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32 The LLVM Getting Started documentation may be out of date.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 ``--enable-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/>`_ | >=2.5 | Automated test suite\ :sup:`3` |
221 +--------------------------------------------------------------+-----------------+---------------------------------------------+
222 | `GNU M4 <http://savannah.gnu.org/projects/m4>`_ | 1.4 | Macro processor for configuration\ :sup:`4` |
223 +--------------------------------------------------------------+-----------------+---------------------------------------------+
224 | `GNU Autoconf <http://www.gnu.org/software/autoconf/>`_ | 2.60 | Configuration script builder\ :sup:`4` |
225 +--------------------------------------------------------------+-----------------+---------------------------------------------+
226 | `GNU Automake <http://www.gnu.org/software/automake/>`_ | 1.9.6 | aclocal macro generator\ :sup:`4` |
227 +--------------------------------------------------------------+-----------------+---------------------------------------------+
228 | `libtool <http://savannah.gnu.org/projects/libtool>`_ | 1.5.22 | Shared library manager\ :sup:`4` |
229 +--------------------------------------------------------------+-----------------+---------------------------------------------+
230 | `zlib <http://zlib.net>`_ | >=1.2.3.4 | Compression library\ :sup:`5` |
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.
246 #. Optional, adds compression/uncompression capabilities to selected LLVM
249 Additionally, your compilation host is expected to have the usual plethora of
250 Unix utilities. Specifically:
252 * **ar** --- archive library builder
253 * **bzip2** --- bzip2 command for distribution generation
254 * **bunzip2** --- bunzip2 command for distribution checking
255 * **chmod** --- change permissions on a file
256 * **cat** --- output concatenation utility
257 * **cp** --- copy files
258 * **date** --- print the current date/time
259 * **echo** --- print to standard output
260 * **egrep** --- extended regular expression search utility
261 * **find** --- find files/dirs in a file system
262 * **grep** --- regular expression search utility
263 * **gzip** --- gzip command for distribution generation
264 * **gunzip** --- gunzip command for distribution checking
265 * **install** --- install directories/files
266 * **mkdir** --- create a directory
267 * **mv** --- move (rename) files
268 * **ranlib** --- symbol table builder for archive libraries
269 * **rm** --- remove (delete) files and directories
270 * **sed** --- stream editor for transforming output
271 * **sh** --- Bourne shell for make build scripts
272 * **tar** --- tape archive for distribution generation
273 * **test** --- test things in file system
274 * **unzip** --- unzip command for distribution checking
275 * **zip** --- zip command for distribution generation
280 Broken versions of GCC and other tools
281 --------------------------------------
283 LLVM is very demanding of the host C++ compiler, and as such tends to expose
284 bugs in the compiler. In particular, several versions of GCC crash when trying
285 to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang. Other
286 versions of GCC will probably work as well. GCC versions listed here are known
287 to not work. If you are using one of these versions, please try to upgrade your
288 GCC to something more recent. If you run into a problem with a version of GCC
289 not listed here, please `let us know <mailto:llvmdev@cs.uiuc.edu>`_. Please use
290 the "``gcc -v``" command to find out which version of GCC you are using.
292 **GCC versions prior to 3.0**: GCC 2.96.x and before had several problems in the
293 STL that effectively prevent it from compiling LLVM.
295 **GCC 3.2.2 and 3.2.3**: These versions of GCC fails to compile LLVM with a
296 bogus template error. This was fixed in later GCCs.
298 **GCC 3.3.2**: This version of GCC suffered from a `serious bug
299 <http://gcc.gnu.org/PR13392>`_ which causes it to crash in the
300 "``convert_from_eh_region_ranges_1``" GCC function.
302 **Cygwin GCC 3.3.3**: The version of GCC 3.3.3 commonly shipped with Cygwin does
305 **SuSE GCC 3.3.3**: The version of GCC 3.3.3 shipped with SuSE 9.1 (and possibly
306 others) does not compile LLVM correctly (it appears that exception handling is
307 broken in some cases). Please download the FSF 3.3.3 or upgrade to a newer
310 **GCC 3.4.0 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
311 generator, causing an infinite loop in the llvm-gcc build when built with
312 optimizations enabled (i.e. a release build).
314 **GCC 3.4.2 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
315 generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0) correctly
316 compiles LLVM at -O2. A work around is to build release LLVM builds with
317 "``make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ...``"
319 **GCC 3.4.x on X86-64/amd64**: GCC `miscompiles portions of LLVM
320 <http://llvm.org/PR1056>`__.
322 **GCC 3.4.4 (CodeSourcery ARM 2005q3-2)**: this compiler miscompiles LLVM when
323 building with optimizations enabled. It appears to work with "``make
324 ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1``" or build a debug build.
326 **IA-64 GCC 4.0.0**: The IA-64 version of GCC 4.0.0 is known to miscompile LLVM.
328 **Apple Xcode 2.3**: GCC crashes when compiling LLVM at -O3 (which is the
329 default with ENABLE_OPTIMIZED=1. To work around this, build with
330 "``ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2``".
332 **GCC 4.1.1**: GCC fails to build LLVM with template concept check errors
333 compiling some files. At the time of this writing, GCC mainline (4.2) did not
336 **GCC 4.1.1 on X86-64/amd64**: GCC `miscompiles portions of LLVM
337 <http://llvm.org/PR1063>`__ when compiling llvm itself into 64-bit code. LLVM
338 will appear to mostly work but will be buggy, e.g. failing portions of its
341 **GCC 4.1.2 on OpenSUSE**: Seg faults during libstdc++ build and on x86_64
342 platforms compiling md5.c gets a mangled constant.
344 **GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian**: Appears to
345 miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining about
346 symbols remaining in the table on destruction.
348 **GCC 4.1.2 20071124 (Red Hat 4.1.2-42)**: Suffers from the same symptoms as the
349 previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).
351 **Cygwin GCC 4.3.2 20080827 (beta) 2**: Users `reported
352 <http://llvm.org/PR4145>`_ various problems related with link errors when using
355 **Debian GCC 4.3.2 on X86**: Crashes building some files in LLVM 2.6.
357 **GCC 4.3.3 (Debian 4.3.3-10) on ARM**: Miscompiles parts of LLVM 2.6 when
358 optimizations are turned on. The symptom is an infinite loop in
359 ``FoldingSetImpl::RemoveNode`` while running the code generator.
361 **SUSE 11 GCC 4.3.4**: Miscompiles LLVM, causing crashes in ValueHandle logic.
363 **GCC 4.3.5 and GCC 4.4.5 on ARM**: These can miscompile ``value >> 1`` even at
364 ``-O0``. A test failure in ``test/Assembler/alignstack.ll`` is one symptom of
367 **GCC 4.6.3 on ARM**: Miscompiles ``llvm-readobj`` at ``-O3``. A test failure
368 in ``test/Object/readobj-shared-object.test`` is one symptom of the problem.
370 **GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
371 warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
372 defined in a discarded section. You can safely ignore these messages as they are
373 erroneous and the linkage is correct. These messages disappear using ld 2.17.
375 **GNU binutils 2.17**: Binutils 2.17 contains `a bug
376 <http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link
377 times (minutes instead of seconds) when building LLVM. We recommend upgrading
378 to a newer version (2.17.50.0.4 or later).
380 **GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
381 <http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes
382 intermittent failures when building LLVM with position independent code. The
383 symptom is an error about cyclic dependencies. We recommend upgrading to a
384 newer version of Gold.
386 **Clang 3.0 with libstdc++ 4.7.x**: a few Linux distributions (Ubuntu 12.10,
387 Fedora 17) have both Clang 3.0 and libstdc++ 4.7 in their repositories. Clang
388 3.0 does not implement a few builtins that are used in this library. We
389 recommend using the system GCC to compile LLVM and Clang in this case.
391 **Clang 3.0 on Mageia 2**. There's a packaging issue: Clang can not find at
392 least some (``cxxabi.h``) libstdc++ headers.
394 .. _Getting Started with LLVM:
396 Getting Started with LLVM
397 =========================
399 The remainder of this guide is meant to get you up and running with LLVM and to
400 give you some basic information about the LLVM environment.
402 The later sections of this guide describe the `general layout`_ of the LLVM
403 source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
404 more information about LLVM or to get help via e-mail.
406 Terminology and Notation
407 ------------------------
409 Throughout this manual, the following names are used to denote paths specific to
410 the local system and working environment. *These are not environment variables
411 you need to set but just strings used in the rest of this document below*. In
412 any of the examples below, simply replace each of these names with the
413 appropriate pathname on your local system. All these paths are absolute:
417 This is the top level directory of the LLVM source tree.
421 This is the top level directory of the LLVM object tree (i.e. the tree where
422 object files and compiled programs will be placed. It can be the same as
425 .. _Setting Up Your Environment:
427 Setting Up Your Environment
428 ---------------------------
430 In order to compile and use LLVM, you may need to set some environment
433 ``LLVM_LIB_SEARCH_PATH=/path/to/your/bitcode/libs``
435 [Optional] This environment variable helps LLVM linking tools find the
436 locations of your bitcode libraries. It is provided only as a convenience
437 since you can specify the paths using the -L options of the tools and the
438 C/C++ front-end will automatically use the bitcode files installed in its
441 Unpacking the LLVM Archives
442 ---------------------------
444 If you have the LLVM distribution, you will need to unpack it before you can
445 begin to compile it. LLVM is distributed as a set of two files: the LLVM suite
446 and the LLVM GCC front end compiled for your platform. There is an additional
447 test suite that is optional. Each file is a TAR archive that is compressed with
450 The files are as follows, with *x.y* marking the version number:
454 Source release for the LLVM libraries and tools.
456 ``llvm-test-x.y.tar.gz``
458 Source release for the LLVM test-suite.
462 Checkout LLVM from Subversion
463 -----------------------------
465 If you have access to our Subversion repository, you can get a fresh copy of the
466 entire source code. All you need to do is check it out from Subversion as
469 * ``cd where-you-want-llvm-to-live``
470 * Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
471 * Read-Write:``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
473 This will create an '``llvm``' directory in the current directory and fully
474 populate it with the LLVM source code, Makefiles, test directories, and local
475 copies of documentation files.
477 If you want to get a specific release (as opposed to the most recent revision),
478 you can checkout it from the '``tags``' directory (instead of '``trunk``'). The
479 following releases are located in the following subdirectories of the '``tags``'
482 * Release 3.3: **RELEASE_33/final**
483 * Release 3.2: **RELEASE_32/final**
484 * Release 3.1: **RELEASE_31/final**
485 * Release 3.0: **RELEASE_30/final**
486 * Release 2.9: **RELEASE_29/final**
487 * Release 2.8: **RELEASE_28**
488 * Release 2.7: **RELEASE_27**
489 * Release 2.6: **RELEASE_26**
490 * Release 2.5: **RELEASE_25**
491 * Release 2.4: **RELEASE_24**
492 * Release 2.3: **RELEASE_23**
493 * Release 2.2: **RELEASE_22**
494 * Release 2.1: **RELEASE_21**
495 * Release 2.0: **RELEASE_20**
496 * Release 1.9: **RELEASE_19**
497 * Release 1.8: **RELEASE_18**
498 * Release 1.7: **RELEASE_17**
499 * Release 1.6: **RELEASE_16**
500 * Release 1.5: **RELEASE_15**
501 * Release 1.4: **RELEASE_14**
502 * Release 1.3: **RELEASE_13**
503 * Release 1.2: **RELEASE_12**
504 * Release 1.1: **RELEASE_11**
505 * Release 1.0: **RELEASE_1**
507 If you would like to get the LLVM test suite (a separate package as of 1.4), you
508 get it from the Subversion repository:
510 .. code-block:: console
513 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
515 By placing it in the ``llvm/projects``, it will be automatically configured by
516 the LLVM configure script as well as automatically updated when you run ``svn
522 Git mirrors are available for a number of LLVM subprojects. These mirrors sync
523 automatically with each Subversion commit and contain all necessary git-svn
524 marks (so, you can recreate git-svn metadata locally). Note that right now
525 mirrors reflect only ``trunk`` for each project. You can do the read-only Git
528 .. code-block:: console
530 % git clone http://llvm.org/git/llvm.git
532 If you want to check out clang too, run:
534 .. code-block:: console
537 % git clone http://llvm.org/git/clang.git
539 If you want to check out compiler-rt too, run:
541 .. code-block:: console
544 % git clone http://llvm.org/git/compiler-rt.git
546 If you want to check out the Test Suite Source Code (optional), run:
548 .. code-block:: console
551 % git clone http://llvm.org/git/test-suite.git
553 Since the upstream repository is in Subversion, you should use ``git
554 pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
555 in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the
556 master branch, run the following command:
558 .. code-block:: console
560 % git config branch.master.rebase true
562 Sending patches with Git
563 ^^^^^^^^^^^^^^^^^^^^^^^^
565 Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
567 Assume ``master`` points the upstream and ``mybranch`` points your working
568 branch, and ``mybranch`` is rebased onto ``master``. At first you may check
569 sanity of whitespaces:
571 .. code-block:: console
573 % git diff --check master..mybranch
575 The easiest way to generate a patch is as below:
577 .. code-block:: console
579 % git diff master..mybranch > /path/to/mybranch.diff
581 It is a little different from svn-generated diff. git-diff-generated diff has
582 prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
583 could be accepted with ``patch -p1 -N``.
585 But you may generate patchset with git-format-patch. It generates by-each-commit
586 patchset. To generate patch files to attach to your article:
588 .. code-block:: console
590 % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
592 If you would like to send patches directly, you may use git-send-email or
593 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
595 .. code-block:: console
597 % git format-patch --attach master..mybranch --stdout | git imap-send
599 Then, your .git/config should have [imap] sections.
604 host = imaps://imap.gmail.com
605 user = your.gmail.account@gmail.com
610 folder = "[Gmail]/Drafts"
611 ; example for Japanese, "Modified UTF-7" encoded.
612 folder = "[Gmail]/&Tgtm+DBN-"
613 ; example for Traditional Chinese
614 folder = "[Gmail]/&g0l6Pw-"
616 For developers to work with git-svn
617 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
619 To set up clone from which you can submit code using ``git-svn``, run:
621 .. code-block:: console
623 % git clone http://llvm.org/git/llvm.git
625 % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
626 % git config svn-remote.svn.fetch :refs/remotes/origin/master
627 % git svn rebase -l # -l avoids fetching ahead of the git mirror.
629 # If you have clang too:
631 % git clone http://llvm.org/git/clang.git
633 % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
634 % git config svn-remote.svn.fetch :refs/remotes/origin/master
637 Likewise for compiler-rt and test-suite.
639 To update this clone without generating git-svn tags that conflict with the
640 upstream Git repo, run:
642 .. code-block:: console
644 % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
645 % git checkout master
648 git checkout master &&
651 Likewise for compiler-rt and test-suite.
653 This leaves your working directories on their master branches, so you'll need to
654 ``checkout`` each working branch individually and ``rebase`` it on top of its
657 For those who wish to be able to update an llvm repo/revert patches easily using
658 git-svn, please look in the directory for the scripts ``git-svnup`` and
661 To perform the aforementioned update steps go into your source directory and
662 just type ``git-svnup`` or ``git svnup`` and everything will just work.
664 If one wishes to revert a commit with git-svn, but do not want the git hash to
665 escape into the commit message, one can use the script ``git-svnrevert`` or
666 ``git svnrevert`` which will take in the git hash for the commit you want to
667 revert, look up the appropriate svn revision, and output a message where all
668 references to the git hash have been replaced with the svn revision.
670 To commit back changes via git-svn, use ``git svn dcommit``:
672 .. code-block:: console
676 Note that git-svn will create one SVN commit for each Git commit you have pending,
677 so squash and edit each commit before executing ``dcommit`` to make sure they all
678 conform to the coding standards and the developers' policy.
680 On success, ``dcommit`` will rebase against the HEAD of SVN, so to avoid conflict,
681 please make sure your current branch is up-to-date (via fetch/rebase) before
684 The git-svn metadata can get out of sync after you mess around with branches and
685 ``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
686 about files with uncommitted changes. The fix is to rebuild the metadata:
688 .. code-block:: console
693 Please, refer to the Git-SVN manual (``man git-svn``) for more information.
695 Local LLVM Configuration
696 ------------------------
698 Once checked out from the Subversion repository, the LLVM suite source code must
699 be configured via the ``configure`` script. This script sets variables in the
700 various ``*.in`` files, most notably ``llvm/Makefile.config`` and
701 ``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the
702 Makefiles needed to begin building LLVM.
704 The following environment variables are used by the ``configure`` script to
705 configure the build system:
707 +------------+-----------------------------------------------------------+
708 | Variable | Purpose |
709 +============+===========================================================+
710 | CC | Tells ``configure`` which C compiler to use. By default, |
711 | | ``configure`` will check ``PATH`` for ``clang`` and GCC C |
712 | | compilers (in this order). Use this variable to override |
713 | | ``configure``\'s default behavior. |
714 +------------+-----------------------------------------------------------+
715 | CXX | Tells ``configure`` which C++ compiler to use. By |
716 | | default, ``configure`` will check ``PATH`` for |
717 | | ``clang++`` and GCC C++ compilers (in this order). Use |
718 | | this variable to override ``configure``'s default |
720 +------------+-----------------------------------------------------------+
722 The following options can be used to set or enable LLVM specific options:
724 ``--enable-optimized``
726 Enables optimized compilation (debugging symbols are removed and GCC
727 optimization flags are enabled). Note that this is the default setting if you
728 are using the LLVM distribution. The default behavior of an Subversion
729 checkout is to use an unoptimized build (also known as a debug build).
731 ``--enable-debug-runtime``
733 Enables debug symbols in the runtime libraries. The default is to strip debug
734 symbols from the runtime libraries.
738 Compile the Just In Time (JIT) compiler functionality. This is not available
739 on all platforms. The default is dependent on platform, so it is best to
740 explicitly enable it if you want it.
742 ``--enable-targets=target-option``
744 Controls which targets will be built and linked into llc. The default value
745 for ``target_options`` is "all" which builds and links all available targets.
746 The value "host-only" can be specified to build only a native compiler (no
747 cross-compiler targets available). The "native" target is selected as the
748 target of the build host. You can also specify a comma separated list of
749 target names that you want available in llc. The target names use all lower
750 case. The current set of targets is:
752 ``arm, cpp, hexagon, mips, mipsel, msp430, powerpc, ptx, sparc, spu,
753 systemz, x86, x86_64, xcore``.
757 Look for the doxygen program and enable construction of doxygen based
758 documentation from the source code. This is disabled by default because
759 generating the documentation can take a long time and producess 100s of
764 LLVM can use external disassembler library for various purposes (now it's used
765 only for examining code produced by JIT). This option will enable usage of
766 `udis86 <http://udis86.sourceforge.net/>`_ x86 (both 32 and 64 bits)
767 disassembler library.
769 To configure LLVM, follow these steps:
771 #. Change directory into the object root directory:
773 .. code-block:: console
777 #. Run the ``configure`` script located in the LLVM source tree:
779 .. code-block:: console
781 % SRC_ROOT/configure --prefix=/install/path [other options]
783 Compiling the LLVM Suite Source Code
784 ------------------------------------
786 Once you have configured LLVM, you can build it. There are three types of
791 These builds are the default when one is using an Subversion checkout and
792 types ``gmake`` (unless the ``--enable-optimized`` option was used during
793 configuration). The build system will compile the tools and libraries with
794 debugging information. To get a Debug Build using the LLVM distribution the
795 ``--disable-optimized`` option must be passed to ``configure``.
797 Release (Optimized) Builds
799 These builds are enabled with the ``--enable-optimized`` option to
800 ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
801 line. For these builds, the build system will compile the tools and libraries
802 with GCC optimizations enabled and strip debugging information from the
803 libraries and executables it generates. Note that Release Builds are default
804 when using an LLVM distribution.
808 These builds are for use with profiling. They compile profiling information
809 into the code for use with programs like ``gprof``. Profile builds must be
810 started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
812 Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
813 directory and issuing the following command:
815 .. code-block:: console
819 If the build fails, please `check here`_ to see if you are using a version of
820 GCC that is known not to compile LLVM.
822 If you have multiple processors in your machine, you may wish to use some of the
823 parallel build options provided by GNU Make. For example, you could use the
826 .. code-block:: console
830 There are several special targets which are useful when working with the LLVM
835 Removes all files generated by the build. This includes object files,
836 generated C/C++ files, libraries, and executables.
840 Removes everything that ``gmake clean`` does, but also removes files generated
841 by ``configure``. It attempts to return the source tree to the original state
842 in which it was shipped.
846 Installs LLVM header files, libraries, tools, and documentation in a hierarchy
847 under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
848 defaults to ``/usr/local``.
850 ``gmake -C runtime install-bytecode``
852 Assuming you built LLVM into $OBJDIR, when this command is run, it will
853 install bitcode libraries into the GCC front end's bitcode library directory.
854 If you need to update your bitcode libraries, this is the target to use once
857 Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
858 these ``make`` targets and descriptions of other targets available.
860 It is also possible to override default values from ``configure`` by declaring
861 variables on the command line. The following are some examples:
863 ``gmake ENABLE_OPTIMIZED=1``
865 Perform a Release (Optimized) build.
867 ``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
869 Perform a Release (Optimized) build without assertions enabled.
871 ``gmake ENABLE_OPTIMIZED=0``
873 Perform a Debug build.
875 ``gmake ENABLE_PROFILING=1``
877 Perform a Profiling build.
881 Print what ``gmake`` is doing on standard output.
883 ``gmake TOOL_VERBOSE=1``
885 Ask each tool invoked by the makefiles to print out what it is doing on
886 the standard output. This also implies ``VERBOSE=1``.
888 Every directory in the LLVM object tree includes a ``Makefile`` to build it and
889 any subdirectories that it contains. Entering any directory inside the LLVM
890 object tree and typing ``gmake`` should rebuild anything in or below that
891 directory that is out of date.
893 This does not apply to building the documentation.
894 LLVM's (non-Doxygen) documentation is produced with the
895 `Sphinx <http://sphinx-doc.org/>`_ documentation generation system.
896 There are some HTML documents that have not yet been converted to the new
897 system (which uses the easy-to-read and easy-to-write
898 `reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup
900 The generated documentation is built in the ``SRC_ROOT/docs`` directory using
902 For instructions on how to install Sphinx, see
903 `Sphinx Introduction for LLVM Developers
904 <http://lld.llvm.org/sphinx_intro.html>`_.
905 After following the instructions there for installing Sphinx, build the LLVM
906 HTML documentation by doing the following:
908 .. code-block:: console
911 $ make -f Makefile.sphinx
913 This creates a ``_build/html`` sub-directory with all of the HTML files, not
914 just the generated ones.
915 This directory corresponds to ``llvm.org/docs``.
916 For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to
917 ``llvm.org/docs/SphinxQuickstartTemplate.html``.
918 The :doc:`SphinxQuickstartTemplate` is useful when creating a new document.
923 It is possible to cross-compile LLVM itself. That is, you can create LLVM
924 executables and libraries to be hosted on a platform different from the platform
925 where they are built (a Canadian Cross build). To configure a cross-compile,
926 supply the configure script with ``--build`` and ``--host`` options that are
927 different. The values of these options must be legal target triples that your
928 GCC compiler supports.
930 The result of such a build is executables that are not runnable on on the build
931 host (--build option) but can be executed on the compile host (--host option).
933 Check :doc:`HowToCrossCompileLLVM` and `Clang docs on how to cross-compile in general
934 <http://clang.llvm.org/docs/CrossCompilation.html>`_ for more information
935 about cross-compiling.
937 The Location of LLVM Object Files
938 ---------------------------------
940 The LLVM build system is capable of sharing a single LLVM source tree among
941 several LLVM builds. Hence, it is possible to build LLVM for several different
942 platforms or configurations using the same source tree.
944 This is accomplished in the typical autoconf manner:
946 * Change directory to where the LLVM object files should live:
948 .. code-block:: console
952 * Run the ``configure`` script found in the LLVM source directory:
954 .. code-block:: console
958 The LLVM build will place files underneath *OBJ_ROOT* in directories named after
961 Debug Builds with assertions enabled (the default)
965 ``OBJ_ROOT/Debug+Asserts/bin``
969 ``OBJ_ROOT/Debug+Asserts/lib``
975 ``OBJ_ROOT/Release/bin``
979 ``OBJ_ROOT/Release/lib``
985 ``OBJ_ROOT/Profile/bin``
989 ``OBJ_ROOT/Profile/lib``
991 Optional Configuration Items
992 ----------------------------
994 If you're running on a Linux system that supports the `binfmt_misc
995 <http://en.wikipedia.org/wiki/binfmt_misc>`_
996 module, and you have root access on the system, you can set your system up to
997 execute LLVM bitcode files directly. To do this, use commands like this (the
998 first command may not be required if you are already using the module):
1000 .. code-block:: console
1002 % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1003 % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1004 % chmod u+x hello.bc (if needed)
1007 This allows you to execute LLVM bitcode files directly. On Debian, you can also
1008 use this command instead of the 'echo' command above:
1010 .. code-block:: console
1012 % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1020 One useful source of information about the LLVM source base is the LLVM `doxygen
1021 <http://www.doxygen.org/>`_ documentation available at
1022 `<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
1028 This directory contains some simple examples of how to use the LLVM IR and JIT.
1033 This directory contains public header files exported from the LLVM library. The
1034 three main subdirectories of this directory are:
1036 ``llvm/include/llvm``
1038 This directory contains all of the LLVM specific header files. This directory
1039 also has subdirectories for different portions of LLVM: ``Analysis``,
1040 ``CodeGen``, ``Target``, ``Transforms``, etc...
1042 ``llvm/include/llvm/Support``
1044 This directory contains generic support libraries that are provided with LLVM
1045 but not necessarily specific to LLVM. For example, some C++ STL utilities and
1046 a Command Line option processing library store their header files here.
1048 ``llvm/include/llvm/Config``
1050 This directory contains header files configured by the ``configure`` script.
1051 They wrap "standard" UNIX and C header files. Source code can include these
1052 header files which automatically take care of the conditional #includes that
1053 the ``configure`` script generates.
1058 This directory contains most of the source files of the LLVM system. In LLVM,
1059 almost all code exists in libraries, making it very easy to share code among the
1062 ``llvm/lib/VMCore/``
1064 This directory holds the core LLVM source files that implement core classes
1065 like Instruction and BasicBlock.
1067 ``llvm/lib/AsmParser/``
1069 This directory holds the source code for the LLVM assembly language parser
1072 ``llvm/lib/Bitcode/``
1074 This directory holds code for reading and write LLVM bitcode.
1076 ``llvm/lib/Analysis/``
1078 This directory contains a variety of different program analyses, such as
1079 Dominator Information, Call Graphs, Induction Variables, Interval
1080 Identification, Natural Loop Identification, etc.
1082 ``llvm/lib/Transforms/``
1084 This directory contains the source code for the LLVM to LLVM program
1085 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1086 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1087 Elimination, and many others.
1089 ``llvm/lib/Target/``
1091 This directory contains files that describe various target architectures for
1092 code generation. For example, the ``llvm/lib/Target/X86`` directory holds the
1093 X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
1096 ``llvm/lib/CodeGen/``
1098 This directory contains the major parts of the code generator: Instruction
1099 Selector, Instruction Scheduling, and Register Allocation.
1105 ``llvm/lib/Debugger/``
1107 This directory contains the source level debugger library that makes it
1108 possible to instrument LLVM programs so that a debugger could identify source
1109 code locations at which the program is executing.
1111 ``llvm/lib/ExecutionEngine/``
1113 This directory contains libraries for executing LLVM bitcode directly at
1114 runtime in both interpreted and JIT compiled fashions.
1116 ``llvm/lib/Support/``
1118 This directory contains the source code that corresponds to the header files
1119 located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
1124 This directory contains projects that are not strictly part of LLVM but are
1125 shipped with LLVM. This is also the directory where you should create your own
1126 LLVM-based projects. See ``llvm/projects/sample`` for an example of how to set
1127 up your own project.
1132 This directory contains libraries which are compiled into LLVM bitcode and used
1133 when linking programs with the Clang front end. Most of these libraries are
1134 skeleton versions of real libraries; for example, libc is a stripped down
1137 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
1143 This directory contains feature and regression tests and other basic sanity
1144 checks on the LLVM infrastructure. These are intended to run quickly and cover a
1145 lot of territory without being exhaustive.
1150 This is not a directory in the normal llvm module; it is a separate Subversion
1151 module that must be checked out (usually to ``projects/test-suite``). This
1152 module contains a comprehensive correctness, performance, and benchmarking test
1153 suite for LLVM. It is a separate Subversion module because not every LLVM user
1154 is interested in downloading or building such a comprehensive test suite. For
1155 further details on this test suite, please see the :doc:`Testing Guide
1156 <TestingGuide>` document.
1163 The **tools** directory contains the executables built out of the libraries
1164 above, which form the main part of the user interface. You can always get help
1165 for a tool by typing ``tool_name -help``. The following is a brief introduction
1166 to the most important tools. More detailed information is in
1167 the `Command Guide <CommandGuide/index.html>`_.
1171 ``bugpoint`` is used to debug optimization passes or code generation backends
1172 by narrowing down the given test case to the minimum number of passes and/or
1173 instructions that still cause a problem, whether it is a crash or
1174 miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
1179 The archiver produces an archive containing the given LLVM bitcode files,
1180 optionally with an index for faster lookup.
1184 The assembler transforms the human readable LLVM assembly to LLVM bitcode.
1188 The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
1192 ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
1197 ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
1198 (although very slowly...). For architectures that support it (currently x86,
1199 Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
1200 compiler (if the functionality was compiled in), and will execute the code
1201 *much* faster than the interpreter.
1205 ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
1206 native code assembly file or to C code (with the ``-march=c`` option).
1210 ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
1211 (which are specified on the command line), and then outputs the resultant
1212 bitcode. The '``opt -help``' command is a good way to get a list of the
1213 program transformations available in LLVM.
1215 ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
1216 file and print out the results. It is primarily useful for debugging
1217 analyses, or familiarizing yourself with what an analysis does.
1222 This directory contains utilities for working with LLVM source code, and some of
1223 the utilities are actually required as part of the build process because they
1224 are code generators for parts of LLVM infrastructure.
1229 ``codegen-diff`` is a script that finds differences between code that LLC
1230 generates and code that LLI generates. This is a useful tool if you are
1231 debugging one of them, assuming that the other generates correct output. For
1232 the full user manual, run ```perldoc codegen-diff'``.
1236 The ``emacs`` directory contains syntax-highlighting files which will work
1237 with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
1238 assembly files and TableGen description files. For information on how to use
1239 the syntax files, consult the ``README`` file in that directory.
1243 The ``getsrcs.sh`` script finds and outputs all non-generated source files,
1244 which is useful if one wishes to do a lot of development across directories
1245 and does not want to individually find each file. One way to use it is to run,
1246 for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
1251 This little tool performs an ``egrep -H -n`` on each source file in LLVM and
1252 passes to it a regular expression provided on ``llvmgrep``'s command
1253 line. This is a very efficient way of searching the source base for a
1254 particular regular expression.
1258 The ``makellvm`` script compiles all files in the current directory and then
1259 compiles and links the tool that is the first argument. For example, assuming
1260 you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
1261 path, simply running ``makellvm llc`` will make a build of the current
1262 directory, switch to directory ``llvm/tools/llc`` and build it, causing a
1267 The ``TableGen`` directory contains the tool used to generate register
1268 descriptions, instruction set descriptions, and even assemblers from common
1269 TableGen description files.
1273 The ``vim`` directory contains syntax-highlighting files which will work with
1274 the VIM editor, providing syntax highlighting support for LLVM assembly files
1275 and TableGen description files. For information on how to use the syntax
1276 files, consult the ``README`` file in that directory.
1280 An Example Using the LLVM Tool Chain
1281 ====================================
1283 This section gives an example of using LLVM with the Clang front end.
1288 #. First, create a simple C file, name it 'hello.c':
1295 printf("hello world\n");
1299 #. Next, compile the C file into a native executable:
1301 .. code-block:: console
1303 % clang hello.c -o hello
1307 Clang works just like GCC by default. The standard -S and -c arguments
1308 work as usual (producing a native .s or .o file, respectively).
1310 #. Next, compile the C file into an LLVM bitcode file:
1312 .. code-block:: console
1314 % clang -O3 -emit-llvm hello.c -c -o hello.bc
1316 The -emit-llvm option can be used with the -S or -c options to emit an LLVM
1317 ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
1318 the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
1320 #. Run the program in both forms. To run the program, use:
1322 .. code-block:: console
1328 .. code-block:: console
1332 The second examples shows how to invoke the LLVM JIT, :doc:`lli
1333 <CommandGuide/lli>`.
1335 #. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
1337 .. code-block:: console
1339 % llvm-dis < hello.bc | less
1341 #. Compile the program to native assembly using the LLC code generator:
1343 .. code-block:: console
1345 % llc hello.bc -o hello.s
1347 #. Assemble the native assembly language file into a program:
1349 .. code-block:: console
1351 % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
1353 % gcc hello.s -o hello.native # On others
1355 #. Execute the native code program:
1357 .. code-block:: console
1361 Note that using clang to compile directly to native code (i.e. when the
1362 ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
1367 If you are having problems building or using LLVM, or if you have any other
1368 general questions about LLVM, please consult the `Frequently Asked
1369 Questions <FAQ.html>`_ page.
1376 This document is just an **introduction** on how to use LLVM to do some simple
1377 things... there are many more interesting and complicated things that you can do
1378 that aren't documented here (but we'll gladly accept a patch if you want to
1379 write something up!). For more information about LLVM, check out:
1381 * `LLVM Homepage <http://llvm.org/>`_
1382 * `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
1383 * `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_