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

[fengchengwen <fengchengwen@huawei.com>]

On 2021/5/14 6:19, Honnappa Nagarahalli wrote:
> <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.
> 

The original is cflags = ['-DCC_SVE_SUPPORT'] which will rewrite cflags
And here we use symbol '+=', it only add extra macro which is CC_SVE_SUPPORT
So it's ok.

>>          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
> 
> 
> .
>