<s>
LLVM	B-Application
is	O
a	O
set	O
of	O
compiler	B-Language
and	O
toolchain	B-General_Concept
technologies	O
that	O
can	O
be	O
used	O
to	O
develop	O
a	O
frontend	O
for	O
any	O
programming	O
language	O
and	O
a	O
backend	O
for	O
any	O
instruction	B-General_Concept
set	I-General_Concept
architecture	I-General_Concept
.	O
</s>
<s>
LLVM	B-Application
is	O
designed	O
around	O
a	O
language-independent	B-Language
intermediate	B-Application
representation	I-Application
(	O
IR	B-Application
)	O
that	O
serves	O
as	O
a	O
portable	B-Architecture
,	O
high-level	O
assembly	B-Language
language	I-Language
that	O
can	O
be	O
optimized	B-Application
with	O
a	O
variety	O
of	O
transformations	O
over	O
multiple	O
passes	O
.	O
</s>
<s>
The	O
name	O
LLVM	B-Application
originally	O
stood	O
for	O
Low	B-Application
Level	I-Application
Virtual	I-Application
Machine	I-Application
,	O
though	O
the	O
project	O
has	O
expanded	O
and	O
the	O
name	O
is	O
no	O
longer	O
officially	O
an	O
acronym	O
.	O
</s>
<s>
LLVM	B-Application
is	O
written	O
in	O
C++	B-Language
and	O
is	O
designed	O
for	O
compile-time	B-Application
,	O
link-time	B-Application
,	O
run-time	B-Library
,	O
and	O
"	O
idle-time	O
"	O
optimization	O
.	O
</s>
<s>
Originally	O
implemented	O
for	O
C	B-Language
and	O
C++	B-Language
,	O
the	O
language-agnostic	O
design	O
of	O
LLVM	B-Application
has	O
since	O
spawned	O
a	O
wide	O
variety	O
of	O
frontends	O
:	O
languages	O
with	O
compilers	B-Language
that	O
use	O
LLVM	B-Application
(	O
or	O
which	O
do	O
not	O
directly	O
use	O
LLVM	B-Application
but	O
can	O
generate	O
compiled	B-Language
programs	O
as	O
LLVM	B-Application
IR	B-Application
)	O
include	O
ActionScript	B-Operating_System
,	O
Ada	B-Language
,	O
C#	B-Application
,	O
Common	B-Language
Lisp	I-Language
,	O
PicoLisp	B-Language
,	O
Crystal	B-Application
,	O
CUDA	B-Architecture
,	O
D	B-Application
,	O
Delphi	B-Language
,	O
Dylan	B-Language
,	O
Forth	B-Application
,	O
Fortran	B-Language
,	O
FreeBASIC	B-Language
,	O
Free	B-Operating_System
Pascal	I-Operating_System
,	O
Graphical	B-Application
G	I-Application
,	O
Halide	B-Operating_System
,	O
Haskell	B-Language
,	O
Java	B-Language
bytecode	I-Language
,	O
Julia	B-Application
,	O
Kotlin	B-Language
,	O
Lua	B-Language
,	O
Objective-C	B-Language
,	O
OpenCL	B-Application
,	O
PostgreSQL	B-Application
's	O
SQL	O
and	O
PLpgSQL	O
,	O
Ruby	B-Language
,	O
Rust	B-Application
,	O
Scala	B-Application
,	O
Swift	B-Application
,	O
XC	O
,	O
Xojo	B-Application
,	O
and	O
Zig	B-Application
.	O
</s>
<s>
The	O
LLVM	B-Application
project	O
started	O
in	O
2000	O
at	O
the	O
University	O
of	O
Illinois	O
at	O
Urbana	O
–	O
Champaign	O
,	O
under	O
the	O
direction	O
of	O
Vikram	O
Adve	O
and	O
Chris	O
Lattner	O
.	O
</s>
<s>
LLVM	B-Application
was	O
originally	O
developed	O
as	O
a	O
research	O
infrastructure	O
to	O
investigate	O
dynamic	B-Application
compilation	I-Application
techniques	O
for	O
static	O
and	O
dynamic	B-Language
programming	I-Language
languages	I-Language
.	O
</s>
<s>
LLVM	B-Application
was	O
released	O
under	O
the	O
University	B-License
of	I-License
Illinois/NCSA	I-License
Open	I-License
Source	I-License
License	I-License
,	O
a	O
permissive	B-License
free	I-License
software	I-License
licence	I-License
.	O
</s>
<s>
In	O
2005	O
,	O
Apple	O
Inc	O
.	O
hired	O
Lattner	O
and	O
formed	O
a	O
team	O
to	O
work	O
on	O
the	O
LLVM	B-Application
system	O
for	O
various	O
uses	O
within	O
Apple	O
's	O
development	O
systems	O
.	O
</s>
<s>
LLVM	B-Application
has	O
been	O
an	O
integral	O
part	O
of	O
Apple	O
's	O
Xcode	B-Operating_System
development	O
tools	O
for	O
macOS	B-Application
and	O
iOS	B-Application
since	O
Xcode	B-Operating_System
4	O
.	O
</s>
<s>
In	O
2006	O
,	O
Lattner	O
started	O
working	O
on	O
a	O
new	O
project	O
called	O
Clang	B-Application
.	O
</s>
<s>
The	O
combination	O
of	O
Clang	B-Application
frontend	O
and	O
LLVM	B-Application
backend	O
is	O
called	O
Clang/LLVM	O
or	O
simply	O
Clang	B-Application
.	O
</s>
<s>
The	O
name	O
LLVM	B-Application
was	O
originally	O
an	O
initialism	O
for	O
Low	B-Application
Level	I-Application
Virtual	I-Application
Machine	I-Application
.	O
</s>
<s>
However	O
,	O
the	O
LLVM	B-Application
project	O
evolved	O
into	O
an	O
umbrella	O
project	O
that	O
has	O
little	O
relationship	O
to	O
what	O
most	O
current	O
developers	O
think	O
of	O
as	O
a	O
virtual	B-Architecture
machine	I-Architecture
.	O
</s>
<s>
This	O
made	O
the	O
initialism	O
"	O
confusing	O
"	O
and	O
"	O
inappropriate	O
"	O
,	O
and	O
since	O
2011	O
LLVM	B-Application
is	O
"	O
officially	O
no	O
longer	O
an	O
acronym	O
"	O
,	O
but	O
a	O
brand	O
that	O
applies	O
to	O
the	O
LLVM	B-Application
umbrella	O
project	O
.	O
</s>
<s>
The	O
project	O
encompasses	O
the	O
LLVM	B-Application
intermediate	B-Application
representation	I-Application
(	O
IR	B-Application
)	O
,	O
the	O
LLVM	B-Application
debugger	B-Application
,	O
the	O
LLVM	B-Application
implementation	O
of	O
the	O
C++	B-Language
Standard	I-Language
Library	I-Language
(	O
with	O
full	O
support	O
of	O
C++11	B-Language
and	O
C++14	B-Language
)	O
,	O
etc	O
.	O
</s>
<s>
LLVM	B-Application
is	O
administered	O
by	O
the	O
LLVM	B-Application
Foundation	O
.	O
</s>
<s>
Compiler	B-Language
engineer	O
Tanya	O
Lattner	O
became	O
its	O
president	O
in	O
2014	O
and	O
was	O
in	O
post	O
.	O
</s>
<s>
"	O
For	O
designing	O
and	O
implementing	O
LLVM	B-Application
"	O
,	O
the	O
Association	O
for	O
Computing	O
Machinery	O
presented	O
Vikram	O
Adve	O
,	O
Chris	O
Lattner	O
,	O
and	O
Evan	O
Cheng	O
with	O
the	O
2012	O
ACM	O
Software	O
System	O
Award	O
.	O
</s>
<s>
The	O
project	O
was	O
originally	O
available	O
under	O
the	O
UIUC	B-License
license	I-License
.	O
</s>
<s>
After	O
v9.0.0	O
released	O
in	O
2019	O
,	O
LLVM	B-Application
relicensed	O
to	O
the	O
Apache	B-Application
License	I-Application
2.0	I-Application
with	O
LLVM	B-Application
Exceptions	O
.	O
</s>
<s>
LLVM	B-Application
can	O
provide	O
the	O
middle	O
layers	O
of	O
a	O
complete	O
compiler	B-Language
system	O
,	O
taking	O
intermediate	B-Application
representation	I-Application
(	O
IR	B-Application
)	O
code	O
from	O
a	O
compiler	B-Language
and	O
emitting	O
an	O
optimized	B-Application
IR	B-Application
.	O
</s>
<s>
This	O
new	O
IR	B-Application
can	O
then	O
be	O
converted	O
and	O
linked	O
into	O
machine-dependent	O
assembly	B-Language
language	I-Language
code	O
for	O
a	O
target	O
platform	O
.	O
</s>
<s>
LLVM	B-Application
can	O
accept	O
the	O
IR	B-Application
from	O
the	O
GNU	B-Application
Compiler	I-Application
Collection	I-Application
(	O
GCC	B-Application
)	O
toolchain	B-General_Concept
,	O
allowing	O
it	O
to	O
be	O
used	O
with	O
a	O
wide	O
array	O
of	O
existing	O
compiler	B-Language
front-ends	O
written	O
for	O
that	O
project	O
.	O
</s>
<s>
LLVM	B-Application
can	O
also	O
generate	O
relocatable	B-Library
machine	I-Library
code	I-Library
at	O
compile-time	B-Application
or	O
link-time	B-Application
or	O
even	O
binary	O
machine	O
code	O
at	O
run-time	B-Library
.	O
</s>
<s>
LLVM	B-Application
supports	O
a	O
language-independent	B-Language
instruction	B-General_Concept
set	I-General_Concept
and	O
type	O
system	O
.	O
</s>
<s>
LLVM	B-Application
allows	O
code	O
to	O
be	O
compiled	B-Language
statically	O
,	O
as	O
it	O
is	O
under	O
the	O
traditional	O
GCC	B-Application
system	O
,	O
or	O
left	O
for	O
late-compiling	O
from	O
the	O
IR	B-Application
to	O
machine	O
code	O
via	O
just-in-time	O
compilation	B-Language
(	O
JIT	O
)	O
,	O
similar	O
to	O
Java	B-Language
.	O
</s>
<s>
The	O
type	O
system	O
consists	O
of	O
basic	O
types	O
such	O
as	O
integer	O
or	O
floating-point	B-Algorithm
numbers	I-Algorithm
and	O
five	O
derived	O
types	O
:	O
pointers	O
,	O
arrays	B-Data_Structure
,	O
vectors	O
,	O
structures	O
,	O
and	O
functions	O
.	O
</s>
<s>
A	O
type	O
construct	O
in	O
a	O
concrete	O
language	O
can	O
be	O
represented	O
by	O
combining	O
these	O
basic	O
types	O
in	O
LLVM	B-Application
.	O
</s>
<s>
For	O
example	O
,	O
a	O
class	O
in	O
C++	B-Language
can	O
be	O
represented	O
by	O
a	O
mix	O
of	O
structures	O
,	O
functions	O
and	O
arrays	B-Data_Structure
of	O
function	B-Language
pointers	I-Language
.	O
</s>
<s>
The	O
LLVM	B-Application
JIT	O
compiler	B-Language
can	O
optimize	O
unneeded	O
static	O
branches	O
out	O
of	O
a	O
program	O
at	B-Library
runtime	I-Library
,	O
and	O
thus	O
is	O
useful	O
for	O
partial	O
evaluation	O
in	O
cases	O
where	O
a	O
program	O
has	O
many	O
options	O
,	O
most	O
of	O
which	O
can	O
easily	O
be	O
determined	O
unneeded	O
in	O
a	O
specific	O
environment	O
.	O
</s>
<s>
This	O
feature	O
is	O
used	O
in	O
the	O
OpenGL	B-Application
pipeline	O
of	O
Mac	B-Application
OS	I-Application
X	I-Application
Leopard	I-Application
(	O
v10.5	O
)	O
to	O
provide	O
support	O
for	O
missing	O
hardware	O
features	O
.	O
</s>
<s>
Graphics	O
code	O
within	O
the	O
OpenGL	B-Application
stack	O
can	O
be	O
left	O
in	O
intermediate	B-Application
representation	I-Application
and	O
then	O
compiled	B-Language
when	O
run	O
on	O
the	O
target	O
machine	O
.	O
</s>
<s>
On	O
systems	O
with	O
high-end	O
graphics	B-Architecture
processing	I-Architecture
units	I-Architecture
(	O
GPUs	B-Architecture
)	O
,	O
the	O
resulting	O
code	O
remains	O
quite	O
thin	O
,	O
passing	O
the	O
instructions	O
on	O
to	O
the	O
GPU	B-Architecture
with	O
minimal	O
changes	O
.	O
</s>
<s>
On	O
systems	O
with	O
low-end	O
GPUs	B-Architecture
,	O
LLVM	B-Application
will	O
compile	B-Language
optional	O
procedures	O
that	O
run	O
on	O
the	O
local	O
central	B-General_Concept
processing	I-General_Concept
unit	I-General_Concept
(	O
CPU	O
)	O
that	O
emulate	O
instructions	O
that	O
the	O
GPU	B-Architecture
cannot	O
run	O
internally	O
.	O
</s>
<s>
LLVM	B-Application
improved	O
performance	O
on	O
low-end	O
machines	O
using	O
Intel	B-Device
GMA	I-Device
chipsets	O
.	O
</s>
<s>
A	O
similar	O
system	O
was	O
developed	O
under	O
the	O
Gallium3D	O
LLVMpipe	O
,	O
and	O
incorporated	O
into	O
the	O
GNOME	B-Application
shell	O
to	O
allow	O
it	O
to	O
run	O
without	O
a	O
proper	O
3D	O
hardware	O
driver	O
loaded	O
.	O
</s>
<s>
For	O
run-time	B-Library
performance	O
of	O
the	O
compiled	B-Language
programs	O
,	O
GCC	B-Application
formerly	O
outperformed	O
LLVM	B-Application
by	O
10%	O
on	O
average	O
in	O
2011	O
.	O
</s>
<s>
Newer	O
results	O
in	O
2013	O
indicate	O
that	O
LLVM	B-Application
has	O
now	O
caught	O
up	O
with	O
GCC	B-Application
in	O
this	O
area	O
,	O
and	O
is	O
now	O
compiling	B-Language
binaries	O
of	O
approximately	O
equal	O
performance	O
.	O
</s>
<s>
LLVM	B-Application
has	O
become	O
an	O
umbrella	O
project	O
containing	O
multiple	O
components	O
.	O
</s>
<s>
LLVM	B-Application
was	O
originally	O
written	O
to	O
be	O
a	O
replacement	O
for	O
the	O
existing	O
code	B-Application
generator	I-Application
in	O
the	O
GCC	B-Application
stack	O
,	O
and	O
many	O
of	O
the	O
GCC	B-Application
frontends	O
have	O
been	O
modified	O
to	O
work	O
with	O
it	O
,	O
resulting	O
in	O
the	O
now-defunct	O
LLVM-GCC	O
suite	O
.	O
</s>
<s>
The	O
modifications	O
generally	O
involve	O
a	O
GIMPLE-to-LLVM	O
IR	B-Application
step	O
so	O
that	O
LLVM	B-Application
optimizers	O
and	O
codegen	O
can	O
be	O
used	O
instead	O
of	O
GCC	B-Application
's	O
GIMPLE	O
system	O
.	O
</s>
<s>
Apple	O
was	O
a	O
significant	O
user	O
of	O
LLVM-GCC	O
through	O
Xcode	B-Operating_System
4.x	O
(	O
2013	O
)	O
.	O
</s>
<s>
This	O
use	O
of	O
the	O
GCC	B-Application
frontend	O
was	O
considered	O
mostly	O
a	O
temporary	O
measure	O
,	O
but	O
with	O
the	O
advent	O
of	O
Clang	B-Application
and	O
advantages	O
of	O
LLVM	B-Application
and	O
Clang	B-Application
's	O
modern	O
and	O
modular	O
codebase	O
(	O
as	O
well	O
as	O
compilation	B-Language
speed	O
)	O
,	O
is	O
mostly	O
obsolete	O
.	O
</s>
<s>
LLVM	B-Application
currently	O
supports	O
compiling	B-Language
of	O
Ada	B-Language
,	O
C	B-Language
,	O
C++	B-Language
,	O
D	B-Application
,	O
Delphi	B-Language
,	O
Fortran	B-Language
,	O
Haskell	B-Language
,	O
Julia	B-Application
,	O
Objective-C	B-Language
,	O
Rust	B-Application
,	O
and	O
Swift	B-Application
using	O
various	O
frontends	O
.	O
</s>
<s>
Widespread	O
interest	O
in	O
LLVM	B-Application
has	O
led	O
to	O
several	O
efforts	O
to	O
develop	O
new	O
frontends	O
for	O
a	O
variety	O
of	O
languages	O
.	O
</s>
<s>
The	O
one	O
that	O
has	O
received	O
the	O
most	O
attention	O
is	O
Clang	B-Application
,	O
a	O
new	O
compiler	B-Language
supporting	O
C	B-Language
,	O
C++	B-Language
,	O
and	O
Objective-C	B-Language
.	O
</s>
<s>
Primarily	O
supported	O
by	O
Apple	O
,	O
Clang	B-Application
is	O
aimed	O
at	O
replacing	O
the	O
C/Objective	O
-C	O
compiler	B-Language
in	O
the	O
GCC	B-Application
system	O
with	O
a	O
system	O
that	O
is	O
more	O
easily	O
integrated	O
with	O
integrated	B-Application
development	I-Application
environments	I-Application
(	O
IDEs	O
)	O
and	O
has	O
wider	O
support	O
for	O
multithreading	B-Operating_System
.	O
</s>
<s>
Support	O
for	O
OpenMP	B-Application
directives	O
has	O
been	O
included	O
in	O
Clang	B-Application
since	O
release	O
3.8	O
.	O
</s>
<s>
The	O
Utrecht	O
Haskell	B-Language
compiler	B-Language
can	O
generate	O
code	O
for	O
LLVM	B-Application
.	O
</s>
<s>
Though	O
the	O
generator	O
is	O
in	O
the	O
early	O
stages	O
of	O
development	O
,	O
in	O
many	O
cases	O
it	O
has	O
been	O
more	O
efficient	O
than	O
the	O
C	B-Language
code	B-Application
generator	I-Application
.	O
</s>
<s>
There	O
is	O
a	O
Glasgow	B-Application
Haskell	I-Application
Compiler	I-Application
(	O
GHC	O
)	O
backend	O
using	O
LLVM	B-Application
that	O
achieves	O
a	O
30%	O
speed-up	O
of	O
the	O
compiled	B-Language
code	O
relative	O
to	O
native	O
code	B-Language
compiling	I-Language
via	O
GHC	O
or	O
C	B-Language
code	B-Application
generation	I-Application
followed	O
by	O
compiling	B-Language
,	O
missing	O
only	O
one	O
of	O
the	O
many	O
optimizing	O
techniques	O
implemented	O
by	O
the	O
GHC	O
.	O
</s>
<s>
Many	O
other	O
components	O
are	O
in	O
various	O
stages	O
of	O
development	O
,	O
including	O
,	O
but	O
not	O
limited	O
to	O
,	O
the	O
Rust	B-Application
compiler	B-Language
,	O
a	O
Java	B-Language
bytecode	I-Language
frontend	O
,	O
a	O
Common	O
Intermediate	O
Language	O
(	O
CIL	O
)	O
frontend	O
,	O
the	O
MacRuby	B-Operating_System
implementation	O
of	O
Ruby	B-Language
1.9	O
,	O
various	O
frontends	O
for	O
Standard	B-Language
ML	I-Language
,	O
and	O
a	O
new	O
graph	O
coloring	O
register	O
allocator	O
.	O
</s>
<s>
The	O
core	O
of	O
LLVM	B-Application
is	O
the	O
intermediate	B-Application
representation	I-Application
(	O
IR	B-Application
)	O
,	O
a	O
low-level	O
programming	O
language	O
similar	O
to	O
assembly	O
.	O
</s>
<s>
IR	B-Application
is	O
a	O
strongly	O
typed	O
reduced	B-Architecture
instruction	I-Architecture
set	I-Architecture
computer	I-Architecture
(	O
RISC	B-Architecture
)	O
instruction	B-General_Concept
set	I-General_Concept
which	O
abstracts	O
away	O
most	O
details	O
of	O
the	O
target	O
.	O
</s>
<s>
Also	O
,	O
instead	O
of	O
a	O
fixed	O
set	O
of	O
registers	O
,	O
IR	B-Application
uses	O
an	O
infinite	O
set	O
of	O
temporaries	O
of	O
the	O
form	O
%0	O
,	O
%1	O
,	O
etc	O
.	O
</s>
<s>
LLVM	B-Application
supports	O
three	O
equivalent	O
forms	O
of	O
IR	B-Application
:	O
a	O
human-readable	O
assembly	O
format	O
,	O
an	O
in-memory	O
format	O
suitable	O
for	O
frontends	O
,	O
and	O
a	O
dense	O
bitcode	O
format	O
for	O
serializing	O
.	O
</s>
<s>
program	O
in	O
the	O
IR	B-Application
format	O
:	O
</s>
<s>
The	O
many	O
different	O
conventions	O
used	O
and	O
features	O
provided	O
by	O
different	O
targets	O
mean	O
that	O
LLVM	B-Application
cannot	O
truly	O
produce	O
a	O
target-independent	O
IR	B-Application
and	O
retarget	O
it	O
without	O
breaking	O
some	O
established	O
rules	O
.	O
</s>
<s>
Examples	O
of	O
target	O
dependence	O
beyond	O
what	O
is	O
explicitly	O
mentioned	O
in	O
the	O
documentation	O
can	O
be	O
found	O
in	O
a	O
2011	O
proposal	O
for	O
"	O
wordcode	O
"	O
,	O
a	O
fully	O
target-independent	O
variant	O
of	O
LLVM	B-Application
IR	B-Application
intended	O
for	O
online	O
distribution	O
.	O
</s>
<s>
The	O
LLVM	B-Application
project	O
also	O
introduces	O
another	O
type	O
of	O
intermediate	B-Application
representation	I-Application
named	O
MLIR	O
which	O
helps	O
build	O
reusable	O
and	O
extensible	O
compiler	B-Language
infrastructure	O
by	O
employing	O
a	O
plugin	O
architecture	O
named	O
Dialect	O
.	O
</s>
<s>
It	O
enables	O
the	O
use	O
of	O
higher-level	O
information	O
on	O
the	O
program	O
structure	O
in	O
the	O
process	O
of	O
optimization	O
including	O
polyhedral	O
compilation	B-Language
.	O
</s>
<s>
At	O
version	O
13	O
,	O
LLVM	B-Application
supports	O
many	O
instruction	B-General_Concept
sets	I-General_Concept
,	O
including	O
IA-32	B-Device
,	O
x86-64	B-Device
,	O
ARM	B-Architecture
,	O
Qualcomm	B-General_Concept
Hexagon	I-General_Concept
,	O
MIPS	B-Device
,	O
NVIDIA	O
Parallel	O
Thread	B-Operating_System
Execution	O
(	O
PTX	O
,	O
also	O
called	O
NVPTX	O
in	O
LLVM	B-Application
documentation	O
)	O
,	O
PowerPC	B-Architecture
,	O
AMD	B-Architecture
TeraScale	I-Architecture
,	O
most	O
AMD	O
GPU	B-Architecture
recent	O
ones	O
(	O
also	O
called	O
AMDGPU	O
in	O
LLVM	B-Application
documentation	O
)	O
,	O
SPARC	B-Architecture
,	O
z/Architecture	B-Device
(	O
also	O
called	O
SystemZ	O
in	O
LLVM	B-Application
documentation	O
)	O
,	O
and	O
XCore	O
.	O
</s>
<s>
Most	O
features	O
are	O
present	O
for	O
IA-32	B-Device
,	O
x86-64	B-Device
,	O
z/Architecture	B-Device
,	O
ARM	B-Architecture
,	O
and	O
PowerPC	B-Architecture
.	O
</s>
<s>
RISC-V	B-Device
is	O
supported	O
as	O
of	O
version	O
7	O
.	O
</s>
<s>
In	O
the	O
past	O
,	O
LLVM	B-Application
also	O
supported	O
other	O
backends	O
,	O
fully	O
or	O
partially	O
,	O
including	O
C	B-Language
backend	O
,	O
Cell	B-General_Concept
SPU	I-General_Concept
,	O
mblaze	O
(	O
MicroBlaze	B-Device
)	O
,	O
AMD	O
R600	O
,	O
DEC/Compaq	O
Alpha	B-Device
(	O
Alpha	B-Device
AXP	I-Device
)	O
and	O
Nios2	B-Device
,	O
but	O
that	O
hardware	O
is	O
mostly	O
obsolete	O
,	O
and	O
LLVM	B-Application
developers	O
decided	O
the	O
support	O
and	O
maintenance	O
costs	O
were	O
no	O
longer	O
justified	O
.	O
</s>
<s>
LLVM	B-Application
also	O
supports	O
WebAssembly	B-Language
as	O
a	O
target	O
,	O
enabling	O
compiled	B-Language
programs	O
to	O
execute	O
in	O
WebAssembly-enabled	O
environments	O
such	O
as	O
Google	B-Application
Chrome	I-Application
/	O
Chromium	B-Language
,	O
Firefox	B-Application
,	O
Microsoft	B-Application
Edge	I-Application
,	O
Apple	B-Application
Safari	I-Application
or	O
WAVM	O
.	O
</s>
<s>
LLVM-compliant	O
WebAssembly	B-Language
compilers	B-Language
typically	O
support	O
mostly	O
unmodified	O
source	O
code	O
written	O
in	O
C	B-Language
,	O
C++	B-Language
,	O
D	B-Application
,	O
Rust	B-Application
,	O
Nim	O
,	O
Kotlin	B-Language
and	O
several	O
other	O
languages	O
.	O
</s>
<s>
The	O
LLVM	B-Application
machine	O
code	O
(	O
MC	O
)	O
subproject	O
is	O
LLVM	B-Application
's	O
framework	O
for	O
translating	O
machine	O
instructions	O
between	O
textual	O
forms	O
and	O
machine	O
code	O
.	O
</s>
<s>
Formerly	O
,	O
LLVM	B-Application
relied	O
on	O
the	O
system	O
assembler	B-Language
,	O
or	O
one	O
provided	O
by	O
a	O
toolchain	B-General_Concept
,	O
to	O
translate	O
assembly	O
into	O
machine	O
code	O
.	O
</s>
<s>
LLVM	B-Application
MC	O
's	O
integrated	O
assembler	B-Language
supports	O
most	O
LLVM	B-Application
targets	O
,	O
including	O
IA-32	B-Device
,	O
x86-64	B-Device
,	O
ARM	B-Architecture
,	O
and	O
ARM64	O
.	O
</s>
<s>
For	O
some	O
targets	O
,	O
including	O
the	O
various	O
MIPS	B-Device
instruction	I-Device
sets	I-Device
,	O
integrated	O
assembly	O
support	O
is	O
usable	O
but	O
still	O
in	O
the	O
beta	O
stage	O
.	O
</s>
<s>
The	O
lld	O
subproject	O
is	O
an	O
attempt	O
to	O
develop	O
a	O
built-in	O
,	O
platform-independent	B-Operating_System
linker	B-Application
for	O
LLVM	B-Application
.	O
</s>
<s>
lld	O
aims	O
to	O
remove	O
dependence	O
on	O
a	O
third-party	O
linker	B-Application
.	O
</s>
<s>
,	O
lld	O
supports	O
ELF	O
,	O
PE/COFF	O
,	O
Mach-O	B-Operating_System
,	O
and	O
WebAssembly	B-Language
in	O
descending	O
order	O
of	O
completeness	O
.	O
</s>
<s>
Unlike	O
the	O
GNU	B-Application
linkers	I-Application
,	O
lld	O
has	O
built-in	O
support	O
for	O
link-time	B-Application
optimization	O
(	O
LTO	O
)	O
.	O
</s>
<s>
This	O
allows	O
for	O
faster	O
code	B-Application
generation	I-Application
as	O
it	O
bypasses	O
the	O
use	O
of	O
a	O
linker	B-Application
plugin	O
,	O
but	O
on	O
the	O
other	O
hand	O
prohibits	O
interoperability	O
with	O
other	O
flavors	O
of	O
LTO	O
.	O
</s>
<s>
The	O
LLVM	B-Application
project	O
includes	O
an	O
implementation	O
of	O
the	O
C++	B-Language
Standard	I-Language
Library	I-Language
called	O
libc++	O
,	O
dual-licensed	O
under	O
the	B-License
MIT	I-License
License	I-License
and	O
the	O
UIUC	B-License
license	I-License
.	O
</s>
<s>
Since	O
v9.0.0	O
,	O
it	O
was	O
relicensed	O
to	O
the	O
Apache	B-Application
License	I-Application
2.0	I-Application
with	O
LLVM	B-Application
Exceptions	O
.	O
</s>
<s>
This	O
implements	O
a	O
suite	O
of	O
cache-locality	O
optimizations	O
as	O
well	O
as	O
auto-parallelism	O
and	O
vectorization	B-General_Concept
using	O
a	O
polyhedral	O
model	O
.	O
</s>
<s>
llvm-libc	O
is	O
an	O
incomplete	O
,	O
upcoming	O
,	O
ABI	O
independent	O
C	B-Language
standard	I-Language
library	I-Language
designed	O
by	O
and	O
for	O
the	O
LLVM	B-Application
project	O
.	O
</s>
<s>
Due	O
to	O
its	O
permissive	B-License
license	I-License
,	O
many	O
vendors	O
release	O
their	O
own	O
tuned	O
forks	O
of	O
LLVM	B-Application
.	O
</s>
<s>
This	O
is	O
officially	O
recognized	O
by	O
LLVM	B-Application
's	O
documentation	O
,	O
which	O
suggests	O
against	O
using	O
version	O
numbers	O
in	O
feature	O
checks	O
for	O
this	O
reason	O
.	O
</s>
<s>
AMD	O
's	O
AMD	B-Application
Optimizing	I-Application
C/C	I-Application
++	I-Application
Compiler	I-Application
is	O
based	O
on	O
LLVM	B-Application
,	O
Clang	B-Application
,	O
and	O
Flang	O
.	O
</s>
<s>
Apple	O
maintains	O
an	O
open-source	O
fork	O
for	O
Xcode	B-Operating_System
.	O
</s>
<s>
ARM	B-Architecture
maintains	O
a	O
fork	O
of	O
LLVM	B-Application
9	O
as	O
the	O
"	O
Arm	B-Architecture
Compiler	B-Language
"	O
.	O
</s>
<s>
IBM	O
is	O
adopting	O
LLVM	B-Application
in	O
its	O
C/C	B-Language
++	I-Language
and	O
Fortran	B-Language
compilers	B-Language
.	O
</s>
<s>
Intel	O
has	O
adopted	O
LLVM	B-Application
for	O
their	O
next	O
generation	O
Intel	B-Language
C++	I-Language
Compiler	I-Language
.	O
</s>
<s>
The	O
Los	O
Alamos	O
National	O
Laboratory	O
has	O
a	O
parallel-computing	O
fork	O
of	O
LLVM	B-Application
8	O
called	O
"	O
Kitsune	O
"	O
.	O
</s>
<s>
Nvidia	O
uses	O
LLVM	B-Application
in	O
the	O
implementation	O
of	O
its	O
NVVM	O
CUDA	B-Architecture
Compiler	B-Language
.	O
</s>
<s>
The	O
NVVM	O
compiler	B-Language
is	O
distinct	O
from	O
the	O
"	O
NVPTX	O
"	O
backend	O
mentioned	O
in	O
the	O
Backends	O
section	O
,	O
although	O
both	O
generate	O
PTX	O
code	O
for	O
Nvidia	O
GPUs	B-Architecture
.	O
</s>
<s>
Since	O
2013	O
,	O
Sony	O
has	O
been	O
using	O
LLVM	B-Application
's	O
primary	O
front-end	O
Clang	B-Application
compiler	B-Language
in	O
the	O
software	B-Application
development	I-Application
kit	I-Application
(	O
SDK	O
)	O
of	O
its	O
PlayStation	B-Operating_System
4	I-Operating_System
console	O
.	O
</s>
