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

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Message-ID: <Y+KOeP0OOiem3lR5@ubun2204.myguest.virtualbox.org>
Date:   Tue, 7 Feb 2023 23:16:32 +0530
From:   Deepak R Varma <drv@...lo.com>
To:     James Bottomley <jejb@...ux.ibm.com>
Cc:     Khalid Aziz <khalid@...ehiking.org>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Saurabh Singh Sengar <ssengar@...rosoft.com>,
        Praveen Kumar <kumarpraveen@...ux.microsoft.com>
Subject: Re: [PATCH] scsi: FlashPoint: Replace arithmetic addition by bitwise
 OR

On Tue, Feb 07, 2023 at 03:26:48PM +0300, James Bottomley wrote:
> On Tue, 2023-02-07 at 16:51 +0530, Deepak R Varma wrote:
> > When adding two bit-field mask values, an OR operation offers higher
> > performance over an arithmetic operation. So, convert such additions
> > to an OR based expressions. Issue identified using orplus.cocci
> > semantic patch script.
> 
> No it doesn't, at least not for constants, which is the entirety of
> this patch: the compiler can find the value at compile time, so the
> whole lot becomes a load immediate of a single value.  Whether the
> compiler sees OR or + is immaterial to the compile time computation. 

Hello James,
Thank you for the feedback. Your comments are useful. I was not aware of the
compile time computation of constant expressions before. Thanks.

> Perhaps Coccinelle should be fixed not to complain about this case?
Yes, sure. I will review the semantic patch and deterrmine if and how to fine
tune the same to avoid false positives.

> 
> James

James, there are a few other patch submissions for the scsi subsystem that I
submitted in last few weeks. I sent couple of reminder request for comments on
those submission, but still waiting. Could you please also review those and
share your feedback?

Best Regards,
deepak.

>