Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20220710142822.52539-1-arthurchang09@gmail.com>
 <20220710142822.52539-3-arthurchang09@gmail.com> <3a1b50d2-a7aa-3e89-56fe-5d14ef9da22f@gmail.com>
 <CAD4RrFPihC+8LScC1RJ5GfOsLs4kze0QwALS1ykNH_m89Z1NGg@mail.gmail.com> <48db247e-f6fd-cb4b-7cc5-455bf26bb153@gmail.com>
In-Reply-To: <48db247e-f6fd-cb4b-7cc5-455bf26bb153@gmail.com>
From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Mon, 11 Jul 2022 17:03:09 +0200
Message-ID: <CAHp75VfH9M=h7UZPrWLwSmUXXPJFrO+zwAbf_g1k2_HPBM4HKw@mail.gmail.com>
Subject: Re: [PATCH 2/2] lib/string.c: Optimize memchr()
To:     Andrey Semashev <andrey.semashev@gmail.com>
Cc:     Yu-Jen Chang <arthurchang09@gmail.com>,
        Andy Shevchenko <andy@kernel.org>,
        Akinobu Mita <akinobu.mita@gmail.com>,
        Ching-Chun Huang <jserv@ccns.ncku.edu.tw>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, Jul 11, 2022 at 5:00 PM Andrey Semashev
<andrey.semashev@gmail.com> wrote:
> On 7/11/22 17:52, Yu-Jen Chang wrote:

...

> I think you're missing the point. Loads at unaligned addresses may not
> be allowed by hardware using conventional load instructions or may be
> inefficient. Given that this memchr implementation is used as a fallback
> when no hardware-specific version is available, you should be
> conservative wrt. hardware capabilities and behavior. You should
> probably have a pre-alignment loop.

Exactly!
The initial code is broken, NAK.

P.S. At least you may look into strscpy() implementation to get a clue.

-- 
With Best Regards,
Andy Shevchenko