Changeset 41232 in webkit for trunk/JavaScriptCore/runtime/JSGlobalObject.h

Timestamp:

Feb 25, 2009, 3:44:07 PM (16 years ago)

Author:

[email protected]

Message:

JavaScriptCore:

2009-02-25 Geoffrey Garen <​[email protected]>

Reviewed by Maciej Stachowiak.

Fixed <rdar://problem/6611174> REGRESSION (r36701): Unable to select
messages on hotmail (24052)

The bug was that for-in enumeration used a cached prototype chain without
validating that it was up-to-date.

This led me to refactor prototype chain caching so it was easier to work
with and harder to get wrong.

After a bit of inlining, this patch is performance-neutral on SunSpider
and the v8 benchmarks.

• interpreter/Interpreter.cpp: (JSC::Interpreter::tryCachePutByID): (JSC::Interpreter::tryCacheGetByID):
• jit/JITStubs.cpp: (JSC::JITStubs::tryCachePutByID): (JSC::JITStubs::tryCacheGetByID): (JSC::JITStubs::cti_op_get_by_id_proto_list): Use the new refactored goodness. See lines beginning with "-" and smile.

• runtime/JSGlobalObject.h: (JSC::Structure::prototypeForLookup): A shout out to const.

• runtime/JSPropertyNameIterator.h: (JSC::JSPropertyNameIterator::next): We can use a pointer comparison to see if our cached structure chain is equal to the object's structure chain, since in the case of a cache hit, we share references to the same structure chain.

• runtime/Operations.h: (JSC::countPrototypeChainEntriesAndCheckForProxies): Use the new refactored goodness.

• runtime/PropertyNameArray.h: (JSC::PropertyNameArray::PropertyNameArray): (JSC::PropertyNameArray::setShouldCache): (JSC::PropertyNameArray::shouldCache): Renamed "cacheable" to "shouldCache" to communicate that the client is specifying a recommendation, not a capability.

• runtime/Structure.cpp: (JSC::Structure::Structure): No need to initialize a RefPtr. (JSC::Structure::getEnumerablePropertyNames): Moved some code into helper functions.

(JSC::Structure::prototypeChain): New centralized accessor for a prototype
chain. Revalidates on every access, since the objects in the prototype
chain may have mutated.

(JSC::Structure::isValid): Helper function for revalidating a cached
prototype chain.

(JSC::Structure::getEnumerableNamesFromPropertyTable):
(JSC::Structure::getEnumerableNamesFromClassInfoTable): Factored out of
getEnumerablePropertyNames.

• runtime/Structure.h:

• runtime/StructureChain.cpp: (JSC::StructureChain::StructureChain):
• runtime/StructureChain.h: (JSC::StructureChain::create): No need for structureChainsAreEqual, since we use pointer equality now. Refactored StructureChain to make a little more sense and eliminate special cases for null prototypes.

LayoutTests:

2009-02-24 Geoffrey Garen <​[email protected]>

Reviewed by Maciej Stachowiak.

Added a test for <rdar://problem/6611174> REGRESSION (r36701): Unable to
select messages on hotmail (24052)

• fast/js/for-in-cached-expected.txt: Added.
• fast/js/for-in-cached.html: Added.
• fast/js/resources/for-in-cached.js: Added. (forIn):

File:

• trunk/JavaScriptCore/runtime/JSGlobalObject.h (modified) (2 diffs)

trunk/JavaScriptCore/runtime/JSGlobalObject.h

@@ -330 +330 @@
     }
 
-    inline JSValuePtr Structure::prototypeForLookup(ExecState* exec)
+    inline JSValuePtr Structure::prototypeForLookup(ExecState* exec) const
     {
         if (typeInfo().type() == ObjectType)
@@ -340 +340 @@
         ASSERT(typeInfo().type() == NumberType);
         return exec->lexicalGlobalObject()->numberPrototype();
+    }
+
+    inline StructureChain* Structure::prototypeChain(ExecState* exec) const
+    {
+        // We cache our prototype chain so our clients can share it.
+        if (!isValid(exec, m_cachedPrototypeChain.get())) {
+            JSValuePtr prototype = prototypeForLookup(exec);
+            m_cachedPrototypeChain = StructureChain::create(prototype.isNull() ? 0 : asObject(prototype)->structure());
+        }
+        return m_cachedPrototypeChain.get();
+    }
+
+    inline bool Structure::isValid(ExecState* exec, StructureChain* cachedPrototypeChain) const
+    {
+        if (!cachedPrototypeChain)
+            return false;
+
+        JSValuePtr prototype = prototypeForLookup(exec);
+        RefPtr<Structure>* cachedStructure = cachedPrototypeChain->head();
+        while(*cachedStructure && !prototype.isNull()) {
+            if (asObject(prototype)->structure() != *cachedStructure)
+                return false;
+            ++cachedStructure;
+            prototype = asObject(prototype)->prototype();
+        }
+        return prototype.isNull() && !*cachedStructure;
     }