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//===--- CGVTT.cpp - Emit LLVM Code for C++ VTTs --------------------------===//
//
// 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 of VTTs (vtable tables).
//
//===----------------------------------------------------------------------===//
#include "CodeGenModule.h"
#include "CGCXXABI.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/VTTBuilder.h"
using namespace clang;
using namespace CodeGen;
static llvm::GlobalVariable *
GetAddrOfVTTVTable(CodeGenVTables &CGVT, CodeGenModule &CGM,
const CXXRecordDecl *MostDerivedClass,
const VTTVTable &VTable,
llvm::GlobalVariable::LinkageTypes Linkage,
VTableLayout::AddressPointsMapTy &AddressPoints) {
if (VTable.getBase() == MostDerivedClass) {
assert(VTable.getBaseOffset().isZero() &&
"Most derived class vtable must have a zero offset!");
// This is a regular vtable.
return CGM.getCXXABI().getAddrOfVTable(MostDerivedClass, CharUnits());
}
return CGVT.GenerateConstructionVTable(MostDerivedClass,
VTable.getBaseSubobject(),
VTable.isVirtual(),
Linkage,
AddressPoints);
}
void
CodeGenVTables::EmitVTTDefinition(llvm::GlobalVariable *VTT,
llvm::GlobalVariable::LinkageTypes Linkage,
const CXXRecordDecl *RD) {
VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/true);
llvm::ArrayType *ArrayType =
llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
SmallVector<llvm::GlobalVariable *, 8> VTables;
SmallVector<VTableAddressPointsMapTy, 8> VTableAddressPoints;
for (const VTTVTable *i = Builder.getVTTVTables().begin(),
*e = Builder.getVTTVTables().end(); i != e; ++i) {
VTableAddressPoints.push_back(VTableAddressPointsMapTy());
VTables.push_back(GetAddrOfVTTVTable(*this, CGM, RD, *i, Linkage,
VTableAddressPoints.back()));
}
SmallVector<llvm::Constant *, 8> VTTComponents;
for (const VTTComponent *i = Builder.getVTTComponents().begin(),
*e = Builder.getVTTComponents().end(); i != e; ++i) {
const VTTVTable &VTTVT = Builder.getVTTVTables()[i->VTableIndex];
llvm::GlobalVariable *VTable = VTables[i->VTableIndex];
VTableLayout::AddressPointLocation AddressPoint;
if (VTTVT.getBase() == RD) {
// Just get the address point for the regular vtable.
AddressPoint =
getItaniumVTableContext().getVTableLayout(RD).getAddressPoint(
i->VTableBase);
} else {
AddressPoint = VTableAddressPoints[i->VTableIndex].lookup(i->VTableBase);
assert(AddressPoint.AddressPointIndex != 0 &&
"Did not find ctor vtable address point!");
}
llvm::Value *Idxs[] = {
llvm::ConstantInt::get(CGM.Int32Ty, 0),
llvm::ConstantInt::get(CGM.Int32Ty, AddressPoint.VTableIndex),
llvm::ConstantInt::get(CGM.Int32Ty, AddressPoint.AddressPointIndex),
};
llvm::Constant *Init = llvm::ConstantExpr::getGetElementPtr(
VTable->getValueType(), VTable, Idxs, /*InBounds=*/true,
/*InRangeIndex=*/1);
Init = llvm::ConstantExpr::getPointerBitCastOrAddrSpaceCast(Init,
CGM.Int8PtrTy);
VTTComponents.push_back(Init);
}
llvm::Constant *Init = llvm::ConstantArray::get(ArrayType, VTTComponents);
VTT->setInitializer(Init);
// Set the correct linkage.
VTT->setLinkage(Linkage);
if (CGM.supportsCOMDAT() && VTT->isWeakForLinker())
VTT->setComdat(CGM.getModule().getOrInsertComdat(VTT->getName()));
}
llvm::GlobalVariable *CodeGenVTables::GetAddrOfVTT(const CXXRecordDecl *RD) {
assert(RD->getNumVBases() && "Only classes with virtual bases need a VTT");
SmallString<256> OutName;
llvm::raw_svector_ostream Out(OutName);
cast<ItaniumMangleContext>(CGM.getCXXABI().getMangleContext())
.mangleCXXVTT(RD, Out);
StringRef Name = OutName.str();
// This will also defer the definition of the VTT.
(void) CGM.getCXXABI().getAddrOfVTable(RD, CharUnits());
VTTBuilder Builder(CGM.getContext(), RD, /*GenerateDefinition=*/false);
llvm::ArrayType *ArrayType =
llvm::ArrayType::get(CGM.Int8PtrTy, Builder.getVTTComponents().size());
llvm::Align Align = CGM.getDataLayout().getABITypeAlign(CGM.Int8PtrTy);
llvm::GlobalVariable *GV = CGM.CreateOrReplaceCXXRuntimeVariable(
Name, ArrayType, llvm::GlobalValue::ExternalLinkage, Align);
GV->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
CGM.setGVProperties(GV, RD);
return GV;
}
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.getContext(), 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.getContext(), 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;
}
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