MCStreamer.h revision 95cf30c444707634bbd950f13405b6c8bcfe496b
1//===- MCStreamer.h - High-level Streaming Machine Code Output --*- 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// This file declares the MCStreamer class. 11// 12//===----------------------------------------------------------------------===// 13 14#ifndef LLVM_MC_MCSTREAMER_H 15#define LLVM_MC_MCSTREAMER_H 16 17#include "llvm/Support/DataTypes.h" 18 19namespace llvm { 20 class MCContext; 21 class MCValue; 22 class MCInst; 23 class MCSection; 24 class MCSymbol; 25 class raw_ostream; 26 27 /// MCStreamer - Streaming machine code generation interface. This interface 28 /// is intended to provide a programatic interface that is very similar to the 29 /// level that an assembler .s file provides. It has callbacks to emit bytes, 30 /// "emit directives", etc. The implementation of this interface retains 31 /// state to know what the current section is etc. 32 /// 33 /// There are multiple implementations of this interface: one for writing out 34 /// a .s file, and implementations that write out .o files of various formats. 35 /// 36 class MCStreamer { 37 public: 38 enum SymbolAttr { 39 Global, /// .globl 40 Hidden, /// .hidden (ELF) 41 IndirectSymbol, /// .indirect_symbol (Apple) 42 Internal, /// .internal (ELF) 43 LazyReference, /// .lazy_reference (Apple) 44 NoDeadStrip, /// .no_dead_strip (Apple) 45 PrivateExtern, /// .private_extern (Apple) 46 Protected, /// .protected (ELF) 47 Reference, /// .reference (Apple) 48 Weak, /// .weak 49 WeakDefinition, /// .weak_definition (Apple) 50 WeakReference, /// .weak_reference (Apple) 51 52 SymbolAttrFirst = Global, 53 SymbolAttrLast = WeakReference 54 }; 55 56 private: 57 MCContext &Context; 58 59 MCStreamer(const MCStreamer&); // DO NOT IMPLEMENT 60 MCStreamer &operator=(const MCStreamer&); // DO NOT IMPLEMENT 61 62 protected: 63 MCStreamer(MCContext &Ctx); 64 65 public: 66 virtual ~MCStreamer(); 67 68 MCContext &getContext() const { return Context; } 69 70 /// @name Symbol & Section Management 71 /// @{ 72 73 /// SwitchSection - Set the current section where code is being emitted to 74 /// @param Section. 75 /// 76 /// This corresponds to assembler directives like .section, .text, etc. 77 virtual void SwitchSection(MCSection *Section) = 0; 78 79 /// EmitLabel - Emit a label for @param Symbol into the current section. 80 /// 81 /// This corresponds to an assembler statement such as: 82 /// foo: 83 /// 84 /// @param Symbol - The symbol to emit. A given symbol should only be 85 /// emitted as a label once, and symbols emitted as a label should never be 86 /// used in an assignment. 87 // 88 // FIXME: What to do about the current section? Should we get rid of the 89 // symbol section in the constructor and initialize it here? 90 virtual void EmitLabel(MCSymbol *Symbol) = 0; 91 92 /// SubsectionsViaSymbols - Note in the output that the conventions used in 93 /// in the assembly file allows the bytes of a section to be divided up at 94 /// the boundaries of the symbols by a link editor for processing as atoms. 95 virtual void SubsectionsViaSymbols(void) = 0; 96 97 /// EmitAssignment - Emit an assignment of @param Value to @param Symbol. 98 /// 99 /// This corresponds to an assembler statement such as: 100 /// symbol = value 101 /// 102 /// The assignment generates no code, but has the side effect of binding the 103 /// value in the current context. For the assembly streamer, this prints the 104 /// binding into the .s file. 105 /// 106 /// @param Symbol - The symbol being assigned to. 107 /// @param Value - The value for the symbol. 108 /// @param MakeAbsolute - If true, then the symbol should be given the 109 /// absolute value of @param Value, even if @param Value would be 110 /// relocatable expression. This corresponds to the ".set" directive. 111 virtual void EmitAssignment(MCSymbol *Symbol, const MCValue &Value, 112 bool MakeAbsolute = false) = 0; 113 114 /// EmitSymbolAttribute - Add the given @param Attribute to @param Symbol. 115 // 116 // FIXME: This doesn't make much sense, could we just have attributes be on 117 // the symbol and make the printer smart enough to add the right symbols? 118 // This should work as long as the order of attributes in the file doesn't 119 // matter. 120 virtual void EmitSymbolAttribute(MCSymbol *Symbol, 121 SymbolAttr Attribute) = 0; 122 123 /// EmitSymbolDesc - Set the @param DescValue for the @param Symbol. 124 /// 125 /// @param Symbol - The symbol to have its n_desc field set. 126 /// @param DescValue - The value to set into the n_desc field. 127 virtual void EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) = 0; 128 129 /// EmitCommonSymbol - Emit a common or local common symbol of @param Size 130 /// with the @param Pow2Alignment if non-zero. 131 /// 132 /// @param Symbol - The common symbol to emit. 133 /// @param Size - The size of the common symbol. 134 /// @param Pow2Alignment - The alignment of the common symbol if non-zero. 135 /// @param IsLocal - If true, then the symbol is to be a local common 136 virtual void EmitCommonSymbol(MCSymbol *Symbol, unsigned Size, 137 unsigned Pow2Alignment, bool IsLocal) = 0; 138 139 /// EmitZerofill - Emit a the zerofill section and possiblity a symbol, if 140 /// @param Symbol is non-NULL, for @param Size and with the @param 141 /// Pow2Alignment if non-zero. 142 /// 143 /// @param Section - The zerofill section to create and or to put the symbol 144 /// @param Symbol - The zerofill symbol to emit, if non-NULL. 145 /// @param Size - The size of the zerofill symbol. 146 /// @param Pow2Alignment - The alignment of the zerofill symbol if non-zero. 147 virtual void EmitZerofill(MCSection *Section, MCSymbol *Symbol = 0, 148 unsigned Size = 0,unsigned Pow2Alignment = 0) = 0; 149 150 /// AbortAssembly - Stop and don't produce output, printing @param 151 /// AbortReason if non-NULL to indicate the reason the assembly is 152 /// terminated. 153 /// 154 /// @param AbortReason - The reason assembly is terminated, if non-NULL. 155 virtual void AbortAssembly(const char *AbortReason) = 0; 156 157 /// @} 158 /// @name Generating Data 159 /// @{ 160 161 /// EmitBytes - Emit @param Length bytes starting at @param Data into the 162 /// output. 163 /// 164 /// This is used to implement assembler directives such as .byte, .ascii, 165 /// etc. 166 virtual void EmitBytes(const char *Data, unsigned Length) = 0; 167 168 /// EmitValue - Emit the expression @param Value into the output as a native 169 /// integer of the given @param Size bytes. 170 /// 171 /// This is used to implement assembler directives such as .word, .quad, 172 /// etc. 173 /// 174 /// @param Value - The value to emit. 175 /// @param Size - The size of the integer (in bytes) to emit. This must 176 /// match a native machine width. 177 virtual void EmitValue(const MCValue &Value, unsigned Size) = 0; 178 179 /// EmitValueToAlignment - Emit some number of copies of @param Value until 180 /// the byte alignment @param ByteAlignment is reached. 181 /// 182 /// If the number of bytes need to emit for the alignment is not a multiple 183 /// of @param ValueSize, then the contents of the emitted fill bytes is 184 /// undefined. 185 /// 186 /// This used to implement the .align assembler directive. 187 /// 188 /// @param ByteAlignment - The alignment to reach. This must be a power of 189 /// two on some targets. 190 /// @param Value - The value to use when filling bytes. 191 /// @param Size - The size of the integer (in bytes) to emit for @param 192 /// Value. This must match a native machine width. 193 /// @param MaxBytesToEmit - The maximum numbers of bytes to emit, or 0. If 194 /// the alignment cannot be reached in this many bytes, no bytes are 195 /// emitted. 196 virtual void EmitValueToAlignment(unsigned ByteAlignment, int64_t Value = 0, 197 unsigned ValueSize = 1, 198 unsigned MaxBytesToEmit = 0) = 0; 199 200 /// EmitValueToOffset - Emit some number of copies of @param Value until the 201 /// byte offset @param Offset is reached. 202 /// 203 /// This is used to implement assembler directives such as .org. 204 /// 205 /// @param Offset - The offset to reach.This may be an expression, but the 206 /// expression must be associated with the current section. 207 /// @param Value - The value to use when filling bytes. 208 // 209 // FIXME: How are we going to signal failures out of this? 210 virtual void EmitValueToOffset(const MCValue &Offset, 211 unsigned char Value = 0) = 0; 212 213 /// @} 214 215 /// EmitInstruction - Emit the given @param Instruction into the current 216 /// section. 217 virtual void EmitInstruction(const MCInst &Inst) = 0; 218 219 /// Finish - Finish emission of machine code and flush any output. 220 virtual void Finish() = 0; 221 }; 222 223 /// createAsmStreamer - Create a machine code streamer which will print out 224 /// assembly for the native target, suitable for compiling with a native 225 /// assembler. 226 MCStreamer *createAsmStreamer(MCContext &Ctx, raw_ostream &OS); 227 228 // FIXME: These two may end up getting rolled into a single 229 // createObjectStreamer interface, which implements the assembler backend, and 230 // is parameterized on an output object file writer. 231 232 /// createMachOStream - Create a machine code streamer which will generative 233 /// Mach-O format object files. 234 MCStreamer *createMachOStreamer(MCContext &Ctx, raw_ostream &OS); 235 236 /// createELFStreamer - Create a machine code streamer which will generative 237 /// ELF format object files. 238 MCStreamer *createELFStreamer(MCContext &Ctx, raw_ostream &OS); 239 240} // end namespace llvm 241 242#endif 243