[Patch]: xcoff: fix 16 bit relative branches

[Richard Sandiford]

Hi Tristan,

Tristan Gingold <gingold@adacore.com> writes:
> now that tc-ppc.c uses bfd_reloc_type_lookup, xcoff needs to
> support BFD_RELOC_PPC_B16 and to support it correctly.
>
> I have added a small testcase, from a reproducer. Before the
> patch, gas crashes.  With the patch, the reproducer is correctly
> assembled and could be run on an AIX machine.

Sorry for the slow reply.  I'm not too confident about reviewing this stuff,
but we already use this reloc as:

  /* Special case some 16 bit reloc */
  if (15 == (internal->r_size & 0x1f))
    {
      if (R_BA == internal->r_type)
	relent->howto = &xcoff_howto_table[0x1c];
      else if (R_RBR == internal->r_type)
	relent->howto = &xcoff_howto_table[0x1d];
      else if (R_RBA == internal->r_type)
	relent->howto = &xcoff_howto_table[0x1e];
    }

Is it really the case that R_RBR is treated as a 4-byte relocation
even when r_rsize specifies a bitsize of 16?  There don't seem to be
any other entries where that's true, and it feels odd for R_RBR to
have different (byte) sizes from R_BA and R_RBA while having the
same bitsize.

I can try to check internally next week if there's any doubt.
Would be great if Alan could have a look too though...

Thanks,
Richard