netdev - Re: [PATCH] net: remove tests on 64bit platforms

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Message-ID: <1295929729.2896.26.camel@localhost>
Date:	Tue, 25 Jan 2011 14:28:49 +1000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Changli Gao <xiaosuo@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	"Pekka Savola (ipv6)" <pekkas@...core.fi>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Subject: Re: [PATCH] net: remove tests on 64bit platforms

On Tue, 2011-01-25 at 12:21 +0800, Changli Gao wrote:
> On 64bit platforms, >31 bit shifting of a unsigned long variable is
> valid, so we can remove the related boundary tests, which may slow
> down the CPU if branch prediction fails.
[...]

It seems like it would be better to define generic shift functions that
correctly handle the case of a shift count >= word size.  There are many
places these would be useful.

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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