| //===--- 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 apart. |
| if (getCodeGenOpts().OptimizationLevel == 0) |
| return true; |
| |
| // If sanitizing memory to check for use-after-dtor, do not emit as |
| // an alias, unless this class owns no members. |
| if (getCodeGenOpts().SanitizeMemoryUseAfterDtor && |
| !D->getParent()->field_empty()) |
| 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(); |
| |
| // We are going to instrument this destructor, so give up even if it is |
| // currently empty. |
| if (Class->mayInsertExtraPadding()) |
| return true; |
| |
| // 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 (const auto *I : Class->fields()) |
| if (I->getType().isDestructedType()) |
| return true; |
| |
| // Try to find a unique base class with a non-trivial destructor. |
| const CXXRecordDecl *UniqueBase = nullptr; |
| for (const auto &I : Class->bases()) { |
| |
| // We're in the base destructor, so skip virtual bases. |
| if (I.isVirtual()) continue; |
| |
| // Skip base classes with trivial destructors. |
| const auto *Base = |
| cast<CXXRecordDecl>(I.getType()->getAs<RecordType>()->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; |
| |
| // Give up if the calling conventions don't match. We could update the call, |
| // but it is probably not worth it. |
| const CXXDestructorDecl *BaseD = UniqueBase->getDestructor(); |
| if (BaseD->getType()->getAs<FunctionType>()->getCallConv() != |
| D->getType()->getAs<FunctionType>()->getCallConv()) |
| return true; |
| |
| GlobalDecl AliasDecl(D, Dtor_Base); |
| GlobalDecl TargetDecl(BaseD, Dtor_Base); |
| |
| // The alias will use the linkage of the referent. 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::Type *AliasValueType = getTypes().GetFunctionType(AliasDecl); |
| llvm::PointerType *AliasType = AliasValueType->getPointerTo(); |
| |
| // Find the referent. Some aliases might require a bitcast, in |
| // which case the caller is responsible for ensuring the soundness |
| // of these semantics. |
| auto *Ref = cast<llvm::GlobalValue>(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 aliasee. |
| if (llvm::GlobalValue::isDiscardableIfUnused(Linkage) && |
| !(TargetLinkage == llvm::GlobalValue::AvailableExternallyLinkage && |
| TargetDecl.getDecl()->hasAttr<AlwaysInlineAttr>())) { |
| // FIXME: An extern template instantiation 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. |
| addReplacement(MangledName, Aliasee); |
| return false; |
| } |
| |
| // If we have a weak, non-discardable alias (weak, weak_odr), like an extern |
| // template instantiation or a dllexported class, avoid forming it on COFF. |
| // A COFF weak external alias cannot satisfy a normal undefined symbol |
| // reference from another TU. The other TU must also mark the referenced |
| // symbol as weak, which we cannot rely on. |
| if (llvm::GlobalValue::isWeakForLinker(Linkage) && |
| getTriple().isOSBinFormatCOFF()) { |
| return true; |
| } |
| |
| // If we don't have a definition for the destructor yet or the definition is |
| // avaialable_externally, don't emit an alias. We can't emit aliases to |
| // declarations; that's just not how aliases work. |
| if (Ref->isDeclarationForLinker()) |
| 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. |
| auto *Alias = llvm::GlobalAlias::create(AliasValueType, 0, Linkage, "", |
| Aliasee, &getModule()); |
| |
| // Destructors are always unnamed_addr. |
| Alias->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global); |
| |
| // 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(AliasDecl, Alias); |
| |
| return false; |
| } |
| |
| llvm::Function *CodeGenModule::codegenCXXStructor(const CXXMethodDecl *MD, |
| StructorType Type) { |
| const CGFunctionInfo &FnInfo = |
| getTypes().arrangeCXXStructorDeclaration(MD, Type); |
| auto *Fn = cast<llvm::Function>( |
| getAddrOfCXXStructor(MD, Type, &FnInfo, /*FnType=*/nullptr, |
| /*DontDefer=*/true, ForDefinition)); |
| |
| GlobalDecl GD; |
| if (const auto *DD = dyn_cast<CXXDestructorDecl>(MD)) { |
| GD = GlobalDecl(DD, toCXXDtorType(Type)); |
| } else { |
| const auto *CD = cast<CXXConstructorDecl>(MD); |
| GD = GlobalDecl(CD, toCXXCtorType(Type)); |
| } |
| |
| setFunctionLinkage(GD, Fn); |
| |
| CodeGenFunction(*this).GenerateCode(GD, Fn, FnInfo); |
| setNonAliasAttributes(GD, Fn); |
| SetLLVMFunctionAttributesForDefinition(MD, Fn); |
| return Fn; |
| } |
| |
| llvm::Constant *CodeGenModule::getAddrOfCXXStructor( |
| const CXXMethodDecl *MD, StructorType Type, const CGFunctionInfo *FnInfo, |
| llvm::FunctionType *FnType, bool DontDefer, |
| ForDefinition_t IsForDefinition) { |
| GlobalDecl GD; |
| if (auto *CD = dyn_cast<CXXConstructorDecl>(MD)) { |
| GD = GlobalDecl(CD, toCXXCtorType(Type)); |
| } else { |
| // Always alias equivalent complete destructors to base destructors in the |
| // MS ABI. |
| if (getTarget().getCXXABI().isMicrosoft() && |
| Type == StructorType::Complete && MD->getParent()->getNumVBases() == 0) |
| Type = StructorType::Base; |
| GD = GlobalDecl(cast<CXXDestructorDecl>(MD), toCXXDtorType(Type)); |
| } |
| |
| if (!FnType) { |
| if (!FnInfo) |
| FnInfo = &getTypes().arrangeCXXStructorDeclaration(MD, Type); |
| FnType = getTypes().GetFunctionType(*FnInfo); |
| } |
| |
| return GetOrCreateLLVMFunction( |
| getMangledName(GD), FnType, GD, /*ForVTable=*/false, DontDefer, |
| /*isThunk=*/false, /*ExtraAttrs=*/llvm::AttributeList(), IsForDefinition); |
| } |
| |
| static CGCallee BuildAppleKextVirtualCall(CodeGenFunction &CGF, |
| GlobalDecl GD, |
| llvm::Type *Ty, |
| const CXXRecordDecl *RD) { |
| assert(!CGF.CGM.getTarget().getCXXABI().isMicrosoft() && |
| "No kext in Microsoft ABI"); |
| 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); |
| const VTableLayout &VTLayout = CGM.getItaniumVTableContext().getVTableLayout(RD); |
| VTableLayout::AddressPointLocation AddressPoint = |
| VTLayout.getAddressPoint(BaseSubobject(RD, CharUnits::Zero())); |
| VTableIndex += VTLayout.getVTableOffset(AddressPoint.VTableIndex) + |
| AddressPoint.AddressPointIndex; |
| llvm::Value *VFuncPtr = |
| CGF.Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfnkxt"); |
| llvm::Value *VFunc = |
| CGF.Builder.CreateAlignedLoad(VFuncPtr, CGF.PointerAlignInBytes); |
| CGCallee Callee(GD.getDecl()->getCanonicalDecl(), VFunc); |
| return Callee; |
| } |
| |
| /// 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. |
| CGCallee |
| 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<RecordType>(); |
| assert(RT && "BuildAppleKextVirtualCall - Qual type must be record"); |
| const auto *RD = cast<CXXRecordDecl>(RT->getDecl()); |
| |
| if (const auto *DD = dyn_cast<CXXDestructorDecl>(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. |
| CGCallee |
| CodeGenFunction::BuildAppleKextVirtualDestructorCall( |
| const CXXDestructorDecl *DD, |
| CXXDtorType Type, |
| const CXXRecordDecl *RD) { |
| assert(DD->isVirtual() && Type != Dtor_Base); |
| // Compute the function type we're calling. |
| const CGFunctionInfo &FInfo = CGM.getTypes().arrangeCXXStructorDeclaration( |
| DD, StructorType::Complete); |
| llvm::Type *Ty = CGM.getTypes().GetFunctionType(FInfo); |
| return ::BuildAppleKextVirtualCall(*this, GlobalDecl(DD, Type), Ty, RD); |
| } |