Move class methods out-of-line. This reduces the indentation, and is more in

line with LLVM's general coding style.
No functionality change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133645 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 1410 insertions, 1289 deletions

diff --git a/lib/MC/MachObjectWriter.cpp b/lib/MC/MachObjectWriter.cpp
index f049b1c6e2..1819c4053b 100644
--- a/lib/MC/MachObjectWriter.cpp
+++ b/lib/MC/MachObjectWriter.cpp
@@ -120,37 +120,8 @@ private:
     return SectionAddress.lookup(SD);
   }
   uint64_t getSymbolAddress(const MCSymbolData* SD,
-                            const MCAsmLayout &Layout) const {
-    const MCSymbol &S = SD->getSymbol();
-
-    // If this is a variable, then recursively evaluate now.
-    if (S.isVariable()) {
-      MCValue Target;
-      if (!S.getVariableValue()->EvaluateAsRelocatable(Target, Layout))
-        report_fatal_error("unable to evaluate offset for variable '" +
-                           S.getName() + "'");
-
-      // Verify that any used symbols are defined.
-      if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined())
-        report_fatal_error("unable to evaluate offset to undefined symbol '" +
-                           Target.getSymA()->getSymbol().getName() + "'");
-      if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined())
-        report_fatal_error("unable to evaluate offset to undefined symbol '" +
-                           Target.getSymB()->getSymbol().getName() + "'");
-
-      uint64_t Address = Target.getConstant();
-      if (Target.getSymA())
-        Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
-                                      Target.getSymA()->getSymbol()), Layout);
-      if (Target.getSymB())
-        Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
-                                      Target.getSymB()->getSymbol()), Layout);
-      return Address;
-    }
+                            const MCAsmLayout &Layout) const;
 
-    return getSectionAddress(SD->getFragment()->getParent()) +
-      Layout.getSymbolOffset(SD);
-  }
   uint64_t getFragmentAddress(const MCFragment *Fragment,
                             const MCAsmLayout &Layout) const {
     return getSectionAddress(Fragment->getParent()) +
@@ -158,18 +129,7 @@ private:
   }
 
   uint64_t getPaddingSize(const MCSectionData *SD,
-                          const MCAsmLayout &Layout) const {
-    uint64_t EndAddr = getSectionAddress(SD) + Layout.getSectionAddressSize(SD);
-    unsigned Next = SD->getLayoutOrder() + 1;
-    if (Next >= Layout.getSectionOrder().size())
-      return 0;
-
-    const MCSectionData &NextSD = *Layout.getSectionOrder()[Next];
-    if (NextSD.getSection().isVirtualSection())
-      return 0;
-    return OffsetToAlignment(EndAddr, NextSD.getAlignment());
-  }
-
+                          const MCAsmLayout &Layout) const;
 public:
   MachObjectWriter(MCMachObjectTargetWriter *MOTW, raw_ostream &_OS,
                    bool _IsLittleEndian)
@@ -188,33 +148,7 @@ public:
   /// @}
 
   void WriteHeader(unsigned NumLoadCommands, unsigned LoadCommandsSize,
-                   bool SubsectionsViaSymbols) {
-    uint32_t Flags = 0;
-
-    if (SubsectionsViaSymbols)
-      Flags |= macho::HF_SubsectionsViaSymbols;
-
-    // struct mach_header (28 bytes) or
-    // struct mach_header_64 (32 bytes)
-
-    uint64_t Start = OS.tell();
-    (void) Start;
-
-    Write32(is64Bit() ? macho::HM_Object64 : macho::HM_Object32);
-
-    Write32(TargetObjectWriter->getCPUType());
-    Write32(TargetObjectWriter->getCPUSubtype());
-
-    Write32(macho::HFT_Object);
-    Write32(NumLoadCommands);
-    Write32(LoadCommandsSize);
-    Write32(Flags);
-    if (is64Bit())
-      Write32(0); // reserved
-
-    assert(OS.tell() - Start ==
-           (is64Bit() ? macho::Header64Size : macho::Header32Size));
-  }
+                   bool SubsectionsViaSymbols);
 
   /// WriteSegmentLoadCommand - Write a segment load command.
   ///
@@ -223,105 +157,15 @@ public:
   void WriteSegmentLoadCommand(unsigned NumSections,
                                uint64_t VMSize,
                                uint64_t SectionDataStartOffset,
-                               uint64_t SectionDataSize) {
-    // struct segment_command (56 bytes) or
-    // struct segment_command_64 (72 bytes)
-
-    uint64_t Start = OS.tell();
-    (void) Start;
-
-    unsigned SegmentLoadCommandSize =
-      is64Bit() ? macho::SegmentLoadCommand64Size:
-      macho::SegmentLoadCommand32Size;
-    Write32(is64Bit() ? macho::LCT_Segment64 : macho::LCT_Segment);
-    Write32(SegmentLoadCommandSize +
-            NumSections * (is64Bit() ? macho::Section64Size :
-                           macho::Section32Size));
-
-    WriteBytes("", 16);
-    if (is64Bit()) {
-      Write64(0); // vmaddr
-      Write64(VMSize); // vmsize
-      Write64(SectionDataStartOffset); // file offset
-      Write64(SectionDataSize); // file size
-    } else {
-      Write32(0); // vmaddr
-      Write32(VMSize); // vmsize
-      Write32(SectionDataStartOffset); // file offset
-      Write32(SectionDataSize); // file size
-    }
-    Write32(0x7); // maxprot
-    Write32(0x7); // initprot
-    Write32(NumSections);
-    Write32(0); // flags
-
-    assert(OS.tell() - Start == SegmentLoadCommandSize);
-  }
+                               uint64_t SectionDataSize);
 
   void WriteSection(const MCAssembler &Asm, const MCAsmLayout &Layout,
                     const MCSectionData &SD, uint64_t FileOffset,
-                    uint64_t RelocationsStart, unsigned NumRelocations) {
-    uint64_t SectionSize = Layout.getSectionAddressSize(&SD);
-
-    // The offset is unused for virtual sections.
-    if (SD.getSection().isVirtualSection()) {
-      assert(Layout.getSectionFileSize(&SD) == 0 && "Invalid file size!");
-      FileOffset = 0;
-    }
-
-    // struct section (68 bytes) or
-    // struct section_64 (80 bytes)
-
-    uint64_t Start = OS.tell();
-    (void) Start;
-
-    const MCSectionMachO &Section = cast<MCSectionMachO>(SD.getSection());
-    WriteBytes(Section.getSectionName(), 16);
-    WriteBytes(Section.getSegmentName(), 16);
-    if (is64Bit()) {
-      Write64(getSectionAddress(&SD)); // address
-      Write64(SectionSize); // size
-    } else {
-      Write32(getSectionAddress(&SD)); // address
-      Write32(SectionSize); // size
-    }
-    Write32(FileOffset);
-
-    unsigned Flags = Section.getTypeAndAttributes();
-    if (SD.hasInstructions())
-      Flags |= MCSectionMachO::S_ATTR_SOME_INSTRUCTIONS;
-
-    assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
-    Write32(Log2_32(SD.getAlignment()));
-    Write32(NumRelocations ? RelocationsStart : 0);
-    Write32(NumRelocations);
-    Write32(Flags);
-    Write32(IndirectSymBase.lookup(&SD)); // reserved1
-    Write32(Section.getStubSize()); // reserved2
-    if (is64Bit())
-      Write32(0); // reserved3
-
-    assert(OS.tell() - Start == (is64Bit() ? macho::Section64Size :
-           macho::Section32Size));
-  }
+                    uint64_t RelocationsStart, unsigned NumRelocations);
 
   void WriteSymtabLoadCommand(uint32_t SymbolOffset, uint32_t NumSymbols,
                               uint32_t StringTableOffset,
-                              uint32_t StringTableSize) {
-    // struct symtab_command (24 bytes)
-
-    uint64_t Start = OS.tell();
-    (void) Start;
-
-    Write32(macho::LCT_Symtab);
-    Write32(macho::SymtabLoadCommandSize);
-    Write32(SymbolOffset);
-    Write32(NumSymbols);
-    Write32(StringTableOffset);
-    Write32(StringTableSize);
-
-    assert(OS.tell() - Start == macho::SymtabLoadCommandSize);
-  }
+                              uint32_t StringTableSize);
 
   void WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
                                 uint32_t NumLocalSymbols,
@@ -330,100 +174,9 @@ public:
                                 uint32_t FirstUndefinedSymbol,
                                 uint32_t NumUndefinedSymbols,
                                 uint32_t IndirectSymbolOffset,
-                                uint32_t NumIndirectSymbols) {
-    // struct dysymtab_command (80 bytes)
-
-    uint64_t Start = OS.tell();
-    (void) Start;
-
-    Write32(macho::LCT_Dysymtab);
-    Write32(macho::DysymtabLoadCommandSize);
-    Write32(FirstLocalSymbol);
-    Write32(NumLocalSymbols);
-    Write32(FirstExternalSymbol);
-    Write32(NumExternalSymbols);
-    Write32(FirstUndefinedSymbol);
-    Write32(NumUndefinedSymbols);
-    Write32(0); // tocoff
-    Write32(0); // ntoc
-    Write32(0); // modtaboff
-    Write32(0); // nmodtab
-    Write32(0); // extrefsymoff
-    Write32(0); // nextrefsyms
-    Write32(IndirectSymbolOffset);
-    Write32(NumIndirectSymbols);
-    Write32(0); // extreloff
-    Write32(0); // nextrel
-    Write32(0); // locreloff
-    Write32(0); // nlocrel
-
-    assert(OS.tell() - Start == macho::DysymtabLoadCommandSize);
-  }
-
-  void WriteNlist(MachSymbolData &MSD, const MCAsmLayout &Layout) {
-    MCSymbolData &Data = *MSD.SymbolData;
-    const MCSymbol &Symbol = Data.getSymbol();
-    uint8_t Type = 0;
-    uint16_t Flags = Data.getFlags();
-    uint32_t Address = 0;
-
-    // Set the N_TYPE bits. See <mach-o/nlist.h>.
-    //
-    // FIXME: Are the prebound or indirect fields possible here?
-    if (Symbol.isUndefined())
-      Type = macho::STT_Undefined;
-    else if (Symbol.isAbsolute())
-      Type = macho::STT_Absolute;
-    else
-      Type = macho::STT_Section;
-
-    // FIXME: Set STAB bits.
-
-    if (Data.isPrivateExtern())
-      Type |= macho::STF_PrivateExtern;
-
-    // Set external bit.
-    if (Data.isExternal() || Symbol.isUndefined())
-      Type |= macho::STF_External;
-
-    // Compute the symbol address.
-    if (Symbol.isDefined()) {
-      if (Symbol.isAbsolute()) {
-        Address = cast<MCConstantExpr>(Symbol.getVariableValue())->getValue();
-      } else {
-        Address = getSymbolAddress(&Data, Layout);
-      }
-    } else if (Data.isCommon()) {
-      // Common symbols are encoded with the size in the address
-      // field, and their alignment in the flags.
-      Address = Data.getCommonSize();
-
-      // Common alignment is packed into the 'desc' bits.
-      if (unsigned Align = Data.getCommonAlignment()) {
-        unsigned Log2Size = Log2_32(Align);
-        assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
-        if (Log2Size > 15)
-          report_fatal_error("invalid 'common' alignment '" +
-                            Twine(Align) + "'");
-        // FIXME: Keep this mask with the SymbolFlags enumeration.
-        Flags = (Flags & 0xF0FF) | (Log2Size << 8);
-      }
-    }
-
-    // struct nlist (12 bytes)
-
-    Write32(MSD.StringIndex);
-    Write8(Type);
-    Write8(MSD.SectionIndex);
+                                uint32_t NumIndirectSymbols);
 
-    // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
-    // value.
-    Write16(Flags);
-    if (is64Bit())
-      Write64(Address);
-    else
-      Write32(Address);
-  }
+  void WriteNlist(MachSymbolData &MSD, const MCAsmLayout &Layout);
 
   // FIXME: We really need to improve the relocation validation. Basically, we
   // want to implement a separate computation which evaluates the relocation
@@ -446,650 +199,453 @@ public:
   void RecordX86_64Relocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
                               const MCFragment *Fragment,
                               const MCFixup &Fixup, MCValue Target,
-                              uint64_t &FixedValue) {
-    unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
-    unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind());
-    unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
-
-    // See <reloc.h>.
-    uint32_t FixupOffset =
-      Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
-    uint32_t FixupAddress =
-      getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
-    int64_t Value = 0;
-    unsigned Index = 0;
-    unsigned IsExtern = 0;
-    unsigned Type = 0;
-
-    Value = Target.getConstant();
-
-    if (IsPCRel) {
-      // Compensate for the relocation offset, Darwin x86_64 relocations only
-      // have the addend and appear to have attempted to define it to be the
-      // actual expression addend without the PCrel bias. However, instructions
-      // with data following the relocation are not accommodated for (see comment
-      // below regarding SIGNED{1,2,4}), so it isn't exactly that either.
-      Value += 1LL << Log2Size;
-    }
-
-    if (Target.isAbsolute()) { // constant
-      // SymbolNum of 0 indicates the absolute section.
-      Type = macho::RIT_X86_64_Unsigned;
-      Index = 0;
-
-      // FIXME: I believe this is broken, I don't think the linker can
-      // understand it. I think it would require a local relocation, but I'm not
-      // sure if that would work either. The official way to get an absolute
-      // PCrel relocation is to use an absolute symbol (which we don't support
-      // yet).
-      if (IsPCRel) {
-        IsExtern = 1;
-        Type = macho::RIT_X86_64_Branch;
-      }
-    } else if (Target.getSymB()) { // A - B + constant
-      const MCSymbol *A = &Target.getSymA()->getSymbol();
-      MCSymbolData &A_SD = Asm.getSymbolData(*A);
-      const MCSymbolData *A_Base = Asm.getAtom(&A_SD);
-
-      const MCSymbol *B = &Target.getSymB()->getSymbol();
-      MCSymbolData &B_SD = Asm.getSymbolData(*B);
-      const MCSymbolData *B_Base = Asm.getAtom(&B_SD);
-
-      // Neither symbol can be modified.
-      if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
-          Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
-        report_fatal_error("unsupported relocation of modified symbol");
-
-      // We don't support PCrel relocations of differences. Darwin 'as' doesn't
-      // implement most of these correctly.
-      if (IsPCRel)
-        report_fatal_error("unsupported pc-relative relocation of difference");
-
-      // The support for the situation where one or both of the symbols would
-      // require a local relocation is handled just like if the symbols were
-      // external.  This is certainly used in the case of debug sections where
-      // the section has only temporary symbols and thus the symbols don't have
-      // base symbols.  This is encoded using the section ordinal and
-      // non-extern relocation entries.
-
-      // Darwin 'as' doesn't emit correct relocations for this (it ends up with
-      // a single SIGNED relocation); reject it for now.  Except the case where
-      // both symbols don't have a base, equal but both NULL.
-      if (A_Base == B_Base && A_Base)
-        report_fatal_error("unsupported relocation with identical base");
-
-      Value += getSymbolAddress(&A_SD, Layout) -
-        (A_Base == NULL ? 0 : getSymbolAddress(A_Base, Layout));
-      Value -= getSymbolAddress(&B_SD, Layout) -
-        (B_Base == NULL ? 0 : getSymbolAddress(B_Base, Layout));
-
-      if (A_Base) {
-        Index = A_Base->getIndex();
-        IsExtern = 1;
-      }
-      else {
-        Index = A_SD.getFragment()->getParent()->getOrdinal() + 1;
-        IsExtern = 0;
-      }
-      Type = macho::RIT_X86_64_Unsigned;
-
-      macho::RelocationEntry MRE;
-      MRE.Word0 = FixupOffset;
-      MRE.Word1 = ((Index     <<  0) |
-                   (IsPCRel   << 24) |
-                   (Log2Size  << 25) |
-                   (IsExtern  << 27) |
-                   (Type      << 28));
-      Relocations[Fragment->getParent()].push_back(MRE);
-
-      if (B_Base) {
-        Index = B_Base->getIndex();
-        IsExtern = 1;
-      }
-      else {
-        Index = B_SD.getFragment()->getParent()->getOrdinal() + 1;
-        IsExtern = 0;
-      }
-      Type = macho::RIT_X86_64_Subtractor;
-    } else {
-      const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
-      MCSymbolData &SD = Asm.getSymbolData(*Symbol);
-      const MCSymbolData *Base = Asm.getAtom(&SD);
-
-      // Relocations inside debug sections always use local relocations when
-      // possible. This seems to be done because the debugger doesn't fully
-      // understand x86_64 relocation entries, and expects to find values that
-      // have already been fixed up.
-      if (Symbol->isInSection()) {
-        const MCSectionMachO &Section = static_cast<const MCSectionMachO&>(
-          Fragment->getParent()->getSection());
-        if (Section.hasAttribute(MCSectionMachO::S_ATTR_DEBUG))
-          Base = 0;
-      }
-
-      // x86_64 almost always uses external relocations, except when there is no
-      // symbol to use as a base address (a local symbol with no preceding
-      // non-local symbol).
-      if (Base) {
-        Index = Base->getIndex();
-        IsExtern = 1;
-
-        // Add the local offset, if needed.
-        if (Base != &SD)
-          Value += Layout.getSymbolOffset(&SD) - Layout.getSymbolOffset(Base);
-      } else if (Symbol->isInSection() && !Symbol->isVariable()) {
-        // The index is the section ordinal (1-based).
-        Index = SD.getFragment()->getParent()->getOrdinal() + 1;
-        IsExtern = 0;
-        Value += getSymbolAddress(&SD, Layout);
-
-        if (IsPCRel)
-          Value -= FixupAddress + (1 << Log2Size);
-      } else if (Symbol->isVariable()) {
-        const MCExpr *Value = Symbol->getVariableValue();
-        int64_t Res;
-        bool isAbs = Value->EvaluateAsAbsolute(Res, Layout, SectionAddress);
-        if (isAbs) {
-          FixedValue = Res;
-          return;
-        } else {
-          report_fatal_error("unsupported relocation of variable '" +
-                             Symbol->getName() + "'");
-        }
-      } else {
-        report_fatal_error("unsupported relocation of undefined symbol '" +
-                           Symbol->getName() + "'");
-      }
-
-      MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
-      if (IsPCRel) {
-        if (IsRIPRel) {
-          if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
-            // x86_64 distinguishes movq foo@GOTPCREL so that the linker can
-            // rewrite the movq to an leaq at link time if the symbol ends up in
-            // the same linkage unit.
-            if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load)
-              Type = macho::RIT_X86_64_GOTLoad;
-            else
-              Type = macho::RIT_X86_64_GOT;
-          }  else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
-            Type = macho::RIT_X86_64_TLV;
-          }  else if (Modifier != MCSymbolRefExpr::VK_None) {
-            report_fatal_error("unsupported symbol modifier in relocation");
-          } else {
-            Type = macho::RIT_X86_64_Signed;
-
-            // The Darwin x86_64 relocation format has a problem where it cannot
-            // encode an address (L<foo> + <constant>) which is outside the atom
-            // containing L<foo>. Generally, this shouldn't occur but it does
-            // happen when we have a RIPrel instruction with data following the
-            // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel
-            // adjustment Darwin x86_64 uses, the offset is still negative and
-            // the linker has no way to recognize this.
-            //
-            // To work around this, Darwin uses several special relocation types
-            // to indicate the offsets. However, the specification or
-            // implementation of these seems to also be incomplete; they should
-            // adjust the addend as well based on the actual encoded instruction
-            // (the additional bias), but instead appear to just look at the
-            // final offset.
-            switch (-(Target.getConstant() + (1LL << Log2Size))) {
-            case 1: Type = macho::RIT_X86_64_Signed1; break;
-            case 2: Type = macho::RIT_X86_64_Signed2; break;
-            case 4: Type = macho::RIT_X86_64_Signed4; break;
-            }
-          }
-        } else {
-          if (Modifier != MCSymbolRefExpr::VK_None)
-            report_fatal_error("unsupported symbol modifier in branch "
-                              "relocation");
-
-          Type = macho::RIT_X86_64_Branch;
-        }
-      } else {
-        if (Modifier == MCSymbolRefExpr::VK_GOT) {
-          Type = macho::RIT_X86_64_GOT;
-        } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
-          // GOTPCREL is allowed as a modifier on non-PCrel instructions, in
-          // which case all we do is set the PCrel bit in the relocation entry;
-          // this is used with exception handling, for example. The source is
-          // required to include any necessary offset directly.
-          Type = macho::RIT_X86_64_GOT;
-          IsPCRel = 1;
-        } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
-          report_fatal_error("TLVP symbol modifier should have been rip-rel");
-        } else if (Modifier != MCSymbolRefExpr::VK_None)
-          report_fatal_error("unsupported symbol modifier in relocation");
-        else
-          Type = macho::RIT_X86_64_Unsigned;
-      }
-    }
-
-    // x86_64 always writes custom values into the fixups.
-    FixedValue = Value;
-
-    // struct relocation_info (8 bytes)
-    macho::RelocationEntry MRE;
-    MRE.Word0 = FixupOffset;
-    MRE.Word1 = ((Index     <<  0) |
-                 (IsPCRel   << 24) |
-                 (Log2Size  << 25) |
-                 (IsExtern  << 27) |
-                 (Type      << 28));
-    Relocations[Fragment->getParent()].push_back(MRE);
-  }
+                              uint64_t &FixedValue);
 
   void RecordScatteredRelocation(const MCAssembler &Asm,
                                  const MCAsmLayout &Layout,
                                  const MCFragment *Fragment,
                                  const MCFixup &Fixup, MCValue Target,
                                  unsigned Log2Size,
-                                 uint64_t &FixedValue) {
-    uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
-    unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
-    unsigned Type = macho::RIT_Vanilla;
-
-    // See <reloc.h>.
-    const MCSymbol *A = &Target.getSymA()->getSymbol();
-    MCSymbolData *A_SD = &Asm.getSymbolData(*A);
-
-    if (!A_SD->getFragment())
-      report_fatal_error("symbol '" + A->getName() +
-                        "' can not be undefined in a subtraction expression");
-
-    uint32_t Value = getSymbolAddress(A_SD, Layout);
-    uint64_t SecAddr = getSectionAddress(A_SD->getFragment()->getParent());
-    FixedValue += SecAddr;
-    uint32_t Value2 = 0;
-
-    if (const MCSymbolRefExpr *B = Target.getSymB()) {
-      MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
-
-      if (!B_SD->getFragment())
-        report_fatal_error("symbol '" + B->getSymbol().getName() +
-                          "' can not be undefined in a subtraction expression");
-
-      // Select the appropriate difference relocation type.
-      //
-      // Note that there is no longer any semantic difference between these two
-      // relocation types from the linkers point of view, this is done solely
-      // for pedantic compatibility with 'as'.
-      Type = A_SD->isExternal() ? (unsigned)macho::RIT_Difference :
-        (unsigned)macho::RIT_Generic_LocalDifference;
-      Value2 = getSymbolAddress(B_SD, Layout);
-      FixedValue -= getSectionAddress(B_SD->getFragment()->getParent());
-    }
-
-    // Relocations are written out in reverse order, so the PAIR comes first.
-    if (Type == macho::RIT_Difference ||
-        Type == macho::RIT_Generic_LocalDifference) {
-      macho::RelocationEntry MRE;
-      MRE.Word0 = ((0         <<  0) |
-                   (macho::RIT_Pair  << 24) |
-                   (Log2Size  << 28) |
-                   (IsPCRel   << 30) |
-                   macho::RF_Scattered);
-      MRE.Word1 = Value2;
-      Relocations[Fragment->getParent()].push_back(MRE);
-    }
-
-    macho::RelocationEntry MRE;
-    MRE.Word0 = ((FixupOffset <<  0) |
-                 (Type        << 24) |
-                 (Log2Size    << 28) |
-                 (IsPCRel     << 30) |
-                 macho::RF_Scattered);
-    MRE.Word1 = Value;
-    Relocations[Fragment->getParent()].push_back(MRE);
-  }
+                                 uint64_t &FixedValue);
 
   void RecordARMScatteredRelocation(const MCAssembler &Asm,
                                     const MCAsmLayout &Layout,
                                     const MCFragment *Fragment,
                                     const MCFixup &Fixup, MCValue Target,
                                     unsigned Log2Size,
-                                    uint64_t &FixedValue) {
-    uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
-    unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
-    unsigned Type = macho::RIT_Vanilla;
+                                    uint64_t &FixedValue);
 
-    // See <reloc.h>.
-    const MCSymbol *A = &Target.getSymA()->getSymbol();
-    MCSymbolData *A_SD = &Asm.getSymbolData(*A);
+  void RecordARMMovwMovtRelocation(const MCAssembler &Asm,
+                                   const MCAsmLayout &Layout,
+                                   const MCFragment *Fragment,
+                                   const MCFixup &Fixup, MCValue Target,
+                                   uint64_t &FixedValue);
 
-    if (!A_SD->getFragment())
-      report_fatal_error("symbol '" + A->getName() +
-                        "' can not be undefined in a subtraction expression");
+  void RecordTLVPRelocation(const MCAssembler &Asm,
+                            const MCAsmLayout &Layout,
+                            const MCFragment *Fragment,
+                            const MCFixup &Fixup, MCValue Target,
+                            uint64_t &FixedValue);
 
-    uint32_t Value = getSymbolAddress(A_SD, Layout);
-    uint64_t SecAddr = getSectionAddress(A_SD->getFragment()->getParent());
-    FixedValue += SecAddr;
-    uint32_t Value2 = 0;
+  static bool getARMFixupKindMachOInfo(unsigned Kind, unsigned &RelocType,
+                                       unsigned &Log2Size);
 
-    if (const MCSymbolRefExpr *B = Target.getSymB()) {
-      MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
+  void RecordARMRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
+                           const MCFragment *Fragment, const MCFixup &Fixup,
+                           MCValue Target, uint64_t &FixedValue);
 
-      if (!B_SD->getFragment())
-        report_fatal_error("symbol '" + B->getSymbol().getName() +
-                          "' can not be undefined in a subtraction expression");
+  void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
+                        const MCFragment *Fragment, const MCFixup &Fixup,
+                        MCValue Target, uint64_t &FixedValue);
 
-      // Select the appropriate difference relocation type.
-      Type = macho::RIT_Difference;
-      Value2 = getSymbolAddress(B_SD, Layout);
-      FixedValue -= getSectionAddress(B_SD->getFragment()->getParent());
-    }
+  void BindIndirectSymbols(MCAssembler &Asm);
 
-    // Relocations are written out in reverse order, so the PAIR comes first.
-    if (Type == macho::RIT_Difference ||
-        Type == macho::RIT_Generic_LocalDifference) {
-      macho::RelocationEntry MRE;
-      MRE.Word0 = ((0         <<  0) |
-                   (macho::RIT_Pair  << 24) |
-                   (Log2Size  << 28) |
-                   (IsPCRel   << 30) |
-                   macho::RF_Scattered);
-      MRE.Word1 = Value2;
-      Relocations[Fragment->getParent()].push_back(MRE);
-    }
+  /// ComputeSymbolTable - Compute the symbol table data
+  ///
+  /// \param StringTable [out] - The string table data.
+  /// \param StringIndexMap [out] - Map from symbol names to offsets in the
+  /// string table.
+  void ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
+                          std::vector<MachSymbolData> &LocalSymbolData,
+                          std::vector<MachSymbolData> &ExternalSymbolData,
+                          std::vector<MachSymbolData> &UndefinedSymbolData);
 
-    macho::RelocationEntry MRE;
-    MRE.Word0 = ((FixupOffset <<  0) |
-                 (Type        << 24) |
-                 (Log2Size    << 28) |
-                 (IsPCRel     << 30) |
-                 macho::RF_Scattered);
-    MRE.Word1 = Value;
-    Relocations[Fragment->getParent()].push_back(MRE);
-  }
+  void computeSectionAddresses(const MCAssembler &Asm,
+                               const MCAsmLayout &Layout);
 
-  void RecordARMMovwMovtRelocation(const MCAssembler &Asm,
-                                   const MCAsmLayout &Layout,
-                                   const MCFragment *Fragment,
-                                   const MCFixup &Fixup, MCValue Target,
-                                   uint64_t &FixedValue) {
-    uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
-    unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
-    unsigned Type = macho::RIT_ARM_Half;
+  void ExecutePostLayoutBinding(MCAssembler &Asm, const MCAsmLayout &Layout);
 
-    // See <reloc.h>.
-    const MCSymbol *A = &Target.getSymA()->getSymbol();
-    MCSymbolData *A_SD = &Asm.getSymbolData(*A);
+  virtual bool IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
+                                                      const MCSymbolData &DataA,
+                                                      const MCFragment &FB,
+                                                      bool InSet,
+                                                      bool IsPCRel) const;
 
-    if (!A_SD->getFragment())
-      report_fatal_error("symbol '" + A->getName() +
-                        "' can not be undefined in a subtraction expression");
+  void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout);
+};
 
-    uint32_t Value = getSymbolAddress(A_SD, Layout);
-    uint32_t Value2 = 0;
-    uint64_t SecAddr = getSectionAddress(A_SD->getFragment()->getParent());
-    FixedValue += SecAddr;
+} // end anonymous namespace
 
-    if (const MCSymbolRefExpr *B = Target.getSymB()) {
-      MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
+uint64_t MachObjectWriter::getSymbolAddress(const MCSymbolData* SD,
+                                            const MCAsmLayout &Layout) const {
+  const MCSymbol &S = SD->getSymbol();
 
-      if (!B_SD->getFragment())
-        report_fatal_error("symbol '" + B->getSymbol().getName() +
-                          "' can not be undefined in a subtraction expression");
+  // If this is a variable, then recursively evaluate now.
+  if (S.isVariable()) {
+    MCValue Target;
+    if (!S.getVariableValue()->EvaluateAsRelocatable(Target, Layout))
+      report_fatal_error("unable to evaluate offset for variable '" +
+                         S.getName() + "'");
 
-      // Select the appropriate difference relocation type.
-      Type = macho::RIT_ARM_HalfDifference;
-      Value2 = getSymbolAddress(B_SD, Layout);
-      FixedValue -= getSectionAddress(B_SD->getFragment()->getParent());
-    }
+    // Verify that any used symbols are defined.
+    if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined())
+      report_fatal_error("unable to evaluate offset to undefined symbol '" +
+                         Target.getSymA()->getSymbol().getName() + "'");
+    if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined())
+      report_fatal_error("unable to evaluate offset to undefined symbol '" +
+                         Target.getSymB()->getSymbol().getName() + "'");
 
-    // Relocations are written out in reverse order, so the PAIR comes first.
-    // ARM_RELOC_HALF and ARM_RELOC_HALF_SECTDIFF abuse the r_length field:
-    //
-    // For these two r_type relocations they always have a pair following them
-    // and the r_length bits are used differently.  The encoding of the
-    // r_length is as follows:
-    // low bit of r_length:
-    //  0 - :lower16: for movw instructions
-    //  1 - :upper16: for movt instructions
-    // high bit of r_length:
-    //  0 - arm instructions
-    //  1 - thumb instructions
-    // the other half of the relocated expression is in the following pair
-    // relocation entry in the the low 16 bits of r_address field.
-    unsigned ThumbBit = 0;
-    unsigned MovtBit = 0;
-    switch ((unsigned)Fixup.getKind()) {
-    default: break;
-    case ARM::fixup_arm_movt_hi16:
-    case ARM::fixup_arm_movt_hi16_pcrel:
-      MovtBit = 1;
-      break;
-    case ARM::fixup_t2_movt_hi16:
-    case ARM::fixup_t2_movt_hi16_pcrel:
-      MovtBit = 1;
-      // Fallthrough
-    case ARM::fixup_t2_movw_lo16:
-    case ARM::fixup_t2_movw_lo16_pcrel:
-      ThumbBit = 1;
-      break;
-    }
+    uint64_t Address = Target.getConstant();
+    if (Target.getSymA())
+      Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
+                                    Target.getSymA()->getSymbol()), Layout);
+    if (Target.getSymB())
+      Address += getSymbolAddress(&Layout.getAssembler().getSymbolData(
+                                    Target.getSymB()->getSymbol()), Layout);
+    return Address;
+  }
 
+  return getSectionAddress(SD->getFragment()->getParent()) +
+    Layout.getSymbolOffset(SD);
+}
 
-    if (Type == macho::RIT_ARM_HalfDifference) {
-      uint32_t OtherHalf = MovtBit
-        ? (FixedValue & 0xffff) : ((FixedValue & 0xffff0000) >> 16);
+uint64_t MachObjectWriter::getPaddingSize(const MCSectionData *SD,
+                                          const MCAsmLayout &Layout) const {
+  uint64_t EndAddr = getSectionAddress(SD) + Layout.getSectionAddressSize(SD);
+  unsigned Next = SD->getLayoutOrder() + 1;
+  if (Next >= Layout.getSectionOrder().size())
+    return 0;
+
+  const MCSectionData &NextSD = *Layout.getSectionOrder()[Next];
+  if (NextSD.getSection().isVirtualSection())
+    return 0;
+  return OffsetToAlignment(EndAddr, NextSD.getAlignment());
+}
 
-      macho::RelocationEntry MRE;
-      MRE.Word0 = ((OtherHalf       <<  0) |
-                   (macho::RIT_Pair << 24) |
-                   (MovtBit         << 28) |
-                   (ThumbBit        << 29) |
-                   (IsPCRel         << 30) |
-                   macho::RF_Scattered);
-      MRE.Word1 = Value2;
-      Relocations[Fragment->getParent()].push_back(MRE);
-    }
+void MachObjectWriter::WriteHeader(unsigned NumLoadCommands,
+                                   unsigned LoadCommandsSize,
+                                   bool SubsectionsViaSymbols) {
+  uint32_t Flags = 0;
 
-    macho::RelocationEntry MRE;
-    MRE.Word0 = ((FixupOffset <<  0) |
-                 (Type        << 24) |
-                 (MovtBit     << 28) |
-                 (ThumbBit    << 29) |
-                 (IsPCRel     << 30) |
-                 macho::RF_Scattered);
-    MRE.Word1 = Value;
-    Relocations[Fragment->getParent()].push_back(MRE);
+  if (SubsectionsViaSymbols)
+    Flags |= macho::HF_SubsectionsViaSymbols;
+
+  // struct mach_header (28 bytes) or
+  // struct mach_header_64 (32 bytes)
+
+  uint64_t Start = OS.tell();
+  (void) Start;
+
+  Write32(is64Bit() ? macho::HM_Object64 : macho::HM_Object32);
+
+  Write32(TargetObjectWriter->getCPUType());
+  Write32(TargetObjectWriter->getCPUSubtype());
+
+  Write32(macho::HFT_Object);
+  Write32(NumLoadCommands);
+  Write32(LoadCommandsSize);
+  Write32(Flags);
+  if (is64Bit())
+    Write32(0); // reserved
+
+  assert(OS.tell() - Start ==
+         (is64Bit() ? macho::Header64Size : macho::Header32Size));
+}
+
+/// WriteSegmentLoadCommand - Write a segment load command.
+///
+/// \arg NumSections - The number of sections in this segment.
+/// \arg SectionDataSize - The total size of the sections.
+void MachObjectWriter::WriteSegmentLoadCommand(unsigned NumSections,
+                                               uint64_t VMSize,
+                                               uint64_t SectionDataStartOffset,
+                                               uint64_t SectionDataSize) {
+  // struct segment_command (56 bytes) or
+  // struct segment_command_64 (72 bytes)
+
+  uint64_t Start = OS.tell();
+  (void) Start;
+
+  unsigned SegmentLoadCommandSize =
+    is64Bit() ? macho::SegmentLoadCommand64Size:
+    macho::SegmentLoadCommand32Size;
+  Write32(is64Bit() ? macho::LCT_Segment64 : macho::LCT_Segment);
+  Write32(SegmentLoadCommandSize +
+          NumSections * (is64Bit() ? macho::Section64Size :
+                         macho::Section32Size));
+
+  WriteBytes("", 16);
+  if (is64Bit()) {
+    Write64(0); // vmaddr
+    Write64(VMSize); // vmsize
+    Write64(SectionDataStartOffset); // file offset
+    Write64(SectionDataSize); // file size
+  } else {
+    Write32(0); // vmaddr
+    Write32(VMSize); // vmsize
+    Write32(SectionDataStartOffset); // file offset
+    Write32(SectionDataSize); // file size
   }
+  Write32(0x7); // maxprot
+  Write32(0x7); // initprot
+  Write32(NumSections);
+  Write32(0); // flags
 
-  void RecordTLVPRelocation(const MCAssembler &Asm,
-                            const MCAsmLayout &Layout,
-                            const MCFragment *Fragment,
-                            const MCFixup &Fixup, MCValue Target,
-                            uint64_t &FixedValue) {
-    assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP &&
-           !is64Bit() &&
-           "Should only be called with a 32-bit TLVP relocation!");
-
-    unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
-    uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
-    unsigned IsPCRel = 0;
-
-    // Get the symbol data.
-    MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol());
-    unsigned Index = SD_A->getIndex();
-
-    // We're only going to have a second symbol in pic mode and it'll be a
-    // subtraction from the picbase. For 32-bit pic the addend is the difference
-    // between the picbase and the next address.  For 32-bit static the addend
-    // is zero.
-    if (Target.getSymB()) {
-      // If this is a subtraction then we're pcrel.
-      uint32_t FixupAddress =
-        getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
-      MCSymbolData *SD_B = &Asm.getSymbolData(Target.getSymB()->getSymbol());
-      IsPCRel = 1;
-      FixedValue = (FixupAddress - getSymbolAddress(SD_B, Layout) +
-                    Target.getConstant());
-      FixedValue += 1ULL << Log2Size;
-    } else {
-      FixedValue = 0;
-    }
+  assert(OS.tell() - Start == SegmentLoadCommandSize);
+}
 
-    // struct relocation_info (8 bytes)
-    macho::RelocationEntry MRE;
-    MRE.Word0 = Value;
-    MRE.Word1 = ((Index                  <<  0) |
-                 (IsPCRel                << 24) |
-                 (Log2Size               << 25) |
-                 (1                      << 27) | // Extern
-                 (macho::RIT_Generic_TLV << 28)); // Type
-    Relocations[Fragment->getParent()].push_back(MRE);
+void MachObjectWriter::WriteSection(const MCAssembler &Asm,
+                                    const MCAsmLayout &Layout,
+                                    const MCSectionData &SD,
+                                    uint64_t FileOffset,
+                                    uint64_t RelocationsStart,
+                                    unsigned NumRelocations) {
+  uint64_t SectionSize = Layout.getSectionAddressSize(&SD);
+
+  // The offset is unused for virtual sections.
+  if (SD.getSection().isVirtualSection()) {
+    assert(Layout.getSectionFileSize(&SD) == 0 && "Invalid file size!");
+    FileOffset = 0;
   }
 
-  static bool getARMFixupKindMachOInfo(unsigned Kind, unsigned &RelocType,
-                                       unsigned &Log2Size) {
-    RelocType = unsigned(macho::RIT_Vanilla);
-    Log2Size = ~0U;
+  // struct section (68 bytes) or
+  // struct section_64 (80 bytes)
+
+  uint64_t Start = OS.tell();
+  (void) Start;
+
+  const MCSectionMachO &Section = cast<MCSectionMachO>(SD.getSection());
+  WriteBytes(Section.getSectionName(), 16);
+  WriteBytes(Section.getSegmentName(), 16);
+  if (is64Bit()) {
+    Write64(getSectionAddress(&SD)); // address
+    Write64(SectionSize); // size
+  } else {
+    Write32(getSectionAddress(&SD)); // address
+    Write32(SectionSize); // size
+  }
+  Write32(FileOffset);
+
+  unsigned Flags = Section.getTypeAndAttributes();
+  if (SD.hasInstructions())
+    Flags |= MCSectionMachO::S_ATTR_SOME_INSTRUCTIONS;
+
+  assert(isPowerOf2_32(SD.getAlignment()) && "Invalid alignment!");
+  Write32(Log2_32(SD.getAlignment()));
+  Write32(NumRelocations ? RelocationsStart : 0);
+  Write32(NumRelocations);
+  Write32(Flags);
+  Write32(IndirectSymBase.lookup(&SD)); // reserved1
+  Write32(Section.getStubSize()); // reserved2
+  if (is64Bit())
+    Write32(0); // reserved3
+
+  assert(OS.tell() - Start == (is64Bit() ? macho::Section64Size :
+                               macho::Section32Size));
+}
 
-    switch (Kind) {
-    default:
-      return false;
+void MachObjectWriter::WriteSymtabLoadCommand(uint32_t SymbolOffset,
+                                              uint32_t NumSymbols,
+                                              uint32_t StringTableOffset,
+                                              uint32_t StringTableSize) {
+  // struct symtab_command (24 bytes)
 
-    case FK_Data_1:
-      Log2Size = llvm::Log2_32(1);
-      return true;
-    case FK_Data_2:
-      Log2Size = llvm::Log2_32(2);
-      return true;
-    case FK_Data_4:
-      Log2Size = llvm::Log2_32(4);
-      return true;
-    case FK_Data_8:
-      Log2Size = llvm::Log2_32(8);
-      return true;
+  uint64_t Start = OS.tell();
+  (void) Start;
 
-      // Handle 24-bit branch kinds.
-    case ARM::fixup_arm_ldst_pcrel_12:
-    case ARM::fixup_arm_pcrel_10:
-    case ARM::fixup_arm_adr_pcrel_12:
-    case ARM::fixup_arm_condbranch:
-    case ARM::fixup_arm_uncondbranch:
-      RelocType = unsigned(macho::RIT_ARM_Branch24Bit);
-      // Report as 'long', even though that is not quite accurate.
-      Log2Size = llvm::Log2_32(4);
-      return true;
+  Write32(macho::LCT_Symtab);
+  Write32(macho::SymtabLoadCommandSize);
+  Write32(SymbolOffset);
+  Write32(NumSymbols);
+  Write32(StringTableOffset);
+  Write32(StringTableSize);
 
-      // Handle Thumb branches.
-    case ARM::fixup_arm_thumb_br:
-      RelocType = unsigned(macho::RIT_ARM_ThumbBranch22Bit);
-      Log2Size = llvm::Log2_32(2);
-      return true;
-      
-    case ARM::fixup_arm_thumb_bl:
-    case ARM::fixup_arm_thumb_blx:
-      RelocType = unsigned(macho::RIT_ARM_ThumbBranch22Bit);
-      Log2Size = llvm::Log2_32(4);
-      return true;
+  assert(OS.tell() - Start == macho::SymtabLoadCommandSize);
+}
 
-    case ARM::fixup_arm_movt_hi16:
-    case ARM::fixup_arm_movt_hi16_pcrel:
-    case ARM::fixup_t2_movt_hi16:
-    case ARM::fixup_t2_movt_hi16_pcrel:
-      RelocType = unsigned(macho::RIT_ARM_HalfDifference);
-      // Report as 'long', even though that is not quite accurate.
-      Log2Size = llvm::Log2_32(4);
-      return true;
+void MachObjectWriter::WriteDysymtabLoadCommand(uint32_t FirstLocalSymbol,
+                                                uint32_t NumLocalSymbols,
+                                                uint32_t FirstExternalSymbol,
+                                                uint32_t NumExternalSymbols,
+                                                uint32_t FirstUndefinedSymbol,
+                                                uint32_t NumUndefinedSymbols,
+                                                uint32_t IndirectSymbolOffset,
+                                                uint32_t NumIndirectSymbols) {
+  // struct dysymtab_command (80 bytes)
+
+  uint64_t Start = OS.tell();
+  (void) Start;
+
+  Write32(macho::LCT_Dysymtab);
+  Write32(macho::DysymtabLoadCommandSize);
+  Write32(FirstLocalSymbol);
+  Write32(NumLocalSymbols);
+  Write32(FirstExternalSymbol);
+  Write32(NumExternalSymbols);
+  Write32(FirstUndefinedSymbol);
+  Write32(NumUndefinedSymbols);
+  Write32(0); // tocoff
+  Write32(0); // ntoc
+  Write32(0); // modtaboff
+  Write32(0); // nmodtab
+  Write32(0); // extrefsymoff
+  Write32(0); // nextrefsyms
+  Write32(IndirectSymbolOffset);
+  Write32(NumIndirectSymbols);
+  Write32(0); // extreloff
+  Write32(0); // nextrel
+  Write32(0); // locreloff
+  Write32(0); // nlocrel
+
+  assert(OS.tell() - Start == macho::DysymtabLoadCommandSize);
+}
 
-    case ARM::fixup_arm_movw_lo16:
-    case ARM::fixup_arm_movw_lo16_pcrel:
-    case ARM::fixup_t2_movw_lo16:
-    case ARM::fixup_t2_movw_lo16_pcrel:
-      RelocType = unsigned(macho::RIT_ARM_Half);
-      // Report as 'long', even though that is not quite accurate.
-      Log2Size = llvm::Log2_32(4);
-      return true;
+void MachObjectWriter::WriteNlist(MachSymbolData &MSD, const MCAsmLayout &Layout) {
+  MCSymbolData &Data = *MSD.SymbolData;
+  const MCSymbol &Symbol = Data.getSymbol();
+  uint8_t Type = 0;
+  uint16_t Flags = Data.getFlags();
+  uint32_t Address = 0;
+
+  // Set the N_TYPE bits. See <mach-o/nlist.h>.
+  //
+  // FIXME: Are the prebound or indirect fields possible here?
+  if (Symbol.isUndefined())
+    Type = macho::STT_Undefined;
+  else if (Symbol.isAbsolute())
+    Type = macho::STT_Absolute;
+  else
+    Type = macho::STT_Section;
+
+  // FIXME: Set STAB bits.
+
+  if (Data.isPrivateExtern())
+    Type |= macho::STF_PrivateExtern;
+
+  // Set external bit.
+  if (Data.isExternal() || Symbol.isUndefined())
+    Type |= macho::STF_External;
+
+  // Compute the symbol address.
+  if (Symbol.isDefined()) {
+    if (Symbol.isAbsolute()) {
+      Address = cast<MCConstantExpr>(Symbol.getVariableValue())->getValue();
+    } else {
+      Address = getSymbolAddress(&Data, Layout);
     }
-  }
-  void RecordARMRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
-                           const MCFragment *Fragment, const MCFixup &Fixup,
-                           MCValue Target, uint64_t &FixedValue) {
-    unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
-    unsigned Log2Size;
-    unsigned RelocType = macho::RIT_Vanilla;
-    if (!getARMFixupKindMachOInfo(Fixup.getKind(), RelocType, Log2Size)) {
-      report_fatal_error("unknown ARM fixup kind!");
-      return;
+  } else if (Data.isCommon()) {
+    // Common symbols are encoded with the size in the address
+    // field, and their alignment in the flags.
+    Address = Data.getCommonSize();
+
+    // Common alignment is packed into the 'desc' bits.
+    if (unsigned Align = Data.getCommonAlignment()) {
+      unsigned Log2Size = Log2_32(Align);
+      assert((1U << Log2Size) == Align && "Invalid 'common' alignment!");
+      if (Log2Size > 15)
+        report_fatal_error("invalid 'common' alignment '" +
+                           Twine(Align) + "'");
+      // FIXME: Keep this mask with the SymbolFlags enumeration.
+      Flags = (Flags & 0xF0FF) | (Log2Size << 8);
     }
+  }
 
-    // If this is a difference or a defined symbol plus an offset, then we need
-    // a scattered relocation entry.  Differences always require scattered
-    // relocations.
-    if (Target.getSymB()) {
-      if (RelocType == macho::RIT_ARM_Half ||
-          RelocType == macho::RIT_ARM_HalfDifference)
-        return RecordARMMovwMovtRelocation(Asm, Layout, Fragment, Fixup,
-                                           Target, FixedValue);
-      return RecordARMScatteredRelocation(Asm, Layout, Fragment, Fixup,
-                                          Target, Log2Size, FixedValue);
-    }
+  // struct nlist (12 bytes)
 
-    // Get the symbol data, if any.
-    MCSymbolData *SD = 0;
-    if (Target.getSymA())
-      SD = &Asm.getSymbolData(Target.getSymA()->getSymbol());
+  Write32(MSD.StringIndex);
+  Write8(Type);
+  Write8(MSD.SectionIndex);
 
-    // FIXME: For other platforms, we need to use scattered relocations for
-    // internal relocations with offsets.  If this is an internal relocation
-    // with an offset, it also needs a scattered relocation entry.
-    //
-    // Is this right for ARM?
-    uint32_t Offset = Target.getConstant();
-    if (IsPCRel && RelocType == macho::RIT_Vanilla)
-      Offset += 1 << Log2Size;
-    if (Offset && SD && !doesSymbolRequireExternRelocation(SD))
-      return RecordARMScatteredRelocation(Asm, Layout, Fragment, Fixup, Target,
-                                          Log2Size, FixedValue);
-
-    // See <reloc.h>.
-    uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
-    unsigned Index = 0;
-    unsigned IsExtern = 0;
-    unsigned Type = 0;
-
-    if (Target.isAbsolute()) { // constant
-      // FIXME!
-      report_fatal_error("FIXME: relocations to absolute targets "
-                         "not yet implemented");
-    } else {
-      // Resolve constant variables.
-      if (SD->getSymbol().isVariable()) {
-        int64_t Res;
-        if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute(
-              Res, Layout, SectionAddress)) {
-          FixedValue = Res;
-          return;
-        }
-      }
+  // The Mach-O streamer uses the lowest 16-bits of the flags for the 'desc'
+  // value.
+  Write16(Flags);
+  if (is64Bit())
+    Write64(Address);
+  else
+    Write32(Address);
+}
 
-      // Check whether we need an external or internal relocation.
-      if (doesSymbolRequireExternRelocation(SD)) {
-        IsExtern = 1;
-        Index = SD->getIndex();
-        // For external relocations, make sure to offset the fixup value to
-        // compensate for the addend of the symbol address, if it was
-        // undefined. This occurs with weak definitions, for example.
-        if (!SD->Symbol->isUndefined())
-          FixedValue -= Layout.getSymbolOffset(SD);
-      } else {
-        // The index is the section ordinal (1-based).
-        const MCSectionData &SymSD = Asm.getSectionData(
-          SD->getSymbol().getSection());
-        Index = SymSD.getOrdinal() + 1;
-        FixedValue += getSectionAddress(&SymSD);
-      }
-      if (IsPCRel)
-        FixedValue -= getSectionAddress(Fragment->getParent());
+void MachObjectWriter::RecordX86_64Relocation(const MCAssembler &Asm,
+                                              const MCAsmLayout &Layout,
+                                              const MCFragment *Fragment,
+                                              const MCFixup &Fixup,
+                                              MCValue Target,
+                                              uint64_t &FixedValue) {
+  unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
+  unsigned IsRIPRel = isFixupKindRIPRel(Fixup.getKind());
+  unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
+
+  // See <reloc.h>.
+  uint32_t FixupOffset =
+    Layout.getFragmentOffset(Fragment) + Fixup.getOffset();
+  uint32_t FixupAddress =
+    getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
+  int64_t Value = 0;
+  unsigned Index = 0;
+  unsigned IsExtern = 0;
+  unsigned Type = 0;
+
+  Value = Target.getConstant();
+
+  if (IsPCRel) {
+    // Compensate for the relocation offset, Darwin x86_64 relocations only have
+    // the addend and appear to have attempted to define it to be the actual
+    // expression addend without the PCrel bias. However, instructions with data
+    // following the relocation are not accommodated for (see comment below
+    // regarding SIGNED{1,2,4}), so it isn't exactly that either.
+    Value += 1LL << Log2Size;
+  }
+
+  if (Target.isAbsolute()) { // constant
+    // SymbolNum of 0 indicates the absolute section.
+    Type = macho::RIT_X86_64_Unsigned;
+    Index = 0;
+
+    // FIXME: I believe this is broken, I don't think the linker can understand
+    // it. I think it would require a local relocation, but I'm not sure if that
+    // would work either. The official way to get an absolute PCrel relocation
+    // is to use an absolute symbol (which we don't support yet).
+    if (IsPCRel) {
+      IsExtern = 1;
+      Type = macho::RIT_X86_64_Branch;
+    }
+  } else if (Target.getSymB()) { // A - B + constant
+    const MCSymbol *A = &Target.getSymA()->getSymbol();
+    MCSymbolData &A_SD = Asm.getSymbolData(*A);
+    const MCSymbolData *A_Base = Asm.getAtom(&A_SD);
+
+    const MCSymbol *B = &Target.getSymB()->getSymbol();
+    MCSymbolData &B_SD = Asm.getSymbolData(*B);
+    const MCSymbolData *B_Base = Asm.getAtom(&B_SD);
 
-      // The type is determined by the fixup kind.
-      Type = RelocType;
+    // Neither symbol can be modified.
+    if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None ||
+        Target.getSymB()->getKind() != MCSymbolRefExpr::VK_None)
+      report_fatal_error("unsupported relocation of modified symbol");
+
+    // We don't support PCrel relocations of differences. Darwin 'as' doesn't
+    // implement most of these correctly.
+    if (IsPCRel)
+      report_fatal_error("unsupported pc-relative relocation of difference");
+
+    // The support for the situation where one or both of the symbols would
+    // require a local relocation is handled just like if the symbols were
+    // external.  This is certainly used in the case of debug sections where the
+    // section has only temporary symbols and thus the symbols don't have base
+    // symbols.  This is encoded using the section ordinal and non-extern
+    // relocation entries.
+
+    // Darwin 'as' doesn't emit correct relocations for this (it ends up with a
+    // single SIGNED relocation); reject it for now.  Except the case where both
+    // symbols don't have a base, equal but both NULL.
+    if (A_Base == B_Base && A_Base)
+      report_fatal_error("unsupported relocation with identical base");
+
+    Value += getSymbolAddress(&A_SD, Layout) -
+      (A_Base == NULL ? 0 : getSymbolAddress(A_Base, Layout));
+    Value -= getSymbolAddress(&B_SD, Layout) -
+      (B_Base == NULL ? 0 : getSymbolAddress(B_Base, Layout));
+
+    if (A_Base) {
+      Index = A_Base->getIndex();
+      IsExtern = 1;
+    }
+    else {
+      Index = A_SD.getFragment()->getParent()->getOrdinal() + 1;
+      IsExtern = 0;
     }
+    Type = macho::RIT_X86_64_Unsigned;
 
-    // struct relocation_info (8 bytes)
     macho::RelocationEntry MRE;
     MRE.Word0 = FixupOffset;
     MRE.Word1 = ((Index     <<  0) |
@@ -1098,523 +654,1088 @@ public:
                  (IsExtern  << 27) |
                  (Type      << 28));
     Relocations[Fragment->getParent()].push_back(MRE);
-  }
 
-  void RecordRelocation(const MCAssembler &Asm, const MCAsmLayout &Layout,
-                        const MCFragment *Fragment, const MCFixup &Fixup,
-                        MCValue Target, uint64_t &FixedValue) {
-    // FIXME: These needs to be factored into the target Mach-O writer.
-    if (isARM()) {
-      RecordARMRelocation(Asm, Layout, Fragment, Fixup, Target, FixedValue);
-      return;
+    if (B_Base) {
+      Index = B_Base->getIndex();
+      IsExtern = 1;
     }
-    if (is64Bit()) {
-      RecordX86_64Relocation(Asm, Layout, Fragment, Fixup, Target, FixedValue);
-      return;
+    else {
+      Index = B_SD.getFragment()->getParent()->getOrdinal() + 1;
+      IsExtern = 0;
     }
-
-    unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
-    unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
-
-    // If this is a 32-bit TLVP reloc it's handled a bit differently.
-    if (Target.getSymA() &&
-        Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) {
-      RecordTLVPRelocation(Asm, Layout, Fragment, Fixup, Target, FixedValue);
-      return;
+    Type = macho::RIT_X86_64_Subtractor;
+  } else {
+    const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
+    MCSymbolData &SD = Asm.getSymbolData(*Symbol);
+    const MCSymbolData *Base = Asm.getAtom(&SD);
+
+    // Relocations inside debug sections always use local relocations when
+    // possible. This seems to be done because the debugger doesn't fully
+    // understand x86_64 relocation entries, and expects to find values that
+    // have already been fixed up.
+    if (Symbol->isInSection()) {
+      const MCSectionMachO &Section = static_cast<const MCSectionMachO&>(
+        Fragment->getParent()->getSection());
+      if (Section.hasAttribute(MCSectionMachO::S_ATTR_DEBUG))
+        Base = 0;
     }
 
-    // If this is a difference or a defined symbol plus an offset, then we need
-    // a scattered relocation entry.
-    // Differences always require scattered relocations.
-    if (Target.getSymB())
-        return RecordScatteredRelocation(Asm, Layout, Fragment, Fixup,
-                                         Target, Log2Size, FixedValue);
+    // x86_64 almost always uses external relocations, except when there is no
+    // symbol to use as a base address (a local symbol with no preceding
+    // non-local symbol).
+    if (Base) {
+      Index = Base->getIndex();
+      IsExtern = 1;
+
+      // Add the local offset, if needed.
+      if (Base != &SD)
+        Value += Layout.getSymbolOffset(&SD) - Layout.getSymbolOffset(Base);
+    } else if (Symbol->isInSection() && !Symbol->isVariable()) {
+      // The index is the section ordinal (1-based).
+      Index = SD.getFragment()->getParent()->getOrdinal() + 1;
+      IsExtern = 0;
+      Value += getSymbolAddress(&SD, Layout);
 
-    // Get the symbol data, if any.
-    MCSymbolData *SD = 0;
-    if (Target.getSymA())
-      SD = &Asm.getSymbolData(Target.getSymA()->getSymbol());
-
-    // If this is an internal relocation with an offset, it also needs a
-    // scattered relocation entry.
-    uint32_t Offset = Target.getConstant();
-    if (IsPCRel)
-      Offset += 1 << Log2Size;
-    if (Offset && SD && !doesSymbolRequireExternRelocation(SD))
-      return RecordScatteredRelocation(Asm, Layout, Fragment, Fixup,
-                                       Target, Log2Size, FixedValue);
-
-    // See <reloc.h>.
-    uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
-    unsigned Index = 0;
-    unsigned IsExtern = 0;
-    unsigned Type = 0;
-
-    if (Target.isAbsolute()) { // constant
-      // SymbolNum of 0 indicates the absolute section.
-      //
-      // FIXME: Currently, these are never generated (see code below). I cannot
-      // find a case where they are actually emitted.
-      Type = macho::RIT_Vanilla;
-    } else {
-      // Resolve constant variables.
-      if (SD->getSymbol().isVariable()) {
-        int64_t Res;
-        if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute(
-              Res, Layout, SectionAddress)) {
-          FixedValue = Res;
-          return;
-        }
+      if (IsPCRel)
+        Value -= FixupAddress + (1 << Log2Size);
+    } else if (Symbol->isVariable()) {
+      const MCExpr *Value = Symbol->getVariableValue();
+      int64_t Res;
+      bool isAbs = Value->EvaluateAsAbsolute(Res, Layout, SectionAddress);
+      if (isAbs) {
+        FixedValue = Res;
+        return;
+      } else {
+        report_fatal_error("unsupported relocation of variable '" +
+                           Symbol->getName() + "'");
       }
+    } else {
+      report_fatal_error("unsupported relocation of undefined symbol '" +
+                         Symbol->getName() + "'");
+    }
 
-      // Check whether we need an external or internal relocation.
-      if (doesSymbolRequireExternRelocation(SD)) {
-        IsExtern = 1;
-        Index = SD->getIndex();
-        // For external relocations, make sure to offset the fixup value to
-        // compensate for the addend of the symbol address, if it was
-        // undefined. This occurs with weak definitions, for example.
-        if (!SD->Symbol->isUndefined())
-          FixedValue -= Layout.getSymbolOffset(SD);
+    MCSymbolRefExpr::VariantKind Modifier = Target.getSymA()->getKind();
+    if (IsPCRel) {
+      if (IsRIPRel) {
+        if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
+          // x86_64 distinguishes movq foo@GOTPCREL so that the linker can
+          // rewrite the movq to an leaq at link time if the symbol ends up in
+          // the same linkage unit.
+          if (unsigned(Fixup.getKind()) == X86::reloc_riprel_4byte_movq_load)
+            Type = macho::RIT_X86_64_GOTLoad;
+          else
+            Type = macho::RIT_X86_64_GOT;
+        }  else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
+          Type = macho::RIT_X86_64_TLV;
+        }  else if (Modifier != MCSymbolRefExpr::VK_None) {
+          report_fatal_error("unsupported symbol modifier in relocation");
+        } else {
+          Type = macho::RIT_X86_64_Signed;
+
+          // The Darwin x86_64 relocation format has a problem where it cannot
+          // encode an address (L<foo> + <constant>) which is outside the atom
+          // containing L<foo>. Generally, this shouldn't occur but it does
+          // happen when we have a RIPrel instruction with data following the
+          // relocation entry (e.g., movb $012, L0(%rip)). Even with the PCrel
+          // adjustment Darwin x86_64 uses, the offset is still negative and the
+          // linker has no way to recognize this.
+          //
+          // To work around this, Darwin uses several special relocation types
+          // to indicate the offsets. However, the specification or
+          // implementation of these seems to also be incomplete; they should
+          // adjust the addend as well based on the actual encoded instruction
+          // (the additional bias), but instead appear to just look at the final
+          // offset.
+          switch (-(Target.getConstant() + (1LL << Log2Size))) {
+          case 1: Type = macho::RIT_X86_64_Signed1; break;
+          case 2: Type = macho::RIT_X86_64_Signed2; break;
+          case 4: Type = macho::RIT_X86_64_Signed4; break;
+          }
+        }
       } else {
-        // The index is the section ordinal (1-based).
-        const MCSectionData &SymSD = Asm.getSectionData(
-          SD->getSymbol().getSection());
-        Index = SymSD.getOrdinal() + 1;
-        FixedValue += getSectionAddress(&SymSD);
-      }
-      if (IsPCRel)
-        FixedValue -= getSectionAddress(Fragment->getParent());
+        if (Modifier != MCSymbolRefExpr::VK_None)
+          report_fatal_error("unsupported symbol modifier in branch "
+                             "relocation");
 
-      Type = macho::RIT_Vanilla;
+        Type = macho::RIT_X86_64_Branch;
+      }
+    } else {
+      if (Modifier == MCSymbolRefExpr::VK_GOT) {
+        Type = macho::RIT_X86_64_GOT;
+      } else if (Modifier == MCSymbolRefExpr::VK_GOTPCREL) {
+        // GOTPCREL is allowed as a modifier on non-PCrel instructions, in which
+        // case all we do is set the PCrel bit in the relocation entry; this is
+        // used with exception handling, for example. The source is required to
+        // include any necessary offset directly.
+        Type = macho::RIT_X86_64_GOT;
+        IsPCRel = 1;
+      } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
+        report_fatal_error("TLVP symbol modifier should have been rip-rel");
+      } else if (Modifier != MCSymbolRefExpr::VK_None)
+        report_fatal_error("unsupported symbol modifier in relocation");
+      else
+        Type = macho::RIT_X86_64_Unsigned;
     }
+  }
+
+  // x86_64 always writes custom values into the fixups.
+  FixedValue = Value;
+
+  // struct relocation_info (8 bytes)
+  macho::RelocationEntry MRE;
+  MRE.Word0 = FixupOffset;
+  MRE.Word1 = ((Index     <<  0) |
+               (IsPCRel   << 24) |
+               (Log2Size  << 25) |
+               (IsExtern  << 27) |
+               (Type      << 28));
+  Relocations[Fragment->getParent()].push_back(MRE);
+}
 
-    // struct relocation_info (8 bytes)
+void MachObjectWriter::RecordScatteredRelocation(const MCAssembler &Asm,
+                                                 const MCAsmLayout &Layout,
+                                                 const MCFragment *Fragment,
+                                                 const MCFixup &Fixup,
+                                                 MCValue Target,
+                                                 unsigned Log2Size,
+                                                 uint64_t &FixedValue) {
+  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
+  unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
+  unsigned Type = macho::RIT_Vanilla;
+
+  // See <reloc.h>.
+  const MCSymbol *A = &Target.getSymA()->getSymbol();
+  MCSymbolData *A_SD = &Asm.getSymbolData(*A);
+
+  if (!A_SD->getFragment())
+    report_fatal_error("symbol '" + A->getName() +
+                       "' can not be undefined in a subtraction expression");
+
+  uint32_t Value = getSymbolAddress(A_SD, Layout);
+  uint64_t SecAddr = getSectionAddress(A_SD->getFragment()->getParent());
+  FixedValue += SecAddr;
+  uint32_t Value2 = 0;
+
+  if (const MCSymbolRefExpr *B = Target.getSymB()) {
+    MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
+
+    if (!B_SD->getFragment())
+      report_fatal_error("symbol '" + B->getSymbol().getName() +
+                         "' can not be undefined in a subtraction expression");
+
+    // Select the appropriate difference relocation type.
+    //
+    // Note that there is no longer any semantic difference between these two
+    // relocation types from the linkers point of view, this is done solely for
+    // pedantic compatibility with 'as'.
+    Type = A_SD->isExternal() ? (unsigned)macho::RIT_Difference :
+      (unsigned)macho::RIT_Generic_LocalDifference;
+    Value2 = getSymbolAddress(B_SD, Layout);
+    FixedValue -= getSectionAddress(B_SD->getFragment()->getParent());
+  }
+
+  // Relocations are written out in reverse order, so the PAIR comes first.
+  if (Type == macho::RIT_Difference ||
+      Type == macho::RIT_Generic_LocalDifference) {
     macho::RelocationEntry MRE;
-    MRE.Word0 = FixupOffset;
-    MRE.Word1 = ((Index     <<  0) |
-                 (IsPCRel   << 24) |
-                 (Log2Size  << 25) |
-                 (IsExtern  << 27) |
-                 (Type      << 28));
+    MRE.Word0 = ((0         <<  0) |
+                 (macho::RIT_Pair  << 24) |
+                 (Log2Size  << 28) |
+                 (IsPCRel   << 30) |
+                 macho::RF_Scattered);
+    MRE.Word1 = Value2;
     Relocations[Fragment->getParent()].push_back(MRE);
   }
 
-  void BindIndirectSymbols(MCAssembler &Asm) {
-    // This is the point where 'as' creates actual symbols for indirect symbols
-    // (in the following two passes). It would be easier for us to do this
-    // sooner when we see the attribute, but that makes getting the order in the
-    // symbol table much more complicated than it is worth.
-    //
-    // FIXME: Revisit this when the dust settles.
+  macho::RelocationEntry MRE;
+  MRE.Word0 = ((FixupOffset <<  0) |
+               (Type        << 24) |
+               (Log2Size    << 28) |
+               (IsPCRel     << 30) |
+               macho::RF_Scattered);
+  MRE.Word1 = Value;
+  Relocations[Fragment->getParent()].push_back(MRE);
+}
 
-    // Bind non lazy symbol pointers first.
-    unsigned IndirectIndex = 0;
-    for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
-           ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
-      const MCSectionMachO &Section =
-        cast<MCSectionMachO>(it->SectionData->getSection());
+void MachObjectWriter::RecordARMScatteredRelocation(const MCAssembler &Asm,
+                                                    const MCAsmLayout &Layout,
+                                                    const MCFragment *Fragment,
+                                                    const MCFixup &Fixup,
+                                                    MCValue Target,
+                                                    unsigned Log2Size,
+                                                    uint64_t &FixedValue) {
+  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
+  unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
+  unsigned Type = macho::RIT_Vanilla;
+
+  // See <reloc.h>.
+  const MCSymbol *A = &Target.getSymA()->getSymbol();
+  MCSymbolData *A_SD = &Asm.getSymbolData(*A);
+
+  if (!A_SD->getFragment())
+    report_fatal_error("symbol '" + A->getName() +
+                       "' can not be undefined in a subtraction expression");
+
+  uint32_t Value = getSymbolAddress(A_SD, Layout);
+  uint64_t SecAddr = getSectionAddress(A_SD->getFragment()->getParent());
+  FixedValue += SecAddr;
+  uint32_t Value2 = 0;
+
+  if (const MCSymbolRefExpr *B = Target.getSymB()) {
+    MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
+
+    if (!B_SD->getFragment())
+      report_fatal_error("symbol '" + B->getSymbol().getName() +
+                         "' can not be undefined in a subtraction expression");
+
+    // Select the appropriate difference relocation type.
+    Type = macho::RIT_Difference;
+    Value2 = getSymbolAddress(B_SD, Layout);
+    FixedValue -= getSectionAddress(B_SD->getFragment()->getParent());
+  }
 
-      if (Section.getType() != MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS)
-        continue;
+  // Relocations are written out in reverse order, so the PAIR comes first.
+  if (Type == macho::RIT_Difference ||
+      Type == macho::RIT_Generic_LocalDifference) {
+    macho::RelocationEntry MRE;
+    MRE.Word0 = ((0         <<  0) |
+                 (macho::RIT_Pair  << 24) |
+                 (Log2Size  << 28) |
+                 (IsPCRel   << 30) |
+                 macho::RF_Scattered);
+    MRE.Word1 = Value2;
+    Relocations[Fragment->getParent()].push_back(MRE);
+  }
 
-      // Initialize the section indirect symbol base, if necessary.
-      if (!IndirectSymBase.count(it->SectionData))
-        IndirectSymBase[it->SectionData] = IndirectIndex;
+  macho::RelocationEntry MRE;
+  MRE.Word0 = ((FixupOffset <<  0) |
+               (Type        << 24) |
+               (Log2Size    << 28) |
+               (IsPCRel     << 30) |
+               macho::RF_Scattered);
+  MRE.Word1 = Value;
+  Relocations[Fragment->getParent()].push_back(MRE);
+}
 
-      Asm.getOrCreateSymbolData(*it->Symbol);
-    }
+void MachObjectWriter::RecordARMMovwMovtRelocation(const MCAssembler &Asm,
+                                                   const MCAsmLayout &Layout,
+                                                   const MCFragment *Fragment,
+                                                   const MCFixup &Fixup,
+                                                   MCValue Target,
+                                                   uint64_t &FixedValue) {
+  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
+  unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
+  unsigned Type = macho::RIT_ARM_Half;
+
+  // See <reloc.h>.
+  const MCSymbol *A = &Target.getSymA()->getSymbol();
+  MCSymbolData *A_SD = &Asm.getSymbolData(*A);
+
+  if (!A_SD->getFragment())
+    report_fatal_error("symbol '" + A->getName() +
+                       "' can not be undefined in a subtraction expression");
+
+  uint32_t Value = getSymbolAddress(A_SD, Layout);
+  uint32_t Value2 = 0;
+  uint64_t SecAddr = getSectionAddress(A_SD->getFragment()->getParent());
+  FixedValue += SecAddr;
+
+  if (const MCSymbolRefExpr *B = Target.getSymB()) {
+    MCSymbolData *B_SD = &Asm.getSymbolData(B->getSymbol());
+
+    if (!B_SD->getFragment())
+      report_fatal_error("symbol '" + B->getSymbol().getName() +
+                         "' can not be undefined in a subtraction expression");
+
+    // Select the appropriate difference relocation type.
+    Type = macho::RIT_ARM_HalfDifference;
+    Value2 = getSymbolAddress(B_SD, Layout);
+    FixedValue -= getSectionAddress(B_SD->getFragment()->getParent());
+  }
 
-    // Then lazy symbol pointers and symbol stubs.
-    IndirectIndex = 0;
-    for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
-           ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
-      const MCSectionMachO &Section =
-        cast<MCSectionMachO>(it->SectionData->getSection());
-
-      if (Section.getType() != MCSectionMachO::S_LAZY_SYMBOL_POINTERS &&
-          Section.getType() != MCSectionMachO::S_SYMBOL_STUBS)
-        continue;
-
-      // Initialize the section indirect symbol base, if necessary.
-      if (!IndirectSymBase.count(it->SectionData))
-        IndirectSymBase[it->SectionData] = IndirectIndex;
-
-      // Set the symbol type to undefined lazy, but only on construction.
-      //
-      // FIXME: Do not hardcode.
-      bool Created;
-      MCSymbolData &Entry = Asm.getOrCreateSymbolData(*it->Symbol, &Created);
-      if (Created)
-        Entry.setFlags(Entry.getFlags() | 0x0001);
-    }
+  // Relocations are written out in reverse order, so the PAIR comes first.
+  // ARM_RELOC_HALF and ARM_RELOC_HALF_SECTDIFF abuse the r_length field:
+  //
+  // For these two r_type relocations they always have a pair following them and
+  // the r_length bits are used differently.  The encoding of the r_length is as
+  // follows:
+  //   low bit of r_length:
+  //      0 - :lower16: for movw instructions
+  //      1 - :upper16: for movt instructions
+  //   high bit of r_length:
+  //      0 - arm instructions
+  //      1 - thumb instructions
+  // the other half of the relocated expression is in the following pair
+  // relocation entry in the the low 16 bits of r_address field.
+  unsigned ThumbBit = 0;
+  unsigned MovtBit = 0;
+  switch ((unsigned)Fixup.getKind()) {
+  default: break;
+  case ARM::fixup_arm_movt_hi16:
+  case ARM::fixup_arm_movt_hi16_pcrel:
+    MovtBit = 1;
+    break;
+  case ARM::fixup_t2_movt_hi16:
+  case ARM::fixup_t2_movt_hi16_pcrel:
+    MovtBit = 1;
+    // Fallthrough
+  case ARM::fixup_t2_movw_lo16:
+  case ARM::fixup_t2_movw_lo16_pcrel:
+    ThumbBit = 1;
+    break;
   }
 
-  /// ComputeSymbolTable - Compute the symbol table data
-  ///
-  /// \param StringTable [out] - The string table data.
-  /// \param StringIndexMap [out] - Map from symbol names to offsets in the
-  /// string table.
-  void ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
-                          std::vector<MachSymbolData> &LocalSymbolData,
-                          std::vector<MachSymbolData> &ExternalSymbolData,
-                          std::vector<MachSymbolData> &UndefinedSymbolData) {
-    // Build section lookup table.
-    DenseMap<const MCSection*, uint8_t> SectionIndexMap;
-    unsigned Index = 1;
-    for (MCAssembler::iterator it = Asm.begin(),
-           ie = Asm.end(); it != ie; ++it, ++Index)
-      SectionIndexMap[&it->getSection()] = Index;
-    assert(Index <= 256 && "Too many sections!");
-
-    // Index 0 is always the empty string.
-    StringMap<uint64_t> StringIndexMap;
-    StringTable += '\x00';
 
-    // Build the symbol arrays and the string table, but only for non-local
-    // symbols.
-    //
-    // The particular order that we collect the symbols and create the string
-    // table, then sort the symbols is chosen to match 'as'. Even though it
-    // doesn't matter for correctness, this is important for letting us diff .o
-    // files.
-    for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
-           ie = Asm.symbol_end(); it != ie; ++it) {
-      const MCSymbol &Symbol = it->getSymbol();
-
-      // Ignore non-linker visible symbols.
-      if (!Asm.isSymbolLinkerVisible(it->getSymbol()))
-        continue;
-
-      if (!it->isExternal() && !Symbol.isUndefined())
-        continue;
-
-      uint64_t &Entry = StringIndexMap[Symbol.getName()];
-      if (!Entry) {
-        Entry = StringTable.size();
-        StringTable += Symbol.getName();
-        StringTable += '\x00';
-      }
+  if (Type == macho::RIT_ARM_HalfDifference) {
+    uint32_t OtherHalf = MovtBit
+      ? (FixedValue & 0xffff) : ((FixedValue & 0xffff0000) >> 16);
 
-      MachSymbolData MSD;
-      MSD.SymbolData = it;
-      MSD.StringIndex = Entry;
+    macho::RelocationEntry MRE;
+    MRE.Word0 = ((OtherHalf       <<  0) |
+                 (macho::RIT_Pair << 24) |
+                 (MovtBit         << 28) |
+                 (ThumbBit        << 29) |
+                 (IsPCRel         << 30) |
+                 macho::RF_Scattered);
+    MRE.Word1 = Value2;
+    Relocations[Fragment->getParent()].push_back(MRE);
+  }
 
-      if (Symbol.isUndefined()) {
-        MSD.SectionIndex = 0;
-        UndefinedSymbolData.push_back(MSD);
-      } else if (Symbol.isAbsolute()) {
-        MSD.SectionIndex = 0;
-        ExternalSymbolData.push_back(MSD);
-      } else {
-        MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
-        assert(MSD.SectionIndex && "Invalid section index!");
-        ExternalSymbolData.push_back(MSD);
-      }
-    }
+  macho::RelocationEntry MRE;
+  MRE.Word0 = ((FixupOffset <<  0) |
+               (Type        << 24) |
+               (MovtBit     << 28) |
+               (ThumbBit    << 29) |
+               (IsPCRel     << 30) |
+               macho::RF_Scattered);
+  MRE.Word1 = Value;
+  Relocations[Fragment->getParent()].push_back(MRE);
+}
 
-    // Now add the data for local symbols.
-    for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
-           ie = Asm.symbol_end(); it != ie; ++it) {
-      const MCSymbol &Symbol = it->getSymbol();
+void MachObjectWriter::RecordTLVPRelocation(const MCAssembler &Asm,
+                                            const MCAsmLayout &Layout,
+                                            const MCFragment *Fragment,
+                                            const MCFixup &Fixup,
+                                            MCValue Target,
+                                            uint64_t &FixedValue) {
+  assert(Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP &&
+         !is64Bit() &&
+         "Should only be called with a 32-bit TLVP relocation!");
+
+  unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
+  uint32_t Value = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
+  unsigned IsPCRel = 0;
+
+  // Get the symbol data.
+  MCSymbolData *SD_A = &Asm.getSymbolData(Target.getSymA()->getSymbol());
+  unsigned Index = SD_A->getIndex();
+
+  // We're only going to have a second symbol in pic mode and it'll be a
+  // subtraction from the picbase. For 32-bit pic the addend is the difference
+  // between the picbase and the next address.  For 32-bit static the addend is
+  // zero.
+  if (Target.getSymB()) {
+    // If this is a subtraction then we're pcrel.
+    uint32_t FixupAddress =
+      getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
+    MCSymbolData *SD_B = &Asm.getSymbolData(Target.getSymB()->getSymbol());
+    IsPCRel = 1;
+    FixedValue = (FixupAddress - getSymbolAddress(SD_B, Layout) +
+                  Target.getConstant());
+    FixedValue += 1ULL << Log2Size;
+  } else {
+    FixedValue = 0;
+  }
 
-      // Ignore non-linker visible symbols.
-      if (!Asm.isSymbolLinkerVisible(it->getSymbol()))
-        continue;
+  // struct relocation_info (8 bytes)
+  macho::RelocationEntry MRE;
+  MRE.Word0 = Value;
+  MRE.Word1 = ((Index                  <<  0) |
+               (IsPCRel                << 24) |
+               (Log2Size               << 25) |
+               (1                      << 27) | // Extern
+               (macho::RIT_Generic_TLV << 28)); // Type
+  Relocations[Fragment->getParent()].push_back(MRE);
+}
 
-      if (it->isExternal() || Symbol.isUndefined())
-        continue;
+bool MachObjectWriter::getARMFixupKindMachOInfo(unsigned Kind, unsigned &RelocType,
+                                                unsigned &Log2Size) {
+  RelocType = unsigned(macho::RIT_Vanilla);
+  Log2Size = ~0U;
 
-      uint64_t &Entry = StringIndexMap[Symbol.getName()];
-      if (!Entry) {
-        Entry = StringTable.size();
-        StringTable += Symbol.getName();
-        StringTable += '\x00';
-      }
+  switch (Kind) {
+  default:
+    return false;
 
-      MachSymbolData MSD;
-      MSD.SymbolData = it;
-      MSD.StringIndex = Entry;
+  case FK_Data_1:
+    Log2Size = llvm::Log2_32(1);
+    return true;
+  case FK_Data_2:
+    Log2Size = llvm::Log2_32(2);
+    return true;
+  case FK_Data_4:
+    Log2Size = llvm::Log2_32(4);
+    return true;
+  case FK_Data_8:
+    Log2Size = llvm::Log2_32(8);
+    return true;
 
-      if (Symbol.isAbsolute()) {
-        MSD.SectionIndex = 0;
-        LocalSymbolData.push_back(MSD);
-      } else {
-        MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
-        assert(MSD.SectionIndex && "Invalid section index!");
-        LocalSymbolData.push_back(MSD);
-      }
-    }
+    // Handle 24-bit branch kinds.
+  case ARM::fixup_arm_ldst_pcrel_12:
+  case ARM::fixup_arm_pcrel_10:
+  case ARM::fixup_arm_adr_pcrel_12:
+  case ARM::fixup_arm_condbranch:
+  case ARM::fixup_arm_uncondbranch:
+    RelocType = unsigned(macho::RIT_ARM_Branch24Bit);
+    // Report as 'long', even though that is not quite accurate.
+    Log2Size = llvm::Log2_32(4);
+    return true;
 
-    // External and undefined symbols are required to be in lexicographic order.
-    std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
-    std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
+    // Handle Thumb branches.
+  case ARM::fixup_arm_thumb_br:
+    RelocType = unsigned(macho::RIT_ARM_ThumbBranch22Bit);
+    Log2Size = llvm::Log2_32(2);
+    return true;
+      
+  case ARM::fixup_arm_thumb_bl:
+  case ARM::fixup_arm_thumb_blx:
+    RelocType = unsigned(macho::RIT_ARM_ThumbBranch22Bit);
+    Log2Size = llvm::Log2_32(4);
+    return true;
 
-    // Set the symbol indices.
-    Index = 0;
-    for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
-      LocalSymbolData[i].SymbolData->setIndex(Index++);
-    for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
-      ExternalSymbolData[i].SymbolData->setIndex(Index++);
-    for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
-      UndefinedSymbolData[i].SymbolData->setIndex(Index++);
+  case ARM::fixup_arm_movt_hi16:
+  case ARM::fixup_arm_movt_hi16_pcrel:
+  case ARM::fixup_t2_movt_hi16:
+  case ARM::fixup_t2_movt_hi16_pcrel:
+    RelocType = unsigned(macho::RIT_ARM_HalfDifference);
+    // Report as 'long', even though that is not quite accurate.
+    Log2Size = llvm::Log2_32(4);
+    return true;
 
-    // The string table is padded to a multiple of 4.
-    while (StringTable.size() % 4)
-      StringTable += '\x00';
+  case ARM::fixup_arm_movw_lo16:
+  case ARM::fixup_arm_movw_lo16_pcrel:
+  case ARM::fixup_t2_movw_lo16:
+  case ARM::fixup_t2_movw_lo16_pcrel:
+    RelocType = unsigned(macho::RIT_ARM_Half);
+    // Report as 'long', even though that is not quite accurate.
+    Log2Size = llvm::Log2_32(4);
+    return true;
+  }
+}
+void MachObjectWriter::RecordARMRelocation(const MCAssembler &Asm,
+                                           const MCAsmLayout &Layout,
+                                           const MCFragment *Fragment,
+                                           const MCFixup &Fixup,
+                                           MCValue Target,
+                                           uint64_t &FixedValue) {
+  unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
+  unsigned Log2Size;
+  unsigned RelocType = macho::RIT_Vanilla;
+  if (!getARMFixupKindMachOInfo(Fixup.getKind(), RelocType, Log2Size)) {
+    report_fatal_error("unknown ARM fixup kind!");
+    return;
   }
 
-  void computeSectionAddresses(const MCAssembler &Asm,
-                               const MCAsmLayout &Layout) {
-    uint64_t StartAddress = 0;
-    const SmallVectorImpl<MCSectionData*> &Order = Layout.getSectionOrder();
-    for (int i = 0, n = Order.size(); i != n ; ++i) {
-      const MCSectionData *SD = Order[i];
-      StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
-      SectionAddress[SD] = StartAddress;
-      StartAddress += Layout.getSectionAddressSize(SD);
-      // Explicitly pad the section to match the alignment requirements of the
-      // following one. This is for 'gas' compatibility, it shouldn't
-      /// strictly be necessary.
-      StartAddress += getPaddingSize(SD, Layout);
-    }
+  // If this is a difference or a defined symbol plus an offset, then we need a
+  // scattered relocation entry.  Differences always require scattered
+  // relocations.
+  if (Target.getSymB()) {
+    if (RelocType == macho::RIT_ARM_Half ||
+        RelocType == macho::RIT_ARM_HalfDifference)
+      return RecordARMMovwMovtRelocation(Asm, Layout, Fragment, Fixup,
+                                         Target, FixedValue);
+    return RecordARMScatteredRelocation(Asm, Layout, Fragment, Fixup,
+                                        Target, Log2Size, FixedValue);
   }
 
-  void ExecutePostLayoutBinding(MCAssembler &Asm, const MCAsmLayout &Layout) {
-    computeSectionAddresses(Asm, Layout);
+  // Get the symbol data, if any.
+  MCSymbolData *SD = 0;
+  if (Target.getSymA())
+    SD = &Asm.getSymbolData(Target.getSymA()->getSymbol());
 
-    // Create symbol data for any indirect symbols.
-    BindIndirectSymbols(Asm);
+  // FIXME: For other platforms, we need to use scattered relocations for
+  // internal relocations with offsets.  If this is an internal relocation with
+  // an offset, it also needs a scattered relocation entry.
+  //
+  // Is this right for ARM?
+  uint32_t Offset = Target.getConstant();
+  if (IsPCRel && RelocType == macho::RIT_Vanilla)
+    Offset += 1 << Log2Size;
+  if (Offset && SD && !doesSymbolRequireExternRelocation(SD))
+    return RecordARMScatteredRelocation(Asm, Layout, Fragment, Fixup, Target,
+                                        Log2Size, FixedValue);
+
+  // See <reloc.h>.
+  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
+  unsigned Index = 0;
+  unsigned IsExtern = 0;
+  unsigned Type = 0;
+
+  if (Target.isAbsolute()) { // constant
+    // FIXME!
+    report_fatal_error("FIXME: relocations to absolute targets "
+                       "not yet implemented");
+  } else {
+    // Resolve constant variables.
+    if (SD->getSymbol().isVariable()) {
+      int64_t Res;
+      if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute(
+            Res, Layout, SectionAddress)) {
+        FixedValue = Res;
+        return;
+      }
+    }
+
+    // Check whether we need an external or internal relocation.
+    if (doesSymbolRequireExternRelocation(SD)) {
+      IsExtern = 1;
+      Index = SD->getIndex();
+
+      // For external relocations, make sure to offset the fixup value to
+      // compensate for the addend of the symbol address, if it was
+      // undefined. This occurs with weak definitions, for example.
+      if (!SD->Symbol->isUndefined())
+        FixedValue -= Layout.getSymbolOffset(SD);
+    } else {
+      // The index is the section ordinal (1-based).
+      const MCSectionData &SymSD = Asm.getSectionData(
+        SD->getSymbol().getSection());
+      Index = SymSD.getOrdinal() + 1;
+      FixedValue += getSectionAddress(&SymSD);
+    }
+    if (IsPCRel)
+      FixedValue -= getSectionAddress(Fragment->getParent());
 
-    // Compute symbol table information and bind symbol indices.
-    ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData,
-                       UndefinedSymbolData);
+    // The type is determined by the fixup kind.
+    Type = RelocType;
   }
 
-  virtual bool IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
-                                                      const MCSymbolData &DataA,
-                                                      const MCFragment &FB,
-                                                      bool InSet,
-                                                      bool IsPCRel) const {
-    if (InSet)
-      return true;
+  // struct relocation_info (8 bytes)
+  macho::RelocationEntry MRE;
+  MRE.Word0 = FixupOffset;
+  MRE.Word1 = ((Index     <<  0) |
+               (IsPCRel   << 24) |
+               (Log2Size  << 25) |
+               (IsExtern  << 27) |
+               (Type      << 28));
+  Relocations[Fragment->getParent()].push_back(MRE);
+}
 
-    // The effective address is
-    //     addr(atom(A)) + offset(A)
-    //   - addr(atom(B)) - offset(B)
-    // and the offsets are not relocatable, so the fixup is fully resolved when
-    //  addr(atom(A)) - addr(atom(B)) == 0.
-    const MCSymbolData *A_Base = 0, *B_Base = 0;
+void MachObjectWriter::RecordRelocation(const MCAssembler &Asm,
+                                        const MCAsmLayout &Layout,
+                                        const MCFragment *Fragment,
+                                        const MCFixup &Fixup,
+                                        MCValue Target,
+                                        uint64_t &FixedValue) {
+  // FIXME: These needs to be factored into the target Mach-O writer.
+  if (isARM()) {
+    RecordARMRelocation(Asm, Layout, Fragment, Fixup, Target, FixedValue);
+    return;
+  }
+  if (is64Bit()) {
+    RecordX86_64Relocation(Asm, Layout, Fragment, Fixup, Target, FixedValue);
+    return;
+  }
 
-    const MCSymbol &SA = DataA.getSymbol().AliasedSymbol();
-    const MCSection &SecA = SA.getSection();
-    const MCSection &SecB = FB.getParent()->getSection();
+  unsigned IsPCRel = isFixupKindPCRel(Asm, Fixup.getKind());
+  unsigned Log2Size = getFixupKindLog2Size(Fixup.getKind());
 
-    if (IsPCRel) {
-      // The simple (Darwin, except on x86_64) way of dealing with this was to
-      // assume that any reference to a temporary symbol *must* be a temporary
-      // symbol in the same atom, unless the sections differ. Therefore, any
-      // PCrel relocation to a temporary symbol (in the same section) is fully
-      // resolved. This also works in conjunction with absolutized .set, which
-      // requires the compiler to use .set to absolutize the differences between
-      // symbols which the compiler knows to be assembly time constants, so we
-      // don't need to worry about considering symbol differences fully
-      // resolved.
-
-      if (!Asm.getBackend().hasReliableSymbolDifference()) {
-        if (!SA.isTemporary() || !SA.isInSection() || &SecA != &SecB)
-          return false;
-        return true;
+  // If this is a 32-bit TLVP reloc it's handled a bit differently.
+  if (Target.getSymA() &&
+      Target.getSymA()->getKind() == MCSymbolRefExpr::VK_TLVP) {
+    RecordTLVPRelocation(Asm, Layout, Fragment, Fixup, Target, FixedValue);
+    return;
+  }
+
+  // If this is a difference or a defined symbol plus an offset, then we need a
+  // scattered relocation entry. Differences always require scattered
+  // relocations.
+  if (Target.getSymB())
+    return RecordScatteredRelocation(Asm, Layout, Fragment, Fixup,
+                                     Target, Log2Size, FixedValue);
+
+  // Get the symbol data, if any.
+  MCSymbolData *SD = 0;
+  if (Target.getSymA())
+    SD = &Asm.getSymbolData(Target.getSymA()->getSymbol());
+
+  // If this is an internal relocation with an offset, it also needs a scattered
+  // relocation entry.
+  uint32_t Offset = Target.getConstant();
+  if (IsPCRel)
+    Offset += 1 << Log2Size;
+  if (Offset && SD && !doesSymbolRequireExternRelocation(SD))
+    return RecordScatteredRelocation(Asm, Layout, Fragment, Fixup,
+                                     Target, Log2Size, FixedValue);
+
+  // See <reloc.h>.
+  uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
+  unsigned Index = 0;
+  unsigned IsExtern = 0;
+  unsigned Type = 0;
+
+  if (Target.isAbsolute()) { // constant
+    // SymbolNum of 0 indicates the absolute section.
+    //
+    // FIXME: Currently, these are never generated (see code below). I cannot
+    // find a case where they are actually emitted.
+    Type = macho::RIT_Vanilla;
+  } else {
+    // Resolve constant variables.
+    if (SD->getSymbol().isVariable()) {
+      int64_t Res;
+      if (SD->getSymbol().getVariableValue()->EvaluateAsAbsolute(
+            Res, Layout, SectionAddress)) {
+        FixedValue = Res;
+        return;
       }
+    }
+
+    // Check whether we need an external or internal relocation.
+    if (doesSymbolRequireExternRelocation(SD)) {
+      IsExtern = 1;
+      Index = SD->getIndex();
+      // For external relocations, make sure to offset the fixup value to
+      // compensate for the addend of the symbol address, if it was
+      // undefined. This occurs with weak definitions, for example.
+      if (!SD->Symbol->isUndefined())
+        FixedValue -= Layout.getSymbolOffset(SD);
     } else {
-      if (!TargetObjectWriter->useAggressiveSymbolFolding())
-        return false;
+      // The index is the section ordinal (1-based).
+      const MCSectionData &SymSD = Asm.getSectionData(
+        SD->getSymbol().getSection());
+      Index = SymSD.getOrdinal() + 1;
+      FixedValue += getSectionAddress(&SymSD);
     }
+    if (IsPCRel)
+      FixedValue -= getSectionAddress(Fragment->getParent());
 
-    const MCFragment &FA = *Asm.getSymbolData(SA).getFragment();
+    Type = macho::RIT_Vanilla;
+  }
 
-    A_Base = FA.getAtom();
-    if (!A_Base)
-      return false;
+  // struct relocation_info (8 bytes)
+  macho::RelocationEntry MRE;
+  MRE.Word0 = FixupOffset;
+  MRE.Word1 = ((Index     <<  0) |
+               (IsPCRel   << 24) |
+               (Log2Size  << 25) |
+               (IsExtern  << 27) |
+               (Type      << 28));
+  Relocations[Fragment->getParent()].push_back(MRE);
+}
 
-    B_Base = FB.getAtom();
-    if (!B_Base)
-      return false;
+void MachObjectWriter::BindIndirectSymbols(MCAssembler &Asm) {
+  // This is the point where 'as' creates actual symbols for indirect symbols
+  // (in the following two passes). It would be easier for us to do this sooner
+  // when we see the attribute, but that makes getting the order in the symbol
+  // table much more complicated than it is worth.
+  //
+  // FIXME: Revisit this when the dust settles.
 
-    // If the atoms are the same, they are guaranteed to have the same address.
-    if (A_Base == B_Base)
-      return true;
+  // Bind non lazy symbol pointers first.
+  unsigned IndirectIndex = 0;
+  for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
+         ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
+    const MCSectionMachO &Section =
+      cast<MCSectionMachO>(it->SectionData->getSection());
 
-    // Otherwise, we can't prove this is fully resolved.
-    return false;
+    if (Section.getType() != MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS)
+      continue;
+
+    // Initialize the section indirect symbol base, if necessary.
+    if (!IndirectSymBase.count(it->SectionData))
+      IndirectSymBase[it->SectionData] = IndirectIndex;
+
+    Asm.getOrCreateSymbolData(*it->Symbol);
   }
 
-  void WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
-    unsigned NumSections = Asm.size();
-
-    // The section data starts after the header, the segment load command (and
-    // section headers) and the symbol table.
-    unsigned NumLoadCommands = 1;
-    uint64_t LoadCommandsSize = is64Bit() ?
-      macho::SegmentLoadCommand64Size + NumSections * macho::Section64Size :
-      macho::SegmentLoadCommand32Size + NumSections * macho::Section32Size;
-
-    // Add the symbol table load command sizes, if used.
-    unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() +
-      UndefinedSymbolData.size();
-    if (NumSymbols) {
-      NumLoadCommands += 2;
-      LoadCommandsSize += (macho::SymtabLoadCommandSize +
-                           macho::DysymtabLoadCommandSize);
-    }
+  // Then lazy symbol pointers and symbol stubs.
+  IndirectIndex = 0;
+  for (MCAssembler::indirect_symbol_iterator it = Asm.indirect_symbol_begin(),
+         ie = Asm.indirect_symbol_end(); it != ie; ++it, ++IndirectIndex) {
+    const MCSectionMachO &Section =
+      cast<MCSectionMachO>(it->SectionData->getSection());
 
-    // Compute the total size of the section data, as well as its file size and
-    // vm size.
-    uint64_t SectionDataStart = (is64Bit() ? macho::Header64Size :
-                                 macho::Header32Size) + LoadCommandsSize;
-    uint64_t SectionDataSize = 0;
-    uint64_t SectionDataFileSize = 0;
-    uint64_t VMSize = 0;
-    for (MCAssembler::const_iterator it = Asm.begin(),
-           ie = Asm.end(); it != ie; ++it) {
-      const MCSectionData &SD = *it;
-      uint64_t Address = getSectionAddress(&SD);
-      uint64_t Size = Layout.getSectionAddressSize(&SD);
-      uint64_t FileSize = Layout.getSectionFileSize(&SD);
-      FileSize += getPaddingSize(&SD, Layout);
-
-      VMSize = std::max(VMSize, Address + Size);
-
-      if (SD.getSection().isVirtualSection())
-        continue;
-
-      SectionDataSize = std::max(SectionDataSize, Address + Size);
-      SectionDataFileSize = std::max(SectionDataFileSize, Address + FileSize);
-    }
+    if (Section.getType() != MCSectionMachO::S_LAZY_SYMBOL_POINTERS &&
+        Section.getType() != MCSectionMachO::S_SYMBOL_STUBS)
+      continue;
+
+    // Initialize the section indirect symbol base, if necessary.
+    if (!IndirectSymBase.count(it->SectionData))
+      IndirectSymBase[it->SectionData] = IndirectIndex;
 
-    // The section data is padded to 4 bytes.
+    // Set the symbol type to undefined lazy, but only on construction.
     //
-    // FIXME: Is this machine dependent?
-    unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4);
-    SectionDataFileSize += SectionDataPadding;
-
-    // Write the prolog, starting with the header and load command...
-    WriteHeader(NumLoadCommands, LoadCommandsSize,
-                Asm.getSubsectionsViaSymbols());
-    WriteSegmentLoadCommand(NumSections, VMSize,
-                            SectionDataStart, SectionDataSize);
-
-    // ... and then the section headers.
-    uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
-    for (MCAssembler::const_iterator it = Asm.begin(),
-           ie = Asm.end(); it != ie; ++it) {
-      std::vector<macho::RelocationEntry> &Relocs = Relocations[it];
-      unsigned NumRelocs = Relocs.size();
-      uint64_t SectionStart = SectionDataStart + getSectionAddress(it);
-      WriteSection(Asm, Layout, *it, SectionStart, RelocTableEnd, NumRelocs);
-      RelocTableEnd += NumRelocs * macho::RelocationInfoSize;
+    // FIXME: Do not hardcode.
+    bool Created;
+    MCSymbolData &Entry = Asm.getOrCreateSymbolData(*it->Symbol, &Created);
+    if (Created)
+      Entry.setFlags(Entry.getFlags() | 0x0001);
+  }
+}
+
+/// ComputeSymbolTable - Compute the symbol table data
+///
+/// \param StringTable [out] - The string table data.
+/// \param StringIndexMap [out] - Map from symbol names to offsets in the
+/// string table.
+void MachObjectWriter::ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
+                                          std::vector<MachSymbolData> &LocalSymbolData,
+                                          std::vector<MachSymbolData> &ExternalSymbolData,
+                                          std::vector<MachSymbolData> &UndefinedSymbolData) {
+  // Build section lookup table.
+  DenseMap<const MCSection*, uint8_t> SectionIndexMap;
+  unsigned Index = 1;
+  for (MCAssembler::iterator it = Asm.begin(),
+         ie = Asm.end(); it != ie; ++it, ++Index)
+    SectionIndexMap[&it->getSection()] = Index;
+  assert(Index <= 256 && "Too many sections!");
+
+  // Index 0 is always the empty string.
+  StringMap<uint64_t> StringIndexMap;
+  StringTable += '\x00';
+
+  // Build the symbol arrays and the string table, but only for non-local
+  // symbols.
+  //
+  // The particular order that we collect the symbols and create the string
+  // table, then sort the symbols is chosen to match 'as'. Even though it
+  // doesn't matter for correctness, this is important for letting us diff .o
+  // files.
+  for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
+         ie = Asm.symbol_end(); it != ie; ++it) {
+    const MCSymbol &Symbol = it->getSymbol();
+
+    // Ignore non-linker visible symbols.
+    if (!Asm.isSymbolLinkerVisible(it->getSymbol()))
+      continue;
+
+    if (!it->isExternal() && !Symbol.isUndefined())
+      continue;
+
+    uint64_t &Entry = StringIndexMap[Symbol.getName()];
+    if (!Entry) {
+      Entry = StringTable.size();
+      StringTable += Symbol.getName();
+      StringTable += '\x00';
     }
 
-    // Write the symbol table load command, if used.
-    if (NumSymbols) {
-      unsigned FirstLocalSymbol = 0;
-      unsigned NumLocalSymbols = LocalSymbolData.size();
-      unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
-      unsigned NumExternalSymbols = ExternalSymbolData.size();
-      unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
-      unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
-      unsigned NumIndirectSymbols = Asm.indirect_symbol_size();
-      unsigned NumSymTabSymbols =
-        NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols;
-      uint64_t IndirectSymbolSize = NumIndirectSymbols * 4;
-      uint64_t IndirectSymbolOffset = 0;
-
-      // If used, the indirect symbols are written after the section data.
-      if (NumIndirectSymbols)
-        IndirectSymbolOffset = RelocTableEnd;
-
-      // The symbol table is written after the indirect symbol data.
-      uint64_t SymbolTableOffset = RelocTableEnd + IndirectSymbolSize;
-
-      // The string table is written after symbol table.
-      uint64_t StringTableOffset =
-        SymbolTableOffset + NumSymTabSymbols * (is64Bit() ? macho::Nlist64Size :
-                                                macho::Nlist32Size);
-      WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
-                             StringTableOffset, StringTable.size());
-
-      WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
-                               FirstExternalSymbol, NumExternalSymbols,
-                               FirstUndefinedSymbol, NumUndefinedSymbols,
-                               IndirectSymbolOffset, NumIndirectSymbols);
+    MachSymbolData MSD;
+    MSD.SymbolData = it;
+    MSD.StringIndex = Entry;
+
+    if (Symbol.isUndefined()) {
+      MSD.SectionIndex = 0;
+      UndefinedSymbolData.push_back(MSD);
+    } else if (Symbol.isAbsolute()) {
+      MSD.SectionIndex = 0;
+      ExternalSymbolData.push_back(MSD);
+    } else {
+      MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
+      assert(MSD.SectionIndex && "Invalid section index!");
+      ExternalSymbolData.push_back(MSD);
     }
+  }
+
+  // Now add the data for local symbols.
+  for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
+         ie = Asm.symbol_end(); it != ie; ++it) {
+    const MCSymbol &Symbol = it->getSymbol();
+
+    // Ignore non-linker visible symbols.
+    if (!Asm.isSymbolLinkerVisible(it->getSymbol()))
+      continue;
 
-    // Write the actual section data.
-    for (MCAssembler::const_iterator it = Asm.begin(),
-           ie = Asm.end(); it != ie; ++it) {
-      Asm.WriteSectionData(it, Layout);
+    if (it->isExternal() || Symbol.isUndefined())
+      continue;
 
-      uint64_t Pad = getPaddingSize(it, Layout);
-      for (unsigned int i = 0; i < Pad; ++i)
-        Write8(0);
+    uint64_t &Entry = StringIndexMap[Symbol.getName()];
+    if (!Entry) {
+      Entry = StringTable.size();
+      StringTable += Symbol.getName();
+      StringTable += '\x00';
     }
 
-    // Write the extra padding.
-    WriteZeros(SectionDataPadding);
-
-    // Write the relocation entries.
-    for (MCAssembler::const_iterator it = Asm.begin(),
-           ie = Asm.end(); it != ie; ++it) {
-      // Write the section relocation entries, in reverse order to match 'as'
-      // (approximately, the exact algorithm is more complicated than this).
-      std::vector<macho::RelocationEntry> &Relocs = Relocations[it];
-      for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
-        Write32(Relocs[e - i - 1].Word0);
-        Write32(Relocs[e - i - 1].Word1);
-      }
+    MachSymbolData MSD;
+    MSD.SymbolData = it;
+    MSD.StringIndex = Entry;
+
+    if (Symbol.isAbsolute()) {
+      MSD.SectionIndex = 0;
+      LocalSymbolData.push_back(MSD);
+    } else {
+      MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
+      assert(MSD.SectionIndex && "Invalid section index!");
+      LocalSymbolData.push_back(MSD);
     }
+  }
 
-    // Write the symbol table data, if used.
-    if (NumSymbols) {
-      // Write the indirect symbol entries.
-      for (MCAssembler::const_indirect_symbol_iterator
-             it = Asm.indirect_symbol_begin(),
-             ie = Asm.indirect_symbol_end(); it != ie; ++it) {
-        // Indirect symbols in the non lazy symbol pointer section have some
-        // special handling.
-        const MCSectionMachO &Section =
-          static_cast<const MCSectionMachO&>(it->SectionData->getSection());
-        if (Section.getType() == MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS) {
-          // If this symbol is defined and internal, mark it as such.
-          if (it->Symbol->isDefined() &&
-              !Asm.getSymbolData(*it->Symbol).isExternal()) {
-            uint32_t Flags = macho::ISF_Local;
-            if (it->Symbol->isAbsolute())
-              Flags |= macho::ISF_Absolute;
-            Write32(Flags);
-            continue;
-          }
-        }
+  // External and undefined symbols are required to be in lexicographic order.
+  std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
+  std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());
+
+  // Set the symbol indices.
+  Index = 0;
+  for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
+    LocalSymbolData[i].SymbolData->setIndex(Index++);
+  for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
+    ExternalSymbolData[i].SymbolData->setIndex(Index++);
+  for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
+    UndefinedSymbolData[i].SymbolData->setIndex(Index++);
+
+  // The string table is padded to a multiple of 4.
+  while (StringTable.size() % 4)
+    StringTable += '\x00';
+}
 
-        Write32(Asm.getSymbolData(*it->Symbol).getIndex());
-      }
+void MachObjectWriter::computeSectionAddresses(const MCAssembler &Asm,
+                                               const MCAsmLayout &Layout) {
+  uint64_t StartAddress = 0;
+  const SmallVectorImpl<MCSectionData*> &Order = Layout.getSectionOrder();
+  for (int i = 0, n = Order.size(); i != n ; ++i) {
+    const MCSectionData *SD = Order[i];
+    StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
+    SectionAddress[SD] = StartAddress;
+    StartAddress += Layout.getSectionAddressSize(SD);
+
+    // Explicitly pad the section to match the alignment requirements of the
+    // following one. This is for 'gas' compatibility, it shouldn't
+    /// strictly be necessary.
+    StartAddress += getPaddingSize(SD, Layout);
+  }
+}
 
-      // FIXME: Check that offsets match computed ones.
+void MachObjectWriter::ExecutePostLayoutBinding(MCAssembler &Asm, const MCAsmLayout &Layout) {
+  computeSectionAddresses(Asm, Layout);
 
-      // Write the symbol table entries.
-      for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
-        WriteNlist(LocalSymbolData[i], Layout);
-      for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
-        WriteNlist(ExternalSymbolData[i], Layout);
-      for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
-        WriteNlist(UndefinedSymbolData[i], Layout);
+  // Create symbol data for any indirect symbols.
+  BindIndirectSymbols(Asm);
 
-      // Write the string table.
-      OS << StringTable.str();
+  // Compute symbol table information and bind symbol indices.
+  ComputeSymbolTable(Asm, StringTable, LocalSymbolData, ExternalSymbolData,
+                     UndefinedSymbolData);
+}
+
+bool MachObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
+                                                              const MCSymbolData &DataA,
+                                                              const MCFragment &FB,
+                                                              bool InSet,
+                                                              bool IsPCRel) const {
+  if (InSet)
+    return true;
+
+  // The effective address is
+  //     addr(atom(A)) + offset(A)
+  //   - addr(atom(B)) - offset(B)
+  // and the offsets are not relocatable, so the fixup is fully resolved when
+  //  addr(atom(A)) - addr(atom(B)) == 0.
+  const MCSymbolData *A_Base = 0, *B_Base = 0;
+
+  const MCSymbol &SA = DataA.getSymbol().AliasedSymbol();
+  const MCSection &SecA = SA.getSection();
+  const MCSection &SecB = FB.getParent()->getSection();
+
+  if (IsPCRel) {
+    // The simple (Darwin, except on x86_64) way of dealing with this was to
+    // assume that any reference to a temporary symbol *must* be a temporary
+    // symbol in the same atom, unless the sections differ. Therefore, any PCrel
+    // relocation to a temporary symbol (in the same section) is fully
+    // resolved. This also works in conjunction with absolutized .set, which
+    // requires the compiler to use .set to absolutize the differences between
+    // symbols which the compiler knows to be assembly time constants, so we
+    // don't need to worry about considering symbol differences fully resolved.
+
+    if (!Asm.getBackend().hasReliableSymbolDifference()) {
+      if (!SA.isTemporary() || !SA.isInSection() || &SecA != &SecB)
+        return false;
+      return true;
     }
+  } else {
+    if (!TargetObjectWriter->useAggressiveSymbolFolding())
+      return false;
+  }
+
+  const MCFragment &FA = *Asm.getSymbolData(SA).getFragment();
+
+  A_Base = FA.getAtom();
+  if (!A_Base)
+    return false;
+
+  B_Base = FB.getAtom();
+  if (!B_Base)
+    return false;
+
+  // If the atoms are the same, they are guaranteed to have the same address.
+  if (A_Base == B_Base)
+    return true;
+
+  // Otherwise, we can't prove this is fully resolved.
+  return false;
+}
+
+void MachObjectWriter::WriteObject(MCAssembler &Asm, const MCAsmLayout &Layout) {
+  unsigned NumSections = Asm.size();
+
+  // The section data starts after the header, the segment load command (and
+  // section headers) and the symbol table.
+  unsigned NumLoadCommands = 1;
+  uint64_t LoadCommandsSize = is64Bit() ?
+    macho::SegmentLoadCommand64Size + NumSections * macho::Section64Size :
+    macho::SegmentLoadCommand32Size + NumSections * macho::Section32Size;
+
+  // Add the symbol table load command sizes, if used.
+  unsigned NumSymbols = LocalSymbolData.size() + ExternalSymbolData.size() +
+    UndefinedSymbolData.size();
+  if (NumSymbols) {
+    NumLoadCommands += 2;
+    LoadCommandsSize += (macho::SymtabLoadCommandSize +
+                         macho::DysymtabLoadCommandSize);
   }
-};
 
+  // Compute the total size of the section data, as well as its file size and vm
+  // size.
+  uint64_t SectionDataStart = (is64Bit() ? macho::Header64Size :
+                               macho::Header32Size) + LoadCommandsSize;
+  uint64_t SectionDataSize = 0;
+  uint64_t SectionDataFileSize = 0;
+  uint64_t VMSize = 0;
+  for (MCAssembler::const_iterator it = Asm.begin(),
+         ie = Asm.end(); it != ie; ++it) {
+    const MCSectionData &SD = *it;
+    uint64_t Address = getSectionAddress(&SD);
+    uint64_t Size = Layout.getSectionAddressSize(&SD);
+    uint64_t FileSize = Layout.getSectionFileSize(&SD);
+    FileSize += getPaddingSize(&SD, Layout);
+
+    VMSize = std::max(VMSize, Address + Size);
+
+    if (SD.getSection().isVirtualSection())
+      continue;
+
+    SectionDataSize = std::max(SectionDataSize, Address + Size);
+    SectionDataFileSize = std::max(SectionDataFileSize, Address + FileSize);
+  }
+
+  // The section data is padded to 4 bytes.
+  //
+  // FIXME: Is this machine dependent?
+  unsigned SectionDataPadding = OffsetToAlignment(SectionDataFileSize, 4);
+  SectionDataFileSize += SectionDataPadding;
+
+  // Write the prolog, starting with the header and load command...
+  WriteHeader(NumLoadCommands, LoadCommandsSize,
+              Asm.getSubsectionsViaSymbols());
+  WriteSegmentLoadCommand(NumSections, VMSize,
+                          SectionDataStart, SectionDataSize);
+
+  // ... and then the section headers.
+  uint64_t RelocTableEnd = SectionDataStart + SectionDataFileSize;
+  for (MCAssembler::const_iterator it = Asm.begin(),
+         ie = Asm.end(); it != ie; ++it) {
+    std::vector<macho::RelocationEntry> &Relocs = Relocations[it];
+    unsigned NumRelocs = Relocs.size();
+    uint64_t SectionStart = SectionDataStart + getSectionAddress(it);
+    WriteSection(Asm, Layout, *it, SectionStart, RelocTableEnd, NumRelocs);
+    RelocTableEnd += NumRelocs * macho::RelocationInfoSize;
+  }
+
+  // Write the symbol table load command, if used.
+  if (NumSymbols) {
+    unsigned FirstLocalSymbol = 0;
+    unsigned NumLocalSymbols = LocalSymbolData.size();
+    unsigned FirstExternalSymbol = FirstLocalSymbol + NumLocalSymbols;
+    unsigned NumExternalSymbols = ExternalSymbolData.size();
+    unsigned FirstUndefinedSymbol = FirstExternalSymbol + NumExternalSymbols;
+    unsigned NumUndefinedSymbols = UndefinedSymbolData.size();
+    unsigned NumIndirectSymbols = Asm.indirect_symbol_size();
+    unsigned NumSymTabSymbols =
+      NumLocalSymbols + NumExternalSymbols + NumUndefinedSymbols;
+    uint64_t IndirectSymbolSize = NumIndirectSymbols * 4;
+    uint64_t IndirectSymbolOffset = 0;
+
+    // If used, the indirect symbols are written after the section data.
+    if (NumIndirectSymbols)
+      IndirectSymbolOffset = RelocTableEnd;
+
+    // The symbol table is written after the indirect symbol data.
+    uint64_t SymbolTableOffset = RelocTableEnd + IndirectSymbolSize;
+
+    // The string table is written after symbol table.
+    uint64_t StringTableOffset =
+      SymbolTableOffset + NumSymTabSymbols * (is64Bit() ? macho::Nlist64Size :
+                                              macho::Nlist32Size);
+    WriteSymtabLoadCommand(SymbolTableOffset, NumSymTabSymbols,
+                           StringTableOffset, StringTable.size());
+
+    WriteDysymtabLoadCommand(FirstLocalSymbol, NumLocalSymbols,
+                             FirstExternalSymbol, NumExternalSymbols,
+                             FirstUndefinedSymbol, NumUndefinedSymbols,
+                             IndirectSymbolOffset, NumIndirectSymbols);
+  }
+
+  // Write the actual section data.
+  for (MCAssembler::const_iterator it = Asm.begin(),
+         ie = Asm.end(); it != ie; ++it) {
+    Asm.WriteSectionData(it, Layout);
+
+    uint64_t Pad = getPaddingSize(it, Layout);
+    for (unsigned int i = 0; i < Pad; ++i)
+      Write8(0);
+  }
+
+  // Write the extra padding.
+  WriteZeros(SectionDataPadding);
+
+  // Write the relocation entries.
+  for (MCAssembler::const_iterator it = Asm.begin(),
+         ie = Asm.end(); it != ie; ++it) {
+    // Write the section relocation entries, in reverse order to match 'as'
+    // (approximately, the exact algorithm is more complicated than this).
+    std::vector<macho::RelocationEntry> &Relocs = Relocations[it];
+    for (unsigned i = 0, e = Relocs.size(); i != e; ++i) {
+      Write32(Relocs[e - i - 1].Word0);
+      Write32(Relocs[e - i - 1].Word1);
+    }
+  }
+
+  // Write the symbol table data, if used.
+  if (NumSymbols) {
+    // Write the indirect symbol entries.
+    for (MCAssembler::const_indirect_symbol_iterator
+           it = Asm.indirect_symbol_begin(),
+           ie = Asm.indirect_symbol_end(); it != ie; ++it) {
+      // Indirect symbols in the non lazy symbol pointer section have some
+      // special handling.
+      const MCSectionMachO &Section =
+        static_cast<const MCSectionMachO&>(it->SectionData->getSection());
+      if (Section.getType() == MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS) {
+        // If this symbol is defined and internal, mark it as such.
+        if (it->Symbol->isDefined() &&
+            !Asm.getSymbolData(*it->Symbol).isExternal()) {
+          uint32_t Flags = macho::ISF_Local;
+          if (it->Symbol->isAbsolute())
+            Flags |= macho::ISF_Absolute;
+          Write32(Flags);
+          continue;
+        }
+      }
+
+      Write32(Asm.getSymbolData(*it->Symbol).getIndex());
+    }
+
+    // FIXME: Check that offsets match computed ones.
+
+    // Write the symbol table entries.
+    for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
+      WriteNlist(LocalSymbolData[i], Layout);
+    for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
+      WriteNlist(ExternalSymbolData[i], Layout);
+    for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
+      WriteNlist(UndefinedSymbolData[i], Layout);
+
+    // Write the string table.
+    OS << StringTable.str();
+  }
 }
 
 MCObjectWriter *llvm::createMachObjectWriter(MCMachObjectTargetWriter *MOTW,