From: Han-Kwang Nienhuys <h.nienhuys@amolf.nl>
To: gcc@gcc.gnu.org
Subject: Re: i386 rounding modes and workaround solution
Date: Tue, 11 Sep 2001 08:36:00 -0000 [thread overview]
Message-ID: <20010911173619.A7435@vd5.amolf.nl> (raw)
In-Reply-To: <006001c13a0c$b65fe140$7edd18ac@amr.corp.intel.com>
Oops, I think I barely missed the flamewar button...
I wasn't aware that my gcc version (included in a major GNU/Linux
distribution, v 2.96) lags a lot behind the development work. Next
time I will do my homework better ;-)
The reason I brought up the issue here was that I couldn't find
much useful information on the web.
On Mon, 10 Sep 2001, Tim Prince wrote:
> If you are familiar with current P4 models, you will be aware
> that using more than 2 values of the fldcw mask will degrade
> performance seriously. Which processors do you consider as
> belonging to the x86 family?
The factor 4 was on a Pentium 3. I also tested it on an Athlon,
without exact timings, but it did have quite an impact as well.
I checked the manuals; you are correct that alternating between two
values of the FLDCW (as with f-i conversion) is no problem on a P4,
but (int) floor() might be. Thank you for the remark.
Han-Kwang Nienhuys
FOM Institute voor Atomic and Molecular Physics,
Amsterdam, The Netherlands
prev parent reply other threads:[~2001-09-11 8:36 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-09-10 7:48 Han-Kwang Nienhuys
2001-09-10 7:53 ` Jan Hubicka
2001-09-10 8:24 ` Tim Prince
2001-09-11 2:13 ` Jan Hubicka
2001-09-11 8:36 ` Han-Kwang Nienhuys [this message]
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