Turning on -funbox-small-strict-fields by default in GHC 7.8

[Edward Z. Yang]

Reboxing would involve a two-word heap allocation.  I guess it is not possible
to argue that this cost would be amortized somewhere else, so you're right.

Edward

Excerpts from Johan Tibell's message of Thu Apr 25 16:01:49 -0700 2013:
> On Thu, Apr 25, 2013 at 1:41 PM, Edward Z. Yang <ezyang at mit.edu> wrote:
> 
> > SGTM.  Actually, I think actually it should be quite simple to argue that
> > there is no way for this change to degrade performance.
> >
> 
> I think you could make up a case where it is a loss. It would boil down to
> repeated reboxing of a value pulled out of a strict field. In practice I
> think it's pretty hard. What did you have in mind?
> 
> -- Johan