Re: dwarf2 unwinding for i386

[Andrew Cagney <ac131313 at cygnus dot com>]

> On Mon, Jun 24, 2002 at 03:39:30PM +0200, Michal Ludvig wrote:
>
> > Hi all,
> > what do you think about adding dwarf2 unwinding (dwarf2cfi.c) to i386 
> > target? On x86-64 we are already using it for some time now and it seems 
> > to be quite stable. GCC folks are about to switch omit-frame-pointer on 
> > by default for i386 in a near future, but are waiting (as I understand 
> > it) for GDB to implement dwarf2 unwinding, so that the resulting code 
> > could be debugged. Can we make at least a testing branch with this 
> > support? Opinions? MarkK?
>
> If we do this, IMHO, we should support it for all architectures and not
> for just x86-64 and i386.  Everyone wins.
The theory is that it should be added here:

/* Using the PC, select a mechanism for unwinding a frame returning
   the previous frame.  The register unwind function should, on
   demand, initialize the ->context object.  */

static void
set_unwind_by_pc (CORE_ADDR pc, CORE_ADDR fp,
                  frame_register_unwind_ftype **unwind)
{
  if (!USE_GENERIC_DUMMY_FRAMES)
    /* Still need to set this to something.  The ``info frame'' code
       calls this function to find out where the saved registers are.
       Hopefully this is robust enough to stop any core dumps and
       return vaguely correct values..  */
    *unwind = frame_saved_regs_register_unwind;
  else if (PC_IN_CALL_DUMMY (pc, fp, fp))
    *unwind = generic_call_dummy_register_unwind;
  else
    *unwind = frame_saved_regs_register_unwind;
}

The i386 doesn't use generic dummy frames and targets need switch to 
generic_unwind_get_saved_register though :-(

Andrew