in-place interleave, memmove and split

void deinterleave_mm_split(int *a, int len)
{
    if (0 == len % 4)
    {
        deinterleave_mm_split(&a[0], len/2);
        deinterleave_mm_split(&a[len/2], len/2);
        for (int i = len/4; i < len/2; i++)
        {
            int t = a[i];
            a[i] = a[i+len/4];
            a[i+len/4] = t;
        }
    }
    else
    {
        deinterleave_mm(a, len);
    }
}

void interleave_mm_split(int *a, int len)
{
    if (0 == len % 4)
    {
        for (int i = len/4; i < len/2; i++)
        {
            int t = a[i];
            a[i] = a[i+len/4];
            a[i+len/4] = t;
        }
        interleave_mm_split(&a[0], len/2);
        interleave_mm_split(&a[len/2], len/2);
    }
    else
    {
        interleave_mm(a, len);
    }
}