fix a bug

tests/4-opt/testcases/9_licm_bad.cminus

@@ -6,6 +6,7 @@ int main(void) {
   int b;
   t = 0;
   b = 1;
+  a = 0;
   while (t < 0) {
     a = b / b + b * b + a;
     a = b / b + b * b + a;