On Thu, 3 Jul 2025 10:12:10 +0200 David Marchand <david.march...@redhat.com> wrote:
> On Thu, Jul 3, 2025 at 10:01 AM Bruce Richardson > <bruce.richard...@intel.com> wrote: > > > > On Wed, Jul 02, 2025 at 11:22:42AM -0700, Stephen Hemminger wrote: > > > On Wed, 2 Jul 2025 17:00:45 +0100 > > > Bruce Richardson <bruce.richard...@intel.com> wrote: > > > > > > > Some older compilers e.g. gcc 8.5, do not support overriding > > > > -march=native with another architecture, leading to build warnings such > > > > as reported in Bugzilla (link below). Add a check for that case, and > > > > explicitly add the avx512 flags if necessary. > > > > > > > > Note: it appears that it is only the "native" flag that isn't > > > > overridden, which makes the issue hard to reproduce e.g. using > > > > godbolt.org, or on a modern machine. For example, testing with gcc 8.5 > > > > on a haswell machine, using 'native' vs explicit 'haswell': > > > > > > > > gcc -march=native -march=skylake-avx512 -dM -E - < /dev/null | grep > > > > AVX512 | wc -l > > > > 0 > > > > > > > > gcc -march=haswell -march=skylake-avx512 -dM -E - < /dev/null | grep > > > > AVX512 | wc -l > > > > 5 > > > > > > > > Bugzilla ID: 1736 > > > > Fixes: e361ae3f59d3 ("build: reduce use of AVX compiler flags") > > > > > > > > Signed-off-by: Bruce Richardson <bruce.richard...@intel.com> > > > > --- > > > > config/x86/meson.build | 7 ++++++- > > > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/config/x86/meson.build b/config/x86/meson.build > > > > index e2ccfb6d12..0dcc5ddee4 100644 > > > > --- a/config/x86/meson.build > > > > +++ b/config/x86/meson.build > > > > @@ -71,8 +71,13 @@ avx512_march_flag = '-march=x86-64-v4' > > > > if not cc.has_argument(avx512_march_flag) > > > > avx512_march_flag = '-march=skylake-avx512' > > > > endif > > > > +# workaround for older compilers, e.g. gcc 8.5 on RHEL 8. > > > > +# if march flag overriding doesn't work, explicitly add flags for > > > > AVX512. > > > > +if cc.get_define('__AVX512F__', args: [machine_args, > > > > avx512_march_flag]) == '' > > > > + avx512_march_flag = ['-mavx512f', '-mavx512bw', '-mavx512cd', > > > > '-mavx512dq', '-mavx512vl'] > > > > +endif > > > > > > RHEL 8.5 reached end of extended support cycle (EOL). > > > Why are we still supporting it? > > > > Folks working for Redhat can answer better than me, but according to [1] > > it's not EOL yet. Also, we support it in DPDK because users are still using > > > > RHEL 8 is not EOL. > > Right but 8.5 is, did compiler get fixed in later 8.X versions?