I mean:

  const uint64_t size = // Some large value
  uint64_t a[size] = // Some random values
  uint64_t b[size] = // Some random values
  uint64_t c[size] = {0};

  uint64_t i = 0;
  while(i < size) {
    c[i] = a[i] + b[i];
  }

  // Disable all optimizations so the above isn't optimized away/vectorized