I Forgot to add my tag:
Reviewed-by: Juraj Linkeš <juraj.lin...@pantheon.tech>
On Mon, Feb 26, 2024 at 8:31 AM Juraj Linkeš <juraj.lin...@pantheon.tech> wrote:
>
> On Mon, Feb 26, 2024 at 8:11 AM Pavan Nikhilesh Bhagavatula
> <pbhagavat...@marvell.com> wrote:
> >
> > > 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']
> > > >
>
> Ah, of course, fallback march is only applied if when candidate_march
> != part_number_config['march']. Thanks.
>
> > > > 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
> > > >
