[PATCH] Fix wrong-debug with i?86/x86_64 _GLOBAL_OFFSET_TABLE_ (PR debug/82630)

[Jakub Jelinek]

On Mon, Oct 23, 2017 at 09:48:50AM +0200, Richard Biener wrote:
> > --- gcc/targhooks.c.jj	2017-10-13 19:02:08.000000000 +0200
> > +++ gcc/targhooks.c	2017-10-20 14:26:07.945464025 +0200
> > @@ -177,6 +177,14 @@ default_legitimize_address_displacement
> >    return false;
> >  }
> >  
> > +bool
> > +default_const_not_ok_for_debug_p (rtx x)
> > +{
> > +  if (GET_CODE (x) == UNSPEC)
> 
> What about UNSPEC_VOLATILE?

This hook is called on the argument of CONST or SYMBOL_REF.
UNSPEC_VOLATILE can't appear inside of CONST, it wouldn't be CONST then.

UNSPEC appearing outside of CONST is rejected unconditionally in
mem_loc_descriptor:
...
    case UNSPEC:
...
      /* If delegitimize_address couldn't do anything with the UNSPEC, we
         can't express it in the debug info.  This can happen e.g. with some
         TLS UNSPECs.  */
      break;
and for UNSPEC_VOLATILE we just ICE, because var-tracking shouldn't let
those through:
    default:
      if (flag_checking)
        {
          print_rtl (stderr, rtl);
          gcc_unreachable ();
        }
      break;

	Jakub