Access components of vector data type (e.g. int4) as array of scalars in OpenCL

I have kernel which evaluate interaction between all pairs of neighbors of an atoms. Each atom has max. 4 neighbors so I store their indexes in int4. But in order to loop over these neighbors I need to access them by index (neighs[0] rather than neighs.x ).

The loop should look something like:

int iatom = get_global_id(0);
int4 ng   = neighs[iatom];   // each atoms has 4 neighbors
float4 p0    = atom_pos[iatom];
float4 force = (float)(0.f,0.f,0.f,0.f);
for(int i=0; i<4; i++){
    int ing = ng[i];         // HERE: index into vector
    float4 pi = atom_pos[ing];
    for(int j=i+1; j<4; j++){
       int jng = ng[j];      // HERE: index into vector
       float4 pj = atom_pos[jng];
       force += evalInteraction( p0, pi, pj ); 
    }
}
forces[iatom]=force;

I have some idea how it can be probably done but not sure:

1. Unroll the loops
   since there are just 4*3/2=6 pair-interactions it would be probably even more efficient. But it would be much less readable and more difficult do modify.
2. cast int4 to int*
   but is it fine ? Doesn't it break something? Doesn't it make some performance issue? I mean this:

int4 ng_  = neighs[iatom]; // make sure we copy it to local memory or register
int* ng   = (int*)&ng_;    // pointer to local memory can be optimized out, right ?
for(int i=0; i<4; i++){
    int ing = ng[i];
    ...
}

You can cast directly, but you can also declare a union for easier access:

union
{
    int  components[4];
    int4 vector;
} neighbors;

neighbors.vector = ng;
neighbors.components[i]; // Works now