lib/Target/X86/X86AsmBackend.cpp

//===-- X86AsmBackend.cpp - X86 Assembler Backend -------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "llvm/Target/TargetAsmBackend.h"
#include "X86.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Target/TargetRegistry.h"
#include "llvm/Target/TargetAsmBackend.h"
using namespace llvm;

namespace {

class X86AsmBackend : public TargetAsmBackend {
public:
  X86AsmBackend(const Target &T)
    : TargetAsmBackend(T) {}
};

class DarwinX86AsmBackend : public X86AsmBackend {
public:
  DarwinX86AsmBackend(const Target &T)
    : X86AsmBackend(T) {
    HasAbsolutizedSet = true;
    HasScatteredSymbols = true;
  }
};

class DarwinX86_32AsmBackend : public DarwinX86AsmBackend {
public:
  DarwinX86_32AsmBackend(const Target &T)
    : DarwinX86AsmBackend(T) {}
};

class DarwinX86_64AsmBackend : public DarwinX86AsmBackend {
public:
  DarwinX86_64AsmBackend(const Target &T)
    : DarwinX86AsmBackend(T) {
    HasReliableSymbolDifference = true;
  }

  virtual bool doesSectionRequireSymbols(const MCSection &Section) const {
    // Temporary labels in the string literals sections require symbols. The
    // issue is that the x86_64 relocation format does not allow symbol +
    // offset, and so the linker does not have enough information to resolve the
    // access to the appropriate atom unless an external relocation is used. For
    // non-cstring sections, we expect the compiler to use a non-temporary label
    // for anything that could have an addend pointing outside the symbol.
    //
    // See <rdar://problem/4765733>.
    const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
    return SMO.getType() == MCSectionMachO::S_CSTRING_LITERALS;
  }
};

}

TargetAsmBackend *llvm::createX86_32AsmBackend(const Target &T,
                                               const std::string &TT) {
  switch (Triple(TT).getOS()) {
  case Triple::Darwin:
    return new DarwinX86_32AsmBackend(T);
  default:
    return new X86AsmBackend(T);
  }
}

TargetAsmBackend *llvm::createX86_64AsmBackend(const Target &T,
                                               const std::string &TT) {
  switch (Triple(TT).getOS()) {
  case Triple::Darwin:
    return new DarwinX86_64AsmBackend(T);
  default:
    return new X86AsmBackend(T);
  }
}