re PR c++/27768 (wrong-code with vectors)

        PR c++/27768
        * tree-ssa-alias.c (compute_flow_insensitive_aliasing): Add
        may_aliases already in the tag's annotations to the bitmap.

From-SVN: r115062

gcc/ChangeLog

+2006-06-28  Jason Merrill  <jason@redhat.com>
+
+	PR c++/27768
+	* tree-ssa-alias.c (compute_flow_insensitive_aliasing): Add
+	may_aliases already in the tag's annotations to the bitmap.
+
 2006-06-28  Roger Sayle  <roger@eyesopen.com>
 
 	* genpreds.c (write_predicate_stmts) <IOR>: Add missing break.

gcc/testsuite/g++.dg/opt/alias4.C

+// PR c++/27768
+// Alias grouping was losing some may_aliases, causing us to think
+// the store to w.p was dead.
+
+// { dg-do run }
+// { dg-options "-O2" }
+
+int N = 1;
+
+struct VA
+{
+  int *p, *q, *r;
+
+  VA() : p(), q() {}
+  VA(const VA&) : p(), q() {}
+  ~VA() { if (p) --N; }
+};
+
+inline void foo(VA, VA, VA) {}
+
+struct VB
+{
+  VA va;
+
+  VB() {}
+
+  VB(const VB&)
+  {
+    va.p = new int(va.q - va.p);
+    va.r = va.p + (va.q - va.p);
+    foo(va, va, va);
+  }
+};
+
+struct VC : VB { char c; };
+struct V : VC {};
+
+struct WA
+{
+  struct X {};
+  X **p, **q, **r;
+
+  WA() : p() {}
+  ~WA() { if (p) --N; }
+};
+
+struct W : WA {};
+
+int main()
+{
+  {
+    V v, u(v);
+    W w;
+  }
+  return N;
+}

gcc/tree-ssa-alias.c

@@ -1162,6 +1162,7 @@ compute_flow_insensitive_aliasing (struct alias_info *ai)
       struct alias_map_d *p_map = ai->pointers[i];
       tree tag = var_ann (p_map->var)->symbol_mem_tag;
       var_ann_t tag_ann = var_ann (tag);
+      tree var;
 
       /* Call-clobbering information is not finalized yet at this point.  */
       if (PTR_IS_REF_ALL (p_map->var))
@@ -1170,11 +1171,15 @@ compute_flow_insensitive_aliasing (struct alias_info *ai)
       p_map->total_alias_vops = 0;
       p_map->may_aliases = BITMAP_ALLOC (&alias_obstack);
 
+      /* Add any pre-existing may_aliases to the bitmap used to represent
+	 TAG's alias set in case we need to group aliases.  */
+      for (j = 0; VEC_iterate (tree, tag_ann->may_aliases, j, var); ++j)
+	bitmap_set_bit (p_map->may_aliases, DECL_UID (var));
+
       for (j = 0; j < ai->num_addressable_vars; j++)
 	{
 	  struct alias_map_d *v_map;
 	  var_ann_t v_ann;
-	  tree var;
 	  bool tag_stored_p, var_stored_p;
 	  
 	  v_map = ai->addressable_vars[j];