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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) 2001-2018 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"
45 #define PERCENT(x,y) ((float)(x) * 100.0 / (float)(y))
47 /* This file builds the SSA form for a function as described in:
48 R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently
49 Computing Static Single Assignment Form and the Control Dependence
50 Graph. ACM Transactions on Programming Languages and Systems,
51 13(4):451-490, October 1991. */
53 /* Structure to map a variable VAR to the set of blocks that contain
54 definitions for VAR. */
55 struct def_blocks
57 /* Blocks that contain definitions of VAR. Bit I will be set if the
58 Ith block contains a definition of VAR. */
59 bitmap def_blocks;
61 /* Blocks that contain a PHI node for VAR. */
62 bitmap phi_blocks;
64 /* Blocks where VAR is live-on-entry. Similar semantics as
65 DEF_BLOCKS. */
66 bitmap livein_blocks;
69 /* Stack of trees used to restore the global currdefs to its original
70 state after completing rewriting of a block and its dominator
71 children. Its elements have the following properties:
73 - An SSA_NAME (N) indicates that the current definition of the
74 underlying variable should be set to the given SSA_NAME. If the
75 symbol associated with the SSA_NAME is not a GIMPLE register, the
76 next slot in the stack must be a _DECL node (SYM). In this case,
77 the name N in the previous slot is the current reaching
78 definition for SYM.
80 - A _DECL node indicates that the underlying variable has no
81 current definition.
83 - A NULL node at the top entry is used to mark the last slot
84 associated with the current block. */
85 static vec<tree> block_defs_stack;
88 /* Set of existing SSA names being replaced by update_ssa. */
89 static sbitmap old_ssa_names;
91 /* Set of new SSA names being added by update_ssa. Note that both
92 NEW_SSA_NAMES and OLD_SSA_NAMES are dense bitmaps because most of
93 the operations done on them are presence tests. */
94 static sbitmap new_ssa_names;
96 static sbitmap interesting_blocks;
98 /* Set of SSA names that have been marked to be released after they
99 were registered in the replacement table. They will be finally
100 released after we finish updating the SSA web. */
101 bitmap names_to_release;
103 /* vec of vec of PHIs to rewrite in a basic block. Element I corresponds
104 the to basic block with index I. Allocated once per compilation, *not*
105 released between different functions. */
106 static vec< vec<gphi *> > phis_to_rewrite;
108 /* The bitmap of non-NULL elements of PHIS_TO_REWRITE. */
109 static bitmap blocks_with_phis_to_rewrite;
111 /* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need
112 to grow as the callers to create_new_def_for will create new names on
113 the fly.
114 FIXME. Currently set to 1/3 to avoid frequent reallocations but still
115 need to find a reasonable growth strategy. */
116 #define NAME_SETS_GROWTH_FACTOR (MAX (3, num_ssa_names / 3))
119 /* The function the SSA updating data structures have been initialized for.
120 NULL if they need to be initialized by create_new_def_for. */
121 static struct function *update_ssa_initialized_fn = NULL;
123 /* Global data to attach to the main dominator walk structure. */
124 struct mark_def_sites_global_data
126 /* This bitmap contains the variables which are set before they
127 are used in a basic block. */
128 bitmap kills;
131 /* It is advantageous to avoid things like life analysis for variables which
132 do not need PHI nodes. This enum describes whether or not a particular
133 variable may need a PHI node. */
135 enum need_phi_state {
136 /* This is the default. If we are still in this state after finding
137 all the definition and use sites, then we will assume the variable
138 needs PHI nodes. This is probably an overly conservative assumption. */
139 NEED_PHI_STATE_UNKNOWN,
141 /* This state indicates that we have seen one or more sets of the
142 variable in a single basic block and that the sets dominate all
143 uses seen so far. If after finding all definition and use sites
144 we are still in this state, then the variable does not need any
145 PHI nodes. */
146 NEED_PHI_STATE_NO,
148 /* This state indicates that we have either seen multiple definitions of
149 the variable in multiple blocks, or that we encountered a use in a
150 block that was not dominated by the block containing the set(s) of
151 this variable. This variable is assumed to need PHI nodes. */
152 NEED_PHI_STATE_MAYBE
155 /* Information stored for both SSA names and decls. */
156 struct common_info
158 /* This field indicates whether or not the variable may need PHI nodes.
159 See the enum's definition for more detailed information about the
160 states. */
161 ENUM_BITFIELD (need_phi_state) need_phi_state : 2;
163 /* The current reaching definition replacing this var. */
164 tree current_def;
166 /* Definitions for this var. */
167 struct def_blocks def_blocks;
170 /* Information stored for decls. */
171 struct var_info
173 /* The variable. */
174 tree var;
176 /* Information stored for both SSA names and decls. */
177 common_info info;
181 /* VAR_INFOS hashtable helpers. */
183 struct var_info_hasher : free_ptr_hash <var_info>
185 static inline hashval_t hash (const value_type &);
186 static inline bool equal (const value_type &, const compare_type &);
189 inline hashval_t
190 var_info_hasher::hash (const value_type &p)
192 return DECL_UID (p->var);
195 inline bool
196 var_info_hasher::equal (const value_type &p1, const compare_type &p2)
198 return p1->var == p2->var;
202 /* Each entry in VAR_INFOS contains an element of type STRUCT
203 VAR_INFO_D. */
204 static hash_table<var_info_hasher> *var_infos;
207 /* Information stored for SSA names. */
208 struct ssa_name_info
210 /* Age of this record (so that info_for_ssa_name table can be cleared
211 quickly); if AGE < CURRENT_INFO_FOR_SSA_NAME_AGE, then the fields
212 are assumed to be null. */
213 unsigned age;
215 /* Replacement mappings, allocated from update_ssa_obstack. */
216 bitmap repl_set;
218 /* Information stored for both SSA names and decls. */
219 common_info info;
222 static vec<ssa_name_info *> info_for_ssa_name;
223 static unsigned current_info_for_ssa_name_age;
225 static bitmap_obstack update_ssa_obstack;
227 /* The set of blocks affected by update_ssa. */
228 static bitmap blocks_to_update;
230 /* The main entry point to the SSA renamer (rewrite_blocks) may be
231 called several times to do different, but related, tasks.
232 Initially, we need it to rename the whole program into SSA form.
233 At other times, we may need it to only rename into SSA newly
234 exposed symbols. Finally, we can also call it to incrementally fix
235 an already built SSA web. */
236 enum rewrite_mode {
237 /* Convert the whole function into SSA form. */
238 REWRITE_ALL,
240 /* Incrementally update the SSA web by replacing existing SSA
241 names with new ones. See update_ssa for details. */
242 REWRITE_UPDATE
245 /* The set of symbols we ought to re-write into SSA form in update_ssa. */
246 static bitmap symbols_to_rename_set;
247 static vec<tree> symbols_to_rename;
249 /* Mark SYM for renaming. */
251 static void
252 mark_for_renaming (tree sym)
254 if (!symbols_to_rename_set)
255 symbols_to_rename_set = BITMAP_ALLOC (NULL);
256 if (bitmap_set_bit (symbols_to_rename_set, DECL_UID (sym)))
257 symbols_to_rename.safe_push (sym);
260 /* Return true if SYM is marked for renaming. */
262 static bool
263 marked_for_renaming (tree sym)
265 if (!symbols_to_rename_set || sym == NULL_TREE)
266 return false;
267 return bitmap_bit_p (symbols_to_rename_set, DECL_UID (sym));
271 /* Return true if STMT needs to be rewritten. When renaming a subset
272 of the variables, not all statements will be processed. This is
273 decided in mark_def_sites. */
275 static inline bool
276 rewrite_uses_p (gimple *stmt)
278 return gimple_visited_p (stmt);
282 /* Set the rewrite marker on STMT to the value given by REWRITE_P. */
284 static inline void
285 set_rewrite_uses (gimple *stmt, bool rewrite_p)
287 gimple_set_visited (stmt, rewrite_p);
291 /* Return true if the DEFs created by statement STMT should be
292 registered when marking new definition sites. This is slightly
293 different than rewrite_uses_p: it's used by update_ssa to
294 distinguish statements that need to have both uses and defs
295 processed from those that only need to have their defs processed.
296 Statements that define new SSA names only need to have their defs
297 registered, but they don't need to have their uses renamed. */
299 static inline bool
300 register_defs_p (gimple *stmt)
302 return gimple_plf (stmt, GF_PLF_1) != 0;
306 /* If REGISTER_DEFS_P is true, mark STMT to have its DEFs registered. */
308 static inline void
309 set_register_defs (gimple *stmt, bool register_defs_p)
311 gimple_set_plf (stmt, GF_PLF_1, register_defs_p);
315 /* Get the information associated with NAME. */
317 static inline ssa_name_info *
318 get_ssa_name_ann (tree name)
320 unsigned ver = SSA_NAME_VERSION (name);
321 unsigned len = info_for_ssa_name.length ();
322 struct ssa_name_info *info;
324 /* Re-allocate the vector at most once per update/into-SSA. */
325 if (ver >= len)
326 info_for_ssa_name.safe_grow_cleared (num_ssa_names);
328 /* But allocate infos lazily. */
329 info = info_for_ssa_name[ver];
330 if (!info)
332 info = XCNEW (struct ssa_name_info);
333 info->age = current_info_for_ssa_name_age;
334 info->info.need_phi_state = NEED_PHI_STATE_UNKNOWN;
335 info_for_ssa_name[ver] = info;
338 if (info->age < current_info_for_ssa_name_age)
340 info->age = current_info_for_ssa_name_age;
341 info->repl_set = NULL;
342 info->info.need_phi_state = NEED_PHI_STATE_UNKNOWN;
343 info->info.current_def = NULL_TREE;
344 info->info.def_blocks.def_blocks = NULL;
345 info->info.def_blocks.phi_blocks = NULL;
346 info->info.def_blocks.livein_blocks = NULL;
349 return info;
352 /* Return and allocate the auxiliar information for DECL. */
354 static inline var_info *
355 get_var_info (tree decl)
357 var_info vi;
358 var_info **slot;
359 vi.var = decl;
360 slot = var_infos->find_slot_with_hash (&vi, DECL_UID (decl), INSERT);
361 if (*slot == NULL)
363 var_info *v = XCNEW (var_info);
364 v->var = decl;
365 *slot = v;
366 return v;
368 return *slot;
372 /* Clears info for SSA names. */
374 static void
375 clear_ssa_name_info (void)
377 current_info_for_ssa_name_age++;
379 /* If current_info_for_ssa_name_age wraps we use stale information.
380 Asser that this does not happen. */
381 gcc_assert (current_info_for_ssa_name_age != 0);
385 /* Get access to the auxiliar information stored per SSA name or decl. */
387 static inline common_info *
388 get_common_info (tree var)
390 if (TREE_CODE (var) == SSA_NAME)
391 return &get_ssa_name_ann (var)->info;
392 else
393 return &get_var_info (var)->info;
397 /* Return the current definition for VAR. */
399 tree
400 get_current_def (tree var)
402 return get_common_info (var)->current_def;
406 /* Sets current definition of VAR to DEF. */
408 void
409 set_current_def (tree var, tree def)
411 get_common_info (var)->current_def = def;
414 /* Cleans up the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags for
415 all statements in basic block BB. */
417 static void
418 initialize_flags_in_bb (basic_block bb)
420 gimple *stmt;
421 gimple_stmt_iterator gsi;
423 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
425 gimple *phi = gsi_stmt (gsi);
426 set_rewrite_uses (phi, false);
427 set_register_defs (phi, false);
430 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
432 stmt = gsi_stmt (gsi);
434 /* We are going to use the operand cache API, such as
435 SET_USE, SET_DEF, and FOR_EACH_IMM_USE_FAST. The operand
436 cache for each statement should be up-to-date. */
437 gcc_checking_assert (!gimple_modified_p (stmt));
438 set_rewrite_uses (stmt, false);
439 set_register_defs (stmt, false);
443 /* Mark block BB as interesting for update_ssa. */
445 static void
446 mark_block_for_update (basic_block bb)
448 gcc_checking_assert (blocks_to_update != NULL);
449 if (!bitmap_set_bit (blocks_to_update, bb->index))
450 return;
451 initialize_flags_in_bb (bb);
454 /* Return the set of blocks where variable VAR is defined and the blocks
455 where VAR is live on entry (livein). If no entry is found in
456 DEF_BLOCKS, a new one is created and returned. */
458 static inline def_blocks *
459 get_def_blocks_for (common_info *info)
461 def_blocks *db_p = &info->def_blocks;
462 if (!db_p->def_blocks)
464 db_p->def_blocks = BITMAP_ALLOC (&update_ssa_obstack);
465 db_p->phi_blocks = BITMAP_ALLOC (&update_ssa_obstack);
466 db_p->livein_blocks = BITMAP_ALLOC (&update_ssa_obstack);
469 return db_p;
473 /* Mark block BB as the definition site for variable VAR. PHI_P is true if
474 VAR is defined by a PHI node. */
476 static void
477 set_def_block (tree var, basic_block bb, bool phi_p)
479 def_blocks *db_p;
480 common_info *info;
482 info = get_common_info (var);
483 db_p = get_def_blocks_for (info);
485 /* Set the bit corresponding to the block where VAR is defined. */
486 bitmap_set_bit (db_p->def_blocks, bb->index);
487 if (phi_p)
488 bitmap_set_bit (db_p->phi_blocks, bb->index);
490 /* Keep track of whether or not we may need to insert PHI nodes.
492 If we are in the UNKNOWN state, then this is the first definition
493 of VAR. Additionally, we have not seen any uses of VAR yet, so
494 we do not need a PHI node for this variable at this time (i.e.,
495 transition to NEED_PHI_STATE_NO).
497 If we are in any other state, then we either have multiple definitions
498 of this variable occurring in different blocks or we saw a use of the
499 variable which was not dominated by the block containing the
500 definition(s). In this case we may need a PHI node, so enter
501 state NEED_PHI_STATE_MAYBE. */
502 if (info->need_phi_state == NEED_PHI_STATE_UNKNOWN)
503 info->need_phi_state = NEED_PHI_STATE_NO;
504 else
505 info->need_phi_state = NEED_PHI_STATE_MAYBE;
509 /* Mark block BB as having VAR live at the entry to BB. */
511 static void
512 set_livein_block (tree var, basic_block bb)
514 common_info *info;
515 def_blocks *db_p;
517 info = get_common_info (var);
518 db_p = get_def_blocks_for (info);
520 /* Set the bit corresponding to the block where VAR is live in. */
521 bitmap_set_bit (db_p->livein_blocks, bb->index);
523 /* Keep track of whether or not we may need to insert PHI nodes.
525 If we reach here in NEED_PHI_STATE_NO, see if this use is dominated
526 by the single block containing the definition(s) of this variable. If
527 it is, then we remain in NEED_PHI_STATE_NO, otherwise we transition to
528 NEED_PHI_STATE_MAYBE. */
529 if (info->need_phi_state == NEED_PHI_STATE_NO)
531 int def_block_index = bitmap_first_set_bit (db_p->def_blocks);
533 if (def_block_index == -1
534 || ! dominated_by_p (CDI_DOMINATORS, bb,
535 BASIC_BLOCK_FOR_FN (cfun, def_block_index)))
536 info->need_phi_state = NEED_PHI_STATE_MAYBE;
538 else
539 info->need_phi_state = NEED_PHI_STATE_MAYBE;
543 /* Return true if NAME is in OLD_SSA_NAMES. */
545 static inline bool
546 is_old_name (tree name)
548 unsigned ver = SSA_NAME_VERSION (name);
549 if (!old_ssa_names)
550 return false;
551 return (ver < SBITMAP_SIZE (old_ssa_names)
552 && bitmap_bit_p (old_ssa_names, ver));
556 /* Return true if NAME is in NEW_SSA_NAMES. */
558 static inline bool
559 is_new_name (tree name)
561 unsigned ver = SSA_NAME_VERSION (name);
562 if (!new_ssa_names)
563 return false;
564 return (ver < SBITMAP_SIZE (new_ssa_names)
565 && bitmap_bit_p (new_ssa_names, ver));
569 /* Return the names replaced by NEW_TREE (i.e., REPL_TBL[NEW_TREE].SET). */
571 static inline bitmap
572 names_replaced_by (tree new_tree)
574 return get_ssa_name_ann (new_tree)->repl_set;
578 /* Add OLD to REPL_TBL[NEW_TREE].SET. */
580 static inline void
581 add_to_repl_tbl (tree new_tree, tree old)
583 bitmap *set = &get_ssa_name_ann (new_tree)->repl_set;
584 if (!*set)
585 *set = BITMAP_ALLOC (&update_ssa_obstack);
586 bitmap_set_bit (*set, SSA_NAME_VERSION (old));
590 /* Add a new mapping NEW_TREE -> OLD REPL_TBL. Every entry N_i in REPL_TBL
591 represents the set of names O_1 ... O_j replaced by N_i. This is
592 used by update_ssa and its helpers to introduce new SSA names in an
593 already formed SSA web. */
595 static void
596 add_new_name_mapping (tree new_tree, tree old)
598 /* OLD and NEW_TREE must be different SSA names for the same symbol. */
599 gcc_checking_assert (new_tree != old
600 && SSA_NAME_VAR (new_tree) == SSA_NAME_VAR (old));
602 /* We may need to grow NEW_SSA_NAMES and OLD_SSA_NAMES because our
603 caller may have created new names since the set was created. */
604 if (SBITMAP_SIZE (new_ssa_names) <= num_ssa_names - 1)
606 unsigned int new_sz = num_ssa_names + NAME_SETS_GROWTH_FACTOR;
607 new_ssa_names = sbitmap_resize (new_ssa_names, new_sz, 0);
608 old_ssa_names = sbitmap_resize (old_ssa_names, new_sz, 0);
611 /* Update the REPL_TBL table. */
612 add_to_repl_tbl (new_tree, old);
614 /* If OLD had already been registered as a new name, then all the
615 names that OLD replaces should also be replaced by NEW_TREE. */
616 if (is_new_name (old))
617 bitmap_ior_into (names_replaced_by (new_tree), names_replaced_by (old));
619 /* Register NEW_TREE and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES,
620 respectively. */
621 bitmap_set_bit (new_ssa_names, SSA_NAME_VERSION (new_tree));
622 bitmap_set_bit (old_ssa_names, SSA_NAME_VERSION (old));
626 /* Call back for walk_dominator_tree used to collect definition sites
627 for every variable in the function. For every statement S in block
630 1- Variables defined by S in the DEFS of S are marked in the bitmap
631 KILLS.
633 2- If S uses a variable VAR and there is no preceding kill of VAR,
634 then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR.
636 This information is used to determine which variables are live
637 across block boundaries to reduce the number of PHI nodes
638 we create. */
640 static void
641 mark_def_sites (basic_block bb, gimple *stmt, bitmap kills)
643 tree def;
644 use_operand_p use_p;
645 ssa_op_iter iter;
647 /* Since this is the first time that we rewrite the program into SSA
648 form, force an operand scan on every statement. */
649 update_stmt (stmt);
651 gcc_checking_assert (blocks_to_update == NULL);
652 set_register_defs (stmt, false);
653 set_rewrite_uses (stmt, false);
655 if (is_gimple_debug (stmt))
657 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
659 tree sym = USE_FROM_PTR (use_p);
660 gcc_checking_assert (DECL_P (sym));
661 set_rewrite_uses (stmt, true);
663 if (rewrite_uses_p (stmt))
664 bitmap_set_bit (interesting_blocks, bb->index);
665 return;
668 /* If a variable is used before being set, then the variable is live
669 across a block boundary, so mark it live-on-entry to BB. */
670 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
672 tree sym = USE_FROM_PTR (use_p);
673 if (TREE_CODE (sym) == SSA_NAME)
674 continue;
675 gcc_checking_assert (DECL_P (sym));
676 if (!bitmap_bit_p (kills, DECL_UID (sym)))
677 set_livein_block (sym, bb);
678 set_rewrite_uses (stmt, true);
681 /* Now process the defs. Mark BB as the definition block and add
682 each def to the set of killed symbols. */
683 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_ALL_DEFS)
685 if (TREE_CODE (def) == SSA_NAME)
686 continue;
687 gcc_checking_assert (DECL_P (def));
688 set_def_block (def, bb, false);
689 bitmap_set_bit (kills, DECL_UID (def));
690 set_register_defs (stmt, true);
693 /* If we found the statement interesting then also mark the block BB
694 as interesting. */
695 if (rewrite_uses_p (stmt) || register_defs_p (stmt))
696 bitmap_set_bit (interesting_blocks, bb->index);
699 /* Structure used by prune_unused_phi_nodes to record bounds of the intervals
700 in the dfs numbering of the dominance tree. */
702 struct dom_dfsnum
704 /* Basic block whose index this entry corresponds to. */
705 unsigned bb_index;
707 /* The dfs number of this node. */
708 unsigned dfs_num;
711 /* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback
712 for qsort. */
714 static int
715 cmp_dfsnum (const void *a, const void *b)
717 const struct dom_dfsnum *const da = (const struct dom_dfsnum *) a;
718 const struct dom_dfsnum *const db = (const struct dom_dfsnum *) b;
720 return (int) da->dfs_num - (int) db->dfs_num;
723 /* Among the intervals starting at the N points specified in DEFS, find
724 the one that contains S, and return its bb_index. */
726 static unsigned
727 find_dfsnum_interval (struct dom_dfsnum *defs, unsigned n, unsigned s)
729 unsigned f = 0, t = n, m;
731 while (t > f + 1)
733 m = (f + t) / 2;
734 if (defs[m].dfs_num <= s)
735 f = m;
736 else
737 t = m;
740 return defs[f].bb_index;
743 /* Clean bits from PHIS for phi nodes whose value cannot be used in USES.
744 KILLS is a bitmap of blocks where the value is defined before any use. */
746 static void
747 prune_unused_phi_nodes (bitmap phis, bitmap kills, bitmap uses)
749 bitmap_iterator bi;
750 unsigned i, b, p, u, top;
751 bitmap live_phis;
752 basic_block def_bb, use_bb;
753 edge e;
754 edge_iterator ei;
755 bitmap to_remove;
756 struct dom_dfsnum *defs;
757 unsigned n_defs, adef;
759 if (bitmap_empty_p (uses))
761 bitmap_clear (phis);
762 return;
765 /* The phi must dominate a use, or an argument of a live phi. Also, we
766 do not create any phi nodes in def blocks, unless they are also livein. */
767 to_remove = BITMAP_ALLOC (NULL);
768 bitmap_and_compl (to_remove, kills, uses);
769 bitmap_and_compl_into (phis, to_remove);
770 if (bitmap_empty_p (phis))
772 BITMAP_FREE (to_remove);
773 return;
776 /* We want to remove the unnecessary phi nodes, but we do not want to compute
777 liveness information, as that may be linear in the size of CFG, and if
778 there are lot of different variables to rewrite, this may lead to quadratic
779 behavior.
781 Instead, we basically emulate standard dce. We put all uses to worklist,
782 then for each of them find the nearest def that dominates them. If this
783 def is a phi node, we mark it live, and if it was not live before, we
784 add the predecessors of its basic block to the worklist.
786 To quickly locate the nearest def that dominates use, we use dfs numbering
787 of the dominance tree (that is already available in order to speed up
788 queries). For each def, we have the interval given by the dfs number on
789 entry to and on exit from the corresponding subtree in the dominance tree.
790 The nearest dominator for a given use is the smallest of these intervals
791 that contains entry and exit dfs numbers for the basic block with the use.
792 If we store the bounds for all the uses to an array and sort it, we can
793 locate the nearest dominating def in logarithmic time by binary search.*/
794 bitmap_ior (to_remove, kills, phis);
795 n_defs = bitmap_count_bits (to_remove);
796 defs = XNEWVEC (struct dom_dfsnum, 2 * n_defs + 1);
797 defs[0].bb_index = 1;
798 defs[0].dfs_num = 0;
799 adef = 1;
800 EXECUTE_IF_SET_IN_BITMAP (to_remove, 0, i, bi)
802 def_bb = BASIC_BLOCK_FOR_FN (cfun, i);
803 defs[adef].bb_index = i;
804 defs[adef].dfs_num = bb_dom_dfs_in (CDI_DOMINATORS, def_bb);
805 defs[adef + 1].bb_index = i;
806 defs[adef + 1].dfs_num = bb_dom_dfs_out (CDI_DOMINATORS, def_bb);
807 adef += 2;
809 BITMAP_FREE (to_remove);
810 gcc_assert (adef == 2 * n_defs + 1);
811 qsort (defs, adef, sizeof (struct dom_dfsnum), cmp_dfsnum);
812 gcc_assert (defs[0].bb_index == 1);
814 /* Now each DEFS entry contains the number of the basic block to that the
815 dfs number corresponds. Change them to the number of basic block that
816 corresponds to the interval following the dfs number. Also, for the
817 dfs_out numbers, increase the dfs number by one (so that it corresponds
818 to the start of the following interval, not to the end of the current
819 one). We use WORKLIST as a stack. */
820 auto_vec<int> worklist (n_defs + 1);
821 worklist.quick_push (1);
822 top = 1;
823 n_defs = 1;
824 for (i = 1; i < adef; i++)
826 b = defs[i].bb_index;
827 if (b == top)
829 /* This is a closing element. Interval corresponding to the top
830 of the stack after removing it follows. */
831 worklist.pop ();
832 top = worklist[worklist.length () - 1];
833 defs[n_defs].bb_index = top;
834 defs[n_defs].dfs_num = defs[i].dfs_num + 1;
836 else
838 /* Opening element. Nothing to do, just push it to the stack and move
839 it to the correct position. */
840 defs[n_defs].bb_index = defs[i].bb_index;
841 defs[n_defs].dfs_num = defs[i].dfs_num;
842 worklist.quick_push (b);
843 top = b;
846 /* If this interval starts at the same point as the previous one, cancel
847 the previous one. */
848 if (defs[n_defs].dfs_num == defs[n_defs - 1].dfs_num)
849 defs[n_defs - 1].bb_index = defs[n_defs].bb_index;
850 else
851 n_defs++;
853 worklist.pop ();
854 gcc_assert (worklist.is_empty ());
856 /* Now process the uses. */
857 live_phis = BITMAP_ALLOC (NULL);
858 EXECUTE_IF_SET_IN_BITMAP (uses, 0, i, bi)
860 worklist.safe_push (i);
863 while (!worklist.is_empty ())
865 b = worklist.pop ();
866 if (b == ENTRY_BLOCK)
867 continue;
869 /* If there is a phi node in USE_BB, it is made live. Otherwise,
870 find the def that dominates the immediate dominator of USE_BB
871 (the kill in USE_BB does not dominate the use). */
872 if (bitmap_bit_p (phis, b))
873 p = b;
874 else
876 use_bb = get_immediate_dominator (CDI_DOMINATORS,
877 BASIC_BLOCK_FOR_FN (cfun, b));
878 p = find_dfsnum_interval (defs, n_defs,
879 bb_dom_dfs_in (CDI_DOMINATORS, use_bb));
880 if (!bitmap_bit_p (phis, p))
881 continue;
884 /* If the phi node is already live, there is nothing to do. */
885 if (!bitmap_set_bit (live_phis, p))
886 continue;
888 /* Add the new uses to the worklist. */
889 def_bb = BASIC_BLOCK_FOR_FN (cfun, p);
890 FOR_EACH_EDGE (e, ei, def_bb->preds)
892 u = e->src->index;
893 if (bitmap_bit_p (uses, u))
894 continue;
896 /* In case there is a kill directly in the use block, do not record
897 the use (this is also necessary for correctness, as we assume that
898 uses dominated by a def directly in their block have been filtered
899 out before). */
900 if (bitmap_bit_p (kills, u))
901 continue;
903 bitmap_set_bit (uses, u);
904 worklist.safe_push (u);
908 bitmap_copy (phis, live_phis);
909 BITMAP_FREE (live_phis);
910 free (defs);
913 /* Return the set of blocks where variable VAR is defined and the blocks
914 where VAR is live on entry (livein). Return NULL, if no entry is
915 found in DEF_BLOCKS. */
917 static inline def_blocks *
918 find_def_blocks_for (tree var)
920 def_blocks *p = &get_common_info (var)->def_blocks;
921 if (!p->def_blocks)
922 return NULL;
923 return p;
927 /* Marks phi node PHI in basic block BB for rewrite. */
929 static void
930 mark_phi_for_rewrite (basic_block bb, gphi *phi)
932 vec<gphi *> phis;
933 unsigned n, idx = bb->index;
935 if (rewrite_uses_p (phi))
936 return;
938 set_rewrite_uses (phi, true);
940 if (!blocks_with_phis_to_rewrite)
941 return;
943 bitmap_set_bit (blocks_with_phis_to_rewrite, idx);
945 n = (unsigned) last_basic_block_for_fn (cfun) + 1;
946 if (phis_to_rewrite.length () < n)
947 phis_to_rewrite.safe_grow_cleared (n);
949 phis = phis_to_rewrite[idx];
950 phis.reserve (10);
952 phis.safe_push (phi);
953 phis_to_rewrite[idx] = phis;
956 /* Insert PHI nodes for variable VAR using the iterated dominance
957 frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
958 function assumes that the caller is incrementally updating the
959 existing SSA form, in which case VAR may be an SSA name instead of
960 a symbol.
962 PHI_INSERTION_POINTS is updated to reflect nodes that already had a
963 PHI node for VAR. On exit, only the nodes that received a PHI node
964 for VAR will be present in PHI_INSERTION_POINTS. */
966 static void
967 insert_phi_nodes_for (tree var, bitmap phi_insertion_points, bool update_p)
969 unsigned bb_index;
970 edge e;
971 gphi *phi;
972 basic_block bb;
973 bitmap_iterator bi;
974 def_blocks *def_map = find_def_blocks_for (var);
976 /* Remove the blocks where we already have PHI nodes for VAR. */
977 bitmap_and_compl_into (phi_insertion_points, def_map->phi_blocks);
979 /* Remove obviously useless phi nodes. */
980 prune_unused_phi_nodes (phi_insertion_points, def_map->def_blocks,
981 def_map->livein_blocks);
983 /* And insert the PHI nodes. */
984 EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points, 0, bb_index, bi)
986 bb = BASIC_BLOCK_FOR_FN (cfun, bb_index);
987 if (update_p)
988 mark_block_for_update (bb);
990 if (dump_file && (dump_flags & TDF_DETAILS))
992 fprintf (dump_file, "creating PHI node in block #%d for ", bb_index);
993 print_generic_expr (dump_file, var, TDF_SLIM);
994 fprintf (dump_file, "\n");
996 phi = NULL;
998 if (TREE_CODE (var) == SSA_NAME)
1000 /* If we are rewriting SSA names, create the LHS of the PHI
1001 node by duplicating VAR. This is useful in the case of
1002 pointers, to also duplicate pointer attributes (alias
1003 information, in particular). */
1004 edge_iterator ei;
1005 tree new_lhs;
1007 gcc_checking_assert (update_p);
1008 new_lhs = duplicate_ssa_name (var, NULL);
1009 phi = create_phi_node (new_lhs, bb);
1010 add_new_name_mapping (new_lhs, var);
1012 /* Add VAR to every argument slot of PHI. We need VAR in
1013 every argument so that rewrite_update_phi_arguments knows
1014 which name is this PHI node replacing. If VAR is a
1015 symbol marked for renaming, this is not necessary, the
1016 renamer will use the symbol on the LHS to get its
1017 reaching definition. */
1018 FOR_EACH_EDGE (e, ei, bb->preds)
1019 add_phi_arg (phi, var, e, UNKNOWN_LOCATION);
1021 else
1023 tree tracked_var;
1025 gcc_checking_assert (DECL_P (var));
1026 phi = create_phi_node (var, bb);
1028 tracked_var = target_for_debug_bind (var);
1029 if (tracked_var)
1031 gimple *note = gimple_build_debug_bind (tracked_var,
1032 PHI_RESULT (phi),
1033 phi);
1034 gimple_stmt_iterator si = gsi_after_labels (bb);
1035 gsi_insert_before (&si, note, GSI_SAME_STMT);
1039 /* Mark this PHI node as interesting for update_ssa. */
1040 set_register_defs (phi, true);
1041 mark_phi_for_rewrite (bb, phi);
1045 /* Sort var_infos after DECL_UID of their var. */
1047 static int
1048 insert_phi_nodes_compare_var_infos (const void *a, const void *b)
1050 const var_info *defa = *(var_info * const *)a;
1051 const var_info *defb = *(var_info * const *)b;
1052 if (DECL_UID (defa->var) < DECL_UID (defb->var))
1053 return -1;
1054 else
1055 return 1;
1058 /* Insert PHI nodes at the dominance frontier of blocks with variable
1059 definitions. DFS contains the dominance frontier information for
1060 the flowgraph. */
1062 static void
1063 insert_phi_nodes (bitmap_head *dfs)
1065 hash_table<var_info_hasher>::iterator hi;
1066 unsigned i;
1067 var_info *info;
1069 timevar_push (TV_TREE_INSERT_PHI_NODES);
1071 /* When the gimplifier introduces SSA names it cannot easily avoid
1072 situations where abnormal edges added by CFG construction break
1073 the use-def dominance requirement. For this case rewrite SSA
1074 names with broken use-def dominance out-of-SSA and register them
1075 for PHI insertion. We only need to do this if abnormal edges
1076 can appear in the function. */
1077 tree name;
1078 if (cfun->calls_setjmp
1079 || cfun->has_nonlocal_label)
1080 FOR_EACH_SSA_NAME (i, name, cfun)
1082 gimple *def_stmt = SSA_NAME_DEF_STMT (name);
1083 if (SSA_NAME_IS_DEFAULT_DEF (name))
1084 continue;
1086 basic_block def_bb = gimple_bb (def_stmt);
1087 imm_use_iterator it;
1088 gimple *use_stmt;
1089 bool need_phis = false;
1090 FOR_EACH_IMM_USE_STMT (use_stmt, it, name)
1092 basic_block use_bb = gimple_bb (use_stmt);
1093 if (use_bb != def_bb
1094 && ! dominated_by_p (CDI_DOMINATORS, use_bb, def_bb))
1095 need_phis = true;
1097 if (need_phis)
1099 tree var = create_tmp_reg (TREE_TYPE (name));
1100 use_operand_p use_p;
1101 FOR_EACH_IMM_USE_STMT (use_stmt, it, name)
1103 basic_block use_bb = gimple_bb (use_stmt);
1104 FOR_EACH_IMM_USE_ON_STMT (use_p, it)
1105 SET_USE (use_p, var);
1106 update_stmt (use_stmt);
1107 set_livein_block (var, use_bb);
1108 set_rewrite_uses (use_stmt, true);
1109 bitmap_set_bit (interesting_blocks, use_bb->index);
1111 def_operand_p def_p;
1112 ssa_op_iter dit;
1113 FOR_EACH_SSA_DEF_OPERAND (def_p, def_stmt, dit, SSA_OP_DEF)
1114 if (DEF_FROM_PTR (def_p) == name)
1115 SET_DEF (def_p, var);
1116 update_stmt (def_stmt);
1117 set_def_block (var, def_bb, false);
1118 set_register_defs (def_stmt, true);
1119 bitmap_set_bit (interesting_blocks, def_bb->index);
1120 release_ssa_name (name);
1124 auto_vec<var_info *> vars (var_infos->elements ());
1125 FOR_EACH_HASH_TABLE_ELEMENT (*var_infos, info, var_info_p, hi)
1126 if (info->info.need_phi_state != NEED_PHI_STATE_NO)
1127 vars.quick_push (info);
1129 /* Do two stages to avoid code generation differences for UID
1130 differences but no UID ordering differences. */
1131 vars.qsort (insert_phi_nodes_compare_var_infos);
1133 FOR_EACH_VEC_ELT (vars, i, info)
1135 bitmap idf = compute_idf (info->info.def_blocks.def_blocks, dfs);
1136 insert_phi_nodes_for (info->var, idf, false);
1137 BITMAP_FREE (idf);
1140 timevar_pop (TV_TREE_INSERT_PHI_NODES);
1144 /* Push SYM's current reaching definition into BLOCK_DEFS_STACK and
1145 register DEF (an SSA_NAME) to be a new definition for SYM. */
1147 static void
1148 register_new_def (tree def, tree sym)
1150 common_info *info = get_common_info (sym);
1151 tree currdef;
1153 /* If this variable is set in a single basic block and all uses are
1154 dominated by the set(s) in that single basic block, then there is
1155 no reason to record anything for this variable in the block local
1156 definition stacks. Doing so just wastes time and memory.
1158 This is the same test to prune the set of variables which may
1159 need PHI nodes. So we just use that information since it's already
1160 computed and available for us to use. */
1161 if (info->need_phi_state == NEED_PHI_STATE_NO)
1163 info->current_def = def;
1164 return;
1167 currdef = info->current_def;
1169 /* If SYM is not a GIMPLE register, then CURRDEF may be a name whose
1170 SSA_NAME_VAR is not necessarily SYM. In this case, also push SYM
1171 in the stack so that we know which symbol is being defined by
1172 this SSA name when we unwind the stack. */
1173 if (currdef && !is_gimple_reg (sym))
1174 block_defs_stack.safe_push (sym);
1176 /* Push the current reaching definition into BLOCK_DEFS_STACK. This
1177 stack is later used by the dominator tree callbacks to restore
1178 the reaching definitions for all the variables defined in the
1179 block after a recursive visit to all its immediately dominated
1180 blocks. If there is no current reaching definition, then just
1181 record the underlying _DECL node. */
1182 block_defs_stack.safe_push (currdef ? currdef : sym);
1184 /* Set the current reaching definition for SYM to be DEF. */
1185 info->current_def = def;
1189 /* Perform a depth-first traversal of the dominator tree looking for
1190 variables to rename. BB is the block where to start searching.
1191 Renaming is a five step process:
1193 1- Every definition made by PHI nodes at the start of the blocks is
1194 registered as the current definition for the corresponding variable.
1196 2- Every statement in BB is rewritten. USE and VUSE operands are
1197 rewritten with their corresponding reaching definition. DEF and
1198 VDEF targets are registered as new definitions.
1200 3- All the PHI nodes in successor blocks of BB are visited. The
1201 argument corresponding to BB is replaced with its current reaching
1202 definition.
1204 4- Recursively rewrite every dominator child block of BB.
1206 5- Restore (in reverse order) the current reaching definition for every
1207 new definition introduced in this block. This is done so that when
1208 we return from the recursive call, all the current reaching
1209 definitions are restored to the names that were valid in the
1210 dominator parent of BB. */
1212 /* Return the current definition for variable VAR. If none is found,
1213 create a new SSA name to act as the zeroth definition for VAR. */
1215 static tree
1216 get_reaching_def (tree var)
1218 common_info *info = get_common_info (var);
1219 tree currdef;
1221 /* Lookup the current reaching definition for VAR. */
1222 currdef = info->current_def;
1224 /* If there is no reaching definition for VAR, create and register a
1225 default definition for it (if needed). */
1226 if (currdef == NULL_TREE)
1228 tree sym = DECL_P (var) ? var : SSA_NAME_VAR (var);
1229 if (! sym)
1230 sym = create_tmp_reg (TREE_TYPE (var));
1231 currdef = get_or_create_ssa_default_def (cfun, sym);
1234 /* Return the current reaching definition for VAR, or the default
1235 definition, if we had to create one. */
1236 return currdef;
1240 /* Helper function for rewrite_stmt. Rewrite uses in a debug stmt. */
1242 static void
1243 rewrite_debug_stmt_uses (gimple *stmt)
1245 use_operand_p use_p;
1246 ssa_op_iter iter;
1247 bool update = false;
1249 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
1251 tree var = USE_FROM_PTR (use_p), def;
1252 common_info *info = get_common_info (var);
1253 gcc_checking_assert (DECL_P (var));
1254 def = info->current_def;
1255 if (!def)
1257 if (TREE_CODE (var) == PARM_DECL
1258 && single_succ_p (ENTRY_BLOCK_PTR_FOR_FN (cfun)))
1260 gimple_stmt_iterator gsi
1262 gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
1263 int lim;
1264 /* Search a few source bind stmts at the start of first bb to
1265 see if a DEBUG_EXPR_DECL can't be reused. */
1266 for (lim = 32;
1267 !gsi_end_p (gsi) && lim > 0;
1268 gsi_next (&gsi), lim--)
1270 gimple *gstmt = gsi_stmt (gsi);
1271 if (!gimple_debug_source_bind_p (gstmt))
1272 break;
1273 if (gimple_debug_source_bind_get_value (gstmt) == var)
1275 def = gimple_debug_source_bind_get_var (gstmt);
1276 if (TREE_CODE (def) == DEBUG_EXPR_DECL)
1277 break;
1278 else
1279 def = NULL_TREE;
1282 /* If not, add a new source bind stmt. */
1283 if (def == NULL_TREE)
1285 gimple *def_temp;
1286 def = make_node (DEBUG_EXPR_DECL);
1287 def_temp = gimple_build_debug_source_bind (def, var, NULL);
1288 DECL_ARTIFICIAL (def) = 1;
1289 TREE_TYPE (def) = TREE_TYPE (var);
1290 SET_DECL_MODE (def, DECL_MODE (var));
1291 gsi =
1292 gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun)));
1293 gsi_insert_before (&gsi, def_temp, GSI_SAME_STMT);
1295 update = true;
1298 else
1300 /* Check if info->current_def can be trusted. */
1301 basic_block bb = gimple_bb (stmt);
1302 basic_block def_bb
1303 = SSA_NAME_IS_DEFAULT_DEF (def)
1304 ? NULL : gimple_bb (SSA_NAME_DEF_STMT (def));
1306 /* If definition is in current bb, it is fine. */
1307 if (bb == def_bb)
1309 /* If definition bb doesn't dominate the current bb,
1310 it can't be used. */
1311 else if (def_bb && !dominated_by_p (CDI_DOMINATORS, bb, def_bb))
1312 def = NULL;
1313 /* If there is just one definition and dominates the current
1314 bb, it is fine. */
1315 else if (info->need_phi_state == NEED_PHI_STATE_NO)
1317 else
1319 def_blocks *db_p = get_def_blocks_for (info);
1321 /* If there are some non-debug uses in the current bb,
1322 it is fine. */
1323 if (bitmap_bit_p (db_p->livein_blocks, bb->index))
1325 /* Otherwise give up for now. */
1326 else
1327 def = NULL;
1330 if (def == NULL)
1332 gimple_debug_bind_reset_value (stmt);
1333 update_stmt (stmt);
1334 return;
1336 SET_USE (use_p, def);
1338 if (update)
1339 update_stmt (stmt);
1342 /* SSA Rewriting Step 2. Rewrite every variable used in each statement in
1343 the block with its immediate reaching definitions. Update the current
1344 definition of a variable when a new real or virtual definition is found. */
1346 static void
1347 rewrite_stmt (gimple_stmt_iterator *si)
1349 use_operand_p use_p;
1350 def_operand_p def_p;
1351 ssa_op_iter iter;
1352 gimple *stmt = gsi_stmt (*si);
1354 /* If mark_def_sites decided that we don't need to rewrite this
1355 statement, ignore it. */
1356 gcc_assert (blocks_to_update == NULL);
1357 if (!rewrite_uses_p (stmt) && !register_defs_p (stmt))
1358 return;
1360 if (dump_file && (dump_flags & TDF_DETAILS))
1362 fprintf (dump_file, "Renaming statement ");
1363 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
1364 fprintf (dump_file, "\n");
1367 /* Step 1. Rewrite USES in the statement. */
1368 if (rewrite_uses_p (stmt))
1370 if (is_gimple_debug (stmt))
1371 rewrite_debug_stmt_uses (stmt);
1372 else
1373 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
1375 tree var = USE_FROM_PTR (use_p);
1376 if (TREE_CODE (var) == SSA_NAME)
1377 continue;
1378 gcc_checking_assert (DECL_P (var));
1379 SET_USE (use_p, get_reaching_def (var));
1383 /* Step 2. Register the statement's DEF operands. */
1384 if (register_defs_p (stmt))
1385 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
1387 tree var = DEF_FROM_PTR (def_p);
1388 tree name;
1389 tree tracked_var;
1391 if (TREE_CODE (var) == SSA_NAME)
1392 continue;
1393 gcc_checking_assert (DECL_P (var));
1395 if (gimple_clobber_p (stmt)
1396 && is_gimple_reg (var))
1398 /* If we rewrite a DECL into SSA form then drop its
1399 clobber stmts and replace uses with a new default def. */
1400 gcc_checking_assert (VAR_P (var) && !gimple_vdef (stmt));
1401 gsi_replace (si, gimple_build_nop (), true);
1402 register_new_def (get_or_create_ssa_default_def (cfun, var), var);
1403 break;
1406 name = make_ssa_name (var, stmt);
1407 SET_DEF (def_p, name);
1408 register_new_def (DEF_FROM_PTR (def_p), var);
1410 tracked_var = target_for_debug_bind (var);
1411 if (tracked_var)
1413 gimple *note = gimple_build_debug_bind (tracked_var, name, stmt);
1414 gsi_insert_after (si, note, GSI_SAME_STMT);
1420 /* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for
1421 PHI nodes. For every PHI node found, add a new argument containing the
1422 current reaching definition for the variable and the edge through which
1423 that definition is reaching the PHI node. */
1425 static void
1426 rewrite_add_phi_arguments (basic_block bb)
1428 edge e;
1429 edge_iterator ei;
1431 FOR_EACH_EDGE (e, ei, bb->succs)
1433 gphi *phi;
1434 gphi_iterator gsi;
1436 for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi);
1437 gsi_next (&gsi))
1439 tree currdef, res, argvar;
1440 location_t loc;
1442 phi = gsi.phi ();
1443 res = gimple_phi_result (phi);
1444 /* If we have pre-existing PHI (via the GIMPLE FE) its args may
1445 be different vars than existing vars and they may be constants
1446 as well. Note the following supports partial SSA for PHI args. */
1447 argvar = gimple_phi_arg_def (phi, e->dest_idx);
1448 if (argvar && ! DECL_P (argvar))
1449 continue;
1450 if (!argvar)
1451 argvar = SSA_NAME_VAR (res);
1452 currdef = get_reaching_def (argvar);
1453 /* Virtual operand PHI args do not need a location. */
1454 if (virtual_operand_p (res))
1455 loc = UNKNOWN_LOCATION;
1456 else
1457 loc = gimple_location (SSA_NAME_DEF_STMT (currdef));
1458 add_phi_arg (phi, currdef, e, loc);
1463 class rewrite_dom_walker : public dom_walker
1465 public:
1466 rewrite_dom_walker (cdi_direction direction)
1467 : dom_walker (direction, ALL_BLOCKS, NULL) {}
1469 virtual edge before_dom_children (basic_block);
1470 virtual void after_dom_children (basic_block);
1473 /* SSA Rewriting Step 1. Initialization, create a block local stack
1474 of reaching definitions for new SSA names produced in this block
1475 (BLOCK_DEFS). Register new definitions for every PHI node in the
1476 block. */
1478 edge
1479 rewrite_dom_walker::before_dom_children (basic_block bb)
1481 if (dump_file && (dump_flags & TDF_DETAILS))
1482 fprintf (dump_file, "\n\nRenaming block #%d\n\n", bb->index);
1484 /* Mark the unwind point for this block. */
1485 block_defs_stack.safe_push (NULL_TREE);
1487 /* Step 1. Register new definitions for every PHI node in the block.
1488 Conceptually, all the PHI nodes are executed in parallel and each PHI
1489 node introduces a new version for the associated variable. */
1490 for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
1491 gsi_next (&gsi))
1493 tree result = gimple_phi_result (gsi_stmt (gsi));
1494 register_new_def (result, SSA_NAME_VAR (result));
1497 /* Step 2. Rewrite every variable used in each statement in the block
1498 with its immediate reaching definitions. Update the current definition
1499 of a variable when a new real or virtual definition is found. */
1500 if (bitmap_bit_p (interesting_blocks, bb->index))
1501 for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi);
1502 gsi_next (&gsi))
1503 rewrite_stmt (&gsi);
1505 /* Step 3. Visit all the successor blocks of BB looking for PHI nodes.
1506 For every PHI node found, add a new argument containing the current
1507 reaching definition for the variable and the edge through which that
1508 definition is reaching the PHI node. */
1509 rewrite_add_phi_arguments (bb);
1511 return NULL;
1516 /* Called after visiting all the statements in basic block BB and all
1517 of its dominator children. Restore CURRDEFS to its original value. */
1519 void
1520 rewrite_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED)
1522 /* Restore CURRDEFS to its original state. */
1523 while (block_defs_stack.length () > 0)
1525 tree tmp = block_defs_stack.pop ();
1526 tree saved_def, var;
1528 if (tmp == NULL_TREE)
1529 break;
1531 if (TREE_CODE (tmp) == SSA_NAME)
1533 /* If we recorded an SSA_NAME, then make the SSA_NAME the
1534 current definition of its underlying variable. Note that
1535 if the SSA_NAME is not for a GIMPLE register, the symbol
1536 being defined is stored in the next slot in the stack.
1537 This mechanism is needed because an SSA name for a
1538 non-register symbol may be the definition for more than
1539 one symbol (e.g., SFTs, aliased variables, etc). */
1540 saved_def = tmp;
1541 var = SSA_NAME_VAR (saved_def);
1542 if (!is_gimple_reg (var))
1543 var = block_defs_stack.pop ();
1545 else
1547 /* If we recorded anything else, it must have been a _DECL
1548 node and its current reaching definition must have been
1549 NULL. */
1550 saved_def = NULL;
1551 var = tmp;
1554 get_common_info (var)->current_def = saved_def;
1559 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1561 DEBUG_FUNCTION void
1562 debug_decl_set (bitmap set)
1564 dump_decl_set (stderr, set);
1565 fprintf (stderr, "\n");
1569 /* Dump the renaming stack (block_defs_stack) to FILE. Traverse the
1570 stack up to a maximum of N levels. If N is -1, the whole stack is
1571 dumped. New levels are created when the dominator tree traversal
1572 used for renaming enters a new sub-tree. */
1574 void
1575 dump_defs_stack (FILE *file, int n)
1577 int i, j;
1579 fprintf (file, "\n\nRenaming stack");
1580 if (n > 0)
1581 fprintf (file, " (up to %d levels)", n);
1582 fprintf (file, "\n\n");
1584 i = 1;
1585 fprintf (file, "Level %d (current level)\n", i);
1586 for (j = (int) block_defs_stack.length () - 1; j >= 0; j--)
1588 tree name, var;
1590 name = block_defs_stack[j];
1591 if (name == NULL_TREE)
1593 i++;
1594 if (n > 0 && i > n)
1595 break;
1596 fprintf (file, "\nLevel %d\n", i);
1597 continue;
1600 if (DECL_P (name))
1602 var = name;
1603 name = NULL_TREE;
1605 else
1607 var = SSA_NAME_VAR (name);
1608 if (!is_gimple_reg (var))
1610 j--;
1611 var = block_defs_stack[j];
1615 fprintf (file, " Previous CURRDEF (");
1616 print_generic_expr (file, var);
1617 fprintf (file, ") = ");
1618 if (name)
1619 print_generic_expr (file, name);
1620 else
1621 fprintf (file, "<NIL>");
1622 fprintf (file, "\n");
1627 /* Dump the renaming stack (block_defs_stack) to stderr. Traverse the
1628 stack up to a maximum of N levels. If N is -1, the whole stack is
1629 dumped. New levels are created when the dominator tree traversal
1630 used for renaming enters a new sub-tree. */
1632 DEBUG_FUNCTION void
1633 debug_defs_stack (int n)
1635 dump_defs_stack (stderr, n);
1639 /* Dump the current reaching definition of every symbol to FILE. */
1641 void
1642 dump_currdefs (FILE *file)
1644 unsigned i;
1645 tree var;
1647 if (symbols_to_rename.is_empty ())
1648 return;
1650 fprintf (file, "\n\nCurrent reaching definitions\n\n");
1651 FOR_EACH_VEC_ELT (symbols_to_rename, i, var)
1653 common_info *info = get_common_info (var);
1654 fprintf (file, "CURRDEF (");
1655 print_generic_expr (file, var);
1656 fprintf (file, ") = ");
1657 if (info->current_def)
1658 print_generic_expr (file, info->current_def);
1659 else
1660 fprintf (file, "<NIL>");
1661 fprintf (file, "\n");
1666 /* Dump the current reaching definition of every symbol to stderr. */
1668 DEBUG_FUNCTION void
1669 debug_currdefs (void)
1671 dump_currdefs (stderr);
1675 /* Dump SSA information to FILE. */
1677 void
1678 dump_tree_ssa (FILE *file)
1680 const char *funcname
1681 = lang_hooks.decl_printable_name (current_function_decl, 2);
1683 fprintf (file, "SSA renaming information for %s\n\n", funcname);
1685 dump_var_infos (file);
1686 dump_defs_stack (file, -1);
1687 dump_currdefs (file);
1688 dump_tree_ssa_stats (file);
1692 /* Dump SSA information to stderr. */
1694 DEBUG_FUNCTION void
1695 debug_tree_ssa (void)
1697 dump_tree_ssa (stderr);
1701 /* Dump statistics for the hash table HTAB. */
1703 static void
1704 htab_statistics (FILE *file, const hash_table<var_info_hasher> &htab)
1706 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1707 (long) htab.size (),
1708 (long) htab.elements (),
1709 htab.collisions ());
1713 /* Dump SSA statistics on FILE. */
1715 void
1716 dump_tree_ssa_stats (FILE *file)
1718 if (var_infos)
1720 fprintf (file, "\nHash table statistics:\n");
1721 fprintf (file, " var_infos: ");
1722 htab_statistics (file, *var_infos);
1723 fprintf (file, "\n");
1728 /* Dump SSA statistics on stderr. */
1730 DEBUG_FUNCTION void
1731 debug_tree_ssa_stats (void)
1733 dump_tree_ssa_stats (stderr);
1737 /* Callback for htab_traverse to dump the VAR_INFOS hash table. */
1740 debug_var_infos_r (var_info **slot, FILE *file)
1742 var_info *info = *slot;
1744 fprintf (file, "VAR: ");
1745 print_generic_expr (file, info->var, dump_flags);
1746 bitmap_print (file, info->info.def_blocks.def_blocks,
1747 ", DEF_BLOCKS: { ", "}");
1748 bitmap_print (file, info->info.def_blocks.livein_blocks,
1749 ", LIVEIN_BLOCKS: { ", "}");
1750 bitmap_print (file, info->info.def_blocks.phi_blocks,
1751 ", PHI_BLOCKS: { ", "}\n");
1753 return 1;
1757 /* Dump the VAR_INFOS hash table on FILE. */
1759 void
1760 dump_var_infos (FILE *file)
1762 fprintf (file, "\n\nDefinition and live-in blocks:\n\n");
1763 if (var_infos)
1764 var_infos->traverse <FILE *, debug_var_infos_r> (file);
1768 /* Dump the VAR_INFOS hash table on stderr. */
1770 DEBUG_FUNCTION void
1771 debug_var_infos (void)
1773 dump_var_infos (stderr);
1777 /* Register NEW_NAME to be the new reaching definition for OLD_NAME. */
1779 static inline void
1780 register_new_update_single (tree new_name, tree old_name)
1782 common_info *info = get_common_info (old_name);
1783 tree currdef = info->current_def;
1785 /* Push the current reaching definition into BLOCK_DEFS_STACK.
1786 This stack is later used by the dominator tree callbacks to
1787 restore the reaching definitions for all the variables
1788 defined in the block after a recursive visit to all its
1789 immediately dominated blocks. */
1790 block_defs_stack.reserve (2);
1791 block_defs_stack.quick_push (currdef);
1792 block_defs_stack.quick_push (old_name);
1794 /* Set the current reaching definition for OLD_NAME to be
1795 NEW_NAME. */
1796 info->current_def = new_name;
1800 /* Register NEW_NAME to be the new reaching definition for all the
1801 names in OLD_NAMES. Used by the incremental SSA update routines to
1802 replace old SSA names with new ones. */
1804 static inline void
1805 register_new_update_set (tree new_name, bitmap old_names)
1807 bitmap_iterator bi;
1808 unsigned i;
1810 EXECUTE_IF_SET_IN_BITMAP (old_names, 0, i, bi)
1811 register_new_update_single (new_name, ssa_name (i));
1816 /* If the operand pointed to by USE_P is a name in OLD_SSA_NAMES or
1817 it is a symbol marked for renaming, replace it with USE_P's current
1818 reaching definition. */
1820 static inline void
1821 maybe_replace_use (use_operand_p use_p)
1823 tree rdef = NULL_TREE;
1824 tree use = USE_FROM_PTR (use_p);
1825 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
1827 if (marked_for_renaming (sym))
1828 rdef = get_reaching_def (sym);
1829 else if (is_old_name (use))
1830 rdef = get_reaching_def (use);
1832 if (rdef && rdef != use)
1833 SET_USE (use_p, rdef);
1837 /* Same as maybe_replace_use, but without introducing default stmts,
1838 returning false to indicate a need to do so. */
1840 static inline bool
1841 maybe_replace_use_in_debug_stmt (use_operand_p use_p)
1843 tree rdef = NULL_TREE;
1844 tree use = USE_FROM_PTR (use_p);
1845 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
1847 if (marked_for_renaming (sym))
1848 rdef = get_var_info (sym)->info.current_def;
1849 else if (is_old_name (use))
1851 rdef = get_ssa_name_ann (use)->info.current_def;
1852 /* We can't assume that, if there's no current definition, the
1853 default one should be used. It could be the case that we've
1854 rearranged blocks so that the earlier definition no longer
1855 dominates the use. */
1856 if (!rdef && SSA_NAME_IS_DEFAULT_DEF (use))
1857 rdef = use;
1859 else
1860 rdef = use;
1862 if (rdef && rdef != use)
1863 SET_USE (use_p, rdef);
1865 return rdef != NULL_TREE;
1869 /* If DEF has x_5 = ASAN_POISON () as its current def, add
1870 ASAN_POISON_USE (x_5) stmt before GSI to denote the stmt writes into
1871 a poisoned (out of scope) variable. */
1873 static void
1874 maybe_add_asan_poison_write (tree def, gimple_stmt_iterator *gsi)
1876 tree cdef = get_current_def (def);
1877 if (cdef != NULL
1878 && TREE_CODE (cdef) == SSA_NAME
1879 && gimple_call_internal_p (SSA_NAME_DEF_STMT (cdef), IFN_ASAN_POISON))
1881 gcall *call
1882 = gimple_build_call_internal (IFN_ASAN_POISON_USE, 1, cdef);
1883 gimple_set_location (call, gimple_location (gsi_stmt (*gsi)));
1884 gsi_insert_before (gsi, call, GSI_SAME_STMT);
1889 /* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
1890 or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
1891 register it as the current definition for the names replaced by
1892 DEF_P. Returns whether the statement should be removed. */
1894 static inline bool
1895 maybe_register_def (def_operand_p def_p, gimple *stmt,
1896 gimple_stmt_iterator gsi)
1898 tree def = DEF_FROM_PTR (def_p);
1899 tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
1900 bool to_delete = false;
1902 /* If DEF is a naked symbol that needs renaming, create a new
1903 name for it. */
1904 if (marked_for_renaming (sym))
1906 if (DECL_P (def))
1908 if (gimple_clobber_p (stmt) && is_gimple_reg (sym))
1910 gcc_checking_assert (VAR_P (sym));
1911 /* Replace clobber stmts with a default def. This new use of a
1912 default definition may make it look like SSA_NAMEs have
1913 conflicting lifetimes, so we need special code to let them
1914 coalesce properly. */
1915 to_delete = true;
1916 def = get_or_create_ssa_default_def (cfun, sym);
1918 else
1920 if (asan_sanitize_use_after_scope ())
1921 maybe_add_asan_poison_write (def, &gsi);
1922 def = make_ssa_name (def, stmt);
1924 SET_DEF (def_p, def);
1926 tree tracked_var = target_for_debug_bind (sym);
1927 if (tracked_var)
1929 gimple *note = gimple_build_debug_bind (tracked_var, def, stmt);
1930 /* If stmt ends the bb, insert the debug stmt on the single
1931 non-EH edge from the stmt. */
1932 if (gsi_one_before_end_p (gsi) && stmt_ends_bb_p (stmt))
1934 basic_block bb = gsi_bb (gsi);
1935 edge_iterator ei;
1936 edge e, ef = NULL;
1937 FOR_EACH_EDGE (e, ei, bb->succs)
1938 if (!(e->flags & EDGE_EH))
1940 gcc_checking_assert (!ef);
1941 ef = e;
1943 /* If there are other predecessors to ef->dest, then
1944 there must be PHI nodes for the modified
1945 variable, and therefore there will be debug bind
1946 stmts after the PHI nodes. The debug bind notes
1947 we'd insert would force the creation of a new
1948 block (diverging codegen) and be redundant with
1949 the post-PHI bind stmts, so don't add them.
1951 As for the exit edge, there wouldn't be redundant
1952 bind stmts, but there wouldn't be a PC to bind
1953 them to either, so avoid diverging the CFG. */
1954 if (ef && single_pred_p (ef->dest)
1955 && ef->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
1957 /* If there were PHI nodes in the node, we'd
1958 have to make sure the value we're binding
1959 doesn't need rewriting. But there shouldn't
1960 be PHI nodes in a single-predecessor block,
1961 so we just add the note. */
1962 gsi_insert_on_edge_immediate (ef, note);
1965 else
1966 gsi_insert_after (&gsi, note, GSI_SAME_STMT);
1970 register_new_update_single (def, sym);
1972 else
1974 /* If DEF is a new name, register it as a new definition
1975 for all the names replaced by DEF. */
1976 if (is_new_name (def))
1977 register_new_update_set (def, names_replaced_by (def));
1979 /* If DEF is an old name, register DEF as a new
1980 definition for itself. */
1981 if (is_old_name (def))
1982 register_new_update_single (def, def);
1985 return to_delete;
1989 /* Update every variable used in the statement pointed-to by SI. The
1990 statement is assumed to be in SSA form already. Names in
1991 OLD_SSA_NAMES used by SI will be updated to their current reaching
1992 definition. Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI
1993 will be registered as a new definition for their corresponding name
1994 in OLD_SSA_NAMES. Returns whether STMT should be removed. */
1996 static bool
1997 rewrite_update_stmt (gimple *stmt, gimple_stmt_iterator gsi)
1999 use_operand_p use_p;
2000 def_operand_p def_p;
2001 ssa_op_iter iter;
2003 /* Only update marked statements. */
2004 if (!rewrite_uses_p (stmt) && !register_defs_p (stmt))
2005 return false;
2007 if (dump_file && (dump_flags & TDF_DETAILS))
2009 fprintf (dump_file, "Updating SSA information for statement ");
2010 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
2013 /* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying
2014 symbol is marked for renaming. */
2015 if (rewrite_uses_p (stmt))
2017 if (is_gimple_debug (stmt))
2019 bool failed = false;
2021 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
2022 if (!maybe_replace_use_in_debug_stmt (use_p))
2024 failed = true;
2025 break;
2028 if (failed)
2030 /* DOM sometimes threads jumps in such a way that a
2031 debug stmt ends up referencing a SSA variable that no
2032 longer dominates the debug stmt, but such that all
2033 incoming definitions refer to the same definition in
2034 an earlier dominator. We could try to recover that
2035 definition somehow, but this will have to do for now.
2037 Introducing a default definition, which is what
2038 maybe_replace_use() would do in such cases, may
2039 modify code generation, for the otherwise-unused
2040 default definition would never go away, modifying SSA
2041 version numbers all over. */
2042 gimple_debug_bind_reset_value (stmt);
2043 update_stmt (stmt);
2046 else
2048 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
2049 maybe_replace_use (use_p);
2053 /* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES.
2054 Also register definitions for names whose underlying symbol is
2055 marked for renaming. */
2056 bool to_delete = false;
2057 if (register_defs_p (stmt))
2058 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
2059 to_delete |= maybe_register_def (def_p, stmt, gsi);
2061 return to_delete;
2065 /* Visit all the successor blocks of BB looking for PHI nodes. For
2066 every PHI node found, check if any of its arguments is in
2067 OLD_SSA_NAMES. If so, and if the argument has a current reaching
2068 definition, replace it. */
2070 static void
2071 rewrite_update_phi_arguments (basic_block bb)
2073 edge e;
2074 edge_iterator ei;
2075 unsigned i;
2077 FOR_EACH_EDGE (e, ei, bb->succs)
2079 gphi *phi;
2080 vec<gphi *> phis;
2082 if (!bitmap_bit_p (blocks_with_phis_to_rewrite, e->dest->index))
2083 continue;
2085 phis = phis_to_rewrite[e->dest->index];
2086 FOR_EACH_VEC_ELT (phis, i, phi)
2088 tree arg, lhs_sym, reaching_def = NULL;
2089 use_operand_p arg_p;
2091 gcc_checking_assert (rewrite_uses_p (phi));
2093 arg_p = PHI_ARG_DEF_PTR_FROM_EDGE (phi, e);
2094 arg = USE_FROM_PTR (arg_p);
2096 if (arg && !DECL_P (arg) && TREE_CODE (arg) != SSA_NAME)
2097 continue;
2099 lhs_sym = SSA_NAME_VAR (gimple_phi_result (phi));
2101 if (arg == NULL_TREE)
2103 /* When updating a PHI node for a recently introduced
2104 symbol we may find NULL arguments. That's why we
2105 take the symbol from the LHS of the PHI node. */
2106 reaching_def = get_reaching_def (lhs_sym);
2109 else
2111 tree sym = DECL_P (arg) ? arg : SSA_NAME_VAR (arg);
2113 if (marked_for_renaming (sym))
2114 reaching_def = get_reaching_def (sym);
2115 else if (is_old_name (arg))
2116 reaching_def = get_reaching_def (arg);
2119 /* Update the argument if there is a reaching def. */
2120 if (reaching_def)
2122 source_location locus;
2123 int arg_i = PHI_ARG_INDEX_FROM_USE (arg_p);
2125 SET_USE (arg_p, reaching_def);
2127 /* Virtual operands do not need a location. */
2128 if (virtual_operand_p (reaching_def))
2129 locus = UNKNOWN_LOCATION;
2130 else
2132 gimple *stmt = SSA_NAME_DEF_STMT (reaching_def);
2133 gphi *other_phi = dyn_cast <gphi *> (stmt);
2135 /* Single element PHI nodes behave like copies, so get the
2136 location from the phi argument. */
2137 if (other_phi
2138 && gimple_phi_num_args (other_phi) == 1)
2139 locus = gimple_phi_arg_location (other_phi, 0);
2140 else
2141 locus = gimple_location (stmt);
2144 gimple_phi_arg_set_location (phi, arg_i, locus);
2148 if (e->flags & EDGE_ABNORMAL)
2149 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p)) = 1;
2154 class rewrite_update_dom_walker : public dom_walker
2156 public:
2157 rewrite_update_dom_walker (cdi_direction direction)
2158 : dom_walker (direction, ALL_BLOCKS, NULL) {}
2160 virtual edge before_dom_children (basic_block);
2161 virtual void after_dom_children (basic_block);
2164 /* Initialization of block data structures for the incremental SSA
2165 update pass. Create a block local stack of reaching definitions
2166 for new SSA names produced in this block (BLOCK_DEFS). Register
2167 new definitions for every PHI node in the block. */
2169 edge
2170 rewrite_update_dom_walker::before_dom_children (basic_block bb)
2172 bool is_abnormal_phi;
2174 if (dump_file && (dump_flags & TDF_DETAILS))
2175 fprintf (dump_file, "Registering new PHI nodes in block #%d\n",
2176 bb->index);
2178 /* Mark the unwind point for this block. */
2179 block_defs_stack.safe_push (NULL_TREE);
2181 if (!bitmap_bit_p (blocks_to_update, bb->index))
2182 return NULL;
2184 /* Mark the LHS if any of the arguments flows through an abnormal
2185 edge. */
2186 is_abnormal_phi = bb_has_abnormal_pred (bb);
2188 /* If any of the PHI nodes is a replacement for a name in
2189 OLD_SSA_NAMES or it's one of the names in NEW_SSA_NAMES, then
2190 register it as a new definition for its corresponding name. Also
2191 register definitions for names whose underlying symbols are
2192 marked for renaming. */
2193 for (gphi_iterator gsi = gsi_start_phis (bb); !gsi_end_p (gsi);
2194 gsi_next (&gsi))
2196 tree lhs, lhs_sym;
2197 gphi *phi = gsi.phi ();
2199 if (!register_defs_p (phi))
2200 continue;
2202 lhs = gimple_phi_result (phi);
2203 lhs_sym = SSA_NAME_VAR (lhs);
2205 if (marked_for_renaming (lhs_sym))
2206 register_new_update_single (lhs, lhs_sym);
2207 else
2210 /* If LHS is a new name, register a new definition for all
2211 the names replaced by LHS. */
2212 if (is_new_name (lhs))
2213 register_new_update_set (lhs, names_replaced_by (lhs));
2215 /* If LHS is an OLD name, register it as a new definition
2216 for itself. */
2217 if (is_old_name (lhs))
2218 register_new_update_single (lhs, lhs);
2221 if (is_abnormal_phi)
2222 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs) = 1;
2225 /* Step 2. Rewrite every variable used in each statement in the block. */
2226 if (bitmap_bit_p (interesting_blocks, bb->index))
2228 gcc_checking_assert (bitmap_bit_p (blocks_to_update, bb->index));
2229 for (gimple_stmt_iterator gsi = gsi_start_bb (bb); !gsi_end_p (gsi); )
2230 if (rewrite_update_stmt (gsi_stmt (gsi), gsi))
2231 gsi_remove (&gsi, true);
2232 else
2233 gsi_next (&gsi);
2236 /* Step 3. Update PHI nodes. */
2237 rewrite_update_phi_arguments (bb);
2239 return NULL;
2242 /* Called after visiting block BB. Unwind BLOCK_DEFS_STACK to restore
2243 the current reaching definition of every name re-written in BB to
2244 the original reaching definition before visiting BB. This
2245 unwinding must be done in the opposite order to what is done in
2246 register_new_update_set. */
2248 void
2249 rewrite_update_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED)
2251 while (block_defs_stack.length () > 0)
2253 tree var = block_defs_stack.pop ();
2254 tree saved_def;
2256 /* NULL indicates the unwind stop point for this block (see
2257 rewrite_update_enter_block). */
2258 if (var == NULL)
2259 return;
2261 saved_def = block_defs_stack.pop ();
2262 get_common_info (var)->current_def = saved_def;
2267 /* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
2268 form.
2270 ENTRY indicates the block where to start. Every block dominated by
2271 ENTRY will be rewritten.
2273 WHAT indicates what actions will be taken by the renamer (see enum
2274 rewrite_mode).
2276 BLOCKS are the set of interesting blocks for the dominator walker
2277 to process. If this set is NULL, then all the nodes dominated
2278 by ENTRY are walked. Otherwise, blocks dominated by ENTRY that
2279 are not present in BLOCKS are ignored. */
2281 static void
2282 rewrite_blocks (basic_block entry, enum rewrite_mode what)
2284 /* Rewrite all the basic blocks in the program. */
2285 timevar_push (TV_TREE_SSA_REWRITE_BLOCKS);
2287 block_defs_stack.create (10);
2289 /* Recursively walk the dominator tree rewriting each statement in
2290 each basic block. */
2291 if (what == REWRITE_ALL)
2292 rewrite_dom_walker (CDI_DOMINATORS).walk (entry);
2293 else if (what == REWRITE_UPDATE)
2294 rewrite_update_dom_walker (CDI_DOMINATORS).walk (entry);
2295 else
2296 gcc_unreachable ();
2298 /* Debugging dumps. */
2299 if (dump_file && (dump_flags & TDF_STATS))
2301 dump_dfa_stats (dump_file);
2302 if (var_infos)
2303 dump_tree_ssa_stats (dump_file);
2306 block_defs_stack.release ();
2308 timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS);
2311 class mark_def_dom_walker : public dom_walker
2313 public:
2314 mark_def_dom_walker (cdi_direction direction);
2315 ~mark_def_dom_walker ();
2317 virtual edge before_dom_children (basic_block);
2319 private:
2320 /* Notice that this bitmap is indexed using variable UIDs, so it must be
2321 large enough to accommodate all the variables referenced in the
2322 function, not just the ones we are renaming. */
2323 bitmap m_kills;
2326 mark_def_dom_walker::mark_def_dom_walker (cdi_direction direction)
2327 : dom_walker (direction, ALL_BLOCKS, NULL), m_kills (BITMAP_ALLOC (NULL))
2331 mark_def_dom_walker::~mark_def_dom_walker ()
2333 BITMAP_FREE (m_kills);
2336 /* Block processing routine for mark_def_sites. Clear the KILLS bitmap
2337 at the start of each block, and call mark_def_sites for each statement. */
2339 edge
2340 mark_def_dom_walker::before_dom_children (basic_block bb)
2342 gimple_stmt_iterator gsi;
2344 bitmap_clear (m_kills);
2345 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
2346 mark_def_sites (bb, gsi_stmt (gsi), m_kills);
2347 return NULL;
2350 /* Initialize internal data needed during renaming. */
2352 static void
2353 init_ssa_renamer (void)
2355 cfun->gimple_df->in_ssa_p = false;
2357 /* Allocate memory for the DEF_BLOCKS hash table. */
2358 gcc_assert (!var_infos);
2359 var_infos = new hash_table<var_info_hasher>
2360 (vec_safe_length (cfun->local_decls));
2362 bitmap_obstack_initialize (&update_ssa_obstack);
2366 /* Deallocate internal data structures used by the renamer. */
2368 static void
2369 fini_ssa_renamer (void)
2371 delete var_infos;
2372 var_infos = NULL;
2374 bitmap_obstack_release (&update_ssa_obstack);
2376 cfun->gimple_df->ssa_renaming_needed = 0;
2377 cfun->gimple_df->rename_vops = 0;
2378 cfun->gimple_df->in_ssa_p = true;
2381 /* Main entry point into the SSA builder. The renaming process
2382 proceeds in four main phases:
2384 1- Compute dominance frontier and immediate dominators, needed to
2385 insert PHI nodes and rename the function in dominator tree
2386 order.
2388 2- Find and mark all the blocks that define variables.
2390 3- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
2392 4- Rename all the blocks (rewrite_blocks) and statements in the program.
2394 Steps 3 and 4 are done using the dominator tree walker
2395 (walk_dominator_tree). */
2397 namespace {
2399 const pass_data pass_data_build_ssa =
2401 GIMPLE_PASS, /* type */
2402 "ssa", /* name */
2403 OPTGROUP_NONE, /* optinfo_flags */
2404 TV_TREE_SSA_OTHER, /* tv_id */
2405 PROP_cfg, /* properties_required */
2406 PROP_ssa, /* properties_provided */
2407 0, /* properties_destroyed */
2408 0, /* todo_flags_start */
2409 TODO_remove_unused_locals, /* todo_flags_finish */
2412 class pass_build_ssa : public gimple_opt_pass
2414 public:
2415 pass_build_ssa (gcc::context *ctxt)
2416 : gimple_opt_pass (pass_data_build_ssa, ctxt)
2419 /* opt_pass methods: */
2420 virtual bool gate (function *fun)
2422 /* Do nothing for funcions that was produced already in SSA form. */
2423 return !(fun->curr_properties & PROP_ssa);
2426 virtual unsigned int execute (function *);
2428 }; // class pass_build_ssa
2430 unsigned int
2431 pass_build_ssa::execute (function *fun)
2433 bitmap_head *dfs;
2434 basic_block bb;
2436 /* Initialize operand data structures. */
2437 init_ssa_operands (fun);
2439 /* Initialize internal data needed by the renamer. */
2440 init_ssa_renamer ();
2442 /* Initialize the set of interesting blocks. The callback
2443 mark_def_sites will add to this set those blocks that the renamer
2444 should process. */
2445 interesting_blocks = sbitmap_alloc (last_basic_block_for_fn (fun));
2446 bitmap_clear (interesting_blocks);
2448 /* Initialize dominance frontier. */
2449 dfs = XNEWVEC (bitmap_head, last_basic_block_for_fn (fun));
2450 FOR_EACH_BB_FN (bb, fun)
2451 bitmap_initialize (&dfs[bb->index], &bitmap_default_obstack);
2453 /* 1- Compute dominance frontiers. */
2454 calculate_dominance_info (CDI_DOMINATORS);
2455 compute_dominance_frontiers (dfs);
2457 /* 2- Find and mark definition sites. */
2458 mark_def_dom_walker (CDI_DOMINATORS).walk (fun->cfg->x_entry_block_ptr);
2460 /* 3- Insert PHI nodes at dominance frontiers of definition blocks. */
2461 insert_phi_nodes (dfs);
2463 /* 4- Rename all the blocks. */
2464 rewrite_blocks (ENTRY_BLOCK_PTR_FOR_FN (fun), REWRITE_ALL);
2466 /* Free allocated memory. */
2467 FOR_EACH_BB_FN (bb, fun)
2468 bitmap_clear (&dfs[bb->index]);
2469 free (dfs);
2471 sbitmap_free (interesting_blocks);
2473 fini_ssa_renamer ();
2475 /* Try to get rid of all gimplifier generated temporaries by making
2476 its SSA names anonymous. This way we can garbage collect them
2477 all after removing unused locals which we do in our TODO. */
2478 unsigned i;
2479 tree name;
2481 FOR_EACH_SSA_NAME (i, name, cfun)
2483 if (SSA_NAME_IS_DEFAULT_DEF (name))
2484 continue;
2485 tree decl = SSA_NAME_VAR (name);
2486 if (decl
2487 && VAR_P (decl)
2488 && !VAR_DECL_IS_VIRTUAL_OPERAND (decl)
2489 && DECL_IGNORED_P (decl))
2490 SET_SSA_NAME_VAR_OR_IDENTIFIER (name, DECL_NAME (decl));
2493 return 0;
2496 } // anon namespace
2498 gimple_opt_pass *
2499 make_pass_build_ssa (gcc::context *ctxt)
2501 return new pass_build_ssa (ctxt);
2505 /* Mark the definition of VAR at STMT and BB as interesting for the
2506 renamer. BLOCKS is the set of blocks that need updating. */
2508 static void
2509 mark_def_interesting (tree var, gimple *stmt, basic_block bb,
2510 bool insert_phi_p)
2512 gcc_checking_assert (bitmap_bit_p (blocks_to_update, bb->index));
2513 set_register_defs (stmt, true);
2515 if (insert_phi_p)
2517 bool is_phi_p = gimple_code (stmt) == GIMPLE_PHI;
2519 set_def_block (var, bb, is_phi_p);
2521 /* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition
2522 site for both itself and all the old names replaced by it. */
2523 if (TREE_CODE (var) == SSA_NAME && is_new_name (var))
2525 bitmap_iterator bi;
2526 unsigned i;
2527 bitmap set = names_replaced_by (var);
2528 if (set)
2529 EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
2530 set_def_block (ssa_name (i), bb, is_phi_p);
2536 /* Mark the use of VAR at STMT and BB as interesting for the
2537 renamer. INSERT_PHI_P is true if we are going to insert new PHI
2538 nodes. */
2540 static inline void
2541 mark_use_interesting (tree var, gimple *stmt, basic_block bb,
2542 bool insert_phi_p)
2544 basic_block def_bb = gimple_bb (stmt);
2546 mark_block_for_update (def_bb);
2547 mark_block_for_update (bb);
2549 if (gimple_code (stmt) == GIMPLE_PHI)
2550 mark_phi_for_rewrite (def_bb, as_a <gphi *> (stmt));
2551 else
2553 set_rewrite_uses (stmt, true);
2555 if (is_gimple_debug (stmt))
2556 return;
2559 /* If VAR has not been defined in BB, then it is live-on-entry
2560 to BB. Note that we cannot just use the block holding VAR's
2561 definition because if VAR is one of the names in OLD_SSA_NAMES,
2562 it will have several definitions (itself and all the names that
2563 replace it). */
2564 if (insert_phi_p)
2566 def_blocks *db_p = get_def_blocks_for (get_common_info (var));
2567 if (!bitmap_bit_p (db_p->def_blocks, bb->index))
2568 set_livein_block (var, bb);
2573 /* Do a dominator walk starting at BB processing statements that
2574 reference symbols in SSA operands. This is very similar to
2575 mark_def_sites, but the scan handles statements whose operands may
2576 already be SSA names.
2578 If INSERT_PHI_P is true, mark those uses as live in the
2579 corresponding block. This is later used by the PHI placement
2580 algorithm to make PHI pruning decisions.
2582 FIXME. Most of this would be unnecessary if we could associate a
2583 symbol to all the SSA names that reference it. But that
2584 sounds like it would be expensive to maintain. Still, it
2585 would be interesting to see if it makes better sense to do
2586 that. */
2588 static void
2589 prepare_block_for_update (basic_block bb, bool insert_phi_p)
2591 basic_block son;
2592 edge e;
2593 edge_iterator ei;
2595 mark_block_for_update (bb);
2597 /* Process PHI nodes marking interesting those that define or use
2598 the symbols that we are interested in. */
2599 for (gphi_iterator si = gsi_start_phis (bb); !gsi_end_p (si);
2600 gsi_next (&si))
2602 gphi *phi = si.phi ();
2603 tree lhs_sym, lhs = gimple_phi_result (phi);
2605 if (TREE_CODE (lhs) == SSA_NAME
2606 && (! virtual_operand_p (lhs)
2607 || ! cfun->gimple_df->rename_vops))
2608 continue;
2610 lhs_sym = DECL_P (lhs) ? lhs : SSA_NAME_VAR (lhs);
2611 mark_for_renaming (lhs_sym);
2612 mark_def_interesting (lhs_sym, phi, bb, insert_phi_p);
2614 /* Mark the uses in phi nodes as interesting. It would be more correct
2615 to process the arguments of the phi nodes of the successor edges of
2616 BB at the end of prepare_block_for_update, however, that turns out
2617 to be significantly more expensive. Doing it here is conservatively
2618 correct -- it may only cause us to believe a value to be live in a
2619 block that also contains its definition, and thus insert a few more
2620 phi nodes for it. */
2621 FOR_EACH_EDGE (e, ei, bb->preds)
2622 mark_use_interesting (lhs_sym, phi, e->src, insert_phi_p);
2625 /* Process the statements. */
2626 for (gimple_stmt_iterator si = gsi_start_bb (bb); !gsi_end_p (si);
2627 gsi_next (&si))
2629 gimple *stmt;
2630 ssa_op_iter i;
2631 use_operand_p use_p;
2632 def_operand_p def_p;
2634 stmt = gsi_stmt (si);
2636 if (cfun->gimple_df->rename_vops
2637 && gimple_vuse (stmt))
2639 tree use = gimple_vuse (stmt);
2640 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
2641 mark_for_renaming (sym);
2642 mark_use_interesting (sym, stmt, bb, insert_phi_p);
2645 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, i, SSA_OP_USE)
2647 tree use = USE_FROM_PTR (use_p);
2648 if (!DECL_P (use))
2649 continue;
2650 mark_for_renaming (use);
2651 mark_use_interesting (use, stmt, bb, insert_phi_p);
2654 if (cfun->gimple_df->rename_vops
2655 && gimple_vdef (stmt))
2657 tree def = gimple_vdef (stmt);
2658 tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
2659 mark_for_renaming (sym);
2660 mark_def_interesting (sym, stmt, bb, insert_phi_p);
2663 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, i, SSA_OP_DEF)
2665 tree def = DEF_FROM_PTR (def_p);
2666 if (!DECL_P (def))
2667 continue;
2668 mark_for_renaming (def);
2669 mark_def_interesting (def, stmt, bb, insert_phi_p);
2673 /* Now visit all the blocks dominated by BB. */
2674 for (son = first_dom_son (CDI_DOMINATORS, bb);
2675 son;
2676 son = next_dom_son (CDI_DOMINATORS, son))
2677 prepare_block_for_update (son, insert_phi_p);
2681 /* Helper for prepare_names_to_update. Mark all the use sites for
2682 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2683 prepare_names_to_update. */
2685 static void
2686 prepare_use_sites_for (tree name, bool insert_phi_p)
2688 use_operand_p use_p;
2689 imm_use_iterator iter;
2691 /* If we rename virtual operands do not update them. */
2692 if (virtual_operand_p (name)
2693 && cfun->gimple_df->rename_vops)
2694 return;
2696 FOR_EACH_IMM_USE_FAST (use_p, iter, name)
2698 gimple *stmt = USE_STMT (use_p);
2699 basic_block bb = gimple_bb (stmt);
2701 if (gimple_code (stmt) == GIMPLE_PHI)
2703 int ix = PHI_ARG_INDEX_FROM_USE (use_p);
2704 edge e = gimple_phi_arg_edge (as_a <gphi *> (stmt), ix);
2705 mark_use_interesting (name, stmt, e->src, insert_phi_p);
2707 else
2709 /* For regular statements, mark this as an interesting use
2710 for NAME. */
2711 mark_use_interesting (name, stmt, bb, insert_phi_p);
2717 /* Helper for prepare_names_to_update. Mark the definition site for
2718 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2719 prepare_names_to_update. */
2721 static void
2722 prepare_def_site_for (tree name, bool insert_phi_p)
2724 gimple *stmt;
2725 basic_block bb;
2727 gcc_checking_assert (names_to_release == NULL
2728 || !bitmap_bit_p (names_to_release,
2729 SSA_NAME_VERSION (name)));
2731 /* If we rename virtual operands do not update them. */
2732 if (virtual_operand_p (name)
2733 && cfun->gimple_df->rename_vops)
2734 return;
2736 stmt = SSA_NAME_DEF_STMT (name);
2737 bb = gimple_bb (stmt);
2738 if (bb)
2740 gcc_checking_assert (bb->index < last_basic_block_for_fn (cfun));
2741 mark_block_for_update (bb);
2742 mark_def_interesting (name, stmt, bb, insert_phi_p);
2747 /* Mark definition and use sites of names in NEW_SSA_NAMES and
2748 OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert
2749 PHI nodes for newly created names. */
2751 static void
2752 prepare_names_to_update (bool insert_phi_p)
2754 unsigned i = 0;
2755 bitmap_iterator bi;
2756 sbitmap_iterator sbi;
2758 /* If a name N from NEW_SSA_NAMES is also marked to be released,
2759 remove it from NEW_SSA_NAMES so that we don't try to visit its
2760 defining basic block (which most likely doesn't exist). Notice
2761 that we cannot do the same with names in OLD_SSA_NAMES because we
2762 want to replace existing instances. */
2763 if (names_to_release)
2764 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
2765 bitmap_clear_bit (new_ssa_names, i);
2767 /* First process names in NEW_SSA_NAMES. Otherwise, uses of old
2768 names may be considered to be live-in on blocks that contain
2769 definitions for their replacements. */
2770 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names, 0, i, sbi)
2771 prepare_def_site_for (ssa_name (i), insert_phi_p);
2773 /* If an old name is in NAMES_TO_RELEASE, we cannot remove it from
2774 OLD_SSA_NAMES, but we have to ignore its definition site. */
2775 EXECUTE_IF_SET_IN_BITMAP (old_ssa_names, 0, i, sbi)
2777 if (names_to_release == NULL || !bitmap_bit_p (names_to_release, i))
2778 prepare_def_site_for (ssa_name (i), insert_phi_p);
2779 prepare_use_sites_for (ssa_name (i), insert_phi_p);
2784 /* Dump all the names replaced by NAME to FILE. */
2786 void
2787 dump_names_replaced_by (FILE *file, tree name)
2789 unsigned i;
2790 bitmap old_set;
2791 bitmap_iterator bi;
2793 print_generic_expr (file, name);
2794 fprintf (file, " -> { ");
2796 old_set = names_replaced_by (name);
2797 EXECUTE_IF_SET_IN_BITMAP (old_set, 0, i, bi)
2799 print_generic_expr (file, ssa_name (i));
2800 fprintf (file, " ");
2803 fprintf (file, "}\n");
2807 /* Dump all the names replaced by NAME to stderr. */
2809 DEBUG_FUNCTION void
2810 debug_names_replaced_by (tree name)
2812 dump_names_replaced_by (stderr, name);
2816 /* Dump SSA update information to FILE. */
2818 void
2819 dump_update_ssa (FILE *file)
2821 unsigned i = 0;
2822 bitmap_iterator bi;
2824 if (!need_ssa_update_p (cfun))
2825 return;
2827 if (new_ssa_names && bitmap_first_set_bit (new_ssa_names) >= 0)
2829 sbitmap_iterator sbi;
2831 fprintf (file, "\nSSA replacement table\n");
2832 fprintf (file, "N_i -> { O_1 ... O_j } means that N_i replaces "
2833 "O_1, ..., O_j\n\n");
2835 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names, 0, i, sbi)
2836 dump_names_replaced_by (file, ssa_name (i));
2839 if (symbols_to_rename_set && !bitmap_empty_p (symbols_to_rename_set))
2841 fprintf (file, "\nSymbols to be put in SSA form\n");
2842 dump_decl_set (file, symbols_to_rename_set);
2843 fprintf (file, "\n");
2846 if (names_to_release && !bitmap_empty_p (names_to_release))
2848 fprintf (file, "\nSSA names to release after updating the SSA web\n\n");
2849 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
2851 print_generic_expr (file, ssa_name (i));
2852 fprintf (file, " ");
2854 fprintf (file, "\n");
2859 /* Dump SSA update information to stderr. */
2861 DEBUG_FUNCTION void
2862 debug_update_ssa (void)
2864 dump_update_ssa (stderr);
2868 /* Initialize data structures used for incremental SSA updates. */
2870 static void
2871 init_update_ssa (struct function *fn)
2873 /* Reserve more space than the current number of names. The calls to
2874 add_new_name_mapping are typically done after creating new SSA
2875 names, so we'll need to reallocate these arrays. */
2876 old_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR);
2877 bitmap_clear (old_ssa_names);
2879 new_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR);
2880 bitmap_clear (new_ssa_names);
2882 bitmap_obstack_initialize (&update_ssa_obstack);
2884 names_to_release = NULL;
2885 update_ssa_initialized_fn = fn;
2889 /* Deallocate data structures used for incremental SSA updates. */
2891 void
2892 delete_update_ssa (void)
2894 unsigned i;
2895 bitmap_iterator bi;
2897 sbitmap_free (old_ssa_names);
2898 old_ssa_names = NULL;
2900 sbitmap_free (new_ssa_names);
2901 new_ssa_names = NULL;
2903 BITMAP_FREE (symbols_to_rename_set);
2904 symbols_to_rename_set = NULL;
2905 symbols_to_rename.release ();
2907 if (names_to_release)
2909 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
2910 release_ssa_name (ssa_name (i));
2911 BITMAP_FREE (names_to_release);
2914 clear_ssa_name_info ();
2916 fini_ssa_renamer ();
2918 if (blocks_with_phis_to_rewrite)
2919 EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite, 0, i, bi)
2921 vec<gphi *> phis = phis_to_rewrite[i];
2922 phis.release ();
2923 phis_to_rewrite[i].create (0);
2926 BITMAP_FREE (blocks_with_phis_to_rewrite);
2927 BITMAP_FREE (blocks_to_update);
2929 update_ssa_initialized_fn = NULL;
2933 /* Create a new name for OLD_NAME in statement STMT and replace the
2934 operand pointed to by DEF_P with the newly created name. If DEF_P
2935 is NULL then STMT should be a GIMPLE assignment.
2936 Return the new name and register the replacement mapping <NEW, OLD> in
2937 update_ssa's tables. */
2939 tree
2940 create_new_def_for (tree old_name, gimple *stmt, def_operand_p def)
2942 tree new_name;
2944 timevar_push (TV_TREE_SSA_INCREMENTAL);
2946 if (!update_ssa_initialized_fn)
2947 init_update_ssa (cfun);
2949 gcc_assert (update_ssa_initialized_fn == cfun);
2951 new_name = duplicate_ssa_name (old_name, stmt);
2952 if (def)
2953 SET_DEF (def, new_name);
2954 else
2955 gimple_assign_set_lhs (stmt, new_name);
2957 if (gimple_code (stmt) == GIMPLE_PHI)
2959 basic_block bb = gimple_bb (stmt);
2961 /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
2962 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name) = bb_has_abnormal_pred (bb);
2965 add_new_name_mapping (new_name, old_name);
2967 /* For the benefit of passes that will be updating the SSA form on
2968 their own, set the current reaching definition of OLD_NAME to be
2969 NEW_NAME. */
2970 get_ssa_name_ann (old_name)->info.current_def = new_name;
2972 timevar_pop (TV_TREE_SSA_INCREMENTAL);
2974 return new_name;
2978 /* Mark virtual operands of FN for renaming by update_ssa. */
2980 void
2981 mark_virtual_operands_for_renaming (struct function *fn)
2983 fn->gimple_df->ssa_renaming_needed = 1;
2984 fn->gimple_df->rename_vops = 1;
2987 /* Replace all uses of NAME by underlying variable and mark it
2988 for renaming. This assumes the defining statement of NAME is
2989 going to be removed. */
2991 void
2992 mark_virtual_operand_for_renaming (tree name)
2994 tree name_var = SSA_NAME_VAR (name);
2995 bool used = false;
2996 imm_use_iterator iter;
2997 use_operand_p use_p;
2998 gimple *stmt;
3000 gcc_assert (VAR_DECL_IS_VIRTUAL_OPERAND (name_var));
3001 FOR_EACH_IMM_USE_STMT (stmt, iter, name)
3003 FOR_EACH_IMM_USE_ON_STMT (use_p, iter)
3004 SET_USE (use_p, name_var);
3005 used = true;
3007 if (used)
3008 mark_virtual_operands_for_renaming (cfun);
3011 /* Replace all uses of the virtual PHI result by its underlying variable
3012 and mark it for renaming. This assumes the PHI node is going to be
3013 removed. */
3015 void
3016 mark_virtual_phi_result_for_renaming (gphi *phi)
3018 if (dump_file && (dump_flags & TDF_DETAILS))
3020 fprintf (dump_file, "Marking result for renaming : ");
3021 print_gimple_stmt (dump_file, phi, 0, TDF_SLIM);
3022 fprintf (dump_file, "\n");
3025 mark_virtual_operand_for_renaming (gimple_phi_result (phi));
3028 /* Return true if there is any work to be done by update_ssa
3029 for function FN. */
3031 bool
3032 need_ssa_update_p (struct function *fn)
3034 gcc_assert (fn != NULL);
3035 return (update_ssa_initialized_fn == fn
3036 || (fn->gimple_df && fn->gimple_df->ssa_renaming_needed));
3039 /* Return true if name N has been registered in the replacement table. */
3041 bool
3042 name_registered_for_update_p (tree n ATTRIBUTE_UNUSED)
3044 if (!update_ssa_initialized_fn)
3045 return false;
3047 gcc_assert (update_ssa_initialized_fn == cfun);
3049 return is_new_name (n) || is_old_name (n);
3053 /* Mark NAME to be released after update_ssa has finished. */
3055 void
3056 release_ssa_name_after_update_ssa (tree name)
3058 gcc_assert (cfun && update_ssa_initialized_fn == cfun);
3060 if (names_to_release == NULL)
3061 names_to_release = BITMAP_ALLOC (NULL);
3063 bitmap_set_bit (names_to_release, SSA_NAME_VERSION (name));
3067 /* Insert new PHI nodes to replace VAR. DFS contains dominance
3068 frontier information. BLOCKS is the set of blocks to be updated.
3070 This is slightly different than the regular PHI insertion
3071 algorithm. The value of UPDATE_FLAGS controls how PHI nodes for
3072 real names (i.e., GIMPLE registers) are inserted:
3074 - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI
3075 nodes inside the region affected by the block that defines VAR
3076 and the blocks that define all its replacements. All these
3077 definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS.
3079 First, we compute the entry point to the region (ENTRY). This is
3080 given by the nearest common dominator to all the definition
3081 blocks. When computing the iterated dominance frontier (IDF), any
3082 block not strictly dominated by ENTRY is ignored.
3084 We then call the standard PHI insertion algorithm with the pruned
3085 IDF.
3087 - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real
3088 names is not pruned. PHI nodes are inserted at every IDF block. */
3090 static void
3091 insert_updated_phi_nodes_for (tree var, bitmap_head *dfs, bitmap blocks,
3092 unsigned update_flags)
3094 basic_block entry;
3095 def_blocks *db;
3096 bitmap idf, pruned_idf;
3097 bitmap_iterator bi;
3098 unsigned i;
3100 if (TREE_CODE (var) == SSA_NAME)
3101 gcc_checking_assert (is_old_name (var));
3102 else
3103 gcc_checking_assert (marked_for_renaming (var));
3105 /* Get all the definition sites for VAR. */
3106 db = find_def_blocks_for (var);
3108 /* No need to do anything if there were no definitions to VAR. */
3109 if (db == NULL || bitmap_empty_p (db->def_blocks))
3110 return;
3112 /* Compute the initial iterated dominance frontier. */
3113 idf = compute_idf (db->def_blocks, dfs);
3114 pruned_idf = BITMAP_ALLOC (NULL);
3116 if (TREE_CODE (var) == SSA_NAME)
3118 if (update_flags == TODO_update_ssa)
3120 /* If doing regular SSA updates for GIMPLE registers, we are
3121 only interested in IDF blocks dominated by the nearest
3122 common dominator of all the definition blocks. */
3123 entry = nearest_common_dominator_for_set (CDI_DOMINATORS,
3124 db->def_blocks);
3125 if (entry != ENTRY_BLOCK_PTR_FOR_FN (cfun))
3126 EXECUTE_IF_SET_IN_BITMAP (idf, 0, i, bi)
3127 if (BASIC_BLOCK_FOR_FN (cfun, i) != entry
3128 && dominated_by_p (CDI_DOMINATORS,
3129 BASIC_BLOCK_FOR_FN (cfun, i), entry))
3130 bitmap_set_bit (pruned_idf, i);
3132 else
3134 /* Otherwise, do not prune the IDF for VAR. */
3135 gcc_checking_assert (update_flags == TODO_update_ssa_full_phi);
3136 bitmap_copy (pruned_idf, idf);
3139 else
3141 /* Otherwise, VAR is a symbol that needs to be put into SSA form
3142 for the first time, so we need to compute the full IDF for
3143 it. */
3144 bitmap_copy (pruned_idf, idf);
3147 if (!bitmap_empty_p (pruned_idf))
3149 /* Make sure that PRUNED_IDF blocks and all their feeding blocks
3150 are included in the region to be updated. The feeding blocks
3151 are important to guarantee that the PHI arguments are renamed
3152 properly. */
3154 /* FIXME, this is not needed if we are updating symbols. We are
3155 already starting at the ENTRY block anyway. */
3156 bitmap_ior_into (blocks, pruned_idf);
3157 EXECUTE_IF_SET_IN_BITMAP (pruned_idf, 0, i, bi)
3159 edge e;
3160 edge_iterator ei;
3161 basic_block bb = BASIC_BLOCK_FOR_FN (cfun, i);
3163 FOR_EACH_EDGE (e, ei, bb->preds)
3164 if (e->src->index >= 0)
3165 bitmap_set_bit (blocks, e->src->index);
3168 insert_phi_nodes_for (var, pruned_idf, true);
3171 BITMAP_FREE (pruned_idf);
3172 BITMAP_FREE (idf);
3175 /* Sort symbols_to_rename after their DECL_UID. */
3177 static int
3178 insert_updated_phi_nodes_compare_uids (const void *a, const void *b)
3180 const_tree syma = *(const const_tree *)a;
3181 const_tree symb = *(const const_tree *)b;
3182 if (DECL_UID (syma) == DECL_UID (symb))
3183 return 0;
3184 return DECL_UID (syma) < DECL_UID (symb) ? -1 : 1;
3187 /* Given a set of newly created SSA names (NEW_SSA_NAMES) and a set of
3188 existing SSA names (OLD_SSA_NAMES), update the SSA form so that:
3190 1- The names in OLD_SSA_NAMES dominated by the definitions of
3191 NEW_SSA_NAMES are all re-written to be reached by the
3192 appropriate definition from NEW_SSA_NAMES.
3194 2- If needed, new PHI nodes are added to the iterated dominance
3195 frontier of the blocks where each of NEW_SSA_NAMES are defined.
3197 The mapping between OLD_SSA_NAMES and NEW_SSA_NAMES is setup by
3198 calling create_new_def_for to create new defs for names that the
3199 caller wants to replace.
3201 The caller cretaes the new names to be inserted and the names that need
3202 to be replaced by calling create_new_def_for for each old definition
3203 to be replaced. Note that the function assumes that the
3204 new defining statement has already been inserted in the IL.
3206 For instance, given the following code:
3208 1 L0:
3209 2 x_1 = PHI (0, x_5)
3210 3 if (x_1 < 10)
3211 4 if (x_1 > 7)
3212 5 y_2 = 0
3213 6 else
3214 7 y_3 = x_1 + x_7
3215 8 endif
3216 9 x_5 = x_1 + 1
3217 10 goto L0;
3218 11 endif
3220 Suppose that we insert new names x_10 and x_11 (lines 4 and 8).
3222 1 L0:
3223 2 x_1 = PHI (0, x_5)
3224 3 if (x_1 < 10)
3225 4 x_10 = ...
3226 5 if (x_1 > 7)
3227 6 y_2 = 0
3228 7 else
3229 8 x_11 = ...
3230 9 y_3 = x_1 + x_7
3231 10 endif
3232 11 x_5 = x_1 + 1
3233 12 goto L0;
3234 13 endif
3236 We want to replace all the uses of x_1 with the new definitions of
3237 x_10 and x_11. Note that the only uses that should be replaced are
3238 those at lines 5, 9 and 11. Also, the use of x_7 at line 9 should
3239 *not* be replaced (this is why we cannot just mark symbol 'x' for
3240 renaming).
3242 Additionally, we may need to insert a PHI node at line 11 because
3243 that is a merge point for x_10 and x_11. So the use of x_1 at line
3244 11 will be replaced with the new PHI node. The insertion of PHI
3245 nodes is optional. They are not strictly necessary to preserve the
3246 SSA form, and depending on what the caller inserted, they may not
3247 even be useful for the optimizers. UPDATE_FLAGS controls various
3248 aspects of how update_ssa operates, see the documentation for
3249 TODO_update_ssa*. */
3251 void
3252 update_ssa (unsigned update_flags)
3254 basic_block bb, start_bb;
3255 bitmap_iterator bi;
3256 unsigned i = 0;
3257 bool insert_phi_p;
3258 sbitmap_iterator sbi;
3259 tree sym;
3261 /* Only one update flag should be set. */
3262 gcc_assert (update_flags == TODO_update_ssa
3263 || update_flags == TODO_update_ssa_no_phi
3264 || update_flags == TODO_update_ssa_full_phi
3265 || update_flags == TODO_update_ssa_only_virtuals);
3267 if (!need_ssa_update_p (cfun))
3268 return;
3270 if (flag_checking)
3272 timevar_push (TV_TREE_STMT_VERIFY);
3274 bool err = false;
3276 FOR_EACH_BB_FN (bb, cfun)
3278 gimple_stmt_iterator gsi;
3279 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
3281 gimple *stmt = gsi_stmt (gsi);
3283 ssa_op_iter i;
3284 use_operand_p use_p;
3285 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, i, SSA_OP_ALL_USES)
3287 tree use = USE_FROM_PTR (use_p);
3288 if (TREE_CODE (use) != SSA_NAME)
3289 continue;
3291 if (SSA_NAME_IN_FREE_LIST (use))
3293 error ("statement uses released SSA name:");
3294 debug_gimple_stmt (stmt);
3295 fprintf (stderr, "The use of ");
3296 print_generic_expr (stderr, use);
3297 fprintf (stderr," should have been replaced\n");
3298 err = true;
3304 if (err)
3305 internal_error ("cannot update SSA form");
3307 timevar_pop (TV_TREE_STMT_VERIFY);
3310 timevar_push (TV_TREE_SSA_INCREMENTAL);
3312 if (dump_file && (dump_flags & TDF_DETAILS))
3313 fprintf (dump_file, "\nUpdating SSA:\n");
3315 if (!update_ssa_initialized_fn)
3316 init_update_ssa (cfun);
3317 else if (update_flags == TODO_update_ssa_only_virtuals)
3319 /* If we only need to update virtuals, remove all the mappings for
3320 real names before proceeding. The caller is responsible for
3321 having dealt with the name mappings before calling update_ssa. */
3322 bitmap_clear (old_ssa_names);
3323 bitmap_clear (new_ssa_names);
3326 gcc_assert (update_ssa_initialized_fn == cfun);
3328 blocks_with_phis_to_rewrite = BITMAP_ALLOC (NULL);
3329 if (!phis_to_rewrite.exists ())
3330 phis_to_rewrite.create (last_basic_block_for_fn (cfun) + 1);
3331 blocks_to_update = BITMAP_ALLOC (NULL);
3333 /* Ensure that the dominance information is up-to-date. */
3334 calculate_dominance_info (CDI_DOMINATORS);
3336 insert_phi_p = (update_flags != TODO_update_ssa_no_phi);
3338 /* If there are names defined in the replacement table, prepare
3339 definition and use sites for all the names in NEW_SSA_NAMES and
3340 OLD_SSA_NAMES. */
3341 if (bitmap_first_set_bit (new_ssa_names) >= 0)
3343 statistics_counter_event (cfun, "Incremental SSA update", 1);
3345 prepare_names_to_update (insert_phi_p);
3347 /* If all the names in NEW_SSA_NAMES had been marked for
3348 removal, and there are no symbols to rename, then there's
3349 nothing else to do. */
3350 if (bitmap_first_set_bit (new_ssa_names) < 0
3351 && !cfun->gimple_df->ssa_renaming_needed)
3352 goto done;
3355 /* Next, determine the block at which to start the renaming process. */
3356 if (cfun->gimple_df->ssa_renaming_needed)
3358 statistics_counter_event (cfun, "Symbol to SSA rewrite", 1);
3360 /* If we rename bare symbols initialize the mapping to
3361 auxiliar info we need to keep track of. */
3362 var_infos = new hash_table<var_info_hasher> (47);
3364 /* If we have to rename some symbols from scratch, we need to
3365 start the process at the root of the CFG. FIXME, it should
3366 be possible to determine the nearest block that had a
3367 definition for each of the symbols that are marked for
3368 updating. For now this seems more work than it's worth. */
3369 start_bb = ENTRY_BLOCK_PTR_FOR_FN (cfun);
3371 /* Traverse the CFG looking for existing definitions and uses of
3372 symbols in SSA operands. Mark interesting blocks and
3373 statements and set local live-in information for the PHI
3374 placement heuristics. */
3375 prepare_block_for_update (start_bb, insert_phi_p);
3377 tree name;
3379 if (flag_checking)
3380 FOR_EACH_SSA_NAME (i, name, cfun)
3382 if (virtual_operand_p (name))
3383 continue;
3385 /* For all but virtual operands, which do not have SSA names
3386 with overlapping life ranges, ensure that symbols marked
3387 for renaming do not have existing SSA names associated with
3388 them as we do not re-write them out-of-SSA before going
3389 into SSA for the remaining symbol uses. */
3390 if (marked_for_renaming (SSA_NAME_VAR (name)))
3392 fprintf (stderr, "Existing SSA name for symbol marked for "
3393 "renaming: ");
3394 print_generic_expr (stderr, name, TDF_SLIM);
3395 fprintf (stderr, "\n");
3396 internal_error ("SSA corruption");
3400 else
3402 /* Otherwise, the entry block to the region is the nearest
3403 common dominator for the blocks in BLOCKS. */
3404 start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS,
3405 blocks_to_update);
3408 /* If requested, insert PHI nodes at the iterated dominance frontier
3409 of every block, creating new definitions for names in OLD_SSA_NAMES
3410 and for symbols found. */
3411 if (insert_phi_p)
3413 bitmap_head *dfs;
3415 /* If the caller requested PHI nodes to be added, compute
3416 dominance frontiers. */
3417 dfs = XNEWVEC (bitmap_head, last_basic_block_for_fn (cfun));
3418 FOR_EACH_BB_FN (bb, cfun)
3419 bitmap_initialize (&dfs[bb->index], &bitmap_default_obstack);
3420 compute_dominance_frontiers (dfs);
3422 if (bitmap_first_set_bit (old_ssa_names) >= 0)
3424 sbitmap_iterator sbi;
3426 /* insert_update_phi_nodes_for will call add_new_name_mapping
3427 when inserting new PHI nodes, so the set OLD_SSA_NAMES
3428 will grow while we are traversing it (but it will not
3429 gain any new members). Copy OLD_SSA_NAMES to a temporary
3430 for traversal. */
3431 auto_sbitmap tmp (SBITMAP_SIZE (old_ssa_names));
3432 bitmap_copy (tmp, old_ssa_names);
3433 EXECUTE_IF_SET_IN_BITMAP (tmp, 0, i, sbi)
3434 insert_updated_phi_nodes_for (ssa_name (i), dfs, blocks_to_update,
3435 update_flags);
3438 symbols_to_rename.qsort (insert_updated_phi_nodes_compare_uids);
3439 FOR_EACH_VEC_ELT (symbols_to_rename, i, sym)
3440 insert_updated_phi_nodes_for (sym, dfs, blocks_to_update,
3441 update_flags);
3443 FOR_EACH_BB_FN (bb, cfun)
3444 bitmap_clear (&dfs[bb->index]);
3445 free (dfs);
3447 /* Insertion of PHI nodes may have added blocks to the region.
3448 We need to re-compute START_BB to include the newly added
3449 blocks. */
3450 if (start_bb != ENTRY_BLOCK_PTR_FOR_FN (cfun))
3451 start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS,
3452 blocks_to_update);
3455 /* Reset the current definition for name and symbol before renaming
3456 the sub-graph. */
3457 EXECUTE_IF_SET_IN_BITMAP (old_ssa_names, 0, i, sbi)
3458 get_ssa_name_ann (ssa_name (i))->info.current_def = NULL_TREE;
3460 FOR_EACH_VEC_ELT (symbols_to_rename, i, sym)
3461 get_var_info (sym)->info.current_def = NULL_TREE;
3463 /* Now start the renaming process at START_BB. */
3464 interesting_blocks = sbitmap_alloc (last_basic_block_for_fn (cfun));
3465 bitmap_clear (interesting_blocks);
3466 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi)
3467 bitmap_set_bit (interesting_blocks, i);
3469 rewrite_blocks (start_bb, REWRITE_UPDATE);
3471 sbitmap_free (interesting_blocks);
3473 /* Debugging dumps. */
3474 if (dump_file)
3476 int c;
3477 unsigned i;
3479 dump_update_ssa (dump_file);
3481 fprintf (dump_file, "Incremental SSA update started at block: %d\n",
3482 start_bb->index);
3484 c = 0;
3485 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi)
3486 c++;
3487 fprintf (dump_file, "Number of blocks in CFG: %d\n",
3488 last_basic_block_for_fn (cfun));
3489 fprintf (dump_file, "Number of blocks to update: %d (%3.0f%%)\n",
3490 c, PERCENT (c, last_basic_block_for_fn (cfun)));
3492 if (dump_flags & TDF_DETAILS)
3494 fprintf (dump_file, "Affected blocks:");
3495 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi)
3496 fprintf (dump_file, " %u", i);
3497 fprintf (dump_file, "\n");
3500 fprintf (dump_file, "\n\n");
3503 /* Free allocated memory. */
3504 done:
3505 delete_update_ssa ();
3507 timevar_pop (TV_TREE_SSA_INCREMENTAL);