lib/Target/MBlaze/MBlazeAsmBackend.cpp

//===-- MBlazeAsmBackend.cpp - MBlaze 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 "MBlaze.h"
#include "MBlazeFixupKinds.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/ELFObjectWriter.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectFormat.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MachObjectWriter.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetRegistry.h"
#include "llvm/Target/TargetAsmBackend.h"
using namespace llvm;

static unsigned getFixupKindSize(unsigned Kind) {
  switch (Kind) {
  default: assert(0 && "invalid fixup kind!");
  case FK_Data_1: return 1;
  case MBlaze::reloc_pcrel_2byte:
  case FK_Data_2: return 2;
  case MBlaze::reloc_pcrel_4byte:
  case FK_Data_4: return 4;
  case FK_Data_8: return 8;
  }
}


namespace {
class MBlazeAsmBackend : public TargetAsmBackend {
public:
  MBlazeAsmBackend(const Target &T)
    : TargetAsmBackend(T) {
  }

  bool MayNeedRelaxation(const MCInst &Inst) const;

  void RelaxInstruction(const MCInst &Inst, MCInst &Res) const;

  bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const;

  unsigned getPointerSize() const {
    return 4;
  }
};

bool MBlazeAsmBackend::MayNeedRelaxation(const MCInst &Inst) const {
  return false;
}

void MBlazeAsmBackend::RelaxInstruction(const MCInst &Inst, MCInst &Res) const {
  assert(0 && "MBlazeAsmBackend::RelaxInstruction() unimplemented");
  return;
}

bool MBlazeAsmBackend::WriteNopData(uint64_t Count, MCObjectWriter *OW) const {
  if ((Count % 4) != 0)
    return false;

  for (uint64_t i = 0; i < Count; i += 4 )
      OW->Write32( 0x00000000 );

  return true;
}
} // end anonymous namespace

namespace {
// FIXME: This should be in a separate file.
// ELF is an ELF of course...
class ELFMBlazeAsmBackend : public MBlazeAsmBackend {
  MCELFObjectFormat Format;

public:
  Triple::OSType OSType;
  ELFMBlazeAsmBackend(const Target &T, Triple::OSType _OSType)
    : MBlazeAsmBackend(T), OSType(_OSType) {
    HasScatteredSymbols = true;
  }

  virtual const MCObjectFormat &getObjectFormat() const {
    return Format;
  }


  void ApplyFixup(const MCFixup &Fixup, MCDataFragment &DF,
                  uint64_t Value) const;

  bool isVirtualSection(const MCSection &Section) const {
    const MCSectionELF &SE = static_cast<const MCSectionELF&>(Section);
    return SE.getType() == MCSectionELF::SHT_NOBITS;
  }

  MCObjectWriter *createObjectWriter(raw_ostream &OS) const {
    return new ELFObjectWriter(OS, /*Is64Bit=*/false,
                               OSType,
                               /*IsLittleEndian=*/false,
                               /*HasRelocationAddend=*/true);
  }
};

void ELFMBlazeAsmBackend::ApplyFixup(const MCFixup &Fixup, MCDataFragment &DF,
                                     uint64_t Value) const {
  unsigned Size = getFixupKindSize(Fixup.getKind());
            
  assert(Fixup.getOffset() + Size <= DF.getContents().size() &&
         "Invalid fixup offset!");

  char *data = DF.getContents().data() + Fixup.getOffset();
  switch (Size) {
  default: llvm_unreachable( "Cannot fixup unknown value." );
  case 1:  llvm_unreachable( "Cannot fixup 1 byte value." );
  case 8:  llvm_unreachable( "Cannot fixup 8 byte value." );

  case 4: 
    *(data+7) = uint8_t(Value);
    *(data+6) = uint8_t(Value >> 8);
    *(data+3) = uint8_t(Value >> 16);
    *(data+2) = uint8_t(Value >> 24);
    break;

  case 2:
    *(data+3) = uint8_t(Value >> 0);
    *(data+2) = uint8_t(Value >> 8);
  }
}
} // end anonymous namespace

TargetAsmBackend *llvm::createMBlazeAsmBackend(const Target &T,
                                            const std::string &TT) {
  switch (Triple(TT).getOS()) {
  case Triple::Darwin:
    assert(0 && "Mac not supported on MBlaze");
  case Triple::MinGW32:
  case Triple::Cygwin:
  case Triple::Win32:
    assert(0 && "Windows not supported on MBlaze");
  default:
    return new ELFMBlazeAsmBackend(T, Triple(TT).getOS());
  }
}