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microwatt/writeback.vhdl

200 lines
6.8 KiB
VHDL

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library work;
use work.common.all;
use work.crhelpers.all;
entity writeback is
port (
clk : in std_ulogic;
rst : in std_ulogic;
e_in : in Execute1ToWritebackType;
l_in : in Loadstore1ToWritebackType;
fp_in : in FPUToWritebackType;
w_out : out WritebackToRegisterFileType;
c_out : out WritebackToCrFileType;
f_out : out WritebackToFetch1Type;
wb_bypass : out bypass_data_t;
-- PMU event bus
events : out WritebackEventType;
flush_out : out std_ulogic;
interrupt_out: out WritebackToExecute1Type;
complete_out : out instr_tag_t
);
end entity writeback;
architecture behaviour of writeback is
begin
writeback_0: process(clk)
variable x : std_ulogic_vector(0 downto 0);
variable y : std_ulogic_vector(0 downto 0);
variable w : std_ulogic_vector(0 downto 0);
begin
if rising_edge(clk) then
-- Do consistency checks only on the clock edge
x(0) := e_in.valid;
y(0) := l_in.valid;
w(0) := fp_in.valid;
assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) +
to_integer(unsigned(w))) <= 1 severity failure;
x(0) := e_in.write_enable;
y(0) := l_in.write_enable;
w(0) := fp_in.write_enable;
assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) +
to_integer(unsigned(w))) <= 1 severity failure;
w(0) := e_in.write_cr_enable;
x(0) := l_in.rc;
y(0) := fp_in.write_cr_enable;
assert (to_integer(unsigned(w)) + to_integer(unsigned(x)) +
to_integer(unsigned(y))) <= 1 severity failure;
assert (e_in.write_xerc_enable and fp_in.write_xerc) /= '1' severity failure;
assert not (e_in.valid = '1' and e_in.instr_tag.valid = '0') severity failure;
assert not (l_in.valid = '1' and l_in.instr_tag.valid = '0') severity failure;
assert not (fp_in.valid = '1' and fp_in.instr_tag.valid = '0') severity failure;
end if;
end process;
writeback_1: process(all)
variable f : WritebackToFetch1Type;
variable scf : std_ulogic_vector(3 downto 0);
variable vec : integer range 0 to 16#fff#;
variable srr1 : std_ulogic_vector(15 downto 0);
variable intr : std_ulogic;
begin
w_out <= WritebackToRegisterFileInit;
c_out <= WritebackToCrFileInit;
f := WritebackToFetch1Init;
vec := 0;
complete_out <= instr_tag_init;
if e_in.valid = '1' then
complete_out <= e_in.instr_tag;
elsif l_in.valid = '1' then
complete_out <= l_in.instr_tag;
elsif fp_in.valid = '1' then
complete_out <= fp_in.instr_tag;
end if;
events.instr_complete <= complete_out.valid;
events.fp_complete <= fp_in.valid;
intr := e_in.interrupt or l_in.interrupt or fp_in.interrupt;
interrupt_out.intr <= intr;
if intr = '1' then
srr1 := (others => '0');
if e_in.interrupt = '1' then
vec := e_in.intr_vec;
srr1 := e_in.srr1;
elsif l_in.interrupt = '1' then
vec := l_in.intr_vec;
srr1 := l_in.srr1;
elsif fp_in.interrupt = '1' then
vec := fp_in.intr_vec;
srr1 := fp_in.srr1;
end if;
interrupt_out.srr1 <= srr1;
else
if e_in.write_enable = '1' then
w_out.write_reg <= e_in.write_reg;
w_out.write_data <= e_in.write_data;
w_out.write_enable <= '1';
end if;
if e_in.write_cr_enable = '1' then
c_out.write_cr_enable <= '1';
c_out.write_cr_mask <= e_in.write_cr_mask;
c_out.write_cr_data <= e_in.write_cr_data;
end if;
if e_in.write_xerc_enable = '1' then
c_out.write_xerc_enable <= '1';
c_out.write_xerc_data <= e_in.xerc;
end if;
if fp_in.write_enable = '1' then
w_out.write_reg <= fp_in.write_reg;
w_out.write_data <= fp_in.write_data;
w_out.write_enable <= '1';
end if;
if fp_in.write_cr_enable = '1' then
c_out.write_cr_enable <= '1';
c_out.write_cr_mask <= fp_in.write_cr_mask;
c_out.write_cr_data <= fp_in.write_cr_data;
end if;
if fp_in.write_xerc = '1' then
c_out.write_xerc_enable <= '1';
c_out.write_xerc_data <= fp_in.xerc;
end if;
if l_in.write_enable = '1' then
w_out.write_reg <= l_in.write_reg;
w_out.write_data <= l_in.write_data;
w_out.write_enable <= '1';
end if;
if l_in.rc = '1' then
-- st*cx. instructions
scf(3) := '0';
scf(2) := '0';
scf(1) := l_in.store_done;
scf(0) := l_in.xerc.so;
c_out.write_cr_enable <= '1';
c_out.write_cr_mask <= num_to_fxm(0);
c_out.write_cr_data(31 downto 28) <= scf;
end if;
end if;
-- Outputs to fetch1
f.redirect := e_in.redirect;
f.br_nia := e_in.last_nia;
f.br_last := e_in.br_last;
f.br_taken := e_in.br_taken;
if intr = '1' then
f.redirect := '1';
f.br_last := '0';
f.redirect_nia := std_ulogic_vector(to_unsigned(vec, 64));
f.virt_mode := '0';
f.priv_mode := '1';
-- XXX need an interrupt LE bit here, e.g. from LPCR
f.big_endian := '0';
f.mode_32bit := '0';
else
if e_in.abs_br = '1' then
f.redirect_nia := e_in.br_offset;
else
f.redirect_nia := std_ulogic_vector(unsigned(e_in.last_nia) + unsigned(e_in.br_offset));
end if;
-- send MSR[IR], ~MSR[PR], ~MSR[LE] and ~MSR[SF] up to fetch1
f.virt_mode := e_in.redir_mode(3);
f.priv_mode := e_in.redir_mode(2);
f.big_endian := e_in.redir_mode(1);
f.mode_32bit := e_in.redir_mode(0);
end if;
f_out <= f;
flush_out <= f_out.redirect;
-- Register write data bypass to decode2
wb_bypass.tag.tag <= complete_out.tag;
wb_bypass.tag.valid <= complete_out.valid and w_out.write_enable;
wb_bypass.data <= w_out.write_data;
end process;
end;