1 ======================== 2 Creating an LLVM Project 3 ======================== 4 5 .. contents:: 6 :local: 7 8 Overview 9 ======== 10 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: 14 15 * Set ``make`` variables. There are several variables that a ``Makefile`` needs 16 to set to use the LLVM build system: 17 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 ``($PROJ_OBJ_ROOT)``. 26 27 * Include ``Makefile.config`` from ``$(LLVM_OBJ_ROOT)``. 28 29 * Include ``Makefile.rules`` from ``$(LLVM_SRC_ROOT)``. 30 31 There are two ways that you can set all of these variables: 32 33 * You can write your own ``Makefiles`` which hard-code these values. 34 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 38 source directory. 39 40 This document assumes that you will base your project on the LLVM sample project 41 found in ``llvm/projects/sample``. If you want to devise your own build system, 42 studying the sample project and LLVM ``Makefiles`` will probably provide enough 43 information on how to write your own ``Makefiles``. 44 45 Create a Project from the Sample Project 46 ======================================== 47 48 Follow these simple steps to start your project: 49 50 1. Copy the ``llvm/projects/sample`` directory to any place of your choosing. 51 You can place it anywhere you like. Rename the directory to match the name 52 of your project. 53 54 2. If you downloaded LLVM using Subversion, remove all the directories named 55 ``.svn`` (and all the files therein) from your project's new source tree. 56 This will keep Subversion from thinking that your project is inside 57 ``llvm/trunk/projects/sample``. 58 59 3. Add your source code and Makefiles to your source tree. 60 61 4. If you want your project to be configured with the ``configure`` script then 62 you need to edit ``autoconf/configure.ac`` as follows: 63 64 * **AC_INIT** - Place the name of your project, its version number and a 65 contact email address for your project as the arguments to this macro 66 67 * **AC_CONFIG_AUX_DIR** - If your project isn't in the ``llvm/projects`` 68 directory then you might need to adjust this so that it specifies a 69 relative path to the ``llvm/autoconf`` directory. 70 71 * **LLVM_CONFIG_PROJECT** - Just leave this alone. 72 73 * **AC_CONFIG_SRCDIR** - Specify a path to a file name that identifies your 74 project; or just leave it at ``Makefile.common.in``. 75 76 * **AC_CONFIG_FILES** - Do not change. 77 78 * **AC_CONFIG_MAKEFILE** - Use one of these macros for each Makefile that 79 your project uses. This macro arranges for your makefiles to be copied from 80 the source directory, unmodified, to the build directory. 81 82 5. After updating ``autoconf/configure.ac``, regenerate the configure script 83 with these commands. (You must be using ``Autoconf`` version 2.59 or later 84 and your ``aclocal`` version should be 1.9 or later.) 85 86 .. code-block:: bash 87 88 % cd autoconf 89 % ./AutoRegen.sh 90 91 6. Run ``configure`` in the directory in which you want to place object code. 92 Use the following options to tell your project where it can find LLVM: 93 94 ``--with-llvmsrc=<directory>`` 95 Tell your project where the LLVM source tree is located. 96 97 ``--with-llvmobj=<directory>`` 98 Tell your project where the LLVM object tree is located. 99 100 ``--prefix=<directory>`` 101 Tell your project where it should get installed. 102 103 That's it! Now all you have to do is type ``gmake`` (or ``make`` if you're on a 104 GNU/Linux system) in the root of your object directory, and your project should 105 build. 106 107 Source Tree Layout 108 ================== 109 110 In order to use the LLVM build system, you will want to organize your source 111 code so that it can benefit from the build system's features. Mainly, you want 112 your source tree layout to look similar to the LLVM source tree layout. The 113 best way to do this is to just copy the project tree from 114 ``llvm/projects/sample`` and modify it to meet your needs, but you can certainly 115 add to it if you want. 116 117 Underneath your top level directory, you should have the following directories: 118 119 **lib** 120 121 This subdirectory should contain all of your library source code. For each 122 library that you build, you will have one directory in **lib** that will 123 contain that library's source code. 124 125 Libraries can be object files, archives, or dynamic libraries. The **lib** 126 directory is just a convenient place for libraries as it places them all in 127 a directory from which they can be linked later. 128 129 **include** 130 131 This subdirectory should contain any header files that are global to your 132 project. By global, we mean that they are used by more than one library or 133 executable of your project. 134 135 By placing your header files in **include**, they will be found 136 automatically by the LLVM build system. For example, if you have a file 137 **include/jazz/note.h**, then your source files can include it simply with 138 **#include "jazz/note.h"**. 139 140 **tools** 141 142 This subdirectory should contain all of your source code for executables. 143 For each program that you build, you will have one directory in **tools** 144 that will contain that program's source code. 145 146 **test** 147 148 This subdirectory should contain tests that verify that your code works 149 correctly. Automated tests are especially useful. 150 151 Currently, the LLVM build system provides basic support for tests. The LLVM 152 system provides the following: 153 154 * LLVM contains regression tests in ``llvm/test``. These tests are run by the 155 :doc:`Lit <CommandGuide/lit>` testing tool. This test procedure uses ``RUN`` 156 lines in the actual test case to determine how to run the test. See the 157 :doc:`TestingGuide` for more details. 158 159 * LLVM contains an optional package called ``llvm-test``, which provides 160 benchmarks and programs that are known to compile with the Clang front 161 end. You can use these programs to test your code, gather statistical 162 information, and compare it to the current LLVM performance statistics. 163 164 Currently, there is no way to hook your tests directly into the ``llvm/test`` 165 testing harness. You will simply need to find a way to use the source 166 provided within that directory on your own. 167 168 Typically, you will want to build your **lib** directory first followed by your 169 **tools** directory. 170 171 Writing LLVM Style Makefiles 172 ============================ 173 174 The LLVM build system provides a convenient way to build libraries and 175 executables. Most of your project Makefiles will only need to define a few 176 variables. Below is a list of the variables one can set and what they can 177 do: 178 179 Required Variables 180 ------------------ 181 182 ``LEVEL`` 183 184 This variable is the relative path from this ``Makefile`` to the top 185 directory of your project's source code. For example, if your source code 186 is in ``/tmp/src``, then the ``Makefile`` in ``/tmp/src/jump/high`` 187 would set ``LEVEL`` to ``"../.."``. 188 189 Variables for Building Subdirectories 190 ------------------------------------- 191 192 ``DIRS`` 193 194 This is a space separated list of subdirectories that should be built. They 195 will be built, one at a time, in the order specified. 196 197 ``PARALLEL_DIRS`` 198 199 This is a list of directories that can be built in parallel. These will be 200 built after the directories in DIRS have been built. 201 202 ``OPTIONAL_DIRS`` 203 204 This is a list of directories that can be built if they exist, but will not 205 cause an error if they do not exist. They are built serially in the order 206 in which they are listed. 207 208 Variables for Building Libraries 209 -------------------------------- 210 211 ``LIBRARYNAME`` 212 213 This variable contains the base name of the library that will be built. For 214 example, to build a library named ``libsample.a``, ``LIBRARYNAME`` should 215 be set to ``sample``. 216 217 ``BUILD_ARCHIVE`` 218 219 By default, a library is a ``.o`` file that is linked directly into a 220 program. To build an archive (also known as a static library), set the 221 ``BUILD_ARCHIVE`` variable. 222 223 ``SHARED_LIBRARY`` 224 225 If ``SHARED_LIBRARY`` is defined in your Makefile, a shared (or dynamic) 226 library will be built. 227 228 Variables for Building Programs 229 ------------------------------- 230 231 ``TOOLNAME`` 232 233 This variable contains the name of the program that will be built. For 234 example, to build an executable named ``sample``, ``TOOLNAME`` should be set 235 to ``sample``. 236 237 ``USEDLIBS`` 238 239 This variable holds a space separated list of libraries that should be 240 linked into the program. These libraries must be libraries that come from 241 your **lib** directory. The libraries must be specified without their 242 ``lib`` prefix. For example, to link ``libsample.a``, you would set 243 ``USEDLIBS`` to ``sample.a``. 244 245 Note that this works only for statically linked libraries. 246 247 ``LLVMLIBS`` 248 249 This variable holds a space separated list of libraries that should be 250 linked into the program. These libraries must be LLVM libraries. The 251 libraries must be specified without their ``lib`` prefix. For example, to 252 link with a driver that performs an IR transformation you might set 253 ``LLVMLIBS`` to this minimal set of libraries ``LLVMSupport.a LLVMCore.a 254 LLVMBitReader.a LLVMAsmParser.a LLVMAnalysis.a LLVMTransformUtils.a 255 LLVMScalarOpts.a LLVMTarget.a``. 256 257 Note that this works only for statically linked libraries. LLVM is split 258 into a large number of static libraries, and the list of libraries you 259 require may be much longer than the list above. To see a full list of 260 libraries use: ``llvm-config --libs all``. Using ``LINK_COMPONENTS`` as 261 described below, obviates the need to set ``LLVMLIBS``. 262 263 ``LINK_COMPONENTS`` 264 265 This variable holds a space separated list of components that the LLVM 266 ``Makefiles`` pass to the ``llvm-config`` tool to generate a link line for 267 the program. For example, to link with all LLVM libraries use 268 ``LINK_COMPONENTS = all``. 269 270 ``LIBS`` 271 272 To link dynamic libraries, add ``-l<library base name>`` to the ``LIBS`` 273 variable. The LLVM build system will look in the same places for dynamic 274 libraries as it does for static libraries. 275 276 For example, to link ``libsample.so``, you would have the following line in 277 your ``Makefile``: 278 279 .. code-block:: makefile 280 281 LIBS += -lsample 282 283 Note that ``LIBS`` must occur in the Makefile after the inclusion of 284 ``Makefile.common``. 285 286 Miscellaneous Variables 287 ----------------------- 288 289 ``CFLAGS`` & ``CPPFLAGS`` 290 291 This variable can be used to add options to the C and C++ compiler, 292 respectively. It is typically used to add options that tell the compiler 293 the location of additional directories to search for header files. 294 295 It is highly suggested that you append to ``CFLAGS`` and ``CPPFLAGS`` as 296 opposed to overwriting them. The master ``Makefiles`` may already have 297 useful options in them that you may not want to overwrite. 298 299 Placement of Object Code 300 ======================== 301 302 The final location of built libraries and executables will depend upon whether 303 you do a ``Debug``, ``Release``, or ``Profile`` build. 304 305 Libraries 306 307 All libraries (static and dynamic) will be stored in 308 ``PROJ_OBJ_ROOT/<type>/lib``, where *type* is ``Debug``, ``Release``, or 309 ``Profile`` for a debug, optimized, or profiled build, respectively. 310 311 Executables 312 313 All executables will be stored in ``PROJ_OBJ_ROOT/<type>/bin``, where *type* 314 is ``Debug``, ``Release``, or ``Profile`` for a debug, optimized, or 315 profiled build, respectively. 316 317 Further Help 318 ============ 319 320 If you have any questions or need any help creating an LLVM project, the LLVM 321 team would be more than happy to help. You can always post your questions to 322 the `LLVM Developers Mailing List 323 <http://lists.cs.uiuc.edu/pipermail/llvmdev/>`_. 324
