Sorry, I didn't even notice the slowdown; I see now that it went from
0.9s to 1.9s on my machine.

The first attached patch is simple and speeds it up to 1.65s.

The second attached patch sort of re-implements what tar would do, using
sh case, but it's more complex.  It clocks in at 1.35s after that.

Jackson

On 12/19/2016 06:49 AM, Stefan Monnier wrote:
>> Would you be amenable to me pushing the attached patch?
> 
> Hmm...
> 
> It works well, but it slows down "make" in the case where there's
> nothing to do by more than a factor 2 (on the slowest machine on which
> I maintain a fully-built `elpa` checkout, it brings the time for "make"
> from 7s to 18s).  The current time is already on the high side for my
> taste, so I think we should try a bit harder to keep it in check.
> 
> 
>         Stefan
>