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.
189 Be aware that Release and RelWithDebInfo use different optimization levels on
192 **CMAKE_INSTALL_PREFIX**:PATH
193 Path where LLVM will be installed if "make install" is invoked or the
194 "install" target is built.
196 **LLVM_LIBDIR_SUFFIX**:STRING
197 Extra suffix to append to the directory where libraries are to be
198 installed. On a 64-bit architecture, one could use ``-DLLVM_LIBDIR_SUFFIX=64``
199 to install libraries to ``/usr/lib64``.
201 **CMAKE_C_FLAGS**:STRING
202 Extra flags to use when compiling C source files.
204 **CMAKE_CXX_FLAGS**:STRING
205 Extra flags to use when compiling C++ source files.
207 .. _LLVM-specific variables:
209 LLVM-specific variables
210 -----------------------
212 **LLVM_TARGETS_TO_BUILD**:STRING
213 Semicolon-separated list of targets to build, or *all* for building all
214 targets. Case-sensitive. Defaults to *all*. Example:
215 ``-DLLVM_TARGETS_TO_BUILD="X86;PowerPC"``.
217 **LLVM_BUILD_TOOLS**:BOOL
218 Build LLVM tools. Defaults to ON. Targets for building each tool are generated
219 in any case. You can build a tool separately by invoking its target. For
220 example, you can build *llvm-as* with a Makefile-based system by executing *make
221 llvm-as* at the root of your build directory.
223 **LLVM_INCLUDE_TOOLS**:BOOL
224 Generate build targets for the LLVM tools. Defaults to ON. You can use this
225 option to disable the generation of build targets for the LLVM tools.
227 **LLVM_INSTALL_BINUTILS_SYMLINKS**:BOOL
228 Install symlinks from the binutils tool names to the corresponding LLVM tools.
229 For example, ar will be symlinked to llvm-ar.
231 **LLVM_INSTALL_CCTOOLS_SYMLINKS**:BOOL
232 Install symliks from the cctools tool names to the corresponding LLVM tools.
233 For example, dsymutil will be symlinked to llvm-dsymutil.
235 **LLVM_BUILD_EXAMPLES**:BOOL
236 Build LLVM examples. Defaults to OFF. Targets for building each example are
237 generated in any case. See documentation for *LLVM_BUILD_TOOLS* above for more
240 **LLVM_INCLUDE_EXAMPLES**:BOOL
241 Generate build targets for the LLVM examples. Defaults to ON. You can use this
242 option to disable the generation of build targets for the LLVM examples.
244 **LLVM_BUILD_TESTS**:BOOL
245 Build LLVM unit tests. Defaults to OFF. Targets for building each unit test
246 are generated in any case. You can build a specific unit test using the
247 targets defined under *unittests*, such as ADTTests, IRTests, SupportTests,
248 etc. (Search for ``add_llvm_unittest`` in the subdirectories of *unittests*
249 for a complete list of unit tests.) It is possible to build all unit tests
250 with the target *UnitTests*.
252 **LLVM_INCLUDE_TESTS**:BOOL
253 Generate build targets for the LLVM unit tests. Defaults to ON. You can use
254 this option to disable the generation of build targets for the LLVM unit
257 **LLVM_APPEND_VC_REV**:BOOL
258 Embed version control revision info (svn revision number or Git revision id).
259 The version info is provided by the ``LLVM_REVISION`` macro in
260 ``llvm/include/llvm/Support/VCSRevision.h``. Developers using git who don't
261 need revision info can disable this option to avoid re-linking most binaries
262 after a branch switch. Defaults to ON.
264 **LLVM_ENABLE_THREADS**:BOOL
265 Build with threads support, if available. Defaults to ON.
267 **LLVM_ENABLE_CXX1Y**:BOOL
268 Build in C++1y mode, if available. Defaults to OFF.
270 **LLVM_ENABLE_ASSERTIONS**:BOOL
271 Enables code assertions. Defaults to ON if and only if ``CMAKE_BUILD_TYPE``
274 **LLVM_ENABLE_EH**:BOOL
275 Build LLVM with exception-handling support. This is necessary if you wish to
276 link against LLVM libraries and make use of C++ exceptions in your own code
277 that need to propagate through LLVM code. Defaults to OFF.
279 **LLVM_ENABLE_EXPENSIVE_CHECKS**:BOOL
280 Enable additional time/memory expensive checking. Defaults to OFF.
282 **LLVM_ENABLE_PIC**:BOOL
283 Add the ``-fPIC`` flag to the compiler command-line, if the compiler supports
284 this flag. Some systems, like Windows, do not need this flag. Defaults to ON.
286 **LLVM_ENABLE_RTTI**:BOOL
287 Build LLVM with run-time type information. Defaults to OFF.
289 **LLVM_ENABLE_WARNINGS**:BOOL
290 Enable all compiler warnings. Defaults to ON.
292 **LLVM_ENABLE_PEDANTIC**:BOOL
293 Enable pedantic mode. This disables compiler-specific extensions, if
294 possible. Defaults to ON.
296 **LLVM_ENABLE_WERROR**:BOOL
297 Stop and fail the build, if a compiler warning is triggered. Defaults to OFF.
299 **LLVM_ABI_BREAKING_CHECKS**:STRING
300 Used to decide if LLVM should be built with ABI breaking checks or
301 not. Allowed values are `WITH_ASSERTS` (default), `FORCE_ON` and
302 `FORCE_OFF`. `WITH_ASSERTS` turns on ABI breaking checks in an
303 assertion enabled build. `FORCE_ON` (`FORCE_OFF`) turns them on
304 (off) irrespective of whether normal (`NDEBUG`-based) assertions are
305 enabled or not. A version of LLVM built with ABI breaking checks
306 is not ABI compatible with a version built without it.
308 **LLVM_BUILD_32_BITS**:BOOL
309 Build 32-bit executables and libraries on 64-bit systems. This option is
310 available only on some 64-bit Unix systems. Defaults to OFF.
312 **LLVM_TARGET_ARCH**:STRING
313 LLVM target to use for native code generation. This is required for JIT
314 generation. It defaults to "host", meaning that it shall pick the architecture
315 of the machine where LLVM is being built. If you are cross-compiling, set it
316 to the target architecture name.
318 **LLVM_TABLEGEN**:STRING
319 Full path to a native TableGen executable (usually named ``llvm-tblgen``). This is
320 intended for cross-compiling: if the user sets this variable, no native
321 TableGen will be created.
323 **LLVM_LIT_ARGS**:STRING
324 Arguments given to lit. ``make check`` and ``make clang-test`` are affected.
325 By default, ``'-sv --no-progress-bar'`` on Visual C++ and Xcode, ``'-sv'`` on
328 **LLVM_LIT_TOOLS_DIR**:PATH
329 The path to GnuWin32 tools for tests. Valid on Windows host. Defaults to
330 the empty string, in which case lit will look for tools needed for tests
331 (e.g. ``grep``, ``sort``, etc.) in your %PATH%. If GnuWin32 is not in your
332 %PATH%, then you can set this variable to the GnuWin32 directory so that
333 lit can find tools needed for tests in that directory.
335 **LLVM_ENABLE_FFI**:BOOL
336 Indicates whether the LLVM Interpreter will be linked with the Foreign Function
337 Interface library (libffi) in order to enable calling external functions.
338 If the library or its headers are installed in a custom
339 location, you can also set the variables FFI_INCLUDE_DIR and
340 FFI_LIBRARY_DIR to the directories where ffi.h and libffi.so can be found,
341 respectively. Defaults to OFF.
343 **LLVM_EXTERNAL_{CLANG,LLD,POLLY}_SOURCE_DIR**:PATH
344 These variables specify the path to the source directory for the external
345 LLVM projects Clang, lld, and Polly, respectively, relative to the top-level
346 source directory. If the in-tree subdirectory for an external project
347 exists (e.g., llvm/tools/clang for Clang), then the corresponding variable
348 will not be used. If the variable for an external project does not point
349 to a valid path, then that project will not be built.
351 **LLVM_ENABLE_PROJECTS**:STRING
352 Semicolon-separated list of projects to build, or *all* for building all
353 (clang, libcxx, libcxxabi, lldb, compiler-rt, lld, polly) projects.
354 This flag assumes that projects are checked out side-by-side and not nested,
355 i.e. clang needs to be in parallel of llvm instead of nested in `llvm/tools`.
356 This feature allows to have one build for only LLVM and another for clang+llvm
357 using the same source checkout.
359 **LLVM_EXTERNAL_PROJECTS**:STRING
360 Semicolon-separated list of additional external projects to build as part of
361 llvm. For each project LLVM_EXTERNAL_<NAME>_SOURCE_DIR have to be specified
362 with the path for the source code of the project. Example:
363 ``-DLLVM_EXTERNAL_PROJECTS="Foo;Bar"
364 -DLLVM_EXTERNAL_FOO_SOURCE_DIR=/src/foo
365 -DLLVM_EXTERNAL_BAR_SOURCE_DIR=/src/bar``.
367 **LLVM_USE_OPROFILE**:BOOL
368 Enable building OProfile JIT support. Defaults to OFF.
370 **LLVM_PROFDATA_FILE**:PATH
371 Path to a profdata file to pass into clang's -fprofile-instr-use flag. This
372 can only be specified if you're building with clang.
374 **LLVM_USE_INTEL_JITEVENTS**:BOOL
375 Enable building support for Intel JIT Events API. Defaults to OFF.
377 **LLVM_ENABLE_LIBPFM**:BOOL
378 Enable building with libpfm to support hardware counter measurements in LLVM
382 **LLVM_ENABLE_ZLIB**:BOOL
383 Enable building with zlib to support compression/uncompression in LLVM tools.
386 **LLVM_ENABLE_DIA_SDK**:BOOL
387 Enable building with MSVC DIA SDK for PDB debugging support. Available
388 only with MSVC. Defaults to ON.
390 **LLVM_USE_SANITIZER**:STRING
391 Define the sanitizer used to build LLVM binaries and tests. Possible values
392 are ``Address``, ``Memory``, ``MemoryWithOrigins``, ``Undefined``, ``Thread``,
393 and ``Address;Undefined``. Defaults to empty string.
395 **LLVM_ENABLE_LTO**:STRING
396 Add ``-flto`` or ``-flto=`` flags to the compile and link command
397 lines, enabling link-time optimization. Possible values are ``Off``,
398 ``On``, ``Thin`` and ``Full``. Defaults to OFF.
400 **LLVM_USE_LINKER**:STRING
401 Add ``-fuse-ld={name}`` to the link invocation. The possible value depend on
402 your compiler, for clang the value can be an absolute path to your custom
403 linker, otherwise clang will prefix the name with ``ld.`` and apply its usual
404 search. For example to link LLVM with the Gold linker, cmake can be invoked
405 with ``-DLLVM_USE_LINKER=gold``.
407 **LLVM_ENABLE_LLD**:BOOL
408 This option is equivalent to `-DLLVM_USE_LINKER=lld`, except during a 2-stage
409 build where a dependency is added from the first stage to the second ensuring
410 that lld is built before stage2 begins.
412 **LLVM_PARALLEL_COMPILE_JOBS**:STRING
413 Define the maximum number of concurrent compilation jobs.
415 **LLVM_PARALLEL_LINK_JOBS**:STRING
416 Define the maximum number of concurrent link jobs.
418 **LLVM_BUILD_DOCS**:BOOL
419 Adds all *enabled* documentation targets (i.e. Doxgyen and Sphinx targets) as
420 dependencies of the default build targets. This results in all of the (enabled)
421 documentation targets being as part of a normal build. If the ``install``
422 target is run then this also enables all built documentation targets to be
423 installed. Defaults to OFF. To enable a particular documentation target, see
424 see LLVM_ENABLE_SPHINX and LLVM_ENABLE_DOXYGEN.
426 **LLVM_ENABLE_DOXYGEN**:BOOL
427 Enables the generation of browsable HTML documentation using doxygen.
430 **LLVM_ENABLE_DOXYGEN_QT_HELP**:BOOL
431 Enables the generation of a Qt Compressed Help file. Defaults to OFF.
432 This affects the make target ``doxygen-llvm``. When enabled, apart from
433 the normal HTML output generated by doxygen, this will produce a QCH file
434 named ``org.llvm.qch``. You can then load this file into Qt Creator.
435 This option is only useful in combination with ``-DLLVM_ENABLE_DOXYGEN=ON``;
436 otherwise this has no effect.
438 **LLVM_DOXYGEN_QCH_FILENAME**:STRING
439 The filename of the Qt Compressed Help file that will be generated when
440 ``-DLLVM_ENABLE_DOXYGEN=ON`` and
441 ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON`` are given. Defaults to
443 This option is only useful in combination with
444 ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON``;
445 otherwise it has no effect.
447 **LLVM_DOXYGEN_QHP_NAMESPACE**:STRING
448 Namespace under which the intermediate Qt Help Project file lives. See `Qt
450 for more information. Defaults to "org.llvm". This option is only useful in
451 combination with ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON``; otherwise
454 **LLVM_DOXYGEN_QHP_CUST_FILTER_NAME**:STRING
455 See `Qt Help Project`_ for
456 more information. Defaults to the CMake variable ``${PACKAGE_STRING}`` which
457 is a combination of the package name and version string. This filter can then
458 be used in Qt Creator to select only documentation from LLVM when browsing
459 through all the help files that you might have loaded. This option is only
460 useful in combination with ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON``;
461 otherwise it has no effect.
463 .. _Qt Help Project: http://qt-project.org/doc/qt-4.8/qthelpproject.html#custom-filters
465 **LLVM_DOXYGEN_QHELPGENERATOR_PATH**:STRING
466 The path to the ``qhelpgenerator`` executable. Defaults to whatever CMake's
467 ``find_program()`` can find. This option is only useful in combination with
468 ``-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON``; otherwise it has no
471 **LLVM_DOXYGEN_SVG**:BOOL
472 Uses .svg files instead of .png files for graphs in the Doxygen output.
475 **LLVM_INSTALL_DOXYGEN_HTML_DIR**:STRING
476 The path to install Doxygen-generated HTML documentation to. This path can
477 either be absolute or relative to the CMAKE_INSTALL_PREFIX. Defaults to
478 `share/doc/llvm/doxygen-html`.
480 **LLVM_ENABLE_SPHINX**:BOOL
481 If specified, CMake will search for the ``sphinx-build`` executable and will make
482 the ``SPHINX_OUTPUT_HTML`` and ``SPHINX_OUTPUT_MAN`` CMake options available.
485 **SPHINX_EXECUTABLE**:STRING
486 The path to the ``sphinx-build`` executable detected by CMake.
487 For installation instructions, see
488 http://www.sphinx-doc.org/en/latest/install.html
490 **SPHINX_OUTPUT_HTML**:BOOL
491 If enabled (and ``LLVM_ENABLE_SPHINX`` is enabled) then the targets for
492 building the documentation as html are added (but not built by default unless
493 ``LLVM_BUILD_DOCS`` is enabled). There is a target for each project in the
494 source tree that uses sphinx (e.g. ``docs-llvm-html``, ``docs-clang-html``
495 and ``docs-lld-html``). Defaults to ON.
497 **SPHINX_OUTPUT_MAN**:BOOL
498 If enabled (and ``LLVM_ENABLE_SPHINX`` is enabled) the targets for building
499 the man pages are added (but not built by default unless ``LLVM_BUILD_DOCS``
500 is enabled). Currently the only target added is ``docs-llvm-man``. Defaults
503 **SPHINX_WARNINGS_AS_ERRORS**:BOOL
504 If enabled then sphinx documentation warnings will be treated as
505 errors. Defaults to ON.
507 **LLVM_INSTALL_SPHINX_HTML_DIR**:STRING
508 The path to install Sphinx-generated HTML documentation to. This path can
509 either be absolute or relative to the CMAKE_INSTALL_PREFIX. Defaults to
510 `share/doc/llvm/html`.
512 **LLVM_INSTALL_OCAMLDOC_HTML_DIR**:STRING
513 The path to install OCamldoc-generated HTML documentation to. This path can
514 either be absolute or relative to the CMAKE_INSTALL_PREFIX. Defaults to
515 `share/doc/llvm/ocaml-html`.
517 **LLVM_CREATE_XCODE_TOOLCHAIN**:BOOL
518 OS X Only: If enabled CMake will generate a target named
519 'install-xcode-toolchain'. This target will create a directory at
520 $CMAKE_INSTALL_PREFIX/Toolchains containing an xctoolchain directory which can
521 be used to override the default system tools.
523 **LLVM_BUILD_LLVM_DYLIB**:BOOL
524 If enabled, the target for building the libLLVM shared library is added.
525 This library contains all of LLVM's components in a single shared library.
526 Defaults to OFF. This cannot be used in conjunction with BUILD_SHARED_LIBS.
527 Tools will only be linked to the libLLVM shared library if LLVM_LINK_LLVM_DYLIB
529 The components in the library can be customised by setting LLVM_DYLIB_COMPONENTS
530 to a list of the desired components.
532 **LLVM_LINK_LLVM_DYLIB**:BOOL
533 If enabled, tools will be linked with the libLLVM shared library. Defaults
534 to OFF. Setting LLVM_LINK_LLVM_DYLIB to ON also sets LLVM_BUILD_LLVM_DYLIB
537 **BUILD_SHARED_LIBS**:BOOL
538 Flag indicating if each LLVM component (e.g. Support) is built as a shared
539 library (ON) or as a static library (OFF). Its default value is OFF. On
540 Windows, shared libraries may be used when building with MinGW, including
541 mingw-w64, but not when building with the Microsoft toolchain.
543 .. note:: BUILD_SHARED_LIBS is only recommended for use by LLVM developers.
544 If you want to build LLVM as a shared library, you should use the
545 ``LLVM_BUILD_LLVM_DYLIB`` option.
547 **LLVM_OPTIMIZED_TABLEGEN**:BOOL
548 If enabled and building a debug or asserts build the CMake build system will
549 generate a Release build tree to build a fully optimized tablegen for use
550 during the build. Enabling this option can significantly speed up build times
551 especially when building LLVM in Debug configurations.
553 **LLVM_REVERSE_ITERATION**:BOOL
554 If enabled, all supported unordered llvm containers would be iterated in
555 reverse order. This is useful for uncovering non-determinism caused by
556 iteration of unordered containers.
558 **LLVM_BUILD_INSTRUMENTED_COVERAGE**:BOOL
559 If enabled, `source-based code coverage
560 <http://clang.llvm.org/docs/SourceBasedCodeCoverage.html>`_ instrumentation
561 is enabled while building llvm.
563 **LLVM_CCACHE_BUILD**:BOOL
564 If enabled and the ``ccache`` program is available, then LLVM will be
565 built using ``ccache`` to speed up rebuilds of LLVM and its components.
566 Defaults to OFF. The size and location of the cache maintained
567 by ``ccache`` can be adjusted via the LLVM_CCACHE_MAXSIZE and LLVM_CCACHE_DIR
568 options, which are passed to the CCACHE_MAXSIZE and CCACHE_DIR environment
569 variables, respectively.
574 Recently LLVM and Clang have been adding some more complicated build system
575 features. Utilizing these new features often involves a complicated chain of
576 CMake variables passed on the command line. Clang provides a collection of CMake
577 cache scripts to make these features more approachable.
579 CMake cache files are utilized using CMake's -C flag:
581 .. code-block:: console
583 $ cmake -C <path to cache file> <path to sources>
585 CMake cache scripts are processed in an isolated scope, only cached variables
586 remain set when the main configuration runs. CMake cached variables do not reset
587 variables that are already set unless the FORCE option is specified.
589 A few notes about CMake Caches:
591 - Order of command line arguments is important
593 - -D arguments specified before -C are set before the cache is processed and
594 can be read inside the cache file
595 - -D arguments specified after -C are set after the cache is processed and
596 are unset inside the cache file
598 - All -D arguments will override cache file settings
599 - CMAKE_TOOLCHAIN_FILE is evaluated after both the cache file and the command
601 - It is recommended that all -D options should be specified *before* -C
603 For more information about some of the advanced build configurations supported
604 via Cache files see :doc:`AdvancedBuilds`.
606 Executing the test suite
607 ========================
609 Testing is performed when the *check-all* target is built. For instance, if you are
610 using Makefiles, execute this command in the root of your build directory:
612 .. code-block:: console
616 On Visual Studio, you may run tests by building the project "check-all".
617 For more information about testing, see the :doc:`TestingGuide`.
622 See `this wiki page <http://www.vtk.org/Wiki/CMake_Cross_Compiling>`_ for
623 generic instructions on how to cross-compile with CMake. It goes into detailed
624 explanations and may seem daunting, but it is not. On the wiki page there are
625 several examples including toolchain files. Go directly to `this section
626 <http://www.vtk.org/Wiki/CMake_Cross_Compiling#Information_how_to_set_up_various_cross_compiling_toolchains>`_
627 for a quick solution.
629 Also see the `LLVM-specific variables`_ section for variables used when
632 Embedding LLVM in your project
633 ==============================
635 From LLVM 3.5 onwards both the CMake and autoconf/Makefile build systems export
636 LLVM libraries as importable CMake targets. This means that clients of LLVM can
637 now reliably use CMake to develop their own LLVM-based projects against an
638 installed version of LLVM regardless of how it was built.
640 Here is a simple example of a CMakeLists.txt file that imports the LLVM libraries
641 and uses them to build a simple application ``simple-tool``.
643 .. code-block:: cmake
645 cmake_minimum_required(VERSION 3.4.3)
646 project(SimpleProject)
648 find_package(LLVM REQUIRED CONFIG)
650 message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
651 message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
653 # Set your project compile flags.
654 # E.g. if using the C++ header files
655 # you will need to enable C++11 support
658 include_directories(${LLVM_INCLUDE_DIRS})
659 add_definitions(${LLVM_DEFINITIONS})
661 # Now build our tools
662 add_executable(simple-tool tool.cpp)
664 # Find the libraries that correspond to the LLVM components
665 # that we wish to use
666 llvm_map_components_to_libnames(llvm_libs support core irreader)
668 # Link against LLVM libraries
669 target_link_libraries(simple-tool ${llvm_libs})
671 The ``find_package(...)`` directive when used in CONFIG mode (as in the above
672 example) will look for the ``LLVMConfig.cmake`` file in various locations (see
673 cmake manual for details). It creates a ``LLVM_DIR`` cache entry to save the
674 directory where ``LLVMConfig.cmake`` is found or allows the user to specify the
675 directory (e.g. by passing ``-DLLVM_DIR=/usr/lib/cmake/llvm`` to
676 the ``cmake`` command or by setting it directly in ``ccmake`` or ``cmake-gui``).
678 This file is available in two different locations.
680 * ``<INSTALL_PREFIX>/lib/cmake/llvm/LLVMConfig.cmake`` where
681 ``<INSTALL_PREFIX>`` is the install prefix of an installed version of LLVM.
682 On Linux typically this is ``/usr/lib/cmake/llvm/LLVMConfig.cmake``.
684 * ``<LLVM_BUILD_ROOT>/lib/cmake/llvm/LLVMConfig.cmake`` where
685 ``<LLVM_BUILD_ROOT>`` is the root of the LLVM build tree. **Note: this is only
686 available when building LLVM with CMake.**
688 If LLVM is installed in your operating system's normal installation prefix (e.g.
689 on Linux this is usually ``/usr/``) ``find_package(LLVM ...)`` will
690 automatically find LLVM if it is installed correctly. If LLVM is not installed
691 or you wish to build directly against the LLVM build tree you can use
692 ``LLVM_DIR`` as previously mentioned.
694 The ``LLVMConfig.cmake`` file sets various useful variables. Notable variables
698 The path to the LLVM CMake directory (i.e. the directory containing
702 A list of preprocessor defines that should be used when building against LLVM.
704 ``LLVM_ENABLE_ASSERTIONS``
705 This is set to ON if LLVM was built with assertions, otherwise OFF.
708 This is set to ON if LLVM was built with exception handling (EH) enabled,
712 This is set to ON if LLVM was built with run time type information (RTTI),
715 ``LLVM_INCLUDE_DIRS``
716 A list of include paths to directories containing LLVM header files.
718 ``LLVM_PACKAGE_VERSION``
719 The LLVM version. This string can be used with CMake conditionals, e.g., ``if
720 (${LLVM_PACKAGE_VERSION} VERSION_LESS "3.5")``.
722 ``LLVM_TOOLS_BINARY_DIR``
723 The path to the directory containing the LLVM tools (e.g. ``llvm-as``).
725 Notice that in the above example we link ``simple-tool`` against several LLVM
726 libraries. The list of libraries is determined by using the
727 ``llvm_map_components_to_libnames()`` CMake function. For a list of available
728 components look at the output of running ``llvm-config --components``.
730 Note that for LLVM < 3.5 ``llvm_map_components_to_libraries()`` was
731 used instead of ``llvm_map_components_to_libnames()``. This is now deprecated
732 and will be removed in a future version of LLVM.
734 .. _cmake-out-of-source-pass:
736 Developing LLVM passes out of source
737 ------------------------------------
739 It is possible to develop LLVM passes out of LLVM's source tree (i.e. against an
740 installed or built LLVM). An example of a project layout is provided below.
753 Contents of ``<project dir>/CMakeLists.txt``:
755 .. code-block:: cmake
757 find_package(LLVM REQUIRED CONFIG)
759 add_definitions(${LLVM_DEFINITIONS})
760 include_directories(${LLVM_INCLUDE_DIRS})
762 add_subdirectory(<pass name>)
764 Contents of ``<project dir>/<pass name>/CMakeLists.txt``:
766 .. code-block:: cmake
768 add_library(LLVMPassname MODULE Pass.cpp)
770 Note if you intend for this pass to be merged into the LLVM source tree at some
771 point in the future it might make more sense to use LLVM's internal
772 ``add_llvm_loadable_module`` function instead by...
775 Adding the following to ``<project dir>/CMakeLists.txt`` (after
776 ``find_package(LLVM ...)``)
778 .. code-block:: cmake
780 list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
783 And then changing ``<project dir>/<pass name>/CMakeLists.txt`` to
785 .. code-block:: cmake
787 add_llvm_loadable_module(LLVMPassname
791 When you are done developing your pass, you may wish to integrate it
792 into the LLVM source tree. You can achieve it in two easy steps:
794 #. Copying ``<pass name>`` folder into ``<LLVM root>/lib/Transform`` directory.
796 #. Adding ``add_subdirectory(<pass name>)`` line into
797 ``<LLVM root>/lib/Transform/CMakeLists.txt``.
799 Compiler/Platform-specific topics
800 =================================
802 Notes for specific compilers and/or platforms.
807 **LLVM_COMPILER_JOBS**:STRING
808 Specifies the maximum number of parallel compiler jobs to use per project
809 when building with msbuild or Visual Studio. Only supported for the Visual
810 Studio 2010 CMake generator. 0 means use all processors. Default is 0.