1 //===-- llvm/CodeGen/MachineRelocation.h - Target Relocation ----*- 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 defines the MachineRelocation class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #ifndef LLVM_CODEGEN_MACHINERELOCATION_H 15 #define LLVM_CODEGEN_MACHINERELOCATION_H 16 17 #include "llvm/Support/DataTypes.h" 18 #include <cassert> 19 20 namespace llvm { 21 class GlobalValue; 22 class MachineBasicBlock; 23 24 /// MachineRelocation - This represents a target-specific relocation value, 25 /// produced by the code emitter. This relocation is resolved after the has 26 /// been emitted, either to an object file or to memory, when the target of the 27 /// relocation can be resolved. 28 /// 29 /// A relocation is made up of the following logical portions: 30 /// 1. An offset in the machine code buffer, the location to modify. 31 /// 2. A target specific relocation type (a number from 0 to 63). 32 /// 3. A symbol being referenced, either as a GlobalValue* or as a string. 33 /// 4. An optional constant value to be added to the reference. 34 /// 5. A bit, CanRewrite, which indicates to the JIT that a function stub is 35 /// not needed for the relocation. 36 /// 6. An index into the GOT, if the target uses a GOT 37 /// 38 class MachineRelocation { 39 enum AddressType { 40 isResult, // Relocation has be transformed into its result pointer. 41 isGV, // The Target.GV field is valid. 42 isIndirectSym, // Relocation of an indirect symbol. 43 isBB, // Relocation of BB address. 44 isExtSym, // The Target.ExtSym field is valid. 45 isConstPool, // Relocation of constant pool address. 46 isJumpTable, // Relocation of jump table address. 47 isGOTIndex // The Target.GOTIndex field is valid. 48 }; 49 50 /// Offset - This is the offset from the start of the code buffer of the 51 /// relocation to perform. 52 uintptr_t Offset; 53 54 /// ConstantVal - A field that may be used by the target relocation type. 55 intptr_t ConstantVal; 56 57 union { 58 void *Result; // If this has been resolved to a resolved pointer 59 GlobalValue *GV; // If this is a pointer to a GV or an indirect ref. 60 MachineBasicBlock *MBB; // If this is a pointer to an LLVM BB 61 const char *ExtSym; // If this is a pointer to a named symbol 62 unsigned Index; // Constant pool / jump table index 63 unsigned GOTIndex; // Index in the GOT of this symbol/global 64 } Target; 65 66 unsigned TargetReloType : 6; // The target relocation ID 67 AddressType AddrType : 4; // The field of Target to use 68 bool MayNeedFarStub : 1; // True if this relocation may require a far-stub 69 bool GOTRelative : 1; // Should this relocation be relative to the GOT? 70 bool TargetResolve : 1; // True if target should resolve the address 71 72 public: 73 // Relocation types used in a generic implementation. Currently, relocation 74 // entries for all things use the generic VANILLA type until they are refined 75 // into target relocation types. 76 enum RelocationType { 77 VANILLA 78 }; 79 80 /// MachineRelocation::getGV - Return a relocation entry for a GlobalValue. 81 /// 82 static MachineRelocation getGV(uintptr_t offset, unsigned RelocationType, 83 GlobalValue *GV, intptr_t cst = 0, 84 bool MayNeedFarStub = 0, 85 bool GOTrelative = 0) { 86 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 87 MachineRelocation Result; 88 Result.Offset = offset; 89 Result.ConstantVal = cst; 90 Result.TargetReloType = RelocationType; 91 Result.AddrType = isGV; 92 Result.MayNeedFarStub = MayNeedFarStub; 93 Result.GOTRelative = GOTrelative; 94 Result.TargetResolve = false; 95 Result.Target.GV = GV; 96 return Result; 97 } 98 99 /// MachineRelocation::getIndirectSymbol - Return a relocation entry for an 100 /// indirect symbol. 101 static MachineRelocation getIndirectSymbol(uintptr_t offset, 102 unsigned RelocationType, 103 GlobalValue *GV, intptr_t cst = 0, 104 bool MayNeedFarStub = 0, 105 bool GOTrelative = 0) { 106 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 107 MachineRelocation Result; 108 Result.Offset = offset; 109 Result.ConstantVal = cst; 110 Result.TargetReloType = RelocationType; 111 Result.AddrType = isIndirectSym; 112 Result.MayNeedFarStub = MayNeedFarStub; 113 Result.GOTRelative = GOTrelative; 114 Result.TargetResolve = false; 115 Result.Target.GV = GV; 116 return Result; 117 } 118 119 /// MachineRelocation::getBB - Return a relocation entry for a BB. 120 /// 121 static MachineRelocation getBB(uintptr_t offset,unsigned RelocationType, 122 MachineBasicBlock *MBB, intptr_t cst = 0) { 123 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 124 MachineRelocation Result; 125 Result.Offset = offset; 126 Result.ConstantVal = cst; 127 Result.TargetReloType = RelocationType; 128 Result.AddrType = isBB; 129 Result.MayNeedFarStub = false; 130 Result.GOTRelative = false; 131 Result.TargetResolve = false; 132 Result.Target.MBB = MBB; 133 return Result; 134 } 135 136 /// MachineRelocation::getExtSym - Return a relocation entry for an external 137 /// symbol, like "free". 138 /// 139 static MachineRelocation getExtSym(uintptr_t offset, unsigned RelocationType, 140 const char *ES, intptr_t cst = 0, 141 bool GOTrelative = 0, 142 bool NeedStub = true) { 143 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 144 MachineRelocation Result; 145 Result.Offset = offset; 146 Result.ConstantVal = cst; 147 Result.TargetReloType = RelocationType; 148 Result.AddrType = isExtSym; 149 Result.MayNeedFarStub = NeedStub; 150 Result.GOTRelative = GOTrelative; 151 Result.TargetResolve = false; 152 Result.Target.ExtSym = ES; 153 return Result; 154 } 155 156 /// MachineRelocation::getConstPool - Return a relocation entry for a constant 157 /// pool entry. 158 /// 159 static MachineRelocation getConstPool(uintptr_t offset,unsigned RelocationType, 160 unsigned CPI, intptr_t cst = 0, 161 bool letTargetResolve = false) { 162 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 163 MachineRelocation Result; 164 Result.Offset = offset; 165 Result.ConstantVal = cst; 166 Result.TargetReloType = RelocationType; 167 Result.AddrType = isConstPool; 168 Result.MayNeedFarStub = false; 169 Result.GOTRelative = false; 170 Result.TargetResolve = letTargetResolve; 171 Result.Target.Index = CPI; 172 return Result; 173 } 174 175 /// MachineRelocation::getJumpTable - Return a relocation entry for a jump 176 /// table entry. 177 /// 178 static MachineRelocation getJumpTable(uintptr_t offset,unsigned RelocationType, 179 unsigned JTI, intptr_t cst = 0, 180 bool letTargetResolve = false) { 181 assert((RelocationType & ~63) == 0 && "Relocation type too large!"); 182 MachineRelocation Result; 183 Result.Offset = offset; 184 Result.ConstantVal = cst; 185 Result.TargetReloType = RelocationType; 186 Result.AddrType = isJumpTable; 187 Result.MayNeedFarStub = false; 188 Result.GOTRelative = false; 189 Result.TargetResolve = letTargetResolve; 190 Result.Target.Index = JTI; 191 return Result; 192 } 193 194 /// getMachineCodeOffset - Return the offset into the code buffer that the 195 /// relocation should be performed. 196 intptr_t getMachineCodeOffset() const { 197 return Offset; 198 } 199 200 /// getRelocationType - Return the target-specific relocation ID for this 201 /// relocation. 202 unsigned getRelocationType() const { 203 return TargetReloType; 204 } 205 206 /// getConstantVal - Get the constant value associated with this relocation. 207 /// This is often an offset from the symbol. 208 /// 209 intptr_t getConstantVal() const { 210 return ConstantVal; 211 } 212 213 /// setConstantVal - Set the constant value associated with this relocation. 214 /// This is often an offset from the symbol. 215 /// 216 void setConstantVal(intptr_t val) { 217 ConstantVal = val; 218 } 219 220 /// isGlobalValue - Return true if this relocation is a GlobalValue, as 221 /// opposed to a constant string. 222 bool isGlobalValue() const { 223 return AddrType == isGV; 224 } 225 226 /// isIndirectSymbol - Return true if this relocation is the address an 227 /// indirect symbol 228 bool isIndirectSymbol() const { 229 return AddrType == isIndirectSym; 230 } 231 232 /// isBasicBlock - Return true if this relocation is a basic block reference. 233 /// 234 bool isBasicBlock() const { 235 return AddrType == isBB; 236 } 237 238 /// isExternalSymbol - Return true if this is a constant string. 239 /// 240 bool isExternalSymbol() const { 241 return AddrType == isExtSym; 242 } 243 244 /// isConstantPoolIndex - Return true if this is a constant pool reference. 245 /// 246 bool isConstantPoolIndex() const { 247 return AddrType == isConstPool; 248 } 249 250 /// isJumpTableIndex - Return true if this is a jump table reference. 251 /// 252 bool isJumpTableIndex() const { 253 return AddrType == isJumpTable; 254 } 255 256 /// isGOTRelative - Return true the target wants the index into the GOT of 257 /// the symbol rather than the address of the symbol. 258 bool isGOTRelative() const { 259 return GOTRelative; 260 } 261 262 /// mayNeedFarStub - This function returns true if the JIT for this target may 263 /// need either a stub function or an indirect global-variable load to handle 264 /// the relocated GlobalValue reference. For example, the x86-64 call 265 /// instruction can only call functions within +/-2GB of the call site. 266 /// Anything farther away needs a longer mov+call sequence, which can't just 267 /// be written on top of the existing call. 268 bool mayNeedFarStub() const { 269 return MayNeedFarStub; 270 } 271 272 /// letTargetResolve - Return true if the target JITInfo is usually 273 /// responsible for resolving the address of this relocation. 274 bool letTargetResolve() const { 275 return TargetResolve; 276 } 277 278 /// getGlobalValue - If this is a global value reference, return the 279 /// referenced global. 280 GlobalValue *getGlobalValue() const { 281 assert((isGlobalValue() || isIndirectSymbol()) && 282 "This is not a global value reference!"); 283 return Target.GV; 284 } 285 286 MachineBasicBlock *getBasicBlock() const { 287 assert(isBasicBlock() && "This is not a basic block reference!"); 288 return Target.MBB; 289 } 290 291 /// getString - If this is a string value, return the string reference. 292 /// 293 const char *getExternalSymbol() const { 294 assert(isExternalSymbol() && "This is not an external symbol reference!"); 295 return Target.ExtSym; 296 } 297 298 /// getConstantPoolIndex - If this is a const pool reference, return 299 /// the index into the constant pool. 300 unsigned getConstantPoolIndex() const { 301 assert(isConstantPoolIndex() && "This is not a constant pool reference!"); 302 return Target.Index; 303 } 304 305 /// getJumpTableIndex - If this is a jump table reference, return 306 /// the index into the jump table. 307 unsigned getJumpTableIndex() const { 308 assert(isJumpTableIndex() && "This is not a jump table reference!"); 309 return Target.Index; 310 } 311 312 /// getResultPointer - Once this has been resolved to point to an actual 313 /// address, this returns the pointer. 314 void *getResultPointer() const { 315 assert(AddrType == isResult && "Result pointer isn't set yet!"); 316 return Target.Result; 317 } 318 319 /// setResultPointer - Set the result to the specified pointer value. 320 /// 321 void setResultPointer(void *Ptr) { 322 Target.Result = Ptr; 323 AddrType = isResult; 324 } 325 326 /// setGOTIndex - Set the GOT index to a specific value. 327 void setGOTIndex(unsigned idx) { 328 AddrType = isGOTIndex; 329 Target.GOTIndex = idx; 330 } 331 332 /// getGOTIndex - Once this has been resolved to an entry in the GOT, 333 /// this returns that index. The index is from the lowest address entry 334 /// in the GOT. 335 unsigned getGOTIndex() const { 336 assert(AddrType == isGOTIndex); 337 return Target.GOTIndex; 338 } 339 }; 340 } 341 342 #endif 343
