Firefox 3 already received some major improvements in JavaScript execution time with the use of profiling. But today the good developers of Firefox landed a new Just-in-Time (JIT) compiler that even further boosts the performance by ±2-22 times.

Although disabled by default in the latest Firefox 3.1 nightlies, due to stability problems at the moment, this new trace-based JIT compiler really pushes Firefox 3.1 on par with Safari's latest Squirrelfish. Of course as a competitor, the new JIT compilers needs a fitting name thus it was dubbed TraceMonkey.

So what kind of performance differences are we talking about? Apple's SunSpider increased in the total test result by a factor of 1.83, and when focusing on SunSpider ubench suite, TraceMonkey achieves a factor of 22x increase.

If you want to know more about this technology I suggest you to read Andreas Gal's extensive blog post. Firefox 3.1 will be a sweet release, no doubt.