%Warning-UNOPT: t/t_unopt_converge.v:18:11: Signal unoptimizable: Feedback to public clock or circular logic: 'x'
   output x;    
          ^
                ... Use "/* verilator lint_off UNOPT */" and lint_on around source to disable this message.
                t/t_unopt_converge.v:18:11:      Example path: x
                t/t_unopt_converge.v:21:4:      Example path: ALWAYS
                t/t_unopt_converge.v:18:11:      Example path: x
%Error: Exiting due to