javascript JIT project : speedups

[Przemek Klosowski]

I saw this article about a project to speed up the Javascript interpreter in 
Mozilla.

http://weblogs.mozillazine.org/roadmap/archives/2008/08/tracemonkey_javascript_lightsp.html

They had a couple of interesting ideas:

 - loop tracking, to detect code that is executed as a loop body.
   This is worthy because:
   - the types are unlikely to change across the loop iterations
   - it's where the time is spent, so optimizing gives highest payoff

 - instrumenting the interpreter as the first step: performance-guided
   optimization