Ajax Girl

For years, many of us have been salivating over the idea of JIT’ed JavaScript in the browser. Adobe’s JIT’ing Flash VM showed a preview of tremendous speed gains to be had, but we’ve had to wait until SquirrelFish from WebKit to see anything dramatic happen in the browser.

Until now.

Mozilla just let the cat out of the bag on their new TraceMonkey project. Brendan Eich, Mozilla’s CTO, describes it thusly:

I’m extremely pleased to announce the launch of TraceMonkey, an evolution of Firefox’s SpiderMonkey JavaScript engine for Firefox 3.1 that uses a new kind of Just-In-Time (JIT) compiler to boost JS performance by an order of magnitude or more. [Emphasis ours.]

There are charts and graphs all over the Web; here’s one from Brendan’s blog:

As Brendan points out, the benchmarks can be generally quite misleading; the best results are the demos. And, here’s a link to Mike “schrep” Schroepfer’s blog entry where he put one together in a screencast:

Brendan goes into significant detail on how all of this came about, and notes some key points:

* We have, right now, x86, x86-64, and ARM support in TraceMonkey. This means we are ready for mobile and desktop target platforms out of the box.
* As the performance keeps going up, people will write and transport code that was “too slow” to run in the browser as JS. This means the web can accomodate workloads that right now require a proprietary plugin.
* As we trace more of the DOM and our other native code, we increase the memory-safe codebase that must be trusted not to have an exploitable bug.
* Tracing follows only the hot paths, and builds a trace-tree cache. Cold code never gets traced or JITted, avoiding the memory bloat that whole-method JITs incur. Tracing is mobile-friendly.

For even more details, check out Andreas Gal’s detailed blog entry on trace trees.

The first phase of Ajax has been all about leveraging the existing platforms as much as we can. This announcement is a major signpost towards the second phase: improving the existing platforms. We couldn’t be more excited.

Brendan puts it in his own understated way:

JS-driven <canvas> rendering, with toolkits, scene graphs, game logic, etc. all in JS, are one wave of the future that is about to crest.

John Resig voices similar sentiments in his excellent blog post on the subject:

[This] means that JavaScript is no longer confined by previously-challenging resource of processing power… I fully expect to see more massive projects being written in JavaScript…

The primary thing holding back most extensive Canvas development hasn’t been rendering - but the processor limitations of the language (performing the challenging mathematical operations related to vectors, matrices, or collision detection). I expect this area to absolutely explode after the release of Firefox 3.1 as we start to see this work take hold.

Speaking of Canvas and JS, we’ve got our own little project we’ve been hacking this year that we can’t wait to try this on… way to go, Mozilla!

Source: Ajaxian » Front Page
Original Article: http://feeds.feedburner.com/~r/ajaxian/~3/372268236/javascript-jit-the-dream-gets-closer-in-firefox