Re: [power-ieee128] OPEN CONV

[Michael Meissner <meissner@linux.ibm.com>]

On Sat, Jan 08, 2022 at 02:15:14PM -0500, David Edelsohn wrote:
> On Sat, Jan 8, 2022 at 1:59 PM Michael Meissner <meissner@linux.ibm.com> wrote:
> >
> > On Sat, Jan 08, 2022 at 03:18:07PM +0100, Jakub Jelinek wrote:
> > > On Sat, Jan 08, 2022 at 03:13:10PM +0100, Thomas Koenig wrote:
> > > >
> > > > On 08.01.22 15:02, Jakub Jelinek via Fortran wrote:
> > > > > Note, as for byteswapping, apparently it wasn't ever working right fox
> > > > > the IBM extended real(kind=16) and complex(kind=16).
> > > >
> > > > The lack of bug reports since the conversion feature was introduced in
> > > > 2006, more than 15 years ago, tells us something, I guess...
> > >
> > > powerpc64le was only introduced in GCC 4.8 in 2013, so slightly less
> > > than that, but still.
> > > Either nobody interchanges/shares fortran unformatted data between
> > > powerpc big and little endian, or if they do, they don't use real(kind=16)
> > > or complex(kind=16) in there...
> >
> > I still wish I had had the forethought when we were setting up the LE ABI to
> > change the default 128-bit format to IEEE instead of IBM.  But alas, I didn't.
> > You would still need converters between the big endian IBM format and little
> > endian IEEE format, but it would have avoided a lot of the problems where GCC
> > assumes there is only one floating point format for each size.
> 
> Mike,
> 
> The LE ABI initial target was Power8 and IEEE128 hardware support was
> added to Power9.  The ABI was a conscious decision. IEEE 128 was not a
> viable requirement for the LE ABI at the time of the transition.

Yes I know, but my memory is we (the GCC group within IBM) at least knew that
IEEE 128-bit was coming towards the end of the ABI definition period.  But
perhaps not.  In any case, it doesn't much matter now, as it is all ancient
history.

-- 
Michael Meissner, IBM
PO Box 98, Ayer, Massachusetts, USA, 01432
email: meissner@linux.ibm.com