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
)
768 unsigned i
, b
, p
, u
, top
;
770 basic_block def_bb
, use_bb
;
774 struct dom_dfsnum
*defs
;
775 unsigned n_defs
, adef
;
777 if (bitmap_empty_p (uses
))
783 /* The phi must dominate a use, or an argument of a live phi. Also, we
784 do not create any phi nodes in def blocks, unless they are also livein. */
785 to_remove
= BITMAP_ALLOC (NULL
);
786 bitmap_and_compl (to_remove
, kills
, uses
);
787 bitmap_and_compl_into (phis
, to_remove
);
788 if (bitmap_empty_p (phis
))
790 BITMAP_FREE (to_remove
);
794 /* We want to remove the unnecessary phi nodes, but we do not want to compute
795 liveness information, as that may be linear in the size of CFG, and if
796 there are lot of different variables to rewrite, this may lead to quadratic
799 Instead, we basically emulate standard dce. We put all uses to worklist,
800 then for each of them find the nearest def that dominates them. If this
801 def is a phi node, we mark it live, and if it was not live before, we
802 add the predecessors of its basic block to the worklist.
804 To quickly locate the nearest def that dominates use, we use dfs numbering
805 of the dominance tree (that is already available in order to speed up
806 queries). For each def, we have the interval given by the dfs number on
807 entry to and on exit from the corresponding subtree in the dominance tree.
808 The nearest dominator for a given use is the smallest of these intervals
809 that contains entry and exit dfs numbers for the basic block with the use.
810 If we store the bounds for all the uses to an array and sort it, we can
811 locate the nearest dominating def in logarithmic time by binary search.*/
812 bitmap_ior (to_remove
, kills
, phis
);
813 n_defs
= bitmap_count_bits (to_remove
);
814 defs
= XNEWVEC (struct dom_dfsnum
, 2 * n_defs
+ 1);
815 defs
[0].bb_index
= 1;
818 EXECUTE_IF_SET_IN_BITMAP (to_remove
, 0, i
, bi
)
820 def_bb
= BASIC_BLOCK (i
);
821 defs
[adef
].bb_index
= i
;
822 defs
[adef
].dfs_num
= bb_dom_dfs_in (CDI_DOMINATORS
, def_bb
);
823 defs
[adef
+ 1].bb_index
= i
;
824 defs
[adef
+ 1].dfs_num
= bb_dom_dfs_out (CDI_DOMINATORS
, def_bb
);
827 BITMAP_FREE (to_remove
);
828 gcc_assert (adef
== 2 * n_defs
+ 1);
829 qsort (defs
, adef
, sizeof (struct dom_dfsnum
), cmp_dfsnum
);
830 gcc_assert (defs
[0].bb_index
== 1);
832 /* Now each DEFS entry contains the number of the basic block to that the
833 dfs number corresponds. Change them to the number of basic block that
834 corresponds to the interval following the dfs number. Also, for the
835 dfs_out numbers, increase the dfs number by one (so that it corresponds
836 to the start of the following interval, not to the end of the current
837 one). We use WORKLIST as a stack. */
838 auto_vec
<int> worklist (n_defs
+ 1);
839 worklist
.quick_push (1);
842 for (i
= 1; i
< adef
; i
++)
844 b
= defs
[i
].bb_index
;
847 /* This is a closing element. Interval corresponding to the top
848 of the stack after removing it follows. */
850 top
= worklist
[worklist
.length () - 1];
851 defs
[n_defs
].bb_index
= top
;
852 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
+ 1;
856 /* Opening element. Nothing to do, just push it to the stack and move
857 it to the correct position. */
858 defs
[n_defs
].bb_index
= defs
[i
].bb_index
;
859 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
;
860 worklist
.quick_push (b
);
864 /* If this interval starts at the same point as the previous one, cancel
866 if (defs
[n_defs
].dfs_num
== defs
[n_defs
- 1].dfs_num
)
867 defs
[n_defs
- 1].bb_index
= defs
[n_defs
].bb_index
;
872 gcc_assert (worklist
.is_empty ());
874 /* Now process the uses. */
875 live_phis
= BITMAP_ALLOC (NULL
);
876 EXECUTE_IF_SET_IN_BITMAP (uses
, 0, i
, bi
)
878 worklist
.safe_push (i
);
881 while (!worklist
.is_empty ())
884 if (b
== ENTRY_BLOCK
)
887 /* If there is a phi node in USE_BB, it is made live. Otherwise,
888 find the def that dominates the immediate dominator of USE_BB
889 (the kill in USE_BB does not dominate the use). */
890 if (bitmap_bit_p (phis
, b
))
894 use_bb
= get_immediate_dominator (CDI_DOMINATORS
, BASIC_BLOCK (b
));
895 p
= find_dfsnum_interval (defs
, n_defs
,
896 bb_dom_dfs_in (CDI_DOMINATORS
, use_bb
));
897 if (!bitmap_bit_p (phis
, p
))
901 /* If the phi node is already live, there is nothing to do. */
902 if (!bitmap_set_bit (live_phis
, p
))
905 /* Add the new uses to the worklist. */
906 def_bb
= BASIC_BLOCK (p
);
907 FOR_EACH_EDGE (e
, ei
, def_bb
->preds
)
910 if (bitmap_bit_p (uses
, u
))
913 /* In case there is a kill directly in the use block, do not record
914 the use (this is also necessary for correctness, as we assume that
915 uses dominated by a def directly in their block have been filtered
917 if (bitmap_bit_p (kills
, u
))
920 bitmap_set_bit (uses
, u
);
921 worklist
.safe_push (u
);
925 bitmap_copy (phis
, live_phis
);
926 BITMAP_FREE (live_phis
);
930 /* Return the set of blocks where variable VAR is defined and the blocks
931 where VAR is live on entry (livein). Return NULL, if no entry is
932 found in DEF_BLOCKS. */
934 static inline struct def_blocks_d
*
935 find_def_blocks_for (tree var
)
937 def_blocks_p p
= &get_common_info (var
)->def_blocks
;
944 /* Marks phi node PHI in basic block BB for rewrite. */
947 mark_phi_for_rewrite (basic_block bb
, gimple phi
)
950 unsigned n
, idx
= bb
->index
;
952 if (rewrite_uses_p (phi
))
955 set_rewrite_uses (phi
, true);
957 if (!blocks_with_phis_to_rewrite
)
960 bitmap_set_bit (blocks_with_phis_to_rewrite
, idx
);
962 n
= (unsigned) last_basic_block
+ 1;
963 if (phis_to_rewrite
.length () < n
)
964 phis_to_rewrite
.safe_grow_cleared (n
);
966 phis
= phis_to_rewrite
[idx
];
969 phis
.safe_push (phi
);
970 phis_to_rewrite
[idx
] = phis
;
973 /* Insert PHI nodes for variable VAR using the iterated dominance
974 frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
975 function assumes that the caller is incrementally updating the
976 existing SSA form, in which case VAR may be an SSA name instead of
979 PHI_INSERTION_POINTS is updated to reflect nodes that already had a
980 PHI node for VAR. On exit, only the nodes that received a PHI node
981 for VAR will be present in PHI_INSERTION_POINTS. */
984 insert_phi_nodes_for (tree var
, bitmap phi_insertion_points
, bool update_p
)
991 struct def_blocks_d
*def_map
= find_def_blocks_for (var
);
993 /* Remove the blocks where we already have PHI nodes for VAR. */
994 bitmap_and_compl_into (phi_insertion_points
, def_map
->phi_blocks
);
996 /* Remove obviously useless phi nodes. */
997 prune_unused_phi_nodes (phi_insertion_points
, def_map
->def_blocks
,
998 def_map
->livein_blocks
);
1000 /* And insert the PHI nodes. */
1001 EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points
, 0, bb_index
, bi
)
1003 bb
= BASIC_BLOCK (bb_index
);
1005 mark_block_for_update (bb
);
1007 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1009 fprintf (dump_file
, "creating PHI node in block #%d for ", bb_index
);
1010 print_generic_expr (dump_file
, var
, TDF_SLIM
);
1011 fprintf (dump_file
, "\n");
1015 if (TREE_CODE (var
) == SSA_NAME
)
1017 /* If we are rewriting SSA names, create the LHS of the PHI
1018 node by duplicating VAR. This is useful in the case of
1019 pointers, to also duplicate pointer attributes (alias
1020 information, in particular). */
1024 gcc_checking_assert (update_p
);
1025 new_lhs
= duplicate_ssa_name (var
, NULL
);
1026 phi
= create_phi_node (new_lhs
, bb
);
1027 add_new_name_mapping (new_lhs
, var
);
1029 /* Add VAR to every argument slot of PHI. We need VAR in
1030 every argument so that rewrite_update_phi_arguments knows
1031 which name is this PHI node replacing. If VAR is a
1032 symbol marked for renaming, this is not necessary, the
1033 renamer will use the symbol on the LHS to get its
1034 reaching definition. */
1035 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1036 add_phi_arg (phi
, var
, e
, UNKNOWN_LOCATION
);
1042 gcc_checking_assert (DECL_P (var
));
1043 phi
= create_phi_node (var
, bb
);
1045 tracked_var
= target_for_debug_bind (var
);
1048 gimple note
= gimple_build_debug_bind (tracked_var
,
1051 gimple_stmt_iterator si
= gsi_after_labels (bb
);
1052 gsi_insert_before (&si
, note
, GSI_SAME_STMT
);
1056 /* Mark this PHI node as interesting for update_ssa. */
1057 set_register_defs (phi
, true);
1058 mark_phi_for_rewrite (bb
, phi
);
1062 /* Sort var_infos after DECL_UID of their var. */
1065 insert_phi_nodes_compare_var_infos (const void *a
, const void *b
)
1067 const struct var_info_d
*defa
= *(struct var_info_d
* const *)a
;
1068 const struct var_info_d
*defb
= *(struct var_info_d
* const *)b
;
1069 if (DECL_UID (defa
->var
) < DECL_UID (defb
->var
))
1075 /* Insert PHI nodes at the dominance frontier of blocks with variable
1076 definitions. DFS contains the dominance frontier information for
1080 insert_phi_nodes (bitmap_head
*dfs
)
1082 hash_table
<var_info_hasher
>::iterator hi
;
1086 timevar_push (TV_TREE_INSERT_PHI_NODES
);
1088 auto_vec
<var_info_p
> vars (var_infos
.elements ());
1089 FOR_EACH_HASH_TABLE_ELEMENT (var_infos
, info
, var_info_p
, hi
)
1090 if (info
->info
.need_phi_state
!= NEED_PHI_STATE_NO
)
1091 vars
.quick_push (info
);
1093 /* Do two stages to avoid code generation differences for UID
1094 differences but no UID ordering differences. */
1095 vars
.qsort (insert_phi_nodes_compare_var_infos
);
1097 FOR_EACH_VEC_ELT (vars
, i
, info
)
1099 bitmap idf
= compute_idf (info
->info
.def_blocks
.def_blocks
, dfs
);
1100 insert_phi_nodes_for (info
->var
, idf
, false);
1104 timevar_pop (TV_TREE_INSERT_PHI_NODES
);
1108 /* Push SYM's current reaching definition into BLOCK_DEFS_STACK and
1109 register DEF (an SSA_NAME) to be a new definition for SYM. */
1112 register_new_def (tree def
, tree sym
)
1114 common_info_p info
= get_common_info (sym
);
1117 /* If this variable is set in a single basic block and all uses are
1118 dominated by the set(s) in that single basic block, then there is
1119 no reason to record anything for this variable in the block local
1120 definition stacks. Doing so just wastes time and memory.
1122 This is the same test to prune the set of variables which may
1123 need PHI nodes. So we just use that information since it's already
1124 computed and available for us to use. */
1125 if (info
->need_phi_state
== NEED_PHI_STATE_NO
)
1127 info
->current_def
= def
;
1131 currdef
= info
->current_def
;
1133 /* If SYM is not a GIMPLE register, then CURRDEF may be a name whose
1134 SSA_NAME_VAR is not necessarily SYM. In this case, also push SYM
1135 in the stack so that we know which symbol is being defined by
1136 this SSA name when we unwind the stack. */
1137 if (currdef
&& !is_gimple_reg (sym
))
1138 block_defs_stack
.safe_push (sym
);
1140 /* Push the current reaching definition into BLOCK_DEFS_STACK. This
1141 stack is later used by the dominator tree callbacks to restore
1142 the reaching definitions for all the variables defined in the
1143 block after a recursive visit to all its immediately dominated
1144 blocks. If there is no current reaching definition, then just
1145 record the underlying _DECL node. */
1146 block_defs_stack
.safe_push (currdef
? currdef
: sym
);
1148 /* Set the current reaching definition for SYM to be DEF. */
1149 info
->current_def
= def
;
1153 /* Perform a depth-first traversal of the dominator tree looking for
1154 variables to rename. BB is the block where to start searching.
1155 Renaming is a five step process:
1157 1- Every definition made by PHI nodes at the start of the blocks is
1158 registered as the current definition for the corresponding variable.
1160 2- Every statement in BB is rewritten. USE and VUSE operands are
1161 rewritten with their corresponding reaching definition. DEF and
1162 VDEF targets are registered as new definitions.
1164 3- All the PHI nodes in successor blocks of BB are visited. The
1165 argument corresponding to BB is replaced with its current reaching
1168 4- Recursively rewrite every dominator child block of BB.
1170 5- Restore (in reverse order) the current reaching definition for every
1171 new definition introduced in this block. This is done so that when
1172 we return from the recursive call, all the current reaching
1173 definitions are restored to the names that were valid in the
1174 dominator parent of BB. */
1176 /* Return the current definition for variable VAR. If none is found,
1177 create a new SSA name to act as the zeroth definition for VAR. */
1180 get_reaching_def (tree var
)
1182 common_info_p info
= get_common_info (var
);
1185 /* Lookup the current reaching definition for VAR. */
1186 currdef
= info
->current_def
;
1188 /* If there is no reaching definition for VAR, create and register a
1189 default definition for it (if needed). */
1190 if (currdef
== NULL_TREE
)
1192 tree sym
= DECL_P (var
) ? var
: SSA_NAME_VAR (var
);
1193 currdef
= get_or_create_ssa_default_def (cfun
, sym
);
1196 /* Return the current reaching definition for VAR, or the default
1197 definition, if we had to create one. */
1202 /* Helper function for rewrite_stmt. Rewrite uses in a debug stmt. */
1205 rewrite_debug_stmt_uses (gimple stmt
)
1207 use_operand_p use_p
;
1209 bool update
= false;
1211 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
1213 tree var
= USE_FROM_PTR (use_p
), def
;
1214 common_info_p info
= get_common_info (var
);
1215 gcc_checking_assert (DECL_P (var
));
1216 def
= info
->current_def
;
1219 if (TREE_CODE (var
) == PARM_DECL
1220 && single_succ_p (ENTRY_BLOCK_PTR_FOR_FN (cfun
)))
1222 gimple_stmt_iterator gsi
1224 gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun
)));
1226 /* Search a few source bind stmts at the start of first bb to
1227 see if a DEBUG_EXPR_DECL can't be reused. */
1229 !gsi_end_p (gsi
) && lim
> 0;
1230 gsi_next (&gsi
), lim
--)
1232 gimple gstmt
= gsi_stmt (gsi
);
1233 if (!gimple_debug_source_bind_p (gstmt
))
1235 if (gimple_debug_source_bind_get_value (gstmt
) == var
)
1237 def
= gimple_debug_source_bind_get_var (gstmt
);
1238 if (TREE_CODE (def
) == DEBUG_EXPR_DECL
)
1244 /* If not, add a new source bind stmt. */
1245 if (def
== NULL_TREE
)
1248 def
= make_node (DEBUG_EXPR_DECL
);
1249 def_temp
= gimple_build_debug_source_bind (def
, var
, NULL
);
1250 DECL_ARTIFICIAL (def
) = 1;
1251 TREE_TYPE (def
) = TREE_TYPE (var
);
1252 DECL_MODE (def
) = DECL_MODE (var
);
1254 gsi_after_labels (single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun
)));
1255 gsi_insert_before (&gsi
, def_temp
, GSI_SAME_STMT
);
1262 /* Check if info->current_def can be trusted. */
1263 basic_block bb
= gimple_bb (stmt
);
1265 = SSA_NAME_IS_DEFAULT_DEF (def
)
1266 ? NULL
: gimple_bb (SSA_NAME_DEF_STMT (def
));
1268 /* If definition is in current bb, it is fine. */
1271 /* If definition bb doesn't dominate the current bb,
1272 it can't be used. */
1273 else if (def_bb
&& !dominated_by_p (CDI_DOMINATORS
, bb
, def_bb
))
1275 /* If there is just one definition and dominates the current
1277 else if (info
->need_phi_state
== NEED_PHI_STATE_NO
)
1281 struct def_blocks_d
*db_p
= get_def_blocks_for (info
);
1283 /* If there are some non-debug uses in the current bb,
1285 if (bitmap_bit_p (db_p
->livein_blocks
, bb
->index
))
1287 /* Otherwise give up for now. */
1294 gimple_debug_bind_reset_value (stmt
);
1298 SET_USE (use_p
, def
);
1304 /* SSA Rewriting Step 2. Rewrite every variable used in each statement in
1305 the block with its immediate reaching definitions. Update the current
1306 definition of a variable when a new real or virtual definition is found. */
1309 rewrite_stmt (gimple_stmt_iterator
*si
)
1311 use_operand_p use_p
;
1312 def_operand_p def_p
;
1314 gimple stmt
= gsi_stmt (*si
);
1316 /* If mark_def_sites decided that we don't need to rewrite this
1317 statement, ignore it. */
1318 gcc_assert (blocks_to_update
== NULL
);
1319 if (!rewrite_uses_p (stmt
) && !register_defs_p (stmt
))
1322 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1324 fprintf (dump_file
, "Renaming statement ");
1325 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1326 fprintf (dump_file
, "\n");
1329 /* Step 1. Rewrite USES in the statement. */
1330 if (rewrite_uses_p (stmt
))
1332 if (is_gimple_debug (stmt
))
1333 rewrite_debug_stmt_uses (stmt
);
1335 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
1337 tree var
= USE_FROM_PTR (use_p
);
1338 gcc_checking_assert (DECL_P (var
));
1339 SET_USE (use_p
, get_reaching_def (var
));
1343 /* Step 2. Register the statement's DEF operands. */
1344 if (register_defs_p (stmt
))
1345 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1347 tree var
= DEF_FROM_PTR (def_p
);
1351 gcc_checking_assert (DECL_P (var
));
1353 if (gimple_clobber_p (stmt
)
1354 && is_gimple_reg (var
))
1356 /* If we rewrite a DECL into SSA form then drop its
1357 clobber stmts and replace uses with a new default def. */
1358 gcc_checking_assert (TREE_CODE (var
) == VAR_DECL
1359 && !gimple_vdef (stmt
));
1360 gsi_replace (si
, gimple_build_nop (), true);
1361 register_new_def (get_or_create_ssa_default_def (cfun
, var
), var
);
1365 name
= make_ssa_name (var
, stmt
);
1366 SET_DEF (def_p
, name
);
1367 register_new_def (DEF_FROM_PTR (def_p
), var
);
1369 tracked_var
= target_for_debug_bind (var
);
1372 gimple note
= gimple_build_debug_bind (tracked_var
, name
, stmt
);
1373 gsi_insert_after (si
, note
, GSI_SAME_STMT
);
1379 /* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for
1380 PHI nodes. For every PHI node found, add a new argument containing the
1381 current reaching definition for the variable and the edge through which
1382 that definition is reaching the PHI node. */
1385 rewrite_add_phi_arguments (basic_block bb
)
1390 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1393 gimple_stmt_iterator gsi
;
1395 for (gsi
= gsi_start_phis (e
->dest
); !gsi_end_p (gsi
);
1401 phi
= gsi_stmt (gsi
);
1402 res
= gimple_phi_result (phi
);
1403 currdef
= get_reaching_def (SSA_NAME_VAR (res
));
1404 /* Virtual operand PHI args do not need a location. */
1405 if (virtual_operand_p (res
))
1406 loc
= UNKNOWN_LOCATION
;
1408 loc
= gimple_location (SSA_NAME_DEF_STMT (currdef
));
1409 add_phi_arg (phi
, currdef
, e
, loc
);
1414 class rewrite_dom_walker
: public dom_walker
1417 rewrite_dom_walker (cdi_direction direction
) : dom_walker (direction
) {}
1419 virtual void before_dom_children (basic_block
);
1420 virtual void after_dom_children (basic_block
);
1423 /* SSA Rewriting Step 1. Initialization, create a block local stack
1424 of reaching definitions for new SSA names produced in this block
1425 (BLOCK_DEFS). Register new definitions for every PHI node in the
1429 rewrite_dom_walker::before_dom_children (basic_block bb
)
1431 gimple_stmt_iterator gsi
;
1433 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1434 fprintf (dump_file
, "\n\nRenaming block #%d\n\n", bb
->index
);
1436 /* Mark the unwind point for this block. */
1437 block_defs_stack
.safe_push (NULL_TREE
);
1439 /* Step 1. Register new definitions for every PHI node in the block.
1440 Conceptually, all the PHI nodes are executed in parallel and each PHI
1441 node introduces a new version for the associated variable. */
1442 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1444 tree result
= gimple_phi_result (gsi_stmt (gsi
));
1445 register_new_def (result
, SSA_NAME_VAR (result
));
1448 /* Step 2. Rewrite every variable used in each statement in the block
1449 with its immediate reaching definitions. Update the current definition
1450 of a variable when a new real or virtual definition is found. */
1451 if (bitmap_bit_p (interesting_blocks
, bb
->index
))
1452 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1453 rewrite_stmt (&gsi
);
1455 /* Step 3. Visit all the successor blocks of BB looking for PHI nodes.
1456 For every PHI node found, add a new argument containing the current
1457 reaching definition for the variable and the edge through which that
1458 definition is reaching the PHI node. */
1459 rewrite_add_phi_arguments (bb
);
1464 /* Called after visiting all the statements in basic block BB and all
1465 of its dominator children. Restore CURRDEFS to its original value. */
1468 rewrite_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED
)
1470 /* Restore CURRDEFS to its original state. */
1471 while (block_defs_stack
.length () > 0)
1473 tree tmp
= block_defs_stack
.pop ();
1474 tree saved_def
, var
;
1476 if (tmp
== NULL_TREE
)
1479 if (TREE_CODE (tmp
) == SSA_NAME
)
1481 /* If we recorded an SSA_NAME, then make the SSA_NAME the
1482 current definition of its underlying variable. Note that
1483 if the SSA_NAME is not for a GIMPLE register, the symbol
1484 being defined is stored in the next slot in the stack.
1485 This mechanism is needed because an SSA name for a
1486 non-register symbol may be the definition for more than
1487 one symbol (e.g., SFTs, aliased variables, etc). */
1489 var
= SSA_NAME_VAR (saved_def
);
1490 if (!is_gimple_reg (var
))
1491 var
= block_defs_stack
.pop ();
1495 /* If we recorded anything else, it must have been a _DECL
1496 node and its current reaching definition must have been
1502 get_common_info (var
)->current_def
= saved_def
;
1507 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1510 debug_decl_set (bitmap set
)
1512 dump_decl_set (stderr
, set
);
1513 fprintf (stderr
, "\n");
1517 /* Dump the renaming stack (block_defs_stack) to FILE. Traverse the
1518 stack up to a maximum of N levels. If N is -1, the whole stack is
1519 dumped. New levels are created when the dominator tree traversal
1520 used for renaming enters a new sub-tree. */
1523 dump_defs_stack (FILE *file
, int n
)
1527 fprintf (file
, "\n\nRenaming stack");
1529 fprintf (file
, " (up to %d levels)", n
);
1530 fprintf (file
, "\n\n");
1533 fprintf (file
, "Level %d (current level)\n", i
);
1534 for (j
= (int) block_defs_stack
.length () - 1; j
>= 0; j
--)
1538 name
= block_defs_stack
[j
];
1539 if (name
== NULL_TREE
)
1544 fprintf (file
, "\nLevel %d\n", i
);
1555 var
= SSA_NAME_VAR (name
);
1556 if (!is_gimple_reg (var
))
1559 var
= block_defs_stack
[j
];
1563 fprintf (file
, " Previous CURRDEF (");
1564 print_generic_expr (file
, var
, 0);
1565 fprintf (file
, ") = ");
1567 print_generic_expr (file
, name
, 0);
1569 fprintf (file
, "<NIL>");
1570 fprintf (file
, "\n");
1575 /* Dump the renaming stack (block_defs_stack) to stderr. Traverse the
1576 stack up to a maximum of N levels. If N is -1, the whole stack is
1577 dumped. New levels are created when the dominator tree traversal
1578 used for renaming enters a new sub-tree. */
1581 debug_defs_stack (int n
)
1583 dump_defs_stack (stderr
, n
);
1587 /* Dump the current reaching definition of every symbol to FILE. */
1590 dump_currdefs (FILE *file
)
1595 if (symbols_to_rename
.is_empty ())
1598 fprintf (file
, "\n\nCurrent reaching definitions\n\n");
1599 FOR_EACH_VEC_ELT (symbols_to_rename
, i
, var
)
1601 common_info_p info
= get_common_info (var
);
1602 fprintf (file
, "CURRDEF (");
1603 print_generic_expr (file
, var
, 0);
1604 fprintf (file
, ") = ");
1605 if (info
->current_def
)
1606 print_generic_expr (file
, info
->current_def
, 0);
1608 fprintf (file
, "<NIL>");
1609 fprintf (file
, "\n");
1614 /* Dump the current reaching definition of every symbol to stderr. */
1617 debug_currdefs (void)
1619 dump_currdefs (stderr
);
1623 /* Dump SSA information to FILE. */
1626 dump_tree_ssa (FILE *file
)
1628 const char *funcname
1629 = lang_hooks
.decl_printable_name (current_function_decl
, 2);
1631 fprintf (file
, "SSA renaming information for %s\n\n", funcname
);
1633 dump_var_infos (file
);
1634 dump_defs_stack (file
, -1);
1635 dump_currdefs (file
);
1636 dump_tree_ssa_stats (file
);
1640 /* Dump SSA information to stderr. */
1643 debug_tree_ssa (void)
1645 dump_tree_ssa (stderr
);
1649 /* Dump statistics for the hash table HTAB. */
1652 htab_statistics (FILE *file
, hash_table
<var_info_hasher
> htab
)
1654 fprintf (file
, "size %ld, %ld elements, %f collision/search ratio\n",
1655 (long) htab
.size (),
1656 (long) htab
.elements (),
1657 htab
.collisions ());
1661 /* Dump SSA statistics on FILE. */
1664 dump_tree_ssa_stats (FILE *file
)
1666 if (var_infos
.is_created ())
1668 fprintf (file
, "\nHash table statistics:\n");
1669 fprintf (file
, " var_infos: ");
1670 htab_statistics (file
, var_infos
);
1671 fprintf (file
, "\n");
1676 /* Dump SSA statistics on stderr. */
1679 debug_tree_ssa_stats (void)
1681 dump_tree_ssa_stats (stderr
);
1685 /* Callback for htab_traverse to dump the VAR_INFOS hash table. */
1688 debug_var_infos_r (var_info_d
**slot
, FILE *file
)
1690 struct var_info_d
*info
= *slot
;
1692 fprintf (file
, "VAR: ");
1693 print_generic_expr (file
, info
->var
, dump_flags
);
1694 bitmap_print (file
, info
->info
.def_blocks
.def_blocks
,
1695 ", DEF_BLOCKS: { ", "}");
1696 bitmap_print (file
, info
->info
.def_blocks
.livein_blocks
,
1697 ", LIVEIN_BLOCKS: { ", "}");
1698 bitmap_print (file
, info
->info
.def_blocks
.phi_blocks
,
1699 ", PHI_BLOCKS: { ", "}\n");
1705 /* Dump the VAR_INFOS hash table on FILE. */
1708 dump_var_infos (FILE *file
)
1710 fprintf (file
, "\n\nDefinition and live-in blocks:\n\n");
1711 if (var_infos
.is_created ())
1712 var_infos
.traverse
<FILE *, debug_var_infos_r
> (file
);
1716 /* Dump the VAR_INFOS hash table on stderr. */
1719 debug_var_infos (void)
1721 dump_var_infos (stderr
);
1725 /* Register NEW_NAME to be the new reaching definition for OLD_NAME. */
1728 register_new_update_single (tree new_name
, tree old_name
)
1730 common_info_p info
= get_common_info (old_name
);
1731 tree currdef
= info
->current_def
;
1733 /* Push the current reaching definition into BLOCK_DEFS_STACK.
1734 This stack is later used by the dominator tree callbacks to
1735 restore the reaching definitions for all the variables
1736 defined in the block after a recursive visit to all its
1737 immediately dominated blocks. */
1738 block_defs_stack
.reserve (2);
1739 block_defs_stack
.quick_push (currdef
);
1740 block_defs_stack
.quick_push (old_name
);
1742 /* Set the current reaching definition for OLD_NAME to be
1744 info
->current_def
= new_name
;
1748 /* Register NEW_NAME to be the new reaching definition for all the
1749 names in OLD_NAMES. Used by the incremental SSA update routines to
1750 replace old SSA names with new ones. */
1753 register_new_update_set (tree new_name
, bitmap old_names
)
1758 EXECUTE_IF_SET_IN_BITMAP (old_names
, 0, i
, bi
)
1759 register_new_update_single (new_name
, ssa_name (i
));
1764 /* If the operand pointed to by USE_P is a name in OLD_SSA_NAMES or
1765 it is a symbol marked for renaming, replace it with USE_P's current
1766 reaching definition. */
1769 maybe_replace_use (use_operand_p use_p
)
1771 tree rdef
= NULL_TREE
;
1772 tree use
= USE_FROM_PTR (use_p
);
1773 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
1775 if (marked_for_renaming (sym
))
1776 rdef
= get_reaching_def (sym
);
1777 else if (is_old_name (use
))
1778 rdef
= get_reaching_def (use
);
1780 if (rdef
&& rdef
!= use
)
1781 SET_USE (use_p
, rdef
);
1785 /* Same as maybe_replace_use, but without introducing default stmts,
1786 returning false to indicate a need to do so. */
1789 maybe_replace_use_in_debug_stmt (use_operand_p use_p
)
1791 tree rdef
= NULL_TREE
;
1792 tree use
= USE_FROM_PTR (use_p
);
1793 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
1795 if (marked_for_renaming (sym
))
1796 rdef
= get_var_info (sym
)->info
.current_def
;
1797 else if (is_old_name (use
))
1799 rdef
= get_ssa_name_ann (use
)->info
.current_def
;
1800 /* We can't assume that, if there's no current definition, the
1801 default one should be used. It could be the case that we've
1802 rearranged blocks so that the earlier definition no longer
1803 dominates the use. */
1804 if (!rdef
&& SSA_NAME_IS_DEFAULT_DEF (use
))
1810 if (rdef
&& rdef
!= use
)
1811 SET_USE (use_p
, rdef
);
1813 return rdef
!= NULL_TREE
;
1817 /* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
1818 or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
1819 register it as the current definition for the names replaced by
1823 maybe_register_def (def_operand_p def_p
, gimple stmt
,
1824 gimple_stmt_iterator gsi
)
1826 tree def
= DEF_FROM_PTR (def_p
);
1827 tree sym
= DECL_P (def
) ? def
: SSA_NAME_VAR (def
);
1829 /* If DEF is a naked symbol that needs renaming, create a new
1831 if (marked_for_renaming (sym
))
1837 def
= make_ssa_name (def
, stmt
);
1838 SET_DEF (def_p
, def
);
1840 tracked_var
= target_for_debug_bind (sym
);
1843 gimple note
= gimple_build_debug_bind (tracked_var
, def
, stmt
);
1844 /* If stmt ends the bb, insert the debug stmt on the single
1845 non-EH edge from the stmt. */
1846 if (gsi_one_before_end_p (gsi
) && stmt_ends_bb_p (stmt
))
1848 basic_block bb
= gsi_bb (gsi
);
1851 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1852 if (!(e
->flags
& EDGE_EH
))
1854 gcc_checking_assert (!ef
);
1857 /* If there are other predecessors to ef->dest, then
1858 there must be PHI nodes for the modified
1859 variable, and therefore there will be debug bind
1860 stmts after the PHI nodes. The debug bind notes
1861 we'd insert would force the creation of a new
1862 block (diverging codegen) and be redundant with
1863 the post-PHI bind stmts, so don't add them.
1865 As for the exit edge, there wouldn't be redundant
1866 bind stmts, but there wouldn't be a PC to bind
1867 them to either, so avoid diverging the CFG. */
1868 if (ef
&& single_pred_p (ef
->dest
)
1869 && ef
->dest
!= EXIT_BLOCK_PTR_FOR_FN (cfun
))
1871 /* If there were PHI nodes in the node, we'd
1872 have to make sure the value we're binding
1873 doesn't need rewriting. But there shouldn't
1874 be PHI nodes in a single-predecessor block,
1875 so we just add the note. */
1876 gsi_insert_on_edge_immediate (ef
, note
);
1880 gsi_insert_after (&gsi
, note
, GSI_SAME_STMT
);
1884 register_new_update_single (def
, sym
);
1888 /* If DEF is a new name, register it as a new definition
1889 for all the names replaced by DEF. */
1890 if (is_new_name (def
))
1891 register_new_update_set (def
, names_replaced_by (def
));
1893 /* If DEF is an old name, register DEF as a new
1894 definition for itself. */
1895 if (is_old_name (def
))
1896 register_new_update_single (def
, def
);
1901 /* Update every variable used in the statement pointed-to by SI. The
1902 statement is assumed to be in SSA form already. Names in
1903 OLD_SSA_NAMES used by SI will be updated to their current reaching
1904 definition. Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI
1905 will be registered as a new definition for their corresponding name
1906 in OLD_SSA_NAMES. */
1909 rewrite_update_stmt (gimple stmt
, gimple_stmt_iterator gsi
)
1911 use_operand_p use_p
;
1912 def_operand_p def_p
;
1915 /* Only update marked statements. */
1916 if (!rewrite_uses_p (stmt
) && !register_defs_p (stmt
))
1919 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1921 fprintf (dump_file
, "Updating SSA information for statement ");
1922 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1925 /* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying
1926 symbol is marked for renaming. */
1927 if (rewrite_uses_p (stmt
))
1929 if (is_gimple_debug (stmt
))
1931 bool failed
= false;
1933 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
1934 if (!maybe_replace_use_in_debug_stmt (use_p
))
1942 /* DOM sometimes threads jumps in such a way that a
1943 debug stmt ends up referencing a SSA variable that no
1944 longer dominates the debug stmt, but such that all
1945 incoming definitions refer to the same definition in
1946 an earlier dominator. We could try to recover that
1947 definition somehow, but this will have to do for now.
1949 Introducing a default definition, which is what
1950 maybe_replace_use() would do in such cases, may
1951 modify code generation, for the otherwise-unused
1952 default definition would never go away, modifying SSA
1953 version numbers all over. */
1954 gimple_debug_bind_reset_value (stmt
);
1960 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
1961 maybe_replace_use (use_p
);
1965 /* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES.
1966 Also register definitions for names whose underlying symbol is
1967 marked for renaming. */
1968 if (register_defs_p (stmt
))
1969 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1970 maybe_register_def (def_p
, stmt
, gsi
);
1974 /* Visit all the successor blocks of BB looking for PHI nodes. For
1975 every PHI node found, check if any of its arguments is in
1976 OLD_SSA_NAMES. If so, and if the argument has a current reaching
1977 definition, replace it. */
1980 rewrite_update_phi_arguments (basic_block bb
)
1986 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1991 if (!bitmap_bit_p (blocks_with_phis_to_rewrite
, e
->dest
->index
))
1994 phis
= phis_to_rewrite
[e
->dest
->index
];
1995 FOR_EACH_VEC_ELT (phis
, i
, phi
)
1997 tree arg
, lhs_sym
, reaching_def
= NULL
;
1998 use_operand_p arg_p
;
2000 gcc_checking_assert (rewrite_uses_p (phi
));
2002 arg_p
= PHI_ARG_DEF_PTR_FROM_EDGE (phi
, e
);
2003 arg
= USE_FROM_PTR (arg_p
);
2005 if (arg
&& !DECL_P (arg
) && TREE_CODE (arg
) != SSA_NAME
)
2008 lhs_sym
= SSA_NAME_VAR (gimple_phi_result (phi
));
2010 if (arg
== NULL_TREE
)
2012 /* When updating a PHI node for a recently introduced
2013 symbol we may find NULL arguments. That's why we
2014 take the symbol from the LHS of the PHI node. */
2015 reaching_def
= get_reaching_def (lhs_sym
);
2020 tree sym
= DECL_P (arg
) ? arg
: SSA_NAME_VAR (arg
);
2022 if (marked_for_renaming (sym
))
2023 reaching_def
= get_reaching_def (sym
);
2024 else if (is_old_name (arg
))
2025 reaching_def
= get_reaching_def (arg
);
2028 /* Update the argument if there is a reaching def. */
2031 source_location locus
;
2032 int arg_i
= PHI_ARG_INDEX_FROM_USE (arg_p
);
2034 SET_USE (arg_p
, reaching_def
);
2036 /* Virtual operands do not need a location. */
2037 if (virtual_operand_p (reaching_def
))
2038 locus
= UNKNOWN_LOCATION
;
2041 gimple stmt
= SSA_NAME_DEF_STMT (reaching_def
);
2043 /* Single element PHI nodes behave like copies, so get the
2044 location from the phi argument. */
2045 if (gimple_code (stmt
) == GIMPLE_PHI
2046 && gimple_phi_num_args (stmt
) == 1)
2047 locus
= gimple_phi_arg_location (stmt
, 0);
2049 locus
= gimple_location (stmt
);
2052 gimple_phi_arg_set_location (phi
, arg_i
, locus
);
2056 if (e
->flags
& EDGE_ABNORMAL
)
2057 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p
)) = 1;
2062 class rewrite_update_dom_walker
: public dom_walker
2065 rewrite_update_dom_walker (cdi_direction direction
) : dom_walker (direction
) {}
2067 virtual void before_dom_children (basic_block
);
2068 virtual void after_dom_children (basic_block
);
2071 /* Initialization of block data structures for the incremental SSA
2072 update pass. Create a block local stack of reaching definitions
2073 for new SSA names produced in this block (BLOCK_DEFS). Register
2074 new definitions for every PHI node in the block. */
2077 rewrite_update_dom_walker::before_dom_children (basic_block bb
)
2079 bool is_abnormal_phi
;
2080 gimple_stmt_iterator gsi
;
2082 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2083 fprintf (dump_file
, "Registering new PHI nodes in block #%d\n",
2086 /* Mark the unwind point for this block. */
2087 block_defs_stack
.safe_push (NULL_TREE
);
2089 if (!bitmap_bit_p (blocks_to_update
, bb
->index
))
2092 /* Mark the LHS if any of the arguments flows through an abnormal
2094 is_abnormal_phi
= bb_has_abnormal_pred (bb
);
2096 /* If any of the PHI nodes is a replacement for a name in
2097 OLD_SSA_NAMES or it's one of the names in NEW_SSA_NAMES, then
2098 register it as a new definition for its corresponding name. Also
2099 register definitions for names whose underlying symbols are
2100 marked for renaming. */
2101 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2104 gimple phi
= gsi_stmt (gsi
);
2106 if (!register_defs_p (phi
))
2109 lhs
= gimple_phi_result (phi
);
2110 lhs_sym
= SSA_NAME_VAR (lhs
);
2112 if (marked_for_renaming (lhs_sym
))
2113 register_new_update_single (lhs
, lhs_sym
);
2117 /* If LHS is a new name, register a new definition for all
2118 the names replaced by LHS. */
2119 if (is_new_name (lhs
))
2120 register_new_update_set (lhs
, names_replaced_by (lhs
));
2122 /* If LHS is an OLD name, register it as a new definition
2124 if (is_old_name (lhs
))
2125 register_new_update_single (lhs
, lhs
);
2128 if (is_abnormal_phi
)
2129 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs
) = 1;
2132 /* Step 2. Rewrite every variable used in each statement in the block. */
2133 if (bitmap_bit_p (interesting_blocks
, bb
->index
))
2135 gcc_checking_assert (bitmap_bit_p (blocks_to_update
, bb
->index
));
2136 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2137 rewrite_update_stmt (gsi_stmt (gsi
), gsi
);
2140 /* Step 3. Update PHI nodes. */
2141 rewrite_update_phi_arguments (bb
);
2144 /* Called after visiting block BB. Unwind BLOCK_DEFS_STACK to restore
2145 the current reaching definition of every name re-written in BB to
2146 the original reaching definition before visiting BB. This
2147 unwinding must be done in the opposite order to what is done in
2148 register_new_update_set. */
2151 rewrite_update_dom_walker::after_dom_children (basic_block bb ATTRIBUTE_UNUSED
)
2153 while (block_defs_stack
.length () > 0)
2155 tree var
= block_defs_stack
.pop ();
2158 /* NULL indicates the unwind stop point for this block (see
2159 rewrite_update_enter_block). */
2163 saved_def
= block_defs_stack
.pop ();
2164 get_common_info (var
)->current_def
= saved_def
;
2169 /* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
2172 ENTRY indicates the block where to start. Every block dominated by
2173 ENTRY will be rewritten.
2175 WHAT indicates what actions will be taken by the renamer (see enum
2178 BLOCKS are the set of interesting blocks for the dominator walker
2179 to process. If this set is NULL, then all the nodes dominated
2180 by ENTRY are walked. Otherwise, blocks dominated by ENTRY that
2181 are not present in BLOCKS are ignored. */
2184 rewrite_blocks (basic_block entry
, enum rewrite_mode what
)
2186 /* Rewrite all the basic blocks in the program. */
2187 timevar_push (TV_TREE_SSA_REWRITE_BLOCKS
);
2189 block_defs_stack
.create (10);
2191 /* Recursively walk the dominator tree rewriting each statement in
2192 each basic block. */
2193 if (what
== REWRITE_ALL
)
2194 rewrite_dom_walker (CDI_DOMINATORS
).walk (entry
);
2195 else if (what
== REWRITE_UPDATE
)
2196 rewrite_update_dom_walker (CDI_DOMINATORS
).walk (entry
);
2200 /* Debugging dumps. */
2201 if (dump_file
&& (dump_flags
& TDF_STATS
))
2203 dump_dfa_stats (dump_file
);
2204 if (var_infos
.is_created ())
2205 dump_tree_ssa_stats (dump_file
);
2208 block_defs_stack
.release ();
2210 timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS
);
2213 class mark_def_dom_walker
: public dom_walker
2216 mark_def_dom_walker (cdi_direction direction
);
2217 ~mark_def_dom_walker ();
2219 virtual void before_dom_children (basic_block
);
2222 /* Notice that this bitmap is indexed using variable UIDs, so it must be
2223 large enough to accommodate all the variables referenced in the
2224 function, not just the ones we are renaming. */
2228 mark_def_dom_walker::mark_def_dom_walker (cdi_direction direction
)
2229 : dom_walker (direction
), m_kills (BITMAP_ALLOC (NULL
))
2233 mark_def_dom_walker::~mark_def_dom_walker ()
2235 BITMAP_FREE (m_kills
);
2238 /* Block processing routine for mark_def_sites. Clear the KILLS bitmap
2239 at the start of each block, and call mark_def_sites for each statement. */
2242 mark_def_dom_walker::before_dom_children (basic_block bb
)
2244 gimple_stmt_iterator gsi
;
2246 bitmap_clear (m_kills
);
2247 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2248 mark_def_sites (bb
, gsi_stmt (gsi
), m_kills
);
2251 /* Initialize internal data needed during renaming. */
2254 init_ssa_renamer (void)
2256 cfun
->gimple_df
->in_ssa_p
= false;
2258 /* Allocate memory for the DEF_BLOCKS hash table. */
2259 gcc_assert (!var_infos
.is_created ());
2260 var_infos
.create (vec_safe_length (cfun
->local_decls
));
2262 bitmap_obstack_initialize (&update_ssa_obstack
);
2266 /* Deallocate internal data structures used by the renamer. */
2269 fini_ssa_renamer (void)
2271 if (var_infos
.is_created ())
2272 var_infos
.dispose ();
2274 bitmap_obstack_release (&update_ssa_obstack
);
2276 cfun
->gimple_df
->ssa_renaming_needed
= 0;
2277 cfun
->gimple_df
->rename_vops
= 0;
2278 cfun
->gimple_df
->in_ssa_p
= true;
2281 /* Main entry point into the SSA builder. The renaming process
2282 proceeds in four main phases:
2284 1- Compute dominance frontier and immediate dominators, needed to
2285 insert PHI nodes and rename the function in dominator tree
2288 2- Find and mark all the blocks that define variables.
2290 3- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
2292 4- Rename all the blocks (rewrite_blocks) and statements in the program.
2294 Steps 3 and 4 are done using the dominator tree walker
2295 (walk_dominator_tree). */
2298 rewrite_into_ssa (void)
2304 /* Initialize operand data structures. */
2305 init_ssa_operands (cfun
);
2307 /* Initialize internal data needed by the renamer. */
2308 init_ssa_renamer ();
2310 /* Initialize the set of interesting blocks. The callback
2311 mark_def_sites will add to this set those blocks that the renamer
2313 interesting_blocks
= sbitmap_alloc (last_basic_block
);
2314 bitmap_clear (interesting_blocks
);
2316 /* Initialize dominance frontier. */
2317 dfs
= XNEWVEC (bitmap_head
, last_basic_block
);
2319 bitmap_initialize (&dfs
[bb
->index
], &bitmap_default_obstack
);
2321 /* 1- Compute dominance frontiers. */
2322 calculate_dominance_info (CDI_DOMINATORS
);
2323 compute_dominance_frontiers (dfs
);
2325 /* 2- Find and mark definition sites. */
2326 mark_def_dom_walker (CDI_DOMINATORS
).walk (cfun
->cfg
->x_entry_block_ptr
);
2328 /* 3- Insert PHI nodes at dominance frontiers of definition blocks. */
2329 insert_phi_nodes (dfs
);
2331 /* 4- Rename all the blocks. */
2332 rewrite_blocks (ENTRY_BLOCK_PTR_FOR_FN (cfun
), REWRITE_ALL
);
2334 /* Free allocated memory. */
2336 bitmap_clear (&dfs
[bb
->index
]);
2339 sbitmap_free (interesting_blocks
);
2341 fini_ssa_renamer ();
2343 /* Try to get rid of all gimplifier generated temporaries by making
2344 its SSA names anonymous. This way we can garbage collect them
2345 all after removing unused locals which we do in our TODO. */
2346 for (i
= 1; i
< num_ssa_names
; ++i
)
2348 tree decl
, name
= ssa_name (i
);
2350 || SSA_NAME_IS_DEFAULT_DEF (name
))
2352 decl
= SSA_NAME_VAR (name
);
2354 && TREE_CODE (decl
) == VAR_DECL
2355 && !VAR_DECL_IS_VIRTUAL_OPERAND (decl
)
2356 && DECL_IGNORED_P (decl
))
2357 SET_SSA_NAME_VAR_OR_IDENTIFIER (name
, DECL_NAME (decl
));
2363 /* Gate for IPCP optimization. */
2366 gate_into_ssa (void)
2368 /* Do nothing for funcions that was produced already in SSA form. */
2369 return !(cfun
->curr_properties
& PROP_ssa
);
2374 const pass_data pass_data_build_ssa
=
2376 GIMPLE_PASS
, /* type */
2378 OPTGROUP_NONE
, /* optinfo_flags */
2379 true, /* has_gate */
2380 true, /* has_execute */
2381 TV_TREE_SSA_OTHER
, /* tv_id */
2382 PROP_cfg
, /* properties_required */
2383 PROP_ssa
, /* properties_provided */
2384 0, /* properties_destroyed */
2385 0, /* todo_flags_start */
2386 ( TODO_verify_ssa
| TODO_remove_unused_locals
), /* todo_flags_finish */
2389 class pass_build_ssa
: public gimple_opt_pass
2392 pass_build_ssa (gcc::context
*ctxt
)
2393 : gimple_opt_pass (pass_data_build_ssa
, ctxt
)
2396 /* opt_pass methods: */
2397 bool gate () { return gate_into_ssa (); }
2398 unsigned int execute () { return rewrite_into_ssa (); }
2400 }; // class pass_build_ssa
2405 make_pass_build_ssa (gcc::context
*ctxt
)
2407 return new pass_build_ssa (ctxt
);
2411 /* Mark the definition of VAR at STMT and BB as interesting for the
2412 renamer. BLOCKS is the set of blocks that need updating. */
2415 mark_def_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2417 gcc_checking_assert (bitmap_bit_p (blocks_to_update
, bb
->index
));
2418 set_register_defs (stmt
, true);
2422 bool is_phi_p
= gimple_code (stmt
) == GIMPLE_PHI
;
2424 set_def_block (var
, bb
, is_phi_p
);
2426 /* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition
2427 site for both itself and all the old names replaced by it. */
2428 if (TREE_CODE (var
) == SSA_NAME
&& is_new_name (var
))
2432 bitmap set
= names_replaced_by (var
);
2434 EXECUTE_IF_SET_IN_BITMAP (set
, 0, i
, bi
)
2435 set_def_block (ssa_name (i
), bb
, is_phi_p
);
2441 /* Mark the use of VAR at STMT and BB as interesting for the
2442 renamer. INSERT_PHI_P is true if we are going to insert new PHI
2446 mark_use_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2448 basic_block def_bb
= gimple_bb (stmt
);
2450 mark_block_for_update (def_bb
);
2451 mark_block_for_update (bb
);
2453 if (gimple_code (stmt
) == GIMPLE_PHI
)
2454 mark_phi_for_rewrite (def_bb
, stmt
);
2457 set_rewrite_uses (stmt
, true);
2459 if (is_gimple_debug (stmt
))
2463 /* If VAR has not been defined in BB, then it is live-on-entry
2464 to BB. Note that we cannot just use the block holding VAR's
2465 definition because if VAR is one of the names in OLD_SSA_NAMES,
2466 it will have several definitions (itself and all the names that
2470 struct def_blocks_d
*db_p
= get_def_blocks_for (get_common_info (var
));
2471 if (!bitmap_bit_p (db_p
->def_blocks
, bb
->index
))
2472 set_livein_block (var
, bb
);
2477 /* Do a dominator walk starting at BB processing statements that
2478 reference symbols in SSA operands. This is very similar to
2479 mark_def_sites, but the scan handles statements whose operands may
2480 already be SSA names.
2482 If INSERT_PHI_P is true, mark those uses as live in the
2483 corresponding block. This is later used by the PHI placement
2484 algorithm to make PHI pruning decisions.
2486 FIXME. Most of this would be unnecessary if we could associate a
2487 symbol to all the SSA names that reference it. But that
2488 sounds like it would be expensive to maintain. Still, it
2489 would be interesting to see if it makes better sense to do
2493 prepare_block_for_update (basic_block bb
, bool insert_phi_p
)
2496 gimple_stmt_iterator si
;
2500 mark_block_for_update (bb
);
2502 /* Process PHI nodes marking interesting those that define or use
2503 the symbols that we are interested in. */
2504 for (si
= gsi_start_phis (bb
); !gsi_end_p (si
); gsi_next (&si
))
2506 gimple phi
= gsi_stmt (si
);
2507 tree lhs_sym
, lhs
= gimple_phi_result (phi
);
2509 if (TREE_CODE (lhs
) == SSA_NAME
2510 && (! virtual_operand_p (lhs
)
2511 || ! cfun
->gimple_df
->rename_vops
))
2514 lhs_sym
= DECL_P (lhs
) ? lhs
: SSA_NAME_VAR (lhs
);
2515 mark_for_renaming (lhs_sym
);
2516 mark_def_interesting (lhs_sym
, phi
, bb
, insert_phi_p
);
2518 /* Mark the uses in phi nodes as interesting. It would be more correct
2519 to process the arguments of the phi nodes of the successor edges of
2520 BB at the end of prepare_block_for_update, however, that turns out
2521 to be significantly more expensive. Doing it here is conservatively
2522 correct -- it may only cause us to believe a value to be live in a
2523 block that also contains its definition, and thus insert a few more
2524 phi nodes for it. */
2525 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
2526 mark_use_interesting (lhs_sym
, phi
, e
->src
, insert_phi_p
);
2529 /* Process the statements. */
2530 for (si
= gsi_start_bb (bb
); !gsi_end_p (si
); gsi_next (&si
))
2534 use_operand_p use_p
;
2535 def_operand_p def_p
;
2537 stmt
= gsi_stmt (si
);
2539 if (cfun
->gimple_df
->rename_vops
2540 && gimple_vuse (stmt
))
2542 tree use
= gimple_vuse (stmt
);
2543 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
2544 mark_for_renaming (sym
);
2545 mark_use_interesting (sym
, stmt
, bb
, insert_phi_p
);
2548 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, i
, SSA_OP_USE
)
2550 tree use
= USE_FROM_PTR (use_p
);
2553 mark_for_renaming (use
);
2554 mark_use_interesting (use
, stmt
, bb
, insert_phi_p
);
2557 if (cfun
->gimple_df
->rename_vops
2558 && gimple_vdef (stmt
))
2560 tree def
= gimple_vdef (stmt
);
2561 tree sym
= DECL_P (def
) ? def
: SSA_NAME_VAR (def
);
2562 mark_for_renaming (sym
);
2563 mark_def_interesting (sym
, stmt
, bb
, insert_phi_p
);
2566 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, i
, SSA_OP_DEF
)
2568 tree def
= DEF_FROM_PTR (def_p
);
2571 mark_for_renaming (def
);
2572 mark_def_interesting (def
, stmt
, bb
, insert_phi_p
);
2576 /* Now visit all the blocks dominated by BB. */
2577 for (son
= first_dom_son (CDI_DOMINATORS
, bb
);
2579 son
= next_dom_son (CDI_DOMINATORS
, son
))
2580 prepare_block_for_update (son
, insert_phi_p
);
2584 /* Helper for prepare_names_to_update. Mark all the use sites for
2585 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2586 prepare_names_to_update. */
2589 prepare_use_sites_for (tree name
, bool insert_phi_p
)
2591 use_operand_p use_p
;
2592 imm_use_iterator iter
;
2594 FOR_EACH_IMM_USE_FAST (use_p
, iter
, name
)
2596 gimple stmt
= USE_STMT (use_p
);
2597 basic_block bb
= gimple_bb (stmt
);
2599 if (gimple_code (stmt
) == GIMPLE_PHI
)
2601 int ix
= PHI_ARG_INDEX_FROM_USE (use_p
);
2602 edge e
= gimple_phi_arg_edge (stmt
, ix
);
2603 mark_use_interesting (name
, stmt
, e
->src
, insert_phi_p
);
2607 /* For regular statements, mark this as an interesting use
2609 mark_use_interesting (name
, stmt
, bb
, insert_phi_p
);
2615 /* Helper for prepare_names_to_update. Mark the definition site for
2616 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2617 prepare_names_to_update. */
2620 prepare_def_site_for (tree name
, bool insert_phi_p
)
2625 gcc_checking_assert (names_to_release
== NULL
2626 || !bitmap_bit_p (names_to_release
,
2627 SSA_NAME_VERSION (name
)));
2629 stmt
= SSA_NAME_DEF_STMT (name
);
2630 bb
= gimple_bb (stmt
);
2633 gcc_checking_assert (bb
->index
< last_basic_block
);
2634 mark_block_for_update (bb
);
2635 mark_def_interesting (name
, stmt
, bb
, insert_phi_p
);
2640 /* Mark definition and use sites of names in NEW_SSA_NAMES and
2641 OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert
2642 PHI nodes for newly created names. */
2645 prepare_names_to_update (bool insert_phi_p
)
2649 sbitmap_iterator sbi
;
2651 /* If a name N from NEW_SSA_NAMES is also marked to be released,
2652 remove it from NEW_SSA_NAMES so that we don't try to visit its
2653 defining basic block (which most likely doesn't exist). Notice
2654 that we cannot do the same with names in OLD_SSA_NAMES because we
2655 want to replace existing instances. */
2656 if (names_to_release
)
2657 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2658 bitmap_clear_bit (new_ssa_names
, i
);
2660 /* First process names in NEW_SSA_NAMES. Otherwise, uses of old
2661 names may be considered to be live-in on blocks that contain
2662 definitions for their replacements. */
2663 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names
, 0, i
, sbi
)
2664 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2666 /* If an old name is in NAMES_TO_RELEASE, we cannot remove it from
2667 OLD_SSA_NAMES, but we have to ignore its definition site. */
2668 EXECUTE_IF_SET_IN_BITMAP (old_ssa_names
, 0, i
, sbi
)
2670 if (names_to_release
== NULL
|| !bitmap_bit_p (names_to_release
, i
))
2671 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2672 prepare_use_sites_for (ssa_name (i
), insert_phi_p
);
2677 /* Dump all the names replaced by NAME to FILE. */
2680 dump_names_replaced_by (FILE *file
, tree name
)
2686 print_generic_expr (file
, name
, 0);
2687 fprintf (file
, " -> { ");
2689 old_set
= names_replaced_by (name
);
2690 EXECUTE_IF_SET_IN_BITMAP (old_set
, 0, i
, bi
)
2692 print_generic_expr (file
, ssa_name (i
), 0);
2693 fprintf (file
, " ");
2696 fprintf (file
, "}\n");
2700 /* Dump all the names replaced by NAME to stderr. */
2703 debug_names_replaced_by (tree name
)
2705 dump_names_replaced_by (stderr
, name
);
2709 /* Dump SSA update information to FILE. */
2712 dump_update_ssa (FILE *file
)
2717 if (!need_ssa_update_p (cfun
))
2720 if (new_ssa_names
&& bitmap_first_set_bit (new_ssa_names
) >= 0)
2722 sbitmap_iterator sbi
;
2724 fprintf (file
, "\nSSA replacement table\n");
2725 fprintf (file
, "N_i -> { O_1 ... O_j } means that N_i replaces "
2726 "O_1, ..., O_j\n\n");
2728 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names
, 0, i
, sbi
)
2729 dump_names_replaced_by (file
, ssa_name (i
));
2732 if (symbols_to_rename_set
&& !bitmap_empty_p (symbols_to_rename_set
))
2734 fprintf (file
, "\nSymbols to be put in SSA form\n");
2735 dump_decl_set (file
, symbols_to_rename_set
);
2736 fprintf (file
, "\n");
2739 if (names_to_release
&& !bitmap_empty_p (names_to_release
))
2741 fprintf (file
, "\nSSA names to release after updating the SSA web\n\n");
2742 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2744 print_generic_expr (file
, ssa_name (i
), 0);
2745 fprintf (file
, " ");
2747 fprintf (file
, "\n");
2752 /* Dump SSA update information to stderr. */
2755 debug_update_ssa (void)
2757 dump_update_ssa (stderr
);
2761 /* Initialize data structures used for incremental SSA updates. */
2764 init_update_ssa (struct function
*fn
)
2766 /* Reserve more space than the current number of names. The calls to
2767 add_new_name_mapping are typically done after creating new SSA
2768 names, so we'll need to reallocate these arrays. */
2769 old_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2770 bitmap_clear (old_ssa_names
);
2772 new_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2773 bitmap_clear (new_ssa_names
);
2775 bitmap_obstack_initialize (&update_ssa_obstack
);
2777 names_to_release
= NULL
;
2778 update_ssa_initialized_fn
= fn
;
2782 /* Deallocate data structures used for incremental SSA updates. */
2785 delete_update_ssa (void)
2790 sbitmap_free (old_ssa_names
);
2791 old_ssa_names
= NULL
;
2793 sbitmap_free (new_ssa_names
);
2794 new_ssa_names
= NULL
;
2796 BITMAP_FREE (symbols_to_rename_set
);
2797 symbols_to_rename_set
= NULL
;
2798 symbols_to_rename
.release ();
2800 if (names_to_release
)
2802 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2803 release_ssa_name (ssa_name (i
));
2804 BITMAP_FREE (names_to_release
);
2807 clear_ssa_name_info ();
2809 fini_ssa_renamer ();
2811 if (blocks_with_phis_to_rewrite
)
2812 EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite
, 0, i
, bi
)
2814 gimple_vec phis
= phis_to_rewrite
[i
];
2816 phis_to_rewrite
[i
].create (0);
2819 BITMAP_FREE (blocks_with_phis_to_rewrite
);
2820 BITMAP_FREE (blocks_to_update
);
2822 update_ssa_initialized_fn
= NULL
;
2826 /* Create a new name for OLD_NAME in statement STMT and replace the
2827 operand pointed to by DEF_P with the newly created name. If DEF_P
2828 is NULL then STMT should be a GIMPLE assignment.
2829 Return the new name and register the replacement mapping <NEW, OLD> in
2830 update_ssa's tables. */
2833 create_new_def_for (tree old_name
, gimple stmt
, def_operand_p def
)
2837 timevar_push (TV_TREE_SSA_INCREMENTAL
);
2839 if (!update_ssa_initialized_fn
)
2840 init_update_ssa (cfun
);
2842 gcc_assert (update_ssa_initialized_fn
== cfun
);
2844 new_name
= duplicate_ssa_name (old_name
, stmt
);
2846 SET_DEF (def
, new_name
);
2848 gimple_assign_set_lhs (stmt
, new_name
);
2850 if (gimple_code (stmt
) == GIMPLE_PHI
)
2852 basic_block bb
= gimple_bb (stmt
);
2854 /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
2855 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name
) = bb_has_abnormal_pred (bb
);
2858 add_new_name_mapping (new_name
, old_name
);
2860 /* For the benefit of passes that will be updating the SSA form on
2861 their own, set the current reaching definition of OLD_NAME to be
2863 get_ssa_name_ann (old_name
)->info
.current_def
= new_name
;
2865 timevar_pop (TV_TREE_SSA_INCREMENTAL
);
2871 /* Mark virtual operands of FN for renaming by update_ssa. */
2874 mark_virtual_operands_for_renaming (struct function
*fn
)
2876 fn
->gimple_df
->ssa_renaming_needed
= 1;
2877 fn
->gimple_df
->rename_vops
= 1;
2880 /* Replace all uses of NAME by underlying variable and mark it
2881 for renaming. This assumes the defining statement of NAME is
2882 going to be removed. */
2885 mark_virtual_operand_for_renaming (tree name
)
2887 tree name_var
= SSA_NAME_VAR (name
);
2889 imm_use_iterator iter
;
2890 use_operand_p use_p
;
2893 gcc_assert (VAR_DECL_IS_VIRTUAL_OPERAND (name_var
));
2894 FOR_EACH_IMM_USE_STMT (stmt
, iter
, name
)
2896 FOR_EACH_IMM_USE_ON_STMT (use_p
, iter
)
2897 SET_USE (use_p
, name_var
);
2901 mark_virtual_operands_for_renaming (cfun
);
2904 /* Replace all uses of the virtual PHI result by its underlying variable
2905 and mark it for renaming. This assumes the PHI node is going to be
2909 mark_virtual_phi_result_for_renaming (gimple phi
)
2911 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2913 fprintf (dump_file
, "Marking result for renaming : ");
2914 print_gimple_stmt (dump_file
, phi
, 0, TDF_SLIM
);
2915 fprintf (dump_file
, "\n");
2918 mark_virtual_operand_for_renaming (gimple_phi_result (phi
));
2921 /* Return true if there is any work to be done by update_ssa
2925 need_ssa_update_p (struct function
*fn
)
2927 gcc_assert (fn
!= NULL
);
2928 return (update_ssa_initialized_fn
== fn
2929 || (fn
->gimple_df
&& fn
->gimple_df
->ssa_renaming_needed
));
2932 /* Return true if name N has been registered in the replacement table. */
2935 name_registered_for_update_p (tree n ATTRIBUTE_UNUSED
)
2937 if (!update_ssa_initialized_fn
)
2940 gcc_assert (update_ssa_initialized_fn
== cfun
);
2942 return is_new_name (n
) || is_old_name (n
);
2946 /* Mark NAME to be released after update_ssa has finished. */
2949 release_ssa_name_after_update_ssa (tree name
)
2951 gcc_assert (cfun
&& update_ssa_initialized_fn
== cfun
);
2953 if (names_to_release
== NULL
)
2954 names_to_release
= BITMAP_ALLOC (NULL
);
2956 bitmap_set_bit (names_to_release
, SSA_NAME_VERSION (name
));
2960 /* Insert new PHI nodes to replace VAR. DFS contains dominance
2961 frontier information. BLOCKS is the set of blocks to be updated.
2963 This is slightly different than the regular PHI insertion
2964 algorithm. The value of UPDATE_FLAGS controls how PHI nodes for
2965 real names (i.e., GIMPLE registers) are inserted:
2967 - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI
2968 nodes inside the region affected by the block that defines VAR
2969 and the blocks that define all its replacements. All these
2970 definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS.
2972 First, we compute the entry point to the region (ENTRY). This is
2973 given by the nearest common dominator to all the definition
2974 blocks. When computing the iterated dominance frontier (IDF), any
2975 block not strictly dominated by ENTRY is ignored.
2977 We then call the standard PHI insertion algorithm with the pruned
2980 - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real
2981 names is not pruned. PHI nodes are inserted at every IDF block. */
2984 insert_updated_phi_nodes_for (tree var
, bitmap_head
*dfs
, bitmap blocks
,
2985 unsigned update_flags
)
2988 struct def_blocks_d
*db
;
2989 bitmap idf
, pruned_idf
;
2993 if (TREE_CODE (var
) == SSA_NAME
)
2994 gcc_checking_assert (is_old_name (var
));
2996 gcc_checking_assert (marked_for_renaming (var
));
2998 /* Get all the definition sites for VAR. */
2999 db
= find_def_blocks_for (var
);
3001 /* No need to do anything if there were no definitions to VAR. */
3002 if (db
== NULL
|| bitmap_empty_p (db
->def_blocks
))
3005 /* Compute the initial iterated dominance frontier. */
3006 idf
= compute_idf (db
->def_blocks
, dfs
);
3007 pruned_idf
= BITMAP_ALLOC (NULL
);
3009 if (TREE_CODE (var
) == SSA_NAME
)
3011 if (update_flags
== TODO_update_ssa
)
3013 /* If doing regular SSA updates for GIMPLE registers, we are
3014 only interested in IDF blocks dominated by the nearest
3015 common dominator of all the definition blocks. */
3016 entry
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3018 if (entry
!= ENTRY_BLOCK_PTR_FOR_FN (cfun
))
3019 EXECUTE_IF_SET_IN_BITMAP (idf
, 0, i
, bi
)
3020 if (BASIC_BLOCK (i
) != entry
3021 && dominated_by_p (CDI_DOMINATORS
, BASIC_BLOCK (i
), entry
))
3022 bitmap_set_bit (pruned_idf
, i
);
3026 /* Otherwise, do not prune the IDF for VAR. */
3027 gcc_checking_assert (update_flags
== TODO_update_ssa_full_phi
);
3028 bitmap_copy (pruned_idf
, idf
);
3033 /* Otherwise, VAR is a symbol that needs to be put into SSA form
3034 for the first time, so we need to compute the full IDF for
3036 bitmap_copy (pruned_idf
, idf
);
3039 if (!bitmap_empty_p (pruned_idf
))
3041 /* Make sure that PRUNED_IDF blocks and all their feeding blocks
3042 are included in the region to be updated. The feeding blocks
3043 are important to guarantee that the PHI arguments are renamed
3046 /* FIXME, this is not needed if we are updating symbols. We are
3047 already starting at the ENTRY block anyway. */
3048 bitmap_ior_into (blocks
, pruned_idf
);
3049 EXECUTE_IF_SET_IN_BITMAP (pruned_idf
, 0, i
, bi
)
3053 basic_block bb
= BASIC_BLOCK (i
);
3055 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
3056 if (e
->src
->index
>= 0)
3057 bitmap_set_bit (blocks
, e
->src
->index
);
3060 insert_phi_nodes_for (var
, pruned_idf
, true);
3063 BITMAP_FREE (pruned_idf
);
3067 /* Sort symbols_to_rename after their DECL_UID. */
3070 insert_updated_phi_nodes_compare_uids (const void *a
, const void *b
)
3072 const_tree syma
= *(const const_tree
*)a
;
3073 const_tree symb
= *(const const_tree
*)b
;
3074 if (DECL_UID (syma
) == DECL_UID (symb
))
3076 return DECL_UID (syma
) < DECL_UID (symb
) ? -1 : 1;
3079 /* Given a set of newly created SSA names (NEW_SSA_NAMES) and a set of
3080 existing SSA names (OLD_SSA_NAMES), update the SSA form so that:
3082 1- The names in OLD_SSA_NAMES dominated by the definitions of
3083 NEW_SSA_NAMES are all re-written to be reached by the
3084 appropriate definition from NEW_SSA_NAMES.
3086 2- If needed, new PHI nodes are added to the iterated dominance
3087 frontier of the blocks where each of NEW_SSA_NAMES are defined.
3089 The mapping between OLD_SSA_NAMES and NEW_SSA_NAMES is setup by
3090 calling create_new_def_for to create new defs for names that the
3091 caller wants to replace.
3093 The caller cretaes the new names to be inserted and the names that need
3094 to be replaced by calling create_new_def_for for each old definition
3095 to be replaced. Note that the function assumes that the
3096 new defining statement has already been inserted in the IL.
3098 For instance, given the following code:
3101 2 x_1 = PHI (0, x_5)
3112 Suppose that we insert new names x_10 and x_11 (lines 4 and 8).
3115 2 x_1 = PHI (0, x_5)
3128 We want to replace all the uses of x_1 with the new definitions of
3129 x_10 and x_11. Note that the only uses that should be replaced are
3130 those at lines 5, 9 and 11. Also, the use of x_7 at line 9 should
3131 *not* be replaced (this is why we cannot just mark symbol 'x' for
3134 Additionally, we may need to insert a PHI node at line 11 because
3135 that is a merge point for x_10 and x_11. So the use of x_1 at line
3136 11 will be replaced with the new PHI node. The insertion of PHI
3137 nodes is optional. They are not strictly necessary to preserve the
3138 SSA form, and depending on what the caller inserted, they may not
3139 even be useful for the optimizers. UPDATE_FLAGS controls various
3140 aspects of how update_ssa operates, see the documentation for
3141 TODO_update_ssa*. */
3144 update_ssa (unsigned update_flags
)
3146 basic_block bb
, start_bb
;
3150 sbitmap_iterator sbi
;
3153 /* Only one update flag should be set. */
3154 gcc_assert (update_flags
== TODO_update_ssa
3155 || update_flags
== TODO_update_ssa_no_phi
3156 || update_flags
== TODO_update_ssa_full_phi
3157 || update_flags
== TODO_update_ssa_only_virtuals
);
3159 if (!need_ssa_update_p (cfun
))
3162 timevar_push (TV_TREE_SSA_INCREMENTAL
);
3164 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3165 fprintf (dump_file
, "\nUpdating SSA:\n");
3167 if (!update_ssa_initialized_fn
)
3168 init_update_ssa (cfun
);
3169 else if (update_flags
== TODO_update_ssa_only_virtuals
)
3171 /* If we only need to update virtuals, remove all the mappings for
3172 real names before proceeding. The caller is responsible for
3173 having dealt with the name mappings before calling update_ssa. */
3174 bitmap_clear (old_ssa_names
);
3175 bitmap_clear (new_ssa_names
);
3178 gcc_assert (update_ssa_initialized_fn
== cfun
);
3180 blocks_with_phis_to_rewrite
= BITMAP_ALLOC (NULL
);
3181 if (!phis_to_rewrite
.exists ())
3182 phis_to_rewrite
.create (last_basic_block
+ 1);
3183 blocks_to_update
= BITMAP_ALLOC (NULL
);
3185 /* Ensure that the dominance information is up-to-date. */
3186 calculate_dominance_info (CDI_DOMINATORS
);
3188 insert_phi_p
= (update_flags
!= TODO_update_ssa_no_phi
);
3190 /* If there are names defined in the replacement table, prepare
3191 definition and use sites for all the names in NEW_SSA_NAMES and
3193 if (bitmap_first_set_bit (new_ssa_names
) >= 0)
3195 prepare_names_to_update (insert_phi_p
);
3197 /* If all the names in NEW_SSA_NAMES had been marked for
3198 removal, and there are no symbols to rename, then there's
3199 nothing else to do. */
3200 if (bitmap_first_set_bit (new_ssa_names
) < 0
3201 && !cfun
->gimple_df
->ssa_renaming_needed
)
3205 /* Next, determine the block at which to start the renaming process. */
3206 if (cfun
->gimple_df
->ssa_renaming_needed
)
3208 /* If we rename bare symbols initialize the mapping to
3209 auxiliar info we need to keep track of. */
3210 var_infos
.create (47);
3212 /* If we have to rename some symbols from scratch, we need to
3213 start the process at the root of the CFG. FIXME, it should
3214 be possible to determine the nearest block that had a
3215 definition for each of the symbols that are marked for
3216 updating. For now this seems more work than it's worth. */
3217 start_bb
= ENTRY_BLOCK_PTR_FOR_FN (cfun
);
3219 /* Traverse the CFG looking for existing definitions and uses of
3220 symbols in SSA operands. Mark interesting blocks and
3221 statements and set local live-in information for the PHI
3222 placement heuristics. */
3223 prepare_block_for_update (start_bb
, insert_phi_p
);
3225 #ifdef ENABLE_CHECKING
3226 for (i
= 1; i
< num_ssa_names
; ++i
)
3228 tree name
= ssa_name (i
);
3230 || virtual_operand_p (name
))
3233 /* For all but virtual operands, which do not have SSA names
3234 with overlapping life ranges, ensure that symbols marked
3235 for renaming do not have existing SSA names associated with
3236 them as we do not re-write them out-of-SSA before going
3237 into SSA for the remaining symbol uses. */
3238 if (marked_for_renaming (SSA_NAME_VAR (name
)))
3240 fprintf (stderr
, "Existing SSA name for symbol marked for "
3242 print_generic_expr (stderr
, name
, TDF_SLIM
);
3243 fprintf (stderr
, "\n");
3244 internal_error ("SSA corruption");
3251 /* Otherwise, the entry block to the region is the nearest
3252 common dominator for the blocks in BLOCKS. */
3253 start_bb
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3257 /* If requested, insert PHI nodes at the iterated dominance frontier
3258 of every block, creating new definitions for names in OLD_SSA_NAMES
3259 and for symbols found. */
3264 /* If the caller requested PHI nodes to be added, compute
3265 dominance frontiers. */
3266 dfs
= XNEWVEC (bitmap_head
, last_basic_block
);
3268 bitmap_initialize (&dfs
[bb
->index
], &bitmap_default_obstack
);
3269 compute_dominance_frontiers (dfs
);
3271 if (bitmap_first_set_bit (old_ssa_names
) >= 0)
3273 sbitmap_iterator sbi
;
3275 /* insert_update_phi_nodes_for will call add_new_name_mapping
3276 when inserting new PHI nodes, so the set OLD_SSA_NAMES
3277 will grow while we are traversing it (but it will not
3278 gain any new members). Copy OLD_SSA_NAMES to a temporary
3280 sbitmap tmp
= sbitmap_alloc (SBITMAP_SIZE (old_ssa_names
));
3281 bitmap_copy (tmp
, old_ssa_names
);
3282 EXECUTE_IF_SET_IN_BITMAP (tmp
, 0, i
, sbi
)
3283 insert_updated_phi_nodes_for (ssa_name (i
), dfs
, blocks_to_update
,
3288 symbols_to_rename
.qsort (insert_updated_phi_nodes_compare_uids
);
3289 FOR_EACH_VEC_ELT (symbols_to_rename
, i
, sym
)
3290 insert_updated_phi_nodes_for (sym
, dfs
, blocks_to_update
,
3294 bitmap_clear (&dfs
[bb
->index
]);
3297 /* Insertion of PHI nodes may have added blocks to the region.
3298 We need to re-compute START_BB to include the newly added
3300 if (start_bb
!= ENTRY_BLOCK_PTR_FOR_FN (cfun
))
3301 start_bb
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3305 /* Reset the current definition for name and symbol before renaming
3307 EXECUTE_IF_SET_IN_BITMAP (old_ssa_names
, 0, i
, sbi
)
3308 get_ssa_name_ann (ssa_name (i
))->info
.current_def
= NULL_TREE
;
3310 FOR_EACH_VEC_ELT (symbols_to_rename
, i
, sym
)
3311 get_var_info (sym
)->info
.current_def
= NULL_TREE
;
3313 /* Now start the renaming process at START_BB. */
3314 interesting_blocks
= sbitmap_alloc (last_basic_block
);
3315 bitmap_clear (interesting_blocks
);
3316 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3317 bitmap_set_bit (interesting_blocks
, i
);
3319 rewrite_blocks (start_bb
, REWRITE_UPDATE
);
3321 sbitmap_free (interesting_blocks
);
3323 /* Debugging dumps. */
3329 dump_update_ssa (dump_file
);
3331 fprintf (dump_file
, "Incremental SSA update started at block: %d\n",
3335 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3337 fprintf (dump_file
, "Number of blocks in CFG: %d\n", last_basic_block
);
3338 fprintf (dump_file
, "Number of blocks to update: %d (%3.0f%%)\n",
3339 c
, PERCENT (c
, last_basic_block
));
3341 if (dump_flags
& TDF_DETAILS
)
3343 fprintf (dump_file
, "Affected blocks:");
3344 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3345 fprintf (dump_file
, " %u", i
);
3346 fprintf (dump_file
, "\n");
3349 fprintf (dump_file
, "\n\n");
3352 /* Free allocated memory. */
3354 delete_update_ssa ();
3356 timevar_pop (TV_TREE_SSA_INCREMENTAL
);