Re: [PATCH 5/6] Indirect inlining of virtual calls

[Martin Jambor <mjambor@suse.cz>]

Hi,

On Mon, Feb 22, 2010 at 05:37:43PM +0100, Jan Hubicka wrote:
> > Index: icln/gcc/ipa-prop.c
> > ===================================================================
> > --- icln.orig/gcc/ipa-prop.c
> > +++ icln/gcc/ipa-prop.c
> > +/* Given that an actual argument is an SSA_NAME that is a result of a phi
> > +   statement PHI, try to find out whether NAME is in fact a
> > +   multiple-inheritance typecast from a descendant into an ancestor of a formal
> > +   parameter and thus can be described by an ancestor jump function and if so,
> > +   write the appropriate function into JFUNC.
> > +
> > +   Essentially we want to match the following pattern:
> > +
> > +     if (obj_2(D) != 0B)
> > +       goto <bb 3>;
> > +     else
> > +       goto <bb 4>;
> > +
> > +   <bb 3>:
> > +     iftmp.1_3 = &obj_2(D)->D.1762;
> > +
> > +   <bb 4>:
> > +     # iftmp.1_1 = PHI <iftmp.1_3(3), 0B(2)>
> > +     D.1879_6 = middleman_1 (iftmp.1_1, i_5(D));
> > +     return D.1879_6;  */
> 
> Hmm, fragile, but this is old code, right?

I don't understand.  This is what typecasting to a second-or-later
ancestor looks like (NULL for NULL, add offset otherwise).  The
function that builds ANCESTOR jump functions needs to match it.

> 
> > +/* Try to find a base info of BINFO that would have its field decl at offset
> > +   OFFSET within the BINFO type and which i of EXPECTED_TYPE.  If it can be
> > +   found, return, otherwise return NULL_TREE.  */
> 
> I guess stuff like this (supporting the overall devirtualization in
> gimple) should go into tree.c or similar common place.

OK, I've moved it there.

> It would be nice if someone C++ FE aware took a look on this.

Indeed.

Thanks,

Martin

> > +
> > +static tree
> > +get_binfo_at_offset (tree binfo, HOST_WIDE_INT offset, tree expected_type)
> > +{
> > +  tree type;
> > +
> > +  if (offset == 0)
> > +    return binfo;
> > +
> > +  type = TREE_TYPE (binfo);
> > +  while (offset > 0)
> > +    {
> > +      tree base_binfo, found_binfo;
> > +      HOST_WIDE_INT pos, size;
> > +      tree fld;
> > +      int i;
> > +
> > +      if (TREE_CODE (type) != RECORD_TYPE)
> > +	return NULL_TREE;
> > +
> > +      for (fld = TYPE_FIELDS (type); fld; fld = TREE_CHAIN (fld))
> > +	{
> > +	  if (TREE_CODE (fld) != FIELD_DECL)
> > +	    continue;
> > +
> > +	  pos = int_bit_position (fld);
> > +	  size = tree_low_cst (DECL_SIZE (fld), 1);
> > +	  if (pos <= offset && (pos + size) > offset)
> > +	    break;
> > +	}
> > +      if (!fld)
> > +	return NULL_TREE;
> > +
> > +      found_binfo = NULL_TREE;
> > +      for (i = 0; BINFO_BASE_ITERATE (binfo, i, base_binfo); i++)
> > +	if (TREE_TYPE (base_binfo) == TREE_TYPE (fld))
> > +	  {
> > +	    found_binfo = base_binfo;
> > +	    break;
> > +	  }
> > +
> > +      if (!found_binfo)
> > +	return NULL_TREE;
> > +
> > +      type = TREE_TYPE (fld);
> > +      binfo = found_binfo;
> > +      offset -= pos;
> > +    }
> > +  if (type != expected_type)
> > +    return NULL_TREE;
> > +  return binfo;
> > +}
> > +
> 
> Patch is OK for pretty-ipa.
> 
> Honza