diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 676c1669298..0427a197503 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,8 @@
+2012-09-19  Marc Glisse  <marc.glisse@inria.fr>
+
+	PR c++/54581
+	* semantics.c (finish_decltype_type): Make vectors not opaque.
+
 2012-09-17  Jason Merrill  <jason@redhat.com>
 
 	PR c++/54575
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index db093e0b98d..1aa5a8b8b56 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -5312,6 +5312,11 @@ finish_decltype_type (tree expr, bool id_expression_or_member_access_p,
 	  cp_lvalue_kind clk = lvalue_kind (expr);
 	  type = unlowered_expr_type (expr);
 	  gcc_assert (TREE_CODE (type) != REFERENCE_TYPE);
+
+	  /* For vector types, pick a non-opaque variant.  */
+	  if (TREE_CODE (type) == VECTOR_TYPE)
+	    type = strip_typedefs (type);
+
 	  if (clk != clk_none && !(clk & clk_class))
 	    type = cp_build_reference_type (type, (clk & clk_rvalueref));
 	}
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index f02d15477e8..09c1d3fee7d 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2012-09-19  Marc Glisse  <marc.glisse@inria.fr>
+
+	PR c++/54581
+	* g++.dg/cpp0x/decltype-54581.C: New testcase.
+
 2012-09-19  Steve Ellcey  <sellcey@mips.com>
 
 	* gcc.target/mips/pr37362.c: Add mips*-mti-elf exception.
diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype-54581.C b/gcc/testsuite/g++.dg/cpp0x/decltype-54581.C
new file mode 100644
index 00000000000..5747e5c7ea6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/decltype-54581.C
@@ -0,0 +1,28 @@
+/* { dg-do compile } */
+/* { dg-options "-std=gnu++11 -Wall" } */
+
+typedef float v4f __attribute__((vector_size(4*sizeof(float))));
+
+template <class T> void eat (T&&) {}
+
+void test1 ()
+{
+  v4f x = {0,1,2,3};
+  typedef decltype (x < x) v4i;
+  v4i y = {4,5,6,7}; // v4i is not opaque
+  eat (y);
+}
+
+template<class V>
+void test2 ()
+{
+  V x = {0,1,2,3};
+  typedef decltype (x < x) v4i;
+  v4i y = {4,5,6,7}; // v4i is not opaque
+  eat (y);
+}
+
+int main(){
+  test1();
+  test2<v4f>();
+}