Creating a Yosys Pass to Append "/* verilator public */" Attributes to Signals

[mmxsrup]

I am currently looking for a way to implement a Yosys pass that adds a /* verilator public */ attribute to a signal, I intend to simulate a Yosys generated Verilog file in Verilator and monitor that signal during the simulation.

The reason I am using Yosys is that the signal to be attributed is itself instrumented with a Yosys pass, and I would like to add the attribute to the signal while it is being instrumented.

[nakengelhardt]

Custom attributes can be added with the setattr command, but "verilator public" is not a valid attribute, as attributes are always of the form (* identifier = "value" *) (value is optional on input and defaults to 1 but is always emitted in write_verilog output). /* */ indicates a comment, and the only way to introduce comments in write_verilog is with the -attr2comment that transforms an attribute into a comment (basically just replaces (* *) with /* */). That doesn't work with the format. So the closest solution I could come up with is to use setattr to set the attribute and then run sed on the output to replace (* verilator = "public" *) with /* verilator public */, but looking at the verilator documentation it also wants the comment in a specific location inside the declaration. That's probably possible to do with sed but exceeds my abilities...

[whitequark]

I would consider this a Verilator bug personally.

[mmxsrup]

I annotated it first with write_verilog and finally replaced it with bash's sed command. Thanks for the advice!