Fast search of some nibbles in two ints at same offset (C, microoptimisation)

Question

My task is to check (>trillions checks), does two int contain any of predefined pairs of nibbles (first pair 0x2 0x7; second 0xd 0x8). For example:

bit offset:           


        

Answer 1

static inline int nibble_check (uint32_t A, uint32_t B)
 __attribute__((always_inline))
{
    // shift x by n nibbles
    #define s(x, n) ((x) << 4 * (n))
    // mask the nth nibble of x
    #define m(x, n) ((x) & s(0xf, n))
    // D^8 and 2^7 both == 5, so check for that first, for speed
    // this is equivalent to
    // (A_nibble == 0XD && B_nibble == 0x8) || (A_nibble == 0x2 && B_nibble == 0x7)
    #define t(n) (m(AB,n) == s(5,n) && (m(B,n) == s(7,n) || m(B,n) == s(8,n))

    uint32_t AB x = A ^ B;

    return t(0) || t(1) || t(2) || t(3) || t(4) || t(5) || t(6) || t(7);
    #undef t
    #undef m
    #undef s
}