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//===--- CGCXXClass.cpp - Emit LLVM Code for C++ classes ------------------===//
//
// 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 classes
//
//===----------------------------------------------------------------------===//
#include "CodeGenFunction.h"
#include "clang/AST/RecordLayout.h"
using namespace clang;
using namespace CodeGen;
static bool
GetNestedPaths(llvm::SmallVectorImpl<const CXXRecordDecl *> &NestedBasePaths,
const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl) {
for (CXXRecordDecl::base_class_const_iterator i = ClassDecl->bases_begin(),
e = ClassDecl->bases_end(); i != e; ++i) {
if (i->isVirtual())
continue;
const CXXRecordDecl *Base =
cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
if (Base == BaseClassDecl) {
NestedBasePaths.push_back(BaseClassDecl);
return true;
}
}
// BaseClassDecl not an immediate base of ClassDecl.
for (CXXRecordDecl::base_class_const_iterator i = ClassDecl->bases_begin(),
e = ClassDecl->bases_end(); i != e; ++i) {
if (i->isVirtual())
continue;
const CXXRecordDecl *Base =
cast<CXXRecordDecl>(i->getType()->getAs<RecordType>()->getDecl());
if (GetNestedPaths(NestedBasePaths, Base, BaseClassDecl)) {
NestedBasePaths.push_back(Base);
return true;
}
}
return false;
}
static uint64_t ComputeBaseClassOffset(ASTContext &Context,
const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl) {
uint64_t Offset = 0;
llvm::SmallVector<const CXXRecordDecl *, 16> NestedBasePaths;
GetNestedPaths(NestedBasePaths, ClassDecl, BaseClassDecl);
assert(NestedBasePaths.size() > 0 &&
"AddressCXXOfBaseClass - inheritence path failed");
NestedBasePaths.push_back(ClassDecl);
for (unsigned i = NestedBasePaths.size() - 1; i > 0; i--) {
const CXXRecordDecl *DerivedClass = NestedBasePaths[i];
const CXXRecordDecl *BaseClass = NestedBasePaths[i-1];
const ASTRecordLayout &Layout =
Context.getASTRecordLayout(DerivedClass);
Offset += Layout.getBaseClassOffset(BaseClass) / 8;
}
return Offset;
}
llvm::Constant *
CodeGenModule::GetCXXBaseClassOffset(const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl) {
if (ClassDecl == BaseClassDecl)
return 0;
QualType BTy =
getContext().getCanonicalType(
getContext().getTypeDeclType(const_cast<CXXRecordDecl*>(BaseClassDecl)));
uint64_t Offset = ComputeBaseClassOffset(getContext(),
ClassDecl, BaseClassDecl);
if (!Offset)
return 0;
const llvm::Type *PtrDiffTy =
Types.ConvertType(getContext().getPointerDiffType());
return llvm::ConstantInt::get(PtrDiffTy, Offset);
}
llvm::Value *
CodeGenFunction::GetAddressCXXOfBaseClass(llvm::Value *BaseValue,
const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl,
bool NullCheckValue) {
llvm::Constant *Offset = CGM.GetCXXBaseClassOffset(ClassDecl, BaseClassDecl);
QualType BTy =
getContext().getCanonicalType(
getContext().getTypeDeclType(const_cast<CXXRecordDecl*>(BaseClassDecl)));
const llvm::Type *BasePtrTy = llvm::PointerType::getUnqual(ConvertType(BTy));
if (!Offset) {
// Just cast back.
return Builder.CreateBitCast(BaseValue, BasePtrTy);
}
llvm::BasicBlock *CastNull = 0;
llvm::BasicBlock *CastNotNull = 0;
llvm::BasicBlock *CastEnd = 0;
if (NullCheckValue) {
CastNull = createBasicBlock("cast.null");
CastNotNull = createBasicBlock("cast.notnull");
CastEnd = createBasicBlock("cast.end");
llvm::Value *IsNull =
Builder.CreateICmpEQ(BaseValue,
llvm::Constant::getNullValue(BaseValue->getType()));
Builder.CreateCondBr(IsNull, CastNull, CastNotNull);
EmitBlock(CastNotNull);
}
const llvm::Type *Int8PtrTy =
llvm::PointerType::getUnqual(llvm::Type::getInt8Ty(VMContext));
// Apply the offset.
BaseValue = Builder.CreateBitCast(BaseValue, Int8PtrTy);
BaseValue = Builder.CreateGEP(BaseValue, Offset, "add.ptr");
// Cast back.
BaseValue = Builder.CreateBitCast(BaseValue, BasePtrTy);
if (NullCheckValue) {
Builder.CreateBr(CastEnd);
EmitBlock(CastNull);
Builder.CreateBr(CastEnd);
EmitBlock(CastEnd);
llvm::PHINode *PHI = Builder.CreatePHI(BaseValue->getType());
PHI->reserveOperandSpace(2);
PHI->addIncoming(BaseValue, CastNotNull);
PHI->addIncoming(llvm::Constant::getNullValue(BaseValue->getType()),
CastNull);
BaseValue = PHI;
}
return BaseValue;
}
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