319 lines
11 KiB
C++
319 lines
11 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 "CGCXXABI.h"
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#include "CodeGenFunction.h"
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#include "CodeGenModule.h"
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#include "Mangle.h"
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#include "clang/AST/ASTContext.h"
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#include "clang/AST/RecordLayout.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/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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/// Determines whether the given function has a trivial body that does
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/// not require any specific codegen.
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static bool HasTrivialBody(const FunctionDecl *FD) {
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Stmt *S = FD->getBody();
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if (!S)
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return true;
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if (isa<CompoundStmt>(S) && cast<CompoundStmt>(S)->body_empty())
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return true;
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return false;
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}
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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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// If the destructor doesn't have a trivial body, we have to emit it
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// separately.
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if (!HasTrivialBody(D))
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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 fields have a non-trivial destructor, we have to emit it
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// 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 (const RecordType *RT = (*I)->getType()->getAs<RecordType>())
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if (!cast<CXXRecordDecl>(RT->getDecl())->hasTrivialDestructor())
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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 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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const CXXDestructorDecl *BaseD = UniqueBase->getDestructor();
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if (!BaseD->isImplicit() && !BaseD->hasBody())
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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.getBaseClassOffsetInBits(UniqueBase) != 0)
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return true;
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return TryEmitDefinitionAsAlias(GlobalDecl(D, Dtor_Base),
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GlobalDecl(BaseD, Dtor_Base));
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}
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/// Try to emit a definition as a global alias for another definition.
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bool CodeGenModule::TryEmitDefinitionAsAlias(GlobalDecl AliasDecl,
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GlobalDecl TargetDecl) {
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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
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= getFunctionLinkage(cast<FunctionDecl>(AliasDecl.getDecl()));
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switch (Linkage) {
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// We can definitely emit aliases to definitions with external linkage.
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case llvm::GlobalValue::ExternalLinkage:
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case llvm::GlobalValue::ExternalWeakLinkage:
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break;
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// Same with local linkage.
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case llvm::GlobalValue::InternalLinkage:
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case llvm::GlobalValue::PrivateLinkage:
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case llvm::GlobalValue::LinkerPrivateLinkage:
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break;
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// We should try to support linkonce linkages.
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case llvm::GlobalValue::LinkOnceAnyLinkage:
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case llvm::GlobalValue::LinkOnceODRLinkage:
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return true;
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// Other linkages will probably never be supported.
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default:
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return true;
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}
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llvm::GlobalValue::LinkageTypes TargetLinkage
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= getFunctionLinkage(cast<FunctionDecl>(TargetDecl.getDecl()));
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if (llvm::GlobalValue::isWeakForLinker(TargetLinkage))
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return true;
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// Derive the type for the alias.
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const 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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// 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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llvm::StringRef MangledName = getMangledName(AliasDecl);
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llvm::GlobalValue *Entry = GetGlobalValue(MangledName);
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if (Entry) {
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assert(Entry->isDeclaration() && "definition already exists for alias");
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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::EmitCXXConstructors(const CXXConstructorDecl *D) {
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// The constructor used for constructing this as a complete class;
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// constucts the virtual bases, then calls the base constructor.
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EmitGlobal(GlobalDecl(D, Ctor_Complete));
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// The constructor used for constructing this as a base class;
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// ignores virtual bases.
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EmitGlobal(GlobalDecl(D, Ctor_Base));
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}
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void CodeGenModule::EmitCXXConstructor(const CXXConstructorDecl *D,
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CXXCtorType Type) {
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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 (Type == Ctor_Complete &&
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!D->getParent()->getNumVBases() &&
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!TryEmitDefinitionAsAlias(GlobalDecl(D, Ctor_Complete),
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GlobalDecl(D, Ctor_Base)))
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return;
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llvm::Function *Fn = cast<llvm::Function>(GetAddrOfCXXConstructor(D, Type));
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setFunctionLinkage(D, Fn);
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CodeGenFunction(*this).GenerateCode(GlobalDecl(D, Type), Fn);
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SetFunctionDefinitionAttributes(D, Fn);
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SetLLVMFunctionAttributesForDefinition(D, Fn);
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}
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llvm::GlobalValue *
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CodeGenModule::GetAddrOfCXXConstructor(const CXXConstructorDecl *D,
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CXXCtorType Type) {
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GlobalDecl GD(D, Type);
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llvm::StringRef Name = getMangledName(GD);
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if (llvm::GlobalValue *V = GetGlobalValue(Name))
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return V;
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const FunctionProtoType *FPT = D->getType()->getAs<FunctionProtoType>();
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const llvm::FunctionType *FTy =
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getTypes().GetFunctionType(getTypes().getFunctionInfo(D, Type),
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FPT->isVariadic());
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return cast<llvm::Function>(GetOrCreateLLVMFunction(Name, FTy, GD));
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}
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void CodeGenModule::EmitCXXDestructors(const CXXDestructorDecl *D) {
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// The destructor in a virtual table is always a 'deleting'
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// destructor, which calls the complete destructor and then uses the
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// appropriate operator delete.
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if (D->isVirtual())
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EmitGlobal(GlobalDecl(D, Dtor_Deleting));
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// The destructor used for destructing this as a most-derived class;
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// call the base destructor and then destructs any virtual bases.
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EmitGlobal(GlobalDecl(D, Dtor_Complete));
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// The destructor used for destructing this as a base class; ignores
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// virtual bases.
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EmitGlobal(GlobalDecl(D, Dtor_Base));
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}
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void CodeGenModule::EmitCXXDestructor(const CXXDestructorDecl *D,
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CXXDtorType Type) {
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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 (Type == Dtor_Complete &&
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!D->getParent()->getNumVBases() &&
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!TryEmitDefinitionAsAlias(GlobalDecl(D, Dtor_Complete),
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GlobalDecl(D, Dtor_Base)))
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return;
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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 (Type == Dtor_Base && !TryEmitBaseDestructorAsAlias(D))
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return;
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llvm::Function *Fn = cast<llvm::Function>(GetAddrOfCXXDestructor(D, Type));
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setFunctionLinkage(D, Fn);
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CodeGenFunction(*this).GenerateCode(GlobalDecl(D, Type), Fn);
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SetFunctionDefinitionAttributes(D, Fn);
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SetLLVMFunctionAttributesForDefinition(D, Fn);
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}
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llvm::GlobalValue *
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CodeGenModule::GetAddrOfCXXDestructor(const CXXDestructorDecl *D,
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CXXDtorType Type) {
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GlobalDecl GD(D, Type);
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llvm::StringRef Name = getMangledName(GD);
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if (llvm::GlobalValue *V = GetGlobalValue(Name))
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return V;
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const llvm::FunctionType *FTy =
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getTypes().GetFunctionType(getTypes().getFunctionInfo(D, Type), false);
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return cast<llvm::Function>(GetOrCreateLLVMFunction(Name, FTy, GD));
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}
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static llvm::Value *BuildVirtualCall(CodeGenFunction &CGF, uint64_t VTableIndex,
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llvm::Value *This, const llvm::Type *Ty) {
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Ty = Ty->getPointerTo()->getPointerTo();
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llvm::Value *VTable = CGF.GetVTablePtr(This, Ty);
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llvm::Value *VFuncPtr =
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CGF.Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfn");
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return CGF.Builder.CreateLoad(VFuncPtr);
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}
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llvm::Value *
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CodeGenFunction::BuildVirtualCall(const CXXMethodDecl *MD, llvm::Value *This,
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const llvm::Type *Ty) {
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MD = MD->getCanonicalDecl();
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uint64_t VTableIndex = CGM.getVTables().getMethodVTableIndex(MD);
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return ::BuildVirtualCall(*this, VTableIndex, This, Ty);
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}
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llvm::Value *
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CodeGenFunction::BuildVirtualCall(const CXXDestructorDecl *DD, CXXDtorType Type,
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llvm::Value *This, const llvm::Type *Ty) {
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DD = cast<CXXDestructorDecl>(DD->getCanonicalDecl());
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uint64_t VTableIndex =
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CGM.getVTables().getMethodVTableIndex(GlobalDecl(DD, Type));
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return ::BuildVirtualCall(*this, VTableIndex, This, Ty);
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}
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