limit check insertion via loop forests

[Jagannathan, Suresh]

Matthew raised some comments that I also had, namely is there some notion of
minimality on (a) the number of labels where limit checks are inserted
(while still preserving safety), and
(b) the size of required space demanded by V, again that is safe?  

I think it's a neat formulation, and is a cool application of
loop forests in that limit checks are inserted at the beginning of loop
headers.  I wonder if this idea could be further refined to coalesce limit
checks.  Do loop forests help here in any way?

-- sj