lkml.org 
[lkml]   [2007]   [Jun]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Optimize is_power_of_2().
Vegard Nossum wrote:
> From: Vegard Nossum <vegard@peltkore.net>
> Date: Fri, 15 Jun 2007 18:35:49 +0200
> Subject: [PATCH] Optimize is_power_of_2().
>
> Rationale: Removes one conditional branch and reduces icache footprint.
> Proof: If n is false, the product of n and any value is false. If n is
> true, the truth of (n * x) is the truth of x.
>

You realize that on a lot of platforms, multiplication is done by an
out-of-line subroutine, and that even on those that aren't, it's
generally a long-pipeline operation, right?

-hpa
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-06-15 20:23    [W:2.129 / U:0.900 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site