re PR tree-optimization/38826 (points-to result wrong for reads from call-clobbered vars)

2009-01-14  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/38826
	PR middle-end/38477
	* tree-ssa-structalias.c (emit_alias_warning): Emit the pointer
	initialization notes only if we actually emitted a warning.
	(intra_create_variable_infos): Add constraints for a result decl
	that is passed by hidden reference.
	(build_pred_graph): Mark all related variables non-direct on
	address-taking.

	* gcc.dg/Wstrict-aliasing-bogus-pta-1.c: New testcase.

From-SVN: r143374

gcc/ChangeLog

+2009-01-14  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/38826
+	PR middle-end/38477
+	* tree-ssa-structalias.c (emit_alias_warning): Emit the pointer
+	initialization notes only if we actually emitted a warning.
+	(intra_create_variable_infos): Add constraints for a result decl
+	that is passed by hidden reference.
+	(build_pred_graph): Mark all related variables non-direct on
+	address-taking.
+
 2009-01-14  Nick Clifton  <nickc@redhat.com>
 
 	* ira-conflicts.c: Include addresses.h for the definition of

gcc/testsuite/ChangeLog

+2009-01-14  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/38826
+	PR middle-end/38477
+	* gcc.dg/Wstrict-aliasing-bogus-pta-1.c: New testcase.
+
 2009-01-13  Sebastian Pop  <sebastian.pop@amd.com>
 
 	* gcc.dg/graphite/pr38786.c: Fix commit problem.

gcc/testsuite/gcc.dg/Wstrict-aliasing-bogus-pta-1.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -Wall" } */
+
+struct S { int *p; int *q; };
+
+void foo (struct S *);
+
+int bar (int b)
+{
+  struct S s;
+  int *p;
+  float f;
+  foo (&s);
+  if (b)
+    p = s.q;
+  else
+    p = (int *)&f;
+  return *p;
+}

gcc/tree-ssa-structalias.c

@@ -1129,6 +1129,8 @@ build_pred_graph (void)
 	}
       else if (rhs.type == ADDRESSOF)
 	{
+	  varinfo_t v;
+
 	  /* x = &y */
 	  if (graph->points_to[lhsvar] == NULL)
 	    graph->points_to[lhsvar] = BITMAP_ALLOC (&predbitmap_obstack);
@@ -1141,7 +1143,19 @@ build_pred_graph (void)
 	  /* Implicitly, *x = y */
 	  add_implicit_graph_edge (graph, FIRST_REF_NODE + lhsvar, rhsvar);
 
+	  /* All related variables are no longer direct nodes.  */
 	  RESET_BIT (graph->direct_nodes, rhsvar);
+	  v = get_varinfo (rhsvar);
+	  if (!v->is_full_var)
+	    {
+	      v = lookup_vi_for_tree (v->decl);
+	      do
+		{
+		  RESET_BIT (graph->direct_nodes, v->id);
+		  v = v->next;
+		}
+	      while (v != NULL);
+	    }
 	  bitmap_set_bit (graph->address_taken, rhsvar);
 	}
       else if (lhsvar > anything_id
@@ -4561,6 +4575,16 @@ intra_create_variable_infos (void)
 	}
     }
 
+  /* Add a constraint for a result decl that is passed by reference.  */
+  if (DECL_RESULT (cfun->decl)
+      && DECL_BY_REFERENCE (DECL_RESULT (cfun->decl)))
+    {
+      varinfo_t p, result_vi = get_vi_for_tree (DECL_RESULT (cfun->decl));
+
+      for (p = result_vi; p; p = p->next)
+        make_constraint_from (p, nonlocal_id);
+    }
+
   /* Add a constraint for the incoming static chain parameter.  */
   if (cfun->static_chain_decl != NULL_TREE)
     {
@@ -4735,7 +4759,7 @@ emit_alias_warning (tree ptr)
 {
   gimple use;
   imm_use_iterator ui;
-  unsigned warned = 0;
+  bool warned = false;
 
   FOR_EACH_IMM_USE_STMT (use, ui, ptr)
     {
@@ -4773,13 +4797,12 @@ emit_alias_warning (tree ptr)
 	  && !TREE_NO_WARNING (deref))
 	{
 	  TREE_NO_WARNING (deref) = 1;
-	  warning_at (gimple_location (use), OPT_Wstrict_aliasing,
-		      "dereferencing pointer %qD does break strict-aliasing "
-		      "rules", SSA_NAME_VAR (ptr));
-	  ++warned;
+	  warned |= warning_at (gimple_location (use), OPT_Wstrict_aliasing,
+				"dereferencing pointer %qD does break "
+				"strict-aliasing rules", SSA_NAME_VAR (ptr));
 	}
     }
-  if (warned > 0)
+  if (warned)
     {
       bitmap visited = BITMAP_ALLOC (NULL);
       emit_pointer_definition (ptr, visited);