From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jonathan Nieder <jrnieder@gmail.com>
Subject: Re: [PATCH maint-1.6.5] block-sha1: avoid unaligned accesses on some
 big-endian systems
Date: Sat, 14 Jul 2012 14:50:22 -0500
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Cc: Michael Cree <mcree@orcon.net.nz>, git@vger.kernel.org,
	Nicolas Pitre <nico@fluxnic.net>
To: Linus Torvalds <torvalds@linux-foundation.org>
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Linus Torvalds wrote:
> On Sat, Jul 14, 2012 at 12:59 AM, Jonathan Nieder <jrnieder@gmail.com> wrote:

>> Unfortunately, on big-endian architectures, if p is a pointer to
>> unsigned int then current gcc assumes it is properly aligned and
>> converts this construct to a 32-bit load.
>
> This patch seems to entirely depend on the location of the cast. And
> as far as I can tell, that workaround will in turn depend on just what
> gets inlined.

After the patch, what reason does gcc have to expect that 'block' is
32-bit aligned except when it is?  The code (including the code I
didn't touch) never casts from char * to int * except in get/put_be32
on arches that don't mind unaligned accesses.

[...]
> Anyway, the whole "noticed on alpha" makes no sense, since alpha isn't
> even big-endian. So the commit log is insane and misleading too.

Yes, true.  Thanks for catching it.

Jonathan