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/ADT/Triple.h"
14 #include "llvm/Support/raw_ostream.h"
15 #include "llvm/Support/DataTypes.h"
23 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 &); // DO NOT IMPLEMENT
40 void operator=(const MCObjectWriter &); // DO NOT IMPLEMENT
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) const = 0;
91 /// Check if a fixup is fully resolved.
93 /// This routine is used by the assembler to let the file format decide
94 /// if a fixup is not fully resolved. For example, one that crosses
95 /// two sections on ELF.
96 virtual bool IsFixupFullyResolved(const MCAssembler &Asm,
99 const MCFragment *DF) const = 0;
101 /// Write the object file.
103 /// This routine is called by the assembler after layout and relaxation is
104 /// complete, fixups have been evaluated and applied, and relocations
106 virtual void WriteObject(MCAssembler &Asm,
107 const MCAsmLayout &Layout) = 0;
110 /// @name Binary Output
113 void Write8(uint8_t Value) {
117 void WriteLE16(uint16_t Value) {
118 Write8(uint8_t(Value >> 0));
119 Write8(uint8_t(Value >> 8));
122 void WriteLE32(uint32_t Value) {
123 WriteLE16(uint16_t(Value >> 0));
124 WriteLE16(uint16_t(Value >> 16));
127 void WriteLE64(uint64_t Value) {
128 WriteLE32(uint32_t(Value >> 0));
129 WriteLE32(uint32_t(Value >> 32));
132 void WriteBE16(uint16_t Value) {
133 Write8(uint8_t(Value >> 8));
134 Write8(uint8_t(Value >> 0));
137 void WriteBE32(uint32_t Value) {
138 WriteBE16(uint16_t(Value >> 16));
139 WriteBE16(uint16_t(Value >> 0));
142 void WriteBE64(uint64_t Value) {
143 WriteBE32(uint32_t(Value >> 32));
144 WriteBE32(uint32_t(Value >> 0));
147 void Write16(uint16_t Value) {
154 void Write32(uint32_t Value) {
161 void Write64(uint64_t Value) {
168 void WriteZeros(unsigned N) {
169 const char Zeros[16] = { 0 };
171 for (unsigned i = 0, e = N / 16; i != e; ++i)
172 OS << StringRef(Zeros, 16);
174 OS << StringRef(Zeros, N % 16);
177 void WriteBytes(StringRef Str, unsigned ZeroFillSize = 0) {
178 assert((ZeroFillSize == 0 || Str.size () <= ZeroFillSize) &&
179 "data size greater than fill size, unexpected large write will occur");
182 WriteZeros(ZeroFillSize - Str.size());
187 /// Utility function to encode a SLEB128 value.
188 static void EncodeSLEB128(int64_t Value, raw_ostream &OS);
189 /// Utility function to encode a ULEB128 value.
190 static void EncodeULEB128(uint64_t Value, raw_ostream &OS);
193 MCObjectWriter *createELFObjectWriter(raw_ostream &OS, bool is64Bit,
194 Triple::OSType OSType, uint16_t EMachine,
196 bool HasRelocationAddend);
197 MCObjectWriter *createWinCOFFObjectWriter(raw_ostream &OS, bool is64Bit);
199 } // End llvm namespace