I'm wondering: would it be possible for a compiler to check if parts of the javascript code could run on another core?

For fun I created a 3D-render-engine in javascript + canvas (path tracing from lightsource). And I'm amazed how javascript speed differs in different browsers. Opera 10.50 and Chrome are like 3 times faster than others. But multi-threading would increase the speed even more (improving my program skills also...): www.thuijzer.nl/jsrender