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Date: Thu, 25 Jun 2020 21:20:06 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Release prep for 1.2.1, and afterwards

On Thu, Jun 25, 2020 at 05:15:42PM -0400, Rich Felker wrote:
> On Thu, Jun 25, 2020 at 04:50:24PM -0400, Rich Felker wrote:
> > > > > but it would be nice if we could get the aarch64
> > > > > memcpy patch in (the c implementation is really
> > > > > slow and i've seen ppl compare aarch64 vs x86
> > > > > server performance with some benchmark on alpine..)
> > > > 
> > > > OK, I'll look again.
> > > 
> > > thanks.
> > > 
> > > (there are more aarch64 string functions in the
> > > optimized-routines github repo but i think they
> > > are not as important as memcpy/memmove/memset)
> > 
> > I found the code. Can you commend on performance and whether memset is
> > needed? (The C memset should be rather good already, moreso than
> > memcpy.)
> 
> Are the assumptions (v8-a, unaligned access) documented in memcpy.S
> valid for all presently supportable aarch64?
> 
> A couple comments for merging if we do, that aren't hard requirements
> but preferences:
> 
> - I'd like to expand out the macros from ../asmdefs.h since that won't
>   be available and they just hide things (I guess they're attractive
>   for Apple/macho users or something but not relevant to musl) and
>   since the symbol name lines need to be changed anyway to public
>   name. "Local var name" macros are ok to leave; changing them would
>   be too error-prone and they make the code more readable anyway.
> 
> - I'd prefer not to have memmove logic in memcpy since it makes it
>   larger and implies that misuse of memcpy when you mean memmove is
>   supported usage. I'd be happy with an approach like x86 though,
>   defining an __memcpy_fwd alias and having memmove tail call to that
>   unless len>128 and reverse is needed, or just leaving memmove.c.

Something like the attached.

Rich

View attachment "memcpy.S" of type "text/plain" (4083 bytes)

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