From: Andi Kleen <andi@firstfloor.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Andi Kleen <andi@firstfloor.org>,
Jim Kukunas <james.t.kukunas@linux.intel.com>,
Linux Raid <linux-raid@vger.kernel.org>,
Linux Kernel <linux-kernel@vger.kernel.org>,
Neil Brown <neilb@suse.de>
Subject: Re: [PATCH] lib/raid6: Add AVX2 optimized recovery functions
Date: Thu, 29 Nov 2012 22:18:28 +0100 [thread overview]
Message-ID: <20121129211828.GZ16230@one.firstfloor.org> (raw)
In-Reply-To: <50B7CFF8.7010401@zytor.com>
> The code is compiled so that the xmm/ymm registers are not available to
> the compiler. Do you have any known examples of asm volatiles being
> reordered *with respect to each other*? My understandings of gcc is
> that volatile operations are ordered with respect to each other (not
> necessarily with respect to non-volatile operations, though.)
Can you quote it from the manual? As I understand volatile as usual
is not clearly defined.
gcc has a lot of optimization passes and volatile bugs are common.
> Either way, this implementatin technique was used for the MMX/SSE
> implementations without any problems for 9 years now.
It's still wrong.
Lying to the compiler usually bites you at some point.
-Andi
next prev parent reply other threads:[~2012-11-29 21:18 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-08 21:47 [PATCH] lib/raid6: Add AVX2 optimized recovery functions Jim Kukunas
2012-11-09 11:35 ` Paul Menzel
2012-11-09 11:39 ` H. Peter Anvin
2012-11-09 11:46 ` Paul Menzel
2012-11-09 11:50 ` NeilBrown
2012-11-09 12:24 ` H. Peter Anvin
2012-11-09 19:56 ` Jim Kukunas
2012-11-19 0:57 ` NeilBrown
2012-11-29 20:09 ` Andi Kleen
2012-11-29 21:13 ` H. Peter Anvin
2012-11-29 21:18 ` Andi Kleen [this message]
2012-11-29 22:27 ` H. Peter Anvin
2012-11-29 22:28 ` H. Peter Anvin
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