verilator/test_regress/t/t_gate_elim.v

// DESCRIPTION: Verilator: Verilog Test module
//
// This file ONLY is placed under the Creative Commons Public Domain.
// SPDX-FileCopyrightText: 2005 Wilson Snyder
// SPDX-License-Identifier: CC0-1.0

module t (
    input clk
);

  integer cyc;
  initial cyc = 1;

  reg b;

  wire vconst1 = 1'b0;
  wire vconst2 = !(vconst1);
  wire vconst3 = !vconst2;
  wire vconst = vconst3;

  wire qa;
  wire qb;
  wire qc;
  wire qd;
  wire qe;
  ta ta (
      .b(b),
      .vconst(vconst),
      .q(qa)
  );
  tb tb (
      .clk(clk),
      .vconst(vconst),
      .q(qb)
  );
  tc tc (
      .b(b),
      .vconst(vconst),
      .q(qc)
  );
  td td (
      .b(b),
      .vconst(vconst),
      .q(qd)
  );
  te te (
      .clk(clk),
      .b(b),
      .vconst(vconst),
      .q(qe)
  );

  always @(posedge clk) begin
`ifdef TEST_VERBOSE
    $display("%b", {qa, qb, qc, qd, qe});
`endif
    if (cyc != 0) begin
      cyc <= cyc + 1;
      if (cyc == 1) begin
        b <= 1'b1;
      end
      if (cyc == 2) begin
        if (qa != 1'b1) $stop;
        if (qb != 1'b0) $stop;
        if (qd != 1'b0) $stop;
        b <= 1'b0;
      end
      if (cyc == 3) begin
        if (qa != 1'b0) $stop;
        if (qb != 1'b0) $stop;
        if (qd != 1'b0) $stop;
        if (qe != 1'b0) $stop;
        b <= 1'b1;
      end
      if (cyc == 4) begin
        if (qa != 1'b1) $stop;
        if (qb != 1'b0) $stop;
        if (qd != 1'b0) $stop;
        if (qe != 1'b1) $stop;
        b <= 1'b0;
      end
      if (cyc == 5) begin
        $write("*-* All Finished *-*\n");
        $finish;
      end
    end
  end
endmodule

module ta (
    input vconst,
    input b,
    output reg q
);

  always @(  /*AS*/ b or vconst) begin
    q = vconst | b;
  end
endmodule

module tb (
    input vconst,
    input clk,
    output reg q
);

  always @(posedge clk) begin
    q <= vconst;
  end
endmodule

module tc (
    input vconst,
    input b,
    output reg q
);
  always @(posedge vconst) begin
    q <= b;
    $stop;
  end
endmodule

module td (
    input vconst,
    input b,
    output reg q
);

  always @(  /*AS*/ vconst) begin
    q = vconst;
  end
endmodule

module te (
    input clk,
    input vconst,
    input b,
    output reg q
);
  reg qmid;
  always @(posedge vconst or posedge clk) begin
    qmid <= b;
  end
  always @(posedge clk or posedge vconst) begin
    q <= qmid;
  end
endmodule