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//===-- llvm/MC/MCObjectWriter.h - Object File Writer Interface -*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_MC_MCOBJECTWRITER_H
#define LLVM_MC_MCOBJECTWRITER_H
#include "llvm/ADT/SmallVector.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/EndianStream.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
namespace llvm {
class MCAsmLayout;
class MCAssembler;
class MCFixup;
class MCFragment;
class MCSymbolData;
class MCSymbolRefExpr;
class MCValue;
/// MCObjectWriter - Defines the object file and target independent interfaces
/// used by the assembler backend to write native file format object files.
///
/// The object writer contains a few callbacks used by the assembler to allow
/// the object writer to modify the assembler data structures at appropriate
/// points. Once assembly is complete, the object writer is given the
/// MCAssembler instance, which contains all the symbol and section data which
/// should be emitted as part of WriteObject().
///
/// The object writer also contains a number of helper methods for writing
/// binary data to the output stream.
class MCObjectWriter {
MCObjectWriter(const MCObjectWriter &) = delete;
void operator=(const MCObjectWriter &) = delete;
protected:
raw_pwrite_stream &OS;
unsigned IsLittleEndian : 1;
protected: // Can only create subclasses.
MCObjectWriter(raw_pwrite_stream &OS, bool IsLittleEndian)
: OS(OS), IsLittleEndian(IsLittleEndian) {}
public:
virtual ~MCObjectWriter();
/// lifetime management
virtual void reset() { }
bool isLittleEndian() const { return IsLittleEndian; }
raw_ostream &getStream() { return OS; }
/// \name High-Level API
/// @{
/// \brief Perform any late binding of symbols (for example, to assign symbol
/// indices for use when generating relocations).
///
/// This routine is called by the assembler after layout and relaxation is
/// complete.
virtual void ExecutePostLayoutBinding(MCAssembler &Asm,
const MCAsmLayout &Layout) = 0;
/// \brief Record a relocation entry.
///
/// This routine is called by the assembler after layout and relaxation, and
/// post layout binding. The implementation is responsible for storing
/// information about the relocation so that it can be emitted during
/// WriteObject().
virtual void RecordRelocation(MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment *Fragment,
const MCFixup &Fixup, MCValue Target,
bool &IsPCRel, uint64_t &FixedValue) = 0;
/// \brief Check whether the difference (A - B) between two symbol
/// references is fully resolved.
///
/// Clients are not required to answer precisely and may conservatively return
/// false, even when a difference is fully resolved.
bool IsSymbolRefDifferenceFullyResolved(const MCAssembler &Asm,
const MCSymbolRefExpr *A,
const MCSymbolRefExpr *B,
bool InSet) const;
virtual bool IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
const MCSymbol &SymA,
const MCFragment &FB,
bool InSet,
bool IsPCRel) const;
/// \brief True if this symbol (which is a variable) is weak. This is not
/// just STB_WEAK, but more generally whether or not we can evaluate
/// past it.
virtual bool isWeak(const MCSymbol &Sym) const;
/// \brief Write the object file.
///
/// This routine is called by the assembler after layout and relaxation is
/// complete, fixups have been evaluated and applied, and relocations
/// generated.
virtual void WriteObject(MCAssembler &Asm,
const MCAsmLayout &Layout) = 0;
/// @}
/// \name Binary Output
/// @{
void Write8(uint8_t Value) {
OS << char(Value);
}
void WriteLE16(uint16_t Value) {
support::endian::Writer<support::little>(OS).write(Value);
}
void WriteLE32(uint32_t Value) {
support::endian::Writer<support::little>(OS).write(Value);
}
void WriteLE64(uint64_t Value) {
support::endian::Writer<support::little>(OS).write(Value);
}
void WriteBE16(uint16_t Value) {
support::endian::Writer<support::big>(OS).write(Value);
}
void WriteBE32(uint32_t Value) {
support::endian::Writer<support::big>(OS).write(Value);
}
void WriteBE64(uint64_t Value) {
support::endian::Writer<support::big>(OS).write(Value);
}
void Write16(uint16_t Value) {
if (IsLittleEndian)
WriteLE16(Value);
else
WriteBE16(Value);
}
void Write32(uint32_t Value) {
if (IsLittleEndian)
WriteLE32(Value);
else
WriteBE32(Value);
}
void Write64(uint64_t Value) {
if (IsLittleEndian)
WriteLE64(Value);
else
WriteBE64(Value);
}
void WriteZeros(unsigned N) {
const char Zeros[16] = { 0 };
for (unsigned i = 0, e = N / 16; i != e; ++i)
OS << StringRef(Zeros, 16);
OS << StringRef(Zeros, N % 16);
}
void WriteBytes(const SmallVectorImpl<char> &ByteVec, unsigned ZeroFillSize = 0) {
WriteBytes(StringRef(ByteVec.data(), ByteVec.size()), ZeroFillSize);
}
void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
// TODO: this version may need to go away once all fragment contents are
// converted to SmallVector<char, N>
assert((ZeroFillSize == 0 || Str.size () <= ZeroFillSize) &&
"data size greater than fill size, unexpected large write will occur");
OS << Str;
if (ZeroFillSize)
WriteZeros(ZeroFillSize - Str.size());
}
/// @}
};
} // End llvm namespace
#endif
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