On Tue, Jan 05, 2021 at 02:17:44PM -0800, David Christensen wrote:

quoted

quoted

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 <redacted>
---
  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

From looking at the patch, setting the "platform" to "native", or the
instruction_set to "native" should do this.
While I consider generic builds a good thing, I wonder if there is an
expectation that "native" is always the default build type for DPDK builds?

/Bruce