Re: [PATCH v2] config/arm: update aarch32 build with gcc13

[Paul Szczepanek <paul.szczepanek@arm.com>]

On 09/10/2023 10:53, Juraj Linkeš wrote:
> The aarch32 with gcc13 fails with:
>
> Compiler for C supports arguments -march=armv8-a: NO
>
> ../config/arm/meson.build:714:12: ERROR: Problem encountered: No
> suitable armv8 march version found.
>
> This is because we test -march=armv8-a alone (without the -mpfu option),
> which is no longer supported in gcc13 aarch32 builds.
>
> The most recent recommendation from the compiler team is to build with
> -march=armv8-a+simd -mfpu=auto, which should work for compilers old and
> new. The suggestion is to first check -march=armv8-a+simd and only then
> check -mfpu=auto.
>
> To address this, add a way to force the architecture (the value of
> the -march option).
>
> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
> Acked-by: Ruifeng Wang <ruifeng.wang@arm.com>
> ---
>   config/arm/meson.build | 12 +++++++++---
>   1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/config/arm/meson.build b/config/arm/meson.build
> index 3f22d8a2fc..5303d0e969 100644
> --- a/config/arm/meson.build
> +++ b/config/arm/meson.build
> @@ -43,7 +43,9 @@ implementer_generic = {
>           },
>           'generic_aarch32': {
>               'march': 'armv8-a',
> -            'compiler_options': ['-mfpu=neon'],
> +            'force_march': true,
> +            'march_features': ['simd'],
> +            'compiler_options': ['-mfpu=auto'],
>               'flags': [
>                   ['RTE_ARCH_ARM_NEON_MEMCPY', false],
>                   ['RTE_ARCH_STRICT_ALIGN', true],
> @@ -711,7 +713,11 @@ if update_flags
>               endif
>           endforeach
>           if candidate_march == ''
> -            error('No suitable armv8 march version found.')
> +            if part_number_config.get('force_march', false)
> +                candidate_march = part_number_config['march']
> +            else
> +                error('No suitable armv8 march version found.')
> +            endif
This section is only used when no candidate is found, this would make it 
not really be a forced arch but more a fallback arch. If we want the 
user to be able to really force the march string we'd need to put the 
"is forced?" check higher. Am I reading the code right?
>           endif
>           if candidate_march != part_number_config['march']
>               warning('Configuration march version is ' +
> @@ -741,7 +747,7 @@ if update_flags
>       # apply supported compiler options
>       if part_number_config.has_key('compiler_options')
>           foreach flag: part_number_config['compiler_options']
> -            if cc.has_argument(flag)
> +            if cc.has_multi_arguments(machine_args + [flag])
>                   machine_args += flag
>               else
>                   warning('Configuration compiler option ' +