diff --git a/firmware/lib/builtins/divmoddi4.c b/firmware/lib/builtins/divmoddi4.c
new file mode 100644
index 0000000..12309d8
--- /dev/null
+++ b/firmware/lib/builtins/divmoddi4.c
@@ -0,0 +1,25 @@
+/*===-- divmoddi4.c - Implement __divmoddi4 --------------------------------===
+ *
+ *                    The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+ *
+ * This file implements __divmoddi4 for the compiler_rt library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
+
+#include "int_lib.h"
+
+/* Returns: a / b, *rem = a % b  */
+
+di_int
+__divmoddi4(di_int a, di_int b, di_int* rem)
+{
+  di_int d = __divdi3(a,b);
+  *rem = a - (d*b);
+  return d;
+}