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1 //===- Relocations.h -------------------------------------------*- C++ -*-===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8
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9 #ifndef LLD_ELF_RELOCATIONS_H
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10 #define LLD_ELF_RELOCATIONS_H
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11
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12 #include "lld/Common/LLVM.h"
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13 #include "llvm/ADT/DenseMap.h"
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14 #include <map>
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15 #include <vector>
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16
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17 namespace lld {
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18 namespace elf {
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19 class Symbol;
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20 class InputSection;
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21 class InputSectionBase;
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22 class OutputSection;
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23 class SectionBase;
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24
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25 // Represents a relocation type, such as R_X86_64_PC32 or R_ARM_THM_CALL.
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26 using RelType = uint32_t;
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173
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27 using JumpModType = uint32_t;
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150
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28
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29 // List of target-independent relocation types. Relocations read
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30 // from files are converted to these types so that the main code
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31 // doesn't have to know about architecture-specific details.
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32 enum RelExpr {
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33 R_ABS,
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34 R_ADDEND,
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35 R_DTPREL,
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36 R_GOT,
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37 R_GOT_OFF,
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38 R_GOT_PC,
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39 R_GOTONLY_PC,
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40 R_GOTPLTONLY_PC,
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41 R_GOTPLT,
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42 R_GOTPLTREL,
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43 R_GOTREL,
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44 R_NEG_TLS,
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45 R_NONE,
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46 R_PC,
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47 R_PLT,
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48 R_PLT_PC,
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49 R_RELAX_GOT_PC,
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50 R_RELAX_GOT_PC_NOPIC,
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51 R_RELAX_TLS_GD_TO_IE,
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52 R_RELAX_TLS_GD_TO_IE_ABS,
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53 R_RELAX_TLS_GD_TO_IE_GOT_OFF,
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54 R_RELAX_TLS_GD_TO_IE_GOTPLT,
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55 R_RELAX_TLS_GD_TO_LE,
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56 R_RELAX_TLS_GD_TO_LE_NEG,
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57 R_RELAX_TLS_IE_TO_LE,
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58 R_RELAX_TLS_LD_TO_LE,
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59 R_RELAX_TLS_LD_TO_LE_ABS,
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60 R_SIZE,
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61 R_TLS,
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62 R_TLSDESC,
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63 R_TLSDESC_CALL,
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64 R_TLSDESC_PC,
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65 R_TLSGD_GOT,
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66 R_TLSGD_GOTPLT,
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67 R_TLSGD_PC,
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68 R_TLSIE_HINT,
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69 R_TLSLD_GOT,
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70 R_TLSLD_GOTPLT,
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71 R_TLSLD_GOT_OFF,
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72 R_TLSLD_HINT,
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73 R_TLSLD_PC,
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74
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75 // The following is abstract relocation types used for only one target.
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76 //
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77 // Even though RelExpr is intended to be a target-neutral representation
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78 // of a relocation type, there are some relocations whose semantics are
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79 // unique to a target. Such relocation are marked with R_<TARGET_NAME>.
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80 R_AARCH64_GOT_PAGE_PC,
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81 R_AARCH64_PAGE_PC,
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82 R_AARCH64_RELAX_TLS_GD_TO_IE_PAGE_PC,
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83 R_AARCH64_TLSDESC_PAGE,
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84 R_ARM_PCA,
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85 R_ARM_SBREL,
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86 R_MIPS_GOTREL,
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87 R_MIPS_GOT_GP,
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88 R_MIPS_GOT_GP_PC,
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89 R_MIPS_GOT_LOCAL_PAGE,
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90 R_MIPS_GOT_OFF,
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91 R_MIPS_GOT_OFF32,
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92 R_MIPS_TLSGD,
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93 R_MIPS_TLSLD,
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94 R_PPC32_PLTREL,
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95 R_PPC64_CALL,
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96 R_PPC64_CALL_PLT,
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97 R_PPC64_RELAX_TOC,
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98 R_PPC64_TOCBASE,
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99 R_RISCV_ADD,
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100 R_RISCV_PC_INDIRECT,
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101 };
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102
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103 // Architecture-neutral representation of relocation.
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104 struct Relocation {
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105 RelExpr expr;
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106 RelType type;
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107 uint64_t offset;
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108 int64_t addend;
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109 Symbol *sym;
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110 };
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111
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173
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112 // Manipulate jump instructions with these modifiers. These are used to relax
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113 // jump instruction opcodes at basic block boundaries and are particularly
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114 // useful when basic block sections are enabled.
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115 struct JumpInstrMod {
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116 JumpModType original;
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117 uint64_t offset;
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118 unsigned size;
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119 };
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120
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121 // This function writes undefined symbol diagnostics to an internal buffer.
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122 // Call reportUndefinedSymbols() after calling scanRelocations() to emit
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123 // the diagnostics.
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124 template <class ELFT> void scanRelocations(InputSectionBase &);
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125
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126 template <class ELFT> void reportUndefinedSymbols();
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127
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128 void hexagonTLSSymbolUpdate(ArrayRef<OutputSection *> outputSections);
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129 bool hexagonNeedsTLSSymbol(ArrayRef<OutputSection *> outputSections);
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130
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131 class ThunkSection;
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132 class Thunk;
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133 struct InputSectionDescription;
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134
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135 class ThunkCreator {
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136 public:
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137 // Return true if Thunks have been added to OutputSections
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138 bool createThunks(ArrayRef<OutputSection *> outputSections);
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139
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140 // The number of completed passes of createThunks this permits us
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141 // to do one time initialization on Pass 0 and put a limit on the
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142 // number of times it can be called to prevent infinite loops.
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143 uint32_t pass = 0;
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144
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145 private:
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146 void mergeThunks(ArrayRef<OutputSection *> outputSections);
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147
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148 ThunkSection *getISDThunkSec(OutputSection *os, InputSection *isec,
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149 InputSectionDescription *isd, uint32_t type,
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150 uint64_t src);
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151
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152 ThunkSection *getISThunkSec(InputSection *isec);
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153
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154 void createInitialThunkSections(ArrayRef<OutputSection *> outputSections);
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155
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156 std::pair<Thunk *, bool> getThunk(InputSection *isec, Relocation &rel,
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157 uint64_t src);
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158
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159 ThunkSection *addThunkSection(OutputSection *os, InputSectionDescription *,
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160 uint64_t off);
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161
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162 bool normalizeExistingThunk(Relocation &rel, uint64_t src);
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163
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164 // Record all the available Thunks for a (Symbol, addend) pair, where Symbol
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165 // is represented as a (section, offset) pair. There may be multiple
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166 // relocations sharing the same (section, offset + addend) pair. We may revert
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167 // a relocation back to its original non-Thunk target, and restore the
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168 // original addend, so we cannot fold offset + addend. A nested pair is used
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169 // because DenseMapInfo is not specialized for std::tuple.
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170 llvm::DenseMap<std::pair<std::pair<SectionBase *, uint64_t>, int64_t>,
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171 std::vector<Thunk *>>
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172 thunkedSymbolsBySectionAndAddend;
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173 llvm::DenseMap<std::pair<Symbol *, int64_t>, std::vector<Thunk *>>
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174 thunkedSymbols;
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175
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176 // Find a Thunk from the Thunks symbol definition, we can use this to find
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177 // the Thunk from a relocation to the Thunks symbol definition.
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178 llvm::DenseMap<Symbol *, Thunk *> thunks;
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179
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180 // Track InputSections that have an inline ThunkSection placed in front
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181 // an inline ThunkSection may have control fall through to the section below
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182 // so we need to make sure that there is only one of them.
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183 // The Mips LA25 Thunk is an example of an inline ThunkSection.
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184 llvm::DenseMap<InputSection *, ThunkSection *> thunkedSections;
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185 };
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186
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187 // Return a int64_t to make sure we get the sign extension out of the way as
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188 // early as possible.
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189 template <class ELFT>
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190 static inline int64_t getAddend(const typename ELFT::Rel &rel) {
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191 return 0;
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192 }
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193 template <class ELFT>
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194 static inline int64_t getAddend(const typename ELFT::Rela &rel) {
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195 return rel.r_addend;
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196 }
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197 } // namespace elf
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198 } // namespace lld
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199
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200 #endif
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