First there was SquirrelFish, now there is SquirrelFish Extreme. The exact nature of what SquirrelFish Extreme is isn’t quite clear at the moment given that it hasn’t yet been announced by the WebKit team. However, some initial benchmarks against TraceMonkey are beginning to appear.
Rummaging around in the source, there is clearly indication of more advanced code generation. It was only merged to trunk in r36244 and is apparently enabled in the latest nightlies - not sure about Windows build though.
Going back to the V8 benchmarks, JSCore has now jumped to: 775 a large improvement over the initial 457. I’d imagine, that given the fact that these nightlies were already pretty competitive with TraceMonkey et al. on SunSpider and Dromaeo, I’d imaging this pushes them ahead. I’m sure we’ll find out soon enough.
This is all based on info gleaned from the Trac - please don’t flame me if this turns out to be wide of the mark. However, something is going to be announced within the next couple of days.
Update: Initial Dromaeo benchmarks: