[PATCH] Fix PR37869, wrong points-to results

[Richard Guenther <rguenther at suse dot de>]

This fixes PR37869.  As analyzed by Danny a memory optimization in
the points-to solver has implementation issues which causes us
to compute empty points-to sets for random dereferenced pointers.

The following patch simply removes this optimization.  Fixing it
properly would need another intermediate bitmap, probably not
worth the trouble.

Bootstrapped and tested on x86_64-unknown-linux-gnu - ok for trunk?

Thanks,
Richard.

2008-11-25  Daniel Berlin  <dberlin@dberlin.org>
	Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/37869
	* tree-ssa-structalias.c (struct constraint_graph): Remove
	pt_used and number_incoming members.
	(build_pred_graph): Do not allocate them.
	(condense_visit): Do not use them.
	(label_visit): Likewise.
	(free_var_substitution_info): Do not free them.

Index: gcc/tree-ssa-structalias.c
===================================================================
*** gcc/tree-ssa-structalias.c	(revision 142204)
--- gcc/tree-ssa-structalias.c	(working copy)
*************** struct constraint_graph
*** 506,521 ****
       taken.  Used for variable substitution.  */
    bitmap address_taken;
  
-   /* True if points_to bitmap for this node is stored in the hash
-      table.  */
-   sbitmap pt_used;
- 
-   /* Number of incoming edges remaining to be processed by pointer
-      equivalence.
-      Used for variable substitution.  */
-   unsigned int *number_incoming;
- 
- 
    /* Vector of complex constraints for each graph node.  Complex
       constraints are those involving dereferences or offsets that are
       not 0.  */
--- 506,511 ----
*************** build_pred_graph (void)
*** 1101,1111 ****
    graph->points_to = XCNEWVEC (bitmap, graph->size);
    graph->eq_rep = XNEWVEC (int, graph->size);
    graph->direct_nodes = sbitmap_alloc (graph->size);
-   graph->pt_used = sbitmap_alloc (graph->size);
    graph->address_taken = BITMAP_ALLOC (&predbitmap_obstack);
-   graph->number_incoming = XCNEWVEC (unsigned int, graph->size);
    sbitmap_zero (graph->direct_nodes);
-   sbitmap_zero (graph->pt_used);
  
    for (j = 0; j < FIRST_REF_NODE; j++)
      {
--- 1091,1098 ----
*************** condense_visit (constraint_graph_t graph
*** 2008,2018 ****
  	      bitmap_ior_into (graph->points_to[n],
  			       graph->points_to[w]);
  	    }
- 	  EXECUTE_IF_IN_NONNULL_BITMAP (graph->preds[n], 0, i, bi)
- 	    {
- 	      unsigned int rep = si->node_mapping[i];
- 	      graph->number_incoming[rep]++;
- 	    }
  	}
        SET_BIT (si->deleted, n);
      }
--- 1995,2000 ----
*************** label_visit (constraint_graph_t graph, s
*** 2041,2061 ****
  
        /* Skip unused edges  */
        if (w == n || graph->pointer_label[w] == 0)
! 	{
! 	  graph->number_incoming[w]--;
! 	  continue;
! 	}
        if (graph->points_to[w])
  	bitmap_ior_into(graph->points_to[n], graph->points_to[w]);
- 
-       /* If all incoming edges to w have been processed and
- 	 graph->points_to[w] was not stored in the hash table, we can
- 	 free it.  */
-       graph->number_incoming[w]--;
-       if (!graph->number_incoming[w] && !TEST_BIT (graph->pt_used, w))
- 	{
- 	  BITMAP_FREE (graph->points_to[w]);
- 	}
      }
    /* Indirect nodes get fresh variables.  */
    if (!TEST_BIT (graph->direct_nodes, n))
--- 2023,2032 ----
  
        /* Skip unused edges  */
        if (w == n || graph->pointer_label[w] == 0)
! 	continue;
! 
        if (graph->points_to[w])
  	bitmap_ior_into(graph->points_to[n], graph->points_to[w]);
      }
    /* Indirect nodes get fresh variables.  */
    if (!TEST_BIT (graph->direct_nodes, n))
*************** label_visit (constraint_graph_t graph, s
*** 2067,2073 ****
  					       graph->points_to[n]);
        if (!label)
  	{
- 	  SET_BIT (graph->pt_used, n);
  	  label = pointer_equiv_class++;
  	  equiv_class_add (pointer_equiv_class_table,
  			   label, graph->points_to[n]);
--- 2038,2043 ----
*************** free_var_substitution_info (struct scc_i
*** 2193,2202 ****
    free (graph->loc_label);
    free (graph->pointed_by);
    free (graph->points_to);
-   free (graph->number_incoming);
    free (graph->eq_rep);
    sbitmap_free (graph->direct_nodes);
-   sbitmap_free (graph->pt_used);
    htab_delete (pointer_equiv_class_table);
    htab_delete (location_equiv_class_table);
    bitmap_obstack_release (&iteration_obstack);
--- 2163,2170 ----