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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <47e6d710-d666-5f5b-5d65-4f31afe4359d@gonehiking.org>
Date:   Tue, 7 Feb 2023 08:28:22 -0700
From:   Khalid Aziz <khalid@...ehiking.org>
To:     jejb@...ux.ibm.com, Deepak R Varma <drv@...lo.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: FlashPoint: Replace arithmetic addition by bitwise
 OR

On 2/7/23 05:26, 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.
> Perhaps Coccinelle should be fixed not to complain about this case?
> 
> James
> 

Agreed. This would be lot of code changes for no benefit.

--
Khalid