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//===--- CGVTT.cpp - Emit LLVM Code for C++ VTTs --------------------------===//
//
// 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 of VTTs (vtable tables).
//
//===----------------------------------------------------------------------===//
#include "CodeGenModule.h"
#include "CGCXXABI.h"
#include "clang/AST/RecordLayout.h"
using namespace clang;
using namespace CodeGen;
#define D1(x)
namespace {
/// VTT builder - Class for building VTT layout information.
class VTTBuilder {
CodeGenModule &CGM;
/// MostDerivedClass - The most derived class for which we're building this
/// vtable.
const CXXRecordDecl *MostDerivedClass;
typedef llvm::SmallVector<llvm::Constant *, 64> VTTComponentsVectorTy;
/// VTTComponents - The VTT components.
VTTComponentsVectorTy VTTComponents;
/// MostDerivedClassLayout - the AST record layout of the most derived class.
const ASTRecordLayout &MostDerivedClassLayout;
typedef llvm::SmallPtrSet<const CXXRecordDecl *, 4> VisitedVirtualBasesSetTy;
typedef llvm::DenseMap<BaseSubobject, uint64_t> AddressPointsMapTy;
/// SubVTTIndicies - The sub-VTT indices for the bases of the most derived
/// class.
llvm::DenseMap<BaseSubobject, uint64_t> SubVTTIndicies;
/// SecondaryVirtualPointerIndices - The secondary virtual pointer indices of
/// all subobjects of the most derived class.
llvm::DenseMap<BaseSubobject, uint64_t> SecondaryVirtualPointerIndices;
/// GenerateDefinition - Whether the VTT builder should generate LLVM IR for
/// the VTT.
bool GenerateDefinition;
/// GetAddrOfVTable - Returns the address of the vtable for the base class in
/// the given vtable class.
///
/// \param AddressPoints - If the returned vtable is a construction vtable,
/// this will hold the address points for it.
llvm::Constant *GetAddrOfVTable(BaseSubobject Base, bool BaseIsVirtual,
AddressPointsMapTy& AddressPoints);
/// AddVTablePointer - Add a vtable pointer to the VTT currently being built.
///
/// \param AddressPoints - If the vtable is a construction vtable, this has
/// the address points for it.
void AddVTablePointer(BaseSubobject Base, llvm::Constant *VTable,
const CXXRecordDecl *VTableClass,
const AddressPointsMapTy& AddressPoints);
/// LayoutSecondaryVTTs - Lay out the secondary VTTs of the given base
/// subobject.
void LayoutSecondaryVTTs(BaseSubobject Base);
/// LayoutSecondaryVirtualPointers - Lay out the secondary virtual pointers
/// for the given base subobject.
///
/// \param BaseIsMorallyVirtual whether the base subobject is a virtual base
/// or a direct or indirect base of a virtual base.
///
/// \param AddressPoints - If the vtable is a construction vtable, this has
/// the address points for it.
void LayoutSecondaryVirtualPointers(BaseSubobject Base,
bool BaseIsMorallyVirtual,
llvm::Constant *VTable,
const CXXRecordDecl *VTableClass,
const AddressPointsMapTy& AddressPoints,
VisitedVirtualBasesSetTy &VBases);
/// LayoutSecondaryVirtualPointers - Lay out the secondary virtual pointers
/// for the given base subobject.
///
/// \param AddressPoints - If the vtable is a construction vtable, this has
/// the address points for it.
void LayoutSecondaryVirtualPointers(BaseSubobject Base,
llvm::Constant *VTable,
const AddressPointsMapTy& AddressPoints);
/// LayoutVirtualVTTs - Lay out the VTTs for the virtual base classes of the
/// given record decl.
void LayoutVirtualVTTs(const CXXRecordDecl *RD,
VisitedVirtualBasesSetTy &VBases);
/// LayoutVTT - Will lay out the VTT for the given subobject, including any
/// secondary VTTs, secondary virtual pointers and virtual VTTs.
void LayoutVTT(BaseSubobject Base, bool BaseIsVirtual);
public:
VTTBuilder(CodeGenModule &CGM, const CXXRecordDecl *MostDerivedClass,
bool GenerateDefinition);
// getVTTComponents - Returns a reference to the VTT components.
const VTTComponentsVectorTy &getVTTComponents() const {
return VTTComponents;
}
/// getSubVTTIndicies - Returns a reference to the sub-VTT indices.
const llvm::DenseMap<BaseSubobject, uint64_t> &getSubVTTIndicies() const {
return SubVTTIndicies;
}
/// getSecondaryVirtualPointerIndices - Returns a reference to the secondary
/// virtual pointer indices.
const llvm::DenseMap<BaseSubobject, uint64_t> &
getSecondaryVirtualPointerIndices() const {
return SecondaryVirtualPointerIndices;
}
};
VTTBuilder::VTTBuilder(CodeGenModule &CGM,
const CXXRecordDecl *MostDerivedClass,
bool GenerateDefinition)
: CGM(CGM), MostDerivedClass(MostDerivedClass),
MostDerivedClassLayout(CGM.getContext().getASTRecordLayout(MostDerivedClass)),
GenerateDefinition(GenerateDefinition) {
// Lay out this VTT.
LayoutVTT(BaseSubobject(MostDerivedClass, 0), /*BaseIsVirtual=*/false);
}
llvm::Constant *
VTTBuilder::GetAddrOfVTable(BaseSubobject Base, bool BaseIsVirtual,
AddressPointsMapTy& AddressPoints) {
if (!GenerateDefinition)
return 0;
if (Base.getBase() == MostDerivedClass) {
assert(Base.getBaseOffset() == 0 &&
"Most derived class vtable must have a zero offset!");
// This is a regular vtable.
return CGM.getVTables().GetAddrOfVTable(MostDerivedClass);
}
return CGM.getVTables().GenerateConstructionVTable(MostDerivedClass,
Base, BaseIsVirtual,
AddressPoints);
}
void VTTBuilder::AddVTablePointer(BaseSubobject Base, llvm::Constant *VTable,
const CXXRecordDecl *VTableClass,
const AddressPointsMapTy& AddressPoints) {
// Store the vtable pointer index if we're generating the primary VTT.
if (VTableClass == MostDerivedClass) {
assert(!SecondaryVirtualPointerIndices.count(Base) &&
"A virtual pointer index already exists for this base subobject!");
SecondaryVirtualPointerIndices[Base] = VTTComponents.size();
}
if (!GenerateDefinition) {
VTTComponents.push_back(0);
return;
}
uint64_t AddressPoint;
if (VTableClass != MostDerivedClass) {
// The vtable is a construction vtable, look in the construction vtable
// address points.
AddressPoint = AddressPoints.lookup(Base);
assert(AddressPoint != 0 && "Did not find ctor vtable address point!");
} else {
// Just get the address point for the regular vtable.
AddressPoint = CGM.getVTables().getAddressPoint(Base, VTableClass);
assert(AddressPoint != 0 && "Did not find vtable address point!");
}
if (!AddressPoint) AddressPoint = 0;
llvm::Value *Idxs[] = {
llvm::ConstantInt::get(llvm::Type::getInt64Ty(CGM.getLLVMContext()), 0),
llvm::ConstantInt::get(llvm::Type::getInt64Ty(CGM.getLLVMContext()),
AddressPoint)
};
llvm::Constant *Init =
llvm::ConstantExpr::getInBoundsGetElementPtr(VTable, Idxs, 2);
const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
Init = llvm::ConstantExpr::getBitCast(Init, Int8PtrTy);
VTTComponents.push_back(Init);
}
void VTTBuilder::LayoutSecondaryVTTs(BaseSubobject Base) {
const CXXRecordDecl *RD = Base.getBase();
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
// Don't layout virtual bases.
if (I->isVirtual())
continue;
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
uint64_t BaseOffset = Base.getBaseOffset() +
Layout.getBaseClassOffsetInBits(BaseDecl);
// Layout the VTT for this base.
LayoutVTT(BaseSubobject(BaseDecl, BaseOffset), /*BaseIsVirtual=*/false);
}
}
void
VTTBuilder::LayoutSecondaryVirtualPointers(BaseSubobject Base,
bool BaseIsMorallyVirtual,
llvm::Constant *VTable,
const CXXRecordDecl *VTableClass,
const AddressPointsMapTy& AddressPoints,
VisitedVirtualBasesSetTy &VBases) {
const CXXRecordDecl *RD = Base.getBase();
// We're not interested in bases that don't have virtual bases, and not
// morally virtual bases.
if (!RD->getNumVBases() && !BaseIsMorallyVirtual)
return;
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
// Itanium C++ ABI 2.6.2:
// Secondary virtual pointers are present for all bases with either
// virtual bases or virtual function declarations overridden along a
// virtual path.
//
// If the base class is not dynamic, we don't want to add it, nor any
// of its base classes.
if (!BaseDecl->isDynamicClass())
continue;
bool BaseDeclIsMorallyVirtual = BaseIsMorallyVirtual;
bool BaseDeclIsNonVirtualPrimaryBase = false;
uint64_t BaseOffset;
if (I->isVirtual()) {
// Ignore virtual bases that we've already visited.
if (!VBases.insert(BaseDecl))
continue;
BaseOffset = MostDerivedClassLayout.getVBaseClassOffsetInBits(BaseDecl);
BaseDeclIsMorallyVirtual = true;
} else {
const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
BaseOffset =
Base.getBaseOffset() + Layout.getBaseClassOffsetInBits(BaseDecl);
if (!Layout.isPrimaryBaseVirtual() &&
Layout.getPrimaryBase() == BaseDecl)
BaseDeclIsNonVirtualPrimaryBase = true;
}
// Itanium C++ ABI 2.6.2:
// Secondary virtual pointers: for each base class X which (a) has virtual
// bases or is reachable along a virtual path from D, and (b) is not a
// non-virtual primary base, the address of the virtual table for X-in-D
// or an appropriate construction virtual table.
if (!BaseDeclIsNonVirtualPrimaryBase &&
(BaseDecl->getNumVBases() || BaseDeclIsMorallyVirtual)) {
// Add the vtable pointer.
AddVTablePointer(BaseSubobject(BaseDecl, BaseOffset), VTable, VTableClass,
AddressPoints);
}
// And lay out the secondary virtual pointers for the base class.
LayoutSecondaryVirtualPointers(BaseSubobject(BaseDecl, BaseOffset),
BaseDeclIsMorallyVirtual, VTable,
VTableClass, AddressPoints, VBases);
}
}
void
VTTBuilder::LayoutSecondaryVirtualPointers(BaseSubobject Base,
llvm::Constant *VTable,
const AddressPointsMapTy& AddressPoints) {
VisitedVirtualBasesSetTy VBases;
LayoutSecondaryVirtualPointers(Base, /*BaseIsMorallyVirtual=*/false,
VTable, Base.getBase(), AddressPoints, VBases);
}
void VTTBuilder::LayoutVirtualVTTs(const CXXRecordDecl *RD,
VisitedVirtualBasesSetTy &VBases) {
for (CXXRecordDecl::base_class_const_iterator I = RD->bases_begin(),
E = RD->bases_end(); I != E; ++I) {
const CXXRecordDecl *BaseDecl =
cast<CXXRecordDecl>(I->getType()->getAs<RecordType>()->getDecl());
// Check if this is a virtual base.
if (I->isVirtual()) {
// Check if we've seen this base before.
if (!VBases.insert(BaseDecl))
continue;
uint64_t BaseOffset =
MostDerivedClassLayout.getVBaseClassOffsetInBits(BaseDecl);
LayoutVTT(BaseSubobject(BaseDecl, BaseOffset), /*BaseIsVirtual=*/true);
}
// We only need to layout virtual VTTs for this base if it actually has
// virtual bases.
if (BaseDecl->getNumVBases())
LayoutVirtualVTTs(BaseDecl, VBases);
}
}
void VTTBuilder::LayoutVTT(BaseSubobject Base, bool BaseIsVirtual) {
const CXXRecordDecl *RD = Base.getBase();
// Itanium C++ ABI 2.6.2:
// An array of virtual table addresses, called the VTT, is declared for
// each class type that has indirect or direct virtual base classes.
if (RD->getNumVBases() == 0)
return;
bool IsPrimaryVTT = Base.getBase() == MostDerivedClass;
if (!IsPrimaryVTT) {
// Remember the sub-VTT index.
SubVTTIndicies[Base] = VTTComponents.size();
}
AddressPointsMapTy AddressPoints;
llvm::Constant *VTable = GetAddrOfVTable(Base, BaseIsVirtual, AddressPoints);
// Add the primary vtable pointer.
AddVTablePointer(Base, VTable, RD, AddressPoints);
// Add the secondary VTTs.
LayoutSecondaryVTTs(Base);
// Add the secondary virtual pointers.
LayoutSecondaryVirtualPointers(Base, VTable, AddressPoints);
// If this is the primary VTT, we want to lay out virtual VTTs as well.
if (IsPrimaryVTT) {
VisitedVirtualBasesSetTy VBases;
LayoutVirtualVTTs(Base.getBase(), VBases);
}
}
}
llvm::GlobalVariable *
CodeGenVTables::GenerateVTT(llvm::GlobalVariable::LinkageTypes Linkage,
bool GenerateDefinition,
const CXXRecordDecl *RD) {
// Only classes that have virtual bases need a VTT.
if (RD->getNumVBases() == 0)
return 0;
llvm::SmallString<256> OutName;
CGM.getCXXABI().getMangleContext().mangleCXXVTT(RD, OutName);
llvm::StringRef Name = OutName.str();
D1(printf("vtt %s\n", RD->getNameAsCString()));
llvm::GlobalVariable *GV = CGM.getModule().getGlobalVariable(Name, true);
if (GV == 0 || GV->isDeclaration()) {
const llvm::Type *Int8PtrTy =
llvm::Type::getInt8PtrTy(CGM.getLLVMContext());
VTTBuilder Builder(CGM, RD, GenerateDefinition);
const llvm::ArrayType *Type =
llvm::ArrayType::get(Int8PtrTy, Builder.getVTTComponents().size());
llvm::Constant *Init = 0;
if (GenerateDefinition)
Init = llvm::ConstantArray::get(Type, Builder.getVTTComponents().data(),
Builder.getVTTComponents().size());
llvm::GlobalVariable *OldGV = GV;
GV = new llvm::GlobalVariable(CGM.getModule(), Type, /*isConstant=*/true,
Linkage, Init, Name);
CGM.setGlobalVisibility(GV, RD, /*ForDefinition*/ GenerateDefinition);
if (OldGV) {
GV->takeName(OldGV);
llvm::Constant *NewPtr =
llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
OldGV->replaceAllUsesWith(NewPtr);
OldGV->eraseFromParent();
}
}
return GV;
}
llvm::GlobalVariable *CodeGenVTables::getVTT(const CXXRecordDecl *RD) {
return GenerateVTT(llvm::GlobalValue::ExternalLinkage,
/*GenerateDefinition=*/false, RD);
}
bool CodeGenVTables::needsVTTParameter(GlobalDecl GD) {
const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
// We don't have any virtual bases, just return early.
if (!MD->getParent()->getNumVBases())
return false;
// Check if we have a base constructor.
if (isa<CXXConstructorDecl>(MD) && GD.getCtorType() == Ctor_Base)
return true;
// Check if we have a base destructor.
if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
return true;
return false;
}
uint64_t CodeGenVTables::getSubVTTIndex(const CXXRecordDecl *RD,
BaseSubobject Base) {
BaseSubobjectPairTy ClassSubobjectPair(RD, Base);
SubVTTIndiciesMapTy::iterator I = SubVTTIndicies.find(ClassSubobjectPair);
if (I != SubVTTIndicies.end())
return I->second;
VTTBuilder Builder(CGM, RD, /*GenerateDefinition=*/false);
for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
Builder.getSubVTTIndicies().begin(),
E = Builder.getSubVTTIndicies().end(); I != E; ++I) {
// Insert all indices.
BaseSubobjectPairTy ClassSubobjectPair(RD, I->first);
SubVTTIndicies.insert(std::make_pair(ClassSubobjectPair, I->second));
}
I = SubVTTIndicies.find(ClassSubobjectPair);
assert(I != SubVTTIndicies.end() && "Did not find index!");
return I->second;
}
uint64_t
CodeGenVTables::getSecondaryVirtualPointerIndex(const CXXRecordDecl *RD,
BaseSubobject Base) {
SecondaryVirtualPointerIndicesMapTy::iterator I =
SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
if (I != SecondaryVirtualPointerIndices.end())
return I->second;
VTTBuilder Builder(CGM, RD, /*GenerateDefinition=*/false);
// Insert all secondary vpointer indices.
for (llvm::DenseMap<BaseSubobject, uint64_t>::const_iterator I =
Builder.getSecondaryVirtualPointerIndices().begin(),
E = Builder.getSecondaryVirtualPointerIndices().end(); I != E; ++I) {
std::pair<const CXXRecordDecl *, BaseSubobject> Pair =
std::make_pair(RD, I->first);
SecondaryVirtualPointerIndices.insert(std::make_pair(Pair, I->second));
}
I = SecondaryVirtualPointerIndices.find(std::make_pair(RD, Base));
assert(I != SecondaryVirtualPointerIndices.end() && "Did not find index!");
return I->second;
}