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32 The LLVM Getting Started documentation may be out of date.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/>`_ | >=2.4 | 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 +--------------------------------------------------------------+-----------------+---------------------------------------------+
232 | `zlib <http://zlib.net>`_ | >=1.2.3.4 | Compression library\ :sup:`5` |
233 +--------------------------------------------------------------+-----------------+---------------------------------------------+
237 #. Only the C and C++ languages are needed so there's no need to build the
238 other languages for LLVM's purposes. See `below` for specific version
240 #. You only need Subversion if you intend to build from the latest LLVM
241 sources. If you're working from a release distribution, you don't need
243 #. Only needed if you want to run the automated test suite in the
244 ``llvm/test`` directory.
245 #. If you want to make changes to the configure scripts, you will need GNU
246 autoconf (2.60), and consequently, GNU M4 (version 1.4 or higher). You
247 will also need automake (1.9.6). We only use aclocal from that package.
248 #. Optional, adds compression/uncompression capabilities to selected LLVM
251 Additionally, your compilation host is expected to have the usual plethora of
252 Unix utilities. Specifically:
254 * **ar** --- archive library builder
255 * **bzip2** --- bzip2 command for distribution generation
256 * **bunzip2** --- bunzip2 command for distribution checking
257 * **chmod** --- change permissions on a file
258 * **cat** --- output concatenation utility
259 * **cp** --- copy files
260 * **date** --- print the current date/time
261 * **echo** --- print to standard output
262 * **egrep** --- extended regular expression search utility
263 * **find** --- find files/dirs in a file system
264 * **grep** --- regular expression search utility
265 * **gzip** --- gzip command for distribution generation
266 * **gunzip** --- gunzip command for distribution checking
267 * **install** --- install directories/files
268 * **mkdir** --- create a directory
269 * **mv** --- move (rename) files
270 * **ranlib** --- symbol table builder for archive libraries
271 * **rm** --- remove (delete) files and directories
272 * **sed** --- stream editor for transforming output
273 * **sh** --- Bourne shell for make build scripts
274 * **tar** --- tape archive for distribution generation
275 * **test** --- test things in file system
276 * **unzip** --- unzip command for distribution checking
277 * **zip** --- zip command for distribution generation
282 Broken versions of GCC and other tools
283 --------------------------------------
285 LLVM is very demanding of the host C++ compiler, and as such tends to expose
286 bugs in the compiler. In particular, several versions of GCC crash when trying
287 to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang. Other
288 versions of GCC will probably work as well. GCC versions listed here are known
289 to not work. If you are using one of these versions, please try to upgrade your
290 GCC to something more recent. If you run into a problem with a version of GCC
291 not listed here, please `let us know <mailto:llvmdev@cs.uiuc.edu>`_. Please use
292 the "``gcc -v``" command to find out which version of GCC you are using.
294 **GCC versions prior to 3.0**: GCC 2.96.x and before had several problems in the
295 STL that effectively prevent it from compiling LLVM.
297 **GCC 3.2.2 and 3.2.3**: These versions of GCC fails to compile LLVM with a
298 bogus template error. This was fixed in later GCCs.
300 **GCC 3.3.2**: This version of GCC suffered from a `serious bug
301 <http://gcc.gnu.org/PR13392>`_ which causes it to crash in the
302 "``convert_from_eh_region_ranges_1``" GCC function.
304 **Cygwin GCC 3.3.3**: The version of GCC 3.3.3 commonly shipped with Cygwin does
307 **SuSE GCC 3.3.3**: The version of GCC 3.3.3 shipped with SuSE 9.1 (and possibly
308 others) does not compile LLVM correctly (it appears that exception handling is
309 broken in some cases). Please download the FSF 3.3.3 or upgrade to a newer
312 **GCC 3.4.0 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
313 generator, causing an infinite loop in the llvm-gcc build when built with
314 optimizations enabled (i.e. a release build).
316 **GCC 3.4.2 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
317 generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0) correctly
318 compiles LLVM at -O2. A work around is to build release LLVM builds with
319 "``make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ...``"
321 **GCC 3.4.x on X86-64/amd64**: GCC `miscompiles portions of LLVM
322 <http://llvm.org/PR1056>`__.
324 **GCC 3.4.4 (CodeSourcery ARM 2005q3-2)**: this compiler miscompiles LLVM when
325 building with optimizations enabled. It appears to work with "``make
326 ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1``" or build a debug build.
328 **IA-64 GCC 4.0.0**: The IA-64 version of GCC 4.0.0 is known to miscompile LLVM.
330 **Apple Xcode 2.3**: GCC crashes when compiling LLVM at -O3 (which is the
331 default with ENABLE_OPTIMIZED=1. To work around this, build with
332 "``ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2``".
334 **GCC 4.1.1**: GCC fails to build LLVM with template concept check errors
335 compiling some files. At the time of this writing, GCC mainline (4.2) did not
338 **GCC 4.1.1 on X86-64/amd64**: GCC `miscompiles portions of LLVM
339 <http://llvm.org/PR1063>`__ when compiling llvm itself into 64-bit code. LLVM
340 will appear to mostly work but will be buggy, e.g. failing portions of its
343 **GCC 4.1.2 on OpenSUSE**: Seg faults during libstdc++ build and on x86_64
344 platforms compiling md5.c gets a mangled constant.
346 **GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian**: Appears to
347 miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining about
348 symbols remaining in the table on destruction.
350 **GCC 4.1.2 20071124 (Red Hat 4.1.2-42)**: Suffers from the same symptoms as the
351 previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).
353 **Cygwin GCC 4.3.2 20080827 (beta) 2**: Users `reported
354 <http://llvm.org/PR4145>`_ various problems related with link errors when using
357 **Debian GCC 4.3.2 on X86**: Crashes building some files in LLVM 2.6.
359 **GCC 4.3.3 (Debian 4.3.3-10) on ARM**: Miscompiles parts of LLVM 2.6 when
360 optimizations are turned on. The symptom is an infinite loop in
361 ``FoldingSetImpl::RemoveNode`` while running the code generator.
363 **SUSE 11 GCC 4.3.4**: Miscompiles LLVM, causing crashes in ValueHandle logic.
365 **GCC 4.3.5 and GCC 4.4.5 on ARM**: These can miscompile ``value >> 1`` even at
366 ``-O0``. A test failure in ``test/Assembler/alignstack.ll`` is one symptom of
369 **GCC 4.6.3 on ARM**: Miscompiles ``llvm-readobj`` at ``-O3``. A test failure
370 in ``test/Object/readobj-shared-object.test`` is one symptom of the problem.
372 **GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
373 warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
374 defined in a discarded section. You can safely ignore these messages as they are
375 erroneous and the linkage is correct. These messages disappear using ld 2.17.
377 **GNU binutils 2.17**: Binutils 2.17 contains `a bug
378 <http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link
379 times (minutes instead of seconds) when building LLVM. We recommend upgrading
380 to a newer version (2.17.50.0.4 or later).
382 **GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
383 <http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes
384 intermittent failures when building LLVM with position independent code. The
385 symptom is an error about cyclic dependencies. We recommend upgrading to a
386 newer version of Gold.
388 **Clang 3.0 with libstdc++ 4.7.x**: a few Linux distributions (Ubuntu 12.10,
389 Fedora 17) have both Clang 3.0 and libstdc++ 4.7 in their repositories. Clang
390 3.0 does not implement a few builtins that are used in this library. We
391 recommend using the system GCC to compile LLVM and Clang in this case.
393 **Clang 3.0 on Mageia 2**. There's a packaging issue: Clang can not find at
394 least some (``cxxabi.h``) libstdc++ headers.
396 .. _Getting Started with LLVM:
398 Getting Started with LLVM
399 =========================
401 The remainder of this guide is meant to get you up and running with LLVM and to
402 give you some basic information about the LLVM environment.
404 The later sections of this guide describe the `general layout`_ of the LLVM
405 source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
406 more information about LLVM or to get help via e-mail.
408 Terminology and Notation
409 ------------------------
411 Throughout this manual, the following names are used to denote paths specific to
412 the local system and working environment. *These are not environment variables
413 you need to set but just strings used in the rest of this document below*. In
414 any of the examples below, simply replace each of these names with the
415 appropriate pathname on your local system. All these paths are absolute:
419 This is the top level directory of the LLVM source tree.
423 This is the top level directory of the LLVM object tree (i.e. the tree where
424 object files and compiled programs will be placed. It can be the same as
427 .. _Setting Up Your Environment:
429 Setting Up Your Environment
430 ---------------------------
432 In order to compile and use LLVM, you may need to set some environment
435 ``LLVM_LIB_SEARCH_PATH=/path/to/your/bitcode/libs``
437 [Optional] This environment variable helps LLVM linking tools find the
438 locations of your bitcode libraries. It is provided only as a convenience
439 since you can specify the paths using the -L options of the tools and the
440 C/C++ front-end will automatically use the bitcode files installed in its
443 Unpacking the LLVM Archives
444 ---------------------------
446 If you have the LLVM distribution, you will need to unpack it before you can
447 begin to compile it. LLVM is distributed as a set of two files: the LLVM suite
448 and the LLVM GCC front end compiled for your platform. There is an additional
449 test suite that is optional. Each file is a TAR archive that is compressed with
452 The files are as follows, with *x.y* marking the version number:
456 Source release for the LLVM libraries and tools.
458 ``llvm-test-x.y.tar.gz``
460 Source release for the LLVM test-suite.
462 ``llvm-gcc-4.2-x.y.source.tar.gz``
464 Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
465 directory for build instructions.
467 ``llvm-gcc-4.2-x.y-platform.tar.gz``
469 Binary release of the llvm-gcc-4.2 front end for a specific platform.
473 Checkout LLVM from Subversion
474 -----------------------------
476 If you have access to our Subversion repository, you can get a fresh copy of the
477 entire source code. All you need to do is check it out from Subversion as
480 * ``cd where-you-want-llvm-to-live``
481 * Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
482 * Read-Write:``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
484 This will create an '``llvm``' directory in the current directory and fully
485 populate it with the LLVM source code, Makefiles, test directories, and local
486 copies of documentation files.
488 If you want to get a specific release (as opposed to the most recent revision),
489 you can checkout it from the '``tags``' directory (instead of '``trunk``'). The
490 following releases are located in the following subdirectories of the '``tags``'
493 * Release 3.1: **RELEASE_31/final**
494 * Release 3.0: **RELEASE_30/final**
495 * Release 2.9: **RELEASE_29/final**
496 * Release 2.8: **RELEASE_28**
497 * Release 2.7: **RELEASE_27**
498 * Release 2.6: **RELEASE_26**
499 * Release 2.5: **RELEASE_25**
500 * Release 2.4: **RELEASE_24**
501 * Release 2.3: **RELEASE_23**
502 * Release 2.2: **RELEASE_22**
503 * Release 2.1: **RELEASE_21**
504 * Release 2.0: **RELEASE_20**
505 * Release 1.9: **RELEASE_19**
506 * Release 1.8: **RELEASE_18**
507 * Release 1.7: **RELEASE_17**
508 * Release 1.6: **RELEASE_16**
509 * Release 1.5: **RELEASE_15**
510 * Release 1.4: **RELEASE_14**
511 * Release 1.3: **RELEASE_13**
512 * Release 1.2: **RELEASE_12**
513 * Release 1.1: **RELEASE_11**
514 * Release 1.0: **RELEASE_1**
516 If you would like to get the LLVM test suite (a separate package as of 1.4), you
517 get it from the Subversion repository:
519 .. code-block:: console
522 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
524 By placing it in the ``llvm/projects``, it will be automatically configured by
525 the LLVM configure script as well as automatically updated when you run ``svn
531 Git mirrors are available for a number of LLVM subprojects. These mirrors sync
532 automatically with each Subversion commit and contain all necessary git-svn
533 marks (so, you can recreate git-svn metadata locally). Note that right now
534 mirrors reflect only ``trunk`` for each project. You can do the read-only Git
537 .. code-block:: console
539 % git clone http://llvm.org/git/llvm.git
541 If you want to check out clang too, run:
543 .. code-block:: console
546 % git clone http://llvm.org/git/clang.git
548 If you want to check out compiler-rt too, run:
550 .. code-block:: console
553 % git clone http://llvm.org/git/compiler-rt.git
555 If you want to check out the Test Suite Source Code (optional), run:
557 .. code-block:: console
560 % git clone http://llvm.org/git/test-suite.git
562 Since the upstream repository is in Subversion, you should use ``git
563 pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
564 in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the
565 master branch, run the following command:
567 .. code-block:: console
569 % git config branch.master.rebase true
571 Sending patches with Git
572 ^^^^^^^^^^^^^^^^^^^^^^^^
574 Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
576 Assume ``master`` points the upstream and ``mybranch`` points your working
577 branch, and ``mybranch`` is rebased onto ``master``. At first you may check
578 sanity of whitespaces:
580 .. code-block:: console
582 % git diff --check master..mybranch
584 The easiest way to generate a patch is as below:
586 .. code-block:: console
588 % git diff master..mybranch > /path/to/mybranch.diff
590 It is a little different from svn-generated diff. git-diff-generated diff has
591 prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
592 could be accepted with ``patch -p1 -N``.
594 But you may generate patchset with git-format-patch. It generates by-each-commit
595 patchset. To generate patch files to attach to your article:
597 .. code-block:: console
599 % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
601 If you would like to send patches directly, you may use git-send-email or
602 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
604 .. code-block:: console
606 % git format-patch --attach master..mybranch --stdout | git imap-send
608 Then, your .git/config should have [imap] sections.
613 host = imaps://imap.gmail.com
614 user = your.gmail.account@gmail.com
619 folder = "[Gmail]/Drafts"
620 ; example for Japanese, "Modified UTF-7" encoded.
621 folder = "[Gmail]/&Tgtm+DBN-"
622 ; example for Traditional Chinese
623 folder = "[Gmail]/&g0l6Pw-"
625 For developers to work with git-svn
626 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
628 To set up clone from which you can submit code using ``git-svn``, run:
630 .. code-block:: console
632 % git clone http://llvm.org/git/llvm.git
634 % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
635 % git config svn-remote.svn.fetch :refs/remotes/origin/master
636 % git svn rebase -l # -l avoids fetching ahead of the git mirror.
638 # If you have clang too:
640 % git clone http://llvm.org/git/clang.git
642 % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
643 % git config svn-remote.svn.fetch :refs/remotes/origin/master
646 Likewise for compiler-rt and test-suite.
648 To update this clone without generating git-svn tags that conflict with the
649 upstream Git repo, run:
651 .. code-block:: console
653 % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
654 % git checkout master
657 git checkout master &&
660 Likewise for compiler-rt and test-suite.
662 This leaves your working directories on their master branches, so you'll need to
663 ``checkout`` each working branch individually and ``rebase`` it on top of its
666 For those who wish to be able to update an llvm repo/revert patches easily using
667 git-svn, please look in the directory for the scripts ``git-svnup`` and
670 To perform the aforementioned update steps go into your source directory and
671 just type ``git-svnup`` or ``git svnup`` and everything will just work.
673 If one wishes to revert a commit with git-svn, but do not want the git hash to
674 escape into the commit message, one can use the script ``git-svnrevert`` or
675 ``git svnrevert`` which will take in the git hash for the commit you want to
676 revert, look up the appropriate svn revision, and output a message where all
677 references to the git hash have been replaced with the svn revision.
679 To commit back changes via git-svn, use ``git svn dcommit``:
681 .. code-block:: console
685 Note that git-svn will create one SVN commit for each Git commit you have pending,
686 so squash and edit each commit before executing ``dcommit`` to make sure they all
687 conform to the coding standards and the developers' policy.
689 On success, ``dcommit`` will rebase against the HEAD of SVN, so to avoid conflict,
690 please make sure your current branch is up-to-date (via fetch/rebase) before
693 The git-svn metadata can get out of sync after you mess around with branches and
694 ``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
695 about files with uncommitted changes. The fix is to rebuild the metadata:
697 .. code-block:: console
702 Please, refer to the Git-SVN manual (``man git-svn``) for more information.
704 Local LLVM Configuration
705 ------------------------
707 Once checked out from the Subversion repository, the LLVM suite source code must
708 be configured via the ``configure`` script. This script sets variables in the
709 various ``*.in`` files, most notably ``llvm/Makefile.config`` and
710 ``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the
711 Makefiles needed to begin building LLVM.
713 The following environment variables are used by the ``configure`` script to
714 configure the build system:
716 +------------+-----------------------------------------------------------+
717 | Variable | Purpose |
718 +============+===========================================================+
719 | CC | Tells ``configure`` which C compiler to use. By default, |
720 | | ``configure`` will check ``PATH`` for ``clang`` and GCC C |
721 | | compilers (in this order). Use this variable to override |
722 | | ``configure``\'s default behavior. |
723 +------------+-----------------------------------------------------------+
724 | CXX | Tells ``configure`` which C++ compiler to use. By |
725 | | default, ``configure`` will check ``PATH`` for |
726 | | ``clang++`` and GCC C++ compilers (in this order). Use |
727 | | this variable to override ``configure``'s default |
729 +------------+-----------------------------------------------------------+
731 The following options can be used to set or enable LLVM specific options:
733 ``--enable-optimized``
735 Enables optimized compilation (debugging symbols are removed and GCC
736 optimization flags are enabled). Note that this is the default setting if you
737 are using the LLVM distribution. The default behavior of an Subversion
738 checkout is to use an unoptimized build (also known as a debug build).
740 ``--enable-debug-runtime``
742 Enables debug symbols in the runtime libraries. The default is to strip debug
743 symbols from the runtime libraries.
747 Compile the Just In Time (JIT) compiler functionality. This is not available
748 on all platforms. The default is dependent on platform, so it is best to
749 explicitly enable it if you want it.
751 ``--enable-targets=target-option``
753 Controls which targets will be built and linked into llc. The default value
754 for ``target_options`` is "all" which builds and links all available targets.
755 The value "host-only" can be specified to build only a native compiler (no
756 cross-compiler targets available). The "native" target is selected as the
757 target of the build host. You can also specify a comma separated list of
758 target names that you want available in llc. The target names use all lower
759 case. The current set of targets is:
761 ``arm, cpp, hexagon, mblaze, mips, mipsel, msp430, powerpc, ptx, sparc, spu,
762 systemz, x86, x86_64, xcore``.
766 Look for the doxygen program and enable construction of doxygen based
767 documentation from the source code. This is disabled by default because
768 generating the documentation can take a long time and producess 100s of
773 LLVM can use external disassembler library for various purposes (now it's used
774 only for examining code produced by JIT). This option will enable usage of
775 `udis86 <http://udis86.sourceforge.net/>`_ x86 (both 32 and 64 bits)
776 disassembler library.
778 To configure LLVM, follow these steps:
780 #. Change directory into the object root directory:
782 .. code-block:: console
786 #. Run the ``configure`` script located in the LLVM source tree:
788 .. code-block:: console
790 % SRC_ROOT/configure --prefix=/install/path [other options]
792 Compiling the LLVM Suite Source Code
793 ------------------------------------
795 Once you have configured LLVM, you can build it. There are three types of
800 These builds are the default when one is using an Subversion checkout and
801 types ``gmake`` (unless the ``--enable-optimized`` option was used during
802 configuration). The build system will compile the tools and libraries with
803 debugging information. To get a Debug Build using the LLVM distribution the
804 ``--disable-optimized`` option must be passed to ``configure``.
806 Release (Optimized) Builds
808 These builds are enabled with the ``--enable-optimized`` option to
809 ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
810 line. For these builds, the build system will compile the tools and libraries
811 with GCC optimizations enabled and strip debugging information from the
812 libraries and executables it generates. Note that Release Builds are default
813 when using an LLVM distribution.
817 These builds are for use with profiling. They compile profiling information
818 into the code for use with programs like ``gprof``. Profile builds must be
819 started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
821 Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
822 directory and issuing the following command:
824 .. code-block:: console
828 If the build fails, please `check here`_ to see if you are using a version of
829 GCC that is known not to compile LLVM.
831 If you have multiple processors in your machine, you may wish to use some of the
832 parallel build options provided by GNU Make. For example, you could use the
835 .. code-block:: console
839 There are several special targets which are useful when working with the LLVM
844 Removes all files generated by the build. This includes object files,
845 generated C/C++ files, libraries, and executables.
849 Removes everything that ``gmake clean`` does, but also removes files generated
850 by ``configure``. It attempts to return the source tree to the original state
851 in which it was shipped.
855 Installs LLVM header files, libraries, tools, and documentation in a hierarchy
856 under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
857 defaults to ``/usr/local``.
859 ``gmake -C runtime install-bytecode``
861 Assuming you built LLVM into $OBJDIR, when this command is run, it will
862 install bitcode libraries into the GCC front end's bitcode library directory.
863 If you need to update your bitcode libraries, this is the target to use once
866 Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
867 these ``make`` targets and descriptions of other targets available.
869 It is also possible to override default values from ``configure`` by declaring
870 variables on the command line. The following are some examples:
872 ``gmake ENABLE_OPTIMIZED=1``
874 Perform a Release (Optimized) build.
876 ``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
878 Perform a Release (Optimized) build without assertions enabled.
880 ``gmake ENABLE_OPTIMIZED=0``
882 Perform a Debug build.
884 ``gmake ENABLE_PROFILING=1``
886 Perform a Profiling build.
890 Print what ``gmake`` is doing on standard output.
892 ``gmake TOOL_VERBOSE=1``
894 Ask each tool invoked by the makefiles to print out what it is doing on
895 the standard output. This also implies ``VERBOSE=1``.
897 Every directory in the LLVM object tree includes a ``Makefile`` to build it and
898 any subdirectories that it contains. Entering any directory inside the LLVM
899 object tree and typing ``gmake`` should rebuild anything in or below that
900 directory that is out of date.
902 This does not apply to building the documentation.
903 LLVM's (non-Doxygen) documentation is produced with the
904 `Sphinx <http://sphinx-doc.org/>`_ documentation generation system.
905 There are some HTML documents that have not yet been converted to the new
906 system (which uses the easy-to-read and easy-to-write
907 `reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup
909 The generated documentation is built in the ``SRC_ROOT/docs`` directory using
911 For instructions on how to install Sphinx, see
912 `Sphinx Introduction for LLVM Developers
913 <http://lld.llvm.org/sphinx_intro.html>`_.
914 After following the instructions there for installing Sphinx, build the LLVM
915 HTML documentation by doing the following:
917 .. code-block:: console
920 $ make -f Makefile.sphinx
922 This creates a ``_build/html`` sub-directory with all of the HTML files, not
923 just the generated ones.
924 This directory corresponds to ``llvm.org/docs``.
925 For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to
926 ``llvm.org/docs/SphinxQuickstartTemplate.html``.
927 The :doc:`SphinxQuickstartTemplate` is useful when creating a new document.
932 It is possible to cross-compile LLVM itself. That is, you can create LLVM
933 executables and libraries to be hosted on a platform different from the platform
934 where they are built (a Canadian Cross build). To configure a cross-compile,
935 supply the configure script with ``--build`` and ``--host`` options that are
936 different. The values of these options must be legal target triples that your
937 GCC compiler supports.
939 The result of such a build is executables that are not runnable on on the build
940 host (--build option) but can be executed on the compile host (--host option).
942 The Location of LLVM Object Files
943 ---------------------------------
945 The LLVM build system is capable of sharing a single LLVM source tree among
946 several LLVM builds. Hence, it is possible to build LLVM for several different
947 platforms or configurations using the same source tree.
949 This is accomplished in the typical autoconf manner:
951 * Change directory to where the LLVM object files should live:
953 .. code-block:: console
957 * Run the ``configure`` script found in the LLVM source directory:
959 .. code-block:: console
963 The LLVM build will place files underneath *OBJ_ROOT* in directories named after
966 Debug Builds with assertions enabled (the default)
970 ``OBJ_ROOT/Debug+Asserts/bin``
974 ``OBJ_ROOT/Debug+Asserts/lib``
980 ``OBJ_ROOT/Release/bin``
984 ``OBJ_ROOT/Release/lib``
990 ``OBJ_ROOT/Profile/bin``
994 ``OBJ_ROOT/Profile/lib``
996 Optional Configuration Items
997 ----------------------------
999 If you're running on a Linux system that supports the `binfmt_misc
1000 <http://en.wikipedia.org/wiki/binfmt_misc>`_
1001 module, and you have root access on the system, you can set your system up to
1002 execute LLVM bitcode files directly. To do this, use commands like this (the
1003 first command may not be required if you are already using the module):
1005 .. code-block:: console
1007 % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1008 % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1009 % chmod u+x hello.bc (if needed)
1012 This allows you to execute LLVM bitcode files directly. On Debian, you can also
1013 use this command instead of the 'echo' command above:
1015 .. code-block:: console
1017 % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1025 One useful source of information about the LLVM source base is the LLVM `doxygen
1026 <http://www.doxygen.org/>`_ documentation available at
1027 `<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
1033 This directory contains some simple examples of how to use the LLVM IR and JIT.
1038 This directory contains public header files exported from the LLVM library. The
1039 three main subdirectories of this directory are:
1041 ``llvm/include/llvm``
1043 This directory contains all of the LLVM specific header files. This directory
1044 also has subdirectories for different portions of LLVM: ``Analysis``,
1045 ``CodeGen``, ``Target``, ``Transforms``, etc...
1047 ``llvm/include/llvm/Support``
1049 This directory contains generic support libraries that are provided with LLVM
1050 but not necessarily specific to LLVM. For example, some C++ STL utilities and
1051 a Command Line option processing library store their header files here.
1053 ``llvm/include/llvm/Config``
1055 This directory contains header files configured by the ``configure`` script.
1056 They wrap "standard" UNIX and C header files. Source code can include these
1057 header files which automatically take care of the conditional #includes that
1058 the ``configure`` script generates.
1063 This directory contains most of the source files of the LLVM system. In LLVM,
1064 almost all code exists in libraries, making it very easy to share code among the
1067 ``llvm/lib/VMCore/``
1069 This directory holds the core LLVM source files that implement core classes
1070 like Instruction and BasicBlock.
1072 ``llvm/lib/AsmParser/``
1074 This directory holds the source code for the LLVM assembly language parser
1077 ``llvm/lib/BitCode/``
1079 This directory holds code for reading and write LLVM bitcode.
1081 ``llvm/lib/Analysis/``
1083 This directory contains a variety of different program analyses, such as
1084 Dominator Information, Call Graphs, Induction Variables, Interval
1085 Identification, Natural Loop Identification, etc.
1087 ``llvm/lib/Transforms/``
1089 This directory contains the source code for the LLVM to LLVM program
1090 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1091 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1092 Elimination, and many others.
1094 ``llvm/lib/Target/``
1096 This directory contains files that describe various target architectures for
1097 code generation. For example, the ``llvm/lib/Target/X86`` directory holds the
1098 X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
1101 ``llvm/lib/CodeGen/``
1103 This directory contains the major parts of the code generator: Instruction
1104 Selector, Instruction Scheduling, and Register Allocation.
1110 ``llvm/lib/Debugger/``
1112 This directory contains the source level debugger library that makes it
1113 possible to instrument LLVM programs so that a debugger could identify source
1114 code locations at which the program is executing.
1116 ``llvm/lib/ExecutionEngine/``
1118 This directory contains libraries for executing LLVM bitcode directly at
1119 runtime in both interpreted and JIT compiled fashions.
1121 ``llvm/lib/Support/``
1123 This directory contains the source code that corresponds to the header files
1124 located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
1129 This directory contains projects that are not strictly part of LLVM but are
1130 shipped with LLVM. This is also the directory where you should create your own
1131 LLVM-based projects. See ``llvm/projects/sample`` for an example of how to set
1132 up your own project.
1137 This directory contains libraries which are compiled into LLVM bitcode and used
1138 when linking programs with the Clang front end. Most of these libraries are
1139 skeleton versions of real libraries; for example, libc is a stripped down
1142 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
1148 This directory contains feature and regression tests and other basic sanity
1149 checks on the LLVM infrastructure. These are intended to run quickly and cover a
1150 lot of territory without being exhaustive.
1155 This is not a directory in the normal llvm module; it is a separate Subversion
1156 module that must be checked out (usually to ``projects/test-suite``). This
1157 module contains a comprehensive correctness, performance, and benchmarking test
1158 suite for LLVM. It is a separate Subversion module because not every LLVM user
1159 is interested in downloading or building such a comprehensive test suite. For
1160 further details on this test suite, please see the :doc:`Testing Guide
1161 <TestingGuide>` document.
1168 The **tools** directory contains the executables built out of the libraries
1169 above, which form the main part of the user interface. You can always get help
1170 for a tool by typing ``tool_name -help``. The following is a brief introduction
1171 to the most important tools. More detailed information is in
1172 the `Command Guide <CommandGuide/index.html>`_.
1176 ``bugpoint`` is used to debug optimization passes or code generation backends
1177 by narrowing down the given test case to the minimum number of passes and/or
1178 instructions that still cause a problem, whether it is a crash or
1179 miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
1184 The archiver produces an archive containing the given LLVM bitcode files,
1185 optionally with an index for faster lookup.
1189 The assembler transforms the human readable LLVM assembly to LLVM bitcode.
1193 The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
1197 ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
1202 ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
1203 (although very slowly...). For architectures that support it (currently x86,
1204 Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
1205 compiler (if the functionality was compiled in), and will execute the code
1206 *much* faster than the interpreter.
1210 ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
1211 native code assembly file or to C code (with the ``-march=c`` option).
1215 ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
1216 (which are specified on the command line), and then outputs the resultant
1217 bitcode. The '``opt -help``' command is a good way to get a list of the
1218 program transformations available in LLVM.
1220 ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
1221 file and print out the results. It is primarily useful for debugging
1222 analyses, or familiarizing yourself with what an analysis does.
1227 This directory contains utilities for working with LLVM source code, and some of
1228 the utilities are actually required as part of the build process because they
1229 are code generators for parts of LLVM infrastructure.
1234 ``codegen-diff`` is a script that finds differences between code that LLC
1235 generates and code that LLI generates. This is a useful tool if you are
1236 debugging one of them, assuming that the other generates correct output. For
1237 the full user manual, run ```perldoc codegen-diff'``.
1241 The ``emacs`` directory contains syntax-highlighting files which will work
1242 with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
1243 assembly files and TableGen description files. For information on how to use
1244 the syntax files, consult the ``README`` file in that directory.
1248 The ``getsrcs.sh`` script finds and outputs all non-generated source files,
1249 which is useful if one wishes to do a lot of development across directories
1250 and does not want to individually find each file. One way to use it is to run,
1251 for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
1256 This little tool performs an ``egrep -H -n`` on each source file in LLVM and
1257 passes to it a regular expression provided on ``llvmgrep``'s command
1258 line. This is a very efficient way of searching the source base for a
1259 particular regular expression.
1263 The ``makellvm`` script compiles all files in the current directory and then
1264 compiles and links the tool that is the first argument. For example, assuming
1265 you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
1266 path, simply running ``makellvm llc`` will make a build of the current
1267 directory, switch to directory ``llvm/tools/llc`` and build it, causing a
1272 The ``TableGen`` directory contains the tool used to generate register
1273 descriptions, instruction set descriptions, and even assemblers from common
1274 TableGen description files.
1278 The ``vim`` directory contains syntax-highlighting files which will work with
1279 the VIM editor, providing syntax highlighting support for LLVM assembly files
1280 and TableGen description files. For information on how to use the syntax
1281 files, consult the ``README`` file in that directory.
1285 An Example Using the LLVM Tool Chain
1286 ====================================
1288 This section gives an example of using LLVM with the Clang front end.
1293 #. First, create a simple C file, name it 'hello.c':
1300 printf("hello world\n");
1304 #. Next, compile the C file into a native executable:
1306 .. code-block:: console
1308 % clang hello.c -o hello
1312 Clang works just like GCC by default. The standard -S and -c arguments
1313 work as usual (producing a native .s or .o file, respectively).
1315 #. Next, compile the C file into a LLVM bitcode file:
1317 .. code-block:: console
1319 % clang -O3 -emit-llvm hello.c -c -o hello.bc
1321 The -emit-llvm option can be used with the -S or -c options to emit an LLVM
1322 ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
1323 the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
1325 #. Run the program in both forms. To run the program, use:
1327 .. code-block:: console
1333 .. code-block:: console
1337 The second examples shows how to invoke the LLVM JIT, :doc:`lli
1338 <CommandGuide/lli>`.
1340 #. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
1342 .. code-block:: console
1344 % llvm-dis < hello.bc | less
1346 #. Compile the program to native assembly using the LLC code generator:
1348 .. code-block:: console
1350 % llc hello.bc -o hello.s
1352 #. Assemble the native assembly language file into a program:
1354 .. code-block:: console
1356 % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
1358 % gcc hello.s -o hello.native # On others
1360 #. Execute the native code program:
1362 .. code-block:: console
1366 Note that using clang to compile directly to native code (i.e. when the
1367 ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
1372 If you are having problems building or using LLVM, or if you have any other
1373 general questions about LLVM, please consult the `Frequently Asked
1374 Questions <FAQ.html>`_ page.
1381 This document is just an **introduction** on how to use LLVM to do some simple
1382 things... there are many more interesting and complicated things that you can do
1383 that aren't documented here (but we'll gladly accept a patch if you want to
1384 write something up!). For more information about LLVM, check out:
1386 * `LLVM Homepage <http://llvm.org/>`_
1387 * `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
1388 * `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_