Re: RFC: Fix ARMv3 support

[Christophe Lyon <christophe dot lyon at linaro dot org>]

On 16 February 2016 at 18:19, Nick Clifton <nickc@redhat.com> wrote:
> Hi Richard, Hi Ramana,
>
>   The ARM backend has some problems compiling for the old ARMv3
>   architecture.  See:
>
>     https://gcc.gnu.org/bugzilla/show_bug.cgi?id=62254
>
>   for an example of this.  v3 is very old now, and I am not sure how
>   much interest there is in continuing to support it, but I am trying to
>   help reduce the gcc priority bug list, so here goes...
>
>   The attached patch fixes the problem, albeit not in a very subtle way.
>   The problem is that arm_reload_[out|in]_hi is being called for a
>   register->register move because the v3 architecture does not support
>   16-bit register moves.  Rather than trace the problem back to the real
>   source and fix it, I chose to just allow the reload functions to
>   generate an SImode register move instead.  Probably not the best
>   solution, but it appears to work.
>
>   The attached patch also includes the test cases derived from PR 62254
>   and PR 69610 (which is a duplicate of PR 62254).  Including all three
>   tests might be overkill, but it seemed like a good idea to be a little
>   bit paranoid, just in case.
>
>   Whilst testing the patch I also discovered that interworking is
>   enabled by default, which is a problem for v3 code generation, so I
>   added a fix to (silently) disable interworking if the target
>   architecture does not support Thumb instructions.
>
>   Any comments or criticisms before I apply the patch ?

Hi Nick,

Could you modify your new testcases, such that they call
check_effective_target_arm_arm_ok ?

Since you force -marm, you need to make sure that the target
cpu actually supports it.

I'm just realizing that we currently generate arm_arch_vX_ok
for X >=4 only. Maybe you should also add v3?

Thanks

Christophe.

>
> Cheers
>   Nick
>
> gcc/ChangeLog
> 2016-02-16  Nick Clifton  <nickc@redhat.com>
>
>         PR target/62554
>         PR target/69610
>         * config/arm/arm.c (arm_option_override_internal): Disable
>         interworking if the target does not support thumb instructions.
>         (arm_reload_in_hi): Handle the case where a register to register
>         move needs reloading because there is no simple pattern to handle
>         it.
>         (arm_reload_out_hi): Likewise.
>
> gcc/testsuite/ChangeLog
> 2016-02-16  Nick Clifton  <nickc@redhat.com>
>
>         PR target/62554
>         PR target/69610
>         * gcc.target/arm/pr62554.c: New test.
>         * gcc.target/arm/pr69610-1.c: New test.
>         * gcc.target/arm/pr69610-2.c: New test.
>