linux-kernel - RE: [RFC PATCH v3 0/4] nolibc x86-64 string functions

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Message-ID: <e4862b01c0e4440f949e240360e438a3@AcuMS.aculab.com>
Date:   Sun, 3 Sep 2023 20:38:22 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Ammar Faizi' <ammarfaizi2@...weeb.org>, Willy Tarreau <w@....eu>,
        Thomas Weißschuh <linux@...ssschuh.net>
CC:     Nicholas Rosenberg <inori@...x.org>,
        Alviro Iskandar Setiawan <alviro.iskandar@...weeb.org>,
        Michael William Jonathan <moe@...weeb.org>,
        GNU/Weeb Mailing List <gwml@...r.gnuweeb.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: RE: [RFC PATCH v3 0/4] nolibc x86-64 string functions

From: Ammar Faizi
> Sent: 02 September 2023 14:35
> 
> This is an RFC patchset v3 for nolibc x86-64 string functions.
> 
> There are 4 patches in this series:
> 
> ## Patch 1-2: Use `rep movsb`, `rep stosb` for:
>     - memcpy() and memmove()
>     - memset()
> respectively. They can simplify the generated ASM code.

It is worth pointing out that while the code size for 'rep xxxb'
is smaller, the performance is terrible.
The only time it is ever good is for the optimised forwards
copies on cpu that support it.

reverse, stos and scas are always horrid.

	David

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