library work;
use work.common.all;
+use work.crhelpers.all;
entity writeback is
- port (
- clk : in std_ulogic;
+ port (
+ clk : in std_ulogic;
- e_in : in Execute2ToWritebackType;
- l_in : in Loadstore2ToWritebackType;
- m_in : in MultiplyToWritebackType;
+ e_in : in Execute1ToWritebackType;
+ l_in : in Loadstore1ToWritebackType;
- w_out : out WritebackToRegisterFileType;
- c_out : out WritebackToCrFileType;
+ w_out : out WritebackToRegisterFileType;
+ c_out : out WritebackToCrFileType;
- complete_out : out std_ulogic
- );
+ complete_out : out std_ulogic
+ );
end entity writeback;
architecture behaviour of writeback is
- signal e : Execute2ToWritebackType;
- signal l : Loadstore2ToWritebackType;
- signal m : MultiplyToWritebackType;
- signal w_tmp : WritebackToRegisterFileType;
- signal c_tmp : WritebackToCrFileType;
begin
- writeback_0: process(clk)
- begin
- if rising_edge(clk) then
- e <= e_in;
- l <= l_in;
- m <= m_in;
- end if;
- end process;
-
- w_out <= w_tmp;
- c_out <= c_tmp;
-
- complete_out <= '1' when e.valid or l.valid or m.valid else '0';
-
- 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);
- begin
- x := "" & e.valid;
- y := "" & l.valid;
- z := "" & m.valid;
- assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z))) <= 1;
-
- x := "" & e.write_enable;
- y := "" & l.write_enable;
- z := "" & m.write_reg_enable;
- assert (to_integer(unsigned(x)) + to_integer(unsigned(y)) + to_integer(unsigned(z))) <= 1;
-
- assert not(e.write_cr_enable = '1' and m.write_cr_enable = '1');
-
- w_tmp <= WritebackToRegisterFileInit;
- c_tmp <= WritebackToCrFileInit;
-
- if e.write_enable = '1' then
- w_tmp.write_reg <= e.write_reg;
- w_tmp.write_data <= e.write_data;
- w_tmp.write_enable <= '1';
- end if;
-
- if e.write_cr_enable = '1' then
- c_tmp.write_cr_enable <= '1';
- c_tmp.write_cr_mask <= e.write_cr_mask;
- c_tmp.write_cr_data <= e.write_cr_data;
- end if;
-
- if l.write_enable = '1' then
- w_tmp.write_reg <= l.write_reg;
- w_tmp.write_data <= l.write_data;
- w_tmp.write_enable <= '1';
- end if;
-
- if m.write_reg_enable = '1' then
- w_tmp.write_enable <= '1';
- w_tmp.write_reg <= m.write_reg_nr;
- w_tmp.write_data <= m.write_reg_data;
- end if;
-
- if m.write_cr_enable = '1' then
- c_tmp.write_cr_enable <= '1';
- c_tmp.write_cr_mask <= m.write_cr_mask;
- c_tmp.write_cr_data <= m.write_cr_data;
- end if;
- end process;
+ 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;
+ assert (to_integer(unsigned(x)) + to_integer(unsigned(y))) <= 1 severity failure;
+
+ x(0) := e_in.write_enable or e_in.exc_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;
+ end if;
+ end process;
+
+ writeback_1: process(all)
+ 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
+ w_out <= WritebackToRegisterFileInit;
+ c_out <= WritebackToCrFileInit;
+
+ complete_out <= '0';
+ if e_in.valid = '1' or l_in.valid = '1' then
+ complete_out <= '1';
+ end if;
+
+ if e_in.exc_write_enable = '1' then
+ w_out.write_reg <= e_in.exc_write_reg;
+ w_out.write_data <= e_in.exc_write_data;
+ w_out.write_enable <= '1';
+ 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 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';
+ 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;
+
+ -- 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);
+ 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 if;
+ end process;
end;
projects / microwatt.git / blobdiff