It's not necessary to do rounding for alloca operations when the requested

alignment is equal to the stack alignment.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 945 insertions, 0 deletions

diff --git a/lib/CodeGen/MachOWriter.cpp b/lib/CodeGen/MachOWriter.cpp
new file mode 100644
index 0000000..36060e1
--- /dev/null
+++ b/lib/CodeGen/MachOWriter.cpp
@@ -0,0 +1,945 @@
+//===-- MachOWriter.cpp - Target-independent Mach-O Writer code -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Nate Begeman and is distributed under the
+// University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the target-independent Mach-O writer.  This file writes
+// out the Mach-O file in the following order:
+//
+//  #1 FatHeader (universal-only)
+//  #2 FatArch (universal-only, 1 per universal arch)
+//  Per arch:
+//    #3 Header
+//    #4 Load Commands
+//    #5 Sections
+//    #6 Relocations
+//    #7 Symbols
+//    #8 Strings
+//
+//===----------------------------------------------------------------------===//
+
+#include "MachOWriter.h"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Module.h"
+#include "llvm/PassManager.h"
+#include "llvm/CodeGen/FileWriters.h"
+#include "llvm/CodeGen/MachineCodeEmitter.h"
+#include "llvm/CodeGen/MachineConstantPool.h"
+#include "llvm/CodeGen/MachineJumpTableInfo.h"
+#include "llvm/Target/TargetAsmInfo.h"
+#include "llvm/Target/TargetJITInfo.h"
+#include "llvm/Support/Mangler.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/OutputBuffer.h"
+#include "llvm/Support/Streams.h"
+#include <algorithm>
+using namespace llvm;
+
+/// AddMachOWriter - Concrete function to add the Mach-O writer to the function
+/// pass manager.
+MachineCodeEmitter *llvm::AddMachOWriter(FunctionPassManager &FPM,
+                                         std::ostream &O,
+                                         TargetMachine &TM) {
+  MachOWriter *MOW = new MachOWriter(O, TM);
+  FPM.add(MOW);
+  return &MOW->getMachineCodeEmitter();
+}
+
+//===----------------------------------------------------------------------===//
+//                       MachOCodeEmitter Implementation
+//===----------------------------------------------------------------------===//
+
+namespace llvm {
+  /// MachOCodeEmitter - This class is used by the MachOWriter to emit the code 
+  /// for functions to the Mach-O file.
+  class MachOCodeEmitter : public MachineCodeEmitter {
+    MachOWriter &MOW;
+
+    /// Target machine description.
+    TargetMachine &TM;
+
+    /// is64Bit/isLittleEndian - This information is inferred from the target
+    /// machine directly, indicating what header values and flags to set.
+    bool is64Bit, isLittleEndian;
+
+    /// Relocations - These are the relocations that the function needs, as
+    /// emitted.
+    std::vector<MachineRelocation> Relocations;
+    
+    /// CPLocations - This is a map of constant pool indices to offsets from the
+    /// start of the section for that constant pool index.
+    std::vector<intptr_t> CPLocations;
+
+    /// CPSections - This is a map of constant pool indices to the MachOSection
+    /// containing the constant pool entry for that index.
+    std::vector<unsigned> CPSections;
+
+    /// JTLocations - This is a map of jump table indices to offsets from the
+    /// start of the section for that jump table index.
+    std::vector<intptr_t> JTLocations;
+
+    /// MBBLocations - This vector is a mapping from MBB ID's to their address.
+    /// It is filled in by the StartMachineBasicBlock callback and queried by
+    /// the getMachineBasicBlockAddress callback.
+    std::vector<intptr_t> MBBLocations;
+    
+  public:
+    MachOCodeEmitter(MachOWriter &mow) : MOW(mow), TM(MOW.TM) {
+      is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
+      isLittleEndian = TM.getTargetData()->isLittleEndian();
+    }
+
+    virtual void startFunction(MachineFunction &MF);
+    virtual bool finishFunction(MachineFunction &MF);
+
+    virtual void addRelocation(const MachineRelocation &MR) {
+      Relocations.push_back(MR);
+    }
+    
+    void emitConstantPool(MachineConstantPool *MCP);
+    void emitJumpTables(MachineJumpTableInfo *MJTI);
+    
+    virtual intptr_t getConstantPoolEntryAddress(unsigned Index) const {
+      assert(CPLocations.size() > Index && "CP not emitted!");
+      return CPLocations[Index];
+    }
+    virtual intptr_t getJumpTableEntryAddress(unsigned Index) const {
+      assert(JTLocations.size() > Index && "JT not emitted!");
+      return JTLocations[Index];
+    }
+
+    virtual void StartMachineBasicBlock(MachineBasicBlock *MBB) {
+      if (MBBLocations.size() <= (unsigned)MBB->getNumber())
+        MBBLocations.resize((MBB->getNumber()+1)*2);
+      MBBLocations[MBB->getNumber()] = getCurrentPCOffset();
+    }
+
+    virtual intptr_t getMachineBasicBlockAddress(MachineBasicBlock *MBB) const {
+      assert(MBBLocations.size() > (unsigned)MBB->getNumber() && 
+             MBBLocations[MBB->getNumber()] && "MBB not emitted!");
+      return MBBLocations[MBB->getNumber()];
+    }
+
+    /// JIT SPECIFIC FUNCTIONS - DO NOT IMPLEMENT THESE HERE!
+    virtual void startFunctionStub(unsigned StubSize, unsigned Alignment = 1) {
+      assert(0 && "JIT specific function called!");
+      abort();
+    }
+    virtual void *finishFunctionStub(const Function *F) {
+      assert(0 && "JIT specific function called!");
+      abort();
+      return 0;
+    }
+  };
+}
+
+/// startFunction - This callback is invoked when a new machine function is
+/// about to be emitted.
+void MachOCodeEmitter::startFunction(MachineFunction &MF) {
+  const TargetData *TD = TM.getTargetData();
+  const Function *F = MF.getFunction();
+
+  // Align the output buffer to the appropriate alignment, power of 2.
+  unsigned FnAlign = F->getAlignment();
+  unsigned TDAlign = TD->getPrefTypeAlignment(F->getType());
+  unsigned Align = Log2_32(std::max(FnAlign, TDAlign));
+  assert(!(Align & (Align-1)) && "Alignment is not a power of two!");
+
+  // Get the Mach-O Section that this function belongs in.
+  MachOWriter::MachOSection *MOS = MOW.getTextSection();
+  
+  // FIXME: better memory management
+  MOS->SectionData.reserve(4096);
+  BufferBegin = &MOS->SectionData[0];
+  BufferEnd = BufferBegin + MOS->SectionData.capacity();
+
+  // Upgrade the section alignment if required.
+  if (MOS->align < Align) MOS->align = Align;
+
+  // Round the size up to the correct alignment for starting the new function.
+  if ((MOS->size & ((1 << Align) - 1)) != 0) {
+    MOS->size += (1 << Align);
+    MOS->size &= ~((1 << Align) - 1);
+  }
+
+  // FIXME: Using MOS->size directly here instead of calculating it from the
+  // output buffer size (impossible because the code emitter deals only in raw
+  // bytes) forces us to manually synchronize size and write padding zero bytes
+  // to the output buffer for all non-text sections.  For text sections, we do
+  // not synchonize the output buffer, and we just blow up if anyone tries to
+  // write non-code to it.  An assert should probably be added to
+  // AddSymbolToSection to prevent calling it on the text section.
+  CurBufferPtr = BufferBegin + MOS->size;
+
+  // Clear per-function data structures.
+  CPLocations.clear();
+  CPSections.clear();
+  JTLocations.clear();
+  MBBLocations.clear();
+}
+
+/// finishFunction - This callback is invoked after the function is completely
+/// finished.
+bool MachOCodeEmitter::finishFunction(MachineFunction &MF) {
+  // Get the Mach-O Section that this function belongs in.
+  MachOWriter::MachOSection *MOS = MOW.getTextSection();
+
+  // Get a symbol for the function to add to the symbol table
+  // FIXME: it seems like we should call something like AddSymbolToSection
+  // in startFunction rather than changing the section size and symbol n_value
+  // here.
+  const GlobalValue *FuncV = MF.getFunction();
+  MachOSym FnSym(FuncV, MOW.Mang->getValueName(FuncV), MOS->Index, TM);
+  FnSym.n_value = MOS->size;
+  MOS->size = CurBufferPtr - BufferBegin;
+  
+  // Emit constant pool to appropriate section(s)
+  emitConstantPool(MF.getConstantPool());
+
+  // Emit jump tables to appropriate section
+  emitJumpTables(MF.getJumpTableInfo());
+  
+  // If we have emitted any relocations to function-specific objects such as 
+  // basic blocks, constant pools entries, or jump tables, record their
+  // addresses now so that we can rewrite them with the correct addresses
+  // later.
+  for (unsigned i = 0, e = Relocations.size(); i != e; ++i) {
+    MachineRelocation &MR = Relocations[i];
+    intptr_t Addr;
+
+    if (MR.isBasicBlock()) {
+      Addr = getMachineBasicBlockAddress(MR.getBasicBlock());
+      MR.setConstantVal(MOS->Index);
+      MR.setResultPointer((void*)Addr);
+    } else if (MR.isJumpTableIndex()) {
+      Addr = getJumpTableEntryAddress(MR.getJumpTableIndex());
+      MR.setConstantVal(MOW.getJumpTableSection()->Index);
+      MR.setResultPointer((void*)Addr);
+    } else if (MR.isConstantPoolIndex()) {
+      Addr = getConstantPoolEntryAddress(MR.getConstantPoolIndex());
+      MR.setConstantVal(CPSections[MR.getConstantPoolIndex()]);
+      MR.setResultPointer((void*)Addr);
+    } else if (MR.isGlobalValue()) {
+      // FIXME: This should be a set or something that uniques
+      MOW.PendingGlobals.push_back(MR.getGlobalValue());
+    } else {
+      assert(0 && "Unhandled relocation type");
+    }
+    MOS->Relocations.push_back(MR);
+  }
+  Relocations.clear();
+  
+  // Finally, add it to the symtab.
+  MOW.SymbolTable.push_back(FnSym);
+  return false;
+}
+
+/// emitConstantPool - For each constant pool entry, figure out which section
+/// the constant should live in, allocate space for it, and emit it to the 
+/// Section data buffer.
+void MachOCodeEmitter::emitConstantPool(MachineConstantPool *MCP) {
+  const std::vector<MachineConstantPoolEntry> &CP = MCP->getConstants();
+  if (CP.empty()) return;
+
+  // FIXME: handle PIC codegen
+  bool isPIC = TM.getRelocationModel() == Reloc::PIC_;
+  assert(!isPIC && "PIC codegen not yet handled for mach-o jump tables!");
+
+  // Although there is no strict necessity that I am aware of, we will do what
+  // gcc for OS X does and put each constant pool entry in a section of constant
+  // objects of a certain size.  That means that float constants go in the
+  // literal4 section, and double objects go in literal8, etc.
+  //
+  // FIXME: revisit this decision if we ever do the "stick everything into one
+  // "giant object for PIC" optimization.
+  for (unsigned i = 0, e = CP.size(); i != e; ++i) {
+    const Type *Ty = CP[i].getType();
+    unsigned Size = TM.getTargetData()->getTypeSize(Ty);
+
+    MachOWriter::MachOSection *Sec = MOW.getConstSection(CP[i].Val.ConstVal);
+    OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);
+
+    CPLocations.push_back(Sec->SectionData.size());
+    CPSections.push_back(Sec->Index);
+    
+    // FIXME: remove when we have unified size + output buffer
+    Sec->size += Size;
+
+    // Allocate space in the section for the global.
+    // FIXME: need alignment?
+    // FIXME: share between here and AddSymbolToSection?
+    for (unsigned j = 0; j < Size; ++j)
+      SecDataOut.outbyte(0);
+
+    MOW.InitMem(CP[i].Val.ConstVal, &Sec->SectionData[0], CPLocations[i],
+                TM.getTargetData(), Sec->Relocations);
+  }
+}
+
+/// emitJumpTables - Emit all the jump tables for a given jump table info
+/// record to the appropriate section.
+void MachOCodeEmitter::emitJumpTables(MachineJumpTableInfo *MJTI) {
+  const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
+  if (JT.empty()) return;
+
+  // FIXME: handle PIC codegen
+  bool isPIC = TM.getRelocationModel() == Reloc::PIC_;
+  assert(!isPIC && "PIC codegen not yet handled for mach-o jump tables!");
+
+  MachOWriter::MachOSection *Sec = MOW.getJumpTableSection();
+  unsigned TextSecIndex = MOW.getTextSection()->Index;
+  OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);
+
+  for (unsigned i = 0, e = JT.size(); i != e; ++i) {
+    // For each jump table, record its offset from the start of the section,
+    // reserve space for the relocations to the MBBs, and add the relocations.
+    const std::vector<MachineBasicBlock*> &MBBs = JT[i].MBBs;
+    JTLocations.push_back(Sec->SectionData.size());
+    for (unsigned mi = 0, me = MBBs.size(); mi != me; ++mi) {
+      MachineRelocation MR(MOW.GetJTRelocation(Sec->SectionData.size(),
+                                               MBBs[mi]));
+      MR.setResultPointer((void *)JTLocations[i]);
+      MR.setConstantVal(TextSecIndex);
+      Sec->Relocations.push_back(MR);
+      SecDataOut.outaddr(0);
+    }
+  }
+  // FIXME: remove when we have unified size + output buffer
+  Sec->size = Sec->SectionData.size();
+}
+
+//===----------------------------------------------------------------------===//
+//                          MachOWriter Implementation
+//===----------------------------------------------------------------------===//
+
+char MachOWriter::ID = 0;
+MachOWriter::MachOWriter(std::ostream &o, TargetMachine &tm) 
+  : MachineFunctionPass((intptr_t)&ID), O(o), TM(tm) {
+  is64Bit = TM.getTargetData()->getPointerSizeInBits() == 64;
+  isLittleEndian = TM.getTargetData()->isLittleEndian();
+
+  // Create the machine code emitter object for this target.
+  MCE = new MachOCodeEmitter(*this);
+}
+
+MachOWriter::~MachOWriter() {
+  delete MCE;
+}
+
+void MachOWriter::AddSymbolToSection(MachOSection *Sec, GlobalVariable *GV) {
+  const Type *Ty = GV->getType()->getElementType();
+  unsigned Size = TM.getTargetData()->getTypeSize(Ty);
+  unsigned Align = GV->getAlignment();
+  if (Align == 0)
+    Align = TM.getTargetData()->getPrefTypeAlignment(Ty);
+  
+  // Reserve space in the .bss section for this symbol while maintaining the
+  // desired section alignment, which must be at least as much as required by
+  // this symbol.
+  OutputBuffer SecDataOut(Sec->SectionData, is64Bit, isLittleEndian);
+
+  if (Align) {
+    uint64_t OrigSize = Sec->size;
+    Align = Log2_32(Align);
+    Sec->align = std::max(unsigned(Sec->align), Align);
+    Sec->size = (Sec->size + Align - 1) & ~(Align-1);
+    
+    // Add alignment padding to buffer as well.
+    // FIXME: remove when we have unified size + output buffer
+    unsigned AlignedSize = Sec->size - OrigSize;
+    for (unsigned i = 0; i < AlignedSize; ++i)
+      SecDataOut.outbyte(0);
+  }
+  // Globals without external linkage apparently do not go in the symbol table.
+  if (GV->getLinkage() != GlobalValue::InternalLinkage) {
+    MachOSym Sym(GV, Mang->getValueName(GV), Sec->Index, TM);
+    Sym.n_value = Sec->size;
+    SymbolTable.push_back(Sym);
+  }
+
+  // Record the offset of the symbol, and then allocate space for it.
+  // FIXME: remove when we have unified size + output buffer
+  Sec->size += Size;
+  
+  // Now that we know what section the GlovalVariable is going to be emitted 
+  // into, update our mappings.
+  // FIXME: We may also need to update this when outputting non-GlobalVariable
+  // GlobalValues such as functions.
+  GVSection[GV] = Sec;
+  GVOffset[GV] = Sec->SectionData.size();
+  
+  // Allocate space in the section for the global.
+  for (unsigned i = 0; i < Size; ++i)
+    SecDataOut.outbyte(0);
+}
+
+void MachOWriter::EmitGlobal(GlobalVariable *GV) {
+  const Type *Ty = GV->getType()->getElementType();
+  unsigned Size = TM.getTargetData()->getTypeSize(Ty);
+  bool NoInit = !GV->hasInitializer();
+  
+  // If this global has a zero initializer, it is part of the .bss or common
+  // section.
+  if (NoInit || GV->getInitializer()->isNullValue()) {
+    // If this global is part of the common block, add it now.  Variables are
+    // part of the common block if they are zero initialized and allowed to be
+    // merged with other symbols.
+    if (NoInit || GV->hasLinkOnceLinkage() || GV->hasWeakLinkage()) {
+      MachOSym ExtOrCommonSym(GV, Mang->getValueName(GV), MachOSym::NO_SECT,TM);
+      // For undefined (N_UNDF) external (N_EXT) types, n_value is the size in
+      // bytes of the symbol.
+      ExtOrCommonSym.n_value = Size;
+      SymbolTable.push_back(ExtOrCommonSym);
+      // Remember that we've seen this symbol
+      GVOffset[GV] = Size;
+      return;
+    }
+    // Otherwise, this symbol is part of the .bss section.
+    MachOSection *BSS = getBSSSection();
+    AddSymbolToSection(BSS, GV);
+    return;
+  }
+  
+  // Scalar read-only data goes in a literal section if the scalar is 4, 8, or
+  // 16 bytes, or a cstring.  Other read only data goes into a regular const
+  // section.  Read-write data goes in the data section.
+  MachOSection *Sec = GV->isConstant() ? getConstSection(GV->getInitializer()) : 
+                                         getDataSection();
+  AddSymbolToSection(Sec, GV);
+  InitMem(GV->getInitializer(), &Sec->SectionData[0], GVOffset[GV],
+          TM.getTargetData(), Sec->Relocations);
+}
+
+
+bool MachOWriter::runOnMachineFunction(MachineFunction &MF) {
+  // Nothing to do here, this is all done through the MCE object.
+  return false;
+}
+
+bool MachOWriter::doInitialization(Module &M) {
+  // Set the magic value, now that we know the pointer size and endianness
+  Header.setMagic(isLittleEndian, is64Bit);
+
+  // Set the file type
+  // FIXME: this only works for object files, we do not support the creation
+  //        of dynamic libraries or executables at this time.
+  Header.filetype = MachOHeader::MH_OBJECT;
+
+  Mang = new Mangler(M);
+  return false;
+}
+
+/// doFinalization - Now that the module has been completely processed, emit
+/// the Mach-O file to 'O'.
+bool MachOWriter::doFinalization(Module &M) {
+  // FIXME: we don't handle debug info yet, we should probably do that.
+
+  // Okay, the.text section has been completed, build the .data, .bss, and 
+  // "common" sections next.
+  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
+       I != E; ++I)
+    EmitGlobal(I);
+  
+  // Emit the header and load commands.
+  EmitHeaderAndLoadCommands();
+
+  // Emit the various sections and their relocation info.
+  EmitSections();
+
+  // Write the symbol table and the string table to the end of the file.
+  O.write((char*)&SymT[0], SymT.size());
+  O.write((char*)&StrT[0], StrT.size());
+
+  // We are done with the abstract symbols.
+  SectionList.clear();
+  SymbolTable.clear();
+  DynamicSymbolTable.clear();
+
+  // Release the name mangler object.
+  delete Mang; Mang = 0;
+  return false;
+}
+
+void MachOWriter::EmitHeaderAndLoadCommands() {
+  // Step #0: Fill in the segment load command size, since we need it to figure
+  //          out the rest of the header fields
+  MachOSegment SEG("", is64Bit);
+  SEG.nsects  = SectionList.size();
+  SEG.cmdsize = SEG.cmdSize(is64Bit) + 
+                SEG.nsects * SectionList[0]->cmdSize(is64Bit);
+  
+  // Step #1: calculate the number of load commands.  We always have at least
+  //          one, for the LC_SEGMENT load command, plus two for the normal
+  //          and dynamic symbol tables, if there are any symbols.
+  Header.ncmds = SymbolTable.empty() ? 1 : 3;
+  
+  // Step #2: calculate the size of the load commands
+  Header.sizeofcmds = SEG.cmdsize;
+  if (!SymbolTable.empty())
+    Header.sizeofcmds += SymTab.cmdsize + DySymTab.cmdsize;
+    
+  // Step #3: write the header to the file
+  // Local alias to shortenify coming code.
+  DataBuffer &FH = Header.HeaderData;
+  OutputBuffer FHOut(FH, is64Bit, isLittleEndian);
+
+  FHOut.outword(Header.magic);
+  FHOut.outword(TM.getMachOWriterInfo()->getCPUType());
+  FHOut.outword(TM.getMachOWriterInfo()->getCPUSubType());
+  FHOut.outword(Header.filetype);
+  FHOut.outword(Header.ncmds);
+  FHOut.outword(Header.sizeofcmds);
+  FHOut.outword(Header.flags);
+  if (is64Bit)
+    FHOut.outword(Header.reserved);
+  
+  // Step #4: Finish filling in the segment load command and write it out
+  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
+         E = SectionList.end(); I != E; ++I)
+    SEG.filesize += (*I)->size;
+
+  SEG.vmsize = SEG.filesize;
+  SEG.fileoff = Header.cmdSize(is64Bit) + Header.sizeofcmds;
+  
+  FHOut.outword(SEG.cmd);
+  FHOut.outword(SEG.cmdsize);
+  FHOut.outstring(SEG.segname, 16);
+  FHOut.outaddr(SEG.vmaddr);
+  FHOut.outaddr(SEG.vmsize);
+  FHOut.outaddr(SEG.fileoff);
+  FHOut.outaddr(SEG.filesize);
+  FHOut.outword(SEG.maxprot);
+  FHOut.outword(SEG.initprot);
+  FHOut.outword(SEG.nsects);
+  FHOut.outword(SEG.flags);
+  
+  // Step #5: Finish filling in the fields of the MachOSections 
+  uint64_t currentAddr = 0;
+  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
+         E = SectionList.end(); I != E; ++I) {
+    MachOSection *MOS = *I;
+    MOS->addr = currentAddr;
+    MOS->offset = currentAddr + SEG.fileoff;
+
+    // FIXME: do we need to do something with alignment here?
+    currentAddr += MOS->size;
+  }
+  
+  // Step #6: Emit the symbol table to temporary buffers, so that we know the
+  // size of the string table when we write the next load command.  This also
+  // sorts and assigns indices to each of the symbols, which is necessary for
+  // emitting relocations to externally-defined objects.
+  BufferSymbolAndStringTable();
+  
+  // Step #7: Calculate the number of relocations for each section and write out
+  // the section commands for each section
+  currentAddr += SEG.fileoff;
+  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
+         E = SectionList.end(); I != E; ++I) {
+    MachOSection *MOS = *I;
+    // Convert the relocations to target-specific relocations, and fill in the
+    // relocation offset for this section.
+    CalculateRelocations(*MOS);
+    MOS->reloff = MOS->nreloc ? currentAddr : 0;
+    currentAddr += MOS->nreloc * 8;
+    
+    // write the finalized section command to the output buffer
+    FHOut.outstring(MOS->sectname, 16);
+    FHOut.outstring(MOS->segname, 16);
+    FHOut.outaddr(MOS->addr);
+    FHOut.outaddr(MOS->size);
+    FHOut.outword(MOS->offset);
+    FHOut.outword(MOS->align);
+    FHOut.outword(MOS->reloff);
+    FHOut.outword(MOS->nreloc);
+    FHOut.outword(MOS->flags);
+    FHOut.outword(MOS->reserved1);
+    FHOut.outword(MOS->reserved2);
+    if (is64Bit)
+      FHOut.outword(MOS->reserved3);
+  }
+  
+  // Step #8: Emit LC_SYMTAB/LC_DYSYMTAB load commands
+  SymTab.symoff  = currentAddr;
+  SymTab.nsyms   = SymbolTable.size();
+  SymTab.stroff  = SymTab.symoff + SymT.size();
+  SymTab.strsize = StrT.size();
+  FHOut.outword(SymTab.cmd);
+  FHOut.outword(SymTab.cmdsize);
+  FHOut.outword(SymTab.symoff);
+  FHOut.outword(SymTab.nsyms);
+  FHOut.outword(SymTab.stroff);
+  FHOut.outword(SymTab.strsize);
+
+  // FIXME: set DySymTab fields appropriately
+  // We should probably just update these in BufferSymbolAndStringTable since
+  // thats where we're partitioning up the different kinds of symbols.
+  FHOut.outword(DySymTab.cmd);
+  FHOut.outword(DySymTab.cmdsize);
+  FHOut.outword(DySymTab.ilocalsym);
+  FHOut.outword(DySymTab.nlocalsym);
+  FHOut.outword(DySymTab.iextdefsym);
+  FHOut.outword(DySymTab.nextdefsym);
+  FHOut.outword(DySymTab.iundefsym);
+  FHOut.outword(DySymTab.nundefsym);
+  FHOut.outword(DySymTab.tocoff);
+  FHOut.outword(DySymTab.ntoc);
+  FHOut.outword(DySymTab.modtaboff);
+  FHOut.outword(DySymTab.nmodtab);
+  FHOut.outword(DySymTab.extrefsymoff);
+  FHOut.outword(DySymTab.nextrefsyms);
+  FHOut.outword(DySymTab.indirectsymoff);
+  FHOut.outword(DySymTab.nindirectsyms);
+  FHOut.outword(DySymTab.extreloff);
+  FHOut.outword(DySymTab.nextrel);
+  FHOut.outword(DySymTab.locreloff);
+  FHOut.outword(DySymTab.nlocrel);
+  
+  O.write((char*)&FH[0], FH.size());
+}
+
+/// EmitSections - Now that we have constructed the file header and load
+/// commands, emit the data for each section to the file.
+void MachOWriter::EmitSections() {
+  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
+         E = SectionList.end(); I != E; ++I)
+    // Emit the contents of each section
+    O.write((char*)&(*I)->SectionData[0], (*I)->size);
+  for (std::vector<MachOSection*>::iterator I = SectionList.begin(),
+         E = SectionList.end(); I != E; ++I)
+    // Emit the relocation entry data for each section.
+    O.write((char*)&(*I)->RelocBuffer[0], (*I)->RelocBuffer.size());
+}
+
+/// PartitionByLocal - Simple boolean predicate that returns true if Sym is
+/// a local symbol rather than an external symbol.
+bool MachOWriter::PartitionByLocal(const MachOSym &Sym) {
+  return (Sym.n_type & (MachOSym::N_EXT | MachOSym::N_PEXT)) == 0;
+}
+
+/// PartitionByDefined - Simple boolean predicate that returns true if Sym is
+/// defined in this module.
+bool MachOWriter::PartitionByDefined(const MachOSym &Sym) {
+  // FIXME: Do N_ABS or N_INDR count as defined?
+  return (Sym.n_type & MachOSym::N_SECT) == MachOSym::N_SECT;
+}
+
+/// BufferSymbolAndStringTable - Sort the symbols we encountered and assign them
+/// each a string table index so that they appear in the correct order in the
+/// output file.
+void MachOWriter::BufferSymbolAndStringTable() {
+  // The order of the symbol table is:
+  // 1. local symbols
+  // 2. defined external symbols (sorted by name)
+  // 3. undefined external symbols (sorted by name)
+  
+  // Before sorting the symbols, check the PendingGlobals for any undefined
+  // globals that need to be put in the symbol table.
+  for (std::vector<GlobalValue*>::iterator I = PendingGlobals.begin(),
+         E = PendingGlobals.end(); I != E; ++I) {
+    if (GVOffset[*I] == 0 && GVSection[*I] == 0) {
+      MachOSym UndfSym(*I, Mang->getValueName(*I), MachOSym::NO_SECT, TM);
+      SymbolTable.push_back(UndfSym);
+      GVOffset[*I] = -1;
+    }
+  }
+  
+  // Sort the symbols by name, so that when we partition the symbols by scope
+  // of definition, we won't have to sort by name within each partition.
+  std::sort(SymbolTable.begin(), SymbolTable.end(), MachOSymCmp());
+
+  // Parition the symbol table entries so that all local symbols come before 
+  // all symbols with external linkage. { 1 | 2 3 }
+  std::partition(SymbolTable.begin(), SymbolTable.end(), PartitionByLocal);
+  
+  // Advance iterator to beginning of external symbols and partition so that
+  // all external symbols defined in this module come before all external
+  // symbols defined elsewhere. { 1 | 2 | 3 }
+  for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
+         E = SymbolTable.end(); I != E; ++I) {
+    if (!PartitionByLocal(*I)) {
+      std::partition(I, E, PartitionByDefined);
+      break;
+    }
+  }
+
+  // Calculate the starting index for each of the local, extern defined, and 
+  // undefined symbols, as well as the number of each to put in the LC_DYSYMTAB
+  // load command.
+  for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
+         E = SymbolTable.end(); I != E; ++I) {
+    if (PartitionByLocal(*I)) {
+      ++DySymTab.nlocalsym;
+      ++DySymTab.iextdefsym;
+      ++DySymTab.iundefsym;
+    } else if (PartitionByDefined(*I)) {
+      ++DySymTab.nextdefsym;
+      ++DySymTab.iundefsym;
+    } else {
+      ++DySymTab.nundefsym;
+    }
+  }
+  
+  // Write out a leading zero byte when emitting string table, for n_strx == 0
+  // which means an empty string.
+  OutputBuffer StrTOut(StrT, is64Bit, isLittleEndian);
+  StrTOut.outbyte(0);
+
+  // The order of the string table is:
+  // 1. strings for external symbols
+  // 2. strings for local symbols
+  // Since this is the opposite order from the symbol table, which we have just
+  // sorted, we can walk the symbol table backwards to output the string table.
+  for (std::vector<MachOSym>::reverse_iterator I = SymbolTable.rbegin(),
+        E = SymbolTable.rend(); I != E; ++I) {
+    if (I->GVName == "") {
+      I->n_strx = 0;
+    } else {
+      I->n_strx = StrT.size();
+      StrTOut.outstring(I->GVName, I->GVName.length()+1);
+    }
+  }
+
+  OutputBuffer SymTOut(SymT, is64Bit, isLittleEndian);
+
+  unsigned index = 0;
+  for (std::vector<MachOSym>::iterator I = SymbolTable.begin(),
+         E = SymbolTable.end(); I != E; ++I, ++index) {
+    // Add the section base address to the section offset in the n_value field
+    // to calculate the full address.
+    // FIXME: handle symbols where the n_value field is not the address
+    GlobalValue *GV = const_cast<GlobalValue*>(I->GV);
+    if (GV && GVSection[GV])
+      I->n_value += GVSection[GV]->addr;
+    if (GV && (GVOffset[GV] == -1))
+      GVOffset[GV] = index;
+         
+    // Emit nlist to buffer
+    SymTOut.outword(I->n_strx);
+    SymTOut.outbyte(I->n_type);
+    SymTOut.outbyte(I->n_sect);
+    SymTOut.outhalf(I->n_desc);
+    SymTOut.outaddr(I->n_value);
+  }
+}
+
+/// CalculateRelocations - For each MachineRelocation in the current section,
+/// calculate the index of the section containing the object to be relocated,
+/// and the offset into that section.  From this information, create the
+/// appropriate target-specific MachORelocation type and add buffer it to be
+/// written out after we are finished writing out sections.
+void MachOWriter::CalculateRelocations(MachOSection &MOS) {
+  for (unsigned i = 0, e = MOS.Relocations.size(); i != e; ++i) {
+    MachineRelocation &MR = MOS.Relocations[i];
+    unsigned TargetSection = MR.getConstantVal();
+    unsigned TargetAddr = 0;
+    unsigned TargetIndex = 0;
+
+    // This is a scattered relocation entry if it points to a global value with
+    // a non-zero offset.
+    bool Scattered = false;
+    bool Extern = false;
+
+    // Since we may not have seen the GlobalValue we were interested in yet at
+    // the time we emitted the relocation for it, fix it up now so that it
+    // points to the offset into the correct section.
+    if (MR.isGlobalValue()) {
+      GlobalValue *GV = MR.getGlobalValue();
+      MachOSection *MOSPtr = GVSection[GV];
+      intptr_t Offset = GVOffset[GV];
+      
+      // If we have never seen the global before, it must be to a symbol
+      // defined in another module (N_UNDF).
+      if (!MOSPtr) {
+        // FIXME: need to append stub suffix
+        Extern = true;
+        TargetAddr = 0;
+        TargetIndex = GVOffset[GV];
+      } else {
+        Scattered = TargetSection != 0;
+        TargetSection = MOSPtr->Index;
+      }
+      MR.setResultPointer((void*)Offset);
+    }
+    
+    // If the symbol is locally defined, pass in the address of the section and
+    // the section index to the code which will generate the target relocation.
+    if (!Extern) {
+        MachOSection &To = *SectionList[TargetSection - 1];
+        TargetAddr = To.addr;
+        TargetIndex = To.Index;
+    }
+
+    OutputBuffer RelocOut(MOS.RelocBuffer, is64Bit, isLittleEndian);
+    OutputBuffer SecOut(MOS.SectionData, is64Bit, isLittleEndian);
+    
+    MOS.nreloc += GetTargetRelocation(MR, MOS.Index, TargetAddr, TargetIndex,
+                                      RelocOut, SecOut, Scattered, Extern);
+  }
+}
+
+// InitMem - Write the value of a Constant to the specified memory location,
+// converting it into bytes and relocations.
+void MachOWriter::InitMem(const Constant *C, void *Addr, intptr_t Offset,
+                          const TargetData *TD, 
+                          std::vector<MachineRelocation> &MRs) {
+  typedef std::pair<const Constant*, intptr_t> CPair;
+  std::vector<CPair> WorkList;
+  
+  WorkList.push_back(CPair(C,(intptr_t)Addr + Offset));
+  
+  intptr_t ScatteredOffset = 0;
+  
+  while (!WorkList.empty()) {
+    const Constant *PC = WorkList.back().first;
+    intptr_t PA = WorkList.back().second;
+    WorkList.pop_back();
+    
+    if (isa<UndefValue>(PC)) {
+      continue;
+    } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(PC)) {
+      unsigned ElementSize = TD->getTypeSize(CP->getType()->getElementType());
+      for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
+        WorkList.push_back(CPair(CP->getOperand(i), PA+i*ElementSize));
+    } else if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(PC)) {
+      //
+      // FIXME: Handle ConstantExpression.  See EE::getConstantValue()
+      //
+      switch (CE->getOpcode()) {
+      case Instruction::GetElementPtr: {
+        SmallVector<Value*, 8> Indices(CE->op_begin()+1, CE->op_end());
+        ScatteredOffset = TD->getIndexedOffset(CE->getOperand(0)->getType(),
+                                               &Indices[0], Indices.size());
+        WorkList.push_back(CPair(CE->getOperand(0), PA));
+        break;
+      }
+      case Instruction::Add:
+      default:
+        cerr << "ConstantExpr not handled as global var init: " << *CE << "\n";
+        abort();
+        break;
+      }
+    } else if (PC->getType()->isFirstClassType()) {
+      unsigned char *ptr = (unsigned char *)PA;
+      switch (PC->getType()->getTypeID()) {
+      case Type::IntegerTyID: {
+        unsigned NumBits = cast<IntegerType>(PC->getType())->getBitWidth();
+        uint64_t val = cast<ConstantInt>(PC)->getZExtValue();
+        if (NumBits <= 8)
+          ptr[0] = val;
+        else if (NumBits <= 16) {
+          if (TD->isBigEndian())
+            val = ByteSwap_16(val);
+          ptr[0] = val;
+          ptr[1] = val >> 8;
+        } else if (NumBits <= 32) {
+          if (TD->isBigEndian())
+            val = ByteSwap_32(val);
+          ptr[0] = val;
+          ptr[1] = val >> 8;
+          ptr[2] = val >> 16;
+          ptr[3] = val >> 24;
+        } else if (NumBits <= 64) {
+          if (TD->isBigEndian())
+            val = ByteSwap_64(val);
+          ptr[0] = val;
+          ptr[1] = val >> 8;
+          ptr[2] = val >> 16;
+          ptr[3] = val >> 24;
+          ptr[4] = val >> 32;
+          ptr[5] = val >> 40;
+          ptr[6] = val >> 48;
+          ptr[7] = val >> 56;
+        } else {
+          assert(0 && "Not implemented: bit widths > 64");
+        }
+        break;
+      }
+      case Type::FloatTyID: {
+        uint64_t val = FloatToBits(cast<ConstantFP>(PC)->getValue());
+        if (TD->isBigEndian())
+          val = ByteSwap_32(val);
+        ptr[0] = val;
+        ptr[1] = val >> 8;
+        ptr[2] = val >> 16;
+        ptr[3] = val >> 24;
+        break;
+      }
+      case Type::DoubleTyID: {
+        uint64_t val = DoubleToBits(cast<ConstantFP>(PC)->getValue());
+        if (TD->isBigEndian())
+          val = ByteSwap_64(val);
+        ptr[0] = val;
+        ptr[1] = val >> 8;
+        ptr[2] = val >> 16;
+        ptr[3] = val >> 24;
+        ptr[4] = val >> 32;
+        ptr[5] = val >> 40;
+        ptr[6] = val >> 48;
+        ptr[7] = val >> 56;
+        break;
+      }
+      case Type::PointerTyID:
+        if (isa<ConstantPointerNull>(PC))
+          memset(ptr, 0, TD->getPointerSize());
+        else if (const GlobalValue* GV = dyn_cast<GlobalValue>(PC)) {
+          // FIXME: what about function stubs?
+          MRs.push_back(MachineRelocation::getGV(PA-(intptr_t)Addr, 
+                                                 MachineRelocation::VANILLA,
+                                                 const_cast<GlobalValue*>(GV),
+                                                 ScatteredOffset));
+          ScatteredOffset = 0;
+        } else
+          assert(0 && "Unknown constant pointer type!");
+        break;
+      default:
+        cerr << "ERROR: Constant unimp for type: " << *PC->getType() << "\n";
+        abort();
+      }
+    } else if (isa<ConstantAggregateZero>(PC)) {
+      memset((void*)PA, 0, (size_t)TD->getTypeSize(PC->getType()));
+    } else if (const ConstantArray *CPA = dyn_cast<ConstantArray>(PC)) {
+      unsigned ElementSize = TD->getTypeSize(CPA->getType()->getElementType());
+      for (unsigned i = 0, e = CPA->getNumOperands(); i != e; ++i)
+        WorkList.push_back(CPair(CPA->getOperand(i), PA+i*ElementSize));
+    } else if (const ConstantStruct *CPS = dyn_cast<ConstantStruct>(PC)) {
+      const StructLayout *SL =
+        TD->getStructLayout(cast<StructType>(CPS->getType()));
+      for (unsigned i = 0, e = CPS->getNumOperands(); i != e; ++i)
+        WorkList.push_back(CPair(CPS->getOperand(i),
+                                 PA+SL->getElementOffset(i)));
+    } else {
+      cerr << "Bad Type: " << *PC->getType() << "\n";
+      assert(0 && "Unknown constant type to initialize memory with!");
+    }
+  }
+}
+
+MachOSym::MachOSym(const GlobalValue *gv, std::string name, uint8_t sect,
+                   TargetMachine &TM) :
+  GV(gv), n_strx(0), n_type(sect == NO_SECT ? N_UNDF : N_SECT), n_sect(sect),
+  n_desc(0), n_value(0) {
+
+  const TargetAsmInfo *TAI = TM.getTargetAsmInfo();  
+  
+  switch (GV->getLinkage()) {
+  default:
+    assert(0 && "Unexpected linkage type!");
+    break;
+  case GlobalValue::WeakLinkage:
+  case GlobalValue::LinkOnceLinkage:
+    assert(!isa<Function>(gv) && "Unexpected linkage type for Function!");
+  case GlobalValue::ExternalLinkage:
+    GVName = TAI->getGlobalPrefix() + name;
+    n_type |= GV->hasHiddenVisibility() ? N_PEXT : N_EXT;
+    break;
+  case GlobalValue::InternalLinkage:
+    GVName = TAI->getGlobalPrefix() + name;
+    break;
+  }
+}