port (
clk : in std_ulogic;
- e_in : in Execute2ToWritebackType;
- l_in : in Loadstore2ToWritebackType;
- m_in : in MultiplyToWritebackType;
- d_in : in DividerToWritebackType;
+ e_in : in Execute1ToWritebackType;
+ l_in : in Loadstore1ToWritebackType;
w_out : out WritebackToRegisterFileType;
c_out : out WritebackToCrFileType;
end entity writeback;
architecture behaviour of writeback is
- subtype byte_index_t is unsigned(2 downto 0);
- type permutation_t is array(0 to 7) of byte_index_t;
- subtype byte_trim_t is std_ulogic_vector(1 downto 0);
- type trim_ctl_t is array(0 to 7) of byte_trim_t;
- type byte_sel_t is array(0 to 7) of std_ulogic;
-
- signal data_len : unsigned(3 downto 0);
- signal data_in : std_ulogic_vector(63 downto 0);
- signal data_permuted : std_ulogic_vector(63 downto 0);
- signal data_trimmed : std_ulogic_vector(63 downto 0);
- signal data_latched : std_ulogic_vector(63 downto 0);
- signal perm : permutation_t;
- signal use_second : byte_sel_t;
- signal byte_offset : unsigned(2 downto 0);
- signal brev_lenm1 : unsigned(2 downto 0);
- signal trim_ctl : trim_ctl_t;
- signal rc : std_ulogic;
- signal partial_write : std_ulogic;
- signal sign_extend : std_ulogic;
- signal negative : std_ulogic;
- signal second_word : std_ulogic;
begin
- writeback_0: process(clk)
- begin
- if rising_edge(clk) then
- if partial_write = '1' then
- data_latched <= data_permuted;
- end if;
- end if;
- end process;
-
writeback_1: process(all)
variable x : std_ulogic_vector(0 downto 0);
variable y : std_ulogic_vector(0 downto 0);
- variable z : std_ulogic_vector(0 downto 0);
variable w : std_ulogic_vector(0 downto 0);
- variable j : integer;
- variable k : unsigned(3 downto 0);
+ variable cf: std_ulogic_vector(3 downto 0);
+ variable zero : std_ulogic;
+ variable sign : std_ulogic;
+ variable scf : std_ulogic_vector(3 downto 0);
begin
- x := "" & e_in.valid;
- y := "" & l_in.valid;
- z := "" & m_in.valid;
- w := "" & d_in.valid;
- assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z)) + to_integer(unsigned(w))) <= 1 severity failure;
-
- x := "" & e_in.write_enable;
- y := "" & l_in.write_enable;
- z := "" & m_in.write_reg_enable;
- w := "" & d_in.write_reg_enable;
- assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z)) + to_integer(unsigned(w))) <= 1 severity failure;
-
- w := "" & e_in.write_cr_enable;
- x := "" & (e_in.write_enable and e_in.rc);
- y := "" & (m_in.valid and m_in.rc);
- z := "" & (d_in.valid and d_in.rc);
- assert (to_integer(unsigned(w)) + to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z))) <= 1 severity failure;
+ x(0) := e_in.valid;
+ y(0) := l_in.valid;
+ assert (to_integer(unsigned(x)) + to_integer(unsigned(y))) <= 1 severity failure;
+
+ x(0) := e_in.write_enable;
+ y(0) := l_in.write_enable;
+ assert (to_integer(unsigned(x)) + to_integer(unsigned(y))) <= 1 severity failure;
+
+ w(0) := e_in.write_cr_enable;
+ x(0) := (e_in.write_enable and e_in.rc);
+ assert (to_integer(unsigned(w)) + to_integer(unsigned(x))) <= 1 severity failure;
w_out <= WritebackToRegisterFileInit;
c_out <= WritebackToCrFileInit;
complete_out <= '0';
- if e_in.valid = '1' or l_in.valid = '1' or m_in.valid = '1' or d_in.valid = '1' then
+ if e_in.valid = '1' or l_in.valid = '1' then
complete_out <= '1';
end if;
- rc <= '0';
- brev_lenm1 <= "000";
- byte_offset <= "000";
- data_len <= x"8";
- partial_write <= '0';
- sign_extend <= '0';
- second_word <= '0';
-
if e_in.write_enable = '1' then
w_out.write_reg <= e_in.write_reg;
- data_in <= e_in.write_data;
+ w_out.write_data <= e_in.write_data;
w_out.write_enable <= '1';
- data_len <= unsigned(e_in.write_len);
- sign_extend <= e_in.sign_extend;
- rc <= e_in.rc;
end if;
if e_in.write_cr_enable = '1' then
c_out.write_cr_data <= e_in.write_cr_data;
end if;
- if l_in.write_enable = '1' then
- w_out.write_reg <= l_in.write_reg;
- data_in <= l_in.write_data;
- data_len <= unsigned(l_in.write_len);
- byte_offset <= unsigned(l_in.write_shift);
- sign_extend <= l_in.sign_extend;
- if l_in.byte_reverse = '1' then
- brev_lenm1 <= unsigned(l_in.write_len(2 downto 0)) - 1;
- end if;
- w_out.write_enable <= '1';
- second_word <= l_in.second_word;
- if l_in.valid = '0' and (data_len + byte_offset > 8) then
- partial_write <= '1';
- end if;
- 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 m_in.write_reg_enable = '1' then
+ if l_in.write_enable = '1' then
+ w_out.write_reg <= gpr_to_gspr(l_in.write_reg);
+ w_out.write_data <= l_in.write_data;
w_out.write_enable <= '1';
- w_out.write_reg <= m_in.write_reg_nr;
- data_in <= m_in.write_reg_data;
- rc <= m_in.rc;
end if;
- if d_in.write_reg_enable = '1' then
- w_out.write_enable <= '1';
- w_out.write_reg <= d_in.write_reg_nr;
- data_in <= d_in.write_reg_data;
- rc <= d_in.rc;
+ 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;
- -- shift and byte-reverse data bytes
- for i in 0 to 7 loop
- k := ('0' & (to_unsigned(i, 3) xor brev_lenm1)) + ('0' & byte_offset);
- perm(i) <= k(2 downto 0);
- use_second(i) <= k(3);
- end loop;
- for i in 0 to 7 loop
- j := to_integer(perm(i)) * 8;
- data_permuted(i * 8 + 7 downto i * 8) <= data_in(j + 7 downto j);
- end loop;
-
- -- If the data can arrive split over two cycles, this will be correct
- -- provided we don't have both sign extension and byte reversal.
- negative <= (data_len(2) and data_permuted(31)) or (data_len(1) and data_permuted(15)) or
- (data_len(0) and data_permuted(7));
-
- -- trim and sign-extend
- for i in 0 to 7 loop
- if i < to_integer(data_len) then
- if second_word = '1' then
- trim_ctl(i) <= '1' & not use_second(i);
- else
- trim_ctl(i) <= not use_second(i) & '0';
- end if;
- else
- trim_ctl(i) <= '0' & (negative and sign_extend);
- end if;
- end loop;
- for i in 0 to 7 loop
- case trim_ctl(i) is
- when "11" =>
- data_trimmed(i * 8 + 7 downto i * 8) <= data_latched(i * 8 + 7 downto i * 8);
- when "10" =>
- data_trimmed(i * 8 + 7 downto i * 8) <= data_permuted(i * 8 + 7 downto i * 8);
- when "01" =>
- data_trimmed(i * 8 + 7 downto i * 8) <= x"FF";
- when others =>
- data_trimmed(i * 8 + 7 downto i * 8) <= x"00";
- end case;
- end loop;
-
- -- deliver to regfile
- w_out.write_data <= data_trimmed;
-
- -- test value against 0 and set CR0 if requested
- if rc = '1' then
+ -- Perform CR0 update for RC forms
+ -- Note that loads never have a form with an RC bit, therefore this can test e_in.write_data
+ if e_in.rc = '1' and e_in.write_enable = '1' then
+ sign := e_in.write_data(63);
+ zero := not (or e_in.write_data);
c_out.write_cr_enable <= '1';
c_out.write_cr_mask <= num_to_fxm(0);
- if data_trimmed(63) = '1' then
- c_out.write_cr_data <= x"80000000";
- elsif or (data_trimmed(62 downto 0)) = '1' then
- c_out.write_cr_data <= x"40000000";
- else
- c_out.write_cr_data <= x"20000000";
- end if;
+ cf(3) := sign;
+ cf(2) := not sign and not zero;
+ cf(1) := zero;
+ cf(0) := e_in.xerc.so;
+ c_out.write_cr_data(31 downto 28) <= cf;
end if;
end process;
end;
projects / microwatt.git / blobdiff