Question: Is there way to use the circular buffer when writing program in C on C6000 platform ?

Answer: The simple answer is no. I'm not aware of any DSP compiler that allows C to use circular buffering hardware. The problem is that C doesn't understand circular modification of pointers.

Most of the customers I've worked with have written their loops - requiring circular buffers - in assembly and then call them from C.

The easiest solution might be trying to find code that already performs the necessary algorithm. Baring that, you might be able to write a simple assembly function to update a pointer with circular modification and then call it from your C routine. This might be faster than managing the whole process in C.