Daily bump.
[official-gcc.git] / gcc / cfgbuild.c
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1 /* Control flow graph building code for GNU compiler.
2 Copyright (C) 1987, 1988, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
3 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2007 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 3, or (at your option) any later
10 version.
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
15 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 /* find_basic_blocks divides the current function's rtl into basic
22 blocks and constructs the CFG. The blocks are recorded in the
23 basic_block_info array; the CFG exists in the edge structures
24 referenced by the blocks.
26 find_basic_blocks also finds any unreachable loops and deletes them.
28 Available functionality:
29 - CFG construction
30 find_basic_blocks */
32 #include "config.h"
33 #include "system.h"
34 #include "coretypes.h"
35 #include "tm.h"
36 #include "tree.h"
37 #include "rtl.h"
38 #include "hard-reg-set.h"
39 #include "basic-block.h"
40 #include "regs.h"
41 #include "flags.h"
42 #include "output.h"
43 #include "function.h"
44 #include "except.h"
45 #include "toplev.h"
46 #include "timevar.h"
48 static int count_basic_blocks (const_rtx);
49 static void find_basic_blocks_1 (rtx);
50 static void make_edges (basic_block, basic_block, int);
51 static void make_label_edge (sbitmap, basic_block, rtx, int);
52 static void find_bb_boundaries (basic_block);
53 static void compute_outgoing_frequencies (basic_block);
55 /* Return true if insn is something that should be contained inside basic
56 block. */
58 bool
59 inside_basic_block_p (const_rtx insn)
61 switch (GET_CODE (insn))
63 case CODE_LABEL:
64 /* Avoid creating of basic block for jumptables. */
65 return (NEXT_INSN (insn) == 0
66 || !JUMP_P (NEXT_INSN (insn))
67 || (GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_VEC
68 && GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_DIFF_VEC));
70 case JUMP_INSN:
71 return (GET_CODE (PATTERN (insn)) != ADDR_VEC
72 && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC);
74 case CALL_INSN:
75 case INSN:
76 return true;
78 case BARRIER:
79 case NOTE:
80 return false;
82 default:
83 gcc_unreachable ();
87 /* Return true if INSN may cause control flow transfer, so it should be last in
88 the basic block. */
90 bool
91 control_flow_insn_p (const_rtx insn)
93 rtx note;
95 switch (GET_CODE (insn))
97 case NOTE:
98 case CODE_LABEL:
99 return false;
101 case JUMP_INSN:
102 /* Jump insn always causes control transfer except for tablejumps. */
103 return (GET_CODE (PATTERN (insn)) != ADDR_VEC
104 && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC);
106 case CALL_INSN:
107 /* Noreturn and sibling call instructions terminate the basic blocks
108 (but only if they happen unconditionally). */
109 if ((SIBLING_CALL_P (insn)
110 || find_reg_note (insn, REG_NORETURN, 0))
111 && GET_CODE (PATTERN (insn)) != COND_EXEC)
112 return true;
113 /* Call insn may return to the nonlocal goto handler. */
114 return ((nonlocal_goto_handler_labels
115 && (0 == (note = find_reg_note (insn, REG_EH_REGION,
116 NULL_RTX))
117 || INTVAL (XEXP (note, 0)) >= 0))
118 /* Or may trap. */
119 || can_throw_internal (insn));
121 case INSN:
122 /* Treat trap instructions like noreturn calls (same provision). */
123 if (GET_CODE (PATTERN (insn)) == TRAP_IF
124 && XEXP (PATTERN (insn), 0) == const1_rtx)
125 return true;
127 return (flag_non_call_exceptions && can_throw_internal (insn));
129 case BARRIER:
130 /* It is nonsense to reach barrier when looking for the
131 end of basic block, but before dead code is eliminated
132 this may happen. */
133 return false;
135 default:
136 gcc_unreachable ();
140 /* Count the basic blocks of the function. */
142 static int
143 count_basic_blocks (const_rtx f)
145 int count = NUM_FIXED_BLOCKS;
146 bool saw_insn = false;
147 const_rtx insn;
149 for (insn = f; insn; insn = NEXT_INSN (insn))
151 /* Code labels and barriers causes current basic block to be
152 terminated at previous real insn. */
153 if ((LABEL_P (insn) || BARRIER_P (insn))
154 && saw_insn)
155 count++, saw_insn = false;
157 /* Start basic block if needed. */
158 if (!saw_insn && inside_basic_block_p (insn))
159 saw_insn = true;
161 /* Control flow insn causes current basic block to be terminated. */
162 if (saw_insn && control_flow_insn_p (insn))
163 count++, saw_insn = false;
166 if (saw_insn)
167 count++;
169 /* The rest of the compiler works a bit smoother when we don't have to
170 check for the edge case of do-nothing functions with no basic blocks. */
171 if (count == NUM_FIXED_BLOCKS)
173 emit_insn (gen_rtx_USE (VOIDmode, const0_rtx));
174 count = NUM_FIXED_BLOCKS + 1;
177 return count;
180 /* Create an edge between two basic blocks. FLAGS are auxiliary information
181 about the edge that is accumulated between calls. */
183 /* Create an edge from a basic block to a label. */
185 static void
186 make_label_edge (sbitmap edge_cache, basic_block src, rtx label, int flags)
188 gcc_assert (LABEL_P (label));
190 /* If the label was never emitted, this insn is junk, but avoid a
191 crash trying to refer to BLOCK_FOR_INSN (label). This can happen
192 as a result of a syntax error and a diagnostic has already been
193 printed. */
195 if (INSN_UID (label) == 0)
196 return;
198 cached_make_edge (edge_cache, src, BLOCK_FOR_INSN (label), flags);
201 /* Create the edges generated by INSN in REGION. */
203 void
204 rtl_make_eh_edge (sbitmap edge_cache, basic_block src, rtx insn)
206 int is_call = CALL_P (insn) ? EDGE_ABNORMAL_CALL : 0;
207 rtx handlers, i;
209 handlers = reachable_handlers (insn);
211 for (i = handlers; i; i = XEXP (i, 1))
212 make_label_edge (edge_cache, src, XEXP (i, 0),
213 EDGE_ABNORMAL | EDGE_EH | is_call);
215 free_INSN_LIST_list (&handlers);
218 /* States of basic block as seen by find_many_sub_basic_blocks. */
219 enum state {
220 /* Basic blocks created via split_block belong to this state.
221 make_edges will examine these basic blocks to see if we need to
222 create edges going out of them. */
223 BLOCK_NEW = 0,
225 /* Basic blocks that do not need examining belong to this state.
226 These blocks will be left intact. In particular, make_edges will
227 not create edges going out of these basic blocks. */
228 BLOCK_ORIGINAL,
230 /* Basic blocks that may need splitting (due to a label appearing in
231 the middle, etc) belong to this state. After splitting them,
232 make_edges will create edges going out of them as needed. */
233 BLOCK_TO_SPLIT
236 #define STATE(BB) (enum state) ((size_t) (BB)->aux)
237 #define SET_STATE(BB, STATE) ((BB)->aux = (void *) (size_t) (STATE))
239 /* Used internally by purge_dead_tablejump_edges, ORed into state. */
240 #define BLOCK_USED_BY_TABLEJUMP 32
241 #define FULL_STATE(BB) ((size_t) (BB)->aux)
243 /* Identify the edges going out of basic blocks between MIN and MAX,
244 inclusive, that have their states set to BLOCK_NEW or
245 BLOCK_TO_SPLIT.
247 UPDATE_P should be nonzero if we are updating CFG and zero if we
248 are building CFG from scratch. */
250 static void
251 make_edges (basic_block min, basic_block max, int update_p)
253 basic_block bb;
254 sbitmap edge_cache = NULL;
256 /* Heavy use of computed goto in machine-generated code can lead to
257 nearly fully-connected CFGs. In that case we spend a significant
258 amount of time searching the edge lists for duplicates. */
259 if (forced_labels || cfun->max_jumptable_ents > 100)
260 edge_cache = sbitmap_alloc (last_basic_block);
262 /* By nature of the way these get numbered, ENTRY_BLOCK_PTR->next_bb block
263 is always the entry. */
264 if (min == ENTRY_BLOCK_PTR->next_bb)
265 make_edge (ENTRY_BLOCK_PTR, min, EDGE_FALLTHRU);
267 FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
269 rtx insn, x;
270 enum rtx_code code;
271 edge e;
272 edge_iterator ei;
274 if (STATE (bb) == BLOCK_ORIGINAL)
275 continue;
277 /* If we have an edge cache, cache edges going out of BB. */
278 if (edge_cache)
280 sbitmap_zero (edge_cache);
281 if (update_p)
283 FOR_EACH_EDGE (e, ei, bb->succs)
284 if (e->dest != EXIT_BLOCK_PTR)
285 SET_BIT (edge_cache, e->dest->index);
289 if (LABEL_P (BB_HEAD (bb))
290 && LABEL_ALT_ENTRY_P (BB_HEAD (bb)))
291 cached_make_edge (NULL, ENTRY_BLOCK_PTR, bb, 0);
293 /* Examine the last instruction of the block, and discover the
294 ways we can leave the block. */
296 insn = BB_END (bb);
297 code = GET_CODE (insn);
299 /* A branch. */
300 if (code == JUMP_INSN)
302 rtx tmp;
304 /* Recognize exception handling placeholders. */
305 if (GET_CODE (PATTERN (insn)) == RESX)
306 rtl_make_eh_edge (edge_cache, bb, insn);
308 /* Recognize a non-local goto as a branch outside the
309 current function. */
310 else if (find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX))
313 /* Recognize a tablejump and do the right thing. */
314 else if (tablejump_p (insn, NULL, &tmp))
316 rtvec vec;
317 int j;
319 if (GET_CODE (PATTERN (tmp)) == ADDR_VEC)
320 vec = XVEC (PATTERN (tmp), 0);
321 else
322 vec = XVEC (PATTERN (tmp), 1);
324 for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j)
325 make_label_edge (edge_cache, bb,
326 XEXP (RTVEC_ELT (vec, j), 0), 0);
328 /* Some targets (eg, ARM) emit a conditional jump that also
329 contains the out-of-range target. Scan for these and
330 add an edge if necessary. */
331 if ((tmp = single_set (insn)) != NULL
332 && SET_DEST (tmp) == pc_rtx
333 && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE
334 && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF)
335 make_label_edge (edge_cache, bb,
336 XEXP (XEXP (SET_SRC (tmp), 2), 0), 0);
339 /* If this is a computed jump, then mark it as reaching
340 everything on the forced_labels list. */
341 else if (computed_jump_p (insn))
343 for (x = forced_labels; x; x = XEXP (x, 1))
344 make_label_edge (edge_cache, bb, XEXP (x, 0), EDGE_ABNORMAL);
347 /* Returns create an exit out. */
348 else if (returnjump_p (insn))
349 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, 0);
351 /* Otherwise, we have a plain conditional or unconditional jump. */
352 else
354 gcc_assert (JUMP_LABEL (insn));
355 make_label_edge (edge_cache, bb, JUMP_LABEL (insn), 0);
359 /* If this is a sibling call insn, then this is in effect a combined call
360 and return, and so we need an edge to the exit block. No need to
361 worry about EH edges, since we wouldn't have created the sibling call
362 in the first place. */
363 if (code == CALL_INSN && SIBLING_CALL_P (insn))
364 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR,
365 EDGE_SIBCALL | EDGE_ABNORMAL);
367 /* If this is a CALL_INSN, then mark it as reaching the active EH
368 handler for this CALL_INSN. If we're handling non-call
369 exceptions then any insn can reach any of the active handlers.
370 Also mark the CALL_INSN as reaching any nonlocal goto handler. */
371 else if (code == CALL_INSN || flag_non_call_exceptions)
373 /* Add any appropriate EH edges. */
374 rtl_make_eh_edge (edge_cache, bb, insn);
376 if (code == CALL_INSN && nonlocal_goto_handler_labels)
378 /* ??? This could be made smarter: in some cases it's possible
379 to tell that certain calls will not do a nonlocal goto.
380 For example, if the nested functions that do the nonlocal
381 gotos do not have their addresses taken, then only calls to
382 those functions or to other nested functions that use them
383 could possibly do nonlocal gotos. */
385 /* We do know that a REG_EH_REGION note with a value less
386 than 0 is guaranteed not to perform a non-local goto. */
387 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
389 if (!note || INTVAL (XEXP (note, 0)) >= 0)
390 for (x = nonlocal_goto_handler_labels; x; x = XEXP (x, 1))
391 make_label_edge (edge_cache, bb, XEXP (x, 0),
392 EDGE_ABNORMAL | EDGE_ABNORMAL_CALL);
396 /* Find out if we can drop through to the next block. */
397 insn = NEXT_INSN (insn);
398 e = find_edge (bb, EXIT_BLOCK_PTR);
399 if (e && e->flags & EDGE_FALLTHRU)
400 insn = NULL;
402 while (insn
403 && NOTE_P (insn)
404 && NOTE_KIND (insn) != NOTE_INSN_BASIC_BLOCK)
405 insn = NEXT_INSN (insn);
407 if (!insn)
408 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, EDGE_FALLTHRU);
409 else if (bb->next_bb != EXIT_BLOCK_PTR)
411 if (insn == BB_HEAD (bb->next_bb))
412 cached_make_edge (edge_cache, bb, bb->next_bb, EDGE_FALLTHRU);
416 if (edge_cache)
417 sbitmap_vector_free (edge_cache);
420 /* Find all basic blocks of the function whose first insn is F.
422 Collect and return a list of labels whose addresses are taken. This
423 will be used in make_edges for use with computed gotos. */
425 static void
426 find_basic_blocks_1 (rtx f)
428 rtx insn, next;
429 rtx bb_note = NULL_RTX;
430 rtx head = NULL_RTX;
431 rtx end = NULL_RTX;
432 basic_block prev = ENTRY_BLOCK_PTR;
434 /* We process the instructions in a slightly different way than we did
435 previously. This is so that we see a NOTE_BASIC_BLOCK after we have
436 closed out the previous block, so that it gets attached at the proper
437 place. Since this form should be equivalent to the previous,
438 count_basic_blocks continues to use the old form as a check. */
440 for (insn = f; insn; insn = next)
442 enum rtx_code code = GET_CODE (insn);
444 next = NEXT_INSN (insn);
446 if ((LABEL_P (insn) || BARRIER_P (insn))
447 && head)
449 prev = create_basic_block_structure (head, end, bb_note, prev);
450 head = end = NULL_RTX;
451 bb_note = NULL_RTX;
454 if (inside_basic_block_p (insn))
456 if (head == NULL_RTX)
457 head = insn;
458 end = insn;
461 if (head && control_flow_insn_p (insn))
463 prev = create_basic_block_structure (head, end, bb_note, prev);
464 head = end = NULL_RTX;
465 bb_note = NULL_RTX;
468 switch (code)
470 case NOTE:
471 /* Look for basic block notes with which to keep the
472 basic_block_info pointers stable. Unthread the note now;
473 we'll put it back at the right place in create_basic_block.
474 Or not at all if we've already found a note in this block. */
475 if (NOTE_INSN_BASIC_BLOCK_P (insn))
477 if (bb_note == NULL_RTX)
478 bb_note = insn;
479 else
480 next = delete_insn (insn);
482 break;
484 case CODE_LABEL:
485 case JUMP_INSN:
486 case CALL_INSN:
487 case INSN:
488 case BARRIER:
489 break;
491 default:
492 gcc_unreachable ();
496 if (head != NULL_RTX)
497 create_basic_block_structure (head, end, bb_note, prev);
498 else if (bb_note)
499 delete_insn (bb_note);
501 gcc_assert (last_basic_block == n_basic_blocks);
503 clear_aux_for_blocks ();
507 /* Find basic blocks of the current function.
508 F is the first insn of the function. */
510 void
511 find_basic_blocks (rtx f)
513 basic_block bb;
515 timevar_push (TV_CFG);
517 /* Flush out existing data. */
518 if (basic_block_info != NULL)
520 clear_edges ();
522 /* Clear bb->aux on all extant basic blocks. We'll use this as a
523 tag for reuse during create_basic_block, just in case some pass
524 copies around basic block notes improperly. */
525 FOR_EACH_BB (bb)
526 bb->aux = NULL;
528 basic_block_info = NULL;
531 n_basic_blocks = count_basic_blocks (f);
532 last_basic_block = NUM_FIXED_BLOCKS;
533 ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR;
534 EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR;
537 /* Size the basic block table. The actual structures will be allocated
538 by find_basic_blocks_1, since we want to keep the structure pointers
539 stable across calls to find_basic_blocks. */
540 /* ??? This whole issue would be much simpler if we called find_basic_blocks
541 exactly once, and thereafter we don't have a single long chain of
542 instructions at all until close to the end of compilation when we
543 actually lay them out. */
545 basic_block_info = VEC_alloc (basic_block, gc, n_basic_blocks);
546 VEC_safe_grow_cleared (basic_block, gc, basic_block_info, n_basic_blocks);
547 SET_BASIC_BLOCK (ENTRY_BLOCK, ENTRY_BLOCK_PTR);
548 SET_BASIC_BLOCK (EXIT_BLOCK, EXIT_BLOCK_PTR);
550 find_basic_blocks_1 (f);
552 profile_status = PROFILE_ABSENT;
554 /* Tell make_edges to examine every block for out-going edges. */
555 FOR_EACH_BB (bb)
556 SET_STATE (bb, BLOCK_NEW);
558 /* Discover the edges of our cfg. */
559 make_edges (ENTRY_BLOCK_PTR->next_bb, EXIT_BLOCK_PTR->prev_bb, 0);
561 /* Do very simple cleanup now, for the benefit of code that runs between
562 here and cleanup_cfg, e.g. thread_prologue_and_epilogue_insns. */
563 tidy_fallthru_edges ();
565 #ifdef ENABLE_CHECKING
566 verify_flow_info ();
567 #endif
568 timevar_pop (TV_CFG);
571 static void
572 mark_tablejump_edge (rtx label)
574 basic_block bb;
576 gcc_assert (LABEL_P (label));
577 /* See comment in make_label_edge. */
578 if (INSN_UID (label) == 0)
579 return;
580 bb = BLOCK_FOR_INSN (label);
581 SET_STATE (bb, FULL_STATE (bb) | BLOCK_USED_BY_TABLEJUMP);
584 static void
585 purge_dead_tablejump_edges (basic_block bb, rtx table)
587 rtx insn = BB_END (bb), tmp;
588 rtvec vec;
589 int j;
590 edge_iterator ei;
591 edge e;
593 if (GET_CODE (PATTERN (table)) == ADDR_VEC)
594 vec = XVEC (PATTERN (table), 0);
595 else
596 vec = XVEC (PATTERN (table), 1);
598 for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j)
599 mark_tablejump_edge (XEXP (RTVEC_ELT (vec, j), 0));
601 /* Some targets (eg, ARM) emit a conditional jump that also
602 contains the out-of-range target. Scan for these and
603 add an edge if necessary. */
604 if ((tmp = single_set (insn)) != NULL
605 && SET_DEST (tmp) == pc_rtx
606 && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE
607 && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF)
608 mark_tablejump_edge (XEXP (XEXP (SET_SRC (tmp), 2), 0));
610 for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
612 if (FULL_STATE (e->dest) & BLOCK_USED_BY_TABLEJUMP)
613 SET_STATE (e->dest, FULL_STATE (e->dest)
614 & ~(size_t) BLOCK_USED_BY_TABLEJUMP);
615 else if (!(e->flags & (EDGE_ABNORMAL | EDGE_EH)))
617 remove_edge (e);
618 continue;
620 ei_next (&ei);
624 /* Scan basic block BB for possible BB boundaries inside the block
625 and create new basic blocks in the progress. */
627 static void
628 find_bb_boundaries (basic_block bb)
630 basic_block orig_bb = bb;
631 rtx insn = BB_HEAD (bb);
632 rtx end = BB_END (bb), x;
633 rtx table;
634 rtx flow_transfer_insn = NULL_RTX;
635 edge fallthru = NULL;
637 if (insn == BB_END (bb))
638 return;
640 if (LABEL_P (insn))
641 insn = NEXT_INSN (insn);
643 /* Scan insn chain and try to find new basic block boundaries. */
644 while (1)
646 enum rtx_code code = GET_CODE (insn);
648 /* On code label, split current basic block. */
649 if (code == CODE_LABEL)
651 fallthru = split_block (bb, PREV_INSN (insn));
652 if (flow_transfer_insn)
654 BB_END (bb) = flow_transfer_insn;
656 /* Clean up the bb field for the insns between the blocks. */
657 for (x = NEXT_INSN (flow_transfer_insn);
658 x != BB_HEAD (fallthru->dest);
659 x = NEXT_INSN (x))
660 if (!BARRIER_P (x))
661 set_block_for_insn (x, NULL);
664 bb = fallthru->dest;
665 remove_edge (fallthru);
666 flow_transfer_insn = NULL_RTX;
667 if (LABEL_ALT_ENTRY_P (insn))
668 make_edge (ENTRY_BLOCK_PTR, bb, 0);
671 /* In case we've previously seen an insn that effects a control
672 flow transfer, split the block. */
673 if (flow_transfer_insn && inside_basic_block_p (insn))
675 fallthru = split_block (bb, PREV_INSN (insn));
676 BB_END (bb) = flow_transfer_insn;
678 /* Clean up the bb field for the insns between the blocks. */
679 for (x = NEXT_INSN (flow_transfer_insn);
680 x != BB_HEAD (fallthru->dest);
681 x = NEXT_INSN (x))
682 if (!BARRIER_P (x))
683 set_block_for_insn (x, NULL);
685 bb = fallthru->dest;
686 remove_edge (fallthru);
687 flow_transfer_insn = NULL_RTX;
690 if (control_flow_insn_p (insn))
691 flow_transfer_insn = insn;
692 if (insn == end)
693 break;
694 insn = NEXT_INSN (insn);
697 /* In case expander replaced normal insn by sequence terminating by
698 return and barrier, or possibly other sequence not behaving like
699 ordinary jump, we need to take care and move basic block boundary. */
700 if (flow_transfer_insn)
702 BB_END (bb) = flow_transfer_insn;
704 /* Clean up the bb field for the insns that do not belong to BB. */
705 x = flow_transfer_insn;
706 while (x != end)
708 x = NEXT_INSN (x);
709 if (!BARRIER_P (x))
710 set_block_for_insn (x, NULL);
714 /* We've possibly replaced the conditional jump by conditional jump
715 followed by cleanup at fallthru edge, so the outgoing edges may
716 be dead. */
717 purge_dead_edges (bb);
719 /* purge_dead_edges doesn't handle tablejump's, but if we have split the
720 basic block, we might need to kill some edges. */
721 if (bb != orig_bb && tablejump_p (BB_END (bb), NULL, &table))
722 purge_dead_tablejump_edges (bb, table);
725 /* Assume that frequency of basic block B is known. Compute frequencies
726 and probabilities of outgoing edges. */
728 static void
729 compute_outgoing_frequencies (basic_block b)
731 edge e, f;
732 edge_iterator ei;
734 if (EDGE_COUNT (b->succs) == 2)
736 rtx note = find_reg_note (BB_END (b), REG_BR_PROB, NULL);
737 int probability;
739 if (note)
741 probability = INTVAL (XEXP (note, 0));
742 e = BRANCH_EDGE (b);
743 e->probability = probability;
744 e->count = ((b->count * probability + REG_BR_PROB_BASE / 2)
745 / REG_BR_PROB_BASE);
746 f = FALLTHRU_EDGE (b);
747 f->probability = REG_BR_PROB_BASE - probability;
748 f->count = b->count - e->count;
749 return;
753 if (single_succ_p (b))
755 e = single_succ_edge (b);
756 e->probability = REG_BR_PROB_BASE;
757 e->count = b->count;
758 return;
760 guess_outgoing_edge_probabilities (b);
761 if (b->count)
762 FOR_EACH_EDGE (e, ei, b->succs)
763 e->count = ((b->count * e->probability + REG_BR_PROB_BASE / 2)
764 / REG_BR_PROB_BASE);
767 /* Assume that some pass has inserted labels or control flow
768 instructions within a basic block. Split basic blocks as needed
769 and create edges. */
771 void
772 find_many_sub_basic_blocks (sbitmap blocks)
774 basic_block bb, min, max;
776 FOR_EACH_BB (bb)
777 SET_STATE (bb,
778 TEST_BIT (blocks, bb->index) ? BLOCK_TO_SPLIT : BLOCK_ORIGINAL);
780 FOR_EACH_BB (bb)
781 if (STATE (bb) == BLOCK_TO_SPLIT)
782 find_bb_boundaries (bb);
784 FOR_EACH_BB (bb)
785 if (STATE (bb) != BLOCK_ORIGINAL)
786 break;
788 min = max = bb;
789 for (; bb != EXIT_BLOCK_PTR; bb = bb->next_bb)
790 if (STATE (bb) != BLOCK_ORIGINAL)
791 max = bb;
793 /* Now re-scan and wire in all edges. This expect simple (conditional)
794 jumps at the end of each new basic blocks. */
795 make_edges (min, max, 1);
797 /* Update branch probabilities. Expect only (un)conditional jumps
798 to be created with only the forward edges. */
799 if (profile_status != PROFILE_ABSENT)
800 FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
802 edge e;
803 edge_iterator ei;
805 if (STATE (bb) == BLOCK_ORIGINAL)
806 continue;
807 if (STATE (bb) == BLOCK_NEW)
809 bb->count = 0;
810 bb->frequency = 0;
811 FOR_EACH_EDGE (e, ei, bb->preds)
813 bb->count += e->count;
814 bb->frequency += EDGE_FREQUENCY (e);
818 compute_outgoing_frequencies (bb);
821 FOR_EACH_BB (bb)
822 SET_STATE (bb, 0);