diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 92c47388f74..d30eeb775de 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,10 @@
+2015-05-27  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/66270
+	* tree.c (build_pointer_type_for_mode): Canonical type does not
+	inherit can_alias_all.
+	(build_reference_type_for_mode): Likewise.
+
 2015-05-24  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/66243
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9afe4489621..1923a2f2fba 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2015-05-27  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/66270
+	* g++.dg/ext/alias-canon3.C: New.
+
 2015-05-27  Richard Biener  <rguenther@suse.de>
 
 	PR tree-optimization/66272
diff --git a/gcc/testsuite/g++.dg/ext/alias-canon3.C b/gcc/testsuite/g++.dg/ext/alias-canon3.C
new file mode 100644
index 00000000000..22e29e8ad58
--- /dev/null
+++ b/gcc/testsuite/g++.dg/ext/alias-canon3.C
@@ -0,0 +1,12 @@
+// { dg-do compile }
+// PR c++/66270
+
+typedef float __m256 __attribute__ (( __vector_size__(32), __may_alias__ ));
+struct A {
+  __m256 ymm;
+  const float &f() const;
+};
+
+const float &A::f() const {
+  return ymm[1];
+}
diff --git a/gcc/tree.c b/gcc/tree.c
index c22fa765f4c..ca48c60dd10 100644
--- a/gcc/tree.c
+++ b/gcc/tree.c
@@ -7719,6 +7719,7 @@ build_pointer_type_for_mode (tree to_type, machine_mode mode,
 			     bool can_alias_all)
 {
   tree t;
+  bool could_alias = can_alias_all;
 
   if (to_type == error_mark_node)
     return error_mark_node;
@@ -7756,7 +7757,7 @@ build_pointer_type_for_mode (tree to_type, machine_mode mode,
 
   if (TYPE_STRUCTURAL_EQUALITY_P (to_type))
     SET_TYPE_STRUCTURAL_EQUALITY (t);
-  else if (TYPE_CANONICAL (to_type) != to_type)
+  else if (TYPE_CANONICAL (to_type) != to_type || could_alias)
     TYPE_CANONICAL (t)
       = build_pointer_type_for_mode (TYPE_CANONICAL (to_type),
 				     mode, false);
@@ -7786,6 +7787,7 @@ build_reference_type_for_mode (tree to_type, machine_mode mode,
 			       bool can_alias_all)
 {
   tree t;
+  bool could_alias = can_alias_all;
 
   if (to_type == error_mark_node)
     return error_mark_node;
@@ -7823,7 +7825,7 @@ build_reference_type_for_mode (tree to_type, machine_mode mode,
 
   if (TYPE_STRUCTURAL_EQUALITY_P (to_type))
     SET_TYPE_STRUCTURAL_EQUALITY (t);
-  else if (TYPE_CANONICAL (to_type) != to_type)
+  else if (TYPE_CANONICAL (to_type) != to_type || could_alias)
     TYPE_CANONICAL (t)
       = build_reference_type_for_mode (TYPE_CANONICAL (to_type),
 				       mode, false);