domwalk.h (struct dom_walk_data): Remove all callbacks except before_dom_children_bef...
[official-gcc.git] / gcc / tree-into-ssa.c
blobab827eadc578a8bd52aaaa945f20fe80d8a388a0
1 /* Rewrite a program in Normal form into SSA.
2 Copyright (C) 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009
3 Free Software Foundation, Inc.
4 Contributed by Diego Novillo <dnovillo@redhat.com>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3, or (at your option)
11 any later version.
13 GCC is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
22 #include "config.h"
23 #include "system.h"
24 #include "coretypes.h"
25 #include "tm.h"
26 #include "tree.h"
27 #include "flags.h"
28 #include "rtl.h"
29 #include "tm_p.h"
30 #include "langhooks.h"
31 #include "hard-reg-set.h"
32 #include "basic-block.h"
33 #include "output.h"
34 #include "expr.h"
35 #include "function.h"
36 #include "diagnostic.h"
37 #include "bitmap.h"
38 #include "tree-flow.h"
39 #include "gimple.h"
40 #include "tree-inline.h"
41 #include "varray.h"
42 #include "timevar.h"
43 #include "hashtab.h"
44 #include "tree-dump.h"
45 #include "tree-pass.h"
46 #include "cfgloop.h"
47 #include "domwalk.h"
48 #include "ggc.h"
49 #include "params.h"
50 #include "vecprim.h"
53 /* This file builds the SSA form for a function as described in:
54 R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently
55 Computing Static Single Assignment Form and the Control Dependence
56 Graph. ACM Transactions on Programming Languages and Systems,
57 13(4):451-490, October 1991. */
59 /* Structure to map a variable VAR to the set of blocks that contain
60 definitions for VAR. */
61 struct def_blocks_d
63 /* The variable. */
64 tree var;
66 /* Blocks that contain definitions of VAR. Bit I will be set if the
67 Ith block contains a definition of VAR. */
68 bitmap def_blocks;
70 /* Blocks that contain a PHI node for VAR. */
71 bitmap phi_blocks;
73 /* Blocks where VAR is live-on-entry. Similar semantics as
74 DEF_BLOCKS. */
75 bitmap livein_blocks;
79 /* Each entry in DEF_BLOCKS contains an element of type STRUCT
80 DEF_BLOCKS_D, mapping a variable VAR to a bitmap describing all the
81 basic blocks where VAR is defined (assigned a new value). It also
82 contains a bitmap of all the blocks where VAR is live-on-entry
83 (i.e., there is a use of VAR in block B without a preceding
84 definition in B). The live-on-entry information is used when
85 computing PHI pruning heuristics. */
86 static htab_t def_blocks;
88 /* Stack of trees used to restore the global currdefs to its original
89 state after completing rewriting of a block and its dominator
90 children. Its elements have the following properties:
92 - An SSA_NAME (N) indicates that the current definition of the
93 underlying variable should be set to the given SSA_NAME. If the
94 symbol associated with the SSA_NAME is not a GIMPLE register, the
95 next slot in the stack must be a _DECL node (SYM). In this case,
96 the name N in the previous slot is the current reaching
97 definition for SYM.
99 - A _DECL node indicates that the underlying variable has no
100 current definition.
102 - A NULL node at the top entry is used to mark the last slot
103 associated with the current block. */
104 static VEC(tree,heap) *block_defs_stack;
107 /* Set of existing SSA names being replaced by update_ssa. */
108 static sbitmap old_ssa_names;
110 /* Set of new SSA names being added by update_ssa. Note that both
111 NEW_SSA_NAMES and OLD_SSA_NAMES are dense bitmaps because most of
112 the operations done on them are presence tests. */
113 static sbitmap new_ssa_names;
115 sbitmap interesting_blocks;
117 /* Set of SSA names that have been marked to be released after they
118 were registered in the replacement table. They will be finally
119 released after we finish updating the SSA web. */
120 static bitmap names_to_release;
122 static VEC(gimple_vec, heap) *phis_to_rewrite;
124 /* The bitmap of non-NULL elements of PHIS_TO_REWRITE. */
125 static bitmap blocks_with_phis_to_rewrite;
127 /* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need
128 to grow as the callers to register_new_name_mapping will typically
129 create new names on the fly. FIXME. Currently set to 1/3 to avoid
130 frequent reallocations but still need to find a reasonable growth
131 strategy. */
132 #define NAME_SETS_GROWTH_FACTOR (MAX (3, num_ssa_names / 3))
134 /* Tuple used to represent replacement mappings. */
135 struct repl_map_d
137 tree name;
138 bitmap set;
142 /* NEW -> OLD_SET replacement table. If we are replacing several
143 existing SSA names O_1, O_2, ..., O_j with a new name N_i,
144 then REPL_TBL[N_i] = { O_1, O_2, ..., O_j }. */
145 static htab_t repl_tbl;
147 /* The function the SSA updating data structures have been initialized for.
148 NULL if they need to be initialized by register_new_name_mapping. */
149 static struct function *update_ssa_initialized_fn = NULL;
151 /* Statistics kept by update_ssa to use in the virtual mapping
152 heuristic. If the number of virtual mappings is beyond certain
153 threshold, the updater will switch from using the mappings into
154 renaming the virtual symbols from scratch. In some cases, the
155 large number of name mappings for virtual names causes significant
156 slowdowns in the PHI insertion code. */
157 struct update_ssa_stats_d
159 unsigned num_virtual_mappings;
160 unsigned num_total_mappings;
161 bitmap virtual_symbols;
162 unsigned num_virtual_symbols;
164 static struct update_ssa_stats_d update_ssa_stats;
166 /* Global data to attach to the main dominator walk structure. */
167 struct mark_def_sites_global_data
169 /* This bitmap contains the variables which are set before they
170 are used in a basic block. */
171 bitmap kills;
175 /* Information stored for SSA names. */
176 struct ssa_name_info
178 /* The current reaching definition replacing this SSA name. */
179 tree current_def;
181 /* This field indicates whether or not the variable may need PHI nodes.
182 See the enum's definition for more detailed information about the
183 states. */
184 ENUM_BITFIELD (need_phi_state) need_phi_state : 2;
186 /* Age of this record (so that info_for_ssa_name table can be cleared
187 quickly); if AGE < CURRENT_INFO_FOR_SSA_NAME_AGE, then the fields
188 are assumed to be null. */
189 unsigned age;
192 /* The information associated with names. */
193 typedef struct ssa_name_info *ssa_name_info_p;
194 DEF_VEC_P (ssa_name_info_p);
195 DEF_VEC_ALLOC_P (ssa_name_info_p, heap);
197 static VEC(ssa_name_info_p, heap) *info_for_ssa_name;
198 static unsigned current_info_for_ssa_name_age;
200 /* The set of blocks affected by update_ssa. */
201 static bitmap blocks_to_update;
203 /* The main entry point to the SSA renamer (rewrite_blocks) may be
204 called several times to do different, but related, tasks.
205 Initially, we need it to rename the whole program into SSA form.
206 At other times, we may need it to only rename into SSA newly
207 exposed symbols. Finally, we can also call it to incrementally fix
208 an already built SSA web. */
209 enum rewrite_mode {
210 /* Convert the whole function into SSA form. */
211 REWRITE_ALL,
213 /* Incrementally update the SSA web by replacing existing SSA
214 names with new ones. See update_ssa for details. */
215 REWRITE_UPDATE
221 /* Prototypes for debugging functions. */
222 extern void dump_tree_ssa (FILE *);
223 extern void debug_tree_ssa (void);
224 extern void debug_def_blocks (void);
225 extern void dump_tree_ssa_stats (FILE *);
226 extern void debug_tree_ssa_stats (void);
227 extern void dump_update_ssa (FILE *);
228 extern void debug_update_ssa (void);
229 extern void dump_names_replaced_by (FILE *, tree);
230 extern void debug_names_replaced_by (tree);
231 extern void dump_def_blocks (FILE *);
232 extern void debug_def_blocks (void);
233 extern void dump_defs_stack (FILE *, int);
234 extern void debug_defs_stack (int);
235 extern void dump_currdefs (FILE *);
236 extern void debug_currdefs (void);
238 /* Return true if STMT needs to be rewritten. When renaming a subset
239 of the variables, not all statements will be processed. This is
240 decided in mark_def_sites. */
242 static inline bool
243 rewrite_uses_p (gimple stmt)
245 return gimple_visited_p (stmt);
249 /* Set the rewrite marker on STMT to the value given by REWRITE_P. */
251 static inline void
252 set_rewrite_uses (gimple stmt, bool rewrite_p)
254 gimple_set_visited (stmt, rewrite_p);
258 /* Return true if the DEFs created by statement STMT should be
259 registered when marking new definition sites. This is slightly
260 different than rewrite_uses_p: it's used by update_ssa to
261 distinguish statements that need to have both uses and defs
262 processed from those that only need to have their defs processed.
263 Statements that define new SSA names only need to have their defs
264 registered, but they don't need to have their uses renamed. */
266 static inline bool
267 register_defs_p (gimple stmt)
269 return gimple_plf (stmt, GF_PLF_1) != 0;
273 /* If REGISTER_DEFS_P is true, mark STMT to have its DEFs registered. */
275 static inline void
276 set_register_defs (gimple stmt, bool register_defs_p)
278 gimple_set_plf (stmt, GF_PLF_1, register_defs_p);
282 /* Get the information associated with NAME. */
284 static inline ssa_name_info_p
285 get_ssa_name_ann (tree name)
287 unsigned ver = SSA_NAME_VERSION (name);
288 unsigned len = VEC_length (ssa_name_info_p, info_for_ssa_name);
289 struct ssa_name_info *info;
291 if (ver >= len)
293 unsigned new_len = num_ssa_names;
295 VEC_reserve (ssa_name_info_p, heap, info_for_ssa_name, new_len);
296 while (len++ < new_len)
298 struct ssa_name_info *info = XCNEW (struct ssa_name_info);
299 info->age = current_info_for_ssa_name_age;
300 VEC_quick_push (ssa_name_info_p, info_for_ssa_name, info);
304 info = VEC_index (ssa_name_info_p, info_for_ssa_name, ver);
305 if (info->age < current_info_for_ssa_name_age)
307 info->need_phi_state = NEED_PHI_STATE_UNKNOWN;
308 info->current_def = NULL_TREE;
309 info->age = current_info_for_ssa_name_age;
312 return info;
316 /* Clears info for SSA names. */
318 static void
319 clear_ssa_name_info (void)
321 current_info_for_ssa_name_age++;
325 /* Get phi_state field for VAR. */
327 static inline enum need_phi_state
328 get_phi_state (tree var)
330 if (TREE_CODE (var) == SSA_NAME)
331 return get_ssa_name_ann (var)->need_phi_state;
332 else
333 return var_ann (var)->need_phi_state;
337 /* Sets phi_state field for VAR to STATE. */
339 static inline void
340 set_phi_state (tree var, enum need_phi_state state)
342 if (TREE_CODE (var) == SSA_NAME)
343 get_ssa_name_ann (var)->need_phi_state = state;
344 else
345 var_ann (var)->need_phi_state = state;
349 /* Return the current definition for VAR. */
351 tree
352 get_current_def (tree var)
354 if (TREE_CODE (var) == SSA_NAME)
355 return get_ssa_name_ann (var)->current_def;
356 else
357 return var_ann (var)->current_def;
361 /* Sets current definition of VAR to DEF. */
363 void
364 set_current_def (tree var, tree def)
366 if (TREE_CODE (var) == SSA_NAME)
367 get_ssa_name_ann (var)->current_def = def;
368 else
369 var_ann (var)->current_def = def;
373 /* Compute global livein information given the set of blocks where
374 an object is locally live at the start of the block (LIVEIN)
375 and the set of blocks where the object is defined (DEF_BLOCKS).
377 Note: This routine augments the existing local livein information
378 to include global livein (i.e., it modifies the underlying bitmap
379 for LIVEIN). */
381 void
382 compute_global_livein (bitmap livein ATTRIBUTE_UNUSED, bitmap def_blocks ATTRIBUTE_UNUSED)
384 basic_block bb, *worklist, *tos;
385 unsigned i;
386 bitmap_iterator bi;
388 tos = worklist
389 = (basic_block *) xmalloc (sizeof (basic_block) * (last_basic_block + 1));
391 EXECUTE_IF_SET_IN_BITMAP (livein, 0, i, bi)
392 *tos++ = BASIC_BLOCK (i);
394 /* Iterate until the worklist is empty. */
395 while (tos != worklist)
397 edge e;
398 edge_iterator ei;
400 /* Pull a block off the worklist. */
401 bb = *--tos;
403 /* For each predecessor block. */
404 FOR_EACH_EDGE (e, ei, bb->preds)
406 basic_block pred = e->src;
407 int pred_index = pred->index;
409 /* None of this is necessary for the entry block. */
410 if (pred != ENTRY_BLOCK_PTR
411 && ! bitmap_bit_p (livein, pred_index)
412 && ! bitmap_bit_p (def_blocks, pred_index))
414 *tos++ = pred;
415 bitmap_set_bit (livein, pred_index);
420 free (worklist);
424 /* Cleans up the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags for
425 all statements in basic block BB. */
427 static void
428 initialize_flags_in_bb (basic_block bb)
430 gimple stmt;
431 gimple_stmt_iterator gsi;
433 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
435 gimple phi = gsi_stmt (gsi);
436 set_rewrite_uses (phi, false);
437 set_register_defs (phi, false);
440 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
442 stmt = gsi_stmt (gsi);
444 /* We are going to use the operand cache API, such as
445 SET_USE, SET_DEF, and FOR_EACH_IMM_USE_FAST. The operand
446 cache for each statement should be up-to-date. */
447 gcc_assert (!gimple_modified_p (stmt));
448 set_rewrite_uses (stmt, false);
449 set_register_defs (stmt, false);
453 /* Mark block BB as interesting for update_ssa. */
455 static void
456 mark_block_for_update (basic_block bb)
458 gcc_assert (blocks_to_update != NULL);
459 if (bitmap_bit_p (blocks_to_update, bb->index))
460 return;
461 bitmap_set_bit (blocks_to_update, bb->index);
462 initialize_flags_in_bb (bb);
465 /* Return the set of blocks where variable VAR is defined and the blocks
466 where VAR is live on entry (livein). If no entry is found in
467 DEF_BLOCKS, a new one is created and returned. */
469 static inline struct def_blocks_d *
470 get_def_blocks_for (tree var)
472 struct def_blocks_d db, *db_p;
473 void **slot;
475 db.var = var;
476 slot = htab_find_slot (def_blocks, (void *) &db, INSERT);
477 if (*slot == NULL)
479 db_p = XNEW (struct def_blocks_d);
480 db_p->var = var;
481 db_p->def_blocks = BITMAP_ALLOC (NULL);
482 db_p->phi_blocks = BITMAP_ALLOC (NULL);
483 db_p->livein_blocks = BITMAP_ALLOC (NULL);
484 *slot = (void *) db_p;
486 else
487 db_p = (struct def_blocks_d *) *slot;
489 return db_p;
493 /* Mark block BB as the definition site for variable VAR. PHI_P is true if
494 VAR is defined by a PHI node. */
496 static void
497 set_def_block (tree var, basic_block bb, bool phi_p)
499 struct def_blocks_d *db_p;
500 enum need_phi_state state;
502 state = get_phi_state (var);
503 db_p = get_def_blocks_for (var);
505 /* Set the bit corresponding to the block where VAR is defined. */
506 bitmap_set_bit (db_p->def_blocks, bb->index);
507 if (phi_p)
508 bitmap_set_bit (db_p->phi_blocks, bb->index);
510 /* Keep track of whether or not we may need to insert PHI nodes.
512 If we are in the UNKNOWN state, then this is the first definition
513 of VAR. Additionally, we have not seen any uses of VAR yet, so
514 we do not need a PHI node for this variable at this time (i.e.,
515 transition to NEED_PHI_STATE_NO).
517 If we are in any other state, then we either have multiple definitions
518 of this variable occurring in different blocks or we saw a use of the
519 variable which was not dominated by the block containing the
520 definition(s). In this case we may need a PHI node, so enter
521 state NEED_PHI_STATE_MAYBE. */
522 if (state == NEED_PHI_STATE_UNKNOWN)
523 set_phi_state (var, NEED_PHI_STATE_NO);
524 else
525 set_phi_state (var, NEED_PHI_STATE_MAYBE);
529 /* Mark block BB as having VAR live at the entry to BB. */
531 static void
532 set_livein_block (tree var, basic_block bb)
534 struct def_blocks_d *db_p;
535 enum need_phi_state state = get_phi_state (var);
537 db_p = get_def_blocks_for (var);
539 /* Set the bit corresponding to the block where VAR is live in. */
540 bitmap_set_bit (db_p->livein_blocks, bb->index);
542 /* Keep track of whether or not we may need to insert PHI nodes.
544 If we reach here in NEED_PHI_STATE_NO, see if this use is dominated
545 by the single block containing the definition(s) of this variable. If
546 it is, then we remain in NEED_PHI_STATE_NO, otherwise we transition to
547 NEED_PHI_STATE_MAYBE. */
548 if (state == NEED_PHI_STATE_NO)
550 int def_block_index = bitmap_first_set_bit (db_p->def_blocks);
552 if (def_block_index == -1
553 || ! dominated_by_p (CDI_DOMINATORS, bb,
554 BASIC_BLOCK (def_block_index)))
555 set_phi_state (var, NEED_PHI_STATE_MAYBE);
557 else
558 set_phi_state (var, NEED_PHI_STATE_MAYBE);
562 /* Return true if symbol SYM is marked for renaming. */
564 static inline bool
565 symbol_marked_for_renaming (tree sym)
567 return bitmap_bit_p (SYMS_TO_RENAME (cfun), DECL_UID (sym));
571 /* Return true if NAME is in OLD_SSA_NAMES. */
573 static inline bool
574 is_old_name (tree name)
576 unsigned ver = SSA_NAME_VERSION (name);
577 if (!new_ssa_names)
578 return false;
579 return ver < new_ssa_names->n_bits && TEST_BIT (old_ssa_names, ver);
583 /* Return true if NAME is in NEW_SSA_NAMES. */
585 static inline bool
586 is_new_name (tree name)
588 unsigned ver = SSA_NAME_VERSION (name);
589 if (!new_ssa_names)
590 return false;
591 return ver < new_ssa_names->n_bits && TEST_BIT (new_ssa_names, ver);
595 /* Hashing and equality functions for REPL_TBL. */
597 static hashval_t
598 repl_map_hash (const void *p)
600 return htab_hash_pointer ((const void *)((const struct repl_map_d *)p)->name);
603 static int
604 repl_map_eq (const void *p1, const void *p2)
606 return ((const struct repl_map_d *)p1)->name
607 == ((const struct repl_map_d *)p2)->name;
610 static void
611 repl_map_free (void *p)
613 BITMAP_FREE (((struct repl_map_d *)p)->set);
614 free (p);
618 /* Return the names replaced by NEW_TREE (i.e., REPL_TBL[NEW_TREE].SET). */
620 static inline bitmap
621 names_replaced_by (tree new_tree)
623 struct repl_map_d m;
624 void **slot;
626 m.name = new_tree;
627 slot = htab_find_slot (repl_tbl, (void *) &m, NO_INSERT);
629 /* If N was not registered in the replacement table, return NULL. */
630 if (slot == NULL || *slot == NULL)
631 return NULL;
633 return ((struct repl_map_d *) *slot)->set;
637 /* Add OLD to REPL_TBL[NEW_TREE].SET. */
639 static inline void
640 add_to_repl_tbl (tree new_tree, tree old)
642 struct repl_map_d m, *mp;
643 void **slot;
645 m.name = new_tree;
646 slot = htab_find_slot (repl_tbl, (void *) &m, INSERT);
647 if (*slot == NULL)
649 mp = XNEW (struct repl_map_d);
650 mp->name = new_tree;
651 mp->set = BITMAP_ALLOC (NULL);
652 *slot = (void *) mp;
654 else
655 mp = (struct repl_map_d *) *slot;
657 bitmap_set_bit (mp->set, SSA_NAME_VERSION (old));
661 /* Add a new mapping NEW_TREE -> OLD REPL_TBL. Every entry N_i in REPL_TBL
662 represents the set of names O_1 ... O_j replaced by N_i. This is
663 used by update_ssa and its helpers to introduce new SSA names in an
664 already formed SSA web. */
666 static void
667 add_new_name_mapping (tree new_tree, tree old)
669 timevar_push (TV_TREE_SSA_INCREMENTAL);
671 /* OLD and NEW_TREE must be different SSA names for the same symbol. */
672 gcc_assert (new_tree != old && SSA_NAME_VAR (new_tree) == SSA_NAME_VAR (old));
674 /* If this mapping is for virtual names, we will need to update
675 virtual operands. If this is a mapping for .MEM, then we gather
676 the symbols associated with each name. */
677 if (!is_gimple_reg (new_tree))
679 tree sym;
681 update_ssa_stats.num_virtual_mappings++;
682 update_ssa_stats.num_virtual_symbols++;
684 /* Keep counts of virtual mappings and symbols to use in the
685 virtual mapping heuristic. If we have large numbers of
686 virtual mappings for a relatively low number of symbols, it
687 will make more sense to rename the symbols from scratch.
688 Otherwise, the insertion of PHI nodes for each of the old
689 names in these mappings will be very slow. */
690 sym = SSA_NAME_VAR (new_tree);
691 bitmap_set_bit (update_ssa_stats.virtual_symbols, DECL_UID (sym));
694 /* We may need to grow NEW_SSA_NAMES and OLD_SSA_NAMES because our
695 caller may have created new names since the set was created. */
696 if (new_ssa_names->n_bits <= num_ssa_names - 1)
698 unsigned int new_sz = num_ssa_names + NAME_SETS_GROWTH_FACTOR;
699 new_ssa_names = sbitmap_resize (new_ssa_names, new_sz, 0);
700 old_ssa_names = sbitmap_resize (old_ssa_names, new_sz, 0);
703 /* Update the REPL_TBL table. */
704 add_to_repl_tbl (new_tree, old);
706 /* If OLD had already been registered as a new name, then all the
707 names that OLD replaces should also be replaced by NEW_TREE. */
708 if (is_new_name (old))
709 bitmap_ior_into (names_replaced_by (new_tree), names_replaced_by (old));
711 /* Register NEW_TREE and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES,
712 respectively. */
713 SET_BIT (new_ssa_names, SSA_NAME_VERSION (new_tree));
714 SET_BIT (old_ssa_names, SSA_NAME_VERSION (old));
716 /* Update mapping counter to use in the virtual mapping heuristic. */
717 update_ssa_stats.num_total_mappings++;
719 timevar_pop (TV_TREE_SSA_INCREMENTAL);
723 /* Call back for walk_dominator_tree used to collect definition sites
724 for every variable in the function. For every statement S in block
727 1- Variables defined by S in the DEFS of S are marked in the bitmap
728 KILLS.
730 2- If S uses a variable VAR and there is no preceding kill of VAR,
731 then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR.
733 This information is used to determine which variables are live
734 across block boundaries to reduce the number of PHI nodes
735 we create. */
737 static void
738 mark_def_sites (basic_block bb, gimple stmt, bitmap kills)
740 tree def;
741 use_operand_p use_p;
742 ssa_op_iter iter;
744 /* Since this is the first time that we rewrite the program into SSA
745 form, force an operand scan on every statement. */
746 update_stmt (stmt);
748 gcc_assert (blocks_to_update == NULL);
749 set_register_defs (stmt, false);
750 set_rewrite_uses (stmt, false);
752 /* If a variable is used before being set, then the variable is live
753 across a block boundary, so mark it live-on-entry to BB. */
754 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
756 tree sym = USE_FROM_PTR (use_p);
757 gcc_assert (DECL_P (sym));
758 if (!bitmap_bit_p (kills, DECL_UID (sym)))
759 set_livein_block (sym, bb);
760 set_rewrite_uses (stmt, true);
763 /* Now process the defs. Mark BB as the definition block and add
764 each def to the set of killed symbols. */
765 FOR_EACH_SSA_TREE_OPERAND (def, stmt, iter, SSA_OP_DEF)
767 gcc_assert (DECL_P (def));
768 set_def_block (def, bb, false);
769 bitmap_set_bit (kills, DECL_UID (def));
770 set_register_defs (stmt, true);
773 /* If we found the statement interesting then also mark the block BB
774 as interesting. */
775 if (rewrite_uses_p (stmt) || register_defs_p (stmt))
776 SET_BIT (interesting_blocks, bb->index);
779 /* Structure used by prune_unused_phi_nodes to record bounds of the intervals
780 in the dfs numbering of the dominance tree. */
782 struct dom_dfsnum
784 /* Basic block whose index this entry corresponds to. */
785 unsigned bb_index;
787 /* The dfs number of this node. */
788 unsigned dfs_num;
791 /* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback
792 for qsort. */
794 static int
795 cmp_dfsnum (const void *a, const void *b)
797 const struct dom_dfsnum *const da = (const struct dom_dfsnum *) a;
798 const struct dom_dfsnum *const db = (const struct dom_dfsnum *) b;
800 return (int) da->dfs_num - (int) db->dfs_num;
803 /* Among the intervals starting at the N points specified in DEFS, find
804 the one that contains S, and return its bb_index. */
806 static unsigned
807 find_dfsnum_interval (struct dom_dfsnum *defs, unsigned n, unsigned s)
809 unsigned f = 0, t = n, m;
811 while (t > f + 1)
813 m = (f + t) / 2;
814 if (defs[m].dfs_num <= s)
815 f = m;
816 else
817 t = m;
820 return defs[f].bb_index;
823 /* Clean bits from PHIS for phi nodes whose value cannot be used in USES.
824 KILLS is a bitmap of blocks where the value is defined before any use. */
826 static void
827 prune_unused_phi_nodes (bitmap phis, bitmap kills, bitmap uses)
829 VEC(int, heap) *worklist;
830 bitmap_iterator bi;
831 unsigned i, b, p, u, top;
832 bitmap live_phis;
833 basic_block def_bb, use_bb;
834 edge e;
835 edge_iterator ei;
836 bitmap to_remove;
837 struct dom_dfsnum *defs;
838 unsigned n_defs, adef;
840 if (bitmap_empty_p (uses))
842 bitmap_clear (phis);
843 return;
846 /* The phi must dominate a use, or an argument of a live phi. Also, we
847 do not create any phi nodes in def blocks, unless they are also livein. */
848 to_remove = BITMAP_ALLOC (NULL);
849 bitmap_and_compl (to_remove, kills, uses);
850 bitmap_and_compl_into (phis, to_remove);
851 if (bitmap_empty_p (phis))
853 BITMAP_FREE (to_remove);
854 return;
857 /* We want to remove the unnecessary phi nodes, but we do not want to compute
858 liveness information, as that may be linear in the size of CFG, and if
859 there are lot of different variables to rewrite, this may lead to quadratic
860 behavior.
862 Instead, we basically emulate standard dce. We put all uses to worklist,
863 then for each of them find the nearest def that dominates them. If this
864 def is a phi node, we mark it live, and if it was not live before, we
865 add the predecessors of its basic block to the worklist.
867 To quickly locate the nearest def that dominates use, we use dfs numbering
868 of the dominance tree (that is already available in order to speed up
869 queries). For each def, we have the interval given by the dfs number on
870 entry to and on exit from the corresponding subtree in the dominance tree.
871 The nearest dominator for a given use is the smallest of these intervals
872 that contains entry and exit dfs numbers for the basic block with the use.
873 If we store the bounds for all the uses to an array and sort it, we can
874 locate the nearest dominating def in logarithmic time by binary search.*/
875 bitmap_ior (to_remove, kills, phis);
876 n_defs = bitmap_count_bits (to_remove);
877 defs = XNEWVEC (struct dom_dfsnum, 2 * n_defs + 1);
878 defs[0].bb_index = 1;
879 defs[0].dfs_num = 0;
880 adef = 1;
881 EXECUTE_IF_SET_IN_BITMAP (to_remove, 0, i, bi)
883 def_bb = BASIC_BLOCK (i);
884 defs[adef].bb_index = i;
885 defs[adef].dfs_num = bb_dom_dfs_in (CDI_DOMINATORS, def_bb);
886 defs[adef + 1].bb_index = i;
887 defs[adef + 1].dfs_num = bb_dom_dfs_out (CDI_DOMINATORS, def_bb);
888 adef += 2;
890 BITMAP_FREE (to_remove);
891 gcc_assert (adef == 2 * n_defs + 1);
892 qsort (defs, adef, sizeof (struct dom_dfsnum), cmp_dfsnum);
893 gcc_assert (defs[0].bb_index == 1);
895 /* Now each DEFS entry contains the number of the basic block to that the
896 dfs number corresponds. Change them to the number of basic block that
897 corresponds to the interval following the dfs number. Also, for the
898 dfs_out numbers, increase the dfs number by one (so that it corresponds
899 to the start of the following interval, not to the end of the current
900 one). We use WORKLIST as a stack. */
901 worklist = VEC_alloc (int, heap, n_defs + 1);
902 VEC_quick_push (int, worklist, 1);
903 top = 1;
904 n_defs = 1;
905 for (i = 1; i < adef; i++)
907 b = defs[i].bb_index;
908 if (b == top)
910 /* This is a closing element. Interval corresponding to the top
911 of the stack after removing it follows. */
912 VEC_pop (int, worklist);
913 top = VEC_index (int, worklist, VEC_length (int, worklist) - 1);
914 defs[n_defs].bb_index = top;
915 defs[n_defs].dfs_num = defs[i].dfs_num + 1;
917 else
919 /* Opening element. Nothing to do, just push it to the stack and move
920 it to the correct position. */
921 defs[n_defs].bb_index = defs[i].bb_index;
922 defs[n_defs].dfs_num = defs[i].dfs_num;
923 VEC_quick_push (int, worklist, b);
924 top = b;
927 /* If this interval starts at the same point as the previous one, cancel
928 the previous one. */
929 if (defs[n_defs].dfs_num == defs[n_defs - 1].dfs_num)
930 defs[n_defs - 1].bb_index = defs[n_defs].bb_index;
931 else
932 n_defs++;
934 VEC_pop (int, worklist);
935 gcc_assert (VEC_empty (int, worklist));
937 /* Now process the uses. */
938 live_phis = BITMAP_ALLOC (NULL);
939 EXECUTE_IF_SET_IN_BITMAP (uses, 0, i, bi)
941 VEC_safe_push (int, heap, worklist, i);
944 while (!VEC_empty (int, worklist))
946 b = VEC_pop (int, worklist);
947 if (b == ENTRY_BLOCK)
948 continue;
950 /* If there is a phi node in USE_BB, it is made live. Otherwise,
951 find the def that dominates the immediate dominator of USE_BB
952 (the kill in USE_BB does not dominate the use). */
953 if (bitmap_bit_p (phis, b))
954 p = b;
955 else
957 use_bb = get_immediate_dominator (CDI_DOMINATORS, BASIC_BLOCK (b));
958 p = find_dfsnum_interval (defs, n_defs,
959 bb_dom_dfs_in (CDI_DOMINATORS, use_bb));
960 if (!bitmap_bit_p (phis, p))
961 continue;
964 /* If the phi node is already live, there is nothing to do. */
965 if (bitmap_bit_p (live_phis, p))
966 continue;
968 /* Mark the phi as live, and add the new uses to the worklist. */
969 bitmap_set_bit (live_phis, p);
970 def_bb = BASIC_BLOCK (p);
971 FOR_EACH_EDGE (e, ei, def_bb->preds)
973 u = e->src->index;
974 if (bitmap_bit_p (uses, u))
975 continue;
977 /* In case there is a kill directly in the use block, do not record
978 the use (this is also necessary for correctness, as we assume that
979 uses dominated by a def directly in their block have been filtered
980 out before). */
981 if (bitmap_bit_p (kills, u))
982 continue;
984 bitmap_set_bit (uses, u);
985 VEC_safe_push (int, heap, worklist, u);
989 VEC_free (int, heap, worklist);
990 bitmap_copy (phis, live_phis);
991 BITMAP_FREE (live_phis);
992 free (defs);
995 /* Return the set of blocks where variable VAR is defined and the blocks
996 where VAR is live on entry (livein). Return NULL, if no entry is
997 found in DEF_BLOCKS. */
999 static inline struct def_blocks_d *
1000 find_def_blocks_for (tree var)
1002 struct def_blocks_d dm;
1003 dm.var = var;
1004 return (struct def_blocks_d *) htab_find (def_blocks, &dm);
1008 /* Retrieve or create a default definition for symbol SYM. */
1010 static inline tree
1011 get_default_def_for (tree sym)
1013 tree ddef = gimple_default_def (cfun, sym);
1015 if (ddef == NULL_TREE)
1017 ddef = make_ssa_name (sym, gimple_build_nop ());
1018 set_default_def (sym, ddef);
1021 return ddef;
1025 /* Marks phi node PHI in basic block BB for rewrite. */
1027 static void
1028 mark_phi_for_rewrite (basic_block bb, gimple phi)
1030 gimple_vec phis;
1031 unsigned i, idx = bb->index;
1033 if (rewrite_uses_p (phi))
1034 return;
1036 set_rewrite_uses (phi, true);
1038 if (!blocks_with_phis_to_rewrite)
1039 return;
1041 bitmap_set_bit (blocks_with_phis_to_rewrite, idx);
1042 VEC_reserve (gimple_vec, heap, phis_to_rewrite, last_basic_block + 1);
1043 for (i = VEC_length (gimple_vec, phis_to_rewrite); i <= idx; i++)
1044 VEC_quick_push (gimple_vec, phis_to_rewrite, NULL);
1046 phis = VEC_index (gimple_vec, phis_to_rewrite, idx);
1047 if (!phis)
1048 phis = VEC_alloc (gimple, heap, 10);
1050 VEC_safe_push (gimple, heap, phis, phi);
1051 VEC_replace (gimple_vec, phis_to_rewrite, idx, phis);
1055 /* Insert PHI nodes for variable VAR using the iterated dominance
1056 frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
1057 function assumes that the caller is incrementally updating the
1058 existing SSA form, in which case VAR may be an SSA name instead of
1059 a symbol.
1061 PHI_INSERTION_POINTS is updated to reflect nodes that already had a
1062 PHI node for VAR. On exit, only the nodes that received a PHI node
1063 for VAR will be present in PHI_INSERTION_POINTS. */
1065 static void
1066 insert_phi_nodes_for (tree var, bitmap phi_insertion_points, bool update_p)
1068 unsigned bb_index;
1069 edge e;
1070 gimple phi;
1071 basic_block bb;
1072 bitmap_iterator bi;
1073 struct def_blocks_d *def_map;
1075 def_map = find_def_blocks_for (var);
1076 gcc_assert (def_map);
1078 /* Remove the blocks where we already have PHI nodes for VAR. */
1079 bitmap_and_compl_into (phi_insertion_points, def_map->phi_blocks);
1081 /* Remove obviously useless phi nodes. */
1082 prune_unused_phi_nodes (phi_insertion_points, def_map->def_blocks,
1083 def_map->livein_blocks);
1085 /* And insert the PHI nodes. */
1086 EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points, 0, bb_index, bi)
1088 bb = BASIC_BLOCK (bb_index);
1089 if (update_p)
1090 mark_block_for_update (bb);
1092 phi = NULL;
1094 if (TREE_CODE (var) == SSA_NAME)
1096 /* If we are rewriting SSA names, create the LHS of the PHI
1097 node by duplicating VAR. This is useful in the case of
1098 pointers, to also duplicate pointer attributes (alias
1099 information, in particular). */
1100 edge_iterator ei;
1101 tree new_lhs;
1103 gcc_assert (update_p);
1104 phi = create_phi_node (var, bb);
1106 new_lhs = duplicate_ssa_name (var, phi);
1107 gimple_phi_set_result (phi, new_lhs);
1108 add_new_name_mapping (new_lhs, var);
1110 /* Add VAR to every argument slot of PHI. We need VAR in
1111 every argument so that rewrite_update_phi_arguments knows
1112 which name is this PHI node replacing. If VAR is a
1113 symbol marked for renaming, this is not necessary, the
1114 renamer will use the symbol on the LHS to get its
1115 reaching definition. */
1116 FOR_EACH_EDGE (e, ei, bb->preds)
1117 add_phi_arg (phi, var, e);
1119 else
1121 gcc_assert (DECL_P (var));
1122 phi = create_phi_node (var, bb);
1125 /* Mark this PHI node as interesting for update_ssa. */
1126 set_register_defs (phi, true);
1127 mark_phi_for_rewrite (bb, phi);
1132 /* Insert PHI nodes at the dominance frontier of blocks with variable
1133 definitions. DFS contains the dominance frontier information for
1134 the flowgraph. */
1136 static void
1137 insert_phi_nodes (bitmap *dfs)
1139 referenced_var_iterator rvi;
1140 tree var;
1142 timevar_push (TV_TREE_INSERT_PHI_NODES);
1144 FOR_EACH_REFERENCED_VAR (var, rvi)
1146 struct def_blocks_d *def_map;
1147 bitmap idf;
1149 def_map = find_def_blocks_for (var);
1150 if (def_map == NULL)
1151 continue;
1153 if (get_phi_state (var) != NEED_PHI_STATE_NO)
1155 idf = compute_idf (def_map->def_blocks, dfs);
1156 insert_phi_nodes_for (var, idf, false);
1157 BITMAP_FREE (idf);
1161 timevar_pop (TV_TREE_INSERT_PHI_NODES);
1165 /* Push SYM's current reaching definition into BLOCK_DEFS_STACK and
1166 register DEF (an SSA_NAME) to be a new definition for SYM. */
1168 static void
1169 register_new_def (tree def, tree sym)
1171 tree currdef;
1173 /* If this variable is set in a single basic block and all uses are
1174 dominated by the set(s) in that single basic block, then there is
1175 no reason to record anything for this variable in the block local
1176 definition stacks. Doing so just wastes time and memory.
1178 This is the same test to prune the set of variables which may
1179 need PHI nodes. So we just use that information since it's already
1180 computed and available for us to use. */
1181 if (get_phi_state (sym) == NEED_PHI_STATE_NO)
1183 set_current_def (sym, def);
1184 return;
1187 currdef = get_current_def (sym);
1189 /* If SYM is not a GIMPLE register, then CURRDEF may be a name whose
1190 SSA_NAME_VAR is not necessarily SYM. In this case, also push SYM
1191 in the stack so that we know which symbol is being defined by
1192 this SSA name when we unwind the stack. */
1193 if (currdef && !is_gimple_reg (sym))
1194 VEC_safe_push (tree, heap, block_defs_stack, sym);
1196 /* Push the current reaching definition into BLOCK_DEFS_STACK. This
1197 stack is later used by the dominator tree callbacks to restore
1198 the reaching definitions for all the variables defined in the
1199 block after a recursive visit to all its immediately dominated
1200 blocks. If there is no current reaching definition, then just
1201 record the underlying _DECL node. */
1202 VEC_safe_push (tree, heap, block_defs_stack, currdef ? currdef : sym);
1204 /* Set the current reaching definition for SYM to be DEF. */
1205 set_current_def (sym, def);
1209 /* Perform a depth-first traversal of the dominator tree looking for
1210 variables to rename. BB is the block where to start searching.
1211 Renaming is a five step process:
1213 1- Every definition made by PHI nodes at the start of the blocks is
1214 registered as the current definition for the corresponding variable.
1216 2- Every statement in BB is rewritten. USE and VUSE operands are
1217 rewritten with their corresponding reaching definition. DEF and
1218 VDEF targets are registered as new definitions.
1220 3- All the PHI nodes in successor blocks of BB are visited. The
1221 argument corresponding to BB is replaced with its current reaching
1222 definition.
1224 4- Recursively rewrite every dominator child block of BB.
1226 5- Restore (in reverse order) the current reaching definition for every
1227 new definition introduced in this block. This is done so that when
1228 we return from the recursive call, all the current reaching
1229 definitions are restored to the names that were valid in the
1230 dominator parent of BB. */
1232 /* Return the current definition for variable VAR. If none is found,
1233 create a new SSA name to act as the zeroth definition for VAR. */
1235 static tree
1236 get_reaching_def (tree var)
1238 tree currdef;
1240 /* Lookup the current reaching definition for VAR. */
1241 currdef = get_current_def (var);
1243 /* If there is no reaching definition for VAR, create and register a
1244 default definition for it (if needed). */
1245 if (currdef == NULL_TREE)
1247 tree sym = DECL_P (var) ? var : SSA_NAME_VAR (var);
1248 currdef = get_default_def_for (sym);
1249 set_current_def (var, currdef);
1252 /* Return the current reaching definition for VAR, or the default
1253 definition, if we had to create one. */
1254 return currdef;
1258 /* SSA Rewriting Step 2. Rewrite every variable used in each statement in
1259 the block with its immediate reaching definitions. Update the current
1260 definition of a variable when a new real or virtual definition is found. */
1262 static void
1263 rewrite_stmt (gimple stmt)
1265 use_operand_p use_p;
1266 def_operand_p def_p;
1267 ssa_op_iter iter;
1269 /* If mark_def_sites decided that we don't need to rewrite this
1270 statement, ignore it. */
1271 gcc_assert (blocks_to_update == NULL);
1272 if (!rewrite_uses_p (stmt) && !register_defs_p (stmt))
1273 return;
1275 if (dump_file && (dump_flags & TDF_DETAILS))
1277 fprintf (dump_file, "Renaming statement ");
1278 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
1279 fprintf (dump_file, "\n");
1282 /* Step 1. Rewrite USES in the statement. */
1283 if (rewrite_uses_p (stmt))
1284 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_USE)
1286 tree var = USE_FROM_PTR (use_p);
1287 gcc_assert (DECL_P (var));
1288 SET_USE (use_p, get_reaching_def (var));
1291 /* Step 2. Register the statement's DEF operands. */
1292 if (register_defs_p (stmt))
1293 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_DEF)
1295 tree var = DEF_FROM_PTR (def_p);
1296 gcc_assert (DECL_P (var));
1297 SET_DEF (def_p, make_ssa_name (var, stmt));
1298 register_new_def (DEF_FROM_PTR (def_p), var);
1303 /* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for
1304 PHI nodes. For every PHI node found, add a new argument containing the
1305 current reaching definition for the variable and the edge through which
1306 that definition is reaching the PHI node. */
1308 static void
1309 rewrite_add_phi_arguments (basic_block bb)
1311 edge e;
1312 edge_iterator ei;
1314 FOR_EACH_EDGE (e, ei, bb->succs)
1316 gimple phi;
1317 gimple_stmt_iterator gsi;
1319 for (gsi = gsi_start_phis (e->dest); !gsi_end_p (gsi);
1320 gsi_next (&gsi))
1322 tree currdef;
1323 phi = gsi_stmt (gsi);
1324 currdef = get_reaching_def (SSA_NAME_VAR (gimple_phi_result (phi)));
1325 add_phi_arg (phi, currdef, e);
1330 /* SSA Rewriting Step 1. Initialization, create a block local stack
1331 of reaching definitions for new SSA names produced in this block
1332 (BLOCK_DEFS). Register new definitions for every PHI node in the
1333 block. */
1335 static void
1336 rewrite_enter_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
1337 basic_block bb)
1339 gimple phi;
1340 gimple_stmt_iterator gsi;
1342 if (dump_file && (dump_flags & TDF_DETAILS))
1343 fprintf (dump_file, "\n\nRenaming block #%d\n\n", bb->index);
1345 /* Mark the unwind point for this block. */
1346 VEC_safe_push (tree, heap, block_defs_stack, NULL_TREE);
1348 /* Step 1. Register new definitions for every PHI node in the block.
1349 Conceptually, all the PHI nodes are executed in parallel and each PHI
1350 node introduces a new version for the associated variable. */
1351 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
1353 tree result;
1355 phi = gsi_stmt (gsi);
1356 result = gimple_phi_result (phi);
1357 gcc_assert (is_gimple_reg (result));
1358 register_new_def (result, SSA_NAME_VAR (result));
1361 /* Step 2. Rewrite every variable used in each statement in the block
1362 with its immediate reaching definitions. Update the current definition
1363 of a variable when a new real or virtual definition is found. */
1364 if (TEST_BIT (interesting_blocks, bb->index))
1365 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
1366 rewrite_stmt (gsi_stmt (gsi));
1368 /* Step 3. Visit all the successor blocks of BB looking for PHI nodes.
1369 For every PHI node found, add a new argument containing the current
1370 reaching definition for the variable and the edge through which that
1371 definition is reaching the PHI node. */
1372 rewrite_add_phi_arguments (bb);
1377 /* Called after visiting all the statements in basic block BB and all
1378 of its dominator children. Restore CURRDEFS to its original value. */
1380 static void
1381 rewrite_leave_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
1382 basic_block bb ATTRIBUTE_UNUSED)
1384 /* Restore CURRDEFS to its original state. */
1385 while (VEC_length (tree, block_defs_stack) > 0)
1387 tree tmp = VEC_pop (tree, block_defs_stack);
1388 tree saved_def, var;
1390 if (tmp == NULL_TREE)
1391 break;
1393 if (TREE_CODE (tmp) == SSA_NAME)
1395 /* If we recorded an SSA_NAME, then make the SSA_NAME the
1396 current definition of its underlying variable. Note that
1397 if the SSA_NAME is not for a GIMPLE register, the symbol
1398 being defined is stored in the next slot in the stack.
1399 This mechanism is needed because an SSA name for a
1400 non-register symbol may be the definition for more than
1401 one symbol (e.g., SFTs, aliased variables, etc). */
1402 saved_def = tmp;
1403 var = SSA_NAME_VAR (saved_def);
1404 if (!is_gimple_reg (var))
1405 var = VEC_pop (tree, block_defs_stack);
1407 else
1409 /* If we recorded anything else, it must have been a _DECL
1410 node and its current reaching definition must have been
1411 NULL. */
1412 saved_def = NULL;
1413 var = tmp;
1416 set_current_def (var, saved_def);
1421 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1423 void
1424 dump_decl_set (FILE *file, bitmap set)
1426 if (set)
1428 bitmap_iterator bi;
1429 unsigned i;
1431 fprintf (file, "{ ");
1433 EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
1435 print_generic_expr (file, referenced_var (i), 0);
1436 fprintf (file, " ");
1439 fprintf (file, "}");
1441 else
1442 fprintf (file, "NIL");
1446 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1448 void
1449 debug_decl_set (bitmap set)
1451 dump_decl_set (stderr, set);
1452 fprintf (stderr, "\n");
1456 /* Dump the renaming stack (block_defs_stack) to FILE. Traverse the
1457 stack up to a maximum of N levels. If N is -1, the whole stack is
1458 dumped. New levels are created when the dominator tree traversal
1459 used for renaming enters a new sub-tree. */
1461 void
1462 dump_defs_stack (FILE *file, int n)
1464 int i, j;
1466 fprintf (file, "\n\nRenaming stack");
1467 if (n > 0)
1468 fprintf (file, " (up to %d levels)", n);
1469 fprintf (file, "\n\n");
1471 i = 1;
1472 fprintf (file, "Level %d (current level)\n", i);
1473 for (j = (int) VEC_length (tree, block_defs_stack) - 1; j >= 0; j--)
1475 tree name, var;
1477 name = VEC_index (tree, block_defs_stack, j);
1478 if (name == NULL_TREE)
1480 i++;
1481 if (n > 0 && i > n)
1482 break;
1483 fprintf (file, "\nLevel %d\n", i);
1484 continue;
1487 if (DECL_P (name))
1489 var = name;
1490 name = NULL_TREE;
1492 else
1494 var = SSA_NAME_VAR (name);
1495 if (!is_gimple_reg (var))
1497 j--;
1498 var = VEC_index (tree, block_defs_stack, j);
1502 fprintf (file, " Previous CURRDEF (");
1503 print_generic_expr (file, var, 0);
1504 fprintf (file, ") = ");
1505 if (name)
1506 print_generic_expr (file, name, 0);
1507 else
1508 fprintf (file, "<NIL>");
1509 fprintf (file, "\n");
1514 /* Dump the renaming stack (block_defs_stack) to stderr. Traverse the
1515 stack up to a maximum of N levels. If N is -1, the whole stack is
1516 dumped. New levels are created when the dominator tree traversal
1517 used for renaming enters a new sub-tree. */
1519 void
1520 debug_defs_stack (int n)
1522 dump_defs_stack (stderr, n);
1526 /* Dump the current reaching definition of every symbol to FILE. */
1528 void
1529 dump_currdefs (FILE *file)
1531 referenced_var_iterator i;
1532 tree var;
1534 fprintf (file, "\n\nCurrent reaching definitions\n\n");
1535 FOR_EACH_REFERENCED_VAR (var, i)
1536 if (SYMS_TO_RENAME (cfun) == NULL
1537 || bitmap_bit_p (SYMS_TO_RENAME (cfun), DECL_UID (var)))
1539 fprintf (file, "CURRDEF (");
1540 print_generic_expr (file, var, 0);
1541 fprintf (file, ") = ");
1542 if (get_current_def (var))
1543 print_generic_expr (file, get_current_def (var), 0);
1544 else
1545 fprintf (file, "<NIL>");
1546 fprintf (file, "\n");
1551 /* Dump the current reaching definition of every symbol to stderr. */
1553 void
1554 debug_currdefs (void)
1556 dump_currdefs (stderr);
1560 /* Dump SSA information to FILE. */
1562 void
1563 dump_tree_ssa (FILE *file)
1565 const char *funcname
1566 = lang_hooks.decl_printable_name (current_function_decl, 2);
1568 fprintf (file, "SSA renaming information for %s\n\n", funcname);
1570 dump_def_blocks (file);
1571 dump_defs_stack (file, -1);
1572 dump_currdefs (file);
1573 dump_tree_ssa_stats (file);
1577 /* Dump SSA information to stderr. */
1579 void
1580 debug_tree_ssa (void)
1582 dump_tree_ssa (stderr);
1586 /* Dump statistics for the hash table HTAB. */
1588 static void
1589 htab_statistics (FILE *file, htab_t htab)
1591 fprintf (file, "size %ld, %ld elements, %f collision/search ratio\n",
1592 (long) htab_size (htab),
1593 (long) htab_elements (htab),
1594 htab_collisions (htab));
1598 /* Dump SSA statistics on FILE. */
1600 void
1601 dump_tree_ssa_stats (FILE *file)
1603 if (def_blocks || repl_tbl)
1604 fprintf (file, "\nHash table statistics:\n");
1606 if (def_blocks)
1608 fprintf (file, " def_blocks: ");
1609 htab_statistics (file, def_blocks);
1612 if (repl_tbl)
1614 fprintf (file, " repl_tbl: ");
1615 htab_statistics (file, repl_tbl);
1618 if (def_blocks || repl_tbl)
1619 fprintf (file, "\n");
1623 /* Dump SSA statistics on stderr. */
1625 void
1626 debug_tree_ssa_stats (void)
1628 dump_tree_ssa_stats (stderr);
1632 /* Hashing and equality functions for DEF_BLOCKS. */
1634 static hashval_t
1635 def_blocks_hash (const void *p)
1637 return htab_hash_pointer
1638 ((const void *)((const struct def_blocks_d *)p)->var);
1641 static int
1642 def_blocks_eq (const void *p1, const void *p2)
1644 return ((const struct def_blocks_d *)p1)->var
1645 == ((const struct def_blocks_d *)p2)->var;
1649 /* Free memory allocated by one entry in DEF_BLOCKS. */
1651 static void
1652 def_blocks_free (void *p)
1654 struct def_blocks_d *entry = (struct def_blocks_d *) p;
1655 BITMAP_FREE (entry->def_blocks);
1656 BITMAP_FREE (entry->phi_blocks);
1657 BITMAP_FREE (entry->livein_blocks);
1658 free (entry);
1662 /* Callback for htab_traverse to dump the DEF_BLOCKS hash table. */
1664 static int
1665 debug_def_blocks_r (void **slot, void *data)
1667 FILE *file = (FILE *) data;
1668 struct def_blocks_d *db_p = (struct def_blocks_d *) *slot;
1670 fprintf (file, "VAR: ");
1671 print_generic_expr (file, db_p->var, dump_flags);
1672 bitmap_print (file, db_p->def_blocks, ", DEF_BLOCKS: { ", "}");
1673 bitmap_print (file, db_p->livein_blocks, ", LIVEIN_BLOCKS: { ", "}");
1674 bitmap_print (file, db_p->phi_blocks, ", PHI_BLOCKS: { ", "}\n");
1676 return 1;
1680 /* Dump the DEF_BLOCKS hash table on FILE. */
1682 void
1683 dump_def_blocks (FILE *file)
1685 fprintf (file, "\n\nDefinition and live-in blocks:\n\n");
1686 if (def_blocks)
1687 htab_traverse (def_blocks, debug_def_blocks_r, file);
1691 /* Dump the DEF_BLOCKS hash table on stderr. */
1693 void
1694 debug_def_blocks (void)
1696 dump_def_blocks (stderr);
1700 /* Register NEW_NAME to be the new reaching definition for OLD_NAME. */
1702 static inline void
1703 register_new_update_single (tree new_name, tree old_name)
1705 tree currdef = get_current_def (old_name);
1707 /* Push the current reaching definition into BLOCK_DEFS_STACK.
1708 This stack is later used by the dominator tree callbacks to
1709 restore the reaching definitions for all the variables
1710 defined in the block after a recursive visit to all its
1711 immediately dominated blocks. */
1712 VEC_reserve (tree, heap, block_defs_stack, 2);
1713 VEC_quick_push (tree, block_defs_stack, currdef);
1714 VEC_quick_push (tree, block_defs_stack, old_name);
1716 /* Set the current reaching definition for OLD_NAME to be
1717 NEW_NAME. */
1718 set_current_def (old_name, new_name);
1722 /* Register NEW_NAME to be the new reaching definition for all the
1723 names in OLD_NAMES. Used by the incremental SSA update routines to
1724 replace old SSA names with new ones. */
1726 static inline void
1727 register_new_update_set (tree new_name, bitmap old_names)
1729 bitmap_iterator bi;
1730 unsigned i;
1732 EXECUTE_IF_SET_IN_BITMAP (old_names, 0, i, bi)
1733 register_new_update_single (new_name, ssa_name (i));
1738 /* If the operand pointed to by USE_P is a name in OLD_SSA_NAMES or
1739 it is a symbol marked for renaming, replace it with USE_P's current
1740 reaching definition. */
1742 static inline void
1743 maybe_replace_use (use_operand_p use_p)
1745 tree rdef = NULL_TREE;
1746 tree use = USE_FROM_PTR (use_p);
1747 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
1749 if (symbol_marked_for_renaming (sym))
1750 rdef = get_reaching_def (sym);
1751 else if (is_old_name (use))
1752 rdef = get_reaching_def (use);
1754 if (rdef && rdef != use)
1755 SET_USE (use_p, rdef);
1759 /* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
1760 or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
1761 register it as the current definition for the names replaced by
1762 DEF_P. */
1764 static inline void
1765 maybe_register_def (def_operand_p def_p, gimple stmt)
1767 tree def = DEF_FROM_PTR (def_p);
1768 tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
1770 /* If DEF is a naked symbol that needs renaming, create a new
1771 name for it. */
1772 if (symbol_marked_for_renaming (sym))
1774 if (DECL_P (def))
1776 def = make_ssa_name (def, stmt);
1777 SET_DEF (def_p, def);
1780 register_new_update_single (def, sym);
1782 else
1784 /* If DEF is a new name, register it as a new definition
1785 for all the names replaced by DEF. */
1786 if (is_new_name (def))
1787 register_new_update_set (def, names_replaced_by (def));
1789 /* If DEF is an old name, register DEF as a new
1790 definition for itself. */
1791 if (is_old_name (def))
1792 register_new_update_single (def, def);
1797 /* Update every variable used in the statement pointed-to by SI. The
1798 statement is assumed to be in SSA form already. Names in
1799 OLD_SSA_NAMES used by SI will be updated to their current reaching
1800 definition. Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI
1801 will be registered as a new definition for their corresponding name
1802 in OLD_SSA_NAMES. */
1804 static void
1805 rewrite_update_stmt (gimple stmt)
1807 use_operand_p use_p;
1808 def_operand_p def_p;
1809 ssa_op_iter iter;
1811 /* Only update marked statements. */
1812 if (!rewrite_uses_p (stmt) && !register_defs_p (stmt))
1813 return;
1815 if (dump_file && (dump_flags & TDF_DETAILS))
1817 fprintf (dump_file, "Updating SSA information for statement ");
1818 print_gimple_stmt (dump_file, stmt, 0, TDF_SLIM);
1819 fprintf (dump_file, "\n");
1822 /* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying
1823 symbol is marked for renaming. */
1824 if (rewrite_uses_p (stmt))
1825 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, iter, SSA_OP_ALL_USES)
1826 maybe_replace_use (use_p);
1828 /* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES.
1829 Also register definitions for names whose underlying symbol is
1830 marked for renaming. */
1831 if (register_defs_p (stmt))
1832 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, iter, SSA_OP_ALL_DEFS)
1833 maybe_register_def (def_p, stmt);
1837 /* Visit all the successor blocks of BB looking for PHI nodes. For
1838 every PHI node found, check if any of its arguments is in
1839 OLD_SSA_NAMES. If so, and if the argument has a current reaching
1840 definition, replace it. */
1842 static void
1843 rewrite_update_phi_arguments (basic_block bb)
1845 edge e;
1846 edge_iterator ei;
1847 unsigned i;
1849 FOR_EACH_EDGE (e, ei, bb->succs)
1851 gimple phi;
1852 gimple_vec phis;
1854 if (!bitmap_bit_p (blocks_with_phis_to_rewrite, e->dest->index))
1855 continue;
1857 phis = VEC_index (gimple_vec, phis_to_rewrite, e->dest->index);
1858 for (i = 0; VEC_iterate (gimple, phis, i, phi); i++)
1860 tree arg, lhs_sym;
1861 use_operand_p arg_p;
1863 gcc_assert (rewrite_uses_p (phi));
1865 arg_p = PHI_ARG_DEF_PTR_FROM_EDGE (phi, e);
1866 arg = USE_FROM_PTR (arg_p);
1868 if (arg && !DECL_P (arg) && TREE_CODE (arg) != SSA_NAME)
1869 continue;
1871 lhs_sym = SSA_NAME_VAR (gimple_phi_result (phi));
1873 if (arg == NULL_TREE)
1875 /* When updating a PHI node for a recently introduced
1876 symbol we may find NULL arguments. That's why we
1877 take the symbol from the LHS of the PHI node. */
1878 SET_USE (arg_p, get_reaching_def (lhs_sym));
1880 else
1882 tree sym = DECL_P (arg) ? arg : SSA_NAME_VAR (arg);
1884 if (symbol_marked_for_renaming (sym))
1885 SET_USE (arg_p, get_reaching_def (sym));
1886 else if (is_old_name (arg))
1887 SET_USE (arg_p, get_reaching_def (arg));
1890 if (e->flags & EDGE_ABNORMAL)
1891 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p)) = 1;
1897 /* Initialization of block data structures for the incremental SSA
1898 update pass. Create a block local stack of reaching definitions
1899 for new SSA names produced in this block (BLOCK_DEFS). Register
1900 new definitions for every PHI node in the block. */
1902 static void
1903 rewrite_update_enter_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
1904 basic_block bb)
1906 edge e;
1907 edge_iterator ei;
1908 bool is_abnormal_phi;
1909 gimple_stmt_iterator gsi;
1911 if (dump_file && (dump_flags & TDF_DETAILS))
1912 fprintf (dump_file, "\n\nRegistering new PHI nodes in block #%d\n\n",
1913 bb->index);
1915 /* Mark the unwind point for this block. */
1916 VEC_safe_push (tree, heap, block_defs_stack, NULL_TREE);
1918 if (!bitmap_bit_p (blocks_to_update, bb->index))
1919 return;
1921 /* Mark the LHS if any of the arguments flows through an abnormal
1922 edge. */
1923 is_abnormal_phi = false;
1924 FOR_EACH_EDGE (e, ei, bb->preds)
1925 if (e->flags & EDGE_ABNORMAL)
1927 is_abnormal_phi = true;
1928 break;
1931 /* If any of the PHI nodes is a replacement for a name in
1932 OLD_SSA_NAMES or it's one of the names in NEW_SSA_NAMES, then
1933 register it as a new definition for its corresponding name. Also
1934 register definitions for names whose underlying symbols are
1935 marked for renaming. */
1936 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
1938 tree lhs, lhs_sym;
1939 gimple phi = gsi_stmt (gsi);
1941 if (!register_defs_p (phi))
1942 continue;
1944 lhs = gimple_phi_result (phi);
1945 lhs_sym = SSA_NAME_VAR (lhs);
1947 if (symbol_marked_for_renaming (lhs_sym))
1948 register_new_update_single (lhs, lhs_sym);
1949 else
1952 /* If LHS is a new name, register a new definition for all
1953 the names replaced by LHS. */
1954 if (is_new_name (lhs))
1955 register_new_update_set (lhs, names_replaced_by (lhs));
1957 /* If LHS is an OLD name, register it as a new definition
1958 for itself. */
1959 if (is_old_name (lhs))
1960 register_new_update_single (lhs, lhs);
1963 if (is_abnormal_phi)
1964 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs) = 1;
1967 /* Step 2. Rewrite every variable used in each statement in the block. */
1968 if (TEST_BIT (interesting_blocks, bb->index))
1970 gcc_assert (bitmap_bit_p (blocks_to_update, bb->index));
1971 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
1972 rewrite_update_stmt (gsi_stmt (gsi));
1975 /* Step 3. Update PHI nodes. */
1976 rewrite_update_phi_arguments (bb);
1979 /* Called after visiting block BB. Unwind BLOCK_DEFS_STACK to restore
1980 the current reaching definition of every name re-written in BB to
1981 the original reaching definition before visiting BB. This
1982 unwinding must be done in the opposite order to what is done in
1983 register_new_update_set. */
1985 static void
1986 rewrite_update_leave_block (struct dom_walk_data *walk_data ATTRIBUTE_UNUSED,
1987 basic_block bb ATTRIBUTE_UNUSED)
1989 while (VEC_length (tree, block_defs_stack) > 0)
1991 tree var = VEC_pop (tree, block_defs_stack);
1992 tree saved_def;
1994 /* NULL indicates the unwind stop point for this block (see
1995 rewrite_update_enter_block). */
1996 if (var == NULL)
1997 return;
1999 saved_def = VEC_pop (tree, block_defs_stack);
2000 set_current_def (var, saved_def);
2005 /* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
2006 form.
2008 ENTRY indicates the block where to start. Every block dominated by
2009 ENTRY will be rewritten.
2011 WHAT indicates what actions will be taken by the renamer (see enum
2012 rewrite_mode).
2014 BLOCKS are the set of interesting blocks for the dominator walker
2015 to process. If this set is NULL, then all the nodes dominated
2016 by ENTRY are walked. Otherwise, blocks dominated by ENTRY that
2017 are not present in BLOCKS are ignored. */
2019 static void
2020 rewrite_blocks (basic_block entry, enum rewrite_mode what)
2022 struct dom_walk_data walk_data;
2024 /* Rewrite all the basic blocks in the program. */
2025 timevar_push (TV_TREE_SSA_REWRITE_BLOCKS);
2027 /* Setup callbacks for the generic dominator tree walker. */
2028 memset (&walk_data, 0, sizeof (walk_data));
2030 walk_data.dom_direction = CDI_DOMINATORS;
2032 if (what == REWRITE_ALL)
2034 walk_data.before_dom_children = rewrite_enter_block;
2035 walk_data.after_dom_children = rewrite_leave_block;
2037 else if (what == REWRITE_UPDATE)
2039 walk_data.before_dom_children = rewrite_update_enter_block;
2040 walk_data.after_dom_children = rewrite_update_leave_block;
2042 else
2043 gcc_unreachable ();
2045 block_defs_stack = VEC_alloc (tree, heap, 10);
2047 /* Initialize the dominator walker. */
2048 init_walk_dominator_tree (&walk_data);
2050 /* Recursively walk the dominator tree rewriting each statement in
2051 each basic block. */
2052 walk_dominator_tree (&walk_data, entry);
2054 /* Finalize the dominator walker. */
2055 fini_walk_dominator_tree (&walk_data);
2057 /* Debugging dumps. */
2058 if (dump_file && (dump_flags & TDF_STATS))
2060 dump_dfa_stats (dump_file);
2061 if (def_blocks)
2062 dump_tree_ssa_stats (dump_file);
2065 VEC_free (tree, heap, block_defs_stack);
2067 timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS);
2071 /* Block processing routine for mark_def_sites. Clear the KILLS bitmap
2072 at the start of each block, and call mark_def_sites for each statement. */
2074 static void
2075 mark_def_sites_block (struct dom_walk_data *walk_data, basic_block bb)
2077 struct mark_def_sites_global_data *gd;
2078 bitmap kills;
2079 gimple_stmt_iterator gsi;
2081 gd = (struct mark_def_sites_global_data *) walk_data->global_data;
2082 kills = gd->kills;
2084 bitmap_clear (kills);
2085 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
2086 mark_def_sites (bb, gsi_stmt (gsi), kills);
2090 /* Mark the definition site blocks for each variable, so that we know
2091 where the variable is actually live.
2093 The INTERESTING_BLOCKS global will be filled in with all the blocks
2094 that should be processed by the renamer. It is assumed that the
2095 caller has already initialized and zeroed it. */
2097 static void
2098 mark_def_site_blocks (void)
2100 struct dom_walk_data walk_data;
2101 struct mark_def_sites_global_data mark_def_sites_global_data;
2103 /* Setup callbacks for the generic dominator tree walker to find and
2104 mark definition sites. */
2105 walk_data.dom_direction = CDI_DOMINATORS;
2106 walk_data.initialize_block_local_data = NULL;
2107 walk_data.before_dom_children = mark_def_sites_block;
2108 walk_data.after_dom_children = NULL;
2110 /* Notice that this bitmap is indexed using variable UIDs, so it must be
2111 large enough to accommodate all the variables referenced in the
2112 function, not just the ones we are renaming. */
2113 mark_def_sites_global_data.kills = BITMAP_ALLOC (NULL);
2114 walk_data.global_data = &mark_def_sites_global_data;
2116 /* We do not have any local data. */
2117 walk_data.block_local_data_size = 0;
2119 /* Initialize the dominator walker. */
2120 init_walk_dominator_tree (&walk_data);
2122 /* Recursively walk the dominator tree. */
2123 walk_dominator_tree (&walk_data, ENTRY_BLOCK_PTR);
2125 /* Finalize the dominator walker. */
2126 fini_walk_dominator_tree (&walk_data);
2128 /* We no longer need this bitmap, clear and free it. */
2129 BITMAP_FREE (mark_def_sites_global_data.kills);
2133 /* Initialize internal data needed during renaming. */
2135 static void
2136 init_ssa_renamer (void)
2138 tree var;
2139 referenced_var_iterator rvi;
2141 cfun->gimple_df->in_ssa_p = false;
2143 /* Allocate memory for the DEF_BLOCKS hash table. */
2144 gcc_assert (def_blocks == NULL);
2145 def_blocks = htab_create (num_referenced_vars, def_blocks_hash,
2146 def_blocks_eq, def_blocks_free);
2148 FOR_EACH_REFERENCED_VAR(var, rvi)
2149 set_current_def (var, NULL_TREE);
2153 /* Deallocate internal data structures used by the renamer. */
2155 static void
2156 fini_ssa_renamer (void)
2158 if (def_blocks)
2160 htab_delete (def_blocks);
2161 def_blocks = NULL;
2164 cfun->gimple_df->in_ssa_p = true;
2167 /* Main entry point into the SSA builder. The renaming process
2168 proceeds in four main phases:
2170 1- Compute dominance frontier and immediate dominators, needed to
2171 insert PHI nodes and rename the function in dominator tree
2172 order.
2174 2- Find and mark all the blocks that define variables
2175 (mark_def_site_blocks).
2177 3- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
2179 4- Rename all the blocks (rewrite_blocks) and statements in the program.
2181 Steps 3 and 4 are done using the dominator tree walker
2182 (walk_dominator_tree). */
2184 static unsigned int
2185 rewrite_into_ssa (void)
2187 bitmap *dfs;
2188 basic_block bb;
2190 timevar_push (TV_TREE_SSA_OTHER);
2192 /* Initialize operand data structures. */
2193 init_ssa_operands ();
2195 /* Initialize internal data needed by the renamer. */
2196 init_ssa_renamer ();
2198 /* Initialize the set of interesting blocks. The callback
2199 mark_def_sites will add to this set those blocks that the renamer
2200 should process. */
2201 interesting_blocks = sbitmap_alloc (last_basic_block);
2202 sbitmap_zero (interesting_blocks);
2204 /* Initialize dominance frontier. */
2205 dfs = XNEWVEC (bitmap, last_basic_block);
2206 FOR_EACH_BB (bb)
2207 dfs[bb->index] = BITMAP_ALLOC (NULL);
2209 /* 1- Compute dominance frontiers. */
2210 calculate_dominance_info (CDI_DOMINATORS);
2211 compute_dominance_frontiers (dfs);
2213 /* 2- Find and mark definition sites. */
2214 mark_def_site_blocks ();
2216 /* 3- Insert PHI nodes at dominance frontiers of definition blocks. */
2217 insert_phi_nodes (dfs);
2219 /* 4- Rename all the blocks. */
2220 rewrite_blocks (ENTRY_BLOCK_PTR, REWRITE_ALL);
2222 /* Free allocated memory. */
2223 FOR_EACH_BB (bb)
2224 BITMAP_FREE (dfs[bb->index]);
2225 free (dfs);
2227 fini_ssa_renamer ();
2229 timevar_pop (TV_TREE_SSA_OTHER);
2230 return 0;
2234 struct gimple_opt_pass pass_build_ssa =
2237 GIMPLE_PASS,
2238 "ssa", /* name */
2239 NULL, /* gate */
2240 rewrite_into_ssa, /* execute */
2241 NULL, /* sub */
2242 NULL, /* next */
2243 0, /* static_pass_number */
2244 TV_NONE, /* tv_id */
2245 PROP_cfg | PROP_referenced_vars, /* properties_required */
2246 PROP_ssa, /* properties_provided */
2247 0, /* properties_destroyed */
2248 0, /* todo_flags_start */
2249 TODO_dump_func
2250 | TODO_update_ssa_only_virtuals
2251 | TODO_verify_ssa
2252 | TODO_remove_unused_locals /* todo_flags_finish */
2257 /* Mark the definition of VAR at STMT and BB as interesting for the
2258 renamer. BLOCKS is the set of blocks that need updating. */
2260 static void
2261 mark_def_interesting (tree var, gimple stmt, basic_block bb, bool insert_phi_p)
2263 gcc_assert (bitmap_bit_p (blocks_to_update, bb->index));
2264 set_register_defs (stmt, true);
2266 if (insert_phi_p)
2268 bool is_phi_p = gimple_code (stmt) == GIMPLE_PHI;
2270 set_def_block (var, bb, is_phi_p);
2272 /* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition
2273 site for both itself and all the old names replaced by it. */
2274 if (TREE_CODE (var) == SSA_NAME && is_new_name (var))
2276 bitmap_iterator bi;
2277 unsigned i;
2278 bitmap set = names_replaced_by (var);
2279 if (set)
2280 EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
2281 set_def_block (ssa_name (i), bb, is_phi_p);
2287 /* Mark the use of VAR at STMT and BB as interesting for the
2288 renamer. INSERT_PHI_P is true if we are going to insert new PHI
2289 nodes. */
2291 static inline void
2292 mark_use_interesting (tree var, gimple stmt, basic_block bb, bool insert_phi_p)
2294 basic_block def_bb = gimple_bb (stmt);
2296 mark_block_for_update (def_bb);
2297 mark_block_for_update (bb);
2299 if (gimple_code (stmt) == GIMPLE_PHI)
2300 mark_phi_for_rewrite (def_bb, stmt);
2301 else
2302 set_rewrite_uses (stmt, true);
2304 /* If VAR has not been defined in BB, then it is live-on-entry
2305 to BB. Note that we cannot just use the block holding VAR's
2306 definition because if VAR is one of the names in OLD_SSA_NAMES,
2307 it will have several definitions (itself and all the names that
2308 replace it). */
2309 if (insert_phi_p)
2311 struct def_blocks_d *db_p = get_def_blocks_for (var);
2312 if (!bitmap_bit_p (db_p->def_blocks, bb->index))
2313 set_livein_block (var, bb);
2318 /* Do a dominator walk starting at BB processing statements that
2319 reference symbols in SYMS_TO_RENAME. This is very similar to
2320 mark_def_sites, but the scan handles statements whose operands may
2321 already be SSA names.
2323 If INSERT_PHI_P is true, mark those uses as live in the
2324 corresponding block. This is later used by the PHI placement
2325 algorithm to make PHI pruning decisions.
2327 FIXME. Most of this would be unnecessary if we could associate a
2328 symbol to all the SSA names that reference it. But that
2329 sounds like it would be expensive to maintain. Still, it
2330 would be interesting to see if it makes better sense to do
2331 that. */
2333 static void
2334 prepare_block_for_update (basic_block bb, bool insert_phi_p)
2336 basic_block son;
2337 gimple_stmt_iterator si;
2338 edge e;
2339 edge_iterator ei;
2341 mark_block_for_update (bb);
2343 /* Process PHI nodes marking interesting those that define or use
2344 the symbols that we are interested in. */
2345 for (si = gsi_start_phis (bb); !gsi_end_p (si); gsi_next (&si))
2347 gimple phi = gsi_stmt (si);
2348 tree lhs_sym, lhs = gimple_phi_result (phi);
2350 lhs_sym = DECL_P (lhs) ? lhs : SSA_NAME_VAR (lhs);
2352 if (!symbol_marked_for_renaming (lhs_sym))
2353 continue;
2355 mark_def_interesting (lhs_sym, phi, bb, insert_phi_p);
2357 /* Mark the uses in phi nodes as interesting. It would be more correct
2358 to process the arguments of the phi nodes of the successor edges of
2359 BB at the end of prepare_block_for_update, however, that turns out
2360 to be significantly more expensive. Doing it here is conservatively
2361 correct -- it may only cause us to believe a value to be live in a
2362 block that also contains its definition, and thus insert a few more
2363 phi nodes for it. */
2364 FOR_EACH_EDGE (e, ei, bb->preds)
2365 mark_use_interesting (lhs_sym, phi, e->src, insert_phi_p);
2368 /* Process the statements. */
2369 for (si = gsi_start_bb (bb); !gsi_end_p (si); gsi_next (&si))
2371 gimple stmt;
2372 ssa_op_iter i;
2373 use_operand_p use_p;
2374 def_operand_p def_p;
2376 stmt = gsi_stmt (si);
2378 FOR_EACH_SSA_USE_OPERAND (use_p, stmt, i, SSA_OP_ALL_USES)
2380 tree use = USE_FROM_PTR (use_p);
2381 tree sym = DECL_P (use) ? use : SSA_NAME_VAR (use);
2382 if (symbol_marked_for_renaming (sym))
2383 mark_use_interesting (sym, stmt, bb, insert_phi_p);
2386 FOR_EACH_SSA_DEF_OPERAND (def_p, stmt, i, SSA_OP_ALL_DEFS)
2388 tree def = DEF_FROM_PTR (def_p);
2389 tree sym = DECL_P (def) ? def : SSA_NAME_VAR (def);
2390 if (symbol_marked_for_renaming (sym))
2391 mark_def_interesting (sym, stmt, bb, insert_phi_p);
2395 /* Now visit all the blocks dominated by BB. */
2396 for (son = first_dom_son (CDI_DOMINATORS, bb);
2397 son;
2398 son = next_dom_son (CDI_DOMINATORS, son))
2399 prepare_block_for_update (son, insert_phi_p);
2403 /* Helper for prepare_names_to_update. Mark all the use sites for
2404 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2405 prepare_names_to_update. */
2407 static void
2408 prepare_use_sites_for (tree name, bool insert_phi_p)
2410 use_operand_p use_p;
2411 imm_use_iterator iter;
2413 FOR_EACH_IMM_USE_FAST (use_p, iter, name)
2415 gimple stmt = USE_STMT (use_p);
2416 basic_block bb = gimple_bb (stmt);
2418 if (gimple_code (stmt) == GIMPLE_PHI)
2420 int ix = PHI_ARG_INDEX_FROM_USE (use_p);
2421 edge e = gimple_phi_arg_edge (stmt, ix);
2422 mark_use_interesting (name, stmt, e->src, insert_phi_p);
2424 else
2426 /* For regular statements, mark this as an interesting use
2427 for NAME. */
2428 mark_use_interesting (name, stmt, bb, insert_phi_p);
2434 /* Helper for prepare_names_to_update. Mark the definition site for
2435 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2436 prepare_names_to_update. */
2438 static void
2439 prepare_def_site_for (tree name, bool insert_phi_p)
2441 gimple stmt;
2442 basic_block bb;
2444 gcc_assert (names_to_release == NULL
2445 || !bitmap_bit_p (names_to_release, SSA_NAME_VERSION (name)));
2447 stmt = SSA_NAME_DEF_STMT (name);
2448 bb = gimple_bb (stmt);
2449 if (bb)
2451 gcc_assert (bb->index < last_basic_block);
2452 mark_block_for_update (bb);
2453 mark_def_interesting (name, stmt, bb, insert_phi_p);
2458 /* Mark definition and use sites of names in NEW_SSA_NAMES and
2459 OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert
2460 PHI nodes for newly created names. */
2462 static void
2463 prepare_names_to_update (bool insert_phi_p)
2465 unsigned i = 0;
2466 bitmap_iterator bi;
2467 sbitmap_iterator sbi;
2469 /* If a name N from NEW_SSA_NAMES is also marked to be released,
2470 remove it from NEW_SSA_NAMES so that we don't try to visit its
2471 defining basic block (which most likely doesn't exist). Notice
2472 that we cannot do the same with names in OLD_SSA_NAMES because we
2473 want to replace existing instances. */
2474 if (names_to_release)
2475 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
2476 RESET_BIT (new_ssa_names, i);
2478 /* First process names in NEW_SSA_NAMES. Otherwise, uses of old
2479 names may be considered to be live-in on blocks that contain
2480 definitions for their replacements. */
2481 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names, 0, i, sbi)
2482 prepare_def_site_for (ssa_name (i), insert_phi_p);
2484 /* If an old name is in NAMES_TO_RELEASE, we cannot remove it from
2485 OLD_SSA_NAMES, but we have to ignore its definition site. */
2486 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi)
2488 if (names_to_release == NULL || !bitmap_bit_p (names_to_release, i))
2489 prepare_def_site_for (ssa_name (i), insert_phi_p);
2490 prepare_use_sites_for (ssa_name (i), insert_phi_p);
2495 /* Dump all the names replaced by NAME to FILE. */
2497 void
2498 dump_names_replaced_by (FILE *file, tree name)
2500 unsigned i;
2501 bitmap old_set;
2502 bitmap_iterator bi;
2504 print_generic_expr (file, name, 0);
2505 fprintf (file, " -> { ");
2507 old_set = names_replaced_by (name);
2508 EXECUTE_IF_SET_IN_BITMAP (old_set, 0, i, bi)
2510 print_generic_expr (file, ssa_name (i), 0);
2511 fprintf (file, " ");
2514 fprintf (file, "}\n");
2518 /* Dump all the names replaced by NAME to stderr. */
2520 void
2521 debug_names_replaced_by (tree name)
2523 dump_names_replaced_by (stderr, name);
2527 /* Dump SSA update information to FILE. */
2529 void
2530 dump_update_ssa (FILE *file)
2532 unsigned i = 0;
2533 bitmap_iterator bi;
2535 if (!need_ssa_update_p (cfun))
2536 return;
2538 if (new_ssa_names && sbitmap_first_set_bit (new_ssa_names) >= 0)
2540 sbitmap_iterator sbi;
2542 fprintf (file, "\nSSA replacement table\n");
2543 fprintf (file, "N_i -> { O_1 ... O_j } means that N_i replaces "
2544 "O_1, ..., O_j\n\n");
2546 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names, 0, i, sbi)
2547 dump_names_replaced_by (file, ssa_name (i));
2549 fprintf (file, "\n");
2550 fprintf (file, "Number of virtual NEW -> OLD mappings: %7u\n",
2551 update_ssa_stats.num_virtual_mappings);
2552 fprintf (file, "Number of real NEW -> OLD mappings: %7u\n",
2553 update_ssa_stats.num_total_mappings
2554 - update_ssa_stats.num_virtual_mappings);
2555 fprintf (file, "Number of total NEW -> OLD mappings: %7u\n",
2556 update_ssa_stats.num_total_mappings);
2558 fprintf (file, "\nNumber of virtual symbols: %u\n",
2559 update_ssa_stats.num_virtual_symbols);
2562 if (!bitmap_empty_p (SYMS_TO_RENAME (cfun)))
2564 fprintf (file, "\n\nSymbols to be put in SSA form\n\n");
2565 dump_decl_set (file, SYMS_TO_RENAME (cfun));
2566 fprintf (file, "\n");
2569 if (names_to_release && !bitmap_empty_p (names_to_release))
2571 fprintf (file, "\n\nSSA names to release after updating the SSA web\n\n");
2572 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
2574 print_generic_expr (file, ssa_name (i), 0);
2575 fprintf (file, " ");
2579 fprintf (file, "\n\n");
2583 /* Dump SSA update information to stderr. */
2585 void
2586 debug_update_ssa (void)
2588 dump_update_ssa (stderr);
2592 /* Initialize data structures used for incremental SSA updates. */
2594 static void
2595 init_update_ssa (struct function *fn)
2597 /* Reserve more space than the current number of names. The calls to
2598 add_new_name_mapping are typically done after creating new SSA
2599 names, so we'll need to reallocate these arrays. */
2600 old_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR);
2601 sbitmap_zero (old_ssa_names);
2603 new_ssa_names = sbitmap_alloc (num_ssa_names + NAME_SETS_GROWTH_FACTOR);
2604 sbitmap_zero (new_ssa_names);
2606 repl_tbl = htab_create (20, repl_map_hash, repl_map_eq, repl_map_free);
2607 names_to_release = NULL;
2608 memset (&update_ssa_stats, 0, sizeof (update_ssa_stats));
2609 update_ssa_stats.virtual_symbols = BITMAP_ALLOC (NULL);
2610 update_ssa_initialized_fn = fn;
2614 /* Deallocate data structures used for incremental SSA updates. */
2616 void
2617 delete_update_ssa (void)
2619 unsigned i;
2620 bitmap_iterator bi;
2622 sbitmap_free (old_ssa_names);
2623 old_ssa_names = NULL;
2625 sbitmap_free (new_ssa_names);
2626 new_ssa_names = NULL;
2628 htab_delete (repl_tbl);
2629 repl_tbl = NULL;
2631 bitmap_clear (SYMS_TO_RENAME (update_ssa_initialized_fn));
2632 BITMAP_FREE (update_ssa_stats.virtual_symbols);
2634 if (names_to_release)
2636 EXECUTE_IF_SET_IN_BITMAP (names_to_release, 0, i, bi)
2637 release_ssa_name (ssa_name (i));
2638 BITMAP_FREE (names_to_release);
2641 clear_ssa_name_info ();
2643 fini_ssa_renamer ();
2645 if (blocks_with_phis_to_rewrite)
2646 EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite, 0, i, bi)
2648 gimple_vec phis = VEC_index (gimple_vec, phis_to_rewrite, i);
2650 VEC_free (gimple, heap, phis);
2651 VEC_replace (gimple_vec, phis_to_rewrite, i, NULL);
2654 BITMAP_FREE (blocks_with_phis_to_rewrite);
2655 BITMAP_FREE (blocks_to_update);
2656 update_ssa_initialized_fn = NULL;
2660 /* Create a new name for OLD_NAME in statement STMT and replace the
2661 operand pointed to by DEF_P with the newly created name. Return
2662 the new name and register the replacement mapping <NEW, OLD> in
2663 update_ssa's tables. */
2665 tree
2666 create_new_def_for (tree old_name, gimple stmt, def_operand_p def)
2668 tree new_name = duplicate_ssa_name (old_name, stmt);
2670 SET_DEF (def, new_name);
2672 if (gimple_code (stmt) == GIMPLE_PHI)
2674 edge e;
2675 edge_iterator ei;
2676 basic_block bb = gimple_bb (stmt);
2678 /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
2679 FOR_EACH_EDGE (e, ei, bb->preds)
2680 if (e->flags & EDGE_ABNORMAL)
2682 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name) = 1;
2683 break;
2687 register_new_name_mapping (new_name, old_name);
2689 /* For the benefit of passes that will be updating the SSA form on
2690 their own, set the current reaching definition of OLD_NAME to be
2691 NEW_NAME. */
2692 set_current_def (old_name, new_name);
2694 return new_name;
2698 /* Register name NEW to be a replacement for name OLD. This function
2699 must be called for every replacement that should be performed by
2700 update_ssa. */
2702 void
2703 register_new_name_mapping (tree new_tree, tree old)
2705 if (!update_ssa_initialized_fn)
2706 init_update_ssa (cfun);
2708 gcc_assert (update_ssa_initialized_fn == cfun);
2710 add_new_name_mapping (new_tree, old);
2714 /* Register symbol SYM to be renamed by update_ssa. */
2716 void
2717 mark_sym_for_renaming (tree sym)
2719 bitmap_set_bit (SYMS_TO_RENAME (cfun), DECL_UID (sym));
2723 /* Register all the symbols in SET to be renamed by update_ssa. */
2725 void
2726 mark_set_for_renaming (bitmap set)
2728 bitmap_iterator bi;
2729 unsigned i;
2731 if (set == NULL || bitmap_empty_p (set))
2732 return;
2734 EXECUTE_IF_SET_IN_BITMAP (set, 0, i, bi)
2735 mark_sym_for_renaming (referenced_var (i));
2739 /* Return true if there is any work to be done by update_ssa
2740 for function FN. */
2742 bool
2743 need_ssa_update_p (struct function *fn)
2745 gcc_assert (fn != NULL);
2746 return (update_ssa_initialized_fn == fn
2747 || (fn->gimple_df
2748 && !bitmap_empty_p (SYMS_TO_RENAME (fn))));
2751 /* Return true if SSA name mappings have been registered for SSA updating. */
2753 bool
2754 name_mappings_registered_p (void)
2756 if (!update_ssa_initialized_fn)
2757 return false;
2759 gcc_assert (update_ssa_initialized_fn == cfun);
2761 return repl_tbl && htab_elements (repl_tbl) > 0;
2764 /* Return true if name N has been registered in the replacement table. */
2766 bool
2767 name_registered_for_update_p (tree n ATTRIBUTE_UNUSED)
2769 if (!update_ssa_initialized_fn)
2770 return false;
2772 gcc_assert (update_ssa_initialized_fn == cfun);
2774 return is_new_name (n) || is_old_name (n);
2778 /* Return the set of all the SSA names marked to be replaced. */
2780 bitmap
2781 ssa_names_to_replace (void)
2783 unsigned i = 0;
2784 bitmap ret;
2785 sbitmap_iterator sbi;
2787 gcc_assert (update_ssa_initialized_fn == NULL
2788 || update_ssa_initialized_fn == cfun);
2790 ret = BITMAP_ALLOC (NULL);
2791 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi)
2792 bitmap_set_bit (ret, i);
2794 return ret;
2798 /* Mark NAME to be released after update_ssa has finished. */
2800 void
2801 release_ssa_name_after_update_ssa (tree name)
2803 gcc_assert (cfun && update_ssa_initialized_fn == cfun);
2805 if (names_to_release == NULL)
2806 names_to_release = BITMAP_ALLOC (NULL);
2808 bitmap_set_bit (names_to_release, SSA_NAME_VERSION (name));
2812 /* Insert new PHI nodes to replace VAR. DFS contains dominance
2813 frontier information. BLOCKS is the set of blocks to be updated.
2815 This is slightly different than the regular PHI insertion
2816 algorithm. The value of UPDATE_FLAGS controls how PHI nodes for
2817 real names (i.e., GIMPLE registers) are inserted:
2819 - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI
2820 nodes inside the region affected by the block that defines VAR
2821 and the blocks that define all its replacements. All these
2822 definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS.
2824 First, we compute the entry point to the region (ENTRY). This is
2825 given by the nearest common dominator to all the definition
2826 blocks. When computing the iterated dominance frontier (IDF), any
2827 block not strictly dominated by ENTRY is ignored.
2829 We then call the standard PHI insertion algorithm with the pruned
2830 IDF.
2832 - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real
2833 names is not pruned. PHI nodes are inserted at every IDF block. */
2835 static void
2836 insert_updated_phi_nodes_for (tree var, bitmap *dfs, bitmap blocks,
2837 unsigned update_flags)
2839 basic_block entry;
2840 struct def_blocks_d *db;
2841 bitmap idf, pruned_idf;
2842 bitmap_iterator bi;
2843 unsigned i;
2845 #if defined ENABLE_CHECKING
2846 if (TREE_CODE (var) == SSA_NAME)
2847 gcc_assert (is_old_name (var));
2848 else
2849 gcc_assert (symbol_marked_for_renaming (var));
2850 #endif
2852 /* Get all the definition sites for VAR. */
2853 db = find_def_blocks_for (var);
2855 /* No need to do anything if there were no definitions to VAR. */
2856 if (db == NULL || bitmap_empty_p (db->def_blocks))
2857 return;
2859 /* Compute the initial iterated dominance frontier. */
2860 idf = compute_idf (db->def_blocks, dfs);
2861 pruned_idf = BITMAP_ALLOC (NULL);
2863 if (TREE_CODE (var) == SSA_NAME)
2865 if (update_flags == TODO_update_ssa)
2867 /* If doing regular SSA updates for GIMPLE registers, we are
2868 only interested in IDF blocks dominated by the nearest
2869 common dominator of all the definition blocks. */
2870 entry = nearest_common_dominator_for_set (CDI_DOMINATORS,
2871 db->def_blocks);
2872 if (entry != ENTRY_BLOCK_PTR)
2873 EXECUTE_IF_SET_IN_BITMAP (idf, 0, i, bi)
2874 if (BASIC_BLOCK (i) != entry
2875 && dominated_by_p (CDI_DOMINATORS, BASIC_BLOCK (i), entry))
2876 bitmap_set_bit (pruned_idf, i);
2878 else
2880 /* Otherwise, do not prune the IDF for VAR. */
2881 gcc_assert (update_flags == TODO_update_ssa_full_phi);
2882 bitmap_copy (pruned_idf, idf);
2885 else
2887 /* Otherwise, VAR is a symbol that needs to be put into SSA form
2888 for the first time, so we need to compute the full IDF for
2889 it. */
2890 bitmap_copy (pruned_idf, idf);
2893 if (!bitmap_empty_p (pruned_idf))
2895 /* Make sure that PRUNED_IDF blocks and all their feeding blocks
2896 are included in the region to be updated. The feeding blocks
2897 are important to guarantee that the PHI arguments are renamed
2898 properly. */
2900 /* FIXME, this is not needed if we are updating symbols. We are
2901 already starting at the ENTRY block anyway. */
2902 bitmap_ior_into (blocks, pruned_idf);
2903 EXECUTE_IF_SET_IN_BITMAP (pruned_idf, 0, i, bi)
2905 edge e;
2906 edge_iterator ei;
2907 basic_block bb = BASIC_BLOCK (i);
2909 FOR_EACH_EDGE (e, ei, bb->preds)
2910 if (e->src->index >= 0)
2911 bitmap_set_bit (blocks, e->src->index);
2914 insert_phi_nodes_for (var, pruned_idf, true);
2917 BITMAP_FREE (pruned_idf);
2918 BITMAP_FREE (idf);
2922 /* Heuristic to determine whether SSA name mappings for virtual names
2923 should be discarded and their symbols rewritten from scratch. When
2924 there is a large number of mappings for virtual names, the
2925 insertion of PHI nodes for the old names in the mappings takes
2926 considerable more time than if we inserted PHI nodes for the
2927 symbols instead.
2929 Currently the heuristic takes these stats into account:
2931 - Number of mappings for virtual SSA names.
2932 - Number of distinct virtual symbols involved in those mappings.
2934 If the number of virtual mappings is much larger than the number of
2935 virtual symbols, then it will be faster to compute PHI insertion
2936 spots for the symbols. Even if this involves traversing the whole
2937 CFG, which is what happens when symbols are renamed from scratch. */
2939 static bool
2940 switch_virtuals_to_full_rewrite_p (void)
2942 if (update_ssa_stats.num_virtual_mappings < (unsigned) MIN_VIRTUAL_MAPPINGS)
2943 return false;
2945 if (update_ssa_stats.num_virtual_mappings
2946 > (unsigned) VIRTUAL_MAPPINGS_TO_SYMS_RATIO
2947 * update_ssa_stats.num_virtual_symbols)
2948 return true;
2950 return false;
2954 /* Remove every virtual mapping and mark all the affected virtual
2955 symbols for renaming. */
2957 static void
2958 switch_virtuals_to_full_rewrite (void)
2960 unsigned i = 0;
2961 sbitmap_iterator sbi;
2963 if (dump_file)
2965 fprintf (dump_file, "\nEnabled virtual name mapping heuristic.\n");
2966 fprintf (dump_file, "\tNumber of virtual mappings: %7u\n",
2967 update_ssa_stats.num_virtual_mappings);
2968 fprintf (dump_file, "\tNumber of unique virtual symbols: %7u\n",
2969 update_ssa_stats.num_virtual_symbols);
2970 fprintf (dump_file, "Updating FUD-chains from top of CFG will be "
2971 "faster than processing\nthe name mappings.\n\n");
2974 /* Remove all virtual names from NEW_SSA_NAMES and OLD_SSA_NAMES.
2975 Note that it is not really necessary to remove the mappings from
2976 REPL_TBL, that would only waste time. */
2977 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names, 0, i, sbi)
2978 if (!is_gimple_reg (ssa_name (i)))
2979 RESET_BIT (new_ssa_names, i);
2981 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi)
2982 if (!is_gimple_reg (ssa_name (i)))
2983 RESET_BIT (old_ssa_names, i);
2985 mark_set_for_renaming (update_ssa_stats.virtual_symbols);
2989 /* Given a set of newly created SSA names (NEW_SSA_NAMES) and a set of
2990 existing SSA names (OLD_SSA_NAMES), update the SSA form so that:
2992 1- The names in OLD_SSA_NAMES dominated by the definitions of
2993 NEW_SSA_NAMES are all re-written to be reached by the
2994 appropriate definition from NEW_SSA_NAMES.
2996 2- If needed, new PHI nodes are added to the iterated dominance
2997 frontier of the blocks where each of NEW_SSA_NAMES are defined.
2999 The mapping between OLD_SSA_NAMES and NEW_SSA_NAMES is setup by
3000 calling register_new_name_mapping for every pair of names that the
3001 caller wants to replace.
3003 The caller identifies the new names that have been inserted and the
3004 names that need to be replaced by calling register_new_name_mapping
3005 for every pair <NEW, OLD>. Note that the function assumes that the
3006 new names have already been inserted in the IL.
3008 For instance, given the following code:
3010 1 L0:
3011 2 x_1 = PHI (0, x_5)
3012 3 if (x_1 < 10)
3013 4 if (x_1 > 7)
3014 5 y_2 = 0
3015 6 else
3016 7 y_3 = x_1 + x_7
3017 8 endif
3018 9 x_5 = x_1 + 1
3019 10 goto L0;
3020 11 endif
3022 Suppose that we insert new names x_10 and x_11 (lines 4 and 8).
3024 1 L0:
3025 2 x_1 = PHI (0, x_5)
3026 3 if (x_1 < 10)
3027 4 x_10 = ...
3028 5 if (x_1 > 7)
3029 6 y_2 = 0
3030 7 else
3031 8 x_11 = ...
3032 9 y_3 = x_1 + x_7
3033 10 endif
3034 11 x_5 = x_1 + 1
3035 12 goto L0;
3036 13 endif
3038 We want to replace all the uses of x_1 with the new definitions of
3039 x_10 and x_11. Note that the only uses that should be replaced are
3040 those at lines 5, 9 and 11. Also, the use of x_7 at line 9 should
3041 *not* be replaced (this is why we cannot just mark symbol 'x' for
3042 renaming).
3044 Additionally, we may need to insert a PHI node at line 11 because
3045 that is a merge point for x_10 and x_11. So the use of x_1 at line
3046 11 will be replaced with the new PHI node. The insertion of PHI
3047 nodes is optional. They are not strictly necessary to preserve the
3048 SSA form, and depending on what the caller inserted, they may not
3049 even be useful for the optimizers. UPDATE_FLAGS controls various
3050 aspects of how update_ssa operates, see the documentation for
3051 TODO_update_ssa*. */
3053 void
3054 update_ssa (unsigned update_flags)
3056 basic_block bb, start_bb;
3057 bitmap_iterator bi;
3058 unsigned i = 0;
3059 bool insert_phi_p;
3060 sbitmap_iterator sbi;
3062 if (!need_ssa_update_p (cfun))
3063 return;
3065 timevar_push (TV_TREE_SSA_INCREMENTAL);
3067 if (!update_ssa_initialized_fn)
3068 init_update_ssa (cfun);
3069 gcc_assert (update_ssa_initialized_fn == cfun);
3071 blocks_with_phis_to_rewrite = BITMAP_ALLOC (NULL);
3072 if (!phis_to_rewrite)
3073 phis_to_rewrite = VEC_alloc (gimple_vec, heap, last_basic_block);
3074 blocks_to_update = BITMAP_ALLOC (NULL);
3076 /* Ensure that the dominance information is up-to-date. */
3077 calculate_dominance_info (CDI_DOMINATORS);
3079 /* Only one update flag should be set. */
3080 gcc_assert (update_flags == TODO_update_ssa
3081 || update_flags == TODO_update_ssa_no_phi
3082 || update_flags == TODO_update_ssa_full_phi
3083 || update_flags == TODO_update_ssa_only_virtuals);
3085 /* If we only need to update virtuals, remove all the mappings for
3086 real names before proceeding. The caller is responsible for
3087 having dealt with the name mappings before calling update_ssa. */
3088 if (update_flags == TODO_update_ssa_only_virtuals)
3090 sbitmap_zero (old_ssa_names);
3091 sbitmap_zero (new_ssa_names);
3092 htab_empty (repl_tbl);
3095 insert_phi_p = (update_flags != TODO_update_ssa_no_phi);
3097 if (insert_phi_p)
3099 /* If the caller requested PHI nodes to be added, initialize
3100 live-in information data structures (DEF_BLOCKS). */
3102 /* For each SSA name N, the DEF_BLOCKS table describes where the
3103 name is defined, which blocks have PHI nodes for N, and which
3104 blocks have uses of N (i.e., N is live-on-entry in those
3105 blocks). */
3106 def_blocks = htab_create (num_ssa_names, def_blocks_hash,
3107 def_blocks_eq, def_blocks_free);
3109 else
3111 def_blocks = NULL;
3114 /* Heuristic to avoid massive slow downs when the replacement
3115 mappings include lots of virtual names. */
3116 if (insert_phi_p && switch_virtuals_to_full_rewrite_p ())
3117 switch_virtuals_to_full_rewrite ();
3119 /* If there are names defined in the replacement table, prepare
3120 definition and use sites for all the names in NEW_SSA_NAMES and
3121 OLD_SSA_NAMES. */
3122 if (sbitmap_first_set_bit (new_ssa_names) >= 0)
3124 prepare_names_to_update (insert_phi_p);
3126 /* If all the names in NEW_SSA_NAMES had been marked for
3127 removal, and there are no symbols to rename, then there's
3128 nothing else to do. */
3129 if (sbitmap_first_set_bit (new_ssa_names) < 0
3130 && bitmap_empty_p (SYMS_TO_RENAME (cfun)))
3131 goto done;
3134 /* Next, determine the block at which to start the renaming process. */
3135 if (!bitmap_empty_p (SYMS_TO_RENAME (cfun)))
3137 /* If we have to rename some symbols from scratch, we need to
3138 start the process at the root of the CFG. FIXME, it should
3139 be possible to determine the nearest block that had a
3140 definition for each of the symbols that are marked for
3141 updating. For now this seems more work than it's worth. */
3142 start_bb = ENTRY_BLOCK_PTR;
3144 /* Traverse the CFG looking for existing definitions and uses of
3145 symbols in SYMS_TO_RENAME. Mark interesting blocks and
3146 statements and set local live-in information for the PHI
3147 placement heuristics. */
3148 prepare_block_for_update (start_bb, insert_phi_p);
3150 else
3152 /* Otherwise, the entry block to the region is the nearest
3153 common dominator for the blocks in BLOCKS. */
3154 start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS,
3155 blocks_to_update);
3158 /* If requested, insert PHI nodes at the iterated dominance frontier
3159 of every block, creating new definitions for names in OLD_SSA_NAMES
3160 and for symbols in SYMS_TO_RENAME. */
3161 if (insert_phi_p)
3163 bitmap *dfs;
3165 /* If the caller requested PHI nodes to be added, compute
3166 dominance frontiers. */
3167 dfs = XNEWVEC (bitmap, last_basic_block);
3168 FOR_EACH_BB (bb)
3169 dfs[bb->index] = BITMAP_ALLOC (NULL);
3170 compute_dominance_frontiers (dfs);
3172 if (sbitmap_first_set_bit (old_ssa_names) >= 0)
3174 sbitmap_iterator sbi;
3176 /* insert_update_phi_nodes_for will call add_new_name_mapping
3177 when inserting new PHI nodes, so the set OLD_SSA_NAMES
3178 will grow while we are traversing it (but it will not
3179 gain any new members). Copy OLD_SSA_NAMES to a temporary
3180 for traversal. */
3181 sbitmap tmp = sbitmap_alloc (old_ssa_names->n_bits);
3182 sbitmap_copy (tmp, old_ssa_names);
3183 EXECUTE_IF_SET_IN_SBITMAP (tmp, 0, i, sbi)
3184 insert_updated_phi_nodes_for (ssa_name (i), dfs, blocks_to_update,
3185 update_flags);
3186 sbitmap_free (tmp);
3189 EXECUTE_IF_SET_IN_BITMAP (SYMS_TO_RENAME (cfun), 0, i, bi)
3190 insert_updated_phi_nodes_for (referenced_var (i), dfs, blocks_to_update,
3191 update_flags);
3193 FOR_EACH_BB (bb)
3194 BITMAP_FREE (dfs[bb->index]);
3195 free (dfs);
3197 /* Insertion of PHI nodes may have added blocks to the region.
3198 We need to re-compute START_BB to include the newly added
3199 blocks. */
3200 if (start_bb != ENTRY_BLOCK_PTR)
3201 start_bb = nearest_common_dominator_for_set (CDI_DOMINATORS,
3202 blocks_to_update);
3205 /* Reset the current definition for name and symbol before renaming
3206 the sub-graph. */
3207 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names, 0, i, sbi)
3208 set_current_def (ssa_name (i), NULL_TREE);
3210 EXECUTE_IF_SET_IN_BITMAP (SYMS_TO_RENAME (cfun), 0, i, bi)
3211 set_current_def (referenced_var (i), NULL_TREE);
3213 /* Now start the renaming process at START_BB. */
3214 interesting_blocks = sbitmap_alloc (last_basic_block);
3215 sbitmap_zero (interesting_blocks);
3216 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi)
3217 SET_BIT (interesting_blocks, i);
3219 rewrite_blocks (start_bb, REWRITE_UPDATE);
3221 sbitmap_free (interesting_blocks);
3223 /* Debugging dumps. */
3224 if (dump_file)
3226 int c;
3227 unsigned i;
3229 dump_update_ssa (dump_file);
3231 fprintf (dump_file, "Incremental SSA update started at block: %d\n\n",
3232 start_bb->index);
3234 c = 0;
3235 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi)
3236 c++;
3237 fprintf (dump_file, "Number of blocks in CFG: %d\n", last_basic_block);
3238 fprintf (dump_file, "Number of blocks to update: %d (%3.0f%%)\n\n",
3239 c, PERCENT (c, last_basic_block));
3241 if (dump_flags & TDF_DETAILS)
3243 fprintf (dump_file, "Affected blocks: ");
3244 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update, 0, i, bi)
3245 fprintf (dump_file, "%u ", i);
3246 fprintf (dump_file, "\n");
3249 fprintf (dump_file, "\n\n");
3252 /* Free allocated memory. */
3253 done:
3254 delete_update_ssa ();
3256 timevar_pop (TV_TREE_SSA_INCREMENTAL);