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  11 <h1>
  12   Getting Started with the LLVM System
  13 </h1>
  14
  15 <ul>
  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>
  19     <ol>
  20       <li><a href="#hardware">Hardware</a></li>
  21       <li><a href="#software">Software</a></li>
  22       <li><a href="#brokengcc">Broken versions of GCC and other tools</a></li>
  23     </ol></li>
  24
  25   <li><a href="#starting">Getting Started with LLVM</a>
  26     <ol>
  27       <li><a href="#terminology">Terminology and Notation</a></li>
  28       <li><a href="#environment">Setting Up Your Environment</a></li>
  29       <li><a href="#unpack">Unpacking the LLVM Archives</a></li>
  30       <li><a href="#checkout">Checkout LLVM from Subversion</a></li>
  31       <li><a href="#git_mirror">LLVM GIT mirror</a></li>
  32       <li><a href="#installcf">Install the GCC Front End</a></li>
  33       <li><a href="#config">Local LLVM Configuration</a></li>
  34       <li><a href="#compile">Compiling the LLVM Suite Source Code</a></li>
  35       <li><a href="#cross-compile">Cross-Compiling LLVM</a></li>
  36       <li><a href="#objfiles">The Location of LLVM Object Files</a></li>
  37       <li><a href="#optionalconfig">Optional Configuration Items</a></li>
  38     </ol></li>
  39
  40   <li><a href="#layout">Program layout</a>
  41     <ol>
  42       <li><a href="#examples"><tt>llvm/examples</tt></a></li>
  43       <li><a href="#include"><tt>llvm/include</tt></a></li>
  44       <li><a href="#lib"><tt>llvm/lib</tt></a></li>
  45       <li><a href="#projects"><tt>llvm/projects</tt></a></li>
  46       <li><a href="#runtime"><tt>llvm/runtime</tt></a></li>
  47       <li><a href="#test"><tt>llvm/test</tt></a></li>
  48       <li><a href="#test-suite"><tt>test-suite</tt></a></li>
  49       <li><a href="#tools"><tt>llvm/tools</tt></a></li>
  50       <li><a href="#utils"><tt>llvm/utils</tt></a></li>
  51     </ol></li>
  52
  53   <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
  54       <ol>
  55          <li><a href="#tutorial4">Example with llvm-gcc4</a></li>
  56       </ol>
  57   <li><a href="#problems">Common Problems</a>
  58   <li><a href="#links">Links</a>
  59 </ul>
  60
  61 <div class="doc_author">
  62   <p>Written by:
  63     <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
  64     <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
  65     <a href="http://misha.brukman.net/">Misha Brukman</a>,
  66     <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
  67     <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
  68   </p>
  69 </div>
  70
  71
  72 <!-- *********************************************************************** -->
  73 <h2>
  74   <a name="overview">Overview</a>
  75 </h2>
  76 <!-- *********************************************************************** -->
  77
  78 <div>
  79
  80 <p>Welcome to LLVM! In order to get started, you first need to know some
  81 basic information.</p>
  82
  83 <p>First, LLVM comes in three pieces. The first piece is the LLVM
  84 suite. This contains all of the tools, libraries, and header files
  85 needed to use the low level virtual machine.  It contains an
  86 assembler, disassembler, bitcode analyzer and bitcode optimizer.  It
  87 also contains basic regression tests that can be used to test the LLVM
  88 tools and the GCC front end.</p>
  89
  90 <p>The second piece is the GCC front end.  This component provides a version of
  91 GCC that compiles C and C++ code into LLVM bitcode.  Currently, the GCC front
  92 end uses the GCC parser to convert code to LLVM.  Once
  93 compiled into LLVM bitcode, a program can be manipulated with the LLVM tools
  94 from the LLVM suite.</p>
  95
  96 <p>
  97 There is a third, optional piece called Test Suite.  It is a suite of programs
  98 with a testing harness that can be used to further test LLVM's functionality
  99 and performance.
 100 </p>
 101
 102 </div>
 103
 104 <!-- *********************************************************************** -->
 105 <h2>
 106   <a name="quickstart">Getting Started Quickly (A Summary)</a>
 107 </h2>
 108 <!-- *********************************************************************** -->
 109
 110 <div>
 111
 112 <p>Here's the short story for getting up and running quickly with LLVM:</p>
 113
 114 <ol>
 115   <li>Read the documentation.</li>
 116   <li>Read the documentation.</li>
 117   <li>Remember that you were warned twice about reading the documentation.</li>
 118   <li>Install the llvm-gcc-4.2 front end if you intend to compile C or C++
 119       (see <a href="#installcf">Install the GCC Front End</a> for details):
 120     <ol>
 121       <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt></li>
 122       <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf -</tt></li>
 123           <li><tt><i>install-binutils-binary-from-MinGW</i></tt> (Windows only)</li>
 124           <li>Note: If the binary extension is "<tt>.bz</tt>" use <tt>bunzip2</tt> instead of <tt>gunzip</tt>.</li>
 125           <li>Note: On Windows, use <a href="http://www.7-zip.org/">7-Zip</a> or a similar archiving tool.</li>
 126           <li>Add <tt>llvm-gcc</tt>'s "<tt>bin</tt>" directory to your <tt>PATH</tt> environment variable.</li>
 127     </ol></li>
 128
 129   <li>Get the LLVM Source Code
 130   <ul>
 131     <li>With the distributed files (or use <a href="#checkout">SVN</a>):
 132     <ol>
 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>
 135     </ol></li>
 136
 137   </ul></li>
 138
 139   <li><b>[Optional]</b> Get the Test Suite Source Code
 140   <ul>
 141     <li>With the distributed files (or use <a href="#checkout">SVN</a>):
 142     <ol>
 143       <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
 144       <li><tt>cd llvm/projects</tt>
 145       <li><tt>gunzip --stdout llvm-test-<i>version</i>.tar.gz | tar -xvf -</tt>
 146       <li><tt>mv llvm-test-<i>version</i> test-suite</tt>
 147     </ol></li>
 148
 149   </ul></li>
 150
 151
 152   <li>Configure the LLVM Build Environment
 153   <ol>
 154     <li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
 155     <li><tt><i>/path/to/llvm/</i>configure [options]</tt><br>
 156     Some common options:
 157
 158       <ul>
 159         <li><tt>--prefix=<i>directory</i></tt>
 160         <p>Specify for <i>directory</i> the full pathname of where you
 161         want the LLVM tools and libraries to be installed (default
 162         <tt>/usr/local</tt>).</p></li>
 163         <li><tt>--with-llvmgccdir=<i>directory</i></tt>
 164         <p>Optionally, specify for <i>directory</i> the full pathname of the
 165         C/C++ front end installation to use with this LLVM configuration. If
 166         not specified, the PATH will be searched.  This is only needed if you
 167         want to run test-suite or do some special kinds of LLVM builds.</p></li>
 168         <li><tt>--enable-spec2000=<i>directory</i></tt>
 169             <p>Enable the SPEC2000 benchmarks for testing.  The SPEC2000
 170             benchmarks should be available in
 171             <tt><i>directory</i></tt>.</p></li>
 172       </ul>
 173   </ol></li>
 174
 175   <li>Build the LLVM Suite:
 176   <ol>
 177       <li><tt>gmake -k |&amp; tee gnumake.out
 178       &nbsp;&nbsp;&nbsp;# this is csh or tcsh syntax</tt></li>
 179       <li>If you get an "internal compiler error (ICE)" or test failures, see
 180           <a href="#brokengcc">below</a>.</li>
 181   </ol>
 182
 183 </ol>
 184
 185 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
 186 detailed information on configuring and compiling LLVM.  See <a
 187 href="#environment">Setting Up Your Environment</a> for tips that simplify
 188 working with the GCC front end and LLVM tools.  Go to <a href="#layout">Program
 189 Layout</a> to learn about the layout of the source code tree.</p>
 190
 191 </div>
 192
 193 <!-- *********************************************************************** -->
 194 <h2>
 195   <a name="requirements">Requirements</a>
 196 </h2>
 197 <!-- *********************************************************************** -->
 198
 199 <div>
 200
 201 <p>Before you begin to use the LLVM system, review the requirements given below.
 202 This may save you some trouble by knowing ahead of time what hardware and
 203 software you will need.</p>
 204
 205 <!-- ======================================================================= -->
 206 <h3>
 207   <a name="hardware">Hardware</a>
 208 </h3>
 209
 210 <div>
 211
 212 <p>LLVM is known to work on the following platforms:</p>
 213
 214 <table cellpadding="3" summary="Known LLVM platforms">
 215 <tr>
 216   <th>OS</th>
 217   <th>Arch</th>
 218   <th>Compilers</th>
 219 </tr>
 220 <tr>
 221   <td>AuroraUX</td>
 222   <td>x86<sup><a href="#pf_1">1</a></sup></td>
 223   <td>GCC</td>
 224 </tr>
 225 <tr>
 226   <td>Linux</td>
 227   <td>x86<sup><a href="#pf_1">1</a></sup></td>
 228   <td>GCC</td>
 229 </tr>
 230 <tr>
 231   <td>Linux</td>
 232   <td>amd64</td>
 233   <td>GCC</td>
 234 </tr>
 235 <tr>
 236   <td>Solaris</td>
 237   <td>V9 (Ultrasparc)</td>
 238   <td>GCC</td>
 239 </tr>
 240 <tr>
 241   <td>FreeBSD</td>
 242   <td>x86<sup><a href="#pf_1">1</a></sup></td>
 243   <td>GCC</td>
 244 </tr>
 245 <tr>
 246   <td>FreeBSD</td>
 247   <td>amd64</td>
 248   <td>GCC</td>
 249 </tr>
 250 <tr>
 251   <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
 252   <td>PowerPC</td>
 253   <td>GCC</td>
 254 </tr>
 255 <tr>
 256   <td>MacOS X<sup><a href="#pf_2">2</a>,<a href="#pf_9">9</a></sup></td>
 257   <td>x86</td>
 258   <td>GCC</td>
 259 </tr>
 260 <tr>
 261   <td>Cygwin/Win32</td>
 262   <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a>,
 263      <a href="#pf_11">11</a></sup></td>
 264   <td>GCC 3.4.X, binutils 2.20</td>
 265 </tr>
 266 <tr>
 267   <td>MinGW/Win32</td>
 268   <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,
 269      <a href="#pf_8">8</a>, <a href="#pf_10">10</a>,
 270      <a href="#pf_11">11</a></sup></td>
 271   <td>GCC 3.4.X, binutils 2.20</td>
 272 </tr>
 273 </table>
 274
 275 <p>LLVM has partial support for the following platforms:</p>
 276
 277 <table summary="LLVM partial platform support">
 278 <tr>
 279   <th>OS</th>
 280   <th>Arch</th>
 281   <th>Compilers</th>
 282 </tr>
 283 <tr>
 284   <td>Windows</td>
 285   <td>x86<sup><a href="#pf_1">1</a></sup></td>
 286   <td>Visual Studio 2005 SP1 or higher<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
 287 <tr>
 288   <td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
 289   <td>PowerPC</td>
 290   <td>GCC</td>
 291 </tr>
 292 <tr>
 293   <td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
 294   <td>PowerPC</td>
 295   <td>GCC</td>
 296 </tr>
 297
 298 <tr>
 299   <td>Linux<sup><a href="#pf_7">7</a></sup></td>
 300   <td>Alpha</td>
 301   <td>GCC</td>
 302 </tr>
 303 <tr>
 304   <td>Linux<sup><a href="#pf_7">7</a></sup></td>
 305   <td>Itanium (IA-64)</td>
 306   <td>GCC</td>
 307 </tr>
 308 <tr>
 309   <td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
 310   <td>Itanium (IA-64)</td>
 311   <td>HP aCC</td>
 312 </tr>
 313 <tr>
 314   <td>Windows x64</td>
 315   <td>x86-64</td>
 316   <td>mingw-w64's GCC-4.5.x<sup><a href="#pf_12">12</a></sup></td>
 317 </tr>
 318 </table>
 319
 320 <p><b>Notes:</b></p>
 321
 322 <div class="doc_notes">
 323 <ol>
 324 <li><a name="pf_1">Code generation supported for Pentium processors and
 325 up</a></li>
 326 <li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
 327 <li><a name="pf_3">No native code generation</a></li>
 328 <li><a name="pf_4">Build is not complete: one or more tools do not link or function</a></li>
 329 <li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
 330 <li><a name="pf_6">The port is done using the MSYS shell.</a></li>
 331 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
 332 <li><a name="pf_8">Binutils 2.20 or later is required to build the assembler
 333     generated by LLVM properly.</a></li>
 334 <li><a name="pf_9">XCode 2.5 and gcc 4.0.1</a> (Apple Build 5370) will trip
 335     internal LLVM assert messages when compiled for Release at optimization
 336     levels greater than 0 (i.e., <i>"-O1"</i> and higher).
 337     Add <i>OPTIMIZE_OPTION="-O0"</i> to the build command line
 338     if compiling for LLVM Release or bootstrapping the LLVM toolchain.</li>
 339 <li><a name="pf_10">For MSYS/MinGW on Windows, be sure to install the MSYS
 340     version of the perl package, and be sure it appears in your path
 341     before any Windows-based versions such as Strawberry Perl and
 342     ActivePerl, as these have Windows-specifics that will cause the
 343     build to fail.</a></li>
 344 <li><a name="pf_11">To use LLVM modules on Win32-based system,
 345     you may configure LLVM with <i>&quot;--enable-shared&quot;</i>.</a></li>
 346 <li><a name="pf_12">To compile SPU backend, you need to add
 347     <tt>&quot;LDFLAGS=-Wl,--stack,16777216&quot;</tt> to configure.</a></li>
 348 </ol>
 349 </div>
 350
 351 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
 352 mode, depending on the system (it is so large because of all the debugging
 353 information and the fact that the libraries are statically linked into multiple
 354 tools).  If you do not need many of the tools and you are space-conscious, you
 355 can pass <tt>ONLY_TOOLS="tools you need"</tt> to make.  The Release build
 356 requires considerably less space.</p>
 357
 358 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
 359 guaranteed to do so.  If compilation is successful, the LLVM utilities should be
 360 able to assemble, disassemble, analyze, and optimize LLVM bitcode.  Code
 361 generation should work as well, although the generated native code may not work
 362 on your platform.</p>
 363
 364 <p>The GCC front end is not very portable at the moment.  If you want to get it
 365 to work on another platform, you can download a copy of the source and <a
 366 href="GCCFEBuildInstrs.html">try to compile it</a> on your platform.</p>
 367
 368 </div>
 369
 370 <!-- ======================================================================= -->
 371 <h3>
 372   <a name="software">Software</a>
 373 </h3>
 374 <div>
 375   <p>Compiling LLVM requires that you have several software packages
 376   installed. The table below lists those required packages. The Package column
 377   is the usual name for the software package that LLVM depends on. The Version
 378   column provides "known to work" versions of the package. The Notes column
 379   describes how LLVM uses the package and provides other details.</p>
 380   <table summary="Packages required to compile LLVM">
 381     <tr><th>Package</th><th>Version</th><th>Notes</th></tr>
 382
 383     <tr>
 384       <td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
 385       <td>3.79, 3.79.1</td>
 386       <td>Makefile/build processor</td>
 387     </tr>
 388
 389     <tr>
 390       <td><a href="http://gcc.gnu.org/">GCC</a></td>
 391       <td>3.4.2</td>
 392       <td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
 393     </tr>
 394
 395     <tr>
 396       <td><a href="http://www.gnu.org/software/texinfo/">TeXinfo</a></td>
 397       <td>4.5</td>
 398       <td>For building the CFE</td>
 399     </tr>
 400
 401     <tr>
 402       <td><a href="http://subversion.tigris.org/project_packages.html">SVN</a></td>
 403       <td>&ge;1.3</td>
 404       <td>Subversion access to LLVM<sup><a href="#sf2">2</a></sup></td>
 405     </tr>
 406
 407     <!-- FIXME:
 408     Do we support dg?
 409     Are DejaGnu and expect obsolete?
 410     Shall we mention Python? -->
 411
 412     <tr>
 413       <td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
 414       <td>1.4.2</td>
 415       <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
 416     </tr>
 417
 418     <tr>
 419       <td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
 420       <td>8.3, 8.4</td>
 421       <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
 422     </tr>
 423
 424     <tr>
 425       <td><a href="http://expect.nist.gov/">expect</a></td>
 426       <td>5.38.0</td>
 427       <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
 428     </tr>
 429
 430     <tr>
 431       <td><a href="http://www.perl.com/download.csp">perl</a></td>
 432       <td>&ge;5.6.0</td>
 433       <td>Nightly tester, utilities</td>
 434     </tr>
 435
 436     <tr>
 437       <td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
 438       <td>1.4</td>
 439       <td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
 440     </tr>
 441
 442     <tr>
 443       <td><a href="http://www.gnu.org/software/autoconf/">GNU Autoconf</a></td>
 444       <td>2.60</td>
 445       <td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
 446     </tr>
 447
 448     <tr>
 449       <td><a href="http://www.gnu.org/software/automake/">GNU Automake</a></td>
 450       <td>1.9.6</td>
 451       <td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
 452     </tr>
 453
 454     <tr>
 455       <td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
 456       <td>1.5.22</td>
 457       <td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
 458     </tr>
 459
 460   </table>
 461
 462   <p><b>Notes:</b></p>
 463   <div class="doc_notes">
 464   <ol>
 465     <li><a name="sf1">Only the C and C++ languages are needed so there's no
 466       need to build the other languages for LLVM's purposes.</a> See
 467       <a href="#brokengcc">below</a> for specific version info.</li>
 468     <li><a name="sf2">You only need Subversion if you intend to build from the
 469       latest LLVM sources. If you're working from a release distribution, you
 470       don't need Subversion.</a></li>
 471     <li><a name="sf3">Only needed if you want to run the automated test
 472       suite in the <tt>llvm/test</tt> directory.</a></li>
 473     <li><a name="sf4">If you want to make changes to the configure scripts,
 474       you will need GNU autoconf (2.60), and consequently, GNU M4 (version 1.4
 475       or higher). You will also need automake (1.9.6). We only use aclocal
 476       from that package.</a></li>
 477   </ol>
 478   </div>
 479
 480   <p>Additionally, your compilation host is expected to have the usual
 481   plethora of Unix utilities. Specifically:</p>
 482   <ul>
 483     <li><b>ar</b> - archive library builder</li>
 484     <li><b>bzip2*</b> - bzip2 command for distribution generation</li>
 485     <li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
 486     <li><b>chmod</b> - change permissions on a file</li>
 487     <li><b>cat</b> - output concatenation utility</li>
 488     <li><b>cp</b> - copy files</li>
 489     <li><b>date</b> - print the current date/time </li>
 490     <li><b>echo</b> - print to standard output</li>
 491     <li><b>egrep</b> - extended regular expression search utility</li>
 492     <li><b>find</b> - find files/dirs in a file system</li>
 493     <li><b>grep</b> - regular expression search utility</li>
 494     <li><b>gzip*</b> - gzip command for distribution generation</li>
 495     <li><b>gunzip*</b> - gunzip command for distribution checking</li>
 496     <li><b>install</b> - install directories/files </li>
 497     <li><b>mkdir</b> - create a directory</li>
 498     <li><b>mv</b> - move (rename) files</li>
 499     <li><b>ranlib</b> - symbol table builder for archive libraries</li>
 500     <li><b>rm</b> - remove (delete) files and directories</li>
 501     <li><b>sed</b> - stream editor for transforming output</li>
 502     <li><b>sh</b> - Bourne shell for make build scripts</li>
 503     <li><b>tar</b> - tape archive for distribution generation</li>
 504     <li><b>test</b> - test things in file system</li>
 505     <li><b>unzip*</b> - unzip command for distribution checking</li>
 506     <li><b>zip*</b> - zip command for distribution generation</li>
 507   </ul>
 508 </div>
 509
 510 <!-- ======================================================================= -->
 511 <h3>
 512   <a name="brokengcc">Broken versions of GCC and other tools</a>
 513 </h3>
 514
 515 <div>
 516
 517 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
 518 bugs in the compiler.  In particular, several versions of GCC crash when trying
 519 to compile LLVM.  We routinely use GCC 3.3.3, 3.4.0, and Apple 4.0.1
 520 successfully with them (however, see important notes below).  Other versions
 521 of GCC will probably work as well.  GCC versions listed
 522 here are known to not work.  If you are using one of these versions, please try
 523 to upgrade your GCC to something more recent.  If you run into a problem with a
 524 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
 525 us know</a>.  Please use the "<tt>gcc -v</tt>" command to find out which version
 526 of GCC you are using.
 527 </p>
 528
 529 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
 530 problems in the STL that effectively prevent it from compiling LLVM.
 531 </p>
 532
 533 <p><b>GCC 3.2.2 and 3.2.3</b>: These versions of GCC fails to compile LLVM with
 534 a bogus template error.  This was fixed in later GCCs.</p>
 535
 536 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
 537 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
 538 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
 539
 540 <p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
 541    Cygwin does not work.  Please <a href="GCCFEBuildInstrs.html#cygwin">upgrade
 542    to a newer version</a> if possible.</p>
 543 <p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
 544    possibly others) does not compile LLVM correctly (it appears that exception
 545    handling is broken in some cases).  Please download the FSF 3.3.3 or upgrade
 546    to a newer version of GCC.</p>
 547 <p><b>GCC 3.4.0 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
 548    code generator, causing an infinite loop in the llvm-gcc build when built
 549    with optimizations enabled (i.e. a release build).</p>
 550 <p><b>GCC 3.4.2 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
 551    code generator at -O3, as with 3.4.0.  However gcc 3.4.2 (unlike 3.4.0)
 552    correctly compiles LLVM at -O2.  A work around is to build release LLVM
 553    builds with "make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ..."</p>
 554 <p><b>GCC 3.4.x on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1056">
 555    miscompiles portions of LLVM</a>.</p>
 556 <p><b>GCC 3.4.4 (CodeSourcery ARM 2005q3-2)</b>: this compiler miscompiles LLVM
 557    when building with optimizations enabled.  It appears to work with
 558    "<tt>make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1</tt>" or build a debug
 559    build.</p>
 560 <p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
 561    miscompile LLVM.</p>
 562 <p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
 563    default with ENABLE_OPTIMIZED=1.  To work around this, build with
 564    "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
 565 <p><b>GCC 4.1.1</b>: GCC fails to build LLVM with template concept check errors
 566       compiling some files.  At the time of this writing, GCC mainline (4.2)
 567       did not share the problem.</p>
 568 <p><b>GCC 4.1.1 on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1063">
 569    miscompiles portions of LLVM</a> when compiling llvm itself into 64-bit
 570    code.  LLVM will appear to mostly work but will be buggy, e.g. failing
 571    portions of its testsuite.</p>
 572 <p><b>GCC 4.1.2 on OpenSUSE</b>: Seg faults during libstdc++ build and on x86_64
 573 platforms compiling md5.c gets a mangled constant.</p>
 574 <p><b>GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian</b>: Appears
 575 to miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining
 576 about symbols remaining in the table on destruction.</p>
 577 <p><b>GCC 4.1.2 20071124 (Red Hat 4.1.2-42)</b>: Suffers from the same symptoms
 578 as the previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).</p>
 579 <p><b>Cygwin GCC 4.3.2 20080827 (beta) 2</b>:
 580   Users <a href="http://llvm.org/PR4145">reported</a> various problems related
 581   with link errors when using this GCC version.</p>
 582 <p><b>Debian GCC 4.3.2 on X86</b>: Crashes building some files in LLVM 2.6.</p>
 583 <p><b>GCC 4.3.3 (Debian 4.3.3-10) on ARM</b>: Miscompiles parts of LLVM 2.6
 584 when optimizations are turned on. The symptom is an infinite loop in
 585 FoldingSetImpl::RemoveNode while running the code generator.</p>
 586 <p><b>GCC 4.3.5 and GCC 4.4.5 on ARM</b>: These can miscompile <tt>value >>
 587 1</tt> even at -O0. A test failure in <tt>test/Assembler/alignstack.ll</tt> is
 588 one symptom of the problem.
 589 <p><b>GNU ld 2.16.X</b>. Some 2.16.X versions of the ld linker will produce very
 590 long warning messages complaining that some ".gnu.linkonce.t.*" symbol was
 591 defined in a discarded section. You can safely ignore these messages as they are
 592 erroneous and the linkage is correct.  These messages disappear using ld
 593 2.17.</p>
 594
 595 <p><b>GNU binutils 2.17</b>: Binutils 2.17 contains <a
 596 href="http://sourceware.org/bugzilla/show_bug.cgi?id=3111">a bug</a> which
 597 causes huge link times (minutes instead of seconds) when building LLVM.  We
 598 recommend upgrading to a newer version (2.17.50.0.4 or later).</p>
 599
 600 <p><b>GNU Binutils 2.19.1 Gold</b>: This version of Gold contained
 601 <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=9836">a bug</a>
 602 which causes intermittent failures when building LLVM with position independent
 603 code.  The symptom is an error about cyclic dependencies.  We recommend
 604 upgrading to a newer version of Gold.</p>
 605
 606 </div>
 607
 608 </div>
 609
 610 <!-- *********************************************************************** -->
 611 <h2>
 612   <a name="starting">Getting Started with LLVM</a>
 613 </h2>
 614 <!-- *********************************************************************** -->
 615
 616 <div>
 617
 618 <p>The remainder of this guide is meant to get you up and running with
 619 LLVM and to give you some basic information about the LLVM environment.</p>
 620
 621 <p>The later sections of this guide describe the <a
 622 href="#layout">general layout</a> of the the LLVM source tree, a <a
 623 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
 624 href="#links">links</a> to find more information about LLVM or to get
 625 help via e-mail.</p>
 626
 627 <!-- ======================================================================= -->
 628 <h3>
 629   <a name="terminology">Terminology and Notation</a>
 630 </h3>
 631
 632 <div>
 633
 634 <p>Throughout this manual, the following names are used to denote paths
 635 specific to the local system and working environment.  <i>These are not
 636 environment variables you need to set but just strings used in the rest
 637 of this document below</i>.  In any of the examples below, simply replace
 638 each of these names with the appropriate pathname on your local system.
 639 All these paths are absolute:</p>
 640
 641 <dl>
 642     <dt>SRC_ROOT
 643     <dd>
 644     This is the top level directory of the LLVM source tree.
 645     <br><br>
 646
 647     <dt>OBJ_ROOT
 648     <dd>
 649     This is the top level directory of the LLVM object tree (i.e. the
 650     tree where object files and compiled programs will be placed.  It
 651     can be the same as SRC_ROOT).
 652     <br><br>
 653
 654     <dt>LLVMGCCDIR
 655     <dd>
 656     This is where the LLVM GCC Front End is installed.
 657     <p>
 658     For the pre-built GCC front end binaries, the LLVMGCCDIR is
 659     <tt>llvm-gcc/<i>platform</i>/llvm-gcc</tt>.
 660 </dl>
 661
 662 </div>
 663
 664 <!-- ======================================================================= -->
 665 <h3>
 666   <a name="environment">Setting Up Your Environment</a>
 667 </h3>
 668
 669 <div>
 670
 671 <p>
 672 In order to compile and use LLVM, you may need to set some environment
 673 variables.
 674
 675 <dl>
 676   <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bitcode/libs</tt></dt>
 677   <dd>[Optional] This environment variable helps LLVM linking tools find the
 678   locations of your bitcode libraries. It is provided only as a
 679   convenience since you can specify the paths using the -L options of the
 680   tools and the C/C++ front-end will automatically use the bitcode files
 681   installed in its
 682   <tt>lib</tt> directory.</dd>
 683 </dl>
 684
 685 </div>
 686
 687 <!-- ======================================================================= -->
 688 <h3>
 689   <a name="unpack">Unpacking the LLVM Archives</a>
 690 </h3>
 691
 692 <div>
 693
 694 <p>
 695 If you have the LLVM distribution, you will need to unpack it before you
 696 can begin to compile it.  LLVM is distributed as a set of two files: the LLVM
 697 suite and the LLVM GCC front end compiled for your platform.  There is an
 698 additional test suite that is optional.  Each file is a TAR archive that is
 699 compressed with the gzip program.
 700 </p>
 701
 702 <p>The files are as follows, with <em>x.y</em> marking the version number:
 703 <dl>
 704   <dt><tt>llvm-x.y.tar.gz</tt></dt>
 705   <dd>Source release for the LLVM libraries and tools.<br></dd>
 706
 707   <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
 708   <dd>Source release for the LLVM test-suite.</dd>
 709
 710   <dt><tt>llvm-gcc-4.2-x.y.source.tar.gz</tt></dt>
 711   <dd>Source release of the llvm-gcc-4.2 front end.  See README.LLVM in the root
 712       directory for build instructions.<br></dd>
 713
 714   <dt><tt>llvm-gcc-4.2-x.y-platform.tar.gz</tt></dt>
 715   <dd>Binary release of the llvm-gcc-4.2 front end for a specific platform.<br></dd>
 716
 717 </dl>
 718
 719 </div>
 720
 721 <!-- ======================================================================= -->
 722 <h3>
 723   <a name="checkout">Checkout LLVM from Subversion</a>
 724 </h3>
 725
 726 <div>
 727
 728 <p>If you have access to our Subversion repository, you can get a fresh copy of
 729 the entire source code.  All you need to do is check it out from Subversion as
 730 follows:</p>
 731
 732 <ul>
 733   <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
 734   <li>Read-Only: <tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
 735   <li>Read-Write:<tt>svn co https://user@llvm.org/svn/llvm-project/llvm/trunk
 736     llvm</tt></li>
 737 </ul>
 738
 739
 740 <p>This will create an '<tt>llvm</tt>' directory in the current
 741 directory and fully populate it with the LLVM source code, Makefiles,
 742 test directories, and local copies of documentation files.</p>
 743
 744 <p>If you want to get a specific release (as opposed to the most recent
 745 revision), you can checkout it from the '<tt>tags</tt>' directory (instead of
 746 '<tt>trunk</tt>'). The following releases are located in the following
 747 subdirectories of the '<tt>tags</tt>' directory:</p>
 748
 749 <ul>
 750 <li>Release 2.9: <b>RELEASE_29/final</b></li>
 751 <li>Release 2.8: <b>RELEASE_28</b></li>
 752 <li>Release 2.7: <b>RELEASE_27</b></li>
 753 <li>Release 2.6: <b>RELEASE_26</b></li>
 754 <li>Release 2.5: <b>RELEASE_25</b></li>
 755 <li>Release 2.4: <b>RELEASE_24</b></li>
 756 <li>Release 2.3: <b>RELEASE_23</b></li>
 757 <li>Release 2.2: <b>RELEASE_22</b></li>
 758 <li>Release 2.1: <b>RELEASE_21</b></li>
 759 <li>Release 2.0: <b>RELEASE_20</b></li>
 760 <li>Release 1.9: <b>RELEASE_19</b></li>
 761 <li>Release 1.8: <b>RELEASE_18</b></li>
 762 <li>Release 1.7: <b>RELEASE_17</b></li>
 763 <li>Release 1.6: <b>RELEASE_16</b></li>
 764 <li>Release 1.5: <b>RELEASE_15</b></li>
 765 <li>Release 1.4: <b>RELEASE_14</b></li>
 766 <li>Release 1.3: <b>RELEASE_13</b></li>
 767 <li>Release 1.2: <b>RELEASE_12</b></li>
 768 <li>Release 1.1: <b>RELEASE_11</b></li>
 769 <li>Release 1.0: <b>RELEASE_1</b></li>
 770 </ul>
 771
 772 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
 773 you get it from the Subversion repository:</p>
 774
 775 <div class="doc_code">
 776 <pre>
 777 % cd llvm/projects
 778 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
 779 </pre>
 780 </div>
 781
 782 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
 783 configured by the LLVM configure script as well as automatically updated when
 784 you run <tt>svn update</tt>.</p>
 785
 786 <p>If you would like to get the GCC front end source code, you can also get it
 787 and build it yourself.  Please follow <a href="GCCFEBuildInstrs.html">these
 788 instructions</a> to successfully get and build the LLVM GCC front-end.</p>
 789
 790 </div>
 791
 792 <!-- ======================================================================= -->
 793 <h3>
 794   <a name="git_mirror">GIT mirror</a>
 795 </h3>
 796
 797 <div>
 798
 799 <p>GIT mirrors are available for a number of LLVM subprojects. These mirrors
 800   sync automatically with each Subversion commit and contain all necessary
 801   git-svn marks (so, you can recreate git-svn metadata locally). Note that right
 802   now mirrors reflect only <tt>trunk</tt> for each project. You can do the
 803   read-only GIT clone of LLVM via:</p>
 804
 805 <pre>
 806 % git clone http://llvm.org/git/llvm.git
 807 </pre>
 808
 809 </div>
 810
 811 <!-- ======================================================================= -->
 812 <h3>
 813   <a name="installcf">Install the GCC Front End</a>
 814 </h3>
 815
 816 <div>
 817
 818 <p>Before configuring and compiling the LLVM suite (or if you want to use just the LLVM
 819 GCC front end) you can optionally extract the front end from the binary distribution.
 820 It is used for running the LLVM test-suite and for compiling C/C++ programs.  Note that
 821 you can optionally <a href="GCCFEBuildInstrs.html">build llvm-gcc yourself</a> after building the
 822 main LLVM repository.</p>
 823
 824 <p>To install the GCC front end, do the following (on Windows, use an archival tool
 825 like <a href="http://www.7-zip.org/">7-zip</a> that understands gzipped tars):</p>
 826
 827 <ol>
 828   <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
 829   <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf
 830       -</tt></li>
 831 </ol>
 832
 833 <p>Once the binary is uncompressed, if you're using a *nix-based system, add a symlink for
 834 <tt>llvm-gcc</tt> and <tt>llvm-g++</tt> to some directory in your path.  If you're using a
 835 Windows-based system, add the <tt>bin</tt> subdirectory of your front end installation directory
 836 to your <tt>PATH</tt> environment variable.  For example, if you uncompressed the binary to
 837 <tt>c:\llvm-gcc</tt>, add <tt>c:\llvm-gcc\bin</tt> to your <tt>PATH</tt>.</p>
 838
 839 <p>If you now want to build LLVM from source, when you configure LLVM, it will
 840 automatically detect <tt>llvm-gcc</tt>'s presence (if it is in your path) enabling its
 841 use in test-suite.  Note that you can always build or install <tt>llvm-gcc</tt> at any
 842 point after building the main LLVM repository: just reconfigure llvm and
 843 test-suite will pick it up.
 844 </p>
 845
 846 <p>As a convenience for Windows users, the front end binaries for MinGW/x86 include
 847 versions of the required w32api and mingw-runtime binaries.  The last remaining step for
 848 Windows users is to simply uncompress the binary binutils package from
 849 <a href="http://mingw.org/">MinGW</a> into your front end installation directory.  While the
 850 front end installation steps are not quite the same as a typical manual MinGW installation,
 851 they should be similar enough to those who have previously installed MinGW on Windows systems.</p>
 852
 853 <p>To install binutils on Windows:</p>
 854
 855 <ol>
 856   <li><tt><i>download GNU Binutils from <a href="http://sourceforge.net/projects/mingw/files/">MinGW Downloads</a></i></tt></li>
 857   <li><tt>cd <i>where-you-uncompressed-the-front-end</i></tt></li>
 858   <li><tt><i>uncompress archived binutils directories (not the tar file) into the current directory</i></tt></li>
 859 </ol>
 860
 861 <p>The binary versions of the LLVM GCC front end may not suit all of your needs.  For
 862 example, the binary distribution may include an old version of a system header
 863 file, not "fix" a header file that needs to be fixed for GCC, or it may be linked with
 864 libraries not available on your system.  In cases like these, you may want to try
 865 <a href="GCCFEBuildInstrs.html">building the GCC front end from source</a>.  Thankfully,
 866 this is much easier now than it was in the past.</p>
 867
 868 <p>We also do not currently support updating of the GCC front end by manually overlaying
 869 newer versions of the w32api and mingw-runtime binary packages that may become available
 870 from MinGW.  At this time, it's best to think of the MinGW LLVM GCC front end binary as
 871 a self-contained convenience package that requires Windows users to simply download and
 872 uncompress the GNU Binutils binary package from the MinGW project.</p>
 873
 874 <p>Regardless of your platform, if you discover that installing the LLVM GCC front end
 875 binaries is not as easy as previously described, or you would like to suggest improvements,
 876 please let us know how you would like to see things improved by dropping us a note on our
 877 <a href="http://llvm.org/docs/#maillist">mailing list</a>.</p>
 878
 879 </div>
 880
 881 <!-- ======================================================================= -->
 882 <h3>
 883   <a name="config">Local LLVM Configuration</a>
 884 </h3>
 885
 886 <div>
 887
 888   <p>Once checked out from the Subversion repository, the LLVM suite source
 889   code must be
 890 configured via the <tt>configure</tt> script.  This script sets variables in the
 891 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
 892 <tt>llvm/include/Config/config.h</tt>.  It also populates <i>OBJ_ROOT</i> with
 893 the Makefiles needed to begin building LLVM.</p>
 894
 895 <p>The following environment variables are used by the <tt>configure</tt>
 896 script to configure the build system:</p>
 897
 898 <table summary="LLVM configure script environment variables">
 899   <tr><th>Variable</th><th>Purpose</th></tr>
 900   <tr>
 901     <td>CC</td>
 902     <td>Tells <tt>configure</tt> which C compiler to use.  By default,
 903         <tt>configure</tt> will look for the first GCC C compiler in
 904         <tt>PATH</tt>.  Use this variable to override
 905         <tt>configure</tt>'s default behavior.</td>
 906   </tr>
 907   <tr>
 908     <td>CXX</td>
 909     <td>Tells <tt>configure</tt> which C++ compiler to use.  By default,
 910        <tt>configure</tt> will look for the first GCC C++ compiler in
 911        <tt>PATH</tt>.  Use this variable to override
 912        <tt>configure</tt>'s default behavior.</td>
 913   </tr>
 914 </table>
 915
 916 <p>The following options can be used to set or enable LLVM specific options:</p>
 917
 918 <dl>
 919   <dt><i>--with-llvmgccdir</i></dt>
 920   <dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
 921   The value of this option should specify the full pathname of the C/C++ Front
 922   End to be used. If this option is not provided, the PATH will be searched for
 923   a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
 924   be inferred from the path found. If the option is not given, and no llvm-gcc
 925   can be found in the path then a warning will be produced by
 926   <tt>configure</tt> indicating this situation. LLVM may still be built with
 927   the <tt>tools-only</tt> target but attempting to build the runtime libraries
 928   will fail as these libraries require llvm-gcc and llvm-g++. See
 929   <a href="#installcf">Install the GCC Front End</a> for details on installing
 930   the C/C++ Front End. See
 931   <a href="GCCFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
 932   for details on building the C/C++ Front End.</dd>
 933   <dt><i>--with-tclinclude</i></dt>
 934   <dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
 935   found. Use this if you have multiple tcl installations on your machine and you
 936   want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
 937   dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
 938   option, the LLVM configure script will search for the tcl 8.4 and 8.3
 939   releases.
 940   <br><br>
 941   </dd>
 942   <dt><i>--enable-optimized</i></dt>
 943   <dd>
 944     Enables optimized compilation (debugging symbols are removed
 945     and GCC optimization flags are enabled). Note that this is the default
 946     setting     if you are using the LLVM distribution. The default behavior
 947     of an Subversion checkout is to use an unoptimized build (also known as a
 948     debug build).
 949     <br><br>
 950   </dd>
 951   <dt><i>--enable-debug-runtime</i></dt>
 952   <dd>
 953     Enables debug symbols in the runtime libraries. The default is to strip
 954     debug symbols from the runtime libraries.
 955   </dd>
 956   <dt><i>--enable-jit</i></dt>
 957   <dd>
 958     Compile the Just In Time (JIT) compiler functionality.  This is not
 959     available
 960     on all platforms.  The default is dependent on platform, so it is best
 961     to explicitly enable it if you want it.
 962     <br><br>
 963   </dd>
 964   <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
 965   <dd>Controls which targets will be built and linked into llc. The default
 966   value for <tt>target_options</tt> is "all" which builds and links all
 967   available targets.  The value "host-only" can be specified to build only a
 968   native compiler (no cross-compiler targets available). The "native" target is
 969   selected as the target of the build host. You can also specify a comma
 970   separated list of target names that you want available in llc. The target
 971   names use all lower case. The current set of targets is: <br>
 972   <tt>alpha, ia64, powerpc, skeleton, sparc, x86</tt>.
 973   <br><br></dd>
 974   <dt><i>--enable-doxygen</i></dt>
 975   <dd>Look for the doxygen program and enable construction of doxygen based
 976   documentation from the source code. This is disabled by default because
 977   generating the documentation can take a long time and producess 100s of
 978   megabytes of output.</dd>
 979   <dt><i>--with-udis86</i></dt>
 980   <dd>LLVM can use external disassembler library for various purposes (now it's
 981   used only for examining code produced by JIT). This option will enable usage
 982   of <a href="http://udis86.sourceforge.net/">udis86</a> x86 (both 32 and 64
 983   bits) disassembler library.</dd>
 984 </dl>
 985
 986 <p>To configure LLVM, follow these steps:</p>
 987
 988 <ol>
 989     <li><p>Change directory into the object root directory:</p>
 990
 991     <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
 992
 993     <li><p>Run the <tt>configure</tt> script located in the LLVM source
 994     tree:</p>
 995
 996     <div class="doc_code">
 997     <pre>% <i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</pre>
 998     </div></li>
 999 </ol>
1000
1001 </div>
1002
1003 <!-- ======================================================================= -->
1004 <h3>
1005   <a name="compile">Compiling the LLVM Suite Source Code</a>
1006 </h3>
1007
1008 <div>
1009
1010 <p>Once you have configured LLVM, you can build it.  There are three types of
1011 builds:</p>
1012
1013 <dl>
1014     <dt>Debug Builds
1015     <dd>
1016     These builds are the default when one is using an Subversion checkout and
1017     types <tt>gmake</tt> (unless the <tt>--enable-optimized</tt> option was
1018     used during configuration).  The build system will compile the tools and
1019     libraries with debugging information.  To get a Debug Build using the
1020     LLVM distribution the <tt>--disable-optimized</tt> option must be passed
1021     to <tt>configure</tt>.
1022     <br><br>
1023
1024     <dt>Release (Optimized) Builds
1025     <dd>
1026     These builds are enabled with the <tt>--enable-optimized</tt> option to
1027     <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
1028     <tt>gmake</tt> command line.  For these builds, the build system will
1029     compile the tools and libraries with GCC optimizations enabled and strip
1030     debugging information from the libraries and executables it generates.
1031     Note that Release Builds are default when using an LLVM distribution.
1032     <br><br>
1033
1034     <dt>Profile Builds
1035     <dd>
1036     These builds are for use with profiling.  They compile profiling
1037     information into the code for use with programs like <tt>gprof</tt>.
1038     Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
1039     on the <tt>gmake</tt> command line.
1040 </dl>
1041
1042 <p>Once you have LLVM configured, you can build it by entering the
1043 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
1044
1045 <div class="doc_code"><pre>% gmake</pre></div>
1046
1047 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
1048 are using a version of GCC that is known not to compile LLVM.</p>
1049
1050 <p>
1051 If you have multiple processors in your machine, you may wish to use some of
1052 the parallel build options provided by GNU Make.  For example, you could use the
1053 command:</p>
1054
1055 <div class="doc_code"><pre>% gmake -j2</pre></div>
1056
1057 <p>There are several special targets which are useful when working with the LLVM
1058 source code:</p>
1059
1060 <dl>
1061   <dt><tt>gmake clean</tt>
1062   <dd>
1063   Removes all files generated by the build.  This includes object files,
1064   generated C/C++ files, libraries, and executables.
1065   <br><br>
1066
1067   <dt><tt>gmake dist-clean</tt>
1068   <dd>
1069   Removes everything that <tt>gmake clean</tt> does, but also removes files
1070   generated by <tt>configure</tt>.  It attempts to return the source tree to the
1071   original state in which it was shipped.
1072   <br><br>
1073
1074   <dt><tt>gmake install</tt>
1075   <dd>
1076   Installs LLVM header files, libraries, tools, and documentation in a
1077   hierarchy
1078   under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
1079   defaults to <tt>/usr/local</tt>.
1080   <br><br>
1081
1082   <dt><tt>gmake -C runtime install-bytecode</tt>
1083   <dd>
1084   Assuming you built LLVM into $OBJDIR, when this command is run, it will
1085   install bitcode libraries into the GCC front end's bitcode library
1086   directory.  If you need to update your bitcode libraries,
1087   this is the target to use once you've built them.
1088   <br><br>
1089 </dl>
1090
1091 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
1092 details on these <tt>make</tt> targets and descriptions of other targets
1093 available.</p>
1094
1095 <p>It is also possible to override default values from <tt>configure</tt> by
1096 declaring variables on the command line.  The following are some examples:</p>
1097
1098 <dl>
1099   <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
1100   <dd>
1101   Perform a Release (Optimized) build.
1102   <br><br>
1103
1104   <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
1105   <dd>
1106   Perform a Release (Optimized) build without assertions enabled.
1107   <br><br>
1108
1109   <dt><tt>gmake ENABLE_OPTIMIZED=0</tt>
1110   <dd>
1111   Perform a Debug build.
1112   <br><br>
1113
1114   <dt><tt>gmake ENABLE_PROFILING=1</tt>
1115   <dd>
1116   Perform a Profiling build.
1117   <br><br>
1118
1119   <dt><tt>gmake VERBOSE=1</tt>
1120   <dd>
1121   Print what <tt>gmake</tt> is doing on standard output.
1122   <br><br>
1123
1124   <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
1125   <dd>Ask each tool invoked by the makefiles to print out what it is doing on
1126   the standard output. This also implies <tt>VERBOSE=1</tt>.
1127   <br><br></dd>
1128 </dl>
1129
1130 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
1131 it and any subdirectories that it contains.  Entering any directory inside the
1132 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
1133 that directory that is out of date.</p>
1134
1135 </div>
1136
1137 <!-- ======================================================================= -->
1138 <h3>
1139   <a name="cross-compile">Cross-Compiling LLVM</a>
1140 </h3>
1141
1142 <div>
1143   <p>It is possible to cross-compile LLVM itself. That is, you can create LLVM
1144   executables and libraries to be hosted on a platform different from the
1145   platform where they are build (a Canadian Cross build). To configure a
1146   cross-compile, supply the configure script with <tt>--build</tt> and
1147   <tt>--host</tt> options that are different. The values of these options must
1148   be legal target triples that your GCC compiler supports.</p>
1149
1150   <p>The result of such a build is executables that are not runnable on
1151   on the build host (--build option) but can be executed on the compile host
1152   (--host option).</p>
1153 </div>
1154
1155 <!-- ======================================================================= -->
1156 <h3>
1157   <a name="objfiles">The Location of LLVM Object Files</a>
1158 </h3>
1159
1160 <div>
1161
1162 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1163 several LLVM builds.  Hence, it is possible to build LLVM for several different
1164 platforms or configurations using the same source tree.</p>
1165
1166 <p>This is accomplished in the typical autoconf manner:</p>
1167
1168 <ul>
1169   <li><p>Change directory to where the LLVM object files should live:</p>
1170
1171       <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1172
1173   <li><p>Run the <tt>configure</tt> script found in the LLVM source
1174       directory:</p>
1175
1176       <div class="doc_code"><pre>% <i>SRC_ROOT</i>/configure</pre></div></li>
1177 </ul>
1178
1179 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1180 named after the build type:</p>
1181
1182 <dl>
1183   <dt>Debug Builds with assertions enabled (the default)
1184   <dd>
1185   <dl>
1186     <dt>Tools
1187     <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/bin</tt>
1188     <dt>Libraries
1189     <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/lib</tt>
1190   </dl>
1191   <br><br>
1192
1193   <dt>Release Builds
1194   <dd>
1195   <dl>
1196     <dt>Tools
1197     <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1198     <dt>Libraries
1199     <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1200   </dl>
1201   <br><br>
1202
1203   <dt>Profile Builds
1204   <dd>
1205   <dl>
1206     <dt>Tools
1207     <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1208     <dt>Libraries
1209     <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1210   </dl>
1211 </dl>
1212
1213 </div>
1214
1215 <!-- ======================================================================= -->
1216 <h3>
1217   <a name="optionalconfig">Optional Configuration Items</a>
1218 </h3>
1219
1220 <div>
1221
1222 <p>
1223 If you're running on a Linux system that supports the "<a
1224 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
1225 module, and you have root access on the system, you can set your system up to
1226 execute LLVM bitcode files directly. To do this, use commands like this (the
1227 first command may not be required if you are already using the module):</p>
1228
1229 <div class="doc_code">
1230 <pre>
1231 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1232 $ echo ':llvm:M::BC::/path/to/lli:' &gt; /proc/sys/fs/binfmt_misc/register
1233 $ chmod u+x hello.bc   (if needed)
1234 $ ./hello.bc
1235 </pre>
1236 </div>
1237
1238 <p>
1239 This allows you to execute LLVM bitcode files directly.  On Debian, you
1240 can also use this command instead of the 'echo' command above:
1241 </p>
1242
1243 <div class="doc_code">
1244 <pre>
1245 $ sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1246 </pre>
1247 </div>
1248
1249 </div>
1250
1251 </div>
1252
1253 <!-- *********************************************************************** -->
1254 <h2>
1255   <a name="layout">Program Layout</a>
1256 </h2>
1257 <!-- *********************************************************************** -->
1258
1259 <div>
1260
1261 <p>One useful source of information about the LLVM source base is the LLVM <a
1262 href="http://www.doxygen.org/">doxygen</a> documentation available at <tt><a
1263 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1264 The following is a brief introduction to code layout:</p>
1265
1266 <!-- ======================================================================= -->
1267 <h3>
1268   <a name="examples"><tt>llvm/examples</tt></a>
1269 </h3>
1270
1271 <div>
1272   <p>This directory contains some simple examples of how to use the LLVM IR and
1273   JIT.</p>
1274 </div>
1275
1276 <!-- ======================================================================= -->
1277 <h3>
1278   <a name="include"><tt>llvm/include</tt></a>
1279 </h3>
1280
1281 <div>
1282
1283 <p>This directory contains public header files exported from the LLVM
1284 library. The three main subdirectories of this directory are:</p>
1285
1286 <dl>
1287   <dt><tt><b>llvm/include/llvm</b></tt></dt>
1288   <dd>This directory contains all of the LLVM specific header files.  This
1289   directory also has subdirectories for different portions of LLVM:
1290   <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1291   etc...</dd>
1292
1293   <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1294   <dd>This directory contains generic support libraries that are provided with
1295   LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1296   and a Command Line option processing library store their header files here.
1297   </dd>
1298
1299   <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1300   <dd>This directory contains header files configured by the <tt>configure</tt>
1301   script.  They wrap "standard" UNIX and C header files.  Source code can
1302   include these header files which automatically take care of the conditional
1303   #includes that the <tt>configure</tt> script generates.</dd>
1304 </dl>
1305 </div>
1306
1307 <!-- ======================================================================= -->
1308 <h3>
1309   <a name="lib"><tt>llvm/lib</tt></a>
1310 </h3>
1311
1312 <div>
1313
1314 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1315 almost all code exists in libraries, making it very easy to share code among the
1316 different <a href="#tools">tools</a>.</p>
1317
1318 <dl>
1319   <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1320   <dd> This directory holds the core LLVM source files that implement core
1321   classes like Instruction and BasicBlock.</dd>
1322
1323   <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1324   <dd>This directory holds the source code for the LLVM assembly language parser
1325   library.</dd>
1326
1327   <dt><tt><b>llvm/lib/BitCode/</b></tt></dt>
1328   <dd>This directory holds code for reading and write LLVM bitcode.</dd>
1329
1330   <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1331   different program analyses, such as Dominator Information, Call Graphs,
1332   Induction Variables, Interval Identification, Natural Loop Identification,
1333   etc.</dd>
1334
1335   <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1336   <dd> This directory contains the source code for the LLVM to LLVM program
1337   transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1338   Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1339   Elimination, and many others.</dd>
1340
1341   <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1342   <dd> This directory contains files that describe various target architectures
1343   for code generation.  For example, the <tt>llvm/lib/Target/X86</tt>
1344   directory holds the X86 machine description while
1345   <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
1346
1347   <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1348   <dd> This directory contains the major parts of the code generator: Instruction
1349   Selector, Instruction Scheduling, and Register Allocation.</dd>
1350
1351   <dt><tt><b>llvm/lib/MC/</b></tt></dt>
1352   <dd>(FIXME: T.B.D.)</dd>
1353
1354   <!--FIXME: obsoleted -->
1355   <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1356   <dd> This directory contains the source level debugger library that makes
1357   it possible to instrument LLVM programs so that a debugger could identify
1358   source code locations at which the program is executing.</dd>
1359
1360   <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1361   <dd> This directory contains libraries for executing LLVM bitcode directly
1362   at runtime in both interpreted and JIT compiled fashions.</dd>
1363
1364   <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1365   <dd> This directory contains the source code that corresponds to the header
1366   files located in <tt>llvm/include/Support/</tt>.</dd>
1367
1368   <!--FIXME: obsoleted -->
1369   <dt><tt><b>llvm/lib/System/</b></tt></dt>
1370   <dd>This directory contains the operating system abstraction layer that
1371   shields LLVM from platform-specific coding.</dd>
1372 </dl>
1373
1374 </div>
1375
1376 <!-- ======================================================================= -->
1377 <h3>
1378   <a name="projects"><tt>llvm/projects</tt></a>
1379 </h3>
1380
1381 <div>
1382   <p>This directory contains projects that are not strictly part of LLVM but are
1383   shipped with LLVM. This is also the directory where you should create your own
1384   LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1385   to set up your own project.</p>
1386 </div>
1387
1388 <!-- ======================================================================= -->
1389 <h3>
1390   <a name="runtime"><tt>llvm/runtime</tt></a>
1391 </h3>
1392
1393 <div>
1394
1395 <p>This directory contains libraries which are compiled into LLVM bitcode and
1396 used when linking programs with the GCC front end.  Most of these libraries are
1397 skeleton versions of real libraries; for example, libc is a stripped down
1398 version of glibc.</p>
1399
1400 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1401 end to compile.</p>
1402
1403 </div>
1404
1405 <!-- ======================================================================= -->
1406 <h3>
1407   <a name="test"><tt>llvm/test</tt></a>
1408 </h3>
1409
1410 <div>
1411   <p>This directory contains feature and regression tests and other basic sanity
1412   checks on the LLVM infrastructure. These are intended to run quickly and cover
1413   a lot of territory without being exhaustive.</p>
1414 </div>
1415
1416 <!-- ======================================================================= -->
1417 <h3>
1418   <a name="test-suite"><tt>test-suite</tt></a>
1419 </h3>
1420
1421 <div>
1422   <p>This is not a directory in the normal llvm module; it is a separate
1423   Subversion
1424   module that must be checked out (usually to <tt>projects/test-suite</tt>).
1425   This
1426   module contains a comprehensive correctness, performance, and benchmarking
1427   test
1428   suite for LLVM. It is a separate Subversion module because not every LLVM
1429   user is
1430   interested in downloading or building such a comprehensive test suite. For
1431   further details on this test suite, please see the
1432   <a href="TestingGuide.html">Testing Guide</a> document.</p>
1433 </div>
1434
1435 <!-- ======================================================================= -->
1436 <h3>
1437   <a name="tools"><tt>llvm/tools</tt></a>
1438 </h3>
1439
1440 <div>
1441
1442 <p>The <b>tools</b> directory contains the executables built out of the
1443 libraries above, which form the main part of the user interface.  You can
1444 always get help for a tool by typing <tt>tool_name -help</tt>.  The
1445 following is a brief introduction to the most important tools.  More detailed
1446 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1447
1448 <dl>
1449
1450   <dt><tt><b>bugpoint</b></tt></dt>
1451   <dd><tt>bugpoint</tt> is used to debug
1452   optimization passes or code generation backends by narrowing down the
1453   given test case to the minimum number of passes and/or instructions that
1454   still cause a problem, whether it is a crash or miscompilation. See <a
1455   href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1456   on using <tt>bugpoint</tt>.</dd>
1457
1458   <dt><tt><b>llvmc</b></tt></dt>
1459   <dd>The LLVM Compiler Driver. This program can
1460   be configured to utilize both LLVM and non-LLVM compilation tools to enable
1461   pre-processing, translation, optimization, assembly, and linking of programs
1462   all from one command line. <tt>llvmc</tt> also takes care of processing the
1463   dependent libraries found in bitcode. This reduces the need to get the
1464   traditional <tt>-l&lt;name&gt;</tt> options right on the command line. Please
1465   note that this tool, while functional, is still experimental and not feature
1466   complete.</dd>
1467
1468   <dt><tt><b>llvm-ar</b></tt></dt>
1469   <dd>The archiver produces an archive containing
1470   the given LLVM bitcode files, optionally with an index for faster
1471   lookup.</dd>
1472
1473   <dt><tt><b>llvm-as</b></tt></dt>
1474   <dd>The assembler transforms the human readable LLVM assembly to LLVM
1475   bitcode.</dd>
1476
1477   <dt><tt><b>llvm-dis</b></tt></dt>
1478   <dd>The disassembler transforms the LLVM bitcode to human readable
1479   LLVM assembly.</dd>
1480
1481   <dt><tt><b>llvm-ld</b></tt></dt>
1482   <dd><tt>llvm-ld</tt> is a general purpose and extensible linker for LLVM.
1483   This is the linker invoked by <tt>llvmc</tt>. It performs standard link time
1484   optimizations and allows optimization modules to be loaded and run so that
1485   language specific optimizations can be applied at link time.</dd>
1486
1487   <dt><tt><b>llvm-link</b></tt></dt>
1488   <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1489   a single program.</dd>
1490
1491   <dt><tt><b>lli</b></tt></dt>
1492   <dd><tt>lli</tt> is the LLVM interpreter, which
1493   can directly execute LLVM bitcode (although very slowly...). For architectures
1494   that support it (currently x86, Sparc, and PowerPC), by default, <tt>lli</tt>
1495   will function as a Just-In-Time compiler (if the functionality was compiled
1496   in), and will execute the code <i>much</i> faster than the interpreter.</dd>
1497
1498   <dt><tt><b>llc</b></tt></dt>
1499   <dd> <tt>llc</tt> is the LLVM backend compiler, which
1500   translates LLVM bitcode to a native code assembly file or to C code (with
1501   the -march=c option).</dd>
1502
1503   <dt><tt><b>llvm-gcc</b></tt></dt>
1504   <dd><tt>llvm-gcc</tt> is a GCC-based C frontend that has been retargeted to
1505   use LLVM as its backend instead of GCC's RTL backend. It can also emit LLVM
1506   bitcode or assembly (with the <tt>-emit-llvm</tt> option) instead of the
1507   usual machine code output.  It works just like any other GCC compiler,
1508   taking the typical <tt>-c, -S, -E, -o</tt> options that are typically used.
1509   Additionally, the the source code for <tt>llvm-gcc</tt> is available as a
1510   separate Subversion module.</dd>
1511
1512   <dt><tt><b>opt</b></tt></dt>
1513   <dd><tt>opt</tt> reads LLVM bitcode, applies a series of LLVM to LLVM
1514   transformations (which are specified on the command line), and then outputs
1515   the resultant bitcode.  The '<tt>opt -help</tt>' command is a good way to
1516   get a list of the program transformations available in LLVM.<br>
1517   <dd><tt>opt</tt> can also be used to run a specific analysis on an input
1518   LLVM bitcode file and print out the results.  It is primarily useful for
1519   debugging analyses, or familiarizing yourself with what an analysis does.</dd>
1520 </dl>
1521 </div>
1522
1523 <!-- ======================================================================= -->
1524 <h3>
1525   <a name="utils"><tt>llvm/utils</tt></a>
1526 </h3>
1527
1528 <div>
1529
1530 <p>This directory contains utilities for working with LLVM source code, and some
1531 of the utilities are actually required as part of the build process because they
1532 are code generators for parts of LLVM infrastructure.</p>
1533
1534 <dl>
1535   <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1536   that finds differences between code that LLC generates and code that LLI
1537   generates. This is a useful tool if you are debugging one of them,
1538   assuming that the other generates correct output. For the full user
1539   manual, run <tt>`perldoc codegen-diff'</tt>.<br><br>
1540
1541   <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1542   syntax-highlighting files which will work with Emacs and XEmacs editors,
1543   providing syntax highlighting support for LLVM assembly files and TableGen
1544   description files. For information on how to use the syntax files, consult
1545   the <tt>README</tt> file in that directory.<br><br>
1546
1547   <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1548   and outputs all non-generated source files, which is useful if one wishes
1549   to do a lot of development across directories and does not want to
1550   individually find each file. One way to use it is to run, for example:
1551   <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1552   tree.<br><br>
1553
1554   <dt><tt><b>llvmgrep</b></tt></dt>
1555   <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1556   passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1557   line. This is a very efficient way of searching the source base for a
1558   particular regular expression.</dd>
1559
1560   <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1561   files in the current directory and then compiles and links the tool that
1562   is the first argument. For example, assuming you are in the directory
1563   <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1564   simply running <tt>makellvm llc</tt> will make a build of the current
1565   directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1566   causing a re-linking of LLC.<br><br>
1567
1568   <dt><tt><b>NewNightlyTest.pl</b></tt> and
1569   <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1570   cron script to generate nightly status reports of the functionality of
1571   tools, and the results can be seen by following the appropriate link on
1572   the <a href="http://llvm.org/">LLVM homepage</a>.<br><br>
1573
1574   <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1575   the tool used to generate register descriptions, instruction set
1576   descriptions, and even assemblers from common TableGen description
1577   files.<br><br>
1578
1579   <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1580   syntax-highlighting files which will work with the VIM editor, providing
1581   syntax highlighting support for LLVM assembly files and TableGen
1582   description files. For information on how to use the syntax files, consult
1583   the <tt>README</tt> file in that directory.<br><br>
1584
1585 </dl>
1586
1587 </div>
1588
1589 </div>
1590
1591 <!-- *********************************************************************** -->
1592 <h2>
1593   <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1594 </h2>
1595 <!-- *********************************************************************** -->
1596
1597 <div>
1598 <p>This section gives an example of using LLVM.  llvm-gcc3 is now obsolete,
1599 so we only include instructions for llvm-gcc4.
1600 </p>
1601
1602 <p><b>Note:</b> The <i>gcc4</i> frontend's invocation is <b><i>considerably different</i></b>
1603 from the previous <i>gcc3</i> frontend. In particular, the <i>gcc4</i> frontend <b><i>does not</i></b>
1604 create bitcode by default: <i>gcc4</i> produces native code. As the example below illustrates,
1605 the '--emit-llvm' flag is needed to produce LLVM bitcode output. For <i>makefiles</i> and
1606 <i>configure</i> scripts, the CFLAGS variable needs '--emit-llvm' to produce bitcode
1607 output.</p>
1608
1609 <!-- ======================================================================= -->
1610 <h3>
1611   <a name="tutorial4">Example with llvm-gcc4</a>
1612 </h3>
1613
1614 <div>
1615
1616 <ol>
1617   <li><p>First, create a simple C file, name it 'hello.c':</p>
1618
1619 <div class="doc_code">
1620 <pre>
1621 #include &lt;stdio.h&gt;
1622
1623 int main() {
1624   printf("hello world\n");
1625   return 0;
1626 }
1627 </pre></div></li>
1628
1629   <li><p>Next, compile the C file into a native executable:</p>
1630
1631       <div class="doc_code"><pre>% llvm-gcc hello.c -o hello</pre></div>
1632
1633       <p>Note that llvm-gcc works just like GCC by default.  The standard -S and
1634         -c arguments work as usual (producing a native .s or .o file,
1635         respectively).</p></li>
1636
1637   <li><p>Next, compile the C file into a LLVM bitcode file:</p>
1638
1639       <div class="doc_code">
1640       <pre>% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc</pre></div>
1641
1642       <p>The -emit-llvm option can be used with the -S or -c options to emit an
1643          LLVM ".ll" or ".bc" file (respectively) for the code.  This allows you
1644          to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
1645          the bitcode file.</p>
1646
1647       <p>Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
1648          </p></li>
1649
1650   <li><p>Run the program in both forms. To run the program, use:</p>
1651
1652       <div class="doc_code"><pre>% ./hello</pre></div>
1653
1654       <p>and</p>
1655
1656       <div class="doc_code"><pre>% lli hello.bc</pre></div>
1657
1658       <p>The second examples shows how to invoke the LLVM JIT, <a
1659        href="CommandGuide/html/lli.html">lli</a>.</p></li>
1660
1661   <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1662       code:</p>
1663
1664 <div class="doc_code">
1665 <pre>llvm-dis &lt; hello.bc | less</pre>
1666 </div></li>
1667
1668   <li><p>Compile the program to native assembly using the LLC code
1669       generator:</p>
1670
1671       <div class="doc_code"><pre>% llc hello.bc -o hello.s</pre></div></li>
1672
1673   <li><p>Assemble the native assembly language file into a program:</p>
1674
1675 <div class="doc_code">
1676 <pre>
1677 <b>Solaris:</b> % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native
1678
1679 <b>Others:</b>  % gcc hello.s -o hello.native
1680 </pre>
1681 </div></li>
1682
1683   <li><p>Execute the native code program:</p>
1684
1685       <div class="doc_code"><pre>% ./hello.native</pre></div>
1686
1687       <p>Note that using llvm-gcc to compile directly to native code (i.e. when
1688          the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
1689         </li>
1690
1691 </ol>
1692
1693 </div>
1694
1695 </div>
1696
1697 <!-- *********************************************************************** -->
1698 <h2>
1699   <a name="problems">Common Problems</a>
1700 </h2>
1701 <!-- *********************************************************************** -->
1702
1703 <div>
1704
1705 <p>If you are having problems building or using LLVM, or if you have any other
1706 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1707 Asked Questions</a> page.</p>
1708
1709 </div>
1710
1711 <!-- *********************************************************************** -->
1712 <h2>
1713   <a name="links">Links</a>
1714 </h2>
1715 <!-- *********************************************************************** -->
1716
1717 <div>
1718
1719 <p>This document is just an <b>introduction</b> on how to use LLVM to do
1720 some simple things... there are many more interesting and complicated things
1721 that you can do that aren't documented here (but we'll gladly accept a patch
1722 if you want to write something up!).  For more information about LLVM, check
1723 out:</p>
1724
1725 <ul>
1726   <li><a href="http://llvm.org/">LLVM homepage</a></li>
1727   <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1728   <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1729   that Uses LLVM</a></li>
1730 </ul>
1731
1732 </div>
1733
1734 <!-- *********************************************************************** -->
1735
1736 <hr>
1737 <address>
1738   <a href="http://jigsaw.w3.org/css-validator/check/referer"><img
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1741   src="http://www.w3.org/Icons/valid-html401-blue" alt="Valid HTML 4.01"></a>
1742
1743   <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1744   <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1745   <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
1746   Last modified: $Date$
1747 </address>
1748 </body>
1749 </html>