Re: [dpdk-dev] [PATCH v2] net/hns3: fix compile error with gcc8.3 and thunderx2

[David Marchand <david.marchand@redhat.com>]

On Wed, May 19, 2021 at 1:57 PM Chengwen Feng <fengchengwen@huawei.com> wrote:
>
> Compile error with gcc8.3 and crossfile arm64_thunderx2_linux_gcc:
>         ../drivers/net/hns3/hns3_rxtx_vec_sve.c
>         cc1: error: switch ‘-mcpu=armv8.1-a’ conflicts with
>         ‘-march=armv8.2-a’ switch [-Werror]
>         ../drivers/net/hns3/hns3_rxtx_vec_sve.c:5:10: fatal error:
>         arm_sve.h: No such file or directory
>             5 | #include <arm_sve.h>
>
> The root cause is that gcc8.3 supports SVE, but it doesn't support
> compile ACLE[1] SVE code, and the hns3_rxtx_vec_sve.c was written
> by ACLE SVE code.

Quite confusing.
What is the difference between the two?


>
> This patch also filters out '-march=' '-mcpu' '-mtune' when compile
> with hns3_rxtx_vec_sve.c.
>
> [1] ACLE: Arm C Language Extensions, user should include <arm_sve.h>
> when writing ACLE SVE code.
>
> Fixes: 203fbaf8813d ("net/hns3: refactor SVE code compile method")
>
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> ---
> v2:
> * fix check tool error
> ---
>  drivers/net/hns3/meson.build | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/hns3/meson.build b/drivers/net/hns3/meson.build
> index 8563d70..5f9af9b 100644
> --- a/drivers/net/hns3/meson.build
> +++ b/drivers/net/hns3/meson.build
> @@ -39,16 +39,22 @@ if arch_subdir == 'arm' and dpdk_conf.get('RTE_ARCH_64')
>      # compile SVE when:
>      # a. support SVE in minimum instruction set baseline
>      # b. it's not minimum instruction set, but compiler support
> -    if cc.get_define('__ARM_FEATURE_SVE', args: machine_args) != ''
> +    if cc.get_define('__ARM_FEATURE_SVE', args: machine_args) != '' and cc.check_header('arm_sve.h')

The rte_vect.h arm header unconditionally includes arm_sve.h if
__ARM_FEATURE_SVE is defined [1].
So it is surprising to see such a check being added.

1: https://git.dpdk.org/dpdk/tree/lib/eal/arm/include/rte_vect.h#n12


-- 
David Marchand