title: How to use ARM intrinsics in iOS?
body: <p>I need to compute MSB (most significant bit) on millions of 32-bit integers on iPad very fast. I have my own (ugly) implementation of MSB written on plain C, which is slow. ARM processors have <strong>CLZ</strong> (count leading zeroes) hardware command, which can be very useful for that. According to <a href="http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0491c/CJAJBHHA.html" rel="nofollow">ARM reference</a> there is an intrinsic C function __CLZ. How can I add support of ARM intrinsic functions to my Xcode project?</p>
  
  <p>P.S. I've managed to find the way of accessing hardware CLZ from NEON (by including arm_neon.h), but that's not what I need, because it's only works with vector, but I need scalar MSB.</p>