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From: "hjl.tools at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/108922] fmod() 13x slowdown in gcc4.9 dropping "fprem"
 and calling fmod()
Date: Tue, 28 Feb 2023 16:51:18 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108922

--- Comment #33 from H.J. Lu <hjl.tools at gmail dot com> ---
(In reply to Uro=C5=A1 Bizjak from comment #20)
> (In reply to Jakub Jelinek from comment #16)
>=20
> > More questionable is the #Z case, where Table 8-11 just talks about
> > Divide or reverse divide operation  Returns an =E2=88=9E signed with th=
e exclusive
> > OR of the
> > with a 0 divisor.                   sign of the two operands to the
> > destination operand.
> > but FPREM does division too, so I hope it is covered too (but not listed
> > explicitly).
>=20
> FYI, the table 3-30 (and 3-31) is wrong. Executing fprem when st(0) =3D=
=3D 1.0
> and st(1) =3D=3D 0.0 results in IA exception, not Z exception.

Thanks for bringing it up.  It will be fixed in the next revision for Intel
SDM.=