From: Daniel Phillips <dphillips@sistina.com>
To: Falk Hueffner <falk.hueffner@student.uni-tuebingen.de>
Cc: <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCH] Faster generic_fls
Date: Wed, 30 Apr 2003 16:07:59 +0200 [thread overview]
Message-ID: <200304301607.59835.dphillips@sistina.com> (raw)
In-Reply-To: <87znm8w2ee.fsf@student.uni-tuebingen.de>
On Wed 30 Apr 03 15:17, Falk Hueffner wrote:
> Daniel Phillips <dphillips@sistina.com> writes:
> > It's somewhat annoying that __builtin_clz leaves the all-ones case
> > dangling instead of returning -1.
>
> I assume you mean all-zero...
:-)
> Well, the semantics of the corresponding
> instructions simply differ too much. clz(0) is 31 on some, 32 on some
> others, and undefined on some more architectures. So nailing it down
> would incur some performance penalty.
It would only penalize stupidly broken architectures; it would help the ones
that got it right. It's hard to imagine how a sane person could think the
result of clz((u32)0) should be other than 32.
Sigh.
Regards,
Daniel
next prev parent reply other threads:[~2003-04-30 13:49 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-30 2:46 [RFC][PATCH] Faster generic_fls Daniel Phillips
2003-04-30 7:19 ` Willy Tarreau
2003-04-30 8:36 ` Aaron Lehmann
2003-04-30 8:43 ` Aaron Lehmann
2003-04-30 8:52 ` Aaron Lehmann
2003-04-30 8:51 ` P
2003-04-30 13:51 ` Daniel Phillips
2003-04-30 11:14 ` Falk Hueffner
2003-04-30 13:03 ` Daniel Phillips
2003-04-30 13:17 ` Falk Hueffner
2003-04-30 14:07 ` Daniel Phillips [this message]
2003-04-30 14:11 ` Linus Torvalds
2003-04-30 14:53 ` Falk Hueffner
2003-04-30 15:28 ` Linus Torvalds
2003-04-30 16:03 ` Falk Hueffner
2003-04-30 16:16 ` Linus Torvalds
2003-04-30 16:43 ` Falk Hueffner
2003-04-30 20:25 ` Alan Cox
2003-04-30 21:59 ` Falk Hueffner
2003-04-30 22:22 ` Alan Cox
2003-04-30 23:41 ` Linus Torvalds
2003-04-30 22:47 ` Alan Cox
2003-05-01 0:12 ` Falk Hueffner
2003-05-01 1:07 ` Linus Torvalds
2003-04-30 19:15 ` Daniel Phillips
2003-04-30 20:59 ` Willy Tarreau
2003-05-01 1:02 ` Daniel Phillips
2003-05-01 9:19 ` Willy Tarreau
2003-05-01 16:02 ` Linus Torvalds
2003-04-30 20:55 ` Andrew Morton
2003-05-01 5:03 ` hugang
2003-05-01 5:11 ` Andrew Morton
2003-05-01 5:33 ` hugang
2003-05-01 7:05 ` hugang
2003-05-01 13:52 ` Willy TARREAU
2003-05-01 14:14 ` Falk Hueffner
2003-05-01 14:26 ` Willy TARREAU
2003-05-01 14:53 ` hugang
2003-05-01 15:54 ` Thomas Schlichter
2003-05-02 0:33 ` hugang
2003-05-01 17:16 ` Willy TARREAU
2003-05-01 23:27 ` Thomas Schlichter
2003-05-02 0:10 ` Willy Tarreau
2003-05-02 0:43 ` Daniel Phillips
2003-05-02 0:54 ` Andrew Morton
2003-05-02 12:21 ` Daniel Phillips
2003-05-02 1:47 ` Thomas Schlichter
2003-05-02 13:24 ` Willy Tarreau
2003-05-02 0:13 ` Daniel Phillips
2003-05-02 0:13 ` Lincoln Dale
2003-05-01 5:16 ` hugang
2003-05-01 10:22 ` Willy TARREAU
2003-05-01 11:17 ` hugang
2003-05-01 11:45 ` Willy TARREAU
[not found] <87d6j34jad.fsf@student.uni-tuebingen.de.suse.lists.linux.kernel>
[not found] ` <Pine.LNX.4.44.0304301801210.20283-100000@home.transmeta.com.suse.lists.linux.kernel>
2003-05-01 1:46 ` Andi Kleen
2003-05-01 4:40 ` Linus Torvalds
2003-05-01 12:00 ` David S. Miller
2003-05-02 5:14 ` Linus Torvalds
-- strict thread matches above, loose matches on Subject: below --
2003-05-01 13:31 linux
2003-05-01 17:15 Chuck Ebbert
2003-05-02 8:50 Chuck Ebbert
2003-05-02 9:37 ` Peter Osterlund
2003-05-02 10:04 Chuck Ebbert
2003-05-02 22:55 ` David S. Miller
2003-05-03 2:21 Chuck Ebbert
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=200304301607.59835.dphillips@sistina.com \
--to=dphillips@sistina.com \
--cc=falk.hueffner@student.uni-tuebingen.de \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.