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microwatt/divider.vhdl

135 lines
4.4 KiB
VHDL

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library work;
use work.common.all;
use work.decode_types.all;
use work.crhelpers.all;
entity divider is
port (
clk : in std_logic;
rst : in std_logic;
d_in : in Decode2ToDividerType;
d_out : out DividerToWritebackType
);
end entity divider;
architecture behaviour of divider is
signal dend : std_ulogic_vector(127 downto 0);
signal div : unsigned(63 downto 0);
signal quot : std_ulogic_vector(63 downto 0);
signal result : std_ulogic_vector(63 downto 0);
signal sresult : std_ulogic_vector(63 downto 0);
signal qbit : std_ulogic;
signal running : std_ulogic;
signal count : unsigned(6 downto 0);
signal neg_result : std_ulogic;
signal is_modulus : std_ulogic;
signal is_32bit : std_ulogic;
signal rc : std_ulogic;
signal write_reg : std_ulogic_vector(4 downto 0);
function compare_zero(value : std_ulogic_vector(63 downto 0); is_32 : std_ulogic)
return std_ulogic_vector is
begin
if is_32 = '1' then
if value(31) = '1' then
return "1000";
elsif unsigned(value(30 downto 0)) > 0 then
return "0100";
else
return "0010";
end if;
else
if value(63) = '1' then
return "1000";
elsif unsigned(value(62 downto 0)) > 0 then
return "0100";
else
return "0010";
end if;
end if;
end function compare_zero;
begin
divider_0: process(clk)
begin
if rising_edge(clk) then
if rst = '1' then
dend <= (others => '0');
div <= (others => '0');
quot <= (others => '0');
running <= '0';
count <= "0000000";
elsif d_in.valid = '1' then
if d_in.is_extended = '1' then
dend <= d_in.dividend & x"0000000000000000";
else
dend <= x"0000000000000000" & d_in.dividend;
end if;
div <= unsigned(d_in.divisor);
quot <= (others => '0');
write_reg <= d_in.write_reg;
neg_result <= d_in.neg_result;
is_modulus <= d_in.is_modulus;
is_32bit <= d_in.is_32bit;
rc <= d_in.rc;
count <= "0000000";
running <= '1';
elsif running = '1' then
if count = "0111111" then
running <= '0';
end if;
if dend(127) = '1' or unsigned(dend(126 downto 63)) >= div then
dend <= std_ulogic_vector(unsigned(dend(126 downto 63)) - div) &
dend(62 downto 0) & '0';
quot <= quot(62 downto 0) & '1';
count <= count + 1;
elsif dend(127 downto 56) = x"000000000000000000" and count(5 downto 3) /= "111" then
-- consume 8 bits of zeroes in one cycle
dend <= dend(119 downto 0) & x"00";
quot <= quot(55 downto 0) & x"00";
count <= count + 8;
else
dend <= dend(126 downto 0) & '0';
quot <= quot(62 downto 0) & '0';
count <= count + 1;
end if;
else
count <= "0000000";
end if;
end if;
end process;
divider_1: process(all)
begin
d_out <= DividerToWritebackInit;
d_out.write_reg_nr <= write_reg;
if is_modulus = '1' then
result <= dend(127 downto 64);
else
result <= quot;
end if;
if neg_result = '1' then
sresult <= std_ulogic_vector(- signed(result));
else
sresult <= result;
end if;
d_out.write_reg_data <= sresult;
if count(6) = '1' then
d_out.valid <= '1';
d_out.write_reg_enable <= '1';
if rc = '1' then
d_out.write_cr_enable <= '1';
d_out.write_cr_mask <= num_to_fxm(0);
d_out.write_cr_data <= compare_zero(sresult, is_32bit) & x"0000000";
end if;
end if;
end process;
end architecture behaviour;