Fastest way of bitwise AND between two arrays on iPhone?

I have two image blocks stored as 1D arrays and have do the following bitwise AND operations among the elements of them.

int compare(unsigned char *a, int a_pitch, 
            unsigned char *b, int b_pitch, int a_lenx, int a_leny) 
{
    int overlap =0 ;

    for(int y=0; y<a_leny; y++) 
        for(int x=0; x<a_lenx; x++) 
        {
            if(a[x + y * a_pitch] & b[x+y*b_pitch]) 
                overlap++ ;
        }
    return overlap ;
}

Actually, I have to do this job about 220,000 times, so it becomes very slow on iphone devices.

How could I accelerate this job on iPhone ?

I heard that NEON could be useful, but I'm not really familiar with it. In addition it seems that NEON doesn't have bitwise AND...