Mozilla is leveraging an impressive new optimization technique to bring a big performance boost to the Firefox JavaScript engine. The code was merged today (but is not yet ready to be enabled by default in the nightly builds) and is planned for inclusion in Firefox 3.1, the next incremental update of the open-source web browser.

To get a real-world performance increase right now, Mozilla has adapted the tracing technology and Adobe’s nanojit so that they can be integrated directly into SpiderMonkey, the JavaScript interpreter that is used in Firefox 3. This has produced a massive speedup that far surpasses what is currently possible with Tamarin-tracing. In addition to empowering web developers, the optimizations will also improve the general performance of the browser itself and many extensions because many components of the program are coded with JavaScript.

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