linux-kernel - Re: [PATCH] Introduce a boolean "single_bit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <4A490D00.4020908@zytor.com>
Date:	Mon, 29 Jun 2009 11:50:40 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Petr Tesarik <ptesarik@...e.cz>
CC:	"Robert P. J. Day" <rpjday@...shcourse.ca>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>
Subject: Re: [PATCH] Introduce a boolean "single_bit_set" function.

Petr Tesarik wrote:
> 
> Ok, then my only concern is that the hweight* functions return the exact
> weight, which might be much less efficient if all we need is to know
> whether it's 1.
> 
> Theoretically, gcc should be able to optimize things out, but I'm not
> all that optimistic about how well it does it.
> 

I can almost guarantee it won't in this case.

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