On Fri, May 05, 2023 at 11:06:31AM +0200, Aldy Hernandez wrote:
> > +/* Compute FUNC (ARG) where FUNC is a mpfr function. If RES_LOW is
> > non-NULL,
> > + set it to low bound of possible range if the function is expected to
> > have
> > + ULPS precision and similarly if RES_HIGH is non-NULL, set it to high
> > bound.
> > + If the function returns false, the results weren't set. */
> > +
> > +static bool
> > +frange_mpfr_arg1 (REAL_VALUE_TYPE *res_low, REAL_VALUE_TYPE *res_high,
> > + int (*func) (mpfr_ptr, mpfr_srcptr, mpfr_rnd_t),
> > + const REAL_VALUE_TYPE &arg, tree type, unsigned ulps)
> > +{
>
> Since you're returning a range of sorts [low, high], would it be cleaner to
> return an frange, or is always calculating low/high too expensive? I notice
> you avoid it when passing NULL.
The point was that the caller can tell which bound it needs, low, high or
both and we don't waste time calculating ones we don't need (especially with
larger values of ulps). E.g. for the sqrt case we only need one of them,
but when I thought about the sin/cos case, I'll probably need both and
calling the function twice would mean repeating the even more expensive mpfr
call.
> Would you mind adding a typedef for the (*func) callback above? I always
> find C callbacks a pain to read.
I can, what I used comes from elsewhere (builtins.cc/fold-const-call.cc
which use it like that).
Jakub
