linux-kernel - Re: [PATCH v2 1/3] lib: find_*

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Date:	2 Feb 2015 06:47:59 -0500
From:	"George Spelvin" <linux@...izon.com>
To:	linux@...musvillemoes.dk, yury.norov@...il.com
Cc:	akpm@...ux-foundation.org, chris@...is-wilson.co.uk,
	davem@...emloft.net, dborkman@...hat.com,
	hannes@...essinduktion.org, klimov.linux@...il.com,
	laijs@...fujitsu.com, linux-kernel@...r.kernel.org,
	linux@...izon.com, msalter@...hat.com, takahiro.akashi@...aro.org,
	tgraf@...g.ch, valentinrothberg@...il.com, y.norov@...sung.com
Subject: Re: [PATCH v2 1/3] lib: find_*_bit reimplementation

Rasmus Villemoes <linux@...musvillemoes.dk> wrote:
> ... and this be part of _find_next_bit? Can find_next_bit not be simply
> 'return _find_next_bit(addr, size, offset, 1);', and similarly for
> find_next_zero_bit? Btw., passing true and false for the boolean
> parameter may be a little clearer.

Looking at the generated code, it would be better to replace the boolean
parameter with 0ul or ~0ul and XOR with it.  The same number of registers,
and saves a conditional branch.

(I was hoping GCC would figure that trick out, but it didn't.)
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