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 "llvm/ADT/MapVector.h"
15 #include "llvm/ADT/STLExtras.h"
16 #include "llvm/ADT/StringSet.h"
17 #include "llvm/CodeGen/AsmPrinter.h"
18 #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
19 #include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
20 #include "llvm/MC/MCAsmInfo.h"
21 #include "llvm/MC/MCContext.h"
22 #include "llvm/MC/MCInstrInfo.h"
23 #include "llvm/MC/MCObjectFileInfo.h"
24 #include "llvm/MC/MCRegisterInfo.h"
25 #include "llvm/MC/MCSectionELF.h"
26 #include "llvm/MC/MCStreamer.h"
27 #include "llvm/MC/MCTargetOptionsCommandFlags.h"
28 #include "llvm/Object/ObjectFile.h"
29 #include "llvm/Support/Compression.h"
30 #include "llvm/Support/DataExtractor.h"
31 #include "llvm/Support/FileSystem.h"
32 #include "llvm/Support/MathExtras.h"
33 #include "llvm/Support/MemoryBuffer.h"
34 #include "llvm/Support/Options.h"
35 #include "llvm/Support/TargetRegistry.h"
36 #include "llvm/Support/TargetSelect.h"
37 #include "llvm/Support/raw_ostream.h"
38 #include "llvm/Target/TargetMachine.h"
39 #include <list>
40 #include <iostream>
41 #include <memory>
42 #include <system_error>
43 #include <unordered_set>
44 
45 using namespace llvm;
46 using namespace llvm::object;
47 using namespace cl;
48 
49 OptionCategory DwpCategory("Specific Options");
50 static list<std::string> InputFiles(Positional, OneOrMore,
51                                     desc("<input files>"), cat(DwpCategory));
52 
53 static opt<std::string> OutputFilename(Required, "o",
54                                        desc("Specify the output file."),
55                                        value_desc("filename"),
56                                        cat(DwpCategory));
57 
58 static int error(const Twine &Error, const Twine &Context) {
59   errs() << Twine("while processing ") + Context + ":\n";
60   errs() << Twine("error: ") + Error + "\n";
61   return 1;
62 }
63 
64 static std::error_code
65 writeStringsAndOffsets(MCStreamer &Out, StringMap<uint32_t> &Strings,
66                        uint32_t &StringOffset, MCSection *StrSection,
67                        MCSection *StrOffsetSection, StringRef CurStrSection,
68                        StringRef CurStrOffsetSection) {
69   // Could possibly produce an error or warning if one of these was non-null but
70   // the other was null.
71   if (CurStrSection.empty() || CurStrOffsetSection.empty())
72     return std::error_code();
73 
74   DenseMap<uint32_t, uint32_t> OffsetRemapping;
75 
76   DataExtractor Data(CurStrSection, true, 0);
77   uint32_t LocalOffset = 0;
78   uint32_t PrevOffset = 0;
79   while (const char *s = Data.getCStr(&LocalOffset)) {
80     StringRef Str(s, LocalOffset - PrevOffset - 1);
81     auto Pair = Strings.insert(std::make_pair(Str, StringOffset));
82     if (Pair.second) {
83       Out.SwitchSection(StrSection);
84       Out.EmitBytes(
85           StringRef(Pair.first->getKeyData(), Pair.first->getKeyLength() + 1));
86       StringOffset += Str.size() + 1;
87     }
88     OffsetRemapping[PrevOffset] = Pair.first->second;
89     PrevOffset = LocalOffset;
90   }
91 
92   Data = DataExtractor(CurStrOffsetSection, true, 0);
93 
94   Out.SwitchSection(StrOffsetSection);
95 
96   uint32_t Offset = 0;
97   uint64_t Size = CurStrOffsetSection.size();
98   while (Offset < Size) {
99     auto OldOffset = Data.getU32(&Offset);
100     auto NewOffset = OffsetRemapping[OldOffset];
101     Out.EmitIntValue(NewOffset, 4);
102   }
103 
104   return std::error_code();
105 }
106 
107 static uint32_t getCUAbbrev(StringRef Abbrev, uint64_t AbbrCode) {
108   uint64_t CurCode;
109   uint32_t Offset = 0;
110   DataExtractor AbbrevData(Abbrev, true, 0);
111   while ((CurCode = AbbrevData.getULEB128(&Offset)) != AbbrCode) {
112     // Tag
113     AbbrevData.getULEB128(&Offset);
114     // DW_CHILDREN
115     AbbrevData.getU8(&Offset);
116     // Attributes
117     while (AbbrevData.getULEB128(&Offset) | AbbrevData.getULEB128(&Offset))
118       ;
119   }
120   return Offset;
121 }
122 
123 static const char *getCUName(StringRef Abbrev, StringRef Info,
124                              StringRef StrOffsets, StringRef Str) {
125   uint32_t Offset = 0;
126   DataExtractor InfoData(Info, true, 0);
127   InfoData.getU32(&Offset); // Length
128   uint16_t Version = InfoData.getU16(&Offset);
129   InfoData.getU32(&Offset); // Abbrev offset (should be zero)
130   uint8_t AddrSize = InfoData.getU8(&Offset);
131 
132   uint32_t AbbrCode = InfoData.getULEB128(&Offset);
133 
134   DataExtractor AbbrevData(Abbrev, true, 0);
135   uint32_t AbbrevOffset = getCUAbbrev(Abbrev, AbbrCode);
136   uint64_t Tag = AbbrevData.getULEB128(&AbbrevOffset);
137   (void)Tag;
138   // FIXME: Real error handling
139   assert(Tag == dwarf::DW_TAG_compile_unit);
140   // DW_CHILDREN
141   AbbrevData.getU8(&AbbrevOffset);
142   uint32_t Name;
143   uint32_t Form;
144   while ((Name = AbbrevData.getULEB128(&AbbrevOffset)) |
145              (Form = AbbrevData.getULEB128(&AbbrevOffset)) &&
146          Name != dwarf::DW_AT_name) {
147     DWARFFormValue::skipValue(Form, InfoData, &Offset, Version, AddrSize);
148   }
149   // FIXME: Real error handling
150   assert(Name == dwarf::DW_AT_name);
151   auto StrIndex = InfoData.getULEB128(&Offset);
152 
153   DataExtractor StrOffsetsData(StrOffsets, true, 0);
154   uint32_t StrOffsetsOffset = 4 * StrIndex;
155   uint32_t StrOffset = StrOffsetsData.getU32(&StrOffsetsOffset);
156   DataExtractor StrData(Str, true, 0);
157   return StrData.getCStr(&StrOffset);
158 }
159 
160 static uint64_t getCUSignature(StringRef Abbrev, StringRef Info) {
161   uint32_t Offset = 0;
162   DataExtractor InfoData(Info, true, 0);
163   InfoData.getU32(&Offset); // Length
164   uint16_t Version = InfoData.getU16(&Offset);
165   InfoData.getU32(&Offset); // Abbrev offset (should be zero)
166   uint8_t AddrSize = InfoData.getU8(&Offset);
167 
168   uint32_t AbbrCode = InfoData.getULEB128(&Offset);
169 
170   DataExtractor AbbrevData(Abbrev, true, 0);
171   uint32_t AbbrevOffset = getCUAbbrev(Abbrev, AbbrCode);
172   uint64_t Tag = AbbrevData.getULEB128(&AbbrevOffset);
173   (void)Tag;
174   // FIXME: Real error handling
175   assert(Tag == dwarf::DW_TAG_compile_unit);
176   // DW_CHILDREN
177   AbbrevData.getU8(&AbbrevOffset);
178   uint32_t Name;
179   uint32_t Form;
180   while ((Name = AbbrevData.getULEB128(&AbbrevOffset)) |
181              (Form = AbbrevData.getULEB128(&AbbrevOffset)) &&
182          Name != dwarf::DW_AT_GNU_dwo_id) {
183     DWARFFormValue::skipValue(Form, InfoData, &Offset, Version, AddrSize);
184   }
185   // FIXME: Real error handling
186   assert(Name == dwarf::DW_AT_GNU_dwo_id);
187   return InfoData.getU64(&Offset);
188 }
189 
190 struct UnitIndexEntry {
191   DWARFUnitIndex::Entry::SectionContribution Contributions[8];
192   std::string Name;
193   StringRef DWPName;
194 };
195 
196 StringRef getSubsection(StringRef Section, const DWARFUnitIndex::Entry &Entry, DWARFSectionKind Kind) {
197   const auto *Off = Entry.getOffset(Kind);
198   if (!Off)
199     return StringRef();
200   return Section.substr(Off->Offset, Off->Length);
201 }
202 
203 static void addAllTypesFromDWP(
204     MCStreamer &Out, MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
205     const DWARFUnitIndex &TUIndex, MCSection *OutputTypes, StringRef Types,
206     const UnitIndexEntry &TUEntry, uint32_t &TypesOffset) {
207   Out.SwitchSection(OutputTypes);
208   for (const DWARFUnitIndex::Entry &E : TUIndex.getRows()) {
209     auto *I = E.getOffsets();
210     if (!I)
211       continue;
212     auto P = TypeIndexEntries.insert(std::make_pair(E.getSignature(), TUEntry));
213     if (!P.second)
214       continue;
215     auto &Entry = P.first->second;
216     // Zero out the debug_info contribution
217     Entry.Contributions[0] = {};
218     for (auto Kind : TUIndex.getColumnKinds()) {
219       auto &C = Entry.Contributions[Kind - DW_SECT_INFO];
220       C.Offset += I->Offset;
221       C.Length = I->Length;
222       ++I;
223     }
224     auto &C = Entry.Contributions[DW_SECT_TYPES - DW_SECT_INFO];
225     Out.EmitBytes(Types.substr(
226         C.Offset - TUEntry.Contributions[DW_SECT_TYPES - DW_SECT_INFO].Offset,
227         C.Length));
228     C.Offset = TypesOffset;
229     TypesOffset += C.Length;
230   }
231 }
232 
233 static void addAllTypes(MCStreamer &Out,
234                         MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
235                         MCSection *OutputTypes, StringRef Types,
236                         const UnitIndexEntry &CUEntry, uint32_t &TypesOffset) {
237   if (Types.empty())
238     return;
239 
240   Out.SwitchSection(OutputTypes);
241   uint32_t Offset = 0;
242   DataExtractor Data(Types, true, 0);
243   while (Data.isValidOffset(Offset)) {
244     UnitIndexEntry Entry = CUEntry;
245     // Zero out the debug_info contribution
246     Entry.Contributions[0] = {};
247     auto &C = Entry.Contributions[DW_SECT_TYPES - DW_SECT_INFO];
248     C.Offset = TypesOffset;
249     auto PrevOffset = Offset;
250     // Length of the unit, including the 4 byte length field.
251     C.Length = Data.getU32(&Offset) + 4;
252 
253     Data.getU16(&Offset); // Version
254     Data.getU32(&Offset); // Abbrev offset
255     Data.getU8(&Offset);  // Address size
256     auto Signature = Data.getU64(&Offset);
257     Offset = PrevOffset + C.Length;
258 
259     auto P = TypeIndexEntries.insert(std::make_pair(Signature, Entry));
260     if (!P.second)
261       continue;
262 
263     Out.EmitBytes(Types.substr(PrevOffset, C.Length));
264     TypesOffset += C.Length;
265   }
266 }
267 
268 static void
269 writeIndexTable(MCStreamer &Out, ArrayRef<unsigned> ContributionOffsets,
270                 const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
271                 uint32_t DWARFUnitIndex::Entry::SectionContribution::*Field) {
272   for (const auto &E : IndexEntries)
273     for (size_t i = 0; i != array_lengthof(E.second.Contributions); ++i)
274       if (ContributionOffsets[i])
275         Out.EmitIntValue(E.second.Contributions[i].*Field, 4);
276 }
277 
278 static void
279 writeIndex(MCStreamer &Out, MCSection *Section,
280            ArrayRef<unsigned> ContributionOffsets,
281            const MapVector<uint64_t, UnitIndexEntry> &IndexEntries) {
282   if (IndexEntries.empty())
283     return;
284 
285   unsigned Columns = 0;
286   for (auto &C : ContributionOffsets)
287     if (C)
288       ++Columns;
289 
290   std::vector<unsigned> Buckets(NextPowerOf2(3 * IndexEntries.size() / 2));
291   uint64_t Mask = Buckets.size() - 1;
292   size_t i = 0;
293   for (const auto &P : IndexEntries) {
294     auto S = P.first;
295     auto H = S & Mask;
296     while (Buckets[H]) {
297       assert(S != IndexEntries.begin()[Buckets[H] - 1].first &&
298              "Duplicate unit");
299       H = (H + (((S >> 32) & Mask) | 1)) % Buckets.size();
300     }
301     Buckets[H] = i + 1;
302     ++i;
303   }
304 
305   Out.SwitchSection(Section);
306   Out.EmitIntValue(2, 4);                   // Version
307   Out.EmitIntValue(Columns, 4);             // Columns
308   Out.EmitIntValue(IndexEntries.size(), 4); // Num Units
309   Out.EmitIntValue(Buckets.size(), 4);      // Num Buckets
310 
311   // Write the signatures.
312   for (const auto &I : Buckets)
313     Out.EmitIntValue(I ? IndexEntries.begin()[I - 1].first : 0, 8);
314 
315   // Write the indexes.
316   for (const auto &I : Buckets)
317     Out.EmitIntValue(I, 4);
318 
319   // Write the column headers (which sections will appear in the table)
320   for (size_t i = 0; i != ContributionOffsets.size(); ++i)
321     if (ContributionOffsets[i])
322       Out.EmitIntValue(i + DW_SECT_INFO, 4);
323 
324   // Write the offsets.
325   writeIndexTable(Out, ContributionOffsets, IndexEntries,
326                   &DWARFUnitIndex::Entry::SectionContribution::Offset);
327 
328   // Write the lengths.
329   writeIndexTable(Out, ContributionOffsets, IndexEntries,
330                   &DWARFUnitIndex::Entry::SectionContribution::Length);
331 }
332 static bool consumeCompressedDebugSectionHeader(StringRef &data,
333                                                 uint64_t &OriginalSize) {
334   // Consume "ZLIB" prefix.
335   if (!data.startswith("ZLIB"))
336     return false;
337   data = data.substr(4);
338   // Consume uncompressed section size (big-endian 8 bytes).
339   DataExtractor extractor(data, false, 8);
340   uint32_t Offset = 0;
341   OriginalSize = extractor.getU64(&Offset);
342   if (Offset == 0)
343     return false;
344   data = data.substr(Offset);
345   return true;
346 }
347 
348 static std::error_code write(MCStreamer &Out, ArrayRef<std::string> Inputs) {
349   const auto &MCOFI = *Out.getContext().getObjectFileInfo();
350   MCSection *const StrSection = MCOFI.getDwarfStrDWOSection();
351   MCSection *const StrOffsetSection = MCOFI.getDwarfStrOffDWOSection();
352   MCSection *const TypesSection = MCOFI.getDwarfTypesDWOSection();
353   MCSection *const CUIndexSection = MCOFI.getDwarfCUIndexSection();
354   MCSection *const TUIndexSection = MCOFI.getDwarfTUIndexSection();
355   const StringMap<std::pair<MCSection *, DWARFSectionKind>> KnownSections = {
356       {"debug_info.dwo", {MCOFI.getDwarfInfoDWOSection(), DW_SECT_INFO}},
357       {"debug_types.dwo", {MCOFI.getDwarfTypesDWOSection(), DW_SECT_TYPES}},
358       {"debug_str_offsets.dwo", {StrOffsetSection, DW_SECT_STR_OFFSETS}},
359       {"debug_str.dwo", {StrSection, static_cast<DWARFSectionKind>(0)}},
360       {"debug_loc.dwo", {MCOFI.getDwarfLocDWOSection(), DW_SECT_LOC}},
361       {"debug_line.dwo", {MCOFI.getDwarfLineDWOSection(), DW_SECT_LINE}},
362       {"debug_abbrev.dwo", {MCOFI.getDwarfAbbrevDWOSection(), DW_SECT_ABBREV}},
363       {"debug_cu_index", {CUIndexSection, static_cast<DWARFSectionKind>(0)}},
364       {"debug_tu_index", {TUIndexSection, static_cast<DWARFSectionKind>(0)}}};
365 
366   MapVector<uint64_t, UnitIndexEntry> IndexEntries;
367   MapVector<uint64_t, UnitIndexEntry> TypeIndexEntries;
368 
369   StringMap<uint32_t> Strings;
370   uint32_t StringOffset = 0;
371 
372   uint32_t ContributionOffsets[8] = {};
373 
374   for (const auto &Input : Inputs) {
375     auto ErrOrObj = object::ObjectFile::createObjectFile(Input);
376     if (!ErrOrObj)
377       return ErrOrObj.getError();
378 
379     UnitIndexEntry CurEntry = {};
380 
381     StringRef CurStrSection;
382     StringRef CurStrOffsetSection;
383     StringRef CurTypesSection;
384     StringRef InfoSection;
385     StringRef AbbrevSection;
386     StringRef CurCUIndexSection;
387     StringRef CurTUIndexSection;
388 
389     SmallVector<SmallString<32>, 4> UncompressedSections;
390 
391     for (const auto &Section : ErrOrObj->getBinary()->sections()) {
392       if (Section.isBSS())
393         continue;
394       if (Section.isVirtual())
395         continue;
396 
397       StringRef Name;
398       if (std::error_code Err = Section.getName(Name))
399         return Err;
400 
401       Name = Name.substr(Name.find_first_not_of("._"));
402 
403       StringRef Contents;
404       if (auto Err = Section.getContents(Contents))
405         return Err;
406 
407       if (Name.startswith("zdebug_")) {
408         uint64_t OriginalSize;
409         if (!zlib::isAvailable() ||
410             !consumeCompressedDebugSectionHeader(Contents, OriginalSize))
411           return make_error_code(std::errc::invalid_argument);
412         UncompressedSections.resize(UncompressedSections.size() + 1);
413         if (zlib::uncompress(Contents, UncompressedSections.back(), OriginalSize) !=
414             zlib::StatusOK) {
415           UncompressedSections.pop_back();
416           continue;
417         }
418         Name = Name.substr(1);
419         Contents = UncompressedSections.back();
420       }
421 
422       auto SectionPair = KnownSections.find(Name);
423       if (SectionPair == KnownSections.end())
424         continue;
425 
426       if (DWARFSectionKind Kind = SectionPair->second.second) {
427         auto Index = Kind - DW_SECT_INFO;
428         if (Kind != DW_SECT_TYPES) {
429           CurEntry.Contributions[Index].Offset = ContributionOffsets[Index];
430           ContributionOffsets[Index] +=
431               (CurEntry.Contributions[Index].Length = Contents.size());
432         }
433 
434         switch (Kind) {
435         case DW_SECT_INFO:
436           InfoSection = Contents;
437           break;
438         case DW_SECT_ABBREV:
439           AbbrevSection = Contents;
440           break;
441         default:
442           break;
443         }
444       }
445 
446       MCSection *OutSection = SectionPair->second.first;
447       if (OutSection == StrOffsetSection)
448         CurStrOffsetSection = Contents;
449       else if (OutSection == StrSection)
450         CurStrSection = Contents;
451       else if (OutSection == TypesSection)
452         CurTypesSection = Contents;
453       else if (OutSection == CUIndexSection)
454         CurCUIndexSection = Contents;
455       else if (OutSection == TUIndexSection)
456         CurTUIndexSection = Contents;
457       else {
458         Out.SwitchSection(OutSection);
459         Out.EmitBytes(Contents);
460       }
461     }
462 
463     if (InfoSection.empty())
464       continue;
465 
466     if (!CurCUIndexSection.empty()) {
467       DWARFUnitIndex CUIndex(DW_SECT_INFO);
468       DataExtractor CUIndexData(CurCUIndexSection,
469                                 ErrOrObj->getBinary()->isLittleEndian(), 0);
470       if (!CUIndex.parse(CUIndexData))
471         return make_error_code(std::errc::invalid_argument);
472 
473       for (const DWARFUnitIndex::Entry &E : CUIndex.getRows()) {
474         auto *I = E.getOffsets();
475         if (!I)
476           continue;
477         auto P =
478             IndexEntries.insert(std::make_pair(E.getSignature(), CurEntry));
479         const char* Name = getCUName(
480             getSubsection(AbbrevSection, E, DW_SECT_ABBREV),
481             getSubsection(InfoSection, E, DW_SECT_INFO),
482             getSubsection(CurStrOffsetSection, E, DW_SECT_STR_OFFSETS),
483             CurStrSection);
484         if (!P.second) {
485           auto &PrevE = *P.first;
486           std::cerr << "Duplicate DWO ID (" << PrevE.first << ") in '" << PrevE.second.Name << "' ";
487           if (!PrevE.second.DWPName.empty())
488             std::cerr << "(from '" << PrevE.second.DWPName.str() << "') ";
489           std::cerr << "and '" << Name << "' (from '" << Input << "')\n";
490           return make_error_code(std::errc::invalid_argument);
491         }
492         auto &NewEntry = P.first->second;
493         NewEntry.Name = Name;
494         NewEntry.DWPName = Input;
495         for (auto Kind : CUIndex.getColumnKinds()) {
496           auto &C = NewEntry.Contributions[Kind - DW_SECT_INFO];
497           C.Offset += I->Offset;
498           C.Length = I->Length;
499           ++I;
500         }
501       }
502 
503       if (!CurTypesSection.empty()) {
504         if (CurTUIndexSection.empty())
505           return make_error_code(std::errc::invalid_argument);
506         DWARFUnitIndex TUIndex(DW_SECT_TYPES);
507         DataExtractor TUIndexData(CurTUIndexSection,
508                                   ErrOrObj->getBinary()->isLittleEndian(), 0);
509         if (!TUIndex.parse(TUIndexData))
510           return make_error_code(std::errc::invalid_argument);
511         addAllTypesFromDWP(Out, TypeIndexEntries, TUIndex, TypesSection,
512                            CurTypesSection, CurEntry,
513                            ContributionOffsets[DW_SECT_TYPES - DW_SECT_INFO]);
514       }
515     } else {
516       auto P = IndexEntries.insert(
517           std::make_pair(getCUSignature(AbbrevSection, InfoSection), CurEntry));
518       const char *Name = getCUName(AbbrevSection, InfoSection,
519                                    CurStrOffsetSection, CurStrSection);
520       if (!P.second) {
521         auto &E = *P.first;
522         std::cerr << "Duplicate DWO ID (" << E.first << ") in '" << Name
523                   << "' ";
524         if (!E.second.DWPName.empty())
525           std::cerr << "(from '" << E.second.DWPName.str() << "') ";
526         std::cerr << "and '" << E.second.Name << "'\n";
527         return make_error_code(std::errc::invalid_argument);
528       }
529       P.first->second.Name = Name;
530       addAllTypes(Out, TypeIndexEntries, TypesSection, CurTypesSection,
531                   CurEntry, ContributionOffsets[DW_SECT_TYPES - DW_SECT_INFO]);
532     }
533 
534     if (auto Err = writeStringsAndOffsets(Out, Strings, StringOffset,
535                                           StrSection, StrOffsetSection,
536                                           CurStrSection, CurStrOffsetSection))
537       return Err;
538   }
539 
540   // Lie about there being no info contributions so the TU index only includes
541   // the type unit contribution
542   ContributionOffsets[0] = 0;
543   writeIndex(Out, MCOFI.getDwarfTUIndexSection(), ContributionOffsets,
544              TypeIndexEntries);
545 
546   // Lie about the type contribution
547   ContributionOffsets[DW_SECT_TYPES - DW_SECT_INFO] = 0;
548   // Unlie about the info contribution
549   ContributionOffsets[0] = 1;
550 
551   writeIndex(Out, MCOFI.getDwarfCUIndexSection(), ContributionOffsets,
552              IndexEntries);
553 
554   return std::error_code();
555 }
556 
557 int main(int argc, char **argv) {
558 
559   ParseCommandLineOptions(argc, argv, "merge split dwarf (.dwo) files");
560 
561   llvm::InitializeAllTargetInfos();
562   llvm::InitializeAllTargetMCs();
563   llvm::InitializeAllTargets();
564   llvm::InitializeAllAsmPrinters();
565 
566   std::string ErrorStr;
567   StringRef Context = "dwarf streamer init";
568 
569   Triple TheTriple("x86_64-linux-gnu");
570 
571   // Get the target.
572   const Target *TheTarget =
573       TargetRegistry::lookupTarget("", TheTriple, ErrorStr);
574   if (!TheTarget)
575     return error(ErrorStr, Context);
576   std::string TripleName = TheTriple.getTriple();
577 
578   // Create all the MC Objects.
579   std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
580   if (!MRI)
581     return error(Twine("no register info for target ") + TripleName, Context);
582 
583   std::unique_ptr<MCAsmInfo> MAI(TheTarget->createMCAsmInfo(*MRI, TripleName));
584   if (!MAI)
585     return error("no asm info for target " + TripleName, Context);
586 
587   MCObjectFileInfo MOFI;
588   MCContext MC(MAI.get(), MRI.get(), &MOFI);
589   MOFI.InitMCObjectFileInfo(TheTriple, Reloc::Default, CodeModel::Default, MC);
590 
591   auto MAB = TheTarget->createMCAsmBackend(*MRI, TripleName, "");
592   if (!MAB)
593     return error("no asm backend for target " + TripleName, Context);
594 
595   std::unique_ptr<MCInstrInfo> MII(TheTarget->createMCInstrInfo());
596   if (!MII)
597     return error("no instr info info for target " + TripleName, Context);
598 
599   std::unique_ptr<MCSubtargetInfo> MSTI(
600       TheTarget->createMCSubtargetInfo(TripleName, "", ""));
601   if (!MSTI)
602     return error("no subtarget info for target " + TripleName, Context);
603 
604   MCCodeEmitter *MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, MC);
605   if (!MCE)
606     return error("no code emitter for target " + TripleName, Context);
607 
608   // Create the output file.
609   std::error_code EC;
610   raw_fd_ostream OutFile(OutputFilename, EC, sys::fs::F_None);
611   if (EC)
612     return error(Twine(OutputFilename) + ": " + EC.message(), Context);
613 
614   MCTargetOptions MCOptions = InitMCTargetOptionsFromFlags();
615   std::unique_ptr<MCStreamer> MS(TheTarget->createMCObjectStreamer(
616       TheTriple, MC, *MAB, OutFile, MCE, *MSTI, MCOptions.MCRelaxAll,
617       MCOptions.MCIncrementalLinkerCompatible,
618       /*DWARFMustBeAtTheEnd*/ false));
619   if (!MS)
620     return error("no object streamer for target " + TripleName, Context);
621 
622   if (auto Err = write(*MS, InputFiles))
623     return error(Err.message(), "Writing DWP file");
624 
625   MS->Finish();
626 }
627