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 Free Software Foundation, Inc.
5 This file is part of GCC.
7 GCC is free software; you can redistribute it and/or modify it under
8 the terms of the GNU General Public License as published by the Free
9 Software Foundation; either version 2, or (at your option) any later
12 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
17 You should have received a copy of the GNU General Public License
18 along with GCC; see the file COPYING. If not, write to the Free
19 Software Foundation, 59 Temple Place - Suite 330, Boston, MA
22 /* This file contains low level functions to manipulate the CFG and
23 analyze it. All other modules should not transform the data structure
24 directly and use abstraction instead. The file is supposed to be
25 ordered bottom-up and should not contain any code dependent on a
26 particular intermediate language (RTL or trees).
28 Available functionality:
29 - Initialization/deallocation
30 init_flow, clear_edges
31 - Low level basic block manipulation
32 alloc_block, expunge_block
34 make_edge, make_single_succ_edge, cached_make_edge, remove_edge
35 - Low level edge redirection (without updating instruction chain)
36 redirect_edge_succ, redirect_edge_succ_nodup, redirect_edge_pred
37 - Dumping and debugging
38 dump_flow_info, debug_flow_info, dump_edge_info
39 - Allocation of AUX fields for basic blocks
40 alloc_aux_for_blocks, free_aux_for_blocks, alloc_aux_for_block
42 - Consistency checking
44 - Dumping and debugging
45 print_rtl_with_bb, dump_bb, debug_bb, debug_bb_n
50 #include "coretypes.h"
54 #include "hard-reg-set.h"
62 #include "alloc-pool.h"
66 /* The obstack on which the flow graph components are allocated. */
68 struct bitmap_obstack reg_obstack;
69 struct obstack flow_obstack;
70 static char *flow_firstobj;
72 /* Number of basic blocks in the current function. */
76 /* First free basic block number. */
80 /* Number of edges in the current function. */
84 /* The basic block array. */
86 varray_type basic_block_info;
88 /* The special entry and exit blocks. */
89 basic_block ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR;
91 /* Memory alloc pool for bb member rbi. */
94 void debug_flow_info (void);
95 static void free_edge (edge);
97 /* Indicate the presence of the profile. */
98 enum profile_status profile_status;
100 /* Called once at initialization time. */
105 static int initialized;
111 gcc_obstack_init (&flow_obstack);
112 flow_firstobj = obstack_alloc (&flow_obstack, 0);
117 obstack_free (&flow_obstack, flow_firstobj);
118 flow_firstobj = obstack_alloc (&flow_obstack, 0);
121 ENTRY_BLOCK_PTR = ggc_alloc_cleared (sizeof (*ENTRY_BLOCK_PTR));
122 ENTRY_BLOCK_PTR->index = ENTRY_BLOCK;
123 EXIT_BLOCK_PTR = ggc_alloc_cleared (sizeof (*EXIT_BLOCK_PTR));
124 EXIT_BLOCK_PTR->index = EXIT_BLOCK;
125 ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR;
126 EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR;
129 /* Helper function for remove_edge and clear_edges. Frees edge structure
130 without actually unlinking it from the pred/succ lists. */
133 free_edge (edge e ATTRIBUTE_UNUSED)
139 /* Free the memory associated with the edge structures. */
150 FOR_EACH_EDGE (e, ei, bb->succs)
152 VEC_truncate (edge, bb->succs, 0);
153 VEC_truncate (edge, bb->preds, 0);
156 FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
158 VEC_truncate (edge, EXIT_BLOCK_PTR->preds, 0);
159 VEC_truncate (edge, ENTRY_BLOCK_PTR->succs, 0);
161 gcc_assert (!n_edges);
164 /* Allocate memory for basic_block. */
170 bb = ggc_alloc_cleared (sizeof (*bb));
174 /* Create memory pool for rbi_pool. */
177 alloc_rbi_pool (void)
179 rbi_pool = create_alloc_pool ("rbi pool",
180 sizeof (struct reorder_block_def),
189 free_alloc_pool (rbi_pool);
192 /* Initialize rbi (the structure containing data used by basic block
193 duplication and reordering) for the given basic block. */
196 initialize_bb_rbi (basic_block bb)
198 gcc_assert (!bb->rbi);
199 bb->rbi = pool_alloc (rbi_pool);
200 memset (bb->rbi, 0, sizeof (struct reorder_block_def));
203 /* Link block B to chain after AFTER. */
205 link_block (basic_block b, basic_block after)
207 b->next_bb = after->next_bb;
210 b->next_bb->prev_bb = b;
213 /* Unlink block B from chain. */
215 unlink_block (basic_block b)
217 b->next_bb->prev_bb = b->prev_bb;
218 b->prev_bb->next_bb = b->next_bb;
223 /* Sequentially order blocks and compact the arrays. */
225 compact_blocks (void)
233 BASIC_BLOCK (i) = bb;
238 gcc_assert (i == n_basic_blocks);
240 for (; i < last_basic_block; i++)
241 BASIC_BLOCK (i) = NULL;
243 last_basic_block = n_basic_blocks;
246 /* Remove block B from the basic block array. */
249 expunge_block (basic_block b)
252 BASIC_BLOCK (b->index) = NULL;
254 /* We should be able to ggc_free here, but we are not.
255 The dead SSA_NAMES are left pointing to dead statements that are pointing
256 to dead basic blocks making garbage collector to die.
257 We should be able to release all dead SSA_NAMES and at the same time we should
258 clear out BB pointer of dead statements consistently. */
261 /* Create an edge connecting SRC and DEST with flags FLAGS. Return newly
262 created edge. Use this only if you are sure that this edge can't
263 possibly already exist. */
266 unchecked_make_edge (basic_block src, basic_block dst, int flags)
269 e = ggc_alloc_cleared (sizeof (*e));
272 VEC_safe_push (edge, src->succs, e);
273 VEC_safe_push (edge, dst->preds, e);
278 e->dest_idx = EDGE_COUNT (dst->preds) - 1;
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)
293 /* Don't bother with edge cache for ENTRY or EXIT, if there aren't that
294 many edges to them, or we didn't allocate memory for it. */
295 use_edge_cache = (edge_cache
296 && src != ENTRY_BLOCK_PTR && dst != EXIT_BLOCK_PTR);
298 /* Make sure we don't add duplicate edges. */
299 switch (use_edge_cache)
302 /* Quick test for non-existence of the edge. */
303 if (! TEST_BIT (edge_cache[src->index], dst->index))
306 /* The edge exists; early exit if no work to do. */
312 FOR_EACH_EDGE (e, ei, src->succs)
321 e = unchecked_make_edge (src, dst, flags);
324 SET_BIT (edge_cache[src->index], dst->index);
329 /* Create an edge connecting SRC and DEST with flags FLAGS. Return newly
330 created edge or NULL if already exist. */
333 make_edge (basic_block src, basic_block dest, int flags)
335 return cached_make_edge (NULL, src, dest, flags);
338 /* Create an edge connecting SRC to DEST and set probability by knowing
339 that it is the single edge leaving SRC. */
342 make_single_succ_edge (basic_block src, basic_block dest, int flags)
344 edge e = make_edge (src, dest, flags);
346 e->probability = REG_BR_PROB_BASE;
347 e->count = src->count;
351 /* This function will remove an edge from the flow graph. */
357 basic_block src, dest;
358 unsigned int dest_idx;
364 dest_idx = e->dest_idx;
366 for (ei = ei_start (src->succs); (tmp = ei_safe_edge (ei)); )
370 VEC_unordered_remove (edge, src->succs, ei.index);
380 VEC_unordered_remove (edge, dest->preds, dest_idx);
382 /* If we removed an edge in the middle of the edge vector, we need
383 to update dest_idx of the edge that moved into the "hole". */
384 if (dest_idx < EDGE_COUNT (dest->preds))
385 EDGE_PRED (dest, dest_idx)->dest_idx = dest_idx;
390 /* Redirect an edge's successor from one block to another. */
393 redirect_edge_succ (edge e, basic_block new_succ)
395 basic_block dest = e->dest;
396 unsigned int dest_idx = e->dest_idx;
398 VEC_unordered_remove (edge, dest->preds, dest_idx);
400 /* If we removed an edge in the middle of the edge vector, we need
401 to update dest_idx of the edge that moved into the "hole". */
402 if (dest_idx < EDGE_COUNT (dest->preds))
403 EDGE_PRED (dest, dest_idx)->dest_idx = dest_idx;
405 /* Reconnect the edge to the new successor block. */
406 VEC_safe_push (edge, new_succ->preds, e);
408 e->dest_idx = EDGE_COUNT (new_succ->preds) - 1;
411 /* Like previous but avoid possible duplicate edge. */
414 redirect_edge_succ_nodup (edge e, basic_block new_succ)
418 s = find_edge (e->src, new_succ);
421 s->flags |= e->flags;
422 s->probability += e->probability;
423 if (s->probability > REG_BR_PROB_BASE)
424 s->probability = REG_BR_PROB_BASE;
425 s->count += e->count;
430 redirect_edge_succ (e, new_succ);
435 /* Redirect an edge's predecessor from one block to another. */
438 redirect_edge_pred (edge e, basic_block new_pred)
444 /* Disconnect the edge from the old predecessor block. */
445 for (ei = ei_start (e->src->succs); (tmp = ei_safe_edge (ei)); )
449 VEC_unordered_remove (edge, e->src->succs, ei.index);
459 /* Reconnect the edge to the new predecessor block. */
460 VEC_safe_push (edge, new_pred->succs, e);
464 /* Clear all basic block flags, with the exception of partitioning. */
466 clear_bb_flags (void)
470 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
471 bb->flags = BB_PARTITION (bb);
474 /* Check the consistency of profile information. We can't do that
475 in verify_flow_info, as the counts may get invalid for incompletely
476 solved graphs, later eliminating of conditionals or roundoff errors.
477 It is still practical to have them reported for debugging of simple
480 check_bb_profile (basic_block bb, FILE * file)
487 if (profile_status == PROFILE_ABSENT)
490 if (bb != EXIT_BLOCK_PTR)
492 FOR_EACH_EDGE (e, ei, bb->succs)
493 sum += e->probability;
494 if (EDGE_COUNT (bb->succs) && abs (sum - REG_BR_PROB_BASE) > 100)
495 fprintf (file, "Invalid sum of outgoing probabilities %.1f%%\n",
496 sum * 100.0 / REG_BR_PROB_BASE);
498 FOR_EACH_EDGE (e, ei, bb->succs)
500 if (EDGE_COUNT (bb->succs)
501 && (lsum - bb->count > 100 || lsum - bb->count < -100))
502 fprintf (file, "Invalid sum of outgoing counts %i, should be %i\n",
503 (int) lsum, (int) bb->count);
505 if (bb != ENTRY_BLOCK_PTR)
508 FOR_EACH_EDGE (e, ei, bb->preds)
509 sum += EDGE_FREQUENCY (e);
510 if (abs (sum - bb->frequency) > 100)
512 "Invalid sum of incoming frequencies %i, should be %i\n",
515 FOR_EACH_EDGE (e, ei, bb->preds)
517 if (lsum - bb->count > 100 || lsum - bb->count < -100)
518 fprintf (file, "Invalid sum of incoming counts %i, should be %i\n",
519 (int) lsum, (int) bb->count);
524 dump_flow_info (FILE *file)
528 static const char * const reg_class_names[] = REG_CLASS_NAMES;
532 int max_regno = max_reg_num ();
533 fprintf (file, "%d registers.\n", max_regno);
534 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
537 enum reg_class class, altclass;
539 fprintf (file, "\nRegister %d used %d times across %d insns",
540 i, REG_N_REFS (i), REG_LIVE_LENGTH (i));
541 if (REG_BASIC_BLOCK (i) >= 0)
542 fprintf (file, " in block %d", REG_BASIC_BLOCK (i));
544 fprintf (file, "; set %d time%s", REG_N_SETS (i),
545 (REG_N_SETS (i) == 1) ? "" : "s");
546 if (regno_reg_rtx[i] != NULL && REG_USERVAR_P (regno_reg_rtx[i]))
547 fprintf (file, "; user var");
548 if (REG_N_DEATHS (i) != 1)
549 fprintf (file, "; dies in %d places", REG_N_DEATHS (i));
550 if (REG_N_CALLS_CROSSED (i) == 1)
551 fprintf (file, "; crosses 1 call");
552 else if (REG_N_CALLS_CROSSED (i))
553 fprintf (file, "; crosses %d calls", REG_N_CALLS_CROSSED (i));
554 if (regno_reg_rtx[i] != NULL
555 && PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
556 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
558 class = reg_preferred_class (i);
559 altclass = reg_alternate_class (i);
560 if (class != GENERAL_REGS || altclass != ALL_REGS)
562 if (altclass == ALL_REGS || class == ALL_REGS)
563 fprintf (file, "; pref %s", reg_class_names[(int) class]);
564 else if (altclass == NO_REGS)
565 fprintf (file, "; %s or none", reg_class_names[(int) class]);
567 fprintf (file, "; pref %s, else %s",
568 reg_class_names[(int) class],
569 reg_class_names[(int) altclass]);
572 if (regno_reg_rtx[i] != NULL && REG_POINTER (regno_reg_rtx[i]))
573 fprintf (file, "; pointer");
574 fprintf (file, ".\n");
578 fprintf (file, "\n%d basic blocks, %d edges.\n", n_basic_blocks, n_edges);
584 fprintf (file, "\nBasic block %d ", bb->index);
585 fprintf (file, "prev %d, next %d, ",
586 bb->prev_bb->index, bb->next_bb->index);
587 fprintf (file, "loop_depth %d, count ", bb->loop_depth);
588 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, bb->count);
589 fprintf (file, ", freq %i", bb->frequency);
590 if (maybe_hot_bb_p (bb))
591 fprintf (file, ", maybe hot");
592 if (probably_never_executed_bb_p (bb))
593 fprintf (file, ", probably never executed");
594 fprintf (file, ".\n");
596 fprintf (file, "Predecessors: ");
597 FOR_EACH_EDGE (e, ei, bb->preds)
598 dump_edge_info (file, e, 0);
600 fprintf (file, "\nSuccessors: ");
601 FOR_EACH_EDGE (e, ei, bb->succs)
602 dump_edge_info (file, e, 1);
604 if (bb->global_live_at_start)
606 fprintf (file, "\nRegisters live at start:");
607 dump_regset (bb->global_live_at_start, file);
610 if (bb->global_live_at_end)
612 fprintf (file, "\nRegisters live at end:");
613 dump_regset (bb->global_live_at_end, file);
617 check_bb_profile (bb, file);
624 debug_flow_info (void)
626 dump_flow_info (stderr);
630 dump_edge_info (FILE *file, edge e, int do_succ)
632 basic_block side = (do_succ ? e->dest : e->src);
634 if (side == ENTRY_BLOCK_PTR)
635 fputs (" ENTRY", file);
636 else if (side == EXIT_BLOCK_PTR)
637 fputs (" EXIT", file);
639 fprintf (file, " %d", side->index);
642 fprintf (file, " [%.1f%%] ", e->probability * 100.0 / REG_BR_PROB_BASE);
646 fprintf (file, " count:");
647 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, e->count);
652 static const char * const bitnames[] = {
653 "fallthru", "ab", "abcall", "eh", "fake", "dfs_back",
654 "can_fallthru", "irreducible", "sibcall", "loop_exit",
655 "true", "false", "exec"
658 int i, flags = e->flags;
661 for (i = 0; flags; i++)
662 if (flags & (1 << i))
668 if (i < (int) ARRAY_SIZE (bitnames))
669 fputs (bitnames[i], file);
671 fprintf (file, "%d", i);
679 /* Simple routines to easily allocate AUX fields of basic blocks. */
681 static struct obstack block_aux_obstack;
682 static void *first_block_aux_obj = 0;
683 static struct obstack edge_aux_obstack;
684 static void *first_edge_aux_obj = 0;
686 /* Allocate a memory block of SIZE as BB->aux. The obstack must
687 be first initialized by alloc_aux_for_blocks. */
690 alloc_aux_for_block (basic_block bb, int size)
692 /* Verify that aux field is clear. */
693 gcc_assert (!bb->aux && first_block_aux_obj);
694 bb->aux = obstack_alloc (&block_aux_obstack, size);
695 memset (bb->aux, 0, size);
698 /* Initialize the block_aux_obstack and if SIZE is nonzero, call
699 alloc_aux_for_block for each basic block. */
702 alloc_aux_for_blocks (int size)
704 static int initialized;
708 gcc_obstack_init (&block_aux_obstack);
712 /* Check whether AUX data are still allocated. */
713 gcc_assert (!first_block_aux_obj);
715 first_block_aux_obj = obstack_alloc (&block_aux_obstack, 0);
720 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
721 alloc_aux_for_block (bb, size);
725 /* Clear AUX pointers of all blocks. */
728 clear_aux_for_blocks (void)
732 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
736 /* Free data allocated in block_aux_obstack and clear AUX pointers
740 free_aux_for_blocks (void)
742 gcc_assert (first_block_aux_obj);
743 obstack_free (&block_aux_obstack, first_block_aux_obj);
744 first_block_aux_obj = NULL;
746 clear_aux_for_blocks ();
749 /* Allocate a memory edge of SIZE as BB->aux. The obstack must
750 be first initialized by alloc_aux_for_edges. */
753 alloc_aux_for_edge (edge e, int size)
755 /* Verify that aux field is clear. */
756 gcc_assert (!e->aux && first_edge_aux_obj);
757 e->aux = obstack_alloc (&edge_aux_obstack, size);
758 memset (e->aux, 0, size);
761 /* Initialize the edge_aux_obstack and if SIZE is nonzero, call
762 alloc_aux_for_edge for each basic edge. */
765 alloc_aux_for_edges (int size)
767 static int initialized;
771 gcc_obstack_init (&edge_aux_obstack);
775 /* Check whether AUX data are still allocated. */
776 gcc_assert (!first_edge_aux_obj);
778 first_edge_aux_obj = obstack_alloc (&edge_aux_obstack, 0);
783 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
788 FOR_EACH_EDGE (e, ei, bb->succs)
789 alloc_aux_for_edge (e, size);
794 /* Clear AUX pointers of all edges. */
797 clear_aux_for_edges (void)
802 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
805 FOR_EACH_EDGE (e, ei, bb->succs)
810 /* Free data allocated in edge_aux_obstack and clear AUX pointers
814 free_aux_for_edges (void)
816 gcc_assert (first_edge_aux_obj);
817 obstack_free (&edge_aux_obstack, first_edge_aux_obj);
818 first_edge_aux_obj = NULL;
820 clear_aux_for_edges ();
824 debug_bb (basic_block bb)
826 dump_bb (bb, stderr, 0);
832 basic_block bb = BASIC_BLOCK (n);
833 dump_bb (bb, stderr, 0);
837 /* Dumps cfg related information about basic block BB to FILE. */
840 dump_cfg_bb_info (FILE *file, basic_block bb)
845 static const char * const bb_bitnames[] =
847 "dirty", "new", "reachable", "visited", "irreducible_loop", "superblock"
849 const unsigned n_bitnames = sizeof (bb_bitnames) / sizeof (char *);
852 fprintf (file, "Basic block %d", bb->index);
853 for (i = 0; i < n_bitnames; i++)
854 if (bb->flags & (1 << i))
857 fprintf (file, " (");
859 fprintf (file, ", ");
861 fprintf (file, bb_bitnames[i]);
865 fprintf (file, "\n");
867 fprintf (file, "Predecessors: ");
868 FOR_EACH_EDGE (e, ei, bb->preds)
869 dump_edge_info (file, e, 0);
871 fprintf (file, "\nSuccessors: ");
872 FOR_EACH_EDGE (e, ei, bb->succs)
873 dump_edge_info (file, e, 1);
874 fprintf (file, "\n\n");
877 /* Dumps a brief description of cfg to FILE. */
880 brief_dump_cfg (FILE *file)
886 dump_cfg_bb_info (file, bb);
890 /* An edge originally destinating BB of FREQUENCY and COUNT has been proved to
891 leave the block by TAKEN_EDGE. Update profile of BB such that edge E can be
892 redirected to destination of TAKEN_EDGE.
894 This function may leave the profile inconsistent in the case TAKEN_EDGE
895 frequency or count is believed to be lower than FREQUENCY or COUNT
898 update_bb_profile_for_threading (basic_block bb, int edge_frequency,
899 gcov_type count, edge taken_edge)
909 /* Compute the probability of TAKEN_EDGE being reached via threaded edge.
910 Watch for overflows. */
912 prob = edge_frequency * REG_BR_PROB_BASE / bb->frequency;
915 if (prob > taken_edge->probability)
918 fprintf (dump_file, "Jump threading proved probability of edge "
919 "%i->%i too small (it is %i, should be %i).\n",
920 taken_edge->src->index, taken_edge->dest->index,
921 taken_edge->probability, prob);
922 prob = taken_edge->probability;
925 /* Now rescale the probabilities. */
926 taken_edge->probability -= prob;
927 prob = REG_BR_PROB_BASE - prob;
928 bb->frequency -= edge_frequency;
929 if (bb->frequency < 0)
934 fprintf (dump_file, "Edge frequencies of bb %i has been reset, "
935 "frequency of block should end up being 0, it is %i\n",
936 bb->index, bb->frequency);
937 EDGE_SUCC (bb, 0)->probability = REG_BR_PROB_BASE;
938 ei = ei_start (bb->succs);
940 for (; (c = ei_safe_edge (ei)); ei_next (&ei))
943 else if (prob != REG_BR_PROB_BASE)
945 int scale = REG_BR_PROB_BASE / prob;
947 FOR_EACH_EDGE (c, ei, bb->succs)
948 c->probability *= scale;
951 if (bb != taken_edge->src)
953 taken_edge->count -= count;
954 if (taken_edge->count < 0)
955 taken_edge->count = 0;