1 /* Rewrite a program in Normal form into SSA.
2 Copyright (C) 2001-2013 Free Software Foundation, Inc.
3 Contributed by Diego Novillo <dnovillo@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
23 #include "coretypes.h"
28 #include "langhooks.h"
29 #include "basic-block.h"
31 #include "gimple-pretty-print.h"
33 #include "gimple-iterator.h"
34 #include "gimple-ssa.h"
36 #include "tree-phinodes.h"
37 #include "ssa-iterators.h"
38 #include "stringpool.h"
39 #include "tree-ssanames.h"
40 #include "tree-into-ssa.h"
44 #include "tree-inline.h"
45 #include "hash-table.h"
46 #include "tree-pass.h"
50 #include "diagnostic-core.h"
51 #include "tree-into-ssa.h"
53 #define PERCENT(x,y) ((float)(x) * 100.0 / (float)(y))
55 /* This file builds the SSA form for a function as described in:
56 R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently
57 Computing Static Single Assignment Form and the Control Dependence
58 Graph. ACM Transactions on Programming Languages and Systems,
59 13(4):451-490, October 1991. */
61 /* Structure to map a variable VAR to the set of blocks that contain
62 definitions for VAR. */
65 /* Blocks that contain definitions of VAR. Bit I will be set if the
66 Ith block contains a definition of VAR. */
69 /* Blocks that contain a PHI node for VAR. */
72 /* Blocks where VAR is live-on-entry. Similar semantics as
77 typedef struct def_blocks_d
*def_blocks_p
;
80 /* Stack of trees used to restore the global currdefs to its original
81 state after completing rewriting of a block and its dominator
82 children. Its elements have the following properties:
84 - An SSA_NAME (N) indicates that the current definition of the
85 underlying variable should be set to the given SSA_NAME. If the
86 symbol associated with the SSA_NAME is not a GIMPLE register, the
87 next slot in the stack must be a _DECL node (SYM). In this case,
88 the name N in the previous slot is the current reaching
91 - A _DECL node indicates that the underlying variable has no
94 - A NULL node at the top entry is used to mark the last slot
95 associated with the current block. */
96 static vec
<tree
> block_defs_stack
;
99 /* Set of existing SSA names being replaced by update_ssa. */
100 static sbitmap old_ssa_names
;
102 /* Set of new SSA names being added by update_ssa. Note that both
103 NEW_SSA_NAMES and OLD_SSA_NAMES are dense bitmaps because most of
104 the operations done on them are presence tests. */
105 static sbitmap new_ssa_names
;
107 static sbitmap interesting_blocks
;
109 /* Set of SSA names that have been marked to be released after they
110 were registered in the replacement table. They will be finally
111 released after we finish updating the SSA web. */
112 static bitmap names_to_release
;
114 /* vec of vec of PHIs to rewrite in a basic block. Element I corresponds
115 the to basic block with index I. Allocated once per compilation, *not*
116 released between different functions. */
117 static vec
<gimple_vec
> phis_to_rewrite
;
119 /* The bitmap of non-NULL elements of PHIS_TO_REWRITE. */
120 static bitmap blocks_with_phis_to_rewrite
;
122 /* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need
123 to grow as the callers to create_new_def_for will create new names on
125 FIXME. Currently set to 1/3 to avoid frequent reallocations but still
126 need to find a reasonable growth strategy. */
127 #define NAME_SETS_GROWTH_FACTOR (MAX (3, num_ssa_names / 3))
130 /* The function the SSA updating data structures have been initialized for.
131 NULL if they need to be initialized by create_new_def_for. */
132 static struct function
*update_ssa_initialized_fn
= NULL
;
134 /* Global data to attach to the main dominator walk structure. */
135 struct mark_def_sites_global_data
137 /* This bitmap contains the variables which are set before they
138 are used in a basic block. */
142 /* It is advantageous to avoid things like life analysis for variables which
143 do not need PHI nodes. This enum describes whether or not a particular
144 variable may need a PHI node. */
146 enum need_phi_state
{
147 /* This is the default. If we are still in this state after finding
148 all the definition and use sites, then we will assume the variable
149 needs PHI nodes. This is probably an overly conservative assumption. */
150 NEED_PHI_STATE_UNKNOWN
,
152 /* This state indicates that we have seen one or more sets of the
153 variable in a single basic block and that the sets dominate all
154 uses seen so far. If after finding all definition and use sites
155 we are still in this state, then the variable does not need any
159 /* This state indicates that we have either seen multiple definitions of
160 the variable in multiple blocks, or that we encountered a use in a
161 block that was not dominated by the block containing the set(s) of
162 this variable. This variable is assumed to need PHI nodes. */
166 /* Information stored for both SSA names and decls. */
169 /* This field indicates whether or not the variable may need PHI nodes.
170 See the enum's definition for more detailed information about the
172 ENUM_BITFIELD (need_phi_state
) need_phi_state
: 2;
174 /* The current reaching definition replacing this var. */
177 /* Definitions for this var. */
178 struct def_blocks_d def_blocks
;
181 /* The information associated with decls and SSA names. */
182 typedef struct common_info_d
*common_info_p
;
184 /* Information stored for decls. */
190 /* Information stored for both SSA names and decls. */
191 struct common_info_d info
;
194 /* The information associated with decls. */
195 typedef struct var_info_d
*var_info_p
;
198 /* VAR_INFOS hashtable helpers. */
200 struct var_info_hasher
: typed_free_remove
<var_info_d
>
202 typedef var_info_d value_type
;
203 typedef var_info_d compare_type
;
204 static inline hashval_t
hash (const value_type
*);
205 static inline bool equal (const value_type
*, const compare_type
*);
209 var_info_hasher::hash (const value_type
*p
)
211 return DECL_UID (p
->var
);
215 var_info_hasher::equal (const value_type
*p1
, const compare_type
*p2
)
217 return p1
->var
== p2
->var
;
221 /* Each entry in VAR_INFOS contains an element of type STRUCT
223 static hash_table
<var_info_hasher
> var_infos
;
226 /* Information stored for SSA names. */
229 /* Age of this record (so that info_for_ssa_name table can be cleared
230 quickly); if AGE < CURRENT_INFO_FOR_SSA_NAME_AGE, then the fields
231 are assumed to be null. */
234 /* Replacement mappings, allocated from update_ssa_obstack. */
237 /* Information stored for both SSA names and decls. */
238 struct common_info_d info
;
241 /* The information associated with names. */
242 typedef struct ssa_name_info
*ssa_name_info_p
;
244 static vec
<ssa_name_info_p
> info_for_ssa_name
;
245 static unsigned current_info_for_ssa_name_age
;
247 static bitmap_obstack update_ssa_obstack
;
249 /* The set of blocks affected by update_ssa. */
250 static bitmap blocks_to_update
;
252 /* The main entry point to the SSA renamer (rewrite_blocks) may be
253 called several times to do different, but related, tasks.
254 Initially, we need it to rename the whole program into SSA form.
255 At other times, we may need it to only rename into SSA newly
256 exposed symbols. Finally, we can also call it to incrementally fix
257 an already built SSA web. */
259 /* Convert the whole function into SSA form. */
262 /* Incrementally update the SSA web by replacing existing SSA
263 names with new ones. See update_ssa for details. */
267 /* The set of symbols we ought to re-write into SSA form in update_ssa. */
268 static bitmap symbols_to_rename_set
;
269 static vec
<tree
> symbols_to_rename
;
271 /* Mark SYM for renaming. */
274 mark_for_renaming (tree sym
)
276 if (!symbols_to_rename_set
)
277 symbols_to_rename_set
= BITMAP_ALLOC (NULL
);
278 if (bitmap_set_bit (symbols_to_rename_set
, DECL_UID (sym
)))
279 symbols_to_rename
.safe_push (sym
);
282 /* Return true if SYM is marked for renaming. */
285 marked_for_renaming (tree sym
)
287 if (!symbols_to_rename_set
|| sym
== NULL_TREE
)
289 return bitmap_bit_p (symbols_to_rename_set
, DECL_UID (sym
));
293 /* Return true if STMT needs to be rewritten. When renaming a subset
294 of the variables, not all statements will be processed. This is
295 decided in mark_def_sites. */
298 rewrite_uses_p (gimple stmt
)
300 return gimple_visited_p (stmt
);
304 /* Set the rewrite marker on STMT to the value given by REWRITE_P. */
307 set_rewrite_uses (gimple stmt
, bool rewrite_p
)
309 gimple_set_visited (stmt
, rewrite_p
);
313 /* Return true if the DEFs created by statement STMT should be
314 registered when marking new definition sites. This is slightly
315 different than rewrite_uses_p: it's used by update_ssa to
316 distinguish statements that need to have both uses and defs
317 processed from those that only need to have their defs processed.
318 Statements that define new SSA names only need to have their defs
319 registered, but they don't need to have their uses renamed. */
322 register_defs_p (gimple stmt
)
324 return gimple_plf (stmt
, GF_PLF_1
) != 0;
328 /* If REGISTER_DEFS_P is true, mark STMT to have its DEFs registered. */
331 set_register_defs (gimple stmt
, bool register_defs_p
)
333 gimple_set_plf (stmt
, GF_PLF_1
, register_defs_p
);
337 /* Get the information associated with NAME. */
339 static inline ssa_name_info_p
340 get_ssa_name_ann (tree name
)
342 unsigned ver
= SSA_NAME_VERSION (name
);
343 unsigned len
= info_for_ssa_name
.length ();
344 struct ssa_name_info
*info
;
346 /* Re-allocate the vector at most once per update/into-SSA. */
348 info_for_ssa_name
.safe_grow_cleared (num_ssa_names
);
350 /* But allocate infos lazily. */
351 info
= info_for_ssa_name
[ver
];
354 info
= XCNEW (struct ssa_name_info
);
355 info
->age
= current_info_for_ssa_name_age
;
356 info
->info
.need_phi_state
= NEED_PHI_STATE_UNKNOWN
;
357 info_for_ssa_name
[ver
] = info
;
360 if (info
->age
< current_info_for_ssa_name_age
)
362 info
->age
= current_info_for_ssa_name_age
;
363 info
->repl_set
= NULL
;
364 info
->info
.need_phi_state
= NEED_PHI_STATE_UNKNOWN
;
365 info
->info
.current_def
= NULL_TREE
;
366 info
->info
.def_blocks
.def_blocks
= NULL
;
367 info
->info
.def_blocks
.phi_blocks
= NULL
;
368 info
->info
.def_blocks
.livein_blocks
= NULL
;
374 /* Return and allocate the auxiliar information for DECL. */
376 static inline var_info_p
377 get_var_info (tree decl
)
379 struct var_info_d vi
;
382 slot
= var_infos
.find_slot_with_hash (&vi
, DECL_UID (decl
), INSERT
);
385 var_info_p v
= XCNEW (struct var_info_d
);
394 /* Clears info for SSA names. */
397 clear_ssa_name_info (void)
399 current_info_for_ssa_name_age
++;
401 /* If current_info_for_ssa_name_age wraps we use stale information.
402 Asser that this does not happen. */
403 gcc_assert (current_info_for_ssa_name_age
!= 0);
407 /* Get access to the auxiliar information stored per SSA name or decl. */
409 static inline common_info_p
410 get_common_info (tree var
)
412 if (TREE_CODE (var
) == SSA_NAME
)
413 return &get_ssa_name_ann (var
)->info
;
415 return &get_var_info (var
)->info
;
419 /* Return the current definition for VAR. */
422 get_current_def (tree var
)
424 return get_common_info (var
)->current_def
;
428 /* Sets current definition of VAR to DEF. */
431 set_current_def (tree var
, tree def
)
433 get_common_info (var
)->current_def
= def
;
436 /* Cleans up the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags for
437 all statements in basic block BB. */
440 initialize_flags_in_bb (basic_block bb
)
443 gimple_stmt_iterator gsi
;
445 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
447 gimple phi
= gsi_stmt (gsi
);
448 set_rewrite_uses (phi
, false);
449 set_register_defs (phi
, false);
452 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
454 stmt
= gsi_stmt (gsi
);
456 /* We are going to use the operand cache API, such as
457 SET_USE, SET_DEF, and FOR_EACH_IMM_USE_FAST. The operand
458 cache for each statement should be up-to-date. */
459 gcc_checking_assert (!gimple_modified_p (stmt
));
460 set_rewrite_uses (stmt
, false);
461 set_register_defs (stmt
, false);
465 /* Mark block BB as interesting for update_ssa. */
468 mark_block_for_update (basic_block bb
)
470 gcc_checking_assert (blocks_to_update
!= NULL
);
471 if (!bitmap_set_bit (blocks_to_update
, bb
->index
))
473 initialize_flags_in_bb (bb
);
476 /* Return the set of blocks where variable VAR is defined and the blocks
477 where VAR is live on entry (livein). If no entry is found in
478 DEF_BLOCKS, a new one is created and returned. */
480 static inline struct def_blocks_d
*
481 get_def_blocks_for (common_info_p info
)
483 struct def_blocks_d
*db_p
= &info
->def_blocks
;
484 if (!db_p
->def_blocks
)
486 db_p
->def_blocks
= BITMAP_ALLOC (&update_ssa_obstack
);
487 db_p
->phi_blocks
= BITMAP_ALLOC (&update_ssa_obstack
);
488 db_p
->livein_blocks
= BITMAP_ALLOC (&update_ssa_obstack
);
495 /* Mark block BB as the definition site for variable VAR. PHI_P is true if
496 VAR is defined by a PHI node. */
499 set_def_block (tree var
, basic_block bb
, bool phi_p
)
501 struct def_blocks_d
*db_p
;
504 info
= get_common_info (var
);
505 db_p
= get_def_blocks_for (info
);
507 /* Set the bit corresponding to the block where VAR is defined. */
508 bitmap_set_bit (db_p
->def_blocks
, bb
->index
);
510 bitmap_set_bit (db_p
->phi_blocks
, bb
->index
);
512 /* Keep track of whether or not we may need to insert PHI nodes.
514 If we are in the UNKNOWN state, then this is the first definition
515 of VAR. Additionally, we have not seen any uses of VAR yet, so
516 we do not need a PHI node for this variable at this time (i.e.,
517 transition to NEED_PHI_STATE_NO).
519 If we are in any other state, then we either have multiple definitions
520 of this variable occurring in different blocks or we saw a use of the
521 variable which was not dominated by the block containing the
522 definition(s). In this case we may need a PHI node, so enter
523 state NEED_PHI_STATE_MAYBE. */
524 if (info
->need_phi_state
== NEED_PHI_STATE_UNKNOWN
)
525 info
->need_phi_state
= NEED_PHI_STATE_NO
;
527 info
->need_phi_state
= NEED_PHI_STATE_MAYBE
;
531 /* Mark block BB as having VAR live at the entry to BB. */
534 set_livein_block (tree var
, basic_block bb
)
537 struct def_blocks_d
*db_p
;
539 info
= get_common_info (var
);
540 db_p
= get_def_blocks_for (info
);
542 /* Set the bit corresponding to the block where VAR is live in. */
543 bitmap_set_bit (db_p
->livein_blocks
, bb
->index
);
545 /* Keep track of whether or not we may need to insert PHI nodes.
547 If we reach here in NEED_PHI_STATE_NO, see if this use is dominated
548 by the single block containing the definition(s) of this variable. If
549 it is, then we remain in NEED_PHI_STATE_NO, otherwise we transition to
550 NEED_PHI_STATE_MAYBE. */
551 if (info
->need_phi_state
== NEED_PHI_STATE_NO
)
553 int def_block_index
= bitmap_first_set_bit (db_p
->def_blocks
);
555 if (def_block_index
== -1
556 || ! dominated_by_p (CDI_DOMINATORS
, bb
,
557 BASIC_BLOCK (def_block_index
)))
558 info
->need_phi_state
= NEED_PHI_STATE_MAYBE
;
561 info
->need_phi_state
= NEED_PHI_STATE_MAYBE
;
565 /* Return true if NAME is in OLD_SSA_NAMES. */
568 is_old_name (tree name
)
570 unsigned ver
= SSA_NAME_VERSION (name
);
573 return (ver
< SBITMAP_SIZE (new_ssa_names
)
574 && bitmap_bit_p (old_ssa_names
, ver
));
578 /* Return true if NAME is in NEW_SSA_NAMES. */
581 is_new_name (tree name
)
583 unsigned ver
= SSA_NAME_VERSION (name
);
586 return (ver
< SBITMAP_SIZE (new_ssa_names
)
587 && bitmap_bit_p (new_ssa_names
, ver
));
591 /* Return the names replaced by NEW_TREE (i.e., REPL_TBL[NEW_TREE].SET). */
594 names_replaced_by (tree new_tree
)
596 return get_ssa_name_ann (new_tree
)->repl_set
;
600 /* Add OLD to REPL_TBL[NEW_TREE].SET. */
603 add_to_repl_tbl (tree new_tree
, tree old
)
605 bitmap
*set
= &get_ssa_name_ann (new_tree
)->repl_set
;
607 *set
= BITMAP_ALLOC (&update_ssa_obstack
);
608 bitmap_set_bit (*set
, SSA_NAME_VERSION (old
));
612 /* Add a new mapping NEW_TREE -> OLD REPL_TBL. Every entry N_i in REPL_TBL
613 represents the set of names O_1 ... O_j replaced by N_i. This is
614 used by update_ssa and its helpers to introduce new SSA names in an
615 already formed SSA web. */
618 add_new_name_mapping (tree new_tree
, tree old
)
620 /* OLD and NEW_TREE must be different SSA names for the same symbol. */
621 gcc_checking_assert (new_tree
!= old
622 && SSA_NAME_VAR (new_tree
) == SSA_NAME_VAR (old
));
624 /* We may need to grow NEW_SSA_NAMES and OLD_SSA_NAMES because our
625 caller may have created new names since the set was created. */
626 if (SBITMAP_SIZE (new_ssa_names
) <= num_ssa_names
- 1)
628 unsigned int new_sz
= num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
;
629 new_ssa_names
= sbitmap_resize (new_ssa_names
, new_sz
, 0);
630 old_ssa_names
= sbitmap_resize (old_ssa_names
, new_sz
, 0);
633 /* Update the REPL_TBL table. */
634 add_to_repl_tbl (new_tree
, old
);
636 /* If OLD had already been registered as a new name, then all the
637 names that OLD replaces should also be replaced by NEW_TREE. */
638 if (is_new_name (old
))
639 bitmap_ior_into (names_replaced_by (new_tree
), names_replaced_by (old
));
641 /* Register NEW_TREE and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES,
643 bitmap_set_bit (new_ssa_names
, SSA_NAME_VERSION (new_tree
));
644 bitmap_set_bit (old_ssa_names
, SSA_NAME_VERSION (old
));
648 /* Call back for walk_dominator_tree used to collect definition sites
649 for every variable in the function. For every statement S in block
652 1- Variables defined by S in the DEFS of S are marked in the bitmap
655 2- If S uses a variable VAR and there is no preceding kill of VAR,
656 then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR.
658 This information is used to determine which variables are live
659 across block boundaries to reduce the number of PHI nodes
663 mark_def_sites (basic_block bb
, gimple stmt
, bitmap kills
)
669 /* Since this is the first time that we rewrite the program into SSA
670 form, force an operand scan on every statement. */
673 gcc_checking_assert (blocks_to_update
== NULL
);
674 set_register_defs (stmt
, false);
675 set_rewrite_uses (stmt
, false);
677 if (is_gimple_debug (stmt
))
679 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
681 tree sym
= USE_FROM_PTR (use_p
);
682 gcc_checking_assert (DECL_P (sym
));
683 set_rewrite_uses (stmt
, true);
685 if (rewrite_uses_p (stmt
))
686 bitmap_set_bit (interesting_blocks
, bb
->index
);
690 /* If a variable is used before being set, then the variable is live
691 across a block boundary, so mark it live-on-entry to BB. */
692 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
694 tree sym
= USE_FROM_PTR (use_p
);
695 gcc_checking_assert (DECL_P (sym
));
696 if (!bitmap_bit_p (kills
, DECL_UID (sym
)))
697 set_livein_block (sym
, bb
);
698 set_rewrite_uses (stmt
, true);
701 /* Now process the defs. Mark BB as the definition block and add
702 each def to the set of killed symbols. */
703 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
705 gcc_checking_assert (DECL_P (def
));
706 set_def_block (def
, bb
, false);
707 bitmap_set_bit (kills
, DECL_UID (def
));
708 set_register_defs (stmt
, true);
711 /* If we found the statement interesting then also mark the block BB
713 if (rewrite_uses_p (stmt
) || register_defs_p (stmt
))
714 bitmap_set_bit (interesting_blocks
, bb
->index
);
717 /* Structure used by prune_unused_phi_nodes to record bounds of the intervals
718 in the dfs numbering of the dominance tree. */
722 /* Basic block whose index this entry corresponds to. */
725 /* The dfs number of this node. */
729 /* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback
733 cmp_dfsnum (const void *a
, const void *b
)
735 const struct dom_dfsnum
*const da
= (const struct dom_dfsnum
*) a
;
736 const struct dom_dfsnum
*const db
= (const struct dom_dfsnum
*) b
;
738 return (int) da
->dfs_num
- (int) db
->dfs_num
;
741 /* Among the intervals starting at the N points specified in DEFS, find
742 the one that contains S, and return its bb_index. */
745 find_dfsnum_interval (struct dom_dfsnum
*defs
, unsigned n
, unsigned s
)
747 unsigned f
= 0, t
= n
, m
;
752 if (defs
[m
].dfs_num
<= s
)
758 return defs
[f
].bb_index
;
761 /* Clean bits from PHIS for phi nodes whose value cannot be used in USES.
762 KILLS is a bitmap of blocks where the value is defined before any use. */
765 prune_unused_phi_nodes (bitmap phis
, bitmap kills
, bitmap uses
)
769 unsigned i
, b
, p
, u
, top
;
771 basic_block def_bb
, use_bb
;
775 struct dom_dfsnum
*defs
;
776 unsigned n_defs
, adef
;
778 if (bitmap_empty_p (uses
))
784 /* The phi must dominate a use, or an argument of a live phi. Also, we
785 do not create any phi nodes in def blocks, unless they are also livein. */
786 to_remove
= BITMAP_ALLOC (NULL
);
787 bitmap_and_compl (to_remove
, kills
, uses
);
788 bitmap_and_compl_into (phis
, to_remove
);
789 if (bitmap_empty_p (phis
))
791 BITMAP_FREE (to_remove
);
795 /* We want to remove the unnecessary phi nodes, but we do not want to compute
796 liveness information, as that may be linear in the size of CFG, and if
797 there are lot of different variables to rewrite, this may lead to quadratic
800 Instead, we basically emulate standard dce. We put all uses to worklist,
801 then for each of them find the nearest def that dominates them. If this
802 def is a phi node, we mark it live, and if it was not live before, we
803 add the predecessors of its basic block to the worklist.
805 To quickly locate the nearest def that dominates use, we use dfs numbering
806 of the dominance tree (that is already available in order to speed up
807 queries). For each def, we have the interval given by the dfs number on
808 entry to and on exit from the corresponding subtree in the dominance tree.
809 The nearest dominator for a given use is the smallest of these intervals
810 that contains entry and exit dfs numbers for the basic block with the use.
811 If we store the bounds for all the uses to an array and sort it, we can
812 locate the nearest dominating def in logarithmic time by binary search.*/
813 bitmap_ior (to_remove
, kills
, phis
);
814 n_defs
= bitmap_count_bits (to_remove
);
815 defs
= XNEWVEC (struct dom_dfsnum
, 2 * n_defs
+ 1);
816 defs
[0].bb_index
= 1;
819 EXECUTE_IF_SET_IN_BITMAP (to_remove
, 0, i
, bi
)
821 def_bb
= BASIC_BLOCK (i
);
822 defs
[adef
].bb_index
= i
;
823 defs
[adef
].dfs_num
= bb_dom_dfs_in (CDI_DOMINATORS
, def_bb
);
824 defs
[adef
+ 1].bb_index
= i
;
825 defs
[adef
+ 1].dfs_num
= bb_dom_dfs_out (CDI_DOMINATORS
, def_bb
);
828 BITMAP_FREE (to_remove
);
829 gcc_assert (adef
== 2 * n_defs
+ 1);
830 qsort (defs
, adef
, sizeof (struct dom_dfsnum
), cmp_dfsnum
);
831 gcc_assert (defs
[0].bb_index
== 1);
833 /* Now each DEFS entry contains the number of the basic block to that the
834 dfs number corresponds. Change them to the number of basic block that
835 corresponds to the interval following the dfs number. Also, for the
836 dfs_out numbers, increase the dfs number by one (so that it corresponds
837 to the start of the following interval, not to the end of the current
838 one). We use WORKLIST as a stack. */
839 worklist
.create (n_defs
+ 1);
840 worklist
.quick_push (1);
843 for (i
= 1; i
< adef
; i
++)
845 b
= defs
[i
].bb_index
;
848 /* This is a closing element. Interval corresponding to the top
849 of the stack after removing it follows. */
851 top
= worklist
[worklist
.length () - 1];
852 defs
[n_defs
].bb_index
= top
;
853 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
+ 1;
857 /* Opening element. Nothing to do, just push it to the stack and move
858 it to the correct position. */
859 defs
[n_defs
].bb_index
= defs
[i
].bb_index
;
860 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
;
861 worklist
.quick_push (b
);
865 /* If this interval starts at the same point as the previous one, cancel
867 if (defs
[n_defs
].dfs_num
== defs
[n_defs
- 1].dfs_num
)
868 defs
[n_defs
- 1].bb_index
= defs
[n_defs
].bb_index
;
873 gcc_assert (worklist
.is_empty ());
875 /* Now process the uses. */
876 live_phis
= BITMAP_ALLOC (NULL
);
877 EXECUTE_IF_SET_IN_BITMAP (uses
, 0, i
, bi
)
879 worklist
.safe_push (i
);
882 while (!worklist
.is_empty ())
885 if (b
== ENTRY_BLOCK
)
888 /* If there is a phi node in USE_BB, it is made live. Otherwise,
889 find the def that dominates the immediate dominator of USE_BB
890 (the kill in USE_BB does not dominate the use). */
891 if (bitmap_bit_p (phis
, b
))
895 use_bb
= get_immediate_dominator (CDI_DOMINATORS
, BASIC_BLOCK (b
));
896 p
= find_dfsnum_interval (defs
, n_defs
,
897 bb_dom_dfs_in (CDI_DOMINATORS
, use_bb
));
898 if (!bitmap_bit_p (phis
, p
))
902 /* If the phi node is already live, there is nothing to do. */
903 if (!bitmap_set_bit (live_phis
, p
))
906 /* Add the new uses to the worklist. */
907 def_bb
= BASIC_BLOCK (p
);
908 FOR_EACH_EDGE (e
, ei
, def_bb
->preds
)
911 if (bitmap_bit_p (uses
, u
))
914 /* In case there is a kill directly in the use block, do not record
915 the use (this is also necessary for correctness, as we assume that
916 uses dominated by a def directly in their block have been filtered
918 if (bitmap_bit_p (kills
, u
))
921 bitmap_set_bit (uses
, u
);
922 worklist
.safe_push (u
);
927 bitmap_copy (phis
, live_phis
);
928 BITMAP_FREE (live_phis
);
932 /* Return the set of blocks where variable VAR is defined and the blocks
933 where VAR is live on entry (livein). Return NULL, if no entry is
934 found in DEF_BLOCKS. */
936 static inline struct def_blocks_d
*
937 find_def_blocks_for (tree var
)
939 def_blocks_p p
= &get_common_info (var
)->def_blocks
;
946 /* Marks phi node PHI in basic block BB for rewrite. */
949 mark_phi_for_rewrite (basic_block bb
, gimple phi
)
952 unsigned n
, idx
= bb
->index
;
954 if (rewrite_uses_p (phi
))
957 set_rewrite_uses (phi
, true);
959 if (!blocks_with_phis_to_rewrite
)
962 bitmap_set_bit (blocks_with_phis_to_rewrite
, idx
);
964 n
= (unsigned) last_basic_block
+ 1;
965 if (phis_to_rewrite
.length () < n
)
966 phis_to_rewrite
.safe_grow_cleared (n
);
968 phis
= phis_to_rewrite
[idx
];
971 phis
.safe_push (phi
);
972 phis_to_rewrite
[idx
] = phis
;
975 /* Insert PHI nodes for variable VAR using the iterated dominance
976 frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
977 function assumes that the caller is incrementally updating the
978 existing SSA form, in which case VAR may be an SSA name instead of
981 PHI_INSERTION_POINTS is updated to reflect nodes that already had a
982 PHI node for VAR. On exit, only the nodes that received a PHI node
983 for VAR will be present in PHI_INSERTION_POINTS. */
986 insert_phi_nodes_for (tree var
, bitmap phi_insertion_points
, bool update_p
)
993 struct def_blocks_d
*def_map
= find_def_blocks_for (var
);
995 /* Remove the blocks where we already have PHI nodes for VAR. */
996 bitmap_and_compl_into (phi_insertion_points
, def_map
->phi_blocks
);
998 /* Remove obviously useless phi nodes. */
999 prune_unused_phi_nodes (phi_insertion_points
, def_map
->def_blocks
,
1000 def_map
->livein_blocks
);
1002 /* And insert the PHI nodes. */
1003 EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points
, 0, bb_index
, bi
)
1005 bb
= BASIC_BLOCK (bb_index
);
1007 mark_block_for_update (bb
);
1009 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1011 fprintf (dump_file
, "creating PHI node in block #%d for ", bb_index
);
1012 print_generic_expr (dump_file
, var
, TDF_SLIM
);
1013 fprintf (dump_file
, "\n");
1017 if (TREE_CODE (var
) == SSA_NAME
)
1019 /* If we are rewriting SSA names, create the LHS of the PHI
1020 node by duplicating VAR. This is useful in the case of
1021 pointers, to also duplicate pointer attributes (alias
1022 information, in particular). */
1026 gcc_checking_assert (update_p
);
1027 new_lhs
= duplicate_ssa_name (var
, NULL
);
1028 phi
= create_phi_node (new_lhs
, bb
);
1029 add_new_name_mapping (new_lhs
, var
);
1031 /* Add VAR to every argument slot of PHI. We need VAR in
1032 every argument so that rewrite_update_phi_arguments knows
1033 which name is this PHI node replacing. If VAR is a
1034 symbol marked for renaming, this is not necessary, the
1035 renamer will use the symbol on the LHS to get its
1036 reaching definition. */
1037 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1038 add_phi_arg (phi
, var
, e
, UNKNOWN_LOCATION
);
1044 gcc_checking_assert (DECL_P (var
));
1045 phi
= create_phi_node (var
, bb
);
1047 tracked_var
= target_for_debug_bind (var
);
1050 gimple note
= gimple_build_debug_bind (tracked_var
,
1053 gimple_stmt_iterator si
= gsi_after_labels (bb
);
1054 gsi_insert_before (&si
, note
, GSI_SAME_STMT
);
1058 /* Mark this PHI node as interesting for update_ssa. */
1059 set_register_defs (phi
, true);
1060 mark_phi_for_rewrite (bb
, phi
);
1064 /* Sort var_infos after DECL_UID of their var. */
1067 insert_phi_nodes_compare_var_infos (const void *a
, const void *b
)
1069 const struct var_info_d
*defa
= *(struct var_info_d
* const *)a
;
1070 const struct var_info_d
*defb
= *(struct var_info_d
* const *)b
;
1071 if (DECL_UID (defa
->var
) < DECL_UID (defb
->var
))
1077 /* Insert PHI nodes at the dominance frontier of blocks with variable
1078 definitions. DFS contains the dominance frontier information for
1082 insert_phi_nodes (bitmap_head
*dfs
)
1084 hash_table
<var_info_hasher
>::iterator hi
;
1087 vec
<var_info_p
> vars
;
1089 timevar_push (TV_TREE_INSERT_PHI_NODES
);
1091 vars
.create (var_infos
.elements ());
1092 FOR_EACH_HASH_TABLE_ELEMENT (var_infos
, info
, var_info_p
, hi
)
1093 if (info
->info
.need_phi_state
!= NEED_PHI_STATE_NO
)
1094 vars
.quick_push (info
);
1096 /* Do two stages to avoid code generation differences for UID
1097 differences but no UID ordering differences. */
1098 vars
.qsort (insert_phi_nodes_compare_var_infos
);
1100 FOR_EACH_VEC_ELT (vars
, i
, info
)
1102 bitmap idf
= compute_idf (info
->info
.def_blocks
.def_blocks
, dfs
);
1103 insert_phi_nodes_for (info
->var
, idf
, false);
1109 timevar_pop (TV_TREE_INSERT_PHI_NODES
);
1113 /* Push SYM's current reaching definition into BLOCK_DEFS_STACK and
1114 register DEF (an SSA_NAME) to be a new definition for SYM. */
1117 register_new_def (tree def
, tree sym
)
1119 common_info_p info
= get_common_info (sym
);
1122 /* If this variable is set in a single basic block and all uses are
1123 dominated by the set(s) in that single basic block, then there is
1124 no reason to record anything for this variable in the block local
1125 definition stacks. Doing so just wastes time and memory.
1127 This is the same test to prune the set of variables which may
1128 need PHI nodes. So we just use that information since it's already
1129 computed and available for us to use. */
1130 if (info
->need_phi_state
== NEED_PHI_STATE_NO
)
1132 info
->current_def
= def
;
1136 currdef
= info
->current_def
;
1138 /* If SYM is not a GIMPLE register, then CURRDEF may be a name whose
1139 SSA_NAME_VAR is not necessarily SYM. In this case, also push SYM
1140 in the stack so that we know which symbol is being defined by
1141 this SSA name when we unwind the stack. */
1142 if (currdef
&& !is_gimple_reg (sym
))
1143 block_defs_stack
.safe_push (sym
);
1145 /* Push the current reaching definition into BLOCK_DEFS_STACK. This
1146 stack is later used by the dominator tree callbacks to restore
1147 the reaching definitions for all the variables defined in the
1148 block after a recursive visit to all its immediately dominated
1149 blocks. If there is no current reaching definition, then just
1150 record the underlying _DECL node. */
1151 block_defs_stack
.safe_push (currdef
? currdef
: sym
);
1153 /* Set the current reaching definition for SYM to be DEF. */
1154 info
->current_def
= def
;
1158 /* Perform a depth-first traversal of the dominator tree looking for
1159 variables to rename. BB is the block where to start searching.
1160 Renaming is a five step process:
1162 1- Every definition made by PHI nodes at the start of the blocks is
1163 registered as the current definition for the corresponding variable.
1165 2- Every statement in BB is rewritten. USE and VUSE operands are
1166 rewritten with their corresponding reaching definition. DEF and
1167 VDEF targets are registered as new definitions.
1169 3- All the PHI nodes in successor blocks of BB are visited. The
1170 argument corresponding to BB is replaced with its current reaching
1173 4- Recursively rewrite every dominator child block of BB.
1175 5- Restore (in reverse order) the current reaching definition for every
1176 new definition introduced in this block. This is done so that when
1177 we return from the recursive call, all the current reaching
1178 definitions are restored to the names that were valid in the
1179 dominator parent of BB. */
1181 /* Return the current definition for variable VAR. If none is found,
1182 create a new SSA name to act as the zeroth definition for VAR. */
1185 get_reaching_def (tree var
)
1187 common_info_p info
= get_common_info (var
);
1190 /* Lookup the current reaching definition for VAR. */
1191 currdef
= info
->current_def
;
1193 /* If there is no reaching definition for VAR, create and register a
1194 default definition for it (if needed). */
1195 if (currdef
== NULL_TREE
)
1197 tree sym
= DECL_P (var
) ? var
: SSA_NAME_VAR (var
);
1198 currdef
= get_or_create_ssa_default_def (cfun
, sym
);
1201 /* Return the current reaching definition for VAR, or the default
1202 definition, if we had to create one. */
1207 /* Helper function for rewrite_stmt. Rewrite uses in a debug stmt. */
1210 rewrite_debug_stmt_uses (gimple stmt
)
1212 use_operand_p use_p
;
1214 bool update
= false;
1216 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
1218 tree var
= USE_FROM_PTR (use_p
), def
;
1219 common_info_p info
= get_common_info (var
);
1220 gcc_checking_assert (DECL_P (var
));
1221 def
= info
->current_def
;
1224 if (TREE_CODE (var
) == PARM_DECL
1225 && single_succ_p (ENTRY_BLOCK_PTR_FOR_FN (cfun
)))
1227 gimple_stmt_iterator gsi
1229 gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun
)));
1231 /* Search a few source bind stmts at the start of first bb to
1232 see if a DEBUG_EXPR_DECL can't be reused. */
1234 !gsi_end_p (gsi
) && lim
> 0;
1235 gsi_next (&gsi
), lim
--)
1237 gimple gstmt
= gsi_stmt (gsi
);
1238 if (!gimple_debug_source_bind_p (gstmt
))
1240 if (gimple_debug_source_bind_get_value (gstmt
) == var
)
1242 def
= gimple_debug_source_bind_get_var (gstmt
);
1243 if (TREE_CODE (def
) == DEBUG_EXPR_DECL
)
1249 /* If not, add a new source bind stmt. */
1250 if (def
== NULL_TREE
)
1253 def
= make_node (DEBUG_EXPR_DECL
);
1254 def_temp
= gimple_build_debug_source_bind (def
, var
, NULL
);
1255 DECL_ARTIFICIAL (def
) = 1;
1256 TREE_TYPE (def
) = TREE_TYPE (var
);
1257 DECL_MODE (def
) = DECL_MODE (var
);
1259 gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun
)));
1260 gsi_insert_before (&gsi
, def_temp
, GSI_SAME_STMT
);
1267 /* Check if info->current_def can be trusted. */
1268 basic_block bb
= gimple_bb (stmt
);
1270 = SSA_NAME_IS_DEFAULT_DEF (def
)
1271 ? NULL
: gimple_bb (SSA_NAME_DEF_STMT (def
));
1273 /* If definition is in current bb, it is fine. */
1276 /* If definition bb doesn't dominate the current bb,
1277 it can't be used. */
1278 else if (def_bb
&& !dominated_by_p (CDI_DOMINATORS
, bb
, def_bb
))
1280 /* If there is just one definition and dominates the current
1282 else if (info
->need_phi_state
== NEED_PHI_STATE_NO
)
1286 struct def_blocks_d
*db_p
= get_def_blocks_for (info
);
1288 /* If there are some non-debug uses in the current bb,
1290 if (bitmap_bit_p (db_p
->livein_blocks
, bb
->index
))
1292 /* Otherwise give up for now. */
1299 gimple_debug_bind_reset_value (stmt
);
1303 SET_USE (use_p
, def
);
1309 /* SSA Rewriting Step 2. Rewrite every variable used in each statement in
1310 the block with its immediate reaching definitions. Update the current
1311 definition of a variable when a new real or virtual definition is found. */
1314 rewrite_stmt (gimple_stmt_iterator
*si
)
1316 use_operand_p use_p
;
1317 def_operand_p def_p
;
1319 gimple stmt
= gsi_stmt (*si
);
1321 /* If mark_def_sites decided that we don't need to rewrite this
1322 statement, ignore it. */
1323 gcc_assert (blocks_to_update
== NULL
);
1324 if (!rewrite_uses_p (stmt
) && !register_defs_p (stmt
))
1327 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1329 fprintf (dump_file
, "Renaming statement ");
1330 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1331 fprintf (dump_file
, "\n");
1334 /* Step 1. Rewrite USES in the statement. */
1335 if (rewrite_uses_p (stmt
))
1337 if (is_gimple_debug (stmt
))
1338 rewrite_debug_stmt_uses (stmt
);
1340 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
1342 tree var
= USE_FROM_PTR (use_p
);
1343 gcc_checking_assert (DECL_P (var
));
1344 SET_USE (use_p
, get_reaching_def (var
));
1348 /* Step 2. Register the statement's DEF operands. */
1349 if (register_defs_p (stmt
))
1350 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1352 tree var
= DEF_FROM_PTR (def_p
);
1356 gcc_checking_assert (DECL_P (var
));
1358 if (gimple_clobber_p (stmt
)
1359 && is_gimple_reg (var
))
1361 /* If we rewrite a DECL into SSA form then drop its
1362 clobber stmts and replace uses with a new default def. */
1363 gcc_checking_assert (TREE_CODE (var
) == VAR_DECL
1364 && !gimple_vdef (stmt
));
1365 gsi_replace (si
, gimple_build_nop (), true);
1366 register_new_def (get_or_create_ssa_default_def (cfun
, var
), var
);
1370 name
= make_ssa_name (var
, stmt
);
1371 SET_DEF (def_p
, name
);
1372 register_new_def (DEF_FROM_PTR (def_p
), var
);
1374 tracked_var
= target_for_debug_bind (var
);
1377 gimple note
= gimple_build_debug_bind (tracked_var
, name
, stmt
);
1378 gsi_insert_after (si
, note
, GSI_SAME_STMT
);
1384 /* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for
1385 PHI nodes. For every PHI node found, add a new argument containing the
1386 current reaching definition for the variable and the edge through which
1387 that definition is reaching the PHI node. */
1390 rewrite_add_phi_arguments (basic_block bb
)
1395 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1398 gimple_stmt_iterator gsi
;
1400 for (gsi
= gsi_start_phis (e
->dest
); !gsi_end_p (gsi
);
1406 phi
= gsi_stmt (gsi
);
1407 res
= gimple_phi_result (phi
);
1408 currdef
= get_reaching_def (SSA_NAME_VAR (res
));
1409 /* Virtual operand PHI args do not need a location. */
1410 if (virtual_operand_p (res
))
1411 loc
= UNKNOWN_LOCATION
;
1413 loc
= gimple_location (SSA_NAME_DEF_STMT (currdef
));
1414 add_phi_arg (phi
, currdef
, e
, loc
);
1419 class rewrite_dom_walker
: public dom_walker
1422 rewrite_dom_walker (cdi_direction direction
) : dom_walker (direction
) {}
1424 virtual void before_dom_children (basic_block
);
1425 virtual void after_dom_children (basic_block
);
1428 /* SSA Rewriting Step 1. Initialization, create a block local stack
1429 of reaching definitions for new SSA names produced in this block
1430 (BLOCK_DEFS). Register new definitions for every PHI node in the
1434 rewrite_dom_walker::before_dom_children (basic_block bb
)
1436 gimple_stmt_iterator gsi
;
1438 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1439 fprintf (dump_file
, "\n\nRenaming block #%d\n\n", bb
->index
);
1441 /* Mark the unwind point for this block. */
1442 block_defs_stack
.safe_push (NULL_TREE
);
1444 /* Step 1. Register new definitions for every PHI node in the block.
1445 Conceptually, all the PHI nodes are executed in parallel and each PHI
1446 node introduces a new version for the associated variable. */
1447 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1449 tree result
= gimple_phi_result (gsi_stmt (gsi
));
1450 register_new_def (result
, SSA_NAME_VAR (result
));
1453 /* Step 2. Rewrite every variable used in each statement in the block
1454 with its immediate reaching definitions. Update the current definition
1455 of a variable when a new real or virtual definition is found. */
1456 if (bitmap_bit_p (interesting_blocks
, bb
->index
))
1457 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1458 rewrite_stmt (&gsi
);
1460 /* Step 3. Visit all the successor blocks of BB looking for PHI nodes.
1461 For every PHI node found, add a new argument containing the current
1462 reaching definition for the variable and the edge through which that
1463 definition is reaching the PHI node. */
1464 rewrite_add_phi_arguments (bb
);
1469 /* Called after visiting all the statements in basic block BB and all
1470 of its dominator children. Restore CURRDEFS to its original value. */
1473 rewrite_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED
)
1475 /* Restore CURRDEFS to its original state. */
1476 while (block_defs_stack
.length () > 0)
1478 tree tmp
= block_defs_stack
.pop ();
1479 tree saved_def
, var
;
1481 if (tmp
== NULL_TREE
)
1484 if (TREE_CODE (tmp
) == SSA_NAME
)
1486 /* If we recorded an SSA_NAME, then make the SSA_NAME the
1487 current definition of its underlying variable. Note that
1488 if the SSA_NAME is not for a GIMPLE register, the symbol
1489 being defined is stored in the next slot in the stack.
1490 This mechanism is needed because an SSA name for a
1491 non-register symbol may be the definition for more than
1492 one symbol (e.g., SFTs, aliased variables, etc). */
1494 var
= SSA_NAME_VAR (saved_def
);
1495 if (!is_gimple_reg (var
))
1496 var
= block_defs_stack
.pop ();
1500 /* If we recorded anything else, it must have been a _DECL
1501 node and its current reaching definition must have been
1507 get_common_info (var
)->current_def
= saved_def
;
1512 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1515 debug_decl_set (bitmap set
)
1517 dump_decl_set (stderr
, set
);
1518 fprintf (stderr
, "\n");
1522 /* Dump the renaming stack (block_defs_stack) to FILE. Traverse the
1523 stack up to a maximum of N levels. If N is -1, the whole stack is
1524 dumped. New levels are created when the dominator tree traversal
1525 used for renaming enters a new sub-tree. */
1528 dump_defs_stack (FILE *file
, int n
)
1532 fprintf (file
, "\n\nRenaming stack");
1534 fprintf (file
, " (up to %d levels)", n
);
1535 fprintf (file
, "\n\n");
1538 fprintf (file
, "Level %d (current level)\n", i
);
1539 for (j
= (int) block_defs_stack
.length () - 1; j
>= 0; j
--)
1543 name
= block_defs_stack
[j
];
1544 if (name
== NULL_TREE
)
1549 fprintf (file
, "\nLevel %d\n", i
);
1560 var
= SSA_NAME_VAR (name
);
1561 if (!is_gimple_reg (var
))
1564 var
= block_defs_stack
[j
];
1568 fprintf (file
, " Previous CURRDEF (");
1569 print_generic_expr (file
, var
, 0);
1570 fprintf (file
, ") = ");
1572 print_generic_expr (file
, name
, 0);
1574 fprintf (file
, "<NIL>");
1575 fprintf (file
, "\n");
1580 /* Dump the renaming stack (block_defs_stack) to stderr. Traverse the
1581 stack up to a maximum of N levels. If N is -1, the whole stack is
1582 dumped. New levels are created when the dominator tree traversal
1583 used for renaming enters a new sub-tree. */
1586 debug_defs_stack (int n
)
1588 dump_defs_stack (stderr
, n
);
1592 /* Dump the current reaching definition of every symbol to FILE. */
1595 dump_currdefs (FILE *file
)
1600 if (symbols_to_rename
.is_empty ())
1603 fprintf (file
, "\n\nCurrent reaching definitions\n\n");
1604 FOR_EACH_VEC_ELT (symbols_to_rename
, i
, var
)
1606 common_info_p info
= get_common_info (var
);
1607 fprintf (file
, "CURRDEF (");
1608 print_generic_expr (file
, var
, 0);
1609 fprintf (file
, ") = ");
1610 if (info
->current_def
)
1611 print_generic_expr (file
, info
->current_def
, 0);
1613 fprintf (file
, "<NIL>");
1614 fprintf (file
, "\n");
1619 /* Dump the current reaching definition of every symbol to stderr. */
1622 debug_currdefs (void)
1624 dump_currdefs (stderr
);
1628 /* Dump SSA information to FILE. */
1631 dump_tree_ssa (FILE *file
)
1633 const char *funcname
1634 = lang_hooks
.decl_printable_name (current_function_decl
, 2);
1636 fprintf (file
, "SSA renaming information for %s\n\n", funcname
);
1638 dump_var_infos (file
);
1639 dump_defs_stack (file
, -1);
1640 dump_currdefs (file
);
1641 dump_tree_ssa_stats (file
);
1645 /* Dump SSA information to stderr. */
1648 debug_tree_ssa (void)
1650 dump_tree_ssa (stderr
);
1654 /* Dump statistics for the hash table HTAB. */
1657 htab_statistics (FILE *file
, hash_table
<var_info_hasher
> htab
)
1659 fprintf (file
, "size %ld, %ld elements, %f collision/search ratio\n",
1660 (long) htab
.size (),
1661 (long) htab
.elements (),
1662 htab
.collisions ());
1666 /* Dump SSA statistics on FILE. */
1669 dump_tree_ssa_stats (FILE *file
)
1671 if (var_infos
.is_created ())
1673 fprintf (file
, "\nHash table statistics:\n");
1674 fprintf (file
, " var_infos: ");
1675 htab_statistics (file
, var_infos
);
1676 fprintf (file
, "\n");
1681 /* Dump SSA statistics on stderr. */
1684 debug_tree_ssa_stats (void)
1686 dump_tree_ssa_stats (stderr
);
1690 /* Callback for htab_traverse to dump the VAR_INFOS hash table. */
1693 debug_var_infos_r (var_info_d
**slot
, FILE *file
)
1695 struct var_info_d
*info
= *slot
;
1697 fprintf (file
, "VAR: ");
1698 print_generic_expr (file
, info
->var
, dump_flags
);
1699 bitmap_print (file
, info
->info
.def_blocks
.def_blocks
,
1700 ", DEF_BLOCKS: { ", "}");
1701 bitmap_print (file
, info
->info
.def_blocks
.livein_blocks
,
1702 ", LIVEIN_BLOCKS: { ", "}");
1703 bitmap_print (file
, info
->info
.def_blocks
.phi_blocks
,
1704 ", PHI_BLOCKS: { ", "}\n");
1710 /* Dump the VAR_INFOS hash table on FILE. */
1713 dump_var_infos (FILE *file
)
1715 fprintf (file
, "\n\nDefinition and live-in blocks:\n\n");
1716 if (var_infos
.is_created ())
1717 var_infos
.traverse
<FILE *, debug_var_infos_r
> (file
);
1721 /* Dump the VAR_INFOS hash table on stderr. */
1724 debug_var_infos (void)
1726 dump_var_infos (stderr
);
1730 /* Register NEW_NAME to be the new reaching definition for OLD_NAME. */
1733 register_new_update_single (tree new_name
, tree old_name
)
1735 common_info_p info
= get_common_info (old_name
);
1736 tree currdef
= info
->current_def
;
1738 /* Push the current reaching definition into BLOCK_DEFS_STACK.
1739 This stack is later used by the dominator tree callbacks to
1740 restore the reaching definitions for all the variables
1741 defined in the block after a recursive visit to all its
1742 immediately dominated blocks. */
1743 block_defs_stack
.reserve (2);
1744 block_defs_stack
.quick_push (currdef
);
1745 block_defs_stack
.quick_push (old_name
);
1747 /* Set the current reaching definition for OLD_NAME to be
1749 info
->current_def
= new_name
;
1753 /* Register NEW_NAME to be the new reaching definition for all the
1754 names in OLD_NAMES. Used by the incremental SSA update routines to
1755 replace old SSA names with new ones. */
1758 register_new_update_set (tree new_name
, bitmap old_names
)
1763 EXECUTE_IF_SET_IN_BITMAP (old_names
, 0, i
, bi
)
1764 register_new_update_single (new_name
, ssa_name (i
));
1769 /* If the operand pointed to by USE_P is a name in OLD_SSA_NAMES or
1770 it is a symbol marked for renaming, replace it with USE_P's current
1771 reaching definition. */
1774 maybe_replace_use (use_operand_p use_p
)
1776 tree rdef
= NULL_TREE
;
1777 tree use
= USE_FROM_PTR (use_p
);
1778 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
1780 if (marked_for_renaming (sym
))
1781 rdef
= get_reaching_def (sym
);
1782 else if (is_old_name (use
))
1783 rdef
= get_reaching_def (use
);
1785 if (rdef
&& rdef
!= use
)
1786 SET_USE (use_p
, rdef
);
1790 /* Same as maybe_replace_use, but without introducing default stmts,
1791 returning false to indicate a need to do so. */
1794 maybe_replace_use_in_debug_stmt (use_operand_p use_p
)
1796 tree rdef
= NULL_TREE
;
1797 tree use
= USE_FROM_PTR (use_p
);
1798 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
1800 if (marked_for_renaming (sym
))
1801 rdef
= get_var_info (sym
)->info
.current_def
;
1802 else if (is_old_name (use
))
1804 rdef
= get_ssa_name_ann (use
)->info
.current_def
;
1805 /* We can't assume that, if there's no current definition, the
1806 default one should be used. It could be the case that we've
1807 rearranged blocks so that the earlier definition no longer
1808 dominates the use. */
1809 if (!rdef
&& SSA_NAME_IS_DEFAULT_DEF (use
))
1815 if (rdef
&& rdef
!= use
)
1816 SET_USE (use_p
, rdef
);
1818 return rdef
!= NULL_TREE
;
1822 /* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
1823 or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
1824 register it as the current definition for the names replaced by
1828 maybe_register_def (def_operand_p def_p
, gimple stmt
,
1829 gimple_stmt_iterator gsi
)
1831 tree def
= DEF_FROM_PTR (def_p
);
1832 tree sym
= DECL_P (def
) ? def
: SSA_NAME_VAR (def
);
1834 /* If DEF is a naked symbol that needs renaming, create a new
1836 if (marked_for_renaming (sym
))
1842 def
= make_ssa_name (def
, stmt
);
1843 SET_DEF (def_p
, def
);
1845 tracked_var
= target_for_debug_bind (sym
);
1848 gimple note
= gimple_build_debug_bind (tracked_var
, def
, stmt
);
1849 /* If stmt ends the bb, insert the debug stmt on the single
1850 non-EH edge from the stmt. */
1851 if (gsi_one_before_end_p (gsi
) && stmt_ends_bb_p (stmt
))
1853 basic_block bb
= gsi_bb (gsi
);
1856 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1857 if (!(e
->flags
& EDGE_EH
))
1859 gcc_checking_assert (!ef
);
1862 /* If there are other predecessors to ef->dest, then
1863 there must be PHI nodes for the modified
1864 variable, and therefore there will be debug bind
1865 stmts after the PHI nodes. The debug bind notes
1866 we'd insert would force the creation of a new
1867 block (diverging codegen) and be redundant with
1868 the post-PHI bind stmts, so don't add them.
1870 As for the exit edge, there wouldn't be redundant
1871 bind stmts, but there wouldn't be a PC to bind
1872 them to either, so avoid diverging the CFG. */
1873 if (ef
&& single_pred_p (ef
->dest
)
1874 && ef
->dest
!= EXIT_BLOCK_PTR_FOR_FN (cfun
))
1876 /* If there were PHI nodes in the node, we'd
1877 have to make sure the value we're binding
1878 doesn't need rewriting. But there shouldn't
1879 be PHI nodes in a single-predecessor block,
1880 so we just add the note. */
1881 gsi_insert_on_edge_immediate (ef
, note
);
1885 gsi_insert_after (&gsi
, note
, GSI_SAME_STMT
);
1889 register_new_update_single (def
, sym
);
1893 /* If DEF is a new name, register it as a new definition
1894 for all the names replaced by DEF. */
1895 if (is_new_name (def
))
1896 register_new_update_set (def
, names_replaced_by (def
));
1898 /* If DEF is an old name, register DEF as a new
1899 definition for itself. */
1900 if (is_old_name (def
))
1901 register_new_update_single (def
, def
);
1906 /* Update every variable used in the statement pointed-to by SI. The
1907 statement is assumed to be in SSA form already. Names in
1908 OLD_SSA_NAMES used by SI will be updated to their current reaching
1909 definition. Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI
1910 will be registered as a new definition for their corresponding name
1911 in OLD_SSA_NAMES. */
1914 rewrite_update_stmt (gimple stmt
, gimple_stmt_iterator gsi
)
1916 use_operand_p use_p
;
1917 def_operand_p def_p
;
1920 /* Only update marked statements. */
1921 if (!rewrite_uses_p (stmt
) && !register_defs_p (stmt
))
1924 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1926 fprintf (dump_file
, "Updating SSA information for statement ");
1927 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1930 /* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying
1931 symbol is marked for renaming. */
1932 if (rewrite_uses_p (stmt
))
1934 if (is_gimple_debug (stmt
))
1936 bool failed
= false;
1938 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
1939 if (!maybe_replace_use_in_debug_stmt (use_p
))
1947 /* DOM sometimes threads jumps in such a way that a
1948 debug stmt ends up referencing a SSA variable that no
1949 longer dominates the debug stmt, but such that all
1950 incoming definitions refer to the same definition in
1951 an earlier dominator. We could try to recover that
1952 definition somehow, but this will have to do for now.
1954 Introducing a default definition, which is what
1955 maybe_replace_use() would do in such cases, may
1956 modify code generation, for the otherwise-unused
1957 default definition would never go away, modifying SSA
1958 version numbers all over. */
1959 gimple_debug_bind_reset_value (stmt
);
1965 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
1966 maybe_replace_use (use_p
);
1970 /* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES.
1971 Also register definitions for names whose underlying symbol is
1972 marked for renaming. */
1973 if (register_defs_p (stmt
))
1974 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1975 maybe_register_def (def_p
, stmt
, gsi
);
1979 /* Visit all the successor blocks of BB looking for PHI nodes. For
1980 every PHI node found, check if any of its arguments is in
1981 OLD_SSA_NAMES. If so, and if the argument has a current reaching
1982 definition, replace it. */
1985 rewrite_update_phi_arguments (basic_block bb
)
1991 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1996 if (!bitmap_bit_p (blocks_with_phis_to_rewrite
, e
->dest
->index
))
1999 phis
= phis_to_rewrite
[e
->dest
->index
];
2000 FOR_EACH_VEC_ELT (phis
, i
, phi
)
2002 tree arg
, lhs_sym
, reaching_def
= NULL
;
2003 use_operand_p arg_p
;
2005 gcc_checking_assert (rewrite_uses_p (phi
));
2007 arg_p
= PHI_ARG_DEF_PTR_FROM_EDGE (phi
, e
);
2008 arg
= USE_FROM_PTR (arg_p
);
2010 if (arg
&& !DECL_P (arg
) && TREE_CODE (arg
) != SSA_NAME
)
2013 lhs_sym
= SSA_NAME_VAR (gimple_phi_result (phi
));
2015 if (arg
== NULL_TREE
)
2017 /* When updating a PHI node for a recently introduced
2018 symbol we may find NULL arguments. That's why we
2019 take the symbol from the LHS of the PHI node. */
2020 reaching_def
= get_reaching_def (lhs_sym
);
2025 tree sym
= DECL_P (arg
) ? arg
: SSA_NAME_VAR (arg
);
2027 if (marked_for_renaming (sym
))
2028 reaching_def
= get_reaching_def (sym
);
2029 else if (is_old_name (arg
))
2030 reaching_def
= get_reaching_def (arg
);
2033 /* Update the argument if there is a reaching def. */
2036 source_location locus
;
2037 int arg_i
= PHI_ARG_INDEX_FROM_USE (arg_p
);
2039 SET_USE (arg_p
, reaching_def
);
2041 /* Virtual operands do not need a location. */
2042 if (virtual_operand_p (reaching_def
))
2043 locus
= UNKNOWN_LOCATION
;
2046 gimple stmt
= SSA_NAME_DEF_STMT (reaching_def
);
2048 /* Single element PHI nodes behave like copies, so get the
2049 location from the phi argument. */
2050 if (gimple_code (stmt
) == GIMPLE_PHI
2051 && gimple_phi_num_args (stmt
) == 1)
2052 locus
= gimple_phi_arg_location (stmt
, 0);
2054 locus
= gimple_location (stmt
);
2057 gimple_phi_arg_set_location (phi
, arg_i
, locus
);
2061 if (e
->flags
& EDGE_ABNORMAL
)
2062 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p
)) = 1;
2067 class rewrite_update_dom_walker
: public dom_walker
2070 rewrite_update_dom_walker (cdi_direction direction
) : dom_walker (direction
) {}
2072 virtual void before_dom_children (basic_block
);
2073 virtual void after_dom_children (basic_block
);
2076 /* Initialization of block data structures for the incremental SSA
2077 update pass. Create a block local stack of reaching definitions
2078 for new SSA names produced in this block (BLOCK_DEFS). Register
2079 new definitions for every PHI node in the block. */
2082 rewrite_update_dom_walker::before_dom_children (basic_block bb
)
2084 bool is_abnormal_phi
;
2085 gimple_stmt_iterator gsi
;
2087 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2088 fprintf (dump_file
, "Registering new PHI nodes in block #%d\n",
2091 /* Mark the unwind point for this block. */
2092 block_defs_stack
.safe_push (NULL_TREE
);
2094 if (!bitmap_bit_p (blocks_to_update
, bb
->index
))
2097 /* Mark the LHS if any of the arguments flows through an abnormal
2099 is_abnormal_phi
= bb_has_abnormal_pred (bb
);
2101 /* If any of the PHI nodes is a replacement for a name in
2102 OLD_SSA_NAMES or it's one of the names in NEW_SSA_NAMES, then
2103 register it as a new definition for its corresponding name. Also
2104 register definitions for names whose underlying symbols are
2105 marked for renaming. */
2106 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2109 gimple phi
= gsi_stmt (gsi
);
2111 if (!register_defs_p (phi
))
2114 lhs
= gimple_phi_result (phi
);
2115 lhs_sym
= SSA_NAME_VAR (lhs
);
2117 if (marked_for_renaming (lhs_sym
))
2118 register_new_update_single (lhs
, lhs_sym
);
2122 /* If LHS is a new name, register a new definition for all
2123 the names replaced by LHS. */
2124 if (is_new_name (lhs
))
2125 register_new_update_set (lhs
, names_replaced_by (lhs
));
2127 /* If LHS is an OLD name, register it as a new definition
2129 if (is_old_name (lhs
))
2130 register_new_update_single (lhs
, lhs
);
2133 if (is_abnormal_phi
)
2134 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs
) = 1;
2137 /* Step 2. Rewrite every variable used in each statement in the block. */
2138 if (bitmap_bit_p (interesting_blocks
, bb
->index
))
2140 gcc_checking_assert (bitmap_bit_p (blocks_to_update
, bb
->index
));
2141 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2142 rewrite_update_stmt (gsi_stmt (gsi
), gsi
);
2145 /* Step 3. Update PHI nodes. */
2146 rewrite_update_phi_arguments (bb
);
2149 /* Called after visiting block BB. Unwind BLOCK_DEFS_STACK to restore
2150 the current reaching definition of every name re-written in BB to
2151 the original reaching definition before visiting BB. This
2152 unwinding must be done in the opposite order to what is done in
2153 register_new_update_set. */
2156 rewrite_update_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED
)
2158 while (block_defs_stack
.length () > 0)
2160 tree var
= block_defs_stack
.pop ();
2163 /* NULL indicates the unwind stop point for this block (see
2164 rewrite_update_enter_block). */
2168 saved_def
= block_defs_stack
.pop ();
2169 get_common_info (var
)->current_def
= saved_def
;
2174 /* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
2177 ENTRY indicates the block where to start. Every block dominated by
2178 ENTRY will be rewritten.
2180 WHAT indicates what actions will be taken by the renamer (see enum
2183 BLOCKS are the set of interesting blocks for the dominator walker
2184 to process. If this set is NULL, then all the nodes dominated
2185 by ENTRY are walked. Otherwise, blocks dominated by ENTRY that
2186 are not present in BLOCKS are ignored. */
2189 rewrite_blocks (basic_block entry
, enum rewrite_mode what
)
2191 /* Rewrite all the basic blocks in the program. */
2192 timevar_push (TV_TREE_SSA_REWRITE_BLOCKS
);
2194 block_defs_stack
.create (10);
2196 /* Recursively walk the dominator tree rewriting each statement in
2197 each basic block. */
2198 if (what
== REWRITE_ALL
)
2199 rewrite_dom_walker (CDI_DOMINATORS
).walk (entry
);
2200 else if (what
== REWRITE_UPDATE
)
2201 rewrite_update_dom_walker (CDI_DOMINATORS
).walk (entry
);
2205 /* Debugging dumps. */
2206 if (dump_file
&& (dump_flags
& TDF_STATS
))
2208 dump_dfa_stats (dump_file
);
2209 if (var_infos
.is_created ())
2210 dump_tree_ssa_stats (dump_file
);
2213 block_defs_stack
.release ();
2215 timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS
);
2218 class mark_def_dom_walker
: public dom_walker
2221 mark_def_dom_walker (cdi_direction direction
);
2222 ~mark_def_dom_walker ();
2224 virtual void before_dom_children (basic_block
);
2227 /* Notice that this bitmap is indexed using variable UIDs, so it must be
2228 large enough to accommodate all the variables referenced in the
2229 function, not just the ones we are renaming. */
2233 mark_def_dom_walker::mark_def_dom_walker (cdi_direction direction
)
2234 : dom_walker (direction
), m_kills (BITMAP_ALLOC (NULL
))
2238 mark_def_dom_walker::~mark_def_dom_walker ()
2240 BITMAP_FREE (m_kills
);
2243 /* Block processing routine for mark_def_sites. Clear the KILLS bitmap
2244 at the start of each block, and call mark_def_sites for each statement. */
2247 mark_def_dom_walker::before_dom_children (basic_block bb
)
2249 gimple_stmt_iterator gsi
;
2251 bitmap_clear (m_kills
);
2252 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2253 mark_def_sites (bb
, gsi_stmt (gsi
), m_kills
);
2256 /* Initialize internal data needed during renaming. */
2259 init_ssa_renamer (void)
2261 cfun
->gimple_df
->in_ssa_p
= false;
2263 /* Allocate memory for the DEF_BLOCKS hash table. */
2264 gcc_assert (!var_infos
.is_created ());
2265 var_infos
.create (vec_safe_length (cfun
->local_decls
));
2267 bitmap_obstack_initialize (&update_ssa_obstack
);
2271 /* Deallocate internal data structures used by the renamer. */
2274 fini_ssa_renamer (void)
2276 if (var_infos
.is_created ())
2277 var_infos
.dispose ();
2279 bitmap_obstack_release (&update_ssa_obstack
);
2281 cfun
->gimple_df
->ssa_renaming_needed
= 0;
2282 cfun
->gimple_df
->rename_vops
= 0;
2283 cfun
->gimple_df
->in_ssa_p
= true;
2286 /* Main entry point into the SSA builder. The renaming process
2287 proceeds in four main phases:
2289 1- Compute dominance frontier and immediate dominators, needed to
2290 insert PHI nodes and rename the function in dominator tree
2293 2- Find and mark all the blocks that define variables.
2295 3- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
2297 4- Rename all the blocks (rewrite_blocks) and statements in the program.
2299 Steps 3 and 4 are done using the dominator tree walker
2300 (walk_dominator_tree). */
2303 rewrite_into_ssa (void)
2309 /* Initialize operand data structures. */
2310 init_ssa_operands (cfun
);
2312 /* Initialize internal data needed by the renamer. */
2313 init_ssa_renamer ();
2315 /* Initialize the set of interesting blocks. The callback
2316 mark_def_sites will add to this set those blocks that the renamer
2318 interesting_blocks
= sbitmap_alloc (last_basic_block
);
2319 bitmap_clear (interesting_blocks
);
2321 /* Initialize dominance frontier. */
2322 dfs
= XNEWVEC (bitmap_head
, last_basic_block
);
2324 bitmap_initialize (&dfs
[bb
->index
], &bitmap_default_obstack
);
2326 /* 1- Compute dominance frontiers. */
2327 calculate_dominance_info (CDI_DOMINATORS
);
2328 compute_dominance_frontiers (dfs
);
2330 /* 2- Find and mark definition sites. */
2331 mark_def_dom_walker (CDI_DOMINATORS
).walk (cfun
->cfg
->x_entry_block_ptr
);
2333 /* 3- Insert PHI nodes at dominance frontiers of definition blocks. */
2334 insert_phi_nodes (dfs
);
2336 /* 4- Rename all the blocks. */
2337 rewrite_blocks (ENTRY_BLOCK_PTR_FOR_FN (cfun
), REWRITE_ALL
);
2339 /* Free allocated memory. */
2341 bitmap_clear (&dfs
[bb
->index
]);
2344 sbitmap_free (interesting_blocks
);
2346 fini_ssa_renamer ();
2348 /* Try to get rid of all gimplifier generated temporaries by making
2349 its SSA names anonymous. This way we can garbage collect them
2350 all after removing unused locals which we do in our TODO. */
2351 for (i
= 1; i
< num_ssa_names
; ++i
)
2353 tree decl
, name
= ssa_name (i
);
2355 || SSA_NAME_IS_DEFAULT_DEF (name
))
2357 decl
= SSA_NAME_VAR (name
);
2359 && TREE_CODE (decl
) == VAR_DECL
2360 && !VAR_DECL_IS_VIRTUAL_OPERAND (decl
)
2361 && DECL_IGNORED_P (decl
))
2362 SET_SSA_NAME_VAR_OR_IDENTIFIER (name
, DECL_NAME (decl
));
2368 /* Gate for IPCP optimization. */
2371 gate_into_ssa (void)
2373 /* Do nothing for funcions that was produced already in SSA form. */
2374 return !(cfun
->curr_properties
& PROP_ssa
);
2379 const pass_data pass_data_build_ssa
=
2381 GIMPLE_PASS
, /* type */
2383 OPTGROUP_NONE
, /* optinfo_flags */
2384 true, /* has_gate */
2385 true, /* has_execute */
2386 TV_TREE_SSA_OTHER
, /* tv_id */
2387 PROP_cfg
, /* properties_required */
2388 PROP_ssa
, /* properties_provided */
2389 0, /* properties_destroyed */
2390 0, /* todo_flags_start */
2391 ( TODO_verify_ssa
| TODO_remove_unused_locals
), /* todo_flags_finish */
2394 class pass_build_ssa
: public gimple_opt_pass
2397 pass_build_ssa (gcc::context
*ctxt
)
2398 : gimple_opt_pass (pass_data_build_ssa
, ctxt
)
2401 /* opt_pass methods: */
2402 bool gate () { return gate_into_ssa (); }
2403 unsigned int execute () { return rewrite_into_ssa (); }
2405 }; // class pass_build_ssa
2410 make_pass_build_ssa (gcc::context
*ctxt
)
2412 return new pass_build_ssa (ctxt
);
2416 /* Mark the definition of VAR at STMT and BB as interesting for the
2417 renamer. BLOCKS is the set of blocks that need updating. */
2420 mark_def_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2422 gcc_checking_assert (bitmap_bit_p (blocks_to_update
, bb
->index
));
2423 set_register_defs (stmt
, true);
2427 bool is_phi_p
= gimple_code (stmt
) == GIMPLE_PHI
;
2429 set_def_block (var
, bb
, is_phi_p
);
2431 /* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition
2432 site for both itself and all the old names replaced by it. */
2433 if (TREE_CODE (var
) == SSA_NAME
&& is_new_name (var
))
2437 bitmap set
= names_replaced_by (var
);
2439 EXECUTE_IF_SET_IN_BITMAP (set
, 0, i
, bi
)
2440 set_def_block (ssa_name (i
), bb
, is_phi_p
);
2446 /* Mark the use of VAR at STMT and BB as interesting for the
2447 renamer. INSERT_PHI_P is true if we are going to insert new PHI
2451 mark_use_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2453 basic_block def_bb
= gimple_bb (stmt
);
2455 mark_block_for_update (def_bb
);
2456 mark_block_for_update (bb
);
2458 if (gimple_code (stmt
) == GIMPLE_PHI
)
2459 mark_phi_for_rewrite (def_bb
, stmt
);
2462 set_rewrite_uses (stmt
, true);
2464 if (is_gimple_debug (stmt
))
2468 /* If VAR has not been defined in BB, then it is live-on-entry
2469 to BB. Note that we cannot just use the block holding VAR's
2470 definition because if VAR is one of the names in OLD_SSA_NAMES,
2471 it will have several definitions (itself and all the names that
2475 struct def_blocks_d
*db_p
= get_def_blocks_for (get_common_info (var
));
2476 if (!bitmap_bit_p (db_p
->def_blocks
, bb
->index
))
2477 set_livein_block (var
, bb
);
2482 /* Do a dominator walk starting at BB processing statements that
2483 reference symbols in SSA operands. This is very similar to
2484 mark_def_sites, but the scan handles statements whose operands may
2485 already be SSA names.
2487 If INSERT_PHI_P is true, mark those uses as live in the
2488 corresponding block. This is later used by the PHI placement
2489 algorithm to make PHI pruning decisions.
2491 FIXME. Most of this would be unnecessary if we could associate a
2492 symbol to all the SSA names that reference it. But that
2493 sounds like it would be expensive to maintain. Still, it
2494 would be interesting to see if it makes better sense to do
2498 prepare_block_for_update (basic_block bb
, bool insert_phi_p
)
2501 gimple_stmt_iterator si
;
2505 mark_block_for_update (bb
);
2507 /* Process PHI nodes marking interesting those that define or use
2508 the symbols that we are interested in. */
2509 for (si
= gsi_start_phis (bb
); !gsi_end_p (si
); gsi_next (&si
))
2511 gimple phi
= gsi_stmt (si
);
2512 tree lhs_sym
, lhs
= gimple_phi_result (phi
);
2514 if (TREE_CODE (lhs
) == SSA_NAME
2515 && (! virtual_operand_p (lhs
)
2516 || ! cfun
->gimple_df
->rename_vops
))
2519 lhs_sym
= DECL_P (lhs
) ? lhs
: SSA_NAME_VAR (lhs
);
2520 mark_for_renaming (lhs_sym
);
2521 mark_def_interesting (lhs_sym
, phi
, bb
, insert_phi_p
);
2523 /* Mark the uses in phi nodes as interesting. It would be more correct
2524 to process the arguments of the phi nodes of the successor edges of
2525 BB at the end of prepare_block_for_update, however, that turns out
2526 to be significantly more expensive. Doing it here is conservatively
2527 correct -- it may only cause us to believe a value to be live in a
2528 block that also contains its definition, and thus insert a few more
2529 phi nodes for it. */
2530 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
2531 mark_use_interesting (lhs_sym
, phi
, e
->src
, insert_phi_p
);
2534 /* Process the statements. */
2535 for (si
= gsi_start_bb (bb
); !gsi_end_p (si
); gsi_next (&si
))
2539 use_operand_p use_p
;
2540 def_operand_p def_p
;
2542 stmt
= gsi_stmt (si
);
2544 if (cfun
->gimple_df
->rename_vops
2545 && gimple_vuse (stmt
))
2547 tree use
= gimple_vuse (stmt
);
2548 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
2549 mark_for_renaming (sym
);
2550 mark_use_interesting (sym
, stmt
, bb
, insert_phi_p
);
2553 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, i
, SSA_OP_USE
)
2555 tree use
= USE_FROM_PTR (use_p
);
2558 mark_for_renaming (use
);
2559 mark_use_interesting (use
, stmt
, bb
, insert_phi_p
);
2562 if (cfun
->gimple_df
->rename_vops
2563 && gimple_vdef (stmt
))
2565 tree def
= gimple_vdef (stmt
);
2566 tree sym
= DECL_P (def
) ? def
: SSA_NAME_VAR (def
);
2567 mark_for_renaming (sym
);
2568 mark_def_interesting (sym
, stmt
, bb
, insert_phi_p
);
2571 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, i
, SSA_OP_DEF
)
2573 tree def
= DEF_FROM_PTR (def_p
);
2576 mark_for_renaming (def
);
2577 mark_def_interesting (def
, stmt
, bb
, insert_phi_p
);
2581 /* Now visit all the blocks dominated by BB. */
2582 for (son
= first_dom_son (CDI_DOMINATORS
, bb
);
2584 son
= next_dom_son (CDI_DOMINATORS
, son
))
2585 prepare_block_for_update (son
, insert_phi_p
);
2589 /* Helper for prepare_names_to_update. Mark all the use sites for
2590 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2591 prepare_names_to_update. */
2594 prepare_use_sites_for (tree name
, bool insert_phi_p
)
2596 use_operand_p use_p
;
2597 imm_use_iterator iter
;
2599 FOR_EACH_IMM_USE_FAST (use_p
, iter
, name
)
2601 gimple stmt
= USE_STMT (use_p
);
2602 basic_block bb
= gimple_bb (stmt
);
2604 if (gimple_code (stmt
) == GIMPLE_PHI
)
2606 int ix
= PHI_ARG_INDEX_FROM_USE (use_p
);
2607 edge e
= gimple_phi_arg_edge (stmt
, ix
);
2608 mark_use_interesting (name
, stmt
, e
->src
, insert_phi_p
);
2612 /* For regular statements, mark this as an interesting use
2614 mark_use_interesting (name
, stmt
, bb
, insert_phi_p
);
2620 /* Helper for prepare_names_to_update. Mark the definition site for
2621 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2622 prepare_names_to_update. */
2625 prepare_def_site_for (tree name
, bool insert_phi_p
)
2630 gcc_checking_assert (names_to_release
== NULL
2631 || !bitmap_bit_p (names_to_release
,
2632 SSA_NAME_VERSION (name
)));
2634 stmt
= SSA_NAME_DEF_STMT (name
);
2635 bb
= gimple_bb (stmt
);
2638 gcc_checking_assert (bb
->index
< last_basic_block
);
2639 mark_block_for_update (bb
);
2640 mark_def_interesting (name
, stmt
, bb
, insert_phi_p
);
2645 /* Mark definition and use sites of names in NEW_SSA_NAMES and
2646 OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert
2647 PHI nodes for newly created names. */
2650 prepare_names_to_update (bool insert_phi_p
)
2654 sbitmap_iterator sbi
;
2656 /* If a name N from NEW_SSA_NAMES is also marked to be released,
2657 remove it from NEW_SSA_NAMES so that we don't try to visit its
2658 defining basic block (which most likely doesn't exist). Notice
2659 that we cannot do the same with names in OLD_SSA_NAMES because we
2660 want to replace existing instances. */
2661 if (names_to_release
)
2662 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2663 bitmap_clear_bit (new_ssa_names
, i
);
2665 /* First process names in NEW_SSA_NAMES. Otherwise, uses of old
2666 names may be considered to be live-in on blocks that contain
2667 definitions for their replacements. */
2668 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names
, 0, i
, sbi
)
2669 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2671 /* If an old name is in NAMES_TO_RELEASE, we cannot remove it from
2672 OLD_SSA_NAMES, but we have to ignore its definition site. */
2673 EXECUTE_IF_SET_IN_BITMAP (old_ssa_names
, 0, i
, sbi
)
2675 if (names_to_release
== NULL
|| !bitmap_bit_p (names_to_release
, i
))
2676 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2677 prepare_use_sites_for (ssa_name (i
), insert_phi_p
);
2682 /* Dump all the names replaced by NAME to FILE. */
2685 dump_names_replaced_by (FILE *file
, tree name
)
2691 print_generic_expr (file
, name
, 0);
2692 fprintf (file
, " -> { ");
2694 old_set
= names_replaced_by (name
);
2695 EXECUTE_IF_SET_IN_BITMAP (old_set
, 0, i
, bi
)
2697 print_generic_expr (file
, ssa_name (i
), 0);
2698 fprintf (file
, " ");
2701 fprintf (file
, "}\n");
2705 /* Dump all the names replaced by NAME to stderr. */
2708 debug_names_replaced_by (tree name
)
2710 dump_names_replaced_by (stderr
, name
);
2714 /* Dump SSA update information to FILE. */
2717 dump_update_ssa (FILE *file
)
2722 if (!need_ssa_update_p (cfun
))
2725 if (new_ssa_names
&& bitmap_first_set_bit (new_ssa_names
) >= 0)
2727 sbitmap_iterator sbi
;
2729 fprintf (file
, "\nSSA replacement table\n");
2730 fprintf (file
, "N_i -> { O_1 ... O_j } means that N_i replaces "
2731 "O_1, ..., O_j\n\n");
2733 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names
, 0, i
, sbi
)
2734 dump_names_replaced_by (file
, ssa_name (i
));
2737 if (symbols_to_rename_set
&& !bitmap_empty_p (symbols_to_rename_set
))
2739 fprintf (file
, "\nSymbols to be put in SSA form\n");
2740 dump_decl_set (file
, symbols_to_rename_set
);
2741 fprintf (file
, "\n");
2744 if (names_to_release
&& !bitmap_empty_p (names_to_release
))
2746 fprintf (file
, "\nSSA names to release after updating the SSA web\n\n");
2747 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2749 print_generic_expr (file
, ssa_name (i
), 0);
2750 fprintf (file
, " ");
2752 fprintf (file
, "\n");
2757 /* Dump SSA update information to stderr. */
2760 debug_update_ssa (void)
2762 dump_update_ssa (stderr
);
2766 /* Initialize data structures used for incremental SSA updates. */
2769 init_update_ssa (struct function
*fn
)
2771 /* Reserve more space than the current number of names. The calls to
2772 add_new_name_mapping are typically done after creating new SSA
2773 names, so we'll need to reallocate these arrays. */
2774 old_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2775 bitmap_clear (old_ssa_names
);
2777 new_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2778 bitmap_clear (new_ssa_names
);
2780 bitmap_obstack_initialize (&update_ssa_obstack
);
2782 names_to_release
= NULL
;
2783 update_ssa_initialized_fn
= fn
;
2787 /* Deallocate data structures used for incremental SSA updates. */
2790 delete_update_ssa (void)
2795 sbitmap_free (old_ssa_names
);
2796 old_ssa_names
= NULL
;
2798 sbitmap_free (new_ssa_names
);
2799 new_ssa_names
= NULL
;
2801 BITMAP_FREE (symbols_to_rename_set
);
2802 symbols_to_rename_set
= NULL
;
2803 symbols_to_rename
.release ();
2805 if (names_to_release
)
2807 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2808 release_ssa_name (ssa_name (i
));
2809 BITMAP_FREE (names_to_release
);
2812 clear_ssa_name_info ();
2814 fini_ssa_renamer ();
2816 if (blocks_with_phis_to_rewrite
)
2817 EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite
, 0, i
, bi
)
2819 gimple_vec phis
= phis_to_rewrite
[i
];
2821 phis_to_rewrite
[i
].create (0);
2824 BITMAP_FREE (blocks_with_phis_to_rewrite
);
2825 BITMAP_FREE (blocks_to_update
);
2827 update_ssa_initialized_fn
= NULL
;
2831 /* Create a new name for OLD_NAME in statement STMT and replace the
2832 operand pointed to by DEF_P with the newly created name. If DEF_P
2833 is NULL then STMT should be a GIMPLE assignment.
2834 Return the new name and register the replacement mapping <NEW, OLD> in
2835 update_ssa's tables. */
2838 create_new_def_for (tree old_name
, gimple stmt
, def_operand_p def
)
2842 timevar_push (TV_TREE_SSA_INCREMENTAL
);
2844 if (!update_ssa_initialized_fn
)
2845 init_update_ssa (cfun
);
2847 gcc_assert (update_ssa_initialized_fn
== cfun
);
2849 new_name
= duplicate_ssa_name (old_name
, stmt
);
2851 SET_DEF (def
, new_name
);
2853 gimple_assign_set_lhs (stmt
, new_name
);
2855 if (gimple_code (stmt
) == GIMPLE_PHI
)
2857 basic_block bb
= gimple_bb (stmt
);
2859 /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
2860 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name
) = bb_has_abnormal_pred (bb
);
2863 add_new_name_mapping (new_name
, old_name
);
2865 /* For the benefit of passes that will be updating the SSA form on
2866 their own, set the current reaching definition of OLD_NAME to be
2868 get_ssa_name_ann (old_name
)->info
.current_def
= new_name
;
2870 timevar_pop (TV_TREE_SSA_INCREMENTAL
);
2876 /* Mark virtual operands of FN for renaming by update_ssa. */
2879 mark_virtual_operands_for_renaming (struct function
*fn
)
2881 fn
->gimple_df
->ssa_renaming_needed
= 1;
2882 fn
->gimple_df
->rename_vops
= 1;
2885 /* Replace all uses of NAME by underlying variable and mark it
2886 for renaming. This assumes the defining statement of NAME is
2887 going to be removed. */
2890 mark_virtual_operand_for_renaming (tree name
)
2892 tree name_var
= SSA_NAME_VAR (name
);
2894 imm_use_iterator iter
;
2895 use_operand_p use_p
;
2898 gcc_assert (VAR_DECL_IS_VIRTUAL_OPERAND (name_var
));
2899 FOR_EACH_IMM_USE_STMT (stmt
, iter
, name
)
2901 FOR_EACH_IMM_USE_ON_STMT (use_p
, iter
)
2902 SET_USE (use_p
, name_var
);
2906 mark_virtual_operands_for_renaming (cfun
);
2909 /* Replace all uses of the virtual PHI result by its underlying variable
2910 and mark it for renaming. This assumes the PHI node is going to be
2914 mark_virtual_phi_result_for_renaming (gimple phi
)
2916 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2918 fprintf (dump_file
, "Marking result for renaming : ");
2919 print_gimple_stmt (dump_file
, phi
, 0, TDF_SLIM
);
2920 fprintf (dump_file
, "\n");
2923 mark_virtual_operand_for_renaming (gimple_phi_result (phi
));
2926 /* Return true if there is any work to be done by update_ssa
2930 need_ssa_update_p (struct function
*fn
)
2932 gcc_assert (fn
!= NULL
);
2933 return (update_ssa_initialized_fn
== fn
2934 || (fn
->gimple_df
&& fn
->gimple_df
->ssa_renaming_needed
));
2937 /* Return true if name N has been registered in the replacement table. */
2940 name_registered_for_update_p (tree n ATTRIBUTE_UNUSED
)
2942 if (!update_ssa_initialized_fn
)
2945 gcc_assert (update_ssa_initialized_fn
== cfun
);
2947 return is_new_name (n
) || is_old_name (n
);
2951 /* Mark NAME to be released after update_ssa has finished. */
2954 release_ssa_name_after_update_ssa (tree name
)
2956 gcc_assert (cfun
&& update_ssa_initialized_fn
== cfun
);
2958 if (names_to_release
== NULL
)
2959 names_to_release
= BITMAP_ALLOC (NULL
);
2961 bitmap_set_bit (names_to_release
, SSA_NAME_VERSION (name
));
2965 /* Insert new PHI nodes to replace VAR. DFS contains dominance
2966 frontier information. BLOCKS is the set of blocks to be updated.
2968 This is slightly different than the regular PHI insertion
2969 algorithm. The value of UPDATE_FLAGS controls how PHI nodes for
2970 real names (i.e., GIMPLE registers) are inserted:
2972 - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI
2973 nodes inside the region affected by the block that defines VAR
2974 and the blocks that define all its replacements. All these
2975 definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS.
2977 First, we compute the entry point to the region (ENTRY). This is
2978 given by the nearest common dominator to all the definition
2979 blocks. When computing the iterated dominance frontier (IDF), any
2980 block not strictly dominated by ENTRY is ignored.
2982 We then call the standard PHI insertion algorithm with the pruned
2985 - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real
2986 names is not pruned. PHI nodes are inserted at every IDF block. */
2989 insert_updated_phi_nodes_for (tree var
, bitmap_head
*dfs
, bitmap blocks
,
2990 unsigned update_flags
)
2993 struct def_blocks_d
*db
;
2994 bitmap idf
, pruned_idf
;
2998 if (TREE_CODE (var
) == SSA_NAME
)
2999 gcc_checking_assert (is_old_name (var
));
3001 gcc_checking_assert (marked_for_renaming (var
));
3003 /* Get all the definition sites for VAR. */
3004 db
= find_def_blocks_for (var
);
3006 /* No need to do anything if there were no definitions to VAR. */
3007 if (db
== NULL
|| bitmap_empty_p (db
->def_blocks
))
3010 /* Compute the initial iterated dominance frontier. */
3011 idf
= compute_idf (db
->def_blocks
, dfs
);
3012 pruned_idf
= BITMAP_ALLOC (NULL
);
3014 if (TREE_CODE (var
) == SSA_NAME
)
3016 if (update_flags
== TODO_update_ssa
)
3018 /* If doing regular SSA updates for GIMPLE registers, we are
3019 only interested in IDF blocks dominated by the nearest
3020 common dominator of all the definition blocks. */
3021 entry
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3023 if (entry
!= ENTRY_BLOCK_PTR_FOR_FN (cfun
))
3024 EXECUTE_IF_SET_IN_BITMAP (idf
, 0, i
, bi
)
3025 if (BASIC_BLOCK (i
) != entry
3026 && dominated_by_p (CDI_DOMINATORS
, BASIC_BLOCK (i
), entry
))
3027 bitmap_set_bit (pruned_idf
, i
);
3031 /* Otherwise, do not prune the IDF for VAR. */
3032 gcc_checking_assert (update_flags
== TODO_update_ssa_full_phi
);
3033 bitmap_copy (pruned_idf
, idf
);
3038 /* Otherwise, VAR is a symbol that needs to be put into SSA form
3039 for the first time, so we need to compute the full IDF for
3041 bitmap_copy (pruned_idf
, idf
);
3044 if (!bitmap_empty_p (pruned_idf
))
3046 /* Make sure that PRUNED_IDF blocks and all their feeding blocks
3047 are included in the region to be updated. The feeding blocks
3048 are important to guarantee that the PHI arguments are renamed
3051 /* FIXME, this is not needed if we are updating symbols. We are
3052 already starting at the ENTRY block anyway. */
3053 bitmap_ior_into (blocks
, pruned_idf
);
3054 EXECUTE_IF_SET_IN_BITMAP (pruned_idf
, 0, i
, bi
)
3058 basic_block bb
= BASIC_BLOCK (i
);
3060 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
3061 if (e
->src
->index
>= 0)
3062 bitmap_set_bit (blocks
, e
->src
->index
);
3065 insert_phi_nodes_for (var
, pruned_idf
, true);
3068 BITMAP_FREE (pruned_idf
);
3072 /* Sort symbols_to_rename after their DECL_UID. */
3075 insert_updated_phi_nodes_compare_uids (const void *a
, const void *b
)
3077 const_tree syma
= *(const const_tree
*)a
;
3078 const_tree symb
= *(const const_tree
*)b
;
3079 if (DECL_UID (syma
) == DECL_UID (symb
))
3081 return DECL_UID (syma
) < DECL_UID (symb
) ? -1 : 1;
3084 /* Given a set of newly created SSA names (NEW_SSA_NAMES) and a set of
3085 existing SSA names (OLD_SSA_NAMES), update the SSA form so that:
3087 1- The names in OLD_SSA_NAMES dominated by the definitions of
3088 NEW_SSA_NAMES are all re-written to be reached by the
3089 appropriate definition from NEW_SSA_NAMES.
3091 2- If needed, new PHI nodes are added to the iterated dominance
3092 frontier of the blocks where each of NEW_SSA_NAMES are defined.
3094 The mapping between OLD_SSA_NAMES and NEW_SSA_NAMES is setup by
3095 calling create_new_def_for to create new defs for names that the
3096 caller wants to replace.
3098 The caller cretaes the new names to be inserted and the names that need
3099 to be replaced by calling create_new_def_for for each old definition
3100 to be replaced. Note that the function assumes that the
3101 new defining statement has already been inserted in the IL.
3103 For instance, given the following code:
3106 2 x_1 = PHI (0, x_5)
3117 Suppose that we insert new names x_10 and x_11 (lines 4 and 8).
3120 2 x_1 = PHI (0, x_5)
3133 We want to replace all the uses of x_1 with the new definitions of
3134 x_10 and x_11. Note that the only uses that should be replaced are
3135 those at lines 5, 9 and 11. Also, the use of x_7 at line 9 should
3136 *not* be replaced (this is why we cannot just mark symbol 'x' for
3139 Additionally, we may need to insert a PHI node at line 11 because
3140 that is a merge point for x_10 and x_11. So the use of x_1 at line
3141 11 will be replaced with the new PHI node. The insertion of PHI
3142 nodes is optional. They are not strictly necessary to preserve the
3143 SSA form, and depending on what the caller inserted, they may not
3144 even be useful for the optimizers. UPDATE_FLAGS controls various
3145 aspects of how update_ssa operates, see the documentation for
3146 TODO_update_ssa*. */
3149 update_ssa (unsigned update_flags
)
3151 basic_block bb
, start_bb
;
3155 sbitmap_iterator sbi
;
3158 /* Only one update flag should be set. */
3159 gcc_assert (update_flags
== TODO_update_ssa
3160 || update_flags
== TODO_update_ssa_no_phi
3161 || update_flags
== TODO_update_ssa_full_phi
3162 || update_flags
== TODO_update_ssa_only_virtuals
);
3164 if (!need_ssa_update_p (cfun
))
3167 timevar_push (TV_TREE_SSA_INCREMENTAL
);
3169 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3170 fprintf (dump_file
, "\nUpdating SSA:\n");
3172 if (!update_ssa_initialized_fn
)
3173 init_update_ssa (cfun
);
3174 else if (update_flags
== TODO_update_ssa_only_virtuals
)
3176 /* If we only need to update virtuals, remove all the mappings for
3177 real names before proceeding. The caller is responsible for
3178 having dealt with the name mappings before calling update_ssa. */
3179 bitmap_clear (old_ssa_names
);
3180 bitmap_clear (new_ssa_names
);
3183 gcc_assert (update_ssa_initialized_fn
== cfun
);
3185 blocks_with_phis_to_rewrite
= BITMAP_ALLOC (NULL
);
3186 if (!phis_to_rewrite
.exists ())
3187 phis_to_rewrite
.create (last_basic_block
+ 1);
3188 blocks_to_update
= BITMAP_ALLOC (NULL
);
3190 /* Ensure that the dominance information is up-to-date. */
3191 calculate_dominance_info (CDI_DOMINATORS
);
3193 insert_phi_p
= (update_flags
!= TODO_update_ssa_no_phi
);
3195 /* If there are names defined in the replacement table, prepare
3196 definition and use sites for all the names in NEW_SSA_NAMES and
3198 if (bitmap_first_set_bit (new_ssa_names
) >= 0)
3200 prepare_names_to_update (insert_phi_p
);
3202 /* If all the names in NEW_SSA_NAMES had been marked for
3203 removal, and there are no symbols to rename, then there's
3204 nothing else to do. */
3205 if (bitmap_first_set_bit (new_ssa_names
) < 0
3206 && !cfun
->gimple_df
->ssa_renaming_needed
)
3210 /* Next, determine the block at which to start the renaming process. */
3211 if (cfun
->gimple_df
->ssa_renaming_needed
)
3213 /* If we rename bare symbols initialize the mapping to
3214 auxiliar info we need to keep track of. */
3215 var_infos
.create (47);
3217 /* If we have to rename some symbols from scratch, we need to
3218 start the process at the root of the CFG. FIXME, it should
3219 be possible to determine the nearest block that had a
3220 definition for each of the symbols that are marked for
3221 updating. For now this seems more work than it's worth. */
3222 start_bb
= ENTRY_BLOCK_PTR_FOR_FN (cfun
);
3224 /* Traverse the CFG looking for existing definitions and uses of
3225 symbols in SSA operands. Mark interesting blocks and
3226 statements and set local live-in information for the PHI
3227 placement heuristics. */
3228 prepare_block_for_update (start_bb
, insert_phi_p
);
3230 #ifdef ENABLE_CHECKING
3231 for (i
= 1; i
< num_ssa_names
; ++i
)
3233 tree name
= ssa_name (i
);
3235 || virtual_operand_p (name
))
3238 /* For all but virtual operands, which do not have SSA names
3239 with overlapping life ranges, ensure that symbols marked
3240 for renaming do not have existing SSA names associated with
3241 them as we do not re-write them out-of-SSA before going
3242 into SSA for the remaining symbol uses. */
3243 if (marked_for_renaming (SSA_NAME_VAR (name
)))
3245 fprintf (stderr
, "Existing SSA name for symbol marked for "
3247 print_generic_expr (stderr
, name
, TDF_SLIM
);
3248 fprintf (stderr
, "\n");
3249 internal_error ("SSA corruption");
3256 /* Otherwise, the entry block to the region is the nearest
3257 common dominator for the blocks in BLOCKS. */
3258 start_bb
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3262 /* If requested, insert PHI nodes at the iterated dominance frontier
3263 of every block, creating new definitions for names in OLD_SSA_NAMES
3264 and for symbols found. */
3269 /* If the caller requested PHI nodes to be added, compute
3270 dominance frontiers. */
3271 dfs
= XNEWVEC (bitmap_head
, last_basic_block
);
3273 bitmap_initialize (&dfs
[bb
->index
], &bitmap_default_obstack
);
3274 compute_dominance_frontiers (dfs
);
3276 if (bitmap_first_set_bit (old_ssa_names
) >= 0)
3278 sbitmap_iterator sbi
;
3280 /* insert_update_phi_nodes_for will call add_new_name_mapping
3281 when inserting new PHI nodes, so the set OLD_SSA_NAMES
3282 will grow while we are traversing it (but it will not
3283 gain any new members). Copy OLD_SSA_NAMES to a temporary
3285 sbitmap tmp
= sbitmap_alloc (SBITMAP_SIZE (old_ssa_names
));
3286 bitmap_copy (tmp
, old_ssa_names
);
3287 EXECUTE_IF_SET_IN_BITMAP (tmp
, 0, i
, sbi
)
3288 insert_updated_phi_nodes_for (ssa_name (i
), dfs
, blocks_to_update
,
3293 symbols_to_rename
.qsort (insert_updated_phi_nodes_compare_uids
);
3294 FOR_EACH_VEC_ELT (symbols_to_rename
, i
, sym
)
3295 insert_updated_phi_nodes_for (sym
, dfs
, blocks_to_update
,
3299 bitmap_clear (&dfs
[bb
->index
]);
3302 /* Insertion of PHI nodes may have added blocks to the region.
3303 We need to re-compute START_BB to include the newly added
3305 if (start_bb
!= ENTRY_BLOCK_PTR_FOR_FN (cfun
))
3306 start_bb
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3310 /* Reset the current definition for name and symbol before renaming
3312 EXECUTE_IF_SET_IN_BITMAP (old_ssa_names
, 0, i
, sbi
)
3313 get_ssa_name_ann (ssa_name (i
))->info
.current_def
= NULL_TREE
;
3315 FOR_EACH_VEC_ELT (symbols_to_rename
, i
, sym
)
3316 get_var_info (sym
)->info
.current_def
= NULL_TREE
;
3318 /* Now start the renaming process at START_BB. */
3319 interesting_blocks
= sbitmap_alloc (last_basic_block
);
3320 bitmap_clear (interesting_blocks
);
3321 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3322 bitmap_set_bit (interesting_blocks
, i
);
3324 rewrite_blocks (start_bb
, REWRITE_UPDATE
);
3326 sbitmap_free (interesting_blocks
);
3328 /* Debugging dumps. */
3334 dump_update_ssa (dump_file
);
3336 fprintf (dump_file
, "Incremental SSA update started at block: %d\n",
3340 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3342 fprintf (dump_file
, "Number of blocks in CFG: %d\n", last_basic_block
);
3343 fprintf (dump_file
, "Number of blocks to update: %d (%3.0f%%)\n",
3344 c
, PERCENT (c
, last_basic_block
));
3346 if (dump_flags
& TDF_DETAILS
)
3348 fprintf (dump_file
, "Affected blocks:");
3349 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3350 fprintf (dump_file
, " %u", i
);
3351 fprintf (dump_file
, "\n");
3354 fprintf (dump_file
, "\n\n");
3357 /* Free allocated memory. */
3359 delete_update_ssa ();
3361 timevar_pop (TV_TREE_SSA_INCREMENTAL
);