1 //===-- Globals.cpp - Implement the GlobalValue & GlobalVariable class ----===// 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 implements the GlobalValue & GlobalVariable classes for the IR 11 // library. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "llvm/ADT/SmallPtrSet.h" 16 #include "llvm/ADT/Triple.h" 17 #include "llvm/IR/Constants.h" 18 #include "llvm/IR/DerivedTypes.h" 19 #include "llvm/IR/GlobalAlias.h" 20 #include "llvm/IR/GlobalValue.h" 21 #include "llvm/IR/GlobalVariable.h" 22 #include "llvm/IR/Module.h" 23 #include "llvm/IR/Operator.h" 24 #include "llvm/Support/ErrorHandling.h" 25 using namespace llvm; 26 27 //===----------------------------------------------------------------------===// 28 // GlobalValue Class 29 //===----------------------------------------------------------------------===// 30 31 bool GlobalValue::isMaterializable() const { 32 if (const Function *F = dyn_cast<Function>(this)) 33 return F->isMaterializable(); 34 return false; 35 } 36 std::error_code GlobalValue::materialize() { 37 return getParent()->materialize(this); 38 } 39 40 /// Override destroyConstantImpl to make sure it doesn't get called on 41 /// GlobalValue's because they shouldn't be treated like other constants. 42 void GlobalValue::destroyConstantImpl() { 43 llvm_unreachable("You can't GV->destroyConstantImpl()!"); 44 } 45 46 Value *GlobalValue::handleOperandChangeImpl(Value *From, Value *To) { 47 llvm_unreachable("Unsupported class for handleOperandChange()!"); 48 } 49 50 /// copyAttributesFrom - copy all additional attributes (those not needed to 51 /// create a GlobalValue) from the GlobalValue Src to this one. 52 void GlobalValue::copyAttributesFrom(const GlobalValue *Src) { 53 setVisibility(Src->getVisibility()); 54 setUnnamedAddr(Src->getUnnamedAddr()); 55 setDLLStorageClass(Src->getDLLStorageClass()); 56 } 57 58 unsigned GlobalValue::getAlignment() const { 59 if (auto *GA = dyn_cast<GlobalAlias>(this)) { 60 // In general we cannot compute this at the IR level, but we try. 61 if (const GlobalObject *GO = GA->getBaseObject()) 62 return GO->getAlignment(); 63 64 // FIXME: we should also be able to handle: 65 // Alias = Global + Offset 66 // Alias = Absolute 67 return 0; 68 } 69 return cast<GlobalObject>(this)->getAlignment(); 70 } 71 72 void GlobalObject::setAlignment(unsigned Align) { 73 assert((Align & (Align-1)) == 0 && "Alignment is not a power of 2!"); 74 assert(Align <= MaximumAlignment && 75 "Alignment is greater than MaximumAlignment!"); 76 unsigned AlignmentData = Log2_32(Align) + 1; 77 unsigned OldData = getGlobalValueSubClassData(); 78 setGlobalValueSubClassData((OldData & ~AlignmentMask) | AlignmentData); 79 assert(getAlignment() == Align && "Alignment representation error!"); 80 } 81 82 unsigned GlobalObject::getGlobalObjectSubClassData() const { 83 unsigned ValueData = getGlobalValueSubClassData(); 84 return ValueData >> GlobalObjectBits; 85 } 86 87 void GlobalObject::setGlobalObjectSubClassData(unsigned Val) { 88 unsigned OldData = getGlobalValueSubClassData(); 89 setGlobalValueSubClassData((OldData & GlobalObjectMask) | 90 (Val << GlobalObjectBits)); 91 assert(getGlobalObjectSubClassData() == Val && "representation error"); 92 } 93 94 void GlobalObject::copyAttributesFrom(const GlobalValue *Src) { 95 GlobalValue::copyAttributesFrom(Src); 96 if (const auto *GV = dyn_cast<GlobalObject>(Src)) { 97 setAlignment(GV->getAlignment()); 98 setSection(GV->getSection()); 99 } 100 } 101 102 std::string GlobalValue::getGlobalIdentifier(StringRef Name, 103 GlobalValue::LinkageTypes Linkage, 104 StringRef FileName) { 105 106 // Value names may be prefixed with a binary '1' to indicate 107 // that the backend should not modify the symbols due to any platform 108 // naming convention. Do not include that '1' in the PGO profile name. 109 if (Name[0] == '\1') 110 Name = Name.substr(1); 111 112 std::string NewName = Name; 113 if (llvm::GlobalValue::isLocalLinkage(Linkage)) { 114 // For local symbols, prepend the main file name to distinguish them. 115 // Do not include the full path in the file name since there's no guarantee 116 // that it will stay the same, e.g., if the files are checked out from 117 // version control in different locations. 118 if (FileName.empty()) 119 NewName = NewName.insert(0, "<unknown>:"); 120 else 121 NewName = NewName.insert(0, FileName.str() + ":"); 122 } 123 return NewName; 124 } 125 126 std::string GlobalValue::getGlobalIdentifier() const { 127 return getGlobalIdentifier(getName(), getLinkage(), 128 getParent()->getSourceFileName()); 129 } 130 131 StringRef GlobalValue::getSection() const { 132 if (auto *GA = dyn_cast<GlobalAlias>(this)) { 133 // In general we cannot compute this at the IR level, but we try. 134 if (const GlobalObject *GO = GA->getBaseObject()) 135 return GO->getSection(); 136 return ""; 137 } 138 return cast<GlobalObject>(this)->getSection(); 139 } 140 141 Comdat *GlobalValue::getComdat() { 142 if (auto *GA = dyn_cast<GlobalAlias>(this)) { 143 // In general we cannot compute this at the IR level, but we try. 144 if (const GlobalObject *GO = GA->getBaseObject()) 145 return const_cast<GlobalObject *>(GO)->getComdat(); 146 return nullptr; 147 } 148 // ifunc and its resolver are separate things so don't use resolver comdat. 149 if (isa<GlobalIFunc>(this)) 150 return nullptr; 151 return cast<GlobalObject>(this)->getComdat(); 152 } 153 154 void GlobalObject::setSection(StringRef S) { 155 Section = S; 156 157 // The C api requires this to be null terminated. 158 Section.c_str(); 159 } 160 161 bool GlobalValue::isDeclaration() const { 162 // Globals are definitions if they have an initializer. 163 if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this)) 164 return GV->getNumOperands() == 0; 165 166 // Functions are definitions if they have a body. 167 if (const Function *F = dyn_cast<Function>(this)) 168 return F->empty() && !F->isMaterializable(); 169 170 // Aliases and ifuncs are always definitions. 171 assert(isa<GlobalIndirectSymbol>(this)); 172 return false; 173 } 174 175 bool GlobalValue::canIncreaseAlignment() const { 176 // Firstly, can only increase the alignment of a global if it 177 // is a strong definition. 178 if (!isStrongDefinitionForLinker()) 179 return false; 180 181 // It also has to either not have a section defined, or, not have 182 // alignment specified. (If it is assigned a section, the global 183 // could be densely packed with other objects in the section, and 184 // increasing the alignment could cause padding issues.) 185 if (hasSection() && getAlignment() > 0) 186 return false; 187 188 // On ELF platforms, we're further restricted in that we can't 189 // increase the alignment of any variable which might be emitted 190 // into a shared library, and which is exported. If the main 191 // executable accesses a variable found in a shared-lib, the main 192 // exe actually allocates memory for and exports the symbol ITSELF, 193 // overriding the symbol found in the library. That is, at link 194 // time, the observed alignment of the variable is copied into the 195 // executable binary. (A COPY relocation is also generated, to copy 196 // the initial data from the shadowed variable in the shared-lib 197 // into the location in the main binary, before running code.) 198 // 199 // And thus, even though you might think you are defining the 200 // global, and allocating the memory for the global in your object 201 // file, and thus should be able to set the alignment arbitrarily, 202 // that's not actually true. Doing so can cause an ABI breakage; an 203 // executable might have already been built with the previous 204 // alignment of the variable, and then assuming an increased 205 // alignment will be incorrect. 206 207 // Conservatively assume ELF if there's no parent pointer. 208 bool isELF = 209 (!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatELF()); 210 if (isELF && hasDefaultVisibility() && !hasLocalLinkage()) 211 return false; 212 213 return true; 214 } 215 216 //===----------------------------------------------------------------------===// 217 // GlobalVariable Implementation 218 //===----------------------------------------------------------------------===// 219 220 GlobalVariable::GlobalVariable(Type *Ty, bool constant, LinkageTypes Link, 221 Constant *InitVal, const Twine &Name, 222 ThreadLocalMode TLMode, unsigned AddressSpace, 223 bool isExternallyInitialized) 224 : GlobalObject(Ty, Value::GlobalVariableVal, 225 OperandTraits<GlobalVariable>::op_begin(this), 226 InitVal != nullptr, Link, Name, AddressSpace), 227 isConstantGlobal(constant), 228 isExternallyInitializedConstant(isExternallyInitialized) { 229 setThreadLocalMode(TLMode); 230 if (InitVal) { 231 assert(InitVal->getType() == Ty && 232 "Initializer should be the same type as the GlobalVariable!"); 233 Op<0>() = InitVal; 234 } 235 } 236 237 GlobalVariable::GlobalVariable(Module &M, Type *Ty, bool constant, 238 LinkageTypes Link, Constant *InitVal, 239 const Twine &Name, GlobalVariable *Before, 240 ThreadLocalMode TLMode, unsigned AddressSpace, 241 bool isExternallyInitialized) 242 : GlobalObject(Ty, Value::GlobalVariableVal, 243 OperandTraits<GlobalVariable>::op_begin(this), 244 InitVal != nullptr, Link, Name, AddressSpace), 245 isConstantGlobal(constant), 246 isExternallyInitializedConstant(isExternallyInitialized) { 247 setThreadLocalMode(TLMode); 248 if (InitVal) { 249 assert(InitVal->getType() == Ty && 250 "Initializer should be the same type as the GlobalVariable!"); 251 Op<0>() = InitVal; 252 } 253 254 if (Before) 255 Before->getParent()->getGlobalList().insert(Before->getIterator(), this); 256 else 257 M.getGlobalList().push_back(this); 258 } 259 260 void GlobalVariable::setParent(Module *parent) { 261 Parent = parent; 262 } 263 264 void GlobalVariable::removeFromParent() { 265 getParent()->getGlobalList().remove(getIterator()); 266 } 267 268 void GlobalVariable::eraseFromParent() { 269 getParent()->getGlobalList().erase(getIterator()); 270 } 271 272 void GlobalVariable::setInitializer(Constant *InitVal) { 273 if (!InitVal) { 274 if (hasInitializer()) { 275 // Note, the num operands is used to compute the offset of the operand, so 276 // the order here matters. Clearing the operand then clearing the num 277 // operands ensures we have the correct offset to the operand. 278 Op<0>().set(nullptr); 279 setGlobalVariableNumOperands(0); 280 } 281 } else { 282 assert(InitVal->getType() == getValueType() && 283 "Initializer type must match GlobalVariable type"); 284 // Note, the num operands is used to compute the offset of the operand, so 285 // the order here matters. We need to set num operands to 1 first so that 286 // we get the correct offset to the first operand when we set it. 287 if (!hasInitializer()) 288 setGlobalVariableNumOperands(1); 289 Op<0>().set(InitVal); 290 } 291 } 292 293 /// Copy all additional attributes (those not needed to create a GlobalVariable) 294 /// from the GlobalVariable Src to this one. 295 void GlobalVariable::copyAttributesFrom(const GlobalValue *Src) { 296 GlobalObject::copyAttributesFrom(Src); 297 if (const GlobalVariable *SrcVar = dyn_cast<GlobalVariable>(Src)) { 298 setThreadLocalMode(SrcVar->getThreadLocalMode()); 299 setExternallyInitialized(SrcVar->isExternallyInitialized()); 300 } 301 } 302 303 void GlobalVariable::dropAllReferences() { 304 User::dropAllReferences(); 305 clearMetadata(); 306 } 307 308 //===----------------------------------------------------------------------===// 309 // GlobalIndirectSymbol Implementation 310 //===----------------------------------------------------------------------===// 311 312 GlobalIndirectSymbol::GlobalIndirectSymbol(Type *Ty, ValueTy VTy, 313 unsigned AddressSpace, LinkageTypes Linkage, const Twine &Name, 314 Constant *Symbol) 315 : GlobalValue(Ty, VTy, &Op<0>(), 1, Linkage, Name, AddressSpace) { 316 Op<0>() = Symbol; 317 } 318 319 320 //===----------------------------------------------------------------------===// 321 // GlobalAlias Implementation 322 //===----------------------------------------------------------------------===// 323 324 GlobalAlias::GlobalAlias(Type *Ty, unsigned AddressSpace, LinkageTypes Link, 325 const Twine &Name, Constant *Aliasee, 326 Module *ParentModule) 327 : GlobalIndirectSymbol(Ty, Value::GlobalAliasVal, AddressSpace, Link, Name, 328 Aliasee) { 329 if (ParentModule) 330 ParentModule->getAliasList().push_back(this); 331 } 332 333 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace, 334 LinkageTypes Link, const Twine &Name, 335 Constant *Aliasee, Module *ParentModule) { 336 return new GlobalAlias(Ty, AddressSpace, Link, Name, Aliasee, ParentModule); 337 } 338 339 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace, 340 LinkageTypes Linkage, const Twine &Name, 341 Module *Parent) { 342 return create(Ty, AddressSpace, Linkage, Name, nullptr, Parent); 343 } 344 345 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace, 346 LinkageTypes Linkage, const Twine &Name, 347 GlobalValue *Aliasee) { 348 return create(Ty, AddressSpace, Linkage, Name, Aliasee, Aliasee->getParent()); 349 } 350 351 GlobalAlias *GlobalAlias::create(LinkageTypes Link, const Twine &Name, 352 GlobalValue *Aliasee) { 353 PointerType *PTy = Aliasee->getType(); 354 return create(PTy->getElementType(), PTy->getAddressSpace(), Link, Name, 355 Aliasee); 356 } 357 358 GlobalAlias *GlobalAlias::create(const Twine &Name, GlobalValue *Aliasee) { 359 return create(Aliasee->getLinkage(), Name, Aliasee); 360 } 361 362 void GlobalAlias::setParent(Module *parent) { 363 Parent = parent; 364 } 365 366 void GlobalAlias::removeFromParent() { 367 getParent()->getAliasList().remove(getIterator()); 368 } 369 370 void GlobalAlias::eraseFromParent() { 371 getParent()->getAliasList().erase(getIterator()); 372 } 373 374 void GlobalAlias::setAliasee(Constant *Aliasee) { 375 assert((!Aliasee || Aliasee->getType() == getType()) && 376 "Alias and aliasee types should match!"); 377 setIndirectSymbol(Aliasee); 378 } 379 380 //===----------------------------------------------------------------------===// 381 // GlobalIFunc Implementation 382 //===----------------------------------------------------------------------===// 383 384 GlobalIFunc::GlobalIFunc(Type *Ty, unsigned AddressSpace, LinkageTypes Link, 385 const Twine &Name, Constant *Resolver, 386 Module *ParentModule) 387 : GlobalIndirectSymbol(Ty, Value::GlobalIFuncVal, AddressSpace, Link, Name, 388 Resolver) { 389 if (ParentModule) 390 ParentModule->getIFuncList().push_back(this); 391 } 392 393 GlobalIFunc *GlobalIFunc::create(Type *Ty, unsigned AddressSpace, 394 LinkageTypes Link, const Twine &Name, 395 Constant *Resolver, Module *ParentModule) { 396 return new GlobalIFunc(Ty, AddressSpace, Link, Name, Resolver, ParentModule); 397 } 398 399 void GlobalIFunc::setParent(Module *parent) { 400 Parent = parent; 401 } 402 403 void GlobalIFunc::removeFromParent() { 404 getParent()->getIFuncList().remove(getIterator()); 405 } 406 407 void GlobalIFunc::eraseFromParent() { 408 getParent()->getIFuncList().erase(getIterator()); 409 } 410