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Date: Wed, 17 May 2017 13:17:24 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Musl libm optimizations for Power and Z

On Wed, May 17, 2017 at 01:05:31PM -0400, David Edelsohn wrote:
> On Wed, May 17, 2017 at 12:33 PM, Rich Felker <dalias@...c.org> wrote:
> > On Wed, May 17, 2017 at 10:52:05AM -0400, David Edelsohn wrote:
> >> On Wed, May 17, 2017 at 10:26 AM, Szabolcs Nagy <nsz@...t70.net> wrote:
> >> > * David Edelsohn <dje.gcc@...il.com> [2017-05-17 09:49:22 -0400]:
> >> >> Are there any musl developers who would be interested to work on musl
> >> >> libm optimizations for Power and Z as financial bounties?
> >> >
> >> > i hope it is something upstreamable
> >> > (i'm interested in libm optimizations, but cant work for bounties)
> >>
> >> I'm not certain what you mean.  We want musl libm to include
> >> optimizations for Power and Z in the musl repository and releases.
> >
> > Upstreamability could include 2 things: both your/contributor's
> > willingness to submit the code upstream, and appropriateness of it for
> > inclusion.
> >
> > In general we avoid having per-arch math code that's more than simple
> > fpu instruction wrappers -- math/i386/*.s is about the upper bound on
> > what I have in mind, as opposed to something like using an entirely
> > different C algorithm that just happens to be faster on the arch or
> > that only tangentially uses arch-specific insns. And more importantly,
> > arch-specific math asm should not be sacrificing correctness/quality
> > of results for performance or other considerations.
> 
> The Power and Z ports deserve the same math instruction optimizations
> as x86 and ARM.

Yes, agreed. My reply was to explain what the rough intent of that
"sameness" is, and the preferred approach going forward (which I want
to eventually move older archs over to as well -- using C files with
asm rather than .s/.S files).

Rich

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