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

["Juraj Linkeš" <juraj.linkes@pantheon.tech>]

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
 
-dpdk_conf.set('RTE_MACHINE', machine)
+dpdk_conf.set('RTE_MACHINE', cpu_instruction_set)
 machine_args = []
 
 # ppc64 does not support -march= at all, use -mcpu and -mtune for that
 if host_machine.cpu_family().startswith('ppc')
-	machine_args += '-mcpu=' + machine
-	machine_args += '-mtune=' + machine
+	machine_args += '-mcpu=' + cpu_instruction_set
+	machine_args += '-mtune=' + cpu_instruction_set
 else
-	machine_args += '-march=' + machine
+	machine_args += '-march=' + cpu_instruction_set
 endif
 
 toolchain = cc.get_id()
diff --git a/devtools/test-meson-builds.sh b/devtools/test-meson-builds.sh
index 7280b7a93..33845d998 100755
--- a/devtools/test-meson-builds.sh
+++ b/devtools/test-meson-builds.sh
@@ -211,11 +211,12 @@ done
 # test compilation with minimal x86 instruction set
 # Set the install path for libraries to "lib" explicitly to prevent problems
 # with pkg-config prefixes if installed in "lib/x86_64-linux-gnu" later.
-default_machine='nehalem'
-if ! check_cc_flags "-march=$default_machine" ; then
-	default_machine='corei7'
+default_isa='nehalem'
+if ! check_cc_flags "-march=$default_isa" ; then
+	default_isa='corei7'
 fi
-build build-x86-default cc -Dlibdir=lib -Dmachine=$default_machine $use_shared
+build build-x86-default cc -Dlibdir=lib -Dcpu_instruction_set=$default_isa \
+      $use_shared
 
 # 32-bit with default compiler
 if check_cc_flags '-m32' ; then
diff --git a/meson_options.txt b/meson_options.txt
index e384e6dbb..9db03a87d 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -1,5 +1,7 @@
 # Please keep these options sorted alphabetically.
 
+option('cpu_instruction_set', type: 'string', value: 'auto',
+	description: 'Set the target machine ISA (instruction set architecture)/')
 option('disable_drivers', type: 'string', value: '',
 	description: 'Comma-separated list of drivers to explicitly disable.')
 option('drivers_install_subdir', type: 'string', value: 'dpdk/pmds-<VERSION>',
@@ -20,14 +22,16 @@ option('kernel_dir', type: 'string', value: '',
 	description: 'Path to the kernel for building kernel modules. Headers must be in $kernel_dir/build. Modules will be installed in $DEST_DIR/$kernel_dir/extra/dpdk.')
 option('lib_musdk_dir', type: 'string', value: '',
 	description: 'path to the MUSDK library installation directory')
-option('machine', type: 'string', value: 'native',
-	description: 'set the target machine type')
+option('machine', type: 'string', value: 'auto',
+	description: 'set the target machine type/ISA')
 option('max_ethports', type: 'integer', value: 32,
 	description: 'maximum number of Ethernet devices')
 option('max_lcores', type: 'integer', value: 128,
 	description: 'maximum number of cores/threads supported by EAL')
 option('max_numa_nodes', type: 'integer', value: 4,
 	description: 'maximum number of NUMA nodes supported by EAL')
+option('platform', type: 'string', value: 'generic',
+	description: 'Platform to build for, either "native" or "generic".')
 option('enable_trace_fp', type: 'boolean', value: false,
 	description: 'enable fast path trace points.')
 option('tests', type: 'boolean', value: true,
-- 
2.20.1