Let me be the first to say ...

Woo-hooooo!!!!

:-)

Chris Becker


> -----Original Message-----
> From: squeak-dev-bounces at lists.squeakfoundation.org [mailto:squeak-dev-
> bounces at lists.squeakfoundation.org] On Behalf Of Dan Ingalls
> Sent: Friday, August 27, 2004 11:52 AM
> To: The general-purpose Squeak developers list
> Subject: Progress on 64-bit port
> 
> Folks -
> 
> First the good news:
> We can now generate, from a single set of sources, four different VMs...
> 
> 	One that will run a 32-bit image on a 32-bit host
> 		same old VM
> 	One that will run a 32-bit image on a 64-bit host
> 		needed to run on 64-bit machines
> 	One that will run a 64-bit image on a 32-bit host
> 		great for testing 64-bit VM on 32-bit machines
> 	One that will run a 64-bit image on a 64-bit host
> 		the thing we were after
> 
> ... and all of them work!
> 
> Ian and I worked together on this, with Ian focused on issues of C
> translation rules, and me focused on properly generalizing all the
> occurrences of 4 (bytes per word), 2 (shift count), and lots of other
> things derived therefrom.  I also wrote a tracer subclass that will write
> images in a 64-bit format, and Ian also contributed the brilliant
> framework that enabled this four-way compatibility.
> 
> 
> Now the fine print...
> The 64-bit format is the simplest change that could work, not the simplest
> format that could work.  For those who understand the object current
> format, here is the change:
> 
> 	All object pointers are 64 bits as you'd expect.
> 
> 	SmallIntegers are still 31-bits, although stored sign-extended to 63
> bits (plus tag bit).
> 
> 	32-bit Object header:
> 	3 bits	reserved for gc (mark, old, dirty)
> 	12 bits	object hash (for HashSets)
> 	5 bits	compact class index
> 	4 bits	object format (includes low bits of size in bytes)
> 	6 bits	object size in 32-bit words
> 	2 bits	header type (0: 3-word, 1: 2-word, 2: forbidden, 3: 1-
> word)
> 
> 	64-bit Object header:
> 	32 bits	all zero
> 	3 bits	reserved for gc (mark, old, dirty)
> 	12 bits	object hash (for HashSets)
> 	5 bits	compact class index
> 	4 bits	object format (includes low bits of size in bytes)
> 	5 bits	object size in 64-bit words
> 	1 bit	extra 4-bit of size in bytes or 32-bit words
> 	2 bits	header type (0: 3-word, 1: 2-word, 2: forbidden, 3: 1-
> word)
> 
> 	The object size field had to be in units of 8 bytes, and therefore
> three
> 	low-order bits are required instead of the 2 that are in the current
> format field.
> 	I simply used the vacated bit of the word size field for the 3rd low
> bit.
> 	It's Byzantine, but it works with few changes.
> 
> We have only converted the core interpreter and 3 plugins (BitBlt,
> BalloonEngine and FilePlugin).  This is enough to run Squeak and test it.
> Moreover we now have a lot of experience with the conversion process, and
> we will write down a set of guidelines for converting the remaining
> plugins. We may ask for help from the Squeak community in converting the
> remaining plugins, and also image segment code.  In some case there is
> clearly someone who knows the code much better than us, and for the rest,
> there may simply be others who want a complete 64-bit system.
> 
> We have not done *any* of the Version 4 changes.  The first reason is that
> we need to release this work soon before we get out of phase with other
> Squeak progress.  The second is some discussion in our group about the
> possibility of making *much* more major changes.  As soon as we get
> clearer about this and confirm our intention, we'll have more to say about
> it.  If were to go ahead with such a rethink, then any time spent of
> Version 4 would have been wasted.
> 
> We have not done any testing beyond the point of bringing up a morphic
> screen with Squeak mouse, opening a browser and running the benchmarks.
> There is lots to test, and surely a number of bugs yet to be found.  The
> Squeak community can be of enormous help here.
> 
> 
> Next steps...
> Ian and I are both pretty busy, but it is our hope to test the build
> process some more, and put out a complete source tree with this work in
> the course of the next month.  At that point others can help us to convert
> the remaining plugins and to test the system as a whole.
> 
> 	- Dan