diff mbox series

[1/2] config/arm: strict use of -mcpu for supported CPUs

Message ID 20241028233139.922029-1-wathsala.vithanage@arm.com (mailing list archive)
State Superseded, archived
Delegated to: Thomas Monjalon
Headers
Series [1/2] config/arm: strict use of -mcpu for supported CPUs |

Checks

Context Check Description
ci/checkpatch success coding style OK

Commit Message

Wathsala Vithanage Oct. 28, 2024, 11:31 p.m. UTC 
Arm recommends using -mcpu over -march and march-extensions when the
compiler supports the target CPU (neoverse-n1 etc.). Arm build so far
has been an amalgam of -mcpu and -march. When march is in use, it has
been the case so far to silently fall back to a downgraded march when
the compiler does not support the requested march. This is unnecessary
and confusing to an end user who could be building DPDK with a
particular ISA version and performance expectations in mind.

This patch aims to rectify both the above issues. For part numbers that
has a corresponding -mcpu, this patch removes all references to march
and march_features from meson.build. For those SOCs that do not have a
corresponding -mcpu, a pseudo cpu name in the format mcpu_<soc_name> is
introduced and referenced in the mcpu field in the part number
dictionary of the part_number_config dictionary. The definition of the
mcpu_<soc_name> must be provided in the mcpu_defs dictionary.
Each mcpu_<soc_name> dictionary in the mcpu_defs have a march field and
a march_extensions field to construct the optimal compiler setting for
an SOC that has no corresponding -mcpu value. This patch alters the
behavior of the build system such that it will no longer silently fall
back to an older ISA version, it will only perform what's specified in
the build dictionaries, if the compiler does not support the specified
configuration it will fail with an error message.

How to add a new SOC to the build system with these changes?
If compiler supports mcpu follow the usual practice but without march
and march_features fields in the part number dictionary. If mcpu is not
available or buggy (misses certain features) for some reason follow the
same process but set mcpu field to a string in the form 'mcpu_foo'
(pseudo mcpu mentioned earlier). Then in the mcpu_defs dictionary add
mcpu_foo dictionary as shown.

'mcpu_foo': {
   'march': 'armv8.2-a',
   'march_extensions': [rcpc]
}

march_extensions is a comma separated list of march extensions supported
by the compiler such as sve, crypto etc. Empty match_extensions allowed
as use of such extensions are optional.

Signed-off-by: Wathsala Vithanage <wathsala.vithanage@arm.com>
Reviewed-by: Dhruv Tripathi <dhruv.tripathi@arm.com>

---
 config/arm/meson.build | 166 +++++++++++++++--------------------------
 1 file changed, 60 insertions(+), 106 deletions(-)

--
2.34.1

Comments

fengchengwen Oct. 29, 2024, 1:06 a.m. UTC | #1 
On 2024/10/29 7:31, Wathsala Vithanage wrote:
> Arm recommends using -mcpu over -march and march-extensions when the
> compiler supports the target CPU (neoverse-n1 etc.). Arm build so far
> has been an amalgam of -mcpu and -march. When march is in use, it has
> been the case so far to silently fall back to a downgraded march when
> the compiler does not support the requested march. This is unnecessary
> and confusing to an end user who could be building DPDK with a
> particular ISA version and performance expectations in mind.

I couldn't understand the problem, current the arm build already prefer use mcpu and then march:

    if (part_number_config.has_key('mcpu') and
	
    elif part_number_config.has_key('march')

> 
> This patch aims to rectify both the above issues. For part numbers that
> has a corresponding -mcpu, this patch removes all references to march
> and march_features from meson.build. For those SOCs that do not have a
> corresponding -mcpu, a pseudo cpu name in the format mcpu_<soc_name> is
> introduced and referenced in the mcpu field in the part number
> dictionary of the part_number_config dictionary. The definition of the
> mcpu_<soc_name> must be provided in the mcpu_defs dictionary.
> Each mcpu_<soc_name> dictionary in the mcpu_defs have a march field and
> a march_extensions field to construct the optimal compiler setting for
> an SOC that has no corresponding -mcpu value. This patch alters the
> behavior of the build system such that it will no longer silently fall
> back to an older ISA version, it will only perform what's specified in
> the build dictionaries, if the compiler does not support the specified
> configuration it will fail with an error message.
> 
> How to add a new SOC to the build system with these changes?
> If compiler supports mcpu follow the usual practice but without march
> and march_features fields in the part number dictionary. If mcpu is not
> available or buggy (misses certain features) for some reason follow the
> same process but set mcpu field to a string in the form 'mcpu_foo'
> (pseudo mcpu mentioned earlier). Then in the mcpu_defs dictionary add
> mcpu_foo dictionary as shown.
> 
> 'mcpu_foo': {
>    'march': 'armv8.2-a',
>    'march_extensions': [rcpc]

Prefer extend or change already existed struct.

In addition, there are many structures in the arm build. But it seemed
there is no document to describe the structure to which a feature should be added.

> }
> 
> march_extensions is a comma separated list of march extensions supported
> by the compiler such as sve, crypto etc. Empty match_extensions allowed
> as use of such extensions are optional.
> 
> Signed-off-by: Wathsala Vithanage <wathsala.vithanage@arm.com>
> Reviewed-by: Dhruv Tripathi <dhruv.tripathi@arm.com>
diff mbox series

Patch

diff --git a/config/arm/meson.build b/config/arm/meson.build
index 55be7c8711..04819e75eb 100644
--- a/config/arm/meson.build
+++ b/config/arm/meson.build
@@ -69,8 +69,6 @@  part_number_config_arm = {
     '0xd0a': {'mcpu': 'cortex-a75'},
     '0xd0b': {'mcpu': 'cortex-a76'},
     '0xd0c': {
-        'march': 'armv8.2-a',
-        'march_features': ['crypto', 'rcpc'],
         'mcpu': 'neoverse-n1',
         'flags': [
             ['RTE_MACHINE', '"neoverse-n1"'],
@@ -81,8 +79,6 @@  part_number_config_arm = {
         ]
     },
     '0xd40': {
-        'march': 'armv8.4-a',
-        'march_features': ['sve'],
         'mcpu': 'neoverse-v1',
         'flags': [
             ['RTE_MACHINE', '"neoverse-v1"'],
@@ -94,9 +90,6 @@  part_number_config_arm = {
         'march': 'armv8.4-a',
     },
     '0xd49': {
-        'march': 'armv9-a',
-        'march_features': ['sve2'],
-        'fallback_march': 'armv8.5-a',
         'mcpu': 'neoverse-n2',
         'flags': [
             ['RTE_MACHINE', '"neoverse-n2"'],
@@ -106,10 +99,7 @@  part_number_config_arm = {
         ]
     },
     '0xd4f': {
-        'march': 'armv9-a',
-        'march_features': ['sve2'],
         'mcpu' : 'neoverse-v2',
-        'fallback_march': 'armv8.5-a',
         'flags': [
             ['RTE_MACHINE', '"neoverse-v2"'],
             ['RTE_ARM_FEATURE_ATOMICS', true],
@@ -171,14 +161,10 @@  implementer_cavium = {
             'flags': flags_part_number_thunderx
         },
         '0xa3': {
-            'march': 'armv8-a',
-            'march_features': ['crc', 'crypto'],
             'mcpu': 'thunderxt83',
             'flags': flags_part_number_thunderx
         },
         '0xaf': {
-            'march': 'armv8.1-a',
-            'march_features': ['crc', 'crypto'],
             'mcpu': 'thunderx2t99',
             'flags': [
                 ['RTE_MACHINE', '"thunderx2"'],
@@ -189,8 +175,6 @@  implementer_cavium = {
             ]
         },
         '0xb2': {
-            'march': 'armv8.2-a',
-            'march_features': ['crc', 'crypto', 'lse'],
             'mcpu': 'octeontx2',
             'flags': [
                 ['RTE_MACHINE', '"cn9k"'],
@@ -212,8 +196,6 @@  implementer_ampere = {
     ],
     'part_number_config': {
         '0x0': {
-            'march': 'armv8-a',
-            'march_features': ['crc', 'crypto'],
             'mcpu': 'emag',
             'flags': [
                 ['RTE_MACHINE', '"eMAG"'],
@@ -222,8 +204,6 @@  implementer_ampere = {
             ]
         },
         '0xac3': {
-            'march': 'armv8.6-a',
-            'march_features': ['crc', 'crypto'],
             'mcpu': 'ampere1',
             'flags': [
                 ['RTE_MACHINE', '"AmpereOne"'],
@@ -232,8 +212,6 @@  implementer_ampere = {
             ]
         },
         '0xac4': {
-            'march': 'armv8.6-a',
-            'march_features': ['crc', 'crypto'],
             'mcpu': 'ampere1a',
             'flags': [
                 ['RTE_MACHINE', '"AmpereOneAC04"'],
@@ -252,8 +230,6 @@  implementer_hisilicon = {
     ],
     'part_number_config': {
         '0xd01': {
-            'march': 'armv8.2-a',
-            'march_features': ['crypto'],
             'mcpu': 'tsv110',
             'flags': [
                 ['RTE_MACHINE', '"Kunpeng 920"'],
@@ -263,8 +239,7 @@  implementer_hisilicon = {
             ]
         },
         '0xd02': {
-            'march': 'armv8.2-a',
-            'march_features': ['crypto', 'sve'],
+            'mcpu': 'mcpu_kunpeng930',
             'flags': [
                 ['RTE_MACHINE', '"Kunpeng 930"'],
                 ['RTE_ARM_FEATURE_ATOMICS', true],
@@ -273,8 +248,7 @@  implementer_hisilicon = {
             ]
         },
         '0xd03': {
-            'march': 'armv8.5-a',
-            'march_features': ['crypto', 'sve'],
+            'mcpu': 'mcpu_hip10',
             'flags': [
                 ['RTE_MACHINE', '"hip10"'],
                 ['RTE_ARM_FEATURE_ATOMICS', true],
@@ -321,16 +295,14 @@  implementer_phytium = {
     ],
     'part_number_config': {
         '0x662': {
-            'march': 'armv8-a',
-            'march_features': ['crc'],
+            'mcpu': 'mcpu_ft2000plus',
             'flags': [
                 ['RTE_MAX_LCORE', 64],
                 ['RTE_MAX_NUMA_NODES', 8]
-             ]
+            ]
         },
-       '0x663': {
-            'march': 'armv8-a',
-            'march_features': ['crc'],
+        '0x663': {
+            'mcpu': 'mcpu_tys2500',
             'flags': [
                 ['RTE_MAX_LCORE', 256],
                 ['RTE_MAX_NUMA_NODES', 32]
@@ -349,13 +321,8 @@  implementer_qualcomm = {
         ['RTE_MAX_NUMA_NODES', 1]
     ],
     'part_number_config': {
-        '0x800': {
-            'march': 'armv8-a',
-            'march_features': ['crc']
-        },
         '0xc00': {
-            'march': 'armv8-a',
-            'march_features': ['crc']
+            'mcpu': 'mcpu_centriq2400'
         }
     }
 }
@@ -659,6 +626,29 @@  soc_v2 = {
     'numa': true
 }

+mcpu_defs = {
+    'mcpu_kunpeng930': {
+        'march': 'armv8.2-a',
+        'march_extensions': ['crypto', 'sve']
+    },
+    'mcpu_hip10': {
+        'march': 'armv8.5-a',
+        'march_extensions': ['crypto', 'sve']
+    },
+    'mcpu_ft2000plus': {
+        'march': 'armv8-a',
+        'march_extensions': ['crc']
+    },
+    'mcpu_tys2500': {
+        'march': 'armv8-a',
+        'march_extensions': ['crc']
+    }
+    'mcpu_centriq2400': {
+        'march': 'armv8-a',
+        'march_extensions': ['crc']
+    }
+}
+
 '''
 Start of SoCs list
 generic:         Generic un-optimized build for armv8 aarch64 execution mode.
@@ -851,82 +841,46 @@  if update_flags
     dpdk_flags = flags_common + implementer_config['flags'] + part_number_config.get('flags', []) + soc_flags

     machine_args = [] # Clear previous machine args
-
-    march_features = []
-    if part_number_config.has_key('march_features')
-        march_features += part_number_config['march_features']
-    endif
-    if soc_config.has_key('extra_march_features')
-        march_features += soc_config['extra_march_features']
+    mcpu = part_number_config.get('mcpu', '')
+    if mcpu == ''
+        error('No suitable Arm mcpu name or custom mcpu definition object found.')
     endif

-    candidate_mcpu = ''
-    candidate_march = ''
+    if mcpu.contains('mcpu_')
+        mcpu_def = mcpu_defs.get(mcpu, {})
+        if mcpu_def.keys().length() == 0
+            error('Custom mcpu definition @0@ is not found.'.format(mcpu))
+        endif

-    if (part_number_config.has_key('mcpu') and
-        cc.has_argument('-mcpu=' + part_number_config['mcpu']))
-        candidate_mcpu = '-mcpu=' + part_number_config['mcpu']
-        foreach feature: march_features
-            if cc.has_argument('+'.join([candidate_mcpu, feature]))
-                candidate_mcpu = '+'.join([candidate_mcpu, feature])
-            else
-                warning('The compiler does not support feature @0@'
-                    .format(feature))
-            endif
-        endforeach
-        machine_args += candidate_mcpu
-    elif part_number_config.has_key('march')
-        # probe supported archs and their features
-        if part_number_config.get('force_march', false)
-            candidate_march = part_number_config['march']
-        else
-            supported_marchs = ['armv9-a', 'armv8.7-a', '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']
-                    # start checking from this version downwards
-                    check_compiler_support = true
-                endif
-                if (check_compiler_support and
-                    cc.has_argument('-march=' + supported_march))
-                    candidate_march = supported_march
-                    # highest supported march version found
-                    break
-                endif
-            endforeach
-            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']))
-                    candidate_march = part_number_config['fallback_march']
-            endif
+        march = mcpu_def.get('march', '')
+        if march == ''
+            error(('march not specified in the custom mcpu definition.'
+                   .format(march)))
         endif
+        march = '-march=' + march

-        if candidate_march != part_number_config['march']
-            warning('Configuration march version is @0@, not supported.'
-                    .format(part_number_config['march']))
-            if candidate_march != ''
-                warning('Using march version @0@.'.format(candidate_march))
-            endif
+        if not cc.has_argument(march)
+            error('Compiler does not support @0@.'.format(march))
         endif

-        if candidate_march != ''
-            candidate_march = '-march=' + candidate_march
-            foreach feature: march_features
-                if cc.has_argument('+'.join([candidate_march, feature]))
-                    candidate_march = '+'.join([candidate_march, feature])
-                else
-                    warning('The compiler does not support feature @0@'
-                        .format(feature))
-                endif
-            endforeach
-            machine_args += candidate_march
+        march_exts = mcpu_def.get('march_extensions', [])
+        foreach ext: march_exts
+            if cc.has_argument('+'.join([march, ext]))
+                march = '+'.join([march, ext])
+            else
+                error('Compiler does not support march extension @0@.'.format(ext))
+            endif
+        endforeach
+        machine_args += march
+    else
+        candidate_mcpu = '-mcpu=' + mcpu
+        if (cc.has_argument(candidate_mcpu))
+            machine_args += candidate_mcpu
+        else
+            error('Compiler does not support -mcpu=@0@.'.format(mcpu))
         endif
     endif

-    if candidate_mcpu == '' and candidate_march == ''
-        error('No suitable ARM march/mcpu version found.')
-    endif

     # apply supported compiler options
     if part_number_config.has_key('compiler_options')