"root" of ChunkPerFunc chunk

[Stephen Weeks]

> I'm  confused  about how the results of the add could be used in the handler.
> Assuming everything is in A-normal form, the result of the add is going  into
> a  new (val) binding, so nothing can be closed over it.  (If it weren't in A-
> normal form then you could do something like
>     x := y + z
> and it could make the contents of the ref x be the destination.)

The input to x86-codegen is the machine IL, which isn't A-normal form.  It is a
register IL.  So, the register destined to hold x could be live in the overflow label.