[arch-dev-public] Create guidelines regarding SIMD instructions/x86 extensions

[Bruno Pagani]

Le 25/05/2019 à 13:27, Allan McRae via arch-dev-public a écrit :
> On 25/5/19 9:19 pm, Bruno Pagani via arch-dev-public wrote:
>> Hi,
>>
>> Le 25/05/2019 à 02:17, Filipe Laíns via arch-dev-public a écrit :
>>> I would also like to explore the idea of adding an "high performance"
>>> architecture which would be able to make use of SSE{,2,3,4,4.1,4.2} and
>>> AVX, which seem to be the standard for newer processors (>=2013). This
>>> would only be available for packages that do high performance computing
>>> (ex. openblas, sdrangel, etc.). Any thoughts on this?
>> As said on IRC, they have been discussions before on having multiple
>> targets and corresponding repos, but the starting point is that we need
>> automated build before going into such a direction, and this in turn has
>> several requirements. I’ve linked to you the pad where we put our ideas
>> together regarding this.
>>
>> In the meantime, we had the case before of whether we should package
>> e.g. $pkgname-{sse4,avx} in a case where it mattered a lot, but it
>> turned out the software in question (embree) is able to do runtime
>> detection of available ISA. Maybe some other packages are doing this
>> too, else we could discuss whether allowing such flavours as a temporary
>> measure would be acceptable for selected packages.
> glibc detects available instruction sets and uses the best for many
> functions.

Great!

> I'd be very, very, very much against providing multiple variants of a
> package in our repos.  Using asp and makepkg are is a hard solution for
> those who really need a few packages rebuilt.

I’m fine with that possibility too.

> PS - I rebuilt [core] with -march=haswell recently as a test.  Automated
> building is not an issue.  Unattended package/database signing is the
> major stumbling block.

Yes, in our discussions it boiled down to “Automated rebuilds” →
“Unattented signing” → “Reproducible builds”.

Out of curiosity, what did you rebuild of [core] lead to?

Bruno


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