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antonblanchard.microwatt/execute1.vhdl
Paul Mackerras d2ca625b3b execute: Do comparisons using the main adder 
This handles OP_CMP like a subtraction; the main adder computes
~RA + RB + 1, and the condition codes are computed from the results.
A direct comparison of the two input operands is used to calculate the
EQ bit of the condition result.  The LT and GT bits are computed from
the MSB of the subtraction result, the carry out from the subtraction,
and the MSBs of the operands.  For a 32-bit comparison, the 32-bit
carry and bit 31 of the result and input operands are used; for a
64-bit comparison, the 64-bit carry and bit 63 of the operands and
result are used.

It turns out to be more convenient to use the 'signed' field of
the decode table to distinguish signed from unsigned comparisons,
rather than the insn_type.  Therefore this uses OP_CMP for both
cmp and cmpl, which also has the benefit of reducing the number
of values in insn_type_t.

Doing this saves over 200 slice LUTs on the Arty A7-100 and improves
timing slightly as well.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2020-01-14 22:29:07 +11:00

738 lines
24 KiB
VHDL
Raw Blame History

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
library work;
use work.decode_types.all;
use work.common.all;
use work.helpers.all;
use work.crhelpers.all;
use work.insn_helpers.all;
use work.ppc_fx_insns.all;
entity execute1 is
port (
clk : in std_ulogic;
rst : in std_ulogic;
-- asynchronous
flush_out : out std_ulogic;
stall_out : out std_ulogic;
e_in : in Decode2ToExecute1Type;
-- asynchronous
f_out : out Execute1ToFetch1Type;
e_out : out Execute1ToWritebackType;
icache_inval : out std_ulogic;
terminate_out : out std_ulogic
);
end entity execute1;
architecture behaviour of execute1 is
type reg_type is record
e : Execute1ToWritebackType;
lr_update : std_ulogic;
next_lr : std_ulogic_vector(63 downto 0);
mul_in_progress : std_ulogic;
div_in_progress : std_ulogic;
slow_op_dest : gpr_index_t;
slow_op_rc : std_ulogic;
slow_op_oe : std_ulogic;
slow_op_xerc : xer_common_t;
end record;
signal r, rin : reg_type;
signal ctrl: ctrl_t := (others => (others => '0'));
signal ctrl_tmp: ctrl_t := (others => (others => '0'));
signal right_shift, rot_clear_left, rot_clear_right: std_ulogic;
signal rotator_result: std_ulogic_vector(63 downto 0);
signal rotator_carry: std_ulogic;
signal logical_result: std_ulogic_vector(63 downto 0);
signal countzero_result: std_ulogic_vector(63 downto 0);
-- multiply signals
signal x_to_multiply: Execute1ToMultiplyType;
signal multiply_to_x: MultiplyToExecute1Type;
-- divider signals
signal x_to_divider: Execute1ToDividerType;
signal divider_to_x: DividerToExecute1Type;
procedure set_carry(e: inout Execute1ToWritebackType;
carry32 : in std_ulogic;
carry : in std_ulogic) is
begin
e.xerc.ca32 := carry32;
e.xerc.ca := carry;
e.write_xerc_enable := '1';
end;
procedure set_ov(e: inout Execute1ToWritebackType;
ov : in std_ulogic;
ov32 : in std_ulogic) is
begin
e.xerc.ov32 := ov32;
e.xerc.ov := ov;
if ov = '1' then
e.xerc.so := '1';
end if;
e.write_xerc_enable := '1';
end;
function calc_ov(msb_a : std_ulogic; msb_b: std_ulogic;
ca: std_ulogic; msb_r: std_ulogic) return std_ulogic is
begin
return (ca xor msb_r) and not (msb_a xor msb_b);
end;
function decode_input_carry(ic : carry_in_t;
xerc : xer_common_t) return std_ulogic is
begin
case ic is
when ZERO =>
return '0';
when CA =>
return xerc.ca;
when ONE =>
return '1';
end case;
end;
begin
rotator_0: entity work.rotator
port map (
rs => e_in.read_data3,
ra => e_in.read_data1,
shift => e_in.read_data2(6 downto 0),
insn => e_in.insn,
is_32bit => e_in.is_32bit,
right_shift => right_shift,
arith => e_in.is_signed,
clear_left => rot_clear_left,
clear_right => rot_clear_right,
result => rotator_result,
carry_out => rotator_carry
);
logical_0: entity work.logical
port map (
rs => e_in.read_data3,
rb => e_in.read_data2,
op => e_in.insn_type,
invert_in => e_in.invert_a,
invert_out => e_in.invert_out,
result => logical_result
);
countzero_0: entity work.zero_counter
port map (
rs => e_in.read_data3,
count_right => e_in.insn(10),
is_32bit => e_in.is_32bit,
result => countzero_result
);
multiply_0: entity work.multiply
port map (
clk => clk,
m_in => x_to_multiply,
m_out => multiply_to_x
);
divider_0: entity work.divider
port map (
clk => clk,
rst => rst,
d_in => x_to_divider,
d_out => divider_to_x
);
execute1_0: process(clk)
begin
if rising_edge(clk) then
r <= rin;
ctrl <= ctrl_tmp;
assert not (r.lr_update = '1' and e_in.valid = '1')
report "LR update collision with valid in EX1"
severity failure;
if r.lr_update = '1' then
report "LR update to " & to_hstring(r.next_lr);
end if;
end if;
end process;
execute1_1: process(all)
variable v : reg_type;
variable a_inv : std_ulogic_vector(63 downto 0);
variable result : std_ulogic_vector(63 downto 0);
variable newcrf : std_ulogic_vector(3 downto 0);
variable result_with_carry : std_ulogic_vector(64 downto 0);
variable result_en : std_ulogic;
variable crnum : crnum_t;
variable crbit : integer range 0 to 31;
variable scrnum : crnum_t;
variable lo, hi : integer;
variable sh, mb, me : std_ulogic_vector(5 downto 0);
variable sh32, mb32, me32 : std_ulogic_vector(4 downto 0);
variable bo, bi : std_ulogic_vector(4 downto 0);
variable bf, bfa : std_ulogic_vector(2 downto 0);
variable cr_op : std_ulogic_vector(9 downto 0);
variable bt, ba, bb : std_ulogic_vector(4 downto 0);
variable btnum, banum, bbnum : integer range 0 to 31;
variable crresult : std_ulogic;
variable l : std_ulogic;
variable next_nia : std_ulogic_vector(63 downto 0);
variable carry_32, carry_64 : std_ulogic;
variable sign1, sign2 : std_ulogic;
variable abs1, abs2 : signed(63 downto 0);
variable overflow : std_ulogic;
variable negative : std_ulogic;
variable zerohi, zerolo : std_ulogic;
variable msb_a, msb_b : std_ulogic;
variable a_lt : std_ulogic;
begin
result := (others => '0');
result_with_carry := (others => '0');
result_en := '0';
newcrf := (others => '0');
v := r;
v.e := Execute1ToWritebackInit;
-- XER forwarding. To avoid having to track XER hazards, we
-- use the previously latched value.
--
-- If the XER was modified by a multiply or a divide, those are
-- single issue, we'll get the up to date value from decode2 from
-- the register file.
--
-- If it was modified by an instruction older than the previous
-- one in EX1, it will have also hit writeback and will be up
-- to date in decode2.
--
-- That leaves us with the case where it was updated by the previous
-- instruction in EX1. In that case, we can forward it back here.
--
-- This will break if we allow pipelining of multiply and divide,
-- but ideally, those should go via EX1 anyway and run as a state
-- machine from here.
--
-- One additional hazard to beware of is an XER:SO modifying instruction
-- in EX1 followed immediately by a store conditional. Due to our
-- writeback latency, the store will go down the LSU with the previous
-- XER value, thus the stcx. will set CR0:SO using an obsolete SO value.
--
-- We will need to handle that if we ever make stcx. not single issue
--
-- We always pass a valid XER value downto writeback even when
-- we aren't updating it, in order for XER:SO -> CR0:SO transfer
-- to work for RC instructions.
--
if r.e.write_xerc_enable = '1' then
v.e.xerc := r.e.xerc;
else
v.e.xerc := e_in.xerc;
end if;
v.lr_update := '0';
v.mul_in_progress := '0';
v.div_in_progress := '0';
-- signals to multiply unit
x_to_multiply <= Execute1ToMultiplyInit;
x_to_multiply.insn_type <= e_in.insn_type;
x_to_multiply.is_32bit <= e_in.is_32bit;
if e_in.is_32bit = '1' then
if e_in.is_signed = '1' then
x_to_multiply.data1 <= (others => e_in.read_data1(31));
x_to_multiply.data1(31 downto 0) <= e_in.read_data1(31 downto 0);
x_to_multiply.data2 <= (others => e_in.read_data2(31));
x_to_multiply.data2(31 downto 0) <= e_in.read_data2(31 downto 0);
else
x_to_multiply.data1 <= '0' & x"00000000" & e_in.read_data1(31 downto 0);
x_to_multiply.data2 <= '0' & x"00000000" & e_in.read_data2(31 downto 0);
end if;
else
if e_in.is_signed = '1' then
x_to_multiply.data1 <= e_in.read_data1(63) & e_in.read_data1;
x_to_multiply.data2 <= e_in.read_data2(63) & e_in.read_data2;
else
x_to_multiply.data1 <= '0' & e_in.read_data1;
x_to_multiply.data2 <= '0' & e_in.read_data2;
end if;
end if;
-- signals to divide unit
sign1 := '0';
sign2 := '0';
if e_in.is_signed = '1' then
if e_in.is_32bit = '1' then
sign1 := e_in.read_data1(31);
sign2 := e_in.read_data2(31);
else
sign1 := e_in.read_data1(63);
sign2 := e_in.read_data2(63);
end if;
end if;
-- take absolute values
if sign1 = '0' then
abs1 := signed(e_in.read_data1);
else
abs1 := - signed(e_in.read_data1);
end if;
if sign2 = '0' then
abs2 := signed(e_in.read_data2);
else
abs2 := - signed(e_in.read_data2);
end if;
x_to_divider <= Execute1ToDividerInit;
x_to_divider.is_signed <= e_in.is_signed;
x_to_divider.is_32bit <= e_in.is_32bit;
if e_in.insn_type = OP_MOD then
x_to_divider.is_modulus <= '1';
end if;
x_to_divider.neg_result <= sign1 xor (sign2 and not x_to_divider.is_modulus);
if e_in.is_32bit = '0' then
-- 64-bit forms
if e_in.insn_type = OP_DIVE then
x_to_divider.is_extended <= '1';
end if;
x_to_divider.dividend <= std_ulogic_vector(abs1);
x_to_divider.divisor <= std_ulogic_vector(abs2);
else
-- 32-bit forms
x_to_divider.is_extended <= '0';
if e_in.insn_type = OP_DIVE then -- extended forms
x_to_divider.dividend <= std_ulogic_vector(abs1(31 downto 0)) & x"00000000";
else
x_to_divider.dividend <= x"00000000" & std_ulogic_vector(abs1(31 downto 0));
end if;
x_to_divider.divisor <= x"00000000" & std_ulogic_vector(abs2(31 downto 0));
end if;
ctrl_tmp <= ctrl;
-- FIXME: run at 512MHz not core freq
ctrl_tmp.tb <= std_ulogic_vector(unsigned(ctrl.tb) + 1);
terminate_out <= '0';
icache_inval <= '0';
stall_out <= '0';
f_out <= Execute1ToFetch1TypeInit;
-- Next insn adder used in a couple of places
next_nia := std_ulogic_vector(unsigned(e_in.nia) + 4);
-- rotator control signals
right_shift <= '1' when e_in.insn_type = OP_SHR else '0';
rot_clear_left <= '1' when e_in.insn_type = OP_RLC or e_in.insn_type = OP_RLCL else '0';
rot_clear_right <= '1' when e_in.insn_type = OP_RLC or e_in.insn_type = OP_RLCR else '0';
if e_in.valid = '1' then
v.e.valid := '1';
v.e.write_reg := e_in.write_reg;
v.slow_op_dest := gspr_to_gpr(e_in.write_reg);
v.slow_op_rc := e_in.rc;
v.slow_op_oe := e_in.oe;
v.slow_op_xerc := v.e.xerc;
case_0: case e_in.insn_type is
when OP_ILLEGAL =>
terminate_out <= '1';
report "illegal";
when OP_NOP =>
-- Do nothing
when OP_ADD | OP_CMP =>
if e_in.invert_a = '0' then
a_inv := e_in.read_data1;
else
a_inv := not e_in.read_data1;
end if;
result_with_carry := ppc_adde(a_inv, e_in.read_data2,
decode_input_carry(e_in.input_carry, v.e.xerc));
result := result_with_carry(63 downto 0);
carry_32 := result(32) xor a_inv(32) xor e_in.read_data2(32);
carry_64 := result_with_carry(64);
if e_in.insn_type = OP_ADD then
if e_in.output_carry = '1' then
set_carry(v.e, carry_32, carry_64);
end if;
if e_in.oe = '1' then
set_ov(v.e,
calc_ov(a_inv(63), e_in.read_data2(63), carry_64, result_with_carry(63)),
calc_ov(a_inv(31), e_in.read_data2(31), carry_32, result_with_carry(31)));
end if;
result_en := '1';
else
-- CMP and CMPL instructions
-- Note, we have done RB - RA, not RA - RB
bf := insn_bf(e_in.insn);
l := insn_l(e_in.insn);
v.e.write_cr_enable := '1';
crnum := to_integer(unsigned(bf));
v.e.write_cr_mask := num_to_fxm(crnum);
zerolo := not (or (e_in.read_data1(31 downto 0) xor e_in.read_data2(31 downto 0)));
zerohi := not (or (e_in.read_data1(63 downto 32) xor e_in.read_data2(63 downto 32)));
if zerolo = '1' and (l = '0' or zerohi = '1') then
-- values are equal
newcrf := "001" & v.e.xerc.so;
else
if l = '1' then
-- 64-bit comparison
msb_a := e_in.read_data1(63);
msb_b := e_in.read_data2(63);
else
-- 32-bit comparison
msb_a := e_in.read_data1(31);
msb_b := e_in.read_data2(31);
end if;
if msb_a /= msb_b then
-- Subtraction might overflow, but
-- comparison is clear from MSB difference.
-- for signed, 0 is greater; for unsigned, 1 is greater
a_lt := msb_a xnor e_in.is_signed;
else
-- Subtraction cannot overflow since MSBs are equal.
-- carry = 1 indicates RA is smaller (signed or unsigned)
a_lt := (not l and carry_32) or (l and carry_64);
end if;
newcrf := a_lt & not a_lt & '0' & v.e.xerc.so;
end if;
for i in 0 to 7 loop
lo := i*4;
hi := lo + 3;
v.e.write_cr_data(hi downto lo) := newcrf;
end loop;
end if;
when OP_AND | OP_OR | OP_XOR =>
result := logical_result;
result_en := '1';
when OP_B =>
f_out.redirect <= '1';
if (insn_aa(e_in.insn)) then
f_out.redirect_nia <= std_ulogic_vector(signed(e_in.read_data2));
else
f_out.redirect_nia <= std_ulogic_vector(signed(e_in.nia) + signed(e_in.read_data2));
end if;
when OP_BC =>
-- read_data1 is CTR
bo := insn_bo(e_in.insn);
bi := insn_bi(e_in.insn);
if bo(4-2) = '0' then
result := std_ulogic_vector(unsigned(e_in.read_data1) - 1);
result_en := '1';
v.e.write_reg := fast_spr_num(SPR_CTR);
end if;
if ppc_bc_taken(bo, bi, e_in.cr, e_in.read_data1) = 1 then
f_out.redirect <= '1';
if (insn_aa(e_in.insn)) then
f_out.redirect_nia <= std_ulogic_vector(signed(e_in.read_data2));
else
f_out.redirect_nia <= std_ulogic_vector(signed(e_in.nia) + signed(e_in.read_data2));
end if;
end if;
when OP_BCREG =>
-- read_data1 is CTR
-- read_data2 is target register (CTR, LR or TAR)
bo := insn_bo(e_in.insn);
bi := insn_bi(e_in.insn);
if bo(4-2) = '0' and e_in.insn(10) = '0' then
result := std_ulogic_vector(unsigned(e_in.read_data1) - 1);
result_en := '1';
v.e.write_reg := fast_spr_num(SPR_CTR);
end if;
if ppc_bc_taken(bo, bi, e_in.cr, e_in.read_data1) = 1 then
f_out.redirect <= '1';
f_out.redirect_nia <= e_in.read_data2(63 downto 2) & "00";
end if;
when OP_CMPB =>
result := ppc_cmpb(e_in.read_data3, e_in.read_data2);
result_en := '1';
when OP_CNTZ =>
result := countzero_result;
result_en := '1';
when OP_EXTS =>
-- note data_len is a 1-hot encoding
negative := (e_in.data_len(0) and e_in.read_data3(7)) or
(e_in.data_len(1) and e_in.read_data3(15)) or
(e_in.data_len(2) and e_in.read_data3(31));
result := (others => negative);
if e_in.data_len(2) = '1' then
result(31 downto 16) := e_in.read_data3(31 downto 16);
end if;
if e_in.data_len(2) = '1' or e_in.data_len(1) = '1' then
result(15 downto 8) := e_in.read_data3(15 downto 8);
end if;
result(7 downto 0) := e_in.read_data3(7 downto 0);
result_en := '1';
when OP_ISEL =>
crbit := to_integer(unsigned(insn_bc(e_in.insn)));
if e_in.cr(31-crbit) = '1' then
result := e_in.read_data1;
else
result := e_in.read_data2;
end if;
result_en := '1';
when OP_MCRF =>
cr_op := insn_cr(e_in.insn);
report "CR OP " & to_hstring(cr_op);
if cr_op(0) = '0' then -- MCRF
bf := insn_bf(e_in.insn);
bfa := insn_bfa(e_in.insn);
v.e.write_cr_enable := '1';
crnum := to_integer(unsigned(bf));
scrnum := to_integer(unsigned(bfa));
v.e.write_cr_mask := num_to_fxm(crnum);
for i in 0 to 7 loop
lo := (7-i)*4;
hi := lo + 3;
if i = scrnum then
newcrf := e_in.cr(hi downto lo);
end if;
end loop;
for i in 0 to 7 loop
lo := i*4;
hi := lo + 3;
v.e.write_cr_data(hi downto lo) := newcrf;
end loop;
else
v.e.write_cr_enable := '1';
bt := insn_bt(e_in.insn);
ba := insn_ba(e_in.insn);
bb := insn_bb(e_in.insn);
btnum := 31 - to_integer(unsigned(bt));
banum := 31 - to_integer(unsigned(ba));
bbnum := 31 - to_integer(unsigned(bb));
case cr_op(8 downto 5) is
when "1001" => -- CREQV
crresult := not(e_in.cr(banum) xor e_in.cr(bbnum));
when "0111" => -- CRNAND
crresult := not(e_in.cr(banum) and e_in.cr(bbnum));
when "0100" => -- CRANDC
crresult := (e_in.cr(banum) and not e_in.cr(bbnum));
when "1000" => -- CRAND
crresult := (e_in.cr(banum) and e_in.cr(bbnum));
when "0001" => -- CRNOR
crresult := not(e_in.cr(banum) or e_in.cr(bbnum));
when "1101" => -- CRORC
crresult := (e_in.cr(banum) or not e_in.cr(bbnum));
when "0110" => -- CRXOR
crresult := (e_in.cr(banum) xor e_in.cr(bbnum));
when "1110" => -- CROR
crresult := (e_in.cr(banum) or e_in.cr(bbnum));
when others =>
crresult := '0';
report "BAD CR?";
end case;
v.e.write_cr_mask := num_to_fxm((31-btnum) / 4);
for i in 0 to 31 loop
if i = btnum then
v.e.write_cr_data(i) := crresult;
else
v.e.write_cr_data(i) := e_in.cr(i);
end if;
end loop;
end if;
when OP_MFSPR =>
if is_fast_spr(e_in.read_reg1) then
result := e_in.read_data1;
if decode_spr_num(e_in.insn) = SPR_XER then
-- bits 0:31 and 35:43 are treated as reserved and return 0s when read using mfxer
result(63 downto 32) := (others => '0');
result(63-32) := v.e.xerc.so;
result(63-33) := v.e.xerc.ov;
result(63-34) := v.e.xerc.ca;
result(63-35 downto 63-43) := "000000000";
result(63-44) := v.e.xerc.ov32;
result(63-45) := v.e.xerc.ca32;
end if;
else
case decode_spr_num(e_in.insn) is
when SPR_TB =>
result := ctrl.tb;
when others =>
result := (others => '0');
end case;
end if;
result_en := '1';
when OP_MFCR =>
if e_in.insn(20) = '0' then
-- mfcr
result := x"00000000" & e_in.cr;
else
-- mfocrf
crnum := fxm_to_num(insn_fxm(e_in.insn));
result := (others => '0');
for i in 0 to 7 loop
lo := (7-i)*4;
hi := lo + 3;
if crnum = i then
result(hi downto lo) := e_in.cr(hi downto lo);
end if;
end loop;
end if;
result_en := '1';
when OP_MTCRF =>
v.e.write_cr_enable := '1';
if e_in.insn(20) = '0' then
-- mtcrf
v.e.write_cr_mask := insn_fxm(e_in.insn);
else
-- mtocrf: We require one hot priority encoding here
crnum := fxm_to_num(insn_fxm(e_in.insn));
v.e.write_cr_mask := num_to_fxm(crnum);
end if;
v.e.write_cr_data := e_in.read_data3(31 downto 0);
when OP_MTSPR =>
report "MTSPR to SPR " & integer'image(decode_spr_num(e_in.insn)) &
"=" & to_hstring(e_in.read_data3);
if is_fast_spr(e_in.write_reg) then
result := e_in.read_data3;
result_en := '1';
if decode_spr_num(e_in.insn) = SPR_XER then
v.e.xerc.so := e_in.read_data3(63-32);
v.e.xerc.ov := e_in.read_data3(63-33);
v.e.xerc.ca := e_in.read_data3(63-34);
v.e.xerc.ov32 := e_in.read_data3(63-44);
v.e.xerc.ca32 := e_in.read_data3(63-45);
v.e.write_xerc_enable := '1';
end if;
else
-- TODO: Implement slow SPRs
-- case decode_spr_num(e_in.insn) is
-- when others =>
-- end case;
end if;
when OP_POPCNTB =>
result := ppc_popcntb(e_in.read_data3);
result_en := '1';
when OP_POPCNTW =>
result := ppc_popcntw(e_in.read_data3);
result_en := '1';
when OP_POPCNTD =>
result := ppc_popcntd(e_in.read_data3);
result_en := '1';
when OP_PRTYD =>
result := ppc_prtyd(e_in.read_data3);
result_en := '1';
when OP_PRTYW =>
result := ppc_prtyw(e_in.read_data3);
result_en := '1';
when OP_RLC | OP_RLCL | OP_RLCR | OP_SHL | OP_SHR =>
result := rotator_result;
if e_in.output_carry = '1' then
set_carry(v.e, rotator_carry, rotator_carry);
end if;
result_en := '1';
when OP_SIM_CONFIG =>
-- bit 0 was used to select the microwatt console, which
-- we no longer support.
result := x"0000000000000000";
result_en := '1';
when OP_TDI =>
-- Keep our test cases happy for now, ignore trap instructions
report "OP_TDI FIXME";
when OP_ISYNC =>
f_out.redirect <= '1';
f_out.redirect_nia <= next_nia;
when OP_ICBI =>
icache_inval <= '1';
when OP_MUL_L64 | OP_MUL_H64 | OP_MUL_H32 =>
v.e.valid := '0';
v.mul_in_progress := '1';
stall_out <= '1';
x_to_multiply.valid <= '1';
when OP_DIV | OP_DIVE | OP_MOD =>
v.e.valid := '0';
v.div_in_progress := '1';
stall_out <= '1';
x_to_divider.valid <= '1';
when others =>
terminate_out <= '1';
report "illegal";
end case;
v.e.rc := e_in.rc and e_in.valid;
-- Update LR on the next cycle after a branch link
--
-- WARNING: The LR update isn't tracked by our hazard tracker. This
-- will work (well I hope) because it only happens on branches
-- which will flush all decoded instructions. By the time
-- fetch catches up, we'll have the new LR. This will
-- *not* work properly however if we have a branch predictor,
-- in which case the solution would probably be to keep a
-- local cache of the updated LR in execute1 (flushed on
-- exceptions) that is used instead of the value from
-- decode when its content is valid.
if e_in.lr = '1' then
v.lr_update := '1';
v.next_lr := next_nia;
v.e.valid := '0';
report "Delayed LR update to " & to_hstring(next_nia);
stall_out <= '1';
end if;
elsif r.lr_update = '1' then
result_en := '1';
result := r.next_lr;
v.e.write_reg := fast_spr_num(SPR_LR);
v.e.valid := '1';
elsif r.mul_in_progress = '1' or r.div_in_progress = '1' then
if (r.mul_in_progress = '1' and multiply_to_x.valid = '1') or
(r.div_in_progress = '1' and divider_to_x.valid = '1') then
if r.mul_in_progress = '1' then
result := multiply_to_x.write_reg_data;
overflow := multiply_to_x.overflow;
else
result := divider_to_x.write_reg_data;
overflow := divider_to_x.overflow;
end if;
result_en := '1';
v.e.write_reg := gpr_to_gspr(v.slow_op_dest);
v.e.rc := v.slow_op_rc;
v.e.xerc := v.slow_op_xerc;
v.e.write_xerc_enable := v.slow_op_oe;
-- We must test oe because the RC update code in writeback
-- will use the xerc value to set CR0:SO so we must not clobber
-- xerc if OE wasn't set.
if v.slow_op_oe = '1' then
v.e.xerc.ov := overflow;
v.e.xerc.ov32 := overflow;
v.e.xerc.so := v.slow_op_xerc.so or overflow;
end if;
v.e.valid := '1';
else
stall_out <= '1';
v.mul_in_progress := r.mul_in_progress;
v.div_in_progress := r.div_in_progress;
end if;
end if;
v.e.write_data := result;
v.e.write_enable := result_en;
-- Update registers
rin <= v;
-- update outputs
--f_out <= r.f;
e_out <= r.e;
flush_out <= f_out.redirect;
end process;
end architecture behaviour;
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