shift_mult.cpp

void CalcMultShift(uint64_t *mult, uint64_t *shift, uint64_t F2, uint64_t F1)
{
    uint64_t m = 1, s;
    uint64_t maxsft = __lzcnt64(F2);
    printf("\nF1:%llu, F2:%llu\n\n", F1,F2);

    for (s = 0; s < maxsft; ++s) {
        uint64_t dividend = F2 << s;
        uint64_t rem;
        uint64_t divider = F1;
        printf("\nNom: %016llx.0000000000000000, Denom: %016llx\n", dividend, divider);

        if (!dividend || !divider)
            break;

        m = _udiv128(dividend, 0L, divider, &rem);
        rem = _shrx_u64(rem, s);

        printf("shift:%llu, mult=%016llx, rem=%016llx\n",s,m,rem);

        if (!rem)
            break;
    }

    *mult = m;
    *shift = s;
}