1
========================
2
Creating an LLVM Project
3
========================
11
The LLVM build system is designed to facilitate the building of third party
12
projects that use LLVM header files, libraries, and tools. In order to use
13
these facilities, a ``Makefile`` from a project must do the following things:
15
* Set ``make`` variables. There are several variables that a ``Makefile`` needs
16
to set to use the LLVM build system:
18
* ``PROJECT_NAME`` - The name by which your project is known.
19
* ``LLVM_SRC_ROOT`` - The root of the LLVM source tree.
20
* ``LLVM_OBJ_ROOT`` - The root of the LLVM object tree.
21
* ``PROJ_SRC_ROOT`` - The root of the project's source tree.
22
* ``PROJ_OBJ_ROOT`` - The root of the project's object tree.
23
* ``PROJ_INSTALL_ROOT`` - The root installation directory.
24
* ``LEVEL`` - The relative path from the current directory to the
25
project's root ``($PROJ_OBJ_ROOT)``.
27
* Include ``Makefile.config`` from ``$(LLVM_OBJ_ROOT)``.
29
* Include ``Makefile.rules`` from ``$(LLVM_SRC_ROOT)``.
31
There are two ways that you can set all of these variables:
33
* You can write your own ``Makefiles`` which hard-code these values.
35
* You can use the pre-made LLVM sample project. This sample project includes
36
``Makefiles``, a configure script that can be used to configure the location
37
of LLVM, and the ability to support multiple object directories from a single
40
If you want to devise your own build system, studying other projects and LLVM
41
``Makefiles`` will probably provide enough information on how to write your own
47
In order to use the LLVM build system, you will want to organize your source
48
code so that it can benefit from the build system's features. Mainly, you want
49
your source tree layout to look similar to the LLVM source tree layout.
51
Underneath your top level directory, you should have the following directories:
55
This subdirectory should contain all of your library source code. For each
56
library that you build, you will have one directory in **lib** that will
57
contain that library's source code.
59
Libraries can be object files, archives, or dynamic libraries. The **lib**
60
directory is just a convenient place for libraries as it places them all in
61
a directory from which they can be linked later.
65
This subdirectory should contain any header files that are global to your
66
project. By global, we mean that they are used by more than one library or
67
executable of your project.
69
By placing your header files in **include**, they will be found
70
automatically by the LLVM build system. For example, if you have a file
71
**include/jazz/note.h**, then your source files can include it simply with
72
**#include "jazz/note.h"**.
76
This subdirectory should contain all of your source code for executables.
77
For each program that you build, you will have one directory in **tools**
78
that will contain that program's source code.
82
This subdirectory should contain tests that verify that your code works
83
correctly. Automated tests are especially useful.
85
Currently, the LLVM build system provides basic support for tests. The LLVM
86
system provides the following:
88
* LLVM contains regression tests in ``llvm/test``. These tests are run by the
89
:doc:`Lit <CommandGuide/lit>` testing tool. This test procedure uses ``RUN``
90
lines in the actual test case to determine how to run the test. See the
91
:doc:`TestingGuide` for more details.
93
* LLVM contains an optional package called ``llvm-test``, which provides
94
benchmarks and programs that are known to compile with the Clang front
95
end. You can use these programs to test your code, gather statistical
96
information, and compare it to the current LLVM performance statistics.
98
Currently, there is no way to hook your tests directly into the ``llvm/test``
99
testing harness. You will simply need to find a way to use the source
100
provided within that directory on your own.
102
Typically, you will want to build your **lib** directory first followed by your
105
Writing LLVM Style Makefiles
106
============================
108
The LLVM build system provides a convenient way to build libraries and
109
executables. Most of your project Makefiles will only need to define a few
110
variables. Below is a list of the variables one can set and what they can
118
This variable is the relative path from this ``Makefile`` to the top
119
directory of your project's source code. For example, if your source code
120
is in ``/tmp/src``, then the ``Makefile`` in ``/tmp/src/jump/high``
121
would set ``LEVEL`` to ``"../.."``.
123
Variables for Building Subdirectories
124
-------------------------------------
128
This is a space separated list of subdirectories that should be built. They
129
will be built, one at a time, in the order specified.
133
This is a list of directories that can be built in parallel. These will be
134
built after the directories in DIRS have been built.
138
This is a list of directories that can be built if they exist, but will not
139
cause an error if they do not exist. They are built serially in the order
140
in which they are listed.
142
Variables for Building Libraries
143
--------------------------------
147
This variable contains the base name of the library that will be built. For
148
example, to build a library named ``libsample.a``, ``LIBRARYNAME`` should
149
be set to ``sample``.
153
By default, a library is a ``.o`` file that is linked directly into a
154
program. To build an archive (also known as a static library), set the
155
``BUILD_ARCHIVE`` variable.
159
If ``SHARED_LIBRARY`` is defined in your Makefile, a shared (or dynamic)
160
library will be built.
162
Variables for Building Programs
163
-------------------------------
167
This variable contains the name of the program that will be built. For
168
example, to build an executable named ``sample``, ``TOOLNAME`` should be set
173
This variable holds a space separated list of libraries that should be
174
linked into the program. These libraries must be libraries that come from
175
your **lib** directory. The libraries must be specified without their
176
``lib`` prefix. For example, to link ``libsample.a``, you would set
177
``USEDLIBS`` to ``sample.a``.
179
Note that this works only for statically linked libraries.
183
This variable holds a space separated list of libraries that should be
184
linked into the program. These libraries must be LLVM libraries. The
185
libraries must be specified without their ``lib`` prefix. For example, to
186
link with a driver that performs an IR transformation you might set
187
``LLVMLIBS`` to this minimal set of libraries ``LLVMSupport.a LLVMCore.a
188
LLVMBitReader.a LLVMAsmParser.a LLVMAnalysis.a LLVMTransformUtils.a
189
LLVMScalarOpts.a LLVMTarget.a``.
191
Note that this works only for statically linked libraries. LLVM is split
192
into a large number of static libraries, and the list of libraries you
193
require may be much longer than the list above. To see a full list of
194
libraries use: ``llvm-config --libs all``. Using ``LINK_COMPONENTS`` as
195
described below, obviates the need to set ``LLVMLIBS``.
199
This variable holds a space separated list of components that the LLVM
200
``Makefiles`` pass to the ``llvm-config`` tool to generate a link line for
201
the program. For example, to link with all LLVM libraries use
202
``LINK_COMPONENTS = all``.
206
To link dynamic libraries, add ``-l<library base name>`` to the ``LIBS``
207
variable. The LLVM build system will look in the same places for dynamic
208
libraries as it does for static libraries.
210
For example, to link ``libsample.so``, you would have the following line in
213
.. code-block:: makefile
217
Note that ``LIBS`` must occur in the Makefile after the inclusion of
220
Miscellaneous Variables
221
-----------------------
223
``CFLAGS`` & ``CPPFLAGS``
225
This variable can be used to add options to the C and C++ compiler,
226
respectively. It is typically used to add options that tell the compiler
227
the location of additional directories to search for header files.
229
It is highly suggested that you append to ``CFLAGS`` and ``CPPFLAGS`` as
230
opposed to overwriting them. The master ``Makefiles`` may already have
231
useful options in them that you may not want to overwrite.
233
Placement of Object Code
234
========================
236
The final location of built libraries and executables will depend upon whether
237
you do a ``Debug``, ``Release``, or ``Profile`` build.
241
All libraries (static and dynamic) will be stored in
242
``PROJ_OBJ_ROOT/<type>/lib``, where *type* is ``Debug``, ``Release``, or
243
``Profile`` for a debug, optimized, or profiled build, respectively.
247
All executables will be stored in ``PROJ_OBJ_ROOT/<type>/bin``, where *type*
248
is ``Debug``, ``Release``, or ``Profile`` for a debug, optimized, or
249
profiled build, respectively.
254
If you have any questions or need any help creating an LLVM project, the LLVM
255
team would be more than happy to help. You can always post your questions to
256
the `LLVM Developers Mailing List
257
<http://lists.cs.uiuc.edu/pipermail/llvmdev/>`_.