Re: [PATCH] Fix for gdb.base/pc-fp.exp.

[Luis Machado <lgustavo@codesourcery.com>]

On 08/23/2016 11:17 AM, Carl E. Love wrote:
> On Tue, 2016-08-23 at 00:17 +0100, Pedro Alves wrote:
>> Can you provide more details?
>>
>> E.g.:
>>
>> What's was wrong?  What failed?  Why is removing this line the
>> right fix?
>>
>> I'm not suggesting that the fix is wrong (or right, I have no
>> idea).  Just pointing out that context is missing.
>>
>> Thanks,
>> Pedro Alves
>>
>
>
>
> Here is an updated patch with the missing detail.
> --------------------------------------------------------------------------
> Fix for gdb.base/pc-fp.exp.
>
> It is my understanding that GDB used to require each architecture to
> define a Frame Pointer (fp).  However, this functionality was deprecated
> some time ago so the call to setup the fp_reg was changed to deprecated
> (set_gdbarch_deprecated_fp_regnum).  It should have been removed from the
> Power code.
>
> That said, the code "set_gdbarch_deprecated_fp_regnum
> (gdbarch, PPC_R0_REGNUM + 1);" sets up register r1 as the frame pointer.
> Register r1 is no longer used to hold the frame pointer on Power.  By
> removing the fp definition for Power in GDB, it causes GDB to fall back
> to the call get_frame_base_address (frame) which returns the correct value
> depending on the specific senario but most of the time is the DWARF
> canonical frame address.

Is this the case for all Power ABI's or only server? I wonder what the 
impact would be on Power embedded.