Re: [RFC] Use address_from_register in dwarf2-frame.c:read_addr_from_reg

["Maciej W. Rozycki" <macro@codesourcery.com>]

On Wed, 27 Aug 2014, Ulrich Weigand wrote:

> Andrew Pinski wrote:
> 
> > I think this patch broke MIPS64 n32 big-endian support.  We assert here:
> > gdb_assert (!gdbarch_convert_register_p (gdbarch, regnum, type));
> > 
> > The convert_register_p code for MIPS does:
> >   return (register_size (gdbarch, regnum) == 8
> >           && regnum % num_regs > 0 && regnum % num_regs < 32
> >           && TYPE_LENGTH (type) < 8);
> > 
> > 
> > Since the register size is 8 byte wide (MIPS64) and the type length is
> > 4 (pointer), we return true.  In MIPS64, the registers are stored
> > 64bits but pointers are 32bits.
> > 
> > Here is the code that is used by mips_register_to_value:
> >       int len = TYPE_LENGTH (type);
> >       CORE_ADDR offset;
> > 
> >       offset = gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG ? 8 - len : 0;
> >       if (!get_frame_register_bytes (frame, regnum, offset, len, to,
> >     optimizedp, unavailablep))
> > return 0;
> > 
> >       *optimizedp = *unavailablep = 0;
> >       return 1;
> 
> Huh, I wasn't aware of that conversion.  Note that for the register_to_value
> case, I don't actually see any difference to the default behavior; it's the
> value_to_register routine that's really special (because of the sign-extension
> in performs).
> 
> > Is there a way to fix this in a target neutral way?  (I might need a
> > way like this for AARCH64 ILP32 also).
> 
> I guess it isn't too hard to support gdbarch_convert_register_p in that
> routine as well; I just didn't have any target to test on.
> 
> Can you try whether something along the following lines works for you?

 I'll see if I can push it through testing, though it may take a few days 
as some of MIPS hardware I use (and especially 64-bit one) is slooow (and 
I already have a test run under way).

 I'd expect the issue to be consistent across all ILP32 64-bit ABIs BTW, 
that is e.g. x32 x86-64 as well.

  Maciej