path: root/lib/CodeGen/CGRTTI.cpp

//===--- CGCXXRTTI.cpp - Emit LLVM Code for C++ RTTI descriptors ----------===//
//
//                     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 RTTI descriptors.
//
//===----------------------------------------------------------------------===//

#include "CodeGenModule.h"
#include "CGCXXABI.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/Type.h"
#include "clang/Frontend/CodeGenOptions.h"

using namespace clang;
using namespace CodeGen;

namespace {
class RTTIBuilder {
  CodeGenModule &CGM;  // Per-module state.
  llvm::LLVMContext &VMContext;
  
  const llvm::Type *Int8PtrTy;
  
  /// Fields - The fields of the RTTI descriptor currently being built.
  llvm::SmallVector<llvm::Constant *, 16> Fields;

  /// GetAddrOfExternalRTTIDescriptor - Returns the constant for the RTTI 
  /// descriptor of the given type.
  llvm::Constant *GetAddrOfExternalRTTIDescriptor(QualType Ty);
  
  /// BuildVTablePointer - Build the vtable pointer for the given type.
  void BuildVTablePointer(const Type *Ty);
  
  /// BuildSIClassTypeInfo - Build an abi::__si_class_type_info, used for single
  /// inheritance, according to the Itanium C++ ABI, 2.9.5p6b.
  void BuildSIClassTypeInfo(const CXXRecordDecl *RD);
  
  /// BuildVMIClassTypeInfo - Build an abi::__vmi_class_type_info, used for
  /// classes with bases that do not satisfy the abi::__si_class_type_info 
  /// constraints, according ti the Itanium C++ ABI, 2.9.5p5c.
  void BuildVMIClassTypeInfo(const CXXRecordDecl *RD);
  
  /// BuildPointerTypeInfo - Build an abi::__pointer_type_info struct, used
  /// for pointer types.
  void BuildPointerTypeInfo(QualType PointeeTy);

  /// BuildObjCObjectTypeInfo - Build the appropriate kind of
  /// type_info for an object type.
  void BuildObjCObjectTypeInfo(const ObjCObjectType *Ty);
  
  /// BuildPointerToMemberTypeInfo - Build an abi::__pointer_to_member_type_info 
  /// struct, used for member pointer types.
  void BuildPointerToMemberTypeInfo(const MemberPointerType *Ty);
  
public:
  RTTIBuilder(CodeGenModule &cgm)
    : CGM(cgm), VMContext(cgm.getModule().getContext()),
      Int8PtrTy(llvm::Type::getInt8PtrTy(VMContext)) { }

  llvm::Constant *BuildName(QualType Ty, bool Hidden, 
                            llvm::GlobalVariable::LinkageTypes Linkage) {
    llvm::SmallString<256> OutName;
    CGM.getCXXABI().getMangleContext().mangleCXXRTTIName(Ty, OutName);
    llvm::StringRef Name = OutName.str();

    llvm::GlobalVariable *OGV = CGM.getModule().getNamedGlobal(Name);
    if (OGV && !OGV->isDeclaration())
      return llvm::ConstantExpr::getBitCast(OGV, Int8PtrTy);

    llvm::Constant *C = llvm::ConstantArray::get(VMContext, Name.substr(4));

    llvm::GlobalVariable *GV = 
      new llvm::GlobalVariable(CGM.getModule(), C->getType(), true, Linkage,
                               C, Name);
    if (OGV) {
      GV->takeName(OGV);
      llvm::Constant *NewPtr = llvm::ConstantExpr::getBitCast(GV,
                                                              OGV->getType());
      OGV->replaceAllUsesWith(NewPtr);
      OGV->eraseFromParent();
    }
    if (Hidden && Linkage != llvm::GlobalValue::InternalLinkage)
      GV->setVisibility(llvm::GlobalVariable::HiddenVisibility);
    return llvm::ConstantExpr::getBitCast(GV, Int8PtrTy);
  }

  // FIXME: unify with DecideExtern
  bool DecideHidden(QualType Ty) {
    // For this type, see if all components are never hidden.
    if (const MemberPointerType *MPT = Ty->getAs<MemberPointerType>())
      return (DecideHidden(MPT->getPointeeType())
              && DecideHidden(QualType(MPT->getClass(), 0)));
    if (const PointerType *PT = Ty->getAs<PointerType>())
      return DecideHidden(PT->getPointeeType());
    if (const FunctionType *FT = Ty->getAs<FunctionType>()) {
      if (DecideHidden(FT->getResultType()) == false)
        return false;
      if (const FunctionProtoType *FPT = Ty->getAs<FunctionProtoType>()) {
        for (unsigned i = 0; i <FPT->getNumArgs(); ++i)
          if (DecideHidden(FPT->getArgType(i)) == false)
            return false;
        for (unsigned i = 0; i <FPT->getNumExceptions(); ++i)
          if (DecideHidden(FPT->getExceptionType(i)) == false)
            return false;
        return true;
      }
    }
    if (const RecordType *RT = Ty->getAs<RecordType>())
      if (const CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(RT->getDecl()))
        return RD->getVisibility() == HiddenVisibility;
    return false;
  }
  
  // Pointer type info flags.
  enum {
    /// PTI_Const - Type has const qualifier.
    PTI_Const =