module mask_encode(false_s1, true_s1, enc_s1);input [14:0] false_s1;input [14:0] true_s1;output [3:0] enc_s1;reg [14:0] tmp_dec_s1;reg [3:0] enc_s1;always @ (false_s1 or true_s1 or tmp_dec_s1)begin  // if both are 0s, mask is 1  tmp_dec_s1 = ~true_s1 & ~false_s1;  case (tmp_dec_s1)    15'h0000: enc_s1 = 0;    15'h0001: enc_s1 = 1;    15'h0003: enc_s1 = 2;    15'h0007: enc_s1 = 3;    15'h000f: enc_s1 = 4;    15'h001f: enc_s1 = 5;    15'h003f: enc_s1 = 6;    15'h007f: enc_s1 = 7;    15'h00ff: enc_s1 = 8;    15'h01ff: enc_s1 = 9;    15'h03ff: enc_s1 = 10;    15'h07ff: enc_s1 = 11;    15'h0fff: enc_s1 = 12;    15'h1fff: enc_s1 = 13;    15'h3fff: enc_s1 = 14;    15'h7fff: enc_s1 = 15;        // this should never happen    default: begin      enc_s1 = 15;      //$display("ERROR mask_encode at %d, tmp_dec_s1 = %x", $time, tmp_dec_s1);    end  endcaseendendmodule // mask_encode