Re: [dpdk-dev] [RFC PATCH v2] build: add platform meson option

[David Christensen <drc@linux.vnet.ibm.com>]

>> The current meson option 'machine' should only specify the ISA, which is not
>> sufficient for Arm, where setting ISA implies other setting as well.
>> Add a new meson option, 'platform', which differentiates the type of the build
>> (native/generic) and sets machine accordingly, unless the user chooses to
>> override it.
>> The 'machine' option also doesn't describe very well what it sets, so introduce a
>> new option 'cpu_instruction_set', but keep 'machine' for backward
>> compatibility.
>> These two new variables, taken together, achieve what 'machine' was setting
>> per architecture - setting the ISA in x86 build and setting native/default 'build
>> type' in aarch64 build - is now properly being set for all architectures in a
>> uniform manner.
>>
>> Signed-off-by: Juraj Linkeš <juraj.linkes@pantheon.tech>
>> ---
>>   config/arm/meson.build        |  4 +--
>>   config/meson.build            | 47 +++++++++++++++++++++++++----------
>>   devtools/test-meson-builds.sh |  9 ++++---
>>   meson_options.txt             |  8 ++++--
>>   4 files changed, 47 insertions(+), 21 deletions(-)
>>
>> diff --git a/config/arm/meson.build b/config/arm/meson.build index
>> 42b4e43c7..6b09a74a7 100644
>> --- a/config/arm/meson.build
>> +++ b/config/arm/meson.build
>> @@ -3,10 +3,10 @@
>>   # Copyright(c) 2017 Cavium, Inc
>>
>>   # for checking defines we need to use the correct compiler flags -march_opt = '-
>> march=@0@'.format(machine)
>> +march_opt = '-march=@0@'.format(cpu_instruction_set)
>>
>>   arm_force_native_march = false
>> -arm_force_default_march = (machine == 'default')
>> +arm_force_default_march = (platform == 'generic')
>>
>>   flags_common_default = [
>>   	# Accelarate rte_memcpy. Be sure to run unit test
>> (memcpy_perf_autotest) diff --git a/config/meson.build b/config/meson.build
>> index a3154e29c..647116513 100644
>> --- a/config/meson.build
>> +++ b/config/meson.build
>> @@ -63,42 +63,63 @@ if not is_windows
>>   			pmd_subdir_opt)
>>   endif
>>
>> -# set the machine type and cflags for it
>> +platform = get_option('platform')
>> +
>> +# set the cpu_instruction_set type and cflags for it
>>   if meson.is_cross_build()
>> -	machine = host_machine.cpu()
>> +	cpu_instruction_set = host_machine.cpu()
>>   else
>> -	machine = get_option('machine')
>> +	cpu_instruction_set = get_option('cpu_instruction_set')
>> +	if get_option('machine') != 'auto'
>> +		warning('The "machine" option is deprecated. ' +
>> +		        'Please use "cpu_instruction_set" instead.')
>> +		if cpu_instruction_set != 'auto'
>> +			error('Setting both "machine" and ' +
>> +			      '"cpu_instruction_set" is unsupported.')
>> +		endif
>> +		cpu_instruction_set = get_option('machine')
>> +	endif
>> +endif
>> +
>> +if platform == 'native'
>> +	if cpu_instruction_set == 'auto'
>> +		cpu_instruction_set = 'native'
>> +	endif
>> +elif platform == 'generic'
>> +	if cpu_instruction_set == 'auto'
>> +		cpu_instruction_set = 'default'
>> +	endif
>>   endif
>>
>> -# machine type 'default' is special, it defaults to the per arch agreed common
>> +if cpu_instruction_set == 'default'
>> +# cpu_instruction_set type 'default' is special, it defaults to the per
>> +arch agreed common
>>   # minimal baseline needed for DPDK.
>>   # That might not be the most optimized, but the most portable version while  #
>> still being able to support the CPU features required for DPDK.
>>   # This can be bumped up by the DPDK project, but it can never be an  # invariant
>> like 'native'
>> -if machine == 'default'
>>   	if host_machine.cpu_family().startswith('x86')
>>   		# matches the old pre-meson build systems default
>> -		machine = 'corei7'
>> +		cpu_instruction_set = 'corei7'
>>   	elif host_machine.cpu_family().startswith('arm')
>> -		machine = 'armv7-a'
>> +		cpu_instruction_set = 'armv7-a'
>>   	elif host_machine.cpu_family().startswith('aarch')
>>   		# arm64 manages defaults in config/arm/meson.build
>> -		machine = 'default'
>> +		cpu_instruction_set = 'default'
>>   	elif host_machine.cpu_family().startswith('ppc')
>> -		machine = 'power8'
>> +		cpu_instruction_set = 'power8'
>>   	endif
>>   endif

This change forces the build on a P9 system to use the P8 instruction 
set.  Prior to this change the "native" machine type was used which 
resulted in P9 instructions when built on a P9 system.  How do I force 
the build to use the power9 instruction set in this case?

Dave