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 Free Software Foundation, Inc.
4
5 This file is part of GCC.
6
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
10 version.
11
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.
16
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, 51 Franklin Street, Fifth Floor, Boston, MA
20 02110-1301, USA. */
21
22 /* find_basic_blocks divides the current function's rtl into basic
23 blocks and constructs the CFG. The blocks are recorded in the
24 basic_block_info array; the CFG exists in the edge structures
25 referenced by the blocks.
26
27 find_basic_blocks also finds any unreachable loops and deletes them.
28
29 Available functionality:
30 - CFG construction
31 find_basic_blocks */
32
33 #include "config.h"
34 #include "system.h"
35 #include "coretypes.h"
36 #include "tm.h"
37 #include "tree.h"
38 #include "rtl.h"
39 #include "hard-reg-set.h"
40 #include "basic-block.h"
41 #include "regs.h"
42 #include "flags.h"
43 #include "output.h"
44 #include "function.h"
45 #include "except.h"
46 #include "toplev.h"
47 #include "timevar.h"
48
49 static int count_basic_blocks (rtx);
50 static void find_basic_blocks_1 (rtx);
51 static void make_edges (basic_block, basic_block, int);
52 static void make_label_edge (sbitmap, basic_block, rtx, int);
53 static void find_bb_boundaries (basic_block);
54 static void compute_outgoing_frequencies (basic_block);
55
56 /* Return true if insn is something that should be contained inside basic
57 block. */
58
59 bool
inside_basic_block_p(rtx insn)60 inside_basic_block_p (rtx insn)
61 {
62 switch (GET_CODE (insn))
63 {
64 case CODE_LABEL:
65 /* Avoid creating of basic block for jumptables. */
66 return (NEXT_INSN (insn) == 0
67 || !JUMP_P (NEXT_INSN (insn))
68 || (GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_VEC
69 && GET_CODE (PATTERN (NEXT_INSN (insn))) != ADDR_DIFF_VEC));
70
71 case JUMP_INSN:
72 return (GET_CODE (PATTERN (insn)) != ADDR_VEC
73 && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC);
74
75 case CALL_INSN:
76 case INSN:
77 return true;
78
79 case BARRIER:
80 case NOTE:
81 return false;
82
83 default:
84 gcc_unreachable ();
85 }
86 }
87
88 /* Return true if INSN may cause control flow transfer, so it should be last in
89 the basic block. */
90
91 bool
control_flow_insn_p(rtx insn)92 control_flow_insn_p (rtx insn)
93 {
94 rtx note;
95
96 switch (GET_CODE (insn))
97 {
98 case NOTE:
99 case CODE_LABEL:
100 return false;
101
102 case JUMP_INSN:
103 /* Jump insn always causes control transfer except for tablejumps. */
104 return (GET_CODE (PATTERN (insn)) != ADDR_VEC
105 && GET_CODE (PATTERN (insn)) != ADDR_DIFF_VEC);
106
107 case CALL_INSN:
108 /* Noreturn and sibling call instructions terminate the basic blocks
109 (but only if they happen unconditionally). */
110 if ((SIBLING_CALL_P (insn)
111 || find_reg_note (insn, REG_NORETURN, 0))
112 && GET_CODE (PATTERN (insn)) != COND_EXEC)
113 return true;
114 /* Call insn may return to the nonlocal goto handler. */
115 return ((nonlocal_goto_handler_labels
116 && (0 == (note = find_reg_note (insn, REG_EH_REGION,
117 NULL_RTX))
118 || INTVAL (XEXP (note, 0)) >= 0))
119 /* Or may trap. */
120 || can_throw_internal (insn));
121
122 case INSN:
123 /* Treat trap instructions like noreturn calls (same provision). */
124 if (GET_CODE (PATTERN (insn)) == TRAP_IF
125 && XEXP (PATTERN (insn), 0) == const1_rtx)
126 return true;
127
128 return (flag_non_call_exceptions && can_throw_internal (insn));
129
130 case BARRIER:
131 /* It is nonsense to reach barrier when looking for the
132 end of basic block, but before dead code is eliminated
133 this may happen. */
134 return false;
135
136 default:
137 gcc_unreachable ();
138 }
139 }
140
141 /* Count the basic blocks of the function. */
142
143 static int
count_basic_blocks(rtx f)144 count_basic_blocks (rtx f)
145 {
146 int count = NUM_FIXED_BLOCKS;
147 bool saw_insn = false;
148 rtx insn;
149
150 for (insn = f; insn; insn = NEXT_INSN (insn))
151 {
152 /* Code labels and barriers causes current basic block to be
153 terminated at previous real insn. */
154 if ((LABEL_P (insn) || BARRIER_P (insn))
155 && saw_insn)
156 count++, saw_insn = false;
157
158 /* Start basic block if needed. */
159 if (!saw_insn && inside_basic_block_p (insn))
160 saw_insn = true;
161
162 /* Control flow insn causes current basic block to be terminated. */
163 if (saw_insn && control_flow_insn_p (insn))
164 count++, saw_insn = false;
165 }
166
167 if (saw_insn)
168 count++;
169
170 /* The rest of the compiler works a bit smoother when we don't have to
171 check for the edge case of do-nothing functions with no basic blocks. */
172 if (count == NUM_FIXED_BLOCKS)
173 {
174 emit_insn (gen_rtx_USE (VOIDmode, const0_rtx));
175 count = NUM_FIXED_BLOCKS + 1;
176 }
177
178 return count;
179 }
180
181 /* Create an edge between two basic blocks. FLAGS are auxiliary information
182 about the edge that is accumulated between calls. */
183
184 /* Create an edge from a basic block to a label. */
185
186 static void
make_label_edge(sbitmap edge_cache,basic_block src,rtx label,int flags)187 make_label_edge (sbitmap edge_cache, basic_block src, rtx label, int flags)
188 {
189 gcc_assert (LABEL_P (label));
190
191 /* If the label was never emitted, this insn is junk, but avoid a
192 crash trying to refer to BLOCK_FOR_INSN (label). This can happen
193 as a result of a syntax error and a diagnostic has already been
194 printed. */
195
196 if (INSN_UID (label) == 0)
197 return;
198
199 cached_make_edge (edge_cache, src, BLOCK_FOR_INSN (label), flags);
200 }
201
202 /* Create the edges generated by INSN in REGION. */
203
204 void
rtl_make_eh_edge(sbitmap edge_cache,basic_block src,rtx insn)205 rtl_make_eh_edge (sbitmap edge_cache, basic_block src, rtx insn)
206 {
207 int is_call = CALL_P (insn) ? EDGE_ABNORMAL_CALL : 0;
208 rtx handlers, i;
209
210 handlers = reachable_handlers (insn);
211
212 for (i = handlers; i; i = XEXP (i, 1))
213 make_label_edge (edge_cache, src, XEXP (i, 0),
214 EDGE_ABNORMAL | EDGE_EH | is_call);
215
216 free_INSN_LIST_list (&handlers);
217 }
218
219 /* States of basic block as seen by find_many_sub_basic_blocks. */
220 enum state {
221 /* Basic blocks created via split_block belong to this state.
222 make_edges will examine these basic blocks to see if we need to
223 create edges going out of them. */
224 BLOCK_NEW = 0,
225
226 /* Basic blocks that do not need examining belong to this state.
227 These blocks will be left intact. In particular, make_edges will
228 not create edges going out of these basic blocks. */
229 BLOCK_ORIGINAL,
230
231 /* Basic blocks that may need splitting (due to a label appearing in
232 the middle, etc) belong to this state. After splitting them,
233 make_edges will create edges going out of them as needed. */
234 BLOCK_TO_SPLIT
235 };
236
237 #define STATE(BB) (enum state) ((size_t) (BB)->aux)
238 #define SET_STATE(BB, STATE) ((BB)->aux = (void *) (size_t) (STATE))
239
240 /* Used internally by purge_dead_tablejump_edges, ORed into state. */
241 #define BLOCK_USED_BY_TABLEJUMP 32
242 #define FULL_STATE(BB) ((size_t) (BB)->aux)
243
244 /* Identify the edges going out of basic blocks between MIN and MAX,
245 inclusive, that have their states set to BLOCK_NEW or
246 BLOCK_TO_SPLIT.
247
248 UPDATE_P should be nonzero if we are updating CFG and zero if we
249 are building CFG from scratch. */
250
251 static void
make_edges(basic_block min,basic_block max,int update_p)252 make_edges (basic_block min, basic_block max, int update_p)
253 {
254 basic_block bb;
255 sbitmap edge_cache = NULL;
256
257 /* Heavy use of computed goto in machine-generated code can lead to
258 nearly fully-connected CFGs. In that case we spend a significant
259 amount of time searching the edge lists for duplicates. */
260 if (forced_labels || cfun->max_jumptable_ents > 100)
261 edge_cache = sbitmap_alloc (last_basic_block);
262
263 /* By nature of the way these get numbered, ENTRY_BLOCK_PTR->next_bb block
264 is always the entry. */
265 if (min == ENTRY_BLOCK_PTR->next_bb)
266 make_edge (ENTRY_BLOCK_PTR, min, EDGE_FALLTHRU);
267
268 FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
269 {
270 rtx insn, x;
271 enum rtx_code code;
272 edge e;
273 edge_iterator ei;
274
275 if (STATE (bb) == BLOCK_ORIGINAL)
276 continue;
277
278 /* If we have an edge cache, cache edges going out of BB. */
279 if (edge_cache)
280 {
281 sbitmap_zero (edge_cache);
282 if (update_p)
283 {
284 FOR_EACH_EDGE (e, ei, bb->succs)
285 if (e->dest != EXIT_BLOCK_PTR)
286 SET_BIT (edge_cache, e->dest->index);
287 }
288 }
289
290 if (LABEL_P (BB_HEAD (bb))
291 && LABEL_ALT_ENTRY_P (BB_HEAD (bb)))
292 cached_make_edge (NULL, ENTRY_BLOCK_PTR, bb, 0);
293
294 /* Examine the last instruction of the block, and discover the
295 ways we can leave the block. */
296
297 insn = BB_END (bb);
298 code = GET_CODE (insn);
299
300 /* A branch. */
301 if (code == JUMP_INSN)
302 {
303 rtx tmp;
304
305 /* Recognize exception handling placeholders. */
306 if (GET_CODE (PATTERN (insn)) == RESX)
307 rtl_make_eh_edge (edge_cache, bb, insn);
308
309 /* Recognize a non-local goto as a branch outside the
310 current function. */
311 else if (find_reg_note (insn, REG_NON_LOCAL_GOTO, NULL_RTX))
312 ;
313
314 /* Recognize a tablejump and do the right thing. */
315 else if (tablejump_p (insn, NULL, &tmp))
316 {
317 rtvec vec;
318 int j;
319
320 if (GET_CODE (PATTERN (tmp)) == ADDR_VEC)
321 vec = XVEC (PATTERN (tmp), 0);
322 else
323 vec = XVEC (PATTERN (tmp), 1);
324
325 for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j)
326 make_label_edge (edge_cache, bb,
327 XEXP (RTVEC_ELT (vec, j), 0), 0);
328
329 /* Some targets (eg, ARM) emit a conditional jump that also
330 contains the out-of-range target. Scan for these and
331 add an edge if necessary. */
332 if ((tmp = single_set (insn)) != NULL
333 && SET_DEST (tmp) == pc_rtx
334 && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE
335 && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF)
336 make_label_edge (edge_cache, bb,
337 XEXP (XEXP (SET_SRC (tmp), 2), 0), 0);
338 }
339
340 /* If this is a computed jump, then mark it as reaching
341 everything on the forced_labels list. */
342 else if (computed_jump_p (insn))
343 {
344 for (x = forced_labels; x; x = XEXP (x, 1))
345 make_label_edge (edge_cache, bb, XEXP (x, 0), EDGE_ABNORMAL);
346 }
347
348 /* Returns create an exit out. */
349 else if (returnjump_p (insn))
350 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, 0);
351
352 /* Otherwise, we have a plain conditional or unconditional jump. */
353 else
354 {
355 gcc_assert (JUMP_LABEL (insn));
356 make_label_edge (edge_cache, bb, JUMP_LABEL (insn), 0);
357 }
358 }
359
360 /* If this is a sibling call insn, then this is in effect a combined call
361 and return, and so we need an edge to the exit block. No need to
362 worry about EH edges, since we wouldn't have created the sibling call
363 in the first place. */
364 if (code == CALL_INSN && SIBLING_CALL_P (insn))
365 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR,
366 EDGE_SIBCALL | EDGE_ABNORMAL);
367
368 /* If this is a CALL_INSN, then mark it as reaching the active EH
369 handler for this CALL_INSN. If we're handling non-call
370 exceptions then any insn can reach any of the active handlers.
371 Also mark the CALL_INSN as reaching any nonlocal goto handler. */
372 else if (code == CALL_INSN || flag_non_call_exceptions)
373 {
374 /* Add any appropriate EH edges. */
375 rtl_make_eh_edge (edge_cache, bb, insn);
376
377 if (code == CALL_INSN && nonlocal_goto_handler_labels)
378 {
379 /* ??? This could be made smarter: in some cases it's possible
380 to tell that certain calls will not do a nonlocal goto.
381 For example, if the nested functions that do the nonlocal
382 gotos do not have their addresses taken, then only calls to
383 those functions or to other nested functions that use them
384 could possibly do nonlocal gotos. */
385
386 /* We do know that a REG_EH_REGION note with a value less
387 than 0 is guaranteed not to perform a non-local goto. */
388 rtx note = find_reg_note (insn, REG_EH_REGION, NULL_RTX);
389
390 if (!note || INTVAL (XEXP (note, 0)) >= 0)
391 for (x = nonlocal_goto_handler_labels; x; x = XEXP (x, 1))
392 make_label_edge (edge_cache, bb, XEXP (x, 0),
393 EDGE_ABNORMAL | EDGE_ABNORMAL_CALL);
394 }
395 }
396
397 /* Find out if we can drop through to the next block. */
398 insn = NEXT_INSN (insn);
399 e = find_edge (bb, EXIT_BLOCK_PTR);
400 if (e && e->flags & EDGE_FALLTHRU)
401 insn = NULL;
402
403 while (insn
404 && NOTE_P (insn)
405 && NOTE_LINE_NUMBER (insn) != NOTE_INSN_BASIC_BLOCK)
406 insn = NEXT_INSN (insn);
407
408 if (!insn)
409 cached_make_edge (edge_cache, bb, EXIT_BLOCK_PTR, EDGE_FALLTHRU);
410 else if (bb->next_bb != EXIT_BLOCK_PTR)
411 {
412 if (insn == BB_HEAD (bb->next_bb))
413 cached_make_edge (edge_cache, bb, bb->next_bb, EDGE_FALLTHRU);
414 }
415 }
416
417 if (edge_cache)
418 sbitmap_vector_free (edge_cache);
419 }
420
421 /* Find all basic blocks of the function whose first insn is F.
422
423 Collect and return a list of labels whose addresses are taken. This
424 will be used in make_edges for use with computed gotos. */
425
426 static void
find_basic_blocks_1(rtx f)427 find_basic_blocks_1 (rtx f)
428 {
429 rtx insn, next;
430 rtx bb_note = NULL_RTX;
431 rtx head = NULL_RTX;
432 rtx end = NULL_RTX;
433 basic_block prev = ENTRY_BLOCK_PTR;
434
435 /* We process the instructions in a slightly different way than we did
436 previously. This is so that we see a NOTE_BASIC_BLOCK after we have
437 closed out the previous block, so that it gets attached at the proper
438 place. Since this form should be equivalent to the previous,
439 count_basic_blocks continues to use the old form as a check. */
440
441 for (insn = f; insn; insn = next)
442 {
443 enum rtx_code code = GET_CODE (insn);
444
445 next = NEXT_INSN (insn);
446
447 if ((LABEL_P (insn) || BARRIER_P (insn))
448 && head)
449 {
450 prev = create_basic_block_structure (head, end, bb_note, prev);
451 head = end = NULL_RTX;
452 bb_note = NULL_RTX;
453 }
454
455 if (inside_basic_block_p (insn))
456 {
457 if (head == NULL_RTX)
458 head = insn;
459 end = insn;
460 }
461
462 if (head && control_flow_insn_p (insn))
463 {
464 prev = create_basic_block_structure (head, end, bb_note, prev);
465 head = end = NULL_RTX;
466 bb_note = NULL_RTX;
467 }
468
469 switch (code)
470 {
471 case NOTE:
472 {
473 int kind = NOTE_LINE_NUMBER (insn);
474
475 /* Look for basic block notes with which to keep the
476 basic_block_info pointers stable. Unthread the note now;
477 we'll put it back at the right place in create_basic_block.
478 Or not at all if we've already found a note in this block. */
479 if (kind == NOTE_INSN_BASIC_BLOCK)
480 {
481 if (bb_note == NULL_RTX)
482 bb_note = insn;
483 else
484 next = delete_insn (insn);
485 }
486 break;
487 }
488
489 case CODE_LABEL:
490 case JUMP_INSN:
491 case CALL_INSN:
492 case INSN:
493 case BARRIER:
494 break;
495
496 default:
497 gcc_unreachable ();
498 }
499 }
500
501 if (head != NULL_RTX)
502 create_basic_block_structure (head, end, bb_note, prev);
503 else if (bb_note)
504 delete_insn (bb_note);
505
506 gcc_assert (last_basic_block == n_basic_blocks);
507
508 clear_aux_for_blocks ();
509 }
510
511
512 /* Find basic blocks of the current function.
513 F is the first insn of the function. */
514
515 void
find_basic_blocks(rtx f)516 find_basic_blocks (rtx f)
517 {
518 basic_block bb;
519
520 timevar_push (TV_CFG);
521
522 /* Flush out existing data. */
523 if (basic_block_info != NULL)
524 {
525 clear_edges ();
526
527 /* Clear bb->aux on all extant basic blocks. We'll use this as a
528 tag for reuse during create_basic_block, just in case some pass
529 copies around basic block notes improperly. */
530 FOR_EACH_BB (bb)
531 bb->aux = NULL;
532
533 basic_block_info = NULL;
534 }
535
536 n_basic_blocks = count_basic_blocks (f);
537 last_basic_block = NUM_FIXED_BLOCKS;
538 ENTRY_BLOCK_PTR->next_bb = EXIT_BLOCK_PTR;
539 EXIT_BLOCK_PTR->prev_bb = ENTRY_BLOCK_PTR;
540
541
542 /* Size the basic block table. The actual structures will be allocated
543 by find_basic_blocks_1, since we want to keep the structure pointers
544 stable across calls to find_basic_blocks. */
545 /* ??? This whole issue would be much simpler if we called find_basic_blocks
546 exactly once, and thereafter we don't have a single long chain of
547 instructions at all until close to the end of compilation when we
548 actually lay them out. */
549
550 basic_block_info = VEC_alloc (basic_block, gc, n_basic_blocks);
551 VEC_safe_grow (basic_block, gc, basic_block_info, n_basic_blocks);
552 memset (VEC_address (basic_block, basic_block_info), 0,
553 sizeof (basic_block) * n_basic_blocks);
554 SET_BASIC_BLOCK (ENTRY_BLOCK, ENTRY_BLOCK_PTR);
555 SET_BASIC_BLOCK (EXIT_BLOCK, EXIT_BLOCK_PTR);
556
557 find_basic_blocks_1 (f);
558
559 profile_status = PROFILE_ABSENT;
560
561 /* Tell make_edges to examine every block for out-going edges. */
562 FOR_EACH_BB (bb)
563 SET_STATE (bb, BLOCK_NEW);
564
565 /* Discover the edges of our cfg. */
566 make_edges (ENTRY_BLOCK_PTR->next_bb, EXIT_BLOCK_PTR->prev_bb, 0);
567
568 /* Do very simple cleanup now, for the benefit of code that runs between
569 here and cleanup_cfg, e.g. thread_prologue_and_epilogue_insns. */
570 tidy_fallthru_edges ();
571
572 #ifdef ENABLE_CHECKING
573 verify_flow_info ();
574 #endif
575 timevar_pop (TV_CFG);
576 }
577
578 static void
mark_tablejump_edge(rtx label)579 mark_tablejump_edge (rtx label)
580 {
581 basic_block bb;
582
583 gcc_assert (LABEL_P (label));
584 /* See comment in make_label_edge. */
585 if (INSN_UID (label) == 0)
586 return;
587 bb = BLOCK_FOR_INSN (label);
588 SET_STATE (bb, FULL_STATE (bb) | BLOCK_USED_BY_TABLEJUMP);
589 }
590
591 static void
purge_dead_tablejump_edges(basic_block bb,rtx table)592 purge_dead_tablejump_edges (basic_block bb, rtx table)
593 {
594 rtx insn = BB_END (bb), tmp;
595 rtvec vec;
596 int j;
597 edge_iterator ei;
598 edge e;
599
600 if (GET_CODE (PATTERN (table)) == ADDR_VEC)
601 vec = XVEC (PATTERN (table), 0);
602 else
603 vec = XVEC (PATTERN (table), 1);
604
605 for (j = GET_NUM_ELEM (vec) - 1; j >= 0; --j)
606 mark_tablejump_edge (XEXP (RTVEC_ELT (vec, j), 0));
607
608 /* Some targets (eg, ARM) emit a conditional jump that also
609 contains the out-of-range target. Scan for these and
610 add an edge if necessary. */
611 if ((tmp = single_set (insn)) != NULL
612 && SET_DEST (tmp) == pc_rtx
613 && GET_CODE (SET_SRC (tmp)) == IF_THEN_ELSE
614 && GET_CODE (XEXP (SET_SRC (tmp), 2)) == LABEL_REF)
615 mark_tablejump_edge (XEXP (XEXP (SET_SRC (tmp), 2), 0));
616
617 for (ei = ei_start (bb->succs); (e = ei_safe_edge (ei)); )
618 {
619 if (FULL_STATE (e->dest) & BLOCK_USED_BY_TABLEJUMP)
620 SET_STATE (e->dest, FULL_STATE (e->dest)
621 & ~(size_t) BLOCK_USED_BY_TABLEJUMP);
622 else if (!(e->flags & (EDGE_ABNORMAL | EDGE_EH)))
623 {
624 remove_edge (e);
625 continue;
626 }
627 ei_next (&ei);
628 }
629 }
630
631 /* Scan basic block BB for possible BB boundaries inside the block
632 and create new basic blocks in the progress. */
633
634 static void
find_bb_boundaries(basic_block bb)635 find_bb_boundaries (basic_block bb)
636 {
637 basic_block orig_bb = bb;
638 rtx insn = BB_HEAD (bb);
639 rtx end = BB_END (bb);
640 rtx table;
641 rtx flow_transfer_insn = NULL_RTX;
642 edge fallthru = NULL;
643
644 if (insn == BB_END (bb))
645 return;
646
647 if (LABEL_P (insn))
648 insn = NEXT_INSN (insn);
649
650 /* Scan insn chain and try to find new basic block boundaries. */
651 while (1)
652 {
653 enum rtx_code code = GET_CODE (insn);
654
655 /* On code label, split current basic block. */
656 if (code == CODE_LABEL)
657 {
658 fallthru = split_block (bb, PREV_INSN (insn));
659 if (flow_transfer_insn)
660 BB_END (bb) = flow_transfer_insn;
661
662 bb = fallthru->dest;
663 remove_edge (fallthru);
664 flow_transfer_insn = NULL_RTX;
665 if (LABEL_ALT_ENTRY_P (insn))
666 make_edge (ENTRY_BLOCK_PTR, bb, 0);
667 }
668
669 /* In case we've previously seen an insn that effects a control
670 flow transfer, split the block. */
671 if (flow_transfer_insn && inside_basic_block_p (insn))
672 {
673 fallthru = split_block (bb, PREV_INSN (insn));
674 BB_END (bb) = flow_transfer_insn;
675 bb = fallthru->dest;
676 remove_edge (fallthru);
677 flow_transfer_insn = NULL_RTX;
678 }
679
680 if (control_flow_insn_p (insn))
681 flow_transfer_insn = insn;
682 if (insn == end)
683 break;
684 insn = NEXT_INSN (insn);
685 }
686
687 /* In case expander replaced normal insn by sequence terminating by
688 return and barrier, or possibly other sequence not behaving like
689 ordinary jump, we need to take care and move basic block boundary. */
690 if (flow_transfer_insn)
691 BB_END (bb) = flow_transfer_insn;
692
693 /* We've possibly replaced the conditional jump by conditional jump
694 followed by cleanup at fallthru edge, so the outgoing edges may
695 be dead. */
696 purge_dead_edges (bb);
697
698 /* purge_dead_edges doesn't handle tablejump's, but if we have split the
699 basic block, we might need to kill some edges. */
700 if (bb != orig_bb && tablejump_p (BB_END (bb), NULL, &table))
701 purge_dead_tablejump_edges (bb, table);
702 }
703
704 /* Assume that frequency of basic block B is known. Compute frequencies
705 and probabilities of outgoing edges. */
706
707 static void
compute_outgoing_frequencies(basic_block b)708 compute_outgoing_frequencies (basic_block b)
709 {
710 edge e, f;
711 edge_iterator ei;
712
713 if (EDGE_COUNT (b->succs) == 2)
714 {
715 rtx note = find_reg_note (BB_END (b), REG_BR_PROB, NULL);
716 int probability;
717
718 if (note)
719 {
720 probability = INTVAL (XEXP (note, 0));
721 e = BRANCH_EDGE (b);
722 e->probability = probability;
723 e->count = ((b->count * probability + REG_BR_PROB_BASE / 2)
724 / REG_BR_PROB_BASE);
725 f = FALLTHRU_EDGE (b);
726 f->probability = REG_BR_PROB_BASE - probability;
727 f->count = b->count - e->count;
728 return;
729 }
730 }
731
732 if (single_succ_p (b))
733 {
734 e = single_succ_edge (b);
735 e->probability = REG_BR_PROB_BASE;
736 e->count = b->count;
737 return;
738 }
739 guess_outgoing_edge_probabilities (b);
740 if (b->count)
741 FOR_EACH_EDGE (e, ei, b->succs)
742 e->count = ((b->count * e->probability + REG_BR_PROB_BASE / 2)
743 / REG_BR_PROB_BASE);
744 }
745
746 /* Assume that some pass has inserted labels or control flow
747 instructions within a basic block. Split basic blocks as needed
748 and create edges. */
749
750 void
find_many_sub_basic_blocks(sbitmap blocks)751 find_many_sub_basic_blocks (sbitmap blocks)
752 {
753 basic_block bb, min, max;
754
755 FOR_EACH_BB (bb)
756 SET_STATE (bb,
757 TEST_BIT (blocks, bb->index) ? BLOCK_TO_SPLIT : BLOCK_ORIGINAL);
758
759 FOR_EACH_BB (bb)
760 if (STATE (bb) == BLOCK_TO_SPLIT)
761 find_bb_boundaries (bb);
762
763 FOR_EACH_BB (bb)
764 if (STATE (bb) != BLOCK_ORIGINAL)
765 break;
766
767 min = max = bb;
768 for (; bb != EXIT_BLOCK_PTR; bb = bb->next_bb)
769 if (STATE (bb) != BLOCK_ORIGINAL)
770 max = bb;
771
772 /* Now re-scan and wire in all edges. This expect simple (conditional)
773 jumps at the end of each new basic blocks. */
774 make_edges (min, max, 1);
775
776 /* Update branch probabilities. Expect only (un)conditional jumps
777 to be created with only the forward edges. */
778 if (profile_status != PROFILE_ABSENT)
779 FOR_BB_BETWEEN (bb, min, max->next_bb, next_bb)
780 {
781 edge e;
782 edge_iterator ei;
783
784 if (STATE (bb) == BLOCK_ORIGINAL)
785 continue;
786 if (STATE (bb) == BLOCK_NEW)
787 {
788 bb->count = 0;
789 bb->frequency = 0;
790 FOR_EACH_EDGE (e, ei, bb->preds)
791 {
792 bb->count += e->count;
793 bb->frequency += EDGE_FREQUENCY (e);
794 }
795 }
796
797 compute_outgoing_frequencies (bb);
798 }
799
800 FOR_EACH_BB (bb)
801 SET_STATE (bb, 0);
802 }
803