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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 <!-- *********************************************************************** -->
78 <div class="doc_text">
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 the low level virtual machine. It contains an
86 assembler, disassembler, bitcode analyzer and bitcode optimizer. It
87 also contains basic regression tests that can be used to test the LLVM
88 tools and the GCC front end.</p>
90 <p>The second piece is the GCC front end. This component provides a version of
91 GCC that compiles C and C++ code into LLVM bitcode. Currently, the GCC front
92 end uses the GCC parser to convert code to LLVM. Once
93 compiled into LLVM bitcode, a program can be manipulated with the LLVM tools
94 from the LLVM suite.</p>
97 There is a third, optional piece called Test Suite. It is a suite of programs
98 with a testing harness that can be used to further test LLVM's functionality
104 <!-- *********************************************************************** -->
106 <a name="quickstart">Getting Started Quickly (A Summary)</a>
108 <!-- *********************************************************************** -->
110 <div class="doc_text">
112 <p>Here's the short story for getting up and running quickly with LLVM:</p>
115 <li>Read the documentation.</li>
116 <li>Read the documentation.</li>
117 <li>Remember that you were warned twice about reading the documentation.</li>
118 <li>Install the llvm-gcc-4.2 front end if you intend to compile C or C++
119 (see <a href="#installcf">Install the GCC Front End</a> for details):
121 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt></li>
122 <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf -</tt></li>
123 <li><tt><i>install-binutils-binary-from-MinGW</i></tt> (Windows only)</li>
124 <li>Note: If the binary extension is "<tt>.bz</tt>" use <tt>bunzip2</tt> instead of <tt>gunzip</tt>.</li>
125 <li>Note: On Windows, use <a href="http://www.7-zip.org/">7-Zip</a> or a similar archiving tool.</li>
126 <li>Add <tt>llvm-gcc</tt>'s "<tt>bin</tt>" directory to your <tt>PATH</tt> environment variable.</li>
129 <li>Get the LLVM Source Code
131 <li>With the distributed files (or use <a href="#checkout">SVN</a>):
133 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
134 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
139 <li><b>[Optional]</b> Get the Test Suite Source Code
141 <li>With the distributed files (or use <a href="#checkout">SVN</a>):
143 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
144 <li><tt>cd llvm/projects</tt>
145 <li><tt>gunzip --stdout llvm-test-<i>version</i>.tar.gz | tar -xvf -</tt>
146 <li><tt>mv llvm-test-<i>version</i> test-suite</tt>
152 <li>Configure the LLVM Build Environment
154 <li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
155 <li><tt><i>/path/to/llvm/</i>configure [options]</tt><br>
159 <li><tt>--prefix=<i>directory</i></tt>
160 <p>Specify for <i>directory</i> the full pathname of where you
161 want the LLVM tools and libraries to be installed (default
162 <tt>/usr/local</tt>).</p></li>
163 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
164 <p>Optionally, specify for <i>directory</i> the full pathname of the
165 C/C++ front end installation to use with this LLVM configuration. If
166 not specified, the PATH will be searched. This is only needed if you
167 want to run test-suite or do some special kinds of LLVM builds.</p></li>
168 <li><tt>--enable-spec2000=<i>directory</i></tt>
169 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
170 benchmarks should be available in
171 <tt><i>directory</i></tt>.</p></li>
175 <li>Build the LLVM Suite:
177 <li><tt>gmake -k |& tee gnumake.out
178 # this is csh or tcsh syntax</tt></li>
179 <li>If you get an "internal compiler error (ICE)" or test failures, see
180 <a href="#brokengcc">below</a>.</li>
185 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
186 detailed information on configuring and compiling LLVM. See <a
187 href="#environment">Setting Up Your Environment</a> for tips that simplify
188 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
189 Layout</a> to learn about the layout of the source code tree.</p>
193 <!-- *********************************************************************** -->
195 <a name="requirements">Requirements</a>
197 <!-- *********************************************************************** -->
199 <div class="doc_text">
201 <p>Before you begin to use the LLVM system, review the requirements given below.
202 This may save you some trouble by knowing ahead of time what hardware and
203 software you will need.</p>
207 <!-- ======================================================================= -->
209 <a name="hardware">Hardware</a>
212 <div class="doc_text">
214 <p>LLVM is known to work on the following platforms:</p>
216 <table cellpadding="3" summary="Known LLVM platforms">
224 <td>x86<sup><a href="#pf_1">1</a></sup></td>
229 <td>x86<sup><a href="#pf_1">1</a></sup></td>
239 <td>V9 (Ultrasparc)</td>
244 <td>x86<sup><a href="#pf_1">1</a></sup></td>
253 <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
258 <td>MacOS X<sup><a href="#pf_2">2</a>,<a href="#pf_9">9</a></sup></td>
263 <td>Cygwin/Win32</td>
264 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a>,
265 <a href="#pf_11">11</a></sup></td>
266 <td>GCC 3.4.X, binutils 2.20</td>
270 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,
271 <a href="#pf_8">8</a>, <a href="#pf_10">10</a>,
272 <a href="#pf_11">11</a></sup></td>
273 <td>GCC 3.4.X, binutils 2.20</td>
277 <p>LLVM has partial support for the following platforms:</p>
279 <table summary="LLVM partial platform support">
287 <td>x86<sup><a href="#pf_1">1</a></sup></td>
288 <td>Visual Studio 2005 SP1 or higher<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
290 <td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
295 <td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
301 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
306 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
307 <td>Itanium (IA-64)</td>
311 <td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
312 <td>Itanium (IA-64)</td>
318 <td>mingw-w64's GCC-4.5.x<sup><a href="#pf_12">12</a></sup></td>
324 <div class="doc_notes">
326 <li><a name="pf_1">Code generation supported for Pentium processors and
328 <li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
329 <li><a name="pf_3">No native code generation</a></li>
330 <li><a name="pf_4">Build is not complete: one or more tools do not link or function</a></li>
331 <li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
332 <li><a name="pf_6">The port is done using the MSYS shell.</a></li>
333 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
334 <li><a name="pf_8">Binutils 2.20 or later is required to build the assembler
335 generated by LLVM properly.</a></li>
336 <li><a name="pf_9">XCode 2.5 and gcc 4.0.1</a> (Apple Build 5370) will trip
337 internal LLVM assert messages when compiled for Release at optimization
338 levels greater than 0 (i.e., <i>"-O1"</i> and higher).
339 Add <i>OPTIMIZE_OPTION="-O0"</i> to the build command line
340 if compiling for LLVM Release or bootstrapping the LLVM toolchain.</li>
341 <li><a name="pf_10">For MSYS/MinGW on Windows, be sure to install the MSYS
342 version of the perl package, and be sure it appears in your path
343 before any Windows-based versions such as Strawberry Perl and
344 ActivePerl, as these have Windows-specifics that will cause the
345 build to fail.</a></li>
346 <li><a name="pf_11">To use LLVM modules on Win32-based system,
347 you may configure LLVM with <i>"--enable-shared"</i>.</a></li>
348 <li><a name="pf_12">To compile SPU backend, you need to add
349 <tt>"LDFLAGS=-Wl,--stack,16777216"</tt> to configure.</a></li>
353 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
354 mode, depending on the system (it is so large because of all the debugging
355 information and the fact that the libraries are statically linked into multiple
356 tools). If you do not need many of the tools and you are space-conscious, you
357 can pass <tt>ONLY_TOOLS="tools you need"</tt> to make. The Release build
358 requires considerably less space.</p>
360 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
361 guaranteed to do so. If compilation is successful, the LLVM utilities should be
362 able to assemble, disassemble, analyze, and optimize LLVM bitcode. Code
363 generation should work as well, although the generated native code may not work
364 on your platform.</p>
366 <p>The GCC front end is not very portable at the moment. If you want to get it
367 to work on another platform, you can download a copy of the source and <a
368 href="GCCFEBuildInstrs.html">try to compile it</a> on your platform.</p>
372 <!-- ======================================================================= -->
374 <a name="software">Software</a>
376 <div class="doc_text">
377 <p>Compiling LLVM requires that you have several software packages
378 installed. The table below lists those required packages. The Package column
379 is the usual name for the software package that LLVM depends on. The Version
380 column provides "known to work" versions of the package. The Notes column
381 describes how LLVM uses the package and provides other details.</p>
382 <table summary="Packages required to compile LLVM">
383 <tr><th>Package</th><th>Version</th><th>Notes</th></tr>
386 <td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
387 <td>3.79, 3.79.1</td>
388 <td>Makefile/build processor</td>
392 <td><a href="http://gcc.gnu.org/">GCC</a></td>
394 <td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
398 <td><a href="http://www.gnu.org/software/texinfo/">TeXinfo</a></td>
400 <td>For building the CFE</td>
404 <td><a href="http://subversion.tigris.org/project_packages.html">SVN</a></td>
406 <td>Subversion access to LLVM<sup><a href="#sf2">2</a></sup></td>
411 Are DejaGnu and expect obsolete?
412 Shall we mention Python? -->
415 <td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
417 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
421 <td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
423 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
427 <td><a href="http://expect.nist.gov/">expect</a></td>
429 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
433 <td><a href="http://www.perl.com/download.csp">perl</a></td>
435 <td>Nightly tester, utilities</td>
439 <td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
441 <td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
445 <td><a href="http://www.gnu.org/software/autoconf/">GNU Autoconf</a></td>
447 <td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
451 <td><a href="http://www.gnu.org/software/automake/">GNU Automake</a></td>
453 <td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
457 <td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
459 <td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
465 <div class="doc_notes">
467 <li><a name="sf1">Only the C and C++ languages are needed so there's no
468 need to build the other languages for LLVM's purposes.</a> See
469 <a href="#brokengcc">below</a> for specific version info.</li>
470 <li><a name="sf2">You only need Subversion if you intend to build from the
471 latest LLVM sources. If you're working from a release distribution, you
472 don't need Subversion.</a></li>
473 <li><a name="sf3">Only needed if you want to run the automated test
474 suite in the <tt>llvm/test</tt> directory.</a></li>
475 <li><a name="sf4">If you want to make changes to the configure scripts,
476 you will need GNU autoconf (2.60), and consequently, GNU M4 (version 1.4
477 or higher). You will also need automake (1.9.6). We only use aclocal
478 from that package.</a></li>
482 <p>Additionally, your compilation host is expected to have the usual
483 plethora of Unix utilities. Specifically:</p>
485 <li><b>ar</b> - archive library builder</li>
486 <li><b>bzip2*</b> - bzip2 command for distribution generation</li>
487 <li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
488 <li><b>chmod</b> - change permissions on a file</li>
489 <li><b>cat</b> - output concatenation utility</li>
490 <li><b>cp</b> - copy files</li>
491 <li><b>date</b> - print the current date/time </li>
492 <li><b>echo</b> - print to standard output</li>
493 <li><b>egrep</b> - extended regular expression search utility</li>
494 <li><b>find</b> - find files/dirs in a file system</li>
495 <li><b>grep</b> - regular expression search utility</li>
496 <li><b>gzip*</b> - gzip command for distribution generation</li>
497 <li><b>gunzip*</b> - gunzip command for distribution checking</li>
498 <li><b>install</b> - install directories/files </li>
499 <li><b>mkdir</b> - create a directory</li>
500 <li><b>mv</b> - move (rename) files</li>
501 <li><b>ranlib</b> - symbol table builder for archive libraries</li>
502 <li><b>rm</b> - remove (delete) files and directories</li>
503 <li><b>sed</b> - stream editor for transforming output</li>
504 <li><b>sh</b> - Bourne shell for make build scripts</li>
505 <li><b>tar</b> - tape archive for distribution generation</li>
506 <li><b>test</b> - test things in file system</li>
507 <li><b>unzip*</b> - unzip command for distribution checking</li>
508 <li><b>zip*</b> - zip command for distribution generation</li>
512 <!-- ======================================================================= -->
514 <a name="brokengcc">Broken versions of GCC and other tools</a>
517 <div class="doc_text">
519 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
520 bugs in the compiler. In particular, several versions of GCC crash when trying
521 to compile LLVM. We routinely use GCC 3.3.3, 3.4.0, and Apple 4.0.1
522 successfully with them (however, see important notes below). Other versions
523 of GCC will probably work as well. GCC versions listed
524 here are known to not work. If you are using one of these versions, please try
525 to upgrade your GCC to something more recent. If you run into a problem with a
526 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
527 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
528 of GCC you are using.
531 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
532 problems in the STL that effectively prevent it from compiling LLVM.
535 <p><b>GCC 3.2.2 and 3.2.3</b>: These versions of GCC fails to compile LLVM with
536 a bogus template error. This was fixed in later GCCs.</p>
538 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
539 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
540 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
542 <p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
543 Cygwin does not work. Please <a href="GCCFEBuildInstrs.html#cygwin">upgrade
544 to a newer version</a> if possible.</p>
545 <p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
546 possibly others) does not compile LLVM correctly (it appears that exception
547 handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
548 to a newer version of GCC.</p>
549 <p><b>GCC 3.4.0 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
550 code generator, causing an infinite loop in the llvm-gcc build when built
551 with optimizations enabled (i.e. a release build).</p>
552 <p><b>GCC 3.4.2 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
553 code generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0)
554 correctly compiles LLVM at -O2. A work around is to build release LLVM
555 builds with "make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ..."</p>
556 <p><b>GCC 3.4.x on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1056">
557 miscompiles portions of LLVM</a>.</p>
558 <p><b>GCC 3.4.4 (CodeSourcery ARM 2005q3-2)</b>: this compiler miscompiles LLVM
559 when building with optimizations enabled. It appears to work with
560 "<tt>make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1</tt>" or build a debug
562 <p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
564 <p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
565 default with ENABLE_OPTIMIZED=1. To work around this, build with
566 "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
567 <p><b>GCC 4.1.1</b>: GCC fails to build LLVM with template concept check errors
568 compiling some files. At the time of this writing, GCC mainline (4.2)
569 did not share the problem.</p>
570 <p><b>GCC 4.1.1 on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1063">
571 miscompiles portions of LLVM</a> when compiling llvm itself into 64-bit
572 code. LLVM will appear to mostly work but will be buggy, e.g. failing
573 portions of its testsuite.</p>
574 <p><b>GCC 4.1.2 on OpenSUSE</b>: Seg faults during libstdc++ build and on x86_64
575 platforms compiling md5.c gets a mangled constant.</p>
576 <p><b>GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian</b>: Appears
577 to miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining
578 about symbols remaining in the table on destruction.</p>
579 <p><b>GCC 4.1.2 20071124 (Red Hat 4.1.2-42)</b>: Suffers from the same symptoms
580 as the previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).</p>
581 <p><b>Cygwin GCC 4.3.2 20080827 (beta) 2</b>:
582 Users <a href="http://llvm.org/PR4145">reported</a> various problems related
583 with link errors when using this GCC version.</p>
584 <p><b>Debian GCC 4.3.2 on X86</b>: Crashes building some files in LLVM 2.6.</p>
585 <p><b>GCC 4.3.3 (Debian 4.3.3-10) on ARM</b>: Miscompiles parts of LLVM 2.6
586 when optimizations are turned on. The symptom is an infinite loop in
587 FoldingSetImpl::RemoveNode while running the code generator.</p>
588 <p><b>GCC 4.3.5 and GCC 4.4.5 on ARM</b>: These can miscompile <tt>value >>
589 1</tt> even at -O0. A test failure in <tt>test/Assembler/alignstack.ll</tt> is
590 one symptom of the problem.
591 <p><b>GNU ld 2.16.X</b>. Some 2.16.X versions of the ld linker will produce very
592 long warning messages complaining that some ".gnu.linkonce.t.*" symbol was
593 defined in a discarded section. You can safely ignore these messages as they are
594 erroneous and the linkage is correct. These messages disappear using ld
597 <p><b>GNU binutils 2.17</b>: Binutils 2.17 contains <a
598 href="http://sourceware.org/bugzilla/show_bug.cgi?id=3111">a bug</a> which
599 causes huge link times (minutes instead of seconds) when building LLVM. We
600 recommend upgrading to a newer version (2.17.50.0.4 or later).</p>
602 <p><b>GNU Binutils 2.19.1 Gold</b>: This version of Gold contained
603 <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=9836">a bug</a>
604 which causes intermittent failures when building LLVM with position independent
605 code. The symptom is an error about cyclic dependencies. We recommend
606 upgrading to a newer version of Gold.</p>
612 <!-- *********************************************************************** -->
614 <a name="starting">Getting Started with LLVM</a>
616 <!-- *********************************************************************** -->
618 <div class="doc_text">
620 <p>The remainder of this guide is meant to get you up and running with
621 LLVM and to give you some basic information about the LLVM environment.</p>
623 <p>The later sections of this guide describe the <a
624 href="#layout">general layout</a> of the the LLVM source tree, a <a
625 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
626 href="#links">links</a> to find more information about LLVM or to get
630 <!-- ======================================================================= -->
632 <a name="terminology">Terminology and Notation</a>
635 <div class="doc_text">
637 <p>Throughout this manual, the following names are used to denote paths
638 specific to the local system and working environment. <i>These are not
639 environment variables you need to set but just strings used in the rest
640 of this document below</i>. In any of the examples below, simply replace
641 each of these names with the appropriate pathname on your local system.
642 All these paths are absolute:</p>
647 This is the top level directory of the LLVM source tree.
652 This is the top level directory of the LLVM object tree (i.e. the
653 tree where object files and compiled programs will be placed. It
654 can be the same as SRC_ROOT).
659 This is where the LLVM GCC Front End is installed.
661 For the pre-built GCC front end binaries, the LLVMGCCDIR is
662 <tt>llvm-gcc/<i>platform</i>/llvm-gcc</tt>.
667 <!-- ======================================================================= -->
669 <a name="environment">Setting Up Your Environment</a>
672 <div class="doc_text">
675 In order to compile and use LLVM, you may need to set some environment
679 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bitcode/libs</tt></dt>
680 <dd>[Optional] This environment variable helps LLVM linking tools find the
681 locations of your bitcode libraries. It is provided only as a
682 convenience since you can specify the paths using the -L options of the
683 tools and the C/C++ front-end will automatically use the bitcode files
685 <tt>lib</tt> directory.</dd>
690 <!-- ======================================================================= -->
692 <a name="unpack">Unpacking the LLVM Archives</a>
695 <div class="doc_text">
698 If you have the LLVM distribution, you will need to unpack it before you
699 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
700 suite and the LLVM GCC front end compiled for your platform. There is an
701 additional test suite that is optional. Each file is a TAR archive that is
702 compressed with the gzip program.
705 <p>The files are as follows, with <em>x.y</em> marking the version number:
707 <dt><tt>llvm-x.y.tar.gz</tt></dt>
708 <dd>Source release for the LLVM libraries and tools.<br></dd>
710 <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
711 <dd>Source release for the LLVM test-suite.</dd>
713 <dt><tt>llvm-gcc-4.2-x.y.source.tar.gz</tt></dt>
714 <dd>Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
715 directory for build instructions.<br></dd>
717 <dt><tt>llvm-gcc-4.2-x.y-platform.tar.gz</tt></dt>
718 <dd>Binary release of the llvm-gcc-4.2 front end for a specific platform.<br></dd>
724 <!-- ======================================================================= -->
726 <a name="checkout">Checkout LLVM from Subversion</a>
729 <div class="doc_text">
731 <p>If you have access to our Subversion repository, you can get a fresh copy of
732 the entire source code. All you need to do is check it out from Subversion as
736 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
737 <li>Read-Only: <tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
738 <li>Read-Write:<tt>svn co https://user@llvm.org/svn/llvm-project/llvm/trunk
743 <p>This will create an '<tt>llvm</tt>' directory in the current
744 directory and fully populate it with the LLVM source code, Makefiles,
745 test directories, and local copies of documentation files.</p>
747 <p>If you want to get a specific release (as opposed to the most recent
748 revision), you can checkout it from the '<tt>tags</tt>' directory (instead of
749 '<tt>trunk</tt>'). The following releases are located in the following
750 subdirectories of the '<tt>tags</tt>' directory:</p>
753 <li>Release 2.9: <b>RELEASE_29/final</b></li>
754 <li>Release 2.8: <b>RELEASE_28</b></li>
755 <li>Release 2.7: <b>RELEASE_27</b></li>
756 <li>Release 2.6: <b>RELEASE_26</b></li>
757 <li>Release 2.5: <b>RELEASE_25</b></li>
758 <li>Release 2.4: <b>RELEASE_24</b></li>
759 <li>Release 2.3: <b>RELEASE_23</b></li>
760 <li>Release 2.2: <b>RELEASE_22</b></li>
761 <li>Release 2.1: <b>RELEASE_21</b></li>
762 <li>Release 2.0: <b>RELEASE_20</b></li>
763 <li>Release 1.9: <b>RELEASE_19</b></li>
764 <li>Release 1.8: <b>RELEASE_18</b></li>
765 <li>Release 1.7: <b>RELEASE_17</b></li>
766 <li>Release 1.6: <b>RELEASE_16</b></li>
767 <li>Release 1.5: <b>RELEASE_15</b></li>
768 <li>Release 1.4: <b>RELEASE_14</b></li>
769 <li>Release 1.3: <b>RELEASE_13</b></li>
770 <li>Release 1.2: <b>RELEASE_12</b></li>
771 <li>Release 1.1: <b>RELEASE_11</b></li>
772 <li>Release 1.0: <b>RELEASE_1</b></li>
775 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
776 you get it from the Subversion repository:</p>
778 <div class="doc_code">
781 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
785 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
786 configured by the LLVM configure script as well as automatically updated when
787 you run <tt>svn update</tt>.</p>
789 <p>If you would like to get the GCC front end source code, you can also get it
790 and build it yourself. Please follow <a href="GCCFEBuildInstrs.html">these
791 instructions</a> to successfully get and build the LLVM GCC front-end.</p>
795 <!-- ======================================================================= -->
797 <a name="git_mirror">GIT mirror</a>
800 <div class="doc_text">
802 <p>GIT mirrors are available for a number of LLVM subprojects. These mirrors
803 sync automatically with each Subversion commit and contain all necessary
804 git-svn marks (so, you can recreate git-svn metadata locally). Note that right
805 now mirrors reflect only <tt>trunk</tt> for each project. You can do the
806 read-only GIT clone of LLVM via:</p>
809 % git clone http://llvm.org/git/llvm.git
814 <!-- ======================================================================= -->
816 <a name="installcf">Install the GCC Front End</a>
819 <div class="doc_text">
821 <p>Before configuring and compiling the LLVM suite (or if you want to use just the LLVM
822 GCC front end) you can optionally extract the front end from the binary distribution.
823 It is used for running the LLVM test-suite and for compiling C/C++ programs. Note that
824 you can optionally <a href="GCCFEBuildInstrs.html">build llvm-gcc yourself</a> after building the
825 main LLVM repository.</p>
827 <p>To install the GCC front end, do the following (on Windows, use an archival tool
828 like <a href="http://www.7-zip.org/">7-zip</a> that understands gzipped tars):</p>
831 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
832 <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf
836 <p>Once the binary is uncompressed, if you're using a *nix-based system, add a symlink for
837 <tt>llvm-gcc</tt> and <tt>llvm-g++</tt> to some directory in your path. If you're using a
838 Windows-based system, add the <tt>bin</tt> subdirectory of your front end installation directory
839 to your <tt>PATH</tt> environment variable. For example, if you uncompressed the binary to
840 <tt>c:\llvm-gcc</tt>, add <tt>c:\llvm-gcc\bin</tt> to your <tt>PATH</tt>.</p>
842 <p>If you now want to build LLVM from source, when you configure LLVM, it will
843 automatically detect <tt>llvm-gcc</tt>'s presence (if it is in your path) enabling its
844 use in test-suite. Note that you can always build or install <tt>llvm-gcc</tt> at any
845 point after building the main LLVM repository: just reconfigure llvm and
846 test-suite will pick it up.
849 <p>As a convenience for Windows users, the front end binaries for MinGW/x86 include
850 versions of the required w32api and mingw-runtime binaries. The last remaining step for
851 Windows users is to simply uncompress the binary binutils package from
852 <a href="http://mingw.org/">MinGW</a> into your front end installation directory. While the
853 front end installation steps are not quite the same as a typical manual MinGW installation,
854 they should be similar enough to those who have previously installed MinGW on Windows systems.</p>
856 <p>To install binutils on Windows:</p>
859 <li><tt><i>download GNU Binutils from <a href="http://sourceforge.net/projects/mingw/files/">MinGW Downloads</a></i></tt></li>
860 <li><tt>cd <i>where-you-uncompressed-the-front-end</i></tt></li>
861 <li><tt><i>uncompress archived binutils directories (not the tar file) into the current directory</i></tt></li>
864 <p>The binary versions of the LLVM GCC front end may not suit all of your needs. For
865 example, the binary distribution may include an old version of a system header
866 file, not "fix" a header file that needs to be fixed for GCC, or it may be linked with
867 libraries not available on your system. In cases like these, you may want to try
868 <a href="GCCFEBuildInstrs.html">building the GCC front end from source</a>. Thankfully,
869 this is much easier now than it was in the past.</p>
871 <p>We also do not currently support updating of the GCC front end by manually overlaying
872 newer versions of the w32api and mingw-runtime binary packages that may become available
873 from MinGW. At this time, it's best to think of the MinGW LLVM GCC front end binary as
874 a self-contained convenience package that requires Windows users to simply download and
875 uncompress the GNU Binutils binary package from the MinGW project.</p>
877 <p>Regardless of your platform, if you discover that installing the LLVM GCC front end
878 binaries is not as easy as previously described, or you would like to suggest improvements,
879 please let us know how you would like to see things improved by dropping us a note on our
880 <a href="http://llvm.org/docs/#maillist">mailing list</a>.</p>
884 <!-- ======================================================================= -->
886 <a name="config">Local LLVM Configuration</a>
889 <div class="doc_text">
891 <p>Once checked out from the Subversion repository, the LLVM suite source
893 configured via the <tt>configure</tt> script. This script sets variables in the
894 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
895 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
896 the Makefiles needed to begin building LLVM.</p>
898 <p>The following environment variables are used by the <tt>configure</tt>
899 script to configure the build system:</p>
901 <table summary="LLVM configure script environment variables">
902 <tr><th>Variable</th><th>Purpose</th></tr>
905 <td>Tells <tt>configure</tt> which C compiler to use. By default,
906 <tt>configure</tt> will look for the first GCC C compiler in
907 <tt>PATH</tt>. Use this variable to override
908 <tt>configure</tt>'s default behavior.</td>
912 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
913 <tt>configure</tt> will look for the first GCC C++ compiler in
914 <tt>PATH</tt>. Use this variable to override
915 <tt>configure</tt>'s default behavior.</td>
919 <p>The following options can be used to set or enable LLVM specific options:</p>
922 <dt><i>--with-llvmgccdir</i></dt>
923 <dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
924 The value of this option should specify the full pathname of the C/C++ Front
925 End to be used. If this option is not provided, the PATH will be searched for
926 a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
927 be inferred from the path found. If the option is not given, and no llvm-gcc
928 can be found in the path then a warning will be produced by
929 <tt>configure</tt> indicating this situation. LLVM may still be built with
930 the <tt>tools-only</tt> target but attempting to build the runtime libraries
931 will fail as these libraries require llvm-gcc and llvm-g++. See
932 <a href="#installcf">Install the GCC Front End</a> for details on installing
933 the C/C++ Front End. See
934 <a href="GCCFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
935 for details on building the C/C++ Front End.</dd>
936 <dt><i>--with-tclinclude</i></dt>
937 <dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
938 found. Use this if you have multiple tcl installations on your machine and you
939 want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
940 dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
941 option, the LLVM configure script will search for the tcl 8.4 and 8.3
945 <dt><i>--enable-optimized</i></dt>
947 Enables optimized compilation (debugging symbols are removed
948 and GCC optimization flags are enabled). Note that this is the default
949 setting if you are using the LLVM distribution. The default behavior
950 of an Subversion checkout is to use an unoptimized build (also known as a
954 <dt><i>--enable-debug-runtime</i></dt>
956 Enables debug symbols in the runtime libraries. The default is to strip
957 debug symbols from the runtime libraries.
959 <dt><i>--enable-jit</i></dt>
961 Compile the Just In Time (JIT) compiler functionality. This is not
963 on all platforms. The default is dependent on platform, so it is best
964 to explicitly enable it if you want it.
967 <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
968 <dd>Controls which targets will be built and linked into llc. The default
969 value for <tt>target_options</tt> is "all" which builds and links all
970 available targets. The value "host-only" can be specified to build only a
971 native compiler (no cross-compiler targets available). The "native" target is
972 selected as the target of the build host. You can also specify a comma
973 separated list of target names that you want available in llc. The target
974 names use all lower case. The current set of targets is: <br>
975 <tt>alpha, ia64, powerpc, skeleton, sparc, x86</tt>.
977 <dt><i>--enable-doxygen</i></dt>
978 <dd>Look for the doxygen program and enable construction of doxygen based
979 documentation from the source code. This is disabled by default because
980 generating the documentation can take a long time and producess 100s of
981 megabytes of output.</dd>
982 <dt><i>--with-udis86</i></dt>
983 <dd>LLVM can use external disassembler library for various purposes (now it's
984 used only for examining code produced by JIT). This option will enable usage
985 of <a href="http://udis86.sourceforge.net/">udis86</a> x86 (both 32 and 64
986 bits) disassembler library.</dd>
989 <p>To configure LLVM, follow these steps:</p>
992 <li><p>Change directory into the object root directory:</p>
994 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
996 <li><p>Run the <tt>configure</tt> script located in the LLVM source
999 <div class="doc_code">
1000 <pre>% <i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</pre>
1006 <!-- ======================================================================= -->
1008 <a name="compile">Compiling the LLVM Suite Source Code</a>
1011 <div class="doc_text">
1013 <p>Once you have configured LLVM, you can build it. There are three types of
1019 These builds are the default when one is using an Subversion checkout and
1020 types <tt>gmake</tt> (unless the <tt>--enable-optimized</tt> option was
1021 used during configuration). The build system will compile the tools and
1022 libraries with debugging information. To get a Debug Build using the
1023 LLVM distribution the <tt>--disable-optimized</tt> option must be passed
1024 to <tt>configure</tt>.
1027 <dt>Release (Optimized) Builds
1029 These builds are enabled with the <tt>--enable-optimized</tt> option to
1030 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
1031 <tt>gmake</tt> command line. For these builds, the build system will
1032 compile the tools and libraries with GCC optimizations enabled and strip
1033 debugging information from the libraries and executables it generates.
1034 Note that Release Builds are default when using an LLVM distribution.
1039 These builds are for use with profiling. They compile profiling
1040 information into the code for use with programs like <tt>gprof</tt>.
1041 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
1042 on the <tt>gmake</tt> command line.
1045 <p>Once you have LLVM configured, you can build it by entering the
1046 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
1048 <div class="doc_code"><pre>% gmake</pre></div>
1050 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
1051 are using a version of GCC that is known not to compile LLVM.</p>
1054 If you have multiple processors in your machine, you may wish to use some of
1055 the parallel build options provided by GNU Make. For example, you could use the
1058 <div class="doc_code"><pre>% gmake -j2</pre></div>
1060 <p>There are several special targets which are useful when working with the LLVM
1064 <dt><tt>gmake clean</tt>
1066 Removes all files generated by the build. This includes object files,
1067 generated C/C++ files, libraries, and executables.
1070 <dt><tt>gmake dist-clean</tt>
1072 Removes everything that <tt>gmake clean</tt> does, but also removes files
1073 generated by <tt>configure</tt>. It attempts to return the source tree to the
1074 original state in which it was shipped.
1077 <dt><tt>gmake install</tt>
1079 Installs LLVM header files, libraries, tools, and documentation in a
1081 under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
1082 defaults to <tt>/usr/local</tt>.
1085 <dt><tt>gmake -C runtime install-bytecode</tt>
1087 Assuming you built LLVM into $OBJDIR, when this command is run, it will
1088 install bitcode libraries into the GCC front end's bitcode library
1089 directory. If you need to update your bitcode libraries,
1090 this is the target to use once you've built them.
1094 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
1095 details on these <tt>make</tt> targets and descriptions of other targets
1098 <p>It is also possible to override default values from <tt>configure</tt> by
1099 declaring variables on the command line. The following are some examples:</p>
1102 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
1104 Perform a Release (Optimized) build.
1107 <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
1109 Perform a Release (Optimized) build without assertions enabled.
1112 <dt><tt>gmake ENABLE_OPTIMIZED=0</tt>
1114 Perform a Debug build.
1117 <dt><tt>gmake ENABLE_PROFILING=1</tt>
1119 Perform a Profiling build.
1122 <dt><tt>gmake VERBOSE=1</tt>
1124 Print what <tt>gmake</tt> is doing on standard output.
1127 <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
1128 <dd>Ask each tool invoked by the makefiles to print out what it is doing on
1129 the standard output. This also implies <tt>VERBOSE=1</tt>.
1133 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
1134 it and any subdirectories that it contains. Entering any directory inside the
1135 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
1136 that directory that is out of date.</p>
1140 <!-- ======================================================================= -->
1142 <a name="cross-compile">Cross-Compiling LLVM</a>
1145 <div class="doc_text">
1146 <p>It is possible to cross-compile LLVM itself. That is, you can create LLVM
1147 executables and libraries to be hosted on a platform different from the
1148 platform where they are build (a Canadian Cross build). To configure a
1149 cross-compile, supply the configure script with <tt>--build</tt> and
1150 <tt>--host</tt> options that are different. The values of these options must
1151 be legal target triples that your GCC compiler supports.</p>
1153 <p>The result of such a build is executables that are not runnable on
1154 on the build host (--build option) but can be executed on the compile host
1155 (--host option).</p>
1158 <!-- ======================================================================= -->
1160 <a name="objfiles">The Location of LLVM Object Files</a>
1163 <div class="doc_text">
1165 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1166 several LLVM builds. Hence, it is possible to build LLVM for several different
1167 platforms or configurations using the same source tree.</p>
1169 <p>This is accomplished in the typical autoconf manner:</p>
1172 <li><p>Change directory to where the LLVM object files should live:</p>
1174 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1176 <li><p>Run the <tt>configure</tt> script found in the LLVM source
1179 <div class="doc_code"><pre>% <i>SRC_ROOT</i>/configure</pre></div></li>
1182 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1183 named after the build type:</p>
1186 <dt>Debug Builds with assertions enabled (the default)
1190 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/bin</tt>
1192 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/lib</tt>
1200 <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1202 <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1210 <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1212 <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1218 <!-- ======================================================================= -->
1220 <a name="optionalconfig">Optional Configuration Items</a>
1223 <div class="doc_text">
1226 If you're running on a Linux system that supports the "<a
1227 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
1228 module, and you have root access on the system, you can set your system up to
1229 execute LLVM bitcode files directly. To do this, use commands like this (the
1230 first command may not be required if you are already using the module):</p>
1232 <div class="doc_code">
1234 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1235 $ echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1236 $ chmod u+x hello.bc (if needed)
1242 This allows you to execute LLVM bitcode files directly. On Debian, you
1243 can also use this command instead of the 'echo' command above:
1246 <div class="doc_code">
1248 $ sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1254 <!-- *********************************************************************** -->
1256 <a name="layout">Program Layout</a>
1258 <!-- *********************************************************************** -->
1260 <div class="doc_text">
1262 <p>One useful source of information about the LLVM source base is the LLVM <a
1263 href="http://www.doxygen.org/">doxygen</a> documentation available at <tt><a
1264 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1265 The following is a brief introduction to code layout:</p>
1269 <!-- ======================================================================= -->
1271 <a name="examples"><tt>llvm/examples</tt></a>
1274 <div class="doc_text">
1275 <p>This directory contains some simple examples of how to use the LLVM IR and
1279 <!-- ======================================================================= -->
1281 <a name="include"><tt>llvm/include</tt></a>
1284 <div class="doc_text">
1286 <p>This directory contains public header files exported from the LLVM
1287 library. The three main subdirectories of this directory are:</p>
1290 <dt><tt><b>llvm/include/llvm</b></tt></dt>
1291 <dd>This directory contains all of the LLVM specific header files. This
1292 directory also has subdirectories for different portions of LLVM:
1293 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1296 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1297 <dd>This directory contains generic support libraries that are provided with
1298 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1299 and a Command Line option processing library store their header files here.
1302 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1303 <dd>This directory contains header files configured by the <tt>configure</tt>
1304 script. They wrap "standard" UNIX and C header files. Source code can
1305 include these header files which automatically take care of the conditional
1306 #includes that the <tt>configure</tt> script generates.</dd>
1310 <!-- ======================================================================= -->
1312 <a name="lib"><tt>llvm/lib</tt></a>
1315 <div class="doc_text">
1317 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1318 almost all code exists in libraries, making it very easy to share code among the
1319 different <a href="#tools">tools</a>.</p>
1322 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1323 <dd> This directory holds the core LLVM source files that implement core
1324 classes like Instruction and BasicBlock.</dd>
1326 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1327 <dd>This directory holds the source code for the LLVM assembly language parser
1330 <dt><tt><b>llvm/lib/BitCode/</b></tt></dt>
1331 <dd>This directory holds code for reading and write LLVM bitcode.</dd>
1333 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1334 different program analyses, such as Dominator Information, Call Graphs,
1335 Induction Variables, Interval Identification, Natural Loop Identification,
1338 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1339 <dd> This directory contains the source code for the LLVM to LLVM program
1340 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1341 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1342 Elimination, and many others.</dd>
1344 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1345 <dd> This directory contains files that describe various target architectures
1346 for code generation. For example, the <tt>llvm/lib/Target/X86</tt>
1347 directory holds the X86 machine description while
1348 <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
1350 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1351 <dd> This directory contains the major parts of the code generator: Instruction
1352 Selector, Instruction Scheduling, and Register Allocation.</dd>
1354 <dt><tt><b>llvm/lib/MC/</b></tt></dt>
1355 <dd>(FIXME: T.B.D.)</dd>
1357 <!--FIXME: obsoleted -->
1358 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1359 <dd> This directory contains the source level debugger library that makes
1360 it possible to instrument LLVM programs so that a debugger could identify
1361 source code locations at which the program is executing.</dd>
1363 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1364 <dd> This directory contains libraries for executing LLVM bitcode directly
1365 at runtime in both interpreted and JIT compiled fashions.</dd>
1367 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1368 <dd> This directory contains the source code that corresponds to the header
1369 files located in <tt>llvm/include/Support/</tt>.</dd>
1371 <!--FIXME: obsoleted -->
1372 <dt><tt><b>llvm/lib/System/</b></tt></dt>
1373 <dd>This directory contains the operating system abstraction layer that
1374 shields LLVM from platform-specific coding.</dd>
1379 <!-- ======================================================================= -->
1381 <a name="projects"><tt>llvm/projects</tt></a>
1384 <div class="doc_text">
1385 <p>This directory contains projects that are not strictly part of LLVM but are
1386 shipped with LLVM. This is also the directory where you should create your own
1387 LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1388 to set up your own project.</p>
1391 <!-- ======================================================================= -->
1393 <a name="runtime"><tt>llvm/runtime</tt></a>
1396 <div class="doc_text">
1398 <p>This directory contains libraries which are compiled into LLVM bitcode and
1399 used when linking programs with the GCC front end. Most of these libraries are
1400 skeleton versions of real libraries; for example, libc is a stripped down
1401 version of glibc.</p>
1403 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1408 <!-- ======================================================================= -->
1410 <a name="test"><tt>llvm/test</tt></a>
1413 <div class="doc_text">
1414 <p>This directory contains feature and regression tests and other basic sanity
1415 checks on the LLVM infrastructure. These are intended to run quickly and cover
1416 a lot of territory without being exhaustive.</p>
1419 <!-- ======================================================================= -->
1421 <a name="test-suite"><tt>test-suite</tt></a>
1424 <div class="doc_text">
1425 <p>This is not a directory in the normal llvm module; it is a separate
1427 module that must be checked out (usually to <tt>projects/test-suite</tt>).
1429 module contains a comprehensive correctness, performance, and benchmarking
1431 suite for LLVM. It is a separate Subversion module because not every LLVM
1433 interested in downloading or building such a comprehensive test suite. For
1434 further details on this test suite, please see the
1435 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1438 <!-- ======================================================================= -->
1440 <a name="tools"><tt>llvm/tools</tt></a>
1443 <div class="doc_text">
1445 <p>The <b>tools</b> directory contains the executables built out of the
1446 libraries above, which form the main part of the user interface. You can
1447 always get help for a tool by typing <tt>tool_name -help</tt>. The
1448 following is a brief introduction to the most important tools. More detailed
1449 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1453 <dt><tt><b>bugpoint</b></tt></dt>
1454 <dd><tt>bugpoint</tt> is used to debug
1455 optimization passes or code generation backends by narrowing down the
1456 given test case to the minimum number of passes and/or instructions that
1457 still cause a problem, whether it is a crash or miscompilation. See <a
1458 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1459 on using <tt>bugpoint</tt>.</dd>
1461 <dt><tt><b>llvmc</b></tt></dt>
1462 <dd>The LLVM Compiler Driver. This program can
1463 be configured to utilize both LLVM and non-LLVM compilation tools to enable
1464 pre-processing, translation, optimization, assembly, and linking of programs
1465 all from one command line. <tt>llvmc</tt> also takes care of processing the
1466 dependent libraries found in bitcode. This reduces the need to get the
1467 traditional <tt>-l<name></tt> options right on the command line. Please
1468 note that this tool, while functional, is still experimental and not feature
1471 <dt><tt><b>llvm-ar</b></tt></dt>
1472 <dd>The archiver produces an archive containing
1473 the given LLVM bitcode files, optionally with an index for faster
1476 <dt><tt><b>llvm-as</b></tt></dt>
1477 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1480 <dt><tt><b>llvm-dis</b></tt></dt>
1481 <dd>The disassembler transforms the LLVM bitcode to human readable
1484 <dt><tt><b>llvm-ld</b></tt></dt>
1485 <dd><tt>llvm-ld</tt> is a general purpose and extensible linker for LLVM.
1486 This is the linker invoked by <tt>llvmc</tt>. It performs standard link time
1487 optimizations and allows optimization modules to be loaded and run so that
1488 language specific optimizations can be applied at link time.</dd>
1490 <dt><tt><b>llvm-link</b></tt></dt>
1491 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1492 a single program.</dd>
1494 <dt><tt><b>lli</b></tt></dt>
1495 <dd><tt>lli</tt> is the LLVM interpreter, which
1496 can directly execute LLVM bitcode (although very slowly...). For architectures
1497 that support it (currently x86, Sparc, and PowerPC), by default, <tt>lli</tt>
1498 will function as a Just-In-Time compiler (if the functionality was compiled
1499 in), and will execute the code <i>much</i> faster than the interpreter.</dd>
1501 <dt><tt><b>llc</b></tt></dt>
1502 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1503 translates LLVM bitcode to a native code assembly file or to C code (with
1504 the -march=c option).</dd>
1506 <dt><tt><b>llvm-gcc</b></tt></dt>
1507 <dd><tt>llvm-gcc</tt> is a GCC-based C frontend that has been retargeted to
1508 use LLVM as its backend instead of GCC's RTL backend. It can also emit LLVM
1509 bitcode or assembly (with the <tt>-emit-llvm</tt> option) instead of the
1510 usual machine code output. It works just like any other GCC compiler,
1511 taking the typical <tt>-c, -S, -E, -o</tt> options that are typically used.
1512 Additionally, the the source code for <tt>llvm-gcc</tt> is available as a
1513 separate Subversion module.</dd>
1515 <dt><tt><b>opt</b></tt></dt>
1516 <dd><tt>opt</tt> reads LLVM bitcode, applies a series of LLVM to LLVM
1517 transformations (which are specified on the command line), and then outputs
1518 the resultant bitcode. The '<tt>opt -help</tt>' command is a good way to
1519 get a list of the program transformations available in LLVM.<br>
1520 <dd><tt>opt</tt> can also be used to run a specific analysis on an input
1521 LLVM bitcode file and print out the results. It is primarily useful for
1522 debugging analyses, or familiarizing yourself with what an analysis does.</dd>
1526 <!-- ======================================================================= -->
1528 <a name="utils"><tt>llvm/utils</tt></a>
1531 <div class="doc_text">
1533 <p>This directory contains utilities for working with LLVM source code, and some
1534 of the utilities are actually required as part of the build process because they
1535 are code generators for parts of LLVM infrastructure.</p>
1538 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1539 that finds differences between code that LLC generates and code that LLI
1540 generates. This is a useful tool if you are debugging one of them,
1541 assuming that the other generates correct output. For the full user
1542 manual, run <tt>`perldoc codegen-diff'</tt>.<br><br>
1544 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1545 syntax-highlighting files which will work with Emacs and XEmacs editors,
1546 providing syntax highlighting support for LLVM assembly files and TableGen
1547 description files. For information on how to use the syntax files, consult
1548 the <tt>README</tt> file in that directory.<br><br>
1550 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1551 and outputs all non-generated source files, which is useful if one wishes
1552 to do a lot of development across directories and does not want to
1553 individually find each file. One way to use it is to run, for example:
1554 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1557 <dt><tt><b>llvmgrep</b></tt></dt>
1558 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1559 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1560 line. This is a very efficient way of searching the source base for a
1561 particular regular expression.</dd>
1563 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1564 files in the current directory and then compiles and links the tool that
1565 is the first argument. For example, assuming you are in the directory
1566 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1567 simply running <tt>makellvm llc</tt> will make a build of the current
1568 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1569 causing a re-linking of LLC.<br><br>
1571 <dt><tt><b>NewNightlyTest.pl</b></tt> and
1572 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1573 cron script to generate nightly status reports of the functionality of
1574 tools, and the results can be seen by following the appropriate link on
1575 the <a href="http://llvm.org/">LLVM homepage</a>.<br><br>
1577 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1578 the tool used to generate register descriptions, instruction set
1579 descriptions, and even assemblers from common TableGen description
1582 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1583 syntax-highlighting files which will work with the VIM editor, providing
1584 syntax highlighting support for LLVM assembly files and TableGen
1585 description files. For information on how to use the syntax files, consult
1586 the <tt>README</tt> file in that directory.<br><br>
1592 <!-- *********************************************************************** -->
1594 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1596 <!-- *********************************************************************** -->
1598 <div class="doc_text">
1599 <p>This section gives an example of using LLVM. llvm-gcc3 is now obsolete,
1600 so we only include instructions for llvm-gcc4.
1603 <p><b>Note:</b> The <i>gcc4</i> frontend's invocation is <b><i>considerably different</i></b>
1604 from the previous <i>gcc3</i> frontend. In particular, the <i>gcc4</i> frontend <b><i>does not</i></b>
1605 create bitcode by default: <i>gcc4</i> produces native code. As the example below illustrates,
1606 the '--emit-llvm' flag is needed to produce LLVM bitcode output. For <i>makefiles</i> and
1607 <i>configure</i> scripts, the CFLAGS variable needs '--emit-llvm' to produce bitcode
1611 <!-- ======================================================================= -->
1613 <a name="tutorial4">Example with llvm-gcc4</a>
1616 <div class="doc_text">
1619 <li><p>First, create a simple C file, name it 'hello.c':</p>
1621 <div class="doc_code">
1623 #include <stdio.h>
1626 printf("hello world\n");
1631 <li><p>Next, compile the C file into a native executable:</p>
1633 <div class="doc_code"><pre>% llvm-gcc hello.c -o hello</pre></div>
1635 <p>Note that llvm-gcc works just like GCC by default. The standard -S and
1636 -c arguments work as usual (producing a native .s or .o file,
1637 respectively).</p></li>
1639 <li><p>Next, compile the C file into a LLVM bitcode file:</p>
1641 <div class="doc_code">
1642 <pre>% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc</pre></div>
1644 <p>The -emit-llvm option can be used with the -S or -c options to emit an
1645 LLVM ".ll" or ".bc" file (respectively) for the code. This allows you
1646 to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
1647 the bitcode file.</p>
1649 <p>Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
1652 <li><p>Run the program in both forms. To run the program, use:</p>
1654 <div class="doc_code"><pre>% ./hello</pre></div>
1658 <div class="doc_code"><pre>% lli hello.bc</pre></div>
1660 <p>The second examples shows how to invoke the LLVM JIT, <a
1661 href="CommandGuide/html/lli.html">lli</a>.</p></li>
1663 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1666 <div class="doc_code">
1667 <pre>llvm-dis < hello.bc | less</pre>
1670 <li><p>Compile the program to native assembly using the LLC code
1673 <div class="doc_code"><pre>% llc hello.bc -o hello.s</pre></div></li>
1675 <li><p>Assemble the native assembly language file into a program:</p>
1677 <div class="doc_code">
1679 <b>Solaris:</b> % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native
1681 <b>Others:</b> % gcc hello.s -o hello.native
1685 <li><p>Execute the native code program:</p>
1687 <div class="doc_code"><pre>% ./hello.native</pre></div>
1689 <p>Note that using llvm-gcc to compile directly to native code (i.e. when
1690 the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
1698 <!-- *********************************************************************** -->
1700 <a name="problems">Common Problems</a>
1702 <!-- *********************************************************************** -->
1704 <div class="doc_text">
1706 <p>If you are having problems building or using LLVM, or if you have any other
1707 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1708 Asked Questions</a> page.</p>
1712 <!-- *********************************************************************** -->
1714 <a name="links">Links</a>
1716 <!-- *********************************************************************** -->
1718 <div class="doc_text">
1720 <p>This document is just an <b>introduction</b> on how to use LLVM to do
1721 some simple things... there are many more interesting and complicated things
1722 that you can do that aren't documented here (but we'll gladly accept a patch
1723 if you want to write something up!). For more information about LLVM, check
1727 <li><a href="http://llvm.org/">LLVM homepage</a></li>
1728 <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1729 <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1730 that Uses LLVM</a></li>
1735 <!-- *********************************************************************** -->
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1744 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1745 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1746 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
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