aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/llvm16/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
blob: cde790cc77fbe4ffa96657ec3493968f11e62b3e (plain) (blame)
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
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
3431
3432
3433
3434
3435
3436
3437
3438
3439
3440
3441
3442
3443
3444
3445
3446
3447
3448
3449
3450
3451
3452
3453
3454
3455
3456
3457
3458
3459
3460
3461
3462
3463
3464
3465
3466
3467
3468
3469
3470
3471
3472
3473
3474
3475
3476
3477
3478
3479
3480
3481
3482
3483
3484
3485
3486
3487
3488
3489
3490
3491
3492
3493
3494
3495
3496
3497
3498
3499
3500
3501
3502
3503
3504
3505
3506
3507
3508
3509
3510
3511
3512
3513
3514
3515
3516
3517
3518
3519
3520
3521
3522
3523
3524
3525
3526
3527
3528
3529
3530
3531
3532
3533
3534
3535
3536
3537
3538
3539
3540
3541
3542
3543
3544
3545
3546
3547
3548
3549
3550
3551
3552
3553
3554
3555
3556
3557
3558
3559
3560
3561
3562
3563
3564
3565
3566
3567
3568
3569
3570
3571
3572
3573
3574
3575
3576
3577
3578
3579
3580
3581
3582
3583
3584
3585
//===- llvm/CodeGen/DwarfDebug.cpp - Dwarf Debug Framework ----------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing dwarf debug info into asm files.
//
//===----------------------------------------------------------------------===//

#include "DwarfDebug.h"
#include "ByteStreamer.h"
#include "DIEHash.h"
#include "DwarfCompileUnit.h"
#include "DwarfExpression.h"
#include "DwarfUnit.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/DIE.h"
#include "llvm/CodeGen/LexicalScopes.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
#include "llvm/DebugInfo/DWARF/DWARFExpression.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/MC/MachineLocation.h"
#include "llvm/MC/SectionKind.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MD5.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include <algorithm>
#include <cstddef>
#include <iterator>
#include <optional>
#include <string>

using namespace llvm;

#define DEBUG_TYPE "dwarfdebug"

STATISTIC(NumCSParams, "Number of dbg call site params created");

static cl::opt<bool> UseDwarfRangesBaseAddressSpecifier(
    "use-dwarf-ranges-base-address-specifier", cl::Hidden,
    cl::desc("Use base address specifiers in debug_ranges"), cl::init(false));

static cl::opt<bool> GenerateARangeSection("generate-arange-section",
                                           cl::Hidden,
                                           cl::desc("Generate dwarf aranges"),
                                           cl::init(false));

static cl::opt<bool>
    GenerateDwarfTypeUnits("generate-type-units", cl::Hidden,
                           cl::desc("Generate DWARF4 type units."),
                           cl::init(false));

static cl::opt<bool> SplitDwarfCrossCuReferences(
    "split-dwarf-cross-cu-references", cl::Hidden,
    cl::desc("Enable cross-cu references in DWO files"), cl::init(false));

enum DefaultOnOff { Default, Enable, Disable };

static cl::opt<DefaultOnOff> UnknownLocations(
    "use-unknown-locations", cl::Hidden,
    cl::desc("Make an absence of debug location information explicit."),
    cl::values(clEnumVal(Default, "At top of block or after label"),
               clEnumVal(Enable, "In all cases"), clEnumVal(Disable, "Never")),
    cl::init(Default));

static cl::opt<AccelTableKind> AccelTables(
    "accel-tables", cl::Hidden, cl::desc("Output dwarf accelerator tables."),
    cl::values(clEnumValN(AccelTableKind::Default, "Default",
                          "Default for platform"),
               clEnumValN(AccelTableKind::None, "Disable", "Disabled."),
               clEnumValN(AccelTableKind::Apple, "Apple", "Apple"),
               clEnumValN(AccelTableKind::Dwarf, "Dwarf", "DWARF")),
    cl::init(AccelTableKind::Default));

static cl::opt<DefaultOnOff>
DwarfInlinedStrings("dwarf-inlined-strings", cl::Hidden,
                 cl::desc("Use inlined strings rather than string section."),
                 cl::values(clEnumVal(Default, "Default for platform"),
                            clEnumVal(Enable, "Enabled"),
                            clEnumVal(Disable, "Disabled")),
                 cl::init(Default));

static cl::opt<bool>
    NoDwarfRangesSection("no-dwarf-ranges-section", cl::Hidden,
                         cl::desc("Disable emission .debug_ranges section."),
                         cl::init(false));

static cl::opt<DefaultOnOff> DwarfSectionsAsReferences(
    "dwarf-sections-as-references", cl::Hidden,
    cl::desc("Use sections+offset as references rather than labels."),
    cl::values(clEnumVal(Default, "Default for platform"),
               clEnumVal(Enable, "Enabled"), clEnumVal(Disable, "Disabled")),
    cl::init(Default));

static cl::opt<bool>
    UseGNUDebugMacro("use-gnu-debug-macro", cl::Hidden,
                     cl::desc("Emit the GNU .debug_macro format with DWARF <5"),
                     cl::init(false));

static cl::opt<DefaultOnOff> DwarfOpConvert(
    "dwarf-op-convert", cl::Hidden,
    cl::desc("Enable use of the DWARFv5 DW_OP_convert operator"),
    cl::values(clEnumVal(Default, "Default for platform"),
               clEnumVal(Enable, "Enabled"), clEnumVal(Disable, "Disabled")),
    cl::init(Default));

enum LinkageNameOption {
  DefaultLinkageNames,
  AllLinkageNames,
  AbstractLinkageNames
};

static cl::opt<LinkageNameOption>
    DwarfLinkageNames("dwarf-linkage-names", cl::Hidden,
                      cl::desc("Which DWARF linkage-name attributes to emit."),
                      cl::values(clEnumValN(DefaultLinkageNames, "Default",
                                            "Default for platform"),
                                 clEnumValN(AllLinkageNames, "All", "All"),
                                 clEnumValN(AbstractLinkageNames, "Abstract",
                                            "Abstract subprograms")),
                      cl::init(DefaultLinkageNames));

static cl::opt<DwarfDebug::MinimizeAddrInV5> MinimizeAddrInV5Option(
    "minimize-addr-in-v5", cl::Hidden,
    cl::desc("Always use DW_AT_ranges in DWARFv5 whenever it could allow more "
             "address pool entry sharing to reduce relocations/object size"),
    cl::values(clEnumValN(DwarfDebug::MinimizeAddrInV5::Default, "Default",
                          "Default address minimization strategy"),
               clEnumValN(DwarfDebug::MinimizeAddrInV5::Ranges, "Ranges",
                          "Use rnglists for contiguous ranges if that allows "
                          "using a pre-existing base address"),
               clEnumValN(DwarfDebug::MinimizeAddrInV5::Expressions,
                          "Expressions",
                          "Use exprloc addrx+offset expressions for any "
                          "address with a prior base address"),
               clEnumValN(DwarfDebug::MinimizeAddrInV5::Form, "Form",
                          "Use addrx+offset extension form for any address "
                          "with a prior base address"),
               clEnumValN(DwarfDebug::MinimizeAddrInV5::Disabled, "Disabled",
                          "Stuff")),
    cl::init(DwarfDebug::MinimizeAddrInV5::Default));

static constexpr unsigned ULEB128PadSize = 4;

void DebugLocDwarfExpression::emitOp(uint8_t Op, const char *Comment) {
  getActiveStreamer().emitInt8(
      Op, Comment ? Twine(Comment) + " " + dwarf::OperationEncodingString(Op)
                  : dwarf::OperationEncodingString(Op));
}

void DebugLocDwarfExpression::emitSigned(int64_t Value) {
  getActiveStreamer().emitSLEB128(Value, Twine(Value));
}

void DebugLocDwarfExpression::emitUnsigned(uint64_t Value) {
  getActiveStreamer().emitULEB128(Value, Twine(Value));
}

void DebugLocDwarfExpression::emitData1(uint8_t Value) {
  getActiveStreamer().emitInt8(Value, Twine(Value));
}

void DebugLocDwarfExpression::emitBaseTypeRef(uint64_t Idx) {
  assert(Idx < (1ULL << (ULEB128PadSize * 7)) && "Idx wont fit");
  getActiveStreamer().emitULEB128(Idx, Twine(Idx), ULEB128PadSize);
}

bool DebugLocDwarfExpression::isFrameRegister(const TargetRegisterInfo &TRI,
                                              llvm::Register MachineReg) {
  // This information is not available while emitting .debug_loc entries.
  return false;
}

void DebugLocDwarfExpression::enableTemporaryBuffer() {
  assert(!IsBuffering && "Already buffering?");
  if (!TmpBuf)
    TmpBuf = std::make_unique<TempBuffer>(OutBS.GenerateComments);
  IsBuffering = true;
}

void DebugLocDwarfExpression::disableTemporaryBuffer() { IsBuffering = false; }

unsigned DebugLocDwarfExpression::getTemporaryBufferSize() {
  return TmpBuf ? TmpBuf->Bytes.size() : 0;
}

void DebugLocDwarfExpression::commitTemporaryBuffer() {
  if (!TmpBuf)
    return;
  for (auto Byte : enumerate(TmpBuf->Bytes)) {
    const char *Comment = (Byte.index() < TmpBuf->Comments.size())
                              ? TmpBuf->Comments[Byte.index()].c_str()
                              : "";
    OutBS.emitInt8(Byte.value(), Comment);
  }
  TmpBuf->Bytes.clear();
  TmpBuf->Comments.clear();
}

const DIType *DbgVariable::getType() const {
  return getVariable()->getType();
}

/// Get .debug_loc entry for the instruction range starting at MI.
static DbgValueLoc getDebugLocValue(const MachineInstr *MI) {
  const DIExpression *Expr = MI->getDebugExpression();
  const bool IsVariadic = MI->isDebugValueList();
  assert(MI->getNumOperands() >= 3);
  SmallVector<DbgValueLocEntry, 4> DbgValueLocEntries;
  for (const MachineOperand &Op : MI->debug_operands()) {
    if (Op.isReg()) {
      MachineLocation MLoc(Op.getReg(),
                           MI->isNonListDebugValue() && MI->isDebugOffsetImm());
      DbgValueLocEntries.push_back(DbgValueLocEntry(MLoc));
    } else if (Op.isTargetIndex()) {
      DbgValueLocEntries.push_back(
          DbgValueLocEntry(TargetIndexLocation(Op.getIndex(), Op.getOffset())));
    } else if (Op.isImm())
      DbgValueLocEntries.push_back(DbgValueLocEntry(Op.getImm()));
    else if (Op.isFPImm())
      DbgValueLocEntries.push_back(DbgValueLocEntry(Op.getFPImm()));
    else if (Op.isCImm())
      DbgValueLocEntries.push_back(DbgValueLocEntry(Op.getCImm()));
    else
      llvm_unreachable("Unexpected debug operand in DBG_VALUE* instruction!");
  }
  return DbgValueLoc(Expr, DbgValueLocEntries, IsVariadic);
}

void DbgVariable::initializeDbgValue(const MachineInstr *DbgValue) {
  assert(FrameIndexExprs.empty() && "Already initialized?");
  assert(!ValueLoc.get() && "Already initialized?");

  assert(getVariable() == DbgValue->getDebugVariable() && "Wrong variable");
  assert(getInlinedAt() == DbgValue->getDebugLoc()->getInlinedAt() &&
         "Wrong inlined-at");

  ValueLoc = std::make_unique<DbgValueLoc>(getDebugLocValue(DbgValue));
  if (auto *E = DbgValue->getDebugExpression())
    if (E->getNumElements())
      FrameIndexExprs.push_back({0, E});
}

ArrayRef<DbgVariable::FrameIndexExpr> DbgVariable::getFrameIndexExprs() const {
  if (FrameIndexExprs.size() == 1)
    return FrameIndexExprs;

  assert(llvm::all_of(FrameIndexExprs,
                      [](const FrameIndexExpr &A) {
                        return A.Expr->isFragment();
                      }) &&
         "multiple FI expressions without DW_OP_LLVM_fragment");
  llvm::sort(FrameIndexExprs,
             [](const FrameIndexExpr &A, const FrameIndexExpr &B) -> bool {
               return A.Expr->getFragmentInfo()->OffsetInBits <
                      B.Expr->getFragmentInfo()->OffsetInBits;
             });

  return FrameIndexExprs;
}

void DbgVariable::addMMIEntry(const DbgVariable &V) {
  assert(DebugLocListIndex == ~0U && !ValueLoc.get() && "not an MMI entry");
  assert(V.DebugLocListIndex == ~0U && !V.ValueLoc.get() && "not an MMI entry");
  assert(V.getVariable() == getVariable() && "conflicting variable");
  assert(V.getInlinedAt() == getInlinedAt() && "conflicting inlined-at location");

  assert(!FrameIndexExprs.empty() && "Expected an MMI entry");
  assert(!V.FrameIndexExprs.empty() && "Expected an MMI entry");

  // FIXME: This logic should not be necessary anymore, as we now have proper
  // deduplication. However, without it, we currently run into the assertion
  // below, which means that we are likely dealing with broken input, i.e. two
  // non-fragment entries for the same variable at different frame indices.
  if (FrameIndexExprs.size()) {
    auto *Expr = FrameIndexExprs.back().Expr;
    if (!Expr || !Expr->isFragment())
      return;
  }

  for (const auto &FIE : V.FrameIndexExprs)
    // Ignore duplicate entries.
    if (llvm::none_of(FrameIndexExprs, [&](const FrameIndexExpr &Other) {
          return FIE.FI == Other.FI && FIE.Expr == Other.Expr;
        }))
      FrameIndexExprs.push_back(FIE);

  assert((FrameIndexExprs.size() == 1 ||
          llvm::all_of(FrameIndexExprs,
                       [](FrameIndexExpr &FIE) {
                         return FIE.Expr && FIE.Expr->isFragment();
                       })) &&
         "conflicting locations for variable");
}

static AccelTableKind computeAccelTableKind(unsigned DwarfVersion,
                                            bool GenerateTypeUnits,
                                            DebuggerKind Tuning,
                                            const Triple &TT) {
  // Honor an explicit request.
  if (AccelTables != AccelTableKind::Default)
    return AccelTables;

  // Accelerator tables with type units are currently not supported.
  if (GenerateTypeUnits)
    return AccelTableKind::None;

  // Accelerator tables get emitted if targetting DWARF v5 or LLDB.  DWARF v5
  // always implies debug_names. For lower standard versions we use apple
  // accelerator tables on apple platforms and debug_names elsewhere.
  if (DwarfVersion >= 5)
    return AccelTableKind::Dwarf;
  if (Tuning == DebuggerKind::LLDB)
    return TT.isOSBinFormatMachO() ? AccelTableKind::Apple
                                   : AccelTableKind::Dwarf;
  return AccelTableKind::None;
}

DwarfDebug::DwarfDebug(AsmPrinter *A)
    : DebugHandlerBase(A), DebugLocs(A->OutStreamer->isVerboseAsm()),
      InfoHolder(A, "info_string", DIEValueAllocator),
      SkeletonHolder(A, "skel_string", DIEValueAllocator),
      IsDarwin(A->TM.getTargetTriple().isOSDarwin()) {
  const Triple &TT = Asm->TM.getTargetTriple();

  // Make sure we know our "debugger tuning".  The target option takes
  // precedence; fall back to triple-based defaults.
  if (Asm->TM.Options.DebuggerTuning != DebuggerKind::Default)
    DebuggerTuning = Asm->TM.Options.DebuggerTuning;
  else if (IsDarwin)
    DebuggerTuning = DebuggerKind::LLDB;
  else if (TT.isPS())
    DebuggerTuning = DebuggerKind::SCE;
  else if (TT.isOSAIX())
    DebuggerTuning = DebuggerKind::DBX;
  else
    DebuggerTuning = DebuggerKind::GDB;

  if (DwarfInlinedStrings == Default)
    UseInlineStrings = TT.isNVPTX() || tuneForDBX();
  else
    UseInlineStrings = DwarfInlinedStrings == Enable;

  UseLocSection = !TT.isNVPTX();

  HasAppleExtensionAttributes = tuneForLLDB();

  // Handle split DWARF.
  HasSplitDwarf = !Asm->TM.Options.MCOptions.SplitDwarfFile.empty();

  // SCE defaults to linkage names only for abstract subprograms.
  if (DwarfLinkageNames == DefaultLinkageNames)
    UseAllLinkageNames = !tuneForSCE();
  else
    UseAllLinkageNames = DwarfLinkageNames == AllLinkageNames;

  unsigned DwarfVersionNumber = Asm->TM.Options.MCOptions.DwarfVersion;
  unsigned DwarfVersion = DwarfVersionNumber ? DwarfVersionNumber
                                    : MMI->getModule()->getDwarfVersion();
  // Use dwarf 4 by default if nothing is requested. For NVPTX, use dwarf 2.
  DwarfVersion =
      TT.isNVPTX() ? 2 : (DwarfVersion ? DwarfVersion : dwarf::DWARF_VERSION);

  bool Dwarf64 = DwarfVersion >= 3 && // DWARF64 was introduced in DWARFv3.
                 TT.isArch64Bit();    // DWARF64 requires 64-bit relocations.

  // Support DWARF64
  // 1: For ELF when requested.
  // 2: For XCOFF64: the AIX assembler will fill in debug section lengths
  //    according to the DWARF64 format for 64-bit assembly, so we must use
  //    DWARF64 in the compiler too for 64-bit mode.
  Dwarf64 &=
      ((Asm->TM.Options.MCOptions.Dwarf64 || MMI->getModule()->isDwarf64()) &&
       TT.isOSBinFormatELF()) ||
      TT.isOSBinFormatXCOFF();

  if (!Dwarf64 && TT.isArch64Bit() && TT.isOSBinFormatXCOFF())
    report_fatal_error("XCOFF requires DWARF64 for 64-bit mode!");

  UseRangesSection = !NoDwarfRangesSection && !TT.isNVPTX();

  // Use sections as references. Force for NVPTX.
  if (DwarfSectionsAsReferences == Default)
    UseSectionsAsReferences = TT.isNVPTX();
  else
    UseSectionsAsReferences = DwarfSectionsAsReferences == Enable;

  // Don't generate type units for unsupported object file formats.
  GenerateTypeUnits = (A->TM.getTargetTriple().isOSBinFormatELF() ||
                       A->TM.getTargetTriple().isOSBinFormatWasm()) &&
                      GenerateDwarfTypeUnits;

  TheAccelTableKind = computeAccelTableKind(
      DwarfVersion, GenerateTypeUnits, DebuggerTuning, A->TM.getTargetTriple());

  // Work around a GDB bug. GDB doesn't support the standard opcode;
  // SCE doesn't support GNU's; LLDB prefers the standard opcode, which
  // is defined as of DWARF 3.
  // See GDB bug 11616 - DW_OP_form_tls_address is unimplemented
  // https://sourceware.org/bugzilla/show_bug.cgi?id=11616
  UseGNUTLSOpcode = tuneForGDB() || DwarfVersion < 3;

  UseDWARF2Bitfields = DwarfVersion < 4;

  // The DWARF v5 string offsets table has - possibly shared - contributions
  // from each compile and type unit each preceded by a header. The string
  // offsets table used by the pre-DWARF v5 split-DWARF implementation uses
  // a monolithic string offsets table without any header.
  UseSegmentedStringOffsetsTable = DwarfVersion >= 5;

  // Emit call-site-param debug info for GDB and LLDB, if the target supports
  // the debug entry values feature. It can also be enabled explicitly.
  EmitDebugEntryValues = Asm->TM.Options.ShouldEmitDebugEntryValues();

  // It is unclear if the GCC .debug_macro extension is well-specified
  // for split DWARF. For now, do not allow LLVM to emit it.
  UseDebugMacroSection =
      DwarfVersion >= 5 || (UseGNUDebugMacro && !useSplitDwarf());
  if (DwarfOpConvert == Default)
    EnableOpConvert = !((tuneForGDB() && useSplitDwarf()) || (tuneForLLDB() && !TT.isOSBinFormatMachO()));
  else
    EnableOpConvert = (DwarfOpConvert == Enable);

  // Split DWARF would benefit object size significantly by trading reductions
  // in address pool usage for slightly increased range list encodings.
  if (DwarfVersion >= 5) {
    MinimizeAddr = MinimizeAddrInV5Option;
    // FIXME: In the future, enable this by default for Split DWARF where the
    // tradeoff is more pronounced due to being able to offload the range
    // lists to the dwo file and shrink object files/reduce relocations there.
    if (MinimizeAddr == MinimizeAddrInV5::Default)
      MinimizeAddr = MinimizeAddrInV5::Disabled;
  }

  Asm->OutStreamer->getContext().setDwarfVersion(DwarfVersion);
  Asm->OutStreamer->getContext().setDwarfFormat(Dwarf64 ? dwarf::DWARF64
                                                        : dwarf::DWARF32);
}

// Define out of line so we don't have to include DwarfUnit.h in DwarfDebug.h.
DwarfDebug::~DwarfDebug() = default;

static bool isObjCClass(StringRef Name) {
  return Name.startswith("+") || Name.startswith("-");
}

static bool hasObjCCategory(StringRef Name) {
  if (!isObjCClass(Name))
    return false;

  return Name.contains(") ");
}

static void getObjCClassCategory(StringRef In, StringRef &Class,
                                 StringRef &Category) {
  if (!hasObjCCategory(In)) {
    Class = In.slice(In.find('[') + 1, In.find(' '));
    Category = "";
    return;
  }

  Class = In.slice(In.find('[') + 1, In.find('('));
  Category = In.slice(In.find('[') + 1, In.find(' '));
}

static StringRef getObjCMethodName(StringRef In) {
  return In.slice(In.find(' ') + 1, In.find(']'));
}

// Add the various names to the Dwarf accelerator table names.
void DwarfDebug::addSubprogramNames(const DICompileUnit &CU,
                                    const DISubprogram *SP, DIE &Die) {
  if (getAccelTableKind() != AccelTableKind::Apple &&
      CU.getNameTableKind() == DICompileUnit::DebugNameTableKind::None)
    return;

  if (!SP->isDefinition())
    return;

  if (SP->getName() != "")
    addAccelName(CU, SP->getName(), Die);

  // If the linkage name is different than the name, go ahead and output that as
  // well into the name table. Only do that if we are going to actually emit
  // that name.
  if (SP->getLinkageName() != "" && SP->getName() != SP->getLinkageName() &&
      (useAllLinkageNames() || InfoHolder.getAbstractSPDies().lookup(SP)))
    addAccelName(CU, SP->getLinkageName(), Die);

  // If this is an Objective-C selector name add it to the ObjC accelerator
  // too.
  if (isObjCClass(SP->getName())) {
    StringRef Class, Category;
    getObjCClassCategory(SP->getName(), Class, Category);
    addAccelObjC(CU, Class, Die);
    if (Category != "")
      addAccelObjC(CU, Category, Die);
    // Also add the base method name to the name table.
    addAccelName(CU, getObjCMethodName(SP->getName()), Die);
  }
}

/// Check whether we should create a DIE for the given Scope, return true
/// if we don't create a DIE (the corresponding DIE is null).
bool DwarfDebug::isLexicalScopeDIENull(LexicalScope *Scope) {
  if (Scope->isAbstractScope())
    return false;

  // We don't create a DIE if there is no Range.
  const SmallVectorImpl<InsnRange> &Ranges = Scope->getRanges();
  if (Ranges.empty())
    return true;

  if (Ranges.size() > 1)
    return false;

  // We don't create a DIE if we have a single Range and the end label
  // is null.
  return !getLabelAfterInsn(Ranges.front().second);
}

template <typename Func> static void forBothCUs(DwarfCompileUnit &CU, Func F) {
  F(CU);
  if (auto *SkelCU = CU.getSkeleton())
    if (CU.getCUNode()->getSplitDebugInlining())
      F(*SkelCU);
}

bool DwarfDebug::shareAcrossDWOCUs() const {
  return SplitDwarfCrossCuReferences;
}

void DwarfDebug::constructAbstractSubprogramScopeDIE(DwarfCompileUnit &SrcCU,
                                                     LexicalScope *Scope) {
  assert(Scope && Scope->getScopeNode());
  assert(Scope->isAbstractScope());
  assert(!Scope->getInlinedAt());

  auto *SP = cast<DISubprogram>(Scope->getScopeNode());

  // Find the subprogram's DwarfCompileUnit in the SPMap in case the subprogram
  // was inlined from another compile unit.
  if (useSplitDwarf() && !shareAcrossDWOCUs() && !SP->getUnit()->getSplitDebugInlining())
    // Avoid building the original CU if it won't be used
    SrcCU.constructAbstractSubprogramScopeDIE(Scope);
  else {
    auto &CU = getOrCreateDwarfCompileUnit(SP->getUnit());
    if (auto *SkelCU = CU.getSkeleton()) {
      (shareAcrossDWOCUs() ? CU : SrcCU)
          .constructAbstractSubprogramScopeDIE(Scope);
      if (CU.getCUNode()->getSplitDebugInlining())
        SkelCU->constructAbstractSubprogramScopeDIE(Scope);
    } else
      CU.constructAbstractSubprogramScopeDIE(Scope);
  }
}

/// Represents a parameter whose call site value can be described by applying a
/// debug expression to a register in the forwarded register worklist.
struct FwdRegParamInfo {
  /// The described parameter register.
  unsigned ParamReg;

  /// Debug expression that has been built up when walking through the
  /// instruction chain that produces the parameter's value.
  const DIExpression *Expr;
};

/// Register worklist for finding call site values.
using FwdRegWorklist = MapVector<unsigned, SmallVector<FwdRegParamInfo, 2>>;
/// Container for the set of registers known to be clobbered on the path to a
/// call site.
using ClobberedRegSet = SmallSet<Register, 16>;

/// Append the expression \p Addition to \p Original and return the result.
static const DIExpression *combineDIExpressions(const DIExpression *Original,
                                                const DIExpression *Addition) {
  std::vector<uint64_t> Elts = Addition->getElements().vec();
  // Avoid multiple DW_OP_stack_values.
  if (Original->isImplicit() && Addition->isImplicit())
    erase_value(Elts, dwarf::DW_OP_stack_value);
  const DIExpression *CombinedExpr =
      (Elts.size() > 0) ? DIExpression::append(Original, Elts) : Original;
  return CombinedExpr;
}

/// Emit call site parameter entries that are described by the given value and
/// debug expression.
template <typename ValT>
static void finishCallSiteParams(ValT Val, const DIExpression *Expr,
                                 ArrayRef<FwdRegParamInfo> DescribedParams,
                                 ParamSet &Params) {
  for (auto Param : DescribedParams) {
    bool ShouldCombineExpressions = Expr && Param.Expr->getNumElements() > 0;

    // TODO: Entry value operations can currently not be combined with any
    // other expressions, so we can't emit call site entries in those cases.
    if (ShouldCombineExpressions && Expr->isEntryValue())
      continue;

    // If a parameter's call site value is produced by a chain of
    // instructions we may have already created an expression for the
    // parameter when walking through the instructions. Append that to the
    // base expression.
    const DIExpression *CombinedExpr =
        ShouldCombineExpressions ? combineDIExpressions(Expr, Param.Expr)
                                 : Expr;
    assert((!CombinedExpr || CombinedExpr->isValid()) &&
           "Combined debug expression is invalid");

    DbgValueLoc DbgLocVal(CombinedExpr, DbgValueLocEntry(Val));
    DbgCallSiteParam CSParm(Param.ParamReg, DbgLocVal);
    Params.push_back(CSParm);
    ++NumCSParams;
  }
}

/// Add \p Reg to the worklist, if it's not already present, and mark that the
/// given parameter registers' values can (potentially) be described using
/// that register and an debug expression.
static void addToFwdRegWorklist(FwdRegWorklist &Worklist, unsigned Reg,
                                const DIExpression *Expr,
                                ArrayRef<FwdRegParamInfo> ParamsToAdd) {
  auto I = Worklist.insert({Reg, {}});
  auto &ParamsForFwdReg = I.first->second;
  for (auto Param : ParamsToAdd) {
    assert(none_of(ParamsForFwdReg,
                   [Param](const FwdRegParamInfo &D) {
                     return D.ParamReg == Param.ParamReg;
                   }) &&
           "Same parameter described twice by forwarding reg");

    // If a parameter's call site value is produced by a chain of
    // instructions we may have already created an expression for the
    // parameter when walking through the instructions. Append that to the
    // new expression.
    const DIExpression *CombinedExpr = combineDIExpressions(Expr, Param.Expr);
    ParamsForFwdReg.push_back({Param.ParamReg, CombinedExpr});
  }
}

/// Interpret values loaded into registers by \p CurMI.
static void interpretValues(const MachineInstr *CurMI,
                            FwdRegWorklist &ForwardedRegWorklist,
                            ParamSet &Params,
                            ClobberedRegSet &ClobberedRegUnits) {

  const MachineFunction *MF = CurMI->getMF();
  const DIExpression *EmptyExpr =
      DIExpression::get(MF->getFunction().getContext(), {});
  const auto &TRI = *MF->getSubtarget().getRegisterInfo();
  const auto &TII = *MF->getSubtarget().getInstrInfo();
  const auto &TLI = *MF->getSubtarget().getTargetLowering();

  // If an instruction defines more than one item in the worklist, we may run
  // into situations where a worklist register's value is (potentially)
  // described by the previous value of another register that is also defined
  // by that instruction.
  //
  // This can for example occur in cases like this:
  //
  //   $r1 = mov 123
  //   $r0, $r1 = mvrr $r1, 456
  //   call @foo, $r0, $r1
  //
  // When describing $r1's value for the mvrr instruction, we need to make sure
  // that we don't finalize an entry value for $r0, as that is dependent on the
  // previous value of $r1 (123 rather than 456).
  //
  // In order to not have to distinguish between those cases when finalizing
  // entry values, we simply postpone adding new parameter registers to the
  // worklist, by first keeping them in this temporary container until the
  // instruction has been handled.
  FwdRegWorklist TmpWorklistItems;

  // If the MI is an instruction defining one or more parameters' forwarding
  // registers, add those defines.
  ClobberedRegSet NewClobberedRegUnits;
  auto getForwardingRegsDefinedByMI = [&](const MachineInstr &MI,
                                          SmallSetVector<unsigned, 4> &Defs) {
    if (MI.isDebugInstr())
      return;

    for (const MachineOperand &MO : MI.operands()) {
      if (MO.isReg() && MO.isDef() && MO.getReg().isPhysical()) {
        for (auto &FwdReg : ForwardedRegWorklist)
          if (TRI.regsOverlap(FwdReg.first, MO.getReg()))
            Defs.insert(FwdReg.first);
        for (MCRegUnitIterator Units(MO.getReg(), &TRI); Units.isValid(); ++Units)
          NewClobberedRegUnits.insert(*Units);
      }
    }
  };

  // Set of worklist registers that are defined by this instruction.
  SmallSetVector<unsigned, 4> FwdRegDefs;

  getForwardingRegsDefinedByMI(*CurMI, FwdRegDefs);
  if (FwdRegDefs.empty()) {
    // Any definitions by this instruction will clobber earlier reg movements.
    ClobberedRegUnits.insert(NewClobberedRegUnits.begin(),
                             NewClobberedRegUnits.end());
    return;
  }

  // It's possible that we find a copy from a non-volatile register to the param
  // register, which is clobbered in the meantime. Test for clobbered reg unit
  // overlaps before completing.
  auto IsRegClobberedInMeantime = [&](Register Reg) -> bool {
    for (auto &RegUnit : ClobberedRegUnits)
      if (TRI.hasRegUnit(Reg, RegUnit))
        return true;
    return false;
  };

  for (auto ParamFwdReg : FwdRegDefs) {
    if (auto ParamValue = TII.describeLoadedValue(*CurMI, ParamFwdReg)) {
      if (ParamValue->first.isImm()) {
        int64_t Val = ParamValue->first.getImm();
        finishCallSiteParams(Val, ParamValue->second,
                             ForwardedRegWorklist[ParamFwdReg], Params);
      } else if (ParamValue->first.isReg()) {
        Register RegLoc = ParamValue->first.getReg();
        Register SP = TLI.getStackPointerRegisterToSaveRestore();
        Register FP = TRI.getFrameRegister(*MF);
        bool IsSPorFP = (RegLoc == SP) || (RegLoc == FP);
        if (!IsRegClobberedInMeantime(RegLoc) &&
            (TRI.isCalleeSavedPhysReg(RegLoc, *MF) || IsSPorFP)) {
          MachineLocation MLoc(RegLoc, /*Indirect=*/IsSPorFP);
          finishCallSiteParams(MLoc, ParamValue->second,
                               ForwardedRegWorklist[ParamFwdReg], Params);
        } else {
          // ParamFwdReg was described by the non-callee saved register
          // RegLoc. Mark that the call site values for the parameters are
          // dependent on that register instead of ParamFwdReg. Since RegLoc
          // may be a register that will be handled in this iteration, we
          // postpone adding the items to the worklist, and instead keep them
          // in a temporary container.
          addToFwdRegWorklist(TmpWorklistItems, RegLoc, ParamValue->second,
                              ForwardedRegWorklist[ParamFwdReg]);
        }
      }
    }
  }

  // Remove all registers that this instruction defines from the worklist.
  for (auto ParamFwdReg : FwdRegDefs)
    ForwardedRegWorklist.erase(ParamFwdReg);

  // Any definitions by this instruction will clobber earlier reg movements.
  ClobberedRegUnits.insert(NewClobberedRegUnits.begin(),
                           NewClobberedRegUnits.end());

  // Now that we are done handling this instruction, add items from the
  // temporary worklist to the real one.
  for (auto &New : TmpWorklistItems)
    addToFwdRegWorklist(ForwardedRegWorklist, New.first, EmptyExpr, New.second);
  TmpWorklistItems.clear();
}

static bool interpretNextInstr(const MachineInstr *CurMI,
                               FwdRegWorklist &ForwardedRegWorklist,
                               ParamSet &Params,
                               ClobberedRegSet &ClobberedRegUnits) {
  // Skip bundle headers.
  if (CurMI->isBundle())
    return true;

  // If the next instruction is a call we can not interpret parameter's
  // forwarding registers or we finished the interpretation of all
  // parameters.
  if (CurMI->isCall())
    return false;

  if (ForwardedRegWorklist.empty())
    return false;

  // Avoid NOP description.
  if (CurMI->getNumOperands() == 0)
    return true;

  interpretValues(CurMI, ForwardedRegWorklist, Params, ClobberedRegUnits);

  return true;
}

/// Try to interpret values loaded into registers that forward parameters
/// for \p CallMI. Store parameters with interpreted value into \p Params.
static void collectCallSiteParameters(const MachineInstr *CallMI,
                                      ParamSet &Params) {
  const MachineFunction *MF = CallMI->getMF();
  const auto &CalleesMap = MF->getCallSitesInfo();
  auto CallFwdRegsInfo = CalleesMap.find(CallMI);

  // There is no information for the call instruction.
  if (CallFwdRegsInfo == CalleesMap.end())
    return;

  const MachineBasicBlock *MBB = CallMI->getParent();

  // Skip the call instruction.
  auto I = std::next(CallMI->getReverseIterator());

  FwdRegWorklist ForwardedRegWorklist;

  const DIExpression *EmptyExpr =
      DIExpression::get(MF->getFunction().getContext(), {});

  // Add all the forwarding registers into the ForwardedRegWorklist.
  for (const auto &ArgReg : CallFwdRegsInfo->second) {
    bool InsertedReg =
        ForwardedRegWorklist.insert({ArgReg.Reg, {{ArgReg.Reg, EmptyExpr}}})
            .second;
    assert(InsertedReg && "Single register used to forward two arguments?");
    (void)InsertedReg;
  }

  // Do not emit CSInfo for undef forwarding registers.
  for (const auto &MO : CallMI->uses())
    if (MO.isReg() && MO.isUndef())
      ForwardedRegWorklist.erase(MO.getReg());

  // We erase, from the ForwardedRegWorklist, those forwarding registers for
  // which we successfully describe a loaded value (by using
  // the describeLoadedValue()). For those remaining arguments in the working
  // list, for which we do not describe a loaded value by
  // the describeLoadedValue(), we try to generate an entry value expression
  // for their call site value description, if the call is within the entry MBB.
  // TODO: Handle situations when call site parameter value can be described
  // as the entry value within basic blocks other than the first one.
  bool ShouldTryEmitEntryVals = MBB->getIterator() == MF->begin();

  // Search for a loading value in forwarding registers inside call delay slot.
  ClobberedRegSet ClobberedRegUnits;
  if (CallMI->hasDelaySlot()) {
    auto Suc = std::next(CallMI->getIterator());
    // Only one-instruction delay slot is supported.
    auto BundleEnd = llvm::getBundleEnd(CallMI->getIterator());
    (void)BundleEnd;
    assert(std::next(Suc) == BundleEnd &&
           "More than one instruction in call delay slot");
    // Try to interpret value loaded by instruction.
    if (!interpretNextInstr(&*Suc, ForwardedRegWorklist, Params, ClobberedRegUnits))
      return;
  }

  // Search for a loading value in forwarding registers.
  for (; I != MBB->rend(); ++I) {
    // Try to interpret values loaded by instruction.
    if (!interpretNextInstr(&*I, ForwardedRegWorklist, Params, ClobberedRegUnits))
      return;
  }

  // Emit the call site parameter's value as an entry value.
  if (ShouldTryEmitEntryVals) {
    // Create an expression where the register's entry value is used.
    DIExpression *EntryExpr = DIExpression::get(
        MF->getFunction().getContext(), {dwarf::DW_OP_LLVM_entry_value, 1});
    for (auto &RegEntry : ForwardedRegWorklist) {
      MachineLocation MLoc(RegEntry.first);
      finishCallSiteParams(MLoc, EntryExpr, RegEntry.second, Params);
    }
  }
}

void DwarfDebug::constructCallSiteEntryDIEs(const DISubprogram &SP,
                                            DwarfCompileUnit &CU, DIE &ScopeDIE,
                                            const MachineFunction &MF) {
  // Add a call site-related attribute (DWARF5, Sec. 3.3.1.3). Do this only if
  // the subprogram is required to have one.
  if (!SP.areAllCallsDescribed() || !SP.isDefinition())
    return;

  // Use DW_AT_call_all_calls to express that call site entries are present
  // for both tail and non-tail calls. Don't use DW_AT_call_all_source_calls
  // because one of its requirements is not met: call site entries for
  // optimized-out calls are elided.
  CU.addFlag(ScopeDIE, CU.getDwarf5OrGNUAttr(dwarf::DW_AT_call_all_calls));

  const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
  assert(TII && "TargetInstrInfo not found: cannot label tail calls");

  // Delay slot support check.
  auto delaySlotSupported = [&](const MachineInstr &MI) {
    if (!MI.isBundledWithSucc())
      return false;
    auto Suc = std::next(MI.getIterator());
    auto CallInstrBundle = getBundleStart(MI.getIterator());
    (void)CallInstrBundle;
    auto DelaySlotBundle = getBundleStart(Suc);
    (void)DelaySlotBundle;
    // Ensure that label after call is following delay slot instruction.
    // Ex. CALL_INSTRUCTION {
    //       DELAY_SLOT_INSTRUCTION }
    //      LABEL_AFTER_CALL
    assert(getLabelAfterInsn(&*CallInstrBundle) ==
               getLabelAfterInsn(&*DelaySlotBundle) &&
           "Call and its successor instruction don't have same label after.");
    return true;
  };

  // Emit call site entries for each call or tail call in the function.
  for (const MachineBasicBlock &MBB : MF) {
    for (const MachineInstr &MI : MBB.instrs()) {
      // Bundles with call in them will pass the isCall() test below but do not
      // have callee operand information so skip them here. Iterator will
      // eventually reach the call MI.
      if (MI.isBundle())
        continue;

      // Skip instructions which aren't calls. Both calls and tail-calling jump
      // instructions (e.g TAILJMPd64) are classified correctly here.
      if (!MI.isCandidateForCallSiteEntry())
        continue;

      // Skip instructions marked as frame setup, as they are not interesting to
      // the user.
      if (MI.getFlag(MachineInstr::FrameSetup))
        continue;

      // Check if delay slot support is enabled.
      if (MI.hasDelaySlot() && !delaySlotSupported(*&MI))
        return;

      // If this is a direct call, find the callee's subprogram.
      // In the case of an indirect call find the register that holds
      // the callee.
      const MachineOperand &CalleeOp = TII->getCalleeOperand(MI);
      if (!CalleeOp.isGlobal() &&
          (!CalleeOp.isReg() || !CalleeOp.getReg().isPhysical()))
        continue;

      unsigned CallReg = 0;
      const DISubprogram *CalleeSP = nullptr;
      const Function *CalleeDecl = nullptr;
      if (CalleeOp.isReg()) {
        CallReg = CalleeOp.getReg();
        if (!CallReg)
          continue;
      } else {
        CalleeDecl = dyn_cast<Function>(CalleeOp.getGlobal());
        if (!CalleeDecl || !CalleeDecl->getSubprogram())
          continue;
        CalleeSP = CalleeDecl->getSubprogram();
      }

      // TODO: Omit call site entries for runtime calls (objc_msgSend, etc).

      bool IsTail = TII->isTailCall(MI);

      // If MI is in a bundle, the label was created after the bundle since
      // EmitFunctionBody iterates over top-level MIs. Get that top-level MI
      // to search for that label below.
      const MachineInstr *TopLevelCallMI =
          MI.isInsideBundle() ? &*getBundleStart(MI.getIterator()) : &MI;

      // For non-tail calls, the return PC is needed to disambiguate paths in
      // the call graph which could lead to some target function. For tail
      // calls, no return PC information is needed, unless tuning for GDB in
      // DWARF4 mode in which case we fake a return PC for compatibility.
      const MCSymbol *PCAddr =
          (!IsTail || CU.useGNUAnalogForDwarf5Feature())
              ? const_cast<MCSymbol *>(getLabelAfterInsn(TopLevelCallMI))
              : nullptr;

      // For tail calls, it's necessary to record the address of the branch
      // instruction so that the debugger can show where the tail call occurred.
      const MCSymbol *CallAddr =
          IsTail ? getLabelBeforeInsn(TopLevelCallMI) : nullptr;

      assert((IsTail || PCAddr) && "Non-tail call without return PC");

      LLVM_DEBUG(dbgs() << "CallSiteEntry: " << MF.getName() << " -> "
                        << (CalleeDecl ? CalleeDecl->getName()
                                       : StringRef(MF.getSubtarget()
                                                       .getRegisterInfo()
                                                       ->getName(CallReg)))
                        << (IsTail ? " [IsTail]" : "") << "\n");

      DIE &CallSiteDIE = CU.constructCallSiteEntryDIE(
          ScopeDIE, CalleeSP, IsTail, PCAddr, CallAddr, CallReg);

      // Optionally emit call-site-param debug info.
      if (emitDebugEntryValues()) {
        ParamSet Params;
        // Try to interpret values of call site parameters.
        collectCallSiteParameters(&MI, Params);
        CU.constructCallSiteParmEntryDIEs(CallSiteDIE, Params);
      }
    }
  }
}

void DwarfDebug::addGnuPubAttributes(DwarfCompileUnit &U, DIE &D) const {
  if (!U.hasDwarfPubSections())
    return;

  U.addFlag(D, dwarf::DW_AT_GNU_pubnames);
}

void DwarfDebug::finishUnitAttributes(const DICompileUnit *DIUnit,
                                      DwarfCompileUnit &NewCU) {
  DIE &Die = NewCU.getUnitDie();
  StringRef FN = DIUnit->getFilename();

  StringRef Producer = DIUnit->getProducer();
  StringRef Flags = DIUnit->getFlags();
  if (!Flags.empty() && !useAppleExtensionAttributes()) {
    std::string ProducerWithFlags = Producer.str() + " " + Flags.str();
    NewCU.addString(Die, dwarf::DW_AT_producer, ProducerWithFlags);
  } else
    NewCU.addString(Die, dwarf::DW_AT_producer, Producer);

  NewCU.addUInt(Die, dwarf::DW_AT_language, dwarf::DW_FORM_data2,
                DIUnit->getSourceLanguage());
  NewCU.addString(Die, dwarf::DW_AT_name, FN);
  StringRef SysRoot = DIUnit->getSysRoot();
  if (!SysRoot.empty())
    NewCU.addString(Die, dwarf::DW_AT_LLVM_sysroot, SysRoot);
  StringRef SDK = DIUnit->getSDK();
  if (!SDK.empty())
    NewCU.addString(Die, dwarf::DW_AT_APPLE_sdk, SDK);

  // Add DW_str_offsets_base to the unit DIE, except for split units.
  if (useSegmentedStringOffsetsTable() && !useSplitDwarf())
    NewCU.addStringOffsetsStart();

  if (!useSplitDwarf()) {
    NewCU.initStmtList();

    // If we're using split dwarf the compilation dir is going to be in the
    // skeleton CU and so we don't need to duplicate it here.
    if (!CompilationDir.empty())
      NewCU.addString(Die, dwarf::DW_AT_comp_dir, CompilationDir);
    addGnuPubAttributes(NewCU, Die);
  }

  if (useAppleExtensionAttributes()) {
    if (DIUnit->isOptimized())
      NewCU.addFlag(Die, dwarf::DW_AT_APPLE_optimized);

    StringRef Flags = DIUnit->getFlags();
    if (!Flags.empty())
      NewCU.addString(Die, dwarf::DW_AT_APPLE_flags, Flags);

    if (unsigned RVer = DIUnit->getRuntimeVersion())
      NewCU.addUInt(Die, dwarf::DW_AT_APPLE_major_runtime_vers,
                    dwarf::DW_FORM_data1, RVer);
  }

  if (DIUnit->getDWOId()) {
    // This CU is either a clang module DWO or a skeleton CU.
    NewCU.addUInt(Die, dwarf::DW_AT_GNU_dwo_id, dwarf::DW_FORM_data8,
                  DIUnit->getDWOId());
    if (!DIUnit->getSplitDebugFilename().empty()) {
      // This is a prefabricated skeleton CU.
      dwarf::Attribute attrDWOName = getDwarfVersion() >= 5
                                         ? dwarf::DW_AT_dwo_name
                                         : dwarf::DW_AT_GNU_dwo_name;
      NewCU.addString(Die, attrDWOName, DIUnit->getSplitDebugFilename());
    }
  }
}
// Create new DwarfCompileUnit for the given metadata node with tag
// DW_TAG_compile_unit.
DwarfCompileUnit &
DwarfDebug::getOrCreateDwarfCompileUnit(const DICompileUnit *DIUnit) {
  if (auto *CU = CUMap.lookup(DIUnit))
    return *CU;

  CompilationDir = DIUnit->getDirectory();

  auto OwnedUnit = std::make_unique<DwarfCompileUnit>(
      InfoHolder.getUnits().size(), DIUnit, Asm, this, &InfoHolder);
  DwarfCompileUnit &NewCU = *OwnedUnit;
  InfoHolder.addUnit(std::move(OwnedUnit));

  for (auto *IE : DIUnit->getImportedEntities())
    NewCU.addImportedEntity(IE);

  // LTO with assembly output shares a single line table amongst multiple CUs.
  // To avoid the compilation directory being ambiguous, let the line table
  // explicitly describe the directory of all files, never relying on the
  // compilation directory.
  if (!Asm->OutStreamer->hasRawTextSupport() || SingleCU)
    Asm->OutStreamer->emitDwarfFile0Directive(
        CompilationDir, DIUnit->getFilename(), getMD5AsBytes(DIUnit->getFile()),
        DIUnit->getSource(), NewCU.getUniqueID());

  if (useSplitDwarf()) {
    NewCU.setSkeleton(constructSkeletonCU(NewCU));
    NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoDWOSection());
  } else {
    finishUnitAttributes(DIUnit, NewCU);
    NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoSection());
  }

  CUMap.insert({DIUnit, &NewCU});
  CUDieMap.insert({&NewCU.getUnitDie(), &NewCU});
  return NewCU;
}

void DwarfDebug::constructAndAddImportedEntityDIE(DwarfCompileUnit &TheCU,
                                                  const DIImportedEntity *N) {
  if (isa<DILocalScope>(N->getScope()))
    return;
  if (DIE *D = TheCU.getOrCreateContextDIE(N->getScope()))
    D->addChild(TheCU.constructImportedEntityDIE(N));
}

/// Sort and unique GVEs by comparing their fragment offset.
static SmallVectorImpl<DwarfCompileUnit::GlobalExpr> &
sortGlobalExprs(SmallVectorImpl<DwarfCompileUnit::GlobalExpr> &GVEs) {
  llvm::sort(
      GVEs, [](DwarfCompileUnit::GlobalExpr A, DwarfCompileUnit::GlobalExpr B) {
        // Sort order: first null exprs, then exprs without fragment
        // info, then sort by fragment offset in bits.
        // FIXME: Come up with a more comprehensive comparator so
        // the sorting isn't non-deterministic, and so the following
        // std::unique call works correctly.
        if (!A.Expr || !B.Expr)
          return !!B.Expr;
        auto FragmentA = A.Expr->getFragmentInfo();
        auto FragmentB = B.Expr->getFragmentInfo();
        if (!FragmentA || !FragmentB)
          return !!FragmentB;
        return FragmentA->OffsetInBits < FragmentB->OffsetInBits;
      });
  GVEs.erase(std::unique(GVEs.begin(), GVEs.end(),
                         [](DwarfCompileUnit::GlobalExpr A,
                            DwarfCompileUnit::GlobalExpr B) {
                           return A.Expr == B.Expr;
                         }),
             GVEs.end());
  return GVEs;
}

// Emit all Dwarf sections that should come prior to the content. Create
// global DIEs and emit initial debug info sections. This is invoked by
// the target AsmPrinter.
void DwarfDebug::beginModule(Module *M) {
  DebugHandlerBase::beginModule(M);

  if (!Asm || !MMI->hasDebugInfo())
    return;

  unsigned NumDebugCUs = std::distance(M->debug_compile_units_begin(),
                                       M->debug_compile_units_end());
  assert(NumDebugCUs > 0 && "Asm unexpectedly initialized");
  assert(MMI->hasDebugInfo() &&
         "DebugInfoAvailabilty unexpectedly not initialized");
  SingleCU = NumDebugCUs == 1;
  DenseMap<DIGlobalVariable *, SmallVector<DwarfCompileUnit::GlobalExpr, 1>>
      GVMap;
  for (const GlobalVariable &Global : M->globals()) {
    SmallVector<DIGlobalVariableExpression *, 1> GVs;
    Global.getDebugInfo(GVs);
    for (auto *GVE : GVs)
      GVMap[GVE->getVariable()].push_back({&Global, GVE->getExpression()});
  }

  // Create the symbol that designates the start of the unit's contribution
  // to the string offsets table. In a split DWARF scenario, only the skeleton
  // unit has the DW_AT_str_offsets_base attribute (and hence needs the symbol).
  if (useSegmentedStringOffsetsTable())
    (useSplitDwarf() ? SkeletonHolder : InfoHolder)
        .setStringOffsetsStartSym(Asm->createTempSymbol("str_offsets_base"));


  // Create the symbols that designates the start of the DWARF v5 range list
  // and locations list tables. They are located past the table headers.
  if (getDwarfVersion() >= 5) {
    DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
    Holder.setRnglistsTableBaseSym(
        Asm->createTempSymbol("rnglists_table_base"));

    if (useSplitDwarf())
      InfoHolder.setRnglistsTableBaseSym(
          Asm->createTempSymbol("rnglists_dwo_table_base"));
  }

  // Create the symbol that points to the first entry following the debug
  // address table (.debug_addr) header.
  AddrPool.setLabel(Asm->createTempSymbol("addr_table_base"));
  DebugLocs.setSym(Asm->createTempSymbol("loclists_table_base"));

  for (DICompileUnit *CUNode : M->debug_compile_units()) {
    // FIXME: Move local imported entities into a list attached to the
    // subprogram, then this search won't be needed and a
    // getImportedEntities().empty() test should go below with the rest.
    bool HasNonLocalImportedEntities = llvm::any_of(
        CUNode->getImportedEntities(), [](const DIImportedEntity *IE) {
          return !isa<DILocalScope>(IE->getScope());
        });

    if (!HasNonLocalImportedEntities && CUNode->getEnumTypes().empty() &&
        CUNode->getRetainedTypes().empty() &&
        CUNode->getGlobalVariables().empty() && CUNode->getMacros().empty())
      continue;

    DwarfCompileUnit &CU = getOrCreateDwarfCompileUnit(CUNode);

    // Global Variables.
    for (auto *GVE : CUNode->getGlobalVariables()) {
      // Don't bother adding DIGlobalVariableExpressions listed in the CU if we
      // already know about the variable and it isn't adding a constant
      // expression.
      auto &GVMapEntry = GVMap[GVE->getVariable()];
      auto *Expr = GVE->getExpression();
      if (!GVMapEntry.size() || (Expr && Expr->isConstant()))
        GVMapEntry.push_back({nullptr, Expr});
    }

    DenseSet<DIGlobalVariable *> Processed;
    for (auto *GVE : CUNode->getGlobalVariables()) {
      DIGlobalVariable *GV = GVE->getVariable();
      if (Processed.insert(GV).second)
        CU.getOrCreateGlobalVariableDIE(GV, sortGlobalExprs(GVMap[GV]));
    }

    for (auto *Ty : CUNode->getEnumTypes())
      CU.getOrCreateTypeDIE(cast<DIType>(Ty));

    for (auto *Ty : CUNode->getRetainedTypes()) {
      // The retained types array by design contains pointers to
      // MDNodes rather than DIRefs. Unique them here.
      if (DIType *RT = dyn_cast<DIType>(Ty))
        // There is no point in force-emitting a forward declaration.
        CU.getOrCreateTypeDIE(RT);
    }
    // Emit imported_modules last so that the relevant context is already
    // available.
    for (auto *IE : CUNode->getImportedEntities())
      constructAndAddImportedEntityDIE(CU, IE);
  }
}

void DwarfDebug::finishEntityDefinitions() {
  for (const auto &Entity : ConcreteEntities) {
    DIE *Die = Entity->getDIE();
    assert(Die);
    // FIXME: Consider the time-space tradeoff of just storing the unit pointer
    // in the ConcreteEntities list, rather than looking it up again here.
    // DIE::getUnit isn't simple - it walks parent pointers, etc.
    DwarfCompileUnit *Unit = CUDieMap.lookup(Die->getUnitDie());
    assert(Unit);
    Unit->finishEntityDefinition(Entity.get());
  }
}

void DwarfDebug::finishSubprogramDefinitions() {
  for (const DISubprogram *SP : ProcessedSPNodes) {
    assert(SP->getUnit()->getEmissionKind() != DICompileUnit::NoDebug);
    forBothCUs(
        getOrCreateDwarfCompileUnit(SP->getUnit()),
        [&](DwarfCompileUnit &CU) { CU.finishSubprogramDefinition(SP); });
  }
}

void DwarfDebug::finalizeModuleInfo() {
  const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();

  finishSubprogramDefinitions();

  finishEntityDefinitions();

  // Include the DWO file name in the hash if there's more than one CU.
  // This handles ThinLTO's situation where imported CUs may very easily be
  // duplicate with the same CU partially imported into another ThinLTO unit.
  StringRef DWOName;
  if (CUMap.size() > 1)
    DWOName = Asm->TM.Options.MCOptions.SplitDwarfFile;

  // Handle anything that needs to be done on a per-unit basis after
  // all other generation.
  for (const auto &P : CUMap) {
    auto &TheCU = *P.second;
    if (TheCU.getCUNode()->isDebugDirectivesOnly())
      continue;
    // Emit DW_AT_containing_type attribute to connect types with their
    // vtable holding type.
    TheCU.constructContainingTypeDIEs();

    // Add CU specific attributes if we need to add any.
    // If we're splitting the dwarf out now that we've got the entire
    // CU then add the dwo id to it.
    auto *SkCU = TheCU.getSkeleton();

    bool HasSplitUnit = SkCU && !TheCU.getUnitDie().children().empty();

    if (HasSplitUnit) {
      dwarf::Attribute attrDWOName = getDwarfVersion() >= 5
                                         ? dwarf::DW_AT_dwo_name
                                         : dwarf::DW_AT_GNU_dwo_name;
      finishUnitAttributes(TheCU.getCUNode(), TheCU);
      TheCU.addString(TheCU.getUnitDie(), attrDWOName,
                      Asm->TM.Options.MCOptions.SplitDwarfFile);
      SkCU->addString(SkCU->getUnitDie(), attrDWOName,
                      Asm->TM.Options.MCOptions.SplitDwarfFile);
      // Emit a unique identifier for this CU.
      uint64_t ID =
          DIEHash(Asm, &TheCU).computeCUSignature(DWOName, TheCU.getUnitDie());
      if (getDwarfVersion() >= 5) {
        TheCU.setDWOId(ID);
        SkCU->setDWOId(ID);
      } else {
        TheCU.addUInt(TheCU.getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
                      dwarf::DW_FORM_data8, ID);
        SkCU->addUInt(SkCU->getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
                      dwarf::DW_FORM_data8, ID);
      }

      if (getDwarfVersion() < 5 && !SkeletonHolder.getRangeLists().empty()) {
        const MCSymbol *Sym = TLOF.getDwarfRangesSection()->getBeginSymbol();
        SkCU->addSectionLabel(SkCU->getUnitDie(), dwarf::DW_AT_GNU_ranges_base,
                              Sym, Sym);
      }
    } else if (SkCU) {
      finishUnitAttributes(SkCU->getCUNode(), *SkCU);
    }

    // If we have code split among multiple sections or non-contiguous
    // ranges of code then emit a DW_AT_ranges attribute on the unit that will
    // remain in the .o file, otherwise add a DW_AT_low_pc.
    // FIXME: We should use ranges allow reordering of code ala
    // .subsections_via_symbols in mach-o. This would mean turning on
    // ranges for all subprogram DIEs for mach-o.
    DwarfCompileUnit &U = SkCU ? *SkCU : TheCU;

    if (unsigned NumRanges = TheCU.getRanges().size()) {
      if (NumRanges > 1 && useRangesSection())
        // A DW_AT_low_pc attribute may also be specified in combination with
        // DW_AT_ranges to specify the default base address for use in
        // location lists (see Section 2.6.2) and range lists (see Section
        // 2.17.3).
        U.addUInt(U.getUnitDie(), dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr, 0);
      else
        U.setBaseAddress(TheCU.getRanges().front().Begin);
      U.attachRangesOrLowHighPC(U.getUnitDie(), TheCU.takeRanges());
    }

    // We don't keep track of which addresses are used in which CU so this
    // is a bit pessimistic under LTO.
    if ((HasSplitUnit || getDwarfVersion() >= 5) && !AddrPool.isEmpty())
      U.addAddrTableBase();

    if (getDwarfVersion() >= 5) {
      if (U.hasRangeLists())
        U.addRnglistsBase();

      if (!DebugLocs.getLists().empty()) {
        if (!useSplitDwarf())
          U.addSectionLabel(U.getUnitDie(), dwarf::DW_AT_loclists_base,
                            DebugLocs.getSym(),
                            TLOF.getDwarfLoclistsSection()->getBeginSymbol());
      }
    }

    auto *CUNode = cast<DICompileUnit>(P.first);
    // If compile Unit has macros, emit "DW_AT_macro_info/DW_AT_macros"
    // attribute.
    if (CUNode->getMacros()) {
      if (UseDebugMacroSection) {
        if (useSplitDwarf())
          TheCU.addSectionDelta(
              TheCU.getUnitDie(), dwarf::DW_AT_macros, U.getMacroLabelBegin(),
              TLOF.getDwarfMacroDWOSection()->getBeginSymbol());
        else {
          dwarf::Attribute MacrosAttr = getDwarfVersion() >= 5
                                            ? dwarf::DW_AT_macros
                                            : dwarf::DW_AT_GNU_macros;
          U.addSectionLabel(U.getUnitDie(), MacrosAttr, U.getMacroLabelBegin(),
                            TLOF.getDwarfMacroSection()->getBeginSymbol());
        }
      } else {
        if (useSplitDwarf())
          TheCU.addSectionDelta(
              TheCU.getUnitDie(), dwarf::DW_AT_macro_info,
              U.getMacroLabelBegin(),
              TLOF.getDwarfMacinfoDWOSection()->getBeginSymbol());
        else
          U.addSectionLabel(U.getUnitDie(), dwarf::DW_AT_macro_info,
                            U.getMacroLabelBegin(),
                            TLOF.getDwarfMacinfoSection()->getBeginSymbol());
      }
    }
    }

  // Emit all frontend-produced Skeleton CUs, i.e., Clang modules.
  for (auto *CUNode : MMI->getModule()->debug_compile_units())
    if (CUNode->getDWOId())
      getOrCreateDwarfCompileUnit(CUNode);

  // Compute DIE offsets and sizes.
  InfoHolder.computeSizeAndOffsets();
  if (useSplitDwarf())
    SkeletonHolder.computeSizeAndOffsets();
}

// Emit all Dwarf sections that should come after the content.
void DwarfDebug::endModule() {
  // Terminate the pending line table.
  if (PrevCU)
    terminateLineTable(PrevCU);
  PrevCU = nullptr;
  assert(CurFn == nullptr);
  assert(CurMI == nullptr);

  for (const auto &P : CUMap) {
    auto &CU = *P.second;
    CU.createBaseTypeDIEs();
  }

  // If we aren't actually generating debug info (check beginModule -
  // conditionalized on the presence of the llvm.dbg.cu metadata node)
  if (!Asm || !MMI->hasDebugInfo())
    return;

  // Finalize the debug info for the module.
  finalizeModuleInfo();

  if (useSplitDwarf())
    // Emit debug_loc.dwo/debug_loclists.dwo section.
    emitDebugLocDWO();
  else
    // Emit debug_loc/debug_loclists section.
    emitDebugLoc();

  // Corresponding abbreviations into a abbrev section.
  emitAbbreviations();

  // Emit all the DIEs into a debug info section.
  emitDebugInfo();

  // Emit info into a debug aranges section.
  if (GenerateARangeSection)
    emitDebugARanges();

  // Emit info into a debug ranges section.
  emitDebugRanges();

  if (useSplitDwarf())
  // Emit info into a debug macinfo.dwo section.
    emitDebugMacinfoDWO();
  else
    // Emit info into a debug macinfo/macro section.
    emitDebugMacinfo();

  emitDebugStr();

  if (useSplitDwarf()) {
    emitDebugStrDWO();
    emitDebugInfoDWO();
    emitDebugAbbrevDWO();
    emitDebugLineDWO();
    emitDebugRangesDWO();
  }

  emitDebugAddr();

  // Emit info into the dwarf accelerator table sections.
  switch (getAccelTableKind()) {
  case AccelTableKind::Apple:
    emitAccelNames();
    emitAccelObjC();
    emitAccelNamespaces();
    emitAccelTypes();
    break;
  case AccelTableKind::Dwarf:
    emitAccelDebugNames();
    break;
  case AccelTableKind::None:
    break;
  case AccelTableKind::Default:
    llvm_unreachable("Default should have already been resolved.");
  }

  // Emit the pubnames and pubtypes sections if requested.
  emitDebugPubSections();

  // clean up.
  // FIXME: AbstractVariables.clear();
}

void DwarfDebug::ensureAbstractEntityIsCreated(DwarfCompileUnit &CU,
                                               const DINode *Node,
                                               const MDNode *ScopeNode) {
  if (CU.getExistingAbstractEntity(Node))
    return;

  CU.createAbstractEntity(Node, LScopes.getOrCreateAbstractScope(
                                       cast<DILocalScope>(ScopeNode)));
}

void DwarfDebug::ensureAbstractEntityIsCreatedIfScoped(DwarfCompileUnit &CU,
    const DINode *Node, const MDNode *ScopeNode) {
  if (CU.getExistingAbstractEntity(Node))
    return;

  if (LexicalScope *Scope =
          LScopes.findAbstractScope(cast_or_null<DILocalScope>(ScopeNode)))
    CU.createAbstractEntity(Node, Scope);
}

// Collect variable information from side table maintained by MF.
void DwarfDebug::collectVariableInfoFromMFTable(
    DwarfCompileUnit &TheCU, DenseSet<InlinedEntity> &Processed) {
  SmallDenseMap<InlinedEntity, DbgVariable *> MFVars;
  LLVM_DEBUG(dbgs() << "DwarfDebug: collecting variables from MF side table\n");
  for (const auto &VI : Asm->MF->getVariableDbgInfo()) {
    if (!VI.Var)
      continue;
    assert(VI.Var->isValidLocationForIntrinsic(VI.Loc) &&
           "Expected inlined-at fields to agree");

    InlinedEntity Var(VI.Var, VI.Loc->getInlinedAt());
    Processed.insert(Var);
    LexicalScope *Scope = LScopes.findLexicalScope(VI.Loc);

    // If variable scope is not found then skip this variable.
    if (!Scope) {
      LLVM_DEBUG(dbgs() << "Dropping debug info for " << VI.Var->getName()
                        << ", no variable scope found\n");
      continue;
    }

    ensureAbstractEntityIsCreatedIfScoped(TheCU, Var.first, Scope->getScopeNode());
    auto RegVar = std::make_unique<DbgVariable>(
                    cast<DILocalVariable>(Var.first), Var.second);
    RegVar->initializeMMI(VI.Expr, VI.Slot);
    LLVM_DEBUG(dbgs() << "Created DbgVariable for " << VI.Var->getName()
                      << "\n");

    if (DbgVariable *DbgVar = MFVars.lookup(Var))
      DbgVar->addMMIEntry(*RegVar);
    else if (InfoHolder.addScopeVariable(Scope, RegVar.get())) {
      MFVars.insert({Var, RegVar.get()});
      ConcreteEntities.push_back(std::move(RegVar));
    }
  }
}

/// Determine whether a *singular* DBG_VALUE is valid for the entirety of its
/// enclosing lexical scope. The check ensures there are no other instructions
/// in the same lexical scope preceding the DBG_VALUE and that its range is
/// either open or otherwise rolls off the end of the scope.
static bool validThroughout(LexicalScopes &LScopes,
                            const MachineInstr *DbgValue,
                            const MachineInstr *RangeEnd,
                            const InstructionOrdering &Ordering) {
  assert(DbgValue->getDebugLoc() && "DBG_VALUE without a debug location");
  auto MBB = DbgValue->getParent();
  auto DL = DbgValue->getDebugLoc();
  auto *LScope = LScopes.findLexicalScope(DL);
  // Scope doesn't exist; this is a dead DBG_VALUE.
  if (!LScope)
    return false;
  auto &LSRange = LScope->getRanges();
  if (LSRange.size() == 0)
    return false;

  const MachineInstr *LScopeBegin = LSRange.front().first;
  // If the scope starts before the DBG_VALUE then we may have a negative
  // result. Otherwise the location is live coming into the scope and we
  // can skip the following checks.
  if (!Ordering.isBefore(DbgValue, LScopeBegin)) {
    // Exit if the lexical scope begins outside of the current block.
    if (LScopeBegin->getParent() != MBB)
      return false;

    MachineBasicBlock::const_reverse_iterator Pred(DbgValue);
    for (++Pred; Pred != MBB->rend(); ++Pred) {
      if (Pred->getFlag(MachineInstr::FrameSetup))
        break;
      auto PredDL = Pred->getDebugLoc();
      if (!PredDL || Pred->isMetaInstruction())
        continue;
      // Check whether the instruction preceding the DBG_VALUE is in the same
      // (sub)scope as the DBG_VALUE.
      if (DL->getScope() == PredDL->getScope())
        return false;
      auto *PredScope = LScopes.findLexicalScope(PredDL);
      if (!PredScope || LScope->dominates(PredScope))
        return false;
    }
  }

  // If the range of the DBG_VALUE is open-ended, report success.
  if (!RangeEnd)
    return true;

  // Single, constant DBG_VALUEs in the prologue are promoted to be live
  // throughout the function. This is a hack, presumably for DWARF v2 and not
  // necessarily correct. It would be much better to use a dbg.declare instead
  // if we know the constant is live throughout the scope.
  if (MBB->pred_empty() &&
      all_of(DbgValue->debug_operands(),
             [](const MachineOperand &Op) { return Op.isImm(); }))
    return true;

  // Test if the location terminates before the end of the scope.
  const MachineInstr *LScopeEnd = LSRange.back().second;
  if (Ordering.isBefore(RangeEnd, LScopeEnd))
    return false;

  // There's a single location which starts at the scope start, and ends at or
  // after the scope end.
  return true;
}

/// Build the location list for all DBG_VALUEs in the function that
/// describe the same variable. The resulting DebugLocEntries will have
/// strict monotonically increasing begin addresses and will never
/// overlap. If the resulting list has only one entry that is valid
/// throughout variable's scope return true.
//
// See the definition of DbgValueHistoryMap::Entry for an explanation of the
// different kinds of history map entries. One thing to be aware of is that if
// a debug value is ended by another entry (rather than being valid until the
// end of the function), that entry's instruction may or may not be included in
// the range, depending on if the entry is a clobbering entry (it has an
// instruction that clobbers one or more preceding locations), or if it is an
// (overlapping) debug value entry. This distinction can be seen in the example
// below. The first debug value is ended by the clobbering entry 2, and the
// second and third debug values are ended by the overlapping debug value entry
// 4.
//
// Input:
//
//   History map entries [type, end index, mi]
//
// 0 |      [DbgValue, 2, DBG_VALUE $reg0, [...] (fragment 0, 32)]
// 1 | |    [DbgValue, 4, DBG_VALUE $reg1, [...] (fragment 32, 32)]
// 2 | |    [Clobber, $reg0 = [...], -, -]
// 3   | |  [DbgValue, 4, DBG_VALUE 123, [...] (fragment 64, 32)]
// 4        [DbgValue, ~0, DBG_VALUE @g, [...] (fragment 0, 96)]
//
// Output [start, end) [Value...]:
//
// [0-1)    [(reg0, fragment 0, 32)]
// [1-3)    [(reg0, fragment 0, 32), (reg1, fragment 32, 32)]
// [3-4)    [(reg1, fragment 32, 32), (123, fragment 64, 32)]
// [4-)     [(@g, fragment 0, 96)]
bool DwarfDebug::buildLocationList(SmallVectorImpl<DebugLocEntry> &DebugLoc,
                                   const DbgValueHistoryMap::Entries &Entries) {
  using OpenRange =
      std::pair<DbgValueHistoryMap::EntryIndex, DbgValueLoc>;
  SmallVector<OpenRange, 4> OpenRanges;
  bool isSafeForSingleLocation = true;
  const MachineInstr *StartDebugMI = nullptr;
  const MachineInstr *EndMI = nullptr;

  for (auto EB = Entries.begin(), EI = EB, EE = Entries.end(); EI != EE; ++EI) {
    const MachineInstr *Instr = EI->getInstr();

    // Remove all values that are no longer live.
    size_t Index = std::distance(EB, EI);
    erase_if(OpenRanges, [&](OpenRange &R) { return R.first <= Index; });

    // If we are dealing with a clobbering entry, this iteration will result in
    // a location list entry starting after the clobbering instruction.
    const MCSymbol *StartLabel =
        EI->isClobber() ? getLabelAfterInsn(Instr) : getLabelBeforeInsn(Instr);
    assert(StartLabel &&
           "Forgot label before/after instruction starting a range!");

    const MCSymbol *EndLabel;
    if (std::next(EI) == Entries.end()) {
      const MachineBasicBlock &EndMBB = Asm->MF->back();
      EndLabel = Asm->MBBSectionRanges[EndMBB.getSectionIDNum()].EndLabel;
      if (EI->isClobber())
        EndMI = EI->getInstr();
    }
    else if (std::next(EI)->isClobber())
      EndLabel = getLabelAfterInsn(std::next(EI)->getInstr());
    else
      EndLabel = getLabelBeforeInsn(std::next(EI)->getInstr());
    assert(EndLabel && "Forgot label after instruction ending a range!");

    if (EI->isDbgValue())
      LLVM_DEBUG(dbgs() << "DotDebugLoc: " << *Instr << "\n");

    // If this history map entry has a debug value, add that to the list of
    // open ranges and check if its location is valid for a single value
    // location.
    if (EI->isDbgValue()) {
      // Do not add undef debug values, as they are redundant information in
      // the location list entries. An undef debug results in an empty location
      // description. If there are any non-undef fragments then padding pieces
      // with empty location descriptions will automatically be inserted, and if
      // all fragments are undef then the whole location list entry is
      // redundant.
      if (!Instr->isUndefDebugValue()) {
        auto Value = getDebugLocValue(Instr);
        OpenRanges.emplace_back(EI->getEndIndex(), Value);

        // TODO: Add support for single value fragment locations.
        if (Instr->getDebugExpression()->isFragment())
          isSafeForSingleLocation = false;

        if (!StartDebugMI)
          StartDebugMI = Instr;
      } else {
        isSafeForSingleLocation = false;
      }
    }

    // Location list entries with empty location descriptions are redundant
    // information in DWARF, so do not emit those.
    if (OpenRanges.empty())
      continue;

    // Omit entries with empty ranges as they do not have any effect in DWARF.
    if (StartLabel == EndLabel) {
      LLVM_DEBUG(dbgs() << "Omitting location list entry with empty range.\n");
      continue;
    }

    SmallVector<DbgValueLoc, 4> Values;
    for (auto &R : OpenRanges)
      Values.push_back(R.second);

    // With Basic block sections, it is posssible that the StartLabel and the
    // Instr are not in the same section.  This happens when the StartLabel is
    // the function begin label and the dbg value appears in a basic block
    // that is not the entry.  In this case, the range needs to be split to
    // span each individual section in the range from StartLabel to EndLabel.
    if (Asm->MF->hasBBSections() && StartLabel == Asm->getFunctionBegin() &&
        !Instr->getParent()->sameSection(&Asm->MF->front())) {
      const MCSymbol *BeginSectionLabel = StartLabel;

      for (const MachineBasicBlock &MBB : *Asm->MF) {
        if (MBB.isBeginSection() && &MBB != &Asm->MF->front())
          BeginSectionLabel = MBB.getSymbol();

        if (MBB.sameSection(Instr->getParent())) {
          DebugLoc.emplace_back(BeginSectionLabel, EndLabel, Values);
          break;
        }
        if (MBB.isEndSection())
          DebugLoc.emplace_back(BeginSectionLabel, MBB.getEndSymbol(), Values);
      }
    } else {
      DebugLoc.emplace_back(StartLabel, EndLabel, Values);
    }

    // Attempt to coalesce the ranges of two otherwise identical
    // DebugLocEntries.
    auto CurEntry = DebugLoc.rbegin();
    LLVM_DEBUG({
      dbgs() << CurEntry->getValues().size() << " Values:\n";
      for (auto &Value : CurEntry->getValues())
        Value.dump();
      dbgs() << "-----\n";
    });

    auto PrevEntry = std::next(CurEntry);
    if (PrevEntry != DebugLoc.rend() && PrevEntry->MergeRanges(*CurEntry))
      DebugLoc.pop_back();
  }

  if (!isSafeForSingleLocation ||
      !validThroughout(LScopes, StartDebugMI, EndMI, getInstOrdering()))
    return false;

  if (DebugLoc.size() == 1)
    return true;

  if (!Asm->MF->hasBBSections())
    return false;

  // Check here to see if loclist can be merged into a single range. If not,
  // we must keep the split loclists per section.  This does exactly what
  // MergeRanges does without sections.  We don't actually merge the ranges
  // as the split ranges must be kept intact if this cannot be collapsed
  // into a single range.
  const MachineBasicBlock *RangeMBB = nullptr;
  if (DebugLoc[0].getBeginSym() == Asm->getFunctionBegin())
    RangeMBB = &Asm->MF->front();
  else
    RangeMBB = Entries.begin()->getInstr()->getParent();
  auto *CurEntry = DebugLoc.begin();
  auto *NextEntry = std::next(CurEntry);
  while (NextEntry != DebugLoc.end()) {
    // Get the last machine basic block of this section.
    while (!RangeMBB->isEndSection())
      RangeMBB = RangeMBB->getNextNode();
    if (!RangeMBB->getNextNode())
      return false;
    // CurEntry should end the current section and NextEntry should start
    // the next section and the Values must match for these two ranges to be
    // merged.
    if (CurEntry->getEndSym() != RangeMBB->getEndSymbol() ||
        NextEntry->getBeginSym() != RangeMBB->getNextNode()->getSymbol() ||
        CurEntry->getValues() != NextEntry->getValues())
      return false;
    RangeMBB = RangeMBB->getNextNode();
    CurEntry = NextEntry;
    NextEntry = std::next(CurEntry);
  }
  return true;
}

DbgEntity *DwarfDebug::createConcreteEntity(DwarfCompileUnit &TheCU,
                                            LexicalScope &Scope,
                                            const DINode *Node,
                                            const DILocation *Location,
                                            const MCSymbol *Sym) {
  ensureAbstractEntityIsCreatedIfScoped(TheCU, Node, Scope.getScopeNode());
  if (isa<const DILocalVariable>(Node)) {
    ConcreteEntities.push_back(
        std::make_unique<DbgVariable>(cast<const DILocalVariable>(Node),
                                       Location));
    InfoHolder.addScopeVariable(&Scope,
        cast<DbgVariable>(ConcreteEntities.back().get()));
  } else if (isa<const DILabel>(Node)) {
    ConcreteEntities.push_back(
        std::make_unique<DbgLabel>(cast<const DILabel>(Node),
                                    Location, Sym));
    InfoHolder.addScopeLabel(&Scope,
        cast<DbgLabel>(ConcreteEntities.back().get()));
  }
  return ConcreteEntities.back().get();
}

// Find variables for each lexical scope.
void DwarfDebug::collectEntityInfo(DwarfCompileUnit &TheCU,
                                   const DISubprogram *SP,
                                   DenseSet<InlinedEntity> &Processed) {
  // Grab the variable info that was squirreled away in the MMI side-table.
  collectVariableInfoFromMFTable(TheCU, Processed);

  for (const auto &I : DbgValues) {
    InlinedEntity IV = I.first;
    if (Processed.count(IV))
      continue;

    // Instruction ranges, specifying where IV is accessible.
    const auto &HistoryMapEntries = I.second;

    // Try to find any non-empty variable location. Do not create a concrete
    // entity if there are no locations.
    if (!DbgValues.hasNonEmptyLocation(HistoryMapEntries))
      continue;

    LexicalScope *Scope = nullptr;
    const DILocalVariable *LocalVar = cast<DILocalVariable>(IV.first);
    if (const DILocation *IA = IV.second)
      Scope = LScopes.findInlinedScope(LocalVar->getScope(), IA);
    else
      Scope = LScopes.findLexicalScope(LocalVar->getScope());
    // If variable scope is not found then skip this variable.
    if (!Scope)
      continue;

    Processed.insert(IV);
    DbgVariable *RegVar = cast<DbgVariable>(createConcreteEntity(TheCU,
                                            *Scope, LocalVar, IV.second));

    const MachineInstr *MInsn = HistoryMapEntries.front().getInstr();
    assert(MInsn->isDebugValue() && "History must begin with debug value");

    // Check if there is a single DBG_VALUE, valid throughout the var's scope.
    // If the history map contains a single debug value, there may be an
    // additional entry which clobbers the debug value.
    size_t HistSize = HistoryMapEntries.size();
    bool SingleValueWithClobber =
        HistSize == 2 && HistoryMapEntries[1].isClobber();
    if (HistSize == 1 || SingleValueWithClobber) {
      const auto *End =
          SingleValueWithClobber ? HistoryMapEntries[1].getInstr() : nullptr;
      if (validThroughout(LScopes, MInsn, End, getInstOrdering())) {
        RegVar->initializeDbgValue(MInsn);
        continue;
      }
    }

    // Do not emit location lists if .debug_loc secton is disabled.
    if (!useLocSection())
      continue;

    // Handle multiple DBG_VALUE instructions describing one variable.
    DebugLocStream::ListBuilder List(DebugLocs, TheCU, *Asm, *RegVar, *MInsn);

    // Build the location list for this variable.
    SmallVector<DebugLocEntry, 8> Entries;
    bool isValidSingleLocation = buildLocationList(Entries, HistoryMapEntries);

    // Check whether buildLocationList managed to merge all locations to one
    // that is valid throughout the variable's scope. If so, produce single
    // value location.
    if (isValidSingleLocation) {
      RegVar->initializeDbgValue(Entries[0].getValues()[0]);
      continue;
    }

    // If the variable has a DIBasicType, extract it.  Basic types cannot have
    // unique identifiers, so don't bother resolving the type with the
    // identifier map.
    const DIBasicType *BT = dyn_cast<DIBasicType>(
        static_cast<const Metadata *>(LocalVar->getType()));

    // Finalize the entry by lowering it into a DWARF bytestream.
    for (auto &Entry : Entries)
      Entry.finalize(*Asm, List, BT, TheCU);
  }

  // For each InlinedEntity collected from DBG_LABEL instructions, convert to
  // DWARF-related DbgLabel.
  for (const auto &I : DbgLabels) {
    InlinedEntity IL = I.first;
    const MachineInstr *MI = I.second;
    if (MI == nullptr)
      continue;

    LexicalScope *Scope = nullptr;
    const DILabel *Label = cast<DILabel>(IL.first);
    // The scope could have an extra lexical block file.
    const DILocalScope *LocalScope =
        Label->getScope()->getNonLexicalBlockFileScope();
    // Get inlined DILocation if it is inlined label.
    if (const DILocation *IA = IL.second)
      Scope = LScopes.findInlinedScope(LocalScope, IA);
    else
      Scope = LScopes.findLexicalScope(LocalScope);
    // If label scope is not found then skip this label.
    if (!Scope)
      continue;

    Processed.insert(IL);
    /// At this point, the temporary label is created.
    /// Save the temporary label to DbgLabel entity to get the
    /// actually address when generating Dwarf DIE.
    MCSymbol *Sym = getLabelBeforeInsn(MI);
    createConcreteEntity(TheCU, *Scope, Label, IL.second, Sym);
  }

  // Collect info for variables/labels that were optimized out.
  for (const DINode *DN : SP->getRetainedNodes()) {
    if (!Processed.insert(InlinedEntity(DN, nullptr)).second)
      continue;
    LexicalScope *Scope = nullptr;
    if (auto *DV = dyn_cast<DILocalVariable>(DN)) {
      Scope = LScopes.findLexicalScope(DV->getScope());
    } else if (auto *DL = dyn_cast<DILabel>(DN)) {
      Scope = LScopes.findLexicalScope(DL->getScope());
    }

    if (Scope)
      createConcreteEntity(TheCU, *Scope, DN, nullptr);
  }
}

// Process beginning of an instruction.
void DwarfDebug::beginInstruction(const MachineInstr *MI) {
  const MachineFunction &MF = *MI->getMF();
  const auto *SP = MF.getFunction().getSubprogram();
  bool NoDebug =
      !SP || SP->getUnit()->getEmissionKind() == DICompileUnit::NoDebug;

  // Delay slot support check.
  auto delaySlotSupported = [](const MachineInstr &MI) {
    if (!MI.isBundledWithSucc())
      return false;
    auto Suc = std::next(MI.getIterator());
    (void)Suc;
    // Ensure that delay slot instruction is successor of the call instruction.
    // Ex. CALL_INSTRUCTION {
    //        DELAY_SLOT_INSTRUCTION }
    assert(Suc->isBundledWithPred() &&
           "Call bundle instructions are out of order");
    return true;
  };

  // When describing calls, we need a label for the call instruction.
  if (!NoDebug && SP->areAllCallsDescribed() &&
      MI->isCandidateForCallSiteEntry(MachineInstr::AnyInBundle) &&
      (!MI->hasDelaySlot() || delaySlotSupported(*MI))) {
    const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
    bool IsTail = TII->isTailCall(*MI);
    // For tail calls, we need the address of the branch instruction for
    // DW_AT_call_pc.
    if (IsTail)
      requestLabelBeforeInsn(MI);
    // For non-tail calls, we need the return address for the call for
    // DW_AT_call_return_pc. Under GDB tuning, this information is needed for
    // tail calls as well.
    requestLabelAfterInsn(MI);
  }

  DebugHandlerBase::beginInstruction(MI);
  if (!CurMI)
    return;

  if (NoDebug)
    return;

  // Check if source location changes, but ignore DBG_VALUE and CFI locations.
  // If the instruction is part of the function frame setup code, do not emit
  // any line record, as there is no correspondence with any user code.
  if (MI->isMetaInstruction() || MI->getFlag(MachineInstr::FrameSetup))
    return;
  const DebugLoc &DL = MI->getDebugLoc();
  unsigned Flags = 0;

  if (MI->getFlag(MachineInstr::FrameDestroy) && DL) {
    const MachineBasicBlock *MBB = MI->getParent();
    if (MBB && (MBB != EpilogBeginBlock)) {
      // First time FrameDestroy has been seen in this basic block
      EpilogBeginBlock = MBB;
      Flags |= DWARF2_FLAG_EPILOGUE_BEGIN;
    }
  }

  // When we emit a line-0 record, we don't update PrevInstLoc; so look at
  // the last line number actually emitted, to see if it was line 0.
  unsigned LastAsmLine =
      Asm->OutStreamer->getContext().getCurrentDwarfLoc().getLine();

  if (DL == PrevInstLoc) {
    // If we have an ongoing unspecified location, nothing to do here.
    if (!DL)
      return;
    // We have an explicit location, same as the previous location.
    // But we might be coming back to it after a line 0 record.
    if ((LastAsmLine == 0 && DL.getLine() != 0) || Flags) {
      // Reinstate the source location but not marked as a statement.
      const MDNode *Scope = DL.getScope();
      recordSourceLine(DL.getLine(), DL.getCol(), Scope, Flags);
    }
    return;
  }

  if (!DL) {
    // We have an unspecified location, which might want to be line 0.
    // If we have already emitted a line-0 record, don't repeat it.
    if (LastAsmLine == 0)
      return;
    // If user said Don't Do That, don't do that.
    if (UnknownLocations == Disable)
      return;
    // See if we have a reason to emit a line-0 record now.
    // Reasons to emit a line-0 record include:
    // - User asked for it (UnknownLocations).
    // - Instruction has a label, so it's referenced from somewhere else,
    //   possibly debug information; we want it to have a source location.
    // - Instruction is at the top of a block; we don't want to inherit the
    //   location from the physically previous (maybe unrelated) block.
    if (UnknownLocations == Enable || PrevLabel ||
        (PrevInstBB && PrevInstBB != MI->getParent())) {
      // Preserve the file and column numbers, if we can, to save space in
      // the encoded line table.
      // Do not update PrevInstLoc, it remembers the last non-0 line.
      const MDNode *Scope = nullptr;
      unsigned Column = 0;
      if (PrevInstLoc) {
        Scope = PrevInstLoc.getScope();
        Column = PrevInstLoc.getCol();
      }
      recordSourceLine(/*Line=*/0, Column, Scope, /*Flags=*/0);
    }
    return;
  }

  // We have an explicit location, different from the previous location.
  // Don't repeat a line-0 record, but otherwise emit the new location.
  // (The new location might be an explicit line 0, which we do emit.)
  if (DL.getLine() == 0 && LastAsmLine == 0)
    return;
  if (DL == PrologEndLoc) {
    Flags |= DWARF2_FLAG_PROLOGUE_END | DWARF2_FLAG_IS_STMT;
    PrologEndLoc = DebugLoc();
  }
  // If the line changed, we call that a new statement; unless we went to
  // line 0 and came back, in which case it is not a new statement.
  unsigned OldLine = PrevInstLoc ? PrevInstLoc.getLine() : LastAsmLine;
  if (DL.getLine() && DL.getLine() != OldLine)
    Flags |= DWARF2_FLAG_IS_STMT;

  const MDNode *Scope = DL.getScope();
  recordSourceLine(DL.getLine(), DL.getCol(), Scope, Flags);

  // If we're not at line 0, remember this location.
  if (DL.getLine())
    PrevInstLoc = DL;
}

static DebugLoc findPrologueEndLoc(const MachineFunction *MF) {
  // First known non-DBG_VALUE and non-frame setup location marks
  // the beginning of the function body.
  DebugLoc LineZeroLoc;
  for (const auto &MBB : *MF) {
    for (const auto &MI : MBB) {
      if (!MI.isMetaInstruction() && !MI.getFlag(MachineInstr::FrameSetup) &&
          MI.getDebugLoc()) {
        // Scan forward to try to find a non-zero line number. The prologue_end
        // marks the first breakpoint in the function after the frame setup, and
        // a compiler-generated line 0 location is not a meaningful breakpoint.
        // If none is found, return the first location after the frame setup.
        if (MI.getDebugLoc().getLine())
          return MI.getDebugLoc();
        LineZeroLoc = MI.getDebugLoc();
      }
    }
  }
  return LineZeroLoc;
}

/// Register a source line with debug info. Returns the  unique label that was
/// emitted and which provides correspondence to the source line list.
static void recordSourceLine(AsmPrinter &Asm, unsigned Line, unsigned Col,
                             const MDNode *S, unsigned Flags, unsigned CUID,
                             uint16_t DwarfVersion,
                             ArrayRef<std::unique_ptr<DwarfCompileUnit>> DCUs) {
  StringRef Fn;
  unsigned FileNo = 1;
  unsigned Discriminator = 0;
  if (auto *Scope = cast_or_null<DIScope>(S)) {
    Fn = Scope->getFilename();
    if (Line != 0 && DwarfVersion >= 4)
      if (auto *LBF = dyn_cast<DILexicalBlockFile>(Scope))
        Discriminator = LBF->getDiscriminator();

    FileNo = static_cast<DwarfCompileUnit &>(*DCUs[CUID])
                 .getOrCreateSourceID(Scope->getFile());
  }
  Asm.OutStreamer->emitDwarfLocDirective(FileNo, Line, Col, Flags, 0,
                                         Discriminator, Fn);
}

DebugLoc DwarfDebug::emitInitialLocDirective(const MachineFunction &MF,
                                             unsigned CUID) {
  // Get beginning of function.
  if (DebugLoc PrologEndLoc = findPrologueEndLoc(&MF)) {
    // Ensure the compile unit is created if the function is called before
    // beginFunction().
    (void)getOrCreateDwarfCompileUnit(
        MF.getFunction().getSubprogram()->getUnit());
    // We'd like to list the prologue as "not statements" but GDB behaves
    // poorly if we do that. Revisit this with caution/GDB (7.5+) testing.
    const DISubprogram *SP = PrologEndLoc->getInlinedAtScope()->getSubprogram();
    ::recordSourceLine(*Asm, SP->getScopeLine(), 0, SP, DWARF2_FLAG_IS_STMT,
                       CUID, getDwarfVersion(), getUnits());
    return PrologEndLoc;
  }
  return DebugLoc();
}

// Gather pre-function debug information.  Assumes being called immediately
// after the function entry point has been emitted.
void DwarfDebug::beginFunctionImpl(const MachineFunction *MF) {
  CurFn = MF;

  auto *SP = MF->getFunction().getSubprogram();
  assert(LScopes.empty() || SP == LScopes.getCurrentFunctionScope()->getScopeNode());
  if (SP->getUnit()->getEmissionKind() == DICompileUnit::NoDebug)
    return;

  DwarfCompileUnit &CU = getOrCreateDwarfCompileUnit(SP->getUnit());

  Asm->OutStreamer->getContext().setDwarfCompileUnitID(
      getDwarfCompileUnitIDForLineTable(CU));

  // Record beginning of function.
  PrologEndLoc = emitInitialLocDirective(
      *MF, Asm->OutStreamer->getContext().getDwarfCompileUnitID());
}

unsigned
DwarfDebug::getDwarfCompileUnitIDForLineTable(const DwarfCompileUnit &CU) {
  // Set DwarfDwarfCompileUnitID in MCContext to the Compile Unit this function
  // belongs to so that we add to the correct per-cu line table in the
  // non-asm case.
  if (Asm->OutStreamer->hasRawTextSupport())
    // Use a single line table if we are generating assembly.
    return 0;
  else
    return CU.getUniqueID();
}

void DwarfDebug::terminateLineTable(const DwarfCompileUnit *CU) {
  const auto &CURanges = CU->getRanges();
  auto &LineTable = Asm->OutStreamer->getContext().getMCDwarfLineTable(
      getDwarfCompileUnitIDForLineTable(*CU));
  // Add the last range label for the given CU.
  LineTable.getMCLineSections().addEndEntry(
      const_cast<MCSymbol *>(CURanges.back().End));
}

void DwarfDebug::skippedNonDebugFunction() {
  // If we don't have a subprogram for this function then there will be a hole
  // in the range information. Keep note of this by setting the previously used
  // section to nullptr.
  // Terminate the pending line table.
  if (PrevCU)
    terminateLineTable(PrevCU);
  PrevCU = nullptr;
  CurFn = nullptr;
}

// Gather and emit post-function debug information.
void DwarfDebug::endFunctionImpl(const MachineFunction *MF) {
  const DISubprogram *SP = MF->getFunction().getSubprogram();

  assert(CurFn == MF &&
      "endFunction should be called with the same function as beginFunction");

  // Set DwarfDwarfCompileUnitID in MCContext to default value.
  Asm->OutStreamer->getContext().setDwarfCompileUnitID(0);

  LexicalScope *FnScope = LScopes.getCurrentFunctionScope();
  assert(!FnScope || SP == FnScope->getScopeNode());
  DwarfCompileUnit &TheCU = *CUMap.lookup(SP->getUnit());
  if (TheCU.getCUNode()->isDebugDirectivesOnly()) {
    PrevLabel = nullptr;
    CurFn = nullptr;
    return;
  }

  DenseSet<InlinedEntity> Processed;
  collectEntityInfo(TheCU, SP, Processed);

  // Add the range of this function to the list of ranges for the CU.
  // With basic block sections, add ranges for all basic block sections.
  for (const auto &R : Asm->MBBSectionRanges)
    TheCU.addRange({R.second.BeginLabel, R.second.EndLabel});

  // Under -gmlt, skip building the subprogram if there are no inlined
  // subroutines inside it. But with -fdebug-info-for-profiling, the subprogram
  // is still needed as we need its source location.
  if (!TheCU.getCUNode()->getDebugInfoForProfiling() &&
      TheCU.getCUNode()->getEmissionKind() == DICompileUnit::LineTablesOnly &&
      LScopes.getAbstractScopesList().empty() && !IsDarwin) {
    assert(InfoHolder.getScopeVariables().empty());
    PrevLabel = nullptr;
    CurFn = nullptr;
    return;
  }

#ifndef NDEBUG
  size_t NumAbstractScopes = LScopes.getAbstractScopesList().size();
#endif
  // Construct abstract scopes.
  for (LexicalScope *AScope : LScopes.getAbstractScopesList()) {
    const auto *SP = cast<DISubprogram>(AScope->getScopeNode());
    for (const DINode *DN : SP->getRetainedNodes()) {
      if (!Processed.insert(InlinedEntity(DN, nullptr)).second)
        continue;

      const MDNode *Scope = nullptr;
      if (auto *DV = dyn_cast<DILocalVariable>(DN))
        Scope = DV->getScope();
      else if (auto *DL = dyn_cast<DILabel>(DN))
        Scope = DL->getScope();
      else
        llvm_unreachable("Unexpected DI type!");

      // Collect info for variables/labels that were optimized out.
      ensureAbstractEntityIsCreated(TheCU, DN, Scope);
      assert(LScopes.getAbstractScopesList().size() == NumAbstractScopes
             && "ensureAbstractEntityIsCreated inserted abstract scopes");
    }
    constructAbstractSubprogramScopeDIE(TheCU, AScope);
  }

  ProcessedSPNodes.insert(SP);
  DIE &ScopeDIE = TheCU.constructSubprogramScopeDIE(SP, FnScope);
  if (auto *SkelCU = TheCU.getSkeleton())
    if (!LScopes.getAbstractScopesList().empty() &&
        TheCU.getCUNode()->getSplitDebugInlining())
      SkelCU->constructSubprogramScopeDIE(SP, FnScope);

  // Construct call site entries.
  constructCallSiteEntryDIEs(*SP, TheCU, ScopeDIE, *MF);

  // Clear debug info
  // Ownership of DbgVariables is a bit subtle - ScopeVariables owns all the
  // DbgVariables except those that are also in AbstractVariables (since they
  // can be used cross-function)
  InfoHolder.getScopeVariables().clear();
  InfoHolder.getScopeLabels().clear();
  PrevLabel = nullptr;
  CurFn = nullptr;
}

// Register a source line with debug info. Returns the  unique label that was
// emitted and which provides correspondence to the source line list.
void DwarfDebug::recordSourceLine(unsigned Line, unsigned Col, const MDNode *S,
                                  unsigned Flags) {
  ::recordSourceLine(*Asm, Line, Col, S, Flags,
                     Asm->OutStreamer->getContext().getDwarfCompileUnitID(),
                     getDwarfVersion(), getUnits());
}

//===----------------------------------------------------------------------===//
// Emit Methods
//===----------------------------------------------------------------------===//

// Emit the debug info section.
void DwarfDebug::emitDebugInfo() {
  DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
  Holder.emitUnits(/* UseOffsets */ false);
}

// Emit the abbreviation section.
void DwarfDebug::emitAbbreviations() {
  DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;

  Holder.emitAbbrevs(Asm->getObjFileLowering().getDwarfAbbrevSection());
}

void DwarfDebug::emitStringOffsetsTableHeader() {
  DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
  Holder.getStringPool().emitStringOffsetsTableHeader(
      *Asm, Asm->getObjFileLowering().getDwarfStrOffSection(),
      Holder.getStringOffsetsStartSym());
}

template <typename AccelTableT>
void DwarfDebug::emitAccel(AccelTableT &Accel, MCSection *Section,
                           StringRef TableName) {
  Asm->OutStreamer->switchSection(Section);

  // Emit the full data.
  emitAppleAccelTable(Asm, Accel, TableName, Section->getBeginSymbol());
}

void DwarfDebug::emitAccelDebugNames() {
  // Don't emit anything if we have no compilation units to index.
  if (getUnits().empty())
    return;

  emitDWARF5AccelTable(Asm, AccelDebugNames, *this, getUnits());
}

// Emit visible names into a hashed accelerator table section.
void DwarfDebug::emitAccelNames() {
  emitAccel(AccelNames, Asm->getObjFileLowering().getDwarfAccelNamesSection(),
            "Names");
}

// Emit objective C classes and categories into a hashed accelerator table
// section.
void DwarfDebug::emitAccelObjC() {
  emitAccel(AccelObjC, Asm->getObjFileLowering().getDwarfAccelObjCSection(),
            "ObjC");
}

// Emit namespace dies into a hashed accelerator table.
void DwarfDebug::emitAccelNamespaces() {
  emitAccel(AccelNamespace,
            Asm->getObjFileLowering().getDwarfAccelNamespaceSection(),
            "namespac");
}

// Emit type dies into a hashed accelerator table.
void DwarfDebug::emitAccelTypes() {
  emitAccel(AccelTypes, Asm->getObjFileLowering().getDwarfAccelTypesSection(),
            "types");
}

// Public name handling.
// The format for the various pubnames:
//
// dwarf pubnames - offset/name pairs where the offset is the offset into the CU
// for the DIE that is named.
//
// gnu pubnames - offset/index value/name tuples where the offset is the offset
// into the CU and the index value is computed according to the type of value
// for the DIE that is named.
//
// For type units the offset is the offset of the skeleton DIE. For split dwarf
// it's the offset within the debug_info/debug_types dwo section, however, the
// reference in the pubname header doesn't change.

/// computeIndexValue - Compute the gdb index value for the DIE and CU.
static dwarf::PubIndexEntryDescriptor computeIndexValue(DwarfUnit *CU,
                                                        const DIE *Die) {
  // Entities that ended up only in a Type Unit reference the CU instead (since
  // the pub entry has offsets within the CU there's no real offset that can be
  // provided anyway). As it happens all such entities (namespaces and types,
  // types only in C++ at that) are rendered as TYPE+EXTERNAL. If this turns out
  // not to be true it would be necessary to persist this information from the
  // point at which the entry is added to the index data structure - since by
  // the time the index is built from that, the original type/namespace DIE in a
  // type unit has already been destroyed so it can't be queried for properties
  // like tag, etc.
  if (Die->getTag() == dwarf::DW_TAG_compile_unit)
    return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_TYPE,
                                          dwarf::GIEL_EXTERNAL);
  dwarf::GDBIndexEntryLinkage Linkage = dwarf::GIEL_STATIC;

  // We could have a specification DIE that has our most of our knowledge,
  // look for that now.
  if (DIEValue SpecVal = Die->findAttribute(dwarf::DW_AT_specification)) {
    DIE &SpecDIE = SpecVal.getDIEEntry().getEntry();
    if (SpecDIE.findAttribute(dwarf::DW_AT_external))
      Linkage = dwarf::GIEL_EXTERNAL;
  } else if (Die->findAttribute(dwarf::DW_AT_external))
    Linkage = dwarf::GIEL_EXTERNAL;

  switch (Die->getTag()) {
  case dwarf::DW_TAG_class_type:
  case dwarf::DW_TAG_structure_type:
  case dwarf::DW_TAG_union_type:
  case dwarf::DW_TAG_enumeration_type:
    return dwarf::PubIndexEntryDescriptor(
        dwarf::GIEK_TYPE,
        dwarf::isCPlusPlus((dwarf::SourceLanguage)CU->getLanguage())
            ? dwarf::GIEL_EXTERNAL
            : dwarf::GIEL_STATIC);
  case dwarf::DW_TAG_typedef:
  case dwarf::DW_TAG_base_type:
  case dwarf::DW_TAG_subrange_type:
    return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_TYPE, dwarf::GIEL_STATIC);
  case dwarf::DW_TAG_namespace:
    return dwarf::GIEK_TYPE;
  case dwarf::DW_TAG_subprogram:
    return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_FUNCTION, Linkage);
  case dwarf::DW_TAG_variable:
    return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_VARIABLE, Linkage);
  case dwarf::DW_TAG_enumerator:
    return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_VARIABLE,
                                          dwarf::GIEL_STATIC);
  default:
    return dwarf::GIEK_NONE;
  }
}

/// emitDebugPubSections - Emit visible names and types into debug pubnames and
/// pubtypes sections.
void DwarfDebug::emitDebugPubSections() {
  for (const auto &NU : CUMap) {
    DwarfCompileUnit *TheU = NU.second;
    if (!TheU->hasDwarfPubSections())
      continue;

    bool GnuStyle = TheU->getCUNode()->getNameTableKind() ==
                    DICompileUnit::DebugNameTableKind::GNU;

    Asm->OutStreamer->switchSection(
        GnuStyle ? Asm->getObjFileLowering().getDwarfGnuPubNamesSection()
                 : Asm->getObjFileLowering().getDwarfPubNamesSection());
    emitDebugPubSection(GnuStyle, "Names", TheU, TheU->getGlobalNames());

    Asm->OutStreamer->switchSection(
        GnuStyle ? Asm->getObjFileLowering().getDwarfGnuPubTypesSection()
                 : Asm->getObjFileLowering().getDwarfPubTypesSection());
    emitDebugPubSection(GnuStyle, "Types", TheU, TheU->getGlobalTypes());
  }
}

void DwarfDebug::emitSectionReference(const DwarfCompileUnit &CU) {
  if (useSectionsAsReferences())
    Asm->emitDwarfOffset(CU.getSection()->getBeginSymbol(),
                         CU.getDebugSectionOffset());
  else
    Asm->emitDwarfSymbolReference(CU.getLabelBegin());
}

void DwarfDebug::emitDebugPubSection(bool GnuStyle, StringRef Name,
                                     DwarfCompileUnit *TheU,
                                     const StringMap<const DIE *> &Globals) {
  if (auto *Skeleton = TheU->getSkeleton())
    TheU = Skeleton;

  // Emit the header.
  MCSymbol *EndLabel = Asm->emitDwarfUnitLength(
      "pub" + Name, "Length of Public " + Name + " Info");

  Asm->OutStreamer->AddComment("DWARF Version");
  Asm->emitInt16(dwarf::DW_PUBNAMES_VERSION);

  Asm->OutStreamer->AddComment("Offset of Compilation Unit Info");
  emitSectionReference(*TheU);

  Asm->OutStreamer->AddComment("Compilation Unit Length");
  Asm->emitDwarfLengthOrOffset(TheU->getLength());

  // Emit the pubnames for this compilation unit.
  for (const auto &GI : Globals) {
    const char *Name = GI.getKeyData();
    const DIE *Entity = GI.second;

    Asm->OutStreamer->AddComment("DIE offset");
    Asm->emitDwarfLengthOrOffset(Entity->getOffset());

    if (GnuStyle) {
      dwarf::PubIndexEntryDescriptor Desc = computeIndexValue(TheU, Entity);
      Asm->OutStreamer->AddComment(
          Twine("Attributes: ") + dwarf::GDBIndexEntryKindString(Desc.Kind) +
          ", " + dwarf::GDBIndexEntryLinkageString(Desc.Linkage));
      Asm->emitInt8(Desc.toBits());
    }

    Asm->OutStreamer->AddComment("External Name");
    Asm->OutStreamer->emitBytes(StringRef(Name, GI.getKeyLength() + 1));
  }

  Asm->OutStreamer->AddComment("End Mark");
  Asm->emitDwarfLengthOrOffset(0);
  Asm->OutStreamer->emitLabel(EndLabel);
}

/// Emit null-terminated strings into a debug str section.
void DwarfDebug::emitDebugStr() {
  MCSection *StringOffsetsSection = nullptr;
  if (useSegmentedStringOffsetsTable()) {
    emitStringOffsetsTableHeader();
    StringOffsetsSection = Asm->getObjFileLowering().getDwarfStrOffSection();
  }
  DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
  Holder.emitStrings(Asm->getObjFileLowering().getDwarfStrSection(),
                     StringOffsetsSection, /* UseRelativeOffsets = */ true);
}

void DwarfDebug::emitDebugLocEntry(ByteStreamer &Streamer,
                                   const DebugLocStream::Entry &Entry,
                                   const DwarfCompileUnit *CU) {
  auto &&Comments = DebugLocs.getComments(Entry);
  auto Comment = Comments.begin();
  auto End = Comments.end();

  // The expressions are inserted into a byte stream rather early (see
  // DwarfExpression::addExpression) so for those ops (e.g. DW_OP_convert) that
  // need to reference a base_type DIE the offset of that DIE is not yet known.
  // To deal with this we instead insert a placeholder early and then extract
  // it here and replace it with the real reference.
  unsigned PtrSize = Asm->MAI->getCodePointerSize();
  DWARFDataExtractor Data(StringRef(DebugLocs.getBytes(Entry).data(),
                                    DebugLocs.getBytes(Entry).size()),
                          Asm->getDataLayout().isLittleEndian(), PtrSize);
  DWARFExpression Expr(Data, PtrSize, Asm->OutContext.getDwarfFormat());

  using Encoding = DWARFExpression::Operation::Encoding;
  uint64_t Offset = 0;
  for (const auto &Op : Expr) {
    assert(Op.getCode() != dwarf::DW_OP_const_type &&
           "3 operand ops not yet supported");
    Streamer.emitInt8(Op.getCode(), Comment != End ? *(Comment++) : "");
    Offset++;
    for (unsigned I = 0; I < 2; ++I) {
      if (Op.getDescription().Op[I] == Encoding::SizeNA)
        continue;
      if (Op.getDescription().Op[I] == Encoding::BaseTypeRef) {
        unsigned Length =
          Streamer.emitDIERef(*CU->ExprRefedBaseTypes[Op.getRawOperand(I)].Die);
        // Make sure comments stay aligned.
        for (unsigned J = 0; J < Length; ++J)
          if (Comment != End)
            Comment++;
      } else {
        for (uint64_t J = Offset; J < Op.getOperandEndOffset(I); ++J)
          Streamer.emitInt8(Data.getData()[J], Comment != End ? *(Comment++) : "");
      }
      Offset = Op.getOperandEndOffset(I);
    }
    assert(Offset == Op.getEndOffset());
  }
}

void DwarfDebug::emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
                                   const DbgValueLoc &Value,
                                   DwarfExpression &DwarfExpr) {
  auto *DIExpr = Value.getExpression();
  DIExpressionCursor ExprCursor(DIExpr);
  DwarfExpr.addFragmentOffset(DIExpr);

  // If the DIExpr is is an Entry Value, we want to follow the same code path
  // regardless of whether the DBG_VALUE is variadic or not.
  if (DIExpr && DIExpr->isEntryValue()) {
    // Entry values can only be a single register with no additional DIExpr,
    // so just add it directly.
    assert(Value.getLocEntries().size() == 1);
    assert(Value.getLocEntries()[0].isLocation());
    MachineLocation Location = Value.getLocEntries()[0].getLoc();
    DwarfExpr.setLocation(Location, DIExpr);

    DwarfExpr.beginEntryValueExpression(ExprCursor);

    const TargetRegisterInfo &TRI = *AP.MF->getSubtarget().getRegisterInfo();
    if (!DwarfExpr.addMachineRegExpression(TRI, ExprCursor, Location.getReg()))
      return;
    return DwarfExpr.addExpression(std::move(ExprCursor));
  }

  // Regular entry.
  auto EmitValueLocEntry = [&DwarfExpr, &BT,
                            &AP](const DbgValueLocEntry &Entry,
                                 DIExpressionCursor &Cursor) -> bool {
    if (Entry.isInt()) {
      if (BT && (BT->getEncoding() == dwarf::DW_ATE_signed ||
                 BT->getEncoding() == dwarf::DW_ATE_signed_char))
        DwarfExpr.addSignedConstant(Entry.getInt());
      else
        DwarfExpr.addUnsignedConstant(Entry.getInt());
    } else if (Entry.isLocation()) {
      MachineLocation Location = Entry.getLoc();
      if (Location.isIndirect())
        DwarfExpr.setMemoryLocationKind();

      const TargetRegisterInfo &TRI = *AP.MF->getSubtarget().getRegisterInfo();
      if (!DwarfExpr.addMachineRegExpression(TRI, Cursor, Location.getReg()))
        return false;
    } else if (Entry.isTargetIndexLocation()) {
      TargetIndexLocation Loc = Entry.getTargetIndexLocation();
      // TODO TargetIndexLocation is a target-independent. Currently only the
      // WebAssembly-specific encoding is supported.
      assert(AP.TM.getTargetTriple().isWasm());
      DwarfExpr.addWasmLocation(Loc.Index, static_cast<uint64_t>(Loc.Offset));
    } else if (Entry.isConstantFP()) {
      if (AP.getDwarfVersion() >= 4 && !AP.getDwarfDebug()->tuneForSCE() &&
          !Cursor) {
        DwarfExpr.addConstantFP(Entry.getConstantFP()->getValueAPF(), AP);
      } else if (Entry.getConstantFP()
                     ->getValueAPF()
                     .bitcastToAPInt()
                     .getBitWidth() <= 64 /*bits*/) {
        DwarfExpr.addUnsignedConstant(
            Entry.getConstantFP()->getValueAPF().bitcastToAPInt());
      } else {
        LLVM_DEBUG(
            dbgs() << "Skipped DwarfExpression creation for ConstantFP of size"
                   << Entry.getConstantFP()
                          ->getValueAPF()
                          .bitcastToAPInt()
                          .getBitWidth()
                   << " bits\n");
        return false;
      }
    }
    return true;
  };

  if (!Value.isVariadic()) {
    if (!EmitValueLocEntry(Value.getLocEntries()[0], ExprCursor))
      return;
    DwarfExpr.addExpression(std::move(ExprCursor));
    return;
  }

  // If any of the location entries are registers with the value 0, then the
  // location is undefined.
  if (any_of(Value.getLocEntries(), [](const DbgValueLocEntry &Entry) {
        return Entry.isLocation() && !Entry.getLoc().getReg();
      }))
    return;

  DwarfExpr.addExpression(
      std::move(ExprCursor),
      [EmitValueLocEntry, &Value](unsigned Idx,
                                  DIExpressionCursor &Cursor) -> bool {
        return EmitValueLocEntry(Value.getLocEntries()[Idx], Cursor);
      });
}

void DebugLocEntry::finalize(const AsmPrinter &AP,
                             DebugLocStream::ListBuilder &List,
                             const DIBasicType *BT,
                             DwarfCompileUnit &TheCU) {
  assert(!Values.empty() &&
         "location list entries without values are redundant");
  assert(Begin != End && "unexpected location list entry with empty range");
  DebugLocStream::EntryBuilder Entry(List, Begin, End);
  BufferByteStreamer Streamer = Entry.getStreamer();
  DebugLocDwarfExpression DwarfExpr(AP.getDwarfVersion(), Streamer, TheCU);
  const DbgValueLoc &Value = Values[0];
  if (Value.isFragment()) {
    // Emit all fragments that belong to the same variable and range.
    assert(llvm::all_of(Values, [](DbgValueLoc P) {
          return P.isFragment();
        }) && "all values are expected to be fragments");
    assert(llvm::is_sorted(Values) && "fragments are expected to be sorted");

    for (const auto &Fragment : Values)
      DwarfDebug::emitDebugLocValue(AP, BT, Fragment, DwarfExpr);

  } else {
    assert(Values.size() == 1 && "only fragments may have >1 value");
    DwarfDebug::emitDebugLocValue(AP, BT, Value, DwarfExpr);
  }
  DwarfExpr.finalize();
  if (DwarfExpr.TagOffset)
    List.setTagOffset(*DwarfExpr.TagOffset);
}

void DwarfDebug::emitDebugLocEntryLocation(const DebugLocStream::Entry &Entry,
                                           const DwarfCompileUnit *CU) {
  // Emit the size.
  Asm->OutStreamer->AddComment("Loc expr size");
  if (getDwarfVersion() >= 5)
    Asm->emitULEB128(DebugLocs.getBytes(Entry).size());
  else if (DebugLocs.getBytes(Entry).size() <= std::numeric_limits<uint16_t>::max())
    Asm->emitInt16(DebugLocs.getBytes(Entry).size());
  else {
    // The entry is too big to fit into 16 bit, drop it as there is nothing we
    // can do.
    Asm->emitInt16(0);
    return;
  }
  // Emit the entry.
  APByteStreamer Streamer(*Asm);
  emitDebugLocEntry(Streamer, Entry, CU);
}

// Emit the header of a DWARF 5 range list table list table. Returns the symbol
// that designates the end of the table for the caller to emit when the table is
// complete.
static MCSymbol *emitRnglistsTableHeader(AsmPrinter *Asm,
                                         const DwarfFile &Holder) {
  MCSymbol *TableEnd = mcdwarf::emitListsTableHeaderStart(*Asm->OutStreamer);

  Asm->OutStreamer->AddComment("Offset entry count");
  Asm->emitInt32(Holder.getRangeLists().size());
  Asm->OutStreamer->emitLabel(Holder.getRnglistsTableBaseSym());

  for (const RangeSpanList &List : Holder.getRangeLists())
    Asm->emitLabelDifference(List.Label, Holder.getRnglistsTableBaseSym(),
                             Asm->getDwarfOffsetByteSize());

  return TableEnd;
}

// Emit the header of a DWARF 5 locations list table. Returns the symbol that
// designates the end of the table for the caller to emit when the table is
// complete.
static MCSymbol *emitLoclistsTableHeader(AsmPrinter *Asm,
                                         const DwarfDebug &DD) {
  MCSymbol *TableEnd = mcdwarf::emitListsTableHeaderStart(*Asm->OutStreamer);

  const auto &DebugLocs = DD.getDebugLocs();

  Asm->OutStreamer->AddComment("Offset entry count");
  Asm->emitInt32(DebugLocs.getLists().size());
  Asm->OutStreamer->emitLabel(DebugLocs.getSym());

  for (const auto &List : DebugLocs.getLists())
    Asm->emitLabelDifference(List.Label, DebugLocs.getSym(),
                             Asm->getDwarfOffsetByteSize());

  return TableEnd;
}

template <typename Ranges, typename PayloadEmitter>
static void emitRangeList(
    DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
    const DwarfCompileUnit &CU, unsigned BaseAddressx, unsigned OffsetPair,
    unsigned StartxLength, unsigned EndOfList,
    StringRef (*StringifyEnum)(unsigned),
    bool ShouldUseBaseAddress,
    PayloadEmitter EmitPayload) {

  auto Size = Asm->MAI->getCodePointerSize();
  bool UseDwarf5 = DD.getDwarfVersion() >= 5;

  // Emit our symbol so we can find the beginning of the range.
  Asm->OutStreamer->emitLabel(Sym);

  // Gather all the ranges that apply to the same section so they can share
  // a base address entry.
  MapVector<const MCSection *, std::vector<decltype(&*R.begin())>> SectionRanges;

  for (const auto &Range : R)
    SectionRanges[&Range.Begin->getSection()].push_back(&Range);

  const MCSymbol *CUBase = CU.getBaseAddress();
  bool BaseIsSet = false;
  for (const auto &P : SectionRanges) {
    auto *Base = CUBase;
    if (!Base && ShouldUseBaseAddress) {
      const MCSymbol *Begin = P.second.front()->Begin;
      const MCSymbol *NewBase = DD.getSectionLabel(&Begin->getSection());
      if (!UseDwarf5) {
        Base = NewBase;
        BaseIsSet = true;
        Asm->OutStreamer->emitIntValue(-1, Size);
        Asm->OutStreamer->AddComment("  base address");
        Asm->OutStreamer->emitSymbolValue(Base, Size);
      } else if (NewBase != Begin || P.second.size() > 1) {
        // Only use a base address if
        //  * the existing pool address doesn't match (NewBase != Begin)
        //  * or, there's more than one entry to share the base address
        Base = NewBase;
        BaseIsSet = true;
        Asm->OutStreamer->AddComment(StringifyEnum(BaseAddressx));
        Asm->emitInt8(BaseAddressx);
        Asm->OutStreamer->AddComment("  base address index");
        Asm->emitULEB128(DD.getAddressPool().getIndex(Base));
      }
    } else if (BaseIsSet && !UseDwarf5) {
      BaseIsSet = false;
      assert(!Base);
      Asm->OutStreamer->emitIntValue(-1, Size);
      Asm->OutStreamer->emitIntValue(0, Size);
    }

    for (const auto *RS : P.second) {
      const MCSymbol *Begin = RS->Begin;
      const MCSymbol *End = RS->End;
      assert(Begin && "Range without a begin symbol?");
      assert(End && "Range without an end symbol?");
      if (Base) {
        if (UseDwarf5) {
          // Emit offset_pair when we have a base.
          Asm->OutStreamer->AddComment(StringifyEnum(OffsetPair));
          Asm->emitInt8(OffsetPair);
          Asm->OutStreamer->AddComment("  starting offset");
          Asm->emitLabelDifferenceAsULEB128(Begin, Base);
          Asm->OutStreamer->AddComment("  ending offset");
          Asm->emitLabelDifferenceAsULEB128(End, Base);
        } else {
          Asm->emitLabelDifference(Begin, Base, Size);
          Asm->emitLabelDifference(End, Base, Size);
        }
      } else if (UseDwarf5) {
        Asm->OutStreamer->AddComment(StringifyEnum(StartxLength));
        Asm->emitInt8(StartxLength);
        Asm->OutStreamer->AddComment("  start index");
        Asm->emitULEB128(DD.getAddressPool().getIndex(Begin));
        Asm->OutStreamer->AddComment("  length");
        Asm->emitLabelDifferenceAsULEB128(End, Begin);
      } else {
        Asm->OutStreamer->emitSymbolValue(Begin, Size);
        Asm->OutStreamer->emitSymbolValue(End, Size);
      }
      EmitPayload(*RS);
    }
  }

  if (UseDwarf5) {
    Asm->OutStreamer->AddComment(StringifyEnum(EndOfList));
    Asm->emitInt8(EndOfList);
  } else {
    // Terminate the list with two 0 values.
    Asm->OutStreamer->emitIntValue(0, Size);
    Asm->OutStreamer->emitIntValue(0, Size);
  }
}

// Handles emission of both debug_loclist / debug_loclist.dwo
static void emitLocList(DwarfDebug &DD, AsmPrinter *Asm, const DebugLocStream::List &List) {
  emitRangeList(DD, Asm, List.Label, DD.getDebugLocs().getEntries(List),
                *List.CU, dwarf::DW_LLE_base_addressx,
                dwarf::DW_LLE_offset_pair, dwarf::DW_LLE_startx_length,
                dwarf::DW_LLE_end_of_list, llvm::dwarf::LocListEncodingString,
                /* ShouldUseBaseAddress */ true,
                [&](const DebugLocStream::Entry &E) {
                  DD.emitDebugLocEntryLocation(E, List.CU);
                });
}

void DwarfDebug::emitDebugLocImpl(MCSection *Sec) {
  if (DebugLocs.getLists().empty())
    return;

  Asm->OutStreamer->switchSection(Sec);

  MCSymbol *TableEnd = nullptr;
  if (getDwarfVersion() >= 5)
    TableEnd = emitLoclistsTableHeader(Asm, *this);

  for (const auto &List : DebugLocs.getLists())
    emitLocList(*this, Asm, List);

  if (TableEnd)
    Asm->OutStreamer->emitLabel(TableEnd);
}

// Emit locations into the .debug_loc/.debug_loclists section.
void DwarfDebug::emitDebugLoc() {
  emitDebugLocImpl(
      getDwarfVersion() >= 5
          ? Asm->getObjFileLowering().getDwarfLoclistsSection()
          : Asm->getObjFileLowering().getDwarfLocSection());
}

// Emit locations into the .debug_loc.dwo/.debug_loclists.dwo section.
void DwarfDebug::emitDebugLocDWO() {
  if (getDwarfVersion() >= 5) {
    emitDebugLocImpl(
        Asm->getObjFileLowering().getDwarfLoclistsDWOSection());

    return;
  }

  for (const auto &List : DebugLocs.getLists()) {
    Asm->OutStreamer->switchSection(
        Asm->getObjFileLowering().getDwarfLocDWOSection());
    Asm->OutStreamer->emitLabel(List.Label);

    for (const auto &Entry : DebugLocs.getEntries(List)) {
      // GDB only supports startx_length in pre-standard split-DWARF.
      // (in v5 standard loclists, it currently* /only/ supports base_address +
      // offset_pair, so the implementations can't really share much since they
      // need to use different representations)
      // * as of October 2018, at least
      //
      // In v5 (see emitLocList), this uses SectionLabels to reuse existing
      // addresses in the address pool to minimize object size/relocations.
      Asm->emitInt8(dwarf::DW_LLE_startx_length);
      unsigned idx = AddrPool.getIndex(Entry.Begin);
      Asm->emitULEB128(idx);
      // Also the pre-standard encoding is slightly different, emitting this as
      // an address-length entry here, but its a ULEB128 in DWARFv5 loclists.
      Asm->emitLabelDifference(Entry.End, Entry.Begin, 4);
      emitDebugLocEntryLocation(Entry, List.CU);
    }
    Asm->emitInt8(dwarf::DW_LLE_end_of_list);
  }
}

struct ArangeSpan {
  const MCSymbol *Start, *End;
};

// Emit a debug aranges section, containing a CU lookup for any
// address we can tie back to a CU.
void DwarfDebug::emitDebugARanges() {
  // Provides a unique id per text section.
  MapVector<MCSection *, SmallVector<SymbolCU, 8>> SectionMap;

  // Filter labels by section.
  for (const SymbolCU &SCU : ArangeLabels) {
    if (SCU.Sym->isInSection()) {
      // Make a note of this symbol and it's section.
      MCSection *Section = &SCU.Sym->getSection();
      if (!Section->getKind().isMetadata())
        SectionMap[Section].push_back(SCU);
    } else {
      // Some symbols (e.g. common/bss on mach-o) can have no section but still
      // appear in the output. This sucks as we rely on sections to build
      // arange spans. We can do it without, but it's icky.
      SectionMap[nullptr].push_back(SCU);
    }
  }

  DenseMap<DwarfCompileUnit *, std::vector<ArangeSpan>> Spans;

  for (auto &I : SectionMap) {
    MCSection *Section = I.first;
    SmallVector<SymbolCU, 8> &List = I.second;
    if (List.size() < 1)
      continue;

    // If we have no section (e.g. common), just write out
    // individual spans for each symbol.
    if (!Section) {
      for (const SymbolCU &Cur : List) {
        ArangeSpan Span;
        Span.Start = Cur.Sym;
        Span.End = nullptr;
        assert(Cur.CU);
        Spans[Cur.CU].push_back(Span);
      }
      continue;
    }

    // Sort the symbols by offset within the section.
    llvm::stable_sort(List, [&](const SymbolCU &A, const SymbolCU &B) {
      unsigned IA = A.Sym ? Asm->OutStreamer->getSymbolOrder(A.Sym) : 0;
      unsigned IB = B.Sym ? Asm->OutStreamer->getSymbolOrder(B.Sym) : 0;

      // Symbols with no order assigned should be placed at the end.
      // (e.g. section end labels)
      if (IA == 0)
        return false;
      if (IB == 0)
        return true;
      return IA < IB;
    });

    // Insert a final terminator.
    List.push_back(SymbolCU(nullptr, Asm->OutStreamer->endSection(Section)));

    // Build spans between each label.
    const MCSymbol *StartSym = List[0].Sym;
    for (size_t n = 1, e = List.size(); n < e; n++) {
      const SymbolCU &Prev = List[n - 1];
      const SymbolCU &Cur = List[n];

      // Try and build the longest span we can within the same CU.
      if (Cur.CU != Prev.CU) {
        ArangeSpan Span;
        Span.Start = StartSym;
        Span.End = Cur.Sym;
        assert(Prev.CU);
        Spans[Prev.CU].push_back(Span);
        StartSym = Cur.Sym;
      }
    }
  }

  // Start the dwarf aranges section.
  Asm->OutStreamer->switchSection(
      Asm->getObjFileLowering().getDwarfARangesSection());

  unsigned PtrSize = Asm->MAI->getCodePointerSize();

  // Build a list of CUs used.
  std::vector<DwarfCompileUnit *> CUs;
  for (const auto &it : Spans) {
    DwarfCompileUnit *CU = it.first;
    CUs.push_back(CU);
  }

  // Sort the CU list (again, to ensure consistent output order).
  llvm::sort(CUs, [](const DwarfCompileUnit *A, const DwarfCompileUnit *B) {
    return A->getUniqueID() < B->getUniqueID();
  });

  // Emit an arange table for each CU we used.
  for (DwarfCompileUnit *CU : CUs) {
    std::vector<ArangeSpan> &List = Spans[CU];

    // Describe the skeleton CU's offset and length, not the dwo file's.
    if (auto *Skel = CU->getSkeleton())
      CU = Skel;

    // Emit size of content not including length itself.
    unsigned ContentSize =
        sizeof(int16_t) +               // DWARF ARange version number
        Asm->getDwarfOffsetByteSize() + // Offset of CU in the .debug_info
                                        // section
        sizeof(int8_t) +                // Pointer Size (in bytes)
        sizeof(int8_t);                 // Segment Size (in bytes)

    unsigned TupleSize = PtrSize * 2;

    // 7.20 in the Dwarf specs requires the table to be aligned to a tuple.
    unsigned Padding = offsetToAlignment(
        Asm->getUnitLengthFieldByteSize() + ContentSize, Align(TupleSize));

    ContentSize += Padding;
    ContentSize += (List.size() + 1) * TupleSize;

    // For each compile unit, write the list of spans it covers.
    Asm->emitDwarfUnitLength(ContentSize, "Length of ARange Set");
    Asm->OutStreamer->AddComment("DWARF Arange version number");
    Asm->emitInt16(dwarf::DW_ARANGES_VERSION);
    Asm->OutStreamer->AddComment("Offset Into Debug Info Section");
    emitSectionReference(*CU);
    Asm->OutStreamer->AddComment("Address Size (in bytes)");
    Asm->emitInt8(PtrSize);
    Asm->OutStreamer->AddComment("Segment Size (in bytes)");
    Asm->emitInt8(0);

    Asm->OutStreamer->emitFill(Padding, 0xff);

    for (const ArangeSpan &Span : List) {
      Asm->emitLabelReference(Span.Start, PtrSize);

      // Calculate the size as being from the span start to its end.
      //
      // If the size is zero, then round it up to one byte. The DWARF
      // specification requires that entries in this table have nonzero
      // lengths.
      auto SizeRef = SymSize.find(Span.Start);
      if ((SizeRef == SymSize.end() || SizeRef->second != 0) && Span.End) {
        Asm->emitLabelDifference(Span.End, Span.Start, PtrSize);
      } else {
        // For symbols without an end marker (e.g. common), we
        // write a single arange entry containing just that one symbol.
        uint64_t Size;
        if (SizeRef == SymSize.end() || SizeRef->second == 0)
          Size = 1;
        else
          Size = SizeRef->second;

        Asm->OutStreamer->emitIntValue(Size, PtrSize);
      }
    }

    Asm->OutStreamer->AddComment("ARange terminator");
    Asm->OutStreamer->emitIntValue(0, PtrSize);
    Asm->OutStreamer->emitIntValue(0, PtrSize);
  }
}

/// Emit a single range list. We handle both DWARF v5 and earlier.
static void emitRangeList(DwarfDebug &DD, AsmPrinter *Asm,
                          const RangeSpanList &List) {
  emitRangeList(DD, Asm, List.Label, List.Ranges, *List.CU,
                dwarf::DW_RLE_base_addressx, dwarf::DW_RLE_offset_pair,
                dwarf::DW_RLE_startx_length, dwarf::DW_RLE_end_of_list,
                llvm::dwarf::RangeListEncodingString,
                List.CU->getCUNode()->getRangesBaseAddress() ||
                    DD.getDwarfVersion() >= 5,
                [](auto) {});
}

void DwarfDebug::emitDebugRangesImpl(const DwarfFile &Holder, MCSection *Section) {
  if (Holder.getRangeLists().empty())
    return;

  assert(useRangesSection());
  assert(!CUMap.empty());
  assert(llvm::any_of(CUMap, [](const decltype(CUMap)::value_type &Pair) {
    return !Pair.second->getCUNode()->isDebugDirectivesOnly();
  }));

  Asm->OutStreamer->switchSection(Section);

  MCSymbol *TableEnd = nullptr;
  if (getDwarfVersion() >= 5)
    TableEnd = emitRnglistsTableHeader(Asm, Holder);

  for (const RangeSpanList &List : Holder.getRangeLists())
    emitRangeList(*this, Asm, List);

  if (TableEnd)
    Asm->OutStreamer->emitLabel(TableEnd);
}

/// Emit address ranges into the .debug_ranges section or into the DWARF v5
/// .debug_rnglists section.
void DwarfDebug::emitDebugRanges() {
  const auto &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;

  emitDebugRangesImpl(Holder,
                      getDwarfVersion() >= 5
                          ? Asm->getObjFileLowering().getDwarfRnglistsSection()
                          : Asm->getObjFileLowering().getDwarfRangesSection());
}

void DwarfDebug::emitDebugRangesDWO() {
  emitDebugRangesImpl(InfoHolder,
                      Asm->getObjFileLowering().getDwarfRnglistsDWOSection());
}

/// Emit the header of a DWARF 5 macro section, or the GNU extension for
/// DWARF 4.
static void emitMacroHeader(AsmPrinter *Asm, const DwarfDebug &DD,
                            const DwarfCompileUnit &CU, uint16_t DwarfVersion) {
  enum HeaderFlagMask {
#define HANDLE_MACRO_FLAG(ID, NAME) MACRO_FLAG_##NAME = ID,
#include "llvm/BinaryFormat/Dwarf.def"
  };
  Asm->OutStreamer->AddComment("Macro information version");
  Asm->emitInt16(DwarfVersion >= 5 ? DwarfVersion : 4);
  // We emit the line offset flag unconditionally here, since line offset should
  // be mostly present.
  if (Asm->isDwarf64()) {
    Asm->OutStreamer->AddComment("Flags: 64 bit, debug_line_offset present");
    Asm->emitInt8(MACRO_FLAG_OFFSET_SIZE | MACRO_FLAG_DEBUG_LINE_OFFSET);
  } else {
    Asm->OutStreamer->AddComment("Flags: 32 bit, debug_line_offset present");
    Asm->emitInt8(MACRO_FLAG_DEBUG_LINE_OFFSET);
  }
  Asm->OutStreamer->AddComment("debug_line_offset");
  if (DD.useSplitDwarf())
    Asm->emitDwarfLengthOrOffset(0);
  else
    Asm->emitDwarfSymbolReference(CU.getLineTableStartSym());
}

void DwarfDebug::handleMacroNodes(DIMacroNodeArray Nodes, DwarfCompileUnit &U) {
  for (auto *MN : Nodes) {
    if (auto *M = dyn_cast<DIMacro>(MN))
      emitMacro(*M);
    else if (auto *F = dyn_cast<DIMacroFile>(MN))
      emitMacroFile(*F, U);
    else
      llvm_unreachable("Unexpected DI type!");
  }
}

void DwarfDebug::emitMacro(DIMacro &M) {
  StringRef Name = M.getName();
  StringRef Value = M.getValue();

  // There should be one space between the macro name and the macro value in
  // define entries. In undef entries, only the macro name is emitted.
  std::string Str = Value.empty() ? Name.str() : (Name + " " + Value).str();

  if (UseDebugMacroSection) {
    if (getDwarfVersion() >= 5) {
      unsigned Type = M.getMacinfoType() == dwarf::DW_MACINFO_define
                          ? dwarf::DW_MACRO_define_strx
                          : dwarf::DW_MACRO_undef_strx;
      Asm->OutStreamer->AddComment(dwarf::MacroString(Type));
      Asm->emitULEB128(Type);
      Asm->OutStreamer->AddComment("Line Number");
      Asm->emitULEB128(M.getLine());
      Asm->OutStreamer->AddComment("Macro String");
      Asm->emitULEB128(
          InfoHolder.getStringPool().getIndexedEntry(*Asm, Str).getIndex());
    } else {
      unsigned Type = M.getMacinfoType() == dwarf::DW_MACINFO_define
                          ? dwarf::DW_MACRO_GNU_define_indirect
                          : dwarf::DW_MACRO_GNU_undef_indirect;
      Asm->OutStreamer->AddComment(dwarf::GnuMacroString(Type));
      Asm->emitULEB128(Type);
      Asm->OutStreamer->AddComment("Line Number");
      Asm->emitULEB128(M.getLine());
      Asm->OutStreamer->AddComment("Macro String");
      Asm->emitDwarfSymbolReference(
          InfoHolder.getStringPool().getEntry(*Asm, Str).getSymbol());
    }
  } else {
    Asm->OutStreamer->AddComment(dwarf::MacinfoString(M.getMacinfoType()));
    Asm->emitULEB128(M.getMacinfoType());
    Asm->OutStreamer->AddComment("Line Number");
    Asm->emitULEB128(M.getLine());
    Asm->OutStreamer->AddComment("Macro String");
    Asm->OutStreamer->emitBytes(Str);
    Asm->emitInt8('\0');
  }
}

void DwarfDebug::emitMacroFileImpl(
    DIMacroFile &MF, DwarfCompileUnit &U, unsigned StartFile, unsigned EndFile,
    StringRef (*MacroFormToString)(unsigned Form)) {

  Asm->OutStreamer->AddComment(MacroFormToString(StartFile));
  Asm->emitULEB128(StartFile);
  Asm->OutStreamer->AddComment("Line Number");
  Asm->emitULEB128(MF.getLine());
  Asm->OutStreamer->AddComment("File Number");
  DIFile &F = *MF.getFile();
  if (useSplitDwarf())
    Asm->emitULEB128(getDwoLineTable(U)->getFile(
        F.getDirectory(), F.getFilename(), getMD5AsBytes(&F),
        Asm->OutContext.getDwarfVersion(), F.getSource()));
  else
    Asm->emitULEB128(U.getOrCreateSourceID(&F));
  handleMacroNodes(MF.getElements(), U);
  Asm->OutStreamer->AddComment(MacroFormToString(EndFile));
  Asm->emitULEB128(EndFile);
}

void DwarfDebug::emitMacroFile(DIMacroFile &F, DwarfCompileUnit &U) {
  // DWARFv5 macro and DWARFv4 macinfo share some common encodings,
  // so for readibility/uniformity, We are explicitly emitting those.
  assert(F.getMacinfoType() == dwarf::DW_MACINFO_start_file);
  if (UseDebugMacroSection)
    emitMacroFileImpl(
        F, U, dwarf::DW_MACRO_start_file, dwarf::DW_MACRO_end_file,
        (getDwarfVersion() >= 5) ? dwarf::MacroString : dwarf::GnuMacroString);
  else
    emitMacroFileImpl(F, U, dwarf::DW_MACINFO_start_file,
                      dwarf::DW_MACINFO_end_file, dwarf::MacinfoString);
}

void DwarfDebug::emitDebugMacinfoImpl(MCSection *Section) {
  for (const auto &P : CUMap) {
    auto &TheCU = *P.second;
    auto *SkCU = TheCU.getSkeleton();
    DwarfCompileUnit &U = SkCU ? *SkCU : TheCU;
    auto *CUNode = cast<DICompileUnit>(P.first);
    DIMacroNodeArray Macros = CUNode->getMacros();
    if (Macros.empty())
      continue;
    Asm->OutStreamer->switchSection(Section);
    Asm->OutStreamer->emitLabel(U.getMacroLabelBegin());
    if (UseDebugMacroSection)
      emitMacroHeader(Asm, *this, U, getDwarfVersion());
    handleMacroNodes(Macros, U);
    Asm->OutStreamer->AddComment("End Of Macro List Mark");
    Asm->emitInt8(0);
  }
}

/// Emit macros into a debug macinfo/macro section.
void DwarfDebug::emitDebugMacinfo() {
  auto &ObjLower = Asm->getObjFileLowering();
  emitDebugMacinfoImpl(UseDebugMacroSection
                           ? ObjLower.getDwarfMacroSection()
                           : ObjLower.getDwarfMacinfoSection());
}

void DwarfDebug::emitDebugMacinfoDWO() {
  auto &ObjLower = Asm->getObjFileLowering();
  emitDebugMacinfoImpl(UseDebugMacroSection
                           ? ObjLower.getDwarfMacroDWOSection()
                           : ObjLower.getDwarfMacinfoDWOSection());
}

// DWARF5 Experimental Separate Dwarf emitters.

void DwarfDebug::initSkeletonUnit(const DwarfUnit &U, DIE &Die,
                                  std::unique_ptr<DwarfCompileUnit> NewU) {

  if (!CompilationDir.empty())
    NewU->addString(Die, dwarf::DW_AT_comp_dir, CompilationDir);
  addGnuPubAttributes(*NewU, Die);

  SkeletonHolder.addUnit(std::move(NewU));
}

DwarfCompileUnit &DwarfDebug::constructSkeletonCU(const DwarfCompileUnit &CU) {

  auto OwnedUnit = std::make_unique<DwarfCompileUnit>(
      CU.getUniqueID(), CU.getCUNode(), Asm, this, &SkeletonHolder,
      UnitKind::Skeleton);
  DwarfCompileUnit &NewCU = *OwnedUnit;
  NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoSection());

  NewCU.initStmtList();

  if (useSegmentedStringOffsetsTable())
    NewCU.addStringOffsetsStart();

  initSkeletonUnit(CU, NewCU.getUnitDie(), std::move(OwnedUnit));

  return NewCU;
}

// Emit the .debug_info.dwo section for separated dwarf. This contains the
// compile units that would normally be in debug_info.
void DwarfDebug::emitDebugInfoDWO() {
  assert(useSplitDwarf() && "No split dwarf debug info?");
  // Don't emit relocations into the dwo file.
  InfoHolder.emitUnits(/* UseOffsets */ true);
}

// Emit the .debug_abbrev.dwo section for separated dwarf. This contains the
// abbreviations for the .debug_info.dwo section.
void DwarfDebug::emitDebugAbbrevDWO() {
  assert(useSplitDwarf() && "No split dwarf?");
  InfoHolder.emitAbbrevs(Asm->getObjFileLowering().getDwarfAbbrevDWOSection());
}

void DwarfDebug::emitDebugLineDWO() {
  assert(useSplitDwarf() && "No split dwarf?");
  SplitTypeUnitFileTable.Emit(
      *Asm->OutStreamer, MCDwarfLineTableParams(),
      Asm->getObjFileLowering().getDwarfLineDWOSection());
}

void DwarfDebug::emitStringOffsetsTableHeaderDWO() {
  assert(useSplitDwarf() && "No split dwarf?");
  InfoHolder.getStringPool().emitStringOffsetsTableHeader(
      *Asm, Asm->getObjFileLowering().getDwarfStrOffDWOSection(),
      InfoHolder.getStringOffsetsStartSym());
}

// Emit the .debug_str.dwo section for separated dwarf. This contains the
// string section and is identical in format to traditional .debug_str
// sections.
void DwarfDebug::emitDebugStrDWO() {
  if (useSegmentedStringOffsetsTable())
    emitStringOffsetsTableHeaderDWO();
  assert(useSplitDwarf() && "No split dwarf?");
  MCSection *OffSec = Asm->getObjFileLowering().getDwarfStrOffDWOSection();
  InfoHolder.emitStrings(Asm->getObjFileLowering().getDwarfStrDWOSection(),
                         OffSec, /* UseRelativeOffsets = */ false);
}

// Emit address pool.
void DwarfDebug::emitDebugAddr() {
  AddrPool.emit(*Asm, Asm->getObjFileLowering().getDwarfAddrSection());
}

MCDwarfDwoLineTable *DwarfDebug::getDwoLineTable(const DwarfCompileUnit &CU) {
  if (!useSplitDwarf())
    return nullptr;
  const DICompileUnit *DIUnit = CU.getCUNode();
  SplitTypeUnitFileTable.maybeSetRootFile(
      DIUnit->getDirectory(), DIUnit->getFilename(),
      getMD5AsBytes(DIUnit->getFile()), DIUnit->getSource());
  return &SplitTypeUnitFileTable;
}

uint64_t DwarfDebug::makeTypeSignature(StringRef Identifier) {
  MD5 Hash;
  Hash.update(Identifier);
  // ... take the least significant 8 bytes and return those. Our MD5
  // implementation always returns its results in little endian, so we actually
  // need the "high" word.
  MD5::MD5Result Result;
  Hash.final(Result);
  return Result.high();
}

void DwarfDebug::addDwarfTypeUnitType(DwarfCompileUnit &CU,
                                      StringRef Identifier, DIE &RefDie,
                                      const DICompositeType *CTy) {
  // Fast path if we're building some type units and one has already used the
  // address pool we know we're going to throw away all this work anyway, so
  // don't bother building dependent types.
  if (!TypeUnitsUnderConstruction.empty() && AddrPool.hasBeenUsed())
    return;

  auto Ins = TypeSignatures.insert(std::make_pair(CTy, 0));
  if (!Ins.second) {
    CU.addDIETypeSignature(RefDie, Ins.first->second);
    return;
  }

  bool TopLevelType = TypeUnitsUnderConstruction.empty();
  AddrPool.resetUsedFlag();

  auto OwnedUnit = std::make_unique<DwarfTypeUnit>(CU, Asm, this, &InfoHolder,
                                                    getDwoLineTable(CU));
  DwarfTypeUnit &NewTU = *OwnedUnit;
  DIE &UnitDie = NewTU.getUnitDie();
  TypeUnitsUnderConstruction.emplace_back(std::move(OwnedUnit), CTy);

  NewTU.addUInt(UnitDie, dwarf::DW_AT_language, dwarf::DW_FORM_data2,
                CU.getLanguage());

  uint64_t Signature = makeTypeSignature(Identifier);
  NewTU.setTypeSignature(Signature);
  Ins.first->second = Signature;

  if (useSplitDwarf()) {
    MCSection *Section =
        getDwarfVersion() <= 4
            ? Asm->getObjFileLowering().getDwarfTypesDWOSection()
            : Asm->getObjFileLowering().getDwarfInfoDWOSection();
    NewTU.setSection(Section);
  } else {
    MCSection *Section =
        getDwarfVersion() <= 4
            ? Asm->getObjFileLowering().getDwarfTypesSection(Signature)
            : Asm->getObjFileLowering().getDwarfInfoSection(Signature);
    NewTU.setSection(Section);
    // Non-split type units reuse the compile unit's line table.
    CU.applyStmtList(UnitDie);
  }

  // Add DW_AT_str_offsets_base to the type unit DIE, but not for split type
  // units.
  if (useSegmentedStringOffsetsTable() && !useSplitDwarf())
    NewTU.addStringOffsetsStart();

  NewTU.setType(NewTU.createTypeDIE(CTy));

  if (TopLevelType) {
    auto TypeUnitsToAdd = std::move(TypeUnitsUnderConstruction);
    TypeUnitsUnderConstruction.clear();

    // Types referencing entries in the address table cannot be placed in type
    // units.
    if (AddrPool.hasBeenUsed()) {

      // Remove all the types built while building this type.
      // This is pessimistic as some of these types might not be dependent on
      // the type that used an address.
      for (const auto &TU : TypeUnitsToAdd)
        TypeSignatures.erase(TU.second);

      // Construct this type in the CU directly.
      // This is inefficient because all the dependent types will be rebuilt
      // from scratch, including building them in type units, discovering that
      // they depend on addresses, throwing them out and rebuilding them.
      CU.constructTypeDIE(RefDie, cast<DICompositeType>(CTy));
      return;
    }

    // If the type wasn't dependent on fission addresses, finish adding the type
    // and all its dependent types.
    for (auto &TU : TypeUnitsToAdd) {
      InfoHolder.computeSizeAndOffsetsForUnit(TU.first.get());
      InfoHolder.emitUnit(TU.first.get(), useSplitDwarf());
    }
  }
  CU.addDIETypeSignature(RefDie, Signature);
}

// Add the Name along with its companion DIE to the appropriate accelerator
// table (for AccelTableKind::Dwarf it's always AccelDebugNames, for
// AccelTableKind::Apple, we use the table we got as an argument). If
// accelerator tables are disabled, this function does nothing.
template <typename DataT>
void DwarfDebug::addAccelNameImpl(const DICompileUnit &CU,
                                  AccelTable<DataT> &AppleAccel, StringRef Name,
                                  const DIE &Die) {
  if (getAccelTableKind() == AccelTableKind::None)
    return;

  if (getAccelTableKind() != AccelTableKind::Apple &&
      CU.getNameTableKind() != DICompileUnit::DebugNameTableKind::Default)
    return;

  DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
  DwarfStringPoolEntryRef Ref = Holder.getStringPool().getEntry(*Asm, Name);

  switch (getAccelTableKind()) {
  case AccelTableKind::Apple:
    AppleAccel.addName(Ref, Die);
    break;
  case AccelTableKind::Dwarf:
    AccelDebugNames.addName(Ref, Die);
    break;
  case AccelTableKind::Default:
    llvm_unreachable("Default should have already been resolved.");
  case AccelTableKind::None:
    llvm_unreachable("None handled above");
  }
}

void DwarfDebug::addAccelName(const DICompileUnit &CU, StringRef Name,
                              const DIE &Die) {
  addAccelNameImpl(CU, AccelNames, Name, Die);
}

void DwarfDebug::addAccelObjC(const DICompileUnit &CU, StringRef Name,
                              const DIE &Die) {
  // ObjC names go only into the Apple accelerator tables.
  if (getAccelTableKind() == AccelTableKind::Apple)
    addAccelNameImpl(CU, AccelObjC, Name, Die);
}

void DwarfDebug::addAccelNamespace(const DICompileUnit &CU, StringRef Name,
                                   const DIE &Die) {
  addAccelNameImpl(CU, AccelNamespace, Name, Die);
}

void DwarfDebug::addAccelType(const DICompileUnit &CU, StringRef Name,
                              const DIE &Die, char Flags) {
  addAccelNameImpl(CU, AccelTypes, Name, Die);
}

uint16_t DwarfDebug::getDwarfVersion() const {
  return Asm->OutStreamer->getContext().getDwarfVersion();
}

dwarf::Form DwarfDebug::getDwarfSectionOffsetForm() const {
  if (Asm->getDwarfVersion() >= 4)
    return dwarf::Form::DW_FORM_sec_offset;
  assert((!Asm->isDwarf64() || (Asm->getDwarfVersion() == 3)) &&
         "DWARF64 is not defined prior DWARFv3");
  return Asm->isDwarf64() ? dwarf::Form::DW_FORM_data8
                          : dwarf::Form::DW_FORM_data4;
}

const MCSymbol *DwarfDebug::getSectionLabel(const MCSection *S) {
  auto I = SectionLabels.find(S);
  if (I == SectionLabels.end())
    return nullptr;
  return I->second;
}
void DwarfDebug::insertSectionLabel(const MCSymbol *S) {
  if (SectionLabels.insert(std::make_pair(&S->getSection(), S)).second)
    if (useSplitDwarf() || getDwarfVersion() >= 5)
      AddrPool.getIndex(S);
}

std::optional<MD5::MD5Result>
DwarfDebug::getMD5AsBytes(const DIFile *File) const {
  assert(File);
  if (getDwarfVersion() < 5)
    return std::nullopt;
  std::optional<DIFile::ChecksumInfo<StringRef>> Checksum = File->getChecksum();
  if (!Checksum || Checksum->Kind != DIFile::CSK_MD5)
    return std::nullopt;

  // Convert the string checksum to an MD5Result for the streamer.
  // The verifier validates the checksum so we assume it's okay.
  // An MD5 checksum is 16 bytes.
  std::string ChecksumString = fromHex(Checksum->Value);
  MD5::MD5Result CKMem;
  std::copy(ChecksumString.begin(), ChecksumString.end(), CKMem.data());
  return CKMem;
}