summaryrefslogtreecommitdiff
path: root/gcc/cfganal.c
blob: 762eea4ca04906dfdc189bea8c158f51ca0179d4 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
/* Control flow graph analysis code for GNU compiler.
   Copyright (C) 1987-2013 Free Software Foundation, Inc.

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

/* This file contains various simple utilities to analyze the CFG.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "basic-block.h"
#include "vec.h"
#include "bitmap.h"
#include "sbitmap.h"
#include "timevar.h"

/* Store the data structures necessary for depth-first search.  */
struct depth_first_search_dsS {
  /* stack for backtracking during the algorithm */
  basic_block *stack;

  /* number of edges in the stack.  That is, positions 0, ..., sp-1
     have edges.  */
  unsigned int sp;

  /* record of basic blocks already seen by depth-first search */
  sbitmap visited_blocks;
};
typedef struct depth_first_search_dsS *depth_first_search_ds;

static void flow_dfs_compute_reverse_init (depth_first_search_ds);
static void flow_dfs_compute_reverse_add_bb (depth_first_search_ds,
					     basic_block);
static basic_block flow_dfs_compute_reverse_execute (depth_first_search_ds,
						     basic_block);
static void flow_dfs_compute_reverse_finish (depth_first_search_ds);

/* Mark the back edges in DFS traversal.
   Return nonzero if a loop (natural or otherwise) is present.
   Inspired by Depth_First_Search_PP described in:

     Advanced Compiler Design and Implementation
     Steven Muchnick
     Morgan Kaufmann, 1997

   and heavily borrowed from pre_and_rev_post_order_compute.  */

bool
mark_dfs_back_edges (void)
{
  edge_iterator *stack;
  int *pre;
  int *post;
  int sp;
  int prenum = 1;
  int postnum = 1;
  sbitmap visited;
  bool found = false;

  /* Allocate the preorder and postorder number arrays.  */
  pre = XCNEWVEC (int, last_basic_block);
  post = XCNEWVEC (int, last_basic_block);

  /* Allocate stack for back-tracking up CFG.  */
  stack = XNEWVEC (edge_iterator, n_basic_blocks + 1);
  sp = 0;

  /* Allocate bitmap to track nodes that have been visited.  */
  visited = sbitmap_alloc (last_basic_block);

  /* None of the nodes in the CFG have been visited yet.  */
  bitmap_clear (visited);

  /* Push the first edge on to the stack.  */
  stack[sp++] = ei_start (ENTRY_BLOCK_PTR->succs);

  while (sp)
    {
      edge_iterator ei;
      basic_block src;
      basic_block dest;

      /* Look at the edge on the top of the stack.  */
      ei = stack[sp - 1];
      src = ei_edge (ei)->src;
      dest = ei_edge (ei)->dest;
      ei_edge (ei)->flags &= ~EDGE_DFS_BACK;

      /* Check if the edge destination has been visited yet.  */
      if (dest != EXIT_BLOCK_PTR && ! bitmap_bit_p (visited, dest->index))
	{
	  /* Mark that we have visited the destination.  */
	  bitmap_set_bit (visited, dest->index);

	  pre[dest->index] = prenum++;
	  if (EDGE_COUNT (dest->succs) > 0)
	    {
	      /* Since the DEST node has been visited for the first
		 time, check its successors.  */
	      stack[sp++] = ei_start (dest->succs);
	    }
	  else
	    post[dest->index] = postnum++;
	}
      else
	{
	  if (dest != EXIT_BLOCK_PTR && src != ENTRY_BLOCK_PTR
	      && pre[src->index] >= pre[dest->index]
	      && post[dest->index] == 0)
	    ei_edge (ei)->flags |= EDGE_DFS_BACK, found = true;

	  if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR)
	    post[src->index] = postnum++;

	  if (!ei_one_before_end_p (ei))
	    ei_next (&stack[sp - 1]);
	  else
	    sp--;
	}
    }

  free (pre);
  free (post);
  free (stack);
  sbitmap_free (visited);

  return found;
}

/* Find unreachable blocks.  An unreachable block will have 0 in
   the reachable bit in block->flags.  A nonzero value indicates the
   block is reachable.  */

void
find_unreachable_blocks (void)
{
  edge e;
  edge_iterator ei;
  basic_block *tos, *worklist, bb;

  tos = worklist = XNEWVEC (basic_block, n_basic_blocks);

  /* Clear all the reachability flags.  */

  FOR_EACH_BB (bb)
    bb->flags &= ~BB_REACHABLE;

  /* Add our starting points to the worklist.  Almost always there will
     be only one.  It isn't inconceivable that we might one day directly
     support Fortran alternate entry points.  */

  FOR_EACH_EDGE (e, ei, ENTRY_BLOCK_PTR->succs)
    {
      *tos++ = e->dest;

      /* Mark the block reachable.  */
      e->dest->flags |= BB_REACHABLE;
    }

  /* Iterate: find everything reachable from what we've already seen.  */

  while (tos != worklist)
    {
      basic_block b = *--tos;

      FOR_EACH_EDGE (e, ei, b->succs)
	{
	  basic_block dest = e->dest;

	  if (!(dest->flags & BB_REACHABLE))
	    {
	      *tos++ = dest;
	      dest->flags |= BB_REACHABLE;
	    }
	}
    }

  free (worklist);
}

/* Functions to access an edge list with a vector representation.
   Enough data is kept such that given an index number, the
   pred and succ that edge represents can be determined, or
   given a pred and a succ, its index number can be returned.
   This allows algorithms which consume a lot of memory to
   represent the normally full matrix of edge (pred,succ) with a
   single indexed vector,  edge (EDGE_INDEX (pred, succ)), with no
   wasted space in the client code due to sparse flow graphs.  */

/* This functions initializes the edge list. Basically the entire
   flowgraph is processed, and all edges are assigned a number,
   and the data structure is filled in.  */

struct edge_list *
create_edge_list (void)
{
  struct edge_list *elist;
  edge e;
  int num_edges;
  basic_block bb;
  edge_iterator ei;

  /* Determine the number of edges in the flow graph by counting successor
     edges on each basic block.  */
  num_edges = 0;
  FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
    {
      num_edges += EDGE_COUNT (bb->succs);
    }

  elist = XNEW (struct edge_list);
  elist->num_edges = num_edges;
  elist->index_to_edge = XNEWVEC (edge, num_edges);

  num_edges = 0;

  /* Follow successors of blocks, and register these edges.  */
  FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
    FOR_EACH_EDGE (e, ei, bb->succs)
      elist->index_to_edge[num_edges++] = e;

  return elist;
}

/* This function free's memory associated with an edge list.  */

void
free_edge_list (struct edge_list *elist)
{
  if (elist)
    {
      free (elist->index_to_edge);
      free (elist);
    }
}

/* This function provides debug output showing an edge list.  */

DEBUG_FUNCTION void
print_edge_list (FILE *f, struct edge_list *elist)
{
  int x;

  fprintf (f, "Compressed edge list, %d BBs + entry & exit, and %d edges\n",
	   n_basic_blocks, elist->num_edges);

  for (x = 0; x < elist->num_edges; x++)
    {
      fprintf (f, " %-4d - edge(", x);
      if (INDEX_EDGE_PRED_BB (elist, x) == ENTRY_BLOCK_PTR)
	fprintf (f, "entry,");
      else
	fprintf (f, "%d,", INDEX_EDGE_PRED_BB (elist, x)->index);

      if (INDEX_EDGE_SUCC_BB (elist, x) == EXIT_BLOCK_PTR)
	fprintf (f, "exit)\n");
      else
	fprintf (f, "%d)\n", INDEX_EDGE_SUCC_BB (elist, x)->index);
    }
}

/* This function provides an internal consistency check of an edge list,
   verifying that all edges are present, and that there are no
   extra edges.  */

DEBUG_FUNCTION void
verify_edge_list (FILE *f, struct edge_list *elist)
{
  int pred, succ, index;
  edge e;
  basic_block bb, p, s;
  edge_iterator ei;

  FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
    {
      FOR_EACH_EDGE (e, ei, bb->succs)
	{
	  pred = e->src->index;
	  succ = e->dest->index;
	  index = EDGE_INDEX (elist, e->src, e->dest);
	  if (index == EDGE_INDEX_NO_EDGE)
	    {
	      fprintf (f, "*p* No index for edge from %d to %d\n", pred, succ);
	      continue;
	    }

	  if (INDEX_EDGE_PRED_BB (elist, index)->index != pred)
	    fprintf (f, "*p* Pred for index %d should be %d not %d\n",
		     index, pred, INDEX_EDGE_PRED_BB (elist, index)->index);
	  if (INDEX_EDGE_SUCC_BB (elist, index)->index != succ)
	    fprintf (f, "*p* Succ for index %d should be %d not %d\n",
		     index, succ, INDEX_EDGE_SUCC_BB (elist, index)->index);
	}
    }

  /* We've verified that all the edges are in the list, now lets make sure
     there are no spurious edges in the list.  This is an expensive check!  */

  FOR_BB_BETWEEN (p, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
    FOR_BB_BETWEEN (s, ENTRY_BLOCK_PTR->next_bb, NULL, next_bb)
      {
	int found_edge = 0;

	FOR_EACH_EDGE (e, ei, p->succs)
	  if (e->dest == s)
	    {
	      found_edge = 1;
	      break;
	    }

	FOR_EACH_EDGE (e, ei, s->preds)
	  if (e->src == p)
	    {
	      found_edge = 1;
	      break;
	    }

	if (EDGE_INDEX (elist, p, s)
	    == EDGE_INDEX_NO_EDGE && found_edge != 0)
	  fprintf (f, "*** Edge (%d, %d) appears to not have an index\n",
		   p->index, s->index);
	if (EDGE_INDEX (elist, p, s)
	    != EDGE_INDEX_NO_EDGE && found_edge == 0)
	  fprintf (f, "*** Edge (%d, %d) has index %d, but there is no edge\n",
		   p->index, s->index, EDGE_INDEX (elist, p, s));
      }
}


/* Functions to compute control dependences.  */

/* Indicate block BB is control dependent on an edge with index EDGE_INDEX.  */
void
control_dependences::set_control_dependence_map_bit (basic_block bb,
						     int edge_index)
{
  if (bb == ENTRY_BLOCK_PTR)
    return;
  gcc_assert (bb != EXIT_BLOCK_PTR);
  bitmap_set_bit (control_dependence_map[bb->index], edge_index);
}

/* Clear all control dependences for block BB.  */
void
control_dependences::clear_control_dependence_bitmap (basic_block bb)
{
  bitmap_clear (control_dependence_map[bb->index]);
}

/* Find the immediate postdominator PDOM of the specified basic block BLOCK.
   This function is necessary because some blocks have negative numbers.  */

static inline basic_block
find_pdom (basic_block block)
{
  gcc_assert (block != ENTRY_BLOCK_PTR);

  if (block == EXIT_BLOCK_PTR)
    return EXIT_BLOCK_PTR;
  else
    {
      basic_block bb = get_immediate_dominator (CDI_POST_DOMINATORS, block);
      if (! bb)
	return EXIT_BLOCK_PTR;
      return bb;
    }
}

/* Determine all blocks' control dependences on the given edge with edge_list
   EL index EDGE_INDEX, ala Morgan, Section 3.6.  */

void
control_dependences::find_control_dependence (int edge_index)
{
  basic_block current_block;
  basic_block ending_block;

  gcc_assert (INDEX_EDGE_PRED_BB (m_el, edge_index) != EXIT_BLOCK_PTR);

  if (INDEX_EDGE_PRED_BB (m_el, edge_index) == ENTRY_BLOCK_PTR)
    ending_block = single_succ (ENTRY_BLOCK_PTR);
  else
    ending_block = find_pdom (INDEX_EDGE_PRED_BB (m_el, edge_index));

  for (current_block = INDEX_EDGE_SUCC_BB (m_el, edge_index);
       current_block != ending_block && current_block != EXIT_BLOCK_PTR;
       current_block = find_pdom (current_block))
    {
      edge e = INDEX_EDGE (m_el, edge_index);

      /* For abnormal edges, we don't make current_block control
	 dependent because instructions that throw are always necessary
	 anyway.  */
      if (e->flags & EDGE_ABNORMAL)
	continue;

      set_control_dependence_map_bit (current_block, edge_index);
    }
}

/* Record all blocks' control dependences on all edges in the edge
   list EL, ala Morgan, Section 3.6.  */

control_dependences::control_dependences (struct edge_list *edges)
  : m_el (edges)
{
  timevar_push (TV_CONTROL_DEPENDENCES);
  control_dependence_map.create (last_basic_block);
  for (int i = 0; i < last_basic_block; ++i)
    control_dependence_map.quick_push (BITMAP_ALLOC (NULL));
  for (int i = 0; i < NUM_EDGES (m_el); ++i)
    find_control_dependence (i);
  timevar_pop (TV_CONTROL_DEPENDENCES);
}

/* Free control dependences and the associated edge list.  */

control_dependences::~control_dependences ()
{
  for (unsigned i = 0; i < control_dependence_map.length (); ++i)
    BITMAP_FREE (control_dependence_map[i]);
  control_dependence_map.release ();
  free_edge_list (m_el);
}

/* Returns the bitmap of edges the basic-block I is dependent on.  */

bitmap
control_dependences::get_edges_dependent_on (int i)
{
  return control_dependence_map[i];
}

/* Returns the edge with index I from the edge list.  */

edge
control_dependences::get_edge (int i)
{
  return INDEX_EDGE (m_el, i);
}


/* Given PRED and SUCC blocks, return the edge which connects the blocks.
   If no such edge exists, return NULL.  */

edge
find_edge (basic_block pred, basic_block succ)
{
  edge e;
  edge_iterator ei;

  if (EDGE_COUNT (pred->succs) <= EDGE_COUNT (succ->preds))
    {
      FOR_EACH_EDGE (e, ei, pred->succs)
	if (e->dest == succ)
	  return e;
    }
  else
    {
      FOR_EACH_EDGE (e, ei, succ->preds)
	if (e->src == pred)
	  return e;
    }

  return NULL;
}

/* This routine will determine what, if any, edge there is between
   a specified predecessor and successor.  */

int
find_edge_index (struct edge_list *edge_list, basic_block pred, basic_block succ)
{
  int x;

  for (x = 0; x < NUM_EDGES (edge_list); x++)
    if (INDEX_EDGE_PRED_BB (edge_list, x) == pred
	&& INDEX_EDGE_SUCC_BB (edge_list, x) == succ)
      return x;

  return (EDGE_INDEX_NO_EDGE);
}

/* This routine will remove any fake predecessor edges for a basic block.
   When the edge is removed, it is also removed from whatever successor
   list it is in.  */

static void
remove_fake_predecessors (basic_block bb)
{
  edge e;
  edge_iterator ei;

  for (ei = ei_start (bb->preds); (e = ei_safe_edge (ei)); )
    {
      if ((e->flags & EDGE_FAKE) == EDGE_FAKE)
	remove_edge (e);
      else
	ei_next (&ei);
    }
}

/* This routine will remove all fake edges from the flow graph.  If
   we remove all fake successors, it will automatically remove all
   fake predecessors.  */

void
remove_fake_edges (void)
{
  basic_block bb;

  FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR->next_bb, NULL, next_bb)
    remove_fake_predecessors (bb);
}

/* This routine will remove all fake edges to the EXIT_BLOCK.  */

void
remove_fake_exit_edges (void)
{
  remove_fake_predecessors (EXIT_BLOCK_PTR);
}


/* This function will add a fake edge between any block which has no
   successors, and the exit block. Some data flow equations require these
   edges to exist.  */

void
add_noreturn_fake_exit_edges (void)
{
  basic_block bb;

  FOR_EACH_BB (bb)
    if (EDGE_COUNT (bb->succs) == 0)
      make_single_succ_edge (bb, EXIT_BLOCK_PTR, EDGE_FAKE);
}

/* This function adds a fake edge between any infinite loops to the
   exit block.  Some optimizations require a path from each node to
   the exit node.

   See also Morgan, Figure 3.10, pp. 82-83.

   The current implementation is ugly, not attempting to minimize the
   number of inserted fake edges.  To reduce the number of fake edges
   to insert, add fake edges from _innermost_ loops containing only
   nodes not reachable from the exit block.  */

void
connect_infinite_loops_to_exit (void)
{
  basic_block unvisited_block = EXIT_BLOCK_PTR;
  basic_block deadend_block;
  struct depth_first_search_dsS dfs_ds;

  /* Perform depth-first search in the reverse graph to find nodes
     reachable from the exit block.  */
  flow_dfs_compute_reverse_init (&dfs_ds);
  flow_dfs_compute_reverse_add_bb (&dfs_ds, EXIT_BLOCK_PTR);

  /* Repeatedly add fake edges, updating the unreachable nodes.  */
  while (1)
    {
      unvisited_block = flow_dfs_compute_reverse_execute (&dfs_ds,
							  unvisited_block);
      if (!unvisited_block)
	break;

      deadend_block = dfs_find_deadend (unvisited_block);
      make_edge (deadend_block, EXIT_BLOCK_PTR, EDGE_FAKE);
      flow_dfs_compute_reverse_add_bb (&dfs_ds, deadend_block);
    }

  flow_dfs_compute_reverse_finish (&dfs_ds);
  return;
}

/* Compute reverse top sort order.  This is computing a post order
   numbering of the graph.  If INCLUDE_ENTRY_EXIT is true, then
   ENTRY_BLOCK and EXIT_BLOCK are included.  If DELETE_UNREACHABLE is
   true, unreachable blocks are deleted.  */

int
post_order_compute (int *post_order, bool include_entry_exit,
		    bool delete_unreachable)
{
  edge_iterator *stack;
  int sp;
  int post_order_num = 0;
  sbitmap visited;
  int count;

  if (include_entry_exit)
    post_order[post_order_num++] = EXIT_BLOCK;

  /* Allocate stack for back-tracking up CFG.  */
  stack = XNEWVEC (edge_iterator, n_basic_blocks + 1);
  sp = 0;

  /* Allocate bitmap to track nodes that have been visited.  */
  visited = sbitmap_alloc (last_basic_block);

  /* None of the nodes in the CFG have been visited yet.  */
  bitmap_clear (visited);

  /* Push the first edge on to the stack.  */
  stack[sp++] = ei_start (ENTRY_BLOCK_PTR->succs);

  while (sp)
    {
      edge_iterator ei;
      basic_block src;
      basic_block dest;

      /* Look at the edge on the top of the stack.  */
      ei = stack[sp - 1];
      src = ei_edge (ei)->src;
      dest = ei_edge (ei)->dest;

      /* Check if the edge destination has been visited yet.  */
      if (dest != EXIT_BLOCK_PTR && ! bitmap_bit_p (visited, dest->index))
	{
	  /* Mark that we have visited the destination.  */
	  bitmap_set_bit (visited, dest->index);

	  if (EDGE_COUNT (dest->succs) > 0)
	    /* Since the DEST node has been visited for the first
	       time, check its successors.  */
	    stack[sp++] = ei_start (dest->succs);
	  else
	    post_order[post_order_num++] = dest->index;
	}
      else
	{
	  if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR)
	    post_order[post_order_num++] = src->index;

	  if (!ei_one_before_end_p (ei))
	    ei_next (&stack[sp - 1]);
	  else
	    sp--;
	}
    }

  if (include_entry_exit)
    {
      post_order[post_order_num++] = ENTRY_BLOCK;
      count = post_order_num;
    }
  else
    count = post_order_num + 2;

  /* Delete the unreachable blocks if some were found and we are
     supposed to do it.  */
  if (delete_unreachable && (count != n_basic_blocks))
    {
      basic_block b;
      basic_block next_bb;
      for (b = ENTRY_BLOCK_PTR->next_bb; b != EXIT_BLOCK_PTR; b = next_bb)
	{
	  next_bb = b->next_bb;

	  if (!(bitmap_bit_p (visited, b->index)))
	    delete_basic_block (b);
	}

      tidy_fallthru_edges ();
    }

  free (stack);
  sbitmap_free (visited);
  return post_order_num;
}


/* Helper routine for inverted_post_order_compute
   flow_dfs_compute_reverse_execute, and the reverse-CFG
   deapth first search in dominance.c.
   BB has to belong to a region of CFG
   unreachable by inverted traversal from the exit.
   i.e. there's no control flow path from ENTRY to EXIT
   that contains this BB.
   This can happen in two cases - if there's an infinite loop
   or if there's a block that has no successor
   (call to a function with no return).
   Some RTL passes deal with this condition by
   calling connect_infinite_loops_to_exit () and/or
   add_noreturn_fake_exit_edges ().
   However, those methods involve modifying the CFG itself
   which may not be desirable.
   Hence, we deal with the infinite loop/no return cases
   by identifying a unique basic block that can reach all blocks
   in such a region by inverted traversal.
   This function returns a basic block that guarantees
   that all blocks in the region are reachable
   by starting an inverted traversal from the returned block.  */

basic_block
dfs_find_deadend (basic_block bb)
{
  bitmap visited = BITMAP_ALLOC (NULL);

  for (;;)
    {
      if (EDGE_COUNT (bb->succs) == 0
	  || ! bitmap_set_bit (visited, bb->index))
        {
          BITMAP_FREE (visited);
          return bb;
        }

      bb = EDGE_SUCC (bb, 0)->dest;
    }

  gcc_unreachable ();
}


/* Compute the reverse top sort order of the inverted CFG
   i.e. starting from the exit block and following the edges backward
   (from successors to predecessors).
   This ordering can be used for forward dataflow problems among others.

   This function assumes that all blocks in the CFG are reachable
   from the ENTRY (but not necessarily from EXIT).

   If there's an infinite loop,
   a simple inverted traversal starting from the blocks
   with no successors can't visit all blocks.
   To solve this problem, we first do inverted traversal
   starting from the blocks with no successor.
   And if there's any block left that's not visited by the regular
   inverted traversal from EXIT,
   those blocks are in such problematic region.
   Among those, we find one block that has
   any visited predecessor (which is an entry into such a region),
   and start looking for a "dead end" from that block
   and do another inverted traversal from that block.  */

int
inverted_post_order_compute (int *post_order)
{
  basic_block bb;
  edge_iterator *stack;
  int sp;
  int post_order_num = 0;
  sbitmap visited;

  /* Allocate stack for back-tracking up CFG.  */
  stack = XNEWVEC (edge_iterator, n_basic_blocks + 1);
  sp = 0;

  /* Allocate bitmap to track nodes that have been visited.  */
  visited = sbitmap_alloc (last_basic_block);

  /* None of the nodes in the CFG have been visited yet.  */
  bitmap_clear (visited);

  /* Put all blocks that have no successor into the initial work list.  */
  FOR_ALL_BB (bb)
    if (EDGE_COUNT (bb->succs) == 0)
      {
        /* Push the initial edge on to the stack.  */
        if (EDGE_COUNT (bb->preds) > 0)
          {
            stack[sp++] = ei_start (bb->preds);
            bitmap_set_bit (visited, bb->index);
          }
      }

  do
    {
      bool has_unvisited_bb = false;

      /* The inverted traversal loop. */
      while (sp)
        {
          edge_iterator ei;
          basic_block pred;

          /* Look at the edge on the top of the stack.  */
          ei = stack[sp - 1];
          bb = ei_edge (ei)->dest;
          pred = ei_edge (ei)->src;

          /* Check if the predecessor has been visited yet.  */
          if (! bitmap_bit_p (visited, pred->index))
            {
              /* Mark that we have visited the destination.  */
              bitmap_set_bit (visited, pred->index);

              if (EDGE_COUNT (pred->preds) > 0)
                /* Since the predecessor node has been visited for the first
                   time, check its predecessors.  */
                stack[sp++] = ei_start (pred->preds);
              else
                post_order[post_order_num++] = pred->index;
            }
          else
            {
              if (bb != EXIT_BLOCK_PTR && ei_one_before_end_p (ei))
                post_order[post_order_num++] = bb->index;

              if (!ei_one_before_end_p (ei))
                ei_next (&stack[sp - 1]);
              else
                sp--;
            }
        }

      /* Detect any infinite loop and activate the kludge.
         Note that this doesn't check EXIT_BLOCK itself
         since EXIT_BLOCK is always added after the outer do-while loop.  */
      FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR, EXIT_BLOCK_PTR, next_bb)
        if (!bitmap_bit_p (visited, bb->index))
          {
            has_unvisited_bb = true;

            if (EDGE_COUNT (bb->preds) > 0)
              {
                edge_iterator ei;
                edge e;
                basic_block visited_pred = NULL;

                /* Find an already visited predecessor.  */
                FOR_EACH_EDGE (e, ei, bb->preds)
                  {
                    if (bitmap_bit_p (visited, e->src->index))
                      visited_pred = e->src;
                  }

                if (visited_pred)
                  {
                    basic_block be = dfs_find_deadend (bb);
                    gcc_assert (be != NULL);
                    bitmap_set_bit (visited, be->index);
                    stack[sp++] = ei_start (be->preds);
                    break;
                  }
              }
          }

      if (has_unvisited_bb && sp == 0)
        {
          /* No blocks are reachable from EXIT at all.
             Find a dead-end from the ENTRY, and restart the iteration. */
          basic_block be = dfs_find_deadend (ENTRY_BLOCK_PTR);
          gcc_assert (be != NULL);
          bitmap_set_bit (visited, be->index);
          stack[sp++] = ei_start (be->preds);
        }

      /* The only case the below while fires is
         when there's an infinite loop.  */
    }
  while (sp);

  /* EXIT_BLOCK is always included.  */
  post_order[post_order_num++] = EXIT_BLOCK;

  free (stack);
  sbitmap_free (visited);
  return post_order_num;
}

/* Compute the depth first search order and store in the array
  PRE_ORDER if nonzero, marking the nodes visited in VISITED.  If
  REV_POST_ORDER is nonzero, return the reverse completion number for each
  node.  Returns the number of nodes visited.  A depth first search
  tries to get as far away from the starting point as quickly as
  possible.

  pre_order is a really a preorder numbering of the graph.
  rev_post_order is really a reverse postorder numbering of the graph.
 */

int
pre_and_rev_post_order_compute (int *pre_order, int *rev_post_order,
				bool include_entry_exit)
{
  edge_iterator *stack;
  int sp;
  int pre_order_num = 0;
  int rev_post_order_num = n_basic_blocks - 1;
  sbitmap visited;

  /* Allocate stack for back-tracking up CFG.  */
  stack = XNEWVEC (edge_iterator, n_basic_blocks + 1);
  sp = 0;

  if (include_entry_exit)
    {
      if (pre_order)
	pre_order[pre_order_num] = ENTRY_BLOCK;
      pre_order_num++;
      if (rev_post_order)
	rev_post_order[rev_post_order_num--] = ENTRY_BLOCK;
    }
  else
    rev_post_order_num -= NUM_FIXED_BLOCKS;

  /* Allocate bitmap to track nodes that have been visited.  */
  visited = sbitmap_alloc (last_basic_block);

  /* None of the nodes in the CFG have been visited yet.  */
  bitmap_clear (visited);

  /* Push the first edge on to the stack.  */
  stack[sp++] = ei_start (ENTRY_BLOCK_PTR->succs);

  while (sp)
    {
      edge_iterator ei;
      basic_block src;
      basic_block dest;

      /* Look at the edge on the top of the stack.  */
      ei = stack[sp - 1];
      src = ei_edge (ei)->src;
      dest = ei_edge (ei)->dest;

      /* Check if the edge destination has been visited yet.  */
      if (dest != EXIT_BLOCK_PTR && ! bitmap_bit_p (visited, dest->index))
	{
	  /* Mark that we have visited the destination.  */
	  bitmap_set_bit (visited, dest->index);

	  if (pre_order)
	    pre_order[pre_order_num] = dest->index;

	  pre_order_num++;

	  if (EDGE_COUNT (dest->succs) > 0)
	    /* Since the DEST node has been visited for the first
	       time, check its successors.  */
	    stack[sp++] = ei_start (dest->succs);
	  else if (rev_post_order)
	    /* There are no successors for the DEST node so assign
	       its reverse completion number.  */
	    rev_post_order[rev_post_order_num--] = dest->index;
	}
      else
	{
	  if (ei_one_before_end_p (ei) && src != ENTRY_BLOCK_PTR
	      && rev_post_order)
	    /* There are no more successors for the SRC node
	       so assign its reverse completion number.  */
	    rev_post_order[rev_post_order_num--] = src->index;

	  if (!ei_one_before_end_p (ei))
	    ei_next (&stack[sp - 1]);
	  else
	    sp--;
	}
    }

  free (stack);
  sbitmap_free (visited);

  if (include_entry_exit)
    {
      if (pre_order)
	pre_order[pre_order_num] = EXIT_BLOCK;
      pre_order_num++;
      if (rev_post_order)
	rev_post_order[rev_post_order_num--] = EXIT_BLOCK;
      /* The number of nodes visited should be the number of blocks.  */
      gcc_assert (pre_order_num == n_basic_blocks);
    }
  else
    /* The number of nodes visited should be the number of blocks minus
       the entry and exit blocks which are not visited here.  */
    gcc_assert (pre_order_num == n_basic_blocks - NUM_FIXED_BLOCKS);

  return pre_order_num;
}

/* Compute the depth first search order on the _reverse_ graph and
   store in the array DFS_ORDER, marking the nodes visited in VISITED.
   Returns the number of nodes visited.

   The computation is split into three pieces:

   flow_dfs_compute_reverse_init () creates the necessary data
   structures.

   flow_dfs_compute_reverse_add_bb () adds a basic block to the data
   structures.  The block will start the search.

   flow_dfs_compute_reverse_execute () continues (or starts) the
   search using the block on the top of the stack, stopping when the
   stack is empty.

   flow_dfs_compute_reverse_finish () destroys the necessary data
   structures.

   Thus, the user will probably call ..._init(), call ..._add_bb() to
   add a beginning basic block to the stack, call ..._execute(),
   possibly add another bb to the stack and again call ..._execute(),
   ..., and finally call _finish().  */

/* Initialize the data structures used for depth-first search on the
   reverse graph.  If INITIALIZE_STACK is nonzero, the exit block is
   added to the basic block stack.  DATA is the current depth-first
   search context.  If INITIALIZE_STACK is nonzero, there is an
   element on the stack.  */

static void
flow_dfs_compute_reverse_init (depth_first_search_ds data)
{
  /* Allocate stack for back-tracking up CFG.  */
  data->stack = XNEWVEC (basic_block, n_basic_blocks);
  data->sp = 0;

  /* Allocate bitmap to track nodes that have been visited.  */
  data->visited_blocks = sbitmap_alloc (last_basic_block);

  /* None of the nodes in the CFG have been visited yet.  */
  bitmap_clear (data->visited_blocks);

  return;
}

/* Add the specified basic block to the top of the dfs data
   structures.  When the search continues, it will start at the
   block.  */

static void
flow_dfs_compute_reverse_add_bb (depth_first_search_ds data, basic_block bb)
{
  data->stack[data->sp++] = bb;
  bitmap_set_bit (data->visited_blocks, bb->index);
}

/* Continue the depth-first search through the reverse graph starting with the
   block at the stack's top and ending when the stack is empty.  Visited nodes
   are marked.  Returns an unvisited basic block, or NULL if there is none
   available.  */

static basic_block
flow_dfs_compute_reverse_execute (depth_first_search_ds data,
				  basic_block last_unvisited)
{
  basic_block bb;
  edge e;
  edge_iterator ei;

  while (data->sp > 0)
    {
      bb = data->stack[--data->sp];

      /* Perform depth-first search on adjacent vertices.  */
      FOR_EACH_EDGE (e, ei, bb->preds)
	if (!bitmap_bit_p (data->visited_blocks, e->src->index))
	  flow_dfs_compute_reverse_add_bb (data, e->src);
    }

  /* Determine if there are unvisited basic blocks.  */
  FOR_BB_BETWEEN (bb, last_unvisited, NULL, prev_bb)
    if (!bitmap_bit_p (data->visited_blocks, bb->index))
      return bb;

  return NULL;
}

/* Destroy the data structures needed for depth-first search on the
   reverse graph.  */

static void
flow_dfs_compute_reverse_finish (depth_first_search_ds data)
{
  free (data->stack);
  sbitmap_free (data->visited_blocks);
}

/* Performs dfs search from BB over vertices satisfying PREDICATE;
   if REVERSE, go against direction of edges.  Returns number of blocks
   found and their list in RSLT.  RSLT can contain at most RSLT_MAX items.  */
int
dfs_enumerate_from (basic_block bb, int reverse,
		    bool (*predicate) (const_basic_block, const void *),
		    basic_block *rslt, int rslt_max, const void *data)
{
  basic_block *st, lbb;
  int sp = 0, tv = 0;
  unsigned size;

  /* A bitmap to keep track of visited blocks.  Allocating it each time
     this function is called is not possible, since dfs_enumerate_from
     is often used on small (almost) disjoint parts of cfg (bodies of
     loops), and allocating a large sbitmap would lead to quadratic
     behavior.  */
  static sbitmap visited;
  static unsigned v_size;

#define MARK_VISITED(BB) (bitmap_set_bit (visited, (BB)->index))
#define UNMARK_VISITED(BB) (bitmap_clear_bit (visited, (BB)->index))
#define VISITED_P(BB) (bitmap_bit_p (visited, (BB)->index))

  /* Resize the VISITED sbitmap if necessary.  */
  size = last_basic_block;
  if (size < 10)
    size = 10;

  if (!visited)
    {

      visited = sbitmap_alloc (size);
      bitmap_clear (visited);
      v_size = size;
    }
  else if (v_size < size)
    {
      /* Ensure that we increase the size of the sbitmap exponentially.  */
      if (2 * v_size > size)
	size = 2 * v_size;

      visited = sbitmap_resize (visited, size, 0);
      v_size = size;
    }

  st = XNEWVEC (basic_block, rslt_max);
  rslt[tv++] = st[sp++] = bb;
  MARK_VISITED (bb);
  while (sp)
    {
      edge e;
      edge_iterator ei;
      lbb = st[--sp];
      if (reverse)
	{
	  FOR_EACH_EDGE (e, ei, lbb->preds)
	    if (!VISITED_P (e->src) && predicate (e->src, data))
	      {
		gcc_assert (tv != rslt_max);
		rslt[tv++] = st[sp++] = e->src;
		MARK_VISITED (e->src);
	      }
	}
      else
	{
	  FOR_EACH_EDGE (e, ei, lbb->succs)
	    if (!VISITED_P (e->dest) && predicate (e->dest, data))
	      {
		gcc_assert (tv != rslt_max);
		rslt[tv++] = st[sp++] = e->dest;
		MARK_VISITED (e->dest);
	      }
	}
    }
  free (st);
  for (sp = 0; sp < tv; sp++)
    UNMARK_VISITED (rslt[sp]);
  return tv;
#undef MARK_VISITED
#undef UNMARK_VISITED
#undef VISITED_P
}


/* Compute dominance frontiers, ala Harvey, Ferrante, et al.

   This algorithm can be found in Timothy Harvey's PhD thesis, at
   http://www.cs.rice.edu/~harv/dissertation.pdf in the section on iterative
   dominance algorithms.

   First, we identify each join point, j (any node with more than one
   incoming edge is a join point).

   We then examine each predecessor, p, of j and walk up the dominator tree
   starting at p.

   We stop the walk when we reach j's immediate dominator - j is in the
   dominance frontier of each of  the nodes in the walk, except for j's
   immediate dominator. Intuitively, all of the rest of j's dominators are
   shared by j's predecessors as well.
   Since they dominate j, they will not have j in their dominance frontiers.

   The number of nodes touched by this algorithm is equal to the size
   of the dominance frontiers, no more, no less.
*/


static void
compute_dominance_frontiers_1 (bitmap_head *frontiers)
{
  edge p;
  edge_iterator ei;
  basic_block b;
  FOR_EACH_BB (b)
    {
      if (EDGE_COUNT (b->preds) >= 2)
	{
	  FOR_EACH_EDGE (p, ei, b->preds)
	    {
	      basic_block runner = p->src;
	      basic_block domsb;
	      if (runner == ENTRY_BLOCK_PTR)
		continue;

	      domsb = get_immediate_dominator (CDI_DOMINATORS, b);
	      while (runner != domsb)
		{
		  if (!bitmap_set_bit (&frontiers[runner->index],
				       b->index))
		    break;
		  runner = get_immediate_dominator (CDI_DOMINATORS,
						    runner);
		}
	    }
	}
    }
}


void
compute_dominance_frontiers (bitmap_head *frontiers)
{
  timevar_push (TV_DOM_FRONTIERS);

  compute_dominance_frontiers_1 (frontiers);

  timevar_pop (TV_DOM_FRONTIERS);
}

/* Given a set of blocks with variable definitions (DEF_BLOCKS),
   return a bitmap with all the blocks in the iterated dominance
   frontier of the blocks in DEF_BLOCKS.  DFS contains dominance
   frontier information as returned by compute_dominance_frontiers.

   The resulting set of blocks are the potential sites where PHI nodes
   are needed.  The caller is responsible for freeing the memory
   allocated for the return value.  */

bitmap
compute_idf (bitmap def_blocks, bitmap_head *dfs)
{
  bitmap_iterator bi;
  unsigned bb_index, i;
  vec<int> work_stack;
  bitmap phi_insertion_points;

  /* Each block can appear at most twice on the work-stack.  */
  work_stack.create (2 * n_basic_blocks);
  phi_insertion_points = BITMAP_ALLOC (NULL);

  /* Seed the work list with all the blocks in DEF_BLOCKS.  We use
     vec::quick_push here for speed.  This is safe because we know that
     the number of definition blocks is no greater than the number of
     basic blocks, which is the initial capacity of WORK_STACK.  */
  EXECUTE_IF_SET_IN_BITMAP (def_blocks, 0, bb_index, bi)
    work_stack.quick_push (bb_index);

  /* Pop a block off the worklist, add every block that appears in
     the original block's DF that we have not already processed to
     the worklist.  Iterate until the worklist is empty.   Blocks
     which are added to the worklist are potential sites for
     PHI nodes.  */
  while (work_stack.length () > 0)
    {
      bb_index = work_stack.pop ();

      /* Since the registration of NEW -> OLD name mappings is done
	 separately from the call to update_ssa, when updating the SSA
	 form, the basic blocks where new and/or old names are defined
	 may have disappeared by CFG cleanup calls.  In this case,
	 we may pull a non-existing block from the work stack.  */
      gcc_checking_assert (bb_index < (unsigned) last_basic_block);

      EXECUTE_IF_AND_COMPL_IN_BITMAP (&dfs[bb_index], phi_insertion_points,
	                              0, i, bi)
	{
	  work_stack.quick_push (i);
	  bitmap_set_bit (phi_insertion_points, i);
	}
    }

  work_stack.release ();

  return phi_insertion_points;
}

/* Intersection and union of preds/succs for sbitmap based data flow
   solvers.  All four functions defined below take the same arguments:
   B is the basic block to perform the operation for.  DST is the
   target sbitmap, i.e. the result.  SRC is an sbitmap vector of size
   last_basic_block so that it can be indexed with basic block indices.
   DST may be (but does not have to be) SRC[B->index].  */

/* Set the bitmap DST to the intersection of SRC of successors of
   basic block B.  */

void
bitmap_intersection_of_succs (sbitmap dst, sbitmap *src, basic_block b)
{
  unsigned int set_size = dst->size;
  edge e;
  unsigned ix;

  gcc_assert (!dst->popcount);

  for (e = NULL, ix = 0; ix < EDGE_COUNT (b->succs); ix++)
    {
      e = EDGE_SUCC (b, ix);
      if (e->dest == EXIT_BLOCK_PTR)
	continue;

      bitmap_copy (dst, src[e->dest->index]);
      break;
    }

  if (e == 0)
    bitmap_ones (dst);
  else
    for (++ix; ix < EDGE_COUNT (b->succs); ix++)
      {
	unsigned int i;
	SBITMAP_ELT_TYPE *p, *r;

	e = EDGE_SUCC (b, ix);
	if (e->dest == EXIT_BLOCK_PTR)
	  continue;

	p = src[e->dest->index]->elms;
	r = dst->elms;
	for (i = 0; i < set_size; i++)
	  *r++ &= *p++;
      }
}

/* Set the bitmap DST to the intersection of SRC of predecessors of
   basic block B.  */

void
bitmap_intersection_of_preds (sbitmap dst, sbitmap *src, basic_block b)
{
  unsigned int set_size = dst->size;
  edge e;
  unsigned ix;

  gcc_assert (!dst->popcount);

  for (e = NULL, ix = 0; ix < EDGE_COUNT (b->preds); ix++)
    {
      e = EDGE_PRED (b, ix);
      if (e->src == ENTRY_BLOCK_PTR)
	continue;

      bitmap_copy (dst, src[e->src->index]);
      break;
    }

  if (e == 0)
    bitmap_ones (dst);
  else
    for (++ix; ix < EDGE_COUNT (b->preds); ix++)
      {
	unsigned int i;
	SBITMAP_ELT_TYPE *p, *r;

	e = EDGE_PRED (b, ix);
	if (e->src == ENTRY_BLOCK_PTR)
	  continue;

	p = src[e->src->index]->elms;
	r = dst->elms;
	for (i = 0; i < set_size; i++)
	  *r++ &= *p++;
      }
}

/* Set the bitmap DST to the union of SRC of successors of
   basic block B.  */

void
bitmap_union_of_succs (sbitmap dst, sbitmap *src, basic_block b)
{
  unsigned int set_size = dst->size;
  edge e;
  unsigned ix;

  gcc_assert (!dst->popcount);

  for (ix = 0; ix < EDGE_COUNT (b->succs); ix++)
    {
      e = EDGE_SUCC (b, ix);
      if (e->dest == EXIT_BLOCK_PTR)
	continue;

      bitmap_copy (dst, src[e->dest->index]);
      break;
    }

  if (ix == EDGE_COUNT (b->succs))
    bitmap_clear (dst);
  else
    for (ix++; ix < EDGE_COUNT (b->succs); ix++)
      {
	unsigned int i;
	SBITMAP_ELT_TYPE *p, *r;

	e = EDGE_SUCC (b, ix);
	if (e->dest == EXIT_BLOCK_PTR)
	  continue;

	p = src[e->dest->index]->elms;
	r = dst->elms;
	for (i = 0; i < set_size; i++)
	  *r++ |= *p++;
      }
}

/* Set the bitmap DST to the union of SRC of predecessors of
   basic block B.  */

void
bitmap_union_of_preds (sbitmap dst, sbitmap *src, basic_block b)
{
  unsigned int set_size = dst->size;
  edge e;
  unsigned ix;

  gcc_assert (!dst->popcount);

  for (ix = 0; ix < EDGE_COUNT (b->preds); ix++)
    {
      e = EDGE_PRED (b, ix);
      if (e->src== ENTRY_BLOCK_PTR)
	continue;

      bitmap_copy (dst, src[e->src->index]);
      break;
    }

  if (ix == EDGE_COUNT (b->preds))
    bitmap_clear (dst);
  else
    for (ix++; ix < EDGE_COUNT (b->preds); ix++)
      {
	unsigned int i;
	SBITMAP_ELT_TYPE *p, *r;

	e = EDGE_PRED (b, ix);
	if (e->src == ENTRY_BLOCK_PTR)
	  continue;

	p = src[e->src->index]->elms;
	r = dst->elms;
	for (i = 0; i < set_size; i++)
	  *r++ |= *p++;
      }
}

/* Returns the list of basic blocks in the function in an order that guarantees
   that if a block X has just a single predecessor Y, then Y is after X in the
   ordering.  */

basic_block *
single_pred_before_succ_order (void)
{
  basic_block x, y;
  basic_block *order = XNEWVEC (basic_block, n_basic_blocks);
  unsigned n = n_basic_blocks - NUM_FIXED_BLOCKS;
  unsigned np, i;
  sbitmap visited = sbitmap_alloc (last_basic_block);

#define MARK_VISITED(BB) (bitmap_set_bit (visited, (BB)->index))
#define VISITED_P(BB) (bitmap_bit_p (visited, (BB)->index))

  bitmap_clear (visited);

  MARK_VISITED (ENTRY_BLOCK_PTR);
  FOR_EACH_BB (x)
    {
      if (VISITED_P (x))
	continue;

      /* Walk the predecessors of x as long as they have precisely one
	 predecessor and add them to the list, so that they get stored
	 after x.  */
      for (y = x, np = 1;
	   single_pred_p (y) && !VISITED_P (single_pred (y));
	   y = single_pred (y))
	np++;
      for (y = x, i = n - np;
	   single_pred_p (y) && !VISITED_P (single_pred (y));
	   y = single_pred (y), i++)
	{
	  order[i] = y;
	  MARK_VISITED (y);
	}
      order[i] = y;
      MARK_VISITED (y);

      gcc_assert (i == n - 1);
      n -= np;
    }

  sbitmap_free (visited);
  gcc_assert (n == 0);
  return order;

#undef MARK_VISITED
#undef VISITED_P
}