Changeset 47601 in webkit for trunk/JavaScriptCore/JavaScriptCore.exp

Timestamp:

Aug 20, 2009, 3:36:36 PM (16 years ago)

Author:

[email protected]

Message:

REGRESSION: significant slowdown on Celtic Kane "AJAX declaration" subtest
​https://bugs.webkit.org/show_bug.cgi?id=28332

Reviewed by Gavin Barraclough.

The method check optimisation made transitions aware of the value being
assigned when a transition was assigning a function. This had the side
effect of making every assignment of a function expression result in a
new transition, and thus a new Structure. The net result of this is that
the common JS idiom of

function MyObject() {

this.myFunction = function(...){...};

}
new MyObject();

Will produce a unique structure on every iteration, meaning that all
caching is defeated and there is a significant amount of structure churn.

The fix is to return the transition to its original form where it is
keyed off a property name + attributes tuple, but have each transition
support an optional transition on a specific value.

File:

• trunk/JavaScriptCore/JavaScriptCore.exp (modified) (1 diff)

trunk/JavaScriptCore/JavaScriptCore.exp

@@ -263 +263 @@
 __ZN3JSC9MarkStack13allocateStackEm
 __ZN3JSC9MarkStack18initializePagesizeEv
+__ZN3JSC9Structure13hasTransitionEPNS_7UString3RepEj
 __ZN3JSC9Structure17stopIgnoringLeaksEv
 __ZN3JSC9Structure18startIgnoringLeaksEv