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Diffstat (limited to 'contrib/llvm-project/clang/lib/CodeGen/CGCXX.cpp')
| -rw-r--r-- | contrib/llvm-project/clang/lib/CodeGen/CGCXX.cpp | 306 |
1 files changed, 306 insertions, 0 deletions
diff --git a/contrib/llvm-project/clang/lib/CodeGen/CGCXX.cpp b/contrib/llvm-project/clang/lib/CodeGen/CGCXX.cpp new file mode 100644 index 000000000000..6d903a0d09e2 --- /dev/null +++ b/contrib/llvm-project/clang/lib/CodeGen/CGCXX.cpp @@ -0,0 +1,306 @@ +//===--- CGCXX.cpp - Emit LLVM Code for declarations ----------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// 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/Basic/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(GlobalDecl GD) { + const CGFunctionInfo &FnInfo = getTypes().arrangeCXXStructorDeclaration(GD); + auto *Fn = cast<llvm::Function>( + getAddrOfCXXStructor(GD, &FnInfo, /*FnType=*/nullptr, + /*DontDefer=*/true, ForDefinition)); + + setFunctionLinkage(GD, Fn); + + CodeGenFunction(*this).GenerateCode(GD, Fn, FnInfo); + setNonAliasAttributes(GD, Fn); + SetLLVMFunctionAttributesForDefinition(cast<CXXMethodDecl>(GD.getDecl()), Fn); + return Fn; +} + +llvm::FunctionCallee CodeGenModule::getAddrAndTypeOfCXXStructor( + GlobalDecl GD, const CGFunctionInfo *FnInfo, llvm::FunctionType *FnType, + bool DontDefer, ForDefinition_t IsForDefinition) { + auto *MD = cast<CXXMethodDecl>(GD.getDecl()); + + if (isa<CXXDestructorDecl>(MD)) { + // Always alias equivalent complete destructors to base destructors in the + // MS ABI. + if (getTarget().getCXXABI().isMicrosoft() && + GD.getDtorType() == Dtor_Complete && + MD->getParent()->getNumVBases() == 0) + GD = GD.getWithDtorType(Dtor_Base); + } + + if (!FnType) { + if (!FnInfo) + FnInfo = &getTypes().arrangeCXXStructorDeclaration(GD); + FnType = getTypes().GetFunctionType(*FnInfo); + } + + llvm::Constant *Ptr = GetOrCreateLLVMFunction( + getMangledName(GD), FnType, GD, /*ForVTable=*/false, DontDefer, + /*IsThunk=*/false, /*ExtraAttrs=*/llvm::AttributeList(), IsForDefinition); + return {FnType, Ptr}; +} + +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, 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( + GlobalDecl(DD, Dtor_Complete)); + llvm::Type *Ty = CGM.getTypes().GetFunctionType(FInfo); + return ::BuildAppleKextVirtualCall(*this, GlobalDecl(DD, Type), Ty, RD); +} |