Re: How to configure a bi-arch PowerPC GCC?

[Sebastian Huber <sebastian.huber@embedded-brains.de>]

Hello Segher,

On 20/01/17 02:04, Segher Boessenkool wrote:
> Hi,
>
> On Thu, Jan 19, 2017 at 01:41:33PM +0100, Sebastian Huber wrote:
>> conftest.c:16:1: error: unrecognizable insn:
>>   }
>>   ^
>> (insn/f 22 21 23 2 (parallel [
>>              (set (reg/f:DI 1 1)
>>                  (plus:SI (reg/f:DI 1 1)
>>                      (const_int 16 [0x10])))
>>              (set (mem:BLK (reg/f:DI 1 1) [0  A8])
>>                  (const_int 0 [0]))
>>              (set (mem:BLK (reg/f:DI 1 1) [0  A8])
>>                  (const_int 0 [0]))
>>          ]) "conftest.c":16 -1
>>       (expr_list:REG_CFA_DEF_CFA (reg/f:DI 1 1)
>>          (nil)))
> This is stack_restore_tie, which requires TARGET_32BIT.
>
> It currently is only generated from rs6000_emit_stack_reset:
>
>    /* This blockage is needed so that sched doesn't decide to move
>       the sp change before the register restores.  */
>    if (DEFAULT_ABI == ABI_V4
>        || (TARGET_SPE_ABI
>            && info->spe_64bit_regs_used != 0
>            && info->first_gp_reg_save != 32))
>      return emit_insn (gen_stack_restore_tie (updt_reg_rtx, frame_reg_rtx,
>                                               GEN_INT (frame_off)));
>
> so you seem to have 64-bit ABI_V4?  I wonder how well tested that is,
> you are likely to run into more problems.  Either stack_restore_tie or
> the above code will need a tweak.

thanks for your help. I would had a hard time to figure this out myself.

I am flexible in terms of the ABI choice for the 64-bit PowerPC. I guess 
the ABI_ELFv2 is the way to go?

I had to provide SUBSUBTARGET_OVERRIDE_OPTIONS in rtems.h (in 
config/rs6000/) to set the ABI. The sysv4.h doesn't care about 
-mabi=elfv2. There seems to be some copy and paste in linux64.h and 
freebsd64.h for their SUBSUBTARGET_OVERRIDE_OPTIONS. Maybe the common 
stuff should move to sysv4.h?

-- 
Sebastian Huber, embedded brains GmbH

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