From: Andi Kleen <ak@suse.de>
To: "David S. Miller" <davem@redhat.com>
Cc: root@chaos.analogic.com, adilger@clusterfs.com,
jlcooke@certainkey.com, shemminger@osdl.org,
alan@lxorguk.ukuu.org.uk, tytso@mit.edu, netdev@oss.sgi.com,
linux-kernel@vger.kernel.org
Subject: Re: [RFC] enhanced version of net_random()
Date: Sun, 22 Aug 2004 17:04:14 +0200 [thread overview]
Message-ID: <20040822170414.3ecab1e5.ak@suse.de> (raw)
In-Reply-To: <20040820124823.071ac1d9.davem@redhat.com>
On Fri, 20 Aug 2004 12:48:23 -0700
"David S. Miller" <davem@redhat.com> wrote:
> > I wouldn't suggest converting it to 'C' because the rotation
> > takes many CPU instructions when one tries to do the test, shift,
> > and OR in 'C',
>
> You only need 2 'shifts' and an 'or' to do a rotate in C.
> No tests are needed.
gcc is clever enough to detect the common C patterns for rotate
and generate a real ROL when the CPU supports it.
-Andi
next prev parent reply other threads:[~2004-08-22 15:04 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-12 17:48 [RFC] enhanced version of net_random() Stephen Hemminger
2004-08-12 19:48 ` David S. Miller
2004-08-13 18:51 ` Stephen Hemminger
2004-08-13 19:28 ` Andi Kleen
2004-08-16 6:27 ` David S. Miller
2004-08-12 20:02 ` Ben Greear
2004-08-20 17:59 ` Jean-Luc Cooke
2004-08-20 18:47 ` David S. Miller
2004-08-20 18:59 ` Andreas Dilger
2004-08-20 19:22 ` Richard B. Johnson
2004-08-20 19:48 ` David S. Miller
2004-08-20 19:53 ` Jean-Luc Cooke
2004-08-22 15:04 ` Andi Kleen [this message]
2004-08-23 17:05 ` Stephen Hemminger
2004-08-23 18:09 ` Richard B. Johnson
2004-08-20 21:24 ` Lee Revell
2004-08-20 23:55 ` Alan Cox
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