1 /* Rewrite a program in Normal form into SSA.
2 Copyright (C) 2001-2014 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"
32 #include "hash-table.h"
33 #include "tree-ssa-alias.h"
34 #include "internal-fn.h"
35 #include "gimple-expr.h"
38 #include "gimple-iterator.h"
39 #include "gimple-ssa.h"
41 #include "tree-phinodes.h"
42 #include "ssa-iterators.h"
43 #include "stringpool.h"
44 #include "tree-ssanames.h"
45 #include "tree-into-ssa.h"
49 #include "tree-inline.h"
50 #include "tree-pass.h"
54 #include "diagnostic-core.h"
55 #include "tree-into-ssa.h"
57 #define PERCENT(x,y) ((float)(x) * 100.0 / (float)(y))
59 /* This file builds the SSA form for a function as described in:
60 R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently
61 Computing Static Single Assignment Form and the Control Dependence
62 Graph. ACM Transactions on Programming Languages and Systems,
63 13(4):451-490, October 1991. */
65 /* Structure to map a variable VAR to the set of blocks that contain
66 definitions for VAR. */
69 /* Blocks that contain definitions of VAR. Bit I will be set if the
70 Ith block contains a definition of VAR. */
73 /* Blocks that contain a PHI node for VAR. */
76 /* Blocks where VAR is live-on-entry. Similar semantics as
81 typedef struct def_blocks_d
*def_blocks_p
;
84 /* Stack of trees used to restore the global currdefs to its original
85 state after completing rewriting of a block and its dominator
86 children. Its elements have the following properties:
88 - An SSA_NAME (N) indicates that the current definition of the
89 underlying variable should be set to the given SSA_NAME. If the
90 symbol associated with the SSA_NAME is not a GIMPLE register, the
91 next slot in the stack must be a _DECL node (SYM). In this case,
92 the name N in the previous slot is the current reaching
95 - A _DECL node indicates that the underlying variable has no
98 - A NULL node at the top entry is used to mark the last slot
99 associated with the current block. */
100 static vec
<tree
> block_defs_stack
;
103 /* Set of existing SSA names being replaced by update_ssa. */
104 static sbitmap old_ssa_names
;
106 /* Set of new SSA names being added by update_ssa. Note that both
107 NEW_SSA_NAMES and OLD_SSA_NAMES are dense bitmaps because most of
108 the operations done on them are presence tests. */
109 static sbitmap new_ssa_names
;
111 static sbitmap interesting_blocks
;
113 /* Set of SSA names that have been marked to be released after they
114 were registered in the replacement table. They will be finally
115 released after we finish updating the SSA web. */
116 static bitmap names_to_release
;
118 /* vec of vec of PHIs to rewrite in a basic block. Element I corresponds
119 the to basic block with index I. Allocated once per compilation, *not*
120 released between different functions. */
121 static vec
<gimple_vec
> phis_to_rewrite
;
123 /* The bitmap of non-NULL elements of PHIS_TO_REWRITE. */
124 static bitmap blocks_with_phis_to_rewrite
;
126 /* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need
127 to grow as the callers to create_new_def_for will create new names on
129 FIXME. Currently set to 1/3 to avoid frequent reallocations but still
130 need to find a reasonable growth strategy. */
131 #define NAME_SETS_GROWTH_FACTOR (MAX (3, num_ssa_names / 3))
134 /* The function the SSA updating data structures have been initialized for.
135 NULL if they need to be initialized by create_new_def_for. */
136 static struct function
*update_ssa_initialized_fn
= NULL
;
138 /* Global data to attach to the main dominator walk structure. */
139 struct mark_def_sites_global_data
141 /* This bitmap contains the variables which are set before they
142 are used in a basic block. */
146 /* It is advantageous to avoid things like life analysis for variables which
147 do not need PHI nodes. This enum describes whether or not a particular
148 variable may need a PHI node. */
150 enum need_phi_state
{
151 /* This is the default. If we are still in this state after finding
152 all the definition and use sites, then we will assume the variable
153 needs PHI nodes. This is probably an overly conservative assumption. */
154 NEED_PHI_STATE_UNKNOWN
,
156 /* This state indicates that we have seen one or more sets of the
157 variable in a single basic block and that the sets dominate all
158 uses seen so far. If after finding all definition and use sites
159 we are still in this state, then the variable does not need any
163 /* This state indicates that we have either seen multiple definitions of
164 the variable in multiple blocks, or that we encountered a use in a
165 block that was not dominated by the block containing the set(s) of
166 this variable. This variable is assumed to need PHI nodes. */
170 /* Information stored for both SSA names and decls. */
173 /* This field indicates whether or not the variable may need PHI nodes.
174 See the enum's definition for more detailed information about the
176 ENUM_BITFIELD (need_phi_state
) need_phi_state
: 2;
178 /* The current reaching definition replacing this var. */
181 /* Definitions for this var. */
182 struct def_blocks_d def_blocks
;
185 /* The information associated with decls and SSA names. */
186 typedef struct common_info_d
*common_info_p
;
188 /* Information stored for decls. */
194 /* Information stored for both SSA names and decls. */
195 struct common_info_d info
;
198 /* The information associated with decls. */
199 typedef struct var_info_d
*var_info_p
;
202 /* VAR_INFOS hashtable helpers. */
204 struct var_info_hasher
: typed_free_remove
<var_info_d
>
206 typedef var_info_d value_type
;
207 typedef var_info_d compare_type
;
208 static inline hashval_t
hash (const value_type
*);
209 static inline bool equal (const value_type
*, const compare_type
*);
213 var_info_hasher::hash (const value_type
*p
)
215 return DECL_UID (p
->var
);
219 var_info_hasher::equal (const value_type
*p1
, const compare_type
*p2
)
221 return p1
->var
== p2
->var
;
225 /* Each entry in VAR_INFOS contains an element of type STRUCT
227 static hash_table
<var_info_hasher
> var_infos
;
230 /* Information stored for SSA names. */
233 /* Age of this record (so that info_for_ssa_name table can be cleared
234 quickly); if AGE < CURRENT_INFO_FOR_SSA_NAME_AGE, then the fields
235 are assumed to be null. */
238 /* Replacement mappings, allocated from update_ssa_obstack. */
241 /* Information stored for both SSA names and decls. */
242 struct common_info_d info
;
245 /* The information associated with names. */
246 typedef struct ssa_name_info
*ssa_name_info_p
;
248 static vec
<ssa_name_info_p
> info_for_ssa_name
;
249 static unsigned current_info_for_ssa_name_age
;
251 static bitmap_obstack update_ssa_obstack
;
253 /* The set of blocks affected by update_ssa. */
254 static bitmap blocks_to_update
;
256 /* The main entry point to the SSA renamer (rewrite_blocks) may be
257 called several times to do different, but related, tasks.
258 Initially, we need it to rename the whole program into SSA form.
259 At other times, we may need it to only rename into SSA newly
260 exposed symbols. Finally, we can also call it to incrementally fix
261 an already built SSA web. */
263 /* Convert the whole function into SSA form. */
266 /* Incrementally update the SSA web by replacing existing SSA
267 names with new ones. See update_ssa for details. */
271 /* The set of symbols we ought to re-write into SSA form in update_ssa. */
272 static bitmap symbols_to_rename_set
;
273 static vec
<tree
> symbols_to_rename
;
275 /* Mark SYM for renaming. */
278 mark_for_renaming (tree sym
)
280 if (!symbols_to_rename_set
)
281 symbols_to_rename_set
= BITMAP_ALLOC (NULL
);
282 if (bitmap_set_bit (symbols_to_rename_set
, DECL_UID (sym
)))
283 symbols_to_rename
.safe_push (sym
);
286 /* Return true if SYM is marked for renaming. */
289 marked_for_renaming (tree sym
)
291 if (!symbols_to_rename_set
|| sym
== NULL_TREE
)
293 return bitmap_bit_p (symbols_to_rename_set
, DECL_UID (sym
));
297 /* Return true if STMT needs to be rewritten. When renaming a subset
298 of the variables, not all statements will be processed. This is
299 decided in mark_def_sites. */
302 rewrite_uses_p (gimple stmt
)
304 return gimple_visited_p (stmt
);
308 /* Set the rewrite marker on STMT to the value given by REWRITE_P. */
311 set_rewrite_uses (gimple stmt
, bool rewrite_p
)
313 gimple_set_visited (stmt
, rewrite_p
);
317 /* Return true if the DEFs created by statement STMT should be
318 registered when marking new definition sites. This is slightly
319 different than rewrite_uses_p: it's used by update_ssa to
320 distinguish statements that need to have both uses and defs
321 processed from those that only need to have their defs processed.
322 Statements that define new SSA names only need to have their defs
323 registered, but they don't need to have their uses renamed. */
326 register_defs_p (gimple stmt
)
328 return gimple_plf (stmt
, GF_PLF_1
) != 0;
332 /* If REGISTER_DEFS_P is true, mark STMT to have its DEFs registered. */
335 set_register_defs (gimple stmt
, bool register_defs_p
)
337 gimple_set_plf (stmt
, GF_PLF_1
, register_defs_p
);
341 /* Get the information associated with NAME. */
343 static inline ssa_name_info_p
344 get_ssa_name_ann (tree name
)
346 unsigned ver
= SSA_NAME_VERSION (name
);
347 unsigned len
= info_for_ssa_name
.length ();
348 struct ssa_name_info
*info
;
350 /* Re-allocate the vector at most once per update/into-SSA. */
352 info_for_ssa_name
.safe_grow_cleared (num_ssa_names
);
354 /* But allocate infos lazily. */
355 info
= info_for_ssa_name
[ver
];
358 info
= XCNEW (struct ssa_name_info
);
359 info
->age
= current_info_for_ssa_name_age
;
360 info
->info
.need_phi_state
= NEED_PHI_STATE_UNKNOWN
;
361 info_for_ssa_name
[ver
] = info
;
364 if (info
->age
< current_info_for_ssa_name_age
)
366 info
->age
= current_info_for_ssa_name_age
;
367 info
->repl_set
= NULL
;
368 info
->info
.need_phi_state
= NEED_PHI_STATE_UNKNOWN
;
369 info
->info
.current_def
= NULL_TREE
;
370 info
->info
.def_blocks
.def_blocks
= NULL
;
371 info
->info
.def_blocks
.phi_blocks
= NULL
;
372 info
->info
.def_blocks
.livein_blocks
= NULL
;
378 /* Return and allocate the auxiliar information for DECL. */
380 static inline var_info_p
381 get_var_info (tree decl
)
383 struct var_info_d vi
;
386 slot
= var_infos
.find_slot_with_hash (&vi
, DECL_UID (decl
), INSERT
);
389 var_info_p v
= XCNEW (struct var_info_d
);
398 /* Clears info for SSA names. */
401 clear_ssa_name_info (void)
403 current_info_for_ssa_name_age
++;
405 /* If current_info_for_ssa_name_age wraps we use stale information.
406 Asser that this does not happen. */
407 gcc_assert (current_info_for_ssa_name_age
!= 0);
411 /* Get access to the auxiliar information stored per SSA name or decl. */
413 static inline common_info_p
414 get_common_info (tree var
)
416 if (TREE_CODE (var
) == SSA_NAME
)
417 return &get_ssa_name_ann (var
)->info
;
419 return &get_var_info (var
)->info
;
423 /* Return the current definition for VAR. */
426 get_current_def (tree var
)
428 return get_common_info (var
)->current_def
;
432 /* Sets current definition of VAR to DEF. */
435 set_current_def (tree var
, tree def
)
437 get_common_info (var
)->current_def
= def
;
440 /* Cleans up the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags for
441 all statements in basic block BB. */
444 initialize_flags_in_bb (basic_block bb
)
447 gimple_stmt_iterator gsi
;
449 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
451 gimple phi
= gsi_stmt (gsi
);
452 set_rewrite_uses (phi
, false);
453 set_register_defs (phi
, false);
456 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
458 stmt
= gsi_stmt (gsi
);
460 /* We are going to use the operand cache API, such as
461 SET_USE, SET_DEF, and FOR_EACH_IMM_USE_FAST. The operand
462 cache for each statement should be up-to-date. */
463 gcc_checking_assert (!gimple_modified_p (stmt
));
464 set_rewrite_uses (stmt
, false);
465 set_register_defs (stmt
, false);
469 /* Mark block BB as interesting for update_ssa. */
472 mark_block_for_update (basic_block bb
)
474 gcc_checking_assert (blocks_to_update
!= NULL
);
475 if (!bitmap_set_bit (blocks_to_update
, bb
->index
))
477 initialize_flags_in_bb (bb
);
480 /* Return the set of blocks where variable VAR is defined and the blocks
481 where VAR is live on entry (livein). If no entry is found in
482 DEF_BLOCKS, a new one is created and returned. */
484 static inline struct def_blocks_d
*
485 get_def_blocks_for (common_info_p info
)
487 struct def_blocks_d
*db_p
= &info
->def_blocks
;
488 if (!db_p
->def_blocks
)
490 db_p
->def_blocks
= BITMAP_ALLOC (&update_ssa_obstack
);
491 db_p
->phi_blocks
= BITMAP_ALLOC (&update_ssa_obstack
);
492 db_p
->livein_blocks
= BITMAP_ALLOC (&update_ssa_obstack
);
499 /* Mark block BB as the definition site for variable VAR. PHI_P is true if
500 VAR is defined by a PHI node. */
503 set_def_block (tree var
, basic_block bb
, bool phi_p
)
505 struct def_blocks_d
*db_p
;
508 info
= get_common_info (var
);
509 db_p
= get_def_blocks_for (info
);
511 /* Set the bit corresponding to the block where VAR is defined. */
512 bitmap_set_bit (db_p
->def_blocks
, bb
->index
);
514 bitmap_set_bit (db_p
->phi_blocks
, bb
->index
);
516 /* Keep track of whether or not we may need to insert PHI nodes.
518 If we are in the UNKNOWN state, then this is the first definition
519 of VAR. Additionally, we have not seen any uses of VAR yet, so
520 we do not need a PHI node for this variable at this time (i.e.,
521 transition to NEED_PHI_STATE_NO).
523 If we are in any other state, then we either have multiple definitions
524 of this variable occurring in different blocks or we saw a use of the
525 variable which was not dominated by the block containing the
526 definition(s). In this case we may need a PHI node, so enter
527 state NEED_PHI_STATE_MAYBE. */
528 if (info
->need_phi_state
== NEED_PHI_STATE_UNKNOWN
)
529 info
->need_phi_state
= NEED_PHI_STATE_NO
;
531 info
->need_phi_state
= NEED_PHI_STATE_MAYBE
;
535 /* Mark block BB as having VAR live at the entry to BB. */
538 set_livein_block (tree var
, basic_block bb
)
541 struct def_blocks_d
*db_p
;
543 info
= get_common_info (var
);
544 db_p
= get_def_blocks_for (info
);
546 /* Set the bit corresponding to the block where VAR is live in. */
547 bitmap_set_bit (db_p
->livein_blocks
, bb
->index
);
549 /* Keep track of whether or not we may need to insert PHI nodes.
551 If we reach here in NEED_PHI_STATE_NO, see if this use is dominated
552 by the single block containing the definition(s) of this variable. If
553 it is, then we remain in NEED_PHI_STATE_NO, otherwise we transition to
554 NEED_PHI_STATE_MAYBE. */
555 if (info
->need_phi_state
== NEED_PHI_STATE_NO
)
557 int def_block_index
= bitmap_first_set_bit (db_p
->def_blocks
);
559 if (def_block_index
== -1
560 || ! dominated_by_p (CDI_DOMINATORS
, bb
,
561 BASIC_BLOCK_FOR_FN (cfun
, def_block_index
)))
562 info
->need_phi_state
= NEED_PHI_STATE_MAYBE
;
565 info
->need_phi_state
= NEED_PHI_STATE_MAYBE
;
569 /* Return true if NAME is in OLD_SSA_NAMES. */
572 is_old_name (tree name
)
574 unsigned ver
= SSA_NAME_VERSION (name
);
577 return (ver
< SBITMAP_SIZE (new_ssa_names
)
578 && bitmap_bit_p (old_ssa_names
, ver
));
582 /* Return true if NAME is in NEW_SSA_NAMES. */
585 is_new_name (tree name
)
587 unsigned ver
= SSA_NAME_VERSION (name
);
590 return (ver
< SBITMAP_SIZE (new_ssa_names
)
591 && bitmap_bit_p (new_ssa_names
, ver
));
595 /* Return the names replaced by NEW_TREE (i.e., REPL_TBL[NEW_TREE].SET). */
598 names_replaced_by (tree new_tree
)
600 return get_ssa_name_ann (new_tree
)->repl_set
;
604 /* Add OLD to REPL_TBL[NEW_TREE].SET. */
607 add_to_repl_tbl (tree new_tree
, tree old
)
609 bitmap
*set
= &get_ssa_name_ann (new_tree
)->repl_set
;
611 *set
= BITMAP_ALLOC (&update_ssa_obstack
);
612 bitmap_set_bit (*set
, SSA_NAME_VERSION (old
));
616 /* Add a new mapping NEW_TREE -> OLD REPL_TBL. Every entry N_i in REPL_TBL
617 represents the set of names O_1 ... O_j replaced by N_i. This is
618 used by update_ssa and its helpers to introduce new SSA names in an
619 already formed SSA web. */
622 add_new_name_mapping (tree new_tree
, tree old
)
624 /* OLD and NEW_TREE must be different SSA names for the same symbol. */
625 gcc_checking_assert (new_tree
!= old
626 && SSA_NAME_VAR (new_tree
) == SSA_NAME_VAR (old
));
628 /* We may need to grow NEW_SSA_NAMES and OLD_SSA_NAMES because our
629 caller may have created new names since the set was created. */
630 if (SBITMAP_SIZE (new_ssa_names
) <= num_ssa_names
- 1)
632 unsigned int new_sz
= num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
;
633 new_ssa_names
= sbitmap_resize (new_ssa_names
, new_sz
, 0);
634 old_ssa_names
= sbitmap_resize (old_ssa_names
, new_sz
, 0);
637 /* Update the REPL_TBL table. */
638 add_to_repl_tbl (new_tree
, old
);
640 /* If OLD had already been registered as a new name, then all the
641 names that OLD replaces should also be replaced by NEW_TREE. */
642 if (is_new_name (old
))
643 bitmap_ior_into (names_replaced_by (new_tree
), names_replaced_by (old
));
645 /* Register NEW_TREE and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES,
647 bitmap_set_bit (new_ssa_names
, SSA_NAME_VERSION (new_tree
));
648 bitmap_set_bit (old_ssa_names
, SSA_NAME_VERSION (old
));
652 /* Call back for walk_dominator_tree used to collect definition sites
653 for every variable in the function. For every statement S in block
656 1- Variables defined by S in the DEFS of S are marked in the bitmap
659 2- If S uses a variable VAR and there is no preceding kill of VAR,
660 then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR.
662 This information is used to determine which variables are live
663 across block boundaries to reduce the number of PHI nodes
667 mark_def_sites (basic_block bb
, gimple stmt
, bitmap kills
)
673 /* Since this is the first time that we rewrite the program into SSA
674 form, force an operand scan on every statement. */
677 gcc_checking_assert (blocks_to_update
== NULL
);
678 set_register_defs (stmt
, false);
679 set_rewrite_uses (stmt
, false);
681 if (is_gimple_debug (stmt
))
683 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
685 tree sym
= USE_FROM_PTR (use_p
);
686 gcc_checking_assert (DECL_P (sym
));
687 set_rewrite_uses (stmt
, true);
689 if (rewrite_uses_p (stmt
))
690 bitmap_set_bit (interesting_blocks
, bb
->index
);
694 /* If a variable is used before being set, then the variable is live
695 across a block boundary, so mark it live-on-entry to BB. */
696 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
698 tree sym
= USE_FROM_PTR (use_p
);
699 gcc_checking_assert (DECL_P (sym
));
700 if (!bitmap_bit_p (kills
, DECL_UID (sym
)))
701 set_livein_block (sym
, bb
);
702 set_rewrite_uses (stmt
, true);
705 /* Now process the defs. Mark BB as the definition block and add
706 each def to the set of killed symbols. */
707 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
709 gcc_checking_assert (DECL_P (def
));
710 set_def_block (def
, bb
, false);
711 bitmap_set_bit (kills
, DECL_UID (def
));
712 set_register_defs (stmt
, true);
715 /* If we found the statement interesting then also mark the block BB
717 if (rewrite_uses_p (stmt
) || register_defs_p (stmt
))
718 bitmap_set_bit (interesting_blocks
, bb
->index
);
721 /* Structure used by prune_unused_phi_nodes to record bounds of the intervals
722 in the dfs numbering of the dominance tree. */
726 /* Basic block whose index this entry corresponds to. */
729 /* The dfs number of this node. */
733 /* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback
737 cmp_dfsnum (const void *a
, const void *b
)
739 const struct dom_dfsnum
*const da
= (const struct dom_dfsnum
*) a
;
740 const struct dom_dfsnum
*const db
= (const struct dom_dfsnum
*) b
;
742 return (int) da
->dfs_num
- (int) db
->dfs_num
;
745 /* Among the intervals starting at the N points specified in DEFS, find
746 the one that contains S, and return its bb_index. */
749 find_dfsnum_interval (struct dom_dfsnum
*defs
, unsigned n
, unsigned s
)
751 unsigned f
= 0, t
= n
, m
;
756 if (defs
[m
].dfs_num
<= s
)
762 return defs
[f
].bb_index
;
765 /* Clean bits from PHIS for phi nodes whose value cannot be used in USES.
766 KILLS is a bitmap of blocks where the value is defined before any use. */
769 prune_unused_phi_nodes (bitmap phis
, bitmap kills
, bitmap uses
)
772 unsigned i
, b
, p
, u
, top
;
774 basic_block def_bb
, use_bb
;
778 struct dom_dfsnum
*defs
;
779 unsigned n_defs
, adef
;
781 if (bitmap_empty_p (uses
))
787 /* The phi must dominate a use, or an argument of a live phi. Also, we
788 do not create any phi nodes in def blocks, unless they are also livein. */
789 to_remove
= BITMAP_ALLOC (NULL
);
790 bitmap_and_compl (to_remove
, kills
, uses
);
791 bitmap_and_compl_into (phis
, to_remove
);
792 if (bitmap_empty_p (phis
))
794 BITMAP_FREE (to_remove
);
798 /* We want to remove the unnecessary phi nodes, but we do not want to compute
799 liveness information, as that may be linear in the size of CFG, and if
800 there are lot of different variables to rewrite, this may lead to quadratic
803 Instead, we basically emulate standard dce. We put all uses to worklist,
804 then for each of them find the nearest def that dominates them. If this
805 def is a phi node, we mark it live, and if it was not live before, we
806 add the predecessors of its basic block to the worklist.
808 To quickly locate the nearest def that dominates use, we use dfs numbering
809 of the dominance tree (that is already available in order to speed up
810 queries). For each def, we have the interval given by the dfs number on
811 entry to and on exit from the corresponding subtree in the dominance tree.
812 The nearest dominator for a given use is the smallest of these intervals
813 that contains entry and exit dfs numbers for the basic block with the use.
814 If we store the bounds for all the uses to an array and sort it, we can
815 locate the nearest dominating def in logarithmic time by binary search.*/
816 bitmap_ior (to_remove
, kills
, phis
);
817 n_defs
= bitmap_count_bits (to_remove
);
818 defs
= XNEWVEC (struct dom_dfsnum
, 2 * n_defs
+ 1);
819 defs
[0].bb_index
= 1;
822 EXECUTE_IF_SET_IN_BITMAP (to_remove
, 0, i
, bi
)
824 def_bb
= BASIC_BLOCK_FOR_FN (cfun
, i
);
825 defs
[adef
].bb_index
= i
;
826 defs
[adef
].dfs_num
= bb_dom_dfs_in (CDI_DOMINATORS
, def_bb
);
827 defs
[adef
+ 1].bb_index
= i
;
828 defs
[adef
+ 1].dfs_num
= bb_dom_dfs_out (CDI_DOMINATORS
, def_bb
);
831 BITMAP_FREE (to_remove
);
832 gcc_assert (adef
== 2 * n_defs
+ 1);
833 qsort (defs
, adef
, sizeof (struct dom_dfsnum
), cmp_dfsnum
);
834 gcc_assert (defs
[0].bb_index
== 1);
836 /* Now each DEFS entry contains the number of the basic block to that the
837 dfs number corresponds. Change them to the number of basic block that
838 corresponds to the interval following the dfs number. Also, for the
839 dfs_out numbers, increase the dfs number by one (so that it corresponds
840 to the start of the following interval, not to the end of the current
841 one). We use WORKLIST as a stack. */
842 auto_vec
<int> worklist (n_defs
+ 1);
843 worklist
.quick_push (1);
846 for (i
= 1; i
< adef
; i
++)
848 b
= defs
[i
].bb_index
;
851 /* This is a closing element. Interval corresponding to the top
852 of the stack after removing it follows. */
854 top
= worklist
[worklist
.length () - 1];
855 defs
[n_defs
].bb_index
= top
;
856 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
+ 1;
860 /* Opening element. Nothing to do, just push it to the stack and move
861 it to the correct position. */
862 defs
[n_defs
].bb_index
= defs
[i
].bb_index
;
863 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
;
864 worklist
.quick_push (b
);
868 /* If this interval starts at the same point as the previous one, cancel
870 if (defs
[n_defs
].dfs_num
== defs
[n_defs
- 1].dfs_num
)
871 defs
[n_defs
- 1].bb_index
= defs
[n_defs
].bb_index
;
876 gcc_assert (worklist
.is_empty ());
878 /* Now process the uses. */
879 live_phis
= BITMAP_ALLOC (NULL
);
880 EXECUTE_IF_SET_IN_BITMAP (uses
, 0, i
, bi
)
882 worklist
.safe_push (i
);
885 while (!worklist
.is_empty ())
888 if (b
== ENTRY_BLOCK
)
891 /* If there is a phi node in USE_BB, it is made live. Otherwise,
892 find the def that dominates the immediate dominator of USE_BB
893 (the kill in USE_BB does not dominate the use). */
894 if (bitmap_bit_p (phis
, b
))
898 use_bb
= get_immediate_dominator (CDI_DOMINATORS
,
899 BASIC_BLOCK_FOR_FN (cfun
, b
));
900 p
= find_dfsnum_interval (defs
, n_defs
,
901 bb_dom_dfs_in (CDI_DOMINATORS
, use_bb
));
902 if (!bitmap_bit_p (phis
, p
))
906 /* If the phi node is already live, there is nothing to do. */
907 if (!bitmap_set_bit (live_phis
, p
))
910 /* Add the new uses to the worklist. */
911 def_bb
= BASIC_BLOCK_FOR_FN (cfun
, p
);
912 FOR_EACH_EDGE (e
, ei
, def_bb
->preds
)
915 if (bitmap_bit_p (uses
, u
))
918 /* In case there is a kill directly in the use block, do not record
919 the use (this is also necessary for correctness, as we assume that
920 uses dominated by a def directly in their block have been filtered
922 if (bitmap_bit_p (kills
, u
))
925 bitmap_set_bit (uses
, u
);
926 worklist
.safe_push (u
);
930 bitmap_copy (phis
, live_phis
);
931 BITMAP_FREE (live_phis
);
935 /* Return the set of blocks where variable VAR is defined and the blocks
936 where VAR is live on entry (livein). Return NULL, if no entry is
937 found in DEF_BLOCKS. */
939 static inline struct def_blocks_d
*
940 find_def_blocks_for (tree var
)
942 def_blocks_p p
= &get_common_info (var
)->def_blocks
;
949 /* Marks phi node PHI in basic block BB for rewrite. */
952 mark_phi_for_rewrite (basic_block bb
, gimple phi
)
955 unsigned n
, idx
= bb
->index
;
957 if (rewrite_uses_p (phi
))
960 set_rewrite_uses (phi
, true);
962 if (!blocks_with_phis_to_rewrite
)
965 bitmap_set_bit (blocks_with_phis_to_rewrite
, idx
);
967 n
= (unsigned) last_basic_block_for_fn (cfun
) + 1;
968 if (phis_to_rewrite
.length () < n
)
969 phis_to_rewrite
.safe_grow_cleared (n
);
971 phis
= phis_to_rewrite
[idx
];
974 phis
.safe_push (phi
);
975 phis_to_rewrite
[idx
] = phis
;
978 /* Insert PHI nodes for variable VAR using the iterated dominance
979 frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
980 function assumes that the caller is incrementally updating the
981 existing SSA form, in which case VAR may be an SSA name instead of
984 PHI_INSERTION_POINTS is updated to reflect nodes that already had a
985 PHI node for VAR. On exit, only the nodes that received a PHI node
986 for VAR will be present in PHI_INSERTION_POINTS. */
989 insert_phi_nodes_for (tree var
, bitmap phi_insertion_points
, bool update_p
)
996 struct def_blocks_d
*def_map
= find_def_blocks_for (var
);
998 /* Remove the blocks where we already have PHI nodes for VAR. */
999 bitmap_and_compl_into (phi_insertion_points
, def_map
->phi_blocks
);
1001 /* Remove obviously useless phi nodes. */
1002 prune_unused_phi_nodes (phi_insertion_points
, def_map
->def_blocks
,
1003 def_map
->livein_blocks
);
1005 /* And insert the PHI nodes. */
1006 EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points
, 0, bb_index
, bi
)
1008 bb
= BASIC_BLOCK_FOR_FN (cfun
, bb_index
);
1010 mark_block_for_update (bb
);
1012 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1014 fprintf (dump_file
, "creating PHI node in block #%d for ", bb_index
);
1015 print_generic_expr (dump_file
, var
, TDF_SLIM
);
1016 fprintf (dump_file
, "\n");
1020 if (TREE_CODE (var
) == SSA_NAME
)
1022 /* If we are rewriting SSA names, create the LHS of the PHI
1023 node by duplicating VAR. This is useful in the case of
1024 pointers, to also duplicate pointer attributes (alias
1025 information, in particular). */
1029 gcc_checking_assert (update_p
);
1030 new_lhs
= duplicate_ssa_name (var
, NULL
);
1031 phi
= create_phi_node (new_lhs
, bb
);
1032 add_new_name_mapping (new_lhs
, var
);
1034 /* Add VAR to every argument slot of PHI. We need VAR in
1035 every argument so that rewrite_update_phi_arguments knows
1036 which name is this PHI node replacing. If VAR is a
1037 symbol marked for renaming, this is not necessary, the
1038 renamer will use the symbol on the LHS to get its
1039 reaching definition. */
1040 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1041 add_phi_arg (phi
, var
, e
, UNKNOWN_LOCATION
);
1047 gcc_checking_assert (DECL_P (var
));
1048 phi
= create_phi_node (var
, bb
);
1050 tracked_var
= target_for_debug_bind (var
);
1053 gimple note
= gimple_build_debug_bind (tracked_var
,
1056 gimple_stmt_iterator si
= gsi_after_labels (bb
);
1057 gsi_insert_before (&si
, note
, GSI_SAME_STMT
);
1061 /* Mark this PHI node as interesting for update_ssa. */
1062 set_register_defs (phi
, true);
1063 mark_phi_for_rewrite (bb
, phi
);
1067 /* Sort var_infos after DECL_UID of their var. */
1070 insert_phi_nodes_compare_var_infos (const void *a
, const void *b
)
1072 const struct var_info_d
*defa
= *(struct var_info_d
* const *)a
;
1073 const struct var_info_d
*defb
= *(struct var_info_d
* const *)b
;
1074 if (DECL_UID (defa
->var
) < DECL_UID (defb
->var
))
1080 /* Insert PHI nodes at the dominance frontier of blocks with variable
1081 definitions. DFS contains the dominance frontier information for
1085 insert_phi_nodes (bitmap_head
*dfs
)
1087 hash_table
<var_info_hasher
>::iterator hi
;
1091 timevar_push (TV_TREE_INSERT_PHI_NODES
);
1093 auto_vec
<var_info_p
> vars (var_infos
.elements ());
1094 FOR_EACH_HASH_TABLE_ELEMENT (var_infos
, info
, var_info_p
, hi
)
1095 if (info
->info
.need_phi_state
!= NEED_PHI_STATE_NO
)
1096 vars
.quick_push (info
);
1098 /* Do two stages to avoid code generation differences for UID
1099 differences but no UID ordering differences. */
1100 vars
.qsort (insert_phi_nodes_compare_var_infos
);
1102 FOR_EACH_VEC_ELT (vars
, i
, info
)
1104 bitmap idf
= compute_idf (info
->info
.def_blocks
.def_blocks
, dfs
);
1105 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_for_fn (cfun
));
2319 bitmap_clear (interesting_blocks
);
2321 /* Initialize dominance frontier. */
2322 dfs
= XNEWVEC (bitmap_head
, last_basic_block_for_fn (cfun
));
2323 FOR_EACH_BB_FN (bb
, cfun
)
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. */
2340 FOR_EACH_BB_FN (bb
, cfun
)
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_execute */
2385 TV_TREE_SSA_OTHER
, /* tv_id */
2386 PROP_cfg
, /* properties_required */
2387 PROP_ssa
, /* properties_provided */
2388 0, /* properties_destroyed */
2389 0, /* todo_flags_start */
2390 ( TODO_verify_ssa
| TODO_remove_unused_locals
), /* todo_flags_finish */
2393 class pass_build_ssa
: public gimple_opt_pass
2396 pass_build_ssa (gcc::context
*ctxt
)
2397 : gimple_opt_pass (pass_data_build_ssa
, ctxt
)
2400 /* opt_pass methods: */
2401 bool gate () { return gate_into_ssa (); }
2402 unsigned int execute () { return rewrite_into_ssa (); }
2404 }; // class pass_build_ssa
2409 make_pass_build_ssa (gcc::context
*ctxt
)
2411 return new pass_build_ssa (ctxt
);
2415 /* Mark the definition of VAR at STMT and BB as interesting for the
2416 renamer. BLOCKS is the set of blocks that need updating. */
2419 mark_def_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2421 gcc_checking_assert (bitmap_bit_p (blocks_to_update
, bb
->index
));
2422 set_register_defs (stmt
, true);
2426 bool is_phi_p
= gimple_code (stmt
) == GIMPLE_PHI
;
2428 set_def_block (var
, bb
, is_phi_p
);
2430 /* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition
2431 site for both itself and all the old names replaced by it. */
2432 if (TREE_CODE (var
) == SSA_NAME
&& is_new_name (var
))
2436 bitmap set
= names_replaced_by (var
);
2438 EXECUTE_IF_SET_IN_BITMAP (set
, 0, i
, bi
)
2439 set_def_block (ssa_name (i
), bb
, is_phi_p
);
2445 /* Mark the use of VAR at STMT and BB as interesting for the
2446 renamer. INSERT_PHI_P is true if we are going to insert new PHI
2450 mark_use_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2452 basic_block def_bb
= gimple_bb (stmt
);
2454 mark_block_for_update (def_bb
);
2455 mark_block_for_update (bb
);
2457 if (gimple_code (stmt
) == GIMPLE_PHI
)
2458 mark_phi_for_rewrite (def_bb
, stmt
);
2461 set_rewrite_uses (stmt
, true);
2463 if (is_gimple_debug (stmt
))
2467 /* If VAR has not been defined in BB, then it is live-on-entry
2468 to BB. Note that we cannot just use the block holding VAR's
2469 definition because if VAR is one of the names in OLD_SSA_NAMES,
2470 it will have several definitions (itself and all the names that
2474 struct def_blocks_d
*db_p
= get_def_blocks_for (get_common_info (var
));
2475 if (!bitmap_bit_p (db_p
->def_blocks
, bb
->index
))
2476 set_livein_block (var
, bb
);
2481 /* Do a dominator walk starting at BB processing statements that
2482 reference symbols in SSA operands. This is very similar to
2483 mark_def_sites, but the scan handles statements whose operands may
2484 already be SSA names.
2486 If INSERT_PHI_P is true, mark those uses as live in the
2487 corresponding block. This is later used by the PHI placement
2488 algorithm to make PHI pruning decisions.
2490 FIXME. Most of this would be unnecessary if we could associate a
2491 symbol to all the SSA names that reference it. But that
2492 sounds like it would be expensive to maintain. Still, it
2493 would be interesting to see if it makes better sense to do
2497 prepare_block_for_update (basic_block bb
, bool insert_phi_p
)
2500 gimple_stmt_iterator si
;
2504 mark_block_for_update (bb
);
2506 /* Process PHI nodes marking interesting those that define or use
2507 the symbols that we are interested in. */
2508 for (si
= gsi_start_phis (bb
); !gsi_end_p (si
); gsi_next (&si
))
2510 gimple phi
= gsi_stmt (si
);
2511 tree lhs_sym
, lhs
= gimple_phi_result (phi
);
2513 if (TREE_CODE (lhs
) == SSA_NAME
2514 && (! virtual_operand_p (lhs
)
2515 || ! cfun
->gimple_df
->rename_vops
))
2518 lhs_sym
= DECL_P (lhs
) ? lhs
: SSA_NAME_VAR (lhs
);
2519 mark_for_renaming (lhs_sym
);
2520 mark_def_interesting (lhs_sym
, phi
, bb
, insert_phi_p
);
2522 /* Mark the uses in phi nodes as interesting. It would be more correct
2523 to process the arguments of the phi nodes of the successor edges of
2524 BB at the end of prepare_block_for_update, however, that turns out
2525 to be significantly more expensive. Doing it here is conservatively
2526 correct -- it may only cause us to believe a value to be live in a
2527 block that also contains its definition, and thus insert a few more
2528 phi nodes for it. */
2529 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
2530 mark_use_interesting (lhs_sym
, phi
, e
->src
, insert_phi_p
);
2533 /* Process the statements. */
2534 for (si
= gsi_start_bb (bb
); !gsi_end_p (si
); gsi_next (&si
))
2538 use_operand_p use_p
;
2539 def_operand_p def_p
;
2541 stmt
= gsi_stmt (si
);
2543 if (cfun
->gimple_df
->rename_vops
2544 && gimple_vuse (stmt
))
2546 tree use
= gimple_vuse (stmt
);
2547 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
2548 mark_for_renaming (sym
);
2549 mark_use_interesting (sym
, stmt
, bb
, insert_phi_p
);
2552 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, i
, SSA_OP_USE
)
2554 tree use
= USE_FROM_PTR (use_p
);
2557 mark_for_renaming (use
);
2558 mark_use_interesting (use
, stmt
, bb
, insert_phi_p
);
2561 if (cfun
->gimple_df
->rename_vops
2562 && gimple_vdef (stmt
))
2564 tree def
= gimple_vdef (stmt
);
2565 tree sym
= DECL_P (def
) ? def
: SSA_NAME_VAR (def
);
2566 mark_for_renaming (sym
);
2567 mark_def_interesting (sym
, stmt
, bb
, insert_phi_p
);
2570 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, i
, SSA_OP_DEF
)
2572 tree def
= DEF_FROM_PTR (def_p
);
2575 mark_for_renaming (def
);
2576 mark_def_interesting (def
, stmt
, bb
, insert_phi_p
);
2580 /* Now visit all the blocks dominated by BB. */
2581 for (son
= first_dom_son (CDI_DOMINATORS
, bb
);
2583 son
= next_dom_son (CDI_DOMINATORS
, son
))
2584 prepare_block_for_update (son
, insert_phi_p
);
2588 /* Helper for prepare_names_to_update. Mark all the use sites for
2589 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2590 prepare_names_to_update. */
2593 prepare_use_sites_for (tree name
, bool insert_phi_p
)
2595 use_operand_p use_p
;
2596 imm_use_iterator iter
;
2598 FOR_EACH_IMM_USE_FAST (use_p
, iter
, name
)
2600 gimple stmt
= USE_STMT (use_p
);
2601 basic_block bb
= gimple_bb (stmt
);
2603 if (gimple_code (stmt
) == GIMPLE_PHI
)
2605 int ix
= PHI_ARG_INDEX_FROM_USE (use_p
);
2606 edge e
= gimple_phi_arg_edge (stmt
, ix
);
2607 mark_use_interesting (name
, stmt
, e
->src
, insert_phi_p
);
2611 /* For regular statements, mark this as an interesting use
2613 mark_use_interesting (name
, stmt
, bb
, insert_phi_p
);
2619 /* Helper for prepare_names_to_update. Mark the definition site for
2620 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2621 prepare_names_to_update. */
2624 prepare_def_site_for (tree name
, bool insert_phi_p
)
2629 gcc_checking_assert (names_to_release
== NULL
2630 || !bitmap_bit_p (names_to_release
,
2631 SSA_NAME_VERSION (name
)));
2633 stmt
= SSA_NAME_DEF_STMT (name
);
2634 bb
= gimple_bb (stmt
);
2637 gcc_checking_assert (bb
->index
< last_basic_block_for_fn (cfun
));
2638 mark_block_for_update (bb
);
2639 mark_def_interesting (name
, stmt
, bb
, insert_phi_p
);
2644 /* Mark definition and use sites of names in NEW_SSA_NAMES and
2645 OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert
2646 PHI nodes for newly created names. */
2649 prepare_names_to_update (bool insert_phi_p
)
2653 sbitmap_iterator sbi
;
2655 /* If a name N from NEW_SSA_NAMES is also marked to be released,
2656 remove it from NEW_SSA_NAMES so that we don't try to visit its
2657 defining basic block (which most likely doesn't exist). Notice
2658 that we cannot do the same with names in OLD_SSA_NAMES because we
2659 want to replace existing instances. */
2660 if (names_to_release
)
2661 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2662 bitmap_clear_bit (new_ssa_names
, i
);
2664 /* First process names in NEW_SSA_NAMES. Otherwise, uses of old
2665 names may be considered to be live-in on blocks that contain
2666 definitions for their replacements. */
2667 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names
, 0, i
, sbi
)
2668 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2670 /* If an old name is in NAMES_TO_RELEASE, we cannot remove it from
2671 OLD_SSA_NAMES, but we have to ignore its definition site. */
2672 EXECUTE_IF_SET_IN_BITMAP (old_ssa_names
, 0, i
, sbi
)
2674 if (names_to_release
== NULL
|| !bitmap_bit_p (names_to_release
, i
))
2675 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2676 prepare_use_sites_for (ssa_name (i
), insert_phi_p
);
2681 /* Dump all the names replaced by NAME to FILE. */
2684 dump_names_replaced_by (FILE *file
, tree name
)
2690 print_generic_expr (file
, name
, 0);
2691 fprintf (file
, " -> { ");
2693 old_set
= names_replaced_by (name
);
2694 EXECUTE_IF_SET_IN_BITMAP (old_set
, 0, i
, bi
)
2696 print_generic_expr (file
, ssa_name (i
), 0);
2697 fprintf (file
, " ");
2700 fprintf (file
, "}\n");
2704 /* Dump all the names replaced by NAME to stderr. */
2707 debug_names_replaced_by (tree name
)
2709 dump_names_replaced_by (stderr
, name
);
2713 /* Dump SSA update information to FILE. */
2716 dump_update_ssa (FILE *file
)
2721 if (!need_ssa_update_p (cfun
))
2724 if (new_ssa_names
&& bitmap_first_set_bit (new_ssa_names
) >= 0)
2726 sbitmap_iterator sbi
;
2728 fprintf (file
, "\nSSA replacement table\n");
2729 fprintf (file
, "N_i -> { O_1 ... O_j } means that N_i replaces "
2730 "O_1, ..., O_j\n\n");
2732 EXECUTE_IF_SET_IN_BITMAP (new_ssa_names
, 0, i
, sbi
)
2733 dump_names_replaced_by (file
, ssa_name (i
));
2736 if (symbols_to_rename_set
&& !bitmap_empty_p (symbols_to_rename_set
))
2738 fprintf (file
, "\nSymbols to be put in SSA form\n");
2739 dump_decl_set (file
, symbols_to_rename_set
);
2740 fprintf (file
, "\n");
2743 if (names_to_release
&& !bitmap_empty_p (names_to_release
))
2745 fprintf (file
, "\nSSA names to release after updating the SSA web\n\n");
2746 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2748 print_generic_expr (file
, ssa_name (i
), 0);
2749 fprintf (file
, " ");
2751 fprintf (file
, "\n");
2756 /* Dump SSA update information to stderr. */
2759 debug_update_ssa (void)
2761 dump_update_ssa (stderr
);
2765 /* Initialize data structures used for incremental SSA updates. */
2768 init_update_ssa (struct function
*fn
)
2770 /* Reserve more space than the current number of names. The calls to
2771 add_new_name_mapping are typically done after creating new SSA
2772 names, so we'll need to reallocate these arrays. */
2773 old_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2774 bitmap_clear (old_ssa_names
);
2776 new_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2777 bitmap_clear (new_ssa_names
);
2779 bitmap_obstack_initialize (&update_ssa_obstack
);
2781 names_to_release
= NULL
;
2782 update_ssa_initialized_fn
= fn
;
2786 /* Deallocate data structures used for incremental SSA updates. */
2789 delete_update_ssa (void)
2794 sbitmap_free (old_ssa_names
);
2795 old_ssa_names
= NULL
;
2797 sbitmap_free (new_ssa_names
);
2798 new_ssa_names
= NULL
;
2800 BITMAP_FREE (symbols_to_rename_set
);
2801 symbols_to_rename_set
= NULL
;
2802 symbols_to_rename
.release ();
2804 if (names_to_release
)
2806 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2807 release_ssa_name (ssa_name (i
));
2808 BITMAP_FREE (names_to_release
);
2811 clear_ssa_name_info ();
2813 fini_ssa_renamer ();
2815 if (blocks_with_phis_to_rewrite
)
2816 EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite
, 0, i
, bi
)
2818 gimple_vec phis
= phis_to_rewrite
[i
];
2820 phis_to_rewrite
[i
].create (0);
2823 BITMAP_FREE (blocks_with_phis_to_rewrite
);
2824 BITMAP_FREE (blocks_to_update
);
2826 update_ssa_initialized_fn
= NULL
;
2830 /* Create a new name for OLD_NAME in statement STMT and replace the
2831 operand pointed to by DEF_P with the newly created name. If DEF_P
2832 is NULL then STMT should be a GIMPLE assignment.
2833 Return the new name and register the replacement mapping <NEW, OLD> in
2834 update_ssa's tables. */
2837 create_new_def_for (tree old_name
, gimple stmt
, def_operand_p def
)
2841 timevar_push (TV_TREE_SSA_INCREMENTAL
);
2843 if (!update_ssa_initialized_fn
)
2844 init_update_ssa (cfun
);
2846 gcc_assert (update_ssa_initialized_fn
== cfun
);
2848 new_name
= duplicate_ssa_name (old_name
, stmt
);
2850 SET_DEF (def
, new_name
);
2852 gimple_assign_set_lhs (stmt
, new_name
);
2854 if (gimple_code (stmt
) == GIMPLE_PHI
)
2856 basic_block bb
= gimple_bb (stmt
);
2858 /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
2859 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name
) = bb_has_abnormal_pred (bb
);
2862 add_new_name_mapping (new_name
, old_name
);
2864 /* For the benefit of passes that will be updating the SSA form on
2865 their own, set the current reaching definition of OLD_NAME to be
2867 get_ssa_name_ann (old_name
)->info
.current_def
= new_name
;
2869 timevar_pop (TV_TREE_SSA_INCREMENTAL
);
2875 /* Mark virtual operands of FN for renaming by update_ssa. */
2878 mark_virtual_operands_for_renaming (struct function
*fn
)
2880 fn
->gimple_df
->ssa_renaming_needed
= 1;
2881 fn
->gimple_df
->rename_vops
= 1;
2884 /* Replace all uses of NAME by underlying variable and mark it
2885 for renaming. This assumes the defining statement of NAME is
2886 going to be removed. */
2889 mark_virtual_operand_for_renaming (tree name
)
2891 tree name_var
= SSA_NAME_VAR (name
);
2893 imm_use_iterator iter
;
2894 use_operand_p use_p
;
2897 gcc_assert (VAR_DECL_IS_VIRTUAL_OPERAND (name_var
));
2898 FOR_EACH_IMM_USE_STMT (stmt
, iter
, name
)
2900 FOR_EACH_IMM_USE_ON_STMT (use_p
, iter
)
2901 SET_USE (use_p
, name_var
);
2905 mark_virtual_operands_for_renaming (cfun
);
2908 /* Replace all uses of the virtual PHI result by its underlying variable
2909 and mark it for renaming. This assumes the PHI node is going to be
2913 mark_virtual_phi_result_for_renaming (gimple phi
)
2915 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2917 fprintf (dump_file
, "Marking result for renaming : ");
2918 print_gimple_stmt (dump_file
, phi
, 0, TDF_SLIM
);
2919 fprintf (dump_file
, "\n");
2922 mark_virtual_operand_for_renaming (gimple_phi_result (phi
));
2925 /* Return true if there is any work to be done by update_ssa
2929 need_ssa_update_p (struct function
*fn
)
2931 gcc_assert (fn
!= NULL
);
2932 return (update_ssa_initialized_fn
== fn
2933 || (fn
->gimple_df
&& fn
->gimple_df
->ssa_renaming_needed
));
2936 /* Return true if name N has been registered in the replacement table. */
2939 name_registered_for_update_p (tree n ATTRIBUTE_UNUSED
)
2941 if (!update_ssa_initialized_fn
)
2944 gcc_assert (update_ssa_initialized_fn
== cfun
);
2946 return is_new_name (n
) || is_old_name (n
);
2950 /* Mark NAME to be released after update_ssa has finished. */
2953 release_ssa_name_after_update_ssa (tree name
)
2955 gcc_assert (cfun
&& update_ssa_initialized_fn
== cfun
);
2957 if (names_to_release
== NULL
)
2958 names_to_release
= BITMAP_ALLOC (NULL
);
2960 bitmap_set_bit (names_to_release
, SSA_NAME_VERSION (name
));
2964 /* Insert new PHI nodes to replace VAR. DFS contains dominance
2965 frontier information. BLOCKS is the set of blocks to be updated.
2967 This is slightly different than the regular PHI insertion
2968 algorithm. The value of UPDATE_FLAGS controls how PHI nodes for
2969 real names (i.e., GIMPLE registers) are inserted:
2971 - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI
2972 nodes inside the region affected by the block that defines VAR
2973 and the blocks that define all its replacements. All these
2974 definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS.
2976 First, we compute the entry point to the region (ENTRY). This is
2977 given by the nearest common dominator to all the definition
2978 blocks. When computing the iterated dominance frontier (IDF), any
2979 block not strictly dominated by ENTRY is ignored.
2981 We then call the standard PHI insertion algorithm with the pruned
2984 - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real
2985 names is not pruned. PHI nodes are inserted at every IDF block. */
2988 insert_updated_phi_nodes_for (tree var
, bitmap_head
*dfs
, bitmap blocks
,
2989 unsigned update_flags
)
2992 struct def_blocks_d
*db
;
2993 bitmap idf
, pruned_idf
;
2997 if (TREE_CODE (var
) == SSA_NAME
)
2998 gcc_checking_assert (is_old_name (var
));
3000 gcc_checking_assert (marked_for_renaming (var
));
3002 /* Get all the definition sites for VAR. */
3003 db
= find_def_blocks_for (var
);
3005 /* No need to do anything if there were no definitions to VAR. */
3006 if (db
== NULL
|| bitmap_empty_p (db
->def_blocks
))
3009 /* Compute the initial iterated dominance frontier. */
3010 idf
= compute_idf (db
->def_blocks
, dfs
);
3011 pruned_idf
= BITMAP_ALLOC (NULL
);
3013 if (TREE_CODE (var
) == SSA_NAME
)
3015 if (update_flags
== TODO_update_ssa
)
3017 /* If doing regular SSA updates for GIMPLE registers, we are
3018 only interested in IDF blocks dominated by the nearest
3019 common dominator of all the definition blocks. */
3020 entry
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3022 if (entry
!= ENTRY_BLOCK_PTR_FOR_FN (cfun
))
3023 EXECUTE_IF_SET_IN_BITMAP (idf
, 0, i
, bi
)
3024 if (BASIC_BLOCK_FOR_FN (cfun
, i
) != entry
3025 && dominated_by_p (CDI_DOMINATORS
,
3026 BASIC_BLOCK_FOR_FN (cfun
, 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_FOR_FN (cfun
, 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_for_fn (cfun
) + 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_for_fn (cfun
));
3272 FOR_EACH_BB_FN (bb
, cfun
)
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
,
3298 FOR_EACH_BB_FN (bb
, cfun
)
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_for_fn (cfun
));
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",
3343 last_basic_block_for_fn (cfun
));
3344 fprintf (dump_file
, "Number of blocks to update: %d (%3.0f%%)\n",
3345 c
, PERCENT (c
, last_basic_block_for_fn (cfun
)));
3347 if (dump_flags
& TDF_DETAILS
)
3349 fprintf (dump_file
, "Affected blocks:");
3350 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3351 fprintf (dump_file
, " %u", i
);
3352 fprintf (dump_file
, "\n");
3355 fprintf (dump_file
, "\n\n");
3358 /* Free allocated memory. */
3360 delete_update_ssa ();
3362 timevar_pop (TV_TREE_SSA_INCREMENTAL
);