summaryrefslogtreecommitdiff
path: root/gcc/alias.c
blob: cdfa6d2d3ac7d195a205706053152164be635db1 (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
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
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
/* Alias analysis for GNU C
   Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
   2007, 2008, 2009 Free Software Foundation, Inc.
   Contributed by John Carr (jfc@mit.edu).

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/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "tm.h"
#include "rtl.h"
#include "tree.h"
#include "tm_p.h"
#include "function.h"
#include "alias.h"
#include "emit-rtl.h"
#include "regs.h"
#include "hard-reg-set.h"
#include "basic-block.h"
#include "flags.h"
#include "output.h"
#include "toplev.h"
#include "cselib.h"
#include "splay-tree.h"
#include "ggc.h"
#include "langhooks.h"
#include "timevar.h"
#include "target.h"
#include "cgraph.h"
#include "varray.h"
#include "tree-pass.h"
#include "ipa-type-escape.h"
#include "df.h"
#include "tree-ssa-alias.h"
#include "pointer-set.h"
#include "tree-flow.h"

/* The aliasing API provided here solves related but different problems:

   Say there exists (in c)

   struct X {
     struct Y y1;
     struct Z z2;
   } x1, *px1,  *px2;

   struct Y y2, *py;
   struct Z z2, *pz;


   py = &px1.y1;
   px2 = &x1;

   Consider the four questions:

   Can a store to x1 interfere with px2->y1?
   Can a store to x1 interfere with px2->z2?
   (*px2).z2
   Can a store to x1 change the value pointed to by with py?
   Can a store to x1 change the value pointed to by with pz?

   The answer to these questions can be yes, yes, yes, and maybe.

   The first two questions can be answered with a simple examination
   of the type system.  If structure X contains a field of type Y then
   a store thru a pointer to an X can overwrite any field that is
   contained (recursively) in an X (unless we know that px1 != px2).

   The last two of the questions can be solved in the same way as the
   first two questions but this is too conservative.  The observation
   is that in some cases analysis we can know if which (if any) fields
   are addressed and if those addresses are used in bad ways.  This
   analysis may be language specific.  In C, arbitrary operations may
   be applied to pointers.  However, there is some indication that
   this may be too conservative for some C++ types.

   The pass ipa-type-escape does this analysis for the types whose
   instances do not escape across the compilation boundary.

   Historically in GCC, these two problems were combined and a single
   data structure was used to represent the solution to these
   problems.  We now have two similar but different data structures,
   The data structure to solve the last two question is similar to the
   first, but does not contain have the fields in it whose address are
   never taken.  For types that do escape the compilation unit, the
   data structures will have identical information.
*/

/* The alias sets assigned to MEMs assist the back-end in determining
   which MEMs can alias which other MEMs.  In general, two MEMs in
   different alias sets cannot alias each other, with one important
   exception.  Consider something like:

     struct S { int i; double d; };

   a store to an `S' can alias something of either type `int' or type
   `double'.  (However, a store to an `int' cannot alias a `double'
   and vice versa.)  We indicate this via a tree structure that looks
   like:
	   struct S
	    /   \
	   /     \
	 |/_     _\|
	 int    double

   (The arrows are directed and point downwards.)
    In this situation we say the alias set for `struct S' is the
   `superset' and that those for `int' and `double' are `subsets'.

   To see whether two alias sets can point to the same memory, we must
   see if either alias set is a subset of the other. We need not trace
   past immediate descendants, however, since we propagate all
   grandchildren up one level.

   Alias set zero is implicitly a superset of all other alias sets.
   However, this is no actual entry for alias set zero.  It is an
   error to attempt to explicitly construct a subset of zero.  */

struct GTY(()) alias_set_entry_d {
  /* The alias set number, as stored in MEM_ALIAS_SET.  */
  alias_set_type alias_set;

  /* Nonzero if would have a child of zero: this effectively makes this
     alias set the same as alias set zero.  */
  int has_zero_child;

  /* The children of the alias set.  These are not just the immediate
     children, but, in fact, all descendants.  So, if we have:

       struct T { struct S s; float f; }

     continuing our example above, the children here will be all of
     `int', `double', `float', and `struct S'.  */
  splay_tree GTY((param1_is (int), param2_is (int))) children;
};
typedef struct alias_set_entry_d *alias_set_entry;

static int rtx_equal_for_memref_p (const_rtx, const_rtx);
static int memrefs_conflict_p (int, rtx, int, rtx, HOST_WIDE_INT);
static void record_set (rtx, const_rtx, void *);
static int base_alias_check (rtx, rtx, enum machine_mode,
			     enum machine_mode);
static rtx find_base_value (rtx);
static int mems_in_disjoint_alias_sets_p (const_rtx, const_rtx);
static int insert_subset_children (splay_tree_node, void*);
static alias_set_entry get_alias_set_entry (alias_set_type);
static const_rtx fixed_scalar_and_varying_struct_p (const_rtx, const_rtx, rtx, rtx,
						    bool (*) (const_rtx, bool));
static int aliases_everything_p (const_rtx);
static bool nonoverlapping_component_refs_p (const_tree, const_tree);
static tree decl_for_component_ref (tree);
static rtx adjust_offset_for_component_ref (tree, rtx);
static int write_dependence_p (const_rtx, const_rtx, int);

static void memory_modified_1 (rtx, const_rtx, void *);

/* Set up all info needed to perform alias analysis on memory references.  */

/* Returns the size in bytes of the mode of X.  */
#define SIZE_FOR_MODE(X) (GET_MODE_SIZE (GET_MODE (X)))

/* Returns nonzero if MEM1 and MEM2 do not alias because they are in
   different alias sets.  We ignore alias sets in functions making use
   of variable arguments because the va_arg macros on some systems are
   not legal ANSI C.  */
#define DIFFERENT_ALIAS_SETS_P(MEM1, MEM2)			\
  mems_in_disjoint_alias_sets_p (MEM1, MEM2)

/* Cap the number of passes we make over the insns propagating alias
   information through set chains.   10 is a completely arbitrary choice.  */
#define MAX_ALIAS_LOOP_PASSES 10

/* reg_base_value[N] gives an address to which register N is related.
   If all sets after the first add or subtract to the current value
   or otherwise modify it so it does not point to a different top level
   object, reg_base_value[N] is equal to the address part of the source
   of the first set.

   A base address can be an ADDRESS, SYMBOL_REF, or LABEL_REF.  ADDRESS
   expressions represent certain special values: function arguments and
   the stack, frame, and argument pointers.

   The contents of an ADDRESS is not normally used, the mode of the
   ADDRESS determines whether the ADDRESS is a function argument or some
   other special value.  Pointer equality, not rtx_equal_p, determines whether
   two ADDRESS expressions refer to the same base address.

   The only use of the contents of an ADDRESS is for determining if the
   current function performs nonlocal memory memory references for the
   purposes of marking the function as a constant function.  */

static GTY(()) VEC(rtx,gc) *reg_base_value;
static rtx *new_reg_base_value;

/* We preserve the copy of old array around to avoid amount of garbage
   produced.  About 8% of garbage produced were attributed to this
   array.  */
static GTY((deletable)) VEC(rtx,gc) *old_reg_base_value;

/* Static hunks of RTL used by the aliasing code; these are initialized
   once per function to avoid unnecessary RTL allocations.  */
static GTY (()) rtx static_reg_base_value[FIRST_PSEUDO_REGISTER];

#define REG_BASE_VALUE(X)				\
  (REGNO (X) < VEC_length (rtx, reg_base_value)		\
   ? VEC_index (rtx, reg_base_value, REGNO (X)) : 0)

/* Vector indexed by N giving the initial (unchanging) value known for
   pseudo-register N.  This array is initialized in init_alias_analysis,
   and does not change until end_alias_analysis is called.  */
static GTY((length("reg_known_value_size"))) rtx *reg_known_value;

/* Indicates number of valid entries in reg_known_value.  */
static GTY(()) unsigned int reg_known_value_size;

/* Vector recording for each reg_known_value whether it is due to a
   REG_EQUIV note.  Future passes (viz., reload) may replace the
   pseudo with the equivalent expression and so we account for the
   dependences that would be introduced if that happens.

   The REG_EQUIV notes created in assign_parms may mention the arg
   pointer, and there are explicit insns in the RTL that modify the
   arg pointer.  Thus we must ensure that such insns don't get
   scheduled across each other because that would invalidate the
   REG_EQUIV notes.  One could argue that the REG_EQUIV notes are
   wrong, but solving the problem in the scheduler will likely give
   better code, so we do it here.  */
static bool *reg_known_equiv_p;

/* True when scanning insns from the start of the rtl to the
   NOTE_INSN_FUNCTION_BEG note.  */
static bool copying_arguments;

DEF_VEC_P(alias_set_entry);
DEF_VEC_ALLOC_P(alias_set_entry,gc);

/* The splay-tree used to store the various alias set entries.  */
static GTY (()) VEC(alias_set_entry,gc) *alias_sets;

/* Build a decomposed reference object for querying the alias-oracle
   from the MEM rtx and store it in *REF.
   Returns false if MEM is not suitable for the alias-oracle.  */

static bool
ao_ref_from_mem (ao_ref *ref, const_rtx mem)
{
  tree expr = MEM_EXPR (mem);
  tree base;

  if (!expr)
    return false;

  /* If MEM_OFFSET or MEM_SIZE are NULL punt.  */
  if (!MEM_OFFSET (mem)
      || !MEM_SIZE (mem))
    return false;

  ao_ref_init (ref, expr);

  /* Get the base of the reference and see if we have to reject or
     adjust it.  */
  base = ao_ref_base (ref);
  if (base == NULL_TREE)
    return false;

  /* If this is a pointer dereference of a non-SSA_NAME punt.
     ???  We could replace it with a pointer to anything.  */
  if (INDIRECT_REF_P (base)
      && TREE_CODE (TREE_OPERAND (base, 0)) != SSA_NAME)
    return false;

  /* The tree oracle doesn't like to have these.  */
  if (TREE_CODE (base) == FUNCTION_DECL
      || TREE_CODE (base) == LABEL_DECL)
    return false;

  /* If this is a reference based on a partitioned decl replace the
     base with an INDIRECT_REF of the pointer representative we
     created during stack slot partitioning.  */
  if (TREE_CODE (base) == VAR_DECL
      && ! TREE_STATIC (base)
      && cfun->gimple_df->decls_to_pointers != NULL)
    {
      void *namep;
      namep = pointer_map_contains (cfun->gimple_df->decls_to_pointers, base);
      if (namep)
	{
	  ref->base_alias_set = get_alias_set (base);
	  ref->base = build1 (INDIRECT_REF, TREE_TYPE (base), *(tree *)namep);
	}
    }

  ref->ref_alias_set = MEM_ALIAS_SET (mem);

  /* If the base decl is a parameter we can have negative MEM_OFFSET in
     case of promoted subregs on bigendian targets.  Trust the MEM_EXPR
     here.  */
  if (INTVAL (MEM_OFFSET (mem)) < 0
      && ((INTVAL (MEM_SIZE (mem)) + INTVAL (MEM_OFFSET (mem)))
	  * BITS_PER_UNIT) == ref->size)
    return true;

  ref->offset += INTVAL (MEM_OFFSET (mem)) * BITS_PER_UNIT;
  ref->size = INTVAL (MEM_SIZE (mem)) * BITS_PER_UNIT;

  /* The MEM may extend into adjacent fields, so adjust max_size if
     necessary.  */
  if (ref->max_size != -1
      && ref->size > ref->max_size)
    ref->max_size = ref->size;

  /* If MEM_OFFSET and MEM_SIZE get us outside of the base object of
     the MEM_EXPR punt.  This happens for STRICT_ALIGNMENT targets a lot.  */
  if (MEM_EXPR (mem) != get_spill_slot_decl (false)
      && (ref->offset < 0
	  || (DECL_P (ref->base)
	      && (!host_integerp (DECL_SIZE (ref->base), 1)
		  || (TREE_INT_CST_LOW (DECL_SIZE ((ref->base)))
		      < (unsigned HOST_WIDE_INT)(ref->offset + ref->size))))))
    return false;

  return true;
}

/* Query the alias-oracle on whether the two memory rtx X and MEM may
   alias.  If TBAA_P is set also apply TBAA.  Returns true if the
   two rtxen may alias, false otherwise.  */

static bool
rtx_refs_may_alias_p (const_rtx x, const_rtx mem, bool tbaa_p)
{
  ao_ref ref1, ref2;

  if (!ao_ref_from_mem (&ref1, x)
      || !ao_ref_from_mem (&ref2, mem))
    return true;

  return refs_may_alias_p_1 (&ref1, &ref2, tbaa_p);
}

/* Returns a pointer to the alias set entry for ALIAS_SET, if there is
   such an entry, or NULL otherwise.  */

static inline alias_set_entry
get_alias_set_entry (alias_set_type alias_set)
{
  return VEC_index (alias_set_entry, alias_sets, alias_set);
}

/* Returns nonzero if the alias sets for MEM1 and MEM2 are such that
   the two MEMs cannot alias each other.  */

static inline int
mems_in_disjoint_alias_sets_p (const_rtx mem1, const_rtx mem2)
{
/* Perform a basic sanity check.  Namely, that there are no alias sets
   if we're not using strict aliasing.  This helps to catch bugs
   whereby someone uses PUT_CODE, but doesn't clear MEM_ALIAS_SET, or
   where a MEM is allocated in some way other than by the use of
   gen_rtx_MEM, and the MEM_ALIAS_SET is not cleared.  If we begin to
   use alias sets to indicate that spilled registers cannot alias each
   other, we might need to remove this check.  */
  gcc_assert (flag_strict_aliasing
	      || (!MEM_ALIAS_SET (mem1) && !MEM_ALIAS_SET (mem2)));

  return ! alias_sets_conflict_p (MEM_ALIAS_SET (mem1), MEM_ALIAS_SET (mem2));
}

/* Insert the NODE into the splay tree given by DATA.  Used by
   record_alias_subset via splay_tree_foreach.  */

static int
insert_subset_children (splay_tree_node node, void *data)
{
  splay_tree_insert ((splay_tree) data, node->key, node->value);

  return 0;
}

/* Return true if the first alias set is a subset of the second.  */

bool
alias_set_subset_of (alias_set_type set1, alias_set_type set2)
{
  alias_set_entry ase;

  /* Everything is a subset of the "aliases everything" set.  */
  if (set2 == 0)
    return true;

  /* Otherwise, check if set1 is a subset of set2.  */
  ase = get_alias_set_entry (set2);
  if (ase != 0
      && ((ase->has_zero_child && set1 == 0)
	  || splay_tree_lookup (ase->children,
			        (splay_tree_key) set1)))
    return true;
  return false;
}

/* Return 1 if the two specified alias sets may conflict.  */

int
alias_sets_conflict_p (alias_set_type set1, alias_set_type set2)
{
  alias_set_entry ase;

  /* The easy case.  */
  if (alias_sets_must_conflict_p (set1, set2))
    return 1;

  /* See if the first alias set is a subset of the second.  */
  ase = get_alias_set_entry (set1);
  if (ase != 0
      && (ase->has_zero_child
	  || splay_tree_lookup (ase->children,
				(splay_tree_key) set2)))
    return 1;

  /* Now do the same, but with the alias sets reversed.  */
  ase = get_alias_set_entry (set2);
  if (ase != 0
      && (ase->has_zero_child
	  || splay_tree_lookup (ase->children,
				(splay_tree_key) set1)))
    return 1;

  /* The two alias sets are distinct and neither one is the
     child of the other.  Therefore, they cannot conflict.  */
  return 0;
}

static int
walk_mems_2 (rtx *x, rtx mem)
{
  if (MEM_P (*x))
    {
      if (alias_sets_conflict_p (MEM_ALIAS_SET(*x), MEM_ALIAS_SET(mem)))
        return 1;
        
      return -1;  
    }
  return 0;
}

static int
walk_mems_1 (rtx *x, rtx *pat)
{
  if (MEM_P (*x))
    {
      /* Visit all MEMs in *PAT and check indepedence.  */
      if (for_each_rtx (pat, (rtx_function) walk_mems_2, *x))
        /* Indicate that dependence was determined and stop traversal.  */
        return 1;
        
      return -1;
    }
  return 0;
}

/* Return 1 if two specified instructions have mem expr with conflict alias sets*/
bool
insn_alias_sets_conflict_p (rtx insn1, rtx insn2)
{
  /* For each pair of MEMs in INSN1 and INSN2 check their independence.  */
  return  for_each_rtx (&PATTERN (insn1), (rtx_function) walk_mems_1,
			 &PATTERN (insn2));
}

/* Return 1 if the two specified alias sets will always conflict.  */

int
alias_sets_must_conflict_p (alias_set_type set1, alias_set_type set2)
{
  if (set1 == 0 || set2 == 0 || set1 == set2)
    return 1;

  return 0;
}

/* Return 1 if any MEM object of type T1 will always conflict (using the
   dependency routines in this file) with any MEM object of type T2.
   This is used when allocating temporary storage.  If T1 and/or T2 are
   NULL_TREE, it means we know nothing about the storage.  */

int
objects_must_conflict_p (tree t1, tree t2)
{
  alias_set_type set1, set2;

  /* If neither has a type specified, we don't know if they'll conflict
     because we may be using them to store objects of various types, for
     example the argument and local variables areas of inlined functions.  */
  if (t1 == 0 && t2 == 0)
    return 0;

  /* If they are the same type, they must conflict.  */
  if (t1 == t2
      /* Likewise if both are volatile.  */
      || (t1 != 0 && TYPE_VOLATILE (t1) && t2 != 0 && TYPE_VOLATILE (t2)))
    return 1;

  set1 = t1 ? get_alias_set (t1) : 0;
  set2 = t2 ? get_alias_set (t2) : 0;

  /* We can't use alias_sets_conflict_p because we must make sure
     that every subtype of t1 will conflict with every subtype of
     t2 for which a pair of subobjects of these respective subtypes
     overlaps on the stack.  */
  return alias_sets_must_conflict_p (set1, set2);
}

/* Return true if all nested component references handled by
   get_inner_reference in T are such that we should use the alias set
   provided by the object at the heart of T.

   This is true for non-addressable components (which don't have their
   own alias set), as well as components of objects in alias set zero.
   This later point is a special case wherein we wish to override the
   alias set used by the component, but we don't have per-FIELD_DECL
   assignable alias sets.  */

bool
component_uses_parent_alias_set (const_tree t)
{
  while (1)
    {
      /* If we're at the end, it vacuously uses its own alias set.  */
      if (!handled_component_p (t))
	return false;

      switch (TREE_CODE (t))
	{
	case COMPONENT_REF:
	  if (DECL_NONADDRESSABLE_P (TREE_OPERAND (t, 1)))
	    return true;
	  break;

	case ARRAY_REF:
	case ARRAY_RANGE_REF:
	  if (TYPE_NONALIASED_COMPONENT (TREE_TYPE (TREE_OPERAND (t, 0))))
	    return true;
	  break;

	case REALPART_EXPR:
	case IMAGPART_EXPR:
	  break;

	default:
	  /* Bitfields and casts are never addressable.  */
	  return true;
	}

      t = TREE_OPERAND (t, 0);
      if (get_alias_set (TREE_TYPE (t)) == 0)
	return true;
    }
}

/* Return the alias set for the memory pointed to by T, which may be
   either a type or an expression.  Return -1 if there is nothing
   special about dereferencing T.  */

static alias_set_type
get_deref_alias_set_1 (tree t)
{
  /* If we're not doing any alias analysis, just assume everything
     aliases everything else.  */
  if (!flag_strict_aliasing)
    return 0;

  /* All we care about is the type.  */
  if (! TYPE_P (t))
    t = TREE_TYPE (t);

  /* If we have an INDIRECT_REF via a void pointer, we don't
     know anything about what that might alias.  Likewise if the
     pointer is marked that way.  */
  if (TREE_CODE (TREE_TYPE (t)) == VOID_TYPE
      || TYPE_REF_CAN_ALIAS_ALL (t))
    return 0;

  return -1;
}

/* Return the alias set for the memory pointed to by T, which may be
   either a type or an expression.  */

alias_set_type
get_deref_alias_set (tree t)
{
  alias_set_type set = get_deref_alias_set_1 (t);

  /* Fall back to the alias-set of the pointed-to type.  */
  if (set == -1)
    {
      if (! TYPE_P (t))
	t = TREE_TYPE (t);
      set = get_alias_set (TREE_TYPE (t));
    }

  return set;
}

/* Return the alias set for T, which may be either a type or an
   expression.  Call language-specific routine for help, if needed.  */

alias_set_type
get_alias_set (tree t)
{
  alias_set_type set;

  /* If we're not doing any alias analysis, just assume everything
     aliases everything else.  Also return 0 if this or its type is
     an error.  */
  if (! flag_strict_aliasing || t == error_mark_node
      || (! TYPE_P (t)
	  && (TREE_TYPE (t) == 0 || TREE_TYPE (t) == error_mark_node)))
    return 0;

  /* We can be passed either an expression or a type.  This and the
     language-specific routine may make mutually-recursive calls to each other
     to figure out what to do.  At each juncture, we see if this is a tree
     that the language may need to handle specially.  First handle things that
     aren't types.  */
  if (! TYPE_P (t))
    {
      tree inner;

      /* Remove any nops, then give the language a chance to do
	 something with this tree before we look at it.  */
      STRIP_NOPS (t);
      set = lang_hooks.get_alias_set (t);
      if (set != -1)
	return set;

      /* Retrieve the original memory reference if needed.  */
      if (TREE_CODE (t) == TARGET_MEM_REF)
	t = TMR_ORIGINAL (t);

      /* First see if the actual object referenced is an INDIRECT_REF from a
	 restrict-qualified pointer or a "void *".  */
      inner = t;
      while (handled_component_p (inner))
	{
	  inner = TREE_OPERAND (inner, 0);
	  STRIP_NOPS (inner);
	}

      if (INDIRECT_REF_P (inner))
	{
	  set = get_deref_alias_set_1 (TREE_OPERAND (inner, 0));
	  if (set != -1)
	    return set;
	}

      /* Otherwise, pick up the outermost object that we could have a pointer
	 to, processing conversions as above.  */
      while (component_uses_parent_alias_set (t))
	{
	  t = TREE_OPERAND (t, 0);
	  STRIP_NOPS (t);
	}

      /* If we've already determined the alias set for a decl, just return
	 it.  This is necessary for C++ anonymous unions, whose component
	 variables don't look like union members (boo!).  */
      if (TREE_CODE (t) == VAR_DECL
	  && DECL_RTL_SET_P (t) && MEM_P (DECL_RTL (t)))
	return MEM_ALIAS_SET (DECL_RTL (t));

      /* Now all we care about is the type.  */
      t = TREE_TYPE (t);
    }

  /* Variant qualifiers don't affect the alias set, so get the main
     variant.  */
  t = TYPE_MAIN_VARIANT (t);

  /* Always use the canonical type as well.  If this is a type that
     requires structural comparisons to identify compatible types
     use alias set zero.  */
  if (TYPE_STRUCTURAL_EQUALITY_P (t))
    {
      /* Allow the language to specify another alias set for this
	 type.  */
      set = lang_hooks.get_alias_set (t);
      if (set != -1)
	return set;
      return 0;
    }
  t = TYPE_CANONICAL (t);
  /* Canonical types shouldn't form a tree nor should the canonical
     type require structural equality checks.  */
  gcc_assert (!TYPE_STRUCTURAL_EQUALITY_P (t) && TYPE_CANONICAL (t) == t);

  /* If this is a type with a known alias set, return it.  */
  if (TYPE_ALIAS_SET_KNOWN_P (t))
    return TYPE_ALIAS_SET (t);

  /* We don't want to set TYPE_ALIAS_SET for incomplete types.  */
  if (!COMPLETE_TYPE_P (t))
    {
      /* For arrays with unknown size the conservative answer is the
	 alias set of the element type.  */
      if (TREE_CODE (t) == ARRAY_TYPE)
	return get_alias_set (TREE_TYPE (t));

      /* But return zero as a conservative answer for incomplete types.  */
      return 0;
    }

  /* See if the language has special handling for this type.  */
  set = lang_hooks.get_alias_set (t);
  if (set != -1)
    return set;

  /* There are no objects of FUNCTION_TYPE, so there's no point in
     using up an alias set for them.  (There are, of course, pointers
     and references to functions, but that's different.)  */
  else if (TREE_CODE (t) == FUNCTION_TYPE
	   || TREE_CODE (t) == METHOD_TYPE)
    set = 0;

  /* Unless the language specifies otherwise, let vector types alias
     their components.  This avoids some nasty type punning issues in
     normal usage.  And indeed lets vectors be treated more like an
     array slice.  */
  else if (TREE_CODE (t) == VECTOR_TYPE)
    set = get_alias_set (TREE_TYPE (t));

  /* Unless the language specifies otherwise, treat array types the
     same as their components.  This avoids the asymmetry we get
     through recording the components.  Consider accessing a
     character(kind=1) through a reference to a character(kind=1)[1:1].
     Or consider if we want to assign integer(kind=4)[0:D.1387] and
     integer(kind=4)[4] the same alias set or not.
     Just be pragmatic here and make sure the array and its element
     type get the same alias set assigned.  */
  else if (TREE_CODE (t) == ARRAY_TYPE
	   && !TYPE_NONALIASED_COMPONENT (t))
    set = get_alias_set (TREE_TYPE (t));

  else
    /* Otherwise make a new alias set for this type.  */
    set = new_alias_set ();

  TYPE_ALIAS_SET (t) = set;

  /* If this is an aggregate type, we must record any component aliasing
     information.  */
  if (AGGREGATE_TYPE_P (t) || TREE_CODE (t) == COMPLEX_TYPE)
    record_component_aliases (t);

  return set;
}

/* Return a brand-new alias set.  */

alias_set_type
new_alias_set (void)
{
  if (flag_strict_aliasing)
    {
      if (alias_sets == 0)
	VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
      VEC_safe_push (alias_set_entry, gc, alias_sets, 0);
      return VEC_length (alias_set_entry, alias_sets) - 1;
    }
  else
    return 0;
}

/* Indicate that things in SUBSET can alias things in SUPERSET, but that
   not everything that aliases SUPERSET also aliases SUBSET.  For example,
   in C, a store to an `int' can alias a load of a structure containing an
   `int', and vice versa.  But it can't alias a load of a 'double' member
   of the same structure.  Here, the structure would be the SUPERSET and
   `int' the SUBSET.  This relationship is also described in the comment at
   the beginning of this file.

   This function should be called only once per SUPERSET/SUBSET pair.

   It is illegal for SUPERSET to be zero; everything is implicitly a
   subset of alias set zero.  */

void
record_alias_subset (alias_set_type superset, alias_set_type subset)
{
  alias_set_entry superset_entry;
  alias_set_entry subset_entry;

  /* It is possible in complex type situations for both sets to be the same,
     in which case we can ignore this operation.  */
  if (superset == subset)
    return;

  gcc_assert (superset);

  superset_entry = get_alias_set_entry (superset);
  if (superset_entry == 0)
    {
      /* Create an entry for the SUPERSET, so that we have a place to
	 attach the SUBSET.  */
      superset_entry = GGC_NEW (struct alias_set_entry_d);
      superset_entry->alias_set = superset;
      superset_entry->children
	= splay_tree_new_ggc (splay_tree_compare_ints);
      superset_entry->has_zero_child = 0;
      VEC_replace (alias_set_entry, alias_sets, superset, superset_entry);
    }

  if (subset == 0)
    superset_entry->has_zero_child = 1;
  else
    {
      subset_entry = get_alias_set_entry (subset);
      /* If there is an entry for the subset, enter all of its children
	 (if they are not already present) as children of the SUPERSET.  */
      if (subset_entry)
	{
	  if (subset_entry->has_zero_child)
	    superset_entry->has_zero_child = 1;

	  splay_tree_foreach (subset_entry->children, insert_subset_children,
			      superset_entry->children);
	}

      /* Enter the SUBSET itself as a child of the SUPERSET.  */
      splay_tree_insert (superset_entry->children,
			 (splay_tree_key) subset, 0);
    }
}

/* Record that component types of TYPE, if any, are part of that type for
   aliasing purposes.  For record types, we only record component types
   for fields that are not marked non-addressable.  For array types, we
   only record the component type if it is not marked non-aliased.  */

void
record_component_aliases (tree type)
{
  alias_set_type superset = get_alias_set (type);
  tree field;

  if (superset == 0)
    return;

  switch (TREE_CODE (type))
    {
    case RECORD_TYPE:
    case UNION_TYPE:
    case QUAL_UNION_TYPE:
      /* Recursively record aliases for the base classes, if there are any.  */
      if (TYPE_BINFO (type))
	{
	  int i;
	  tree binfo, base_binfo;

	  for (binfo = TYPE_BINFO (type), i = 0;
	       BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
	    record_alias_subset (superset,
				 get_alias_set (BINFO_TYPE (base_binfo)));
	}
      for (field = TYPE_FIELDS (type); field != 0; field = TREE_CHAIN (field))
	if (TREE_CODE (field) == FIELD_DECL && !DECL_NONADDRESSABLE_P (field))
	  record_alias_subset (superset, get_alias_set (TREE_TYPE (field)));
      break;

    case COMPLEX_TYPE:
      record_alias_subset (superset, get_alias_set (TREE_TYPE (type)));
      break;

    /* VECTOR_TYPE and ARRAY_TYPE share the alias set with their
       element type.  */

    default:
      break;
    }
}

/* Allocate an alias set for use in storing and reading from the varargs
   spill area.  */

static GTY(()) alias_set_type varargs_set = -1;

alias_set_type
get_varargs_alias_set (void)
{
#if 1
  /* We now lower VA_ARG_EXPR, and there's currently no way to attach the
     varargs alias set to an INDIRECT_REF (FIXME!), so we can't
     consistently use the varargs alias set for loads from the varargs
     area.  So don't use it anywhere.  */
  return 0;
#else
  if (varargs_set == -1)
    varargs_set = new_alias_set ();

  return varargs_set;
#endif
}

/* Likewise, but used for the fixed portions of the frame, e.g., register
   save areas.  */

static GTY(()) alias_set_type frame_set = -1;

alias_set_type
get_frame_alias_set (void)
{
  if (frame_set == -1)
    frame_set = new_alias_set ();

  return frame_set;
}

/* Inside SRC, the source of a SET, find a base address.  */

static rtx
find_base_value (rtx src)
{
  unsigned int regno;

#if defined (FIND_BASE_TERM)
  /* Try machine-dependent ways to find the base term.  */
  src = FIND_BASE_TERM (src);
#endif

  switch (GET_CODE (src))
    {
    case SYMBOL_REF:
    case LABEL_REF:
      return src;

    case REG:
      regno = REGNO (src);
      /* At the start of a function, argument registers have known base
	 values which may be lost later.  Returning an ADDRESS
	 expression here allows optimization based on argument values
	 even when the argument registers are used for other purposes.  */
      if (regno < FIRST_PSEUDO_REGISTER && copying_arguments)
	return new_reg_base_value[regno];

      /* If a pseudo has a known base value, return it.  Do not do this
	 for non-fixed hard regs since it can result in a circular
	 dependency chain for registers which have values at function entry.

	 The test above is not sufficient because the scheduler may move
	 a copy out of an arg reg past the NOTE_INSN_FUNCTION_BEGIN.  */
      if ((regno >= FIRST_PSEUDO_REGISTER || fixed_regs[regno])
	  && regno < VEC_length (rtx, reg_base_value))
	{
	  /* If we're inside init_alias_analysis, use new_reg_base_value
	     to reduce the number of relaxation iterations.  */
	  if (new_reg_base_value && new_reg_base_value[regno]
	      && DF_REG_DEF_COUNT (regno) == 1)
	    return new_reg_base_value[regno];

	  if (VEC_index (rtx, reg_base_value, regno))
	    return VEC_index (rtx, reg_base_value, regno);
	}

      return 0;

    case MEM:
      /* Check for an argument passed in memory.  Only record in the
	 copying-arguments block; it is too hard to track changes
	 otherwise.  */
      if (copying_arguments
	  && (XEXP (src, 0) == arg_pointer_rtx
	      || (GET_CODE (XEXP (src, 0)) == PLUS
		  && XEXP (XEXP (src, 0), 0) == arg_pointer_rtx)))
	return gen_rtx_ADDRESS (VOIDmode, src);
      return 0;

    case CONST:
      src = XEXP (src, 0);
      if (GET_CODE (src) != PLUS && GET_CODE (src) != MINUS)
	break;

      /* ... fall through ...  */

    case PLUS:
    case MINUS:
      {
	rtx temp, src_0 = XEXP (src, 0), src_1 = XEXP (src, 1);

	/* If either operand is a REG that is a known pointer, then it
	   is the base.  */
	if (REG_P (src_0) && REG_POINTER (src_0))
	  return find_base_value (src_0);
	if (REG_P (src_1) && REG_POINTER (src_1))
	  return find_base_value (src_1);

	/* If either operand is a REG, then see if we already have
	   a known value for it.  */
	if (REG_P (src_0))
	  {
	    temp = find_base_value (src_0);
	    if (temp != 0)
	      src_0 = temp;
	  }

	if (REG_P (src_1))
	  {
	    temp = find_base_value (src_1);
	    if (temp!= 0)
	      src_1 = temp;
	  }

	/* If either base is named object or a special address
	   (like an argument or stack reference), then use it for the
	   base term.  */
	if (src_0 != 0
	    && (GET_CODE (src_0) == SYMBOL_REF
		|| GET_CODE (src_0) == LABEL_REF
		|| (GET_CODE (src_0) == ADDRESS
		    && GET_MODE (src_0) != VOIDmode)))
	  return src_0;

	if (src_1 != 0
	    && (GET_CODE (src_1) == SYMBOL_REF
		|| GET_CODE (src_1) == LABEL_REF
		|| (GET_CODE (src_1) == ADDRESS
		    && GET_MODE (src_1) != VOIDmode)))
	  return src_1;

	/* Guess which operand is the base address:
	   If either operand is a symbol, then it is the base.  If
	   either operand is a CONST_INT, then the other is the base.  */
	if (CONST_INT_P (src_1) || CONSTANT_P (src_0))
	  return find_base_value (src_0);
	else if (CONST_INT_P (src_0) || CONSTANT_P (src_1))
	  return find_base_value (src_1);

	return 0;
      }

    case LO_SUM:
      /* The standard form is (lo_sum reg sym) so look only at the
	 second operand.  */
      return find_base_value (XEXP (src, 1));

    case AND:
      /* If the second operand is constant set the base
	 address to the first operand.  */
      if (CONST_INT_P (XEXP (src, 1)) && INTVAL (XEXP (src, 1)) != 0)
	return find_base_value (XEXP (src, 0));
      return 0;

    case TRUNCATE:
      /* As we do not know which address space the pointer is refering to, we can
	 handle this only if the target does not support different pointer or
	 address modes depending on the address space.  */
      if (!target_default_pointer_address_modes_p ())
	break;
      if (GET_MODE_SIZE (GET_MODE (src)) < GET_MODE_SIZE (Pmode))
	break;
      /* Fall through.  */
    case HIGH:
    case PRE_INC:
    case PRE_DEC:
    case POST_INC:
    case POST_DEC:
    case PRE_MODIFY:
    case POST_MODIFY:
      return find_base_value (XEXP (src, 0));

    case ZERO_EXTEND:
    case SIGN_EXTEND:	/* used for NT/Alpha pointers */
      /* As we do not know which address space the pointer is refering to, we can
	 handle this only if the target does not support different pointer or
	 address modes depending on the address space.  */
      if (!target_default_pointer_address_modes_p ())
	break;

      {
	rtx temp = find_base_value (XEXP (src, 0));

	if (temp != 0 && CONSTANT_P (temp))
	  temp = convert_memory_address (Pmode, temp);

	return temp;
      }

    default:
      break;
    }

  return 0;
}

/* Called from init_alias_analysis indirectly through note_stores.  */

/* While scanning insns to find base values, reg_seen[N] is nonzero if
   register N has been set in this function.  */
static char *reg_seen;

/* Addresses which are known not to alias anything else are identified
   by a unique integer.  */
static int unique_id;

static void
record_set (rtx dest, const_rtx set, void *data ATTRIBUTE_UNUSED)
{
  unsigned regno;
  rtx src;
  int n;

  if (!REG_P (dest))
    return;

  regno = REGNO (dest);

  gcc_assert (regno < VEC_length (rtx, reg_base_value));

  /* If this spans multiple hard registers, then we must indicate that every
     register has an unusable value.  */
  if (regno < FIRST_PSEUDO_REGISTER)
    n = hard_regno_nregs[regno][GET_MODE (dest)];
  else
    n = 1;
  if (n != 1)
    {
      while (--n >= 0)
	{
	  reg_seen[regno + n] = 1;
	  new_reg_base_value[regno + n] = 0;
	}
      return;
    }

  if (set)
    {
      /* A CLOBBER wipes out any old value but does not prevent a previously
	 unset register from acquiring a base address (i.e. reg_seen is not
	 set).  */
      if (GET_CODE (set) == CLOBBER)
	{
	  new_reg_base_value[regno] = 0;
	  return;
	}
      src = SET_SRC (set);
    }
  else
    {
      if (reg_seen[regno])
	{
	  new_reg_base_value[regno] = 0;
	  return;
	}
      reg_seen[regno] = 1;
      new_reg_base_value[regno] = gen_rtx_ADDRESS (Pmode,
						   GEN_INT (unique_id++));
      return;
    }

  /* If this is not the first set of REGNO, see whether the new value
     is related to the old one.  There are two cases of interest:

	(1) The register might be assigned an entirely new value
	    that has the same base term as the original set.

	(2) The set might be a simple self-modification that
	    cannot change REGNO's base value.

     If neither case holds, reject the original base value as invalid.
     Note that the following situation is not detected:

	 extern int x, y;  int *p = &x; p += (&y-&x);

     ANSI C does not allow computing the difference of addresses
     of distinct top level objects.  */
  if (new_reg_base_value[regno] != 0
      && find_base_value (src) != new_reg_base_value[regno])
    switch (GET_CODE (src))
      {
      case LO_SUM:
      case MINUS:
	if (XEXP (src, 0) != dest && XEXP (src, 1) != dest)
	  new_reg_base_value[regno] = 0;
	break;
      case PLUS:
	/* If the value we add in the PLUS is also a valid base value,
	   this might be the actual base value, and the original value
	   an index.  */
	{
	  rtx other = NULL_RTX;

	  if (XEXP (src, 0) == dest)
	    other = XEXP (src, 1);
	  else if (XEXP (src, 1) == dest)
	    other = XEXP (src, 0);

	  if (! other || find_base_value (other))
	    new_reg_base_value[regno] = 0;
	  break;
	}
      case AND:
	if (XEXP (src, 0) != dest || !CONST_INT_P (XEXP (src, 1)))
	  new_reg_base_value[regno] = 0;
	break;
      default:
	new_reg_base_value[regno] = 0;
	break;
      }
  /* If this is the first set of a register, record the value.  */
  else if ((regno >= FIRST_PSEUDO_REGISTER || ! fixed_regs[regno])
	   && ! reg_seen[regno] && new_reg_base_value[regno] == 0)
    new_reg_base_value[regno] = find_base_value (src);

  reg_seen[regno] = 1;
}

/* If a value is known for REGNO, return it.  */

rtx
get_reg_known_value (unsigned int regno)
{
  if (regno >= FIRST_PSEUDO_REGISTER)
    {
      regno -= FIRST_PSEUDO_REGISTER;
      if (regno < reg_known_value_size)
	return reg_known_value[regno];
    }
  return NULL;
}

/* Set it.  */

static void
set_reg_known_value (unsigned int regno, rtx val)
{
  if (regno >= FIRST_PSEUDO_REGISTER)
    {
      regno -= FIRST_PSEUDO_REGISTER;
      if (regno < reg_known_value_size)
	reg_known_value[regno] = val;
    }
}

/* Similarly for reg_known_equiv_p.  */

bool
get_reg_known_equiv_p (unsigned int regno)
{
  if (regno >= FIRST_PSEUDO_REGISTER)
    {
      regno -= FIRST_PSEUDO_REGISTER;
      if (regno < reg_known_value_size)
	return reg_known_equiv_p[regno];
    }
  return false;
}

static void
set_reg_known_equiv_p (unsigned int regno, bool val)
{
  if (regno >= FIRST_PSEUDO_REGISTER)
    {
      regno -= FIRST_PSEUDO_REGISTER;
      if (regno < reg_known_value_size)
	reg_known_equiv_p[regno] = val;
    }
}


/* Returns a canonical version of X, from the point of view alias
   analysis.  (For example, if X is a MEM whose address is a register,
   and the register has a known value (say a SYMBOL_REF), then a MEM
   whose address is the SYMBOL_REF is returned.)  */

rtx
canon_rtx (rtx x)
{
  /* Recursively look for equivalences.  */
  if (REG_P (x) && REGNO (x) >= FIRST_PSEUDO_REGISTER)
    {
      rtx t = get_reg_known_value (REGNO (x));
      if (t == x)
	return x;
      if (t)
	return canon_rtx (t);
    }

  if (GET_CODE (x) == PLUS)
    {
      rtx x0 = canon_rtx (XEXP (x, 0));
      rtx x1 = canon_rtx (XEXP (x, 1));

      if (x0 != XEXP (x, 0) || x1 != XEXP (x, 1))
	{
	  if (CONST_INT_P (x0))
	    return plus_constant (x1, INTVAL (x0));
	  else if (CONST_INT_P (x1))
	    return plus_constant (x0, INTVAL (x1));
	  return gen_rtx_PLUS (GET_MODE (x), x0, x1);
	}
    }

  /* This gives us much better alias analysis when called from
     the loop optimizer.   Note we want to leave the original
     MEM alone, but need to return the canonicalized MEM with
     all the flags with their original values.  */
  else if (MEM_P (x))
    x = replace_equiv_address_nv (x, canon_rtx (XEXP (x, 0)));

  return x;
}

/* Return 1 if X and Y are identical-looking rtx's.
   Expect that X and Y has been already canonicalized.

   We use the data in reg_known_value above to see if two registers with
   different numbers are, in fact, equivalent.  */

static int
rtx_equal_for_memref_p (const_rtx x, const_rtx y)
{
  int i;
  int j;
  enum rtx_code code;
  const char *fmt;

  if (x == 0 && y == 0)
    return 1;
  if (x == 0 || y == 0)
    return 0;

  if (x == y)
    return 1;

  code = GET_CODE (x);
  /* Rtx's of different codes cannot be equal.  */
  if (code != GET_CODE (y))
    return 0;

  /* (MULT:SI x y) and (MULT:HI x y) are NOT equivalent.
     (REG:SI x) and (REG:HI x) are NOT equivalent.  */

  if (GET_MODE (x) != GET_MODE (y))
    return 0;

  /* Some RTL can be compared without a recursive examination.  */
  switch (code)
    {
    case REG:
      return REGNO (x) == REGNO (y);

    case LABEL_REF:
      return XEXP (x, 0) == XEXP (y, 0);

    case SYMBOL_REF:
      return XSTR (x, 0) == XSTR (y, 0);

    case VALUE:
    case CONST_INT:
    case CONST_DOUBLE:
    case CONST_FIXED:
      /* There's no need to compare the contents of CONST_DOUBLEs or
	 CONST_INTs because pointer equality is a good enough
	 comparison for these nodes.  */
      return 0;

    default:
      break;
    }

  /* canon_rtx knows how to handle plus.  No need to canonicalize.  */
  if (code == PLUS)
    return ((rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 0))
	     && rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 1)))
	    || (rtx_equal_for_memref_p (XEXP (x, 0), XEXP (y, 1))
		&& rtx_equal_for_memref_p (XEXP (x, 1), XEXP (y, 0))));
  /* For commutative operations, the RTX match if the operand match in any
     order.  Also handle the simple binary and unary cases without a loop.  */
  if (COMMUTATIVE_P (x))
    {
      rtx xop0 = canon_rtx (XEXP (x, 0));
      rtx yop0 = canon_rtx (XEXP (y, 0));
      rtx yop1 = canon_rtx (XEXP (y, 1));

      return ((rtx_equal_for_memref_p (xop0, yop0)
	       && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop1))
	      || (rtx_equal_for_memref_p (xop0, yop1)
		  && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)), yop0)));
    }
  else if (NON_COMMUTATIVE_P (x))
    {
      return (rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
				      canon_rtx (XEXP (y, 0)))
	      && rtx_equal_for_memref_p (canon_rtx (XEXP (x, 1)),
					 canon_rtx (XEXP (y, 1))));
    }
  else if (UNARY_P (x))
    return rtx_equal_for_memref_p (canon_rtx (XEXP (x, 0)),
				   canon_rtx (XEXP (y, 0)));

  /* Compare the elements.  If any pair of corresponding elements
     fail to match, return 0 for the whole things.

     Limit cases to types which actually appear in addresses.  */

  fmt = GET_RTX_FORMAT (code);
  for (i = GET_RTX_LENGTH (code) - 1; i >= 0; i--)
    {
      switch (fmt[i])
	{
	case 'i':
	  if (XINT (x, i) != XINT (y, i))
	    return 0;
	  break;

	case 'E':
	  /* Two vectors must have the same length.  */
	  if (XVECLEN (x, i) != XVECLEN (y, i))
	    return 0;

	  /* And the corresponding elements must match.  */
	  for (j = 0; j < XVECLEN (x, i); j++)
	    if (rtx_equal_for_memref_p (canon_rtx (XVECEXP (x, i, j)),
					canon_rtx (XVECEXP (y, i, j))) == 0)
	      return 0;
	  break;

	case 'e':
	  if (rtx_equal_for_memref_p (canon_rtx (XEXP (x, i)),
				      canon_rtx (XEXP (y, i))) == 0)
	    return 0;
	  break;

	  /* This can happen for asm operands.  */
	case 's':
	  if (strcmp (XSTR (x, i), XSTR (y, i)))
	    return 0;
	  break;

	/* This can happen for an asm which clobbers memory.  */
	case '0':
	  break;

	  /* It is believed that rtx's at this level will never
	     contain anything but integers and other rtx's,
	     except for within LABEL_REFs and SYMBOL_REFs.  */
	default:
	  gcc_unreachable ();
	}
    }
  return 1;
}

rtx
find_base_term (rtx x)
{
  cselib_val *val;
  struct elt_loc_list *l;

#if defined (FIND_BASE_TERM)
  /* Try machine-dependent ways to find the base term.  */
  x = FIND_BASE_TERM (x);
#endif

  switch (GET_CODE (x))
    {
    case REG:
      return REG_BASE_VALUE (x);

    case TRUNCATE:
      /* As we do not know which address space the pointer is refering to, we can
	 handle this only if the target does not support different pointer or
	 address modes depending on the address space.  */
      if (!target_default_pointer_address_modes_p ())
	return 0;
      if (GET_MODE_SIZE (GET_MODE (x)) < GET_MODE_SIZE (Pmode))
	return 0;
      /* Fall through.  */
    case HIGH:
    case PRE_INC:
    case PRE_DEC:
    case POST_INC:
    case POST_DEC:
    case PRE_MODIFY:
    case POST_MODIFY:
      return find_base_term (XEXP (x, 0));

    case ZERO_EXTEND:
    case SIGN_EXTEND:	/* Used for Alpha/NT pointers */
      /* As we do not know which address space the pointer is refering to, we can
	 handle this only if the target does not support different pointer or
	 address modes depending on the address space.  */
      if (!target_default_pointer_address_modes_p ())
	return 0;

      {
	rtx temp = find_base_term (XEXP (x, 0));

	if (temp != 0 && CONSTANT_P (temp))
	  temp = convert_memory_address (Pmode, temp);

	return temp;
      }

    case VALUE:
      val = CSELIB_VAL_PTR (x);
      if (!val)
	return 0;
      for (l = val->locs; l; l = l->next)
	if ((x = find_base_term (l->loc)) != 0)
	  return x;
      return 0;

    case LO_SUM:
      /* The standard form is (lo_sum reg sym) so look only at the
         second operand.  */
      return find_base_term (XEXP (x, 1));

    case CONST:
      x = XEXP (x, 0);
      if (GET_CODE (x) != PLUS && GET_CODE (x) != MINUS)
	return 0;
      /* Fall through.  */
    case PLUS:
    case MINUS:
      {
	rtx tmp1 = XEXP (x, 0);
	rtx tmp2 = XEXP (x, 1);

	/* This is a little bit tricky since we have to determine which of
	   the two operands represents the real base address.  Otherwise this
	   routine may return the index register instead of the base register.

	   That may cause us to believe no aliasing was possible, when in
	   fact aliasing is possible.

	   We use a few simple tests to guess the base register.  Additional
	   tests can certainly be added.  For example, if one of the operands
	   is a shift or multiply, then it must be the index register and the
	   other operand is the base register.  */

	if (tmp1 == pic_offset_table_rtx && CONSTANT_P (tmp2))
	  return find_base_term (tmp2);

	/* If either operand is known to be a pointer, then use it
	   to determine the base term.  */
	if (REG_P (tmp1) && REG_POINTER (tmp1))
	  {
	    rtx base = find_base_term (tmp1);
	    if (base)
	      return base;
	  }

	if (REG_P (tmp2) && REG_POINTER (tmp2))
	  {
	    rtx base = find_base_term (tmp2);
	    if (base)
	      return base;
	  }

	/* Neither operand was known to be a pointer.  Go ahead and find the
	   base term for both operands.  */
	tmp1 = find_base_term (tmp1);
	tmp2 = find_base_term (tmp2);

	/* If either base term is named object or a special address
	   (like an argument or stack reference), then use it for the
	   base term.  */
	if (tmp1 != 0
	    && (GET_CODE (tmp1) == SYMBOL_REF
		|| GET_CODE (tmp1) == LABEL_REF
		|| (GET_CODE (tmp1) == ADDRESS
		    && GET_MODE (tmp1) != VOIDmode)))
	  return tmp1;

	if (tmp2 != 0
	    && (GET_CODE (tmp2) == SYMBOL_REF
		|| GET_CODE (tmp2) == LABEL_REF
		|| (GET_CODE (tmp2) == ADDRESS
		    && GET_MODE (tmp2) != VOIDmode)))
	  return tmp2;

	/* We could not determine which of the two operands was the
	   base register and which was the index.  So we can determine
	   nothing from the base alias check.  */
	return 0;
      }

    case AND:
      if (CONST_INT_P (XEXP (x, 1)) && INTVAL (XEXP (x, 1)) != 0)
	return find_base_term (XEXP (x, 0));
      return 0;

    case SYMBOL_REF:
    case LABEL_REF:
      return x;

    default:
      return 0;
    }
}

/* Return 0 if the addresses X and Y are known to point to different
   objects, 1 if they might be pointers to the same object.  */

static int
base_alias_check (rtx x, rtx y, enum machine_mode x_mode,
		  enum machine_mode y_mode)
{
  rtx x_base = find_base_term (x);
  rtx y_base = find_base_term (y);

  /* If the address itself has no known base see if a known equivalent
     value has one.  If either address still has no known base, nothing
     is known about aliasing.  */
  if (x_base == 0)
    {
      rtx x_c;

      if (! flag_expensive_optimizations || (x_c = canon_rtx (x)) == x)
	return 1;

      x_base = find_base_term (x_c);
      if (x_base == 0)
	return 1;
    }

  if (y_base == 0)
    {
      rtx y_c;
      if (! flag_expensive_optimizations || (y_c = canon_rtx (y)) == y)
	return 1;

      y_base = find_base_term (y_c);
      if (y_base == 0)
	return 1;
    }

  /* If the base addresses are equal nothing is known about aliasing.  */
  if (rtx_equal_p (x_base, y_base))
    return 1;

  /* The base addresses are different expressions.  If they are not accessed
     via AND, there is no conflict.  We can bring knowledge of object
     alignment into play here.  For example, on alpha, "char a, b;" can
     alias one another, though "char a; long b;" cannot.  AND addesses may
     implicitly alias surrounding objects; i.e. unaligned access in DImode
     via AND address can alias all surrounding object types except those
     with aligment 8 or higher.  */
  if (GET_CODE (x) == AND && GET_CODE (y) == AND)
    return 1;
  if (GET_CODE (x) == AND
      && (!CONST_INT_P (XEXP (x, 1))
	  || (int) GET_MODE_UNIT_SIZE (y_mode) < -INTVAL (XEXP (x, 1))))
    return 1;
  if (GET_CODE (y) == AND
      && (!CONST_INT_P (XEXP (y, 1))
	  || (int) GET_MODE_UNIT_SIZE (x_mode) < -INTVAL (XEXP (y, 1))))
    return 1;

  /* Differing symbols not accessed via AND never alias.  */
  if (GET_CODE (x_base) != ADDRESS && GET_CODE (y_base) != ADDRESS)
    return 0;

  /* If one address is a stack reference there can be no alias:
     stack references using different base registers do not alias,
     a stack reference can not alias a parameter, and a stack reference
     can not alias a global.  */
  if ((GET_CODE (x_base) == ADDRESS && GET_MODE (x_base) == Pmode)
      || (GET_CODE (y_base) == ADDRESS && GET_MODE (y_base) == Pmode))
    return 0;

  if (! flag_argument_noalias)
    return 1;

  if (flag_argument_noalias > 1)
    return 0;

  /* Weak noalias assertion (arguments are distinct, but may match globals).  */
  return ! (GET_MODE (x_base) == VOIDmode && GET_MODE (y_base) == VOIDmode);
}

/* Convert the address X into something we can use.  This is done by returning
   it unchanged unless it is a value; in the latter case we call cselib to get
   a more useful rtx.  */

rtx
get_addr (rtx x)
{
  cselib_val *v;
  struct elt_loc_list *l;

  if (GET_CODE (x) != VALUE)
    return x;
  v = CSELIB_VAL_PTR (x);
  if (v)
    {
      for (l = v->locs; l; l = l->next)
	if (CONSTANT_P (l->loc))
	  return l->loc;
      for (l = v->locs; l; l = l->next)
	if (!REG_P (l->loc) && !MEM_P (l->loc))
	  return l->loc;
      if (v->locs)
	return v->locs->loc;
    }
  return x;
}

/*  Return the address of the (N_REFS + 1)th memory reference to ADDR
    where SIZE is the size in bytes of the memory reference.  If ADDR
    is not modified by the memory reference then ADDR is returned.  */

static rtx
addr_side_effect_eval (rtx addr, int size, int n_refs)
{
  int offset = 0;

  switch (GET_CODE (addr))
    {
    case PRE_INC:
      offset = (n_refs + 1) * size;
      break;
    case PRE_DEC:
      offset = -(n_refs + 1) * size;
      break;
    case POST_INC:
      offset = n_refs * size;
      break;
    case POST_DEC:
      offset = -n_refs * size;
      break;

    default:
      return addr;
    }

  if (offset)
    addr = gen_rtx_PLUS (GET_MODE (addr), XEXP (addr, 0),
			 GEN_INT (offset));
  else
    addr = XEXP (addr, 0);
  addr = canon_rtx (addr);

  return addr;
}

/* Return nonzero if X and Y (memory addresses) could reference the
   same location in memory.  C is an offset accumulator.  When
   C is nonzero, we are testing aliases between X and Y + C.
   XSIZE is the size in bytes of the X reference,
   similarly YSIZE is the size in bytes for Y.
   Expect that canon_rtx has been already called for X and Y.

   If XSIZE or YSIZE is zero, we do not know the amount of memory being
   referenced (the reference was BLKmode), so make the most pessimistic
   assumptions.

   If XSIZE or YSIZE is negative, we may access memory outside the object
   being referenced as a side effect.  This can happen when using AND to
   align memory references, as is done on the Alpha.

   Nice to notice that varying addresses cannot conflict with fp if no
   local variables had their addresses taken, but that's too hard now.  */

static int
memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
{
  if (GET_CODE (x) == VALUE)
    x = get_addr (x);
  if (GET_CODE (y) == VALUE)
    y = get_addr (y);
  if (GET_CODE (x) == HIGH)
    x = XEXP (x, 0);
  else if (GET_CODE (x) == LO_SUM)
    x = XEXP (x, 1);
  else
    x = addr_side_effect_eval (x, xsize, 0);
  if (GET_CODE (y) == HIGH)
    y = XEXP (y, 0);
  else if (GET_CODE (y) == LO_SUM)
    y = XEXP (y, 1);
  else
    y = addr_side_effect_eval (y, ysize, 0);

  if (rtx_equal_for_memref_p (x, y))
    {
      if (xsize <= 0 || ysize <= 0)
	return 1;
      if (c >= 0 && xsize > c)
	return 1;
      if (c < 0 && ysize+c > 0)
	return 1;
      return 0;
    }

  /* This code used to check for conflicts involving stack references and
     globals but the base address alias code now handles these cases.  */

  if (GET_CODE (x) == PLUS)
    {
      /* The fact that X is canonicalized means that this
	 PLUS rtx is canonicalized.  */
      rtx x0 = XEXP (x, 0);
      rtx x1 = XEXP (x, 1);

      if (GET_CODE (y) == PLUS)
	{
	  /* The fact that Y is canonicalized means that this
	     PLUS rtx is canonicalized.  */
	  rtx y0 = XEXP (y, 0);
	  rtx y1 = XEXP (y, 1);

	  if (rtx_equal_for_memref_p (x1, y1))
	    return memrefs_conflict_p (xsize, x0, ysize, y0, c);
	  if (rtx_equal_for_memref_p (x0, y0))
	    return memrefs_conflict_p (xsize, x1, ysize, y1, c);
	  if (CONST_INT_P (x1))
	    {
	      if (CONST_INT_P (y1))
		return memrefs_conflict_p (xsize, x0, ysize, y0,
					   c - INTVAL (x1) + INTVAL (y1));
	      else
		return memrefs_conflict_p (xsize, x0, ysize, y,
					   c - INTVAL (x1));
	    }
	  else if (CONST_INT_P (y1))
	    return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));

	  return 1;
	}
      else if (CONST_INT_P (x1))
	return memrefs_conflict_p (xsize, x0, ysize, y, c - INTVAL (x1));
    }
  else if (GET_CODE (y) == PLUS)
    {
      /* The fact that Y is canonicalized means that this
	 PLUS rtx is canonicalized.  */
      rtx y0 = XEXP (y, 0);
      rtx y1 = XEXP (y, 1);

      if (CONST_INT_P (y1))
	return memrefs_conflict_p (xsize, x, ysize, y0, c + INTVAL (y1));
      else
	return 1;
    }

  if (GET_CODE (x) == GET_CODE (y))
    switch (GET_CODE (x))
      {
      case MULT:
	{
	  /* Handle cases where we expect the second operands to be the
	     same, and check only whether the first operand would conflict
	     or not.  */
	  rtx x0, y0;
	  rtx x1 = canon_rtx (XEXP (x, 1));
	  rtx y1 = canon_rtx (XEXP (y, 1));
	  if (! rtx_equal_for_memref_p (x1, y1))
	    return 1;
	  x0 = canon_rtx (XEXP (x, 0));
	  y0 = canon_rtx (XEXP (y, 0));
	  if (rtx_equal_for_memref_p (x0, y0))
	    return (xsize == 0 || ysize == 0
		    || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));

	  /* Can't properly adjust our sizes.  */
	  if (!CONST_INT_P (x1))
	    return 1;
	  xsize /= INTVAL (x1);
	  ysize /= INTVAL (x1);
	  c /= INTVAL (x1);
	  return memrefs_conflict_p (xsize, x0, ysize, y0, c);
	}

      default:
	break;
      }

  /* Treat an access through an AND (e.g. a subword access on an Alpha)
     as an access with indeterminate size.  Assume that references
     besides AND are aligned, so if the size of the other reference is
     at least as large as the alignment, assume no other overlap.  */
  if (GET_CODE (x) == AND && CONST_INT_P (XEXP (x, 1)))
    {
      if (GET_CODE (y) == AND || ysize < -INTVAL (XEXP (x, 1)))
	xsize = -1;
      return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)), ysize, y, c);
    }
  if (GET_CODE (y) == AND && CONST_INT_P (XEXP (y, 1)))
    {
      /* ??? If we are indexing far enough into the array/structure, we
	 may yet be able to determine that we can not overlap.  But we
	 also need to that we are far enough from the end not to overlap
	 a following reference, so we do nothing with that for now.  */
      if (GET_CODE (x) == AND || xsize < -INTVAL (XEXP (y, 1)))
	ysize = -1;
      return memrefs_conflict_p (xsize, x, ysize, canon_rtx (XEXP (y, 0)), c);
    }

  if (CONSTANT_P (x))
    {
      if (CONST_INT_P (x) && CONST_INT_P (y))
	{
	  c += (INTVAL (y) - INTVAL (x));
	  return (xsize <= 0 || ysize <= 0
		  || (c >= 0 && xsize > c) || (c < 0 && ysize+c > 0));
	}

      if (GET_CODE (x) == CONST)
	{
	  if (GET_CODE (y) == CONST)
	    return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
				       ysize, canon_rtx (XEXP (y, 0)), c);
	  else
	    return memrefs_conflict_p (xsize, canon_rtx (XEXP (x, 0)),
				       ysize, y, c);
	}
      if (GET_CODE (y) == CONST)
	return memrefs_conflict_p (xsize, x, ysize,
				   canon_rtx (XEXP (y, 0)), c);

      if (CONSTANT_P (y))
	return (xsize <= 0 || ysize <= 0
		|| (rtx_equal_for_memref_p (x, y)
		    && ((c >= 0 && xsize > c) || (c < 0 && ysize+c > 0))));

      return 1;
    }
  return 1;
}

/* Functions to compute memory dependencies.

   Since we process the insns in execution order, we can build tables
   to keep track of what registers are fixed (and not aliased), what registers
   are varying in known ways, and what registers are varying in unknown
   ways.

   If both memory references are volatile, then there must always be a
   dependence between the two references, since their order can not be
   changed.  A volatile and non-volatile reference can be interchanged
   though.

   A MEM_IN_STRUCT reference at a non-AND varying address can never
   conflict with a non-MEM_IN_STRUCT reference at a fixed address.  We
   also must allow AND addresses, because they may generate accesses
   outside the object being referenced.  This is used to generate
   aligned addresses from unaligned addresses, for instance, the alpha
   storeqi_unaligned pattern.  */

/* Read dependence: X is read after read in MEM takes place.  There can
   only be a dependence here if both reads are volatile.  */

int
read_dependence (const_rtx mem, const_rtx x)
{
  return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
}

/* Returns MEM1 if and only if MEM1 is a scalar at a fixed address and
   MEM2 is a reference to a structure at a varying address, or returns
   MEM2 if vice versa.  Otherwise, returns NULL_RTX.  If a non-NULL
   value is returned MEM1 and MEM2 can never alias.  VARIES_P is used
   to decide whether or not an address may vary; it should return
   nonzero whenever variation is possible.
   MEM1_ADDR and MEM2_ADDR are the addresses of MEM1 and MEM2.  */

static const_rtx
fixed_scalar_and_varying_struct_p (const_rtx mem1, const_rtx mem2, rtx mem1_addr,
				   rtx mem2_addr,
				   bool (*varies_p) (const_rtx, bool))
{
  if (! flag_strict_aliasing)
    return NULL_RTX;

  if (MEM_ALIAS_SET (mem2)
      && MEM_SCALAR_P (mem1) && MEM_IN_STRUCT_P (mem2)
      && !varies_p (mem1_addr, 1) && varies_p (mem2_addr, 1))
    /* MEM1 is a scalar at a fixed address; MEM2 is a struct at a
       varying address.  */
    return mem1;

  if (MEM_ALIAS_SET (mem1)
      && MEM_IN_STRUCT_P (mem1) && MEM_SCALAR_P (mem2)
      && varies_p (mem1_addr, 1) && !varies_p (mem2_addr, 1))
    /* MEM2 is a scalar at a fixed address; MEM1 is a struct at a
       varying address.  */
    return mem2;

  return NULL_RTX;
}

/* Returns nonzero if something about the mode or address format MEM1
   indicates that it might well alias *anything*.  */

static int
aliases_everything_p (const_rtx mem)
{
  if (GET_CODE (XEXP (mem, 0)) == AND)
    /* If the address is an AND, it's very hard to know at what it is
       actually pointing.  */
    return 1;

  return 0;
}

/* Return true if we can determine that the fields referenced cannot
   overlap for any pair of objects.  */

static bool
nonoverlapping_component_refs_p (const_tree x, const_tree y)
{
  const_tree fieldx, fieldy, typex, typey, orig_y;

  if (!flag_strict_aliasing)
    return false;

  do
    {
      /* The comparison has to be done at a common type, since we don't
	 know how the inheritance hierarchy works.  */
      orig_y = y;
      do
	{
	  fieldx = TREE_OPERAND (x, 1);
	  typex = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldx));

	  y = orig_y;
	  do
	    {
	      fieldy = TREE_OPERAND (y, 1);
	      typey = TYPE_MAIN_VARIANT (DECL_FIELD_CONTEXT (fieldy));

	      if (typex == typey)
		goto found;

	      y = TREE_OPERAND (y, 0);
	    }
	  while (y && TREE_CODE (y) == COMPONENT_REF);

	  x = TREE_OPERAND (x, 0);
	}
      while (x && TREE_CODE (x) == COMPONENT_REF);
      /* Never found a common type.  */
      return false;

    found:
      /* If we're left with accessing different fields of a structure,
	 then no overlap.  */
      if (TREE_CODE (typex) == RECORD_TYPE
	  && fieldx != fieldy)
	return true;

      /* The comparison on the current field failed.  If we're accessing
	 a very nested structure, look at the next outer level.  */
      x = TREE_OPERAND (x, 0);
      y = TREE_OPERAND (y, 0);
    }
  while (x && y
	 && TREE_CODE (x) == COMPONENT_REF
	 && TREE_CODE (y) == COMPONENT_REF);

  return false;
}

/* Look at the bottom of the COMPONENT_REF list for a DECL, and return it.  */

static tree
decl_for_component_ref (tree x)
{
  do
    {
      x = TREE_OPERAND (x, 0);
    }
  while (x && TREE_CODE (x) == COMPONENT_REF);

  return x && DECL_P (x) ? x : NULL_TREE;
}

/* Walk up the COMPONENT_REF list and adjust OFFSET to compensate for the
   offset of the field reference.  */

static rtx
adjust_offset_for_component_ref (tree x, rtx offset)
{
  HOST_WIDE_INT ioffset;

  if (! offset)
    return NULL_RTX;

  ioffset = INTVAL (offset);
  do
    {
      tree offset = component_ref_field_offset (x);
      tree field = TREE_OPERAND (x, 1);

      if (! host_integerp (offset, 1))
	return NULL_RTX;
      ioffset += (tree_low_cst (offset, 1)
		  + (tree_low_cst (DECL_FIELD_BIT_OFFSET (field), 1)
		     / BITS_PER_UNIT));

      x = TREE_OPERAND (x, 0);
    }
  while (x && TREE_CODE (x) == COMPONENT_REF);

  return GEN_INT (ioffset);
}

/* Return nonzero if we can determine the exprs corresponding to memrefs
   X and Y and they do not overlap.  */

int
nonoverlapping_memrefs_p (const_rtx x, const_rtx y)
{
  tree exprx = MEM_EXPR (x), expry = MEM_EXPR (y);
  rtx rtlx, rtly;
  rtx basex, basey;
  rtx moffsetx, moffsety;
  HOST_WIDE_INT offsetx = 0, offsety = 0, sizex, sizey, tem;

  /* Unless both have exprs, we can't tell anything.  */
  if (exprx == 0 || expry == 0)
    return 0;

  /* If both are field references, we may be able to determine something.  */
  if (TREE_CODE (exprx) == COMPONENT_REF
      && TREE_CODE (expry) == COMPONENT_REF
      && nonoverlapping_component_refs_p (exprx, expry))
    return 1;


  /* If the field reference test failed, look at the DECLs involved.  */
  moffsetx = MEM_OFFSET (x);
  if (TREE_CODE (exprx) == COMPONENT_REF)
    {
      if (TREE_CODE (expry) == VAR_DECL
	  && POINTER_TYPE_P (TREE_TYPE (expry)))
	{
	 tree field = TREE_OPERAND (exprx, 1);
	 tree fieldcontext = DECL_FIELD_CONTEXT (field);
	 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
						       TREE_TYPE (field)))
	   return 1;
	}
      {
	tree t = decl_for_component_ref (exprx);
	if (! t)
	  return 0;
	moffsetx = adjust_offset_for_component_ref (exprx, moffsetx);
	exprx = t;
      }
    }
  else if (INDIRECT_REF_P (exprx))
    {
      exprx = TREE_OPERAND (exprx, 0);
      if (flag_argument_noalias < 2
	  || TREE_CODE (exprx) != PARM_DECL)
	return 0;
    }

  moffsety = MEM_OFFSET (y);
  if (TREE_CODE (expry) == COMPONENT_REF)
    {
      if (TREE_CODE (exprx) == VAR_DECL
	  && POINTER_TYPE_P (TREE_TYPE (exprx)))
	{
	 tree field = TREE_OPERAND (expry, 1);
	 tree fieldcontext = DECL_FIELD_CONTEXT (field);
	 if (ipa_type_escape_field_does_not_clobber_p (fieldcontext,
						       TREE_TYPE (field)))
	   return 1;
	}
      {
	tree t = decl_for_component_ref (expry);
	if (! t)
	  return 0;
	moffsety = adjust_offset_for_component_ref (expry, moffsety);
	expry = t;
      }
    }
  else if (INDIRECT_REF_P (expry))
    {
      expry = TREE_OPERAND (expry, 0);
      if (flag_argument_noalias < 2
	  || TREE_CODE (expry) != PARM_DECL)
	return 0;
    }

  if (! DECL_P (exprx) || ! DECL_P (expry))
    return 0;

  /* With invalid code we can end up storing into the constant pool.
     Bail out to avoid ICEing when creating RTL for this.
     See gfortran.dg/lto/20091028-2_0.f90.  */
  if (TREE_CODE (exprx) == CONST_DECL
      || TREE_CODE (expry) == CONST_DECL)
    return 1;

  rtlx = DECL_RTL (exprx);
  rtly = DECL_RTL (expry);

  /* If either RTL is not a MEM, it must be a REG or CONCAT, meaning they
     can't overlap unless they are the same because we never reuse that part
     of the stack frame used for locals for spilled pseudos.  */
  if ((!MEM_P (rtlx) || !MEM_P (rtly))
      && ! rtx_equal_p (rtlx, rtly))
    return 1;

  /* If we have MEMs refering to different address spaces (which can
     potentially overlap), we cannot easily tell from the addresses
     whether the references overlap.  */
  if (MEM_P (rtlx) && MEM_P (rtly)
      && MEM_ADDR_SPACE (rtlx) != MEM_ADDR_SPACE (rtly))
    return 0;

  /* Get the base and offsets of both decls.  If either is a register, we
     know both are and are the same, so use that as the base.  The only
     we can avoid overlap is if we can deduce that they are nonoverlapping
     pieces of that decl, which is very rare.  */
  basex = MEM_P (rtlx) ? XEXP (rtlx, 0) : rtlx;
  if (GET_CODE (basex) == PLUS && CONST_INT_P (XEXP (basex, 1)))
    offsetx = INTVAL (XEXP (basex, 1)), basex = XEXP (basex, 0);

  basey = MEM_P (rtly) ? XEXP (rtly, 0) : rtly;
  if (GET_CODE (basey) == PLUS && CONST_INT_P (XEXP (basey, 1)))
    offsety = INTVAL (XEXP (basey, 1)), basey = XEXP (basey, 0);

  /* If the bases are different, we know they do not overlap if both
     are constants or if one is a constant and the other a pointer into the
     stack frame.  Otherwise a different base means we can't tell if they
     overlap or not.  */
  if (! rtx_equal_p (basex, basey))
    return ((CONSTANT_P (basex) && CONSTANT_P (basey))
	    || (CONSTANT_P (basex) && REG_P (basey)
		&& REGNO_PTR_FRAME_P (REGNO (basey)))
	    || (CONSTANT_P (basey) && REG_P (basex)
		&& REGNO_PTR_FRAME_P (REGNO (basex))));

  sizex = (!MEM_P (rtlx) ? (int) GET_MODE_SIZE (GET_MODE (rtlx))
	   : MEM_SIZE (rtlx) ? INTVAL (MEM_SIZE (rtlx))
	   : -1);
  sizey = (!MEM_P (rtly) ? (int) GET_MODE_SIZE (GET_MODE (rtly))
	   : MEM_SIZE (rtly) ? INTVAL (MEM_SIZE (rtly)) :
	   -1);

  /* If we have an offset for either memref, it can update the values computed
     above.  */
  if (moffsetx)
    offsetx += INTVAL (moffsetx), sizex -= INTVAL (moffsetx);
  if (moffsety)
    offsety += INTVAL (moffsety), sizey -= INTVAL (moffsety);

  /* If a memref has both a size and an offset, we can use the smaller size.
     We can't do this if the offset isn't known because we must view this
     memref as being anywhere inside the DECL's MEM.  */
  if (MEM_SIZE (x) && moffsetx)
    sizex = INTVAL (MEM_SIZE (x));
  if (MEM_SIZE (y) && moffsety)
    sizey = INTVAL (MEM_SIZE (y));

  /* Put the values of the memref with the lower offset in X's values.  */
  if (offsetx > offsety)
    {
      tem = offsetx, offsetx = offsety, offsety = tem;
      tem = sizex, sizex = sizey, sizey = tem;
    }

  /* If we don't know the size of the lower-offset value, we can't tell
     if they conflict.  Otherwise, we do the test.  */
  return sizex >= 0 && offsety >= offsetx + sizex;
}

/* True dependence: X is read after store in MEM takes place.  */

int
true_dependence (const_rtx mem, enum machine_mode mem_mode, const_rtx x,
		 bool (*varies) (const_rtx, bool))
{
  rtx x_addr, mem_addr;
  rtx base;

  if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
    return 1;

  /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
     This is used in epilogue deallocation functions, and in cselib.  */
  if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
    return 1;
  if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
    return 1;
  if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
      || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
    return 1;

  if (DIFFERENT_ALIAS_SETS_P (x, mem))
    return 0;

  /* Read-only memory is by definition never modified, and therefore can't
     conflict with anything.  We don't expect to find read-only set on MEM,
     but stupid user tricks can produce them, so don't die.  */
  if (MEM_READONLY_P (x))
    return 0;

  if (nonoverlapping_memrefs_p (mem, x))
    return 0;

  /* If we have MEMs refering to different address spaces (which can
     potentially overlap), we cannot easily tell from the addresses
     whether the references overlap.  */
  if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x))
    return 1;

  if (mem_mode == VOIDmode)
    mem_mode = GET_MODE (mem);

  x_addr = get_addr (XEXP (x, 0));
  mem_addr = get_addr (XEXP (mem, 0));

  base = find_base_term (x_addr);
  if (base && (GET_CODE (base) == LABEL_REF
	       || (GET_CODE (base) == SYMBOL_REF
		   && CONSTANT_POOL_ADDRESS_P (base))))
    return 0;

  if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
    return 0;

  x_addr = canon_rtx (x_addr);
  mem_addr = canon_rtx (mem_addr);

  if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
			    SIZE_FOR_MODE (x), x_addr, 0))
    return 0;

  if (aliases_everything_p (x))
    return 1;

  /* We cannot use aliases_everything_p to test MEM, since we must look
     at MEM_MODE, rather than GET_MODE (MEM).  */
  if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
    return 1;

  /* In true_dependence we also allow BLKmode to alias anything.  Why
     don't we do this in anti_dependence and output_dependence?  */
  if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
    return 1;

  if (fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, varies))
    return 0;

  return rtx_refs_may_alias_p (x, mem, true);
}

/* Canonical true dependence: X is read after store in MEM takes place.
   Variant of true_dependence which assumes MEM has already been
   canonicalized (hence we no longer do that here).
   The mem_addr argument has been added, since true_dependence computed
   this value prior to canonicalizing.
   If x_addr is non-NULL, it is used in preference of XEXP (x, 0).  */

int
canon_true_dependence (const_rtx mem, enum machine_mode mem_mode, rtx mem_addr,
		       const_rtx x, rtx x_addr, bool (*varies) (const_rtx, bool))
{
  if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
    return 1;

  /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
     This is used in epilogue deallocation functions.  */
  if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
    return 1;
  if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
    return 1;
  if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
      || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
    return 1;

  if (DIFFERENT_ALIAS_SETS_P (x, mem))
    return 0;

  /* Read-only memory is by definition never modified, and therefore can't
     conflict with anything.  We don't expect to find read-only set on MEM,
     but stupid user tricks can produce them, so don't die.  */
  if (MEM_READONLY_P (x))
    return 0;

  if (nonoverlapping_memrefs_p (x, mem))
    return 0;

  /* If we have MEMs refering to different address spaces (which can
     potentially overlap), we cannot easily tell from the addresses
     whether the references overlap.  */
  if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x))
    return 1;

  if (! x_addr)
    x_addr = get_addr (XEXP (x, 0));

  if (! base_alias_check (x_addr, mem_addr, GET_MODE (x), mem_mode))
    return 0;

  x_addr = canon_rtx (x_addr);
  if (! memrefs_conflict_p (GET_MODE_SIZE (mem_mode), mem_addr,
			    SIZE_FOR_MODE (x), x_addr, 0))
    return 0;

  if (aliases_everything_p (x))
    return 1;

  /* We cannot use aliases_everything_p to test MEM, since we must look
     at MEM_MODE, rather than GET_MODE (MEM).  */
  if (mem_mode == QImode || GET_CODE (mem_addr) == AND)
    return 1;

  /* In true_dependence we also allow BLKmode to alias anything.  Why
     don't we do this in anti_dependence and output_dependence?  */
  if (mem_mode == BLKmode || GET_MODE (x) == BLKmode)
    return 1;

  if (fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr, varies))
    return 0;

  return rtx_refs_may_alias_p (x, mem, true);
}

/* Returns nonzero if a write to X might alias a previous read from
   (or, if WRITEP is nonzero, a write to) MEM.  */

static int
write_dependence_p (const_rtx mem, const_rtx x, int writep)
{
  rtx x_addr, mem_addr;
  const_rtx fixed_scalar;
  rtx base;

  if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
    return 1;

  /* (mem:BLK (scratch)) is a special mechanism to conflict with everything.
     This is used in epilogue deallocation functions.  */
  if (GET_MODE (x) == BLKmode && GET_CODE (XEXP (x, 0)) == SCRATCH)
    return 1;
  if (GET_MODE (mem) == BLKmode && GET_CODE (XEXP (mem, 0)) == SCRATCH)
    return 1;
  if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
      || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
    return 1;

  /* A read from read-only memory can't conflict with read-write memory.  */
  if (!writep && MEM_READONLY_P (mem))
    return 0;

  if (nonoverlapping_memrefs_p (x, mem))
    return 0;

  /* If we have MEMs refering to different address spaces (which can
     potentially overlap), we cannot easily tell from the addresses
     whether the references overlap.  */
  if (MEM_ADDR_SPACE (mem) != MEM_ADDR_SPACE (x))
    return 1;

  x_addr = get_addr (XEXP (x, 0));
  mem_addr = get_addr (XEXP (mem, 0));

  if (! writep)
    {
      base = find_base_term (mem_addr);
      if (base && (GET_CODE (base) == LABEL_REF
		   || (GET_CODE (base) == SYMBOL_REF
		       && CONSTANT_POOL_ADDRESS_P (base))))
	return 0;
    }

  if (! base_alias_check (x_addr, mem_addr, GET_MODE (x),
			  GET_MODE (mem)))
    return 0;

  x_addr = canon_rtx (x_addr);
  mem_addr = canon_rtx (mem_addr);

  if (!memrefs_conflict_p (SIZE_FOR_MODE (mem), mem_addr,
			   SIZE_FOR_MODE (x), x_addr, 0))
    return 0;

  fixed_scalar
    = fixed_scalar_and_varying_struct_p (mem, x, mem_addr, x_addr,
					 rtx_addr_varies_p);

  if ((fixed_scalar == mem && !aliases_everything_p (x))
      || (fixed_scalar == x && !aliases_everything_p (mem)))
    return 0;

  return rtx_refs_may_alias_p (x, mem, false);
}

/* Anti dependence: X is written after read in MEM takes place.  */

int
anti_dependence (const_rtx mem, const_rtx x)
{
  return write_dependence_p (mem, x, /*writep=*/0);
}

/* Output dependence: X is written after store in MEM takes place.  */

int
output_dependence (const_rtx mem, const_rtx x)
{
  return write_dependence_p (mem, x, /*writep=*/1);
}


void
init_alias_target (void)
{
  int i;

  memset (static_reg_base_value, 0, sizeof static_reg_base_value);

  for (i = 0; i < FIRST_PSEUDO_REGISTER; i++)
    /* Check whether this register can hold an incoming pointer
       argument.  FUNCTION_ARG_REGNO_P tests outgoing register
       numbers, so translate if necessary due to register windows.  */
    if (FUNCTION_ARG_REGNO_P (OUTGOING_REGNO (i))
	&& HARD_REGNO_MODE_OK (i, Pmode))
      static_reg_base_value[i]
	= gen_rtx_ADDRESS (VOIDmode, gen_rtx_REG (Pmode, i));

  static_reg_base_value[STACK_POINTER_REGNUM]
    = gen_rtx_ADDRESS (Pmode, stack_pointer_rtx);
  static_reg_base_value[ARG_POINTER_REGNUM]
    = gen_rtx_ADDRESS (Pmode, arg_pointer_rtx);
  static_reg_base_value[FRAME_POINTER_REGNUM]
    = gen_rtx_ADDRESS (Pmode, frame_pointer_rtx);
#if HARD_FRAME_POINTER_REGNUM != FRAME_POINTER_REGNUM
  static_reg_base_value[HARD_FRAME_POINTER_REGNUM]
    = gen_rtx_ADDRESS (Pmode, hard_frame_pointer_rtx);
#endif
}

/* Set MEMORY_MODIFIED when X modifies DATA (that is assumed
   to be memory reference.  */
static bool memory_modified;
static void
memory_modified_1 (rtx x, const_rtx pat ATTRIBUTE_UNUSED, void *data)
{
  if (MEM_P (x))
    {
      if (anti_dependence (x, (const_rtx)data) || output_dependence (x, (const_rtx)data))
	memory_modified = true;
    }
}


/* Return true when INSN possibly modify memory contents of MEM
   (i.e. address can be modified).  */
bool
memory_modified_in_insn_p (const_rtx mem, const_rtx insn)
{
  if (!INSN_P (insn))
    return false;
  memory_modified = false;
  note_stores (PATTERN (insn), memory_modified_1, CONST_CAST_RTX(mem));
  return memory_modified;
}

/* Initialize the aliasing machinery.  Initialize the REG_KNOWN_VALUE
   array.  */

void
init_alias_analysis (void)
{
  unsigned int maxreg = max_reg_num ();
  int changed, pass;
  int i;
  unsigned int ui;
  rtx insn;

  timevar_push (TV_ALIAS_ANALYSIS);

  reg_known_value_size = maxreg - FIRST_PSEUDO_REGISTER;
  reg_known_value = GGC_CNEWVEC (rtx, reg_known_value_size);
  reg_known_equiv_p = XCNEWVEC (bool, reg_known_value_size);

  /* If we have memory allocated from the previous run, use it.  */
  if (old_reg_base_value)
    reg_base_value = old_reg_base_value;

  if (reg_base_value)
    VEC_truncate (rtx, reg_base_value, 0);

  VEC_safe_grow_cleared (rtx, gc, reg_base_value, maxreg);

  new_reg_base_value = XNEWVEC (rtx, maxreg);
  reg_seen = XNEWVEC (char, maxreg);

  /* The basic idea is that each pass through this loop will use the
     "constant" information from the previous pass to propagate alias
     information through another level of assignments.

     This could get expensive if the assignment chains are long.  Maybe
     we should throttle the number of iterations, possibly based on
     the optimization level or flag_expensive_optimizations.

     We could propagate more information in the first pass by making use
     of DF_REG_DEF_COUNT to determine immediately that the alias information
     for a pseudo is "constant".

     A program with an uninitialized variable can cause an infinite loop
     here.  Instead of doing a full dataflow analysis to detect such problems
     we just cap the number of iterations for the loop.

     The state of the arrays for the set chain in question does not matter
     since the program has undefined behavior.  */

  pass = 0;
  do
    {
      /* Assume nothing will change this iteration of the loop.  */
      changed = 0;

      /* We want to assign the same IDs each iteration of this loop, so
	 start counting from zero each iteration of the loop.  */
      unique_id = 0;

      /* We're at the start of the function each iteration through the
	 loop, so we're copying arguments.  */
      copying_arguments = true;

      /* Wipe the potential alias information clean for this pass.  */
      memset (new_reg_base_value, 0, maxreg * sizeof (rtx));

      /* Wipe the reg_seen array clean.  */
      memset (reg_seen, 0, maxreg);

      /* Mark all hard registers which may contain an address.
	 The stack, frame and argument pointers may contain an address.
	 An argument register which can hold a Pmode value may contain
	 an address even if it is not in BASE_REGS.

	 The address expression is VOIDmode for an argument and
	 Pmode for other registers.  */

      memcpy (new_reg_base_value, static_reg_base_value,
	      FIRST_PSEUDO_REGISTER * sizeof (rtx));

      /* Walk the insns adding values to the new_reg_base_value array.  */
      for (insn = get_insns (); insn; insn = NEXT_INSN (insn))
	{
	  if (INSN_P (insn))
	    {
	      rtx note, set;

#if defined (HAVE_prologue) || defined (HAVE_epilogue)
	      /* The prologue/epilogue insns are not threaded onto the
		 insn chain until after reload has completed.  Thus,
		 there is no sense wasting time checking if INSN is in
		 the prologue/epilogue until after reload has completed.  */
	      if (reload_completed
		  && prologue_epilogue_contains (insn))
		continue;
#endif

	      /* If this insn has a noalias note, process it,  Otherwise,
		 scan for sets.  A simple set will have no side effects
		 which could change the base value of any other register.  */

	      if (GET_CODE (PATTERN (insn)) == SET
		  && REG_NOTES (insn) != 0
		  && find_reg_note (insn, REG_NOALIAS, NULL_RTX))
		record_set (SET_DEST (PATTERN (insn)), NULL_RTX, NULL);
	      else
		note_stores (PATTERN (insn), record_set, NULL);

	      set = single_set (insn);

	      if (set != 0
		  && REG_P (SET_DEST (set))
		  && REGNO (SET_DEST (set)) >= FIRST_PSEUDO_REGISTER)
		{
		  unsigned int regno = REGNO (SET_DEST (set));
		  rtx src = SET_SRC (set);
		  rtx t;

		  note = find_reg_equal_equiv_note (insn);
		  if (note && REG_NOTE_KIND (note) == REG_EQUAL
		      && DF_REG_DEF_COUNT (regno) != 1)
		    note = NULL_RTX;

		  if (note != NULL_RTX
		      && GET_CODE (XEXP (note, 0)) != EXPR_LIST
		      && ! rtx_varies_p (XEXP (note, 0), 1)
		      && ! reg_overlap_mentioned_p (SET_DEST (set),
						    XEXP (note, 0)))
		    {
		      set_reg_known_value (regno, XEXP (note, 0));
		      set_reg_known_equiv_p (regno,
			REG_NOTE_KIND (note) == REG_EQUIV);
		    }
		  else if (DF_REG_DEF_COUNT (regno) == 1
			   && GET_CODE (src) == PLUS
			   && REG_P (XEXP (src, 0))
			   && (t = get_reg_known_value (REGNO (XEXP (src, 0))))
			   && CONST_INT_P (XEXP (src, 1)))
		    {
		      t = plus_constant (t, INTVAL (XEXP (src, 1)));
		      set_reg_known_value (regno, t);
		      set_reg_known_equiv_p (regno, 0);
		    }
		  else if (DF_REG_DEF_COUNT (regno) == 1
			   && ! rtx_varies_p (src, 1))
		    {
		      set_reg_known_value (regno, src);
		      set_reg_known_equiv_p (regno, 0);
		    }
		}
	    }
	  else if (NOTE_P (insn)
		   && NOTE_KIND (insn) == NOTE_INSN_FUNCTION_BEG)
	    copying_arguments = false;
	}

      /* Now propagate values from new_reg_base_value to reg_base_value.  */
      gcc_assert (maxreg == (unsigned int) max_reg_num ());

      for (ui = 0; ui < maxreg; ui++)
	{
	  if (new_reg_base_value[ui]
	      && new_reg_base_value[ui] != VEC_index (rtx, reg_base_value, ui)
	      && ! rtx_equal_p (new_reg_base_value[ui],
				VEC_index (rtx, reg_base_value, ui)))
	    {
	      VEC_replace (rtx, reg_base_value, ui, new_reg_base_value[ui]);
	      changed = 1;
	    }
	}
    }
  while (changed && ++pass < MAX_ALIAS_LOOP_PASSES);

  /* Fill in the remaining entries.  */
  for (i = 0; i < (int)reg_known_value_size; i++)
    if (reg_known_value[i] == 0)
      reg_known_value[i] = regno_reg_rtx[i + FIRST_PSEUDO_REGISTER];

  /* Clean up.  */
  free (new_reg_base_value);
  new_reg_base_value = 0;
  free (reg_seen);
  reg_seen = 0;
  timevar_pop (TV_ALIAS_ANALYSIS);
}

void
end_alias_analysis (void)
{
  old_reg_base_value = reg_base_value;
  ggc_free (reg_known_value);
  reg_known_value = 0;
  reg_known_value_size = 0;
  free (reg_known_equiv_p);
  reg_known_equiv_p = 0;
}

#include "gt-alias.h"