PR c++/71896 - constexpr pointer-to-member comparison.

	* constexpr.c (cxx_eval_binary_expression): Handle comparison
	between lowered and unlowered PTRMEM_CST.

From-SVN: r238562

gcc/cp/ChangeLog

 2016-07-21  Jason Merrill  <jason@redhat.com>
 
+	PR c++/71896
+	* constexpr.c (cxx_eval_binary_expression): Handle comparison
+	between lowered and unlowered PTRMEM_CST.
+
 	PR c++/65168
 	* typeck.c (cp_truthvalue_conversion): Compare pointers to nullptr.
 	Don't set c_inhibit_evaluation_warnings.

gcc/cp/constexpr.c

@@ -1838,6 +1838,10 @@ cxx_eval_binary_expression (const constexpr_ctx *ctx, tree t,
 	       && (null_member_pointer_value_p (lhs)
 		   || null_member_pointer_value_p (rhs)))
 	r = constant_boolean_node (!is_code_eq, type);
+      else if (TREE_CODE (lhs) == PTRMEM_CST)
+	lhs = cplus_expand_constant (lhs);
+      else if (TREE_CODE (rhs) == PTRMEM_CST)
+	rhs = cplus_expand_constant (rhs);
     }
 
   if (r == NULL_TREE)

gcc/testsuite/g++.dg/cpp0x/constexpr-ptrmem6.C

+// PR c++/71896
+// { dg-do compile { target c++11 } }
+
+struct Foo {
+  int x;
+};
+
+constexpr bool compare(int Foo::*t) { return t == &Foo::x; }
+
+constexpr bool b = compare(&Foo::x);
+
+#define SA(X) static_assert ((X),#X)
+SA(b);