aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/llvm16/lib/MC/MCDwarf.cpp
blob: 30b8aadbf63c3fed785dd58fcd99c1b3e5e0d600 (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
//===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
//
// 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
//
//===----------------------------------------------------------------------===//

#include "llvm/MC/MCDwarf.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/Config/config.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/EndianStream.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdint>
#include <optional>
#include <string>
#include <utility>
#include <vector>

using namespace llvm;

MCSymbol *mcdwarf::emitListsTableHeaderStart(MCStreamer &S) {
  MCSymbol *Start = S.getContext().createTempSymbol("debug_list_header_start");
  MCSymbol *End = S.getContext().createTempSymbol("debug_list_header_end");
  auto DwarfFormat = S.getContext().getDwarfFormat();
  if (DwarfFormat == dwarf::DWARF64) {
    S.AddComment("DWARF64 mark");
    S.emitInt32(dwarf::DW_LENGTH_DWARF64);
  }
  S.AddComment("Length");
  S.emitAbsoluteSymbolDiff(End, Start,
                           dwarf::getDwarfOffsetByteSize(DwarfFormat));
  S.emitLabel(Start);
  S.AddComment("Version");
  S.emitInt16(S.getContext().getDwarfVersion());
  S.AddComment("Address size");
  S.emitInt8(S.getContext().getAsmInfo()->getCodePointerSize());
  S.AddComment("Segment selector size");
  S.emitInt8(0);
  return End;
}

static inline uint64_t ScaleAddrDelta(MCContext &Context, uint64_t AddrDelta) {
  unsigned MinInsnLength = Context.getAsmInfo()->getMinInstAlignment();
  if (MinInsnLength == 1)
    return AddrDelta;
  if (AddrDelta % MinInsnLength != 0) {
    // TODO: report this error, but really only once.
    ;
  }
  return AddrDelta / MinInsnLength;
}

MCDwarfLineStr::MCDwarfLineStr(MCContext &Ctx) {
  UseRelocs = Ctx.getAsmInfo()->doesDwarfUseRelocationsAcrossSections();
  if (UseRelocs)
    LineStrLabel =
        Ctx.getObjectFileInfo()->getDwarfLineStrSection()->getBeginSymbol();
}

//
// This is called when an instruction is assembled into the specified section
// and if there is information from the last .loc directive that has yet to have
// a line entry made for it is made.
//
void MCDwarfLineEntry::make(MCStreamer *MCOS, MCSection *Section) {
  if (!MCOS->getContext().getDwarfLocSeen())
    return;

  // Create a symbol at in the current section for use in the line entry.
  MCSymbol *LineSym = MCOS->getContext().createTempSymbol();
  // Set the value of the symbol to use for the MCDwarfLineEntry.
  MCOS->emitLabel(LineSym);

  // Get the current .loc info saved in the context.
  const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();

  // Create a (local) line entry with the symbol and the current .loc info.
  MCDwarfLineEntry LineEntry(LineSym, DwarfLoc);

  // clear DwarfLocSeen saying the current .loc info is now used.
  MCOS->getContext().clearDwarfLocSeen();

  // Add the line entry to this section's entries.
  MCOS->getContext()
      .getMCDwarfLineTable(MCOS->getContext().getDwarfCompileUnitID())
      .getMCLineSections()
      .addLineEntry(LineEntry, Section);
}

//
// This helper routine returns an expression of End - Start - IntVal .
//
static inline const MCExpr *makeEndMinusStartExpr(MCContext &Ctx,
                                                  const MCSymbol &Start,
                                                  const MCSymbol &End,
                                                  int IntVal) {
  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
  const MCExpr *Res = MCSymbolRefExpr::create(&End, Variant, Ctx);
  const MCExpr *RHS = MCSymbolRefExpr::create(&Start, Variant, Ctx);
  const MCExpr *Res1 = MCBinaryExpr::create(MCBinaryExpr::Sub, Res, RHS, Ctx);
  const MCExpr *Res2 = MCConstantExpr::create(IntVal, Ctx);
  const MCExpr *Res3 = MCBinaryExpr::create(MCBinaryExpr::Sub, Res1, Res2, Ctx);
  return Res3;
}

//
// This helper routine returns an expression of Start + IntVal .
//
static inline const MCExpr *
makeStartPlusIntExpr(MCContext &Ctx, const MCSymbol &Start, int IntVal) {
  MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
  const MCExpr *LHS = MCSymbolRefExpr::create(&Start, Variant, Ctx);
  const MCExpr *RHS = MCConstantExpr::create(IntVal, Ctx);
  const MCExpr *Res = MCBinaryExpr::create(MCBinaryExpr::Add, LHS, RHS, Ctx);
  return Res;
}

void MCLineSection::addEndEntry(MCSymbol *EndLabel) {
  auto *Sec = &EndLabel->getSection();
  // The line table may be empty, which we should skip adding an end entry.
  // There are two cases:
  // (1) MCAsmStreamer - emitDwarfLocDirective emits a location directive in
  //     place instead of adding a line entry if the target has
  //     usesDwarfFileAndLocDirectives.
  // (2) MCObjectStreamer - if a function has incomplete debug info where
  //     instructions don't have DILocations, the line entries are missing.
  auto I = MCLineDivisions.find(Sec);
  if (I != MCLineDivisions.end()) {
    auto &Entries = I->second;
    auto EndEntry = Entries.back();
    EndEntry.setEndLabel(EndLabel);
    Entries.push_back(EndEntry);
  }
}

//
// This emits the Dwarf line table for the specified section from the entries
// in the LineSection.
//
void MCDwarfLineTable::emitOne(
    MCStreamer *MCOS, MCSection *Section,
    const MCLineSection::MCDwarfLineEntryCollection &LineEntries) {

  unsigned FileNum, LastLine, Column, Flags, Isa, Discriminator;
  MCSymbol *LastLabel;
  auto init = [&]() {
    FileNum = 1;
    LastLine = 1;
    Column = 0;
    Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
    Isa = 0;
    Discriminator = 0;
    LastLabel = nullptr;
  };
  init();

  // Loop through each MCDwarfLineEntry and encode the dwarf line number table.
  bool EndEntryEmitted = false;
  for (const MCDwarfLineEntry &LineEntry : LineEntries) {
    MCSymbol *Label = LineEntry.getLabel();
    const MCAsmInfo *asmInfo = MCOS->getContext().getAsmInfo();
    if (LineEntry.IsEndEntry) {
      MCOS->emitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, Label,
                                     asmInfo->getCodePointerSize());
      init();
      EndEntryEmitted = true;
      continue;
    }

    int64_t LineDelta = static_cast<int64_t>(LineEntry.getLine()) - LastLine;

    if (FileNum != LineEntry.getFileNum()) {
      FileNum = LineEntry.getFileNum();
      MCOS->emitInt8(dwarf::DW_LNS_set_file);
      MCOS->emitULEB128IntValue(FileNum);
    }
    if (Column != LineEntry.getColumn()) {
      Column = LineEntry.getColumn();
      MCOS->emitInt8(dwarf::DW_LNS_set_column);
      MCOS->emitULEB128IntValue(Column);
    }
    if (Discriminator != LineEntry.getDiscriminator() &&
        MCOS->getContext().getDwarfVersion() >= 4) {
      Discriminator = LineEntry.getDiscriminator();
      unsigned Size = getULEB128Size(Discriminator);
      MCOS->emitInt8(dwarf::DW_LNS_extended_op);
      MCOS->emitULEB128IntValue(Size + 1);
      MCOS->emitInt8(dwarf::DW_LNE_set_discriminator);
      MCOS->emitULEB128IntValue(Discriminator);
    }
    if (Isa != LineEntry.getIsa()) {
      Isa = LineEntry.getIsa();
      MCOS->emitInt8(dwarf::DW_LNS_set_isa);
      MCOS->emitULEB128IntValue(Isa);
    }
    if ((LineEntry.getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
      Flags = LineEntry.getFlags();
      MCOS->emitInt8(dwarf::DW_LNS_negate_stmt);
    }
    if (LineEntry.getFlags() & DWARF2_FLAG_BASIC_BLOCK)
      MCOS->emitInt8(dwarf::DW_LNS_set_basic_block);
    if (LineEntry.getFlags() & DWARF2_FLAG_PROLOGUE_END)
      MCOS->emitInt8(dwarf::DW_LNS_set_prologue_end);
    if (LineEntry.getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
      MCOS->emitInt8(dwarf::DW_LNS_set_epilogue_begin);

    // At this point we want to emit/create the sequence to encode the delta in
    // line numbers and the increment of the address from the previous Label
    // and the current Label.
    MCOS->emitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label,
                                   asmInfo->getCodePointerSize());

    Discriminator = 0;
    LastLine = LineEntry.getLine();
    LastLabel = Label;
  }

  // Generate DWARF line end entry.
  // We do not need this for DwarfDebug that explicitly terminates the line
  // table using ranges whenever CU or section changes. However, the MC path
  // does not track ranges nor terminate the line table. In that case,
  // conservatively use the section end symbol to end the line table.
  if (!EndEntryEmitted)
    MCOS->emitDwarfLineEndEntry(Section, LastLabel);
}

//
// This emits the Dwarf file and the line tables.
//
void MCDwarfLineTable::emit(MCStreamer *MCOS, MCDwarfLineTableParams Params) {
  MCContext &context = MCOS->getContext();

  auto &LineTables = context.getMCDwarfLineTables();

  // Bail out early so we don't switch to the debug_line section needlessly and
  // in doing so create an unnecessary (if empty) section.
  if (LineTables.empty())
    return;

  // In a v5 non-split line table, put the strings in a separate section.
  std::optional<MCDwarfLineStr> LineStr;
  if (context.getDwarfVersion() >= 5)
    LineStr.emplace(context);

  // Switch to the section where the table will be emitted into.
  MCOS->switchSection(context.getObjectFileInfo()->getDwarfLineSection());

  // Handle the rest of the Compile Units.
  for (const auto &CUIDTablePair : LineTables) {
    CUIDTablePair.second.emitCU(MCOS, Params, LineStr);
  }

  if (LineStr)
    LineStr->emitSection(MCOS);
}

void MCDwarfDwoLineTable::Emit(MCStreamer &MCOS, MCDwarfLineTableParams Params,
                               MCSection *Section) const {
  if (!HasSplitLineTable)
    return;
  std::optional<MCDwarfLineStr> NoLineStr(std::nullopt);
  MCOS.switchSection(Section);
  MCOS.emitLabel(Header.Emit(&MCOS, Params, std::nullopt, NoLineStr).second);
}

std::pair<MCSymbol *, MCSymbol *>
MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
                             std::optional<MCDwarfLineStr> &LineStr) const {
  static const char StandardOpcodeLengths[] = {
      0, // length of DW_LNS_copy
      1, // length of DW_LNS_advance_pc
      1, // length of DW_LNS_advance_line
      1, // length of DW_LNS_set_file
      1, // length of DW_LNS_set_column
      0, // length of DW_LNS_negate_stmt
      0, // length of DW_LNS_set_basic_block
      0, // length of DW_LNS_const_add_pc
      1, // length of DW_LNS_fixed_advance_pc
      0, // length of DW_LNS_set_prologue_end
      0, // length of DW_LNS_set_epilogue_begin
      1  // DW_LNS_set_isa
  };
  assert(std::size(StandardOpcodeLengths) >=
         (Params.DWARF2LineOpcodeBase - 1U));
  return Emit(MCOS, Params,
              ArrayRef(StandardOpcodeLengths, Params.DWARF2LineOpcodeBase - 1),
              LineStr);
}

static const MCExpr *forceExpAbs(MCStreamer &OS, const MCExpr* Expr) {
  MCContext &Context = OS.getContext();
  assert(!isa<MCSymbolRefExpr>(Expr));
  if (Context.getAsmInfo()->hasAggressiveSymbolFolding())
    return Expr;

  MCSymbol *ABS = Context.createTempSymbol();
  OS.emitAssignment(ABS, Expr);
  return MCSymbolRefExpr::create(ABS, Context);
}

static void emitAbsValue(MCStreamer &OS, const MCExpr *Value, unsigned Size) {
  const MCExpr *ABS = forceExpAbs(OS, Value);
  OS.emitValue(ABS, Size);
}

void MCDwarfLineStr::emitSection(MCStreamer *MCOS) {
  // Switch to the .debug_line_str section.
  MCOS->switchSection(
      MCOS->getContext().getObjectFileInfo()->getDwarfLineStrSection());
  SmallString<0> Data = getFinalizedData();
  MCOS->emitBinaryData(Data.str());
}

SmallString<0> MCDwarfLineStr::getFinalizedData() {
  // Emit the strings without perturbing the offsets we used.
  if (!LineStrings.isFinalized())
    LineStrings.finalizeInOrder();
  SmallString<0> Data;
  Data.resize(LineStrings.getSize());
  LineStrings.write((uint8_t *)Data.data());
  return Data;
}

void MCDwarfLineStr::emitRef(MCStreamer *MCOS, StringRef Path) {
  int RefSize =
      dwarf::getDwarfOffsetByteSize(MCOS->getContext().getDwarfFormat());
  size_t Offset = LineStrings.add(Path);
  if (UseRelocs) {
    MCContext &Ctx = MCOS->getContext();
    MCOS->emitValue(makeStartPlusIntExpr(Ctx, *LineStrLabel, Offset), RefSize);
  } else
    MCOS->emitIntValue(Offset, RefSize);
}

void MCDwarfLineTableHeader::emitV2FileDirTables(MCStreamer *MCOS) const {
  // First the directory table.
  for (auto &Dir : MCDwarfDirs) {
    MCOS->emitBytes(Dir);                // The DirectoryName, and...
    MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
  }
  MCOS->emitInt8(0); // Terminate the directory list.

  // Second the file table.
  for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
    assert(!MCDwarfFiles[i].Name.empty());
    MCOS->emitBytes(MCDwarfFiles[i].Name); // FileName and...
    MCOS->emitBytes(StringRef("\0", 1));   // its null terminator.
    MCOS->emitULEB128IntValue(MCDwarfFiles[i].DirIndex); // Directory number.
    MCOS->emitInt8(0); // Last modification timestamp (always 0).
    MCOS->emitInt8(0); // File size (always 0).
  }
  MCOS->emitInt8(0); // Terminate the file list.
}

static void emitOneV5FileEntry(MCStreamer *MCOS, const MCDwarfFile &DwarfFile,
                               bool EmitMD5, bool HasSource,
                               std::optional<MCDwarfLineStr> &LineStr) {
  assert(!DwarfFile.Name.empty());
  if (LineStr)
    LineStr->emitRef(MCOS, DwarfFile.Name);
  else {
    MCOS->emitBytes(DwarfFile.Name);     // FileName and...
    MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
  }
  MCOS->emitULEB128IntValue(DwarfFile.DirIndex); // Directory number.
  if (EmitMD5) {
    const MD5::MD5Result &Cksum = *DwarfFile.Checksum;
    MCOS->emitBinaryData(
        StringRef(reinterpret_cast<const char *>(Cksum.data()), Cksum.size()));
  }
  if (HasSource) {
    if (LineStr)
      LineStr->emitRef(MCOS, DwarfFile.Source.value_or(StringRef()));
    else {
      MCOS->emitBytes(DwarfFile.Source.value_or(StringRef())); // Source and...
      MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
    }
  }
}

void MCDwarfLineTableHeader::emitV5FileDirTables(
    MCStreamer *MCOS, std::optional<MCDwarfLineStr> &LineStr) const {
  // The directory format, which is just a list of the directory paths.  In a
  // non-split object, these are references to .debug_line_str; in a split
  // object, they are inline strings.
  MCOS->emitInt8(1);
  MCOS->emitULEB128IntValue(dwarf::DW_LNCT_path);
  MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
                                    : dwarf::DW_FORM_string);
  MCOS->emitULEB128IntValue(MCDwarfDirs.size() + 1);
  // Try not to emit an empty compilation directory.
  SmallString<256> Dir;
  StringRef CompDir = MCOS->getContext().getCompilationDir();
  if (!CompilationDir.empty()) {
    Dir = CompilationDir;
    MCOS->getContext().remapDebugPath(Dir);
    CompDir = Dir.str();
    if (LineStr)
      CompDir = LineStr->getSaver().save(CompDir);
  }
  if (LineStr) {
    // Record path strings, emit references here.
    LineStr->emitRef(MCOS, CompDir);
    for (const auto &Dir : MCDwarfDirs)
      LineStr->emitRef(MCOS, Dir);
  } else {
    // The list of directory paths.  Compilation directory comes first.
    MCOS->emitBytes(CompDir);
    MCOS->emitBytes(StringRef("\0", 1));
    for (const auto &Dir : MCDwarfDirs) {
      MCOS->emitBytes(Dir);                // The DirectoryName, and...
      MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
    }
  }

  // The file format, which is the inline null-terminated filename and a
  // directory index.  We don't track file size/timestamp so don't emit them
  // in the v5 table.  Emit MD5 checksums and source if we have them.
  uint64_t Entries = 2;
  if (HasAllMD5)
    Entries += 1;
  if (HasSource)
    Entries += 1;
  MCOS->emitInt8(Entries);
  MCOS->emitULEB128IntValue(dwarf::DW_LNCT_path);
  MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
                                    : dwarf::DW_FORM_string);
  MCOS->emitULEB128IntValue(dwarf::DW_LNCT_directory_index);
  MCOS->emitULEB128IntValue(dwarf::DW_FORM_udata);
  if (HasAllMD5) {
    MCOS->emitULEB128IntValue(dwarf::DW_LNCT_MD5);
    MCOS->emitULEB128IntValue(dwarf::DW_FORM_data16);
  }
  if (HasSource) {
    MCOS->emitULEB128IntValue(dwarf::DW_LNCT_LLVM_source);
    MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
                                      : dwarf::DW_FORM_string);
  }
  // Then the counted list of files. The root file is file #0, then emit the
  // files as provide by .file directives.
  // MCDwarfFiles has an unused element [0] so use size() not size()+1.
  // But sometimes MCDwarfFiles is empty, in which case we still emit one file.
  MCOS->emitULEB128IntValue(MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size());
  // To accommodate assembler source written for DWARF v4 but trying to emit
  // v5: If we didn't see a root file explicitly, replicate file #1.
  assert((!RootFile.Name.empty() || MCDwarfFiles.size() >= 1) &&
         "No root file and no .file directives");
  emitOneV5FileEntry(MCOS, RootFile.Name.empty() ? MCDwarfFiles[1] : RootFile,
                     HasAllMD5, HasSource, LineStr);
  for (unsigned i = 1; i < MCDwarfFiles.size(); ++i)
    emitOneV5FileEntry(MCOS, MCDwarfFiles[i], HasAllMD5, HasSource, LineStr);
}

std::pair<MCSymbol *, MCSymbol *>
MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
                             ArrayRef<char> StandardOpcodeLengths,
                             std::optional<MCDwarfLineStr> &LineStr) const {
  MCContext &context = MCOS->getContext();

  // Create a symbol at the beginning of the line table.
  MCSymbol *LineStartSym = Label;
  if (!LineStartSym)
    LineStartSym = context.createTempSymbol();

  // Set the value of the symbol, as we are at the start of the line table.
  MCOS->emitDwarfLineStartLabel(LineStartSym);

  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());

  MCSymbol *LineEndSym = MCOS->emitDwarfUnitLength("debug_line", "unit length");

  // Next 2 bytes is the Version.
  unsigned LineTableVersion = context.getDwarfVersion();
  MCOS->emitInt16(LineTableVersion);

  // In v5, we get address info next.
  if (LineTableVersion >= 5) {
    MCOS->emitInt8(context.getAsmInfo()->getCodePointerSize());
    MCOS->emitInt8(0); // Segment selector; same as EmitGenDwarfAranges.
  }

  // Create symbols for the start/end of the prologue.
  MCSymbol *ProStartSym = context.createTempSymbol("prologue_start");
  MCSymbol *ProEndSym = context.createTempSymbol("prologue_end");

  // Length of the prologue, is the next 4 bytes (8 bytes for DWARF64). This is
  // actually the length from after the length word, to the end of the prologue.
  MCOS->emitAbsoluteSymbolDiff(ProEndSym, ProStartSym, OffsetSize);

  MCOS->emitLabel(ProStartSym);

  // Parameters of the state machine, are next.
  MCOS->emitInt8(context.getAsmInfo()->getMinInstAlignment());
  // maximum_operations_per_instruction
  // For non-VLIW architectures this field is always 1.
  // FIXME: VLIW architectures need to update this field accordingly.
  if (LineTableVersion >= 4)
    MCOS->emitInt8(1);
  MCOS->emitInt8(DWARF2_LINE_DEFAULT_IS_STMT);
  MCOS->emitInt8(Params.DWARF2LineBase);
  MCOS->emitInt8(Params.DWARF2LineRange);
  MCOS->emitInt8(StandardOpcodeLengths.size() + 1);

  // Standard opcode lengths
  for (char Length : StandardOpcodeLengths)
    MCOS->emitInt8(Length);

  // Put out the directory and file tables.  The formats vary depending on
  // the version.
  if (LineTableVersion >= 5)
    emitV5FileDirTables(MCOS, LineStr);
  else
    emitV2FileDirTables(MCOS);

  // This is the end of the prologue, so set the value of the symbol at the
  // end of the prologue (that was used in a previous expression).
  MCOS->emitLabel(ProEndSym);

  return std::make_pair(LineStartSym, LineEndSym);
}

void MCDwarfLineTable::emitCU(MCStreamer *MCOS, MCDwarfLineTableParams Params,
                              std::optional<MCDwarfLineStr> &LineStr) const {
  MCSymbol *LineEndSym = Header.Emit(MCOS, Params, LineStr).second;

  // Put out the line tables.
  for (const auto &LineSec : MCLineSections.getMCLineEntries())
    emitOne(MCOS, LineSec.first, LineSec.second);

  // This is the end of the section, so set the value of the symbol at the end
  // of this section (that was used in a previous expression).
  MCOS->emitLabel(LineEndSym);
}

Expected<unsigned>
MCDwarfLineTable::tryGetFile(StringRef &Directory, StringRef &FileName,
                             std::optional<MD5::MD5Result> Checksum,
                             std::optional<StringRef> Source,
                             uint16_t DwarfVersion, unsigned FileNumber) {
  return Header.tryGetFile(Directory, FileName, Checksum, Source, DwarfVersion,
                           FileNumber);
}

static bool isRootFile(const MCDwarfFile &RootFile, StringRef &Directory,
                       StringRef &FileName,
                       std::optional<MD5::MD5Result> Checksum) {
  if (RootFile.Name.empty() || StringRef(RootFile.Name) != FileName)
    return false;
  return RootFile.Checksum == Checksum;
}

Expected<unsigned>
MCDwarfLineTableHeader::tryGetFile(StringRef &Directory, StringRef &FileName,
                                   std::optional<MD5::MD5Result> Checksum,
                                   std::optional<StringRef> Source,
                                   uint16_t DwarfVersion, unsigned FileNumber) {
  if (Directory == CompilationDir)
    Directory = "";
  if (FileName.empty()) {
    FileName = "<stdin>";
    Directory = "";
  }
  assert(!FileName.empty());
  // Keep track of whether any or all files have an MD5 checksum.
  // If any files have embedded source, they all must.
  if (MCDwarfFiles.empty()) {
    trackMD5Usage(Checksum.has_value());
    HasSource = (Source != std::nullopt);
  }
  if (DwarfVersion >= 5 && isRootFile(RootFile, Directory, FileName, Checksum))
    return 0;
  if (FileNumber == 0) {
    // File numbers start with 1 and/or after any file numbers
    // allocated by inline-assembler .file directives.
    FileNumber = MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size();
    SmallString<256> Buffer;
    auto IterBool = SourceIdMap.insert(
        std::make_pair((Directory + Twine('\0') + FileName).toStringRef(Buffer),
                       FileNumber));
    if (!IterBool.second)
      return IterBool.first->second;
  }
  // Make space for this FileNumber in the MCDwarfFiles vector if needed.
  if (FileNumber >= MCDwarfFiles.size())
    MCDwarfFiles.resize(FileNumber + 1);

  // Get the new MCDwarfFile slot for this FileNumber.
  MCDwarfFile &File = MCDwarfFiles[FileNumber];

  // It is an error to see the same number more than once.
  if (!File.Name.empty())
    return make_error<StringError>("file number already allocated",
                                   inconvertibleErrorCode());

  // If any files have embedded source, they all must.
  if (HasSource != (Source != std::nullopt))
    return make_error<StringError>("inconsistent use of embedded source",
                                   inconvertibleErrorCode());

  if (Directory.empty()) {
    // Separate the directory part from the basename of the FileName.
    StringRef tFileName = sys::path::filename(FileName);
    if (!tFileName.empty()) {
      Directory = sys::path::parent_path(FileName);
      if (!Directory.empty())
        FileName = tFileName;
    }
  }

  // Find or make an entry in the MCDwarfDirs vector for this Directory.
  // Capture directory name.
  unsigned DirIndex;
  if (Directory.empty()) {
    // For FileNames with no directories a DirIndex of 0 is used.
    DirIndex = 0;
  } else {
    DirIndex = llvm::find(MCDwarfDirs, Directory) - MCDwarfDirs.begin();
    if (DirIndex >= MCDwarfDirs.size())
      MCDwarfDirs.push_back(std::string(Directory));
    // The DirIndex is one based, as DirIndex of 0 is used for FileNames with
    // no directories.  MCDwarfDirs[] is unlike MCDwarfFiles[] in that the
    // directory names are stored at MCDwarfDirs[DirIndex-1] where FileNames
    // are stored at MCDwarfFiles[FileNumber].Name .
    DirIndex++;
  }

  File.Name = std::string(FileName);
  File.DirIndex = DirIndex;
  File.Checksum = Checksum;
  trackMD5Usage(Checksum.has_value());
  File.Source = Source;
  if (Source)
    HasSource = true;

  // return the allocated FileNumber.
  return FileNumber;
}

/// Utility function to emit the encoding to a streamer.
void MCDwarfLineAddr::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
                           int64_t LineDelta, uint64_t AddrDelta) {
  MCContext &Context = MCOS->getContext();
  SmallString<256> Tmp;
  raw_svector_ostream OS(Tmp);
  MCDwarfLineAddr::Encode(Context, Params, LineDelta, AddrDelta, OS);
  MCOS->emitBytes(OS.str());
}

/// Given a special op, return the address skip amount (in units of
/// DWARF2_LINE_MIN_INSN_LENGTH).
static uint64_t SpecialAddr(MCDwarfLineTableParams Params, uint64_t op) {
  return (op - Params.DWARF2LineOpcodeBase) / Params.DWARF2LineRange;
}

/// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
void MCDwarfLineAddr::Encode(MCContext &Context, MCDwarfLineTableParams Params,
                             int64_t LineDelta, uint64_t AddrDelta,
                             raw_ostream &OS) {
  uint64_t Temp, Opcode;
  bool NeedCopy = false;

  // The maximum address skip amount that can be encoded with a special op.
  uint64_t MaxSpecialAddrDelta = SpecialAddr(Params, 255);

  // Scale the address delta by the minimum instruction length.
  AddrDelta = ScaleAddrDelta(Context, AddrDelta);

  // A LineDelta of INT64_MAX is a signal that this is actually a
  // DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
  // end_sequence to emit the matrix entry.
  if (LineDelta == INT64_MAX) {
    if (AddrDelta == MaxSpecialAddrDelta)
      OS << char(dwarf::DW_LNS_const_add_pc);
    else if (AddrDelta) {
      OS << char(dwarf::DW_LNS_advance_pc);
      encodeULEB128(AddrDelta, OS);
    }
    OS << char(dwarf::DW_LNS_extended_op);
    OS << char(1);
    OS << char(dwarf::DW_LNE_end_sequence);
    return;
  }

  // Bias the line delta by the base.
  Temp = LineDelta - Params.DWARF2LineBase;

  // If the line increment is out of range of a special opcode, we must encode
  // it with DW_LNS_advance_line.
  if (Temp >= Params.DWARF2LineRange ||
      Temp + Params.DWARF2LineOpcodeBase > 255) {
    OS << char(dwarf::DW_LNS_advance_line);
    encodeSLEB128(LineDelta, OS);

    LineDelta = 0;
    Temp = 0 - Params.DWARF2LineBase;
    NeedCopy = true;
  }

  // Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
  if (LineDelta == 0 && AddrDelta == 0) {
    OS << char(dwarf::DW_LNS_copy);
    return;
  }

  // Bias the opcode by the special opcode base.
  Temp += Params.DWARF2LineOpcodeBase;

  // Avoid overflow when addr_delta is large.
  if (AddrDelta < 256 + MaxSpecialAddrDelta) {
    // Try using a special opcode.
    Opcode = Temp + AddrDelta * Params.DWARF2LineRange;
    if (Opcode <= 255) {
      OS << char(Opcode);
      return;
    }

    // Try using DW_LNS_const_add_pc followed by special op.
    Opcode = Temp + (AddrDelta - MaxSpecialAddrDelta) * Params.DWARF2LineRange;
    if (Opcode <= 255) {
      OS << char(dwarf::DW_LNS_const_add_pc);
      OS << char(Opcode);
      return;
    }
  }

  // Otherwise use DW_LNS_advance_pc.
  OS << char(dwarf::DW_LNS_advance_pc);
  encodeULEB128(AddrDelta, OS);

  if (NeedCopy)
    OS << char(dwarf::DW_LNS_copy);
  else {
    assert(Temp <= 255 && "Buggy special opcode encoding.");
    OS << char(Temp);
  }
}

// Utility function to write a tuple for .debug_abbrev.
static void EmitAbbrev(MCStreamer *MCOS, uint64_t Name, uint64_t Form) {
  MCOS->emitULEB128IntValue(Name);
  MCOS->emitULEB128IntValue(Form);
}

// When generating dwarf for assembly source files this emits
// the data for .debug_abbrev section which contains three DIEs.
static void EmitGenDwarfAbbrev(MCStreamer *MCOS) {
  MCContext &context = MCOS->getContext();
  MCOS->switchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());

  // DW_TAG_compile_unit DIE abbrev (1).
  MCOS->emitULEB128IntValue(1);
  MCOS->emitULEB128IntValue(dwarf::DW_TAG_compile_unit);
  MCOS->emitInt8(dwarf::DW_CHILDREN_yes);
  dwarf::Form SecOffsetForm =
      context.getDwarfVersion() >= 4
          ? dwarf::DW_FORM_sec_offset
          : (context.getDwarfFormat() == dwarf::DWARF64 ? dwarf::DW_FORM_data8
                                                        : dwarf::DW_FORM_data4);
  EmitAbbrev(MCOS, dwarf::DW_AT_stmt_list, SecOffsetForm);
  if (context.getGenDwarfSectionSyms().size() > 1 &&
      context.getDwarfVersion() >= 3) {
    EmitAbbrev(MCOS, dwarf::DW_AT_ranges, SecOffsetForm);
  } else {
    EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
    EmitAbbrev(MCOS, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr);
  }
  EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
  if (!context.getCompilationDir().empty())
    EmitAbbrev(MCOS, dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string);
  StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
  if (!DwarfDebugFlags.empty())
    EmitAbbrev(MCOS, dwarf::DW_AT_APPLE_flags, dwarf::DW_FORM_string);
  EmitAbbrev(MCOS, dwarf::DW_AT_producer, dwarf::DW_FORM_string);
  EmitAbbrev(MCOS, dwarf::DW_AT_language, dwarf::DW_FORM_data2);
  EmitAbbrev(MCOS, 0, 0);

  // DW_TAG_label DIE abbrev (2).
  MCOS->emitULEB128IntValue(2);
  MCOS->emitULEB128IntValue(dwarf::DW_TAG_label);
  MCOS->emitInt8(dwarf::DW_CHILDREN_no);
  EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
  EmitAbbrev(MCOS, dwarf::DW_AT_decl_file, dwarf::DW_FORM_data4);
  EmitAbbrev(MCOS, dwarf::DW_AT_decl_line, dwarf::DW_FORM_data4);
  EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
  EmitAbbrev(MCOS, 0, 0);

  // Terminate the abbreviations for this compilation unit.
  MCOS->emitInt8(0);
}

// When generating dwarf for assembly source files this emits the data for
// .debug_aranges section. This section contains a header and a table of pairs
// of PointerSize'ed values for the address and size of section(s) with line
// table entries.
static void EmitGenDwarfAranges(MCStreamer *MCOS,
                                const MCSymbol *InfoSectionSymbol) {
  MCContext &context = MCOS->getContext();

  auto &Sections = context.getGenDwarfSectionSyms();

  MCOS->switchSection(context.getObjectFileInfo()->getDwarfARangesSection());

  unsigned UnitLengthBytes =
      dwarf::getUnitLengthFieldByteSize(context.getDwarfFormat());
  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());

  // This will be the length of the .debug_aranges section, first account for
  // the size of each item in the header (see below where we emit these items).
  int Length = UnitLengthBytes + 2 + OffsetSize + 1 + 1;

  // Figure the padding after the header before the table of address and size
  // pairs who's values are PointerSize'ed.
  const MCAsmInfo *asmInfo = context.getAsmInfo();
  int AddrSize = asmInfo->getCodePointerSize();
  int Pad = 2 * AddrSize - (Length & (2 * AddrSize - 1));
  if (Pad == 2 * AddrSize)
    Pad = 0;
  Length += Pad;

  // Add the size of the pair of PointerSize'ed values for the address and size
  // of each section we have in the table.
  Length += 2 * AddrSize * Sections.size();
  // And the pair of terminating zeros.
  Length += 2 * AddrSize;

  // Emit the header for this section.
  if (context.getDwarfFormat() == dwarf::DWARF64)
    // The DWARF64 mark.
    MCOS->emitInt32(dwarf::DW_LENGTH_DWARF64);
  // The 4 (8 for DWARF64) byte length not including the length of the unit
  // length field itself.
  MCOS->emitIntValue(Length - UnitLengthBytes, OffsetSize);
  // The 2 byte version, which is 2.
  MCOS->emitInt16(2);
  // The 4 (8 for DWARF64) byte offset to the compile unit in the .debug_info
  // from the start of the .debug_info.
  if (InfoSectionSymbol)
    MCOS->emitSymbolValue(InfoSectionSymbol, OffsetSize,
                          asmInfo->needsDwarfSectionOffsetDirective());
  else
    MCOS->emitIntValue(0, OffsetSize);
  // The 1 byte size of an address.
  MCOS->emitInt8(AddrSize);
  // The 1 byte size of a segment descriptor, we use a value of zero.
  MCOS->emitInt8(0);
  // Align the header with the padding if needed, before we put out the table.
  for(int i = 0; i < Pad; i++)
    MCOS->emitInt8(0);

  // Now emit the table of pairs of PointerSize'ed values for the section
  // addresses and sizes.
  for (MCSection *Sec : Sections) {
    const MCSymbol *StartSymbol = Sec->getBeginSymbol();
    MCSymbol *EndSymbol = Sec->getEndSymbol(context);
    assert(StartSymbol && "StartSymbol must not be NULL");
    assert(EndSymbol && "EndSymbol must not be NULL");

    const MCExpr *Addr = MCSymbolRefExpr::create(
      StartSymbol, MCSymbolRefExpr::VK_None, context);
    const MCExpr *Size =
        makeEndMinusStartExpr(context, *StartSymbol, *EndSymbol, 0);
    MCOS->emitValue(Addr, AddrSize);
    emitAbsValue(*MCOS, Size, AddrSize);
  }

  // And finally the pair of terminating zeros.
  MCOS->emitIntValue(0, AddrSize);
  MCOS->emitIntValue(0, AddrSize);
}

// When generating dwarf for assembly source files this emits the data for
// .debug_info section which contains three parts.  The header, the compile_unit
// DIE and a list of label DIEs.
static void EmitGenDwarfInfo(MCStreamer *MCOS,
                             const MCSymbol *AbbrevSectionSymbol,
                             const MCSymbol *LineSectionSymbol,
                             const MCSymbol *RangesSymbol) {
  MCContext &context = MCOS->getContext();

  MCOS->switchSection(context.getObjectFileInfo()->getDwarfInfoSection());

  // Create a symbol at the start and end of this section used in here for the
  // expression to calculate the length in the header.
  MCSymbol *InfoStart = context.createTempSymbol();
  MCOS->emitLabel(InfoStart);
  MCSymbol *InfoEnd = context.createTempSymbol();

  // First part: the header.

  unsigned UnitLengthBytes =
      dwarf::getUnitLengthFieldByteSize(context.getDwarfFormat());
  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(context.getDwarfFormat());

  if (context.getDwarfFormat() == dwarf::DWARF64)
    // Emit DWARF64 mark.
    MCOS->emitInt32(dwarf::DW_LENGTH_DWARF64);

  // The 4 (8 for DWARF64) byte total length of the information for this
  // compilation unit, not including the unit length field itself.
  const MCExpr *Length =
      makeEndMinusStartExpr(context, *InfoStart, *InfoEnd, UnitLengthBytes);
  emitAbsValue(*MCOS, Length, OffsetSize);

  // The 2 byte DWARF version.
  MCOS->emitInt16(context.getDwarfVersion());

  // The DWARF v5 header has unit type, address size, abbrev offset.
  // Earlier versions have abbrev offset, address size.
  const MCAsmInfo &AsmInfo = *context.getAsmInfo();
  int AddrSize = AsmInfo.getCodePointerSize();
  if (context.getDwarfVersion() >= 5) {
    MCOS->emitInt8(dwarf::DW_UT_compile);
    MCOS->emitInt8(AddrSize);
  }
  // The 4 (8 for DWARF64) byte offset to the debug abbrevs from the start of
  // the .debug_abbrev.
  if (AbbrevSectionSymbol)
    MCOS->emitSymbolValue(AbbrevSectionSymbol, OffsetSize,
                          AsmInfo.needsDwarfSectionOffsetDirective());
  else
    // Since the abbrevs are at the start of the section, the offset is zero.
    MCOS->emitIntValue(0, OffsetSize);
  if (context.getDwarfVersion() <= 4)
    MCOS->emitInt8(AddrSize);

  // Second part: the compile_unit DIE.

  // The DW_TAG_compile_unit DIE abbrev (1).
  MCOS->emitULEB128IntValue(1);

  // DW_AT_stmt_list, a 4 (8 for DWARF64) byte offset from the start of the
  // .debug_line section.
  if (LineSectionSymbol)
    MCOS->emitSymbolValue(LineSectionSymbol, OffsetSize,
                          AsmInfo.needsDwarfSectionOffsetDirective());
  else
    // The line table is at the start of the section, so the offset is zero.
    MCOS->emitIntValue(0, OffsetSize);

  if (RangesSymbol) {
    // There are multiple sections containing code, so we must use
    // .debug_ranges/.debug_rnglists. AT_ranges, the 4/8 byte offset from the
    // start of the .debug_ranges/.debug_rnglists.
    MCOS->emitSymbolValue(RangesSymbol, OffsetSize);
  } else {
    // If we only have one non-empty code section, we can use the simpler
    // AT_low_pc and AT_high_pc attributes.

    // Find the first (and only) non-empty text section
    auto &Sections = context.getGenDwarfSectionSyms();
    const auto TextSection = Sections.begin();
    assert(TextSection != Sections.end() && "No text section found");

    MCSymbol *StartSymbol = (*TextSection)->getBeginSymbol();
    MCSymbol *EndSymbol = (*TextSection)->getEndSymbol(context);
    assert(StartSymbol && "StartSymbol must not be NULL");
    assert(EndSymbol && "EndSymbol must not be NULL");

    // AT_low_pc, the first address of the default .text section.
    const MCExpr *Start = MCSymbolRefExpr::create(
        StartSymbol, MCSymbolRefExpr::VK_None, context);
    MCOS->emitValue(Start, AddrSize);

    // AT_high_pc, the last address of the default .text section.
    const MCExpr *End = MCSymbolRefExpr::create(
      EndSymbol, MCSymbolRefExpr::VK_None, context);
    MCOS->emitValue(End, AddrSize);
  }

  // AT_name, the name of the source file.  Reconstruct from the first directory
  // and file table entries.
  const SmallVectorImpl<std::string> &MCDwarfDirs = context.getMCDwarfDirs();
  if (MCDwarfDirs.size() > 0) {
    MCOS->emitBytes(MCDwarfDirs[0]);
    MCOS->emitBytes(sys::path::get_separator());
  }
  const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles = context.getMCDwarfFiles();
  // MCDwarfFiles might be empty if we have an empty source file.
  // If it's not empty, [0] is unused and [1] is the first actual file.
  assert(MCDwarfFiles.empty() || MCDwarfFiles.size() >= 2);
  const MCDwarfFile &RootFile =
      MCDwarfFiles.empty()
          ? context.getMCDwarfLineTable(/*CUID=*/0).getRootFile()
          : MCDwarfFiles[1];
  MCOS->emitBytes(RootFile.Name);
  MCOS->emitInt8(0); // NULL byte to terminate the string.

  // AT_comp_dir, the working directory the assembly was done in.
  if (!context.getCompilationDir().empty()) {
    MCOS->emitBytes(context.getCompilationDir());
    MCOS->emitInt8(0); // NULL byte to terminate the string.
  }

  // AT_APPLE_flags, the command line arguments of the assembler tool.
  StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
  if (!DwarfDebugFlags.empty()){
    MCOS->emitBytes(DwarfDebugFlags);
    MCOS->emitInt8(0); // NULL byte to terminate the string.
  }

  // AT_producer, the version of the assembler tool.
  StringRef DwarfDebugProducer = context.getDwarfDebugProducer();
  if (!DwarfDebugProducer.empty())
    MCOS->emitBytes(DwarfDebugProducer);
  else
    MCOS->emitBytes(StringRef("llvm-mc (based on LLVM " PACKAGE_VERSION ")"));
  MCOS->emitInt8(0); // NULL byte to terminate the string.

  // AT_language, a 4 byte value.  We use DW_LANG_Mips_Assembler as the dwarf2
  // draft has no standard code for assembler.
  MCOS->emitInt16(dwarf::DW_LANG_Mips_Assembler);

  // Third part: the list of label DIEs.

  // Loop on saved info for dwarf labels and create the DIEs for them.
  const std::vector<MCGenDwarfLabelEntry> &Entries =
      MCOS->getContext().getMCGenDwarfLabelEntries();
  for (const auto &Entry : Entries) {
    // The DW_TAG_label DIE abbrev (2).
    MCOS->emitULEB128IntValue(2);

    // AT_name, of the label without any leading underbar.
    MCOS->emitBytes(Entry.getName());
    MCOS->emitInt8(0); // NULL byte to terminate the string.

    // AT_decl_file, index into the file table.
    MCOS->emitInt32(Entry.getFileNumber());

    // AT_decl_line, source line number.
    MCOS->emitInt32(Entry.getLineNumber());

    // AT_low_pc, start address of the label.
    const MCExpr *AT_low_pc = MCSymbolRefExpr::create(Entry.getLabel(),
                                             MCSymbolRefExpr::VK_None, context);
    MCOS->emitValue(AT_low_pc, AddrSize);
  }

  // Add the NULL DIE terminating the Compile Unit DIE's.
  MCOS->emitInt8(0);

  // Now set the value of the symbol at the end of the info section.
  MCOS->emitLabel(InfoEnd);
}

// When generating dwarf for assembly source files this emits the data for
// .debug_ranges section. We only emit one range list, which spans all of the
// executable sections of this file.
static MCSymbol *emitGenDwarfRanges(MCStreamer *MCOS) {
  MCContext &context = MCOS->getContext();
  auto &Sections = context.getGenDwarfSectionSyms();

  const MCAsmInfo *AsmInfo = context.getAsmInfo();
  int AddrSize = AsmInfo->getCodePointerSize();
  MCSymbol *RangesSymbol;

  if (MCOS->getContext().getDwarfVersion() >= 5) {
    MCOS->switchSection(context.getObjectFileInfo()->getDwarfRnglistsSection());
    MCSymbol *EndSymbol = mcdwarf::emitListsTableHeaderStart(*MCOS);
    MCOS->AddComment("Offset entry count");
    MCOS->emitInt32(0);
    RangesSymbol = context.createTempSymbol("debug_rnglist0_start");
    MCOS->emitLabel(RangesSymbol);
    for (MCSection *Sec : Sections) {
      const MCSymbol *StartSymbol = Sec->getBeginSymbol();
      const MCSymbol *EndSymbol = Sec->getEndSymbol(context);
      const MCExpr *SectionStartAddr = MCSymbolRefExpr::create(
          StartSymbol, MCSymbolRefExpr::VK_None, context);
      const MCExpr *SectionSize =
          makeEndMinusStartExpr(context, *StartSymbol, *EndSymbol, 0);
      MCOS->emitInt8(dwarf::DW_RLE_start_length);
      MCOS->emitValue(SectionStartAddr, AddrSize);
      MCOS->emitULEB128Value(SectionSize);
    }
    MCOS->emitInt8(dwarf::DW_RLE_end_of_list);
    MCOS->emitLabel(EndSymbol);
  } else {
    MCOS->switchSection(context.getObjectFileInfo()->getDwarfRangesSection());
    RangesSymbol = context.createTempSymbol("debug_ranges_start");
    MCOS->emitLabel(RangesSymbol);
    for (MCSection *Sec : Sections) {
      const MCSymbol *StartSymbol = Sec->getBeginSymbol();
      const MCSymbol *EndSymbol = Sec->getEndSymbol(context);

      // Emit a base address selection entry for the section start.
      const MCExpr *SectionStartAddr = MCSymbolRefExpr::create(
          StartSymbol, MCSymbolRefExpr::VK_None, context);
      MCOS->emitFill(AddrSize, 0xFF);
      MCOS->emitValue(SectionStartAddr, AddrSize);

      // Emit a range list entry spanning this section.
      const MCExpr *SectionSize =
          makeEndMinusStartExpr(context, *StartSymbol, *EndSymbol, 0);
      MCOS->emitIntValue(0, AddrSize);
      emitAbsValue(*MCOS, SectionSize, AddrSize);
    }

    // Emit end of list entry
    MCOS->emitIntValue(0, AddrSize);
    MCOS->emitIntValue(0, AddrSize);
  }

  return RangesSymbol;
}

//
// When generating dwarf for assembly source files this emits the Dwarf
// sections.
//
void MCGenDwarfInfo::Emit(MCStreamer *MCOS) {
  MCContext &context = MCOS->getContext();

  // Create the dwarf sections in this order (.debug_line already created).
  const MCAsmInfo *AsmInfo = context.getAsmInfo();
  bool CreateDwarfSectionSymbols =
      AsmInfo->doesDwarfUseRelocationsAcrossSections();
  MCSymbol *LineSectionSymbol = nullptr;
  if (CreateDwarfSectionSymbols)
    LineSectionSymbol = MCOS->getDwarfLineTableSymbol(0);
  MCSymbol *AbbrevSectionSymbol = nullptr;
  MCSymbol *InfoSectionSymbol = nullptr;
  MCSymbol *RangesSymbol = nullptr;

  // Create end symbols for each section, and remove empty sections
  MCOS->getContext().finalizeDwarfSections(*MCOS);

  // If there are no sections to generate debug info for, we don't need
  // to do anything
  if (MCOS->getContext().getGenDwarfSectionSyms().empty())
    return;

  // We only use the .debug_ranges section if we have multiple code sections,
  // and we are emitting a DWARF version which supports it.
  const bool UseRangesSection =
      MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
      MCOS->getContext().getDwarfVersion() >= 3;
  CreateDwarfSectionSymbols |= UseRangesSection;

  MCOS->switchSection(context.getObjectFileInfo()->getDwarfInfoSection());
  if (CreateDwarfSectionSymbols) {
    InfoSectionSymbol = context.createTempSymbol();
    MCOS->emitLabel(InfoSectionSymbol);
  }
  MCOS->switchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
  if (CreateDwarfSectionSymbols) {
    AbbrevSectionSymbol = context.createTempSymbol();
    MCOS->emitLabel(AbbrevSectionSymbol);
  }

  MCOS->switchSection(context.getObjectFileInfo()->getDwarfARangesSection());

  // Output the data for .debug_aranges section.
  EmitGenDwarfAranges(MCOS, InfoSectionSymbol);

  if (UseRangesSection) {
    RangesSymbol = emitGenDwarfRanges(MCOS);
    assert(RangesSymbol);
  }

  // Output the data for .debug_abbrev section.
  EmitGenDwarfAbbrev(MCOS);

  // Output the data for .debug_info section.
  EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol, RangesSymbol);
}

//
// When generating dwarf for assembly source files this is called when symbol
// for a label is created.  If this symbol is not a temporary and is in the
// section that dwarf is being generated for, save the needed info to create
// a dwarf label.
//
void MCGenDwarfLabelEntry::Make(MCSymbol *Symbol, MCStreamer *MCOS,
                                     SourceMgr &SrcMgr, SMLoc &Loc) {
  // We won't create dwarf labels for temporary symbols.
  if (Symbol->isTemporary())
    return;
  MCContext &context = MCOS->getContext();
  // We won't create dwarf labels for symbols in sections that we are not
  // generating debug info for.
  if (!context.getGenDwarfSectionSyms().count(MCOS->getCurrentSectionOnly()))
    return;

  // The dwarf label's name does not have the symbol name's leading
  // underbar if any.
  StringRef Name = Symbol->getName();
  if (Name.startswith("_"))
    Name = Name.substr(1, Name.size()-1);

  // Get the dwarf file number to be used for the dwarf label.
  unsigned FileNumber = context.getGenDwarfFileNumber();

  // Finding the line number is the expensive part which is why we just don't
  // pass it in as for some symbols we won't create a dwarf label.
  unsigned CurBuffer = SrcMgr.FindBufferContainingLoc(Loc);
  unsigned LineNumber = SrcMgr.FindLineNumber(Loc, CurBuffer);

  // We create a temporary symbol for use for the AT_high_pc and AT_low_pc
  // values so that they don't have things like an ARM thumb bit from the
  // original symbol. So when used they won't get a low bit set after
  // relocation.
  MCSymbol *Label = context.createTempSymbol();
  MCOS->emitLabel(Label);

  // Create and entry for the info and add it to the other entries.
  MCOS->getContext().addMCGenDwarfLabelEntry(
      MCGenDwarfLabelEntry(Name, FileNumber, LineNumber, Label));
}

static int getDataAlignmentFactor(MCStreamer &streamer) {
  MCContext &context = streamer.getContext();
  const MCAsmInfo *asmInfo = context.getAsmInfo();
  int size = asmInfo->getCalleeSaveStackSlotSize();
  if (asmInfo->isStackGrowthDirectionUp())
    return size;
  else
    return -size;
}

static unsigned getSizeForEncoding(MCStreamer &streamer,
                                   unsigned symbolEncoding) {
  MCContext &context = streamer.getContext();
  unsigned format = symbolEncoding & 0x0f;
  switch (format) {
  default: llvm_unreachable("Unknown Encoding");
  case dwarf::DW_EH_PE_absptr:
  case dwarf::DW_EH_PE_signed:
    return context.getAsmInfo()->getCodePointerSize();
  case dwarf::DW_EH_PE_udata2:
  case dwarf::DW_EH_PE_sdata2:
    return 2;
  case dwarf::DW_EH_PE_udata4:
  case dwarf::DW_EH_PE_sdata4:
    return 4;
  case dwarf::DW_EH_PE_udata8:
  case dwarf::DW_EH_PE_sdata8:
    return 8;
  }
}

static void emitFDESymbol(MCObjectStreamer &streamer, const MCSymbol &symbol,
                       unsigned symbolEncoding, bool isEH) {
  MCContext &context = streamer.getContext();
  const MCAsmInfo *asmInfo = context.getAsmInfo();
  const MCExpr *v = asmInfo->getExprForFDESymbol(&symbol,
                                                 symbolEncoding,
                                                 streamer);
  unsigned size = getSizeForEncoding(streamer, symbolEncoding);
  if (asmInfo->doDwarfFDESymbolsUseAbsDiff() && isEH)
    emitAbsValue(streamer, v, size);
  else
    streamer.emitValue(v, size);
}

static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
                            unsigned symbolEncoding) {
  MCContext &context = streamer.getContext();
  const MCAsmInfo *asmInfo = context.getAsmInfo();
  const MCExpr *v = asmInfo->getExprForPersonalitySymbol(&symbol,
                                                         symbolEncoding,
                                                         streamer);
  unsigned size = getSizeForEncoding(streamer, symbolEncoding);
  streamer.emitValue(v, size);
}

namespace {

class FrameEmitterImpl {
  int CFAOffset = 0;
  int InitialCFAOffset = 0;
  bool IsEH;
  MCObjectStreamer &Streamer;

public:
  FrameEmitterImpl(bool IsEH, MCObjectStreamer &Streamer)
      : IsEH(IsEH), Streamer(Streamer) {}

  /// Emit the unwind information in a compact way.
  void EmitCompactUnwind(const MCDwarfFrameInfo &frame);

  const MCSymbol &EmitCIE(const MCDwarfFrameInfo &F);
  void EmitFDE(const MCSymbol &cieStart, const MCDwarfFrameInfo &frame,
               bool LastInSection, const MCSymbol &SectionStart);
  void emitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
                           MCSymbol *BaseLabel);
  void emitCFIInstruction(const MCCFIInstruction &Instr);
};

} // end anonymous namespace

static void emitEncodingByte(MCObjectStreamer &Streamer, unsigned Encoding) {
  Streamer.emitInt8(Encoding);
}

void FrameEmitterImpl::emitCFIInstruction(const MCCFIInstruction &Instr) {
  int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
  auto *MRI = Streamer.getContext().getRegisterInfo();

  switch (Instr.getOperation()) {
  case MCCFIInstruction::OpRegister: {
    unsigned Reg1 = Instr.getRegister();
    unsigned Reg2 = Instr.getRegister2();
    if (!IsEH) {
      Reg1 = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg1);
      Reg2 = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg2);
    }
    Streamer.emitInt8(dwarf::DW_CFA_register);
    Streamer.emitULEB128IntValue(Reg1);
    Streamer.emitULEB128IntValue(Reg2);
    return;
  }
  case MCCFIInstruction::OpWindowSave:
    Streamer.emitInt8(dwarf::DW_CFA_GNU_window_save);
    return;

  case MCCFIInstruction::OpNegateRAState:
    Streamer.emitInt8(dwarf::DW_CFA_AARCH64_negate_ra_state);
    return;

  case MCCFIInstruction::OpUndefined: {
    unsigned Reg = Instr.getRegister();
    Streamer.emitInt8(dwarf::DW_CFA_undefined);
    Streamer.emitULEB128IntValue(Reg);
    return;
  }
  case MCCFIInstruction::OpAdjustCfaOffset:
  case MCCFIInstruction::OpDefCfaOffset: {
    const bool IsRelative =
      Instr.getOperation() == MCCFIInstruction::OpAdjustCfaOffset;

    Streamer.emitInt8(dwarf::DW_CFA_def_cfa_offset);

    if (IsRelative)
      CFAOffset += Instr.getOffset();
    else
      CFAOffset = Instr.getOffset();

    Streamer.emitULEB128IntValue(CFAOffset);

    return;
  }
  case MCCFIInstruction::OpDefCfa: {
    unsigned Reg = Instr.getRegister();
    if (!IsEH)
      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
    Streamer.emitInt8(dwarf::DW_CFA_def_cfa);
    Streamer.emitULEB128IntValue(Reg);
    CFAOffset = Instr.getOffset();
    Streamer.emitULEB128IntValue(CFAOffset);

    return;
  }
  case MCCFIInstruction::OpDefCfaRegister: {
    unsigned Reg = Instr.getRegister();
    if (!IsEH)
      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
    Streamer.emitInt8(dwarf::DW_CFA_def_cfa_register);
    Streamer.emitULEB128IntValue(Reg);

    return;
  }
  // TODO: Implement `_sf` variants if/when they need to be emitted.
  case MCCFIInstruction::OpLLVMDefAspaceCfa: {
    unsigned Reg = Instr.getRegister();
    if (!IsEH)
      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
    Streamer.emitIntValue(dwarf::DW_CFA_LLVM_def_aspace_cfa, 1);
    Streamer.emitULEB128IntValue(Reg);
    CFAOffset = Instr.getOffset();
    Streamer.emitULEB128IntValue(CFAOffset);
    Streamer.emitULEB128IntValue(Instr.getAddressSpace());

    return;
  }
  case MCCFIInstruction::OpOffset:
  case MCCFIInstruction::OpRelOffset: {
    const bool IsRelative =
      Instr.getOperation() == MCCFIInstruction::OpRelOffset;

    unsigned Reg = Instr.getRegister();
    if (!IsEH)
      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);

    int Offset = Instr.getOffset();
    if (IsRelative)
      Offset -= CFAOffset;
    Offset = Offset / dataAlignmentFactor;

    if (Offset < 0) {
      Streamer.emitInt8(dwarf::DW_CFA_offset_extended_sf);
      Streamer.emitULEB128IntValue(Reg);
      Streamer.emitSLEB128IntValue(Offset);
    } else if (Reg < 64) {
      Streamer.emitInt8(dwarf::DW_CFA_offset + Reg);
      Streamer.emitULEB128IntValue(Offset);
    } else {
      Streamer.emitInt8(dwarf::DW_CFA_offset_extended);
      Streamer.emitULEB128IntValue(Reg);
      Streamer.emitULEB128IntValue(Offset);
    }
    return;
  }
  case MCCFIInstruction::OpRememberState:
    Streamer.emitInt8(dwarf::DW_CFA_remember_state);
    return;
  case MCCFIInstruction::OpRestoreState:
    Streamer.emitInt8(dwarf::DW_CFA_restore_state);
    return;
  case MCCFIInstruction::OpSameValue: {
    unsigned Reg = Instr.getRegister();
    Streamer.emitInt8(dwarf::DW_CFA_same_value);
    Streamer.emitULEB128IntValue(Reg);
    return;
  }
  case MCCFIInstruction::OpRestore: {
    unsigned Reg = Instr.getRegister();
    if (!IsEH)
      Reg = MRI->getDwarfRegNumFromDwarfEHRegNum(Reg);
    if (Reg < 64) {
      Streamer.emitInt8(dwarf::DW_CFA_restore | Reg);
    } else {
      Streamer.emitInt8(dwarf::DW_CFA_restore_extended);
      Streamer.emitULEB128IntValue(Reg);
    }
    return;
  }
  case MCCFIInstruction::OpGnuArgsSize:
    Streamer.emitInt8(dwarf::DW_CFA_GNU_args_size);
    Streamer.emitULEB128IntValue(Instr.getOffset());
    return;

  case MCCFIInstruction::OpEscape:
    Streamer.emitBytes(Instr.getValues());
    return;
  }
  llvm_unreachable("Unhandled case in switch");
}

/// Emit frame instructions to describe the layout of the frame.
void FrameEmitterImpl::emitCFIInstructions(ArrayRef<MCCFIInstruction> Instrs,
                                           MCSymbol *BaseLabel) {
  for (const MCCFIInstruction &Instr : Instrs) {
    MCSymbol *Label = Instr.getLabel();
    // Throw out move if the label is invalid.
    if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.

    // Advance row if new location.
    if (BaseLabel && Label) {
      MCSymbol *ThisSym = Label;
      if (ThisSym != BaseLabel) {
        Streamer.emitDwarfAdvanceFrameAddr(BaseLabel, ThisSym);
        BaseLabel = ThisSym;
      }
    }

    emitCFIInstruction(Instr);
  }
}

/// Emit the unwind information in a compact way.
void FrameEmitterImpl::EmitCompactUnwind(const MCDwarfFrameInfo &Frame) {
  MCContext &Context = Streamer.getContext();
  const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();

  // range-start range-length  compact-unwind-enc personality-func   lsda
  //  _foo       LfooEnd-_foo  0x00000023          0                 0
  //  _bar       LbarEnd-_bar  0x00000025         __gxx_personality  except_tab1
  //
  //   .section __LD,__compact_unwind,regular,debug
  //
  //   # compact unwind for _foo
  //   .quad _foo
  //   .set L1,LfooEnd-_foo
  //   .long L1
  //   .long 0x01010001
  //   .quad 0
  //   .quad 0
  //
  //   # compact unwind for _bar
  //   .quad _bar
  //   .set L2,LbarEnd-_bar
  //   .long L2
  //   .long 0x01020011
  //   .quad __gxx_personality
  //   .quad except_tab1

  uint32_t Encoding = Frame.CompactUnwindEncoding;
  if (!Encoding) return;
  bool DwarfEHFrameOnly = (Encoding == MOFI->getCompactUnwindDwarfEHFrameOnly());

  // The encoding needs to know we have an LSDA.
  if (!DwarfEHFrameOnly && Frame.Lsda)
    Encoding |= 0x40000000;

  // Range Start
  unsigned FDEEncoding = MOFI->getFDEEncoding();
  unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
  Streamer.emitSymbolValue(Frame.Begin, Size);

  // Range Length
  const MCExpr *Range =
      makeEndMinusStartExpr(Context, *Frame.Begin, *Frame.End, 0);
  emitAbsValue(Streamer, Range, 4);

  // Compact Encoding
  Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_udata4);
  Streamer.emitIntValue(Encoding, Size);

  // Personality Function
  Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
  if (!DwarfEHFrameOnly && Frame.Personality)
    Streamer.emitSymbolValue(Frame.Personality, Size);
  else
    Streamer.emitIntValue(0, Size); // No personality fn

  // LSDA
  Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
  if (!DwarfEHFrameOnly && Frame.Lsda)
    Streamer.emitSymbolValue(Frame.Lsda, Size);
  else
    Streamer.emitIntValue(0, Size); // No LSDA
}

static unsigned getCIEVersion(bool IsEH, unsigned DwarfVersion) {
  if (IsEH)
    return 1;
  switch (DwarfVersion) {
  case 2:
    return 1;
  case 3:
    return 3;
  case 4:
  case 5:
    return 4;
  }
  llvm_unreachable("Unknown version");
}

const MCSymbol &FrameEmitterImpl::EmitCIE(const MCDwarfFrameInfo &Frame) {
  MCContext &context = Streamer.getContext();
  const MCRegisterInfo *MRI = context.getRegisterInfo();
  const MCObjectFileInfo *MOFI = context.getObjectFileInfo();

  MCSymbol *sectionStart = context.createTempSymbol();
  Streamer.emitLabel(sectionStart);

  MCSymbol *sectionEnd = context.createTempSymbol();

  dwarf::DwarfFormat Format = IsEH ? dwarf::DWARF32 : context.getDwarfFormat();
  unsigned UnitLengthBytes = dwarf::getUnitLengthFieldByteSize(Format);
  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(Format);
  bool IsDwarf64 = Format == dwarf::DWARF64;

  if (IsDwarf64)
    // DWARF64 mark
    Streamer.emitInt32(dwarf::DW_LENGTH_DWARF64);

  // Length
  const MCExpr *Length = makeEndMinusStartExpr(context, *sectionStart,
                                               *sectionEnd, UnitLengthBytes);
  emitAbsValue(Streamer, Length, OffsetSize);

  // CIE ID
  uint64_t CIE_ID =
      IsEH ? 0 : (IsDwarf64 ? dwarf::DW64_CIE_ID : dwarf::DW_CIE_ID);
  Streamer.emitIntValue(CIE_ID, OffsetSize);

  // Version
  uint8_t CIEVersion = getCIEVersion(IsEH, context.getDwarfVersion());
  Streamer.emitInt8(CIEVersion);

  if (IsEH) {
    SmallString<8> Augmentation;
    Augmentation += "z";
    if (Frame.Personality)
      Augmentation += "P";
    if (Frame.Lsda)
      Augmentation += "L";
    Augmentation += "R";
    if (Frame.IsSignalFrame)
      Augmentation += "S";
    if (Frame.IsBKeyFrame)
      Augmentation += "B";
    if (Frame.IsMTETaggedFrame)
      Augmentation += "G";
    Streamer.emitBytes(Augmentation);
  }
  Streamer.emitInt8(0);

  if (CIEVersion >= 4) {
    // Address Size
    Streamer.emitInt8(context.getAsmInfo()->getCodePointerSize());

    // Segment Descriptor Size
    Streamer.emitInt8(0);
  }

  // Code Alignment Factor
  Streamer.emitULEB128IntValue(context.getAsmInfo()->getMinInstAlignment());

  // Data Alignment Factor
  Streamer.emitSLEB128IntValue(getDataAlignmentFactor(Streamer));

  // Return Address Register
  unsigned RAReg = Frame.RAReg;
  if (RAReg == static_cast<unsigned>(INT_MAX))
    RAReg = MRI->getDwarfRegNum(MRI->getRARegister(), IsEH);

  if (CIEVersion == 1) {
    assert(RAReg <= 255 &&
           "DWARF 2 encodes return_address_register in one byte");
    Streamer.emitInt8(RAReg);
  } else {
    Streamer.emitULEB128IntValue(RAReg);
  }

  // Augmentation Data Length (optional)
  unsigned augmentationLength = 0;
  if (IsEH) {
    if (Frame.Personality) {
      // Personality Encoding
      augmentationLength += 1;
      // Personality
      augmentationLength +=
          getSizeForEncoding(Streamer, Frame.PersonalityEncoding);
    }
    if (Frame.Lsda)
      augmentationLength += 1;
    // Encoding of the FDE pointers
    augmentationLength += 1;

    Streamer.emitULEB128IntValue(augmentationLength);

    // Augmentation Data (optional)
    if (Frame.Personality) {
      // Personality Encoding
      emitEncodingByte(Streamer, Frame.PersonalityEncoding);
      // Personality
      EmitPersonality(Streamer, *Frame.Personality, Frame.PersonalityEncoding);
    }

    if (Frame.Lsda)
      emitEncodingByte(Streamer, Frame.LsdaEncoding);

    // Encoding of the FDE pointers
    emitEncodingByte(Streamer, MOFI->getFDEEncoding());
  }

  // Initial Instructions

  const MCAsmInfo *MAI = context.getAsmInfo();
  if (!Frame.IsSimple) {
    const std::vector<MCCFIInstruction> &Instructions =
        MAI->getInitialFrameState();
    emitCFIInstructions(Instructions, nullptr);
  }

  InitialCFAOffset = CFAOffset;

  // Padding
  Streamer.emitValueToAlignment(Align(IsEH ? 4 : MAI->getCodePointerSize()));

  Streamer.emitLabel(sectionEnd);
  return *sectionStart;
}

void FrameEmitterImpl::EmitFDE(const MCSymbol &cieStart,
                               const MCDwarfFrameInfo &frame,
                               bool LastInSection,
                               const MCSymbol &SectionStart) {
  MCContext &context = Streamer.getContext();
  MCSymbol *fdeStart = context.createTempSymbol();
  MCSymbol *fdeEnd = context.createTempSymbol();
  const MCObjectFileInfo *MOFI = context.getObjectFileInfo();

  CFAOffset = InitialCFAOffset;

  dwarf::DwarfFormat Format = IsEH ? dwarf::DWARF32 : context.getDwarfFormat();
  unsigned OffsetSize = dwarf::getDwarfOffsetByteSize(Format);

  if (Format == dwarf::DWARF64)
    // DWARF64 mark
    Streamer.emitInt32(dwarf::DW_LENGTH_DWARF64);

  // Length
  const MCExpr *Length = makeEndMinusStartExpr(context, *fdeStart, *fdeEnd, 0);
  emitAbsValue(Streamer, Length, OffsetSize);

  Streamer.emitLabel(fdeStart);

  // CIE Pointer
  const MCAsmInfo *asmInfo = context.getAsmInfo();
  if (IsEH) {
    const MCExpr *offset =
        makeEndMinusStartExpr(context, cieStart, *fdeStart, 0);
    emitAbsValue(Streamer, offset, OffsetSize);
  } else if (!asmInfo->doesDwarfUseRelocationsAcrossSections()) {
    const MCExpr *offset =
        makeEndMinusStartExpr(context, SectionStart, cieStart, 0);
    emitAbsValue(Streamer, offset, OffsetSize);
  } else {
    Streamer.emitSymbolValue(&cieStart, OffsetSize,
                             asmInfo->needsDwarfSectionOffsetDirective());
  }

  // PC Begin
  unsigned PCEncoding =
      IsEH ? MOFI->getFDEEncoding() : (unsigned)dwarf::DW_EH_PE_absptr;
  unsigned PCSize = getSizeForEncoding(Streamer, PCEncoding);
  emitFDESymbol(Streamer, *frame.Begin, PCEncoding, IsEH);

  // PC Range
  const MCExpr *Range =
      makeEndMinusStartExpr(context, *frame.Begin, *frame.End, 0);
  emitAbsValue(Streamer, Range, PCSize);

  if (IsEH) {
    // Augmentation Data Length
    unsigned augmentationLength = 0;

    if (frame.Lsda)
      augmentationLength += getSizeForEncoding(Streamer, frame.LsdaEncoding);

    Streamer.emitULEB128IntValue(augmentationLength);

    // Augmentation Data
    if (frame.Lsda)
      emitFDESymbol(Streamer, *frame.Lsda, frame.LsdaEncoding, true);
  }

  // Call Frame Instructions
  emitCFIInstructions(frame.Instructions, frame.Begin);

  // Padding
  // The size of a .eh_frame section has to be a multiple of the alignment
  // since a null CIE is interpreted as the end. Old systems overaligned
  // .eh_frame, so we do too and account for it in the last FDE.
  unsigned Alignment = LastInSection ? asmInfo->getCodePointerSize() : PCSize;
  Streamer.emitValueToAlignment(Align(Alignment));

  Streamer.emitLabel(fdeEnd);
}

namespace {

struct CIEKey {
  static const CIEKey getEmptyKey() {
    return CIEKey(nullptr, 0, -1, false, false, static_cast<unsigned>(INT_MAX),
                  false, false);
  }

  static const CIEKey getTombstoneKey() {
    return CIEKey(nullptr, -1, 0, false, false, static_cast<unsigned>(INT_MAX),
                  false, false);
  }

  CIEKey(const MCSymbol *Personality, unsigned PersonalityEncoding,
         unsigned LSDAEncoding, bool IsSignalFrame, bool IsSimple,
         unsigned RAReg, bool IsBKeyFrame, bool IsMTETaggedFrame)
      : Personality(Personality), PersonalityEncoding(PersonalityEncoding),
        LsdaEncoding(LSDAEncoding), IsSignalFrame(IsSignalFrame),
        IsSimple(IsSimple), RAReg(RAReg), IsBKeyFrame(IsBKeyFrame),
        IsMTETaggedFrame(IsMTETaggedFrame) {}

  explicit CIEKey(const MCDwarfFrameInfo &Frame)
      : Personality(Frame.Personality),
        PersonalityEncoding(Frame.PersonalityEncoding),
        LsdaEncoding(Frame.LsdaEncoding), IsSignalFrame(Frame.IsSignalFrame),
        IsSimple(Frame.IsSimple), RAReg(Frame.RAReg),
        IsBKeyFrame(Frame.IsBKeyFrame),
        IsMTETaggedFrame(Frame.IsMTETaggedFrame) {}

  StringRef PersonalityName() const {
    if (!Personality)
      return StringRef();
    return Personality->getName();
  }

  bool operator<(const CIEKey &Other) const {
    return std::make_tuple(PersonalityName(), PersonalityEncoding, LsdaEncoding,
                           IsSignalFrame, IsSimple, RAReg, IsBKeyFrame,
                           IsMTETaggedFrame) <
           std::make_tuple(Other.PersonalityName(), Other.PersonalityEncoding,
                           Other.LsdaEncoding, Other.IsSignalFrame,
                           Other.IsSimple, Other.RAReg, Other.IsBKeyFrame,
                           Other.IsMTETaggedFrame);
  }

  const MCSymbol *Personality;
  unsigned PersonalityEncoding;
  unsigned LsdaEncoding;
  bool IsSignalFrame;
  bool IsSimple;
  unsigned RAReg;
  bool IsBKeyFrame;
  bool IsMTETaggedFrame;
};

} // end anonymous namespace

namespace llvm {

template <> struct DenseMapInfo<CIEKey> {
  static CIEKey getEmptyKey() { return CIEKey::getEmptyKey(); }
  static CIEKey getTombstoneKey() { return CIEKey::getTombstoneKey(); }

  static unsigned getHashValue(const CIEKey &Key) {
    return static_cast<unsigned>(
        hash_combine(Key.Personality, Key.PersonalityEncoding, Key.LsdaEncoding,
                     Key.IsSignalFrame, Key.IsSimple, Key.RAReg,
                     Key.IsBKeyFrame, Key.IsMTETaggedFrame));
  }

  static bool isEqual(const CIEKey &LHS, const CIEKey &RHS) {
    return LHS.Personality == RHS.Personality &&
           LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
           LHS.LsdaEncoding == RHS.LsdaEncoding &&
           LHS.IsSignalFrame == RHS.IsSignalFrame &&
           LHS.IsSimple == RHS.IsSimple && LHS.RAReg == RHS.RAReg &&
           LHS.IsBKeyFrame == RHS.IsBKeyFrame &&
           LHS.IsMTETaggedFrame == RHS.IsMTETaggedFrame;
  }
};

} // end namespace llvm

void MCDwarfFrameEmitter::Emit(MCObjectStreamer &Streamer, MCAsmBackend *MAB,
                               bool IsEH) {
  MCContext &Context = Streamer.getContext();
  const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
  const MCAsmInfo *AsmInfo = Context.getAsmInfo();
  FrameEmitterImpl Emitter(IsEH, Streamer);
  ArrayRef<MCDwarfFrameInfo> FrameArray = Streamer.getDwarfFrameInfos();

  // Emit the compact unwind info if available.
  bool NeedsEHFrameSection = !MOFI->getSupportsCompactUnwindWithoutEHFrame();
  if (IsEH && MOFI->getCompactUnwindSection()) {
    Streamer.generateCompactUnwindEncodings(MAB);
    bool SectionEmitted = false;
    for (const MCDwarfFrameInfo &Frame : FrameArray) {
      if (Frame.CompactUnwindEncoding == 0) continue;
      if (!SectionEmitted) {
        Streamer.switchSection(MOFI->getCompactUnwindSection());
        Streamer.emitValueToAlignment(Align(AsmInfo->getCodePointerSize()));
        SectionEmitted = true;
      }
      NeedsEHFrameSection |=
        Frame.CompactUnwindEncoding ==
          MOFI->getCompactUnwindDwarfEHFrameOnly();
      Emitter.EmitCompactUnwind(Frame);
    }
  }

  if (!NeedsEHFrameSection) return;

  MCSection &Section =
      IsEH ? *const_cast<MCObjectFileInfo *>(MOFI)->getEHFrameSection()
           : *MOFI->getDwarfFrameSection();

  Streamer.switchSection(&Section);
  MCSymbol *SectionStart = Context.createTempSymbol();
  Streamer.emitLabel(SectionStart);

  DenseMap<CIEKey, const MCSymbol *> CIEStarts;

  const MCSymbol *DummyDebugKey = nullptr;
  bool CanOmitDwarf = MOFI->getOmitDwarfIfHaveCompactUnwind();
  // Sort the FDEs by their corresponding CIE before we emit them.
  // This isn't technically necessary according to the DWARF standard,
  // but the Android libunwindstack rejects eh_frame sections where
  // an FDE refers to a CIE other than the closest previous CIE.
  std::vector<MCDwarfFrameInfo> FrameArrayX(FrameArray.begin(), FrameArray.end());
  llvm::stable_sort(FrameArrayX,
                    [](const MCDwarfFrameInfo &X, const MCDwarfFrameInfo &Y) {
                      return CIEKey(X) < CIEKey(Y);
                    });
  for (auto I = FrameArrayX.begin(), E = FrameArrayX.end(); I != E;) {
    const MCDwarfFrameInfo &Frame = *I;
    ++I;
    if (CanOmitDwarf && Frame.CompactUnwindEncoding !=
          MOFI->getCompactUnwindDwarfEHFrameOnly())
      // Don't generate an EH frame if we don't need one. I.e., it's taken care
      // of by the compact unwind encoding.
      continue;

    CIEKey Key(Frame);
    const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
    if (!CIEStart)
      CIEStart = &Emitter.EmitCIE(Frame);

    Emitter.EmitFDE(*CIEStart, Frame, I == E, *SectionStart);
  }
}

void MCDwarfFrameEmitter::EmitAdvanceLoc(MCObjectStreamer &Streamer,
                                         uint64_t AddrDelta) {
  MCContext &Context = Streamer.getContext();
  SmallString<256> Tmp;
  raw_svector_ostream OS(Tmp);
  MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OS);
  Streamer.emitBytes(OS.str());
}

void MCDwarfFrameEmitter::EncodeAdvanceLoc(MCContext &Context,
                                           uint64_t AddrDelta,
                                           raw_ostream &OS) {
  // Scale the address delta by the minimum instruction length.
  AddrDelta = ScaleAddrDelta(Context, AddrDelta);
  if (AddrDelta == 0)
    return;

  support::endianness E =
      Context.getAsmInfo()->isLittleEndian() ? support::little : support::big;

  if (isUIntN(6, AddrDelta)) {
    uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
    OS << Opcode;
  } else if (isUInt<8>(AddrDelta)) {
    OS << uint8_t(dwarf::DW_CFA_advance_loc1);
    OS << uint8_t(AddrDelta);
  } else if (isUInt<16>(AddrDelta)) {
    OS << uint8_t(dwarf::DW_CFA_advance_loc2);
    support::endian::write<uint16_t>(OS, AddrDelta, E);
  } else {
    assert(isUInt<32>(AddrDelta));
    OS << uint8_t(dwarf::DW_CFA_advance_loc4);
    support::endian::write<uint32_t>(OS, AddrDelta, E);
  }
}