Log Message:
cad/verilator: import verilator-4.006

Verilator is the fastest free Verilog HDL simulator, and outperforms
most commercial simulators. Verilator compiles synthesizable
SystemVerilog (generally not test-bench code), plus some SystemVerilog
and Synthesis assertions into single- or multithreaded C++ or
SystemC code. Verilator is designed for large projects where fast
simulation performance is of primary concern, and is especially
well suited to generate executable models of CPUs for embedded
software design teams.