verilator/test_regress/t/t_mod_recurse.v

// DESCRIPTION: Verilator: Verilog Test module
//
// This file ONLY is placed into the Public Domain, for any use,
// without warranty, 2013 by Sean Moore.

module t (/*AUTOARG*/
   // Inputs
   clk
   );
   input clk;

   integer 	cyc=0;
   reg [63:0] 	crc;
   reg [63:0] 	sum;

   // Take CRC data and apply to testblock inputs
   wire [7:0]  tripline = crc[7:0];

   /*AUTOWIRE*/

   wire         valid;
   wire [3-1:0] value;

   PriorityChoice #(.OCODEWIDTH(3))
   pe (.out(valid), .outN(value[2:0]), .tripline(tripline));

   // Aggregate outputs into a single result vector
   wire [63:0] result = {60'h0, valid, value};

   // Test loop
   always @ (posedge clk) begin
`ifdef TEST_VERBOSE
      $write("[%0t] cyc==%0d crc=%x result=%x\n",$time, cyc, crc, result);
`endif
      cyc <= cyc + 1;
      crc <= {crc[62:0], crc[63]^crc[2]^crc[0]};
      sum <= result ^ {sum[62:0],sum[63]^sum[2]^sum[0]};
      if (cyc==0) begin
	 // Setup
	 crc <= 64'h5aef0c8d_d70a4497;
	 sum <= 64'h0;
      end
      else if (cyc<10) begin
	 sum <= 64'h0;
      end
      else if (cyc<90) begin
      end
      else if (cyc==99) begin
	 $write("[%0t] cyc==%0d crc=%x sum=%x\n",$time, cyc, crc, sum);
	 if (crc !== 64'hc77bb9b3784ea091) $stop;
	 // What checksum will we end up with (above print should match)
`define EXPECTED_SUM 64'hc5fc632f816568fb
	 if (sum !== `EXPECTED_SUM) $stop;
	 $write("*-* All Finished *-*\n");
	 $finish;
      end
   end

endmodule

module PriorityChoice (out, outN, tripline);
   parameter OCODEWIDTH = 1;
   localparam CODEWIDTH=OCODEWIDTH-1;
   localparam SCODEWIDTH= (CODEWIDTH<1) ? 1 : CODEWIDTH;

   output reg             out;
   output reg [OCODEWIDTH-1:0] outN;
   input wire [(1<<OCODEWIDTH)-1:0] tripline;
   wire 			    left;
   wire [SCODEWIDTH-1:0] 	    leftN;
   wire 			    right;
   wire [SCODEWIDTH-1:0] 	    rightN;

   generate
      if(OCODEWIDTH==1) begin
	 assign left = tripline[1];
	 assign right = tripline[0];

	 always @(*) begin
	    out = left || right ;
	    if(right) begin outN = {1'b0}; end
	    else  begin outN = {1'b1}; end
	 end
      end else begin
	 PriorityChoice #(.OCODEWIDTH(OCODEWIDTH-1))
	 leftMap
	   (
	    .out(left),
	    .outN(leftN),
	    .tripline(tripline[(2<<CODEWIDTH)-1:(1<<CODEWIDTH)])
	    );
	 PriorityChoice #(.OCODEWIDTH(OCODEWIDTH-1))
	 rightMap
	   (
	    .out(right),
	    .outN(rightN),
	    .tripline(tripline[(1<<CODEWIDTH)-1:0])
	    );
	 always @(*) begin
	    if(right) begin
               out  = right;
               outN = {1'b0, rightN[OCODEWIDTH-2:0]};
	    end else begin
               out  = left;
               outN = {1'b1, leftN[OCODEWIDTH-2:0]};
	    end
	 end
      end
   endgenerate
endmodule