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Re: thumb2 support


>> Hello, I'm working with the BeagleBone and gcc-4.5.4 on Gentoo.  If I
>> try to compile the 3.6 kernel with CONFIG_THUMB2_KERNEL, I get:
>>
>> arch/arm/boot/compressed/head.S:127: Error: selected processor does
>> not support requested special purpose register -- `mrs r2,cpsr'
>> arch/arm/boot/compressed/head.S:134: Error: selected processor does
>> not support requested special purpose register -- `mrs r2,cpsr'
>> arch/arm/boot/compressed/head.S:136: Error: selected processor does
>> not support requested special purpose register -- `msr cpsr_c,r2'
>>
>> This post indicates that mainline gcc does not currently support thumb2:
>>
>> https://groups.google.com/d/msg/beagleboard/P52fgMDzp8A/vupzuh71vdYJ
>>
>> However, this indicates that thumb2 has been supported since 4.3:
>>
>> http://gcc.gnu.org/gcc-4.3/changes.html
>>
>> Can anyone clear this up?
>
> The errors are coming from an assembler file that is not part of the
> GCC sources.  Are those instructions valid for Thumb2?  I don't know.
> If they are valid, then the issue is with the assembler, which is not
> part of GCC; check the version of the GNU binutils that you have
> installed.  If those instructions are not valid, then you need to
> change your source.

Thanks Ian.  I'm using binutils-2.22-r1.  Do you happen to know which
version of binutils should support thumb2?

- Grant


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