Re: [PATCH 2/2] config/arm: add support for fallback march

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

+Cc

On 2024/1/21 5:36 PM, pbhagavatula@marvell.com wrote:
> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
> 
> Some ARM CPUs have specific march requirements and
> are not compatible with the supported march list.
> Add fallback march in case the mcpu and the march
> advertised in the part_number_config are not supported
> by the compiler.
> 
> Example
> 	mcpu = neoverse-n2
> 	march = armv9-a
> 	fallback_march = armv8.5-a
> 
> 	mcpu, march not supported
> 	machine_args = ['-march=armv8.5-a']
> 
> 	mcpu, march, fallback_march not supported
> 	least march supported = armv8-a
> 
> 	machine_args = ['-march=armv8-a']
> 
> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
> ---
>   config/arm/meson.build | 15 +++++++++++++--
>   1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/config/arm/meson.build b/config/arm/meson.build
> index 8c8cfccca0..2aaf78a81a 100644
> --- a/config/arm/meson.build
> +++ b/config/arm/meson.build
> @@ -94,6 +94,7 @@ part_number_config_arm = {
>       '0xd49': {
>           'march': 'armv9-a',
>           'march_features': ['sve2'],
> +        'fallback_march': 'armv8.5-a',
>           'mcpu': 'neoverse-n2',
>           'flags': [
>               ['RTE_MACHINE', '"neoverse-n2"'],
> @@ -709,14 +710,14 @@ if update_flags
> 
>       # probe supported archs and their features
>       candidate_march = ''
> +    supported_marchs = ['armv9-a', 'armv8.6-a', 'armv8.5-a', 'armv8.4-a',
> +                        'armv8.3-a', 'armv8.2-a', 'armv8.1-a', 'armv8-a']
>       if part_number_config.has_key('march')
>           if part_number_config.get('force_march', false) or support_mcpu
>               if cc.has_argument('-march=' +  part_number_config['march'])
>                   candidate_march = part_number_config['march']
>               endif
>           else
> -            supported_marchs = ['armv8.6-a', 'armv8.5-a', 'armv8.4-a', 'armv8.3-a',
> -                                'armv8.2-a', 'armv8.1-a', 'armv8-a']
>               check_compiler_support = false
>               foreach supported_march: supported_marchs
>                   if supported_march == part_number_config['march']
> @@ -733,6 +734,16 @@ if update_flags
>           endif
> 
>           if candidate_march != part_number_config['march']
> +            if part_number_config.has_key('fallback_march') and not support_mcpu
> +                fallback_march = part_number_config['fallback_march']
> +                foreach supported_march: supported_marchs
> +                    if (supported_march == fallback_march
> +                        and cc.has_argument('-march=' + supported_march))
> +                        candidate_march = supported_march
> +                        break
> +                    endif
> +                endforeach
> +            endif
>               warning('Configuration march version is @0@, not supported.'
>                       .format(part_number_config['march']))
>               if candidate_march != ''
> --
> 2.25.1
>