diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1fa764086228..6bbf5c252f76 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+2008-10-14  Douglas Gregor  <doug.gregor@gmail.com>
+
+       PR c++/37553
+       * tree.c (build_type_attribute_qual_variant): Hash on the
+       unqualified type, and don't overwrite an existing
+       (type_hash_eq): Make the TYPE_NAME of the types significant, to
+       allow distinguishing between wchar_t and its underlying type. This
+       also means that we'll retain a little more typedef information.
+
 2008-10-14  Andrey Belevantsev  <abel@ispras.ru>
 	    Dmitry Melnik  <dm@ispras.ru>
 	    Dmitry Zhurikhin  <zhur@ispras.ru>
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 32773afccda2..e4f3da8c6fed 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2008-10-14  Douglas Gregor  <doug.gregor@gmail.com>
+
+       PR c++/37553
+       * g++.dg/ext/alias-canon2.C: New.
+
 2008-10-13  Jerry DeLisle  <jvdelisle@gcc.gnu.org
 
 	PR libfortran/37083
diff --git a/gcc/testsuite/g++.dg/ext/alias-canon2.C b/gcc/testsuite/g++.dg/ext/alias-canon2.C
new file mode 100644
index 000000000000..4833db852d33
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/alias-canon2.C
@@ -0,0 +1,36 @@
+// { dg-do compile }
+// PR c++/37553
+typedef unsigned int ui32;
+__extension__ typedef unsigned long long int ui64;
+
+typedef ui32 __attribute__ ((__may_alias__)) ui32a;
+typedef ui64 __attribute__ ((__may_alias__)) ui64a;
+
+union u_u32
+{
+  ui32a v;
+} __attribute__ ((__may_alias__));
+
+union u_u64
+{
+  ui64a v;
+  struct
+  {
+    union u_u32 lo32, hi32;
+  } u;
+} __attribute__ ((__may_alias__));
+
+void
+out_long (ui64 longVal)
+{
+  if ((*(union u_u64 *) &longVal).u.lo32.v < 0x10000000ul)
+    {
+      if ((ui32) ((*(union u_u64 *) &longVal).u.lo32.v) < 0x4000u)
+        {
+          /* do something useful */
+        }
+    }
+}
+
+void f(ui32 *) { }
+void f(ui32a *) { }
diff --git a/gcc/tree.c b/gcc/tree.c
index 33ab8b7078bd..b131a20875c5 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -3704,10 +3704,10 @@ build_type_attribute_qual_variant (tree ttype, tree attribute, int quals)
 	  return build_qualified_type (ttype, quals);
 	}
 
+      ttype = build_qualified_type (ttype, TYPE_UNQUALIFIED);
       ntype = build_distinct_type_copy (ttype);
 
       TYPE_ATTRIBUTES (ntype) = attribute;
-      set_type_quals (ntype, TYPE_UNQUALIFIED);
 
       hashcode = iterative_hash_object (code, hashcode);
       if (TREE_TYPE (ntype))
@@ -3746,12 +3746,11 @@ build_type_attribute_qual_variant (tree ttype, tree attribute, int quals)
 
       /* If the target-dependent attributes make NTYPE different from
 	 its canonical type, we will need to use structural equality
-	 checks for this qualified type. */
-      ttype = build_qualified_type (ttype, TYPE_UNQUALIFIED);
+	 checks for this type. */
       if (TYPE_STRUCTURAL_EQUALITY_P (ttype)
           || !targetm.comp_type_attributes (ntype, ttype))
 	SET_TYPE_STRUCTURAL_EQUALITY (ntype);
-      else
+      else if (TYPE_CANONICAL (ntype) == ntype)
 	TYPE_CANONICAL (ntype) = TYPE_CANONICAL (ttype);
 
       ttype = build_qualified_type (ntype, quals);
@@ -4585,7 +4584,9 @@ type_hash_eq (const void *va, const void *vb)
       || !attribute_list_equal (TYPE_ATTRIBUTES (a->type),
 				 TYPE_ATTRIBUTES (b->type))
       || TYPE_ALIGN (a->type) != TYPE_ALIGN (b->type)
-      || TYPE_MODE (a->type) != TYPE_MODE (b->type))
+      || TYPE_MODE (a->type) != TYPE_MODE (b->type)
+      || (TREE_CODE (a->type) != COMPLEX_TYPE 
+          && TYPE_NAME (a->type) != TYPE_NAME (b->type)))
     return 0;
 
   switch (TREE_CODE (a->type))