diff --git a/jerry-core/api/jerryscript.c b/jerry-core/api/jerryscript.c
index 60f8023fd0..d7e19dd645 100644
--- a/jerry-core/api/jerryscript.c
+++ b/jerry-core/api/jerryscript.c
@@ -5993,7 +5993,7 @@ jerry_arraybuffer_external (uint8_t *buffer_p, /**< the backing store used by th
 
     if (buffer_p != NULL)
     {
-      arraybuffer_pointer_p->extended_object.u.cls.u1.array_buffer_flags |= ECMA_ARRAYBUFFER_ALLOCATED;
+      arraybuffer_pointer_p->extended_object.u.clz.arraybuffer.flags |= ECMA_ARRAYBUFFER_ALLOCATED;
       arraybuffer_pointer_p->buffer_p = buffer_p;
     }
   }
@@ -6081,7 +6081,7 @@ jerry_shared_arraybuffer_external (uint8_t *buffer_p, /**< the backing store use
 
     if (buffer_p != NULL)
     {
-      shared_arraybuffer_pointer_p->extended_object.u.cls.u1.array_buffer_flags |= ECMA_ARRAYBUFFER_ALLOCATED;
+      shared_arraybuffer_pointer_p->extended_object.u.clz.arraybuffer.flags |= ECMA_ARRAYBUFFER_ALLOCATED;
       shared_arraybuffer_pointer_p->buffer_p = buffer_p;
     }
   }
@@ -6529,7 +6529,7 @@ jerry_dataview_buffer (const jerry_value_t value, /**< DataView to get the array
 
   if (byte_length != NULL)
   {
-    *byte_length = dataview_p->header.u.cls.u3.length;
+    *byte_length = dataview_p->header.u.clz.dataview.length;
   }
 
   ecma_object_t *arraybuffer_p = dataview_p->buffer_p;
diff --git a/jerry-core/ecma/base/ecma-gc.c b/jerry-core/ecma/base/ecma-gc.c
index 0cba365dee..1a9f9e3863 100644
--- a/jerry-core/ecma/base/ecma-gc.c
+++ b/jerry-core/ecma/base/ecma-gc.c
@@ -208,7 +208,7 @@ ecma_gc_mark_arguments_object (ecma_extended_object_t *ext_object_p) /**< argume
 
   ecma_value_t *argv_p = (ecma_value_t *) (arguments_p + 1);
 
-  if (ext_object_p->u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED)
+  if (ext_object_p->u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED)
   {
     ecma_mapped_arguments_t *mapped_arguments_p = (ecma_mapped_arguments_t *) ext_object_p;
     argv_p = (ecma_value_t *) (mapped_arguments_p + 1);
@@ -216,7 +216,7 @@ ecma_gc_mark_arguments_object (ecma_extended_object_t *ext_object_p) /**< argume
     ecma_gc_set_object_visited (ECMA_GET_INTERNAL_VALUE_POINTER (ecma_object_t, mapped_arguments_p->lex_env));
   }
 
-  uint32_t arguments_number = arguments_p->header.u.cls.u3.arguments_number;
+  uint32_t arguments_number = arguments_p->header.u.clz.arguments.number;
 
   for (uint32_t i = 0; i < arguments_number; i++)
   {
@@ -1336,13 +1336,13 @@ ecma_free_arguments_object (ecma_extended_object_t *ext_object_p) /**< arguments
 
   size_t object_size = sizeof (ecma_unmapped_arguments_t);
 
-  if (ext_object_p->u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED)
+  if (ext_object_p->u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED)
   {
     ecma_mapped_arguments_t *mapped_arguments_p = (ecma_mapped_arguments_t *) ext_object_p;
     object_size = sizeof (ecma_mapped_arguments_t);
 
 #if JERRY_SNAPSHOT_EXEC
-    if (!(mapped_arguments_p->unmapped.header.u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_STATIC_BYTECODE))
+    if (!(mapped_arguments_p->unmapped.header.u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_STATIC_BYTECODE))
 #endif /* JERRY_SNAPSHOT_EXEC */
     {
       ecma_compiled_code_t *byte_code_p =
@@ -1354,14 +1354,15 @@ ecma_free_arguments_object (ecma_extended_object_t *ext_object_p) /**< arguments
 
   ecma_value_t *argv_p = (ecma_value_t *) (((uint8_t *) ext_object_p) + object_size);
   ecma_unmapped_arguments_t *arguments_p = (ecma_unmapped_arguments_t *) ext_object_p;
-  uint32_t arguments_number = arguments_p->header.u.cls.u3.arguments_number;
+  uint32_t arguments_number = arguments_p->header.u.clz.arguments.number;
 
   for (uint32_t i = 0; i < arguments_number; i++)
   {
     ecma_free_value_if_not_object (argv_p[i]);
   }
 
-  uint32_t saved_argument_count = JERRY_MAX (arguments_number, arguments_p->header.u.cls.u2.formal_params_number);
+  uint32_t saved_argument_count =
+    JERRY_MAX (arguments_number, arguments_p->header.u.clz.arguments.formal_params_number);
 
   return object_size + (saved_argument_count * sizeof (ecma_value_t));
 } /* ecma_free_arguments_object */
@@ -1781,7 +1782,7 @@ ecma_gc_free_object (ecma_object_t *object_p) /**< object to free */
 #if JERRY_BUILTIN_TYPEDARRAY
         case ECMA_OBJECT_CLASS_TYPEDARRAY:
         {
-          if (ext_object_p->u.cls.u2.typedarray_flags & ECMA_TYPEDARRAY_IS_EXTENDED)
+          if (ext_object_p->u.clz.typedarray.flags & ECMA_TYPEDARRAY_IS_EXTENDED)
           {
             ext_object_size = sizeof (ecma_extended_typedarray_object_t);
           }
@@ -1858,7 +1859,7 @@ ecma_gc_free_object (ecma_object_t *object_p) /**< object to free */
         {
           if (!(ECMA_ARRAYBUFFER_GET_FLAGS (ext_object_p) & ECMA_ARRAYBUFFER_HAS_POINTER))
           {
-            ext_object_size += ext_object_p->u.cls.u3.length;
+            ext_object_size += ext_object_p->u.clz.arraybuffer.length;
             break;
           }
 
diff --git a/jerry-core/ecma/base/ecma-globals.h b/jerry-core/ecma/base/ecma-globals.h
index 75c70e196b..d685aa963d 100644
--- a/jerry-core/ecma/base/ecma-globals.h
+++ b/jerry-core/ecma/base/ecma-globals.h
@@ -1025,7 +1025,6 @@ typedef struct
        */
       union
       {
-        uint8_t arguments_flags; /**< arguments object flags */
         uint8_t error_type; /**< jerry_error_t type of native error objects */
 #if JERRY_BUILTIN_DATE
         uint8_t date_flags; /**< flags for date objects */
@@ -1039,17 +1038,12 @@ typedef struct
 #if JERRY_BUILTIN_CONTAINER
         uint8_t container_flags; /**< container object flags */
 #endif /* JERRY_BUILTIN_CONTAINER */
-#if JERRY_BUILTIN_TYPEDARRAY
-        uint8_t array_buffer_flags; /**< ArrayBuffer flags */
-        uint8_t typedarray_type; /**< type of typed array */
-#endif /* JERRY_BUILTIN_TYPEDARRAY */
       } u1;
       /**
        * Description of 16 bit extra fields. These extra fields depend on the type.
        */
       union
       {
-        uint16_t formal_params_number; /**< for arguments: formal parameters number */
 #if JERRY_MODULE_SYSTEM
         uint16_t module_flags; /**< Module flags */
 #endif /* JERRY_MODULE_SYSTEM */
@@ -1058,9 +1052,6 @@ typedef struct
 #if JERRY_BUILTIN_CONTAINER
         uint16_t container_id; /**< magic string id of a container */
 #endif /* JERRY_BUILTIN_CONTAINER */
-#if JERRY_BUILTIN_TYPEDARRAY
-        uint16_t typedarray_flags; /**< typed array object flags */
-#endif /* JERRY_BUILTIN_TYPEDARRAY */
       } u2;
       /**
        * Description of 32 bit / value. These extra fields depend on the type.
@@ -1069,23 +1060,63 @@ typedef struct
       {
         ecma_value_t value; /**< value of the object (e.g. boolean, number, string, etc.) */
         ecma_value_t target; /**< [[ProxyTarget]] or [[WeakRefTarget]] internal property */
-#if JERRY_BUILTIN_TYPEDARRAY
-        ecma_value_t arraybuffer; /**< for typedarray: ArrayBuffer reference */
-#endif /* JERRY_BUILTIN_TYPEDARRAY */
         ecma_value_t head; /**< points to the async generator task queue head item */
         ecma_value_t iterated_value; /**< for %Iterator%: [[IteratedObject]] property */
         ecma_value_t promise; /**< PromiseCapability[[Promise]] internal slot */
         ecma_value_t sync_iterator; /**< IteratorRecord [[Iterator]] internal slot for AsyncFromSyncIterator */
         ecma_value_t spread_value; /**< for spread object: spreaded element */
         int32_t tza; /**< TimeZone adjustment for date objects */
-        uint32_t length; /**< length related property (e.g. length of ArrayBuffer) */
-        uint32_t arguments_number; /**< for arguments: arguments number */
 #if JERRY_MODULE_SYSTEM
         uint32_t dfs_ancestor_index; /**< module dfs ancestor index (ES2020 15.2.1.16) */
 #endif /* JERRY_MODULE_SYSTEM */
       } u3;
     } cls;
 
+    union
+    {
+      /**
+       * Fields can only used by Arguments Exotic Object
+       */
+      struct
+      {
+        uint8_t cls_type; /**< class type of the object */
+        uint8_t flags; /**< arguments object flags */
+        uint16_t formal_params_number; /**< for arguments: formal parameters number */
+        uint32_t number; /**< for arguments: arguments number */
+      } arguments;
+#if JERRY_BUILTIN_TYPEDARRAY
+      /**
+       * Fields can only used by ArrayBuffer Object
+       */
+      struct
+      {
+        uint8_t cls_type; /**< class type of the object */
+        uint8_t flags; /**< ArrayBuffer flags */
+        uint32_t length; /**< length of ArrayBuffer */
+      } arraybuffer;
+      /**
+       * Fields can only used by TypedArray Object
+       */
+      struct
+      {
+        uint8_t cls_type; /**< class type of the object */
+        uint8_t type; /**< type of typed array */
+        uint16_t flags; /**< typed array object flags */
+        ecma_value_t arraybuffer; /**< for typedarray: ArrayBuffer reference */
+      } typedarray;
+#endif /* JERRY_BUILTIN_TYPEDARRAY */
+#if JERRY_BUILTIN_DATAVIEW
+      /**
+       * Fields can only used by DataView Object
+       */
+      struct
+      {
+        uint8_t cls_type; /**< class type of the object */
+        uint32_t length; /**< length of DataView */
+      } dataview;
+#endif /* JERRY_BUILTIN_DATAVIEW */
+    } clz;
+
     /**
      * Description of function objects.
      */
diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-dataview-prototype.c b/jerry-core/ecma/builtin-objects/ecma-builtin-dataview-prototype.c
index 6cb9ba3a65..1ec775797c 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-dataview-prototype.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-dataview-prototype.c
@@ -124,7 +124,7 @@ ecma_builtin_dataview_prototype_object_getters (ecma_value_t this_arg, /**< this
       {
         return ecma_raise_type_error (ECMA_ERR_ARRAYBUFFER_IS_DETACHED);
       }
-      return ecma_make_uint32_value (obj_p->header.u.cls.u3.length);
+      return ecma_make_uint32_value (obj_p->header.u.clz.arraybuffer.length);
     }
     default:
     {
diff --git a/jerry-core/ecma/builtin-objects/typedarray/ecma-builtin-typedarray-prototype.c b/jerry-core/ecma/builtin-objects/typedarray/ecma-builtin-typedarray-prototype.c
index 553cffda74..40b3797092 100644
--- a/jerry-core/ecma/builtin-objects/typedarray/ecma-builtin-typedarray-prototype.c
+++ b/jerry-core/ecma/builtin-objects/typedarray/ecma-builtin-typedarray-prototype.c
@@ -2086,7 +2086,7 @@ ecma_builtin_typedarray_prototype_dispatch_routine (uint8_t builtin_routine_id,
     case ECMA_TYPEDARRAY_PROTOTYPE_ROUTINE_TO_STRING_TAG_GETTER:
     {
       ecma_extended_object_t *object_p = (ecma_extended_object_t *) typedarray_p;
-      return ecma_make_magic_string_value (ecma_get_typedarray_magic_string_id (object_p->u.cls.u1.typedarray_type));
+      return ecma_make_magic_string_value (ecma_get_typedarray_magic_string_id (object_p->u.clz.typedarray.type));
     }
     default:
     {
diff --git a/jerry-core/ecma/operations/ecma-arguments-object.c b/jerry-core/ecma/operations/ecma-arguments-object.c
index fd0c679804..e4fc5cb552 100644
--- a/jerry-core/ecma/operations/ecma-arguments-object.c
+++ b/jerry-core/ecma/operations/ecma-arguments-object.c
@@ -76,9 +76,9 @@ ecma_op_create_arguments_object (vm_frame_ctx_shared_args_t *shared_p, /**< shar
   ecma_unmapped_arguments_t *arguments_p = (ecma_unmapped_arguments_t *) obj_p;
 
   arguments_p->header.u.cls.type = ECMA_OBJECT_CLASS_ARGUMENTS;
-  arguments_p->header.u.cls.u1.arguments_flags = ECMA_ARGUMENTS_OBJECT_NO_FLAGS;
-  arguments_p->header.u.cls.u2.formal_params_number = formal_params_number;
-  arguments_p->header.u.cls.u3.arguments_number = 0;
+  arguments_p->header.u.clz.arguments.flags = ECMA_ARGUMENTS_OBJECT_NO_FLAGS;
+  arguments_p->header.u.clz.arguments.formal_params_number = formal_params_number;
+  arguments_p->header.u.clz.arguments.number = 0;
   arguments_p->callee = ecma_make_object_value (func_obj_p);
 
   ecma_value_t *argv_p = (ecma_value_t *) (((uint8_t *) obj_p) + object_size);
@@ -93,19 +93,19 @@ ecma_op_create_arguments_object (vm_frame_ctx_shared_args_t *shared_p, /**< shar
     argv_p[i] = ECMA_VALUE_UNDEFINED;
   }
 
-  arguments_p->header.u.cls.u3.arguments_number = shared_p->arg_list_len;
+  arguments_p->header.u.clz.arguments.number = shared_p->arg_list_len;
 
   if (bytecode_data_p->status_flags & CBC_CODE_FLAGS_MAPPED_ARGUMENTS_NEEDED)
   {
     ecma_mapped_arguments_t *mapped_arguments_p = (ecma_mapped_arguments_t *) obj_p;
 
     ECMA_SET_INTERNAL_VALUE_POINTER (mapped_arguments_p->lex_env, lex_env_p);
-    arguments_p->header.u.cls.u1.arguments_flags |= ECMA_ARGUMENTS_OBJECT_MAPPED;
+    arguments_p->header.u.clz.arguments.flags |= ECMA_ARGUMENTS_OBJECT_MAPPED;
 
 #if JERRY_SNAPSHOT_EXEC
     if (bytecode_data_p->status_flags & CBC_CODE_FLAGS_STATIC_FUNCTION)
     {
-      arguments_p->header.u.cls.u1.arguments_flags |= ECMA_ARGUMENTS_OBJECT_STATIC_BYTECODE;
+      arguments_p->header.u.clz.arguments.flags |= ECMA_ARGUMENTS_OBJECT_STATIC_BYTECODE;
       mapped_arguments_p->u.byte_code_p = (ecma_compiled_code_t *) bytecode_data_p;
     }
     else
@@ -166,7 +166,7 @@ ecma_op_arguments_object_define_own_property (ecma_object_t *object_p, /**< the
   ecma_value_t ret_value = ecma_op_general_object_define_own_property (object_p, property_name_p, property_desc_p);
 
   if (ECMA_IS_VALUE_ERROR (ret_value)
-      || !(((ecma_extended_object_t *) object_p)->u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED))
+      || !(((ecma_extended_object_t *) object_p)->u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED))
   {
     return ret_value;
   }
@@ -174,7 +174,7 @@ ecma_op_arguments_object_define_own_property (ecma_object_t *object_p, /**< the
   ecma_mapped_arguments_t *mapped_arguments_p = (ecma_mapped_arguments_t *) object_p;
   uint32_t index = ecma_string_get_array_index (property_name_p);
 
-  if (index >= mapped_arguments_p->unmapped.header.u.cls.u2.formal_params_number)
+  if (index >= mapped_arguments_p->unmapped.header.u.clz.arguments.formal_params_number)
   {
     return ret_value;
   }
@@ -228,8 +228,8 @@ ecma_op_arguments_object_try_to_lazy_instantiate_property (ecma_object_t *object
   ecma_value_t *argv_p = (ecma_value_t *) (arguments_p + 1);
   ecma_property_value_t *prop_value_p;
   ecma_property_t *prop_p;
-  uint32_t arguments_number = arguments_p->header.u.cls.u3.arguments_number;
-  uint8_t flags = arguments_p->header.u.cls.u1.arguments_flags;
+  uint32_t arguments_number = arguments_p->header.u.clz.arguments.number;
+  uint8_t flags = arguments_p->header.u.clz.arguments.flags;
 
   if (flags & ECMA_ARGUMENTS_OBJECT_MAPPED)
   {
@@ -327,27 +327,27 @@ ecma_op_arguments_delete_built_in_property (ecma_object_t *object_p, /**< the ob
 
   if (ecma_compare_ecma_string_to_magic_id (property_name_p, LIT_MAGIC_STRING_LENGTH))
   {
-    JERRY_ASSERT (!(arguments_p->header.u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_LENGTH_INITIALIZED));
+    JERRY_ASSERT (!(arguments_p->header.u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_LENGTH_INITIALIZED));
 
-    arguments_p->header.u.cls.u1.arguments_flags |= ECMA_ARGUMENTS_OBJECT_LENGTH_INITIALIZED;
+    arguments_p->header.u.clz.arguments.flags |= ECMA_ARGUMENTS_OBJECT_LENGTH_INITIALIZED;
     return;
   }
 
   if (ecma_compare_ecma_string_to_magic_id (property_name_p, LIT_MAGIC_STRING_CALLEE))
   {
-    JERRY_ASSERT (!(arguments_p->header.u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_CALLEE_INITIALIZED));
-    JERRY_ASSERT (arguments_p->header.u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED);
+    JERRY_ASSERT (!(arguments_p->header.u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_CALLEE_INITIALIZED));
+    JERRY_ASSERT (arguments_p->header.u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED);
 
-    arguments_p->header.u.cls.u1.arguments_flags |= ECMA_ARGUMENTS_OBJECT_CALLEE_INITIALIZED;
+    arguments_p->header.u.clz.arguments.flags |= ECMA_ARGUMENTS_OBJECT_CALLEE_INITIALIZED;
     return;
   }
 
   if (ecma_prop_name_is_symbol (property_name_p))
   {
-    JERRY_ASSERT (!(arguments_p->header.u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_ITERATOR_INITIALIZED));
+    JERRY_ASSERT (!(arguments_p->header.u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_ITERATOR_INITIALIZED));
     JERRY_ASSERT (ecma_op_compare_string_to_global_symbol (property_name_p, LIT_GLOBAL_SYMBOL_ITERATOR));
 
-    arguments_p->header.u.cls.u1.arguments_flags |= ECMA_ARGUMENTS_OBJECT_ITERATOR_INITIALIZED;
+    arguments_p->header.u.clz.arguments.flags |= ECMA_ARGUMENTS_OBJECT_ITERATOR_INITIALIZED;
     return;
   }
 
@@ -355,7 +355,7 @@ ecma_op_arguments_delete_built_in_property (ecma_object_t *object_p, /**< the ob
 
   ecma_value_t *argv_p = (ecma_value_t *) (arguments_p + 1);
 
-  if (arguments_p->header.u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED)
+  if (arguments_p->header.u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED)
   {
     argv_p = (ecma_value_t *) (((ecma_mapped_arguments_t *) object_p) + 1);
   }
@@ -378,8 +378,8 @@ ecma_op_arguments_object_list_lazy_property_names (ecma_object_t *obj_p, /**< ar
 
   ecma_unmapped_arguments_t *arguments_p = (ecma_unmapped_arguments_t *) obj_p;
 
-  uint32_t arguments_number = arguments_p->header.u.cls.u3.arguments_number;
-  uint8_t flags = arguments_p->header.u.cls.u1.arguments_flags;
+  uint32_t arguments_number = arguments_p->header.u.clz.arguments.number;
+  uint8_t flags = arguments_p->header.u.clz.arguments.flags;
 
   if (!(filter & JERRY_PROPERTY_FILTER_EXCLUDE_INTEGER_INDICES))
   {
@@ -434,13 +434,13 @@ ecma_op_arguments_object_get_formal_parameter (ecma_mapped_arguments_t *mapped_a
                                                                                              *   object */
                                                uint32_t index) /**< formal parameter index */
 {
-  JERRY_ASSERT (mapped_arguments_p->unmapped.header.u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED);
-  JERRY_ASSERT (index < mapped_arguments_p->unmapped.header.u.cls.u2.formal_params_number);
+  JERRY_ASSERT (mapped_arguments_p->unmapped.header.u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED);
+  JERRY_ASSERT (index < mapped_arguments_p->unmapped.header.u.clz.arguments.formal_params_number);
 
   ecma_compiled_code_t *byte_code_p;
 
 #if JERRY_SNAPSHOT_EXEC
-  if (mapped_arguments_p->unmapped.header.u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_STATIC_BYTECODE)
+  if (mapped_arguments_p->unmapped.header.u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_STATIC_BYTECODE)
   {
     byte_code_p = mapped_arguments_p->u.byte_code_p;
   }
diff --git a/jerry-core/ecma/operations/ecma-arraybuffer-object.c b/jerry-core/ecma/operations/ecma-arraybuffer-object.c
index 3a436d1f80..34d6f97b95 100644
--- a/jerry-core/ecma/operations/ecma-arraybuffer-object.c
+++ b/jerry-core/ecma/operations/ecma-arraybuffer-object.c
@@ -65,8 +65,8 @@ ecma_arraybuffer_create_object (uint8_t type, /**< type of the arraybuffer */
 
   ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) object_p;
   ext_object_p->u.cls.type = type;
-  ext_object_p->u.cls.u1.array_buffer_flags = ECMA_ARRAYBUFFER_ALLOCATED;
-  ext_object_p->u.cls.u3.length = length;
+  ext_object_p->u.clz.arraybuffer.flags = ECMA_ARRAYBUFFER_ALLOCATED;
+  ext_object_p->u.clz.arraybuffer.length = length;
 
   memset ((uint8_t *) (ext_object_p + 1), 0, length);
   return object_p;
@@ -99,8 +99,8 @@ ecma_arraybuffer_create_object_with_buffer (uint8_t type, /**< type of the array
 
   ecma_arraybuffer_pointer_t *arraybuffer_pointer_p = (ecma_arraybuffer_pointer_t *) object_p;
   arraybuffer_pointer_p->extended_object.u.cls.type = type;
-  arraybuffer_pointer_p->extended_object.u.cls.u1.array_buffer_flags = ECMA_ARRAYBUFFER_HAS_POINTER;
-  arraybuffer_pointer_p->extended_object.u.cls.u3.length = length;
+  arraybuffer_pointer_p->extended_object.u.clz.arraybuffer.flags = ECMA_ARRAYBUFFER_HAS_POINTER;
+  arraybuffer_pointer_p->extended_object.u.clz.arraybuffer.length = length;
 
   arraybuffer_pointer_p->buffer_p = NULL;
   arraybuffer_pointer_p->arraybuffer_user_p = NULL;
@@ -139,11 +139,11 @@ ecma_arraybuffer_allocate_buffer (ecma_object_t *arraybuffer_p) /**< ArrayBuffer
 
   if (ECMA_ARRAYBUFFER_GET_FLAGS (arraybuffer_p) & ECMA_ARRAYBUFFER_DETACHED)
   {
-    extended_object_p->u.cls.u1.array_buffer_flags |= ECMA_ARRAYBUFFER_ALLOCATED;
+    extended_object_p->u.clz.arraybuffer.flags |= ECMA_ARRAYBUFFER_ALLOCATED;
     return ECMA_VALUE_UNDEFINED;
   }
 
-  uint32_t arraybuffer_length = extended_object_p->u.cls.u3.length;
+  uint32_t arraybuffer_length = extended_object_p->u.clz.arraybuffer.length;
   ecma_arraybuffer_pointer_t *arraybuffer_pointer_p = (ecma_arraybuffer_pointer_t *) arraybuffer_p;
   jerry_arraybuffer_allocate_cb_t arraybuffer_allocate_callback = JERRY_CONTEXT (arraybuffer_allocate_callback);
   uint8_t *buffer_p;
@@ -175,7 +175,7 @@ ecma_arraybuffer_allocate_buffer (ecma_object_t *arraybuffer_p) /**< ArrayBuffer
   }
 
   arraybuffer_pointer_p->buffer_p = buffer_p;
-  extended_object_p->u.cls.u1.array_buffer_flags |= ECMA_ARRAYBUFFER_ALLOCATED;
+  extended_object_p->u.clz.arraybuffer.flags |= ECMA_ARRAYBUFFER_ALLOCATED;
 
   memset (buffer_p, 0, arraybuffer_length);
   return ECMA_VALUE_UNDEFINED;
@@ -212,7 +212,7 @@ ecma_arraybuffer_release_buffer (ecma_object_t *arraybuffer_p) /**< ArrayBuffer
     return;
   }
 
-  uint32_t arraybuffer_length = arraybuffer_pointer_p->extended_object.u.cls.u3.length;
+  uint32_t arraybuffer_length = arraybuffer_pointer_p->extended_object.u.clz.arraybuffer.length;
 
   if (free_callback == NULL)
   {
@@ -329,7 +329,7 @@ ecma_arraybuffer_get_length (ecma_object_t *object_p) /**< pointer to the ArrayB
                 || ecma_object_is_shared_arraybuffer (object_p));
 
   ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) object_p;
-  return ecma_arraybuffer_is_detached (object_p) ? 0 : ext_object_p->u.cls.u3.length;
+  return ecma_arraybuffer_is_detached (object_p) ? 0 : ext_object_p->u.clz.arraybuffer.length;
 } /* ecma_arraybuffer_get_length */
 
 /**
@@ -386,14 +386,14 @@ ecma_arraybuffer_detach (ecma_object_t *object_p) /**< pointer to the ArrayBuffe
   }
 
   ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) object_p;
-  ext_object_p->u.cls.u1.array_buffer_flags |= ECMA_ARRAYBUFFER_DETACHED;
+  ext_object_p->u.clz.arraybuffer.flags |= ECMA_ARRAYBUFFER_DETACHED;
 
   if (!(ECMA_ARRAYBUFFER_GET_FLAGS (object_p) & ECMA_ARRAYBUFFER_ALLOCATED))
   {
     return true;
   }
 
-  ext_object_p->u.cls.u1.array_buffer_flags &= (uint8_t) ~ECMA_ARRAYBUFFER_ALLOCATED;
+  ext_object_p->u.clz.arraybuffer.flags &= (uint8_t) ~ECMA_ARRAYBUFFER_ALLOCATED;
 
   if (!(ECMA_ARRAYBUFFER_GET_FLAGS (object_p) & ECMA_ARRAYBUFFER_HAS_POINTER))
   {
diff --git a/jerry-core/ecma/operations/ecma-arraybuffer-object.h b/jerry-core/ecma/operations/ecma-arraybuffer-object.h
index 6dc28b59bc..16c41160ae 100644
--- a/jerry-core/ecma/operations/ecma-arraybuffer-object.h
+++ b/jerry-core/ecma/operations/ecma-arraybuffer-object.h
@@ -31,7 +31,7 @@
  * Get array buffer flags.
  */
 #define ECMA_ARRAYBUFFER_GET_FLAGS(arraybuffer_p) \
-  (((ecma_extended_object_t *) (arraybuffer_p))->u.cls.u1.array_buffer_flags)
+  (((ecma_extended_object_t *) (arraybuffer_p))->u.clz.arraybuffer.flags)
 
 /**
  * Check whether the backing store is allocated for an array buffer.
diff --git a/jerry-core/ecma/operations/ecma-dataview-object.c b/jerry-core/ecma/operations/ecma-dataview-object.c
index db2ae0a68b..6b361f3547 100644
--- a/jerry-core/ecma/operations/ecma-dataview-object.c
+++ b/jerry-core/ecma/operations/ecma-dataview-object.c
@@ -149,7 +149,7 @@ ecma_op_dataview_create (const ecma_value_t *arguments_list_p, /**< arguments li
   /* 11 - 14. */
   ecma_dataview_object_t *dataview_obj_p = (ecma_dataview_object_t *) object_p;
   dataview_obj_p->header.u.cls.type = ECMA_OBJECT_CLASS_DATAVIEW;
-  dataview_obj_p->header.u.cls.u3.length = view_byte_length;
+  dataview_obj_p->header.u.clz.dataview.length = view_byte_length;
   dataview_obj_p->buffer_p = buffer_p;
   dataview_obj_p->byte_offset = (uint32_t) offset;
 
@@ -315,7 +315,7 @@ ecma_op_dataview_get_set_view_value (ecma_value_t view, /**< the operation's 'vi
   uint32_t view_offset = view_p->byte_offset;
 
   /* GetViewValue 8., SetViewValue 10. */
-  uint32_t view_size = view_p->header.u.cls.u3.length;
+  uint32_t view_size = view_p->header.u.clz.dataview.length;
 
   /* GetViewValue 9., SetViewValue 11. */
   uint8_t element_size = (uint8_t) (1 << (ecma_typedarray_helper_get_shift_size (id)));
diff --git a/jerry-core/ecma/operations/ecma-objects.c b/jerry-core/ecma/operations/ecma-objects.c
index f06a307d8e..ef7bc221a1 100644
--- a/jerry-core/ecma/operations/ecma-objects.c
+++ b/jerry-core/ecma/operations/ecma-objects.c
@@ -342,13 +342,13 @@ ecma_op_object_get_own_property (ecma_object_t *object_p, /**< the object */
   }
   else if (type == ECMA_OBJECT_TYPE_CLASS
            && ((ecma_extended_object_t *) object_p)->u.cls.type == ECMA_OBJECT_CLASS_ARGUMENTS
-           && (((ecma_extended_object_t *) object_p)->u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED))
+           && (((ecma_extended_object_t *) object_p)->u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED))
   {
     ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) object_p;
 
     uint32_t index = ecma_string_get_array_index (property_name_p);
 
-    if (index < ext_object_p->u.cls.u2.formal_params_number)
+    if (index < ext_object_p->u.clz.arguments.formal_params_number)
     {
       ecma_mapped_arguments_t *mapped_arguments_p = (ecma_mapped_arguments_t *) ext_object_p;
 
@@ -507,14 +507,14 @@ ecma_op_object_find_own (ecma_value_t base_value, /**< base value */
         }
         case ECMA_OBJECT_CLASS_ARGUMENTS:
         {
-          if (!(ext_object_p->u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED))
+          if (!(ext_object_p->u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED))
           {
             break;
           }
 
           uint32_t index = ecma_string_get_array_index (property_name_p);
 
-          if (index < ext_object_p->u.cls.u2.formal_params_number)
+          if (index < ext_object_p->u.clz.arguments.formal_params_number)
           {
             ecma_mapped_arguments_t *mapped_arguments_p = (ecma_mapped_arguments_t *) ext_object_p;
 
@@ -1287,14 +1287,14 @@ ecma_op_object_put_with_receiver (ecma_object_t *object_p, /**< the object */
       {
         case ECMA_OBJECT_CLASS_ARGUMENTS:
         {
-          if (!(ext_object_p->u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED))
+          if (!(ext_object_p->u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED))
           {
             break;
           }
 
           uint32_t index = ecma_string_get_array_index (property_name_p);
 
-          if (index < ext_object_p->u.cls.u2.formal_params_number)
+          if (index < ext_object_p->u.clz.arguments.formal_params_number)
           {
             ecma_mapped_arguments_t *mapped_arguments_p = (ecma_mapped_arguments_t *) ext_object_p;
 
@@ -1560,7 +1560,7 @@ ecma_op_object_put_with_receiver (ecma_object_t *object_p, /**< the object */
         ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) object_p;
 
         if (ext_object_p->u.cls.type == ECMA_OBJECT_CLASS_ARGUMENTS
-            && ext_object_p->u.cls.u1.arguments_flags & ECMA_ARGUMENTS_OBJECT_MAPPED)
+            && ext_object_p->u.clz.arguments.flags & ECMA_ARGUMENTS_OBJECT_MAPPED)
         {
           const uint32_t flags = ECMA_PROPERTY_CONFIGURABLE_ENUMERABLE_WRITABLE | JERRY_PROP_SHOULD_THROW;
           return ecma_builtin_helper_def_prop (object_p, property_name_p, value, flags);
@@ -2816,7 +2816,7 @@ ecma_object_get_class_name (ecma_object_t *obj_p) /**< object */
 #if JERRY_BUILTIN_TYPEDARRAY
         case ECMA_OBJECT_CLASS_TYPEDARRAY:
         {
-          return ecma_get_typedarray_magic_string_id (ext_object_p->u.cls.u1.typedarray_type);
+          return ecma_get_typedarray_magic_string_id (ext_object_p->u.clz.typedarray.type);
         }
 #endif /* JERRY_BUILTIN_TYPEDARRAY */
 #if JERRY_BUILTIN_CONTAINER
diff --git a/jerry-core/ecma/operations/ecma-typedarray-object.c b/jerry-core/ecma/operations/ecma-typedarray-object.c
index c4c4f41052..80349932ab 100644
--- a/jerry-core/ecma/operations/ecma-typedarray-object.c
+++ b/jerry-core/ecma/operations/ecma-typedarray-object.c
@@ -765,7 +765,7 @@ ecma_get_typedarray_id (ecma_object_t *obj_p) /**< typedarray object **/
 
   ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) obj_p;
 
-  return (ecma_typedarray_type_t) ext_object_p->u.cls.u1.typedarray_type;
+  return (ecma_typedarray_type_t) ext_object_p->u.clz.typedarray.type;
 } /* ecma_get_typedarray_id */
 
 /**
@@ -860,9 +860,9 @@ ecma_typedarray_create_object_with_length (uint32_t array_length, /**< length of
 
   ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) object_p;
   ext_object_p->u.cls.type = ECMA_OBJECT_CLASS_TYPEDARRAY;
-  ext_object_p->u.cls.u1.typedarray_type = (uint8_t) typedarray_id;
-  ext_object_p->u.cls.u2.typedarray_flags = 0;
-  ext_object_p->u.cls.u3.arraybuffer = ecma_make_object_value (new_arraybuffer_p);
+  ext_object_p->u.clz.typedarray.type = (uint8_t) typedarray_id;
+  ext_object_p->u.clz.typedarray.flags = 0;
+  ext_object_p->u.clz.typedarray.arraybuffer = ecma_make_object_value (new_arraybuffer_p);
 
   ecma_deref_object (new_arraybuffer_p);
 
@@ -1527,7 +1527,7 @@ ecma_typedarray_get_arraybuffer (ecma_object_t *typedarray_p) /**< the pointer t
 
   ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) typedarray_p;
 
-  return ecma_get_object_from_value (ext_object_p->u.cls.u3.arraybuffer);
+  return ecma_get_object_from_value (ext_object_p->u.clz.typedarray.arraybuffer);
 } /* ecma_typedarray_get_arraybuffer */
 
 /**
@@ -1555,11 +1555,11 @@ ecma_typedarray_get_length (ecma_object_t *typedarray_p) /**< the pointer to the
 
   ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) typedarray_p;
 
-  if (!(ext_object_p->u.cls.u2.typedarray_flags & ECMA_TYPEDARRAY_IS_EXTENDED))
+  if (!(ext_object_p->u.clz.typedarray.flags & ECMA_TYPEDARRAY_IS_EXTENDED))
   {
-    ecma_object_t *arraybuffer_p = ecma_get_object_from_value (ext_object_p->u.cls.u3.arraybuffer);
+    ecma_object_t *arraybuffer_p = ecma_get_object_from_value (ext_object_p->u.clz.typedarray.arraybuffer);
     ecma_extended_object_t *arraybuffer_object_p = (ecma_extended_object_t *) arraybuffer_p;
-    uint32_t buffer_length = arraybuffer_object_p->u.cls.u3.length;
+    uint32_t buffer_length = arraybuffer_object_p->u.clz.arraybuffer.length;
     uint8_t shift = ecma_typedarray_get_element_size_shift (typedarray_p);
 
     return buffer_length >> shift;
@@ -1589,7 +1589,7 @@ ecma_typedarray_get_offset (ecma_object_t *typedarray_p) /**< the pointer to the
 
   ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) typedarray_p;
 
-  if (!(ext_object_p->u.cls.u2.typedarray_flags & ECMA_TYPEDARRAY_IS_EXTENDED))
+  if (!(ext_object_p->u.clz.typedarray.flags & ECMA_TYPEDARRAY_IS_EXTENDED))
   {
     return 0;
   }
@@ -1766,13 +1766,13 @@ ecma_op_create_typedarray (const ecma_value_t *arguments_list_p, /**< the arg li
 
   ecma_extended_object_t *ext_object_p = (ecma_extended_object_t *) object_p;
   ext_object_p->u.cls.type = ECMA_OBJECT_CLASS_TYPEDARRAY;
-  ext_object_p->u.cls.u1.typedarray_type = (uint8_t) typedarray_id;
-  ext_object_p->u.cls.u2.typedarray_flags = 0;
-  ext_object_p->u.cls.u3.arraybuffer = ecma_make_object_value (arraybuffer_p);
+  ext_object_p->u.clz.typedarray.type = (uint8_t) typedarray_id;
+  ext_object_p->u.clz.typedarray.flags = 0;
+  ext_object_p->u.clz.typedarray.arraybuffer = ecma_make_object_value (arraybuffer_p);
 
   if (needs_ext_typedarray_obj)
   {
-    ext_object_p->u.cls.u2.typedarray_flags |= ECMA_TYPEDARRAY_IS_EXTENDED;
+    ext_object_p->u.clz.typedarray.flags |= ECMA_TYPEDARRAY_IS_EXTENDED;
 
     ecma_extended_typedarray_object_t *typedarray_info_p = (ecma_extended_typedarray_object_t *) object_p;
     typedarray_info_p->array_length = new_byte_length >> element_size_shift;