1 //===--- CGCXX.cpp - Emit LLVM Code for declarations ----------------------===// 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 contains code dealing with C++ code generation. 11 // 12 //===----------------------------------------------------------------------===// 13 14 // We might split this into multiple files if it gets too unwieldy 15 16 #include "CodeGenModule.h" 17 #include "CGCXXABI.h" 18 #include "CodeGenFunction.h" 19 #include "clang/AST/ASTContext.h" 20 #include "clang/AST/Decl.h" 21 #include "clang/AST/DeclCXX.h" 22 #include "clang/AST/DeclObjC.h" 23 #include "clang/AST/Mangle.h" 24 #include "clang/AST/RecordLayout.h" 25 #include "clang/AST/StmtCXX.h" 26 #include "clang/Frontend/CodeGenOptions.h" 27 #include "llvm/ADT/StringExtras.h" 28 using namespace clang; 29 using namespace CodeGen; 30 31 /// Try to emit a base destructor as an alias to its primary 32 /// base-class destructor. 33 bool CodeGenModule::TryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D) { 34 if (!getCodeGenOpts().CXXCtorDtorAliases) 35 return true; 36 37 // If the destructor doesn't have a trivial body, we have to emit it 38 // separately. 39 if (!D->hasTrivialBody()) 40 return true; 41 42 const CXXRecordDecl *Class = D->getParent(); 43 44 // If we need to manipulate a VTT parameter, give up. 45 if (Class->getNumVBases()) { 46 // Extra Credit: passing extra parameters is perfectly safe 47 // in many calling conventions, so only bail out if the ctor's 48 // calling convention is nonstandard. 49 return true; 50 } 51 52 // If any field has a non-trivial destructor, we have to emit the 53 // destructor separately. 54 for (CXXRecordDecl::field_iterator I = Class->field_begin(), 55 E = Class->field_end(); I != E; ++I) 56 if (I->getType().isDestructedType()) 57 return true; 58 59 // Try to find a unique base class with a non-trivial destructor. 60 const CXXRecordDecl *UniqueBase = 0; 61 for (CXXRecordDecl::base_class_const_iterator I = Class->bases_begin(), 62 E = Class->bases_end(); I != E; ++I) { 63 64 // We're in the base destructor, so skip virtual bases. 65 if (I->isVirtual()) continue; 66 67 // Skip base classes with trivial destructors. 68 const CXXRecordDecl *Base 69 = cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl()); 70 if (Base->hasTrivialDestructor()) continue; 71 72 // If we've already found a base class with a non-trivial 73 // destructor, give up. 74 if (UniqueBase) return true; 75 UniqueBase = Base; 76 } 77 78 // If we didn't find any bases with a non-trivial destructor, then 79 // the base destructor is actually effectively trivial, which can 80 // happen if it was needlessly user-defined or if there are virtual 81 // bases with non-trivial destructors. 82 if (!UniqueBase) 83 return true; 84 85 /// If we don't have a definition for the destructor yet, don't 86 /// emit. We can't emit aliases to declarations; that's just not 87 /// how aliases work. 88 const CXXDestructorDecl *BaseD = UniqueBase->getDestructor(); 89 if (!BaseD->isImplicit() && !BaseD->hasBody()) 90 return true; 91 92 // If the base is at a non-zero offset, give up. 93 const ASTRecordLayout &ClassLayout = Context.getASTRecordLayout(Class); 94 if (!ClassLayout.getBaseClassOffset(UniqueBase).isZero()) 95 return true; 96 97 return TryEmitDefinitionAsAlias(GlobalDecl(D, Dtor_Base), 98 GlobalDecl(BaseD, Dtor_Base)); 99 } 100 101 /// Try to emit a definition as a global alias for another definition. 102 bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl, 103 GlobalDecl TargetDecl) { 104 if (!getCodeGenOpts().CXXCtorDtorAliases) 105 return true; 106 107 // The alias will use the linkage of the referrent. If we can't 108 // support aliases with that linkage, fail. 109 llvm::GlobalValue::LinkageTypes Linkage 110 = getFunctionLinkage(cast<FunctionDecl>(AliasDecl.getDecl())); 111 112 switch (Linkage) { 113 // We can definitely emit aliases to definitions with external linkage. 114 case llvm::GlobalValue::ExternalLinkage: 115 case llvm::GlobalValue::ExternalWeakLinkage: 116 break; 117 118 // Same with local linkage. 119 case llvm::GlobalValue::InternalLinkage: 120 case llvm::GlobalValue::PrivateLinkage: 121 case llvm::GlobalValue::LinkerPrivateLinkage: 122 break; 123 124 // We should try to support linkonce linkages. 125 case llvm::GlobalValue::LinkOnceAnyLinkage: 126 case llvm::GlobalValue::LinkOnceODRLinkage: 127 return true; 128 129 // Other linkages will probably never be supported. 130 default: 131 return true; 132 } 133 134 llvm::GlobalValue::LinkageTypes TargetLinkage 135 = getFunctionLinkage(cast<FunctionDecl>(TargetDecl.getDecl())); 136 137 if (llvm::GlobalValue::isWeakForLinker(TargetLinkage)) 138 return true; 139 140 // Derive the type for the alias. 141 llvm::PointerType *AliasType 142 = getTypes().GetFunctionType(AliasDecl)->getPointerTo(); 143 144 // Find the referrent. Some aliases might require a bitcast, in 145 // which case the caller is responsible for ensuring the soundness 146 // of these semantics. 147 llvm::GlobalValue *Ref = cast<llvm::GlobalValue>(GetAddrOfGlobal(TargetDecl)); 148 llvm::Constant *Aliasee = Ref; 149 if (Ref->getType() != AliasType) 150 Aliasee = llvm::ConstantExpr::getBitCast(Ref, AliasType); 151 152 // Create the alias with no name. 153 llvm::GlobalAlias *Alias = 154 new llvm::GlobalAlias(AliasType, Linkage, "", Aliasee, &getModule()); 155 156 // Switch any previous uses to the alias. 157 StringRef MangledName = getMangledName(AliasDecl); 158 llvm::GlobalValue *Entry = GetGlobalValue(MangledName); 159 if (Entry) { 160 assert(Entry->isDeclaration() && "definition already exists for alias"); 161 assert(Entry->getType() == AliasType && 162 "declaration exists with different type"); 163 Alias->takeName(Entry); 164 Entry->replaceAllUsesWith(Alias); 165 Entry->eraseFromParent(); 166 } else { 167 Alias->setName(MangledName); 168 } 169 170 // Finally, set up the alias with its proper name and attributes. 171 SetCommonAttributes(cast<NamedDecl>(AliasDecl.getDecl()), Alias); 172 173 return false; 174 } 175 176 void CodeGenModule::EmitCXXConstructors(const CXXConstructorDecl *D) { 177 // The constructor used for constructing this as a complete class; 178 // constucts the virtual bases, then calls the base constructor. 179 if (!D->getParent()->isAbstract()) { 180 // We don't need to emit the complete ctor if the class is abstract. 181 EmitGlobal(GlobalDecl(D, Ctor_Complete)); 182 } 183 184 // The constructor used for constructing this as a base class; 185 // ignores virtual bases. 186 if (getTarget().getCXXABI().hasConstructorVariants()) 187 EmitGlobal(GlobalDecl(D, Ctor_Base)); 188 } 189 190 void CodeGenModule::EmitCXXConstructor(const CXXConstructorDecl *ctor, 191 CXXCtorType ctorType) { 192 // The complete constructor is equivalent to the base constructor 193 // for classes with no virtual bases. Try to emit it as an alias. 194 if (getTarget().getCXXABI().hasConstructorVariants() && 195 ctorType == Ctor_Complete && 196 !ctor->getParent()->getNumVBases() && 197 !TryEmitDefinitionAsAlias(GlobalDecl(ctor, Ctor_Complete), 198 GlobalDecl(ctor, Ctor_Base))) 199 return; 200 201 const CGFunctionInfo &fnInfo = 202 getTypes().arrangeCXXConstructorDeclaration(ctor, ctorType); 203 204 llvm::Function *fn = 205 cast<llvm::Function>(GetAddrOfCXXConstructor(ctor, ctorType, &fnInfo)); 206 setFunctionLinkage(ctor, fn); 207 208 CodeGenFunction(*this).GenerateCode(GlobalDecl(ctor, ctorType), fn, fnInfo); 209 210 SetFunctionDefinitionAttributes(ctor, fn); 211 SetLLVMFunctionAttributesForDefinition(ctor, fn); 212 } 213 214 llvm::GlobalValue * 215 CodeGenModule::GetAddrOfCXXConstructor(const CXXConstructorDecl *ctor, 216 CXXCtorType ctorType, 217 const CGFunctionInfo *fnInfo) { 218 GlobalDecl GD(ctor, ctorType); 219 220 StringRef name = getMangledName(GD); 221 if (llvm::GlobalValue *existing = GetGlobalValue(name)) 222 return existing; 223 224 if (!fnInfo) 225 fnInfo = &getTypes().arrangeCXXConstructorDeclaration(ctor, ctorType); 226 227 llvm::FunctionType *fnType = getTypes().GetFunctionType(*fnInfo); 228 return cast<llvm::Function>(GetOrCreateLLVMFunction(name, fnType, GD, 229 /*ForVTable=*/false)); 230 } 231 232 void CodeGenModule::EmitCXXDestructors(const CXXDestructorDecl *D) { 233 // The destructor in a virtual table is always a 'deleting' 234 // destructor, which calls the complete destructor and then uses the 235 // appropriate operator delete. 236 if (D->isVirtual()) 237 EmitGlobal(GlobalDecl(D, Dtor_Deleting)); 238 239 // The destructor used for destructing this as a most-derived class; 240 // call the base destructor and then destructs any virtual bases. 241 EmitGlobal(GlobalDecl(D, Dtor_Complete)); 242 243 // The destructor used for destructing this as a base class; ignores 244 // virtual bases. 245 EmitGlobal(GlobalDecl(D, Dtor_Base)); 246 } 247 248 void CodeGenModule::EmitCXXDestructor(const CXXDestructorDecl *dtor, 249 CXXDtorType dtorType) { 250 // The complete destructor is equivalent to the base destructor for 251 // classes with no virtual bases, so try to emit it as an alias. 252 if (dtorType == Dtor_Complete && 253 !dtor->getParent()->getNumVBases() && 254 !TryEmitDefinitionAsAlias(GlobalDecl(dtor, Dtor_Complete), 255 GlobalDecl(dtor, Dtor_Base))) 256 return; 257 258 // The base destructor is equivalent to the base destructor of its 259 // base class if there is exactly one non-virtual base class with a 260 // non-trivial destructor, there are no fields with a non-trivial 261 // destructor, and the body of the destructor is trivial. 262 if (dtorType == Dtor_Base && !TryEmitBaseDestructorAsAlias(dtor)) 263 return; 264 265 const CGFunctionInfo &fnInfo = 266 getTypes().arrangeCXXDestructor(dtor, dtorType); 267 268 llvm::Function *fn = 269 cast<llvm::Function>(GetAddrOfCXXDestructor(dtor, dtorType, &fnInfo)); 270 setFunctionLinkage(dtor, fn); 271 272 CodeGenFunction(*this).GenerateCode(GlobalDecl(dtor, dtorType), fn, fnInfo); 273 274 SetFunctionDefinitionAttributes(dtor, fn); 275 SetLLVMFunctionAttributesForDefinition(dtor, fn); 276 } 277 278 llvm::GlobalValue * 279 CodeGenModule::GetAddrOfCXXDestructor(const CXXDestructorDecl *dtor, 280 CXXDtorType dtorType, 281 const CGFunctionInfo *fnInfo) { 282 GlobalDecl GD(dtor, dtorType); 283 284 StringRef name = getMangledName(GD); 285 if (llvm::GlobalValue *existing = GetGlobalValue(name)) 286 return existing; 287 288 if (!fnInfo) fnInfo = &getTypes().arrangeCXXDestructor(dtor, dtorType); 289 290 llvm::FunctionType *fnType = getTypes().GetFunctionType(*fnInfo); 291 return cast<llvm::Function>(GetOrCreateLLVMFunction(name, fnType, GD, 292 /*ForVTable=*/false)); 293 } 294 295 static llvm::Value *BuildVirtualCall(CodeGenFunction &CGF, uint64_t VTableIndex, 296 llvm::Value *This, llvm::Type *Ty) { 297 Ty = Ty->getPointerTo()->getPointerTo(); 298 299 llvm::Value *VTable = CGF.GetVTablePtr(This, Ty); 300 llvm::Value *VFuncPtr = 301 CGF.Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfn"); 302 return CGF.Builder.CreateLoad(VFuncPtr); 303 } 304 305 llvm::Value * 306 CodeGenFunction::BuildVirtualCall(const CXXMethodDecl *MD, llvm::Value *This, 307 llvm::Type *Ty) { 308 MD = MD->getCanonicalDecl(); 309 uint64_t VTableIndex = CGM.getVTableContext().getMethodVTableIndex(MD); 310 311 return ::BuildVirtualCall(*this, VTableIndex, This, Ty); 312 } 313 314 /// BuildVirtualCall - This routine is to support gcc's kext ABI making 315 /// indirect call to virtual functions. It makes the call through indexing 316 /// into the vtable. 317 llvm::Value * 318 CodeGenFunction::BuildAppleKextVirtualCall(const CXXMethodDecl *MD, 319 NestedNameSpecifier *Qual, 320 llvm::Type *Ty) { 321 llvm::Value *VTable = 0; 322 assert((Qual->getKind() == NestedNameSpecifier::TypeSpec) && 323 "BuildAppleKextVirtualCall - bad Qual kind"); 324 325 const Type *QTy = Qual->getAsType(); 326 QualType T = QualType(QTy, 0); 327 const RecordType *RT = T->getAs<RecordType>(); 328 assert(RT && "BuildAppleKextVirtualCall - Qual type must be record"); 329 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 330 331 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) 332 return BuildAppleKextVirtualDestructorCall(DD, Dtor_Complete, RD); 333 334 VTable = CGM.getVTables().GetAddrOfVTable(RD); 335 Ty = Ty->getPointerTo()->getPointerTo(); 336 VTable = Builder.CreateBitCast(VTable, Ty); 337 assert(VTable && "BuildVirtualCall = kext vtbl pointer is null"); 338 MD = MD->getCanonicalDecl(); 339 uint64_t VTableIndex = CGM.getVTableContext().getMethodVTableIndex(MD); 340 uint64_t AddressPoint = 341 CGM.getVTableContext().getVTableLayout(RD) 342 .getAddressPoint(BaseSubobject(RD, CharUnits::Zero())); 343 VTableIndex += AddressPoint; 344 llvm::Value *VFuncPtr = 345 Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfnkxt"); 346 return Builder.CreateLoad(VFuncPtr); 347 } 348 349 /// BuildVirtualCall - This routine makes indirect vtable call for 350 /// call to virtual destructors. It returns 0 if it could not do it. 351 llvm::Value * 352 CodeGenFunction::BuildAppleKextVirtualDestructorCall( 353 const CXXDestructorDecl *DD, 354 CXXDtorType Type, 355 const CXXRecordDecl *RD) { 356 llvm::Value * Callee = 0; 357 const CXXMethodDecl *MD = cast<CXXMethodDecl>(DD); 358 // FIXME. Dtor_Base dtor is always direct!! 359 // It need be somehow inline expanded into the caller. 360 // -O does that. But need to support -O0 as well. 361 if (MD->isVirtual() && Type != Dtor_Base) { 362 // Compute the function type we're calling. 363 const CGFunctionInfo &FInfo = 364 CGM.getTypes().arrangeCXXDestructor(cast<CXXDestructorDecl>(MD), 365 Dtor_Complete); 366 llvm::Type *Ty = CGM.getTypes().GetFunctionType(FInfo); 367 368 llvm::Value *VTable = CGM.getVTables().GetAddrOfVTable(RD); 369 Ty = Ty->getPointerTo()->getPointerTo(); 370 VTable = Builder.CreateBitCast(VTable, Ty); 371 DD = cast<CXXDestructorDecl>(DD->getCanonicalDecl()); 372 uint64_t VTableIndex = 373 CGM.getVTableContext().getMethodVTableIndex(GlobalDecl(DD, Type)); 374 uint64_t AddressPoint = 375 CGM.getVTableContext().getVTableLayout(RD) 376 .getAddressPoint(BaseSubobject(RD, CharUnits::Zero())); 377 VTableIndex += AddressPoint; 378 llvm::Value *VFuncPtr = 379 Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfnkxt"); 380 Callee = Builder.CreateLoad(VFuncPtr); 381 } 382 return Callee; 383 } 384 385 llvm::Value * 386 CodeGenFunction::BuildVirtualCall(const CXXDestructorDecl *DD, CXXDtorType Type, 387 llvm::Value *This, llvm::Type *Ty) { 388 DD = cast<CXXDestructorDecl>(DD->getCanonicalDecl()); 389 uint64_t VTableIndex = 390 CGM.getVTableContext().getMethodVTableIndex(GlobalDecl(DD, Type)); 391 392 return ::BuildVirtualCall(*this, VTableIndex, This, Ty); 393 } 394 395
