Rewrite some jump.c routines to use flags

[Eric Botcazou]

> I'm not sure using flags_to_condition really buys anything then,
> since you have to think about each individual case to see whether
> it belongs in the switch or not.  I also don't have any proof
> that the no-op cases are the common ones (since adding this
> fast path of course slows down the others).

Really?  Branch prediction is rather efficient these days.

> I think I'll just use the new routines for the new optimisation
> and leave the existing ones as-is.

OK, your call.

-- 
Eric Botcazou