title: '_umul128': identifier not found
body: <p>In VS2010, I tested the following sample code of _umul128. The compile error occured:</p>
  
  <p>"error C3861: '_umul128': identifier not found".</p>
  
  <pre><code>// umul128.c
  // processor: IPF, x64
  
  #include &lt;stdio.h&gt;
  #include &lt;intrin.h&gt;
  
  #pragma intrinsic(_umul128)
  
  int main()
  {
      unsigned __int64 a = 0x0fffffffffffffffI64;
      unsigned __int64 b = 0xf0000000I64;
      unsigned __int64 c, d;
  
      d = _umul128(a, b, &amp;c);
  
      printf_s("%#I64x * %#I64x = %#I64x%I64x\n", a, b, c, d);
  }
  </code></pre>
  
  <p>The source code is from MSDN: <a href="http://msdn.microsoft.com/en-US/library/vstudio/3dayytw9(v=vs.100).aspx" rel="nofollow">http://msdn.microsoft.com/en-US/library/vstudio/3dayytw9(v=vs.100).aspx</a>.</p>
  
  <p>The OS is Windows8, 64-bit. Is it caused by compile environment? How to fix it?
  Thanks in advance.</p>