title: How to set that compiler flag?
body: <p>Shark told me this:</p>
  
  <blockquote>
    <p>This instruction is the start of a
    loop that is not aligned to a 16-byte
    address boundary. For optimal
    performance, you should align the
    start of a hot loop using a compiler
    directive. With gcc 3.3 or later, use
    the -falign-loops=16 compiler flag.</p>
  </blockquote>
  
  <pre><code>for (int i=0; i &lt; 4; i++) { // line with the info
     //...code
  }
  </code></pre>
  
  <p>How would I set that flag, and does it really improve performance?</p>