1 /* Control flow graph manipulation code for GNU compiler.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001, 2002, 2003, 2004, 2005
4 Free Software Foundation, Inc.
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 2, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING. If not, write to the Free
20 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
23 /* This file contains low level functions to manipulate the CFG and
24 analyze it. All other modules should not transform the data structure
25 directly and use abstraction instead. The file is supposed to be
26 ordered bottom-up and should not contain any code dependent on a
27 particular intermediate language (RTL or trees).
29 Available functionality:
30 - Initialization/deallocation
31 init_flow, clear_edges
32 - Low level basic block manipulation
33 alloc_block, expunge_block
35 make_edge, make_single_succ_edge, cached_make_edge, remove_edge
36 - Low level edge redirection (without updating instruction chain)
37 redirect_edge_succ, redirect_edge_succ_nodup, redirect_edge_pred
38 - Dumping and debugging
39 dump_flow_info, debug_flow_info, dump_edge_info
40 - Allocation of AUX fields for basic blocks
41 alloc_aux_for_blocks, free_aux_for_blocks, alloc_aux_for_block
43 - Consistency checking
45 - Dumping and debugging
46 print_rtl_with_bb, dump_bb, debug_bb, debug_bb_n
51 #include "coretypes.h"
55 #include "hard-reg-set.h"
67 /* The obstack on which the flow graph components are allocated. */
69 struct bitmap_obstack reg_obstack;
71 void debug_flow_info (void);
72 static void free_edge (edge);
74 #define RDIV(X,Y) (((X) + (Y) / 2) / (Y))
76 /* Called once at initialization time. */
82 ENTRY_BLOCK_PTR = ggc_alloc_cleared (sizeof (struct basic_block_def));
83 ENTRY_BLOCK_PTR->index = ENTRY_BLOCK;
84 EXIT_BLOCK_PTR = ggc_alloc_cleared (sizeof (struct basic_block_def));
85 EXIT_BLOCK_PTR->index = EXIT_BLOCK;
86 ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR;
87 EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR;
90 /* Helper function for remove_edge and clear_edges. Frees edge structure
91 without actually unlinking it from the pred/succ lists. */
94 free_edge (edge e ATTRIBUTE_UNUSED)
100 /* Free the memory associated with the edge structures. */
111 FOR_EACH_EDGE (e, ei, bb->succs)
113 VEC_truncate (edge, bb->succs, 0);
114 VEC_truncate (edge, bb->preds, 0);
117 FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
119 VEC_truncate (edge, EXIT_BLOCK_PTR->preds, 0);
120 VEC_truncate (edge, ENTRY_BLOCK_PTR->succs, 0);
122 gcc_assert (!n_edges);
125 /* Allocate memory for basic_block. */
131 bb = ggc_alloc_cleared (sizeof (*bb));
135 /* Initialize rbi (the structure containing data used by basic block
136 duplication and reordering) for the given basic block. */
139 initialize_bb_rbi (basic_block bb)
141 gcc_assert (!bb->rbi);
142 bb->rbi = ggc_alloc_cleared (sizeof (struct reorder_block_def));
145 /* Link block B to chain after AFTER. */
147 link_block (basic_block b, basic_block after)
149 b->next_bb = after->next_bb;
152 b->next_bb->prev_bb = b;
155 /* Unlink block B from chain. */
157 unlink_block (basic_block b)
159 b->next_bb->prev_bb = b->prev_bb;
160 b->prev_bb->next_bb = b->next_bb;
165 /* Sequentially order blocks and compact the arrays. */
167 compact_blocks (void)
175 BASIC_BLOCK (i) = bb;
180 gcc_assert (i == n_basic_blocks);
182 for (; i < last_basic_block; i++)
183 BASIC_BLOCK (i) = NULL;
185 last_basic_block = n_basic_blocks;
188 /* Remove block B from the basic block array. */
191 expunge_block (basic_block b)
194 BASIC_BLOCK (b->index) = NULL;
196 /* We should be able to ggc_free here, but we are not.
197 The dead SSA_NAMES are left pointing to dead statements that are pointing
198 to dead basic blocks making garbage collector to die.
199 We should be able to release all dead SSA_NAMES and at the same time we should
200 clear out BB pointer of dead statements consistently. */
203 /* Connect E to E->src. */
208 VEC_safe_push (edge, gc, e->src->succs, e);
211 /* Connect E to E->dest. */
214 connect_dest (edge e)
216 basic_block dest = e->dest;
217 VEC_safe_push (edge, gc, dest->preds, e);
218 e->dest_idx = EDGE_COUNT (dest->preds) - 1;
221 /* Disconnect edge E from E->src. */
224 disconnect_src (edge e)
226 basic_block src = e->src;
230 for (ei = ei_start (src->succs); (tmp = ei_safe_edge (ei)); )
234 VEC_unordered_remove (edge, src->succs, ei.index);
244 /* Disconnect edge E from E->dest. */
247 disconnect_dest (edge e)
249 basic_block dest = e->dest;
250 unsigned int dest_idx = e->dest_idx;
252 VEC_unordered_remove (edge, dest->preds, dest_idx);
254 /* If we removed an edge in the middle of the edge vector, we need
255 to update dest_idx of the edge that moved into the "hole". */
256 if (dest_idx < EDGE_COUNT (dest->preds))
257 EDGE_PRED (dest, dest_idx)->dest_idx = dest_idx;
260 /* Create an edge connecting SRC and DEST with flags FLAGS. Return newly
261 created edge. Use this only if you are sure that this edge can't
262 possibly already exist. */
265 unchecked_make_edge (basic_block src, basic_block dst, int flags)
268 e = ggc_alloc_cleared (sizeof (*e));
278 execute_on_growing_pred (e);
283 /* Create an edge connecting SRC and DST with FLAGS optionally using
284 edge cache CACHE. Return the new edge, NULL if already exist. */
287 cached_make_edge (sbitmap edge_cache, basic_block src, basic_block dst, int flags)
289 if (edge_cache == NULL
290 || src == ENTRY_BLOCK_PTR
291 || dst == EXIT_BLOCK_PTR)
292 return make_edge (src, dst, flags);
294 /* Does the requested edge already exist? */
295 if (! TEST_BIT (edge_cache, dst->index))
297 /* The edge does not exist. Create one and update the
299 SET_BIT (edge_cache, dst->index);
300 return unchecked_make_edge (src, dst, flags);
303 /* At this point, we know that the requested edge exists. Adjust
304 flags if necessary. */
307 edge e = find_edge (src, dst);
314 /* Create an edge connecting SRC and DEST with flags FLAGS. Return newly
315 created edge or NULL if already exist. */
318 make_edge (basic_block src, basic_block dest, int flags)
320 edge e = find_edge (src, dest);
322 /* Make sure we don't add duplicate edges. */
329 return unchecked_make_edge (src, dest, flags);
332 /* Create an edge connecting SRC to DEST and set probability by knowing
333 that it is the single edge leaving SRC. */
336 make_single_succ_edge (basic_block src, basic_block dest, int flags)
338 edge e = make_edge (src, dest, flags);
340 e->probability = REG_BR_PROB_BASE;
341 e->count = src->count;
345 /* This function will remove an edge from the flow graph. */
350 execute_on_shrinking_pred (e);
358 /* Redirect an edge's successor from one block to another. */
361 redirect_edge_succ (edge e, basic_block new_succ)
363 execute_on_shrinking_pred (e);
369 /* Reconnect the edge to the new successor block. */
372 execute_on_growing_pred (e);
375 /* Like previous but avoid possible duplicate edge. */
378 redirect_edge_succ_nodup (edge e, basic_block new_succ)
382 s = find_edge (e->src, new_succ);
385 s->flags |= e->flags;
386 s->probability += e->probability;
387 if (s->probability > REG_BR_PROB_BASE)
388 s->probability = REG_BR_PROB_BASE;
389 s->count += e->count;
394 redirect_edge_succ (e, new_succ);
399 /* Redirect an edge's predecessor from one block to another. */
402 redirect_edge_pred (edge e, basic_block new_pred)
408 /* Reconnect the edge to the new predecessor block. */
412 /* Clear all basic block flags, with the exception of partitioning. */
414 clear_bb_flags (void)
418 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
419 bb->flags = BB_PARTITION (bb) | (bb->flags & BB_DISABLE_SCHEDULE);
422 /* Check the consistency of profile information. We can't do that
423 in verify_flow_info, as the counts may get invalid for incompletely
424 solved graphs, later eliminating of conditionals or roundoff errors.
425 It is still practical to have them reported for debugging of simple
428 check_bb_profile (basic_block bb, FILE * file)
435 if (profile_status == PROFILE_ABSENT)
438 if (bb != EXIT_BLOCK_PTR)
440 FOR_EACH_EDGE (e, ei, bb->succs)
441 sum += e->probability;
442 if (EDGE_COUNT (bb->succs) && abs (sum - REG_BR_PROB_BASE) > 100)
443 fprintf (file, "Invalid sum of outgoing probabilities %.1f%%\n",
444 sum * 100.0 / REG_BR_PROB_BASE);
446 FOR_EACH_EDGE (e, ei, bb->succs)
448 if (EDGE_COUNT (bb->succs)
449 && (lsum - bb->count > 100 || lsum - bb->count < -100))
450 fprintf (file, "Invalid sum of outgoing counts %i, should be %i\n",
451 (int) lsum, (int) bb->count);
453 if (bb != ENTRY_BLOCK_PTR)
456 FOR_EACH_EDGE (e, ei, bb->preds)
457 sum += EDGE_FREQUENCY (e);
458 if (abs (sum - bb->frequency) > 100)
460 "Invalid sum of incoming frequencies %i, should be %i\n",
463 FOR_EACH_EDGE (e, ei, bb->preds)
465 if (lsum - bb->count > 100 || lsum - bb->count < -100)
466 fprintf (file, "Invalid sum of incoming counts %i, should be %i\n",
467 (int) lsum, (int) bb->count);
472 dump_flow_info (FILE *file)
476 /* There are no pseudo registers after reload. Don't dump them. */
477 if (reg_n_info && !reload_completed)
479 unsigned int i, max = max_reg_num ();
480 fprintf (file, "%d registers.\n", max);
481 for (i = FIRST_PSEUDO_REGISTER; i < max; i++)
484 enum reg_class class, altclass;
486 fprintf (file, "\nRegister %d used %d times across %d insns",
487 i, REG_N_REFS (i), REG_LIVE_LENGTH (i));
488 if (REG_BASIC_BLOCK (i) >= 0)
489 fprintf (file, " in block %d", REG_BASIC_BLOCK (i));
491 fprintf (file, "; set %d time%s", REG_N_SETS (i),
492 (REG_N_SETS (i) == 1) ? "" : "s");
493 if (regno_reg_rtx[i] != NULL && REG_USERVAR_P (regno_reg_rtx[i]))
494 fprintf (file, "; user var");
495 if (REG_N_DEATHS (i) != 1)
496 fprintf (file, "; dies in %d places", REG_N_DEATHS (i));
497 if (REG_N_CALLS_CROSSED (i) == 1)
498 fprintf (file, "; crosses 1 call");
499 else if (REG_N_CALLS_CROSSED (i))
500 fprintf (file, "; crosses %d calls", REG_N_CALLS_CROSSED (i));
501 if (regno_reg_rtx[i] != NULL
502 && PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
503 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
505 class = reg_preferred_class (i);
506 altclass = reg_alternate_class (i);
507 if (class != GENERAL_REGS || altclass != ALL_REGS)
509 if (altclass == ALL_REGS || class == ALL_REGS)
510 fprintf (file, "; pref %s", reg_class_names[(int) class]);
511 else if (altclass == NO_REGS)
512 fprintf (file, "; %s or none", reg_class_names[(int) class]);
514 fprintf (file, "; pref %s, else %s",
515 reg_class_names[(int) class],
516 reg_class_names[(int) altclass]);
519 if (regno_reg_rtx[i] != NULL && REG_POINTER (regno_reg_rtx[i]))
520 fprintf (file, "; pointer");
521 fprintf (file, ".\n");
525 fprintf (file, "\n%d basic blocks, %d edges.\n", n_basic_blocks, n_edges);
531 fprintf (file, "\nBasic block %d ", bb->index);
532 fprintf (file, "prev %d, next %d, ",
533 bb->prev_bb->index, bb->next_bb->index);
534 fprintf (file, "loop_depth %d, count ", bb->loop_depth);
535 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, bb->count);
536 fprintf (file, ", freq %i", bb->frequency);
537 if (maybe_hot_bb_p (bb))
538 fprintf (file, ", maybe hot");
539 if (probably_never_executed_bb_p (bb))
540 fprintf (file, ", probably never executed");
541 fprintf (file, ".\n");
543 fprintf (file, "Predecessors: ");
544 FOR_EACH_EDGE (e, ei, bb->preds)
545 dump_edge_info (file, e, 0);
547 fprintf (file, "\nSuccessors: ");
548 FOR_EACH_EDGE (e, ei, bb->succs)
549 dump_edge_info (file, e, 1);
551 if (bb->global_live_at_start)
553 fprintf (file, "\nRegisters live at start:");
554 dump_regset (bb->global_live_at_start, file);
557 if (bb->global_live_at_end)
559 fprintf (file, "\nRegisters live at end:");
560 dump_regset (bb->global_live_at_end, file);
564 check_bb_profile (bb, file);
571 debug_flow_info (void)
573 dump_flow_info (stderr);
577 dump_edge_info (FILE *file, edge e, int do_succ)
579 basic_block side = (do_succ ? e->dest : e->src);
581 if (side == ENTRY_BLOCK_PTR)
582 fputs (" ENTRY", file);
583 else if (side == EXIT_BLOCK_PTR)
584 fputs (" EXIT", file);
586 fprintf (file, " %d", side->index);
589 fprintf (file, " [%.1f%%] ", e->probability * 100.0 / REG_BR_PROB_BASE);
593 fprintf (file, " count:");
594 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, e->count);
599 static const char * const bitnames[] = {
600 "fallthru", "ab", "abcall", "eh", "fake", "dfs_back",
601 "can_fallthru", "irreducible", "sibcall", "loop_exit",
602 "true", "false", "exec"
605 int i, flags = e->flags;
608 for (i = 0; flags; i++)
609 if (flags & (1 << i))
615 if (i < (int) ARRAY_SIZE (bitnames))
616 fputs (bitnames[i], file);
618 fprintf (file, "%d", i);
626 /* Simple routines to easily allocate AUX fields of basic blocks. */
628 static struct obstack block_aux_obstack;
629 static void *first_block_aux_obj = 0;
630 static struct obstack edge_aux_obstack;
631 static void *first_edge_aux_obj = 0;
633 /* Allocate a memory block of SIZE as BB->aux. The obstack must
634 be first initialized by alloc_aux_for_blocks. */
637 alloc_aux_for_block (basic_block bb, int size)
639 /* Verify that aux field is clear. */
640 gcc_assert (!bb->aux && first_block_aux_obj);
641 bb->aux = obstack_alloc (&block_aux_obstack, size);
642 memset (bb->aux, 0, size);
645 /* Initialize the block_aux_obstack and if SIZE is nonzero, call
646 alloc_aux_for_block for each basic block. */
649 alloc_aux_for_blocks (int size)
651 static int initialized;
655 gcc_obstack_init (&block_aux_obstack);
659 /* Check whether AUX data are still allocated. */
660 gcc_assert (!first_block_aux_obj);
662 first_block_aux_obj = obstack_alloc (&block_aux_obstack, 0);
667 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
668 alloc_aux_for_block (bb, size);
672 /* Clear AUX pointers of all blocks. */
675 clear_aux_for_blocks (void)
679 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
683 /* Free data allocated in block_aux_obstack and clear AUX pointers
687 free_aux_for_blocks (void)
689 gcc_assert (first_block_aux_obj);
690 obstack_free (&block_aux_obstack, first_block_aux_obj);
691 first_block_aux_obj = NULL;
693 clear_aux_for_blocks ();
696 /* Allocate a memory edge of SIZE as BB->aux. The obstack must
697 be first initialized by alloc_aux_for_edges. */
700 alloc_aux_for_edge (edge e, int size)
702 /* Verify that aux field is clear. */
703 gcc_assert (!e->aux && first_edge_aux_obj);
704 e->aux = obstack_alloc (&edge_aux_obstack, size);
705 memset (e->aux, 0, size);
708 /* Initialize the edge_aux_obstack and if SIZE is nonzero, call
709 alloc_aux_for_edge for each basic edge. */
712 alloc_aux_for_edges (int size)
714 static int initialized;
718 gcc_obstack_init (&edge_aux_obstack);
722 /* Check whether AUX data are still allocated. */
723 gcc_assert (!first_edge_aux_obj);
725 first_edge_aux_obj = obstack_alloc (&edge_aux_obstack, 0);
730 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
735 FOR_EACH_EDGE (e, ei, bb->succs)
736 alloc_aux_for_edge (e, size);
741 /* Clear AUX pointers of all edges. */
744 clear_aux_for_edges (void)
749 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
752 FOR_EACH_EDGE (e, ei, bb->succs)
757 /* Free data allocated in edge_aux_obstack and clear AUX pointers
761 free_aux_for_edges (void)
763 gcc_assert (first_edge_aux_obj);
764 obstack_free (&edge_aux_obstack, first_edge_aux_obj);
765 first_edge_aux_obj = NULL;
767 clear_aux_for_edges ();
771 debug_bb (basic_block bb)
773 dump_bb (bb, stderr, 0);
779 basic_block bb = BASIC_BLOCK (n);
780 dump_bb (bb, stderr, 0);
784 /* Dumps cfg related information about basic block BB to FILE. */
787 dump_cfg_bb_info (FILE *file, basic_block bb)
792 static const char * const bb_bitnames[] =
794 "dirty", "new", "reachable", "visited", "irreducible_loop", "superblock"
796 const unsigned n_bitnames = sizeof (bb_bitnames) / sizeof (char *);
799 fprintf (file, "Basic block %d", bb->index);
800 for (i = 0; i < n_bitnames; i++)
801 if (bb->flags & (1 << i))
804 fprintf (file, " (");
806 fprintf (file, ", ");
808 fprintf (file, bb_bitnames[i]);
812 fprintf (file, "\n");
814 fprintf (file, "Predecessors: ");
815 FOR_EACH_EDGE (e, ei, bb->preds)
816 dump_edge_info (file, e, 0);
818 fprintf (file, "\nSuccessors: ");
819 FOR_EACH_EDGE (e, ei, bb->succs)
820 dump_edge_info (file, e, 1);
821 fprintf (file, "\n\n");
824 /* Dumps a brief description of cfg to FILE. */
827 brief_dump_cfg (FILE *file)
833 dump_cfg_bb_info (file, bb);
837 /* An edge originally destinating BB of FREQUENCY and COUNT has been proved to
838 leave the block by TAKEN_EDGE. Update profile of BB such that edge E can be
839 redirected to destination of TAKEN_EDGE.
841 This function may leave the profile inconsistent in the case TAKEN_EDGE
842 frequency or count is believed to be lower than FREQUENCY or COUNT
845 update_bb_profile_for_threading (basic_block bb, int edge_frequency,
846 gcov_type count, edge taken_edge)
856 /* Compute the probability of TAKEN_EDGE being reached via threaded edge.
857 Watch for overflows. */
859 prob = edge_frequency * REG_BR_PROB_BASE / bb->frequency;
862 if (prob > taken_edge->probability)
865 fprintf (dump_file, "Jump threading proved probability of edge "
866 "%i->%i too small (it is %i, should be %i).\n",
867 taken_edge->src->index, taken_edge->dest->index,
868 taken_edge->probability, prob);
869 prob = taken_edge->probability;
872 /* Now rescale the probabilities. */
873 taken_edge->probability -= prob;
874 prob = REG_BR_PROB_BASE - prob;
875 bb->frequency -= edge_frequency;
876 if (bb->frequency < 0)
881 fprintf (dump_file, "Edge frequencies of bb %i has been reset, "
882 "frequency of block should end up being 0, it is %i\n",
883 bb->index, bb->frequency);
884 EDGE_SUCC (bb, 0)->probability = REG_BR_PROB_BASE;
885 ei = ei_start (bb->succs);
887 for (; (c = ei_safe_edge (ei)); ei_next (&ei))
890 else if (prob != REG_BR_PROB_BASE)
892 int scale = 65536 * REG_BR_PROB_BASE / prob;
894 FOR_EACH_EDGE (c, ei, bb->succs)
895 c->probability *= scale / 65536;
898 gcc_assert (bb == taken_edge->src);
899 taken_edge->count -= count;
900 if (taken_edge->count < 0)
901 taken_edge->count = 0;
904 /* Multiply all frequencies of basic blocks in array BBS of length NBBS
905 by NUM/DEN, in int arithmetic. May lose some accuracy. */
907 scale_bbs_frequencies_int (basic_block *bbs, int nbbs, int num, int den)
911 for (i = 0; i < nbbs; i++)
914 bbs[i]->frequency = (bbs[i]->frequency * num) / den;
915 bbs[i]->count = RDIV (bbs[i]->count * num, den);
916 FOR_EACH_EDGE (e, ei, bbs[i]->succs)
917 e->count = (e->count * num) /den;
921 /* Multiply all frequencies of basic blocks in array BBS of length NBBS
922 by NUM/DEN, in gcov_type arithmetic. More accurate than previous
923 function but considerably slower. */
925 scale_bbs_frequencies_gcov_type (basic_block *bbs, int nbbs, gcov_type num,
931 for (i = 0; i < nbbs; i++)
934 bbs[i]->frequency = (bbs[i]->frequency * num) / den;
935 bbs[i]->count = RDIV (bbs[i]->count * num, den);
936 FOR_EACH_EDGE (e, ei, bbs[i]->succs)
937 e->count = (e->count * num) /den;