title: Enable compiler optimisation only for individual functions/files
body: <p>I am working on a C++ code in Visual Studio 2012 environment.
  The code base is not very huge (contained in around 10-12 source files). The execution time for some of the functions in my project is huge (say 10 sec in REL mode, 50 sec in DEBUG mode)</p>
  
  <p>Now while debugging, I often require to look at functions executing towards the end of my application lifetime. Is there a way to disable compiler optimisation only for specific functions and/or files in my project.
  This would enable me to have optimised execution for some of the computationally extensive functions</p>
  
  <p>NOTE: I had erroneously mentioned "debug symbols" instead of "compiler optimisation" previously. I was basically asking this questions w.r.t. compiler optimisation because of which it can become difficult to inspect variable values while debugging with break points.</p>