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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-6fd772df642sm104286906d6.74.2025.07.02.11.22.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 02 Jul 2025 11:22:46 -0700 (PDT) Date: Wed, 2 Jul 2025 11:22:42 -0700 From: Stephen Hemminger To: Bruce Richardson Cc: dev@dpdk.org, Konstantin Ananyev , Vipin Varghese Subject: Re: [PATCH v2] build/x86: fix support for older compilers Message-ID: <20250702112242.7b93d978@hermes.local> In-Reply-To: <20250702160138.3441279-1-bruce.richardson@intel.com> References: <20250702155129.3440210-1-bruce.richardson@intel.com> <20250702160138.3441279-1-bruce.richardson@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Wed, 2 Jul 2025 17:00:45 +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 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 > --- > 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?