There is a simple Very Sleepy profiler released under GNU Public License. In contrast to Visual Studio stand-alone profiler, it has some GUI and doesn't require compiling the module with /PROFILE switch. To see the functions and source code, before compilation in Visual Studio "Generate Map File" option should be switched ON and MAP, PDB files should be located in the same directory where module binary is located.

There is a good article related to Profile Guided Optimization that explains what kind of optimization is made in the code.

Regards,
Armen.