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antonblanchard.microwatt/common.vhdl
Paul Mackerras 6687aae4d6 core: Implement a simple branch predictor 
This implements a simple branch predictor in the decode1 stage.  If it
sees that the instruction is b or bc and the branch is predicted to be
taken, it sends a flush and redirect upstream (to icache and fetch1)
to redirect fetching to the branch target.  The prediction is sent
downstream with the branch instruction, and execute1 now only sends
a flush/redirect upstream if the prediction was wrong.  Unconditional
branches are always predicted to be taken, and conditional branches
are predicted to be taken if and only if the offset is negative.
Branches that take the branch address from a register (bclr, bcctr)
are predicted not taken, as we don't have any way to predict the
branch address.

Since we can now have a mflr being executed immediately after a bl
or bcl, we now track the update to LR in the hazard tracker, using
the second write register field that is used to track RA updates for
update-form loads and stores.

For those branches that update LR but don't write any other result
(i.e. that don't decrementer CTR), we now write back LR in the same
cycle as the instruction rather than taking a second cycle for the
LR writeback.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
2020-06-15 17:46:33 +10:00

476 lines
17 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;
package common is
-- MSR bit numbers
constant MSR_SF : integer := (63 - 0); -- Sixty-Four bit mode
constant MSR_EE : integer := (63 - 48); -- External interrupt Enable
constant MSR_PR : integer := (63 - 49); -- PRoblem state
constant MSR_IR : integer := (63 - 58); -- Instruction Relocation
constant MSR_DR : integer := (63 - 59); -- Data Relocation
constant MSR_RI : integer := (63 - 62); -- Recoverable Interrupt
constant MSR_LE : integer := (63 - 63); -- Little Endian
-- SPR numbers
subtype spr_num_t is integer range 0 to 1023;
function decode_spr_num(insn: std_ulogic_vector(31 downto 0)) return spr_num_t;
constant SPR_XER : spr_num_t := 1;
constant SPR_LR : spr_num_t := 8;
constant SPR_CTR : spr_num_t := 9;
constant SPR_DSISR : spr_num_t := 18;
constant SPR_DAR : spr_num_t := 19;
constant SPR_TB : spr_num_t := 268;
constant SPR_DEC : spr_num_t := 22;
constant SPR_SRR0 : spr_num_t := 26;
constant SPR_SRR1 : spr_num_t := 27;
constant SPR_HSRR0 : spr_num_t := 314;
constant SPR_HSRR1 : spr_num_t := 315;
constant SPR_SPRG0 : spr_num_t := 272;
constant SPR_SPRG1 : spr_num_t := 273;
constant SPR_SPRG2 : spr_num_t := 274;
constant SPR_SPRG3 : spr_num_t := 275;
constant SPR_SPRG3U : spr_num_t := 259;
constant SPR_HSPRG0 : spr_num_t := 304;
constant SPR_HSPRG1 : spr_num_t := 305;
constant SPR_PID : spr_num_t := 48;
constant SPR_PRTBL : spr_num_t := 720;
-- GPR indices in the register file (GPR only)
subtype gpr_index_t is std_ulogic_vector(4 downto 0);
-- Extended GPR indice (can hold an SPR)
subtype gspr_index_t is std_ulogic_vector(5 downto 0);
-- Some SPRs are stored in the register file, they use the magic
-- GPR numbers above 31.
--
-- The function fast_spr_num() returns the corresponding fast
-- pseudo-GPR number for a given SPR number. The result MSB
-- indicates if this is indeed a fast SPR. If clear, then
-- the SPR is not stored in the GPR file.
--
function fast_spr_num(spr: spr_num_t) return gspr_index_t;
-- Indices conversion functions
function gspr_to_gpr(i: gspr_index_t) return gpr_index_t;
function gpr_to_gspr(i: gpr_index_t) return gspr_index_t;
function gpr_or_spr_to_gspr(g: gpr_index_t; s: gspr_index_t) return gspr_index_t;
function is_fast_spr(s: gspr_index_t) return std_ulogic;
-- The XER is split: the common bits (CA, OV, SO, OV32 and CA32) are
-- in the CR file as a kind of CR extension (with a separate write
-- control). The rest is stored as a fast SPR.
type xer_common_t is record
ca : std_ulogic;
ca32 : std_ulogic;
ov : std_ulogic;
ov32 : std_ulogic;
so : std_ulogic;
end record;
constant xerc_init : xer_common_t := (others => '0');
type irq_state_t is (WRITE_SRR0, WRITE_SRR1);
-- This needs to die...
type ctrl_t is record
tb: std_ulogic_vector(63 downto 0);
dec: std_ulogic_vector(63 downto 0);
msr: std_ulogic_vector(63 downto 0);
irq_state : irq_state_t;
irq_nia: std_ulogic_vector(63 downto 0);
srr1: std_ulogic_vector(63 downto 0);
end record;
type Fetch1ToIcacheType is record
req: std_ulogic;
virt_mode : std_ulogic;
priv_mode : std_ulogic;
stop_mark: std_ulogic;
sequential: std_ulogic;
nia: std_ulogic_vector(63 downto 0);
end record;
type IcacheToDecode1Type is record
valid: std_ulogic;
stop_mark: std_ulogic;
fetch_failed: std_ulogic;
nia: std_ulogic_vector(63 downto 0);
insn: std_ulogic_vector(31 downto 0);
end record;
type Decode1ToDecode2Type is record
valid: std_ulogic;
stop_mark : std_ulogic;
nia: std_ulogic_vector(63 downto 0);
insn: std_ulogic_vector(31 downto 0);
ispr1: gspr_index_t; -- (G)SPR used for branch condition (CTR) or mfspr
ispr2: gspr_index_t; -- (G)SPR used for branch target (CTR, LR, TAR)
decode: decode_rom_t;
br_pred: std_ulogic; -- Branch was predicted to be taken
end record;
constant Decode1ToDecode2Init : Decode1ToDecode2Type :=
(valid => '0', stop_mark => '0', nia => (others => '0'), insn => (others => '0'),
ispr1 => (others => '0'), ispr2 => (others => '0'), decode => decode_rom_init, br_pred => '0');
type Decode1ToFetch1Type is record
redirect : std_ulogic;
redirect_nia : std_ulogic_vector(63 downto 0);
end record;
type Decode2ToExecute1Type is record
valid: std_ulogic;
unit : unit_t;
insn_type: insn_type_t;
nia: std_ulogic_vector(63 downto 0);
write_reg: gspr_index_t;
read_reg1: gspr_index_t;
read_reg2: gspr_index_t;
read_data1: std_ulogic_vector(63 downto 0);
read_data2: std_ulogic_vector(63 downto 0);
read_data3: std_ulogic_vector(63 downto 0);
bypass_data1: std_ulogic;
bypass_data2: std_ulogic;
bypass_data3: std_ulogic;
cr: std_ulogic_vector(31 downto 0);
xerc: xer_common_t;
lr: std_ulogic;
rc: std_ulogic;
oe: std_ulogic;
invert_a: std_ulogic;
invert_out: std_ulogic;
input_carry: carry_in_t;
output_carry: std_ulogic;
input_cr: std_ulogic;
output_cr: std_ulogic;
is_32bit: std_ulogic;
is_signed: std_ulogic;
insn: std_ulogic_vector(31 downto 0);
data_len: std_ulogic_vector(3 downto 0);
byte_reverse : std_ulogic;
sign_extend : std_ulogic; -- do we need to sign extend?
update : std_ulogic; -- is this an update instruction?
reserve : std_ulogic; -- set for larx/stcx
br_pred : std_ulogic;
end record;
constant Decode2ToExecute1Init : Decode2ToExecute1Type :=
(valid => '0', unit => NONE, insn_type => OP_ILLEGAL, bypass_data1 => '0', bypass_data2 => '0', bypass_data3 => '0',
lr => '0', rc => '0', oe => '0', invert_a => '0',
invert_out => '0', input_carry => ZERO, output_carry => '0', input_cr => '0', output_cr => '0',
is_32bit => '0', is_signed => '0', xerc => xerc_init, reserve => '0', br_pred => '0',
byte_reverse => '0', sign_extend => '0', update => '0', nia => (others => '0'), read_data1 => (others => '0'), read_data2 => (others => '0'), read_data3 => (others => '0'), cr => (others => '0'), insn => (others => '0'), data_len => (others => '0'), others => (others => '0'));
type Execute1ToMultiplyType is record
valid: std_ulogic;
data1: std_ulogic_vector(63 downto 0);
data2: std_ulogic_vector(63 downto 0);
is_32bit: std_ulogic;
neg_result: std_ulogic;
end record;
constant Execute1ToMultiplyInit : Execute1ToMultiplyType := (valid => '0',
is_32bit => '0', neg_result => '0',
others => (others => '0'));
type Execute1ToDividerType is record
valid: std_ulogic;
dividend: std_ulogic_vector(63 downto 0);
divisor: std_ulogic_vector(63 downto 0);
is_signed: std_ulogic;
is_32bit: std_ulogic;
is_extended: std_ulogic;
is_modulus: std_ulogic;
neg_result: std_ulogic;
end record;
constant Execute1ToDividerInit: Execute1ToDividerType := (valid => '0', is_signed => '0', is_32bit => '0',
is_extended => '0', is_modulus => '0',
neg_result => '0', others => (others => '0'));
type Decode2ToRegisterFileType is record
read1_enable : std_ulogic;
read1_reg : gspr_index_t;
read2_enable : std_ulogic;
read2_reg : gspr_index_t;
read3_enable : std_ulogic;
read3_reg : gpr_index_t;
end record;
type RegisterFileToDecode2Type is record
read1_data : std_ulogic_vector(63 downto 0);
read2_data : std_ulogic_vector(63 downto 0);
read3_data : std_ulogic_vector(63 downto 0);
end record;
type Decode2ToCrFileType is record
read : std_ulogic;
end record;
type CrFileToDecode2Type is record
read_cr_data : std_ulogic_vector(31 downto 0);
read_xerc_data : xer_common_t;
end record;
type Execute1ToFetch1Type is record
redirect: std_ulogic;
virt_mode: std_ulogic;
priv_mode: std_ulogic;
redirect_nia: std_ulogic_vector(63 downto 0);
end record;
constant Execute1ToFetch1TypeInit : Execute1ToFetch1Type := (redirect => '0', virt_mode => '0',
priv_mode => '0', others => (others => '0'));
type Execute1ToLoadstore1Type is record
valid : std_ulogic;
op : insn_type_t; -- what ld/st or m[tf]spr or TLB op to do
nia : std_ulogic_vector(63 downto 0);
insn : std_ulogic_vector(31 downto 0);
addr1 : std_ulogic_vector(63 downto 0);
addr2 : std_ulogic_vector(63 downto 0);
data : std_ulogic_vector(63 downto 0); -- data to write, unused for read
write_reg : gpr_index_t;
length : std_ulogic_vector(3 downto 0);
ci : std_ulogic; -- cache-inhibited load/store
byte_reverse : std_ulogic;
sign_extend : std_ulogic; -- do we need to sign extend?
update : std_ulogic; -- is this an update instruction?
update_reg : gpr_index_t; -- if so, the register to update
xerc : xer_common_t;
reserve : std_ulogic; -- set for larx/stcx.
rc : std_ulogic; -- set for stcx.
virt_mode : std_ulogic; -- do translation through TLB
priv_mode : std_ulogic; -- privileged mode (MSR[PR] = 0)
end record;
constant Execute1ToLoadstore1Init : Execute1ToLoadstore1Type := (valid => '0', op => OP_ILLEGAL, ci => '0', byte_reverse => '0',
sign_extend => '0', update => '0', xerc => xerc_init,
reserve => '0', rc => '0', virt_mode => '0', priv_mode => '0',
nia => (others => '0'), insn => (others => '0'),
addr1 => (others => '0'), addr2 => (others => '0'), data => (others => '0'), length => (others => '0'),
others => (others => '0'));
type Loadstore1ToExecute1Type is record
busy : std_ulogic;
exception : std_ulogic;
invalid : std_ulogic;
perm_error : std_ulogic;
rc_error : std_ulogic;
badtree : std_ulogic;
segment_fault : std_ulogic;
instr_fault : std_ulogic;
end record;
type Loadstore1ToDcacheType is record
valid : std_ulogic;
load : std_ulogic; -- is this a load
dcbz : std_ulogic;
nc : std_ulogic;
reserve : std_ulogic;
virt_mode : std_ulogic;
priv_mode : std_ulogic;
addr : std_ulogic_vector(63 downto 0);
data : std_ulogic_vector(63 downto 0);
byte_sel : std_ulogic_vector(7 downto 0);
end record;
type DcacheToLoadstore1Type is record
valid : std_ulogic;
data : std_ulogic_vector(63 downto 0);
store_done : std_ulogic;
error : std_ulogic;
cache_paradox : std_ulogic;
end record;
type Loadstore1ToMmuType is record
valid : std_ulogic;
tlbie : std_ulogic;
slbia : std_ulogic;
mtspr : std_ulogic;
iside : std_ulogic;
load : std_ulogic;
priv : std_ulogic;
sprn : std_ulogic_vector(9 downto 0);
addr : std_ulogic_vector(63 downto 0);
rs : std_ulogic_vector(63 downto 0);
end record;
type MmuToLoadstore1Type is record
done : std_ulogic;
invalid : std_ulogic;
badtree : std_ulogic;
segerr : std_ulogic;
perm_error : std_ulogic;
rc_error : std_ulogic;
sprval : std_ulogic_vector(63 downto 0);
end record;
type MmuToDcacheType is record
valid : std_ulogic;
tlbie : std_ulogic;
doall : std_ulogic;
tlbld : std_ulogic;
addr : std_ulogic_vector(63 downto 0);
pte : std_ulogic_vector(63 downto 0);
end record;
type DcacheToMmuType is record
stall : std_ulogic;
done : std_ulogic;
err : std_ulogic;
data : std_ulogic_vector(63 downto 0);
end record;
type MmuToIcacheType is record
tlbld : std_ulogic;
tlbie : std_ulogic;
doall : std_ulogic;
addr : std_ulogic_vector(63 downto 0);
pte : std_ulogic_vector(63 downto 0);
end record;
type Loadstore1ToWritebackType is record
valid : std_ulogic;
write_enable: std_ulogic;
write_reg : gpr_index_t;
write_data : std_ulogic_vector(63 downto 0);
xerc : xer_common_t;
rc : std_ulogic;
store_done : std_ulogic;
end record;
constant Loadstore1ToWritebackInit : Loadstore1ToWritebackType := (valid => '0', write_enable => '0', xerc => xerc_init,
rc => '0', store_done => '0', write_data => (others => '0'), others => (others => '0'));
type Execute1ToWritebackType is record
valid: std_ulogic;
rc : std_ulogic;
write_enable : std_ulogic;
write_reg: gspr_index_t;
write_data: std_ulogic_vector(63 downto 0);
write_cr_enable : std_ulogic;
write_cr_mask : std_ulogic_vector(7 downto 0);
write_cr_data : std_ulogic_vector(31 downto 0);
write_xerc_enable : std_ulogic;
xerc : xer_common_t;
exc_write_enable : std_ulogic;
exc_write_reg : gspr_index_t;
exc_write_data : std_ulogic_vector(63 downto 0);
end record;
constant Execute1ToWritebackInit : Execute1ToWritebackType := (valid => '0', rc => '0', write_enable => '0',
write_cr_enable => '0', exc_write_enable => '0',
write_xerc_enable => '0', xerc => xerc_init,
write_data => (others => '0'), write_cr_mask => (others => '0'),
write_cr_data => (others => '0'), write_reg => (others => '0'),
exc_write_reg => (others => '0'), exc_write_data => (others => '0'));
type MultiplyToExecute1Type is record
valid: std_ulogic;
result: std_ulogic_vector(127 downto 0);
overflow : std_ulogic;
end record;
constant MultiplyToExecute1Init : MultiplyToExecute1Type := (valid => '0', overflow => '0',
others => (others => '0'));
type DividerToExecute1Type is record
valid: std_ulogic;
write_reg_data: std_ulogic_vector(63 downto 0);
overflow : std_ulogic;
end record;
constant DividerToExecute1Init : DividerToExecute1Type := (valid => '0', overflow => '0',
others => (others => '0'));
type WritebackToRegisterFileType is record
write_reg : gspr_index_t;
write_data : std_ulogic_vector(63 downto 0);
write_enable : std_ulogic;
end record;
constant WritebackToRegisterFileInit : WritebackToRegisterFileType := (write_enable => '0', write_data => (others => '0'), others => (others => '0'));
type WritebackToCrFileType is record
write_cr_enable : std_ulogic;
write_cr_mask : std_ulogic_vector(7 downto 0);
write_cr_data : std_ulogic_vector(31 downto 0);
write_xerc_enable : std_ulogic;
write_xerc_data : xer_common_t;
end record;
constant WritebackToCrFileInit : WritebackToCrFileType := (write_cr_enable => '0', write_xerc_enable => '0',
write_xerc_data => xerc_init,
write_cr_mask => (others => '0'),
write_cr_data => (others => '0'));
end common;
package body common is
function decode_spr_num(insn: std_ulogic_vector(31 downto 0)) return spr_num_t is
begin
return to_integer(unsigned(insn(15 downto 11) & insn(20 downto 16)));
end;
function fast_spr_num(spr: spr_num_t) return gspr_index_t is
variable n : integer range 0 to 31;
-- tmp variable introduced as workaround for VCS compilation
-- simulation was failing with subtype constraint mismatch error
-- see GitHub PR #173
variable tmp : std_ulogic_vector(4 downto 0);
begin
case spr is
when SPR_LR =>
n := 0;
when SPR_CTR =>
n:= 1;
when SPR_SRR0 =>
n := 2;
when SPR_SRR1 =>
n := 3;
when SPR_HSRR0 =>
n := 4;
when SPR_HSRR1 =>
n := 5;
when SPR_SPRG0 =>
n := 6;
when SPR_SPRG1 =>
n := 7;
when SPR_SPRG2 =>
n := 8;
when SPR_SPRG3 | SPR_SPRG3U =>
n := 9;
when SPR_HSPRG0 =>
n := 10;
when SPR_HSPRG1 =>
n := 11;
when SPR_XER =>
n := 12;
when others =>
n := 0;
return "000000";
end case;
tmp := std_ulogic_vector(to_unsigned(n, 5));
return "1" & tmp;
end;
function gspr_to_gpr(i: gspr_index_t) return gpr_index_t is
begin
return i(4 downto 0);
end;
function gpr_to_gspr(i: gpr_index_t) return gspr_index_t is
begin
return "0" & i;
end;
function gpr_or_spr_to_gspr(g: gpr_index_t; s: gspr_index_t) return gspr_index_t is
begin
if s(5) = '1' then
return s;
else
return gpr_to_gspr(g);
end if;
end;
function is_fast_spr(s: gspr_index_t) return std_ulogic is
begin
return s(5);
end;
end common;
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