Getting started with developing pyhdl-if

[penguali]

Hi Matthew,

I am currently tweaking with pyhdl-if and would like to contribute in a way.
I want to pass float arguments to tasks from Python to a SystemVerilog task that takes real arguments.
Currently, this is not implemented, or not properly handled (please correct me if I am wrong).

Inside gen_sv_class.py the functions py2sv_func and sv2py_func have declared the PyObjects corresponding to ctypes.c_double as real. I assume they should be assigned PyFloat_AsDouble and PyFloat_FromDouble, respectively.
This would probably require tweaking py_object.svh and pytf.py a small bit.

Until now, I have installed pyhdl-if using PyPi and it worked perfectly.
Now, I have cloned the repo and installed it locally, but cannot run my Python testbenches because the shared library libpyhdl_if.so cannot be found when running PYTHONPATH=$(pwd) make.

Can you help me run testbenches from a local pyhdl-if? I would like to try and implement passing the float arguments and test it if you don't mind ;)

Appreciate the help!

[mballance]

Hi Ali,
I would very much welcome your help in improving PyHDL-IF. Your intuition about what you would need to change to support floating-point types is accurate.
I've added a few 'developer' instructions to the root README in the repo. Hpoe that helps to get you started, and please let me know if you run into issues.
To address your specific question, once you build pyhdl-if locally (the python3 setup.py build_ext ... step in the instructions), you can run that build with your own testbench by setting PYTHONPATH to include the project's src directory.

-Matthew

[penguali]

Hi Matthew,
thanks for letting me help.
I have followed your instructions by building pyhdl-if locally. Before making any changes, I wanted to check if the testbenches run correctly with a local pyhdl-if. Unfortunately, they failed.
During the run, I am printing the output of hdl_if.get_entry() and hdl_if.share(), which return the path of the local pyhdl-if as path/to/pyhdl-if/src/hdl_if/libpyhdl_if.so and path/to/pyhdl-if/src/hdl_if/share, respectively.
The problem that I am facing now is coming from the hdl_call_if_api.svh during elaboration.
The errors I am getting are of this kind:

*E,UNDIDN (hdl_call_if_api.svh,247|27): 'pyhdl_if': undeclared identifier Expecting a class type name.
*E,EXPSMC (hdl_call_if_api.svh,247|50): expecting a semicolon (';') [10.3.1(IEEE)].
        pyhdl_if::PyObject __args, __cls_m, __cls_t, __obj;

It seems that the pyhdl-if package is not recognized anymore?
I assume that I have to add an extra makelib compilation argument to the makefile, but I am not exactly sure.
Do you have any idea what the problem might be?
Appreciate the help!

-Ali

[penguali]

I have resolved the issue. After appending PYTHONPATH with the src directory of pyhdl-if, I thought that I could now run the tests simply using make, but it turned out, I still need to run them using PYTHONPATH=$(pwd) make.

I have no idea why, but it works.
I will now work on supporting the floating-point types

[mballance]

Ah, that makes sense. Yes, manaully setting PYTHONPATH is required when in development mode.

[penguali]

Alongside the small tweaks in gen_sv_class.py, pytf.py, py_objects.svh, py_utils.svh, I needed to include the PyFloat_ API and adjust gen_vpi_utils inside gen_py_if.py in order to generate the correct header files.
After doing that, I felt optimistic that this would work and went straight to the examples and tried implementing a simple task that takes real arguments. However, this did not work, and I am getting errors from Xcelium that the new types pyhdl_if::PyFloat_FromDouble and pyhdl_if::PyFloat_AsDouble are not found in pyhdl_if. Moreover, I am getting the following error

        real ret = PyFloat_FromDouble(obj);
                                    |
*E,TYCMPAT (pyhdl-if/src/hdl_if/share/dpi/py_object.svh,178|36): assignment operator type check failed (expecting datatype compatible with 'real' but found 'pyhdl_if::PyObject (chandle)' instead).

This is originating from the adjusted py_object.svh as I had to append the following functions for obtaining the float value of the objects:

    virtual function real to_double();
       real ret = PyFloat_FromDouble(obj);
       return ret;
   endfunction
   
    virtual function real as_double();
       return PyFloat_AsDouble(obj);
   endfunction

I realized that I was probably skipping steps and wanted to run the pyhdl-if tests first (like tests/sys/dpi/test_dpi_if.py), but this also failed due to wrong naming of modules like import hdl_pi_if which should be import hdl_if I assume. So I adjusted it and still got the following error from Xcelium: *F,BADOPT: unknown or ambiguous options (-L).
Could it be that the tests are not up-to-date?
I am not sure what is the best way to approach this problem and get the floating types to work. Should I create a draft PR where you can check the new changes? I would appreciate your advice!