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  10
  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):
 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>,
 272      <a href="#pf_11">11</a></sup></td>
 273   <td>GCC 3.4.X, binutils 2.20</td>
 274 </tr>
 275 </table>
 276
 277 <p>LLVM has partial support for the following platforms:</p>
 278
 279 <table summary="LLVM partial platform support">
 280 <tr>
 281   <th>OS</th>
 282   <th>Arch</th>
 283   <th>Compilers</th>
 284 </tr>
 285 <tr>
 286   <td>Windows</td>
 287   <td>x86<sup><a href="#pf_1">1</a></sup></td>
 288   <td>Visual Studio 2005 SP1 or higher<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
 289 <tr>
 290   <td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
 291   <td>PowerPC</td>
 292   <td>GCC</td>
 293 </tr>
 294 <tr>
 295   <td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
 296   <td>PowerPC</td>
 297   <td>GCC</td>
 298 </tr>
 299
 300 <tr>
 301   <td>Linux<sup><a href="#pf_7">7</a></sup></td>
 302   <td>Alpha</td>
 303   <td>GCC</td>
 304 </tr>
 305 <tr>
 306   <td>Linux<sup><a href="#pf_7">7</a></sup></td>
 307   <td>Itanium (IA-64)</td>
 308   <td>GCC</td>
 309 </tr>
 310 <tr>
 311   <td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
 312   <td>Itanium (IA-64)</td>
 313   <td>HP aCC</td>
 314 </tr>
 315 <tr>
 316   <td>Windows x64</td>
 317   <td>x86-64</td>
 318   <td>mingw-w64's GCC-4.5.x<sup><a href="#pf_12">12</a></sup></td>
 319 </tr>
 320 </table>
 321
 322 <p><b>Notes:</b></p>
 323
 324 <div class="doc_notes">
 325 <ol>
 326 <li><a name="pf_1">Code generation supported for Pentium processors and
 327 up</a></li>
 328 <li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
 329 <li><a name="pf_3">No native code generation</a></li>
 330 <li><a name="pf_4">Build is not complete: one or more tools do not link or function</a></li>
 331 <li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
 332 <li><a name="pf_6">The port is done using the MSYS shell.</a></li>
 333 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
 334 <li><a name="pf_8">Binutils 2.20 or later is required to build the assembler
 335     generated by LLVM properly.</a></li>
 336 <li><a name="pf_9">XCode 2.5 and gcc 4.0.1</a> (Apple Build 5370) will trip
 337     internal LLVM assert messages when compiled for Release at optimization
 338     levels greater than 0 (i.e., <i>"-O1"</i> and higher).
 339     Add <i>OPTIMIZE_OPTION="-O0"</i> to the build command line
 340     if compiling for LLVM Release or bootstrapping the LLVM toolchain.</li>
 341 <li><a name="pf_10">For MSYS/MinGW on Windows, be sure to install the MSYS
 342     version of the perl package, and be sure it appears in your path
 343     before any Windows-based versions such as Strawberry Perl and
 344     ActivePerl, as these have Windows-specifics that will cause the
 345     build to fail.</a></li>
 346 <li><a name="pf_11">To use LLVM modules on Win32-based system,
 347     you may configure LLVM with <i>&quot;--enable-shared&quot;</i>.</a></li>
 348 <li><a name="pf_12">To compile SPU backend, you need to add
 349     <tt>&quot;LDFLAGS=-Wl,--stack,16777216&quot;</tt> to configure.</a></li>
 350 </ol>
 351 </div>
 352
 353 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
 354 mode, depending on the system (it is so large because of all the debugging
 355 information and the fact that the libraries are statically linked into multiple
 356 tools).  If you do not need many of the tools and you are space-conscious, you
 357 can pass <tt>ONLY_TOOLS="tools you need"</tt> to make.  The Release build
 358 requires considerably less space.</p>
 359
 360 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
 361 guaranteed to do so.  If compilation is successful, the LLVM utilities should be
 362 able to assemble, disassemble, analyze, and optimize LLVM bitcode.  Code
 363 generation should work as well, although the generated native code may not work
 364 on your platform.</p>
 365
 366 <p>The GCC front end is not very portable at the moment.  If you want to get it
 367 to work on another platform, you can download a copy of the source and <a
 368 href="GCCFEBuildInstrs.html">try to compile it</a> on your platform.</p>
 369
 370 </div>
 371
 372 <!-- ======================================================================= -->
 373 <div class="doc_subsection"><a name="software"><b>Software</b></a></div>
 374 <div class="doc_text">
 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 <div class="doc_subsection">
 512   <a name="brokengcc">Broken versions of GCC and other tools</a>
 513 </div>
 514
 515 <div class="doc_text">
 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
 609
 610 <!-- *********************************************************************** -->
 611 <div class="doc_section">
 612   <a name="starting"><b>Getting Started with LLVM</b></a>
 613 </div>
 614 <!-- *********************************************************************** -->
 615
 616 <div class="doc_text">
 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 </div>
 627
 628 <!-- ======================================================================= -->
 629 <div class="doc_subsection">
 630   <a name="terminology">Terminology and Notation</a>
 631 </div>
 632
 633 <div class="doc_text">
 634
 635 <p>Throughout this manual, the following names are used to denote paths
 636 specific to the local system and working environment.  <i>These are not
 637 environment variables you need to set but just strings used in the rest
 638 of this document below</i>.  In any of the examples below, simply replace
 639 each of these names with the appropriate pathname on your local system.
 640 All these paths are absolute:</p>
 641
 642 <dl>
 643     <dt>SRC_ROOT
 644     <dd>
 645     This is the top level directory of the LLVM source tree.
 646     <br><br>
 647
 648     <dt>OBJ_ROOT
 649     <dd>
 650     This is the top level directory of the LLVM object tree (i.e. the
 651     tree where object files and compiled programs will be placed.  It
 652     can be the same as SRC_ROOT).
 653     <br><br>
 654
 655     <dt>LLVMGCCDIR
 656     <dd>
 657     This is where the LLVM GCC Front End is installed.
 658     <p>
 659     For the pre-built GCC front end binaries, the LLVMGCCDIR is
 660     <tt>llvm-gcc/<i>platform</i>/llvm-gcc</tt>.
 661 </dl>
 662
 663 </div>
 664
 665 <!-- ======================================================================= -->
 666 <div class="doc_subsection">
 667   <a name="environment">Setting Up Your Environment</a>
 668 </div>
 669
 670 <div class="doc_text">
 671
 672 <p>
 673 In order to compile and use LLVM, you may need to set some environment
 674 variables.
 675
 676 <dl>
 677   <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bitcode/libs</tt></dt>
 678   <dd>[Optional] This environment variable helps LLVM linking tools find the
 679   locations of your bitcode libraries. It is provided only as a
 680   convenience since you can specify the paths using the -L options of the
 681   tools and the C/C++ front-end will automatically use the bitcode files
 682   installed in its
 683   <tt>lib</tt> directory.</dd>
 684 </dl>
 685
 686 </div>
 687
 688 <!-- ======================================================================= -->
 689 <div class="doc_subsection">
 690   <a name="unpack">Unpacking the LLVM Archives</a>
 691 </div>
 692
 693 <div class="doc_text">
 694
 695 <p>
 696 If you have the LLVM distribution, you will need to unpack it before you
 697 can begin to compile it.  LLVM is distributed as a set of two files: the LLVM
 698 suite and the LLVM GCC front end compiled for your platform.  There is an
 699 additional test suite that is optional.  Each file is a TAR archive that is
 700 compressed with the gzip program.
 701 </p>
 702
 703 <p>The files are as follows, with <em>x.y</em> marking the version number:
 704 <dl>
 705   <dt><tt>llvm-x.y.tar.gz</tt></dt>
 706   <dd>Source release for the LLVM libraries and tools.<br></dd>
 707
 708   <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
 709   <dd>Source release for the LLVM test-suite.</dd>
 710
 711   <dt><tt>llvm-gcc-4.2-x.y.source.tar.gz</tt></dt>
 712   <dd>Source release of the llvm-gcc-4.2 front end.  See README.LLVM in the root
 713       directory for build instructions.<br></dd>
 714
 715   <dt><tt>llvm-gcc-4.2-x.y-platform.tar.gz</tt></dt>
 716   <dd>Binary release of the llvm-gcc-4.2 front end for a specific platform.<br></dd>
 717
 718 </dl>
 719
 720 </div>
 721
 722 <!-- ======================================================================= -->
 723 <div class="doc_subsection">
 724   <a name="checkout">Checkout LLVM from Subversion</a>
 725 </div>
 726
 727 <div class="doc_text">
 728
 729 <p>If you have access to our Subversion repository, you can get a fresh copy of
 730 the entire source code.  All you need to do is check it out from Subversion as
 731 follows:</p>
 732
 733 <ul>
 734   <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
 735   <li>Read-Only: <tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
 736   <li>Read-Write:<tt>svn co https://user@llvm.org/svn/llvm-project/llvm/trunk
 737     llvm</tt></li>
 738 </ul>
 739
 740
 741 <p>This will create an '<tt>llvm</tt>' directory in the current
 742 directory and fully populate it with the LLVM source code, Makefiles,
 743 test directories, and local copies of documentation files.</p>
 744
 745 <p>If you want to get a specific release (as opposed to the most recent
 746 revision), you can checkout it from the '<tt>tags</tt>' directory (instead of
 747 '<tt>trunk</tt>'). The following releases are located in the following
 748 subdirectories of the '<tt>tags</tt>' directory:</p>
 749
 750 <ul>
 751 <li>Release 2.9: <b>RELEASE_29/final</b></li>
 752 <li>Release 2.8: <b>RELEASE_28</b></li>
 753 <li>Release 2.7: <b>RELEASE_27</b></li>
 754 <li>Release 2.6: <b>RELEASE_26</b></li>
 755 <li>Release 2.5: <b>RELEASE_25</b></li>
 756 <li>Release 2.4: <b>RELEASE_24</b></li>
 757 <li>Release 2.3: <b>RELEASE_23</b></li>
 758 <li>Release 2.2: <b>RELEASE_22</b></li>
 759 <li>Release 2.1: <b>RELEASE_21</b></li>
 760 <li>Release 2.0: <b>RELEASE_20</b></li>
 761 <li>Release 1.9: <b>RELEASE_19</b></li>
 762 <li>Release 1.8: <b>RELEASE_18</b></li>
 763 <li>Release 1.7: <b>RELEASE_17</b></li>
 764 <li>Release 1.6: <b>RELEASE_16</b></li>
 765 <li>Release 1.5: <b>RELEASE_15</b></li>
 766 <li>Release 1.4: <b>RELEASE_14</b></li>
 767 <li>Release 1.3: <b>RELEASE_13</b></li>
 768 <li>Release 1.2: <b>RELEASE_12</b></li>
 769 <li>Release 1.1: <b>RELEASE_11</b></li>
 770 <li>Release 1.0: <b>RELEASE_1</b></li>
 771 </ul>
 772
 773 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
 774 you get it from the Subversion repository:</p>
 775
 776 <div class="doc_code">
 777 <pre>
 778 % cd llvm/projects
 779 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
 780 </pre>
 781 </div>
 782
 783 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
 784 configured by the LLVM configure script as well as automatically updated when
 785 you run <tt>svn update</tt>.</p>
 786
 787 <p>If you would like to get the GCC front end source code, you can also get it
 788 and build it yourself.  Please follow <a href="GCCFEBuildInstrs.html">these
 789 instructions</a> to successfully get and build the LLVM GCC front-end.</p>
 790
 791 </div>
 792
 793 <!-- ======================================================================= -->
 794 <div class="doc_subsection">
 795   <a name="git_mirror">GIT mirror</a>
 796 </div>
 797
 798 <div class="doc_text">
 799
 800 <p>GIT mirrors are available for a number of LLVM subprojects. These mirrors
 801   sync automatically with each Subversion commit and contain all necessary
 802   git-svn marks (so, you can recreate git-svn metadata locally). Note that right
 803   now mirrors reflect only <tt>trunk</tt> for each project. You can do the
 804   read-only GIT clone of LLVM via:</p>
 805
 806 <pre>
 807 % git clone http://llvm.org/git/llvm.git
 808 </pre>
 809
 810 </div>
 811
 812 <!-- ======================================================================= -->
 813 <div class="doc_subsection">
 814   <a name="installcf">Install the GCC Front End</a>
 815 </div>
 816
 817 <div class="doc_text">
 818
 819 <p>Before configuring and compiling the LLVM suite (or if you want to use just the LLVM
 820 GCC front end) you can optionally extract the front end from the binary distribution.
 821 It is used for running the LLVM test-suite and for compiling C/C++ programs.  Note that
 822 you can optionally <a href="GCCFEBuildInstrs.html">build llvm-gcc yourself</a> after building the
 823 main LLVM repository.</p>
 824
 825 <p>To install the GCC front end, do the following (on Windows, use an archival tool
 826 like <a href="http://www.7-zip.org/">7-zip</a> that understands gzipped tars):</p>
 827
 828 <ol>
 829   <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
 830   <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf
 831       -</tt></li>
 832 </ol>
 833
 834 <p>Once the binary is uncompressed, if you're using a *nix-based system, add a symlink for
 835 <tt>llvm-gcc</tt> and <tt>llvm-g++</tt> to some directory in your path.  If you're using a
 836 Windows-based system, add the <tt>bin</tt> subdirectory of your front end installation directory
 837 to your <tt>PATH</tt> environment variable.  For example, if you uncompressed the binary to
 838 <tt>c:\llvm-gcc</tt>, add <tt>c:\llvm-gcc\bin</tt> to your <tt>PATH</tt>.</p>
 839
 840 <p>If you now want to build LLVM from source, when you configure LLVM, it will
 841 automatically detect <tt>llvm-gcc</tt>'s presence (if it is in your path) enabling its
 842 use in test-suite.  Note that you can always build or install <tt>llvm-gcc</tt> at any
 843 point after building the main LLVM repository: just reconfigure llvm and
 844 test-suite will pick it up.
 845 </p>
 846
 847 <p>As a convenience for Windows users, the front end binaries for MinGW/x86 include
 848 versions of the required w32api and mingw-runtime binaries.  The last remaining step for
 849 Windows users is to simply uncompress the binary binutils package from
 850 <a href="http://mingw.org/">MinGW</a> into your front end installation directory.  While the
 851 front end installation steps are not quite the same as a typical manual MinGW installation,
 852 they should be similar enough to those who have previously installed MinGW on Windows systems.</p>
 853
 854 <p>To install binutils on Windows:</p>
 855
 856 <ol>
 857   <li><tt><i>download GNU Binutils from <a href="http://sourceforge.net/projects/mingw/files/">MinGW Downloads</a></i></tt></li>
 858   <li><tt>cd <i>where-you-uncompressed-the-front-end</i></tt></li>
 859   <li><tt><i>uncompress archived binutils directories (not the tar file) into the current directory</i></tt></li>
 860 </ol>
 861
 862 <p>The binary versions of the LLVM GCC front end may not suit all of your needs.  For
 863 example, the binary distribution may include an old version of a system header
 864 file, not "fix" a header file that needs to be fixed for GCC, or it may be linked with
 865 libraries not available on your system.  In cases like these, you may want to try
 866 <a href="GCCFEBuildInstrs.html">building the GCC front end from source</a>.  Thankfully,
 867 this is much easier now than it was in the past.</p>
 868
 869 <p>We also do not currently support updating of the GCC front end by manually overlaying
 870 newer versions of the w32api and mingw-runtime binary packages that may become available
 871 from MinGW.  At this time, it's best to think of the MinGW LLVM GCC front end binary as
 872 a self-contained convenience package that requires Windows users to simply download and
 873 uncompress the GNU Binutils binary package from the MinGW project.</p>
 874
 875 <p>Regardless of your platform, if you discover that installing the LLVM GCC front end
 876 binaries is not as easy as previously described, or you would like to suggest improvements,
 877 please let us know how you would like to see things improved by dropping us a note on our
 878 <a href="http://llvm.org/docs/#maillist">mailing list</a>.</p>
 879
 880 </div>
 881
 882 <!-- ======================================================================= -->
 883 <div class="doc_subsection">
 884   <a name="config">Local LLVM Configuration</a>
 885 </div>
 886
 887 <div class="doc_text">
 888
 889   <p>Once checked out from the Subversion repository, the LLVM suite source
 890   code must be
 891 configured via the <tt>configure</tt> script.  This script sets variables in the
 892 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
 893 <tt>llvm/include/Config/config.h</tt>.  It also populates <i>OBJ_ROOT</i> with
 894 the Makefiles needed to begin building LLVM.</p>
 895
 896 <p>The following environment variables are used by the <tt>configure</tt>
 897 script to configure the build system:</p>
 898
 899 <table summary="LLVM configure script environment variables">
 900   <tr><th>Variable</th><th>Purpose</th></tr>
 901   <tr>
 902     <td>CC</td>
 903     <td>Tells <tt>configure</tt> which C compiler to use.  By default,
 904         <tt>configure</tt> will look for the first GCC C compiler in
 905         <tt>PATH</tt>.  Use this variable to override
 906         <tt>configure</tt>'s default behavior.</td>
 907   </tr>
 908   <tr>
 909     <td>CXX</td>
 910     <td>Tells <tt>configure</tt> which C++ compiler to use.  By default,
 911        <tt>configure</tt> will look for the first GCC C++ compiler in
 912        <tt>PATH</tt>.  Use this variable to override
 913        <tt>configure</tt>'s default behavior.</td>
 914   </tr>
 915 </table>
 916
 917 <p>The following options can be used to set or enable LLVM specific options:</p>
 918
 919 <dl>
 920   <dt><i>--with-llvmgccdir</i></dt>
 921   <dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
 922   The value of this option should specify the full pathname of the C/C++ Front
 923   End to be used. If this option is not provided, the PATH will be searched for
 924   a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
 925   be inferred from the path found. If the option is not given, and no llvm-gcc
 926   can be found in the path then a warning will be produced by
 927   <tt>configure</tt> indicating this situation. LLVM may still be built with
 928   the <tt>tools-only</tt> target but attempting to build the runtime libraries
 929   will fail as these libraries require llvm-gcc and llvm-g++. See
 930   <a href="#installcf">Install the GCC Front End</a> for details on installing
 931   the C/C++ Front End. See
 932   <a href="GCCFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
 933   for details on building the C/C++ Front End.</dd>
 934   <dt><i>--with-tclinclude</i></dt>
 935   <dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
 936   found. Use this if you have multiple tcl installations on your machine and you
 937   want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
 938   dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
 939   option, the LLVM configure script will search for the tcl 8.4 and 8.3
 940   releases.
 941   <br><br>
 942   </dd>
 943   <dt><i>--enable-optimized</i></dt>
 944   <dd>
 945     Enables optimized compilation (debugging symbols are removed
 946     and GCC optimization flags are enabled). Note that this is the default
 947     setting     if you are using the LLVM distribution. The default behavior
 948     of an Subversion checkout is to use an unoptimized build (also known as a
 949     debug build).
 950     <br><br>
 951   </dd>
 952   <dt><i>--enable-debug-runtime</i></dt>
 953   <dd>
 954     Enables debug symbols in the runtime libraries. The default is to strip
 955     debug symbols from the runtime libraries.
 956   </dd>
 957   <dt><i>--enable-jit</i></dt>
 958   <dd>
 959     Compile the Just In Time (JIT) compiler functionality.  This is not
 960     available
 961     on all platforms.  The default is dependent on platform, so it is best
 962     to explicitly enable it if you want it.
 963     <br><br>
 964   </dd>
 965   <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
 966   <dd>Controls which targets will be built and linked into llc. The default
 967   value for <tt>target_options</tt> is "all" which builds and links all
 968   available targets.  The value "host-only" can be specified to build only a
 969   native compiler (no cross-compiler targets available). The "native" target is
 970   selected as the target of the build host. You can also specify a comma
 971   separated list of target names that you want available in llc. The target
 972   names use all lower case. The current set of targets is: <br>
 973   <tt>alpha, ia64, powerpc, skeleton, sparc, x86</tt>.
 974   <br><br></dd>
 975   <dt><i>--enable-doxygen</i></dt>
 976   <dd>Look for the doxygen program and enable construction of doxygen based
 977   documentation from the source code. This is disabled by default because
 978   generating the documentation can take a long time and producess 100s of
 979   megabytes of output.</dd>
 980   <dt><i>--with-udis86</i></dt>
 981   <dd>LLVM can use external disassembler library for various purposes (now it's
 982   used only for examining code produced by JIT). This option will enable usage
 983   of <a href="http://udis86.sourceforge.net/">udis86</a> x86 (both 32 and 64
 984   bits) disassembler library.</dd>
 985 </dl>
 986
 987 <p>To configure LLVM, follow these steps:</p>
 988
 989 <ol>
 990     <li><p>Change directory into the object root directory:</p>
 991
 992     <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
 993
 994     <li><p>Run the <tt>configure</tt> script located in the LLVM source
 995     tree:</p>
 996
 997     <div class="doc_code">
 998     <pre>% <i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</pre>
 999     </div></li>
1000 </ol>
1001
1002 </div>
1003
1004 <!-- ======================================================================= -->
1005 <div class="doc_subsection">
1006   <a name="compile">Compiling the LLVM Suite Source Code</a>
1007 </div>
1008
1009 <div class="doc_text">
1010
1011 <p>Once you have configured LLVM, you can build it.  There are three types of
1012 builds:</p>
1013
1014 <dl>
1015     <dt>Debug Builds
1016     <dd>
1017     These builds are the default when one is using an Subversion checkout and
1018     types <tt>gmake</tt> (unless the <tt>--enable-optimized</tt> option was
1019     used during configuration).  The build system will compile the tools and
1020     libraries with debugging information.  To get a Debug Build using the
1021     LLVM distribution the <tt>--disable-optimized</tt> option must be passed
1022     to <tt>configure</tt>.
1023     <br><br>
1024
1025     <dt>Release (Optimized) Builds
1026     <dd>
1027     These builds are enabled with the <tt>--enable-optimized</tt> option to
1028     <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
1029     <tt>gmake</tt> command line.  For these builds, the build system will
1030     compile the tools and libraries with GCC optimizations enabled and strip
1031     debugging information from the libraries and executables it generates.
1032     Note that Release Builds are default when using an LLVM distribution.
1033     <br><br>
1034
1035     <dt>Profile Builds
1036     <dd>
1037     These builds are for use with profiling.  They compile profiling
1038     information into the code for use with programs like <tt>gprof</tt>.
1039     Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
1040     on the <tt>gmake</tt> command line.
1041 </dl>
1042
1043 <p>Once you have LLVM configured, you can build it by entering the
1044 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
1045
1046 <div class="doc_code"><pre>% gmake</pre></div>
1047
1048 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
1049 are using a version of GCC that is known not to compile LLVM.</p>
1050
1051 <p>
1052 If you have multiple processors in your machine, you may wish to use some of
1053 the parallel build options provided by GNU Make.  For example, you could use the
1054 command:</p>
1055
1056 <div class="doc_code"><pre>% gmake -j2</pre></div>
1057
1058 <p>There are several special targets which are useful when working with the LLVM
1059 source code:</p>
1060
1061 <dl>
1062   <dt><tt>gmake clean</tt>
1063   <dd>
1064   Removes all files generated by the build.  This includes object files,
1065   generated C/C++ files, libraries, and executables.
1066   <br><br>
1067
1068   <dt><tt>gmake dist-clean</tt>
1069   <dd>
1070   Removes everything that <tt>gmake clean</tt> does, but also removes files
1071   generated by <tt>configure</tt>.  It attempts to return the source tree to the
1072   original state in which it was shipped.
1073   <br><br>
1074
1075   <dt><tt>gmake install</tt>
1076   <dd>
1077   Installs LLVM header files, libraries, tools, and documentation in a
1078   hierarchy
1079   under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
1080   defaults to <tt>/usr/local</tt>.
1081   <br><br>
1082
1083   <dt><tt>gmake -C runtime install-bytecode</tt>
1084   <dd>
1085   Assuming you built LLVM into $OBJDIR, when this command is run, it will
1086   install bitcode libraries into the GCC front end's bitcode library
1087   directory.  If you need to update your bitcode libraries,
1088   this is the target to use once you've built them.
1089   <br><br>
1090 </dl>
1091
1092 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
1093 details on these <tt>make</tt> targets and descriptions of other targets
1094 available.</p>
1095
1096 <p>It is also possible to override default values from <tt>configure</tt> by
1097 declaring variables on the command line.  The following are some examples:</p>
1098
1099 <dl>
1100   <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
1101   <dd>
1102   Perform a Release (Optimized) build.
1103   <br><br>
1104
1105   <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
1106   <dd>
1107   Perform a Release (Optimized) build without assertions enabled.
1108   <br><br>
1109
1110   <dt><tt>gmake ENABLE_OPTIMIZED=0</tt>
1111   <dd>
1112   Perform a Debug build.
1113   <br><br>
1114
1115   <dt><tt>gmake ENABLE_PROFILING=1</tt>
1116   <dd>
1117   Perform a Profiling build.
1118   <br><br>
1119
1120   <dt><tt>gmake VERBOSE=1</tt>
1121   <dd>
1122   Print what <tt>gmake</tt> is doing on standard output.
1123   <br><br>
1124
1125   <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
1126   <dd>Ask each tool invoked by the makefiles to print out what it is doing on
1127   the standard output. This also implies <tt>VERBOSE=1</tt>.
1128   <br><br></dd>
1129 </dl>
1130
1131 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
1132 it and any subdirectories that it contains.  Entering any directory inside the
1133 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
1134 that directory that is out of date.</p>
1135
1136 </div>
1137
1138 <!-- ======================================================================= -->
1139 <div class="doc_subsection">
1140   <a name="cross-compile">Cross-Compiling LLVM</a>
1141 </div>
1142
1143 <div class="doc_text">
1144   <p>It is possible to cross-compile LLVM itself. That is, you can create LLVM
1145   executables and libraries to be hosted on a platform different from the
1146   platform where they are build (a Canadian Cross build). To configure a
1147   cross-compile, supply the configure script with <tt>--build</tt> and
1148   <tt>--host</tt> options that are different. The values of these options must
1149   be legal target triples that your GCC compiler supports.</p>
1150
1151   <p>The result of such a build is executables that are not runnable on
1152   on the build host (--build option) but can be executed on the compile host
1153   (--host option).</p>
1154 </div>
1155
1156 <!-- ======================================================================= -->
1157 <div class="doc_subsection">
1158   <a name="objfiles">The Location of LLVM Object Files</a>
1159 </div>
1160
1161 <div class="doc_text">
1162
1163 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1164 several LLVM builds.  Hence, it is possible to build LLVM for several different
1165 platforms or configurations using the same source tree.</p>
1166
1167 <p>This is accomplished in the typical autoconf manner:</p>
1168
1169 <ul>
1170   <li><p>Change directory to where the LLVM object files should live:</p>
1171
1172       <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1173
1174   <li><p>Run the <tt>configure</tt> script found in the LLVM source
1175       directory:</p>
1176
1177       <div class="doc_code"><pre>% <i>SRC_ROOT</i>/configure</pre></div></li>
1178 </ul>
1179
1180 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1181 named after the build type:</p>
1182
1183 <dl>
1184   <dt>Debug Builds with assertions enabled (the default)
1185   <dd>
1186   <dl>
1187     <dt>Tools
1188     <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/bin</tt>
1189     <dt>Libraries
1190     <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/lib</tt>
1191   </dl>
1192   <br><br>
1193
1194   <dt>Release Builds
1195   <dd>
1196   <dl>
1197     <dt>Tools
1198     <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1199     <dt>Libraries
1200     <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1201   </dl>
1202   <br><br>
1203
1204   <dt>Profile Builds
1205   <dd>
1206   <dl>
1207     <dt>Tools
1208     <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1209     <dt>Libraries
1210     <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1211   </dl>
1212 </dl>
1213
1214 </div>
1215
1216 <!-- ======================================================================= -->
1217 <div class="doc_subsection">
1218   <a name="optionalconfig">Optional Configuration Items</a>
1219 </div>
1220
1221 <div class="doc_text">
1222
1223 <p>
1224 If you're running on a Linux system that supports the "<a
1225 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
1226 module, and you have root access on the system, you can set your system up to
1227 execute LLVM bitcode files directly. To do this, use commands like this (the
1228 first command may not be required if you are already using the module):</p>
1229
1230 <div class="doc_code">
1231 <pre>
1232 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1233 $ echo ':llvm:M::BC::/path/to/lli:' &gt; /proc/sys/fs/binfmt_misc/register
1234 $ chmod u+x hello.bc   (if needed)
1235 $ ./hello.bc
1236 </pre>
1237 </div>
1238
1239 <p>
1240 This allows you to execute LLVM bitcode files directly.  On Debian, you
1241 can also use this command instead of the 'echo' command above:
1242 </p>
1243
1244 <div class="doc_code">
1245 <pre>
1246 $ sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1247 </pre>
1248 </div>
1249
1250 </div>
1251
1252 <!-- *********************************************************************** -->
1253 <div class="doc_section">
1254   <a name="layout"><b>Program Layout</b></a>
1255 </div>
1256 <!-- *********************************************************************** -->
1257
1258 <div class="doc_text">
1259
1260 <p>One useful source of information about the LLVM source base is the LLVM <a
1261 href="http://www.doxygen.org/">doxygen</a> documentation available at <tt><a
1262 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1263 The following is a brief introduction to code layout:</p>
1264
1265 </div>
1266
1267 <!-- ======================================================================= -->
1268 <div class="doc_subsection"><a name="examples"><tt>llvm/examples</tt></a></div>
1269 <div class="doc_text">
1270   <p>This directory contains some simple examples of how to use the LLVM IR and
1271   JIT.</p>
1272 </div>
1273
1274 <!-- ======================================================================= -->
1275 <div class="doc_subsection"><a name="include"><tt>llvm/include</tt></a></div>
1276 <div class="doc_text">
1277
1278 <p>This directory contains public header files exported from the LLVM
1279 library. The three main subdirectories of this directory are:</p>
1280
1281 <dl>
1282   <dt><tt><b>llvm/include/llvm</b></tt></dt>
1283   <dd>This directory contains all of the LLVM specific header files.  This
1284   directory also has subdirectories for different portions of LLVM:
1285   <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1286   etc...</dd>
1287
1288   <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1289   <dd>This directory contains generic support libraries that are provided with
1290   LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1291   and a Command Line option processing library store their header files here.
1292   </dd>
1293
1294   <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1295   <dd>This directory contains header files configured by the <tt>configure</tt>
1296   script.  They wrap "standard" UNIX and C header files.  Source code can
1297   include these header files which automatically take care of the conditional
1298   #includes that the <tt>configure</tt> script generates.</dd>
1299 </dl>
1300 </div>
1301
1302 <!-- ======================================================================= -->
1303 <div class="doc_subsection"><a name="lib"><tt>llvm/lib</tt></a></div>
1304 <div class="doc_text">
1305
1306 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1307 almost all code exists in libraries, making it very easy to share code among the
1308 different <a href="#tools">tools</a>.</p>
1309
1310 <dl>
1311   <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1312   <dd> This directory holds the core LLVM source files that implement core
1313   classes like Instruction and BasicBlock.</dd>
1314
1315   <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1316   <dd>This directory holds the source code for the LLVM assembly language parser
1317   library.</dd>
1318
1319   <dt><tt><b>llvm/lib/BitCode/</b></tt></dt>
1320   <dd>This directory holds code for reading and write LLVM bitcode.</dd>
1321
1322   <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1323   different program analyses, such as Dominator Information, Call Graphs,
1324   Induction Variables, Interval Identification, Natural Loop Identification,
1325   etc.</dd>
1326
1327   <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1328   <dd> This directory contains the source code for the LLVM to LLVM program
1329   transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1330   Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1331   Elimination, and many others.</dd>
1332
1333   <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1334   <dd> This directory contains files that describe various target architectures
1335   for code generation.  For example, the <tt>llvm/lib/Target/X86</tt>
1336   directory holds the X86 machine description while
1337   <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
1338
1339   <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1340   <dd> This directory contains the major parts of the code generator: Instruction
1341   Selector, Instruction Scheduling, and Register Allocation.</dd>
1342
1343   <dt><tt><b>llvm/lib/MC/</b></tt></dt>
1344   <dd>(FIXME: T.B.D.)</dd>
1345
1346   <!--FIXME: obsoleted -->
1347   <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1348   <dd> This directory contains the source level debugger library that makes
1349   it possible to instrument LLVM programs so that a debugger could identify
1350   source code locations at which the program is executing.</dd>
1351
1352   <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1353   <dd> This directory contains libraries for executing LLVM bitcode directly
1354   at runtime in both interpreted and JIT compiled fashions.</dd>
1355
1356   <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1357   <dd> This directory contains the source code that corresponds to the header
1358   files located in <tt>llvm/include/Support/</tt>.</dd>
1359
1360   <!--FIXME: obsoleted -->
1361   <dt><tt><b>llvm/lib/System/</b></tt></dt>
1362   <dd>This directory contains the operating system abstraction layer that
1363   shields LLVM from platform-specific coding.</dd>
1364 </dl>
1365
1366 </div>
1367
1368 <!-- ======================================================================= -->
1369 <div class="doc_subsection"><a name="projects"><tt>llvm/projects</tt></a></div>
1370 <div class="doc_text">
1371   <p>This directory contains projects that are not strictly part of LLVM but are
1372   shipped with LLVM. This is also the directory where you should create your own
1373   LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1374   to set up your own project.</p>
1375 </div>
1376
1377 <!-- ======================================================================= -->
1378 <div class="doc_subsection"><a name="runtime"><tt>llvm/runtime</tt></a></div>
1379 <div class="doc_text">
1380
1381 <p>This directory contains libraries which are compiled into LLVM bitcode and
1382 used when linking programs with the GCC front end.  Most of these libraries are
1383 skeleton versions of real libraries; for example, libc is a stripped down
1384 version of glibc.</p>
1385
1386 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1387 end to compile.</p>
1388
1389 </div>
1390
1391 <!-- ======================================================================= -->
1392 <div class="doc_subsection"><a name="test"><tt>llvm/test</tt></a></div>
1393 <div class="doc_text">
1394   <p>This directory contains feature and regression tests and other basic sanity
1395   checks on the LLVM infrastructure. These are intended to run quickly and cover
1396   a lot of territory without being exhaustive.</p>
1397 </div>
1398
1399 <!-- ======================================================================= -->
1400 <div class="doc_subsection"><a name="test-suite"><tt>test-suite</tt></a></div>
1401 <div class="doc_text">
1402   <p>This is not a directory in the normal llvm module; it is a separate
1403   Subversion
1404   module that must be checked out (usually to <tt>projects/test-suite</tt>).
1405   This
1406   module contains a comprehensive correctness, performance, and benchmarking
1407   test
1408   suite for LLVM. It is a separate Subversion module because not every LLVM
1409   user is
1410   interested in downloading or building such a comprehensive test suite. For
1411   further details on this test suite, please see the
1412   <a href="TestingGuide.html">Testing Guide</a> document.</p>
1413 </div>
1414
1415 <!-- ======================================================================= -->
1416 <div class="doc_subsection"><a name="tools"><tt>llvm/tools</tt></a></div>
1417 <div class="doc_text">
1418
1419 <p>The <b>tools</b> directory contains the executables built out of the
1420 libraries above, which form the main part of the user interface.  You can
1421 always get help for a tool by typing <tt>tool_name -help</tt>.  The
1422 following is a brief introduction to the most important tools.  More detailed
1423 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1424
1425 <dl>
1426
1427   <dt><tt><b>bugpoint</b></tt></dt>
1428   <dd><tt>bugpoint</tt> is used to debug
1429   optimization passes or code generation backends by narrowing down the
1430   given test case to the minimum number of passes and/or instructions that
1431   still cause a problem, whether it is a crash or miscompilation. See <a
1432   href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1433   on using <tt>bugpoint</tt>.</dd>
1434
1435   <dt><tt><b>llvmc</b></tt></dt>
1436   <dd>The LLVM Compiler Driver. This program can
1437   be configured to utilize both LLVM and non-LLVM compilation tools to enable
1438   pre-processing, translation, optimization, assembly, and linking of programs
1439   all from one command line. <tt>llvmc</tt> also takes care of processing the
1440   dependent libraries found in bitcode. This reduces the need to get the
1441   traditional <tt>-l&lt;name&gt;</tt> options right on the command line. Please
1442   note that this tool, while functional, is still experimental and not feature
1443   complete.</dd>
1444
1445   <dt><tt><b>llvm-ar</b></tt></dt>
1446   <dd>The archiver produces an archive containing
1447   the given LLVM bitcode files, optionally with an index for faster
1448   lookup.</dd>
1449
1450   <dt><tt><b>llvm-as</b></tt></dt>
1451   <dd>The assembler transforms the human readable LLVM assembly to LLVM
1452   bitcode.</dd>
1453
1454   <dt><tt><b>llvm-dis</b></tt></dt>
1455   <dd>The disassembler transforms the LLVM bitcode to human readable
1456   LLVM assembly.</dd>
1457
1458   <dt><tt><b>llvm-ld</b></tt></dt>
1459   <dd><tt>llvm-ld</tt> is a general purpose and extensible linker for LLVM.
1460   This is the linker invoked by <tt>llvmc</tt>. It performs standard link time
1461   optimizations and allows optimization modules to be loaded and run so that
1462   language specific optimizations can be applied at link time.</dd>
1463
1464   <dt><tt><b>llvm-link</b></tt></dt>
1465   <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1466   a single program.</dd>
1467
1468   <dt><tt><b>lli</b></tt></dt>
1469   <dd><tt>lli</tt> is the LLVM interpreter, which
1470   can directly execute LLVM bitcode (although very slowly...). For architectures
1471   that support it (currently x86, Sparc, and PowerPC), by default, <tt>lli</tt>
1472   will function as a Just-In-Time compiler (if the functionality was compiled
1473   in), and will execute the code <i>much</i> faster than the interpreter.</dd>
1474
1475   <dt><tt><b>llc</b></tt></dt>
1476   <dd> <tt>llc</tt> is the LLVM backend compiler, which
1477   translates LLVM bitcode to a native code assembly file or to C code (with
1478   the -march=c option).</dd>
1479
1480   <dt><tt><b>llvm-gcc</b></tt></dt>
1481   <dd><tt>llvm-gcc</tt> is a GCC-based C frontend that has been retargeted to
1482   use LLVM as its backend instead of GCC's RTL backend. It can also emit LLVM
1483   bitcode or assembly (with the <tt>-emit-llvm</tt> option) instead of the
1484   usual machine code output.  It works just like any other GCC compiler,
1485   taking the typical <tt>-c, -S, -E, -o</tt> options that are typically used.
1486   Additionally, the the source code for <tt>llvm-gcc</tt> is available as a
1487   separate Subversion module.</dd>
1488
1489   <dt><tt><b>opt</b></tt></dt>
1490   <dd><tt>opt</tt> reads LLVM bitcode, applies a series of LLVM to LLVM
1491   transformations (which are specified on the command line), and then outputs
1492   the resultant bitcode.  The '<tt>opt -help</tt>' command is a good way to
1493   get a list of the program transformations available in LLVM.<br>
1494   <dd><tt>opt</tt> can also be used to run a specific analysis on an input
1495   LLVM bitcode file and print out the results.  It is primarily useful for
1496   debugging analyses, or familiarizing yourself with what an analysis does.</dd>
1497 </dl>
1498 </div>
1499
1500 <!-- ======================================================================= -->
1501 <div class="doc_subsection"><a name="utils"><tt>llvm/utils</tt></a></div>
1502 <div class="doc_text">
1503
1504 <p>This directory contains utilities for working with LLVM source code, and some
1505 of the utilities are actually required as part of the build process because they
1506 are code generators for parts of LLVM infrastructure.</p>
1507
1508 <dl>
1509   <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1510   that finds differences between code that LLC generates and code that LLI
1511   generates. This is a useful tool if you are debugging one of them,
1512   assuming that the other generates correct output. For the full user
1513   manual, run <tt>`perldoc codegen-diff'</tt>.<br><br>
1514
1515   <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1516   syntax-highlighting files which will work with Emacs and XEmacs editors,
1517   providing syntax highlighting support for LLVM assembly files and TableGen
1518   description files. For information on how to use the syntax files, consult
1519   the <tt>README</tt> file in that directory.<br><br>
1520
1521   <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1522   and outputs all non-generated source files, which is useful if one wishes
1523   to do a lot of development across directories and does not want to
1524   individually find each file. One way to use it is to run, for example:
1525   <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1526   tree.<br><br>
1527
1528   <dt><tt><b>llvmgrep</b></tt></dt>
1529   <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1530   passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1531   line. This is a very efficient way of searching the source base for a
1532   particular regular expression.</dd>
1533
1534   <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1535   files in the current directory and then compiles and links the tool that
1536   is the first argument. For example, assuming you are in the directory
1537   <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1538   simply running <tt>makellvm llc</tt> will make a build of the current
1539   directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1540   causing a re-linking of LLC.<br><br>
1541
1542   <dt><tt><b>NewNightlyTest.pl</b></tt> and
1543   <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1544   cron script to generate nightly status reports of the functionality of
1545   tools, and the results can be seen by following the appropriate link on
1546   the <a href="http://llvm.org/">LLVM homepage</a>.<br><br>
1547
1548   <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1549   the tool used to generate register descriptions, instruction set
1550   descriptions, and even assemblers from common TableGen description
1551   files.<br><br>
1552
1553   <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1554   syntax-highlighting files which will work with the VIM editor, providing
1555   syntax highlighting support for LLVM assembly files and TableGen
1556   description files. For information on how to use the syntax files, consult
1557   the <tt>README</tt> file in that directory.<br><br>
1558
1559 </dl>
1560
1561 </div>
1562
1563 <!-- *********************************************************************** -->
1564 <div class="doc_section">
1565   <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1566 </div>
1567 <!-- *********************************************************************** -->
1568
1569 <div class="doc_text">
1570 <p>This section gives an example of using LLVM.  llvm-gcc3 is now obsolete,
1571 so we only include instructions for llvm-gcc4.
1572 </p>
1573
1574 <p><b>Note:</b> The <i>gcc4</i> frontend's invocation is <b><i>considerably different</i></b>
1575 from the previous <i>gcc3</i> frontend. In particular, the <i>gcc4</i> frontend <b><i>does not</i></b>
1576 create bitcode by default: <i>gcc4</i> produces native code. As the example below illustrates,
1577 the '--emit-llvm' flag is needed to produce LLVM bitcode output. For <i>makefiles</i> and
1578 <i>configure</i> scripts, the CFLAGS variable needs '--emit-llvm' to produce bitcode
1579 output.</p>
1580 </div>
1581
1582 <!-- ======================================================================= -->
1583 <div class="doc_subsection"><a name="tutorial4">Example with llvm-gcc4</a></div>
1584
1585 <div class="doc_text">
1586
1587 <ol>
1588   <li><p>First, create a simple C file, name it 'hello.c':</p>
1589
1590 <div class="doc_code">
1591 <pre>
1592 #include &lt;stdio.h&gt;
1593
1594 int main() {
1595   printf("hello world\n");
1596   return 0;
1597 }
1598 </pre></div></li>
1599
1600   <li><p>Next, compile the C file into a native executable:</p>
1601
1602       <div class="doc_code"><pre>% llvm-gcc hello.c -o hello</pre></div>
1603
1604       <p>Note that llvm-gcc works just like GCC by default.  The standard -S and
1605         -c arguments work as usual (producing a native .s or .o file,
1606         respectively).</p></li>
1607
1608   <li><p>Next, compile the C file into a LLVM bitcode file:</p>
1609
1610       <div class="doc_code">
1611       <pre>% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc</pre></div>
1612
1613       <p>The -emit-llvm option can be used with the -S or -c options to emit an
1614          LLVM ".ll" or ".bc" file (respectively) for the code.  This allows you
1615          to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
1616          the bitcode file.</p>
1617
1618       <p>Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
1619          </p></li>
1620
1621   <li><p>Run the program in both forms. To run the program, use:</p>
1622
1623       <div class="doc_code"><pre>% ./hello</pre></div>
1624
1625       <p>and</p>
1626
1627       <div class="doc_code"><pre>% lli hello.bc</pre></div>
1628
1629       <p>The second examples shows how to invoke the LLVM JIT, <a
1630        href="CommandGuide/html/lli.html">lli</a>.</p></li>
1631
1632   <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1633       code:</p>
1634
1635 <div class="doc_code">
1636 <pre>llvm-dis &lt; hello.bc | less</pre>
1637 </div></li>
1638
1639   <li><p>Compile the program to native assembly using the LLC code
1640       generator:</p>
1641
1642       <div class="doc_code"><pre>% llc hello.bc -o hello.s</pre></div></li>
1643
1644   <li><p>Assemble the native assembly language file into a program:</p>
1645
1646 <div class="doc_code">
1647 <pre>
1648 <b>Solaris:</b> % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native
1649
1650 <b>Others:</b>  % gcc hello.s -o hello.native
1651 </pre>
1652 </div></li>
1653
1654   <li><p>Execute the native code program:</p>
1655
1656       <div class="doc_code"><pre>% ./hello.native</pre></div>
1657
1658       <p>Note that using llvm-gcc to compile directly to native code (i.e. when
1659          the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
1660         </li>
1661
1662 </ol>
1663
1664 </div>
1665
1666
1667 <!-- *********************************************************************** -->
1668 <div class="doc_section">
1669   <a name="problems">Common Problems</a>
1670 </div>
1671 <!-- *********************************************************************** -->
1672
1673 <div class="doc_text">
1674
1675 <p>If you are having problems building or using LLVM, or if you have any other
1676 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1677 Asked Questions</a> page.</p>
1678
1679 </div>
1680
1681 <!-- *********************************************************************** -->
1682 <div class="doc_section">
1683   <a name="links">Links</a>
1684 </div>
1685 <!-- *********************************************************************** -->
1686
1687 <div class="doc_text">
1688
1689 <p>This document is just an <b>introduction</b> on how to use LLVM to do
1690 some simple things... there are many more interesting and complicated things
1691 that you can do that aren't documented here (but we'll gladly accept a patch
1692 if you want to write something up!).  For more information about LLVM, check
1693 out:</p>
1694
1695 <ul>
1696   <li><a href="http://llvm.org/">LLVM homepage</a></li>
1697   <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1698   <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1699   that Uses LLVM</a></li>
1700 </ul>
1701
1702 </div>
1703
1704 <!-- *********************************************************************** -->
1705
1706 <hr>
1707 <address>
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1712
1713   <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1714   <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1715   <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
1716   Last modified: $Date$
1717 </address>
1718 </body>
1719 </html>