<s>
SIMD	B-General_Concept
within	I-General_Concept
a	I-General_Concept
register	I-General_Concept
(	O
SWAR	B-General_Concept
)	O
,	O
also	O
known	O
by	O
the	O
name	O
"	O
packed	O
SIMD	B-Device
"	O
is	O
a	O
technique	O
for	O
performing	O
parallel	O
operations	O
on	O
data	O
contained	O
in	O
a	O
processor	B-General_Concept
register	I-General_Concept
.	O
</s>
<s>
SIMD	B-Device
stands	O
for	O
single	B-Device
instruction	I-Device
,	I-Device
multiple	I-Device
data	I-Device
.	O
</s>
<s>
Flynn	O
's	O
1972	O
taxonomy	O
categorises	O
SWAR	B-General_Concept
as	O
"	O
pipelined	O
processing	O
"	O
.	O
</s>
<s>
Many	O
modern	O
general-purpose	O
computer	O
processors	O
have	O
some	O
provisions	O
for	O
SIMD	B-Device
,	O
in	O
the	O
form	O
of	O
a	O
group	O
of	O
registers	O
and	O
instructions	O
to	O
make	O
use	O
of	O
them	O
.	O
</s>
<s>
SWAR	B-General_Concept
refers	O
to	O
the	O
use	O
of	O
those	O
registers	O
and	O
instructions	O
,	O
as	O
opposed	O
to	O
using	O
specialized	O
processing	O
engines	O
designed	O
to	O
be	O
better	O
at	O
SIMD	B-Device
operations	O
.	O
</s>
<s>
It	O
also	O
refers	O
to	O
the	O
use	O
of	O
SIMD	B-Device
with	O
general-purpose	O
registers	O
and	O
instructions	O
that	O
were	O
not	O
meant	O
to	O
do	O
it	O
at	O
the	O
time	O
,	O
by	O
way	O
of	O
various	O
novel	O
software	O
tricks	O
.	O
</s>
<s>
A	O
SWAR	B-General_Concept
architecture	O
is	O
one	O
that	O
includes	O
instructions	O
explicitly	O
intended	O
to	O
perform	O
parallel	O
operations	O
across	O
data	O
that	O
is	O
stored	O
in	O
the	O
independent	O
subwords	O
or	O
fields	O
of	O
a	O
register	O
.	O
</s>
<s>
A	O
SWAR-capable	O
architecture	O
is	O
one	O
that	O
includes	O
a	O
set	O
of	O
instructions	O
that	O
is	O
sufficient	O
to	O
allow	O
data	O
stored	O
in	O
these	O
fields	O
to	O
be	O
treated	O
independently	O
even	O
though	O
the	O
architecture	O
does	O
not	O
include	O
instructions	O
that	O
are	O
explicitly	O
intended	O
for	O
that	O
purpose	O
.	O
</s>
<s>
An	O
early	O
example	O
of	O
a	O
SWAR	B-General_Concept
architecture	O
was	O
the	O
Intel	B-General_Concept
Pentium	I-General_Concept
with	O
MMX	B-Architecture
,	O
which	O
implemented	O
the	O
MMX	B-Architecture
extension	I-Architecture
set	I-Architecture
.	O
</s>
<s>
The	O
Intel	B-General_Concept
Pentium	I-General_Concept
,	O
by	O
contrast	O
,	O
did	O
not	O
include	O
such	O
instructions	O
,	O
but	O
could	O
still	O
act	O
as	O
a	O
SWAR	B-General_Concept
architecture	O
through	O
careful	O
hand-coding	O
or	O
compiler	O
techniques	O
.	O
</s>
<s>
Early	O
SWAR	B-General_Concept
architectures	O
include	O
DEC	B-Device
Alpha	I-Device
,	O
Hewlett-Packard	O
'	O
s	O
PA-RISC	B-Device
MAX	B-General_Concept
,	O
Silicon	O
Graphics	O
Incorporated	O
's	O
MIPS	B-Device
MDMX	B-General_Concept
,	O
and	O
Sun	O
's	O
SPARC	B-Architecture
V9	I-Architecture
VIS	B-General_Concept
.	O
</s>
<s>
Like	O
MMX	B-Architecture
,	O
many	O
of	O
the	O
SWAR	B-General_Concept
instruction	O
sets	O
are	O
intended	O
for	O
faster	O
video	O
coding	O
.	O
</s>
<s>
This	O
can	O
be	O
seen	O
as	O
a	O
very	O
early	O
predecessor	O
to	O
SWAR	B-General_Concept
.	O
</s>
<s>
Leslie	O
Lamport	O
presented	O
SWAR	B-General_Concept
techniques	O
in	O
his	O
paper	O
titled	O
"	O
Multiple	O
byte	O
processing	O
with	O
full-word	O
instructions	O
"	O
in	O
1975	O
.	O
</s>
<s>
With	O
the	O
introduction	O
of	O
Intel	O
's	O
MMX	B-Architecture
multimedia	O
instruction	O
set	O
extensions	O
in	O
1996	O
,	O
desktop	O
processors	O
with	O
SIMD	B-Device
parallel	O
processing	O
capabilities	O
became	O
common	O
.	O
</s>
<s>
For	O
this	O
course	O
,	O
he	O
assigned	O
a	O
series	O
of	O
projects	O
in	O
which	O
the	O
students	O
would	O
build	O
a	O
simple	O
compiler	O
targeting	O
MMX	B-Architecture
.	O
</s>
<s>
The	O
input	O
language	O
was	O
a	O
subset	O
dialect	O
of	O
MasPar	B-Device
's	O
MPL	O
called	O
NEMPL	O
(	O
Not	O
Exactly	O
MPL	O
)	O
.	O
</s>
<s>
During	O
the	O
course	O
of	O
the	O
semester	O
,	O
it	O
became	O
clear	O
to	O
the	O
course	O
teaching	O
assistant	O
,	O
Randall	O
(	O
Randy	O
)	O
Fisher	O
,	O
that	O
there	O
were	O
a	O
number	O
of	O
issues	O
with	O
MMX	B-Architecture
that	O
would	O
make	O
it	O
difficult	O
to	O
build	O
the	O
back-end	O
of	O
the	O
NEMPL	O
compiler	O
.	O
</s>
<s>
For	O
example	O
,	O
MMX	B-Architecture
has	O
an	O
instruction	O
for	O
multiplying	O
16-bit	O
data	O
but	O
not	O
multiplying	O
8-bit	O
data	O
.	O
</s>
<s>
Intel	O
's	O
x86	B-Operating_System
architecture	I-Operating_System
was	O
not	O
the	O
only	O
architecture	O
to	O
include	O
SIMD-like	O
parallel	O
instructions	O
.	O
</s>
<s>
Sun	O
's	O
VIS	B-General_Concept
,	O
SGI	O
's	O
MDMX	B-General_Concept
,	O
and	O
other	O
multimedia	O
instruction	O
sets	O
had	O
been	O
added	O
to	O
other	O
manufacturers	O
 '	O
existing	O
instruction	O
set	O
architectures	O
to	O
support	O
so-called	O
new	O
media	O
applications	O
.	O
</s>
<s>
The	O
acronym	O
"	O
SWAR	B-General_Concept
"	O
was	O
coined	O
by	O
Dietz	O
and	O
Fisher	O
one	O
day	O
in	O
Hank	O
's	O
office	O
in	O
the	O
MSEE	O
building	O
at	O
Purdue	O
University	O
.	O
</s>
