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Date: Wed, 5 Aug 2015 19:30:59 -0500
From: Segher Boessenkool <segher@kernel.crashing.org>
To: Christophe Leroy <christophe.leroy@c-s.fr>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Michael Ellerman <mpe@ellerman.id.au>, scottwood@freescale.com,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 2/2] powerpc32: optimise csum_partial() loop
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References: <cover.1435655733.git.christophe.leroy@c-s.fr> <67cf476f657e87b2ea586951a57ae3ba3c1e3c0c.1435655733.git.christophe.leroy@c-s.fr>
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On Wed, Aug 05, 2015 at 03:29:35PM +0200, Christophe Leroy wrote:
> On the 8xx, load latency is 2 cycles and taking branches also takes
> 2 cycles. So let's unroll the loop.

This is not true for most other 32-bit PowerPC; this patch makes
performance worse on e.g. 6xx/7xx/7xxx.  Let's not!


Segher