llvm/lib/MC/WinCOFFObjectWriter.cpp

   1 //===- llvm/MC/WinCOFFObjectWriter.cpp ------------------------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file contains an implementation of a Win32 COFF object file writer.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/ADT/DenseMap.h"
  14 #include "llvm/ADT/DenseSet.h"
  15 #include "llvm/ADT/STLExtras.h"
  16 #include "llvm/ADT/SmallString.h"
  17 #include "llvm/ADT/SmallVector.h"
  18 #include "llvm/ADT/StringRef.h"
  19 #include "llvm/ADT/Twine.h"
  20 #include "llvm/BinaryFormat/COFF.h"
  21 #include "llvm/MC/MCAssembler.h"
  22 #include "llvm/MC/MCContext.h"
  23 #include "llvm/MC/MCExpr.h"
  24 #include "llvm/MC/MCFixup.h"
  25 #include "llvm/MC/MCFragment.h"
  26 #include "llvm/MC/MCObjectWriter.h"
  27 #include "llvm/MC/MCSection.h"
  28 #include "llvm/MC/MCSectionCOFF.h"
  29 #include "llvm/MC/MCSymbol.h"
  30 #include "llvm/MC/MCSymbolCOFF.h"
  31 #include "llvm/MC/MCValue.h"
  32 #include "llvm/MC/MCWinCOFFObjectWriter.h"
  33 #include "llvm/MC/StringTableBuilder.h"
  34 #include "llvm/Support/CRC.h"
  35 #include "llvm/Support/Casting.h"
  36 #include "llvm/Support/EndianStream.h"
  37 #include "llvm/Support/ErrorHandling.h"
  38 #include "llvm/Support/LEB128.h"
  39 #include "llvm/Support/MathExtras.h"
  40 #include "llvm/Support/raw_ostream.h"
  41 #include <algorithm>
  42 #include <cassert>
  43 #include <cstdint>
  44 #include <cstring>
  45 #include <ctime>
  46 #include <memory>
  47 #include <string>
  48 #include <vector>
  49
  50 using namespace llvm;
  51 using llvm::support::endian::write32le;
  52
  53 #define DEBUG_TYPE "WinCOFFObjectWriter"
  54
  55 namespace {
  56
  57 constexpr int OffsetLabelIntervalBits = 20;
  58
  59 using name = SmallString<COFF::NameSize>;
  60
  61 enum AuxiliaryType { ATWeakExternal, ATFile, ATSectionDefinition };
  62
  63 struct AuxSymbol {
  64   AuxiliaryType AuxType;
  65   COFF::Auxiliary Aux;
  66 };
  67
  68 class COFFSection;
  69
  70 class COFFSymbol {
  71 public:
  72   COFF::symbol Data = {};
  73
  74   using AuxiliarySymbols = SmallVector<AuxSymbol, 1>;
  75
  76   name Name;
  77   int Index = 0;
  78   AuxiliarySymbols Aux;
  79   COFFSymbol *Other = nullptr;
  80   COFFSection *Section = nullptr;
  81   int Relocations = 0;
  82   const MCSymbol *MC = nullptr;
  83
  84   COFFSymbol(StringRef Name) : Name(Name) {}
  85
  86   void set_name_offset(uint32_t Offset);
  87
  88   int64_t getIndex() const { return Index; }
  89   void setIndex(int Value) {
  90     Index = Value;
  91     if (MC)
  92       MC->setIndex(static_cast<uint32_t>(Value));
  93   }
  94 };
  95
  96 // This class contains staging data for a COFF relocation entry.
  97 struct COFFRelocation {
  98   COFF::relocation Data;
  99   COFFSymbol *Symb = nullptr;
 100
 101   COFFRelocation() = default;
 102
 103   static size_t size() { return COFF::RelocationSize; }
 104 };
 105
 106 using relocations = std::vector<COFFRelocation>;
 107
 108 class COFFSection {
 109 public:
 110   COFF::section Header = {};
 111
 112   std::string Name;
 113   int Number = 0;
 114   MCSectionCOFF const *MCSection = nullptr;
 115   COFFSymbol *Symbol = nullptr;
 116   relocations Relocations;
 117
 118   COFFSection(StringRef Name) : Name(std::string(Name)) {}
 119
 120   SmallVector<COFFSymbol *, 1> OffsetSymbols;
 121 };
 122 } // namespace
 123
 124 class llvm::WinCOFFWriter {
 125   WinCOFFObjectWriter &OWriter;
 126   support::endian::Writer W;
 127
 128   using symbols = std::vector<std::unique_ptr<COFFSymbol>>;
 129   using sections = std::vector<std::unique_ptr<COFFSection>>;
 130
 131   using symbol_map = DenseMap<MCSymbol const *, COFFSymbol *>;
 132   using section_map = DenseMap<MCSection const *, COFFSection *>;
 133
 134   using symbol_list = DenseSet<COFFSymbol *>;
 135
 136   // Root level file contents.
 137   COFF::header Header = {};
 138   sections Sections;
 139   symbols Symbols;
 140   StringTableBuilder Strings{StringTableBuilder::WinCOFF};
 141
 142   // Maps used during object file creation.
 143   section_map SectionMap;
 144   symbol_map SymbolMap;
 145
 146   symbol_list WeakDefaults;
 147
 148   bool UseBigObj;
 149   bool UseOffsetLabels = false;
 150
 151 public:
 152   enum DwoMode {
 153     AllSections,
 154     NonDwoOnly,
 155     DwoOnly,
 156   } Mode;
 157
 158   WinCOFFWriter(WinCOFFObjectWriter &OWriter, raw_pwrite_stream &OS,
 159                 DwoMode Mode);
 160
 161   void reset();
 162   void executePostLayoutBinding(MCAssembler &Asm);
 163   void recordRelocation(MCAssembler &Asm, const MCFragment *Fragment,
 164                         const MCFixup &Fixup, MCValue Target,
 165                         uint64_t &FixedValue);
 166   uint64_t writeObject(MCAssembler &Asm);
 167
 168 private:
 169   COFFSymbol *createSymbol(StringRef Name);
 170   COFFSymbol *GetOrCreateCOFFSymbol(const MCSymbol *Symbol);
 171   COFFSection *createSection(StringRef Name);
 172
 173   void defineSection(const MCAssembler &Asm, MCSectionCOFF const &Sec);
 174
 175   COFFSymbol *getLinkedSymbol(const MCSymbol &Symbol);
 176   void defineSymbol(const MCAssembler &Asm, const MCSymbol &Symbol);
 177
 178   void SetSymbolName(COFFSymbol &S);
 179   void SetSectionName(COFFSection &S);
 180
 181   bool IsPhysicalSection(COFFSection *S);
 182
 183   // Entity writing methods.
 184   void WriteFileHeader(const COFF::header &Header);
 185   void WriteSymbol(const COFFSymbol &S);
 186   void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
 187   void writeSectionHeaders();
 188   void WriteRelocation(const COFF::relocation &R);
 189   uint32_t writeSectionContents(MCAssembler &Asm, const MCSection &MCSec);
 190   void writeSection(MCAssembler &Asm, const COFFSection &Sec);
 191
 192   void createFileSymbols(MCAssembler &Asm);
 193   void setWeakDefaultNames();
 194   void assignSectionNumbers();
 195   void assignFileOffsets(MCAssembler &Asm);
 196 };
 197
 198 WinCOFFObjectWriter::WinCOFFObjectWriter(
 199     std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS)
 200     : TargetObjectWriter(std::move(MOTW)),
 201       ObjWriter(std::make_unique<WinCOFFWriter>(*this, OS,
 202                                                 WinCOFFWriter::AllSections)) {}
 203 WinCOFFObjectWriter::WinCOFFObjectWriter(
 204     std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS,
 205     raw_pwrite_stream &DwoOS)
 206     : TargetObjectWriter(std::move(MOTW)),
 207       ObjWriter(std::make_unique<WinCOFFWriter>(*this, OS,
 208                                                 WinCOFFWriter::NonDwoOnly)),
 209       DwoWriter(std::make_unique<WinCOFFWriter>(*this, DwoOS,
 210                                                 WinCOFFWriter::DwoOnly)) {}
 211
 212 static bool isDwoSection(const MCSection &Sec) {
 213   return Sec.getName().ends_with(".dwo");
 214 }
 215
 216 //------------------------------------------------------------------------------
 217 // Symbol class implementation
 218
 219 // In the case that the name does not fit within 8 bytes, the offset
 220 // into the string table is stored in the last 4 bytes instead, leaving
 221 // the first 4 bytes as 0.
 222 void COFFSymbol::set_name_offset(uint32_t Offset) {
 223   write32le(Data.Name + 0, 0);
 224   write32le(Data.Name + 4, Offset);
 225 }
 226
 227 //------------------------------------------------------------------------------
 228 // WinCOFFWriter class implementation
 229
 230 WinCOFFWriter::WinCOFFWriter(WinCOFFObjectWriter &OWriter,
 231                              raw_pwrite_stream &OS, DwoMode Mode)
 232     : OWriter(OWriter), W(OS, llvm::endianness::little), Mode(Mode) {
 233   Header.Machine = OWriter.TargetObjectWriter->getMachine();
 234   // Some relocations on ARM64 (the 21 bit ADRP relocations) have a slightly
 235   // limited range for the immediate offset (+/- 1 MB); create extra offset
 236   // label symbols with regular intervals to allow referencing a
 237   // non-temporary symbol that is close enough.
 238   UseOffsetLabels = COFF::isAnyArm64(Header.Machine);
 239 }
 240
 241 COFFSymbol *WinCOFFWriter::createSymbol(StringRef Name) {
 242   Symbols.push_back(std::make_unique<COFFSymbol>(Name));
 243   return Symbols.back().get();
 244 }
 245
 246 COFFSymbol *WinCOFFWriter::GetOrCreateCOFFSymbol(const MCSymbol *Symbol) {
 247   COFFSymbol *&Ret = SymbolMap[Symbol];
 248   if (!Ret)
 249     Ret = createSymbol(Symbol->getName());
 250   return Ret;
 251 }
 252
 253 COFFSection *WinCOFFWriter::createSection(StringRef Name) {
 254   Sections.emplace_back(std::make_unique<COFFSection>(Name));
 255   return Sections.back().get();
 256 }
 257
 258 static uint32_t getAlignment(const MCSectionCOFF &Sec) {
 259   switch (Sec.getAlign().value()) {
 260   case 1:
 261     return COFF::IMAGE_SCN_ALIGN_1BYTES;
 262   case 2:
 263     return COFF::IMAGE_SCN_ALIGN_2BYTES;
 264   case 4:
 265     return COFF::IMAGE_SCN_ALIGN_4BYTES;
 266   case 8:
 267     return COFF::IMAGE_SCN_ALIGN_8BYTES;
 268   case 16:
 269     return COFF::IMAGE_SCN_ALIGN_16BYTES;
 270   case 32:
 271     return COFF::IMAGE_SCN_ALIGN_32BYTES;
 272   case 64:
 273     return COFF::IMAGE_SCN_ALIGN_64BYTES;
 274   case 128:
 275     return COFF::IMAGE_SCN_ALIGN_128BYTES;
 276   case 256:
 277     return COFF::IMAGE_SCN_ALIGN_256BYTES;
 278   case 512:
 279     return COFF::IMAGE_SCN_ALIGN_512BYTES;
 280   case 1024:
 281     return COFF::IMAGE_SCN_ALIGN_1024BYTES;
 282   case 2048:
 283     return COFF::IMAGE_SCN_ALIGN_2048BYTES;
 284   case 4096:
 285     return COFF::IMAGE_SCN_ALIGN_4096BYTES;
 286   case 8192:
 287     return COFF::IMAGE_SCN_ALIGN_8192BYTES;
 288   }
 289   llvm_unreachable("unsupported section alignment");
 290 }
 291
 292 /// This function takes a section data object from the assembler
 293 /// and creates the associated COFF section staging object.
 294 void WinCOFFWriter::defineSection(const MCAssembler &Asm,
 295                                   const MCSectionCOFF &MCSec) {
 296   COFFSection *Section = createSection(MCSec.getName());
 297   COFFSymbol *Symbol = createSymbol(MCSec.getName());
 298   Section->Symbol = Symbol;
 299   SymbolMap[MCSec.getBeginSymbol()] = Symbol;
 300   Symbol->Section = Section;
 301   Symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
 302
 303   // Create a COMDAT symbol if needed.
 304   if (MCSec.getSelection() != COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE) {
 305     if (const MCSymbol *S = MCSec.getCOMDATSymbol()) {
 306       COFFSymbol *COMDATSymbol = GetOrCreateCOFFSymbol(S);
 307       if (COMDATSymbol->Section)
 308         report_fatal_error("two sections have the same comdat");
 309       COMDATSymbol->Section = Section;
 310     }
 311   }
 312
 313   // In this case the auxiliary symbol is a Section Definition.
 314   Symbol->Aux.resize(1);
 315   Symbol->Aux[0] = {};
 316   Symbol->Aux[0].AuxType = ATSectionDefinition;
 317   Symbol->Aux[0].Aux.SectionDefinition.Selection = MCSec.getSelection();
 318
 319   // Set section alignment.
 320   Section->Header.Characteristics = MCSec.getCharacteristics();
 321   Section->Header.Characteristics |= getAlignment(MCSec);
 322
 323   // Bind internal COFF section to MC section.
 324   Section->MCSection = &MCSec;
 325   SectionMap[&MCSec] = Section;
 326
 327   if (UseOffsetLabels && !MCSec.empty()) {
 328     const uint32_t Interval = 1 << OffsetLabelIntervalBits;
 329     uint32_t N = 1;
 330     for (uint32_t Off = Interval, E = Asm.getSectionAddressSize(MCSec); Off < E;
 331          Off += Interval) {
 332       auto Name = ("$L" + MCSec.getName() + "_" + Twine(N++)).str();
 333       COFFSymbol *Label = createSymbol(Name);
 334       Label->Section = Section;
 335       Label->Data.StorageClass = COFF::IMAGE_SYM_CLASS_LABEL;
 336       Label->Data.Value = Off;
 337       Section->OffsetSymbols.push_back(Label);
 338     }
 339   }
 340 }
 341
 342 static uint64_t getSymbolValue(const MCSymbol &Symbol, const MCAssembler &Asm) {
 343   if (Symbol.isCommon() && Symbol.isExternal())
 344     return Symbol.getCommonSize();
 345
 346   uint64_t Res;
 347   if (!Asm.getSymbolOffset(Symbol, Res))
 348     return 0;
 349
 350   return Res;
 351 }
 352
 353 COFFSymbol *WinCOFFWriter::getLinkedSymbol(const MCSymbol &Symbol) {
 354   if (!Symbol.isVariable())
 355     return nullptr;
 356
 357   const MCSymbolRefExpr *SymRef =
 358       dyn_cast<MCSymbolRefExpr>(Symbol.getVariableValue());
 359   if (!SymRef)
 360     return nullptr;
 361
 362   const MCSymbol &Aliasee = SymRef->getSymbol();
 363   if (Aliasee.isUndefined() || Aliasee.isExternal())
 364     return GetOrCreateCOFFSymbol(&Aliasee);
 365   else
 366     return nullptr;
 367 }
 368
 369 /// This function takes a symbol data object from the assembler
 370 /// and creates the associated COFF symbol staging object.
 371 void WinCOFFWriter::defineSymbol(const MCAssembler &Asm,
 372                                  const MCSymbol &MCSym) {
 373   const MCSymbol *Base = Asm.getBaseSymbol(MCSym);
 374   COFFSection *Sec = nullptr;
 375   MCSectionCOFF *MCSec = nullptr;
 376   if (Base && Base->getFragment()) {
 377     MCSec = cast<MCSectionCOFF>(Base->getFragment()->getParent());
 378     Sec = SectionMap[MCSec];
 379   }
 380
 381   if (Mode == NonDwoOnly && MCSec && isDwoSection(*MCSec))
 382     return;
 383
 384   COFFSymbol *Sym = GetOrCreateCOFFSymbol(&MCSym);
 385   COFFSymbol *Local = nullptr;
 386   if (cast<MCSymbolCOFF>(MCSym).getWeakExternalCharacteristics()) {
 387     Sym->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
 388     Sym->Section = nullptr;
 389
 390     COFFSymbol *WeakDefault = getLinkedSymbol(MCSym);
 391     if (!WeakDefault) {
 392       std::string WeakName = (".weak." + MCSym.getName() + ".default").str();
 393       WeakDefault = createSymbol(WeakName);
 394       if (!Sec)
 395         WeakDefault->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
 396       else
 397         WeakDefault->Section = Sec;
 398       WeakDefaults.insert(WeakDefault);
 399       Local = WeakDefault;
 400     }
 401
 402     Sym->Other = WeakDefault;
 403
 404     // Setup the Weak External auxiliary symbol.
 405     Sym->Aux.resize(1);
 406     memset(&Sym->Aux[0], 0, sizeof(Sym->Aux[0]));
 407     Sym->Aux[0].AuxType = ATWeakExternal;
 408     Sym->Aux[0].Aux.WeakExternal.TagIndex = 0; // Filled in later
 409     Sym->Aux[0].Aux.WeakExternal.Characteristics =
 410         cast<MCSymbolCOFF>(MCSym).getWeakExternalCharacteristics();
 411   } else {
 412     if (!Base)
 413       Sym->Data.SectionNumber = COFF::IMAGE_SYM_ABSOLUTE;
 414     else
 415       Sym->Section = Sec;
 416     Local = Sym;
 417   }
 418
 419   if (Local) {
 420     Local->Data.Value = getSymbolValue(MCSym, Asm);
 421
 422     const MCSymbolCOFF &SymbolCOFF = cast<MCSymbolCOFF>(MCSym);
 423     Local->Data.Type = SymbolCOFF.getType();
 424     Local->Data.StorageClass = SymbolCOFF.getClass();
 425
 426     // If no storage class was specified in the streamer, define it here.
 427     if (Local->Data.StorageClass == COFF::IMAGE_SYM_CLASS_NULL) {
 428       bool IsExternal =
 429           MCSym.isExternal() || (!MCSym.getFragment() && !MCSym.isVariable());
 430
 431       Local->Data.StorageClass = IsExternal ? COFF::IMAGE_SYM_CLASS_EXTERNAL
 432                                             : COFF::IMAGE_SYM_CLASS_STATIC;
 433     }
 434   }
 435
 436   Sym->MC = &MCSym;
 437 }
 438
 439 void WinCOFFWriter::SetSectionName(COFFSection &S) {
 440   if (S.Name.size() <= COFF::NameSize) {
 441     std::memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
 442     return;
 443   }
 444
 445   uint64_t StringTableEntry = Strings.getOffset(S.Name);
 446   if (!COFF::encodeSectionName(S.Header.Name, StringTableEntry))
 447     report_fatal_error("COFF string table is greater than 64 GB.");
 448 }
 449
 450 void WinCOFFWriter::SetSymbolName(COFFSymbol &S) {
 451   if (S.Name.size() > COFF::NameSize)
 452     S.set_name_offset(Strings.getOffset(S.Name));
 453   else
 454     std::memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
 455 }
 456
 457 bool WinCOFFWriter::IsPhysicalSection(COFFSection *S) {
 458   return (S->Header.Characteristics & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) ==
 459          0;
 460 }
 461
 462 //------------------------------------------------------------------------------
 463 // entity writing methods
 464
 465 void WinCOFFWriter::WriteFileHeader(const COFF::header &Header) {
 466   if (UseBigObj) {
 467     W.write<uint16_t>(COFF::IMAGE_FILE_MACHINE_UNKNOWN);
 468     W.write<uint16_t>(0xFFFF);
 469     W.write<uint16_t>(COFF::BigObjHeader::MinBigObjectVersion);
 470     W.write<uint16_t>(Header.Machine);
 471     W.write<uint32_t>(Header.TimeDateStamp);
 472     W.OS.write(COFF::BigObjMagic, sizeof(COFF::BigObjMagic));
 473     W.write<uint32_t>(0);
 474     W.write<uint32_t>(0);
 475     W.write<uint32_t>(0);
 476     W.write<uint32_t>(0);
 477     W.write<uint32_t>(Header.NumberOfSections);
 478     W.write<uint32_t>(Header.PointerToSymbolTable);
 479     W.write<uint32_t>(Header.NumberOfSymbols);
 480   } else {
 481     W.write<uint16_t>(Header.Machine);
 482     W.write<uint16_t>(static_cast<int16_t>(Header.NumberOfSections));
 483     W.write<uint32_t>(Header.TimeDateStamp);
 484     W.write<uint32_t>(Header.PointerToSymbolTable);
 485     W.write<uint32_t>(Header.NumberOfSymbols);
 486     W.write<uint16_t>(Header.SizeOfOptionalHeader);
 487     W.write<uint16_t>(Header.Characteristics);
 488   }
 489 }
 490
 491 void WinCOFFWriter::WriteSymbol(const COFFSymbol &S) {
 492   W.OS.write(S.Data.Name, COFF::NameSize);
 493   W.write<uint32_t>(S.Data.Value);
 494   if (UseBigObj)
 495     W.write<uint32_t>(S.Data.SectionNumber);
 496   else
 497     W.write<uint16_t>(static_cast<int16_t>(S.Data.SectionNumber));
 498   W.write<uint16_t>(S.Data.Type);
 499   W.OS << char(S.Data.StorageClass);
 500   W.OS << char(S.Data.NumberOfAuxSymbols);
 501   WriteAuxiliarySymbols(S.Aux);
 502 }
 503
 504 void WinCOFFWriter::WriteAuxiliarySymbols(
 505     const COFFSymbol::AuxiliarySymbols &S) {
 506   for (const AuxSymbol &i : S) {
 507     switch (i.AuxType) {
 508     case ATWeakExternal:
 509       W.write<uint32_t>(i.Aux.WeakExternal.TagIndex);
 510       W.write<uint32_t>(i.Aux.WeakExternal.Characteristics);
 511       W.OS.write_zeros(sizeof(i.Aux.WeakExternal.unused));
 512       if (UseBigObj)
 513         W.OS.write_zeros(COFF::Symbol32Size - COFF::Symbol16Size);
 514       break;
 515     case ATFile:
 516       W.OS.write(reinterpret_cast<const char *>(&i.Aux),
 517                  UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size);
 518       break;
 519     case ATSectionDefinition:
 520       W.write<uint32_t>(i.Aux.SectionDefinition.Length);
 521       W.write<uint16_t>(i.Aux.SectionDefinition.NumberOfRelocations);
 522       W.write<uint16_t>(i.Aux.SectionDefinition.NumberOfLinenumbers);
 523       W.write<uint32_t>(i.Aux.SectionDefinition.CheckSum);
 524       W.write<uint16_t>(static_cast<int16_t>(i.Aux.SectionDefinition.Number));
 525       W.OS << char(i.Aux.SectionDefinition.Selection);
 526       W.OS.write_zeros(sizeof(i.Aux.SectionDefinition.unused));
 527       W.write<uint16_t>(
 528           static_cast<int16_t>(i.Aux.SectionDefinition.Number >> 16));
 529       if (UseBigObj)
 530         W.OS.write_zeros(COFF::Symbol32Size - COFF::Symbol16Size);
 531       break;
 532     }
 533   }
 534 }
 535
 536 // Write the section header.
 537 void WinCOFFWriter::writeSectionHeaders() {
 538   // Section numbers must be monotonically increasing in the section
 539   // header, but our Sections array is not sorted by section number,
 540   // so make a copy of Sections and sort it.
 541   std::vector<COFFSection *> Arr;
 542   for (auto &Section : Sections)
 543     Arr.push_back(Section.get());
 544   llvm::sort(Arr, [](const COFFSection *A, const COFFSection *B) {
 545     return A->Number < B->Number;
 546   });
 547
 548   for (auto &Section : Arr) {
 549     if (Section->Number == -1)
 550       continue;
 551
 552     COFF::section &S = Section->Header;
 553     if (Section->Relocations.size() >= 0xffff)
 554       S.Characteristics |= COFF::IMAGE_SCN_LNK_NRELOC_OVFL;
 555     W.OS.write(S.Name, COFF::NameSize);
 556     W.write<uint32_t>(S.VirtualSize);
 557     W.write<uint32_t>(S.VirtualAddress);
 558     W.write<uint32_t>(S.SizeOfRawData);
 559     W.write<uint32_t>(S.PointerToRawData);
 560     W.write<uint32_t>(S.PointerToRelocations);
 561     W.write<uint32_t>(S.PointerToLineNumbers);
 562     W.write<uint16_t>(S.NumberOfRelocations);
 563     W.write<uint16_t>(S.NumberOfLineNumbers);
 564     W.write<uint32_t>(S.Characteristics);
 565   }
 566 }
 567
 568 void WinCOFFWriter::WriteRelocation(const COFF::relocation &R) {
 569   W.write<uint32_t>(R.VirtualAddress);
 570   W.write<uint32_t>(R.SymbolTableIndex);
 571   W.write<uint16_t>(R.Type);
 572 }
 573
 574 // Write MCSec's contents. What this function does is essentially
 575 // "Asm.writeSectionData(&MCSec)", but it's a bit complicated
 576 // because it needs to compute a CRC.
 577 uint32_t WinCOFFWriter::writeSectionContents(MCAssembler &Asm,
 578                                              const MCSection &MCSec) {
 579   // Save the contents of the section to a temporary buffer, we need this
 580   // to CRC the data before we dump it into the object file.
 581   SmallVector<char, 128> Buf;
 582   raw_svector_ostream VecOS(Buf);
 583   Asm.writeSectionData(VecOS, &MCSec);
 584
 585   // Write the section contents to the object file.
 586   W.OS << Buf;
 587
 588   // Calculate our CRC with an initial value of '0', this is not how
 589   // JamCRC is specified but it aligns with the expected output.
 590   JamCRC JC(/*Init=*/0);
 591   JC.update(ArrayRef(reinterpret_cast<uint8_t *>(Buf.data()), Buf.size()));
 592   return JC.getCRC();
 593 }
 594
 595 void WinCOFFWriter::writeSection(MCAssembler &Asm, const COFFSection &Sec) {
 596   if (Sec.Number == -1)
 597     return;
 598
 599   // Write the section contents.
 600   if (Sec.Header.PointerToRawData != 0) {
 601     assert(W.OS.tell() == Sec.Header.PointerToRawData &&
 602            "Section::PointerToRawData is insane!");
 603
 604     uint32_t CRC = writeSectionContents(Asm, *Sec.MCSection);
 605
 606     // Update the section definition auxiliary symbol to record the CRC.
 607     COFFSymbol::AuxiliarySymbols &AuxSyms = Sec.Symbol->Aux;
 608     assert(AuxSyms.size() == 1 && AuxSyms[0].AuxType == ATSectionDefinition);
 609     AuxSymbol &SecDef = AuxSyms[0];
 610     SecDef.Aux.SectionDefinition.CheckSum = CRC;
 611   }
 612
 613   // Write relocations for this section.
 614   if (Sec.Relocations.empty()) {
 615     assert(Sec.Header.PointerToRelocations == 0 &&
 616            "Section::PointerToRelocations is insane!");
 617     return;
 618   }
 619
 620   assert(W.OS.tell() == Sec.Header.PointerToRelocations &&
 621          "Section::PointerToRelocations is insane!");
 622
 623   if (Sec.Relocations.size() >= 0xffff) {
 624     // In case of overflow, write actual relocation count as first
 625     // relocation. Including the synthetic reloc itself (+ 1).
 626     COFF::relocation R;
 627     R.VirtualAddress = Sec.Relocations.size() + 1;
 628     R.SymbolTableIndex = 0;
 629     R.Type = 0;
 630     WriteRelocation(R);
 631   }
 632
 633   for (const auto &Relocation : Sec.Relocations)
 634     WriteRelocation(Relocation.Data);
 635 }
 636
 637 // Create .file symbols.
 638 void WinCOFFWriter::createFileSymbols(MCAssembler &Asm) {
 639   for (const std::pair<std::string, size_t> &It : OWriter.getFileNames()) {
 640     // round up to calculate the number of auxiliary symbols required
 641     const std::string &Name = It.first;
 642     unsigned SymbolSize = UseBigObj ? COFF::Symbol32Size : COFF::Symbol16Size;
 643     unsigned Count = (Name.size() + SymbolSize - 1) / SymbolSize;
 644
 645     COFFSymbol *File = createSymbol(".file");
 646     File->Data.SectionNumber = COFF::IMAGE_SYM_DEBUG;
 647     File->Data.StorageClass = COFF::IMAGE_SYM_CLASS_FILE;
 648     File->Aux.resize(Count);
 649
 650     unsigned Offset = 0;
 651     unsigned Length = Name.size();
 652     for (auto &Aux : File->Aux) {
 653       Aux.AuxType = ATFile;
 654
 655       if (Length > SymbolSize) {
 656         memcpy(&Aux.Aux, Name.c_str() + Offset, SymbolSize);
 657         Length = Length - SymbolSize;
 658       } else {
 659         memcpy(&Aux.Aux, Name.c_str() + Offset, Length);
 660         memset((char *)&Aux.Aux + Length, 0, SymbolSize - Length);
 661         break;
 662       }
 663
 664       Offset += SymbolSize;
 665     }
 666   }
 667 }
 668
 669 void WinCOFFWriter::setWeakDefaultNames() {
 670   if (WeakDefaults.empty())
 671     return;
 672
 673   // If multiple object files use a weak symbol (either with a regular
 674   // defined default, or an absolute zero symbol as default), the defaults
 675   // cause duplicate definitions unless their names are made unique. Look
 676   // for a defined extern symbol, that isn't comdat - that should be unique
 677   // unless there are other duplicate definitions. And if none is found,
 678   // allow picking a comdat symbol, as that's still better than nothing.
 679
 680   COFFSymbol *Unique = nullptr;
 681   for (bool AllowComdat : {false, true}) {
 682     for (auto &Sym : Symbols) {
 683       // Don't include the names of the defaults themselves
 684       if (WeakDefaults.count(Sym.get()))
 685         continue;
 686       // Only consider external symbols
 687       if (Sym->Data.StorageClass != COFF::IMAGE_SYM_CLASS_EXTERNAL)
 688         continue;
 689       // Only consider symbols defined in a section or that are absolute
 690       if (!Sym->Section && Sym->Data.SectionNumber != COFF::IMAGE_SYM_ABSOLUTE)
 691         continue;
 692       if (!AllowComdat && Sym->Section &&
 693           Sym->Section->Header.Characteristics & COFF::IMAGE_SCN_LNK_COMDAT)
 694         continue;
 695       Unique = Sym.get();
 696       break;
 697     }
 698     if (Unique)
 699       break;
 700   }
 701   // If we didn't find any unique symbol to use for the names, just skip this.
 702   if (!Unique)
 703     return;
 704   for (auto *Sym : WeakDefaults) {
 705     Sym->Name.append(".");
 706     Sym->Name.append(Unique->Name);
 707   }
 708 }
 709
 710 static bool isAssociative(const COFFSection &Section) {
 711   return Section.Symbol->Aux[0].Aux.SectionDefinition.Selection ==
 712          COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
 713 }
 714
 715 void WinCOFFWriter::assignSectionNumbers() {
 716   size_t I = 1;
 717   auto Assign = [&](COFFSection &Section) {
 718     Section.Number = I;
 719     Section.Symbol->Data.SectionNumber = I;
 720     Section.Symbol->Aux[0].Aux.SectionDefinition.Number = I;
 721     ++I;
 722   };
 723
 724   // Although it is not explicitly requested by the Microsoft COFF spec,
 725   // we should avoid emitting forward associative section references,
 726   // because MSVC link.exe as of 2017 cannot handle that.
 727   for (const std::unique_ptr<COFFSection> &Section : Sections)
 728     if (!isAssociative(*Section))
 729       Assign(*Section);
 730   for (const std::unique_ptr<COFFSection> &Section : Sections)
 731     if (isAssociative(*Section))
 732       Assign(*Section);
 733 }
 734
 735 // Assign file offsets to COFF object file structures.
 736 void WinCOFFWriter::assignFileOffsets(MCAssembler &Asm) {
 737   unsigned Offset = W.OS.tell();
 738
 739   Offset += UseBigObj ? COFF::Header32Size : COFF::Header16Size;
 740   Offset += COFF::SectionSize * Header.NumberOfSections;
 741
 742   for (const auto &Section : Asm) {
 743     COFFSection *Sec = SectionMap[&Section];
 744
 745     if (!Sec || Sec->Number == -1)
 746       continue;
 747
 748     Sec->Header.SizeOfRawData = Asm.getSectionAddressSize(Section);
 749
 750     if (IsPhysicalSection(Sec)) {
 751       Sec->Header.PointerToRawData = Offset;
 752       Offset += Sec->Header.SizeOfRawData;
 753     }
 754
 755     if (!Sec->Relocations.empty()) {
 756       bool RelocationsOverflow = Sec->Relocations.size() >= 0xffff;
 757
 758       if (RelocationsOverflow) {
 759         // Signal overflow by setting NumberOfRelocations to max value. Actual
 760         // size is found in reloc #0. Microsoft tools understand this.
 761         Sec->Header.NumberOfRelocations = 0xffff;
 762       } else {
 763         Sec->Header.NumberOfRelocations = Sec->Relocations.size();
 764       }
 765       Sec->Header.PointerToRelocations = Offset;
 766
 767       if (RelocationsOverflow) {
 768         // Reloc #0 will contain actual count, so make room for it.
 769         Offset += COFF::RelocationSize;
 770       }
 771
 772       Offset += COFF::RelocationSize * Sec->Relocations.size();
 773
 774       for (auto &Relocation : Sec->Relocations) {
 775         assert(Relocation.Symb->getIndex() != -1);
 776         Relocation.Data.SymbolTableIndex = Relocation.Symb->getIndex();
 777       }
 778     }
 779
 780     assert(Sec->Symbol->Aux.size() == 1 &&
 781            "Section's symbol must have one aux!");
 782     AuxSymbol &Aux = Sec->Symbol->Aux[0];
 783     assert(Aux.AuxType == ATSectionDefinition &&
 784            "Section's symbol's aux symbol must be a Section Definition!");
 785     Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
 786     Aux.Aux.SectionDefinition.NumberOfRelocations =
 787         Sec->Header.NumberOfRelocations;
 788     Aux.Aux.SectionDefinition.NumberOfLinenumbers =
 789         Sec->Header.NumberOfLineNumbers;
 790   }
 791
 792   Header.PointerToSymbolTable = Offset;
 793 }
 794
 795 void WinCOFFWriter::reset() {
 796   memset(&Header, 0, sizeof(Header));
 797   Header.Machine = OWriter.TargetObjectWriter->getMachine();
 798   Sections.clear();
 799   Symbols.clear();
 800   Strings.clear();
 801   SectionMap.clear();
 802   SymbolMap.clear();
 803   WeakDefaults.clear();
 804 }
 805
 806 void WinCOFFWriter::executePostLayoutBinding(MCAssembler &Asm) {
 807   // "Define" each section & symbol. This creates section & symbol
 808   // entries in the staging area.
 809   for (const auto &Section : Asm) {
 810     if ((Mode == NonDwoOnly && isDwoSection(Section)) ||
 811         (Mode == DwoOnly && !isDwoSection(Section)))
 812       continue;
 813     defineSection(Asm, static_cast<const MCSectionCOFF &>(Section));
 814   }
 815
 816   if (Mode != DwoOnly)
 817     for (const MCSymbol &Symbol : Asm.symbols())
 818       // Define non-temporary or temporary static (private-linkage) symbols
 819       if (!Symbol.isTemporary() ||
 820           cast<MCSymbolCOFF>(Symbol).getClass() == COFF::IMAGE_SYM_CLASS_STATIC)
 821         defineSymbol(Asm, Symbol);
 822 }
 823
 824 void WinCOFFWriter::recordRelocation(MCAssembler &Asm,
 825                                      const MCFragment *Fragment,
 826                                      const MCFixup &Fixup, MCValue Target,
 827                                      uint64_t &FixedValue) {
 828   assert(Target.getSymA() && "Relocation must reference a symbol!");
 829
 830   const MCSymbol &A = Target.getSymA()->getSymbol();
 831   if (!A.isRegistered()) {
 832     Asm.getContext().reportError(Fixup.getLoc(), Twine("symbol '") +
 833                                                      A.getName() +
 834                                                      "' can not be undefined");
 835     return;
 836   }
 837   if (A.isTemporary() && A.isUndefined()) {
 838     Asm.getContext().reportError(Fixup.getLoc(), Twine("assembler label '") +
 839                                                      A.getName() +
 840                                                      "' can not be undefined");
 841     return;
 842   }
 843
 844   MCSection *MCSec = Fragment->getParent();
 845
 846   // Mark this symbol as requiring an entry in the symbol table.
 847   assert(SectionMap.contains(MCSec) &&
 848          "Section must already have been defined in executePostLayoutBinding!");
 849
 850   COFFSection *Sec = SectionMap[MCSec];
 851   const MCSymbolRefExpr *SymB = Target.getSymB();
 852
 853   if (SymB) {
 854     const MCSymbol *B = &SymB->getSymbol();
 855     if (!B->getFragment()) {
 856       Asm.getContext().reportError(
 857           Fixup.getLoc(),
 858           Twine("symbol '") + B->getName() +
 859               "' can not be undefined in a subtraction expression");
 860       return;
 861     }
 862
 863     // Offset of the symbol in the section
 864     int64_t OffsetOfB = Asm.getSymbolOffset(*B);
 865
 866     // Offset of the relocation in the section
 867     int64_t OffsetOfRelocation =
 868         Asm.getFragmentOffset(*Fragment) + Fixup.getOffset();
 869
 870     FixedValue = (OffsetOfRelocation - OffsetOfB) + Target.getConstant();
 871   } else {
 872     FixedValue = Target.getConstant();
 873   }
 874
 875   COFFRelocation Reloc;
 876
 877   Reloc.Data.SymbolTableIndex = 0;
 878   Reloc.Data.VirtualAddress = Asm.getFragmentOffset(*Fragment);
 879
 880   // Turn relocations for temporary symbols into section relocations.
 881   if (A.isTemporary() && !SymbolMap[&A]) {
 882     MCSection *TargetSection = &A.getSection();
 883     assert(
 884         SectionMap.contains(TargetSection) &&
 885         "Section must already have been defined in executePostLayoutBinding!");
 886     COFFSection *Section = SectionMap[TargetSection];
 887     Reloc.Symb = Section->Symbol;
 888     FixedValue += Asm.getSymbolOffset(A);
 889     // Technically, we should do the final adjustments of FixedValue (below)
 890     // before picking an offset symbol, otherwise we might choose one which
 891     // is slightly too far away. The relocations where it really matters
 892     // (arm64 adrp relocations) don't get any offset though.
 893     if (UseOffsetLabels && !Section->OffsetSymbols.empty()) {
 894       uint64_t LabelIndex = FixedValue >> OffsetLabelIntervalBits;
 895       if (LabelIndex > 0) {
 896         if (LabelIndex <= Section->OffsetSymbols.size())
 897           Reloc.Symb = Section->OffsetSymbols[LabelIndex - 1];
 898         else
 899           Reloc.Symb = Section->OffsetSymbols.back();
 900         FixedValue -= Reloc.Symb->Data.Value;
 901       }
 902     }
 903   } else {
 904     assert(
 905         SymbolMap.contains(&A) &&
 906         "Symbol must already have been defined in executePostLayoutBinding!");
 907     Reloc.Symb = SymbolMap[&A];
 908   }
 909
 910   ++Reloc.Symb->Relocations;
 911
 912   Reloc.Data.VirtualAddress += Fixup.getOffset();
 913   Reloc.Data.Type = OWriter.TargetObjectWriter->getRelocType(
 914       Asm.getContext(), Target, Fixup, SymB, Asm.getBackend());
 915
 916   // The *_REL32 relocations are relative to the end of the relocation,
 917   // not to the start.
 918   if ((Header.Machine == COFF::IMAGE_FILE_MACHINE_AMD64 &&
 919        Reloc.Data.Type == COFF::IMAGE_REL_AMD64_REL32) ||
 920       (Header.Machine == COFF::IMAGE_FILE_MACHINE_I386 &&
 921        Reloc.Data.Type == COFF::IMAGE_REL_I386_REL32) ||
 922       (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT &&
 923        Reloc.Data.Type == COFF::IMAGE_REL_ARM_REL32) ||
 924       (COFF::isAnyArm64(Header.Machine) &&
 925        Reloc.Data.Type == COFF::IMAGE_REL_ARM64_REL32))
 926     FixedValue += 4;
 927
 928   if (Header.Machine == COFF::IMAGE_FILE_MACHINE_ARMNT) {
 929     switch (Reloc.Data.Type) {
 930     case COFF::IMAGE_REL_ARM_ABSOLUTE:
 931     case COFF::IMAGE_REL_ARM_ADDR32:
 932     case COFF::IMAGE_REL_ARM_ADDR32NB:
 933     case COFF::IMAGE_REL_ARM_TOKEN:
 934     case COFF::IMAGE_REL_ARM_SECTION:
 935     case COFF::IMAGE_REL_ARM_SECREL:
 936       break;
 937     case COFF::IMAGE_REL_ARM_BRANCH11:
 938     case COFF::IMAGE_REL_ARM_BLX11:
 939     // IMAGE_REL_ARM_BRANCH11 and IMAGE_REL_ARM_BLX11 are only used for
 940     // pre-ARMv7, which implicitly rules it out of ARMNT (it would be valid
 941     // for Windows CE).
 942     case COFF::IMAGE_REL_ARM_BRANCH24:
 943     case COFF::IMAGE_REL_ARM_BLX24:
 944     case COFF::IMAGE_REL_ARM_MOV32A:
 945       // IMAGE_REL_ARM_BRANCH24, IMAGE_REL_ARM_BLX24, IMAGE_REL_ARM_MOV32A are
 946       // only used for ARM mode code, which is documented as being unsupported
 947       // by Windows on ARM.  Empirical proof indicates that masm is able to
 948       // generate the relocations however the rest of the MSVC toolchain is
 949       // unable to handle it.
 950       llvm_unreachable("unsupported relocation");
 951       break;
 952     case COFF::IMAGE_REL_ARM_MOV32T:
 953       break;
 954     case COFF::IMAGE_REL_ARM_BRANCH20T:
 955     case COFF::IMAGE_REL_ARM_BRANCH24T:
 956     case COFF::IMAGE_REL_ARM_BLX23T:
 957       // IMAGE_REL_BRANCH20T, IMAGE_REL_ARM_BRANCH24T, IMAGE_REL_ARM_BLX23T all
 958       // perform a 4 byte adjustment to the relocation.  Relative branches are
 959       // offset by 4 on ARM, however, because there is no RELA relocations, all
 960       // branches are offset by 4.
 961       FixedValue = FixedValue + 4;
 962       break;
 963     }
 964   }
 965
 966   // The fixed value never makes sense for section indices, ignore it.
 967   if (Fixup.getKind() == FK_SecRel_2)
 968     FixedValue = 0;
 969
 970   if (OWriter.TargetObjectWriter->recordRelocation(Fixup))
 971     Sec->Relocations.push_back(Reloc);
 972 }
 973
 974 static std::time_t getTime() {
 975   std::time_t Now = time(nullptr);
 976   if (Now < 0 || !isUInt<32>(Now))
 977     return UINT32_MAX;
 978   return Now;
 979 }
 980
 981 uint64_t WinCOFFWriter::writeObject(MCAssembler &Asm) {
 982   uint64_t StartOffset = W.OS.tell();
 983
 984   if (Sections.size() > INT32_MAX)
 985     report_fatal_error(
 986         "PE COFF object files can't have more than 2147483647 sections");
 987
 988   UseBigObj = Sections.size() > COFF::MaxNumberOfSections16;
 989   Header.NumberOfSections = Sections.size();
 990   Header.NumberOfSymbols = 0;
 991
 992   setWeakDefaultNames();
 993   assignSectionNumbers();
 994   if (Mode != DwoOnly)
 995     createFileSymbols(Asm);
 996
 997   for (auto &Symbol : Symbols) {
 998     // Update section number & offset for symbols that have them.
 999     if (Symbol->Section)
1000       Symbol->Data.SectionNumber = Symbol->Section->Number;
1001     Symbol->setIndex(Header.NumberOfSymbols++);
1002     // Update auxiliary symbol info.
1003     Symbol->Data.NumberOfAuxSymbols = Symbol->Aux.size();
1004     Header.NumberOfSymbols += Symbol->Data.NumberOfAuxSymbols;
1005   }
1006
1007   // Build string table.
1008   for (const auto &S : Sections)
1009     if (S->Name.size() > COFF::NameSize)
1010       Strings.add(S->Name);
1011   for (const auto &S : Symbols)
1012     if (S->Name.size() > COFF::NameSize)
1013       Strings.add(S->Name);
1014   Strings.finalize();
1015
1016   // Set names.
1017   for (const auto &S : Sections)
1018     SetSectionName(*S);
1019   for (auto &S : Symbols)
1020     SetSymbolName(*S);
1021
1022   // Fixup weak external references.
1023   for (auto &Symbol : Symbols) {
1024     if (Symbol->Other) {
1025       assert(Symbol->getIndex() != -1);
1026       assert(Symbol->Aux.size() == 1 && "Symbol must contain one aux symbol!");
1027       assert(Symbol->Aux[0].AuxType == ATWeakExternal &&
1028              "Symbol's aux symbol must be a Weak External!");
1029       Symbol->Aux[0].Aux.WeakExternal.TagIndex = Symbol->Other->getIndex();
1030     }
1031   }
1032
1033   // Fixup associative COMDAT sections.
1034   for (auto &Section : Sections) {
1035     if (Section->Symbol->Aux[0].Aux.SectionDefinition.Selection !=
1036         COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
1037       continue;
1038
1039     const MCSectionCOFF &MCSec = *Section->MCSection;
1040     const MCSymbol *AssocMCSym = MCSec.getCOMDATSymbol();
1041     assert(AssocMCSym);
1042
1043     // It's an error to try to associate with an undefined symbol or a symbol
1044     // without a section.
1045     if (!AssocMCSym->isInSection()) {
1046       Asm.getContext().reportError(
1047           SMLoc(), Twine("cannot make section ") + MCSec.getName() +
1048                        Twine(" associative with sectionless symbol ") +
1049                        AssocMCSym->getName());
1050       continue;
1051     }
1052
1053     const auto *AssocMCSec = cast<MCSectionCOFF>(&AssocMCSym->getSection());
1054     assert(SectionMap.count(AssocMCSec));
1055     COFFSection *AssocSec = SectionMap[AssocMCSec];
1056
1057     // Skip this section if the associated section is unused.
1058     if (AssocSec->Number == -1)
1059       continue;
1060
1061     Section->Symbol->Aux[0].Aux.SectionDefinition.Number = AssocSec->Number;
1062   }
1063
1064   // Create the contents of the .llvm_addrsig section.
1065   if (Mode != DwoOnly && OWriter.getEmitAddrsigSection()) {
1066     auto *Sec = Asm.getContext().getCOFFSection(
1067         ".llvm_addrsig", COFF::IMAGE_SCN_LNK_REMOVE);
1068     auto *Frag = cast<MCDataFragment>(Sec->curFragList()->Head);
1069     raw_svector_ostream OS(Frag->getContents());
1070     for (const MCSymbol *S : OWriter.AddrsigSyms) {
1071       if (!S->isRegistered())
1072         continue;
1073       if (!S->isTemporary()) {
1074         encodeULEB128(S->getIndex(), OS);
1075         continue;
1076       }
1077
1078       MCSection *TargetSection = &S->getSection();
1079       assert(SectionMap.contains(TargetSection) &&
1080              "Section must already have been defined in "
1081              "executePostLayoutBinding!");
1082       encodeULEB128(SectionMap[TargetSection]->Symbol->getIndex(), OS);
1083     }
1084   }
1085
1086   // Create the contents of the .llvm.call-graph-profile section.
1087   if (Mode != DwoOnly && !OWriter.getCGProfile().empty()) {
1088     auto *Sec = Asm.getContext().getCOFFSection(
1089         ".llvm.call-graph-profile", COFF::IMAGE_SCN_LNK_REMOVE);
1090     auto *Frag = cast<MCDataFragment>(Sec->curFragList()->Head);
1091     raw_svector_ostream OS(Frag->getContents());
1092     for (const auto &CGPE : OWriter.getCGProfile()) {
1093       uint32_t FromIndex = CGPE.From->getSymbol().getIndex();
1094       uint32_t ToIndex = CGPE.To->getSymbol().getIndex();
1095       support::endian::write(OS, FromIndex, W.Endian);
1096       support::endian::write(OS, ToIndex, W.Endian);
1097       support::endian::write(OS, CGPE.Count, W.Endian);
1098     }
1099   }
1100
1101   assignFileOffsets(Asm);
1102
1103   // MS LINK expects to be able to use this timestamp to implement their
1104   // /INCREMENTAL feature.
1105   if (OWriter.IncrementalLinkerCompatible) {
1106     Header.TimeDateStamp = getTime();
1107   } else {
1108     // Have deterministic output if /INCREMENTAL isn't needed. Also matches GNU.
1109     Header.TimeDateStamp = 0;
1110   }
1111
1112   // Write it all to disk...
1113   WriteFileHeader(Header);
1114   writeSectionHeaders();
1115
1116 #ifndef NDEBUG
1117   sections::iterator I = Sections.begin();
1118   sections::iterator IE = Sections.end();
1119   auto J = Asm.begin();
1120   auto JE = Asm.end();
1121   for (; I != IE && J != JE; ++I, ++J) {
1122     while (J != JE && ((Mode == NonDwoOnly && isDwoSection(*J)) ||
1123                        (Mode == DwoOnly && !isDwoSection(*J))))
1124       ++J;
1125     assert(J != JE && (**I).MCSection == &*J && "Wrong bound MCSection");
1126   }
1127 #endif
1128
1129   // Write section contents.
1130   for (std::unique_ptr<COFFSection> &Sec : Sections)
1131     writeSection(Asm, *Sec);
1132
1133   assert(W.OS.tell() == Header.PointerToSymbolTable &&
1134          "Header::PointerToSymbolTable is insane!");
1135
1136   // Write a symbol table.
1137   for (auto &Symbol : Symbols)
1138     if (Symbol->getIndex() != -1)
1139       WriteSymbol(*Symbol);
1140
1141   // Write a string table, which completes the entire COFF file.
1142   Strings.write(W.OS);
1143
1144   return W.OS.tell() - StartOffset;
1145 }
1146
1147 //------------------------------------------------------------------------------
1148 // WinCOFFObjectWriter class implementation
1149
1150 ////////////////////////////////////////////////////////////////////////////////
1151 // MCObjectWriter interface implementations
1152
1153 void WinCOFFObjectWriter::reset() {
1154   IncrementalLinkerCompatible = false;
1155   ObjWriter->reset();
1156   if (DwoWriter)
1157     DwoWriter->reset();
1158   MCObjectWriter::reset();
1159 }
1160
1161 bool WinCOFFObjectWriter::isSymbolRefDifferenceFullyResolvedImpl(
1162     const MCAssembler &Asm, const MCSymbol &SymA, const MCFragment &FB,
1163     bool InSet, bool IsPCRel) const {
1164   // Don't drop relocations between functions, even if they are in the same text
1165   // section. Multiple Visual C++ linker features depend on having the
1166   // relocations present. The /INCREMENTAL flag will cause these relocations to
1167   // point to thunks, and the /GUARD:CF flag assumes that it can use relocations
1168   // to approximate the set of all address taken functions. LLD's implementation
1169   // of /GUARD:CF also relies on the existance of these relocations.
1170   uint16_t Type = cast<MCSymbolCOFF>(SymA).getType();
1171   if ((Type >> COFF::SCT_COMPLEX_TYPE_SHIFT) == COFF::IMAGE_SYM_DTYPE_FUNCTION)
1172     return false;
1173   return &SymA.getSection() == FB.getParent();
1174 }
1175
1176 void WinCOFFObjectWriter::executePostLayoutBinding(MCAssembler &Asm) {
1177   ObjWriter->executePostLayoutBinding(Asm);
1178   if (DwoWriter)
1179     DwoWriter->executePostLayoutBinding(Asm);
1180 }
1181
1182 void WinCOFFObjectWriter::recordRelocation(MCAssembler &Asm,
1183                                            const MCFragment *Fragment,
1184                                            const MCFixup &Fixup, MCValue Target,
1185                                            uint64_t &FixedValue) {
1186   assert(!isDwoSection(*Fragment->getParent()) &&
1187          "No relocation in Dwo sections");
1188   ObjWriter->recordRelocation(Asm, Fragment, Fixup, Target, FixedValue);
1189 }
1190
1191 uint64_t WinCOFFObjectWriter::writeObject(MCAssembler &Asm) {
1192   uint64_t TotalSize = ObjWriter->writeObject(Asm);
1193   if (DwoWriter)
1194     TotalSize += DwoWriter->writeObject(Asm);
1195   return TotalSize;
1196 }
1197
1198 MCWinCOFFObjectTargetWriter::MCWinCOFFObjectTargetWriter(unsigned Machine_)
1199     : Machine(Machine_) {}
1200
1201 // Pin the vtable to this file.
1202 void MCWinCOFFObjectTargetWriter::anchor() {}
1203
1204 //------------------------------------------------------------------------------
1205 // WinCOFFObjectWriter factory function
1206
1207 std::unique_ptr<MCObjectWriter> llvm::createWinCOFFObjectWriter(
1208     std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS) {
1209   return std::make_unique<WinCOFFObjectWriter>(std::move(MOTW), OS);
1210 }
1211
1212 std::unique_ptr<MCObjectWriter> llvm::createWinCOFFDwoObjectWriter(
1213     std::unique_ptr<MCWinCOFFObjectTargetWriter> MOTW, raw_pwrite_stream &OS,
1214     raw_pwrite_stream &DwoOS) {
1215   return std::make_unique<WinCOFFObjectWriter>(std::move(MOTW), OS, DwoOS);
1216 }