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
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
|
/* Control flow graph analysis code for GNU compiler.
Copyright (C) 1987-2021 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 "backend.h"
#include "cfghooks.h"
#include "timevar.h"
#include "cfganal.h"
#include "cfgloop.h"
namespace {
/* Store the data structures necessary for depth-first search. */
class depth_first_search
{
public:
depth_first_search ();
basic_block execute (basic_block);
void add_bb (basic_block);
private:
/* stack for backtracking during the algorithm */
auto_vec<basic_block, 20> m_stack;
/* record of basic blocks already seen by depth-first search */
auto_sbitmap m_visited_blocks;
};
}
/* 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)
{
int *pre;
int *post;
int prenum = 1;
int postnum = 1;
bool found = false;
/* Allocate the preorder and postorder number arrays. */
pre = XCNEWVEC (int, last_basic_block_for_fn (cfun));
post = XCNEWVEC (int, last_basic_block_for_fn (cfun));
/* Allocate stack for back-tracking up CFG. */
auto_vec<edge_iterator, 20> stack (n_basic_blocks_for_fn (cfun) + 1);
/* Allocate bitmap to track nodes that have been visited. */
auto_sbitmap visited (last_basic_block_for_fn (cfun));
/* None of the nodes in the CFG have been visited yet. */
bitmap_clear (visited);
/* Push the first edge on to the stack. */
stack.quick_push (ei_start (ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs));
while (!stack.is_empty ())
{
basic_block src;
basic_block dest;
/* Look at the edge on the top of the stack. */
edge_iterator ei = stack.last ();
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_FOR_FN (cfun) && ! 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.quick_push (ei_start (dest->succs));
}
else
post[dest->index] = postnum++;
}
else
{
if (dest != EXIT_BLOCK_PTR_FOR_FN (cfun)
&& src != ENTRY_BLOCK_PTR_FOR_FN (cfun)
&& 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_FOR_FN (cfun))
post[src->index] = postnum++;
if (!ei_one_before_end_p (ei))
ei_next (&stack.last ());
else
stack.pop ();
}
}
free (pre);
free (post);
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_for_fn (cfun));
/* Clear all the reachability flags. */
FOR_EACH_BB_FN (bb, cfun)
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_FOR_FN (cfun)->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);
}
/* Verify that there are no unreachable blocks in the current function. */
void
verify_no_unreachable_blocks (void)
{
find_unreachable_blocks ();
basic_block bb;
FOR_EACH_BB_FN (bb, cfun)
gcc_assert ((bb->flags & BB_REACHABLE) != 0);
}
/* 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_FOR_FN (cfun),
EXIT_BLOCK_PTR_FOR_FN (cfun), 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_FOR_FN (cfun),
EXIT_BLOCK_PTR_FOR_FN (cfun), 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_for_fn (cfun), 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_FOR_FN (cfun))
fprintf (f, "entry,");
else
fprintf (f, "%d,", INDEX_EDGE_PRED_BB (elist, x)->index);
if (INDEX_EDGE_SUCC_BB (elist, x) == EXIT_BLOCK_PTR_FOR_FN (cfun))
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_FOR_FN (cfun),
EXIT_BLOCK_PTR_FOR_FN (cfun), 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_FOR_FN (cfun),
EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
FOR_BB_BETWEEN (s, ENTRY_BLOCK_PTR_FOR_FN (cfun)->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_FOR_FN (cfun))
return;
gcc_assert (bb != EXIT_BLOCK_PTR_FOR_FN (cfun));
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_FOR_FN (cfun));
if (block == EXIT_BLOCK_PTR_FOR_FN (cfun))
return EXIT_BLOCK_PTR_FOR_FN (cfun);
else
{
basic_block bb = get_immediate_dominator (CDI_POST_DOMINATORS, block);
if (! bb)
return EXIT_BLOCK_PTR_FOR_FN (cfun);
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 (get_edge_src (edge_index) != EXIT_BLOCK_PTR_FOR_FN (cfun));
/* For abnormal edges, we don't make current_block control
dependent because instructions that throw are always necessary
anyway. */
edge e = find_edge (get_edge_src (edge_index), get_edge_dest (edge_index));
if (e->flags & EDGE_ABNORMAL)
return;
if (get_edge_src (edge_index) == ENTRY_BLOCK_PTR_FOR_FN (cfun))
ending_block = single_succ (ENTRY_BLOCK_PTR_FOR_FN (cfun));
else
ending_block = find_pdom (get_edge_src (edge_index));
for (current_block = get_edge_dest (edge_index);
current_block != ending_block
&& current_block != EXIT_BLOCK_PTR_FOR_FN (cfun);
current_block = find_pdom (current_block))
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 ()
{
timevar_push (TV_CONTROL_DEPENDENCES);
/* Initialize the edge list. */
int num_edges = 0;
basic_block bb;
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun),
EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
num_edges += EDGE_COUNT (bb->succs);
m_el.create (num_edges);
edge e;
edge_iterator ei;
FOR_BB_BETWEEN (bb, ENTRY_BLOCK_PTR_FOR_FN (cfun),
EXIT_BLOCK_PTR_FOR_FN (cfun), next_bb)
FOR_EACH_EDGE (e, ei, bb->succs)
m_el.quick_push (std::make_pair (e->src->index, e->dest->index));
control_dependence_map.create (last_basic_block_for_fn (cfun));
for (int i = 0; i < last_basic_block_for_fn (cfun); ++i)
control_dependence_map.quick_push (BITMAP_ALLOC (NULL));
for (int i = 0; i < num_edges; ++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 ();
m_el.release ();
}
/* 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 source with index I from the edge list. */
basic_block
control_dependences::get_edge_src (int i)
{
return BASIC_BLOCK_FOR_FN (cfun, m_el[i].first);
}
/* Returns the edge destination with index I from the edge list. */
basic_block
control_dependences::get_edge_dest (int i)
{
return BASIC_BLOCK_FOR_FN (cfun, m_el[i].second);
}
/* 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_FOR_FN (cfun)->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_FOR_FN (cfun));
}
/* 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_FN (bb, cfun)
if (EDGE_COUNT (bb->succs) == 0)
make_single_succ_edge (bb, EXIT_BLOCK_PTR_FOR_FN (cfun), EDGE_FAKE);
}
/* This function adds a fake edge between any noreturn block and
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)
{
/* First add fake exits to noreturn blocks, this is required to
discover only truly infinite loops below. */
add_noreturn_fake_exit_edges ();
/* Perform depth-first search in the reverse graph to find nodes
reachable from the exit block. */
depth_first_search dfs;
dfs.add_bb (EXIT_BLOCK_PTR_FOR_FN (cfun));
/* Repeatedly add fake edges, updating the unreachable nodes. */
basic_block unvisited_block = EXIT_BLOCK_PTR_FOR_FN (cfun);
while (1)
{
unvisited_block = dfs.execute (unvisited_block);
if (!unvisited_block)
break;
basic_block deadend_block = dfs_find_deadend (unvisited_block);
edge e = make_edge (deadend_block, EXIT_BLOCK_PTR_FOR_FN (cfun),
EDGE_FAKE);
e->probability = profile_probability::never ();
dfs.add_bb (deadend_block);
}
}
/* 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)
{
int post_order_num = 0;
int count;
if (include_entry_exit)
post_order[post_order_num++] = EXIT_BLOCK;
/* Allocate stack for back-tracking up CFG. */
auto_vec<edge_iterator, 20> stack (n_basic_blocks_for_fn (cfun) + 1);
/* Allocate bitmap to track nodes that have been visited. */
auto_sbitmap visited (last_basic_block_for_fn (cfun));
/* None of the nodes in the CFG have been visited yet. */
bitmap_clear (visited);
/* Push the first edge on to the stack. */
stack.quick_push (ei_start (ENTRY_BLOCK_PTR_FOR_FN (cfun)->succs));
while (!stack.is_empty ())
{
basic_block src;
basic_block dest;
/* Look at the edge on the top of the stack. */
edge_iterator ei = stack.last ();
src = ei_edge (ei)->src;
dest = ei_edge (ei)->dest;
/* Check if the edge destination has been visited yet. */
if (dest != EXIT_BLOCK_PTR_FOR_FN (cfun)
&& ! 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.quick_push (ei_start (dest->succs));
else
post_order[post_order_num++] = dest->index;
}
else
{
if (ei_one_before_end_p (ei)
&& src != ENTRY_BLOCK_PTR_FOR_FN (cfun))
post_order[post_order_num++] = src->index;
if (!ei_one_before_end_p (ei))
ei_next (&stack.last ());
else
stack.pop ();
}
}
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_for_fn (cfun)))
{
basic_block b;
basic_block next_bb;
for (b = ENTRY_BLOCK_PTR_FOR_FN (cfun)->next_bb; b
!= EXIT_BLOCK_PTR_FOR_FN (cfun); b = next_bb)
{
next_bb = b->next_bb;
if (!(bitmap_bit_p (visited, b->index)))
delete_basic_block (b);
}
tidy_fallthru_edges ();
}
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)
{
auto_bitmap visited;
basic_block next = bb;
for (;;)
{
if (EDGE_COUNT (next->succs) == 0)
return next;
if (! bitmap_set_bit (visited, next->index))
return bb;
bb = next;
/* If we are in an analyzed cycle make sure to try exiting it.
Note this is a heuristic only and expected to work when loop
fixup is needed as well. */
if (! bb->loop_father
|| ! loop_outer (bb->loop_father))
next = EDGE_SUCC (bb, 0)->dest;
else
{
edge_iterator ei;
edge e;
FOR_EACH_EDGE (e, ei, bb->succs)
if (loop_exit_edge_p (bb->loop_father, e))
break;
next = e ? e->dest : 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.
Optionally if START_POINTS is specified, start from exit block and all
basic blocks in START_POINTS. This is used by CD-DCE.
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. */
void
inverted_post_order_compute (vec<int> *post_order,
sbitmap *start_points)
{
basic_block bb;
post_order->reserve_exact (n_basic_blocks_for_fn (cfun));
if (flag_checking)
verify_no_unreachable_blocks ();
/* Allocate stack for back-tracking up CFG. */
auto_vec<edge_iterator, 20> stack (n_basic_blocks_for_fn (cfun) + 1);
/* Allocate bitmap to track nodes that have been visited. */
auto_sbitmap visited (last_basic_block_for_fn (cfun));
/* None of the nodes in the CFG have been visited yet. */
bitmap_clear (visited);
if (start_points)
{
FOR_ALL_BB_FN (bb, cfun)
if (bitmap_bit_p (*start_points, bb->index)
&& EDGE_COUNT (bb->preds) > 0)
{
stack.quick_push (ei_start (bb->preds));
bitmap_set_bit (visited, bb->index);
}
if (EDGE_COUNT (EXIT_BLOCK_PTR_FOR_FN (cfun)->preds))
{
stack.quick_push (ei_start (EXIT_BLOCK_PTR_FOR_FN (cfun)->preds));
bitmap_set_bit (visited, EXIT_BLOCK_PTR_FOR_FN (cfun)->index);
}
}
else
/* Put all blocks that have no successor into the initial work list. */
FOR_ALL_BB_FN (bb, cfun)
if (EDGE_COUNT (bb->succs) == 0)
{
/* Push the initial edge on to the stack. */
if (EDGE_COUNT (bb->preds) > 0)
{
stack.quick_push (ei_start (bb->preds));
bitmap_set_bit (visited, bb->index);
}
}
do
{
bool has_unvisited_bb = false;
/* The inverted traversal loop. */
while (!stack.is_empty ())
{
edge_iterator ei;
basic_block pred;
/* Look at the edge on the top of the stack. */
ei = stack.last ();
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.quick_push (ei_start (pred->preds));
else
post_order->quick_push (pred->index);
}
else
{
if (bb != EXIT_BLOCK_PTR_FOR_FN (cfun)
&& ei_one_before_end_p (ei))
post_order->quick_push (bb->index);
if (!ei_one_before_end_p (ei))
ei_next (&stack.last ());
else
stack.pop ();
}
}
/* 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_FOR_FN (cfun),
EXIT_BLOCK_PTR_FOR_FN (cfun), 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.quick_push (ei_start (be->preds));
break;
}
}
}
if (has_unvisited_bb && stack.is_empty ())
{
/* 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_FOR_FN (cfun));
gcc_assert (be != NULL);
bitmap_set_bit (visited, be->index);
stack.quick_push (ei_start (be->preds));
}
/* The only case the below while fires is
when there's an infinite loop. */
}
while (!stack.is_empty ());
/* EXIT_BLOCK is always included. */
post_order->quick_push (EXIT_BLOCK);
}
/* Compute the depth first search order of FN and store in the array
PRE_ORDER if nonzero. 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.
In case the function has unreachable blocks the number of nodes
visited does not include them.
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_fn (struct function *fn,
int *pre_order, int *rev_post_order,
bool include_entry_exit)
{
int pre_order_num = 0;
int rev_post_order_num = n_basic_blocks_for_fn (fn) - 1;
/* Allocate stack for back-tracking up CFG. */
auto_vec<edge_iterator, 20> stack (n_basic_blocks_for_fn (fn) + 1);
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--] = EXIT_BLOCK;
}
else
rev_post_order_num -= NUM_FIXED_BLOCKS;
/* BB flag to track nodes that have been visited. */
auto_bb_flag visited (fn);
/* Push the first edge on to the stack. */
stack.quick_push (ei_start (ENTRY_BLOCK_PTR_FOR_FN (fn)->succs));
while (!stack.is_empty ())
{
basic_block src;
basic_block dest;
/* Look at the edge on the top of the stack. */
edge_iterator ei = stack.last ();
src = ei_edge (ei)->src;
dest = ei_edge (ei)->dest;
/* Check if the edge destination has been visited yet. */
if (dest != EXIT_BLOCK_PTR_FOR_FN (fn)
&& ! (dest->flags & visited))
{
/* Mark that we have visited the destination. */
dest->flags |= visited;
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.quick_push (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_FOR_FN (fn)
&& 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.last ());
else
stack.pop ();
}
}
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--] = ENTRY_BLOCK;
}
/* Clear the temporarily allocated flag. */
if (!rev_post_order)
rev_post_order = pre_order;
for (int i = 0; i < pre_order_num; ++i)
BASIC_BLOCK_FOR_FN (fn, rev_post_order[i])->flags &= ~visited;
return pre_order_num;
}
/* Like pre_and_rev_post_order_compute_fn but operating on the
current function and asserting that all nodes were visited. */
int
pre_and_rev_post_order_compute (int *pre_order, int *rev_post_order,
bool include_entry_exit)
{
int pre_order_num
= pre_and_rev_post_order_compute_fn (cfun, pre_order, rev_post_order,
include_entry_exit);
if (include_entry_exit)
/* The number of nodes visited should be the number of blocks. */
gcc_assert (pre_order_num == n_basic_blocks_for_fn (cfun));
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_for_fn (cfun) - NUM_FIXED_BLOCKS));
return pre_order_num;
}
/* Per basic-block data for rev_post_order_and_mark_dfs_back_seme,
element of a sparsely populated array indexed by basic-block number. */
typedef auto_vec<int, 2> scc_exit_vec_t;
struct rpoamdbs_bb_data {
int depth;
int bb_to_pre;
/* The basic-block index of the SCC entry of the block visited first
(the SCC leader). */
int scc;
/* The index into the RPO array where the blocks SCC entries end
(only valid for the SCC leader). */
int scc_end;
/* The indexes of the exits destinations of this SCC (only valid
for the SCC leader). Initialized upon discovery of SCC leaders. */
scc_exit_vec_t scc_exits;
};
/* Tag H as a header of B, weaving H and its loop header list into the
current loop header list of B. */
static void
tag_header (int b, int h, rpoamdbs_bb_data *bb_data)
{
if (h == -1 || b == h)
return;
int cur1 = b;
int cur2 = h;
while (bb_data[cur1].scc != -1)
{
int ih = bb_data[cur1].scc;
if (ih == cur2)
return;
if (bb_data[ih].depth < bb_data[cur2].depth)
{
bb_data[cur1].scc = cur2;
cur1 = cur2;
cur2 = ih;
}
else
cur1 = ih;
}
bb_data[cur1].scc = cur2;
}
/* Comparator for a sort of two edges destinations E1 and E2 after their index
in the PRE array as specified by BB_TO_PRE. */
static int
cmp_edge_dest_pre (const void *e1_, const void *e2_, void *data_)
{
const int *e1 = (const int *)e1_;
const int *e2 = (const int *)e2_;
rpoamdbs_bb_data *bb_data = (rpoamdbs_bb_data *)data_;
return (bb_data[*e1].bb_to_pre - bb_data[*e2].bb_to_pre);
}
/* Compute the reverse completion number of a depth first search
on the SEME region denoted by the ENTRY edge and the EXIT_BBS set of
exit block indexes and store it in the array REV_POST_ORDER.
Also sets the EDGE_DFS_BACK edge flags according to this visitation
order.
Returns the number of nodes visited.
In case the function has unreachable blocks the number of nodes
visited does not include them.
If FOR_ITERATION is true then compute an RPO where SCCs form a
contiguous region in the RPO array.
*TOPLEVEL_SCC_EXTENTS if not NULL is filled with pairs of
*REV_POST_ORDER indexes denoting extents of the toplevel SCCs in
this region. */
int
rev_post_order_and_mark_dfs_back_seme (struct function *fn, edge entry,
bitmap exit_bbs, bool for_iteration,
int *rev_post_order,
vec<std::pair<int, int> >
*toplevel_scc_extents)
{
int rev_post_order_num = 0;
/* BB flag to track nodes that have been visited. */
auto_bb_flag visited (fn);
/* Lazily initialized per-BB data for the two DFS walks below. */
rpoamdbs_bb_data *bb_data
= XNEWVEC (rpoamdbs_bb_data, last_basic_block_for_fn (fn));
/* First DFS walk, loop discovery according to
A New Algorithm for Identifying Loops in Decompilation
by Tao Wei, Jian Mao, Wei Zou and You Chen of the Institute of
Computer Science and Technology of the Peking University. */
auto_vec<edge_iterator, 20> ei_stack (n_basic_blocks_for_fn (fn) + 1);
auto_bb_flag is_header (fn);
int depth = 1;
unsigned n_sccs = 0;
basic_block dest = entry->dest;
edge_iterator ei;
int pre_num = 0;
/* DFS process DEST. */
find_loops:
bb_data[dest->index].bb_to_pre = pre_num++;
bb_data[dest->index].depth = depth;
bb_data[dest->index].scc = -1;
depth++;
gcc_assert ((dest->flags & (is_header|visited)) == 0);
dest->flags |= visited;
ei = ei_start (dest->succs);
while (!ei_end_p (ei))
{
ei_edge (ei)->flags &= ~EDGE_DFS_BACK;
if (bitmap_bit_p (exit_bbs, ei_edge (ei)->dest->index))
;
else if (!(ei_edge (ei)->dest->flags & visited))
{
ei_stack.quick_push (ei);
dest = ei_edge (ei)->dest;
/* DFS recurse on DEST. */
goto find_loops;
ret_from_find_loops:
/* Return point of DFS recursion. */
ei = ei_stack.pop ();
dest = ei_edge (ei)->src;
int header = bb_data[ei_edge (ei)->dest->index].scc;
tag_header (dest->index, header, bb_data);
depth = bb_data[dest->index].depth + 1;
}
else
{
if (bb_data[ei_edge (ei)->dest->index].depth > 0) /* on the stack */
{
ei_edge (ei)->flags |= EDGE_DFS_BACK;
n_sccs++;
ei_edge (ei)->dest->flags |= is_header;
::new (&bb_data[ei_edge (ei)->dest->index].scc_exits)
auto_vec<int, 2> ();
tag_header (dest->index, ei_edge (ei)->dest->index, bb_data);
}
else if (bb_data[ei_edge (ei)->dest->index].scc == -1)
;
else
{
int header = bb_data[ei_edge (ei)->dest->index].scc;
if (bb_data[header].depth > 0)
tag_header (dest->index, header, bb_data);
else
{
/* A re-entry into an existing loop. */
/* ??? Need to mark is_header? */
while (bb_data[header].scc != -1)
{
header = bb_data[header].scc;
if (bb_data[header].depth > 0)
{
tag_header (dest->index, header, bb_data);
break;
}
}
}
}
}
ei_next (&ei);
}
rev_post_order[rev_post_order_num++] = dest->index;
/* not on the stack anymore */
bb_data[dest->index].depth = -bb_data[dest->index].depth;
if (!ei_stack.is_empty ())
/* Return from DFS recursion. */
goto ret_from_find_loops;
/* Optimize for no SCCs found or !for_iteration. */
if (n_sccs == 0 || !for_iteration)
{
/* Clear the temporarily allocated flags. */
for (int i = 0; i < rev_post_order_num; ++i)
BASIC_BLOCK_FOR_FN (fn, rev_post_order[i])->flags
&= ~(is_header|visited);
/* And swap elements. */
for (int i = 0; i < rev_post_order_num/2; ++i)
std::swap (rev_post_order[i], rev_post_order[rev_post_order_num-i-1]);
XDELETEVEC (bb_data);
return rev_post_order_num;
}
/* Next find SCC exits, clear the visited flag and compute an upper bound
for the edge stack below. */
unsigned edge_count = 0;
for (int i = 0; i < rev_post_order_num; ++i)
{
int bb = rev_post_order[i];
BASIC_BLOCK_FOR_FN (fn, bb)->flags &= ~visited;
edge e;
FOR_EACH_EDGE (e, ei, BASIC_BLOCK_FOR_FN (fn, bb)->succs)
{
if (bitmap_bit_p (exit_bbs, e->dest->index))
continue;
edge_count++;
/* if e is an exit from e->src, record it for
bb_data[e->src].scc. */
int src_scc = e->src->index;
if (!(e->src->flags & is_header))
src_scc = bb_data[src_scc].scc;
if (src_scc == -1)
continue;
int dest_scc = e->dest->index;
if (!(e->dest->flags & is_header))
dest_scc = bb_data[dest_scc].scc;
if (src_scc == dest_scc)
continue;
/* When dest_scc is nested insde src_scc it's not an
exit. */
int tem_dest_scc = dest_scc;
unsigned dest_scc_depth = 0;
while (tem_dest_scc != -1)
{
dest_scc_depth++;
if ((tem_dest_scc = bb_data[tem_dest_scc].scc) == src_scc)
break;
}
if (tem_dest_scc != -1)
continue;
/* When src_scc is nested inside dest_scc record an
exit from the outermost SCC this edge exits. */
int tem_src_scc = src_scc;
unsigned src_scc_depth = 0;
while (tem_src_scc != -1)
{
if (bb_data[tem_src_scc].scc == dest_scc)
{
edge_count++;
bb_data[tem_src_scc].scc_exits.safe_push (e->dest->index);
break;
}
tem_src_scc = bb_data[tem_src_scc].scc;
src_scc_depth++;
}
/* Else find the outermost SCC this edge exits (exits
from the inner SCCs are not important for the DFS
walk adjustment). Do so by computing the common
ancestor SCC where the immediate child it to the source
SCC is the exited SCC. */
if (tem_src_scc == -1)
{
edge_count++;
while (src_scc_depth > dest_scc_depth)
{
src_scc = bb_data[src_scc].scc;
src_scc_depth--;
}
while (dest_scc_depth > src_scc_depth)
{
dest_scc = bb_data[dest_scc].scc;
dest_scc_depth--;
}
while (bb_data[src_scc].scc != bb_data[dest_scc].scc)
{
src_scc = bb_data[src_scc].scc;
dest_scc = bb_data[dest_scc].scc;
}
bb_data[src_scc].scc_exits.safe_push (e->dest->index);
}
}
}
/* Now the second DFS walk to compute a RPO where the extent of SCCs
is minimized thus SCC members are adjacent in the RPO array.
This is done by performing a DFS walk computing RPO with first visiting
extra direct edges from SCC entry to its exits.
That simulates a DFS walk over the graph with SCCs collapsed and
walking the SCCs themselves only when all outgoing edges from the
SCCs have been visited.
SCC_END[scc-header-index] is the position in the RPO array of the
last member of the SCC. */
auto_vec<std::pair<basic_block, basic_block>, 20> estack (edge_count + 1);
int idx = rev_post_order_num;
basic_block edest;
dest = entry->dest;
/* DFS process DEST. */
dfs_rpo:
gcc_checking_assert ((dest->flags & visited) == 0);
/* Verify we enter SCCs through the same header and SCC nesting appears
the same. */
gcc_assert (bb_data[dest->index].scc == -1
|| (BASIC_BLOCK_FOR_FN (fn, bb_data[dest->index].scc)->flags
& visited));
dest->flags |= visited;
bb_data[dest->index].scc_end = -1;
if ((dest->flags & is_header)
&& !bb_data[dest->index].scc_exits.is_empty ())
{
/* Push the all SCC exits as outgoing edges from its header to
be visited first.
To process exits in the same relative order as in the first
DFS walk sort them after their destination PRE order index. */
gcc_sort_r (&bb_data[dest->index].scc_exits[0],
bb_data[dest->index].scc_exits.length (),
sizeof (int), cmp_edge_dest_pre, bb_data);
/* Process edges in reverse to match previous DFS walk order. */
for (int i = bb_data[dest->index].scc_exits.length () - 1; i >= 0; --i)
estack.quick_push (std::make_pair
(dest, BASIC_BLOCK_FOR_FN (fn, bb_data[dest->index].scc_exits[i])));
}
else
{
if (dest->flags & is_header)
bb_data[dest->index].scc_end = idx - 1;
/* Push the edge vector in reverse to match the iteration order
from the DFS walk above. */
for (int i = EDGE_COUNT (dest->succs) - 1; i >= 0; --i)
if (!bitmap_bit_p (exit_bbs, EDGE_SUCC (dest, i)->dest->index))
estack.quick_push (std::make_pair (dest,
EDGE_SUCC (dest, i)->dest));
}
while (!estack.is_empty ()
&& estack.last ().first == dest)
{
edest = estack.last ().second;
if (!(edest->flags & visited))
{
dest = edest;
/* DFS recurse on DEST. */
goto dfs_rpo;
ret_from_dfs_rpo:
/* Return point of DFS recursion. */
dest = estack.last ().first;
}
estack.pop ();
/* If we processed all SCC exits from DEST mark the SCC end
since all RPO entries up to DEST itself will now belong
to its SCC. The special-case of no SCC exits is already
dealt with above. */
if (dest->flags & is_header
/* When the last exit edge was processed mark the SCC end
and push the regular edges. */
&& bb_data[dest->index].scc_end == -1
&& (estack.is_empty ()
|| estack.last ().first != dest))
{
bb_data[dest->index].scc_end = idx - 1;
/* Push the edge vector in reverse to match the iteration order
from the DFS walk above. */
for (int i = EDGE_COUNT (dest->succs) - 1; i >= 0; --i)
if (!bitmap_bit_p (exit_bbs, EDGE_SUCC (dest, i)->dest->index))
estack.quick_push (std::make_pair (dest,
EDGE_SUCC (dest, i)->dest));
}
}
rev_post_order[--idx] = dest->index;
if (!estack.is_empty ())
/* Return from DFS recursion. */
goto ret_from_dfs_rpo;
/* Each SCC extends are from the position of the header inside
the RPO array up to RPO array index scc_end[header-index]. */
if (toplevel_scc_extents)
for (int i = 0; i < rev_post_order_num; i++)
{
basic_block bb = BASIC_BLOCK_FOR_FN (fn, rev_post_order[i]);
if (bb->flags & is_header)
{
toplevel_scc_extents->safe_push
(std::make_pair (i, bb_data[bb->index].scc_end));
i = bb_data[bb->index].scc_end;
}
}
/* Clear the temporarily allocated flags and free memory. */
for (int i = 0; i < rev_post_order_num; ++i)
{
basic_block bb = BASIC_BLOCK_FOR_FN (fn, rev_post_order[i]);
if (bb->flags & is_header)
bb_data[bb->index].scc_exits.~scc_exit_vec_t ();
bb->flags &= ~(visited|is_header);
}
XDELETEVEC (bb_data);
return rev_post_order_num;
}
/* Compute the depth first search order on the _reverse_ graph and
store it 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. */
depth_first_search::depth_first_search () :
m_stack (n_basic_blocks_for_fn (cfun)),
m_visited_blocks (last_basic_block_for_fn (cfun))
{
bitmap_clear (m_visited_blocks);
}
/* Add the specified basic block to the top of the dfs data
structures. When the search continues, it will start at the
block. */
void
depth_first_search::add_bb (basic_block bb)
{
m_stack.quick_push (bb);
bitmap_set_bit (m_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. */
basic_block
depth_first_search::execute (basic_block last_unvisited)
{
basic_block bb;
edge e;
edge_iterator ei;
while (!m_stack.is_empty ())
{
bb = m_stack.pop ();
/* Perform depth-first search on adjacent vertices. */
FOR_EACH_EDGE (e, ei, bb->preds)
if (!bitmap_bit_p (m_visited_blocks, e->src->index))
add_bb (e->src);
}
/* Determine if there are unvisited basic blocks. */
FOR_BB_BETWEEN (bb, last_unvisited, NULL, prev_bb)
if (!bitmap_bit_p (m_visited_blocks, bb->index))
return bb;
return NULL;
}
/* 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;
auto_bb_flag visited (cfun);
#define MARK_VISITED(BB) ((BB)->flags |= visited)
#define UNMARK_VISITED(BB) ((BB)->flags &= ~visited)
#define VISITED_P(BB) (((BB)->flags & visited) != 0)
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.
*/
void
compute_dominance_frontiers (bitmap_head *frontiers)
{
timevar_push (TV_DOM_FRONTIERS);
edge p;
edge_iterator ei;
basic_block b;
FOR_EACH_BB_FN (b, cfun)
{
if (EDGE_COUNT (b->preds) >= 2)
{
basic_block domsb = get_immediate_dominator (CDI_DOMINATORS, b);
FOR_EACH_EDGE (p, ei, b->preds)
{
basic_block runner = p->src;
if (runner == ENTRY_BLOCK_PTR_FOR_FN (cfun))
continue;
while (runner != domsb)
{
if (!bitmap_set_bit (&frontiers[runner->index], b->index))
break;
runner = get_immediate_dominator (CDI_DOMINATORS, runner);
}
}
}
}
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;
bitmap phi_insertion_points;
phi_insertion_points = BITMAP_ALLOC (NULL);
/* Seed the work set with all the blocks in DEF_BLOCKS. */
auto_bitmap work_set;
bitmap_copy (work_set, def_blocks);
bitmap_tree_view (work_set);
/* Pop a block off the workset, add every block that appears in
the original block's DF that we have not already processed to
the workset. Iterate until the workset is empty. Blocks
which are added to the workset are potential sites for
PHI nodes. */
while (!bitmap_empty_p (work_set))
{
/* The dominance frontier of a block is blocks after it so iterating
on earlier blocks first is better.
??? Basic blocks are by no means guaranteed to be ordered in
optimal order for this iteration. */
bb_index = bitmap_first_set_bit (work_set);
bitmap_clear_bit (work_set, bb_index);
/* 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_for_fn (cfun));
EXECUTE_IF_AND_COMPL_IN_BITMAP (&dfs[bb_index], phi_insertion_points,
0, i, bi)
{
bitmap_set_bit (work_set, i);
bitmap_set_bit (phi_insertion_points, i);
}
}
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;
for (e = NULL, ix = 0; ix < EDGE_COUNT (b->succs); ix++)
{
e = EDGE_SUCC (b, ix);
if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
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_FOR_FN (cfun))
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;
for (e = NULL, ix = 0; ix < EDGE_COUNT (b->preds); ix++)
{
e = EDGE_PRED (b, ix);
if (e->src == ENTRY_BLOCK_PTR_FOR_FN (cfun))
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_FOR_FN (cfun))
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;
for (ix = 0; ix < EDGE_COUNT (b->succs); ix++)
{
e = EDGE_SUCC (b, ix);
if (e->dest == EXIT_BLOCK_PTR_FOR_FN (cfun))
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_FOR_FN (cfun))
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;
for (ix = 0; ix < EDGE_COUNT (b->preds); ix++)
{
e = EDGE_PRED (b, ix);
if (e->src== ENTRY_BLOCK_PTR_FOR_FN (cfun))
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_FOR_FN (cfun))
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_for_fn (cfun));
unsigned n = n_basic_blocks_for_fn (cfun) - NUM_FIXED_BLOCKS;
unsigned np, i;
auto_sbitmap visited (last_basic_block_for_fn (cfun));
#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_FN (cfun));
FOR_EACH_BB_FN (x, cfun)
{
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;
}
gcc_assert (n == 0);
return order;
#undef MARK_VISITED
#undef VISITED_P
}
/* Ignoring loop backedges, if BB has precisely one incoming edge then
return that edge. Otherwise return NULL.
When IGNORE_NOT_EXECUTABLE is true, also ignore edges that are not marked
as executable. */
edge
single_pred_edge_ignoring_loop_edges (basic_block bb,
bool ignore_not_executable)
{
edge retval = NULL;
edge e;
edge_iterator ei;
FOR_EACH_EDGE (e, ei, bb->preds)
{
/* A loop back edge can be identified by the destination of
the edge dominating the source of the edge. */
if (dominated_by_p (CDI_DOMINATORS, e->src, e->dest))
continue;
/* We can safely ignore edges that are not executable. */
if (ignore_not_executable
&& (e->flags & EDGE_EXECUTABLE) == 0)
continue;
/* If we have already seen a non-loop edge, then we must have
multiple incoming non-loop edges and thus we return NULL. */
if (retval)
return NULL;
/* This is the first non-loop incoming edge we have found. Record
it. */
retval = e;
}
return retval;
}
|