library ieee; use ieee.std_logic_1164.all; use ieee.numeric_std.all; library work; use work.common.all; use work.helpers.all; use work.wishbone_types.all; -- 2 cycle LSU -- In this cycle we read or write any data and do sign extension and update if required. entity loadstore2 is port ( clk : in std_ulogic; l_in : in Loadstore1ToLoadstore2Type; w_out : out Loadstore2ToWritebackType; m_in : in wishbone_slave_out; m_out : out wishbone_master_out ); end loadstore2; architecture behave of loadstore2 is signal l_saved : Loadstore1ToLoadstore2Type; signal w_tmp : Loadstore2ToWritebackType; signal m_tmp : wishbone_master_out; type state_t is (IDLE, WAITING_FOR_READ_ACK, WAITING_FOR_WRITE_ACK); signal state : state_t := IDLE; function length_to_sel(length : in std_logic_vector(3 downto 0)) return std_ulogic_vector is begin case length is when "0001" => return "00000001"; when "0010" => return "00000011"; when "0100" => return "00001111"; when "1000" => return "11111111"; when others => return "00000000"; end case; end function length_to_sel; function wishbone_data_shift(address : in std_ulogic_vector(63 downto 0)) return natural is begin return to_integer(unsigned(address(2 downto 0))) * 8; end function wishbone_data_shift; function wishbone_data_sel(size : in std_logic_vector(3 downto 0); address : in std_logic_vector(63 downto 0)) return std_ulogic_vector is begin return std_ulogic_vector(shift_left(unsigned(length_to_sel(size)), to_integer(unsigned(address(2 downto 0))))); end function wishbone_data_sel; begin w_out <= w_tmp; m_out <= m_tmp; loadstore2_0: process(clk) variable tmp : std_ulogic_vector(63 downto 0); variable data : std_ulogic_vector(63 downto 0); begin if rising_edge(clk) then tmp := (others => '0'); data := (others => '0'); w_tmp <= Loadstore2ToWritebackInit; l_saved <= l_saved; case_0: case state is when IDLE => if l_in.valid = '1' then m_tmp <= wishbone_master_out_init; m_tmp.sel <= wishbone_data_sel(l_in.length, l_in.addr); m_tmp.adr <= l_in.addr(63 downto 3) & "000"; m_tmp.cyc <= '1'; m_tmp.stb <= '1'; l_saved <= l_in; if l_in.load = '1' then m_tmp.we <= '0'; -- Load with update instructions write two GPR destinations. -- We don't want the expense of two write ports, so make it -- single in the pipeline and write back the update GPR now -- and the load once we get the data back. We'll have to -- revisit this when loads can take exceptions. if l_in.update = '1' then w_tmp.write_enable <= '1'; w_tmp.write_reg <= l_in.update_reg; w_tmp.write_data <= l_in.addr; end if; state <= WAITING_FOR_READ_ACK; else m_tmp.we <= '1'; data := l_in.data; if l_in.byte_reverse = '1' then data := byte_reverse(data, to_integer(unsigned(l_in.length))); end if; m_tmp.dat <= std_logic_vector(shift_left(unsigned(data), wishbone_data_shift(l_in.addr))); assert l_in.sign_extend = '0' report "sign extension doesn't make sense for stores" severity failure; state <= WAITING_FOR_WRITE_ACK; end if; end if; when WAITING_FOR_READ_ACK => if m_in.ack = '1' then tmp := std_logic_vector(shift_right(unsigned(m_in.dat), wishbone_data_shift(l_saved.addr))); case to_integer(unsigned(l_saved.length)) is when 0 => when 1 => data(7 downto 0) := tmp(7 downto 0); when 2 => data(15 downto 0) := tmp(15 downto 0); when 4 => data(31 downto 0) := tmp(31 downto 0); when 8 => data(63 downto 0) := tmp(63 downto 0); when others => assert false report "invalid length" severity failure; end case; if l_saved.sign_extend = '1' then data := sign_extend(data, to_integer(unsigned(l_saved.length))); end if; if l_saved.byte_reverse = '1' then data := byte_reverse(data, to_integer(unsigned(l_saved.length))); end if; w_tmp.write_data <= data; -- write data to register file w_tmp.valid <= '1'; w_tmp.write_enable <= '1'; w_tmp.write_reg <= l_saved.write_reg; m_tmp <= wishbone_master_out_init; state <= IDLE; end if; when WAITING_FOR_WRITE_ACK => if m_in.ack = '1' then w_tmp.valid <= '1'; if l_saved.update = '1' then w_tmp.write_enable <= '1'; w_tmp.write_reg <= l_saved.update_reg; w_tmp.write_data <= l_saved.addr; end if; m_tmp <= wishbone_master_out_init; state <= IDLE; end if; end case; end if; end process; end;