MapCache simplification. It is now a FixedArray that maps number of properties to a WeakCell with...

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 796fd13c089f541c37f73ee2632fc3c1526cad77..e68ac9b6fa41e91586e547a311a247e4841c0436 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -2420,35 +2420,42 @@ Handle<JSFunction> Factory::CreateApiFunction(
 }
 
 
-Handle<MapCache> Factory::AddToMapCache(Handle<Context> context,
-                                        Handle<FixedArray> keys,
-                                        Handle<Map> map) {
-  Handle<MapCache> map_cache = handle(MapCache::cast(context->map_cache()));
-  Handle<MapCache> result = MapCache::Put(map_cache, keys, map);
-  context->set_map_cache(*result);
-  return result;
-}
-
-
 Handle<Map> Factory::ObjectLiteralMapFromCache(Handle<Context> context,
-                                               Handle<FixedArray> keys) {
+                                               int number_of_properties,
+                                               bool* is_result_from_cache) {
+  const int kMapCacheSize = 128;
+
+  if (number_of_properties > kMapCacheSize) {
+    *is_result_from_cache = false;
+    return Map::Create(isolate(), number_of_properties);
+  }
+  *is_result_from_cache = true;
+  if (number_of_properties == 0) {
+    // Reuse the initial map of the Object function if the literal has no
+    // predeclared properties.
+    return handle(context->object_function()->initial_map(), isolate());
+  }
+  int cache_index = number_of_properties - 1;
   if (context->map_cache()->IsUndefined()) {
     // Allocate the new map cache for the native context.
-    Handle<MapCache> new_cache = MapCache::New(isolate(), 24);
+    Handle<FixedArray> new_cache = NewFixedArray(kMapCacheSize, TENURED);
     context->set_map_cache(*new_cache);
   }
   // Check to see whether there is a matching element in the cache.
-  Handle<MapCache> cache =
-      Handle<MapCache>(MapCache::cast(context->map_cache()));
-  Handle<Object> result = Handle<Object>(cache->Lookup(*keys), isolate());
-  if (result->IsMap()) return Handle<Map>::cast(result);
-  int length = keys->length();
-  // Create a new map and add it to the cache. Reuse the initial map of the
-  // Object function if the literal has no predeclared properties.
-  Handle<Map> map = length == 0
-                        ? handle(context->object_function()->initial_map())
-                        : Map::Create(isolate(), length);
-  AddToMapCache(context, keys, map);
+  Handle<FixedArray> cache(FixedArray::cast(context->map_cache()));
+  {
+    Object* result = cache->get(cache_index);
+    if (result->IsWeakCell()) {
+      WeakCell* cell = WeakCell::cast(result);
+      if (!cell->cleared()) {
+        return handle(Map::cast(cell->value()), isolate());
+      }
+    }
+  }
+  // Create a new map and add it to the cache.
+  Handle<Map> map = Map::Create(isolate(), number_of_properties);
+  Handle<WeakCell> cell = NewWeakCell(map);
+  cache->set(cache_index, *cell);
   return map;
 }
 
@@ -2467,6 +2474,7 @@ void Factory::SetRegExpAtomData(Handle<JSRegExp> regexp,
   regexp->set_data(*store);
 }
 
+
 void Factory::SetRegExpIrregexpData(Handle<JSRegExp> regexp,
                                     JSRegExp::Type type,
                                     Handle<String> source,
@@ -2488,7 +2496,6 @@ void Factory::SetRegExpIrregexpData(Handle<JSRegExp> regexp,
 }
 
 
-
 MaybeHandle<FunctionTemplateInfo> Factory::ConfigureInstance(
     Handle<FunctionTemplateInfo> desc, Handle<JSObject> instance) {
   // Configure the instance by adding the properties specified by the