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5 <title>Creating an LLVM Project</title>
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10 <div class="doc_title">Creating an LLVM Project</div>
13 <li><a href="#overview">Overview</a></li>
14 <li><a href="#create">Create a project from the Sample Project</a></li>
15 <li><a href="#source">Source tree layout</a></li>
16 <li><a href="#makefiles">Writing LLVM-style Makefiles</a>
18 <li><a href="#reqVars">Required Variables</a></li>
19 <li><a href="#varsBuildDir">Variables for Building Subdirectories</a></li>
20 <li><a href="#varsBuildLib">Variables for Building Libraries</a></li>
21 <li><a href="#varsBuildProg">Variables for Building Programs</a></li>
22 <li><a href="#miscVars">Miscellaneous Variables</a></li>
24 <li><a href="#objcode">Placement of object code</a></li>
25 <li><a href="#help">Further help</a></li>
28 <div class="doc_author">
29 <p>Written by John Criswell</p>
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33 <div class="doc_section"><a name="overview">Overview</a></div>
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36 <div class="doc_text">
38 <p>The LLVM build system is designed to facilitate the building of third party
39 projects that use LLVM header files, libraries, and tools. In order to use
40 these facilities, a Makefile from a project must do the following things:</p>
43 <li>Set environment variables.There are several environment variables that a
44 Makefile needs to set to use the LLVM build system:
47 <li><tt>LLVM_SRC_ROOT</tt> - The root of the LLVM source tree.</li>
48 <li><tt>LLVM_OBJ_ROOT</tt> - The root of the LLVM object tree.</li>
49 <li><tt>BUILD_SRC_ROOT</tt> - The root of the project's source tree.</li>
50 <li><tt>BUILD_OBJ_ROOT</tt> - The root of the project's object tree.</li>
51 <li><tt>BUILD_SRC_DIR</tt> - The directory containing the current source to be
53 <li><tt>BUILD_OBJ_DIR</tt> - The directory where the current source will place
54 the new object files. This should always be the current directory.</li>
55 <li><tt>LEVEL</tt> - The relative path from the current directory to the root
56 of the object tree.</li>
58 <li>Include <tt>Makefile.config</tt> from <tt>$(LLVM_OBJ_ROOT)</tt>.</li>
59 <li>Include <tt>Makefile.rules</tt> from <tt>$(LLVM_SRC_ROOT)</tt>.</li>
62 <p>There are two ways that you can set all of these variables:</p>
65 <li>You can write your own Makefiles which hard-code these values.</li>
67 <li> You can use the pre-made LLVM sample project. This sample project includes
68 Makefiles, a configure script that can be used to configure the location of
69 LLVM, and the ability to support multiple object directories from a single
70 source directory.</li>
73 <p>This document assumes that you will base your project off of the LLVM sample
74 project found in <tt>llvm/projects/sample</tt>. If you want to devise your own
75 build system, studying the sample project and LLVM Makefiles will probably
76 provide enough information on how to write your own Makefiles.</p>
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81 <div class="doc_section">
82 <a name="create">Create a Project from the Sample Project</a>
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86 <div class="doc_text">
88 <p>Follow these simple steps to start your project:</p>
91 <li>Copy the <tt>llvm/projects/sample</tt> directory to any place of your
92 choosing. You can place it anywhere you like. Rename the directory to match
93 the name of your project.</li>
95 <li>Add your source code and Makefiles to your source tree.</li>
97 <li>If you want your Makefiles to be configured by the <tt>configure</tt>
98 script, or if you want to support multiple object directories, add your
99 Makefiles to the <tt>configure</tt> script by adding them into the
100 <tt>autoconf/configure.ac</tt> file. The macro <tt>AC_CONFIG_MAKEFILE</tt> will
101 copy a file, unmodified, from the source directory to the object directory.</li>
103 <li>After updating <tt>autoconf/configure.ac</tt>, regenerate the
104 configure script with these commands:
106 <div class="doc_code">
107 <p><tt>% cd autoconf<br>
108 % autoconf -o ../configure</tt></p>
111 <p>You must be using Autoconf version 2.57 or higher.</p></li>
113 <li>Run <tt>configure</tt> in the directory in which you want to place
114 object code. Use the following options to tell your project where it
118 <dt><tt>--with-llvmsrc=<directory></tt>
120 Tell your project where the LLVM source tree is located.
122 <dt><tt>--with-llvmobj=<directory></tt>
124 Tell your project where the LLVM object tree is located.
128 <p>That's it! Now all you have to do is type <tt>gmake</tt> in the root of
129 your object directory, and your project should build.</p>
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134 <div class="doc_section">
135 <a name="source">Source Tree Layout</a>
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139 <div class="doc_text">
141 <p>In order to use the LLVM build system, you will want to organize your
142 source code so that it can benefit from the build system's features.
143 Mainly, you want your source tree layout to look similar to the LLVM
144 source tree layout. The best way to do this is to just copy the
145 project tree from <tt>llvm/projects/sample</tt> and modify it to meet
146 your needs, but you can certainly add to it if you want.</p>
148 <p>Underneath your top level directory, you should have the following
154 This subdirectory should contain all of your library source
155 code. For each library that you build, you will have one
156 directory in <b>lib</b> that will contain that library's source
160 Libraries can be object files, archives, or dynamic libraries.
161 The <b>lib</b> directory is just a convenient place for libraries
162 as it places them all in a directory from which they can be linked
167 This subdirectory should contain any header files that are
168 global to your project. By global, we mean that they are used
169 by more than one library or executable of your project.
171 By placing your header files in <b>include</b>, they will be
172 found automatically by the LLVM build system. For example, if
173 you have a file <b>include/jazz/note.h</b>, then your source
174 files can include it simply with <b>#include "jazz/note.h"</b>.
178 This subdirectory should contain all of your source
179 code for executables. For each program that you build, you
180 will have one directory in <b>tools</b> that will contain that
181 program's source code.
186 This subdirectory should contain tests that verify that your code
187 works correctly. Automated tests are especially useful.
189 Currently, the LLVM build system provides little support for tests,
190 although some exists. Expanded support for tests will hopefully
191 occur in the future. In the meantime, the LLVM system does provide the
195 LLVM provides several QMTest test classes that can be used to
196 create tests. They can be found in
197 <tt>llvm/test/QMTest/llvm.py</tt>. These test classes perform a
198 variety of functions, including code optimization tests, assembly
199 tests, and code analysis tests. The Makefile in
200 <tt>llvm/test</tt> provides the QMTest context needed by LLVM test
205 The LLVM source tree provides benchmarks and programs which are
206 known to compile with the LLVM GCC front ends. You can use these
207 programs to test your code, gather statistics information, and
208 compare it to the current LLVM performance statistics. These
209 programs are found in the <tt>llvm/test/Programs</tt> directory.
211 Currently, there is no way to hook your tests directly into the
212 <tt>llvm/test/Programs</tt> testing harness. You will simply
213 need to find a way to use the source provided within that directory
218 <p>Typically, you will want to build your <b>lib</b> directory first followed by
219 your <b>tools</b> directory.</p>
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224 <div class="doc_section">
225 <a name="makefiles">Writing LLVM Style Makefiles</a>
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229 <div class="doc_text">
231 <p>The LLVM build system provides a convenient way to build libraries and
232 executables. Most of your project Makefiles will only need to define a few
233 variables. Below is a list of the variables one can set and what they can
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239 <div class="doc_subsection">
240 <a name="reqVars">Required Variables</a>
243 <div class="doc_text">
248 This variable is the relative path from this Makefile to the
249 top directory of your project's source code. For example, if
250 your source code is in <tt>/tmp/src</tt>, then the Makefile in
251 <tt>/tmp/src/jump/high</tt> would set <tt>LEVEL</tt> to <tt>"../.."</tt>.
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257 <div class="doc_subsection">
258 <a name="varsBuildDir">Variables for Building Subdirectories</a>
261 <div class="doc_text">
266 This is a space separated list of subdirectories that should be
267 built. They will be built, one at a time, in the order
273 This is a list of directories that can be built in parallel.
274 These will be built after the directories in DIRS have been
280 This is a list of directories that can be built if they exist,
281 but will not cause an error if they do not exist. They are
282 built serially in the order in which they are listed.
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288 <div class="doc_subsection">
289 <a name="varsBuildLib">Variables for Building Libraries</a>
292 <div class="doc_text">
297 This variable contains the base name of the library that will
298 be built. For example, to build a library named
299 <tt>libsample.a</tt>, LIBRARYNAME should be set to
305 By default, a library is a <tt>.o</tt> file that is linked
306 directly into a program. To build an archive (also known as
307 a static library), set the BUILD_ARCHIVE variable.
312 If SHARED_LIBRARY is defined in your Makefile, a shared
313 (or dynamic) library will be built.
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319 <div class="doc_subsection">
320 <a name="varsBuildProg">Variables for Building Programs</a>
323 <div class="doc_text">
328 This variable contains the name of the program that will
329 be built. For example, to build an executable named
330 <tt>sample</tt>, TOOLNAME should be set to <tt>sample</tt>.
335 This variable holds a space separated list of libraries that
336 should be linked into the program. These libraries must either
337 be LLVM libraries or libraries that come from your <b>lib</b>
338 directory. The libraries must be specified by their base name.
339 For example, to link libsample.a, you would set USEDLIBS to
342 Note that this works only for statically linked libraries.
347 To link dynamic libraries, add <tt>-l<library base name></tt> to
348 the LIBS variable. The LLVM build system will look in the same places
349 for dynamic libraries as it does for static libraries.
351 For example, to link <tt>libsample.so</tt>, you would have the
352 following line in your <tt>Makefile</tt>:
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362 <div class="doc_subsection">
363 <a name="miscVars">Miscellaneous Variables</a>
366 <div class="doc_text">
371 This variable contains a space separated list of extra source
372 files that need to be built. It is useful for including the
373 output of Lex and Yacc programs.
379 This variable can be used to add options to the C and C++
380 compiler, respectively. It is typically used to add options
381 that tell the compiler the location of additional directories
382 to search for header files.
384 It is highly suggested that you append to CFLAGS and CPPFLAGS as
385 opposed to overwriting them. The master Makefiles may already
386 have useful options in them that you may not want to overwrite.
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393 <div class="doc_section">
394 <a name="objcode">Placement of Object Code</a>
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398 <div class="doc_text">
400 <p>The final location of built libraries and executables will depend upon
401 whether you do a Debug, Release, or Profile build.</p>
406 All libraries (static and dynamic) will be stored in
407 <tt>BUILD_OBJ_ROOT/lib/<type></tt>, where type is <tt>Debug</tt>,
408 <tt>Release</tt>, or <tt>Profile</tt> for a debug, optimized, or
409 profiled build, respectively.<p>
412 <dd>All executables will be stored in
413 <tt>BUILD_OBJ_ROOT/tools/<type></tt>, where type is <tt>Debug</tt>,
414 <tt>Release</tt>, or <tt>Profile</tt> for a debug, optimized, or profiled
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421 <div class="doc_section">
422 <a name="help">Further Help</a>
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426 <div class="doc_text">
428 <p>If you have any questions or need any help creating an LLVM project,
429 the LLVM team would be more than happy to help. You can always post your
431 href="http://mail.cs.uiuc.edu/mailman/listinfo/llvmdev">LLVM Developers
432 Mailing List</a>.</p>
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444 <a href="mailto:criswell@uiuc.edu">John Criswell</a><br>
445 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
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