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11 <div class="doc_title">
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>
21 <li><a href="#software">Software</a>
22 <li><a href="#brokengcc">Broken versions of GCC</a>
25 <li><a href="#starting">Getting Started with LLVM</a>
27 <li><a href="#terminology">Terminology and Notation</a>
28 <li><a href="#environment">Setting Up Your Environment</a>
29 <li><a href="#unpack">Unpacking the LLVM Archives</a>
30 <li><a href="#checkout">Checkout LLVM from CVS</a>
31 <li><a href="#installcf">Install the GCC Front End</a>
32 <li><a href="#config">Local LLVM Configuration</a>
33 <li><a href="#compile">Compiling the LLVM Suite Source Code</a>
34 <li><a href="#cross-compile">Cross-Compiling LLVM</a>
35 <li><a href="#objfiles">The Location of LLVM Object Files</a>
36 <li><a href="#optionalconfig">Optional Configuration Items</a>
39 <li><a href="#layout">Program layout</a>
41 <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
42 <li><a href="#examples"><tt>llvm/examples</tt></a>
43 <li><a href="#include"><tt>llvm/include</tt></a>
44 <li><a href="#lib"><tt>llvm/lib</tt></a>
45 <li><a href="#projects"><tt>llvm/projects</tt></a>
46 <li><a href="#runtime"><tt>llvm/runtime</tt></a>
47 <li><a href="#test"><tt>llvm/test</tt></a>
48 <li><a href="#llvmtest"><tt>llvm-test</tt></a>
49 <li><a href="#tools"><tt>llvm/tools</tt></a>
50 <li><a href="#utils"><tt>llvm/utils</tt></a>
51 <li><a href="#win32"><tt>llvm/win32</tt></a>
54 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
55 <li><a href="#problems">Common Problems</a>
56 <li><a href="#links">Links</a>
59 <div class="doc_author">
61 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
62 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
63 <a href="http://misha.brukman.net">Misha Brukman</a>,
64 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
65 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
70 <!-- *********************************************************************** -->
71 <div class="doc_section">
72 <a name="overview"><b>Overview</b></a>
74 <!-- *********************************************************************** -->
76 <div class="doc_text">
78 <p>Welcome to LLVM! In order to get started, you first need to know some
79 basic information.</p>
81 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
82 contains all of the tools, libraries, and header files needed to use the low
83 level virtual machine. It contains an assembler, disassembler, bytecode
84 analyzer, and bytecode optimizer. It also contains a test suite that can be
85 used to test the LLVM tools and the GCC front end.</p>
87 <p>The second piece is the GCC front end. This component provides a version of
88 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
89 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
90 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
91 from the LLVM suite.</p>
94 There is a third, optional piece called llvm-test. It is a suite of programs
95 with a testing harness that can be used to further test LLVM's functionality
101 <!-- *********************************************************************** -->
102 <div class="doc_section">
103 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
105 <!-- *********************************************************************** -->
107 <div class="doc_text">
109 <p>Here's the short story for getting up and running quickly with LLVM:</p>
112 <li>Read the documentation.</li>
113 <li>Read the documentation.</li>
114 <li>Remember that you were warned twice about reading the documentation.</li>
115 <li>Install the GCC front end if you intend to compile C or C++:
117 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt></li>
118 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
120 <li><tt>cd cfrontend/<i>platform</i><br>
121 ./fixheaders</tt></li>
122 <li>Add the cfrontend's "bin" directory to your PATH variable.</li>
125 <li>Get the LLVM Source Code
127 <li>With the distributed files (or use <a href="#checkout">CVS</a>):
129 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
130 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
135 <li><b>[Optional]</b> Get the Test Suite Source Code
137 <li>With the distributed files (or use <a href="#checkout">CVS</a>):
139 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
140 <li><tt>cd llvm/projects</tt>
141 <li><tt>gunzip --stdout llvm-test-<i>version</i>.tar.gz | tar -xvf -</tt>
147 <li>Configure the LLVM Build Environment
149 <li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
150 <li><tt><i>/path/to/llvm/</i>configure [options]</tt><br>
154 <li><tt>--prefix=<i>directory</i></tt>
155 <p>Specify for <i>directory</i> the full pathname of where you
156 want the LLVM tools and libraries to be installed (default
157 <tt>/usr/local</tt>).</p></li>
158 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
159 <p>Optionally, specify for <i>directory</i> the full pathname of the
160 C/C++ front end installation to use with this LLVM configuration. If
161 not specified, the PATH will be searched.</p></li>
162 <li><tt>--enable-spec2000=<i>directory</i></tt>
163 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
164 benchmarks should be available in
165 <tt><i>directory</i></tt>.</p></li>
169 <li>Build the LLVM Suite:
171 <li><tt>gmake -k |& tee gnumake.out
172 # this is csh or tcsh syntax</tt></li>
173 <li>If you get an "internal compiler error (ICE)" see <a href="#brokengcc">below</a>.</li>
178 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
179 detailed information on configuring and compiling LLVM. See <a
180 href="#environment">Setting Up Your Environment</a> for tips that simplify
181 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
182 Layout</a> to learn about the layout of the source code tree.</p>
186 <!-- *********************************************************************** -->
187 <div class="doc_section">
188 <a name="requirements"><b>Requirements</b></a>
190 <!-- *********************************************************************** -->
192 <div class="doc_text">
194 <p>Before you begin to use the LLVM system, review the requirements given below.
195 This may save you some trouble by knowing ahead of time what hardware and
196 software you will need.</p>
200 <!-- ======================================================================= -->
201 <div class="doc_subsection">
202 <a name="hardware"><b>Hardware</b></a>
205 <div class="doc_text">
207 <p>LLVM is known to work on the following platforms:</p>
209 <table cellpadding="3">
217 <td>x86<sup><a href="#pf_1">1</a></sup></td>
222 <td>V9 (Ultrasparc)</td>
227 <td>x86<sup><a href="#pf_1">1</a></sup></td>
231 <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
236 <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
242 <td>Cygwin/Win32</td>
243 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a></sup></td>
244 <td>GCC 3.4.X, binutils 2.15</td>
248 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,<a href="#pf_8">8</a></sup></td>
249 <td>GCC 3.4.X, binutils 2.15</td>
253 <td>amd64<sup><a href="#pf_3">3</a></sup></td>
258 <p>LLVM has partial support for the following platforms:</p>
268 <td>x86<sup><a href="#pf_1">1</a></sup></td>
269 <td>Visual Studio .NET<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
271 <td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
276 <td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
282 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
287 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
288 <td>Itanium (IA-64)</td>
292 <td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
293 <td>Itanium (IA-64)</td>
300 <div class="doc_notes">
302 <li><a name="pf_1">Code generation supported for Pentium processors and
304 <li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
305 <li><a name="pf_3">No native code generation</a></li>
306 <li><a name="pf_4">Build is not complete: one or more tools don't link</a></li>
307 <li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
308 <li><a name="pf_6">The port is done using the MSYS shell.</a>
309 <a href="http://www.mingw.org/MinGWiki/">Download</a> and install
310 bison (excl. M4.exe) and flex in that order. Build binutils-2.15 from source,
311 if necessary. Bison & flex can be also grabbed from GNUWin32 sf.net
313 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
314 <li><a name="pf_8">Binutils</a> up to post-2.17 has bug in bfd/cofflink.c
315 preventing LLVM from building correctly. Several workarounds have been
316 introduced into LLVM build system, but the bug can occur anytime in the
317 future. We highly recommend that you rebuild your current binutils with the
318 patch from <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=2659">
319 Binutils bugzilla</a>, if it wasn't already applied.</li>
323 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
324 mode, depending on the system (it is so large because of all the debugging
325 information and the fact that the libraries are statically linked into multiple
326 tools). If you do not need many of the tools and you are space-conscious,
327 you can disable them individually in <tt>llvm/tools/Makefile</tt>. The Release
328 build requires considerably less space.</p>
330 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
331 guaranteed to do so. If compilation is successful, the LLVM utilities should be
332 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
333 generation should work as well, although the generated native code may not work
334 on your platform.</p>
336 <p>The GCC front end is not very portable at the moment. If you want to get it
337 to work on another platform, you can download a copy of the source and <a
338 href="CFEBuildInstrs.html">try to compile it</a> on your platform.</p>
342 <!-- ======================================================================= -->
343 <div class="doc_subsection"><a name="software"><b>Software</b></a></div>
344 <div class="doc_text">
345 <p>Compiling LLVM requires that you have several software packages
346 installed. The table below lists those required packages. The Package column
347 is the usual name for the software package that LLVM depends on. The Version
348 column provides "known to work" versions of the package. The Notes column
349 describes how LLVM uses the package and provides other details.</p>
351 <tr><th>Package</th><th>Version</th><th>Notes</th></tr>
354 <td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
355 <td>3.79, 3.79.1</td>
356 <td>Makefile/build processor</td>
360 <td><a href="http://gcc.gnu.org">GCC</a></td>
362 <td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
366 <td><a href="http://www.gnu.org/software/texinfo">TeXinfo</a></td>
368 <td>For building the CFE</td>
372 <td><a href="http://www.gnu.org/software/flex">Flex</a></td>
374 <td>LEX compiler</td>
378 <td><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></td>
379 <td>1.28, 1.35, 1.75, 1.875d, 2.0, or 2.1<br>(not 1.85 or 1.875)</td>
380 <td>YACC compiler</td>
384 <td><a href="https://www.cvshome.org/downloads.html">CVS</a></td>
386 <td>CVS access to LLVM<sup><a href="#sf2">2</a></sup></td>
390 <td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
392 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
396 <td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
398 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
402 <td><a href="http://expect.nist.gov/">expect</a></td>
404 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
408 <td><a href="http://www.perl.com/download.csp">perl</a></td>
410 <td>Nightly tester, utilities</td>
414 <td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
416 <td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
420 <td><a href="http://www.gnu.org/software/autoconf">GNU Autoconf</a></td>
422 <td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
426 <td><a href="http://www.gnu.org/software/automake">GNU Automake</a></td>
428 <td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
432 <td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
434 <td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
440 <div class="doc_notes">
442 <li><a name="sf3">Only the C and C++ languages are needed so there's no
443 need to build the other languages for LLVM's purposes.</a> See
444 <a href="#brokengcc">below</a> for specific version info.</li>
445 <li><a name="sf2">You only need CVS if you intend to build from the
446 latest LLVM sources. If you're working from a release distribution, you
447 don't need CVS.</a></li>
448 <li><a name="sf3">Only needed if you want to run the automated test
449 suite in the <tt>llvm/test</tt> directory.</a></li>
450 <li><a name="sf4">If you want to make changes to the configure scripts,
451 you will need GNU autoconf (2.59), and consequently, GNU M4 (version 1.4
452 or higher). You will also need automake (1.9.2). We only use aclocal
453 from that package.</a></li>
457 <p>Additionally, your compilation host is expected to have the usual
458 plethora of Unix utilities. Specifically:</p>
460 <li><b>ar</b> - archive library builder</li>
461 <li><b>bzip2*</b> - bzip2 command for distribution generation</li>
462 <li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
463 <li><b>chmod</b> - change permissions on a file</li>
464 <li><b>cat</b> - output concatenation utility</li>
465 <li><b>cp</b> - copy files</li>
466 <li><b>date</b> - print the current date/time </li>
467 <li><b>echo</b> - print to standard output</li>
468 <li><b>egrep</b> - extended regular expression search utility</li>
469 <li><b>etags</b> - C/C++ tag file creator for vim/emacs</li>
470 <li><b>find</b> - find files/dirs in a file system</li>
471 <li><b>grep</b> - regular expression search utility</li>
472 <li><b>gzip*</b> - gzip command for distribution generation</li>
473 <li><b>gunzip*</b> - gunzip command for distribution checking</li>
474 <li><b>install</b> - install directories/files </li>
475 <li><b>mkdir</b> - create a directory</li>
476 <li><b>mv</b> - move (rename) files</li>
477 <li><b>ranlib</b> - symbol table builder for archive libraries</li>
478 <li><b>rm</b> - remove (delete) files and directories</li>
479 <li><b>sed</b> - stream editor for transforming output</li>
480 <li><b>sh</b> - Bourne shell for make build scripts</li>
481 <li><b>tar</b> - tape archive for distribution generation</li>
482 <li><b>test</b> - test things in file system</li>
483 <li><b>unzip*</b> - unzip command for distribution checking</li>
484 <li><b>zip*</b> - zip command for distribution generation</li>
488 <!-- ======================================================================= -->
489 <div class="doc_subsection">
490 <a name="brokengcc">Broken versions of GCC</a>
493 <div class="doc_text">
495 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
496 bugs in the compiler. In particular, several versions of GCC crash when trying
497 to compile LLVM. We routinely use GCC 3.3.3, 3.4.0, and Apple 4.0.1
498 successfully with them (however, see below). Other versions of GCC will
499 probably work as well. GCC versions listed
500 here are known to not work. If you are using one of these versions, please try
501 to upgrade your GCC to something more recent. If you run into a problem with a
502 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
503 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
504 of GCC you are using.
507 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
508 problems in the STL that effectively prevent it from compiling LLVM.
511 <p><b>GCC 3.2.2</b>: This version of GCC fails to compile LLVM.</p>
513 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
514 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
515 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
517 <p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
518 Cygwin does not work. Please <a href="CFEBuildInstrs.html#cygwin">upgrade
519 to a newer version</a> if possible.</p>
520 <p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
521 possibly others) does not compile LLVM correctly (it appears that exception
522 handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
523 to a newer version of GCC.</p>
524 <p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
526 <p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
527 default with ENABLE_OPTIMIZED=1. To work around this, build with
528 "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
533 <!-- *********************************************************************** -->
534 <div class="doc_section">
535 <a name="starting"><b>Getting Started with LLVM</b></a>
537 <!-- *********************************************************************** -->
539 <div class="doc_text">
541 <p>The remainder of this guide is meant to get you up and running with
542 LLVM and to give you some basic information about the LLVM environment.</p>
544 <p>The later sections of this guide describe the <a
545 href="#layout">general layout</a> of the the LLVM source tree, a <a
546 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
547 href="#links">links</a> to find more information about LLVM or to get
551 <!-- ======================================================================= -->
552 <div class="doc_subsection">
553 <a name="terminology">Terminology and Notation</a>
556 <div class="doc_text">
558 <p>Throughout this manual, the following names are used to denote paths
559 specific to the local system and working environment. <i>These are not
560 environment variables you need to set but just strings used in the rest
561 of this document below</i>. In any of the examples below, simply replace
562 each of these names with the appropriate pathname on your local system.
563 All these paths are absolute:</p>
568 This is the top level directory of the LLVM source tree.
573 This is the top level directory of the LLVM object tree (i.e. the
574 tree where object files and compiled programs will be placed. It
575 can be the same as SRC_ROOT).
580 This is where the LLVM GCC Front End is installed.
582 For the pre-built GCC front end binaries, the LLVMGCCDIR is
583 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
588 <!-- ======================================================================= -->
589 <div class="doc_subsection">
590 <a name="environment">Setting Up Your Environment</a>
593 <div class="doc_text">
596 In order to compile and use LLVM, you may need to set some environment
600 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bytecode/libs</tt></dt>
601 <dd>[Optional] This environment variable helps LLVM linking tools find the
602 locations of your bytecode libraries. It is provided only as a
603 convenience since you can specify the paths using the -L options of the
604 tools and the C/C++ front-end will automatically use the bytecode files
606 <tt>lib</tt> directory.</dd>
611 <!-- ======================================================================= -->
612 <div class="doc_subsection">
613 <a name="unpack">Unpacking the LLVM Archives</a>
616 <div class="doc_text">
619 If you have the LLVM distribution, you will need to unpack it before you
620 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
621 suite and the LLVM GCC front end compiled for your platform. There is an
622 additional test suite that is optional. Each file is a TAR archive that is
623 compressed with the gzip program.
626 <p>The files are as follows, with <em>x.y</em> marking the version number:
628 <dt><tt>llvm-x.y.tar.gz</tt></dt>
629 <dd>Source release for the LLVM libraries and tools.<br/></dd>
631 <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
632 <dd>Source release for the LLVM test suite.</dd>
634 <dt><tt>cfrontend-x.y.source.tar.gz</tt></dt>
635 <dd>Source release of the GCC front end.<br/></dd>
637 <dt><tt>cfrontend-x.y.i686-redhat-linux-gnu.tar.gz</tt></dt>
638 <dd>Binary release of the GCC front end for Linux/x86.<br/></dd>
640 <dt><tt>llvm-gcc4-x.y.source.tar.gz</tt></dt>
641 <dd>Source release of the llvm-gcc4 front end. See README.LLVM in the root
642 directory for build instructions.<br/></dd>
644 <dt><tt>llvm-gcc4-x.y.powerpc-apple-darwin8.6.0.tar.gz</tt></dt>
645 <dd>Binary release of the llvm-gcc4 front end for MacOS X/PowerPC.<br/></dd>
647 <dt><tt>llvm-gcc4-x.y.i686-apple-darwin8.6.1.tar.gz</tt></dt>
648 <dd>Binary release of the llvm-gcc4 front end for MacOS X/X86.<br/></dd>
651 <p>It is also possible to download the sources of the llvm-gcc4 front end from a
652 read-only subversion mirror at
653 svn://anonsvn.opensource.apple.com/svn/llvm/trunk. </p>
657 <!-- ======================================================================= -->
658 <div class="doc_subsection">
659 <a name="checkout">Checkout LLVM from CVS</a>
662 <div class="doc_text">
664 <p>If you have access to our CVS repository, you can get a fresh copy of
665 the entire source code. All you need to do is check it out from CVS as
669 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
670 <li><tt>cvs -d :pserver:anon@llvm.org:/var/cvs/llvm login</tt>
671 <li>Hit the return key when prompted for the password.
672 <li><tt>cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co
676 <p>This will create an '<tt>llvm</tt>' directory in the current
677 directory and fully populate it with the LLVM source code, Makefiles,
678 test directories, and local copies of documentation files.</p>
680 <p>If you want to get a specific release (as opposed to the most recent
681 revision), you can specify a label. The following releases have the following
685 <li>Release 1.7: <b>RELEASE_17</b></li>
686 <li>Release 1.6: <b>RELEASE_16</b></li>
687 <li>Release 1.5: <b>RELEASE_15</b></li>
688 <li>Release 1.4: <b>RELEASE_14</b></li>
689 <li>Release 1.3: <b>RELEASE_13</b></li>
690 <li>Release 1.2: <b>RELEASE_12</b></li>
691 <li>Release 1.1: <b>RELEASE_11</b></li>
692 <li>Release 1.0: <b>RELEASE_1</b></li>
695 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
696 you get it from the CVS repository:</p>
699 cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co llvm-test
701 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
702 configured by the LLVM configure script as well as automatically updated when
703 you run <tt>cvs update</tt>.</p>
705 <p>If you would like to get the GCC 3.4 front end source code, you can also get it from the CVS repository:</p>
708 cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co llvm-gcc
711 <p>Please note that you must follow <a href="CFEBuildInstrs.html">these
712 instructions</a> to successfully build the LLVM GCC front-end.</p>
716 <!-- ======================================================================= -->
717 <div class="doc_subsection">
718 <a name="installcf">Install the GCC Front End</a>
721 <div class="doc_text">
723 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
724 GCC front end from the binary distribution. It is used for building the
725 bytecode libraries later used by the GCC front end for linking programs, and its
726 location must be specified when the LLVM suite is configured.</p>
728 <p>To install the GCC front end, do the following:</p>
731 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
732 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
736 <p>Next, you will need to fix your system header files:</p>
738 <p><tt>cd cfrontend/<i>platform</i><br>
739 ./fixheaders</tt></p>
741 <p>The binary versions of the GCC front end may not suit all of your needs. For
742 example, the binary distribution may include an old version of a system header
743 file, not "fix" a header file that needs to be fixed for GCC, or it may be
744 linked with libraries not available on your system.</p>
746 <p>In cases like these, you may want to try <a
747 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
748 not for the faint of heart, so be forewarned.</p>
752 <!-- ======================================================================= -->
753 <div class="doc_subsection">
754 <a name="config">Local LLVM Configuration</a>
757 <div class="doc_text">
759 <p>Once checked out from the CVS repository, the LLVM suite source code must be
760 configured via the <tt>configure</tt> script. This script sets variables in the
761 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
762 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
763 the Makefiles needed to begin building LLVM.</p>
765 <p>The following environment variables are used by the <tt>configure</tt>
766 script to configure the build system:</p>
769 <tr><th>Variable</th><th>Purpose</th></tr>
772 <td>Tells <tt>configure</tt> which C compiler to use. By default,
773 <tt>configure</tt> will look for the first GCC C compiler in
774 <tt>PATH</tt>. Use this variable to override
775 <tt>configure</tt>'s default behavior.</td>
779 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
780 <tt>configure</tt> will look for the first GCC C++ compiler in
781 <tt>PATH</tt>. Use this variable to override
782 <tt>configure</tt>'s default behavior.</td>
786 <p>The following options can be used to set or enable LLVM specific options:</p>
789 <dt><i>--with-llvmgccdir</i></dt>
790 <dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
791 The value of this option should specify the full pathname of the C/C++ Front
792 End to be used. If this option is not provided, the PATH will be searched for
793 a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
794 be inferred from the path found. If the option is not given, and no llvm-gcc
795 can be found in the path then a warning will be produced by
796 <tt>configure</tt> indicating this situation. LLVM may still be built with
797 the <tt>tools-only</tt> target but attempting to build the runtime libraries
798 will fail as these libraries require llvm-gcc and llvm-g++. See
799 <a href="#installcf">Install the GCC Front End</a> for details on installing
800 the C/C++ Front End. See
801 <a href="CFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
802 for details on building the C/C++ Front End.</dd>
803 <dt><i>--with-tclinclude</i></dt>
804 <dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
805 found. Use this if you have multiple tcl installations on your machine and you
806 want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
807 dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
808 option, the LLVM configure script will search for the tcl 8.4 and 8.3
812 <dt><i>--enable-optimized</i></dt>
814 Enables optimized compilation by default (debugging symbols are removed
815 and GCC optimization flags are enabled). The default is to use an
816 unoptimized build (also known as a debug build).
819 <dt><i>--enable-debug-runtime</i></dt>
821 Enables debug symbols in the runtime libraries. The default is to strip
822 debug symbols from the runtime libraries.
824 <dt><i>--enable-jit</i></dt>
826 Compile the Just In Time (JIT) compiler functionality. This is not
828 on all platforms. The default is dependent on platform, so it is best
829 to explicitly enable it if you want it.
832 <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
833 <dd>Controls which targets will be built and linked into llc. The default
834 value for <tt>target_options</tt> is "all" which builds and links all
835 available targets. The value "host-only" can be specified to build only a
836 native compiler (no cross-compiler targets available). The "native" target is
837 selected as the target of the build host. You can also specify a comma
838 separated list of target names that you want available in llc. The target
839 names use all lower case. The current set of targets is: <br/>
840 <tt>alpha, ia64, powerpc, skeleton, sparc, x86</tt>.
842 <dt><i>--enable-doxygen</i></dt>
843 <dd>Look for the doxygen program and enable construction of doxygen based
844 documentation from the source code. This is disabled by default because
845 generating the documentation can take a long time and producess 100s of
846 megabytes of output.</dd>
849 <p>To configure LLVM, follow these steps:</p>
852 <li>Change directory into the object root directory:
854 <tt>cd <i>OBJ_ROOT</i></tt>
857 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
859 <tt><i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</tt>
865 <!-- ======================================================================= -->
866 <div class="doc_subsection">
867 <a name="compile">Compiling the LLVM Suite Source Code</a>
870 <div class="doc_text">
872 <p>Once you have configured LLVM, you can build it. There are three types of
878 These builds are the default when one types <tt>gmake</tt> (unless the
879 <tt>--enable-optimized</tt> option was used during configuration). The
880 build system will compile the tools and libraries with debugging
884 <dt>Release (Optimized) Builds
886 These builds are enabled with the <tt>--enable-optimized</tt> option to
887 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
888 <tt>gmake</tt> command line. For these builds, the build system will
889 compile the tools and libraries with GCC optimizations enabled and strip
890 debugging information from the libraries and executables it generates.
895 These builds are for use with profiling. They compile profiling
896 information into the code for use with programs like <tt>gprof</tt>.
897 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
898 on the <tt>gmake</tt> command line.
901 <p>Once you have LLVM configured, you can build it by entering the
902 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
904 <p><tt>gmake</tt></p>
906 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
907 are using a version of GCC that is known not to compile LLVM.</p>
910 If you have multiple processors in your machine, you may wish to use some of
911 the parallel build options provided by GNU Make. For example, you could use the
914 <p><tt>gmake -j2</tt></p>
916 <p>There are several special targets which are useful when working with the LLVM
920 <dt><tt>gmake clean</tt>
922 Removes all files generated by the build. This includes object files,
923 generated C/C++ files, libraries, and executables.
926 <dt><tt>gmake dist-clean</tt>
928 Removes everything that <tt>gmake clean</tt> does, but also removes files
929 generated by <tt>configure</tt>. It attempts to return the source tree to the
930 original state in which it was shipped.
933 <dt><tt>gmake install</tt>
935 Installs LLVM header files, libraries, tools, and documentation in a
937 under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
938 defaults to <tt>/usr/local</tt>.
941 <dt><tt>gmake -C runtime install-bytecode</tt>
943 Assuming you built LLVM into $OBJDIR, when this command is run, it will
944 install bytecode libraries into the GCC front end's bytecode library
945 directory. If you need to update your bytecode libraries,
946 this is the target to use once you've built them.
950 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
951 details on these <tt>make</tt> targets and descriptions of other targets
954 <p>It is also possible to override default values from <tt>configure</tt> by
955 declaring variables on the command line. The following are some examples:</p>
958 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
960 Perform a Release (Optimized) build.
963 <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
965 Perform a Release (Optimized) build without assertions enabled.
968 <dt><tt>gmake ENABLE_PROFILING=1</tt>
970 Perform a Profiling build.
973 <dt><tt>gmake VERBOSE=1</tt>
975 Print what <tt>gmake</tt> is doing on standard output.
978 <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
979 <dd>Ask each tool invoked by the makefiles to print out what it is doing on
980 the standard output. This also implies <tt>VERBOSE=1</tt>.
984 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
985 it and any subdirectories that it contains. Entering any directory inside the
986 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
987 that directory that is out of date.</p>
991 <!-- ======================================================================= -->
992 <div class="doc_subsection">
993 <a name="cross-compile">Cross-Compiling LLVM</a>
996 <div class="doc_text">
997 <p>It is possible to cross-compile LLVM. That is, you can create LLVM
998 executables and libraries for a platform different than the one one which you
999 are compiling. To do this, a few additional steps are
1000 required. <sup><a href="#ccn_1">1</a></sup> To cross-compile LLVM, use
1001 these instructions:</p>
1003 <li>Configure and build LLVM as a native compiler. You will need
1004 just <tt>TableGen</tt> from that build.
1006 <li>If you have <tt>$LLVM_OBJ_ROOT=$LLVM_SRC_ROOT</tt> just execute
1007 <tt>make -C utils/TableGen</tt> after configuring.</li>
1008 <li>Otherwise you will need to monitor building process and terminate
1009 it just after <tt>TableGen</tt> was built.</li>
1012 <li>Copy the TableGen binary to somewhere safe (out of your build tree).
1014 <li>Configure LLVM to build with a cross-compiler. To do this, supply the
1015 configure script with <tt>--build</tt> and <tt>--host</tt> options that
1016 are different. The values of these options must be legal target triples
1017 that your GCC compiler supports.</li>
1018 <li>Put the saved <tt>TableGen</tt> executable into the
1019 into <tt>$LLVM_OBJ_ROOT/{BUILD_TYPE}/bin</tt> directory (e.g. into
1020 <tt>.../Release/bin</tt> for a Release build).</li>
1021 <li>Build LLVM as usual.</li>
1023 <p>The result of such a build will produce executables that are not executable
1024 on your build host (--build option) but can be executed on your compile host
1025 (--host option).</p>
1026 <p><b>Notes:</b></p>
1027 <div class="doc_notes">
1029 <li><a name="ccn_1">Cross-compiling</a> was tested only with Linux as
1030 build platform and Windows as host using mingw32 cross-compiler. Other
1031 combinations have not been tested.</li>
1036 <!-- ======================================================================= -->
1037 <div class="doc_subsection">
1038 <a name="objfiles">The Location of LLVM Object Files</a>
1041 <div class="doc_text">
1043 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1044 several LLVM builds. Hence, it is possible to build LLVM for several different
1045 platforms or configurations using the same source tree.</p>
1047 <p>This is accomplished in the typical autoconf manner:</p>
1050 <li><p>Change directory to where the LLVM object files should live:</p>
1052 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
1054 <li><p>Run the <tt>configure</tt> script found in the LLVM source
1057 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
1060 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1061 named after the build type:</p>
1068 <dd><tt><i>OBJ_ROOT</i>/Debug/bin</tt>
1070 <dd><tt><i>OBJ_ROOT</i>/Debug/lib</tt>
1078 <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1080 <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1088 <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1090 <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1096 <!-- ======================================================================= -->
1097 <div class="doc_subsection">
1098 <a name="optionalconfig">Optional Configuration Items</a>
1101 <div class="doc_text">
1104 If you're running on a Linux system that supports the "<a
1105 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">
1107 module, and you have root access on the system, you can set your system up to
1108 execute LLVM bytecode files directly. To do this, use commands like this (the
1109 first command may not be required if you are already using the module):</p>
1111 <div class="doc_code">
1113 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1114 $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1115 $ chmod u+x hello.bc (if needed)
1121 This allows you to execute LLVM bytecode files directly. Thanks to Jack
1122 Cummings for pointing this out!
1128 <!-- *********************************************************************** -->
1129 <div class="doc_section">
1130 <a name="layout"><b>Program Layout</b></a>
1132 <!-- *********************************************************************** -->
1134 <div class="doc_text">
1136 <p>One useful source of information about the LLVM source base is the LLVM <a
1137 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
1138 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1139 The following is a brief introduction to code layout:</p>
1143 <!-- ======================================================================= -->
1144 <div class="doc_subsection"><a name="cvsdir"><tt>CVS</tt> directories</a></div>
1145 <div class="doc_text">
1146 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
1147 the most part these can just be ignored.</p>
1150 <!-- ======================================================================= -->
1151 <div class="doc_subsection"><a name="examples"><tt>llvm/examples</tt></a></div>
1152 <div class="doc_text">
1153 <p>This directory contains some simple examples of how to use the LLVM IR and
1157 <!-- ======================================================================= -->
1158 <div class="doc_subsection"><a name="include"><tt>llvm/include</tt></a></div>
1159 <div class="doc_text">
1161 <p>This directory contains public header files exported from the LLVM
1162 library. The three main subdirectories of this directory are:</p>
1165 <dt><tt><b>llvm/include/llvm</b></tt></dt>
1166 <dd>This directory contains all of the LLVM specific header files. This
1167 directory also has subdirectories for different portions of LLVM:
1168 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1171 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1172 <dd>This directory contains generic support libraries that are provided with
1173 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1174 and a Command Line option processing library store their header files here.
1177 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1178 <dd>This directory contains header files configured by the <tt>configure</tt>
1179 script. They wrap "standard" UNIX and C header files. Source code can
1180 include these header files which automatically take care of the conditional
1181 #includes that the <tt>configure</tt> script generates.</dd>
1185 <!-- ======================================================================= -->
1186 <div class="doc_subsection"><a name="lib"><tt>llvm/lib</tt></a></div>
1187 <div class="doc_text">
1189 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1190 almost all code exists in libraries, making it very easy to share code among the
1191 different <a href="#tools">tools</a>.</p>
1194 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1195 <dd> This directory holds the core LLVM source files that implement core
1196 classes like Instruction and BasicBlock.</dd>
1198 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1199 <dd>This directory holds the source code for the LLVM assembly language parser
1202 <dt><tt><b>llvm/lib/ByteCode/</b></tt></dt>
1203 <dd>This directory holds code for reading and write LLVM bytecode.</dd>
1205 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1206 different program analyses, such as Dominator Information, Call Graphs,
1207 Induction Variables, Interval Identification, Natural Loop Identification,
1210 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1211 <dd> This directory contains the source code for the LLVM to LLVM program
1212 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1213 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1214 Elimination, and many others.</dd>
1216 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1217 <dd> This directory contains files that describe various target architectures
1218 for code generation. For example, the <tt>llvm/lib/Target/X86</tt>
1219 directory holds the X86 machine description while
1220 <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
1222 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1223 <dd> This directory contains the major parts of the code generator: Instruction
1224 Selector, Instruction Scheduling, and Register Allocation.</dd>
1226 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1227 <dd> This directory contains the source level debugger library that makes
1228 it possible to instrument LLVM programs so that a debugger could identify
1229 source code locations at which the program is executing.</dd>
1231 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1232 <dd> This directory contains libraries for executing LLVM bytecode directly
1233 at runtime in both interpreted and JIT compiled fashions.</dd>
1235 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1236 <dd> This directory contains the source code that corresponds to the header
1237 files located in <tt>llvm/include/Support/</tt>.</dd>
1239 <dt><tt><b>llvm/lib/System/</b></tt></dt>
1240 <dd>This directory contains the operating system abstraction layer that
1241 shields LLVM from platform-specific coding.</dd>
1246 <!-- ======================================================================= -->
1247 <div class="doc_subsection"><a name="projects"><tt>llvm/projects</tt></a></div>
1248 <div class="doc_text">
1249 <p>This directory contains projects that are not strictly part of LLVM but are
1250 shipped with LLVM. This is also the directory where you should create your own
1251 LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1252 to set up your own project. See <tt>llvm/projects/Stacker</tt> for a fully
1253 functional example of a compiler front end.</p>
1256 <!-- ======================================================================= -->
1257 <div class="doc_subsection"><a name="runtime"><tt>llvm/runtime</tt></a></div>
1258 <div class="doc_text">
1260 <p>This directory contains libraries which are compiled into LLVM bytecode and
1261 used when linking programs with the GCC front end. Most of these libraries are
1262 skeleton versions of real libraries; for example, libc is a stripped down
1263 version of glibc.</p>
1265 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1270 <!-- ======================================================================= -->
1271 <div class="doc_subsection"><a name="test"><tt>llvm/test</tt></a></div>
1272 <div class="doc_text">
1273 <p>This directory contains feature and regression tests and other basic sanity
1274 checks on the LLVM infrastructure. These are intended to run quickly and cover
1275 a lot of territory without being exhaustive.</p>
1278 <!-- ======================================================================= -->
1279 <div class="doc_subsection"><a name="llvmtest"><tt>llvm-test</tt></a></div>
1280 <div class="doc_text">
1281 <p>This is not a directory in the normal llvm module; it is a separate CVS
1282 module that must be checked out (usually to <tt>projects/llvm-test</tt>). This
1283 module contains a comprehensive correctness, performance, and benchmarking
1285 suite for LLVM. It is a separate CVS module because not every LLVM user is
1286 interested in downloading or building such a comprehensive test suite. For
1287 further details on this test suite, please see the
1288 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1291 <!-- ======================================================================= -->
1292 <div class="doc_subsection"><a name="tools"><tt>llvm/tools</tt></a></div>
1293 <div class="doc_text">
1295 <p>The <b>tools</b> directory contains the executables built out of the
1296 libraries above, which form the main part of the user interface. You can
1297 always get help for a tool by typing <tt>tool_name --help</tt>. The
1298 following is a brief introduction to the most important tools. More detailed
1299 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1302 <dt><tt><b>analyze</b></tt></dt>
1303 <dd><tt>analyze</tt> is used to run a specific
1304 analysis on an input LLVM bytecode file and print out the results. It is
1305 primarily useful for debugging analyses, or familiarizing yourself with
1306 what an analysis does.</dd>
1308 <dt><tt><b>bugpoint</b></tt></dt>
1309 <dd><tt>bugpoint</tt> is used to debug
1310 optimization passes or code generation backends by narrowing down the
1311 given test case to the minimum number of passes and/or instructions that
1312 still cause a problem, whether it is a crash or miscompilation. See <a
1313 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1314 on using <tt>bugpoint</tt>.</dd>
1316 <dt><tt><b>llvmc</b></tt></dt>
1317 <dd>The LLVM Compiler Driver. This program can
1318 be configured to utilize both LLVM and non-LLVM compilation tools to enable
1319 pre-processing, translation, optimization, assembly, and linking of programs
1320 all from one command line. <tt>llvmc</tt> also takes care of processing the
1321 dependent libraries found in bytecode. This reduces the need to get the
1322 traditional <tt>-l<name></tt> options right on the command line. Please
1323 note that this tool, while functional, is still experimental and not feature
1326 <dt><tt><b>llvm-ar</b></tt></dt>
1327 <dd>The archiver produces an archive containing
1328 the given LLVM bytecode files, optionally with an index for faster
1331 <dt><tt><b>llvm-as</b></tt></dt>
1332 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1335 <dt><tt><b>llvm-dis</b></tt></dt>
1336 <dd>The disassembler transforms the LLVM bytecode to human readable
1339 <dt><tt><b>llvm-ld</b></tt></dt>
1340 <dd><tt>llvm-ld</tt> is very similar to gccld and provides a general purpose
1341 and extensible linker for LLVM. This is the linker invoked by <tt>llvmc</tt>.
1342 It allows optimization modules to be loaded so that language specific
1343 optimizations can be applied at link time. This tool is considered
1346 <dt><tt><b>llvm-link</b></tt></dt>
1347 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1348 a single program.</dd>
1350 <dt><tt><b>lli</b></tt></dt>
1351 <dd><tt>lli</tt> is the LLVM interpreter, which
1352 can directly execute LLVM bytecode (although very slowly...). In addition
1353 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
1354 specifying <tt>-trace</tt> on the command line). Finally, for
1355 architectures that support it (currently x86, Sparc, and PowerPC), by default,
1356 <tt>lli</tt> will function as a Just-In-Time compiler (if the
1357 functionality was compiled in), and will execute the code <i>much</i>
1358 faster than the interpreter.</dd>
1360 <dt><tt><b>llc</b></tt></dt>
1361 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1362 translates LLVM bytecode to a native code assembly file or to C code (with
1363 the -march=c option).</dd>
1365 <dt><tt><b>llvm-gcc</b></tt></dt>
1366 <dd><tt>llvm-gcc</tt> is a GCC-based C frontend
1367 that has been retargeted to emit LLVM code as the machine code output. It
1368 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
1369 -o</tt> options that are typically used. The source code for the
1370 <tt>llvm-gcc</tt> tool is available as a separate CVS module.
1373 <dt><tt><b>gccas</b></tt></dt>
1374 <dd>This tool is invoked by the <tt>llvm-gcc</tt> frontend as the
1375 "assembler" part of the compiler. This tool actually assembles LLVM
1376 assembly to LLVM bytecode, performs a variety of optimizations, and
1377 outputs LLVM bytecode. Thus when you invoke
1378 <tt>llvm-gcc -c x.c -o x.o</tt>, you are causing <tt>gccas</tt> to be
1379 run, which writes the <tt>x.o</tt> file (which is an LLVM bytecode file
1380 that can be disassembled or manipulated just like any other bytecode
1381 file). The command line interface to <tt>gccas</tt> is designed to be
1382 as close as possible to the <b>system</b> `<tt>as</tt>' utility so that
1383 the gcc frontend itself did not have to be modified to interface to
1384 a "weird" assembler.</dd>
1386 <dt><tt><b>gccld</b></tt></dt>
1387 <dd><tt>gccld</tt> links together several LLVM bytecode files into one
1388 bytecode file and does some optimization. It is the linker invoked by
1389 the GCC frontend when multiple .o files need to be linked together.
1390 Like <tt>gccas</tt>, the command line interface of <tt>gccld</tt> is
1391 designed to match the system linker, to aid interfacing with the GCC
1397 <dt><tt><b>opt</b></tt></dt>
1398 <dd><tt>opt</tt> reads LLVM bytecode, applies a
1399 series of LLVM to LLVM transformations (which are specified on the command
1400 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
1401 command is a good way to get a list of the program transformations
1402 available in LLVM.</dd>
1406 <!-- ======================================================================= -->
1407 <div class="doc_subsection"><a name="utils"><tt>llvm/utils</tt></a></div>
1408 <div class="doc_text">
1410 <p>This directory contains utilities for working with LLVM source code, and some
1411 of the utilities are actually required as part of the build process because they
1412 are code generators for parts of LLVM infrastructure.</p>
1415 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1416 that finds differences between code that LLC generates and code that LLI
1417 generates. This is a useful tool if you are debugging one of them,
1418 assuming that the other generates correct output. For the full user
1419 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
1421 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1422 update your CVS tree, but produce a much cleaner and more organized output
1423 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1424 together all the new and updated files and modified files in separate
1425 sections, so you can see at a glance what has changed. If you are at the
1426 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1427 preferred way of updating the tree.<p>
1429 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1430 syntax-highlighting files which will work with Emacs and XEmacs editors,
1431 providing syntax highlighting support for LLVM assembly files and TableGen
1432 description files. For information on how to use the syntax files, consult
1433 the <tt>README</tt> file in that directory.<p>
1435 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1436 and outputs all non-generated source files, which is useful if one wishes
1437 to do a lot of development across directories and does not want to
1438 individually find each file. One way to use it is to run, for example:
1439 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1442 <dt><tt><b>llvmgrep</b></tt></dt>
1443 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1444 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1445 line. This is a very efficient way of searching the source base for a
1446 particular regular expression.</dd>
1448 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1449 files in the current directory and then compiles and links the tool that
1450 is the first argument. For example, assuming you are in the directory
1451 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1452 simply running <tt>makellvm llc</tt> will make a build of the current
1453 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1454 causing a re-linking of LLC.<p>
1456 <dt><tt><b>NightlyTest.pl</b></tt> and
1457 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1458 cron script to generate nightly status reports of the functionality of
1459 tools, and the results can be seen by following the appropriate link on
1460 the <a href="http://llvm.org/">LLVM homepage</a>.<p>
1462 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1463 the tool used to generate register descriptions, instruction set
1464 descriptions, and even assemblers from common TableGen description
1467 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1468 syntax-highlighting files which will work with the VIM editor, providing
1469 syntax highlighting support for LLVM assembly files and TableGen
1470 description files. For information on how to use the syntax files, consult
1471 the <tt>README</tt> file in that directory.<p>
1477 <!-- ======================================================================= -->
1478 <div class="doc_subsection"><a name="win32"><tt>llvm/win32</tt></a></div>
1479 <div class="doc_text">
1480 <p>This directory contains build scripts and project files for use with
1481 Visual C++. This allows developers on Windows to build LLVM without the need
1482 for Cygwin. The contents of this directory should be considered experimental
1486 <!-- *********************************************************************** -->
1487 <div class="doc_section">
1488 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1490 <!-- *********************************************************************** -->
1492 <div class="doc_text">
1493 <p>This section gives an example of using LLVM. Since we are currently
1494 transitioning from llvm-gcc3 to llvm-gcc4, we include examples for both.
1498 <!-- ======================================================================= -->
1499 <div class="doc_subsection"><a name="tutorial3">Example with llvm-gcc4</a></div>
1501 <div class="doc_text">
1504 <li>First, create a simple C file, name it 'hello.c':
1506 #include <stdio.h>
1508 printf("hello world\n");
1513 <li><p>Next, compile the C file into a native executable:</p>
1515 <p><tt>% llvm-gcc hello.c -o hello</tt></p>
1517 <p>Note that llvm-gcc works just like GCC by default. The standard -S and
1518 -c arguments work as usual (producing a native .s or .o file,
1521 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1522 <p><tt>% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc</tt></p>
1524 <p>The -emit-llvm option can be used with the -S or -c options to emit an
1525 LLVM ".ll" or ".bc" file (respectively) for the code. This allows you
1526 to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
1527 the bytecode file.</p>
1529 <p>Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
1532 <li><p>Run the program in both forms. To run the program, use:</p>
1534 <p><tt>% ./hello</tt></p>
1538 <p><tt>% lli hello.bc</tt></p>
1540 <p>The second examples shows how to invoke the LLVM JIT, <a
1541 href="CommandGuide/html/lli.html">lli</a>.</p></li>
1543 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1546 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1548 <li><p>Compile the program to native assembly using the LLC code
1551 <p><tt>% llc hello.bc -o hello.s</tt></p>
1553 <li><p>Assemble the native assembly language file into a program:</p>
1555 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1556 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1558 <li><p>Execute the native code program:</p>
1560 <p><tt>% ./hello.native</tt></p>
1562 <p>Note that using llvm-gcc to compile directly to native code (i.e. when
1563 the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
1570 <!-- ======================================================================= -->
1571 <div class="doc_subsection"><a name="tutorial3">Example with llvm-gcc3</a></div>
1573 <div class="doc_text">
1576 <li>First, create a simple C file, name it 'hello.c':
1578 #include <stdio.h>
1580 printf("hello world\n");
1585 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1586 <p><tt>% llvm-gcc hello.c -o hello</tt></p>
1588 <p>Note that you should have already built the tools and they have to be
1589 in your path, at least <tt>gccas</tt> and <tt>gccld</tt>.</p>
1591 <p>This will create two result files: <tt>hello</tt> and
1592 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1593 corresponds the the compiled program and the library facilities that it
1594 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1595 file with <tt>lli</tt>, making the result directly executable. Note that
1596 all LLVM optimizations are enabled by default, so there is no need for a
1597 "-O3" switch.</p></li>
1599 <li><p>Run the program. To make sure the program ran, execute one of the
1600 following commands:</p>
1602 <p><tt>% ./hello</tt></p>
1606 <p><tt>% lli hello.bc</tt></p></li>
1608 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1611 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1613 <li><p>Compile the program to native assembly using the LLC code
1616 <p><tt>% llc hello.bc -o hello.s</tt></p>
1618 <li><p>Assemble the native assembly language file into a program:</p>
1620 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1621 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1623 <li><p>Execute the native code program:</p>
1625 <p><tt>% ./hello.native</tt></p></li>
1631 <!-- *********************************************************************** -->
1632 <div class="doc_section">
1633 <a name="problems">Common Problems</a>
1635 <!-- *********************************************************************** -->
1637 <div class="doc_text">
1639 <p>If you are having problems building or using LLVM, or if you have any other
1640 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1641 Asked Questions</a> page.</p>
1645 <!-- *********************************************************************** -->
1646 <div class="doc_section">
1647 <a name="links">Links</a>
1649 <!-- *********************************************************************** -->
1651 <div class="doc_text">
1653 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1654 some simple things... there are many more interesting and complicated things
1655 that you can do that aren't documented here (but we'll gladly accept a patch
1656 if you want to write something up!). For more information about LLVM, check
1660 <li><a href="http://llvm.org/">LLVM homepage</a></li>
1661 <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1662 <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1663 that Uses LLVM</a></li>
1668 <!-- *********************************************************************** -->
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1677 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1678 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1679 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
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