<s>
In	O
computer	B-General_Concept
science	I-General_Concept
,	O
register	B-Application
transfer	I-Application
language	I-Application
(	O
RTL	O
)	O
is	O
a	O
kind	O
of	O
intermediate	B-Application
representation	I-Application
(	O
IR	B-Application
)	O
that	O
is	O
very	O
close	O
to	O
assembly	B-Language
language	I-Language
,	O
such	O
as	O
that	O
which	O
is	O
used	O
in	O
a	O
compiler	B-Language
.	O
</s>
<s>
It	O
is	O
used	O
to	O
describe	O
data	O
flow	O
at	O
the	O
register-transfer	O
level	O
of	O
an	O
architecture	B-General_Concept
.	O
</s>
<s>
Academic	O
papers	O
and	O
textbooks	O
often	O
use	O
a	O
form	O
of	O
RTL	O
as	O
an	O
architecture-neutral	O
assembly	B-Language
language	I-Language
.	O
</s>
<s>
RTL	O
is	O
used	O
as	O
the	O
name	O
of	O
a	O
specific	O
intermediate	B-Application
representation	I-Application
in	O
several	O
compilers	B-Language
,	O
including	O
the	O
GNU	B-Application
Compiler	I-Application
Collection	I-Application
(	O
GCC	B-Application
)	O
,	O
Zephyr	O
,	O
and	O
the	O
European	O
compiler	B-Language
projects	O
CerCo	O
and	O
CompCert	B-Application
.	O
</s>
<s>
In	O
GCC	B-Application
,	O
RTL	O
is	O
generated	O
from	O
the	O
GIMPLE	O
representation	O
,	O
transformed	O
by	O
various	O
passes	O
in	O
the	O
GCC	B-Application
middle-end	O
,	O
and	O
then	O
converted	O
to	O
assembly	B-Language
language	I-Language
.	O
</s>
<s>
GCC	B-Application
's	O
RTL	O
is	O
usually	O
written	O
in	O
a	O
form	O
which	O
looks	O
like	O
a	O
Lisp	B-Language
S-expression	B-Protocol
:	O
</s>
<s>
The	O
sequence	O
of	O
RTL	O
generated	O
has	O
some	O
dependency	O
on	O
the	O
characteristics	O
of	O
the	O
processor	O
for	O
which	O
GCC	B-Application
is	O
generating	O
code	O
.	O
</s>
<s>
A	O
register	B-Application
transfer	I-Application
language	I-Application
is	O
a	O
system	O
for	O
expressing	O
in	O
symbolic	O
form	O
the	O
microoperation	O
sequences	O
among	O
the	O
registers	O
of	O
a	O
digital	O
module	O
.	O
</s>
