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Date: Thu, 18 May 2017 12:31:08 -0400
From: David Edelsohn <dje.gcc@...il.com>
To: musl@...ts.openwall.com
Subject: Re: Musl libm optimizations for Power and Z

On Wed, May 17, 2017 at 1:17 PM, Rich Felker <dalias@...c.org> wrote:
> 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).

I had hoped that Bobby Bingham would be interested to work on this,
but I have not heard from him in a while.  Is there anyone else in the
community who would be interested to work on this?

Thanks, David

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