countzero_tb.vhdl

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

library work;
use work.common.all;
use work.glibc_random.all;

entity countzero_tb is
end countzero_tb;

architecture behave of countzero_tb is
    constant clk_period: time := 10 ns;
    signal rs: std_ulogic_vector(63 downto 0);
    signal is_32bit, count_right: std_ulogic := '0';
    signal result: std_ulogic_vector(63 downto 0);
    signal randno: std_ulogic_vector(63 downto 0);
    signal clk: std_ulogic;

begin
    zerocounter_0: entity work.zero_counter
	port map (
            clk => clk,
	    rs => rs,
	    result => result,
	    count_right => count_right,
	    is_32bit => is_32bit
	);

    clk_process: process
    begin
        clk <= '0';
        wait for clk_period/2;
        clk <= '1';
        wait for clk_period/2;
    end process;

    stim_process: process
        variable r: std_ulogic_vector(63 downto 0);
    begin
        -- test with input = 0
        report "test zero input";
        rs <= (others => '0');
        is_32bit <= '0';
        count_right <= '0';
        wait for clk_period;
        assert result = x"0000000000000040"
            report "bad cntlzd 0 = " & to_hstring(result);
        count_right <= '1';
        wait for clk_period;
        assert result = x"0000000000000040"
            report "bad cnttzd 0 = " & to_hstring(result);
        is_32bit <= '1';
        count_right <= '0';
        wait for clk_period;
        assert result = x"0000000000000020"
            report "bad cntlzw 0 = " & to_hstring(result);
        count_right <= '1';
        wait for clk_period;
        assert result = x"0000000000000020"
            report "bad cnttzw 0 = " & to_hstring(result);

        report "test cntlzd/w";
        count_right <= '0';
        for j in 0 to 100 loop
            r := pseudorand(64);
            r(63) := '1';
            for i in 0 to 63 loop
                rs <= r;
                is_32bit <= '0';
                wait for clk_period;
                assert to_integer(unsigned(result)) = i
                    report "bad cntlzd " & to_hstring(rs) & " -> " & to_hstring(result);
                rs <= r(31 downto 0) & r(63 downto 32);
                is_32bit <= '1';
                wait for clk_period;
                if i < 32 then
                    assert to_integer(unsigned(result)) = i
                        report "bad cntlzw " & to_hstring(rs) & " -> " & to_hstring(result);
                else
                    assert to_integer(unsigned(result)) = 32
                        report "bad cntlzw " & to_hstring(rs) & " -> " & to_hstring(result);
                end if;
                r := '0' & r(63 downto 1);
            end loop;
        end loop;

        report "test cnttzd/w";
        count_right <= '1';
        for j in 0 to 100 loop
            r := pseudorand(64);
            r(0) := '1';
            for i in 0 to 63 loop
                rs <= r;
                is_32bit <= '0';
                wait for clk_period;
                assert to_integer(unsigned(result)) = i
                    report "bad cnttzd " & to_hstring(rs) & " -> " & to_hstring(result);
                is_32bit <= '1';
                wait for clk_period;
                if i < 32 then
                    assert to_integer(unsigned(result)) = i
                        report "bad cnttzw " & to_hstring(rs) & " -> " & to_hstring(result);
                else
                    assert to_integer(unsigned(result)) = 32
                        report "bad cnttzw " & to_hstring(rs) & " -> " & to_hstring(result);
                end if;
                r := r(62 downto 0) & '0';
            end loop;
        end loop;

	std.env.finish;
    end process;
end behave;