[OE-core] [PATCH] arch-armv7a.inc: default to Thumb2 instruction set for armv7a and above

[Khem Raj]

On Tue, May 22, 2018 at 5:58 AM,  <Jef.Driesen at niko.eu> wrote:
> Andre McCurdy wrote:
>> Although there may still be specific cases which can benefit from the
>> ARM instruction set, the Thumb2 instruction set is generally a better
>> default for armv7a class CPUs. Distros such as Debian and Fedora have
>> been targeting Thumb2 by default for some time.
>>
>> Note that setting ARM_INSTRUCTION_SET has no effect unless
>> TUNE_FEATURES contains "thumb" (which is controlled by the "t" suffix
>> in DEFAULTTUNE, e.g. armv7vehf-neon -vs- armv7vethf-neon, etc) so out
>> of tree machine configs may need to update their DEFAULTTUNE to take
>> advantage of this change.
>
> I recently ran into some major problems due to thumb vs arm. It turns out glibc doesn't support systems with thumb disabled anymore. See this bug report for details:
>
> https://sourceware.org/bugzilla/show_bug.cgi?id=23031
>
> This might be useful input for this discussion also.
>

Thanks, this would be useful for us to check if kernel defconfig does
not disable CONFIG_ARM_THUMB
on armv6t2+ regardless of this patch. This patch however will require
this option enabled too.