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
);
626 /* Set all block pointer in debug stmt to NULL if the block is unused,
627 so that they will not be streamed out. */
630 clear_unused_block_pointer ()
633 gimple_stmt_iterator gsi
;
637 FOR_EACH_LOCAL_DECL (cfun
, i
, t
)
638 if (TREE_CODE (t
) == VAR_DECL
&& DECL_DEBUG_EXPR_IS_FROM (t
))
640 tree debug_expr
= DECL_DEBUG_EXPR (t
);
641 walk_tree (&debug_expr
, clear_unused_block_pointer_1
, NULL
, NULL
);
645 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
649 gimple stmt
= gsi_stmt (gsi
);
651 if (!is_gimple_debug (stmt
))
653 b
= gimple_block (stmt
);
654 if (b
&& !TREE_USED (b
))
655 gimple_set_block (stmt
, NULL
);
656 for (i
= 0; i
< gimple_num_ops (stmt
); i
++)
657 walk_tree (gimple_op_ptr (stmt
, i
), clear_unused_block_pointer_1
,
662 /* Dump scope blocks starting at SCOPE to FILE. INDENT is the
663 indentation level and FLAGS is as in print_generic_expr. */
666 dump_scope_block (FILE *file
, int indent
, tree scope
, int flags
)
671 fprintf (file
, "\n%*s{ Scope block #%i%s%s",indent
, "" , BLOCK_NUMBER (scope
),
672 TREE_USED (scope
) ? "" : " (unused)",
673 BLOCK_ABSTRACT (scope
) ? " (abstract)": "");
674 if (!IS_UNKNOWN_LOCATION (BLOCK_SOURCE_LOCATION (scope
)))
676 expanded_location s
= expand_location (BLOCK_SOURCE_LOCATION (scope
));
677 fprintf (file
, " %s:%i", s
.file
, s
.line
);
679 if (BLOCK_ABSTRACT_ORIGIN (scope
))
681 tree origin
= block_ultimate_origin (scope
);
684 fprintf (file
, " Originating from :");
686 print_generic_decl (file
, origin
, flags
);
688 fprintf (file
, "#%i", BLOCK_NUMBER (origin
));
691 fprintf (file
, " \n");
692 for (var
= BLOCK_VARS (scope
); var
; var
= DECL_CHAIN (var
))
694 fprintf (file
, "%*s", indent
, "");
695 print_generic_decl (file
, var
, flags
);
696 fprintf (file
, "\n");
698 for (i
= 0; i
< BLOCK_NUM_NONLOCALIZED_VARS (scope
); i
++)
700 fprintf (file
, "%*s",indent
, "");
701 print_generic_decl (file
, BLOCK_NONLOCALIZED_VAR (scope
, i
),
703 fprintf (file
, " (nonlocalized)\n");
705 for (t
= BLOCK_SUBBLOCKS (scope
); t
; t
= BLOCK_CHAIN (t
))
706 dump_scope_block (file
, indent
+ 2, t
, flags
);
707 fprintf (file
, "\n%*s}\n",indent
, "");
710 /* Dump the tree of lexical scopes starting at SCOPE to stderr. FLAGS
711 is as in print_generic_expr. */
714 debug_scope_block (tree scope
, int flags
)
716 dump_scope_block (stderr
, 0, scope
, flags
);
720 /* Dump the tree of lexical scopes of current_function_decl to FILE.
721 FLAGS is as in print_generic_expr. */
724 dump_scope_blocks (FILE *file
, int flags
)
726 dump_scope_block (file
, 0, DECL_INITIAL (current_function_decl
), flags
);
730 /* Dump the tree of lexical scopes of current_function_decl to stderr.
731 FLAGS is as in print_generic_expr. */
734 debug_scope_blocks (int flags
)
736 dump_scope_blocks (stderr
, flags
);
739 /* Remove local variables that are not referenced in the IL. */
742 remove_unused_locals (void)
746 unsigned srcidx
, dstidx
, num
;
747 bool have_local_clobbers
= false;
749 /* Removing declarations from lexical blocks when not optimizing is
750 not only a waste of time, it actually causes differences in stack
755 timevar_push (TV_REMOVE_UNUSED
);
757 mark_scope_block_unused (DECL_INITIAL (current_function_decl
));
759 usedvars
= BITMAP_ALLOC (NULL
);
761 /* Walk the CFG marking all referenced symbols. */
764 gimple_stmt_iterator gsi
;
769 /* Walk the statements. */
770 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
772 gimple stmt
= gsi_stmt (gsi
);
773 tree b
= gimple_block (stmt
);
775 if (is_gimple_debug (stmt
))
778 if (gimple_clobber_p (stmt
))
780 have_local_clobbers
= true;
785 TREE_USED (b
) = true;
787 for (i
= 0; i
< gimple_num_ops (stmt
); i
++)
788 mark_all_vars_used (gimple_op_ptr (gsi_stmt (gsi
), i
));
791 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
796 gimple phi
= gsi_stmt (gsi
);
798 if (virtual_operand_p (gimple_phi_result (phi
)))
801 def
= gimple_phi_result (phi
);
802 mark_all_vars_used (&def
);
804 FOR_EACH_PHI_ARG (arg_p
, phi
, i
, SSA_OP_ALL_USES
)
806 tree arg
= USE_FROM_PTR (arg_p
);
807 int index
= PHI_ARG_INDEX_FROM_USE (arg_p
);
809 LOCATION_BLOCK (gimple_phi_arg_location (phi
, index
));
811 TREE_USED (block
) = true;
812 mark_all_vars_used (&arg
);
816 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
818 TREE_USED (LOCATION_BLOCK (e
->goto_locus
)) = true;
821 /* We do a two-pass approach about the out-of-scope clobbers. We want
822 to remove them if they are the only references to a local variable,
823 but we want to retain them when there's any other. So the first pass
824 ignores them, and the second pass (if there were any) tries to remove
826 if (have_local_clobbers
)
829 gimple_stmt_iterator gsi
;
831 for (gsi
= gsi_start_bb (bb
); !gsi_end_p (gsi
);)
833 gimple stmt
= gsi_stmt (gsi
);
834 tree b
= gimple_block (stmt
);
836 if (gimple_clobber_p (stmt
))
838 tree lhs
= gimple_assign_lhs (stmt
);
839 if (TREE_CODE (lhs
) == VAR_DECL
&& !is_used_p (lhs
))
841 unlink_stmt_vdef (stmt
);
842 gsi_remove (&gsi
, true);
847 TREE_USED (b
) = true;
853 cfun
->has_local_explicit_reg_vars
= false;
855 /* Remove unmarked local and global vars from local_decls. */
856 num
= VEC_length (tree
, cfun
->local_decls
);
857 for (srcidx
= 0, dstidx
= 0; srcidx
< num
; srcidx
++)
859 var
= VEC_index (tree
, cfun
->local_decls
, srcidx
);
860 if (TREE_CODE (var
) == VAR_DECL
)
862 if (!is_used_p (var
))
865 if (cfun
->nonlocal_goto_save_area
866 && TREE_OPERAND (cfun
->nonlocal_goto_save_area
, 0) == var
)
867 cfun
->nonlocal_goto_save_area
= NULL
;
868 /* Release any default def associated with var. */
869 if ((def
= ssa_default_def (cfun
, var
)) != NULL_TREE
)
871 set_ssa_default_def (cfun
, var
, NULL_TREE
);
872 release_ssa_name (def
);
877 if (TREE_CODE (var
) == VAR_DECL
878 && DECL_HARD_REGISTER (var
)
879 && !is_global_var (var
))
880 cfun
->has_local_explicit_reg_vars
= true;
882 if (srcidx
!= dstidx
)
883 VEC_replace (tree
, cfun
->local_decls
, dstidx
, var
);
887 VEC_truncate (tree
, cfun
->local_decls
, dstidx
);
889 remove_unused_scope_block_p (DECL_INITIAL (current_function_decl
));
890 clear_unused_block_pointer ();
892 BITMAP_FREE (usedvars
);
894 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
896 fprintf (dump_file
, "Scope blocks after cleanups:\n");
897 dump_scope_blocks (dump_file
, dump_flags
);
900 timevar_pop (TV_REMOVE_UNUSED
);
903 /* Obstack for globale liveness info bitmaps. We don't want to put these
904 on the default obstack because these bitmaps can grow quite large and
905 we'll hold on to all that memory until the end of the compiler run.
906 As a bonus, delete_tree_live_info can destroy all the bitmaps by just
907 releasing the whole obstack. */
908 static bitmap_obstack liveness_bitmap_obstack
;
910 /* Allocate and return a new live range information object base on MAP. */
912 static tree_live_info_p
913 new_tree_live_info (var_map map
)
915 tree_live_info_p live
;
918 live
= XNEW (struct tree_live_info_d
);
920 live
->num_blocks
= last_basic_block
;
922 live
->livein
= XNEWVEC (bitmap_head
, last_basic_block
);
924 bitmap_initialize (&live
->livein
[bb
->index
], &liveness_bitmap_obstack
);
926 live
->liveout
= XNEWVEC (bitmap_head
, last_basic_block
);
928 bitmap_initialize (&live
->liveout
[bb
->index
], &liveness_bitmap_obstack
);
930 live
->work_stack
= XNEWVEC (int, last_basic_block
);
931 live
->stack_top
= live
->work_stack
;
933 live
->global
= BITMAP_ALLOC (&liveness_bitmap_obstack
);
938 /* Free storage for live range info object LIVE. */
941 delete_tree_live_info (tree_live_info_p live
)
943 bitmap_obstack_release (&liveness_bitmap_obstack
);
944 free (live
->work_stack
);
945 free (live
->liveout
);
951 /* Visit basic block BB and propagate any required live on entry bits from
952 LIVE into the predecessors. VISITED is the bitmap of visited blocks.
953 TMP is a temporary work bitmap which is passed in to avoid reallocating
957 loe_visit_block (tree_live_info_p live
, basic_block bb
, sbitmap visited
,
965 gcc_assert (!TEST_BIT (visited
, bb
->index
));
967 SET_BIT (visited
, bb
->index
);
968 loe
= live_on_entry (live
, bb
);
970 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
973 if (pred_bb
== ENTRY_BLOCK_PTR
)
975 /* TMP is variables live-on-entry from BB that aren't defined in the
976 predecessor block. This should be the live on entry vars to pred.
977 Note that liveout is the DEFs in a block while live on entry is
979 bitmap_and_compl (tmp
, loe
, &live
->liveout
[pred_bb
->index
]);
981 /* Add these bits to live-on-entry for the pred. if there are any
982 changes, and pred_bb has been visited already, add it to the
984 change
= bitmap_ior_into (live_on_entry (live
, pred_bb
), tmp
);
985 if (TEST_BIT (visited
, pred_bb
->index
) && change
)
987 RESET_BIT (visited
, pred_bb
->index
);
988 *(live
->stack_top
)++ = pred_bb
->index
;
994 /* Using LIVE, fill in all the live-on-entry blocks between the defs and uses
995 of all the variables. */
998 live_worklist (tree_live_info_p live
)
1002 sbitmap visited
= sbitmap_alloc (last_basic_block
+ 1);
1003 bitmap tmp
= BITMAP_ALLOC (&liveness_bitmap_obstack
);
1005 sbitmap_zero (visited
);
1007 /* Visit all the blocks in reverse order and propagate live on entry values
1008 into the predecessors blocks. */
1009 FOR_EACH_BB_REVERSE (bb
)
1010 loe_visit_block (live
, bb
, visited
, tmp
);
1012 /* Process any blocks which require further iteration. */
1013 while (live
->stack_top
!= live
->work_stack
)
1015 b
= *--(live
->stack_top
);
1016 loe_visit_block (live
, BASIC_BLOCK (b
), visited
, tmp
);
1020 sbitmap_free (visited
);
1024 /* Calculate the initial live on entry vector for SSA_NAME using immediate_use
1025 links. Set the live on entry fields in LIVE. Def's are marked temporarily
1026 in the liveout vector. */
1029 set_var_live_on_entry (tree ssa_name
, tree_live_info_p live
)
1034 basic_block def_bb
= NULL
;
1035 imm_use_iterator imm_iter
;
1036 bool global
= false;
1038 p
= var_to_partition (live
->map
, ssa_name
);
1039 if (p
== NO_PARTITION
)
1042 stmt
= SSA_NAME_DEF_STMT (ssa_name
);
1045 def_bb
= gimple_bb (stmt
);
1046 /* Mark defs in liveout bitmap temporarily. */
1048 bitmap_set_bit (&live
->liveout
[def_bb
->index
], p
);
1051 def_bb
= ENTRY_BLOCK_PTR
;
1053 /* Visit each use of SSA_NAME and if it isn't in the same block as the def,
1054 add it to the list of live on entry blocks. */
1055 FOR_EACH_IMM_USE_FAST (use
, imm_iter
, ssa_name
)
1057 gimple use_stmt
= USE_STMT (use
);
1058 basic_block add_block
= NULL
;
1060 if (gimple_code (use_stmt
) == GIMPLE_PHI
)
1062 /* Uses in PHI's are considered to be live at exit of the SRC block
1063 as this is where a copy would be inserted. Check to see if it is
1064 defined in that block, or whether its live on entry. */
1065 int index
= PHI_ARG_INDEX_FROM_USE (use
);
1066 edge e
= gimple_phi_arg_edge (use_stmt
, index
);
1067 if (e
->src
!= ENTRY_BLOCK_PTR
)
1069 if (e
->src
!= def_bb
)
1073 else if (is_gimple_debug (use_stmt
))
1077 /* If its not defined in this block, its live on entry. */
1078 basic_block use_bb
= gimple_bb (use_stmt
);
1079 if (use_bb
!= def_bb
)
1083 /* If there was a live on entry use, set the bit. */
1087 bitmap_set_bit (&live
->livein
[add_block
->index
], p
);
1091 /* If SSA_NAME is live on entry to at least one block, fill in all the live
1092 on entry blocks between the def and all the uses. */
1094 bitmap_set_bit (live
->global
, p
);
1098 /* Calculate the live on exit vectors based on the entry info in LIVEINFO. */
1101 calculate_live_on_exit (tree_live_info_p liveinfo
)
1107 /* live on entry calculations used liveout vectors for defs, clear them. */
1109 bitmap_clear (&liveinfo
->liveout
[bb
->index
]);
1111 /* Set all the live-on-exit bits for uses in PHIs. */
1114 gimple_stmt_iterator gsi
;
1117 /* Mark the PHI arguments which are live on exit to the pred block. */
1118 for (gsi
= gsi_start_phis (bb
); !gsi_end_p (gsi
); gsi_next (&gsi
))
1120 gimple phi
= gsi_stmt (gsi
);
1121 for (i
= 0; i
< gimple_phi_num_args (phi
); i
++)
1123 tree t
= PHI_ARG_DEF (phi
, i
);
1126 if (TREE_CODE (t
) != SSA_NAME
)
1129 p
= var_to_partition (liveinfo
->map
, t
);
1130 if (p
== NO_PARTITION
)
1132 e
= gimple_phi_arg_edge (phi
, i
);
1133 if (e
->src
!= ENTRY_BLOCK_PTR
)
1134 bitmap_set_bit (&liveinfo
->liveout
[e
->src
->index
], p
);
1138 /* Add each successors live on entry to this bock live on exit. */
1139 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1140 if (e
->dest
!= EXIT_BLOCK_PTR
)
1141 bitmap_ior_into (&liveinfo
->liveout
[bb
->index
],
1142 live_on_entry (liveinfo
, e
->dest
));
1147 /* Given partition map MAP, calculate all the live on entry bitmaps for
1148 each partition. Return a new live info object. */
1151 calculate_live_ranges (var_map map
)
1155 tree_live_info_p live
;
1157 bitmap_obstack_initialize (&liveness_bitmap_obstack
);
1158 live
= new_tree_live_info (map
);
1159 for (i
= 0; i
< num_var_partitions (map
); i
++)
1161 var
= partition_to_var (map
, i
);
1162 if (var
!= NULL_TREE
)
1163 set_var_live_on_entry (var
, live
);
1166 live_worklist (live
);
1168 #ifdef ENABLE_CHECKING
1169 verify_live_on_entry (live
);
1172 calculate_live_on_exit (live
);
1177 /* Output partition map MAP to file F. */
1180 dump_var_map (FILE *f
, var_map map
)
1186 fprintf (f
, "\nPartition map \n\n");
1188 for (x
= 0; x
< map
->num_partitions
; x
++)
1190 if (map
->view_to_partition
!= NULL
)
1191 p
= map
->view_to_partition
[x
];
1195 if (ssa_name (p
) == NULL_TREE
1196 || virtual_operand_p (ssa_name (p
)))
1200 for (y
= 1; y
< num_ssa_names
; y
++)
1202 p
= partition_find (map
->var_partition
, y
);
1203 if (map
->partition_to_view
)
1204 p
= map
->partition_to_view
[p
];
1209 fprintf(f
, "Partition %d (", x
);
1210 print_generic_expr (f
, partition_to_var (map
, p
), TDF_SLIM
);
1213 fprintf (f
, "%d ", y
);
1223 /* Output live range info LIVE to file F, controlled by FLAG. */
1226 dump_live_info (FILE *f
, tree_live_info_p live
, int flag
)
1230 var_map map
= live
->map
;
1233 if ((flag
& LIVEDUMP_ENTRY
) && live
->livein
)
1237 fprintf (f
, "\nLive on entry to BB%d : ", bb
->index
);
1238 EXECUTE_IF_SET_IN_BITMAP (&live
->livein
[bb
->index
], 0, i
, bi
)
1240 print_generic_expr (f
, partition_to_var (map
, i
), TDF_SLIM
);
1247 if ((flag
& LIVEDUMP_EXIT
) && live
->liveout
)
1251 fprintf (f
, "\nLive on exit from BB%d : ", bb
->index
);
1252 EXECUTE_IF_SET_IN_BITMAP (&live
->liveout
[bb
->index
], 0, i
, bi
)
1254 print_generic_expr (f
, partition_to_var (map
, i
), TDF_SLIM
);
1262 #ifdef ENABLE_CHECKING
1263 /* Verify that SSA_VAR is a non-virtual SSA_NAME. */
1266 register_ssa_partition_check (tree ssa_var
)
1268 gcc_assert (TREE_CODE (ssa_var
) == SSA_NAME
);
1269 if (virtual_operand_p (ssa_var
))
1271 fprintf (stderr
, "Illegally registering a virtual SSA name :");
1272 print_generic_expr (stderr
, ssa_var
, TDF_SLIM
);
1273 fprintf (stderr
, " in the SSA->Normal phase.\n");
1274 internal_error ("SSA corruption");
1279 /* Verify that the info in LIVE matches the current cfg. */
1282 verify_live_on_entry (tree_live_info_p live
)
1291 var_map map
= live
->map
;
1293 /* Check for live on entry partitions and report those with a DEF in
1294 the program. This will typically mean an optimization has done
1296 bb
= ENTRY_BLOCK_PTR
;
1298 FOR_EACH_EDGE (e
, ei
, bb
->succs
)
1300 int entry_block
= e
->dest
->index
;
1301 if (e
->dest
== EXIT_BLOCK_PTR
)
1303 for (i
= 0; i
< (unsigned)num_var_partitions (map
); i
++)
1308 var
= partition_to_var (map
, i
);
1309 stmt
= SSA_NAME_DEF_STMT (var
);
1310 tmp
= gimple_bb (stmt
);
1311 if (SSA_NAME_VAR (var
))
1312 d
= ssa_default_def (cfun
, SSA_NAME_VAR (var
));
1314 loe
= live_on_entry (live
, e
->dest
);
1315 if (loe
&& bitmap_bit_p (loe
, i
))
1317 if (!gimple_nop_p (stmt
))
1320 print_generic_expr (stderr
, var
, TDF_SLIM
);
1321 fprintf (stderr
, " is defined ");
1323 fprintf (stderr
, " in BB%d, ", tmp
->index
);
1324 fprintf (stderr
, "by:\n");
1325 print_gimple_stmt (stderr
, stmt
, 0, TDF_SLIM
);
1326 fprintf (stderr
, "\nIt is also live-on-entry to entry BB %d",
1328 fprintf (stderr
, " So it appears to have multiple defs.\n");
1335 print_generic_expr (stderr
, var
, TDF_SLIM
);
1336 fprintf (stderr
, " is live-on-entry to BB%d ",
1340 fprintf (stderr
, " but is not the default def of ");
1341 print_generic_expr (stderr
, d
, TDF_SLIM
);
1342 fprintf (stderr
, "\n");
1345 fprintf (stderr
, " and there is no default def.\n");
1352 /* The only way this var shouldn't be marked live on entry is
1353 if it occurs in a PHI argument of the block. */
1356 gimple_stmt_iterator gsi
;
1357 for (gsi
= gsi_start_phis (e
->dest
);
1358 !gsi_end_p (gsi
) && !ok
;
1361 gimple phi
= gsi_stmt (gsi
);
1362 for (z
= 0; z
< gimple_phi_num_args (phi
); z
++)
1363 if (var
== gimple_phi_arg_def (phi
, z
))
1372 print_generic_expr (stderr
, var
, TDF_SLIM
);
1373 fprintf (stderr
, " is not marked live-on-entry to entry BB%d ",
1375 fprintf (stderr
, "but it is a default def so it should be.\n");
1379 gcc_assert (num
<= 0);