Hi Pavan,
> The compiler options march and mtune are a subset of mcpu and will lead to
> conflicts if improper march is chosen for a given mcpu.
> To avoid conflicts, force part number march when mcpu is available and is
> supported by the compiler.
Why would one force the march specified in the part number when mcpu for
that part number is also available and supported by the compiler?
>
> Example:
> march = armv9-a
> mcpu = neoverse-n2
>
> mcpu supported, march supported
> machine_args = ['-mcpu=neoverse-n2', '-march=armv9-a']
-march restricts the compiler to baseline architecture of the -mcpu.
For instance, Neoverse-n1's baseline architecture is armv8.2-a,
but it has some extensions from armv8.3-a, armv8.4-a, and armv8.5-a.
By setting -march to armv8.2-a the compiler will strictly omit extensions
from 8.3, 8.4 and 8.5 resulting in a suboptimal outcome.
>
> mcpu supported, march not supported
> machine_args = ['-mcpu=neoverse-n2']
This will result in the best outcome.
>
> mcpu not supported, march supported
> machine_args = ['-march=armv9-a']
This too may result in a suboptimal outcome as optimization space
is limited to the given march (not using extensions from later
architectures when available).
>
> mcpu not supported, march not supported
> machine_args = ['-march=armv8.6-a']
Compiler knows nothing about the target CPU or the architecture.
I think it's better to exit the build process with an error.
>
> Signed-off-by: Pavan Nikhilesh <pbhagavat...@marvell.com>
> ---
> v2 Changes:
> - Cleanup march inconsistencies. (Juraj Linkes)
> - Unify fallback march selection. (Juraj Linkes)
> - Tag along ARM WFE patch.
> v3 Changes:
> - Fix missing 'fallback_march' key check.
>
> config/arm/meson.build | 108 +++++++++++++++++++++++++---------------
> -
> 1 file changed, 66 insertions(+), 42 deletions(-)
>
> diff --git a/config/arm/meson.build b/config/arm/meson.build index
> 36f21d22599a..ba859bd060b5 100644
> --- a/config/arm/meson.build
> +++ b/config/arm/meson.build
> @@ -58,18 +58,18 @@ implementer_generic = { }
>
> part_number_config_arm = {
> - '0xd03': {'compiler_options': ['-mcpu=cortex-a53']},
> - '0xd04': {'compiler_options': ['-mcpu=cortex-a35']},
> - '0xd05': {'compiler_options': ['-mcpu=cortex-a55']},
> - '0xd07': {'compiler_options': ['-mcpu=cortex-a57']},
> - '0xd08': {'compiler_options': ['-mcpu=cortex-a72']},
> - '0xd09': {'compiler_options': ['-mcpu=cortex-a73']},
> - '0xd0a': {'compiler_options': ['-mcpu=cortex-a75']},
> - '0xd0b': {'compiler_options': ['-mcpu=cortex-a76']},
> + '0xd03': {'mcpu': 'cortex-a53'},
> + '0xd04': {'mcpu': 'cortex-a35'},
> + '0xd05': {'mcpu': 'cortex-a55'},
> + '0xd07': {'mcpu': 'cortex-a57'},
> + '0xd08': {'mcpu': 'cortex-a72'},
> + '0xd09': {'mcpu': 'cortex-a73'},
> + '0xd0a': {'mcpu': 'cortex-a75'},
> + '0xd0b': {'mcpu': 'cortex-a76'},
> '0xd0c': {
> 'march': 'armv8.2-a',
> 'march_features': ['crypto', 'rcpc'],
> - 'compiler_options': ['-mcpu=neoverse-n1'],
> + 'mcpu': 'neoverse-n1',
> 'flags': [
> ['RTE_MACHINE', '"neoverse-n1"'],
> ['RTE_ARM_FEATURE_ATOMICS', true], @@ -81,7 +81,7 @@
> part_number_config_arm = {
> '0xd40': {
> 'march': 'armv8.4-a',
> 'march_features': ['sve'],
> - 'compiler_options': ['-mcpu=neoverse-v1'],
> + 'mcpu': 'neoverse-v1',
> 'flags': [
> ['RTE_MACHINE', '"neoverse-v1"'],
> ['RTE_ARM_FEATURE_ATOMICS', true], @@ -92,8 +92,9 @@
> part_number_config_arm = {
> 'march': 'armv8.4-a',
> },
> '0xd49': {
> + 'march': 'armv9-a',
> 'march_features': ['sve2'],
> - 'compiler_options': ['-mcpu=neoverse-n2'],
> + 'mcpu': 'neoverse-n2',
> 'flags': [
> ['RTE_MACHINE', '"neoverse-n2"'],
> ['RTE_ARM_FEATURE_ATOMICS', true], @@ -127,21 +128,23 @@
> implementer_cavium = {
> ],
> 'part_number_config': {
> '0xa1': {
> - 'compiler_options': ['-mcpu=thunderxt88'],
> + 'mcpu': 'thunderxt88',
> 'flags': flags_part_number_thunderx
> },
> '0xa2': {
> - 'compiler_options': ['-mcpu=thunderxt81'],
> + 'mcpu': 'thunderxt81',
> 'flags': flags_part_number_thunderx
> },
> '0xa3': {
> - 'compiler_options': ['-march=armv8-a+crc', '-mcpu=thunderxt83'],
> + 'march': 'armv8-a',
> + 'march_features': ['crc'],
> + 'mcpu': 'thunderxt83',
> 'flags': flags_part_number_thunderx
> },
> '0xaf': {
> 'march': 'armv8.1-a',
> 'march_features': ['crc', 'crypto'],
> - 'compiler_options': ['-mcpu=thunderx2t99'],
> + 'mcpu': 'thunderx2t99',
> 'flags': [
> ['RTE_MACHINE', '"thunderx2"'],
> ['RTE_ARM_FEATURE_ATOMICS', true], @@ -153,7 +156,7 @@
> implementer_cavium = {
> '0xb2': {
> 'march': 'armv8.2-a',
> 'march_features': ['crc', 'crypto', 'lse'],
> - 'compiler_options': ['-mcpu=octeontx2'],
> + 'mcpu': 'octeontx2',
> 'flags': [
> ['RTE_MACHINE', '"cn9k"'],
> ['RTE_ARM_FEATURE_ATOMICS', true], @@ -176,7 +179,7 @@
> implementer_ampere = {
> '0x0': {
> 'march': 'armv8-a',
> 'march_features': ['crc', 'crypto'],
> - 'compiler_options': ['-mtune=emag'],
> + 'mcpu': 'emag',
> 'flags': [
> ['RTE_MACHINE', '"eMAG"'],
> ['RTE_MAX_LCORE', 32],
> @@ -186,7 +189,7 @@ implementer_ampere = {
> '0xac3': {
> 'march': 'armv8.6-a',
> 'march_features': ['crc', 'crypto'],
> - 'compiler_options': ['-mcpu=ampere1'],
> + 'mcpu': 'ampere1',
> 'flags': [
> ['RTE_MACHINE', '"AmpereOne"'],
> ['RTE_MAX_LCORE', 320], @@ -206,7 +209,7 @@
> implementer_hisilicon = {
> '0xd01': {
> 'march': 'armv8.2-a',
> 'march_features': ['crypto'],
> - 'compiler_options': ['-mtune=tsv110'],
> + 'mcpu': 'tsv110',
> 'flags': [
> ['RTE_MACHINE', '"Kunpeng 920"'],
> ['RTE_ARM_FEATURE_ATOMICS', true], @@ -695,11 +698,21 @@ if
> update_flags
>
> machine_args = [] # Clear previous machine args
>
> + candidate_mcpu = ''
> + if part_number_config.has_key('mcpu')
> + mcpu = part_number_config['mcpu']
> + if (cc.has_argument('-mcpu=' + mcpu))
> + candidate_mcpu = mcpu
> + endif
> + endif
> +
> # probe supported archs and their features
> candidate_march = ''
> if part_number_config.has_key('march')
> - if part_number_config.get('force_march', false)
> - candidate_march = part_number_config['march']
> + if part_number_config.get('force_march', false) or candidate_mcpu !=
> ''
> + if cc.has_argument('-march=' + part_number_config['march'])
> + candidate_march = part_number_config['march']
> + endif
> else
> supported_marchs = ['armv8.6-a', 'armv8.5-a', 'armv8.4-a',
> 'armv8.3-
> a',
> 'armv8.2-a', 'armv8.1-a', 'armv8-a'] @@
> -717,32 +730,43
> @@ if update_flags
> endif
> endforeach
> endif
> - if candidate_march == ''
> - error('No suitable armv8 march version found.')
> - endif
> +
> if candidate_march != part_number_config['march']
> - warning('Configuration march version is ' +
> - '@0@, but the compiler supports only @1@.'
> - .format(part_number_config['march'], candidate_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
> endif
> - candidate_march = '-march=' + candidate_march
>
> - 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']
> + if candidate_march == '' and candidate_mcpu == ''
> + error('No suitable ARM march/mcpu version found.')
> endif
> - 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))
> +
> + if candidate_march != ''
> + candidate_march = '-march=' + candidate_march
> + march_features = []
> + if part_number_config.has_key('march_features')
> + march_features += part_number_config['march_features']
> endif
> - endforeach
> - machine_args += candidate_march
> + if soc_config.has_key('extra_march_features')
> + march_features += soc_config['extra_march_features']
> + endif
> + 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
> + endif
> + endif
> +
> + if candidate_mcpu != ''
> + candidate_mcpu = '-mcpu=' + candidate_mcpu
> + machine_args += candidate_mcpu
> endif
>
> # apply supported compiler options
> --
> 2.43.0
