@ -15,6 +15,7 @@ entity fpu is
port (
clk : in std_ulogic;
rst : in std_ulogic;
flush_in : in std_ulogic;
e_in : in Execute1ToFPUType;
e_out : out FPUToExecute1Type;
@ -35,7 +36,7 @@ architecture behaviour of fpu is
mantissa : std_ulogic_vector(63 downto 0); -- 10.54 format
end record;
type state_t is (IDLE,
type state_t is (IDLE, DO_ILLEGAL,
DO_MCRFS, DO_MTFSB, DO_MTFSFI, DO_MFFS, DO_MTFSF,
DO_FMR, DO_FMRG, DO_FCMP, DO_FTDIV, DO_FTSQRT,
DO_FCFID, DO_FCTI,
@ -71,7 +72,9 @@ architecture behaviour of fpu is
type reg_type is record
state : state_t;
busy : std_ulogic;
f2stall : std_ulogic;
instr_done : std_ulogic;
complete : std_ulogic;
do_intr : std_ulogic;
illegal : std_ulogic;
op : insn_type_t;
@ -83,7 +86,9 @@ architecture behaviour of fpu is
rc : std_ulogic;
is_cmp : std_ulogic;
single_prec : std_ulogic;
sp_result : std_ulogic;
fpscr : std_ulogic_vector(31 downto 0);
comm_fpscr : std_ulogic_vector(31 downto 0); -- committed FPSCR value
a : fpu_reg_type;
b : fpu_reg_type;
c : fpu_reg_type;
@ -96,13 +101,17 @@ architecture behaviour of fpu is
result_class : fp_number_class;
result_exp : signed(EXP_BITS-1 downto 0);
shift : signed(EXP_BITS-1 downto 0);
writing_back : std_ulogic;
writing_fpr : std_ulogic;
write_reg : gspr_index_t;
complete_tag : instr_tag_t;
writing_cr : std_ulogic;
int_result : std_ulogic;
cr_result : std_ulogic_vector(3 downto 0);
cr_mask : std_ulogic_vector(7 downto 0);
old_exc : std_ulogic_vector(4 downto 0);
update_fprf : std_ulogic;
quieten_nan : std_ulogic;
nsnan_result : std_ulogic;
tiny : std_ulogic;
denorm : std_ulogic;
round_mode : std_ulogic_vector(2 downto 0);
@ -542,17 +551,30 @@ begin
fpu_0: process(clk)
begin
if rising_edge(clk) then
if rst = '1' then
if rst = '1' or flush_in = '1' then
r.state <= IDLE;
r.busy <= '0';
r.f2stall <= '0';
r.instr_done <= '0';
r.complete <= '0';
r.illegal <= '0';
r.do_intr <= '0';
r.writing_fpr <= '0';
r.writing_cr <= '0';
r.fpscr <= (others => '0');
r.writing_back <= '0';
r.dest_fpr <= (others =>'0');
r.write_reg <= (others =>'0');
r.complete_tag.valid <= '0';
r.cr_mask <= (others =>'0');
r.cr_result <= (others =>'0');
r.instr_tag.valid <= '0';
if rst = '1' then
r.fpscr <= (others => '0');
r.comm_fpscr <= (others => '0');
elsif r.do_intr = '0' then
-- flush_in = 1 and not due to us generating an interrupt,
-- roll back to committed fpscr
r.fpscr <= r.comm_fpscr;
end if;
else
assert not (r.state /= IDLE and e_in.valid = '1') severity failure;
r <= rin;
@ -577,14 +599,19 @@ begin
end process;
e_out.busy <= r.busy;
e_out.f2stall <= r.f2stall;
e_out.exception <= r.fpscr(FPSCR_FEX);
w_out.valid <= r.instr_done and not r.do_intr;
w_out.instr_tag <= r.instr_tag;
w_out.write_enable <= r.writing_back;
w_out.write_reg <= r.dest_fpr;
-- Note that the cycle where r.complete = 1 for an instruction can be as
-- late as the second cycle of the following instruction (i.e. in the state
-- following IDLE state). Hence it is important that none of the fields of
-- r that are used below are modified in IDLE state.
w_out.valid <= r.complete;
w_out.instr_tag <= r.complete_tag;
w_out.write_enable <= r.writing_fpr and r.complete;
w_out.write_reg <= r.write_reg;
w_out.write_data <= fp_result;
w_out.write_cr_enable <= r.instr_done and (r.rc or r.is_cmp);
w_out.write_cr_enable <= r.writing_cr and r.complete;
w_out.write_cr_mask <= r.cr_mask;
w_out.write_cr_data <= r.cr_result & r.cr_result & r.cr_result & r.cr_result &
r.cr_result & r.cr_result & r.cr_result & r.cr_result;
@ -599,7 +626,6 @@ begin
variable bdec : fpu_reg_type;
variable cdec : fpu_reg_type;
variable fpscr_mask : std_ulogic_vector(31 downto 0);
variable illegal : std_ulogic;
variable j, k : integer;
variable flm : std_ulogic_vector(7 downto 0);
variable int_input : std_ulogic;
@ -644,12 +670,22 @@ begin
variable maddend : std_ulogic_vector(127 downto 0);
variable sum : std_ulogic_vector(63 downto 0);
variable round_inc : std_ulogic_vector(63 downto 0);
variable int_result : std_ulogic;
variable illegal : std_ulogic;
begin
v := r;
illegal := '0';
v.busy := '0';
v.complete := '0';
v.do_intr := '0';
int_input := '0';
if r.complete = '1' or r.do_intr = '1' then
v.instr_done := '0';
v.writing_fpr := '0';
v.writing_cr := '0';
v.comm_fpscr := r.fpscr;
v.illegal := '0';
end if;
-- capture incoming instruction
if e_in.valid = '1' then
v.insn := e_in.insn;
@ -660,14 +696,8 @@ begin
v.dest_fpr := e_in.frt;
v.single_prec := e_in.single;
v.longmask := e_in.single;
v.int_result := '0';
v.rc := e_in.rc;
v.is_cmp := e_in.out_cr;
if e_in.out_cr = '0' then
v.cr_mask := num_to_fxm(1);
else
v.cr_mask := num_to_fxm(to_integer(unsigned(insn_bf(e_in.insn))));
end if;
int_input := '0';
if e_in.op = OP_FPOP_I then
int_input := '1';
@ -741,8 +771,6 @@ begin
pcmpb_lt := '1';
end if;
v.writing_back := '0';
v.instr_done := '0';
v.update_fprf := '0';
v.shift := to_signed(0, EXP_BITS);
v.first := '0';
@ -777,6 +805,8 @@ begin
pshift := '0';
renorm_sqrt := '0';
shiftin := '0';
int_result := '0';
illegal := '0';
case r.state is
when IDLE =>
v.use_a := '0';
@ -785,6 +815,7 @@ begin
v.invalid := '0';
v.negate := '0';
if e_in.valid = '1' then
v.busy := '1';
case e_in.insn(5 downto 1) is
when "00000" =>
if e_in.insn(8) = '1' then
@ -876,13 +907,17 @@ begin
end if;
v.state := DO_FMADD;
when others =>
illegal := '1';
v.state := DO_ILLEGAL;
end case;
end if;
v.x := '0';
v.old_exc := r.fpscr(FPSCR_VX downto FPSCR_XX);
set_s := '1';
when DO_ILLEGAL =>
illegal := '1';
v.instr_done := '1';
when DO_MCRFS =>
j := to_integer(unsigned(insn_bfa(r.insn)));
for i in 0 to 7 loop
@ -894,11 +929,9 @@ begin
end loop;
v.fpscr := r.fpscr and (fpscr_mask or x"6007F8FF");
v.instr_done := '1';
v.state := IDLE;
when DO_FTDIV =>
v.instr_done := '1';
v.state := IDLE;
v.cr_result := "0000";
if r.a.class = INFINITY or r.b.class = ZERO or r.b.class = INFINITY or
(r.b.class = FINITE and r.b.mantissa(53) = '0') then
@ -917,7 +950,6 @@ begin
when DO_FTSQRT =>
v.instr_done := '1';
v.state := IDLE;
v.cr_result := "0000";
if r.b.class = ZERO or r.b.class = INFINITY or
(r.b.class = FINITE and r.b.mantissa(53) = '0') then
@ -932,7 +964,6 @@ begin
-- fcmp[uo]
-- r.opsel_a = AIN_B
v.instr_done := '1';
v.state := IDLE;
update_fx := '1';
v.result_exp := r.b.exponent;
if (r.a.class = NAN and r.a.mantissa(53) = '0') or
@ -993,7 +1024,6 @@ begin
end if;
end loop;
v.instr_done := '1';
v.state := IDLE;
when DO_MTFSFI =>
-- mtfsfi
@ -1007,20 +1037,17 @@ begin
end loop;
end if;
v.instr_done := '1';
v.state := IDLE;
when DO_FMRG =>
-- fmrgew, fmrgow
opsel_r <= RES_MISC;
misc_sel <= "01" & r.insn(8) & '0';
v.int_result := '1';
v.writing_back := '1';
int_result := '1';
v.writing_fpr := '1';
v.instr_done := '1';
v.state := IDLE;
when DO_MFFS =>
v.int_result := '1';
v.writing_back := '1';
v.writing_fpr := '1';
opsel_r <= RES_MISC;
case r.insn(20 downto 16) is
when "00000" =>
@ -1044,10 +1071,11 @@ begin
-- mffsl
fpscr_mask := x"0007F0FF";
when others =>
illegal := '1';
v.illegal := '1';
v.writing_fpr := '0';
end case;
int_result := '1';
v.instr_done := '1';
v.state := IDLE;
when DO_MTFSF =>
if r.insn(25) = '1' then
@ -1064,7 +1092,6 @@ begin
end if;
end loop;
v.instr_done := '1';
v.state := IDLE;
when DO_FMR =>
-- r.opsel_a = AIN_B
@ -1082,9 +1109,8 @@ begin
else
v.result_sign := r.a.negative; -- fcpsgn
end if;
v.writing_back := '1';
v.writing_fpr := '1';
v.instr_done := '1';
v.state := IDLE;
when DO_FRI => -- fri[nzpm]
-- r.opsel_a = AIN_B
@ -1153,7 +1179,7 @@ begin
invalid := '1';
end if;
v.int_result := '1';
int_result := '1';
case r.b.class is
when ZERO =>
arith_done := '1';
@ -1671,7 +1697,6 @@ begin
end if;
v.fpscr(FPSCR_FL downto FPSCR_FU) := v.cr_result;
v.instr_done := '1';
v.state := IDLE;
when MULT_1 =>
f_to_multiply.valid <= r.first;
@ -1849,7 +1874,6 @@ begin
v.cr_result(1) := exp_tiny or exp_huge;
if exp_tiny = '1' or exp_huge = '1' or r.a.class = ZERO or r.first = '0' then
v.instr_done := '1';
v.state := IDLE;
else
v.shift := r.a.exponent;
v.doing_ftdiv := "10";
@ -2054,6 +2078,7 @@ begin
when others => -- fctidu[z]
need_check := r.r(63);
end case;
int_result := '1';
if need_check = '1' then
v.state := INT_CHECK;
else
@ -2080,6 +2105,7 @@ begin
v.fpscr(FPSCR_XX) := '1';
end if;
end if;
int_result := '1';
arith_done := '1';
when INT_OFLOW =>
@ -2090,6 +2116,7 @@ begin
end if;
v.fpscr(FPSCR_VXCVI) := '1';
invalid := '1';
int_result := '1';
arith_done := '1';
when FRI_1 =>
@ -2306,11 +2333,10 @@ begin
-- Neither does enabled zero-divide exception
if (v.invalid and r.fpscr(FPSCR_VE)) = '0' and
(zero_divide and r.fpscr(FPSCR_ZE)) = '0' then
v.writing_back := '1';
v.writing_fpr := '1';
v.update_fprf := '1';
end if;
v.instr_done := '1';
v.state := IDLE;
update_fx := '1';
end if;
@ -2530,12 +2556,6 @@ begin
v.shift := resize(signed('0' & clz) - 9, EXP_BITS);
end if;
if r.int_result = '1' then
fp_result <= r.r;
else
fp_result <= pack_dp(r.result_sign, r.result_class, r.result_exp, r.r,
r.single_prec, r.quieten_nan);
end if;
if r.update_fprf = '1' then
v.fpscr(FPSCR_C downto FPSCR_FU) := result_flags(r.result_sign, r.result_class,
r.r(54) and not r.denorm);
@ -2549,22 +2569,47 @@ begin
(v.fpscr(FPSCR_VX downto FPSCR_XX) and not r.old_exc) /= "00000" then
v.fpscr(FPSCR_FX) := '1';
end if;
if v.instr_done = '1' then
if r.state /= IDLE then
v.state := IDLE;
v.busy := '0';
v.f2stall := '0';
if r.rc = '1' then
v.cr_result := v.fpscr(FPSCR_FX downto FPSCR_OX);
end if;
v.sp_result := r.single_prec;
v.int_result := int_result;
v.illegal := illegal;
if illegal = '1' then
v.instr_done := '0';
v.do_intr := '1';
v.writing_back := '0';
v.busy := '0';
v.state := IDLE;
v.nsnan_result := v.quieten_nan;
if r.is_cmp = '0' then
v.cr_mask := num_to_fxm(1);
else
v.do_intr := v.instr_done and v.fpscr(FPSCR_FEX) and r.fe_mode;
if v.state /= IDLE or v.do_intr = '1' then
v.busy := '1';
v.cr_mask := num_to_fxm(to_integer(unsigned(insn_bf(r.insn))));
end if;
v.writing_cr := r.is_cmp or r.rc;
v.write_reg := r.dest_fpr;
v.complete_tag := r.instr_tag;
end if;
if e_in.stall = '0' then
v.complete := not v.illegal;
v.do_intr := (v.fpscr(FPSCR_FEX) and r.fe_mode) or v.illegal;
end if;
-- N.B. We rely on execute1 to prevent any new instruction
-- coming in while e_in.stall = 1, without us needing to
-- have busy asserted.
else
if r.state /= IDLE and e_in.stall = '0' then
v.f2stall := '1';
end if;
end if;
-- This mustn't depend on any fields of r that are modified in IDLE state.
if r.int_result = '1' then
fp_result <= r.r;
else
fp_result <= pack_dp(r.result_sign, r.result_class, r.result_exp, r.r,
r.sp_result, r.nsnan_result);
end if;
rin <= v;
