IS_ACTIVE
DEBUG_PRINT2 (" active=%d", IS_ACTIVE (reg_info[this_reg])); \
IS_ACTIVE (reg_info[mcnt]) = 0;
IS_ACTIVE (reg_info[*p]) = 1;
IS_ACTIVE (reg_info[*p]) = 0;
while (r > 0 && !IS_ACTIVE (reg_info[r]))