Re: [dpdk-dev] [PATCH v4 2/2] net/hns3: refactor SVE code compile method

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>

> 
> Currently, the SVE code is compiled only when -march supports SVE (e.g. '-
> march=armv8.2a+sve'), there maybe some problem[1] with this approach.
> 
> The solution:
> a. If the minimum instruction set support SVE then compiles it.
> b. Else if the compiler support SVE then compiles it.
> c. Otherwise don't compile it.
> 
> [1] https://mails.dpdk.org/archives/dev/2021-April/208189.html
> 
> Fixes: 8c25b02b082a ("net/hns3: fix enabling SVE Rx/Tx")
> Fixes: 952ebacce4f2 ("net/hns3: support SVE Rx")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
> ---
>  drivers/net/hns3/hns3_rxtx.c |  2 +-
>  drivers/net/hns3/meson.build | 13 +++++++++++++
>  2 files changed, 14 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/hns3/hns3_rxtx.c b/drivers/net/hns3/hns3_rxtx.c
> index 1d7a769..4ef20c6 100644
> --- a/drivers/net/hns3/hns3_rxtx.c
> +++ b/drivers/net/hns3/hns3_rxtx.c
> @@ -2808,7 +2808,7 @@ hns3_get_default_vec_support(void)
>  static bool
>  hns3_get_sve_support(void)
>  {
> -#if defined(RTE_ARCH_ARM64) && defined(__ARM_FEATURE_SVE)
> +#if defined(CC_SVE_SUPPORT)
>  	if (rte_vect_get_max_simd_bitwidth() < RTE_VECT_SIMD_256)
>  		return false;
>  	if (rte_cpu_get_flag_enabled(RTE_CPUFLAG_SVE))
> diff --git a/drivers/net/hns3/meson.build b/drivers/net/hns3/meson.build
> index 53c7df7..8563d70 100644
> --- a/drivers/net/hns3/meson.build
> +++ b/drivers/net/hns3/meson.build
> @@ -35,7 +35,20 @@ deps += ['hash']
> 
>  if arch_subdir == 'arm' and dpdk_conf.get('RTE_ARCH_64')
>      sources += files('hns3_rxtx_vec.c')
> +
> +    # 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) != ''
> +        cflags += ['-DCC_SVE_SUPPORT']
Can you please look at commit 21c4f1c7b2f8e637ecff9b9180e21f6b4505715f? This commit removed the CC_SVE_SUPPORT flag due to a compilation error.

>          sources += files('hns3_rxtx_vec_sve.c')
> +    elif cc.has_argument('-march=armv8.2-a+sve')
> +        cflags += ['-DCC_SVE_SUPPORT']
> +        hns3_sve_lib = static_library('hns3_sve_lib',
> +                        'hns3_rxtx_vec_sve.c',
> +                        dependencies: [static_rte_ethdev],
> +                        include_directories: includes,
> +                        c_args: [cflags, '-march=armv8.2-a+sve'])
> +        objs += hns3_sve_lib.extract_objects('hns3_rxtx_vec_sve.c')
>      endif
>  endif
> --
> 2.8.1