read_rtlil << EOT
attribute \top 1
module \top
  wire width 1 \sig
  wire width 1 \val

  process $2
    switch \sig [0]
      case 1'0
      case 1'1
      case
        assign \val [0] 1'1
    end
  end
end
EOT
proc_rmdead
proc_clean
select -assert-none p:*