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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="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="#installcf">Install the GCC Front End</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 llvm-gcc4</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 the low level virtual machine. 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 GCC front end.</p>
<p>The second piece is the GCC front end. This component provides a version of
GCC that compiles C and C++ code into LLVM bitcode. Currently, the GCC front
end uses the GCC parser to convert code to LLVM. 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>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>Install the llvm-gcc-4.2 front end if you intend to compile C or C++
(see <a href="#installcf">Install the GCC Front End</a> for details):
<ol>
<li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt></li>
<li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf -</tt></li>
<li><tt><i>install-binutils-binary-from-MinGW</i></tt> (Windows only)</li>
<li>Note: If the binary extension is "<tt>.bz</tt>" use <tt>bunzip2</tt> instead of <tt>gunzip</tt>.</li>
<li>Note: On Windows, use <a href="http://www.7-zip.org/">7-Zip</a> or a similar archiving tool.</li>
<li>Add <tt>llvm-gcc</tt>'s "<tt>bin</tt>" directory to your <tt>PATH</tt> environment variable.</li>
</ol></li>
<li>Get the LLVM Source Code
<ul>
<li>With the distributed files (or use <a href="#checkout">SVN</a>):
<ol>
<li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
<li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
</ol></li>
</ul></li>
<li><b>[Optional]</b> Get the Test Suite Source Code
<ul>
<li>With the distributed files (or use <a href="#checkout">SVN</a>):
<ol>
<li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
<li><tt>cd llvm/projects</tt>
<li><tt>gunzip --stdout llvm-test-<i>version</i>.tar.gz | tar -xvf -</tt>
<li><tt>mv llvm-test-<i>version</i> test-suite</tt>
</ol></li>
</ul></li>
<li>Configure the LLVM Build Environment
<ol>
<li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
<li><tt><i>/path/to/llvm/</i>configure [options]</tt><br>
Some common options:
<ul>
<li><tt>--prefix=<i>directory</i></tt>
<p>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>).</p></li>
<li><tt>--with-llvmgccdir=<i>directory</i></tt>
<p>Optionally, specify for <i>directory</i> the full pathname of the
C/C++ front end installation to use with this LLVM configuration. If
not specified, the PATH will be searched. This is only needed if you
want to run test-suite or do some special kinds of LLVM builds.</p></li>
<li><tt>--enable-spec2000=<i>directory</i></tt>
<p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
benchmarks should be available in
<tt><i>directory</i></tt>.</p></li>
</ul>
</ol></li>
<li>Build the LLVM Suite:
<ol>
<li><tt>gmake -k |& tee gnumake.out
# this is csh or tcsh syntax</tt></li>
<li>If you get an "internal compiler error (ICE)" or test failures, see
<a href="#brokengcc">below</a>.</li>
</ol>
</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 GCC 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 2005 SP1 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>
<p>The GCC front end is not very portable at the moment. If you want to get it
to work on another platform, you can download a copy of the source and <a
href="GCCFEBuildInstrs.html">try to compile it</a> 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>Nightly tester, 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 3.3.3, 3.4.0, and Apple 4.0.1
successfully with them (however, see important notes below). 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. Please <a href="GCCFEBuildInstrs.html#cygwin">upgrade
to a newer version</a> if possible.</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>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>
<dt>LLVMGCCDIR
<dd>
This is where the LLVM GCC Front End is installed.
<p>
For the pre-built GCC front end binaries, the LLVMGCCDIR is
<tt>llvm-gcc/<i>platform</i>/llvm-gcc</tt>.
</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 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>
<p>If you would like to get the GCC front end source code, you can also get it
and build it yourself. Please follow <a href="GCCFEBuildInstrs.html">these
instructions</a> to successfully get and build the LLVM GCC front-end.</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>
% git clone http://llvm.org/git/llvm.git
</pre>
</div>
<!-- ======================================================================= -->
<h3>
<a name="installcf">Install the GCC Front End</a>
</h3>
<div>
<p>Before configuring and compiling the LLVM suite (or if you want to use just the LLVM
GCC front end) you can optionally extract the front end from the binary distribution.
It is used for running the LLVM test-suite and for compiling C/C++ programs. Note that
you can optionally <a href="GCCFEBuildInstrs.html">build llvm-gcc yourself</a> after building the
main LLVM repository.</p>
<p>To install the GCC front end, do the following (on Windows, use an archival tool
like <a href="http://www.7-zip.org/">7-zip</a> that understands gzipped tars):</p>
<ol>
<li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
<li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf
-</tt></li>
</ol>
<p>Once the binary is uncompressed, if you're using a *nix-based system, add a symlink for
<tt>llvm-gcc</tt> and <tt>llvm-g++</tt> to some directory in your path. If you're using a
Windows-based system, add the <tt>bin</tt> subdirectory of your front end installation directory
to your <tt>PATH</tt> environment variable. For example, if you uncompressed the binary to
<tt>c:\llvm-gcc</tt>, add <tt>c:\llvm-gcc\bin</tt> to your <tt>PATH</tt>.</p>
<p>If you now want to build LLVM from source, when you configure LLVM, it will
automatically detect <tt>llvm-gcc</tt>'s presence (if it is in your path) enabling its
use in test-suite. Note that you can always build or install <tt>llvm-gcc</tt> at any
point after building the main LLVM repository: just reconfigure llvm and
test-suite will pick it up.
</p>
<p>As a convenience for Windows users, the front end binaries for MinGW/x86 include
versions of the required w32api and mingw-runtime binaries. The last remaining step for
Windows users is to simply uncompress the binary binutils package from
<a href="http://mingw.org/">MinGW</a> into your front end installation directory. While the
front end installation steps are not quite the same as a typical manual MinGW installation,
they should be similar enough to those who have previously installed MinGW on Windows systems.</p>
<p>To install binutils on Windows:</p>
<ol>
<li><tt><i>download GNU Binutils from <a href="http://sourceforge.net/projects/mingw/files/">MinGW Downloads</a></i></tt></li>
<li><tt>cd <i>where-you-uncompressed-the-front-end</i></tt></li>
<li><tt><i>uncompress archived binutils directories (not the tar file) into the current directory</i></tt></li>
</ol>
<p>The binary versions of the LLVM GCC front end may not suit all of your needs. For
example, the binary distribution may include an old version of a system header
file, not "fix" a header file that needs to be fixed for GCC, or it may be linked with
libraries not available on your system. In cases like these, you may want to try
<a href="GCCFEBuildInstrs.html">building the GCC front end from source</a>. Thankfully,
this is much easier now than it was in the past.</p>
<p>We also do not currently support updating of the GCC front end by manually overlaying
newer versions of the w32api and mingw-runtime binary packages that may become available
from MinGW. At this time, it's best to think of the MinGW LLVM GCC front end binary as
a self-contained convenience package that requires Windows users to simply download and
uncompress the GNU Binutils binary package from the MinGW project.</p>
<p>Regardless of your platform, if you discover that installing the LLVM GCC front end
binaries is not as easy as previously described, or you would like to suggest improvements,
please let us know how you would like to see things improved by dropping us a note on our
<a href="http://llvm.org/docs/#maillist">mailing list</a>.</p>
</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>--with-llvmgccdir</i></dt>
<dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
The value of this option should specify the full pathname of the C/C++ Front
End to be used. If this option is not provided, the PATH will be searched for
a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
be inferred from the path found. If the option is not given, and no llvm-gcc
can be found in the path then a warning will be produced by
<tt>configure</tt> indicating this situation. LLVM may still be built with
the <tt>tools-only</tt> target but attempting to build the runtime libraries
will fail as these libraries require llvm-gcc and llvm-g++. See
<a href="#installcf">Install the GCC Front End</a> for details on installing
the C/C++ Front End. See
<a href="GCCFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
for details on building the C/C++ Front End.</dd>
<dt><i>--with-tclinclude</i></dt>
<dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
found. Use this if you have multiple tcl installations on your machine and you
want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
option, the LLVM configure script will search for the tcl 8.4 and 8.3
releases.
<br><br>
</dd>
<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>
<dd>
Enables debug symbols in the runtime libraries. The default is to strip
debug symbols from the runtime libraries.
</dd>
<dt><i>--enable-jit</i></dt>
<dd>
Compile the Just In Time (JIT) compiler functionality. This is not
available
on all platforms. The default is dependent on platform, so it is best
to explicitly enable it if you want it.
<br><br>
</dd>
<dt><i>--enable-targets=</i><tt>target-option</tt></dt>
<dd>Controls which targets will be built and linked into llc. The default
value for <tt>target_options</tt> is "all" which builds and links all
available targets. The value "host-only" can be specified to build only a
native compiler (no cross-compiler targets available). The "native" target is
selected as the target of the build host. You can also specify a comma
separated list of target names that you want available in llc. The target
names use all lower case. The current set of targets is: <br>
<tt>alpha, ia64, powerpc, skeleton, sparc, x86</tt>.
<br><br></dd>
<dt><i>--enable-doxygen</i></dt>
<dd>Look for the doxygen program and enable construction of doxygen based
documentation from the source code. This is disabled by default because
generating the documentation can take a long time and producess 100s of
megabytes of output.</dd>
<dt><i>--with-udis86</i></dt>
<dd>LLVM can use external disassembler library for various purposes (now it's
used only for examining code produced by JIT). This option will enable usage
of <a href="http://udis86.sourceforge.net/">udis86</a> x86 (both 32 and 64
bits) disassembler library.</dd>
</dl>
<p>To configure LLVM, follow these steps:</p>
<ol>
<li><p>Change directory into the object root directory:</p>
<div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
<li><p>Run the <tt>configure</tt> script located in the LLVM source
tree:</p>
<div class="doc_code">
<pre>% <i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</pre>
</div></li>
</ol>