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
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
|
//===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass transforms simple global variables that never have their address
// taken. If obviously true, it marks read/write globals as constant, deletes
// variables only stored to, etc.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "globalopt"
#include "llvm/Transforms/IPO.h"
#include "llvm/CallingConv.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Module.h"
#include "llvm/Operator.h"
#include "llvm/Pass.h"
#include "llvm/Analysis/ConstantFolding.h"
#include "llvm/Analysis/MemoryBuiltins.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetLibraryInfo.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/SmallPtrSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include <algorithm>
using namespace llvm;
STATISTIC(NumMarked , "Number of globals marked constant");
STATISTIC(NumUnnamed , "Number of globals marked unnamed_addr");
STATISTIC(NumSRA , "Number of aggregate globals broken into scalars");
STATISTIC(NumHeapSRA , "Number of heap objects SRA'd");
STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
STATISTIC(NumDeleted , "Number of globals deleted");
STATISTIC(NumFnDeleted , "Number of functions deleted");
STATISTIC(NumGlobUses , "Number of global uses devirtualized");
STATISTIC(NumLocalized , "Number of globals localized");
STATISTIC(NumShrunkToBool , "Number of global vars shrunk to booleans");
STATISTIC(NumFastCallFns , "Number of functions converted to fastcc");
STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
STATISTIC(NumNestRemoved , "Number of nest attributes removed");
STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed");
namespace {
struct GlobalStatus;
struct GlobalOpt : public ModulePass {
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<TargetLibraryInfo>();
}
static char ID; // Pass identification, replacement for typeid
GlobalOpt() : ModulePass(ID) {
initializeGlobalOptPass(*PassRegistry::getPassRegistry());
}
bool runOnModule(Module &M);
private:
GlobalVariable *FindGlobalCtors(Module &M);
bool OptimizeFunctions(Module &M);
bool OptimizeGlobalVars(Module &M);
bool OptimizeGlobalAliases(Module &M);
bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
bool ProcessGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI,
const SmallPtrSet<const PHINode*, 16> &PHIUsers,
const GlobalStatus &GS);
bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn);
TargetData *TD;
TargetLibraryInfo *TLI;
};
}
char GlobalOpt::ID = 0;
INITIALIZE_PASS_BEGIN(GlobalOpt, "globalopt",
"Global Variable Optimizer", false, false)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
INITIALIZE_PASS_END(GlobalOpt, "globalopt",
"Global Variable Optimizer", false, false)
ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
namespace {
/// GlobalStatus - As we analyze each global, keep track of some information
/// about it. If we find out that the address of the global is taken, none of
/// this info will be accurate.
struct GlobalStatus {
/// isCompared - True if the global's address is used in a comparison.
bool isCompared;
/// isLoaded - True if the global is ever loaded. If the global isn't ever
/// loaded it can be deleted.
bool isLoaded;
/// StoredType - Keep track of what stores to the global look like.
///
enum StoredType {
/// NotStored - There is no store to this global. It can thus be marked
/// constant.
NotStored,
/// isInitializerStored - This global is stored to, but the only thing
/// stored is the constant it was initialized with. This is only tracked
/// for scalar globals.
isInitializerStored,
/// isStoredOnce - This global is stored to, but only its initializer and
/// one other value is ever stored to it. If this global isStoredOnce, we
/// track the value stored to it in StoredOnceValue below. This is only
/// tracked for scalar globals.
isStoredOnce,
/// isStored - This global is stored to by multiple values or something else
/// that we cannot track.
isStored
} StoredType;
/// StoredOnceValue - If only one value (besides the initializer constant) is
/// ever stored to this global, keep track of what value it is.
Value *StoredOnceValue;
/// AccessingFunction/HasMultipleAccessingFunctions - These start out
/// null/false. When the first accessing function is noticed, it is recorded.
/// When a second different accessing function is noticed,
/// HasMultipleAccessingFunctions is set to true.
const Function *AccessingFunction;
bool HasMultipleAccessingFunctions;
/// HasNonInstructionUser - Set to true if this global has a user that is not
/// an instruction (e.g. a constant expr or GV initializer).
bool HasNonInstructionUser;
/// HasPHIUser - Set to true if this global has a user that is a PHI node.
bool HasPHIUser;
/// AtomicOrdering - Set to the strongest atomic ordering requirement.
AtomicOrdering Ordering;
GlobalStatus() : isCompared(false), isLoaded(false), StoredType(NotStored),
StoredOnceValue(0), AccessingFunction(0),
HasMultipleAccessingFunctions(false),
HasNonInstructionUser(false), HasPHIUser(false),
Ordering(NotAtomic) {}
};
}
/// StrongerOrdering - Return the stronger of the two ordering. If the two
/// orderings are acquire and release, then return AcquireRelease.
///
static AtomicOrdering StrongerOrdering(AtomicOrdering X, AtomicOrdering Y) {
if (X == Acquire && Y == Release) return AcquireRelease;
if (Y == Acquire && X == Release) return AcquireRelease;
return (AtomicOrdering)std::max(X, Y);
}
/// SafeToDestroyConstant - It is safe to destroy a constant iff it is only used
/// by constants itself. Note that constants cannot be cyclic, so this test is
/// pretty easy to implement recursively.
///
static bool SafeToDestroyConstant(const Constant *C) {
if (isa<GlobalValue>(C)) return false;
for (Value::const_use_iterator UI = C->use_begin(), E = C->use_end(); UI != E;
++UI)
if (const Constant *CU = dyn_cast<Constant>(*UI)) {
if (!SafeToDestroyConstant(CU)) return false;
} else
return false;
return true;
}
/// AnalyzeGlobal - Look at all uses of the global and fill in the GlobalStatus
/// structure. If the global has its address taken, return true to indicate we
/// can't do anything with it.
///
static bool AnalyzeGlobal(const Value *V, GlobalStatus &GS,
SmallPtrSet<const PHINode*, 16> &PHIUsers) {
for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
++UI) {
const User *U = *UI;
if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
GS.HasNonInstructionUser = true;
// If the result of the constantexpr isn't pointer type, then we won't
// know to expect it in various places. Just reject early.
if (!isa<PointerType>(CE->getType())) return true;
if (AnalyzeGlobal(CE, GS, PHIUsers)) return true;
} else if (const Instruction *I = dyn_cast<Instruction>(U)) {
if (!GS.HasMultipleAccessingFunctions) {
const Function *F = I->getParent()->getParent();
if (GS.AccessingFunction == 0)
GS.AccessingFunction = F;
else if (GS.AccessingFunction != F)
GS.HasMultipleAccessingFunctions = true;
}
if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
GS.isLoaded = true;
// Don't hack on volatile loads.
if (LI->isVolatile()) return true;
GS.Ordering = StrongerOrdering(GS.Ordering, LI->getOrdering());
} else if (const StoreInst *SI = dyn_cast<StoreInst>(I)) {
// Don't allow a store OF the address, only stores TO the address.
if (SI->getOperand(0) == V) return true;
// Don't hack on volatile stores.
if (SI->isVolatile()) return true;
GS.Ordering = StrongerOrdering(GS.Ordering, SI->getOrdering());
// If this is a direct store to the global (i.e., the global is a scalar
// value, not an aggregate), keep more specific information about
// stores.
if (GS.StoredType != GlobalStatus::isStored) {
if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(
SI->getOperand(1))) {
Value *StoredVal = SI->getOperand(0);
if (StoredVal == GV->getInitializer()) {
if (GS.StoredType < GlobalStatus::isInitializerStored)
GS.StoredType = GlobalStatus::isInitializerStored;
} else if (isa<LoadInst>(StoredVal) &&
cast<LoadInst>(StoredVal)->getOperand(0) == GV) {
if (GS.StoredType < GlobalStatus::isInitializerStored)
GS.StoredType = GlobalStatus::isInitializerStored;
} else if (GS.StoredType < GlobalStatus::isStoredOnce) {
GS.StoredType = GlobalStatus::isStoredOnce;
GS.StoredOnceValue = StoredVal;
} else if (GS.StoredType == GlobalStatus::isStoredOnce &&
GS.StoredOnceValue == StoredVal) {
// noop.
} else {
GS.StoredType = GlobalStatus::isStored;
}
} else {
GS.StoredType = GlobalStatus::isStored;
}
}
} else if (isa<GetElementPtrInst>(I)) {
if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
} else if (isa<SelectInst>(I)) {
if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
} else if (const PHINode *PN = dyn_cast<PHINode>(I)) {
// PHI nodes we can check just like select or GEP instructions, but we
// have to be careful about infinite recursion.
if (PHIUsers.insert(PN)) // Not already visited.
if (AnalyzeGlobal(I, GS, PHIUsers)) return true;
GS.HasPHIUser = true;
} else if (isa<CmpInst>(I)) {
GS.isCompared = true;
} else if (const MemTransferInst *MTI = dyn_cast<MemTransferInst>(I)) {
if (MTI->isVolatile()) return true;
if (MTI->getArgOperand(0) == V)
GS.StoredType = GlobalStatus::isStored;
if (MTI->getArgOperand(1) == V)
GS.isLoaded = true;
} else if (const MemSetInst *MSI = dyn_cast<MemSetInst>(I)) {
assert(MSI->getArgOperand(0) == V && "Memset only takes one pointer!");
if (MSI->isVolatile()) return true;
GS.StoredType = GlobalStatus::isStored;
} else {
return true; // Any other non-load instruction might take address!
}
} else if (const Constant *C = dyn_cast<Constant>(U)) {
GS.HasNonInstructionUser = true;
// We might have a dead and dangling constant hanging off of here.
if (!SafeToDestroyConstant(C))
return true;
} else {
GS.HasNonInstructionUser = true;
// Otherwise must be some other user.
return true;
}
}
return false;
}
/// CleanupConstantGlobalUsers - We just marked GV constant. Loop over all
/// users of the global, cleaning up the obvious ones. This is largely just a
/// quick scan over the use list to clean up the easy and obvious cruft. This
/// returns true if it made a change.
static bool CleanupConstantGlobalUsers(Value *V, Constant *Init,
TargetData *TD, TargetLibraryInfo *TLI) {
bool Changed = false;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;) {
User *U = *UI++;
if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
if (Init) {
// Replace the load with the initializer.
LI->replaceAllUsesWith(Init);
LI->eraseFromParent();
Changed = true;
}
} else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
// Store must be unreachable or storing Init into the global.
SI->eraseFromParent();
Changed = true;
} else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
if (CE->getOpcode() == Instruction::GetElementPtr) {
Constant *SubInit = 0;
if (Init)
SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
Changed |= CleanupConstantGlobalUsers(CE, SubInit, TD, TLI);
} else if (CE->getOpcode() == Instruction::BitCast &&
CE->getType()->isPointerTy()) {
// Pointer cast, delete any stores and memsets to the global.
Changed |= CleanupConstantGlobalUsers(CE, 0, TD, TLI);
}
if (CE->use_empty()) {
CE->destroyConstant();
Changed = true;
}
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
// Do not transform "gepinst (gep constexpr (GV))" here, because forming
// "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
// and will invalidate our notion of what Init is.
Constant *SubInit = 0;
if (!isa<ConstantExpr>(GEP->getOperand(0))) {
ConstantExpr *CE =
dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP, TD, TLI));
if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
// If the initializer is an all-null value and we have an inbounds GEP,
// we already know what the result of any load from that GEP is.
// TODO: Handle splats.
if (Init && isa<ConstantAggregateZero>(Init) && GEP->isInBounds())
SubInit = Constant::getNullValue(GEP->getType()->getElementType());
}
Changed |= CleanupConstantGlobalUsers(GEP, SubInit, TD, TLI);
if (GEP->use_empty()) {
GEP->eraseFromParent();
Changed = true;
}
} else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
if (MI->getRawDest() == V) {
MI->eraseFromParent();
Changed = true;
}
} else if (Constant *C = dyn_cast<Constant>(U)) {
// If we have a chain of dead constantexprs or other things dangling from
// us, and if they are all dead, nuke them without remorse.
if (SafeToDestroyConstant(C)) {
C->destroyConstant();
// This could have invalidated UI, start over from scratch.
CleanupConstantGlobalUsers(V, Init, TD, TLI);
return true;
}
}
}
return Changed;
}
/// isSafeSROAElementUse - Return true if the specified instruction is a safe
/// user of a derived expression from a global that we want to SROA.
static bool isSafeSROAElementUse(Value *V) {
// We might have a dead and dangling constant hanging off of here.
if (Constant *C = dyn_cast<Constant>(V))
return SafeToDestroyConstant(C);
Instruction *I = dyn_cast<Instruction>(V);
if (!I) return false;
// Loads are ok.
if (isa<LoadInst>(I)) return true;
// Stores *to* the pointer are ok.
if (StoreInst *SI = dyn_cast<StoreInst>(I))
return SI->getOperand(0) != V;
// Otherwise, it must be a GEP.
GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
if (GEPI == 0) return false;
if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
!cast<Constant>(GEPI->getOperand(1))->isNullValue())
return false;
for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
I != E; ++I)
if (!isSafeSROAElementUse(*I))
return false;
return true;
}
/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
/// Look at it and its uses and decide whether it is safe to SROA this global.
///
static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
// The user of the global must be a GEP Inst or a ConstantExpr GEP.
if (!isa<GetElementPtrInst>(U) &&
(!isa<ConstantExpr>(U) ||
cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
return false;
// Check to see if this ConstantExpr GEP is SRA'able. In particular, we
// don't like < 3 operand CE's, and we don't like non-constant integer
// indices. This enforces that all uses are 'gep GV, 0, C, ...' for some
// value of C.
if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
!cast<Constant>(U->getOperand(1))->isNullValue() ||
!isa<ConstantInt>(U->getOperand(2)))
return false;
gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
++GEPI; // Skip over the pointer index.
// If this is a use of an array allocation, do a bit more checking for sanity.
if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
uint64_t NumElements = AT->getNumElements();
ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
// Check to make sure that index falls within the array. If not,
// something funny is going on, so we won't do the optimization.
//
if (Idx->getZExtValue() >= NumElements)
return false;
// We cannot scalar repl this level of the array unless any array
// sub-indices are in-range constants. In particular, consider:
// A[0][i]. We cannot know that the user isn't doing invalid things like
// allowing i to index an out-of-range subscript that accesses A[1].
//
// Scalar replacing *just* the outer index of the array is probably not
// going to be a win anyway, so just give up.
for (++GEPI; // Skip array index.
GEPI != E;
++GEPI) {
uint64_t NumElements;
if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
NumElements = SubArrayTy->getNumElements();
else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
NumElements = SubVectorTy->getNumElements();
else {
assert((*GEPI)->isStructTy() &&
"Indexed GEP type is not array, vector, or struct!");
continue;
}
ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
return false;
}
}
for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
if (!isSafeSROAElementUse(*I))
return false;
return true;
}
/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
/// is safe for us to perform this transformation.
///
static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
UI != E; ++UI) {
if (!IsUserOfGlobalSafeForSRA(*UI, GV))
return false;
}
return true;
}
/// SRAGlobal - Perform scalar replacement of aggregates on the specified global
/// variable. This opens the door for other optimizations by exposing the
/// behavior of the program in a more fine-grained way. We have determined that
/// this transformation is safe already. We return the first global variable we
/// insert so that the caller can reprocess it.
static GlobalVariable *SRAGlobal(GlobalVariable *GV, const TargetData &TD) {
// Make sure this global only has simple uses that we can SRA.
if (!GlobalUsersSafeToSRA(GV))
return 0;
assert(GV->hasLocalLinkage() && !GV->isConstant());
Constant *Init = GV->getInitializer();
Type *Ty = Init->getType();
std::vector<GlobalVariable*> NewGlobals;
Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
// Get the alignment of the global, either explicit or target-specific.
unsigned StartAlignment = GV->getAlignment();
if (StartAlignment == 0)
StartAlignment = TD.getABITypeAlignment(GV->getType());
if (StructType *STy = dyn_cast<StructType>(Ty)) {
NewGlobals.reserve(STy->getNumElements());
const StructLayout &Layout = *TD.getStructLayout(STy);
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
Constant *In = Init->getAggregateElement(i);
assert(In && "Couldn't get element of initializer?");
GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
GlobalVariable::InternalLinkage,
In, GV->getName()+"."+Twine(i),
GV->isThreadLocal(),
GV->getType()->getAddressSpace());
Globals.insert(GV, NGV);
NewGlobals.push_back(NGV);
// Calculate the known alignment of the field. If the original aggregate
// had 256 byte alignment for example, something might depend on that:
// propagate info to each field.
uint64_t FieldOffset = Layout.getElementOffset(i);
unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
NGV->setAlignment(NewAlign);
}
} else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
unsigned NumElements = 0;
if (ArrayType *ATy = dyn_cast<ArrayType>(STy))
NumElements = ATy->getNumElements();
else
NumElements = cast<VectorType>(STy)->getNumElements();
if (NumElements > 16 && GV->hasNUsesOrMore(16))
return 0; // It's not worth it.
NewGlobals.reserve(NumElements);
uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
for (unsigned i = 0, e = NumElements; i != e; ++i) {
Constant *In = Init->getAggregateElement(i);
assert(In && "Couldn't get element of initializer?");
GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
GlobalVariable::InternalLinkage,
In, GV->getName()+"."+Twine(i),
GV->isThreadLocal(),
GV->getType()->getAddressSpace());
Globals.insert(GV, NGV);
NewGlobals.push_back(NGV);
// Calculate the known alignment of the field. If the original aggregate
// had 256 byte alignment for example, something might depend on that:
// propagate info to each field.
unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
if (NewAlign > EltAlign)
NGV->setAlignment(NewAlign);
}
}
if (NewGlobals.empty())
return 0;
DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV);
Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext()));
// Loop over all of the uses of the global, replacing the constantexpr geps,
// with smaller constantexpr geps or direct references.
while (!GV->use_empty()) {
User *GEP = GV->use_back();
assert(((isa<ConstantExpr>(GEP) &&
cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
// Ignore the 1th operand, which has to be zero or else the program is quite
// broken (undefined). Get the 2nd operand, which is the structure or array
// index.
unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
Value *NewPtr = NewGlobals[Val];
// Form a shorter GEP if needed.
if (GEP->getNumOperands() > 3) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
SmallVector<Constant*, 8> Idxs;
Idxs.push_back(NullInt);
for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
Idxs.push_back(CE->getOperand(i));
NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
} else {
GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
SmallVector<Value*, 8> Idxs;
Idxs.push_back(NullInt);
for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
Idxs.push_back(GEPI->getOperand(i));
NewPtr = GetElementPtrInst::Create(NewPtr, Idxs,
GEPI->getName()+"."+Twine(Val),GEPI);
}
}
GEP->replaceAllUsesWith(NewPtr);
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
GEPI->eraseFromParent();
else
cast<ConstantExpr>(GEP)->destroyConstant();
}
// Delete the old global, now that it is dead.
Globals.erase(GV);
++NumSRA;
// Loop over the new globals array deleting any globals that are obviously
// dead. This can arise due to scalarization of a structure or an array that
// has elements that are dead.
unsigned FirstGlobal = 0;
for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
if (NewGlobals[i]->use_empty()) {
Globals.erase(NewGlobals[i]);
if (FirstGlobal == i) ++FirstGlobal;
}
return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
}
/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
/// value will trap if the value is dynamically null. PHIs keeps track of any
/// phi nodes we've seen to avoid reprocessing them.
static bool AllUsesOfValueWillTrapIfNull(const Value *V,
SmallPtrSet<const PHINode*, 8> &PHIs) {
for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
++UI) {
const User *U = *UI;
if (isa<LoadInst>(U)) {
// Will trap.
} else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
if (SI->getOperand(0) == V) {
//cerr << "NONTRAPPING USE: " << *U;
return false; // Storing the value.
}
} else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
if (CI->getCalledValue() != V) {
//cerr << "NONTRAPPING USE: " << *U;
return false; // Not calling the ptr
}
} else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) {
if (II->getCalledValue() != V) {
//cerr << "NONTRAPPING USE: " << *U;
return false; // Not calling the ptr
}
} else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) {
if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
} else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
} else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
// If we've already seen this phi node, ignore it, it has already been
// checked.
if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
return false;
} else if (isa<ICmpInst>(U) &&
isa<ConstantPointerNull>(UI->getOperand(1))) {
// Ignore icmp X, null
} else {
//cerr << "NONTRAPPING USE: " << *U;
return false;
}
}
return true;
}
/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
/// from GV will trap if the loaded value is null. Note that this also permits
/// comparisons of the loaded value against null, as a special case.
static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
UI != E; ++UI) {
const User *U = *UI;
if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
SmallPtrSet<const PHINode*, 8> PHIs;
if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
return false;
} else if (isa<StoreInst>(U)) {
// Ignore stores to the global.
} else {
// We don't know or understand this user, bail out.
//cerr << "UNKNOWN USER OF GLOBAL!: " << *U;
return false;
}
}
return true;
}
static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
bool Changed = false;
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
Instruction *I = cast<Instruction>(*UI++);
if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
LI->setOperand(0, NewV);
Changed = true;
} else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
if (SI->getOperand(1) == V) {
SI->setOperand(1, NewV);
Changed = true;
}
} else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
CallSite CS(I);
if (CS.getCalledValue() == V) {
// Calling through the pointer! Turn into a direct call, but be careful
// that the pointer is not also being passed as an argument.
CS.setCalledFunction(NewV);
Changed = true;
bool PassedAsArg = false;
for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
if (CS.getArgument(i) == V) {
PassedAsArg = true;
CS.setArgument(i, NewV);
}
if (PassedAsArg) {
// Being passed as an argument also. Be careful to not invalidate UI!
UI = V->use_begin();
}
}
} else if (CastInst *CI = dyn_cast<CastInst>(I)) {
Changed |= OptimizeAwayTrappingUsesOfValue(CI,
ConstantExpr::getCast(CI->getOpcode(),
NewV, CI->getType()));
if (CI->use_empty()) {
Changed = true;
CI->eraseFromParent();
}
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
// Should handle GEP here.
SmallVector<Constant*, 8> Idxs;
Idxs.reserve(GEPI->getNumOperands()-1);
for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
i != e; ++i)
if (Constant *C = dyn_cast<Constant>(*i))
Idxs.push_back(C);
else
break;
if (Idxs.size() == GEPI->getNumOperands()-1)
Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
ConstantExpr::getGetElementPtr(NewV, Idxs));
if (GEPI->use_empty()) {
Changed = true;
GEPI->eraseFromParent();
}
}
}
return Changed;
}
/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
/// value stored into it. If there are uses of the loaded value that would trap
/// if the loaded value is dynamically null, then we know that they cannot be
/// reachable with a null optimize away the load.
static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV,
TargetData *TD,
TargetLibraryInfo *TLI) {
bool Changed = false;
// Keep track of whether we are able to remove all the uses of the global
// other than the store that defines it.
bool AllNonStoreUsesGone = true;
// Replace all uses of loads with uses of uses of the stored value.
for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
User *GlobalUser = *GUI++;
if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
// If we were able to delete all uses of the loads
if (LI->use_empty()) {
LI->eraseFromParent();
Changed = true;
} else {
AllNonStoreUsesGone = false;
}
} else if (isa<StoreInst>(GlobalUser)) {
// Ignore the store that stores "LV" to the global.
assert(GlobalUser->getOperand(1) == GV &&
"Must be storing *to* the global");
} else {
AllNonStoreUsesGone = false;
// If we get here we could have other crazy uses that are transitively
// loaded.
assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser)) &&
"Only expect load and stores!");
}
}
if (Changed) {
DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
++NumGlobUses;
}
// If we nuked all of the loads, then none of the stores are needed either,
// nor is the global.
if (AllNonStoreUsesGone) {
DEBUG(dbgs() << " *** GLOBAL NOW DEAD!\n");
CleanupConstantGlobalUsers(GV, 0, TD, TLI);
if (GV->use_empty()) {
GV->eraseFromParent();
++NumDeleted;
}
Changed = true;
}
return Changed;
}
/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
/// instructions that are foldable.
static void ConstantPropUsersOf(Value *V,
TargetData *TD, TargetLibraryInfo *TLI) {
for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
if (Instruction *I = dyn_cast<Instruction>(*UI++))
if (Constant *NewC = ConstantFoldInstruction(I, TD, TLI)) {
I->replaceAllUsesWith(NewC);
// Advance UI to the next non-I use to avoid invalidating it!
// Instructions could multiply use V.
while (UI != E && *UI == I)
++UI;
I->eraseFromParent();
}
}
/// OptimizeGlobalAddressOfMalloc - This function takes the specified global
/// variable, and transforms the program as if it always contained the result of
/// the specified malloc. Because it is always the result of the specified
/// malloc, there is no reason to actually DO the malloc. Instead, turn the
/// malloc into a global, and any loads of GV as uses of the new global.
static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
CallInst *CI,
Type *AllocTy,
ConstantInt *NElements,
TargetData *TD,
TargetLibraryInfo *TLI) {
DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << " CALL = " << *CI << '\n');
Type *GlobalType;
if (NElements->getZExtValue() == 1)
GlobalType = AllocTy;
else
// If we have an array allocation, the global variable is of an array.
GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue());
// Create the new global variable. The contents of the malloc'd memory is
// undefined, so initialize with an undef value.
GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
GlobalType, false,
GlobalValue::InternalLinkage,
UndefValue::get(GlobalType),
GV->getName()+".body",
GV,
GV->isThreadLocal());
// If there are bitcast users of the malloc (which is typical, usually we have
// a malloc + bitcast) then replace them with uses of the new global. Update
// other users to use the global as well.
BitCastInst *TheBC = 0;
while (!CI->use_empty()) {
Instruction *User = cast<Instruction>(CI->use_back());
if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
if (BCI->getType() == NewGV->getType()) {
BCI->replaceAllUsesWith(NewGV);
BCI->eraseFromParent();
} else {
BCI->setOperand(0, NewGV);
}
} else {
if (TheBC == 0)
TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI);
User->replaceUsesOfWith(CI, TheBC);
}
}
Constant *RepValue = NewGV;
if (NewGV->getType() != GV->getType()->getElementType())
RepValue = ConstantExpr::getBitCast(RepValue,
GV->getType()->getElementType());
// If there is a comparison against null, we will insert a global bool to
// keep track of whether the global was initialized yet or not.
GlobalVariable *InitBool =
new GlobalVariable(Type::getInt1Ty(GV->getContext()), false,
GlobalValue::InternalLinkage,
ConstantInt::getFalse(GV->getContext()),
GV->getName()+".init", GV->isThreadLocal());
bool InitBoolUsed = false;
// Loop over all uses of GV, processing them in turn.
while (!GV->use_empty()) {
if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) {
// The global is initialized when the store to it occurs.
new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0,
SI->getOrdering(), SI->getSynchScope(), SI);
SI->eraseFromParent();
continue;
}
LoadInst *LI = cast<LoadInst>(GV->use_back());
while (!LI->use_empty()) {
Use &LoadUse = LI->use_begin().getUse();
if (!isa<ICmpInst>(LoadUse.getUser())) {
LoadUse = RepValue;
continue;
}
ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser());
// Replace the cmp X, 0 with a use of the bool value.
// Sink the load to where the compare was, if atomic rules allow us to.
Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", false, 0,
LI->getOrdering(), LI->getSynchScope(),
LI->isUnordered() ? (Instruction*)ICI : LI);
InitBoolUsed = true;
switch (ICI->getPredicate()) {
default: llvm_unreachable("Unknown ICmp Predicate!");
case ICmpInst::ICMP_ULT:
case ICmpInst::ICMP_SLT: // X < null -> always false
LV = ConstantInt::getFalse(GV->getContext());
break;
case ICmpInst::ICMP_ULE:
case ICmpInst::ICMP_SLE:
case ICmpInst::ICMP_EQ:
LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
break;
case ICmpInst::ICMP_NE:
case ICmpInst::ICMP_UGE:
case ICmpInst::ICMP_SGE:
case ICmpInst::ICMP_UGT:
case ICmpInst::ICMP_SGT:
break; // no change.
}
ICI->replaceAllUsesWith(LV);
ICI->eraseFromParent();
}
LI->eraseFromParent();
}
// If the initialization boolean was used, insert it, otherwise delete it.
if (!InitBoolUsed) {
while (!InitBool->use_empty()) // Delete initializations
cast<StoreInst>(InitBool->use_back())->eraseFromParent();
delete InitBool;
} else
GV->getParent()->getGlobalList().insert(GV, InitBool);
// Now the GV is dead, nuke it and the malloc..
GV->eraseFromParent();
CI->eraseFromParent();
// To further other optimizations, loop over all users of NewGV and try to
// constant prop them. This will promote GEP instructions with constant
// indices into GEP constant-exprs, which will allow global-opt to hack on it.
ConstantPropUsersOf(NewGV, TD, TLI);
if (RepValue != NewGV)
ConstantPropUsersOf(RepValue, TD, TLI);
return NewGV;
}
/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
/// to make sure that there are no complex uses of V. We permit simple things
/// like dereferencing the pointer, but not storing through the address, unless
/// it is to the specified global.
static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V,
const GlobalVariable *GV,
SmallPtrSet<const PHINode*, 8> &PHIs) {
for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end();
UI != E; ++UI) {
const Instruction *Inst = cast<Instruction>(*UI);
if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
continue; // Fine, ignore.
}
if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
return false; // Storing the pointer itself... bad.
continue; // Otherwise, storing through it, or storing into GV... fine.
}
// Must index into the array and into the struct.
if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) {
if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
return false;
continue;
}
if (const PHINode *PN = dyn_cast<PHINode>(Inst)) {
// PHIs are ok if all uses are ok. Don't infinitely recurse through PHI
// cycles.
if (PHIs.insert(PN))
if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
return false;
continue;
}
if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
return false;
continue;
}
return false;
}
return true;
}
/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
/// somewhere. Transform all uses of the allocation into loads from the
/// global and uses of the resultant pointer. Further, delete the store into
/// GV. This assumes that these value pass the
/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
GlobalVariable *GV) {
while (!Alloc->use_empty()) {
Instruction *U = cast<Instruction>(*Alloc->use_begin());
Instruction *InsertPt = U;
if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
// If this is the store of the allocation into the global, remove it.
if (SI->getOperand(1) == GV) {
SI->eraseFromParent();
continue;
}
} else if (PHINode *PN = dyn_cast<PHINode>(U)) {
// Insert the load in the corresponding predecessor, not right before the
// PHI.
InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
} else if (isa<BitCastInst>(U)) {
// Must be bitcast between the malloc and store to initialize the global.
ReplaceUsesOfMallocWithGlobal(U, GV);
U->eraseFromParent();
continue;
} else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
// If this is a "GEP bitcast" and the user is a store to the global, then
// just process it as a bitcast.
if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
if (SI->getOperand(1) == GV) {
// Must be bitcast GEP between the malloc and store to initialize
// the global.
ReplaceUsesOfMallocWithGlobal(GEPI, GV);
GEPI->eraseFromParent();
continue;
}
}
// Insert a load from the global, and use it instead of the malloc.
Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
U->replaceUsesOfWith(Alloc, NL);
}
}
/// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
/// of a load) are simple enough to perform heap SRA on. This permits GEP's
/// that index through the array and struct field, icmps of null, and PHIs.
static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V,
SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs,
SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) {
// We permit two users of the load: setcc comparing against the null
// pointer, and a getelementptr of a specific form.
for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
++UI) {
const Instruction *User = cast<Instruction>(*UI);
// Comparison against null is ok.
if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
return false;
continue;
}
// getelementptr is also ok, but only a simple form.
if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
// Must index into the array and into the struct.
if (GEPI->getNumOperands() < 3)
return false;
// Otherwise the GEP is ok.
continue;
}
if (const PHINode *PN = dyn_cast<PHINode>(User)) {
if (!LoadUsingPHIsPerLoad.insert(PN))
// This means some phi nodes are dependent on each other.
// Avoid infinite looping!
return false;
if (!LoadUsingPHIs.insert(PN))
// If we have already analyzed this PHI, then it is safe.
continue;
// Make sure all uses of the PHI are simple enough to transform.
if (!LoadUsesSimpleEnoughForHeapSRA(PN,
LoadUsingPHIs, LoadUsingPHIsPerLoad))
return false;
continue;
}
// Otherwise we don't know what this is, not ok.
return false;
}
return true;
}
/// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
/// GV are simple enough to perform HeapSRA, return true.
static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV,
Instruction *StoredVal) {
SmallPtrSet<const PHINode*, 32> LoadUsingPHIs;
SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad;
for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
UI != E; ++UI)
if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
LoadUsingPHIsPerLoad))
return false;
LoadUsingPHIsPerLoad.clear();
}
// If we reach here, we know that all uses of the loads and transitive uses
// (through PHI nodes) are simple enough to transform. However, we don't know
// that all inputs the to the PHI nodes are in the same equivalence sets.
// Check to verify that all operands of the PHIs are either PHIS that can be
// transformed, loads from GV, or MI itself.
for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin()
, E = LoadUsingPHIs.end(); I != E; ++I) {
const PHINode *PN = *I;
for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
Value *InVal = PN->getIncomingValue(op);
// PHI of the stored value itself is ok.
if (InVal == StoredVal) continue;
if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) {
// One of the PHIs in our set is (optimistically) ok.
if (LoadUsingPHIs.count(InPN))
continue;
return false;
}
// Load from GV is ok.
if (const LoadInst *LI = dyn_cast<LoadInst>(InVal))
if (LI->getOperand(0) == GV)
continue;
// UNDEF? NULL?
// Anything else is rejected.
return false;
}
}
return true;
}
static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
if (FieldNo >= FieldVals.size())
FieldVals.resize(FieldNo+1);
// If we already have this value, just reuse the previously scalarized
// version.
if (Value *FieldVal = FieldVals[FieldNo])
return FieldVal;
// Depending on what instruction this is, we have several cases.
Value *Result;
if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
// This is a scalarized version of the load from the global. Just create
// a new Load of the scalarized global.
Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
InsertedScalarizedValues,
PHIsToRewrite),
LI->getName()+".f"+Twine(FieldNo), LI);
} else if (PHINode *PN = dyn_cast<PHINode>(V)) {
// PN's type is pointer to struct. Make a new PHI of pointer to struct
// field.
StructType *ST =
cast<StructType>(cast<PointerType>(PN->getType())->getElementType());
PHINode *NewPN =
PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
PN->getNumIncomingValues(),
PN->getName()+".f"+Twine(FieldNo), PN);
Result = NewPN;
PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
} else {
llvm_unreachable("Unknown usable value");
}
return FieldVals[FieldNo] = Result;
}
/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
/// the load, rewrite the derived value to use the HeapSRoA'd load.
static void RewriteHeapSROALoadUser(Instruction *LoadUser,
DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
// If this is a comparison against null, handle it.
if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
// If we have a setcc of the loaded pointer, we can use a setcc of any
// field.
Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
InsertedScalarizedValues, PHIsToRewrite);
Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
Constant::getNullValue(NPtr->getType()),
SCI->getName());
SCI->replaceAllUsesWith(New);
SCI->eraseFromParent();
return;
}
// Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
&& "Unexpected GEPI!");
// Load the pointer for this field.
unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
InsertedScalarizedValues, PHIsToRewrite);
// Create the new GEP idx vector.
SmallVector<Value*, 8> GEPIdx;
GEPIdx.push_back(GEPI->getOperand(1));
GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx,
GEPI->getName(), GEPI);
GEPI->replaceAllUsesWith(NGEPI);
GEPI->eraseFromParent();
return;
}
// Recursively transform the users of PHI nodes. This will lazily create the
// PHIs that are needed for individual elements. Keep track of what PHIs we
// see in InsertedScalarizedValues so that we don't get infinite loops (very
// antisocial). If the PHI is already in InsertedScalarizedValues, it has
// already been seen first by another load, so its uses have already been
// processed.
PHINode *PN = cast<PHINode>(LoadUser);
if (!InsertedScalarizedValues.insert(std::make_pair(PN,
std::vector<Value*>())).second)
return;
// If this is the first time we've seen this PHI, recursively process all
// users.
for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
Instruction *User = cast<Instruction>(*UI++);
RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
}
}
/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global. Ptr
/// is a value loaded from the global. Eliminate all uses of Ptr, making them
/// use FieldGlobals instead. All uses of loaded values satisfy
/// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
UI != E; ) {
Instruction *User = cast<Instruction>(*UI++);
RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
}
if (Load->use_empty()) {
Load->eraseFromParent();
InsertedScalarizedValues.erase(Load);
}
}
/// PerformHeapAllocSRoA - CI is an allocation of an array of structures. Break
/// it up into multiple allocations of arrays of the fields.
static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI,
Value *NElems, TargetData *TD) {
DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << " MALLOC = " << *CI << '\n');
Type *MAT = getMallocAllocatedType(CI);
StructType *STy = cast<StructType>(MAT);
// There is guaranteed to be at least one use of the malloc (storing
// it into GV). If there are other uses, change them to be uses of
// the global to simplify later code. This also deletes the store
// into GV.
ReplaceUsesOfMallocWithGlobal(CI, GV);
// Okay, at this point, there are no users of the malloc. Insert N
// new mallocs at the same place as CI, and N globals.
std::vector<Value*> FieldGlobals;
std::vector<Value*> FieldMallocs;
for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
Type *FieldTy = STy->getElementType(FieldNo);
PointerType *PFieldTy = PointerType::getUnqual(FieldTy);
GlobalVariable *NGV =
new GlobalVariable(*GV->getParent(),
PFieldTy, false, GlobalValue::InternalLinkage,
Constant::getNullValue(PFieldTy),
GV->getName() + ".f" + Twine(FieldNo), GV,
GV->isThreadLocal());
FieldGlobals.push_back(NGV);
unsigned TypeSize = TD->getTypeAllocSize(FieldTy);
if (StructType *ST = dyn_cast<StructType>(FieldTy))
TypeSize = TD->getStructLayout(ST)->getSizeInBytes();
Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy,
ConstantInt::get(IntPtrTy, TypeSize),
NElems, 0,
CI->getName() + ".f" + Twine(FieldNo));
FieldMallocs.push_back(NMI);
new StoreInst(NMI, NGV, CI);
}
// The tricky aspect of this transformation is handling the case when malloc
// fails. In the original code, malloc failing would set the result pointer
// of malloc to null. In this case, some mallocs could succeed and others
// could fail. As such, we emit code that looks like this:
// F0 = malloc(field0)
// F1 = malloc(field1)
// F2 = malloc(field2)
// if (F0 == 0 || F1 == 0 || F2 == 0) {
// if (F0) { free(F0); F0 = 0; }
// if (F1) { free(F1); F1 = 0; }
// if (F2) { free(F2); F2 = 0; }
// }
// The malloc can also fail if its argument is too large.
Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0);
Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0),
ConstantZero, "isneg");
for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i],
Constant::getNullValue(FieldMallocs[i]->getType()),
"isnull");
RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI);
}
// Split the basic block at the old malloc.
BasicBlock *OrigBB = CI->getParent();
BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont");
// Create the block to check the first condition. Put all these blocks at the
// end of the function as they are unlikely to be executed.
BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(),
"malloc_ret_null",
OrigBB->getParent());
// Remove the uncond branch from OrigBB to ContBB, turning it into a cond
// branch on RunningOr.
OrigBB->getTerminator()->eraseFromParent();
BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
// Within the NullPtrBlock, we need to emit a comparison and branch for each
// pointer, because some may be null while others are not.
for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
Constant::getNullValue(GVVal->getType()));
BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it",
OrigBB->getParent());
BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next",
OrigBB->getParent());
Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
Cmp, NullPtrBlock);
// Fill in FreeBlock.
CallInst::CreateFree(GVVal, BI);
new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
FreeBlock);
BranchInst::Create(NextBlock, FreeBlock);
NullPtrBlock = NextBlock;
}
BranchInst::Create(ContBB, NullPtrBlock);
// CI is no longer needed, remove it.
CI->eraseFromParent();
/// InsertedScalarizedLoads - As we process loads, if we can't immediately
/// update all uses of the load, keep track of what scalarized loads are
/// inserted for a given load.
DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
InsertedScalarizedValues[GV] = FieldGlobals;
std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
// Okay, the malloc site is completely handled. All of the uses of GV are now
// loads, and all uses of those loads are simple. Rewrite them to use loads
// of the per-field globals instead.
for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
Instruction *User = cast<Instruction>(*UI++);
if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
continue;
}
// Must be a store of null.
StoreInst *SI = cast<StoreInst>(User);
assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
"Unexpected heap-sra user!");
// Insert a store of null into each global.
for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
Constant *Null = Constant::getNullValue(PT->getElementType());
new StoreInst(Null, FieldGlobals[i], SI);
}
// Erase the original store.
SI->eraseFromParent();
}
// While we have PHIs that are interesting to rewrite, do it.
while (!PHIsToRewrite.empty()) {
PHINode *PN = PHIsToRewrite.back().first;
unsigned FieldNo = PHIsToRewrite.back().second;
PHIsToRewrite.pop_back();
PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
// Add all the incoming values. This can materialize more phis.
for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
Value *InVal = PN->getIncomingValue(i);
InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
PHIsToRewrite);
FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
}
}
// Drop all inter-phi links and any loads that made it this far.
for (DenseMap<Value*, std::vector<Value*> >::iterator
I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
I != E; ++I) {
if (PHINode *PN = dyn_cast<PHINode>(I->first))
PN->dropAllReferences();
else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
LI->dropAllReferences();
}
// Delete all the phis and loads now that inter-references are dead.
for (DenseMap<Value*, std::vector<Value*> >::iterator
I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
I != E; ++I) {
if (PHINode *PN = dyn_cast<PHINode>(I->first))
PN->eraseFromParent();
else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
LI->eraseFromParent();
}
// The old global is now dead, remove it.
GV->eraseFromParent();
++NumHeapSRA;
return cast<GlobalVariable>(FieldGlobals[0]);
}
/// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
/// pointer global variable with a single value stored it that is a malloc or
/// cast of malloc.
static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
CallInst *CI,
Type *AllocTy,
AtomicOrdering Ordering,
Module::global_iterator &GVI,
TargetData *TD,
TargetLibraryInfo *TLI) {
if (!TD)
return false;
// If this is a malloc of an abstract type, don't touch it.
if (!AllocTy->isSized())
return false;
// We can't optimize this global unless all uses of it are *known* to be
// of the malloc value, not of the null initializer value (consider a use
// that compares the global's value against zero to see if the malloc has
// been reached). To do this, we check to see if all uses of the global
// would trap if the global were null: this proves that they must all
// happen after the malloc.
if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
return false;
// We can't optimize this if the malloc itself is used in a complex way,
// for example, being stored into multiple globals. This allows the
// malloc to be stored into the specified global, loaded icmp'd, and
// GEP'd. These are all things we could transform to using the global
// for.
SmallPtrSet<const PHINode*, 8> PHIs;
if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs))
return false;
// If we have a global that is only initialized with a fixed size malloc,
// transform the program to use global memory instead of malloc'd memory.
// This eliminates dynamic allocation, avoids an indirection accessing the
// data, and exposes the resultant global to further GlobalOpt.
// We cannot optimize the malloc if we cannot determine malloc array size.
Value *NElems = getMallocArraySize(CI, TD, true);
if (!NElems)
return false;
if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
// Restrict this transformation to only working on small allocations
// (2048 bytes currently), as we don't want to introduce a 16M global or
// something.
if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) {
GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD, TLI);
return true;
}
// If the allocation is an array of structures, consider transforming this
// into multiple malloc'd arrays, one for each field. This is basically
// SRoA for malloc'd memory.
if (Ordering != NotAtomic)
return false;
// If this is an allocation of a fixed size array of structs, analyze as a
// variable size array. malloc [100 x struct],1 -> malloc struct, 100
if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
AllocTy = AT->getElementType();
StructType *AllocSTy = dyn_cast<StructType>(AllocTy);
if (!AllocSTy)
return false;
// This the structure has an unreasonable number of fields, leave it
// alone.
if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) {
// If this is a fixed size array, transform the Malloc to be an alloc of
// structs. malloc [100 x struct],1 -> malloc struct, 100
if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI))) {
Type *IntPtrTy = TD->getIntPtrType(CI->getContext());
unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes();
Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize);
Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements());
Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy,
AllocSize, NumElements,
0, CI->getName());
Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI);
CI->replaceAllUsesWith(Cast);
CI->eraseFromParent();
CI = dyn_cast<BitCastInst>(Malloc) ?
extractMallocCallFromBitCast(Malloc) : cast<CallInst>(Malloc);
}
GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, true), TD);
return true;
}
return false;
}
// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
// that only one value (besides its initializer) is ever stored to the global.
static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
AtomicOrdering Ordering,
Module::global_iterator &GVI,
TargetData *TD, TargetLibraryInfo *TLI) {
// Ignore no-op GEPs and bitcasts.
StoredOnceVal = StoredOnceVal->stripPointerCasts();
// If we are dealing with a pointer global that is initialized to null and
// only has one (non-null) value stored into it, then we can optimize any
// users of the loaded value (often calls and loads) that would trap if the
// value was null.
if (GV->getInitializer()->getType()->isPointerTy() &&
GV->getInitializer()->isNullValue()) {
if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
if (GV->getInitializer()->getType() != SOVC->getType())
SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
// Optimize away any trapping uses of the loaded value.
if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, TD, TLI))
return true;
} else if (CallInst *CI = extractMallocCall(StoredOnceVal)) {
Type *MallocType = getMallocAllocatedType(CI);
if (MallocType &&
TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, Ordering, GVI,
TD, TLI))
return true;
}
}
return false;
}
/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
/// two values ever stored into GV are its initializer and OtherVal. See if we
/// can shrink the global into a boolean and select between the two values
/// whenever it is used. This exposes the values to other scalar optimizations.
static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
Type *GVElType = GV->getType()->getElementType();
// If GVElType is already i1, it is already shrunk. If the type of the GV is
// an FP value, pointer or vector, don't do this optimization because a select
// between them is very expensive and unlikely to lead to later
// simplification. In these cases, we typically end up with "cond ? v1 : v2"
// where v1 and v2 both require constant pool loads, a big loss.
if (GVElType == Type::getInt1Ty(GV->getContext()) ||
GVElType->isFloatingPointTy() ||
GVElType->isPointerTy() || GVElType->isVectorTy())
return false;
// Walk the use list of the global seeing if all the uses are load or store.
// If there is anything else, bail out.
for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
User *U = *I;
if (!isa<LoadInst>(U) && !isa<StoreInst>(U))
return false;
}
DEBUG(dbgs() << " *** SHRINKING TO BOOL: " << *GV);
// Create the new global, initializing it to false.
GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
false,
GlobalValue::InternalLinkage,
ConstantInt::getFalse(GV->getContext()),
GV->getName()+".b",
GV->isThreadLocal());
GV->getParent()->getGlobalList().insert(GV, NewGV);
Constant *InitVal = GV->getInitializer();
assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
"No reason to shrink to bool!");
// If initialized to zero and storing one into the global, we can use a cast
// instead of a select to synthesize the desired value.
bool IsOneZero = false;
if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
IsOneZero = InitVal->isNullValue() && CI->isOne();
while (!GV->use_empty()) {
Instruction *UI = cast<Instruction>(GV->use_back());
if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
// Change the store into a boolean store.
bool StoringOther = SI->getOperand(0) == OtherVal;
// Only do this if we weren't storing a loaded value.
Value *StoreVal;
if (StoringOther || SI->getOperand(0) == InitVal)
StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()),
StoringOther);
else {
// Otherwise, we are storing a previously loaded copy. To do this,
// change the copy from copying the original value to just copying the
// bool.
Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
// If we've already replaced the input, StoredVal will be a cast or
// select instruction. If not, it will be a load of the original
// global.
if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
assert(LI->getOperand(0) == GV && "Not a copy!");
// Insert a new load, to preserve the saved value.
StoreVal = new LoadInst(NewGV, LI->getName()+".b", false, 0,
LI->getOrdering(), LI->getSynchScope(), LI);
} else {
assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
"This is not a form that we understand!");
StoreVal = StoredVal->getOperand(0);
assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
}
}
new StoreInst(StoreVal, NewGV, false, 0,
SI->getOrdering(), SI->getSynchScope(), SI);
} else {
// Change the load into a load of bool then a select.
LoadInst *LI = cast<LoadInst>(UI);
LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0,
LI->getOrdering(), LI->getSynchScope(), LI);
Value *NSI;
if (IsOneZero)
NSI = new ZExtInst(NLI, LI->getType(), "", LI);
else
NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
NSI->takeName(LI);
LI->replaceAllUsesWith(NSI);
}
UI->eraseFromParent();
}
GV->eraseFromParent();
return true;
}
/// ProcessGlobal - Analyze the specified global variable and optimize it if
/// possible. If we make a change, return true.
bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
Module::global_iterator &GVI) {
if (!GV->hasLocalLinkage())
return false;
// Do more involved optimizations if the global is internal.
GV->removeDeadConstantUsers();
if (GV->use_empty()) {
DEBUG(dbgs() << "GLOBAL DEAD: " << *GV);
GV->eraseFromParent();
++NumDeleted;
return true;
}
SmallPtrSet<const PHINode*, 16> PHIUsers;
GlobalStatus GS;
if (AnalyzeGlobal(GV, GS, PHIUsers))
return false;
if (!GS.isCompared && !GV->hasUnnamedAddr()) {
GV->setUnnamedAddr(true);
NumUnnamed++;
}
if (GV->isConstant() || !GV->hasInitializer())
return false;
return ProcessInternalGlobal(GV, GVI, PHIUsers, GS);
}
/// ProcessInternalGlobal - Analyze the specified global variable and optimize
/// it if possible. If we make a change, return true.
bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
Module::global_iterator &GVI,
const SmallPtrSet<const PHINode*, 16> &PHIUsers,
const GlobalStatus &GS) {
// If this is a first class global and has only one accessing function
// and this function is main (which we know is not recursive we can make
// this global a local variable) we replace the global with a local alloca
// in this function.
//
// NOTE: It doesn't make sense to promote non single-value types since we
// are just replacing static memory to stack memory.
//
// If the global is in different address space, don't bring it to stack.
if (!GS.HasMultipleAccessingFunctions &&
GS.AccessingFunction && !GS.HasNonInstructionUser &&
GV->getType()->getElementType()->isSingleValueType() &&
GS.AccessingFunction->getName() == "main" &&
GS.AccessingFunction->hasExternalLinkage() &&
GV->getType()->getAddressSpace() == 0) {
DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV);
Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction
->getEntryBlock().begin());
Type *ElemTy = GV->getType()->getElementType();
// FIXME: Pass Global's alignment when globals have alignment
AllocaInst *Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI);
if (!isa<UndefValue>(GV->getInitializer()))
new StoreInst(GV->getInitializer(), Alloca, &FirstI);
GV->replaceAllUsesWith(Alloca);
GV->eraseFromParent();
++NumLocalized;
return true;
}
// If the global is never loaded (but may be stored to), it is dead.
// Delete it now.
if (!GS.isLoaded) {
DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV);
// Delete any stores we can find to the global. We may not be able to
// make it completely dead though.
bool Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(),
TD, TLI);
// If the global is dead now, delete it.
if (GV->use_empty()) {
GV->eraseFromParent();
++NumDeleted;
Changed = true;
}
return Changed;
} else if (GS.StoredType <= GlobalStatus::isInitializerStored) {
DEBUG(dbgs() << "MARKING CONSTANT: " << *GV);
GV->setConstant(true);
// Clean up any obviously simplifiable users now.
CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
// If the global is dead now, just nuke it.
if (GV->use_empty()) {
DEBUG(dbgs() << " *** Marking constant allowed us to simplify "
<< "all users and delete global!\n");
GV->eraseFromParent();
++NumDeleted;
}
++NumMarked;
return true;
} else if (!GV->getInitializer()->getType()->isSingleValueType()) {
if (TargetData *TD = getAnalysisIfAvailable<TargetData>())
if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) {
GVI = FirstNewGV; // Don't skip the newly produced globals!
return true;
}
} else if (GS.StoredType == GlobalStatus::isStoredOnce) {
// If the initial value for the global was an undef value, and if only
// one other value was stored into it, we can just change the
// initializer to be the stored value, then delete all stores to the
// global. This allows us to mark it constant.
if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
if (isa<UndefValue>(GV->getInitializer())) {
// Change the initial value here.
GV->setInitializer(SOVConstant);
// Clean up any obviously simplifiable users now.
CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
if (GV->use_empty()) {
DEBUG(dbgs() << " *** Substituting initializer allowed us to "
<< "simplify all users and delete global!\n");
GV->eraseFromParent();
++NumDeleted;
} else {
GVI = GV;
}
++NumSubstitute;
return true;
}
// Try to optimize globals based on the knowledge that only one value
// (besides its initializer) is ever stored to the global.
if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, GVI,
TD, TLI))
return true;
// Otherwise, if the global was not a boolean, we can shrink it to be a
// boolean.
if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
++NumShrunkToBool;
return true;
}
}
return false;
}
/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
/// function, changing them to FastCC.
static void ChangeCalleesToFastCall(Function *F) {
for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
CallSite User(cast<Instruction>(*UI));
User.setCallingConv(CallingConv::Fast);
}
}
static AttrListPtr StripNest(const AttrListPtr &Attrs) {
for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
if ((Attrs.getSlot(i).Attrs & Attribute::Nest) == 0)
continue;
// There can be only one.
return Attrs.removeAttr(Attrs.getSlot(i).Index, Attribute::Nest);
}
return Attrs;
}
static void RemoveNestAttribute(Function *F) {
F->setAttributes(StripNest(F->getAttributes()));
for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
CallSite User(cast<Instruction>(*UI));
User.setAttributes(StripNest(User.getAttributes()));
}
}
bool GlobalOpt::OptimizeFunctions(Module &M) {
bool Changed = false;
// Optimize functions.
for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
Function *F = FI++;
// Functions without names cannot be referenced outside this module.
if (!F->hasName() && !F->isDeclaration())
F->setLinkage(GlobalValue::InternalLinkage);
F->removeDeadConstantUsers();
if (F->isDefTriviallyDead()) {
F->eraseFromParent();
Changed = true;
++NumFnDeleted;
} else if (F->hasLocalLinkage()) {
if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
!F->hasAddressTaken()) {
// If this function has C calling conventions, is not a varargs
// function, and is only called directly, promote it to use the Fast
// calling convention.
F->setCallingConv(CallingConv::Fast);
ChangeCalleesToFastCall(F);
++NumFastCallFns;
Changed = true;
}
if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
!F->hasAddressTaken()) {
// The function is not used by a trampoline intrinsic, so it is safe
// to remove the 'nest' attribute.
RemoveNestAttribute(F);
++NumNestRemoved;
Changed = true;
}
}
}
return Changed;
}
bool GlobalOpt::OptimizeGlobalVars(Module &M) {
bool Changed = false;
for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
GVI != E; ) {
GlobalVariable *GV = GVI++;
// Global variables without names cannot be referenced outside this module.
if (!GV->hasName() && !GV->isDeclaration())
GV->setLinkage(GlobalValue::InternalLinkage);
// Simplify the initializer.
if (GV->hasInitializer())
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
Constant *New = ConstantFoldConstantExpression(CE, TD, TLI);
if (New && New != CE)
GV->setInitializer(New);
}
Changed |= ProcessGlobal(GV, GVI);
}
return Changed;
}
/// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all
/// initializers have an init priority of 65535.
GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
if (GV == 0) return 0;
// Verify that the initializer is simple enough for us to handle. We are
// only allowed to optimize the initializer if it is unique.
if (!GV->hasUniqueInitializer()) return 0;
if (isa<ConstantAggregateZero>(GV->getInitializer()))
return GV;
ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
if (isa<ConstantAggregateZero>(*i))
continue;
ConstantStruct *CS = cast<ConstantStruct>(*i);
if (isa<ConstantPointerNull>(CS->getOperand(1)))
continue;
// Must have a function or null ptr.
if (!isa<Function>(CS->getOperand(1)))
return 0;
// Init priority must be standard.
ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0));
if (CI->getZExtValue() != 65535)
return 0;
}
return GV;
}
/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
/// return a list of the functions and null terminator as a vector.
static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
if (GV->getInitializer()->isNullValue())
return std::vector<Function*>();
ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
std::vector<Function*> Result;
Result.reserve(CA->getNumOperands());
for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
ConstantStruct *CS = cast<ConstantStruct>(*i);
Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
}
return Result;
}
/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
/// specified array, returning the new global to use.
static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
const std::vector<Function*> &Ctors) {
// If we made a change, reassemble the initializer list.
Constant *CSVals[2];
CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535);
CSVals[1] = 0;
StructType *StructTy =
cast <StructType>(
cast<ArrayType>(GCL->getType()->getElementType())->getElementType());
// Create the new init list.
std::vector<Constant*> CAList;
for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
if (Ctors[i]) {
CSVals[1] = Ctors[i];
} else {
Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()),
false);
PointerType *PFTy = PointerType::getUnqual(FTy);
CSVals[1] = Constant::getNullValue(PFTy);
CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()),
0x7fffffff);
}
CAList.push_back(ConstantStruct::get(StructTy, CSVals));
}
// Create the array initializer.
Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
CAList.size()), CAList);
// If we didn't change the number of elements, don't create a new GV.
if (CA->getType() == GCL->getInitializer()->getType()) {
GCL->setInitializer(CA);
return GCL;
}
// Create the new global and insert it next to the existing list.
GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
GCL->getLinkage(), CA, "",
GCL->isThreadLocal());
GCL->getParent()->getGlobalList().insert(GCL, NGV);
NGV->takeName(GCL);
// Nuke the old list, replacing any uses with the new one.
if (!GCL->use_empty()) {
Constant *V = NGV;
if (V->getType() != GCL->getType())
V = ConstantExpr::getBitCast(V, GCL->getType());
GCL->replaceAllUsesWith(V);
}
GCL->eraseFromParent();
if (Ctors.size())
return NGV;
else
return 0;
}
static inline bool
isSimpleEnoughValueToCommit(Constant *C,
SmallPtrSet<Constant*, 8> &SimpleConstants,
const TargetData *TD);
/// isSimpleEnoughValueToCommit - Return true if the specified constant can be
/// handled by the code generator. We don't want to generate something like:
/// void *X = &X/42;
/// because the code generator doesn't have a relocation that can handle that.
///
/// This function should be called if C was not found (but just got inserted)
/// in SimpleConstants to avoid having to rescan the same constants all the
/// time.
static bool isSimpleEnoughValueToCommitHelper(Constant *C,
SmallPtrSet<Constant*, 8> &SimpleConstants,
const TargetData *TD) {
// Simple integer, undef, constant aggregate zero, global addresses, etc are
// all supported.
if (C->getNumOperands() == 0 || isa<BlockAddress>(C) ||
isa<GlobalValue>(C))
return true;
// Aggregate values are safe if all their elements are.
if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
isa<ConstantVector>(C)) {
for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
Constant *Op = cast<Constant>(C->getOperand(i));
if (!isSimpleEnoughValueToCommit(Op, SimpleConstants, TD))
return false;
}
return true;
}
// We don't know exactly what relocations are allowed in constant expressions,
// so we allow &global+constantoffset, which is safe and uniformly supported
// across targets.
ConstantExpr *CE = cast<ConstantExpr>(C);
switch (CE->getOpcode()) {
case Instruction::BitCast:
// Bitcast is fine if the casted value is fine.
return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
case Instruction::IntToPtr:
case Instruction::PtrToInt:
// int <=> ptr is fine if the int type is the same size as the
// pointer type.
if (!TD || TD->getTypeSizeInBits(CE->getType()) !=
TD->getTypeSizeInBits(CE->getOperand(0)->getType()))
return false;
return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
// GEP is fine if it is simple + constant offset.
case Instruction::GetElementPtr:
for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
if (!isa<ConstantInt>(CE->getOperand(i)))
return false;
return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
case Instruction::Add:
// We allow simple+cst.
if (!isa<ConstantInt>(CE->getOperand(1)))
return false;
return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
}
return false;
}
static inline bool
isSimpleEnoughValueToCommit(Constant *C,
SmallPtrSet<Constant*, 8> &SimpleConstants,
const TargetData *TD) {
// If we already checked this constant, we win.
if (!SimpleConstants.insert(C)) return true;
// Check the constant.
return isSimpleEnoughValueToCommitHelper(C, SimpleConstants, TD);
}
/// isSimpleEnoughPointerToCommit - Return true if this constant is simple
/// enough for us to understand. In particular, if it is a cast to anything
/// other than from one pointer type to another pointer type, we punt.
/// We basically just support direct accesses to globals and GEP's of
/// globals. This should be kept up to date with CommitValueTo.
static bool isSimpleEnoughPointerToCommit(Constant *C) {
// Conservatively, avoid aggregate types. This is because we don't
// want to worry about them partially overlapping other stores.
if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType())
return false;
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
// Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
// external globals.
return GV->hasUniqueInitializer();
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
// Handle a constantexpr gep.
if (CE->getOpcode() == Instruction::GetElementPtr &&
isa<GlobalVariable>(CE->getOperand(0)) &&
cast<GEPOperator>(CE)->isInBounds()) {
GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
// Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
// external globals.
if (!GV->hasUniqueInitializer())
return false;
// The first index must be zero.
ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin()));
if (!CI || !CI->isZero()) return false;
// The remaining indices must be compile-time known integers within the
// notional bounds of the corresponding static array types.
if (!CE->isGEPWithNoNotionalOverIndexing())
return false;
return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
// A constantexpr bitcast from a pointer to another pointer is a no-op,
// and we know how to evaluate it by moving the bitcast from the pointer
// operand to the value operand.
} else if (CE->getOpcode() == Instruction::BitCast &&
isa<GlobalVariable>(CE->getOperand(0))) {
// Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
// external globals.
return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer();
}
}
return false;
}
/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
/// initializer. This returns 'Init' modified to reflect 'Val' stored into it.
/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
ConstantExpr *Addr, unsigned OpNo) {
// Base case of the recursion.
if (OpNo == Addr->getNumOperands()) {
assert(Val->getType() == Init->getType() && "Type mismatch!");
return Val;
}
SmallVector<Constant*, 32> Elts;
if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
// Break up the constant into its elements.
for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
Elts.push_back(Init->getAggregateElement(i));
// Replace the element that we are supposed to.
ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
unsigned Idx = CU->getZExtValue();
assert(Idx < STy->getNumElements() && "Struct index out of range!");
Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
// Return the modified struct.
return ConstantStruct::get(STy, Elts);
}
ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
SequentialType *InitTy = cast<SequentialType>(Init->getType());
uint64_t NumElts;
if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy))
NumElts = ATy->getNumElements();
else
NumElts = InitTy->getVectorNumElements();
// Break up the array into elements.
for (uint64_t i = 0, e = NumElts; i != e; ++i)
Elts.push_back(Init->getAggregateElement(i));
assert(CI->getZExtValue() < NumElts);
Elts[CI->getZExtValue()] =
EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
if (Init->getType()->isArrayTy())
return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
return ConstantVector::get(Elts);
}
/// CommitValueTo - We have decided that Addr (which satisfies the predicate
/// isSimpleEnoughPointerToCommit) should get Val as its value. Make it happen.
static void CommitValueTo(Constant *Val, Constant *Addr) {
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
assert(GV->hasInitializer());
GV->setInitializer(Val);
return;
}
ConstantExpr *CE = cast<ConstantExpr>(Addr);
GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
}
namespace {
/// Evaluator - This class evaluates LLVM IR, producing the Constant
/// representing each SSA instruction. Changes to global variables are stored
/// in a mapping that can be iterated over after the evaluation is complete.
/// Once an evaluation call fails, the evaluation object should not be reused.
class Evaluator {
public:
Evaluator(const TargetData *TD, const TargetLibraryInfo *TLI)
: TD(TD), TLI(TLI) {
ValueStack.push_back(new DenseMap<Value*, Constant*>);
}
~Evaluator() {
DeleteContainerPointers(ValueStack);
while (!AllocaTmps.empty()) {
GlobalVariable *Tmp = AllocaTmps.back();
AllocaTmps.pop_back();
// If there are still users of the alloca, the program is doing something
// silly, e.g. storing the address of the alloca somewhere and using it
// later. Since this is undefined, we'll just make it be null.
if (!Tmp->use_empty())
Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
delete Tmp;
}
}
/// EvaluateFunction - Evaluate a call to function F, returning true if
/// successful, false if we can't evaluate it. ActualArgs contains the formal
/// arguments for the function.
bool EvaluateFunction(Function *F, Constant *&RetVal,
const SmallVectorImpl<Constant*> &ActualArgs);
/// EvaluateBlock - Evaluate all instructions in block BB, returning true if
/// successful, false if we can't evaluate it. NewBB returns the next BB that
/// control flows into, or null upon return.
bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB);
Constant *getVal(Value *V) {
if (Constant *CV = dyn_cast<Constant>(V)) return CV;
Constant *R = ValueStack.back()->lookup(V);
assert(R && "Reference to an uncomputed value!");
return R;
}
void setVal(Value *V, Constant *C) {
ValueStack.back()->operator[](V) = C;
}
const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
return MutatedMemory;
}
const SmallPtrSet<GlobalVariable*, 8> &getInvariants() const {
return Invariants;
}
private:
Constant *ComputeLoadResult(Constant *P);
/// ValueStack - As we compute SSA register values, we store their contents
/// here. The back of the vector contains the current function and the stack
/// contains the values in the calling frames.
SmallVector<DenseMap<Value*, Constant*>*, 4> ValueStack;
/// CallStack - This is used to detect recursion. In pathological situations
/// we could hit exponential behavior, but at least there is nothing
/// unbounded.
SmallVector<Function*, 4> CallStack;
/// MutatedMemory - For each store we execute, we update this map. Loads
/// check this to get the most up-to-date value. If evaluation is successful,
/// this state is committed to the process.
DenseMap<Constant*, Constant*> MutatedMemory;
/// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
/// to represent its body. This vector is needed so we can delete the
/// temporary globals when we are done.
SmallVector<GlobalVariable*, 32> AllocaTmps;
/// Invariants - These global variables have been marked invariant by the
/// static constructor.
SmallPtrSet<GlobalVariable*, 8> Invariants;
/// SimpleConstants - These are constants we have checked and know to be
/// simple enough to live in a static initializer of a global.
SmallPtrSet<Constant*, 8> SimpleConstants;
const TargetData *TD;
const TargetLibraryInfo *TLI;
};
} // anonymous namespace
/// ComputeLoadResult - Return the value that would be computed by a load from
/// P after the stores reflected by 'memory' have been performed. If we can't
/// decide, return null.
Constant *Evaluator::ComputeLoadResult(Constant *P) {
// If this memory location has been recently stored, use the stored value: it
// is the most up-to-date.
DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P);
if (I != MutatedMemory.end()) return I->second;
// Access it.
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
if (GV->hasDefinitiveInitializer())
return GV->getInitializer();
return 0;
}
// Handle a constantexpr getelementptr.
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
if (CE->getOpcode() == Instruction::GetElementPtr &&
isa<GlobalVariable>(CE->getOperand(0))) {
GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
if (GV->hasDefinitiveInitializer())
return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
}
return 0; // don't know how to evaluate.
}
/// EvaluateBlock - Evaluate all instructions in block BB, returning true if
/// successful, false if we can't evaluate it. NewBB returns the next BB that
/// control flows into, or null upon return.
bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
BasicBlock *&NextBB) {
// This is the main evaluation loop.
while (1) {
Constant *InstResult = 0;
if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
if (!SI->isSimple()) return false; // no volatile/atomic accesses.
Constant *Ptr = getVal(SI->getOperand(1));
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
if (!isSimpleEnoughPointerToCommit(Ptr))
// If this is too complex for us to commit, reject it.
return false;
Constant *Val = getVal(SI->getOperand(0));
// If this might be too difficult for the backend to handle (e.g. the addr
// of one global variable divided by another) then we can't commit it.
if (!isSimpleEnoughValueToCommit(Val, SimpleConstants, TD))
return false;
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
if (CE->getOpcode() == Instruction::BitCast) {
// If we're evaluating a store through a bitcast, then we need
// to pull the bitcast off the pointer type and push it onto the
// stored value.
Ptr = CE->getOperand(0);
Type *NewTy = cast<PointerType>(Ptr->getType())->getElementType();
// In order to push the bitcast onto the stored value, a bitcast
// from NewTy to Val's type must be legal. If it's not, we can try
// introspecting NewTy to find a legal conversion.
while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) {
// If NewTy is a struct, we can convert the pointer to the struct
// into a pointer to its first member.
// FIXME: This could be extended to support arrays as well.
if (StructType *STy = dyn_cast<StructType>(NewTy)) {
NewTy = STy->getTypeAtIndex(0U);
IntegerType *IdxTy = IntegerType::get(NewTy->getContext(), 32);
Constant *IdxZero = ConstantInt::get(IdxTy, 0, false);
Constant * const IdxList[] = {IdxZero, IdxZero};
Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList);
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
// If we can't improve the situation by introspecting NewTy,
// we have to give up.
} else {
return false;
}
}
// If we found compatible types, go ahead and push the bitcast
// onto the stored value.
Val = ConstantExpr::getBitCast(Val, NewTy);
}
MutatedMemory[Ptr] = Val;
} else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
InstResult = ConstantExpr::get(BO->getOpcode(),
getVal(BO->getOperand(0)),
getVal(BO->getOperand(1)));
} else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
InstResult = ConstantExpr::getCompare(CI->getPredicate(),
getVal(CI->getOperand(0)),
getVal(CI->getOperand(1)));
} else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
InstResult = ConstantExpr::getCast(CI->getOpcode(),
getVal(CI->getOperand(0)),
CI->getType());
} else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
InstResult = ConstantExpr::getSelect(getVal(SI->getOperand(0)),
getVal(SI->getOperand(1)),
getVal(SI->getOperand(2)));
} else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
Constant *P = getVal(GEP->getOperand(0));
SmallVector<Constant*, 8> GEPOps;
for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
i != e; ++i)
GEPOps.push_back(getVal(*i));
InstResult =
ConstantExpr::getGetElementPtr(P, GEPOps,
cast<GEPOperator>(GEP)->isInBounds());
} else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
if (!LI->isSimple()) return false; // no volatile/atomic accesses.
Constant *Ptr = getVal(LI->getOperand(0));
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
InstResult = ComputeLoadResult(Ptr);
if (InstResult == 0) return false; // Could not evaluate load.
} else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
if (AI->isArrayAllocation()) return false; // Cannot handle array allocs.
Type *Ty = AI->getType()->getElementType();
AllocaTmps.push_back(new GlobalVariable(Ty, false,
GlobalValue::InternalLinkage,
UndefValue::get(Ty),
AI->getName()));
InstResult = AllocaTmps.back();
} else if (isa<CallInst>(CurInst) || isa<InvokeInst>(CurInst)) {
CallSite CS(CurInst);
// Debug info can safely be ignored here.
if (isa<DbgInfoIntrinsic>(CS.getInstruction())) {
++CurInst;
continue;
}
// Cannot handle inline asm.
if (isa<InlineAsm>(CS.getCalledValue())) return false;
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
if (MemSetInst *MSI = dyn_cast<MemSetInst>(II)) {
if (MSI->isVolatile()) return false;
Constant *Ptr = getVal(MSI->getDest());
Constant *Val = getVal(MSI->getValue());
Constant *DestVal = ComputeLoadResult(getVal(Ptr));
if (Val->isNullValue() && DestVal && DestVal->isNullValue()) {
// This memset is a no-op.
++CurInst;
continue;
}
}
if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
II->getIntrinsicID() == Intrinsic::lifetime_end) {
++CurInst;
continue;
}
if (II->getIntrinsicID() == Intrinsic::invariant_start) {
// We don't insert an entry into Values, as it doesn't have a
// meaningful return value.
if (!II->use_empty())
return false;
ConstantInt *Size = cast<ConstantInt>(II->getArgOperand(0));
Value *PtrArg = getVal(II->getArgOperand(1));
Value *Ptr = PtrArg->stripPointerCasts();
if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
Type *ElemTy = cast<PointerType>(GV->getType())->getElementType();
if (!Size->isAllOnesValue() &&
Size->getValue().getLimitedValue() >=
TD->getTypeStoreSize(ElemTy))
Invariants.insert(GV);
}
// Continue even if we do nothing.
++CurInst;
continue;
}
return false;
}
// Resolve function pointers.
Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue()));
if (!Callee || Callee->mayBeOverridden())
return false; // Cannot resolve.
SmallVector<Constant*, 8> Formals;
for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end(); i != e; ++i)
Formals.push_back(getVal(*i));
if (Callee->isDeclaration()) {
// If this is a function we can constant fold, do it.
if (Constant *C = ConstantFoldCall(Callee, Formals, TLI)) {
InstResult = C;
} else {
return false;
}
} else {
if (Callee->getFunctionType()->isVarArg())
return false;
Constant *RetVal;
// Execute the call, if successful, use the return value.
ValueStack.push_back(new DenseMap<Value*, Constant*>);
if (!EvaluateFunction(Callee, RetVal, Formals))
return false;
delete ValueStack.pop_back_val();
InstResult = RetVal;
}
} else if (isa<TerminatorInst>(CurInst)) {
if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
if (BI->isUnconditional()) {
NextBB = BI->getSuccessor(0);
} else {
ConstantInt *Cond =
dyn_cast<ConstantInt>(getVal(BI->getCondition()));
if (!Cond) return false; // Cannot determine.
NextBB = BI->getSuccessor(!Cond->getZExtValue());
}
} else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
ConstantInt *Val =
dyn_cast<ConstantInt>(getVal(SI->getCondition()));
if (!Val) return false; // Cannot determine.
NextBB = SI->findCaseValue(Val).getCaseSuccessor();
} else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
Value *Val = getVal(IBI->getAddress())->stripPointerCasts();
if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))
NextBB = BA->getBasicBlock();
else
return false; // Cannot determine.
} else if (isa<ReturnInst>(CurInst)) {
NextBB = 0;
} else {
// invoke, unwind, resume, unreachable.
return false; // Cannot handle this terminator.
}
// We succeeded at evaluating this block!
return true;
} else {
// Did not know how to evaluate this!
return false;
}
if (!CurInst->use_empty()) {
if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult))
InstResult = ConstantFoldConstantExpression(CE, TD, TLI);
setVal(CurInst, InstResult);
}
// If we just processed an invoke, we finished evaluating the block.
if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) {
NextBB = II->getNormalDest();
return true;
}
// Advance program counter.
++CurInst;
}
}
/// EvaluateFunction - Evaluate a call to function F, returning true if
/// successful, false if we can't evaluate it. ActualArgs contains the formal
/// arguments for the function.
bool Evaluator::EvaluateFunction(Function *F, Constant *&RetVal,
const SmallVectorImpl<Constant*> &ActualArgs) {
// Check to see if this function is already executing (recursion). If so,
// bail out. TODO: we might want to accept limited recursion.
if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
return false;
CallStack.push_back(F);
// Initialize arguments to the incoming values specified.
unsigned ArgNo = 0;
for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
++AI, ++ArgNo)
setVal(AI, ActualArgs[ArgNo]);
// ExecutedBlocks - We only handle non-looping, non-recursive code. As such,
// we can only evaluate any one basic block at most once. This set keeps
// track of what we have executed so we can detect recursive cases etc.
SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
// CurBB - The current basic block we're evaluating.
BasicBlock *CurBB = F->begin();
BasicBlock::iterator CurInst = CurBB->begin();
while (1) {
BasicBlock *NextBB = 0; // Initialized to avoid compiler warnings.
if (!EvaluateBlock(CurInst, NextBB))
return false;
if (NextBB == 0) {
// Successfully running until there's no next block means that we found
// the return. Fill it the return value and pop the call stack.
ReturnInst *RI = cast<ReturnInst>(CurBB->getTerminator());
if (RI->getNumOperands())
RetVal = getVal(RI->getOperand(0));
CallStack.pop_back();
return true;
}
// Okay, we succeeded in evaluating this control flow. See if we have
// executed the new block before. If so, we have a looping function,
// which we cannot evaluate in reasonable time.
if (!ExecutedBlocks.insert(NextBB))
return false; // looped!
// Okay, we have never been in this block before. Check to see if there
// are any PHI nodes. If so, evaluate them with information about where
// we came from.
PHINode *PN = 0;
for (CurInst = NextBB->begin();
(PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
setVal(PN, getVal(PN->getIncomingValueForBlock(CurBB)));
// Advance to the next block.
CurBB = NextBB;
}
}
/// EvaluateStaticConstructor - Evaluate static constructors in the function, if
/// we can. Return true if we can, false otherwise.
static bool EvaluateStaticConstructor(Function *F, const TargetData *TD,
const TargetLibraryInfo *TLI) {
// Call the function.
Evaluator Eval(TD, TLI);
Constant *RetValDummy;
bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy,
SmallVector<Constant*, 0>());
if (EvalSuccess) {
// We succeeded at evaluation: commit the result.
DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
<< F->getName() << "' to " << Eval.getMutatedMemory().size()
<< " stores.\n");
for (DenseMap<Constant*, Constant*>::const_iterator I =
Eval.getMutatedMemory().begin(), E = Eval.getMutatedMemory().end();
I != E; ++I)
CommitValueTo(I->second, I->first);
for (SmallPtrSet<GlobalVariable*, 8>::const_iterator I =
Eval.getInvariants().begin(), E = Eval.getInvariants().end();
I != E; ++I)
(*I)->setConstant(true);
}
return EvalSuccess;
}
/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
/// Return true if anything changed.
bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
bool MadeChange = false;
if (Ctors.empty()) return false;
// Loop over global ctors, optimizing them when we can.
for (unsigned i = 0; i != Ctors.size(); ++i) {
Function *F = Ctors[i];
// Found a null terminator in the middle of the list, prune off the rest of
// the list.
if (F == 0) {
if (i != Ctors.size()-1) {
Ctors.resize(i+1);
MadeChange = true;
}
break;
}
// We cannot simplify external ctor functions.
if (F->empty()) continue;
// If we can evaluate the ctor at compile time, do.
if (EvaluateStaticConstructor(F, TD, TLI)) {
Ctors.erase(Ctors.begin()+i);
MadeChange = true;
--i;
++NumCtorsEvaluated;
continue;
}
}
if (!MadeChange) return false;
GCL = InstallGlobalCtors(GCL, Ctors);
return true;
}
bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
bool Changed = false;
for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
I != E;) {
Module::alias_iterator J = I++;
// Aliases without names cannot be referenced outside this module.
if (!J->hasName() && !J->isDeclaration())
J->setLinkage(GlobalValue::InternalLinkage);
// If the aliasee may change at link time, nothing can be done - bail out.
if (J->mayBeOverridden())
continue;
Constant *Aliasee = J->getAliasee();
GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
Target->removeDeadConstantUsers();
bool hasOneUse = Target->hasOneUse() && Aliasee->hasOneUse();
// Make all users of the alias use the aliasee instead.
if (!J->use_empty()) {
J->replaceAllUsesWith(Aliasee);
++NumAliasesResolved;
Changed = true;
}
// If the alias is externally visible, we may still be able to simplify it.
if (!J->hasLocalLinkage()) {
// If the aliasee has internal linkage, give it the name and linkage
// of the alias, and delete the alias. This turns:
// define internal ... @f(...)
// @a = alias ... @f
// into:
// define ... @a(...)
if (!Target->hasLocalLinkage())
continue;
// Do not perform the transform if multiple aliases potentially target the
// aliasee. This check also ensures that it is safe to replace the section
// and other attributes of the aliasee with those of the alias.
if (!hasOneUse)
continue;
// Give the aliasee the name, linkage and other attributes of the alias.
Target->takeName(J);
Target->setLinkage(J->getLinkage());
Target->GlobalValue::copyAttributesFrom(J);
}
// Delete the alias.
M.getAliasList().erase(J);
++NumAliasesRemoved;
Changed = true;
}
return Changed;
}
static Function *FindCXAAtExit(Module &M, TargetLibraryInfo *TLI) {
if (!TLI->has(LibFunc::cxa_atexit))
return 0;
Function *Fn = M.getFunction(TLI->getName(LibFunc::cxa_atexit));
if (!Fn)
return 0;
FunctionType *FTy = Fn->getFunctionType();
// Checking that the function has the right return type, the right number of
// parameters and that they all have pointer types should be enough.
if (!FTy->getReturnType()->isIntegerTy() ||
FTy->getNumParams() != 3 ||
!FTy->getParamType(0)->isPointerTy() ||
!FTy->getParamType(1)->isPointerTy() ||
!FTy->getParamType(2)->isPointerTy())
return 0;
return Fn;
}
/// cxxDtorIsEmpty - Returns whether the given function is an empty C++
/// destructor and can therefore be eliminated.
/// Note that we assume that other optimization passes have already simplified
/// the code so we only look for a function with a single basic block, where
/// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and
/// other side-effect free instructions.
static bool cxxDtorIsEmpty(const Function &Fn,
SmallPtrSet<const Function *, 8> &CalledFunctions) {
// FIXME: We could eliminate C++ destructors if they're readonly/readnone and
// nounwind, but that doesn't seem worth doing.
if (Fn.isDeclaration())
return false;
if (++Fn.begin() != Fn.end())
return false;
const BasicBlock &EntryBlock = Fn.getEntryBlock();
for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end();
I != E; ++I) {
if (const CallInst *CI = dyn_cast<CallInst>(I)) {
// Ignore debug intrinsics.
if (isa<DbgInfoIntrinsic>(CI))
continue;
const Function *CalledFn = CI->getCalledFunction();
if (!CalledFn)
return false;
SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions);
// Don't treat recursive functions as empty.
if (!NewCalledFunctions.insert(CalledFn))
return false;
if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions))
return false;
} else if (isa<ReturnInst>(*I))
return true; // We're done.
else if (I->mayHaveSideEffects())
return false; // Destructor with side effects, bail.
}
return false;
}
bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) {
/// Itanium C++ ABI p3.3.5:
///
/// After constructing a global (or local static) object, that will require
/// destruction on exit, a termination function is registered as follows:
///
/// extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
///
/// This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the
/// call f(p) when DSO d is unloaded, before all such termination calls
/// registered before this one. It returns zero if registration is
/// successful, nonzero on failure.
// This pass will look for calls to __cxa_atexit where the function is trivial
// and remove them.
bool Changed = false;
for (Function::use_iterator I = CXAAtExitFn->use_begin(),
E = CXAAtExitFn->use_end(); I != E;) {
// We're only interested in calls. Theoretically, we could handle invoke
// instructions as well, but neither llvm-gcc nor clang generate invokes
// to __cxa_atexit.
CallInst *CI = dyn_cast<CallInst>(*I++);
if (!CI)
continue;
Function *DtorFn =
dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts());
if (!DtorFn)
continue;
SmallPtrSet<const Function *, 8> CalledFunctions;
if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions))
continue;
// Just remove the call.
CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
CI->eraseFromParent();
++NumCXXDtorsRemoved;
Changed |= true;
}
return Changed;
}
bool GlobalOpt::runOnModule(Module &M) {
bool Changed = false;
TD = getAnalysisIfAvailable<TargetData>();
TLI = &getAnalysis<TargetLibraryInfo>();
// Try to find the llvm.globalctors list.
GlobalVariable *GlobalCtors = FindGlobalCtors(M);
Function *CXAAtExitFn = FindCXAAtExit(M, TLI);
bool LocalChange = true;
while (LocalChange) {
LocalChange = false;
// Delete functions that are trivially dead, ccc -> fastcc
LocalChange |= OptimizeFunctions(M);
// Optimize global_ctors list.
if (GlobalCtors)
LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
// Optimize non-address-taken globals.
LocalChange |= OptimizeGlobalVars(M);
// Resolve aliases, when possible.
LocalChange |= OptimizeGlobalAliases(M);
// Try to remove trivial global destructors.
if (CXAAtExitFn)
LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn);
Changed |= LocalChange;
}
// TODO: Move all global ctors functions to the end of the module for code
// layout.
return Changed;
}
|