> On Thu, Feb 22, 2024 at 1:45 PM <pbhagavat...@marvell.com> wrote:
> >
> > From: Pavan Nikhilesh <pbhagavat...@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 <pbhagavat...@marvell.com>
> > ---
> > config/arm/meson.build | 14 +++++++++++---
> > 1 file changed, 11 insertions(+), 3 deletions(-)
> >
> > diff --git a/config/arm/meson.build b/config/arm/meson.build
> > index d05d54b564..87ff5039f6 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"'],
> > @@ -708,6 +709,7 @@ if update_flags
> >
> > candidate_mcpu = ''
> > candidate_march = ''
> > + fallback_march = ''
> >
> > if part_number_config.has_key('mcpu') and
> > cc.has_argument('-mcpu=' + part_number_config['mcpu'])
> > @@ -736,16 +738,22 @@ if update_flags
> > # start checking from this version downwards
> > check_compiler_support = true
> > endif
> > - if (check_compiler_support and
> > + if (check_compiler_support and candidate_march == '' and
> > cc.has_argument('-march=' + supported_march))
> > candidate_march = supported_march
> > - # highest supported march version found
> > - break
> > + endif
> > + if (part_number_config.has_key('fallback_march') and
> > + supported_march ==
> > part_number_config['fallback_march'] and
> > + cc.has_argument('-march=' + supported_march))
> > + fallback_march = supported_march
>
> If both fallback_march and march are supported, fallback_march is
> going to be chosen over march.
The current flow still chooses the march
Message: Arm implementer: Arm
Message: Arm part number: 0xd49
Compiler for C supports arguments -march=armv9-a: YES
Compiler for C supports arguments -march=armv8.5-a: YES
Compiler for C supports arguments -march=armv9-a+sve2: YES
Compiler for C supports arguments -march=armv9-a+sve2+crypto: YES
Message: Using machine args: ['-march=armv9-a+sve2+crypto']
> I think this is what we want instead:
> Use march if supported,
> then use fallback_march if supported,
> then use the other fallback marchs.
>
> If the above is indeed what we want, we could just put this after
> endforeach (in the original version):
>
> # at this point, candidate march is either
> part_number_config['fallback_march'] or some other lower version
> if (part_number_config.has_key('fallback_march') and
> candidate_march != part_number_config['march'] and
> cc.has_argument('-march=' + part_number_config['fallback_march']))
> # this overwrites only the lower version with preferred
> fallback_march, if supported
> candidate_march = part_number_config['fallback_march']
> endif
>
> This way we won't even need the fallback_march variable.
Sure, I will change remove fallback_march variable, Thanks.
>
> > endif
> > endforeach
> > endif
> >
> > if candidate_march != part_number_config['march']
> > + if fallback_march != ''
> > + candidate_march = fallback_march
> > + endif
> > warning('Configuration march version is @0@, not supported.'
> > .format(part_number_config['march']))
> > if candidate_march != ''
> > --
> > 2.25.1
> >
