2018-05-07 Edward Smith-Rowland <3dw4rd@verizon.net>
[official-gcc.git] / gcc / tree-ssa-live.c
blob62316bac79295eb719f7342ec3770cd945f05749
1 /* Liveness for SSA trees.
2 Copyright (C) 2003-2018 Free Software Foundation, Inc.
3 Contributed by Andrew MacLeod <amacleod@redhat.com>
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
10 any later version.
12 GCC is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING3. If not see
19 <http://www.gnu.org/licenses/>. */
21 #include "config.h"
22 #include "system.h"
23 #include "coretypes.h"
24 #include "backend.h"
25 #include "rtl.h"
26 #include "tree.h"
27 #include "gimple.h"
28 #include "timevar.h"
29 #include "ssa.h"
30 #include "cgraph.h"
31 #include "gimple-pretty-print.h"
32 #include "diagnostic-core.h"
33 #include "gimple-iterator.h"
34 #include "tree-dfa.h"
35 #include "dumpfile.h"
36 #include "tree-ssa-live.h"
37 #include "debug.h"
38 #include "tree-ssa.h"
39 #include "ipa-utils.h"
40 #include "cfgloop.h"
41 #include "stringpool.h"
42 #include "attribs.h"
44 static void verify_live_on_entry (tree_live_info_p);
47 /* VARMAP maintains a mapping from SSA version number to real variables.
49 All SSA_NAMES are divided into partitions. Initially each ssa_name is the
50 only member of it's own partition. Coalescing will attempt to group any
51 ssa_names which occur in a copy or in a PHI node into the same partition.
53 At the end of out-of-ssa, each partition becomes a "real" variable and is
54 rewritten as a compiler variable.
56 The var_map data structure is used to manage these partitions. It allows
57 partitions to be combined, and determines which partition belongs to what
58 ssa_name or variable, and vice versa. */
61 /* Remove the base table in MAP. */
63 static void
64 var_map_base_fini (var_map map)
66 /* Free the basevar info if it is present. */
67 if (map->partition_to_base_index != NULL)
69 free (map->partition_to_base_index);
70 map->partition_to_base_index = NULL;
71 map->num_basevars = 0;
74 /* Create a variable partition map of SIZE, initialize and return it. */
76 var_map
77 init_var_map (int size)
79 var_map map;
81 map = (var_map) xmalloc (sizeof (struct _var_map));
82 map->var_partition = partition_new (size);
84 map->partition_to_view = NULL;
85 map->view_to_partition = NULL;
86 map->num_partitions = size;
87 map->partition_size = size;
88 map->num_basevars = 0;
89 map->partition_to_base_index = NULL;
90 return map;
94 /* Free memory associated with MAP. */
96 void
97 delete_var_map (var_map map)
99 var_map_base_fini (map);
100 partition_delete (map->var_partition);
101 free (map->partition_to_view);
102 free (map->view_to_partition);
103 free (map);
107 /* This function will combine the partitions in MAP for VAR1 and VAR2. It
108 Returns the partition which represents the new partition. If the two
109 partitions cannot be combined, NO_PARTITION is returned. */
112 var_union (var_map map, tree var1, tree var2)
114 int p1, p2, p3;
116 gcc_assert (TREE_CODE (var1) == SSA_NAME);
117 gcc_assert (TREE_CODE (var2) == SSA_NAME);
119 /* This is independent of partition_to_view. If partition_to_view is
120 on, then whichever one of these partitions is absorbed will never have a
121 dereference into the partition_to_view array any more. */
123 p1 = partition_find (map->var_partition, SSA_NAME_VERSION (var1));
124 p2 = partition_find (map->var_partition, SSA_NAME_VERSION (var2));
126 gcc_assert (p1 != NO_PARTITION);
127 gcc_assert (p2 != NO_PARTITION);
129 if (p1 == p2)
130 p3 = p1;
131 else
132 p3 = partition_union (map->var_partition, p1, p2);
134 if (map->partition_to_view)
135 p3 = map->partition_to_view[p3];
137 return p3;
141 /* Compress the partition numbers in MAP such that they fall in the range
142 0..(num_partitions-1) instead of wherever they turned out during
143 the partitioning exercise. This removes any references to unused
144 partitions, thereby allowing bitmaps and other vectors to be much
145 denser.
147 This is implemented such that compaction doesn't affect partitioning.
148 Ie., once partitions are created and possibly merged, running one
149 or more different kind of compaction will not affect the partitions
150 themselves. Their index might change, but all the same variables will
151 still be members of the same partition group. This allows work on reduced
152 sets, and no loss of information when a larger set is later desired.
154 In particular, coalescing can work on partitions which have 2 or more
155 definitions, and then 'recompact' later to include all the single
156 definitions for assignment to program variables. */
159 /* Set MAP back to the initial state of having no partition view. Return a
160 bitmap which has a bit set for each partition number which is in use in the
161 varmap. */
163 static bitmap
164 partition_view_init (var_map map)
166 bitmap used;
167 int tmp;
168 unsigned int x;
170 used = BITMAP_ALLOC (NULL);
172 /* Already in a view? Abandon the old one. */
173 if (map->partition_to_view)
175 free (map->partition_to_view);
176 map->partition_to_view = NULL;
178 if (map->view_to_partition)
180 free (map->view_to_partition);
181 map->view_to_partition = NULL;
184 /* Find out which partitions are actually referenced. */
185 for (x = 0; x < map->partition_size; x++)
187 tmp = partition_find (map->var_partition, x);
188 if (ssa_name (tmp) != NULL_TREE && !virtual_operand_p (ssa_name (tmp))
189 && (!has_zero_uses (ssa_name (tmp))
190 || !SSA_NAME_IS_DEFAULT_DEF (ssa_name (tmp))
191 || (SSA_NAME_VAR (ssa_name (tmp))
192 && !VAR_P (SSA_NAME_VAR (ssa_name (tmp))))))
193 bitmap_set_bit (used, tmp);
196 map->num_partitions = map->partition_size;
197 return used;
201 /* This routine will finalize the view data for MAP based on the partitions
202 set in SELECTED. This is either the same bitmap returned from
203 partition_view_init, or a trimmed down version if some of those partitions
204 were not desired in this view. SELECTED is freed before returning. */
206 static void
207 partition_view_fini (var_map map, bitmap selected)
209 bitmap_iterator bi;
210 unsigned count, i, x, limit;
212 gcc_assert (selected);
214 count = bitmap_count_bits (selected);
215 limit = map->partition_size;
217 /* If its a one-to-one ratio, we don't need any view compaction. */
218 if (count < limit)
220 map->partition_to_view = (int *)xmalloc (limit * sizeof (int));
221 memset (map->partition_to_view, 0xff, (limit * sizeof (int)));
222 map->view_to_partition = (int *)xmalloc (count * sizeof (int));
224 i = 0;
225 /* Give each selected partition an index. */
226 EXECUTE_IF_SET_IN_BITMAP (selected, 0, x, bi)
228 map->partition_to_view[x] = i;
229 map->view_to_partition[i] = x;
230 i++;
232 gcc_assert (i == count);
233 map->num_partitions = i;
236 BITMAP_FREE (selected);
240 /* Create a partition view which includes all the used partitions in MAP. */
242 void
243 partition_view_normal (var_map map)
245 bitmap used;
247 used = partition_view_init (map);
248 partition_view_fini (map, used);
250 var_map_base_fini (map);
254 /* Create a partition view in MAP which includes just partitions which occur in
255 the bitmap ONLY. If WANT_BASES is true, create the base variable map
256 as well. */
258 void
259 partition_view_bitmap (var_map map, bitmap only)
261 bitmap used;
262 bitmap new_partitions = BITMAP_ALLOC (NULL);
263 unsigned x, p;
264 bitmap_iterator bi;
266 used = partition_view_init (map);
267 EXECUTE_IF_SET_IN_BITMAP (only, 0, x, bi)
269 p = partition_find (map->var_partition, x);
270 gcc_assert (bitmap_bit_p (used, p));
271 bitmap_set_bit (new_partitions, p);
273 partition_view_fini (map, new_partitions);
275 var_map_base_fini (map);
279 static bitmap usedvars;
281 /* Mark VAR as used, so that it'll be preserved during rtl expansion.
282 Returns true if VAR wasn't marked before. */
284 static inline bool
285 set_is_used (tree var)
287 return bitmap_set_bit (usedvars, DECL_UID (var));
290 /* Return true if VAR is marked as used. */
292 static inline bool
293 is_used_p (tree var)
295 return bitmap_bit_p (usedvars, DECL_UID (var));
298 static inline void mark_all_vars_used (tree *);
300 /* Helper function for mark_all_vars_used, called via walk_tree. */
302 static tree
303 mark_all_vars_used_1 (tree *tp, int *walk_subtrees, void *data ATTRIBUTE_UNUSED)
305 tree t = *tp;
306 enum tree_code_class c = TREE_CODE_CLASS (TREE_CODE (t));
307 tree b;
309 if (TREE_CODE (t) == SSA_NAME)
311 *walk_subtrees = 0;
312 t = SSA_NAME_VAR (t);
313 if (!t)
314 return NULL;
317 if (IS_EXPR_CODE_CLASS (c)
318 && (b = TREE_BLOCK (t)) != NULL)
319 TREE_USED (b) = true;
321 /* Ignore TMR_OFFSET and TMR_STEP for TARGET_MEM_REFS, as those
322 fields do not contain vars. */
323 if (TREE_CODE (t) == TARGET_MEM_REF)
325 mark_all_vars_used (&TMR_BASE (t));
326 mark_all_vars_used (&TMR_INDEX (t));
327 mark_all_vars_used (&TMR_INDEX2 (t));
328 *walk_subtrees = 0;
329 return NULL;
332 /* Only need to mark VAR_DECLS; parameters and return results are not
333 eliminated as unused. */
334 if (VAR_P (t))
336 /* When a global var becomes used for the first time also walk its
337 initializer (non global ones don't have any). */
338 if (set_is_used (t) && is_global_var (t)
339 && DECL_CONTEXT (t) == current_function_decl)
340 mark_all_vars_used (&DECL_INITIAL (t));
342 /* remove_unused_scope_block_p requires information about labels
343 which are not DECL_IGNORED_P to tell if they might be used in the IL. */
344 else if (TREE_CODE (t) == LABEL_DECL)
345 /* Although the TREE_USED values that the frontend uses would be
346 acceptable (albeit slightly over-conservative) for our purposes,
347 init_vars_expansion clears TREE_USED for LABEL_DECLs too, so we
348 must re-compute it here. */
349 TREE_USED (t) = 1;
351 if (IS_TYPE_OR_DECL_P (t))
352 *walk_subtrees = 0;
354 return NULL;
357 /* Mark the scope block SCOPE and its subblocks unused when they can be
358 possibly eliminated if dead. */
360 static void
361 mark_scope_block_unused (tree scope)
363 tree t;
364 TREE_USED (scope) = false;
365 if (!(*debug_hooks->ignore_block) (scope))
366 TREE_USED (scope) = true;
367 for (t = BLOCK_SUBBLOCKS (scope); t ; t = BLOCK_CHAIN (t))
368 mark_scope_block_unused (t);
371 /* Look if the block is dead (by possibly eliminating its dead subblocks)
372 and return true if so.
373 Block is declared dead if:
374 1) No statements are associated with it.
375 2) Declares no live variables
376 3) All subblocks are dead
377 or there is precisely one subblocks and the block
378 has same abstract origin as outer block and declares
379 no variables, so it is pure wrapper.
380 When we are not outputting full debug info, we also eliminate dead variables
381 out of scope blocks to let them to be recycled by GGC and to save copying work
382 done by the inliner. */
384 static bool
385 remove_unused_scope_block_p (tree scope, bool in_ctor_dtor_block)
387 tree *t, *next;
388 bool unused = !TREE_USED (scope);
389 int nsubblocks = 0;
391 /* For ipa-polymorphic-call.c purposes, preserve blocks:
392 1) with BLOCK_ABSTRACT_ORIGIN of a ctor/dtor or their clones */
393 if (inlined_polymorphic_ctor_dtor_block_p (scope, true))
395 in_ctor_dtor_block = true;
396 unused = false;
398 /* 2) inside such blocks, the outermost block with block_ultimate_origin
399 being a FUNCTION_DECL. */
400 else if (in_ctor_dtor_block)
402 tree fn = block_ultimate_origin (scope);
403 if (fn && TREE_CODE (fn) == FUNCTION_DECL)
405 in_ctor_dtor_block = false;
406 unused = false;
410 for (t = &BLOCK_VARS (scope); *t; t = next)
412 next = &DECL_CHAIN (*t);
414 /* Debug info of nested function refers to the block of the
415 function. We might stil call it even if all statements
416 of function it was nested into was elliminated.
418 TODO: We can actually look into cgraph to see if function
419 will be output to file. */
420 if (TREE_CODE (*t) == FUNCTION_DECL)
421 unused = false;
423 /* If a decl has a value expr, we need to instantiate it
424 regardless of debug info generation, to avoid codegen
425 differences in memory overlap tests. update_equiv_regs() may
426 indirectly call validate_equiv_mem() to test whether a
427 SET_DEST overlaps with others, and if the value expr changes
428 by virtual register instantiation, we may get end up with
429 different results. */
430 else if (VAR_P (*t) && DECL_HAS_VALUE_EXPR_P (*t))
431 unused = false;
433 /* Remove everything we don't generate debug info for. */
434 else if (DECL_IGNORED_P (*t))
436 *t = DECL_CHAIN (*t);
437 next = t;
440 /* When we are outputting debug info, we usually want to output
441 info about optimized-out variables in the scope blocks.
442 Exception are the scope blocks not containing any instructions
443 at all so user can't get into the scopes at first place. */
444 else if (is_used_p (*t))
445 unused = false;
446 else if (TREE_CODE (*t) == LABEL_DECL && TREE_USED (*t))
447 /* For labels that are still used in the IL, the decision to
448 preserve them must not depend DEBUG_INFO_LEVEL, otherwise we
449 risk having different ordering in debug vs. non-debug builds
450 during inlining or versioning.
451 A label appearing here (we have already checked DECL_IGNORED_P)
452 should not be used in the IL unless it has been explicitly used
453 before, so we use TREE_USED as an approximation. */
454 /* In principle, we should do the same here as for the debug case
455 below, however, when debugging, there might be additional nested
456 levels that keep an upper level with a label live, so we have to
457 force this block to be considered used, too. */
458 unused = false;
460 /* When we are not doing full debug info, we however can keep around
461 only the used variables for cfgexpand's memory packing saving quite
462 a lot of memory.
464 For sake of -g3, we keep around those vars but we don't count this as
465 use of block, so innermost block with no used vars and no instructions
466 can be considered dead. We only want to keep around blocks user can
467 breakpoint into and ask about value of optimized out variables.
469 Similarly we need to keep around types at least until all
470 variables of all nested blocks are gone. We track no
471 information on whether given type is used or not, so we have
472 to keep them even when not emitting debug information,
473 otherwise we may end up remapping variables and their (local)
474 types in different orders depending on whether debug
475 information is being generated. */
477 else if (TREE_CODE (*t) == TYPE_DECL
478 || debug_info_level == DINFO_LEVEL_NORMAL
479 || debug_info_level == DINFO_LEVEL_VERBOSE)
481 else
483 *t = DECL_CHAIN (*t);
484 next = t;
488 for (t = &BLOCK_SUBBLOCKS (scope); *t ;)
489 if (remove_unused_scope_block_p (*t, in_ctor_dtor_block))
491 if (BLOCK_SUBBLOCKS (*t))
493 tree next = BLOCK_CHAIN (*t);
494 tree supercontext = BLOCK_SUPERCONTEXT (*t);
496 *t = BLOCK_SUBBLOCKS (*t);
497 while (BLOCK_CHAIN (*t))
499 BLOCK_SUPERCONTEXT (*t) = supercontext;
500 t = &BLOCK_CHAIN (*t);
502 BLOCK_CHAIN (*t) = next;
503 BLOCK_SUPERCONTEXT (*t) = supercontext;
504 t = &BLOCK_CHAIN (*t);
505 nsubblocks ++;
507 else
508 *t = BLOCK_CHAIN (*t);
510 else
512 t = &BLOCK_CHAIN (*t);
513 nsubblocks ++;
517 if (!unused)
519 /* Outer scope is always used. */
520 else if (!BLOCK_SUPERCONTEXT (scope)
521 || TREE_CODE (BLOCK_SUPERCONTEXT (scope)) == FUNCTION_DECL)
522 unused = false;
523 /* Innermost blocks with no live variables nor statements can be always
524 eliminated. */
525 else if (!nsubblocks)
527 /* When not generating debug info we can eliminate info on unused
528 variables. */
529 else if (!flag_auto_profile && debug_info_level == DINFO_LEVEL_NONE)
531 /* Even for -g0 don't prune outer scopes from artificial
532 functions, otherwise diagnostics using tree_nonartificial_location
533 will not be emitted properly. */
534 if (inlined_function_outer_scope_p (scope))
536 tree ao = scope;
538 while (ao
539 && TREE_CODE (ao) == BLOCK
540 && BLOCK_ABSTRACT_ORIGIN (ao) != ao)
541 ao = BLOCK_ABSTRACT_ORIGIN (ao);
542 if (ao
543 && TREE_CODE (ao) == FUNCTION_DECL
544 && DECL_DECLARED_INLINE_P (ao)
545 && lookup_attribute ("artificial", DECL_ATTRIBUTES (ao)))
546 unused = false;
549 else if (BLOCK_VARS (scope) || BLOCK_NUM_NONLOCALIZED_VARS (scope))
550 unused = false;
551 /* See if this block is important for representation of inlined
552 function. Inlined functions are always represented by block
553 with block_ultimate_origin being set to FUNCTION_DECL and
554 DECL_SOURCE_LOCATION set, unless they expand to nothing... */
555 else if (inlined_function_outer_scope_p (scope))
556 unused = false;
557 else
558 /* Verfify that only blocks with source location set
559 are entry points to the inlined functions. */
560 gcc_assert (LOCATION_LOCUS (BLOCK_SOURCE_LOCATION (scope))
561 == UNKNOWN_LOCATION);
563 TREE_USED (scope) = !unused;
564 return unused;
567 /* Mark all VAR_DECLS under *EXPR_P as used, so that they won't be
568 eliminated during the tree->rtl conversion process. */
570 static inline void
571 mark_all_vars_used (tree *expr_p)
573 walk_tree (expr_p, mark_all_vars_used_1, NULL, NULL);
576 /* Helper function for clear_unused_block_pointer, called via walk_tree. */
578 static tree
579 clear_unused_block_pointer_1 (tree *tp, int *, void *)
581 if (EXPR_P (*tp) && TREE_BLOCK (*tp)
582 && !TREE_USED (TREE_BLOCK (*tp)))
583 TREE_SET_BLOCK (*tp, NULL);
584 return NULL_TREE;
587 /* Set all block pointer in debug or clobber stmt to NULL if the block
588 is unused, so that they will not be streamed out. */
590 static void
591 clear_unused_block_pointer (void)
593 basic_block bb;
594 gimple_stmt_iterator gsi;
596 FOR_EACH_BB_FN (bb, cfun)
597 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
599 unsigned i;
600 tree b;
601 gimple *stmt = gsi_stmt (gsi);
603 if (!is_gimple_debug (stmt) && !gimple_clobber_p (stmt))
604 continue;
605 b = gimple_block (stmt);
606 if (b && !TREE_USED (b))
607 gimple_set_block (stmt, NULL);
608 for (i = 0; i < gimple_num_ops (stmt); i++)
609 walk_tree (gimple_op_ptr (stmt, i), clear_unused_block_pointer_1,
610 NULL, NULL);
614 /* Dump scope blocks starting at SCOPE to FILE. INDENT is the
615 indentation level and FLAGS is as in print_generic_expr. */
617 static void
618 dump_scope_block (FILE *file, int indent, tree scope, dump_flags_t flags)
620 tree var, t;
621 unsigned int i;
623 fprintf (file, "\n%*s{ Scope block #%i%s%s",indent, "" , BLOCK_NUMBER (scope),
624 TREE_USED (scope) ? "" : " (unused)",
625 BLOCK_ABSTRACT (scope) ? " (abstract)": "");
626 if (LOCATION_LOCUS (BLOCK_SOURCE_LOCATION (scope)) != UNKNOWN_LOCATION)
628 expanded_location s = expand_location (BLOCK_SOURCE_LOCATION (scope));
629 fprintf (file, " %s:%i", s.file, s.line);
631 if (BLOCK_ABSTRACT_ORIGIN (scope))
633 tree origin = block_ultimate_origin (scope);
634 if (origin)
636 fprintf (file, " Originating from :");
637 if (DECL_P (origin))
638 print_generic_decl (file, origin, flags);
639 else
640 fprintf (file, "#%i", BLOCK_NUMBER (origin));
643 if (BLOCK_FRAGMENT_ORIGIN (scope))
644 fprintf (file, " Fragment of : #%i",
645 BLOCK_NUMBER (BLOCK_FRAGMENT_ORIGIN (scope)));
646 else if (BLOCK_FRAGMENT_CHAIN (scope))
648 fprintf (file, " Fragment chain :");
649 for (t = BLOCK_FRAGMENT_CHAIN (scope); t ;
650 t = BLOCK_FRAGMENT_CHAIN (t))
651 fprintf (file, " #%i", BLOCK_NUMBER (t));
653 fprintf (file, " \n");
654 for (var = BLOCK_VARS (scope); var; var = DECL_CHAIN (var))
656 fprintf (file, "%*s", indent, "");
657 print_generic_decl (file, var, flags);
658 fprintf (file, "\n");
660 for (i = 0; i < BLOCK_NUM_NONLOCALIZED_VARS (scope); i++)
662 fprintf (file, "%*s",indent, "");
663 print_generic_decl (file, BLOCK_NONLOCALIZED_VAR (scope, i),
664 flags);
665 fprintf (file, " (nonlocalized)\n");
667 for (t = BLOCK_SUBBLOCKS (scope); t ; t = BLOCK_CHAIN (t))
668 dump_scope_block (file, indent + 2, t, flags);
669 fprintf (file, "\n%*s}\n",indent, "");
672 /* Dump the tree of lexical scopes starting at SCOPE to stderr. FLAGS
673 is as in print_generic_expr. */
675 DEBUG_FUNCTION void
676 debug_scope_block (tree scope, dump_flags_t flags)
678 dump_scope_block (stderr, 0, scope, flags);
682 /* Dump the tree of lexical scopes of current_function_decl to FILE.
683 FLAGS is as in print_generic_expr. */
685 void
686 dump_scope_blocks (FILE *file, dump_flags_t flags)
688 dump_scope_block (file, 0, DECL_INITIAL (current_function_decl), flags);
692 /* Dump the tree of lexical scopes of current_function_decl to stderr.
693 FLAGS is as in print_generic_expr. */
695 DEBUG_FUNCTION void
696 debug_scope_blocks (dump_flags_t flags)
698 dump_scope_blocks (stderr, flags);
701 /* Remove local variables that are not referenced in the IL. */
703 void
704 remove_unused_locals (void)
706 basic_block bb;
707 tree var;
708 unsigned srcidx, dstidx, num;
709 bool have_local_clobbers = false;
711 /* Removing declarations from lexical blocks when not optimizing is
712 not only a waste of time, it actually causes differences in stack
713 layout. */
714 if (!optimize)
715 return;
717 timevar_push (TV_REMOVE_UNUSED);
719 mark_scope_block_unused (DECL_INITIAL (current_function_decl));
721 usedvars = BITMAP_ALLOC (NULL);
723 /* Walk the CFG marking all referenced symbols. */
724 FOR_EACH_BB_FN (bb, cfun)
726 gimple_stmt_iterator gsi;
727 size_t i;
728 edge_iterator ei;
729 edge e;
731 /* Walk the statements. */
732 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi); gsi_next (&gsi))
734 gimple *stmt = gsi_stmt (gsi);
735 tree b = gimple_block (stmt);
737 /* If we wanted to mark the block referenced by the inline
738 entry point marker as used, this would be a good spot to
739 do it. If the block is not otherwise used, the stmt will
740 be cleaned up in clean_unused_block_pointer. */
741 if (is_gimple_debug (stmt))
742 continue;
744 if (gimple_clobber_p (stmt))
746 have_local_clobbers = true;
747 continue;
750 if (b)
751 TREE_USED (b) = true;
753 for (i = 0; i < gimple_num_ops (stmt); i++)
754 mark_all_vars_used (gimple_op_ptr (gsi_stmt (gsi), i));
757 for (gphi_iterator gpi = gsi_start_phis (bb);
758 !gsi_end_p (gpi);
759 gsi_next (&gpi))
761 use_operand_p arg_p;
762 ssa_op_iter i;
763 tree def;
764 gphi *phi = gpi.phi ();
766 if (virtual_operand_p (gimple_phi_result (phi)))
767 continue;
769 def = gimple_phi_result (phi);
770 mark_all_vars_used (&def);
772 FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_ALL_USES)
774 tree arg = USE_FROM_PTR (arg_p);
775 int index = PHI_ARG_INDEX_FROM_USE (arg_p);
776 tree block =
777 LOCATION_BLOCK (gimple_phi_arg_location (phi, index));
778 if (block != NULL)
779 TREE_USED (block) = true;
780 mark_all_vars_used (&arg);
784 FOR_EACH_EDGE (e, ei, bb->succs)
785 if (LOCATION_BLOCK (e->goto_locus) != NULL)
786 TREE_USED (LOCATION_BLOCK (e->goto_locus)) = true;
789 /* We do a two-pass approach about the out-of-scope clobbers. We want
790 to remove them if they are the only references to a local variable,
791 but we want to retain them when there's any other. So the first pass
792 ignores them, and the second pass (if there were any) tries to remove
793 them. */
794 if (have_local_clobbers)
795 FOR_EACH_BB_FN (bb, cfun)
797 gimple_stmt_iterator gsi;
799 for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi);)
801 gimple *stmt = gsi_stmt (gsi);
802 tree b = gimple_block (stmt);
804 if (gimple_clobber_p (stmt))
806 tree lhs = gimple_assign_lhs (stmt);
807 tree base = get_base_address (lhs);
808 /* Remove clobbers referencing unused vars, or clobbers
809 with MEM_REF lhs referencing uninitialized pointers. */
810 if ((VAR_P (base) && !is_used_p (base))
811 || (TREE_CODE (lhs) == MEM_REF
812 && TREE_CODE (TREE_OPERAND (lhs, 0)) == SSA_NAME
813 && SSA_NAME_IS_DEFAULT_DEF (TREE_OPERAND (lhs, 0))
814 && (TREE_CODE (SSA_NAME_VAR (TREE_OPERAND (lhs, 0)))
815 != PARM_DECL)))
817 unlink_stmt_vdef (stmt);
818 gsi_remove (&gsi, true);
819 release_defs (stmt);
820 continue;
822 if (b)
823 TREE_USED (b) = true;
825 gsi_next (&gsi);
829 if (cfun->has_simduid_loops)
831 struct loop *loop;
832 FOR_EACH_LOOP (loop, 0)
833 if (loop->simduid && !is_used_p (loop->simduid))
834 loop->simduid = NULL_TREE;
837 cfun->has_local_explicit_reg_vars = false;
839 /* Remove unmarked local and global vars from local_decls. */
840 num = vec_safe_length (cfun->local_decls);
841 for (srcidx = 0, dstidx = 0; srcidx < num; srcidx++)
843 var = (*cfun->local_decls)[srcidx];
844 if (VAR_P (var))
846 if (!is_used_p (var))
848 tree def;
849 if (cfun->nonlocal_goto_save_area
850 && TREE_OPERAND (cfun->nonlocal_goto_save_area, 0) == var)
851 cfun->nonlocal_goto_save_area = NULL;
852 /* Release any default def associated with var. */
853 if ((def = ssa_default_def (cfun, var)) != NULL_TREE)
855 set_ssa_default_def (cfun, var, NULL_TREE);
856 release_ssa_name (def);
858 continue;
861 if (VAR_P (var) && DECL_HARD_REGISTER (var) && !is_global_var (var))
862 cfun->has_local_explicit_reg_vars = true;
864 if (srcidx != dstidx)
865 (*cfun->local_decls)[dstidx] = var;
866 dstidx++;
868 if (dstidx != num)
870 statistics_counter_event (cfun, "unused VAR_DECLs removed", num - dstidx);
871 cfun->local_decls->truncate (dstidx);
874 remove_unused_scope_block_p (DECL_INITIAL (current_function_decl),
875 polymorphic_ctor_dtor_p (current_function_decl,
876 true) != NULL_TREE);
877 clear_unused_block_pointer ();
879 BITMAP_FREE (usedvars);
881 if (dump_file && (dump_flags & TDF_DETAILS))
883 fprintf (dump_file, "Scope blocks after cleanups:\n");
884 dump_scope_blocks (dump_file, dump_flags);
887 timevar_pop (TV_REMOVE_UNUSED);
890 /* Allocate and return a new live range information object base on MAP. */
892 static tree_live_info_p
893 new_tree_live_info (var_map map)
895 tree_live_info_p live;
896 basic_block bb;
898 live = XNEW (struct tree_live_info_d);
899 live->map = map;
900 live->num_blocks = last_basic_block_for_fn (cfun);
902 bitmap_obstack_initialize (&live->livein_obstack);
903 bitmap_obstack_initialize (&live->liveout_obstack);
904 live->livein = XNEWVEC (bitmap_head, last_basic_block_for_fn (cfun));
905 FOR_EACH_BB_FN (bb, cfun)
906 bitmap_initialize (&live->livein[bb->index], &live->livein_obstack);
908 live->liveout = XNEWVEC (bitmap_head, last_basic_block_for_fn (cfun));
909 FOR_EACH_BB_FN (bb, cfun)
910 bitmap_initialize (&live->liveout[bb->index], &live->liveout_obstack);
912 live->work_stack = XNEWVEC (int, last_basic_block_for_fn (cfun));
913 live->stack_top = live->work_stack;
915 live->global = BITMAP_ALLOC (NULL);
916 return live;
920 /* Free storage for live range info object LIVE. */
922 void
923 delete_tree_live_info (tree_live_info_p live)
925 if (live->livein)
927 bitmap_obstack_release (&live->livein_obstack);
928 free (live->livein);
930 if (live->liveout)
932 bitmap_obstack_release (&live->liveout_obstack);
933 free (live->liveout);
935 BITMAP_FREE (live->global);
936 free (live->work_stack);
937 free (live);
941 /* Visit basic block BB and propagate any required live on entry bits from
942 LIVE into the predecessors. VISITED is the bitmap of visited blocks.
943 TMP is a temporary work bitmap which is passed in to avoid reallocating
944 it each time. */
946 static void
947 loe_visit_block (tree_live_info_p live, basic_block bb, sbitmap visited)
949 edge e;
950 bool change;
951 edge_iterator ei;
952 basic_block pred_bb;
953 bitmap loe;
955 gcc_checking_assert (!bitmap_bit_p (visited, bb->index));
956 bitmap_set_bit (visited, bb->index);
958 loe = live_on_entry (live, bb);
960 FOR_EACH_EDGE (e, ei, bb->preds)
962 pred_bb = e->src;
963 if (pred_bb == ENTRY_BLOCK_PTR_FOR_FN (cfun))
964 continue;
965 /* Variables live-on-entry from BB that aren't defined in the
966 predecessor block. This should be the live on entry vars to pred.
967 Note that liveout is the DEFs in a block while live on entry is
968 being calculated.
969 Add these bits to live-on-entry for the pred. if there are any
970 changes, and pred_bb has been visited already, add it to the
971 revisit stack. */
972 change = bitmap_ior_and_compl_into (live_on_entry (live, pred_bb),
973 loe, &live->liveout[pred_bb->index]);
974 if (change
975 && bitmap_bit_p (visited, pred_bb->index))
977 bitmap_clear_bit (visited, pred_bb->index);
978 *(live->stack_top)++ = pred_bb->index;
984 /* Using LIVE, fill in all the live-on-entry blocks between the defs and uses
985 of all the variables. */
987 static void
988 live_worklist (tree_live_info_p live)
990 unsigned b;
991 basic_block bb;
992 auto_sbitmap visited (last_basic_block_for_fn (cfun) + 1);
994 bitmap_clear (visited);
996 /* Visit all the blocks in reverse order and propagate live on entry values
997 into the predecessors blocks. */
998 FOR_EACH_BB_REVERSE_FN (bb, cfun)
999 loe_visit_block (live, bb, visited);
1001 /* Process any blocks which require further iteration. */
1002 while (live->stack_top != live->work_stack)
1004 b = *--(live->stack_top);
1005 loe_visit_block (live, BASIC_BLOCK_FOR_FN (cfun, b), visited);
1010 /* Calculate the initial live on entry vector for SSA_NAME using immediate_use
1011 links. Set the live on entry fields in LIVE. Def's are marked temporarily
1012 in the liveout vector. */
1014 static void
1015 set_var_live_on_entry (tree ssa_name, tree_live_info_p live)
1017 int p;
1018 gimple *stmt;
1019 use_operand_p use;
1020 basic_block def_bb = NULL;
1021 imm_use_iterator imm_iter;
1022 bool global = false;
1024 p = var_to_partition (live->map, ssa_name);
1025 if (p == NO_PARTITION)
1026 return;
1028 stmt = SSA_NAME_DEF_STMT (ssa_name);
1029 if (stmt)
1031 def_bb = gimple_bb (stmt);
1032 /* Mark defs in liveout bitmap temporarily. */
1033 if (def_bb)
1034 bitmap_set_bit (&live->liveout[def_bb->index], p);
1036 else
1037 def_bb = ENTRY_BLOCK_PTR_FOR_FN (cfun);
1039 /* An undefined local variable does not need to be very alive. */
1040 if (ssa_undefined_value_p (ssa_name, false))
1041 return;
1043 /* Visit each use of SSA_NAME and if it isn't in the same block as the def,
1044 add it to the list of live on entry blocks. */
1045 FOR_EACH_IMM_USE_FAST (use, imm_iter, ssa_name)
1047 gimple *use_stmt = USE_STMT (use);
1048 basic_block add_block = NULL;
1050 if (gimple_code (use_stmt) == GIMPLE_PHI)
1052 /* Uses in PHI's are considered to be live at exit of the SRC block
1053 as this is where a copy would be inserted. Check to see if it is
1054 defined in that block, or whether its live on entry. */
1055 int index = PHI_ARG_INDEX_FROM_USE (use);
1056 edge e = gimple_phi_arg_edge (as_a <gphi *> (use_stmt), index);
1057 if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun))
1059 if (e->src != def_bb)
1060 add_block = e->src;
1063 else if (is_gimple_debug (use_stmt))
1064 continue;
1065 else
1067 /* If its not defined in this block, its live on entry. */
1068 basic_block use_bb = gimple_bb (use_stmt);
1069 if (use_bb != def_bb)
1070 add_block = use_bb;
1073 /* If there was a live on entry use, set the bit. */
1074 if (add_block)
1076 global = true;
1077 bitmap_set_bit (&live->livein[add_block->index], p);
1081 /* If SSA_NAME is live on entry to at least one block, fill in all the live
1082 on entry blocks between the def and all the uses. */
1083 if (global)
1084 bitmap_set_bit (live->global, p);
1088 /* Calculate the live on exit vectors based on the entry info in LIVEINFO. */
1090 static void
1091 calculate_live_on_exit (tree_live_info_p liveinfo)
1093 basic_block bb;
1094 edge e;
1095 edge_iterator ei;
1097 /* live on entry calculations used liveout vectors for defs, clear them. */
1098 FOR_EACH_BB_FN (bb, cfun)
1099 bitmap_clear (&liveinfo->liveout[bb->index]);
1101 /* Set all the live-on-exit bits for uses in PHIs. */
1102 FOR_EACH_BB_FN (bb, cfun)
1104 gphi_iterator gsi;
1105 size_t i;
1107 /* Mark the PHI arguments which are live on exit to the pred block. */
1108 for (gsi = gsi_start_phis (bb); !gsi_end_p (gsi); gsi_next (&gsi))
1110 gphi *phi = gsi.phi ();
1111 for (i = 0; i < gimple_phi_num_args (phi); i++)
1113 tree t = PHI_ARG_DEF (phi, i);
1114 int p;
1116 if (TREE_CODE (t) != SSA_NAME)
1117 continue;
1119 p = var_to_partition (liveinfo->map, t);
1120 if (p == NO_PARTITION)
1121 continue;
1122 e = gimple_phi_arg_edge (phi, i);
1123 if (e->src != ENTRY_BLOCK_PTR_FOR_FN (cfun))
1124 bitmap_set_bit (&liveinfo->liveout[e->src->index], p);
1128 /* Add each successors live on entry to this bock live on exit. */
1129 FOR_EACH_EDGE (e, ei, bb->succs)
1130 if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
1131 bitmap_ior_into (&liveinfo->liveout[bb->index],
1132 live_on_entry (liveinfo, e->dest));
1137 /* Given partition map MAP, calculate all the live on entry bitmaps for
1138 each partition. Return a new live info object. */
1140 tree_live_info_p
1141 calculate_live_ranges (var_map map, bool want_livein)
1143 tree var;
1144 unsigned i;
1145 tree_live_info_p live;
1147 live = new_tree_live_info (map);
1148 for (i = 0; i < num_var_partitions (map); i++)
1150 var = partition_to_var (map, i);
1151 if (var != NULL_TREE)
1152 set_var_live_on_entry (var, live);
1155 live_worklist (live);
1157 if (flag_checking)
1158 verify_live_on_entry (live);
1160 calculate_live_on_exit (live);
1162 if (!want_livein)
1164 bitmap_obstack_release (&live->livein_obstack);
1165 free (live->livein);
1166 live->livein = NULL;
1169 return live;
1173 /* Output partition map MAP to file F. */
1175 void
1176 dump_var_map (FILE *f, var_map map)
1178 int t;
1179 unsigned x, y;
1180 int p;
1182 fprintf (f, "\nPartition map \n\n");
1184 for (x = 0; x < map->num_partitions; x++)
1186 if (map->view_to_partition != NULL)
1187 p = map->view_to_partition[x];
1188 else
1189 p = x;
1191 if (ssa_name (p) == NULL_TREE
1192 || virtual_operand_p (ssa_name (p)))
1193 continue;
1195 t = 0;
1196 for (y = 1; y < num_ssa_names; y++)
1198 p = partition_find (map->var_partition, y);
1199 if (map->partition_to_view)
1200 p = map->partition_to_view[p];
1201 if (p == (int)x)
1203 if (t++ == 0)
1205 fprintf (f, "Partition %d (", x);
1206 print_generic_expr (f, partition_to_var (map, p), TDF_SLIM);
1207 fprintf (f, " - ");
1209 fprintf (f, "%d ", y);
1212 if (t != 0)
1213 fprintf (f, ")\n");
1215 fprintf (f, "\n");
1219 /* Generic dump for the above. */
1221 DEBUG_FUNCTION void
1222 debug (_var_map &ref)
1224 dump_var_map (stderr, &ref);
1227 DEBUG_FUNCTION void
1228 debug (_var_map *ptr)
1230 if (ptr)
1231 debug (*ptr);
1232 else
1233 fprintf (stderr, "<nil>\n");
1237 /* Output live range info LIVE to file F, controlled by FLAG. */
1239 void
1240 dump_live_info (FILE *f, tree_live_info_p live, int flag)
1242 basic_block bb;
1243 unsigned i;
1244 var_map map = live->map;
1245 bitmap_iterator bi;
1247 if ((flag & LIVEDUMP_ENTRY) && live->livein)
1249 FOR_EACH_BB_FN (bb, cfun)
1251 fprintf (f, "\nLive on entry to BB%d : ", bb->index);
1252 EXECUTE_IF_SET_IN_BITMAP (&live->livein[bb->index], 0, i, bi)
1254 print_generic_expr (f, partition_to_var (map, i), TDF_SLIM);
1255 fprintf (f, " ");
1257 fprintf (f, "\n");
1261 if ((flag & LIVEDUMP_EXIT) && live->liveout)
1263 FOR_EACH_BB_FN (bb, cfun)
1265 fprintf (f, "\nLive on exit from BB%d : ", bb->index);
1266 EXECUTE_IF_SET_IN_BITMAP (&live->liveout[bb->index], 0, i, bi)
1268 print_generic_expr (f, partition_to_var (map, i), TDF_SLIM);
1269 fprintf (f, " ");
1271 fprintf (f, "\n");
1277 /* Generic dump for the above. */
1279 DEBUG_FUNCTION void
1280 debug (tree_live_info_d &ref)
1282 dump_live_info (stderr, &ref, 0);
1285 DEBUG_FUNCTION void
1286 debug (tree_live_info_d *ptr)
1288 if (ptr)
1289 debug (*ptr);
1290 else
1291 fprintf (stderr, "<nil>\n");
1295 /* Verify that the info in LIVE matches the current cfg. */
1297 static void
1298 verify_live_on_entry (tree_live_info_p live)
1300 unsigned i;
1301 tree var;
1302 gimple *stmt;
1303 basic_block bb;
1304 edge e;
1305 int num;
1306 edge_iterator ei;
1307 var_map map = live->map;
1309 /* Check for live on entry partitions and report those with a DEF in
1310 the program. This will typically mean an optimization has done
1311 something wrong. */
1312 bb = ENTRY_BLOCK_PTR_FOR_FN (cfun);
1313 num = 0;
1314 FOR_EACH_EDGE (e, ei, bb->succs)
1316 int entry_block = e->dest->index;
1317 if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
1318 continue;
1319 for (i = 0; i < (unsigned)num_var_partitions (map); i++)
1321 basic_block tmp;
1322 tree d = NULL_TREE;
1323 bitmap loe;
1324 var = partition_to_var (map, i);
1325 stmt = SSA_NAME_DEF_STMT (var);
1326 tmp = gimple_bb (stmt);
1327 if (SSA_NAME_VAR (var))
1328 d = ssa_default_def (cfun, SSA_NAME_VAR (var));
1330 loe = live_on_entry (live, e->dest);
1331 if (loe && bitmap_bit_p (loe, i))
1333 if (!gimple_nop_p (stmt))
1335 num++;
1336 print_generic_expr (stderr, var, TDF_SLIM);
1337 fprintf (stderr, " is defined ");
1338 if (tmp)
1339 fprintf (stderr, " in BB%d, ", tmp->index);
1340 fprintf (stderr, "by:\n");
1341 print_gimple_stmt (stderr, stmt, 0, TDF_SLIM);
1342 fprintf (stderr, "\nIt is also live-on-entry to entry BB %d",
1343 entry_block);
1344 fprintf (stderr, " So it appears to have multiple defs.\n");
1346 else
1348 if (d != var)
1350 num++;
1351 print_generic_expr (stderr, var, TDF_SLIM);
1352 fprintf (stderr, " is live-on-entry to BB%d ",
1353 entry_block);
1354 if (d)
1356 fprintf (stderr, " but is not the default def of ");
1357 print_generic_expr (stderr, d, TDF_SLIM);
1358 fprintf (stderr, "\n");
1360 else
1361 fprintf (stderr, " and there is no default def.\n");
1365 else
1366 if (d == var)
1368 /* An undefined local variable does not need to be very
1369 alive. */
1370 if (ssa_undefined_value_p (var, false))
1371 continue;
1373 /* The only way this var shouldn't be marked live on entry is
1374 if it occurs in a PHI argument of the block. */
1375 size_t z;
1376 bool ok = false;
1377 gphi_iterator gsi;
1378 for (gsi = gsi_start_phis (e->dest);
1379 !gsi_end_p (gsi) && !ok;
1380 gsi_next (&gsi))
1382 gphi *phi = gsi.phi ();
1383 for (z = 0; z < gimple_phi_num_args (phi); z++)
1384 if (var == gimple_phi_arg_def (phi, z))
1386 ok = true;
1387 break;
1390 if (ok)
1391 continue;
1392 /* Expand adds unused default defs for PARM_DECLs and
1393 RESULT_DECLs. They're ok. */
1394 if (has_zero_uses (var)
1395 && SSA_NAME_VAR (var)
1396 && !VAR_P (SSA_NAME_VAR (var)))
1397 continue;
1398 num++;
1399 print_generic_expr (stderr, var, TDF_SLIM);
1400 fprintf (stderr, " is not marked live-on-entry to entry BB%d ",
1401 entry_block);
1402 fprintf (stderr, "but it is a default def so it should be.\n");
1406 gcc_assert (num <= 0);