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Rework CR file and add forwarding

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Handle the CR as a single field with per nibble enables. Forward any
writes in the same cycle.

If this proves to be an issue for timing, we may want to revisit
this in the future. For now, it keeps things simple.

Signed-off-by: Anton Blanchard <anton@linux.ibm.com>
pull/24/head
Anton Blanchard 5 years ago committed by Anton Blanchard
parent 7c2a2b7414
commit 9fbaea6f08
5 changed files with 37 additions and 45 deletions
Show Stats Download Patch File Download Diff File

5
common.vhdl
Unescape Escape View File

@ -79,14 +79,11 @@ package common is
end record;

type Decode2ToCrFileType is record
read_cr_nr_1 : integer;
read_cr_nr_2 : integer;
read : std_ulogic;
end record;

type CrFileToDecode2Type is record
read_cr_data : std_ulogic_vector(31 downto 0);
read_cr_data_1 : std_ulogic_vector(3 downto 0);
read_cr_data_2 : std_ulogic_vector(3 downto 0);
end record;

type Execute1ToFetch1Type is record

55
cr_file.vhdl
Unescape Escape View File

@ -18,48 +18,43 @@ end entity cr_file;

architecture behaviour of cr_file is
signal crs : std_ulogic_vector(31 downto 0) := (others => '0');
signal crs_updated : std_ulogic_vector(31 downto 0) := (others => '0');
begin
cr_create_0: process(all)
variable hi, lo : integer := 0;
begin
for i in 0 to 7 loop
if w_in.write_cr_mask(i) = '1' then
lo := i*4;
hi := lo + 3;
crs_updated(hi downto lo) <= w_in.write_cr_data(hi downto lo);
end if;
end loop;
end process;

-- synchronous writes
cr_write_0: process(clk)
variable hi, lo : integer := 0;
begin
if rising_edge(clk) then
if w_in.write_cr_enable = '1' then
report "Writing " & to_hstring(w_in.write_cr_data) & " to CR mask " & to_hstring(w_in.write_cr_mask);

for i in 0 to 7 loop
if w_in.write_cr_mask(i) = '1' then
lo := i*4;
hi := lo + 3;
crs(hi downto lo) <= w_in.write_cr_data(hi downto lo);
end if;
end loop;
crs <= crs_updated;
end if;
end if;
end process cr_write_0;
end process;

-- asynchronous reads
cr_read_0: process(all)
variable hi, lo : integer := 0;
begin
--lo := (7-d_in.read_cr_nr_1)*4;
--hi := lo + 3;

--report "read " & integer'image(d_in.read_cr_nr_1) & " from CR " & to_hstring(crs(hi downto lo));
--d_out.read_cr_data_1 <= crs(hi downto lo);

-- Also return the entire CR to make mfcrf easier for now
report "read CR " & to_hstring(crs);
d_out.read_cr_data <= crs;

-- -- Forward any written data
-- if w_in.write_cr_enable = '1' then
-- if d_in.read_cr_nr_1 = w_in.write_cr_nr then
-- d_out.read_cr_data_1 <= w_in.write_cr_data;
-- end if;
-- if d_in.read_cr_nr_2 = w_in.write_cr_nr then
-- d_out.read_cr_data_2 <= w_in.write_cr_data;
-- end if;
-- end if;
end process cr_read_0;
-- just return the entire CR to make mfcrf easier for now
if d_in.read = '1' then
report "Reading CR " & to_hstring(crs_updated);
end if;
if w_in.write_cr_enable then
d_out.read_cr_data <= crs_updated;
else
d_out.read_cr_data <= crs;
end if;
end process;
end architecture behaviour;

18
decode1.vhdl
Unescape Escape View File

@ -43,19 +43,19 @@ architecture behaviour of decode1 is
PPC_ATTN => (ALU, OP_ILLEGAL, NONE, NONE, NONE, NONE, NONE, NONE, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0'),
PPC_B => (ALU, OP_B, NONE, CONST_LI, NONE, NONE, NONE, NONE, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '1'),
--PPC_BA
PPC_BC => (ALU, OP_BC, NONE, CONST_BD, NONE, NONE, BO, BI, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '1'),
PPC_BC => (ALU, OP_BC, NONE, CONST_BD, NONE, NONE, BO, BI, NONE, '1', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '1'),
--PPC_BCA
PPC_BCCTR => (ALU, OP_BCCTR, NONE, NONE, NONE, NONE, BO, BI, BH, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '1'),
PPC_BCCTR => (ALU, OP_BCCTR, NONE, NONE, NONE, NONE, BO, BI, BH, '1', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '1'),
--PPC_BCLA
PPC_BCLR => (ALU, OP_BCLR, NONE, NONE, NONE, NONE, BO, BI, BH, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '1'),
PPC_BCLR => (ALU, OP_BCLR, NONE, NONE, NONE, NONE, BO, BI, BH, '1', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '1'),
--PPC_BCTAR
--PPC_BPERM
PPC_CMP => (ALU, OP_CMP, RA, RB, NONE, NONE, BF, L, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_CMPB => (ALU, OP_CMPB, RS, RB, NONE, RA, NONE, NONE, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_CMP => (ALU, OP_CMP, RA, RB, NONE, NONE, BF, L, NONE, '0', '1', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_CMPB => (ALU, OP_CMPB, RS, RB, NONE, RA, NONE, NONE, NONE, '0', '1', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
--PPC_CMPEQB
PPC_CMPI => (ALU, OP_CMP, RA, CONST_SI, NONE, NONE, BF, L, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_CMPL => (ALU, OP_CMPL, RA, RB, NONE, NONE, BF, L, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_CMPLI => (ALU, OP_CMPL, RA, CONST_UI, NONE, NONE, BF, L, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_CMPI => (ALU, OP_CMP, RA, CONST_SI, NONE, NONE, BF, L, NONE, '0', '1', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_CMPL => (ALU, OP_CMPL, RA, RB, NONE, NONE, BF, L, NONE, '0', '1', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_CMPLI => (ALU, OP_CMPL, RA, CONST_UI, NONE, NONE, BF, L, NONE, '0', '1', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
--PPC_CMPRB
PPC_CNTLZD => (ALU, OP_CNTLZD, RS, NONE, NONE, RA, NONE, NONE, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0'),
PPC_CNTLZW => (ALU, OP_CNTLZW, RS, NONE, NONE, RA, NONE, NONE, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', RC, '0'),
@ -90,7 +90,7 @@ architecture behaviour of decode1 is
--PPC_EXTSWSLI
--PPC_ICBI
PPC_ICBT => (ALU, OP_NOP, NONE, NONE, NONE, NONE, NONE, NONE, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_ISEL => (ALU, OP_ISEL, RA_OR_ZERO, RB, NONE, RT, BC, NONE, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_ISEL => (ALU, OP_ISEL, RA_OR_ZERO, RB, NONE, RT, BC, NONE, NONE, '1', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_ISYNC => (ALU, OP_NOP, NONE, NONE, NONE, NONE, NONE, NONE, NONE, '0', '0', '0', '0', NONE, '0', '0', '0', '0', '0', '0', NONE, '0'),
PPC_LBARX => (LDST, OP_LOAD, RA, RB, NONE, RT, NONE, NONE, NONE, '0', '0', '0', '0', is1B, '0', '0', '0', '1', '0', '0', NONE, '0'),
--CONST_LI matches CONST_SI, so reuse it

2
decode2.vhdl
Unescape Escape View File

@ -184,6 +184,8 @@ begin
r_out.read3_reg <= insn_rs(d.insn) when d.decode.input_reg_c = RS else
(others => '0');

c_out.read <= d.decode.input_cr;

decode2_1: process(all)
variable mul_a : std_ulogic_vector(63 downto 0);
variable mul_b : std_ulogic_vector(63 downto 0);

2
writeback.vhdl
Unescape Escape View File

@ -56,7 +56,6 @@ begin
end if;

if e.write_cr_enable = '1' then
report "Writing CR ";
c_tmp.write_cr_enable <= '1';
c_tmp.write_cr_mask <= e.write_cr_mask;
c_tmp.write_cr_data <= e.write_cr_data;
@ -81,7 +80,6 @@ begin
w_tmp.write_data <= m.write_reg_data;
end if;
if m.write_cr_enable = '1' then
report "Writing CR ";
c_tmp.write_cr_enable <= '1';
c_tmp.write_cr_mask <= m.write_cr_mask;
c_tmp.write_cr_data <= m.write_cr_data;

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