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;
280 execute_on_growing_pred (e);
285 /* Create an edge connecting SRC and DST with FLAGS optionally using
286 edge cache CACHE. Return the new edge, NULL if already exist. */
289 cached_make_edge (sbitmap *edge_cache, basic_block src, basic_block dst, int flags)
294 /* Don't bother with edge cache for ENTRY or EXIT, if there aren't that
295 many edges to them, or we didn't allocate memory for it. */
296 use_edge_cache = (edge_cache
297 && src != ENTRY_BLOCK_PTR && dst != EXIT_BLOCK_PTR);
299 /* Make sure we don't add duplicate edges. */
300 switch (use_edge_cache)
303 /* Quick test for non-existence of the edge. */
304 if (! TEST_BIT (edge_cache[src->index], dst->index))
307 /* The edge exists; early exit if no work to do. */
313 e = find_edge (src, dst);
322 e = unchecked_make_edge (src, dst, flags);
325 SET_BIT (edge_cache[src->index], dst->index);
330 /* Create an edge connecting SRC and DEST with flags FLAGS. Return newly
331 created edge or NULL if already exist. */
334 make_edge (basic_block src, basic_block dest, int flags)
336 return cached_make_edge (NULL, src, dest, flags);
339 /* Create an edge connecting SRC to DEST and set probability by knowing
340 that it is the single edge leaving SRC. */
343 make_single_succ_edge (basic_block src, basic_block dest, int flags)
345 edge e = make_edge (src, dest, flags);
347 e->probability = REG_BR_PROB_BASE;
348 e->count = src->count;
352 /* This function will remove an edge from the flow graph. */
358 basic_block src, dest;
359 unsigned int dest_idx;
363 execute_on_shrinking_pred (e);
367 dest_idx = e->dest_idx;
369 for (ei = ei_start (src->succs); (tmp = ei_safe_edge (ei)); )
373 VEC_unordered_remove (edge, src->succs, ei.index);
383 VEC_unordered_remove (edge, dest->preds, dest_idx);
385 /* If we removed an edge in the middle of the edge vector, we need
386 to update dest_idx of the edge that moved into the "hole". */
387 if (dest_idx < EDGE_COUNT (dest->preds))
388 EDGE_PRED (dest, dest_idx)->dest_idx = dest_idx;
393 /* Redirect an edge's successor from one block to another. */
396 redirect_edge_succ (edge e, basic_block new_succ)
398 basic_block dest = e->dest;
399 unsigned int dest_idx = e->dest_idx;
401 execute_on_shrinking_pred (e);
403 VEC_unordered_remove (edge, dest->preds, dest_idx);
405 /* If we removed an edge in the middle of the edge vector, we need
406 to update dest_idx of the edge that moved into the "hole". */
407 if (dest_idx < EDGE_COUNT (dest->preds))
408 EDGE_PRED (dest, dest_idx)->dest_idx = dest_idx;
410 /* Reconnect the edge to the new successor block. */
411 VEC_safe_push (edge, new_succ->preds, e);
413 e->dest_idx = EDGE_COUNT (new_succ->preds) - 1;
414 execute_on_growing_pred (e);
417 /* Like previous but avoid possible duplicate edge. */
420 redirect_edge_succ_nodup (edge e, basic_block new_succ)
424 s = find_edge (e->src, new_succ);
427 s->flags |= e->flags;
428 s->probability += e->probability;
429 if (s->probability > REG_BR_PROB_BASE)
430 s->probability = REG_BR_PROB_BASE;
431 s->count += e->count;
436 redirect_edge_succ (e, new_succ);
441 /* Redirect an edge's predecessor from one block to another. */
444 redirect_edge_pred (edge e, basic_block new_pred)
450 /* Disconnect the edge from the old predecessor block. */
451 for (ei = ei_start (e->src->succs); (tmp = ei_safe_edge (ei)); )
455 VEC_unordered_remove (edge, e->src->succs, ei.index);
465 /* Reconnect the edge to the new predecessor block. */
466 VEC_safe_push (edge, new_pred->succs, e);
470 /* Clear all basic block flags, with the exception of partitioning. */
472 clear_bb_flags (void)
476 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
477 bb->flags = BB_PARTITION (bb);
480 /* Check the consistency of profile information. We can't do that
481 in verify_flow_info, as the counts may get invalid for incompletely
482 solved graphs, later eliminating of conditionals or roundoff errors.
483 It is still practical to have them reported for debugging of simple
486 check_bb_profile (basic_block bb, FILE * file)
493 if (profile_status == PROFILE_ABSENT)
496 if (bb != EXIT_BLOCK_PTR)
498 FOR_EACH_EDGE (e, ei, bb->succs)
499 sum += e->probability;
500 if (EDGE_COUNT (bb->succs) && abs (sum - REG_BR_PROB_BASE) > 100)
501 fprintf (file, "Invalid sum of outgoing probabilities %.1f%%\n",
502 sum * 100.0 / REG_BR_PROB_BASE);
504 FOR_EACH_EDGE (e, ei, bb->succs)
506 if (EDGE_COUNT (bb->succs)
507 && (lsum - bb->count > 100 || lsum - bb->count < -100))
508 fprintf (file, "Invalid sum of outgoing counts %i, should be %i\n",
509 (int) lsum, (int) bb->count);
511 if (bb != ENTRY_BLOCK_PTR)
514 FOR_EACH_EDGE (e, ei, bb->preds)
515 sum += EDGE_FREQUENCY (e);
516 if (abs (sum - bb->frequency) > 100)
518 "Invalid sum of incoming frequencies %i, should be %i\n",
521 FOR_EACH_EDGE (e, ei, bb->preds)
523 if (lsum - bb->count > 100 || lsum - bb->count < -100)
524 fprintf (file, "Invalid sum of incoming counts %i, should be %i\n",
525 (int) lsum, (int) bb->count);
530 dump_flow_info (FILE *file)
534 static const char * const reg_class_names[] = REG_CLASS_NAMES;
538 int max_regno = max_reg_num ();
539 fprintf (file, "%d registers.\n", max_regno);
540 for (i = FIRST_PSEUDO_REGISTER; i < max_regno; i++)
543 enum reg_class class, altclass;
545 fprintf (file, "\nRegister %d used %d times across %d insns",
546 i, REG_N_REFS (i), REG_LIVE_LENGTH (i));
547 if (REG_BASIC_BLOCK (i) >= 0)
548 fprintf (file, " in block %d", REG_BASIC_BLOCK (i));
550 fprintf (file, "; set %d time%s", REG_N_SETS (i),
551 (REG_N_SETS (i) == 1) ? "" : "s");
552 if (regno_reg_rtx[i] != NULL && REG_USERVAR_P (regno_reg_rtx[i]))
553 fprintf (file, "; user var");
554 if (REG_N_DEATHS (i) != 1)
555 fprintf (file, "; dies in %d places", REG_N_DEATHS (i));
556 if (REG_N_CALLS_CROSSED (i) == 1)
557 fprintf (file, "; crosses 1 call");
558 else if (REG_N_CALLS_CROSSED (i))
559 fprintf (file, "; crosses %d calls", REG_N_CALLS_CROSSED (i));
560 if (regno_reg_rtx[i] != NULL
561 && PSEUDO_REGNO_BYTES (i) != UNITS_PER_WORD)
562 fprintf (file, "; %d bytes", PSEUDO_REGNO_BYTES (i));
564 class = reg_preferred_class (i);
565 altclass = reg_alternate_class (i);
566 if (class != GENERAL_REGS || altclass != ALL_REGS)
568 if (altclass == ALL_REGS || class == ALL_REGS)
569 fprintf (file, "; pref %s", reg_class_names[(int) class]);
570 else if (altclass == NO_REGS)
571 fprintf (file, "; %s or none", reg_class_names[(int) class]);
573 fprintf (file, "; pref %s, else %s",
574 reg_class_names[(int) class],
575 reg_class_names[(int) altclass]);
578 if (regno_reg_rtx[i] != NULL && REG_POINTER (regno_reg_rtx[i]))
579 fprintf (file, "; pointer");
580 fprintf (file, ".\n");
584 fprintf (file, "\n%d basic blocks, %d edges.\n", n_basic_blocks, n_edges);
590 fprintf (file, "\nBasic block %d ", bb->index);
591 fprintf (file, "prev %d, next %d, ",
592 bb->prev_bb->index, bb->next_bb->index);
593 fprintf (file, "loop_depth %d, count ", bb->loop_depth);
594 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, bb->count);
595 fprintf (file, ", freq %i", bb->frequency);
596 if (maybe_hot_bb_p (bb))
597 fprintf (file, ", maybe hot");
598 if (probably_never_executed_bb_p (bb))
599 fprintf (file, ", probably never executed");
600 fprintf (file, ".\n");
602 fprintf (file, "Predecessors: ");
603 FOR_EACH_EDGE (e, ei, bb->preds)
604 dump_edge_info (file, e, 0);
606 fprintf (file, "\nSuccessors: ");
607 FOR_EACH_EDGE (e, ei, bb->succs)
608 dump_edge_info (file, e, 1);
610 if (bb->global_live_at_start)
612 fprintf (file, "\nRegisters live at start:");
613 dump_regset (bb->global_live_at_start, file);
616 if (bb->global_live_at_end)
618 fprintf (file, "\nRegisters live at end:");
619 dump_regset (bb->global_live_at_end, file);
623 check_bb_profile (bb, file);
630 debug_flow_info (void)
632 dump_flow_info (stderr);
636 dump_edge_info (FILE *file, edge e, int do_succ)
638 basic_block side = (do_succ ? e->dest : e->src);
640 if (side == ENTRY_BLOCK_PTR)
641 fputs (" ENTRY", file);
642 else if (side == EXIT_BLOCK_PTR)
643 fputs (" EXIT", file);
645 fprintf (file, " %d", side->index);
648 fprintf (file, " [%.1f%%] ", e->probability * 100.0 / REG_BR_PROB_BASE);
652 fprintf (file, " count:");
653 fprintf (file, HOST_WIDEST_INT_PRINT_DEC, e->count);
658 static const char * const bitnames[] = {
659 "fallthru", "ab", "abcall", "eh", "fake", "dfs_back",
660 "can_fallthru", "irreducible", "sibcall", "loop_exit",
661 "true", "false", "exec"
664 int i, flags = e->flags;
667 for (i = 0; flags; i++)
668 if (flags & (1 << i))
674 if (i < (int) ARRAY_SIZE (bitnames))
675 fputs (bitnames[i], file);
677 fprintf (file, "%d", i);
685 /* Simple routines to easily allocate AUX fields of basic blocks. */
687 static struct obstack block_aux_obstack;
688 static void *first_block_aux_obj = 0;
689 static struct obstack edge_aux_obstack;
690 static void *first_edge_aux_obj = 0;
692 /* Allocate a memory block of SIZE as BB->aux. The obstack must
693 be first initialized by alloc_aux_for_blocks. */
696 alloc_aux_for_block (basic_block bb, int size)
698 /* Verify that aux field is clear. */
699 gcc_assert (!bb->aux && first_block_aux_obj);
700 bb->aux = obstack_alloc (&block_aux_obstack, size);
701 memset (bb->aux, 0, size);
704 /* Initialize the block_aux_obstack and if SIZE is nonzero, call
705 alloc_aux_for_block for each basic block. */
708 alloc_aux_for_blocks (int size)
710 static int initialized;
714 gcc_obstack_init (&block_aux_obstack);
718 /* Check whether AUX data are still allocated. */
719 gcc_assert (!first_block_aux_obj);
721 first_block_aux_obj = obstack_alloc (&block_aux_obstack, 0);
726 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
727 alloc_aux_for_block (bb, size);
731 /* Clear AUX pointers of all blocks. */
734 clear_aux_for_blocks (void)
738 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, NULL, next_bb)
742 /* Free data allocated in block_aux_obstack and clear AUX pointers
746 free_aux_for_blocks (void)
748 gcc_assert (first_block_aux_obj);
749 obstack_free (&block_aux_obstack, first_block_aux_obj);
750 first_block_aux_obj = NULL;
752 clear_aux_for_blocks ();
755 /* Allocate a memory edge of SIZE as BB->aux. The obstack must
756 be first initialized by alloc_aux_for_edges. */
759 alloc_aux_for_edge (edge e, int size)
761 /* Verify that aux field is clear. */
762 gcc_assert (!e->aux && first_edge_aux_obj);
763 e->aux = obstack_alloc (&edge_aux_obstack, size);
764 memset (e->aux, 0, size);
767 /* Initialize the edge_aux_obstack and if SIZE is nonzero, call
768 alloc_aux_for_edge for each basic edge. */
771 alloc_aux_for_edges (int size)
773 static int initialized;
777 gcc_obstack_init (&edge_aux_obstack);
781 /* Check whether AUX data are still allocated. */
782 gcc_assert (!first_edge_aux_obj);
784 first_edge_aux_obj = obstack_alloc (&edge_aux_obstack, 0);
789 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
794 FOR_EACH_EDGE (e, ei, bb->succs)
795 alloc_aux_for_edge (e, size);
800 /* Clear AUX pointers of all edges. */
803 clear_aux_for_edges (void)
808 FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
811 FOR_EACH_EDGE (e, ei, bb->succs)
816 /* Free data allocated in edge_aux_obstack and clear AUX pointers
820 free_aux_for_edges (void)
822 gcc_assert (first_edge_aux_obj);
823 obstack_free (&edge_aux_obstack, first_edge_aux_obj);
824 first_edge_aux_obj = NULL;
826 clear_aux_for_edges ();
830 debug_bb (basic_block bb)
832 dump_bb (bb, stderr, 0);
838 basic_block bb = BASIC_BLOCK (n);
839 dump_bb (bb, stderr, 0);
843 /* Dumps cfg related information about basic block BB to FILE. */
846 dump_cfg_bb_info (FILE *file, basic_block bb)
851 static const char * const bb_bitnames[] =
853 "dirty", "new", "reachable", "visited", "irreducible_loop", "superblock"
855 const unsigned n_bitnames = sizeof (bb_bitnames) / sizeof (char *);
858 fprintf (file, "Basic block %d", bb->index);
859 for (i = 0; i < n_bitnames; i++)
860 if (bb->flags & (1 << i))
863 fprintf (file, " (");
865 fprintf (file, ", ");
867 fprintf (file, bb_bitnames[i]);
871 fprintf (file, "\n");
873 fprintf (file, "Predecessors: ");
874 FOR_EACH_EDGE (e, ei, bb->preds)
875 dump_edge_info (file, e, 0);
877 fprintf (file, "\nSuccessors: ");
878 FOR_EACH_EDGE (e, ei, bb->succs)
879 dump_edge_info (file, e, 1);
880 fprintf (file, "\n\n");
883 /* Dumps a brief description of cfg to FILE. */
886 brief_dump_cfg (FILE *file)
892 dump_cfg_bb_info (file, bb);
896 /* An edge originally destinating BB of FREQUENCY and COUNT has been proved to
897 leave the block by TAKEN_EDGE. Update profile of BB such that edge E can be
898 redirected to destination of TAKEN_EDGE.
900 This function may leave the profile inconsistent in the case TAKEN_EDGE
901 frequency or count is believed to be lower than FREQUENCY or COUNT
904 update_bb_profile_for_threading (basic_block bb, int edge_frequency,
905 gcov_type count, edge taken_edge)
915 /* Compute the probability of TAKEN_EDGE being reached via threaded edge.
916 Watch for overflows. */
918 prob = edge_frequency * REG_BR_PROB_BASE / bb->frequency;
921 if (prob > taken_edge->probability)
924 fprintf (dump_file, "Jump threading proved probability of edge "
925 "%i->%i too small (it is %i, should be %i).\n",
926 taken_edge->src->index, taken_edge->dest->index,
927 taken_edge->probability, prob);
928 prob = taken_edge->probability;
931 /* Now rescale the probabilities. */
932 taken_edge->probability -= prob;
933 prob = REG_BR_PROB_BASE - prob;
934 bb->frequency -= edge_frequency;
935 if (bb->frequency < 0)
940 fprintf (dump_file, "Edge frequencies of bb %i has been reset, "
941 "frequency of block should end up being 0, it is %i\n",
942 bb->index, bb->frequency);
943 EDGE_SUCC (bb, 0)->probability = REG_BR_PROB_BASE;
944 ei = ei_start (bb->succs);
946 for (; (c = ei_safe_edge (ei)); ei_next (&ei))
949 else if (prob != REG_BR_PROB_BASE)
951 int scale = REG_BR_PROB_BASE / prob;
953 FOR_EACH_EDGE (c, ei, bb->succs)
954 c->probability *= scale;
957 if (bb != taken_edge->src)
959 taken_edge->count -= count;
960 if (taken_edge->count < 0)
961 taken_edge->count = 0;