//===--- CGCXX.cpp - Emit LLVM Code for declarations ----------------------===// // // The LLVM Compiler Infrastructure // // This file is distributed under the University of Illinois Open Source // License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This contains code dealing with C++ code generation. // //===----------------------------------------------------------------------===// // We might split this into multiple files if it gets too unwieldy #include "CodeGenModule.h" #include "CGCXXABI.h" #include "CodeGenFunction.h" #include "clang/AST/ASTContext.h" #include "clang/AST/Decl.h" #include "clang/AST/DeclCXX.h" #include "clang/AST/DeclObjC.h" #include "clang/AST/Mangle.h" #include "clang/AST/RecordLayout.h" #include "clang/AST/StmtCXX.h" #include "clang/Frontend/CodeGenOptions.h" #include "llvm/ADT/StringExtras.h" using namespace clang; using namespace CodeGen; /// Try to emit a base destructor as an alias to its primary /// base-class destructor. bool CodeGenModule::TryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D) { if (!getCodeGenOpts().CXXCtorDtorAliases) return true; // Producing an alias to a base class ctor/dtor can degrade debug quality // as the debugger cannot tell them appart. if (getCodeGenOpts().OptimizationLevel == 0) return true; // If the destructor doesn't have a trivial body, we have to emit it // separately. if (!D->hasTrivialBody()) return true; const CXXRecordDecl *Class = D->getParent(); // If we need to manipulate a VTT parameter, give up. if (Class->getNumVBases()) { // Extra Credit: passing extra parameters is perfectly safe // in many calling conventions, so only bail out if the ctor's // calling convention is nonstandard. return true; } // If any field has a non-trivial destructor, we have to emit the // destructor separately. for (CXXRecordDecl::field_iterator I = Class->field_begin(), E = Class->field_end(); I != E; ++I) if (I->getType().isDestructedType()) return true; // Try to find a unique base class with a non-trivial destructor. const CXXRecordDecl *UniqueBase = 0; for (CXXRecordDecl::base_class_const_iterator I = Class->bases_begin(), E = Class->bases_end(); I != E; ++I) { // We're in the base destructor, so skip virtual bases. if (I->isVirtual()) continue; // Skip base classes with trivial destructors. const CXXRecordDecl *Base = cast(I->getType()->getAs()->getDecl()); if (Base->hasTrivialDestructor()) continue; // If we've already found a base class with a non-trivial // destructor, give up. if (UniqueBase) return true; UniqueBase = Base; } // If we didn't find any bases with a non-trivial destructor, then // the base destructor is actually effectively trivial, which can // happen if it was needlessly user-defined or if there are virtual // bases with non-trivial destructors. if (!UniqueBase) return true; // If the base is at a non-zero offset, give up. const ASTRecordLayout &ClassLayout = Context.getASTRecordLayout(Class); if (!ClassLayout.getBaseClassOffset(UniqueBase).isZero()) return true; const CXXDestructorDecl *BaseD = UniqueBase->getDestructor(); return TryEmitDefinitionAsAlias(GlobalDecl(D, Dtor_Base), GlobalDecl(BaseD, Dtor_Base), false); } /// Try to emit a definition as a global alias for another definition. /// If \p InEveryTU is true, we know that an equivalent alias can be produced /// in every translation unit. bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl, GlobalDecl TargetDecl, bool InEveryTU) { if (!getCodeGenOpts().CXXCtorDtorAliases) return true; // The alias will use the linkage of the referrent. If we can't // support aliases with that linkage, fail. llvm::GlobalValue::LinkageTypes Linkage = getFunctionLinkage(AliasDecl); // We can't use an alias if the linkage is not valid for one. if (!llvm::GlobalAlias::isValidLinkage(Linkage)) return true; llvm::GlobalValue::LinkageTypes TargetLinkage = getFunctionLinkage(TargetDecl); // Check if we have it already. StringRef MangledName = getMangledName(AliasDecl); llvm::GlobalValue *Entry = GetGlobalValue(MangledName); if (Entry && !Entry->isDeclaration()) return false; if (Replacements.count(MangledName)) return false; // Derive the type for the alias. llvm::PointerType *AliasType = getTypes().GetFunctionType(AliasDecl)->getPointerTo(); // Find the referrent. Some aliases might require a bitcast, in // which case the caller is responsible for ensuring the soundness // of these semantics. llvm::GlobalValue *Ref = cast(GetAddrOfGlobal(TargetDecl)); llvm::Constant *Aliasee = Ref; if (Ref->getType() != AliasType) Aliasee = llvm::ConstantExpr::getBitCast(Ref, AliasType); // Instead of creating as alias to a linkonce_odr, replace all of the uses // of the aliassee. if (llvm::GlobalValue::isDiscardableIfUnused(Linkage) && (TargetLinkage != llvm::GlobalValue::AvailableExternallyLinkage || !TargetDecl.getDecl()->hasAttr())) { // FIXME: An extern template instanciation will create functions with // linkage "AvailableExternally". In libc++, some classes also define // members with attribute "AlwaysInline" and expect no reference to // be generated. It is desirable to reenable this optimisation after // corresponding LLVM changes. Replacements[MangledName] = Aliasee; return false; } if (!InEveryTU) { /// If we don't have a definition for the destructor yet, don't /// emit. We can't emit aliases to declarations; that's just not /// how aliases work. if (Ref->isDeclaration()) return true; } // Don't create an alias to a linker weak symbol. This avoids producing // different COMDATs in different TUs. Another option would be to // output the alias both for weak_odr and linkonce_odr, but that // requires explicit comdat support in the IL. if (llvm::GlobalValue::isWeakForLinker(TargetLinkage)) return true; // Create the alias with no name. llvm::GlobalAlias *Alias = new llvm::GlobalAlias(AliasType, Linkage, "", Aliasee, &getModule()); // Switch any previous uses to the alias. if (Entry) { assert(Entry->getType() == AliasType && "declaration exists with different type"); Alias->takeName(Entry); Entry->replaceAllUsesWith(Alias); Entry->eraseFromParent(); } else { Alias->setName(MangledName); } // Finally, set up the alias with its proper name and attributes. SetCommonAttributes(cast(AliasDecl.getDecl()), Alias); return false; } void CodeGenModule::EmitCXXConstructor(const CXXConstructorDecl *ctor, CXXCtorType ctorType) { // The complete constructor is equivalent to the base constructor // for classes with no virtual bases. Try to emit it as an alias. if (getTarget().getCXXABI().hasConstructorVariants() && !ctor->getParent()->getNumVBases() && (ctorType == Ctor_Complete || ctorType == Ctor_Base)) { bool ProducedAlias = !TryEmitDefinitionAsAlias(GlobalDecl(ctor, Ctor_Complete), GlobalDecl(ctor, Ctor_Base), true); if (ctorType == Ctor_Complete && ProducedAlias) return; } const CGFunctionInfo &fnInfo = getTypes().arrangeCXXConstructorDeclaration(ctor, ctorType); llvm::Function *fn = cast(GetAddrOfCXXConstructor(ctor, ctorType, &fnInfo)); setFunctionLinkage(GlobalDecl(ctor, ctorType), fn); CodeGenFunction(*this).GenerateCode(GlobalDecl(ctor, ctorType), fn, fnInfo); SetFunctionDefinitionAttributes(ctor, fn); SetLLVMFunctionAttributesForDefinition(ctor, fn); } llvm::GlobalValue * CodeGenModule::GetAddrOfCXXConstructor(const CXXConstructorDecl *ctor, CXXCtorType ctorType, const CGFunctionInfo *fnInfo) { GlobalDecl GD(ctor, ctorType); StringRef name = getMangledName(GD); if (llvm::GlobalValue *existing = GetGlobalValue(name)) return existing; if (!fnInfo) fnInfo = &getTypes().arrangeCXXConstructorDeclaration(ctor, ctorType); llvm::FunctionType *fnType = getTypes().GetFunctionType(*fnInfo); return cast(GetOrCreateLLVMFunction(name, fnType, GD, /*ForVTable=*/false)); } void CodeGenModule::EmitCXXDestructor(const CXXDestructorDecl *dtor, CXXDtorType dtorType) { // The complete destructor is equivalent to the base destructor for // classes with no virtual bases, so try to emit it as an alias. if (!dtor->getParent()->getNumVBases() && (dtorType == Dtor_Complete || dtorType == Dtor_Base)) { bool ProducedAlias = !TryEmitDefinitionAsAlias(GlobalDecl(dtor, Dtor_Complete), GlobalDecl(dtor, Dtor_Base), true); if (ProducedAlias) { if (dtorType == Dtor_Complete) return; if (dtor->isVirtual()) getVTables().EmitThunks(GlobalDecl(dtor, Dtor_Complete)); } } // The base destructor is equivalent to the base destructor of its // base class if there is exactly one non-virtual base class with a // non-trivial destructor, there are no fields with a non-trivial // destructor, and the body of the destructor is trivial. if (dtorType == Dtor_Base && !TryEmitBaseDestructorAsAlias(dtor)) return; const CGFunctionInfo &fnInfo = getTypes().arrangeCXXDestructor(dtor, dtorType); llvm::Function *fn = cast(GetAddrOfCXXDestructor(dtor, dtorType, &fnInfo)); setFunctionLinkage(GlobalDecl(dtor, dtorType), fn); CodeGenFunction(*this).GenerateCode(GlobalDecl(dtor, dtorType), fn, fnInfo); SetFunctionDefinitionAttributes(dtor, fn); SetLLVMFunctionAttributesForDefinition(dtor, fn); } llvm::GlobalValue * CodeGenModule::GetAddrOfCXXDestructor(const CXXDestructorDecl *dtor, CXXDtorType dtorType, const CGFunctionInfo *fnInfo, llvm::FunctionType *fnType) { GlobalDecl GD(dtor, dtorType); StringRef name = getMangledName(GD); if (llvm::GlobalValue *existing = GetGlobalValue(name)) return existing; if (!fnType) { if (!fnInfo) fnInfo = &getTypes().arrangeCXXDestructor(dtor, dtorType); fnType = getTypes().GetFunctionType(*fnInfo); } return cast(GetOrCreateLLVMFunction(name, fnType, GD, /*ForVTable=*/false)); } static llvm::Value *BuildAppleKextVirtualCall(CodeGenFunction &CGF, GlobalDecl GD, llvm::Type *Ty, const CXXRecordDecl *RD) { assert(!CGF.CGM.getTarget().getCXXABI().isMicrosoft() && "No kext in Microsoft ABI"); GD = GD.getCanonicalDecl(); CodeGenModule &CGM = CGF.CGM; llvm::Value *VTable = CGM.getCXXABI().getAddrOfVTable(RD, CharUnits()); Ty = Ty->getPointerTo()->getPointerTo(); VTable = CGF.Builder.CreateBitCast(VTable, Ty); assert(VTable && "BuildVirtualCall = kext vtbl pointer is null"); uint64_t VTableIndex = CGM.getItaniumVTableContext().getMethodVTableIndex(GD); uint64_t AddressPoint = CGM.getItaniumVTableContext().getVTableLayout(RD) .getAddressPoint(BaseSubobject(RD, CharUnits::Zero())); VTableIndex += AddressPoint; llvm::Value *VFuncPtr = CGF.Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfnkxt"); return CGF.Builder.CreateLoad(VFuncPtr); } /// BuildAppleKextVirtualCall - This routine is to support gcc's kext ABI making /// indirect call to virtual functions. It makes the call through indexing /// into the vtable. llvm::Value * CodeGenFunction::BuildAppleKextVirtualCall(const CXXMethodDecl *MD, NestedNameSpecifier *Qual, llvm::Type *Ty) { assert((Qual->getKind() == NestedNameSpecifier::TypeSpec) && "BuildAppleKextVirtualCall - bad Qual kind"); const Type *QTy = Qual->getAsType(); QualType T = QualType(QTy, 0); const RecordType *RT = T->getAs(); assert(RT && "BuildAppleKextVirtualCall - Qual type must be record"); const CXXRecordDecl *RD = cast(RT->getDecl()); if (const CXXDestructorDecl *DD = dyn_cast(MD)) return BuildAppleKextVirtualDestructorCall(DD, Dtor_Complete, RD); return ::BuildAppleKextVirtualCall(*this, MD, Ty, RD); } /// BuildVirtualCall - This routine makes indirect vtable call for /// call to virtual destructors. It returns 0 if it could not do it. llvm::Value * CodeGenFunction::BuildAppleKextVirtualDestructorCall( const CXXDestructorDecl *DD, CXXDtorType Type, const CXXRecordDecl *RD) { const CXXMethodDecl *MD = cast(DD); // FIXME. Dtor_Base dtor is always direct!! // It need be somehow inline expanded into the caller. // -O does that. But need to support -O0 as well. if (MD->isVirtual() && Type != Dtor_Base) { // Compute the function type we're calling. const CGFunctionInfo &FInfo = CGM.getTypes().arrangeCXXDestructor(DD, Dtor_Complete); llvm::Type *Ty = CGM.getTypes().GetFunctionType(FInfo); return ::BuildAppleKextVirtualCall(*this, GlobalDecl(DD, Type), Ty, RD); } return 0; }