new snapshot

[Stephen Weeks]

> Good timing.  I just squashed last known bug in my current version of the
> x86 backend.

Ahhh.  The last bug.  :-)

> Those all look reasonable.  I'll also investigate the right types of
> property lists.  One question, if I don't make a property destructable,
> will it just last until the end of the compilation?  I tended to make
> properties destructable if I knew when I was going to be done with it.
> Maybe that's not necessarily the most efficient?

If you don't make a property (on, say, variables) destructable and then attach
that property to a variable, then the property will live as long as the variable
does or until the property list on the variable is cleared.  All that making it
destructable does is keep an extra list of all the property lists that the
property is attached to so you can delete the property from the lists when you
call destroy().  If you already have another data structure that makes it easy
to get at all of the property lists (say a syntax tree or list of basic blocks),
then it's more efficient to make the property nondestructable and to clear the
property lists yourself.