yosys/tests/arch/xilinx/mux.v

module mux2 (S,A,B,Y);
    input S;
    input A,B;
    output reg Y;

    always @(*)
		Y = (S)? B : A;
endmodule

module mux4 ( S, D, Y );

input[1:0] S;
input[3:0] D;
output Y;

reg Y;
wire[1:0] S;
wire[3:0] D;

always @*
begin
    case( S )
       0 : Y = D[0];
       1 : Y = D[1];
       2 : Y = D[2];
       3 : Y = D[3];
   endcase
end

endmodule

module mux8 ( S, D, Y );

input[2:0] S;
input[7:0] D;
output Y;

reg Y;
wire[2:0] S;
wire[7:0] D;

always @*
begin
   case( S )
       0 : Y = D[0];
       1 : Y = D[1];
       2 : Y = D[2];
       3 : Y = D[3];
       4 : Y = D[4];
       5 : Y = D[5];
       6 : Y = D[6];
       7 : Y = D[7];
   endcase
end

endmodule

module mux16 (D, S, Y);
 	input  [15:0] D;
 	input  [3:0] S;
 	output Y;

assign Y = D[S];

endmodule