Re: [dpdk-dev] [PATCH 2/2] net/hns3: fix SVE code compile error with gcc8.3

[Ruifeng Wang <Ruifeng.Wang@arm.com>]

> -----Original Message-----
> From: Chengwen Feng <fengchengwen@huawei.com>
> Sent: Monday, June 28, 2021 10:58 AM
> To: thomas@monjalon.net; ferruh.yigit@intel.com; Ruifeng Wang
> <Ruifeng.Wang@arm.com>
> Cc: dev@dpdk.org; bruce.richardson@intel.com;
> vladimir.medvedkin@intel.com; viktorin@rehivetech.com;
> jerinj@marvell.com; Honnappa Nagarahalli
> <Honnappa.Nagarahalli@arm.com>; jerinjacobk@gmail.com;
> juraj.linkes@pantheon.tech
> Subject: [PATCH 2/2] net/hns3: fix SVE code compile error with gcc8.3
> 
> If the target machine has SVE feature (e.g. '-march=armv8.2-a+sve'), and
> compiler are gcc8.3, it will compile error, the error is arm_sve.h no such file or
> directory.
> 
> The solution:
> a. If RTE_HAS_SVE_ACLE defined (it means the minimum instruction set
> support SVE ACLE) then compiles it.
> b. Else if the compiler support SVE ACLE then compiles it.
> c. Otherwise don't compile it.
> 
> 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>
> Acked-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
>  drivers/net/hns3/hns3_rxtx.c |  2 +-
>  drivers/net/hns3/meson.build | 20 +++++++++++++++++++-
>  2 files changed, 20 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/hns3/hns3_rxtx.c b/drivers/net/hns3/hns3_rxtx.c
> index cb9eccf..a86e105 100644
> --- a/drivers/net/hns3/hns3_rxtx.c
> +++ b/drivers/net/hns3/hns3_rxtx.c
> @@ -2811,7 +2811,7 @@ hns3_get_default_vec_support(void)
>  static bool
>  hns3_get_sve_support(void)
>  {
> -#if defined(RTE_ARCH_ARM64) && defined(__ARM_FEATURE_SVE)
> +#if defined(RTE_HAS_SVE_ACLE)
>  	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..a99e0db 100644
> --- a/drivers/net/hns3/meson.build
> +++ b/drivers/net/hns3/meson.build
> @@ -35,7 +35,25 @@ deps += ['hash']
> 
>  if arch_subdir == 'arm' and dpdk_conf.get('RTE_ARCH_64')
>      sources += files('hns3_rxtx_vec.c')
> -    if cc.get_define('__ARM_FEATURE_SVE', args: machine_args) != ''
> +
> +    # compile SVE when:
> +    # a. support SVE in minimum instruction set baseline
> +    # b. it's not minimum instruction set, but compiler support
> +    if dpdk_conf.has('RTE_HAS_SVE_ACLE')
>          sources += files('hns3_rxtx_vec_sve.c')
> +    elif cc.has_argument('-march=armv8.2-a+sve') and
> cc.check_header('arm_sve.h')
> +        cflags += ['-DRTE_HAS_SVE_ACLE=1']
> +        sve_cflags = []
Global cflags will be changed here. I think it is not very good as build of other parts could be without SVE support.
How about " sve_cflags = ['-DRTE_HAS_SVE_ACLE=1']" and drop changes to cflags?
In this way, the additional flag will be limited to hns3_sve_lib.

> +        foreach flag: cflags
> +            if not (flag.startswith('-march=') or flag.startswith('-mcpu=') or
> flag.startswith('-mtune='))
> +                sve_cflags += flag
> +            endif
> +        endforeach
> +        hns3_sve_lib = static_library('hns3_sve_lib',
> +                        'hns3_rxtx_vec_sve.c',
> +                        dependencies: [static_rte_ethdev],
> +                        include_directories: includes,
> +                        c_args: [sve_cflags, '-march=armv8.2-a+sve'])
> +        objs += hns3_sve_lib.extract_objects('hns3_rxtx_vec_sve.c')
>      endif
>  endif
> --
> 2.8.1