Re: RFC: [GUPC] UPC-related front-end changes

[Gary Funck <gary at intrepid dot com>]

On 07/01/11 22:42:55, Jakub Jelinek wrote:
> On Fri, Jul 01, 2011 at 11:31:45AM -0700, Gary Funck wrote:
> > @@ -2405,6 +2469,9 @@ struct GTY(()) tree_type_common {
> >    alias_set_type alias_set;
> >    tree pointer_to;
> >    tree reference_to;
> > +  /* UPC: for block-distributed arrays */
> > +  tree block_factor;
> > 
> 
> I think this is undesirable.  Using a single bit and looking
> it up in a hash table might be a better solution, the vast majority
> of the types aren't going to be UPC block distributed arrays.

Jakub, it is true that the vast majority of types will
not have a UPC blocking factor.  However, building a hash table
will be complicated by questions of the scope and lifetime
of the type that references the blocking factor in
a hash table.  Implementing the hash table sounds like
it might be quite a bit of work.

Is there precedent for this technique being used in other GCC front-ends?

Some other fields in a tree_type_common node
are also likely not used by very many types
(or in the case of the symtab info. are only used,
for example, if debug info. is being generated?):

  * attributes
  * reference_to
  * tree_type_symtab
  * name

Is there some way to use the language specific information hook?

    struct GTY(()) tree_type_with_lang_specific {
      struct tree_type_common common;
      /* Points to a structure whose details depend on the language in use.  */
      struct lang_type *lang_specific;
    };

- Gary