http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56113
--- Comment #10 from rguenther at suse dot de <rguenther at suse dot de> 2013-01-29 09:52:12 UTC --- On Mon, 28 Jan 2013, steven at gcc dot gnu.org wrote: > > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56113 > > --- Comment #9 from Steven Bosscher <steven at gcc dot gnu.org> 2013-01-28 > 23:34:36 UTC --- > (In reply to comment #7) > > With the patch from comment #7: > > n=1000 6.18user 254976k maxresident > n=2000 16.76user 509184k maxresident > n=4000 54.23user 1432576l maxresident > n=8000 201.31user 1343296k maxresident > > Without: > n=1000 6.45user 255616k maxresident > n=2000 17.65user 572096k maxresident > n=4000 55.10user 1485184k maxresident > n=8000 199.49user 1456000k maxresident > > So there appears to be some small effect on memory footprint but > nothing to get excited about, and no effect on compile time. Yeah, I sort-of expected that ... the following should help more (apart from the fact that we do not optimize the visiting order to minimize the number of life bitmaps). I was thinking of sth like the following - but this of course leaves the equiv hashtable pointing to freed bitmaps ... As finding all equivalences of U recursive-preds (n) for all nodes n is the goal there doesn't seem to be a good way of avoiding the excessive memory use (we can free those that get their pointer_label shared - but that should be the minority). I'm out of ideas - apart from killing this whole unification on the base that it cannot be very effective. Index: gcc/tree-ssa-structalias.c =================================================================== --- gcc/tree-ssa-structalias.c (revision 195530) +++ gcc/tree-ssa-structalias.c (working copy) @@ -507,6 +507,10 @@ struct constraint_graph /* Explicit predecessors of each node (Used for variable substitution). */ bitmap *preds; + /* Number of nodes this is in their preds (used to track lifetime of + points_to). */ + unsigned *n_pred_of; + /* Indirect cycle representatives, or -1 if the node has no indirect cycles. */ int *indirect_cycles; @@ -2112,10 +2116,14 @@ label_visit (constraint_graph_t graph, s /* Skip unused edges */ if (w == n || graph->pointer_label[w] == 0) - continue; - - if (graph->points_to[w]) + ; + else bitmap_ior_into(graph->points_to[n], graph->points_to[w]); + + /* If we were the last unvisited successor of w free + its points-to set. */ + if (--graph->n_pred_of[w] == 0 && w != n) + BITMAP_FREE (graph->points_to[w]); } /* Indirect nodes get fresh variables. */ if (!bitmap_bit_p (graph->direct_nodes, n)) @@ -2133,6 +2141,10 @@ label_visit (constraint_graph_t graph, s } graph->pointer_label[n] = label; } + + /* If n has itself as predecessor we delayed freeing points_to. */ + if (graph->n_pred_of[n] == 0) + BITMAP_FREE (graph->points_to[n]); } /* Perform offline variable substitution, discovering equivalence @@ -2159,12 +2171,26 @@ perform_var_substitution (constraint_gra if (!bitmap_bit_p (si->visited, si->node_mapping[i])) condense_visit (graph, si, si->node_mapping[i]); + /* Count the number of nodes a node is predecessor of. */ + graph->n_pred_of = XCNEWVEC (unsigned, graph->size); + for (i = 0; i < graph->size; i++) + { + bitmap_iterator bi; + unsigned int j; + if (si->node_mapping[i] != i) + continue; + EXECUTE_IF_IN_NONNULL_BITMAP (graph->preds[i], 0, j, bi) + graph->n_pred_of[si->node_mapping[j]]++; + } + bitmap_clear (si->visited); /* Actually the label the nodes for pointer equivalences */ for (i = 0; i < FIRST_REF_NODE; i++) if (!bitmap_bit_p (si->visited, si->node_mapping[i])) label_visit (graph, si, si->node_mapping[i]); + free (graph->n_pred_of); + /* Calculate location equivalence labels. */ for (i = 0; i < FIRST_REF_NODE; i++) {
