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

[Michael Snyder <msnyder@redhat.com>]

Andrew Cagney wrote:
> 
> > These two functions need to be able to read/write
> > a pseudo-register as well as a real register.
> >
> > 2002-01-28  Michael Snyder  <msnyder@redhat.com>
> >
> > * regcache.c (legacy_read_register_gen): Need to be able to
> >       read pseudo-register as well as real register.
> >       (legacy_write_register_gen): Ditto.
> 
> Michael,
> 
> When is this occuring?  Dig dig, I've a similar patch sitting in my
> sand-pit so, hmm, I've also seen it but don't remember why :-(
> 
> Andrew

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.

> > Index: regcache.c
> > ===================================================================
> > RCS file: /cvs/src/src/gdb/regcache.c,v
> > retrieving revision 1.30
> > diff -c -3 -p -r1.30 regcache.c
> > *** regcache.c        2002/01/15 02:06:46     1.30
> > --- regcache.c        2002/01/29 01:02:29
> > *************** legacy_read_register_gen (int regnum, ch
> > *** 310,316 ****
> >   void
> >   regcache_read (int rawnum, char *buf)
> >   {
> > !   gdb_assert (rawnum >= 0 && rawnum < NUM_REGS);
> >     /* For moment, just use underlying legacy code. Ulgh!!! */
> >     legacy_read_register_gen (rawnum, buf);
> >   }
> > --- 310,316 ----
> >   void
> >   regcache_read (int rawnum, char *buf)
> >   {
> > !   gdb_assert (rawnum >= 0 && rawnum < (NUM_REGS + NUM_PSEUDO_REGS));
> >     /* For moment, just use underlying legacy code. Ulgh!!! */
> >     legacy_read_register_gen (rawnum, buf);
> >   }
> > *************** legacy_write_register_gen (int regnum, c
> > *** 369,375 ****
> >   void
> >   regcache_write (int rawnum, char *buf)
> >   {
> > !   gdb_assert (rawnum >= 0 && rawnum < NUM_REGS);
> >     /* For moment, just use underlying legacy code. Ulgh!!! */
> >     legacy_write_register_gen (rawnum, buf);
> >   }
> > --- 369,375 ----
> >   void
> >   regcache_write (int rawnum, char *buf)
> >   {
> > !   gdb_assert (rawnum >= 0 && rawnum < (NUM_REGS + NUM_PSEUDO_REGS));
> >     /* For moment, just use underlying legacy code. Ulgh!!! */
> >     legacy_write_register_gen (rawnum, buf);
> >   }
> >
> >
> >