verilator/test_regress/t/t_covergroup_bin_counts.v

// DESCRIPTION: Verilator: Verilog Test module
//
// Tests bin counts, mixed bin types (single values, lists, ranges), and
// coverage database format (verifies coverage.dat contains covergroup entries).
//
// This file ONLY is placed under the Creative Commons Public Domain.
// SPDX-FileCopyrightText: 2026 Matthew Ballance
// SPDX-License-Identifier: CC0-1.0

// verilog_format: off
`define stop $stop
`define checkr(gotv,expv) do if ((gotv) != (expv)) begin $write("%%Error: %s:%0d:  got=%f exp=%f\n", `__FILE__,`__LINE__, (gotv), (expv)); `stop; end while(0);
// verilog_format: on

module t;
  logic [3:0] data;
  logic [7:0] opcode;
  logic signed [3:0] sdata;

  typedef struct packed {bit [7:0] value;} f_t;
  f_t f1;

  // cg: basic bin count tracking
  covergroup cg;
    coverpoint data {bins zero = {0}; bins low = {[1 : 3]};}
  endgroup

  // cg_mixed: mixed bin types - single values, multi-value lists, ranges
  covergroup cg_mixed;
    coverpoint opcode {
      bins nop = {8'h00};
      bins load = {8'h01, 8'h02, 8'h03};
      bins store = {8'h04, 8'h05};
      bins arith = {[8'h10 : 8'h1F]};
      bins other = {[8'h20 : 8'hFE]};
    }
  endgroup

  // cg_db: labeled coverpoint - verifies the coverage database records the correct hierarchy path
  covergroup cg_db;
    cp: coverpoint data {bins low = {[0 : 3]}; bins high = {[8 : 15]};}
  endgroup

  // cg_unbounded: open-ended bin range - '$' resolves to the coverpoint domain max (15 for 4-bit)
  covergroup cg_unbounded;
    cp: coverpoint data {
      bins lo = {[0 : 9]};  // 1 bin: values 0..9
      bins others = {[10 : $]};  // 1 bin: values 10..15 ($ == domain max)
    }
  endgroup

  // cg_unbounded_lo: open-ended LOWER bound - '$' resolves to the domain min (0)
  covergroup cg_unbounded_lo;
    cp: coverpoint data {
      bins start = {[$ : 5]};  // 1 bin: values 0..5  ($ == domain min) -> expr <= 5
      bins rest = {[6 : 15]};
    }
  endgroup

  // cg_unbounded_all: both bounds open ('[$:$]' covers the entire domain -> always true)
  covergroup cg_unbounded_all;
    cp: coverpoint data {
      bins all = {[$ : $]};  // 1 bin: every value
    }
  endgroup

  // cg_unbounded_signed: signed coverpoint with open-ended bounds in both directions
  covergroup cg_unbounded_signed;
    cp: coverpoint sdata {
      bins hi = {[2 : $]};  // sdata >= 2   (signed >=)
      bins lo = {[$ : -2]};  // sdata <= -2  (signed <=)
    }
  endgroup

  // cg_sel: coverpoint over a struct-member part-select expression (AstSel)
  covergroup cg_sel;
    cp: coverpoint f1.value[3:0] {  // low nibble only; upper bits ignored
      bins lo = {[0 : 7]}; bins hi = {[8 : 15]};
    }
  endgroup

  cg cg_inst;
  cg_mixed cg_mixed_inst;
  cg_db cg_db_inst;
  cg_unbounded cg_unbounded_inst;
  cg_unbounded_lo cg_unbounded_lo_inst;
  cg_unbounded_all cg_unbounded_all_inst;
  cg_unbounded_signed cg_unbounded_signed_inst;
  cg_sel cg_sel_inst;

  initial begin
    cg_inst = new;
    cg_mixed_inst = new;
    cg_db_inst = new;
    cg_unbounded_inst = new;
    cg_unbounded_lo_inst = new;
    cg_unbounded_all_inst = new;
    cg_unbounded_signed_inst = new;
    cg_sel_inst = new;

    data = 0;
    cg_inst.sample();  // zero: 1
    `checkr(cg_inst.get_inst_coverage(), 50.0);
    data = 1;
    cg_inst.sample();  // low: 1
    `checkr(cg_inst.get_inst_coverage(), 100.0);
    data = 2;
    cg_inst.sample();  // low: 2
    data = 2;
    cg_inst.sample();  // low: 3

    opcode = 8'h00;
    cg_mixed_inst.sample();  // nop
    `checkr(cg_mixed_inst.get_inst_coverage(), 20.0);
    opcode = 8'h02;
    cg_mixed_inst.sample();  // load
    `checkr(cg_mixed_inst.get_inst_coverage(), 40.0);
    opcode = 8'h05;
    cg_mixed_inst.sample();  // store
    `checkr(cg_mixed_inst.get_inst_coverage(), 60.0);
    opcode = 8'h15;
    cg_mixed_inst.sample();  // arith
    `checkr(cg_mixed_inst.get_inst_coverage(), 80.0);
    opcode = 8'h80;
    cg_mixed_inst.sample();  // other
    `checkr(cg_mixed_inst.get_inst_coverage(), 100.0);

    data = 1;
    cg_db_inst.sample();  // low
    `checkr(cg_db_inst.get_inst_coverage(), 50.0);
    data = 10;
    cg_db_inst.sample();  // high
    `checkr(cg_db_inst.get_inst_coverage(), 100.0);

    // Open-ended range: '$' upper bound covers values up to the domain max
    data = 5;
    cg_unbounded_inst.sample();  // lo
    `checkr(cg_unbounded_inst.get_inst_coverage(), 50.0);
    data = 12;
    cg_unbounded_inst.sample();  // others ([10:$] covers 12)
    `checkr(cg_unbounded_inst.get_inst_coverage(), 100.0);

    // Open-ended lower bound: '$' min covers values down to 0
    data = 3;
    cg_unbounded_lo_inst.sample();  // start ([$:5] covers 3)
    `checkr(cg_unbounded_lo_inst.get_inst_coverage(), 50.0);
    data = 10;
    cg_unbounded_lo_inst.sample();  // rest
    `checkr(cg_unbounded_lo_inst.get_inst_coverage(), 100.0);

    // Both-open range '[$:$]' matches any value
    data = 7;
    cg_unbounded_all_inst.sample();  // all
    `checkr(cg_unbounded_all_inst.get_inst_coverage(), 100.0);

    // Signed open-ended bounds: '$' resolves to signed domain max/min
    sdata = 5;
    cg_unbounded_signed_inst.sample();  // hi ([2:$] covers 5)
    `checkr(cg_unbounded_signed_inst.get_inst_coverage(), 50.0);
    sdata = -5;
    cg_unbounded_signed_inst.sample();  // lo ([$:-2] covers -5)
    `checkr(cg_unbounded_signed_inst.get_inst_coverage(), 100.0);

    // Part-select coverpoint: only the low nibble is sampled (upper bits ignored)
    f1.value = 8'h03;
    cg_sel_inst.sample();  // nibble 3 -> lo
    `checkr(cg_sel_inst.get_inst_coverage(), 50.0);
    f1.value = 8'hF9;
    cg_sel_inst.sample();  // nibble 9 -> hi (upper bits F ignored)
    `checkr(cg_sel_inst.get_inst_coverage(), 100.0);

    $write("*-* All Finished *-*\n");
    $finish;
  end

endmodule