In their blog, developers Andreas Gal and Michael Franz explain how the tracing mechanism in TraceMonkey works. One of the main tricks performed by Tracemonkey is that, where branching occurs, it generates not only the required code, but also considers and compiles the other branches and saves the code for subsequent use. The just-in-time compiler can generate code for x86 and ARM systems, which should also be a boost for the in-development Mobile Firefox.
Firefox 3.1 is scheduled for release at the end of this year. The new acceleration technology is currently disabled in the pre-release version and users will need to activate it via the