On Wed, Jul 02, 2025 at 04:51:29PM +0100, Bruce Richardson 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 AVX > > gcc -march=haswell -march=skylake-avx512 -dM -E - < /dev/null | grep AVX > ... >
... and of course the output lines get stripped since they start with '#' for '#define' :-( > 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 > cc_avx512_flags = [] > -if (binutils_ok and cc.has_argument(avx512_march_flag) > +if (binutils_ok and cc.has_multi_arguments(avx512_march_flag) > and '-mno-avx512f' not in get_option('c_args')) > # check if compiler is working with _mm512_extracti64x4_epi64 > # Ref: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82887 > -- > 2.48.1 >