[OE-core] [PATCH V3] arm-tunes: Remove -march option if mcpu is already added

[Mark Hatle]

I reviewed this patch set.  It looks good to me.  Moving to -mcpu makes sense,
as well as manually specifying the override feature info when necessary.

--Mark

On 1/28/19 4:56 AM, 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.
> 
> Signed-off-by: Khem Raj <raj.khem at gmail.com>
> ---
> v2: Only delete -march if -mcpu is set
> v3: Stop recursing into arch specific tunes