[PATCH 07/13] OpenACC 2.6 deep copy: libgomp parts

[Julian Brown]

On Wed, 20 May 2020 16:52:02 +0200
Thomas Schwinge <thomas@codesourcery.com> wrote:

> Hi!
> 
> On 2019-12-17T22:03:47-0800, Julian Brown <julian@codesourcery.com>
> wrote:
> > --- a/libgomp/oacc-mem.c
> > +++ b/libgomp/oacc-mem.c  
> 
> >  static int
> > -find_group_last (int pos, size_t mapnum, unsigned short *kinds)
> > +find_group_last (int pos, size_t mapnum, size_t *sizes, unsigned
> > short *kinds) {
> >    unsigned char kind0 = kinds[pos] & 0xff;
> > -  int first_pos = pos, last_pos = pos;
> > +  int first_pos = pos;
> >  
> > -  if (kind0 == GOMP_MAP_TO_PSET)
> > +  switch (kind0)
> >      {
> > +    case GOMP_MAP_TO_PSET:
> >        while (pos + 1 < mapnum && (kinds[pos + 1] & 0xff) ==
> > GOMP_MAP_POINTER)
> > -	last_pos = ++pos;
> > +	pos++;
> >        /* We expect at least one GOMP_MAP_POINTER after a
> > GOMP_MAP_TO_PSET.  */
> > -      assert (last_pos > first_pos);
> > -    }
> > -  else
> > -    {
> > +      assert (pos > first_pos);
> > +      break;
> > +
> > +    case GOMP_MAP_STRUCT:
> > +      pos += sizes[pos];
> > +      break;
> > +
> > +    case GOMP_MAP_POINTER:
> > +    case GOMP_MAP_ALWAYS_POINTER:
> > +      /* These mappings are only expected after some other
> > mapping.  If we
> > +	 see one by itself, something has gone wrong.  */
> > +      gomp_fatal ("unexpected mapping");
> > +      break;
> > +
> > +    default:
> >        /* GOMP_MAP_ALWAYS_POINTER can only appear directly after
> > some other mapping.  */
> > -      if (pos + 1 < mapnum
> > -	  && (kinds[pos + 1] & 0xff) == GOMP_MAP_ALWAYS_POINTER)
> > -	return pos + 1;
> > +      if (pos + 1 < mapnum)
> > +	{
> > +	  unsigned char kind1 = kinds[pos + 1] & 0xff;
> > +	  if (kind1 == GOMP_MAP_ALWAYS_POINTER)
> > +	    return pos + 1;
> > +	}
> >  
> > -      /* We can have one or several GOMP_MAP_POINTER mappings
> > after a to/from
> > +      /* We can have zero or more GOMP_MAP_POINTER mappings after
> > a to/from (etc.) mapping.  */
> >        while (pos + 1 < mapnum && (kinds[pos + 1] & 0xff) ==
> > GOMP_MAP_POINTER)
> > -	last_pos = ++pos;
> > +	pos++;
> >      }
> >  
> > -  return last_pos;
> > +  return pos;
> >  }  
> 
> So this now causes grouped (!) mapping of all of 'GOMP_MAP_STRUCT',
> that is, all its "members" at once.
> 
> This, I suppose, mandated the removal of (some of) the
> 'is_tgt_unmapped' checking (unfortunately committed not here, but as
> part of r279621 "OpenACC reference count overhaul"), where we had
> unmapping code (conceptually) similar to:
> 
>     bool is_tgt_unmapped = gomp_remove_var (acc_dev, n);
>     assert (is_tgt_unmapped);
> 
> I'd introduced this a little bit earlier, finding this a simple yet
> effective run-time, low-overhead consistency checking of (certain
> aspects of) reference counting -- so just noting here that it's
> somewhat bad that we can't have this anymore "just" because of
> 'GOMP_MAP_STRUCT'.  (Maybe there is a way to get it back; that's for
> later?)

I'm actually looking at this now as part of revisiting the refcounting
work. I'm seeing what I can come up with in terms of being able to keep
the runtime test (and fixing the other part you mentioned).

Thanks,

Julian