8bitworkshop/test/cli/verilog/t_var_life.v

// DESCRIPTION: Verilator: Verilog Test module
//
// This file ONLY is placed under the Creative Commons Public Domain, for
// any use, without warranty, 2003 by Wilson Snyder.
// SPDX-License-Identifier: CC0-1.0

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

   input clk;
   integer cyc; initial cyc=1;

   // Life analysis checks
   reg [15:0] life;

   // Ding case
   reg [7:0]  din;
   reg [15:0] fixin;
   always @* begin
      fixin = {din[7:0],din[7:0]};
      case (din[1:0])
	2'b00: begin
	   fixin = {fixin[14:0], 1'b1};
	   if (cyc==101) $display("Prevent ?: optimization a");
	end
	2'b01: begin
	   fixin = {fixin[13:0], 2'b11};
	   if (cyc==101) $display("Prevent ?: optimization b");
	end
	2'b10: begin
	   fixin = {fixin[12:0], 3'b111};
	   if (cyc==101) $display("Prevent ?: optimization c");
	end
	2'b11: begin
	   fixin = {fixin[11:0], 4'b1111};
	   if (cyc==101) $display("Prevent ?: optimization d");
	end
      endcase
   end

   always @ (posedge clk) begin
      if (cyc!=0) begin
	 cyc<=cyc+1;
	 if (cyc==1) begin
	    life = 16'h8000;	// Dropped
	    life = 16'h0010;	// Used below
	    if (life != 16'h0010) $stop;
	    //
	    life = 16'h0020;	// Used below
	    if ($time < 10000)
	      if (life != 16'h0020) $stop;
	    //
	    life = 16'h8000;	// Dropped
	    if ($time > 100000) begin
	       if ($time != 0) $stop;	// Prevent conversion to ?:
	       life = 16'h1030;
	    end
	    else
	        life = 16'h0030;
	    if (life != 16'h0030) $stop;
	    //
	    life = 16'h0040;	// Not dropped, no else below
	    if ($time > 100000)
	      life = 16'h1040;
	    if (life != 16'h0040) $stop;
	    //
	    life = 16'h8000;	// Dropped
	    if ($time > 100000) begin
	       life = 16'h1050;
	       if (life != 0) $stop;  // Ignored, as set is first
	    end
	    else begin
	       if ($time > 100010)
		 life = 16'h1050;
	       else life = 16'h0050;
	    end
	    if (life != 16'h0050) $stop;
	 end
	 if (cyc==2) begin
	    din <= 8'haa;
	 end
	 if (cyc==3) begin
	    din <= 8'hfb;
	    if (fixin != 16'h5557) $stop;
	 end
	 if (cyc==4) begin
	    din <= 8'h5c;
	    if (fixin != 16'hbfbf) $stop;
	 end
	 if (cyc==5) begin
	    din <= 8'hed;
	    if (fixin != 16'hb8b9) $stop;
	 end
	 if (cyc==6) begin
	    if (fixin != 16'hb7b7) $stop;
	 end
	 if (cyc==9) begin
	    $write("*-* All Finished *-*\n");
	    $finish;
	 end
      end
   end
endmodule