diff mbox series

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

Message ID 20220920182223.2019637-1-aldyh@redhat.com
State New, archived
Headers
Series [COMMITTED] frange::maybe_isnan() should return FALSE for undefined ranges. |

Commit Message

Aldy Hernandez Sept. 20, 2022, 6:22 p.m. UTC 
  Undefined ranges have undefined NAN bits.  We can't depend on them,
as they may contain garbage.  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(+)

Comments

Richard Biener Sept. 21, 2022, 7:38 a.m. UTC | #1 
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
>
Aldy Hernandez Sept. 21, 2022, 7:52 a.m. UTC | #2 
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?

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
> >
>
Richard Biener Sept. 21, 2022, 9:36 a.m. UTC | #3 
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
> > >
> >
diff mbox series

Patch

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;
 }