Changeset 39593 in webkit for trunk/JavaScriptCore/runtime/Structure.h

Timestamp:

Jan 4, 2009, 4:18:53 PM (16 years ago)

Author:

[email protected]

Message:

2009-01-04 Alice Liu <​[email protected]>

<rdar://problem/6341776> Merge m_transitionCount and m_offset in Structure.

Reviewed by Darin Adler.

• runtime/Structure.cpp: (JSC::Structure::Structure): Remove m_transitionCount (JSC::Structure::addPropertyTransitionToExistingStructure): No need to wait until after the assignment to offset to assert if it's notFound; move it up. (JSC::Structure::addPropertyTransition): Use method for transitionCount instead of m_transitionCount. Remove line that maintains the m_transitionCount. (JSC::Structure::changePrototypeTransition): Remove line that maintains the m_transitionCount. (JSC::Structure::getterSetterTransition): Remove line that maintains the m_transitionCount.
• runtime/Structure.h: Changed s_maxTransitionLength and m_offset from size_t to signed char. m_offset will never become greater than 64 because the structure transitions to a dictionary at that time. (JSC::Structure::transitionCount): method to replace the data member

File:

• trunk/JavaScriptCore/runtime/Structure.h (modified) (4 diffs)

trunk/JavaScriptCore/runtime/Structure.h

@@ -107 +107 @@
         void setHasGetterSetterProperties(bool hasGetterSetterProperties) { m_hasGetterSetterProperties = hasGetterSetterProperties; }
 
-        bool isEmpty() const { return m_propertyTable ? !m_propertyTable->keyCount : m_offset == WTF::notFound; }
+        bool isEmpty() const { return m_propertyTable ? !m_propertyTable->keyCount : m_offset == noOffset; }
 
     private:
@@ -140 +140 @@
         }
 
+        signed char transitionCount() const
+        {
+            // Since the number of transitions is always the same as m_offset, we keep the size of Structure down by not storing both.
+            return m_offset == noOffset ? 0 : m_offset + 1;
+        }
+
         static const unsigned emptyEntryIndex = 0;
     
-        static const size_t s_maxTransitionLength = 64;
+        static const signed char s_maxTransitionLength = 64;
+
+        static const signed char noOffset = -1;
 
         TypeInfo m_typeInfo;
@@ -152 +160 @@
         RefPtr<UString::Rep> m_nameInPrevious;
 
-        size_t m_transitionCount;
         union {
             Structure* singleTransition;
@@ -163 +170 @@
 
         size_t m_propertyStorageCapacity;
-        size_t m_offset;
+        signed char m_offset;
 
         bool m_isDictionary : 1;