title: Best way to negate a float in an XMM register
body: <p>If I'm correct, there is no native assembly function to calculate <code>-x</code> from a float value <code>x</code> stored in an Xmm register. So, what is the best (i.e., fastest) way to do that?</p>
  <p>Of course, I could do <code>0 - x</code> or <code>-1 * x</code>, but that seems overly laborious. Since a float stores a single &quot;sign&quot; bit, it should be simpler (and more efficient?) to just flip that bit. Is that so? And how would that work?</p>
  <p>(If there's an essential difference between single and double precision, please elaborate.)</p>