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

[Allan McRae]

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.

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.

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.

Allan