<s>
SpiderMonkey	B-Language
is	O
the	O
first	O
JavaScript	B-Language
engine	I-Language
,	O
written	O
by	O
Brendan	O
Eich	O
at	O
Netscape	B-Protocol
Communications	O
,	O
later	O
released	O
as	O
open	B-Application
source	I-Application
and	O
currently	O
maintained	O
by	O
the	B-Operating_System
Mozilla	I-Operating_System
Foundation	I-Operating_System
.	O
</s>
<s>
It	O
is	O
used	O
in	O
the	O
Firefox	B-Application
web	I-Application
browser	I-Application
.	O
</s>
<s>
SpiderMonkey	B-Language
was	O
released	O
1995	O
.	O
</s>
<s>
It	O
implements	O
the	O
ECMA-262	B-Language
specification	O
(	O
ECMAScript	B-Language
)	O
and	O
is	O
written	O
in	O
C/C	O
++	O
.	O
</s>
<s>
TraceMonkey	O
was	O
the	O
first	O
JIT	O
compiler	O
for	O
JavaScript	O
,	O
but	O
it	O
became	O
obsolete	O
with	O
the	O
development	O
of	O
JägerMonkey	O
and	O
the	O
SpiderMonkey	B-Language
type	O
inference	O
engine	O
.	O
</s>
<s>
OdinMonkey	O
is	O
Mozilla	O
's	O
optimization	O
module	O
for	O
asm.js	B-Language
,	O
a	O
subset	O
of	O
JavaScript	O
.	O
</s>
<s>
SpiderMonkey	B-Language
is	O
intended	O
to	O
be	O
embedded	O
in	O
applications	O
that	O
provide	O
host	O
environments	O
for	O
JavaScript	O
.	O
</s>
<s>
having	O
been	O
"	O
recruited	O
to	O
Netscape	B-Protocol
with	O
the	O
promise	O
of	O
'	O
doing	O
Scheme	B-Language
 '	O
in	O
the	O
browser	B-Application
"	O
.	O
</s>
<s>
(	O
The	O
idea	O
of	O
using	O
Scheme	B-Language
was	O
abandoned	O
when	O
"	O
engineering	O
management	O
 [ decided ] 	O
that	O
the	O
language	O
must	O
'	O
look	O
like	O
Java	O
.	O
)	O
</s>
<s>
In	O
late	O
1996	O
,	O
Eich	O
,	O
needing	O
to	O
"	O
pay	O
off	O
 [ the ] 	O
substantial	O
technical	O
debt	O
"	O
left	O
from	O
the	O
first	O
year	O
,	O
"	O
stayed	O
home	O
for	O
two	O
weeks	O
to	O
rewrite	O
Mocha	O
as	O
the	O
codebase	O
that	O
became	O
known	O
as	O
SpiderMonkey	B-Language
"	O
.	O
</s>
<s>
In	O
2011	O
,	O
Eich	O
transferred	O
management	O
of	O
the	O
SpiderMonkey	B-Language
code	O
to	O
Dave	O
Mandelin	O
.	O
</s>
<s>
SpiderMonkey	B-Language
implements	O
the	O
ECMA-262	B-Language
specification	O
(	O
ECMAScript	B-Language
)	O
.	O
</s>
<s>
ECMA-357	B-Language
(	O
ECMAScript	B-Language
for	I-Language
XML	I-Language
(	O
E4X	B-Language
)	O
)	O
was	O
dropped	O
in	O
early	O
2013	O
.	O
</s>
<s>
SpiderMonkey	B-Language
is	O
written	O
in	O
C/C	O
++	O
and	O
contains	O
an	O
interpreter	B-Application
,	O
the	O
IonMonkey	O
JIT	O
compiler	O
,	O
and	O
a	O
garbage	B-General_Concept
collector	I-General_Concept
.	O
</s>
<s>
Initially	O
introduced	O
as	O
an	O
option	O
in	O
a	O
beta	O
release	O
and	O
introduced	O
in	O
Brendan	O
Eich	O
's	O
blog	O
on	O
August	O
23	O
,	O
2008	O
,	O
the	O
compiler	O
became	O
part	O
of	O
the	O
mainline	O
release	O
as	O
part	O
of	O
SpiderMonkey	B-Language
in	O
Firefox	B-Language
3.5	I-Language
,	O
providing	O
"	O
performance	O
improvements	O
ranging	O
between	O
20	O
and	O
40	O
times	O
faster	O
"	O
than	O
the	O
baseline	O
interpreter	B-Application
in	O
Firefox	B-Language
3	I-Language
.	O
</s>
<s>
Instead	O
of	O
compiling	O
whole	O
functions	O
,	O
TraceMonkey	O
was	O
a	O
tracing	B-Application
JIT	I-Application
,	O
which	O
operates	O
by	O
recording	O
control	O
flow	O
and	O
data	O
types	O
during	O
interpreter	B-Application
execution	O
.	O
</s>
<s>
This	O
data	O
then	O
informed	O
the	O
construction	O
of	O
trace	B-Application
trees	I-Application
,	O
highly	O
specialized	O
paths	O
of	O
native	B-Language
code	I-Language
.	O
</s>
<s>
Improvements	O
to	O
JägerMonkey	O
eventually	O
made	O
TraceMonkey	O
obsolete	O
,	O
especially	O
with	O
the	O
development	O
of	O
the	O
SpiderMonkey	B-Language
type	O
inference	O
engine	O
.	O
</s>
<s>
TraceMonkey	O
is	O
absent	O
from	O
SpiderMonkey	B-Language
from	O
Firefox	B-Application
11	O
onward	O
.	O
</s>
<s>
JägerMonkey	O
,	O
internally	O
named	O
MethodJIT	O
,	O
was	O
a	O
whole-method	O
JIT	O
compiler	O
designed	O
to	O
improve	O
performance	O
in	O
cases	O
where	O
TraceMonkey	O
could	O
not	O
generate	O
stable	O
native	B-Language
code	I-Language
.	O
</s>
<s>
It	O
was	O
first	O
released	O
in	O
Firefox	B-Application
4	I-Application
and	O
eventually	O
entirely	O
supplanted	O
TraceMonkey	O
.	O
</s>
<s>
JägerMonkey	O
operated	O
very	O
differently	O
from	O
other	O
compilers	O
in	O
its	O
class	O
:	O
while	O
typical	O
compilers	O
worked	O
by	O
constructing	O
and	O
optimizing	O
a	O
control-flow	O
graph	O
representing	O
the	O
function	O
,	O
JägerMonkey	O
instead	O
operated	O
by	O
iterating	O
linearly	O
forward	O
through	O
SpiderMonkey	B-Language
bytecode	O
,	O
the	O
internal	O
function	O
representation	O
.	O
</s>
<s>
A	O
more	O
in-depth	O
explanation	O
of	O
the	O
technical	O
details	O
was	O
provided	O
by	O
Chris	O
Leary	O
,	O
one	O
of	O
SpiderMonkey	B-Language
's	O
developers	O
,	O
.	O
</s>
<s>
IonMonkey	O
was	O
a	O
more	O
traditional	O
compiler	O
:	O
it	O
translated	O
SpiderMonkey	B-Language
bytecode	O
into	O
a	O
control-flow	O
graph	O
,	O
using	O
static	O
single	O
assignment	O
form	O
(	O
SSA	O
)	O
for	O
the	O
intermediate	B-Application
representation	I-Application
.	O
</s>
<s>
The	O
compiler	O
can	O
emit	O
fast	O
native	B-Language
code	I-Language
translations	O
of	O
JavaScript	O
functions	O
on	O
the	O
ARM	B-Architecture
,	O
x86	B-Operating_System
,	O
and	O
x86-64	B-Device
platforms	O
.	O
</s>
<s>
It	O
has	O
been	O
the	O
default	O
engine	O
since	O
Firefox	B-Application
18	O
.	O
</s>
<s>
OdinMonkey	O
is	O
the	O
name	O
of	O
Mozilla	O
's	O
new	O
optimization	O
module	O
for	O
asm.js	B-Language
,	O
an	O
easily	O
compilable	O
subset	O
of	O
JavaScript	O
.	O
</s>
<s>
It	O
's	O
included	O
with	O
Firefox	B-Application
from	O
release	O
22	O
.	O
</s>
<s>
It	O
translates	O
the	O
bytecode	O
and	O
Inline	O
Cache	O
data	O
into	O
a	O
Mid-level	O
Intermediate	B-Application
Representation	I-Application
(	O
Ion	O
MIR	O
)	O
representation	O
.	O
</s>
<s>
This	O
graph	O
is	O
transformed	O
and	O
optimized	O
before	O
being	O
lowered	O
to	O
a	O
Low-level	O
Intermediate	B-Application
Representation	I-Application
(	O
Ion	O
LIR	O
)	O
.	O
</s>
<s>
This	O
LIR	O
performs	O
register	O
allocation	O
and	O
then	O
generates	O
native	O
machine	B-Language
code	I-Language
in	O
a	O
process	O
called	O
Code	O
Generation	O
.	O
</s>
<s>
The	O
bailout	O
mechanism	O
reconstructs	O
the	O
native	O
machine	O
stack	O
frame	O
to	O
match	O
the	O
layout	O
used	O
by	O
the	O
Baseline	O
Interpreter	B-Application
and	O
then	O
branches	O
to	O
that	O
interpreter	B-Application
as	O
though	O
we	O
were	O
running	O
it	O
all	O
along	O
.	O
</s>
<s>
SpiderMonkey	B-Language
is	O
intended	O
to	O
be	O
embedded	O
in	O
other	O
applications	O
that	O
provide	O
host	O
environments	O
for	O
JavaScript	O
.	O
</s>
<s>
Forks	B-Application
of	O
Firefox	B-Application
including	O
the	O
Pale	B-Protocol
Moon	I-Protocol
,	O
Basilisk	O
and	O
Waterfox	B-Language
web	B-Application
browsers	I-Application
.	O
</s>
<s>
CouchDB	B-Application
database	O
system	O
(	O
written	O
in	O
Erlang	B-Operating_System
)	O
.	O
</s>
<s>
Adobe	B-Application
Acrobat	I-Application
and	O
Adobe	B-Application
Reader	I-Application
,	O
Adobe	B-Operating_System
Flash	I-Operating_System
Professional	I-Operating_System
,	O
and	O
Adobe	B-Language
Dreamweaver	I-Language
.	O
</s>
<s>
Adobe	B-Application
Acrobat	I-Application
DC	I-Application
uses	O
Spidermonkey	B-Language
24.2	O
with	O
ECMA-357	B-Language
support	O
forward	O
ported	O
.	O
</s>
<s>
SpiderMonkey	B-Language
is	O
also	O
used	O
in	O
many	O
other	O
open-source	B-Application
projects	O
;	O
an	O
external	O
list	O
is	O
maintained	O
at	O
Mozilla	O
's	O
developer	O
site	O
.	O
</s>
<s>
SpiderMonkey	B-Language
includes	O
a	O
JavaScript	O
Shell	O
for	O
interactive	O
JavaScript	O
development	O
and	O
for	O
command-line	O
invocation	O
of	O
JavaScript	O
program	O
files	O
.	O
</s>
