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From: "egallager at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/59666] IBM long double arithmetic results invalid in
 non-default rounding modes
Date: Wed, 31 May 2023 06:05:42 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D59666

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |egallager at gcc dot gnu.o=
rg,
                   |                            |iains at gcc dot gnu.org

--- Comment #9 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Sergey Fedorov from comment #8)
> (In reply to Vincent Lef=C3=A8vre from comment #1)
> > (In reply to Joseph S. Myers from comment #0)
> > It seems to be like that "by design" (though this is not satisfactory) =
and
> > part of the ppc64 ABI for instance:
> >=20
> > http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html#PREC
> >=20
> > "The software support is restricted to round-to-nearest mode. Programs =
that
> > use extended precision must ensure that this rounding mode is in effect=
 when
> > extended-precision calculations are performed."
>=20
> Also true for AIX:
> https://www.ibm.com/docs/sr/xcafbg/9.0.0?topic=3DSS3KZ4_9.0.0/com.ibm.xlf=
111.
> bg.doc/xlfopg/fp-overview.html
>=20
> Does anyone know whether this is also true for Darwin on PowerPC though?

I don't, but Iain might...=