Changeset 48883 in webkit for trunk/JavaScriptCore/runtime/JSGlobalObject.h

Timestamp:

Sep 29, 2009, 10:54:39 AM (16 years ago)

Author:

[email protected]

Message:

Removed virtual destructor from JSGlobalObjectData to eliminate pointer
fix-ups when accessing JSGlobalObject::d.

Patch by Geoffrey Garen <​[email protected]> on 2009-09-28
Reviewed by Sam Weinig.

JavaScriptCore:

Replaced with an explicit destructor function pointer.

6% speedup on bench-alloc-nonretained.js.

• JavaScriptCore.exp:
• runtime/JSGlobalObject.cpp:

(JSC::JSGlobalObject::~JSGlobalObject):
(JSC::JSGlobalObject::destroyJSGlobalObjectData):

• runtime/JSGlobalObject.h:

(JSC::JSGlobalObject::JSGlobalObjectData::JSGlobalObjectData):
(JSC::JSGlobalObject::JSGlobalObject):

JavaScriptGlue:

Replaced with an explicit destructor function pointer.

• JSRun.cpp:

(JSGlueGlobalObject::destroyData):

• JSRun.h:

(JSGlueGlobalObject::Data::Data):

WebCore:

Replaced with an explicit destructor function pointer.

• bindings/js/JSDOMGlobalObject.cpp:

(WebCore::JSDOMGlobalObject::destroyJSDOMGlobalObjectData):

• bindings/js/JSDOMGlobalObject.h:

(WebCore::JSDOMGlobalObject::JSDOMGlobalObjectData::JSDOMGlobalObjectData):

File:

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

trunk/JavaScriptCore/runtime/JSGlobalObject.h

@@ -53 +53 @@
 
     typedef Vector<ExecState*, 16> ExecStateStack;
-
+    
     class JSGlobalObject : public JSVariableObject {
     protected:
@@ -59 +59 @@
 
         struct JSGlobalObjectData : public JSVariableObjectData {
-            JSGlobalObjectData()
+            // We use an explicit destructor function pointer instead of a
+            // virtual destructor because we want to avoid adding a vtable
+            // pointer to this struct. Adding a vtable pointer would force the
+            // compiler to emit costly pointer fixup code when casting from
+            // JSVariableObjectData* to JSGlobalObjectData*.
+            typedef void (*Destructor)(void*);
+
+            JSGlobalObjectData(Destructor destructor)
                 : JSVariableObjectData(&symbolTable, 0)
+                , destructor(destructor)
                 , registerArraySize(0)
                 , globalScopeChain(NoScopeChain())
@@ -86 +94 @@
             }
             
-            virtual ~JSGlobalObjectData()
-            {
-            }
-
+            Destructor destructor;
+            
             size_t registerArraySize;
 
@@ -154 +160 @@
 
         explicit JSGlobalObject()
-            : JSVariableObject(JSGlobalObject::createStructure(jsNull()), new JSGlobalObjectData)
+            : JSVariableObject(JSGlobalObject::createStructure(jsNull()), new JSGlobalObjectData(destroyJSGlobalObjectData))
         {
             init(this);
@@ -281 +287 @@
 
     private:
+        static void destroyJSGlobalObjectData(void*);
+
         // FIXME: Fold reset into init.
         void init(JSObject* thisValue);