commit 34ef3b1602847bb7e1af4b7c0eb918dcdfcfea97
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Feb 13 00:01:52 2013 -0500

    	PR c++/55879
    	* semantics.c (cxx_bind_parameters_in_call): Undo DECL_BY_REFERENCE.

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 59a50f2..7d93d72 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -6512,6 +6512,15 @@ cxx_bind_parameters_in_call (const constexpr_call *old_call, tree t,
       if (i == 0 && DECL_CONSTRUCTOR_P (fun))
         goto next;
       x = get_nth_callarg (t, i);
+      if (parms && DECL_BY_REFERENCE (parms))
+	{
+	  /* cp_genericize made this a reference for argument passing, but
+	     we don't want to treat it like one for constexpr evaluation.  */
+	  gcc_assert (TREE_CODE (type) == REFERENCE_TYPE);
+	  gcc_assert (TREE_CODE (TREE_TYPE (x)) == REFERENCE_TYPE);
+	  type = TREE_TYPE (type);
+	  x = convert_from_reference (x);
+	}
       arg = cxx_eval_constant_expression (old_call, x, allow_non_constant,
 					  TREE_CODE (type) == REFERENCE_TYPE,
 					  non_constant_p, overflow_p);
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-invisiref1.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-invisiref1.C
new file mode 100644
index 0000000..e0ede73
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-invisiref1.C
@@ -0,0 +1,36 @@
+// PR c++/55879
+// { dg-do compile { target c++11 } }
+
+class CAddress
+{
+public:
+  constexpr CAddress(unsigned long begin) : m_Begin(begin) {}
+  constexpr CAddress(const CAddress &other) : m_Begin(other.m_Begin) {}
+
+private:
+  unsigned long m_Begin;
+};
+
+extern "C" char _lnkDDRRAM;
+/* internal compiler error on gcc 4.6.3 */
+const CAddress s_Memmap[2]
+{
+  {(unsigned long)&_lnkDDRRAM}, /* segmentation fault */
+  {0x40000000},
+};
+
+class CNested {
+public:
+  constexpr CNested(const CAddress primary)
+    : m_PrimaryBlock(primary) {}
+
+private:
+  CAddress m_PrimaryBlock;
+};
+
+/* internal compiler error on gcc 4.7.2 */
+const CNested s_taskDescriptions[2]
+{
+  {{0x42000000}},
+  {{0x43000000}},
+};