1 /* Rewrite a program in Normal form into SSA.
2 Copyright (C) 2001, 2002, 2003, 2004, 2005, 2007, 2008, 2009
3 Free Software Foundation, Inc.
4 Contributed by Diego Novillo <dnovillo@redhat.com>
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 3, or (at your option)
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"
30 #include "langhooks.h"
31 #include "hard-reg-set.h"
32 #include "basic-block.h"
36 #include "diagnostic.h"
38 #include "tree-flow.h"
40 #include "tree-inline.h"
44 #include "tree-dump.h"
45 #include "tree-pass.h"
53 /* This file builds the SSA form for a function as described in:
54 R. Cytron, J. Ferrante, B. Rosen, M. Wegman, and K. Zadeck. Efficiently
55 Computing Static Single Assignment Form and the Control Dependence
56 Graph. ACM Transactions on Programming Languages and Systems,
57 13(4):451-490, October 1991. */
59 /* Structure to map a variable VAR to the set of blocks that contain
60 definitions for VAR. */
66 /* Blocks that contain definitions of VAR. Bit I will be set if the
67 Ith block contains a definition of VAR. */
70 /* Blocks that contain a PHI node for VAR. */
73 /* Blocks where VAR is live-on-entry. Similar semantics as
79 /* Each entry in DEF_BLOCKS contains an element of type STRUCT
80 DEF_BLOCKS_D, mapping a variable VAR to a bitmap describing all the
81 basic blocks where VAR is defined (assigned a new value). It also
82 contains a bitmap of all the blocks where VAR is live-on-entry
83 (i.e., there is a use of VAR in block B without a preceding
84 definition in B). The live-on-entry information is used when
85 computing PHI pruning heuristics. */
86 static htab_t def_blocks
;
88 /* Stack of trees used to restore the global currdefs to its original
89 state after completing rewriting of a block and its dominator
90 children. Its elements have the following properties:
92 - An SSA_NAME (N) indicates that the current definition of the
93 underlying variable should be set to the given SSA_NAME. If the
94 symbol associated with the SSA_NAME is not a GIMPLE register, the
95 next slot in the stack must be a _DECL node (SYM). In this case,
96 the name N in the previous slot is the current reaching
99 - A _DECL node indicates that the underlying variable has no
102 - A NULL node at the top entry is used to mark the last slot
103 associated with the current block. */
104 static VEC(tree
,heap
) *block_defs_stack
;
107 /* Set of existing SSA names being replaced by update_ssa. */
108 static sbitmap old_ssa_names
;
110 /* Set of new SSA names being added by update_ssa. Note that both
111 NEW_SSA_NAMES and OLD_SSA_NAMES are dense bitmaps because most of
112 the operations done on them are presence tests. */
113 static sbitmap new_ssa_names
;
115 sbitmap interesting_blocks
;
117 /* Set of SSA names that have been marked to be released after they
118 were registered in the replacement table. They will be finally
119 released after we finish updating the SSA web. */
120 static bitmap names_to_release
;
122 static VEC(gimple_vec
, heap
) *phis_to_rewrite
;
124 /* The bitmap of non-NULL elements of PHIS_TO_REWRITE. */
125 static bitmap blocks_with_phis_to_rewrite
;
127 /* Growth factor for NEW_SSA_NAMES and OLD_SSA_NAMES. These sets need
128 to grow as the callers to register_new_name_mapping will typically
129 create new names on the fly. FIXME. Currently set to 1/3 to avoid
130 frequent reallocations but still need to find a reasonable growth
132 #define NAME_SETS_GROWTH_FACTOR (MAX (3, num_ssa_names / 3))
134 /* Tuple used to represent replacement mappings. */
142 /* NEW -> OLD_SET replacement table. If we are replacing several
143 existing SSA names O_1, O_2, ..., O_j with a new name N_i,
144 then REPL_TBL[N_i] = { O_1, O_2, ..., O_j }. */
145 static htab_t repl_tbl
;
147 /* The function the SSA updating data structures have been initialized for.
148 NULL if they need to be initialized by register_new_name_mapping. */
149 static struct function
*update_ssa_initialized_fn
= NULL
;
151 /* Statistics kept by update_ssa to use in the virtual mapping
152 heuristic. If the number of virtual mappings is beyond certain
153 threshold, the updater will switch from using the mappings into
154 renaming the virtual symbols from scratch. In some cases, the
155 large number of name mappings for virtual names causes significant
156 slowdowns in the PHI insertion code. */
157 struct update_ssa_stats_d
159 unsigned num_virtual_mappings
;
160 unsigned num_total_mappings
;
161 bitmap virtual_symbols
;
162 unsigned num_virtual_symbols
;
164 static struct update_ssa_stats_d update_ssa_stats
;
166 /* Global data to attach to the main dominator walk structure. */
167 struct mark_def_sites_global_data
169 /* This bitmap contains the variables which are set before they
170 are used in a basic block. */
175 /* Information stored for SSA names. */
178 /* The current reaching definition replacing this SSA name. */
181 /* This field indicates whether or not the variable may need PHI nodes.
182 See the enum's definition for more detailed information about the
184 ENUM_BITFIELD (need_phi_state
) need_phi_state
: 2;
186 /* Age of this record (so that info_for_ssa_name table can be cleared
187 quickly); if AGE < CURRENT_INFO_FOR_SSA_NAME_AGE, then the fields
188 are assumed to be null. */
192 /* The information associated with names. */
193 typedef struct ssa_name_info
*ssa_name_info_p
;
194 DEF_VEC_P (ssa_name_info_p
);
195 DEF_VEC_ALLOC_P (ssa_name_info_p
, heap
);
197 static VEC(ssa_name_info_p
, heap
) *info_for_ssa_name
;
198 static unsigned current_info_for_ssa_name_age
;
200 /* The set of blocks affected by update_ssa. */
201 static bitmap blocks_to_update
;
203 /* The main entry point to the SSA renamer (rewrite_blocks) may be
204 called several times to do different, but related, tasks.
205 Initially, we need it to rename the whole program into SSA form.
206 At other times, we may need it to only rename into SSA newly
207 exposed symbols. Finally, we can also call it to incrementally fix
208 an already built SSA web. */
210 /* Convert the whole function into SSA form. */
213 /* Incrementally update the SSA web by replacing existing SSA
214 names with new ones. See update_ssa for details. */
221 /* Prototypes for debugging functions. */
222 extern void dump_tree_ssa (FILE *);
223 extern void debug_tree_ssa (void);
224 extern void debug_def_blocks (void);
225 extern void dump_tree_ssa_stats (FILE *);
226 extern void debug_tree_ssa_stats (void);
227 extern void dump_update_ssa (FILE *);
228 extern void debug_update_ssa (void);
229 extern void dump_names_replaced_by (FILE *, tree
);
230 extern void debug_names_replaced_by (tree
);
231 extern void dump_def_blocks (FILE *);
232 extern void debug_def_blocks (void);
233 extern void dump_defs_stack (FILE *, int);
234 extern void debug_defs_stack (int);
235 extern void dump_currdefs (FILE *);
236 extern void debug_currdefs (void);
238 /* Return true if STMT needs to be rewritten. When renaming a subset
239 of the variables, not all statements will be processed. This is
240 decided in mark_def_sites. */
243 rewrite_uses_p (gimple stmt
)
245 return gimple_visited_p (stmt
);
249 /* Set the rewrite marker on STMT to the value given by REWRITE_P. */
252 set_rewrite_uses (gimple stmt
, bool rewrite_p
)
254 gimple_set_visited (stmt
, rewrite_p
);
258 /* Return true if the DEFs created by statement STMT should be
259 registered when marking new definition sites. This is slightly
260 different than rewrite_uses_p: it's used by update_ssa to
261 distinguish statements that need to have both uses and defs
262 processed from those that only need to have their defs processed.
263 Statements that define new SSA names only need to have their defs
264 registered, but they don't need to have their uses renamed. */
267 register_defs_p (gimple stmt
)
269 return gimple_plf (stmt
, GF_PLF_1
) != 0;
273 /* If REGISTER_DEFS_P is true, mark STMT to have its DEFs registered. */
276 set_register_defs (gimple stmt
, bool register_defs_p
)
278 gimple_set_plf (stmt
, GF_PLF_1
, register_defs_p
);
282 /* Get the information associated with NAME. */
284 static inline ssa_name_info_p
285 get_ssa_name_ann (tree name
)
287 unsigned ver
= SSA_NAME_VERSION (name
);
288 unsigned len
= VEC_length (ssa_name_info_p
, info_for_ssa_name
);
289 struct ssa_name_info
*info
;
293 unsigned new_len
= num_ssa_names
;
295 VEC_reserve (ssa_name_info_p
, heap
, info_for_ssa_name
, new_len
);
296 while (len
++ < new_len
)
298 struct ssa_name_info
*info
= XCNEW (struct ssa_name_info
);
299 info
->age
= current_info_for_ssa_name_age
;
300 VEC_quick_push (ssa_name_info_p
, info_for_ssa_name
, info
);
304 info
= VEC_index (ssa_name_info_p
, info_for_ssa_name
, ver
);
305 if (info
->age
< current_info_for_ssa_name_age
)
307 info
->need_phi_state
= NEED_PHI_STATE_UNKNOWN
;
308 info
->current_def
= NULL_TREE
;
309 info
->age
= current_info_for_ssa_name_age
;
316 /* Clears info for SSA names. */
319 clear_ssa_name_info (void)
321 current_info_for_ssa_name_age
++;
325 /* Get phi_state field for VAR. */
327 static inline enum need_phi_state
328 get_phi_state (tree var
)
330 if (TREE_CODE (var
) == SSA_NAME
)
331 return get_ssa_name_ann (var
)->need_phi_state
;
333 return var_ann (var
)->need_phi_state
;
337 /* Sets phi_state field for VAR to STATE. */
340 set_phi_state (tree var
, enum need_phi_state state
)
342 if (TREE_CODE (var
) == SSA_NAME
)
343 get_ssa_name_ann (var
)->need_phi_state
= state
;
345 var_ann (var
)->need_phi_state
= state
;
349 /* Return the current definition for VAR. */
352 get_current_def (tree var
)
354 if (TREE_CODE (var
) == SSA_NAME
)
355 return get_ssa_name_ann (var
)->current_def
;
357 return var_ann (var
)->current_def
;
361 /* Sets current definition of VAR to DEF. */
364 set_current_def (tree var
, tree def
)
366 if (TREE_CODE (var
) == SSA_NAME
)
367 get_ssa_name_ann (var
)->current_def
= def
;
369 var_ann (var
)->current_def
= def
;
373 /* Compute global livein information given the set of blocks where
374 an object is locally live at the start of the block (LIVEIN)
375 and the set of blocks where the object is defined (DEF_BLOCKS).
377 Note: This routine augments the existing local livein information
378 to include global livein (i.e., it modifies the underlying bitmap
382 compute_global_livein (bitmap livein ATTRIBUTE_UNUSED
, bitmap def_blocks ATTRIBUTE_UNUSED
)
384 basic_block bb
, *worklist
, *tos
;
389 = (basic_block
*) xmalloc (sizeof (basic_block
) * (last_basic_block
+ 1));
391 EXECUTE_IF_SET_IN_BITMAP (livein
, 0, i
, bi
)
392 *tos
++ = BASIC_BLOCK (i
);
394 /* Iterate until the worklist is empty. */
395 while (tos
!= worklist
)
400 /* Pull a block off the worklist. */
403 /* For each predecessor block. */
404 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
406 basic_block pred
= e
->src
;
407 int pred_index
= pred
->index
;
409 /* None of this is necessary for the entry block. */
410 if (pred
!= ENTRY_BLOCK_PTR
411 && ! bitmap_bit_p (livein
, pred_index
)
412 && ! bitmap_bit_p (def_blocks
, pred_index
))
415 bitmap_set_bit (livein
, pred_index
);
424 /* Cleans up the REWRITE_THIS_STMT and REGISTER_DEFS_IN_THIS_STMT flags for
425 all statements in basic block BB. */
428 initialize_flags_in_bb (basic_block bb
)
431 gimple_stmt_iterator gsi
;
433 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
435 gimple phi
= gsi_stmt (gsi
);
436 set_rewrite_uses (phi
, false);
437 set_register_defs (phi
, false);
440 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
442 stmt
= gsi_stmt (gsi
);
444 /* We are going to use the operand cache API, such as
445 SET_USE, SET_DEF, and FOR_EACH_IMM_USE_FAST. The operand
446 cache for each statement should be up-to-date. */
447 gcc_assert (!gimple_modified_p (stmt
));
448 set_rewrite_uses (stmt
, false);
449 set_register_defs (stmt
, false);
453 /* Mark block BB as interesting for update_ssa. */
456 mark_block_for_update (basic_block bb
)
458 gcc_assert (blocks_to_update
!= NULL
);
459 if (bitmap_bit_p (blocks_to_update
, bb
->index
))
461 bitmap_set_bit (blocks_to_update
, bb
->index
);
462 initialize_flags_in_bb (bb
);
465 /* Return the set of blocks where variable VAR is defined and the blocks
466 where VAR is live on entry (livein). If no entry is found in
467 DEF_BLOCKS, a new one is created and returned. */
469 static inline struct def_blocks_d
*
470 get_def_blocks_for (tree var
)
472 struct def_blocks_d db
, *db_p
;
476 slot
= htab_find_slot (def_blocks
, (void *) &db
, INSERT
);
479 db_p
= XNEW (struct def_blocks_d
);
481 db_p
->def_blocks
= BITMAP_ALLOC (NULL
);
482 db_p
->phi_blocks
= BITMAP_ALLOC (NULL
);
483 db_p
->livein_blocks
= BITMAP_ALLOC (NULL
);
484 *slot
= (void *) db_p
;
487 db_p
= (struct def_blocks_d
*) *slot
;
493 /* Mark block BB as the definition site for variable VAR. PHI_P is true if
494 VAR is defined by a PHI node. */
497 set_def_block (tree var
, basic_block bb
, bool phi_p
)
499 struct def_blocks_d
*db_p
;
500 enum need_phi_state state
;
502 state
= get_phi_state (var
);
503 db_p
= get_def_blocks_for (var
);
505 /* Set the bit corresponding to the block where VAR is defined. */
506 bitmap_set_bit (db_p
->def_blocks
, bb
->index
);
508 bitmap_set_bit (db_p
->phi_blocks
, bb
->index
);
510 /* Keep track of whether or not we may need to insert PHI nodes.
512 If we are in the UNKNOWN state, then this is the first definition
513 of VAR. Additionally, we have not seen any uses of VAR yet, so
514 we do not need a PHI node for this variable at this time (i.e.,
515 transition to NEED_PHI_STATE_NO).
517 If we are in any other state, then we either have multiple definitions
518 of this variable occurring in different blocks or we saw a use of the
519 variable which was not dominated by the block containing the
520 definition(s). In this case we may need a PHI node, so enter
521 state NEED_PHI_STATE_MAYBE. */
522 if (state
== NEED_PHI_STATE_UNKNOWN
)
523 set_phi_state (var
, NEED_PHI_STATE_NO
);
525 set_phi_state (var
, NEED_PHI_STATE_MAYBE
);
529 /* Mark block BB as having VAR live at the entry to BB. */
532 set_livein_block (tree var
, basic_block bb
)
534 struct def_blocks_d
*db_p
;
535 enum need_phi_state state
= get_phi_state (var
);
537 db_p
= get_def_blocks_for (var
);
539 /* Set the bit corresponding to the block where VAR is live in. */
540 bitmap_set_bit (db_p
->livein_blocks
, bb
->index
);
542 /* Keep track of whether or not we may need to insert PHI nodes.
544 If we reach here in NEED_PHI_STATE_NO, see if this use is dominated
545 by the single block containing the definition(s) of this variable. If
546 it is, then we remain in NEED_PHI_STATE_NO, otherwise we transition to
547 NEED_PHI_STATE_MAYBE. */
548 if (state
== NEED_PHI_STATE_NO
)
550 int def_block_index
= bitmap_first_set_bit (db_p
->def_blocks
);
552 if (def_block_index
== -1
553 || ! dominated_by_p (CDI_DOMINATORS
, bb
,
554 BASIC_BLOCK (def_block_index
)))
555 set_phi_state (var
, NEED_PHI_STATE_MAYBE
);
558 set_phi_state (var
, NEED_PHI_STATE_MAYBE
);
562 /* Return true if symbol SYM is marked for renaming. */
565 symbol_marked_for_renaming (tree sym
)
567 return bitmap_bit_p (SYMS_TO_RENAME (cfun
), DECL_UID (sym
));
571 /* Return true if NAME is in OLD_SSA_NAMES. */
574 is_old_name (tree name
)
576 unsigned ver
= SSA_NAME_VERSION (name
);
579 return ver
< new_ssa_names
->n_bits
&& TEST_BIT (old_ssa_names
, ver
);
583 /* Return true if NAME is in NEW_SSA_NAMES. */
586 is_new_name (tree name
)
588 unsigned ver
= SSA_NAME_VERSION (name
);
591 return ver
< new_ssa_names
->n_bits
&& TEST_BIT (new_ssa_names
, ver
);
595 /* Hashing and equality functions for REPL_TBL. */
598 repl_map_hash (const void *p
)
600 return htab_hash_pointer ((const void *)((const struct repl_map_d
*)p
)->name
);
604 repl_map_eq (const void *p1
, const void *p2
)
606 return ((const struct repl_map_d
*)p1
)->name
607 == ((const struct repl_map_d
*)p2
)->name
;
611 repl_map_free (void *p
)
613 BITMAP_FREE (((struct repl_map_d
*)p
)->set
);
618 /* Return the names replaced by NEW_TREE (i.e., REPL_TBL[NEW_TREE].SET). */
621 names_replaced_by (tree new_tree
)
627 slot
= htab_find_slot (repl_tbl
, (void *) &m
, NO_INSERT
);
629 /* If N was not registered in the replacement table, return NULL. */
630 if (slot
== NULL
|| *slot
== NULL
)
633 return ((struct repl_map_d
*) *slot
)->set
;
637 /* Add OLD to REPL_TBL[NEW_TREE].SET. */
640 add_to_repl_tbl (tree new_tree
, tree old
)
642 struct repl_map_d m
, *mp
;
646 slot
= htab_find_slot (repl_tbl
, (void *) &m
, INSERT
);
649 mp
= XNEW (struct repl_map_d
);
651 mp
->set
= BITMAP_ALLOC (NULL
);
655 mp
= (struct repl_map_d
*) *slot
;
657 bitmap_set_bit (mp
->set
, SSA_NAME_VERSION (old
));
661 /* Add a new mapping NEW_TREE -> OLD REPL_TBL. Every entry N_i in REPL_TBL
662 represents the set of names O_1 ... O_j replaced by N_i. This is
663 used by update_ssa and its helpers to introduce new SSA names in an
664 already formed SSA web. */
667 add_new_name_mapping (tree new_tree
, tree old
)
669 timevar_push (TV_TREE_SSA_INCREMENTAL
);
671 /* OLD and NEW_TREE must be different SSA names for the same symbol. */
672 gcc_assert (new_tree
!= old
&& SSA_NAME_VAR (new_tree
) == SSA_NAME_VAR (old
));
674 /* If this mapping is for virtual names, we will need to update
675 virtual operands. If this is a mapping for .MEM, then we gather
676 the symbols associated with each name. */
677 if (!is_gimple_reg (new_tree
))
681 update_ssa_stats
.num_virtual_mappings
++;
682 update_ssa_stats
.num_virtual_symbols
++;
684 /* Keep counts of virtual mappings and symbols to use in the
685 virtual mapping heuristic. If we have large numbers of
686 virtual mappings for a relatively low number of symbols, it
687 will make more sense to rename the symbols from scratch.
688 Otherwise, the insertion of PHI nodes for each of the old
689 names in these mappings will be very slow. */
690 sym
= SSA_NAME_VAR (new_tree
);
691 bitmap_set_bit (update_ssa_stats
.virtual_symbols
, DECL_UID (sym
));
694 /* We may need to grow NEW_SSA_NAMES and OLD_SSA_NAMES because our
695 caller may have created new names since the set was created. */
696 if (new_ssa_names
->n_bits
<= num_ssa_names
- 1)
698 unsigned int new_sz
= num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
;
699 new_ssa_names
= sbitmap_resize (new_ssa_names
, new_sz
, 0);
700 old_ssa_names
= sbitmap_resize (old_ssa_names
, new_sz
, 0);
703 /* Update the REPL_TBL table. */
704 add_to_repl_tbl (new_tree
, old
);
706 /* If OLD had already been registered as a new name, then all the
707 names that OLD replaces should also be replaced by NEW_TREE. */
708 if (is_new_name (old
))
709 bitmap_ior_into (names_replaced_by (new_tree
), names_replaced_by (old
));
711 /* Register NEW_TREE and OLD in NEW_SSA_NAMES and OLD_SSA_NAMES,
713 SET_BIT (new_ssa_names
, SSA_NAME_VERSION (new_tree
));
714 SET_BIT (old_ssa_names
, SSA_NAME_VERSION (old
));
716 /* Update mapping counter to use in the virtual mapping heuristic. */
717 update_ssa_stats
.num_total_mappings
++;
719 timevar_pop (TV_TREE_SSA_INCREMENTAL
);
723 /* Call back for walk_dominator_tree used to collect definition sites
724 for every variable in the function. For every statement S in block
727 1- Variables defined by S in the DEFS of S are marked in the bitmap
730 2- If S uses a variable VAR and there is no preceding kill of VAR,
731 then it is marked in the LIVEIN_BLOCKS bitmap associated with VAR.
733 This information is used to determine which variables are live
734 across block boundaries to reduce the number of PHI nodes
738 mark_def_sites (basic_block bb
, gimple stmt
, bitmap kills
)
744 /* Since this is the first time that we rewrite the program into SSA
745 form, force an operand scan on every statement. */
748 gcc_assert (blocks_to_update
== NULL
);
749 set_register_defs (stmt
, false);
750 set_rewrite_uses (stmt
, false);
752 /* If a variable is used before being set, then the variable is live
753 across a block boundary, so mark it live-on-entry to BB. */
754 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
756 tree sym
= USE_FROM_PTR (use_p
);
757 gcc_assert (DECL_P (sym
));
758 if (!bitmap_bit_p (kills
, DECL_UID (sym
)))
759 set_livein_block (sym
, bb
);
760 set_rewrite_uses (stmt
, true);
763 /* Now process the defs. Mark BB as the definition block and add
764 each def to the set of killed symbols. */
765 FOR_EACH_SSA_TREE_OPERAND (def
, stmt
, iter
, SSA_OP_DEF
)
767 gcc_assert (DECL_P (def
));
768 set_def_block (def
, bb
, false);
769 bitmap_set_bit (kills
, DECL_UID (def
));
770 set_register_defs (stmt
, true);
773 /* If we found the statement interesting then also mark the block BB
775 if (rewrite_uses_p (stmt
) || register_defs_p (stmt
))
776 SET_BIT (interesting_blocks
, bb
->index
);
779 /* Structure used by prune_unused_phi_nodes to record bounds of the intervals
780 in the dfs numbering of the dominance tree. */
784 /* Basic block whose index this entry corresponds to. */
787 /* The dfs number of this node. */
791 /* Compares two entries of type struct dom_dfsnum by dfs_num field. Callback
795 cmp_dfsnum (const void *a
, const void *b
)
797 const struct dom_dfsnum
*const da
= (const struct dom_dfsnum
*) a
;
798 const struct dom_dfsnum
*const db
= (const struct dom_dfsnum
*) b
;
800 return (int) da
->dfs_num
- (int) db
->dfs_num
;
803 /* Among the intervals starting at the N points specified in DEFS, find
804 the one that contains S, and return its bb_index. */
807 find_dfsnum_interval (struct dom_dfsnum
*defs
, unsigned n
, unsigned s
)
809 unsigned f
= 0, t
= n
, m
;
814 if (defs
[m
].dfs_num
<= s
)
820 return defs
[f
].bb_index
;
823 /* Clean bits from PHIS for phi nodes whose value cannot be used in USES.
824 KILLS is a bitmap of blocks where the value is defined before any use. */
827 prune_unused_phi_nodes (bitmap phis
, bitmap kills
, bitmap uses
)
829 VEC(int, heap
) *worklist
;
831 unsigned i
, b
, p
, u
, top
;
833 basic_block def_bb
, use_bb
;
837 struct dom_dfsnum
*defs
;
838 unsigned n_defs
, adef
;
840 if (bitmap_empty_p (uses
))
846 /* The phi must dominate a use, or an argument of a live phi. Also, we
847 do not create any phi nodes in def blocks, unless they are also livein. */
848 to_remove
= BITMAP_ALLOC (NULL
);
849 bitmap_and_compl (to_remove
, kills
, uses
);
850 bitmap_and_compl_into (phis
, to_remove
);
851 if (bitmap_empty_p (phis
))
853 BITMAP_FREE (to_remove
);
857 /* We want to remove the unnecessary phi nodes, but we do not want to compute
858 liveness information, as that may be linear in the size of CFG, and if
859 there are lot of different variables to rewrite, this may lead to quadratic
862 Instead, we basically emulate standard dce. We put all uses to worklist,
863 then for each of them find the nearest def that dominates them. If this
864 def is a phi node, we mark it live, and if it was not live before, we
865 add the predecessors of its basic block to the worklist.
867 To quickly locate the nearest def that dominates use, we use dfs numbering
868 of the dominance tree (that is already available in order to speed up
869 queries). For each def, we have the interval given by the dfs number on
870 entry to and on exit from the corresponding subtree in the dominance tree.
871 The nearest dominator for a given use is the smallest of these intervals
872 that contains entry and exit dfs numbers for the basic block with the use.
873 If we store the bounds for all the uses to an array and sort it, we can
874 locate the nearest dominating def in logarithmic time by binary search.*/
875 bitmap_ior (to_remove
, kills
, phis
);
876 n_defs
= bitmap_count_bits (to_remove
);
877 defs
= XNEWVEC (struct dom_dfsnum
, 2 * n_defs
+ 1);
878 defs
[0].bb_index
= 1;
881 EXECUTE_IF_SET_IN_BITMAP (to_remove
, 0, i
, bi
)
883 def_bb
= BASIC_BLOCK (i
);
884 defs
[adef
].bb_index
= i
;
885 defs
[adef
].dfs_num
= bb_dom_dfs_in (CDI_DOMINATORS
, def_bb
);
886 defs
[adef
+ 1].bb_index
= i
;
887 defs
[adef
+ 1].dfs_num
= bb_dom_dfs_out (CDI_DOMINATORS
, def_bb
);
890 BITMAP_FREE (to_remove
);
891 gcc_assert (adef
== 2 * n_defs
+ 1);
892 qsort (defs
, adef
, sizeof (struct dom_dfsnum
), cmp_dfsnum
);
893 gcc_assert (defs
[0].bb_index
== 1);
895 /* Now each DEFS entry contains the number of the basic block to that the
896 dfs number corresponds. Change them to the number of basic block that
897 corresponds to the interval following the dfs number. Also, for the
898 dfs_out numbers, increase the dfs number by one (so that it corresponds
899 to the start of the following interval, not to the end of the current
900 one). We use WORKLIST as a stack. */
901 worklist
= VEC_alloc (int, heap
, n_defs
+ 1);
902 VEC_quick_push (int, worklist
, 1);
905 for (i
= 1; i
< adef
; i
++)
907 b
= defs
[i
].bb_index
;
910 /* This is a closing element. Interval corresponding to the top
911 of the stack after removing it follows. */
912 VEC_pop (int, worklist
);
913 top
= VEC_index (int, worklist
, VEC_length (int, worklist
) - 1);
914 defs
[n_defs
].bb_index
= top
;
915 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
+ 1;
919 /* Opening element. Nothing to do, just push it to the stack and move
920 it to the correct position. */
921 defs
[n_defs
].bb_index
= defs
[i
].bb_index
;
922 defs
[n_defs
].dfs_num
= defs
[i
].dfs_num
;
923 VEC_quick_push (int, worklist
, b
);
927 /* If this interval starts at the same point as the previous one, cancel
929 if (defs
[n_defs
].dfs_num
== defs
[n_defs
- 1].dfs_num
)
930 defs
[n_defs
- 1].bb_index
= defs
[n_defs
].bb_index
;
934 VEC_pop (int, worklist
);
935 gcc_assert (VEC_empty (int, worklist
));
937 /* Now process the uses. */
938 live_phis
= BITMAP_ALLOC (NULL
);
939 EXECUTE_IF_SET_IN_BITMAP (uses
, 0, i
, bi
)
941 VEC_safe_push (int, heap
, worklist
, i
);
944 while (!VEC_empty (int, worklist
))
946 b
= VEC_pop (int, worklist
);
947 if (b
== ENTRY_BLOCK
)
950 /* If there is a phi node in USE_BB, it is made live. Otherwise,
951 find the def that dominates the immediate dominator of USE_BB
952 (the kill in USE_BB does not dominate the use). */
953 if (bitmap_bit_p (phis
, b
))
957 use_bb
= get_immediate_dominator (CDI_DOMINATORS
, BASIC_BLOCK (b
));
958 p
= find_dfsnum_interval (defs
, n_defs
,
959 bb_dom_dfs_in (CDI_DOMINATORS
, use_bb
));
960 if (!bitmap_bit_p (phis
, p
))
964 /* If the phi node is already live, there is nothing to do. */
965 if (bitmap_bit_p (live_phis
, p
))
968 /* Mark the phi as live, and add the new uses to the worklist. */
969 bitmap_set_bit (live_phis
, p
);
970 def_bb
= BASIC_BLOCK (p
);
971 FOR_EACH_EDGE (e
, ei
, def_bb
->preds
)
974 if (bitmap_bit_p (uses
, u
))
977 /* In case there is a kill directly in the use block, do not record
978 the use (this is also necessary for correctness, as we assume that
979 uses dominated by a def directly in their block have been filtered
981 if (bitmap_bit_p (kills
, u
))
984 bitmap_set_bit (uses
, u
);
985 VEC_safe_push (int, heap
, worklist
, u
);
989 VEC_free (int, heap
, worklist
);
990 bitmap_copy (phis
, live_phis
);
991 BITMAP_FREE (live_phis
);
995 /* Return the set of blocks where variable VAR is defined and the blocks
996 where VAR is live on entry (livein). Return NULL, if no entry is
997 found in DEF_BLOCKS. */
999 static inline struct def_blocks_d
*
1000 find_def_blocks_for (tree var
)
1002 struct def_blocks_d dm
;
1004 return (struct def_blocks_d
*) htab_find (def_blocks
, &dm
);
1008 /* Retrieve or create a default definition for symbol SYM. */
1011 get_default_def_for (tree sym
)
1013 tree ddef
= gimple_default_def (cfun
, sym
);
1015 if (ddef
== NULL_TREE
)
1017 ddef
= make_ssa_name (sym
, gimple_build_nop ());
1018 set_default_def (sym
, ddef
);
1025 /* Marks phi node PHI in basic block BB for rewrite. */
1028 mark_phi_for_rewrite (basic_block bb
, gimple phi
)
1031 unsigned i
, idx
= bb
->index
;
1033 if (rewrite_uses_p (phi
))
1036 set_rewrite_uses (phi
, true);
1038 if (!blocks_with_phis_to_rewrite
)
1041 bitmap_set_bit (blocks_with_phis_to_rewrite
, idx
);
1042 VEC_reserve (gimple_vec
, heap
, phis_to_rewrite
, last_basic_block
+ 1);
1043 for (i
= VEC_length (gimple_vec
, phis_to_rewrite
); i
<= idx
; i
++)
1044 VEC_quick_push (gimple_vec
, phis_to_rewrite
, NULL
);
1046 phis
= VEC_index (gimple_vec
, phis_to_rewrite
, idx
);
1048 phis
= VEC_alloc (gimple
, heap
, 10);
1050 VEC_safe_push (gimple
, heap
, phis
, phi
);
1051 VEC_replace (gimple_vec
, phis_to_rewrite
, idx
, phis
);
1055 /* Insert PHI nodes for variable VAR using the iterated dominance
1056 frontier given in PHI_INSERTION_POINTS. If UPDATE_P is true, this
1057 function assumes that the caller is incrementally updating the
1058 existing SSA form, in which case VAR may be an SSA name instead of
1061 PHI_INSERTION_POINTS is updated to reflect nodes that already had a
1062 PHI node for VAR. On exit, only the nodes that received a PHI node
1063 for VAR will be present in PHI_INSERTION_POINTS. */
1066 insert_phi_nodes_for (tree var
, bitmap phi_insertion_points
, bool update_p
)
1073 struct def_blocks_d
*def_map
;
1075 def_map
= find_def_blocks_for (var
);
1076 gcc_assert (def_map
);
1078 /* Remove the blocks where we already have PHI nodes for VAR. */
1079 bitmap_and_compl_into (phi_insertion_points
, def_map
->phi_blocks
);
1081 /* Remove obviously useless phi nodes. */
1082 prune_unused_phi_nodes (phi_insertion_points
, def_map
->def_blocks
,
1083 def_map
->livein_blocks
);
1085 /* And insert the PHI nodes. */
1086 EXECUTE_IF_SET_IN_BITMAP (phi_insertion_points
, 0, bb_index
, bi
)
1088 bb
= BASIC_BLOCK (bb_index
);
1090 mark_block_for_update (bb
);
1094 if (TREE_CODE (var
) == SSA_NAME
)
1096 /* If we are rewriting SSA names, create the LHS of the PHI
1097 node by duplicating VAR. This is useful in the case of
1098 pointers, to also duplicate pointer attributes (alias
1099 information, in particular). */
1103 gcc_assert (update_p
);
1104 phi
= create_phi_node (var
, bb
);
1106 new_lhs
= duplicate_ssa_name (var
, phi
);
1107 gimple_phi_set_result (phi
, new_lhs
);
1108 add_new_name_mapping (new_lhs
, var
);
1110 /* Add VAR to every argument slot of PHI. We need VAR in
1111 every argument so that rewrite_update_phi_arguments knows
1112 which name is this PHI node replacing. If VAR is a
1113 symbol marked for renaming, this is not necessary, the
1114 renamer will use the symbol on the LHS to get its
1115 reaching definition. */
1116 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1117 add_phi_arg (phi
, var
, e
, UNKNOWN_LOCATION
);
1121 gcc_assert (DECL_P (var
));
1122 phi
= create_phi_node (var
, bb
);
1125 /* Mark this PHI node as interesting for update_ssa. */
1126 set_register_defs (phi
, true);
1127 mark_phi_for_rewrite (bb
, phi
);
1132 /* Insert PHI nodes at the dominance frontier of blocks with variable
1133 definitions. DFS contains the dominance frontier information for
1137 insert_phi_nodes (bitmap
*dfs
)
1139 referenced_var_iterator rvi
;
1142 timevar_push (TV_TREE_INSERT_PHI_NODES
);
1144 FOR_EACH_REFERENCED_VAR (var
, rvi
)
1146 struct def_blocks_d
*def_map
;
1149 def_map
= find_def_blocks_for (var
);
1150 if (def_map
== NULL
)
1153 if (get_phi_state (var
) != NEED_PHI_STATE_NO
)
1155 idf
= compute_idf (def_map
->def_blocks
, dfs
);
1156 insert_phi_nodes_for (var
, idf
, false);
1161 timevar_pop (TV_TREE_INSERT_PHI_NODES
);
1165 /* Push SYM's current reaching definition into BLOCK_DEFS_STACK and
1166 register DEF (an SSA_NAME) to be a new definition for SYM. */
1169 register_new_def (tree def
, tree sym
)
1173 /* If this variable is set in a single basic block and all uses are
1174 dominated by the set(s) in that single basic block, then there is
1175 no reason to record anything for this variable in the block local
1176 definition stacks. Doing so just wastes time and memory.
1178 This is the same test to prune the set of variables which may
1179 need PHI nodes. So we just use that information since it's already
1180 computed and available for us to use. */
1181 if (get_phi_state (sym
) == NEED_PHI_STATE_NO
)
1183 set_current_def (sym
, def
);
1187 currdef
= get_current_def (sym
);
1189 /* If SYM is not a GIMPLE register, then CURRDEF may be a name whose
1190 SSA_NAME_VAR is not necessarily SYM. In this case, also push SYM
1191 in the stack so that we know which symbol is being defined by
1192 this SSA name when we unwind the stack. */
1193 if (currdef
&& !is_gimple_reg (sym
))
1194 VEC_safe_push (tree
, heap
, block_defs_stack
, sym
);
1196 /* Push the current reaching definition into BLOCK_DEFS_STACK. This
1197 stack is later used by the dominator tree callbacks to restore
1198 the reaching definitions for all the variables defined in the
1199 block after a recursive visit to all its immediately dominated
1200 blocks. If there is no current reaching definition, then just
1201 record the underlying _DECL node. */
1202 VEC_safe_push (tree
, heap
, block_defs_stack
, currdef
? currdef
: sym
);
1204 /* Set the current reaching definition for SYM to be DEF. */
1205 set_current_def (sym
, def
);
1209 /* Perform a depth-first traversal of the dominator tree looking for
1210 variables to rename. BB is the block where to start searching.
1211 Renaming is a five step process:
1213 1- Every definition made by PHI nodes at the start of the blocks is
1214 registered as the current definition for the corresponding variable.
1216 2- Every statement in BB is rewritten. USE and VUSE operands are
1217 rewritten with their corresponding reaching definition. DEF and
1218 VDEF targets are registered as new definitions.
1220 3- All the PHI nodes in successor blocks of BB are visited. The
1221 argument corresponding to BB is replaced with its current reaching
1224 4- Recursively rewrite every dominator child block of BB.
1226 5- Restore (in reverse order) the current reaching definition for every
1227 new definition introduced in this block. This is done so that when
1228 we return from the recursive call, all the current reaching
1229 definitions are restored to the names that were valid in the
1230 dominator parent of BB. */
1232 /* Return the current definition for variable VAR. If none is found,
1233 create a new SSA name to act as the zeroth definition for VAR. */
1236 get_reaching_def (tree var
)
1240 /* Lookup the current reaching definition for VAR. */
1241 currdef
= get_current_def (var
);
1243 /* If there is no reaching definition for VAR, create and register a
1244 default definition for it (if needed). */
1245 if (currdef
== NULL_TREE
)
1247 tree sym
= DECL_P (var
) ? var
: SSA_NAME_VAR (var
);
1248 currdef
= get_default_def_for (sym
);
1249 set_current_def (var
, currdef
);
1252 /* Return the current reaching definition for VAR, or the default
1253 definition, if we had to create one. */
1258 /* SSA Rewriting Step 2. Rewrite every variable used in each statement in
1259 the block with its immediate reaching definitions. Update the current
1260 definition of a variable when a new real or virtual definition is found. */
1263 rewrite_stmt (gimple stmt
)
1265 use_operand_p use_p
;
1266 def_operand_p def_p
;
1269 /* If mark_def_sites decided that we don't need to rewrite this
1270 statement, ignore it. */
1271 gcc_assert (blocks_to_update
== NULL
);
1272 if (!rewrite_uses_p (stmt
) && !register_defs_p (stmt
))
1275 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1277 fprintf (dump_file
, "Renaming statement ");
1278 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1279 fprintf (dump_file
, "\n");
1282 /* Step 1. Rewrite USES in the statement. */
1283 if (rewrite_uses_p (stmt
))
1284 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_USE
)
1286 tree var
= USE_FROM_PTR (use_p
);
1287 gcc_assert (DECL_P (var
));
1288 SET_USE (use_p
, get_reaching_def (var
));
1291 /* Step 2. Register the statement's DEF operands. */
1292 if (register_defs_p (stmt
))
1293 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, iter
, SSA_OP_DEF
)
1295 tree var
= DEF_FROM_PTR (def_p
);
1296 gcc_assert (DECL_P (var
));
1297 SET_DEF (def_p
, make_ssa_name (var
, stmt
));
1298 register_new_def (DEF_FROM_PTR (def_p
), var
);
1303 /* SSA Rewriting Step 3. Visit all the successor blocks of BB looking for
1304 PHI nodes. For every PHI node found, add a new argument containing the
1305 current reaching definition for the variable and the edge through which
1306 that definition is reaching the PHI node. */
1309 rewrite_add_phi_arguments (basic_block bb
)
1314 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1317 gimple_stmt_iterator gsi
;
1319 for (gsi
= gsi_start_phis (e
->dest
); !gsi_end_p (gsi
);
1325 phi
= gsi_stmt (gsi
);
1326 currdef
= get_reaching_def (SSA_NAME_VAR (gimple_phi_result (phi
)));
1327 stmt
= SSA_NAME_DEF_STMT (currdef
);
1328 add_phi_arg (phi
, currdef
, e
, gimple_location (stmt
));
1333 /* SSA Rewriting Step 1. Initialization, create a block local stack
1334 of reaching definitions for new SSA names produced in this block
1335 (BLOCK_DEFS). Register new definitions for every PHI node in the
1339 rewrite_enter_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
1343 gimple_stmt_iterator gsi
;
1345 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1346 fprintf (dump_file
, "\n\nRenaming block #%d\n\n", bb
->index
);
1348 /* Mark the unwind point for this block. */
1349 VEC_safe_push (tree
, heap
, block_defs_stack
, NULL_TREE
);
1351 /* Step 1. Register new definitions for every PHI node in the block.
1352 Conceptually, all the PHI nodes are executed in parallel and each PHI
1353 node introduces a new version for the associated variable. */
1354 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1358 phi
= gsi_stmt (gsi
);
1359 result
= gimple_phi_result (phi
);
1360 gcc_assert (is_gimple_reg (result
));
1361 register_new_def (result
, SSA_NAME_VAR (result
));
1364 /* Step 2. Rewrite every variable used in each statement in the block
1365 with its immediate reaching definitions. Update the current definition
1366 of a variable when a new real or virtual definition is found. */
1367 if (TEST_BIT (interesting_blocks
, bb
->index
))
1368 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1369 rewrite_stmt (gsi_stmt (gsi
));
1371 /* Step 3. Visit all the successor blocks of BB looking for PHI nodes.
1372 For every PHI node found, add a new argument containing the current
1373 reaching definition for the variable and the edge through which that
1374 definition is reaching the PHI node. */
1375 rewrite_add_phi_arguments (bb
);
1380 /* Called after visiting all the statements in basic block BB and all
1381 of its dominator children. Restore CURRDEFS to its original value. */
1384 rewrite_leave_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
1385 basic_block bb ATTRIBUTE_UNUSED
)
1387 /* Restore CURRDEFS to its original state. */
1388 while (VEC_length (tree
, block_defs_stack
) > 0)
1390 tree tmp
= VEC_pop (tree
, block_defs_stack
);
1391 tree saved_def
, var
;
1393 if (tmp
== NULL_TREE
)
1396 if (TREE_CODE (tmp
) == SSA_NAME
)
1398 /* If we recorded an SSA_NAME, then make the SSA_NAME the
1399 current definition of its underlying variable. Note that
1400 if the SSA_NAME is not for a GIMPLE register, the symbol
1401 being defined is stored in the next slot in the stack.
1402 This mechanism is needed because an SSA name for a
1403 non-register symbol may be the definition for more than
1404 one symbol (e.g., SFTs, aliased variables, etc). */
1406 var
= SSA_NAME_VAR (saved_def
);
1407 if (!is_gimple_reg (var
))
1408 var
= VEC_pop (tree
, block_defs_stack
);
1412 /* If we recorded anything else, it must have been a _DECL
1413 node and its current reaching definition must have been
1419 set_current_def (var
, saved_def
);
1424 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1427 dump_decl_set (FILE *file
, bitmap set
)
1434 fprintf (file
, "{ ");
1436 EXECUTE_IF_SET_IN_BITMAP (set
, 0, i
, bi
)
1438 print_generic_expr (file
, referenced_var (i
), 0);
1439 fprintf (file
, " ");
1442 fprintf (file
, "}");
1445 fprintf (file
, "NIL");
1449 /* Dump bitmap SET (assumed to contain VAR_DECLs) to FILE. */
1452 debug_decl_set (bitmap set
)
1454 dump_decl_set (stderr
, set
);
1455 fprintf (stderr
, "\n");
1459 /* Dump the renaming stack (block_defs_stack) to FILE. Traverse the
1460 stack up to a maximum of N levels. If N is -1, the whole stack is
1461 dumped. New levels are created when the dominator tree traversal
1462 used for renaming enters a new sub-tree. */
1465 dump_defs_stack (FILE *file
, int n
)
1469 fprintf (file
, "\n\nRenaming stack");
1471 fprintf (file
, " (up to %d levels)", n
);
1472 fprintf (file
, "\n\n");
1475 fprintf (file
, "Level %d (current level)\n", i
);
1476 for (j
= (int) VEC_length (tree
, block_defs_stack
) - 1; j
>= 0; j
--)
1480 name
= VEC_index (tree
, block_defs_stack
, j
);
1481 if (name
== NULL_TREE
)
1486 fprintf (file
, "\nLevel %d\n", i
);
1497 var
= SSA_NAME_VAR (name
);
1498 if (!is_gimple_reg (var
))
1501 var
= VEC_index (tree
, block_defs_stack
, j
);
1505 fprintf (file
, " Previous CURRDEF (");
1506 print_generic_expr (file
, var
, 0);
1507 fprintf (file
, ") = ");
1509 print_generic_expr (file
, name
, 0);
1511 fprintf (file
, "<NIL>");
1512 fprintf (file
, "\n");
1517 /* Dump the renaming stack (block_defs_stack) to stderr. Traverse the
1518 stack up to a maximum of N levels. If N is -1, the whole stack is
1519 dumped. New levels are created when the dominator tree traversal
1520 used for renaming enters a new sub-tree. */
1523 debug_defs_stack (int n
)
1525 dump_defs_stack (stderr
, n
);
1529 /* Dump the current reaching definition of every symbol to FILE. */
1532 dump_currdefs (FILE *file
)
1534 referenced_var_iterator i
;
1537 fprintf (file
, "\n\nCurrent reaching definitions\n\n");
1538 FOR_EACH_REFERENCED_VAR (var
, i
)
1539 if (SYMS_TO_RENAME (cfun
) == NULL
1540 || bitmap_bit_p (SYMS_TO_RENAME (cfun
), DECL_UID (var
)))
1542 fprintf (file
, "CURRDEF (");
1543 print_generic_expr (file
, var
, 0);
1544 fprintf (file
, ") = ");
1545 if (get_current_def (var
))
1546 print_generic_expr (file
, get_current_def (var
), 0);
1548 fprintf (file
, "<NIL>");
1549 fprintf (file
, "\n");
1554 /* Dump the current reaching definition of every symbol to stderr. */
1557 debug_currdefs (void)
1559 dump_currdefs (stderr
);
1563 /* Dump SSA information to FILE. */
1566 dump_tree_ssa (FILE *file
)
1568 const char *funcname
1569 = lang_hooks
.decl_printable_name (current_function_decl
, 2);
1571 fprintf (file
, "SSA renaming information for %s\n\n", funcname
);
1573 dump_def_blocks (file
);
1574 dump_defs_stack (file
, -1);
1575 dump_currdefs (file
);
1576 dump_tree_ssa_stats (file
);
1580 /* Dump SSA information to stderr. */
1583 debug_tree_ssa (void)
1585 dump_tree_ssa (stderr
);
1589 /* Dump statistics for the hash table HTAB. */
1592 htab_statistics (FILE *file
, htab_t htab
)
1594 fprintf (file
, "size %ld, %ld elements, %f collision/search ratio\n",
1595 (long) htab_size (htab
),
1596 (long) htab_elements (htab
),
1597 htab_collisions (htab
));
1601 /* Dump SSA statistics on FILE. */
1604 dump_tree_ssa_stats (FILE *file
)
1606 if (def_blocks
|| repl_tbl
)
1607 fprintf (file
, "\nHash table statistics:\n");
1611 fprintf (file
, " def_blocks: ");
1612 htab_statistics (file
, def_blocks
);
1617 fprintf (file
, " repl_tbl: ");
1618 htab_statistics (file
, repl_tbl
);
1621 if (def_blocks
|| repl_tbl
)
1622 fprintf (file
, "\n");
1626 /* Dump SSA statistics on stderr. */
1629 debug_tree_ssa_stats (void)
1631 dump_tree_ssa_stats (stderr
);
1635 /* Hashing and equality functions for DEF_BLOCKS. */
1638 def_blocks_hash (const void *p
)
1640 return htab_hash_pointer
1641 ((const void *)((const struct def_blocks_d
*)p
)->var
);
1645 def_blocks_eq (const void *p1
, const void *p2
)
1647 return ((const struct def_blocks_d
*)p1
)->var
1648 == ((const struct def_blocks_d
*)p2
)->var
;
1652 /* Free memory allocated by one entry in DEF_BLOCKS. */
1655 def_blocks_free (void *p
)
1657 struct def_blocks_d
*entry
= (struct def_blocks_d
*) p
;
1658 BITMAP_FREE (entry
->def_blocks
);
1659 BITMAP_FREE (entry
->phi_blocks
);
1660 BITMAP_FREE (entry
->livein_blocks
);
1665 /* Callback for htab_traverse to dump the DEF_BLOCKS hash table. */
1668 debug_def_blocks_r (void **slot
, void *data
)
1670 FILE *file
= (FILE *) data
;
1671 struct def_blocks_d
*db_p
= (struct def_blocks_d
*) *slot
;
1673 fprintf (file
, "VAR: ");
1674 print_generic_expr (file
, db_p
->var
, dump_flags
);
1675 bitmap_print (file
, db_p
->def_blocks
, ", DEF_BLOCKS: { ", "}");
1676 bitmap_print (file
, db_p
->livein_blocks
, ", LIVEIN_BLOCKS: { ", "}");
1677 bitmap_print (file
, db_p
->phi_blocks
, ", PHI_BLOCKS: { ", "}\n");
1683 /* Dump the DEF_BLOCKS hash table on FILE. */
1686 dump_def_blocks (FILE *file
)
1688 fprintf (file
, "\n\nDefinition and live-in blocks:\n\n");
1690 htab_traverse (def_blocks
, debug_def_blocks_r
, file
);
1694 /* Dump the DEF_BLOCKS hash table on stderr. */
1697 debug_def_blocks (void)
1699 dump_def_blocks (stderr
);
1703 /* Register NEW_NAME to be the new reaching definition for OLD_NAME. */
1706 register_new_update_single (tree new_name
, tree old_name
)
1708 tree currdef
= get_current_def (old_name
);
1710 /* Push the current reaching definition into BLOCK_DEFS_STACK.
1711 This stack is later used by the dominator tree callbacks to
1712 restore the reaching definitions for all the variables
1713 defined in the block after a recursive visit to all its
1714 immediately dominated blocks. */
1715 VEC_reserve (tree
, heap
, block_defs_stack
, 2);
1716 VEC_quick_push (tree
, block_defs_stack
, currdef
);
1717 VEC_quick_push (tree
, block_defs_stack
, old_name
);
1719 /* Set the current reaching definition for OLD_NAME to be
1721 set_current_def (old_name
, new_name
);
1725 /* Register NEW_NAME to be the new reaching definition for all the
1726 names in OLD_NAMES. Used by the incremental SSA update routines to
1727 replace old SSA names with new ones. */
1730 register_new_update_set (tree new_name
, bitmap old_names
)
1735 EXECUTE_IF_SET_IN_BITMAP (old_names
, 0, i
, bi
)
1736 register_new_update_single (new_name
, ssa_name (i
));
1741 /* If the operand pointed to by USE_P is a name in OLD_SSA_NAMES or
1742 it is a symbol marked for renaming, replace it with USE_P's current
1743 reaching definition. */
1746 maybe_replace_use (use_operand_p use_p
)
1748 tree rdef
= NULL_TREE
;
1749 tree use
= USE_FROM_PTR (use_p
);
1750 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
1752 if (symbol_marked_for_renaming (sym
))
1753 rdef
= get_reaching_def (sym
);
1754 else if (is_old_name (use
))
1755 rdef
= get_reaching_def (use
);
1757 if (rdef
&& rdef
!= use
)
1758 SET_USE (use_p
, rdef
);
1762 /* If the operand pointed to by DEF_P is an SSA name in NEW_SSA_NAMES
1763 or OLD_SSA_NAMES, or if it is a symbol marked for renaming,
1764 register it as the current definition for the names replaced by
1768 maybe_register_def (def_operand_p def_p
, gimple stmt
)
1770 tree def
= DEF_FROM_PTR (def_p
);
1771 tree sym
= DECL_P (def
) ? def
: SSA_NAME_VAR (def
);
1773 /* If DEF is a naked symbol that needs renaming, create a new
1775 if (symbol_marked_for_renaming (sym
))
1779 def
= make_ssa_name (def
, stmt
);
1780 SET_DEF (def_p
, def
);
1783 register_new_update_single (def
, sym
);
1787 /* If DEF is a new name, register it as a new definition
1788 for all the names replaced by DEF. */
1789 if (is_new_name (def
))
1790 register_new_update_set (def
, names_replaced_by (def
));
1792 /* If DEF is an old name, register DEF as a new
1793 definition for itself. */
1794 if (is_old_name (def
))
1795 register_new_update_single (def
, def
);
1800 /* Update every variable used in the statement pointed-to by SI. The
1801 statement is assumed to be in SSA form already. Names in
1802 OLD_SSA_NAMES used by SI will be updated to their current reaching
1803 definition. Names in OLD_SSA_NAMES or NEW_SSA_NAMES defined by SI
1804 will be registered as a new definition for their corresponding name
1805 in OLD_SSA_NAMES. */
1808 rewrite_update_stmt (gimple stmt
)
1810 use_operand_p use_p
;
1811 def_operand_p def_p
;
1814 /* Only update marked statements. */
1815 if (!rewrite_uses_p (stmt
) && !register_defs_p (stmt
))
1818 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1820 fprintf (dump_file
, "Updating SSA information for statement ");
1821 print_gimple_stmt (dump_file
, stmt
, 0, TDF_SLIM
);
1822 fprintf (dump_file
, "\n");
1825 /* Rewrite USES included in OLD_SSA_NAMES and USES whose underlying
1826 symbol is marked for renaming. */
1827 if (rewrite_uses_p (stmt
))
1828 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, iter
, SSA_OP_ALL_USES
)
1829 maybe_replace_use (use_p
);
1831 /* Register definitions of names in NEW_SSA_NAMES and OLD_SSA_NAMES.
1832 Also register definitions for names whose underlying symbol is
1833 marked for renaming. */
1834 if (register_defs_p (stmt
))
1835 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, iter
, SSA_OP_ALL_DEFS
)
1836 maybe_register_def (def_p
, stmt
);
1840 /* Visit all the successor blocks of BB looking for PHI nodes. For
1841 every PHI node found, check if any of its arguments is in
1842 OLD_SSA_NAMES. If so, and if the argument has a current reaching
1843 definition, replace it. */
1846 rewrite_update_phi_arguments (basic_block bb
)
1852 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1857 if (!bitmap_bit_p (blocks_with_phis_to_rewrite
, e
->dest
->index
))
1860 phis
= VEC_index (gimple_vec
, phis_to_rewrite
, e
->dest
->index
);
1861 for (i
= 0; VEC_iterate (gimple
, phis
, i
, phi
); i
++)
1863 tree arg
, lhs_sym
, reaching_def
= NULL
;
1864 use_operand_p arg_p
;
1866 gcc_assert (rewrite_uses_p (phi
));
1868 arg_p
= PHI_ARG_DEF_PTR_FROM_EDGE (phi
, e
);
1869 arg
= USE_FROM_PTR (arg_p
);
1871 if (arg
&& !DECL_P (arg
) && TREE_CODE (arg
) != SSA_NAME
)
1874 lhs_sym
= SSA_NAME_VAR (gimple_phi_result (phi
));
1876 if (arg
== NULL_TREE
)
1878 /* When updating a PHI node for a recently introduced
1879 symbol we may find NULL arguments. That's why we
1880 take the symbol from the LHS of the PHI node. */
1881 reaching_def
= get_reaching_def (lhs_sym
);
1886 tree sym
= DECL_P (arg
) ? arg
: SSA_NAME_VAR (arg
);
1888 if (symbol_marked_for_renaming (sym
))
1889 reaching_def
= get_reaching_def (sym
);
1890 else if (is_old_name (arg
))
1891 reaching_def
= get_reaching_def (arg
);
1894 /* Update the argument if there is a reaching def. */
1898 source_location locus
;
1899 int arg_i
= PHI_ARG_INDEX_FROM_USE (arg_p
);
1901 SET_USE (arg_p
, reaching_def
);
1902 stmt
= SSA_NAME_DEF_STMT (reaching_def
);
1904 /* Single element PHI nodes behave like copies, so get the
1905 location from the phi argument. */
1906 if (gimple_code (stmt
) == GIMPLE_PHI
&&
1907 gimple_phi_num_args (stmt
) == 1)
1908 locus
= gimple_phi_arg_location (stmt
, 0);
1910 locus
= gimple_location (stmt
);
1912 gimple_phi_arg_set_location (phi
, arg_i
, locus
);
1916 if (e
->flags
& EDGE_ABNORMAL
)
1917 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (USE_FROM_PTR (arg_p
)) = 1;
1923 /* Initialization of block data structures for the incremental SSA
1924 update pass. Create a block local stack of reaching definitions
1925 for new SSA names produced in this block (BLOCK_DEFS). Register
1926 new definitions for every PHI node in the block. */
1929 rewrite_update_enter_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
1934 bool is_abnormal_phi
;
1935 gimple_stmt_iterator gsi
;
1937 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1938 fprintf (dump_file
, "\n\nRegistering new PHI nodes in block #%d\n\n",
1941 /* Mark the unwind point for this block. */
1942 VEC_safe_push (tree
, heap
, block_defs_stack
, NULL_TREE
);
1944 if (!bitmap_bit_p (blocks_to_update
, bb
->index
))
1947 /* Mark the LHS if any of the arguments flows through an abnormal
1949 is_abnormal_phi
= false;
1950 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
1951 if (e
->flags
& EDGE_ABNORMAL
)
1953 is_abnormal_phi
= true;
1957 /* If any of the PHI nodes is a replacement for a name in
1958 OLD_SSA_NAMES or it's one of the names in NEW_SSA_NAMES, then
1959 register it as a new definition for its corresponding name. Also
1960 register definitions for names whose underlying symbols are
1961 marked for renaming. */
1962 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1965 gimple phi
= gsi_stmt (gsi
);
1967 if (!register_defs_p (phi
))
1970 lhs
= gimple_phi_result (phi
);
1971 lhs_sym
= SSA_NAME_VAR (lhs
);
1973 if (symbol_marked_for_renaming (lhs_sym
))
1974 register_new_update_single (lhs
, lhs_sym
);
1978 /* If LHS is a new name, register a new definition for all
1979 the names replaced by LHS. */
1980 if (is_new_name (lhs
))
1981 register_new_update_set (lhs
, names_replaced_by (lhs
));
1983 /* If LHS is an OLD name, register it as a new definition
1985 if (is_old_name (lhs
))
1986 register_new_update_single (lhs
, lhs
);
1989 if (is_abnormal_phi
)
1990 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (lhs
) = 1;
1993 /* Step 2. Rewrite every variable used in each statement in the block. */
1994 if (TEST_BIT (interesting_blocks
, bb
->index
))
1996 gcc_assert (bitmap_bit_p (blocks_to_update
, bb
->index
));
1997 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1998 rewrite_update_stmt (gsi_stmt (gsi
));
2001 /* Step 3. Update PHI nodes. */
2002 rewrite_update_phi_arguments (bb
);
2005 /* Called after visiting block BB. Unwind BLOCK_DEFS_STACK to restore
2006 the current reaching definition of every name re-written in BB to
2007 the original reaching definition before visiting BB. This
2008 unwinding must be done in the opposite order to what is done in
2009 register_new_update_set. */
2012 rewrite_update_leave_block (struct dom_walk_data
*walk_data ATTRIBUTE_UNUSED
,
2013 basic_block bb ATTRIBUTE_UNUSED
)
2015 while (VEC_length (tree
, block_defs_stack
) > 0)
2017 tree var
= VEC_pop (tree
, block_defs_stack
);
2020 /* NULL indicates the unwind stop point for this block (see
2021 rewrite_update_enter_block). */
2025 saved_def
= VEC_pop (tree
, block_defs_stack
);
2026 set_current_def (var
, saved_def
);
2031 /* Rewrite the actual blocks, statements, and PHI arguments, to be in SSA
2034 ENTRY indicates the block where to start. Every block dominated by
2035 ENTRY will be rewritten.
2037 WHAT indicates what actions will be taken by the renamer (see enum
2040 BLOCKS are the set of interesting blocks for the dominator walker
2041 to process. If this set is NULL, then all the nodes dominated
2042 by ENTRY are walked. Otherwise, blocks dominated by ENTRY that
2043 are not present in BLOCKS are ignored. */
2046 rewrite_blocks (basic_block entry
, enum rewrite_mode what
)
2048 struct dom_walk_data walk_data
;
2050 /* Rewrite all the basic blocks in the program. */
2051 timevar_push (TV_TREE_SSA_REWRITE_BLOCKS
);
2053 /* Setup callbacks for the generic dominator tree walker. */
2054 memset (&walk_data
, 0, sizeof (walk_data
));
2056 walk_data
.dom_direction
= CDI_DOMINATORS
;
2058 if (what
== REWRITE_ALL
)
2060 walk_data
.before_dom_children
= rewrite_enter_block
;
2061 walk_data
.after_dom_children
= rewrite_leave_block
;
2063 else if (what
== REWRITE_UPDATE
)
2065 walk_data
.before_dom_children
= rewrite_update_enter_block
;
2066 walk_data
.after_dom_children
= rewrite_update_leave_block
;
2071 block_defs_stack
= VEC_alloc (tree
, heap
, 10);
2073 /* Initialize the dominator walker. */
2074 init_walk_dominator_tree (&walk_data
);
2076 /* Recursively walk the dominator tree rewriting each statement in
2077 each basic block. */
2078 walk_dominator_tree (&walk_data
, entry
);
2080 /* Finalize the dominator walker. */
2081 fini_walk_dominator_tree (&walk_data
);
2083 /* Debugging dumps. */
2084 if (dump_file
&& (dump_flags
& TDF_STATS
))
2086 dump_dfa_stats (dump_file
);
2088 dump_tree_ssa_stats (dump_file
);
2091 VEC_free (tree
, heap
, block_defs_stack
);
2093 timevar_pop (TV_TREE_SSA_REWRITE_BLOCKS
);
2097 /* Block processing routine for mark_def_sites. Clear the KILLS bitmap
2098 at the start of each block, and call mark_def_sites for each statement. */
2101 mark_def_sites_block (struct dom_walk_data
*walk_data
, basic_block bb
)
2103 struct mark_def_sites_global_data
*gd
;
2105 gimple_stmt_iterator gsi
;
2107 gd
= (struct mark_def_sites_global_data
*) walk_data
->global_data
;
2110 bitmap_clear (kills
);
2111 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
2112 mark_def_sites (bb
, gsi_stmt (gsi
), kills
);
2116 /* Mark the definition site blocks for each variable, so that we know
2117 where the variable is actually live.
2119 The INTERESTING_BLOCKS global will be filled in with all the blocks
2120 that should be processed by the renamer. It is assumed that the
2121 caller has already initialized and zeroed it. */
2124 mark_def_site_blocks (void)
2126 struct dom_walk_data walk_data
;
2127 struct mark_def_sites_global_data mark_def_sites_global_data
;
2129 /* Setup callbacks for the generic dominator tree walker to find and
2130 mark definition sites. */
2131 walk_data
.dom_direction
= CDI_DOMINATORS
;
2132 walk_data
.initialize_block_local_data
= NULL
;
2133 walk_data
.before_dom_children
= mark_def_sites_block
;
2134 walk_data
.after_dom_children
= NULL
;
2136 /* Notice that this bitmap is indexed using variable UIDs, so it must be
2137 large enough to accommodate all the variables referenced in the
2138 function, not just the ones we are renaming. */
2139 mark_def_sites_global_data
.kills
= BITMAP_ALLOC (NULL
);
2140 walk_data
.global_data
= &mark_def_sites_global_data
;
2142 /* We do not have any local data. */
2143 walk_data
.block_local_data_size
= 0;
2145 /* Initialize the dominator walker. */
2146 init_walk_dominator_tree (&walk_data
);
2148 /* Recursively walk the dominator tree. */
2149 walk_dominator_tree (&walk_data
, ENTRY_BLOCK_PTR
);
2151 /* Finalize the dominator walker. */
2152 fini_walk_dominator_tree (&walk_data
);
2154 /* We no longer need this bitmap, clear and free it. */
2155 BITMAP_FREE (mark_def_sites_global_data
.kills
);
2159 /* Initialize internal data needed during renaming. */
2162 init_ssa_renamer (void)
2165 referenced_var_iterator rvi
;
2167 cfun
->gimple_df
->in_ssa_p
= false;
2169 /* Allocate memory for the DEF_BLOCKS hash table. */
2170 gcc_assert (def_blocks
== NULL
);
2171 def_blocks
= htab_create (num_referenced_vars
, def_blocks_hash
,
2172 def_blocks_eq
, def_blocks_free
);
2174 FOR_EACH_REFERENCED_VAR(var
, rvi
)
2175 set_current_def (var
, NULL_TREE
);
2179 /* Deallocate internal data structures used by the renamer. */
2182 fini_ssa_renamer (void)
2186 htab_delete (def_blocks
);
2190 cfun
->gimple_df
->in_ssa_p
= true;
2193 /* Main entry point into the SSA builder. The renaming process
2194 proceeds in four main phases:
2196 1- Compute dominance frontier and immediate dominators, needed to
2197 insert PHI nodes and rename the function in dominator tree
2200 2- Find and mark all the blocks that define variables
2201 (mark_def_site_blocks).
2203 3- Insert PHI nodes at dominance frontiers (insert_phi_nodes).
2205 4- Rename all the blocks (rewrite_blocks) and statements in the program.
2207 Steps 3 and 4 are done using the dominator tree walker
2208 (walk_dominator_tree). */
2211 rewrite_into_ssa (void)
2216 timevar_push (TV_TREE_SSA_OTHER
);
2218 /* Initialize operand data structures. */
2219 init_ssa_operands ();
2221 /* Initialize internal data needed by the renamer. */
2222 init_ssa_renamer ();
2224 /* Initialize the set of interesting blocks. The callback
2225 mark_def_sites will add to this set those blocks that the renamer
2227 interesting_blocks
= sbitmap_alloc (last_basic_block
);
2228 sbitmap_zero (interesting_blocks
);
2230 /* Initialize dominance frontier. */
2231 dfs
= XNEWVEC (bitmap
, last_basic_block
);
2233 dfs
[bb
->index
] = BITMAP_ALLOC (NULL
);
2235 /* 1- Compute dominance frontiers. */
2236 calculate_dominance_info (CDI_DOMINATORS
);
2237 compute_dominance_frontiers (dfs
);
2239 /* 2- Find and mark definition sites. */
2240 mark_def_site_blocks ();
2242 /* 3- Insert PHI nodes at dominance frontiers of definition blocks. */
2243 insert_phi_nodes (dfs
);
2245 /* 4- Rename all the blocks. */
2246 rewrite_blocks (ENTRY_BLOCK_PTR
, REWRITE_ALL
);
2248 /* Free allocated memory. */
2250 BITMAP_FREE (dfs
[bb
->index
]);
2253 fini_ssa_renamer ();
2255 timevar_pop (TV_TREE_SSA_OTHER
);
2260 struct gimple_opt_pass pass_build_ssa
=
2266 rewrite_into_ssa
, /* execute */
2269 0, /* static_pass_number */
2270 TV_NONE
, /* tv_id */
2271 PROP_cfg
| PROP_referenced_vars
, /* properties_required */
2272 PROP_ssa
, /* properties_provided */
2273 0, /* properties_destroyed */
2274 0, /* todo_flags_start */
2276 | TODO_update_ssa_only_virtuals
2278 | TODO_remove_unused_locals
/* todo_flags_finish */
2283 /* Mark the definition of VAR at STMT and BB as interesting for the
2284 renamer. BLOCKS is the set of blocks that need updating. */
2287 mark_def_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2289 gcc_assert (bitmap_bit_p (blocks_to_update
, bb
->index
));
2290 set_register_defs (stmt
, true);
2294 bool is_phi_p
= gimple_code (stmt
) == GIMPLE_PHI
;
2296 set_def_block (var
, bb
, is_phi_p
);
2298 /* If VAR is an SSA name in NEW_SSA_NAMES, this is a definition
2299 site for both itself and all the old names replaced by it. */
2300 if (TREE_CODE (var
) == SSA_NAME
&& is_new_name (var
))
2304 bitmap set
= names_replaced_by (var
);
2306 EXECUTE_IF_SET_IN_BITMAP (set
, 0, i
, bi
)
2307 set_def_block (ssa_name (i
), bb
, is_phi_p
);
2313 /* Mark the use of VAR at STMT and BB as interesting for the
2314 renamer. INSERT_PHI_P is true if we are going to insert new PHI
2318 mark_use_interesting (tree var
, gimple stmt
, basic_block bb
, bool insert_phi_p
)
2320 basic_block def_bb
= gimple_bb (stmt
);
2322 mark_block_for_update (def_bb
);
2323 mark_block_for_update (bb
);
2325 if (gimple_code (stmt
) == GIMPLE_PHI
)
2326 mark_phi_for_rewrite (def_bb
, stmt
);
2328 set_rewrite_uses (stmt
, true);
2330 /* If VAR has not been defined in BB, then it is live-on-entry
2331 to BB. Note that we cannot just use the block holding VAR's
2332 definition because if VAR is one of the names in OLD_SSA_NAMES,
2333 it will have several definitions (itself and all the names that
2337 struct def_blocks_d
*db_p
= get_def_blocks_for (var
);
2338 if (!bitmap_bit_p (db_p
->def_blocks
, bb
->index
))
2339 set_livein_block (var
, bb
);
2344 /* Do a dominator walk starting at BB processing statements that
2345 reference symbols in SYMS_TO_RENAME. This is very similar to
2346 mark_def_sites, but the scan handles statements whose operands may
2347 already be SSA names.
2349 If INSERT_PHI_P is true, mark those uses as live in the
2350 corresponding block. This is later used by the PHI placement
2351 algorithm to make PHI pruning decisions.
2353 FIXME. Most of this would be unnecessary if we could associate a
2354 symbol to all the SSA names that reference it. But that
2355 sounds like it would be expensive to maintain. Still, it
2356 would be interesting to see if it makes better sense to do
2360 prepare_block_for_update (basic_block bb
, bool insert_phi_p
)
2363 gimple_stmt_iterator si
;
2367 mark_block_for_update (bb
);
2369 /* Process PHI nodes marking interesting those that define or use
2370 the symbols that we are interested in. */
2371 for (si
= gsi_start_phis (bb
); !gsi_end_p (si
); gsi_next (&si
))
2373 gimple phi
= gsi_stmt (si
);
2374 tree lhs_sym
, lhs
= gimple_phi_result (phi
);
2376 lhs_sym
= DECL_P (lhs
) ? lhs
: SSA_NAME_VAR (lhs
);
2378 if (!symbol_marked_for_renaming (lhs_sym
))
2381 mark_def_interesting (lhs_sym
, phi
, bb
, insert_phi_p
);
2383 /* Mark the uses in phi nodes as interesting. It would be more correct
2384 to process the arguments of the phi nodes of the successor edges of
2385 BB at the end of prepare_block_for_update, however, that turns out
2386 to be significantly more expensive. Doing it here is conservatively
2387 correct -- it may only cause us to believe a value to be live in a
2388 block that also contains its definition, and thus insert a few more
2389 phi nodes for it. */
2390 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
2391 mark_use_interesting (lhs_sym
, phi
, e
->src
, insert_phi_p
);
2394 /* Process the statements. */
2395 for (si
= gsi_start_bb (bb
); !gsi_end_p (si
); gsi_next (&si
))
2399 use_operand_p use_p
;
2400 def_operand_p def_p
;
2402 stmt
= gsi_stmt (si
);
2404 FOR_EACH_SSA_USE_OPERAND (use_p
, stmt
, i
, SSA_OP_ALL_USES
)
2406 tree use
= USE_FROM_PTR (use_p
);
2407 tree sym
= DECL_P (use
) ? use
: SSA_NAME_VAR (use
);
2408 if (symbol_marked_for_renaming (sym
))
2409 mark_use_interesting (sym
, stmt
, bb
, insert_phi_p
);
2412 FOR_EACH_SSA_DEF_OPERAND (def_p
, stmt
, i
, SSA_OP_ALL_DEFS
)
2414 tree def
= DEF_FROM_PTR (def_p
);
2415 tree sym
= DECL_P (def
) ? def
: SSA_NAME_VAR (def
);
2416 if (symbol_marked_for_renaming (sym
))
2417 mark_def_interesting (sym
, stmt
, bb
, insert_phi_p
);
2421 /* Now visit all the blocks dominated by BB. */
2422 for (son
= first_dom_son (CDI_DOMINATORS
, bb
);
2424 son
= next_dom_son (CDI_DOMINATORS
, son
))
2425 prepare_block_for_update (son
, insert_phi_p
);
2429 /* Helper for prepare_names_to_update. Mark all the use sites for
2430 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2431 prepare_names_to_update. */
2434 prepare_use_sites_for (tree name
, bool insert_phi_p
)
2436 use_operand_p use_p
;
2437 imm_use_iterator iter
;
2439 FOR_EACH_IMM_USE_FAST (use_p
, iter
, name
)
2441 gimple stmt
= USE_STMT (use_p
);
2442 basic_block bb
= gimple_bb (stmt
);
2444 if (gimple_code (stmt
) == GIMPLE_PHI
)
2446 int ix
= PHI_ARG_INDEX_FROM_USE (use_p
);
2447 edge e
= gimple_phi_arg_edge (stmt
, ix
);
2448 mark_use_interesting (name
, stmt
, e
->src
, insert_phi_p
);
2452 /* For regular statements, mark this as an interesting use
2454 mark_use_interesting (name
, stmt
, bb
, insert_phi_p
);
2460 /* Helper for prepare_names_to_update. Mark the definition site for
2461 NAME as interesting. BLOCKS and INSERT_PHI_P are as in
2462 prepare_names_to_update. */
2465 prepare_def_site_for (tree name
, bool insert_phi_p
)
2470 gcc_assert (names_to_release
== NULL
2471 || !bitmap_bit_p (names_to_release
, SSA_NAME_VERSION (name
)));
2473 stmt
= SSA_NAME_DEF_STMT (name
);
2474 bb
= gimple_bb (stmt
);
2477 gcc_assert (bb
->index
< last_basic_block
);
2478 mark_block_for_update (bb
);
2479 mark_def_interesting (name
, stmt
, bb
, insert_phi_p
);
2484 /* Mark definition and use sites of names in NEW_SSA_NAMES and
2485 OLD_SSA_NAMES. INSERT_PHI_P is true if the caller wants to insert
2486 PHI nodes for newly created names. */
2489 prepare_names_to_update (bool insert_phi_p
)
2493 sbitmap_iterator sbi
;
2495 /* If a name N from NEW_SSA_NAMES is also marked to be released,
2496 remove it from NEW_SSA_NAMES so that we don't try to visit its
2497 defining basic block (which most likely doesn't exist). Notice
2498 that we cannot do the same with names in OLD_SSA_NAMES because we
2499 want to replace existing instances. */
2500 if (names_to_release
)
2501 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2502 RESET_BIT (new_ssa_names
, i
);
2504 /* First process names in NEW_SSA_NAMES. Otherwise, uses of old
2505 names may be considered to be live-in on blocks that contain
2506 definitions for their replacements. */
2507 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names
, 0, i
, sbi
)
2508 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2510 /* If an old name is in NAMES_TO_RELEASE, we cannot remove it from
2511 OLD_SSA_NAMES, but we have to ignore its definition site. */
2512 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names
, 0, i
, sbi
)
2514 if (names_to_release
== NULL
|| !bitmap_bit_p (names_to_release
, i
))
2515 prepare_def_site_for (ssa_name (i
), insert_phi_p
);
2516 prepare_use_sites_for (ssa_name (i
), insert_phi_p
);
2521 /* Dump all the names replaced by NAME to FILE. */
2524 dump_names_replaced_by (FILE *file
, tree name
)
2530 print_generic_expr (file
, name
, 0);
2531 fprintf (file
, " -> { ");
2533 old_set
= names_replaced_by (name
);
2534 EXECUTE_IF_SET_IN_BITMAP (old_set
, 0, i
, bi
)
2536 print_generic_expr (file
, ssa_name (i
), 0);
2537 fprintf (file
, " ");
2540 fprintf (file
, "}\n");
2544 /* Dump all the names replaced by NAME to stderr. */
2547 debug_names_replaced_by (tree name
)
2549 dump_names_replaced_by (stderr
, name
);
2553 /* Dump SSA update information to FILE. */
2556 dump_update_ssa (FILE *file
)
2561 if (!need_ssa_update_p (cfun
))
2564 if (new_ssa_names
&& sbitmap_first_set_bit (new_ssa_names
) >= 0)
2566 sbitmap_iterator sbi
;
2568 fprintf (file
, "\nSSA replacement table\n");
2569 fprintf (file
, "N_i -> { O_1 ... O_j } means that N_i replaces "
2570 "O_1, ..., O_j\n\n");
2572 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names
, 0, i
, sbi
)
2573 dump_names_replaced_by (file
, ssa_name (i
));
2575 fprintf (file
, "\n");
2576 fprintf (file
, "Number of virtual NEW -> OLD mappings: %7u\n",
2577 update_ssa_stats
.num_virtual_mappings
);
2578 fprintf (file
, "Number of real NEW -> OLD mappings: %7u\n",
2579 update_ssa_stats
.num_total_mappings
2580 - update_ssa_stats
.num_virtual_mappings
);
2581 fprintf (file
, "Number of total NEW -> OLD mappings: %7u\n",
2582 update_ssa_stats
.num_total_mappings
);
2584 fprintf (file
, "\nNumber of virtual symbols: %u\n",
2585 update_ssa_stats
.num_virtual_symbols
);
2588 if (!bitmap_empty_p (SYMS_TO_RENAME (cfun
)))
2590 fprintf (file
, "\n\nSymbols to be put in SSA form\n\n");
2591 dump_decl_set (file
, SYMS_TO_RENAME (cfun
));
2592 fprintf (file
, "\n");
2595 if (names_to_release
&& !bitmap_empty_p (names_to_release
))
2597 fprintf (file
, "\n\nSSA names to release after updating the SSA web\n\n");
2598 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2600 print_generic_expr (file
, ssa_name (i
), 0);
2601 fprintf (file
, " ");
2605 fprintf (file
, "\n\n");
2609 /* Dump SSA update information to stderr. */
2612 debug_update_ssa (void)
2614 dump_update_ssa (stderr
);
2618 /* Initialize data structures used for incremental SSA updates. */
2621 init_update_ssa (struct function
*fn
)
2623 /* Reserve more space than the current number of names. The calls to
2624 add_new_name_mapping are typically done after creating new SSA
2625 names, so we'll need to reallocate these arrays. */
2626 old_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2627 sbitmap_zero (old_ssa_names
);
2629 new_ssa_names
= sbitmap_alloc (num_ssa_names
+ NAME_SETS_GROWTH_FACTOR
);
2630 sbitmap_zero (new_ssa_names
);
2632 repl_tbl
= htab_create (20, repl_map_hash
, repl_map_eq
, repl_map_free
);
2633 names_to_release
= NULL
;
2634 memset (&update_ssa_stats
, 0, sizeof (update_ssa_stats
));
2635 update_ssa_stats
.virtual_symbols
= BITMAP_ALLOC (NULL
);
2636 update_ssa_initialized_fn
= fn
;
2640 /* Deallocate data structures used for incremental SSA updates. */
2643 delete_update_ssa (void)
2648 sbitmap_free (old_ssa_names
);
2649 old_ssa_names
= NULL
;
2651 sbitmap_free (new_ssa_names
);
2652 new_ssa_names
= NULL
;
2654 htab_delete (repl_tbl
);
2657 bitmap_clear (SYMS_TO_RENAME (update_ssa_initialized_fn
));
2658 BITMAP_FREE (update_ssa_stats
.virtual_symbols
);
2660 if (names_to_release
)
2662 EXECUTE_IF_SET_IN_BITMAP (names_to_release
, 0, i
, bi
)
2663 release_ssa_name (ssa_name (i
));
2664 BITMAP_FREE (names_to_release
);
2667 clear_ssa_name_info ();
2669 fini_ssa_renamer ();
2671 if (blocks_with_phis_to_rewrite
)
2672 EXECUTE_IF_SET_IN_BITMAP (blocks_with_phis_to_rewrite
, 0, i
, bi
)
2674 gimple_vec phis
= VEC_index (gimple_vec
, phis_to_rewrite
, i
);
2676 VEC_free (gimple
, heap
, phis
);
2677 VEC_replace (gimple_vec
, phis_to_rewrite
, i
, NULL
);
2680 BITMAP_FREE (blocks_with_phis_to_rewrite
);
2681 BITMAP_FREE (blocks_to_update
);
2682 update_ssa_initialized_fn
= NULL
;
2686 /* Create a new name for OLD_NAME in statement STMT and replace the
2687 operand pointed to by DEF_P with the newly created name. Return
2688 the new name and register the replacement mapping <NEW, OLD> in
2689 update_ssa's tables. */
2692 create_new_def_for (tree old_name
, gimple stmt
, def_operand_p def
)
2694 tree new_name
= duplicate_ssa_name (old_name
, stmt
);
2696 SET_DEF (def
, new_name
);
2698 if (gimple_code (stmt
) == GIMPLE_PHI
)
2702 basic_block bb
= gimple_bb (stmt
);
2704 /* If needed, mark NEW_NAME as occurring in an abnormal PHI node. */
2705 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
2706 if (e
->flags
& EDGE_ABNORMAL
)
2708 SSA_NAME_OCCURS_IN_ABNORMAL_PHI (new_name
) = 1;
2713 register_new_name_mapping (new_name
, old_name
);
2715 /* For the benefit of passes that will be updating the SSA form on
2716 their own, set the current reaching definition of OLD_NAME to be
2718 set_current_def (old_name
, new_name
);
2724 /* Register name NEW to be a replacement for name OLD. This function
2725 must be called for every replacement that should be performed by
2729 register_new_name_mapping (tree new_tree
, tree old
)
2731 if (!update_ssa_initialized_fn
)
2732 init_update_ssa (cfun
);
2734 gcc_assert (update_ssa_initialized_fn
== cfun
);
2736 add_new_name_mapping (new_tree
, old
);
2740 /* Register symbol SYM to be renamed by update_ssa. */
2743 mark_sym_for_renaming (tree sym
)
2745 bitmap_set_bit (SYMS_TO_RENAME (cfun
), DECL_UID (sym
));
2749 /* Register all the symbols in SET to be renamed by update_ssa. */
2752 mark_set_for_renaming (bitmap set
)
2757 if (set
== NULL
|| bitmap_empty_p (set
))
2760 EXECUTE_IF_SET_IN_BITMAP (set
, 0, i
, bi
)
2761 mark_sym_for_renaming (referenced_var (i
));
2765 /* Return true if there is any work to be done by update_ssa
2769 need_ssa_update_p (struct function
*fn
)
2771 gcc_assert (fn
!= NULL
);
2772 return (update_ssa_initialized_fn
== fn
2774 && !bitmap_empty_p (SYMS_TO_RENAME (fn
))));
2777 /* Return true if SSA name mappings have been registered for SSA updating. */
2780 name_mappings_registered_p (void)
2782 if (!update_ssa_initialized_fn
)
2785 gcc_assert (update_ssa_initialized_fn
== cfun
);
2787 return repl_tbl
&& htab_elements (repl_tbl
) > 0;
2790 /* Return true if name N has been registered in the replacement table. */
2793 name_registered_for_update_p (tree n ATTRIBUTE_UNUSED
)
2795 if (!update_ssa_initialized_fn
)
2798 gcc_assert (update_ssa_initialized_fn
== cfun
);
2800 return is_new_name (n
) || is_old_name (n
);
2804 /* Return the set of all the SSA names marked to be replaced. */
2807 ssa_names_to_replace (void)
2811 sbitmap_iterator sbi
;
2813 gcc_assert (update_ssa_initialized_fn
== NULL
2814 || update_ssa_initialized_fn
== cfun
);
2816 ret
= BITMAP_ALLOC (NULL
);
2817 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names
, 0, i
, sbi
)
2818 bitmap_set_bit (ret
, i
);
2824 /* Mark NAME to be released after update_ssa has finished. */
2827 release_ssa_name_after_update_ssa (tree name
)
2829 gcc_assert (cfun
&& update_ssa_initialized_fn
== cfun
);
2831 if (names_to_release
== NULL
)
2832 names_to_release
= BITMAP_ALLOC (NULL
);
2834 bitmap_set_bit (names_to_release
, SSA_NAME_VERSION (name
));
2838 /* Insert new PHI nodes to replace VAR. DFS contains dominance
2839 frontier information. BLOCKS is the set of blocks to be updated.
2841 This is slightly different than the regular PHI insertion
2842 algorithm. The value of UPDATE_FLAGS controls how PHI nodes for
2843 real names (i.e., GIMPLE registers) are inserted:
2845 - If UPDATE_FLAGS == TODO_update_ssa, we are only interested in PHI
2846 nodes inside the region affected by the block that defines VAR
2847 and the blocks that define all its replacements. All these
2848 definition blocks are stored in DEF_BLOCKS[VAR]->DEF_BLOCKS.
2850 First, we compute the entry point to the region (ENTRY). This is
2851 given by the nearest common dominator to all the definition
2852 blocks. When computing the iterated dominance frontier (IDF), any
2853 block not strictly dominated by ENTRY is ignored.
2855 We then call the standard PHI insertion algorithm with the pruned
2858 - If UPDATE_FLAGS == TODO_update_ssa_full_phi, the IDF for real
2859 names is not pruned. PHI nodes are inserted at every IDF block. */
2862 insert_updated_phi_nodes_for (tree var
, bitmap
*dfs
, bitmap blocks
,
2863 unsigned update_flags
)
2866 struct def_blocks_d
*db
;
2867 bitmap idf
, pruned_idf
;
2871 #if defined ENABLE_CHECKING
2872 if (TREE_CODE (var
) == SSA_NAME
)
2873 gcc_assert (is_old_name (var
));
2875 gcc_assert (symbol_marked_for_renaming (var
));
2878 /* Get all the definition sites for VAR. */
2879 db
= find_def_blocks_for (var
);
2881 /* No need to do anything if there were no definitions to VAR. */
2882 if (db
== NULL
|| bitmap_empty_p (db
->def_blocks
))
2885 /* Compute the initial iterated dominance frontier. */
2886 idf
= compute_idf (db
->def_blocks
, dfs
);
2887 pruned_idf
= BITMAP_ALLOC (NULL
);
2889 if (TREE_CODE (var
) == SSA_NAME
)
2891 if (update_flags
== TODO_update_ssa
)
2893 /* If doing regular SSA updates for GIMPLE registers, we are
2894 only interested in IDF blocks dominated by the nearest
2895 common dominator of all the definition blocks. */
2896 entry
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
2898 if (entry
!= ENTRY_BLOCK_PTR
)
2899 EXECUTE_IF_SET_IN_BITMAP (idf
, 0, i
, bi
)
2900 if (BASIC_BLOCK (i
) != entry
2901 && dominated_by_p (CDI_DOMINATORS
, BASIC_BLOCK (i
), entry
))
2902 bitmap_set_bit (pruned_idf
, i
);
2906 /* Otherwise, do not prune the IDF for VAR. */
2907 gcc_assert (update_flags
== TODO_update_ssa_full_phi
);
2908 bitmap_copy (pruned_idf
, idf
);
2913 /* Otherwise, VAR is a symbol that needs to be put into SSA form
2914 for the first time, so we need to compute the full IDF for
2916 bitmap_copy (pruned_idf
, idf
);
2919 if (!bitmap_empty_p (pruned_idf
))
2921 /* Make sure that PRUNED_IDF blocks and all their feeding blocks
2922 are included in the region to be updated. The feeding blocks
2923 are important to guarantee that the PHI arguments are renamed
2926 /* FIXME, this is not needed if we are updating symbols. We are
2927 already starting at the ENTRY block anyway. */
2928 bitmap_ior_into (blocks
, pruned_idf
);
2929 EXECUTE_IF_SET_IN_BITMAP (pruned_idf
, 0, i
, bi
)
2933 basic_block bb
= BASIC_BLOCK (i
);
2935 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
2936 if (e
->src
->index
>= 0)
2937 bitmap_set_bit (blocks
, e
->src
->index
);
2940 insert_phi_nodes_for (var
, pruned_idf
, true);
2943 BITMAP_FREE (pruned_idf
);
2948 /* Heuristic to determine whether SSA name mappings for virtual names
2949 should be discarded and their symbols rewritten from scratch. When
2950 there is a large number of mappings for virtual names, the
2951 insertion of PHI nodes for the old names in the mappings takes
2952 considerable more time than if we inserted PHI nodes for the
2955 Currently the heuristic takes these stats into account:
2957 - Number of mappings for virtual SSA names.
2958 - Number of distinct virtual symbols involved in those mappings.
2960 If the number of virtual mappings is much larger than the number of
2961 virtual symbols, then it will be faster to compute PHI insertion
2962 spots for the symbols. Even if this involves traversing the whole
2963 CFG, which is what happens when symbols are renamed from scratch. */
2966 switch_virtuals_to_full_rewrite_p (void)
2968 if (update_ssa_stats
.num_virtual_mappings
< (unsigned) MIN_VIRTUAL_MAPPINGS
)
2971 if (update_ssa_stats
.num_virtual_mappings
2972 > (unsigned) VIRTUAL_MAPPINGS_TO_SYMS_RATIO
2973 * update_ssa_stats
.num_virtual_symbols
)
2980 /* Remove every virtual mapping and mark all the affected virtual
2981 symbols for renaming. */
2984 switch_virtuals_to_full_rewrite (void)
2987 sbitmap_iterator sbi
;
2991 fprintf (dump_file
, "\nEnabled virtual name mapping heuristic.\n");
2992 fprintf (dump_file
, "\tNumber of virtual mappings: %7u\n",
2993 update_ssa_stats
.num_virtual_mappings
);
2994 fprintf (dump_file
, "\tNumber of unique virtual symbols: %7u\n",
2995 update_ssa_stats
.num_virtual_symbols
);
2996 fprintf (dump_file
, "Updating FUD-chains from top of CFG will be "
2997 "faster than processing\nthe name mappings.\n\n");
3000 /* Remove all virtual names from NEW_SSA_NAMES and OLD_SSA_NAMES.
3001 Note that it is not really necessary to remove the mappings from
3002 REPL_TBL, that would only waste time. */
3003 EXECUTE_IF_SET_IN_SBITMAP (new_ssa_names
, 0, i
, sbi
)
3004 if (!is_gimple_reg (ssa_name (i
)))
3005 RESET_BIT (new_ssa_names
, i
);
3007 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names
, 0, i
, sbi
)
3008 if (!is_gimple_reg (ssa_name (i
)))
3009 RESET_BIT (old_ssa_names
, i
);
3011 mark_set_for_renaming (update_ssa_stats
.virtual_symbols
);
3015 /* Given a set of newly created SSA names (NEW_SSA_NAMES) and a set of
3016 existing SSA names (OLD_SSA_NAMES), update the SSA form so that:
3018 1- The names in OLD_SSA_NAMES dominated by the definitions of
3019 NEW_SSA_NAMES are all re-written to be reached by the
3020 appropriate definition from NEW_SSA_NAMES.
3022 2- If needed, new PHI nodes are added to the iterated dominance
3023 frontier of the blocks where each of NEW_SSA_NAMES are defined.
3025 The mapping between OLD_SSA_NAMES and NEW_SSA_NAMES is setup by
3026 calling register_new_name_mapping for every pair of names that the
3027 caller wants to replace.
3029 The caller identifies the new names that have been inserted and the
3030 names that need to be replaced by calling register_new_name_mapping
3031 for every pair <NEW, OLD>. Note that the function assumes that the
3032 new names have already been inserted in the IL.
3034 For instance, given the following code:
3037 2 x_1 = PHI (0, x_5)
3048 Suppose that we insert new names x_10 and x_11 (lines 4 and 8).
3051 2 x_1 = PHI (0, x_5)
3064 We want to replace all the uses of x_1 with the new definitions of
3065 x_10 and x_11. Note that the only uses that should be replaced are
3066 those at lines 5, 9 and 11. Also, the use of x_7 at line 9 should
3067 *not* be replaced (this is why we cannot just mark symbol 'x' for
3070 Additionally, we may need to insert a PHI node at line 11 because
3071 that is a merge point for x_10 and x_11. So the use of x_1 at line
3072 11 will be replaced with the new PHI node. The insertion of PHI
3073 nodes is optional. They are not strictly necessary to preserve the
3074 SSA form, and depending on what the caller inserted, they may not
3075 even be useful for the optimizers. UPDATE_FLAGS controls various
3076 aspects of how update_ssa operates, see the documentation for
3077 TODO_update_ssa*. */
3080 update_ssa (unsigned update_flags
)
3082 basic_block bb
, start_bb
;
3086 sbitmap_iterator sbi
;
3088 if (!need_ssa_update_p (cfun
))
3091 timevar_push (TV_TREE_SSA_INCREMENTAL
);
3093 if (!update_ssa_initialized_fn
)
3094 init_update_ssa (cfun
);
3095 gcc_assert (update_ssa_initialized_fn
== cfun
);
3097 blocks_with_phis_to_rewrite
= BITMAP_ALLOC (NULL
);
3098 if (!phis_to_rewrite
)
3099 phis_to_rewrite
= VEC_alloc (gimple_vec
, heap
, last_basic_block
);
3100 blocks_to_update
= BITMAP_ALLOC (NULL
);
3102 /* Ensure that the dominance information is up-to-date. */
3103 calculate_dominance_info (CDI_DOMINATORS
);
3105 /* Only one update flag should be set. */
3106 gcc_assert (update_flags
== TODO_update_ssa
3107 || update_flags
== TODO_update_ssa_no_phi
3108 || update_flags
== TODO_update_ssa_full_phi
3109 || update_flags
== TODO_update_ssa_only_virtuals
);
3111 /* If we only need to update virtuals, remove all the mappings for
3112 real names before proceeding. The caller is responsible for
3113 having dealt with the name mappings before calling update_ssa. */
3114 if (update_flags
== TODO_update_ssa_only_virtuals
)
3116 sbitmap_zero (old_ssa_names
);
3117 sbitmap_zero (new_ssa_names
);
3118 htab_empty (repl_tbl
);
3121 insert_phi_p
= (update_flags
!= TODO_update_ssa_no_phi
);
3125 /* If the caller requested PHI nodes to be added, initialize
3126 live-in information data structures (DEF_BLOCKS). */
3128 /* For each SSA name N, the DEF_BLOCKS table describes where the
3129 name is defined, which blocks have PHI nodes for N, and which
3130 blocks have uses of N (i.e., N is live-on-entry in those
3132 def_blocks
= htab_create (num_ssa_names
, def_blocks_hash
,
3133 def_blocks_eq
, def_blocks_free
);
3140 /* Heuristic to avoid massive slow downs when the replacement
3141 mappings include lots of virtual names. */
3142 if (insert_phi_p
&& switch_virtuals_to_full_rewrite_p ())
3143 switch_virtuals_to_full_rewrite ();
3145 /* If there are names defined in the replacement table, prepare
3146 definition and use sites for all the names in NEW_SSA_NAMES and
3148 if (sbitmap_first_set_bit (new_ssa_names
) >= 0)
3150 prepare_names_to_update (insert_phi_p
);
3152 /* If all the names in NEW_SSA_NAMES had been marked for
3153 removal, and there are no symbols to rename, then there's
3154 nothing else to do. */
3155 if (sbitmap_first_set_bit (new_ssa_names
) < 0
3156 && bitmap_empty_p (SYMS_TO_RENAME (cfun
)))
3160 /* Next, determine the block at which to start the renaming process. */
3161 if (!bitmap_empty_p (SYMS_TO_RENAME (cfun
)))
3163 /* If we have to rename some symbols from scratch, we need to
3164 start the process at the root of the CFG. FIXME, it should
3165 be possible to determine the nearest block that had a
3166 definition for each of the symbols that are marked for
3167 updating. For now this seems more work than it's worth. */
3168 start_bb
= ENTRY_BLOCK_PTR
;
3170 /* Traverse the CFG looking for existing definitions and uses of
3171 symbols in SYMS_TO_RENAME. Mark interesting blocks and
3172 statements and set local live-in information for the PHI
3173 placement heuristics. */
3174 prepare_block_for_update (start_bb
, insert_phi_p
);
3178 /* Otherwise, the entry block to the region is the nearest
3179 common dominator for the blocks in BLOCKS. */
3180 start_bb
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3184 /* If requested, insert PHI nodes at the iterated dominance frontier
3185 of every block, creating new definitions for names in OLD_SSA_NAMES
3186 and for symbols in SYMS_TO_RENAME. */
3191 /* If the caller requested PHI nodes to be added, compute
3192 dominance frontiers. */
3193 dfs
= XNEWVEC (bitmap
, last_basic_block
);
3195 dfs
[bb
->index
] = BITMAP_ALLOC (NULL
);
3196 compute_dominance_frontiers (dfs
);
3198 if (sbitmap_first_set_bit (old_ssa_names
) >= 0)
3200 sbitmap_iterator sbi
;
3202 /* insert_update_phi_nodes_for will call add_new_name_mapping
3203 when inserting new PHI nodes, so the set OLD_SSA_NAMES
3204 will grow while we are traversing it (but it will not
3205 gain any new members). Copy OLD_SSA_NAMES to a temporary
3207 sbitmap tmp
= sbitmap_alloc (old_ssa_names
->n_bits
);
3208 sbitmap_copy (tmp
, old_ssa_names
);
3209 EXECUTE_IF_SET_IN_SBITMAP (tmp
, 0, i
, sbi
)
3210 insert_updated_phi_nodes_for (ssa_name (i
), dfs
, blocks_to_update
,
3215 EXECUTE_IF_SET_IN_BITMAP (SYMS_TO_RENAME (cfun
), 0, i
, bi
)
3216 insert_updated_phi_nodes_for (referenced_var (i
), dfs
, blocks_to_update
,
3220 BITMAP_FREE (dfs
[bb
->index
]);
3223 /* Insertion of PHI nodes may have added blocks to the region.
3224 We need to re-compute START_BB to include the newly added
3226 if (start_bb
!= ENTRY_BLOCK_PTR
)
3227 start_bb
= nearest_common_dominator_for_set (CDI_DOMINATORS
,
3231 /* Reset the current definition for name and symbol before renaming
3233 EXECUTE_IF_SET_IN_SBITMAP (old_ssa_names
, 0, i
, sbi
)
3234 set_current_def (ssa_name (i
), NULL_TREE
);
3236 EXECUTE_IF_SET_IN_BITMAP (SYMS_TO_RENAME (cfun
), 0, i
, bi
)
3237 set_current_def (referenced_var (i
), NULL_TREE
);
3239 /* Now start the renaming process at START_BB. */
3240 interesting_blocks
= sbitmap_alloc (last_basic_block
);
3241 sbitmap_zero (interesting_blocks
);
3242 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3243 SET_BIT (interesting_blocks
, i
);
3245 rewrite_blocks (start_bb
, REWRITE_UPDATE
);
3247 sbitmap_free (interesting_blocks
);
3249 /* Debugging dumps. */
3255 dump_update_ssa (dump_file
);
3257 fprintf (dump_file
, "Incremental SSA update started at block: %d\n\n",
3261 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3263 fprintf (dump_file
, "Number of blocks in CFG: %d\n", last_basic_block
);
3264 fprintf (dump_file
, "Number of blocks to update: %d (%3.0f%%)\n\n",
3265 c
, PERCENT (c
, last_basic_block
));
3267 if (dump_flags
& TDF_DETAILS
)
3269 fprintf (dump_file
, "Affected blocks: ");
3270 EXECUTE_IF_SET_IN_BITMAP (blocks_to_update
, 0, i
, bi
)
3271 fprintf (dump_file
, "%u ", i
);
3272 fprintf (dump_file
, "\n");
3275 fprintf (dump_file
, "\n\n");
3278 /* Free allocated memory. */
3280 delete_update_ssa ();
3282 timevar_pop (TV_TREE_SSA_INCREMENTAL
);