On Tue, Mar 21, 2023 at 02:28:31PM +0100, Aldy Hernandez wrote:
> > /* Temporarily disable -ffinite-math-only, so that frange::set doesn't
> > reduce the range back to real_min_representable (type) as lower bound
> > or real_max_representable (type) as upper bound. */
> > bool save_flag_finite_math_only = flag_finite_math_only;
> > flag_finite_math_only = false;
> > ret.set (type, lb, ub);
> > if (lhs.kind () != VR_VARYING)
> > {
> > ret.clear_nan ();
> > ret.union_ (lhs);
> > }
> > flag_finite_math_only = save_flag_finite_math_only;
>
> It looks like what you want to do is be able to create a range with a known
> NAN state, but without the setter reducing the range to
> min/max_representable.
>
> How about we enhance the API to provide:
>
> 1. Constructor with a known NAN state.
> 2. Setter with a flag to keep it from canonicalizing into
> min/max_representable.
>
> The flag in 2 could in the future be saved in the frange object to keep
> union and friends from further canonicalization.
>
> So the above could be written as:
>
> // Construct [lb, ub] with a known NAN state.
> frange tmp (lb, ub, lhs.get_nan_state ());
>
> // Set RET without dropping/reducing the range to MIN/MAX.
> ret.set (tmp, FRANGE_FLAG_NO_REPRESENTABLE_REDUCTION);
>
> An alternative is to allow the setter to set everything:
>
> ret.set (type, lb, ub,
> lhs.get_nan_state (),
> FRANGE_FLAG_NO_REPRESENTABLE_REDUCTION);
>
> Would this work? I'd be happy to whip up something this week, or if
> preferred, leave it to the next release.
The latter would be better, I really don't need a temporary range in that
spot, the union_ is only to copy the NaN state.
Though, I think right now set actually doesn't do reduction to representable
at all, all it does is equality compare bounds against the applicable
boundaries and if both are equal and NaN state is appropriate, change it
into VR_VARYING.
So maybe for now all we need is the 4 argument set.
Jakub
