From: Andi Kleen <ak@suse.de>
To: Linus Torvalds <torvalds@transmeta.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH] Faster generic_fls
Date: 01 May 2003 03:46:18 +0200 [thread overview]
Message-ID: <p73ade730d1.fsf@oldwotan.suse.de> (raw)
In-Reply-To: <Pine.LNX.4.44.0304301801210.20283-100000@home.transmeta.com.suse.lists.linux.kernel>
Linus Torvalds <torvalds@transmeta.com> writes:
> Yeah, except if you want best code generation you should probably use
>
> static inline int fls(int x)
> {
> int bit;
> /* Only well-defined for non-zero */
> asm("bsrl %1,%0":"=r" (bit):"rm" (x));
"g" should work for the second operand too and it'll give gcc
slightly more choices with possibly better code.
But the __builtin is probably preferable if gcc supports it because
a builtin can be scheduled, inline assembly can't.
-Andi
next parent reply other threads:[~2003-05-01 1:34 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
[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 [this message]
2003-05-01 4:40 ` [RFC][PATCH] Faster generic_fls Linus Torvalds
2003-05-01 12:00 ` David S. Miller
2003-05-02 5:14 ` Linus Torvalds
2003-05-03 2:21 Chuck Ebbert
-- strict thread matches above, loose matches on Subject: below --
2003-05-02 10:04 Chuck Ebbert
2003-05-02 22:55 ` David S. Miller
2003-05-02 8:50 Chuck Ebbert
2003-05-02 9:37 ` Peter Osterlund
2003-05-01 17:15 Chuck Ebbert
2003-05-01 13:31 linux
2003-04-30 2:46 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
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
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