linux-ext4 - Re: [PATCH] lib/ext2fs/bitops.h: Use the optmized/documented byteswapping routines

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Message-ID: <20130114141356.GA12052@thunk.org>
Date:	Mon, 14 Jan 2013 09:13:56 -0500
From:	Theodore Ts'o <tytso@....edu>
To:	Cristian Rodríguez <crrodriguez@...nsuse.org>
Cc:	linux-ext4@...r.kernel.org
Subject: Re: [PATCH] lib/ext2fs/bitops.h: Use the optmized/documented
 byteswapping routines

On Sat, Jan 12, 2013 at 04:32:25PM -0300, Cristian Rodríguez wrote:
> In x86, it will not make much difference but other targets that
> are not covered by the old code will be able to generate better code.
> 
> Signed-off-by: Cristian Rodríguez <crrodriguez@...nsuse.org>

The problem is that bswap_{16,32,64}() and the existence of
<byteswap.h> is not guaranted by any standard that I'm not aware of.
A quick Google search indicates that it's not available for the
following platforms:

	* Mac OS X 10.5
	* FreeBSD 6.0
	* NetBSD 5.0
	* OpenBSD 3.8
	* Minix 3.1.8
	* AIX 5.1
	* HP-UX 11
	* IRIX 6.5
	* OSF/1 5.1
	* Solaris 11 2011-11
	* Cygwin
	* mingw
	* MSVC 9
	* Interix 3.5
	* BeOS

So the only way we could use bswap_{16,32,64} if there is a proper
configure.in test for them.

Regards,

					- Ted
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