Re: [patch, nios2] Use "sstatus" as preferred name of r30

[Pedro Alves <palves at redhat dot com>]

Hi Sandra,

On 10/14/2013 02:08 AM, Sandra Loosemore wrote:
> Altera has requested that the register r30 disassemble using the 
> symbolic name "sstatus" rather than "ba". Both names are documented in 
> the Nios II processor reference handbook.
> 
> The binutils changes to support this are already checked in:
> https://sourceware.org/ml/binutils/2013-10/msg00211.html
> 
> I've also checked in this patch to make the corresponding changes to 
> GDB's lists of register names.

I think this means that GDB will no longer accept target descriptions
that used the old register name?

  /* Check any target description for validity.  */
  if (tdesc_has_registers (tdesc))
    {
      const struct tdesc_feature *feature;
      int valid_p;

      feature = tdesc_find_feature (tdesc, "org.gnu.gdb.nios2.cpu");
      if (feature == NULL)
	return NULL;

      tdesc_data = tdesc_data_alloc ();

      valid_p = 1;

      for (i = 0; i < NIOS2_NUM_REGS; i++)
	valid_p &= tdesc_numbered_register (feature, tdesc_data, i,
					    nios2_reg_names[i]);

      if (!valid_p)
	{
	  tdesc_data_cleanup (tdesc_data);
	  return NULL;
	}
    }


Not sure this is a good idea.  An older gdb against a newer gdbserver
will also not accept the target description for not finding "ba"
in the org.gnu.gdb.nios2.cpu feature.

If we want to change the description, then I think we should
do it with new alternative target descriptions and features instead.

But since this is a core register that GDB knows about, another option
would be to leave the "ba" spelling in the descriptions as it was,
and instead special case r30 in nios2_register_name.

-- 
Pedro Alves