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 a new contributor**, please start with the :doc:`GettingStarted`
16 page. This page is geared for existing contributors moving from the
17 legacy configure/make system.
19 If you are really anxious about getting a functional LLVM build, go to the
20 `Quick start`_ section. If you are a CMake novice, start with `Basic CMake usage`_
21 and then go back to the `Quick start`_ section once you know what you are doing. The
22 `Options and variables`_ section is a reference for customizing your build. If
23 you already have experience with CMake, this is the recommended starting point.
25 This page is geared towards users of the LLVM CMake build. If you're looking for
26 information about modifying the LLVM CMake build system you may want to see the
27 :doc:`CMakePrimer` page. It has a basic overview of the CMake language.
34 We use here the command-line, non-interactive CMake interface.
36 #. `Download <http://www.cmake.org/cmake/resources/software.html>`_ and install
37 CMake. Version 3.4.3 is the minimum required.
39 #. Open a shell. Your development tools must be reachable from this shell
40 through the PATH environment variable.
42 #. Create a build directory. Building LLVM in the source
43 directory is not supported. cd to this directory:
45 .. code-block:: console
50 #. Execute this command in the shell replacing `path/to/llvm/source/root` with
51 the path to the root of your LLVM source tree:
53 .. code-block:: console
55 $ cmake path/to/llvm/source/root
57 CMake will detect your development environment, perform a series of tests, and
58 generate the files required for building LLVM. CMake will use default values
59 for all build parameters. See the `Options and variables`_ section for
60 a list of build parameters that you can modify.
62 This can fail if CMake can't detect your toolset, or if it thinks that the
63 environment is not sane enough. In this case, make sure that the toolset that
64 you intend to use is the only one reachable from the shell, and that the shell
65 itself is the correct one for your development environment. CMake will refuse
66 to build MinGW makefiles if you have a POSIX shell reachable through the PATH
67 environment variable, for instance. You can force CMake to use a given build
68 tool; for instructions, see the `Usage`_ section, below.
70 #. After CMake has finished running, proceed to use IDE project files, or start
71 the build from the build directory:
73 .. code-block:: console
77 The ``--build`` option tells ``cmake`` to invoke the underlying build
78 tool (``make``, ``ninja``, ``xcodebuild``, ``msbuild``, etc.)
80 The underlying build tool can be invoked directly, of course, but
81 the ``--build`` option is portable.
83 #. After LLVM has finished building, install it from the build directory:
85 .. code-block:: console
87 $ cmake --build . --target install
89 The ``--target`` option with ``install`` parameter in addition to
90 the ``--build`` option tells ``cmake`` to build the ``install`` target.
92 It is possible to set a different install prefix at installation time
93 by invoking the ``cmake_install.cmake`` script generated in the
96 .. code-block:: console
98 $ cmake -DCMAKE_INSTALL_PREFIX=/tmp/llvm -P cmake_install.cmake
100 .. _Basic CMake usage:
106 This section explains basic aspects of CMake
107 which you may need in your day-to-day usage.
109 CMake comes with extensive documentation, in the form of html files, and as
110 online help accessible via the ``cmake`` executable itself. Execute ``cmake
111 --help`` for further help options.
113 CMake allows you to specify a build tool (e.g., GNU make, Visual Studio,
114 or Xcode). If not specified on the command line, CMake tries to guess which
115 build tool to use, based on your environment. Once it has identified your
116 build tool, CMake uses the corresponding *Generator* to create files for your
117 build tool (e.g., Makefiles or Visual Studio or Xcode project files). You can
118 explicitly specify the generator with the command line option ``-G "Name of the
119 generator"``. To see a list of the available generators on your system, execute
121 .. code-block:: console
125 This will list the generator names at the end of the help text.
127 Generators' names are case-sensitive, and may contain spaces. For this reason,
128 you should enter them exactly as they are listed in the ``cmake --help``
129 output, in quotes. For example, to generate project files specifically for
130 Visual Studio 12, you can execute:
132 .. code-block:: console
134 $ cmake -G "Visual Studio 12" path/to/llvm/source/root
136 For a given development platform there can be more than one adequate
137 generator. If you use Visual Studio, "NMake Makefiles" is a generator you can use
138 for building with NMake. By default, CMake chooses the most specific generator
139 supported by your development environment. If you want an alternative generator,
140 you must tell this to CMake with the ``-G`` option.
144 Explain variables and cache. Move explanation here from #options section.
146 .. _Options and variables:
148 Options and variables
149 =====================
151 Variables customize how the build will be generated. Options are boolean
152 variables, with possible values ON/OFF. Options and variables are defined on the
153 CMake command line like this:
155 .. code-block:: console
157 $ cmake -DVARIABLE=value path/to/llvm/source
159 You can set a variable after the initial CMake invocation to change its
160 value. You can also undefine a variable:
162 .. code-block:: console
164 $ cmake -UVARIABLE path/to/llvm/source
166 Variables are stored in the CMake cache. This is a file named ``CMakeCache.txt``
167 stored at the root of your build directory that is generated by ``cmake``.
168 Editing it yourself is not recommended.
170 Variables are listed in the CMake cache and later in this document with
171 the variable name and type separated by a colon. You can also specify the
172 variable and type on the CMake command line:
174 .. code-block:: console
176 $ cmake -DVARIABLE:TYPE=value path/to/llvm/source
178 Frequently-used CMake variables
179 -------------------------------
181 Here are some of the CMake variables that are used often, along with a
182 brief explanation and LLVM-specific notes. For full documentation, consult the
183 CMake manual, or execute ``cmake --help-variable VARIABLE_NAME``.
185 **CMAKE_BUILD_TYPE**:STRING
186 Sets the build type for ``make``-based generators. Possible values are
187 Release, Debug, RelWithDebInfo and MinSizeRel. If you are using an IDE such as
188 Visual Studio, you should use the IDE settings to set the build type.
190 **CMAKE_INSTALL_PREFIX**:PATH
191 Path where LLVM will be installed if "make install" is invoked or the
192 "install" target is built.
194 **LLVM_LIBDIR_SUFFIX**:STRING
195 Extra suffix to append to the directory where libraries are to be
196 installed. On a 64-bit architecture, one could use ``-DLLVM_LIBDIR_SUFFIX=64``
197 to install libraries to ``/usr/lib64``.
199 **CMAKE_C_FLAGS**:STRING
200 Extra flags to use when compiling C source files.
202 **CMAKE_CXX_FLAGS**:STRING
203 Extra flags to use when compiling C++ source files.
205 .. _LLVM-specific variables:
207 LLVM-specific variables
208 -----------------------
210 **LLVM_TARGETS_TO_BUILD**:STRING
211 Semicolon-separated list of targets to build, or *all* for building all
212 targets. Case-sensitive. Defaults to *all*. Example:
213 ``-DLLVM_TARGETS_TO_BUILD="X86;PowerPC"``.
215 **LLVM_BUILD_TOOLS**:BOOL
216 Build LLVM tools. Defaults to ON. Targets for building each tool are generated
217 in any case. You can build a tool separately by invoking its target. For
218 example, you can build *llvm-as* with a Makefile-based system by executing *make
219 llvm-as* at the root of your build directory.
221 **LLVM_INCLUDE_TOOLS**:BOOL
222 Generate build targets for the LLVM tools. Defaults to ON. You can use this
223 option to disable the generation of build targets for the LLVM tools.
225 **LLVM_BUILD_EXAMPLES**:BOOL
226 Build LLVM examples. Defaults to OFF. Targets for building each example are
227 generated in any case. See documentation for *LLVM_BUILD_TOOLS* above for more
230 **LLVM_INCLUDE_EXAMPLES**:BOOL
231 Generate build targets for the LLVM examples. Defaults to ON. You can use this
232 option to disable the generation of build targets for the LLVM examples.
234 **LLVM_BUILD_TESTS**:BOOL
235 Build LLVM unit tests. Defaults to OFF. Targets for building each unit test
236 are generated in any case. You can build a specific unit test using the
237 targets defined under *unittests*, such as ADTTests, IRTests, SupportTests,
238 etc. (Search for ``add_llvm_unittest`` in the subdirectories of *unittests*
239 for a complete list of unit tests.) It is possible to build all unit tests
240 with the target *UnitTests*.
242 **LLVM_INCLUDE_TESTS**:BOOL
243 Generate build targets for the LLVM unit tests. Defaults to ON. You can use
244 this option to disable the generation of build targets for the LLVM unit
247 **LLVM_APPEND_VC_REV**:BOOL
248 Append version control revision info (svn revision number or Git revision id)
249 to LLVM version string (stored in the PACKAGE_VERSION macro). For this to work
250 cmake must be invoked before the build. Defaults to OFF.
252 **LLVM_ENABLE_THREADS**:BOOL
253 Build with threads support, if available. Defaults to ON.
255 **LLVM_ENABLE_CXX1Y**:BOOL
256 Build in C++1y mode, if available. Defaults to OFF.
258 **LLVM_ENABLE_ASSERTIONS**:BOOL
259 Enables code assertions. Defaults to ON if and only if ``CMAKE_BUILD_TYPE``
262 **LLVM_ENABLE_EH**:BOOL
263 Build LLVM with exception-handling support. This is necessary if you wish to
264 link against LLVM libraries and make use of C++ exceptions in your own code
265 that need to propagate through LLVM code. Defaults to OFF.
267 **LLVM_ENABLE_EXPENSIVE_CHECKS**:BOOL
268 Enable additional time/memory expensive checking. Defaults to OFF.
270 **LLVM_ENABLE_PIC**:BOOL
271 Add the ``-fPIC`` flag to the compiler command-line, if the compiler supports
272 this flag. Some systems, like Windows, do not need this flag. Defaults to ON.
274 **LLVM_ENABLE_RTTI**:BOOL
275 Build LLVM with run-time type information. Defaults to OFF.
277 **LLVM_ENABLE_WARNINGS**:BOOL
278 Enable all compiler warnings. Defaults to ON.
280 **LLVM_ENABLE_PEDANTIC**:BOOL
281 Enable pedantic mode. This disables compiler-specific extensions, if
282 possible. Defaults to ON.
284 **LLVM_ENABLE_WERROR**:BOOL
285 Stop and fail the build, if a compiler warning is triggered. Defaults to OFF.
287 **LLVM_ABI_BREAKING_CHECKS**:STRING
288 Used to decide if LLVM should be built with ABI breaking checks or
289 not. Allowed values are `WITH_ASSERTS` (default), `FORCE_ON` and
290 `FORCE_OFF`. `WITH_ASSERTS` turns on ABI breaking checks in an
291 assertion enabled build. `FORCE_ON` (`FORCE_OFF`) turns them on
292 (off) irrespective of whether normal (`NDEBUG`-based) assertions are
293 enabled or not. A version of LLVM built with ABI breaking checks
294 is not ABI compatible with a version built without it.
296 **LLVM_BUILD_32_BITS**:BOOL
297 Build 32-bit executables and libraries on 64-bit systems. This option is
298 available only on some 64-bit Unix systems. Defaults to OFF.
300 **LLVM_TARGET_ARCH**:STRING
301 LLVM target to use for native code generation. This is required for JIT
302 generation. It defaults to "host", meaning that it shall pick the architecture
303 of the machine where LLVM is being built. If you are cross-compiling, set it
304 to the target architecture name.
306 **LLVM_TABLEGEN**:STRING
307 Full path to a native TableGen executable (usually named ``llvm-tblgen``). This is
308 intended for cross-compiling: if the user sets this variable, no native
309 TableGen will be created.
311 **LLVM_LIT_ARGS**:STRING
312 Arguments given to lit. ``make check`` and ``make clang-test`` are affected.
313 By default, ``'-sv --no-progress-bar'`` on Visual C++ and Xcode, ``'-sv'`` on
316 **LLVM_LIT_TOOLS_DIR**:PATH
317 The path to GnuWin32 tools for tests. Valid on Windows host. Defaults to
318 the empty string, in which case lit will look for tools needed for tests
319 (e.g. ``grep``, ``sort``, etc.) in your %PATH%. If GnuWin32 is not in your
320 %PATH%, then you can set this variable to the GnuWin32 directory so that
321 lit can find tools needed for tests in that directory.
323 **LLVM_ENABLE_FFI**:BOOL
324 Indicates whether the LLVM Interpreter will be linked with the Foreign Function
325 Interface library (libffi) in order to enable calling external functions.
326 If the library or its headers are installed in a custom
327 location, you can also set the variables FFI_INCLUDE_DIR and
328 FFI_LIBRARY_DIR to the directories where ffi.h and libffi.so can be found,
329 respectively. Defaults to OFF.
331 **LLVM_EXTERNAL_{CLANG,LLD,POLLY}_SOURCE_DIR**:PATH
332 These variables specify the path to the source directory for the external
333 LLVM projects Clang, lld, and Polly, respectively, relative to the top-level
334 source directory. If the in-tree subdirectory for an external project
335 exists (e.g., llvm/tools/clang for Clang), then the corresponding variable
336 will not be used. If the variable for an external project does not point
337 to a valid path, then that project will not be built.
339 **LLVM_ENABLE_PROJECTS**:STRING
340 Semicolon-separated list of projects to build, or *all* for building all
341 (clang, libcxx, libcxxabi, lldb, compiler-rt, lld, polly) projects.
342 This flag assumes that projects are checked out side-by-side and not nested,
343 i.e. clang needs to be in parallel of llvm instead of nested in `llvm/tools`.
344 This feature allows to have one build for only LLVM and another for clang+llvm
345 using the same source checkout.
347 **LLVM_EXTERNAL_PROJECTS**:STRING
348 Semicolon-separated list of additional external projects to build as part of
349 llvm. For each project LLVM_EXTERNAL_<NAME>_SOURCE_DIR have to be specified
350 with the path for the source code of the project. Example:
351 ``-DLLVM_EXTERNAL_PROJECTS="Foo;Bar"
352 -DLLVM_EXTERNAL_FOO_SOURCE_DIR=/src/foo
353 -DLLVM_EXTERNAL_BAR_SOURCE_DIR=/src/bar``.
355 **LLVM_USE_OPROFILE**:BOOL
356 Enable building OProfile JIT support. Defaults to OFF.
358 **LLVM_PROFDATA_FILE**:PATH
359 Path to a profdata file to pass into clang's -fprofile-instr-use flag. This
360 can only be specified if you're building with clang.
362 **LLVM_USE_INTEL_JITEVENTS**:BOOL
363 Enable building support for Intel JIT Events API. Defaults to OFF.
365 **LLVM_ENABLE_ZLIB**:BOOL
366 Enable building with zlib to support compression/uncompression in LLVM tools.
369 **LLVM_USE_SANITIZER**:STRING
370 Define the sanitizer used to build LLVM binaries and tests. Possible values
371 are ``Address``, ``Memory``, ``MemoryWithOrigins``, ``Undefined``, ``Thread``,
372 and ``Address;Undefined``. Defaults to empty string.
374 **LLVM_ENABLE_LTO**:STRING
375 Add ``-flto`` or ``-flto=`` flags to the compile and link command
376 lines, enabling link-time optimization. Possible values are ``Off``,
377 ``On``, ``Thin`` and ``Full``. Defaults to OFF.
379 **LLVM_PARALLEL_COMPILE_JOBS**:STRING
380 Define the maximum number of concurrent compilation jobs.
382 **LLVM_PARALLEL_LINK_JOBS**:STRING
383 Define the maximum number of concurrent link jobs.
385 **LLVM_BUILD_DOCS**:BOOL
386 Adds all *enabled* documentation targets (i.e. Doxgyen and Sphinx targets) as
387 dependencies of the default build targets. This results in all of the (enabled)
388 documentation targets being as part of a normal build. If the ``install``
389 target is run then this also enables all built documentation targets to be
390 installed. Defaults to OFF. To enable a particular documentation target, see
391 see LLVM_ENABLE_SPHINX and LLVM_ENABLE_DOXYGEN.
393 **LLVM_ENABLE_DOXYGEN**:BOOL
394 Enables the generation of browsable HTML documentation using doxygen.
397 **LLVM_ENABLE_DOXYGEN_QT_HELP**:BOOL
398 Enables the generation of a Qt Compressed Help file. Defaults to OFF.
399 This affects the make target ``doxygen-llvm``. When enabled, apart from
400 the normal HTML output generated by doxygen, this will produce a QCH file
401 named ``org.llvm.qch``. You can then load this file into Qt Creator.
402 This option is only useful in combination with ``-DLLVM_ENABLE_DOXYGEN=ON``;
403 otherwise this has no effect.
405 **LLVM_DOXYGEN_QCH_FILENAME**:STRING
406 The filename of the Qt Compressed Help file that will be generated when
407 ``-DLLVM_ENABLE_DOXYGEN=ON`` and
408 ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON`` are given. Defaults to
410 This option is only useful in combination with
411 ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON``;
412 otherwise it has no effect.
414 **LLVM_DOXYGEN_QHP_NAMESPACE**:STRING
415 Namespace under which the intermediate Qt Help Project file lives. See `Qt
417 for more information. Defaults to "org.llvm". This option is only useful in
418 combination with ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON``; otherwise
421 **LLVM_DOXYGEN_QHP_CUST_FILTER_NAME**:STRING
422 See `Qt Help Project`_ for
423 more information. Defaults to the CMake variable ``${PACKAGE_STRING}`` which
424 is a combination of the package name and version string. This filter can then
425 be used in Qt Creator to select only documentation from LLVM when browsing
426 through all the help files that you might have loaded. This option is only
427 useful in combination with ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON``;
428 otherwise it has no effect.
430 .. _Qt Help Project: http://qt-project.org/doc/qt-4.8/qthelpproject.html#custom-filters
432 **LLVM_DOXYGEN_QHELPGENERATOR_PATH**:STRING
433 The path to the ``qhelpgenerator`` executable. Defaults to whatever CMake's
434 ``find_program()`` can find. This option is only useful in combination with
435 ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON``; otherwise it has no
438 **LLVM_DOXYGEN_SVG**:BOOL
439 Uses .svg files instead of .png files for graphs in the Doxygen output.
442 **LLVM_INSTALL_DOXYGEN_HTML_DIR**:STRING
443 The path to install Doxygen-generated HTML documentation to. This path can
444 either be absolute or relative to the CMAKE_INSTALL_PREFIX. Defaults to
445 `share/doc/llvm/doxygen-html`.
447 **LLVM_ENABLE_SPHINX**:BOOL
448 If specified, CMake will search for the ``sphinx-build`` executable and will make
449 the ``SPHINX_OUTPUT_HTML`` and ``SPHINX_OUTPUT_MAN`` CMake options available.
452 **SPHINX_EXECUTABLE**:STRING
453 The path to the ``sphinx-build`` executable detected by CMake.
455 **SPHINX_OUTPUT_HTML**:BOOL
456 If enabled (and ``LLVM_ENABLE_SPHINX`` is enabled) then the targets for
457 building the documentation as html are added (but not built by default unless
458 ``LLVM_BUILD_DOCS`` is enabled). There is a target for each project in the
459 source tree that uses sphinx (e.g. ``docs-llvm-html``, ``docs-clang-html``
460 and ``docs-lld-html``). Defaults to ON.
462 **SPHINX_OUTPUT_MAN**:BOOL
463 If enabled (and ``LLVM_ENABLE_SPHINX`` is enabled) the targets for building
464 the man pages are added (but not built by default unless ``LLVM_BUILD_DOCS``
465 is enabled). Currently the only target added is ``docs-llvm-man``. Defaults
468 **SPHINX_WARNINGS_AS_ERRORS**:BOOL
469 If enabled then sphinx documentation warnings will be treated as
470 errors. Defaults to ON.
472 **LLVM_INSTALL_SPHINX_HTML_DIR**:STRING
473 The path to install Sphinx-generated HTML documentation to. This path can
474 either be absolute or relative to the CMAKE_INSTALL_PREFIX. Defaults to
475 `share/doc/llvm/html`.
477 **LLVM_INSTALL_OCAMLDOC_HTML_DIR**:STRING
478 The path to install OCamldoc-generated HTML documentation to. This path can
479 either be absolute or relative to the CMAKE_INSTALL_PREFIX. Defaults to
480 `share/doc/llvm/ocaml-html`.
482 **LLVM_CREATE_XCODE_TOOLCHAIN**:BOOL
483 OS X Only: If enabled CMake will generate a target named
484 'install-xcode-toolchain'. This target will create a directory at
485 $CMAKE_INSTALL_PREFIX/Toolchains containing an xctoolchain directory which can
486 be used to override the default system tools.
488 **LLVM_BUILD_LLVM_DYLIB**:BOOL
489 If enabled, the target for building the libLLVM shared library is added.
490 This library contains all of LLVM's components in a single shared library.
491 Defaults to OFF. This cannot be used in conjunction with BUILD_SHARED_LIBS.
492 Tools will only be linked to the libLLVM shared library if LLVM_LINK_LLVM_DYLIB
494 The components in the library can be customised by setting LLVM_DYLIB_COMPONENTS
495 to a list of the desired components.
497 **LLVM_LINK_LLVM_DYLIB**:BOOL
498 If enabled, tools will be linked with the libLLVM shared library. Defaults
499 to OFF. Setting LLVM_LINK_LLVM_DYLIB to ON also sets LLVM_BUILD_LLVM_DYLIB
502 **BUILD_SHARED_LIBS**:BOOL
503 Flag indicating if each LLVM component (e.g. Support) is built as a shared
504 library (ON) or as a static library (OFF). Its default value is OFF. On
505 Windows, shared libraries may be used when building with MinGW, including
506 mingw-w64, but not when building with the Microsoft toolchain.
508 .. note:: BUILD_SHARED_LIBS is only recommended for use by LLVM developers.
509 If you want to build LLVM as a shared library, you should use the
510 ``LLVM_BUILD_LLVM_DYLIB`` option.
512 **LLVM_OPTIMIZED_TABLEGEN**:BOOL
513 If enabled and building a debug or asserts build the CMake build system will
514 generate a Release build tree to build a fully optimized tablegen for use
515 during the build. Enabling this option can significantly speed up build times
516 especially when building LLVM in Debug configurations.
521 Recently LLVM and Clang have been adding some more complicated build system
522 features. Utilizing these new features often involves a complicated chain of
523 CMake variables passed on the command line. Clang provides a collection of CMake
524 cache scripts to make these features more approachable.
526 CMake cache files are utilized using CMake's -C flag:
528 .. code-block:: console
530 $ cmake -C <path to cache file> <path to sources>
532 CMake cache scripts are processed in an isolated scope, only cached variables
533 remain set when the main configuration runs. CMake cached variables do not reset
534 variables that are already set unless the FORCE option is specified.
536 A few notes about CMake Caches:
538 - Order of command line arguments is important
540 - -D arguments specified before -C are set before the cache is processed and
541 can be read inside the cache file
542 - -D arguments specified after -C are set after the cache is processed and
543 are unset inside the cache file
545 - All -D arguments will override cache file settings
546 - CMAKE_TOOLCHAIN_FILE is evaluated after both the cache file and the command
548 - It is recommended that all -D options should be specified *before* -C
550 For more information about some of the advanced build configurations supported
551 via Cache files see :doc:`AdvancedBuilds`.
553 Executing the test suite
554 ========================
556 Testing is performed when the *check-all* target is built. For instance, if you are
557 using Makefiles, execute this command in the root of your build directory:
559 .. code-block:: console
563 On Visual Studio, you may run tests by building the project "check-all".
564 For more information about testing, see the :doc:`TestingGuide`.
569 See `this wiki page <http://www.vtk.org/Wiki/CMake_Cross_Compiling>`_ for
570 generic instructions on how to cross-compile with CMake. It goes into detailed
571 explanations and may seem daunting, but it is not. On the wiki page there are
572 several examples including toolchain files. Go directly to `this section
573 <http://www.vtk.org/Wiki/CMake_Cross_Compiling#Information_how_to_set_up_various_cross_compiling_toolchains>`_
574 for a quick solution.
576 Also see the `LLVM-specific variables`_ section for variables used when
579 Embedding LLVM in your project
580 ==============================
582 From LLVM 3.5 onwards both the CMake and autoconf/Makefile build systems export
583 LLVM libraries as importable CMake targets. This means that clients of LLVM can
584 now reliably use CMake to develop their own LLVM-based projects against an
585 installed version of LLVM regardless of how it was built.
587 Here is a simple example of a CMakeLists.txt file that imports the LLVM libraries
588 and uses them to build a simple application ``simple-tool``.
590 .. code-block:: cmake
592 cmake_minimum_required(VERSION 3.4.3)
593 project(SimpleProject)
595 find_package(LLVM REQUIRED CONFIG)
597 message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
598 message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
600 # Set your project compile flags.
601 # E.g. if using the C++ header files
602 # you will need to enable C++11 support
605 include_directories(${LLVM_INCLUDE_DIRS})
606 add_definitions(${LLVM_DEFINITIONS})
608 # Now build our tools
609 add_executable(simple-tool tool.cpp)
611 # Find the libraries that correspond to the LLVM components
612 # that we wish to use
613 llvm_map_components_to_libnames(llvm_libs support core irreader)
615 # Link against LLVM libraries
616 target_link_libraries(simple-tool ${llvm_libs})
618 The ``find_package(...)`` directive when used in CONFIG mode (as in the above
619 example) will look for the ``LLVMConfig.cmake`` file in various locations (see
620 cmake manual for details). It creates a ``LLVM_DIR`` cache entry to save the
621 directory where ``LLVMConfig.cmake`` is found or allows the user to specify the
622 directory (e.g. by passing ``-DLLVM_DIR=/usr/lib/cmake/llvm`` to
623 the ``cmake`` command or by setting it directly in ``ccmake`` or ``cmake-gui``).
625 This file is available in two different locations.
627 * ``<INSTALL_PREFIX>/lib/cmake/llvm/LLVMConfig.cmake`` where
628 ``<INSTALL_PREFIX>`` is the install prefix of an installed version of LLVM.
629 On Linux typically this is ``/usr/lib/cmake/llvm/LLVMConfig.cmake``.
631 * ``<LLVM_BUILD_ROOT>/lib/cmake/llvm/LLVMConfig.cmake`` where
632 ``<LLVM_BUILD_ROOT>`` is the root of the LLVM build tree. **Note: this is only
633 available when building LLVM with CMake.**
635 If LLVM is installed in your operating system's normal installation prefix (e.g.
636 on Linux this is usually ``/usr/``) ``find_package(LLVM ...)`` will
637 automatically find LLVM if it is installed correctly. If LLVM is not installed
638 or you wish to build directly against the LLVM build tree you can use
639 ``LLVM_DIR`` as previously mentioned.
641 The ``LLVMConfig.cmake`` file sets various useful variables. Notable variables
645 The path to the LLVM CMake directory (i.e. the directory containing
649 A list of preprocessor defines that should be used when building against LLVM.
651 ``LLVM_ENABLE_ASSERTIONS``
652 This is set to ON if LLVM was built with assertions, otherwise OFF.
655 This is set to ON if LLVM was built with exception handling (EH) enabled,
659 This is set to ON if LLVM was built with run time type information (RTTI),
662 ``LLVM_INCLUDE_DIRS``
663 A list of include paths to directories containing LLVM header files.
665 ``LLVM_PACKAGE_VERSION``
666 The LLVM version. This string can be used with CMake conditionals, e.g., ``if
667 (${LLVM_PACKAGE_VERSION} VERSION_LESS "3.5")``.
669 ``LLVM_TOOLS_BINARY_DIR``
670 The path to the directory containing the LLVM tools (e.g. ``llvm-as``).
672 Notice that in the above example we link ``simple-tool`` against several LLVM
673 libraries. The list of libraries is determined by using the
674 ``llvm_map_components_to_libnames()`` CMake function. For a list of available
675 components look at the output of running ``llvm-config --components``.
677 Note that for LLVM < 3.5 ``llvm_map_components_to_libraries()`` was
678 used instead of ``llvm_map_components_to_libnames()``. This is now deprecated
679 and will be removed in a future version of LLVM.
681 .. _cmake-out-of-source-pass:
683 Developing LLVM passes out of source
684 ------------------------------------
686 It is possible to develop LLVM passes out of LLVM's source tree (i.e. against an
687 installed or built LLVM). An example of a project layout is provided below.
700 Contents of ``<project dir>/CMakeLists.txt``:
702 .. code-block:: cmake
704 find_package(LLVM REQUIRED CONFIG)
706 add_definitions(${LLVM_DEFINITIONS})
707 include_directories(${LLVM_INCLUDE_DIRS})
709 add_subdirectory(<pass name>)
711 Contents of ``<project dir>/<pass name>/CMakeLists.txt``:
713 .. code-block:: cmake
715 add_library(LLVMPassname MODULE Pass.cpp)
717 Note if you intend for this pass to be merged into the LLVM source tree at some
718 point in the future it might make more sense to use LLVM's internal
719 ``add_llvm_loadable_module`` function instead by...
722 Adding the following to ``<project dir>/CMakeLists.txt`` (after
723 ``find_package(LLVM ...)``)
725 .. code-block:: cmake
727 list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
730 And then changing ``<project dir>/<pass name>/CMakeLists.txt`` to
732 .. code-block:: cmake
734 add_llvm_loadable_module(LLVMPassname
738 When you are done developing your pass, you may wish to integrate it
739 into the LLVM source tree. You can achieve it in two easy steps:
741 #. Copying ``<pass name>`` folder into ``<LLVM root>/lib/Transform`` directory.
743 #. Adding ``add_subdirectory(<pass name>)`` line into
744 ``<LLVM root>/lib/Transform/CMakeLists.txt``.
746 Compiler/Platform-specific topics
747 =================================
749 Notes for specific compilers and/or platforms.
754 **LLVM_COMPILER_JOBS**:STRING
755 Specifies the maximum number of parallel compiler jobs to use per project
756 when building with msbuild or Visual Studio. Only supported for the Visual
757 Studio 2010 CMake generator. 0 means use all processors. Default is 0.