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   5   <title>Building LLVM with CMake</title>
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   9 <div class="doc_title">
  10   Building LLVM with CMake
  11 </div>
  12
  13 <ul>
  14   <li><a href="#intro">Introduction</a></li>
  15   <li><a href="#quickstart">Quick start</a></li>
  16   <li><a href="#usage">Basic CMake usage</a>
  17   <li><a href="#options">Options and variables</a>
  18     <ul>
  19     <li><a href="#freccmake">Frequently-used CMake variables</a></li>
  20     <li><a href="#llvmvars">LLVM-specific variables</a></li>
  21   </ul></li>
  22   <li><a href="#testing">Executing the test suite</a>
  23   <li><a href="#cross">Cross compiling</a>
  24   <li><a href="#embedding">Embedding LLVM in your project</a>
  25   <li><a href="#specifics">Compiler/Platform specific topics</a>
  26     <ul>
  27     <li><a href="#msvc">Microsoft Visual C++</a></li>
  28   </ul></li>
  29 </ul>
  30
  31 <div class="doc_author">
  32 <p>Written by <a href="mailto:ofv@wanadoo.es">Oscar Fuentes</a></p>
  33 </div>
  34
  35 <!-- *********************************************************************** -->
  36 <div class="doc_section">
  37 <a name="intro">Introduction</a>
  38 </div>
  39 <!-- *********************************************************************** -->
  40
  41 <div class="doc_text">
  42
  43   <p><a href="http://www.cmake.org/">CMake</a> is a cross-platform
  44     build-generator tool. CMake does not build the project, it generates
  45     the files needed by your build tool (GNU make, Visual Studio, etc) for
  46     building LLVM.</p>
  47
  48   <p>If you are really anxious about getting a functional LLVM build,
  49     go to the <a href="#quickstart">Quick start</a> section. If you
  50     are a CMake novice, start on <a href="#usage">Basic CMake
  51       usage</a> and then go back to the <a href="#quickstart">Quick
  52       start</a> once you know what you are
  53     doing. The <a href="#options">Options and variables</a> section
  54     is a reference for customizing your build. If you already have
  55     experience with CMake, this is the recommended starting point.
  56 </div>
  57
  58 <!-- *********************************************************************** -->
  59 <div class="doc_section">
  60 <a name="quickstart">Quick start</a>
  61 </div>
  62 <!-- *********************************************************************** -->
  63
  64 <div class="doc_text">
  65
  66 <p> We use here the command-line, non-interactive CMake interface </p>
  67
  68 <ol>
  69
  70   <li><p><a href="http://www.cmake.org/cmake/resources/software.html">Download</a>
  71       and install CMake. Version 2.6.2 is the minimum required.</p>
  72
  73   <li><p>Open a shell. Your development tools must be reachable from this
  74       shell through the PATH environment variable.</p>
  75
  76   <li><p>Create a directory for containing the build. It is not
  77       supported to build LLVM on the source directory. cd to this
  78       directory:</p>
  79     <div class="doc_code">
  80       <p><tt>mkdir mybuilddir</tt></p>
  81       <p><tt>cd mybuilddir</tt></p>
  82     </div>
  83
  84   <li><p>Execute this command on the shell
  85       replacing <i>path/to/llvm/source/root</i> with the path to the
  86       root of your LLVM source tree:</p>
  87     <div class="doc_code">
  88       <p><tt>cmake path/to/llvm/source/root</tt></p>
  89     </div>
  90
  91     <p>CMake will detect your development environment, perform a
  92       series of test and generate the files required for building
  93       LLVM. CMake will use default values for all build
  94       parameters. See the <a href="#options">Options and variables</a>
  95       section for fine-tuning your build</p>
  96
  97     <p>This can fail if CMake can't detect your toolset, or if it
  98       thinks that the environment is not sane enough. On this case
  99       make sure that the toolset that you intend to use is the only
 100       one reachable from the shell and that the shell itself is the
 101       correct one for you development environment. CMake will refuse
 102       to build MinGW makefiles if you have a POSIX shell reachable
 103       through the PATH environment variable, for instance. You can
 104       force CMake to use a given build tool, see
 105       the <a href="#usage">Usage</a> section.</p>
 106
 107 </ol>
 108
 109 </div>
 110
 111 <!-- *********************************************************************** -->
 112 <div class="doc_section">
 113   <a name="usage">Basic CMake usage</a>
 114 </div>
 115 <!-- *********************************************************************** -->
 116
 117 <div class="doc_text">
 118
 119   <p>This section explains basic aspects of CMake, mostly for
 120     explaining those options which you may need on your day-to-day
 121     usage.</p>
 122
 123   <p>CMake comes with extensive documentation in the form of html
 124     files and on the cmake executable itself. Execute <i>cmake
 125     --help</i> for further help options.</p>
 126
 127   <p>CMake requires to know for which build tool it shall generate
 128     files (GNU make, Visual Studio, Xcode, etc). If not specified on
 129     the command line, it tries to guess it based on you
 130     environment. Once identified the build tool, CMake uses the
 131     corresponding <i>Generator</i> for creating files for your build
 132     tool. You can explicitly specify the generator with the command
 133     line option <i>-G "Name of the generator"</i>. For knowing the
 134     available generators on your platform, execute</p>
 135
 136     <div class="doc_code">
 137       <p><tt>cmake --help</tt></p>
 138     </div>
 139
 140     <p>This will list the generator's names at the end of the help
 141       text. Generator's names are case-sensitive. Example:</p>
 142
 143     <div class="doc_code">
 144       <p><tt>cmake -G "Visual Studio 8 2005" path/to/llvm/source/root</tt></p>
 145     </div>
 146
 147     <p>For a given development platform there can be more than one
 148       adequate generator. If you use Visual Studio "NMake Makefiles"
 149       is a generator you can use for building with NMake. By default,
 150       CMake chooses the more specific generator supported by your
 151       development environment. If you want an alternative generator,
 152       you must tell this to CMake with the <i>-G</i> option.</p>
 153
 154     <p>TODO: explain variables and cache. Move explanation here from
 155       #options section.</p>
 156
 157 </div>
 158
 159 <!-- *********************************************************************** -->
 160 <div class="doc_section">
 161   <a name="options">Options and variables</a>
 162 </div>
 163 <!-- *********************************************************************** -->
 164
 165 <div class="doc_text">
 166
 167   <p>Variables customize how the build will be generated. Options are
 168     boolean variables, with possible values ON/OFF. Options and
 169     variables are defined on the CMake command line like this:</p>
 170
 171   <div class="doc_code">
 172     <p><tt>cmake -DVARIABLE=value path/to/llvm/source</tt></p>
 173   </div>
 174
 175   <p>You can set a variable after the initial CMake invocation for
 176     changing its value. You can also undefine a variable:</p>
 177
 178   <div class="doc_code">
 179     <p><tt>cmake -UVARIABLE path/to/llvm/source</tt></p>
 180   </div>
 181
 182   <p>Variables are stored on the CMake cache. This is a file
 183     named <tt>CMakeCache.txt</tt> on the root of the build
 184     directory. Do not hand-edit it.</p>
 185
 186   <p>Variables are listed here appending its type after a colon. It is
 187     correct to write the variable and the type on the CMake command
 188     line:</p>
 189
 190   <div class="doc_code">
 191     <p><tt>cmake -DVARIABLE:TYPE=value path/to/llvm/source</tt></p>
 192   </div>
 193
 194 </div>
 195
 196 <!-- ======================================================================= -->
 197 <div class="doc_subsection">
 198   <a name="freccmake">Frequently-used CMake variables</a>
 199 </div>
 200
 201 <div class="doc_text">
 202
 203 <p>Here are listed some of the CMake variables that are used often,
 204   along with a brief explanation and LLVM-specific notes. For full
 205   documentation, check the CMake docs or execute <i>cmake
 206   --help-variable VARIABLE_NAME</i>.</p>
 207
 208 <dl>
 209   <dt><b>CMAKE_BUILD_TYPE</b>:STRING</dt>
 210
 211   <dd>Sets the build type for <i>make</i> based generators. Possible
 212     values are Release, Debug, RelWithDebInfo and MinSizeRel. On
 213     systems like Visual Studio the user sets the build type with the IDE
 214     settings.</dd>
 215
 216   <dt><b>CMAKE_INSTALL_PREFIX</b>:PATH</dt>
 217   <dd>Path where LLVM will be installed if "make install" is invoked
 218     or the "INSTALL" target is built.</dd>
 219
 220   <dt><b>LLVM_LIBDIR_SUFFIX</b>:STRING</dt>
 221   <dd>Extra suffix to append to the directory where libraries are to
 222     be installed. On a 64-bit architecture, one could use
 223     -DLLVM_LIBDIR_SUFFIX=64 to install libraries to /usr/lib64.</dd>
 224
 225   <dt><b>CMAKE_C_FLAGS</b>:STRING</dt>
 226   <dd>Extra flags to use when compiling C source files.</dd>
 227
 228   <dt><b>CMAKE_CXX_FLAGS</b>:STRING</dt>
 229   <dd>Extra flags to use when compiling C++ source files.</dd>
 230
 231   <dt><b>BUILD_SHARED_LIBS</b>:BOOL</dt>
 232   <dd>Flag indicating is shared libraries will be built. Its default
 233     value is OFF. Shared libraries are not supported on Windows and
 234     not recommended in the other OSes.</dd>
 235 </dl>
 236
 237 </div>
 238
 239 <!-- ======================================================================= -->
 240 <div class="doc_subsection">
 241   <a name="llvmvars">LLVM-specific variables</a>
 242 </div>
 243
 244 <div class="doc_text">
 245
 246 <dl>
 247   <dt><b>LLVM_TARGETS_TO_BUILD</b>:STRING</dt>
 248   <dd>Semicolon-separated list of targets to build, or <i>all</i> for
 249     building all targets. Case-sensitive. For Visual C++ defaults
 250     to <i>X86</i>. On the other cases defaults to <i>all</i>. Example:
 251     <i>-DLLVM_TARGETS_TO_BUILD="X86;PowerPC;Alpha"</i>.</dd>
 252
 253   <dt><b>LLVM_BUILD_TOOLS</b>:BOOL</dt>
 254   <dd>Build LLVM tools. Defaults to ON. Targets for building each tool
 255     are generated in any case. You can build an tool separately by
 256     invoking its target. For example, you can build <i>llvm-as</i>
 257     with a makefile-based system executing <i>make llvm-as</i> on the
 258     root of your build directory.</dd>
 259
 260   <dt><b>LLVM_INCLUDE_TOOLS</b>:BOOL</dt>
 261   <dd>Generate build targets for the LLVM tools. Defaults to
 262     ON. You can use that option for disabling the generation of build
 263     targets for the LLVM tools.</dd>
 264
 265   <dt><b>LLVM_BUILD_EXAMPLES</b>:BOOL</dt>
 266   <dd>Build LLVM examples. Defaults to OFF. Targets for building each
 267     example are generated in any case. See documentation
 268     for <i>LLVM_BUILD_TOOLS</i> above for more details.</dd>
 269
 270   <dt><b>LLVM_INCLUDE_EXAMPLES</b>:BOOL</dt>
 271   <dd>Generate build targets for the LLVM examples. Defaults to
 272     ON. You can use that option for disabling the generation of build
 273     targets for the LLVM examples.</dd>
 274
 275   <dt><b>LLVM_BUILD_TESTS</b>:BOOL</dt>
 276   <dd>Build LLVM unit tests. Defaults to OFF. Targets for building
 277     each unit test are generated in any case. You can build a specific
 278     unit test with the target <i>UnitTestNameTests</i> (where at this
 279     time <i>UnitTestName</i> can be ADT, Analysis, ExecutionEngine,
 280     JIT, Support, Transform, VMCore; see the subdirectories
 281     of <i>unittests</i> for an updated list.) It is possible to build
 282     all unit tests with the target <i>UnitTests</i>.</dd>
 283
 284   <dt><b>LLVM_INCLUDE_TESTS</b>:BOOL</dt>
 285   <dd>Generate build targets for the LLVM unit tests. Defaults to
 286     ON. You can use that option for disabling the generation of build
 287     targets for the LLVM unit tests.</dd>
 288
 289   <dt><b>LLVM_ENABLE_THREADS</b>:BOOL</dt>
 290   <dd>Build with threads support, if available. Defaults to ON.</dd>
 291
 292   <dt><b>LLVM_ENABLE_ASSERTIONS</b>:BOOL</dt>
 293   <dd>Enables code assertions. Defaults to OFF if and only if
 294     CMAKE_BUILD_TYPE is <i>Release</i>.</dd>
 295
 296   <dt><b>LLVM_ENABLE_PIC</b>:BOOL</dt>
 297   <dd>Add the <i>-fPIC</i> flag for the compiler command-line, if the
 298     compiler supports this flag. Some systems, like Windows, do not
 299     need this flag. Defaults to ON.</dd>
 300
 301   <dt><b>LLVM_ENABLE_WARNINGS</b>:BOOL</dt>
 302   <dd>Enable all compiler warnings. Defaults to ON.</dd>
 303
 304   <dt><b>LLVM_ENABLE_PEDANTIC</b>:BOOL</dt>
 305   <dd>Enable pedantic mode. This disable compiler specific extensions, is
 306     possible. Defaults to ON.</dd>
 307
 308   <dt><b>LLVM_ENABLE_WERROR</b>:BOOL</dt>
 309   <dd>Stop and fail build, if a compiler warning is
 310     triggered. Defaults to OFF.</dd>
 311
 312   <dt><b>LLVM_BUILD_32_BITS</b>:BOOL</dt>
 313   <dd>Build 32-bits executables and libraries on 64-bits systems. This
 314     option is available only on some 64-bits unix systems. Defaults to
 315     OFF.</dd>
 316
 317   <dt><b>LLVM_TARGET_ARCH</b>:STRING</dt>
 318   <dd>LLVM target to use for native code generation. This is required
 319     for JIT generation. It defaults to "host", meaning that it shall
 320     pick the architecture of the machine where LLVM is being built. If
 321     you are cross-compiling, set it to the target architecture
 322     name.</dd>
 323
 324   <dt><b>LLVM_TABLEGEN</b>:STRING</dt>
 325   <dd>Full path to a native TableGen executable (usually
 326     named <i>tblgen</i>). This is intented for cross-compiling: if the
 327     user sets this variable, no native TableGen will be created.</dd>
 328 </dl>
 329
 330 </div>
 331
 332 <!-- *********************************************************************** -->
 333 <div class="doc_section">
 334   <a name="testing">Executing the test suite</a>
 335 </div>
 336 <!-- *********************************************************************** -->
 337
 338 <div class="doc_text">
 339
 340 <p>Testing is performed when the <i>check</i> target is built. For
 341   instance, if you are using makefiles, execute this command while on
 342   the top level of your build directory:</p>
 343
 344 <div class="doc_code">
 345   <p><tt>make check</tt></p>
 346 </div>
 347
 348 <p>Testing is not supported on Visual Studio.</p>
 349
 350 </div>
 351
 352 <!-- *********************************************************************** -->
 353 <div class="doc_section">
 354   <a name="cross">Cross compiling</a>
 355 </div>
 356 <!-- *********************************************************************** -->
 357
 358 <div class="doc_text">
 359
 360 <p>See <a href="http://www.vtk.org/Wiki/CMake_Cross_Compiling">this
 361     wiki page</a> for generic instructions on how to cross-compile
 362     with CMake. It goes into detailed explanations and may seem
 363     daunting, but it is not. On the wiki page there are several
 364     examples including toolchain files. Go directly to
 365     <a href="http://www.vtk.org/Wiki/CMake_Cross_Compiling#Information_how_to_set_up_various_cross_compiling_toolchains">this
 366     section</a> for a quick solution.</p>
 367
 368 <p>Also see the <a href="#llvmvars">LLVM-specific variables</a>
 369   section for variables used when cross-compiling.</p>
 370
 371 </div>
 372
 373 <!-- *********************************************************************** -->
 374 <div class="doc_section">
 375   <a name="embedding">Embedding LLVM in your project</a>
 376 </div>
 377 <!-- *********************************************************************** -->
 378
 379 <div class="doc_text">
 380
 381   <p>The most difficult part of adding LLVM to the build of a project
 382     is to determine the set of LLVM libraries corresponding to the set
 383     of required LLVM features. What follows is an example of how to
 384     obtain this information:</p>
 385
 386   <div class="doc_code">
 387     <pre>
 388     <b># A convenience variable:</b>
 389     set(LLVM_ROOT "" CACHE PATH "Root of LLVM install.")
 390     <b># A bit of a sanity check:</b>
 391     if( NOT EXISTS ${LLVM_ROOT}/include/llvm )
 392     message(FATAL_ERROR "LLVM_ROOT (${LLVM_ROOT}) is not a valid LLVM install")
 393     endif()
 394     <b># We incorporate the CMake features provided by LLVM:</b>
 395     set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${LLVM_ROOT}/share/llvm/cmake")
 396     include(LLVM)
 397     <b># Now set the header and library paths:</b>
 398     include_directories( ${LLVM_ROOT}/include )
 399     link_directories( ${LLVM_ROOT}/lib )
 400     <b># Let's suppose we want to build a JIT compiler with support for
 401     # binary code (no interpreter):</b>
 402     llvm_map_components_to_libraries(REQ_LLVM_LIBRARIES jit native)
 403     <b># Finally, we link the LLVM libraries to our executable:</b>
 404     target_link_libraries(mycompiler ${REQ_LLVM_LIBRARIES})
 405     </pre>
 406   </div>
 407
 408   <p>This assumes that LLVM_ROOT points to an install of LLVM. The
 409     procedure works too for uninstalled builds although we need to take
 410     care to add an <i>include_directories</i> for the location of the
 411     headers on the LLVM source directory (if we are building
 412     out-of-source.)</p>
 413
 414 </div>
 415
 416 <!-- *********************************************************************** -->
 417
 418 <!-- *********************************************************************** -->
 419 <div class="doc_section">
 420   <a name="specifics">Compiler/Platform specific topics</a>
 421 </div>
 422 <!-- *********************************************************************** -->
 423
 424 <div class="doc_text">
 425
 426 <p>Notes for specific compilers and/or platforms.</p>
 427
 428 </div>
 429
 430 <!-- *********************************************************************** -->
 431
 432 <hr>
 433 <address>
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 438
 439   <a href="mailto:ofv@wanadoo.es">Oscar Fuentes</a><br>
 440   <a href="http://llvm.org">LLVM Compiler Infrastructure</a><br>
 441   Last modified: $Date: 2010-08-09 03:59:36 +0100 (Mon, 9 Aug 2010) $
 442 </address>
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