Changeset 54696 in webkit for trunk/JavaScriptCore/runtime/JSPropertyNameIterator.cpp

Timestamp:

Feb 11, 2010, 6:51:35 PM (15 years ago)

Author:

[email protected]

Message:

2010-02-11 Geoffrey Garen <​[email protected]>

Reviewed by Gavin Barraclough.

Some progress toward fixing
​https://bugs.webkit.org/show_bug.cgi?id=34864 | <rdar://problem/7594198>
Many objects left uncollected after visiting mail.google.com and closing
window

SunSpider reports no change.

Keep weak references, rather than protected references, to cached for-in
property name enumerators.

One problem with protected references is that a chain like

[ gc object 1 ] => [ non-gc object ] => [ gc object 2 ]

takes two GC passes to break, since the first pass collects [ gc object 1 ],
releasing [ non-gc object ] and unprotecting [ gc object 2 ], and only
then can a second pass collect [ gc object 2 ].

Another problem with protected references is that they can keep a bunch
of strings alive long after they're useful. In SunSpider and a few popular
websites, the size-speed tradeoff seems to favor weak references.

• runtime/JSPropertyNameIterator.cpp: (JSC::JSPropertyNameIterator::JSPropertyNameIterator): Moved this constructor into the .cpp file, since it's not used elsewhere.

(JSC::JSPropertyNameIterator::~JSPropertyNameIterator): Added a destructor
to support our weak reference.

• runtime/JSPropertyNameIterator.h: (JSC::Structure::setEnumerationCache): (JSC::Structure::clearEnumerationCache): (JSC::Structure::enumerationCache): Added a function for clearing a Structure's enumeration cache, used by our new destructor. Also fixed indentation to match the rest of the file.

• runtime/Structure.h: Changed from protected pointer to weak pointer.

File:

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

trunk/JavaScriptCore/runtime/JSPropertyNameIterator.cpp

@@ -35 +35 @@
 
 ASSERT_CLASS_FITS_IN_CELL(JSPropertyNameIterator);
+
+inline JSPropertyNameIterator::JSPropertyNameIterator(ExecState* exec, PropertyNameArrayData* propertyNameArrayData, size_t numCacheableSlots)
+    : JSCell(exec->globalData().propertyNameIteratorStructure.get())
+    , m_cachedStructure(0)
+    , m_numCacheableSlots(numCacheableSlots)
+    , m_jsStringsSize(propertyNameArrayData->propertyNameVector().size())
+    , m_jsStrings(new JSValue[m_jsStringsSize])
+{
+    PropertyNameArrayData::PropertyNameVector& propertyNameVector = propertyNameArrayData->propertyNameVector();
+    for (size_t i = 0; i < m_jsStringsSize; ++i)
+        m_jsStrings[i] = jsOwnedString(exec, propertyNameVector[i].ustring());
+}
+
+JSPropertyNameIterator::~JSPropertyNameIterator()
+{
+    if (m_cachedStructure)
+        m_cachedStructure->clearEnumerationCache(this);
+}
 
 JSPropertyNameIterator* JSPropertyNameIterator::create(ExecState* exec, JSObject* o)