Automatically provide x86_64 subarchitecture levels

[dirkmueller]

Recently RPM has gained support for x86_64 subarchitecture levels (see rpm-software-management/rpm#2315). These identify the CPU capabilities and allow via a GLIBC HWCAPS overlay to dynamically select more optimized shared libraries for loading. This functionality has been implemented in openSUSE Tumbleweed now.

What is missing is that the libzypp stack is automatically adding a system provide when the host cpu is capable to execute this level. One could do that via the assembly code in the PR above, or by parsing the output of "ld.so --help" (which might be highly unstable). Unfortunately afaik there is no glibc interface to reliably query the glibc information.

Please let me know if you're willing to implement this functionality as it could be useful to select those overlay libraries for supporting architectures automatically.

[Vogtinator]

What is missing is that the libzypp stack is automatically adding a system provide when the host cpu is capable to execute this level. One could do that via the assembly code in the PR above, or by parsing the output of "ld.so --help" (which might be highly unstable). Unfortunately afaik there is no glibc interface to reliably query the glibc information.

If it's an option to rely on GCC specific builtins, then just __builtin_cpu_supports("x86-64-vX") is available since GCC 12.2.

[mlandres]

__builtin_cpu_supports("x86-64-vX") is available since GCC 12.2.

Unfortunately we need a solution that works for the whole Code15 family.

[Vogtinator]

Unfortunately it looks like you copied the code before rpm-software-management/rpm#2412 was merged, can you include that as well?

[mlandres]

I'll do.

[mlandres]

Thanks @Vogtinator