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