add div64 and mod64

llrtc/lib/mod64.c

@@ -0,0 +1,15 @@
+#include "llrt.h"
+
+uint64_t umod64(uint64_t dividend, uint64_t divisor)
+{
+    uint64_t rem;
+    udivmod64(dividend, divisor, &rem);
+    return rem;
+}
+
+int64_t smod64(int64_t dividend, int64_t divisor)
+{
+    int64_t rem;
+    sdivmod64(dividend, divisor, &rem);
+    return rem;
+}