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From: "Ananyev, Konstantin" <konstantin.ananyev@intel.com>
To: Zoltan Kiss <zoltan.kiss@linaro.org>, "dev@dpdk.org" <dev@dpdk.org>
Thread-Topic: [dpdk-dev] [PATCH] acl: fix target arch detection
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Date: Tue, 29 Sep 2015 09:42:35 +0000
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Subject: Re: [dpdk-dev] [PATCH] acl: fix target arch detection
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Hi Zoltan,

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Zoltan Kiss
> Sent: Saturday, September 26, 2015 6:59 AM
> To: dev@dpdk.org
> Subject: [dpdk-dev] [PATCH] acl: fix target arch detection
>=20
> This test selects AVX2 code even if the target architecture doesn't suppo=
rt it.
>=20
> Signed-off-by: Zoltan Kiss <zoltan.kiss@linaro.org>
> ---
> diff --git a/lib/librte_acl/Makefile b/lib/librte_acl/Makefile
> index 46acc2b..17a9f96 100644
> --- a/lib/librte_acl/Makefile
> +++ b/lib/librte_acl/Makefile
> @@ -57,7 +57,7 @@ CFLAGS_acl_run_sse.o +=3D -msse4.1
>  # then add support for AVX2 classify method.
>  #
>=20
> -CC_AVX2_SUPPORT=3D$(shell $(CC) -march=3Dcore-avx2 -dM -E - </dev/null 2=
>&1 | \
> +CC_AVX2_SUPPORT=3D$(shell $(CC) $(MACHINE_FLAGS) -dM -E - </dev/null 2>&=
1 | \
>  grep -q AVX2 && echo 1)
>=20
>  ifeq ($(CC_AVX2_SUPPORT), 1)

The purpose of that code is to check does compiler supports AVX2 or not.
If it does, even if selected target doesn't support AVX2, we still compile =
in AVX2  version of acl_classify (same for SSE4).
Then  at startup, rte_acl_init() selects the highest supported on that box =
implementation (scalar/sse/avx2).
So NACK.
Konstantin

BTW, why MACHINE_FLAGS?
Shouldn't it be MACHINE_CFLAGS, instead?