calculating amount of memory freed

I believe you mean these functions:  free() for C and delete() for C++. Both are defined by the RTS library (runt-time support library). Because both are implemented according to the current C standards, TI does not  have its APIs explicitly defined in our documentation. In other words, such information is widely available on the internet. What I mean is that this is more a C programming question than a TI-related question. As a hint, one link that can help you understand it better is this one:

http://www.codersource.net/c++_dynamic_memory_allocation.aspx 

There is a similar function defined for DSP/BIOS programs called MEM_free (you can look at document http://focus.ti.com/general/docs/techdocsabstract.tsp?abstractName=spru403o).