PR c++/80562 - ICE with constexpr if.

	* semantics.c (finish_if_stmt_cond): Call
	instantiate_non_dependent_expr.

From-SVN: r249387

gcc/cp/ChangeLog

 2017-06-19  Jason Merrill  <jason@redhat.com>
 
+	PR c++/80562 - ICE with constexpr if.
+	* semantics.c (finish_if_stmt_cond): Call
+	instantiate_non_dependent_expr.
+
 	PR c++/80829 - ICE with constexpr copy of base subobject.
 	* constexpr.c (clear_no_implicit_zero): New.
 	(cxx_eval_call_expression): Call it.

gcc/cp/semantics.c

@@ -733,7 +733,10 @@ finish_if_stmt_cond (tree cond, tree if_stmt)
   if (IF_STMT_CONSTEXPR_P (if_stmt)
       && require_potential_rvalue_constant_expression (cond)
       && !value_dependent_expression_p (cond))
-    cond = cxx_constant_value (cond, NULL_TREE);
+    {
+      cond = instantiate_non_dependent_expr (cond);
+      cond = cxx_constant_value (cond, NULL_TREE);
+    }
   finish_cond (&IF_COND (if_stmt), cond);
   add_stmt (if_stmt);
   THEN_CLAUSE (if_stmt) = push_stmt_list ();

gcc/testsuite/g++.dg/cpp1z/constexpr-if12.C

+// PR c++/80562
+// { dg-options -std=c++1z }
+
+struct T {
+  constexpr auto foo() { return false; }
+};
+
+template <class MustBeTemplate>
+constexpr auto bf(T t) {
+    if constexpr(t.foo()) {
+        return false;
+    }
+    return true;
+}