Function reuseTableCompare

Try to reuse the switch table index compare. Following pattern: \code if (idx < tablesize) r = table[idx]; // table does not contain default_value else r = default_value; if (r != default_value) ... \endcode Is optimized to: \code cond = idx < tablesize; if (cond) r = table[idx]; else r = default_value; if (cond) ... \endcode Jump threading will then eliminate the second if(cond).