Re: [RFA] legacy_[read/write]_register_gen

[Michael Snyder <msnyder@redhat.com>]

Andrew Cagney wrote:
> 
> > Simplest case -- say you want to have a pseudo-register that
> > mirrors the contents of a real register.
> >
> > static void
> > my_fetch_pseudo_register (int regnum)
> > {
> >   if (regnum == MY_MIRROR_REGNUM)
> >     {
> >       char buf[REGISTER_SIZE];
> >       regcache_read (MY_REAL_REGNUM, buf);
> >       regcache_write (MY_MIRROR_REGNUM, buf);
> >     }
> > }
> >
> > You can't do that unles legacy_write_register_bytes can address
> > the regcache location of your pseudo-register.
> 
> That should be implemented as:
> 
>         my_register_read (int regnum, ...)
>         {
>           if (regnum == MY_MIRROR_REGNUM)
>             regcache_read (MY_REAL_REGNUM, buf)
>           else
>             regcache_read (regnum, buf);
>         }
> 
> GDB no longer needs to have duplicated register values in the regcache.
> 
> Anyway, I have figured out why the change is needed.  You can end up
> with ``real'' registers in the [NUM_REGS .. NUM_REGS+NUM_PSEUDO_REGS)
> range.  This happens (at present still theory) when a register that
> isn't in the G packet is fetched.

Shall I check it in?