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GettingStarted.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
"http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>Getting Started with LLVM System</title>
<link rel="stylesheet" href="_static/llvm.css" type="text/css">
</head>
<body>
<h1>
Getting Started with the LLVM System
</h1>
<ul>
<li><a href="#overview">Overview</a>
<li><a href="#quickstart">Getting Started Quickly (A Summary)</a>
<li><a href="#requirements">Requirements</a>
<ol>
<li><a href="#hardware">Hardware</a></li>
<li><a href="#software">Software</a></li>
<li><a href="#brokengcc">Broken versions of GCC and other tools</a></li>
</ol></li>
<li><a href="#starting">Getting Started with LLVM</a>
<ol>
<li><a href="#terminology">Terminology and Notation</a></li>
<li><a href="#environment">Setting Up Your Environment</a></li>
<li><a href="#unpack">Unpacking the LLVM Archives</a></li>
<li><a href="#checkout">Checkout LLVM from Subversion</a></li>
<li><a href="#git_mirror">LLVM GIT mirror</a></li>
<li><a href="#config">Local LLVM Configuration</a></li>
<li><a href="#compile">Compiling the LLVM Suite Source Code</a></li>
<li><a href="#cross-compile">Cross-Compiling LLVM</a></li>
<li><a href="#objfiles">The Location of LLVM Object Files</a></li>
<li><a href="#optionalconfig">Optional Configuration Items</a></li>
</ol></li>
<li><a href="#layout">Program layout</a>
<ol>
<li><a href="#examples"><tt>llvm/examples</tt></a></li>
<li><a href="#include"><tt>llvm/include</tt></a></li>
<li><a href="#lib"><tt>llvm/lib</tt></a></li>
<li><a href="#projects"><tt>llvm/projects</tt></a></li>
<li><a href="#runtime"><tt>llvm/runtime</tt></a></li>
<li><a href="#test"><tt>llvm/test</tt></a></li>
<li><a href="#test-suite"><tt>test-suite</tt></a></li>
<li><a href="#tools"><tt>llvm/tools</tt></a></li>
<li><a href="#utils"><tt>llvm/utils</tt></a></li>
</ol></li>
<li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
<ol>
<li><a href="#tutorial4">Example with Clang</a></li>
</ol>
<li><a href="#problems">Common Problems</a>
<li><a href="#links">Links</a>
</ul>
<div class="doc_author">
<p>Written by:
<a href="mailto:[email protected]">John Criswell</a>,
<a href="mailto:[email protected]">Chris Lattner</a>,
<a href="http://misha.brukman.net/">Misha Brukman</a>,
<a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
<a href="mailto:[email protected]">Guochun Shi</a>.
</p>
</div>
<!-- *********************************************************************** -->
<h2>
<a name="overview">Overview</a>
</h2>
<!-- *********************************************************************** -->
<div>
<p>Welcome to LLVM! In order to get started, you first need to know some
basic information.</p>
<p>First, LLVM comes in three pieces. The first piece is the LLVM
suite. This contains all of the tools, libraries, and header files
needed to use LLVM. It contains an assembler, disassembler, bitcode
analyzer and bitcode optimizer. It also contains basic regression tests that
can be used to test the LLVM tools and the Clang front end.</p>
<p>The second piece is the <a href="http://clang.llvm.org/">Clang</a> front end.
This component compiles C, C++, Objective C, and Objective C++ code into LLVM
bitcode. Once compiled into LLVM bitcode, a program can be manipulated with the
LLVM tools from the LLVM suite.
</p>
<p>
There is a third, optional piece called Test Suite. It is a suite of programs
with a testing harness that can be used to further test LLVM's functionality
and performance.
</p>
</div>
<!-- *********************************************************************** -->
<h2>
<a name="quickstart">Getting Started Quickly (A Summary)</a>
</h2>
<!-- *********************************************************************** -->
<div>
<p>The LLVM Getting Started documentation may be out of date. So, the Clang
<a href="http://clang.llvm.org/get_started.html">Getting Started</a> page might
also be a good place to start.</p>
<p>Here's the short story for getting up and running quickly with LLVM:</p>
<ol>
<li>Read the documentation.</li>
<li>Read the documentation.</li>
<li>Remember that you were warned twice about reading the documentation.</li>
<li>Checkout LLVM:
<ul>
<li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
<li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
</ul>
</li>
<li>Checkout Clang:
<ul>
<li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
<li><tt>cd llvm/tools</tt>
<li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
</ul>
</li>
<li>Checkout Compiler-RT:
<ul>
<li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
<li><tt>cd llvm/projects</tt>
<li><tt>svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk
compiler-rt</tt></li>
</ul>
</li>
<li>Get the Test Suite Source Code <b>[Optional]</b>
<ul>
<li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
<li><tt>cd llvm/projects</tt>
<li><tt>svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite</tt></li>
</ul>
</li>
<li>Configure and build LLVM and Clang:
<ul>
<li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
<li><tt>mkdir build</tt> (for building without polluting the source dir)</li>
<li><tt>cd build</tt></li>
<li><tt>../llvm/configure [options]</tt>
<br>Some common options:
<ul>
<li><tt>--prefix=<i>directory</i></tt> -
Specify for <i>directory</i> the full pathname of where you
want the LLVM tools and libraries to be installed (default
<tt>/usr/local</tt>).</li>
</ul>
<ul>
<li><tt>--enable-optimized</tt> -
Compile with optimizations enabled (default is NO).</li>
</ul>
<ul>
<li><tt>--enable-assertions</tt> -
Compile with assertion checks enabled (default is YES).</li>
</ul>
</li>
<li><tt>make [-j]</tt> - The -j specifies the number of jobs (commands) to
run simultaneously. This builds both LLVM and Clang for Debug+Asserts mode.
The --enabled-optimized configure option is used to specify a Release build.</li>
<li><tt>make check-all</tt> -
This run the regression tests to ensure everything is in working order.</li>
<li><tt>make update</tt> -
This command is used to update all the svn repositories at once, rather then
having to <tt>cd</tt> into the individual repositories and running
<tt>svn update</tt>.</li>
<li>It is also possible to use CMake instead of the makefiles. With CMake
it is also possible to generate project files for several IDEs: Eclipse
CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.</li>
<li>If you get an "internal compiler error (ICE)" or test failures, see
<a href="#brokengcc">below</a>.</li>
</ul>
</li>
</ol>
<p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
detailed information on configuring and compiling LLVM. See <a
href="#environment">Setting Up Your Environment</a> for tips that simplify
working with the Clang front end and LLVM tools. Go to <a href="#layout">Program
Layout</a> to learn about the layout of the source code tree.</p>
</div>
<!-- *********************************************************************** -->
<h2>
<a name="requirements">Requirements</a>
</h2>
<!-- *********************************************************************** -->
<div>
<p>Before you begin to use the LLVM system, review the requirements given below.
This may save you some trouble by knowing ahead of time what hardware and
software you will need.</p>
<!-- ======================================================================= -->
<h3>
<a name="hardware">Hardware</a>
</h3>
<div>
<p>LLVM is known to work on the following platforms:</p>
<table cellpadding="3" summary="Known LLVM platforms">
<tr>
<th>OS</th>
<th>Arch</th>
<th>Compilers</th>
</tr>
<tr>
<td>AuroraUX</td>
<td>x86<sup><a href="#pf_1">1</a></sup></td>
<td>GCC</td>
</tr>
<tr>
<td>Linux</td>
<td>x86<sup><a href="#pf_1">1</a></sup></td>
<td>GCC</td>
</tr>
<tr>
<td>Linux</td>
<td>amd64</td>
<td>GCC</td>
</tr>
<tr>
<td>Solaris</td>
<td>V9 (Ultrasparc)</td>
<td>GCC</td>
</tr>
<tr>
<td>FreeBSD</td>
<td>x86<sup><a href="#pf_1">1</a></sup></td>
<td>GCC</td>
</tr>
<tr>
<td>FreeBSD</td>
<td>amd64</td>
<td>GCC</td>
</tr>
<tr>
<td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
<td>PowerPC</td>
<td>GCC</td>
</tr>
<tr>
<td>MacOS X<sup><a href="#pf_2">2</a>,<a href="#pf_9">9</a></sup></td>
<td>x86</td>
<td>GCC</td>
</tr>
<tr>
<td>Cygwin/Win32</td>
<td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a>,
<a href="#pf_11">11</a></sup></td>
<td>GCC 3.4.X, binutils 2.20</td>
</tr>
<tr>
<td>MinGW/Win32</td>
<td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,
<a href="#pf_8">8</a>, <a href="#pf_10">10</a>,
<a href="#pf_11">11</a></sup></td>
<td>GCC 3.4.X, binutils 2.20</td>
</tr>
</table>
<p>LLVM has partial support for the following platforms:</p>
<table summary="LLVM partial platform support">
<tr>
<th>OS</th>
<th>Arch</th>
<th>Compilers</th>
</tr>
<tr>
<td>Windows</td>
<td>x86<sup><a href="#pf_1">1</a></sup></td>
<td>Visual Studio 2008 or higher<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
<tr>
<td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
<td>PowerPC</td>
<td>GCC</td>
</tr>
<tr>
<td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
<td>PowerPC</td>
<td>GCC</td>
</tr>
<tr>
<td>Linux<sup><a href="#pf_7">7</a></sup></td>
<td>Alpha</td>
<td>GCC</td>
</tr>
<tr>
<td>Linux<sup><a href="#pf_7">7</a></sup></td>
<td>Itanium (IA-64)</td>
<td>GCC</td>
</tr>
<tr>
<td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
<td>Itanium (IA-64)</td>
<td>HP aCC</td>
</tr>
<tr>
<td>Windows x64</td>
<td>x86-64</td>
<td>mingw-w64's GCC-4.5.x<sup><a href="#pf_12">12</a></sup></td>
</tr>
</table>
<p><b>Notes:</b></p>
<div class="doc_notes">
<ol>
<li><a name="pf_1">Code generation supported for Pentium processors and
up</a></li>
<li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
<li><a name="pf_3">No native code generation</a></li>
<li><a name="pf_4">Build is not complete: one or more tools do not link or function</a></li>
<li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
<li><a name="pf_6">The port is done using the MSYS shell.</a></li>
<li><a name="pf_7">Native code generation exists but is not complete.</a></li>
<li><a name="pf_8">Binutils 2.20 or later is required to build the assembler
generated by LLVM properly.</a></li>
<li><a name="pf_9">Xcode 2.5 and gcc 4.0.1</a> (Apple Build 5370) will trip
internal LLVM assert messages when compiled for Release at optimization
levels greater than 0 (i.e., <i>"-O1"</i> and higher).
Add <i>OPTIMIZE_OPTION="-O0"</i> to the build command line
if compiling for LLVM Release or bootstrapping the LLVM toolchain.</li>
<li><a name="pf_10">For MSYS/MinGW on Windows, be sure to install the MSYS
version of the perl package, and be sure it appears in your path
before any Windows-based versions such as Strawberry Perl and
ActivePerl, as these have Windows-specifics that will cause the
build to fail.</a></li>
<li><a name="pf_11">To use LLVM modules on Win32-based system,
you may configure LLVM with <i>"--enable-shared"</i>.</a></li>
<li><a name="pf_12">To compile SPU backend, you need to add
<tt>"LDFLAGS=-Wl,--stack,16777216"</tt> to configure.</a></li>
</ol>
</div>
<p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
mode, depending on the system (it is so large because of all the debugging
information and the fact that the libraries are statically linked into multiple
tools). If you do not need many of the tools and you are space-conscious, you
can pass <tt>ONLY_TOOLS="tools you need"</tt> to make. The Release build
requires considerably less space.</p>
<p>The LLVM suite <i>may</i> compile on other platforms, but it is not
guaranteed to do so. If compilation is successful, the LLVM utilities should be
able to assemble, disassemble, analyze, and optimize LLVM bitcode. Code
generation should work as well, although the generated native code may not work
on your platform.</p>
</div>
<!-- ======================================================================= -->
<h3>
<a name="software">Software</a>
</h3>
<div>
<p>Compiling LLVM requires that you have several software packages
installed. The table below lists those required packages. The Package column
is the usual name for the software package that LLVM depends on. The Version
column provides "known to work" versions of the package. The Notes column
describes how LLVM uses the package and provides other details.</p>
<table summary="Packages required to compile LLVM">
<tr><th>Package</th><th>Version</th><th>Notes</th></tr>
<tr>
<td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
<td>3.79, 3.79.1</td>
<td>Makefile/build processor</td>
</tr>
<tr>
<td><a href="http://gcc.gnu.org/">GCC</a></td>
<td>3.4.2</td>
<td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
</tr>
<tr>
<td><a href="http://www.gnu.org/software/texinfo/">TeXinfo</a></td>
<td>4.5</td>
<td>For building the CFE</td>
</tr>
<tr>
<td><a href="http://subversion.tigris.org/project_packages.html">SVN</a></td>
<td>≥1.3</td>
<td>Subversion access to LLVM<sup><a href="#sf2">2</a></sup></td>
</tr>
<!-- FIXME:
Do we support dg?
Are DejaGnu and expect obsolete?
Shall we mention Python? -->
<tr>
<td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
<td>1.4.2</td>
<td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
</tr>
<tr>
<td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
<td>8.3, 8.4</td>
<td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
</tr>
<tr>
<td><a href="http://expect.nist.gov/">expect</a></td>
<td>5.38.0</td>
<td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
</tr>
<tr>
<td><a href="http://www.perl.com/download.csp">perl</a></td>
<td>≥5.6.0</td>
<td>Utilities</td>
</tr>
<tr>
<td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
<td>1.4</td>
<td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
</tr>
<tr>
<td><a href="http://www.gnu.org/software/autoconf/">GNU Autoconf</a></td>
<td>2.60</td>
<td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
</tr>
<tr>
<td><a href="http://www.gnu.org/software/automake/">GNU Automake</a></td>
<td>1.9.6</td>
<td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
</tr>
<tr>
<td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
<td>1.5.22</td>
<td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
</tr>
</table>
<p><b>Notes:</b></p>
<div class="doc_notes">
<ol>
<li><a name="sf1">Only the C and C++ languages are needed so there's no
need to build the other languages for LLVM's purposes.</a> See
<a href="#brokengcc">below</a> for specific version info.</li>
<li><a name="sf2">You only need Subversion if you intend to build from the
latest LLVM sources. If you're working from a release distribution, you
don't need Subversion.</a></li>
<li><a name="sf3">Only needed if you want to run the automated test
suite in the <tt>llvm/test</tt> directory.</a></li>
<li><a name="sf4">If you want to make changes to the configure scripts,
you will need GNU autoconf (2.60), and consequently, GNU M4 (version 1.4
or higher). You will also need automake (1.9.6). We only use aclocal
from that package.</a></li>
</ol>
</div>
<p>Additionally, your compilation host is expected to have the usual
plethora of Unix utilities. Specifically:</p>
<ul>
<li><b>ar</b> - archive library builder</li>
<li><b>bzip2*</b> - bzip2 command for distribution generation</li>
<li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
<li><b>chmod</b> - change permissions on a file</li>
<li><b>cat</b> - output concatenation utility</li>
<li><b>cp</b> - copy files</li>
<li><b>date</b> - print the current date/time </li>
<li><b>echo</b> - print to standard output</li>
<li><b>egrep</b> - extended regular expression search utility</li>
<li><b>find</b> - find files/dirs in a file system</li>
<li><b>grep</b> - regular expression search utility</li>
<li><b>gzip*</b> - gzip command for distribution generation</li>
<li><b>gunzip*</b> - gunzip command for distribution checking</li>
<li><b>install</b> - install directories/files </li>
<li><b>mkdir</b> - create a directory</li>
<li><b>mv</b> - move (rename) files</li>
<li><b>ranlib</b> - symbol table builder for archive libraries</li>
<li><b>rm</b> - remove (delete) files and directories</li>
<li><b>sed</b> - stream editor for transforming output</li>
<li><b>sh</b> - Bourne shell for make build scripts</li>
<li><b>tar</b> - tape archive for distribution generation</li>
<li><b>test</b> - test things in file system</li>
<li><b>unzip*</b> - unzip command for distribution checking</li>
<li><b>zip*</b> - zip command for distribution generation</li>
</ul>
</div>
<!-- ======================================================================= -->
<h3>
<a name="brokengcc">Broken versions of GCC and other tools</a>
</h3>
<div>
<p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
bugs in the compiler. In particular, several versions of GCC crash when trying
to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang.
Other versions of GCC will probably work as well. GCC versions listed
here are known to not work. If you are using one of these versions, please try
to upgrade your GCC to something more recent. If you run into a problem with a
version of GCC not listed here, please <a href="mailto:[email protected]">let
us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
of GCC you are using.
</p>
<p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
problems in the STL that effectively prevent it from compiling LLVM.
</p>
<p><b>GCC 3.2.2 and 3.2.3</b>: These versions of GCC fails to compile LLVM with
a bogus template error. This was fixed in later GCCs.</p>
<p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
<p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
Cygwin does not work.</p>
<p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
possibly others) does not compile LLVM correctly (it appears that exception
handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
to a newer version of GCC.</p>
<p><b>GCC 3.4.0 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
code generator, causing an infinite loop in the llvm-gcc build when built
with optimizations enabled (i.e. a release build).</p>
<p><b>GCC 3.4.2 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
code generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0)
correctly compiles LLVM at -O2. A work around is to build release LLVM
builds with "make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ..."</p>
<p><b>GCC 3.4.x on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1056">
miscompiles portions of LLVM</a>.</p>
<p><b>GCC 3.4.4 (CodeSourcery ARM 2005q3-2)</b>: this compiler miscompiles LLVM
when building with optimizations enabled. It appears to work with
"<tt>make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1</tt>" or build a debug
build.</p>
<p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
miscompile LLVM.</p>
<p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
default with ENABLE_OPTIMIZED=1. To work around this, build with
"ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
<p><b>GCC 4.1.1</b>: GCC fails to build LLVM with template concept check errors
compiling some files. At the time of this writing, GCC mainline (4.2)
did not share the problem.</p>
<p><b>GCC 4.1.1 on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1063">
miscompiles portions of LLVM</a> when compiling llvm itself into 64-bit
code. LLVM will appear to mostly work but will be buggy, e.g. failing
portions of its testsuite.</p>
<p><b>GCC 4.1.2 on OpenSUSE</b>: Seg faults during libstdc++ build and on x86_64
platforms compiling md5.c gets a mangled constant.</p>
<p><b>GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian</b>: Appears
to miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining
about symbols remaining in the table on destruction.</p>
<p><b>GCC 4.1.2 20071124 (Red Hat 4.1.2-42)</b>: Suffers from the same symptoms
as the previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).</p>
<p><b>Cygwin GCC 4.3.2 20080827 (beta) 2</b>:
Users <a href="http://llvm.org/PR4145">reported</a> various problems related
with link errors when using this GCC version.</p>
<p><b>Debian GCC 4.3.2 on X86</b>: Crashes building some files in LLVM 2.6.</p>
<p><b>GCC 4.3.3 (Debian 4.3.3-10) on ARM</b>: Miscompiles parts of LLVM 2.6
when optimizations are turned on. The symptom is an infinite loop in
FoldingSetImpl::RemoveNode while running the code generator.</p>
<p><b>SUSE 11 GCC 4.3.4</b>: Miscompiles LLVM, causing crashes in ValueHandle logic.</p>
<p><b>GCC 4.3.5 and GCC 4.4.5 on ARM</b>: These can miscompile <tt>value >>
1</tt> even at -O0. A test failure in <tt>test/Assembler/alignstack.ll</tt> is
one symptom of the problem.
<p><b>GNU ld 2.16.X</b>. Some 2.16.X versions of the ld linker will produce very
long warning messages complaining that some ".gnu.linkonce.t.*" symbol was
defined in a discarded section. You can safely ignore these messages as they are
erroneous and the linkage is correct. These messages disappear using ld
2.17.</p>
<p><b>GNU binutils 2.17</b>: Binutils 2.17 contains <a
href="http://sourceware.org/bugzilla/show_bug.cgi?id=3111">a bug</a> which
causes huge link times (minutes instead of seconds) when building LLVM. We
recommend upgrading to a newer version (2.17.50.0.4 or later).</p>
<p><b>GNU Binutils 2.19.1 Gold</b>: This version of Gold contained
<a href="http://sourceware.org/bugzilla/show_bug.cgi?id=9836">a bug</a>
which causes intermittent failures when building LLVM with position independent
code. The symptom is an error about cyclic dependencies. We recommend
upgrading to a newer version of Gold.</p>
</div>
</div>
<!-- *********************************************************************** -->
<h2>
<a name="starting">Getting Started with LLVM</a>
</h2>
<!-- *********************************************************************** -->
<div>
<p>The remainder of this guide is meant to get you up and running with
LLVM and to give you some basic information about the LLVM environment.</p>
<p>The later sections of this guide describe the <a
href="#layout">general layout</a> of the the LLVM source tree, a <a
href="#tutorial">simple example</a> using the LLVM tool chain, and <a
href="#links">links</a> to find more information about LLVM or to get
help via e-mail.</p>
<!-- ======================================================================= -->
<h3>
<a name="terminology">Terminology and Notation</a>
</h3>
<div>
<p>Throughout this manual, the following names are used to denote paths
specific to the local system and working environment. <i>These are not
environment variables you need to set but just strings used in the rest
of this document below</i>. In any of the examples below, simply replace
each of these names with the appropriate pathname on your local system.
All these paths are absolute:</p>
<dl>
<dt>SRC_ROOT
<dd>
This is the top level directory of the LLVM source tree.
<br><br>
<dt>OBJ_ROOT
<dd>
This is the top level directory of the LLVM object tree (i.e. the
tree where object files and compiled programs will be placed. It
can be the same as SRC_ROOT).
<br><br>
</dl>
</div>
<!-- ======================================================================= -->
<h3>
<a name="environment">Setting Up Your Environment</a>
</h3>
<div>
<p>
In order to compile and use LLVM, you may need to set some environment
variables.
<dl>
<dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bitcode/libs</tt></dt>
<dd>[Optional] This environment variable helps LLVM linking tools find the
locations of your bitcode libraries. It is provided only as a
convenience since you can specify the paths using the -L options of the
tools and the C/C++ front-end will automatically use the bitcode files
installed in its
<tt>lib</tt> directory.</dd>
</dl>
</div>
<!-- ======================================================================= -->
<h3>
<a name="unpack">Unpacking the LLVM Archives</a>
</h3>
<div>
<p>
If you have the LLVM distribution, you will need to unpack it before you
can begin to compile it. LLVM is distributed as a set of two files: the LLVM
suite and the LLVM GCC front end compiled for your platform. There is an
additional test suite that is optional. Each file is a TAR archive that is
compressed with the gzip program.
</p>
<p>The files are as follows, with <em>x.y</em> marking the version number:
<dl>
<dt><tt>llvm-x.y.tar.gz</tt></dt>
<dd>Source release for the LLVM libraries and tools.<br></dd>
<dt><tt>llvm-test-x.y.tar.gz</tt></dt>
<dd>Source release for the LLVM test-suite.</dd>
<dt><tt>llvm-gcc-4.2-x.y.source.tar.gz</tt></dt>
<dd>Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
directory for build instructions.<br></dd>
<dt><tt>llvm-gcc-4.2-x.y-platform.tar.gz</tt></dt>
<dd>Binary release of the llvm-gcc-4.2 front end for a specific platform.<br></dd>
</dl>
</div>
<!-- ======================================================================= -->
<h3>
<a name="checkout">Checkout LLVM from Subversion</a>
</h3>
<div>
<p>If you have access to our Subversion repository, you can get a fresh copy of
the entire source code. All you need to do is check it out from Subversion as
follows:</p>
<ul>
<li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
<li>Read-Only: <tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
<li>Read-Write:<tt>svn co https://[email protected]/svn/llvm-project/llvm/trunk
llvm</tt></li>
</ul>
<p>This will create an '<tt>llvm</tt>' directory in the current
directory and fully populate it with the LLVM source code, Makefiles,
test directories, and local copies of documentation files.</p>
<p>If you want to get a specific release (as opposed to the most recent
revision), you can checkout it from the '<tt>tags</tt>' directory (instead of
'<tt>trunk</tt>'). The following releases are located in the following
subdirectories of the '<tt>tags</tt>' directory:</p>
<ul>
<li>Release 3.1: <b>RELEASE_31/final</b></li>
<li>Release 3.0: <b>RELEASE_30/final</b></li>
<li>Release 2.9: <b>RELEASE_29/final</b></li>
<li>Release 2.8: <b>RELEASE_28</b></li>
<li>Release 2.7: <b>RELEASE_27</b></li>
<li>Release 2.6: <b>RELEASE_26</b></li>
<li>Release 2.5: <b>RELEASE_25</b></li>
<li>Release 2.4: <b>RELEASE_24</b></li>
<li>Release 2.3: <b>RELEASE_23</b></li>
<li>Release 2.2: <b>RELEASE_22</b></li>
<li>Release 2.1: <b>RELEASE_21</b></li>
<li>Release 2.0: <b>RELEASE_20</b></li>
<li>Release 1.9: <b>RELEASE_19</b></li>
<li>Release 1.8: <b>RELEASE_18</b></li>
<li>Release 1.7: <b>RELEASE_17</b></li>
<li>Release 1.6: <b>RELEASE_16</b></li>
<li>Release 1.5: <b>RELEASE_15</b></li>
<li>Release 1.4: <b>RELEASE_14</b></li>
<li>Release 1.3: <b>RELEASE_13</b></li>
<li>Release 1.2: <b>RELEASE_12</b></li>
<li>Release 1.1: <b>RELEASE_11</b></li>
<li>Release 1.0: <b>RELEASE_1</b></li>
</ul>
<p>If you would like to get the LLVM test suite (a separate package as of 1.4),
you get it from the Subversion repository:</p>
<div class="doc_code">
<pre>
% cd llvm/projects
% svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
</pre>
</div>
<p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
configured by the LLVM configure script as well as automatically updated when
you run <tt>svn update</tt>.</p>
</div>
<!-- ======================================================================= -->
<h3>
<a name="git_mirror">GIT mirror</a>
</h3>
<div>
<p>GIT mirrors are available for a number of LLVM subprojects. These mirrors
sync automatically with each Subversion commit and contain all necessary
git-svn marks (so, you can recreate git-svn metadata locally). Note that right
now mirrors reflect only <tt>trunk</tt> for each project. You can do the
read-only GIT clone of LLVM via:</p>
<pre class="doc_code">
git clone http://llvm.org/git/llvm.git
</pre>
<p>If you want to check out clang too, run:</p>
<pre class="doc_code">
git clone http://llvm.org/git/llvm.git
cd llvm/tools
git clone http://llvm.org/git/clang.git
</pre>
<p>
Since the upstream repository is in Subversion, you should use
<tt>"git pull --rebase"</tt>
instead of <tt>"git pull"</tt> to avoid generating a non-linear
history in your clone.
To configure <tt>"git pull"</tt> to pass <tt>--rebase</tt> by default
on the master branch, run the following command:
</p>
<pre class="doc_code">
git config branch.master.rebase true
</pre>
<h4>Sending patches with Git</h4>
<div>
<p>
Please read <a href="DeveloperPolicy.html#patches">Developer Policy</a>, too.
</p>
<p>
Assume <tt>master</tt> points the upstream and <tt>mybranch</tt> points your
working branch, and <tt>mybranch</tt> is rebased onto <tt>master</tt>.
At first you may check sanity of whitespaces:
</p>
<pre class="doc_code">
git diff --check master..mybranch
</pre>
<p>
The easiest way to generate a patch is as below:
</p>
<pre class="doc_code">
git diff master..mybranch > /path/to/mybranch.diff
</pre>
<p>
It is a little different from svn-generated diff. git-diff-generated diff has
prefixes like <tt>a/</tt> and <tt>b/</tt>. Don't worry, most developers might
know it could be accepted with <tt>patch -p1 -N</tt>.
</p>
<p>
But you may generate patchset with git-format-patch. It generates
by-each-commit patchset. To generate patch files to attach to your article:
</p>
<pre class="doc_code">
git format-patch --no-attach master..mybranch -o /path/to/your/patchset
</pre>
<p>
If you would like to send patches directly, you may use git-send-email or
git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
</p>
<pre class="doc_code">
git format-patch --attach master..mybranch --stdout | git imap-send
</pre>
<p>
Then, your .git/config should have [imap] sections.
</p>
<pre class="doc_code">
[imap]
host = imaps://imap.gmail.com
user = <em>your.gmail.account</em>@gmail.com
pass = <em>himitsu!</em>
port = 993
sslverify = false
; in English
folder = "[Gmail]/Drafts"
; example for Japanese, "Modified UTF-7" encoded.
folder = "[Gmail]/&Tgtm+DBN-"
; example for Traditional Chinese
folder = "[Gmail]/&g0l6Pw-"
</pre>
</div>
<h4>For developers to work with git-svn</h4>
<div>
<p>To set up clone from which you can submit code using
<tt>git-svn</tt>, run:</p>
<pre class="doc_code">
git clone http://llvm.org/git/llvm.git
cd llvm
git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
git config svn-remote.svn.fetch :refs/remotes/origin/master
git svn rebase -l # -l avoids fetching ahead of the git mirror.
# If you have clang too:
cd tools
git clone http://llvm.org/git/clang.git
cd clang
git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
git config svn-remote.svn.fetch :refs/remotes/origin/master
git svn rebase -l
</pre>
<p>To update this clone without generating git-svn tags that conflict
with the upstream git repo, run:</p>
<pre class="doc_code">
git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
git checkout master
git svn rebase -l
(cd tools/clang &&
git checkout master &&
git svn rebase -l)
</pre>
<p>This leaves your working directories on their master branches, so
you'll need to <tt>checkout</tt> each working branch individually and
<tt>rebase</tt> it on top of its parent branch. (Note: This script is
intended for relative newbies to git. If you have more experience,
you can likely improve on it.)</p>
<p>The git-svn metadata can get out of sync after you mess around with
branches and <code>dcommit</code>. When that happens, <code>git svn
dcommit</code> stops working, complaining about files with uncommitted
changes. The fix is to rebuild the metadata:</p>
<pre class="doc_code">
rm -rf .git/svn
git svn rebase -l
</pre>
</div>
</div>
<!-- ======================================================================= -->
<h3>
<a name="config">Local LLVM Configuration</a>
</h3>
<div>
<p>Once checked out from the Subversion repository, the LLVM suite source
code must be
configured via the <tt>configure</tt> script. This script sets variables in the
various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
<tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
the Makefiles needed to begin building LLVM.</p>
<p>The following environment variables are used by the <tt>configure</tt>
script to configure the build system:</p>
<table summary="LLVM configure script environment variables">
<tr><th>Variable</th><th>Purpose</th></tr>
<tr>
<td>CC</td>
<td>Tells <tt>configure</tt> which C compiler to use. By default,
<tt>configure</tt> will look for the first GCC C compiler in
<tt>PATH</tt>. Use this variable to override
<tt>configure</tt>'s default behavior.</td>
</tr>
<tr>
<td>CXX</td>
<td>Tells <tt>configure</tt> which C++ compiler to use. By default,
<tt>configure</tt> will look for the first GCC C++ compiler in
<tt>PATH</tt>. Use this variable to override
<tt>configure</tt>'s default behavior.</td>
</tr>
</table>
<p>The following options can be used to set or enable LLVM specific options:</p>
<dl>
<dt><i>--enable-optimized</i></dt>
<dd>
Enables optimized compilation (debugging symbols are removed
and GCC optimization flags are enabled). Note that this is the default
setting if you are using the LLVM distribution. The default behavior
of an Subversion checkout is to use an unoptimized build (also known as a
debug build).
<br><br>
</dd>
<dt><i>--enable-debug-runtime</i></dt>