Building LLVM with CMake
CMake is a cross-platform build-generator tool. CMake
does not build the project, it generates the files needed by your build tool
(GNU make, Visual Studio, etc) for building LLVM.
If you are really anxious about getting a functional LLVM build, go to the
Quick start section. If you are a CMake novice, start on Basic CMake usage
and then go back to the Quick start once you know what you are doing. The
Options and variables section is a reference for customizing your build. If
you already have experience with CMake, this is the recommended starting point.
We use here the command-line, non-interactive CMake interface.
Download and install
CMake. Version 2.8 is the minimum required.
Open a shell. Your development tools must be reachable from this shell
through the PATH environment variable.
Create a directory for containing the build. It is not supported to build
LLVM on the source directory. cd to this directory:
$ mkdir mybuilddir
$ cd mybuilddir
Execute this command on the shell replacing path/to/llvm/source/root with
the path to the root of your LLVM source tree:
$ cmake path/to/llvm/source/root
CMake will detect your development environment, perform a series of test and
generate the files required for building LLVM. CMake will use default values
for all build parameters. See the Options and variables section for
fine-tuning your build
This can fail if CMake can’t detect your toolset, or if it thinks that the
environment is not sane enough. On this case make sure that the toolset that
you intend to use is the only one reachable from the shell and that the shell
itself is the correct one for you development environment. CMake will refuse
to build MinGW makefiles if you have a POSIX shell reachable through the PATH
environment variable, for instance. You can force CMake to use a given build
tool, see the Usage section.
This section explains basic aspects of CMake, mostly for explaining those
options which you may need on your day-to-day usage.
CMake comes with extensive documentation in the form of html files and on the
cmake executable itself. Execute cmake --help for further help options.
CMake requires to know for which build tool it shall generate files (GNU make,
Visual Studio, Xcode, etc). If not specified on the command line, it tries to
guess it based on you environment. Once identified the build tool, CMake uses
the corresponding Generator for creating files for your build tool. You can
explicitly specify the generator with the command line option -G "Name of the
generator". For knowing the available generators on your platform, execute
This will list the generator’s names at the end of the help text. Generator’s
names are case-sensitive. Example:
$ cmake -G "Visual Studio 11" path/to/llvm/source/root
For a given development platform there can be more than one adequate
generator. If you use Visual Studio “NMake Makefiles” is a generator you can use
for building with NMake. By default, CMake chooses the more specific generator
supported by your development environment. If you want an alternative generator,
you must tell this to CMake with the -G option.
Variables customize how the build will be generated. Options are boolean
variables, with possible values ON/OFF. Options and variables are defined on the
CMake command line like this:
$ cmake -DVARIABLE=value path/to/llvm/source
You can set a variable after the initial CMake invocation for changing its
value. You can also undefine a variable:
$ cmake -UVARIABLE path/to/llvm/source
Variables are stored on the CMake cache. This is a file named CMakeCache.txt
on the root of the build directory. Do not hand-edit it.
Variables are listed here appending its type after a colon. It is correct to
write the variable and the type on the CMake command line:
$ cmake -DVARIABLE:TYPE=value path/to/llvm/source
Here are some of the CMake variables that are used often, along with a
brief explanation and LLVM-specific notes. For full documentation, check the
CMake docs or execute cmake --help-variable VARIABLE_NAME.
- CMAKE_BUILD_TYPE:STRING
- Sets the build type for make based generators. Possible values are
Release, Debug, RelWithDebInfo and MinSizeRel. On systems like Visual Studio
the user sets the build type with the IDE settings.
- CMAKE_INSTALL_PREFIX:PATH
- Path where LLVM will be installed if “make install” is invoked or the
“INSTALL” target is built.
- LLVM_LIBDIR_SUFFIX:STRING
- Extra suffix to append to the directory where libraries are to be
installed. On a 64-bit architecture, one could use -DLLVM_LIBDIR_SUFFIX=64
to install libraries to /usr/lib64.
- CMAKE_C_FLAGS:STRING
- Extra flags to use when compiling C source files.
- CMAKE_CXX_FLAGS:STRING
- Extra flags to use when compiling C++ source files.
- BUILD_SHARED_LIBS:BOOL
- Flag indicating if shared libraries will be built. Its default value is
OFF. Shared libraries are not supported on Windows and not recommended on the
other OSes.
- LLVM_TARGETS_TO_BUILD:STRING
- Semicolon-separated list of targets to build, or all for building all
targets. Case-sensitive. Defaults to all. Example:
-DLLVM_TARGETS_TO_BUILD="X86;PowerPC".
- LLVM_BUILD_TOOLS:BOOL
- Build LLVM tools. Defaults to ON. Targets for building each tool are generated
in any case. You can build an tool separately by invoking its target. For
example, you can build llvm-as with a makefile-based system executing make
llvm-as on the root of your build directory.
- LLVM_INCLUDE_TOOLS:BOOL
- Generate build targets for the LLVM tools. Defaults to ON. You can use that
option for disabling the generation of build targets for the LLVM tools.
- LLVM_BUILD_EXAMPLES:BOOL
- Build LLVM examples. Defaults to OFF. Targets for building each example are
generated in any case. See documentation for LLVM_BUILD_TOOLS above for more
details.
- LLVM_INCLUDE_EXAMPLES:BOOL
- Generate build targets for the LLVM examples. Defaults to ON. You can use that
option for disabling the generation of build targets for the LLVM examples.
- LLVM_BUILD_TESTS:BOOL
- Build LLVM unit tests. Defaults to OFF. Targets for building each unit test
are generated in any case. You can build a specific unit test with the target
UnitTestNameTests (where at this time UnitTestName can be ADT, Analysis,
ExecutionEngine, JIT, Support, Transform, VMCore; see the subdirectories of
unittests for an updated list.) It is possible to build all unit tests with
the target UnitTests.
- LLVM_INCLUDE_TESTS:BOOL
- Generate build targets for the LLVM unit tests. Defaults to ON. You can use
that option for disabling the generation of build targets for the LLVM unit
tests.
- LLVM_APPEND_VC_REV:BOOL
- Append version control revision info (svn revision number or Git revision id)
to LLVM version string (stored in the PACKAGE_VERSION macro). For this to work
cmake must be invoked before the build. Defaults to OFF.
- LLVM_ENABLE_THREADS:BOOL
- Build with threads support, if available. Defaults to ON.
- LLVM_ENABLE_CXX1Y:BOOL
- Build in C++1y mode, if available. Defaults to OFF.
- LLVM_ENABLE_ASSERTIONS:BOOL
- Enables code assertions. Defaults to OFF if and only if CMAKE_BUILD_TYPE
is Release.
- LLVM_ENABLE_EH:BOOL
- Build LLVM with exception handling support. This is necessary if you wish to
link against LLVM libraries and make use of C++ exceptions in your own code
that need to propagate through LLVM code. Defaults to OFF.
- LLVM_ENABLE_PIC:BOOL
- Add the -fPIC flag for the compiler command-line, if the compiler supports
this flag. Some systems, like Windows, do not need this flag. Defaults to ON.
- LLVM_ENABLE_RTTI:BOOL
- Build LLVM with run time type information. Defaults to OFF.
- LLVM_ENABLE_WARNINGS:BOOL
- Enable all compiler warnings. Defaults to ON.
- LLVM_ENABLE_PEDANTIC:BOOL
- Enable pedantic mode. This disables compiler specific extensions, if
possible. Defaults to ON.
- LLVM_ENABLE_WERROR:BOOL
- Stop and fail build, if a compiler warning is triggered. Defaults to OFF.
- LLVM_BUILD_32_BITS:BOOL
- Build 32-bits executables and libraries on 64-bits systems. This option is
available only on some 64-bits unix systems. Defaults to OFF.
- LLVM_TARGET_ARCH:STRING
- LLVM target to use for native code generation. This is required for JIT
generation. It defaults to “host”, meaning that it shall pick the architecture
of the machine where LLVM is being built. If you are cross-compiling, set it
to the target architecture name.
- LLVM_TABLEGEN:STRING
- Full path to a native TableGen executable (usually named tblgen). This is
intended for cross-compiling: if the user sets this variable, no native
TableGen will be created.
- LLVM_LIT_ARGS:STRING
- Arguments given to lit. make check and make clang-test are affected.
By default, '-sv --no-progress-bar' on Visual C++ and Xcode, '-sv' on
others.
- LLVM_LIT_TOOLS_DIR:PATH
- The path to GnuWin32 tools for tests. Valid on Windows host. Defaults to “”,
then Lit seeks tools according to %PATH%. Lit can find tools(eg. grep, sort,
&c) on LLVM_LIT_TOOLS_DIR at first, without specifying GnuWin32 to %PATH%.
- LLVM_ENABLE_FFI:BOOL
- Indicates whether LLVM Interpreter will be linked with Foreign Function
Interface library. If the library or its headers are installed on a custom
location, you can set the variables FFI_INCLUDE_DIR and
FFI_LIBRARY_DIR. Defaults to OFF.
- LLVM_EXTERNAL_{CLANG,LLD,POLLY}_SOURCE_DIR:PATH
- Path to {Clang,lld,Polly}‘s source directory. Defaults to
tools/{clang,lld,polly}. {Clang,lld,Polly} will not be built when it
is empty or it does not point to a valid path.
- LLVM_USE_OPROFILE:BOOL
- Enable building OProfile JIT support. Defaults to OFF
- LLVM_USE_INTEL_JITEVENTS:BOOL
- Enable building support for Intel JIT Events API. Defaults to OFF
- LLVM_ENABLE_ZLIB:BOOL
- Build with zlib to support compression/uncompression in LLVM tools.
Defaults to ON.
- LLVM_USE_SANITIZER:STRING
- Define the sanitizer used to build LLVM binaries and tests. Possible values
are Address, Memory, MemoryWithOrigins and Undefined.
Defaults to empty string.
- LLVM_PARALLEL_COMPILE_JOBS:STRING
- Define the maximum number of concurrent compilation jobs.
- LLVM_PARALLEL_LINK_JOBS:STRING
- Define the maximum number of concurrent link jobs.
- LLVM_BUILD_DOCS:BOOL
- Enables all enabled documentation targets (i.e. Doxgyen and Sphinx targets) to
be built as part of the normal build. If the install target is run then
this also enables all built documentation targets to be installed. Defaults to
OFF.
- LLVM_ENABLE_DOXYGEN:BOOL
- Enables the generation of browsable HTML documentation using doxygen.
Defaults to OFF.
- LLVM_ENABLE_DOXYGEN_QT_HELP:BOOL
- Enables the generation of a Qt Compressed Help file. Defaults to OFF.
This affects the make target doxygen-llvm. When enabled, apart from
the normal HTML output generated by doxygen, this will produce a QCH file
named org.llvm.qch. You can then load this file into Qt Creator.
This option is only useful in combination with -DLLVM_ENABLE_DOXYGEN=ON;
otherwise this has no effect.
- LLVM_DOXYGEN_QCH_FILENAME:STRING
- The filename of the Qt Compressed Help file that will be genrated when
-DLLVM_ENABLE_DOXYGEN=ON and
-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON are given. Defaults to
org.llvm.qch.
This option is only useful in combination with
-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON;
otherwise this has no effect.
- LLVM_DOXYGEN_QHP_NAMESPACE:STRING
- Namespace under which the intermediate Qt Help Project file lives. See Qt
Help Project
for more information. Defaults to “org.llvm”. This option is only useful in
combination with -DLLVM_ENABLE_DOXYGEN_QT_HELP=ON; otherwise
this has no effect.
- LLVM_DOXYGEN_QHP_CUST_FILTER_NAME:STRING
- See Qt Help Project for
more information. Defaults to the CMake variable ${PACKAGE_STRING} which
is a combination of the package name and version string. This filter can then
be used in Qt Creator to select only documentation from LLVM when browsing
through all the help files that you might have loaded. This option is only
useful in combination with -DLLVM_ENABLE_DOXYGEN_QT_HELP=ON;
otherwise this has no effect.
- LLVM_DOXYGEN_QHELPGENERATOR_PATH:STRING
- The path to the qhelpgenerator executable. Defaults to whatever CMake’s
find_program() can find. This option is only useful in combination with
-DLLVM_ENABLE_DOXYGEN_QT_HELP=ON; otherwise this has no
effect.
- LLVM_ENABLE_SPHINX:BOOL
- If enabled CMake will search for the sphinx-build executable and will make
the SPHINX_OUTPUT_HTML and SPHINX_OUTPUT_MAN CMake options available.
Defaults to OFF.
- SPHINX_EXECUTABLE:STRING
- The path to the sphinx-build executable detected by CMake.
- SPHINX_OUTPUT_HTML:BOOL
- If enabled (and LLVM_ENABLE_SPHINX is enabled) then the targets for
building the documentation as html are added (but not built by default unless
LLVM_BUILD_DOCS is enabled). There is a target for each project in the
source tree that uses sphinx (e.g. docs-llvm-html, docs-clang-html
and docs-lld-html). Defaults to ON.
- SPHINX_OUTPUT_MAN:BOOL
- If enabled (and LLVM_ENABLE_SPHINX is enabled) the targets for building
the man pages are added (but not built by default unless LLVM_BUILD_DOCS
is enabled). Currently the only target added is docs-llvm-man. Defaults
to ON.
- SPHINX_WARNINGS_AS_ERRORS:BOOL
- If enabled then sphinx documentation warnings will be treated as
errors. Defaults to ON.
Testing is performed when the check target is built. For instance, if you are
using makefiles, execute this command while on the top level of your build
directory:
On Visual Studio, you may run tests to build the project “check”.
See this wiki page for
generic instructions on how to cross-compile with CMake. It goes into detailed
explanations and may seem daunting, but it is not. On the wiki page there are
several examples including toolchain files. Go directly to this section
for a quick solution.
Also see the LLVM-specific variables section for variables used when
cross-compiling.
From LLVM 3.5 onwards both the CMake and autoconf/Makefile build systems export
LLVM libraries as importable CMake targets. This means that clients of LLVM can
now reliably use CMake to develop their own LLVM based projects against an
installed version of LLVM regardless of how it was built.
Here is a simple example of CMakeLists.txt file that imports the LLVM libraries
and uses them to build a simple application simple-tool.
cmake_minimum_required(VERSION 2.8.8)
project(SimpleProject)
find_package(LLVM REQUIRED CONFIG)
message(STATUS "Found LLVM ${LLVM_PACKAGE_VERSION}")
message(STATUS "Using LLVMConfig.cmake in: ${LLVM_DIR}")
# Set your project compile flags.
# E.g. if using the C++ header files
# you will need to enable C++11 support
# for your compiler.
include_directories(${LLVM_INCLUDE_DIRS})
add_definitions(${LLVM_DEFINITIONS})
# Now build our tools
add_excutable(simple-tool tool.cpp)
# Find the libraries that correspond to the LLVM components
# that we wish to use
llvm_map_components_to_libnames(llvm_libs support core irreader)
# Link against LLVM libraries
target_link_libraries(simple-tool ${llvm_libs})
The find_package(...) directive when used in CONFIG mode (as in the above
example) will look for the LLVMConfig.cmake file in various locations (see
cmake manual for details). It creates a LLVM_DIR cache entry to save the
directory where LLVMConfig.cmake is found or allows the user to specify the
directory (e.g. by passing -DLLVM_DIR=/usr/share/llvm/cmake to
the cmake command or by setting it directly in ccmake or cmake-gui).
This file is available in two different locations.
- <INSTALL_PREFIX>/share/llvm/cmake/LLVMConfig.cmake where
<INSTALL_PREFIX> is the install prefix of an installed version of LLVM.
On Linux typically this is /usr/share/llvm/cmake/LLVMConfig.cmake.
- <LLVM_BUILD_ROOT>/share/llvm/cmake/LLVMConfig.cmake where
<LLVM_BUILD_ROOT> is the root of the LLVM build tree. Note this only
available when building LLVM with CMake
If LLVM is installed in your operating system’s normal installation prefix (e.g.
on Linux this is usually /usr/) find_package(LLVM ...) will
automatically find LLVM if it is installed correctly. If LLVM is not installed
or you wish to build directly against the LLVM build tree you can use
LLVM_DIR as previously mentioned.
The LLVMConfig.cmake file sets various useful variables. Notable variables
include
- LLVM_CMAKE_DIR
- The path to the LLVM CMake directory (i.e. the directory containing
LLVMConfig.cmake).
- LLVM_DEFINITIONS
- A list of preprocessor defines that should be used when building against LLVM.
- LLVM_ENABLE_ASSERTIONS
- This is set to ON if LLVM was built with assertions, otherwise OFF.
- LLVM_ENABLE_EH
- This is set to ON if LLVM was built with exception handling (EH) enabled,
otherwise OFF.
- LLVM_ENABLE_RTTI
- This is set to ON if LLVM was built with run time type information (RTTI),
otherwise OFF.
- LLVM_INCLUDE_DIRS
- A list of include paths to directories containing LLVM header files.
- LLVM_PACKAGE_VERSION
- The LLVM version. This string can be used with CMake conditionals. E.g. if
(${LLVM_PACKAGE_VERSION} VERSION_LESS "3.5").
- LLVM_TOOLS_BINARY_DIR
- The path to the directory containing the LLVM tools (e.g. llvm-as).
Notice that in the above example we link simple-tool against several LLVM
libraries. The list of libraries is determined by using the
llvm_map_components_to_libnames() CMake function. For a list of available
components look at the output of running llvm-config --components.
Note that for LLVM < 3.5 llvm_map_components_to_libraries() was
used instead of llvm_map_components_to_libnames(). This is now deprecated
and will be removed in a future version of LLVM.
It is possible to develop LLVM passes out of LLVM’s source tree (i.e. against an
installed or built LLVM). An example of a project layout is provided below.
<project dir>/
|
CMakeLists.txt
<pass name>/
|
CMakeLists.txt
Pass.cpp
...
Contents of <project dir>/CMakeLists.txt:
find_package(LLVM REQUIRED CONFIG)
add_definitions(${LLVM_DEFINITIONS})
include_directories(${LLVM_INCLUDE_DIRS})
add_subdirectory(<pass name>)
Contents of <project dir>/<pass name>/CMakeLists.txt:
add_library(LLVMPassname MODULE Pass.cpp)
Note if you intend for this pass to be merged into the LLVM source tree at some
point in the future it might make more sense to use LLVM’s internal
add_llvm_loadable_module function instead by...
Adding the following to <project dir>/CMakeLists.txt (after
find_package(LLVM ...))
list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
include(AddLLVM)
And then changing <project dir>/<pass name>/CMakeLists.txt to
add_llvm_loadable_module(LLVMPassname
Pass.cpp
)
When you are done developing your pass, you may wish to integrate it
into LLVM source tree. You can achieve it in two easy steps:
- Copying <pass name> folder into <LLVM root>/lib/Transform directory.
- Adding add_subdirectory(<pass name>) line into
<LLVM root>/lib/Transform/CMakeLists.txt.
