Basic support for tracking smi-only arrays on ia32.

src/objects.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2896 matching lines @@
   FixedArrayBase* array = FixedArrayBase::cast(elements());
   Map* old_map = array->map();
   bool is_arguments =
       (old_map == old_map->heap()->non_strict_arguments_elements_map());
   if (is_arguments) {
     array = FixedArrayBase::cast(FixedArray::cast(array)->get(1));
   }
   if (array->IsDictionary()) return array;
 
   ASSERT(HasFastElements() ||
+         HasFastSmiOnlyElements() ||
          HasFastDoubleElements() ||
          HasFastArgumentsElements());
   // Compute the effective length and allocate a new backing store.
   int length = IsJSArray()
       ? Smi::cast(JSArray::cast(this)->length())->value()
       : array->length();
   int old_capacity = 0;
   int used_elements = 0;
   GetElementsCapacityAndUsage(&old_capacity, &used_elements);
   NumberDictionary* dictionary = NULL;
@@ skipping 14 matching lines @@
       } else {
         // Objects must be allocated in the old object space, since the
         // overall number of HeapNumbers needed for the conversion might
         // exceed the capacity of new space, and we would fail repeatedly
         // trying to convert the FixedDoubleArray.
         MaybeObject* maybe_value_object =
             GetHeap()->AllocateHeapNumber(double_array->get_scalar(i), TENURED);
         if (!maybe_value_object->ToObject(&value)) return maybe_value_object;
       }
     } else {
-      ASSERT(old_map->has_fast_elements());
+      ASSERT(old_map->has_fast_elements() ||
+             old_map->has_fast_smi_only_elements());
       value = FixedArray::cast(array)->get(i);
     }
     PropertyDetails details = PropertyDetails(NONE, NORMAL);
     if (!value->IsTheHole()) {
       Object* result;
       MaybeObject* maybe_result =
           dictionary->AddNumberEntry(i, value, details);
       if (!maybe_result->ToObject(&result)) return maybe_result;
       dictionary = NumberDictionary::cast(result);
     }
@@ skipping 286 matching lines @@
     }
     // Make sure the properties are normalized before removing the entry.
     return DeleteNormalizedProperty(name, mode);
   }
 }
 
 
 bool JSObject::ReferencesObjectFromElements(FixedArray* elements,
                                             ElementsKind kind,
                                             Object* object) {
-  ASSERT(kind == FAST_ELEMENTS || kind == DICTIONARY_ELEMENTS);
+  ASSERT(kind == FAST_ELEMENTS ||
+         kind == FAST_SMI_ONLY_ELEMENTS ||
+         kind == DICTIONARY_ELEMENTS);
   if (kind == FAST_ELEMENTS) {
     int length = IsJSArray()
         ? Smi::cast(JSArray::cast(this)->length())->value()
         : elements->length();
     for (int i = 0; i < length; ++i) {
       Object* element = elements->get(i);
       if (!element->IsTheHole() && element == object) return true;
     }
-  } else {
+  } else if (kind != FAST_SMI_ONLY_ELEMENTS) {

[Rico, 2011/09/16 09:40:10]

kind == DICTIONARY_ELEMENTS
seems much more readable here

[danno, 2011/09/21 14:32:04]

Done.

     Object* key = NumberDictionary::cast(elements)->SlowReverseLookup(object);
     if (!key->IsUndefined()) return true;
   }
   return false;
 }
 
 
 // Check whether this object references another object.
 bool JSObject::ReferencesObject(Object* obj) {
   Map* map_of_this = map();
@@ skipping 25 matching lines @@
     case EXTERNAL_SHORT_ELEMENTS:
     case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
     case EXTERNAL_INT_ELEMENTS:
     case EXTERNAL_UNSIGNED_INT_ELEMENTS:
     case EXTERNAL_FLOAT_ELEMENTS:
     case EXTERNAL_DOUBLE_ELEMENTS:
     case FAST_DOUBLE_ELEMENTS:
       // Raw pixels and external arrays do not reference other
       // objects.
       break;
+    case FAST_SMI_ONLY_ELEMENTS:

[Rico, 2011/09/16 09:40:10]

Why not just break here and remove the new extra kind support from
ReferencesObjectsFromElements?

[danno, 2011/09/21 14:32:04]

Done.

     case FAST_ELEMENTS:
     case DICTIONARY_ELEMENTS: {
       FixedArray* elements = FixedArray::cast(this->elements());
       if (ReferencesObjectFromElements(elements, kind, obj)) return true;
       break;
     }
     case NON_STRICT_ARGUMENTS_ELEMENTS: {
       FixedArray* parameter_map = FixedArray::cast(elements());
       // Check the mapped parameters.
       int length = parameter_map->length();
@@ skipping 272 matching lines @@
 
   if (!CanSetCallback(name)) {
     return heap->undefined_value();
   }
 
   uint32_t index = 0;
   bool is_element = name->AsArrayIndex(&index);
 
   if (is_element) {
     switch (GetElementsKind()) {
+      case FAST_SMI_ONLY_ELEMENTS:
       case FAST_ELEMENTS:
       case FAST_DOUBLE_ELEMENTS:
         break;
       case EXTERNAL_PIXEL_ELEMENTS:
       case EXTERNAL_BYTE_ELEMENTS:
       case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
       case EXTERNAL_SHORT_ELEMENTS:
       case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
       case EXTERNAL_INT_ELEMENTS:
       case EXTERNAL_UNSIGNED_INT_ELEMENTS:
@@ skipping 229 matching lines @@
   }
 
   uint32_t index = 0;
   bool is_element = name->AsArrayIndex(&index);
 
   if (is_element) {
     if (IsJSArray()) return isolate->heap()->undefined_value();
 
     // Accessors overwrite previous callbacks (cf. with getters/setters).
     switch (GetElementsKind()) {
+      case FAST_SMI_ONLY_ELEMENTS:
       case FAST_ELEMENTS:
       case FAST_DOUBLE_ELEMENTS:
         break;
       case EXTERNAL_PIXEL_ELEMENTS:
       case EXTERNAL_BYTE_ELEMENTS:
       case EXTERNAL_UNSIGNED_BYTE_ELEMENTS:
       case EXTERNAL_SHORT_ELEMENTS:
       case EXTERNAL_UNSIGNED_SHORT_ELEMENTS:
       case EXTERNAL_INT_ELEMENTS:
       case EXTERNAL_UNSIGNED_INT_ELEMENTS:
@@ skipping 3388 matching lines @@
   for (int i = 0; i < source->Capacity(); ++i) {
     Object* key = source->KeyAt(i);
     if (key->IsNumber()) {
       uint32_t entry = static_cast<uint32_t>(key->Number());
       destination->set(entry, source->ValueAt(i), mode);
     }
   }
 }
 
 
-MaybeObject* JSObject::SetFastElementsCapacityAndLength(int capacity,
-                                                        int length) {
+MaybeObject* JSObject::SetFastElementsCapacityAndLength(
+    int capacity,
+    int length,
+    SetFastElementsCapacityMode set_capacity_mode) {
   Heap* heap = GetHeap();
   // We should never end in here with a pixel or external array.
   ASSERT(!HasExternalArrayElements());
 
   // Allocate a new fast elements backing store.
   FixedArray* new_elements = NULL;
   { Object* object;
     MaybeObject* maybe = heap->AllocateFixedArrayWithHoles(capacity);
     if (!maybe->ToObject(&object)) return maybe;
     new_elements = FixedArray::cast(object);
   }
 
   // Find the new map to use for this object if there is a map change.
   Map* new_map = NULL;
   if (elements()->map() != heap->non_strict_arguments_elements_map()) {
     Object* object;
-    MaybeObject* maybe = GetElementsTransitionMap(FAST_ELEMENTS);
+    bool has_fast_smi_only_elements =
+        FLAG_smi_only_arrays &&
+        (set_capacity_mode == kAllowSmiOnlyElements) &&
+        (elements()->map()->has_fast_smi_only_elements() ||
+         elements() == heap->empty_fixed_array());
+    ElementsKind elements_kind = has_fast_smi_only_elements
+        ? FAST_SMI_ONLY_ELEMENTS
+        : FAST_ELEMENTS;
+    MaybeObject* maybe = GetElementsTransitionMap(elements_kind);
     if (!maybe->ToObject(&object)) return maybe;
     new_map = Map::cast(object);
   }
 
-  switch (GetElementsKind()) {
+  ElementsKind elements_kind = GetElementsKind();
+  switch (elements_kind) {
+    case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS: {
       AssertNoAllocation no_gc;
-      WriteBarrierMode mode = new_elements->GetWriteBarrierMode(no_gc);
+      WriteBarrierMode mode(new_elements->GetWriteBarrierMode(no_gc));
       CopyFastElementsToFast(FixedArray::cast(elements()), new_elements, mode);
       set_map(new_map);
       set_elements(new_elements);
       break;
     }
     case DICTIONARY_ELEMENTS: {
       AssertNoAllocation no_gc;
       WriteBarrierMode mode = new_elements->GetWriteBarrierMode(no_gc);
       CopySlowElementsToFast(NumberDictionary::cast(elements()),
                              new_elements,
@@ skipping 82 matching lines @@
   FixedDoubleArray* elems = FixedDoubleArray::cast(obj);
 
   { MaybeObject* maybe_obj =
         GetElementsTransitionMap(FAST_DOUBLE_ELEMENTS);
     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
   }
   Map* new_map = Map::cast(obj);
 
   AssertNoAllocation no_gc;
   switch (GetElementsKind()) {
+    case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS: {
       elems->Initialize(FixedArray::cast(elements()));
       break;
     }
     case FAST_DOUBLE_ELEMENTS: {
       elems->Initialize(FixedDoubleArray::cast(elements()));
       break;
     }
     case DICTIONARY_ELEMENTS: {
       elems->Initialize(NumberDictionary::cast(elements()));
@@ skipping 17 matching lines @@
 }
 
 
 MaybeObject* JSObject::SetSlowElements(Object* len) {
   // We should never end in here with a pixel or external array.
   ASSERT(!HasExternalArrayElements());
 
   uint32_t new_length = static_cast<uint32_t>(len->Number());
 
   switch (GetElementsKind()) {
-    case FAST_ELEMENTS: {
-    case FAST_DOUBLE_ELEMENTS:
+    case FAST_SMI_ONLY_ELEMENTS:
+    case FAST_ELEMENTS:
+    case FAST_DOUBLE_ELEMENTS: {
       // Make sure we never try to shrink dense arrays into sparse arrays.
       ASSERT(static_cast<uint32_t>(
           FixedArrayBase::cast(elements())->length()) <= new_length);
       MaybeObject* result = NormalizeElements();
       if (result->IsFailure()) return result;
 
       // Update length for JSArrays.
       if (IsJSArray()) JSArray::cast(this)->set_length(len);
       break;
     }
@@ skipping 45 matching lines @@
 
 
 void JSArray::Expand(int required_size) {
   Handle<JSArray> self(this);
   Handle<FixedArray> old_backing(FixedArray::cast(elements()));
   int old_size = old_backing->length();
   int new_size = required_size > old_size ? required_size : old_size;
   Handle<FixedArray> new_backing = FACTORY->NewFixedArray(new_size);
   // Can't use this any more now because we may have had a GC!
   for (int i = 0; i < old_size; i++) new_backing->set(i, old_backing->get(i));
-  self->SetContent(*new_backing);
+  GetIsolate()->factory()->SetContent(self, new_backing);
 }
 
 
 static Failure* ArrayLengthRangeError(Heap* heap) {
   HandleScope scope(heap->isolate());
   return heap->isolate()->Throw(
       *FACTORY->NewRangeError("invalid_array_length",
           HandleVector<Object>(NULL, 0)));
 }
 
 
 MaybeObject* JSObject::SetElementsLength(Object* len) {
   // We should never end in here with a pixel or external array.
   ASSERT(AllowsSetElementsLength());
 
   MaybeObject* maybe_smi_length = len->ToSmi();
   Object* smi_length = Smi::FromInt(0);
   if (maybe_smi_length->ToObject(&smi_length) && smi_length->IsSmi()) {
     const int value = Smi::cast(smi_length)->value();
     if (value < 0) return ArrayLengthRangeError(GetHeap());
     ElementsKind elements_kind = GetElementsKind();
     switch (elements_kind) {
+      case FAST_SMI_ONLY_ELEMENTS:
       case FAST_ELEMENTS:
       case FAST_DOUBLE_ELEMENTS: {
         int old_capacity = FixedArrayBase::cast(elements())->length();
         if (value <= old_capacity) {
           if (IsJSArray()) {
             Object* obj;
-            if (elements_kind == FAST_ELEMENTS) {
+            if (elements_kind != FAST_DOUBLE_ELEMENTS) {
+              ASSERT(elements_kind == FAST_ELEMENTS ||
+                     elements_kind == FAST_SMI_ONLY_ELEMENTS);
               MaybeObject* maybe_obj = EnsureWritableFastElements();
               if (!maybe_obj->ToObject(&obj)) return maybe_obj;
             }
             if (2 * value <= old_capacity) {
               // If more than half the elements won't be used, trim the array.
               if (value == 0) {
                 initialize_elements();
               } else {
                 Address filler_start;
                 int filler_size;
-                if (GetElementsKind() == FAST_ELEMENTS) {
+                if (elements_kind == FAST_ELEMENTS ||
+                    elements_kind == FAST_SMI_ONLY_ELEMENTS) {
                   FixedArray* fast_elements = FixedArray::cast(elements());
                   fast_elements->set_length(value);
                   filler_start = fast_elements->address() +
                       FixedArray::OffsetOfElementAt(value);
                   filler_size = (old_capacity - value) * kPointerSize;
                 } else {
                   ASSERT(GetElementsKind() == FAST_DOUBLE_ELEMENTS);
                   FixedDoubleArray* fast_double_elements =
                       FixedDoubleArray::cast(elements());
                   fast_double_elements->set_length(value);
                   filler_start = fast_double_elements->address() +
                       FixedDoubleArray::OffsetOfElementAt(value);
                   filler_size = (old_capacity - value) * kDoubleSize;
                 }
                 GetHeap()->CreateFillerObjectAt(filler_start, filler_size);
               }
             } else {
               // Otherwise, fill the unused tail with holes.
               int old_length = FastD2I(JSArray::cast(this)->length()->Number());
-              if (GetElementsKind() == FAST_ELEMENTS) {
+              if (elements_kind == FAST_ELEMENTS ||
+                  elements_kind == FAST_SMI_ONLY_ELEMENTS) {
                 FixedArray* fast_elements = FixedArray::cast(elements());
                 for (int i = value; i < old_length; i++) {
                   fast_elements->set_the_hole(i);
                 }
               } else {
-                ASSERT(GetElementsKind() == FAST_DOUBLE_ELEMENTS);
+                ASSERT(elements_kind == FAST_DOUBLE_ELEMENTS);
                 FixedDoubleArray* fast_double_elements =
                     FixedDoubleArray::cast(elements());
                 for (int i = value; i < old_length; i++) {
                   fast_double_elements->set_the_hole(i);
                 }
               }
             }
             JSArray::cast(this)->set_length(Smi::cast(smi_length));
           }
           return this;
         }
         int min = NewElementsCapacity(old_capacity);
         int new_capacity = value > min ? value : min;
         if (!ShouldConvertToSlowElements(new_capacity)) {
           MaybeObject* result;
-          if (GetElementsKind() == FAST_ELEMENTS) {
-            result = SetFastElementsCapacityAndLength(new_capacity, value);
+          if (elements_kind == FAST_ELEMENTS ||
+              elements_kind == FAST_SMI_ONLY_ELEMENTS) {
+            SetFastElementsCapacityMode set_capacity_mode =
+                elements_kind == FAST_SMI_ONLY_ELEMENTS
+                    ? kAllowSmiOnlyElements
+                    : kDontAllowSmiOnlyElements;
+            result = SetFastElementsCapacityAndLength(new_capacity,
+                                                      value,
+                                                      set_capacity_mode);
           }  else {
-            ASSERT(GetElementsKind() == FAST_DOUBLE_ELEMENTS);
+            ASSERT(elements_kind == FAST_DOUBLE_ELEMENTS);
             result = SetFastDoubleElementsCapacityAndLength(new_capacity,
                                                             value);
           }
           if (result->IsFailure()) return result;
           return this;
         }
         break;
       }
       case DICTIONARY_ELEMENTS: {
         if (IsJSArray()) {
@@ skipping 36 matching lines @@
     if (len->ToArrayIndex(&length)) {
       return SetSlowElements(len);
     } else {
       return ArrayLengthRangeError(GetHeap());
     }
   }
 
   // len is not a number so make the array size one and
   // set only element to len.
   Object* obj;
-  { MaybeObject* maybe_obj = GetHeap()->AllocateFixedArray(1);
-    if (!maybe_obj->ToObject(&obj)) return maybe_obj;
-  }
+  MaybeObject* maybe_obj = GetHeap()->AllocateFixedArray(1);
+  if (!maybe_obj->ToObject(&obj)) return maybe_obj;
   FixedArray::cast(obj)->set(0, len);
+
+  maybe_obj = EnsureCanContainElements(&len, 1);
+  if (maybe_obj->IsFailure()) return maybe_obj;
+
   if (IsJSArray()) JSArray::cast(this)->set_length(Smi::FromInt(1));
   set_elements(FixedArray::cast(obj));
   return this;
 }
 
 
 Object* Map::GetPrototypeTransition(Object* prototype) {
   FixedArray* cache = prototype_transitions();
   int number_of_transitions = NumberOfProtoTransitions();
   const int proto_offset =
@@ skipping 127 matching lines @@
   }
   ASSERT(Map::cast(new_map)->prototype() == value);
   real_receiver->set_map(Map::cast(new_map));
 
   heap->ClearInstanceofCache();
   ASSERT(size == Size());
   return value;
 }
 
 
+MaybeObject* JSObject::EnsureCanContainElements(Arguments* args,
+                                                uint32_t first_arg,
+                                                uint32_t arg_count) {
+  return EnsureCanContainElements(args->arguments() - first_arg, arg_count);
+}
+
+
 bool JSObject::HasElementPostInterceptor(JSReceiver* receiver, uint32_t index) {
   switch (GetElementsKind()) {
+    case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS: {
       uint32_t length = IsJSArray() ?
           static_cast<uint32_t>
               (Smi::cast(JSArray::cast(this)->length())->value()) :
           static_cast<uint32_t>(FixedArray::cast(elements())->length());
       if ((index < length) &&
           !FixedArray::cast(elements())->get(index)->IsTheHole()) {
         return true;
       }
       break;
@@ skipping 116 matching lines @@
     return HasElementWithInterceptor(this, index) ? INTERCEPTED_ELEMENT
                                                   : UNDEFINED_ELEMENT;
   }
 
   // Handle [] on String objects.
   if (this->IsStringObjectWithCharacterAt(index)) {
     return STRING_CHARACTER_ELEMENT;
   }
 
   switch (GetElementsKind()) {
+    case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS: {
       uint32_t length = IsJSArray() ?
           static_cast<uint32_t>
               (Smi::cast(JSArray::cast(this)->length())->value()) :
           static_cast<uint32_t>(FixedArray::cast(elements())->length());
       if ((index < length) &&
           !FixedArray::cast(elements())->get(index)->IsTheHole()) {
         return FAST_ELEMENT;
       }
       break;
@@ skipping 94 matching lines @@
     }
   }
 
   // Check for lookup interceptor
   if (HasIndexedInterceptor()) {
     return HasElementWithInterceptor(receiver, index);
   }
 
   ElementsKind kind = GetElementsKind();
   switch (kind) {
+    case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS: {
       uint32_t length = IsJSArray() ?
           static_cast<uint32_t>
               (Smi::cast(JSArray::cast(this)->length())->value()) :
           static_cast<uint32_t>(FixedArray::cast(elements())->length());
       if ((index < length) &&
           !FixedArray::cast(elements())->get(index)->IsTheHole()) return true;
       break;
     }
     case FAST_DOUBLE_ELEMENTS: {
@@ skipping 226 matching lines @@
     return false;
   }
   FixedArray* arguments = FixedArray::cast(elements->get(1));
   return arguments->IsDictionary();
 }
 
 
 // Adding n elements in fast case is O(n*n).
 // Note: revisit design to have dual undefined values to capture absent
 // elements.
-MaybeObject* JSObject::SetFastElement(uint32_t index,
-                                      Object* value,
-                                      StrictModeFlag strict_mode,
-                                      bool check_prototype) {
-  ASSERT(HasFastElements() || HasFastArgumentsElements());
+MaybeObject* JSObject::SetFastElement(
+    uint32_t index,

[Jakob Kummerow, 2011/09/16 16:30:34]

Why the new line break?

[danno, 2011/09/21 14:32:04]

Done.

+    Object* value,
+    StrictModeFlag strict_mode,
+    bool check_prototype) {
+  ASSERT(HasFastElements() ||
+         HasFastSmiOnlyElements() ||
+         HasFastArgumentsElements());
 
   FixedArray* backing_store = FixedArray::cast(elements());
   if (backing_store->map() == GetHeap()->non_strict_arguments_elements_map()) {
     backing_store = FixedArray::cast(backing_store->get(1));
   } else {
     Object* writable;
     MaybeObject* maybe = EnsureWritableFastElements();
     if (!maybe->ToObject(&writable)) return maybe;
     backing_store = FixedArray::cast(writable);
   }
   uint32_t length = static_cast<uint32_t>(backing_store->length());
 
   if (check_prototype &&
       (index >= length || backing_store->get(index)->IsTheHole())) {
     bool found;
     MaybeObject* result = SetElementWithCallbackSetterInPrototypes(index,
                                                                    value,
                                                                    &found,
                                                                    strict_mode);
     if (found) return result;
   }
 
   // Check whether there is extra space in fixed array.
   if (index < length) {
+    if (HasFastSmiOnlyElements()) {
+      if (!value->IsSmi()) {
+        // If the value is a number, transition from smi-only to
+        // FastDoubleElements

[Jakob Kummerow, 2011/09/16 16:30:34]

nit: missing period

[danno, 2011/09/21 14:32:04]

Done.

+        if (value->IsNumber()) {
+          MaybeObject* maybe =
+              SetFastDoubleElementsCapacityAndLength(length, length);
+          if (maybe->IsFailure()) return maybe;
+          FixedDoubleArray::cast(elements())->set(index, value->Number());
+          return value;
+        }
+        // Value is not a number, transition to generic fast elements.
+        MaybeObject* maybe_new_map = GetElementsTransitionMap(FAST_ELEMENTS);
+        Map* new_map;
+        if (!maybe_new_map->To<Map>(&new_map)) return maybe_new_map;
+        set_map(new_map);
+      }
+    }
     backing_store->set(index, value);
     if (IsJSArray()) {
       // Update the length of the array if needed.
       uint32_t array_length = 0;
       CHECK(JSArray::cast(this)->length()->ToArrayIndex(&array_length));
       if (index >= array_length) {
         JSArray::cast(this)->set_length(Smi::FromInt(index + 1));
       }
     }
     return value;
   }
 
   // Allow gap in fast case.
   if ((index - length) < kMaxGap) {
     // Try allocating extra space.
     int new_capacity = NewElementsCapacity(index + 1);
     if (!ShouldConvertToSlowElements(new_capacity)) {
       ASSERT(static_cast<uint32_t>(new_capacity) > index);
       Object* new_elements;
+      SetFastElementsCapacityMode set_capacity_mode =
+          value->IsSmi() && HasFastSmiOnlyElements()
+              ? kAllowSmiOnlyElements
+              : kDontAllowSmiOnlyElements;
       MaybeObject* maybe =
-          SetFastElementsCapacityAndLength(new_capacity, index + 1);
+          SetFastElementsCapacityAndLength(new_capacity,
+                                           index + 1,
+                                           set_capacity_mode);
       if (!maybe->ToObject(&new_elements)) return maybe;
       FixedArray::cast(new_elements)->set(index, value);
       return value;
     }
   }
 
   // Otherwise default to slow case.
   MaybeObject* result = NormalizeElements();
   if (result->IsFailure()) return result;
   return SetDictionaryElement(index, value, strict_mode, check_prototype);
@@ skipping 85 matching lines @@
   // Attempt to put this object back in fast case.
   if (ShouldConvertToFastElements()) {
     uint32_t new_length = 0;
     if (IsJSArray()) {
       CHECK(JSArray::cast(this)->length()->ToArrayIndex(&new_length));
     } else {
       new_length = dictionary->max_number_key() + 1;
     }
     MaybeObject* result = CanConvertToFastDoubleElements()
         ? SetFastDoubleElementsCapacityAndLength(new_length, new_length)
-        : SetFastElementsCapacityAndLength(new_length, new_length);
+        : SetFastElementsCapacityAndLength(new_length,
+                                           new_length,
+                                           kDontAllowSmiOnlyElements);
     if (result->IsFailure()) return result;
 #ifdef DEBUG
     if (FLAG_trace_normalization) {
       PrintF("Object elements are fast case again:\n");
       Print();
     }
 #endif
   }
   return value;
 }
@@ skipping 23 matching lines @@
 
   // If the value object is not a heap number, switch to fast elements and try
   // again.
   bool value_is_smi = value->IsSmi();
   if (!value->IsNumber()) {
     Object* obj;
     uint32_t length = elms_length;
     if (IsJSArray()) {
       CHECK(JSArray::cast(this)->length()->ToArrayIndex(&length));
     }
-    MaybeObject* maybe_obj =
-        SetFastElementsCapacityAndLength(elms_length, length);
+    MaybeObject* maybe_obj = SetFastElementsCapacityAndLength(
+        elms_length,
+        length,
+        kDontAllowSmiOnlyElements);
     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
-    return SetFastElement(index, value, strict_mode, check_prototype);
+    return SetFastElement(index,

[Jakob Kummerow, 2011/09/16 16:30:34]

Why the line breaks?

+                          value,
+                          strict_mode,
+                          check_prototype);
   }
 
   double double_value = value_is_smi
       ? static_cast<double>(Smi::cast(value)->value())
       : HeapNumber::cast(value)->value();
 
   // Check whether there is extra space in the fixed array.
   if (index < elms_length) {
     elms->set(index, double_value);
     if (IsJSArray()) {
@@ skipping 76 matching lines @@
                                       check_prototype);
 }
 
 
 MaybeObject* JSObject::SetElementWithoutInterceptor(uint32_t index,
                                                     Object* value,
                                                     StrictModeFlag strict_mode,
                                                     bool check_prototype) {
   Isolate* isolate = GetIsolate();
   switch (GetElementsKind()) {
+    case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS:
       return SetFastElement(index, value, strict_mode, check_prototype);
     case FAST_DOUBLE_ELEMENTS:
       return SetFastDoubleElement(index, value, strict_mode, check_prototype);
     case EXTERNAL_PIXEL_ELEMENTS: {
       ExternalPixelArray* pixels = ExternalPixelArray::cast(elements());
       return pixels->SetValue(index, value);
     }
     case EXTERNAL_BYTE_ELEMENTS: {
       ExternalByteArray* array = ExternalByteArray::cast(elements());
@@ skipping 142 matching lines @@
       backing_store_base =
           FixedArray::cast(FixedArray::cast(backing_store_base)->get(1));
       backing_store = FixedArray::cast(backing_store_base);
       if (backing_store->IsDictionary()) {
         NumberDictionary* dictionary = NumberDictionary::cast(backing_store);
         *capacity = dictionary->Capacity();
         *used = dictionary->NumberOfElements();
         break;
       }
       // Fall through.
+    case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS:
       backing_store = FixedArray::cast(backing_store_base);
       *capacity = backing_store->length();
       for (int i = 0; i < *capacity; ++i) {
         if (!backing_store->get(i)->IsTheHole()) ++(*used);
       }
       break;
     case DICTIONARY_ELEMENTS: {
       NumberDictionary* dictionary =
           NumberDictionary::cast(FixedArray::cast(elements()));
@@ skipping 255 matching lines @@
     if (!heap->isolate()->MayIndexedAccess(this, index, v8::ACCESS_HAS)) {
       heap->isolate()->ReportFailedAccessCheck(this, v8::ACCESS_HAS);
       return false;
     }
   }
 
   // Handle [] on String objects.
   if (this->IsStringObjectWithCharacterAt(index)) return true;
 
   switch (GetElementsKind()) {
+    case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS: {
       uint32_t length = IsJSArray() ?
           static_cast<uint32_t>(
               Smi::cast(JSArray::cast(this)->length())->value()) :
           static_cast<uint32_t>(FixedArray::cast(elements())->length());
       return (index < length) &&
           !FixedArray::cast(elements())->get(index)->IsTheHole();
     }
     case FAST_DOUBLE_ELEMENTS: {
       uint32_t length = IsJSArray() ?
@@ skipping 219 matching lines @@
   }
   // Compute the number of enumerable elements.
   return NumberOfLocalElements(static_cast<PropertyAttributes>(DONT_ENUM));
 }
 
 
 int JSObject::GetLocalElementKeys(FixedArray* storage,
                                   PropertyAttributes filter) {
   int counter = 0;
   switch (GetElementsKind()) {
+    case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS: {
       int length = IsJSArray() ?
           Smi::cast(JSArray::cast(this)->length())->value() :
           FixedArray::cast(elements())->length();
       for (int i = 0; i < length; i++) {
         if (!FixedArray::cast(elements())->get(i)->IsTheHole()) {
           if (storage != NULL) {
             storage->set(counter, Smi::FromInt(i));
           }
           counter++;
@@ skipping 882 matching lines @@
     dict->CopyValuesTo(fast_elements);
 
     set_map(new_map);
     set_elements(fast_elements);
   } else if (!HasFastDoubleElements()) {
     Object* obj;
     { MaybeObject* maybe_obj = EnsureWritableFastElements();
       if (!maybe_obj->ToObject(&obj)) return maybe_obj;
     }
   }
-  ASSERT(HasFastElements() || HasFastDoubleElements());
+  ASSERT(HasFastElements() ||
+         HasFastSmiOnlyElements() ||
+         HasFastDoubleElements());
 
   // Collect holes at the end, undefined before that and the rest at the
   // start, and return the number of non-hole, non-undefined values.
 
   FixedArrayBase* elements_base = FixedArrayBase::cast(this->elements());
   uint32_t elements_length = static_cast<uint32_t>(elements_base->length());
   if (limit > elements_length) {
     limit = elements_length ;
   }
   if (limit == 0) {
@@ skipping 1414 matching lines @@
   if (break_point_objects()->IsUndefined()) return 0;
   // Single break point.
   if (!break_point_objects()->IsFixedArray()) return 1;
   // Multiple break points.
   return FixedArray::cast(break_point_objects())->length();
 }
 #endif
 
 
 } }  // namespace v8::internal