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microwatt/gpr_hazard.vhdl

71 lines
1.9 KiB
VHDL

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
entity gpr_hazard is
generic (
PIPELINE_DEPTH : natural := 2
);
port(
clk : in std_ulogic;
stall_in : in std_ulogic;
gpr_write_valid_in : in std_ulogic;
gpr_write_in : in std_ulogic_vector(5 downto 0);
gpr_read_valid_in : in std_ulogic;
gpr_read_in : in std_ulogic_vector(5 downto 0);
stall_out : out std_ulogic
);
end entity gpr_hazard;
architecture behaviour of gpr_hazard is
type pipeline_entry_type is record
valid : std_ulogic;
gpr : std_ulogic_vector(5 downto 0);
end record;
constant pipeline_entry_init : pipeline_entry_type := (valid => '0', gpr => (others => '0'));
type pipeline_t is array(0 to PIPELINE_DEPTH-1) of pipeline_entry_type;
constant pipeline_t_init : pipeline_t := (others => pipeline_entry_init);
signal r, rin : pipeline_t := pipeline_t_init;
begin
gpr_hazard0: process(clk)
begin
if rising_edge(clk) then
if stall_in = '0' then
r <= rin;
end if;
end if;
end process;
gpr_hazard1: process(all)
variable v : pipeline_t;
begin
v := r;
stall_out <= '0';
loop_0: for i in 0 to PIPELINE_DEPTH-1 loop
if ((r(i).valid = gpr_read_valid_in) and r(i).gpr = gpr_read_in) then
stall_out <= '1';
end if;
end loop;
v(0).valid := gpr_write_valid_in;
v(0).gpr := gpr_write_in;
loop_1: for i in 0 to PIPELINE_DEPTH-2 loop
-- propagate to next slot
v(i+1) := r(i);
end loop;
-- asynchronous output
if gpr_read_valid_in = '0' then
stall_out <= '0';
end if;
-- update registers
rin <= v;
end process;
end;