Hi César, Hi Andreas Andreas Tille, on 2023-07-04: > Am Tue, Jul 04, 2023 at 04:19:45PM +0200 schrieb César Pomar: > > > I did not checked (yet) but you might like to have a look into > > > SIMDEverywhere[3] > > > > Thank you, but I meant that I was enabling AMD64 features on ARM. I've > > taken a > > look at the log and I see what the problem might be. Considering that > > aarch64-linux-gnu-g++ is being used, it appears to be a compilation for > > ARM, > > but with BUILD_ARCH=amd64 and HOST_ARCH=arm64, shouldn't it be the other > > way > > around? In any case, if this isn't an error, I would look for when > > HOST_ARCH=arm64 and wouldn't use USE_AVX2=ON, which is the parameter that > > sends -mavx2. Because right now, I'm using BUILD_ARCH, and since it's > > amd64, > > it assumes it should use USE_AVX2=ON. > > I admit I'm not very educated with ARM. However, mixing two different > architectures in BUILD_ARCH and HOST_ARCH sounds suspicious to me and is > IMHO only relevant for cross-building (but I repeat I'm not very > educated here).
If that helps, about the cross-building point, I believe that I
identified a couple of the issues. The missing definition of
DEB_*_ARCH makefile variables can be obtained from dpkg
resources, either with the following general directive in
debian/rules:
include /usr/share/dpkg/default.mk
or by loading only architecture specific variables:
include /usr/share/dpkg/architecture.mk
The second difficulty is that in Debian vernacular[1], the build
architecture is the architecture of the build environment, while
the host architecture is the architecture of the binary packages
to be produced, so you're after the DEB_HOST_ARCH variable. My
understanding is that there are contexts where the two concepts
are the opposite, which can be very confusing.
Besides, Debian handles a few more architectures than just
x86_64 and Arm[2], so you might like to enable amd64 specific
flags only when DEB_HOST_ARCH is amd64, not just when it's not
Arm.
Which leads me to the use of avx2 in build options: beware that
some users of your package may not have an avx2 capable x86_64
machines. If your program doesn't gracefully fallback to the
generic instruction set, then those users will witness "Illegal
instruction" errors instead of being able to run your software.
In such situation, the pointer from Andreas toward SIMDe would
make very much sense to investigate[3] (otherwise the easy
option would have been to disable avx2 extensions entirely, but
I guess you would prefer to avoid penalizing performances on
high end machines).
[1]: https://wiki.debian.org/CrossBuildPackagingGuidelines
[2]: https://release.debian.org/testing/arch_qualify.html
> > > [3]: https://wiki.debian.org/SIMDEverywhere
In hope this helps and is not too overwhelming,
Have a nide day, :)
--
.''`. Étienne Mollier <emoll...@debian.org>
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