Distinguish slow from fast sloppy arguments

src/elements.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/arguments.h"
 #include "src/conversions.h"
 #include "src/elements.h"
 #include "src/messages.h"
@@ skipping 29 matching lines @@
 //     - FixedInt8ElementsAccessor
 //     - FixedUint16ElementsAccessor
 //     - FixedInt16ElementsAccessor
 //     - FixedUint32ElementsAccessor
 //     - FixedInt32ElementsAccessor
 //     - FixedFloat32ElementsAccessor
 //     - FixedFloat64ElementsAccessor
 //     - FixedUint8ClampedElementsAccessor
 //   - DictionaryElementsAccessor
 //   - SloppyArgumentsElementsAccessor
+//     - FastSloppyArgumentsElementsAccessor
+//     - SlowSloppyArgumentsElementsAccessor
 
 
 namespace v8 {
 namespace internal {
 
 
 static const int kPackedSizeNotKnown = -1;
 
 
 // First argument in list is the accessor class, the second argument is the
 // accessor ElementsKind, and the third is the backing store class.  Use the
 // fast element handler for smi-only arrays.  The implementation is currently
 // identical.  Note that the order must match that of the ElementsKind enum for
 // the |accessor_array[]| below to work.
-#define ELEMENTS_LIST(V)                                                \
-  V(FastPackedSmiElementsAccessor, FAST_SMI_ELEMENTS, FixedArray)       \
-  V(FastHoleySmiElementsAccessor, FAST_HOLEY_SMI_ELEMENTS,              \
-    FixedArray)                                                         \
-  V(FastPackedObjectElementsAccessor, FAST_ELEMENTS, FixedArray)        \
-  V(FastHoleyObjectElementsAccessor, FAST_HOLEY_ELEMENTS, FixedArray)   \
-  V(FastPackedDoubleElementsAccessor, FAST_DOUBLE_ELEMENTS,             \
-    FixedDoubleArray)                                                   \
-  V(FastHoleyDoubleElementsAccessor, FAST_HOLEY_DOUBLE_ELEMENTS,        \
-    FixedDoubleArray)                                                   \
-  V(DictionaryElementsAccessor, DICTIONARY_ELEMENTS,                    \
-    SeededNumberDictionary)                                             \
-  V(SloppyArgumentsElementsAccessor, SLOPPY_ARGUMENTS_ELEMENTS,         \
-    FixedArray)                                                         \
-  V(ExternalInt8ElementsAccessor, EXTERNAL_INT8_ELEMENTS,               \
-    ExternalInt8Array)                                                  \
-  V(ExternalUint8ElementsAccessor,                                      \
-    EXTERNAL_UINT8_ELEMENTS, ExternalUint8Array)                        \
-  V(ExternalInt16ElementsAccessor, EXTERNAL_INT16_ELEMENTS,             \
-    ExternalInt16Array)                                                 \
-  V(ExternalUint16ElementsAccessor,                                     \
-    EXTERNAL_UINT16_ELEMENTS, ExternalUint16Array)                      \
-  V(ExternalInt32ElementsAccessor, EXTERNAL_INT32_ELEMENTS,             \
-    ExternalInt32Array)                                                 \
-  V(ExternalUint32ElementsAccessor,                                     \
-    EXTERNAL_UINT32_ELEMENTS, ExternalUint32Array)                      \
-  V(ExternalFloat32ElementsAccessor,                                    \
-    EXTERNAL_FLOAT32_ELEMENTS, ExternalFloat32Array)                    \
-  V(ExternalFloat64ElementsAccessor,                                    \
-    EXTERNAL_FLOAT64_ELEMENTS, ExternalFloat64Array)                    \
-  V(ExternalUint8ClampedElementsAccessor,                               \
-    EXTERNAL_UINT8_CLAMPED_ELEMENTS,                                    \
-    ExternalUint8ClampedArray)                                          \
-  V(FixedUint8ElementsAccessor, UINT8_ELEMENTS, FixedUint8Array)        \
-  V(FixedInt8ElementsAccessor, INT8_ELEMENTS, FixedInt8Array)           \
-  V(FixedUint16ElementsAccessor, UINT16_ELEMENTS, FixedUint16Array)     \
-  V(FixedInt16ElementsAccessor, INT16_ELEMENTS, FixedInt16Array)        \
-  V(FixedUint32ElementsAccessor, UINT32_ELEMENTS, FixedUint32Array)     \
-  V(FixedInt32ElementsAccessor, INT32_ELEMENTS, FixedInt32Array)        \
-  V(FixedFloat32ElementsAccessor, FLOAT32_ELEMENTS, FixedFloat32Array)  \
-  V(FixedFloat64ElementsAccessor, FLOAT64_ELEMENTS, FixedFloat64Array)  \
-  V(FixedUint8ClampedElementsAccessor, UINT8_CLAMPED_ELEMENTS,          \
+#define ELEMENTS_LIST(V)                                                      \
+  V(FastPackedSmiElementsAccessor, FAST_SMI_ELEMENTS, FixedArray)             \
+  V(FastHoleySmiElementsAccessor, FAST_HOLEY_SMI_ELEMENTS, FixedArray)        \
+  V(FastPackedObjectElementsAccessor, FAST_ELEMENTS, FixedArray)              \
+  V(FastHoleyObjectElementsAccessor, FAST_HOLEY_ELEMENTS, FixedArray)         \
+  V(FastPackedDoubleElementsAccessor, FAST_DOUBLE_ELEMENTS, FixedDoubleArray) \
+  V(FastHoleyDoubleElementsAccessor, FAST_HOLEY_DOUBLE_ELEMENTS,              \
+    FixedDoubleArray)                                                         \
+  V(DictionaryElementsAccessor, DICTIONARY_ELEMENTS, SeededNumberDictionary)  \
+  V(FastSloppyArgumentsElementsAccessor, FAST_SLOPPY_ARGUMENTS_ELEMENTS,      \
+    FixedArray)                                                               \
+  V(SlowSloppyArgumentsElementsAccessor, SLOW_SLOPPY_ARGUMENTS_ELEMENTS,      \
+    FixedArray)                                                               \
+  V(ExternalInt8ElementsAccessor, EXTERNAL_INT8_ELEMENTS, ExternalInt8Array)  \
+  V(ExternalUint8ElementsAccessor, EXTERNAL_UINT8_ELEMENTS,                   \
+    ExternalUint8Array)                                                       \
+  V(ExternalInt16ElementsAccessor, EXTERNAL_INT16_ELEMENTS,                   \
+    ExternalInt16Array)                                                       \
+  V(ExternalUint16ElementsAccessor, EXTERNAL_UINT16_ELEMENTS,                 \
+    ExternalUint16Array)                                                      \
+  V(ExternalInt32ElementsAccessor, EXTERNAL_INT32_ELEMENTS,                   \
+    ExternalInt32Array)                                                       \
+  V(ExternalUint32ElementsAccessor, EXTERNAL_UINT32_ELEMENTS,                 \
+    ExternalUint32Array)                                                      \
+  V(ExternalFloat32ElementsAccessor, EXTERNAL_FLOAT32_ELEMENTS,               \
+    ExternalFloat32Array)                                                     \
+  V(ExternalFloat64ElementsAccessor, EXTERNAL_FLOAT64_ELEMENTS,               \
+    ExternalFloat64Array)                                                     \
+  V(ExternalUint8ClampedElementsAccessor, EXTERNAL_UINT8_CLAMPED_ELEMENTS,    \
+    ExternalUint8ClampedArray)                                                \
+  V(FixedUint8ElementsAccessor, UINT8_ELEMENTS, FixedUint8Array)              \
+  V(FixedInt8ElementsAccessor, INT8_ELEMENTS, FixedInt8Array)                 \
+  V(FixedUint16ElementsAccessor, UINT16_ELEMENTS, FixedUint16Array)           \
+  V(FixedInt16ElementsAccessor, INT16_ELEMENTS, FixedInt16Array)              \
+  V(FixedUint32ElementsAccessor, UINT32_ELEMENTS, FixedUint32Array)           \
+  V(FixedInt32ElementsAccessor, INT32_ELEMENTS, FixedInt32Array)              \
+  V(FixedFloat32ElementsAccessor, FLOAT32_ELEMENTS, FixedFloat32Array)        \
+  V(FixedFloat64ElementsAccessor, FLOAT64_ELEMENTS, FixedFloat64Array)        \
+  V(FixedUint8ClampedElementsAccessor, UINT8_CLAMPED_ELEMENTS,                \
     FixedUint8ClampedArray)
 
 
 template<ElementsKind Kind> class ElementsKindTraits {
  public:
   typedef FixedArrayBase BackingStore;
 };
 
 #define ELEMENTS_TRAITS(Class, KindParam, Store)               \
 template<> class ElementsKindTraits<KindParam> {               \
@@ skipping 427 matching lines @@
 //   }
 //
 // This is an example of the Curiously Recurring Template Pattern (see
 // http://en.wikipedia.org/wiki/Curiously_recurring_template_pattern).  We use
 // CRTP to guarantee aggressive compile time optimizations (i.e.  inlining and
 // specialization of SomeElementsAccessor methods).
 template <typename ElementsAccessorSubclass,
           typename ElementsTraitsParam>
 class ElementsAccessorBase : public ElementsAccessor {
  protected:
+  template <typename SloppyArgumentsElementsAccessorSubclass,
+            typename ArgumentsAccessor, typename KindTraits>
+  friend class SloppyArgumentsElementsAccessor;
   explicit ElementsAccessorBase(const char* name)
       : ElementsAccessor(name) { }
 
   typedef ElementsTraitsParam ElementsTraits;
   typedef typename ElementsTraitsParam::BackingStore BackingStore;
 
   static ElementsKind kind() { return ElementsTraits::Kind; }
 
   static void ValidateContents(Handle<JSObject> holder, int length) {
   }
@@ skipping 352 matching lines @@
   virtual PropertyDetails GetDetails(FixedArrayBase* backing_store,
                                      uint32_t index) final {
     return ElementsAccessorSubclass::GetDetailsImpl(backing_store, index);
   }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ElementsAccessorBase);
 };
 
 
+class FastSloppyArgumentsElementsAccessor;
+class FastHoleyObjectElementsAccessor;
+template <typename SloppyArgumentsElementsAccessorSubclass,
+          typename ArgumentsAccessor, typename KindTraits>
+class SloppyArgumentsElementsAccessor;
+
 // Super class for all fast element arrays.
 template<typename FastElementsAccessorSubclass,
          typename KindTraits>
 class FastElementsAccessor
     : public ElementsAccessorBase<FastElementsAccessorSubclass, KindTraits> {
  public:
   explicit FastElementsAccessor(const char* name)
       : ElementsAccessorBase<FastElementsAccessorSubclass,
                              KindTraits>(name) {}
 
  protected:
   friend class ElementsAccessorBase<FastElementsAccessorSubclass, KindTraits>;
-  friend class SloppyArgumentsElementsAccessor;
+  friend class SloppyArgumentsElementsAccessor<
+      FastSloppyArgumentsElementsAccessor, FastHoleyObjectElementsAccessor,
+      ElementsKindTraits<FAST_SLOPPY_ARGUMENTS_ELEMENTS> >;
 
   typedef typename KindTraits::BackingStore BackingStore;
 
   static void DeleteCommon(Handle<JSObject> obj, uint32_t key,
                            LanguageMode language_mode) {
     DCHECK(obj->HasFastSmiOrObjectElements() ||
            obj->HasFastDoubleElements() ||
            obj->HasFastArgumentsElements());
     Isolate* isolate = obj->GetIsolate();
     Heap* heap = obj->GetHeap();
@@ skipping 111 matching lines @@
         DCHECK(BackingStore::get(backing_store, i)->IsSmi() ||
                (IsFastHoleyElementsKind(KindTraits::Kind) &&
                 backing_store->is_the_hole(i)));
       }
     }
 #endif
   }
 };
 
 
-static inline ElementsKind ElementsKindForArray(FixedArrayBase* array) {
-  switch (array->map()->instance_type()) {
-    case FIXED_ARRAY_TYPE:
-      if (array->IsDictionary()) {
-        return DICTIONARY_ELEMENTS;
-      } else {
-        return FAST_HOLEY_ELEMENTS;
-      }
-    case FIXED_DOUBLE_ARRAY_TYPE:
-      return FAST_HOLEY_DOUBLE_ELEMENTS;
-
-#define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size)                       \
-    case EXTERNAL_##TYPE##_ARRAY_TYPE:                                        \
-      return EXTERNAL_##TYPE##_ELEMENTS;                                      \
-    case FIXED_##TYPE##_ARRAY_TYPE:                                           \
-      return TYPE##_ELEMENTS;
-
-    TYPED_ARRAYS(TYPED_ARRAY_CASE)
-#undef TYPED_ARRAY_CASE
-
-    default:
-      UNREACHABLE();
-  }
-  return FAST_HOLEY_ELEMENTS;
-}
-
-
 template<typename FastElementsAccessorSubclass,
          typename KindTraits>
 class FastSmiOrObjectElementsAccessor
     : public FastElementsAccessor<FastElementsAccessorSubclass, KindTraits> {
  public:
   explicit FastSmiOrObjectElementsAccessor(const char* name)
       : FastElementsAccessor<FastElementsAccessorSubclass,
                              KindTraits>(name) {}
 
   // NOTE: this method violates the handlified function signature convention:
@@ skipping 19 matching lines @@
       case FAST_HOLEY_DOUBLE_ELEMENTS: {
         AllowHeapAllocation allow_allocation;
         CopyDoubleToObjectElements(
             from, from_start, to, to_kind, to_start, copy_size);
         break;
       }
       case DICTIONARY_ELEMENTS:
         CopyDictionaryToObjectElements(from, from_start, to, to_kind, to_start,
                                        copy_size);
         break;
-      case SLOPPY_ARGUMENTS_ELEMENTS: {
-        // TODO(verwaest): This is a temporary hack to support extending
-        // SLOPPY_ARGUMENTS_ELEMENTS in GrowCapacityAndConvert.
-        // This case should be UNREACHABLE().
-        FixedArray* parameter_map = FixedArray::cast(from);
-        FixedArrayBase* arguments = FixedArrayBase::cast(parameter_map->get(1));
-        ElementsKind from_kind = ElementsKindForArray(arguments);
-        CopyElementsImpl(arguments, from_start, to, from_kind,
-                         to_start, packed_size, copy_size);
-        break;
-      }
+      case FAST_SLOPPY_ARGUMENTS_ELEMENTS:
+      case SLOW_SLOPPY_ARGUMENTS_ELEMENTS:
+        UNREACHABLE();
 #define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size)                       \
       case EXTERNAL_##TYPE##_ELEMENTS:                                        \
       case TYPE##_ELEMENTS:                                                   \
         UNREACHABLE();
       TYPED_ARRAYS(TYPED_ARRAY_CASE)
 #undef TYPED_ARRAY_CASE
     }
   }
 };
 
@@ skipping 74 matching lines @@
         CopyDoubleToDoubleElements(from, from_start, to, to_start, copy_size);
         break;
       case FAST_ELEMENTS:
       case FAST_HOLEY_ELEMENTS:
         CopyObjectToDoubleElements(from, from_start, to, to_start, copy_size);
         break;
       case DICTIONARY_ELEMENTS:
         CopyDictionaryToDoubleElements(from, from_start, to, to_start,
                                        copy_size);
         break;
-      case SLOPPY_ARGUMENTS_ELEMENTS:
+      case FAST_SLOPPY_ARGUMENTS_ELEMENTS:
+      case SLOW_SLOPPY_ARGUMENTS_ELEMENTS:
         UNREACHABLE();
 
 #define TYPED_ARRAY_CASE(Type, type, TYPE, ctype, size)                       \
       case EXTERNAL_##TYPE##_ELEMENTS:                                        \
       case TYPE##_ELEMENTS:                                                   \
         UNREACHABLE();
       TYPED_ARRAYS(TYPED_ARRAY_CASE)
 #undef TYPED_ARRAY_CASE
     }
   }
@@ skipping 97 matching lines @@
 #undef EXTERNAL_ELEMENTS_ACCESSOR
 
 #define FIXED_ELEMENTS_ACCESSOR(Type, type, TYPE, ctype, size)       \
   typedef TypedElementsAccessor<TYPE##_ELEMENTS >                    \
       Fixed##Type##ElementsAccessor;
 
 TYPED_ARRAYS(FIXED_ELEMENTS_ACCESSOR)
 #undef FIXED_ELEMENTS_ACCESSOR
 
 
+class SlowSloppyArgumentsElementsAccessor;
+
 
 class DictionaryElementsAccessor
     : public ElementsAccessorBase<DictionaryElementsAccessor,
                                   ElementsKindTraits<DICTIONARY_ELEMENTS> > {
  public:
   explicit DictionaryElementsAccessor(const char* name)
       : ElementsAccessorBase<DictionaryElementsAccessor,
                              ElementsKindTraits<DICTIONARY_ELEMENTS> >(name) {}
 
   static void SetLengthImpl(Handle<JSArray> array, uint32_t length,
@@ skipping 42 matching lines @@
 
         // Update the number of elements.
         dict->ElementsRemoved(removed_entries);
       }
     }
 
     Handle<Object> length_obj = isolate->factory()->NewNumberFromUint(length);
     array->set_length(*length_obj);
   }
 
+  static void CopyElementsImpl(FixedArrayBase* from, uint32_t from_start,
+                               FixedArrayBase* to, ElementsKind from_kind,
+                               uint32_t to_start, int packed_size,
+                               int copy_size) {
+    UNREACHABLE();
+  }
+
+
+ protected:
+  friend class ElementsAccessorBase<DictionaryElementsAccessor,
+                                    ElementsKindTraits<DICTIONARY_ELEMENTS> >;
+  friend class SlowSloppyArgumentsElementsAccessor;
+  friend class SloppyArgumentsElementsAccessor<
+      SlowSloppyArgumentsElementsAccessor, DictionaryElementsAccessor,
+      ElementsKindTraits<SLOW_SLOPPY_ARGUMENTS_ELEMENTS> >;
+
   static void DeleteCommon(Handle<JSObject> obj, uint32_t key,
                            LanguageMode language_mode) {
     Isolate* isolate = obj->GetIsolate();
     Handle<FixedArray> backing_store(FixedArray::cast(obj->elements()),
                                      isolate);
-    bool is_arguments =
-        (obj->GetElementsKind() == SLOPPY_ARGUMENTS_ELEMENTS);
+    bool is_arguments = obj->HasSloppyArgumentsElements();
     if (is_arguments) {
       backing_store = handle(FixedArray::cast(backing_store->get(1)), isolate);
     }
     Handle<SeededNumberDictionary> dictionary =
         Handle<SeededNumberDictionary>::cast(backing_store);
     int entry = dictionary->FindEntry(key);
     if (entry != SeededNumberDictionary::kNotFound) {
       Handle<Object> result =
           SeededNumberDictionary::DeleteProperty(dictionary, entry);
       USE(result);
       DCHECK(result->IsTrue());
       Handle<FixedArray> new_elements =
           SeededNumberDictionary::Shrink(dictionary, key);
 
       if (is_arguments) {
         FixedArray::cast(obj->elements())->set(1, *new_elements);
       } else {
         obj->set_elements(*new_elements);
       }
     }
   }
 
-  static void CopyElementsImpl(FixedArrayBase* from, uint32_t from_start,
-                               FixedArrayBase* to, ElementsKind from_kind,
-                               uint32_t to_start, int packed_size,
-                               int copy_size) {
-    UNREACHABLE();
-  }
-
-
- protected:
-  friend class ElementsAccessorBase<DictionaryElementsAccessor,
-                                    ElementsKindTraits<DICTIONARY_ELEMENTS> >;
-
   virtual void Delete(Handle<JSObject> obj, uint32_t key,
                       LanguageMode language_mode) final {
     DeleteCommon(obj, key, language_mode);
   }
 
   static Handle<Object> GetImpl(Handle<JSObject> obj, uint32_t key,
                                 Handle<FixedArrayBase> store) {
     Handle<SeededNumberDictionary> backing_store =
         Handle<SeededNumberDictionary>::cast(store);
     Isolate* isolate = backing_store->GetIsolate();
@@ skipping 78 matching lines @@
                : static_cast<uint32_t>(entry);
   }
 
   static PropertyDetails GetDetailsImpl(FixedArrayBase* backing_store,
                                         uint32_t index) {
     return SeededNumberDictionary::cast(backing_store)->DetailsAt(index);
   }
 };
 
 
-class SloppyArgumentsElementsAccessor : public ElementsAccessorBase<
-    SloppyArgumentsElementsAccessor,
-    ElementsKindTraits<SLOPPY_ARGUMENTS_ELEMENTS> > {
+template <typename SloppyArgumentsElementsAccessorSubclass,
+          typename ArgumentsAccessor, typename KindTraits>
+class SloppyArgumentsElementsAccessor
+    : public ElementsAccessorBase<SloppyArgumentsElementsAccessorSubclass,
+                                  KindTraits> {
  public:
   explicit SloppyArgumentsElementsAccessor(const char* name)
-      : ElementsAccessorBase<
-          SloppyArgumentsElementsAccessor,
-          ElementsKindTraits<SLOPPY_ARGUMENTS_ELEMENTS> >(name) {}
+      : ElementsAccessorBase<SloppyArgumentsElementsAccessorSubclass,
+                             KindTraits>(name) {}
+
  protected:
-  friend class ElementsAccessorBase<
-      SloppyArgumentsElementsAccessor,
-      ElementsKindTraits<SLOPPY_ARGUMENTS_ELEMENTS> >;
+  friend class ElementsAccessorBase<SloppyArgumentsElementsAccessorSubclass,
+                                    KindTraits>;
 
   static Handle<Object> GetImpl(Handle<JSObject> obj, uint32_t key,
                                 Handle<FixedArrayBase> parameters) {
     Isolate* isolate = obj->GetIsolate();
     Handle<FixedArray> parameter_map = Handle<FixedArray>::cast(parameters);
     Handle<Object> probe(GetParameterMapArg(*parameter_map, key), isolate);
     if (!probe->IsTheHole()) {
       DisallowHeapAllocation no_gc;
       Context* context = Context::cast(parameter_map->get(0));
       int context_index = Handle<Smi>::cast(probe)->value();
       DCHECK(!context->get(context_index)->IsTheHole());
       return handle(context->get(context_index), isolate);
     } else {
       // Object is not mapped, defer to the arguments.
       Handle<FixedArray> arguments(FixedArray::cast(parameter_map->get(1)),
                                    isolate);
-      Handle<Object> result =
-          ElementsAccessor::ForArray(arguments)->Get(obj, key, arguments);
+      Handle<Object> result = ArgumentsAccessor::GetImpl(obj, key, arguments);
       // Elements of the arguments object in slow mode might be slow aliases.
       if (result->IsAliasedArgumentsEntry()) {
         DisallowHeapAllocation no_gc;
         AliasedArgumentsEntry* entry = AliasedArgumentsEntry::cast(*result);
         Context* context = Context::cast(parameter_map->get(0));
         int context_index = entry->aliased_context_slot();
         DCHECK(!context->get(context_index)->IsTheHole());
         return handle(context->get(context_index), isolate);
       } else {
         return result;
       }
     }
   }
 
+  virtual void Delete(Handle<JSObject> obj, uint32_t key,
+                      LanguageMode language_mode) final {
+    FixedArray* parameter_map = FixedArray::cast(obj->elements());
+    if (!GetParameterMapArg(parameter_map, key)->IsTheHole()) {
+      // TODO(kmillikin): We could check if this was the last aliased
+      // parameter, and revert to normal elements in that case.  That
+      // would enable GC of the context.
+      parameter_map->set_the_hole(key + 2);
+    } else {
+      ArgumentsAccessor::DeleteCommon(obj, key, language_mode);
+    }
+  }
+
   static void GrowCapacityAndConvertImpl(Handle<JSObject> object,
                                          uint32_t capacity) {
-    Handle<FixedArray> parameter_map(FixedArray::cast(object->elements()));
-    Handle<FixedArray> old_elements(FixedArray::cast(parameter_map->get(1)));
-    ElementsKind from_kind = old_elements->IsDictionary() ? DICTIONARY_ELEMENTS
-                                                          : FAST_HOLEY_ELEMENTS;
-    // This method should only be called if there's a reason to update the
-    // elements.
-    DCHECK(IsDictionaryElementsKind(from_kind) ||
-           static_cast<uint32_t>(old_elements->length()) < capacity);
-    Handle<FixedArrayBase> elements =
-        ConvertElementsWithCapacity(object, old_elements, from_kind, capacity);
-    parameter_map->set(1, *elements);
-    JSObject::ValidateElements(object);
+    UNREACHABLE();
   }
 
   static void SetImpl(FixedArrayBase* store, uint32_t key, Object* value) {
     FixedArray* parameter_map = FixedArray::cast(store);
     Object* probe = GetParameterMapArg(parameter_map, key);
     if (!probe->IsTheHole()) {
       Context* context = Context::cast(parameter_map->get(0));
       int context_index = Smi::cast(probe)->value();
       DCHECK(!context->get(context_index)->IsTheHole());
       context->set(context_index, value);
     } else {
       FixedArray* arguments = FixedArray::cast(parameter_map->get(1));
-      ElementsAccessor::ForArray(arguments)->Set(arguments, key, value);
+      ArgumentsAccessor::SetImpl(arguments, key, value);
     }
   }
 
-  static void ReconfigureImpl(Handle<JSObject> object,
-                              Handle<FixedArrayBase> store, uint32_t index,
-                              Handle<Object> value,
-                              PropertyAttributes attributes) {
-    Handle<FixedArray> parameter_map = Handle<FixedArray>::cast(store);
-    uint32_t length = parameter_map->length() - 2;
-    if (index < length) {
-      Object* probe = parameter_map->get(index + 2);
-      DCHECK(!probe->IsTheHole());
-      Context* context = Context::cast(parameter_map->get(0));
-      int context_index = Smi::cast(probe)->value();
-      DCHECK(!context->get(context_index)->IsTheHole());
-      context->set(context_index, *value);
-
-      // Redefining attributes of an aliased element destroys fast aliasing.
-      parameter_map->set_the_hole(index + 2);
-      // For elements that are still writable we re-establish slow aliasing.
-      if ((attributes & READ_ONLY) == 0) {
-        Isolate* isolate = store->GetIsolate();
-        value = isolate->factory()->NewAliasedArgumentsEntry(context_index);
-      }
-
-      PropertyDetails details(attributes, DATA, 0, PropertyCellType::kNoCell);
-      Handle<SeededNumberDictionary> arguments =
-          parameter_map->get(1)->IsSeededNumberDictionary()
-              ? handle(SeededNumberDictionary::cast(parameter_map->get(1)))
-              : JSObject::NormalizeElements(object);
-      arguments = SeededNumberDictionary::AddNumberEntry(arguments, index,
-                                                         value, details);
-      parameter_map->set(1, *arguments);
-    } else {
-      Handle<FixedArrayBase> arguments(
-          FixedArrayBase::cast(parameter_map->get(1)));
-      ElementsAccessor::ForArray(arguments)
-          ->Reconfigure(object, arguments, index - length, value, attributes);
-    }
-  }
-
-  static void AddImpl(Handle<JSObject> object, uint32_t key,
-                      Handle<Object> value, PropertyAttributes attributes,
-                      uint32_t new_capacity) {
-    DCHECK_EQ(NONE, attributes);
-    Handle<FixedArray> parameter_map(FixedArray::cast(object->elements()));
-    Handle<FixedArrayBase> old_elements(
-        FixedArrayBase::cast(parameter_map->get(1)));
-    if (old_elements->IsSeededNumberDictionary() ||
-        static_cast<uint32_t>(old_elements->length()) < new_capacity) {
-      GrowCapacityAndConvertImpl(object, new_capacity);
-    }
-    SetImpl(object->elements(), key, *value);
-  }
-
   static MaybeHandle<AccessorPair> GetAccessorPairImpl(
       Handle<JSObject> obj, uint32_t key, Handle<FixedArrayBase> parameters) {
     Handle<FixedArray> parameter_map = Handle<FixedArray>::cast(parameters);
     Handle<Object> probe(GetParameterMapArg(*parameter_map, key),
                          obj->GetIsolate());
     if (!probe->IsTheHole()) {
       return MaybeHandle<AccessorPair>();
     } else {
       // If not aliased, check the arguments.
       Handle<FixedArray> arguments(FixedArray::cast(parameter_map->get(1)));
-      return ElementsAccessor::ForArray(arguments)
-          ->GetAccessorPair(obj, key, arguments);
+      return ArgumentsAccessor::GetAccessorPairImpl(obj, key, arguments);
     }
   }
 
   static void SetLengthImpl(Handle<JSArray> array, uint32_t length,
                             Handle<FixedArrayBase> parameter_map) {
     // Sloppy arguments objects are not arrays.
     UNREACHABLE();
   }
 
-  virtual void Delete(Handle<JSObject> obj, uint32_t key,
-                      LanguageMode language_mode) final {
-    Isolate* isolate = obj->GetIsolate();
-    Handle<FixedArray> parameter_map(FixedArray::cast(obj->elements()));
-    Handle<Object> probe(GetParameterMapArg(*parameter_map, key), isolate);
-    if (!probe->IsTheHole()) {
-      // TODO(kmillikin): We could check if this was the last aliased
-      // parameter, and revert to normal elements in that case.  That
-      // would enable GC of the context.
-      parameter_map->set_the_hole(key + 2);
-    } else {
-      Handle<FixedArray> arguments(FixedArray::cast(parameter_map->get(1)));
-      if (arguments->IsDictionary()) {
-        DictionaryElementsAccessor::DeleteCommon(obj, key, language_mode);
-      } else {
-        // It's difficult to access the version of DeleteCommon that is declared
-        // in the templatized super class, call the concrete implementation in
-        // the class for the most generalized ElementsKind subclass.
-        FastHoleyObjectElementsAccessor::DeleteCommon(obj, key, language_mode);
-      }
-    }
-  }
-
-  static void CopyElementsImpl(FixedArrayBase* from, uint32_t from_start,
-                               FixedArrayBase* to, ElementsKind from_kind,
-                               uint32_t to_start, int packed_size,
-                               int copy_size) {
-    DCHECK(!to->IsDictionary());
-    if (from_kind == DICTIONARY_ELEMENTS) {
-      CopyDictionaryToObjectElements(from, from_start, to, FAST_HOLEY_ELEMENTS,
-                                     to_start, copy_size);
-    } else {
-      DCHECK_EQ(FAST_HOLEY_ELEMENTS, from_kind);
-      CopyObjectToObjectElements(from, from_kind, from_start, to,
-                                 FAST_HOLEY_ELEMENTS, to_start, copy_size);
-    }
-  }
-
   static uint32_t GetCapacityImpl(JSObject* holder,
                                   FixedArrayBase* backing_store) {
     FixedArray* parameter_map = FixedArray::cast(backing_store);
     FixedArrayBase* arguments = FixedArrayBase::cast(parameter_map->get(1));
     return parameter_map->length() - 2 +
-           ForArray(arguments)->GetCapacity(holder, arguments);
+           ArgumentsAccessor::GetCapacityImpl(holder, arguments);
   }
 
   static bool HasIndexImpl(FixedArrayBase* parameters, uint32_t index) {
     FixedArray* parameter_map = FixedArray::cast(parameters);
     uint32_t length = parameter_map->length() - 2;
     if (index < length) {
       return !GetParameterMapArg(parameter_map, index)->IsTheHole();
     }
 
     FixedArrayBase* arguments = FixedArrayBase::cast(parameter_map->get(1));
-    return ForArray(arguments)->HasIndex(arguments, index - length);
+    return ArgumentsAccessor::HasIndexImpl(arguments, index - length);
   }
 
   static uint32_t GetKeyForIndexImpl(FixedArrayBase* parameters,
                                      uint32_t index) {
     FixedArray* parameter_map = FixedArray::cast(parameters);
     uint32_t length = parameter_map->length() - 2;
     if (index < length) return index;
 
     FixedArray* arguments = FixedArray::cast(parameter_map->get(1));
-    return ForArray(arguments)->GetKeyForIndex(arguments, index - length);
+    return ArgumentsAccessor::GetKeyForIndexImpl(arguments, index - length);
   }
 
   static uint32_t GetIndexForKeyImpl(JSObject* holder,
                                      FixedArrayBase* parameters, uint32_t key) {
     FixedArray* parameter_map = FixedArray::cast(parameters);
     Object* probe = GetParameterMapArg(parameter_map, key);
     if (!probe->IsTheHole()) return key;
 
     FixedArray* arguments = FixedArray::cast(parameter_map->get(1));
-    uint32_t index = ElementsAccessor::ForArray(arguments)
-                         ->GetIndexForKey(holder, arguments, key);
+    uint32_t index =
+        ArgumentsAccessor::GetIndexForKeyImpl(holder, arguments, key);
     if (index == kMaxUInt32) return index;
     return (parameter_map->length() - 2) + index;
   }
 
   static PropertyDetails GetDetailsImpl(FixedArrayBase* parameters,
                                         uint32_t index) {
     FixedArray* parameter_map = FixedArray::cast(parameters);
     uint32_t length = parameter_map->length() - 2;
     if (index < length) {
       return PropertyDetails(NONE, DATA, 0, PropertyCellType::kNoCell);
     }
     index -= length;
     FixedArray* arguments = FixedArray::cast(parameter_map->get(1));
-    return ElementsAccessor::ForArray(arguments)->GetDetails(arguments, index);
+    return ArgumentsAccessor::GetDetailsImpl(arguments, index);
   }
 
- private:
   static Object* GetParameterMapArg(FixedArray* parameter_map, uint32_t key) {
     uint32_t length = parameter_map->length() - 2;
     return key < length
                ? parameter_map->get(key + 2)
                : Object::cast(parameter_map->GetHeap()->the_hole_value());
   }
 };
 
 
-ElementsAccessor* ElementsAccessor::ForArray(FixedArrayBase* array) {
-  return elements_accessors_[ElementsKindForArray(array)];
-}
+class FastSloppyArgumentsElementsAccessor
+    : public SloppyArgumentsElementsAccessor<
+          FastSloppyArgumentsElementsAccessor, FastHoleyObjectElementsAccessor,
+          ElementsKindTraits<FAST_SLOPPY_ARGUMENTS_ELEMENTS> > {
+ public:
+  friend class SloppyArgumentsElementsAccessor<
+      FastSloppyArgumentsElementsAccessor, FastHoleyObjectElementsAccessor,
+      ElementsKindTraits<FAST_SLOPPY_ARGUMENTS_ELEMENTS> >;
+  friend class ElementsAccessorBase<
+      FastSloppyArgumentsElementsAccessor,
+      ElementsKindTraits<FAST_SLOPPY_ARGUMENTS_ELEMENTS> >;
+  explicit FastSloppyArgumentsElementsAccessor(const char* name)
+      : SloppyArgumentsElementsAccessor<
+            FastSloppyArgumentsElementsAccessor,
+            FastHoleyObjectElementsAccessor,
+            ElementsKindTraits<FAST_SLOPPY_ARGUMENTS_ELEMENTS> >(name) {}
+
+ protected:
+  static void AddImpl(Handle<JSObject> object, uint32_t key,
+                      Handle<Object> value, PropertyAttributes attributes,
+                      uint32_t new_capacity) {
+    DCHECK_EQ(NONE, attributes);
+    Handle<FixedArray> parameter_map(FixedArray::cast(object->elements()));
+    Handle<FixedArrayBase> old_elements(
+        FixedArrayBase::cast(parameter_map->get(1)));
+    if (old_elements->IsSeededNumberDictionary() ||
+        static_cast<uint32_t>(old_elements->length()) < new_capacity) {
+      GrowCapacityAndConvertImpl(object, new_capacity);
+    }
+    SetImpl(object->elements(), key, *value);
+  }
+
+  static void ReconfigureImpl(Handle<JSObject> object,
+                              Handle<FixedArrayBase> store, uint32_t index,
+                              Handle<Object> value,
+                              PropertyAttributes attributes) {
+    Handle<SeededNumberDictionary> dictionary =
+        JSObject::NormalizeElements(object);
+    FixedArray::cast(*store)->set(1, *dictionary);
+    uint32_t length = static_cast<uint32_t>(store->length()) - 2;
+    if (index >= length) {
+      index = dictionary->FindEntry(index - length) + length;
+    }
+    object->GetElementsAccessor()->Reconfigure(object, store, index, value,
+                                               attributes);
+  }
+
+  static void CopyElementsImpl(FixedArrayBase* from, uint32_t from_start,
+                               FixedArrayBase* to, ElementsKind from_kind,
+                               uint32_t to_start, int packed_size,
+                               int copy_size) {
+    DCHECK(!to->IsDictionary());
+    if (from_kind == SLOW_SLOPPY_ARGUMENTS_ELEMENTS) {
+      CopyDictionaryToObjectElements(from, from_start, to, FAST_HOLEY_ELEMENTS,
+                                     to_start, copy_size);
+    } else {
+      DCHECK_EQ(FAST_SLOPPY_ARGUMENTS_ELEMENTS, from_kind);
+      CopyObjectToObjectElements(from, FAST_HOLEY_ELEMENTS, from_start, to,
+                                 FAST_HOLEY_ELEMENTS, to_start, copy_size);
+    }
+  }
+
+  static void GrowCapacityAndConvertImpl(Handle<JSObject> object,
+                                         uint32_t capacity) {
+    Handle<FixedArray> parameter_map(FixedArray::cast(object->elements()));
+    Handle<FixedArray> old_elements(FixedArray::cast(parameter_map->get(1)));
+    ElementsKind from_kind = object->GetElementsKind();
+    // This method should only be called if there's a reason to update the
+    // elements.
+    DCHECK(from_kind == SLOW_SLOPPY_ARGUMENTS_ELEMENTS ||
+           static_cast<uint32_t>(old_elements->length()) < capacity);
+    Handle<FixedArrayBase> elements =
+        ConvertElementsWithCapacity(object, old_elements, from_kind, capacity);
+    Handle<Map> new_map = JSObject::GetElementsTransitionMap(
+        object, FAST_SLOPPY_ARGUMENTS_ELEMENTS);
+    JSObject::MigrateToMap(object, new_map);
+    parameter_map->set(1, *elements);
+    JSObject::ValidateElements(object);
+  }
+};
 
 
-ElementsAccessor* ElementsAccessor::ForArray(Handle<FixedArrayBase> array) {
-  return ForArray(*array);
-}
+class SlowSloppyArgumentsElementsAccessor
+    : public SloppyArgumentsElementsAccessor<
+          SlowSloppyArgumentsElementsAccessor, DictionaryElementsAccessor,
+          ElementsKindTraits<SLOW_SLOPPY_ARGUMENTS_ELEMENTS> > {
+ public:
+  friend class ElementsAccessorBase<
+      SlowSloppyArgumentsElementsAccessor,
+      ElementsKindTraits<SLOW_SLOPPY_ARGUMENTS_ELEMENTS> >;
+  friend class SloppyArgumentsElementsAccessor<
+      SlowSloppyArgumentsElementsAccessor, DictionaryElementsAccessor,
+      ElementsKindTraits<SLOW_SLOPPY_ARGUMENTS_ELEMENTS> >;
+  explicit SlowSloppyArgumentsElementsAccessor(const char* name)
+      : SloppyArgumentsElementsAccessor<
+            SlowSloppyArgumentsElementsAccessor, DictionaryElementsAccessor,
+            ElementsKindTraits<SLOW_SLOPPY_ARGUMENTS_ELEMENTS> >(name) {}
+
+ protected:
+  static void AddImpl(Handle<JSObject> object, uint32_t key,
+                      Handle<Object> value, PropertyAttributes attributes,
+                      uint32_t new_capacity) {
+    Handle<FixedArray> parameter_map(FixedArray::cast(object->elements()));
+    Handle<FixedArrayBase> old_elements(
+        FixedArrayBase::cast(parameter_map->get(1)));
+    Handle<SeededNumberDictionary> dictionary =
+        old_elements->IsSeededNumberDictionary()
+            ? Handle<SeededNumberDictionary>::cast(old_elements)
+            : JSObject::NormalizeElements(object);
+    PropertyDetails details(attributes, DATA, 0, PropertyCellType::kNoCell);
+    Handle<SeededNumberDictionary> new_dictionary =
+        SeededNumberDictionary::AddNumberEntry(dictionary, key, value, details);
+    if (attributes != NONE) new_dictionary->set_requires_slow_elements();
+    if (*dictionary != *new_dictionary) {
+      FixedArray::cast(object->elements())->set(1, *new_dictionary);
+    }
+  }
+
+  static void ReconfigureImpl(Handle<JSObject> object,
+                              Handle<FixedArrayBase> store, uint32_t index,
+                              Handle<Object> value,
+                              PropertyAttributes attributes) {
+    Handle<FixedArray> parameter_map = Handle<FixedArray>::cast(store);
+    uint32_t length = parameter_map->length() - 2;
+    if (index < length) {
+      Object* probe = parameter_map->get(index + 2);
+      DCHECK(!probe->IsTheHole());
+      Context* context = Context::cast(parameter_map->get(0));
+      int context_index = Smi::cast(probe)->value();
+      DCHECK(!context->get(context_index)->IsTheHole());
+      context->set(context_index, *value);
+
+      // Redefining attributes of an aliased element destroys fast aliasing.
+      parameter_map->set_the_hole(index + 2);
+      // For elements that are still writable we re-establish slow aliasing.
+      if ((attributes & READ_ONLY) == 0) {
+        Isolate* isolate = store->GetIsolate();
+        value = isolate->factory()->NewAliasedArgumentsEntry(context_index);
+      }
+
+      PropertyDetails details(attributes, DATA, 0, PropertyCellType::kNoCell);
+      Handle<SeededNumberDictionary> arguments(
+          SeededNumberDictionary::cast(parameter_map->get(1)));
+      arguments = SeededNumberDictionary::AddNumberEntry(arguments, index,
+                                                         value, details);
+      parameter_map->set(1, *arguments);
+    } else {
+      Handle<FixedArrayBase> arguments(
+          FixedArrayBase::cast(parameter_map->get(1)));
+      DictionaryElementsAccessor::ReconfigureImpl(
+          object, arguments, index - length, value, attributes);
+    }
+  }
+};
 
 
 void ElementsAccessor::InitializeOncePerProcess() {
   static ElementsAccessor* accessor_array[] = {
 #define ACCESSOR_ARRAY(Class, Kind, Store) new Class(#Kind),
     ELEMENTS_LIST(ACCESSOR_ARRAY)
 #undef ACCESSOR_ARRAY
   };
 
   STATIC_ASSERT((sizeof(accessor_array) / sizeof(*accessor_array)) ==
@@ skipping 143 matching lines @@
       break;
   }
 
   array->set_elements(*elms);
   array->set_length(Smi::FromInt(number_of_elements));
   return array;
 }
 
 }  // namespace internal
 }  // namespace v8