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 struct CompileUnitIdentifiers {
124   uint64_t Signature = 0;
125   const char *Name = "";
126   const char *DWOName = "";
127 };
128 
129 static const char *getIndexedString(uint32_t StrIndex, StringRef StrOffsets,
130                                     StringRef Str) {
131   DataExtractor StrOffsetsData(StrOffsets, true, 0);
132   uint32_t StrOffsetsOffset = 4 * StrIndex;
133   uint32_t StrOffset = StrOffsetsData.getU32(&StrOffsetsOffset);
134   DataExtractor StrData(Str, true, 0);
135   return StrData.getCStr(&StrOffset);
136 }
137 
138 static CompileUnitIdentifiers getCUIdentifiers(StringRef Abbrev, StringRef Info,
139                                                StringRef StrOffsets,
140                                                StringRef Str) {
141   uint32_t Offset = 0;
142   DataExtractor InfoData(Info, true, 0);
143   InfoData.getU32(&Offset); // Length
144   uint16_t Version = InfoData.getU16(&Offset);
145   InfoData.getU32(&Offset); // Abbrev offset (should be zero)
146   uint8_t AddrSize = InfoData.getU8(&Offset);
147 
148   uint32_t AbbrCode = InfoData.getULEB128(&Offset);
149 
150   DataExtractor AbbrevData(Abbrev, true, 0);
151   uint32_t AbbrevOffset = getCUAbbrev(Abbrev, AbbrCode);
152   uint64_t Tag = AbbrevData.getULEB128(&AbbrevOffset);
153   (void)Tag;
154   // FIXME: Real error handling
155   assert(Tag == dwarf::DW_TAG_compile_unit);
156   // DW_CHILDREN
157   AbbrevData.getU8(&AbbrevOffset);
158   uint32_t Name;
159   uint32_t Form;
160   CompileUnitIdentifiers ID;
161   while ((Name = AbbrevData.getULEB128(&AbbrevOffset)) |
162              (Form = AbbrevData.getULEB128(&AbbrevOffset)) &&
163          (Name != 0 || Form != 0)) {
164     switch (Name) {
165     case dwarf::DW_AT_name: {
166       ID.Name = getIndexedString(InfoData.getULEB128(&Offset), StrOffsets, Str);
167       break;
168     }
169     case dwarf::DW_AT_GNU_dwo_name: {
170       ID.DWOName =
171           getIndexedString(InfoData.getULEB128(&Offset), StrOffsets, Str);
172       break;
173     }
174     case dwarf::DW_AT_GNU_dwo_id:
175       ID.Signature = InfoData.getU64(&Offset);
176       break;
177     default:
178       DWARFFormValue::skipValue(Form, InfoData, &Offset, Version, AddrSize);
179     }
180   }
181   return ID;
182 }
183 
184 struct UnitIndexEntry {
185   DWARFUnitIndex::Entry::SectionContribution Contributions[8];
186   std::string Name;
187   std::string DWOName;
188   StringRef DWPName;
189 };
190 
191 StringRef getSubsection(StringRef Section, const DWARFUnitIndex::Entry &Entry, DWARFSectionKind Kind) {
192   const auto *Off = Entry.getOffset(Kind);
193   if (!Off)
194     return StringRef();
195   return Section.substr(Off->Offset, Off->Length);
196 }
197 
198 static void addAllTypesFromDWP(
199     MCStreamer &Out, MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
200     const DWARFUnitIndex &TUIndex, MCSection *OutputTypes, StringRef Types,
201     const UnitIndexEntry &TUEntry, uint32_t &TypesOffset) {
202   Out.SwitchSection(OutputTypes);
203   for (const DWARFUnitIndex::Entry &E : TUIndex.getRows()) {
204     auto *I = E.getOffsets();
205     if (!I)
206       continue;
207     auto P = TypeIndexEntries.insert(std::make_pair(E.getSignature(), TUEntry));
208     if (!P.second)
209       continue;
210     auto &Entry = P.first->second;
211     // Zero out the debug_info contribution
212     Entry.Contributions[0] = {};
213     for (auto Kind : TUIndex.getColumnKinds()) {
214       auto &C = Entry.Contributions[Kind - DW_SECT_INFO];
215       C.Offset += I->Offset;
216       C.Length = I->Length;
217       ++I;
218     }
219     auto &C = Entry.Contributions[DW_SECT_TYPES - DW_SECT_INFO];
220     Out.EmitBytes(Types.substr(
221         C.Offset - TUEntry.Contributions[DW_SECT_TYPES - DW_SECT_INFO].Offset,
222         C.Length));
223     C.Offset = TypesOffset;
224     TypesOffset += C.Length;
225   }
226 }
227 
228 static void addAllTypes(MCStreamer &Out,
229                         MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
230                         MCSection *OutputTypes, StringRef Types,
231                         const UnitIndexEntry &CUEntry, uint32_t &TypesOffset) {
232   if (Types.empty())
233     return;
234 
235   Out.SwitchSection(OutputTypes);
236   uint32_t Offset = 0;
237   DataExtractor Data(Types, true, 0);
238   while (Data.isValidOffset(Offset)) {
239     UnitIndexEntry Entry = CUEntry;
240     // Zero out the debug_info contribution
241     Entry.Contributions[0] = {};
242     auto &C = Entry.Contributions[DW_SECT_TYPES - DW_SECT_INFO];
243     C.Offset = TypesOffset;
244     auto PrevOffset = Offset;
245     // Length of the unit, including the 4 byte length field.
246     C.Length = Data.getU32(&Offset) + 4;
247 
248     Data.getU16(&Offset); // Version
249     Data.getU32(&Offset); // Abbrev offset
250     Data.getU8(&Offset);  // Address size
251     auto Signature = Data.getU64(&Offset);
252     Offset = PrevOffset + C.Length;
253 
254     auto P = TypeIndexEntries.insert(std::make_pair(Signature, Entry));
255     if (!P.second)
256       continue;
257 
258     Out.EmitBytes(Types.substr(PrevOffset, C.Length));
259     TypesOffset += C.Length;
260   }
261 }
262 
263 static void
264 writeIndexTable(MCStreamer &Out, ArrayRef<unsigned> ContributionOffsets,
265                 const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
266                 uint32_t DWARFUnitIndex::Entry::SectionContribution::*Field) {
267   for (const auto &E : IndexEntries)
268     for (size_t i = 0; i != array_lengthof(E.second.Contributions); ++i)
269       if (ContributionOffsets[i])
270         Out.EmitIntValue(E.second.Contributions[i].*Field, 4);
271 }
272 
273 static void
274 writeIndex(MCStreamer &Out, MCSection *Section,
275            ArrayRef<unsigned> ContributionOffsets,
276            const MapVector<uint64_t, UnitIndexEntry> &IndexEntries) {
277   if (IndexEntries.empty())
278     return;
279 
280   unsigned Columns = 0;
281   for (auto &C : ContributionOffsets)
282     if (C)
283       ++Columns;
284 
285   std::vector<unsigned> Buckets(NextPowerOf2(3 * IndexEntries.size() / 2));
286   uint64_t Mask = Buckets.size() - 1;
287   size_t i = 0;
288   for (const auto &P : IndexEntries) {
289     auto S = P.first;
290     auto H = S & Mask;
291     while (Buckets[H]) {
292       assert(S != IndexEntries.begin()[Buckets[H] - 1].first &&
293              "Duplicate unit");
294       H = (H + (((S >> 32) & Mask) | 1)) % Buckets.size();
295     }
296     Buckets[H] = i + 1;
297     ++i;
298   }
299 
300   Out.SwitchSection(Section);
301   Out.EmitIntValue(2, 4);                   // Version
302   Out.EmitIntValue(Columns, 4);             // Columns
303   Out.EmitIntValue(IndexEntries.size(), 4); // Num Units
304   Out.EmitIntValue(Buckets.size(), 4);      // Num Buckets
305 
306   // Write the signatures.
307   for (const auto &I : Buckets)
308     Out.EmitIntValue(I ? IndexEntries.begin()[I - 1].first : 0, 8);
309 
310   // Write the indexes.
311   for (const auto &I : Buckets)
312     Out.EmitIntValue(I, 4);
313 
314   // Write the column headers (which sections will appear in the table)
315   for (size_t i = 0; i != ContributionOffsets.size(); ++i)
316     if (ContributionOffsets[i])
317       Out.EmitIntValue(i + DW_SECT_INFO, 4);
318 
319   // Write the offsets.
320   writeIndexTable(Out, ContributionOffsets, IndexEntries,
321                   &DWARFUnitIndex::Entry::SectionContribution::Offset);
322 
323   // Write the lengths.
324   writeIndexTable(Out, ContributionOffsets, IndexEntries,
325                   &DWARFUnitIndex::Entry::SectionContribution::Length);
326 }
327 static bool consumeCompressedDebugSectionHeader(StringRef &data,
328                                                 uint64_t &OriginalSize) {
329   // Consume "ZLIB" prefix.
330   if (!data.startswith("ZLIB"))
331     return false;
332   data = data.substr(4);
333   // Consume uncompressed section size (big-endian 8 bytes).
334   DataExtractor extractor(data, false, 8);
335   uint32_t Offset = 0;
336   OriginalSize = extractor.getU64(&Offset);
337   if (Offset == 0)
338     return false;
339   data = data.substr(Offset);
340   return true;
341 }
342 
343 void printDuplicateError(const std::pair<uint64_t, UnitIndexEntry> &PrevE,
344                          const CompileUnitIdentifiers &ID, StringRef DWPName) {
345   errs() << "Duplicate DWO ID (" << PrevE.first << ") in '" << PrevE.second.Name
346          << '\'';
347   if (!PrevE.second.DWPName.empty()) {
348     errs() << " (from ";
349     if (!PrevE.second.DWOName.empty())
350       errs() << '\'' << PrevE.second.DWOName << "' in ";
351     errs() << "'" << PrevE.second.DWPName.str() << "')";
352   }
353   errs() << " and '" << ID.Name << '\'';
354   if (!DWPName.empty()) {
355     errs() << " (from ";
356     if (*ID.DWOName)
357       errs() << '\'' << ID.DWOName << "\' in ";
358     errs() << '\'' << DWPName << "')";
359   }
360   errs() << '\n';
361 }
362 static std::error_code write(MCStreamer &Out, ArrayRef<std::string> Inputs) {
363   const auto &MCOFI = *Out.getContext().getObjectFileInfo();
364   MCSection *const StrSection = MCOFI.getDwarfStrDWOSection();
365   MCSection *const StrOffsetSection = MCOFI.getDwarfStrOffDWOSection();
366   MCSection *const TypesSection = MCOFI.getDwarfTypesDWOSection();
367   MCSection *const CUIndexSection = MCOFI.getDwarfCUIndexSection();
368   MCSection *const TUIndexSection = MCOFI.getDwarfTUIndexSection();
369   const StringMap<std::pair<MCSection *, DWARFSectionKind>> KnownSections = {
370       {"debug_info.dwo", {MCOFI.getDwarfInfoDWOSection(), DW_SECT_INFO}},
371       {"debug_types.dwo", {MCOFI.getDwarfTypesDWOSection(), DW_SECT_TYPES}},
372       {"debug_str_offsets.dwo", {StrOffsetSection, DW_SECT_STR_OFFSETS}},
373       {"debug_str.dwo", {StrSection, static_cast<DWARFSectionKind>(0)}},
374       {"debug_loc.dwo", {MCOFI.getDwarfLocDWOSection(), DW_SECT_LOC}},
375       {"debug_line.dwo", {MCOFI.getDwarfLineDWOSection(), DW_SECT_LINE}},
376       {"debug_abbrev.dwo", {MCOFI.getDwarfAbbrevDWOSection(), DW_SECT_ABBREV}},
377       {"debug_cu_index", {CUIndexSection, static_cast<DWARFSectionKind>(0)}},
378       {"debug_tu_index", {TUIndexSection, static_cast<DWARFSectionKind>(0)}}};
379 
380   MapVector<uint64_t, UnitIndexEntry> IndexEntries;
381   MapVector<uint64_t, UnitIndexEntry> TypeIndexEntries;
382 
383   StringMap<uint32_t> Strings;
384   uint32_t StringOffset = 0;
385 
386   uint32_t ContributionOffsets[8] = {};
387 
388   for (const auto &Input : Inputs) {
389     auto ErrOrObj = object::ObjectFile::createObjectFile(Input);
390     if (!ErrOrObj)
391       return ErrOrObj.getError();
392 
393     UnitIndexEntry CurEntry = {};
394 
395     StringRef CurStrSection;
396     StringRef CurStrOffsetSection;
397     StringRef CurTypesSection;
398     StringRef InfoSection;
399     StringRef AbbrevSection;
400     StringRef CurCUIndexSection;
401     StringRef CurTUIndexSection;
402 
403     SmallVector<SmallString<32>, 4> UncompressedSections;
404 
405     for (const auto &Section : ErrOrObj->getBinary()->sections()) {
406       if (Section.isBSS())
407         continue;
408       if (Section.isVirtual())
409         continue;
410 
411       StringRef Name;
412       if (std::error_code Err = Section.getName(Name))
413         return Err;
414 
415       Name = Name.substr(Name.find_first_not_of("._"));
416 
417       StringRef Contents;
418       if (auto Err = Section.getContents(Contents))
419         return Err;
420 
421       if (Name.startswith("zdebug_")) {
422         uint64_t OriginalSize;
423         if (!zlib::isAvailable() ||
424             !consumeCompressedDebugSectionHeader(Contents, OriginalSize))
425           return make_error_code(std::errc::invalid_argument);
426         UncompressedSections.resize(UncompressedSections.size() + 1);
427         if (zlib::uncompress(Contents, UncompressedSections.back(), OriginalSize) !=
428             zlib::StatusOK) {
429           UncompressedSections.pop_back();
430           continue;
431         }
432         Name = Name.substr(1);
433         Contents = UncompressedSections.back();
434       }
435 
436       auto SectionPair = KnownSections.find(Name);
437       if (SectionPair == KnownSections.end())
438         continue;
439 
440       if (DWARFSectionKind Kind = SectionPair->second.second) {
441         auto Index = Kind - DW_SECT_INFO;
442         if (Kind != DW_SECT_TYPES) {
443           CurEntry.Contributions[Index].Offset = ContributionOffsets[Index];
444           ContributionOffsets[Index] +=
445               (CurEntry.Contributions[Index].Length = Contents.size());
446         }
447 
448         switch (Kind) {
449         case DW_SECT_INFO:
450           InfoSection = Contents;
451           break;
452         case DW_SECT_ABBREV:
453           AbbrevSection = Contents;
454           break;
455         default:
456           break;
457         }
458       }
459 
460       MCSection *OutSection = SectionPair->second.first;
461       if (OutSection == StrOffsetSection)
462         CurStrOffsetSection = Contents;
463       else if (OutSection == StrSection)
464         CurStrSection = Contents;
465       else if (OutSection == TypesSection)
466         CurTypesSection = Contents;
467       else if (OutSection == CUIndexSection)
468         CurCUIndexSection = Contents;
469       else if (OutSection == TUIndexSection)
470         CurTUIndexSection = Contents;
471       else {
472         Out.SwitchSection(OutSection);
473         Out.EmitBytes(Contents);
474       }
475     }
476 
477     if (InfoSection.empty())
478       continue;
479 
480     if (!CurCUIndexSection.empty()) {
481       DWARFUnitIndex CUIndex(DW_SECT_INFO);
482       DataExtractor CUIndexData(CurCUIndexSection,
483                                 ErrOrObj->getBinary()->isLittleEndian(), 0);
484       if (!CUIndex.parse(CUIndexData))
485         return make_error_code(std::errc::invalid_argument);
486 
487       for (const DWARFUnitIndex::Entry &E : CUIndex.getRows()) {
488         auto *I = E.getOffsets();
489         if (!I)
490           continue;
491         auto P =
492             IndexEntries.insert(std::make_pair(E.getSignature(), CurEntry));
493         CompileUnitIdentifiers ID = getCUIdentifiers(
494             getSubsection(AbbrevSection, E, DW_SECT_ABBREV),
495             getSubsection(InfoSection, E, DW_SECT_INFO),
496             getSubsection(CurStrOffsetSection, E, DW_SECT_STR_OFFSETS),
497             CurStrSection);
498         if (!P.second) {
499           printDuplicateError(*P.first, ID, Input);
500           return make_error_code(std::errc::invalid_argument);
501         }
502         auto &NewEntry = P.first->second;
503         NewEntry.Name = ID.Name;
504         NewEntry.DWOName = ID.DWOName;
505         NewEntry.DWPName = Input;
506         for (auto Kind : CUIndex.getColumnKinds()) {
507           auto &C = NewEntry.Contributions[Kind - DW_SECT_INFO];
508           C.Offset += I->Offset;
509           C.Length = I->Length;
510           ++I;
511         }
512       }
513 
514       if (!CurTypesSection.empty()) {
515         if (CurTUIndexSection.empty())
516           return make_error_code(std::errc::invalid_argument);
517         DWARFUnitIndex TUIndex(DW_SECT_TYPES);
518         DataExtractor TUIndexData(CurTUIndexSection,
519                                   ErrOrObj->getBinary()->isLittleEndian(), 0);
520         if (!TUIndex.parse(TUIndexData))
521           return make_error_code(std::errc::invalid_argument);
522         addAllTypesFromDWP(Out, TypeIndexEntries, TUIndex, TypesSection,
523                            CurTypesSection, CurEntry,
524                            ContributionOffsets[DW_SECT_TYPES - DW_SECT_INFO]);
525       }
526     } else {
527       CompileUnitIdentifiers ID = getCUIdentifiers(
528           AbbrevSection, InfoSection, CurStrOffsetSection, CurStrSection);
529       auto P = IndexEntries.insert(std::make_pair(ID.Signature, CurEntry));
530       if (!P.second) {
531         printDuplicateError(*P.first, ID, "");
532         return make_error_code(std::errc::invalid_argument);
533       }
534       P.first->second.Name = ID.Name;
535       P.first->second.DWOName = ID.DWOName;
536       addAllTypes(Out, TypeIndexEntries, TypesSection, CurTypesSection,
537                   CurEntry, ContributionOffsets[DW_SECT_TYPES - DW_SECT_INFO]);
538     }
539 
540     if (auto Err = writeStringsAndOffsets(Out, Strings, StringOffset,
541                                           StrSection, StrOffsetSection,
542                                           CurStrSection, CurStrOffsetSection))
543       return Err;
544   }
545 
546   // Lie about there being no info contributions so the TU index only includes
547   // the type unit contribution
548   ContributionOffsets[0] = 0;
549   writeIndex(Out, MCOFI.getDwarfTUIndexSection(), ContributionOffsets,
550              TypeIndexEntries);
551 
552   // Lie about the type contribution
553   ContributionOffsets[DW_SECT_TYPES - DW_SECT_INFO] = 0;
554   // Unlie about the info contribution
555   ContributionOffsets[0] = 1;
556 
557   writeIndex(Out, MCOFI.getDwarfCUIndexSection(), ContributionOffsets,
558              IndexEntries);
559 
560   return std::error_code();
561 }
562 
563 int main(int argc, char **argv) {
564 
565   ParseCommandLineOptions(argc, argv, "merge split dwarf (.dwo) files");
566 
567   llvm::InitializeAllTargetInfos();
568   llvm::InitializeAllTargetMCs();
569   llvm::InitializeAllTargets();
570   llvm::InitializeAllAsmPrinters();
571 
572   std::string ErrorStr;
573   StringRef Context = "dwarf streamer init";
574 
575   Triple TheTriple("x86_64-linux-gnu");
576 
577   // Get the target.
578   const Target *TheTarget =
579       TargetRegistry::lookupTarget("", TheTriple, ErrorStr);
580   if (!TheTarget)
581     return error(ErrorStr, Context);
582   std::string TripleName = TheTriple.getTriple();
583 
584   // Create all the MC Objects.
585   std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
586   if (!MRI)
587     return error(Twine("no register info for target ") + TripleName, Context);
588 
589   std::unique_ptr<MCAsmInfo> MAI(TheTarget->createMCAsmInfo(*MRI, TripleName));
590   if (!MAI)
591     return error("no asm info for target " + TripleName, Context);
592 
593   MCObjectFileInfo MOFI;
594   MCContext MC(MAI.get(), MRI.get(), &MOFI);
595   MOFI.InitMCObjectFileInfo(TheTriple, Reloc::Default, CodeModel::Default, MC);
596 
597   auto MAB = TheTarget->createMCAsmBackend(*MRI, TripleName, "");
598   if (!MAB)
599     return error("no asm backend for target " + TripleName, Context);
600 
601   std::unique_ptr<MCInstrInfo> MII(TheTarget->createMCInstrInfo());
602   if (!MII)
603     return error("no instr info info for target " + TripleName, Context);
604 
605   std::unique_ptr<MCSubtargetInfo> MSTI(
606       TheTarget->createMCSubtargetInfo(TripleName, "", ""));
607   if (!MSTI)
608     return error("no subtarget info for target " + TripleName, Context);
609 
610   MCCodeEmitter *MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, MC);
611   if (!MCE)
612     return error("no code emitter for target " + TripleName, Context);
613 
614   // Create the output file.
615   std::error_code EC;
616   raw_fd_ostream OutFile(OutputFilename, EC, sys::fs::F_None);
617   if (EC)
618     return error(Twine(OutputFilename) + ": " + EC.message(), Context);
619 
620   MCTargetOptions MCOptions = InitMCTargetOptionsFromFlags();
621   std::unique_ptr<MCStreamer> MS(TheTarget->createMCObjectStreamer(
622       TheTriple, MC, *MAB, OutFile, MCE, *MSTI, MCOptions.MCRelaxAll,
623       MCOptions.MCIncrementalLinkerCompatible,
624       /*DWARFMustBeAtTheEnd*/ false));
625   if (!MS)
626     return error("no object streamer for target " + TripleName, Context);
627 
628   if (auto Err = write(*MS, InputFiles))
629     return error(Err.message(), "Writing DWP file");
630 
631   MS->Finish();
632 }
633