[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20230903211942.GA31739@1wt.eu>
Date: Sun, 3 Sep 2023 23:19:42 +0200
From: Willy Tarreau <w@....eu>
To: David Laight <David.Laight@...LAB.COM>
Cc: "'Ammar Faizi'" <ammarfaizi2@...weeb.org>,
Thomas Weißschuh <linux@...ssschuh.net>,
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
On Sun, Sep 03, 2023 at 08:38:22PM +0000, David Laight wrote:
> 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.
It's terrible compared to other approaches but not *that* bad. Also we
absolutely don't care about performance here, rather about correctness
and compact size.
Regards,
Willy
Powered by blists - more mailing lists