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 = getFunctionLinkage(AliasDecl); 110 111 switch (Linkage) { 112 // We can definitely emit aliases to definitions with external linkage. 113 case llvm::GlobalValue::ExternalLinkage: 114 case llvm::GlobalValue::ExternalWeakLinkage: 115 break; 116 117 // Same with local linkage. 118 case llvm::GlobalValue::InternalLinkage: 119 case llvm::GlobalValue::PrivateLinkage: 120 case llvm::GlobalValue::LinkerPrivateLinkage: 121 break; 122 123 // We should try to support linkonce linkages. 124 case llvm::GlobalValue::LinkOnceAnyLinkage: 125 case llvm::GlobalValue::LinkOnceODRLinkage: 126 return true; 127 128 // Other linkages will probably never be supported. 129 default: 130 return true; 131 } 132 133 llvm::GlobalValue::LinkageTypes TargetLinkage 134 = getFunctionLinkage(TargetDecl); 135 136 if (llvm::GlobalValue::isWeakForLinker(TargetLinkage)) 137 return true; 138 139 // Derive the type for the alias. 140 llvm::PointerType *AliasType 141 = getTypes().GetFunctionType(AliasDecl)->getPointerTo(); 142 143 // Find the referrent. Some aliases might require a bitcast, in 144 // which case the caller is responsible for ensuring the soundness 145 // of these semantics. 146 llvm::GlobalValue *Ref = cast<llvm::GlobalValue>(GetAddrOfGlobal(TargetDecl)); 147 llvm::Constant *Aliasee = Ref; 148 if (Ref->getType() != AliasType) 149 Aliasee = llvm::ConstantExpr::getBitCast(Ref, AliasType); 150 151 // Create the alias with no name. 152 llvm::GlobalAlias *Alias = 153 new llvm::GlobalAlias(AliasType, Linkage, "", Aliasee, &getModule()); 154 155 // Switch any previous uses to the alias. 156 StringRef MangledName = getMangledName(AliasDecl); 157 llvm::GlobalValue *Entry = GetGlobalValue(MangledName); 158 if (Entry) { 159 assert(Entry->isDeclaration() && "definition already exists for alias"); 160 assert(Entry->getType() == AliasType && 161 "declaration exists with different type"); 162 Alias->takeName(Entry); 163 Entry->replaceAllUsesWith(Alias); 164 Entry->eraseFromParent(); 165 } else { 166 Alias->setName(MangledName); 167 } 168 169 // Finally, set up the alias with its proper name and attributes. 170 SetCommonAttributes(cast<NamedDecl>(AliasDecl.getDecl()), Alias); 171 172 return false; 173 } 174 175 void CodeGenModule::EmitCXXConstructor(const CXXConstructorDecl *ctor, 176 CXXCtorType ctorType) { 177 // The complete constructor is equivalent to the base constructor 178 // for classes with no virtual bases. Try to emit it as an alias. 179 if (getTarget().getCXXABI().hasConstructorVariants() && 180 ctorType == Ctor_Complete && 181 !ctor->getParent()->getNumVBases() && 182 !TryEmitDefinitionAsAlias(GlobalDecl(ctor, Ctor_Complete), 183 GlobalDecl(ctor, Ctor_Base))) 184 return; 185 186 const CGFunctionInfo &fnInfo = 187 getTypes().arrangeCXXConstructorDeclaration(ctor, ctorType); 188 189 llvm::Function *fn = 190 cast<llvm::Function>(GetAddrOfCXXConstructor(ctor, ctorType, &fnInfo)); 191 setFunctionLinkage(GlobalDecl(ctor, ctorType), fn); 192 193 CodeGenFunction(*this).GenerateCode(GlobalDecl(ctor, ctorType), fn, fnInfo); 194 195 SetFunctionDefinitionAttributes(ctor, fn); 196 SetLLVMFunctionAttributesForDefinition(ctor, fn); 197 } 198 199 llvm::GlobalValue * 200 CodeGenModule::GetAddrOfCXXConstructor(const CXXConstructorDecl *ctor, 201 CXXCtorType ctorType, 202 const CGFunctionInfo *fnInfo) { 203 GlobalDecl GD(ctor, ctorType); 204 205 StringRef name = getMangledName(GD); 206 if (llvm::GlobalValue *existing = GetGlobalValue(name)) 207 return existing; 208 209 if (!fnInfo) 210 fnInfo = &getTypes().arrangeCXXConstructorDeclaration(ctor, ctorType); 211 212 llvm::FunctionType *fnType = getTypes().GetFunctionType(*fnInfo); 213 return cast<llvm::Function>(GetOrCreateLLVMFunction(name, fnType, GD, 214 /*ForVTable=*/false)); 215 } 216 217 void CodeGenModule::EmitCXXDestructor(const CXXDestructorDecl *dtor, 218 CXXDtorType dtorType) { 219 // The complete destructor is equivalent to the base destructor for 220 // classes with no virtual bases, so try to emit it as an alias. 221 if (dtorType == Dtor_Complete && 222 !dtor->getParent()->getNumVBases() && 223 !TryEmitDefinitionAsAlias(GlobalDecl(dtor, Dtor_Complete), 224 GlobalDecl(dtor, Dtor_Base))) 225 return; 226 227 // The base destructor is equivalent to the base destructor of its 228 // base class if there is exactly one non-virtual base class with a 229 // non-trivial destructor, there are no fields with a non-trivial 230 // destructor, and the body of the destructor is trivial. 231 if (dtorType == Dtor_Base && !TryEmitBaseDestructorAsAlias(dtor)) 232 return; 233 234 const CGFunctionInfo &fnInfo = 235 getTypes().arrangeCXXDestructor(dtor, dtorType); 236 237 llvm::Function *fn = 238 cast<llvm::Function>(GetAddrOfCXXDestructor(dtor, dtorType, &fnInfo)); 239 setFunctionLinkage(GlobalDecl(dtor, dtorType), fn); 240 241 CodeGenFunction(*this).GenerateCode(GlobalDecl(dtor, dtorType), fn, fnInfo); 242 243 SetFunctionDefinitionAttributes(dtor, fn); 244 SetLLVMFunctionAttributesForDefinition(dtor, fn); 245 } 246 247 llvm::GlobalValue * 248 CodeGenModule::GetAddrOfCXXDestructor(const CXXDestructorDecl *dtor, 249 CXXDtorType dtorType, 250 const CGFunctionInfo *fnInfo, 251 llvm::FunctionType *fnType) { 252 // If the class has no virtual bases, then the complete and base destructors 253 // are equivalent, for all C++ ABIs supported by clang. We can save on code 254 // size by calling the base dtor directly, especially if we'd have to emit a 255 // thunk otherwise. 256 // FIXME: We should do this for Itanium, after verifying that nothing breaks. 257 if (dtorType == Dtor_Complete && dtor->getParent()->getNumVBases() == 0 && 258 getCXXABI().useThunkForDtorVariant(dtor, Dtor_Complete)) 259 dtorType = Dtor_Base; 260 261 GlobalDecl GD(dtor, dtorType); 262 263 StringRef name = getMangledName(GD); 264 if (llvm::GlobalValue *existing = GetGlobalValue(name)) 265 return existing; 266 267 if (!fnType) { 268 if (!fnInfo) fnInfo = &getTypes().arrangeCXXDestructor(dtor, dtorType); 269 fnType = getTypes().GetFunctionType(*fnInfo); 270 } 271 return cast<llvm::Function>(GetOrCreateLLVMFunction(name, fnType, GD, 272 /*ForVTable=*/false)); 273 } 274 275 llvm::Value * 276 CodeGenFunction::BuildVirtualCall(GlobalDecl GD, llvm::Value *This, 277 llvm::Type *Ty) { 278 GD = GD.getCanonicalDecl(); 279 uint64_t VTableIndex = CGM.getVTableContext().getMethodVTableIndex(GD); 280 281 Ty = Ty->getPointerTo()->getPointerTo(); 282 llvm::Value *VTable = GetVTablePtr(This, Ty); 283 llvm::Value *VFuncPtr = 284 Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfn"); 285 return Builder.CreateLoad(VFuncPtr); 286 } 287 288 static llvm::Value *BuildAppleKextVirtualCall(CodeGenFunction &CGF, 289 GlobalDecl GD, 290 llvm::Type *Ty, 291 const CXXRecordDecl *RD) { 292 GD = GD.getCanonicalDecl(); 293 CodeGenModule &CGM = CGF.CGM; 294 llvm::Value *VTable = CGM.getVTables().GetAddrOfVTable(RD); 295 Ty = Ty->getPointerTo()->getPointerTo(); 296 VTable = CGF.Builder.CreateBitCast(VTable, Ty); 297 assert(VTable && "BuildVirtualCall = kext vtbl pointer is null"); 298 uint64_t VTableIndex = CGM.getVTableContext().getMethodVTableIndex(GD); 299 uint64_t AddressPoint = 300 CGM.getVTableContext().getVTableLayout(RD) 301 .getAddressPoint(BaseSubobject(RD, CharUnits::Zero())); 302 VTableIndex += AddressPoint; 303 llvm::Value *VFuncPtr = 304 CGF.Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfnkxt"); 305 return CGF.Builder.CreateLoad(VFuncPtr); 306 } 307 308 /// BuildAppleKextVirtualCall - This routine is to support gcc's kext ABI making 309 /// indirect call to virtual functions. It makes the call through indexing 310 /// into the vtable. 311 llvm::Value * 312 CodeGenFunction::BuildAppleKextVirtualCall(const CXXMethodDecl *MD, 313 NestedNameSpecifier *Qual, 314 llvm::Type *Ty) { 315 assert((Qual->getKind() == NestedNameSpecifier::TypeSpec) && 316 "BuildAppleKextVirtualCall - bad Qual kind"); 317 318 const Type *QTy = Qual->getAsType(); 319 QualType T = QualType(QTy, 0); 320 const RecordType *RT = T->getAs<RecordType>(); 321 assert(RT && "BuildAppleKextVirtualCall - Qual type must be record"); 322 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl()); 323 324 if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) 325 return BuildAppleKextVirtualDestructorCall(DD, Dtor_Complete, RD); 326 327 return ::BuildAppleKextVirtualCall(*this, MD, Ty, RD); 328 } 329 330 /// BuildVirtualCall - This routine makes indirect vtable call for 331 /// call to virtual destructors. It returns 0 if it could not do it. 332 llvm::Value * 333 CodeGenFunction::BuildAppleKextVirtualDestructorCall( 334 const CXXDestructorDecl *DD, 335 CXXDtorType Type, 336 const CXXRecordDecl *RD) { 337 const CXXMethodDecl *MD = cast<CXXMethodDecl>(DD); 338 // FIXME. Dtor_Base dtor is always direct!! 339 // It need be somehow inline expanded into the caller. 340 // -O does that. But need to support -O0 as well. 341 if (MD->isVirtual() && Type != Dtor_Base) { 342 // Compute the function type we're calling. 343 const CGFunctionInfo &FInfo = 344 CGM.getTypes().arrangeCXXDestructor(DD, Dtor_Complete); 345 llvm::Type *Ty = CGM.getTypes().GetFunctionType(FInfo); 346 return ::BuildAppleKextVirtualCall(*this, GlobalDecl(DD, Type), Ty, RD); 347 } 348 return 0; 349 } 350
