1 /* Liveness for SSA trees.
2 Copyright (C) 2003, 2004, 2005, 2007, 2008, 2009, 2010, 2011
3 Free Software Foundation, Inc.
4 Contributed by Andrew MacLeod <amacleod@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"
27 #include "gimple-pretty-print.h"
29 #include "tree-flow.h"
32 #include "tree-ssa-live.h"
33 #include "diagnostic-core.h"
38 #ifdef ENABLE_CHECKING
39 static void verify_live_on_entry (tree_live_info_p
);
43 /* VARMAP maintains a mapping from SSA version number to real variables.
45 All SSA_NAMES are divided into partitions. Initially each ssa_name is the
46 only member of it's own partition. Coalescing will attempt to group any
47 ssa_names which occur in a copy or in a PHI node into the same partition.
49 At the end of out-of-ssa, each partition becomes a "real" variable and is
50 rewritten as a compiler variable.
52 The var_map data structure is used to manage these partitions. It allows
53 partitions to be combined, and determines which partition belongs to what
54 ssa_name or variable, and vice versa. */
57 /* This routine will initialize the basevar fields of MAP. */
60 var_map_base_init (var_map map
)
65 struct tree_int_map
*m
, *mapstorage
;
67 num_part
= num_var_partitions (map
);
68 tree_to_index
= htab_create (num_part
, tree_map_base_hash
,
69 tree_int_map_eq
, NULL
);
70 /* We can have at most num_part entries in the hash tables, so it's
71 enough to allocate so many map elements once, saving some malloc
73 mapstorage
= m
= XNEWVEC (struct tree_int_map
, num_part
);
75 /* If a base table already exists, clear it, otherwise create it. */
76 free (map
->partition_to_base_index
);
77 map
->partition_to_base_index
= (int *) xmalloc (sizeof (int) * num_part
);
79 /* Build the base variable list, and point partitions at their bases. */
80 for (x
= 0; x
< num_part
; x
++)
82 struct tree_int_map
**slot
;
84 var
= partition_to_var (map
, x
);
85 if (SSA_NAME_VAR (var
))
86 m
->base
.from
= SSA_NAME_VAR (var
);
88 /* This restricts what anonymous SSA names we can coalesce
89 as it restricts the sets we compute conflicts for.
90 Using TREE_TYPE to generate sets is the easies as
91 type equivalency also holds for SSA names with the same
93 m
->base
.from
= TREE_TYPE (var
);
94 /* If base variable hasn't been seen, set it up. */
95 slot
= (struct tree_int_map
**) htab_find_slot (tree_to_index
,
99 baseindex
= m
- mapstorage
;
105 baseindex
= (*slot
)->to
;
106 map
->partition_to_base_index
[x
] = baseindex
;
109 map
->num_basevars
= m
- mapstorage
;
112 htab_delete (tree_to_index
);
116 /* Remove the base table in MAP. */
119 var_map_base_fini (var_map map
)
121 /* Free the basevar info if it is present. */
122 if (map
->partition_to_base_index
!= NULL
)
124 free (map
->partition_to_base_index
);
125 map
->partition_to_base_index
= NULL
;
126 map
->num_basevars
= 0;
129 /* Create a variable partition map of SIZE, initialize and return it. */
132 init_var_map (int size
)
136 map
= (var_map
) xmalloc (sizeof (struct _var_map
));
137 map
->var_partition
= partition_new (size
);
139 map
->partition_to_view
= NULL
;
140 map
->view_to_partition
= NULL
;
141 map
->num_partitions
= size
;
142 map
->partition_size
= size
;
143 map
->num_basevars
= 0;
144 map
->partition_to_base_index
= NULL
;
149 /* Free memory associated with MAP. */
152 delete_var_map (var_map map
)
154 var_map_base_fini (map
);
155 partition_delete (map
->var_partition
);
156 free (map
->partition_to_view
);
157 free (map
->view_to_partition
);
162 /* This function will combine the partitions in MAP for VAR1 and VAR2. It
163 Returns the partition which represents the new partition. If the two
164 partitions cannot be combined, NO_PARTITION is returned. */
167 var_union (var_map map
, tree var1
, tree var2
)
171 gcc_assert (TREE_CODE (var1
) == SSA_NAME
);
172 gcc_assert (TREE_CODE (var2
) == SSA_NAME
);
174 /* This is independent of partition_to_view. If partition_to_view is
175 on, then whichever one of these partitions is absorbed will never have a
176 dereference into the partition_to_view array any more. */
178 p1
= partition_find (map
->var_partition
, SSA_NAME_VERSION (var1
));
179 p2
= partition_find (map
->var_partition
, SSA_NAME_VERSION (var2
));
181 gcc_assert (p1
!= NO_PARTITION
);
182 gcc_assert (p2
!= NO_PARTITION
);
187 p3
= partition_union (map
->var_partition
, p1
, p2
);
189 if (map
->partition_to_view
)
190 p3
= map
->partition_to_view
[p3
];
196 /* Compress the partition numbers in MAP such that they fall in the range
197 0..(num_partitions-1) instead of wherever they turned out during
198 the partitioning exercise. This removes any references to unused
199 partitions, thereby allowing bitmaps and other vectors to be much
202 This is implemented such that compaction doesn't affect partitioning.
203 Ie., once partitions are created and possibly merged, running one
204 or more different kind of compaction will not affect the partitions
205 themselves. Their index might change, but all the same variables will
206 still be members of the same partition group. This allows work on reduced
207 sets, and no loss of information when a larger set is later desired.
209 In particular, coalescing can work on partitions which have 2 or more
210 definitions, and then 'recompact' later to include all the single
211 definitions for assignment to program variables. */
214 /* Set MAP back to the initial state of having no partition view. Return a
215 bitmap which has a bit set for each partition number which is in use in the
219 partition_view_init (var_map map
)
225 used
= BITMAP_ALLOC (NULL
);
227 /* Already in a view? Abandon the old one. */
228 if (map
->partition_to_view
)
230 free (map
->partition_to_view
);
231 map
->partition_to_view
= NULL
;
233 if (map
->view_to_partition
)
235 free (map
->view_to_partition
);
236 map
->view_to_partition
= NULL
;
239 /* Find out which partitions are actually referenced. */
240 for (x
= 0; x
< map
->partition_size
; x
++)
242 tmp
= partition_find (map
->var_partition
, x
);
243 if (ssa_name (tmp
) != NULL_TREE
&& !virtual_operand_p (ssa_name (tmp
))
244 && (!has_zero_uses (ssa_name (tmp
))
245 || !SSA_NAME_IS_DEFAULT_DEF (ssa_name (tmp
))))
246 bitmap_set_bit (used
, tmp
);
249 map
->num_partitions
= map
->partition_size
;
254 /* This routine will finalize the view data for MAP based on the partitions
255 set in SELECTED. This is either the same bitmap returned from
256 partition_view_init, or a trimmed down version if some of those partitions
257 were not desired in this view. SELECTED is freed before returning. */
260 partition_view_fini (var_map map
, bitmap selected
)
263 unsigned count
, i
, x
, limit
;
265 gcc_assert (selected
);
267 count
= bitmap_count_bits (selected
);
268 limit
= map
->partition_size
;
270 /* If its a one-to-one ratio, we don't need any view compaction. */
273 map
->partition_to_view
= (int *)xmalloc (limit
* sizeof (int));
274 memset (map
->partition_to_view
, 0xff, (limit
* sizeof (int)));
275 map
->view_to_partition
= (int *)xmalloc (count
* sizeof (int));
278 /* Give each selected partition an index. */
279 EXECUTE_IF_SET_IN_BITMAP (selected
, 0, x
, bi
)
281 map
->partition_to_view
[x
] = i
;
282 map
->view_to_partition
[i
] = x
;
285 gcc_assert (i
== count
);
286 map
->num_partitions
= i
;
289 BITMAP_FREE (selected
);
293 /* Create a partition view which includes all the used partitions in MAP. If
294 WANT_BASES is true, create the base variable map as well. */
297 partition_view_normal (var_map map
, bool want_bases
)
301 used
= partition_view_init (map
);
302 partition_view_fini (map
, used
);
305 var_map_base_init (map
);
307 var_map_base_fini (map
);
311 /* Create a partition view in MAP which includes just partitions which occur in
312 the bitmap ONLY. If WANT_BASES is true, create the base variable map
316 partition_view_bitmap (var_map map
, bitmap only
, bool want_bases
)
319 bitmap new_partitions
= BITMAP_ALLOC (NULL
);
323 used
= partition_view_init (map
);
324 EXECUTE_IF_SET_IN_BITMAP (only
, 0, x
, bi
)
326 p
= partition_find (map
->var_partition
, x
);
327 gcc_assert (bitmap_bit_p (used
, p
));
328 bitmap_set_bit (new_partitions
, p
);
330 partition_view_fini (map
, new_partitions
);
333 var_map_base_init (map
);
335 var_map_base_fini (map
);
339 static bitmap usedvars
;
341 /* Mark VAR as used, so that it'll be preserved during rtl expansion.
342 Returns true if VAR wasn't marked before. */
345 set_is_used (tree var
)
347 return bitmap_set_bit (usedvars
, DECL_UID (var
));
350 /* Return true if VAR is marked as used. */
355 return bitmap_bit_p (usedvars
, DECL_UID (var
));
358 static inline void mark_all_vars_used (tree
*);
360 /* Helper function for mark_all_vars_used, called via walk_tree. */
363 mark_all_vars_used_1 (tree
*tp
, int *walk_subtrees
, void *data ATTRIBUTE_UNUSED
)
366 enum tree_code_class c
= TREE_CODE_CLASS (TREE_CODE (t
));
369 if (TREE_CODE (t
) == SSA_NAME
)
372 t
= SSA_NAME_VAR (t
);
377 if (IS_EXPR_CODE_CLASS (c
)
378 && (b
= TREE_BLOCK (t
)) != NULL
)
379 TREE_USED (b
) = true;
381 /* Ignore TMR_OFFSET and TMR_STEP for TARGET_MEM_REFS, as those
382 fields do not contain vars. */
383 if (TREE_CODE (t
) == TARGET_MEM_REF
)
385 mark_all_vars_used (&TMR_BASE (t
));
386 mark_all_vars_used (&TMR_INDEX (t
));
387 mark_all_vars_used (&TMR_INDEX2 (t
));
392 /* Only need to mark VAR_DECLS; parameters and return results are not
393 eliminated as unused. */
394 if (TREE_CODE (t
) == VAR_DECL
)
396 /* When a global var becomes used for the first time also walk its
397 initializer (non global ones don't have any). */
398 if (set_is_used (t
) && is_global_var (t
))
399 mark_all_vars_used (&DECL_INITIAL (t
));
401 /* remove_unused_scope_block_p requires information about labels
402 which are not DECL_IGNORED_P to tell if they might be used in the IL. */
403 else if (TREE_CODE (t
) == LABEL_DECL
)
404 /* Although the TREE_USED values that the frontend uses would be
405 acceptable (albeit slightly over-conservative) for our purposes,
406 init_vars_expansion clears TREE_USED for LABEL_DECLs too, so we
407 must re-compute it here. */
410 if (IS_TYPE_OR_DECL_P (t
))
416 /* Mark the scope block SCOPE and its subblocks unused when they can be
417 possibly eliminated if dead. */
420 mark_scope_block_unused (tree scope
)
423 TREE_USED (scope
) = false;
424 if (!(*debug_hooks
->ignore_block
) (scope
))
425 TREE_USED (scope
) = true;
426 for (t
= BLOCK_SUBBLOCKS (scope
); t
; t
= BLOCK_CHAIN (t
))
427 mark_scope_block_unused (t
);
430 /* Look if the block is dead (by possibly eliminating its dead subblocks)
431 and return true if so.
432 Block is declared dead if:
433 1) No statements are associated with it.
434 2) Declares no live variables
435 3) All subblocks are dead
436 or there is precisely one subblocks and the block
437 has same abstract origin as outer block and declares
438 no variables, so it is pure wrapper.
439 When we are not outputting full debug info, we also eliminate dead variables
440 out of scope blocks to let them to be recycled by GGC and to save copying work
441 done by the inliner. */
444 remove_unused_scope_block_p (tree scope
)
447 bool unused
= !TREE_USED (scope
);
450 for (t
= &BLOCK_VARS (scope
); *t
; t
= next
)
452 next
= &DECL_CHAIN (*t
);
454 /* Debug info of nested function refers to the block of the
455 function. We might stil call it even if all statements
456 of function it was nested into was elliminated.
458 TODO: We can actually look into cgraph to see if function
459 will be output to file. */
460 if (TREE_CODE (*t
) == FUNCTION_DECL
)
463 /* If a decl has a value expr, we need to instantiate it
464 regardless of debug info generation, to avoid codegen
465 differences in memory overlap tests. update_equiv_regs() may
466 indirectly call validate_equiv_mem() to test whether a
467 SET_DEST overlaps with others, and if the value expr changes
468 by virtual register instantiation, we may get end up with
469 different results. */
470 else if (TREE_CODE (*t
) == VAR_DECL
&& DECL_HAS_VALUE_EXPR_P (*t
))
473 /* Remove everything we don't generate debug info for. */
474 else if (DECL_IGNORED_P (*t
))
476 *t
= DECL_CHAIN (*t
);
480 /* When we are outputting debug info, we usually want to output
481 info about optimized-out variables in the scope blocks.
482 Exception are the scope blocks not containing any instructions
483 at all so user can't get into the scopes at first place. */
484 else if (is_used_p (*t
))
486 else if (TREE_CODE (*t
) == LABEL_DECL
&& TREE_USED (*t
))
487 /* For labels that are still used in the IL, the decision to
488 preserve them must not depend DEBUG_INFO_LEVEL, otherwise we
489 risk having different ordering in debug vs. non-debug builds
490 during inlining or versioning.
491 A label appearing here (we have already checked DECL_IGNORED_P)
492 should not be used in the IL unless it has been explicitly used
493 before, so we use TREE_USED as an approximation. */
494 /* In principle, we should do the same here as for the debug case
495 below, however, when debugging, there might be additional nested
496 levels that keep an upper level with a label live, so we have to
497 force this block to be considered used, too. */
500 /* When we are not doing full debug info, we however can keep around
501 only the used variables for cfgexpand's memory packing saving quite
504 For sake of -g3, we keep around those vars but we don't count this as
505 use of block, so innermost block with no used vars and no instructions
506 can be considered dead. We only want to keep around blocks user can
507 breakpoint into and ask about value of optimized out variables.
509 Similarly we need to keep around types at least until all
510 variables of all nested blocks are gone. We track no
511 information on whether given type is used or not, so we have
512 to keep them even when not emitting debug information,
513 otherwise we may end up remapping variables and their (local)
514 types in different orders depending on whether debug
515 information is being generated. */
517 else if (TREE_CODE (*t
) == TYPE_DECL
518 || debug_info_level
== DINFO_LEVEL_NORMAL
519 || debug_info_level
== DINFO_LEVEL_VERBOSE
)
523 *t
= DECL_CHAIN (*t
);
528 for (t
= &BLOCK_SUBBLOCKS (scope
); *t
;)
529 if (remove_unused_scope_block_p (*t
))
531 if (BLOCK_SUBBLOCKS (*t
))
533 tree next
= BLOCK_CHAIN (*t
);
534 tree supercontext
= BLOCK_SUPERCONTEXT (*t
);
536 *t
= BLOCK_SUBBLOCKS (*t
);
537 while (BLOCK_CHAIN (*t
))
539 BLOCK_SUPERCONTEXT (*t
) = supercontext
;
540 t
= &BLOCK_CHAIN (*t
);
542 BLOCK_CHAIN (*t
) = next
;
543 BLOCK_SUPERCONTEXT (*t
) = supercontext
;
544 t
= &BLOCK_CHAIN (*t
);
548 *t
= BLOCK_CHAIN (*t
);
552 t
= &BLOCK_CHAIN (*t
);
559 /* Outer scope is always used. */
560 else if (!BLOCK_SUPERCONTEXT (scope
)
561 || TREE_CODE (BLOCK_SUPERCONTEXT (scope
)) == FUNCTION_DECL
)
563 /* Innermost blocks with no live variables nor statements can be always
565 else if (!nsubblocks
)
567 /* For terse debug info we can eliminate info on unused variables. */
568 else if (debug_info_level
== DINFO_LEVEL_NONE
569 || debug_info_level
== DINFO_LEVEL_TERSE
)
571 /* Even for -g0/-g1 don't prune outer scopes from artificial
572 functions, otherwise diagnostics using tree_nonartificial_location
573 will not be emitted properly. */
574 if (inlined_function_outer_scope_p (scope
))
579 && TREE_CODE (ao
) == BLOCK
580 && BLOCK_ABSTRACT_ORIGIN (ao
) != ao
)
581 ao
= BLOCK_ABSTRACT_ORIGIN (ao
);
583 && TREE_CODE (ao
) == FUNCTION_DECL
584 && DECL_DECLARED_INLINE_P (ao
)
585 && lookup_attribute ("artificial", DECL_ATTRIBUTES (ao
)))
589 else if (BLOCK_VARS (scope
) || BLOCK_NUM_NONLOCALIZED_VARS (scope
))
591 /* See if this block is important for representation of inlined function.
592 Inlined functions are always represented by block with
593 block_ultimate_origin being set to FUNCTION_DECL and DECL_SOURCE_LOCATION
595 else if (inlined_function_outer_scope_p (scope
))
598 /* Verfify that only blocks with source location set
599 are entry points to the inlined functions. */
600 gcc_assert (IS_UNKNOWN_LOCATION (BLOCK_SOURCE_LOCATION (scope
)));
602 TREE_USED (scope
) = !unused
;
606 /* Mark all VAR_DECLS under *EXPR_P as used, so that they won't be
607 eliminated during the tree->rtl conversion process. */
610 mark_all_vars_used (tree
*expr_p
)
612 walk_tree (expr_p
, mark_all_vars_used_1
, NULL
, NULL
);
615 /* Helper function for clear_unused_block_pointer, called via walk_tree. */
618 clear_unused_block_pointer_1 (tree
*tp
, int *, void *)
620 if (EXPR_P (*tp
) && TREE_BLOCK (*tp
)
621 && !TREE_USED (TREE_BLOCK (*tp
)))
622 TREE_SET_BLOCK (*tp
, NULL
);
623 if (TREE_CODE (*tp
) == VAR_DECL
&& DECL_DEBUG_EXPR_IS_FROM (*tp
))
625 tree debug_expr
= DECL_DEBUG_EXPR (*tp
);
626 walk_tree (&debug_expr
, clear_unused_block_pointer_1
, NULL
, NULL
);
631 /* Set all block pointer in debug stmt to NULL if the block is unused,
632 so that they will not be streamed out. */
635 clear_unused_block_pointer ()
638 gimple_stmt_iterator gsi
;
640 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
644 gimple stmt
= gsi_stmt (gsi
);
646 if (!is_gimple_debug (stmt
))
648 b
= gimple_block (stmt
);
649 if (b
&& !TREE_USED (b
))
650 gimple_set_block (stmt
, NULL
);
651 for (i
= 0; i
< gimple_num_ops (stmt
); i
++)
652 walk_tree (gimple_op_ptr (stmt
, i
), clear_unused_block_pointer_1
,
657 /* Dump scope blocks starting at SCOPE to FILE. INDENT is the
658 indentation level and FLAGS is as in print_generic_expr. */
661 dump_scope_block (FILE *file
, int indent
, tree scope
, int flags
)
666 fprintf (file
, "\n%*s{ Scope block #%i%s%s",indent
, "" , BLOCK_NUMBER (scope
),
667 TREE_USED (scope
) ? "" : " (unused)",
668 BLOCK_ABSTRACT (scope
) ? " (abstract)": "");
669 if (!IS_UNKNOWN_LOCATION (BLOCK_SOURCE_LOCATION (scope
)))
671 expanded_location s
= expand_location (BLOCK_SOURCE_LOCATION (scope
));
672 fprintf (file
, " %s:%i", s
.file
, s
.line
);
674 if (BLOCK_ABSTRACT_ORIGIN (scope
))
676 tree origin
= block_ultimate_origin (scope
);
679 fprintf (file
, " Originating from :");
681 print_generic_decl (file
, origin
, flags
);
683 fprintf (file
, "#%i", BLOCK_NUMBER (origin
));
686 fprintf (file
, " \n");
687 for (var
= BLOCK_VARS (scope
); var
; var
= DECL_CHAIN (var
))
689 fprintf (file
, "%*s", indent
, "");
690 print_generic_decl (file
, var
, flags
);
691 fprintf (file
, "\n");
693 for (i
= 0; i
< BLOCK_NUM_NONLOCALIZED_VARS (scope
); i
++)
695 fprintf (file
, "%*s",indent
, "");
696 print_generic_decl (file
, BLOCK_NONLOCALIZED_VAR (scope
, i
),
698 fprintf (file
, " (nonlocalized)\n");
700 for (t
= BLOCK_SUBBLOCKS (scope
); t
; t
= BLOCK_CHAIN (t
))
701 dump_scope_block (file
, indent
+ 2, t
, flags
);
702 fprintf (file
, "\n%*s}\n",indent
, "");
705 /* Dump the tree of lexical scopes starting at SCOPE to stderr. FLAGS
706 is as in print_generic_expr. */
709 debug_scope_block (tree scope
, int flags
)
711 dump_scope_block (stderr
, 0, scope
, flags
);
715 /* Dump the tree of lexical scopes of current_function_decl to FILE.
716 FLAGS is as in print_generic_expr. */
719 dump_scope_blocks (FILE *file
, int flags
)
721 dump_scope_block (file
, 0, DECL_INITIAL (current_function_decl
), flags
);
725 /* Dump the tree of lexical scopes of current_function_decl to stderr.
726 FLAGS is as in print_generic_expr. */
729 debug_scope_blocks (int flags
)
731 dump_scope_blocks (stderr
, flags
);
734 /* Remove local variables that are not referenced in the IL. */
737 remove_unused_locals (void)
741 unsigned srcidx
, dstidx
, num
;
742 bool have_local_clobbers
= false;
744 /* Removing declarations from lexical blocks when not optimizing is
745 not only a waste of time, it actually causes differences in stack
750 timevar_push (TV_REMOVE_UNUSED
);
752 mark_scope_block_unused (DECL_INITIAL (current_function_decl
));
754 usedvars
= BITMAP_ALLOC (NULL
);
756 /* Walk the CFG marking all referenced symbols. */
759 gimple_stmt_iterator gsi
;
764 /* Walk the statements. */
765 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
767 gimple stmt
= gsi_stmt (gsi
);
768 tree b
= gimple_block (stmt
);
770 if (is_gimple_debug (stmt
))
773 if (gimple_clobber_p (stmt
))
775 have_local_clobbers
= true;
780 TREE_USED (b
) = true;
782 for (i
= 0; i
< gimple_num_ops (stmt
); i
++)
783 mark_all_vars_used (gimple_op_ptr (gsi_stmt (gsi
), i
));
786 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
791 gimple phi
= gsi_stmt (gsi
);
793 if (virtual_operand_p (gimple_phi_result (phi
)))
796 def
= gimple_phi_result (phi
);
797 mark_all_vars_used (&def
);
799 FOR_EACH_PHI_ARG (arg_p
, phi
, i
, SSA_OP_ALL_USES
)
801 tree arg
= USE_FROM_PTR (arg_p
);
802 int index
= PHI_ARG_INDEX_FROM_USE (arg_p
);
804 LOCATION_BLOCK (gimple_phi_arg_location (phi
, index
));
806 TREE_USED (block
) = true;
807 mark_all_vars_used (&arg
);
811 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
813 TREE_USED (LOCATION_BLOCK (e
->goto_locus
)) = true;
816 /* We do a two-pass approach about the out-of-scope clobbers. We want
817 to remove them if they are the only references to a local variable,
818 but we want to retain them when there's any other. So the first pass
819 ignores them, and the second pass (if there were any) tries to remove
821 if (have_local_clobbers
)
824 gimple_stmt_iterator gsi
;
826 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
);)
828 gimple stmt
= gsi_stmt (gsi
);
829 tree b
= gimple_block (stmt
);
831 if (gimple_clobber_p (stmt
))
833 tree lhs
= gimple_assign_lhs (stmt
);
834 if (TREE_CODE (lhs
) == VAR_DECL
&& !is_used_p (lhs
))
836 unlink_stmt_vdef (stmt
);
837 gsi_remove (&gsi
, true);
842 TREE_USED (b
) = true;
848 cfun
->has_local_explicit_reg_vars
= false;
850 /* Remove unmarked local and global vars from local_decls. */
851 num
= VEC_length (tree
, cfun
->local_decls
);
852 for (srcidx
= 0, dstidx
= 0; srcidx
< num
; srcidx
++)
854 var
= VEC_index (tree
, cfun
->local_decls
, srcidx
);
855 if (TREE_CODE (var
) == VAR_DECL
)
857 if (!is_used_p (var
))
860 if (cfun
->nonlocal_goto_save_area
861 && TREE_OPERAND (cfun
->nonlocal_goto_save_area
, 0) == var
)
862 cfun
->nonlocal_goto_save_area
= NULL
;
863 /* Release any default def associated with var. */
864 if ((def
= ssa_default_def (cfun
, var
)) != NULL_TREE
)
866 set_ssa_default_def (cfun
, var
, NULL_TREE
);
867 release_ssa_name (def
);
872 if (TREE_CODE (var
) == VAR_DECL
873 && DECL_HARD_REGISTER (var
)
874 && !is_global_var (var
))
875 cfun
->has_local_explicit_reg_vars
= true;
877 if (srcidx
!= dstidx
)
878 VEC_replace (tree
, cfun
->local_decls
, dstidx
, var
);
882 VEC_truncate (tree
, cfun
->local_decls
, dstidx
);
884 remove_unused_scope_block_p (DECL_INITIAL (current_function_decl
));
885 clear_unused_block_pointer ();
887 BITMAP_FREE (usedvars
);
889 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
891 fprintf (dump_file
, "Scope blocks after cleanups:\n");
892 dump_scope_blocks (dump_file
, dump_flags
);
895 timevar_pop (TV_REMOVE_UNUSED
);
898 /* Obstack for globale liveness info bitmaps. We don't want to put these
899 on the default obstack because these bitmaps can grow quite large and
900 we'll hold on to all that memory until the end of the compiler run.
901 As a bonus, delete_tree_live_info can destroy all the bitmaps by just
902 releasing the whole obstack. */
903 static bitmap_obstack liveness_bitmap_obstack
;
905 /* Allocate and return a new live range information object base on MAP. */
907 static tree_live_info_p
908 new_tree_live_info (var_map map
)
910 tree_live_info_p live
;
913 live
= XNEW (struct tree_live_info_d
);
915 live
->num_blocks
= last_basic_block
;
917 live
->livein
= XNEWVEC (bitmap_head
, last_basic_block
);
919 bitmap_initialize (&live
->livein
[bb
->index
], &liveness_bitmap_obstack
);
921 live
->liveout
= XNEWVEC (bitmap_head
, last_basic_block
);
923 bitmap_initialize (&live
->liveout
[bb
->index
], &liveness_bitmap_obstack
);
925 live
->work_stack
= XNEWVEC (int, last_basic_block
);
926 live
->stack_top
= live
->work_stack
;
928 live
->global
= BITMAP_ALLOC (&liveness_bitmap_obstack
);
933 /* Free storage for live range info object LIVE. */
936 delete_tree_live_info (tree_live_info_p live
)
938 bitmap_obstack_release (&liveness_bitmap_obstack
);
939 free (live
->work_stack
);
940 free (live
->liveout
);
946 /* Visit basic block BB and propagate any required live on entry bits from
947 LIVE into the predecessors. VISITED is the bitmap of visited blocks.
948 TMP is a temporary work bitmap which is passed in to avoid reallocating
952 loe_visit_block (tree_live_info_p live
, basic_block bb
, sbitmap visited
,
960 gcc_assert (!TEST_BIT (visited
, bb
->index
));
962 SET_BIT (visited
, bb
->index
);
963 loe
= live_on_entry (live
, bb
);
965 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
968 if (pred_bb
== ENTRY_BLOCK_PTR
)
970 /* TMP is variables live-on-entry from BB that aren't defined in the
971 predecessor block. This should be the live on entry vars to pred.
972 Note that liveout is the DEFs in a block while live on entry is
974 bitmap_and_compl (tmp
, loe
, &live
->liveout
[pred_bb
->index
]);
976 /* Add these bits to live-on-entry for the pred. if there are any
977 changes, and pred_bb has been visited already, add it to the
979 change
= bitmap_ior_into (live_on_entry (live
, pred_bb
), tmp
);
980 if (TEST_BIT (visited
, pred_bb
->index
) && change
)
982 RESET_BIT (visited
, pred_bb
->index
);
983 *(live
->stack_top
)++ = pred_bb
->index
;
989 /* Using LIVE, fill in all the live-on-entry blocks between the defs and uses
990 of all the variables. */
993 live_worklist (tree_live_info_p live
)
997 sbitmap visited
= sbitmap_alloc (last_basic_block
+ 1);
998 bitmap tmp
= BITMAP_ALLOC (&liveness_bitmap_obstack
);
1000 sbitmap_zero (visited
);
1002 /* Visit all the blocks in reverse order and propagate live on entry values
1003 into the predecessors blocks. */
1004 FOR_EACH_BB_REVERSE (bb
)
1005 loe_visit_block (live
, bb
, visited
, tmp
);
1007 /* Process any blocks which require further iteration. */
1008 while (live
->stack_top
!= live
->work_stack
)
1010 b
= *--(live
->stack_top
);
1011 loe_visit_block (live
, BASIC_BLOCK (b
), visited
, tmp
);
1015 sbitmap_free (visited
);
1019 /* Calculate the initial live on entry vector for SSA_NAME using immediate_use
1020 links. Set the live on entry fields in LIVE. Def's are marked temporarily
1021 in the liveout vector. */
1024 set_var_live_on_entry (tree ssa_name
, tree_live_info_p live
)
1029 basic_block def_bb
= NULL
;
1030 imm_use_iterator imm_iter
;
1031 bool global
= false;
1033 p
= var_to_partition (live
->map
, ssa_name
);
1034 if (p
== NO_PARTITION
)
1037 stmt
= SSA_NAME_DEF_STMT (ssa_name
);
1040 def_bb
= gimple_bb (stmt
);
1041 /* Mark defs in liveout bitmap temporarily. */
1043 bitmap_set_bit (&live
->liveout
[def_bb
->index
], p
);
1046 def_bb
= ENTRY_BLOCK_PTR
;
1048 /* Visit each use of SSA_NAME and if it isn't in the same block as the def,
1049 add it to the list of live on entry blocks. */
1050 FOR_EACH_IMM_USE_FAST (use
, imm_iter
, ssa_name
)
1052 gimple use_stmt
= USE_STMT (use
);
1053 basic_block add_block
= NULL
;
1055 if (gimple_code (use_stmt
) == GIMPLE_PHI
)
1057 /* Uses in PHI's are considered to be live at exit of the SRC block
1058 as this is where a copy would be inserted. Check to see if it is
1059 defined in that block, or whether its live on entry. */
1060 int index
= PHI_ARG_INDEX_FROM_USE (use
);
1061 edge e
= gimple_phi_arg_edge (use_stmt
, index
);
1062 if (e
->src
!= ENTRY_BLOCK_PTR
)
1064 if (e
->src
!= def_bb
)
1068 else if (is_gimple_debug (use_stmt
))
1072 /* If its not defined in this block, its live on entry. */
1073 basic_block use_bb
= gimple_bb (use_stmt
);
1074 if (use_bb
!= def_bb
)
1078 /* If there was a live on entry use, set the bit. */
1082 bitmap_set_bit (&live
->livein
[add_block
->index
], p
);
1086 /* If SSA_NAME is live on entry to at least one block, fill in all the live
1087 on entry blocks between the def and all the uses. */
1089 bitmap_set_bit (live
->global
, p
);
1093 /* Calculate the live on exit vectors based on the entry info in LIVEINFO. */
1096 calculate_live_on_exit (tree_live_info_p liveinfo
)
1102 /* live on entry calculations used liveout vectors for defs, clear them. */
1104 bitmap_clear (&liveinfo
->liveout
[bb
->index
]);
1106 /* Set all the live-on-exit bits for uses in PHIs. */
1109 gimple_stmt_iterator gsi
;
1112 /* Mark the PHI arguments which are live on exit to the pred block. */
1113 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1115 gimple phi
= gsi_stmt (gsi
);
1116 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
1118 tree t
= PHI_ARG_DEF (phi
, i
);
1121 if (TREE_CODE (t
) != SSA_NAME
)
1124 p
= var_to_partition (liveinfo
->map
, t
);
1125 if (p
== NO_PARTITION
)
1127 e
= gimple_phi_arg_edge (phi
, i
);
1128 if (e
->src
!= ENTRY_BLOCK_PTR
)
1129 bitmap_set_bit (&liveinfo
->liveout
[e
->src
->index
], p
);
1133 /* Add each successors live on entry to this bock live on exit. */
1134 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1135 if (e
->dest
!= EXIT_BLOCK_PTR
)
1136 bitmap_ior_into (&liveinfo
->liveout
[bb
->index
],
1137 live_on_entry (liveinfo
, e
->dest
));
1142 /* Given partition map MAP, calculate all the live on entry bitmaps for
1143 each partition. Return a new live info object. */
1146 calculate_live_ranges (var_map map
)
1150 tree_live_info_p live
;
1152 bitmap_obstack_initialize (&liveness_bitmap_obstack
);
1153 live
= new_tree_live_info (map
);
1154 for (i
= 0; i
< num_var_partitions (map
); i
++)
1156 var
= partition_to_var (map
, i
);
1157 if (var
!= NULL_TREE
)
1158 set_var_live_on_entry (var
, live
);
1161 live_worklist (live
);
1163 #ifdef ENABLE_CHECKING
1164 verify_live_on_entry (live
);
1167 calculate_live_on_exit (live
);
1172 /* Output partition map MAP to file F. */
1175 dump_var_map (FILE *f
, var_map map
)
1181 fprintf (f
, "\nPartition map \n\n");
1183 for (x
= 0; x
< map
->num_partitions
; x
++)
1185 if (map
->view_to_partition
!= NULL
)
1186 p
= map
->view_to_partition
[x
];
1190 if (ssa_name (p
) == NULL_TREE
1191 || virtual_operand_p (ssa_name (p
)))
1195 for (y
= 1; y
< num_ssa_names
; y
++)
1197 p
= partition_find (map
->var_partition
, y
);
1198 if (map
->partition_to_view
)
1199 p
= map
->partition_to_view
[p
];
1204 fprintf(f
, "Partition %d (", x
);
1205 print_generic_expr (f
, partition_to_var (map
, p
), TDF_SLIM
);
1208 fprintf (f
, "%d ", y
);
1218 /* Output live range info LIVE to file F, controlled by FLAG. */
1221 dump_live_info (FILE *f
, tree_live_info_p live
, int flag
)
1225 var_map map
= live
->map
;
1228 if ((flag
& LIVEDUMP_ENTRY
) && live
->livein
)
1232 fprintf (f
, "\nLive on entry to BB%d : ", bb
->index
);
1233 EXECUTE_IF_SET_IN_BITMAP (&live
->livein
[bb
->index
], 0, i
, bi
)
1235 print_generic_expr (f
, partition_to_var (map
, i
), TDF_SLIM
);
1242 if ((flag
& LIVEDUMP_EXIT
) && live
->liveout
)
1246 fprintf (f
, "\nLive on exit from BB%d : ", bb
->index
);
1247 EXECUTE_IF_SET_IN_BITMAP (&live
->liveout
[bb
->index
], 0, i
, bi
)
1249 print_generic_expr (f
, partition_to_var (map
, i
), TDF_SLIM
);
1257 #ifdef ENABLE_CHECKING
1258 /* Verify that SSA_VAR is a non-virtual SSA_NAME. */
1261 register_ssa_partition_check (tree ssa_var
)
1263 gcc_assert (TREE_CODE (ssa_var
) == SSA_NAME
);
1264 if (virtual_operand_p (ssa_var
))
1266 fprintf (stderr
, "Illegally registering a virtual SSA name :");
1267 print_generic_expr (stderr
, ssa_var
, TDF_SLIM
);
1268 fprintf (stderr
, " in the SSA->Normal phase.\n");
1269 internal_error ("SSA corruption");
1274 /* Verify that the info in LIVE matches the current cfg. */
1277 verify_live_on_entry (tree_live_info_p live
)
1286 var_map map
= live
->map
;
1288 /* Check for live on entry partitions and report those with a DEF in
1289 the program. This will typically mean an optimization has done
1291 bb
= ENTRY_BLOCK_PTR
;
1293 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1295 int entry_block
= e
->dest
->index
;
1296 if (e
->dest
== EXIT_BLOCK_PTR
)
1298 for (i
= 0; i
< (unsigned)num_var_partitions (map
); i
++)
1303 var
= partition_to_var (map
, i
);
1304 stmt
= SSA_NAME_DEF_STMT (var
);
1305 tmp
= gimple_bb (stmt
);
1306 if (SSA_NAME_VAR (var
))
1307 d
= ssa_default_def (cfun
, SSA_NAME_VAR (var
));
1309 loe
= live_on_entry (live
, e
->dest
);
1310 if (loe
&& bitmap_bit_p (loe
, i
))
1312 if (!gimple_nop_p (stmt
))
1315 print_generic_expr (stderr
, var
, TDF_SLIM
);
1316 fprintf (stderr
, " is defined ");
1318 fprintf (stderr
, " in BB%d, ", tmp
->index
);
1319 fprintf (stderr
, "by:\n");
1320 print_gimple_stmt (stderr
, stmt
, 0, TDF_SLIM
);
1321 fprintf (stderr
, "\nIt is also live-on-entry to entry BB %d",
1323 fprintf (stderr
, " So it appears to have multiple defs.\n");
1330 print_generic_expr (stderr
, var
, TDF_SLIM
);
1331 fprintf (stderr
, " is live-on-entry to BB%d ",
1335 fprintf (stderr
, " but is not the default def of ");
1336 print_generic_expr (stderr
, d
, TDF_SLIM
);
1337 fprintf (stderr
, "\n");
1340 fprintf (stderr
, " and there is no default def.\n");
1347 /* The only way this var shouldn't be marked live on entry is
1348 if it occurs in a PHI argument of the block. */
1351 gimple_stmt_iterator gsi
;
1352 for (gsi
= gsi_start_phis (e
->dest
);
1353 !gsi_end_p (gsi
) && !ok
;
1356 gimple phi
= gsi_stmt (gsi
);
1357 for (z
= 0; z
< gimple_phi_num_args (phi
); z
++)
1358 if (var
== gimple_phi_arg_def (phi
, z
))
1367 print_generic_expr (stderr
, var
, TDF_SLIM
);
1368 fprintf (stderr
, " is not marked live-on-entry to entry BB%d ",
1370 fprintf (stderr
, "but it is a default def so it should be.\n");
1374 gcc_assert (num
<= 0);