Re: [Patch]: xcoff: fix 16 bit relative branches

[Tristan Gingold <gingold at adacore dot com>]

On Jul 17, 2013, at 1:45 PM, Richard Sandiford wrote:

> Hi Tristan,
> 
> Sorry for the very slow response.  Hope it doesn't put you off fixing
> more of this stuff.  The patches are very welcome. :-)
> 
> Tristan Gingold <gingold@adacore.com> writes:
>>> 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 think that currently many entries of xcoff_howto_table have
>> junk values.  Some comments are even misleading (eg: R_RBA is
>> not a relative branch).  I plan to fix that later, but currently
>> I just want to have gas + ld in a working shape.
> 
> It looks like the current size of 1 is right in this case though.
> I just tried:
> 
> 	.extern	c
> 	bne	c
> 
> with the AIX assembler and got:
> 
>             Vaddr      Symndx  Sign  Fixup     Len      Type  Name
> .text:
>        0x00000002  0x00000002     1      0  0x000f  Brn_Selx  c
> 
> whereas gas with the patch gives:
> 
>             Vaddr      Symndx  Sign  Fixup     Len      Type  Name
> .text:
>        0x00000000  0x00000002     1      0  0x000f  Brn_Selx  c
> 
> (of course, gas without the patch aborts...)
> 
> So AIX as does put the reloc against the 16-bit field rather than the full
> instruction, which is what I'd naively have expected from a 16-bit rsize.

So you right.  Point taken :-)  I will rework this patch.

Thanks,
Tristan.