"root" of ChunkPerFunc chunk

[Stephen Weeks]

> Another interesting comparison would be the cost of Int = IntInf.
> Also, to get good code, you would have to simplify some of the tests when one
> of the operands is a constant (and small).  Still, I would be curious to see
> the cost of Int = IntInf vs. detecting overflow.

Not as easy to get, since it would require rewriting some of the basis library.
I just reran a benchmark we did a while back (the slow.sml and fast.sml
regression tests) and it costs 2X-3X to use IntInf on my machine.