1.. _projects: 2 3======================== 4Creating an LLVM Project 5======================== 6 7.. contents:: 8 :local: 9 10Overview 11======== 12 13The LLVM build system is designed to facilitate the building of third party 14projects that use LLVM header files, libraries, and tools. In order to use 15these facilities, a ``Makefile`` from a project must do the following things: 16 17* Set ``make`` variables. There are several variables that a ``Makefile`` needs 18 to set to use the LLVM build system: 19 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 ``($PROJ_OBJ_ROOT)``. 28 29* Include ``Makefile.config`` from ``$(LLVM_OBJ_ROOT)``. 30 31* Include ``Makefile.rules`` from ``$(LLVM_SRC_ROOT)``. 32 33There are two ways that you can set all of these variables: 34 35* You can write your own ``Makefiles`` which hard-code these values. 36 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 40 source directory. 41 42This document assumes that you will base your project on the LLVM sample project 43found in ``llvm/projects/sample``. If you want to devise your own build system, 44studying the sample project and LLVM ``Makefiles`` will probably provide enough 45information on how to write your own ``Makefiles``. 46 47Create a Project from the Sample Project 48======================================== 49 50Follow these simple steps to start your project: 51 521. 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 54 of your project. 55 562. 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``. 60 613. Add your source code and Makefiles to your source tree. 62 634. If you want your project to be configured with the ``configure`` script then 64 you need to edit ``autoconf/configure.ac`` as follows: 65 66 * **AC_INIT** - Place the name of your project, its version number and a 67 contact email address for your project as the arguments to this macro 68 69 * **AC_CONFIG_AUX_DIR** - If your project isn't in the ``llvm/projects`` 70 directory then you might need to adjust this so that it specifies a 71 relative path to the ``llvm/autoconf`` directory. 72 73 * **LLVM_CONFIG_PROJECT** - Just leave this alone. 74 75 * **AC_CONFIG_SRCDIR** - Specify a path to a file name that identifies your 76 project; or just leave it at ``Makefile.common.in``. 77 78 * **AC_CONFIG_FILES** - Do not change. 79 80 * **AC_CONFIG_MAKEFILE** - Use one of these macros for each Makefile that 81 your project uses. This macro arranges for your makefiles to be copied from 82 the source directory, unmodified, to the build directory. 83 845. After updating ``autoconf/configure.ac``, regenerate the configure script 85 with these commands. (You must be using ``Autoconf`` version 2.59 or later 86 and your ``aclocal`` version should be 1.9 or later.) 87 88 .. code-block:: bash 89 90 % cd autoconf 91 % ./AutoRegen.sh 92 936. Run ``configure`` in the directory in which you want to place object code. 94 Use the following options to tell your project where it can find LLVM: 95 96 ``--with-llvmsrc=<directory>`` 97 Tell your project where the LLVM source tree is located. 98 99 ``--with-llvmobj=<directory>`` 100 Tell your project where the LLVM object tree is located. 101 102 ``--prefix=<directory>`` 103 Tell your project where it should get installed. 104 105That's it! Now all you have to do is type ``gmake`` (or ``make`` if you're on a 106GNU/Linux system) in the root of your object directory, and your project should 107build. 108 109Source Tree Layout 110================== 111 112In order to use the LLVM build system, you will want to organize your source 113code so that it can benefit from the build system's features. Mainly, you want 114your source tree layout to look similar to the LLVM source tree layout. The 115best way to do this is to just copy the project tree from 116``llvm/projects/sample`` and modify it to meet your needs, but you can certainly 117add to it if you want. 118 119Underneath your top level directory, you should have the following directories: 120 121**lib** 122 123 This subdirectory should contain all of your library source code. For each 124 library that you build, you will have one directory in **lib** that will 125 contain that library's source code. 126 127 Libraries can be object files, archives, or dynamic libraries. The **lib** 128 directory is just a convenient place for libraries as it places them all in 129 a directory from which they can be linked later. 130 131**include** 132 133 This subdirectory should contain any header files that are global to your 134 project. By global, we mean that they are used by more than one library or 135 executable of your project. 136 137 By placing your header files in **include**, they will be found 138 automatically by the LLVM build system. For example, if you have a file 139 **include/jazz/note.h**, then your source files can include it simply with 140 **#include "jazz/note.h"**. 141 142**tools** 143 144 This subdirectory should contain all of your source code for executables. 145 For each program that you build, you will have one directory in **tools** 146 that will contain that program's source code. 147 148**test** 149 150 This subdirectory should contain tests that verify that your code works 151 correctly. Automated tests are especially useful. 152 153 Currently, the LLVM build system provides basic support for tests. The LLVM 154 system provides the following: 155 156* LLVM provides a ``tcl`` procedure that is used by ``Dejagnu`` to run tests. 157 It can be found in ``llvm/lib/llvm-dg.exp``. This test procedure uses ``RUN`` 158 lines in the actual test case to determine how to run the test. See the 159 `TestingGuide <TestingGuide.html>`_ for more details. You can easily write 160 Makefile support similar to the Makefiles in ``llvm/test`` to use ``Dejagnu`` 161 to run your project's tests. 162 163* LLVM contains an optional package called ``llvm-test``, which provides 164 benchmarks and programs that are known to compile with the Clang front 165 end. You can use these programs to test your code, gather statistical 166 information, and compare it to the current LLVM performance statistics. 167 168 Currently, there is no way to hook your tests directly into the ``llvm/test`` 169 testing harness. You will simply need to find a way to use the source 170 provided within that directory on your own. 171 172Typically, you will want to build your **lib** directory first followed by your 173**tools** directory. 174 175Writing LLVM Style Makefiles 176============================ 177 178The LLVM build system provides a convenient way to build libraries and 179executables. Most of your project Makefiles will only need to define a few 180variables. Below is a list of the variables one can set and what they can 181do: 182 183Required Variables 184------------------ 185 186``LEVEL`` 187 188 This variable is the relative path from this ``Makefile`` to the top 189 directory of your project's source code. For example, if your source code 190 is in ``/tmp/src``, then the ``Makefile`` in ``/tmp/src/jump/high`` 191 would set ``LEVEL`` to ``"../.."``. 192 193Variables for Building Subdirectories 194------------------------------------- 195 196``DIRS`` 197 198 This is a space separated list of subdirectories that should be built. They 199 will be built, one at a time, in the order specified. 200 201``PARALLEL_DIRS`` 202 203 This is a list of directories that can be built in parallel. These will be 204 built after the directories in DIRS have been built. 205 206``OPTIONAL_DIRS`` 207 208 This is a list of directories that can be built if they exist, but will not 209 cause an error if they do not exist. They are built serially in the order 210 in which they are listed. 211 212Variables for Building Libraries 213-------------------------------- 214 215``LIBRARYNAME`` 216 217 This variable contains the base name of the library that will be built. For 218 example, to build a library named ``libsample.a``, ``LIBRARYNAME`` should 219 be set to ``sample``. 220 221``BUILD_ARCHIVE`` 222 223 By default, a library is a ``.o`` file that is linked directly into a 224 program. To build an archive (also known as a static library), set the 225 ``BUILD_ARCHIVE`` variable. 226 227``SHARED_LIBRARY`` 228 229 If ``SHARED_LIBRARY`` is defined in your Makefile, a shared (or dynamic) 230 library will be built. 231 232Variables for Building Programs 233------------------------------- 234 235``TOOLNAME`` 236 237 This variable contains the name of the program that will be built. For 238 example, to build an executable named ``sample``, ``TOOLNAME`` should be set 239 to ``sample``. 240 241``USEDLIBS`` 242 243 This variable holds a space separated list of libraries that should be 244 linked into the program. These libraries must be libraries that come from 245 your **lib** directory. The libraries must be specified without their 246 ``lib`` prefix. For example, to link ``libsample.a``, you would set 247 ``USEDLIBS`` to ``sample.a``. 248 249 Note that this works only for statically linked libraries. 250 251``LLVMLIBS`` 252 253 This variable holds a space separated list of libraries that should be 254 linked into the program. These libraries must be LLVM libraries. The 255 libraries must be specified without their ``lib`` prefix. For example, to 256 link with a driver that performs an IR transformation you might set 257 ``LLVMLIBS`` to this minimal set of libraries ``LLVMSupport.a LLVMCore.a 258 LLVMBitReader.a LLVMAsmParser.a LLVMAnalysis.a LLVMTransformUtils.a 259 LLVMScalarOpts.a LLVMTarget.a``. 260 261 Note that this works only for statically linked libraries. LLVM is split 262 into a large number of static libraries, and the list of libraries you 263 require may be much longer than the list above. To see a full list of 264 libraries use: ``llvm-config --libs all``. Using ``LINK_COMPONENTS`` as 265 described below, obviates the need to set ``LLVMLIBS``. 266 267``LINK_COMPONENTS`` 268 269 This variable holds a space separated list of components that the LLVM 270 ``Makefiles`` pass to the ``llvm-config`` tool to generate a link line for 271 the program. For example, to link with all LLVM libraries use 272 ``LINK_COMPONENTS = all``. 273 274``LIBS`` 275 276 To link dynamic libraries, add ``-l<library base name>`` to the ``LIBS`` 277 variable. The LLVM build system will look in the same places for dynamic 278 libraries as it does for static libraries. 279 280 For example, to link ``libsample.so``, you would have the following line in 281 your ``Makefile``: 282 283 .. code-block:: makefile 284 285 LIBS += -lsample 286 287Note that ``LIBS`` must occur in the Makefile after the inclusion of 288``Makefile.common``. 289 290Miscellaneous Variables 291----------------------- 292 293``CFLAGS`` & ``CPPFLAGS`` 294 295 This variable can be used to add options to the C and C++ compiler, 296 respectively. It is typically used to add options that tell the compiler 297 the location of additional directories to search for header files. 298 299 It is highly suggested that you append to ``CFLAGS`` and ``CPPFLAGS`` as 300 opposed to overwriting them. The master ``Makefiles`` may already have 301 useful options in them that you may not want to overwrite. 302 303Placement of Object Code 304======================== 305 306The final location of built libraries and executables will depend upon whether 307you do a ``Debug``, ``Release``, or ``Profile`` build. 308 309Libraries 310 311 All libraries (static and dynamic) will be stored in 312 ``PROJ_OBJ_ROOT/<type>/lib``, where *type* is ``Debug``, ``Release``, or 313 ``Profile`` for a debug, optimized, or profiled build, respectively. 314 315Executables 316 317 All executables will be stored in ``PROJ_OBJ_ROOT/<type>/bin``, where *type* 318 is ``Debug``, ``Release``, or ``Profile`` for a debug, optimized, or 319 profiled build, respectively. 320 321Further Help 322============ 323 324If you have any questions or need any help creating an LLVM project, the LLVM 325team would be more than happy to help. You can always post your questions to 326the `LLVM Developers Mailing List 327<http://lists.cs.uiuc.edu/pipermail/llvmdev/>`_. 328