Store transitioned JSArray maps in global context

src/runtime.cc

-// Copyright 2012 the V8 project authors. All rights reserved.
+j// Copyright 2012 the V8 project authors. All rights reserved.

[Jakob Kummerow, 2012/01/23 17:16:55]

nit: superfluous "j" (does this compile?)

[danno, 2012/01/26 21:32:34]

Done.

 // 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
 //       with the distribution.
@@ skipping 409 matching lines @@
   // constant function properties.
   if (should_transform && !has_function_literal) {
     JSObject::TransformToFastProperties(
         boilerplate, boilerplate->map()->unused_property_fields());
   }
 
   return boilerplate;
 }
 
 
+MaybeObject* TransitionElements(Handle<Object> object,
+                                ElementsKind to_kind,
+                                Isolate* isolate) {
+  HandleScope scope(isolate);
+  if (!object->IsJSObject()) return isolate->ThrowIllegalOperation();
+  ElementsKind from_kind =
+      Handle<JSObject>::cast(object)->map()->elements_kind();
+  if (Map::IsValidElementsTransition(from_kind, to_kind)) {
+    Handle<Object> result = JSObject::TransitionElementsKind(
+        Handle<JSObject>::cast(object), to_kind);
+    if (result.is_null()) return isolate->ThrowIllegalOperation();
+    return *result;
+  }
+  return isolate->ThrowIllegalOperation();
+}
+
+
 static const int kSmiOnlyLiteralMinimumLength = 1024;
 
 
 Handle<Object> Runtime::CreateArrayLiteralBoilerplate(
     Isolate* isolate,
     Handle<FixedArray> literals,
     Handle<FixedArray> elements) {
   // Create the JSArray.
   Handle<JSFunction> constructor(
       JSFunction::GlobalContextFromLiterals(*literals)->array_function());
   Handle<JSArray> object =
       Handle<JSArray>::cast(isolate->factory()->NewJSObject(constructor));
 
   ElementsKind constant_elements_kind =
       static_cast<ElementsKind>(Smi::cast(elements->get(0))->value());
   Handle<FixedArrayBase> constant_elements_values(
       FixedArrayBase::cast(elements->get(1)));
 
-  ASSERT(FLAG_smi_only_arrays || constant_elements_kind == FAST_ELEMENTS ||
-         constant_elements_kind == FAST_SMI_ONLY_ELEMENTS);
-  bool allow_literal_kind_transition = FLAG_smi_only_arrays &&
-      constant_elements_kind > object->GetElementsKind();
-
-  if (!FLAG_smi_only_arrays &&
-      constant_elements_values->length() > kSmiOnlyLiteralMinimumLength &&
-      constant_elements_kind != object->GetElementsKind()) {
-    allow_literal_kind_transition = true;
-  }
-
-  // If the ElementsKind of the constant values of the array literal are less
-  // specific than the ElementsKind of the boilerplate array object, change the
-  // boilerplate array object's map to reflect that kind.
-  if (allow_literal_kind_transition) {
-    Handle<Map> transitioned_array_map =
-        isolate->factory()->GetElementsTransitionMap(object,
-                                                     constant_elements_kind);
-    object->set_map(*transitioned_array_map);
+  Context* global_context = isolate->context()->global_context();
+  if (constant_elements_kind == FAST_SMI_ONLY_ELEMENTS) {
+    object->set_map(Map::cast(global_context->smi_js_array_map()));
+  } else if (constant_elements_kind == FAST_DOUBLE_ELEMENTS) {
+    object->set_map(Map::cast(global_context->double_js_array_map()));
+  } else {
+    object->set_map(Map::cast(global_context->object_js_array_map()));
   }
 
   Handle<FixedArrayBase> copied_elements_values;
   if (constant_elements_kind == FAST_DOUBLE_ELEMENTS) {
     ASSERT(FLAG_smi_only_arrays);
     copied_elements_values = isolate->factory()->CopyFixedDoubleArray(
         Handle<FixedDoubleArray>::cast(constant_elements_values));
   } else {
     ASSERT(constant_elements_kind == FAST_SMI_ONLY_ELEMENTS ||
            constant_elements_kind == FAST_ELEMENTS);
@@ skipping 24 matching lines @@
           Handle<Object> result =
               CreateLiteralBoilerplate(isolate, literals, fa);
           if (result.is_null()) return result;
           fixed_array_values_copy->set(i, *result);
         }
       }
     }
   }
   object->set_elements(*copied_elements_values);
   object->set_length(Smi::FromInt(copied_elements_values->length()));
+
+  // If the ElementsKind of the constant values of the array literal are less

[Jakob Kummerow, 2012/01/23 17:16:55]

This comment is confusing. Suggestion:
"Ensure that the boilerplate object has FAST_ELEMENTS, unless the flag is on or
the object is larger than the threshold."

[danno, 2012/01/26 21:32:34]

Done.

+  // specific than the ElementsKind of the boilerplate array object, change
+  // the boilerplate array object's map to reflect that kind.
+  if (!FLAG_smi_only_arrays &&
+      constant_elements_values->length() < kSmiOnlyLiteralMinimumLength) {
+    if (object->GetElementsKind() != FAST_ELEMENTS) {
+      CHECK(!TransitionElements(object, FAST_ELEMENTS, isolate)->IsFailure());
+    }
+  }
+
   return object;
 }
 
 
 static Handle<Object> CreateLiteralBoilerplate(
     Isolate* isolate,
     Handle<FixedArray> literals,
     Handle<FixedArray> array) {
   Handle<FixedArray> elements = CompileTimeValue::GetElements(array);
   const bool kHasNoFunctionLiteral = false;
@@ skipping 3673 matching lines @@
   NoHandleAllocation ha;
   ASSERT(args.length() == 2);
 
   Handle<Object> object = args.at<Object>(0);
   Handle<Object> key = args.at<Object>(1);
 
   return Runtime::GetObjectProperty(isolate, object, key);
 }
 
 
-MaybeObject* TransitionElements(Handle<Object> object,
-                                ElementsKind to_kind,
-                                Isolate* isolate) {
-  HandleScope scope(isolate);
-  if (!object->IsJSObject()) return isolate->ThrowIllegalOperation();
-  ElementsKind from_kind =
-      Handle<JSObject>::cast(object)->map()->elements_kind();
-  if (Map::IsValidElementsTransition(from_kind, to_kind)) {
-    Handle<Object> result = JSObject::TransitionElementsKind(
-        Handle<JSObject>::cast(object), to_kind);
-    if (result.is_null()) return isolate->ThrowIllegalOperation();
-    return *result;
-  }
-  return isolate->ThrowIllegalOperation();
-}
-
-
 // KeyedStringGetProperty is called from KeyedLoadIC::GenerateGeneric.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_KeyedGetProperty) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 2);
 
   // Fast cases for getting named properties of the receiver JSObject
   // itself.
   //
   // The global proxy objects has to be excluded since LocalLookup on
   // the global proxy object can return a valid result even though the
@@ skipping 5992 matching lines @@
   ElementsKind elements_kind;
   if (new_elements->map() == isolate->heap()->fixed_array_map() ||
       new_elements->map() == isolate->heap()->fixed_cow_array_map()) {
     elements_kind = FAST_ELEMENTS;
   } else if (new_elements->map() ==
              isolate->heap()->fixed_double_array_map()) {
     elements_kind = FAST_DOUBLE_ELEMENTS;
   } else {
     elements_kind = DICTIONARY_ELEMENTS;
   }
-  maybe_new_map = to->GetElementsTransitionMap(elements_kind);
+  maybe_new_map = to->GetElementsTransitionMap(isolate, elements_kind);
   Object* new_map;
   if (!maybe_new_map->ToObject(&new_map)) return maybe_new_map;
   to->set_map(Map::cast(new_map));
   to->set_elements(new_elements);
   to->set_length(from->length());
   Object* obj;
   { MaybeObject* maybe_obj = from->ResetElements();
     if (!maybe_obj->ToObject(&obj)) return maybe_obj;
   }
   from->set_length(Smi::FromInt(0));
@@ skipping 3390 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags);
   }
 }
 
 
 } }  // namespace v8::internal