Add waveform traces output to testbench to simulator

[vincent-mirian-google]

Currently, XLS supports iverilog for simulating verilog module with a testbench. When simulating iverilog, the waveform of the testbench can be created for viewing by other open source tools (e.g. gtkwave).

To produce the waveform traces, the following can be added to the initial block of the testbench.

  $dumpfile("some_file_name.vcd");
  $dumpvars(0, test_bench_module_name);

Then, viewed by gtkwave:

gtkwave some_file_name.vcd

[Forchapeatl]

@vincent-mirian-google please may I take this issue ?

[vincent-mirian-google]

Hi @Forchapeatl You are welcome to tackle this issue. I assigned it to you. Thank you.

[Forchapeatl]

  $dumpfile("some_file_name.vcd");
  $dumpvars(0, test_bench_module_name);

Then, viewed by gtkwave:

gtkwave some_file_name.vcd

Please are we to include it in these two files

• xls/uncore_rtl/ice40/wrap_io_ice40_repeat_byte_4_testbench.v
• xls/uncore_rtl/ice40/wrap_io_ice40_testbench.v

[vincent-mirian-google]

These files do not need to change. The GH issue is to programatically update the generated testbench (found in https://github.com/google/xls/blob/main/xls/simulation/module_testbench.h#L253) to output the waveform trace file.