1 //===-- llvm/MC/MCFixup.h - Instruction Relocation and Patching -*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 9 #ifndef LLVM_MC_MCFIXUP_H 10 #define LLVM_MC_MCFIXUP_H 11 12 #include "llvm/Support/DataTypes.h" 13 #include "llvm/Support/ErrorHandling.h" 14 #include "llvm/Support/SMLoc.h" 15 #include <cassert> 16 17 namespace llvm { 18 class MCExpr; 19 20 /// Extensible enumeration to represent the type of a fixup. 21 enum MCFixupKind { 22 FK_NONE = 0, ///< A no-op fixup. 23 FK_Data_1, ///< A one-byte fixup. 24 FK_Data_2, ///< A two-byte fixup. 25 FK_Data_4, ///< A four-byte fixup. 26 FK_Data_8, ///< A eight-byte fixup. 27 FK_Data_6b, ///< A six-bits fixup. 28 FK_PCRel_1, ///< A one-byte pc relative fixup. 29 FK_PCRel_2, ///< A two-byte pc relative fixup. 30 FK_PCRel_4, ///< A four-byte pc relative fixup. 31 FK_PCRel_8, ///< A eight-byte pc relative fixup. 32 FK_GPRel_1, ///< A one-byte gp relative fixup. 33 FK_GPRel_2, ///< A two-byte gp relative fixup. 34 FK_GPRel_4, ///< A four-byte gp relative fixup. 35 FK_GPRel_8, ///< A eight-byte gp relative fixup. 36 FK_DTPRel_4, ///< A four-byte dtp relative fixup. 37 FK_DTPRel_8, ///< A eight-byte dtp relative fixup. 38 FK_TPRel_4, ///< A four-byte tp relative fixup. 39 FK_TPRel_8, ///< A eight-byte tp relative fixup. 40 FK_SecRel_1, ///< A one-byte section relative fixup. 41 FK_SecRel_2, ///< A two-byte section relative fixup. 42 FK_SecRel_4, ///< A four-byte section relative fixup. 43 FK_SecRel_8, ///< A eight-byte section relative fixup. 44 FK_Data_Add_1, ///< A one-byte add fixup. 45 FK_Data_Add_2, ///< A two-byte add fixup. 46 FK_Data_Add_4, ///< A four-byte add fixup. 47 FK_Data_Add_8, ///< A eight-byte add fixup. 48 FK_Data_Add_6b, ///< A six-bits add fixup. 49 FK_Data_Sub_1, ///< A one-byte sub fixup. 50 FK_Data_Sub_2, ///< A two-byte sub fixup. 51 FK_Data_Sub_4, ///< A four-byte sub fixup. 52 FK_Data_Sub_8, ///< A eight-byte sub fixup. 53 FK_Data_Sub_6b, ///< A six-bits sub fixup. 54 55 FirstTargetFixupKind = 128, 56 57 /// The range [FirstLiteralRelocationKind, MaxTargetFixupKind) is used for 58 /// relocations coming from .reloc directive. Fixup kind 59 /// FirstLiteralRelocationKind+V represents the relocation type with number V. 60 FirstLiteralRelocationKind = 256, 61 62 /// Set limit to accommodate the highest reloc type in use for all Targets, 63 /// currently R_AARCH64_IRELATIVE at 1032, including room for expansion. 64 MaxFixupKind = FirstLiteralRelocationKind + 1032 + 32, 65 }; 66 67 /// Encode information on a single operation to perform on a byte 68 /// sequence (e.g., an encoded instruction) which requires assemble- or run- 69 /// time patching. 70 /// 71 /// Fixups are used any time the target instruction encoder needs to represent 72 /// some value in an instruction which is not yet concrete. The encoder will 73 /// encode the instruction assuming the value is 0, and emit a fixup which 74 /// communicates to the assembler backend how it should rewrite the encoded 75 /// value. 76 /// 77 /// During the process of relaxation, the assembler will apply fixups as 78 /// symbolic values become concrete. When relaxation is complete, any remaining 79 /// fixups become relocations in the object file (or errors, if the fixup cannot 80 /// be encoded on the target). 81 class MCFixup { 82 /// The value to put into the fixup location. The exact interpretation of the 83 /// expression is target dependent, usually it will be one of the operands to 84 /// an instruction or an assembler directive. 85 const MCExpr *Value = nullptr; 86 87 /// The byte index of start of the relocation inside the MCFragment. 88 uint32_t Offset = 0; 89 90 /// The target dependent kind of fixup item this is. The kind is used to 91 /// determine how the operand value should be encoded into the instruction. 92 MCFixupKind Kind = FK_NONE; 93 94 /// The source location which gave rise to the fixup, if any. 95 SMLoc Loc; 96 public: 97 static MCFixup create(uint32_t Offset, const MCExpr *Value, 98 MCFixupKind Kind, SMLoc Loc = SMLoc()) { 99 assert(Kind <= MaxFixupKind && "Kind out of range!"); 100 MCFixup FI; 101 FI.Value = Value; 102 FI.Offset = Offset; 103 FI.Kind = Kind; 104 FI.Loc = Loc; 105 return FI; 106 } 107 108 /// Return a fixup corresponding to the add half of a add/sub fixup pair for 109 /// the given Fixup. 110 static MCFixup createAddFor(const MCFixup &Fixup) { 111 MCFixup FI; 112 FI.Value = Fixup.getValue(); 113 FI.Offset = Fixup.getOffset(); 114 FI.Kind = getAddKindForKind(Fixup.getKind()); 115 FI.Loc = Fixup.getLoc(); 116 return FI; 117 } 118 119 /// Return a fixup corresponding to the sub half of a add/sub fixup pair for 120 /// the given Fixup. 121 static MCFixup createSubFor(const MCFixup &Fixup) { 122 MCFixup FI; 123 FI.Value = Fixup.getValue(); 124 FI.Offset = Fixup.getOffset(); 125 FI.Kind = getSubKindForKind(Fixup.getKind()); 126 FI.Loc = Fixup.getLoc(); 127 return FI; 128 } 129 130 MCFixupKind getKind() const { return Kind; } 131 132 unsigned getTargetKind() const { return Kind; } 133 134 uint32_t getOffset() const { return Offset; } 135 void setOffset(uint32_t Value) { Offset = Value; } 136 137 const MCExpr *getValue() const { return Value; } 138 139 /// Return the generic fixup kind for a value with the given size. It 140 /// is an error to pass an unsupported size. 141 static MCFixupKind getKindForSize(unsigned Size, bool IsPCRel) { 142 switch (Size) { 143 default: llvm_unreachable("Invalid generic fixup size!"); 144 case 1: 145 return IsPCRel ? FK_PCRel_1 : FK_Data_1; 146 case 2: 147 return IsPCRel ? FK_PCRel_2 : FK_Data_2; 148 case 4: 149 return IsPCRel ? FK_PCRel_4 : FK_Data_4; 150 case 8: 151 return IsPCRel ? FK_PCRel_8 : FK_Data_8; 152 } 153 } 154 155 /// Return the generic fixup kind for a value with the given size in bits. 156 /// It is an error to pass an unsupported size. 157 static MCFixupKind getKindForSizeInBits(unsigned Size, bool IsPCRel) { 158 switch (Size) { 159 default: 160 llvm_unreachable("Invalid generic fixup size!"); 161 case 6: 162 assert(!IsPCRel && "Invalid pc-relative fixup size!"); 163 return FK_Data_6b; 164 case 8: 165 return IsPCRel ? FK_PCRel_1 : FK_Data_1; 166 case 16: 167 return IsPCRel ? FK_PCRel_2 : FK_Data_2; 168 case 32: 169 return IsPCRel ? FK_PCRel_4 : FK_Data_4; 170 case 64: 171 return IsPCRel ? FK_PCRel_8 : FK_Data_8; 172 } 173 } 174 175 /// Return the generic fixup kind for an addition with a given size. It 176 /// is an error to pass an unsupported size. 177 static MCFixupKind getAddKindForKind(MCFixupKind Kind) { 178 switch (Kind) { 179 default: llvm_unreachable("Unknown type to convert!"); 180 case FK_Data_1: return FK_Data_Add_1; 181 case FK_Data_2: return FK_Data_Add_2; 182 case FK_Data_4: return FK_Data_Add_4; 183 case FK_Data_8: return FK_Data_Add_8; 184 case FK_Data_6b: return FK_Data_Add_6b; 185 } 186 } 187 188 /// Return the generic fixup kind for an subtraction with a given size. It 189 /// is an error to pass an unsupported size. 190 static MCFixupKind getSubKindForKind(MCFixupKind Kind) { 191 switch (Kind) { 192 default: llvm_unreachable("Unknown type to convert!"); 193 case FK_Data_1: return FK_Data_Sub_1; 194 case FK_Data_2: return FK_Data_Sub_2; 195 case FK_Data_4: return FK_Data_Sub_4; 196 case FK_Data_8: return FK_Data_Sub_8; 197 case FK_Data_6b: return FK_Data_Sub_6b; 198 } 199 } 200 201 SMLoc getLoc() const { return Loc; } 202 }; 203 204 } // End llvm namespace 205 206 #endif 207
Indexes created Mon Jun 08 00:24:58 UTC 2026