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