title: What gcc versions support the __int128 intrinsic type?
body: <p>Under the <a href="http://gcc.gnu.org/onlinedocs/gcc/_005f_005fint128.html">gcc docs 128-bit</a> integers is:</p>
  
  <blockquote>
    <p>As an extension the integer scalar type <code>__int128</code> is supported for targets which have an integer mode wide enough to hold 128 bits.
    Simply write <code>__int128</code> for a signed 128-bit integer, or <code>unsigned __int128</code> for an unsigned 128-bit integer. </p>
    
    <p>There is no support in GCC for expressing an integer constant of type <code>__int128</code> for targets with
    long long integer less than 128 bits wide.</p>
  </blockquote>
  
  <p>I was wondering what gcc version added support for this type, or if there's a macro that can be used directly to test for its existence.</p>