Hi Ishan,
As per my understanding, you have a MATLAB model which has two other models inside the main model. You would like to auto code in such a way that one of the modules gets auto coded in plain C++ and the other models gets auto coded in CUDA.
MathWorks provides several products for code generation from MATLAB and Simulink models. You can generate optimized C, C++, CUDA, Verilog and VHDL that compiles with standards. You can partition the model and use the available resources to generate the codes respectively.
For Generating C++ code, you can use MATLAB Coder and Simulink Coder, it allows you to automatically generate C and C++ code from MATLAB Code:
For Generating CUDA code, you can use GPU Coder, it generates optimized CUDA code from Simulink models containing MATLAB Function blocks.
Please refer to the following reference to know more about:
I hope this resolves the issue you were facing.