Re: thumb2 support

[Michael Hope <michael dot hope at linaro dot org>]

On 11 October 2012 17:58, Grant <emailgrant@gmail.com> wrote:
>>> 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?

Hi Grant.  I'm pretty sure this was fixed by:

commit c0d796cf810a84f10703c0390f7b1c5887b837c9
Author: Nick Clifton <nickc@redhat.com>
Date:   Wed Jun 13 14:18:59 2012 +0000

        PR gas/12698
        * config/tc-arm.c (do_t_mrs): Do not require an m-profile
        architecure when assembling for all archiectures.
        (do_t_msr): Likewise.

which will be in the upcoming binutils 2.23.  Debian/Ubuntu carry this
as a patch on top of their 2.22.

-- Michael