1 ========================
2 Building LLVM with CMake
3 ========================
11 `CMake <http://www.cmake.org/>`_ is a cross-platform build-generator tool. CMake
12 does not build the project, it generates the files needed by your build tool
13 (GNU make, Visual Studio, etc) for building LLVM.
15 If you are really anxious about getting a functional LLVM build, go to the
16 `Quick start`_ section. If you are a CMake novice, start on `Basic CMake usage`_
17 and then go back to the `Quick start`_ once you know what you are doing. The
18 `Options and variables`_ section is a reference for customizing your build. If
19 you already have experience with CMake, this is the recommended starting point.
26 We use here the command-line, non-interactive CMake interface.
28 #. `Download <http://www.cmake.org/cmake/resources/software.html>`_ and install
29 CMake. Version 2.8 is the minimum required.
31 #. Open a shell. Your development tools must be reachable from this shell
32 through the PATH environment variable.
34 #. Create a directory for containing the build. It is not supported to build
35 LLVM on the source directory. cd to this directory:
37 .. code-block:: console
42 #. Execute this command on the shell replacing `path/to/llvm/source/root` with
43 the path to the root of your LLVM source tree:
45 .. code-block:: console
47 $ cmake path/to/llvm/source/root
49 CMake will detect your development environment, perform a series of test and
50 generate the files required for building LLVM. CMake will use default values
51 for all build parameters. See the `Options and variables`_ section for
52 fine-tuning your build
54 This can fail if CMake can't detect your toolset, or if it thinks that the
55 environment is not sane enough. On this case make sure that the toolset that
56 you intend to use is the only one reachable from the shell and that the shell
57 itself is the correct one for you development environment. CMake will refuse
58 to build MinGW makefiles if you have a POSIX shell reachable through the PATH
59 environment variable, for instance. You can force CMake to use a given build
60 tool, see the `Usage`_ section.
62 .. _Basic CMake usage:
68 This section explains basic aspects of CMake, mostly for explaining those
69 options which you may need on your day-to-day usage.
71 CMake comes with extensive documentation in the form of html files and on the
72 cmake executable itself. Execute ``cmake --help`` for further help options.
74 CMake requires to know for which build tool it shall generate files (GNU make,
75 Visual Studio, Xcode, etc). If not specified on the command line, it tries to
76 guess it based on you environment. Once identified the build tool, CMake uses
77 the corresponding *Generator* for creating files for your build tool. You can
78 explicitly specify the generator with the command line option ``-G "Name of the
79 generator"``. For knowing the available generators on your platform, execute
81 .. code-block:: console
85 This will list the generator's names at the end of the help text. Generator's
86 names are case-sensitive. Example:
88 .. code-block:: console
90 $ cmake -G "Visual Studio 9 2008" path/to/llvm/source/root
92 For a given development platform there can be more than one adequate
93 generator. If you use Visual Studio "NMake Makefiles" is a generator you can use
94 for building with NMake. By default, CMake chooses the more specific generator
95 supported by your development environment. If you want an alternative generator,
96 you must tell this to CMake with the ``-G`` option.
100 Explain variables and cache. Move explanation here from #options section.
102 .. _Options and variables:
104 Options and variables
105 =====================
107 Variables customize how the build will be generated. Options are boolean
108 variables, with possible values ON/OFF. Options and variables are defined on the
109 CMake command line like this:
111 .. code-block:: console
113 $ cmake -DVARIABLE=value path/to/llvm/source
115 You can set a variable after the initial CMake invocation for changing its
116 value. You can also undefine a variable:
118 .. code-block:: console
120 $ cmake -UVARIABLE path/to/llvm/source
122 Variables are stored on the CMake cache. This is a file named ``CMakeCache.txt``
123 on the root of the build directory. Do not hand-edit it.
125 Variables are listed here appending its type after a colon. It is correct to
126 write the variable and the type on the CMake command line:
128 .. code-block:: console
130 $ cmake -DVARIABLE:TYPE=value path/to/llvm/source
132 Frequently-used CMake variables
133 -------------------------------
135 Here are listed some of the CMake variables that are used often, along with a
136 brief explanation and LLVM-specific notes. For full documentation, check the
137 CMake docs or execute ``cmake --help-variable VARIABLE_NAME``.
139 **CMAKE_BUILD_TYPE**:STRING
140 Sets the build type for ``make`` based generators. Possible values are
141 Release, Debug, RelWithDebInfo and MinSizeRel. On systems like Visual Studio
142 the user sets the build type with the IDE settings.
144 **CMAKE_INSTALL_PREFIX**:PATH
145 Path where LLVM will be installed if "make install" is invoked or the
146 "INSTALL" target is built.
148 **LLVM_LIBDIR_SUFFIX**:STRING
149 Extra suffix to append to the directory where libraries are to be
150 installed. On a 64-bit architecture, one could use ``-DLLVM_LIBDIR_SUFFIX=64``
151 to install libraries to ``/usr/lib64``.
153 **CMAKE_C_FLAGS**:STRING
154 Extra flags to use when compiling C source files.
156 **CMAKE_CXX_FLAGS**:STRING
157 Extra flags to use when compiling C++ source files.
159 **BUILD_SHARED_LIBS**:BOOL
160 Flag indicating is shared libraries will be built. Its default value is
161 OFF. Shared libraries are not supported on Windows and not recommended in the
164 .. _LLVM-specific variables:
166 LLVM-specific variables
167 -----------------------
169 **LLVM_TARGETS_TO_BUILD**:STRING
170 Semicolon-separated list of targets to build, or *all* for building all
171 targets. Case-sensitive. Defaults to *all*. Example:
172 ``-DLLVM_TARGETS_TO_BUILD="X86;PowerPC"``.
174 **LLVM_BUILD_TOOLS**:BOOL
175 Build LLVM tools. Defaults to ON. Targets for building each tool are generated
176 in any case. You can build an tool separately by invoking its target. For
177 example, you can build *llvm-as* with a makefile-based system executing *make
178 llvm-as* on the root of your build directory.
180 **LLVM_INCLUDE_TOOLS**:BOOL
181 Generate build targets for the LLVM tools. Defaults to ON. You can use that
182 option for disabling the generation of build targets for the LLVM tools.
184 **LLVM_BUILD_EXAMPLES**:BOOL
185 Build LLVM examples. Defaults to OFF. Targets for building each example are
186 generated in any case. See documentation for *LLVM_BUILD_TOOLS* above for more
189 **LLVM_INCLUDE_EXAMPLES**:BOOL
190 Generate build targets for the LLVM examples. Defaults to ON. You can use that
191 option for disabling the generation of build targets for the LLVM examples.
193 **LLVM_BUILD_TESTS**:BOOL
194 Build LLVM unit tests. Defaults to OFF. Targets for building each unit test
195 are generated in any case. You can build a specific unit test with the target
196 *UnitTestNameTests* (where at this time *UnitTestName* can be ADT, Analysis,
197 ExecutionEngine, JIT, Support, Transform, VMCore; see the subdirectories of
198 *unittests* for an updated list.) It is possible to build all unit tests with
199 the target *UnitTests*.
201 **LLVM_INCLUDE_TESTS**:BOOL
202 Generate build targets for the LLVM unit tests. Defaults to ON. You can use
203 that option for disabling the generation of build targets for the LLVM unit
206 **LLVM_APPEND_VC_REV**:BOOL
207 Append version control revision info (svn revision number or Git revision id)
208 to LLVM version string (stored in the PACKAGE_VERSION macro). For this to work
209 cmake must be invoked before the build. Defaults to OFF.
211 **LLVM_ENABLE_THREADS**:BOOL
212 Build with threads support, if available. Defaults to ON.
214 **LLVM_ENABLE_ASSERTIONS**:BOOL
215 Enables code assertions. Defaults to OFF if and only if ``CMAKE_BUILD_TYPE``
218 **LLVM_ENABLE_PIC**:BOOL
219 Add the ``-fPIC`` flag for the compiler command-line, if the compiler supports
220 this flag. Some systems, like Windows, do not need this flag. Defaults to ON.
222 **LLVM_ENABLE_WARNINGS**:BOOL
223 Enable all compiler warnings. Defaults to ON.
225 **LLVM_ENABLE_PEDANTIC**:BOOL
226 Enable pedantic mode. This disable compiler specific extensions, is
227 possible. Defaults to ON.
229 **LLVM_ENABLE_WERROR**:BOOL
230 Stop and fail build, if a compiler warning is triggered. Defaults to OFF.
232 **LLVM_BUILD_32_BITS**:BOOL
233 Build 32-bits executables and libraries on 64-bits systems. This option is
234 available only on some 64-bits unix systems. Defaults to OFF.
236 **LLVM_TARGET_ARCH**:STRING
237 LLVM target to use for native code generation. This is required for JIT
238 generation. It defaults to "host", meaning that it shall pick the architecture
239 of the machine where LLVM is being built. If you are cross-compiling, set it
240 to the target architecture name.
242 **LLVM_TABLEGEN**:STRING
243 Full path to a native TableGen executable (usually named ``tblgen``). This is
244 intended for cross-compiling: if the user sets this variable, no native
245 TableGen will be created.
247 **LLVM_LIT_ARGS**:STRING
248 Arguments given to lit. ``make check`` and ``make clang-test`` are affected.
249 By default, ``'-sv --no-progress-bar'`` on Visual C++ and Xcode, ``'-sv'`` on
252 **LLVM_LIT_TOOLS_DIR**:PATH
253 The path to GnuWin32 tools for tests. Valid on Windows host. Defaults to "",
254 then Lit seeks tools according to %PATH%. Lit can find tools(eg. grep, sort,
255 &c) on LLVM_LIT_TOOLS_DIR at first, without specifying GnuWin32 to %PATH%.
257 **LLVM_ENABLE_FFI**:BOOL
258 Indicates whether LLVM Interpreter will be linked with Foreign Function
259 Interface library. If the library or its headers are installed on a custom
260 location, you can set the variables FFI_INCLUDE_DIR and
261 FFI_LIBRARY_DIR. Defaults to OFF.
263 **LLVM_EXTERNAL_{CLANG,LLD,POLLY}_SOURCE_DIR**:PATH
264 Path to ``{Clang,lld,Polly}``\'s source directory. Defaults to
265 ``tools/{clang,lld,polly}``. ``{Clang,lld,Polly}`` will not be built when it
266 is empty or it does not point valid path.
268 **LLVM_USE_OPROFILE**:BOOL
269 Enable building OProfile JIT support. Defaults to OFF
271 **LLVM_USE_INTEL_JITEVENTS**:BOOL
272 Enable building support for Intel JIT Events API. Defaults to OFF
274 **LLVM_ENABLE_ZLIB**:BOOL
275 Build with zlib to support compression/uncompression in LLVM tools.
278 Executing the test suite
279 ========================
281 Testing is performed when the *check* target is built. For instance, if you are
282 using makefiles, execute this command while on the top level of your build
285 .. code-block:: console
289 On Visual Studio, you may run tests to build the project "check".
294 See `this wiki page <http://www.vtk.org/Wiki/CMake_Cross_Compiling>`_ for
295 generic instructions on how to cross-compile with CMake. It goes into detailed
296 explanations and may seem daunting, but it is not. On the wiki page there are
297 several examples including toolchain files. Go directly to `this section
298 <http://www.vtk.org/Wiki/CMake_Cross_Compiling#Information_how_to_set_up_various_cross_compiling_toolchains>`_
299 for a quick solution.
301 Also see the `LLVM-specific variables`_ section for variables used when
304 Embedding LLVM in your project
305 ==============================
307 The most difficult part of adding LLVM to the build of a project is to determine
308 the set of LLVM libraries corresponding to the set of required LLVM
309 features. What follows is an example of how to obtain this information:
311 .. code-block:: cmake
313 # A convenience variable:
314 set(LLVM_ROOT "" CACHE PATH "Root of LLVM install.")
316 # A bit of a sanity check:
317 if( NOT EXISTS ${LLVM_ROOT}/include/llvm )
318 message(FATAL_ERROR "LLVM_ROOT (${LLVM_ROOT}) is not a valid LLVM install")
321 # We incorporate the CMake features provided by LLVM:
322 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${LLVM_ROOT}/share/llvm/cmake")
325 # Now set the header and library paths:
326 include_directories( ${LLVM_INCLUDE_DIRS} )
327 link_directories( ${LLVM_LIBRARY_DIRS} )
328 add_definitions( ${LLVM_DEFINITIONS} )
330 # Let's suppose we want to build a JIT compiler with support for
331 # binary code (no interpreter):
332 llvm_map_components_to_libraries(REQ_LLVM_LIBRARIES jit native)
334 # Finally, we link the LLVM libraries to our executable:
335 target_link_libraries(mycompiler ${REQ_LLVM_LIBRARIES})
337 This assumes that LLVM_ROOT points to an install of LLVM. The procedure works
338 too for uninstalled builds although we need to take care to add an
339 `include_directories` for the location of the headers on the LLVM source
340 directory (if we are building out-of-source.)
342 Alternativaly, you can utilize CMake's ``find_package`` functionality. Here is
343 an equivalent variant of snippet shown above:
345 .. code-block:: cmake
350 message(FATAL_ERROR "LLVM package can't be found. Set CMAKE_PREFIX_PATH variable to LLVM's installation prefix.")
353 include_directories( ${LLVM_INCLUDE_DIRS} )
354 link_directories( ${LLVM_LIBRARY_DIRS} )
356 llvm_map_components_to_libraries(REQ_LLVM_LIBRARIES jit native)
358 target_link_libraries(mycompiler ${REQ_LLVM_LIBRARIES})
360 .. _cmake-out-of-source-pass:
362 Developing LLVM pass out of source
363 ----------------------------------
365 It is possible to develop LLVM passes against installed LLVM. An example of
366 project layout provided below:
379 Contents of ``<project dir>/CMakeLists.txt``:
381 .. code-block:: cmake
385 # Define add_llvm_* macro's.
388 add_definitions(${LLVM_DEFINITIONS})
389 include_directories(${LLVM_INCLUDE_DIRS})
390 link_directories(${LLVM_LIBRARY_DIRS})
392 add_subdirectory(<pass name>)
394 Contents of ``<project dir>/<pass name>/CMakeLists.txt``:
396 .. code-block:: cmake
398 add_llvm_loadable_module(LLVMPassname
402 When you are done developing your pass, you may wish to integrate it
403 into LLVM source tree. You can achieve it in two easy steps:
405 #. Copying ``<pass name>`` folder into ``<LLVM root>/lib/Transform`` directory.
407 #. Adding ``add_subdirectory(<pass name>)`` line into
408 ``<LLVM root>/lib/Transform/CMakeLists.txt``.
410 Compiler/Platform specific topics
411 =================================
413 Notes for specific compilers and/or platforms.
418 **LLVM_COMPILER_JOBS**:STRING
419 Specifies the maximum number of parallell compiler jobs to use per project
420 when building with msbuild or Visual Studio. Only supported for Visual Studio
421 2008 and Visual Studio 2010 CMake generators. 0 means use all
422 processors. Default is 0.