Apple Implements LLVM JIT Back-End For WebKit JavaScript

For speeding up the JavaScript performance within upstream WebKit, Apple developers have implemented a new just-in-time (JIT) back-end that's based upon LLVM.

WebKit's newly-enabled JavaScript JIT support is based on LLVM. The new LLVM-based JIT compiler is called FTL, for the Fourth Tier LLVM. For right now this new high-performance JavaScript back-end is enabled for the Mac OS X and iOS versions of the open-source web-browser rendering engine.

Apple developers have been working on this LLVM FTL support for the past year and have now finally been able to turn it on. By basing it on LLVM, they are taking advantage of new optimization approaches previously not applicable to WebKit's JavaScript.

Early performance figures by Apple show the FTL JIT support being much faster than their earlier DFG JIT back-end along with other comparison pipelines. While these early results are good, developers still have more performance optimizations planned for the LLVM FTL JIT support.

This WebKit LLVM support was brought up Tuesday on the LLVM developers' list and you can learn a lot more in detail via the WebKit.org blog.