Changeset 21019 in webkit for trunk/JavaScriptCore/kjs/function.cpp

Timestamp:

Apr 22, 2007, 9:16:42 PM (18 years ago)

Author:

mjs

Message:

Reviewed by Darin.

• discard the arguments List for an ActivationImp when the corresponding Context is destroyed (1.7% speedup) ​http://bugs.webkit.org/show_bug.cgi?id=13385

Based an idea by Christopher E. Hyde <​[email protected]>. His patch to do
this also had many other List changes and I found this much simpler subset of the changes
was actually a hair faster.

This optimization is valid because the arguments list is only kept around to
lazily make the arguments object. If it's not made by the time the function
exits, it never will be, since any function that captures the continuation will
have its own local arguments variable in scope.

Besides the 1.7% speed improvement, it shrinks List by 4 bytes
(which in turn shrinks ActivationImp by 4 bytes).

• kjs/Context.cpp: (KJS::Context::~Context): Clear the activation's arguments list.
• kjs/function.cpp: (KJS::ActivationImp::ActivationImp): Adjusted for list changes. (KJS::ActivationImp::mark): No need to mark, lists are always protected (this doesn't cause a ref-cycle for reasons stated above). (KJS::ActivationImp::createArgumentsObject): Clear arguments list.
• kjs/function.h:
• kjs/list.cpp: (KJS::List::List): No more needsMarking boolean (KJS::List::operator=): ditto
• kjs/list.h: (KJS::List::List): ditto (KJS::List::reset): ditto (KJS::List::deref): ditto

File:

• trunk/JavaScriptCore/kjs/function.cpp (modified) (3 diffs)

trunk/JavaScriptCore/kjs/function.cpp

@@ -510 +510 @@
 // ECMA 10.1.6
 ActivationImp::ActivationImp(FunctionImp* function, const List& arguments)
-    : _function(function), _arguments(true), _argumentsObject(0)
-{
-  _arguments.copyFrom(arguments);
+    : _function(function), _arguments(arguments), _argumentsObject(0)
+{
   // FIXME: Do we need to support enumerating the arguments property?
 }
@@ -571 +570 @@
     if (_function && !_function->marked()) 
         _function->mark();
-    _arguments.mark();
     if (_argumentsObject && !_argumentsObject->marked())
         _argumentsObject->mark();
@@ -577 +575 @@
 }
 
-void ActivationImp::createArgumentsObject(ExecState* exec) const
+void ActivationImp::createArgumentsObject(ExecState* exec)
 {
   _argumentsObject = new Arguments(exec, _function, _arguments, const_cast<ActivationImp*>(this));
+  // The arguments list is only needed to create the arguments object, so discard it now
+  _arguments.reset();
 }