diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index bf7518ea8a7..e4b074c8c4c 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,11 @@
+2009-08-12  Richard Guenther  <rguenther@suse.de>
+
+	* alias.c (get_alias_set): Honor TYPE_STRUCTURAL_EQUALITY_P.
+	* gimplify.c (gimplify_modify_expr): Do not use
+	lang_hooks.types_compatible_p.
+	* tree-ssa.c (useless_type_conversion_p): For aggregates
+	just return false if the canonical types differ.
+
 2009-08-12  Sebastian Pop  <sebastian.pop@amd.com>
 
 	PR middle-end/40980
diff --git a/gcc/alias.c b/gcc/alias.c
index 442be827a75..eaa127ec8e5 100644
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -680,11 +680,20 @@ get_alias_set (tree t)
     }
 
   /* Variant qualifiers don't affect the alias set, so get the main
-     variant.  Always use the canonical type as well.
-     If this is a type with a known alias set, return it.  */
+     variant.  */
   t = TYPE_MAIN_VARIANT (t);
-  if (TYPE_CANONICAL (t))
-    t = TYPE_CANONICAL (t);
+
+  /* Always use the canonical type as well.  If this is a type that
+     requires structural comparisons to identify compatible types
+     use alias set zero.  */
+  if (TYPE_STRUCTURAL_EQUALITY_P (t))
+    return 0;
+  t = TYPE_CANONICAL (t);
+  /* Canonical types shouldn't form a tree nor should the canonical
+     type require structural equality checks.  */
+  gcc_assert (!TYPE_STRUCTURAL_EQUALITY_P (t) && TYPE_CANONICAL (t) == t);
+
+  /* If this is a type with a known alias set, return it.  */
   if (TYPE_ALIAS_SET_KNOWN_P (t))
     return TYPE_ALIAS_SET (t);
 
diff --git a/gcc/gimplify.c b/gcc/gimplify.c
index dc8d0c089a4..eaea16df19c 100644
--- a/gcc/gimplify.c
+++ b/gcc/gimplify.c
@@ -4322,8 +4322,7 @@ gimplify_modify_expr (tree *expr_p, gimple_seq *pre_p, gimple_seq *post_p,
   /* Insert pointer conversions required by the middle-end that are not
      required by the frontend.  This fixes middle-end type checking for
      for example gcc.dg/redecl-6.c.  */
-  if (POINTER_TYPE_P (TREE_TYPE (*to_p))
-      && lang_hooks.types_compatible_p (TREE_TYPE (*to_p), TREE_TYPE (*from_p)))
+  if (POINTER_TYPE_P (TREE_TYPE (*to_p)))
     {
       STRIP_USELESS_TYPE_CONVERSION (*from_p);
       if (!useless_type_conversion_p (TREE_TYPE (*to_p), TREE_TYPE (*from_p)))
diff --git a/gcc/tree-ssa.c b/gcc/tree-ssa.c
index 97e15aeaef1..a40270335df 100644
--- a/gcc/tree-ssa.c
+++ b/gcc/tree-ssa.c
@@ -1102,17 +1102,12 @@ useless_type_conversion_p (tree outer_type, tree inner_type)
       return true;
     }
 
-  /* For aggregates we may need to fall back to structural equality
-     checks.  */
+  /* For aggregates we rely on TYPE_CANONICAL exclusively and require
+     explicit conversions for types involving to be structurally
+     compared types.  */
   else if (AGGREGATE_TYPE_P (inner_type)
 	   && TREE_CODE (inner_type) == TREE_CODE (outer_type))
-    {
-      if (TYPE_STRUCTURAL_EQUALITY_P (outer_type)
-	  || TYPE_STRUCTURAL_EQUALITY_P (inner_type))
-	return lang_hooks.types_compatible_p (inner_type, outer_type);
-
-      return false;
-    }
+    return false;
   
   return false;
 }