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1 //===- MCSymbol.h - Machine Code Symbols ------------------------*- C++ -*-===//
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2 //
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3 // The LLVM Compiler Infrastructure
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4 //
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5 // This file is distributed under the University of Illinois Open Source
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6 // License. See LICENSE.TXT for details.
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7 //
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8 //===----------------------------------------------------------------------===//
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9 //
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10 // This file contains the declaration of the MCSymbol class.
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11 //
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12 //===----------------------------------------------------------------------===//
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13
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14 #ifndef LLVM_MC_MCSYMBOL_H
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15 #define LLVM_MC_MCSYMBOL_H
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16
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17 #include "llvm/ADT/PointerIntPair.h"
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18 #include "llvm/ADT/PointerUnion.h"
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19 #include "llvm/ADT/StringMap.h"
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120
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20 #include "llvm/MC/MCFragment.h"
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21 #include "llvm/Support/Compiler.h"
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22
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23 namespace llvm {
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95
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24 class MCAsmInfo;
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25 class MCExpr;
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26 class MCSymbol;
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27 class MCFragment;
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28 class MCSection;
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29 class MCContext;
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30 class raw_ostream;
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31
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32 /// MCSymbol - Instances of this class represent a symbol name in the MC file,
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33 /// and MCSymbols are created and uniqued by the MCContext class. MCSymbols
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34 /// should only be constructed with valid names for the object file.
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35 ///
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36 /// If the symbol is defined/emitted into the current translation unit, the
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37 /// Section member is set to indicate what section it lives in. Otherwise, if
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38 /// it is a reference to an external entity, it has a null section.
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39 class MCSymbol {
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40 protected:
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41 /// The kind of the symbol. If it is any value other than unset then this
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42 /// class is actually one of the appropriate subclasses of MCSymbol.
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43 enum SymbolKind {
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44 SymbolKindUnset,
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45 SymbolKindCOFF,
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46 SymbolKindELF,
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47 SymbolKindMachO,
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48 };
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49
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50 /// A symbol can contain an Offset, or Value, or be Common, but never more
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51 /// than one of these.
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52 enum Contents : uint8_t {
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53 SymContentsUnset,
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54 SymContentsOffset,
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55 SymContentsVariable,
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56 SymContentsCommon,
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57 };
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58
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59 // Special sentinal value for the absolute pseudo fragment.
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60 static MCFragment *AbsolutePseudoFragment;
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61
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62 /// If a symbol has a Fragment, the section is implied, so we only need
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63 /// one pointer.
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64 /// The special AbsolutePseudoFragment value is for absolute symbols.
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65 /// If this is a variable symbol, this caches the variable value's fragment.
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66 /// FIXME: We might be able to simplify this by having the asm streamer create
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67 /// dummy fragments.
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68 /// If this is a section, then it gives the symbol is defined in. This is null
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69 /// for undefined symbols.
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70 ///
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71 /// If this is a fragment, then it gives the fragment this symbol's value is
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72 /// relative to, if any.
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73 ///
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74 /// For the 'HasName' integer, this is true if this symbol is named.
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75 /// A named symbol will have a pointer to the name allocated in the bytes
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76 /// immediately prior to the MCSymbol.
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77 mutable PointerIntPair<MCFragment *, 1> FragmentAndHasName;
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78
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79 /// IsTemporary - True if this is an assembler temporary label, which
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80 /// typically does not survive in the .o file's symbol table. Usually
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81 /// "Lfoo" or ".foo".
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82 unsigned IsTemporary : 1;
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83
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83
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84 /// \brief True if this symbol can be redefined.
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85 unsigned IsRedefinable : 1;
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86
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87 /// IsUsed - True if this symbol has been used.
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88 mutable unsigned IsUsed : 1;
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89
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90 mutable unsigned IsRegistered : 1;
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91
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95
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92 /// This symbol is visible outside this translation unit.
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93 mutable unsigned IsExternal : 1;
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94
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95 /// This symbol is private extern.
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96 mutable unsigned IsPrivateExtern : 1;
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97
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98 /// LLVM RTTI discriminator. This is actually a SymbolKind enumerator, but is
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99 /// unsigned to avoid sign extension and achieve better bitpacking with MSVC.
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100 unsigned Kind : 2;
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101
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102 /// True if we have created a relocation that uses this symbol.
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103 mutable unsigned IsUsedInReloc : 1;
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104
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105 /// This is actually a Contents enumerator, but is unsigned to avoid sign
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106 /// extension and achieve better bitpacking with MSVC.
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107 unsigned SymbolContents : 2;
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108
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109 /// The alignment of the symbol, if it is 'common', or -1.
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110 ///
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111 /// The alignment is stored as log2(align) + 1. This allows all values from
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112 /// 0 to 2^31 to be stored which is every power of 2 representable by an
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113 /// unsigned.
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114 enum : unsigned { NumCommonAlignmentBits = 5 };
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115 unsigned CommonAlignLog2 : NumCommonAlignmentBits;
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116
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117 /// The Flags field is used by object file implementations to store
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118 /// additional per symbol information which is not easily classified.
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119 enum : unsigned { NumFlagsBits = 16 };
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120 mutable uint32_t Flags : NumFlagsBits;
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121
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95
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122 /// Index field, for use by the object file implementation.
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123 mutable uint32_t Index = 0;
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124
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125 union {
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126 /// The offset to apply to the fragment address to form this symbol's value.
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127 uint64_t Offset;
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128
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129 /// The size of the symbol, if it is 'common'.
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130 uint64_t CommonSize;
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131
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132 /// If non-null, the value for a variable symbol.
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133 const MCExpr *Value;
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134 };
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135
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136 protected: // MCContext creates and uniques these.
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137 friend class MCExpr;
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138 friend class MCContext;
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139
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140 /// \brief The name for a symbol.
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141 /// MCSymbol contains a uint64_t so is probably aligned to 8. On a 32-bit
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142 /// system, the name is a pointer so isn't going to satisfy the 8 byte
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143 /// alignment of uint64_t. Account for that here.
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144 typedef union {
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145 const StringMapEntry<bool> *NameEntry;
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146 uint64_t AlignmentPadding;
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147 } NameEntryStorageTy;
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148
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149 MCSymbol(SymbolKind Kind, const StringMapEntry<bool> *Name, bool isTemporary)
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150 : IsTemporary(isTemporary), IsRedefinable(false), IsUsed(false),
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151 IsRegistered(false), IsExternal(false), IsPrivateExtern(false),
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152 Kind(Kind), IsUsedInReloc(false), SymbolContents(SymContentsUnset),
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153 CommonAlignLog2(0), Flags(0) {
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154 Offset = 0;
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155 FragmentAndHasName.setInt(!!Name);
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156 if (Name)
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157 getNameEntryPtr() = Name;
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158 }
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159
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160 // Provide custom new/delete as we will only allocate space for a name
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161 // if we need one.
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162 void *operator new(size_t s, const StringMapEntry<bool> *Name,
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163 MCContext &Ctx);
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164
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165 private:
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166
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167 void operator delete(void *);
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168 /// \brief Placement delete - required by std, but never called.
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169 void operator delete(void*, unsigned) {
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170 llvm_unreachable("Constructor throws?");
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171 }
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172 /// \brief Placement delete - required by std, but never called.
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173 void operator delete(void*, unsigned, bool) {
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174 llvm_unreachable("Constructor throws?");
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175 }
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176
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177 MCSymbol(const MCSymbol &) = delete;
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178 void operator=(const MCSymbol &) = delete;
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179 MCSection *getSectionPtr(bool SetUsed = true) const {
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180 if (MCFragment *F = getFragment(SetUsed)) {
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181 assert(F != AbsolutePseudoFragment);
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182 return F->getParent();
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183 }
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184 return nullptr;
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185 }
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186
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187 /// \brief Get a reference to the name field. Requires that we have a name
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188 const StringMapEntry<bool> *&getNameEntryPtr() {
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189 assert(FragmentAndHasName.getInt() && "Name is required");
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190 NameEntryStorageTy *Name = reinterpret_cast<NameEntryStorageTy *>(this);
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191 return (*(Name - 1)).NameEntry;
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192 }
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193 const StringMapEntry<bool> *&getNameEntryPtr() const {
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194 return const_cast<MCSymbol*>(this)->getNameEntryPtr();
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195 }
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196
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197 public:
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198 /// getName - Get the symbol name.
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199 StringRef getName() const {
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200 if (!FragmentAndHasName.getInt())
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201 return StringRef();
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202
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203 return getNameEntryPtr()->first();
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204 }
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205
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206 bool isRegistered() const { return IsRegistered; }
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207 void setIsRegistered(bool Value) const { IsRegistered = Value; }
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208
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209 void setUsedInReloc() const { IsUsedInReloc = true; }
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210 bool isUsedInReloc() const { return IsUsedInReloc; }
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211
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212 /// \name Accessors
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213 /// @{
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214
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215 /// isTemporary - Check if this is an assembler temporary symbol.
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216 bool isTemporary() const { return IsTemporary; }
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217
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218 /// isUsed - Check if this is used.
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219 bool isUsed() const { return IsUsed; }
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220 void setUsed(bool Value) const { IsUsed |= Value; }
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221
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222 /// \brief Check if this symbol is redefinable.
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223 bool isRedefinable() const { return IsRedefinable; }
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224 /// \brief Mark this symbol as redefinable.
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225 void setRedefinable(bool Value) { IsRedefinable = Value; }
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226 /// \brief Prepare this symbol to be redefined.
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227 void redefineIfPossible() {
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228 if (IsRedefinable) {
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229 if (SymbolContents == SymContentsVariable) {
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230 Value = nullptr;
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231 SymbolContents = SymContentsUnset;
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232 }
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233 setUndefined();
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234 IsRedefinable = false;
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235 }
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236 }
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237
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238 /// @}
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239 /// \name Associated Sections
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240 /// @{
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241
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242 /// isDefined - Check if this symbol is defined (i.e., it has an address).
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243 ///
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244 /// Defined symbols are either absolute or in some section.
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245 bool isDefined(bool SetUsed = true) const {
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246 return getFragment(SetUsed) != nullptr;
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247 }
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248
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249 /// isInSection - Check if this symbol is defined in some section (i.e., it
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250 /// is defined but not absolute).
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251 bool isInSection(bool SetUsed = true) const {
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252 return isDefined(SetUsed) && !isAbsolute(SetUsed);
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253 }
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254
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255 /// isUndefined - Check if this symbol undefined (i.e., implicitly defined).
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256 bool isUndefined(bool SetUsed = true) const { return !isDefined(SetUsed); }
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257
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258 /// isAbsolute - Check if this is an absolute symbol.
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259 bool isAbsolute(bool SetUsed = true) const {
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260 return getFragment(SetUsed) == AbsolutePseudoFragment;
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261 }
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262
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263 /// Get the section associated with a defined, non-absolute symbol.
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264 MCSection &getSection(bool SetUsed = true) const {
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265 assert(isInSection(SetUsed) && "Invalid accessor!");
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266 return *getSectionPtr(SetUsed);
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267 }
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268
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269 /// Mark the symbol as defined in the fragment \p F.
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270 void setFragment(MCFragment *F) const {
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271 assert(!isVariable() && "Cannot set fragment of variable");
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272 FragmentAndHasName.setPointer(F);
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273 }
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95
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274
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275 /// Mark the symbol as undefined.
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276 void setUndefined() { FragmentAndHasName.setPointer(nullptr); }
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277
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278 bool isELF() const { return Kind == SymbolKindELF; }
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279
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280 bool isCOFF() const { return Kind == SymbolKindCOFF; }
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281
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282 bool isMachO() const { return Kind == SymbolKindMachO; }
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283
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284 /// @}
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285 /// \name Variable Symbols
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286 /// @{
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287
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288 /// isVariable - Check if this is a variable symbol.
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289 bool isVariable() const {
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290 return SymbolContents == SymContentsVariable;
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|
291 }
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292
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293 /// getVariableValue - Get the value for variable symbols.
|
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294 const MCExpr *getVariableValue(bool SetUsed = true) const {
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295 assert(isVariable() && "Invalid accessor!");
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296 IsUsed |= SetUsed;
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297 return Value;
|
|
298 }
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299
|
|
300 void setVariableValue(const MCExpr *Value);
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301
|
|
302 /// @}
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303
|
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304 /// Get the (implementation defined) index.
|
|
305 uint32_t getIndex() const {
|
|
306 return Index;
|
|
307 }
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308
|
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309 /// Set the (implementation defined) index.
|
|
310 void setIndex(uint32_t Value) const {
|
|
311 Index = Value;
|
|
312 }
|
|
313
|
|
314 uint64_t getOffset() const {
|
|
315 assert((SymbolContents == SymContentsUnset ||
|
|
316 SymbolContents == SymContentsOffset) &&
|
|
317 "Cannot get offset for a common/variable symbol");
|
|
318 return Offset;
|
|
319 }
|
|
320 void setOffset(uint64_t Value) {
|
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321 assert((SymbolContents == SymContentsUnset ||
|
|
322 SymbolContents == SymContentsOffset) &&
|
|
323 "Cannot set offset for a common/variable symbol");
|
|
324 Offset = Value;
|
|
325 SymbolContents = SymContentsOffset;
|
|
326 }
|
|
327
|
|
328 /// Return the size of a 'common' symbol.
|
|
329 uint64_t getCommonSize() const {
|
|
330 assert(isCommon() && "Not a 'common' symbol!");
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|
331 return CommonSize;
|
|
332 }
|
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333
|
|
334 /// Mark this symbol as being 'common'.
|
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335 ///
|
|
336 /// \param Size - The size of the symbol.
|
|
337 /// \param Align - The alignment of the symbol.
|
|
338 void setCommon(uint64_t Size, unsigned Align) {
|
|
339 assert(getOffset() == 0);
|
|
340 CommonSize = Size;
|
|
341 SymbolContents = SymContentsCommon;
|
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342
|
|
343 assert((!Align || isPowerOf2_32(Align)) &&
|
|
344 "Alignment must be a power of 2");
|
|
345 unsigned Log2Align = Log2_32(Align) + 1;
|
|
346 assert(Log2Align < (1U << NumCommonAlignmentBits) &&
|
|
347 "Out of range alignment");
|
|
348 CommonAlignLog2 = Log2Align;
|
|
349 }
|
|
350
|
|
351 /// Return the alignment of a 'common' symbol.
|
|
352 unsigned getCommonAlignment() const {
|
|
353 assert(isCommon() && "Not a 'common' symbol!");
|
|
354 return CommonAlignLog2 ? (1U << (CommonAlignLog2 - 1)) : 0;
|
|
355 }
|
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356
|
|
357 /// Declare this symbol as being 'common'.
|
|
358 ///
|
|
359 /// \param Size - The size of the symbol.
|
|
360 /// \param Align - The alignment of the symbol.
|
|
361 /// \return True if symbol was already declared as a different type
|
|
362 bool declareCommon(uint64_t Size, unsigned Align) {
|
|
363 assert(isCommon() || getOffset() == 0);
|
|
364 if(isCommon()) {
|
|
365 if(CommonSize != Size || getCommonAlignment() != Align)
|
|
366 return true;
|
|
367 } else
|
|
368 setCommon(Size, Align);
|
|
369 return false;
|
|
370 }
|
|
371
|
|
372 /// Is this a 'common' symbol.
|
|
373 bool isCommon() const {
|
|
374 return SymbolContents == SymContentsCommon;
|
|
375 }
|
|
376
|
|
377 MCFragment *getFragment(bool SetUsed = true) const {
|
|
378 MCFragment *Fragment = FragmentAndHasName.getPointer();
|
|
379 if (Fragment || !isVariable())
|
|
380 return Fragment;
|
|
381 Fragment = getVariableValue(SetUsed)->findAssociatedFragment();
|
|
382 FragmentAndHasName.setPointer(Fragment);
|
|
383 return Fragment;
|
|
384 }
|
|
385
|
|
386 bool isExternal() const { return IsExternal; }
|
|
387 void setExternal(bool Value) const { IsExternal = Value; }
|
|
388
|
|
389 bool isPrivateExtern() const { return IsPrivateExtern; }
|
|
390 void setPrivateExtern(bool Value) { IsPrivateExtern = Value; }
|
|
391
|
|
392 /// print - Print the value to the stream \p OS.
|
|
393 void print(raw_ostream &OS, const MCAsmInfo *MAI) const;
|
|
394
|
|
395 /// dump - Print the value to stderr.
|
|
396 void dump() const;
|
|
397
|
|
398 protected:
|
|
399 /// Get the (implementation defined) symbol flags.
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400 uint32_t getFlags() const { return Flags; }
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401
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402 /// Set the (implementation defined) symbol flags.
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403 void setFlags(uint32_t Value) const {
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404 assert(Value < (1U << NumFlagsBits) && "Out of range flags");
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405 Flags = Value;
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406 }
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407
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408 /// Modify the flags via a mask
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409 void modifyFlags(uint32_t Value, uint32_t Mask) const {
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410 assert(Value < (1U << NumFlagsBits) && "Out of range flags");
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411 Flags = (Flags & ~Mask) | Value;
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412 }
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413 };
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414
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415 inline raw_ostream &operator<<(raw_ostream &OS, const MCSymbol &Sym) {
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416 Sym.print(OS, nullptr);
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417 return OS;
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418 }
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Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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419 } // end namespace llvm
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Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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420
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Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
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421 #endif
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