[OE-core] [PATCH V2] arch-arm: Do not add -march options for arm architecture along with -mcpu

[Richard Purdie]

On Wed, 2019-01-23 at 16:18 -0800, Khem Raj wrote:
> tune files which inherit the arch definitions already define
> appropriate
> -mcpu option, which is equivalent of right -march and -mtune
> combination
> and is preferred since gcc is getting stricter and stricter with
> option
> check semantics and can now find incompatible -march and -mcpu
> options
> better with every release. It does internal feature consistency check
> and if it finds out discrepency between what -mcpu would expand to as
> compared to -march it will flag the options to be incompatible, for
> naked eye it sounds wrong but gcc would translate -mcpu to a given
> -march internally and it might not match to what we set in these arch
> files.
> 
> The effects are quite subtle, where this can result in configure test
> failing to compile due to these incompatible options and a feature
> option getting disabled for a recipe for no reason.
> 
> e.g. with gcc9 which can now detect that -mcpu=cortex-a5 and
> -march=armv7-a are incompatible, many features in libstdc++ ends up
> disabled due to configure check failures e.g. size_t size, ptrdiff_t
> sizes, which inturn results in compiling libstdc++ with unwanted
> disabled features.
> 
> If user has machine definitions which do not inherit the arm tune
> files
> then they can still use the -march switch as such
> 
> Signed-off-by: Khem Raj <raj.khem at gmail.com>
> ---
> v2: Only delete -march if -mcpu is set

I suspect this might cause:

https://autobuilder.yoctoproject.org/typhoon/#/builders/46/builds/212

Cheers,

Richard