[result] starts with all bits on zero.
On every iteration of the algorithm something similar to this happens to
calculate a bit of the result;
cp %A[x],%A[y]
cpc %B[x],%B[y]
cpc %C[x],%C[y]
cpc %D[x],%D[y]
brcs dont_set
sub %A[x],%A[y]
sbc %B[x],%B[y]
sbc %C[x],%C[y]
sbc %D[x],%D[y]
ori %[result],1<<bit_index
dont_set:
W3Jlc3VsdF0gc3RhcnRzIHdpdGggYWxsIGJpdHMgb24gemVyby4KT24gZXZlcnkgaXRlcmF0aW9uIG9mIHRoZSBhbGdvcml0aG0gc29tZXRoaW5nIHNpbWlsYXIgdG8gdGhpcyBoYXBwZW5zIHRvCmNhbGN1bGF0ZSBhIGJpdCBvZiB0aGUgcmVzdWx0OwoKICAgIGNwICVBW3hdLCVBW3ldCiAgICBjcGMgJUJbeF0sJUJbeV0KICAgIGNwYyAlQ1t4XSwlQ1t5XQogICAgY3BjICVEW3hdLCVEW3ldCmJyY3MgZG9udF9zZXQKICAgIHN1YiAlQVt4XSwlQVt5XQogICAgc2JjICVCW3hdLCVCW3ldCiAgICBzYmMgJUNbeF0sJUNbeV0KICAgIHNiYyAlRFt4XSwlRFt5XQogICAgb3JpICVbcmVzdWx0XSwxPDxiaXRfaW5kZXgKZG9udF9zZXQ6Cg==