title: How to generate a sse4.2 popcnt machine instruction
body: <p>Using the c program:</p>
  
  <pre><code>int main(int argc , char** argv)
  {
  
    return  __builtin_popcountll(0xf0f0f0f0f0f0f0f0);
  
  }
  </code></pre>
  
  <p>and the compiler line (gcc 4.4 - Intel Xeon L3426):</p>
  
  <pre><code>gcc -msse4.2 poptest.c -o poptest
  </code></pre>
  
  <p>I do NOT get the builtin popcnt insruction rather the compiler generates a lookup table and computes the popcount that way.  The resulting binary is over 8000 bytes.  (Yuk!)</p>
  
  <p>Thanks so much for any assistance.</p>