linux-kernel - Re: [PATCH v2] vhost: replace % with & on data path

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Message-ID: <CAHp75VcnkCZUF1dP7B8G4qv-JNBah+MzZn_v-aW9i8iWUDA6TQ@mail.gmail.com>
Date:	Sun, 13 Dec 2015 02:01:22 +0200
From:	Andy Shevchenko <andy.shevchenko@...il.com>
To:	Venkatesh Srinivas <venkateshs@...gle.com>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>, kvm@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2] vhost: replace % with & on data path

On Fri, Dec 4, 2015 at 10:19 PM, Venkatesh Srinivas
<venkateshs@...gle.com> wrote:
> On Mon, Nov 30, 2015 at 11:15:23AM +0200, Michael S. Tsirkin wrote:
>> We know vring num is a power of 2, so use &
>> to mask the high bits.
>>
>> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
>> ---
>
> The generated code switches from DIV -> masking, source is clearer as well.

First impression was why, now it seems that compiler can't predict
this for variables.
For constants it would be optimized to the same, I suppose.

>
> Tested-by: Venkatesh Srinivas <venkateshs@...gle.com>
>
> -- vs;
> --
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-- 
With Best Regards,
Andy Shevchenko
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