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//===--- CGClass.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/CXXInheritance.h"
#include "clang/AST/RecordLayout.h"
using namespace clang;
using namespace CodeGen;
static uint64_t
ComputeNonVirtualBaseClassOffset(ASTContext &Context, CXXBasePaths &Paths,
unsigned Start) {
uint64_t Offset = 0;
const CXXBasePath &Path = Paths.front();
for (unsigned i = Start, e = Path.size(); i != e; ++i) {
const CXXBasePathElement& Element = Path[i];
// Get the layout.
const ASTRecordLayout &Layout = Context.getASTRecordLayout(Element.Class);
const CXXBaseSpecifier *BS = Element.Base;
assert(!BS->isVirtual() && "Should not see virtual bases here!");
const CXXRecordDecl *Base =
cast<CXXRecordDecl>(BS->getType()->getAs<RecordType>()->getDecl());
// Add the offset.
Offset += Layout.getBaseClassOffset(Base) / 8;
}
return Offset;
}
llvm::Constant *
CodeGenModule::GetCXXBaseClassOffset(const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl) {
if (ClassDecl == BaseClassDecl)
return 0;
CXXBasePaths Paths(/*FindAmbiguities=*/false,
/*RecordPaths=*/true, /*DetectVirtual=*/false);
if (!const_cast<CXXRecordDecl *>(ClassDecl)->
isDerivedFrom(const_cast<CXXRecordDecl *>(BaseClassDecl), Paths)) {
assert(false && "Class must be derived from the passed in base class!");
return 0;
}
uint64_t Offset = ComputeNonVirtualBaseClassOffset(getContext(), Paths, 0);
if (!Offset)
return 0;
const llvm::Type *PtrDiffTy =
Types.ConvertType(getContext().getPointerDiffType());
return llvm::ConstantInt::get(PtrDiffTy, Offset);
}
static llvm::Value *GetCXXBaseClassOffset(CodeGenFunction &CGF,
llvm::Value *BaseValue,
const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl) {
CXXBasePaths Paths(/*FindAmbiguities=*/false,
/*RecordPaths=*/true, /*DetectVirtual=*/false);
if (!const_cast<CXXRecordDecl *>(ClassDecl)->
isDerivedFrom(const_cast<CXXRecordDecl *>(BaseClassDecl), Paths)) {
assert(false && "Class must be derived from the passed in base class!");
return 0;
}
unsigned Start = 0;
llvm::Value *VirtualOffset = 0;
const CXXBasePath &Path = Paths.front();
const CXXRecordDecl *VBase = 0;
for (unsigned i = 0, e = Path.size(); i != e; ++i) {
const CXXBasePathElement& Element = Path[i];
if (Element.Base->isVirtual()) {
Start = i+1;
QualType VBaseType = Element.Base->getType();
VBase = cast<CXXRecordDecl>(VBaseType->getAs<RecordType>()->getDecl());
}
}
if (VBase)
VirtualOffset =
CGF.GetVirtualCXXBaseClassOffset(BaseValue, ClassDecl, VBase);
uint64_t Offset =
ComputeNonVirtualBaseClassOffset(CGF.getContext(), Paths, Start);
if (!Offset)
return VirtualOffset;
const llvm::Type *PtrDiffTy =
CGF.ConvertType(CGF.getContext().getPointerDiffType());
llvm::Value *NonVirtualOffset = llvm::ConstantInt::get(PtrDiffTy, Offset);
if (VirtualOffset)
return CGF.Builder.CreateAdd(VirtualOffset, NonVirtualOffset);
return NonVirtualOffset;
}
llvm::Value *
CodeGenFunction::GetAddressOfBaseClass(llvm::Value *Value,
const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *BaseClassDecl,
bool NullCheckValue) {
QualType BTy =
getContext().getCanonicalType(
getContext().getTypeDeclType(const_cast<CXXRecordDecl*>(BaseClassDecl)));
const llvm::Type *BasePtrTy = llvm::PointerType::getUnqual(ConvertType(BTy));
if (ClassDecl == BaseClassDecl) {
// Just cast back.
return Builder.CreateBitCast(Value, 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(Value,
llvm::Constant::getNullValue(Value->getType()));
Builder.CreateCondBr(IsNull, CastNull, CastNotNull);
EmitBlock(CastNotNull);
}
const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(VMContext);
llvm::Value *Offset =
GetCXXBaseClassOffset(*this, Value, ClassDecl, BaseClassDecl);
if (Offset) {
// Apply the offset.
Value = Builder.CreateBitCast(Value, Int8PtrTy);
Value = Builder.CreateGEP(Value, Offset, "add.ptr");
}
// Cast back.
Value = Builder.CreateBitCast(Value, BasePtrTy);
if (NullCheckValue) {
Builder.CreateBr(CastEnd);
EmitBlock(CastNull);
Builder.CreateBr(CastEnd);
EmitBlock(CastEnd);
llvm::PHINode *PHI = Builder.CreatePHI(Value->getType());
PHI->reserveOperandSpace(2);
PHI->addIncoming(Value, CastNotNull);
PHI->addIncoming(llvm::Constant::getNullValue(Value->getType()),
CastNull);
Value = PHI;
}
return Value;
}
llvm::Value *
CodeGenFunction::GetAddressOfDerivedClass(llvm::Value *Value,
const CXXRecordDecl *ClassDecl,
const CXXRecordDecl *DerivedClassDecl,
bool NullCheckValue) {
QualType DerivedTy =
getContext().getCanonicalType(
getContext().getTypeDeclType(const_cast<CXXRecordDecl*>(DerivedClassDecl)));
const llvm::Type *DerivedPtrTy = ConvertType(DerivedTy)->getPointerTo();
if (ClassDecl == DerivedClassDecl) {
// Just cast back.
return Builder.CreateBitCast(Value, DerivedPtrTy);
}
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(Value,
llvm::Constant::getNullValue(Value->getType()));
Builder.CreateCondBr(IsNull, CastNull, CastNotNull);
EmitBlock(CastNotNull);
}
llvm::Value *Offset = GetCXXBaseClassOffset(*this, Value, DerivedClassDecl,
ClassDecl);
if (Offset) {
// Apply the offset.
Value = Builder.CreatePtrToInt(Value, Offset->getType());
Value = Builder.CreateSub(Value, Offset);
Value = Builder.CreateIntToPtr(Value, DerivedPtrTy);
} else {
// Just cast.
Value = Builder.CreateBitCast(Value, DerivedPtrTy);
}
if (NullCheckValue) {
Builder.CreateBr(CastEnd);
EmitBlock(CastNull);
Builder.CreateBr(CastEnd);
EmitBlock(CastEnd);
llvm::PHINode *PHI = Builder.CreatePHI(Value->getType());
PHI->reserveOperandSpace(2);
PHI->addIncoming(Value, CastNotNull);
PHI->addIncoming(llvm::Constant::getNullValue(Value->getType()),
CastNull);
Value = PHI;
}
return Value;
}
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