1 //===-- llvm/MC/MCAsmBack.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 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. 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. 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. 66 virtual bool doesSectionRequireSymbols(const MCSection &Section) const { 67 return false; 68 } 69 70 /// isSectionAtomizable - Check whether the given section can be split into 71 /// atoms. 72 /// 73 /// \see MCAssembler::isSymbolLinkerVisible(). 74 virtual bool isSectionAtomizable(const MCSection &Section) const { 75 return true; 76 } 77 78 /// @name Target Fixup Interfaces 79 /// @{ 80 81 /// getNumFixupKinds - Get the number of target specific fixup kinds. 82 virtual unsigned getNumFixupKinds() const = 0; 83 84 /// getFixupKindInfo - Get information on a fixup kind. 85 virtual const MCFixupKindInfo &getFixupKindInfo(MCFixupKind Kind) const; 86 87 /// processFixupValue - Target hook to adjust the literal value of a fixup 88 /// if necessary. IsResolved signals whether the caller believes a relocation 89 /// is needed; the target can modify the value. The default does nothing. 90 virtual void processFixupValue(const MCAssembler &Asm, 91 const MCAsmLayout &Layout, 92 const MCFixup &Fixup, const MCFragment *DF, 93 const MCValue &Target, uint64_t &Value, 94 bool &IsResolved) {} 95 96 /// applyFixup - Apply the \p Value for given \p Fixup into the provided 97 /// data fragment, at the offset specified by the fixup and following the 98 /// fixup kind as appropriate. 99 virtual void applyFixup(const MCFixup &Fixup, char *Data, unsigned DataSize, 100 uint64_t Value, bool IsPCRel) const = 0; 101 102 /// @} 103 104 /// @name Target Relaxation Interfaces 105 /// @{ 106 107 /// mayNeedRelaxation - Check whether the given instruction may need 108 /// relaxation. 109 /// 110 /// \param Inst - The instruction to test. 111 virtual bool mayNeedRelaxation(const MCInst &Inst) const = 0; 112 113 /// fixupNeedsRelaxation - Target specific predicate for whether a given 114 /// fixup requires the associated instruction to be relaxed. 115 virtual bool fixupNeedsRelaxation(const MCFixup &Fixup, uint64_t Value, 116 const MCRelaxableFragment *DF, 117 const MCAsmLayout &Layout) const = 0; 118 119 /// RelaxInstruction - Relax the instruction in the given fragment to the next 120 /// wider instruction. 121 /// 122 /// \param Inst The instruction to relax, which may be the same as the 123 /// output. 124 /// \param [out] Res On return, the relaxed instruction. 125 virtual void relaxInstruction(const MCInst &Inst, MCInst &Res) const = 0; 126 127 /// @} 128 129 /// getMinimumNopSize - Returns the minimum size of a nop in bytes on this 130 /// target. The assembler will use this to emit excess padding in situations 131 /// where the padding required for simple alignment would be less than the 132 /// minimum nop size. 133 /// 134 virtual unsigned getMinimumNopSize() const { return 1; } 135 136 /// 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 138 /// error. 139 /// 140 /// \return - True on success. 141 virtual bool writeNopData(uint64_t Count, MCObjectWriter *OW) const = 0; 142 143 /// handleAssemblerFlag - Handle any target-specific assembler flags. 144 /// By default, do nothing. 145 virtual void handleAssemblerFlag(MCAssemblerFlag Flag) {} 146 147 /// \brief Generate the compact unwind encoding for the CFI instructions. 148 virtual uint32_t 149 generateCompactUnwindEncoding(ArrayRef<MCCFIInstruction>) const { 150 return 0; 151 } 152 }; 153 154 } // End llvm namespace 155 156 #endif 157
