1 ====================================
2 Getting Started with the LLVM System
3 ====================================
11 Welcome to LLVM! In order to get started, you first need to know some basic
14 First, LLVM comes in three pieces. The first piece is the LLVM suite. This
15 contains all of the tools, libraries, and header files needed to use LLVM. It
16 contains an assembler, disassembler, bitcode analyzer and bitcode optimizer. It
17 also contains basic regression tests that can be used to test the LLVM tools and
20 The second piece is the `Clang <http://clang.llvm.org/>`_ front end. This
21 component compiles C, C++, Objective C, and Objective C++ code into LLVM
22 bitcode. Once compiled into LLVM bitcode, a program can be manipulated with the
23 LLVM tools from the LLVM suite.
25 There is a third, optional piece called Test Suite. It is a suite of programs
26 with a testing harness that can be used to further test LLVM's functionality
29 Getting Started Quickly (A Summary)
30 ===================================
32 The LLVM Getting Started documentation may be out of date. So, the `Clang
33 Getting Started <http://clang.llvm.org/get_started.html>`_ page might also be a
36 Here's the short story for getting up and running quickly with LLVM:
38 #. Read the documentation.
39 #. Read the documentation.
40 #. Remember that you were warned twice about reading the documentation.
43 * ``cd where-you-want-llvm-to-live``
44 * ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
48 * ``cd where-you-want-llvm-to-live``
50 * ``svn co http://llvm.org/svn/llvm-project/cfe/trunk clang``
52 #. Checkout Compiler-RT:
54 * ``cd where-you-want-llvm-to-live``
55 * ``cd llvm/projects``
56 * ``svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk compiler-rt``
58 #. Get the Test Suite Source Code **[Optional]**
60 * ``cd where-you-want-llvm-to-live``
61 * ``cd llvm/projects``
62 * ``svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite``
64 #. Configure and build LLVM and Clang:
66 The usual build uses `CMake <CMake.html>`_. If you would rather use
67 autotools, see `Building LLVM with autotools <BuildingLLVMWithAutotools.html>`_.
69 * ``cd where you want to build llvm``
72 * ``cmake -G <generator> [options] <path to llvm sources>``
74 Some common generators are:
76 * ``Unix Makefiles`` --- for generating make-compatible parallel makefiles.
77 * ``Ninja`` --- for generating `Ninja <http://martine.github.io/ninja/>`
79 * ``Visual Studio`` --- for generating Visual Studio projects and
81 * ``Xcode`` --- for generating Xcode projects.
85 * ``-DCMAKE_INSTALL_PREFIX=directory`` --- Specify for *directory* the full
86 pathname of where you want the LLVM tools and libraries to be installed
87 (default ``/usr/local``).
89 * ``-DCMAKE_BUILD_TYPE=type`` --- Valid options for *type* are Debug,
90 Release, RelWithDebInfo, and MinSizeRel. Default is Debug.
92 * ``-DLLVM_ENABLE_ASSERTIONS=On`` --- Compile with assertion checks enabled
93 (default is Yes for Debug builds, No for all other build types).
95 * Run your build tool of choice!
97 * The default target (i.e. ``make``) will build all of LLVM
99 * The ``check-all`` target (i.e. ``make check-all``) will run the
100 regression tests to ensure everything is in working order.
102 * CMake will generate build targets for each tool and library, and most
103 LLVM sub-projects generate their own ``check-<project>`` target.
105 * For more information see `CMake <CMake.html>`_
107 * If you get an "internal compiler error (ICE)" or test failures, see
110 Consult the `Getting Started with LLVM`_ section for detailed information on
111 configuring and compiling LLVM. See `Setting Up Your Environment`_ for tips
112 that simplify working with the Clang front end and LLVM tools. Go to `Program
113 Layout`_ to learn about the layout of the source code tree.
118 Before you begin to use the LLVM system, review the requirements given below.
119 This may save you some trouble by knowing ahead of time what hardware and
120 software you will need.
125 LLVM is known to work on the following host platforms:
127 ================== ===================== =============
129 ================== ===================== =============
130 Linux x86\ :sup:`1` GCC, Clang
131 Linux amd64 GCC, Clang
132 Linux ARM\ :sup:`4` GCC, Clang
133 Linux PowerPC GCC, Clang
134 Solaris V9 (Ultrasparc) GCC
135 FreeBSD x86\ :sup:`1` GCC, Clang
136 FreeBSD amd64 GCC, Clang
137 MacOS X\ :sup:`2` PowerPC GCC
138 MacOS X x86 GCC, Clang
139 Cygwin/Win32 x86\ :sup:`1, 3` GCC
140 Windows x86\ :sup:`1` Visual Studio
141 Windows x64 x86-64 Visual Studio
142 ================== ===================== =============
146 #. Code generation supported for Pentium processors and up
147 #. Code generation supported for 32-bit ABI only
148 #. To use LLVM modules on Win32-based system, you may configure LLVM
149 with ``-DBUILD_SHARED_LIBS=On`` for CMake builds or ``--enable-shared``
150 for configure builds.
151 #. MCJIT not working well pre-v7, old JIT engine not supported any more.
153 Note that you will need about 1-3 GB of space for a full LLVM build in Debug
154 mode, depending on the system (it is so large because of all the debugging
155 information and the fact that the libraries are statically linked into multiple
156 tools). If you do not need many of the tools and you are space-conscious, you
157 can pass ``ONLY_TOOLS="tools you need"`` to make. The Release build requires
158 considerably less space.
160 The LLVM suite *may* compile on other platforms, but it is not guaranteed to do
161 so. If compilation is successful, the LLVM utilities should be able to
162 assemble, disassemble, analyze, and optimize LLVM bitcode. Code generation
163 should work as well, although the generated native code may not work on your
169 Compiling LLVM requires that you have several software packages installed. The
170 table below lists those required packages. The Package column is the usual name
171 for the software package that LLVM depends on. The Version column provides
172 "known to work" versions of the package. The Notes column describes how LLVM
173 uses the package and provides other details.
175 =========================================================== ============ ==========================================
176 Package Version Notes
177 =========================================================== ============ ==========================================
178 `GNU Make <http://savannah.gnu.org/projects/make>`_ 3.79, 3.79.1 Makefile/build processor
179 `GCC <http://gcc.gnu.org/>`_ >=4.7.0 C/C++ compiler\ :sup:`1`
180 `python <http://www.python.org/>`_ >=2.7 Automated test suite\ :sup:`2`
181 `GNU M4 <http://savannah.gnu.org/projects/m4>`_ 1.4 Macro processor for configuration\ :sup:`3`
182 `GNU Autoconf <http://www.gnu.org/software/autoconf/>`_ 2.60 Configuration script builder\ :sup:`3`
183 `GNU Automake <http://www.gnu.org/software/automake/>`_ 1.9.6 aclocal macro generator\ :sup:`3`
184 `libtool <http://savannah.gnu.org/projects/libtool>`_ 1.5.22 Shared library manager\ :sup:`3`
185 `zlib <http://zlib.net>`_ >=1.2.3.4 Compression library\ :sup:`4`
186 =========================================================== ============ ==========================================
190 #. Only the C and C++ languages are needed so there's no need to build the
191 other languages for LLVM's purposes. See `below` for specific version
193 #. Only needed if you want to run the automated test suite in the
194 ``llvm/test`` directory.
195 #. If you want to make changes to the configure scripts, you will need GNU
196 autoconf (2.60), and consequently, GNU M4 (version 1.4 or higher). You
197 will also need automake (1.9.6). We only use aclocal from that package.
198 #. Optional, adds compression / uncompression capabilities to selected LLVM
201 Additionally, your compilation host is expected to have the usual plethora of
202 Unix utilities. Specifically:
204 * **ar** --- archive library builder
205 * **bzip2** --- bzip2 command for distribution generation
206 * **bunzip2** --- bunzip2 command for distribution checking
207 * **chmod** --- change permissions on a file
208 * **cat** --- output concatenation utility
209 * **cp** --- copy files
210 * **date** --- print the current date/time
211 * **echo** --- print to standard output
212 * **egrep** --- extended regular expression search utility
213 * **find** --- find files/dirs in a file system
214 * **grep** --- regular expression search utility
215 * **gzip** --- gzip command for distribution generation
216 * **gunzip** --- gunzip command for distribution checking
217 * **install** --- install directories/files
218 * **mkdir** --- create a directory
219 * **mv** --- move (rename) files
220 * **ranlib** --- symbol table builder for archive libraries
221 * **rm** --- remove (delete) files and directories
222 * **sed** --- stream editor for transforming output
223 * **sh** --- Bourne shell for make build scripts
224 * **tar** --- tape archive for distribution generation
225 * **test** --- test things in file system
226 * **unzip** --- unzip command for distribution checking
227 * **zip** --- zip command for distribution generation
232 Host C++ Toolchain, both Compiler and Standard Library
233 ------------------------------------------------------
235 LLVM is very demanding of the host C++ compiler, and as such tends to expose
236 bugs in the compiler. We are also planning to follow improvements and
237 developments in the C++ language and library reasonably closely. As such, we
238 require a modern host C++ toolchain, both compiler and standard library, in
241 For the most popular host toolchains we check for specific minimum versions in
248 Anything older than these toolchains *may* work, but will require forcing the
249 build system with a special option and is not really a supported host platform.
250 Also note that older versions of these compilers have often crashed or
253 For less widely used host toolchains such as ICC or xlC, be aware that a very
254 recent version may be required to support all of the C++ features used in LLVM.
256 We track certain versions of software that are *known* to fail when used as
257 part of the host toolchain. These even include linkers at times.
259 **GCC 4.6.3 on ARM**: Miscompiles ``llvm-readobj`` at ``-O3``. A test failure
260 in ``test/Object/readobj-shared-object.test`` is one symptom of the problem.
262 **GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
263 warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
264 defined in a discarded section. You can safely ignore these messages as they are
265 erroneous and the linkage is correct. These messages disappear using ld 2.17.
267 **GNU binutils 2.17**: Binutils 2.17 contains `a bug
268 <http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link
269 times (minutes instead of seconds) when building LLVM. We recommend upgrading
270 to a newer version (2.17.50.0.4 or later).
272 **GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
273 <http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes
274 intermittent failures when building LLVM with position independent code. The
275 symptom is an error about cyclic dependencies. We recommend upgrading to a
276 newer version of Gold.
278 **Clang 3.0 with libstdc++ 4.7.x**: a few Linux distributions (Ubuntu 12.10,
279 Fedora 17) have both Clang 3.0 and libstdc++ 4.7 in their repositories. Clang
280 3.0 does not implement a few builtins that are used in this library. We
281 recommend using the system GCC to compile LLVM and Clang in this case.
283 **Clang 3.0 on Mageia 2**. There's a packaging issue: Clang can not find at
284 least some (``cxxabi.h``) libstdc++ headers.
286 **Clang in C++11 mode and libstdc++ 4.7.2**. This version of libstdc++
287 contained `a bug <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53841>`__ which
288 causes Clang to refuse to compile condition_variable header file. At the time
289 of writing, this breaks LLD build.
291 Getting a Modern Host C++ Toolchain
292 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
294 This section mostly applies to Linux and older BSDs. On Mac OS X, you should
295 have a sufficiently modern Xcode, or you will likely need to upgrade until you
296 do. On Windows, just use Visual Studio 2013 as the host compiler, it is
297 explicitly supported and widely available. FreeBSD 10.0 and newer have a modern
298 Clang as the system compiler.
300 However, some Linux distributions and some other or older BSDs sometimes have
301 extremely old versions of GCC. These steps attempt to help you upgrade you
302 compiler even on such a system. However, if at all possible, we encourage you
303 to use a recent version of a distribution with a modern system compiler that
304 meets these requirements. Note that it is tempting to to install a prior
305 version of Clang and libc++ to be the host compiler, however libc++ was not
306 well tested or set up to build on Linux until relatively recently. As
307 a consequence, this guide suggests just using libstdc++ and a modern GCC as the
308 initial host in a bootstrap, and then using Clang (and potentially libc++).
310 The first step is to get a recent GCC toolchain installed. The most common
311 distribution on which users have struggled with the version requirements is
312 Ubuntu Precise, 12.04 LTS. For this distribution, one easy option is to install
313 the `toolchain testing PPA`_ and use it to install a modern GCC. There is
314 a really nice discussions of this on the `ask ubuntu stack exchange`_. However,
315 not all users can use PPAs and there are many other distributions, so it may be
316 necessary (or just useful, if you're here you *are* doing compiler development
317 after all) to build and install GCC from source. It is also quite easy to do
320 .. _toolchain testing PPA:
321 https://launchpad.net/~ubuntu-toolchain-r/+archive/test
322 .. _ask ubuntu stack exchange:
323 http://askubuntu.com/questions/271388/how-to-install-gcc-4-8-in-ubuntu-12-04-from-the-terminal
325 Easy steps for installing GCC 4.8.2:
327 .. code-block:: console
329 % wget ftp://ftp.gnu.org/gnu/gcc/gcc-4.8.2/gcc-4.8.2.tar.bz2
330 % tar -xvjf gcc-4.8.2.tar.bz2
332 % ./contrib/download_prerequisites
334 % mkdir gcc-4.8.2-build
336 % $PWD/../gcc-4.8.2/configure --prefix=$HOME/toolchains --enable-languages=c,c++
340 For more details, check out the excellent `GCC wiki entry`_, where I got most
341 of this information from.
344 http://gcc.gnu.org/wiki/InstallingGCC
346 Once you have a GCC toolchain, configure your build of LLVM to use the new
347 toolchain for your host compiler and C++ standard library. Because the new
348 version of libstdc++ is not on the system library search path, you need to pass
349 extra linker flags so that it can be found at link time (``-L``) and at runtime
350 (``-rpath``). If you are using CMake, this invocation should produce working
353 .. code-block:: console
357 % CC=$HOME/toolchains/bin/gcc CXX=$HOME/toolchains/bin/g++ \
358 cmake .. -DCMAKE_CXX_LINK_FLAGS="-Wl,-rpath,$HOME/toolchains/lib64 -L$HOME/toolchains/lib64"
360 If you fail to set rpath, most LLVM binaries will fail on startup with a message
361 from the loader similar to ``libstdc++.so.6: version `GLIBCXX_3.4.20' not
362 found``. This means you need to tweak the -rpath linker flag.
364 When you build Clang, you will need to give *it* access to modern C++11
365 standard library in order to use it as your new host in part of a bootstrap.
366 There are two easy ways to do this, either build (and install) libc++ along
367 with Clang and then use it with the ``-stdlib=libc++`` compile and link flag,
368 or install Clang into the same prefix (``$HOME/toolchains`` above) as GCC.
369 Clang will look within its own prefix for libstdc++ and use it if found. You
370 can also add an explicit prefix for Clang to look in for a GCC toolchain with
371 the ``--gcc-toolchain=/opt/my/gcc/prefix`` flag, passing it to both compile and
372 link commands when using your just-built-Clang to bootstrap.
374 .. _Getting Started with LLVM:
376 Getting Started with LLVM
377 =========================
379 The remainder of this guide is meant to get you up and running with LLVM and to
380 give you some basic information about the LLVM environment.
382 The later sections of this guide describe the `general layout`_ of the LLVM
383 source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
384 more information about LLVM or to get help via e-mail.
386 Terminology and Notation
387 ------------------------
389 Throughout this manual, the following names are used to denote paths specific to
390 the local system and working environment. *These are not environment variables
391 you need to set but just strings used in the rest of this document below*. In
392 any of the examples below, simply replace each of these names with the
393 appropriate pathname on your local system. All these paths are absolute:
397 This is the top level directory of the LLVM source tree.
401 This is the top level directory of the LLVM object tree (i.e. the tree where
402 object files and compiled programs will be placed. It can be the same as
405 .. _Setting Up Your Environment:
407 Setting Up Your Environment
408 ---------------------------
410 In order to compile and use LLVM, you may need to set some environment
413 ``LLVM_LIB_SEARCH_PATH=/path/to/your/bitcode/libs``
415 [Optional] This environment variable helps LLVM linking tools find the
416 locations of your bitcode libraries. It is provided only as a convenience
417 since you can specify the paths using the -L options of the tools and the
418 C/C++ front-end will automatically use the bitcode files installed in its
421 Unpacking the LLVM Archives
422 ---------------------------
424 If you have the LLVM distribution, you will need to unpack it before you can
425 begin to compile it. LLVM is distributed as a set of two files: the LLVM suite
426 and the LLVM GCC front end compiled for your platform. There is an additional
427 test suite that is optional. Each file is a TAR archive that is compressed with
430 The files are as follows, with *x.y* marking the version number:
434 Source release for the LLVM libraries and tools.
436 ``llvm-test-x.y.tar.gz``
438 Source release for the LLVM test-suite.
442 Checkout LLVM from Subversion
443 -----------------------------
445 If you have access to our Subversion repository, you can get a fresh copy of the
446 entire source code. All you need to do is check it out from Subversion as
449 * ``cd where-you-want-llvm-to-live``
450 * Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
451 * Read-Write: ``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
453 This will create an '``llvm``' directory in the current directory and fully
454 populate it with the LLVM source code, Makefiles, test directories, and local
455 copies of documentation files.
457 If you want to get a specific release (as opposed to the most recent revision),
458 you can checkout it from the '``tags``' directory (instead of '``trunk``'). The
459 following releases are located in the following subdirectories of the '``tags``'
462 * Release 3.4: **RELEASE_34/final**
463 * Release 3.3: **RELEASE_33/final**
464 * Release 3.2: **RELEASE_32/final**
465 * Release 3.1: **RELEASE_31/final**
466 * Release 3.0: **RELEASE_30/final**
467 * Release 2.9: **RELEASE_29/final**
468 * Release 2.8: **RELEASE_28**
469 * Release 2.7: **RELEASE_27**
470 * Release 2.6: **RELEASE_26**
471 * Release 2.5: **RELEASE_25**
472 * Release 2.4: **RELEASE_24**
473 * Release 2.3: **RELEASE_23**
474 * Release 2.2: **RELEASE_22**
475 * Release 2.1: **RELEASE_21**
476 * Release 2.0: **RELEASE_20**
477 * Release 1.9: **RELEASE_19**
478 * Release 1.8: **RELEASE_18**
479 * Release 1.7: **RELEASE_17**
480 * Release 1.6: **RELEASE_16**
481 * Release 1.5: **RELEASE_15**
482 * Release 1.4: **RELEASE_14**
483 * Release 1.3: **RELEASE_13**
484 * Release 1.2: **RELEASE_12**
485 * Release 1.1: **RELEASE_11**
486 * Release 1.0: **RELEASE_1**
488 If you would like to get the LLVM test suite (a separate package as of 1.4), you
489 get it from the Subversion repository:
491 .. code-block:: console
494 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
496 By placing it in the ``llvm/projects``, it will be automatically configured by
497 the LLVM configure script as well as automatically updated when you run ``svn
503 Git mirrors are available for a number of LLVM subprojects. These mirrors sync
504 automatically with each Subversion commit and contain all necessary git-svn
505 marks (so, you can recreate git-svn metadata locally). Note that right now
506 mirrors reflect only ``trunk`` for each project. You can do the read-only Git
509 .. code-block:: console
511 % git clone http://llvm.org/git/llvm.git
513 If you want to check out clang too, run:
515 .. code-block:: console
518 % git clone http://llvm.org/git/clang.git
520 If you want to check out compiler-rt too, run:
522 .. code-block:: console
525 % git clone http://llvm.org/git/compiler-rt.git
527 If you want to check out the Test Suite Source Code (optional), run:
529 .. code-block:: console
532 % git clone http://llvm.org/git/test-suite.git
534 Since the upstream repository is in Subversion, you should use ``git
535 pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
536 in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the
537 master branch, run the following command:
539 .. code-block:: console
541 % git config branch.master.rebase true
543 Sending patches with Git
544 ^^^^^^^^^^^^^^^^^^^^^^^^
546 Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
548 Assume ``master`` points the upstream and ``mybranch`` points your working
549 branch, and ``mybranch`` is rebased onto ``master``. At first you may check
550 sanity of whitespaces:
552 .. code-block:: console
554 % git diff --check master..mybranch
556 The easiest way to generate a patch is as below:
558 .. code-block:: console
560 % git diff master..mybranch > /path/to/mybranch.diff
562 It is a little different from svn-generated diff. git-diff-generated diff has
563 prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
564 could be accepted with ``patch -p1 -N``.
566 But you may generate patchset with git-format-patch. It generates by-each-commit
567 patchset. To generate patch files to attach to your article:
569 .. code-block:: console
571 % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
573 If you would like to send patches directly, you may use git-send-email or
574 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
576 .. code-block:: console
578 % git format-patch --attach master..mybranch --stdout | git imap-send
580 Then, your .git/config should have [imap] sections.
585 host = imaps://imap.gmail.com
586 user = your.gmail.account@gmail.com
591 folder = "[Gmail]/Drafts"
592 ; example for Japanese, "Modified UTF-7" encoded.
593 folder = "[Gmail]/&Tgtm+DBN-"
594 ; example for Traditional Chinese
595 folder = "[Gmail]/&g0l6Pw-"
597 For developers to work with git-svn
598 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
600 To set up clone from which you can submit code using ``git-svn``, run:
602 .. code-block:: console
604 % git clone http://llvm.org/git/llvm.git
606 % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
607 % git config svn-remote.svn.fetch :refs/remotes/origin/master
608 % git svn rebase -l # -l avoids fetching ahead of the git mirror.
610 # If you have clang too:
612 % git clone http://llvm.org/git/clang.git
614 % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
615 % git config svn-remote.svn.fetch :refs/remotes/origin/master
618 Likewise for compiler-rt and test-suite.
620 To update this clone without generating git-svn tags that conflict with the
621 upstream Git repo, run:
623 .. code-block:: console
625 % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
626 % git checkout master
629 git checkout master &&
632 Likewise for compiler-rt and test-suite.
634 This leaves your working directories on their master branches, so you'll need to
635 ``checkout`` each working branch individually and ``rebase`` it on top of its
638 For those who wish to be able to update an llvm repo/revert patches easily using
639 git-svn, please look in the directory for the scripts ``git-svnup`` and
642 To perform the aforementioned update steps go into your source directory and
643 just type ``git-svnup`` or ``git svnup`` and everything will just work.
645 If one wishes to revert a commit with git-svn, but do not want the git hash to
646 escape into the commit message, one can use the script ``git-svnrevert`` or
647 ``git svnrevert`` which will take in the git hash for the commit you want to
648 revert, look up the appropriate svn revision, and output a message where all
649 references to the git hash have been replaced with the svn revision.
651 To commit back changes via git-svn, use ``git svn dcommit``:
653 .. code-block:: console
657 Note that git-svn will create one SVN commit for each Git commit you have pending,
658 so squash and edit each commit before executing ``dcommit`` to make sure they all
659 conform to the coding standards and the developers' policy.
661 On success, ``dcommit`` will rebase against the HEAD of SVN, so to avoid conflict,
662 please make sure your current branch is up-to-date (via fetch/rebase) before
665 The git-svn metadata can get out of sync after you mess around with branches and
666 ``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
667 about files with uncommitted changes. The fix is to rebuild the metadata:
669 .. code-block:: console
674 Please, refer to the Git-SVN manual (``man git-svn``) for more information.
676 Local LLVM Configuration
677 ------------------------
679 Once checked out from the Subversion repository, the LLVM suite source code must
680 be configured before being built. For instructions using autotools please see
681 `Building LLVM With Autotools <BuildingLLVMWithAutotools.html>`_. The
682 recommended process uses CMake. Unlinke the normal ``configure`` script, CMake
683 generates the build files in whatever format you request as well as various
684 ``*.inc`` files, and ``llvm/include/Config/config.h``.
686 Variables are passed to ``cmake`` on the command line using the format
687 ``-D<variable name>=<value>``. The following variables are some common options
688 used by people developing LLVM.
690 +-------------------------+----------------------------------------------------+
691 | Variable | Purpose |
692 +=========================+====================================================+
693 | CMAKE_C_COMPILER | Tells ``cmake`` which C compiler to use. By |
694 | | default, this will be /usr/bin/cc. |
695 +-------------------------+----------------------------------------------------+
696 | CMAKE_CXX_COMPILER | Tells ``cmake`` which C++ compiler to use. By |
697 | | default, this will be /usr/bin/c++. |
698 +-------------------------+----------------------------------------------------+
699 | CMAKE_BUILD_TYPE | Tells ``cmake`` what type of build you are trying |
700 | | to generate files for. Valid options are Debug, |
701 | | Release, RelWithDebInfo, and MinSizeRel. Default |
703 +-------------------------+----------------------------------------------------+
704 | CMAKE_INSTALL_PREFIX | Specifies the install directory to target when |
705 | | running the install action of the build files. |
706 +-------------------------+----------------------------------------------------+
707 | LLVM_TARGETS_TO_BUILD | A semicolon delimited list controlling which |
708 | | targets will be built and linked into llc. This is |
709 | | equivalent to the ``--enable-targets`` option in |
710 | | the configure script. The default list is defined |
711 | | as ``LLVM_ALL_TARGETS``, and can be set to include |
712 | | out-of-tree targets. The default value includes: |
713 | | ``AArch64, ARM, CppBackend, Hexagon, |
714 | | Mips, MSP430, NVPTX, PowerPC, AMDGPU, Sparc, |
715 | | SystemZ, X86, XCore``. |
716 +-------------------------+----------------------------------------------------+
717 | LLVM_ENABLE_DOXYGEN | Build doxygen-based documentation from the source |
718 | | code This is disabled by default because it is |
719 | | slow and generates a lot of output. |
720 +-------------------------+----------------------------------------------------+
721 | LLVM_ENABLE_SPHINX | Build sphinx-based documentation from the source |
722 | | code. This is disabled by default because it is |
723 | | slow and generates a lot of output. |
724 +-------------------------+----------------------------------------------------+
725 | LLVM_BUILD_LLVM_DYLIB | Generate libLLVM.so. This library contains a |
726 | | default set of LLVM components that can be |
727 | | overridden with ``LLVM_DYLIB_COMPONENTS``. The |
728 | | default contains most of LLVM and is defined in |
729 | | ``tools/llvm-shlib/CMakelists.txt``. |
730 +-------------------------+----------------------------------------------------+
731 | LLVM_OPTIMIZED_TABLEGEN | Builds a release tablegen that gets used during |
732 | | the LLVM build. This can dramatically speed up |
734 +-------------------------+----------------------------------------------------+
736 To configure LLVM, follow these steps:
738 #. Change directory into the object root directory:
740 .. code-block:: console
744 #. Run the ``cmake``:
746 .. code-block:: console
748 % cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=prefix=/install/path
749 [other options] SRC_ROOT
751 Compiling the LLVM Suite Source Code
752 ------------------------------------
754 Unlike with autotools, with CMake your build type is defined at configuration.
755 If you want to change your build type, you can re-run cmake with the following
758 .. code-block:: console
760 % cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=type SRC_ROOT
762 Between runs, CMake preserves the values set for all options. CMake has the
763 following build types defined:
767 These builds are the default. The build system will compile the tools and
768 libraries unoptimized, with debugging information, and asserts enabled.
772 For these builds, the build system will compile the tools and libraries
773 with optimizations enabled and not generate debug info. CMakes default
774 optimization level is -O3. This can be configured by setting the
775 ``CMAKE_CXX_FLAGS_RELEASE`` variable on the CMake command line.
779 These builds are useful when debugging. They generate optimized binaries with
780 debug information. CMakes default optimization level is -O2. This can be
781 configured by setting the ``CMAKE_CXX_FLAGS_RELWITHDEBINFO`` variable on the
784 Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
785 directory and issuing the following command:
787 .. code-block:: console
791 If the build fails, please `check here`_ to see if you are using a version of
792 GCC that is known not to compile LLVM.
794 If you have multiple processors in your machine, you may wish to use some of the
795 parallel build options provided by GNU Make. For example, you could use the
798 .. code-block:: console
802 There are several special targets which are useful when working with the LLVM
807 Removes all files generated by the build. This includes object files,
808 generated C/C++ files, libraries, and executables.
812 Installs LLVM header files, libraries, tools, and documentation in a hierarchy
813 under ``$PREFIX``, specified with ``CMAKE_INSTALL_PREFIX``, which
814 defaults to ``/usr/local``.
816 ``make docs-llvm-html``
818 If configured with ``-DLLVM_ENABLE_SPHINX=On``, this will generate a directory
819 at ``OBJ_ROOT/docs/html`` which contains the HTML formatted documentation.
824 It is possible to cross-compile LLVM itself. That is, you can create LLVM
825 executables and libraries to be hosted on a platform different from the platform
826 where they are built (a Canadian Cross build). To generate build files for
827 cross-compiling CMake provides a variable ``CMAKE_TOOLCHAIN_FILE`` which can
828 define compiler flags and variables used during the CMake test operations.
830 The result of such a build is executables that are not runnable on on the build
831 host but can be executed on the target. As an example the following CMake
832 invocation can generate build files targeting iOS. This will work on Mac OS X
833 with the latest Xcode:
835 .. code-block:: console
837 % cmake -G "Ninja" -DCMAKE_OSX_ARCHITECTURES=“armv7;armv7s;arm64"
838 -DCMAKE_TOOLCHAIN_FILE=<PATH_TO_LLVM>/cmake/platforms/iOS.cmake
839 -DCMAKE_BUILD_TYPE=Release -DLLVM_BUILD_RUNTIME=Off -DLLVM_INCLUDE_TESTS=Off
840 -DLLVM_INCLUDE_EXAMPLES=Off -DLLVM_ENABLE_BACKTRACES=Off [options]
843 Note: There are some additional flags that need to be passed when building for
844 iOS due to limitations in the iOS SDK.
846 Check :doc:`HowToCrossCompileLLVM` and `Clang docs on how to cross-compile in general
847 <http://clang.llvm.org/docs/CrossCompilation.html>`_ for more information
848 about cross-compiling.
850 The Location of LLVM Object Files
851 ---------------------------------
853 The LLVM build system is capable of sharing a single LLVM source tree among
854 several LLVM builds. Hence, it is possible to build LLVM for several different
855 platforms or configurations using the same source tree.
857 This is accomplished in the typical autoconf manner:
859 * Change directory to where the LLVM object files should live:
861 .. code-block:: console
867 .. code-block:: console
869 % cmake -G "Unix Makefiles" SRC_ROOT
871 The LLVM build will create a structure underneath *OBJ_ROOT* that matches the
872 LLVM source tree. At each level where source files are present in the source
873 tree there will be a corresponding ``CMakeFiles`` directory in the *OBJ_ROOT*.
874 Underneath that directory there is another directory with a name ending in
875 ``.dir`` under which you'll find object files for each source.
879 .. code-block:: console
882 % find lib/Support/ -name APFloat*
883 lib/Support/CMakeFiles/LLVMSupport.dir/APFloat.cpp.o
885 Optional Configuration Items
886 ----------------------------
888 If you're running on a Linux system that supports the `binfmt_misc
889 <http://en.wikipedia.org/wiki/binfmt_misc>`_
890 module, and you have root access on the system, you can set your system up to
891 execute LLVM bitcode files directly. To do this, use commands like this (the
892 first command may not be required if you are already using the module):
894 .. code-block:: console
896 % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
897 % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
898 % chmod u+x hello.bc (if needed)
901 This allows you to execute LLVM bitcode files directly. On Debian, you can also
902 use this command instead of the 'echo' command above:
904 .. code-block:: console
906 % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
914 One useful source of information about the LLVM source base is the LLVM `doxygen
915 <http://www.doxygen.org/>`_ documentation available at
916 `<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
922 This directory contains some simple examples of how to use the LLVM IR and JIT.
927 This directory contains public header files exported from the LLVM library. The
928 three main subdirectories of this directory are:
930 ``llvm/include/llvm``
932 This directory contains all of the LLVM specific header files. This directory
933 also has subdirectories for different portions of LLVM: ``Analysis``,
934 ``CodeGen``, ``Target``, ``Transforms``, etc...
936 ``llvm/include/llvm/Support``
938 This directory contains generic support libraries that are provided with LLVM
939 but not necessarily specific to LLVM. For example, some C++ STL utilities and
940 a Command Line option processing library store their header files here.
942 ``llvm/include/llvm/Config``
944 This directory contains header files configured by the ``configure`` script.
945 They wrap "standard" UNIX and C header files. Source code can include these
946 header files which automatically take care of the conditional #includes that
947 the ``configure`` script generates.
952 This directory contains most of the source files of the LLVM system. In LLVM,
953 almost all code exists in libraries, making it very easy to share code among the
958 This directory holds the core LLVM source files that implement core classes
959 like Instruction and BasicBlock.
961 ``llvm/lib/AsmParser/``
963 This directory holds the source code for the LLVM assembly language parser
966 ``llvm/lib/Bitcode/``
968 This directory holds code for reading and write LLVM bitcode.
970 ``llvm/lib/Analysis/``
972 This directory contains a variety of different program analyses, such as
973 Dominator Information, Call Graphs, Induction Variables, Interval
974 Identification, Natural Loop Identification, etc.
976 ``llvm/lib/Transforms/``
978 This directory contains the source code for the LLVM to LLVM program
979 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
980 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
981 Elimination, and many others.
985 This directory contains files that describe various target architectures for
986 code generation. For example, the ``llvm/lib/Target/X86`` directory holds the
987 X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
990 ``llvm/lib/CodeGen/``
992 This directory contains the major parts of the code generator: Instruction
993 Selector, Instruction Scheduling, and Register Allocation.
999 ``llvm/lib/Debugger/``
1001 This directory contains the source level debugger library that makes it
1002 possible to instrument LLVM programs so that a debugger could identify source
1003 code locations at which the program is executing.
1005 ``llvm/lib/ExecutionEngine/``
1007 This directory contains libraries for executing LLVM bitcode directly at
1008 runtime in both interpreted and JIT compiled fashions.
1010 ``llvm/lib/Support/``
1012 This directory contains the source code that corresponds to the header files
1013 located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
1018 This directory contains projects that are not strictly part of LLVM but are
1019 shipped with LLVM. This is also the directory where you should create your own
1020 LLVM-based projects.
1025 This directory contains libraries which are compiled into LLVM bitcode and used
1026 when linking programs with the Clang front end. Most of these libraries are
1027 skeleton versions of real libraries; for example, libc is a stripped down
1030 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
1036 This directory contains feature and regression tests and other basic sanity
1037 checks on the LLVM infrastructure. These are intended to run quickly and cover a
1038 lot of territory without being exhaustive.
1043 This is not a directory in the normal llvm module; it is a separate Subversion
1044 module that must be checked out (usually to ``projects/test-suite``). This
1045 module contains a comprehensive correctness, performance, and benchmarking test
1046 suite for LLVM. It is a separate Subversion module because not every LLVM user
1047 is interested in downloading or building such a comprehensive test suite. For
1048 further details on this test suite, please see the :doc:`Testing Guide
1049 <TestingGuide>` document.
1056 The **tools** directory contains the executables built out of the libraries
1057 above, which form the main part of the user interface. You can always get help
1058 for a tool by typing ``tool_name -help``. The following is a brief introduction
1059 to the most important tools. More detailed information is in
1060 the `Command Guide <CommandGuide/index.html>`_.
1064 ``bugpoint`` is used to debug optimization passes or code generation backends
1065 by narrowing down the given test case to the minimum number of passes and/or
1066 instructions that still cause a problem, whether it is a crash or
1067 miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
1072 The archiver produces an archive containing the given LLVM bitcode files,
1073 optionally with an index for faster lookup.
1077 The assembler transforms the human readable LLVM assembly to LLVM bitcode.
1081 The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
1085 ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
1090 ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
1091 (although very slowly...). For architectures that support it (currently x86,
1092 Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
1093 compiler (if the functionality was compiled in), and will execute the code
1094 *much* faster than the interpreter.
1098 ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
1099 native code assembly file or to C code (with the ``-march=c`` option).
1103 ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
1104 (which are specified on the command line), and then outputs the resultant
1105 bitcode. The '``opt -help``' command is a good way to get a list of the
1106 program transformations available in LLVM.
1108 ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
1109 file and print out the results. It is primarily useful for debugging
1110 analyses, or familiarizing yourself with what an analysis does.
1115 This directory contains utilities for working with LLVM source code, and some of
1116 the utilities are actually required as part of the build process because they
1117 are code generators for parts of LLVM infrastructure.
1122 ``codegen-diff`` is a script that finds differences between code that LLC
1123 generates and code that LLI generates. This is a useful tool if you are
1124 debugging one of them, assuming that the other generates correct output. For
1125 the full user manual, run ```perldoc codegen-diff'``.
1129 The ``emacs`` directory contains syntax-highlighting files which will work
1130 with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
1131 assembly files and TableGen description files. For information on how to use
1132 the syntax files, consult the ``README`` file in that directory.
1136 The ``getsrcs.sh`` script finds and outputs all non-generated source files,
1137 which is useful if one wishes to do a lot of development across directories
1138 and does not want to individually find each file. One way to use it is to run,
1139 for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
1144 This little tool performs an ``egrep -H -n`` on each source file in LLVM and
1145 passes to it a regular expression provided on ``llvmgrep``'s command
1146 line. This is a very efficient way of searching the source base for a
1147 particular regular expression.
1151 The ``makellvm`` script compiles all files in the current directory and then
1152 compiles and links the tool that is the first argument. For example, assuming
1153 you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
1154 path, simply running ``makellvm llc`` will make a build of the current
1155 directory, switch to directory ``llvm/tools/llc`` and build it, causing a
1160 The ``TableGen`` directory contains the tool used to generate register
1161 descriptions, instruction set descriptions, and even assemblers from common
1162 TableGen description files.
1166 The ``vim`` directory contains syntax-highlighting files which will work with
1167 the VIM editor, providing syntax highlighting support for LLVM assembly files
1168 and TableGen description files. For information on how to use the syntax
1169 files, consult the ``README`` file in that directory.
1173 An Example Using the LLVM Tool Chain
1174 ====================================
1176 This section gives an example of using LLVM with the Clang front end.
1181 #. First, create a simple C file, name it 'hello.c':
1188 printf("hello world\n");
1192 #. Next, compile the C file into a native executable:
1194 .. code-block:: console
1196 % clang hello.c -o hello
1200 Clang works just like GCC by default. The standard -S and -c arguments
1201 work as usual (producing a native .s or .o file, respectively).
1203 #. Next, compile the C file into an LLVM bitcode file:
1205 .. code-block:: console
1207 % clang -O3 -emit-llvm hello.c -c -o hello.bc
1209 The -emit-llvm option can be used with the -S or -c options to emit an LLVM
1210 ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
1211 the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
1213 #. Run the program in both forms. To run the program, use:
1215 .. code-block:: console
1221 .. code-block:: console
1225 The second examples shows how to invoke the LLVM JIT, :doc:`lli
1226 <CommandGuide/lli>`.
1228 #. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
1230 .. code-block:: console
1232 % llvm-dis < hello.bc | less
1234 #. Compile the program to native assembly using the LLC code generator:
1236 .. code-block:: console
1238 % llc hello.bc -o hello.s
1240 #. Assemble the native assembly language file into a program:
1242 .. code-block:: console
1244 % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
1246 % gcc hello.s -o hello.native # On others
1248 #. Execute the native code program:
1250 .. code-block:: console
1254 Note that using clang to compile directly to native code (i.e. when the
1255 ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
1260 If you are having problems building or using LLVM, or if you have any other
1261 general questions about LLVM, please consult the `Frequently Asked
1262 Questions <FAQ.html>`_ page.
1269 This document is just an **introduction** on how to use LLVM to do some simple
1270 things... there are many more interesting and complicated things that you can do
1271 that aren't documented here (but we'll gladly accept a patch if you want to
1272 write something up!). For more information about LLVM, check out:
1274 * `LLVM Homepage <http://llvm.org/>`_
1275 * `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
1276 * `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_