I think BaselineCompiler is far enough to declare it at phase 3 (i.e., basically working, but still has bugs and does not yet pass the test suite), so I've dropped a "save point" tonight per my promise in the last blog post for those of you in the audience who are interested. It is still suffering from some significant glitches but is now able to run about half of V8 successfully and I think this is far enough to try to get everything else to pass (since that will be easier than figuring out all the places it could go wrong in V8), so if you're interested in helping out the changesets are now available from the downloads tab. I have not tried to actually build the rest of the browser yet; just build up to js/src inclusive only. You should apply it to mozilla-aurora at the designated rev, not to tip unless you think merging patches is a great way to spend your day. Follow along in issue 224.
Also, as promised, I've made available the customized gdb I'm using for this work. In addition to optimizing getting registers from the current frame and stifling the warning about gdb being unable to find object files, it adds two new commands: ct, which skips a trap instruction inserted into the code and automatically continues in one step, and sii, which is a macro to step through 10 instructions at once. For my next trick, I aim to make it stop spuriously removing display items on traps, but I haven't figured out how to do that reliably yet. Source and a binary for PPC 10.4/10.5 are available from the downloads tab. It is based on gdb-768, which is the debugger Apple includes with Xcode 3.
I am going to try to get a 24 beta out at the same time as 17.0.10, the last 17 release, but you should assume we will have at least one more interim 22 release before then; I don't think I'm going to be ready with a 24 beta for 17.0.9.