SpiderMonkey's Warp Upgrade Is Ready For Firefox 83

Back in September Firefox Nightly enabled the JavaScript "Warp" code for SpiderMonkey and now for next week's Firefox 83.0 release it is remaining on by default for this web browser update.

Warp is a big upgrade to Mozilla's JavaScript just-in-time (JIT) compiler code. Thanks to a variety of optimizations the Warp functionality should yield more responsiveness and faster page load speeds, commonly around 5~15% faster but some cases ~20%+ speed-ups.

Mozilla engineers confirmed in a Mozilla Hacks blog post today that this Warp update to the SpiderMonkey JavaScript engine will indeed be the default for next week's Firefox 83 release.

They report around a 20% improvement for the Google Docs load time and 10~12% faster in benchmarks like Speedometer and other select JavaScript workloads. They do acknowledge though they currently regress in some JavaScript benchmarks like Kraken and Octane.

This blog post covers the architecture of Warp for speeding up the JIT compilation and optimizations, the IR handling, and more.

In that post they outline their next steps being the removal of the old code and architecture, which will likely happen for Firefox 85 and further improve the performance and memory usage. Ultimately they also hope to further enhance the IonMonkey JIT capabilities.

Firefox 83.0 is scheduled for release on 17 November.