<s>
A	O
multi-pass	B-Application
compiler	I-Application
is	O
a	O
type	O
of	O
compiler	B-Language
that	O
processes	O
the	O
source	O
code	O
or	O
abstract	B-Data_Structure
syntax	I-Data_Structure
tree	I-Data_Structure
of	O
a	O
program	O
several	O
times	O
.	O
</s>
<s>
This	O
is	O
in	O
contrast	O
to	O
a	O
one-pass	B-Language
compiler	I-Language
,	O
which	O
traverses	O
the	O
program	O
only	O
once	O
.	O
</s>
<s>
Multi-pass	B-Application
compilers	I-Application
are	O
sometimes	O
called	O
wide	O
compilers	B-Language
,	O
referring	O
to	O
the	O
greater	O
scope	O
of	O
the	O
passes	O
:	O
they	O
can	O
"	O
see	O
"	O
the	O
entire	O
program	O
being	O
compiled	B-Language
,	O
instead	O
of	O
just	O
a	O
small	O
portion	O
of	O
it	O
.	O
</s>
<s>
The	O
wider	O
scope	O
thus	O
available	O
to	O
these	O
compilers	B-Language
allows	O
better	O
code	B-Application
generation	I-Application
(	O
e.g.	O
</s>
<s>
smaller	O
code	O
size	O
,	O
faster	O
code	O
)	O
compared	O
to	O
the	O
output	O
of	O
one-pass	B-Language
compilers	I-Language
,	O
at	O
the	O
cost	O
of	O
higher	O
compiler	B-Language
time	O
and	O
memory	O
consumption	O
.	O
</s>
<s>
In	O
addition	O
,	O
some	O
languages	O
cannot	O
be	O
compiled	B-Language
in	O
a	O
single	O
pass	O
,	O
as	O
a	O
result	O
of	O
their	O
design	O
.	O
</s>
<s>
This	O
stage	O
of	O
a	O
multi-pass	B-Application
compiler	I-Application
is	O
to	O
remove	O
irrelevant	O
information	O
from	O
the	O
source	O
program	O
that	O
syntax	O
analysis	O
will	O
not	O
be	O
able	O
to	O
use	O
or	O
interpret	O
.	O
</s>
<s>
This	O
step	O
means	O
that	O
forward	O
declaration	O
is	O
generally	O
not	O
necessary	O
if	O
a	O
multi-pass	B-Application
compiler	I-Application
is	O
used	O
.	O
</s>
<s>
An	O
example	O
of	O
this	O
intermediate	O
representation	O
could	O
be	O
something	O
like	O
an	O
abstract	B-Data_Structure
syntax	I-Data_Structure
tree	I-Data_Structure
or	O
a	O
directed	O
acyclic	O
graph	O
.	O
</s>
<s>
In	O
addition	O
to	O
performing	O
semantic	O
analysis	O
at	O
this	O
stage	O
of	O
compilation	B-Language
,	O
often	O
symbol	B-Application
tables	I-Application
are	O
created	O
in	O
order	O
to	O
assist	O
in	O
code	B-Application
generation	I-Application
.	O
</s>
<s>
This	B-Application
final	I-Application
stage	I-Application
of	O
a	O
typical	O
compiler	B-Language
converts	O
the	O
intermediate	O
representation	O
of	O
program	O
into	O
an	O
executable	O
set	O
of	O
instructions	O
(	O
often	O
assembly	B-Language
)	O
.	O
</s>
<s>
This	O
last	O
stage	O
is	O
the	O
only	O
stage	O
in	O
compilation	B-Language
that	O
is	O
machine	O
dependent	O
.	O
</s>
<s>
There	O
can	O
also	O
be	O
optimization	O
done	O
at	O
this	O
stage	O
of	O
compilation	B-Language
that	O
make	O
the	O
program	O
more	O
efficient	O
.	O
</s>
<s>
Other	O
passes	O
of	O
compiler	B-Language
include	O
intermediate	B-Application
code	I-Application
generation	I-Application
phase	O
which	O
takes	O
place	O
before	O
code	B-Application
generation	I-Application
and	O
code	O
optimization	O
phase	O
which	O
can	O
take	O
place	O
when	O
the	O
source	O
program	O
is	O
written	O
,	O
or	O
after	O
intermediate	B-Application
code	I-Application
generation	I-Application
phase	O
,	O
or	O
after	O
code	B-Application
generation	I-Application
phase	O
.	O
</s>
<s>
Machine	O
Independent	O
:	O
Since	O
the	O
multiple	O
passes	O
include	O
a	O
modular	O
structure	O
,	O
and	O
the	O
code	B-Application
generation	I-Application
decoupled	O
from	O
the	O
other	O
steps	O
of	O
the	O
compiler	B-Language
,	O
the	O
passes	O
can	O
be	O
reused	O
for	O
different	O
hardware/machines	O
.	O
</s>
<s>
The	O
prime	O
examples	O
of	O
languages	O
requiring	O
forward	O
declarations	O
due	O
to	O
the	O
requirement	O
of	O
being	O
compilable	O
in	O
a	O
single	O
pass	O
include	O
C	B-Language
and	O
Pascal	B-Application
,	O
whereas	O
Java	B-Language
does	O
not	O
have	O
forward	O
declarations	O
.	O
</s>
