re PR c++/63996 (Infinite loop in invalid C++14 constexpr fn)

	PR c++/63996
	* constexpr.c (cxx_eval_loop_expr): Don't loop
	endless on none-constant expression.

From-SVN: r218682

gcc/cp/ChangeLog

+2014-12-12  Kai Tietz  <ktietz@redhat.com>
+
+	PR c++/63996
+	* constexpr.c (cxx_eval_loop_expr): Don't loop
+	endless on none-constant expression.
+
 2014-12-12  Jason Merrill  <jason@redhat.com>
 
 	PR c++/61402

gcc/cp/constexpr.c

@@ -2841,7 +2841,7 @@ cxx_eval_loop_expr (const constexpr_ctx *ctx, tree t,
     {
       cxx_eval_statement_list (ctx, body,
 			       non_constant_p, overflow_p, jump_target);
-      if (returns (jump_target) || breaks (jump_target))
+      if (returns (jump_target) || breaks (jump_target) || *non_constant_p)
 	break;
     }
   if (breaks (jump_target))