yosys/tests/techmap/bmuxmap_pmux.ys

read_rtlil << EOT

module \top
  wire width 4 input 0 \S
  wire width 5 output 1 \Y

  cell $bmux $0
    parameter \WIDTH 5
    parameter \S_WIDTH 4
    connect \A 80'10110100011101110001110010001110101010111000110011111111111110100000110100111000
    connect \S \S
    connect \Y \Y
  end
end

EOT

hierarchy -auto-top
equiv_opt -assert bmuxmap -pmux

###
design -reset

read_rtlil << EOT

module \top
  wire width 10 input 0 \A
  wire input 1 \S
  wire width 5 output 2 \Y

  cell $bmux $0
    parameter \WIDTH 5
    parameter \S_WIDTH 1
    connect \A \A
    connect \S \S
    connect \Y \Y
  end
end

EOT

hierarchy -auto-top
equiv_opt -assert bmuxmap -pmux