1/* Control flow graph building code for GNU compiler.
2 Copyright (C) 1987-2023 Free Software Foundation, Inc.
3
4This file is part of GCC.
5
6GCC is free software; you can redistribute it and/or modify it under
7the terms of the GNU General Public License as published by the Free
8Software Foundation; either version 3, or (at your option) any later
9version.
10
11GCC is distributed in the hope that it will be useful, but WITHOUT ANY
12WARRANTY; without even the implied warranty of MERCHANTABILITY or
13FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14for more details.
15
16You should have received a copy of the GNU General Public License
17along with GCC; see the file COPYING3. If not see
18<http://www.gnu.org/licenses/>. */
19
20
21#include "config.h"
22#include "system.h"
23#include "coretypes.h"
24#include "backend.h"
25#include "rtl.h"
26#include "cfghooks.h"
27#include "memmodel.h"
28#include "emit-rtl.h"
29#include "cfgrtl.h"
30#include "cfganal.h"
31#include "cfgbuild.h"
32#include "except.h"
33#include "stmt.h"
34
35static void make_edges (basic_block, basic_block, int);
36static void make_label_edge (sbitmap, basic_block, rtx, int);
37static void find_bb_boundaries (basic_block);
38static void compute_outgoing_frequencies (basic_block);
39
40/* Return true if insn is something that should be contained inside basic
41 block. */
42
43bool
44inside_basic_block_p (const rtx_insn *insn)
45{
46 switch (GET_CODE (insn))
47 {
48 case CODE_LABEL:
49 /* Avoid creating of basic block for jumptables. */
50 return (NEXT_INSN (insn) == 0
51 || ! JUMP_TABLE_DATA_P (NEXT_INSN (insn)));
52
53 case JUMP_INSN:
54 case CALL_INSN:
55 case INSN:
56 case DEBUG_INSN:
57 return true;
58
59 case JUMP_TABLE_DATA:
60 case BARRIER:
61 case NOTE:
62 return false;
63
64 default:
65 gcc_unreachable ();
66 }
67}
68
69/* Return true if INSN may cause control flow transfer, so it should be last in
70 the basic block. */
71
72bool
73control_flow_insn_p (const rtx_insn *insn)
74{
75 switch (GET_CODE (insn))
76 {
77 case NOTE:
78 case CODE_LABEL:
79 case DEBUG_INSN:
80 return false;
81
82 case JUMP_INSN:
83 return true;
84
85 case CALL_INSN:
86 /* Noreturn and sibling call instructions terminate the basic blocks
87 (but only if they happen unconditionally). */
88 if ((SIBLING_CALL_P (insn)
89 || find_reg_note (insn, REG_NORETURN, 0))
90 && GET_CODE (PATTERN (insn)) != COND_EXEC)
91 return true;
92
93 /* Call insn may return to the nonlocal goto handler. */
94 if (can_nonlocal_goto (insn))
95 return true;
96 break;
97
98 case INSN:
99 /* Treat trap instructions like noreturn calls (same provision). */
100 if (GET_CODE (PATTERN (insn)) == TRAP_IF
101 && XEXP (PATTERN (insn), 0) == const1_rtx)
102 return true;
103 if (!cfun->can_throw_non_call_exceptions)
104 return false;
105 break;
106
107 case JUMP_TABLE_DATA:
108 case BARRIER:
109 /* It is nonsense to reach this when looking for the
110 end of basic block, but before dead code is eliminated
111 this may happen. */
112 return false;
113
114 default:
115 gcc_unreachable ();
116 }
117
118 return can_throw_internal (insn);
119}
120
121
122/* Create an edge between two basic blocks. FLAGS are auxiliary information
123 about the edge that is accumulated between calls. */
124
125/* Create an edge from a basic block to a label. */
126
127static void
128make_label_edge (sbitmap edge_cache, basic_block src, rtx label, int flags)
129{
130 gcc_assert (LABEL_P (label));
131
132 /* If the label was never emitted, this insn is junk, but avoid a
133 crash trying to refer to BLOCK_FOR_INSN (label). This can happen
134 as a result of a syntax error and a diagnostic has already been
135 printed. */
136
137 if (INSN_UID (insn: label) == 0)
138 return;
139
140 cached_make_edge (edge_cache, src, BLOCK_FOR_INSN (insn: label), flags);
141}
142
143/* Create the edges generated by INSN in REGION. */
144
145void
146rtl_make_eh_edge (sbitmap edge_cache, basic_block src, rtx insn)
147{
148 eh_landing_pad lp = get_eh_landing_pad_from_rtx (insn);
149
150 if (lp)
151 {
152 rtx_insn *label = lp->landing_pad;
153
154 /* During initial rtl generation, use the post_landing_pad. */
155 if (label == NULL)
156 {
157 gcc_assert (lp->post_landing_pad);
158 label = label_rtx (lp->post_landing_pad);
159 }
160
161 make_label_edge (edge_cache, src, label,
162 flags: EDGE_ABNORMAL | EDGE_EH
163 | (CALL_P (insn) ? EDGE_ABNORMAL_CALL : 0));
164 }
165}
166
167/* States of basic block as seen by find_many_sub_basic_blocks. */
168enum state {
169 /* Basic blocks created via split_block belong to this state.
170 make_edges will examine these basic blocks to see if we need to
171 create edges going out of them. */
172 BLOCK_NEW = 0,
173
174 /* Basic blocks that do not need examining belong to this state.
175 These blocks will be left intact. In particular, make_edges will
176 not create edges going out of these basic blocks. */
177 BLOCK_ORIGINAL,
178
179 /* Basic blocks that may need splitting (due to a label appearing in
180 the middle, etc) belong to this state. After splitting them,
181 make_edges will create edges going out of them as needed. */
182 BLOCK_TO_SPLIT
183};
184
185#define STATE(BB) (enum state) ((size_t) (BB)->aux)
186#define SET_STATE(BB, STATE) ((BB)->aux = (void *) (size_t) (STATE))
187
188/* Used internally by purge_dead_tablejump_edges, ORed into state. */
189#define BLOCK_USED_BY_TABLEJUMP 32
190#define FULL_STATE(BB) ((size_t) (BB)->aux)
191
192/* Identify the edges going out of basic blocks between MIN and MAX,
193 inclusive, that have their states set to BLOCK_NEW or
194 BLOCK_TO_SPLIT.
195
196 UPDATE_P should be nonzero if we are updating CFG and zero if we
197 are building CFG from scratch. */
198
199static void
200make_edges (basic_block min, basic_block max, int update_p)
201{
202 basic_block bb;
203 sbitmap edge_cache = NULL;
204
205 /* Heavy use of computed goto in machine-generated code can lead to
206 nearly fully-connected CFGs. In that case we spend a significant
207 amount of time searching the edge lists for duplicates. */
208 if (!vec_safe_is_empty (forced_labels)
209 || cfun->cfg->max_jumptable_ents > 100)
210 edge_cache = sbitmap_alloc (last_basic_block_for_fn (cfun));
211
212 /* By nature of the way these get numbered, ENTRY_BLOCK_PTR->next_bb block
213 is always the entry. */
214 if (min == ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb)
215 make_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun), min, EDGE_FALLTHRU);
216
217 FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
218 {
219 rtx_insn *insn;
220 enum rtx_code code;
221 edge e;
222 edge_iterator ei;
223
224 if (STATE (bb) == BLOCK_ORIGINAL)
225 continue;
226
227 /* If we have an edge cache, cache edges going out of BB. */
228 if (edge_cache)
229 {
230 bitmap_clear (edge_cache);
231 if (update_p)
232 {
233 FOR_EACH_EDGE (e, ei, bb->succs)
234 if (e->dest != EXIT_BLOCK_PTR_FOR_FN (cfun))
235 bitmap_set_bit (map: edge_cache, bitno: e->dest->index);
236 }
237 }
238
239 if (LABEL_P (BB_HEAD (bb))
240 && LABEL_ALT_ENTRY_P (BB_HEAD (bb)))
241 cached_make_edge (NULL, ENTRY_BLOCK_PTR_FOR_FN (cfun), bb, 0);
242
243 /* Examine the last instruction of the block, and discover the
244 ways we can leave the block. */
245
246 insn = BB_END (bb);
247 code = GET_CODE (insn);
248
249 /* A branch. */
250 if (code == JUMP_INSN)
251 {
252 rtx tmp;
253 rtx_jump_table_data *table;
254
255 /* Recognize a non-local goto as a branch outside the
256 current function. */
257 if (find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX))
258 ;
259
260 /* Recognize a tablejump and do the right thing. */
261 else if (tablejump_p (insn, NULL, &table))
262 {
263 rtvec vec = table->get_labels ();
264 int j;
265
266 for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j)
267 make_label_edge (edge_cache, src: bb,
268 XEXP (RTVEC_ELT (vec, j), 0), flags: 0);
269
270 /* Some targets (eg, ARM) emit a conditional jump that also
271 contains the out-of-range target. Scan for these and
272 add an edge if necessary. */
273 if ((tmp = single_set (insn)) != NULL
274 && SET_DEST (tmp) == pc_rtx
275 && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE
276 && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF)
277 make_label_edge (edge_cache, src: bb,
278 label: label_ref_label (XEXP (SET_SRC (tmp), 2)), flags: 0);
279 }
280
281 /* If this is a computed jump, then mark it as reaching
282 everything on the forced_labels list. */
283 else if (computed_jump_p (insn))
284 {
285 rtx_insn *insn;
286 unsigned int i;
287 FOR_EACH_VEC_SAFE_ELT (forced_labels, i, insn)
288 make_label_edge (edge_cache, src: bb, label: insn, flags: EDGE_ABNORMAL);
289 }
290
291 /* Returns create an exit out. */
292 else if (returnjump_p (insn))
293 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR_FOR_FN (cfun), 0);
294
295 /* Recognize asm goto and do the right thing. */
296 else if ((tmp = extract_asm_operands (PATTERN (insn))) != NULL)
297 {
298 int i, n = ASM_OPERANDS_LABEL_LENGTH (tmp);
299 for (i = 0; i < n; ++i)
300 make_label_edge (edge_cache, src: bb,
301 XEXP (ASM_OPERANDS_LABEL (tmp, i), 0), flags: 0);
302 }
303
304 /* Otherwise, we have a plain conditional or unconditional jump. */
305 else
306 {
307 gcc_assert (JUMP_LABEL (insn));
308 make_label_edge (edge_cache, src: bb, JUMP_LABEL (insn), flags: 0);
309 }
310 }
311
312 /* If this is a sibling call insn, then this is in effect a combined call
313 and return, and so we need an edge to the exit block. No need to
314 worry about EH edges, since we wouldn't have created the sibling call
315 in the first place. */
316 if (code == CALL_INSN && SIBLING_CALL_P (insn))
317 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR_FOR_FN (cfun),
318 EDGE_SIBCALL | EDGE_ABNORMAL);
319
320 /* If this is a CALL_INSN, then mark it as reaching the active EH
321 handler for this CALL_INSN. If we're handling non-call
322 exceptions then any insn can reach any of the active handlers.
323 Also mark the CALL_INSN as reaching any nonlocal goto handler. */
324 else if (code == CALL_INSN || cfun->can_throw_non_call_exceptions)
325 {
326 /* Add any appropriate EH edges. */
327 rtl_make_eh_edge (edge_cache, src: bb, insn);
328
329 if (code == CALL_INSN)
330 {
331 if (can_nonlocal_goto (insn))
332 {
333 /* ??? This could be made smarter: in some cases it's
334 possible to tell that certain calls will not do a
335 nonlocal goto. For example, if the nested functions
336 that do the nonlocal gotos do not have their addresses
337 taken, then only calls to those functions or to other
338 nested functions that use them could possibly do
339 nonlocal gotos. */
340 for (rtx_insn_list *x = nonlocal_goto_handler_labels;
341 x;
342 x = x->next ())
343 make_label_edge (edge_cache, src: bb, label: x->insn (),
344 flags: EDGE_ABNORMAL | EDGE_ABNORMAL_CALL);
345 }
346
347 if (flag_tm)
348 {
349 rtx note;
350 for (note = REG_NOTES (insn); note; note = XEXP (note, 1))
351 if (REG_NOTE_KIND (note) == REG_TM)
352 make_label_edge (edge_cache, src: bb, XEXP (note, 0),
353 flags: EDGE_ABNORMAL | EDGE_ABNORMAL_CALL);
354 }
355 }
356 }
357
358 /* Find out if we can drop through to the next block. */
359 insn = NEXT_INSN (insn);
360 e = find_edge (bb, EXIT_BLOCK_PTR_FOR_FN (cfun));
361 if (e && e->flags & EDGE_FALLTHRU)
362 insn = NULL;
363
364 while (insn
365 && NOTE_P (insn)
366 && NOTE_KIND (insn) != NOTE_INSN_BASIC_BLOCK)
367 insn = NEXT_INSN (insn);
368
369 if (!insn)
370 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR_FOR_FN (cfun),
371 EDGE_FALLTHRU);
372 else if (bb->next_bb != EXIT_BLOCK_PTR_FOR_FN (cfun))
373 {
374 if (insn == BB_HEAD (bb->next_bb))
375 cached_make_edge (edge_cache, bb, bb->next_bb, EDGE_FALLTHRU);
376 }
377 }
378
379 if (edge_cache)
380 sbitmap_free (map: edge_cache);
381}
382
383static void
384mark_tablejump_edge (rtx label)
385{
386 basic_block bb;
387
388 gcc_assert (LABEL_P (label));
389 /* See comment in make_label_edge. */
390 if (INSN_UID (insn: label) == 0)
391 return;
392 bb = BLOCK_FOR_INSN (insn: label);
393 SET_STATE (bb, FULL_STATE (bb) | BLOCK_USED_BY_TABLEJUMP);
394}
395
396static void
397purge_dead_tablejump_edges (basic_block bb, rtx_jump_table_data *table)
398{
399 rtx_insn *insn = BB_END (bb);
400 rtx tmp;
401 rtvec vec;
402 int j;
403 edge_iterator ei;
404 edge e;
405
406 vec = table->get_labels ();
407
408 for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j)
409 mark_tablejump_edge (XEXP (RTVEC_ELT (vec, j), 0));
410
411 /* Some targets (eg, ARM) emit a conditional jump that also
412 contains the out-of-range target. Scan for these and
413 add an edge if necessary. */
414 if ((tmp = single_set (insn)) != NULL
415 && SET_DEST (tmp) == pc_rtx
416 && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE
417 && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF)
418 mark_tablejump_edge (label: label_ref_label (XEXP (SET_SRC (tmp), 2)));
419
420 for (ei = ei_start (bb->succs); (e = ei_safe_edge (i: ei)); )
421 {
422 if (FULL_STATE (e->dest) & BLOCK_USED_BY_TABLEJUMP)
423 SET_STATE (e->dest, FULL_STATE (e->dest)
424 & ~(size_t) BLOCK_USED_BY_TABLEJUMP);
425 else if (!(e->flags & (EDGE_ABNORMAL | EDGE_EH)))
426 {
427 remove_edge (e);
428 continue;
429 }
430 ei_next (i: &ei);
431 }
432}
433
434/* Scan basic block BB for possible BB boundaries inside the block
435 and create new basic blocks in the progress. */
436
437static void
438find_bb_boundaries (basic_block bb)
439{
440 basic_block orig_bb = bb;
441 rtx_insn *insn = BB_HEAD (bb);
442 rtx_insn *end = BB_END (bb), *x;
443 rtx_jump_table_data *table;
444 rtx_insn *flow_transfer_insn = NULL;
445 rtx_insn *debug_insn = NULL;
446 edge fallthru = NULL;
447 bool skip_purge;
448 bool seen_note_after_debug = false;
449
450 if (insn == end)
451 return;
452
453 if (DEBUG_INSN_P (insn) || DEBUG_INSN_P (end))
454 {
455 /* Check whether, without debug insns, the insn==end test above
456 would have caused us to return immediately, and behave the
457 same way even with debug insns. If we don't do this, debug
458 insns could cause us to purge dead edges at different times,
459 which could in turn change the cfg and affect codegen
460 decisions in subtle but undesirable ways. */
461 while (insn != end && DEBUG_INSN_P (insn))
462 insn = NEXT_INSN (insn);
463 rtx_insn *e = end;
464 while (insn != e && DEBUG_INSN_P (e))
465 e = PREV_INSN (insn: e);
466 if (insn == e)
467 {
468 /* If there are debug insns after a single insn that is a
469 control flow insn in the block, we'd have left right
470 away, but we should clean up the debug insns after the
471 control flow insn, because they can't remain in the same
472 block. So, do the debug insn cleaning up, but then bail
473 out without purging dead edges as we would if the debug
474 insns hadn't been there. */
475 if (e != end && !DEBUG_INSN_P (e) && control_flow_insn_p (insn: e))
476 {
477 skip_purge = true;
478 flow_transfer_insn = e;
479 goto clean_up_debug_after_control_flow;
480 }
481 return;
482 }
483 }
484
485 if (LABEL_P (insn))
486 insn = NEXT_INSN (insn);
487
488 /* Scan insn chain and try to find new basic block boundaries. */
489 while (1)
490 {
491 enum rtx_code code = GET_CODE (insn);
492
493 if (code == DEBUG_INSN)
494 {
495 if (flow_transfer_insn && !debug_insn)
496 {
497 debug_insn = insn;
498 seen_note_after_debug = false;
499 }
500 }
501 /* In case we've previously seen an insn that effects a control
502 flow transfer, split the block. */
503 else if ((flow_transfer_insn || code == CODE_LABEL)
504 && inside_basic_block_p (insn))
505 {
506 rtx_insn *prev = PREV_INSN (insn);
507
508 /* If the first non-debug inside_basic_block_p insn after a control
509 flow transfer is not a label, split the block before the debug
510 insn instead of before the non-debug insn, so that the debug
511 insns are not lost. */
512 if (debug_insn && code != CODE_LABEL && code != BARRIER)
513 {
514 prev = PREV_INSN (insn: debug_insn);
515 if (seen_note_after_debug)
516 {
517 /* Though, if there are NOTEs intermixed with DEBUG_INSNs,
518 move the NOTEs before the DEBUG_INSNs and split after
519 the last NOTE. */
520 rtx_insn *first = NULL, *last = NULL;
521 for (x = debug_insn; x != insn; x = NEXT_INSN (insn: x))
522 {
523 if (NOTE_P (x))
524 {
525 if (first == NULL)
526 first = x;
527 last = x;
528 }
529 else
530 {
531 gcc_assert (DEBUG_INSN_P (x));
532 if (first)
533 {
534 reorder_insns_nobb (first, last, prev);
535 prev = last;
536 first = last = NULL;
537 }
538 }
539 }
540 if (first)
541 {
542 reorder_insns_nobb (first, last, prev);
543 prev = last;
544 }
545 }
546 }
547 fallthru = split_block (bb, prev);
548 if (flow_transfer_insn)
549 {
550 BB_END (bb) = flow_transfer_insn;
551
552 rtx_insn *next;
553 /* Clean up the bb field for the insns between the blocks. */
554 for (x = NEXT_INSN (insn: flow_transfer_insn);
555 x != BB_HEAD (fallthru->dest);
556 x = next)
557 {
558 next = NEXT_INSN (insn: x);
559 /* Debug insns should not be in between basic blocks,
560 drop them on the floor. */
561 if (DEBUG_INSN_P (x))
562 delete_insn (x);
563 else if (!BARRIER_P (x))
564 set_block_for_insn (insn: x, NULL);
565 }
566 }
567
568 bb = fallthru->dest;
569 remove_edge (fallthru);
570 /* BB is unreachable at this point - we need to determine its profile
571 once edges are built. */
572 bb->count = profile_count::uninitialized ();
573 flow_transfer_insn = NULL;
574 debug_insn = NULL;
575 if (code == CODE_LABEL && LABEL_ALT_ENTRY_P (insn))
576 make_edge (ENTRY_BLOCK_PTR_FOR_FN (cfun), bb, 0);
577 }
578 else if (code == BARRIER)
579 {
580 /* __builtin_unreachable () may cause a barrier to be emitted in
581 the middle of a BB. We need to split it in the same manner as
582 if the barrier were preceded by a control_flow_insn_p insn. */
583 if (!flow_transfer_insn)
584 flow_transfer_insn = prev_nonnote_nondebug_insn_bb (insn);
585 debug_insn = NULL;
586 }
587 else if (debug_insn)
588 {
589 if (code == NOTE)
590 seen_note_after_debug = true;
591 else
592 /* Jump tables. */
593 debug_insn = NULL;
594 }
595
596 if (control_flow_insn_p (insn))
597 flow_transfer_insn = insn;
598 if (insn == end)
599 break;
600 insn = NEXT_INSN (insn);
601 }
602
603 /* In case expander replaced normal insn by sequence terminating by
604 return and barrier, or possibly other sequence not behaving like
605 ordinary jump, we need to take care and move basic block boundary. */
606 if (flow_transfer_insn && flow_transfer_insn != end)
607 {
608 skip_purge = false;
609
610 clean_up_debug_after_control_flow:
611 BB_END (bb) = flow_transfer_insn;
612
613 /* Clean up the bb field for the insns that do not belong to BB. */
614 rtx_insn *next;
615 for (x = NEXT_INSN (insn: flow_transfer_insn); ; x = next)
616 {
617 next = NEXT_INSN (insn: x);
618 /* Debug insns should not be in between basic blocks,
619 drop them on the floor. */
620 if (DEBUG_INSN_P (x))
621 delete_insn (x);
622 else if (!BARRIER_P (x))
623 set_block_for_insn (insn: x, NULL);
624 if (x == end)
625 break;
626 }
627
628 if (skip_purge)
629 return;
630 }
631
632 /* We've possibly replaced the conditional jump by conditional jump
633 followed by cleanup at fallthru edge, so the outgoing edges may
634 be dead. */
635 purge_dead_edges (bb);
636
637 /* purge_dead_edges doesn't handle tablejump's, but if we have split the
638 basic block, we might need to kill some edges. */
639 if (bb != orig_bb && tablejump_p (BB_END (bb), NULL, &table))
640 purge_dead_tablejump_edges (bb, table);
641}
642
643/* Assume that frequency of basic block B is known. Compute frequencies
644 and probabilities of outgoing edges. */
645
646static void
647compute_outgoing_frequencies (basic_block b)
648{
649 edge e, f;
650 edge_iterator ei;
651
652 if (EDGE_COUNT (b->succs) == 2)
653 {
654 rtx note = find_reg_note (BB_END (b), REG_BR_PROB, NULL);
655 int probability;
656
657 if (note)
658 {
659 probability = XINT (note, 0);
660 e = BRANCH_EDGE (b);
661 e->probability
662 = profile_probability::from_reg_br_prob_note (v: probability);
663 f = FALLTHRU_EDGE (b);
664 f->probability = e->probability.invert ();
665 return;
666 }
667 else
668 {
669 guess_outgoing_edge_probabilities (b);
670 }
671 }
672 else if (single_succ_p (bb: b))
673 {
674 e = single_succ_edge (bb: b);
675 e->probability = profile_probability::always ();
676 return;
677 }
678 else
679 {
680 /* We rely on BBs with more than two successors to have sane probabilities
681 and do not guess them here. For BBs terminated by switch statements
682 expanded to jump-table jump, we have done the right thing during
683 expansion. For EH edges, we still guess the probabilities here. */
684 bool complex_edge = false;
685 FOR_EACH_EDGE (e, ei, b->succs)
686 if (e->flags & EDGE_COMPLEX)
687 {
688 complex_edge = true;
689 break;
690 }
691 if (complex_edge)
692 guess_outgoing_edge_probabilities (b);
693 }
694}
695
696/* Update the profile information for BB, which was created by splitting
697 an RTL block that had a non-final jump. */
698
699static void
700update_profile_for_new_sub_basic_block (basic_block bb)
701{
702 edge e;
703 edge_iterator ei;
704
705 bool initialized_src = false, uninitialized_src = false;
706 bb->count = profile_count::zero ();
707 FOR_EACH_EDGE (e, ei, bb->preds)
708 {
709 if (e->count ().initialized_p ())
710 {
711 bb->count += e->count ();
712 initialized_src = true;
713 }
714 else
715 uninitialized_src = true;
716 }
717 /* When some edges are missing with read profile, this is
718 most likely because RTL expansion introduced loop.
719 When profile is guessed we may have BB that is reachable
720 from unlikely path as well as from normal path.
721
722 TODO: We should handle loops created during BB expansion
723 correctly here. For now we assume all those loop to cycle
724 precisely once. */
725 if (!initialized_src
726 || (uninitialized_src
727 && profile_status_for_fn (cfun) < PROFILE_GUESSED))
728 bb->count = profile_count::uninitialized ();
729
730 compute_outgoing_frequencies (b: bb);
731}
732
733/* Assume that some pass has inserted labels or control flow
734 instructions within a basic block. Split basic blocks as needed
735 and create edges. */
736
737void
738find_many_sub_basic_blocks (sbitmap blocks)
739{
740 basic_block bb, min, max;
741 bool found = false;
742 auto_vec<unsigned int> n_succs;
743 n_succs.safe_grow_cleared (last_basic_block_for_fn (cfun), exact: true);
744
745 FOR_EACH_BB_FN (bb, cfun)
746 SET_STATE (bb,
747 bitmap_bit_p (blocks, bb->index) ? BLOCK_TO_SPLIT : BLOCK_ORIGINAL);
748
749 FOR_EACH_BB_FN (bb, cfun)
750 if (STATE (bb) == BLOCK_TO_SPLIT)
751 {
752 int n = last_basic_block_for_fn (cfun);
753 unsigned int ns = EDGE_COUNT (bb->succs);
754
755 find_bb_boundaries (bb);
756 if (n == last_basic_block_for_fn (cfun) && ns == EDGE_COUNT (bb->succs))
757 n_succs[bb->index] = EDGE_COUNT (bb->succs);
758 }
759
760 FOR_EACH_BB_FN (bb, cfun)
761 if (STATE (bb) != BLOCK_ORIGINAL)
762 {
763 found = true;
764 break;
765 }
766
767 if (!found)
768 return;
769
770 min = max = bb;
771 for (; bb != EXIT_BLOCK_PTR_FOR_FN (cfun); bb = bb->next_bb)
772 if (STATE (bb) != BLOCK_ORIGINAL)
773 max = bb;
774
775 /* Now re-scan and wire in all edges. This expect simple (conditional)
776 jumps at the end of each new basic blocks. */
777 make_edges (min, max, update_p: 1);
778
779 /* Update branch probabilities. Expect only (un)conditional jumps
780 to be created with only the forward edges. */
781 if (profile_status_for_fn (cfun) != PROFILE_ABSENT)
782 FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
783 {
784 if (STATE (bb) == BLOCK_ORIGINAL)
785 continue;
786 if (STATE (bb) == BLOCK_NEW)
787 {
788 update_profile_for_new_sub_basic_block (bb);
789 continue;
790 }
791 /* If nothing changed, there is no need to create new BBs. */
792 if (EDGE_COUNT (bb->succs) == n_succs[bb->index])
793 {
794 /* In rare occassions RTL expansion might have mistakely assigned
795 a probabilities different from what is in CFG. This happens
796 when we try to split branch to two but optimize out the
797 second branch during the way. See PR81030. */
798 if (JUMP_P (BB_END (bb)) && any_condjump_p (BB_END (bb))
799 && EDGE_COUNT (bb->succs) >= 2)
800 update_br_prob_note (bb);
801 continue;
802 }
803 compute_outgoing_frequencies (b: bb);
804 }
805
806 FOR_EACH_BB_FN (bb, cfun)
807 SET_STATE (bb, 0);
808}
809
810/* Like find_many_sub_basic_blocks, but look only within BB. */
811
812void
813find_sub_basic_blocks (basic_block bb)
814{
815 basic_block end_bb = bb->next_bb;
816 find_bb_boundaries (bb);
817 if (bb->next_bb == end_bb)
818 return;
819
820 /* Re-scan and wire in all edges. This expects simple (conditional)
821 jumps at the end of each new basic blocks. */
822 make_edges (min: bb, max: end_bb->prev_bb, update_p: 1);
823
824 /* Update branch probabilities. Expect only (un)conditional jumps
825 to be created with only the forward edges. */
826 if (profile_status_for_fn (cfun) != PROFILE_ABSENT)
827 {
828 compute_outgoing_frequencies (b: bb);
829 for (bb = bb->next_bb; bb != end_bb; bb = bb->next_bb)
830 update_profile_for_new_sub_basic_block (bb);
831 }
832}
833

source code of gcc/cfgbuild.cc