Messages in this thread | | | Date | Sun, 3 Sep 2023 23:19:42 +0200 | From | Willy Tarreau <> | Subject | Re: [RFC PATCH v3 0/4] nolibc x86-64 string functions |
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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
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