1 //===-- llvm/MC/MCObjectWriter.h - Object File Writer Interface -*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #ifndef LLVM_MC_MCOBJECTWRITER_H
11 #define LLVM_MC_MCOBJECTWRITER_H
13 #include "llvm/Support/Compiler.h"
14 #include "llvm/Support/DataTypes.h"
15 #include "llvm/Support/raw_ostream.h"
24 class MCSymbolRefExpr;
27 /// MCObjectWriter - Defines the object file and target independent interfaces
28 /// used by the assembler backend to write native file format object files.
30 /// The object writer contains a few callbacks used by the assembler to allow
31 /// the object writer to modify the assembler data structures at appropriate
32 /// points. Once assembly is complete, the object writer is given the
33 /// MCAssembler instance, which contains all the symbol and section data which
34 /// should be emitted as part of WriteObject().
36 /// The object writer also contains a number of helper methods for writing
37 /// binary data to the output stream.
38 class MCObjectWriter {
39 MCObjectWriter(const MCObjectWriter &) LLVM_DELETED_FUNCTION;
40 void operator=(const MCObjectWriter &) LLVM_DELETED_FUNCTION;
45 unsigned IsLittleEndian : 1;
47 protected: // Can only create subclasses.
48 MCObjectWriter(raw_ostream &_OS, bool _IsLittleEndian)
49 : OS(_OS), IsLittleEndian(_IsLittleEndian) {}
52 virtual ~MCObjectWriter();
54 bool isLittleEndian() const { return IsLittleEndian; }
56 raw_ostream &getStream() { return OS; }
58 /// @name High-Level API
61 /// Perform any late binding of symbols (for example, to assign symbol indices
62 /// for use when generating relocations).
64 /// This routine is called by the assembler after layout and relaxation is
66 virtual void ExecutePostLayoutBinding(MCAssembler &Asm,
67 const MCAsmLayout &Layout) = 0;
69 /// Record a relocation entry.
71 /// This routine is called by the assembler after layout and relaxation, and
72 /// post layout binding. The implementation is responsible for storing
73 /// information about the relocation so that it can be emitted during
75 virtual void RecordRelocation(const MCAssembler &Asm,
76 const MCAsmLayout &Layout,
77 const MCFragment *Fragment,
78 const MCFixup &Fixup, MCValue Target,
79 uint64_t &FixedValue) = 0;
81 /// \brief Check whether the difference (A - B) between two symbol
82 /// references is fully resolved.
84 /// Clients are not required to answer precisely and may conservatively return
85 /// false, even when a difference is fully resolved.
87 IsSymbolRefDifferenceFullyResolved(const MCAssembler &Asm,
88 const MCSymbolRefExpr *A,
89 const MCSymbolRefExpr *B,
93 IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
94 const MCSymbolData &DataA,
100 /// Write the object file.
102 /// This routine is called by the assembler after layout and relaxation is
103 /// complete, fixups have been evaluated and applied, and relocations
105 virtual void WriteObject(MCAssembler &Asm,
106 const MCAsmLayout &Layout) = 0;
109 /// @name Binary Output
112 void Write8(uint8_t Value) {
116 void WriteLE16(uint16_t Value) {
117 Write8(uint8_t(Value >> 0));
118 Write8(uint8_t(Value >> 8));
121 void WriteLE32(uint32_t Value) {
122 WriteLE16(uint16_t(Value >> 0));
123 WriteLE16(uint16_t(Value >> 16));
126 void WriteLE64(uint64_t Value) {
127 WriteLE32(uint32_t(Value >> 0));
128 WriteLE32(uint32_t(Value >> 32));
131 void WriteBE16(uint16_t Value) {
132 Write8(uint8_t(Value >> 8));
133 Write8(uint8_t(Value >> 0));
136 void WriteBE32(uint32_t Value) {
137 WriteBE16(uint16_t(Value >> 16));
138 WriteBE16(uint16_t(Value >> 0));
141 void WriteBE64(uint64_t Value) {
142 WriteBE32(uint32_t(Value >> 32));
143 WriteBE32(uint32_t(Value >> 0));
146 void Write16(uint16_t Value) {
153 void Write32(uint32_t Value) {
160 void Write64(uint64_t Value) {
167 void WriteZeros(unsigned N) {
168 const char Zeros[16] = { 0 };
170 for (unsigned i = 0, e = N / 16; i != e; ++i)
171 OS << StringRef(Zeros, 16);
173 OS << StringRef(Zeros, N % 16);
176 void WriteBytes(SmallVectorImpl<char> &ByteVec, unsigned ZeroFillSize = 0) {
177 WriteBytes(StringRef(ByteVec.data(), ByteVec.size()), ZeroFillSize);
180 void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
181 // TODO: this version may need to go away once all fragment contents are
182 // converted to SmallVector<char, N>
183 assert((ZeroFillSize == 0 || Str.size () <= ZeroFillSize) &&
184 "data size greater than fill size, unexpected large write will occur");
187 WriteZeros(ZeroFillSize - Str.size());
194 } // End llvm namespace