Changeset 48264 in webkit for trunk/JavaScriptCore/runtime/Structure.h

Timestamp:

Sep 10, 2009, 1:01:57 PM (16 years ago)

Author:

[email protected]

Message:

Refactor StructureTransitionTable and Structure to unify handling of the single slot optimization
​https://bugs.webkit.org/show_bug.cgi?id=29141

Reviewed by Geoff Garen

Make StructureTransitionTable encapsulate the single transition slot optimization.

File:

• trunk/JavaScriptCore/runtime/Structure.h (modified) (5 diffs)

trunk/JavaScriptCore/runtime/Structure.h

@@ -53 +53 @@
     public:
         friend class JIT;
+        friend class StructureTransitionTable;
         static PassRefPtr<Structure> create(JSValue prototype, const TypeInfo& typeInfo)
         {
@@ -175 +176 @@
         JSCell* m_specificValueInPrevious;
 
-        union {
-            Structure* singleTransition;
-            StructureTransitionTable* table;
-        } m_transitions;
+        StructureTransitionTable table;
 
         RefPtr<PropertyNameArrayData> m_cachedPropertyNameArrayData;
@@ -190 +188 @@
         bool m_isPinnedPropertyTable : 1;
         bool m_hasGetterSetterProperties : 1;
-        bool m_usingSingleTransitionSlot : 1;
         unsigned m_attributesInPrevious : 7;
     };
@@ -241 +238 @@
     bool StructureTransitionTable::contains(const StructureTransitionTableHash::Key& key, JSCell* specificValue)
     {
-        TransitionTable::iterator find = m_table.find(key);
-        if (find == m_table.end())
+        if (usingSingleTransitionSlot()) {
+            Structure* existingTransition = singleTransition();
+            return existingTransition && existingTransition->m_nameInPrevious.get() == key.first
+                   && existingTransition->m_attributesInPrevious == key.second
+                   && (existingTransition->m_specificValueInPrevious == specificValue || existingTransition->m_specificValueInPrevious == 0);
+        }
+        TransitionTable::iterator find = table()->find(key);
+        if (find == table()->end())
             return false;
 
@@ -250 +253 @@
     Structure* StructureTransitionTable::get(const StructureTransitionTableHash::Key& key, JSCell* specificValue) const
     {
-        Transition transition = m_table.get(key);
+        if (usingSingleTransitionSlot()) {
+            Structure* existingTransition = singleTransition();
+            if (existingTransition && existingTransition->m_nameInPrevious.get() == key.first
+                && existingTransition->m_attributesInPrevious == key.second
+                && (existingTransition->m_specificValueInPrevious == specificValue || existingTransition->m_specificValueInPrevious == 0))
+                return existingTransition;
+            return 0;
+        }
+
+        Transition transition = table()->get(key);
         if (transition.second && transition.second->transitionedFor(specificValue))
             return transition.second;
         return transition.first;
     }
+
+    bool StructureTransitionTable::hasTransition(const StructureTransitionTableHash::Key& key) const
+    {
+        if (usingSingleTransitionSlot()) {
+            Structure* transition = singleTransition();
+            return transition && transition->m_nameInPrevious == key.first
+            && transition->m_attributesInPrevious == key.second;
+        }
+        return table()->contains(key);
+    }
+    
+    void StructureTransitionTable::reifySingleTransition()
+    {
+        ASSERT(usingSingleTransitionSlot());
+        Structure* existingTransition = singleTransition();
+        ASSERT(existingTransition);
+        TransitionTable* transitionTable = new TransitionTable;
+        setTransitionTable(transitionTable);
+        add(make_pair(existingTransition->m_nameInPrevious.get(), existingTransition->m_attributesInPrevious), existingTransition, existingTransition->m_specificValueInPrevious);
+    }
 } // namespace JSC