1 .. _building-with-cmake:
3 ========================
4 Building LLVM with CMake
5 ========================
13 `CMake <http://www.cmake.org/>`_ is a cross-platform build-generator tool. CMake
14 does not build the project, it generates the files needed by your build tool
15 (GNU make, Visual Studio, etc) for building LLVM.
17 If you are really anxious about getting a functional LLVM build, go to the
18 `Quick start`_ section. If you are a CMake novice, start on `Basic CMake usage`_
19 and then go back to the `Quick start`_ once you know what you are doing. The
20 `Options and variables`_ section is a reference for customizing your build. If
21 you already have experience with CMake, this is the recommended starting point.
28 We use here the command-line, non-interactive CMake interface.
30 #. `Download <http://www.cmake.org/cmake/resources/software.html>`_ and install
31 CMake. Version 2.8 is the minimum required.
33 #. Open a shell. Your development tools must be reachable from this shell
34 through the PATH environment variable.
36 #. Create a directory for containing the build. It is not supported to build
37 LLVM on the source directory. cd to this directory:
39 .. code-block:: console
44 #. Execute this command on the shell replacing `path/to/llvm/source/root` with
45 the path to the root of your LLVM source tree:
47 .. code-block:: console
49 $ cmake path/to/llvm/source/root
51 CMake will detect your development environment, perform a series of test and
52 generate the files required for building LLVM. CMake will use default values
53 for all build parameters. See the `Options and variables`_ section for
54 fine-tuning your build
56 This can fail if CMake can't detect your toolset, or if it thinks that the
57 environment is not sane enough. On this case make sure that the toolset that
58 you intend to use is the only one reachable from the shell and that the shell
59 itself is the correct one for you development environment. CMake will refuse
60 to build MinGW makefiles if you have a POSIX shell reachable through the PATH
61 environment variable, for instance. You can force CMake to use a given build
62 tool, see the `Usage`_ section.
64 .. _Basic CMake usage:
70 This section explains basic aspects of CMake, mostly for explaining those
71 options which you may need on your day-to-day usage.
73 CMake comes with extensive documentation in the form of html files and on the
74 cmake executable itself. Execute ``cmake --help`` for further help options.
76 CMake requires to know for which build tool it shall generate files (GNU make,
77 Visual Studio, Xcode, etc). If not specified on the command line, it tries to
78 guess it based on you environment. Once identified the build tool, CMake uses
79 the corresponding *Generator* for creating files for your build tool. You can
80 explicitly specify the generator with the command line option ``-G "Name of the
81 generator"``. For knowing the available generators on your platform, execute
83 .. code-block:: console
87 This will list the generator's names at the end of the help text. Generator's
88 names are case-sensitive. Example:
90 .. code-block:: console
92 $ cmake -G "Visual Studio 9 2008" path/to/llvm/source/root
94 For a given development platform there can be more than one adequate
95 generator. If you use Visual Studio "NMake Makefiles" is a generator you can use
96 for building with NMake. By default, CMake chooses the more specific generator
97 supported by your development environment. If you want an alternative generator,
98 you must tell this to CMake with the ``-G`` option.
102 Explain variables and cache. Move explanation here from #options section.
104 .. _Options and variables:
106 Options and variables
107 =====================
109 Variables customize how the build will be generated. Options are boolean
110 variables, with possible values ON/OFF. Options and variables are defined on the
111 CMake command line like this:
113 .. code-block:: console
115 $ cmake -DVARIABLE=value path/to/llvm/source
117 You can set a variable after the initial CMake invocation for changing its
118 value. You can also undefine a variable:
120 .. code-block:: console
122 $ cmake -UVARIABLE path/to/llvm/source
124 Variables are stored on the CMake cache. This is a file named ``CMakeCache.txt``
125 on the root of the build directory. Do not hand-edit it.
127 Variables are listed here appending its type after a colon. It is correct to
128 write the variable and the type on the CMake command line:
130 .. code-block:: console
132 $ cmake -DVARIABLE:TYPE=value path/to/llvm/source
134 Frequently-used CMake variables
135 -------------------------------
137 Here are listed some of the CMake variables that are used often, along with a
138 brief explanation and LLVM-specific notes. For full documentation, check the
139 CMake docs or execute ``cmake --help-variable VARIABLE_NAME``.
141 **CMAKE_BUILD_TYPE**:STRING
142 Sets the build type for ``make`` based generators. Possible values are
143 Release, Debug, RelWithDebInfo and MinSizeRel. On systems like Visual Studio
144 the user sets the build type with the IDE settings.
146 **CMAKE_INSTALL_PREFIX**:PATH
147 Path where LLVM will be installed if "make install" is invoked or the
148 "INSTALL" target is built.
150 **LLVM_LIBDIR_SUFFIX**:STRING
151 Extra suffix to append to the directory where libraries are to be
152 installed. On a 64-bit architecture, one could use ``-DLLVM_LIBDIR_SUFFIX=64``
153 to install libraries to ``/usr/lib64``.
155 **CMAKE_C_FLAGS**:STRING
156 Extra flags to use when compiling C source files.
158 **CMAKE_CXX_FLAGS**:STRING
159 Extra flags to use when compiling C++ source files.
161 **BUILD_SHARED_LIBS**:BOOL
162 Flag indicating is shared libraries will be built. Its default value is
163 OFF. Shared libraries are not supported on Windows and not recommended in the
166 .. _LLVM-specific variables:
168 LLVM-specific variables
169 -----------------------
171 **LLVM_TARGETS_TO_BUILD**:STRING
172 Semicolon-separated list of targets to build, or *all* for building all
173 targets. Case-sensitive. For Visual C++ defaults to *X86*. On the other cases
174 defaults to *all*. Example: ``-DLLVM_TARGETS_TO_BUILD="X86;PowerPC"``.
176 **LLVM_BUILD_TOOLS**:BOOL
177 Build LLVM tools. Defaults to ON. Targets for building each tool are generated
178 in any case. You can build an tool separately by invoking its target. For
179 example, you can build *llvm-as* with a makefile-based system executing *make
180 llvm-as* on the root of your build directory.
182 **LLVM_INCLUDE_TOOLS**:BOOL
183 Generate build targets for the LLVM tools. Defaults to ON. You can use that
184 option for disabling the generation of build targets for the LLVM tools.
186 **LLVM_BUILD_EXAMPLES**:BOOL
187 Build LLVM examples. Defaults to OFF. Targets for building each example are
188 generated in any case. See documentation for *LLVM_BUILD_TOOLS* above for more
191 **LLVM_INCLUDE_EXAMPLES**:BOOL
192 Generate build targets for the LLVM examples. Defaults to ON. You can use that
193 option for disabling the generation of build targets for the LLVM examples.
195 **LLVM_BUILD_TESTS**:BOOL
196 Build LLVM unit tests. Defaults to OFF. Targets for building each unit test
197 are generated in any case. You can build a specific unit test with the target
198 *UnitTestNameTests* (where at this time *UnitTestName* can be ADT, Analysis,
199 ExecutionEngine, JIT, Support, Transform, VMCore; see the subdirectories of
200 *unittests* for an updated list.) It is possible to build all unit tests with
201 the target *UnitTests*.
203 **LLVM_INCLUDE_TESTS**:BOOL
204 Generate build targets for the LLVM unit tests. Defaults to ON. You can use
205 that option for disabling the generation of build targets for the LLVM unit
208 **LLVM_APPEND_VC_REV**:BOOL
209 Append version control revision info (svn revision number or git revision id)
210 to LLVM version string (stored in the PACKAGE_VERSION macro). For this to work
211 cmake must be invoked before the build. Defaults to OFF.
213 **LLVM_ENABLE_THREADS**:BOOL
214 Build with threads support, if available. Defaults to ON.
216 **LLVM_ENABLE_ASSERTIONS**:BOOL
217 Enables code assertions. Defaults to OFF if and only if ``CMAKE_BUILD_TYPE``
220 **LLVM_ENABLE_PIC**:BOOL
221 Add the ``-fPIC`` flag for the compiler command-line, if the compiler supports
222 this flag. Some systems, like Windows, do not need this flag. Defaults to ON.
224 **LLVM_ENABLE_WARNINGS**:BOOL
225 Enable all compiler warnings. Defaults to ON.
227 **LLVM_ENABLE_PEDANTIC**:BOOL
228 Enable pedantic mode. This disable compiler specific extensions, is
229 possible. Defaults to ON.
231 **LLVM_ENABLE_WERROR**:BOOL
232 Stop and fail build, if a compiler warning is triggered. Defaults to OFF.
234 **LLVM_BUILD_32_BITS**:BOOL
235 Build 32-bits executables and libraries on 64-bits systems. This option is
236 available only on some 64-bits unix systems. Defaults to OFF.
238 **LLVM_TARGET_ARCH**:STRING
239 LLVM target to use for native code generation. This is required for JIT
240 generation. It defaults to "host", meaning that it shall pick the architecture
241 of the machine where LLVM is being built. If you are cross-compiling, set it
242 to the target architecture name.
244 **LLVM_TABLEGEN**:STRING
245 Full path to a native TableGen executable (usually named ``tblgen``). This is
246 intended for cross-compiling: if the user sets this variable, no native
247 TableGen will be created.
249 **LLVM_LIT_ARGS**:STRING
250 Arguments given to lit. ``make check`` and ``make clang-test`` are affected.
251 By default, ``'-sv --no-progress-bar'`` on Visual C++ and Xcode, ``'-sv'`` on
254 **LLVM_LIT_TOOLS_DIR**:PATH
255 The path to GnuWin32 tools for tests. Valid on Windows host. Defaults to "",
256 then Lit seeks tools according to %PATH%. Lit can find tools(eg. grep, sort,
257 &c) on LLVM_LIT_TOOLS_DIR at first, without specifying GnuWin32 to %PATH%.
259 **LLVM_ENABLE_FFI**:BOOL
260 Indicates whether LLVM Interpreter will be linked with Foreign Function
261 Interface library. If the library or its headers are installed on a custom
262 location, you can set the variables FFI_INCLUDE_DIR and
263 FFI_LIBRARY_DIR. Defaults to OFF.
265 **LLVM_EXTERNAL_{CLANG,LLD,POLLY}_SOURCE_DIR**:PATH
266 Path to ``{Clang,lld,Polly}``\'s source directory. Defaults to
267 ``tools/{clang,lld,polly}``. ``{Clang,lld,Polly}`` will not be built when it
268 is empty or it does not point valid path.
270 **LLVM_USE_OPROFILE**:BOOL
271 Enable building OProfile JIT support. Defaults to OFF
273 **LLVM_USE_INTEL_JITEVENTS**:BOOL
274 Enable building support for Intel JIT Events API. Defaults to OFF
276 Executing the test suite
277 ========================
279 Testing is performed when the *check* target is built. For instance, if you are
280 using makefiles, execute this command while on the top level of your build
283 .. code-block:: console
287 On Visual Studio, you may run tests to build the project "check".
292 See `this wiki page <http://www.vtk.org/Wiki/CMake_Cross_Compiling>`_ for
293 generic instructions on how to cross-compile with CMake. It goes into detailed
294 explanations and may seem daunting, but it is not. On the wiki page there are
295 several examples including toolchain files. Go directly to `this section
296 <http://www.vtk.org/Wiki/CMake_Cross_Compiling#Information_how_to_set_up_various_cross_compiling_toolchains>`_
297 for a quick solution.
299 Also see the `LLVM-specific variables`_ section for variables used when
302 Embedding LLVM in your project
303 ==============================
305 The most difficult part of adding LLVM to the build of a project is to determine
306 the set of LLVM libraries corresponding to the set of required LLVM
307 features. What follows is an example of how to obtain this information:
309 .. code-block:: cmake
311 # A convenience variable:
312 set(LLVM_ROOT "" CACHE PATH "Root of LLVM install.")
314 # A bit of a sanity check:
315 if( NOT EXISTS ${LLVM_ROOT}/include/llvm )
316 message(FATAL_ERROR "LLVM_ROOT (${LLVM_ROOT}) is not a valid LLVM install")
319 # We incorporate the CMake features provided by LLVM:
320 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${LLVM_ROOT}/share/llvm/cmake")
323 # Now set the header and library paths:
324 include_directories( ${LLVM_INCLUDE_DIRS} )
325 link_directories( ${LLVM_LIBRARY_DIRS} )
326 add_definitions( ${LLVM_DEFINITIONS} )
328 # Let's suppose we want to build a JIT compiler with support for
329 # binary code (no interpreter):
330 llvm_map_components_to_libraries(REQ_LLVM_LIBRARIES jit native)
332 # Finally, we link the LLVM libraries to our executable:
333 target_link_libraries(mycompiler ${REQ_LLVM_LIBRARIES})
335 This assumes that LLVM_ROOT points to an install of LLVM. The procedure works
336 too for uninstalled builds although we need to take care to add an
337 `include_directories` for the location of the headers on the LLVM source
338 directory (if we are building out-of-source.)
340 Alternativaly, you can utilize CMake's ``find_package`` functionality. Here is
341 an equivalent variant of snippet shown above:
343 .. code-block:: cmake
348 message(FATAL_ERROR "LLVM package can't be found. Set CMAKE_PREFIX_PATH variable to LLVM's installation prefix.")
351 include_directories( ${LLVM_INCLUDE_DIRS} )
352 link_directories( ${LLVM_LIBRARY_DIRS} )
354 llvm_map_components_to_libraries(REQ_LLVM_LIBRARIES jit native)
356 target_link_libraries(mycompiler ${REQ_LLVM_LIBRARIES})
358 .. _cmake-out-of-source-pass:
360 Developing LLVM pass out of source
361 ----------------------------------
363 It is possible to develop LLVM passes against installed LLVM. An example of
364 project layout provided below:
377 Contents of ``<project dir>/CMakeLists.txt``:
379 .. code-block:: cmake
383 # Define add_llvm_* macro's.
386 add_definitions(${LLVM_DEFINITIONS})
387 include_directories(${LLVM_INCLUDE_DIRS})
388 link_directories(${LLVM_LIBRARY_DIRS})
390 add_subdirectory(<pass name>)
392 Contents of ``<project dir>/<pass name>/CMakeLists.txt``:
394 .. code-block:: cmake
396 add_llvm_loadable_module(LLVMPassname
400 When you are done developing your pass, you may wish to integrate it
401 into LLVM source tree. You can achieve it in two easy steps:
403 #. Copying ``<pass name>`` folder into ``<LLVM root>/lib/Transform`` directory.
405 #. Adding ``add_subdirectory(<pass name>)`` line into
406 ``<LLVM root>/lib/Transform/CMakeLists.txt``.
408 Compiler/Platform specific topics
409 =================================
411 Notes for specific compilers and/or platforms.
416 **LLVM_COMPILER_JOBS**:STRING
417 Specifies the maximum number of parallell compiler jobs to use per project
418 when building with msbuild or Visual Studio. Only supported for Visual Studio
419 2008 and Visual Studio 2010 CMake generators. 0 means use all
420 processors. Default is 0.