`default_nettype none

module saw2sin_poly
( input  var [15:0] i_saw
, output var [15:0] o_sin
);

logic invert;
always_comb invert = i_saw[15];

logic reverse;
always_comb reverse = i_saw[14];

logic [15:0] qsaw;
always_comb qsaw = reverse
  ? {~i_saw[13:0], 2'b01} // Reverse
  : {i_saw[13:0], 2'b00}; // Normal

logic [63:0] x_in, x_17;
always_comb x_in = {48'd0, qsaw};
always_comb x_17 = 64'd131072 - x_in;

logic [63:0] qsin;
always_comb qsin = (64'd262144 * x_in * x_17) / (64'd21474836480 - (x_in * x_17));

always_comb o_sin = invert
  ? ~{1'b1, qsin[15:1]} + 1 // Invert
  : {1'b1, qsin[15:1]};     // Normal

endmodule