1 /* Rewrite a program in Normal form into SSA.
2 Copyright (C) 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011
3 Free Software Foundation, Inc.
4 Contributed by Diego Novillo <dnovillo@redhat.com>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3, or (at your option)
13 GCC is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
24 #include "coretypes.h"
29 #include "langhooks.h"
30 #include "basic-block.h"
32 #include "gimple-pretty-print.h"
34 #include "tree-flow.h"
36 #include "tree-inline.h"
38 #include "tree-pass.h"
43 #include "diagnostic-core.h"
46 /* This file builds the SSA form for a function as described in:
47 R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently
48 Computing Static Single Assignment Form and the Control Dependence
49 Graph. ACM Transactions on Programming Languages and Systems,
50 13(4):451-490, October 1991. */
52 /* Structure to map a variable VAR to the set of blocks that contain
53 definitions for VAR. */
56 /* Blocks that contain definitions of VAR. Bit I will be set if the
57 Ith block contains a definition of VAR. */
60 /* Blocks that contain a PHI node for VAR. */
63 /* Blocks where VAR is live-on-entry. Similar semantics as
68 typedef struct def_blocks_d
*def_blocks_p
;
71 /* Stack of trees used to restore the global currdefs to its original
72 state after completing rewriting of a block and its dominator
73 children. Its elements have the following properties:
75 - An SSA_NAME (N) indicates that the current definition of the
76 underlying variable should be set to the given SSA_NAME. If the
77 symbol associated with the SSA_NAME is not a GIMPLE register, the
78 next slot in the stack must be a _DECL node (SYM). In this case,
79 the name N in the previous slot is the current reaching
82 - A _DECL node indicates that the underlying variable has no
85 - A NULL node at the top entry is used to mark the last slot
86 associated with the current block. */
87 static VEC(tree
,heap
) *block_defs_stack
;
90 /* Set of existing SSA names being replaced by update_ssa. */
91 static sbitmap old_ssa_names
;
93 /* Set of new SSA names being added by update_ssa. Note that both
94 NEW_SSA_NAMES and OLD_SSA_NAMES are dense bitmaps because most of
95 the operations done on them are presence tests. */
96 static sbitmap new_ssa_names
;
98 sbitmap interesting_blocks
;
100 /* Set of SSA names that have been marked to be released after they
101 were registered in the replacement table. They will be finally
102 released after we finish updating the SSA web. */
103 static bitmap names_to_release
;
105 /* VEC of VECs of PHIs to rewrite in a basic block. Element I corresponds
106 the to basic block with index I. Allocated once per compilation, *not*
107 released between different functions. */
108 static VEC(gimple_vec
, heap
) *phis_to_rewrite
;
110 /* The bitmap of non-NULL elements of PHIS_TO_REWRITE. */
111 static bitmap blocks_with_phis_to_rewrite
;
113 /* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need
114 to grow as the callers to register_new_name_mapping will typically
115 create new names on the fly. FIXME. Currently set to 1/3 to avoid
116 frequent reallocations but still need to find a reasonable growth
118 #define NAME_SETS_GROWTH_FACTOR (MAX (3, num_ssa_names / 3))
121 /* The function the SSA updating data structures have been initialized for.
122 NULL if they need to be initialized by register_new_name_mapping. */
123 static struct function
*update_ssa_initialized_fn
= NULL
;
125 /* Global data to attach to the main dominator walk structure. */
126 struct mark_def_sites_global_data
128 /* This bitmap contains the variables which are set before they
129 are used in a basic block. */
133 /* Information stored for both SSA names and decls. */
136 /* This field indicates whether or not the variable may need PHI nodes.
137 See the enum's definition for more detailed information about the
139 ENUM_BITFIELD (need_phi_state
) need_phi_state
: 2;
141 /* The current reaching definition replacing this var. */
144 /* Definitions for this var. */
145 struct def_blocks_d def_blocks
;
148 /* The information associated with decls and SSA names. */
149 typedef struct common_info_d
*common_info_p
;
151 /* Information stored for decls. */
157 /* Information stored for both SSA names and decls. */
158 struct common_info_d info
;
161 /* The information associated with decls. */
162 typedef struct var_info_d
*var_info_p
;
164 DEF_VEC_P(var_info_p
);
165 DEF_VEC_ALLOC_P(var_info_p
,heap
);
167 /* Each entry in VAR_INFOS contains an element of type STRUCT
169 static htab_t var_infos
;
172 /* Information stored for SSA names. */
175 /* Age of this record (so that info_for_ssa_name table can be cleared
176 quickly); if AGE < CURRENT_INFO_FOR_SSA_NAME_AGE, then the fields
177 are assumed to be null. */
180 /* Replacement mappings, allocated from update_ssa_obstack. */
183 /* Information stored for both SSA names and decls. */
184 struct common_info_d info
;
187 /* The information associated with names. */
188 typedef struct ssa_name_info
*ssa_name_info_p
;
189 DEF_VEC_P (ssa_name_info_p
);
190 DEF_VEC_ALLOC_P (ssa_name_info_p
, heap
);
192 static VEC(ssa_name_info_p
, heap
) *info_for_ssa_name
;
193 static unsigned current_info_for_ssa_name_age
;
195 static bitmap_obstack update_ssa_obstack
;
197 /* The set of blocks affected by update_ssa. */
198 static bitmap blocks_to_update
;
200 /* The main entry point to the SSA renamer (rewrite_blocks) may be
201 called several times to do different, but related, tasks.
202 Initially, we need it to rename the whole program into SSA form.
203 At other times, we may need it to only rename into SSA newly
204 exposed symbols. Finally, we can also call it to incrementally fix
205 an already built SSA web. */
207 /* Convert the whole function into SSA form. */
210 /* Incrementally update the SSA web by replacing existing SSA
211 names with new ones. See update_ssa for details. */
218 /* Prototypes for debugging functions. */
219 extern void dump_tree_ssa (FILE *);
220 extern void debug_tree_ssa (void);
221 extern void debug_def_blocks (void);
222 extern void dump_tree_ssa_stats (FILE *);
223 extern void debug_tree_ssa_stats (void);
224 extern void dump_update_ssa (FILE *);
225 extern void debug_update_ssa (void);
226 extern void dump_names_replaced_by (FILE *, tree
);
227 extern void debug_names_replaced_by (tree
);
228 extern void dump_var_infos (FILE *);
229 extern void debug_var_infos (void);
230 extern void dump_defs_stack (FILE *, int);
231 extern void debug_defs_stack (int);
232 extern void dump_currdefs (FILE *);
233 extern void debug_currdefs (void);
236 /* The set of symbols we ought to re-write into SSA form in update_ssa. */
237 static bitmap symbols_to_rename_set
;
238 static VEC(tree
,heap
) *symbols_to_rename
;
240 /* Mark SYM for renaming. */
243 mark_for_renaming (tree sym
)
245 if (!symbols_to_rename_set
)
246 symbols_to_rename_set
= BITMAP_ALLOC (NULL
);
247 if (bitmap_set_bit (symbols_to_rename_set
, DECL_UID (sym
)))
248 VEC_safe_push (tree
, heap
, symbols_to_rename
, sym
);
251 /* Return true if SYM is marked for renaming. */
254 marked_for_renaming (tree sym
)
256 if (!symbols_to_rename_set
|| sym
== NULL_TREE
)
258 return bitmap_bit_p (symbols_to_rename_set
, DECL_UID (sym
));
262 /* Return true if STMT needs to be rewritten. When renaming a subset
263 of the variables, not all statements will be processed. This is
264 decided in mark_def_sites. */
267 rewrite_uses_p (gimple stmt
)
269 return gimple_visited_p (stmt
);
273 /* Set the rewrite marker on STMT to the value given by REWRITE_P. */
276 set_rewrite_uses (gimple stmt
, bool rewrite_p
)
278 gimple_set_visited (stmt
, rewrite_p
);
282 /* Return true if the DEFs created by statement STMT should be
283 registered when marking new definition sites. This is slightly
284 different than rewrite_uses_p: it's used by update_ssa to
285 distinguish statements that need to have both uses and defs
286 processed from those that only need to have their defs processed.
287 Statements that define new SSA names only need to have their defs
288 registered, but they don't need to have their uses renamed. */
291 register_defs_p (gimple stmt
)
293 return gimple_plf (stmt
, GF_PLF_1
) != 0;
297 /* If REGISTER_DEFS_P is true, mark STMT to have its DEFs registered. */
300 set_register_defs (gimple stmt
, bool register_defs_p
)
302 gimple_set_plf (stmt
, GF_PLF_1
, register_defs_p
);
306 /* Get the information associated with NAME. */
308 static inline ssa_name_info_p
309 get_ssa_name_ann (tree name
)
311 unsigned ver
= SSA_NAME_VERSION (name
);
312 unsigned len
= VEC_length (ssa_name_info_p
, info_for_ssa_name
);
313 struct ssa_name_info
*info
;
317 unsigned old_len
= VEC_length (ssa_name_info_p
, info_for_ssa_name
);
318 unsigned new_len
= num_ssa_names
;
320 VEC_reserve (ssa_name_info_p
, heap
, info_for_ssa_name
,
322 while (len
++ < new_len
)
324 struct ssa_name_info
*info
= XCNEW (struct ssa_name_info
);
325 info
->age
= current_info_for_ssa_name_age
;
326 VEC_quick_push (ssa_name_info_p
, info_for_ssa_name
, info
);
330 info
= VEC_index (ssa_name_info_p
, info_for_ssa_name
, ver
);
331 if (info
->age
< current_info_for_ssa_name_age
)
333 info
->age
= current_info_for_ssa_name_age
;
334 info
->repl_set
= NULL
;
335 info
->info
.need_phi_state
= NEED_PHI_STATE_UNKNOWN
;
336 info
->info
.current_def
= NULL_TREE
;
337 info
->info
.def_blocks
.def_blocks
= NULL
;
338 info
->info
.def_blocks
.phi_blocks
= NULL
;
339 info
->info
.def_blocks
.livein_blocks
= NULL
;
345 /* Return and allocate the auxiliar information for DECL. */
347 static inline var_info_p
348 get_var_info (tree decl
)
350 struct var_info_d vi
;
353 slot
= htab_find_slot_with_hash (var_infos
, &vi
, DECL_UID (decl
), INSERT
);
356 var_info_p v
= XCNEW (struct var_info_d
);
361 return (var_info_p
) *slot
;
365 /* Clears info for SSA names. */
368 clear_ssa_name_info (void)
370 current_info_for_ssa_name_age
++;
372 /* If current_info_for_ssa_name_age wraps we use stale information.
373 Asser that this does not happen. */
374 gcc_assert (current_info_for_ssa_name_age
!= 0);
378 /* Get access to the auxiliar information stored per SSA name or decl. */
380 static inline common_info_p
381 get_common_info (tree var
)
383 if (TREE_CODE (var
) == SSA_NAME
)
384 return &get_ssa_name_ann (var
)->info
;
386 return &get_var_info (var
)->info
;
390 /* Return the current definition for VAR. */
393 get_current_def (tree var
)
395 return get_common_info (var
)->current_def
;
399 /* Sets current definition of VAR to DEF. */
402 set_current_def (tree var
, tree def
)
404 get_common_info (var
)->current_def
= def
;
407 /* Cleans up the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags for
408 all statements in basic block BB. */
411 initialize_flags_in_bb (basic_block bb
)
414 gimple_stmt_iterator gsi
;
416 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
418 gimple phi
= gsi_stmt (gsi
);
419 set_rewrite_uses (phi
, false);
420 set_register_defs (phi
, false);
423 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
425 stmt
= gsi_stmt (gsi
);
427 /* We are going to use the operand cache API, such as
428 SET_USE, SET_DEF, and FOR_EACH_IMM_USE_FAST. The operand
429 cache for each statement should be up-to-date. */
430 gcc_assert (!gimple_modified_p (stmt
));
431 set_rewrite_uses (stmt
, false);
432 set_register_defs (stmt
, false);
436 /* Mark block BB as interesting for update_ssa. */
439 mark_block_for_update (basic_block bb
)
441 gcc_assert (blocks_to_update
!= NULL
);
442 if (!bitmap_set_bit (blocks_to_update
, bb
->index
))
444 initialize_flags_in_bb (bb
);
447 /* Return the set of blocks where variable VAR is defined and the blocks
448 where VAR is live on entry (livein). If no entry is found in
449 DEF_BLOCKS, a new one is created and returned. */
451 static inline struct def_blocks_d
*
452 get_def_blocks_for (common_info_p info
)
454 struct def_blocks_d
*db_p
= &info
->def_blocks
;
455 if (!db_p
->def_blocks
)
457 db_p
->def_blocks
= BITMAP_ALLOC (&update_ssa_obstack
);
458 db_p
->phi_blocks
= BITMAP_ALLOC (&update_ssa_obstack
);
459 db_p
->livein_blocks
= BITMAP_ALLOC (&update_ssa_obstack
);
466 /* Mark block BB as the definition site for variable VAR. PHI_P is true if
467 VAR is defined by a PHI node. */
470 set_def_block (tree var
, basic_block bb
, bool phi_p
)
472 struct def_blocks_d
*db_p
;
475 info
= get_common_info (var
);
476 db_p
= get_def_blocks_for (info
);
478 /* Set the bit corresponding to the block where VAR is defined. */
479 bitmap_set_bit (db_p
->def_blocks
, bb
->index
);
481 bitmap_set_bit (db_p
->phi_blocks
, bb
->index
);
483 /* Keep track of whether or not we may need to insert PHI nodes.
485 If we are in the UNKNOWN state, then this is the first definition
486 of VAR. Additionally, we have not seen any uses of VAR yet, so
487 we do not need a PHI node for this variable at this time (i.e.,
488 transition to NEED_PHI_STATE_NO).
490 If we are in any other state, then we either have multiple definitions
491 of this variable occurring in different blocks or we saw a use of the
492 variable which was not dominated by the block containing the
493 definition(s). In this case we may need a PHI node, so enter
494 state NEED_PHI_STATE_MAYBE. */
495 if (info
->need_phi_state
== NEED_PHI_STATE_UNKNOWN
)
496 info
->need_phi_state
= NEED_PHI_STATE_NO
;
498 info
->need_phi_state
= NEED_PHI_STATE_MAYBE
;
502 /* Mark block BB as having VAR live at the entry to BB. */
505 set_livein_block (tree var
, basic_block bb
)
508 struct def_blocks_d
*db_p
;
510 info
= get_common_info (var
);
511 db_p
= get_def_blocks_for (info
);
513 /* Set the bit corresponding to the block where VAR is live in. */
514 bitmap_set_bit (db_p
->livein_blocks
, bb
->index
);
516 /* Keep track of whether or not we may need to insert PHI nodes.
518 If we reach here in NEED_PHI_STATE_NO, see if this use is dominated
519 by the single block containing the definition(s) of this variable. If
520 it is, then we remain in NEED_PHI_STATE_NO, otherwise we transition to
521 NEED_PHI_STATE_MAYBE. */
522 if (info
->need_phi_state
== NEED_PHI_STATE_NO
)
524 int def_block_index
= bitmap_first_set_bit (db_p
->def_blocks
);
526 if (def_block_index
== -1
527 || ! dominated_by_p (CDI_DOMINATORS
, bb
,
528 BASIC_BLOCK (def_block_index
)))
529 info
->need_phi_state
= NEED_PHI_STATE_MAYBE
;
532 info
->need_phi_state
= NEED_PHI_STATE_MAYBE
;
536 /* Return true if NAME is in OLD_SSA_NAMES. */
539 is_old_name (tree name
)
541 unsigned ver
= SSA_NAME_VERSION (name
);
544 return (ver
< SBITMAP_SIZE (new_ssa_names
)
545 && TEST_BIT (old_ssa_names
, ver
));
549 /* Return true if NAME is in NEW_SSA_NAMES. */
552 is_new_name (tree name
)
554 unsigned ver
= SSA_NAME_VERSION (name
);
557 return (ver
< SBITMAP_SIZE (new_ssa_names
)
558 && TEST_BIT (new_ssa_names
, ver
));
562 /* Return the names replaced by NEW_TREE (i.e., REPL_TBL[NEW_TREE].SET). */
565 names_replaced_by (tree new_tree
)
567 return get_ssa_name_ann (new_tree
)->repl_set
;
571 /* Add OLD to REPL_TBL[NEW_TREE].SET. */
574 add_to_repl_tbl (tree new_tree
, tree old
)
576 bitmap
*set
= &get_ssa_name_ann (new_tree
)->repl_set
;
578 *set
= BITMAP_ALLOC (&update_ssa_obstack
);
579 bitmap_set_bit (*set
, SSA_NAME_VERSION (old
));
583 /* Add a new mapping NEW_TREE -> OLD REPL_TBL. Every entry N_i in REPL_TBL
584 represents the set of names O_1 ... O_j replaced by N_i. This is
585 used by update_ssa and its helpers to introduce new SSA names in an
586 already formed SSA web. */
589 add_new_name_mapping (tree new_tree
, tree old
)
591 timevar_push (TV_TREE_SSA_INCREMENTAL
);
593 /* OLD and NEW_TREE must be different SSA names for the same symbol. */
594 gcc_assert (new_tree
!= old
&& SSA_NAME_VAR (new_tree
) == SSA_NAME_VAR (old
));
596 /* We may need to grow NEW_SSA_NAMES and OLD_SSA_NAMES because our
597 caller may have created new names since the set was created. */
598 if (SBITMAP_SIZE (new_ssa_names
) <= num_ssa_names
- 1)
600 unsigned int new_sz
= num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
;
601 new_ssa_names
= sbitmap_resize (new_ssa_names
, new_sz
, 0);
602 old_ssa_names
= sbitmap_resize (old_ssa_names
, new_sz
, 0);
605 /* Update the REPL_TBL table. */
606 add_to_repl_tbl (new_tree
, old
);
608 /* If OLD had already been registered as a new name, then all the
609 names that OLD replaces should also be replaced by NEW_TREE. */
610 if (is_new_name (old
))
611 bitmap_ior_into (names_replaced_by (new_tree
), names_replaced_by (old
));
613 /* Register NEW_TREE and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES,
615 SET_BIT (new_ssa_names
, SSA_NAME_VERSION (new_tree
));
616 SET_BIT (old_ssa_names
, SSA_NAME_VERSION (old
));
618 timevar_pop (TV_TREE_SSA_INCREMENTAL
);
622 /* Call back for walk_dominator_tree used to collect definition sites
623 for every variable in the function. For every statement S in block
626 1- Variables defined by S in the DEFS of S are marked in the bitmap
629 2- If S uses a variable VAR and there is no preceding kill of VAR,
630 then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR.
632 This information is used to determine which variables are live
633 across block boundaries to reduce the number of PHI nodes
637 mark_def_sites (basic_block bb
, gimple stmt
, bitmap kills
)
643 /* Since this is the first time that we rewrite the program into SSA
644 form, force an operand scan on every statement. */
647 gcc_assert (blocks_to_update
== NULL
);
648 set_register_defs (stmt
, false);
649 set_rewrite_uses (stmt
, false);
651 if (is_gimple_debug (stmt
))
653 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
655 tree sym
= USE_FROM_PTR (use_p
);
656 gcc_assert (DECL_P (sym
));
657 set_rewrite_uses (stmt
, true);
659 if (rewrite_uses_p (stmt
))
660 SET_BIT (interesting_blocks
, bb
->index
);
664 /* If a variable is used before being set, then the variable is live
665 across a block boundary, so mark it live-on-entry to BB. */
666 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
668 tree sym
= USE_FROM_PTR (use_p
);
669 gcc_assert (DECL_P (sym
));
670 if (!bitmap_bit_p (kills
, DECL_UID (sym
)))
671 set_livein_block (sym
, bb
);
672 set_rewrite_uses (stmt
, true);
675 /* Now process the defs. Mark BB as the definition block and add
676 each def to the set of killed symbols. */
677 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_ALL_DEFS
)
679 gcc_assert (DECL_P (def
));
680 set_def_block (def
, bb
, false);
681 bitmap_set_bit (kills
, DECL_UID (def
));
682 set_register_defs (stmt
, true);
685 /* If we found the statement interesting then also mark the block BB
687 if (rewrite_uses_p (stmt
) || register_defs_p (stmt
))
688 SET_BIT (interesting_blocks
, bb
->index
);
691 /* Structure used by prune_unused_phi_nodes to record bounds of the intervals
692 in the dfs numbering of the dominance tree. */
696 /* Basic block whose index this entry corresponds to. */
699 /* The dfs number of this node. */
703 /* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback
707 cmp_dfsnum (const void *a
, const void *b
)
709 const struct dom_dfsnum
*const da
= (const struct dom_dfsnum
*) a
;
710 const struct dom_dfsnum
*const db
= (const struct dom_dfsnum
*) b
;
712 return (int) da
->dfs_num
- (int) db
->dfs_num
;
715 /* Among the intervals starting at the N points specified in DEFS, find
716 the one that contains S, and return its bb_index. */
719 find_dfsnum_interval (struct dom_dfsnum
*defs
, unsigned n
, unsigned s
)
721 unsigned f
= 0, t
= n
, m
;
726 if (defs
[m
].dfs_num
<= s
)
732 return defs
[f
].bb_index
;
735 /* Clean bits from PHIS for phi nodes whose value cannot be used in USES.
736 KILLS is a bitmap of blocks where the value is defined before any use. */
739 prune_unused_phi_nodes (bitmap phis
, bitmap kills
, bitmap uses
)
741 VEC(int, heap
) *worklist
;
743 unsigned i
, b
, p
, u
, top
;
745 basic_block def_bb
, use_bb
;
749 struct dom_dfsnum
*defs
;
750 unsigned n_defs
, adef
;
752 if (bitmap_empty_p (uses
))
758 /* The phi must dominate a use, or an argument of a live phi. Also, we
759 do not create any phi nodes in def blocks, unless they are also livein. */
760 to_remove
= BITMAP_ALLOC (NULL
);
761 bitmap_and_compl (to_remove
, kills
, uses
);
762 bitmap_and_compl_into (phis
, to_remove
);
763 if (bitmap_empty_p (phis
))
765 BITMAP_FREE (to_remove
);
769 /* We want to remove the unnecessary phi nodes, but we do not want to compute
770 liveness information, as that may be linear in the size of CFG, and if
771 there are lot of different variables to rewrite, this may lead to quadratic
774 Instead, we basically emulate standard dce. We put all uses to worklist,
775 then for each of them find the nearest def that dominates them. If this
776 def is a phi node, we mark it live, and if it was not live before, we
777 add the predecessors of its basic block to the worklist.
779 To quickly locate the nearest def that dominates use, we use dfs numbering
780 of the dominance tree (that is already available in order to speed up
781 queries). For each def, we have the interval given by the dfs number on
782 entry to and on exit from the corresponding subtree in the dominance tree.
783 The nearest dominator for a given use is the smallest of these intervals
784 that contains entry and exit dfs numbers for the basic block with the use.
785 If we store the bounds for all the uses to an array and sort it, we can
786 locate the nearest dominating def in logarithmic time by binary search.*/
787 bitmap_ior (to_remove
, kills
, phis
);
788 n_defs
= bitmap_count_bits (to_remove
);
789 defs
= XNEWVEC (struct dom_dfsnum
, 2 * n_defs
+ 1);
790 defs
[0].bb_index
= 1;
793 EXECUTE_IF_SET_IN_BITMAP (to_remove
, 0, i
, bi
)
795 def_bb
= BASIC_BLOCK (i
);
796 defs
[adef
].bb_index
= i
;
797 defs
[adef
].dfs_num
= bb_dom_dfs_in (CDI_DOMINATORS
, def_bb
);
798 defs
[adef
+ 1].bb_index
= i
;
799 defs
[adef
+ 1].dfs_num
= bb_dom_dfs_out (CDI_DOMINATORS
, def_bb
);
802 BITMAP_FREE (to_remove
);
803 gcc_assert (adef
== 2 * n_defs
+ 1);
804 qsort (defs
, adef
, sizeof (struct dom_dfsnum
), cmp_dfsnum
);
805 gcc_assert (defs
[0].bb_index
== 1);
807 /* Now each DEFS entry contains the number of the basic block to that the
808 dfs number corresponds. Change them to the number of basic block that
809 corresponds to the interval following the dfs number. Also, for the
810 dfs_out numbers, increase the dfs number by one (so that it corresponds
811 to the start of the following interval, not to the end of the current
812 one). We use WORKLIST as a stack. */
813 worklist
= VEC_alloc (int, heap
, n_defs
+ 1);
814 VEC_quick_push (int, worklist
, 1);
817 for (i
= 1; i
< adef
; i
++)
819 b
= defs
[i
].bb_index
;
822 /* This is a closing element. Interval corresponding to the top
823 of the stack after removing it follows. */
824 VEC_pop (int, worklist
);
825 top
= VEC_index (int, worklist
, VEC_length (int, worklist
) - 1);
826 defs
[n_defs
].bb_index
= top
;
827 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
+ 1;
831 /* Opening element. Nothing to do, just push it to the stack and move
832 it to the correct position. */
833 defs
[n_defs
].bb_index
= defs
[i
].bb_index
;
834 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
;
835 VEC_quick_push (int, worklist
, b
);
839 /* If this interval starts at the same point as the previous one, cancel
841 if (defs
[n_defs
].dfs_num
== defs
[n_defs
- 1].dfs_num
)
842 defs
[n_defs
- 1].bb_index
= defs
[n_defs
].bb_index
;
846 VEC_pop (int, worklist
);
847 gcc_assert (VEC_empty (int, worklist
));
849 /* Now process the uses. */
850 live_phis
= BITMAP_ALLOC (NULL
);
851 EXECUTE_IF_SET_IN_BITMAP (uses
, 0, i
, bi
)
853 VEC_safe_push (int, heap
, worklist
, i
);
856 while (!VEC_empty (int, worklist
))
858 b
= VEC_pop (int, worklist
);
859 if (b
== ENTRY_BLOCK
)
862 /* If there is a phi node in USE_BB, it is made live. Otherwise,
863 find the def that dominates the immediate dominator of USE_BB
864 (the kill in USE_BB does not dominate the use). */
865 if (bitmap_bit_p (phis
, b
))
869 use_bb
= get_immediate_dominator (CDI_DOMINATORS
, BASIC_BLOCK (b
));
870 p
= find_dfsnum_interval (defs
, n_defs
,
871 bb_dom_dfs_in (CDI_DOMINATORS
, use_bb
));
872 if (!bitmap_bit_p (phis
, p
))
876 /* If the phi node is already live, there is nothing to do. */
877 if (!bitmap_set_bit (live_phis
, p
))
880 /* Add the new uses to the worklist. */
881 def_bb
= BASIC_BLOCK (p
);
882 FOR_EACH_EDGE (e
, ei
, def_bb
->preds
)
885 if (bitmap_bit_p (uses
, u
))
888 /* In case there is a kill directly in the use block, do not record
889 the use (this is also necessary for correctness, as we assume that
890 uses dominated by a def directly in their block have been filtered
892 if (bitmap_bit_p (kills
, u
))
895 bitmap_set_bit (uses
, u
);
896 VEC_safe_push (int, heap
, worklist
, u
);
900 VEC_free (int, heap
, worklist
);
901 bitmap_copy (phis
, live_phis
);
902 BITMAP_FREE (live_phis
);
906 /* Return the set of blocks where variable VAR is defined and the blocks
907 where VAR is live on entry (livein). Return NULL, if no entry is
908 found in DEF_BLOCKS. */
910 static inline struct def_blocks_d
*
911 find_def_blocks_for (tree var
)
913 def_blocks_p p
= &get_common_info (var
)->def_blocks
;
920 /* Marks phi node PHI in basic block BB for rewrite. */
923 mark_phi_for_rewrite (basic_block bb
, gimple phi
)
926 unsigned n
, idx
= bb
->index
;
928 if (rewrite_uses_p (phi
))
931 set_rewrite_uses (phi
, true);
933 if (!blocks_with_phis_to_rewrite
)
936 bitmap_set_bit (blocks_with_phis_to_rewrite
, idx
);
938 n
= (unsigned) last_basic_block
+ 1;
939 if (VEC_length (gimple_vec
, phis_to_rewrite
) < n
)
940 VEC_safe_grow_cleared (gimple_vec
, heap
, phis_to_rewrite
, n
);
942 phis
= VEC_index (gimple_vec
, phis_to_rewrite
, idx
);
944 phis
= VEC_alloc (gimple
, heap
, 10);
946 VEC_safe_push (gimple
, heap
, phis
, phi
);
947 VEC_replace (gimple_vec
, phis_to_rewrite
, idx
, phis
);
950 /* Insert PHI nodes for variable VAR using the iterated dominance
951 frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
952 function assumes that the caller is incrementally updating the
953 existing SSA form, in which case VAR may be an SSA name instead of
956 PHI_INSERTION_POINTS is updated to reflect nodes that already had a
957 PHI node for VAR. On exit, only the nodes that received a PHI node
958 for VAR will be present in PHI_INSERTION_POINTS. */
961 insert_phi_nodes_for (tree var
, bitmap phi_insertion_points
, bool update_p
)
968 struct def_blocks_d
*def_map
;
970 def_map
= find_def_blocks_for (var
);
971 gcc_assert (def_map
);
973 /* Remove the blocks where we already have PHI nodes for VAR. */
974 bitmap_and_compl_into (phi_insertion_points
, def_map
->phi_blocks
);
976 /* Remove obviously useless phi nodes. */
977 prune_unused_phi_nodes (phi_insertion_points
, def_map
->def_blocks
,
978 def_map
->livein_blocks
);
980 /* And insert the PHI nodes. */
981 EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points
, 0, bb_index
, bi
)
983 bb
= BASIC_BLOCK (bb_index
);
985 mark_block_for_update (bb
);
989 if (TREE_CODE (var
) == SSA_NAME
)
991 /* If we are rewriting SSA names, create the LHS of the PHI
992 node by duplicating VAR. This is useful in the case of
993 pointers, to also duplicate pointer attributes (alias
994 information, in particular). */
998 gcc_assert (update_p
);
999 new_lhs
= duplicate_ssa_name (var
, NULL
);
1000 phi
= create_phi_node (new_lhs
, bb
);
1001 add_new_name_mapping (new_lhs
, var
);
1003 /* Add VAR to every argument slot of PHI. We need VAR in
1004 every argument so that rewrite_update_phi_arguments knows
1005 which name is this PHI node replacing. If VAR is a
1006 symbol marked for renaming, this is not necessary, the
1007 renamer will use the symbol on the LHS to get its
1008 reaching definition. */
1009 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1010 add_phi_arg (phi
, var
, e
, UNKNOWN_LOCATION
);
1016 gcc_assert (DECL_P (var
));
1017 phi
= create_phi_node (var
, bb
);
1019 tracked_var
= target_for_debug_bind (var
);
1022 gimple note
= gimple_build_debug_bind (tracked_var
,
1025 gimple_stmt_iterator si
= gsi_after_labels (bb
);
1026 gsi_insert_before (&si
, note
, GSI_SAME_STMT
);
1030 /* Mark this PHI node as interesting for update_ssa. */
1031 set_register_defs (phi
, true);
1032 mark_phi_for_rewrite (bb
, phi
);
1036 /* Sort var_infos after DECL_UID of their var. */
1039 insert_phi_nodes_compare_var_infos (const void *a
, const void *b
)
1041 const struct var_info_d
*defa
= *(struct var_info_d
* const *)a
;
1042 const struct var_info_d
*defb
= *(struct var_info_d
* const *)b
;
1043 if (DECL_UID (defa
->var
) < DECL_UID (defb
->var
))
1049 /* Insert PHI nodes at the dominance frontier of blocks with variable
1050 definitions. DFS contains the dominance frontier information for
1054 insert_phi_nodes (bitmap_head
*dfs
)
1059 VEC(var_info_p
,heap
) *vars
;
1061 timevar_push (TV_TREE_INSERT_PHI_NODES
);
1063 vars
= VEC_alloc (var_info_p
, heap
, htab_elements (var_infos
));
1064 FOR_EACH_HTAB_ELEMENT (var_infos
, info
, var_info_p
, hi
)
1065 if (info
->info
.need_phi_state
!= NEED_PHI_STATE_NO
)
1066 VEC_quick_push (var_info_p
, vars
, info
);
1068 /* Do two stages to avoid code generation differences for UID
1069 differences but no UID ordering differences. */
1070 VEC_qsort (var_info_p
, vars
, insert_phi_nodes_compare_var_infos
);
1072 FOR_EACH_VEC_ELT (var_info_p
, vars
, i
, info
)
1074 bitmap idf
= compute_idf (info
->info
.def_blocks
.def_blocks
, dfs
);
1075 insert_phi_nodes_for (info
->var
, idf
, false);
1079 VEC_free(var_info_p
, heap
, vars
);
1081 timevar_pop (TV_TREE_INSERT_PHI_NODES
);
1085 /* Push SYM's current reaching definition into BLOCK_DEFS_STACK and
1086 register DEF (an SSA_NAME) to be a new definition for SYM. */
1089 register_new_def (tree def
, tree sym
)
1091 common_info_p info
= get_common_info (sym
);
1094 /* If this variable is set in a single basic block and all uses are
1095 dominated by the set(s) in that single basic block, then there is
1096 no reason to record anything for this variable in the block local
1097 definition stacks. Doing so just wastes time and memory.
1099 This is the same test to prune the set of variables which may
1100 need PHI nodes. So we just use that information since it's already
1101 computed and available for us to use. */
1102 if (info
->need_phi_state
== NEED_PHI_STATE_NO
)
1104 info
->current_def
= def
;
1108 currdef
= info
->current_def
;
1110 /* If SYM is not a GIMPLE register, then CURRDEF may be a name whose
1111 SSA_NAME_VAR is not necessarily SYM. In this case, also push SYM
1112 in the stack so that we know which symbol is being defined by
1113 this SSA name when we unwind the stack. */
1114 if (currdef
&& !is_gimple_reg (sym
))
1115 VEC_safe_push (tree
, heap
, block_defs_stack
, sym
);
1117 /* Push the current reaching definition into BLOCK_DEFS_STACK. This
1118 stack is later used by the dominator tree callbacks to restore
1119 the reaching definitions for all the variables defined in the
1120 block after a recursive visit to all its immediately dominated
1121 blocks. If there is no current reaching definition, then just
1122 record the underlying _DECL node. */
1123 VEC_safe_push (tree
, heap
, block_defs_stack
, currdef
? currdef
: sym
);
1125 /* Set the current reaching definition for SYM to be DEF. */
1126 info
->current_def
= def
;
1130 /* Perform a depth-first traversal of the dominator tree looking for
1131 variables to rename. BB is the block where to start searching.
1132 Renaming is a five step process:
1134 1- Every definition made by PHI nodes at the start of the blocks is
1135 registered as the current definition for the corresponding variable.
1137 2- Every statement in BB is rewritten. USE and VUSE operands are
1138 rewritten with their corresponding reaching definition. DEF and
1139 VDEF targets are registered as new definitions.
1141 3- All the PHI nodes in successor blocks of BB are visited. The
1142 argument corresponding to BB is replaced with its current reaching
1145 4- Recursively rewrite every dominator child block of BB.
1147 5- Restore (in reverse order) the current reaching definition for every
1148 new definition introduced in this block. This is done so that when
1149 we return from the recursive call, all the current reaching
1150 definitions are restored to the names that were valid in the
1151 dominator parent of BB. */
1153 /* Return the current definition for variable VAR. If none is found,
1154 create a new SSA name to act as the zeroth definition for VAR. */
1157 get_reaching_def (tree var
)
1159 common_info_p info
= get_common_info (var
);
1162 /* Lookup the current reaching definition for VAR. */
1163 currdef
= info
->current_def
;
1165 /* If there is no reaching definition for VAR, create and register a
1166 default definition for it (if needed). */
1167 if (currdef
== NULL_TREE
)
1169 tree sym
= DECL_P (var
) ? var
: SSA_NAME_VAR (var
);
1170 currdef
= get_or_create_ssa_default_def (cfun
, sym
);
1173 /* Return the current reaching definition for VAR, or the default
1174 definition, if we had to create one. */
1179 /* Helper function for rewrite_stmt. Rewrite uses in a debug stmt. */
1182 rewrite_debug_stmt_uses (gimple stmt
)
1184 use_operand_p use_p
;
1186 bool update
= false;
1188 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
1190 tree var
= USE_FROM_PTR (use_p
), def
;
1191 common_info_p info
= get_common_info (var
);
1192 gcc_assert (DECL_P (var
));
1193 def
= info
->current_def
;
1196 if (TREE_CODE (var
) == PARM_DECL
&& single_succ_p (ENTRY_BLOCK_PTR
))
1198 gimple_stmt_iterator gsi
1199 = gsi_after_labels (single_succ (ENTRY_BLOCK_PTR
));
1201 /* Search a few source bind stmts at the start of first bb to
1202 see if a DEBUG_EXPR_DECL can't be reused. */
1204 !gsi_end_p (gsi
) && lim
> 0;
1205 gsi_next (&gsi
), lim
--)
1207 gimple gstmt
= gsi_stmt (gsi
);
1208 if (!gimple_debug_source_bind_p (gstmt
))
1210 if (gimple_debug_source_bind_get_value (gstmt
) == var
)
1212 def
= gimple_debug_source_bind_get_var (gstmt
);
1213 if (TREE_CODE (def
) == DEBUG_EXPR_DECL
)
1219 /* If not, add a new source bind stmt. */
1220 if (def
== NULL_TREE
)
1223 def
= make_node (DEBUG_EXPR_DECL
);
1224 def_temp
= gimple_build_debug_source_bind (def
, var
, NULL
);
1225 DECL_ARTIFICIAL (def
) = 1;
1226 TREE_TYPE (def
) = TREE_TYPE (var
);
1227 DECL_MODE (def
) = DECL_MODE (var
);
1228 gsi
= gsi_after_labels (single_succ (ENTRY_BLOCK_PTR
));
1229 gsi_insert_before (&gsi
, def_temp
, GSI_SAME_STMT
);
1236 /* Check if info->current_def can be trusted. */
1237 basic_block bb
= gimple_bb (stmt
);
1239 = SSA_NAME_IS_DEFAULT_DEF (def
)
1240 ? NULL
: gimple_bb (SSA_NAME_DEF_STMT (def
));
1242 /* If definition is in current bb, it is fine. */
1245 /* If definition bb doesn't dominate the current bb,
1246 it can't be used. */
1247 else if (def_bb
&& !dominated_by_p (CDI_DOMINATORS
, bb
, def_bb
))
1249 /* If there is just one definition and dominates the current
1251 else if (info
->need_phi_state
== NEED_PHI_STATE_NO
)
1255 struct def_blocks_d
*db_p
= get_def_blocks_for (info
);
1257 /* If there are some non-debug uses in the current bb,
1259 if (bitmap_bit_p (db_p
->livein_blocks
, bb
->index
))
1261 /* Otherwise give up for now. */
1268 gimple_debug_bind_reset_value (stmt
);
1272 SET_USE (use_p
, def
);
1278 /* SSA Rewriting Step 2. Rewrite every variable used in each statement in
1279 the block with its immediate reaching definitions. Update the current
1280 definition of a variable when a new real or virtual definition is found. */
1283 rewrite_stmt (gimple_stmt_iterator
*si
)
1285 use_operand_p use_p
;
1286 def_operand_p def_p
;
1288 gimple stmt
= gsi_stmt (*si
);
1290 /* If mark_def_sites decided that we don't need to rewrite this
1291 statement, ignore it. */
1292 gcc_assert (blocks_to_update
== NULL
);
1293 if (!rewrite_uses_p (stmt
) && !register_defs_p (stmt
))
1296 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1298 fprintf (dump_file
, "Renaming statement ");
1299 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1300 fprintf (dump_file
, "\n");
1303 /* Step 1. Rewrite USES in the statement. */
1304 if (rewrite_uses_p (stmt
))
1306 if (is_gimple_debug (stmt
))
1307 rewrite_debug_stmt_uses (stmt
);
1309 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
1311 tree var
= USE_FROM_PTR (use_p
);
1312 gcc_assert (DECL_P (var
));
1313 SET_USE (use_p
, get_reaching_def (var
));
1317 /* Step 2. Register the statement's DEF operands. */
1318 if (register_defs_p (stmt
))
1319 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1321 tree var
= DEF_FROM_PTR (def_p
);
1325 gcc_assert (DECL_P (var
));
1327 if (gimple_clobber_p (stmt
)
1328 && is_gimple_reg (var
))
1330 /* If we rewrite a DECL into SSA form then drop its
1331 clobber stmts and replace uses with a new default def. */
1332 gcc_assert (TREE_CODE (var
) == VAR_DECL
1333 && !gimple_vdef (stmt
));
1334 gsi_replace (si
, gimple_build_nop (), true);
1335 register_new_def (get_or_create_ssa_default_def (cfun
, var
), var
);
1339 name
= make_ssa_name (var
, stmt
);
1340 SET_DEF (def_p
, name
);
1341 register_new_def (DEF_FROM_PTR (def_p
), var
);
1343 tracked_var
= target_for_debug_bind (var
);
1346 gimple note
= gimple_build_debug_bind (tracked_var
, name
, stmt
);
1347 gsi_insert_after (si
, note
, GSI_SAME_STMT
);
1353 /* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for
1354 PHI nodes. For every PHI node found, add a new argument containing the
1355 current reaching definition for the variable and the edge through which
1356 that definition is reaching the PHI node. */
1359 rewrite_add_phi_arguments (basic_block bb
)
1364 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1367 gimple_stmt_iterator gsi
;
1369 for (gsi
= gsi_start_phis (e
->dest
); !gsi_end_p (gsi
);
1375 phi
= gsi_stmt (gsi
);
1376 currdef
= get_reaching_def (SSA_NAME_VAR (gimple_phi_result (phi
)));
1377 stmt
= SSA_NAME_DEF_STMT (currdef
);
1378 add_phi_arg (phi
, currdef
, e
, gimple_location (stmt
));
1383 /* SSA Rewriting Step 1. Initialization, create a block local stack
1384 of reaching definitions for new SSA names produced in this block
1385 (BLOCK_DEFS). Register new definitions for every PHI node in the
1389 rewrite_enter_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
1392 gimple_stmt_iterator gsi
;
1394 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1395 fprintf (dump_file
, "\n\nRenaming block #%d\n\n", bb
->index
);
1397 /* Mark the unwind point for this block. */
1398 VEC_safe_push (tree
, heap
, block_defs_stack
, NULL_TREE
);
1400 /* Step 1. Register new definitions for every PHI node in the block.
1401 Conceptually, all the PHI nodes are executed in parallel and each PHI
1402 node introduces a new version for the associated variable. */
1403 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1405 tree result
= gimple_phi_result (gsi_stmt (gsi
));
1406 register_new_def (result
, SSA_NAME_VAR (result
));
1409 /* Step 2. Rewrite every variable used in each statement in the block
1410 with its immediate reaching definitions. Update the current definition
1411 of a variable when a new real or virtual definition is found. */
1412 if (TEST_BIT (interesting_blocks
, bb
->index
))
1413 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1414 rewrite_stmt (&gsi
);
1416 /* Step 3. Visit all the successor blocks of BB looking for PHI nodes.
1417 For every PHI node found, add a new argument containing the current
1418 reaching definition for the variable and the edge through which that
1419 definition is reaching the PHI node. */
1420 rewrite_add_phi_arguments (bb
);
1425 /* Called after visiting all the statements in basic block BB and all
1426 of its dominator children. Restore CURRDEFS to its original value. */
1429 rewrite_leave_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
1430 basic_block bb ATTRIBUTE_UNUSED
)
1432 /* Restore CURRDEFS to its original state. */
1433 while (VEC_length (tree
, block_defs_stack
) > 0)
1435 tree tmp
= VEC_pop (tree
, block_defs_stack
);
1436 tree saved_def
, var
;
1438 if (tmp
== NULL_TREE
)
1441 if (TREE_CODE (tmp
) == SSA_NAME
)
1443 /* If we recorded an SSA_NAME, then make the SSA_NAME the
1444 current definition of its underlying variable. Note that
1445 if the SSA_NAME is not for a GIMPLE register, the symbol
1446 being defined is stored in the next slot in the stack.
1447 This mechanism is needed because an SSA name for a
1448 non-register symbol may be the definition for more than
1449 one symbol (e.g., SFTs, aliased variables, etc). */
1451 var
= SSA_NAME_VAR (saved_def
);
1452 if (!is_gimple_reg (var
))
1453 var
= VEC_pop (tree
, block_defs_stack
);
1457 /* If we recorded anything else, it must have been a _DECL
1458 node and its current reaching definition must have been
1464 get_common_info (var
)->current_def
= saved_def
;
1469 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1472 dump_decl_set (FILE *file
, bitmap set
)
1479 fprintf (file
, "{ ");
1481 EXECUTE_IF_SET_IN_BITMAP (set
, 0, i
, bi
)
1483 fprintf (file
, "D.%u", i
);
1484 fprintf (file
, " ");
1487 fprintf (file
, "}");
1490 fprintf (file
, "NIL");
1494 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1497 debug_decl_set (bitmap set
)
1499 dump_decl_set (stderr
, set
);
1500 fprintf (stderr
, "\n");
1504 /* Dump the renaming stack (block_defs_stack) to FILE. Traverse the
1505 stack up to a maximum of N levels. If N is -1, the whole stack is
1506 dumped. New levels are created when the dominator tree traversal
1507 used for renaming enters a new sub-tree. */
1510 dump_defs_stack (FILE *file
, int n
)
1514 fprintf (file
, "\n\nRenaming stack");
1516 fprintf (file
, " (up to %d levels)", n
);
1517 fprintf (file
, "\n\n");
1520 fprintf (file
, "Level %d (current level)\n", i
);
1521 for (j
= (int) VEC_length (tree
, block_defs_stack
) - 1; j
>= 0; j
--)
1525 name
= VEC_index (tree
, block_defs_stack
, j
);
1526 if (name
== NULL_TREE
)
1531 fprintf (file
, "\nLevel %d\n", i
);
1542 var
= SSA_NAME_VAR (name
);
1543 if (!is_gimple_reg (var
))
1546 var
= VEC_index (tree
, block_defs_stack
, j
);
1550 fprintf (file
, " Previous CURRDEF (");
1551 print_generic_expr (file
, var
, 0);
1552 fprintf (file
, ") = ");
1554 print_generic_expr (file
, name
, 0);
1556 fprintf (file
, "<NIL>");
1557 fprintf (file
, "\n");
1562 /* Dump the renaming stack (block_defs_stack) to stderr. Traverse the
1563 stack up to a maximum of N levels. If N is -1, the whole stack is
1564 dumped. New levels are created when the dominator tree traversal
1565 used for renaming enters a new sub-tree. */
1568 debug_defs_stack (int n
)
1570 dump_defs_stack (stderr
, n
);
1574 /* Dump the current reaching definition of every symbol to FILE. */
1577 dump_currdefs (FILE *file
)
1582 if (VEC_empty (tree
, symbols_to_rename
))
1585 fprintf (file
, "\n\nCurrent reaching definitions\n\n");
1586 FOR_EACH_VEC_ELT (tree
, symbols_to_rename
, i
, var
)
1588 common_info_p info
= get_common_info (var
);
1589 fprintf (file
, "CURRDEF (");
1590 print_generic_expr (file
, var
, 0);
1591 fprintf (file
, ") = ");
1592 if (info
->current_def
)
1593 print_generic_expr (file
, info
->current_def
, 0);
1595 fprintf (file
, "<NIL>");
1596 fprintf (file
, "\n");
1601 /* Dump the current reaching definition of every symbol to stderr. */
1604 debug_currdefs (void)
1606 dump_currdefs (stderr
);
1610 /* Dump SSA information to FILE. */
1613 dump_tree_ssa (FILE *file
)
1615 const char *funcname
1616 = lang_hooks
.decl_printable_name (current_function_decl
, 2);
1618 fprintf (file
, "SSA renaming information for %s\n\n", funcname
);
1620 dump_var_infos (file
);
1621 dump_defs_stack (file
, -1);
1622 dump_currdefs (file
);
1623 dump_tree_ssa_stats (file
);
1627 /* Dump SSA information to stderr. */
1630 debug_tree_ssa (void)
1632 dump_tree_ssa (stderr
);
1636 /* Dump statistics for the hash table HTAB. */
1639 htab_statistics (FILE *file
, htab_t htab
)
1641 fprintf (file
, "size %ld, %ld elements, %f collision/search ratio\n",
1642 (long) htab_size (htab
),
1643 (long) htab_elements (htab
),
1644 htab_collisions (htab
));
1648 /* Dump SSA statistics on FILE. */
1651 dump_tree_ssa_stats (FILE *file
)
1655 fprintf (file
, "\nHash table statistics:\n");
1656 fprintf (file
, " var_infos: ");
1657 htab_statistics (file
, var_infos
);
1658 fprintf (file
, "\n");
1663 /* Dump SSA statistics on stderr. */
1666 debug_tree_ssa_stats (void)
1668 dump_tree_ssa_stats (stderr
);
1672 /* Hashing and equality functions for VAR_INFOS. */
1675 var_info_hash (const void *p
)
1677 return DECL_UID (((const struct var_info_d
*)p
)->var
);
1681 var_info_eq (const void *p1
, const void *p2
)
1683 return ((const struct var_info_d
*)p1
)->var
1684 == ((const struct var_info_d
*)p2
)->var
;
1688 /* Callback for htab_traverse to dump the VAR_INFOS hash table. */
1691 debug_var_infos_r (void **slot
, void *data
)
1693 FILE *file
= (FILE *) data
;
1694 struct var_info_d
*info
= (struct var_info_d
*) *slot
;
1696 fprintf (file
, "VAR: ");
1697 print_generic_expr (file
, info
->var
, dump_flags
);
1698 bitmap_print (file
, info
->info
.def_blocks
.def_blocks
,
1699 ", DEF_BLOCKS: { ", "}");
1700 bitmap_print (file
, info
->info
.def_blocks
.livein_blocks
,
1701 ", LIVEIN_BLOCKS: { ", "}");
1702 bitmap_print (file
, info
->info
.def_blocks
.phi_blocks
,
1703 ", PHI_BLOCKS: { ", "}\n");
1709 /* Dump the VAR_INFOS hash table on FILE. */
1712 dump_var_infos (FILE *file
)
1714 fprintf (file
, "\n\nDefinition and live-in blocks:\n\n");
1716 htab_traverse (var_infos
, debug_var_infos_r
, file
);
1720 /* Dump the VAR_INFOS hash table on stderr. */
1723 debug_var_infos (void)
1725 dump_var_infos (stderr
);
1729 /* Register NEW_NAME to be the new reaching definition for OLD_NAME. */
1732 register_new_update_single (tree new_name
, tree old_name
)
1734 common_info_p info
= get_common_info (old_name
);
1735 tree currdef
= info
->current_def
;
1737 /* Push the current reaching definition into BLOCK_DEFS_STACK.
1738 This stack is later used by the dominator tree callbacks to
1739 restore the reaching definitions for all the variables
1740 defined in the block after a recursive visit to all its
1741 immediately dominated blocks. */
1742 VEC_reserve (tree
, heap
, block_defs_stack
, 2);
1743 VEC_quick_push (tree
, block_defs_stack
, currdef
);
1744 VEC_quick_push (tree
, block_defs_stack
, old_name
);
1746 /* Set the current reaching definition for OLD_NAME to be
1748 info
->current_def
= new_name
;
1752 /* Register NEW_NAME to be the new reaching definition for all the
1753 names in OLD_NAMES. Used by the incremental SSA update routines to
1754 replace old SSA names with new ones. */
1757 register_new_update_set (tree new_name
, bitmap old_names
)
1762 EXECUTE_IF_SET_IN_BITMAP (old_names
, 0, i
, bi
)
1763 register_new_update_single (new_name
, ssa_name (i
));
1768 /* If the operand pointed to by USE_P is a name in OLD_SSA_NAMES or
1769 it is a symbol marked for renaming, replace it with USE_P's current
1770 reaching definition. */
1773 maybe_replace_use (use_operand_p use_p
)
1775 tree rdef
= NULL_TREE
;
1776 tree use
= USE_FROM_PTR (use_p
);
1777 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
1779 if (marked_for_renaming (sym
))
1780 rdef
= get_reaching_def (sym
);
1781 else if (is_old_name (use
))
1782 rdef
= get_reaching_def (use
);
1784 if (rdef
&& rdef
!= use
)
1785 SET_USE (use_p
, rdef
);
1789 /* Same as maybe_replace_use, but without introducing default stmts,
1790 returning false to indicate a need to do so. */
1793 maybe_replace_use_in_debug_stmt (use_operand_p use_p
)
1795 tree rdef
= NULL_TREE
;
1796 tree use
= USE_FROM_PTR (use_p
);
1797 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
1799 if (marked_for_renaming (sym
))
1800 rdef
= get_var_info (sym
)->info
.current_def
;
1801 else if (is_old_name (use
))
1803 rdef
= get_ssa_name_ann (use
)->info
.current_def
;
1804 /* We can't assume that, if there's no current definition, the
1805 default one should be used. It could be the case that we've
1806 rearranged blocks so that the earlier definition no longer
1807 dominates the use. */
1808 if (!rdef
&& SSA_NAME_IS_DEFAULT_DEF (use
))
1814 if (rdef
&& rdef
!= use
)
1815 SET_USE (use_p
, rdef
);
1817 return rdef
!= NULL_TREE
;
1821 /* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
1822 or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
1823 register it as the current definition for the names replaced by
1827 maybe_register_def (def_operand_p def_p
, gimple stmt
,
1828 gimple_stmt_iterator gsi
)
1830 tree def
= DEF_FROM_PTR (def_p
);
1831 tree sym
= DECL_P (def
) ? def
: SSA_NAME_VAR (def
);
1833 /* If DEF is a naked symbol that needs renaming, create a new
1835 if (marked_for_renaming (sym
))
1841 def
= make_ssa_name (def
, stmt
);
1842 SET_DEF (def_p
, def
);
1844 tracked_var
= target_for_debug_bind (sym
);
1847 gimple note
= gimple_build_debug_bind (tracked_var
, def
, stmt
);
1848 /* If stmt ends the bb, insert the debug stmt on the single
1849 non-EH edge from the stmt. */
1850 if (gsi_one_before_end_p (gsi
) && stmt_ends_bb_p (stmt
))
1852 basic_block bb
= gsi_bb (gsi
);
1855 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1856 if (!(e
->flags
& EDGE_EH
))
1861 /* If there are other predecessors to ef->dest, then
1862 there must be PHI nodes for the modified
1863 variable, and therefore there will be debug bind
1864 stmts after the PHI nodes. The debug bind notes
1865 we'd insert would force the creation of a new
1866 block (diverging codegen) and be redundant with
1867 the post-PHI bind stmts, so don't add them.
1869 As for the exit edge, there wouldn't be redundant
1870 bind stmts, but there wouldn't be a PC to bind
1871 them to either, so avoid diverging the CFG. */
1872 if (ef
&& single_pred_p (ef
->dest
)
1873 && ef
->dest
!= EXIT_BLOCK_PTR
)
1875 /* If there were PHI nodes in the node, we'd
1876 have to make sure the value we're binding
1877 doesn't need rewriting. But there shouldn't
1878 be PHI nodes in a single-predecessor block,
1879 so we just add the note. */
1880 gsi_insert_on_edge_immediate (ef
, note
);
1884 gsi_insert_after (&gsi
, note
, GSI_SAME_STMT
);
1888 register_new_update_single (def
, sym
);
1892 /* If DEF is a new name, register it as a new definition
1893 for all the names replaced by DEF. */
1894 if (is_new_name (def
))
1895 register_new_update_set (def
, names_replaced_by (def
));
1897 /* If DEF is an old name, register DEF as a new
1898 definition for itself. */
1899 if (is_old_name (def
))
1900 register_new_update_single (def
, def
);
1905 /* Update every variable used in the statement pointed-to by SI. The
1906 statement is assumed to be in SSA form already. Names in
1907 OLD_SSA_NAMES used by SI will be updated to their current reaching
1908 definition. Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI
1909 will be registered as a new definition for their corresponding name
1910 in OLD_SSA_NAMES. */
1913 rewrite_update_stmt (gimple stmt
, gimple_stmt_iterator gsi
)
1915 use_operand_p use_p
;
1916 def_operand_p def_p
;
1919 /* Only update marked statements. */
1920 if (!rewrite_uses_p (stmt
) && !register_defs_p (stmt
))
1923 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1925 fprintf (dump_file
, "Updating SSA information for statement ");
1926 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1929 /* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying
1930 symbol is marked for renaming. */
1931 if (rewrite_uses_p (stmt
))
1933 if (is_gimple_debug (stmt
))
1935 bool failed
= false;
1937 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
1938 if (!maybe_replace_use_in_debug_stmt (use_p
))
1946 /* DOM sometimes threads jumps in such a way that a
1947 debug stmt ends up referencing a SSA variable that no
1948 longer dominates the debug stmt, but such that all
1949 incoming definitions refer to the same definition in
1950 an earlier dominator. We could try to recover that
1951 definition somehow, but this will have to do for now.
1953 Introducing a default definition, which is what
1954 maybe_replace_use() would do in such cases, may
1955 modify code generation, for the otherwise-unused
1956 default definition would never go away, modifying SSA
1957 version numbers all over. */
1958 gimple_debug_bind_reset_value (stmt
);
1964 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
1965 maybe_replace_use (use_p
);
1969 /* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES.
1970 Also register definitions for names whose underlying symbol is
1971 marked for renaming. */
1972 if (register_defs_p (stmt
))
1973 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1974 maybe_register_def (def_p
, stmt
, gsi
);
1978 /* Visit all the successor blocks of BB looking for PHI nodes. For
1979 every PHI node found, check if any of its arguments is in
1980 OLD_SSA_NAMES. If so, and if the argument has a current reaching
1981 definition, replace it. */
1984 rewrite_update_phi_arguments (basic_block bb
)
1990 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1995 if (!bitmap_bit_p (blocks_with_phis_to_rewrite
, e
->dest
->index
))
1998 phis
= VEC_index (gimple_vec
, phis_to_rewrite
, e
->dest
->index
);
1999 FOR_EACH_VEC_ELT (gimple
, phis
, i
, phi
)
2001 tree arg
, lhs_sym
, reaching_def
= NULL
;
2002 use_operand_p arg_p
;
2004 gcc_assert (rewrite_uses_p (phi
));
2006 arg_p
= PHI_ARG_DEF_PTR_FROM_EDGE (phi
, e
);
2007 arg
= USE_FROM_PTR (arg_p
);
2009 if (arg
&& !DECL_P (arg
) && TREE_CODE (arg
) != SSA_NAME
)
2012 lhs_sym
= SSA_NAME_VAR (gimple_phi_result (phi
));
2014 if (arg
== NULL_TREE
)
2016 /* When updating a PHI node for a recently introduced
2017 symbol we may find NULL arguments. That's why we
2018 take the symbol from the LHS of the PHI node. */
2019 reaching_def
= get_reaching_def (lhs_sym
);
2024 tree sym
= DECL_P (arg
) ? arg
: SSA_NAME_VAR (arg
);
2026 if (marked_for_renaming (sym
))
2027 reaching_def
= get_reaching_def (sym
);
2028 else if (is_old_name (arg
))
2029 reaching_def
= get_reaching_def (arg
);
2032 /* 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
);
2040 stmt
= SSA_NAME_DEF_STMT (reaching_def
);
2042 /* Single element PHI nodes behave like copies, so get the
2043 location from the phi argument. */
2044 if (gimple_code (stmt
) == GIMPLE_PHI
&&
2045 gimple_phi_num_args (stmt
) == 1)
2046 locus
= gimple_phi_arg_location (stmt
, 0);
2048 locus
= gimple_location (stmt
);
2050 gimple_phi_arg_set_location (phi
, arg_i
, locus
);
2054 if (e
->flags
& EDGE_ABNORMAL
)
2055 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p
)) = 1;
2061 /* Initialization of block data structures for the incremental SSA
2062 update pass. Create a block local stack of reaching definitions
2063 for new SSA names produced in this block (BLOCK_DEFS). Register
2064 new definitions for every PHI node in the block. */
2067 rewrite_update_enter_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
2070 bool is_abnormal_phi
;
2071 gimple_stmt_iterator gsi
;
2073 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
2074 fprintf (dump_file
, "Registering new PHI nodes in block #%d\n",
2077 /* Mark the unwind point for this block. */
2078 VEC_safe_push (tree
, heap
, block_defs_stack
, NULL_TREE
);
2080 if (!bitmap_bit_p (blocks_to_update
, bb
->index
))
2083 /* Mark the LHS if any of the arguments flows through an abnormal
2085 is_abnormal_phi
= bb_has_abnormal_pred (bb
);
2087 /* If any of the PHI nodes is a replacement for a name in
2088 OLD_SSA_NAMES or it's one of the names in NEW_SSA_NAMES, then
2089 register it as a new definition for its corresponding name. Also
2090 register definitions for names whose underlying symbols are
2091 marked for renaming. */
2092 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2095 gimple phi
= gsi_stmt (gsi
);
2097 if (!register_defs_p (phi
))
2100 lhs
= gimple_phi_result (phi
);
2101 lhs_sym
= SSA_NAME_VAR (lhs
);
2103 if (marked_for_renaming (lhs_sym
))
2104 register_new_update_single (lhs
, lhs_sym
);
2108 /* If LHS is a new name, register a new definition for all
2109 the names replaced by LHS. */
2110 if (is_new_name (lhs
))
2111 register_new_update_set (lhs
, names_replaced_by (lhs
));
2113 /* If LHS is an OLD name, register it as a new definition
2115 if (is_old_name (lhs
))
2116 register_new_update_single (lhs
, lhs
);
2119 if (is_abnormal_phi
)
2120 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs
) = 1;
2123 /* Step 2. Rewrite every variable used in each statement in the block. */
2124 if (TEST_BIT (interesting_blocks
, bb
->index
))
2126 gcc_assert (bitmap_bit_p (blocks_to_update
, bb
->index
));
2127 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2128 rewrite_update_stmt (gsi_stmt (gsi
), gsi
);
2131 /* Step 3. Update PHI nodes. */
2132 rewrite_update_phi_arguments (bb
);
2135 /* Called after visiting block BB. Unwind BLOCK_DEFS_STACK to restore
2136 the current reaching definition of every name re-written in BB to
2137 the original reaching definition before visiting BB. This
2138 unwinding must be done in the opposite order to what is done in
2139 register_new_update_set. */
2142 rewrite_update_leave_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
2143 basic_block bb ATTRIBUTE_UNUSED
)
2145 while (VEC_length (tree
, block_defs_stack
) > 0)
2147 tree var
= VEC_pop (tree
, block_defs_stack
);
2150 /* NULL indicates the unwind stop point for this block (see
2151 rewrite_update_enter_block). */
2155 saved_def
= VEC_pop (tree
, block_defs_stack
);
2156 get_common_info (var
)->current_def
= saved_def
;
2161 /* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
2164 ENTRY indicates the block where to start. Every block dominated by
2165 ENTRY will be rewritten.
2167 WHAT indicates what actions will be taken by the renamer (see enum
2170 BLOCKS are the set of interesting blocks for the dominator walker
2171 to process. If this set is NULL, then all the nodes dominated
2172 by ENTRY are walked. Otherwise, blocks dominated by ENTRY that
2173 are not present in BLOCKS are ignored. */
2176 rewrite_blocks (basic_block entry
, enum rewrite_mode what
)
2178 struct dom_walk_data walk_data
;
2180 /* Rewrite all the basic blocks in the program. */
2181 timevar_push (TV_TREE_SSA_REWRITE_BLOCKS
);
2183 /* Setup callbacks for the generic dominator tree walker. */
2184 memset (&walk_data
, 0, sizeof (walk_data
));
2186 walk_data
.dom_direction
= CDI_DOMINATORS
;
2188 if (what
== REWRITE_ALL
)
2190 walk_data
.before_dom_children
= rewrite_enter_block
;
2191 walk_data
.after_dom_children
= rewrite_leave_block
;
2193 else if (what
== REWRITE_UPDATE
)
2195 walk_data
.before_dom_children
= rewrite_update_enter_block
;
2196 walk_data
.after_dom_children
= rewrite_update_leave_block
;
2201 block_defs_stack
= VEC_alloc (tree
, heap
, 10);
2203 /* Initialize the dominator walker. */
2204 init_walk_dominator_tree (&walk_data
);
2206 /* Recursively walk the dominator tree rewriting each statement in
2207 each basic block. */
2208 walk_dominator_tree (&walk_data
, entry
);
2210 /* Finalize the dominator walker. */
2211 fini_walk_dominator_tree (&walk_data
);
2213 /* Debugging dumps. */
2214 if (dump_file
&& (dump_flags
& TDF_STATS
))
2216 dump_dfa_stats (dump_file
);
2218 dump_tree_ssa_stats (dump_file
);
2221 VEC_free (tree
, heap
, block_defs_stack
);
2223 timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS
);
2227 /* Block processing routine for mark_def_sites. Clear the KILLS bitmap
2228 at the start of each block, and call mark_def_sites for each statement. */
2231 mark_def_sites_block (struct dom_walk_data
*walk_data
, basic_block bb
)
2233 struct mark_def_sites_global_data
*gd
;
2235 gimple_stmt_iterator gsi
;
2237 gd
= (struct mark_def_sites_global_data
*) walk_data
->global_data
;
2240 bitmap_clear (kills
);
2241 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2242 mark_def_sites (bb
, gsi_stmt (gsi
), kills
);
2246 /* Mark the definition site blocks for each variable, so that we know
2247 where the variable is actually live.
2249 The INTERESTING_BLOCKS global will be filled in with all the blocks
2250 that should be processed by the renamer. It is assumed that the
2251 caller has already initialized and zeroed it. */
2254 mark_def_site_blocks (void)
2256 struct dom_walk_data walk_data
;
2257 struct mark_def_sites_global_data mark_def_sites_global_data
;
2259 /* Setup callbacks for the generic dominator tree walker to find and
2260 mark definition sites. */
2261 walk_data
.dom_direction
= CDI_DOMINATORS
;
2262 walk_data
.initialize_block_local_data
= NULL
;
2263 walk_data
.before_dom_children
= mark_def_sites_block
;
2264 walk_data
.after_dom_children
= NULL
;
2266 /* Notice that this bitmap is indexed using variable UIDs, so it must be
2267 large enough to accommodate all the variables referenced in the
2268 function, not just the ones we are renaming. */
2269 mark_def_sites_global_data
.kills
= BITMAP_ALLOC (NULL
);
2270 walk_data
.global_data
= &mark_def_sites_global_data
;
2272 /* We do not have any local data. */
2273 walk_data
.block_local_data_size
= 0;
2275 /* Initialize the dominator walker. */
2276 init_walk_dominator_tree (&walk_data
);
2278 /* Recursively walk the dominator tree. */
2279 walk_dominator_tree (&walk_data
, ENTRY_BLOCK_PTR
);
2281 /* Finalize the dominator walker. */
2282 fini_walk_dominator_tree (&walk_data
);
2284 /* We no longer need this bitmap, clear and free it. */
2285 BITMAP_FREE (mark_def_sites_global_data
.kills
);
2289 /* Initialize internal data needed during renaming. */
2292 init_ssa_renamer (void)
2294 cfun
->gimple_df
->in_ssa_p
= false;
2296 /* Allocate memory for the DEF_BLOCKS hash table. */
2297 gcc_assert (var_infos
== NULL
);
2298 var_infos
= htab_create (VEC_length (tree
, cfun
->local_decls
),
2299 var_info_hash
, var_info_eq
, NULL
);
2301 bitmap_obstack_initialize (&update_ssa_obstack
);
2305 /* Deallocate internal data structures used by the renamer. */
2308 fini_ssa_renamer (void)
2312 htab_delete (var_infos
);
2316 bitmap_obstack_release (&update_ssa_obstack
);
2318 cfun
->gimple_df
->ssa_renaming_needed
= 0;
2319 cfun
->gimple_df
->rename_vops
= 0;
2320 cfun
->gimple_df
->in_ssa_p
= true;
2323 /* Main entry point into the SSA builder. The renaming process
2324 proceeds in four main phases:
2326 1- Compute dominance frontier and immediate dominators, needed to
2327 insert PHI nodes and rename the function in dominator tree
2330 2- Find and mark all the blocks that define variables
2331 (mark_def_site_blocks).
2333 3- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
2335 4- Rename all the blocks (rewrite_blocks) and statements in the program.
2337 Steps 3 and 4 are done using the dominator tree walker
2338 (walk_dominator_tree). */
2341 rewrite_into_ssa (void)
2347 /* Initialize operand data structures. */
2348 init_ssa_operands (cfun
);
2350 /* Initialize internal data needed by the renamer. */
2351 init_ssa_renamer ();
2353 /* Initialize the set of interesting blocks. The callback
2354 mark_def_sites will add to this set those blocks that the renamer
2356 interesting_blocks
= sbitmap_alloc (last_basic_block
);
2357 sbitmap_zero (interesting_blocks
);
2359 /* Initialize dominance frontier. */
2360 dfs
= XNEWVEC (bitmap_head
, last_basic_block
);
2362 bitmap_initialize (&dfs
[bb
->index
], &bitmap_default_obstack
);
2364 /* 1- Compute dominance frontiers. */
2365 calculate_dominance_info (CDI_DOMINATORS
);
2366 compute_dominance_frontiers (dfs
);
2368 /* 2- Find and mark definition sites. */
2369 mark_def_site_blocks ();
2371 /* 3- Insert PHI nodes at dominance frontiers of definition blocks. */
2372 insert_phi_nodes (dfs
);
2374 /* 4- Rename all the blocks. */
2375 rewrite_blocks (ENTRY_BLOCK_PTR
, REWRITE_ALL
);
2377 /* Free allocated memory. */
2379 bitmap_clear (&dfs
[bb
->index
]);
2382 sbitmap_free (interesting_blocks
);
2384 fini_ssa_renamer ();
2386 /* Try to get rid of all gimplifier generated temporaries by making
2387 its SSA names anonymous. This way we can garbage collect them
2388 all after removing unused locals which we do in our TODO. */
2389 for (i
= 1; i
< num_ssa_names
; ++i
)
2391 tree decl
, name
= ssa_name (i
);
2393 || SSA_NAME_IS_DEFAULT_DEF (name
))
2395 decl
= SSA_NAME_VAR (name
);
2397 && TREE_CODE (decl
) == VAR_DECL
2398 && !VAR_DECL_IS_VIRTUAL_OPERAND (decl
)
2399 && DECL_ARTIFICIAL (decl
)
2400 && DECL_IGNORED_P (decl
)
2401 && !DECL_NAME (decl
))
2402 SET_SSA_NAME_VAR_OR_IDENTIFIER (name
, NULL_TREE
);
2409 struct gimple_opt_pass pass_build_ssa
=
2415 rewrite_into_ssa
, /* execute */
2418 0, /* static_pass_number */
2419 TV_TREE_SSA_OTHER
, /* tv_id */
2420 PROP_cfg
, /* properties_required */
2421 PROP_ssa
, /* properties_provided */
2422 0, /* properties_destroyed */
2423 0, /* todo_flags_start */
2425 | TODO_remove_unused_locals
/* todo_flags_finish */
2430 /* Mark the definition of VAR at STMT and BB as interesting for the
2431 renamer. BLOCKS is the set of blocks that need updating. */
2434 mark_def_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2436 gcc_assert (bitmap_bit_p (blocks_to_update
, bb
->index
));
2437 set_register_defs (stmt
, true);
2441 bool is_phi_p
= gimple_code (stmt
) == GIMPLE_PHI
;
2443 set_def_block (var
, bb
, is_phi_p
);
2445 /* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition
2446 site for both itself and all the old names replaced by it. */
2447 if (TREE_CODE (var
) == SSA_NAME
&& is_new_name (var
))
2451 bitmap set
= names_replaced_by (var
);
2453 EXECUTE_IF_SET_IN_BITMAP (set
, 0, i
, bi
)
2454 set_def_block (ssa_name (i
), bb
, is_phi_p
);
2460 /* Mark the use of VAR at STMT and BB as interesting for the
2461 renamer. INSERT_PHI_P is true if we are going to insert new PHI
2465 mark_use_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2467 basic_block def_bb
= gimple_bb (stmt
);
2469 mark_block_for_update (def_bb
);
2470 mark_block_for_update (bb
);
2472 if (gimple_code (stmt
) == GIMPLE_PHI
)
2473 mark_phi_for_rewrite (def_bb
, stmt
);
2476 set_rewrite_uses (stmt
, true);
2478 if (is_gimple_debug (stmt
))
2482 /* If VAR has not been defined in BB, then it is live-on-entry
2483 to BB. Note that we cannot just use the block holding VAR's
2484 definition because if VAR is one of the names in OLD_SSA_NAMES,
2485 it will have several definitions (itself and all the names that
2489 struct def_blocks_d
*db_p
= get_def_blocks_for (get_common_info (var
));
2490 if (!bitmap_bit_p (db_p
->def_blocks
, bb
->index
))
2491 set_livein_block (var
, bb
);
2496 /* Do a dominator walk starting at BB processing statements that
2497 reference symbols in SSA operands. This is very similar to
2498 mark_def_sites, but the scan handles statements whose operands may
2499 already be SSA names.
2501 If INSERT_PHI_P is true, mark those uses as live in the
2502 corresponding block. This is later used by the PHI placement
2503 algorithm to make PHI pruning decisions.
2505 FIXME. Most of this would be unnecessary if we could associate a
2506 symbol to all the SSA names that reference it. But that
2507 sounds like it would be expensive to maintain. Still, it
2508 would be interesting to see if it makes better sense to do
2512 prepare_block_for_update (basic_block bb
, bool insert_phi_p
)
2515 gimple_stmt_iterator si
;
2519 mark_block_for_update (bb
);
2521 /* Process PHI nodes marking interesting those that define or use
2522 the symbols that we are interested in. */
2523 for (si
= gsi_start_phis (bb
); !gsi_end_p (si
); gsi_next (&si
))
2525 gimple phi
= gsi_stmt (si
);
2526 tree lhs_sym
, lhs
= gimple_phi_result (phi
);
2528 if (TREE_CODE (lhs
) == SSA_NAME
2529 && (! virtual_operand_p (lhs
)
2530 || ! cfun
->gimple_df
->rename_vops
))
2533 lhs_sym
= DECL_P (lhs
) ? lhs
: SSA_NAME_VAR (lhs
);
2534 mark_for_renaming (lhs_sym
);
2535 mark_def_interesting (lhs_sym
, phi
, bb
, insert_phi_p
);
2537 /* Mark the uses in phi nodes as interesting. It would be more correct
2538 to process the arguments of the phi nodes of the successor edges of
2539 BB at the end of prepare_block_for_update, however, that turns out
2540 to be significantly more expensive. Doing it here is conservatively
2541 correct -- it may only cause us to believe a value to be live in a
2542 block that also contains its definition, and thus insert a few more
2543 phi nodes for it. */
2544 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
2545 mark_use_interesting (lhs_sym
, phi
, e
->src
, insert_phi_p
);
2548 /* Process the statements. */
2549 for (si
= gsi_start_bb (bb
); !gsi_end_p (si
); gsi_next (&si
))
2553 use_operand_p use_p
;
2554 def_operand_p def_p
;
2556 stmt
= gsi_stmt (si
);
2558 if (cfun
->gimple_df
->rename_vops
2559 && gimple_vuse (stmt
))
2561 tree use
= gimple_vuse (stmt
);
2562 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
2563 mark_for_renaming (sym
);
2564 mark_use_interesting (sym
, stmt
, bb
, insert_phi_p
);
2567 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, i
, SSA_OP_USE
)
2569 tree use
= USE_FROM_PTR (use_p
);
2572 mark_for_renaming (use
);
2573 mark_use_interesting (use
, stmt
, bb
, insert_phi_p
);
2576 if (cfun
->gimple_df
->rename_vops
2577 && gimple_vdef (stmt
))
2579 tree def
= gimple_vdef (stmt
);
2580 tree sym
= DECL_P (def
) ? def
: SSA_NAME_VAR (def
);
2581 mark_for_renaming (sym
);
2582 mark_def_interesting (sym
, stmt
, bb
, insert_phi_p
);
2585 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, i
, SSA_OP_DEF
)
2587 tree def
= DEF_FROM_PTR (def_p
);
2590 mark_for_renaming (def
);
2591 mark_def_interesting (def
, stmt
, bb
, insert_phi_p
);
2595 /* Now visit all the blocks dominated by BB. */
2596 for (son
= first_dom_son (CDI_DOMINATORS
, bb
);
2598 son
= next_dom_son (CDI_DOMINATORS
, son
))
2599 prepare_block_for_update (son
, insert_phi_p
);
2603 /* Helper for prepare_names_to_update. Mark all the use sites for
2604 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2605 prepare_names_to_update. */
2608 prepare_use_sites_for (tree name
, bool insert_phi_p
)
2610 use_operand_p use_p
;
2611 imm_use_iterator iter
;
2613 FOR_EACH_IMM_USE_FAST (use_p
, iter
, name
)
2615 gimple stmt
= USE_STMT (use_p
);
2616 basic_block bb
= gimple_bb (stmt
);
2618 if (gimple_code (stmt
) == GIMPLE_PHI
)
2620 int ix
= PHI_ARG_INDEX_FROM_USE (use_p
);
2621 edge e
= gimple_phi_arg_edge (stmt
, ix
);
2622 mark_use_interesting (name
, stmt
, e
->src
, insert_phi_p
);
2626 /* For regular statements, mark this as an interesting use
2628 mark_use_interesting (name
, stmt
, bb
, insert_phi_p
);
2634 /* Helper for prepare_names_to_update. Mark the definition site for
2635 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2636 prepare_names_to_update. */
2639 prepare_def_site_for (tree name
, bool insert_phi_p
)
2644 gcc_assert (names_to_release
== NULL
2645 || !bitmap_bit_p (names_to_release
, SSA_NAME_VERSION (name
)));
2647 stmt
= SSA_NAME_DEF_STMT (name
);
2648 bb
= gimple_bb (stmt
);
2651 gcc_assert (bb
->index
< last_basic_block
);
2652 mark_block_for_update (bb
);
2653 mark_def_interesting (name
, stmt
, bb
, insert_phi_p
);
2658 /* Mark definition and use sites of names in NEW_SSA_NAMES and
2659 OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert
2660 PHI nodes for newly created names. */
2663 prepare_names_to_update (bool insert_phi_p
)
2667 sbitmap_iterator sbi
;
2669 /* If a name N from NEW_SSA_NAMES is also marked to be released,
2670 remove it from NEW_SSA_NAMES so that we don't try to visit its
2671 defining basic block (which most likely doesn't exist). Notice
2672 that we cannot do the same with names in OLD_SSA_NAMES because we
2673 want to replace existing instances. */
2674 if (names_to_release
)
2675 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2676 RESET_BIT (new_ssa_names
, i
);
2678 /* First process names in NEW_SSA_NAMES. Otherwise, uses of old
2679 names may be considered to be live-in on blocks that contain
2680 definitions for their replacements. */
2681 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names
, 0, i
, sbi
)
2682 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2684 /* If an old name is in NAMES_TO_RELEASE, we cannot remove it from
2685 OLD_SSA_NAMES, but we have to ignore its definition site. */
2686 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names
, 0, i
, sbi
)
2688 if (names_to_release
== NULL
|| !bitmap_bit_p (names_to_release
, i
))
2689 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2690 prepare_use_sites_for (ssa_name (i
), insert_phi_p
);
2695 /* Dump all the names replaced by NAME to FILE. */
2698 dump_names_replaced_by (FILE *file
, tree name
)
2704 print_generic_expr (file
, name
, 0);
2705 fprintf (file
, " -> { ");
2707 old_set
= names_replaced_by (name
);
2708 EXECUTE_IF_SET_IN_BITMAP (old_set
, 0, i
, bi
)
2710 print_generic_expr (file
, ssa_name (i
), 0);
2711 fprintf (file
, " ");
2714 fprintf (file
, "}\n");
2718 /* Dump all the names replaced by NAME to stderr. */
2721 debug_names_replaced_by (tree name
)
2723 dump_names_replaced_by (stderr
, name
);
2727 /* Dump SSA update information to FILE. */
2730 dump_update_ssa (FILE *file
)
2735 if (!need_ssa_update_p (cfun
))
2738 if (new_ssa_names
&& sbitmap_first_set_bit (new_ssa_names
) >= 0)
2740 sbitmap_iterator sbi
;
2742 fprintf (file
, "\nSSA replacement table\n");
2743 fprintf (file
, "N_i -> { O_1 ... O_j } means that N_i replaces "
2744 "O_1, ..., O_j\n\n");
2746 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names
, 0, i
, sbi
)
2747 dump_names_replaced_by (file
, ssa_name (i
));
2750 if (symbols_to_rename_set
&& !bitmap_empty_p (symbols_to_rename_set
))
2752 fprintf (file
, "\nSymbols to be put in SSA form\n");
2753 dump_decl_set (file
, symbols_to_rename_set
);
2754 fprintf (file
, "\n");
2757 if (names_to_release
&& !bitmap_empty_p (names_to_release
))
2759 fprintf (file
, "\nSSA names to release after updating the SSA web\n\n");
2760 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2762 print_generic_expr (file
, ssa_name (i
), 0);
2763 fprintf (file
, " ");
2765 fprintf (file
, "\n");
2770 /* Dump SSA update information to stderr. */
2773 debug_update_ssa (void)
2775 dump_update_ssa (stderr
);
2779 /* Initialize data structures used for incremental SSA updates. */
2782 init_update_ssa (struct function
*fn
)
2784 /* Reserve more space than the current number of names. The calls to
2785 add_new_name_mapping are typically done after creating new SSA
2786 names, so we'll need to reallocate these arrays. */
2787 old_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2788 sbitmap_zero (old_ssa_names
);
2790 new_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2791 sbitmap_zero (new_ssa_names
);
2793 bitmap_obstack_initialize (&update_ssa_obstack
);
2795 names_to_release
= NULL
;
2796 update_ssa_initialized_fn
= fn
;
2800 /* Deallocate data structures used for incremental SSA updates. */
2803 delete_update_ssa (void)
2808 sbitmap_free (old_ssa_names
);
2809 old_ssa_names
= NULL
;
2811 sbitmap_free (new_ssa_names
);
2812 new_ssa_names
= NULL
;
2814 BITMAP_FREE (symbols_to_rename_set
);
2815 symbols_to_rename_set
= NULL
;
2816 VEC_free (tree
, heap
, symbols_to_rename
);
2818 if (names_to_release
)
2820 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2821 release_ssa_name (ssa_name (i
));
2822 BITMAP_FREE (names_to_release
);
2825 clear_ssa_name_info ();
2827 fini_ssa_renamer ();
2829 if (blocks_with_phis_to_rewrite
)
2830 EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite
, 0, i
, bi
)
2832 gimple_vec phis
= VEC_index (gimple_vec
, phis_to_rewrite
, i
);
2834 VEC_free (gimple
, heap
, phis
);
2835 VEC_replace (gimple_vec
, phis_to_rewrite
, i
, NULL
);
2838 BITMAP_FREE (blocks_with_phis_to_rewrite
);
2839 BITMAP_FREE (blocks_to_update
);
2841 update_ssa_initialized_fn
= NULL
;
2845 /* Create a new name for OLD_NAME in statement STMT and replace the
2846 operand pointed to by DEF_P with the newly created name. Return
2847 the new name and register the replacement mapping <NEW, OLD> in
2848 update_ssa's tables. */
2851 create_new_def_for (tree old_name
, gimple stmt
, def_operand_p def
)
2853 tree new_name
= duplicate_ssa_name (old_name
, stmt
);
2855 SET_DEF (def
, new_name
);
2857 if (gimple_code (stmt
) == GIMPLE_PHI
)
2859 basic_block bb
= gimple_bb (stmt
);
2861 /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
2862 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name
) = bb_has_abnormal_pred (bb
);
2865 register_new_name_mapping (new_name
, old_name
);
2867 /* For the benefit of passes that will be updating the SSA form on
2868 their own, set the current reaching definition of OLD_NAME to be
2870 get_ssa_name_ann (old_name
)->info
.current_def
= new_name
;
2876 /* Register name NEW to be a replacement for name OLD. This function
2877 must be called for every replacement that should be performed by
2881 register_new_name_mapping (tree new_tree
, tree old
)
2883 if (!update_ssa_initialized_fn
)
2884 init_update_ssa (cfun
);
2886 gcc_assert (update_ssa_initialized_fn
== cfun
);
2888 add_new_name_mapping (new_tree
, old
);
2892 /* Mark virtual operands of FN for renaming by update_ssa. */
2895 mark_virtual_operands_for_renaming (struct function
*fn
)
2897 fn
->gimple_df
->ssa_renaming_needed
= 1;
2898 fn
->gimple_df
->rename_vops
= 1;
2902 /* Return true if there is any work to be done by update_ssa
2906 need_ssa_update_p (struct function
*fn
)
2908 gcc_assert (fn
!= NULL
);
2909 return (update_ssa_initialized_fn
== fn
2910 || (fn
->gimple_df
&& fn
->gimple_df
->ssa_renaming_needed
));
2913 /* Return true if name N has been registered in the replacement table. */
2916 name_registered_for_update_p (tree n ATTRIBUTE_UNUSED
)
2918 if (!update_ssa_initialized_fn
)
2921 gcc_assert (update_ssa_initialized_fn
== cfun
);
2923 return is_new_name (n
) || is_old_name (n
);
2927 /* Mark NAME to be released after update_ssa has finished. */
2930 release_ssa_name_after_update_ssa (tree name
)
2932 gcc_assert (cfun
&& update_ssa_initialized_fn
== cfun
);
2934 if (names_to_release
== NULL
)
2935 names_to_release
= BITMAP_ALLOC (NULL
);
2937 bitmap_set_bit (names_to_release
, SSA_NAME_VERSION (name
));
2941 /* Insert new PHI nodes to replace VAR. DFS contains dominance
2942 frontier information. BLOCKS is the set of blocks to be updated.
2944 This is slightly different than the regular PHI insertion
2945 algorithm. The value of UPDATE_FLAGS controls how PHI nodes for
2946 real names (i.e., GIMPLE registers) are inserted:
2948 - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI
2949 nodes inside the region affected by the block that defines VAR
2950 and the blocks that define all its replacements. All these
2951 definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS.
2953 First, we compute the entry point to the region (ENTRY). This is
2954 given by the nearest common dominator to all the definition
2955 blocks. When computing the iterated dominance frontier (IDF), any
2956 block not strictly dominated by ENTRY is ignored.
2958 We then call the standard PHI insertion algorithm with the pruned
2961 - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real
2962 names is not pruned. PHI nodes are inserted at every IDF block. */
2965 insert_updated_phi_nodes_for (tree var
, bitmap_head
*dfs
, bitmap blocks
,
2966 unsigned update_flags
)
2969 struct def_blocks_d
*db
;
2970 bitmap idf
, pruned_idf
;
2974 if (TREE_CODE (var
) == SSA_NAME
)
2975 gcc_checking_assert (is_old_name (var
));
2977 gcc_checking_assert (marked_for_renaming (var
));
2979 /* Get all the definition sites for VAR. */
2980 db
= find_def_blocks_for (var
);
2982 /* No need to do anything if there were no definitions to VAR. */
2983 if (db
== NULL
|| bitmap_empty_p (db
->def_blocks
))
2986 /* Compute the initial iterated dominance frontier. */
2987 idf
= compute_idf (db
->def_blocks
, dfs
);
2988 pruned_idf
= BITMAP_ALLOC (NULL
);
2990 if (TREE_CODE (var
) == SSA_NAME
)
2992 if (update_flags
== TODO_update_ssa
)
2994 /* If doing regular SSA updates for GIMPLE registers, we are
2995 only interested in IDF blocks dominated by the nearest
2996 common dominator of all the definition blocks. */
2997 entry
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
2999 if (entry
!= ENTRY_BLOCK_PTR
)
3000 EXECUTE_IF_SET_IN_BITMAP (idf
, 0, i
, bi
)
3001 if (BASIC_BLOCK (i
) != entry
3002 && dominated_by_p (CDI_DOMINATORS
, BASIC_BLOCK (i
), entry
))
3003 bitmap_set_bit (pruned_idf
, i
);
3007 /* Otherwise, do not prune the IDF for VAR. */
3008 gcc_assert (update_flags
== TODO_update_ssa_full_phi
);
3009 bitmap_copy (pruned_idf
, idf
);
3014 /* Otherwise, VAR is a symbol that needs to be put into SSA form
3015 for the first time, so we need to compute the full IDF for
3017 bitmap_copy (pruned_idf
, idf
);
3020 if (!bitmap_empty_p (pruned_idf
))
3022 /* Make sure that PRUNED_IDF blocks and all their feeding blocks
3023 are included in the region to be updated. The feeding blocks
3024 are important to guarantee that the PHI arguments are renamed
3027 /* FIXME, this is not needed if we are updating symbols. We are
3028 already starting at the ENTRY block anyway. */
3029 bitmap_ior_into (blocks
, pruned_idf
);
3030 EXECUTE_IF_SET_IN_BITMAP (pruned_idf
, 0, i
, bi
)
3034 basic_block bb
= BASIC_BLOCK (i
);
3036 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
3037 if (e
->src
->index
>= 0)
3038 bitmap_set_bit (blocks
, e
->src
->index
);
3041 insert_phi_nodes_for (var
, pruned_idf
, true);
3044 BITMAP_FREE (pruned_idf
);
3049 /* Given a set of newly created SSA names (NEW_SSA_NAMES) and a set of
3050 existing SSA names (OLD_SSA_NAMES), update the SSA form so that:
3052 1- The names in OLD_SSA_NAMES dominated by the definitions of
3053 NEW_SSA_NAMES are all re-written to be reached by the
3054 appropriate definition from NEW_SSA_NAMES.
3056 2- If needed, new PHI nodes are added to the iterated dominance
3057 frontier of the blocks where each of NEW_SSA_NAMES are defined.
3059 The mapping between OLD_SSA_NAMES and NEW_SSA_NAMES is setup by
3060 calling register_new_name_mapping for every pair of names that the
3061 caller wants to replace.
3063 The caller identifies the new names that have been inserted and the
3064 names that need to be replaced by calling register_new_name_mapping
3065 for every pair <NEW, OLD>. Note that the function assumes that the
3066 new names have already been inserted in the IL.
3068 For instance, given the following code:
3071 2 x_1 = PHI (0, x_5)
3082 Suppose that we insert new names x_10 and x_11 (lines 4 and 8).
3085 2 x_1 = PHI (0, x_5)
3098 We want to replace all the uses of x_1 with the new definitions of
3099 x_10 and x_11. Note that the only uses that should be replaced are
3100 those at lines 5, 9 and 11. Also, the use of x_7 at line 9 should
3101 *not* be replaced (this is why we cannot just mark symbol 'x' for
3104 Additionally, we may need to insert a PHI node at line 11 because
3105 that is a merge point for x_10 and x_11. So the use of x_1 at line
3106 11 will be replaced with the new PHI node. The insertion of PHI
3107 nodes is optional. They are not strictly necessary to preserve the
3108 SSA form, and depending on what the caller inserted, they may not
3109 even be useful for the optimizers. UPDATE_FLAGS controls various
3110 aspects of how update_ssa operates, see the documentation for
3111 TODO_update_ssa*. */
3114 update_ssa (unsigned update_flags
)
3116 basic_block bb
, start_bb
;
3120 sbitmap_iterator sbi
;
3123 /* Only one update flag should be set. */
3124 gcc_assert (update_flags
== TODO_update_ssa
3125 || update_flags
== TODO_update_ssa_no_phi
3126 || update_flags
== TODO_update_ssa_full_phi
3127 || update_flags
== TODO_update_ssa_only_virtuals
);
3129 if (!need_ssa_update_p (cfun
))
3132 timevar_push (TV_TREE_SSA_INCREMENTAL
);
3134 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
3135 fprintf (dump_file
, "\nUpdating SSA:\n");
3137 if (!update_ssa_initialized_fn
)
3138 init_update_ssa (cfun
);
3139 else if (update_flags
== TODO_update_ssa_only_virtuals
)
3141 /* If we only need to update virtuals, remove all the mappings for
3142 real names before proceeding. The caller is responsible for
3143 having dealt with the name mappings before calling update_ssa. */
3144 sbitmap_zero (old_ssa_names
);
3145 sbitmap_zero (new_ssa_names
);
3148 gcc_assert (update_ssa_initialized_fn
== cfun
);
3150 blocks_with_phis_to_rewrite
= BITMAP_ALLOC (NULL
);
3151 if (!phis_to_rewrite
)
3152 phis_to_rewrite
= VEC_alloc (gimple_vec
, heap
, last_basic_block
+ 1);
3153 blocks_to_update
= BITMAP_ALLOC (NULL
);
3155 /* Ensure that the dominance information is up-to-date. */
3156 calculate_dominance_info (CDI_DOMINATORS
);
3158 insert_phi_p
= (update_flags
!= TODO_update_ssa_no_phi
);
3160 /* If there are names defined in the replacement table, prepare
3161 definition and use sites for all the names in NEW_SSA_NAMES and
3163 if (sbitmap_first_set_bit (new_ssa_names
) >= 0)
3165 prepare_names_to_update (insert_phi_p
);
3167 /* If all the names in NEW_SSA_NAMES had been marked for
3168 removal, and there are no symbols to rename, then there's
3169 nothing else to do. */
3170 if (sbitmap_first_set_bit (new_ssa_names
) < 0
3171 && !cfun
->gimple_df
->ssa_renaming_needed
)
3175 /* Next, determine the block at which to start the renaming process. */
3176 if (cfun
->gimple_df
->ssa_renaming_needed
)
3178 /* If we rename bare symbols initialize the mapping to
3179 auxiliar info we need to keep track of. */
3180 var_infos
= htab_create (47, var_info_hash
, var_info_eq
, NULL
);
3182 /* If we have to rename some symbols from scratch, we need to
3183 start the process at the root of the CFG. FIXME, it should
3184 be possible to determine the nearest block that had a
3185 definition for each of the symbols that are marked for
3186 updating. For now this seems more work than it's worth. */
3187 start_bb
= ENTRY_BLOCK_PTR
;
3189 /* Traverse the CFG looking for existing definitions and uses of
3190 symbols in SSA operands. Mark interesting blocks and
3191 statements and set local live-in information for the PHI
3192 placement heuristics. */
3193 prepare_block_for_update (start_bb
, insert_phi_p
);
3195 #ifdef ENABLE_CHECKING
3196 for (i
= 1; i
< num_ssa_names
; ++i
)
3198 tree name
= ssa_name (i
);
3200 || virtual_operand_p (name
))
3203 /* For all but virtual operands, which do not have SSA names
3204 with overlapping life ranges, ensure that symbols marked
3205 for renaming do not have existing SSA names associated with
3206 them as we do not re-write them out-of-SSA before going
3207 into SSA for the remaining symbol uses. */
3208 if (marked_for_renaming (SSA_NAME_VAR (name
)))
3210 fprintf (stderr
, "Existing SSA name for symbol marked for "
3212 print_generic_expr (stderr
, name
, TDF_SLIM
);
3213 fprintf (stderr
, "\n");
3214 internal_error ("SSA corruption");
3221 /* Otherwise, the entry block to the region is the nearest
3222 common dominator for the blocks in BLOCKS. */
3223 start_bb
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3227 /* If requested, insert PHI nodes at the iterated dominance frontier
3228 of every block, creating new definitions for names in OLD_SSA_NAMES
3229 and for symbols found. */
3234 /* If the caller requested PHI nodes to be added, compute
3235 dominance frontiers. */
3236 dfs
= XNEWVEC (bitmap_head
, last_basic_block
);
3238 bitmap_initialize (&dfs
[bb
->index
], &bitmap_default_obstack
);
3239 compute_dominance_frontiers (dfs
);
3241 if (sbitmap_first_set_bit (old_ssa_names
) >= 0)
3243 sbitmap_iterator sbi
;
3245 /* insert_update_phi_nodes_for will call add_new_name_mapping
3246 when inserting new PHI nodes, so the set OLD_SSA_NAMES
3247 will grow while we are traversing it (but it will not
3248 gain any new members). Copy OLD_SSA_NAMES to a temporary
3250 sbitmap tmp
= sbitmap_alloc (SBITMAP_SIZE (old_ssa_names
));
3251 sbitmap_copy (tmp
, old_ssa_names
);
3252 EXECUTE_IF_SET_IN_SBITMAP (tmp
, 0, i
, sbi
)
3253 insert_updated_phi_nodes_for (ssa_name (i
), dfs
, blocks_to_update
,
3258 FOR_EACH_VEC_ELT (tree
, symbols_to_rename
, i
, sym
)
3259 insert_updated_phi_nodes_for (sym
, dfs
, blocks_to_update
,
3263 bitmap_clear (&dfs
[bb
->index
]);
3266 /* Insertion of PHI nodes may have added blocks to the region.
3267 We need to re-compute START_BB to include the newly added
3269 if (start_bb
!= ENTRY_BLOCK_PTR
)
3270 start_bb
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3274 /* Reset the current definition for name and symbol before renaming
3276 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names
, 0, i
, sbi
)
3277 get_ssa_name_ann (ssa_name (i
))->info
.current_def
= NULL_TREE
;
3279 FOR_EACH_VEC_ELT (tree
, symbols_to_rename
, i
, sym
)
3280 get_var_info (sym
)->info
.current_def
= NULL_TREE
;
3282 /* Now start the renaming process at START_BB. */
3283 interesting_blocks
= sbitmap_alloc (last_basic_block
);
3284 sbitmap_zero (interesting_blocks
);
3285 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3286 SET_BIT (interesting_blocks
, i
);
3288 rewrite_blocks (start_bb
, REWRITE_UPDATE
);
3290 sbitmap_free (interesting_blocks
);
3292 /* Debugging dumps. */
3298 dump_update_ssa (dump_file
);
3300 fprintf (dump_file
, "Incremental SSA update started at block: %d\n",
3304 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3306 fprintf (dump_file
, "Number of blocks in CFG: %d\n", last_basic_block
);
3307 fprintf (dump_file
, "Number of blocks to update: %d (%3.0f%%)\n",
3308 c
, PERCENT (c
, last_basic_block
));
3310 if (dump_flags
& TDF_DETAILS
)
3312 fprintf (dump_file
, "Affected blocks:");
3313 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3314 fprintf (dump_file
, " %u", i
);
3315 fprintf (dump_file
, "\n");
3318 fprintf (dump_file
, "\n\n");
3321 /* Free allocated memory. */
3323 delete_update_ssa ();
3325 timevar_pop (TV_TREE_SSA_INCREMENTAL
);