title: What does '#pragma GCC optimize ("O3")' mean?
body: <p>I came through this line in project source code written before a function. I want to know, what is the use of it ?</p>
  
  <pre><code>#pragma GCC optimize ("O3")
  
  void somefunction()
  {
    ....
  }
  </code></pre>
  
  <p>Requesting to explain every argument used in the directive.</p>
  
  <p>Thanks and Regards.</p>