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Subject: Re: [PATCH 1/2] ARM: copypage-fa: add kto and kfrom to input operands
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To:     Nicolas Pitre <nicolas.pitre@linaro.org>,
        Stefan Agner <stefan@agner.ch>
Cc:     Arnd Bergmann <arnd@arndb.de>, Roman Yeryomin <roman@advem.lv>,
        Linus Walleij <linus.walleij@linaro.org>,
        Russell King - ARM Linux <linux@armlinux.org.uk>,
        linux-kernel@vger.kernel.org, Joel Stanley <joel@jms.id.au>,
        Hans Ulli Kroll <ulli.kroll@googlemail.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>
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From:   Robin Murphy <robin.murphy@arm.com>
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Date:   Tue, 6 Nov 2018 13:16:24 +0000
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On 06/11/2018 04:49, Nicolas Pitre wrote:
[...]
>> r3 and r5 are not used above, so no need to have them in the clobber
>> list.
> 
> They are used. ldrd and strd instructions always use a pair of
> consecutive registers. So "ldrd r2, ..." loads into r2-r3 and "ldrd r4, ..."
> loads into r4-r5.

FWIW, since we should now be enabling unified syntax everywhere, I guess 
we could probably rewrite all those ldrd/strd to the UAL 3-operand form 
- i.e. "ldrd r2, r3, [...]" - if we really cared for the extra clarity.

Robin.