llvm/lib/Target/X86/MCTargetDesc/X86MachObjectWriter.cpp - llvm-project - Git at Google

 //===-- X86MachObjectWriter.cpp - X86 Mach-O Writer -----------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//

 #include "MCTargetDesc/X86FixupKinds.h"
 #include "MCTargetDesc/X86MCTargetDesc.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/BinaryFormat/MachO.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCAsmLayout.h"
 #include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCMachObjectWriter.h"
 #include "llvm/MC/MCSectionMachO.h"
 #include "llvm/MC/MCValue.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/Format.h"

 using namespace llvm;

 namespace {
 class X86MachObjectWriter : public MCMachObjectTargetWriter {
   bool recordScatteredRelocation(MachObjectWriter *Writer,
                                  const MCAssembler &Asm,
                                  const MCAsmLayout &Layout,
                                  const MCFragment *Fragment,
                                  const MCFixup &Fixup,
                                  MCValue Target,
                                  unsigned Log2Size,
                                  uint64_t &FixedValue);
   void recordTLVPRelocation(MachObjectWriter *Writer,
                             const MCAssembler &Asm,
                             const MCAsmLayout &Layout,
                             const MCFragment *Fragment,
                             const MCFixup &Fixup,
                             MCValue Target,
                             uint64_t &FixedValue);

   void RecordX86Relocation(MachObjectWriter *Writer,
                               const MCAssembler &Asm,
                               const MCAsmLayout &Layout,
                               const MCFragment *Fragment,
                               const MCFixup &Fixup,
                               MCValue Target,
                               uint64_t &FixedValue);
   void RecordX86_64Relocation(MachObjectWriter *Writer, MCAssembler &Asm,
                               const MCAsmLayout &Layout,
                               const MCFragment *Fragment, const MCFixup &Fixup,
                               MCValue Target, uint64_t &FixedValue);

 public:
   X86MachObjectWriter(bool Is64Bit, uint32_t CPUType, uint32_t CPUSubtype)
       : MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype) {}

   void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
                         const MCAsmLayout &Layout, const MCFragment *Fragment,
                         const MCFixup &Fixup, MCValue Target,
                         uint64_t &FixedValue) override {
     if (Writer->is64Bit())
       RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
                              FixedValue);
     else
       RecordX86Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
                           FixedValue);
   }
 };
 } // namespace

 static bool isFixupKindRIPRel(unsigned Kind) {
   return Kind == X86::reloc_riprel_4byte ||
          Kind == X86::reloc_riprel_4byte_movq_load ||
          Kind == X86::reloc_riprel_4byte_relax ||
          Kind == X86::reloc_riprel_4byte_relax_rex;
 }

 static unsigned getFixupKindLog2Size(unsigned Kind) {
   switch (Kind) {
   default:
     llvm_unreachable("invalid fixup kind!");
   case FK_PCRel_1:
   case FK_Data_1: return 0;
   case FK_PCRel_2:
   case FK_Data_2: return 1;
   case FK_PCRel_4:
     // FIXME: Remove these!!!
   case X86::reloc_riprel_4byte:
   case X86::reloc_riprel_4byte_relax:
   case X86::reloc_riprel_4byte_relax_rex:
   case X86::reloc_riprel_4byte_movq_load:
   case X86::reloc_signed_4byte:
   case X86::reloc_signed_4byte_relax:
   case X86::reloc_branch_4byte_pcrel:
   case FK_Data_4: return 2;
   case FK_Data_8: return 3;
   }
 }

 void X86MachObjectWriter::RecordX86_64Relocation(
     MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
     const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
     uint64_t &FixedValue) {
   unsigned IsPCRel = Writer->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 =
     Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
   int64_t Value = 0;
   unsigned Index = 0;
   unsigned IsExtern = 0;
   unsigned Type = 0;
   const MCSymbol *RelSymbol = nullptr;

   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::X86_64_RELOC_UNSIGNED;

     // 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::X86_64_RELOC_BRANCH;
     }
   } else if (Target.getSymB()) { // A - B + constant
     const MCSymbol *A = &Target.getSymA()->getSymbol();
     if (A->isTemporary())
       A = &Writer->findAliasedSymbol(*A);
     const MCSymbol *A_Base = Asm.getAtom(*A);

     const MCSymbol *B = &Target.getSymB()->getSymbol();
     if (B->isTemporary())
       B = &Writer->findAliasedSymbol(*B);
     const MCSymbol *B_Base = Asm.getAtom(*B);

     // Neither symbol can be modified.
     if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None) {
       Asm.getContext().reportError(Fixup.getLoc(),
                                    "unsupported relocation of modified symbol");
       return;
     }

     // We don't support PCrel relocations of differences. Darwin 'as' doesn't
     // implement most of these correctly.
     if (IsPCRel) {
       Asm.getContext().reportError(
           Fixup.getLoc(), "unsupported pc-relative relocation of difference");
       return;
     }

     // 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) {
       Asm.getContext().reportError(
           Fixup.getLoc(), "unsupported relocation with identical base");
       return;
     }

     // A subtraction expression where either symbol is undefined is a
     // non-relocatable expression.
     if (A->isUndefined() || B->isUndefined()) {
       StringRef Name = A->isUndefined() ? A->getName() : B->getName();
       Asm.getContext().reportError(Fixup.getLoc(),
         "unsupported relocation with subtraction expression, symbol '" +
         Name + "' can not be undefined in a subtraction expression");
       return;
     }

     Value += Writer->getSymbolAddress(*A, Layout) -
              (!A_Base ? 0 : Writer->getSymbolAddress(*A_Base, Layout));
     Value -= Writer->getSymbolAddress(*B, Layout) -
              (!B_Base ? 0 : Writer->getSymbolAddress(*B_Base, Layout));

     if (!A_Base)
       Index = A->getFragment()->getParent()->getOrdinal() + 1;
     Type = MachO::X86_64_RELOC_UNSIGNED;

     MachO::any_relocation_info MRE;
     MRE.r_word0 = FixupOffset;
     MRE.r_word1 =
         (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
     Writer->addRelocation(A_Base, Fragment->getParent(), MRE);

     if (B_Base)
       RelSymbol = B_Base;
     else
       Index = B->getFragment()->getParent()->getOrdinal() + 1;
     Type = MachO::X86_64_RELOC_SUBTRACTOR;
   } else {
     const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
     if (Symbol->isTemporary() && Value) {
       const MCSection &Sec = Symbol->getSection();
       if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
         Symbol->setUsedInReloc();
     }
     RelSymbol = Asm.getAtom(*Symbol);

     // 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());
       if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
         RelSymbol = nullptr;
     }

     // 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 (RelSymbol) {
       // Add the local offset, if needed.
       if (RelSymbol != Symbol)
         Value += Layout.getSymbolOffset(*Symbol) -
                  Layout.getSymbolOffset(*RelSymbol);
     } else if (Symbol->isInSection() && !Symbol->isVariable()) {
       // The index is the section ordinal (1-based).
       Index = Symbol->getFragment()->getParent()->getOrdinal() + 1;
       Value += Writer->getSymbolAddress(*Symbol, 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,
                                              Writer->getSectionAddressMap());
       if (isAbs) {
         FixedValue = Res;
         return;
       } else {
         Asm.getContext().reportError(Fixup.getLoc(),
                                      "unsupported relocation of variable '" +
                                          Symbol->getName() + "'");
         return;
       }
     } else {
       Asm.getContext().reportError(
           Fixup.getLoc(), "unsupported relocation of undefined symbol '" +
                               Symbol->getName() + "'");
       return;
     }

     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 (Fixup.getTargetKind() == X86::reloc_riprel_4byte_movq_load)
             Type = MachO::X86_64_RELOC_GOT_LOAD;
           else
             Type = MachO::X86_64_RELOC_GOT;
         }  else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
           Type = MachO::X86_64_RELOC_TLV;
         }  else if (Modifier != MCSymbolRefExpr::VK_None) {
           Asm.getContext().reportError(
               Fixup.getLoc(), "unsupported symbol modifier in relocation");
           return;
         } else {
           Type = MachO::X86_64_RELOC_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::X86_64_RELOC_SIGNED_1; break;
           case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break;
           case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break;
           }
         }
       } else {
         if (Modifier != MCSymbolRefExpr::VK_None) {
           Asm.getContext().reportError(
               Fixup.getLoc(),
               "unsupported symbol modifier in branch relocation");
           return;
         }

         Type = MachO::X86_64_RELOC_BRANCH;
       }
     } else {
       if (Modifier == MCSymbolRefExpr::VK_GOT) {
         Type = MachO::X86_64_RELOC_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::X86_64_RELOC_GOT;
         IsPCRel = 1;
       } else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
         Asm.getContext().reportError(
             Fixup.getLoc(), "TLVP symbol modifier should have been rip-rel");
         return;
       } else if (Modifier != MCSymbolRefExpr::VK_None) {
         Asm.getContext().reportError(
             Fixup.getLoc(), "unsupported symbol modifier in relocation");
         return;
       } else {
         Type = MachO::X86_64_RELOC_UNSIGNED;
         if (Fixup.getTargetKind() == X86::reloc_signed_4byte) {
           Asm.getContext().reportError(
               Fixup.getLoc(),
               "32-bit absolute addressing is not supported in 64-bit mode");
           return;
         }
       }
     }
   }

   // x86_64 always writes custom values into the fixups.
   FixedValue = Value;

   // struct relocation_info (8 bytes)
   MachO::any_relocation_info MRE;
   MRE.r_word0 = FixupOffset;
   MRE.r_word1 = (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) |
                 (IsExtern << 27) | (Type << 28);
   Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
 }

 bool X86MachObjectWriter::recordScatteredRelocation(MachObjectWriter *Writer,
                                                     const MCAssembler &Asm,
                                                     const MCAsmLayout &Layout,
                                                     const MCFragment *Fragment,
                                                     const MCFixup &Fixup,
                                                     MCValue Target,
                                                     unsigned Log2Size,
                                                     uint64_t &FixedValue) {
   uint64_t OriginalFixedValue = FixedValue;
   uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
   unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
   unsigned Type = MachO::GENERIC_RELOC_VANILLA;

   // See <reloc.h>.
   const MCSymbol *A = &Target.getSymA()->getSymbol();

   if (!A->getFragment()) {
     Asm.getContext().reportError(
         Fixup.getLoc(),
         "symbol '" + A->getName() +
             "' can not be undefined in a subtraction expression");
     return false;
   }

   uint32_t Value = Writer->getSymbolAddress(*A, Layout);
   uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent());
   FixedValue += SecAddr;
   uint32_t Value2 = 0;

   if (const MCSymbolRefExpr *B = Target.getSymB()) {
     const MCSymbol *SB = &B->getSymbol();

     if (!SB->getFragment()) {
       Asm.getContext().reportError(
           Fixup.getLoc(),
           "symbol '" + SB->getName() +
               "' can not be undefined in a subtraction expression");
       return false;
     }

     // 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->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF
                            : (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF;
     Value2 = Writer->getSymbolAddress(*SB, Layout);
     FixedValue -= Writer->getSectionAddress(SB->getFragment()->getParent());
   }

   // Relocations are written out in reverse order, so the PAIR comes first.
   if (Type == MachO::GENERIC_RELOC_SECTDIFF ||
       Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) {
     // If the offset is too large to fit in a scattered relocation,
     // we're hosed. It's an unfortunate limitation of the MachO format.
     if (FixupOffset > 0xffffff) {
       char Buffer[32];
       format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer));
       Asm.getContext().reportError(Fixup.getLoc(),
                          Twine("Section too large, can't encode "
                                 "r_address (") + Buffer +
                          ") into 24 bits of scattered "
                          "relocation entry.");
       return false;
     }

     MachO::any_relocation_info MRE;
     MRE.r_word0 = ((0                         <<  0) | // r_address
                    (MachO::GENERIC_RELOC_PAIR << 24) | // r_type
                    (Log2Size                  << 28) |
                    (IsPCRel                   << 30) |
                    MachO::R_SCATTERED);
     MRE.r_word1 = Value2;
     Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
   } else {
     // If the offset is more than 24-bits, it won't fit in a scattered
     // relocation offset field, so we fall back to using a non-scattered
     // relocation. This is a bit risky, as if the offset reaches out of
     // the block and the linker is doing scattered loading on this
     // symbol, things can go badly.
     //
     // Required for 'as' compatibility.
     if (FixupOffset > 0xffffff) {
       FixedValue = OriginalFixedValue;
       return false;
     }
   }

   MachO::any_relocation_info MRE;
   MRE.r_word0 = ((FixupOffset <<  0) |
                  (Type        << 24) |
                  (Log2Size    << 28) |
                  (IsPCRel     << 30) |
                  MachO::R_SCATTERED);
   MRE.r_word1 = Value;
   Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
   return true;
 }

 void X86MachObjectWriter::recordTLVPRelocation(MachObjectWriter *Writer,
                                                const MCAssembler &Asm,
                                                const MCAsmLayout &Layout,
                                                const MCFragment *Fragment,
                                                const MCFixup &Fixup,
                                                MCValue Target,
                                                uint64_t &FixedValue) {
   const MCSymbolRefExpr *SymA = Target.getSymA();
   assert(SymA->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;

   // 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 (auto *SymB = Target.getSymB()) {
     // If this is a subtraction then we're pcrel.
     uint32_t FixupAddress =
       Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
     IsPCRel = 1;
     FixedValue = FixupAddress -
                  Writer->getSymbolAddress(SymB->getSymbol(), Layout) +
                  Target.getConstant();
     FixedValue += 1ULL << Log2Size;
   } else {
     FixedValue = 0;
   }

   // struct relocation_info (8 bytes)
   MachO::any_relocation_info MRE;
   MRE.r_word0 = Value;
   MRE.r_word1 =
       (IsPCRel << 24) | (Log2Size << 25) | (MachO::GENERIC_RELOC_TLV << 28);
   Writer->addRelocation(&SymA->getSymbol(), Fragment->getParent(), MRE);
 }

 void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
                                               const MCAssembler &Asm,
                                               const MCAsmLayout &Layout,
                                               const MCFragment *Fragment,
                                               const MCFixup &Fixup,
                                               MCValue Target,
                                               uint64_t &FixedValue) {
   unsigned IsPCRel = Writer->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(Writer, 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()) {
     recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
                               Target, Log2Size, FixedValue);
     return;
   }

   // Get the symbol data, if any.
   const MCSymbol *A = nullptr;
   if (Target.getSymA())
     A = &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;

   // Try to record the scattered relocation if needed. Fall back to non
   // scattered if necessary (see comments in recordScatteredRelocation()
   // for details).
   if (Offset && A && !Writer->doesSymbolRequireExternRelocation(*A) &&
       recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
                                 Log2Size, FixedValue))
     return;

   // See <reloc.h>.
   uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
   unsigned Index = 0;
   unsigned Type = 0;
   const MCSymbol *RelSymbol = nullptr;

   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::GENERIC_RELOC_VANILLA;
   } else {
     assert(A && "Unknown symbol data");

     // Resolve constant variables.
     if (A->isVariable()) {
       int64_t Res;
       if (A->getVariableValue()->evaluateAsAbsolute(
               Res, Layout, Writer->getSectionAddressMap())) {
         FixedValue = Res;
         return;
       }
     }

     // Check whether we need an external or internal relocation.
     if (Writer->doesSymbolRequireExternRelocation(*A)) {
       RelSymbol = A;
       // 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 (!A->isUndefined())
         FixedValue -= Layout.getSymbolOffset(*A);
     } else {
       // The index is the section ordinal (1-based).
       const MCSection &Sec = A->getSection();
       Index = Sec.getOrdinal() + 1;
       FixedValue += Writer->getSectionAddress(&Sec);
     }
     if (IsPCRel)
       FixedValue -= Writer->getSectionAddress(Fragment->getParent());

     Type = MachO::GENERIC_RELOC_VANILLA;
   }

   // struct relocation_info (8 bytes)
   MachO::any_relocation_info MRE;
   MRE.r_word0 = FixupOffset;
   MRE.r_word1 =
       (Index << 0) | (IsPCRel << 24) | (Log2Size << 25) | (Type << 28);
   Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
 }

 std::unique_ptr<MCObjectTargetWriter>
 llvm::createX86MachObjectWriter(bool Is64Bit, uint32_t CPUType,
                                 uint32_t CPUSubtype) {
   return std::make_unique<X86MachObjectWriter>(Is64Bit, CPUType, CPUSubtype);
 }
	//===-- X86MachObjectWriter.cpp - X86 Mach-O Writer -----------------------===//
	//
	// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
	// See https://llvm.org/LICENSE.txt for license information.
	// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
	//
	//===----------------------------------------------------------------------===//

	#include "MCTargetDesc/X86FixupKinds.h"
	#include "MCTargetDesc/X86MCTargetDesc.h"
	#include "llvm/ADT/Twine.h"
	#include "llvm/BinaryFormat/MachO.h"
	#include "llvm/MC/MCAsmInfo.h"
	#include "llvm/MC/MCAsmLayout.h"
	#include "llvm/MC/MCAssembler.h"
	#include "llvm/MC/MCContext.h"
	#include "llvm/MC/MCMachObjectWriter.h"
	#include "llvm/MC/MCSectionMachO.h"
	#include "llvm/MC/MCValue.h"
	#include "llvm/Support/ErrorHandling.h"
	#include "llvm/Support/Format.h"

	using namespace llvm;

	namespace {
	class X86MachObjectWriter : public MCMachObjectTargetWriter {
	bool recordScatteredRelocation(MachObjectWriter *Writer,
	const MCAssembler &Asm,
	const MCAsmLayout &Layout,
	const MCFragment *Fragment,
	const MCFixup &Fixup,
	MCValue Target,
	unsigned Log2Size,
	uint64_t &FixedValue);
	void recordTLVPRelocation(MachObjectWriter *Writer,
	const MCAssembler &Asm,
	const MCAsmLayout &Layout,
	const MCFragment *Fragment,
	const MCFixup &Fixup,
	MCValue Target,
	uint64_t &FixedValue);

	void RecordX86Relocation(MachObjectWriter *Writer,
	const MCAssembler &Asm,
	const MCAsmLayout &Layout,
	const MCFragment *Fragment,
	const MCFixup &Fixup,
	MCValue Target,
	uint64_t &FixedValue);
	void RecordX86_64Relocation(MachObjectWriter *Writer, MCAssembler &Asm,
	const MCAsmLayout &Layout,
	const MCFragment *Fragment, const MCFixup &Fixup,
	MCValue Target, uint64_t &FixedValue);

	public:
	X86MachObjectWriter(bool Is64Bit, uint32_t CPUType, uint32_t CPUSubtype)
	: MCMachObjectTargetWriter(Is64Bit, CPUType, CPUSubtype) {}

	void recordRelocation(MachObjectWriter *Writer, MCAssembler &Asm,
	const MCAsmLayout &Layout, const MCFragment *Fragment,
	const MCFixup &Fixup, MCValue Target,
	uint64_t &FixedValue) override {
	if (Writer->is64Bit())
	RecordX86_64Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
	FixedValue);
	else
	RecordX86Relocation(Writer, Asm, Layout, Fragment, Fixup, Target,
	FixedValue);
	}
	};
	} // namespace

	static bool isFixupKindRIPRel(unsigned Kind) {
	return Kind == X86::reloc_riprel_4byte \|\|
	Kind == X86::reloc_riprel_4byte_movq_load \|\|
	Kind == X86::reloc_riprel_4byte_relax \|\|
	Kind == X86::reloc_riprel_4byte_relax_rex;
	}

	static unsigned getFixupKindLog2Size(unsigned Kind) {
	switch (Kind) {
	default:
	llvm_unreachable("invalid fixup kind!");
	case FK_PCRel_1:
	case FK_Data_1: return 0;
	case FK_PCRel_2:
	case FK_Data_2: return 1;
	case FK_PCRel_4:
	// FIXME: Remove these!!!
	case X86::reloc_riprel_4byte:
	case X86::reloc_riprel_4byte_relax:
	case X86::reloc_riprel_4byte_relax_rex:
	case X86::reloc_riprel_4byte_movq_load:
	case X86::reloc_signed_4byte:
	case X86::reloc_signed_4byte_relax:
	case X86::reloc_branch_4byte_pcrel:
	case FK_Data_4: return 2;
	case FK_Data_8: return 3;
	}
	}

	void X86MachObjectWriter::RecordX86_64Relocation(
	MachObjectWriter *Writer, MCAssembler &Asm, const MCAsmLayout &Layout,
	const MCFragment *Fragment, const MCFixup &Fixup, MCValue Target,
	uint64_t &FixedValue) {
	unsigned IsPCRel = Writer->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 =
	Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
	int64_t Value = 0;
	unsigned Index = 0;
	unsigned IsExtern = 0;
	unsigned Type = 0;
	const MCSymbol *RelSymbol = nullptr;

	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::X86_64_RELOC_UNSIGNED;

	// 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::X86_64_RELOC_BRANCH;
	}
	} else if (Target.getSymB()) { // A - B + constant
	const MCSymbol *A = &Target.getSymA()->getSymbol();
	if (A->isTemporary())
	A = &Writer->findAliasedSymbol(*A);
	const MCSymbol A_Base = Asm.getAtom(A);

	const MCSymbol *B = &Target.getSymB()->getSymbol();
	if (B->isTemporary())
	B = &Writer->findAliasedSymbol(*B);
	const MCSymbol B_Base = Asm.getAtom(B);

	// Neither symbol can be modified.
	if (Target.getSymA()->getKind() != MCSymbolRefExpr::VK_None) {
	Asm.getContext().reportError(Fixup.getLoc(),
	"unsupported relocation of modified symbol");
	return;
	}

	// We don't support PCrel relocations of differences. Darwin 'as' doesn't
	// implement most of these correctly.
	if (IsPCRel) {
	Asm.getContext().reportError(
	Fixup.getLoc(), "unsupported pc-relative relocation of difference");
	return;
	}

	// 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) {
	Asm.getContext().reportError(
	Fixup.getLoc(), "unsupported relocation with identical base");
	return;
	}

	// A subtraction expression where either symbol is undefined is a
	// non-relocatable expression.
	if (A->isUndefined() \|\| B->isUndefined()) {
	StringRef Name = A->isUndefined() ? A->getName() : B->getName();
	Asm.getContext().reportError(Fixup.getLoc(),
	"unsupported relocation with subtraction expression, symbol '" +
	Name + "' can not be undefined in a subtraction expression");
	return;
	}

	Value += Writer->getSymbolAddress(*A, Layout) -
	(!A_Base ? 0 : Writer->getSymbolAddress(*A_Base, Layout));
	Value -= Writer->getSymbolAddress(*B, Layout) -
	(!B_Base ? 0 : Writer->getSymbolAddress(*B_Base, Layout));

	if (!A_Base)
	Index = A->getFragment()->getParent()->getOrdinal() + 1;
	Type = MachO::X86_64_RELOC_UNSIGNED;

	MachO::any_relocation_info MRE;
	MRE.r_word0 = FixupOffset;
	MRE.r_word1 =
	(Index << 0) \| (IsPCRel << 24) \| (Log2Size << 25) \| (Type << 28);
	Writer->addRelocation(A_Base, Fragment->getParent(), MRE);

	if (B_Base)
	RelSymbol = B_Base;
	else
	Index = B->getFragment()->getParent()->getOrdinal() + 1;
	Type = MachO::X86_64_RELOC_SUBTRACTOR;
	} else {
	const MCSymbol *Symbol = &Target.getSymA()->getSymbol();
	if (Symbol->isTemporary() && Value) {
	const MCSection &Sec = Symbol->getSection();
	if (!Asm.getContext().getAsmInfo()->isSectionAtomizableBySymbols(Sec))
	Symbol->setUsedInReloc();
	}
	RelSymbol = Asm.getAtom(*Symbol);

	// 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());
	if (Section.hasAttribute(MachO::S_ATTR_DEBUG))
	RelSymbol = nullptr;
	}

	// 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 (RelSymbol) {
	// Add the local offset, if needed.
	if (RelSymbol != Symbol)
	Value += Layout.getSymbolOffset(*Symbol) -
	Layout.getSymbolOffset(*RelSymbol);
	} else if (Symbol->isInSection() && !Symbol->isVariable()) {
	// The index is the section ordinal (1-based).
	Index = Symbol->getFragment()->getParent()->getOrdinal() + 1;
	Value += Writer->getSymbolAddress(*Symbol, 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,
	Writer->getSectionAddressMap());
	if (isAbs) {
	FixedValue = Res;
	return;
	} else {
	Asm.getContext().reportError(Fixup.getLoc(),
	"unsupported relocation of variable '" +
	Symbol->getName() + "'");
	return;
	}
	} else {
	Asm.getContext().reportError(
	Fixup.getLoc(), "unsupported relocation of undefined symbol '" +
	Symbol->getName() + "'");
	return;
	}

	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 (Fixup.getTargetKind() == X86::reloc_riprel_4byte_movq_load)
	Type = MachO::X86_64_RELOC_GOT_LOAD;
	else
	Type = MachO::X86_64_RELOC_GOT;
	} else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
	Type = MachO::X86_64_RELOC_TLV;
	} else if (Modifier != MCSymbolRefExpr::VK_None) {
	Asm.getContext().reportError(
	Fixup.getLoc(), "unsupported symbol modifier in relocation");
	return;
	} else {
	Type = MachO::X86_64_RELOC_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::X86_64_RELOC_SIGNED_1; break;
	case 2: Type = MachO::X86_64_RELOC_SIGNED_2; break;
	case 4: Type = MachO::X86_64_RELOC_SIGNED_4; break;
	}
	}
	} else {
	if (Modifier != MCSymbolRefExpr::VK_None) {
	Asm.getContext().reportError(
	Fixup.getLoc(),
	"unsupported symbol modifier in branch relocation");
	return;
	}

	Type = MachO::X86_64_RELOC_BRANCH;
	}
	} else {
	if (Modifier == MCSymbolRefExpr::VK_GOT) {
	Type = MachO::X86_64_RELOC_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::X86_64_RELOC_GOT;
	IsPCRel = 1;
	} else if (Modifier == MCSymbolRefExpr::VK_TLVP) {
	Asm.getContext().reportError(
	Fixup.getLoc(), "TLVP symbol modifier should have been rip-rel");
	return;
	} else if (Modifier != MCSymbolRefExpr::VK_None) {
	Asm.getContext().reportError(
	Fixup.getLoc(), "unsupported symbol modifier in relocation");
	return;
	} else {
	Type = MachO::X86_64_RELOC_UNSIGNED;
	if (Fixup.getTargetKind() == X86::reloc_signed_4byte) {
	Asm.getContext().reportError(
	Fixup.getLoc(),
	"32-bit absolute addressing is not supported in 64-bit mode");
	return;
	}
	}
	}
	}

	// x86_64 always writes custom values into the fixups.
	FixedValue = Value;

	// struct relocation_info (8 bytes)
	MachO::any_relocation_info MRE;
	MRE.r_word0 = FixupOffset;
	MRE.r_word1 = (Index << 0) \| (IsPCRel << 24) \| (Log2Size << 25) \|
	(IsExtern << 27) \| (Type << 28);
	Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
	}

	bool X86MachObjectWriter::recordScatteredRelocation(MachObjectWriter *Writer,
	const MCAssembler &Asm,
	const MCAsmLayout &Layout,
	const MCFragment *Fragment,
	const MCFixup &Fixup,
	MCValue Target,
	unsigned Log2Size,
	uint64_t &FixedValue) {
	uint64_t OriginalFixedValue = FixedValue;
	uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
	unsigned IsPCRel = Writer->isFixupKindPCRel(Asm, Fixup.getKind());
	unsigned Type = MachO::GENERIC_RELOC_VANILLA;

	// See <reloc.h>.
	const MCSymbol *A = &Target.getSymA()->getSymbol();

	if (!A->getFragment()) {
	Asm.getContext().reportError(
	Fixup.getLoc(),
	"symbol '" + A->getName() +
	"' can not be undefined in a subtraction expression");
	return false;
	}

	uint32_t Value = Writer->getSymbolAddress(*A, Layout);
	uint64_t SecAddr = Writer->getSectionAddress(A->getFragment()->getParent());
	FixedValue += SecAddr;
	uint32_t Value2 = 0;

	if (const MCSymbolRefExpr *B = Target.getSymB()) {
	const MCSymbol *SB = &B->getSymbol();

	if (!SB->getFragment()) {
	Asm.getContext().reportError(
	Fixup.getLoc(),
	"symbol '" + SB->getName() +
	"' can not be undefined in a subtraction expression");
	return false;
	}

	// 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->isExternal() ? (unsigned)MachO::GENERIC_RELOC_SECTDIFF
	: (unsigned)MachO::GENERIC_RELOC_LOCAL_SECTDIFF;
	Value2 = Writer->getSymbolAddress(*SB, Layout);
	FixedValue -= Writer->getSectionAddress(SB->getFragment()->getParent());
	}

	// Relocations are written out in reverse order, so the PAIR comes first.
	if (Type == MachO::GENERIC_RELOC_SECTDIFF \|\|
	Type == MachO::GENERIC_RELOC_LOCAL_SECTDIFF) {
	// If the offset is too large to fit in a scattered relocation,
	// we're hosed. It's an unfortunate limitation of the MachO format.
	if (FixupOffset > 0xffffff) {
	char Buffer[32];
	format("0x%x", FixupOffset).print(Buffer, sizeof(Buffer));
	Asm.getContext().reportError(Fixup.getLoc(),
	Twine("Section too large, can't encode "
	"r_address (") + Buffer +
	") into 24 bits of scattered "
	"relocation entry.");
	return false;
	}

	MachO::any_relocation_info MRE;
	MRE.r_word0 = ((0 << 0) \| // r_address
	(MachO::GENERIC_RELOC_PAIR << 24) \| // r_type
	(Log2Size << 28) \|
	(IsPCRel << 30) \|
	MachO::R_SCATTERED);
	MRE.r_word1 = Value2;
	Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
	} else {
	// If the offset is more than 24-bits, it won't fit in a scattered
	// relocation offset field, so we fall back to using a non-scattered
	// relocation. This is a bit risky, as if the offset reaches out of
	// the block and the linker is doing scattered loading on this
	// symbol, things can go badly.
	//
	// Required for 'as' compatibility.
	if (FixupOffset > 0xffffff) {
	FixedValue = OriginalFixedValue;
	return false;
	}
	}

	MachO::any_relocation_info MRE;
	MRE.r_word0 = ((FixupOffset << 0) \|
	(Type << 24) \|
	(Log2Size << 28) \|
	(IsPCRel << 30) \|
	MachO::R_SCATTERED);
	MRE.r_word1 = Value;
	Writer->addRelocation(nullptr, Fragment->getParent(), MRE);
	return true;
	}

	void X86MachObjectWriter::recordTLVPRelocation(MachObjectWriter *Writer,
	const MCAssembler &Asm,
	const MCAsmLayout &Layout,
	const MCFragment *Fragment,
	const MCFixup &Fixup,
	MCValue Target,
	uint64_t &FixedValue) {
	const MCSymbolRefExpr *SymA = Target.getSymA();
	assert(SymA->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;

	// 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 (auto *SymB = Target.getSymB()) {
	// If this is a subtraction then we're pcrel.
	uint32_t FixupAddress =
	Writer->getFragmentAddress(Fragment, Layout) + Fixup.getOffset();
	IsPCRel = 1;
	FixedValue = FixupAddress -
	Writer->getSymbolAddress(SymB->getSymbol(), Layout) +
	Target.getConstant();
	FixedValue += 1ULL << Log2Size;
	} else {
	FixedValue = 0;
	}

	// struct relocation_info (8 bytes)
	MachO::any_relocation_info MRE;
	MRE.r_word0 = Value;
	MRE.r_word1 =
	(IsPCRel << 24) \| (Log2Size << 25) \| (MachO::GENERIC_RELOC_TLV << 28);
	Writer->addRelocation(&SymA->getSymbol(), Fragment->getParent(), MRE);
	}

	void X86MachObjectWriter::RecordX86Relocation(MachObjectWriter *Writer,
	const MCAssembler &Asm,
	const MCAsmLayout &Layout,
	const MCFragment *Fragment,
	const MCFixup &Fixup,
	MCValue Target,
	uint64_t &FixedValue) {
	unsigned IsPCRel = Writer->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(Writer, 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()) {
	recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup,
	Target, Log2Size, FixedValue);
	return;
	}

	// Get the symbol data, if any.
	const MCSymbol *A = nullptr;
	if (Target.getSymA())
	A = &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;

	// Try to record the scattered relocation if needed. Fall back to non
	// scattered if necessary (see comments in recordScatteredRelocation()
	// for details).
	if (Offset && A && !Writer->doesSymbolRequireExternRelocation(*A) &&
	recordScatteredRelocation(Writer, Asm, Layout, Fragment, Fixup, Target,
	Log2Size, FixedValue))
	return;

	// See <reloc.h>.
	uint32_t FixupOffset = Layout.getFragmentOffset(Fragment)+Fixup.getOffset();
	unsigned Index = 0;
	unsigned Type = 0;
	const MCSymbol *RelSymbol = nullptr;

	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::GENERIC_RELOC_VANILLA;
	} else {
	assert(A && "Unknown symbol data");

	// Resolve constant variables.
	if (A->isVariable()) {
	int64_t Res;
	if (A->getVariableValue()->evaluateAsAbsolute(
	Res, Layout, Writer->getSectionAddressMap())) {
	FixedValue = Res;
	return;
	}
	}

	// Check whether we need an external or internal relocation.
	if (Writer->doesSymbolRequireExternRelocation(*A)) {
	RelSymbol = A;
	// 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 (!A->isUndefined())
	FixedValue -= Layout.getSymbolOffset(*A);
	} else {
	// The index is the section ordinal (1-based).
	const MCSection &Sec = A->getSection();
	Index = Sec.getOrdinal() + 1;
	FixedValue += Writer->getSectionAddress(&Sec);
	}
	if (IsPCRel)
	FixedValue -= Writer->getSectionAddress(Fragment->getParent());

	Type = MachO::GENERIC_RELOC_VANILLA;
	}

	// struct relocation_info (8 bytes)
	MachO::any_relocation_info MRE;
	MRE.r_word0 = FixupOffset;
	MRE.r_word1 =
	(Index << 0) \| (IsPCRel << 24) \| (Log2Size << 25) \| (Type << 28);
	Writer->addRelocation(RelSymbol, Fragment->getParent(), MRE);
	}

	std::unique_ptr<MCObjectTargetWriter>
	llvm::createX86MachObjectWriter(bool Is64Bit, uint32_t CPUType,
	uint32_t CPUSubtype) {
	return std::make_unique<X86MachObjectWriter>(Is64Bit, CPUType, CPUSubtype);
	}