Re: [PATCH] Add optional __Bfloat16 support

[Hongtao Liu <crazylht@gmail.com>]

On Sat, Jun 11, 2022 at 1:46 AM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> On Fri, Jun 10, 2022 at 7:44 AM H.J. Lu <hjl.tools@gmail.com> wrote:
> >
> > On Fri, Jun 10, 2022 at 2:38 AM Florian Weimer <fweimer@redhat.com> wrote:
> > >
> > > * liuhongt via Libc-alpha:
> > >
> > > > +\subsubsection{Special Types}
> > > > +
> > > > +The \code{__Bfloat16} type uses a 8-bit exponent and 7-bit mantissa.
> > > > +It is used for \code{BF16} related intrinsics, it cannot be
> >
> > Please mention that this is an alternate encoding format for 16-bit floating
> > point.  It has the same size and alignment as _Float16.
>
> It also follows the same rules as _Float16 for parameter passing and function
> return.

How about
+\subsubsection{Special Types}
+
+The \code{__Bfloat16} type has an alternate encoding format for 16-bit
+floating point with 8-bit exponent and 7-bit mantissa. It has the same size,
+alignment, parameter passing and return rules as _Float16.
+It is used for \code{BF16} related intrinsics, it cannot be used with standard
+C operators.
+
>
> > > > +used with standard C operators.
> > >
> > > I think it's not necessary to specify whether the type supports certain
> > > C operators (surely assignment will work?).  If they are added later,
> > > the ABI won't need changing.
> > >
> >
> > If _Bfloat16 becomes a fundamental type, the ABI should be changed to
> > move it together with other scalar types.
> >
> > --
> > H.J.
>
>
>
> --
> H.J.
>
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-- 
BR,
Hongtao