[llvm-dev] thumbv7 build errors "requires arm-mode"

[Steve King via llvm-dev]

On Thu, Nov 19, 2015 at 9:24 AM, Tim Northover <t.p.northover at gmail.com> wrote:
> Hi Steve,
>
> On 19 November 2015 at 08:59, Steve King via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>> After a recent upstream pull, my builds for ARM thumbv7 suddenly fail
>> with messages like:
>>
>> error: instruction requires: arm-mode
>>  21         uxtah   r6, r0, r6
>>
>> I use llc with -mtriple=thumbv7-unknown-unknown and llvm-mc with
>> -triple=thumbv7-unknown-unkown.
>>
>> What's the right way to generate thumbv7 binaries?
>
> We recently refactored how the triple generated a default CPU, and it
> seems support for uxtah was dropped from thumbv7. I suspect it's a
> bug, but I'll check with Bradley if it was intentional.
>
> Meanwhile, it should work again if you specify a CPU directly (e.g.
> -mcpu=cortex-a15 ought to support all the nice v7 bits).
>

Hi Tim, thanks for helping out.  For the record, what worked for me
was "clang --target=armv7m" and "llvm-mc -triple=armv7m".  I didn't
realize until today, but llc doesn't need an explicit command line
target since the .ll file provides that information
Thanks,
-steve