I just checked in a fairly large set of changes from Sergiy, Kris, and Darko that represent stage 1 in the 64 bit port of the opt compiler.  I tested on Linux/IA32, and AIX/PowerPC (32 and 64), but haven't tested the OSX or Linux/PowerPC.

Once we get a clean nightly run on all platforms from those changes, I plan to commit Daniel's changes for a forward scalar object model (most likely in a couple of stages).  

We'll be as careful as possible, but if you are living on the cvs head there may be a few days of instability ahead as we make some fairly pervasive changes/improvements to the system.  Be warned and definitely don't do an update without checking on the results of the nightly regression tests for platforms that you care about. ;-)