path: root/lib/CodeGen/CGClass.cpp

//===--- 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