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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">Compiling LLVM As A Cross-Compiler</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.
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 project</li>
312 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
313 <li><a name="pf_8">Binutils up to post-2.17 has bug in bfd/cofflink.c
314 preventing LLVM from building correctly. Several workarounds have been
315 introduced into LLVM build system, but the bug can occur anytime in the
316 future. It's highly recommended to rebuild your current binutils with the
317 patch from <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=2659">
318 Binutils bugzilla</a>, if it's wasn't already applied. </a></li>
322 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
323 mode, depending on the system (it is so large because of all the debugging
324 information and the fact that the libraries are statically linked into multiple
325 tools). If you do not need many of the tools and you are space-conscious,
326 you can disable them individually in <tt>llvm/tools/Makefile</tt>. The Release
327 build requires considerably less space.</p>
329 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
330 guaranteed to do so. If compilation is successful, the LLVM utilities should be
331 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
332 generation should work as well, although the generated native code may not work
333 on your platform.</p>
335 <p>The GCC front end is not very portable at the moment. If you want to get it
336 to work on another platform, you can download a copy of the source and <a
337 href="CFEBuildInstrs.html">try to compile it</a> on your platform.</p>
341 <!-- ======================================================================= -->
342 <div class="doc_subsection"><a name="software"><b>Software</b></a></div>
343 <div class="doc_text">
344 <p>Compiling LLVM requires that you have several software packages
345 installed. The table below lists those required packages. The Package column
346 is the usual name for the software package that LLVM depends on. The Version
347 column provides "known to work" versions of the package. The Notes column
348 describes how LLVM uses the package and provides other details.</p>
350 <tr><th>Package</th><th>Version</th><th>Notes</th></tr>
353 <td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
354 <td>3.79, 3.79.1</td>
355 <td>Makefile/build processor</td>
359 <td><a href="http://gcc.gnu.org">GCC</a></td>
361 <td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
365 <td><a href="http://www.gnu.org/software/texinfo">TeXinfo</a></td>
367 <td>For building the CFE</td>
371 <td><a href="http://www.gnu.org/software/flex">Flex</a></td>
373 <td>LEX compiler</td>
377 <td><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></td>
378 <td>1.28, 1.35, 1.75, 1.875d, 2.0, or 2.1<br>(not 1.85 or 1.875)</td>
379 <td>YACC compiler</td>
383 <td><a href="https://www.cvshome.org/downloads.html">CVS</a></td>
385 <td>CVS access to LLVM<sup><a href="#sf2">2</a></sup></td>
389 <td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
391 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
395 <td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
397 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
401 <td><a href="http://expect.nist.gov/">expect</a></td>
403 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
407 <td><a href="http://www.perl.com/download.csp">perl</a></td>
409 <td>Nightly tester, utilities</td>
413 <td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
415 <td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
419 <td><a href="http://www.gnu.org/software/autoconf">GNU Autoconf</a></td>
421 <td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
425 <td><a href="http://www.gnu.org/software/automake">GNU Automake</a></td>
427 <td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
431 <td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
433 <td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
439 <div class="doc_notes">
441 <li><a name="sf3">Only the C and C++ languages are needed so there's no
442 need to build the other languages for LLVM's purposes.</a> See
443 <a href="#brokengcc">below</a> for specific version info.</li>
444 <li><a name="sf2">You only need CVS if you intend to build from the
445 latest LLVM sources. If you're working from a release distribution, you
446 don't need CVS.</a></li>
447 <li><a name="sf3">Only needed if you want to run the automated test
448 suite in the <tt>llvm/test</tt> directory.</a></li>
449 <li><a name="sf4">If you want to make changes to the configure scripts,
450 you will need GNU autoconf (2.59), and consequently, GNU M4 (version 1.4
451 or higher). You will also need automake (1.9.2). We only use aclocal
452 from that package.</a></li>
456 <p>Additionally, your compilation host is expected to have the usual
457 plethora of Unix utilities. Specifically:</p>
459 <li><b>ar</b> - archive library builder</li>
460 <li><b>bzip2*</b> - bzip2 command for distribution generation</li>
461 <li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
462 <li><b>chmod</b> - change permissions on a file</li>
463 <li><b>cat</b> - output concatenation utility</li>
464 <li><b>cp</b> - copy files</li>
465 <li><b>date</b> - print the current date/time </li>
466 <li><b>echo</b> - print to standard output</li>
467 <li><b>egrep</b> - extended regular expression search utility</li>
468 <li><b>etags</b> - C/C++ tag file creator for vim/emacs</li>
469 <li><b>find</b> - find files/dirs in a file system</li>
470 <li><b>grep</b> - regular expression search utility</li>
471 <li><b>gzip*</b> - gzip command for distribution generation</li>
472 <li><b>gunzip*</b> - gunzip command for distribution checking</li>
473 <li><b>install</b> - install directories/files </li>
474 <li><b>mkdir</b> - create a directory</li>
475 <li><b>mv</b> - move (rename) files</li>
476 <li><b>ranlib</b> - symbol table builder for archive libraries</li>
477 <li><b>rm</b> - remove (delete) files and directories</li>
478 <li><b>sed</b> - stream editor for transforming output</li>
479 <li><b>sh</b> - Bourne shell for make build scripts</li>
480 <li><b>tar</b> - tape archive for distribution generation</li>
481 <li><b>test</b> - test things in file system</li>
482 <li><b>unzip*</b> - unzip command for distribution checking</li>
483 <li><b>zip*</b> - zip command for distribution generation</li>
487 <!-- ======================================================================= -->
488 <div class="doc_subsection">
489 <a name="brokengcc">Broken versions of GCC</a>
492 <div class="doc_text">
494 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
495 bugs in the compiler. In particular, several versions of GCC crash when trying
496 to compile LLVM. We routinely use GCC 3.3.3, 3.4.0, and Apple 4.0.1
497 successfully with them (however, see below). Other versions of GCC will
498 probably work as well. GCC versions listed
499 here are known to not work. If you are using one of these versions, please try
500 to upgrade your GCC to something more recent. If you run into a problem with a
501 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
502 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
503 of GCC you are using.
506 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
507 problems in the STL that effectively prevent it from compiling LLVM.
510 <p><b>GCC 3.2.2</b>: This version of GCC fails to compile LLVM.</p>
512 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
513 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
514 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
516 <p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
517 Cygwin does not work. Please <a href="CFEBuildInstrs.html#cygwin">upgrade
518 to a newer version</a> if possible.</p>
519 <p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
520 possibly others) does not compile LLVM correctly (it appears that exception
521 handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
522 to a newer version of GCC.</p>
523 <p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
525 <p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
526 default with ENABLE_OPTIMIZED=1. To work around this, build with
527 "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
532 <!-- *********************************************************************** -->
533 <div class="doc_section">
534 <a name="starting"><b>Getting Started with LLVM</b></a>
536 <!-- *********************************************************************** -->
538 <div class="doc_text">
540 <p>The remainder of this guide is meant to get you up and running with
541 LLVM and to give you some basic information about the LLVM environment.</p>
543 <p>The later sections of this guide describe the <a
544 href="#layout">general layout</a> of the the LLVM source tree, a <a
545 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
546 href="#links">links</a> to find more information about LLVM or to get
550 <!-- ======================================================================= -->
551 <div class="doc_subsection">
552 <a name="terminology">Terminology and Notation</a>
555 <div class="doc_text">
557 <p>Throughout this manual, the following names are used to denote paths
558 specific to the local system and working environment. <i>These are not
559 environment variables you need to set but just strings used in the rest
560 of this document below</i>. In any of the examples below, simply replace
561 each of these names with the appropriate pathname on your local system.
562 All these paths are absolute:</p>
567 This is the top level directory of the LLVM source tree.
572 This is the top level directory of the LLVM object tree (i.e. the
573 tree where object files and compiled programs will be placed. It
574 can be the same as SRC_ROOT).
579 This is where the LLVM GCC Front End is installed.
581 For the pre-built GCC front end binaries, the LLVMGCCDIR is
582 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
587 <!-- ======================================================================= -->
588 <div class="doc_subsection">
589 <a name="environment">Setting Up Your Environment</a>
592 <div class="doc_text">
595 In order to compile and use LLVM, you may need to set some environment
599 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bytecode/libs</tt></dt>
600 <dd>[Optional] This environment variable helps LLVM linking tools find the
601 locations of your bytecode libraries. It is provided only as a
602 convenience since you can specify the paths using the -L options of the
603 tools and the C/C++ front-end will automatically use the bytecode files
605 <tt>lib</tt> directory.</dd>
610 <!-- ======================================================================= -->
611 <div class="doc_subsection">
612 <a name="unpack">Unpacking the LLVM Archives</a>
615 <div class="doc_text">
618 If you have the LLVM distribution, you will need to unpack it before you
619 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
620 suite and the LLVM GCC front end compiled for your platform. There is an
621 additional test suite that is optional. Each file is a TAR archive that is
622 compressed with the gzip program.
625 <p>The files are as follows, with <em>x.y</em> marking the version number:
627 <dt><tt>llvm-x.y.tar.gz</tt></dt>
628 <dd>Source release for the LLVM libraries and tools.<br/></dd>
630 <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
631 <dd>Source release for the LLVM test suite.</dd>
633 <dt><tt>cfrontend-x.y.source.tar.gz</tt></dt>
634 <dd>Source release of the GCC front end.<br/></dd>
636 <dt><tt>cfrontend-x.y.i686-redhat-linux-gnu.tar.gz</tt></dt>
637 <dd>Binary release of the GCC front end for Linux/x86.<br/></dd>
639 <dt><tt>llvm-gcc4-x.y.source.tar.gz</tt></dt>
640 <dd>Source release of the llvm-gcc4 front end. See README.LLVM in the root
641 directory for build instructions.<br/></dd>
643 <dt><tt>llvm-gcc4-x.y.powerpc-apple-darwin8.6.0.tar.gz</tt></dt>
644 <dd>Binary release of the llvm-gcc4 front end for MacOS X/PowerPC.<br/></dd>
646 <dt><tt>llvm-gcc4-x.y.i686-apple-darwin8.6.1.tar.gz</tt></dt>
647 <dd>Binary release of the llvm-gcc4 front end for MacOS X/X86.<br/></dd>
650 <p>It is also possible to download the sources of the llvm-gcc4 front end from
651 a read-only subversion mirror at svn://anonsvn.opensource.apple.com/svn/llvm.
656 <!-- ======================================================================= -->
657 <div class="doc_subsection">
658 <a name="checkout">Checkout LLVM from CVS</a>
661 <div class="doc_text">
663 <p>If you have access to our CVS repository, you can get a fresh copy of
664 the entire source code. All you need to do is check it out from CVS as
668 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
669 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
670 <li>Hit the return key when prompted for the password.
671 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
675 <p>This will create an '<tt>llvm</tt>' directory in the current
676 directory and fully populate it with the LLVM source code, Makefiles,
677 test directories, and local copies of documentation files.</p>
679 <p>If you want to get a specific release (as opposed to the most recent
680 revision), you can specify a label. The following releases have the following
684 <li>Release 1.7: <b>RELEASE_17</b></li>
685 <li>Release 1.6: <b>RELEASE_16</b></li>
686 <li>Release 1.5: <b>RELEASE_15</b></li>
687 <li>Release 1.4: <b>RELEASE_14</b></li>
688 <li>Release 1.3: <b>RELEASE_13</b></li>
689 <li>Release 1.2: <b>RELEASE_12</b></li>
690 <li>Release 1.1: <b>RELEASE_11</b></li>
691 <li>Release 1.0: <b>RELEASE_1</b></li>
694 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
695 you get it from the CVS repository:</p>
698 cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-test
700 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
701 configured by the LLVM configure script as well as automatically updated when
702 you run <tt>cvs update</tt>.</p>
704 <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>
707 cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-gcc
710 <p>Please note that you must follow <a href="CFEBuildInstrs.html">these
711 instructions</a> to successfully build the LLVM GCC front-end.</p>
715 <!-- ======================================================================= -->
716 <div class="doc_subsection">
717 <a name="installcf">Install the GCC Front End</a>
720 <div class="doc_text">
722 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
723 GCC front end from the binary distribution. It is used for building the
724 bytecode libraries later used by the GCC front end for linking programs, and its
725 location must be specified when the LLVM suite is configured.</p>
727 <p>To install the GCC front end, do the following:</p>
730 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
731 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
735 <p>Next, you will need to fix your system header files:</p>
737 <p><tt>cd cfrontend/<i>platform</i><br>
738 ./fixheaders</tt></p>
740 <p>The binary versions of the GCC front end may not suit all of your needs. For
741 example, the binary distribution may include an old version of a system header
742 file, not "fix" a header file that needs to be fixed for GCC, or it may be
743 linked with libraries not available on your system.</p>
745 <p>In cases like these, you may want to try <a
746 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
747 not for the faint of heart, so be forewarned.</p>
751 <!-- ======================================================================= -->
752 <div class="doc_subsection">
753 <a name="config">Local LLVM Configuration</a>
756 <div class="doc_text">
758 <p>Once checked out from the CVS repository, the LLVM suite source code must be
759 configured via the <tt>configure</tt> script. This script sets variables in the
760 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
761 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
762 the Makefiles needed to begin building LLVM.</p>
764 <p>The following environment variables are used by the <tt>configure</tt>
765 script to configure the build system:</p>
768 <tr><th>Variable</th><th>Purpose</th></tr>
771 <td>Tells <tt>configure</tt> which C compiler to use. By default,
772 <tt>configure</tt> will look for the first GCC C compiler in
773 <tt>PATH</tt>. Use this variable to override
774 <tt>configure</tt>'s default behavior.</td>
778 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
779 <tt>configure</tt> will look for the first GCC C++ compiler in
780 <tt>PATH</tt>. Use this variable to override
781 <tt>configure</tt>'s default behavior.</td>
785 <p>The following options can be used to set or enable LLVM specific options:</p>
788 <dt><i>--with-llvmgccdir</i></dt>
789 <dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
790 The value of this option should specify the full pathname of the C/C++ Front
791 End to be used. If this option is not provided, the PATH will be searched for
792 a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
793 be inferred from the path found. If the option is not given, and no llvm-gcc
794 can be found in the path then a warning will be produced by
795 <tt>configure</tt> indicating this situation. LLVM may still be built with
796 the <tt>tools-only</tt> target but attempting to build the runtime libraries
797 will fail as these libraries require llvm-gcc and llvm-g++. See
798 <a href="#installcf">Install the GCC Front End</a> for details on installing
799 the C/C++ Front End. See
800 <a href="CFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
801 for details on building the C/C++ Front End.</dd>
802 <dt><i>--with-tclinclude</i></dt>
803 <dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
804 found. Use this if you have multiple tcl installations on your machine and you
805 want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
806 dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
807 option, the LLVM configure script will search for the tcl 8.4 and 8.3
811 <dt><i>--enable-optimized</i></dt>
813 Enables optimized compilation by default (debugging symbols are removed
814 and GCC optimization flags are enabled). The default is to use an
815 unoptimized build (also known as a debug build).
818 <dt><i>--enable-debug-runtime</i></dt>
820 Enables debug symbols in the runtime libraries. The default is to strip
821 debug symbols from the runtime libraries.
823 <dt><i>--enable-jit</i></dt>
825 Compile the Just In Time (JIT) compiler functionality. This is not
827 on all platforms. The default is dependent on platform, so it is best
828 to explicitly enable it if you want it.
831 <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
832 <dd>Controls which targets will be built and linked into llc. The default
833 value for <tt>target_options</tt> is "all" which builds and links all
834 available targets. The value "host-only" can be specified to build only a
835 native compiler (no cross-compiler targets available). The "native" target is
836 selected as the target of the build host. You can also specify a comma
837 separated list of target names that you want available in llc. The target
838 names use all lower case. The current set of targets is: <br/>
839 <tt>alpha, ia64, powerpc, skeleton, sparc, x86</tt>.
841 <dt><i>--enable-doxygen</i></dt>
842 <dd>Look for the doxygen program and enable construction of doxygen based
843 documentation from the source code. This is disabled by default because
844 generating the documentation can take a long time and producess 100s of
845 megabytes of output.</dd>
848 <p>To configure LLVM, follow these steps:</p>
851 <li>Change directory into the object root directory:
853 <tt>cd <i>OBJ_ROOT</i></tt>
856 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
858 <tt><i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</tt>
864 <!-- ======================================================================= -->
865 <div class="doc_subsection">
866 <a name="compile">Compiling the LLVM Suite Source Code</a>
869 <div class="doc_text">
871 <p>Once you have configured LLVM, you can build it. There are three types of
877 These builds are the default when one types <tt>gmake</tt> (unless the
878 <tt>--enable-optimized</tt> option was used during configuration). The
879 build system will compile the tools and libraries with debugging
883 <dt>Release (Optimized) Builds
885 These builds are enabled with the <tt>--enable-optimized</tt> option to
886 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
887 <tt>gmake</tt> command line. For these builds, the build system will
888 compile the tools and libraries with GCC optimizations enabled and strip
889 debugging information from the libraries and executables it generates.
894 These builds are for use with profiling. They compile profiling
895 information into the code for use with programs like <tt>gprof</tt>.
896 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
897 on the <tt>gmake</tt> command line.
900 <p>Once you have LLVM configured, you can build it by entering the
901 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
903 <p><tt>gmake</tt></p>
905 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
906 are using a version of GCC that is known not to compile LLVM.</p>
909 If you have multiple processors in your machine, you may wish to use some of
910 the parallel build options provided by GNU Make. For example, you could use the
913 <p><tt>gmake -j2</tt></p>
915 <p>There are several special targets which are useful when working with the LLVM
919 <dt><tt>gmake clean</tt>
921 Removes all files generated by the build. This includes object files,
922 generated C/C++ files, libraries, and executables.
925 <dt><tt>gmake dist-clean</tt>
927 Removes everything that <tt>gmake clean</tt> does, but also removes files
928 generated by <tt>configure</tt>. It attempts to return the source tree to the
929 original state in which it was shipped.
932 <dt><tt>gmake install</tt>
934 Installs LLVM header files, libraries, tools, and documentation in a
936 under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
937 defaults to <tt>/usr/local</tt>.
940 <dt><tt>gmake -C runtime install-bytecode</tt>
942 Assuming you built LLVM into $OBJDIR, when this command is run, it will
943 install bytecode libraries into the GCC front end's bytecode library
944 directory. If you need to update your bytecode libraries,
945 this is the target to use once you've built them.
949 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
950 details on these <tt>make</tt> targets and descriptions of other targets
953 <p>It is also possible to override default values from <tt>configure</tt> by
954 declaring variables on the command line. The following are some examples:</p>
957 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
959 Perform a Release (Optimized) build.
962 <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
964 Perform a Release (Optimized) build without assertions enabled.
967 <dt><tt>gmake ENABLE_PROFILING=1</tt>
969 Perform a Profiling build.
972 <dt><tt>gmake VERBOSE=1</tt>
974 Print what <tt>gmake</tt> is doing on standard output.
977 <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
978 <dd>Ask each tool invoked by the makefiles to print out what it is doing on
979 the standard output. This also implies <tt>VERBOSE=1</tt>.
983 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
984 it and any subdirectories that it contains. Entering any directory inside the
985 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
986 that directory that is out of date.</p>
990 <!-- ======================================================================= -->
991 <div class="doc_subsection">
992 <a name="cross-compile">Compiling LLVM As A Cross-compiler</a>
995 <div class="doc_text">
996 <p>LLVM can be built as a cross-compiler, however some additional steps are
997 required.<sup><a href="#ccn_1">1</a></sup> To build a cross-compiler, use
998 these instructions:</p>
1000 <li>Configure and build LLVM Suite as a native compiler. You will need
1001 just <tt>TableGen</tt> from that build.
1003 <li>If you have <tt>$LLVM_OBJ_ROOT=$LLVM_SRC_ROOT</tt> just execute
1004 <tt>make -C utils/TableGen</tt> after configuring.</li>
1005 <li>Otherwise you will need to monitor building process and terminate
1006 it just after <tt>TableGen</tt> was built.</li>
1009 <li>Copy the TableGen binary to somewhere safe (out of your build tree).
1011 <li>Configure LLVM to build as a cross-compiler. To do this, supply the
1012 configure script with <tt>--build</tt> and <tt>--host</tt> options that
1013 are different. The values of these options must be legal target triples and
1014 should specify a processor for which LLVM supports code generation.</li>
1015 <li>Put the saved <tt>TableGen</tt> executable into the
1016 into <tt>$LLVM_OBJ_ROOT/{BUILD_TYPE}/bin</tt> directory (e.g. into
1017 <tt>.../Release/bin</tt> for a Release build).</li>
1018 <li>Build LLVM as usual.</li>
1020 <p><b>Notes:</b></p>
1021 <div class="doc_notes">
1023 <li><a name="ccn_1">Cross-compiling</a> was tested only with Linux as
1024 build platform and Windows as host using mingw32 cross-compiler. Other
1025 combinations have not been tested.</li>
1030 <!-- ======================================================================= -->
1031 <div class="doc_subsection">
1032 <a name="objfiles">The Location of LLVM Object Files</a>
1035 <div class="doc_text">
1037 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1038 several LLVM builds. Hence, it is possible to build LLVM for several different
1039 platforms or configurations using the same source tree.</p>
1041 <p>This is accomplished in the typical autoconf manner:</p>
1044 <li><p>Change directory to where the LLVM object files should live:</p>
1046 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
1048 <li><p>Run the <tt>configure</tt> script found in the LLVM source
1051 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
1054 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1055 named after the build type:</p>
1062 <dd><tt><i>OBJ_ROOT</i>/Debug/bin</tt>
1064 <dd><tt><i>OBJ_ROOT</i>/Debug/lib</tt>
1072 <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1074 <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1082 <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1084 <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1090 <!-- ======================================================================= -->
1091 <div class="doc_subsection">
1092 <a name="optionalconfig">Optional Configuration Items</a>
1095 <div class="doc_text">
1098 If you're running on a Linux system that supports the "<a
1099 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">
1101 module, and you have root access on the system, you can set your system up to
1102 execute LLVM bytecode files directly. To do this, use commands like this (the
1103 first command may not be required if you are already using the module):</p>
1105 <div class="doc_code">
1107 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1108 $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1109 $ chmod u+x hello.bc (if needed)
1115 This allows you to execute LLVM bytecode files directly. Thanks to Jack
1116 Cummings for pointing this out!
1122 <!-- *********************************************************************** -->
1123 <div class="doc_section">
1124 <a name="layout"><b>Program Layout</b></a>
1126 <!-- *********************************************************************** -->
1128 <div class="doc_text">
1130 <p>One useful source of information about the LLVM source base is the LLVM <a
1131 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
1132 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1133 The following is a brief introduction to code layout:</p>
1137 <!-- ======================================================================= -->
1138 <div class="doc_subsection"><a name="cvsdir"><tt>CVS</tt> directories</a></div>
1139 <div class="doc_text">
1140 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
1141 the most part these can just be ignored.</p>
1144 <!-- ======================================================================= -->
1145 <div class="doc_subsection"><a name="examples"><tt>llvm/examples</tt></a></div>
1146 <div class="doc_text">
1147 <p>This directory contains some simple examples of how to use the LLVM IR and
1151 <!-- ======================================================================= -->
1152 <div class="doc_subsection"><a name="include"><tt>llvm/include</tt></a></div>
1153 <div class="doc_text">
1155 <p>This directory contains public header files exported from the LLVM
1156 library. The three main subdirectories of this directory are:</p>
1159 <dt><tt><b>llvm/include/llvm</b></tt></dt>
1160 <dd>This directory contains all of the LLVM specific header files. This
1161 directory also has subdirectories for different portions of LLVM:
1162 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1165 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1166 <dd>This directory contains generic support libraries that are provided with
1167 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1168 and a Command Line option processing library store their header files here.
1171 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1172 <dd>This directory contains header files configured by the <tt>configure</tt>
1173 script. They wrap "standard" UNIX and C header files. Source code can
1174 include these header files which automatically take care of the conditional
1175 #includes that the <tt>configure</tt> script generates.</dd>
1179 <!-- ======================================================================= -->
1180 <div class="doc_subsection"><a name="lib"><tt>llvm/lib</tt></a></div>
1181 <div class="doc_text">
1183 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1184 almost all code exists in libraries, making it very easy to share code among the
1185 different <a href="#tools">tools</a>.</p>
1188 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1189 <dd> This directory holds the core LLVM source files that implement core
1190 classes like Instruction and BasicBlock.</dd>
1192 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1193 <dd>This directory holds the source code for the LLVM assembly language parser
1196 <dt><tt><b>llvm/lib/ByteCode/</b></tt></dt>
1197 <dd>This directory holds code for reading and write LLVM bytecode.</dd>
1199 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1200 different program analyses, such as Dominator Information, Call Graphs,
1201 Induction Variables, Interval Identification, Natural Loop Identification,
1204 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1205 <dd> This directory contains the source code for the LLVM to LLVM program
1206 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1207 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1208 Elimination, and many others.</dd>
1210 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1211 <dd> This directory contains files that describe various target architectures
1212 for code generation. For example, the <tt>llvm/lib/Target/X86</tt>
1213 directory holds the X86 machine description while
1214 <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
1216 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1217 <dd> This directory contains the major parts of the code generator: Instruction
1218 Selector, Instruction Scheduling, and Register Allocation.</dd>
1220 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1221 <dd> This directory contains the source level debugger library that makes
1222 it possible to instrument LLVM programs so that a debugger could identify
1223 source code locations at which the program is executing.</dd>
1225 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1226 <dd> This directory contains libraries for executing LLVM bytecode directly
1227 at runtime in both interpreted and JIT compiled fashions.</dd>
1229 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1230 <dd> This directory contains the source code that corresponds to the header
1231 files located in <tt>llvm/include/Support/</tt>.</dd>
1233 <dt><tt><b>llvm/lib/System/</b></tt></dt>
1234 <dd>This directory contains the operating system abstraction layer that
1235 shields LLVM from platform-specific coding.</dd>
1240 <!-- ======================================================================= -->
1241 <div class="doc_subsection"><a name="projects"><tt>llvm/projects</tt></a></div>
1242 <div class="doc_text">
1243 <p>This directory contains projects that are not strictly part of LLVM but are
1244 shipped with LLVM. This is also the directory where you should create your own
1245 LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1246 to set up your own project. See <tt>llvm/projects/Stacker</tt> for a fully
1247 functional example of a compiler front end.</p>
1250 <!-- ======================================================================= -->
1251 <div class="doc_subsection"><a name="runtime"><tt>llvm/runtime</tt></a></div>
1252 <div class="doc_text">
1254 <p>This directory contains libraries which are compiled into LLVM bytecode and
1255 used when linking programs with the GCC front end. Most of these libraries are
1256 skeleton versions of real libraries; for example, libc is a stripped down
1257 version of glibc.</p>
1259 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1264 <!-- ======================================================================= -->
1265 <div class="doc_subsection"><a name="test"><tt>llvm/test</tt></a></div>
1266 <div class="doc_text">
1267 <p>This directory contains feature and regression tests and other basic sanity
1268 checks on the LLVM infrastructure. These are intended to run quickly and cover
1269 a lot of territory without being exhaustive.</p>
1272 <!-- ======================================================================= -->
1273 <div class="doc_subsection"><a name="llvmtest"><tt>llvm-test</tt></a></div>
1274 <div class="doc_text">
1275 <p>This is not a directory in the normal llvm module; it is a separate CVS
1276 module that must be checked out (usually to <tt>projects/llvm-test</tt>). This
1277 module contains a comprehensive correctness, performance, and benchmarking
1279 suite for LLVM. It is a separate CVS module because not every LLVM user is
1280 interested in downloading or building such a comprehensive test suite. For
1281 further details on this test suite, please see the
1282 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1285 <!-- ======================================================================= -->
1286 <div class="doc_subsection"><a name="tools"><tt>llvm/tools</tt></a></div>
1287 <div class="doc_text">
1289 <p>The <b>tools</b> directory contains the executables built out of the
1290 libraries above, which form the main part of the user interface. You can
1291 always get help for a tool by typing <tt>tool_name --help</tt>. The
1292 following is a brief introduction to the most important tools. More detailed
1293 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1296 <dt><tt><b>analyze</b></tt></dt>
1297 <dd><tt>analyze</tt> is used to run a specific
1298 analysis on an input LLVM bytecode file and print out the results. It is
1299 primarily useful for debugging analyses, or familiarizing yourself with
1300 what an analysis does.</dd>
1302 <dt><tt><b>bugpoint</b></tt></dt>
1303 <dd><tt>bugpoint</tt> is used to debug
1304 optimization passes or code generation backends by narrowing down the
1305 given test case to the minimum number of passes and/or instructions that
1306 still cause a problem, whether it is a crash or miscompilation. See <a
1307 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1308 on using <tt>bugpoint</tt>.</dd>
1310 <dt><tt><b>llvmc</b></tt></dt>
1311 <dd>The LLVM Compiler Driver. This program can
1312 be configured to utilize both LLVM and non-LLVM compilation tools to enable
1313 pre-processing, translation, optimization, assembly, and linking of programs
1314 all from one command line. <tt>llvmc</tt> also takes care of processing the
1315 dependent libraries found in bytecode. This reduces the need to get the
1316 traditional <tt>-l<name></tt> options right on the command line. Please
1317 note that this tool, while functional, is still experimental and not feature
1320 <dt><tt><b>llvm-ar</b></tt></dt>
1321 <dd>The archiver produces an archive containing
1322 the given LLVM bytecode files, optionally with an index for faster
1325 <dt><tt><b>llvm-as</b></tt></dt>
1326 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1329 <dt><tt><b>llvm-dis</b></tt></dt>
1330 <dd>The disassembler transforms the LLVM bytecode to human readable
1333 <dt><tt><b>llvm-ld</b></tt></dt>
1334 <dd><tt>llvm-ld</tt> is very similar to gccld and provides a general purpose
1335 and extensible linker for LLVM. This is the linker invoked by <tt>llvmc</tt>.
1336 It allows optimization modules to be loaded so that language specific
1337 optimizations can be applied at link time. This tool is considered
1340 <dt><tt><b>llvm-link</b></tt></dt>
1341 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1342 a single program.</dd>
1344 <dt><tt><b>lli</b></tt></dt>
1345 <dd><tt>lli</tt> is the LLVM interpreter, which
1346 can directly execute LLVM bytecode (although very slowly...). In addition
1347 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
1348 specifying <tt>-trace</tt> on the command line). Finally, for
1349 architectures that support it (currently x86, Sparc, and PowerPC), by default,
1350 <tt>lli</tt> will function as a Just-In-Time compiler (if the
1351 functionality was compiled in), and will execute the code <i>much</i>
1352 faster than the interpreter.</dd>
1354 <dt><tt><b>llc</b></tt></dt>
1355 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1356 translates LLVM bytecode to a native code assembly file or to C code (with
1357 the -march=c option).</dd>
1359 <dt><tt><b>llvm-gcc</b></tt></dt>
1360 <dd><tt>llvm-gcc</tt> is a GCC-based C frontend
1361 that has been retargeted to emit LLVM code as the machine code output. It
1362 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
1363 -o</tt> options that are typically used. The source code for the
1364 <tt>llvm-gcc</tt> tool is available as a separate CVS module.
1367 <dt><tt><b>gccas</b></tt></dt>
1368 <dd>This tool is invoked by the <tt>llvm-gcc</tt> frontend as the
1369 "assembler" part of the compiler. This tool actually assembles LLVM
1370 assembly to LLVM bytecode, performs a variety of optimizations, and
1371 outputs LLVM bytecode. Thus when you invoke
1372 <tt>llvm-gcc -c x.c -o x.o</tt>, you are causing <tt>gccas</tt> to be
1373 run, which writes the <tt>x.o</tt> file (which is an LLVM bytecode file
1374 that can be disassembled or manipulated just like any other bytecode
1375 file). The command line interface to <tt>gccas</tt> is designed to be
1376 as close as possible to the <b>system</b> `<tt>as</tt>' utility so that
1377 the gcc frontend itself did not have to be modified to interface to
1378 a "weird" assembler.</dd>
1380 <dt><tt><b>gccld</b></tt></dt>
1381 <dd><tt>gccld</tt> links together several LLVM bytecode files into one
1382 bytecode file and does some optimization. It is the linker invoked by
1383 the GCC frontend when multiple .o files need to be linked together.
1384 Like <tt>gccas</tt>, the command line interface of <tt>gccld</tt> is
1385 designed to match the system linker, to aid interfacing with the GCC
1391 <dt><tt><b>opt</b></tt></dt>
1392 <dd><tt>opt</tt> reads LLVM bytecode, applies a
1393 series of LLVM to LLVM transformations (which are specified on the command
1394 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
1395 command is a good way to get a list of the program transformations
1396 available in LLVM.</dd>
1400 <!-- ======================================================================= -->
1401 <div class="doc_subsection"><a name="utils"><tt>llvm/utils</tt></a></div>
1402 <div class="doc_text">
1404 <p>This directory contains utilities for working with LLVM source code, and some
1405 of the utilities are actually required as part of the build process because they
1406 are code generators for parts of LLVM infrastructure.</p>
1409 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1410 that finds differences between code that LLC generates and code that LLI
1411 generates. This is a useful tool if you are debugging one of them,
1412 assuming that the other generates correct output. For the full user
1413 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
1415 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1416 update your CVS tree, but produce a much cleaner and more organized output
1417 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1418 together all the new and updated files and modified files in separate
1419 sections, so you can see at a glance what has changed. If you are at the
1420 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1421 preferred way of updating the tree.<p>
1423 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1424 syntax-highlighting files which will work with Emacs and XEmacs editors,
1425 providing syntax highlighting support for LLVM assembly files and TableGen
1426 description files. For information on how to use the syntax files, consult
1427 the <tt>README</tt> file in that directory.<p>
1429 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1430 and outputs all non-generated source files, which is useful if one wishes
1431 to do a lot of development across directories and does not want to
1432 individually find each file. One way to use it is to run, for example:
1433 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1436 <dt><tt><b>llvmgrep</b></tt></dt>
1437 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1438 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1439 line. This is a very efficient way of searching the source base for a
1440 particular regular expression.</dd>
1442 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1443 files in the current directory and then compiles and links the tool that
1444 is the first argument. For example, assuming you are in the directory
1445 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1446 simply running <tt>makellvm llc</tt> will make a build of the current
1447 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1448 causing a re-linking of LLC.<p>
1450 <dt><tt><b>NightlyTest.pl</b></tt> and
1451 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1452 cron script to generate nightly status reports of the functionality of
1453 tools, and the results can be seen by following the appropriate link on
1454 the <a href="http://llvm.org/">LLVM homepage</a>.<p>
1456 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1457 the tool used to generate register descriptions, instruction set
1458 descriptions, and even assemblers from common TableGen description
1461 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1462 syntax-highlighting files which will work with the VIM editor, providing
1463 syntax highlighting support for LLVM assembly files and TableGen
1464 description files. For information on how to use the syntax files, consult
1465 the <tt>README</tt> file in that directory.<p>
1471 <!-- ======================================================================= -->
1472 <div class="doc_subsection"><a name="win32"><tt>llvm/win32</tt></a></div>
1473 <div class="doc_text">
1474 <p>This directory contains build scripts and project files for use with
1475 Visual C++. This allows developers on Windows to build LLVM without the need
1476 for Cygwin. The contents of this directory should be considered experimental
1480 <!-- *********************************************************************** -->
1481 <div class="doc_section">
1482 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1484 <!-- *********************************************************************** -->
1486 <div class="doc_text">
1489 <li>First, create a simple C file, name it 'hello.c':
1491 #include <stdio.h>
1493 printf("hello world\n");
1498 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1499 <p><tt>% llvm-gcc hello.c -o hello</tt></p>
1501 <p>Note that you should have already built the tools and they have to be
1502 in your path, at least <tt>gccas</tt> and <tt>gccld</tt>.</p>
1504 <p>This will create two result files: <tt>hello</tt> and
1505 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1506 corresponds the the compiled program and the library facilities that it
1507 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1508 file with <tt>lli</tt>, making the result directly executable. Note that
1509 all LLVM optimizations are enabled by default, so there is no need for a
1510 "-O3" switch.</p></li>
1512 <li><p>Run the program. To make sure the program ran, execute one of the
1513 following commands:</p>
1515 <p><tt>% ./hello</tt></p>
1519 <p><tt>% lli hello.bc</tt></p></li>
1521 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1524 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1526 <li><p>Compile the program to native assembly using the LLC code
1529 <p><tt>% llc hello.bc -o hello.s</tt></p>
1531 <li><p>Assemble the native assembly language file into a program:</p>
1533 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1534 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1536 <li><p>Execute the native code program:</p>
1538 <p><tt>% ./hello.native</tt></p></li>
1544 <!-- *********************************************************************** -->
1545 <div class="doc_section">
1546 <a name="problems">Common Problems</a>
1548 <!-- *********************************************************************** -->
1550 <div class="doc_text">
1552 <p>If you are having problems building or using LLVM, or if you have any other
1553 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1554 Asked Questions</a> page.</p>
1558 <!-- *********************************************************************** -->
1559 <div class="doc_section">
1560 <a name="links">Links</a>
1562 <!-- *********************************************************************** -->
1564 <div class="doc_text">
1566 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1567 some simple things... there are many more interesting and complicated things
1568 that you can do that aren't documented here (but we'll gladly accept a patch
1569 if you want to write something up!). For more information about LLVM, check
1573 <li><a href="http://llvm.org/">LLVM homepage</a></li>
1574 <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1575 <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1576 that Uses LLVM</a></li>
1581 <!-- *********************************************************************** -->
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1590 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1591 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1592 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
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