Dynamic Scheduling - University of Washington...Dynamic Scheduling Spring 2005 CSE P548 2 Why come...
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Spring 2005 CSE P548 1 Dynamic Scheduling Why go out of style? • expensive hardware for the time (actually, still is, relatively) • register files grew so less register pressure • early RISCs had lower CPIs
Transcript of Dynamic Scheduling - University of Washington...Dynamic Scheduling Spring 2005 CSE P548 2 Why come...
Spri
ng 2
005
CSE
P54
81
Dyn
amic
Sch
edu
ling
Wh
y g
o o
ut
of
styl
e?
•ex
pens
ive
hard
war
e fo
r th
e tim
e (a
ctua
lly, s
till i
s, r
elat
ivel
y)
•re
gist
er fi
les
grew
so
less
reg
iste
r pr
essu
re
•ea
rly R
ISC
s ha
d lo
wer
CP
Is
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ng 2
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Dyn
amic
Sch
edu
ling
Wh
y co
me
bac
k?•
high
er c
hip
dens
ities
•gr
eate
r ne
ed to
hid
e la
tenc
ies
as:
•di
scre
panc
y be
twee
n C
PU
& m
emor
y sp
eeds
incr
ease
s•
bran
ch m
ispr
edic
tion
pena
lty in
crea
ses
from
sup
erpi
pelin
ing
•dy
nam
ic s
ched
ulin
g w
as g
ener
aliz
ed to
cov
er m
ore
than
floa
ting
poin
t ope
ratio
ns•
hand
les
bran
ches
& h
ides
bra
nch
late
ncie
s•
hide
s ca
che
mis
ses
•ca
n be
impl
emen
ted
with
a m
ore
gene
ral r
egis
ter
rena
min
g m
echa
nism
•co
mm
its in
stru
ctio
ns in
-ord
er to
pre
serv
e pr
ecis
e in
terr
upts
•pr
oces
sors
now
issu
e m
ultip
le in
stru
ctio
ns a
t the
sam
e tim
e•
mor
e ne
ed to
exp
loit
ILP
2 st
yles
:la
rge
phys
ical
reg
iste
r fil
e&
reor
der
buffe
r(R
1000
0-st
yle)
(P
entiu
mP
ro-s
tyle
)
Spri
ng 2
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Reg
iste
r R
enam
ing
wit
h A
Ph
ysic
al R
egis
ter
File
Reg
iste
r re
nam
ing
prov
ides
a m
app
ing
betw
een
2 re
gist
er s
ets
•ar
chit
ectu
ral r
egis
ters
defin
ed b
y th
e IS
A•
ph
ysic
al r
egis
ters
impl
emen
ted
in th
e C
PU
•ho
ld r
esul
ts o
f the
inst
ruct
ions
com
mitt
ed s
o fa
r•
hold
res
ults
of s
ubse
quen
t, in
depe
nden
t ins
truc
tions
that
hav
e no
t yet
com
mitt
ed•
mor
e of
them
than
arc
hite
ctur
al r
egis
ters
•~
issu
e w
idth
* #
pip
elin
e st
ages
bet
wee
n re
gist
er
rena
min
g &
com
mit
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Reg
iste
r R
enam
ing
wit
h A
Ph
ysic
al R
egis
ter
File
How
doe
s it
wor
k?:
•an
arc
hite
ctur
al r
egis
ter
is m
appe
d to
a ph
ysic
al r
egis
ter
durin
g a
regi
ster
ren
amin
g st
age
in th
e pi
pelin
e
•op
eran
ds th
erea
fter
are
calle
d by
thei
r ph
ysic
al r
egis
ter
num
ber
•ha
zard
s de
term
ined
by
com
parin
g ph
ysic
al r
egis
ter
num
bers
, no
t arc
hite
ctur
al r
egis
ter
num
bers
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A R
egis
ter
Ren
amin
g E
xam
ple
Cod
e S
egm
ent
Reg
iste
r M
appi
ng
Com
men
ts
ld r7,0(r6)
r7 -> p1
p1
is a
lloca
ted
...
add r8, r9, r7
r8 -> p2
use
p1,
not
r7
...
sub r7, r2, r3
r7 -> p3
p3
is a
lloca
ted
p1
is d
eallo
cate
d w
hen sub
com
mits
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Reg
iste
r R
enam
ing
wit
h A
Ph
ysic
al R
egis
ter
File
Effe
cts: •
elim
inat
es W
AW
and
WA
R h
azar
ds(f
alse
nam
ede
pend
ence
s)•
incr
ease
s IL
P
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An
Imp
lem
enta
tio
n (
R10
000)
Mod
ular
des
ign
with
reg
ular
har
dwar
e da
ta s
truc
ture
s
Str
uctu
res
for
regi
ster
ren
amin
g
•64
ph
ysic
alre
gis
ters
(eac
h, fo
r in
tege
r &
FP
)
•m
ap t
able
sfo
r th
e cu
rren
tar
chite
ctur
al-t
o-ph
ysic
al r
egis
ter
map
ping
(se
para
te, f
or in
tege
r &
FP
)
•ac
cess
ed w
ith a
n ar
chite
ctur
al r
egis
ter
num
ber
•pr
oduc
es a
phy
sica
l reg
iste
r nu
mbe
r
•a
dest
inat
ion
regi
ster
is a
ssig
ned
a ne
w p
hysi
cal r
egis
ter
num
ber
from
a f
ree
reg
iste
r lis
t (s
epar
ate,
for
inte
ger
& F
P)
•so
urce
ope
rand
s re
fer
to th
e la
test
def
ined
des
tinat
ion
regi
ster
,i.e
., th
e cu
rren
t map
ping
s
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An
Imp
lem
enta
tio
n (
R10
000)
Inst
ruct
ion
“q
ueu
es”
(inte
ger,
FP
& d
ata
tran
sfer
)
•co
ntai
ns d
ecod
ed &
map
ped
inst
ruct
ions
with
the
curr
ent
phys
ical
reg
iste
r m
appi
ngs
•in
stru
ctio
ns e
nter
ed in
to fr
ee lo
catio
ns in
the
IQ
•si
t the
re u
ntil
they
are
dis
patc
hed
to fu
nctio
nal u
nits
•so
mew
hat a
nalo
gous
to T
omas
ulo
rese
rvat
ion
stat
ions
w
ithou
t val
ue fi
elds
or
valid
bits
•us
ed to
det
erm
ine
whe
n op
eran
ds a
re a
vaila
ble
•co
mpa
re e
ach
sour
ce o
pera
nd o
fins
truc
tions
in th
e IQ
to
des
tinat
ion
valu
es ju
st c
ompu
ted
•de
term
ines
whe
n an
app
ropr
iate
func
tiona
l uni
t is
avai
labl
e
•di
spat
ches
inst
ruct
ions
to fu
nctio
nal u
nits
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An
Imp
lem
enta
tio
n (
R10
000)
acti
ve li
stfo
r al
l unc
omm
itted
inst
ruct
ions
•th
e m
echa
nism
for
mai
ntai
ning
pre
cise
inte
rrup
ts•
inst
ruct
ions
ent
ered
in p
rogr
am-g
ener
ated
ord
er•
allo
ws
inst
ruct
ions
to c
ompl
ete
in p
rogr
am-g
ener
ated
ord
er•
inst
ruct
ions
rem
oved
from
the
activ
e lis
t whe
n:•
an in
stru
ctio
n co
mm
its:
•th
e in
stru
ctio
n ha
s co
mpl
eted
exe
cutio
n•
all i
nstr
uctio
ns a
head
of i
t hav
e al
so c
ompl
eted
•br
anch
is m
ispr
edic
ted
•an
exc
eptio
n oc
curs
•co
ntai
ns th
e p
revi
ou
sar
chite
ctur
al-t
o-ph
ysic
al d
estin
atio
n re
gist
er
map
ping
•us
ed to
rec
reat
e th
e m
ap ta
ble
for
inst
ruct
ion
rest
art a
fter
an
exce
ptio
n•
inst
ruct
ions
in th
e ot
her
hard
war
e st
ruct
ures
& th
e fu
nctio
nal u
nits
ar
e id
entif
ied
by th
eir
activ
e lis
t loc
atio
n
Spri
ng 2
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P54
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An
Imp
lem
enta
tio
n (
R10
000)
bu
sy-r
egis
ter
tab
le(in
tege
r &
FP
):
•in
dica
tes
whe
ther
a p
hysi
cal r
egis
ter
cont
ains
a v
alue
•so
mew
hat a
nalo
gous
to T
omas
ulo’
sre
gist
er s
tatu
s
•us
ed to
det
erm
ine
oper
and
avai
labi
lity
•bi
t is
set w
hen
a re
gist
er is
map
ped
& le
aves
the
free
list
(not
av
aila
ble
yet)
•cl
eare
d w
hen
a F
U w
rites
the
regi
ster
(now
ther
e’s
a va
lue)
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P54
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6464
Spri
ng 2
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CSE
P54
812
Th
e R
1000
0 in
Act
ion
1
Spri
ng 2
005
CSE
P54
813
Th
e R
1000
0 in
Act
ion
2
Py
Spri
ng 2
005
CSE
P54
814
Th
e R
1000
0 in
Act
ion
3
20
Spri
ng 2
005
CSE
P54
815
Th
e R
1000
0 in
Act
ion
4
Pz
Spri
ng 2
005
CSE
P54
816
Th
e R
1000
0 in
Act
ion
: In
terr
up
ts 1
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ng 2
005
CSE
P54
817
Th
e R
1000
0 in
Act
ion
: In
terr
up
ts 2
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ng 2
005
CSE
P54
818
Th
e R
1000
0 in
Act
ion
: In
terr
up
ts 3
Spri
ng 2
005
CSE
P54
819
Th
e R
1000
0 in
Act
ion
: In
terr
up
ts 4
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ng 2
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P54
820
R10
000
Exe
cuti
on
In-o
rder
issu
e (h
ave
alre
ady
fetc
hed
inst
ruct
ions
)•
rena
me
arch
itect
ural
reg
iste
rs to
phy
sica
l reg
iste
rs v
ia a
map
tabl
e•
dete
ct s
truc
tura
l haz
ards
for
inst
ruct
ion
queu
es (
inte
ger,
mem
ory
&
FP
) &
act
ive
list
•is
sue
up to
4 in
stru
ctio
ns to
the
inst
ruct
ion
queu
es
Ou
t-o
f-o
rder
exe
cuti
on
(to
incr
ease
ILP
)•
rese
rvat
ion-
stat
ion-
like
inst
ruct
ion
queu
es th
at in
dica
te w
hen
an
oper
and
has
been
cal
cula
ted
•ea
ch in
stru
ctio
n m
onito
rs th
e se
tting
of t
he b
usy-
regi
ster
tabl
e•
set b
usy-
regi
ster
tabl
e en
try
for
the
dest
inat
ion
regi
ster
•de
tect
func
tiona
l uni
t str
uctu
ral &
RA
W h
azar
ds•
disp
atch
inst
ruct
ions
to fu
nctio
nal u
nits
In-o
rder
co
mm
it(t
o pr
eser
ve p
reci
se in
terr
upts
)•
this
& p
revi
ous
prog
ram
-gen
erat
ed in
stru
ctio
ns h
ave
com
plet
ed•
phys
ical
reg
iste
r in
pre
viou
s m
appi
ng r
etur
ned
to fr
ee li
st•
rollb
ack
on in
terr
upts
