linux-kernel - Re: [PATCH] scsi: qla1280: Replace arithmetic addition by bitwise OR

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Message-ID: <aed35866-507c-870c-7e8a-c1868bcaa084@acm.org>
Date:   Sat, 11 Feb 2023 15:25:03 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     Deepak R Varma <drv@...lo.com>, Michael Reed <mdr@....com>,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Saurabh Singh Sengar <ssengar@...rosoft.com>,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>
Subject: Re: [PATCH] scsi: qla1280: Replace arithmetic addition by bitwise OR

On 2/7/23 03:54, Deepak R Varma wrote:
> When adding two bit-field mask values, an OR operation offers higher
> performance over an arithmetic operation. So, convert such addition to
> an OR based expression.

Where is the evidence that supports this claim? On the following page I 
read that there is no performance difference when using a modern CPU: 
https://cs.stackexchange.com/questions/75811/why-is-addition-as-fast-as-bit-wise-operations-in-modern-processors

> Issue identified using orplus.cocci semantic patch script.

Where is that script located? Can it be deleted such that submission of 
patches similar to this patch stops?

Thanks,

Bart.