linear scan questions

   I understand the linear scan isnt the default allocator anymore.
However, I havent still switched from it and so i was wondering if I
can ask a few questions.

1) I do see the availability of a register maintained as a
non-boolean and so addRegUse/delreguse etc increment/decrement it. I
am wondering in what scenario would it be non 0/1

2) On similar lines, what is the motivation of inactiveacount - isnt
that always unity since its incremented once for each inactive
interval except if a register in inactive interval
has aliases ?