1 //===-- llvm/MC/MCAsmBackend.h - MC Asm Backend -----------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 #ifndef LLVM_MC_MCASMBACKEND_H 11 #define LLVM_MC_MCASMBACKEND_H 12 13 #include "llvm/ADT/ArrayRef.h" 14 #include "llvm/MC/MCDirectives.h" 15 #include "llvm/MC/MCDwarf.h" 16 #include "llvm/MC/MCFixup.h" 17 #include "llvm/Support/DataTypes.h" 18 #include "llvm/Support/ErrorHandling.h" 19 20 namespace llvm { 21 class MCAsmLayout; 22 class MCAssembler; 23 class MCELFObjectTargetWriter; 24 struct MCFixupKindInfo; 25 class MCFragment; 26 class MCInst; 27 class MCRelaxableFragment; 28 class MCObjectWriter; 29 class MCSection; 30 class MCValue; 31 class raw_ostream; 32 33 /// MCAsmBackend - Generic interface to target specific assembler backends. 34 class MCAsmBackend { 35 MCAsmBackend(const MCAsmBackend &) LLVM_DELETED_FUNCTION; 36 void operator=(const MCAsmBackend &) LLVM_DELETED_FUNCTION; 37 38 protected: // Can only create subclasses. 39 MCAsmBackend(); 40 41 unsigned HasDataInCodeSupport : 1; 42 43 public: 44 virtual ~MCAsmBackend(); 45 46 /// lifetime management reset()47 virtual void reset() {} 48 49 /// createObjectWriter - Create a new MCObjectWriter instance for use by the 50 /// assembler backend to emit the final object file. 51 virtual MCObjectWriter *createObjectWriter(raw_ostream &OS) const = 0; 52 53 /// createELFObjectTargetWriter - Create a new ELFObjectTargetWriter to enable 54 /// non-standard ELFObjectWriters. createELFObjectTargetWriter()55 virtual MCELFObjectTargetWriter *createELFObjectTargetWriter() const { 56 llvm_unreachable("createELFObjectTargetWriter is not supported by asm " 57 "backend"); 58 } 59 60 /// hasDataInCodeSupport - Check whether this target implements data-in-code 61 /// markers. If not, data region directives will be ignored. hasDataInCodeSupport()62 bool hasDataInCodeSupport() const { return HasDataInCodeSupport; } 63 64 /// doesSectionRequireSymbols - Check whether the given section requires that 65 /// all symbols (even temporaries) have symbol table entries. doesSectionRequireSymbols(const MCSection & Section)66 virtual bool doesSectionRequireSymbols(const MCSection &Section) const { 67 return false; 68 } 69 70 /// @name Target Fixup Interfaces 71 /// @{ 72 73 /// getNumFixupKinds - Get the number of target specific fixup kinds. 74 virtual unsigned getNumFixupKinds() const = 0; 75 76 /// getFixupKindInfo - Get information on a fixup kind. 77 virtual const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const; 78 79 /// processFixupValue - Target hook to adjust the literal value of a fixup 80 /// if necessary. IsResolved signals whether the caller believes a relocation 81 /// is needed; the target can modify the value. The default does nothing. processFixupValue(const MCAssembler & Asm,const MCAsmLayout & Layout,const MCFixup & Fixup,const MCFragment * DF,const MCValue & Target,uint64_t & Value,bool & IsResolved)82 virtual void processFixupValue(const MCAssembler &Asm, 83 const MCAsmLayout &Layout, 84 const MCFixup &Fixup, const MCFragment *DF, 85 const MCValue &Target, uint64_t &Value, 86 bool &IsResolved) {} 87 88 /// applyFixup - Apply the \p Value for given \p Fixup into the provided 89 /// data fragment, at the offset specified by the fixup and following the 90 /// fixup kind as appropriate. 91 virtual void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize, 92 uint64_t Value, bool IsPCRel) const = 0; 93 94 /// @} 95 96 /// @name Target Relaxation Interfaces 97 /// @{ 98 99 /// mayNeedRelaxation - Check whether the given instruction may need 100 /// relaxation. 101 /// 102 /// \param Inst - The instruction to test. 103 virtual bool mayNeedRelaxation(const MCInst &Inst) const = 0; 104 105 /// fixupNeedsRelaxation - Target specific predicate for whether a given 106 /// fixup requires the associated instruction to be relaxed. 107 virtual bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value, 108 const MCRelaxableFragment *DF, 109 const MCAsmLayout &Layout) const = 0; 110 111 /// RelaxInstruction - Relax the instruction in the given fragment to the next 112 /// wider instruction. 113 /// 114 /// \param Inst The instruction to relax, which may be the same as the 115 /// output. 116 /// \param [out] Res On return, the relaxed instruction. 117 virtual void relaxInstruction(const MCInst &Inst, MCInst &Res) const = 0; 118 119 /// @} 120 121 /// getMinimumNopSize - Returns the minimum size of a nop in bytes on this 122 /// target. The assembler will use this to emit excess padding in situations 123 /// where the padding required for simple alignment would be less than the 124 /// minimum nop size. 125 /// getMinimumNopSize()126 virtual unsigned getMinimumNopSize() const { return 1; } 127 128 /// writeNopData - Write an (optimal) nop sequence of Count bytes to the given 129 /// output. If the target cannot generate such a sequence, it should return an 130 /// error. 131 /// 132 /// \return - True on success. 133 virtual bool writeNopData(uint64_t Count, MCObjectWriter *OW) const = 0; 134 135 /// handleAssemblerFlag - Handle any target-specific assembler flags. 136 /// By default, do nothing. handleAssemblerFlag(MCAssemblerFlag Flag)137 virtual void handleAssemblerFlag(MCAssemblerFlag Flag) {} 138 139 /// \brief Generate the compact unwind encoding for the CFI instructions. 140 virtual uint32_t generateCompactUnwindEncoding(ArrayRef<MCCFIInstruction>)141 generateCompactUnwindEncoding(ArrayRef<MCCFIInstruction>) const { 142 return 0; 143 } 144 }; 145 146 } // End llvm namespace 147 148 #endif 149