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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>
56 <li><a href="#tutorial4">Example with llvm-gcc4</a></li>
57 <li><a href="#tutorial3">Example with llvm-gcc3</a></li>
59 <li><a href="#problems">Common Problems</a>
60 <li><a href="#links">Links</a>
63 <div class="doc_author">
65 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
66 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
67 <a href="http://misha.brukman.net">Misha Brukman</a>,
68 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
69 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
74 <!-- *********************************************************************** -->
75 <div class="doc_section">
76 <a name="overview"><b>Overview</b></a>
78 <!-- *********************************************************************** -->
80 <div class="doc_text">
82 <p>Welcome to LLVM! In order to get started, you first need to know some
83 basic information.</p>
85 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
86 contains all of the tools, libraries, and header files needed to use the low
87 level virtual machine. It contains an assembler, disassembler, bytecode
88 analyzer and bytecode optimizer. It also contains a test suite that can be
89 used to test the LLVM tools and the GCC front end.</p>
91 <p>The second piece is the GCC front end. This component provides a version of
92 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
93 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
94 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
95 from the LLVM suite.</p>
98 There is a third, optional piece called llvm-test. It is a suite of programs
99 with a testing harness that can be used to further test LLVM's functionality
105 <!-- *********************************************************************** -->
106 <div class="doc_section">
107 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
109 <!-- *********************************************************************** -->
111 <div class="doc_text">
113 <p>Here's the short story for getting up and running quickly with LLVM:</p>
116 <li>Read the documentation.</li>
117 <li>Read the documentation.</li>
118 <li>Remember that you were warned twice about reading the documentation.</li>
119 <li>Install the GCC front end if you intend to compile C or C++:
121 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt></li>
122 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
124 <li><tt>cd cfrontend/<i>platform</i><br>
125 ./fixheaders</tt></li>
126 <li>Add the cfrontend's "bin" directory to your PATH variable.</li>
129 <li>Get the LLVM Source Code
131 <li>With the distributed files (or use <a href="#checkout">CVS</a>):
133 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
134 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
139 <li><b>[Optional]</b> Get the Test Suite Source Code
141 <li>With the distributed files (or use <a href="#checkout">CVS</a>):
143 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
144 <li><tt>cd llvm/projects</tt>
145 <li><tt>gunzip --stdout llvm-test-<i>version</i>.tar.gz | tar -xvf -</tt>
151 <li>Configure the LLVM Build Environment
153 <li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
154 <li><tt><i>/path/to/llvm/</i>configure [options]</tt><br>
158 <li><tt>--prefix=<i>directory</i></tt>
159 <p>Specify for <i>directory</i> the full pathname of where you
160 want the LLVM tools and libraries to be installed (default
161 <tt>/usr/local</tt>).</p></li>
162 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
163 <p>Optionally, specify for <i>directory</i> the full pathname of the
164 C/C++ front end installation to use with this LLVM configuration. If
165 not specified, the PATH will be searched.</p></li>
166 <li><tt>--enable-spec2000=<i>directory</i></tt>
167 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
168 benchmarks should be available in
169 <tt><i>directory</i></tt>.</p></li>
173 <li>Build the LLVM Suite:
175 <li><tt>gmake -k |& tee gnumake.out
176 # this is csh or tcsh syntax</tt></li>
177 <li>If you get an "internal compiler error (ICE)" see <a href="#brokengcc">below</a>.</li>
182 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
183 detailed information on configuring and compiling LLVM. See <a
184 href="#environment">Setting Up Your Environment</a> for tips that simplify
185 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
186 Layout</a> to learn about the layout of the source code tree.</p>
190 <!-- *********************************************************************** -->
191 <div class="doc_section">
192 <a name="requirements"><b>Requirements</b></a>
194 <!-- *********************************************************************** -->
196 <div class="doc_text">
198 <p>Before you begin to use the LLVM system, review the requirements given below.
199 This may save you some trouble by knowing ahead of time what hardware and
200 software you will need.</p>
204 <!-- ======================================================================= -->
205 <div class="doc_subsection">
206 <a name="hardware"><b>Hardware</b></a>
209 <div class="doc_text">
211 <p>LLVM is known to work on the following platforms:</p>
213 <table cellpadding="3" summary="Known LLVM platforms">
221 <td>x86<sup><a href="#pf_1">1</a></sup></td>
226 <td>V9 (Ultrasparc)</td>
231 <td>x86<sup><a href="#pf_1">1</a></sup></td>
235 <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
240 <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
246 <td>Cygwin/Win32</td>
247 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a></sup></td>
248 <td>GCC 3.4.X, binutils 2.15</td>
252 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,<a href="#pf_8">8</a></sup></td>
253 <td>GCC 3.4.X, binutils 2.15</td>
257 <td>amd64<sup><a href="#pf_3">3</a></sup></td>
262 <p>LLVM has partial support for the following platforms:</p>
264 <table summary="LLVM partial platform support">
272 <td>x86<sup><a href="#pf_1">1</a></sup></td>
273 <td>Visual Studio .NET<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
275 <td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
280 <td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
286 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
291 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
292 <td>Itanium (IA-64)</td>
296 <td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
297 <td>Itanium (IA-64)</td>
304 <div class="doc_notes">
306 <li><a name="pf_1">Code generation supported for Pentium processors and
308 <li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
309 <li><a name="pf_3">No native code generation</a></li>
310 <li><a name="pf_4">Build is not complete: one or more tools don't link</a></li>
311 <li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
312 <li><a name="pf_6">The port is done using the MSYS shell.</a>
313 <a href="http://www.mingw.org/MinGWiki/">Download</a> and install
314 bison (excl. M4.exe) and flex in that order. Build binutils-2.15 from source,
315 if necessary. Bison & flex can be also grabbed from GNUWin32 sf.net
317 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
318 <li><a name="pf_8">Binutils</a> up to post-2.17 has bug in bfd/cofflink.c
319 preventing LLVM from building correctly. Several workarounds have been
320 introduced into LLVM build system, but the bug can occur anytime in the
321 future. We highly recommend that you rebuild your current binutils with the
322 patch from <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=2659">
323 Binutils bugzilla</a>, if it wasn't already applied.</li>
327 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
328 mode, depending on the system (it is so large because of all the debugging
329 information and the fact that the libraries are statically linked into multiple
330 tools). If you do not need many of the tools and you are space-conscious,
331 you can disable them individually in <tt>llvm/tools/Makefile</tt>. The Release
332 build requires considerably less space.</p>
334 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
335 guaranteed to do so. If compilation is successful, the LLVM utilities should be
336 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
337 generation should work as well, although the generated native code may not work
338 on your platform.</p>
340 <p>The GCC front end is not very portable at the moment. If you want to get it
341 to work on another platform, you can download a copy of the source and <a
342 href="CFEBuildInstrs.html">try to compile it</a> on your platform.</p>
346 <!-- ======================================================================= -->
347 <div class="doc_subsection"><a name="software"><b>Software</b></a></div>
348 <div class="doc_text">
349 <p>Compiling LLVM requires that you have several software packages
350 installed. The table below lists those required packages. The Package column
351 is the usual name for the software package that LLVM depends on. The Version
352 column provides "known to work" versions of the package. The Notes column
353 describes how LLVM uses the package and provides other details.</p>
354 <table summary="Packages required to compile LLVM">
355 <tr><th>Package</th><th>Version</th><th>Notes</th></tr>
358 <td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
359 <td>3.79, 3.79.1</td>
360 <td>Makefile/build processor</td>
364 <td><a href="http://gcc.gnu.org">GCC</a></td>
366 <td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
370 <td><a href="http://www.gnu.org/software/texinfo">TeXinfo</a></td>
372 <td>For building the CFE</td>
376 <td><a href="http://www.gnu.org/software/flex">Flex</a></td>
378 <td>LEX compiler</td>
382 <td><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></td>
383 <td>1.28, 1.35, 1.75, 1.875d, 2.0, or 2.1<br>(not 1.85 or 1.875)</td>
384 <td>YACC compiler</td>
388 <td><a href="https://www.cvshome.org/downloads.html">CVS</a></td>
390 <td>CVS access to LLVM<sup><a href="#sf2">2</a></sup></td>
394 <td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
396 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
400 <td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
402 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
406 <td><a href="http://expect.nist.gov/">expect</a></td>
408 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
412 <td><a href="http://www.perl.com/download.csp">perl</a></td>
414 <td>Nightly tester, utilities</td>
418 <td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
420 <td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
424 <td><a href="http://www.gnu.org/software/autoconf">GNU Autoconf</a></td>
426 <td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
430 <td><a href="http://www.gnu.org/software/automake">GNU Automake</a></td>
432 <td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
436 <td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
438 <td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
444 <div class="doc_notes">
446 <li><a name="sf1">Only the C and C++ languages are needed so there's no
447 need to build the other languages for LLVM's purposes.</a> See
448 <a href="#brokengcc">below</a> for specific version info.</li>
449 <li><a name="sf2">You only need CVS if you intend to build from the
450 latest LLVM sources. If you're working from a release distribution, you
451 don't need CVS.</a></li>
452 <li><a name="sf3">Only needed if you want to run the automated test
453 suite in the <tt>llvm/test</tt> directory.</a></li>
454 <li><a name="sf4">If you want to make changes to the configure scripts,
455 you will need GNU autoconf (2.59), and consequently, GNU M4 (version 1.4
456 or higher). You will also need automake (1.9.2). We only use aclocal
457 from that package.</a></li>
461 <p>Additionally, your compilation host is expected to have the usual
462 plethora of Unix utilities. Specifically:</p>
464 <li><b>ar</b> - archive library builder</li>
465 <li><b>bzip2*</b> - bzip2 command for distribution generation</li>
466 <li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
467 <li><b>chmod</b> - change permissions on a file</li>
468 <li><b>cat</b> - output concatenation utility</li>
469 <li><b>cp</b> - copy files</li>
470 <li><b>date</b> - print the current date/time </li>
471 <li><b>echo</b> - print to standard output</li>
472 <li><b>egrep</b> - extended regular expression search utility</li>
473 <li><b>etags</b> - C/C++ tag file creator for vim/emacs</li>
474 <li><b>find</b> - find files/dirs in a file system</li>
475 <li><b>grep</b> - regular expression search utility</li>
476 <li><b>gzip*</b> - gzip command for distribution generation</li>
477 <li><b>gunzip*</b> - gunzip command for distribution checking</li>
478 <li><b>install</b> - install directories/files </li>
479 <li><b>mkdir</b> - create a directory</li>
480 <li><b>mv</b> - move (rename) files</li>
481 <li><b>ranlib</b> - symbol table builder for archive libraries</li>
482 <li><b>rm</b> - remove (delete) files and directories</li>
483 <li><b>sed</b> - stream editor for transforming output</li>
484 <li><b>sh</b> - Bourne shell for make build scripts</li>
485 <li><b>tar</b> - tape archive for distribution generation</li>
486 <li><b>test</b> - test things in file system</li>
487 <li><b>unzip*</b> - unzip command for distribution checking</li>
488 <li><b>zip*</b> - zip command for distribution generation</li>
492 <!-- ======================================================================= -->
493 <div class="doc_subsection">
494 <a name="brokengcc">Broken versions of GCC</a>
497 <div class="doc_text">
499 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
500 bugs in the compiler. In particular, several versions of GCC crash when trying
501 to compile LLVM. We routinely use GCC 3.3.3, 3.4.0, and Apple 4.0.1
502 successfully with them (however, see below). Other versions of GCC will
503 probably work as well. GCC versions listed
504 here are known to not work. If you are using one of these versions, please try
505 to upgrade your GCC to something more recent. If you run into a problem with a
506 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
507 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
508 of GCC you are using.
511 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
512 problems in the STL that effectively prevent it from compiling LLVM.
515 <p><b>GCC 3.2.2</b>: This version of GCC fails to compile LLVM.</p>
517 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
518 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
519 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
521 <p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
522 Cygwin does not work. Please <a href="CFEBuildInstrs.html#cygwin">upgrade
523 to a newer version</a> if possible.</p>
524 <p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
525 possibly others) does not compile LLVM correctly (it appears that exception
526 handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
527 to a newer version of GCC.</p>
528 <p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
530 <p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
531 default with ENABLE_OPTIMIZED=1. To work around this, build with
532 "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
533 <p><b>GCC 4.1.1</b>: GCC fails to build LLVM with template concept check errors
534 compiling some files. At the time of this writing, GCC mainline (4.2)
535 did not share the problem.</p>
540 <!-- *********************************************************************** -->
541 <div class="doc_section">
542 <a name="starting"><b>Getting Started with LLVM</b></a>
544 <!-- *********************************************************************** -->
546 <div class="doc_text">
548 <p>The remainder of this guide is meant to get you up and running with
549 LLVM and to give you some basic information about the LLVM environment.</p>
551 <p>The later sections of this guide describe the <a
552 href="#layout">general layout</a> of the the LLVM source tree, a <a
553 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
554 href="#links">links</a> to find more information about LLVM or to get
558 <!-- ======================================================================= -->
559 <div class="doc_subsection">
560 <a name="terminology">Terminology and Notation</a>
563 <div class="doc_text">
565 <p>Throughout this manual, the following names are used to denote paths
566 specific to the local system and working environment. <i>These are not
567 environment variables you need to set but just strings used in the rest
568 of this document below</i>. In any of the examples below, simply replace
569 each of these names with the appropriate pathname on your local system.
570 All these paths are absolute:</p>
575 This is the top level directory of the LLVM source tree.
580 This is the top level directory of the LLVM object tree (i.e. the
581 tree where object files and compiled programs will be placed. It
582 can be the same as SRC_ROOT).
587 This is where the LLVM GCC Front End is installed.
589 For the pre-built GCC front end binaries, the LLVMGCCDIR is
590 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
595 <!-- ======================================================================= -->
596 <div class="doc_subsection">
597 <a name="environment">Setting Up Your Environment</a>
600 <div class="doc_text">
603 In order to compile and use LLVM, you may need to set some environment
607 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bytecode/libs</tt></dt>
608 <dd>[Optional] This environment variable helps LLVM linking tools find the
609 locations of your bytecode libraries. It is provided only as a
610 convenience since you can specify the paths using the -L options of the
611 tools and the C/C++ front-end will automatically use the bytecode files
613 <tt>lib</tt> directory.</dd>
618 <!-- ======================================================================= -->
619 <div class="doc_subsection">
620 <a name="unpack">Unpacking the LLVM Archives</a>
623 <div class="doc_text">
626 If you have the LLVM distribution, you will need to unpack it before you
627 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
628 suite and the LLVM GCC front end compiled for your platform. There is an
629 additional test suite that is optional. Each file is a TAR archive that is
630 compressed with the gzip program.
633 <p>The files are as follows, with <em>x.y</em> marking the version number:
635 <dt><tt>llvm-x.y.tar.gz</tt></dt>
636 <dd>Source release for the LLVM libraries and tools.<br/></dd>
638 <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
639 <dd>Source release for the LLVM test suite.</dd>
641 <dt><tt>cfrontend-x.y.source.tar.gz</tt></dt>
642 <dd>Source release of the GCC front end.<br/></dd>
644 <dt><tt>cfrontend-x.y.i686-redhat-linux-gnu.tar.gz</tt></dt>
645 <dd>Binary release of the GCC front end for Linux/x86.<br/></dd>
647 <dt><tt>llvm-gcc4-x.y.source.tar.gz</tt></dt>
648 <dd>Source release of the llvm-gcc4 front end. See README.LLVM in the root
649 directory for build instructions.<br/></dd>
651 <dt><tt>llvm-gcc4-x.y.powerpc-apple-darwin8.6.0.tar.gz</tt></dt>
652 <dd>Binary release of the llvm-gcc4 front end for MacOS X/PowerPC.<br/></dd>
654 <dt><tt>llvm-gcc4-x.y.i686-apple-darwin8.6.1.tar.gz</tt></dt>
655 <dd>Binary release of the llvm-gcc4 front end for MacOS X/X86.<br/></dd>
658 <p>It is also possible to download the sources of the llvm-gcc4 front end from a
659 read-only subversion mirror at
660 svn://anonsvn.opensource.apple.com/svn/llvm/trunk. </p>
664 <!-- ======================================================================= -->
665 <div class="doc_subsection">
666 <a name="checkout">Checkout LLVM from CVS</a>
669 <div class="doc_text">
671 <p>If you have access to our CVS repository, you can get a fresh copy of
672 the entire source code. All you need to do is check it out from CVS as
676 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
677 <li><tt>cvs -d :pserver:anon@llvm.org:/var/cvs/llvm login</tt>
678 <li>Hit the return key when prompted for the password.
679 <li><tt>cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co
683 <p>This will create an '<tt>llvm</tt>' directory in the current
684 directory and fully populate it with the LLVM source code, Makefiles,
685 test directories, and local copies of documentation files.</p>
687 <p>If you want to get a specific release (as opposed to the most recent
688 revision), you can specify a label. The following releases have the following
692 <li>Release 1.7: <b>RELEASE_17</b></li>
693 <li>Release 1.6: <b>RELEASE_16</b></li>
694 <li>Release 1.5: <b>RELEASE_15</b></li>
695 <li>Release 1.4: <b>RELEASE_14</b></li>
696 <li>Release 1.3: <b>RELEASE_13</b></li>
697 <li>Release 1.2: <b>RELEASE_12</b></li>
698 <li>Release 1.1: <b>RELEASE_11</b></li>
699 <li>Release 1.0: <b>RELEASE_1</b></li>
702 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
703 you get it from the CVS repository:</p>
706 cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co llvm-test
708 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
709 configured by the LLVM configure script as well as automatically updated when
710 you run <tt>cvs update</tt>.</p>
712 <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>
715 cvs -z3 -d :pserver:anon@llvm.org:/var/cvs/llvm co llvm-gcc
718 <p>Please note that you must follow <a href="CFEBuildInstrs.html">these
719 instructions</a> to successfully build the LLVM GCC front-end.</p>
723 <!-- ======================================================================= -->
724 <div class="doc_subsection">
725 <a name="installcf">Install the GCC Front End</a>
728 <div class="doc_text">
730 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
731 GCC front end from the binary distribution. It is used for building the
732 bytecode libraries later used by the GCC front end for linking programs, and its
733 location must be specified when the LLVM suite is configured.</p>
735 <p>To install the GCC front end, do the following:</p>
738 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
739 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
743 <p>Next, you will need to fix your system header files:</p>
745 <p><tt>cd cfrontend/<i>platform</i><br>
746 ./fixheaders</tt></p>
748 <p>The binary versions of the GCC front end may not suit all of your needs. For
749 example, the binary distribution may include an old version of a system header
750 file, not "fix" a header file that needs to be fixed for GCC, or it may be
751 linked with libraries not available on your system.</p>
753 <p>In cases like these, you may want to try <a
754 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
755 not for the faint of heart, so be forewarned.</p>
759 <!-- ======================================================================= -->
760 <div class="doc_subsection">
761 <a name="config">Local LLVM Configuration</a>
764 <div class="doc_text">
766 <p>Once checked out from the CVS repository, the LLVM suite source code must be
767 configured via the <tt>configure</tt> script. This script sets variables in the
768 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
769 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
770 the Makefiles needed to begin building LLVM.</p>
772 <p>The following environment variables are used by the <tt>configure</tt>
773 script to configure the build system:</p>
775 <table summary="LLVM configure script environment variables">
776 <tr><th>Variable</th><th>Purpose</th></tr>
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 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
787 <tt>configure</tt> will look for the first GCC C++ compiler in
788 <tt>PATH</tt>. Use this variable to override
789 <tt>configure</tt>'s default behavior.</td>
793 <p>The following options can be used to set or enable LLVM specific options:</p>
796 <dt><i>--with-llvmgccdir</i></dt>
797 <dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
798 The value of this option should specify the full pathname of the C/C++ Front
799 End to be used. If this option is not provided, the PATH will be searched for
800 a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
801 be inferred from the path found. If the option is not given, and no llvm-gcc
802 can be found in the path then a warning will be produced by
803 <tt>configure</tt> indicating this situation. LLVM may still be built with
804 the <tt>tools-only</tt> target but attempting to build the runtime libraries
805 will fail as these libraries require llvm-gcc and llvm-g++. See
806 <a href="#installcf">Install the GCC Front End</a> for details on installing
807 the C/C++ Front End. See
808 <a href="CFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
809 for details on building the C/C++ Front End.</dd>
810 <dt><i>--with-tclinclude</i></dt>
811 <dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
812 found. Use this if you have multiple tcl installations on your machine and you
813 want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
814 dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
815 option, the LLVM configure script will search for the tcl 8.4 and 8.3
819 <dt><i>--enable-optimized</i></dt>
821 Enables optimized compilation by default (debugging symbols are removed
822 and GCC optimization flags are enabled). The default is to use an
823 unoptimized build (also known as a debug build).
826 <dt><i>--enable-debug-runtime</i></dt>
828 Enables debug symbols in the runtime libraries. The default is to strip
829 debug symbols from the runtime libraries.
831 <dt><i>--enable-jit</i></dt>
833 Compile the Just In Time (JIT) compiler functionality. This is not
835 on all platforms. The default is dependent on platform, so it is best
836 to explicitly enable it if you want it.
839 <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
840 <dd>Controls which targets will be built and linked into llc. The default
841 value for <tt>target_options</tt> is "all" which builds and links all
842 available targets. The value "host-only" can be specified to build only a
843 native compiler (no cross-compiler targets available). The "native" target is
844 selected as the target of the build host. You can also specify a comma
845 separated list of target names that you want available in llc. The target
846 names use all lower case. The current set of targets is: <br/>
847 <tt>alpha, ia64, powerpc, skeleton, sparc, x86</tt>.
849 <dt><i>--enable-doxygen</i></dt>
850 <dd>Look for the doxygen program and enable construction of doxygen based
851 documentation from the source code. This is disabled by default because
852 generating the documentation can take a long time and producess 100s of
853 megabytes of output.</dd>
856 <p>To configure LLVM, follow these steps:</p>
859 <li>Change directory into the object root directory:
861 <tt>cd <i>OBJ_ROOT</i></tt>
864 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
866 <tt><i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</tt>
872 <!-- ======================================================================= -->
873 <div class="doc_subsection">
874 <a name="compile">Compiling the LLVM Suite Source Code</a>
877 <div class="doc_text">
879 <p>Once you have configured LLVM, you can build it. There are three types of
885 These builds are the default when one types <tt>gmake</tt> (unless the
886 <tt>--enable-optimized</tt> option was used during configuration). The
887 build system will compile the tools and libraries with debugging
891 <dt>Release (Optimized) Builds
893 These builds are enabled with the <tt>--enable-optimized</tt> option to
894 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
895 <tt>gmake</tt> command line. For these builds, the build system will
896 compile the tools and libraries with GCC optimizations enabled and strip
897 debugging information from the libraries and executables it generates.
902 These builds are for use with profiling. They compile profiling
903 information into the code for use with programs like <tt>gprof</tt>.
904 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
905 on the <tt>gmake</tt> command line.
908 <p>Once you have LLVM configured, you can build it by entering the
909 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
911 <p><tt>gmake</tt></p>
913 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
914 are using a version of GCC that is known not to compile LLVM.</p>
917 If you have multiple processors in your machine, you may wish to use some of
918 the parallel build options provided by GNU Make. For example, you could use the
921 <p><tt>gmake -j2</tt></p>
923 <p>There are several special targets which are useful when working with the LLVM
927 <dt><tt>gmake clean</tt>
929 Removes all files generated by the build. This includes object files,
930 generated C/C++ files, libraries, and executables.
933 <dt><tt>gmake dist-clean</tt>
935 Removes everything that <tt>gmake clean</tt> does, but also removes files
936 generated by <tt>configure</tt>. It attempts to return the source tree to the
937 original state in which it was shipped.
940 <dt><tt>gmake install</tt>
942 Installs LLVM header files, libraries, tools, and documentation in a
944 under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
945 defaults to <tt>/usr/local</tt>.
948 <dt><tt>gmake -C runtime install-bytecode</tt>
950 Assuming you built LLVM into $OBJDIR, when this command is run, it will
951 install bytecode libraries into the GCC front end's bytecode library
952 directory. If you need to update your bytecode libraries,
953 this is the target to use once you've built them.
957 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
958 details on these <tt>make</tt> targets and descriptions of other targets
961 <p>It is also possible to override default values from <tt>configure</tt> by
962 declaring variables on the command line. The following are some examples:</p>
965 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
967 Perform a Release (Optimized) build.
970 <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
972 Perform a Release (Optimized) build without assertions enabled.
975 <dt><tt>gmake ENABLE_PROFILING=1</tt>
977 Perform a Profiling build.
980 <dt><tt>gmake VERBOSE=1</tt>
982 Print what <tt>gmake</tt> is doing on standard output.
985 <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
986 <dd>Ask each tool invoked by the makefiles to print out what it is doing on
987 the standard output. This also implies <tt>VERBOSE=1</tt>.
991 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
992 it and any subdirectories that it contains. Entering any directory inside the
993 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
994 that directory that is out of date.</p>
998 <!-- ======================================================================= -->
999 <div class="doc_subsection">
1000 <a name="cross-compile">Cross-Compiling LLVM</a>
1003 <div class="doc_text">
1004 <p>It is possible to cross-compile LLVM. That is, you can create LLVM
1005 executables and libraries for a platform different than the one one which you
1006 are compiling. To do this, a few additional steps are
1007 required. <sup><a href="#ccn_1">1</a></sup> To cross-compile LLVM, use
1008 these instructions:</p>
1010 <li>Configure and build LLVM as a native compiler. You will need
1011 just <tt>TableGen</tt> from that build.
1013 <li>If you have <tt>$LLVM_OBJ_ROOT=$LLVM_SRC_ROOT</tt> just execute
1014 <tt>make -C utils/TableGen</tt> after configuring.</li>
1015 <li>Otherwise you will need to monitor building process and terminate
1016 it just after <tt>TableGen</tt> was built.</li>
1019 <li>Copy the TableGen binary to somewhere safe (out of your build tree).
1021 <li>Configure LLVM to build with a cross-compiler. To do this, supply the
1022 configure script with <tt>--build</tt> and <tt>--host</tt> options that
1023 are different. The values of these options must be legal target triples
1024 that your GCC compiler supports.</li>
1025 <li>Put the saved <tt>TableGen</tt> executable into the
1026 into <tt>$LLVM_OBJ_ROOT/{BUILD_TYPE}/bin</tt> directory (e.g. into
1027 <tt>.../Release/bin</tt> for a Release build).</li>
1028 <li>Build LLVM as usual.</li>
1030 <p>The result of such a build will produce executables that are not executable
1031 on your build host (--build option) but can be executed on your compile host
1032 (--host option).</p>
1033 <p><b>Notes:</b></p>
1034 <div class="doc_notes">
1036 <li><a name="ccn_1">Cross-compiling</a> was tested only with Linux as
1037 build platform and Windows as host using mingw32 cross-compiler. Other
1038 combinations have not been tested.</li>
1043 <!-- ======================================================================= -->
1044 <div class="doc_subsection">
1045 <a name="objfiles">The Location of LLVM Object Files</a>
1048 <div class="doc_text">
1050 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1051 several LLVM builds. Hence, it is possible to build LLVM for several different
1052 platforms or configurations using the same source tree.</p>
1054 <p>This is accomplished in the typical autoconf manner:</p>
1057 <li><p>Change directory to where the LLVM object files should live:</p>
1059 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
1061 <li><p>Run the <tt>configure</tt> script found in the LLVM source
1064 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
1067 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1068 named after the build type:</p>
1075 <dd><tt><i>OBJ_ROOT</i>/Debug/bin</tt>
1077 <dd><tt><i>OBJ_ROOT</i>/Debug/lib</tt>
1085 <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1087 <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1095 <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1097 <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1103 <!-- ======================================================================= -->
1104 <div class="doc_subsection">
1105 <a name="optionalconfig">Optional Configuration Items</a>
1108 <div class="doc_text">
1111 If you're running on a Linux system that supports the "<a
1112 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">
1114 module, and you have root access on the system, you can set your system up to
1115 execute LLVM bytecode files directly. To do this, use commands like this (the
1116 first command may not be required if you are already using the module):</p>
1118 <div class="doc_code">
1120 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1121 $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1122 $ chmod u+x hello.bc (if needed)
1128 This allows you to execute LLVM bytecode files directly. Thanks to Jack
1129 Cummings for pointing this out!
1135 <!-- *********************************************************************** -->
1136 <div class="doc_section">
1137 <a name="layout"><b>Program Layout</b></a>
1139 <!-- *********************************************************************** -->
1141 <div class="doc_text">
1143 <p>One useful source of information about the LLVM source base is the LLVM <a
1144 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
1145 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1146 The following is a brief introduction to code layout:</p>
1150 <!-- ======================================================================= -->
1151 <div class="doc_subsection"><a name="cvsdir"><tt>CVS</tt> directories</a></div>
1152 <div class="doc_text">
1153 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
1154 the most part these can just be ignored.</p>
1157 <!-- ======================================================================= -->
1158 <div class="doc_subsection"><a name="examples"><tt>llvm/examples</tt></a></div>
1159 <div class="doc_text">
1160 <p>This directory contains some simple examples of how to use the LLVM IR and
1164 <!-- ======================================================================= -->
1165 <div class="doc_subsection"><a name="include"><tt>llvm/include</tt></a></div>
1166 <div class="doc_text">
1168 <p>This directory contains public header files exported from the LLVM
1169 library. The three main subdirectories of this directory are:</p>
1172 <dt><tt><b>llvm/include/llvm</b></tt></dt>
1173 <dd>This directory contains all of the LLVM specific header files. This
1174 directory also has subdirectories for different portions of LLVM:
1175 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1178 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1179 <dd>This directory contains generic support libraries that are provided with
1180 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1181 and a Command Line option processing library store their header files here.
1184 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1185 <dd>This directory contains header files configured by the <tt>configure</tt>
1186 script. They wrap "standard" UNIX and C header files. Source code can
1187 include these header files which automatically take care of the conditional
1188 #includes that the <tt>configure</tt> script generates.</dd>
1192 <!-- ======================================================================= -->
1193 <div class="doc_subsection"><a name="lib"><tt>llvm/lib</tt></a></div>
1194 <div class="doc_text">
1196 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1197 almost all code exists in libraries, making it very easy to share code among the
1198 different <a href="#tools">tools</a>.</p>
1201 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1202 <dd> This directory holds the core LLVM source files that implement core
1203 classes like Instruction and BasicBlock.</dd>
1205 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1206 <dd>This directory holds the source code for the LLVM assembly language parser
1209 <dt><tt><b>llvm/lib/ByteCode/</b></tt></dt>
1210 <dd>This directory holds code for reading and write LLVM bytecode.</dd>
1212 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1213 different program analyses, such as Dominator Information, Call Graphs,
1214 Induction Variables, Interval Identification, Natural Loop Identification,
1217 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1218 <dd> This directory contains the source code for the LLVM to LLVM program
1219 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1220 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1221 Elimination, and many others.</dd>
1223 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1224 <dd> This directory contains files that describe various target architectures
1225 for code generation. For example, the <tt>llvm/lib/Target/X86</tt>
1226 directory holds the X86 machine description while
1227 <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
1229 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1230 <dd> This directory contains the major parts of the code generator: Instruction
1231 Selector, Instruction Scheduling, and Register Allocation.</dd>
1233 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1234 <dd> This directory contains the source level debugger library that makes
1235 it possible to instrument LLVM programs so that a debugger could identify
1236 source code locations at which the program is executing.</dd>
1238 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1239 <dd> This directory contains libraries for executing LLVM bytecode directly
1240 at runtime in both interpreted and JIT compiled fashions.</dd>
1242 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1243 <dd> This directory contains the source code that corresponds to the header
1244 files located in <tt>llvm/include/Support/</tt>.</dd>
1246 <dt><tt><b>llvm/lib/System/</b></tt></dt>
1247 <dd>This directory contains the operating system abstraction layer that
1248 shields LLVM from platform-specific coding.</dd>
1253 <!-- ======================================================================= -->
1254 <div class="doc_subsection"><a name="projects"><tt>llvm/projects</tt></a></div>
1255 <div class="doc_text">
1256 <p>This directory contains projects that are not strictly part of LLVM but are
1257 shipped with LLVM. This is also the directory where you should create your own
1258 LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1259 to set up your own project. See <tt>llvm/projects/Stacker</tt> for a fully
1260 functional example of a compiler front end.</p>
1263 <!-- ======================================================================= -->
1264 <div class="doc_subsection"><a name="runtime"><tt>llvm/runtime</tt></a></div>
1265 <div class="doc_text">
1267 <p>This directory contains libraries which are compiled into LLVM bytecode and
1268 used when linking programs with the GCC front end. Most of these libraries are
1269 skeleton versions of real libraries; for example, libc is a stripped down
1270 version of glibc.</p>
1272 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1277 <!-- ======================================================================= -->
1278 <div class="doc_subsection"><a name="test"><tt>llvm/test</tt></a></div>
1279 <div class="doc_text">
1280 <p>This directory contains feature and regression tests and other basic sanity
1281 checks on the LLVM infrastructure. These are intended to run quickly and cover
1282 a lot of territory without being exhaustive.</p>
1285 <!-- ======================================================================= -->
1286 <div class="doc_subsection"><a name="llvmtest"><tt>llvm-test</tt></a></div>
1287 <div class="doc_text">
1288 <p>This is not a directory in the normal llvm module; it is a separate CVS
1289 module that must be checked out (usually to <tt>projects/llvm-test</tt>). This
1290 module contains a comprehensive correctness, performance, and benchmarking
1292 suite for LLVM. It is a separate CVS module because not every LLVM user is
1293 interested in downloading or building such a comprehensive test suite. For
1294 further details on this test suite, please see the
1295 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1298 <!-- ======================================================================= -->
1299 <div class="doc_subsection"><a name="tools"><tt>llvm/tools</tt></a></div>
1300 <div class="doc_text">
1302 <p>The <b>tools</b> directory contains the executables built out of the
1303 libraries above, which form the main part of the user interface. You can
1304 always get help for a tool by typing <tt>tool_name --help</tt>. The
1305 following is a brief introduction to the most important tools. More detailed
1306 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1310 <dt><tt><b>bugpoint</b></tt></dt>
1311 <dd><tt>bugpoint</tt> is used to debug
1312 optimization passes or code generation backends by narrowing down the
1313 given test case to the minimum number of passes and/or instructions that
1314 still cause a problem, whether it is a crash or miscompilation. See <a
1315 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1316 on using <tt>bugpoint</tt>.</dd>
1318 <dt><tt><b>llvmc</b></tt></dt>
1319 <dd>The LLVM Compiler Driver. This program can
1320 be configured to utilize both LLVM and non-LLVM compilation tools to enable
1321 pre-processing, translation, optimization, assembly, and linking of programs
1322 all from one command line. <tt>llvmc</tt> also takes care of processing the
1323 dependent libraries found in bytecode. This reduces the need to get the
1324 traditional <tt>-l<name></tt> options right on the command line. Please
1325 note that this tool, while functional, is still experimental and not feature
1328 <dt><tt><b>llvm-ar</b></tt></dt>
1329 <dd>The archiver produces an archive containing
1330 the given LLVM bytecode files, optionally with an index for faster
1333 <dt><tt><b>llvm-as</b></tt></dt>
1334 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1337 <dt><tt><b>llvm-dis</b></tt></dt>
1338 <dd>The disassembler transforms the LLVM bytecode to human readable
1341 <dt><tt><b>llvm-ld</b></tt></dt>
1342 <dd><tt>llvm-ld</tt> is very similar to gccld and provides a general purpose
1343 and extensible linker for LLVM. This is the linker invoked by <tt>llvmc</tt>.
1344 It allows optimization modules to be loaded so that language specific
1345 optimizations can be applied at link time. This tool is considered
1348 <dt><tt><b>llvm-link</b></tt></dt>
1349 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1350 a single program.</dd>
1352 <dt><tt><b>lli</b></tt></dt>
1353 <dd><tt>lli</tt> is the LLVM interpreter, which
1354 can directly execute LLVM bytecode (although very slowly...). In addition
1355 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
1356 specifying <tt>-trace</tt> on the command line). Finally, for
1357 architectures that support it (currently x86, Sparc, and PowerPC), by default,
1358 <tt>lli</tt> will function as a Just-In-Time compiler (if the
1359 functionality was compiled in), and will execute the code <i>much</i>
1360 faster than the interpreter.</dd>
1362 <dt><tt><b>llc</b></tt></dt>
1363 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1364 translates LLVM bytecode to a native code assembly file or to C code (with
1365 the -march=c option).</dd>
1367 <dt><tt><b>llvm-gcc</b></tt></dt>
1368 <dd><tt>llvm-gcc</tt> is a GCC-based C frontend
1369 that has been retargeted to emit LLVM code as the machine code output. It
1370 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
1371 -o</tt> options that are typically used. The source code for the
1372 <tt>llvm-gcc</tt> tool is available as a separate CVS module.
1375 <dt><tt><b>gccas</b></tt></dt>
1376 <dd>This tool is invoked by the <tt>llvm-gcc</tt> frontend as the
1377 "assembler" part of the compiler. This tool actually assembles LLVM
1378 assembly to LLVM bytecode, performs a variety of optimizations, and
1379 outputs LLVM bytecode. Thus when you invoke
1380 <tt>llvm-gcc -c x.c -o x.o</tt>, you are causing <tt>gccas</tt> to be
1381 run, which writes the <tt>x.o</tt> file (which is an LLVM bytecode file
1382 that can be disassembled or manipulated just like any other bytecode
1383 file). The command line interface to <tt>gccas</tt> is designed to be
1384 as close as possible to the <b>system</b> `<tt>as</tt>' utility so that
1385 the gcc frontend itself did not have to be modified to interface to
1386 a "weird" assembler.</dd>
1388 <dt><tt><b>gccld</b></tt></dt>
1389 <dd><tt>gccld</tt> links together several LLVM bytecode files into one
1390 bytecode file and does some optimization. It is the linker invoked by
1391 the GCC frontend when multiple .o files need to be linked together.
1392 Like <tt>gccas</tt>, the command line interface of <tt>gccld</tt> is
1393 designed to match the system linker, to aid interfacing with the GCC
1399 <dt><tt><b>opt</b></tt></dt>
1400 <dd><tt>opt</tt> reads LLVM bytecode, applies a series of LLVM to LLVM
1401 transformations (which are specified on the command line), and then outputs
1402 the resultant bytecode. The '<tt>opt --help</tt>' command is a good way to
1403 get a list of the program transformations available in LLVM.<br/>
1404 <dd><tt>opt</tt> can also be used to run a specific analysis on an input
1405 LLVM bytecode file and print out the results. It is primarily useful for
1406 debugging analyses, or familiarizing yourself with what an analysis does.</dd>
1410 <!-- ======================================================================= -->
1411 <div class="doc_subsection"><a name="utils"><tt>llvm/utils</tt></a></div>
1412 <div class="doc_text">
1414 <p>This directory contains utilities for working with LLVM source code, and some
1415 of the utilities are actually required as part of the build process because they
1416 are code generators for parts of LLVM infrastructure.</p>
1419 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1420 that finds differences between code that LLC generates and code that LLI
1421 generates. This is a useful tool if you are debugging one of them,
1422 assuming that the other generates correct output. For the full user
1423 manual, run <tt>`perldoc codegen-diff'</tt>.<br><br>
1425 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1426 update your CVS tree, but produce a much cleaner and more organized output
1427 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1428 together all the new and updated files and modified files in separate
1429 sections, so you can see at a glance what has changed. If you are at the
1430 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1431 preferred way of updating the tree.<br><br>
1433 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1434 syntax-highlighting files which will work with Emacs and XEmacs editors,
1435 providing syntax highlighting support for LLVM assembly files and TableGen
1436 description files. For information on how to use the syntax files, consult
1437 the <tt>README</tt> file in that directory.<br><br>
1439 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1440 and outputs all non-generated source files, which is useful if one wishes
1441 to do a lot of development across directories and does not want to
1442 individually find each file. One way to use it is to run, for example:
1443 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1446 <dt><tt><b>llvmgrep</b></tt></dt>
1447 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1448 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1449 line. This is a very efficient way of searching the source base for a
1450 particular regular expression.</dd>
1452 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1453 files in the current directory and then compiles and links the tool that
1454 is the first argument. For example, assuming you are in the directory
1455 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1456 simply running <tt>makellvm llc</tt> will make a build of the current
1457 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1458 causing a re-linking of LLC.<br><br>
1460 <dt><tt><b>NightlyTest.pl</b></tt> and
1461 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1462 cron script to generate nightly status reports of the functionality of
1463 tools, and the results can be seen by following the appropriate link on
1464 the <a href="http://llvm.org/">LLVM homepage</a>.<br><br>
1466 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1467 the tool used to generate register descriptions, instruction set
1468 descriptions, and even assemblers from common TableGen description
1471 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1472 syntax-highlighting files which will work with the VIM editor, providing
1473 syntax highlighting support for LLVM assembly files and TableGen
1474 description files. For information on how to use the syntax files, consult
1475 the <tt>README</tt> file in that directory.<br><br>
1481 <!-- ======================================================================= -->
1482 <div class="doc_subsection"><a name="win32"><tt>llvm/win32</tt></a></div>
1483 <div class="doc_text">
1484 <p>This directory contains build scripts and project files for use with
1485 Visual C++. This allows developers on Windows to build LLVM without the need
1486 for Cygwin. The contents of this directory should be considered experimental
1490 <!-- *********************************************************************** -->
1491 <div class="doc_section">
1492 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1494 <!-- *********************************************************************** -->
1496 <div class="doc_text">
1497 <p>This section gives an example of using LLVM. Since we are currently
1498 transitioning from llvm-gcc3 to llvm-gcc4, we include examples for both.
1501 <p><b>Note:</b> The <i>gcc4</i> frontend's invocation is <b><i>considerably different</i></b>
1502 from the previous <i>gcc3</i> frontend. In particular, the <i>gcc4</i> frontend <b><i>does not</i></b>
1503 create bytecode by default: <i>gcc4</i> produces native code. As the example below illustrates,
1504 the '--emit-llvm' flag is needed to produce LLVM bytecode output. For <i>makefiles</i> and
1505 <i>configure</i> scripts, the CFLAGS variable needs '--emit-llvm' to produce bytecode
1509 <!-- ======================================================================= -->
1510 <div class="doc_subsection"><a name="tutorial4">Example with llvm-gcc4</a></div>
1512 <div class="doc_text">
1515 <li>First, create a simple C file, name it 'hello.c':
1517 #include <stdio.h>
1519 printf("hello world\n");
1524 <li><p>Next, compile the C file into a native executable:</p>
1526 <p><tt>% llvm-gcc hello.c -o hello</tt></p>
1528 <p>Note that llvm-gcc works just like GCC by default. The standard -S and
1529 -c arguments work as usual (producing a native .s or .o file,
1532 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1533 <p><tt>% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc</tt></p>
1535 <p>The -emit-llvm option can be used with the -S or -c options to emit an
1536 LLVM ".ll" or ".bc" file (respectively) for the code. This allows you
1537 to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
1538 the bytecode file.</p>
1540 <p>Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
1543 <li><p>Run the program in both forms. To run the program, use:</p>
1545 <p><tt>% ./hello</tt></p>
1549 <p><tt>% lli hello.bc</tt></p>
1551 <p>The second examples shows how to invoke the LLVM JIT, <a
1552 href="CommandGuide/html/lli.html">lli</a>.</p></li>
1554 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1557 <p><tt>% llvm-dis < hello.bc | less</tt><br><br></li>
1559 <li><p>Compile the program to native assembly using the LLC code
1562 <p><tt>% llc hello.bc -o hello.s</tt></p>
1564 <li><p>Assemble the native assembly language file into a program:</p>
1566 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1567 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1569 <li><p>Execute the native code program:</p>
1571 <p><tt>% ./hello.native</tt></p>
1573 <p>Note that using llvm-gcc to compile directly to native code (i.e. when
1574 the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
1581 <!-- ======================================================================= -->
1582 <div class="doc_subsection"><a name="tutorial3">Example with llvm-gcc3</a></div>
1584 <div class="doc_text">
1587 <li>First, create a simple C file, name it 'hello.c':
1589 #include <stdio.h>
1591 printf("hello world\n");
1596 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1597 <p><tt>% llvm-gcc hello.c -o hello</tt></p>
1599 <p>Note that you should have already built the tools and they have to be
1600 in your path, at least <tt>gccas</tt> and <tt>gccld</tt>.</p>
1602 <p>This will create two result files: <tt>hello</tt> and
1603 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1604 corresponds the the compiled program and the library facilities that it
1605 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1606 file with <tt>lli</tt>, making the result directly executable. Note that
1607 all LLVM optimizations are enabled by default, so there is no need for a
1608 "-O3" switch.</p></li>
1610 <li><p>Run the program. To make sure the program ran, execute one of the
1611 following commands:</p>
1613 <p><tt>% ./hello</tt></p>
1617 <p><tt>% lli hello.bc</tt></p></li>
1619 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1622 <p><tt>% llvm-dis < hello.bc | less</tt><br><br></li>
1624 <li><p>Compile the program to native assembly using the LLC code
1627 <p><tt>% llc hello.bc -o hello.s</tt></p>
1629 <li><p>Assemble the native assembly language file into a program:</p>
1631 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1632 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1634 <li><p>Execute the native code program:</p>
1636 <p><tt>% ./hello.native</tt></p></li>
1642 <!-- *********************************************************************** -->
1643 <div class="doc_section">
1644 <a name="problems">Common Problems</a>
1646 <!-- *********************************************************************** -->
1648 <div class="doc_text">
1650 <p>If you are having problems building or using LLVM, or if you have any other
1651 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1652 Asked Questions</a> page.</p>
1656 <!-- *********************************************************************** -->
1657 <div class="doc_section">
1658 <a name="links">Links</a>
1660 <!-- *********************************************************************** -->
1662 <div class="doc_text">
1664 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1665 some simple things... there are many more interesting and complicated things
1666 that you can do that aren't documented here (but we'll gladly accept a patch
1667 if you want to write something up!). For more information about LLVM, check
1671 <li><a href="http://llvm.org/">LLVM homepage</a></li>
1672 <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1673 <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1674 that Uses LLVM</a></li>
1679 <!-- *********************************************************************** -->
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1688 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1689 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1690 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a><br>
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