[dpdk-dev] [PATCH] build: add -moutline-atomics to default Arm build

[Thomas Monjalon]

09/10/2020 07:29, Ruifeng Wang:
> From: Thomas Monjalon <thomas at monjalon.net>
> > 01/10/2020 08:19, Juraj Linkeš:
> > > -moutline-atomics allows LSE instructions to be used if available when
> > > compiling for ARMv8.0 instruction set. It's enabled by default on
> > > newer compilers, such as gcc-10.1. Enable the option so that earlier
> > > compiler versions that support it but don't enable it by default build with it.
> > >
> > > Signed-off-by: Juraj Linkeš <juraj.linkes at pantheon.tech>
> > > ---
> > >  machine_args_generic = [
> > > -	['default', ['-march=armv8-a+crc']],
> > > +	['default', ['-march=armv8-a+crc', '-moutline-atomics']],
> > >  	['native', ['-march=native']],
> > >  	['0xd03', ['-mcpu=cortex-a53']],
> > >  	['0xd04', ['-mcpu=cortex-a35']],
> > 
> > Why is it added only to the target "default"?
> > 
> Because 'default' target generates Armv8.0 instruction set which doesn't include LSE extension. 
> The flag enables LSE instructions when code runs on platforms that implements LSE extension.
> 
> For other targets, machine specific 'mcpu' or 'march' flags are used. LSE extension availability can be inferred from the given flags.
> So there is not need to add '-moutline-atomics' to them. 

OK
It's not obvious that the -mcpu flags implicitly include it.
What do you think adding such explanation in a v2?