MC: Add WinCOFFObjectWriter implementation.

Origonal Windows COFF implementation by Nathan Jedffords.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@109389 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 674 insertions, 14 deletions

diff --git a/lib/MC/WinCOFFObjectWriter.cpp b/lib/MC/WinCOFFObjectWriter.cpp
index 6804766..6be27f4 100644
--- a/lib/MC/WinCOFFObjectWriter.cpp
+++ b/lib/MC/WinCOFFObjectWriter.cpp
@@ -12,41 +12,537 @@
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "WinCOFFObjectWriter"
+
 #include "llvm/MC/MCObjectWriter.h"
+#include "llvm/MC/MCSection.h"
+#include "llvm/MC/MCContext.h"
+#include "llvm/MC/MCSymbol.h"
+#include "llvm/MC/MCExpr.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCAsmLayout.h"
+#include "llvm/MC/MCSectionCOFF.h"
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/StringRef.h"
+
+#include "llvm/Support/COFF.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+
+#include <cstdio>
+
 using namespace llvm;
 
 namespace {
+typedef llvm::SmallString<COFF::NameSize> name;
+
+enum AuxiliaryType {
+  ATFunctionDefinition,
+  ATbfAndefSymbol,
+  ATWeakExternal,
+  ATFile,
+  ATSectionDefinition
+};
+
+struct AuxSymbol {
+  AuxiliaryType   AuxType;
+  COFF::Auxiliary Aux;
+};
+
+class COFFSymbol {
+public:
+  COFF::symbol Data;
+
+  typedef llvm::SmallVector<AuxSymbol, 1> AuxiliarySymbols;
+
+  name             Name;
+  size_t           Index;
+  AuxiliarySymbols Aux;
+  COFFSymbol      *Other;
+
+  MCSymbolData const *MCData;
+
+  COFFSymbol(llvm::StringRef name, size_t index);
+  size_t size() const;
+  void set_name_offset(uint32_t Offset);
+};
+
+// This class contains staging data for a COFF relocation entry.
+struct COFFRelocation {
+  COFF::relocation Data;
+  COFFSymbol          *Symb;
+
+  COFFRelocation() : Symb(NULL) {}
+  static size_t size() { return COFF::RelocationSize; }
+};
+
+typedef std::vector<COFFRelocation> relocations;
+
+class COFFSection {
+public:
+  COFF::section Header;
+
+  std::string          Name;
+  size_t               Number;
+  MCSectionData const *MCData;
+  COFFSymbol              *Symb;
+  relocations          Relocations;
+
+  COFFSection(llvm::StringRef name, size_t Index);
+  static size_t size();
+};
+
+// This class holds the COFF string table.
+class StringTable {
+  typedef llvm::StringMap<size_t> map;
+  map Map;
+
+  void update_length();
+public:
+  std::vector<char> Data;
+
+  StringTable();
+  size_t size() const;
+  size_t insert(llvm::StringRef String);
+};
+
+class WinCOFFObjectWriter : public MCObjectWriter {
+public:
+
+  typedef std::vector<COFFSymbol*>  symbols;
+  typedef std::vector<COFFSection*> sections;
 
-  class WinCOFFObjectWriter : public MCObjectWriter {
-  public:
-    WinCOFFObjectWriter(raw_ostream &OS);
+  typedef StringMap<COFFSymbol *>  name_symbol_map;
+  typedef StringMap<COFFSection *> name_section_map;
 
-    // MCObjectWriter interface implementation.
+  typedef DenseMap<MCSymbolData const *, COFFSymbol *>   symbol_map;
+  typedef DenseMap<MCSectionData const *, COFFSection *> section_map;
 
-    void ExecutePostLayoutBinding(MCAssembler &Asm);
+  // Root level file contents.
+  COFF::header Header;
+  sections     Sections;
+  symbols      Symbols;
+  StringTable  Strings;
 
-    void RecordRelocation(const MCAssembler &Asm,
-                          const MCAsmLayout &Layout,
-                          const MCFragment *Fragment,
-                          const MCFixup &Fixup,
-                          MCValue Target,
-                          uint64_t &FixedValue);
+  // Maps used during object file creation.
+  section_map SectionMap;
+  symbol_map  SymbolMap;
+
+  WinCOFFObjectWriter(raw_ostream &OS);
+
+  COFFSymbol *createSymbol(llvm::StringRef Name);
+  COFFSection *createSection(llvm::StringRef Name);
+
+  void InitCOFFEntity(COFFSymbol &Symbol);
+  void InitCOFFEntity(COFFSection &Section);
+
+  template <typename object_t, typename list_t>
+  object_t *createCOFFEntity(llvm::StringRef Name, list_t &List);
+
+  void DefineSection(MCSectionData const &SectionData);
+  void DefineSymbol(MCSymbolData const &SymbolData, MCAssembler &Assembler);
+
+  bool ExportSection(COFFSection *S);
+  bool ExportSymbol(MCSymbolData const &SymbolData, MCAssembler &Asm);
+
+  // Entity writing methods.
+
+  void WriteFileHeader(const COFF::header &Header);
+  void WriteSymbol(const COFFSymbol *S);
+  void WriteAuxiliarySymbols(const COFFSymbol::AuxiliarySymbols &S);
+  void WriteSectionHeader(const COFF::section &S);
+  void WriteRelocation(const COFF::relocation &R);
+
+  // MCObjectWriter interface implementation.
+
+  void ExecutePostLayoutBinding(MCAssembler &Asm);
+
+  void RecordRelocation(const MCAssembler &Asm,
+                        const MCAsmLayout &Layout,
+                        const MCFragment *Fragment,
+                        const MCFixup &Fixup,
+                        MCValue Target,
+                        uint64_t &FixedValue);
+
+  void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout);
+};
+}
+
+static inline void write_uint32_le(void *Data, uint32_t const &Value) {
+  uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
+  Ptr[0] = (Value & 0x000000FF) >>  0;
+  Ptr[1] = (Value & 0x0000FF00) >>  8;
+  Ptr[2] = (Value & 0x00FF0000) >> 16;
+  Ptr[3] = (Value & 0xFF000000) >> 24;
+}
+
+static inline void write_uint16_le(void *Data, uint16_t const &Value) {
+  uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
+  Ptr[0] = (Value & 0x00FF) >> 0;
+  Ptr[1] = (Value & 0xFF00) >> 8;
+}
+
+static inline void write_uint8_le(void *Data, uint8_t const &Value) {
+  uint8_t *Ptr = reinterpret_cast<uint8_t *>(Data);
+  Ptr[0] = (Value & 0xFF) >> 0;
+}
+
+//------------------------------------------------------------------------------
+// Symbol class implementation
+
+COFFSymbol::COFFSymbol(llvm::StringRef name, size_t index)
+      : Name(name.begin(), name.end()), Index(-1)
+      , Other(NULL), MCData(NULL) {
+  memset(&Data, 0, sizeof(Data));
+}
 
-    void WriteObject(const MCAssembler &Asm, const MCAsmLayout &Layout);
-  };
+size_t COFFSymbol::size() const {
+  return COFF::SymbolSize + (Data.NumberOfAuxSymbols * COFF::SymbolSize);
 }
 
+// In the case that the name does not fit within 8 bytes, the offset
+// into the string table is stored in the last 4 bytes instead, leaving
+// the first 4 bytes as 0.
+void COFFSymbol::set_name_offset(uint32_t Offset) {
+  write_uint32_le(Data.Name + 0, 0);
+  write_uint32_le(Data.Name + 4, Offset);
+}
+
+//------------------------------------------------------------------------------
+// Section class implementation
+
+COFFSection::COFFSection(llvm::StringRef name, size_t Index)
+       : Name(name), Number(Index + 1)
+       , MCData(NULL), Symb(NULL) {
+  memset(&Header, 0, sizeof(Header));
+}
+
+size_t COFFSection::size() {
+  return COFF::SectionSize;
+}
+
+//------------------------------------------------------------------------------
+// StringTable class implementation
+
+/// Write the length of the string table into Data.
+/// The length of the string table includes uint32 length header.
+void StringTable::update_length() {
+  write_uint32_le(&Data.front(), Data.size());
+}
+
+StringTable::StringTable() {
+  // The string table data begins with the length of the entire string table
+  // including the length header. Allocate space for this header.
+  Data.resize(4);
+}
+
+size_t StringTable::size() const {
+  return Data.size();
+}
+
+/// Add String to the table iff it is not already there.
+/// @returns the index into the string table where the string is now located.
+size_t StringTable::insert(llvm::StringRef String) {
+  map::iterator i = Map.find(String);
+
+  if (i != Map.end())
+    return i->second;
+
+  size_t Offset = Data.size();
+
+  // Insert string data into string table.
+  Data.insert(Data.end(), String.begin(), String.end());
+  Data.push_back('\0');
+
+  // Put a reference to it in the map.
+  Map[String] = Offset;
+
+  // Update the internal length field.
+  update_length();
+
+  return Offset;
+}
+
+//------------------------------------------------------------------------------
+// WinCOFFObjectWriter class implementation
+
 WinCOFFObjectWriter::WinCOFFObjectWriter(raw_ostream &OS)
                                 : MCObjectWriter(OS, true) {
+  memset(&Header, 0, sizeof(Header));
+  // TODO: Move magic constant out to COFF.h
+  Header.Machine = 0x14C; // x86
+}
+
+COFFSymbol *WinCOFFObjectWriter::createSymbol(llvm::StringRef Name) {
+  return createCOFFEntity<COFFSymbol>(Name, Symbols);
+}
+
+COFFSection *WinCOFFObjectWriter::createSection(llvm::StringRef Name) {
+  return createCOFFEntity<COFFSection>(Name, Sections);
+}
+
+/// This function initializes a symbol by entering its name into the string
+/// table if it is too long to fit in the symbol table header.
+void WinCOFFObjectWriter::InitCOFFEntity(COFFSymbol &S) {
+  if (S.Name.size() > COFF::NameSize) {
+    size_t StringTableEntry = Strings.insert(S.Name.c_str());
+
+    S.set_name_offset(StringTableEntry);
+  } else
+    memcpy(S.Data.Name, S.Name.c_str(), S.Name.size());
+}
+
+/// This function initializes a section by entering its name into the string
+/// table if it is too long to fit in the section table header.
+void WinCOFFObjectWriter::InitCOFFEntity(COFFSection &S) {
+  if (S.Name.size() > COFF::NameSize) {
+    size_t StringTableEntry = Strings.insert(S.Name.c_str());
+
+    // FIXME: Why is this number 999999? This number is never mentioned in the
+    // spec. I'm assuming this is due to the printed value needing to fit into
+    // the S.Header.Name field. In which case why not 9999999 (7 9's instead of
+    // 6)? The spec does not state if this entry should be null terminated in
+    // this case, and thus this seems to be the best way to do it. I think I
+    // just solved my own FIXME...
+    if (StringTableEntry > 999999)
+      report_fatal_error("COFF string table is greater than 999999 bytes.");
+
+    sprintf(S.Header.Name, "/%d", StringTableEntry);
+  } else
+    memcpy(S.Header.Name, S.Name.c_str(), S.Name.size());
+}
+
+/// A template used to lookup or create a symbol/section, and initialize it if
+/// needed.
+template <typename object_t, typename list_t>
+object_t *WinCOFFObjectWriter::createCOFFEntity(llvm::StringRef Name,
+                                                list_t &List) {
+  object_t *Object = new object_t(Name, List.size());
+
+  InitCOFFEntity(*Object);
+
+  List.push_back(Object);
+
+  return Object;
+}
+
+/// This function takes a section data object from the assembler
+/// and creates the associated COFF section staging object.
+void WinCOFFObjectWriter::DefineSection(MCSectionData const &SectionData) {
+  // FIXME: Not sure how to verify this (at least in a debug build).
+  MCSectionCOFF const &Sec =
+    static_cast<MCSectionCOFF const &>(SectionData.getSection());
+
+  COFFSection *coff_section = createSection(Sec.getSectionName());
+  COFFSymbol  *coff_symbol = createSymbol(Sec.getSectionName());
+
+  coff_section->Symb = coff_symbol;
+  coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_STATIC;
+  coff_symbol->Data.SectionNumber = coff_section->Number;
+
+  // In this case the auxiliary symbol is a Section Definition.
+  coff_symbol->Aux.resize(1);
+  memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
+  coff_symbol->Aux[0].AuxType = ATSectionDefinition;
+  coff_symbol->Aux[0].Aux.SectionDefinition.Number = coff_section->Number;
+  coff_symbol->Aux[0].Aux.SectionDefinition.Selection = Sec.getSelection();
+
+  coff_section->Header.Characteristics = Sec.getCharacteristics();
+
+  uint32_t &Characteristics = coff_section->Header.Characteristics;
+  switch (SectionData.getAlignment()) {
+  case 1:    Characteristics |= COFF::IMAGE_SCN_ALIGN_1BYTES;    break;
+  case 2:    Characteristics |= COFF::IMAGE_SCN_ALIGN_2BYTES;    break;
+  case 4:    Characteristics |= COFF::IMAGE_SCN_ALIGN_4BYTES;    break;
+  case 8:    Characteristics |= COFF::IMAGE_SCN_ALIGN_8BYTES;    break;
+  case 16:   Characteristics |= COFF::IMAGE_SCN_ALIGN_16BYTES;   break;
+  case 32:   Characteristics |= COFF::IMAGE_SCN_ALIGN_32BYTES;   break;
+  case 64:   Characteristics |= COFF::IMAGE_SCN_ALIGN_64BYTES;   break;
+  case 128:  Characteristics |= COFF::IMAGE_SCN_ALIGN_128BYTES;  break;
+  case 256:  Characteristics |= COFF::IMAGE_SCN_ALIGN_256BYTES;  break;
+  case 512:  Characteristics |= COFF::IMAGE_SCN_ALIGN_512BYTES;  break;
+  case 1024: Characteristics |= COFF::IMAGE_SCN_ALIGN_1024BYTES; break;
+  case 2048: Characteristics |= COFF::IMAGE_SCN_ALIGN_2048BYTES; break;
+  case 4096: Characteristics |= COFF::IMAGE_SCN_ALIGN_4096BYTES; break;
+  case 8192: Characteristics |= COFF::IMAGE_SCN_ALIGN_8192BYTES; break;
+  default:
+    llvm_unreachable("unsupported section alignment");
+  }
+
+  // Bind internal COFF section to MC section.
+  coff_section->MCData = &SectionData;
+  SectionMap[&SectionData] = coff_section;
+}
+
+/// This function takes a section data object from the assembler
+/// and creates the associated COFF symbol staging object.
+void WinCOFFObjectWriter::DefineSymbol(MCSymbolData const &SymbolData,
+                                        MCAssembler &Assembler) {
+  COFFSymbol *coff_symbol = createSymbol(SymbolData.getSymbol().getName());
+
+  coff_symbol->Data.Type         = (SymbolData.getFlags() & 0x0000FFFF) >>  0;
+  coff_symbol->Data.StorageClass = (SymbolData.getFlags() & 0x00FF0000) >> 16;
+
+  // If no storage class was specified in the streamer, define it here.
+  if (coff_symbol->Data.StorageClass == 0) {
+    bool external = SymbolData.isExternal() || (SymbolData.Fragment == NULL);
+
+    coff_symbol->Data.StorageClass =
+      external ? COFF::IMAGE_SYM_CLASS_EXTERNAL : COFF::IMAGE_SYM_CLASS_STATIC;
+  }
+
+  if (SymbolData.getFlags() & COFF::SF_WeakReference) {
+    coff_symbol->Data.StorageClass = COFF::IMAGE_SYM_CLASS_WEAK_EXTERNAL;
+
+    const MCExpr *Value = SymbolData.getSymbol().getVariableValue();
+
+    // FIXME: This assert message isn't very good.
+    assert(Value->getKind() == MCExpr::SymbolRef &&
+           "Value must be a SymbolRef!");
+
+    const MCSymbolRefExpr *SymbolRef =
+      static_cast<const MCSymbolRefExpr *>(Value);
+
+    const MCSymbolData &OtherSymbolData =
+      Assembler.getSymbolData(SymbolRef->getSymbol());
+
+    // FIXME: This assert message isn't very good.
+    assert(SymbolMap.find(&OtherSymbolData) != SymbolMap.end() &&
+           "OtherSymbolData must be in the symbol map!");
+
+    coff_symbol->Other = SymbolMap[&OtherSymbolData];
+
+    // Setup the Weak External auxiliary symbol.
+    coff_symbol->Aux.resize(1);
+    memset(&coff_symbol->Aux[0], 0, sizeof(coff_symbol->Aux[0]));
+    coff_symbol->Aux[0].AuxType = ATWeakExternal;
+    coff_symbol->Aux[0].Aux.WeakExternal.TagIndex = 0;
+    coff_symbol->Aux[0].Aux.WeakExternal.Characteristics =
+                                        COFF::IMAGE_WEAK_EXTERN_SEARCH_LIBRARY;
+  }
+
+  // Bind internal COFF symbol to MC symbol.
+  coff_symbol->MCData = &SymbolData;
+  SymbolMap[&SymbolData] = coff_symbol;
+}
+
+bool WinCOFFObjectWriter::ExportSection(COFFSection *S) {
+  return (S->Header.Characteristics
+         & COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA) == 0;
+}
+
+bool WinCOFFObjectWriter::ExportSymbol(MCSymbolData const &SymbolData,
+                                       MCAssembler &Asm) {
+  // This doesn't seem to be right. Strings referred to from the .data section
+  // need symbols so they can be linked to code in the .text section right?
+
+  // return Asm.isSymbolLinkerVisible (&SymbolData);
+
+  // For now, all symbols are exported, the linker will sort it out for us.
+  return true;
+}
+
+//------------------------------------------------------------------------------
+// entity writing methods
+
+void WinCOFFObjectWriter::WriteFileHeader(const COFF::header &Header) {
+  WriteLE16(Header.Machine);
+  WriteLE16(Header.NumberOfSections);
+  WriteLE32(Header.TimeDateStamp);
+  WriteLE32(Header.PointerToSymbolTable);
+  WriteLE32(Header.NumberOfSymbols);
+  WriteLE16(Header.SizeOfOptionalHeader);
+  WriteLE16(Header.Characteristics);
+}
+
+void WinCOFFObjectWriter::WriteSymbol(const COFFSymbol *S) {
+  WriteBytes(StringRef(S->Data.Name, COFF::NameSize));
+  WriteLE32(S->Data.Value);
+  WriteLE16(S->Data.SectionNumber);
+  WriteLE16(S->Data.Type);
+  Write8(S->Data.StorageClass);
+  Write8(S->Data.NumberOfAuxSymbols);
+  WriteAuxiliarySymbols(S->Aux);
+}
+
+void WinCOFFObjectWriter::WriteAuxiliarySymbols(
+                                        const COFFSymbol::AuxiliarySymbols &S) {
+  for(COFFSymbol::AuxiliarySymbols::const_iterator i = S.begin(), e = S.end();
+      i != e; ++i) {
+    switch(i->AuxType) {
+    case ATFunctionDefinition:
+      WriteLE32(i->Aux.FunctionDefinition.TagIndex);
+      WriteLE32(i->Aux.FunctionDefinition.TotalSize);
+      WriteLE32(i->Aux.FunctionDefinition.PointerToLinenumber);
+      WriteLE32(i->Aux.FunctionDefinition.PointerToNextFunction);
+      WriteZeros(sizeof(i->Aux.FunctionDefinition.unused));
+      break;
+    case ATbfAndefSymbol:
+      WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused1));
+      WriteLE16(i->Aux.bfAndefSymbol.Linenumber);
+      WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused2));
+      WriteLE32(i->Aux.bfAndefSymbol.PointerToNextFunction);
+      WriteZeros(sizeof(i->Aux.bfAndefSymbol.unused3));
+      break;
+    case ATWeakExternal:
+      WriteLE32(i->Aux.WeakExternal.TagIndex);
+      WriteLE32(i->Aux.WeakExternal.Characteristics);
+      WriteZeros(sizeof(i->Aux.WeakExternal.unused));
+      break;
+    case ATFile:
+      WriteBytes(StringRef(reinterpret_cast<const char *>(i->Aux.File.FileName),
+                 sizeof(i->Aux.File.FileName)));
+      break;
+    case ATSectionDefinition:
+      WriteLE32(i->Aux.SectionDefinition.Length);
+      WriteLE16(i->Aux.SectionDefinition.NumberOfRelocations);
+      WriteLE16(i->Aux.SectionDefinition.NumberOfLinenumbers);
+      WriteLE32(i->Aux.SectionDefinition.CheckSum);
+      WriteLE16(i->Aux.SectionDefinition.Number);
+      Write8(i->Aux.SectionDefinition.Selection);
+      WriteZeros(sizeof(i->Aux.SectionDefinition.unused));
+      break;
+    }
+  }
+}
+
+void WinCOFFObjectWriter::WriteSectionHeader(const COFF::section &S) {
+  WriteBytes(StringRef(S.Name, COFF::NameSize));
+
+  WriteLE32(S.VirtualSize);
+  WriteLE32(S.VirtualAddress);
+  WriteLE32(S.SizeOfRawData);
+  WriteLE32(S.PointerToRawData);
+  WriteLE32(S.PointerToRelocations);
+  WriteLE32(S.PointerToLineNumbers);
+  WriteLE16(S.NumberOfRelocations);
+  WriteLE16(S.NumberOfLineNumbers);
+  WriteLE32(S.Characteristics);
+}
+
+void WinCOFFObjectWriter::WriteRelocation(const COFF::relocation &R) {
+  WriteLE32(R.VirtualAddress);
+  WriteLE32(R.SymbolTableIndex);
+  WriteLE16(R.Type);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // MCObjectWriter interface implementations
 
 void WinCOFFObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm) {
+  // "Define" each section & symbol. This creates section & symbol
+  // entries in the staging area and gives them their final indexes.
+
+  for (MCAssembler::const_iterator i = Asm.begin(), e = Asm.end(); i != e; i++)
+    DefineSection(*i);
+
+  for (MCAssembler::const_symbol_iterator i = Asm.symbol_begin(),
+                                          e = Asm.symbol_end(); i != e; i++) {
+    if (ExportSymbol(*i, Asm))
+      DefineSymbol(*i, Asm);
+  }
 }
 
 void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
@@ -55,10 +551,174 @@ void WinCOFFObjectWriter::RecordRelocation(const MCAssembler &Asm,
                                            const MCFixup &Fixup,
                                            MCValue Target,
                                            uint64_t &FixedValue) {
+  assert(Target.getSymA() != NULL && "Relocation must reference a symbol!");
+  assert(Target.getSymB() == NULL &&
+         "Relocation must reference only one symbol!");
+
+  MCSectionData const *SectionData = Fragment->getParent();
+  MCSymbolData const *SymbolData =
+                              &Asm.getSymbolData(Target.getSymA()->getSymbol());
+
+  assert(SectionMap.find(SectionData) != SectionMap.end() &&
+         "Section must already have been defined in ExecutePostLayoutBinding!");
+  assert(SymbolMap.find(SymbolData) != SymbolMap.end() &&
+         "Symbol must already have been defined in ExecutePostLayoutBinding!");
+
+  COFFSection *coff_section = SectionMap[SectionData];
+  COFFSymbol *coff_symbol = SymbolMap[SymbolData];
+
+  FixedValue = Target.getConstant();
+
+  COFFRelocation Reloc;
+
+  Reloc.Data.VirtualAddress = Layout.getFragmentOffset(Fragment);
+  Reloc.Symb = coff_symbol;
+
+  Reloc.Data.VirtualAddress += Fixup.getOffset();
+
+  switch (Fixup.getKind()) {
+  case FirstTargetFixupKind: // reloc_pcrel_4byte
+    Reloc.Data.Type = COFF::IMAGE_REL_I386_REL32;
+    FixedValue += 4;
+    break;
+  case FK_Data_4:
+    Reloc.Data.Type = COFF::IMAGE_REL_I386_DIR32;
+    break;
+  default:
+    llvm_unreachable("unsupported relocation type");
+  }
+
+  coff_section->Relocations.push_back(Reloc);
 }
 
 void WinCOFFObjectWriter::WriteObject(const MCAssembler &Asm,
                                       const MCAsmLayout &Layout) {
+  // Assign symbol and section indexes and offsets.
+
+  Header.NumberOfSymbols = 0;
+
+  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
+    COFFSymbol *coff_symbol = *i;
+    MCSymbolData const *SymbolData = coff_symbol->MCData;
+
+    coff_symbol->Index = Header.NumberOfSymbols++;
+
+    // Update section number & offset for symbols that have them.
+    if ((SymbolData != NULL) && (SymbolData->Fragment != NULL)) {
+      COFFSection *coff_section = SectionMap[SymbolData->Fragment->getParent()];
+
+      coff_symbol->Data.SectionNumber = coff_section->Number;
+      coff_symbol->Data.Value = Layout.getFragmentOffset(SymbolData->Fragment);
+    }
+
+    // Update auxiliary symbol info.
+    coff_symbol->Data.NumberOfAuxSymbols = coff_symbol->Aux.size();
+    Header.NumberOfSymbols += coff_symbol->Data.NumberOfAuxSymbols;
+  }
+
+  // Fixup weak external references.
+  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++) {
+    COFFSymbol *symb = *i;
+
+    if (symb->Other != NULL) {
+      assert(symb->Aux.size() == 1 &&
+             "Symbol must contain one aux symbol!");
+      assert(symb->Aux[0].AuxType == ATWeakExternal &&
+             "Symbol's aux symbol must be a Weak External!");
+      symb->Aux[0].Aux.WeakExternal.TagIndex = symb->Other->Index;
+    }
+  }
+
+  // Assign file offsets to COFF object file structures.
+
+  unsigned offset = 0;
+
+  offset += COFF::HeaderSize;
+  offset += COFF::SectionSize * Asm.size();
+
+  Header.NumberOfSections = Sections.size();
+
+  for (MCAssembler::const_iterator i = Asm.begin(),
+                                   e = Asm.end();
+                                   i != e; i++) {
+    COFFSection *Sec = SectionMap[i];
+
+    Sec->Header.SizeOfRawData = Layout.getSectionFileSize(i);
+
+    if (ExportSection(Sec)) {
+      Sec->Header.PointerToRawData = offset;
+
+      offset += Sec->Header.SizeOfRawData;
+    }
+
+    if (Sec->Relocations.size() > 0) {
+      Sec->Header.NumberOfRelocations = Sec->Relocations.size();
+      Sec->Header.PointerToRelocations = offset;
+
+      offset += COFF::RelocationSize * Sec->Relocations.size();
+
+      for (relocations::iterator cr = Sec->Relocations.begin(),
+                                 er = Sec->Relocations.end();
+                                 cr != er; cr++) {
+        (*cr).Data.SymbolTableIndex = (*cr).Symb->Index;
+      }
+    }
+
+    assert(Sec->Symb->Aux.size() == 1 && "Section's symbol must have one aux!");
+    AuxSymbol &Aux = Sec->Symb->Aux[0];
+    assert(Aux.AuxType == ATSectionDefinition &&
+           "Section's symbol's aux symbol must be a Section Definition!");
+    Aux.Aux.SectionDefinition.Length = Sec->Header.SizeOfRawData;
+    Aux.Aux.SectionDefinition.NumberOfRelocations =
+                                                Sec->Header.NumberOfRelocations;
+    Aux.Aux.SectionDefinition.NumberOfLinenumbers =
+                                                Sec->Header.NumberOfLineNumbers;
+  }
+
+  Header.PointerToSymbolTable = offset;
+
+  // Write it all to disk...
+  WriteFileHeader(Header);
+
+  {
+    sections::iterator i, ie;
+    MCAssembler::const_iterator j, je;
+
+    for (i = Sections.begin(), ie = Sections.end(); i != ie; i++)
+      WriteSectionHeader((*i)->Header);
+
+    for (i = Sections.begin(), ie = Sections.end(),
+         j = Asm.begin(), je = Asm.end();
+         (i != ie) && (j != je); i++, j++) {
+      if ((*i)->Header.PointerToRawData != 0) {
+        assert(OS.tell() == (*i)->Header.PointerToRawData &&
+               "Section::PointerToRawData is insane!");
+
+        Asm.WriteSectionData(j, Layout, this);
+      }
+
+      if ((*i)->Relocations.size() > 0) {
+        assert(OS.tell() == (*i)->Header.PointerToRelocations &&
+               "Section::PointerToRelocations is insane!");
+
+        for (relocations::const_iterator k = (*i)->Relocations.begin(),
+                                               ke = (*i)->Relocations.end();
+                                               k != ke; k++) {
+          WriteRelocation(k->Data);
+        }
+      } else
+        assert((*i)->Header.PointerToRelocations == 0 &&
+               "Section::PointerToRelocations is insane!");
+    }
+  }
+
+  assert(OS.tell() == Header.PointerToSymbolTable &&
+         "Header::PointerToSymbolTable is insane!");
+
+  for (symbols::iterator i = Symbols.begin(), e = Symbols.end(); i != e; i++)
+    WriteSymbol(*i);
+
+  OS.write((char const *)&Strings.Data.front(), Strings.Data.size());
 }
 
 //------------------------------------------------------------------------------
@@ -68,4 +728,4 @@ namespace llvm {
   MCObjectWriter *createWinCOFFObjectWriter(raw_ostream &OS) {
     return new WinCOFFObjectWriter(OS);
   }
-}
+}
\ No newline at end of file