Store transitioned JSArray maps in global context

src/objects.cc

 // Copyright 2012 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 2438 matching lines @@
   }
   set_instance_descriptors(DescriptorArray::cast(new_descriptors));
   return this;
 }
 
 
 Handle<Map> JSObject::GetElementsTransitionMap(Handle<JSObject> object,
                                                ElementsKind to_kind) {
   Isolate* isolate = object->GetIsolate();
   CALL_HEAP_FUNCTION(isolate,
-                     object->GetElementsTransitionMap(to_kind),
+                     object->GetElementsTransitionMap(isolate, to_kind),
                      Map);
 }
 
 
-MaybeObject* JSObject::GetElementsTransitionMap(ElementsKind to_kind) {
+MaybeObject* JSObject::GetElementsTransitionMapSlow(ElementsKind to_kind) {
   Map* current_map = map();
   ElementsKind from_kind = current_map->elements_kind();
 
   if (from_kind == to_kind) return current_map;
 
   // Only objects with FastProperties can have DescriptorArrays and can track
   // element-related maps. Also don't add descriptors to maps that are shared.
   bool safe_to_add_transition = HasFastProperties() &&
       !current_map->IsUndefined() &&
       !current_map->is_shared();
@@ skipping 21 matching lines @@
   // one.
   { MaybeObject* maybe_map = current_map->CopyDropTransitions();
     if (!maybe_map->To(&new_map)) return maybe_map;
   }
 
   new_map->set_elements_kind(to_kind);
 
   // Only remember the map transition if the object's map is NOT equal to the
   // global object_function's map and there is not an already existing
   // non-matching element transition.
+  Context* global_context = GetIsolate()->context()->global_context();
   bool allow_map_transition = safe_to_add_transition &&
-      (GetIsolate()->context()->global_context()->object_function()->map() !=
-       map());
+      (global_context->object_function()->map() != map());
   if (allow_map_transition) {
     MaybeObject* maybe_transition =
         current_map->AddElementsTransition(to_kind, new_map);
     if (maybe_transition->IsFailure()) return maybe_transition;
   }
   return new_map;
 }
 
 
 void JSObject::LocalLookupRealNamedProperty(String* name,
@@ skipping 1052 matching lines @@
     }
   }
 
   // Switch to using the dictionary as the backing storage for elements.
   if (is_arguments) {
     FixedArray::cast(elements())->set(1, dictionary);
   } else {
     // Set the new map first to satify the elements type assert in
     // set_elements().
     Object* new_map;
-    MaybeObject* maybe = GetElementsTransitionMap(DICTIONARY_ELEMENTS);
+    MaybeObject* maybe = GetElementsTransitionMap(GetIsolate(),
+                                                  DICTIONARY_ELEMENTS);
     if (!maybe->ToObject(&new_map)) return maybe;
     set_map(Map::cast(new_map));
     set_elements(dictionary);
   }
 
   old_map->GetHeap()->isolate()->counters()->elements_to_dictionary()->
       Increment();
 
 #ifdef DEBUG
   if (FLAG_trace_normalization) {
@@ skipping 3702 matching lines @@
   if (!shared_info->script()->IsScript()) return false;
   if (shared_info->optimization_disabled()) return false;
   Code* code = shared_info->code();
   if (code->kind() == Code::OPTIMIZED_FUNCTION) return true;
   // If we never ran this (unlikely) then lets try to optimize it.
   if (code->kind() != Code::FUNCTION) return true;
   return code->optimizable();
 }
 
 
-Object* JSFunction::SetInstancePrototype(Object* value) {
+MaybeObject* JSFunction::SetInstancePrototype(Object* value) {
   ASSERT(value->IsJSObject());
   Heap* heap = GetHeap();
   if (has_initial_map()) {
-    initial_map()->set_prototype(value);
+    // If the function has allocated the initial map
+    // replace it with a copy containing the new prototype.
+    Map* new_map;
+    MaybeObject* maybe_new_map = initial_map()->CopyDropTransitions();
+    if (!maybe_new_map->To(&new_map)) return maybe_new_map;
+    new_map->set_prototype(value);
+    MaybeObject* maybe_object =
+        set_initial_map_and_cache_transitions(new_map);
+    if (maybe_object->IsFailure()) return maybe_object;
   } else {
     // Put the value in the initial map field until an initial map is
     // needed.  At that point, a new initial map is created and the
     // prototype is put into the initial map where it belongs.
     set_prototype_or_initial_map(value);
   }
   heap->ClearInstanceofCache();
   return value;
 }
 
@@ skipping 995 matching lines @@
     // The resized array has FAST_SMI_ONLY_ELEMENTS if the capacity mode forces
     // it, or if it's allowed and the old elements array contained only SMIs.
     bool has_fast_smi_only_elements =
         (set_capacity_mode == kForceSmiOnlyElements) ||
         ((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);
+    MaybeObject* maybe = GetElementsTransitionMap(GetIsolate(), elements_kind);
     if (!maybe->ToObject(&object)) return maybe;
     new_map = Map::cast(object);
   }
 
   FixedArrayBase* old_elements_raw = elements();
   ElementsKind elements_kind = GetElementsKind();
   switch (elements_kind) {
     case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS: {
       AssertNoAllocation no_gc;
@@ skipping 63 matching lines @@
     case EXTERNAL_UNSIGNED_INT_ELEMENTS:
     case EXTERNAL_FLOAT_ELEMENTS:
     case EXTERNAL_DOUBLE_ELEMENTS:
     case EXTERNAL_PIXEL_ELEMENTS:
       UNREACHABLE();
       break;
   }
 
   if (FLAG_trace_elements_transitions) {
     PrintElementsTransition(stdout, elements_kind, old_elements_raw,
-                            FAST_ELEMENTS, new_elements);
+                            GetElementsKind(), new_elements);
   }
 
   // Update the length if necessary.
   if (IsJSArray()) {
     JSArray::cast(this)->set_length(Smi::FromInt(length));
   }
 
   return new_elements;
 }
 
 
 MaybeObject* JSObject::SetFastDoubleElementsCapacityAndLength(
     int capacity,
     int length) {
   Heap* heap = GetHeap();
   // We should never end in here with a pixel or external array.
   ASSERT(!HasExternalArrayElements());
 
   Object* obj;
   { MaybeObject* maybe_obj =
         heap->AllocateUninitializedFixedDoubleArray(capacity);
     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
   }
   FixedDoubleArray* elems = FixedDoubleArray::cast(obj);
 
   { MaybeObject* maybe_obj =
-        GetElementsTransitionMap(FAST_DOUBLE_ELEMENTS);
+        GetElementsTransitionMap(heap->isolate(), FAST_DOUBLE_ELEMENTS);
     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
   }
   Map* new_map = Map::cast(obj);
 
   FixedArrayBase* old_elements = elements();
   ElementsKind elements_kind(GetElementsKind());
   AssertNoAllocation no_gc;
   switch (elements_kind) {
     case FAST_SMI_ONLY_ELEMENTS:
     case FAST_ELEMENTS: {
@@ skipping 789 matching lines @@
   // Convert to fast double elements if appropriate.
   if (HasFastSmiOnlyElements() && !value->IsSmi() && value->IsNumber()) {
     MaybeObject* maybe =
         SetFastDoubleElementsCapacityAndLength(new_capacity, array_length);
     if (maybe->IsFailure()) return maybe;
     FixedDoubleArray::cast(elements())->set(index, value->Number());
     return value;
   }
   // Change elements kind from SMI_ONLY to generic FAST if necessary.
   if (HasFastSmiOnlyElements() && !value->IsSmi()) {
-    MaybeObject* maybe_new_map = GetElementsTransitionMap(FAST_ELEMENTS);
+    MaybeObject* maybe_new_map = GetElementsTransitionMap(GetIsolate(),
+                                                          FAST_ELEMENTS);
     Map* new_map;
     if (!maybe_new_map->To<Map>(&new_map)) return maybe_new_map;
     set_map(new_map);
     if (FLAG_trace_elements_transitions) {
       PrintElementsTransition(stdout, FAST_SMI_ONLY_ELEMENTS, elements(),
                               FAST_ELEMENTS, elements());
     }
   }
   // Increase backing store capacity if that's been decided previously.
   if (new_capacity != capacity) {
@@ skipping 389 matching lines @@
 
 
 Handle<Object> JSObject::TransitionElementsKind(Handle<JSObject> object,
                                                 ElementsKind to_kind) {
   CALL_HEAP_FUNCTION(object->GetIsolate(),
                      object->TransitionElementsKind(to_kind),
                      Object);
 }
 
 
-MUST_USE_RESULT MaybeObject* JSObject::TransitionElementsKind(
-    ElementsKind to_kind) {
+MaybeObject* JSObject::TransitionElementsKind(ElementsKind to_kind) {
   ElementsKind from_kind = map()->elements_kind();
+
+  Isolate* isolate = GetIsolate();
+  if (from_kind == FAST_SMI_ONLY_ELEMENTS &&
+      (to_kind == FAST_ELEMENTS ||
+       elements() == isolate->heap()->empty_fixed_array())) {
+    MaybeObject* maybe_new_map = GetElementsTransitionMap(isolate, to_kind);
+    Map* new_map;
+    if (!maybe_new_map->To(&new_map)) return maybe_new_map;
+    set_map(new_map);
+    if (FLAG_trace_elements_transitions) {
+      FixedArrayBase* elms = FixedArrayBase::cast(elements());
+      PrintElementsTransition(stdout, from_kind, elms, to_kind, elms);
+    }
+    return this;
+  }
+
   FixedArrayBase* elms = FixedArrayBase::cast(elements());
   uint32_t capacity = static_cast<uint32_t>(elms->length());
   uint32_t length = capacity;
 
   if (IsJSArray()) {
     Object* raw_length = JSArray::cast(this)->length();
     if (raw_length->IsUndefined()) {
       // If length is undefined, then JSArray is being initialized and has no
       // elements, assume a length of zero.
       length = 0;
     } else {
       CHECK(JSArray::cast(this)->length()->ToArrayIndex(&length));
     }
   }
 
-  if ((from_kind == FAST_SMI_ONLY_ELEMENTS && to_kind == FAST_ELEMENTS) ||
-      (length == 0)) {
-    MaybeObject* maybe_new_map = GetElementsTransitionMap(to_kind);
-    Map* new_map;
-    if (!maybe_new_map->To(&new_map)) return maybe_new_map;
-    if (FLAG_trace_elements_transitions) {
-      PrintElementsTransition(stdout, from_kind, elms, to_kind, elms);
-    }
-    set_map(new_map);
-    return this;
-  }
-
   if (from_kind == FAST_SMI_ONLY_ELEMENTS &&
       to_kind == FAST_DOUBLE_ELEMENTS) {
     MaybeObject* maybe_result =
         SetFastDoubleElementsCapacityAndLength(capacity, length);
     if (maybe_result->IsFailure()) return maybe_result;
     return this;
   }
 
   if (from_kind == FAST_DOUBLE_ELEMENTS && to_kind == FAST_ELEMENTS) {
     MaybeObject* maybe_result = SetFastElementsCapacityAndLength(
@@ skipping 1546 matching lines @@
     // Convert to fast elements containing only the existing properties.
     // Ordering is irrelevant, since we are going to sort anyway.
     SeededNumberDictionary* dict = element_dictionary();
     if (IsJSArray() || dict->requires_slow_elements() ||
         dict->max_number_key() >= limit) {
       return PrepareSlowElementsForSort(limit);
     }
     // Convert to fast elements.
 
     Object* obj;
-    { MaybeObject* maybe_obj = GetElementsTransitionMap(FAST_ELEMENTS);
+    { MaybeObject* maybe_obj = GetElementsTransitionMap(GetIsolate(),
+                                                        FAST_ELEMENTS);
       if (!maybe_obj->ToObject(&obj)) return maybe_obj;
     }
     Map* new_map = Map::cast(obj);
 
     PretenureFlag tenure = heap->InNewSpace(this) ? NOT_TENURED: TENURED;
     Object* new_array;
     { MaybeObject* maybe_new_array =
           heap->AllocateFixedArray(dict->NumberOfElements(), tenure);
       if (!maybe_new_array->ToObject(&new_array)) return maybe_new_array;
     }
@@ skipping 1547 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  // ENABLE_DEBUGGER_SUPPORT
 
 
 } }  // namespace v8::internal