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12 Getting Started with the LLVM System
16 <li><a href="#overview">Overview</a>
17 <li><a href="#quickstart">Getting Started Quickly (A Summary)</a>
18 <li><a href="#requirements">Requirements</a>
20 <li><a href="#hardware">Hardware</a></li>
21 <li><a href="#software">Software</a></li>
22 <li><a href="#brokengcc">Broken versions of GCC and other tools</a></li>
25 <li><a href="#starting">Getting Started with LLVM</a>
27 <li><a href="#terminology">Terminology and Notation</a></li>
28 <li><a href="#environment">Setting Up Your Environment</a></li>
29 <li><a href="#unpack">Unpacking the LLVM Archives</a></li>
30 <li><a href="#checkout">Checkout LLVM from Subversion</a></li>
31 <li><a href="#git_mirror">LLVM GIT mirror</a></li>
32 <li><a href="#installcf">Install the GCC Front End</a></li>
33 <li><a href="#config">Local LLVM Configuration</a></li>
34 <li><a href="#compile">Compiling the LLVM Suite Source Code</a></li>
35 <li><a href="#cross-compile">Cross-Compiling LLVM</a></li>
36 <li><a href="#objfiles">The Location of LLVM Object Files</a></li>
37 <li><a href="#optionalconfig">Optional Configuration Items</a></li>
40 <li><a href="#layout">Program layout</a>
42 <li><a href="#examples"><tt>llvm/examples</tt></a></li>
43 <li><a href="#include"><tt>llvm/include</tt></a></li>
44 <li><a href="#lib"><tt>llvm/lib</tt></a></li>
45 <li><a href="#projects"><tt>llvm/projects</tt></a></li>
46 <li><a href="#runtime"><tt>llvm/runtime</tt></a></li>
47 <li><a href="#test"><tt>llvm/test</tt></a></li>
48 <li><a href="#test-suite"><tt>test-suite</tt></a></li>
49 <li><a href="#tools"><tt>llvm/tools</tt></a></li>
50 <li><a href="#utils"><tt>llvm/utils</tt></a></li>
53 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
55 <li><a href="#tutorial4">Example with llvm-gcc4</a></li>
57 <li><a href="#problems">Common Problems</a>
58 <li><a href="#links">Links</a>
61 <div class="doc_author">
63 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
64 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
65 <a href="http://misha.brukman.net/">Misha Brukman</a>,
66 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
67 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
72 <!-- *********************************************************************** -->
74 <a name="overview">Overview</a>
76 <!-- *********************************************************************** -->
80 <p>Welcome to LLVM! In order to get started, you first need to know some
81 basic information.</p>
83 <p>First, LLVM comes in three pieces. The first piece is the LLVM
84 suite. This contains all of the tools, libraries, and header files
85 needed to use LLVM. It contains an assembler, disassembler, bitcode
86 analyzer and bitcode optimizer. It also contains basic regression tests that
87 can be used to test the LLVM tools and the GCC front end.</p>
89 <p>The second piece is the GCC front end. This component provides a version of
90 GCC that compiles C and C++ code into LLVM bitcode. Currently, the GCC front
91 end uses the GCC parser to convert code to LLVM. Once
92 compiled into LLVM bitcode, a program can be manipulated with the LLVM tools
93 from the LLVM suite.</p>
96 There is a third, optional piece called Test Suite. It is a suite of programs
97 with a testing harness that can be used to further test LLVM's functionality
103 <!-- *********************************************************************** -->
105 <a name="quickstart">Getting Started Quickly (A Summary)</a>
107 <!-- *********************************************************************** -->
111 <p>The LLVM Getting Started documentation is <b>wildly</b> out of date and is
112 in dire need of an update. Most notably, Clang has replaced the GCC front end
113 entirely and building with the LLVM GCC front end is no longer supported.
114 The Clang <a href="http://clang.llvm.org/get_started.html">Getting Started</a>
115 page might be a better place to start.</p>
117 <p>Here's the short story for getting up and running quickly with LLVM:</p>
120 <li>Read the documentation.</li>
121 <li>Read the documentation.</li>
122 <li>Remember that you were warned twice about reading the documentation.</li>
123 <li>Install the llvm-gcc-4.2 front end if you intend to compile C or C++
124 (see <a href="#installcf">Install the GCC Front End</a> for details):
126 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt></li>
127 <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf -</tt></li>
128 <li><tt><i>install-binutils-binary-from-MinGW</i></tt> (Windows only)</li>
129 <li>Note: If the binary extension is "<tt>.bz</tt>" use <tt>bunzip2</tt> instead of <tt>gunzip</tt>.</li>
130 <li>Note: On Windows, use <a href="http://www.7-zip.org/">7-Zip</a> or a similar archiving tool.</li>
131 <li>Add <tt>llvm-gcc</tt>'s "<tt>bin</tt>" directory to your <tt>PATH</tt> environment variable.</li>
134 <li>Get the LLVM Source Code
136 <li>With the distributed files (or use <a href="#checkout">SVN</a>):
138 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
139 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
144 <li><b>[Optional]</b> Get the Test Suite Source Code
146 <li>With the distributed files (or use <a href="#checkout">SVN</a>):
148 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
149 <li><tt>cd llvm/projects</tt>
150 <li><tt>gunzip --stdout llvm-test-<i>version</i>.tar.gz | tar -xvf -</tt>
151 <li><tt>mv llvm-test-<i>version</i> test-suite</tt>
157 <li>Configure the LLVM Build Environment
159 <li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
160 <li><tt><i>/path/to/llvm/</i>configure [options]</tt><br>
164 <li><tt>--prefix=<i>directory</i></tt>
165 <p>Specify for <i>directory</i> the full pathname of where you
166 want the LLVM tools and libraries to be installed (default
167 <tt>/usr/local</tt>).</p></li>
168 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
169 <p>Optionally, specify for <i>directory</i> the full pathname of the
170 C/C++ front end installation to use with this LLVM configuration. If
171 not specified, the PATH will be searched. This is only needed if you
172 want to run test-suite or do some special kinds of LLVM builds.</p></li>
173 <li><tt>--enable-spec2000=<i>directory</i></tt>
174 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
175 benchmarks should be available in
176 <tt><i>directory</i></tt>.</p></li>
180 <li>Build the LLVM Suite:
182 <li><tt>gmake -k |& tee gnumake.out
183 # this is csh or tcsh syntax</tt></li>
184 <li>If you get an "internal compiler error (ICE)" or test failures, see
185 <a href="#brokengcc">below</a>.</li>
190 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
191 detailed information on configuring and compiling LLVM. See <a
192 href="#environment">Setting Up Your Environment</a> for tips that simplify
193 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
194 Layout</a> to learn about the layout of the source code tree.</p>
198 <!-- *********************************************************************** -->
200 <a name="requirements">Requirements</a>
202 <!-- *********************************************************************** -->
206 <p>Before you begin to use the LLVM system, review the requirements given below.
207 This may save you some trouble by knowing ahead of time what hardware and
208 software you will need.</p>
210 <!-- ======================================================================= -->
212 <a name="hardware">Hardware</a>
217 <p>LLVM is known to work on the following platforms:</p>
219 <table cellpadding="3" summary="Known LLVM platforms">
227 <td>x86<sup><a href="#pf_1">1</a></sup></td>
232 <td>x86<sup><a href="#pf_1">1</a></sup></td>
242 <td>V9 (Ultrasparc)</td>
247 <td>x86<sup><a href="#pf_1">1</a></sup></td>
256 <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
261 <td>MacOS X<sup><a href="#pf_2">2</a>,<a href="#pf_9">9</a></sup></td>
266 <td>Cygwin/Win32</td>
267 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a>,
268 <a href="#pf_11">11</a></sup></td>
269 <td>GCC 3.4.X, binutils 2.20</td>
273 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,
274 <a href="#pf_8">8</a>, <a href="#pf_10">10</a>,
275 <a href="#pf_11">11</a></sup></td>
276 <td>GCC 3.4.X, binutils 2.20</td>
280 <p>LLVM has partial support for the following platforms:</p>
282 <table summary="LLVM partial platform support">
290 <td>x86<sup><a href="#pf_1">1</a></sup></td>
291 <td>Visual Studio 2008 or higher<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
293 <td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
298 <td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
304 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
309 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
310 <td>Itanium (IA-64)</td>
314 <td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
315 <td>Itanium (IA-64)</td>
321 <td>mingw-w64's GCC-4.5.x<sup><a href="#pf_12">12</a></sup></td>
327 <div class="doc_notes">
329 <li><a name="pf_1">Code generation supported for Pentium processors and
331 <li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
332 <li><a name="pf_3">No native code generation</a></li>
333 <li><a name="pf_4">Build is not complete: one or more tools do not link or function</a></li>
334 <li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
335 <li><a name="pf_6">The port is done using the MSYS shell.</a></li>
336 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
337 <li><a name="pf_8">Binutils 2.20 or later is required to build the assembler
338 generated by LLVM properly.</a></li>
339 <li><a name="pf_9">XCode 2.5 and gcc 4.0.1</a> (Apple Build 5370) will trip
340 internal LLVM assert messages when compiled for Release at optimization
341 levels greater than 0 (i.e., <i>"-O1"</i> and higher).
342 Add <i>OPTIMIZE_OPTION="-O0"</i> to the build command line
343 if compiling for LLVM Release or bootstrapping the LLVM toolchain.</li>
344 <li><a name="pf_10">For MSYS/MinGW on Windows, be sure to install the MSYS
345 version of the perl package, and be sure it appears in your path
346 before any Windows-based versions such as Strawberry Perl and
347 ActivePerl, as these have Windows-specifics that will cause the
348 build to fail.</a></li>
349 <li><a name="pf_11">To use LLVM modules on Win32-based system,
350 you may configure LLVM with <i>"--enable-shared"</i>.</a></li>
351 <li><a name="pf_12">To compile SPU backend, you need to add
352 <tt>"LDFLAGS=-Wl,--stack,16777216"</tt> to configure.</a></li>
356 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
357 mode, depending on the system (it is so large because of all the debugging
358 information and the fact that the libraries are statically linked into multiple
359 tools). If you do not need many of the tools and you are space-conscious, you
360 can pass <tt>ONLY_TOOLS="tools you need"</tt> to make. The Release build
361 requires considerably less space.</p>
363 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
364 guaranteed to do so. If compilation is successful, the LLVM utilities should be
365 able to assemble, disassemble, analyze, and optimize LLVM bitcode. Code
366 generation should work as well, although the generated native code may not work
367 on your platform.</p>
369 <p>The GCC front end is not very portable at the moment. If you want to get it
370 to work on another platform, you can download a copy of the source and <a
371 href="GCCFEBuildInstrs.html">try to compile it</a> on your platform.</p>
375 <!-- ======================================================================= -->
377 <a name="software">Software</a>
380 <p>Compiling LLVM requires that you have several software packages
381 installed. The table below lists those required packages. The Package column
382 is the usual name for the software package that LLVM depends on. The Version
383 column provides "known to work" versions of the package. The Notes column
384 describes how LLVM uses the package and provides other details.</p>
385 <table summary="Packages required to compile LLVM">
386 <tr><th>Package</th><th>Version</th><th>Notes</th></tr>
389 <td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
390 <td>3.79, 3.79.1</td>
391 <td>Makefile/build processor</td>
395 <td><a href="http://gcc.gnu.org/">GCC</a></td>
397 <td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
401 <td><a href="http://www.gnu.org/software/texinfo/">TeXinfo</a></td>
403 <td>For building the CFE</td>
407 <td><a href="http://subversion.tigris.org/project_packages.html">SVN</a></td>
409 <td>Subversion access to LLVM<sup><a href="#sf2">2</a></sup></td>
414 Are DejaGnu and expect obsolete?
415 Shall we mention Python? -->
418 <td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
420 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
424 <td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
426 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
430 <td><a href="http://expect.nist.gov/">expect</a></td>
432 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
436 <td><a href="http://www.perl.com/download.csp">perl</a></td>
442 <td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
444 <td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
448 <td><a href="http://www.gnu.org/software/autoconf/">GNU Autoconf</a></td>
450 <td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
454 <td><a href="http://www.gnu.org/software/automake/">GNU Automake</a></td>
456 <td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
460 <td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
462 <td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
468 <div class="doc_notes">
470 <li><a name="sf1">Only the C and C++ languages are needed so there's no
471 need to build the other languages for LLVM's purposes.</a> See
472 <a href="#brokengcc">below</a> for specific version info.</li>
473 <li><a name="sf2">You only need Subversion if you intend to build from the
474 latest LLVM sources. If you're working from a release distribution, you
475 don't need Subversion.</a></li>
476 <li><a name="sf3">Only needed if you want to run the automated test
477 suite in the <tt>llvm/test</tt> directory.</a></li>
478 <li><a name="sf4">If you want to make changes to the configure scripts,
479 you will need GNU autoconf (2.60), and consequently, GNU M4 (version 1.4
480 or higher). You will also need automake (1.9.6). We only use aclocal
481 from that package.</a></li>
485 <p>Additionally, your compilation host is expected to have the usual
486 plethora of Unix utilities. Specifically:</p>
488 <li><b>ar</b> - archive library builder</li>
489 <li><b>bzip2*</b> - bzip2 command for distribution generation</li>
490 <li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
491 <li><b>chmod</b> - change permissions on a file</li>
492 <li><b>cat</b> - output concatenation utility</li>
493 <li><b>cp</b> - copy files</li>
494 <li><b>date</b> - print the current date/time </li>
495 <li><b>echo</b> - print to standard output</li>
496 <li><b>egrep</b> - extended regular expression search utility</li>
497 <li><b>find</b> - find files/dirs in a file system</li>
498 <li><b>grep</b> - regular expression search utility</li>
499 <li><b>gzip*</b> - gzip command for distribution generation</li>
500 <li><b>gunzip*</b> - gunzip command for distribution checking</li>
501 <li><b>install</b> - install directories/files </li>
502 <li><b>mkdir</b> - create a directory</li>
503 <li><b>mv</b> - move (rename) files</li>
504 <li><b>ranlib</b> - symbol table builder for archive libraries</li>
505 <li><b>rm</b> - remove (delete) files and directories</li>
506 <li><b>sed</b> - stream editor for transforming output</li>
507 <li><b>sh</b> - Bourne shell for make build scripts</li>
508 <li><b>tar</b> - tape archive for distribution generation</li>
509 <li><b>test</b> - test things in file system</li>
510 <li><b>unzip*</b> - unzip command for distribution checking</li>
511 <li><b>zip*</b> - zip command for distribution generation</li>
515 <!-- ======================================================================= -->
517 <a name="brokengcc">Broken versions of GCC and other tools</a>
522 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
523 bugs in the compiler. In particular, several versions of GCC crash when trying
524 to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang.
525 Other versions of GCC will probably work as well. GCC versions listed
526 here are known to not work. If you are using one of these versions, please try
527 to upgrade your GCC to something more recent. If you run into a problem with a
528 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
529 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
530 of GCC you are using.
533 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
534 problems in the STL that effectively prevent it from compiling LLVM.
537 <p><b>GCC 3.2.2 and 3.2.3</b>: These versions of GCC fails to compile LLVM with
538 a bogus template error. This was fixed in later GCCs.</p>
540 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
541 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
542 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
544 <p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
545 Cygwin does not work. Please <a href="GCCFEBuildInstrs.html#cygwin">upgrade
546 to a newer version</a> if possible.</p>
547 <p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
548 possibly others) does not compile LLVM correctly (it appears that exception
549 handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
550 to a newer version of GCC.</p>
551 <p><b>GCC 3.4.0 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
552 code generator, causing an infinite loop in the llvm-gcc build when built
553 with optimizations enabled (i.e. a release build).</p>
554 <p><b>GCC 3.4.2 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
555 code generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0)
556 correctly compiles LLVM at -O2. A work around is to build release LLVM
557 builds with "make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ..."</p>
558 <p><b>GCC 3.4.x on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1056">
559 miscompiles portions of LLVM</a>.</p>
560 <p><b>GCC 3.4.4 (CodeSourcery ARM 2005q3-2)</b>: this compiler miscompiles LLVM
561 when building with optimizations enabled. It appears to work with
562 "<tt>make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1</tt>" or build a debug
564 <p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
566 <p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
567 default with ENABLE_OPTIMIZED=1. To work around this, build with
568 "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
569 <p><b>GCC 4.1.1</b>: GCC fails to build LLVM with template concept check errors
570 compiling some files. At the time of this writing, GCC mainline (4.2)
571 did not share the problem.</p>
572 <p><b>GCC 4.1.1 on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1063">
573 miscompiles portions of LLVM</a> when compiling llvm itself into 64-bit
574 code. LLVM will appear to mostly work but will be buggy, e.g. failing
575 portions of its testsuite.</p>
576 <p><b>GCC 4.1.2 on OpenSUSE</b>: Seg faults during libstdc++ build and on x86_64
577 platforms compiling md5.c gets a mangled constant.</p>
578 <p><b>GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian</b>: Appears
579 to miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining
580 about symbols remaining in the table on destruction.</p>
581 <p><b>GCC 4.1.2 20071124 (Red Hat 4.1.2-42)</b>: Suffers from the same symptoms
582 as the previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).</p>
583 <p><b>Cygwin GCC 4.3.2 20080827 (beta) 2</b>:
584 Users <a href="http://llvm.org/PR4145">reported</a> various problems related
585 with link errors when using this GCC version.</p>
586 <p><b>Debian GCC 4.3.2 on X86</b>: Crashes building some files in LLVM 2.6.</p>
587 <p><b>GCC 4.3.3 (Debian 4.3.3-10) on ARM</b>: Miscompiles parts of LLVM 2.6
588 when optimizations are turned on. The symptom is an infinite loop in
589 FoldingSetImpl::RemoveNode while running the code generator.</p>
590 <p><b>GCC 4.3.5 and GCC 4.4.5 on ARM</b>: These can miscompile <tt>value >>
591 1</tt> even at -O0. A test failure in <tt>test/Assembler/alignstack.ll</tt> is
592 one symptom of the problem.
593 <p><b>GNU ld 2.16.X</b>. Some 2.16.X versions of the ld linker will produce very
594 long warning messages complaining that some ".gnu.linkonce.t.*" symbol was
595 defined in a discarded section. You can safely ignore these messages as they are
596 erroneous and the linkage is correct. These messages disappear using ld
599 <p><b>GNU binutils 2.17</b>: Binutils 2.17 contains <a
600 href="http://sourceware.org/bugzilla/show_bug.cgi?id=3111">a bug</a> which
601 causes huge link times (minutes instead of seconds) when building LLVM. We
602 recommend upgrading to a newer version (2.17.50.0.4 or later).</p>
604 <p><b>GNU Binutils 2.19.1 Gold</b>: This version of Gold contained
605 <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=9836">a bug</a>
606 which causes intermittent failures when building LLVM with position independent
607 code. The symptom is an error about cyclic dependencies. We recommend
608 upgrading to a newer version of Gold.</p>
614 <!-- *********************************************************************** -->
616 <a name="starting">Getting Started with LLVM</a>
618 <!-- *********************************************************************** -->
622 <p>The remainder of this guide is meant to get you up and running with
623 LLVM and to give you some basic information about the LLVM environment.</p>
625 <p>The later sections of this guide describe the <a
626 href="#layout">general layout</a> of the the LLVM source tree, a <a
627 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
628 href="#links">links</a> to find more information about LLVM or to get
631 <!-- ======================================================================= -->
633 <a name="terminology">Terminology and Notation</a>
638 <p>Throughout this manual, the following names are used to denote paths
639 specific to the local system and working environment. <i>These are not
640 environment variables you need to set but just strings used in the rest
641 of this document below</i>. In any of the examples below, simply replace
642 each of these names with the appropriate pathname on your local system.
643 All these paths are absolute:</p>
648 This is the top level directory of the LLVM source tree.
653 This is the top level directory of the LLVM object tree (i.e. the
654 tree where object files and compiled programs will be placed. It
655 can be the same as SRC_ROOT).
660 This is where the LLVM GCC Front End is installed.
662 For the pre-built GCC front end binaries, the LLVMGCCDIR is
663 <tt>llvm-gcc/<i>platform</i>/llvm-gcc</tt>.
668 <!-- ======================================================================= -->
670 <a name="environment">Setting Up Your Environment</a>
676 In order to compile and use LLVM, you may need to set some environment
680 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bitcode/libs</tt></dt>
681 <dd>[Optional] This environment variable helps LLVM linking tools find the
682 locations of your bitcode libraries. It is provided only as a
683 convenience since you can specify the paths using the -L options of the
684 tools and the C/C++ front-end will automatically use the bitcode files
686 <tt>lib</tt> directory.</dd>
691 <!-- ======================================================================= -->
693 <a name="unpack">Unpacking the LLVM Archives</a>
699 If you have the LLVM distribution, you will need to unpack it before you
700 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
701 suite and the LLVM GCC front end compiled for your platform. There is an
702 additional test suite that is optional. Each file is a TAR archive that is
703 compressed with the gzip program.
706 <p>The files are as follows, with <em>x.y</em> marking the version number:
708 <dt><tt>llvm-x.y.tar.gz</tt></dt>
709 <dd>Source release for the LLVM libraries and tools.<br></dd>
711 <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
712 <dd>Source release for the LLVM test-suite.</dd>
714 <dt><tt>llvm-gcc-4.2-x.y.source.tar.gz</tt></dt>
715 <dd>Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
716 directory for build instructions.<br></dd>
718 <dt><tt>llvm-gcc-4.2-x.y-platform.tar.gz</tt></dt>
719 <dd>Binary release of the llvm-gcc-4.2 front end for a specific platform.<br></dd>
725 <!-- ======================================================================= -->
727 <a name="checkout">Checkout LLVM from Subversion</a>
732 <p>If you have access to our Subversion repository, you can get a fresh copy of
733 the entire source code. All you need to do is check it out from Subversion as
737 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
738 <li>Read-Only: <tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
739 <li>Read-Write:<tt>svn co https://user@llvm.org/svn/llvm-project/llvm/trunk
744 <p>This will create an '<tt>llvm</tt>' directory in the current
745 directory and fully populate it with the LLVM source code, Makefiles,
746 test directories, and local copies of documentation files.</p>
748 <p>If you want to get a specific release (as opposed to the most recent
749 revision), you can checkout it from the '<tt>tags</tt>' directory (instead of
750 '<tt>trunk</tt>'). The following releases are located in the following
751 subdirectories of the '<tt>tags</tt>' directory:</p>
754 <li>Release 2.9: <b>RELEASE_29/final</b></li>
755 <li>Release 2.8: <b>RELEASE_28</b></li>
756 <li>Release 2.7: <b>RELEASE_27</b></li>
757 <li>Release 2.6: <b>RELEASE_26</b></li>
758 <li>Release 2.5: <b>RELEASE_25</b></li>
759 <li>Release 2.4: <b>RELEASE_24</b></li>
760 <li>Release 2.3: <b>RELEASE_23</b></li>
761 <li>Release 2.2: <b>RELEASE_22</b></li>
762 <li>Release 2.1: <b>RELEASE_21</b></li>
763 <li>Release 2.0: <b>RELEASE_20</b></li>
764 <li>Release 1.9: <b>RELEASE_19</b></li>
765 <li>Release 1.8: <b>RELEASE_18</b></li>
766 <li>Release 1.7: <b>RELEASE_17</b></li>
767 <li>Release 1.6: <b>RELEASE_16</b></li>
768 <li>Release 1.5: <b>RELEASE_15</b></li>
769 <li>Release 1.4: <b>RELEASE_14</b></li>
770 <li>Release 1.3: <b>RELEASE_13</b></li>
771 <li>Release 1.2: <b>RELEASE_12</b></li>
772 <li>Release 1.1: <b>RELEASE_11</b></li>
773 <li>Release 1.0: <b>RELEASE_1</b></li>
776 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
777 you get it from the Subversion repository:</p>
779 <div class="doc_code">
782 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
786 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
787 configured by the LLVM configure script as well as automatically updated when
788 you run <tt>svn update</tt>.</p>
790 <p>If you would like to get the GCC front end source code, you can also get it
791 and build it yourself. Please follow <a href="GCCFEBuildInstrs.html">these
792 instructions</a> to successfully get and build the LLVM GCC front-end.</p>
796 <!-- ======================================================================= -->
798 <a name="git_mirror">GIT mirror</a>
803 <p>GIT mirrors are available for a number of LLVM subprojects. These mirrors
804 sync automatically with each Subversion commit and contain all necessary
805 git-svn marks (so, you can recreate git-svn metadata locally). Note that right
806 now mirrors reflect only <tt>trunk</tt> for each project. You can do the
807 read-only GIT clone of LLVM via:</p>
809 <pre class="doc_code">
810 git clone http://llvm.org/git/llvm.git
813 <p>If you want to check out clang too, run:</p>
815 <pre class="doc_code">
816 git clone http://llvm.org/git/llvm.git
818 git clone http://llvm.org/git/clang.git
822 Since the upstream repository is in Subversion, you should use
823 <tt>"git pull --rebase"</tt>
824 instead of <tt>"git pull"</tt> to avoid generating a non-linear
825 history in your clone.
826 To configure <tt>"git pull"</tt> to pass <tt>--rebase</tt> by default
827 on the master branch, run the following command:
830 <pre class="doc_code">
831 git config branch.master.rebase true
834 <h4>Sending patches with Git</h4>
837 Please read <a href="DeveloperPolicy.html#patches">Developer Policy</a>, too.
841 Assume <tt>master</tt> points the upstream and <tt>mybranch</tt> points your
842 working branch, and <tt>mybranch</tt> is rebased onto <tt>master</tt>.
843 At first you may check sanity of whitespaces:
846 <pre class="doc_code">
847 git diff --check master..mybranch
851 The easiest way to generate a patch is as below:
854 <pre class="doc_code">
855 git diff master..mybranch > /path/to/mybranch.diff
859 It is a little different from svn-generated diff. git-diff-generated diff has
860 prefixes like <tt>a/</tt> and <tt>b/</tt>. Don't worry, most developers might
861 know it could be accepted with <tt>patch -p1 -N</tt>.
865 But you may generate patchset with git-format-patch. It generates
866 by-each-commit patchset. To generate patch files to attach to your article:
869 <pre class="doc_code">
870 git format-patch --no-attach master..mybranch -o /path/to/your/patchset
874 If you would like to send patches directly, you may use git-send-email or
875 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
878 <pre class="doc_code">
879 git format-patch --attach master..mybranch --stdout | git imap-send
883 Then, your .git/config should have [imap] sections.
886 <pre class="doc_code">
888 host = imaps://imap.gmail.com
889 user = <em>your.gmail.account</em>@gmail.com
890 pass = <em>himitsu!</em>
894 folder = "[Gmail]/Drafts"
895 ; example for Japanese, "Modified UTF-7" encoded.
896 folder = "[Gmail]/&Tgtm+DBN-"
897 ; example for Traditional Chinese
898 folder = "[Gmail]/&g0l6Pw-"
903 <h4>For developers to work with git-svn</h4>
906 <p>To set up clone from which you can submit code using
907 <tt>git-svn</tt>, run:</p>
909 <pre class="doc_code">
910 git clone http://llvm.org/git/llvm.git
912 git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
913 git config svn-remote.svn.fetch :refs/remotes/origin/master
914 git svn rebase -l # -l avoids fetching ahead of the git mirror.
916 # If you have clang too:
918 git clone http://llvm.org/git/clang.git
920 git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
921 git config svn-remote.svn.fetch :refs/remotes/origin/master
925 <p>To update this clone without generating git-svn tags that conflict
926 with the upstream git repo, run:</p>
928 <pre class="doc_code">
929 git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
933 git checkout master &&
937 <p>This leaves your working directories on their master branches, so
938 you'll need to <tt>checkout</tt> each working branch individually and
939 <tt>rebase</tt> it on top of its parent branch. (Note: This script is
940 intended for relative newbies to git. If you have more experience,
941 you can likely improve on it.)</p>
943 <p>The git-svn metadata can get out of sync after you mess around with
944 branches and <code>dcommit</code>. When that happens, <code>git svn
945 dcommit</code> stops working, complaining about files with uncommitted
946 changes. The fix is to rebuild the metadata:</p>
948 <pre class="doc_code">
957 <!-- ======================================================================= -->
959 <a name="installcf">Install the GCC Front End</a>
964 <p>Before configuring and compiling the LLVM suite (or if you want to use just the LLVM
965 GCC front end) you can optionally extract the front end from the binary distribution.
966 It is used for running the LLVM test-suite and for compiling C/C++ programs. Note that
967 you can optionally <a href="GCCFEBuildInstrs.html">build llvm-gcc yourself</a> after building the
968 main LLVM repository.</p>
970 <p>To install the GCC front end, do the following (on Windows, use an archival tool
971 like <a href="http://www.7-zip.org/">7-zip</a> that understands gzipped tars):</p>
974 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
975 <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf
979 <p>Once the binary is uncompressed, if you're using a *nix-based system, add a symlink for
980 <tt>llvm-gcc</tt> and <tt>llvm-g++</tt> to some directory in your path. If you're using a
981 Windows-based system, add the <tt>bin</tt> subdirectory of your front end installation directory
982 to your <tt>PATH</tt> environment variable. For example, if you uncompressed the binary to
983 <tt>c:\llvm-gcc</tt>, add <tt>c:\llvm-gcc\bin</tt> to your <tt>PATH</tt>.</p>
985 <p>If you now want to build LLVM from source, when you configure LLVM, it will
986 automatically detect <tt>llvm-gcc</tt>'s presence (if it is in your path) enabling its
987 use in test-suite. Note that you can always build or install <tt>llvm-gcc</tt> at any
988 point after building the main LLVM repository: just reconfigure llvm and
989 test-suite will pick it up.
992 <p>As a convenience for Windows users, the front end binaries for MinGW/x86 include
993 versions of the required w32api and mingw-runtime binaries. The last remaining step for
994 Windows users is to simply uncompress the binary binutils package from
995 <a href="http://mingw.org/">MinGW</a> into your front end installation directory. While the
996 front end installation steps are not quite the same as a typical manual MinGW installation,
997 they should be similar enough to those who have previously installed MinGW on Windows systems.</p>
999 <p>To install binutils on Windows:</p>
1002 <li><tt><i>download GNU Binutils from <a href="http://sourceforge.net/projects/mingw/files/">MinGW Downloads</a></i></tt></li>
1003 <li><tt>cd <i>where-you-uncompressed-the-front-end</i></tt></li>
1004 <li><tt><i>uncompress archived binutils directories (not the tar file) into the current directory</i></tt></li>
1007 <p>The binary versions of the LLVM GCC front end may not suit all of your needs. For
1008 example, the binary distribution may include an old version of a system header
1009 file, not "fix" a header file that needs to be fixed for GCC, or it may be linked with
1010 libraries not available on your system. In cases like these, you may want to try
1011 <a href="GCCFEBuildInstrs.html">building the GCC front end from source</a>. Thankfully,
1012 this is much easier now than it was in the past.</p>
1014 <p>We also do not currently support updating of the GCC front end by manually overlaying
1015 newer versions of the w32api and mingw-runtime binary packages that may become available
1016 from MinGW. At this time, it's best to think of the MinGW LLVM GCC front end binary as
1017 a self-contained convenience package that requires Windows users to simply download and
1018 uncompress the GNU Binutils binary package from the MinGW project.</p>
1020 <p>Regardless of your platform, if you discover that installing the LLVM GCC front end
1021 binaries is not as easy as previously described, or you would like to suggest improvements,
1022 please let us know how you would like to see things improved by dropping us a note on our
1023 <a href="http://llvm.org/docs/#maillist">mailing list</a>.</p>
1027 <!-- ======================================================================= -->
1029 <a name="config">Local LLVM Configuration</a>
1034 <p>Once checked out from the Subversion repository, the LLVM suite source
1036 configured via the <tt>configure</tt> script. This script sets variables in the
1037 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
1038 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
1039 the Makefiles needed to begin building LLVM.</p>
1041 <p>The following environment variables are used by the <tt>configure</tt>
1042 script to configure the build system:</p>
1044 <table summary="LLVM configure script environment variables">
1045 <tr><th>Variable</th><th>Purpose</th></tr>
1048 <td>Tells <tt>configure</tt> which C compiler to use. By default,
1049 <tt>configure</tt> will look for the first GCC C compiler in
1050 <tt>PATH</tt>. Use this variable to override
1051 <tt>configure</tt>'s default behavior.</td>
1055 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
1056 <tt>configure</tt> will look for the first GCC C++ compiler in
1057 <tt>PATH</tt>. Use this variable to override
1058 <tt>configure</tt>'s default behavior.</td>
1062 <p>The following options can be used to set or enable LLVM specific options:</p>
1065 <dt><i>--with-llvmgccdir</i></dt>
1066 <dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
1067 The value of this option should specify the full pathname of the C/C++ Front
1068 End to be used. If this option is not provided, the PATH will be searched for
1069 a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
1070 be inferred from the path found. If the option is not given, and no llvm-gcc
1071 can be found in the path then a warning will be produced by
1072 <tt>configure</tt> indicating this situation. LLVM may still be built with
1073 the <tt>tools-only</tt> target but attempting to build the runtime libraries
1074 will fail as these libraries require llvm-gcc and llvm-g++. See
1075 <a href="#installcf">Install the GCC Front End</a> for details on installing
1076 the C/C++ Front End. See
1077 <a href="GCCFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
1078 for details on building the C/C++ Front End.</dd>
1079 <dt><i>--with-tclinclude</i></dt>
1080 <dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
1081 found. Use this if you have multiple tcl installations on your machine and you
1082 want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
1083 dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
1084 option, the LLVM configure script will search for the tcl 8.4 and 8.3
1088 <dt><i>--enable-optimized</i></dt>
1090 Enables optimized compilation (debugging symbols are removed
1091 and GCC optimization flags are enabled). Note that this is the default
1092 setting if you are using the LLVM distribution. The default behavior
1093 of an Subversion checkout is to use an unoptimized build (also known as a
1097 <dt><i>--enable-debug-runtime</i></dt>
1099 Enables debug symbols in the runtime libraries. The default is to strip
1100 debug symbols from the runtime libraries.
1102 <dt><i>--enable-jit</i></dt>
1104 Compile the Just In Time (JIT) compiler functionality. This is not
1106 on all platforms. The default is dependent on platform, so it is best
1107 to explicitly enable it if you want it.
1110 <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
1111 <dd>Controls which targets will be built and linked into llc. The default
1112 value for <tt>target_options</tt> is "all" which builds and links all
1113 available targets. The value "host-only" can be specified to build only a
1114 native compiler (no cross-compiler targets available). The "native" target is
1115 selected as the target of the build host. You can also specify a comma
1116 separated list of target names that you want available in llc. The target
1117 names use all lower case. The current set of targets is: <br>
1118 <tt>arm, cbe, cpp, hexagon, mblaze, mips, mipsel, msp430, powerpc, ptx, sparc, spu, x86, x86_64, xcore</tt>.
1120 <dt><i>--enable-doxygen</i></dt>
1121 <dd>Look for the doxygen program and enable construction of doxygen based
1122 documentation from the source code. This is disabled by default because
1123 generating the documentation can take a long time and producess 100s of
1124 megabytes of output.</dd>
1125 <dt><i>--with-udis86</i></dt>
1126 <dd>LLVM can use external disassembler library for various purposes (now it's
1127 used only for examining code produced by JIT). This option will enable usage
1128 of <a href="http://udis86.sourceforge.net/">udis86</a> x86 (both 32 and 64
1129 bits) disassembler library.</dd>
1132 <p>To configure LLVM, follow these steps:</p>
1135 <li><p>Change directory into the object root directory:</p>
1137 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1139 <li><p>Run the <tt>configure</tt> script located in the LLVM source
1142 <div class="doc_code">
1143 <pre>% <i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</pre>
1149 <!-- ======================================================================= -->
1151 <a name="compile">Compiling the LLVM Suite Source Code</a>
1156 <p>Once you have configured LLVM, you can build it. There are three types of
1162 These builds are the default when one is using an Subversion checkout and
1163 types <tt>gmake</tt> (unless the <tt>--enable-optimized</tt> option was
1164 used during configuration). The build system will compile the tools and
1165 libraries with debugging information. To get a Debug Build using the
1166 LLVM distribution the <tt>--disable-optimized</tt> option must be passed
1167 to <tt>configure</tt>.
1170 <dt>Release (Optimized) Builds
1172 These builds are enabled with the <tt>--enable-optimized</tt> option to
1173 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
1174 <tt>gmake</tt> command line. For these builds, the build system will
1175 compile the tools and libraries with GCC optimizations enabled and strip
1176 debugging information from the libraries and executables it generates.
1177 Note that Release Builds are default when using an LLVM distribution.
1182 These builds are for use with profiling. They compile profiling
1183 information into the code for use with programs like <tt>gprof</tt>.
1184 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
1185 on the <tt>gmake</tt> command line.
1188 <p>Once you have LLVM configured, you can build it by entering the
1189 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
1191 <div class="doc_code"><pre>% gmake</pre></div>
1193 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
1194 are using a version of GCC that is known not to compile LLVM.</p>
1197 If you have multiple processors in your machine, you may wish to use some of
1198 the parallel build options provided by GNU Make. For example, you could use the
1201 <div class="doc_code"><pre>% gmake -j2</pre></div>
1203 <p>There are several special targets which are useful when working with the LLVM
1207 <dt><tt>gmake clean</tt>
1209 Removes all files generated by the build. This includes object files,
1210 generated C/C++ files, libraries, and executables.
1213 <dt><tt>gmake dist-clean</tt>
1215 Removes everything that <tt>gmake clean</tt> does, but also removes files
1216 generated by <tt>configure</tt>. It attempts to return the source tree to the
1217 original state in which it was shipped.
1220 <dt><tt>gmake install</tt>
1222 Installs LLVM header files, libraries, tools, and documentation in a
1224 under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
1225 defaults to <tt>/usr/local</tt>.
1228 <dt><tt>gmake -C runtime install-bytecode</tt>
1230 Assuming you built LLVM into $OBJDIR, when this command is run, it will
1231 install bitcode libraries into the GCC front end's bitcode library
1232 directory. If you need to update your bitcode libraries,
1233 this is the target to use once you've built them.
1237 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
1238 details on these <tt>make</tt> targets and descriptions of other targets
1241 <p>It is also possible to override default values from <tt>configure</tt> by
1242 declaring variables on the command line. The following are some examples:</p>
1245 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
1247 Perform a Release (Optimized) build.
1250 <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
1252 Perform a Release (Optimized) build without assertions enabled.
1255 <dt><tt>gmake ENABLE_OPTIMIZED=0</tt>
1257 Perform a Debug build.
1260 <dt><tt>gmake ENABLE_PROFILING=1</tt>
1262 Perform a Profiling build.
1265 <dt><tt>gmake VERBOSE=1</tt>
1267 Print what <tt>gmake</tt> is doing on standard output.
1270 <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
1271 <dd>Ask each tool invoked by the makefiles to print out what it is doing on
1272 the standard output. This also implies <tt>VERBOSE=1</tt>.
1276 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
1277 it and any subdirectories that it contains. Entering any directory inside the
1278 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
1279 that directory that is out of date.</p>
1283 <!-- ======================================================================= -->
1285 <a name="cross-compile">Cross-Compiling LLVM</a>
1289 <p>It is possible to cross-compile LLVM itself. That is, you can create LLVM
1290 executables and libraries to be hosted on a platform different from the
1291 platform where they are build (a Canadian Cross build). To configure a
1292 cross-compile, supply the configure script with <tt>--build</tt> and
1293 <tt>--host</tt> options that are different. The values of these options must
1294 be legal target triples that your GCC compiler supports.</p>
1296 <p>The result of such a build is executables that are not runnable on
1297 on the build host (--build option) but can be executed on the compile host
1298 (--host option).</p>
1301 <!-- ======================================================================= -->
1303 <a name="objfiles">The Location of LLVM Object Files</a>
1308 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1309 several LLVM builds. Hence, it is possible to build LLVM for several different
1310 platforms or configurations using the same source tree.</p>
1312 <p>This is accomplished in the typical autoconf manner:</p>
1315 <li><p>Change directory to where the LLVM object files should live:</p>
1317 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1319 <li><p>Run the <tt>configure</tt> script found in the LLVM source
1322 <div class="doc_code"><pre>% <i>SRC_ROOT</i>/configure</pre></div></li>
1325 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1326 named after the build type:</p>
1329 <dt>Debug Builds with assertions enabled (the default)
1333 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/bin</tt>
1335 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/lib</tt>
1343 <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1345 <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1353 <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1355 <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1361 <!-- ======================================================================= -->
1363 <a name="optionalconfig">Optional Configuration Items</a>
1369 If you're running on a Linux system that supports the "<a
1370 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
1371 module, and you have root access on the system, you can set your system up to
1372 execute LLVM bitcode files directly. To do this, use commands like this (the
1373 first command may not be required if you are already using the module):</p>
1375 <div class="doc_code">
1377 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1378 $ echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1379 $ chmod u+x hello.bc (if needed)
1385 This allows you to execute LLVM bitcode files directly. On Debian, you
1386 can also use this command instead of the 'echo' command above:
1389 <div class="doc_code">
1391 $ sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1399 <!-- *********************************************************************** -->
1401 <a name="layout">Program Layout</a>
1403 <!-- *********************************************************************** -->
1407 <p>One useful source of information about the LLVM source base is the LLVM <a
1408 href="http://www.doxygen.org/">doxygen</a> documentation available at <tt><a
1409 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1410 The following is a brief introduction to code layout:</p>
1412 <!-- ======================================================================= -->
1414 <a name="examples"><tt>llvm/examples</tt></a>
1418 <p>This directory contains some simple examples of how to use the LLVM IR and
1422 <!-- ======================================================================= -->
1424 <a name="include"><tt>llvm/include</tt></a>
1429 <p>This directory contains public header files exported from the LLVM
1430 library. The three main subdirectories of this directory are:</p>
1433 <dt><tt><b>llvm/include/llvm</b></tt></dt>
1434 <dd>This directory contains all of the LLVM specific header files. This
1435 directory also has subdirectories for different portions of LLVM:
1436 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1439 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1440 <dd>This directory contains generic support libraries that are provided with
1441 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1442 and a Command Line option processing library store their header files here.
1445 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1446 <dd>This directory contains header files configured by the <tt>configure</tt>
1447 script. They wrap "standard" UNIX and C header files. Source code can
1448 include these header files which automatically take care of the conditional
1449 #includes that the <tt>configure</tt> script generates.</dd>
1453 <!-- ======================================================================= -->
1455 <a name="lib"><tt>llvm/lib</tt></a>
1460 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1461 almost all code exists in libraries, making it very easy to share code among the
1462 different <a href="#tools">tools</a>.</p>
1465 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1466 <dd> This directory holds the core LLVM source files that implement core
1467 classes like Instruction and BasicBlock.</dd>
1469 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1470 <dd>This directory holds the source code for the LLVM assembly language parser
1473 <dt><tt><b>llvm/lib/BitCode/</b></tt></dt>
1474 <dd>This directory holds code for reading and write LLVM bitcode.</dd>
1476 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1477 different program analyses, such as Dominator Information, Call Graphs,
1478 Induction Variables, Interval Identification, Natural Loop Identification,
1481 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1482 <dd> This directory contains the source code for the LLVM to LLVM program
1483 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1484 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1485 Elimination, and many others.</dd>
1487 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1488 <dd> This directory contains files that describe various target architectures
1489 for code generation. For example, the <tt>llvm/lib/Target/X86</tt>
1490 directory holds the X86 machine description while
1491 <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
1493 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1494 <dd> This directory contains the major parts of the code generator: Instruction
1495 Selector, Instruction Scheduling, and Register Allocation.</dd>
1497 <dt><tt><b>llvm/lib/MC/</b></tt></dt>
1498 <dd>(FIXME: T.B.D.)</dd>
1500 <!--FIXME: obsoleted -->
1501 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1502 <dd> This directory contains the source level debugger library that makes
1503 it possible to instrument LLVM programs so that a debugger could identify
1504 source code locations at which the program is executing.</dd>
1506 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1507 <dd> This directory contains libraries for executing LLVM bitcode directly
1508 at runtime in both interpreted and JIT compiled fashions.</dd>
1510 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1511 <dd> This directory contains the source code that corresponds to the header
1512 files located in <tt>llvm/include/ADT/</tt>
1513 and <tt>llvm/include/Support/</tt>.</dd>
1518 <!-- ======================================================================= -->
1520 <a name="projects"><tt>llvm/projects</tt></a>
1524 <p>This directory contains projects that are not strictly part of LLVM but are
1525 shipped with LLVM. This is also the directory where you should create your own
1526 LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1527 to set up your own project.</p>
1530 <!-- ======================================================================= -->
1532 <a name="runtime"><tt>llvm/runtime</tt></a>
1537 <p>This directory contains libraries which are compiled into LLVM bitcode and
1538 used when linking programs with the GCC front end. Most of these libraries are
1539 skeleton versions of real libraries; for example, libc is a stripped down
1540 version of glibc.</p>
1542 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1547 <!-- ======================================================================= -->
1549 <a name="test"><tt>llvm/test</tt></a>
1553 <p>This directory contains feature and regression tests and other basic sanity
1554 checks on the LLVM infrastructure. These are intended to run quickly and cover
1555 a lot of territory without being exhaustive.</p>
1558 <!-- ======================================================================= -->
1560 <a name="test-suite"><tt>test-suite</tt></a>
1564 <p>This is not a directory in the normal llvm module; it is a separate
1566 module that must be checked out (usually to <tt>projects/test-suite</tt>).
1568 module contains a comprehensive correctness, performance, and benchmarking
1570 suite for LLVM. It is a separate Subversion module because not every LLVM
1572 interested in downloading or building such a comprehensive test suite. For
1573 further details on this test suite, please see the
1574 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1577 <!-- ======================================================================= -->
1579 <a name="tools"><tt>llvm/tools</tt></a>
1584 <p>The <b>tools</b> directory contains the executables built out of the
1585 libraries above, which form the main part of the user interface. You can
1586 always get help for a tool by typing <tt>tool_name -help</tt>. The
1587 following is a brief introduction to the most important tools. More detailed
1588 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1592 <dt><tt><b>bugpoint</b></tt></dt>
1593 <dd><tt>bugpoint</tt> is used to debug
1594 optimization passes or code generation backends by narrowing down the
1595 given test case to the minimum number of passes and/or instructions that
1596 still cause a problem, whether it is a crash or miscompilation. See <a
1597 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1598 on using <tt>bugpoint</tt>.</dd>
1600 <dt><tt><b>llvm-ar</b></tt></dt>
1601 <dd>The archiver produces an archive containing
1602 the given LLVM bitcode files, optionally with an index for faster
1605 <dt><tt><b>llvm-as</b></tt></dt>
1606 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1609 <dt><tt><b>llvm-dis</b></tt></dt>
1610 <dd>The disassembler transforms the LLVM bitcode to human readable
1613 <dt><tt><b>llvm-ld</b></tt></dt>
1614 <dd><tt>llvm-ld</tt> is a general purpose and extensible linker for LLVM.
1615 It performs standard link time optimizations and allows optimization
1616 modules to be loaded and run so that language specific optimizations can
1617 be applied at link time.</dd>
1619 <dt><tt><b>llvm-link</b></tt></dt>
1620 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1621 a single program.</dd>
1623 <dt><tt><b>lli</b></tt></dt>
1624 <dd><tt>lli</tt> is the LLVM interpreter, which
1625 can directly execute LLVM bitcode (although very slowly...). For architectures
1626 that support it (currently x86, Sparc, and PowerPC), by default, <tt>lli</tt>
1627 will function as a Just-In-Time compiler (if the functionality was compiled
1628 in), and will execute the code <i>much</i> faster than the interpreter.</dd>
1630 <dt><tt><b>llc</b></tt></dt>
1631 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1632 translates LLVM bitcode to a native code assembly file or to C code (with
1633 the -march=c option).</dd>
1635 <dt><tt><b>llvm-gcc</b></tt></dt>
1636 <dd><tt>llvm-gcc</tt> is a GCC-based C frontend that has been retargeted to
1637 use LLVM as its backend instead of GCC's RTL backend. It can also emit LLVM
1638 bitcode or assembly (with the <tt>-emit-llvm</tt> option) instead of the
1639 usual machine code output. It works just like any other GCC compiler,
1640 taking the typical <tt>-c, -S, -E, -o</tt> options that are typically used.
1641 Additionally, the the source code for <tt>llvm-gcc</tt> is available as a
1642 separate Subversion module.</dd>
1644 <dt><tt><b>opt</b></tt></dt>
1645 <dd><tt>opt</tt> reads LLVM bitcode, applies a series of LLVM to LLVM
1646 transformations (which are specified on the command line), and then outputs
1647 the resultant bitcode. The '<tt>opt -help</tt>' command is a good way to
1648 get a list of the program transformations available in LLVM.<br>
1649 <dd><tt>opt</tt> can also be used to run a specific analysis on an input
1650 LLVM bitcode file and print out the results. It is primarily useful for
1651 debugging analyses, or familiarizing yourself with what an analysis does.</dd>
1655 <!-- ======================================================================= -->
1657 <a name="utils"><tt>llvm/utils</tt></a>
1662 <p>This directory contains utilities for working with LLVM source code, and some
1663 of the utilities are actually required as part of the build process because they
1664 are code generators for parts of LLVM infrastructure.</p>
1667 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1668 that finds differences between code that LLC generates and code that LLI
1669 generates. This is a useful tool if you are debugging one of them,
1670 assuming that the other generates correct output. For the full user
1671 manual, run <tt>`perldoc codegen-diff'</tt>.<br><br>
1673 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1674 syntax-highlighting files which will work with Emacs and XEmacs editors,
1675 providing syntax highlighting support for LLVM assembly files and TableGen
1676 description files. For information on how to use the syntax files, consult
1677 the <tt>README</tt> file in that directory.<br><br>
1679 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1680 and outputs all non-generated source files, which is useful if one wishes
1681 to do a lot of development across directories and does not want to
1682 individually find each file. One way to use it is to run, for example:
1683 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1686 <dt><tt><b>llvmgrep</b></tt></dt>
1687 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1688 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1689 line. This is a very efficient way of searching the source base for a
1690 particular regular expression.</dd>
1692 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1693 files in the current directory and then compiles and links the tool that
1694 is the first argument. For example, assuming you are in the directory
1695 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1696 simply running <tt>makellvm llc</tt> will make a build of the current
1697 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1698 causing a re-linking of LLC.<br><br>
1700 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1701 the tool used to generate register descriptions, instruction set
1702 descriptions, and even assemblers from common TableGen description
1705 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1706 syntax-highlighting files which will work with the VIM editor, providing
1707 syntax highlighting support for LLVM assembly files and TableGen
1708 description files. For information on how to use the syntax files, consult
1709 the <tt>README</tt> file in that directory.<br><br>
1717 <!-- *********************************************************************** -->
1719 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1721 <!-- *********************************************************************** -->
1724 <p>This section gives an example of using LLVM. llvm-gcc3 is now obsolete,
1725 so we only include instructions for llvm-gcc4.
1728 <p><b>Note:</b> The <i>gcc4</i> frontend's invocation is <b><i>considerably different</i></b>
1729 from the previous <i>gcc3</i> frontend. In particular, the <i>gcc4</i> frontend <b><i>does not</i></b>
1730 create bitcode by default: <i>gcc4</i> produces native code. As the example below illustrates,
1731 the '--emit-llvm' flag is needed to produce LLVM bitcode output. For <i>makefiles</i> and
1732 <i>configure</i> scripts, the CFLAGS variable needs '--emit-llvm' to produce bitcode
1735 <!-- ======================================================================= -->
1737 <a name="tutorial4">Example with llvm-gcc4</a>
1743 <li><p>First, create a simple C file, name it 'hello.c':</p>
1745 <div class="doc_code">
1747 #include <stdio.h>
1750 printf("hello world\n");
1755 <li><p>Next, compile the C file into a native executable:</p>
1757 <div class="doc_code"><pre>% llvm-gcc hello.c -o hello</pre></div>
1759 <p>Note that llvm-gcc works just like GCC by default. The standard -S and
1760 -c arguments work as usual (producing a native .s or .o file,
1761 respectively).</p></li>
1763 <li><p>Next, compile the C file into a LLVM bitcode file:</p>
1765 <div class="doc_code">
1766 <pre>% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc</pre></div>
1768 <p>The -emit-llvm option can be used with the -S or -c options to emit an
1769 LLVM ".ll" or ".bc" file (respectively) for the code. This allows you
1770 to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
1771 the bitcode file.</p>
1773 <p>Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
1776 <li><p>Run the program in both forms. To run the program, use:</p>
1778 <div class="doc_code"><pre>% ./hello</pre></div>
1782 <div class="doc_code"><pre>% lli hello.bc</pre></div>
1784 <p>The second examples shows how to invoke the LLVM JIT, <a
1785 href="CommandGuide/html/lli.html">lli</a>.</p></li>
1787 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1790 <div class="doc_code">
1791 <pre>llvm-dis < hello.bc | less</pre>
1794 <li><p>Compile the program to native assembly using the LLC code
1797 <div class="doc_code"><pre>% llc hello.bc -o hello.s</pre></div></li>
1799 <li><p>Assemble the native assembly language file into a program:</p>
1801 <div class="doc_code">
1803 <b>Solaris:</b> % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native
1805 <b>Others:</b> % gcc hello.s -o hello.native
1809 <li><p>Execute the native code program:</p>
1811 <div class="doc_code"><pre>% ./hello.native</pre></div>
1813 <p>Note that using llvm-gcc to compile directly to native code (i.e. when
1814 the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
1823 <!-- *********************************************************************** -->
1825 <a name="problems">Common Problems</a>
1827 <!-- *********************************************************************** -->
1831 <p>If you are having problems building or using LLVM, or if you have any other
1832 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1833 Asked Questions</a> page.</p>
1837 <!-- *********************************************************************** -->
1839 <a name="links">Links</a>
1841 <!-- *********************************************************************** -->
1845 <p>This document is just an <b>introduction</b> on how to use LLVM to do
1846 some simple things... there are many more interesting and complicated things
1847 that you can do that aren't documented here (but we'll gladly accept a patch
1848 if you want to write something up!). For more information about LLVM, check
1852 <li><a href="http://llvm.org/">LLVM homepage</a></li>
1853 <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1854 <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1855 that Uses LLVM</a></li>
1860 <!-- *********************************************************************** -->
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1869 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1870 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1871 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
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