diff --git a/include/llvm/ExecutionEngine/RuntimeDyld.h b/include/llvm/ExecutionEngine/RuntimeDyld.h
index 3dc65e3..724b9f0 100644
--- a/include/llvm/ExecutionEngine/RuntimeDyld.h
+++ b/include/llvm/ExecutionEngine/RuntimeDyld.h
@@ -53,6 +53,7 @@
   // RuntimeDyldImpl is the actual class. RuntimeDyld is just the public
   // interface.
   RuntimeDyldImpl *Dyld;
+  RTDyldMemoryManager *MM;
 public:
   RuntimeDyld(RTDyldMemoryManager*);
   ~RuntimeDyld();
diff --git a/lib/ExecutionEngine/RuntimeDyld/CMakeLists.txt b/lib/ExecutionEngine/RuntimeDyld/CMakeLists.txt
index 9e53f87..59bdfee3 100644
--- a/lib/ExecutionEngine/RuntimeDyld/CMakeLists.txt
+++ b/lib/ExecutionEngine/RuntimeDyld/CMakeLists.txt
@@ -1,3 +1,4 @@
 add_llvm_library(LLVMRuntimeDyld
   RuntimeDyld.cpp
+  RuntimeDyldMachO.cpp
   )
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
index eda4cbb..33dd705 100644
--- a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
@@ -1,4 +1,4 @@
-//===-- RuntimeDyld.h - Run-time dynamic linker for MC-JIT ------*- C++ -*-===//
+//===-- RuntimeDyld.cpp - Run-time dynamic linker for MC-JIT ------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -12,118 +12,15 @@
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "dyld"
-#include "llvm/ADT/OwningPtr.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/StringMap.h"
-#include "llvm/ADT/StringRef.h"
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/ADT/Twine.h"
-#include "llvm/ExecutionEngine/RuntimeDyld.h"
-#include "llvm/Object/MachOObject.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/Format.h"
-#include "llvm/Support/Memory.h"
-#include "llvm/Support/MemoryBuffer.h"
-#include "llvm/Support/system_error.h"
-#include "llvm/Support/raw_ostream.h"
+#include "RuntimeDyldImpl.h"
 using namespace llvm;
 using namespace llvm::object;
 
 // Empty out-of-line virtual destructor as the key function.
 RTDyldMemoryManager::~RTDyldMemoryManager() {}
+RuntimeDyldImpl::~RuntimeDyldImpl() {}
 
 namespace llvm {
-class RuntimeDyldImpl {
-  unsigned CPUType;
-  unsigned CPUSubtype;
-
-  // The MemoryManager to load objects into.
-  RTDyldMemoryManager *MemMgr;
-
-  // FIXME: This all assumes we're dealing with external symbols for anything
-  //        explicitly referenced. I.e., we can index by name and things
-  //        will work out. In practice, this may not be the case, so we
-  //        should find a way to effectively generalize.
-
-  // For each function, we have a MemoryBlock of it's instruction data.
-  StringMap<sys::MemoryBlock> Functions;
-
-  // Master symbol table. As modules are loaded and external symbols are
-  // resolved, their addresses are stored here.
-  StringMap<uint8_t*> SymbolTable;
-
-  // For each symbol, keep a list of relocations based on it. Anytime
-  // its address is reassigned (the JIT re-compiled the function, e.g.),
-  // the relocations get re-resolved.
-  struct RelocationEntry {
-    std::string Target;     // Object this relocation is contained in.
-    uint64_t    Offset;     // Offset into the object for the relocation.
-    uint32_t    Data;       // Second word of the raw macho relocation entry.
-    int64_t     Addend;     // Addend encoded in the instruction itself, if any.
-    bool        isResolved; // Has this relocation been resolved previously?
-
-    RelocationEntry(StringRef t, uint64_t offset, uint32_t data, int64_t addend)
-      : Target(t), Offset(offset), Data(data), Addend(addend),
-        isResolved(false) {}
-  };
-  typedef SmallVector<RelocationEntry, 4> RelocationList;
-  StringMap<RelocationList> Relocations;
-
-  // FIXME: Also keep a map of all the relocations contained in an object. Use
-  // this to dynamically answer whether all of the relocations in it have
-  // been resolved or not.
-
-  bool HasError;
-  std::string ErrorStr;
-
-  // Set the error state and record an error string.
-  bool Error(const Twine &Msg) {
-    ErrorStr = Msg.str();
-    HasError = true;
-    return true;
-  }
-
-  void extractFunction(StringRef Name, uint8_t *StartAddress,
-                       uint8_t *EndAddress);
-  bool resolveRelocation(uint8_t *Address, uint8_t *Value, bool isPCRel,
-                         unsigned Type, unsigned Size);
-  bool resolveX86_64Relocation(uintptr_t Address, uintptr_t Value, bool isPCRel,
-                               unsigned Type, unsigned Size);
-  bool resolveARMRelocation(uintptr_t Address, uintptr_t Value, bool isPCRel,
-                            unsigned Type, unsigned Size);
-
-  bool loadSegment32(const MachOObject *Obj,
-                     const MachOObject::LoadCommandInfo *SegmentLCI,
-                     const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC);
-  bool loadSegment64(const MachOObject *Obj,
-                     const MachOObject::LoadCommandInfo *SegmentLCI,
-                     const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC);
-
-public:
-  RuntimeDyldImpl(RTDyldMemoryManager *mm) : MemMgr(mm), HasError(false) {}
-
-  bool loadObject(MemoryBuffer *InputBuffer);
-
-  void *getSymbolAddress(StringRef Name) {
-    // FIXME: Just look up as a function for now. Overly simple of course.
-    // Work in progress.
-    return SymbolTable.lookup(Name);
-  }
-
-  void resolveRelocations();
-
-  void reassignSymbolAddress(StringRef Name, uint8_t *Addr);
-
-  // Is the linker in an error state?
-  bool hasError() { return HasError; }
-
-  // Mark the error condition as handled and continue.
-  void clearError() { HasError = false; }
-
-  // Get the error message.
-  StringRef getErrorString() { return ErrorStr; }
-};
 
 void RuntimeDyldImpl::extractFunction(StringRef Name, uint8_t *StartAddress,
                                       uint8_t *EndAddress) {
@@ -144,472 +41,6 @@
   DEBUG(dbgs() << "    allocated to [" << Mem << ", " << Mem + Size << "]\n");
 }
 
-bool RuntimeDyldImpl::
-resolveRelocation(uint8_t *Address, uint8_t *Value, bool isPCRel,
-                  unsigned Type, unsigned Size) {
-  // This just dispatches to the proper target specific routine.
-  switch (CPUType) {
-  default: assert(0 && "Unsupported CPU type!");
-  case mach::CTM_x86_64:
-    return resolveX86_64Relocation((uintptr_t)Address, (uintptr_t)Value,
-                                   isPCRel, Type, Size);
-  case mach::CTM_ARM:
-    return resolveARMRelocation((uintptr_t)Address, (uintptr_t)Value,
-                                isPCRel, Type, Size);
-  }
-  llvm_unreachable("");
-}
-
-bool RuntimeDyldImpl::
-resolveX86_64Relocation(uintptr_t Address, uintptr_t Value,
-                        bool isPCRel, unsigned Type,
-                        unsigned Size) {
-  // If the relocation is PC-relative, the value to be encoded is the
-  // pointer difference.
-  if (isPCRel)
-    // FIXME: It seems this value needs to be adjusted by 4 for an effective PC
-    // address. Is that expected? Only for branches, perhaps?
-    Value -= Address + 4;
-
-  switch(Type) {
-  default:
-    llvm_unreachable("Invalid relocation type!");
-  case macho::RIT_X86_64_Unsigned:
-  case macho::RIT_X86_64_Branch: {
-    // Mask in the target value a byte at a time (we don't have an alignment
-    // guarantee for the target address, so this is safest).
-    uint8_t *p = (uint8_t*)Address;
-    for (unsigned i = 0; i < Size; ++i) {
-      *p++ = (uint8_t)Value;
-      Value >>= 8;
-    }
-    return false;
-  }
-  case macho::RIT_X86_64_Signed:
-  case macho::RIT_X86_64_GOTLoad:
-  case macho::RIT_X86_64_GOT:
-  case macho::RIT_X86_64_Subtractor:
-  case macho::RIT_X86_64_Signed1:
-  case macho::RIT_X86_64_Signed2:
-  case macho::RIT_X86_64_Signed4:
-  case macho::RIT_X86_64_TLV:
-    return Error("Relocation type not implemented yet!");
-  }
-  return false;
-}
-
-bool RuntimeDyldImpl::resolveARMRelocation(uintptr_t Address, uintptr_t Value,
-                                           bool isPCRel, unsigned Type,
-                                           unsigned Size) {
-  // If the relocation is PC-relative, the value to be encoded is the
-  // pointer difference.
-  if (isPCRel) {
-    Value -= Address;
-    // ARM PCRel relocations have an effective-PC offset of two instructions
-    // (four bytes in Thumb mode, 8 bytes in ARM mode).
-    // FIXME: For now, assume ARM mode.
-    Value -= 8;
-  }
-
-  switch(Type) {
-  default:
-    llvm_unreachable("Invalid relocation type!");
-  case macho::RIT_Vanilla: {
-    llvm_unreachable("Invalid relocation type!");
-    // Mask in the target value a byte at a time (we don't have an alignment
-    // guarantee for the target address, so this is safest).
-    uint8_t *p = (uint8_t*)Address;
-    for (unsigned i = 0; i < Size; ++i) {
-      *p++ = (uint8_t)Value;
-      Value >>= 8;
-    }
-    break;
-  }
-  case macho::RIT_ARM_Branch24Bit: {
-    // Mask the value into the target address. We know instructions are
-    // 32-bit aligned, so we can do it all at once.
-    uint32_t *p = (uint32_t*)Address;
-    // The low two bits of the value are not encoded.
-    Value >>= 2;
-    // Mask the value to 24 bits.
-    Value &= 0xffffff;
-    // FIXME: If the destination is a Thumb function (and the instruction
-    // is a non-predicated BL instruction), we need to change it to a BLX
-    // instruction instead.
-
-    // Insert the value into the instruction.
-    *p = (*p & ~0xffffff) | Value;
-    break;
-  }
-  case macho::RIT_ARM_ThumbBranch22Bit:
-  case macho::RIT_ARM_ThumbBranch32Bit:
-  case macho::RIT_ARM_Half:
-  case macho::RIT_ARM_HalfDifference:
-  case macho::RIT_Pair:
-  case macho::RIT_Difference:
-  case macho::RIT_ARM_LocalDifference:
-  case macho::RIT_ARM_PreboundLazyPointer:
-    return Error("Relocation type not implemented yet!");
-  }
-  return false;
-}
-
-bool RuntimeDyldImpl::
-loadSegment32(const MachOObject *Obj,
-              const MachOObject::LoadCommandInfo *SegmentLCI,
-              const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
-  InMemoryStruct<macho::SegmentLoadCommand> SegmentLC;
-  Obj->ReadSegmentLoadCommand(*SegmentLCI, SegmentLC);
-  if (!SegmentLC)
-    return Error("unable to load segment load command");
-
-  for (unsigned SectNum = 0; SectNum != SegmentLC->NumSections; ++SectNum) {
-    InMemoryStruct<macho::Section> Sect;
-    Obj->ReadSection(*SegmentLCI, SectNum, Sect);
-    if (!Sect)
-      return Error("unable to load section: '" + Twine(SectNum) + "'");
-
-    // FIXME: For the time being, we're only loading text segments.
-    if (Sect->Flags != 0x80000400)
-      continue;
-
-    // Address and names of symbols in the section.
-    typedef std::pair<uint64_t, StringRef> SymbolEntry;
-    SmallVector<SymbolEntry, 64> Symbols;
-    // Index of all the names, in this section or not. Used when we're
-    // dealing with relocation entries.
-    SmallVector<StringRef, 64> SymbolNames;
-    for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
-      InMemoryStruct<macho::SymbolTableEntry> STE;
-      Obj->ReadSymbolTableEntry(SymtabLC->SymbolTableOffset, i, STE);
-      if (!STE)
-        return Error("unable to read symbol: '" + Twine(i) + "'");
-      if (STE->SectionIndex > SegmentLC->NumSections)
-        return Error("invalid section index for symbol: '" + Twine(i) + "'");
-      // Get the symbol name.
-      StringRef Name = Obj->getStringAtIndex(STE->StringIndex);
-      SymbolNames.push_back(Name);
-
-      // Just skip symbols not defined in this section.
-      if ((unsigned)STE->SectionIndex - 1 != SectNum)
-        continue;
-
-      // FIXME: Check the symbol type and flags.
-      if (STE->Type != 0xF)  // external, defined in this section.
-        continue;
-      // Flags == 0x8 marks a thumb function for ARM, which is fine as it
-      // doesn't require any special handling here.
-      if (STE->Flags != 0x0 && STE->Flags != 0x8)
-        continue;
-
-      // Remember the symbol.
-      Symbols.push_back(SymbolEntry(STE->Value, Name));
-
-      DEBUG(dbgs() << "Function sym: '" << Name << "' @ " <<
-            (Sect->Address + STE->Value) << "\n");
-    }
-    // Sort the symbols by address, just in case they didn't come in that way.
-    array_pod_sort(Symbols.begin(), Symbols.end());
-
-    // If there weren't any functions (odd, but just in case...)
-    if (!Symbols.size())
-      continue;
-
-    // Extract the function data.
-    uint8_t *Base = (uint8_t*)Obj->getData(SegmentLC->FileOffset,
-                                           SegmentLC->FileSize).data();
-    for (unsigned i = 0, e = Symbols.size() - 1; i != e; ++i) {
-      uint64_t StartOffset = Sect->Address + Symbols[i].first;
-      uint64_t EndOffset = Symbols[i + 1].first - 1;
-      DEBUG(dbgs() << "Extracting function: " << Symbols[i].second
-                   << " from [" << StartOffset << ", " << EndOffset << "]\n");
-      extractFunction(Symbols[i].second, Base + StartOffset, Base + EndOffset);
-    }
-    // The last symbol we do after since the end address is calculated
-    // differently because there is no next symbol to reference.
-    uint64_t StartOffset = Symbols[Symbols.size() - 1].first;
-    uint64_t EndOffset = Sect->Size - 1;
-    DEBUG(dbgs() << "Extracting function: " << Symbols[Symbols.size()-1].second
-                 << " from [" << StartOffset << ", " << EndOffset << "]\n");
-    extractFunction(Symbols[Symbols.size()-1].second,
-                    Base + StartOffset, Base + EndOffset);
-
-    // Now extract the relocation information for each function and process it.
-    for (unsigned j = 0; j != Sect->NumRelocationTableEntries; ++j) {
-      InMemoryStruct<macho::RelocationEntry> RE;
-      Obj->ReadRelocationEntry(Sect->RelocationTableOffset, j, RE);
-      if (RE->Word0 & macho::RF_Scattered)
-        return Error("NOT YET IMPLEMENTED: scattered relocations.");
-      // Word0 of the relocation is the offset into the section where the
-      // relocation should be applied. We need to translate that into an
-      // offset into a function since that's our atom.
-      uint32_t Offset = RE->Word0;
-      // Look for the function containing the address. This is used for JIT
-      // code, so the number of functions in section is almost always going
-      // to be very small (usually just one), so until we have use cases
-      // where that's not true, just use a trivial linear search.
-      unsigned SymbolNum;
-      unsigned NumSymbols = Symbols.size();
-      assert(NumSymbols > 0 && Symbols[0].first <= Offset &&
-             "No symbol containing relocation!");
-      for (SymbolNum = 0; SymbolNum < NumSymbols - 1; ++SymbolNum)
-        if (Symbols[SymbolNum + 1].first > Offset)
-          break;
-      // Adjust the offset to be relative to the symbol.
-      Offset -= Symbols[SymbolNum].first;
-      // Get the name of the symbol containing the relocation.
-      StringRef TargetName = SymbolNames[SymbolNum];
-
-      bool isExtern = (RE->Word1 >> 27) & 1;
-      // Figure out the source symbol of the relocation. If isExtern is true,
-      // this relocation references the symbol table, otherwise it references
-      // a section in the same object, numbered from 1 through NumSections
-      // (SectionBases is [0, NumSections-1]).
-      // FIXME: Some targets (ARM) use internal relocations even for
-      // externally visible symbols, if the definition is in the same
-      // file as the reference. We need to convert those back to by-name
-      // references. We can resolve the address based on the section
-      // offset and see if we have a symbol at that address. If we do,
-      // use that; otherwise, puke.
-      if (!isExtern)
-        return Error("Internal relocations not supported.");
-      uint32_t SourceNum = RE->Word1 & 0xffffff; // 24-bit value
-      StringRef SourceName = SymbolNames[SourceNum];
-
-      // FIXME: Get the relocation addend from the target address.
-
-      // Now store the relocation information. Associate it with the source
-      // symbol.
-      Relocations[SourceName].push_back(RelocationEntry(TargetName,
-                                                        Offset,
-                                                        RE->Word1,
-                                                        0 /*Addend*/));
-      DEBUG(dbgs() << "Relocation at '" << TargetName << "' + " << Offset
-                   << " from '" << SourceName << "(Word1: "
-                   << format("0x%x", RE->Word1) << ")\n");
-    }
-  }
-  return false;
-}
-
-
-bool RuntimeDyldImpl::
-loadSegment64(const MachOObject *Obj,
-              const MachOObject::LoadCommandInfo *SegmentLCI,
-              const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
-  InMemoryStruct<macho::Segment64LoadCommand> Segment64LC;
-  Obj->ReadSegment64LoadCommand(*SegmentLCI, Segment64LC);
-  if (!Segment64LC)
-    return Error("unable to load segment load command");
-
-  for (unsigned SectNum = 0; SectNum != Segment64LC->NumSections; ++SectNum) {
-    InMemoryStruct<macho::Section64> Sect;
-    Obj->ReadSection64(*SegmentLCI, SectNum, Sect);
-    if (!Sect)
-      return Error("unable to load section: '" + Twine(SectNum) + "'");
-
-    // FIXME: For the time being, we're only loading text segments.
-    if (Sect->Flags != 0x80000400)
-      continue;
-
-    // Address and names of symbols in the section.
-    typedef std::pair<uint64_t, StringRef> SymbolEntry;
-    SmallVector<SymbolEntry, 64> Symbols;
-    // Index of all the names, in this section or not. Used when we're
-    // dealing with relocation entries.
-    SmallVector<StringRef, 64> SymbolNames;
-    for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
-      InMemoryStruct<macho::Symbol64TableEntry> STE;
-      Obj->ReadSymbol64TableEntry(SymtabLC->SymbolTableOffset, i, STE);
-      if (!STE)
-        return Error("unable to read symbol: '" + Twine(i) + "'");
-      if (STE->SectionIndex > Segment64LC->NumSections)
-        return Error("invalid section index for symbol: '" + Twine(i) + "'");
-      // Get the symbol name.
-      StringRef Name = Obj->getStringAtIndex(STE->StringIndex);
-      SymbolNames.push_back(Name);
-
-      // Just skip symbols not defined in this section.
-      if ((unsigned)STE->SectionIndex - 1 != SectNum)
-        continue;
-
-      // FIXME: Check the symbol type and flags.
-      if (STE->Type != 0xF)  // external, defined in this section.
-        continue;
-      if (STE->Flags != 0x0)
-        continue;
-
-      // Remember the symbol.
-      Symbols.push_back(SymbolEntry(STE->Value, Name));
-
-      DEBUG(dbgs() << "Function sym: '" << Name << "' @ " <<
-            (Sect->Address + STE->Value) << "\n");
-    }
-    // Sort the symbols by address, just in case they didn't come in that way.
-    array_pod_sort(Symbols.begin(), Symbols.end());
-
-    // If there weren't any functions (odd, but just in case...)
-    if (!Symbols.size())
-      continue;
-
-    // Extract the function data.
-    uint8_t *Base = (uint8_t*)Obj->getData(Segment64LC->FileOffset,
-                                           Segment64LC->FileSize).data();
-    for (unsigned i = 0, e = Symbols.size() - 1; i != e; ++i) {
-      uint64_t StartOffset = Sect->Address + Symbols[i].first;
-      uint64_t EndOffset = Symbols[i + 1].first - 1;
-      DEBUG(dbgs() << "Extracting function: " << Symbols[i].second
-                   << " from [" << StartOffset << ", " << EndOffset << "]\n");
-      extractFunction(Symbols[i].second, Base + StartOffset, Base + EndOffset);
-    }
-    // The last symbol we do after since the end address is calculated
-    // differently because there is no next symbol to reference.
-    uint64_t StartOffset = Symbols[Symbols.size() - 1].first;
-    uint64_t EndOffset = Sect->Size - 1;
-    DEBUG(dbgs() << "Extracting function: " << Symbols[Symbols.size()-1].second
-                 << " from [" << StartOffset << ", " << EndOffset << "]\n");
-    extractFunction(Symbols[Symbols.size()-1].second,
-                    Base + StartOffset, Base + EndOffset);
-
-    // Now extract the relocation information for each function and process it.
-    for (unsigned j = 0; j != Sect->NumRelocationTableEntries; ++j) {
-      InMemoryStruct<macho::RelocationEntry> RE;
-      Obj->ReadRelocationEntry(Sect->RelocationTableOffset, j, RE);
-      if (RE->Word0 & macho::RF_Scattered)
-        return Error("NOT YET IMPLEMENTED: scattered relocations.");
-      // Word0 of the relocation is the offset into the section where the
-      // relocation should be applied. We need to translate that into an
-      // offset into a function since that's our atom.
-      uint32_t Offset = RE->Word0;
-      // Look for the function containing the address. This is used for JIT
-      // code, so the number of functions in section is almost always going
-      // to be very small (usually just one), so until we have use cases
-      // where that's not true, just use a trivial linear search.
-      unsigned SymbolNum;
-      unsigned NumSymbols = Symbols.size();
-      assert(NumSymbols > 0 && Symbols[0].first <= Offset &&
-             "No symbol containing relocation!");
-      for (SymbolNum = 0; SymbolNum < NumSymbols - 1; ++SymbolNum)
-        if (Symbols[SymbolNum + 1].first > Offset)
-          break;
-      // Adjust the offset to be relative to the symbol.
-      Offset -= Symbols[SymbolNum].first;
-      // Get the name of the symbol containing the relocation.
-      StringRef TargetName = SymbolNames[SymbolNum];
-
-      bool isExtern = (RE->Word1 >> 27) & 1;
-      // Figure out the source symbol of the relocation. If isExtern is true,
-      // this relocation references the symbol table, otherwise it references
-      // a section in the same object, numbered from 1 through NumSections
-      // (SectionBases is [0, NumSections-1]).
-      if (!isExtern)
-        return Error("Internal relocations not supported.");
-      uint32_t SourceNum = RE->Word1 & 0xffffff; // 24-bit value
-      StringRef SourceName = SymbolNames[SourceNum];
-
-      // FIXME: Get the relocation addend from the target address.
-
-      // Now store the relocation information. Associate it with the source
-      // symbol.
-      Relocations[SourceName].push_back(RelocationEntry(TargetName,
-                                                        Offset,
-                                                        RE->Word1,
-                                                        0 /*Addend*/));
-      DEBUG(dbgs() << "Relocation at '" << TargetName << "' + " << Offset
-                   << " from '" << SourceName << "(Word1: "
-                   << format("0x%x", RE->Word1) << ")\n");
-    }
-  }
-  return false;
-}
-
-bool RuntimeDyldImpl::loadObject(MemoryBuffer *InputBuffer) {
-  // If the linker is in an error state, don't do anything.
-  if (hasError())
-    return true;
-  // Load the Mach-O wrapper object.
-  std::string ErrorStr;
-  OwningPtr<MachOObject> Obj(
-    MachOObject::LoadFromBuffer(InputBuffer, &ErrorStr));
-  if (!Obj)
-    return Error("unable to load object: '" + ErrorStr + "'");
-
-  // Get the CPU type information from the header.
-  const macho::Header &Header = Obj->getHeader();
-
-  // FIXME: Error checking that the loaded object is compatible with
-  //        the system we're running on.
-  CPUType = Header.CPUType;
-  CPUSubtype = Header.CPUSubtype;
-
-  // Validate that the load commands match what we expect.
-  const MachOObject::LoadCommandInfo *SegmentLCI = 0, *SymtabLCI = 0,
-    *DysymtabLCI = 0;
-  for (unsigned i = 0; i != Header.NumLoadCommands; ++i) {
-    const MachOObject::LoadCommandInfo &LCI = Obj->getLoadCommandInfo(i);
-    switch (LCI.Command.Type) {
-    case macho::LCT_Segment:
-    case macho::LCT_Segment64:
-      if (SegmentLCI)
-        return Error("unexpected input object (multiple segments)");
-      SegmentLCI = &LCI;
-      break;
-    case macho::LCT_Symtab:
-      if (SymtabLCI)
-        return Error("unexpected input object (multiple symbol tables)");
-      SymtabLCI = &LCI;
-      break;
-    case macho::LCT_Dysymtab:
-      if (DysymtabLCI)
-        return Error("unexpected input object (multiple symbol tables)");
-      DysymtabLCI = &LCI;
-      break;
-    default:
-      return Error("unexpected input object (unexpected load command");
-    }
-  }
-
-  if (!SymtabLCI)
-    return Error("no symbol table found in object");
-  if (!SegmentLCI)
-    return Error("no symbol table found in object");
-
-  // Read and register the symbol table data.
-  InMemoryStruct<macho::SymtabLoadCommand> SymtabLC;
-  Obj->ReadSymtabLoadCommand(*SymtabLCI, SymtabLC);
-  if (!SymtabLC)
-    return Error("unable to load symbol table load command");
-  Obj->RegisterStringTable(*SymtabLC);
-
-  // Read the dynamic link-edit information, if present (not present in static
-  // objects).
-  if (DysymtabLCI) {
-    InMemoryStruct<macho::DysymtabLoadCommand> DysymtabLC;
-    Obj->ReadDysymtabLoadCommand(*DysymtabLCI, DysymtabLC);
-    if (!DysymtabLC)
-      return Error("unable to load dynamic link-exit load command");
-
-    // FIXME: We don't support anything interesting yet.
-//    if (DysymtabLC->LocalSymbolsIndex != 0)
-//      return Error("NOT YET IMPLEMENTED: local symbol entries");
-//    if (DysymtabLC->ExternalSymbolsIndex != 0)
-//      return Error("NOT YET IMPLEMENTED: non-external symbol entries");
-//    if (DysymtabLC->UndefinedSymbolsIndex != SymtabLC->NumSymbolTableEntries)
-//      return Error("NOT YET IMPLEMENTED: undefined symbol entries");
-  }
-
-  // Load the segment load command.
-  if (SegmentLCI->Command.Type == macho::LCT_Segment) {
-    if (loadSegment32(Obj.get(), SegmentLCI, SymtabLC))
-      return true;
-  } else {
-    if (loadSegment64(Obj.get(), SegmentLCI, SymtabLC))
-      return true;
-  }
-
-  return false;
-}
-
 // Resolve the relocations for all symbols we currently know about.
 void RuntimeDyldImpl::resolveRelocations() {
   // Just iterate over the symbols in our symbol table and assign their
@@ -620,35 +51,11 @@
     reassignSymbolAddress(i->getKey(), i->getValue());
 }
 
-// Assign an address to a symbol name and resolve all the relocations
-// associated with it.
-void RuntimeDyldImpl::reassignSymbolAddress(StringRef Name, uint8_t *Addr) {
-  // Assign the address in our symbol table.
-  SymbolTable[Name] = Addr;
-
-  RelocationList &Relocs = Relocations[Name];
-  for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
-    RelocationEntry &RE = Relocs[i];
-    uint8_t *Target = SymbolTable[RE.Target] + RE.Offset;
-    bool isPCRel = (RE.Data >> 24) & 1;
-    unsigned Type = (RE.Data >> 28) & 0xf;
-    unsigned Size = 1 << ((RE.Data >> 25) & 3);
-
-    DEBUG(dbgs() << "Resolving relocation at '" << RE.Target
-          << "' + " << RE.Offset << " (" << format("%p", Target) << ")"
-          << " from '" << Name << " (" << format("%p", Addr) << ")"
-          << "(" << (isPCRel ? "pcrel" : "absolute")
-          << ", type: " << Type << ", Size: " << Size << ").\n");
-
-    resolveRelocation(Target, Addr, isPCRel, Type, Size);
-    RE.isResolved = true;
-  }
-}
-
 //===----------------------------------------------------------------------===//
 // RuntimeDyld class implementation
-RuntimeDyld::RuntimeDyld(RTDyldMemoryManager *MM) {
-  Dyld = new RuntimeDyldImpl(MM);
+RuntimeDyld::RuntimeDyld(RTDyldMemoryManager *mm) {
+  Dyld = 0;
+  MM = mm;
 }
 
 RuntimeDyld::~RuntimeDyld() {
@@ -656,6 +63,16 @@
 }
 
 bool RuntimeDyld::loadObject(MemoryBuffer *InputBuffer) {
+  if (!Dyld) {
+    if (RuntimeDyldMachO::isKnownFormat(InputBuffer))
+      Dyld = new RuntimeDyldMachO(MM);
+    else
+      report_fatal_error("Unknown object format!");
+  } else {
+    if(!Dyld->isCompatibleFormat(InputBuffer))
+      report_fatal_error("Incompatible object format!");
+  }
+
   return Dyld->loadObject(InputBuffer);
 }
 
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
new file mode 100644
index 0000000..bcdfb04
--- /dev/null
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldImpl.h
@@ -0,0 +1,152 @@
+//===-- RuntimeDyldImpl.h - Run-time dynamic linker for MC-JIT ------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Interface for the implementations of runtime dynamic linker facilities.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_RUNTIME_DYLD_IMPL_H
+#define LLVM_RUNTIME_DYLD_IMPL_H
+
+#include "llvm/ExecutionEngine/RuntimeDyld.h"
+#include "llvm/Object/MachOObject.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/Support/Format.h"
+#include "llvm/Support/Memory.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/system_error.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+
+using namespace llvm;
+using namespace llvm::object;
+
+namespace llvm {
+class RuntimeDyldImpl {
+protected:
+  unsigned CPUType;
+  unsigned CPUSubtype;
+
+  // The MemoryManager to load objects into.
+  RTDyldMemoryManager *MemMgr;
+
+  // FIXME: This all assumes we're dealing with external symbols for anything
+  //        explicitly referenced. I.e., we can index by name and things
+  //        will work out. In practice, this may not be the case, so we
+  //        should find a way to effectively generalize.
+
+  // For each function, we have a MemoryBlock of it's instruction data.
+  StringMap<sys::MemoryBlock> Functions;
+
+  // Master symbol table. As modules are loaded and external symbols are
+  // resolved, their addresses are stored here.
+  StringMap<uint8_t*> SymbolTable;
+
+  bool HasError;
+  std::string ErrorStr;
+
+  // Set the error state and record an error string.
+  bool Error(const Twine &Msg) {
+    ErrorStr = Msg.str();
+    HasError = true;
+    return true;
+  }
+
+  void extractFunction(StringRef Name, uint8_t *StartAddress,
+                       uint8_t *EndAddress);
+
+public:
+  RuntimeDyldImpl(RTDyldMemoryManager *mm) : MemMgr(mm), HasError(false) {}
+
+  virtual ~RuntimeDyldImpl();
+
+  virtual bool loadObject(MemoryBuffer *InputBuffer) = 0;
+
+  void *getSymbolAddress(StringRef Name) {
+    // FIXME: Just look up as a function for now. Overly simple of course.
+    // Work in progress.
+    return SymbolTable.lookup(Name);
+  }
+
+  void resolveRelocations();
+
+  virtual void reassignSymbolAddress(StringRef Name, uint8_t *Addr) = 0;
+
+  // Is the linker in an error state?
+  bool hasError() { return HasError; }
+
+  // Mark the error condition as handled and continue.
+  void clearError() { HasError = false; }
+
+  // Get the error message.
+  StringRef getErrorString() { return ErrorStr; }
+
+  virtual bool isCompatibleFormat(const MemoryBuffer *InputBuffer) const = 0;
+};
+
+
+class RuntimeDyldMachO : public RuntimeDyldImpl {
+
+  // For each symbol, keep a list of relocations based on it. Anytime
+  // its address is reassigned (the JIT re-compiled the function, e.g.),
+  // the relocations get re-resolved.
+  struct RelocationEntry {
+    std::string Target;     // Object this relocation is contained in.
+    uint64_t    Offset;     // Offset into the object for the relocation.
+    uint32_t    Data;       // Second word of the raw macho relocation entry.
+    int64_t     Addend;     // Addend encoded in the instruction itself, if any.
+    bool        isResolved; // Has this relocation been resolved previously?
+
+    RelocationEntry(StringRef t, uint64_t offset, uint32_t data, int64_t addend)
+      : Target(t), Offset(offset), Data(data), Addend(addend),
+        isResolved(false) {}
+  };
+  typedef SmallVector<RelocationEntry, 4> RelocationList;
+  StringMap<RelocationList> Relocations;
+
+  // FIXME: Also keep a map of all the relocations contained in an object. Use
+  // this to dynamically answer whether all of the relocations in it have
+  // been resolved or not.
+
+  bool resolveRelocation(uint8_t *Address, uint8_t *Value, bool isPCRel,
+                         unsigned Type, unsigned Size);
+  bool resolveX86_64Relocation(uintptr_t Address, uintptr_t Value, bool isPCRel,
+                               unsigned Type, unsigned Size);
+  bool resolveARMRelocation(uintptr_t Address, uintptr_t Value, bool isPCRel,
+                            unsigned Type, unsigned Size);
+
+  bool loadSegment32(const MachOObject *Obj,
+                     const MachOObject::LoadCommandInfo *SegmentLCI,
+                     const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC);
+  bool loadSegment64(const MachOObject *Obj,
+                     const MachOObject::LoadCommandInfo *SegmentLCI,
+                     const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC);
+
+public:
+  RuntimeDyldMachO(RTDyldMemoryManager *mm) : RuntimeDyldImpl(mm) {}
+
+  bool loadObject(MemoryBuffer *InputBuffer);
+
+  void reassignSymbolAddress(StringRef Name, uint8_t *Addr);
+
+  static bool isKnownFormat(const MemoryBuffer *InputBuffer);
+
+  bool isCompatibleFormat(const MemoryBuffer *InputBuffer) const {
+    return isKnownFormat(InputBuffer);
+  };
+};
+
+} // end namespace llvm
+
+
+#endif
diff --git a/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
new file mode 100644
index 0000000..623e9b2
--- /dev/null
+++ b/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
@@ -0,0 +1,524 @@
+//===-- RuntimeDyldMachO.cpp - Run-time dynamic linker for MC-JIT ------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Implementation of the MC-JIT runtime dynamic linker.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "dyld"
+#include "llvm/ADT/OwningPtr.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/ADT/STLExtras.h"
+#include "RuntimeDyldImpl.h"
+using namespace llvm;
+using namespace llvm::object;
+
+namespace llvm {
+
+bool RuntimeDyldMachO::
+resolveRelocation(uint8_t *Address, uint8_t *Value, bool isPCRel,
+                  unsigned Type, unsigned Size) {
+  // This just dispatches to the proper target specific routine.
+  switch (CPUType) {
+  default: assert(0 && "Unsupported CPU type!");
+  case mach::CTM_x86_64:
+    return resolveX86_64Relocation((uintptr_t)Address, (uintptr_t)Value,
+                                   isPCRel, Type, Size);
+  case mach::CTM_ARM:
+    return resolveARMRelocation((uintptr_t)Address, (uintptr_t)Value,
+                                isPCRel, Type, Size);
+  }
+  llvm_unreachable("");
+}
+
+bool RuntimeDyldMachO::
+resolveX86_64Relocation(uintptr_t Address, uintptr_t Value,
+                        bool isPCRel, unsigned Type,
+                        unsigned Size) {
+  // If the relocation is PC-relative, the value to be encoded is the
+  // pointer difference.
+  if (isPCRel)
+    // FIXME: It seems this value needs to be adjusted by 4 for an effective PC
+    // address. Is that expected? Only for branches, perhaps?
+    Value -= Address + 4;
+
+  switch(Type) {
+  default:
+    llvm_unreachable("Invalid relocation type!");
+  case macho::RIT_X86_64_Unsigned:
+  case macho::RIT_X86_64_Branch: {
+    // Mask in the target value a byte at a time (we don't have an alignment
+    // guarantee for the target address, so this is safest).
+    uint8_t *p = (uint8_t*)Address;
+    for (unsigned i = 0; i < Size; ++i) {
+      *p++ = (uint8_t)Value;
+      Value >>= 8;
+    }
+    return false;
+  }
+  case macho::RIT_X86_64_Signed:
+  case macho::RIT_X86_64_GOTLoad:
+  case macho::RIT_X86_64_GOT:
+  case macho::RIT_X86_64_Subtractor:
+  case macho::RIT_X86_64_Signed1:
+  case macho::RIT_X86_64_Signed2:
+  case macho::RIT_X86_64_Signed4:
+  case macho::RIT_X86_64_TLV:
+    return Error("Relocation type not implemented yet!");
+  }
+  return false;
+}
+
+bool RuntimeDyldMachO::resolveARMRelocation(uintptr_t Address, uintptr_t Value,
+                                         bool isPCRel, unsigned Type,
+                                         unsigned Size) {
+  // If the relocation is PC-relative, the value to be encoded is the
+  // pointer difference.
+  if (isPCRel) {
+    Value -= Address;
+    // ARM PCRel relocations have an effective-PC offset of two instructions
+    // (four bytes in Thumb mode, 8 bytes in ARM mode).
+    // FIXME: For now, assume ARM mode.
+    Value -= 8;
+  }
+
+  switch(Type) {
+  default:
+    llvm_unreachable("Invalid relocation type!");
+  case macho::RIT_Vanilla: {
+    llvm_unreachable("Invalid relocation type!");
+    // Mask in the target value a byte at a time (we don't have an alignment
+    // guarantee for the target address, so this is safest).
+    uint8_t *p = (uint8_t*)Address;
+    for (unsigned i = 0; i < Size; ++i) {
+      *p++ = (uint8_t)Value;
+      Value >>= 8;
+    }
+    break;
+  }
+  case macho::RIT_ARM_Branch24Bit: {
+    // Mask the value into the target address. We know instructions are
+    // 32-bit aligned, so we can do it all at once.
+    uint32_t *p = (uint32_t*)Address;
+    // The low two bits of the value are not encoded.
+    Value >>= 2;
+    // Mask the value to 24 bits.
+    Value &= 0xffffff;
+    // FIXME: If the destination is a Thumb function (and the instruction
+    // is a non-predicated BL instruction), we need to change it to a BLX
+    // instruction instead.
+
+    // Insert the value into the instruction.
+    *p = (*p & ~0xffffff) | Value;
+    break;
+  }
+  case macho::RIT_ARM_ThumbBranch22Bit:
+  case macho::RIT_ARM_ThumbBranch32Bit:
+  case macho::RIT_ARM_Half:
+  case macho::RIT_ARM_HalfDifference:
+  case macho::RIT_Pair:
+  case macho::RIT_Difference:
+  case macho::RIT_ARM_LocalDifference:
+  case macho::RIT_ARM_PreboundLazyPointer:
+    return Error("Relocation type not implemented yet!");
+  }
+  return false;
+}
+
+bool RuntimeDyldMachO::
+loadSegment32(const MachOObject *Obj,
+              const MachOObject::LoadCommandInfo *SegmentLCI,
+              const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
+  InMemoryStruct<macho::SegmentLoadCommand> SegmentLC;
+  Obj->ReadSegmentLoadCommand(*SegmentLCI, SegmentLC);
+  if (!SegmentLC)
+    return Error("unable to load segment load command");
+
+  for (unsigned SectNum = 0; SectNum != SegmentLC->NumSections; ++SectNum) {
+    InMemoryStruct<macho::Section> Sect;
+    Obj->ReadSection(*SegmentLCI, SectNum, Sect);
+    if (!Sect)
+      return Error("unable to load section: '" + Twine(SectNum) + "'");
+
+    // FIXME: For the time being, we're only loading text segments.
+    if (Sect->Flags != 0x80000400)
+      continue;
+
+    // Address and names of symbols in the section.
+    typedef std::pair<uint64_t, StringRef> SymbolEntry;
+    SmallVector<SymbolEntry, 64> Symbols;
+    // Index of all the names, in this section or not. Used when we're
+    // dealing with relocation entries.
+    SmallVector<StringRef, 64> SymbolNames;
+    for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
+      InMemoryStruct<macho::SymbolTableEntry> STE;
+      Obj->ReadSymbolTableEntry(SymtabLC->SymbolTableOffset, i, STE);
+      if (!STE)
+        return Error("unable to read symbol: '" + Twine(i) + "'");
+      if (STE->SectionIndex > SegmentLC->NumSections)
+        return Error("invalid section index for symbol: '" + Twine(i) + "'");
+      // Get the symbol name.
+      StringRef Name = Obj->getStringAtIndex(STE->StringIndex);
+      SymbolNames.push_back(Name);
+
+      // Just skip symbols not defined in this section.
+      if ((unsigned)STE->SectionIndex - 1 != SectNum)
+        continue;
+
+      // FIXME: Check the symbol type and flags.
+      if (STE->Type != 0xF)  // external, defined in this section.
+        continue;
+      // Flags == 0x8 marks a thumb function for ARM, which is fine as it
+      // doesn't require any special handling here.
+      if (STE->Flags != 0x0 && STE->Flags != 0x8)
+        continue;
+
+      // Remember the symbol.
+      Symbols.push_back(SymbolEntry(STE->Value, Name));
+
+      DEBUG(dbgs() << "Function sym: '" << Name << "' @ " <<
+            (Sect->Address + STE->Value) << "\n");
+    }
+    // Sort the symbols by address, just in case they didn't come in that way.
+    array_pod_sort(Symbols.begin(), Symbols.end());
+
+    // If there weren't any functions (odd, but just in case...)
+    if (!Symbols.size())
+      continue;
+
+    // Extract the function data.
+    uint8_t *Base = (uint8_t*)Obj->getData(SegmentLC->FileOffset,
+                                           SegmentLC->FileSize).data();
+    for (unsigned i = 0, e = Symbols.size() - 1; i != e; ++i) {
+      uint64_t StartOffset = Sect->Address + Symbols[i].first;
+      uint64_t EndOffset = Symbols[i + 1].first - 1;
+      DEBUG(dbgs() << "Extracting function: " << Symbols[i].second
+                   << " from [" << StartOffset << ", " << EndOffset << "]\n");
+      extractFunction(Symbols[i].second, Base + StartOffset, Base + EndOffset);
+    }
+    // The last symbol we do after since the end address is calculated
+    // differently because there is no next symbol to reference.
+    uint64_t StartOffset = Symbols[Symbols.size() - 1].first;
+    uint64_t EndOffset = Sect->Size - 1;
+    DEBUG(dbgs() << "Extracting function: " << Symbols[Symbols.size()-1].second
+                 << " from [" << StartOffset << ", " << EndOffset << "]\n");
+    extractFunction(Symbols[Symbols.size()-1].second,
+                    Base + StartOffset, Base + EndOffset);
+
+    // Now extract the relocation information for each function and process it.
+    for (unsigned j = 0; j != Sect->NumRelocationTableEntries; ++j) {
+      InMemoryStruct<macho::RelocationEntry> RE;
+      Obj->ReadRelocationEntry(Sect->RelocationTableOffset, j, RE);
+      if (RE->Word0 & macho::RF_Scattered)
+        return Error("NOT YET IMPLEMENTED: scattered relocations.");
+      // Word0 of the relocation is the offset into the section where the
+      // relocation should be applied. We need to translate that into an
+      // offset into a function since that's our atom.
+      uint32_t Offset = RE->Word0;
+      // Look for the function containing the address. This is used for JIT
+      // code, so the number of functions in section is almost always going
+      // to be very small (usually just one), so until we have use cases
+      // where that's not true, just use a trivial linear search.
+      unsigned SymbolNum;
+      unsigned NumSymbols = Symbols.size();
+      assert(NumSymbols > 0 && Symbols[0].first <= Offset &&
+             "No symbol containing relocation!");
+      for (SymbolNum = 0; SymbolNum < NumSymbols - 1; ++SymbolNum)
+        if (Symbols[SymbolNum + 1].first > Offset)
+          break;
+      // Adjust the offset to be relative to the symbol.
+      Offset -= Symbols[SymbolNum].first;
+      // Get the name of the symbol containing the relocation.
+      StringRef TargetName = SymbolNames[SymbolNum];
+
+      bool isExtern = (RE->Word1 >> 27) & 1;
+      // Figure out the source symbol of the relocation. If isExtern is true,
+      // this relocation references the symbol table, otherwise it references
+      // a section in the same object, numbered from 1 through NumSections
+      // (SectionBases is [0, NumSections-1]).
+      // FIXME: Some targets (ARM) use internal relocations even for
+      // externally visible symbols, if the definition is in the same
+      // file as the reference. We need to convert those back to by-name
+      // references. We can resolve the address based on the section
+      // offset and see if we have a symbol at that address. If we do,
+      // use that; otherwise, puke.
+      if (!isExtern)
+        return Error("Internal relocations not supported.");
+      uint32_t SourceNum = RE->Word1 & 0xffffff; // 24-bit value
+      StringRef SourceName = SymbolNames[SourceNum];
+
+      // FIXME: Get the relocation addend from the target address.
+
+      // Now store the relocation information. Associate it with the source
+      // symbol.
+      Relocations[SourceName].push_back(RelocationEntry(TargetName,
+                                                        Offset,
+                                                        RE->Word1,
+                                                        0 /*Addend*/));
+      DEBUG(dbgs() << "Relocation at '" << TargetName << "' + " << Offset
+                   << " from '" << SourceName << "(Word1: "
+                   << format("0x%x", RE->Word1) << ")\n");
+    }
+  }
+  return false;
+}
+
+
+bool RuntimeDyldMachO::
+loadSegment64(const MachOObject *Obj,
+              const MachOObject::LoadCommandInfo *SegmentLCI,
+              const InMemoryStruct<macho::SymtabLoadCommand> &SymtabLC) {
+  InMemoryStruct<macho::Segment64LoadCommand> Segment64LC;
+  Obj->ReadSegment64LoadCommand(*SegmentLCI, Segment64LC);
+  if (!Segment64LC)
+    return Error("unable to load segment load command");
+
+  for (unsigned SectNum = 0; SectNum != Segment64LC->NumSections; ++SectNum) {
+    InMemoryStruct<macho::Section64> Sect;
+    Obj->ReadSection64(*SegmentLCI, SectNum, Sect);
+    if (!Sect)
+      return Error("unable to load section: '" + Twine(SectNum) + "'");
+
+    // FIXME: For the time being, we're only loading text segments.
+    if (Sect->Flags != 0x80000400)
+      continue;
+
+    // Address and names of symbols in the section.
+    typedef std::pair<uint64_t, StringRef> SymbolEntry;
+    SmallVector<SymbolEntry, 64> Symbols;
+    // Index of all the names, in this section or not. Used when we're
+    // dealing with relocation entries.
+    SmallVector<StringRef, 64> SymbolNames;
+    for (unsigned i = 0; i != SymtabLC->NumSymbolTableEntries; ++i) {
+      InMemoryStruct<macho::Symbol64TableEntry> STE;
+      Obj->ReadSymbol64TableEntry(SymtabLC->SymbolTableOffset, i, STE);
+      if (!STE)
+        return Error("unable to read symbol: '" + Twine(i) + "'");
+      if (STE->SectionIndex > Segment64LC->NumSections)
+        return Error("invalid section index for symbol: '" + Twine(i) + "'");
+      // Get the symbol name.
+      StringRef Name = Obj->getStringAtIndex(STE->StringIndex);
+      SymbolNames.push_back(Name);
+
+      // Just skip symbols not defined in this section.
+      if ((unsigned)STE->SectionIndex - 1 != SectNum)
+        continue;
+
+      // FIXME: Check the symbol type and flags.
+      if (STE->Type != 0xF)  // external, defined in this section.
+        continue;
+      if (STE->Flags != 0x0)
+        continue;
+
+      // Remember the symbol.
+      Symbols.push_back(SymbolEntry(STE->Value, Name));
+
+      DEBUG(dbgs() << "Function sym: '" << Name << "' @ " <<
+            (Sect->Address + STE->Value) << "\n");
+    }
+    // Sort the symbols by address, just in case they didn't come in that way.
+    array_pod_sort(Symbols.begin(), Symbols.end());
+
+    // If there weren't any functions (odd, but just in case...)
+    if (!Symbols.size())
+      continue;
+
+    // Extract the function data.
+    uint8_t *Base = (uint8_t*)Obj->getData(Segment64LC->FileOffset,
+                                           Segment64LC->FileSize).data();
+    for (unsigned i = 0, e = Symbols.size() - 1; i != e; ++i) {
+      uint64_t StartOffset = Sect->Address + Symbols[i].first;
+      uint64_t EndOffset = Symbols[i + 1].first - 1;
+      DEBUG(dbgs() << "Extracting function: " << Symbols[i].second
+                   << " from [" << StartOffset << ", " << EndOffset << "]\n");
+      extractFunction(Symbols[i].second, Base + StartOffset, Base + EndOffset);
+    }
+    // The last symbol we do after since the end address is calculated
+    // differently because there is no next symbol to reference.
+    uint64_t StartOffset = Symbols[Symbols.size() - 1].first;
+    uint64_t EndOffset = Sect->Size - 1;
+    DEBUG(dbgs() << "Extracting function: " << Symbols[Symbols.size()-1].second
+                 << " from [" << StartOffset << ", " << EndOffset << "]\n");
+    extractFunction(Symbols[Symbols.size()-1].second,
+                    Base + StartOffset, Base + EndOffset);
+
+    // Now extract the relocation information for each function and process it.
+    for (unsigned j = 0; j != Sect->NumRelocationTableEntries; ++j) {
+      InMemoryStruct<macho::RelocationEntry> RE;
+      Obj->ReadRelocationEntry(Sect->RelocationTableOffset, j, RE);
+      if (RE->Word0 & macho::RF_Scattered)
+        return Error("NOT YET IMPLEMENTED: scattered relocations.");
+      // Word0 of the relocation is the offset into the section where the
+      // relocation should be applied. We need to translate that into an
+      // offset into a function since that's our atom.
+      uint32_t Offset = RE->Word0;
+      // Look for the function containing the address. This is used for JIT
+      // code, so the number of functions in section is almost always going
+      // to be very small (usually just one), so until we have use cases
+      // where that's not true, just use a trivial linear search.
+      unsigned SymbolNum;
+      unsigned NumSymbols = Symbols.size();
+      assert(NumSymbols > 0 && Symbols[0].first <= Offset &&
+             "No symbol containing relocation!");
+      for (SymbolNum = 0; SymbolNum < NumSymbols - 1; ++SymbolNum)
+        if (Symbols[SymbolNum + 1].first > Offset)
+          break;
+      // Adjust the offset to be relative to the symbol.
+      Offset -= Symbols[SymbolNum].first;
+      // Get the name of the symbol containing the relocation.
+      StringRef TargetName = SymbolNames[SymbolNum];
+
+      bool isExtern = (RE->Word1 >> 27) & 1;
+      // Figure out the source symbol of the relocation. If isExtern is true,
+      // this relocation references the symbol table, otherwise it references
+      // a section in the same object, numbered from 1 through NumSections
+      // (SectionBases is [0, NumSections-1]).
+      if (!isExtern)
+        return Error("Internal relocations not supported.");
+      uint32_t SourceNum = RE->Word1 & 0xffffff; // 24-bit value
+      StringRef SourceName = SymbolNames[SourceNum];
+
+      // FIXME: Get the relocation addend from the target address.
+
+      // Now store the relocation information. Associate it with the source
+      // symbol.
+      Relocations[SourceName].push_back(RelocationEntry(TargetName,
+                                                        Offset,
+                                                        RE->Word1,
+                                                        0 /*Addend*/));
+      DEBUG(dbgs() << "Relocation at '" << TargetName << "' + " << Offset
+                   << " from '" << SourceName << "(Word1: "
+                   << format("0x%x", RE->Word1) << ")\n");
+    }
+  }
+  return false;
+}
+
+bool RuntimeDyldMachO::loadObject(MemoryBuffer *InputBuffer) {
+  // If the linker is in an error state, don't do anything.
+  if (hasError())
+    return true;
+  // Load the Mach-O wrapper object.
+  std::string ErrorStr;
+  OwningPtr<MachOObject> Obj(
+    MachOObject::LoadFromBuffer(InputBuffer, &ErrorStr));
+  if (!Obj)
+    return Error("unable to load object: '" + ErrorStr + "'");
+
+  // Get the CPU type information from the header.
+  const macho::Header &Header = Obj->getHeader();
+
+  // FIXME: Error checking that the loaded object is compatible with
+  //        the system we're running on.
+  CPUType = Header.CPUType;
+  CPUSubtype = Header.CPUSubtype;
+
+  // Validate that the load commands match what we expect.
+  const MachOObject::LoadCommandInfo *SegmentLCI = 0, *SymtabLCI = 0,
+    *DysymtabLCI = 0;
+  for (unsigned i = 0; i != Header.NumLoadCommands; ++i) {
+    const MachOObject::LoadCommandInfo &LCI = Obj->getLoadCommandInfo(i);
+    switch (LCI.Command.Type) {
+    case macho::LCT_Segment:
+    case macho::LCT_Segment64:
+      if (SegmentLCI)
+        return Error("unexpected input object (multiple segments)");
+      SegmentLCI = &LCI;
+      break;
+    case macho::LCT_Symtab:
+      if (SymtabLCI)
+        return Error("unexpected input object (multiple symbol tables)");
+      SymtabLCI = &LCI;
+      break;
+    case macho::LCT_Dysymtab:
+      if (DysymtabLCI)
+        return Error("unexpected input object (multiple symbol tables)");
+      DysymtabLCI = &LCI;
+      break;
+    default:
+      return Error("unexpected input object (unexpected load command");
+    }
+  }
+
+  if (!SymtabLCI)
+    return Error("no symbol table found in object");
+  if (!SegmentLCI)
+    return Error("no symbol table found in object");
+
+  // Read and register the symbol table data.
+  InMemoryStruct<macho::SymtabLoadCommand> SymtabLC;
+  Obj->ReadSymtabLoadCommand(*SymtabLCI, SymtabLC);
+  if (!SymtabLC)
+    return Error("unable to load symbol table load command");
+  Obj->RegisterStringTable(*SymtabLC);
+
+  // Read the dynamic link-edit information, if present (not present in static
+  // objects).
+  if (DysymtabLCI) {
+    InMemoryStruct<macho::DysymtabLoadCommand> DysymtabLC;
+    Obj->ReadDysymtabLoadCommand(*DysymtabLCI, DysymtabLC);
+    if (!DysymtabLC)
+      return Error("unable to load dynamic link-exit load command");
+
+    // FIXME: We don't support anything interesting yet.
+//    if (DysymtabLC->LocalSymbolsIndex != 0)
+//      return Error("NOT YET IMPLEMENTED: local symbol entries");
+//    if (DysymtabLC->ExternalSymbolsIndex != 0)
+//      return Error("NOT YET IMPLEMENTED: non-external symbol entries");
+//    if (DysymtabLC->UndefinedSymbolsIndex != SymtabLC->NumSymbolTableEntries)
+//      return Error("NOT YET IMPLEMENTED: undefined symbol entries");
+  }
+
+  // Load the segment load command.
+  if (SegmentLCI->Command.Type == macho::LCT_Segment) {
+    if (loadSegment32(Obj.get(), SegmentLCI, SymtabLC))
+      return true;
+  } else {
+    if (loadSegment64(Obj.get(), SegmentLCI, SymtabLC))
+      return true;
+  }
+
+  return false;
+}
+
+// Assign an address to a symbol name and resolve all the relocations
+// associated with it.
+void RuntimeDyldMachO::reassignSymbolAddress(StringRef Name, uint8_t *Addr) {
+  // Assign the address in our symbol table.
+  SymbolTable[Name] = Addr;
+
+  RelocationList &Relocs = Relocations[Name];
+  for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
+    RelocationEntry &RE = Relocs[i];
+    uint8_t *Target = SymbolTable[RE.Target] + RE.Offset;
+    bool isPCRel = (RE.Data >> 24) & 1;
+    unsigned Type = (RE.Data >> 28) & 0xf;
+    unsigned Size = 1 << ((RE.Data >> 25) & 3);
+
+    DEBUG(dbgs() << "Resolving relocation at '" << RE.Target
+          << "' + " << RE.Offset << " (" << format("%p", Target) << ")"
+          << " from '" << Name << " (" << format("%p", Addr) << ")"
+          << "(" << (isPCRel ? "pcrel" : "absolute")
+          << ", type: " << Type << ", Size: " << Size << ").\n");
+
+    resolveRelocation(Target, Addr, isPCRel, Type, Size);
+    RE.isResolved = true;
+  }
+}
+
+bool RuntimeDyldMachO::isKnownFormat(const MemoryBuffer *InputBuffer) {
+  StringRef Magic = InputBuffer->getBuffer().slice(0, 4);
+  if (Magic == "\xFE\xED\xFA\xCE") return true;
+  if (Magic == "\xCE\xFA\xED\xFE") return true;
+  if (Magic == "\xFE\xED\xFA\xCF") return true;
+  if (Magic == "\xCF\xFA\xED\xFE") return true;
+  return false;
+}
+
+} // end namespace llvm