Re: [dpdk-dev] [PATCH] build: use generic march on arm64 when using 'default' machine

[Bruce Richardson <bruce.richardson@intel.com>]

On Mon, Dec 24, 2018 at 01:56:27PM +0100, Luca Boccassi wrote:
> When building for generic distribution we need a stable baseline
> architecture, or depending on the build worker the result will vary.
> 
> Force the default flags if the user explicitly sets marchine=default
typo: marchine

> at configuration time.
> 
> Fixes: b1d48c41189a ("build: support ARM with meson")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Luca Boccassi <bluca@debian.org>
> ---
>  config/arm/meson.build | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/config/arm/meson.build b/config/arm/meson.build
> index dae55d6b2..fa21a2fd2 100644
> --- a/config/arm/meson.build
> +++ b/config/arm/meson.build
> @@ -6,6 +6,7 @@
>  march_opt = '-march=@0@'.format(machine)
>  
>  arm_force_native_march = false
> +arm_force_default_march = machine == 'default'

Do we need a new variable here? Given it only seems to be used once below,
I think just having the boolean expression directly in the if statement is
clearer. If you do keep the variable, suggest putting braces around the
comparison, otherwise at first glance it looks like a chained assignment
like you get in C e.g. x = y = 0;

>  
>  machine_args_generic = [
>  	['default', ['-march=armv8-a+crc+crypto']],
> @@ -105,7 +106,11 @@ else
>  	cmd_generic = ['generic', '', '', 'default', '']
>  	cmd_output = cmd_generic # Set generic by default
>  	machine_args = [] # Clear previous machine args
> -	if not meson.is_cross_build()
> +	if arm_force_default_march and not meson.is_cross_build()
> +		machine = impl_generic
> +		cmd_output = cmd_generic
> +		impl_pn = 'default'
> +	elif not meson.is_cross_build()
>  		# The script returns ['Implementer', 'Variant', 'Architecture',
>  		# 'Primary Part number', 'Revision']
>  		detect_vendor = find_program(join_paths(
> -- 
> 2.19.2
> 
With these comments, looks ok to me from a meson viewpoint. I think an ack
from the arm side would be good to get too though.

Acked-by: Bruce Richardson <bruce.richardson@intel.com>