3 ========================
4 Creating an LLVM Project
5 ========================
13 The LLVM build system is designed to facilitate the building of third party
14 projects that use LLVM header files, libraries, and tools. In order to use
15 these facilities, a ``Makefile`` from a project must do the following things:
17 * Set ``make`` variables. There are several variables that a ``Makefile`` needs
18 to set to use the LLVM build system:
20 * ``PROJECT_NAME`` — The name by which your project is known.
21 * ``LLVM_SRC_ROOT`` — The root of the LLVM source tree.
22 * ``LLVM_OBJ_ROOT`` — The root of the LLVM object tree.
23 * ``PROJ_SRC_ROOT`` — The root of the project's source tree.
24 * ``PROJ_OBJ_ROOT`` — The root of the project's object tree.
25 * ``PROJ_INSTALL_ROOT`` — The root installation directory.
26 * ``LEVEL`` — The relative path from the current directory to the
27 project's root ``($PROJ_OBJ_ROOT)``.
29 * Include ``Makefile.config`` from ``$(LLVM_OBJ_ROOT)``.
31 * Include ``Makefile.rules`` from ``$(LLVM_SRC_ROOT)``.
33 There are two ways that you can set all of these variables:
35 * You can write your own ``Makefiles`` which hard-code these values.
37 * You can use the pre-made LLVM sample project. This sample project includes
38 ``Makefiles``, a configure script that can be used to configure the location
39 of LLVM, and the ability to support multiple object directories from a single
42 This document assumes that you will base your project on the LLVM sample project
43 found in ``llvm/projects/sample``. If you want to devise your own build system,
44 studying the sample project and LLVM ``Makefiles`` will probably provide enough
45 information on how to write your own ``Makefiles``.
47 Create a Project from the Sample Project
48 ========================================
50 Follow these simple steps to start your project:
52 #. Copy the ``llvm/projects/sample`` directory to any place of your choosing.
53 You can place it anywhere you like. Rename the directory to match the name
56 #. If you downloaded LLVM using Subversion, remove all the directories named
57 ``.svn`` (and all the files therein) from your project's new source tree.
58 This will keep Subversion from thinking that your project is inside
59 ``llvm/trunk/projects/sample``.
61 #. Add your source code and Makefiles to your source tree.
63 #. If you want your project to be configured with the ``configure`` script then
64 you need to edit ``autoconf/configure.ac`` as follows:
66 * **``AC_INIT``** — Place the name of your project, its version number
67 and a contact email address for your project as the arguments to this macro
69 * **``AC_CONFIG_AUX_DIR``** — If your project isn't in the
70 ``llvm/projects`` directory then you might need to adjust this so that it
71 specifies a relative path to the ``llvm/autoconf`` directory.
73 * **``LLVM_CONFIG_PROJECT``** — Just leave this alone.
75 * **``AC_CONFIG_SRCDIR``** — Specify a path to a file name that
76 identifies your project; or just leave it at ``Makefile.common.in``.
78 * **``AC_CONFIG_FILES``** — Do not change.
80 * **``AC_CONFIG_MAKEFILE``** — Use one of these macros for each
81 Makefile that your project uses. This macro arranges for your makefiles to
82 be copied from the source directory, unmodified, to the build directory.
84 #. After updating ``autoconf/configure.ac``, regenerate the configure script
92 You must be using Autoconf version 2.59 or later and your ``aclocal`` version
93 should be 1.9 or later.
95 #. Run ``configure`` in the directory in which you want to place object code.
96 Use the following options to tell your project where it can find LLVM:
98 ``--with-llvmsrc=<directory>``
99 Tell your project where the LLVM source tree is located.
101 ``--with-llvmobj=<directory>``
102 Tell your project where the LLVM object tree is located.
104 ``--prefix=<directory>``
105 Tell your project where it should get installed.
107 That's it! Now all you have to do is type ``gmake`` (or ``make`` if your on a
108 GNU/Linux system) in the root of your object directory, and your project should
114 In order to use the LLVM build system, you will want to organize your source
115 code so that it can benefit from the build system's features. Mainly, you want
116 your source tree layout to look similar to the LLVM source tree layout. The
117 best way to do this is to just copy the project tree from
118 ``llvm/projects/sample`` and modify it to meet your needs, but you can certainly
119 add to it if you want.
121 Underneath your top level directory, you should have the following directories:
125 This subdirectory should contain all of your library source code. For each
126 library that you build, you will have one directory in **``lib``** that will
127 contain that library's source code.
129 Libraries can be object files, archives, or dynamic libraries. The
130 **``lib``** directory is just a convenient place for libraries as it places
131 them all in a directory from which they can be linked later.
135 This subdirectory should contain any header files that are global to your
136 project. By global, we mean that they are used by more than one library or
137 executable of your project.
139 By placing your header files in **``include``**, they will be found
140 automatically by the LLVM build system. For example, if you have a file
141 **``include/jazz/note.h``**, then your source files can include it simply
142 with **``#include "jazz/note.h"``**.
146 This subdirectory should contain all of your source code for executables.
147 For each program that you build, you will have one directory in
148 **``tools``** that will contain that program's source code.
152 This subdirectory should contain tests that verify that your code works
153 correctly. Automated tests are especially useful.
155 Currently, the LLVM build system provides basic support for tests. The LLVM
156 system provides the following:
158 * LLVM provides a ``tcl`` procedure that is used by ``Dejagnu`` to run tests.
159 It can be found in ``llvm/lib/llvm-dg.exp``. This test procedure uses ``RUN``
160 lines in the actual test case to determine how to run the test. See the
161 `TestingGuide`_TestingGuide.html for more details. You can easily write
162 Makefile support similar to the Makefiles in ``llvm/test`` to use ``Dejagnu``
163 to run your project's tests.
165 * LLVM contains an optional package called ``llvm-test``, which provides
166 benchmarks and programs that are known to compile with the Clang front
167 end. You can use these programs to test your code, gather statistical
168 information, and compare it to the current LLVM performance statistics.
170 Currently, there is no way to hook your tests directly into the ``llvm/test``
171 testing harness. You will simply need to find a way to use the source
172 provided within that directory on your own.
174 Typically, you will want to build your **``lib``** directory first followed by
175 your **``tools``** directory.
177 Writing LLVM Style Makefiles
178 ============================
180 The LLVM build system provides a convenient way to build libraries and
181 executables. Most of your project Makefiles will only need to define a few
182 variables. Below is a list of the variables one can set and what they can
190 This variable is the relative path from this ``Makefile`` to the top
191 directory of your project's source code. For example, if your source code
192 is in ``/tmp/src``, then the ``Makefile`` in ``/tmp/src/jump/high``
193 would set ``LEVEL`` to ``"../.."``.
195 Variables for Building Subdirectories
196 -------------------------------------
200 This is a space separated list of subdirectories that should be built. They
201 will be built, one at a time, in the order specified.
205 This is a list of directories that can be built in parallel. These will be
206 built after the directories in DIRS have been built.
210 This is a list of directories that can be built if they exist, but will not
211 cause an error if they do not exist. They are built serially in the order
212 in which they are listed.
214 Variables for Building Libraries
215 --------------------------------
219 This variable contains the base name of the library that will be built. For
220 example, to build a library named ``libsample.a``, ``LIBRARYNAME`` should
221 be set to ``sample``.
225 By default, a library is a ``.o`` file that is linked directly into a
226 program. To build an archive (also known as a static library), set the
227 ``BUILD_ARCHIVE`` variable.
231 If ``SHARED_LIBRARY`` is defined in your Makefile, a shared (or dynamic)
232 library will be built.
234 Variables for Building Programs
235 -------------------------------
239 This variable contains the name of the program that will be built. For
240 example, to build an executable named ``sample``, ``TOOLNAME`` should be set
245 This variable holds a space separated list of libraries that should be
246 linked into the program. These libraries must be libraries that come from
247 your **``lib``** directory. The libraries must be specified without their
248 ``lib`` prefix. For example, to link ``libsample.a``, you would set
249 ``USEDLIBS`` to ``sample.a``.
251 Note that this works only for statically linked libraries.
255 This variable holds a space separated list of libraries that should be
256 linked into the program. These libraries must be LLVM libraries. The
257 libraries must be specified without their ``lib`` prefix. For example, to
258 link with a driver that performs an IR transformation you might set
259 ``LLVMLIBS`` to this minimal set of libraries ``LLVMSupport.a LLVMCore.a
260 LLVMBitReader.a LLVMAsmParser.a LLVMAnalysis.a LLVMTransformUtils.a
261 LLVMScalarOpts.a LLVMTarget.a``.
263 Note that this works only for statically linked libraries. LLVM is split
264 into a large number of static libraries, and the list of libraries you
265 require may be much longer than the list above. To see a full list of
266 libraries use: ``llvm-config --libs all``. Using ``LINK_COMPONENTS`` as
267 described below, obviates the need to set ``LLVMLIBS``.
271 This variable holds a space separated list of components that the LLVM
272 ``Makefiles`` pass to the ``llvm-config`` tool to generate a link line for
273 the program. For example, to link with all LLVM libraries use
274 ``LINK_COMPONENTS = all``.
278 To link dynamic libraries, add <tt>-l<library base name></tt> to the
279 ``LIBS`` variable. The LLVM build system will look in the same places for
280 dynamic libraries as it does for static libraries.
282 For example, to link ``libsample.so``, you would have the following line in
285 .. code-block: Makefile
289 Note that ``LIBS`` must occur in the Makefile after the inclusion of
292 Miscellaneous Variables
293 -----------------------
298 This variable can be used to add options to the C and C++ compiler,
299 respectively. It is typically used to add options that tell the compiler
300 the location of additional directories to search for header files.
302 It is highly suggested that you append to ``CFLAGS`` and ``CPPFLAGS`` as
303 opposed to overwriting them. The master ``Makefiles`` may already have
304 useful options in them that you may not want to overwrite.
306 Placement of Object Code
307 ========================
309 The final location of built libraries and executables will depend upon whether
310 you do a ``Debug``, ``Release``, or ``Profile`` build.
314 All libraries (static and dynamic) will be stored in
315 ``PROJ_OBJ_ROOT/<type>/lib``, where *``type``* is ``Debug``, ``Release``, or
316 ``Profile`` for a debug, optimized, or profiled build, respectively.
320 All executables will be stored in ``PROJ_OBJ_ROOT/<type>/bin``, where
321 *``type``* is ``Debug``, ``Release``, or ``Profile`` for a debug, optimized,
322 or profiled build, respectively.
327 If you have any questions or need any help creating an LLVM project, the LLVM
328 team would be more than happy to help. You can always post your questions to
329 the `LLVM Developers Mailing List`_http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev.