docs/UsingLibraries.html

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   4         <title>Using The LLVM Libraries</title>
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   8 <div class="doc_title">Using The LLVM Libraries</div>
   9 <ol>
  10   <li><a href="#abstract">Abstract</a></li>
  11   <li><a href="#introduction">Introduction</a></li>
  12   <li><a href="#descriptions">Library Descriptions</a></li>
  13   <li><a href="#dependencies">Library Dependencies</a></li>
  14   <li><a href="#rot">Linkage Rules Of Thumb</a>
  15           <ol>
  16       <li><a href="#always">Always link LLVMCore, LLVMSupport, LLVMSystem</a>
  17                         <li><a href="#onlyone">Never link both archive and re-linked</a>
  18                 </ol>
  19         </li>
  20 </ol>
  21
  22 <div class="doc_author">
  23   <p>Written by <a href="mailto:rspencer@x10sys.com">Reid Spencer</a></p>
  24 </div>
  25
  26 <p class="doc_warning">Warning: This document is out of date, please see <a href="CommandGuide/html/llvm-config.html">llvm-config</a> for more information.</p>
  27
  28 <!-- ======================================================================= -->
  29 <div class="doc_section"><a name="abstract">Abstract</a></div>
  30 <div class="doc_text">
  31   <p>Amongst other things, LLVM is a toolkit for building compilers, linkers,
  32   runtime executives, virtual machines, and other program execution related
  33   tools. In addition to the LLVM tool set, the functionality of LLVM is
  34   available through a set of libraries.  To use LLVM as a toolkit for
  35   constructing tools, a developer needs to understand what is contained in the
  36   various libraries, what they depend on, and how to use them.  Fortunately,
  37   there is a tool, <tt>llvm-config</tt> to aid with this. This document
  38   describes the contents of the libraries and how to use <tt>llvm-config</tt>
  39   to generate command line options.
  40 </p>
  41 </div>
  42
  43 <!-- ======================================================================= -->
  44 <div class="doc_section"> <a name="introduction">Introduction</a></div>
  45 <div class="doc_text">
  46   <p>If you're writing a compiler, virtual machine, or any other utility based
  47   on LLVM, you'll need to figure out which of the many libraries files you will
  48   need to link with to be successful. An understanding of the contents of these
  49   libraries will be useful in coming up with an optimal specification for the
  50   libraries to link with. The purpose of this document is to reduce some of
  51   the trial and error that the author experienced in using LLVM.</p>
  52   <p>LLVM produces two types of libraries: archives (ending in <tt>.a</tt>) and
  53   objects (ending in <tt>.o</tt>). However, both are libraries. Libraries ending
  54   in <tt>.o</tt> are known as re-linked libraries because they contain all the
  55   compilation units of the library linked together as a single <tt>.o</tt> file.
  56   Furthermore, several of the libraries have <em>both</em> forms of library. The
  57   re-linked libraries are used whenever you want to include all symbols from the
  58   library. The archive libraries are used whenever you want to only resolve
  59   outstanding symbols at that point in the link without including everything in
  60   the library. </p>
  61   <p>If you're using the LLVM Makefile system to link your tools,you will use
  62   the <tt>LLVMLIBS</tt> make variable.
  63   (see the <a href="MakefileGuide.html#LLVMLIBS">Makefile Guide</a> for
  64   details). This variable specifies which LLVM libraries to link into your tool
  65   and the order in which they will be linked. You specify re-linked libraries by
  66   naming the library without a suffix. You specify archive libraries by naming
  67   the library with a <tt>.a</tt> suffix but without the <tt>lib</tt> prefix. The
  68   order in which the libraries appear in the <tt>LLVMLIBS</tt> variable
  69   definition is the order in which they will be linked. Getting this order
  70   correct for your tool can sometimes be challenging.
  71 </div>
  72 <!-- ======================================================================= -->
  73 <div class="doc_section"><a name="descriptions"></a>Library Descriptions</div>
  74 <div class="doc_text">
  75   <p>The table below categorizes each library
  76 <table style="text-align:left">
  77   <tr><th>Library</th><th>Forms</th><th>Description</th></tr>
  78   <tr><th colspan="3">Core Libraries</th></tr>
  79   <tr><td>LLVMArchive</td><td><tt>.a</tt></td>
  80     <td>LLVM archive reading and writing</td></tr>
  81   <tr><td>LLVMAsmParser</td><td><tt>.a</tt></td>
  82     <td>LLVM assembly parsing</td></tr>
  83   <tr><td>LLVMBCReader</td><td><tt>.a</tt></td>
  84     <td>LLVM bitcode reading</td></tr>
  85   <tr><td>LLVMBCWriter</td><td><tt>.a</tt></td>
  86     <td>LLVM bitcode writing</td></tr>
  87   <tr><td>LLVMCore</td><td><tt>.a</tt></td>
  88     <td>LLVM core intermediate representation</td></tr>
  89   <tr><td>LLVMDebugger</td><td><tt>.a</tt></td>
  90     <td>Source level debugging support</td></tr>
  91   <tr><td>LLVMLinker</td><td><tt>.a</tt></td>
  92     <td>Bitcode and archive linking interface</td></tr>
  93   <tr><td>LLVMSupport</td><td><tt>.a</tt></td>
  94     <td>General support utilities</td></tr>
  95   <tr><td>LLVMSystem</td><td><tt>.a</tt></td>
  96     <td>Operating system abstraction layer</td></tr>
  97   <tr><td>LLVMbzip2</td><td><tt>.a</tt></td>
  98     <td>BZip2 compression library</td></tr>
  99
 100   <tr><th colspan="3">Analysis Libraries</th></tr>
 101   <tr><td>LLVMAnalysis</td><td><tt>.a</tt></td>
 102     <td>Various analysis passes.</td></tr>
 103   <tr><td>LLVMDataStructure</td><td><tt>.o</tt></td>
 104     <td>Data structure analysis passes.</td></tr>
 105   <tr><td>LLVMipa</td><td><tt>.a</tt></td>
 106     <td>Inter-procedural analysis passes.</td></tr>
 107
 108   <tr><th colspan="3">Transformation Libraries</th></tr>
 109   <tr><td>LLVMInstrumentation</td><td><tt>.a</tt></td>
 110     <td>Instrumentation passes.</td></tr>
 111   <tr><td>LLVMipo</td><td><tt>.a</tt></td>
 112     <td>All inter-procedural optimization passes.</td></tr>
 113   <tr><td>LLVMScalarOpts</td><td><tt>.a</tt></td>
 114     <td>All scalar optimization passes.</td></tr>
 115   <tr><td>LLVMTransformUtils</td><td><tt>.a</tt></td>
 116     <td>Transformation utilities used by many passes.</td></tr>
 117
 118   <tr><th colspan="3">Code Generation Libraries </th></tr>
 119   <tr><td>LLVMCodeGen</td><td><tt>.o</tt></td>
 120     <td>Native code generation infrastructure</td></tr>
 121   <tr><td>LLVMSelectionDAG</td><td><tt>.o</tt></td>
 122     <td>Aggressive instruction selector for directed acyclic graphs</td></tr>
 123
 124   <tr><th colspan="3">Target Libraries</th></tr>
 125   <tr><td>LLVMAlpha</td><td><tt>.o</tt></td>
 126     <td>Code generation for Alpha architecture</td></tr>
 127   <tr><td>LLVMARM</td><td><tt>.o</tt></td>
 128     <td>Code generation for ARM architecture</td></tr>
 129   <tr><td>LLVMCBackend</td><td><tt>.o</tt></td>
 130     <td>'C' language code generator.</td></tr>
 131   <tr><td>LLVMIA64</td><td><tt>.o</tt></td>
 132     <td>Code generation for IA64 architecture</td></tr>
 133   <tr><td>LLVMPowerPC</td><td><tt>.o</tt></td>
 134     <td>Code generation for PowerPC architecture</td></tr>
 135   <tr><td>LLVMSparc</td><td><tt>.o</tt></td>
 136     <td>Code generation for Sparc architecture</td></tr>
 137   <tr><td>LLVMTarget</td><td><tt>.a</tt></td>
 138     <td>Generic code generation utilities.</td></tr>
 139   <tr><td>LLVMX86</td><td><tt>.o</tt></td>
 140     <td>Code generation for Intel x86 architecture</td></tr>
 141
 142   <tr><th colspan="3">Runtime Libraries</th></tr>
 143   <tr><td>LLVMInterpreter</td><td><tt>.o</tt></td>
 144     <td>Bitcode Interpreter</td></tr>
 145   <tr><td>LLVMJIT</td><td><tt>.o</tt></td>
 146     <td>Bitcode JIT Compiler</td></tr>
 147   <tr><td>LLVMExecutionEngine</td><td><tt>.o</tt></td>
 148     <td>Virtual machine engine</td></tr>
 149 </table>
 150 </div>
 151
 152 <!-- ======================================================================= -->
 153 <div class="doc_section"><a name="dependencies"></a>Using llvm-config</div>
 154 <div class="doc_text">
 155   <p>The <tt>llvm-config</tt> tool is a perl script that produces on its output
 156   various kinds of information. For example, the source or object directories
 157   used to build LLVM can be accessed by passing options to <tt>llvm-config</tt>.
 158   For complete details on this tool, please see the
 159   <a href="CommandGuide/html/llvm-config.html">manual page</a>.</p>
 160   <p>To understand the relationships between libraries, the <tt>llvm-config</tt>
 161   can be very useful. If all you know is that you want certain libraries to
 162   be available, you can generate the complete set of libraries to link with
 163   using one of four options, as below:</p>
 164   <ol>
 165     <li><tt>--ldflags</tt>. This generates the command line options necessary to
 166     be passed to the <tt>ld</tt> tool in order to link with LLVM. Most notably,
 167     the <tt>-L</tt> option is provided to specify a library search directory
 168     that contains the LLVM libraries.</li>
 169     <li><tt>--libs</tt>. This generates command line options suitable for
 170     use with a gcc-style linker. That is, libraries are given with a -l option
 171     and object files are given with a full path.</li>
 172     <li><tt>--libnames</tt>. This generates a list of just the library file
 173     names. If you know the directory in which these files reside (see --ldflags)
 174     then you can find the libraries there.</li>
 175     <li><tt>--libfiles</tt>. This generates the full path names of the
 176     LLVM library files.</li>
 177   </ol>
 178   <p>If you wish to delve further into how <tt>llvm-config</tt> generates the
 179   correct order (based on library dependencies), please see the tool named
 180   <tt>GenLibDeps.pl</tt> in the <tt>utils</tt> source directory of LLVM.</p>
 181
 182   <!-- =======NOTE: =========================================================-->
 183   <!-- === The following graphs and <dl> list are generated automatically ===-->
 184   <!-- === by the util named GenLibDeps.pl in the llvm/utils directory.   ===-->
 185   <!-- === This should be updated whenever new libraries are added,       ===-->
 186   <!-- === removed, or changed                                            ===-->
 187   <!-- =======NOTE: =========================================================-->
 188   <h2>Dependency Relationships Of Libraries</h2>
 189   <p>This graph shows the dependency of archive libraries on other archive
 190   libraries or objects. Where a library has both archive and object forms, only
 191   the archive form is shown.</p>
 192   <img src="img/libdeps.gif" alt="Library Dependencies"/>
 193   <h2>Dependency Relationships Of Object Files</h2>
 194   <p>This graph shows the dependency of object files on archive libraries or
 195   other objects. Where a library has both object and archive forms, only the
 196   dependency to the archive form is shown.</p>
 197   <img src="img/objdeps.gif" alt="Object File Dependencies"/>
 198   <p>The following list shows the dependency relationships between libraries in
 199   textual form. The information is the same as shown on the graphs but arranged
 200   alphabetically.</p>
 201 <dl>
 202   <dt><b>libLLVMAnalysis.a</b></dt><dd><ul>
 203     <li>libLLVMCore.a</li>
 204     <li>libLLVMSupport.a</li>
 205     <li>libLLVMSystem.a</li>
 206     <li>libLLVMTarget.a</li>
 207   </ul></dd>
 208   <dt><b>libLLVMArchive.a</b></dt><dd><ul>
 209     <li>libLLVMBCReader.a</li>
 210     <li>libLLVMCore.a</li>
 211     <li>libLLVMSupport.a</li>
 212     <li>libLLVMSystem.a</li>
 213   </ul></dd>
 214   <dt><b>libLLVMAsmParser.a</b></dt><dd><ul>
 215     <li>libLLVMCore.a</li>
 216     <li>libLLVMSystem.a</li>
 217   </ul></dd>
 218   <dt><b>libLLVMBCReader.a</b></dt><dd><ul>
 219     <li>libLLVMCore.a</li>
 220     <li>libLLVMSupport.a</li>
 221     <li>libLLVMSystem.a</li>
 222   </ul></dd>
 223   <dt><b>libLLVMBCWriter.a</b></dt><dd><ul>
 224     <li>libLLVMCore.a</li>
 225     <li>libLLVMSupport.a</li>
 226     <li>libLLVMSystem.a</li>
 227   </ul></dd>
 228   <dt><b>libLLVMCodeGen.a</b></dt><dd><ul>
 229     <li>libLLVMAnalysis.a</li>
 230     <li>libLLVMCore.a</li>
 231     <li>libLLVMScalarOpts.a</li>
 232     <li>libLLVMSupport.a</li>
 233     <li>libLLVMSystem.a</li>
 234     <li>libLLVMTarget.a</li>
 235     <li>libLLVMTransformUtils.a</li>
 236   </ul></dd>
 237   <dt><b>libLLVMCore.a</b></dt><dd><ul>
 238     <li>libLLVMSupport.a</li>
 239     <li>libLLVMSystem.a</li>
 240   </ul></dd>
 241   <dt><b>libLLVMDebugger.a</b></dt><dd><ul>
 242     <li>libLLVMBCReader.a</li>
 243     <li>libLLVMCore.a</li>
 244     <li>libLLVMSupport.a</li>
 245     <li>libLLVMSystem.a</li>
 246   </ul></dd>
 247   <dt><b>libLLVMInstrumentation.a</b></dt><dd><ul>
 248     <li>libLLVMCore.a</li>
 249     <li>libLLVMScalarOpts.a</li>
 250     <li>libLLVMSupport.a</li>
 251     <li>libLLVMTransformUtils.a</li>
 252   </ul></dd>
 253   <dt><b>libLLVMLinker.a</b></dt><dd><ul>
 254     <li>libLLVMArchive.a</li>
 255     <li>libLLVMBCReader.a</li>
 256     <li>libLLVMCore.a</li>
 257     <li>libLLVMSupport.a</li>
 258     <li>libLLVMSystem.a</li>
 259   </ul></dd>
 260   <dt><b>libLLVMScalarOpts.a</b></dt><dd><ul>
 261     <li>libLLVMAnalysis.a</li>
 262     <li>libLLVMCore.a</li>
 263     <li>libLLVMSupport.a</li>
 264     <li>libLLVMSystem.a</li>
 265     <li>libLLVMTarget.a</li>
 266     <li>libLLVMTransformUtils.a</li>
 267   </ul></dd>
 268   <dt><b>libLLVMSelectionDAG.a</b></dt><dd><ul>
 269     <li>libLLVMAnalysis.a</li>
 270     <li>libLLVMCodeGen.a</li>
 271     <li>libLLVMCore.a</li>
 272     <li>libLLVMSupport.a</li>
 273     <li>libLLVMSystem.a</li>
 274     <li>libLLVMTarget.a</li>
 275     <li>libLLVMTransformUtils.a</li>
 276   </ul></dd>
 277   <dt><b>libLLVMSupport.a</b></dt><dd><ul>
 278     <li>libLLVMSystem.a</li>
 279     <li>libLLVMbzip2.a</li>
 280   </ul></dd>
 281   <dt><b>libLLVMSystem.a</b></dt><dd><ul>
 282   </ul></dd>
 283   <dt><b>libLLVMTarget.a</b></dt><dd><ul>
 284     <li>libLLVMCore.a</li>
 285     <li>libLLVMSupport.a</li>
 286     <li>libLLVMSystem.a</li>
 287   </ul></dd>
 288   <dt><b>libLLVMTransformUtils.a</b></dt><dd><ul>
 289     <li>libLLVMAnalysis.a</li>
 290     <li>libLLVMCore.a</li>
 291     <li>libLLVMSupport.a</li>
 292     <li>libLLVMSystem.a</li>
 293     <li>libLLVMTarget.a</li>
 294     <li>libLLVMipa.a</li>
 295   </ul></dd>
 296   <dt><b>libLLVMbzip2.a</b></dt><dd><ul>
 297   </ul></dd>
 298   <dt><b>libLLVMipa.a</b></dt><dd><ul>
 299     <li>libLLVMAnalysis.a</li>
 300     <li>libLLVMCore.a</li>
 301     <li>libLLVMSupport.a</li>
 302     <li>libLLVMSystem.a</li>
 303   </ul></dd>
 304   <dt><b>libLLVMipo.a</b></dt><dd><ul>
 305     <li>libLLVMAnalysis.a</li>
 306     <li>libLLVMCore.a</li>
 307     <li>libLLVMSupport.a</li>
 308     <li>libLLVMSystem.a</li>
 309     <li>libLLVMTarget.a</li>
 310     <li>libLLVMTransformUtils.a</li>
 311     <li>libLLVMipa.a</li>
 312   </ul></dd>
 313   <dt><b>libLLVMlto.a</b></dt><dd><ul>
 314     <li>libLLVMAnalysis.a</li>
 315     <li>libLLVMBCReader.a</li>
 316     <li>libLLVMBCWriter.a</li>
 317     <li>libLLVMCore.a</li>
 318     <li>libLLVMLinker.a</li>
 319     <li>libLLVMScalarOpts.a</li>
 320     <li>libLLVMSupport.a</li>
 321     <li>libLLVMSystem.a</li>
 322     <li>libLLVMTarget.a</li>
 323     <li>libLLVMipa.a</li>
 324     <li>libLLVMipo.a</li>
 325   </ul></dd>
 326   <dt><b>LLVMARM.o</b></dt><dd><ul>
 327     <li>libLLVMCodeGen.a</li>
 328     <li>libLLVMCore.a</li>
 329     <li>libLLVMSelectionDAG.a</li>
 330     <li>libLLVMSupport.a</li>
 331     <li>libLLVMSystem.a</li>
 332     <li>libLLVMTarget.a</li>
 333   </ul></dd>
 334   <dt><b>LLVMAlpha.o</b></dt><dd><ul>
 335     <li>libLLVMCodeGen.a</li>
 336     <li>libLLVMCore.a</li>
 337     <li>libLLVMSelectionDAG.a</li>
 338     <li>libLLVMSupport.a</li>
 339     <li>libLLVMSystem.a</li>
 340     <li>libLLVMTarget.a</li>
 341   </ul></dd>
 342   <dt><b>LLVMCBackend.o</b></dt><dd><ul>
 343     <li>libLLVMAnalysis.a</li>
 344     <li>libLLVMCodeGen.a</li>
 345     <li>libLLVMCore.a</li>
 346     <li>libLLVMScalarOpts.a</li>
 347     <li>libLLVMSupport.a</li>
 348     <li>libLLVMSystem.a</li>
 349     <li>libLLVMTarget.a</li>
 350     <li>libLLVMTransformUtils.a</li>
 351     <li>libLLVMipa.a</li>
 352   </ul></dd>
 353   <dt><b>LLVMExecutionEngine.o</b></dt><dd><ul>
 354     <li>libLLVMCore.a</li>
 355     <li>libLLVMSupport.a</li>
 356     <li>libLLVMSystem.a</li>
 357     <li>libLLVMTarget.a</li>
 358   </ul></dd>
 359   <dt><b>LLVMIA64.o</b></dt><dd><ul>
 360     <li>libLLVMCodeGen.a</li>
 361     <li>libLLVMCore.a</li>
 362     <li>libLLVMSelectionDAG.a</li>
 363     <li>libLLVMSupport.a</li>
 364     <li>libLLVMSystem.a</li>
 365     <li>libLLVMTarget.a</li>
 366   </ul></dd>
 367   <dt><b>LLVMInterpreter.o</b></dt><dd><ul>
 368     <li>LLVMExecutionEngine.o</li>
 369     <li>libLLVMCodeGen.a</li>
 370     <li>libLLVMCore.a</li>
 371     <li>libLLVMSupport.a</li>
 372     <li>libLLVMSystem.a</li>
 373     <li>libLLVMTarget.a</li>
 374   </ul></dd>
 375   <dt><b>LLVMJIT.o</b></dt><dd><ul>
 376     <li>LLVMExecutionEngine.o</li>
 377     <li>libLLVMCore.a</li>
 378     <li>libLLVMSupport.a</li>
 379     <li>libLLVMSystem.a</li>
 380     <li>libLLVMTarget.a</li>
 381   </ul></dd>
 382   <dt><b>LLVMPowerPC.o</b></dt><dd><ul>
 383     <li>libLLVMCodeGen.a</li>
 384     <li>libLLVMCore.a</li>
 385     <li>libLLVMSelectionDAG.a</li>
 386     <li>libLLVMSupport.a</li>
 387     <li>libLLVMSystem.a</li>
 388     <li>libLLVMTarget.a</li>
 389   </ul></dd>
 390   <dt><b>LLVMSparc.o</b></dt><dd><ul>
 391     <li>libLLVMCodeGen.a</li>
 392     <li>libLLVMCore.a</li>
 393     <li>libLLVMSelectionDAG.a</li>
 394     <li>libLLVMSupport.a</li>
 395     <li>libLLVMSystem.a</li>
 396     <li>libLLVMTarget.a</li>
 397   </ul></dd>
 398   <dt><b>LLVMX86.o</b></dt><dd><ul>
 399     <li>libLLVMCodeGen.a</li>
 400     <li>libLLVMCore.a</li>
 401     <li>libLLVMSelectionDAG.a</li>
 402     <li>libLLVMSupport.a</li>
 403     <li>libLLVMSystem.a</li>
 404     <li>libLLVMTarget.a</li>
 405   </ul></dd>
 406 </dl>
 407 </div>
 408
 409 <!-- ======================================================================= -->
 410 <div class="doc_section"><a name="rot">Linkage Rules Of Thumb</a></div>
 411 <div class="doc_text">
 412         <p>This section contains various "rules of thumb" about what files you
 413         should link into your programs.</p>
 414 </div>
 415 <!-- ======================================================================= -->
 416 <div class="doc_subsection"><a name="always">Always Link LLVMCore, LLVMSupport,
 417     and LLVMSystem</a></div>
 418 <div class="doc_text">
 419   <p>No matter what you do with LLVM, the last three entries in the value of
 420   your LLVMLIBS make variable should always be:
 421   <tt>LLVMCore LLVMSupport.a LLVMSystem.a</tt>. There are no <tt>LLVM</tt>
 422   programs that don't depend on these three.</p>
 423 </div>
 424 <!-- ======================================================================= -->
 425 <div class="doc_subsection"><a name="onlyone">Never link both archive and
 426     re-linked library</a></div>
 427 <div class="doc_text">
 428   <p>There is never any point to linking both the re-linked (<tt>.o</tt>) and
 429   the archive (<tt>.a</tt>) versions of a library. Since the re-linked version
 430   includes the entire library, the archive version will not resolve any symbols.
 431   You could even end up with link error if you place the archive version before
 432   the re-linked version on the linker's command line.</p>
 433 </div>
 434 <!-- ======================================================================= -->
 435 <hr>
 436 <div class="doc_footer">
 437 <address>
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 442   <a href="mailto:rspencer@x10sys.com">Reid Spencer</a>
 443 </address>
 444 <a href="http://llvm.org">The LLVM Compiler Infrastructure</a>
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