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            <head>

            
              <title>Building LLVM with CMake</title>

            
              <link rel="stylesheet" href="llvm.css" type="text/css">

            
            </head>


            <h1>

            
              Building LLVM with CMake

            
            </h1>


            <ul>

            
              <li><a href="#intro">Introduction</a></li>

            
              <li><a href="#quickstart">Quick start</a></li>

            
              <li><a href="#usage">Basic CMake usage</a>

            
              <li><a href="#options">Options and variables</a>

            
                <ul>

            
                <li><a href="#freccmake">Frequently-used CMake variables</a></li>

            
                <li><a href="#llvmvars">LLVM-specific variables</a></li>

            
              </ul></li>

            
              <li><a href="#testing">Executing the test suite</a>

            
              <li><a href="#cross">Cross compiling</a>

            
              <li><a href="#embedding">Embedding LLVM in your project</a>

            
                <ul>

            
                <li><a href="#passdev">Developing LLVM pass out of source</a></li>

            
              </ul></li>

            
              <li><a href="#specifics">Compiler/Platform specific topics</a>

            
                <ul>

            
                <li><a href="#msvc">Microsoft Visual C++</a></li>

            
              </ul></li>

            
            </ul>


            <div class="doc_author">

            
            <p>Written by <a href="mailto:ofv@wanadoo.es">Oscar Fuentes</a></p>

            
            </div>


            <!-- *********************************************************************** -->

            
            <h2>

            
            <a name="intro">Introduction</a>

            
            </h2>

            
            <!-- *********************************************************************** -->


            <div>


              <p><a href="http://www.cmake.org/">CMake</a> 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.</p>


              <p>If you are really anxious about getting a functional LLVM build,

            
                go to the <a href="#quickstart">Quick start</a> section. If you

            
                are a CMake novice, start on <a href="#usage">Basic CMake

            
                  usage</a> and then go back to the <a href="#quickstart">Quick

            
                  start</a> once you know what you are

            
                doing. The <a href="#options">Options and variables</a> section

            
                is a reference for customizing your build. If you already have

            
                experience with CMake, this is the recommended starting point.

            
            </div>


            <!-- *********************************************************************** -->

            
            <h2>

            
            <a name="quickstart">Quick start</a>

            
            </h2>

            
            <!-- *********************************************************************** -->


            <div>


            <p> We use here the command-line, non-interactive CMake interface </p>


            <ol>


              <li><p><a href="http://www.cmake.org/cmake/resources/software.html">Download</a>

            
                  and install CMake. Version 2.8 is the minimum required.</p>


              <li><p>Open a shell. Your development tools must be reachable from this

            
                  shell through the PATH environment variable.</p>


              <li><p>Create a directory for containing the build. It is not

            
                  supported to build LLVM on the source directory. cd to this

            
                  directory:</p>

            
                <div class="doc_code">

            
                  <p><tt>mkdir mybuilddir</tt></p>

            
                  <p><tt>cd mybuilddir</tt></p>

            
                </div>


              <li><p>Execute this command on the shell

            
                  replacing <i>path/to/llvm/source/root</i> with the path to the

            
                  root of your LLVM source tree:</p>

            
                <div class="doc_code">

            
                  <p><tt>cmake path/to/llvm/source/root</tt></p>

            
                </div>


                <p>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 <a href="#options">Options and variables</a>

            
                  section for fine-tuning your build</p>


                <p>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 <a href="#usage">Usage</a> section.</p>


            </ol>


            </div>


            <!-- *********************************************************************** -->

            
            <h2>

            
              <a name="usage">Basic CMake usage</a>

            
            </h2>

            
            <!-- *********************************************************************** -->


            <div>


              <p>This section explains basic aspects of CMake, mostly for

            
                explaining those options which you may need on your day-to-day

            
                usage.</p>


              <p>CMake comes with extensive documentation in the form of html

            
                files and on the cmake executable itself. Execute <i>cmake

            
                --help</i> for further help options.</p>


              <p>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 <i>Generator</i> for creating files for your build

            
                tool. You can explicitly specify the generator with the command

            
                line option <i>-G "Name of the generator"</i>. For knowing the

            
                available generators on your platform, execute</p>


                <div class="doc_code">

            
                  <p><tt>cmake --help</tt></p>

            
                </div>


                <p>This will list the generator's names at the end of the help

            
                  text. Generator's names are case-sensitive. Example:</p>


                <div class="doc_code">

            
                  <p><tt>cmake -G "Visual Studio 8 2005" path/to/llvm/source/root</tt></p>

            
                </div>


                <p>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 <i>-G</i> option.</p>


                <p>TODO: explain variables and cache. Move explanation here from

            
                  #options section.</p>


            </div>


            <!-- *********************************************************************** -->

            
            <h2>

            
              <a name="options">Options and variables</a>

            
            </h2>

            
            <!-- *********************************************************************** -->


            <div>


              <p>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:</p>


              <div class="doc_code">

            
                <p><tt>cmake -DVARIABLE=value path/to/llvm/source</tt></p>

            
              </div>


              <p>You can set a variable after the initial CMake invocation for

            
                changing its value. You can also undefine a variable:</p>


              <div class="doc_code">

            
                <p><tt>cmake -UVARIABLE path/to/llvm/source</tt></p>

            
              </div>


              <p>Variables are stored on the CMake cache. This is a file

            
                named <tt>CMakeCache.txt</tt> on the root of the build

            
                directory. Do not hand-edit it.</p>


              <p>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:</p>


              <div class="doc_code">

            
                <p><tt>cmake -DVARIABLE:TYPE=value path/to/llvm/source</tt></p>

            
              </div>


            <!-- ======================================================================= -->

            
            <h3>

            
              <a name="freccmake">Frequently-used CMake variables</a>

            
            </h3>


            <div>


            <p>Here are listed 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 <i>cmake

            
              --help-variable VARIABLE_NAME</i>.</p>


            <dl>

            
              <dt><b>CMAKE_BUILD_TYPE</b>:STRING</dt>


              <dd>Sets the build type for <i>make</i> 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.</dd>


              <dt><b>CMAKE_INSTALL_PREFIX</b>:PATH</dt>

            
              <dd>Path where LLVM will be installed if "make install" is invoked

            
                or the "INSTALL" target is built.</dd>


              <dt><b>LLVM_LIBDIR_SUFFIX</b>:STRING</dt>

            
              <dd>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.</dd>


              <dt><b>CMAKE_C_FLAGS</b>:STRING</dt>

            
              <dd>Extra flags to use when compiling C source files.</dd>


              <dt><b>CMAKE_CXX_FLAGS</b>:STRING</dt>

            
              <dd>Extra flags to use when compiling C++ source files.</dd>


              <dt><b>BUILD_SHARED_LIBS</b>:BOOL</dt>

            
              <dd>Flag indicating is shared libraries will be built. Its default

            
                value is OFF. Shared libraries are not supported on Windows and

            
                not recommended in the other OSes.</dd>

            
            </dl>


            </div>


            <!-- ======================================================================= -->

            
            <h3>

            
              <a name="llvmvars">LLVM-specific variables</a>

            
            </h3>


            <div>


            <dl>

            
              <dt><b>LLVM_TARGETS_TO_BUILD</b>:STRING</dt>

            
              <dd>Semicolon-separated list of targets to build, or <i>all</i> for

            
                building all targets. Case-sensitive. For Visual C++ defaults

            
                to <i>X86</i>. On the other cases defaults to <i>all</i>. Example:

            
                <i>-DLLVM_TARGETS_TO_BUILD="X86;PowerPC;Alpha"</i>.</dd>


              <dt><b>LLVM_BUILD_TOOLS</b>:BOOL</dt>

            
              <dd>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 <i>llvm-as</i>

            
                with a makefile-based system executing <i>make llvm-as</i> on the

            
                root of your build directory.</dd>


              <dt><b>LLVM_INCLUDE_TOOLS</b>:BOOL</dt>

            
              <dd>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.</dd>


              <dt><b>LLVM_BUILD_EXAMPLES</b>:BOOL</dt>

            
              <dd>Build LLVM examples. Defaults to OFF. Targets for building each

            
                example are generated in any case. See documentation

            
                for <i>LLVM_BUILD_TOOLS</i> above for more details.</dd>


              <dt><b>LLVM_INCLUDE_EXAMPLES</b>:BOOL</dt>

            
              <dd>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.</dd>


              <dt><b>LLVM_BUILD_TESTS</b>:BOOL</dt>

            
              <dd>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 <i>UnitTestNameTests</i> (where at this

            
                time <i>UnitTestName</i> can be ADT, Analysis, ExecutionEngine,

            
                JIT, Support, Transform, VMCore; see the subdirectories

            
                of <i>unittests</i> for an updated list.) It is possible to build

            
                all unit tests with the target <i>UnitTests</i>.</dd>


              <dt><b>LLVM_INCLUDE_TESTS</b>:BOOL</dt>

            
              <dd>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.</dd>


              <dt><b>LLVM_APPEND_VC_REV</b>:BOOL</dt>

            
              <dd>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.</dd>


              <dt><b>LLVM_ENABLE_THREADS</b>:BOOL</dt>

            
              <dd>Build with threads support, if available. Defaults to ON.</dd>


              <dt><b>LLVM_ENABLE_ASSERTIONS</b>:BOOL</dt>

            
              <dd>Enables code assertions. Defaults to OFF if and only if

            
                CMAKE_BUILD_TYPE is <i>Release</i>.</dd>


              <dt><b>LLVM_ENABLE_PIC</b>:BOOL</dt>

            
              <dd>Add the <i>-fPIC</i> flag for the compiler command-line, if the

            
                compiler supports this flag. Some systems, like Windows, do not

            
                need this flag. Defaults to ON.</dd>


              <dt><b>LLVM_ENABLE_WARNINGS</b>:BOOL</dt>

            
              <dd>Enable all compiler warnings. Defaults to ON.</dd>


              <dt><b>LLVM_ENABLE_PEDANTIC</b>:BOOL</dt>

            
              <dd>Enable pedantic mode. This disable compiler specific extensions, is

            
                possible. Defaults to ON.</dd>


              <dt><b>LLVM_ENABLE_WERROR</b>:BOOL</dt>

            
              <dd>Stop and fail build, if a compiler warning is

            
                triggered. Defaults to OFF.</dd>


              <dt><b>LLVM_BUILD_32_BITS</b>:BOOL</dt>

            
              <dd>Build 32-bits executables and libraries on 64-bits systems. This

            
                option is available only on some 64-bits unix systems. Defaults to

            
                OFF.</dd>


              <dt><b>LLVM_TARGET_ARCH</b>:STRING</dt>

            
              <dd>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.</dd>


              <dt><b>LLVM_TABLEGEN</b>:STRING</dt>

            
              <dd>Full path to a native TableGen executable (usually

            
                named <i>tblgen</i>). This is intented for cross-compiling: if the

            
                user sets this variable, no native TableGen will be created.</dd>


              <dt><b>LLVM_LIT_ARGS</b>:STRING</dt>

            
              <dd>Arguments given to lit.

            
                <tt>make check</tt> and <tt>make clang-test</tt> are affected.

            
                By default, <tt>&quot;-sv --no-progress-bar&quot;</tt>

            
                on Visual C++ and Xcode,

            
                <tt>&quot;-sv&quot;</tt> on others.</dd>


              <dt><b>LLVM_LIT_TOOLS_DIR</b>:PATH</dt>

            
              <dd>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, &amp;c) on LLVM_LIT_TOOLS_DIR at first,

            
                without specifying GnuWin32 to %PATH%.</dd>


              <dt><b>LLVM_ENABLE_FFI</b>:BOOL</dt>

            
              <dd>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.</dd>

            
            </dl>


            </div>


            </div>


            <!-- *********************************************************************** -->

            
            <h2>

            
              <a name="testing">Executing the test suite</a>

            
            </h2>

            
            <!-- *********************************************************************** -->


            <div>


            <p>Testing is performed when the <i>check</i> target is built. For

            
              instance, if you are using makefiles, execute this command while on

            
              the top level of your build directory:</p>


            <div class="doc_code">

            
              <p><tt>make check</tt></p>

            
            </div>


            <p>On Visual Studio, you may run tests to build the project "check".</p>


            </div>


            <!-- *********************************************************************** -->

            
            <h2>

            
              <a name="cross">Cross compiling</a>

            
            </h2>

            
            <!-- *********************************************************************** -->


            <div>


            <p>See <a href="http://www.vtk.org/Wiki/CMake_Cross_Compiling">this

            
                wiki page</a> 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

            
                <a href="http://www.vtk.org/Wiki/CMake_Cross_Compiling#Information_how_to_set_up_various_cross_compiling_toolchains">this

            
                section</a> for a quick solution.</p>


            <p>Also see the <a href="#llvmvars">LLVM-specific variables</a>

            
              section for variables used when cross-compiling.</p>


            </div>


            <!-- *********************************************************************** -->

            
            <h2>

            
              <a name="embedding">Embedding LLVM in your project</a>

            
            </h2>

            
            <!-- *********************************************************************** -->


            <div>


              <p>The most difficult part of adding LLVM to the build of a project

            
                is to determine the set of LLVM libraries corresponding to the set

            
                of required LLVM features. What follows is an example of how to

            
                obtain this information:</p>


              <div class="doc_code">

            
                <pre>

            
                <b># A convenience variable:</b>

            
                set(LLVM_ROOT "" CACHE PATH "Root of LLVM install.")

            
                <b># A bit of a sanity check:</b>

            
                if( NOT EXISTS ${LLVM_ROOT}/include/llvm )

            
                message(FATAL_ERROR "LLVM_ROOT (${LLVM_ROOT}) is not a valid LLVM install")

            
                endif()

            
                <b># We incorporate the CMake features provided by LLVM:</b>

            
                set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${LLVM_ROOT}/share/llvm/cmake")

            
                include(LLVMConfig)

            
                <b># Now set the header and library paths:</b>

            
                include_directories( ${LLVM_INCLUDE_DIRS} )

            
                link_directories( ${LLVM_LIBRARY_DIRS} )

            
                add_definitions( ${LLVM_DEFINITIONS} )

            
                <b># Let's suppose we want to build a JIT compiler with support for

            
                # binary code (no interpreter):</b>

            
                llvm_map_components_to_libraries(REQ_LLVM_LIBRARIES jit native)

            
                <b># Finally, we link the LLVM libraries to our executable:</b>

            
                target_link_libraries(mycompiler ${REQ_LLVM_LIBRARIES})

            
                </pre>

            
              </div>


              <p>This assumes that LLVM_ROOT points to an install of LLVM. The

            
                procedure works too for uninstalled builds although we need to take

            
                care to add an <i>include_directories</i> for the location of the

            
                headers on the LLVM source directory (if we are building

            
                out-of-source.)</p>


              <p>Alternativaly, you can utilize CMake's <i>find_package</i>

            
                functionality. Here is an equivalent variant of snippet shown above:</p>


              <div class="doc_code">

            
                <pre>

            
                find_package(LLVM)


                if( NOT LLVM_FOUND )

            
                  message(FATAL_ERROR "LLVM package can't be found. Set CMAKE_PREFIX_PATH variable to LLVM's installation prefix.")

            
                endif()


                include_directories( ${LLVM_INCLUDE_DIRS} )

            
                link_directories( ${LLVM_LIBRARY_DIRS} )


                llvm_map_components_to_libraries(REQ_LLVM_LIBRARIES jit native)


                target_link_libraries(mycompiler ${REQ_LLVM_LIBRARIES})

            
                </pre>

            
              </div>


            <!-- ======================================================================= -->

            
            <h3>

            
              <a name="passdev">Developing LLVM pass out of source</a>

            
            </h3>


            <div>


              <p>It is possible to develop LLVM passes against installed LLVM.

            
                 An example of project layout provided below:</p>


              <div class="doc_code">

            
                <pre>

            
                  &lt;project dir&gt;/

            
                      |

            
                      CMakeLists.txt

            
                      &lt;pass name&gt;/

            
                          |

            
                          CMakeLists.txt

            
                          Pass.cpp

            
                          ...

            
                </pre>

            
              </div>


              <p>Contents of &lt;project dir&gt;/CMakeLists.txt:</p>


              <div class="doc_code">

            
                <pre>

            
                find_package(LLVM)


                <b># Define add_llvm_* macro's.</b>

            
                include(AddLLVM)


                add_definitions(${LLVM_DEFINITIONS})

            
                include_directories(${LLVM_INCLUDE_DIRS})

            
                link_directories(${LLVM_LIBRARY_DIRS})


                add_subdirectory(&lt;pass name&gt;)

            
                </pre>

            
              </div>


              <p>Contents of &lt;project dir&gt;/&lt;pass name&gt;/CMakeLists.txt:</p>


              <div class="doc_code">

            
                <pre>

            
                add_llvm_loadable_module(LLVMPassname

            
                  Pass.cpp

            
                  )

            
                </pre>

            
              </div>


              <p>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:<br>

            
                 1. Copying &lt;pass name&gt; folder into &lt;LLVM root&gt;/lib/Transform directory.<br>

            
                 2. Adding "add_subdirectory(&lt;pass name&gt;)" line into &lt;LLVM root&gt;/lib/Transform/CMakeLists.txt</p>

            
            </div>

            
            <!-- *********************************************************************** -->


            </div>


            <!-- *********************************************************************** -->

            
            <h2>

            
              <a name="specifics">Compiler/Platform specific topics</a>

            
            </h2>

            
            <!-- *********************************************************************** -->


            <div>


            <p>Notes for specific compilers and/or platforms.</p>


            <h3>

            
              <a name="msvc">Microsoft Visual C++</a>

            
            </h3>


            <div>


            <dl>

            
              <dt><b>LLVM_COMPILER_JOBS</b>:STRING</dt>

            
              <dd>Specifies the maximum number of parallell compiler jobs to use

            
                per project when building with msbuild or Visual Studio. Only supported for

            
                Visual Studio 2008 and Visual Studio 2010 CMake generators. 0 means use all

            
                processors. Default is 0.</dd>

            
            </dl>


            </div>


            </div>


            <!-- *********************************************************************** -->


            <hr>

            
            <address>

            
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              <a href="mailto:ofv@wanadoo.es">Oscar Fuentes</a><br>

            
              <a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>

            
              Last modified: $Date: 2010-08-09 03:59:36 +0100 (Mon, 9 Aug 2010) $

            
            </address>


            </body>

            
            </html>
	<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
	"http://www.w3.org/TR/html4/strict.dtd">
	<html>
	<head>
	<title>Building LLVM with CMake</title>
	<link rel="stylesheet" href="llvm.css" type="text/css">
	</head>

	<h1>
	Building LLVM with CMake
	</h1>

	<ul>
	<li><a href="#intro">Introduction</a></li>
	<li><a href="#quickstart">Quick start</a></li>
	<li><a href="#usage">Basic CMake usage</a>
	<li><a href="#options">Options and variables</a>
	<ul>
	<li><a href="#freccmake">Frequently-used CMake variables</a></li>
	<li><a href="#llvmvars">LLVM-specific variables</a></li>
	</ul></li>
	<li><a href="#testing">Executing the test suite</a>
	<li><a href="#cross">Cross compiling</a>
	<li><a href="#embedding">Embedding LLVM in your project</a>
	<ul>
	<li><a href="#passdev">Developing LLVM pass out of source</a></li>
	</ul></li>
	<li><a href="#specifics">Compiler/Platform specific topics</a>
	<ul>
	<li><a href="#msvc">Microsoft Visual C++</a></li>
	</ul></li>
	</ul>

	<div class="doc_author">
	<p>Written by <a href="mailto:ofv@wanadoo.es">Oscar Fuentes</a></p>
	</div>

	<!-- *********************************************************************** -->
	<h2>
	<a name="intro">Introduction</a>
	</h2>
	<!-- *********************************************************************** -->

	<div>

	<p><a href="http://www.cmake.org/">CMake</a> 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.</p>

	<p>If you are really anxious about getting a functional LLVM build,
	go to the <a href="#quickstart">Quick start</a> section. If you
	are a CMake novice, start on <a href="#usage">Basic CMake
	usage</a> and then go back to the <a href="#quickstart">Quick
	start</a> once you know what you are
	doing. The <a href="#options">Options and variables</a> section
	is a reference for customizing your build. If you already have
	experience with CMake, this is the recommended starting point.
	</div>

	<!-- *********************************************************************** -->
	<h2>
	<a name="quickstart">Quick start</a>
	</h2>
	<!-- *********************************************************************** -->

	<div>

	<p> We use here the command-line, non-interactive CMake interface </p>

	<ol>

	<li><p><a href="http://www.cmake.org/cmake/resources/software.html">Download</a>
	and install CMake. Version 2.8 is the minimum required.</p>

	<li><p>Open a shell. Your development tools must be reachable from this
	shell through the PATH environment variable.</p>

	<li><p>Create a directory for containing the build. It is not
	supported to build LLVM on the source directory. cd to this
	directory:</p>
	<div class="doc_code">
	<p><tt>mkdir mybuilddir</tt></p>
	<p><tt>cd mybuilddir</tt></p>
	</div>

	<li><p>Execute this command on the shell
	replacing <i>path/to/llvm/source/root</i> with the path to the
	root of your LLVM source tree:</p>
	<div class="doc_code">
	<p><tt>cmake path/to/llvm/source/root</tt></p>
	</div>

	<p>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 <a href="#options">Options and variables</a>
	section for fine-tuning your build</p>

	<p>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 <a href="#usage">Usage</a> section.</p>

	</ol>

	</div>

	<!-- *********************************************************************** -->
	<h2>
	<a name="usage">Basic CMake usage</a>
	</h2>
	<!-- *********************************************************************** -->

	<div>

	<p>This section explains basic aspects of CMake, mostly for
	explaining those options which you may need on your day-to-day
	usage.</p>

	<p>CMake comes with extensive documentation in the form of html
	files and on the cmake executable itself. Execute <i>cmake
	--help</i> for further help options.</p>

	<p>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 <i>Generator</i> for creating files for your build
	tool. You can explicitly specify the generator with the command
	line option <i>-G "Name of the generator"</i>. For knowing the
	available generators on your platform, execute</p>

	<div class="doc_code">
	<p><tt>cmake --help</tt></p>
	</div>

	<p>This will list the generator's names at the end of the help
	text. Generator's names are case-sensitive. Example:</p>

	<div class="doc_code">
	<p><tt>cmake -G "Visual Studio 8 2005" path/to/llvm/source/root</tt></p>
	</div>

	<p>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 <i>-G</i> option.</p>

	<p>TODO: explain variables and cache. Move explanation here from
	#options section.</p>

	</div>

	<!-- *********************************************************************** -->
	<h2>
	<a name="options">Options and variables</a>
	</h2>
	<!-- *********************************************************************** -->

	<div>

	<p>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:</p>

	<div class="doc_code">
	<p><tt>cmake -DVARIABLE=value path/to/llvm/source</tt></p>
	</div>

	<p>You can set a variable after the initial CMake invocation for
	changing its value. You can also undefine a variable:</p>

	<div class="doc_code">
	<p><tt>cmake -UVARIABLE path/to/llvm/source</tt></p>
	</div>

	<p>Variables are stored on the CMake cache. This is a file
	named <tt>CMakeCache.txt</tt> on the root of the build
	directory. Do not hand-edit it.</p>

	<p>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:</p>

	<div class="doc_code">
	<p><tt>cmake -DVARIABLE:TYPE=value path/to/llvm/source</tt></p>
	</div>

	<!-- ======================================================================= -->
	<h3>
	<a name="freccmake">Frequently-used CMake variables</a>
	</h3>

	<div>

	<p>Here are listed 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 <i>cmake
	--help-variable VARIABLE_NAME</i>.</p>

	<dl>
	<dt><b>CMAKE_BUILD_TYPE</b>:STRING</dt>

	<dd>Sets the build type for <i>make</i> 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.</dd>

	<dt><b>CMAKE_INSTALL_PREFIX</b>:PATH</dt>
	<dd>Path where LLVM will be installed if "make install" is invoked
	or the "INSTALL" target is built.</dd>

	<dt><b>LLVM_LIBDIR_SUFFIX</b>:STRING</dt>
	<dd>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.</dd>

	<dt><b>CMAKE_C_FLAGS</b>:STRING</dt>
	<dd>Extra flags to use when compiling C source files.</dd>

	<dt><b>CMAKE_CXX_FLAGS</b>:STRING</dt>
	<dd>Extra flags to use when compiling C++ source files.</dd>

	<dt><b>BUILD_SHARED_LIBS</b>:BOOL</dt>
	<dd>Flag indicating is shared libraries will be built. Its default
	value is OFF. Shared libraries are not supported on Windows and
	not recommended in the other OSes.</dd>
	</dl>

	</div>

	<!-- ======================================================================= -->
	<h3>
	<a name="llvmvars">LLVM-specific variables</a>
	</h3>

	<div>

	<dl>
	<dt><b>LLVM_TARGETS_TO_BUILD</b>:STRING</dt>
	<dd>Semicolon-separated list of targets to build, or <i>all</i> for
	building all targets. Case-sensitive. For Visual C++ defaults
	to <i>X86</i>. On the other cases defaults to <i>all</i>. Example:
	<i>-DLLVM_TARGETS_TO_BUILD="X86;PowerPC;Alpha"</i>.</dd>

	<dt><b>LLVM_BUILD_TOOLS</b>:BOOL</dt>
	<dd>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 <i>llvm-as</i>
	with a makefile-based system executing <i>make llvm-as</i> on the
	root of your build directory.</dd>

	<dt><b>LLVM_INCLUDE_TOOLS</b>:BOOL</dt>
	<dd>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.</dd>

	<dt><b>LLVM_BUILD_EXAMPLES</b>:BOOL</dt>
	<dd>Build LLVM examples. Defaults to OFF. Targets for building each
	example are generated in any case. See documentation
	for <i>LLVM_BUILD_TOOLS</i> above for more details.</dd>

	<dt><b>LLVM_INCLUDE_EXAMPLES</b>:BOOL</dt>
	<dd>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.</dd>

	<dt><b>LLVM_BUILD_TESTS</b>:BOOL</dt>
	<dd>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 <i>UnitTestNameTests</i> (where at this
	time <i>UnitTestName</i> can be ADT, Analysis, ExecutionEngine,
	JIT, Support, Transform, VMCore; see the subdirectories
	of <i>unittests</i> for an updated list.) It is possible to build
	all unit tests with the target <i>UnitTests</i>.</dd>

	<dt><b>LLVM_INCLUDE_TESTS</b>:BOOL</dt>
	<dd>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.</dd>

	<dt><b>LLVM_APPEND_VC_REV</b>:BOOL</dt>
	<dd>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.</dd>

	<dt><b>LLVM_ENABLE_THREADS</b>:BOOL</dt>
	<dd>Build with threads support, if available. Defaults to ON.</dd>

	<dt><b>LLVM_ENABLE_ASSERTIONS</b>:BOOL</dt>
	<dd>Enables code assertions. Defaults to OFF if and only if
	CMAKE_BUILD_TYPE is <i>Release</i>.</dd>

	<dt><b>LLVM_ENABLE_PIC</b>:BOOL</dt>
	<dd>Add the <i>-fPIC</i> flag for the compiler command-line, if the
	compiler supports this flag. Some systems, like Windows, do not
	need this flag. Defaults to ON.</dd>

	<dt><b>LLVM_ENABLE_WARNINGS</b>:BOOL</dt>
	<dd>Enable all compiler warnings. Defaults to ON.</dd>

	<dt><b>LLVM_ENABLE_PEDANTIC</b>:BOOL</dt>
	<dd>Enable pedantic mode. This disable compiler specific extensions, is
	possible. Defaults to ON.</dd>

	<dt><b>LLVM_ENABLE_WERROR</b>:BOOL</dt>
	<dd>Stop and fail build, if a compiler warning is
	triggered. Defaults to OFF.</dd>

	<dt><b>LLVM_BUILD_32_BITS</b>:BOOL</dt>
	<dd>Build 32-bits executables and libraries on 64-bits systems. This
	option is available only on some 64-bits unix systems. Defaults to
	OFF.</dd>

	<dt><b>LLVM_TARGET_ARCH</b>:STRING</dt>
	<dd>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.</dd>

	<dt><b>LLVM_TABLEGEN</b>:STRING</dt>
	<dd>Full path to a native TableGen executable (usually
	named <i>tblgen</i>). This is intented for cross-compiling: if the
	user sets this variable, no native TableGen will be created.</dd>

	<dt><b>LLVM_LIT_ARGS</b>:STRING</dt>
	<dd>Arguments given to lit.
	<tt>make check</tt> and <tt>make clang-test</tt> are affected.
	By default, <tt>"-sv --no-progress-bar"</tt>
	on Visual C++ and Xcode,
	<tt>"-sv"</tt> on others.</dd>

	<dt><b>LLVM_LIT_TOOLS_DIR</b>:PATH</dt>
	<dd>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%.</dd>

	<dt><b>LLVM_ENABLE_FFI</b>:BOOL</dt>
	<dd>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.</dd>
	</dl>

	</div>

	</div>

	<!-- *********************************************************************** -->
	<h2>
	<a name="testing">Executing the test suite</a>
	</h2>
	<!-- *********************************************************************** -->

	<div>

	<p>Testing is performed when the <i>check</i> target is built. For
	instance, if you are using makefiles, execute this command while on
	the top level of your build directory:</p>

	<div class="doc_code">
	<p><tt>make check</tt></p>
	</div>

	<p>On Visual Studio, you may run tests to build the project "check".</p>

	</div>

	<!-- *********************************************************************** -->
	<h2>
	<a name="cross">Cross compiling</a>
	</h2>
	<!-- *********************************************************************** -->

	<div>

	<p>See <a href="http://www.vtk.org/Wiki/CMake_Cross_Compiling">this
	wiki page</a> 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
	<a href="http://www.vtk.org/Wiki/CMake_Cross_Compiling#Information_how_to_set_up_various_cross_compiling_toolchains">this
	section</a> for a quick solution.</p>

	<p>Also see the <a href="#llvmvars">LLVM-specific variables</a>
	section for variables used when cross-compiling.</p>

	</div>

	<!-- *********************************************************************** -->
	<h2>
	<a name="embedding">Embedding LLVM in your project</a>
	</h2>
	<!-- *********************************************************************** -->

	<div>

	<p>The most difficult part of adding LLVM to the build of a project
	is to determine the set of LLVM libraries corresponding to the set
	of required LLVM features. What follows is an example of how to
	obtain this information:</p>

	<div class="doc_code">
	<pre>
	<b># A convenience variable:</b>
	set(LLVM_ROOT "" CACHE PATH "Root of LLVM install.")
	<b># A bit of a sanity check:</b>
	if( NOT EXISTS ${LLVM_ROOT}/include/llvm )
	message(FATAL_ERROR "LLVM_ROOT (${LLVM_ROOT}) is not a valid LLVM install")
	endif()
	<b># We incorporate the CMake features provided by LLVM:</b>
	set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${LLVM_ROOT}/share/llvm/cmake")
	include(LLVMConfig)
	<b># Now set the header and library paths:</b>
	include_directories( ${LLVM_INCLUDE_DIRS} )
	link_directories( ${LLVM_LIBRARY_DIRS} )
	add_definitions( ${LLVM_DEFINITIONS} )
	<b># Let's suppose we want to build a JIT compiler with support for
	# binary code (no interpreter):</b>
	llvm_map_components_to_libraries(REQ_LLVM_LIBRARIES jit native)
	<b># Finally, we link the LLVM libraries to our executable:</b>
	target_link_libraries(mycompiler ${REQ_LLVM_LIBRARIES})
	</pre>
	</div>

	<p>This assumes that LLVM_ROOT points to an install of LLVM. The
	procedure works too for uninstalled builds although we need to take
	care to add an <i>include_directories</i> for the location of the
	headers on the LLVM source directory (if we are building
	out-of-source.)</p>

	<p>Alternativaly, you can utilize CMake's <i>find_package</i>
	functionality. Here is an equivalent variant of snippet shown above:</p>

	<div class="doc_code">
	<pre>
	find_package(LLVM)

	if( NOT LLVM_FOUND )
	message(FATAL_ERROR "LLVM package can't be found. Set CMAKE_PREFIX_PATH variable to LLVM's installation prefix.")
	endif()

	include_directories( ${LLVM_INCLUDE_DIRS} )
	link_directories( ${LLVM_LIBRARY_DIRS} )

	llvm_map_components_to_libraries(REQ_LLVM_LIBRARIES jit native)

	target_link_libraries(mycompiler ${REQ_LLVM_LIBRARIES})
	</pre>
	</div>

	<!-- ======================================================================= -->
	<h3>
	<a name="passdev">Developing LLVM pass out of source</a>
	</h3>

	<div>

	<p>It is possible to develop LLVM passes against installed LLVM.
	An example of project layout provided below:</p>

	<div class="doc_code">
	<pre>
	<project dir>/
	\|
	CMakeLists.txt
	<pass name>/
	\|
	CMakeLists.txt
	Pass.cpp
	...
	</pre>
	</div>

	<p>Contents of <project dir>/CMakeLists.txt:</p>

	<div class="doc_code">
	<pre>
	find_package(LLVM)

	<b># Define add_llvm_* macro's.</b>
	include(AddLLVM)

	add_definitions(${LLVM_DEFINITIONS})
	include_directories(${LLVM_INCLUDE_DIRS})
	link_directories(${LLVM_LIBRARY_DIRS})

	add_subdirectory(<pass name>)
	</pre>
	</div>

	<p>Contents of <project dir>/<pass name>/CMakeLists.txt:</p>

	<div class="doc_code">
	<pre>
	add_llvm_loadable_module(LLVMPassname
	Pass.cpp
	)
	</pre>
	</div>

	<p>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:<br>
	1. Copying <pass name> folder into <LLVM root>/lib/Transform directory.<br>
	2. Adding "add_subdirectory(<pass name>)" line into <LLVM root>/lib/Transform/CMakeLists.txt</p>
	</div>
	<!-- *********************************************************************** -->

	</div>

	<!-- *********************************************************************** -->
	<h2>
	<a name="specifics">Compiler/Platform specific topics</a>
	</h2>
	<!-- *********************************************************************** -->

	<div>

	<p>Notes for specific compilers and/or platforms.</p>

	<h3>
	<a name="msvc">Microsoft Visual C++</a>
	</h3>

	<div>

	<dl>
	<dt><b>LLVM_COMPILER_JOBS</b>:STRING</dt>
	<dd>Specifies the maximum number of parallell compiler jobs to use
	per project when building with msbuild or Visual Studio. Only supported for
	Visual Studio 2008 and Visual Studio 2010 CMake generators. 0 means use all
	processors. Default is 0.</dd>
	</dl>

	</div>

	</div>

	<!-- *********************************************************************** -->

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	<a href="mailto:ofv@wanadoo.es">Oscar Fuentes</a><br>
	<a href="http://llvm.org/">LLVM Compiler Infrastructure</a><br>
	Last modified: $Date: 2010-08-09 03:59:36 +0100 (Mon, 9 Aug 2010) $
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