Re: [COMMITTED] frange::maybe_isnan() should return FALSE for undefined ranges.

[Richard Biener <richard.guenther@gmail.com>]

On Wed, Sep 21, 2022 at 9:52 AM Aldy Hernandez <aldyh@redhat.com> wrote:
>
> The reason the flags were uninitialized was because they were unused,
> similarly for m_type.  But you're right, it is icky and prone to bugs.
> I just thought it was cheap to set_undefined by just flipping
> m_kind=VR_UNDEFINED, but it smells like premature optimization.
>
> How about this?

LGTM

>
> Aldy
>
> On Wed, Sep 21, 2022 at 9:39 AM Richard Biener
> <richard.guenther@gmail.com> wrote:
> >
> > On Tue, Sep 20, 2022 at 8:23 PM Aldy Hernandez via Gcc-patches
> > <gcc-patches@gcc.gnu.org> wrote:
> > >
> > > Undefined ranges have undefined NAN bits.  We can't depend on them,
> > > as they may contain garbage.
> >
> > Ick ;)  Can you add a comment at least?
> >
> > > This patch returns false from
> > > maybe_isnan() for undefined ranges (the empty set).
> > >
> > > gcc/ChangeLog:
> > >
> > >         * value-range.h (frange::maybe_isnan): Return false for
> > >         undefined ranges.
> > > ---
> > >  gcc/value-range.h | 2 ++
> > >  1 file changed, 2 insertions(+)
> > >
> > > diff --git a/gcc/value-range.h b/gcc/value-range.h
> > > index 7d5584a9294..325ed08f290 100644
> > > --- a/gcc/value-range.h
> > > +++ b/gcc/value-range.h
> > > @@ -1210,6 +1210,8 @@ frange::known_isinf () const
> > >  inline bool
> > >  frange::maybe_isnan () const
> > >  {
> > > +  if (undefined_p ())
> > > +    return false;
> > >    return m_pos_nan || m_neg_nan;
> > >  }
> > >
> > > --
> > > 2.37.1
> > >
> >