming (cfun);
3056 /* Replace all uses of the virtual PHI result by its underlying variable
3057 and mark it for renaming. This assumes the PHI node is going to be
3058 removed. */
3060 void
3061 mark_virtual_phi_result_for_renaming (gphi *phi)
3063 if (dump_file && (dump_flags & TDF_DETAILS))
3065 fprintf (dump_file, "Marking result for renaming : ");
3066 print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
3067 fprintf (dump_file, "\n");
3070 mark_virtual_operand_for_renaming (gimple_phi_result (phi));
3073 /* Return true if there is any work to be done by update_ssa
3074 for function FN. */
3076 bool
3077 need_ssa_update_p (struct function *fn)
3079 gcc_assert (fn != NULL);
3080 return (update_ssa_initialized_fn == fn
3081 || (fn->gimple_df && fn->gimple_df->ssa_renaming_needed));
3084 /* Return true if name N has been registered in the replacement table. */
3086 bool
3087 name_registered_for_update_p (tree n ATTRIBUTE_UNUSED)
3089 if (!update_ssa_initialized_fn)
3090 return false;
3092 gcc_assert (update_ssa_initialized_fn == cfun);
3094 return is_new_name (n) || is_old_name (n);
3098 /* Mark NAME to be released after update_ssa has finished. */
3100 void
3101 release_ssa_name_after_update_ssa (tree name)
3103 gcc_assert (cfun && update_ssa_initialized_fn == cfun);
3105 if (names_to_release == NULL)
3106 names_to_release = BITMAP_ALLOC (NULL);
3108 bitmap_set_bit (names_to_release, SSA_NAME_VERSION (name));
3112 /* Insert new PHI nodes to replace VAR. DFS contains dominance
3113 frontier information. BLOCKS is the set of blocks to be updated.
3115 This is slightly different than the regular PHI insertion
3116 algorithm. The value of UPDATE_FLAGS controls how PHI nodes for
3117 real names (i.e., GIMPLE registers) are inserted:
3119 - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI
3120 nodes inside the region affected by the block that defines VAR
3121 and the blocks that define all its replacements. All these
3122 definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS.
3124 First, we compute the entry point to the region (ENTRY). This is
3125 given by the nearest common dominator to all the definition
3126 blocks. When computing the iterated dominance frontier (IDF), any
3127 block not strictly dominated by ENTRY is ignored.
3129 We then call the standard PHI insertion algorithm with the pruned
3130 IDF.
3132 - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real
3133 names is not pruned. PHI nodes are inserted at every IDF block. */
3135 static void
3136 insert_updated_phi_nodes_for (tree var, bitmap_head *dfs, bitmap blocks,
3137 unsigned update_flags)
3139 basic_block entry;
3140 def_blocks *db;
3141 bitmap idf, pruned_idf;
3142 bitmap_iterator bi;
3143 unsigned i;
3145 if (TREE_CODE (var) == SSA_NAME)
3146 gcc_checking_assert (is_old_name (var));
3147 else
3148 gcc_checking_assert (marked_for_renaming (var));
3150 /* Get all the definition sites for VAR. */
3151 db = find_def_blocks_for (var);
3153 /* No need to do anything if there were no definitions to VAR. */
3154 if (db == NULL || bitmap_empty_p (db->def_blocks))
3155 return;
3157 /* Compute the initial iterated dominance frontier. */
3158 idf = compute_idf (db->def_blocks, dfs);
3159 pruned_idf = BITMAP_ALLOC (NULL);
3161 if (TREE_CODE (var) == SSA_NAME)
3163 if (update_flags == TODO_update_ssa)
3165 /* If doing regular SSA updates for GIMPLE registers, we are
3166 only interested in IDF blocks dominated by the nearest
3167 common dominator of all the definition blocks. */
3168 entry = nearest_common_dominator_for_set (CDI_DOMINATORS,
3169 db->def_blocks);
3170 if (entry != ENTRY_BLOCK_PTR_FOR_FN (cfun))
3171 EXECUTE_IF_SET_IN_BITMAP (idf, 0, i, bi)
3172 if (BASIC_BLOCK_FOR_FN (cfun, i) != entry
3173 && dominated_by_p (CDI_DOMINATORS,
3174 BASIC_BLOCK_FOR_FN (cfun, i), entry))
3175 bitmap_set_bit (pruned_idf, i);
3177 else
3179 /* Otherwise, do not prune the IDF for VAR. */
3180 gcc_checking_assert (update_flags == TODO_update_ssa_full_phi);
3181 bitmap_copy (pruned_idf, idf);
3184 else
3186 /* Otherwise, VAR is a symbol that needs to be put into SSA form
3187 for the first time, so we need to compute the full IDF for
3188 it. */
3189 bitmap_copy (pruned_idf, idf);
3192 if (!bitmap_empty_p (pruned_idf))
3194 /* Make sure that PRUNED_IDF blocks and all their feeding blocks
3195 are included in the region to be updated. The feeding blocks
3196 are important to guarantee that the PHI arguments are renamed
3197 properly. */
3199 /* FIXME, this is not needed if we are updating symbols. We are
3200 already starting at the ENTRY block anyway. */
3201 bitmap_ior_into (blocks, pruned_idf);
3202 EXECUTE_IF_SET_IN_BITMAP (pruned_idf, 0, i, bi)
3204 edge e;
3205 edge_iterator ei;
3206 basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i);
3208 FOR_EACH_EDGE (e, ei, bb->preds)
3209 if (e->src->index >= 0)
3210 bitmap_set_bit (blocks, e->src->index);
3213 insert_phi_nodes_for (var, pruned_idf, true);
3216 BITMAP_FREE (pruned_idf);
3217 BITMAP_FREE (idf);
3220 /* Sort symbols_to_rename after their DECL_UID. */
3222 static int
3223 insert_updated_phi_nodes_compare_uids (const void *a, const void *b)
3225 const_tree syma = *(const const_tree *)a;
3226 const_tree symb = *(const const_tree *)b;
3227 if (DECL_UID (syma) == DECL_UID (symb))
3228 return 0;
3229 return DECL_UID (syma) < DECL_UID (symb) ? -1 : 1;
3232 /* Given a set of newly created SSA names (NEW_SSA_NAMES) and a set of
3233 existing SSA names (OLD_SSA_NAMES), update the SSA form so that:
3235 1- The names in OLD_SSA_NAMES dominated by the definitions of
3236 NEW_SSA_NAMES are all re-written to be reached by the
3237 appropriate definition from NEW_SSA_NAMES.
3239 2- If needed, new PHI nodes are added to the iterated dominance
3240 frontier of the blocks where each of NEW_SSA_NAMES are defined.
3242 The mapping between OLD_SSA_NAMES and NEW_SSA_NAMES is setup by
3243 calling create_new_def_for to create new defs for names that the
3244 caller wants to replace.
3246 The caller cretaes the new names to be inserted and the names that need
3247 to be replaced by calling create_new_def_for for each old definition
3248 to be replaced. Note that the function assumes that the
3249 new defining statement has already been inserted in the IL.
3251 For instance, given the following code:
3253 1 L0:
3254 2 x_1 = PHI (0, x_5)
3255 3 if (x_1 < 10)
3256 4 if (x_1 > 7)
3257 5 y_2 = 0
3258 6 else
3259 7 y_3 = x_1 + x_7
3260 8 endif
3261 9 x_5 = x_1 + 1
3262 10 goto L0;
3263 11 endif
3265 Suppose that we insert new names x_10 and x_11 (lines 4 and 8).
3267 1 L0:
3268 2 x_1 = PHI (0, x_5)
3269 3 if (x_1 < 10)
3270 4 x_10 = ...
3271 5 if (x_1 > 7)
3272 6 y_2 = 0
3273 7 else
3274 8 x_11 = ...
3275 9 y_3 = x_1 + x_7
3276 10 endif
3277 11 x_5 = x_1 + 1
3278 12 goto L0;
3279 13 endif
3281 We want to replace all the uses of x_1 with the new definitions of
3282 x_10 and x_11. Note that the only uses that should be replaced are
3283 those at lines 5, 9 and 11. Also, the use of x_7 at line 9 should
3284 *not* be replaced (this is why we cannot just mark symbol 'x' for
3285 renaming).
3287 Additionally, we may need to insert a PHI node at line 11 because
3288 that is a merge point for x_10 and x_11. So the use of x_1 at line
3289 11 will be replaced with the new PHI node. The insertion of PHI
3290 nodes is optional. They are not strictly necessary to preserve the
3291 SSA form, and depending on what the caller inserted, they may not
3292 even be useful for the optimizers. UPDATE_FLAGS controls various
3293 aspects of how update_ssa operates, see the documentation for
3294 TODO_update_ssa*. */
3296 void
3297 update_ssa (unsigned update_flags)
3299 basic_block bb, start_bb;
3300 bitmap_iterator bi;
3301 unsigned i = 0;
3302 bool insert_phi_p;
3303 sbitmap_iterator sbi;
3304 tree sym;
3306 /* Only one update flag should be set. */
3307 gcc_assert (update_flags == TODO_update_ssa
3308 || update_flags == TODO_update_ssa_no_phi
3309 || update_flags == TODO_update_ssa_full_phi
3310 || update_flags == TODO_update_ssa_only_virtuals);
3312 if (!need_ssa_update_p (cfun))
3313 return;
3315 if (flag_checking)
3317 timevar_push (TV_TREE_STMT_VERIFY);
3319 bool err = false;
3321 FOR_EACH_BB_FN (bb, cfun)
3323 gimple_stmt_iterator gsi;
3324 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
3326 gimple *stmt = gsi_stmt (gsi);
3328 ssa_op_iter i;
3329 use_operand_p use_p;
3330 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, i, SSA_OP_ALL_USES)
3332 tree use = USE_FROM_PTR (use_p);
3333 if (TREE_CODE (use) != SSA_NAME)
3334 continue;
3336 if (SSA_NAME_IN_FREE_LIST (use))
3338 error ("statement uses released SSA name");
3339 debug_gimple_stmt (stmt);
3340 fprintf (stderr, "The use of ");
3341 print_generic_expr (stderr, use);
3342 fprintf (stderr," should have been replaced\n");
3343 err = true;
3349 if (err)
3350 internal_error ("cannot update SSA form");
3352 timevar_pop (TV_TREE_STMT_VERIFY);
3355 timevar_push (TV_TREE_SSA_INCREMENTAL);
3357 if (dump_file && (dump_flags & TDF_DETAILS))
3358 fprintf (dump_file, "\nUpdating SSA:\n");
3360 if (!update_ssa_initialized_fn)
3361 init_update_ssa (cfun);
3362 else if (update_flags == TODO_update_ssa_only_virtuals)
3364 /* If we only need to update virtuals, remove all the mappings for
3365 real names before proceeding. The caller is responsible for
3366 having dealt with the name mappings before calling update_ssa. */
3367 bitmap_clear (old_ssa_names);
3368 bitmap_clear (new_ssa_names);
3371 gcc_assert (update_ssa_initialized_fn == cfun);
3373 blocks_with_phis_to_rewrite = BITMAP_ALLOC (NULL);
3374 if (!phis_to_rewrite.exists ())
3375 phis_to_rewrite.create (last_basic_block_for_fn (cfun) + 1);
3376 blocks_to_update = BITMAP_ALLOC (NULL);
3378 /* Ensure that the dominance information is up-to-date. */
3379 calculate_dominance_info (CDI_DOMINATORS);
3381 insert_phi_p = (update_flags != TODO_update_ssa_no_phi);
3383 /* If there are names defined in the replacement table, prepare
3384 definition and use sites for all the names in NEW_SSA_NAMES and
3385 OLD_SSA_NAMES. */
3386 if (bitmap_first_set_bit (new_ssa_names) >= 0)
3388 statistics_counter_event (cfun, "Incremental SSA update", 1);
3390 prepare_names_to_update (insert_phi_p);
3392 /* If all the names in NEW_SSA_NAMES had been marked for
3393 removal, and there are no symbols to rename, then there's
3394 nothing else to do. */
3395 if (bitmap_first_set_bit (new_ssa_names) < 0
3396 && !cfun->gimple_df->ssa_renaming_needed)
3397 goto done;
3400 /* Next, determine the block at which to start the renaming process. */
3401 if (cfun->gimple_df->ssa_renaming_needed)
3403 statistics_counter_event (cfun, "Symbol to SSA rewrite", 1);
3405 /* If we rename bare symbols initialize the mapping to
3406 auxiliar info we need to keep track of. */
3407 var_infos = new hash_table<var_info_hasher> (47);
3409 /* If we have to rename some symbols from scratch, we need to
3410 start the process at the root of the CFG. FIXME, it should
3411 be possible to determine the nearest block that had a
3412 definition for each of the symbols that are marked for
3413 updating. For now this seems more work than it's worth. */
3414 start_bb = ENTRY_BLOCK_PTR_FOR_FN (cfun);
3416 /* Traverse the CFG looking for existing definitions and uses of
3417 symbols in SSA operands. Mark interesting blocks and
3418 statements and set local live-in information for the PHI
3419 placement heuristics. */
3420 prepare_block_for_update (start_bb, insert_phi_p);
3422 tree name;
3424 if (flag_checking)
3425 FOR_EACH_SSA_NAME (i, name, cfun)
3427 if (virtual_operand_p (name))
3428 continue;
3430 /* For all but virtual operands, which do not have SSA names
3431 with overlapping life ranges, ensure that symbols marked
3432 for renaming do not have existing SSA names associated with
3433 them as we do not re-write them out-of-SSA before going
3434 into SSA for the remaining symbol uses. */
3435 if (marked_for_renaming (SSA_NAME_VAR (name)))
3437 fprintf (stderr, "Existing SSA name for symbol marked for "
3438 "renaming: ");
3439 print_generic_expr (stderr, name, TDF_SLIM);
3440 fprintf (stderr, "\n");
3441 internal_error ("SSA corruption");
3445 else
3447 /* Otherwise, the entry block to the region is the nearest
3448 common dominator for the blocks in BLOCKS. */
3449 start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS,
3450 blocks_to_update);
3453 /* If requested, insert PHI nodes at the iterated dominance frontier
3454 of every block, creating new definitions for names in OLD_SSA_NAMES
3455 and for symbols found. */
3456 if (insert_phi_p)
3458 bitmap_head *dfs;
3460 /* If the caller requested PHI nodes to be added, compute
3461 dominance frontiers. */
3462 dfs = XNEWVEC (bitmap_head, last_basic_block_for_fn (cfun));
3463 FOR_EACH_BB_FN (bb, cfun)
3464 bitmap_initialize (&dfs[bb->index], &bitmap_default_obstack);
3465 compute_dominance_frontiers (dfs);
3467 if (bitmap_first_set_bit (old_ssa_names) >= 0)
3469 sbitmap_iterator sbi;
3471 /* insert_update_phi_nodes_for will call add_new_name_mapping
3472 when inserting new PHI nodes, so the set OLD_SSA_NAMES
3473 will grow while we are traversing it (but it will not
3474 gain any new members). Copy OLD_SSA_NAMES to a temporary
3475 for traversal. */
3476 auto_sbitmap tmp (SBITMAP_SIZE (old_ssa_names));
3477 bitmap_copy (tmp, old_ssa_names);
3478 EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, sbi)
3479 insert_updated_phi_nodes_for (ssa_name (i), dfs, blocks_to_update,
3480 update_flags);
3483 symbols_to_rename.qsort (insert_updated_phi_nodes_compare_uids);
3484 FOR_EACH_VEC_ELT (symbols_to_rename, i, sym)
3485 insert_updated_phi_nodes_for (sym, dfs, blocks_to_update,
3486 update_flags);
3488 FOR_EACH_BB_FN (bb, cfun)
3489 bitmap_clear (&dfs[bb->index]);
3490 free (dfs);
3492 /* Insertion of PHI nodes may have added blocks to the region.
3493 We need to re-compute START_BB to include the newly added
3494 blocks. */
3495 if (start_bb != ENTRY_BLOCK_PTR_FOR_FN (cfun))
3496 start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS,
3497 blocks_to_update);
3500 /* Reset the current definition for name and symbol before renaming
3501 the sub-graph. */
3502 EXECUTE_IF_SET_IN_BITMAP (old_ssa_names, 0, i, sbi)
3503 get_ssa_name_ann (ssa_name (i))->info.current_def = NULL_TREE;
3505 FOR_EACH_VEC_ELT (symbols_to_rename, i, sym)
3506 get_var_info (sym)->info.current_def = NULL_TREE;
3508 /* Now start the renaming process at START_BB. */
3509 interesting_blocks = sbitmap_alloc (last_basic_block_for_fn (cfun));
3510 bitmap_clear (interesting_blocks);
3511 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi)
3512 bitmap_set_bit (interesting_blocks, i);
3514 rewrite_blocks (start_bb, REWRITE_UPDATE);
3516 sbitmap_free (interesting_blocks);
3518 /* Debugging dumps. */
3519 if (dump_file)
3521 int c;
3522 unsigned i;
3524 dump_update_ssa (dump_file);
3526 fprintf (dump_file, "Incremental SSA update started at block: %d\n",
3527 start_bb->index);
3529 c = 0;
3530 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi)
3531 c++;
3532 fprintf (dump_file, "Number of blocks in CFG: %d\n",
3533 last_basic_block_for_fn (cfun));
3534 fprintf (dump_file, "Number of blocks to update: %d (%3.0f%%)\n",
3535 c, PERCENT (c, last_basic_block_for_fn (cfun)));
3537 if (dump_flags & TDF_DETAILS)
3539 fprintf (dump_file, "Affected blocks:");
3540 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi)
3541 fprintf (dump_file, " %u", i);
3542 fprintf (dump_file, "\n");
3545 fprintf (dump_file, "\n\n");
3548 /* Free allocated memory. */
3549 done:
3550 delete_update_ssa ();
3552 timevar_pop (TV_TREE_SSA_INCREMENTAL);