A SystemVerilog logger to help designers to log events in a circuit during a simulation in a consistent way. SVLogger is a simple class, easy to instantiate and use, with no dependencies.

Just include in source file:

`include "svlogger.sv"

and into the fileset:

+incdir+SVLOGGER_PATH

Please notice this project has been developed and tested with Icarus Verilog 11 and Verilator 5. It can't work with oldest versions. SVlogger could probably work with other (commercial) simulators but it never has been tested oustide iverilog and verilator scope.

First instantiate and setup it in a module:

    svlogger mylog;

    initial begin
        mylog = new("MyFSM", `SVL_VERBOSE_DEBUG, `SVL_ROUTE_TERM);
    end

Then call a function to print a message:

    always @ (posedge aclk or negedge aresetn) begin

        ...
            case (fsm)
                default: begin
                    mylog.debug("Start in IDLE state");
                    fsm <= ONE;
                end
        ...
            endcase
        end
    end

A complete example of svlogger usage is present in example folder.

The class is setup with three arguments:

• name: the identifier printed first in the log associated to the module under debug.
• verbosity: 0 deactivate all logs, upper values define the filtering level of the logging.
• route: 1 print in console, 2 print in a log file (name.log), 3 in both.

Five functions are available to print a message by severity level:

• ⬜️ debug, printed in white
• 🟦 info, printed in blue
• 🟨 warning, printed in yellow
• 🟪 critical, printed in pink
• 🟥 error, printed in red

Another function named msg is available to print a message without prepended severity prefix.

If verbosity is 0, no messages are logged. If equal to 1, everything is logged. If verbosity=2, only info, warning, critical and errors and so on until 5. All logs below the verbosity are discarded, all above are logged.

For convenience, multiple defines can be used:

• `SVL_VERBOSE_OFF (0)
• `SVL_VERBOSE_DEBUG (1)
• `SVL_VERBOSE_INFO` (2)
• `SVL_VERBOSE_WARNING (3)
• `SVL_VERBOSE_CRITICAL (4)
• `SVL_VERBOSE_ERROR (5)

Defines exist also to define the output routing:

• `SVL_ROUTE_TERM (1)
• `SVL_ROUTE_FILE (2)
• `SVL_ROUTE_ALL (3)

Messages are logged with embedded timeframe. To have a pretty-print of $realtime, you can setup the format with the next trick, for instance in your testbench:

// $timeformat(<unit_number>, <precision>, <suffix_string>, <minimum field width>);
initial $timeformat(-9, 1, "ns", 8);

This should produce a similar output:

MyCircuit: ERROR: (@ 406.0ns) Moving in a new state

By default, the file to log the messages is named with the name attribute passed to the constructor. But the filename can be set up with a custom name with a task:

    ...
    initial begin
        mylog = new("MyFSM", `SVL_VERBOSE_DEBUG, `SVL_ROUTE_ALL);
        mylog.set_filename("mySuperFSM.txt");
    end
    ...

If using Verilator, the first file is suppressed and a new file is created; but with Icarus Verilog the first file is kept because the tool limitation to use $system().

SVLogger includes a Python script to merge multiple log files into a single chronological file. This is useful when you have logs from multiple modules logging and want to see the complete simulation timeline.

# Merge specific log files into svlogger.log (default file name)
python3 svlogger.py file1.txt file2.txt

# Merge all .txt files in a directory
python3 svlogger.py logs/*.txt --output simulation_run.log

# Scan a directory recursively for all log files
python3 svlogger.py logs/ --output merged.log

# Verbose mode
python3 svlogger.py *.txt --output merged.log --verbose

The script extracts simulation time using Python regular expressions. By default, it looks for the SVLogger format:

(@ 10.0ns) or (@42us)

The default regex pattern is: r"\(@\s*([0-9]+\.?[0-9]*)([a-zA-Z]+)\)"

You can customize this with the --time-pattern option to match different log formats:

# For format [10.5ns]
python3 svlogger.py logs/ --time-pattern '\\[([0-9]+\\.?[0-9]*)([a-zA-Z]+)\\]'

# For format @10ns (no parentheses)
python3 svlogger.py logs/ --time-pattern '@([0-9]+\.?[0-9]*)([a-zA-Z]+)'

# For format time=10.2us
python3 svlogger.py logs/ --time-pattern 'time=([0-9]+\.?[0-9]*)([a-zA-Z]+)'

Note: The pattern must contain two capture groups:

1. First group: the numeric value (e.g., 10.5)
2. Second group: the time unit (e.g., ns, us)

Supported time units: ns, us, ms, s, ps, fs (case insensitive)

The script:

• Extracts simulation time from each log line
• Sorts all entries chronologically by converting times to nanoseconds
• Preserves ANSI color codes
• Requires only Python 3 standard library (no external dependencies)

This repo is licensed under MIT license. It grants nearly all rights to use, modify and distribute these sources. However, consider to contribute and provide updates to this core if you add feature and fix, would be greatly appreciated :)