linux-kernel - Re: [PATCH] MPILIB: Provide count_leading/trailing

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Message-ID: <alpine.LNX.2.01.1208101451280.23731@frira.zrqbmnf.qr>
Date:	Fri, 10 Aug 2012 14:51:49 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...i.de>
To:	David Miller <davem@...emloft.net>
cc:	dhowells@...hat.com, arnd@...db.de,
	linux-security-module@...r.kernel.org,
	linux-kernel@...r.kernel.org, dmitry.kasatkin@...el.com
Subject: Re: [PATCH] MPILIB: Provide count_leading/trailing_zeros() based on
 arch functions


On Saturday 2012-07-21 02:46, David Miller wrote:
>> Arnd Bergmann <arnd@...db.de> wrote:
>> 
>>> I don't generally like to put stuff into asm-generic when it's unlikely
>>> to be overridden by architectures. It would really belong into
>>> include/linux, but then again we have all the other bitops in asm-generic
>>> as well, so whatever...
>> 
>> Some arches (such as Sparc, I think) have count-leading-zero instructions.
>
>Yes, newer sparc64 chips have leading-zero-detect, and I was pretty
>sure that powerpc had something similar.  It's called count-leading-
>zeros or something like that.

And gcc has a __builtin_clz.
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