linux-kernel - Re: [RFC][PATCH] introduce ptr

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Message-ID: <5790.1282219392@redhat.com>
Date:	Thu, 19 Aug 2010 13:03:12 +0100
From:	David Howells <dhowells@...hat.com>
To:	Namhyung Kim <namhyung@...il.com>
Cc:	dhowells@...hat.com, Arnd Bergmann <arnd@...db.de>,
	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC][PATCH] introduce ptr_diff()

Namhyung Kim <namhyung@...il.com> wrote:

> +	if (is_power_of_2(__size))				\
> +		__diff = (__addr1 - __addr2) >> ilog2(__size);	\
> +	else							\
> +		__diff = (__addr1 - __addr2) / __size;		\

You shouldn't need to do this.  The compiler's optimiser should switch a
divide to a shift for a power-of-2 divisor.

David
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