>>   If there are only six interrupts, how about:
>> 
>> char map_bits_to_intr[64] = {<intr # for each combination>};
>
> Except that the 6 bits in question are not contiguous, so you have to
> use 8 bits and a 256 entry array.

Memory references of 256 byte array in tight loop may hurt direct
mapped data cache efficiency, although it's supportedly less dominant
than interrupt processing code/data path themselves.

Tohru Nishimura