1 //===-- llvm/MC/MCAsmBack.h - MC Asm Backend --------------------*- 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_MCASMBACKEND_H
11 #define LLVM_MC_MCASMBACKEND_H
13 #include "llvm/MC/MCDirectives.h"
14 #include "llvm/MC/MCFixup.h"
15 #include "llvm/MC/MCFixupKindInfo.h"
16 #include "llvm/Support/DataTypes.h"
21 class MCELFObjectTargetWriter;
30 class SmallVectorImpl;
33 /// MCAsmBackend - Generic interface to target specific assembler backends.
35 MCAsmBackend(const MCAsmBackend &); // DO NOT IMPLEMENT
36 void operator=(const MCAsmBackend &); // DO NOT IMPLEMENT
37 protected: // Can only create subclasses.
40 unsigned HasReliableSymbolDifference : 1;
43 virtual ~MCAsmBackend();
45 /// createObjectWriter - Create a new MCObjectWriter instance for use by the
46 /// assembler backend to emit the final object file.
47 virtual MCObjectWriter *createObjectWriter(raw_ostream &OS) const = 0;
49 /// createELFObjectTargetWriter - Create a new ELFObjectTargetWriter to enable
50 /// non-standard ELFObjectWriters.
51 virtual MCELFObjectTargetWriter *createELFObjectTargetWriter() const {
52 assert(0 && "createELFObjectTargetWriter is not supported by asm backend");
56 /// hasReliableSymbolDifference - Check whether this target implements
57 /// accurate relocations for differences between symbols. If not, differences
58 /// between symbols will always be relocatable expressions and any references
59 /// to temporary symbols will be assumed to be in the same atom, unless they
60 /// reside in a different section.
62 /// This should always be true (since it results in fewer relocations with no
63 /// loss of functionality), but is currently supported as a way to maintain
64 /// exact object compatibility with Darwin 'as' (on non-x86_64). It should
65 /// eventually should be eliminated.
66 bool hasReliableSymbolDifference() const {
67 return HasReliableSymbolDifference;
70 /// doesSectionRequireSymbols - Check whether the given section requires that
71 /// all symbols (even temporaries) have symbol table entries.
72 virtual bool doesSectionRequireSymbols(const MCSection &Section) const {
76 /// isSectionAtomizable - Check whether the given section can be split into
79 /// \see MCAssembler::isSymbolLinkerVisible().
80 virtual bool isSectionAtomizable(const MCSection &Section) const {
84 /// @name Target Fixup Interfaces
87 /// getNumFixupKinds - Get the number of target specific fixup kinds.
88 virtual unsigned getNumFixupKinds() const = 0;
90 /// getFixupKindInfo - Get information on a fixup kind.
91 virtual const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const;
93 /// processFixupValue - Target hook to adjust the literal value of a fixup
94 /// if necessary. The default does nothing.
95 virtual void processFixupValue(const MCAssembler &Asm,
96 const MCAsmLayout &Layout,
97 const MCFixup &Fixup, const MCFragment *DF,
98 MCValue &Target, uint64_t &Value) {}
102 /// ApplyFixup - Apply the \arg Value for given \arg Fixup into the provided
103 /// data fragment, at the offset specified by the fixup and following the
104 /// fixup kind as appropriate.
105 virtual void ApplyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize,
106 uint64_t Value) const = 0;
110 /// @name Target Relaxation Interfaces
113 /// MayNeedRelaxation - Check whether the given instruction may need
116 /// \param Inst - The instruction to test.
117 virtual bool MayNeedRelaxation(const MCInst &Inst) const = 0;
119 /// fixupNeedsRelaxation - Target specific predicate for whether a given
120 /// fixup requires the associated instruction to be relaxed.
121 virtual bool fixupNeedsRelaxation(const MCFixup &Fixup,
123 const MCInstFragment *DF,
124 const MCAsmLayout &Layout) const = 0;
126 /// RelaxInstruction - Relax the instruction in the given fragment to the next
127 /// wider instruction.
129 /// \param Inst - The instruction to relax, which may be the same as the
131 /// \parm Res [output] - On return, the relaxed instruction.
132 virtual void RelaxInstruction(const MCInst &Inst, MCInst &Res) const = 0;
136 /// WriteNopData - Write an (optimal) nop sequence of Count bytes to the given
137 /// output. If the target cannot generate such a sequence, it should return an
140 /// \return - True on success.
141 virtual bool WriteNopData(uint64_t Count, MCObjectWriter *OW) const = 0;
143 /// HandleAssemblerFlag - Handle any target-specific assembler flags.
144 /// By default, do nothing.
145 virtual void HandleAssemblerFlag(MCAssemblerFlag Flag) {}
148 } // End llvm namespace