@ -75,7 +75,19 @@ architecture behaviour of fpu is
RENORM_A, RENORM_A2,
RENORM_B, RENORM_B2,
RENORM_C, RENORM_C2,
NAN_RESULT, EXC_RESULT);
NAN_RESULT, EXC_RESULT,
DO_IDIVMOD,
IDIV_NORMB, IDIV_NORMB2, IDIV_NORMB3,
IDIV_CLZA, IDIV_CLZA2, IDIV_CLZA3,
IDIV_NR0, IDIV_NR1, IDIV_NR2, IDIV_USE0_5,
IDIV_DODIV,
IDIV_DIV, IDIV_DIV2, IDIV_DIV3, IDIV_DIV4, IDIV_DIV5,
IDIV_DIV6, IDIV_DIV7, IDIV_DIV8, IDIV_DIV9,
IDIV_EXT_TBH, IDIV_EXT_TBH2, IDIV_EXT_TBH3,
IDIV_EXT_TBH4, IDIV_EXT_TBH5,
IDIV_EXTDIV, IDIV_EXTDIV1, IDIV_EXTDIV2, IDIV_EXTDIV3,
IDIV_EXTDIV4, IDIV_EXTDIV5, IDIV_EXTDIV6,
IDIV_MODADJ, IDIV_MODSUB, IDIV_DIVADJ, IDIV_OVFCHK, IDIV_DONE, IDIV_ZERO);
type reg_type is record
state : state_t;
@ -139,6 +151,14 @@ architecture behaviour of fpu is
invalid : std_ulogic;
negate : std_ulogic;
longmask : std_ulogic;
divext : std_ulogic;
divmod : std_ulogic;
is_signed : std_ulogic;
int_ovf : std_ulogic;
div_close : std_ulogic;
inc_quot : std_ulogic;
a_hi : std_ulogic_vector(7 downto 0);
a_lo : std_ulogic_vector(55 downto 0);
end record;
type lookup_table is array(0 to 1023) of std_ulogic_vector(17 downto 0);
@ -159,6 +179,7 @@ architecture behaviour of fpu is
signal lost_bits : std_ulogic;
signal r_hi_nz : std_ulogic;
signal r_lo_nz : std_ulogic;
signal r_gt_1 : std_ulogic;
signal s_nz : std_ulogic;
signal misc_sel : std_ulogic_vector(3 downto 0);
signal f_to_multiply : MultiplyInputType;
@ -663,7 +684,12 @@ begin
variable msb : std_ulogic;
variable is_add : std_ulogic;
variable set_a : std_ulogic;
variable set_a_exp : std_ulogic;
variable set_a_mant : std_ulogic;
variable set_a_hi : std_ulogic;
variable set_a_lo : std_ulogic;
variable set_b : std_ulogic;
variable set_b_mant : std_ulogic;
variable set_c : std_ulogic;
variable set_y : std_ulogic;
variable set_s : std_ulogic;
@ -671,10 +697,13 @@ begin
variable px_nz : std_ulogic;
variable pcmpb_eq : std_ulogic;
variable pcmpb_lt : std_ulogic;
variable pcmpc_eq : std_ulogic;
variable pcmpc_lt : std_ulogic;
variable pshift : std_ulogic;
variable renorm_sqrt : std_ulogic;
variable sqrt_exp : signed(EXP_BITS-1 downto 0);
variable shiftin : std_ulogic;
variable shiftin0 : std_ulogic;
variable mulexp : signed(EXP_BITS-1 downto 0);
variable maddend : std_ulogic_vector(127 downto 0);
variable sum : std_ulogic_vector(63 downto 0);
@ -722,6 +751,11 @@ begin
v.is_sqrt := '0';
v.add_bsmall := '0';
v.doing_ftdiv := "00";
v.divext := e_in.insn(8) and not e_in.insn(7);
v.divmod := not e_in.insn(8);
v.is_signed := e_in.is_signed;
v.int_ovf := '0';
v.div_close := '0';
adec := decode_dp(e_in.fra, int_input);
bdec := decode_dp(e_in.frb, int_input);
@ -738,10 +772,14 @@ begin
if (adec.exponent + cdec.exponent + 1) >= bdec.exponent then
v.madd_cmp := '1';
end if;
v.a_hi := 8x"0";
v.a_lo := 56x"0";
end if;
r_hi_nz <= or (r.r(UNIT_BIT + 1 downto SP_LSB));
r_lo_nz <= or (r.r(SP_LSB - 1 downto DP_LSB));
r_gt_1 <= or (r.r(63 downto 1));
s_nz <= or (r.s);
if r.single_prec = '0' then
@ -781,6 +819,14 @@ begin
if unsigned(r.p(59 downto 4)) < unsigned(r.b.mantissa(UNIT_BIT + 1 downto DP_RBIT)) then
pcmpb_lt := '1';
end if;
pcmpc_eq := '0';
if r.p = r.c.mantissa then
pcmpc_eq := '1';
end if;
pcmpc_lt := '0';
if unsigned(r.p) < unsigned(r.c.mantissa) then
pcmpc_lt := '1';
end if;
v.update_fprf := '0';
v.shift := to_signed(0, EXP_BITS);
@ -803,7 +849,12 @@ begin
set_x := '0';
qnan_result := '0';
set_a := '0';
set_a_exp := '0';
set_a_mant := '0';
set_a_hi := '0';
set_a_lo := '0';
set_b := '0';
set_b_mant := '0';
set_c := '0';
set_s := '0';
f_to_multiply.is_32bit <= '0';
@ -816,6 +867,7 @@ begin
pshift := '0';
renorm_sqrt := '0';
shiftin := '0';
shiftin0 := '0';
rbit_inc := '0';
mult_mask := '0';
int_result := '0';
@ -866,6 +918,10 @@ begin
else
v.state := DO_FRI;
end if;
when "01001" =>
-- integer divides and mods, major opcode 31
v.opsel_a := AIN_B;
v.state := DO_IDIVMOD;
when "01100" =>
v.opsel_a := AIN_B;
v.state := DO_FRSP;
@ -2327,6 +2383,451 @@ begin
end case;
arith_done := '1';
when DO_IDIVMOD =>
-- r.opsel_a = AIN_B
v.result_sign := r.is_signed and (r.a.negative xor (r.b.negative and not r.divmod));
if r.b.class = ZERO then
-- B is zero, signal overflow
v.int_ovf := '1';
v.state := IDIV_ZERO;
elsif r.a.class = ZERO then
-- A is zero, result is zero (both for div and for mod)
v.state := IDIV_ZERO;
else
-- take absolute value for signed division, and
-- normalize and round up B to 8.56 format, like fcfid[u]
if r.is_signed = '1' and r.b.negative = '1' then
opsel_ainv <= '1';
carry_in <= '1';
end if;
v.result_class := FINITE;
v.result_exp := to_signed(UNIT_BIT, EXP_BITS);
v.state := IDIV_NORMB;
end if;
when IDIV_NORMB =>
-- do count-leading-zeroes on B (now in R)
renormalize := '1';
-- save the original value of B or |B| in C
set_c := '1';
v.state := IDIV_NORMB2;
when IDIV_NORMB2 =>
-- get B into the range [1, 2) in 8.56 format
set_x := '1'; -- record if any 1 bits shifted out
opsel_r <= RES_SHIFT;
v.state := IDIV_NORMB3;
when IDIV_NORMB3 =>
-- add the X bit onto R to round up B
carry_in <= r.x;
-- prepare to do count-leading-zeroes on A
v.opsel_a := AIN_A;
v.state := IDIV_CLZA;
when IDIV_CLZA =>
set_b := '1'; -- put R back into B
-- r.opsel_a = AIN_A
if r.is_signed = '1' and r.a.negative = '1' then
opsel_ainv <= '1';
carry_in <= '1';
end if;
v.result_exp := to_signed(UNIT_BIT, EXP_BITS);
v.opsel_a := AIN_C;
v.state := IDIV_CLZA2;
when IDIV_CLZA2 =>
-- r.opsel_a = AIN_C
renormalize := '1';
-- write the dividend back into A in case we negated it
set_a_mant := '1';
-- while doing the count-leading-zeroes on A,
-- also compute A - B to tell us whether A >= B
-- (using the original value of B, which is now in C)
opsel_b <= BIN_R;
opsel_ainv <= '1';
carry_in <= '1';
v.state := IDIV_CLZA3;
when IDIV_CLZA3 =>
-- save the exponent of A (but don't overwrite the mantissa)
v.a.exponent := new_exp;
v.div_close := '0';
if new_exp = r.b.exponent then
v.div_close := '1';
end if;
v.state := IDIV_NR0;
if new_exp > r.b.exponent or (v.div_close = '1' and r.r(63) = '0') then
-- A >= B, overflow if extended division
if r.divext = '1' then
v.int_ovf := '1';
-- return 0 in overflow cases
v.state := IDIV_ZERO;
end if;
else
-- A < B, result is zero for normal division
if r.divmod = '0' and r.divext = '0' then
v.state := IDIV_ZERO;
end if;
end if;
when IDIV_NR0 =>
-- reduce number of Newton-Raphson iterations for small A
if r.divext = '1' or new_exp >= to_signed(32, EXP_BITS) then
v.count := "00";
elsif new_exp >= to_signed(16, EXP_BITS) then
v.count := "01";
else
v.count := "10";
end if;
-- first NR iteration does Y = LUT; P = 2 - B * LUT
msel_1 <= MUL1_B;
msel_add <= MULADD_CONST;
msel_inv <= '1';
msel_2 <= MUL2_LUT;
set_y := '1';
if r.b.mantissa(UNIT_BIT + 1) = '1' then
-- rounding up of the mantissa caused overflow, meaning the
-- normalized B is 2.0. Since this is outside the range
-- of the LUT, just use 0.5 as the estimated inverse.
v.state := IDIV_USE0_5;
else
-- start the first multiply now
f_to_multiply.valid <= '1';
-- note we don't set v.first, thus the following IDIV_NR1
-- state doesn't start a multiply (we already did that)
v.state := IDIV_NR1;
end if;
when IDIV_NR1 =>
-- subsequent NR iterations do Y = P; P = 2 - B * P
msel_1 <= MUL1_B;
msel_add <= MULADD_CONST;
msel_inv <= '1';
msel_2 <= MUL2_P;
set_y := r.first;
pshift := '1';
f_to_multiply.valid <= r.first;
if multiply_to_f.valid = '1' then
v.first := '1';
v.count := r.count + 1;
v.state := IDIV_NR2;
end if;
when IDIV_NR2 =>
-- compute P = Y * P
msel_1 <= MUL1_Y;
msel_2 <= MUL2_P;
f_to_multiply.valid <= r.first;
pshift := '1';
v.opsel_a := AIN_A;
v.shift := to_signed(64, EXP_BITS);
-- Get 0.5 into R in case the inverse estimate turns out to be
-- less than 0.5, in which case we want to use 0.5, to avoid
-- infinite loops in some cases.
opsel_r <= RES_MISC;
misc_sel <= "0001";
if multiply_to_f.valid = '1' then
v.first := '1';
if r.count = "11" then
v.state := IDIV_DODIV;
else
v.state := IDIV_NR1;
end if;
end if;
when IDIV_USE0_5 =>
-- Get 0.5 into R; it turns out the generated
-- QNaN mantissa is actually what we want
opsel_r <= RES_MISC;
misc_sel <= "0001";
v.opsel_a := AIN_A;
v.shift := to_signed(64, EXP_BITS);
v.state := IDIV_DODIV;
when IDIV_DODIV =>
-- r.opsel_a = AIN_A
-- r.shift = 64
-- inverse estimate is in P or in R; copy it to Y
if r.b.mantissa(UNIT_BIT + 1) = '1' or
(r.p(UNIT_BIT) = '0' and r.p(UNIT_BIT - 1) = '0') then
msel_2 <= MUL2_R;
else
msel_2 <= MUL2_P;
end if;
set_y := '1';
-- shift_res is 0 because r.shift = 64;
-- put that into B, which now holds the quotient
set_b_mant := '1';
if r.divext = '0' then
v.shift := to_signed(-UNIT_BIT, EXP_BITS);
v.first := '1';
v.state := IDIV_DIV;
elsif r.div_close = '0' then
v.shift := to_signed(64 - UNIT_BIT, EXP_BITS);
v.state := IDIV_EXTDIV;
else
-- handle top bit of quotient specially
-- for this we need the divisor left-justified in B
v.opsel_a := AIN_C;
v.state := IDIV_EXT_TBH;
end if;
when IDIV_DIV =>
-- Dividing A by C, r.shift = -56; A is in R
-- Put A into the bottom 64 bits of Ahi/A/Alo
set_a_mant := r.first;
set_a_lo := r.first;
-- compute R = R * Y (quotient estimate)
msel_1 <= MUL1_Y;
msel_2 <= MUL2_R;
f_to_multiply.valid <= r.first;
pshift := '1';
opsel_r <= RES_MULT;
v.shift := - r.b.exponent;
if multiply_to_f.valid = '1' then
v.state := IDIV_DIV2;
end if;
when IDIV_DIV2 =>
-- r.shift = - b.exponent
-- shift the quotient estimate right by b.exponent bits
opsel_r <= RES_SHIFT;
v.first := '1';
v.state := IDIV_DIV3;
when IDIV_DIV3 =>
-- quotient (so far) is in R; multiply by C and subtract from A
msel_1 <= MUL1_R;
msel_2 <= MUL2_C;
msel_add <= MULADD_A;
msel_inv <= '1';
f_to_multiply.valid <= r.first;
-- store the current quotient estimate in B
set_b_mant := r.first;
opsel_r <= RES_MULT;
opsel_s <= S_MULT;
set_s := '1';
if multiply_to_f.valid = '1' then
v.state := IDIV_DIV4;
end if;
when IDIV_DIV4 =>
-- remainder is in R/S and P
msel_1 <= MUL1_Y;
msel_2 <= MUL2_P;
v.inc_quot := not pcmpc_lt and not r.divmod;
if r.divmod = '0' then
v.opsel_a := AIN_B;
end if;
v.shift := to_signed(UNIT_BIT, EXP_BITS);
if pcmpc_lt = '1' or pcmpc_eq = '1' then
if r.divmod = '0' then
v.state := IDIV_DIVADJ;
elsif pcmpc_eq = '1' then
v.state := IDIV_ZERO;
else
v.state := IDIV_MODADJ;
end if;
else
-- need to do another iteration, compute P * Y
f_to_multiply.valid <= '1';
v.state := IDIV_DIV5;
end if;
when IDIV_DIV5 =>
pshift := '1';
opsel_r <= RES_MULT;
v.shift := - r.b.exponent;
if multiply_to_f.valid = '1' then
v.state := IDIV_DIV6;
end if;
when IDIV_DIV6 =>
-- r.shift = - b.exponent
-- shift the quotient estimate right by b.exponent bits
opsel_r <= RES_SHIFT;
v.opsel_a := AIN_B;
v.first := '1';
v.state := IDIV_DIV7;
when IDIV_DIV7 =>
-- r.opsel_a = AIN_B
-- add shifted quotient delta onto the total quotient
opsel_b <= BIN_R;
v.first := '1';
v.state := IDIV_DIV8;
when IDIV_DIV8 =>
-- quotient (so far) is in R; multiply by C and subtract from A
msel_1 <= MUL1_R;
msel_2 <= MUL2_C;
msel_add <= MULADD_A;
msel_inv <= '1';
f_to_multiply.valid <= r.first;
-- store the current quotient estimate in B
set_b_mant := r.first;
opsel_r <= RES_MULT;
opsel_s <= S_MULT;
set_s := '1';
if multiply_to_f.valid = '1' then
v.state := IDIV_DIV9;
end if;
when IDIV_DIV9 =>
-- remainder is in R/S and P
msel_1 <= MUL1_Y;
msel_2 <= MUL2_P;
v.inc_quot := not pcmpc_lt and not r.divmod;
if r.divmod = '0' then
v.opsel_a := AIN_B;
end if;
v.shift := to_signed(UNIT_BIT, EXP_BITS);
if r.divmod = '0' then
v.state := IDIV_DIVADJ;
elsif pcmpc_eq = '1' then
v.state := IDIV_ZERO;
else
v.state := IDIV_MODADJ;
end if;
when IDIV_EXT_TBH =>
-- r.opsel_a = AIN_C; get divisor into R and prepare to shift left
v.shift := to_signed(63, EXP_BITS) - r.b.exponent;
v.opsel_a := AIN_A;
v.state := IDIV_EXT_TBH2;
when IDIV_EXT_TBH2 =>
-- r.opsel_a = AIN_A; divisor is in R
-- r.shift = 63 - b.exponent; shift and put into B
set_b_mant := '1';
v.shift := to_signed(64 - UNIT_BIT, EXP_BITS);
v.state := IDIV_EXT_TBH3;
when IDIV_EXT_TBH3 =>
-- Dividing (A << 64) by C
-- r.shift = 8
-- Put A in the top 64 bits of Ahi/A/Alo
set_a_hi := '1';
set_a_mant := '1';
v.shift := to_signed(64, EXP_BITS) - r.b.exponent;
v.state := IDIV_EXT_TBH4;
when IDIV_EXT_TBH4 =>
-- dividend (A) is in R
-- r.shift = 64 - B.exponent, so is at least 1
opsel_r <= RES_SHIFT;
-- top bit of A gets lost in the shift, so handle it specially
v.opsel_a := AIN_B;
v.shift := to_signed(63, EXP_BITS);
v.state := IDIV_EXT_TBH5;
when IDIV_EXT_TBH5 =>
-- r.opsel_a = AIN_B, r.shift = 63
-- shifted dividend is in R, subtract left-justified divisor
opsel_b <= BIN_R;
opsel_ainv <= '1';
carry_in <= '1';
-- and put 1<<63 into B as the divisor (S is still 0)
shiftin0 := '1';
set_b_mant := '1';
v.first := '1';
v.state := IDIV_EXTDIV2;
when IDIV_EXTDIV =>
-- Dividing (A << 64) by C
-- r.shift = 8
-- Put A in the top 64 bits of Ahi/A/Alo
set_a_hi := '1';
set_a_mant := '1';
v.shift := to_signed(64, EXP_BITS) - r.b.exponent;
v.state := IDIV_EXTDIV1;
when IDIV_EXTDIV1 =>
-- dividend is in R
-- r.shift = 64 - B.exponent
opsel_r <= RES_SHIFT;
v.first := '1';
v.state := IDIV_EXTDIV2;
when IDIV_EXTDIV2 =>
-- shifted remainder is in R; compute R = R * Y (quotient estimate)
msel_1 <= MUL1_Y;
msel_2 <= MUL2_R;
f_to_multiply.valid <= r.first;
pshift := '1';
v.opsel_a := AIN_B;
opsel_r <= RES_MULT;
if multiply_to_f.valid = '1' then
v.first := '1';
v.state := IDIV_EXTDIV3;
end if;
when IDIV_EXTDIV3 =>
-- r.opsel_a = AIN_B
-- delta quotient is in R; add it to B
opsel_b <= BIN_R;
v.first := '1';
v.state := IDIV_EXTDIV4;
when IDIV_EXTDIV4 =>
-- quotient is in R; put it in B and compute remainder
set_b_mant := r.first;
msel_1 <= MUL1_R;
msel_2 <= MUL2_C;
msel_add <= MULADD_A;
msel_inv <= '1';
f_to_multiply.valid <= r.first;
opsel_r <= RES_MULT;
opsel_s <= S_MULT;
set_s := '1';
v.shift := to_signed(UNIT_BIT, EXP_BITS) - r.b.exponent;
if multiply_to_f.valid = '1' then
v.state := IDIV_EXTDIV5;
end if;
when IDIV_EXTDIV5 =>
-- r.shift = r.b.exponent - 56
-- remainder is in R/S; shift it right r.b.exponent bits
opsel_r <= RES_SHIFT;
-- test LS 64b of remainder in P against divisor in C
v.inc_quot := not pcmpc_lt;
v.opsel_a := AIN_B;
v.state := IDIV_EXTDIV6;
when IDIV_EXTDIV6 =>
-- r.opsel_a = AIN_B
-- shifted remainder is in R, see if it is > 1
-- and compute R = R * Y if so
msel_1 <= MUL1_Y;
msel_2 <= MUL2_R;
pshift := '1';
if r_gt_1 = '1' then
f_to_multiply.valid <= '1';
v.state := IDIV_EXTDIV2;
else
v.state := IDIV_DIVADJ;
end if;
when IDIV_MODADJ =>
-- r.shift = 56
-- result is in R/S
opsel_r <= RES_SHIFT;
if pcmpc_lt = '0' then
v.opsel_a := AIN_C;
v.state := IDIV_MODSUB;
elsif r.result_sign = '0' then
v.state := IDIV_DONE;
else
v.state := IDIV_DIVADJ;
end if;
when IDIV_MODSUB =>
-- r.opsel_a = AIN_C
-- Subtract divisor from remainder
opsel_ainv <= '1';
carry_in <= '1';
opsel_b <= BIN_R;
if r.result_sign = '0' then
v.state := IDIV_DONE;
else
v.state := IDIV_DIVADJ;
end if;
when IDIV_DIVADJ =>
-- result (so far) is on the A input of the adder
-- set carry to increment quotient if needed
-- and also negate R if the answer is negative
opsel_ainv <= r.result_sign;
carry_in <= r.inc_quot xor r.result_sign;
if r.is_signed = '0' then
v.state := IDIV_DONE;
else
v.state := IDIV_OVFCHK;
end if;
when IDIV_OVFCHK =>
v.int_ovf := r.r(63) xor r.result_sign;
if v.int_ovf = '1' then
v.state := IDIV_ZERO;
else
v.state := IDIV_DONE;
end if;
when IDIV_DONE =>
int_result := '1';
v.writing_fpr := '1';
v.instr_done := '1';
when IDIV_ZERO =>
opsel_r <= RES_MISC;
misc_sel <= "0101";
int_result := '1';
v.writing_fpr := '1';
v.instr_done := '1';
end case;
if zero_divide = '1' then
@ -2388,7 +2889,9 @@ begin
end if;
when MULADD_A =>
-- addend is A in 16.112 format
maddend(127 downto UNIT_BIT + 64) := r.a_hi;
maddend(UNIT_BIT + 63 downto UNIT_BIT) := r.a.mantissa;
maddend(UNIT_BIT - 1 downto 0) := r.a_lo;
when MULADD_RS =>
-- addend is concatenation of R and S in 16.112 format
maddend(UNIT_BIT + 63 downto UNIT_BIT) := r.r;
@ -2465,7 +2968,8 @@ begin
end if;
in_b <= in_b0;
if r.shift >= to_signed(-64, EXP_BITS) and r.shift <= to_signed(63, EXP_BITS) then
shift_res := shifter_64(r.r & (shiftin or r.s(55)) & r.s(54 downto 0),
shift_res := shifter_64(r.r(63 downto 1) & (shiftin0 or r.r(0)) &
(shiftin or r.s(55)) & r.s(54 downto 0),
std_ulogic_vector(r.shift(6 downto 0)));
else
shift_res := (others => '0');
@ -2556,12 +3060,27 @@ begin
end case;
end if;
if set_a = '1' then
if set_a = '1' or set_a_exp = '1' then
v.a.exponent := new_exp;
end if;
if set_a = '1' or set_a_mant = '1' then
v.a.mantissa := shift_res;
end if;
if e_in.valid = '1' then
v.a_hi := (others => '0');
v.a_lo := (others => '0');
else
if set_a_hi = '1' then
v.a_hi := r.r(63 downto 56);
end if;
if set_a_lo = '1' then
v.a_lo := r.r(55 downto 0);
end if;
end if;
if set_b = '1' then
v.b.exponent := new_exp;
end if;
if set_b = '1' or set_b_mant = '1' then
v.b.mantissa := shift_res;
end if;
if set_c = '1' then
