On Thu, May 04, 2017 at 05:54:47PM +0200, Richard Biener wrote:
> >2017-05-04 Jakub Jelinek <ja...@redhat.com>
> >
> > * tree.c (next_type_uid): Change type to unsigned.
> > (type_hash_canon): Decrement back next_type_uid if
> > freeing a type node with the highest TYPE_UID. For INTEGER_TYPEs
> > also ggc_free TYPE_MIN_VALUE, TYPE_MAX_VALUE and TYPE_CACHED_VALUES
> > if possible.
> >
> >--- gcc/tree.c.jj 2017-05-03 16:55:39.688052581 +0200
> >+++ gcc/tree.c 2017-05-03 18:49:30.662185944 +0200
> >@@ -151,7 +151,7 @@ static const char * const tree_node_kind
> > /* Unique id for next decl created. */
> > static GTY(()) int next_decl_uid;
> > /* Unique id for next type created. */
> >-static GTY(()) int next_type_uid = 1;
> >+static GTY(()) unsigned next_type_uid = 1;
> > /* Unique id for next debug decl created. Use negative numbers,
> > to catch erroneous uses. */
> > static GTY(()) int next_debug_decl_uid;
> >@@ -7188,6 +7188,19 @@ type_hash_canon (unsigned int hashcode,
> > {
> > tree t1 = ((type_hash *) *loc)->type;
> > gcc_assert (TYPE_MAIN_VARIANT (t1) == t1);
> >+ if (TYPE_UID (type) + 1 == next_type_uid)
> >+ --next_type_uid;
> >+ if (TREE_CODE (type) == INTEGER_TYPE)
> >+ {
> >+ if (TYPE_MIN_VALUE (type)
> >+ && TREE_TYPE (TYPE_MIN_VALUE (type)) == type)
> >+ ggc_free (TYPE_MIN_VALUE (type));
> >+ if (TYPE_MAX_VALUE (type)
> >+ && TREE_TYPE (TYPE_MAX_VALUE (type)) == type)
> >+ ggc_free (TYPE_MAX_VALUE (type));
> >+ if (TYPE_CACHED_VALUES_P (type))
> >+ ggc_free (TYPE_CACHED_VALUES (type));
> >+ }
> > free_node (type);
>
> Shouldn't free_node handle this? That said, is freeing min/max safe? The
> constants are shared after all.
The next_type_uid handling, I think it is better in type_hash_canon, the
only other user after all calls free_node in a loop, so it is highly
unlikely it would do anything there.
If you mean the INTEGER_TYPE handling, then yes, I guess it could be
done in free_node too and can move it there. If it was without
the && TREE_TYPE (TYPE_M*_VALUE (type)) == type extra checks, then it
is certainly unsafe and breaks bootstrap even, e.g. build_range_type
and other spots happily create INTEGER_TYPEs with min/max value that
have some other type. But when the type of the INTEGER_CSTs is the
type we are ggc_freeing, anything that would refer to those constants
afterwards would be necessarily broken (as their TREE_TYPE would be
ggc_freed, possibly reused for something completely unrelated).
Thus I think it should be safe even in the LTO case and thus doable
in free_node.
Jakub
