10b57cec5SDimitry Andric //===--- CGCXX.cpp - Emit LLVM Code for declarations ----------------------===//
20b57cec5SDimitry Andric //
30b57cec5SDimitry Andric // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
40b57cec5SDimitry Andric // See https://llvm.org/LICENSE.txt for license information.
50b57cec5SDimitry Andric // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
60b57cec5SDimitry Andric //
70b57cec5SDimitry Andric //===----------------------------------------------------------------------===//
80b57cec5SDimitry Andric //
90b57cec5SDimitry Andric // This contains code dealing with C++ code generation.
100b57cec5SDimitry Andric //
110b57cec5SDimitry Andric //===----------------------------------------------------------------------===//
120b57cec5SDimitry Andric
130b57cec5SDimitry Andric // We might split this into multiple files if it gets too unwieldy
140b57cec5SDimitry Andric
150b57cec5SDimitry Andric #include "CGCXXABI.h"
160b57cec5SDimitry Andric #include "CodeGenFunction.h"
17480093f4SDimitry Andric #include "CodeGenModule.h"
180b57cec5SDimitry Andric #include "clang/AST/ASTContext.h"
19480093f4SDimitry Andric #include "clang/AST/Attr.h"
200b57cec5SDimitry Andric #include "clang/AST/Decl.h"
210b57cec5SDimitry Andric #include "clang/AST/DeclCXX.h"
220b57cec5SDimitry Andric #include "clang/AST/DeclObjC.h"
230b57cec5SDimitry Andric #include "clang/AST/Mangle.h"
240b57cec5SDimitry Andric #include "clang/AST/RecordLayout.h"
250b57cec5SDimitry Andric #include "clang/AST/StmtCXX.h"
260b57cec5SDimitry Andric #include "clang/Basic/CodeGenOptions.h"
270b57cec5SDimitry Andric #include "llvm/ADT/StringExtras.h"
280b57cec5SDimitry Andric using namespace clang;
290b57cec5SDimitry Andric using namespace CodeGen;
300b57cec5SDimitry Andric
310b57cec5SDimitry Andric
320b57cec5SDimitry Andric /// Try to emit a base destructor as an alias to its primary
330b57cec5SDimitry Andric /// base-class destructor.
TryEmitBaseDestructorAsAlias(const CXXDestructorDecl * D)340b57cec5SDimitry Andric bool CodeGenModule::TryEmitBaseDestructorAsAlias(const CXXDestructorDecl *D) {
350b57cec5SDimitry Andric if (!getCodeGenOpts().CXXCtorDtorAliases)
360b57cec5SDimitry Andric return true;
370b57cec5SDimitry Andric
380b57cec5SDimitry Andric // Producing an alias to a base class ctor/dtor can degrade debug quality
390b57cec5SDimitry Andric // as the debugger cannot tell them apart.
400b57cec5SDimitry Andric if (getCodeGenOpts().OptimizationLevel == 0)
410b57cec5SDimitry Andric return true;
420b57cec5SDimitry Andric
437a6dacacSDimitry Andric // Disable this optimization for ARM64EC. FIXME: This probably should work,
447a6dacacSDimitry Andric // but getting the symbol table correct is complicated.
457a6dacacSDimitry Andric if (getTarget().getTriple().isWindowsArm64EC())
467a6dacacSDimitry Andric return true;
477a6dacacSDimitry Andric
480b57cec5SDimitry Andric // If sanitizing memory to check for use-after-dtor, do not emit as
490b57cec5SDimitry Andric // an alias, unless this class owns no members.
500b57cec5SDimitry Andric if (getCodeGenOpts().SanitizeMemoryUseAfterDtor &&
510b57cec5SDimitry Andric !D->getParent()->field_empty())
520b57cec5SDimitry Andric return true;
530b57cec5SDimitry Andric
540b57cec5SDimitry Andric // If the destructor doesn't have a trivial body, we have to emit it
550b57cec5SDimitry Andric // separately.
560b57cec5SDimitry Andric if (!D->hasTrivialBody())
570b57cec5SDimitry Andric return true;
580b57cec5SDimitry Andric
590b57cec5SDimitry Andric const CXXRecordDecl *Class = D->getParent();
600b57cec5SDimitry Andric
610b57cec5SDimitry Andric // We are going to instrument this destructor, so give up even if it is
620b57cec5SDimitry Andric // currently empty.
630b57cec5SDimitry Andric if (Class->mayInsertExtraPadding())
640b57cec5SDimitry Andric return true;
650b57cec5SDimitry Andric
660b57cec5SDimitry Andric // If we need to manipulate a VTT parameter, give up.
670b57cec5SDimitry Andric if (Class->getNumVBases()) {
680b57cec5SDimitry Andric // Extra Credit: passing extra parameters is perfectly safe
690b57cec5SDimitry Andric // in many calling conventions, so only bail out if the ctor's
700b57cec5SDimitry Andric // calling convention is nonstandard.
710b57cec5SDimitry Andric return true;
720b57cec5SDimitry Andric }
730b57cec5SDimitry Andric
740b57cec5SDimitry Andric // If any field has a non-trivial destructor, we have to emit the
750b57cec5SDimitry Andric // destructor separately.
760b57cec5SDimitry Andric for (const auto *I : Class->fields())
770b57cec5SDimitry Andric if (I->getType().isDestructedType())
780b57cec5SDimitry Andric return true;
790b57cec5SDimitry Andric
800b57cec5SDimitry Andric // Try to find a unique base class with a non-trivial destructor.
810b57cec5SDimitry Andric const CXXRecordDecl *UniqueBase = nullptr;
820b57cec5SDimitry Andric for (const auto &I : Class->bases()) {
830b57cec5SDimitry Andric
840b57cec5SDimitry Andric // We're in the base destructor, so skip virtual bases.
850b57cec5SDimitry Andric if (I.isVirtual()) continue;
860b57cec5SDimitry Andric
870b57cec5SDimitry Andric // Skip base classes with trivial destructors.
880b57cec5SDimitry Andric const auto *Base =
89a7dea167SDimitry Andric cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
900b57cec5SDimitry Andric if (Base->hasTrivialDestructor()) continue;
910b57cec5SDimitry Andric
920b57cec5SDimitry Andric // If we've already found a base class with a non-trivial
930b57cec5SDimitry Andric // destructor, give up.
940b57cec5SDimitry Andric if (UniqueBase) return true;
950b57cec5SDimitry Andric UniqueBase = Base;
960b57cec5SDimitry Andric }
970b57cec5SDimitry Andric
980b57cec5SDimitry Andric // If we didn't find any bases with a non-trivial destructor, then
990b57cec5SDimitry Andric // the base destructor is actually effectively trivial, which can
1000b57cec5SDimitry Andric // happen if it was needlessly user-defined or if there are virtual
1010b57cec5SDimitry Andric // bases with non-trivial destructors.
1020b57cec5SDimitry Andric if (!UniqueBase)
1030b57cec5SDimitry Andric return true;
1040b57cec5SDimitry Andric
1050b57cec5SDimitry Andric // If the base is at a non-zero offset, give up.
1060b57cec5SDimitry Andric const ASTRecordLayout &ClassLayout = Context.getASTRecordLayout(Class);
1070b57cec5SDimitry Andric if (!ClassLayout.getBaseClassOffset(UniqueBase).isZero())
1080b57cec5SDimitry Andric return true;
1090b57cec5SDimitry Andric
1100b57cec5SDimitry Andric // Give up if the calling conventions don't match. We could update the call,
1110b57cec5SDimitry Andric // but it is probably not worth it.
1120b57cec5SDimitry Andric const CXXDestructorDecl *BaseD = UniqueBase->getDestructor();
113a7dea167SDimitry Andric if (BaseD->getType()->castAs<FunctionType>()->getCallConv() !=
114a7dea167SDimitry Andric D->getType()->castAs<FunctionType>()->getCallConv())
1150b57cec5SDimitry Andric return true;
1160b57cec5SDimitry Andric
1170b57cec5SDimitry Andric GlobalDecl AliasDecl(D, Dtor_Base);
1180b57cec5SDimitry Andric GlobalDecl TargetDecl(BaseD, Dtor_Base);
1190b57cec5SDimitry Andric
1200b57cec5SDimitry Andric // The alias will use the linkage of the referent. If we can't
1210b57cec5SDimitry Andric // support aliases with that linkage, fail.
1220b57cec5SDimitry Andric llvm::GlobalValue::LinkageTypes Linkage = getFunctionLinkage(AliasDecl);
1230b57cec5SDimitry Andric
1240b57cec5SDimitry Andric // We can't use an alias if the linkage is not valid for one.
1250b57cec5SDimitry Andric if (!llvm::GlobalAlias::isValidLinkage(Linkage))
1260b57cec5SDimitry Andric return true;
1270b57cec5SDimitry Andric
1280b57cec5SDimitry Andric llvm::GlobalValue::LinkageTypes TargetLinkage =
1290b57cec5SDimitry Andric getFunctionLinkage(TargetDecl);
1300b57cec5SDimitry Andric
1310b57cec5SDimitry Andric // Check if we have it already.
1320b57cec5SDimitry Andric StringRef MangledName = getMangledName(AliasDecl);
1330b57cec5SDimitry Andric llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
1340b57cec5SDimitry Andric if (Entry && !Entry->isDeclaration())
1350b57cec5SDimitry Andric return false;
1360b57cec5SDimitry Andric if (Replacements.count(MangledName))
1370b57cec5SDimitry Andric return false;
1380b57cec5SDimitry Andric
1390b57cec5SDimitry Andric llvm::Type *AliasValueType = getTypes().GetFunctionType(AliasDecl);
1400b57cec5SDimitry Andric
14106c3fb27SDimitry Andric // Find the referent.
14206c3fb27SDimitry Andric auto *Aliasee = cast<llvm::GlobalValue>(GetAddrOfGlobal(TargetDecl));
1430b57cec5SDimitry Andric
1440b57cec5SDimitry Andric // Instead of creating as alias to a linkonce_odr, replace all of the uses
1450b57cec5SDimitry Andric // of the aliasee.
1460b57cec5SDimitry Andric if (llvm::GlobalValue::isDiscardableIfUnused(Linkage) &&
1470b57cec5SDimitry Andric !(TargetLinkage == llvm::GlobalValue::AvailableExternallyLinkage &&
1480b57cec5SDimitry Andric TargetDecl.getDecl()->hasAttr<AlwaysInlineAttr>())) {
1490b57cec5SDimitry Andric // FIXME: An extern template instantiation will create functions with
1500b57cec5SDimitry Andric // linkage "AvailableExternally". In libc++, some classes also define
1510b57cec5SDimitry Andric // members with attribute "AlwaysInline" and expect no reference to
1520b57cec5SDimitry Andric // be generated. It is desirable to reenable this optimisation after
1530b57cec5SDimitry Andric // corresponding LLVM changes.
1540b57cec5SDimitry Andric addReplacement(MangledName, Aliasee);
1550b57cec5SDimitry Andric return false;
1560b57cec5SDimitry Andric }
1570b57cec5SDimitry Andric
1580b57cec5SDimitry Andric // If we have a weak, non-discardable alias (weak, weak_odr), like an extern
1590b57cec5SDimitry Andric // template instantiation or a dllexported class, avoid forming it on COFF.
1600b57cec5SDimitry Andric // A COFF weak external alias cannot satisfy a normal undefined symbol
1610b57cec5SDimitry Andric // reference from another TU. The other TU must also mark the referenced
1620b57cec5SDimitry Andric // symbol as weak, which we cannot rely on.
1630b57cec5SDimitry Andric if (llvm::GlobalValue::isWeakForLinker(Linkage) &&
1640b57cec5SDimitry Andric getTriple().isOSBinFormatCOFF()) {
1650b57cec5SDimitry Andric return true;
1660b57cec5SDimitry Andric }
1670b57cec5SDimitry Andric
1680b57cec5SDimitry Andric // If we don't have a definition for the destructor yet or the definition is
1690b57cec5SDimitry Andric // avaialable_externally, don't emit an alias. We can't emit aliases to
1700b57cec5SDimitry Andric // declarations; that's just not how aliases work.
17106c3fb27SDimitry Andric if (Aliasee->isDeclarationForLinker())
1720b57cec5SDimitry Andric return true;
1730b57cec5SDimitry Andric
1740b57cec5SDimitry Andric // Don't create an alias to a linker weak symbol. This avoids producing
1750b57cec5SDimitry Andric // different COMDATs in different TUs. Another option would be to
1760b57cec5SDimitry Andric // output the alias both for weak_odr and linkonce_odr, but that
1770b57cec5SDimitry Andric // requires explicit comdat support in the IL.
1780b57cec5SDimitry Andric if (llvm::GlobalValue::isWeakForLinker(TargetLinkage))
1790b57cec5SDimitry Andric return true;
1800b57cec5SDimitry Andric
1810b57cec5SDimitry Andric // Create the alias with no name.
1820b57cec5SDimitry Andric auto *Alias = llvm::GlobalAlias::create(AliasValueType, 0, Linkage, "",
1830b57cec5SDimitry Andric Aliasee, &getModule());
1840b57cec5SDimitry Andric
1850b57cec5SDimitry Andric // Destructors are always unnamed_addr.
1860b57cec5SDimitry Andric Alias->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
1870b57cec5SDimitry Andric
1880b57cec5SDimitry Andric // Switch any previous uses to the alias.
1890b57cec5SDimitry Andric if (Entry) {
19006c3fb27SDimitry Andric assert(Entry->getValueType() == AliasValueType &&
19106c3fb27SDimitry Andric Entry->getAddressSpace() == Alias->getAddressSpace() &&
1920b57cec5SDimitry Andric "declaration exists with different type");
1930b57cec5SDimitry Andric Alias->takeName(Entry);
1940b57cec5SDimitry Andric Entry->replaceAllUsesWith(Alias);
1950b57cec5SDimitry Andric Entry->eraseFromParent();
1960b57cec5SDimitry Andric } else {
1970b57cec5SDimitry Andric Alias->setName(MangledName);
1980b57cec5SDimitry Andric }
1990b57cec5SDimitry Andric
2000b57cec5SDimitry Andric // Finally, set up the alias with its proper name and attributes.
2010b57cec5SDimitry Andric SetCommonAttributes(AliasDecl, Alias);
2020b57cec5SDimitry Andric
2030b57cec5SDimitry Andric return false;
2040b57cec5SDimitry Andric }
2050b57cec5SDimitry Andric
codegenCXXStructor(GlobalDecl GD)2060b57cec5SDimitry Andric llvm::Function *CodeGenModule::codegenCXXStructor(GlobalDecl GD) {
2070b57cec5SDimitry Andric const CGFunctionInfo &FnInfo = getTypes().arrangeCXXStructorDeclaration(GD);
2080b57cec5SDimitry Andric auto *Fn = cast<llvm::Function>(
2090b57cec5SDimitry Andric getAddrOfCXXStructor(GD, &FnInfo, /*FnType=*/nullptr,
2100b57cec5SDimitry Andric /*DontDefer=*/true, ForDefinition));
2110b57cec5SDimitry Andric
2120b57cec5SDimitry Andric setFunctionLinkage(GD, Fn);
2130b57cec5SDimitry Andric
2140b57cec5SDimitry Andric CodeGenFunction(*this).GenerateCode(GD, Fn, FnInfo);
2150b57cec5SDimitry Andric setNonAliasAttributes(GD, Fn);
2160b57cec5SDimitry Andric SetLLVMFunctionAttributesForDefinition(cast<CXXMethodDecl>(GD.getDecl()), Fn);
2170b57cec5SDimitry Andric return Fn;
2180b57cec5SDimitry Andric }
2190b57cec5SDimitry Andric
getAddrAndTypeOfCXXStructor(GlobalDecl GD,const CGFunctionInfo * FnInfo,llvm::FunctionType * FnType,bool DontDefer,ForDefinition_t IsForDefinition)2200b57cec5SDimitry Andric llvm::FunctionCallee CodeGenModule::getAddrAndTypeOfCXXStructor(
2210b57cec5SDimitry Andric GlobalDecl GD, const CGFunctionInfo *FnInfo, llvm::FunctionType *FnType,
2220b57cec5SDimitry Andric bool DontDefer, ForDefinition_t IsForDefinition) {
2230b57cec5SDimitry Andric auto *MD = cast<CXXMethodDecl>(GD.getDecl());
2240b57cec5SDimitry Andric
2250b57cec5SDimitry Andric if (isa<CXXDestructorDecl>(MD)) {
2260b57cec5SDimitry Andric // Always alias equivalent complete destructors to base destructors in the
2270b57cec5SDimitry Andric // MS ABI.
2280b57cec5SDimitry Andric if (getTarget().getCXXABI().isMicrosoft() &&
2290b57cec5SDimitry Andric GD.getDtorType() == Dtor_Complete &&
2300b57cec5SDimitry Andric MD->getParent()->getNumVBases() == 0)
2310b57cec5SDimitry Andric GD = GD.getWithDtorType(Dtor_Base);
2320b57cec5SDimitry Andric }
2330b57cec5SDimitry Andric
2340b57cec5SDimitry Andric if (!FnType) {
2350b57cec5SDimitry Andric if (!FnInfo)
2360b57cec5SDimitry Andric FnInfo = &getTypes().arrangeCXXStructorDeclaration(GD);
2370b57cec5SDimitry Andric FnType = getTypes().GetFunctionType(*FnInfo);
2380b57cec5SDimitry Andric }
2390b57cec5SDimitry Andric
2400b57cec5SDimitry Andric llvm::Constant *Ptr = GetOrCreateLLVMFunction(
2410b57cec5SDimitry Andric getMangledName(GD), FnType, GD, /*ForVTable=*/false, DontDefer,
2420b57cec5SDimitry Andric /*IsThunk=*/false, /*ExtraAttrs=*/llvm::AttributeList(), IsForDefinition);
2430b57cec5SDimitry Andric return {FnType, Ptr};
2440b57cec5SDimitry Andric }
2450b57cec5SDimitry Andric
BuildAppleKextVirtualCall(CodeGenFunction & CGF,GlobalDecl GD,llvm::Type * Ty,const CXXRecordDecl * RD)2460b57cec5SDimitry Andric static CGCallee BuildAppleKextVirtualCall(CodeGenFunction &CGF,
2470b57cec5SDimitry Andric GlobalDecl GD,
2480b57cec5SDimitry Andric llvm::Type *Ty,
2490b57cec5SDimitry Andric const CXXRecordDecl *RD) {
2500b57cec5SDimitry Andric assert(!CGF.CGM.getTarget().getCXXABI().isMicrosoft() &&
2510b57cec5SDimitry Andric "No kext in Microsoft ABI");
2520b57cec5SDimitry Andric CodeGenModule &CGM = CGF.CGM;
2530b57cec5SDimitry Andric llvm::Value *VTable = CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());
25406c3fb27SDimitry Andric Ty = llvm::PointerType::getUnqual(CGM.getLLVMContext());
2550b57cec5SDimitry Andric assert(VTable && "BuildVirtualCall = kext vtbl pointer is null");
2560b57cec5SDimitry Andric uint64_t VTableIndex = CGM.getItaniumVTableContext().getMethodVTableIndex(GD);
2570b57cec5SDimitry Andric const VTableLayout &VTLayout = CGM.getItaniumVTableContext().getVTableLayout(RD);
2580b57cec5SDimitry Andric VTableLayout::AddressPointLocation AddressPoint =
2590b57cec5SDimitry Andric VTLayout.getAddressPoint(BaseSubobject(RD, CharUnits::Zero()));
2600b57cec5SDimitry Andric VTableIndex += VTLayout.getVTableOffset(AddressPoint.VTableIndex) +
2610b57cec5SDimitry Andric AddressPoint.AddressPointIndex;
2620b57cec5SDimitry Andric llvm::Value *VFuncPtr =
263fe6060f1SDimitry Andric CGF.Builder.CreateConstInBoundsGEP1_64(Ty, VTable, VTableIndex, "vfnkxt");
2645ffd83dbSDimitry Andric llvm::Value *VFunc = CGF.Builder.CreateAlignedLoad(
265fe6060f1SDimitry Andric Ty, VFuncPtr, llvm::Align(CGF.PointerAlignInBytes));
2660b57cec5SDimitry Andric CGCallee Callee(GD, VFunc);
2670b57cec5SDimitry Andric return Callee;
2680b57cec5SDimitry Andric }
2690b57cec5SDimitry Andric
2700b57cec5SDimitry Andric /// BuildAppleKextVirtualCall - This routine is to support gcc's kext ABI making
2710b57cec5SDimitry Andric /// indirect call to virtual functions. It makes the call through indexing
2720b57cec5SDimitry Andric /// into the vtable.
2730b57cec5SDimitry Andric CGCallee
BuildAppleKextVirtualCall(const CXXMethodDecl * MD,NestedNameSpecifier * Qual,llvm::Type * Ty)2740b57cec5SDimitry Andric CodeGenFunction::BuildAppleKextVirtualCall(const CXXMethodDecl *MD,
2750b57cec5SDimitry Andric NestedNameSpecifier *Qual,
2760b57cec5SDimitry Andric llvm::Type *Ty) {
2770b57cec5SDimitry Andric assert((Qual->getKind() == NestedNameSpecifier::TypeSpec) &&
2780b57cec5SDimitry Andric "BuildAppleKextVirtualCall - bad Qual kind");
2790b57cec5SDimitry Andric
2800b57cec5SDimitry Andric const Type *QTy = Qual->getAsType();
2810b57cec5SDimitry Andric QualType T = QualType(QTy, 0);
2820b57cec5SDimitry Andric const RecordType *RT = T->getAs<RecordType>();
2830b57cec5SDimitry Andric assert(RT && "BuildAppleKextVirtualCall - Qual type must be record");
2840b57cec5SDimitry Andric const auto *RD = cast<CXXRecordDecl>(RT->getDecl());
2850b57cec5SDimitry Andric
2860b57cec5SDimitry Andric if (const auto *DD = dyn_cast<CXXDestructorDecl>(MD))
2870b57cec5SDimitry Andric return BuildAppleKextVirtualDestructorCall(DD, Dtor_Complete, RD);
2880b57cec5SDimitry Andric
2890b57cec5SDimitry Andric return ::BuildAppleKextVirtualCall(*this, MD, Ty, RD);
2900b57cec5SDimitry Andric }
2910b57cec5SDimitry Andric
2920b57cec5SDimitry Andric /// BuildVirtualCall - This routine makes indirect vtable call for
2930b57cec5SDimitry Andric /// call to virtual destructors. It returns 0 if it could not do it.
2940b57cec5SDimitry Andric CGCallee
BuildAppleKextVirtualDestructorCall(const CXXDestructorDecl * DD,CXXDtorType Type,const CXXRecordDecl * RD)2950b57cec5SDimitry Andric CodeGenFunction::BuildAppleKextVirtualDestructorCall(
2960b57cec5SDimitry Andric const CXXDestructorDecl *DD,
2970b57cec5SDimitry Andric CXXDtorType Type,
2980b57cec5SDimitry Andric const CXXRecordDecl *RD) {
2990b57cec5SDimitry Andric assert(DD->isVirtual() && Type != Dtor_Base);
3000b57cec5SDimitry Andric // Compute the function type we're calling.
3010b57cec5SDimitry Andric const CGFunctionInfo &FInfo = CGM.getTypes().arrangeCXXStructorDeclaration(
3020b57cec5SDimitry Andric GlobalDecl(DD, Dtor_Complete));
3030b57cec5SDimitry Andric llvm::Type *Ty = CGM.getTypes().GetFunctionType(FInfo);
3040b57cec5SDimitry Andric return ::BuildAppleKextVirtualCall(*this, GlobalDecl(DD, Type), Ty, RD);
3050b57cec5SDimitry Andric }
306