code: private void opNullCheckEndMemST() {
          int mem = code[ip++];   /* mem: null check id */
          int isNull = nullCheckMemSt(mem, s);
  
          if (isNull != 0) {
              if (Config.DEBUG_MATCH) {
                  Config.log.println("NULL_CHECK_END_MEMST: skip  id:" + mem + ", s:" + s);
              }
  
              if (isNull == -1) {opFail(); return;}
              nullCheckFound();
          }
      }
docs: USE_INFINITE_REPEAT_MONOMANIAC_MEM_STATUS_CHECK