Cannot specify a command file for Icarus from compile_args - Needed for setting timescale

[gretzteam]

To set the icarus timescale, a cmds.f file with the following content is created:

+timescale+1ns/1ns

Then compile_args is set to: compile_args = ["-f /home/cmds.f"]

However, icarus complains that the file cannot be read:

INFO cocotb: Running command: iverilog -o /home/sim_build/toplevel.vvp -D COCOTB_SIM=1 -s toplevel -g2012 -f /home/cmds.f  /home/toplevel.sv 
INFO cocotb: iverilog: cannot open command file  /home/cmds.f for reading.
ERROR cocotb: Command terminated with error 1
AssertionError: Simulation terminated abnormally. Results file not found.

Interestingly, if I then manually go in /sim_build and type the exact same command, there are no errors and subsequent run work fine... iverilog -o /home/sim_build/toplevel.vvp -D COCOTB_SIM=1 -s toplevel -g2012 -f /home/cmds.f /home/toplevel.sv

[themperek]

Try : compile_args = ["-f", "/home/cmds.f"]

Should probably split this in code before passing to subprocess.

[gretzteam]

This worked fine, thanks!

Related to this, would it make sense to add a default cmds.f file with decent timescale directive? I believe Icarus is mostly not usable as it is for most people and they will all have to figure out the funny way to set the timescale...

Something along those lines, but I'm sure there is a better way.

class icarus_custom(Icarus):
    def compile_command(self):
        if '-f' in self.compile_args:
            print('A command file is already provided.')
        else:
            print('Override default icarus timescale to 1ns/1ns. Create cmds.f file and add to compile_args')
            with open(self.sim_dir+"/cmds.f", 'w') as f:
                f.write("+timescale+1ns/1ns")  
            self.compile_args.extend(["-f", self.sim_dir+"/cmds.f"])

        cmd_compile = (
            ["iverilog", "-o", self.sim_file, "-D", "COCOTB_SIM=1", "-s", self.toplevel, "-g2012"]
            + self.get_define_commands(self.defines)
            + self.get_include_commands(self.includes)
            + self.compile_args
            + self.verilog_sources
        )

        return cmd_compile

[themperek]

I am closing it. In case it is still an issue please reopen.

[shuckc]

This is one of the things I imagine every Icarus user has to solve when moving from cocotb to cocotb-test - why is Icarus now complaining about timescales?

The Cocotb Makefile takes care of writing a default timescale to cmds.f file and including it here: https://github.com/cocotb/cocotb/blob/master/cocotb/share/makefiles/simulators/Makefile.icarus#L69 When cocotb-test invokes icarus it has no equivalent to set timescale https://github.com/themperek/cocotb-test/blob/master/cocotb_test/simulator.py#L421

Setting compile_args on every test is clunky, and it's not obvious how to replace SIM=icarus pytest . with a custom Icarus subclass (like icarus_custom above) without losing the ability to switch simulators from the command line. Here is one way:

from cocotb_test.simulator import run, Icarus
from cocotb_test import simulator

class IcarusAutoTimescale(Icarus):
    def compile_command(self):
        with open(self.sim_dir+"/cmds.f", 'w') as f:
            f.write("+timescale+1ns/1ns\n")
        self.compile_args.extend(["-f", self.sim_dir+"/cmds.f"])
        return super().compile_command()

simulator.Icarus = IcarusAutoTimescale

def test_fen_decode():
    run(
        verilog_sources=["hw/fen_decode.sv", "hw/ascii_int_to_bin.sv", "hw/onehot_to_bin.v"],
        toplevel="fen_decode",
        module="cocotb_fen_decode"
    )

It's especially odd given all the support to handle Icarus.waves = True which writes a custom modules and adds a new top level.