ASTContext.cpp

  // expression is an lvalue.
  // FIXME: C++ shouldn't be going through here!  The rules are different
  // enough that they should be handled separately.
  if (const ReferenceType *RT = LHS->getAsReferenceType())
    LHS = RT->getPointeeType();
  if (const ReferenceType *RT = RHS->getAsReferenceType())
    RHS = RT->getPointeeType();

  QualType LHSCan = getCanonicalType(LHS),
           RHSCan = getCanonicalType(RHS);

  // If two types are identical, they are compatible.
  if (LHSCan == RHSCan)
    return LHS;

  // If the qualifiers are different, the types aren't compatible
  if (LHSCan.getCVRQualifiers() != RHSCan.getCVRQualifiers() ||
      LHSCan.getAddressSpace() != RHSCan.getAddressSpace())
    return QualType();

  Type::TypeClass LHSClass = LHSCan->getTypeClass();
  Type::TypeClass RHSClass = RHSCan->getTypeClass();

  // We want to consider the two function types to be the same for these
  // comparisons, just force one to the other.
  if (LHSClass == Type::FunctionProto) LHSClass = Type::FunctionNoProto;
  if (RHSClass == Type::FunctionProto) RHSClass = Type::FunctionNoProto;

  // Same as above for arrays
  if (LHSClass == Type::VariableArray || LHSClass == Type::IncompleteArray)
    LHSClass = Type::ConstantArray;
  if (RHSClass == Type::VariableArray || RHSClass == Type::IncompleteArray)
    RHSClass = Type::ConstantArray;
  
  // Canonicalize ExtVector -> Vector.
  if (LHSClass == Type::ExtVector) LHSClass = Type::Vector;
  if (RHSClass == Type::ExtVector) RHSClass = Type::Vector;
  
  // Consider qualified interfaces and interfaces the same.
  if (LHSClass == Type::ObjCQualifiedInterface) LHSClass = Type::ObjCInterface;
  if (RHSClass == Type::ObjCQualifiedInterface) RHSClass = Type::ObjCInterface;

  // If the canonical type classes don't match.
  if (LHSClass != RHSClass) {
    // ID is compatible with all qualified id types.
    if (LHS->isObjCQualifiedIdType()) {
      if (const PointerType *PT = RHS->getAsPointerType()) {
        QualType pType = PT->getPointeeType();
        if (isObjCIdType(pType))
          return LHS;
        // FIXME: need to use ObjCQualifiedIdTypesAreCompatible(LHS, RHS, true).
        // Unfortunately, this API is part of Sema (which we don't have access
        // to. Need to refactor. The following check is insufficient, since we 
        // need to make sure the class implements the protocol.
        if (pType->isObjCInterfaceType())
          return LHS;
      }
    }
    if (RHS->isObjCQualifiedIdType()) {
      if (const PointerType *PT = LHS->getAsPointerType()) {
        QualType pType = PT->getPointeeType();
        if (isObjCIdType(pType))
          return RHS;
        // FIXME: need to use ObjCQualifiedIdTypesAreCompatible(LHS, RHS, true).
        // Unfortunately, this API is part of Sema (which we don't have access
        // to. Need to refactor. The following check is insufficient, since we 
        // need to make sure the class implements the protocol.
        if (pType->isObjCInterfaceType())
          return RHS;
      }
    }

    // C99 6.7.2.2p4: Each enumerated type shall be compatible with char,
    // a signed integer type, or an unsigned integer type. 
    if (const EnumType* ETy = LHS->getAsEnumType()) {
      if (ETy->getDecl()->getIntegerType() == RHSCan.getUnqualifiedType())
        return RHS;
    }
    if (const EnumType* ETy = RHS->getAsEnumType()) {
      if (ETy->getDecl()->getIntegerType() == LHSCan.getUnqualifiedType())
        return LHS;
    }

    return QualType();
  }

  // The canonical type classes match.
  switch (LHSClass) {
  case Type::Pointer:
  {
    // Merge two pointer types, while trying to preserve typedef info
    QualType LHSPointee = LHS->getAsPointerType()->getPointeeType();
    QualType RHSPointee = RHS->getAsPointerType()->getPointeeType();
    QualType ResultType = mergeTypes(LHSPointee, RHSPointee);
    if (ResultType.isNull()) return QualType();
    if (getCanonicalType(LHSPointee) == getCanonicalType(ResultType))
      return LHS;
    if (getCanonicalType(RHSPointee) == getCanonicalType(ResultType))
      return RHS;
    return getPointerType(ResultType);
  }
  case Type::ConstantArray:
  {
    const ConstantArrayType* LCAT = getAsConstantArrayType(LHS);
    const ConstantArrayType* RCAT = getAsConstantArrayType(RHS);
    if (LCAT && RCAT && RCAT->getSize() != LCAT->getSize())
      return QualType();

    QualType LHSElem = getAsArrayType(LHS)->getElementType();
    QualType RHSElem = getAsArrayType(RHS)->getElementType();
    QualType ResultType = mergeTypes(LHSElem, RHSElem);
    if (ResultType.isNull()) return QualType();
    if (LCAT && getCanonicalType(LHSElem) == getCanonicalType(ResultType))
      return LHS;
    if (RCAT && getCanonicalType(RHSElem) == getCanonicalType(ResultType))
      return RHS;
    if (LCAT) return getConstantArrayType(ResultType, LCAT->getSize(),
                                          ArrayType::ArraySizeModifier(), 0);
    if (RCAT) return getConstantArrayType(ResultType, RCAT->getSize(),
                                          ArrayType::ArraySizeModifier(), 0);
    const VariableArrayType* LVAT = getAsVariableArrayType(LHS);
    const VariableArrayType* RVAT = getAsVariableArrayType(RHS);
    if (LVAT && getCanonicalType(LHSElem) == getCanonicalType(ResultType))
      return LHS;
    if (RVAT && getCanonicalType(RHSElem) == getCanonicalType(ResultType))
      return RHS;
    if (LVAT) {
      // FIXME: This isn't correct! But tricky to implement because
      // the array's size has to be the size of LHS, but the type
      // has to be different.
      return LHS;
    }
    if (RVAT) {
      // FIXME: This isn't correct! But tricky to implement because
      // the array's size has to be the size of RHS, but the type
      // has to be different.
      return RHS;
    }
    if (getCanonicalType(LHSElem) == getCanonicalType(ResultType)) return LHS;
    if (getCanonicalType(RHSElem) == getCanonicalType(ResultType)) return RHS;
    return getIncompleteArrayType(ResultType, ArrayType::ArraySizeModifier(),0);
  }
  case Type::FunctionNoProto:
    return mergeFunctionTypes(LHS, RHS);
  case Type::Tagged:
    // FIXME: Why are these compatible?
    if (isObjCIdType(LHS) && isObjCClassType(RHS)) return LHS;
    if (isObjCClassType(LHS) && isObjCIdType(RHS)) return LHS;
    return QualType();
  case Type::Builtin:
    // Only exactly equal builtin types are compatible, which is tested above.
    return QualType();
  case Type::Vector:
    if (areCompatVectorTypes(LHS->getAsVectorType(), RHS->getAsVectorType()))
      return LHS;
    return QualType();
  case Type::ObjCInterface:
    // Distinct ObjC interfaces are not compatible; see canAssignObjCInterfaces
    // for checking assignment/comparison safety
    return QualType();
  default:
    assert(0 && "unexpected type");
    return QualType();
  }
}

//===----------------------------------------------------------------------===//
//                         Integer Predicates
//===----------------------------------------------------------------------===//
unsigned ASTContext::getIntWidth(QualType T) {
  if (T == BoolTy)
    return 1;
  // At the moment, only bool has padding bits
  return (unsigned)getTypeSize(T);
}

QualType ASTContext::getCorrespondingUnsignedType(QualType T) {
  assert(T->isSignedIntegerType() && "Unexpected type");
  if (const EnumType* ETy = T->getAsEnumType())
    T = ETy->getDecl()->getIntegerType();
  const BuiltinType* BTy = T->getAsBuiltinType();
  assert (BTy && "Unexpected signed integer type");
  switch (BTy->getKind()) {
  case BuiltinType::Char_S:
  case BuiltinType::SChar:
    return UnsignedCharTy;
  case BuiltinType::Short:
    return UnsignedShortTy;
  case BuiltinType::Int:
    return UnsignedIntTy;
  case BuiltinType::Long:
    return UnsignedLongTy;
  case BuiltinType::LongLong:
    return UnsignedLongLongTy;
  default:
    assert(0 && "Unexpected signed integer type");
    return QualType();
  }
}


//===----------------------------------------------------------------------===//
//                         Serialization Support
//===----------------------------------------------------------------------===//

/// Emit - Serialize an ASTContext object to Bitcode.
void ASTContext::Emit(llvm::Serializer& S) const {
  S.Emit(LangOpts);
  S.EmitRef(SourceMgr);
  S.EmitRef(Target);
  S.EmitRef(Idents);
  S.EmitRef(Selectors);

  // Emit the size of the type vector so that we can reserve that size
  // when we reconstitute the ASTContext object.
  S.EmitInt(Types.size());
  
  for (std::vector<Type*>::const_iterator I=Types.begin(), E=Types.end(); 
                                          I!=E;++I)    
    (*I)->Emit(S);

  S.EmitOwnedPtr(TUDecl);

  // FIXME: S.EmitOwnedPtr(CFConstantStringTypeDecl);
}

ASTContext* ASTContext::Create(llvm::Deserializer& D) {
  
  // Read the language options.
  LangOptions LOpts;
  LOpts.Read(D);
  
  SourceManager &SM = D.ReadRef<SourceManager>();
  TargetInfo &t = D.ReadRef<TargetInfo>();
  IdentifierTable &idents = D.ReadRef<IdentifierTable>();
  SelectorTable &sels = D.ReadRef<SelectorTable>();

  unsigned size_reserve = D.ReadInt();
  
  ASTContext* A = new ASTContext(LOpts, SM, t, idents, sels, size_reserve);
  
  for (unsigned i = 0; i < size_reserve; ++i)
    Type::Create(*A,i,D);
  
  A->TUDecl = cast<TranslationUnitDecl>(D.ReadOwnedPtr<Decl>(*A));

  // FIXME: A->CFConstantStringTypeDecl = D.ReadOwnedPtr<RecordDecl>();
  
  return A;
}