diff mbox series

[v4,2/3] config/arm: add support for fallback march

Message ID 20240221202018.14179-2-pbhagavatula@marvell.com (mailing list archive)
State Superseded, archived
Delegated to: Thomas Monjalon
Headers
Series [v4,1/3] config/arm: avoid mcpu and march conflicts |

Checks

Context Check Description
ci/checkpatch success coding style OK

Commit Message

Pavan Nikhilesh Bhagavatula Feb. 21, 2024, 8:20 p.m. UTC 
  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 | 10 ++++++++++
 1 file changed, 10 insertions(+)

Comments

Juraj Linkeš Feb. 22, 2024, 10:47 a.m. UTC | #1 
On Wed, Feb 21, 2024 at 9:20 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 | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/config/arm/meson.build b/config/arm/meson.build
> index e77b696d8e..f6521653c8 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"'],
> @@ -716,6 +717,7 @@ if update_flags
>
>      # probe supported archs and their features
>      candidate_march = ''
> +    fallback_march = ''
>      if part_number_config.has_key('march') and candidate_mcpu == ''
>          if part_number_config.get('force_march', false)
>              if cc.has_argument('-march=' +  part_number_config['march'])
> @@ -736,10 +738,18 @@ if update_flags
>                      # 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
> +                endif

I'm trying to wrap my head around this. If I understand this
correctly, fallback_march is going to be set only if fallback_march >
part_number_config['march'] (fallback_march must be higher than the
one in part_number_config, otherwise the loop will end with break
before setting fallback_march).

The added fallback_march configuration above is the opposite
(fallback_march < part_number_config['march']) so I'm not sure what
we're trying to accomplish here. Is the intention to specify a
fallback_march that's lower than the one the original fallback
mechanism would find? If so, we'll need to remove the break (and
probably set check_compiler_support to false) so that the loop could
continue.

>              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
>
Pavan Nikhilesh Bhagavatula Feb. 22, 2024, 12:32 p.m. UTC | #2 
> On Wed, Feb 21, 2024 at 9:20 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 | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> >
> > diff --git a/config/arm/meson.build b/config/arm/meson.build
> > index e77b696d8e..f6521653c8 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"'],
> > @@ -716,6 +717,7 @@ if update_flags
> >
> >      # probe supported archs and their features
> >      candidate_march = ''
> > +    fallback_march = ''
> >      if part_number_config.has_key('march') and candidate_mcpu == ''
> >          if part_number_config.get('force_march', false)
> >              if cc.has_argument('-march=' +  part_number_config['march'])
> > @@ -736,10 +738,18 @@ if update_flags
> >                      # 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
> > +                endif
> 
> I'm trying to wrap my head around this. If I understand this
> correctly, fallback_march is going to be set only if fallback_march >
> part_number_config['march'] (fallback_march must be higher than the
> one in part_number_config, otherwise the loop will end with break
> before setting fallback_march).
> 

Fallback_march will always be < part_number_config['march'].
If part_number_config['march'] is supported by the compiler then we don’t need
fallback march.

> The added fallback_march configuration above is the opposite
> (fallback_march < part_number_config['march']) so I'm not sure what
> we're trying to accomplish here. Is the intention to specify a
> fallback_march that's lower than the one the original fallback
> mechanism would find? If so, we'll need to remove the break

I missed the break part, will add that in along with candidate_march == '' check.

> (and
> probably set check_compiler_support to false) so that the loop could
> continue.
> 
> >              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
> >
diff mbox series

Patch

diff --git a/config/arm/meson.build b/config/arm/meson.build
index e77b696d8e..f6521653c8 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"'],
@@ -716,6 +717,7 @@  if update_flags
 
     # probe supported archs and their features
     candidate_march = ''
+    fallback_march = ''
     if part_number_config.has_key('march') and candidate_mcpu == ''
         if part_number_config.get('force_march', false)
             if cc.has_argument('-march=' +  part_number_config['march'])
@@ -736,10 +738,18 @@  if update_flags
                     # 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
+                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 != ''