linux-kernel - Re: [PATCH 2/2] lib/string.c: Optimize memchr()

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Message-ID: <CAHp75VfH9M=h7UZPrWLwSmUXXPJFrO+zwAbf_g1k2_HPBM4HKw@mail.gmail.com>
Date:   Mon, 11 Jul 2022 17:03:09 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Andrey Semashev <andrey.semashev@...il.com>
Cc:     Yu-Jen Chang <arthurchang09@...il.com>,
        Andy Shevchenko <andy@...nel.org>,
        Akinobu Mita <akinobu.mita@...il.com>,
        Ching-Chun Huang <jserv@...s.ncku.edu.tw>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] lib/string.c: Optimize memchr()

On Mon, Jul 11, 2022 at 5:00 PM Andrey Semashev
<andrey.semashev@...il.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