Changeset 50254 in webkit for trunk/JavaScriptCore/runtime/JSPropertyNameIterator.cpp

Timestamp:

Oct 28, 2009, 6:25:02 PM (16 years ago)

Author:

[email protected]

Message:

Improve for..in enumeration performance
​https://bugs.webkit.org/show_bug.cgi?id=30887

Reviewed by Geoff Garen.

Improve indexing of an object with a for..in iterator by
identifying cases where get_by_val is being used with a iterator
as the subscript and replace it with a new get_by_pname
bytecode. get_by_pname then optimizes lookups that directly access
the base object.

File:

• trunk/JavaScriptCore/runtime/JSPropertyNameIterator.cpp (modified) (1 diff)

trunk/JavaScriptCore/runtime/JSPropertyNameIterator.cpp

@@ -44 +44 @@
     PropertyNameArray propertyNames(exec);
     o->getPropertyNames(exec, propertyNames);
-    JSPropertyNameIterator* jsPropertyNameIterator = new (exec) JSPropertyNameIterator(exec, propertyNames.data());
+    size_t numCacheableSlots = 0;
+    if (!o->structure()->hasNonEnumerableProperties() && !o->structure()->hasAnonymousSlots() &&
+        !o->structure()->isUncacheableDictionary() && !o->structure()->typeInfo().overridesGetPropertyNames())
+        numCacheableSlots = o->structure()->propertyStorageSize();
+
+    JSPropertyNameIterator* jsPropertyNameIterator = new (exec) JSPropertyNameIterator(exec, propertyNames.data(), numCacheableSlots);
 
     if (o->structure()->isDictionary())