microwatt/fetch1.vhdl

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

library work;
use work.common.all;

entity fetch1 is
	generic(
		RESET_ADDRESS : std_logic_vector(63 downto 0) := (others => '0')
	);
	port(
		clk           : in std_ulogic;
		rst           : in std_ulogic;

		-- Control inputs:
		stall_in      : in std_ulogic;
		flush_in      : in std_ulogic;

		-- redirect from execution unit
		e_in          : in Execute1ToFetch1Type;

		-- fetch data out
		f_out         : out Fetch1ToFetch2Type
	);
end entity fetch1;

architecture behaviour of fetch1 is
	type reg_internal_type is record
		nia_next : std_ulogic_vector(63 downto 0);
	end record;
	signal r_int, rin_int : reg_internal_type;
	signal r, rin : Fetch1ToFetch2Type;
begin
	regs : process(clk)
	begin
		if rising_edge(clk) then
			r <= rin;
			r_int <= rin_int;
		end if;
	end process;

	comb : process(all)
		variable v     : Fetch1ToFetch2Type;
		variable v_int : reg_internal_type;
	begin
		v := r;
		v_int := r_int;

		if stall_in = '0' then
			v.nia := r_int.nia_next;
			v_int.nia_next := std_logic_vector(unsigned(r_int.nia_next) + 4);
		end if;

		if e_in.redirect = '1' then
			v.nia := e_in.redirect_nia;
			v_int.nia_next := std_logic_vector(unsigned(e_in.redirect_nia) + 4);
		end if;

		if rst = '1' then
			v.nia := RESET_ADDRESS;
			v_int.nia_next := std_logic_vector(unsigned(RESET_ADDRESS) + 4);
		end if;

		-- Update registers
		rin <= v;
		rin_int <= v_int;

		-- Update outputs
		f_out <= r;
	end process;

end architecture behaviour;