Changeset 27068 in webkit for trunk/JavaScriptCore/kjs/function.h

Timestamp:

Oct 25, 2007, 2:37:45 PM (18 years ago)

Author:

ggaren

Message:

Reviewed by Oliver Hunt.

Fixed ​http://bugs.webkit.org/show_bug.cgi?id=15694
Shrink the size of an activation object by 1 word

This is in preparation for adding a symbol table to the activation
object.

The basic strategy here is to rely on the mutual exclusion between
the arguments object pointer and the function pointer (you only need
the latter in order to create the former), and store them in the same
place. The LazyArgumentsObject class encapsulates this strategy.

Also inlined the ArgumentsImp constructor, for good measure.

SunSpider reports no regression. Regression tests pass.

• JavaScriptCore.xcodeproj/project.pbxproj:
• kjs/Context.cpp: (KJS::Context::~Context):
• kjs/function.cpp: (KJS::ActivationImp::LazyArgumentsObject::createArgumentsObject): (KJS::ActivationImp::LazyArgumentsObject::mark): (KJS::): (KJS::ActivationImp::argumentsGetter): (KJS::ActivationImp::mark):
• kjs/function.h: (KJS::ActivationImp::LazyArgumentsObject::LazyArgumentsObject): (KJS::ActivationImp::LazyArgumentsObject::getOrCreate): (KJS::ActivationImp::LazyArgumentsObject::resetArguments): (KJS::ActivationImp::LazyArgumentsObject::setArgumentsObject): (KJS::ActivationImp::LazyArgumentsObject::argumentsObject): (KJS::ActivationImp::LazyArgumentsObject::setFunction): (KJS::ActivationImp::LazyArgumentsObject::function): (KJS::ActivationImp::LazyArgumentsObject::createdArgumentsObject): (KJS::ActivationImp::LazyArgumentsObject::): (KJS::ActivationImp::ActivationImp::ActivationImp): (KJS::ActivationImp::resetArguments):

File:

• trunk/JavaScriptCore/kjs/function.h (modified) (2 diffs)

trunk/JavaScriptCore/kjs/function.h

@@ -144 +144 @@
   class ActivationImp : public JSObject {
   public:
-    ActivationImp(FunctionImp* function, const List& arguments);
+    class LazyArgumentsObject {
+    public:
+        LazyArgumentsObject(FunctionImp* f, const List& a)
+            : arguments(a)
+        {
+            ASSERT(f);
+            setFunction(f);
+        }
+
+        Arguments* getOrCreate(ExecState* exec, ActivationImp* activationImp)
+        {
+            if (!createdArgumentsObject())
+                createArgumentsObject(exec, activationImp);
+            return argumentsObject();
+        }
+
+        void resetArguments() { arguments.reset(); }
+        void mark();
+
+    private:
+        static const uintptr_t TagMask = 1; // Pointer alignment leaves this bit open for tagging.
+        
+        void setArgumentsObject(Arguments* a)
+        { 
+            u.argumentsObject = a;
+            u.bits |= TagMask;
+        }
+
+        Arguments* argumentsObject()
+        {
+            ASSERT(createdArgumentsObject());
+            return reinterpret_cast<Arguments*>(u.bits & ~TagMask);
+        }
+
+        void setFunction(FunctionImp* f) { u.function = f; }
+        FunctionImp* function()
+        {
+            ASSERT(!createdArgumentsObject());
+            return u.function;
+        }
+
+        bool createdArgumentsObject() { return (u.bits & TagMask) != 0; }
+        void createArgumentsObject(ExecState*, ActivationImp*);
+
+        List arguments;
+        union {
+            // The low bit in this union is a flag: 0 means the union holds a 
+            // FunctionImp*; 1 means the union holds an Arguments*.
+            uintptr_t bits;
+            FunctionImp* function;
+            Arguments* argumentsObject;
+        } u;
+    };
+    
+    ActivationImp::ActivationImp(FunctionImp* function, const List& arguments)
+        : m_lazyArgumentsObject(function, arguments)
+    {
+    }
 
     virtual bool getOwnPropertySlot(ExecState*, const Identifier&, PropertySlot&);
@@ -157 +214 @@
     bool isActivation() { return true; }
 
-    void releaseArguments() { _arguments.reset(); }
+    void resetArguments() { m_lazyArgumentsObject.resetArguments(); }
 
   private:
     static PropertySlot::GetValueFunc getArgumentsGetter();
     static JSValue* argumentsGetter(ExecState*, JSObject*, const Identifier&, const PropertySlot& slot);
-    void createArgumentsObject(ExecState*);
-
-    FunctionImp* _function;
-    List _arguments;
-    mutable Arguments* _argumentsObject;
+    
+    LazyArgumentsObject m_lazyArgumentsObject;
   };