title: gcc generic march for all the x64 platforms
body: <p>GCC have <code>-march=</code> and <code>-mtune</code> option as described <a href="http://gcc.gnu.org/onlinedocs/gcc/i386-and-x86_002d64-Options.html" rel="noreferrer">here</a>. But it is not obvious which of the options to choose for <strong>x64</strong> platform as generic one. Say, <code>-mtune=</code> have the <code>generic</code> value, but <code>-march=</code> for <strong>x64</strong> have no.</p>
  
  <p>I suspect that <code>-march=nocona</code> (as frequently seen everywhere) or even <code>-march=i686 -m64</code> is the solution, but I'm not sure.</p>