1 //===-- llvm-dwp.cpp - Split DWARF merging tool for llvm ------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // A utility for merging DWARF 5 Split DWARF .dwo files into .dwp (DWARF
11 // package files).
12 //
13 //===----------------------------------------------------------------------===//
14 #include "DWPError.h"
15 #include "DWPStringPool.h"
16 #include "llvm/ADT/MapVector.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
19 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
20 #include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
21 #include "llvm/MC/MCAsmBackend.h"
22 #include "llvm/MC/MCAsmInfo.h"
23 #include "llvm/MC/MCCodeEmitter.h"
24 #include "llvm/MC/MCContext.h"
25 #include "llvm/MC/MCInstrInfo.h"
26 #include "llvm/MC/MCObjectFileInfo.h"
27 #include "llvm/MC/MCObjectWriter.h"
28 #include "llvm/MC/MCRegisterInfo.h"
29 #include "llvm/MC/MCStreamer.h"
30 #include "llvm/MC/MCTargetOptionsCommandFlags.inc"
31 #include "llvm/Object/Decompressor.h"
32 #include "llvm/Object/ObjectFile.h"
33 #include "llvm/Support/DataExtractor.h"
34 #include "llvm/Support/Error.h"
35 #include "llvm/Support/FileSystem.h"
36 #include "llvm/Support/InitLLVM.h"
37 #include "llvm/Support/MathExtras.h"
38 #include "llvm/Support/MemoryBuffer.h"
39 #include "llvm/Support/Path.h"
40 #include "llvm/Support/TargetRegistry.h"
41 #include "llvm/Support/TargetSelect.h"
42 #include "llvm/Support/raw_ostream.h"
43 
44 using namespace llvm;
45 using namespace llvm::object;
46 
47 cl::OptionCategory DwpCategory("Specific Options");
48 static cl::list<std::string> InputFiles(cl::Positional, cl::ZeroOrMore,
49                                         cl::desc("<input files>"),
50                                         cl::cat(DwpCategory));
51 
52 static cl::list<std::string> ExecFilenames(
53     "e", cl::ZeroOrMore,
54     cl::desc("Specify the executable/library files to get the list of *.dwo from"),
55     cl::value_desc("filename"), cl::cat(DwpCategory));
56 
57 static cl::opt<std::string> OutputFilename(cl::Required, "o",
58                                            cl::desc("Specify the output file."),
59                                            cl::value_desc("filename"),
60                                            cl::cat(DwpCategory));
61 
62 static void writeStringsAndOffsets(MCStreamer &Out, DWPStringPool &Strings,
63                                    MCSection *StrOffsetSection,
64                                    StringRef CurStrSection,
65                                    StringRef CurStrOffsetSection) {
66   // Could possibly produce an error or warning if one of these was non-null but
67   // the other was null.
68   if (CurStrSection.empty() || CurStrOffsetSection.empty())
69     return;
70 
71   DenseMap<uint32_t, uint32_t> OffsetRemapping;
72 
73   DataExtractor Data(CurStrSection, true, 0);
74   uint32_t LocalOffset = 0;
75   uint32_t PrevOffset = 0;
76   while (const char *s = Data.getCStr(&LocalOffset)) {
77     OffsetRemapping[PrevOffset] =
78         Strings.getOffset(s, LocalOffset - PrevOffset);
79     PrevOffset = LocalOffset;
80   }
81 
82   Data = DataExtractor(CurStrOffsetSection, true, 0);
83 
84   Out.SwitchSection(StrOffsetSection);
85 
86   uint32_t Offset = 0;
87   uint64_t Size = CurStrOffsetSection.size();
88   while (Offset < Size) {
89     auto OldOffset = Data.getU32(&Offset);
90     auto NewOffset = OffsetRemapping[OldOffset];
91     Out.EmitIntValue(NewOffset, 4);
92   }
93 }
94 
95 static uint32_t getCUAbbrev(StringRef Abbrev, uint64_t AbbrCode) {
96   uint64_t CurCode;
97   uint32_t Offset = 0;
98   DataExtractor AbbrevData(Abbrev, true, 0);
99   while ((CurCode = AbbrevData.getULEB128(&Offset)) != AbbrCode) {
100     // Tag
101     AbbrevData.getULEB128(&Offset);
102     // DW_CHILDREN
103     AbbrevData.getU8(&Offset);
104     // Attributes
105     while (AbbrevData.getULEB128(&Offset) | AbbrevData.getULEB128(&Offset))
106       ;
107   }
108   return Offset;
109 }
110 
111 struct CompileUnitIdentifiers {
112   uint64_t Signature = 0;
113   const char *Name = "";
114   const char *DWOName = "";
115 };
116 
117 static Expected<const char *>
118 getIndexedString(dwarf::Form Form, DataExtractor InfoData,
119                  uint32_t &InfoOffset, StringRef StrOffsets, StringRef Str) {
120   if (Form == dwarf::DW_FORM_string)
121     return InfoData.getCStr(&InfoOffset);
122   if (Form != dwarf::DW_FORM_GNU_str_index)
123     return make_error<DWPError>(
124         "string field encoded without DW_FORM_string or DW_FORM_GNU_str_index");
125   auto StrIndex = InfoData.getULEB128(&InfoOffset);
126   DataExtractor StrOffsetsData(StrOffsets, true, 0);
127   uint32_t StrOffsetsOffset = 4 * StrIndex;
128   uint32_t StrOffset = StrOffsetsData.getU32(&StrOffsetsOffset);
129   DataExtractor StrData(Str, true, 0);
130   return StrData.getCStr(&StrOffset);
131 }
132 
133 static Expected<CompileUnitIdentifiers> getCUIdentifiers(StringRef Abbrev,
134                                                          StringRef Info,
135                                                          StringRef StrOffsets,
136                                                          StringRef Str) {
137   uint32_t Offset = 0;
138   DataExtractor InfoData(Info, true, 0);
139   dwarf::DwarfFormat Format = dwarf::DwarfFormat::DWARF32;
140   uint64_t Length = InfoData.getU32(&Offset);
141   // If the length is 0xffffffff, then this indictes that this is a DWARF 64
142   // stream and the length is actually encoded into a 64 bit value that follows.
143   if (Length == 0xffffffffU) {
144     Format = dwarf::DwarfFormat::DWARF64;
145     Length = InfoData.getU64(&Offset);
146   }
147   uint16_t Version = InfoData.getU16(&Offset);
148   InfoData.getU32(&Offset); // Abbrev offset (should be zero)
149   uint8_t AddrSize = InfoData.getU8(&Offset);
150 
151   uint32_t AbbrCode = InfoData.getULEB128(&Offset);
152 
153   DataExtractor AbbrevData(Abbrev, true, 0);
154   uint32_t AbbrevOffset = getCUAbbrev(Abbrev, AbbrCode);
155   auto Tag = static_cast<dwarf::Tag>(AbbrevData.getULEB128(&AbbrevOffset));
156   if (Tag != dwarf::DW_TAG_compile_unit)
157     return make_error<DWPError>("top level DIE is not a compile unit");
158   // DW_CHILDREN
159   AbbrevData.getU8(&AbbrevOffset);
160   uint32_t Name;
161   dwarf::Form Form;
162   CompileUnitIdentifiers ID;
163   while ((Name = AbbrevData.getULEB128(&AbbrevOffset)) |
164          (Form = static_cast<dwarf::Form>(AbbrevData.getULEB128(&AbbrevOffset))) &&
165          (Name != 0 || Form != 0)) {
166     switch (Name) {
167     case dwarf::DW_AT_name: {
168       Expected<const char *> EName =
169           getIndexedString(Form, InfoData, Offset, StrOffsets, Str);
170       if (!EName)
171         return EName.takeError();
172       ID.Name = *EName;
173       break;
174     }
175     case dwarf::DW_AT_GNU_dwo_name: {
176       Expected<const char *> EName =
177           getIndexedString(Form, InfoData, Offset, StrOffsets, Str);
178       if (!EName)
179         return EName.takeError();
180       ID.DWOName = *EName;
181       break;
182     }
183     case dwarf::DW_AT_GNU_dwo_id:
184       ID.Signature = InfoData.getU64(&Offset);
185       break;
186     default:
187       DWARFFormValue::skipValue(Form, InfoData, &Offset,
188                                 dwarf::FormParams({Version, AddrSize, Format}));
189     }
190   }
191   return ID;
192 }
193 
194 struct UnitIndexEntry {
195   DWARFUnitIndex::Entry::SectionContribution Contributions[8];
196   std::string Name;
197   std::string DWOName;
198   StringRef DWPName;
199 };
200 
201 static StringRef getSubsection(StringRef Section,
202                                const DWARFUnitIndex::Entry &Entry,
203                                DWARFSectionKind Kind) {
204   const auto *Off = Entry.getOffset(Kind);
205   if (!Off)
206     return StringRef();
207   return Section.substr(Off->Offset, Off->Length);
208 }
209 
210 static void addAllTypesFromDWP(
211     MCStreamer &Out, MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
212     const DWARFUnitIndex &TUIndex, MCSection *OutputTypes, StringRef Types,
213     const UnitIndexEntry &TUEntry, uint32_t &TypesOffset) {
214   Out.SwitchSection(OutputTypes);
215   for (const DWARFUnitIndex::Entry &E : TUIndex.getRows()) {
216     auto *I = E.getOffsets();
217     if (!I)
218       continue;
219     auto P = TypeIndexEntries.insert(std::make_pair(E.getSignature(), TUEntry));
220     if (!P.second)
221       continue;
222     auto &Entry = P.first->second;
223     // Zero out the debug_info contribution
224     Entry.Contributions[0] = {};
225     for (auto Kind : TUIndex.getColumnKinds()) {
226       auto &C = Entry.Contributions[Kind - DW_SECT_INFO];
227       C.Offset += I->Offset;
228       C.Length = I->Length;
229       ++I;
230     }
231     auto &C = Entry.Contributions[DW_SECT_TYPES - DW_SECT_INFO];
232     Out.EmitBytes(Types.substr(
233         C.Offset - TUEntry.Contributions[DW_SECT_TYPES - DW_SECT_INFO].Offset,
234         C.Length));
235     C.Offset = TypesOffset;
236     TypesOffset += C.Length;
237   }
238 }
239 
240 static void addAllTypes(MCStreamer &Out,
241                         MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
242                         MCSection *OutputTypes,
243                         const std::vector<StringRef> &TypesSections,
244                         const UnitIndexEntry &CUEntry, uint32_t &TypesOffset) {
245   for (StringRef Types : TypesSections) {
246     Out.SwitchSection(OutputTypes);
247     uint32_t Offset = 0;
248     DataExtractor Data(Types, true, 0);
249     while (Data.isValidOffset(Offset)) {
250       UnitIndexEntry Entry = CUEntry;
251       // Zero out the debug_info contribution
252       Entry.Contributions[0] = {};
253       auto &C = Entry.Contributions[DW_SECT_TYPES - DW_SECT_INFO];
254       C.Offset = TypesOffset;
255       auto PrevOffset = Offset;
256       // Length of the unit, including the 4 byte length field.
257       C.Length = Data.getU32(&Offset) + 4;
258 
259       Data.getU16(&Offset); // Version
260       Data.getU32(&Offset); // Abbrev offset
261       Data.getU8(&Offset);  // Address size
262       auto Signature = Data.getU64(&Offset);
263       Offset = PrevOffset + C.Length;
264 
265       auto P = TypeIndexEntries.insert(std::make_pair(Signature, Entry));
266       if (!P.second)
267         continue;
268 
269       Out.EmitBytes(Types.substr(PrevOffset, C.Length));
270       TypesOffset += C.Length;
271     }
272   }
273 }
274 
275 static void
276 writeIndexTable(MCStreamer &Out, ArrayRef<unsigned> ContributionOffsets,
277                 const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
278                 uint32_t DWARFUnitIndex::Entry::SectionContribution::*Field) {
279   for (const auto &E : IndexEntries)
280     for (size_t i = 0; i != array_lengthof(E.second.Contributions); ++i)
281       if (ContributionOffsets[i])
282         Out.EmitIntValue(E.second.Contributions[i].*Field, 4);
283 }
284 
285 static void
286 writeIndex(MCStreamer &Out, MCSection *Section,
287            ArrayRef<unsigned> ContributionOffsets,
288            const MapVector<uint64_t, UnitIndexEntry> &IndexEntries) {
289   if (IndexEntries.empty())
290     return;
291 
292   unsigned Columns = 0;
293   for (auto &C : ContributionOffsets)
294     if (C)
295       ++Columns;
296 
297   std::vector<unsigned> Buckets(NextPowerOf2(3 * IndexEntries.size() / 2));
298   uint64_t Mask = Buckets.size() - 1;
299   size_t i = 0;
300   for (const auto &P : IndexEntries) {
301     auto S = P.first;
302     auto H = S & Mask;
303     auto HP = ((S >> 32) & Mask) | 1;
304     while (Buckets[H]) {
305       assert(S != IndexEntries.begin()[Buckets[H] - 1].first &&
306              "Duplicate unit");
307       H = (H + HP) & Mask;
308     }
309     Buckets[H] = i + 1;
310     ++i;
311   }
312 
313   Out.SwitchSection(Section);
314   Out.EmitIntValue(2, 4);                   // Version
315   Out.EmitIntValue(Columns, 4);             // Columns
316   Out.EmitIntValue(IndexEntries.size(), 4); // Num Units
317   Out.EmitIntValue(Buckets.size(), 4);      // Num Buckets
318 
319   // Write the signatures.
320   for (const auto &I : Buckets)
321     Out.EmitIntValue(I ? IndexEntries.begin()[I - 1].first : 0, 8);
322 
323   // Write the indexes.
324   for (const auto &I : Buckets)
325     Out.EmitIntValue(I, 4);
326 
327   // Write the column headers (which sections will appear in the table)
328   for (size_t i = 0; i != ContributionOffsets.size(); ++i)
329     if (ContributionOffsets[i])
330       Out.EmitIntValue(i + DW_SECT_INFO, 4);
331 
332   // Write the offsets.
333   writeIndexTable(Out, ContributionOffsets, IndexEntries,
334                   &DWARFUnitIndex::Entry::SectionContribution::Offset);
335 
336   // Write the lengths.
337   writeIndexTable(Out, ContributionOffsets, IndexEntries,
338                   &DWARFUnitIndex::Entry::SectionContribution::Length);
339 }
340 
341 std::string buildDWODescription(StringRef Name, StringRef DWPName, StringRef DWOName) {
342   std::string Text = "\'";
343   Text += Name;
344   Text += '\'';
345   if (!DWPName.empty()) {
346     Text += " (from ";
347     if (!DWOName.empty()) {
348       Text += '\'';
349       Text += DWOName;
350       Text += "' in ";
351     }
352     Text += '\'';
353     Text += DWPName;
354     Text += "')";
355   }
356   return Text;
357 }
358 
359 static Error createError(StringRef Name, Error E) {
360   return make_error<DWPError>(
361       ("failure while decompressing compressed section: '" + Name + "', " +
362        llvm::toString(std::move(E)))
363           .str());
364 }
365 
366 static Error
367 handleCompressedSection(std::deque<SmallString<32>> &UncompressedSections,
368                         StringRef &Name, StringRef &Contents) {
369   if (!Decompressor::isGnuStyle(Name))
370     return Error::success();
371 
372   Expected<Decompressor> Dec =
373       Decompressor::create(Name, Contents, false /*IsLE*/, false /*Is64Bit*/);
374   if (!Dec)
375     return createError(Name, Dec.takeError());
376 
377   UncompressedSections.emplace_back();
378   if (Error E = Dec->resizeAndDecompress(UncompressedSections.back()))
379     return createError(Name, std::move(E));
380 
381   Name = Name.substr(2); // Drop ".z"
382   Contents = UncompressedSections.back();
383   return Error::success();
384 }
385 
386 static Error handleSection(
387     const StringMap<std::pair<MCSection *, DWARFSectionKind>> &KnownSections,
388     const MCSection *StrSection, const MCSection *StrOffsetSection,
389     const MCSection *TypesSection, const MCSection *CUIndexSection,
390     const MCSection *TUIndexSection, const SectionRef &Section, MCStreamer &Out,
391     std::deque<SmallString<32>> &UncompressedSections,
392     uint32_t (&ContributionOffsets)[8], UnitIndexEntry &CurEntry,
393     StringRef &CurStrSection, StringRef &CurStrOffsetSection,
394     std::vector<StringRef> &CurTypesSection, StringRef &InfoSection,
395     StringRef &AbbrevSection, StringRef &CurCUIndexSection,
396     StringRef &CurTUIndexSection) {
397   if (Section.isBSS())
398     return Error::success();
399 
400   if (Section.isVirtual())
401     return Error::success();
402 
403   StringRef Name;
404   if (std::error_code Err = Section.getName(Name))
405     return errorCodeToError(Err);
406 
407   StringRef Contents;
408   if (auto Err = Section.getContents(Contents))
409     return errorCodeToError(Err);
410 
411   if (auto Err = handleCompressedSection(UncompressedSections, Name, Contents))
412     return Err;
413 
414   Name = Name.substr(Name.find_first_not_of("._"));
415 
416   auto SectionPair = KnownSections.find(Name);
417   if (SectionPair == KnownSections.end())
418     return Error::success();
419 
420   if (DWARFSectionKind Kind = SectionPair->second.second) {
421     auto Index = Kind - DW_SECT_INFO;
422     if (Kind != DW_SECT_TYPES) {
423       CurEntry.Contributions[Index].Offset = ContributionOffsets[Index];
424       ContributionOffsets[Index] +=
425           (CurEntry.Contributions[Index].Length = Contents.size());
426     }
427 
428     switch (Kind) {
429     case DW_SECT_INFO:
430       InfoSection = Contents;
431       break;
432     case DW_SECT_ABBREV:
433       AbbrevSection = Contents;
434       break;
435     default:
436       break;
437     }
438   }
439 
440   MCSection *OutSection = SectionPair->second.first;
441   if (OutSection == StrOffsetSection)
442     CurStrOffsetSection = Contents;
443   else if (OutSection == StrSection)
444     CurStrSection = Contents;
445   else if (OutSection == TypesSection)
446     CurTypesSection.push_back(Contents);
447   else if (OutSection == CUIndexSection)
448     CurCUIndexSection = Contents;
449   else if (OutSection == TUIndexSection)
450     CurTUIndexSection = Contents;
451   else {
452     Out.SwitchSection(OutSection);
453     Out.EmitBytes(Contents);
454   }
455   return Error::success();
456 }
457 
458 static Error
459 buildDuplicateError(const std::pair<uint64_t, UnitIndexEntry> &PrevE,
460                     const CompileUnitIdentifiers &ID, StringRef DWPName) {
461   return make_error<DWPError>(
462       std::string("Duplicate DWO ID (") + utohexstr(PrevE.first) + ") in " +
463       buildDWODescription(PrevE.second.Name, PrevE.second.DWPName,
464                           PrevE.second.DWOName) +
465       " and " + buildDWODescription(ID.Name, DWPName, ID.DWOName));
466 }
467 
468 static Expected<SmallVector<std::string, 16>>
469 getDWOFilenames(StringRef ExecFilename) {
470   auto ErrOrObj = object::ObjectFile::createObjectFile(ExecFilename);
471   if (!ErrOrObj)
472     return ErrOrObj.takeError();
473 
474   const ObjectFile &Obj = *ErrOrObj.get().getBinary();
475   std::unique_ptr<DWARFContext> DWARFCtx = DWARFContext::create(Obj);
476 
477   SmallVector<std::string, 16> DWOPaths;
478   for (const auto &CU : DWARFCtx->compile_units()) {
479     const DWARFDie &Die = CU->getUnitDIE();
480     std::string DWOName = dwarf::toString(
481         Die.find({dwarf::DW_AT_dwo_name, dwarf::DW_AT_GNU_dwo_name}), "");
482     if (DWOName.empty())
483       continue;
484     std::string DWOCompDir =
485         dwarf::toString(Die.find(dwarf::DW_AT_comp_dir), "");
486     if (!DWOCompDir.empty()) {
487       SmallString<16> DWOPath;
488       sys::path::append(DWOPath, DWOCompDir, DWOName);
489       DWOPaths.emplace_back(DWOPath.data(), DWOPath.size());
490     } else {
491       DWOPaths.push_back(std::move(DWOName));
492     }
493   }
494   return std::move(DWOPaths);
495 }
496 
497 static Error write(MCStreamer &Out, ArrayRef<std::string> Inputs) {
498   const auto &MCOFI = *Out.getContext().getObjectFileInfo();
499   MCSection *const StrSection = MCOFI.getDwarfStrDWOSection();
500   MCSection *const StrOffsetSection = MCOFI.getDwarfStrOffDWOSection();
501   MCSection *const TypesSection = MCOFI.getDwarfTypesDWOSection();
502   MCSection *const CUIndexSection = MCOFI.getDwarfCUIndexSection();
503   MCSection *const TUIndexSection = MCOFI.getDwarfTUIndexSection();
504   const StringMap<std::pair<MCSection *, DWARFSectionKind>> KnownSections = {
505       {"debug_info.dwo", {MCOFI.getDwarfInfoDWOSection(), DW_SECT_INFO}},
506       {"debug_types.dwo", {MCOFI.getDwarfTypesDWOSection(), DW_SECT_TYPES}},
507       {"debug_str_offsets.dwo", {StrOffsetSection, DW_SECT_STR_OFFSETS}},
508       {"debug_str.dwo", {StrSection, static_cast<DWARFSectionKind>(0)}},
509       {"debug_loc.dwo", {MCOFI.getDwarfLocDWOSection(), DW_SECT_LOC}},
510       {"debug_line.dwo", {MCOFI.getDwarfLineDWOSection(), DW_SECT_LINE}},
511       {"debug_abbrev.dwo", {MCOFI.getDwarfAbbrevDWOSection(), DW_SECT_ABBREV}},
512       {"debug_cu_index", {CUIndexSection, static_cast<DWARFSectionKind>(0)}},
513       {"debug_tu_index", {TUIndexSection, static_cast<DWARFSectionKind>(0)}}};
514 
515   MapVector<uint64_t, UnitIndexEntry> IndexEntries;
516   MapVector<uint64_t, UnitIndexEntry> TypeIndexEntries;
517 
518   uint32_t ContributionOffsets[8] = {};
519 
520   DWPStringPool Strings(Out, StrSection);
521 
522   SmallVector<OwningBinary<object::ObjectFile>, 128> Objects;
523   Objects.reserve(Inputs.size());
524 
525   std::deque<SmallString<32>> UncompressedSections;
526 
527   for (const auto &Input : Inputs) {
528     auto ErrOrObj = object::ObjectFile::createObjectFile(Input);
529     if (!ErrOrObj)
530       return ErrOrObj.takeError();
531 
532     auto &Obj = *ErrOrObj->getBinary();
533     Objects.push_back(std::move(*ErrOrObj));
534 
535     UnitIndexEntry CurEntry = {};
536 
537     StringRef CurStrSection;
538     StringRef CurStrOffsetSection;
539     std::vector<StringRef> CurTypesSection;
540     StringRef InfoSection;
541     StringRef AbbrevSection;
542     StringRef CurCUIndexSection;
543     StringRef CurTUIndexSection;
544 
545     for (const auto &Section : Obj.sections())
546       if (auto Err = handleSection(
547               KnownSections, StrSection, StrOffsetSection, TypesSection,
548               CUIndexSection, TUIndexSection, Section, Out,
549               UncompressedSections, ContributionOffsets, CurEntry,
550               CurStrSection, CurStrOffsetSection, CurTypesSection, InfoSection,
551               AbbrevSection, CurCUIndexSection, CurTUIndexSection))
552         return Err;
553 
554     if (InfoSection.empty())
555       continue;
556 
557     writeStringsAndOffsets(Out, Strings, StrOffsetSection, CurStrSection,
558                            CurStrOffsetSection);
559 
560     if (CurCUIndexSection.empty()) {
561       Expected<CompileUnitIdentifiers> EID = getCUIdentifiers(
562           AbbrevSection, InfoSection, CurStrOffsetSection, CurStrSection);
563       if (!EID)
564         return EID.takeError();
565       const auto &ID = *EID;
566       auto P = IndexEntries.insert(std::make_pair(ID.Signature, CurEntry));
567       if (!P.second)
568         return buildDuplicateError(*P.first, ID, "");
569       P.first->second.Name = ID.Name;
570       P.first->second.DWOName = ID.DWOName;
571       addAllTypes(Out, TypeIndexEntries, TypesSection, CurTypesSection,
572                   CurEntry, ContributionOffsets[DW_SECT_TYPES - DW_SECT_INFO]);
573       continue;
574     }
575 
576     DWARFUnitIndex CUIndex(DW_SECT_INFO);
577     DataExtractor CUIndexData(CurCUIndexSection, Obj.isLittleEndian(), 0);
578     if (!CUIndex.parse(CUIndexData))
579       return make_error<DWPError>("Failed to parse cu_index");
580 
581     for (const DWARFUnitIndex::Entry &E : CUIndex.getRows()) {
582       auto *I = E.getOffsets();
583       if (!I)
584         continue;
585       auto P = IndexEntries.insert(std::make_pair(E.getSignature(), CurEntry));
586       Expected<CompileUnitIdentifiers> EID = getCUIdentifiers(
587           getSubsection(AbbrevSection, E, DW_SECT_ABBREV),
588           getSubsection(InfoSection, E, DW_SECT_INFO),
589           getSubsection(CurStrOffsetSection, E, DW_SECT_STR_OFFSETS),
590           CurStrSection);
591       if (!EID)
592         return EID.takeError();
593       const auto &ID = *EID;
594       if (!P.second)
595         return buildDuplicateError(*P.first, ID, Input);
596       auto &NewEntry = P.first->second;
597       NewEntry.Name = ID.Name;
598       NewEntry.DWOName = ID.DWOName;
599       NewEntry.DWPName = Input;
600       for (auto Kind : CUIndex.getColumnKinds()) {
601         auto &C = NewEntry.Contributions[Kind - DW_SECT_INFO];
602         C.Offset += I->Offset;
603         C.Length = I->Length;
604         ++I;
605       }
606     }
607 
608     if (!CurTypesSection.empty()) {
609       if (CurTypesSection.size() != 1)
610         return make_error<DWPError>("multiple type unit sections in .dwp file");
611       DWARFUnitIndex TUIndex(DW_SECT_TYPES);
612       DataExtractor TUIndexData(CurTUIndexSection, Obj.isLittleEndian(), 0);
613       if (!TUIndex.parse(TUIndexData))
614         return make_error<DWPError>("Failed to parse tu_index");
615       addAllTypesFromDWP(Out, TypeIndexEntries, TUIndex, TypesSection,
616                          CurTypesSection.front(), CurEntry,
617                          ContributionOffsets[DW_SECT_TYPES - DW_SECT_INFO]);
618     }
619   }
620 
621   // Lie about there being no info contributions so the TU index only includes
622   // the type unit contribution
623   ContributionOffsets[0] = 0;
624   writeIndex(Out, MCOFI.getDwarfTUIndexSection(), ContributionOffsets,
625              TypeIndexEntries);
626 
627   // Lie about the type contribution
628   ContributionOffsets[DW_SECT_TYPES - DW_SECT_INFO] = 0;
629   // Unlie about the info contribution
630   ContributionOffsets[0] = 1;
631 
632   writeIndex(Out, MCOFI.getDwarfCUIndexSection(), ContributionOffsets,
633              IndexEntries);
634 
635   return Error::success();
636 }
637 
638 static int error(const Twine &Error, const Twine &Context) {
639   errs() << Twine("while processing ") + Context + ":\n";
640   errs() << Twine("error: ") + Error + "\n";
641   return 1;
642 }
643 
644 int main(int argc, char **argv) {
645   InitLLVM X(argc, argv);
646 
647   cl::ParseCommandLineOptions(argc, argv, "merge split dwarf (.dwo) files\n");
648 
649   llvm::InitializeAllTargetInfos();
650   llvm::InitializeAllTargetMCs();
651   llvm::InitializeAllTargets();
652   llvm::InitializeAllAsmPrinters();
653 
654   std::string ErrorStr;
655   StringRef Context = "dwarf streamer init";
656 
657   Triple TheTriple("x86_64-linux-gnu");
658 
659   // Get the target.
660   const Target *TheTarget =
661       TargetRegistry::lookupTarget("", TheTriple, ErrorStr);
662   if (!TheTarget)
663     return error(ErrorStr, Context);
664   std::string TripleName = TheTriple.getTriple();
665 
666   // Create all the MC Objects.
667   std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
668   if (!MRI)
669     return error(Twine("no register info for target ") + TripleName, Context);
670 
671   std::unique_ptr<MCAsmInfo> MAI(TheTarget->createMCAsmInfo(*MRI, TripleName));
672   if (!MAI)
673     return error("no asm info for target " + TripleName, Context);
674 
675   MCObjectFileInfo MOFI;
676   MCContext MC(MAI.get(), MRI.get(), &MOFI);
677   MOFI.InitMCObjectFileInfo(TheTriple, /*PIC*/ false, MC);
678 
679   std::unique_ptr<MCSubtargetInfo> MSTI(
680       TheTarget->createMCSubtargetInfo(TripleName, "", ""));
681   if (!MSTI)
682     return error("no subtarget info for target " + TripleName, Context);
683 
684   MCTargetOptions Options;
685   auto MAB = TheTarget->createMCAsmBackend(*MSTI, *MRI, Options);
686   if (!MAB)
687     return error("no asm backend for target " + TripleName, Context);
688 
689   std::unique_ptr<MCInstrInfo> MII(TheTarget->createMCInstrInfo());
690   if (!MII)
691     return error("no instr info info for target " + TripleName, Context);
692 
693   MCCodeEmitter *MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, MC);
694   if (!MCE)
695     return error("no code emitter for target " + TripleName, Context);
696 
697   // Create the output file.
698   std::error_code EC;
699   raw_fd_ostream OutFile(OutputFilename, EC, sys::fs::F_None);
700   Optional<buffer_ostream> BOS;
701   raw_pwrite_stream *OS;
702   if (EC)
703     return error(Twine(OutputFilename) + ": " + EC.message(), Context);
704   if (OutFile.supportsSeeking()) {
705     OS = &OutFile;
706   } else {
707     BOS.emplace(OutFile);
708     OS = BOS.getPointer();
709   }
710 
711   MCTargetOptions MCOptions = InitMCTargetOptionsFromFlags();
712   std::unique_ptr<MCStreamer> MS(TheTarget->createMCObjectStreamer(
713       TheTriple, MC, std::unique_ptr<MCAsmBackend>(MAB),
714       MAB->createObjectWriter(*OS), std::unique_ptr<MCCodeEmitter>(MCE),
715       *MSTI, MCOptions.MCRelaxAll, MCOptions.MCIncrementalLinkerCompatible,
716       /*DWARFMustBeAtTheEnd*/ false));
717   if (!MS)
718     return error("no object streamer for target " + TripleName, Context);
719 
720   std::vector<std::string> DWOFilenames = InputFiles;
721   for (const auto &ExecFilename : ExecFilenames) {
722     auto DWOs = getDWOFilenames(ExecFilename);
723     if (!DWOs) {
724       logAllUnhandledErrors(DWOs.takeError(), errs(), "error: ");
725       return 1;
726     }
727     DWOFilenames.insert(DWOFilenames.end(),
728                         std::make_move_iterator(DWOs->begin()),
729                         std::make_move_iterator(DWOs->end()));
730   }
731 
732   if (auto Err = write(*MS, DWOFilenames)) {
733     logAllUnhandledErrors(std::move(Err), errs(), "error: ");
734     return 1;
735   }
736 
737   MS->Finish();
738 }
739