<s>
Open64	B-Application
is	O
a	O
free	B-Application
,	O
open-source	B-Application
,	O
optimizing	O
compiler	B-Language
for	O
the	O
Itanium	B-General_Concept
and	O
x86-64	B-Device
microprocessor	B-Architecture
architectures	O
.	O
</s>
<s>
It	O
derives	O
from	O
the	O
SGI	O
compilers	B-Language
for	O
the	O
MIPS	B-Device
R10000	B-General_Concept
processor	O
,	O
called	O
MIPSPro	B-Application
.	O
</s>
<s>
It	O
was	O
initially	O
released	O
in	O
2000	O
as	O
GNU	B-License
GPL	I-License
software	O
under	O
the	O
name	O
Pro64	O
.	O
</s>
<s>
The	O
following	O
year	O
,	O
University	O
of	O
Delaware	O
adopted	O
the	O
project	O
and	O
renamed	O
the	O
compiler	B-Language
to	O
Open64	B-Application
.	O
</s>
<s>
It	O
now	O
mostly	O
serves	O
as	O
a	O
research	O
platform	O
for	O
compiler	B-Language
and	O
computer	B-General_Concept
architecture	I-General_Concept
research	O
groups	O
.	O
</s>
<s>
Open64	B-Application
supports	O
Fortran	B-Application
77/95	O
and	O
C/C	O
++	O
,	O
as	O
well	O
as	O
the	O
shared	B-Operating_System
memory	I-Operating_System
programming	I-Operating_System
model	O
OpenMP	B-Application
.	O
</s>
<s>
Its	O
major	O
components	O
are	O
the	O
frontend	B-General_Concept
for	O
C/C	O
++	O
(	O
using	O
GCC	B-Application
)	O
and	O
Fortran	B-Application
77/90	O
(	O
using	O
the	O
CraySoft	O
front-end	O
and	O
libraries	O
)	O
,	O
Interprocedural	O
analysis	O
(	O
IPA	O
)	O
,	O
loop	O
nest	O
optimizer	O
(	O
LNO	O
)	O
,	O
global	O
optimizer	O
(	O
WOPT	O
)	O
,	O
and	O
code	B-Application
generator	I-Application
(	O
CG	O
)	O
.	O
</s>
<s>
Despite	O
being	O
initially	O
written	O
for	O
a	O
single	O
computer	B-General_Concept
architecture	I-General_Concept
,	O
Open64	B-Application
has	O
proven	O
that	O
it	O
can	O
generate	O
efficient	O
code	O
for	O
CISC	B-Architecture
,	O
RISC	B-Architecture
,	O
and	O
VLIW	B-General_Concept
architectures	O
,	O
including	O
MIPS	B-Device
,	O
x86	B-Operating_System
,	O
IA-64	B-General_Concept
,	O
ARM	B-Architecture
,	O
and	O
others	O
.	O
</s>
<s>
A	O
hierarchical	O
intermediate	B-Application
representation	I-Application
(	O
IR	B-Application
)	O
with	O
five	O
main	O
levels	O
is	O
used	O
in	O
this	O
compiler	B-Language
to	O
serve	O
as	O
the	O
common	O
interface	O
among	O
all	O
the	O
frontend	B-General_Concept
and	O
backend	O
components	O
.	O
</s>
<s>
This	O
IR	B-Application
is	O
named	O
WHIRL	O
.	O
</s>
<s>
The	O
original	O
version	O
of	O
Open64	B-Application
that	O
was	O
released	O
in	O
2002	O
was	O
missing	O
its	O
very	O
advanced	O
software	O
pipelining	O
code	B-Application
generator	I-Application
,	O
and	O
had	O
only	O
a	O
rudimentary	O
code	B-Application
generator	I-Application
for	O
Itanium	B-General_Concept
.	O
</s>
<s>
The	O
entire	O
original	O
MIPSPro	B-Application
compiler	B-Language
,	O
with	O
this	O
code	B-Application
generator	I-Application
,	O
is	O
available	O
under	O
a	O
commercial	O
license	O
as	O
the	O
Blackbird	O
compiler	B-Language
from	O
Reservoir	O
Labs	O
.	O
</s>
<s>
The	O
documents	O
the	O
code	B-Application
generator	I-Application
that	O
was	O
not	O
included	O
in	O
Open64	B-Application
.	O
</s>
<s>
The	O
very	O
advanced	O
compiler	B-Language
from	O
Tilera	O
,	O
for	O
its	O
64-core	O
TILE64	O
chip	O
,	O
is	O
based	O
on	O
Blackbird	O
.	O
</s>
<s>
Open64	B-Application
exists	O
in	O
many	O
forks	B-Application
,	O
each	O
of	O
which	O
has	O
different	O
features	O
and	O
limitations	O
.	O
</s>
<s>
The	O
"	O
classic	O
"	O
Open64	B-Application
branch	O
is	O
the	O
Open	O
Research	O
Compiler	B-Language
(	O
ORC	O
)	O
,	O
which	O
produces	O
code	O
only	O
for	O
the	O
Itanium	B-General_Concept
(	O
IA-64	B-General_Concept
)	O
,	O
and	O
was	O
funded	O
by	O
Intel	O
.	O
</s>
<s>
The	O
ORC	O
effort	O
ended	O
in	O
2003	O
,	O
and	O
the	O
current	O
official	O
branch	O
(	O
which	O
originated	O
from	O
the	O
Intel	O
ORC	O
project	O
)	O
is	O
managed	O
by	O
Hewlett	O
Packard	O
and	O
the	O
University	O
of	O
Delaware	O
's	O
Computer	B-General_Concept
Architecture	I-General_Concept
and	O
Parallel	O
Systems	O
Laboratory	O
(	O
CAPSL	O
)	O
.	O
</s>
<s>
Other	O
important	O
branches	O
include	O
the	O
compilers	B-Language
from	O
Tensilica	B-General_Concept
and	O
the	O
AMD	O
x86	B-Operating_System
Open64	B-Application
Compiler	B-Language
Suite	O
.	O
</s>
<s>
Nvidia	O
is	O
also	O
using	O
an	O
Open64	B-Application
fork	B-Application
to	O
optimize	O
code	O
in	O
its	O
CUDA	B-Architecture
toolchain	O
.	O
</s>
<s>
Open64	B-Application
is	O
used	O
as	O
the	O
backend	O
for	O
the	O
HPE	B-Architecture
NonStop	I-Architecture
OS	I-Architecture
compilers	B-Language
on	O
the	O
x86-64	B-Device
platform	O
.	O
</s>
<s>
Open64	B-Application
is	O
also	O
used	O
in	O
a	O
number	O
of	O
research	O
projects	O
,	O
such	O
as	O
the	O
Unified	B-Operating_System
Parallel	I-Operating_System
C	I-Operating_System
(	O
UPC	O
)	O
and	O
speculative	B-Operating_System
multithreading	I-Operating_System
work	O
at	O
various	O
universities	O
.	O
</s>
<s>
The	O
2010	O
Open64	B-Application
Developers	O
Forum	O
describes	O
projects	O
done	O
at	O
Absoft	B-Application
,	O
AMD	O
,	O
Chinese	O
Academy	O
of	O
Sciences	O
,	O
Fudan	O
University	O
,	O
HP	O
,	O
National	O
Tsing	O
Hua	O
University	O
,	O
Nvidia	O
,	O
Tensilica	B-General_Concept
,	O
Tsinghua	O
University	O
,	O
and	O
University	O
of	O
Houston	O
.	O
</s>
<s>
The	O
Chinese	O
Academy	O
of	O
Sciences	O
ported	O
Open64	B-Application
to	O
the	O
Loongson	B-Language
II	O
platform	O
.	O
</s>
<s>
AMD	O
has	O
extended	O
and	O
productized	O
Open64	B-Application
with	O
optimizations	O
designed	O
for	O
x86	B-Operating_System
multi-core	O
processor	O
advancements	O
and	O
multi-threaded	O
code	O
development	O
.	O
</s>
<s>
AMD	O
supports	O
Open64	B-Application
as	O
a	O
complementary	O
compiler	B-Language
to	O
GCC	B-Application
.	O
</s>
<s>
The	O
University	O
of	O
Houston	O
's	O
OpenUH	O
project	O
,	O
which	O
is	O
based	O
on	O
Open64	B-Application
,	O
released	O
a	O
new	O
version	O
of	O
its	O
compiler	B-Language
suite	O
in	O
November	O
2015	O
.	O
</s>
