title: Visual C++ x64 add with carry
body: <p>Since there doesn't seem to be an intrinsic for ADC and I can't use inline assembler for x64 architecture with Visual C++, what should I do if I want to write a function using add with carry but include it in a C++ namespace?</p>
  
  <p>(Emulating with comparison operators is not an option.  This 256 megabit add is performance critical.)</p>