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32 The LLVM Getting Started documentation may be out of date.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
541 % git clone http://llvm.org/git/llvm.git
543 % git clone http://llvm.org/git/clang.git
545 Since the upstream repository is in Subversion, you should use ``git
546 pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
547 in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the
548 master branch, run the following command:
550 .. code-block:: console
552 % git config branch.master.rebase true
554 Sending patches with Git
555 ^^^^^^^^^^^^^^^^^^^^^^^^
557 Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
559 Assume ``master`` points the upstream and ``mybranch`` points your working
560 branch, and ``mybranch`` is rebased onto ``master``. At first you may check
561 sanity of whitespaces:
563 .. code-block:: console
565 % git diff --check master..mybranch
567 The easiest way to generate a patch is as below:
569 .. code-block:: console
571 % git diff master..mybranch > /path/to/mybranch.diff
573 It is a little different from svn-generated diff. git-diff-generated diff has
574 prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
575 could be accepted with ``patch -p1 -N``.
577 But you may generate patchset with git-format-patch. It generates by-each-commit
578 patchset. To generate patch files to attach to your article:
580 .. code-block:: console
582 % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
584 If you would like to send patches directly, you may use git-send-email or
585 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
587 .. code-block:: console
589 % git format-patch --attach master..mybranch --stdout | git imap-send
591 Then, your .git/config should have [imap] sections.
596 host = imaps://imap.gmail.com
597 user = your.gmail.account@gmail.com
602 folder = "[Gmail]/Drafts"
603 ; example for Japanese, "Modified UTF-7" encoded.
604 folder = "[Gmail]/&Tgtm+DBN-"
605 ; example for Traditional Chinese
606 folder = "[Gmail]/&g0l6Pw-"
608 For developers to work with git-svn
609 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
611 To set up clone from which you can submit code using ``git-svn``, run:
613 .. code-block:: console
615 % git clone http://llvm.org/git/llvm.git
617 % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
618 % git config svn-remote.svn.fetch :refs/remotes/origin/master
619 % git svn rebase -l # -l avoids fetching ahead of the git mirror.
621 # If you have clang too:
623 % git clone http://llvm.org/git/clang.git
625 % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
626 % git config svn-remote.svn.fetch :refs/remotes/origin/master
629 To update this clone without generating git-svn tags that conflict with the
630 upstream git repo, run:
632 .. code-block:: console
634 % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
635 % git checkout master
638 git checkout master &&
641 This leaves your working directories on their master branches, so you'll need to
642 ``checkout`` each working branch individually and ``rebase`` it on top of its
645 For those who wish to be able to update an llvm repo in a simpler fashion,
646 consider placing the following git script in your path under the name
653 STATUS=$(git status -s | grep -v "??")
655 if [ ! -z "$STATUS" ]; then
661 OLD_BRANCH=$(git rev-parse --abbrev-ref HEAD)
662 git checkout master 2> /dev/null
664 git checkout $OLD_BRANCH 2> /dev/null
666 if [ ! -z $STASH ]; then
667 git stash pop >/dev/null
670 Then to perform the aforementioned update steps go into your source directory
671 and just type ``git-svnup`` or ``git svnup`` and everything will just work.
673 To commit back changes via git-svn, use ``dcommit``:
675 .. code-block:: console
679 Note that git-svn will create one SVN commit for each Git commit you have pending,
680 so squash and edit each commit before executing ``dcommit`` to make sure they all
681 conform to the coding standards and the developers' policy.
683 On success, ``dcommit`` will rebase against the HEAD of SVN, so to avoid conflict,
684 please make sure your current branch is up-to-date (via fetch/rebase) before
687 The git-svn metadata can get out of sync after you mess around with branches and
688 ``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
689 about files with uncommitted changes. The fix is to rebuild the metadata:
691 .. code-block:: console
696 Please, refer to the Git-SVN manual (``man git-svn``) for more information.
698 Local LLVM Configuration
699 ------------------------
701 Once checked out from the Subversion repository, the LLVM suite source code must
702 be configured via the ``configure`` script. This script sets variables in the
703 various ``*.in`` files, most notably ``llvm/Makefile.config`` and
704 ``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the
705 Makefiles needed to begin building LLVM.
707 The following environment variables are used by the ``configure`` script to
708 configure the build system:
710 +------------+-----------------------------------------------------------+
711 | Variable | Purpose |
712 +============+===========================================================+
713 | CC | Tells ``configure`` which C compiler to use. By default, |
714 | | ``configure`` will check ``PATH`` for ``clang`` and GCC C |
715 | | compilers (in this order). Use this variable to override |
716 | | ``configure``\'s default behavior. |
717 +------------+-----------------------------------------------------------+
718 | CXX | Tells ``configure`` which C++ compiler to use. By |
719 | | default, ``configure`` will check ``PATH`` for |
720 | | ``clang++`` and GCC C++ compilers (in this order). Use |
721 | | this variable to override ``configure``'s default |
723 +------------+-----------------------------------------------------------+
725 The following options can be used to set or enable LLVM specific options:
727 ``--enable-optimized``
729 Enables optimized compilation (debugging symbols are removed and GCC
730 optimization flags are enabled). Note that this is the default setting if you
731 are using the LLVM distribution. The default behavior of an Subversion
732 checkout is to use an unoptimized build (also known as a debug build).
734 ``--enable-debug-runtime``
736 Enables debug symbols in the runtime libraries. The default is to strip debug
737 symbols from the runtime libraries.
741 Compile the Just In Time (JIT) compiler functionality. This is not available
742 on all platforms. The default is dependent on platform, so it is best to
743 explicitly enable it if you want it.
745 ``--enable-targets=target-option``
747 Controls which targets will be built and linked into llc. The default value
748 for ``target_options`` is "all" which builds and links all available targets.
749 The value "host-only" can be specified to build only a native compiler (no
750 cross-compiler targets available). The "native" target is selected as the
751 target of the build host. You can also specify a comma separated list of
752 target names that you want available in llc. The target names use all lower
753 case. The current set of targets is:
755 ``arm, cpp, hexagon, mblaze, mips, mipsel, msp430, powerpc, ptx, sparc, spu,
756 x86, x86_64, xcore``.
760 Look for the doxygen program and enable construction of doxygen based
761 documentation from the source code. This is disabled by default because
762 generating the documentation can take a long time and producess 100s of
767 LLVM can use external disassembler library for various purposes (now it's used
768 only for examining code produced by JIT). This option will enable usage of
769 `udis86 <http://udis86.sourceforge.net/>`_ x86 (both 32 and 64 bits)
770 disassembler library.
772 To configure LLVM, follow these steps:
774 #. Change directory into the object root directory:
776 .. code-block:: console
780 #. Run the ``configure`` script located in the LLVM source tree:
782 .. code-block:: console
784 % SRC_ROOT/configure --prefix=/install/path [other options]
786 Compiling the LLVM Suite Source Code
787 ------------------------------------
789 Once you have configured LLVM, you can build it. There are three types of
794 These builds are the default when one is using an Subversion checkout and
795 types ``gmake`` (unless the ``--enable-optimized`` option was used during
796 configuration). The build system will compile the tools and libraries with
797 debugging information. To get a Debug Build using the LLVM distribution the
798 ``--disable-optimized`` option must be passed to ``configure``.
800 Release (Optimized) Builds
802 These builds are enabled with the ``--enable-optimized`` option to
803 ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
804 line. For these builds, the build system will compile the tools and libraries
805 with GCC optimizations enabled and strip debugging information from the
806 libraries and executables it generates. Note that Release Builds are default
807 when using an LLVM distribution.
811 These builds are for use with profiling. They compile profiling information
812 into the code for use with programs like ``gprof``. Profile builds must be
813 started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
815 Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
816 directory and issuing the following command:
818 .. code-block:: console
822 If the build fails, please `check here`_ to see if you are using a version of
823 GCC that is known not to compile LLVM.
825 If you have multiple processors in your machine, you may wish to use some of the
826 parallel build options provided by GNU Make. For example, you could use the
829 .. code-block:: console
833 There are several special targets which are useful when working with the LLVM
838 Removes all files generated by the build. This includes object files,
839 generated C/C++ files, libraries, and executables.
843 Removes everything that ``gmake clean`` does, but also removes files generated
844 by ``configure``. It attempts to return the source tree to the original state
845 in which it was shipped.
849 Installs LLVM header files, libraries, tools, and documentation in a hierarchy
850 under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
851 defaults to ``/usr/local``.
853 ``gmake -C runtime install-bytecode``
855 Assuming you built LLVM into $OBJDIR, when this command is run, it will
856 install bitcode libraries into the GCC front end's bitcode library directory.
857 If you need to update your bitcode libraries, this is the target to use once
860 Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
861 these ``make`` targets and descriptions of other targets available.
863 It is also possible to override default values from ``configure`` by declaring
864 variables on the command line. The following are some examples:
866 ``gmake ENABLE_OPTIMIZED=1``
868 Perform a Release (Optimized) build.
870 ``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
872 Perform a Release (Optimized) build without assertions enabled.
874 ``gmake ENABLE_OPTIMIZED=0``
876 Perform a Debug build.
878 ``gmake ENABLE_PROFILING=1``
880 Perform a Profiling build.
884 Print what ``gmake`` is doing on standard output.
886 ``gmake TOOL_VERBOSE=1``
888 Ask each tool invoked by the makefiles to print out what it is doing on
889 the standard output. This also implies ``VERBOSE=1``.
891 Every directory in the LLVM object tree includes a ``Makefile`` to build it and
892 any subdirectories that it contains. Entering any directory inside the LLVM
893 object tree and typing ``gmake`` should rebuild anything in or below that
894 directory that is out of date.
896 This does not apply to building the documentation.
897 LLVM's (non-Doxygen) documentation is produced with the
898 `Sphinx <http://sphinx-doc.org/>`_ documentation generation system.
899 There are some HTML documents that have not yet been converted to the new
900 system (which uses the easy-to-read and easy-to-write
901 `reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup
903 The generated documentation is built in the ``SRC_ROOT/docs`` directory using
905 For instructions on how to install Sphinx, see
906 `Sphinx Introduction for LLVM Developers
907 <http://lld.llvm.org/sphinx_intro.html>`_.
908 After following the instructions there for installing Sphinx, build the LLVM
909 HTML documentation by doing the following:
911 .. code-block:: console
914 $ make -f Makefile.sphinx
916 This creates a ``_build/html`` sub-directory with all of the HTML files, not
917 just the generated ones.
918 This directory corresponds to ``llvm.org/docs``.
919 For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to
920 ``llvm.org/docs/SphinxQuickstartTemplate.html``.
921 The :doc:`SphinxQuickstartTemplate` is useful when creating a new document.
926 It is possible to cross-compile LLVM itself. That is, you can create LLVM
927 executables and libraries to be hosted on a platform different from the platform
928 where they are built (a Canadian Cross build). To configure a cross-compile,
929 supply the configure script with ``--build`` and ``--host`` options that are
930 different. The values of these options must be legal target triples that your
931 GCC compiler supports.
933 The result of such a build is executables that are not runnable on on the build
934 host (--build option) but can be executed on the compile host (--host option).
936 The Location of LLVM Object Files
937 ---------------------------------
939 The LLVM build system is capable of sharing a single LLVM source tree among
940 several LLVM builds. Hence, it is possible to build LLVM for several different
941 platforms or configurations using the same source tree.
943 This is accomplished in the typical autoconf manner:
945 * Change directory to where the LLVM object files should live:
947 .. code-block:: console
951 * Run the ``configure`` script found in the LLVM source directory:
953 .. code-block:: console
957 The LLVM build will place files underneath *OBJ_ROOT* in directories named after
960 Debug Builds with assertions enabled (the default)
964 ``OBJ_ROOT/Debug+Asserts/bin``
968 ``OBJ_ROOT/Debug+Asserts/lib``
974 ``OBJ_ROOT/Release/bin``
978 ``OBJ_ROOT/Release/lib``
984 ``OBJ_ROOT/Profile/bin``
988 ``OBJ_ROOT/Profile/lib``
990 Optional Configuration Items
991 ----------------------------
993 If you're running on a Linux system that supports the `binfmt_misc
994 <http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html>`_
995 module, and you have root access on the system, you can set your system up to
996 execute LLVM bitcode files directly. To do this, use commands like this (the
997 first command may not be required if you are already using the module):
999 .. code-block:: console
1001 % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1002 % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1003 % chmod u+x hello.bc (if needed)
1006 This allows you to execute LLVM bitcode files directly. On Debian, you can also
1007 use this command instead of the 'echo' command above:
1009 .. code-block:: console
1011 % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1019 One useful source of information about the LLVM source base is the LLVM `doxygen
1020 <http://www.doxygen.org/>`_ documentation available at
1021 `<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
1027 This directory contains some simple examples of how to use the LLVM IR and JIT.
1032 This directory contains public header files exported from the LLVM library. The
1033 three main subdirectories of this directory are:
1035 ``llvm/include/llvm``
1037 This directory contains all of the LLVM specific header files. This directory
1038 also has subdirectories for different portions of LLVM: ``Analysis``,
1039 ``CodeGen``, ``Target``, ``Transforms``, etc...
1041 ``llvm/include/llvm/Support``
1043 This directory contains generic support libraries that are provided with LLVM
1044 but not necessarily specific to LLVM. For example, some C++ STL utilities and
1045 a Command Line option processing library store their header files here.
1047 ``llvm/include/llvm/Config``
1049 This directory contains header files configured by the ``configure`` script.
1050 They wrap "standard" UNIX and C header files. Source code can include these
1051 header files which automatically take care of the conditional #includes that
1052 the ``configure`` script generates.
1057 This directory contains most of the source files of the LLVM system. In LLVM,
1058 almost all code exists in libraries, making it very easy to share code among the
1061 ``llvm/lib/VMCore/``
1063 This directory holds the core LLVM source files that implement core classes
1064 like Instruction and BasicBlock.
1066 ``llvm/lib/AsmParser/``
1068 This directory holds the source code for the LLVM assembly language parser
1071 ``llvm/lib/BitCode/``
1073 This directory holds code for reading and write LLVM bitcode.
1075 ``llvm/lib/Analysis/``
1077 This directory contains a variety of different program analyses, such as
1078 Dominator Information, Call Graphs, Induction Variables, Interval
1079 Identification, Natural Loop Identification, etc.
1081 ``llvm/lib/Transforms/``
1083 This directory contains the source code for the LLVM to LLVM program
1084 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1085 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1086 Elimination, and many others.
1088 ``llvm/lib/Target/``
1090 This directory contains files that describe various target architectures for
1091 code generation. For example, the ``llvm/lib/Target/X86`` directory holds the
1092 X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
1095 ``llvm/lib/CodeGen/``
1097 This directory contains the major parts of the code generator: Instruction
1098 Selector, Instruction Scheduling, and Register Allocation.
1104 ``llvm/lib/Debugger/``
1106 This directory contains the source level debugger library that makes it
1107 possible to instrument LLVM programs so that a debugger could identify source
1108 code locations at which the program is executing.
1110 ``llvm/lib/ExecutionEngine/``
1112 This directory contains libraries for executing LLVM bitcode directly at
1113 runtime in both interpreted and JIT compiled fashions.
1115 ``llvm/lib/Support/``
1117 This directory contains the source code that corresponds to the header files
1118 located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
1123 This directory contains projects that are not strictly part of LLVM but are
1124 shipped with LLVM. This is also the directory where you should create your own
1125 LLVM-based projects. See ``llvm/projects/sample`` for an example of how to set
1126 up your own project.
1131 This directory contains libraries which are compiled into LLVM bitcode and used
1132 when linking programs with the Clang front end. Most of these libraries are
1133 skeleton versions of real libraries; for example, libc is a stripped down
1136 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
1142 This directory contains feature and regression tests and other basic sanity
1143 checks on the LLVM infrastructure. These are intended to run quickly and cover a
1144 lot of territory without being exhaustive.
1149 This is not a directory in the normal llvm module; it is a separate Subversion
1150 module that must be checked out (usually to ``projects/test-suite``). This
1151 module contains a comprehensive correctness, performance, and benchmarking test
1152 suite for LLVM. It is a separate Subversion module because not every LLVM user
1153 is interested in downloading or building such a comprehensive test suite. For
1154 further details on this test suite, please see the :doc:`Testing Guide
1155 <TestingGuide>` document.
1162 The **tools** directory contains the executables built out of the libraries
1163 above, which form the main part of the user interface. You can always get help
1164 for a tool by typing ``tool_name -help``. The following is a brief introduction
1165 to the most important tools. More detailed information is in
1166 the `Command Guide <CommandGuide/index.html>`_.
1170 ``bugpoint`` is used to debug optimization passes or code generation backends
1171 by narrowing down the given test case to the minimum number of passes and/or
1172 instructions that still cause a problem, whether it is a crash or
1173 miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
1178 The archiver produces an archive containing the given LLVM bitcode files,
1179 optionally with an index for faster lookup.
1183 The assembler transforms the human readable LLVM assembly to LLVM bitcode.
1187 The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
1191 ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
1196 ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
1197 (although very slowly...). For architectures that support it (currently x86,
1198 Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
1199 compiler (if the functionality was compiled in), and will execute the code
1200 *much* faster than the interpreter.
1204 ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
1205 native code assembly file or to C code (with the ``-march=c`` option).
1209 ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
1210 (which are specified on the command line), and then outputs the resultant
1211 bitcode. The '``opt -help``' command is a good way to get a list of the
1212 program transformations available in LLVM.
1214 ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
1215 file and print out the results. It is primarily useful for debugging
1216 analyses, or familiarizing yourself with what an analysis does.
1221 This directory contains utilities for working with LLVM source code, and some of
1222 the utilities are actually required as part of the build process because they
1223 are code generators for parts of LLVM infrastructure.
1228 ``codegen-diff`` is a script that finds differences between code that LLC
1229 generates and code that LLI generates. This is a useful tool if you are
1230 debugging one of them, assuming that the other generates correct output. For
1231 the full user manual, run ```perldoc codegen-diff'``.
1235 The ``emacs`` directory contains syntax-highlighting files which will work
1236 with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
1237 assembly files and TableGen description files. For information on how to use
1238 the syntax files, consult the ``README`` file in that directory.
1242 The ``getsrcs.sh`` script finds and outputs all non-generated source files,
1243 which is useful if one wishes to do a lot of development across directories
1244 and does not want to individually find each file. One way to use it is to run,
1245 for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
1250 This little tool performs an ``egrep -H -n`` on each source file in LLVM and
1251 passes to it a regular expression provided on ``llvmgrep``'s command
1252 line. This is a very efficient way of searching the source base for a
1253 particular regular expression.
1257 The ``makellvm`` script compiles all files in the current directory and then
1258 compiles and links the tool that is the first argument. For example, assuming
1259 you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
1260 path, simply running ``makellvm llc`` will make a build of the current
1261 directory, switch to directory ``llvm/tools/llc`` and build it, causing a
1266 The ``TableGen`` directory contains the tool used to generate register
1267 descriptions, instruction set descriptions, and even assemblers from common
1268 TableGen description files.
1272 The ``vim`` directory contains syntax-highlighting files which will work with
1273 the VIM editor, providing syntax highlighting support for LLVM assembly files
1274 and TableGen description files. For information on how to use the syntax
1275 files, consult the ``README`` file in that directory.
1279 An Example Using the LLVM Tool Chain
1280 ====================================
1282 This section gives an example of using LLVM with the Clang front end.
1287 #. First, create a simple C file, name it 'hello.c':
1294 printf("hello world\n");
1298 #. Next, compile the C file into a native executable:
1300 .. code-block:: console
1302 % clang hello.c -o hello
1306 Clang works just like GCC by default. The standard -S and -c arguments
1307 work as usual (producing a native .s or .o file, respectively).
1309 #. Next, compile the C file into a LLVM bitcode file:
1311 .. code-block:: console
1313 % clang -O3 -emit-llvm hello.c -c -o hello.bc
1315 The -emit-llvm option can be used with the -S or -c options to emit an LLVM
1316 ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
1317 the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
1319 #. Run the program in both forms. To run the program, use:
1321 .. code-block:: console
1327 .. code-block:: console
1331 The second examples shows how to invoke the LLVM JIT, :doc:`lli
1332 <CommandGuide/lli>`.
1334 #. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
1336 .. code-block:: console
1338 % llvm-dis < hello.bc | less
1340 #. Compile the program to native assembly using the LLC code generator:
1342 .. code-block:: console
1344 % llc hello.bc -o hello.s
1346 #. Assemble the native assembly language file into a program:
1348 .. code-block:: console
1350 % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
1352 % gcc hello.s -o hello.native # On others
1354 #. Execute the native code program:
1356 .. code-block:: console
1360 Note that using clang to compile directly to native code (i.e. when the
1361 ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
1366 If you are having problems building or using LLVM, or if you have any other
1367 general questions about LLVM, please consult the `Frequently Asked
1368 Questions <FAQ.html>`_ page.
1375 This document is just an **introduction** on how to use LLVM to do some simple
1376 things... there are many more interesting and complicated things that you can do
1377 that aren't documented here (but we'll gladly accept a patch if you want to
1378 write something up!). For more information about LLVM, check out:
1380 * `LLVM Homepage <http://llvm.org/>`_
1381 * `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
1382 * `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_