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32 The LLVM Getting Started documentation may be out of date.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 * ``cd where-you-want-to-build-llvm``
67 * ``mkdir build`` (for building without polluting the source dir)
69 * ``../llvm/configure [options]``
72 * ``--prefix=directory`` --- Specify for *directory* the full pathname of
73 where you want the LLVM tools and libraries to be installed (default
76 * ``--enable-optimized`` --- Compile with optimizations enabled (default
79 * ``--enable-assertions`` --- Compile with assertion checks enabled
82 * ``make [-j]`` --- The ``-j`` specifies the number of jobs (commands) to run
83 simultaneously. This builds both LLVM and Clang for Debug+Asserts mode.
84 The ``--enabled-optimized`` configure option is used to specify a Release
87 * ``make check-all`` --- This run the regression tests to ensure everything
90 * ``make update`` --- This command is used to update all the svn repositories
91 at once, rather then having to ``cd`` into the individual repositories and
92 running ``svn update``.
94 * It is also possible to use CMake instead of the makefiles. With CMake it is
95 possible to generate project files for several IDEs: Xcode, Eclipse CDT4,
96 CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.
98 * If you get an "internal compiler error (ICE)" or test failures, see
101 Consult the `Getting Started with LLVM`_ section for detailed information on
102 configuring and compiling LLVM. See `Setting Up Your Environment`_ for tips
103 that simplify working with the Clang front end and LLVM tools. Go to `Program
104 Layout`_ to learn about the layout of the source code tree.
109 Before you begin to use the LLVM system, review the requirements given below.
110 This may save you some trouble by knowing ahead of time what hardware and
111 software you will need.
116 LLVM is known to work on the following platforms:
118 +-----------------+----------------------+-------------------------+
119 |OS | Arch | Compilers |
120 +=================+======================+=========================+
121 |AuroraUX | x86\ :sup:`1` | GCC |
122 +-----------------+----------------------+-------------------------+
123 |Linux | x86\ :sup:`1` | GCC |
124 +-----------------+----------------------+-------------------------+
125 |Linux | amd64 | GCC |
126 +-----------------+----------------------+-------------------------+
127 |Linux | ARM\ :sup:`13` | GCC |
128 +-----------------+----------------------+-------------------------+
129 |Solaris | V9 (Ultrasparc) | GCC |
130 +-----------------+----------------------+-------------------------+
131 |FreeBSD | x86\ :sup:`1` | GCC |
132 +-----------------+----------------------+-------------------------+
133 |FreeBSD | amd64 | GCC |
134 +-----------------+----------------------+-------------------------+
135 |MacOS X\ :sup:`2`| PowerPC | GCC |
136 +-----------------+----------------------+-------------------------+
137 |MacOS X\ :sup:`9`| x86 | GCC |
138 +-----------------+----------------------+-------------------------+
139 |Cygwin/Win32 | x86\ :sup:`1, 8, 11` | GCC 3.4.X, binutils 2.20|
140 +-----------------+----------------------+-------------------------+
142 LLVM has partial support for the following platforms:
144 +-------------------+----------------------+-------------------------------------------+
145 |OS | Arch | Compilers |
146 +===================+======================+===========================================+
147 | Windows | x86\ :sup:`1` | Visual Studio 2000 or higher\ :sup:`4,5` |
148 +-------------------+----------------------+-------------------------------------------+
149 | AIX\ :sup:`3,4` | PowerPC | GCC |
150 +-------------------+----------------------+-------------------------------------------+
151 | Linux\ :sup:`3,5` | PowerPC | GCC |
152 +-------------------+----------------------+-------------------------------------------+
153 | Linux\ :sup:`7` | Alpha | GCC |
154 +-------------------+----------------------+-------------------------------------------+
155 | Linux\ :sup:`7` | Itanium (IA-64) | GCC |
156 +-------------------+----------------------+-------------------------------------------+
157 | HP-UX\ :sup:`7` | Itanium (IA-64) | HP aCC |
158 +-------------------+----------------------+-------------------------------------------+
159 | Windows x64 | x86-64 | mingw-w64's GCC-4.5.x\ :sup:`12` |
160 +-------------------+----------------------+-------------------------------------------+
164 #. Code generation supported for Pentium processors and up
165 #. Code generation supported for 32-bit ABI only
166 #. No native code generation
167 #. Build is not complete: one or more tools do not link or function
168 #. The GCC-based C/C++ frontend does not build
169 #. The port is done using the MSYS shell.
170 #. Native code generation exists but is not complete.
171 #. Binutils 2.20 or later is required to build the assembler generated by LLVM properly.
172 #. Xcode 2.5 and gcc 4.0.1 (Apple Build 5370) will trip internal LLVM assert
173 messages when compiled for Release at optimization levels greater than 0
174 (i.e., ``-O1`` and higher). Add ``OPTIMIZE_OPTION="-O0"`` to the build
175 command line if compiling for LLVM Release or bootstrapping the LLVM
177 #. For MSYS/MinGW on Windows, be sure to install the MSYS version of the perl
178 package, and be sure it appears in your path before any Windows-based
179 versions such as Strawberry Perl and ActivePerl, as these have
180 Windows-specifics that will cause the build to fail.
181 #. To use LLVM modules on Win32-based system, you may configure LLVM
182 with ``--enable-shared``.
183 #. To compile SPU backend, you need to add ``LDFLAGS=-Wl,--stack,16777216`` to
185 #. MCJIT not working well pre-v7, old JIT engine not supported any more.
187 Note that you will need about 1-3 GB of space for a full LLVM build in Debug
188 mode, depending on the system (it is so large because of all the debugging
189 information and the fact that the libraries are statically linked into multiple
190 tools). If you do not need many of the tools and you are space-conscious, you
191 can pass ``ONLY_TOOLS="tools you need"`` to make. The Release build requires
192 considerably less space.
194 The LLVM suite *may* compile on other platforms, but it is not guaranteed to do
195 so. If compilation is successful, the LLVM utilities should be able to
196 assemble, disassemble, analyze, and optimize LLVM bitcode. Code generation
197 should work as well, although the generated native code may not work on your
203 Compiling LLVM requires that you have several software packages installed. The
204 table below lists those required packages. The Package column is the usual name
205 for the software package that LLVM depends on. The Version column provides
206 "known to work" versions of the package. The Notes column describes how LLVM
207 uses the package and provides other details.
209 +--------------------------------------------------------------+-----------------+---------------------------------------------+
210 | Package | Version | Notes |
211 +==============================================================+=================+=============================================+
212 | `GNU Make <http://savannah.gnu.org/projects/make>`_ | 3.79, 3.79.1 | Makefile/build processor |
213 +--------------------------------------------------------------+-----------------+---------------------------------------------+
214 | `GCC <http://gcc.gnu.org/>`_ | 3.4.2 | C/C++ compiler\ :sup:`1` |
215 +--------------------------------------------------------------+-----------------+---------------------------------------------+
216 | `TeXinfo <http://www.gnu.org/software/texinfo/>`_ | 4.5 | For building the CFE |
217 +--------------------------------------------------------------+-----------------+---------------------------------------------+
218 | `SVN <http://subversion.tigris.org/project_packages.html>`_ | >=1.3 | Subversion access to LLVM\ :sup:`2` |
219 +--------------------------------------------------------------+-----------------+---------------------------------------------+
220 | `python <http://www.python.org/>`_ | >=2.4 | Automated test suite\ :sup:`3` |
221 +--------------------------------------------------------------+-----------------+---------------------------------------------+
222 | `perl <http://www.perl.com/download.csp>`_ | >=5.6.0 | Utilities |
223 +--------------------------------------------------------------+-----------------+---------------------------------------------+
224 | `GNU M4 <http://savannah.gnu.org/projects/m4>`_ | 1.4 | Macro processor for configuration\ :sup:`4` |
225 +--------------------------------------------------------------+-----------------+---------------------------------------------+
226 | `GNU Autoconf <http://www.gnu.org/software/autoconf/>`_ | 2.60 | Configuration script builder\ :sup:`4` |
227 +--------------------------------------------------------------+-----------------+---------------------------------------------+
228 | `GNU Automake <http://www.gnu.org/software/automake/>`_ | 1.9.6 | aclocal macro generator\ :sup:`4` |
229 +--------------------------------------------------------------+-----------------+---------------------------------------------+
230 | `libtool <http://savannah.gnu.org/projects/libtool>`_ | 1.5.22 | Shared library manager\ :sup:`4` |
231 +--------------------------------------------------------------+-----------------+---------------------------------------------+
235 #. Only the C and C++ languages are needed so there's no need to build the
236 other languages for LLVM's purposes. See `below` for specific version
238 #. You only need Subversion if you intend to build from the latest LLVM
239 sources. If you're working from a release distribution, you don't need
241 #. Only needed if you want to run the automated test suite in the
242 ``llvm/test`` directory.
243 #. If you want to make changes to the configure scripts, you will need GNU
244 autoconf (2.60), and consequently, GNU M4 (version 1.4 or higher). You
245 will also need automake (1.9.6). We only use aclocal from that package.
247 Additionally, your compilation host is expected to have the usual plethora of
248 Unix utilities. Specifically:
250 * **ar** --- archive library builder
251 * **bzip2** --- bzip2 command for distribution generation
252 * **bunzip2** --- bunzip2 command for distribution checking
253 * **chmod** --- change permissions on a file
254 * **cat** --- output concatenation utility
255 * **cp** --- copy files
256 * **date** --- print the current date/time
257 * **echo** --- print to standard output
258 * **egrep** --- extended regular expression search utility
259 * **find** --- find files/dirs in a file system
260 * **grep** --- regular expression search utility
261 * **gzip** --- gzip command for distribution generation
262 * **gunzip** --- gunzip command for distribution checking
263 * **install** --- install directories/files
264 * **mkdir** --- create a directory
265 * **mv** --- move (rename) files
266 * **ranlib** --- symbol table builder for archive libraries
267 * **rm** --- remove (delete) files and directories
268 * **sed** --- stream editor for transforming output
269 * **sh** --- Bourne shell for make build scripts
270 * **tar** --- tape archive for distribution generation
271 * **test** --- test things in file system
272 * **unzip** --- unzip command for distribution checking
273 * **zip** --- zip command for distribution generation
278 Broken versions of GCC and other tools
279 --------------------------------------
281 LLVM is very demanding of the host C++ compiler, and as such tends to expose
282 bugs in the compiler. In particular, several versions of GCC crash when trying
283 to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang. Other
284 versions of GCC will probably work as well. GCC versions listed here are known
285 to not work. If you are using one of these versions, please try to upgrade your
286 GCC to something more recent. If you run into a problem with a version of GCC
287 not listed here, please `let us know <mailto:llvmdev@cs.uiuc.edu>`_. Please use
288 the "``gcc -v``" command to find out which version of GCC you are using.
290 **GCC versions prior to 3.0**: GCC 2.96.x and before had several problems in the
291 STL that effectively prevent it from compiling LLVM.
293 **GCC 3.2.2 and 3.2.3**: These versions of GCC fails to compile LLVM with a
294 bogus template error. This was fixed in later GCCs.
296 **GCC 3.3.2**: This version of GCC suffered from a `serious bug
297 <http://gcc.gnu.org/PR13392>`_ which causes it to crash in the
298 "``convert_from_eh_region_ranges_1``" GCC function.
300 **Cygwin GCC 3.3.3**: The version of GCC 3.3.3 commonly shipped with Cygwin does
303 **SuSE GCC 3.3.3**: The version of GCC 3.3.3 shipped with SuSE 9.1 (and possibly
304 others) does not compile LLVM correctly (it appears that exception handling is
305 broken in some cases). Please download the FSF 3.3.3 or upgrade to a newer
308 **GCC 3.4.0 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
309 generator, causing an infinite loop in the llvm-gcc build when built with
310 optimizations enabled (i.e. a release build).
312 **GCC 3.4.2 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
313 generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0) correctly
314 compiles LLVM at -O2. A work around is to build release LLVM builds with
315 "``make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ...``"
317 **GCC 3.4.x on X86-64/amd64**: GCC `miscompiles portions of LLVM
318 <http://llvm.org/PR1056>`__.
320 **GCC 3.4.4 (CodeSourcery ARM 2005q3-2)**: this compiler miscompiles LLVM when
321 building with optimizations enabled. It appears to work with "``make
322 ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1``" or build a debug build.
324 **IA-64 GCC 4.0.0**: The IA-64 version of GCC 4.0.0 is known to miscompile LLVM.
326 **Apple Xcode 2.3**: GCC crashes when compiling LLVM at -O3 (which is the
327 default with ENABLE_OPTIMIZED=1. To work around this, build with
328 "``ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2``".
330 **GCC 4.1.1**: GCC fails to build LLVM with template concept check errors
331 compiling some files. At the time of this writing, GCC mainline (4.2) did not
334 **GCC 4.1.1 on X86-64/amd64**: GCC `miscompiles portions of LLVM
335 <http://llvm.org/PR1063>`__ when compiling llvm itself into 64-bit code. LLVM
336 will appear to mostly work but will be buggy, e.g. failing portions of its
339 **GCC 4.1.2 on OpenSUSE**: Seg faults during libstdc++ build and on x86_64
340 platforms compiling md5.c gets a mangled constant.
342 **GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian**: Appears to
343 miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining about
344 symbols remaining in the table on destruction.
346 **GCC 4.1.2 20071124 (Red Hat 4.1.2-42)**: Suffers from the same symptoms as the
347 previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).
349 **Cygwin GCC 4.3.2 20080827 (beta) 2**: Users `reported
350 <http://llvm.org/PR4145>`_ various problems related with link errors when using
353 **Debian GCC 4.3.2 on X86**: Crashes building some files in LLVM 2.6.
355 **GCC 4.3.3 (Debian 4.3.3-10) on ARM**: Miscompiles parts of LLVM 2.6 when
356 optimizations are turned on. The symptom is an infinite loop in
357 ``FoldingSetImpl::RemoveNode`` while running the code generator.
359 **SUSE 11 GCC 4.3.4**: Miscompiles LLVM, causing crashes in ValueHandle logic.
361 **GCC 4.3.5 and GCC 4.4.5 on ARM**: These can miscompile ``value >> 1`` even at
362 ``-O0``. A test failure in ``test/Assembler/alignstack.ll`` is one symptom of
365 **GCC 4.6.3 on ARM**: Miscompiles ``llvm-readobj`` at ``-O3``. A test failure
366 in ``test/Object/readobj-shared-object.test`` is one symptom of the problem.
368 **GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
369 warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
370 defined in a discarded section. You can safely ignore these messages as they are
371 erroneous and the linkage is correct. These messages disappear using ld 2.17.
373 **GNU binutils 2.17**: Binutils 2.17 contains `a bug
374 <http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link
375 times (minutes instead of seconds) when building LLVM. We recommend upgrading
376 to a newer version (2.17.50.0.4 or later).
378 **GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
379 <http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes
380 intermittent failures when building LLVM with position independent code. The
381 symptom is an error about cyclic dependencies. We recommend upgrading to a
382 newer version of Gold.
384 **Clang 3.0 with libstdc++ 4.7.x**: a few Linux distributions (Ubuntu 12.10,
385 Fedora 17) have both Clang 3.0 and libstdc++ 4.7 in their repositories. Clang
386 3.0 does not implement a few builtins that are used in this library. We
387 recommend using the system GCC to compile LLVM and Clang in this case.
389 **Clang 3.0 on Mageia 2**. There's a packaging issue: Clang can not find at
390 least some (``cxxabi.h``) libstdc++ headers.
392 .. _Getting Started with LLVM:
394 Getting Started with LLVM
395 =========================
397 The remainder of this guide is meant to get you up and running with LLVM and to
398 give you some basic information about the LLVM environment.
400 The later sections of this guide describe the `general layout`_ of the LLVM
401 source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
402 more information about LLVM or to get help via e-mail.
404 Terminology and Notation
405 ------------------------
407 Throughout this manual, the following names are used to denote paths specific to
408 the local system and working environment. *These are not environment variables
409 you need to set but just strings used in the rest of this document below*. In
410 any of the examples below, simply replace each of these names with the
411 appropriate pathname on your local system. All these paths are absolute:
415 This is the top level directory of the LLVM source tree.
419 This is the top level directory of the LLVM object tree (i.e. the tree where
420 object files and compiled programs will be placed. It can be the same as
423 .. _Setting Up Your Environment:
425 Setting Up Your Environment
426 ---------------------------
428 In order to compile and use LLVM, you may need to set some environment
431 ``LLVM_LIB_SEARCH_PATH=/path/to/your/bitcode/libs``
433 [Optional] This environment variable helps LLVM linking tools find the
434 locations of your bitcode libraries. It is provided only as a convenience
435 since you can specify the paths using the -L options of the tools and the
436 C/C++ front-end will automatically use the bitcode files installed in its
439 Unpacking the LLVM Archives
440 ---------------------------
442 If you have the LLVM distribution, you will need to unpack it before you can
443 begin to compile it. LLVM is distributed as a set of two files: the LLVM suite
444 and the LLVM GCC front end compiled for your platform. There is an additional
445 test suite that is optional. Each file is a TAR archive that is compressed with
448 The files are as follows, with *x.y* marking the version number:
452 Source release for the LLVM libraries and tools.
454 ``llvm-test-x.y.tar.gz``
456 Source release for the LLVM test-suite.
458 ``llvm-gcc-4.2-x.y.source.tar.gz``
460 Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
461 directory for build instructions.
463 ``llvm-gcc-4.2-x.y-platform.tar.gz``
465 Binary release of the llvm-gcc-4.2 front end for a specific platform.
469 Checkout LLVM from Subversion
470 -----------------------------
472 If you have access to our Subversion repository, you can get a fresh copy of the
473 entire source code. All you need to do is check it out from Subversion as
476 * ``cd where-you-want-llvm-to-live``
477 * Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
478 * Read-Write:``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
480 This will create an '``llvm``' directory in the current directory and fully
481 populate it with the LLVM source code, Makefiles, test directories, and local
482 copies of documentation files.
484 If you want to get a specific release (as opposed to the most recent revision),
485 you can checkout it from the '``tags``' directory (instead of '``trunk``'). The
486 following releases are located in the following subdirectories of the '``tags``'
489 * Release 3.1: **RELEASE_31/final**
490 * Release 3.0: **RELEASE_30/final**
491 * Release 2.9: **RELEASE_29/final**
492 * Release 2.8: **RELEASE_28**
493 * Release 2.7: **RELEASE_27**
494 * Release 2.6: **RELEASE_26**
495 * Release 2.5: **RELEASE_25**
496 * Release 2.4: **RELEASE_24**
497 * Release 2.3: **RELEASE_23**
498 * Release 2.2: **RELEASE_22**
499 * Release 2.1: **RELEASE_21**
500 * Release 2.0: **RELEASE_20**
501 * Release 1.9: **RELEASE_19**
502 * Release 1.8: **RELEASE_18**
503 * Release 1.7: **RELEASE_17**
504 * Release 1.6: **RELEASE_16**
505 * Release 1.5: **RELEASE_15**
506 * Release 1.4: **RELEASE_14**
507 * Release 1.3: **RELEASE_13**
508 * Release 1.2: **RELEASE_12**
509 * Release 1.1: **RELEASE_11**
510 * Release 1.0: **RELEASE_1**
512 If you would like to get the LLVM test suite (a separate package as of 1.4), you
513 get it from the Subversion repository:
515 .. code-block:: console
518 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
520 By placing it in the ``llvm/projects``, it will be automatically configured by
521 the LLVM configure script as well as automatically updated when you run ``svn
527 GIT mirrors are available for a number of LLVM subprojects. These mirrors sync
528 automatically with each Subversion commit and contain all necessary git-svn
529 marks (so, you can recreate git-svn metadata locally). Note that right now
530 mirrors reflect only ``trunk`` for each project. You can do the read-only GIT
533 .. code-block:: console
535 % git clone http://llvm.org/git/llvm.git
537 If you want to check out clang too, run:
539 .. code-block:: console
542 % git clone http://llvm.org/git/clang.git
544 If you want to check out compiler-rt too, run:
546 .. code-block:: console
549 % git clone http://llvm.org/git/compiler-rt.git
551 If you want to check out the Test Suite Source Code (optional), run:
553 .. code-block:: console
556 % git clone http://llvm.org/git/test-suite.git
558 Since the upstream repository is in Subversion, you should use ``git
559 pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
560 in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the
561 master branch, run the following command:
563 .. code-block:: console
565 % git config branch.master.rebase true
567 Sending patches with Git
568 ^^^^^^^^^^^^^^^^^^^^^^^^
570 Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
572 Assume ``master`` points the upstream and ``mybranch`` points your working
573 branch, and ``mybranch`` is rebased onto ``master``. At first you may check
574 sanity of whitespaces:
576 .. code-block:: console
578 % git diff --check master..mybranch
580 The easiest way to generate a patch is as below:
582 .. code-block:: console
584 % git diff master..mybranch > /path/to/mybranch.diff
586 It is a little different from svn-generated diff. git-diff-generated diff has
587 prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
588 could be accepted with ``patch -p1 -N``.
590 But you may generate patchset with git-format-patch. It generates by-each-commit
591 patchset. To generate patch files to attach to your article:
593 .. code-block:: console
595 % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
597 If you would like to send patches directly, you may use git-send-email or
598 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
600 .. code-block:: console
602 % git format-patch --attach master..mybranch --stdout | git imap-send
604 Then, your .git/config should have [imap] sections.
609 host = imaps://imap.gmail.com
610 user = your.gmail.account@gmail.com
615 folder = "[Gmail]/Drafts"
616 ; example for Japanese, "Modified UTF-7" encoded.
617 folder = "[Gmail]/&Tgtm+DBN-"
618 ; example for Traditional Chinese
619 folder = "[Gmail]/&g0l6Pw-"
621 For developers to work with git-svn
622 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
624 To set up clone from which you can submit code using ``git-svn``, run:
626 .. code-block:: console
628 % git clone http://llvm.org/git/llvm.git
630 % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
631 % git config svn-remote.svn.fetch :refs/remotes/origin/master
632 % git svn rebase -l # -l avoids fetching ahead of the git mirror.
634 # If you have clang too:
636 % git clone http://llvm.org/git/clang.git
638 % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
639 % git config svn-remote.svn.fetch :refs/remotes/origin/master
642 Likewise for compiler-rt and test-suite.
644 To update this clone without generating git-svn tags that conflict with the
645 upstream git repo, run:
647 .. code-block:: console
649 % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
650 % git checkout master
653 git checkout master &&
656 Likewise for compiler-rt and test-suite.
658 This leaves your working directories on their master branches, so you'll need to
659 ``checkout`` each working branch individually and ``rebase`` it on top of its
662 For those who wish to be able to update an llvm repo in a simpler fashion,
663 consider placing the following git script in your path under the name
670 STATUS=$(git status -s | grep -v "??")
672 if [ ! -z "$STATUS" ]; then
678 OLD_BRANCH=$(git rev-parse --abbrev-ref HEAD)
679 git checkout master 2> /dev/null
681 git checkout $OLD_BRANCH 2> /dev/null
683 if [ ! -z $STASH ]; then
684 git stash pop >/dev/null
687 Then to perform the aforementioned update steps go into your source directory
688 and just type ``git-svnup`` or ``git svnup`` and everything will just work.
690 To commit back changes via git-svn, use ``dcommit``:
692 .. code-block:: console
696 Note that git-svn will create one SVN commit for each Git commit you have pending,
697 so squash and edit each commit before executing ``dcommit`` to make sure they all
698 conform to the coding standards and the developers' policy.
700 On success, ``dcommit`` will rebase against the HEAD of SVN, so to avoid conflict,
701 please make sure your current branch is up-to-date (via fetch/rebase) before
704 The git-svn metadata can get out of sync after you mess around with branches and
705 ``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
706 about files with uncommitted changes. The fix is to rebuild the metadata:
708 .. code-block:: console
713 Please, refer to the Git-SVN manual (``man git-svn``) for more information.
715 Local LLVM Configuration
716 ------------------------
718 Once checked out from the Subversion repository, the LLVM suite source code must
719 be configured via the ``configure`` script. This script sets variables in the
720 various ``*.in`` files, most notably ``llvm/Makefile.config`` and
721 ``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the
722 Makefiles needed to begin building LLVM.
724 The following environment variables are used by the ``configure`` script to
725 configure the build system:
727 +------------+-----------------------------------------------------------+
728 | Variable | Purpose |
729 +============+===========================================================+
730 | CC | Tells ``configure`` which C compiler to use. By default, |
731 | | ``configure`` will check ``PATH`` for ``clang`` and GCC C |
732 | | compilers (in this order). Use this variable to override |
733 | | ``configure``\'s default behavior. |
734 +------------+-----------------------------------------------------------+
735 | CXX | Tells ``configure`` which C++ compiler to use. By |
736 | | default, ``configure`` will check ``PATH`` for |
737 | | ``clang++`` and GCC C++ compilers (in this order). Use |
738 | | this variable to override ``configure``'s default |
740 +------------+-----------------------------------------------------------+
742 The following options can be used to set or enable LLVM specific options:
744 ``--enable-optimized``
746 Enables optimized compilation (debugging symbols are removed and GCC
747 optimization flags are enabled). Note that this is the default setting if you
748 are using the LLVM distribution. The default behavior of an Subversion
749 checkout is to use an unoptimized build (also known as a debug build).
751 ``--enable-debug-runtime``
753 Enables debug symbols in the runtime libraries. The default is to strip debug
754 symbols from the runtime libraries.
758 Compile the Just In Time (JIT) compiler functionality. This is not available
759 on all platforms. The default is dependent on platform, so it is best to
760 explicitly enable it if you want it.
762 ``--enable-targets=target-option``
764 Controls which targets will be built and linked into llc. The default value
765 for ``target_options`` is "all" which builds and links all available targets.
766 The value "host-only" can be specified to build only a native compiler (no
767 cross-compiler targets available). The "native" target is selected as the
768 target of the build host. You can also specify a comma separated list of
769 target names that you want available in llc. The target names use all lower
770 case. The current set of targets is:
772 ``arm, cpp, hexagon, mblaze, mips, mipsel, msp430, powerpc, ptx, sparc, spu,
773 x86, x86_64, xcore``.
777 Look for the doxygen program and enable construction of doxygen based
778 documentation from the source code. This is disabled by default because
779 generating the documentation can take a long time and producess 100s of
784 LLVM can use external disassembler library for various purposes (now it's used
785 only for examining code produced by JIT). This option will enable usage of
786 `udis86 <http://udis86.sourceforge.net/>`_ x86 (both 32 and 64 bits)
787 disassembler library.
789 To configure LLVM, follow these steps:
791 #. Change directory into the object root directory:
793 .. code-block:: console
797 #. Run the ``configure`` script located in the LLVM source tree:
799 .. code-block:: console
801 % SRC_ROOT/configure --prefix=/install/path [other options]
803 Compiling the LLVM Suite Source Code
804 ------------------------------------
806 Once you have configured LLVM, you can build it. There are three types of
811 These builds are the default when one is using an Subversion checkout and
812 types ``gmake`` (unless the ``--enable-optimized`` option was used during
813 configuration). The build system will compile the tools and libraries with
814 debugging information. To get a Debug Build using the LLVM distribution the
815 ``--disable-optimized`` option must be passed to ``configure``.
817 Release (Optimized) Builds
819 These builds are enabled with the ``--enable-optimized`` option to
820 ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
821 line. For these builds, the build system will compile the tools and libraries
822 with GCC optimizations enabled and strip debugging information from the
823 libraries and executables it generates. Note that Release Builds are default
824 when using an LLVM distribution.
828 These builds are for use with profiling. They compile profiling information
829 into the code for use with programs like ``gprof``. Profile builds must be
830 started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
832 Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
833 directory and issuing the following command:
835 .. code-block:: console
839 If the build fails, please `check here`_ to see if you are using a version of
840 GCC that is known not to compile LLVM.
842 If you have multiple processors in your machine, you may wish to use some of the
843 parallel build options provided by GNU Make. For example, you could use the
846 .. code-block:: console
850 There are several special targets which are useful when working with the LLVM
855 Removes all files generated by the build. This includes object files,
856 generated C/C++ files, libraries, and executables.
860 Removes everything that ``gmake clean`` does, but also removes files generated
861 by ``configure``. It attempts to return the source tree to the original state
862 in which it was shipped.
866 Installs LLVM header files, libraries, tools, and documentation in a hierarchy
867 under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
868 defaults to ``/usr/local``.
870 ``gmake -C runtime install-bytecode``
872 Assuming you built LLVM into $OBJDIR, when this command is run, it will
873 install bitcode libraries into the GCC front end's bitcode library directory.
874 If you need to update your bitcode libraries, this is the target to use once
877 Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
878 these ``make`` targets and descriptions of other targets available.
880 It is also possible to override default values from ``configure`` by declaring
881 variables on the command line. The following are some examples:
883 ``gmake ENABLE_OPTIMIZED=1``
885 Perform a Release (Optimized) build.
887 ``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
889 Perform a Release (Optimized) build without assertions enabled.
891 ``gmake ENABLE_OPTIMIZED=0``
893 Perform a Debug build.
895 ``gmake ENABLE_PROFILING=1``
897 Perform a Profiling build.
901 Print what ``gmake`` is doing on standard output.
903 ``gmake TOOL_VERBOSE=1``
905 Ask each tool invoked by the makefiles to print out what it is doing on
906 the standard output. This also implies ``VERBOSE=1``.
908 Every directory in the LLVM object tree includes a ``Makefile`` to build it and
909 any subdirectories that it contains. Entering any directory inside the LLVM
910 object tree and typing ``gmake`` should rebuild anything in or below that
911 directory that is out of date.
913 This does not apply to building the documentation.
914 LLVM's (non-Doxygen) documentation is produced with the
915 `Sphinx <http://sphinx-doc.org/>`_ documentation generation system.
916 There are some HTML documents that have not yet been converted to the new
917 system (which uses the easy-to-read and easy-to-write
918 `reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup
920 The generated documentation is built in the ``SRC_ROOT/docs`` directory using
922 For instructions on how to install Sphinx, see
923 `Sphinx Introduction for LLVM Developers
924 <http://lld.llvm.org/sphinx_intro.html>`_.
925 After following the instructions there for installing Sphinx, build the LLVM
926 HTML documentation by doing the following:
928 .. code-block:: console
931 $ make -f Makefile.sphinx
933 This creates a ``_build/html`` sub-directory with all of the HTML files, not
934 just the generated ones.
935 This directory corresponds to ``llvm.org/docs``.
936 For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to
937 ``llvm.org/docs/SphinxQuickstartTemplate.html``.
938 The :doc:`SphinxQuickstartTemplate` is useful when creating a new document.
943 It is possible to cross-compile LLVM itself. That is, you can create LLVM
944 executables and libraries to be hosted on a platform different from the platform
945 where they are built (a Canadian Cross build). To configure a cross-compile,
946 supply the configure script with ``--build`` and ``--host`` options that are
947 different. The values of these options must be legal target triples that your
948 GCC compiler supports.
950 The result of such a build is executables that are not runnable on on the build
951 host (--build option) but can be executed on the compile host (--host option).
953 The Location of LLVM Object Files
954 ---------------------------------
956 The LLVM build system is capable of sharing a single LLVM source tree among
957 several LLVM builds. Hence, it is possible to build LLVM for several different
958 platforms or configurations using the same source tree.
960 This is accomplished in the typical autoconf manner:
962 * Change directory to where the LLVM object files should live:
964 .. code-block:: console
968 * Run the ``configure`` script found in the LLVM source directory:
970 .. code-block:: console
974 The LLVM build will place files underneath *OBJ_ROOT* in directories named after
977 Debug Builds with assertions enabled (the default)
981 ``OBJ_ROOT/Debug+Asserts/bin``
985 ``OBJ_ROOT/Debug+Asserts/lib``
991 ``OBJ_ROOT/Release/bin``
995 ``OBJ_ROOT/Release/lib``
1001 ``OBJ_ROOT/Profile/bin``
1005 ``OBJ_ROOT/Profile/lib``
1007 Optional Configuration Items
1008 ----------------------------
1010 If you're running on a Linux system that supports the `binfmt_misc
1011 <http://en.wikipedia.org/wiki/binfmt_misc>`_
1012 module, and you have root access on the system, you can set your system up to
1013 execute LLVM bitcode files directly. To do this, use commands like this (the
1014 first command may not be required if you are already using the module):
1016 .. code-block:: console
1018 % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1019 % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1020 % chmod u+x hello.bc (if needed)
1023 This allows you to execute LLVM bitcode files directly. On Debian, you can also
1024 use this command instead of the 'echo' command above:
1026 .. code-block:: console
1028 % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1036 One useful source of information about the LLVM source base is the LLVM `doxygen
1037 <http://www.doxygen.org/>`_ documentation available at
1038 `<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
1044 This directory contains some simple examples of how to use the LLVM IR and JIT.
1049 This directory contains public header files exported from the LLVM library. The
1050 three main subdirectories of this directory are:
1052 ``llvm/include/llvm``
1054 This directory contains all of the LLVM specific header files. This directory
1055 also has subdirectories for different portions of LLVM: ``Analysis``,
1056 ``CodeGen``, ``Target``, ``Transforms``, etc...
1058 ``llvm/include/llvm/Support``
1060 This directory contains generic support libraries that are provided with LLVM
1061 but not necessarily specific to LLVM. For example, some C++ STL utilities and
1062 a Command Line option processing library store their header files here.
1064 ``llvm/include/llvm/Config``
1066 This directory contains header files configured by the ``configure`` script.
1067 They wrap "standard" UNIX and C header files. Source code can include these
1068 header files which automatically take care of the conditional #includes that
1069 the ``configure`` script generates.
1074 This directory contains most of the source files of the LLVM system. In LLVM,
1075 almost all code exists in libraries, making it very easy to share code among the
1078 ``llvm/lib/VMCore/``
1080 This directory holds the core LLVM source files that implement core classes
1081 like Instruction and BasicBlock.
1083 ``llvm/lib/AsmParser/``
1085 This directory holds the source code for the LLVM assembly language parser
1088 ``llvm/lib/BitCode/``
1090 This directory holds code for reading and write LLVM bitcode.
1092 ``llvm/lib/Analysis/``
1094 This directory contains a variety of different program analyses, such as
1095 Dominator Information, Call Graphs, Induction Variables, Interval
1096 Identification, Natural Loop Identification, etc.
1098 ``llvm/lib/Transforms/``
1100 This directory contains the source code for the LLVM to LLVM program
1101 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1102 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1103 Elimination, and many others.
1105 ``llvm/lib/Target/``
1107 This directory contains files that describe various target architectures for
1108 code generation. For example, the ``llvm/lib/Target/X86`` directory holds the
1109 X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
1112 ``llvm/lib/CodeGen/``
1114 This directory contains the major parts of the code generator: Instruction
1115 Selector, Instruction Scheduling, and Register Allocation.
1121 ``llvm/lib/Debugger/``
1123 This directory contains the source level debugger library that makes it
1124 possible to instrument LLVM programs so that a debugger could identify source
1125 code locations at which the program is executing.
1127 ``llvm/lib/ExecutionEngine/``
1129 This directory contains libraries for executing LLVM bitcode directly at
1130 runtime in both interpreted and JIT compiled fashions.
1132 ``llvm/lib/Support/``
1134 This directory contains the source code that corresponds to the header files
1135 located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
1140 This directory contains projects that are not strictly part of LLVM but are
1141 shipped with LLVM. This is also the directory where you should create your own
1142 LLVM-based projects. See ``llvm/projects/sample`` for an example of how to set
1143 up your own project.
1148 This directory contains libraries which are compiled into LLVM bitcode and used
1149 when linking programs with the Clang front end. Most of these libraries are
1150 skeleton versions of real libraries; for example, libc is a stripped down
1153 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
1159 This directory contains feature and regression tests and other basic sanity
1160 checks on the LLVM infrastructure. These are intended to run quickly and cover a
1161 lot of territory without being exhaustive.
1166 This is not a directory in the normal llvm module; it is a separate Subversion
1167 module that must be checked out (usually to ``projects/test-suite``). This
1168 module contains a comprehensive correctness, performance, and benchmarking test
1169 suite for LLVM. It is a separate Subversion module because not every LLVM user
1170 is interested in downloading or building such a comprehensive test suite. For
1171 further details on this test suite, please see the :doc:`Testing Guide
1172 <TestingGuide>` document.
1179 The **tools** directory contains the executables built out of the libraries
1180 above, which form the main part of the user interface. You can always get help
1181 for a tool by typing ``tool_name -help``. The following is a brief introduction
1182 to the most important tools. More detailed information is in
1183 the `Command Guide <CommandGuide/index.html>`_.
1187 ``bugpoint`` is used to debug optimization passes or code generation backends
1188 by narrowing down the given test case to the minimum number of passes and/or
1189 instructions that still cause a problem, whether it is a crash or
1190 miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
1195 The archiver produces an archive containing the given LLVM bitcode files,
1196 optionally with an index for faster lookup.
1200 The assembler transforms the human readable LLVM assembly to LLVM bitcode.
1204 The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
1208 ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
1213 ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
1214 (although very slowly...). For architectures that support it (currently x86,
1215 Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
1216 compiler (if the functionality was compiled in), and will execute the code
1217 *much* faster than the interpreter.
1221 ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
1222 native code assembly file or to C code (with the ``-march=c`` option).
1226 ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
1227 (which are specified on the command line), and then outputs the resultant
1228 bitcode. The '``opt -help``' command is a good way to get a list of the
1229 program transformations available in LLVM.
1231 ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
1232 file and print out the results. It is primarily useful for debugging
1233 analyses, or familiarizing yourself with what an analysis does.
1238 This directory contains utilities for working with LLVM source code, and some of
1239 the utilities are actually required as part of the build process because they
1240 are code generators for parts of LLVM infrastructure.
1245 ``codegen-diff`` is a script that finds differences between code that LLC
1246 generates and code that LLI generates. This is a useful tool if you are
1247 debugging one of them, assuming that the other generates correct output. For
1248 the full user manual, run ```perldoc codegen-diff'``.
1252 The ``emacs`` directory contains syntax-highlighting files which will work
1253 with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
1254 assembly files and TableGen description files. For information on how to use
1255 the syntax files, consult the ``README`` file in that directory.
1259 The ``getsrcs.sh`` script finds and outputs all non-generated source files,
1260 which is useful if one wishes to do a lot of development across directories
1261 and does not want to individually find each file. One way to use it is to run,
1262 for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
1267 This little tool performs an ``egrep -H -n`` on each source file in LLVM and
1268 passes to it a regular expression provided on ``llvmgrep``'s command
1269 line. This is a very efficient way of searching the source base for a
1270 particular regular expression.
1274 The ``makellvm`` script compiles all files in the current directory and then
1275 compiles and links the tool that is the first argument. For example, assuming
1276 you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
1277 path, simply running ``makellvm llc`` will make a build of the current
1278 directory, switch to directory ``llvm/tools/llc`` and build it, causing a
1283 The ``TableGen`` directory contains the tool used to generate register
1284 descriptions, instruction set descriptions, and even assemblers from common
1285 TableGen description files.
1289 The ``vim`` directory contains syntax-highlighting files which will work with
1290 the VIM editor, providing syntax highlighting support for LLVM assembly files
1291 and TableGen description files. For information on how to use the syntax
1292 files, consult the ``README`` file in that directory.
1296 An Example Using the LLVM Tool Chain
1297 ====================================
1299 This section gives an example of using LLVM with the Clang front end.
1304 #. First, create a simple C file, name it 'hello.c':
1311 printf("hello world\n");
1315 #. Next, compile the C file into a native executable:
1317 .. code-block:: console
1319 % clang hello.c -o hello
1323 Clang works just like GCC by default. The standard -S and -c arguments
1324 work as usual (producing a native .s or .o file, respectively).
1326 #. Next, compile the C file into a LLVM bitcode file:
1328 .. code-block:: console
1330 % clang -O3 -emit-llvm hello.c -c -o hello.bc
1332 The -emit-llvm option can be used with the -S or -c options to emit an LLVM
1333 ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
1334 the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
1336 #. Run the program in both forms. To run the program, use:
1338 .. code-block:: console
1344 .. code-block:: console
1348 The second examples shows how to invoke the LLVM JIT, :doc:`lli
1349 <CommandGuide/lli>`.
1351 #. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
1353 .. code-block:: console
1355 % llvm-dis < hello.bc | less
1357 #. Compile the program to native assembly using the LLC code generator:
1359 .. code-block:: console
1361 % llc hello.bc -o hello.s
1363 #. Assemble the native assembly language file into a program:
1365 .. code-block:: console
1367 % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
1369 % gcc hello.s -o hello.native # On others
1371 #. Execute the native code program:
1373 .. code-block:: console
1377 Note that using clang to compile directly to native code (i.e. when the
1378 ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
1383 If you are having problems building or using LLVM, or if you have any other
1384 general questions about LLVM, please consult the `Frequently Asked
1385 Questions <FAQ.html>`_ page.
1392 This document is just an **introduction** on how to use LLVM to do some simple
1393 things... there are many more interesting and complicated things that you can do
1394 that aren't documented here (but we'll gladly accept a patch if you want to
1395 write something up!). For more information about LLVM, check out:
1397 * `LLVM Homepage <http://llvm.org/>`_
1398 * `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
1399 * `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_