While there is existing ANSI C/C++ code for Brep in BRL-CAD it is not GPU parallel. Porting it to the GPU with OpenCL should be rather complex because much of this code is written in object oriented C++.
So the first task you should make to start an OpenCL port of this is to make a simplified version of the code which uses just ANSI C. Alternatively you can also look into incorporating SYCL for the Brep code. SYCL is a GPU parallel language based on C++ which should be possible to interface with OpenCL.