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32 The LLVM Getting Started documentation may be out of date.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 |Solaris | V9 (Ultrasparc) | GCC |
128 +-----------------+----------------------+-------------------------+
129 |FreeBSD | x86\ :sup:`1` | GCC |
130 +-----------------+----------------------+-------------------------+
131 |FreeBSD | amd64 | GCC |
132 +-----------------+----------------------+-------------------------+
133 |MacOS X\ :sup:`2`| PowerPC | GCC |
134 +-----------------+----------------------+-------------------------+
135 |MacOS X\ :sup:`9`| x86 | GCC |
136 +-----------------+----------------------+-------------------------+
137 |Cygwin/Win32 | x86\ :sup:`1, 8, 11` | GCC 3.4.X, binutils 2.20|
138 +-----------------+----------------------+-------------------------+
140 LLVM has partial support for the following platforms:
142 +-------------------+----------------------+-------------------------------------------+
143 |OS | Arch | Compilers |
144 +===================+======================+===========================================+
145 | Windows | x86\ :sup:`1` | Visual Studio 2000 or higher\ :sup:`4,5` |
146 +-------------------+----------------------+-------------------------------------------+
147 | AIX\ :sup:`3,4` | PowerPC | GCC |
148 +-------------------+----------------------+-------------------------------------------+
149 | Linux\ :sup:`3,5` | PowerPC | GCC |
150 +-------------------+----------------------+-------------------------------------------+
151 | Linux\ :sup:`7` | Alpha | GCC |
152 +-------------------+----------------------+-------------------------------------------+
153 | Linux\ :sup:`7` | Itanium (IA-64) | GCC |
154 +-------------------+----------------------+-------------------------------------------+
155 | HP-UX\ :sup:`7` | Itanium (IA-64) | HP aCC |
156 +-------------------+----------------------+-------------------------------------------+
157 | Windows x64 | x86-64 | mingw-w64's GCC-4.5.x\ :sup:`12` |
158 +-------------------+----------------------+-------------------------------------------+
162 Code generation supported for Pentium processors and up
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``.
184 #. To compile SPU backend, you need to add ``LDFLAGS=-Wl,--stack,16777216`` to
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 | `DejaGnu <http://savannah.gnu.org/projects/dejagnu>`_ | 1.4.2 | Automated test suite\ :sup:`3` |
221 +--------------------------------------------------------------+-----------------+---------------------------------------------+
222 | `tcl <http://www.tcl.tk/software/tcltk/>`_ | 8.3, 8.4 | Automated test suite\ :sup:`3` |
223 +--------------------------------------------------------------+-----------------+---------------------------------------------+
224 | `expect <http://expect.nist.gov/>`_ | 5.38.0 | Automated test suite\ :sup:`3` |
225 +--------------------------------------------------------------+-----------------+---------------------------------------------+
226 | `perl <http://www.perl.com/download.csp>`_ | >=5.6.0 | Utilities |
227 +--------------------------------------------------------------+-----------------+---------------------------------------------+
228 | `GNU M4 <http://savannah.gnu.org/projects/m4>`_ | 1.4 | Macro processor for configuration\ :sup:`4` |
229 +--------------------------------------------------------------+-----------------+---------------------------------------------+
230 | `GNU Autoconf <http://www.gnu.org/software/autoconf/>`_ | 2.60 | Configuration script builder\ :sup:`4` |
231 +--------------------------------------------------------------+-----------------+---------------------------------------------+
232 | `GNU Automake <http://www.gnu.org/software/automake/>`_ | 1.9.6 | aclocal macro generator\ :sup:`4` |
233 +--------------------------------------------------------------+-----------------+---------------------------------------------+
234 | `libtool <http://savannah.gnu.org/projects/libtool>`_ | 1.5.22 | Shared library manager\ :sup:`4` |
235 +--------------------------------------------------------------+-----------------+---------------------------------------------+
239 #. Only the C and C++ languages are needed so there's no need to build the
240 other languages for LLVM's purposes. See `below` for specific version
242 #. You only need Subversion if you intend to build from the latest LLVM
243 sources. If you're working from a release distribution, you don't need
245 #. Only needed if you want to run the automated test suite in the
246 ``llvm/test`` directory.
247 #. If you want to make changes to the configure scripts, you will need GNU
248 autoconf (2.60), and consequently, GNU M4 (version 1.4 or higher). You
249 will also need automake (1.9.6). We only use aclocal from that package.
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 **GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
370 warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
371 defined in a discarded section. You can safely ignore these messages as they are
372 erroneous and the linkage is correct. These messages disappear using ld 2.17.
374 **GNU binutils 2.17**: Binutils 2.17 contains `a bug
375 <http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link
376 times (minutes instead of seconds) when building LLVM. We recommend upgrading
377 to a newer version (2.17.50.0.4 or later).
379 **GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
380 <http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes
381 intermittent failures when building LLVM with position independent code. The
382 symptom is an error about cyclic dependencies. We recommend upgrading to a
383 newer version of Gold.
385 **Clang 3.0 with libstdc++ 4.7.x**: a few Linux distributions (Ubuntu 12.10,
386 Fedora 17) have both Clang 3.0 and libstdc++ 4.7 in their repositories. Clang
387 3.0 does not implement a few builtins that are used in this library. We
388 recommend using the system GCC to compile LLVM and Clang in this case.
390 **Clang 3.0 on Mageia 2**. There's a packaging issue: Clang can not find at
391 least some (``cxxabi.h``) libstdc++ headers.
393 .. _Getting Started with LLVM:
395 Getting Started with LLVM
396 =========================
398 The remainder of this guide is meant to get you up and running with LLVM and to
399 give you some basic information about the LLVM environment.
401 The later sections of this guide describe the `general layout`_ of the LLVM
402 source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
403 more information about LLVM or to get help via e-mail.
405 Terminology and Notation
406 ------------------------
408 Throughout this manual, the following names are used to denote paths specific to
409 the local system and working environment. *These are not environment variables
410 you need to set but just strings used in the rest of this document below*. In
411 any of the examples below, simply replace each of these names with the
412 appropriate pathname on your local system. All these paths are absolute:
416 This is the top level directory of the LLVM source tree.
420 This is the top level directory of the LLVM object tree (i.e. the tree where
421 object files and compiled programs will be placed. It can be the same as
424 .. _Setting Up Your Environment:
426 Setting Up Your Environment
427 ---------------------------
429 In order to compile and use LLVM, you may need to set some environment
432 ``LLVM_LIB_SEARCH_PATH=/path/to/your/bitcode/libs``
434 [Optional] This environment variable helps LLVM linking tools find the
435 locations of your bitcode libraries. It is provided only as a convenience
436 since you can specify the paths using the -L options of the tools and the
437 C/C++ front-end will automatically use the bitcode files installed in its
440 Unpacking the LLVM Archives
441 ---------------------------
443 If you have the LLVM distribution, you will need to unpack it before you can
444 begin to compile it. LLVM is distributed as a set of two files: the LLVM suite
445 and the LLVM GCC front end compiled for your platform. There is an additional
446 test suite that is optional. Each file is a TAR archive that is compressed with
449 The files are as follows, with *x.y* marking the version number:
453 Source release for the LLVM libraries and tools.
455 ``llvm-test-x.y.tar.gz``
457 Source release for the LLVM test-suite.
459 ``llvm-gcc-4.2-x.y.source.tar.gz``
461 Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
462 directory for build instructions.
464 ``llvm-gcc-4.2-x.y-platform.tar.gz``
466 Binary release of the llvm-gcc-4.2 front end for a specific platform.
470 Checkout LLVM from Subversion
471 -----------------------------
473 If you have access to our Subversion repository, you can get a fresh copy of the
474 entire source code. All you need to do is check it out from Subversion as
477 * ``cd where-you-want-llvm-to-live``
478 * Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
479 * Read-Write:``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
481 This will create an '``llvm``' directory in the current directory and fully
482 populate it with the LLVM source code, Makefiles, test directories, and local
483 copies of documentation files.
485 If you want to get a specific release (as opposed to the most recent revision),
486 you can checkout it from the '``tags``' directory (instead of '``trunk``'). The
487 following releases are located in the following subdirectories of the '``tags``'
490 * Release 3.1: **RELEASE_31/final**
491 * Release 3.0: **RELEASE_30/final**
492 * Release 2.9: **RELEASE_29/final**
493 * Release 2.8: **RELEASE_28**
494 * Release 2.7: **RELEASE_27**
495 * Release 2.6: **RELEASE_26**
496 * Release 2.5: **RELEASE_25**
497 * Release 2.4: **RELEASE_24**
498 * Release 2.3: **RELEASE_23**
499 * Release 2.2: **RELEASE_22**
500 * Release 2.1: **RELEASE_21**
501 * Release 2.0: **RELEASE_20**
502 * Release 1.9: **RELEASE_19**
503 * Release 1.8: **RELEASE_18**
504 * Release 1.7: **RELEASE_17**
505 * Release 1.6: **RELEASE_16**
506 * Release 1.5: **RELEASE_15**
507 * Release 1.4: **RELEASE_14**
508 * Release 1.3: **RELEASE_13**
509 * Release 1.2: **RELEASE_12**
510 * Release 1.1: **RELEASE_11**
511 * Release 1.0: **RELEASE_1**
513 If you would like to get the LLVM test suite (a separate package as of 1.4), you
514 get it from the Subversion repository:
516 .. code-block:: console
519 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
521 By placing it in the ``llvm/projects``, it will be automatically configured by
522 the LLVM configure script as well as automatically updated when you run ``svn
528 GIT mirrors are available for a number of LLVM subprojects. These mirrors sync
529 automatically with each Subversion commit and contain all necessary git-svn
530 marks (so, you can recreate git-svn metadata locally). Note that right now
531 mirrors reflect only ``trunk`` for each project. You can do the read-only GIT
534 .. code-block:: console
536 % git clone http://llvm.org/git/llvm.git
538 If you want to check out clang too, run:
540 .. code-block:: console
542 % git clone http://llvm.org/git/llvm.git
544 % git clone http://llvm.org/git/clang.git
546 Since the upstream repository is in Subversion, you should use ``git
547 pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
548 in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the
549 master branch, run the following command:
551 .. code-block:: console
553 % git config branch.master.rebase true
555 Sending patches with Git
556 ^^^^^^^^^^^^^^^^^^^^^^^^
558 Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
560 Assume ``master`` points the upstream and ``mybranch`` points your working
561 branch, and ``mybranch`` is rebased onto ``master``. At first you may check
562 sanity of whitespaces:
564 .. code-block:: console
566 % git diff --check master..mybranch
568 The easiest way to generate a patch is as below:
570 .. code-block:: console
572 % git diff master..mybranch > /path/to/mybranch.diff
574 It is a little different from svn-generated diff. git-diff-generated diff has
575 prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
576 could be accepted with ``patch -p1 -N``.
578 But you may generate patchset with git-format-patch. It generates by-each-commit
579 patchset. To generate patch files to attach to your article:
581 .. code-block:: console
583 % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
585 If you would like to send patches directly, you may use git-send-email or
586 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
588 .. code-block:: console
590 % git format-patch --attach master..mybranch --stdout | git imap-send
592 Then, your .git/config should have [imap] sections.
597 host = imaps://imap.gmail.com
598 user = your.gmail.account@gmail.com
603 folder = "[Gmail]/Drafts"
604 ; example for Japanese, "Modified UTF-7" encoded.
605 folder = "[Gmail]/&Tgtm+DBN-"
606 ; example for Traditional Chinese
607 folder = "[Gmail]/&g0l6Pw-"
609 For developers to work with git-svn
610 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
612 To set up clone from which you can submit code using ``git-svn``, run:
614 .. code-block:: console
616 % git clone http://llvm.org/git/llvm.git
618 % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
619 % git config svn-remote.svn.fetch :refs/remotes/origin/master
620 % git svn rebase -l # -l avoids fetching ahead of the git mirror.
622 # If you have clang too:
624 % git clone http://llvm.org/git/clang.git
626 % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
627 % git config svn-remote.svn.fetch :refs/remotes/origin/master
630 To update this clone without generating git-svn tags that conflict with the
631 upstream git repo, run:
633 .. code-block:: console
635 % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
636 % git checkout master
639 git checkout master &&
642 This leaves your working directories on their master branches, so you'll need to
643 ``checkout`` each working branch individually and ``rebase`` it on top of its
646 To commit back changes via git-svn, use ``dcommit``:
648 .. code-block:: console
652 Note that git-svn will create one SVN commit for each Git commit you have pending,
653 so squash and edit each commit before executing ``dcommit`` to make sure they all
654 conform to the coding standards and the developers' policy.
656 On success, ``dcommit`` will rebase against the HEAD of SVN, so to avoid conflict,
657 please make sure your current branch is up-to-date (via fetch/rebase) before
660 The git-svn metadata can get out of sync after you mess around with branches and
661 ``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
662 about files with uncommitted changes. The fix is to rebuild the metadata:
664 .. code-block:: console
669 Please, refer to the Git-SVN manual (``man git-svn``) for more information.
671 Local LLVM Configuration
672 ------------------------
674 Once checked out from the Subversion repository, the LLVM suite source code must
675 be configured via the ``configure`` script. This script sets variables in the
676 various ``*.in`` files, most notably ``llvm/Makefile.config`` and
677 ``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the
678 Makefiles needed to begin building LLVM.
680 The following environment variables are used by the ``configure`` script to
681 configure the build system:
683 +------------+-----------------------------------------------------------+
684 | Variable | Purpose |
685 +============+===========================================================+
686 | CC | Tells ``configure`` which C compiler to use. By default, |
687 | | ``configure`` will check ``PATH`` for ``clang`` and GCC C |
688 | | compilers (in this order). Use this variable to override |
689 | | ``configure``\'s default behavior. |
690 +------------+-----------------------------------------------------------+
691 | CXX | Tells ``configure`` which C++ compiler to use. By |
692 | | default, ``configure`` will check ``PATH`` for |
693 | | ``clang++`` and GCC C++ compilers (in this order). Use |
694 | | this variable to override ``configure``'s default |
696 +------------+-----------------------------------------------------------+
698 The following options can be used to set or enable LLVM specific options:
700 ``--enable-optimized``
702 Enables optimized compilation (debugging symbols are removed and GCC
703 optimization flags are enabled). Note that this is the default setting if you
704 are using the LLVM distribution. The default behavior of an Subversion
705 checkout is to use an unoptimized build (also known as a debug build).
707 ``--enable-debug-runtime``
709 Enables debug symbols in the runtime libraries. The default is to strip debug
710 symbols from the runtime libraries.
714 Compile the Just In Time (JIT) compiler functionality. This is not available
715 on all platforms. The default is dependent on platform, so it is best to
716 explicitly enable it if you want it.
718 ``--enable-targets=target-option``
720 Controls which targets will be built and linked into llc. The default value
721 for ``target_options`` is "all" which builds and links all available targets.
722 The value "host-only" can be specified to build only a native compiler (no
723 cross-compiler targets available). The "native" target is selected as the
724 target of the build host. You can also specify a comma separated list of
725 target names that you want available in llc. The target names use all lower
726 case. The current set of targets is:
728 ``arm, cpp, hexagon, mblaze, mips, mipsel, msp430, powerpc, ptx, sparc, spu,
729 x86, x86_64, xcore``.
733 Look for the doxygen program and enable construction of doxygen based
734 documentation from the source code. This is disabled by default because
735 generating the documentation can take a long time and producess 100s of
740 LLVM can use external disassembler library for various purposes (now it's used
741 only for examining code produced by JIT). This option will enable usage of
742 `udis86 <http://udis86.sourceforge.net/>`_ x86 (both 32 and 64 bits)
743 disassembler library.
745 To configure LLVM, follow these steps:
747 #. Change directory into the object root directory:
749 .. code-block:: console
753 #. Run the ``configure`` script located in the LLVM source tree:
755 .. code-block:: console
757 % SRC_ROOT/configure --prefix=/install/path [other options]
759 Compiling the LLVM Suite Source Code
760 ------------------------------------
762 Once you have configured LLVM, you can build it. There are three types of
767 These builds are the default when one is using an Subversion checkout and
768 types ``gmake`` (unless the ``--enable-optimized`` option was used during
769 configuration). The build system will compile the tools and libraries with
770 debugging information. To get a Debug Build using the LLVM distribution the
771 ``--disable-optimized`` option must be passed to ``configure``.
773 Release (Optimized) Builds
775 These builds are enabled with the ``--enable-optimized`` option to
776 ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
777 line. For these builds, the build system will compile the tools and libraries
778 with GCC optimizations enabled and strip debugging information from the
779 libraries and executables it generates. Note that Release Builds are default
780 when using an LLVM distribution.
784 These builds are for use with profiling. They compile profiling information
785 into the code for use with programs like ``gprof``. Profile builds must be
786 started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
788 Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
789 directory and issuing the following command:
791 .. code-block:: console
795 If the build fails, please `check here`_ to see if you are using a version of
796 GCC that is known not to compile LLVM.
798 If you have multiple processors in your machine, you may wish to use some of the
799 parallel build options provided by GNU Make. For example, you could use the
802 .. code-block:: console
806 There are several special targets which are useful when working with the LLVM
811 Removes all files generated by the build. This includes object files,
812 generated C/C++ files, libraries, and executables.
816 Removes everything that ``gmake clean`` does, but also removes files generated
817 by ``configure``. It attempts to return the source tree to the original state
818 in which it was shipped.
822 Installs LLVM header files, libraries, tools, and documentation in a hierarchy
823 under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
824 defaults to ``/usr/local``.
826 ``gmake -C runtime install-bytecode``
828 Assuming you built LLVM into $OBJDIR, when this command is run, it will
829 install bitcode libraries into the GCC front end's bitcode library directory.
830 If you need to update your bitcode libraries, this is the target to use once
833 Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
834 these ``make`` targets and descriptions of other targets available.
836 It is also possible to override default values from ``configure`` by declaring
837 variables on the command line. The following are some examples:
839 ``gmake ENABLE_OPTIMIZED=1``
841 Perform a Release (Optimized) build.
843 ``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
845 Perform a Release (Optimized) build without assertions enabled.
847 ``gmake ENABLE_OPTIMIZED=0``
849 Perform a Debug build.
851 ``gmake ENABLE_PROFILING=1``
853 Perform a Profiling build.
857 Print what ``gmake`` is doing on standard output.
859 ``gmake TOOL_VERBOSE=1``
861 Ask each tool invoked by the makefiles to print out what it is doing on
862 the standard output. This also implies ``VERBOSE=1``.
864 Every directory in the LLVM object tree includes a ``Makefile`` to build it and
865 any subdirectories that it contains. Entering any directory inside the LLVM
866 object tree and typing ``gmake`` should rebuild anything in or below that
867 directory that is out of date.
869 This does not apply to building the documentation.
870 LLVM's (non-Doxygen) documentation is produced with the
871 `Sphinx <http://sphinx-doc.org/>`_ documentation generation system.
872 There are some HTML documents that have not yet been converted to the new
873 system (which uses the easy-to-read and easy-to-write
874 `reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup
876 The generated documentation is built in the ``SRC_ROOT/docs`` directory using
878 For instructions on how to install Sphinx, see
879 `Sphinx Introduction for LLVM Developers
880 <http://lld.llvm.org/sphinx_intro.html>`_.
881 After following the instructions there for installing Sphinx, build the LLVM
882 HTML documentation by doing the following:
884 .. code-block:: console
887 $ make -f Makefile.sphinx
889 This creates a ``_build/html`` sub-directory with all of the HTML files, not
890 just the generated ones.
891 This directory corresponds to ``llvm.org/docs``.
892 For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to
893 ``llvm.org/docs/SphinxQuickstartTemplate.html``.
894 The :doc:`SphinxQuickstartTemplate` is useful when creating a new document.
899 It is possible to cross-compile LLVM itself. That is, you can create LLVM
900 executables and libraries to be hosted on a platform different from the platform
901 where they are built (a Canadian Cross build). To configure a cross-compile,
902 supply the configure script with ``--build`` and ``--host`` options that are
903 different. The values of these options must be legal target triples that your
904 GCC compiler supports.
906 The result of such a build is executables that are not runnable on on the build
907 host (--build option) but can be executed on the compile host (--host option).
909 The Location of LLVM Object Files
910 ---------------------------------
912 The LLVM build system is capable of sharing a single LLVM source tree among
913 several LLVM builds. Hence, it is possible to build LLVM for several different
914 platforms or configurations using the same source tree.
916 This is accomplished in the typical autoconf manner:
918 * Change directory to where the LLVM object files should live:
920 .. code-block:: console
924 * Run the ``configure`` script found in the LLVM source directory:
926 .. code-block:: console
930 The LLVM build will place files underneath *OBJ_ROOT* in directories named after
933 Debug Builds with assertions enabled (the default)
937 ``OBJ_ROOT/Debug+Asserts/bin``
941 ``OBJ_ROOT/Debug+Asserts/lib``
947 ``OBJ_ROOT/Release/bin``
951 ``OBJ_ROOT/Release/lib``
957 ``OBJ_ROOT/Profile/bin``
961 ``OBJ_ROOT/Profile/lib``
963 Optional Configuration Items
964 ----------------------------
966 If you're running on a Linux system that supports the `binfmt_misc
967 <http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html>`_
968 module, and you have root access on the system, you can set your system up to
969 execute LLVM bitcode files directly. To do this, use commands like this (the
970 first command may not be required if you are already using the module):
972 .. code-block:: console
974 % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
975 % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
976 % chmod u+x hello.bc (if needed)
979 This allows you to execute LLVM bitcode files directly. On Debian, you can also
980 use this command instead of the 'echo' command above:
982 .. code-block:: console
984 % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
992 One useful source of information about the LLVM source base is the LLVM `doxygen
993 <http://www.doxygen.org/>`_ documentation available at
994 `<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
1000 This directory contains some simple examples of how to use the LLVM IR and JIT.
1005 This directory contains public header files exported from the LLVM library. The
1006 three main subdirectories of this directory are:
1008 ``llvm/include/llvm``
1010 This directory contains all of the LLVM specific header files. This directory
1011 also has subdirectories for different portions of LLVM: ``Analysis``,
1012 ``CodeGen``, ``Target``, ``Transforms``, etc...
1014 ``llvm/include/llvm/Support``
1016 This directory contains generic support libraries that are provided with LLVM
1017 but not necessarily specific to LLVM. For example, some C++ STL utilities and
1018 a Command Line option processing library store their header files here.
1020 ``llvm/include/llvm/Config``
1022 This directory contains header files configured by the ``configure`` script.
1023 They wrap "standard" UNIX and C header files. Source code can include these
1024 header files which automatically take care of the conditional #includes that
1025 the ``configure`` script generates.
1030 This directory contains most of the source files of the LLVM system. In LLVM,
1031 almost all code exists in libraries, making it very easy to share code among the
1034 ``llvm/lib/VMCore/``
1036 This directory holds the core LLVM source files that implement core classes
1037 like Instruction and BasicBlock.
1039 ``llvm/lib/AsmParser/``
1041 This directory holds the source code for the LLVM assembly language parser
1044 ``llvm/lib/BitCode/``
1046 This directory holds code for reading and write LLVM bitcode.
1048 ``llvm/lib/Analysis/``
1050 This directory contains a variety of different program analyses, such as
1051 Dominator Information, Call Graphs, Induction Variables, Interval
1052 Identification, Natural Loop Identification, etc.
1054 ``llvm/lib/Transforms/``
1056 This directory contains the source code for the LLVM to LLVM program
1057 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1058 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1059 Elimination, and many others.
1061 ``llvm/lib/Target/``
1063 This directory contains files that describe various target architectures for
1064 code generation. For example, the ``llvm/lib/Target/X86`` directory holds the
1065 X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
1068 ``llvm/lib/CodeGen/``
1070 This directory contains the major parts of the code generator: Instruction
1071 Selector, Instruction Scheduling, and Register Allocation.
1077 ``llvm/lib/Debugger/``
1079 This directory contains the source level debugger library that makes it
1080 possible to instrument LLVM programs so that a debugger could identify source
1081 code locations at which the program is executing.
1083 ``llvm/lib/ExecutionEngine/``
1085 This directory contains libraries for executing LLVM bitcode directly at
1086 runtime in both interpreted and JIT compiled fashions.
1088 ``llvm/lib/Support/``
1090 This directory contains the source code that corresponds to the header files
1091 located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
1096 This directory contains projects that are not strictly part of LLVM but are
1097 shipped with LLVM. This is also the directory where you should create your own
1098 LLVM-based projects. See ``llvm/projects/sample`` for an example of how to set
1099 up your own project.
1104 This directory contains libraries which are compiled into LLVM bitcode and used
1105 when linking programs with the Clang front end. Most of these libraries are
1106 skeleton versions of real libraries; for example, libc is a stripped down
1109 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
1115 This directory contains feature and regression tests and other basic sanity
1116 checks on the LLVM infrastructure. These are intended to run quickly and cover a
1117 lot of territory without being exhaustive.
1122 This is not a directory in the normal llvm module; it is a separate Subversion
1123 module that must be checked out (usually to ``projects/test-suite``). This
1124 module contains a comprehensive correctness, performance, and benchmarking test
1125 suite for LLVM. It is a separate Subversion module because not every LLVM user
1126 is interested in downloading or building such a comprehensive test suite. For
1127 further details on this test suite, please see the :doc:`Testing Guide
1128 <TestingGuide>` document.
1135 The **tools** directory contains the executables built out of the libraries
1136 above, which form the main part of the user interface. You can always get help
1137 for a tool by typing ``tool_name -help``. The following is a brief introduction
1138 to the most important tools. More detailed information is in
1139 the `Command Guide <CommandGuide/index.html>`_.
1143 ``bugpoint`` is used to debug optimization passes or code generation backends
1144 by narrowing down the given test case to the minimum number of passes and/or
1145 instructions that still cause a problem, whether it is a crash or
1146 miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
1151 The archiver produces an archive containing the given LLVM bitcode files,
1152 optionally with an index for faster lookup.
1156 The assembler transforms the human readable LLVM assembly to LLVM bitcode.
1160 The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
1164 ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
1169 ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
1170 (although very slowly...). For architectures that support it (currently x86,
1171 Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
1172 compiler (if the functionality was compiled in), and will execute the code
1173 *much* faster than the interpreter.
1177 ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
1178 native code assembly file or to C code (with the ``-march=c`` option).
1182 ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
1183 (which are specified on the command line), and then outputs the resultant
1184 bitcode. The '``opt -help``' command is a good way to get a list of the
1185 program transformations available in LLVM.
1187 ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
1188 file and print out the results. It is primarily useful for debugging
1189 analyses, or familiarizing yourself with what an analysis does.
1194 This directory contains utilities for working with LLVM source code, and some of
1195 the utilities are actually required as part of the build process because they
1196 are code generators for parts of LLVM infrastructure.
1201 ``codegen-diff`` is a script that finds differences between code that LLC
1202 generates and code that LLI generates. This is a useful tool if you are
1203 debugging one of them, assuming that the other generates correct output. For
1204 the full user manual, run ```perldoc codegen-diff'``.
1208 The ``emacs`` directory contains syntax-highlighting files which will work
1209 with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
1210 assembly files and TableGen description files. For information on how to use
1211 the syntax files, consult the ``README`` file in that directory.
1215 The ``getsrcs.sh`` script finds and outputs all non-generated source files,
1216 which is useful if one wishes to do a lot of development across directories
1217 and does not want to individually find each file. One way to use it is to run,
1218 for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
1223 This little tool performs an ``egrep -H -n`` on each source file in LLVM and
1224 passes to it a regular expression provided on ``llvmgrep``'s command
1225 line. This is a very efficient way of searching the source base for a
1226 particular regular expression.
1230 The ``makellvm`` script compiles all files in the current directory and then
1231 compiles and links the tool that is the first argument. For example, assuming
1232 you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
1233 path, simply running ``makellvm llc`` will make a build of the current
1234 directory, switch to directory ``llvm/tools/llc`` and build it, causing a
1239 The ``TableGen`` directory contains the tool used to generate register
1240 descriptions, instruction set descriptions, and even assemblers from common
1241 TableGen description files.
1245 The ``vim`` directory contains syntax-highlighting files which will work with
1246 the VIM editor, providing syntax highlighting support for LLVM assembly files
1247 and TableGen description files. For information on how to use the syntax
1248 files, consult the ``README`` file in that directory.
1252 An Example Using the LLVM Tool Chain
1253 ====================================
1255 This section gives an example of using LLVM with the Clang front end.
1260 #. First, create a simple C file, name it 'hello.c':
1267 printf("hello world\n");
1271 #. Next, compile the C file into a native executable:
1273 .. code-block:: console
1275 % clang hello.c -o hello
1279 Clang works just like GCC by default. The standard -S and -c arguments
1280 work as usual (producing a native .s or .o file, respectively).
1282 #. Next, compile the C file into a LLVM bitcode file:
1284 .. code-block:: console
1286 % clang -O3 -emit-llvm hello.c -c -o hello.bc
1288 The -emit-llvm option can be used with the -S or -c options to emit an LLVM
1289 ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
1290 the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
1292 #. Run the program in both forms. To run the program, use:
1294 .. code-block:: console
1300 .. code-block:: console
1304 The second examples shows how to invoke the LLVM JIT, :doc:`lli
1305 <CommandGuide/lli>`.
1307 #. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
1309 .. code-block:: console
1311 % llvm-dis < hello.bc | less
1313 #. Compile the program to native assembly using the LLC code generator:
1315 .. code-block:: console
1317 % llc hello.bc -o hello.s
1319 #. Assemble the native assembly language file into a program:
1321 .. code-block:: console
1323 % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
1325 % gcc hello.s -o hello.native # On others
1327 #. Execute the native code program:
1329 .. code-block:: console
1333 Note that using clang to compile directly to native code (i.e. when the
1334 ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
1339 If you are having problems building or using LLVM, or if you have any other
1340 general questions about LLVM, please consult the `Frequently Asked
1341 Questions <FAQ.html>`_ page.
1348 This document is just an **introduction** on how to use LLVM to do some simple
1349 things... there are many more interesting and complicated things that you can do
1350 that aren't documented here (but we'll gladly accept a patch if you want to
1351 write something up!). For more information about LLVM, check out:
1353 * `LLVM Homepage <http://llvm.org/>`_
1354 * `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
1355 * `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_