Hi Tim and others,

Code related to unwind and exceptions have been rewritten in VI4.  In
particular, primitiveValueUninterruptably is no longer used and has been
removed.  Also, with the new CompiledMethod structure (without needing
to encode numLiterals) there are unused bits in the method header even
with 11 bits for primitive.

I will officially release the latest version of VI4 later this week. 
However, you can get the latest code now from
http://minnow.cc.gatech.edu/squeak/VI4.  It is basically complete,
except for some documentation.  Sorry, this version took so long, I
rewrote most of it, cleaning up the code considerably.  But I now think
the code is good and ready for prime time and don't anticipate any major
redesigns.

Cheers,
Anthony

PS. BlockClosure valueUninterruptably is implemented as follows in VI4:

valueUninterruptably
	"Prevent remote returns from escaping the sender.  Even attempts to
terminate (unwind) this process will be halted and the process will
resume here.  A terminate message is needed for every one of these in
the sender chain to get the entire process unwound."

	^ self ifCurtailed: [^ self]