Re: Register numbers on hppa64

[Randolph Chung <randolph at tausq dot org>]

> Well, the ppc64 situation was a real mess, because the GCC people
> screwed up, and used *their* internal mapping instead of the
> officially documented numbers defined in the ELF ABI for DWARF2, and
> this mapping was also used for GCC's exception handling info (which is
> based on DWARF2).  I'm not sure at all whether the issue has been
> resolved.
>
> For hppa64 the situation is much better since...

I thought one of the problems was that because the "dbx" and "dwarf" 
mappings in gcc are different, it would use the dbx mappings in debug 
info but the dwarf numbers elsewhere (e.g. for exception handling?). Is 
that an issue at all?

> > Any comments or suggestions on how to sort this out? Should I just 
> > change gdb to match what gcc outputs? Should we change gcc to match what 
> > gdb expects? (safer?)
>
> ...we (GDB) are the ones that screwed up.  Fortunately it's really
> easy to fix things.  We just need to provide the appropriate
> xxx_reg_to_regnum functions in the acrhitecture vector.

Right, this does work for gcc, but I wonder if I'm breaking HP compiler 
compatibility (which I cannot test...)

> Actually the fix seems to be partly implemented already: there's a
> #ifdeffed out hppa_dwarf_reg_to_regnum in hppa-linux-tdep.c.  I think
> it should be moved to hppa-tdep.c, and a 64-bit version should be
> created.  

I wrote that code... :) but I think it's actually wrong; for 32-bit we 
have a 1:1 mapping between what gcc outputs for "dbx" register numbers 
in dwarf debug mode and the gdb internal register numbering, so we 
shouldn't need this mapping function for 32-bit.

> Anyway, see i386-tdep.c for a complicated example of how
> registers are mapped differently for several debugging formats and
> executable formats.

I believe HP compilers for hppa64-hpux also use dwarf; I don't see where 
the register numbering is documented in the ABI. I can easily implement 
a hppa64_dwarf_reg_to_regnum method, but I need to know if all hppa64 
compilers have the same view of register numbers.

randolph