From: degger@fhm.edu
To: dje@watson.ibm.com
Cc: gcc-patches@gcc.gnu.org, gcc@gcc.gnu.org
Subject: Re: Patch to add missing PPC instruction
Date: Mon, 17 Dec 2001 13:31:00 -0000 [thread overview]
Message-ID: <20011217223533.628706E18@Nicole.fhm.edu> (raw)
In-Reply-To: <200112172109.QAA22442@makai.watson.ibm.com>
On 17 Dec, David Edelsohn wrote:
> fres is floating-point reciprocal ESTIMATE Single, not a
> single-precision reciprocal.
Right, I got that wrong.
> It is accurate to one part in either 256 or 4096,
According to the PPC Programming Environment manual page 8-88,
the error is less or equal to 1/256.
> not IEEE 754 Single Precision accuracy.
A candidate for -ffast-math? I originally meant it that way but forgot
about it between the time I wrote the patch and sent it here
(>4 months).
For some applications (those who are using single precision arithmetics)
it might actually be enough to such an unaccurate reciprocal but I
definitely see your point when you say it's not acceptable to be used in
general.
--
Servus,
Daniel
prev parent reply other threads:[~2001-12-17 21:28 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-17 12:54 degger
2001-12-17 13:11 ` David Edelsohn
2001-12-17 13:31 ` degger [this message]
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