3 ====================================
4 Getting Started with the LLVM System
5 ====================================
13 Welcome to LLVM! In order to get started, you first need to know some basic
16 First, LLVM comes in three pieces. The first piece is the LLVM suite. This
17 contains all of the tools, libraries, and header files needed to use LLVM. It
18 contains an assembler, disassembler, bitcode analyzer and bitcode optimizer. It
19 also contains basic regression tests that can be used to test the LLVM tools and
22 The second piece is the `Clang <http://clang.llvm.org/>`_ front end. This
23 component compiles C, C++, Objective C, and Objective C++ code into LLVM
24 bitcode. Once compiled into LLVM bitcode, a program can be manipulated with the
25 LLVM tools from the LLVM suite.
27 There is a third, optional piece called Test Suite. It is a suite of programs
28 with a testing harness that can be used to further test LLVM's functionality
31 Getting Started Quickly (A Summary)
32 ===================================
34 The LLVM Getting Started documentation may be out of date. So, the `Clang
35 Getting Started <http://clang.llvm.org/get_started.html>`_ page might also be a
38 Here's the short story for getting up and running quickly with LLVM:
40 #. Read the documentation.
41 #. Read the documentation.
42 #. Remember that you were warned twice about reading the documentation.
45 * ``cd where-you-want-llvm-to-live``
46 * ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
50 * ``cd where-you-want-llvm-to-live``
52 * ``svn co http://llvm.org/svn/llvm-project/cfe/trunk clang``
54 #. Checkout Compiler-RT:
56 * ``cd where-you-want-llvm-to-live``
57 * ``cd llvm/projects``
58 * ``svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk compiler-rt``
60 #. Get the Test Suite Source Code **[Optional]**
62 * ``cd where-you-want-llvm-to-live``
63 * ``cd llvm/projects``
64 * ``svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite``
66 #. Configure and build LLVM and Clang:
68 * ``cd where-you-want-to-build-llvm``
69 * ``mkdir build`` (for building without polluting the source dir)
71 * ``../llvm/configure [options]``
74 * ``--prefix=directory`` ---
76 Specify for *directory* the full pathname of where you want the LLVM
77 tools and libraries to be installed (default ``/usr/local``).
79 * ``--enable-optimized`` ---
81 Compile with optimizations enabled (default is NO).
83 * ``--enable-assertions`` ---
85 Compile with assertion checks enabled (default is YES).
87 * ``make [-j]`` --- The ``-j`` specifies the number of jobs (commands) to run
88 simultaneously. This builds both LLVM and Clang for Debug+Asserts mode.
89 The --enabled-optimized configure option is used to specify a Release
92 * ``make check-all`` --- This run the regression tests to ensure everything
95 * ``make update`` --- This command is used to update all the svn repositories
96 at once, rather then having to ``cd`` into the individual repositories and
97 running ``svn update``.
99 * It is also possible to use CMake instead of the makefiles. With CMake it is
100 possible to generate project files for several IDEs: Xcode, Eclipse CDT4,
101 CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.
103 * If you get an "internal compiler error (ICE)" or test failures, see
106 Consult the `Getting Started with LLVM`_ section for detailed information on
107 configuring and compiling LLVM. See `Setting Up Your Environment`_ for tips
108 that simplify working with the Clang front end and LLVM tools. Go to `Program
109 Layout`_ to learn about the layout of the source code tree.
114 Before you begin to use the LLVM system, review the requirements given below.
115 This may save you some trouble by knowing ahead of time what hardware and
116 software you will need.
121 LLVM is known to work on the following platforms:
123 +-----------------+----------------------+-------------------------+
124 |OS | Arch | Compilers |
125 +=================+======================+=========================+
126 |AuroraUX | x86\ :sup:`1` | GCC |
127 +-----------------+----------------------+-------------------------+
128 |Linux | x86\ :sup:`1` | GCC |
129 +-----------------+----------------------+-------------------------+
130 |Linux | amd64 | GCC |
131 +-----------------+----------------------+-------------------------+
132 |Solaris | V9 (Ultrasparc) | GCC |
133 +-----------------+----------------------+-------------------------+
134 |FreeBSD | x86\ :sup:`1` | GCC |
135 +-----------------+----------------------+-------------------------+
136 |FreeBSD | amd64 | GCC |
137 +-----------------+----------------------+-------------------------+
138 |MacOS X\ :sup:`2`| PowerPC | GCC |
139 +-----------------+----------------------+-------------------------+
140 |MacOS X\ :sup:`9`| x86 | GCC |
141 +-----------------+----------------------+-------------------------+
142 |Cygwin/Win32 | x86\ :sup:`1, 8, 11` | GCC 3.4.X, binutils 2.20|
143 +-----------------+----------------------+-------------------------+
145 LLVM has partial support for the following platforms:
147 +-------------------+----------------------+-------------------------------------------+
148 |OS | Arch | Compilers |
149 +===================+======================+===========================================+
150 | Windows | x86\ :sup:`1` | Visual Studio 2000 or higher\ :sup:`4,5` |
151 +-------------------+----------------------+-------------------------------------------+
152 | AIX\ :sup:`3,4` | PowerPC | GCC |
153 +-------------------+----------------------+-------------------------------------------+
154 | Linux\ :sup:`3,5` | PowerPC | GCC |
155 +-------------------+----------------------+-------------------------------------------+
156 | Linux\ :sup:`7` | Alpha | GCC |
157 +-------------------+----------------------+-------------------------------------------+
158 | Linux\ :sup:`7` | Itanium (IA-64) | GCC |
159 +-------------------+----------------------+-------------------------------------------+
160 | HP-UX\ :sup:`7` | Itanium (IA-64) | HP aCC |
161 +-------------------+----------------------+-------------------------------------------+
162 | Windows x64 | x86-64 | mingw-w64's GCC-4.5.x\ :sup:`12` |
163 +-------------------+----------------------+-------------------------------------------+
167 Code generation supported for Pentium processors and up
169 #. Code generation supported for Pentium processors and up
170 #. Code generation supported for 32-bit ABI only
171 #. No native code generation
172 #. Build is not complete: one or more tools do not link or function
173 #. The GCC-based C/C++ frontend does not build
174 #. The port is done using the MSYS shell.
175 #. Native code generation exists but is not complete.
176 #. Binutils 2.20 or later is required to build the assembler generated by LLVM properly.
177 #. Xcode 2.5 and gcc 4.0.1 (Apple Build 5370) will trip internal LLVM assert
178 messages when compiled for Release at optimization levels greater than 0
179 (i.e., ``-O1`` and higher). Add ``OPTIMIZE_OPTION="-O0"`` to the build
180 command line if compiling for LLVM Release or bootstrapping the LLVM
182 #. For MSYS/MinGW on Windows, be sure to install the MSYS version of the perl
183 package, and be sure it appears in your path before any Windows-based
184 versions such as Strawberry Perl and ActivePerl, as these have
185 Windows-specifics that will cause the build to fail.
186 #. To use LLVM modules on Win32-based system, you may configure LLVM
187 with ``--enable-shared``.
189 #. To compile SPU backend, you need to add ``LDFLAGS=-Wl,--stack,16777216`` to
192 Note that you will need about 1-3 GB of space for a full LLVM build in Debug
193 mode, depending on the system (it is so large because of all the debugging
194 information and the fact that the libraries are statically linked into multiple
195 tools). If you do not need many of the tools and you are space-conscious, you
196 can pass ``ONLY_TOOLS="tools you need"`` to make. The Release build requires
197 considerably less space.
199 The LLVM suite *may* compile on other platforms, but it is not guaranteed to do
200 so. If compilation is successful, the LLVM utilities should be able to
201 assemble, disassemble, analyze, and optimize LLVM bitcode. Code generation
202 should work as well, although the generated native code may not work on your
208 Compiling LLVM requires that you have several software packages installed. The
209 table below lists those required packages. The Package column is the usual name
210 for the software package that LLVM depends on. The Version column provides
211 "known to work" versions of the package. The Notes column describes how LLVM
212 uses the package and provides other details.
214 +--------------------------------------------------------------+-----------------+---------------------------------------------+
215 | Package | Version | Notes |
216 +==============================================================+=================+=============================================+
217 | `GNU Make <http://savannah.gnu.org/projects/make>`_ | 3.79, 3.79.1 | Makefile/build processor |
218 +--------------------------------------------------------------+-----------------+---------------------------------------------+
219 | `GCC <http://gcc.gnu.org/>`_ | 3.4.2 | C/C++ compiler\ :sup:`1` |
220 +--------------------------------------------------------------+-----------------+---------------------------------------------+
221 | `TeXinfo <http://www.gnu.org/software/texinfo/>`_ | 4.5 | For building the CFE |
222 +--------------------------------------------------------------+-----------------+---------------------------------------------+
223 | `SVN <http://subversion.tigris.org/project_packages.html>`_ | >=1.3 | Subversion access to LLVM\ :sup:`2` |
224 +--------------------------------------------------------------+-----------------+---------------------------------------------+
225 | `DejaGnu <http://savannah.gnu.org/projects/dejagnu>`_ | 1.4.2 | Automated test suite\ :sup:`3` |
226 +--------------------------------------------------------------+-----------------+---------------------------------------------+
227 | `tcl <http://www.tcl.tk/software/tcltk/>`_ | 8.3, 8.4 | Automated test suite\ :sup:`3` |
228 +--------------------------------------------------------------+-----------------+---------------------------------------------+
229 | `expect <http://expect.nist.gov/>`_ | 5.38.0 | Automated test suite\ :sup:`3` |
230 +--------------------------------------------------------------+-----------------+---------------------------------------------+
231 | `perl <http://www.perl.com/download.csp>`_ | >=5.6.0 | Utilities |
232 +--------------------------------------------------------------+-----------------+---------------------------------------------+
233 | `GNU M4 <http://savannah.gnu.org/projects/m4>`_ | 1.4 | Macro processor for configuration\ :sup:`4` |
234 +--------------------------------------------------------------+-----------------+---------------------------------------------+
235 | `GNU Autoconf <http://www.gnu.org/software/autoconf/>`_ | 2.60 | Configuration script builder\ :sup:`4` |
236 +--------------------------------------------------------------+-----------------+---------------------------------------------+
237 | `GNU Automake <http://www.gnu.org/software/automake/>`_ | 1.9.6 | aclocal macro generator\ :sup:`4` |
238 +--------------------------------------------------------------+-----------------+---------------------------------------------+
239 | `libtool <http://savannah.gnu.org/projects/libtool>`_ | 1.5.22 | Shared library manager\ :sup:`4` |
240 +--------------------------------------------------------------+-----------------+---------------------------------------------+
244 #. Only the C and C++ languages are needed so there's no need to build the
245 other languages for LLVM's purposes. See `below` for specific version
247 #. You only need Subversion if you intend to build from the latest LLVM
248 sources. If you're working from a release distribution, you don't need
250 #. Only needed if you want to run the automated test suite in the
251 ``llvm/test`` directory.
252 #. If you want to make changes to the configure scripts, you will need GNU
253 autoconf (2.60), and consequently, GNU M4 (version 1.4 or higher). You
254 will also need automake (1.9.6). We only use aclocal from that package.
256 Additionally, your compilation host is expected to have the usual plethora of
257 Unix utilities. Specifically:
259 * **ar** --- archive library builder
260 * **bzip2** --- bzip2 command for distribution generation
261 * **bunzip2** --- bunzip2 command for distribution checking
262 * **chmod** --- change permissions on a file
263 * **cat** --- output concatenation utility
264 * **cp** --- copy files
265 * **date** --- print the current date/time
266 * **echo** --- print to standard output
267 * **egrep** --- extended regular expression search utility
268 * **find** --- find files/dirs in a file system
269 * **grep** --- regular expression search utility
270 * **gzip** --- gzip command for distribution generation
271 * **gunzip** --- gunzip command for distribution checking
272 * **install** --- install directories/files
273 * **mkdir** --- create a directory
274 * **mv** --- move (rename) files
275 * **ranlib** --- symbol table builder for archive libraries
276 * **rm** --- remove (delete) files and directories
277 * **sed** --- stream editor for transforming output
278 * **sh** --- Bourne shell for make build scripts
279 * **tar** --- tape archive for distribution generation
280 * **test** --- test things in file system
281 * **unzip** --- unzip command for distribution checking
282 * **zip** --- zip command for distribution generation
287 Broken versions of GCC and other tools
288 --------------------------------------
290 LLVM is very demanding of the host C++ compiler, and as such tends to expose
291 bugs in the compiler. In particular, several versions of GCC crash when trying
292 to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang. Other
293 versions of GCC will probably work as well. GCC versions listed here are known
294 to not work. If you are using one of these versions, please try to upgrade your
295 GCC to something more recent. If you run into a problem with a version of GCC
296 not listed here, please `let us know <mailto:llvmdev@cs.uiuc.edu>`_. Please use
297 the "``gcc -v``" command to find out which version of GCC you are using.
299 **GCC versions prior to 3.0**: GCC 2.96.x and before had several problems in the
300 STL that effectively prevent it from compiling LLVM.
302 **GCC 3.2.2 and 3.2.3**: These versions of GCC fails to compile LLVM with a
303 bogus template error. This was fixed in later GCCs.
305 **GCC 3.3.2**: This version of GCC suffered from a `serious bug
306 <http://gcc.gnu.org/PR13392>`_ which causes it to crash in the
307 "``convert_from_eh_region_ranges_1``" GCC function.
309 **Cygwin GCC 3.3.3**: The version of GCC 3.3.3 commonly shipped with Cygwin does
312 **SuSE GCC 3.3.3**: The version of GCC 3.3.3 shipped with SuSE 9.1 (and possibly
313 others) does not compile LLVM correctly (it appears that exception handling is
314 broken in some cases). Please download the FSF 3.3.3 or upgrade to a newer
317 **GCC 3.4.0 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
318 generator, causing an infinite loop in the llvm-gcc build when built with
319 optimizations enabled (i.e. a release build).
321 **GCC 3.4.2 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
322 generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0) correctly
323 compiles LLVM at -O2. A work around is to build release LLVM builds with
324 "``make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ...``"
326 **GCC 3.4.x on X86-64/amd64**: GCC `miscompiles portions of LLVM
327 <http://llvm.org/PR1056>`__.
329 **GCC 3.4.4 (CodeSourcery ARM 2005q3-2)**: this compiler miscompiles LLVM when
330 building with optimizations enabled. It appears to work with "``make
331 ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1``" or build a debug build.
333 **IA-64 GCC 4.0.0**: The IA-64 version of GCC 4.0.0 is known to miscompile LLVM.
335 **Apple Xcode 2.3**: GCC crashes when compiling LLVM at -O3 (which is the
336 default with ENABLE_OPTIMIZED=1. To work around this, build with
337 "``ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2``".
339 **GCC 4.1.1**: GCC fails to build LLVM with template concept check errors
340 compiling some files. At the time of this writing, GCC mainline (4.2) did not
343 **GCC 4.1.1 on X86-64/amd64**: GCC `miscompiles portions of LLVM
344 <http://llvm.org/PR1063>`__ when compiling llvm itself into 64-bit code. LLVM
345 will appear to mostly work but will be buggy, e.g. failing portions of its
348 **GCC 4.1.2 on OpenSUSE**: Seg faults during libstdc++ build and on x86_64
349 platforms compiling md5.c gets a mangled constant.
351 **GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian**: Appears to
352 miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining about
353 symbols remaining in the table on destruction.
355 **GCC 4.1.2 20071124 (Red Hat 4.1.2-42)**: Suffers from the same symptoms as the
356 previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).
358 **Cygwin GCC 4.3.2 20080827 (beta) 2**: Users `reported
359 <http://llvm.org/PR4145>`_ various problems related with link errors when using
362 **Debian GCC 4.3.2 on X86**: Crashes building some files in LLVM 2.6.
364 **GCC 4.3.3 (Debian 4.3.3-10) on ARM**: Miscompiles parts of LLVM 2.6 when
365 optimizations are turned on. The symptom is an infinite loop in
366 ``FoldingSetImpl::RemoveNode`` while running the code generator.
368 **SUSE 11 GCC 4.3.4**: Miscompiles LLVM, causing crashes in ValueHandle logic.
370 **GCC 4.3.5 and GCC 4.4.5 on ARM**: These can miscompile ``value >> 1`` even at
371 ``-O0``. A test failure in ``test/Assembler/alignstack.ll`` is one symptom of
374 **GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
375 warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
376 defined in a discarded section. You can safely ignore these messages as they are
377 erroneous and the linkage is correct. These messages disappear using ld 2.17.
379 **GNU binutils 2.17**: Binutils 2.17 contains `a bug
380 <http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link
381 times (minutes instead of seconds) when building LLVM. We recommend upgrading
382 to a newer version (2.17.50.0.4 or later).
384 **GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
385 <http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes
386 intermittent failures when building LLVM with position independent code. The
387 symptom is an error about cyclic dependencies. We recommend upgrading to a
388 newer version of Gold.
390 .. _Getting Started with LLVM:
392 Getting Started with LLVM
393 =========================
395 The remainder of this guide is meant to get you up and running with LLVM and to
396 give you some basic information about the LLVM environment.
398 The later sections of this guide describe the `general layout`_ of the LLVM
399 source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
400 more information about LLVM or to get help via e-mail.
402 Terminology and Notation
403 ------------------------
405 Throughout this manual, the following names are used to denote paths specific to
406 the local system and working environment. *These are not environment variables
407 you need to set but just strings used in the rest of this document below*. In
408 any of the examples below, simply replace each of these names with the
409 appropriate pathname on your local system. All these paths are absolute:
413 This is the top level directory of the LLVM source tree.
417 This is the top level directory of the LLVM object tree (i.e. the tree where
418 object files and compiled programs will be placed. It can be the same as
421 .. _Setting Up Your Environment:
423 Setting Up Your Environment
424 ---------------------------
426 In order to compile and use LLVM, you may need to set some environment
429 ``LLVM_LIB_SEARCH_PATH=/path/to/your/bitcode/libs``
431 [Optional] This environment variable helps LLVM linking tools find the
432 locations of your bitcode libraries. It is provided only as a convenience
433 since you can specify the paths using the -L options of the tools and the
434 C/C++ front-end will automatically use the bitcode files installed in its
437 Unpacking the LLVM Archives
438 ---------------------------
440 If you have the LLVM distribution, you will need to unpack it before you can
441 begin to compile it. LLVM is distributed as a set of two files: the LLVM suite
442 and the LLVM GCC front end compiled for your platform. There is an additional
443 test suite that is optional. Each file is a TAR archive that is compressed with
446 The files are as follows, with *x.y* marking the version number:
450 Source release for the LLVM libraries and tools.
452 ``llvm-test-x.y.tar.gz``
454 Source release for the LLVM test-suite.
456 ``llvm-gcc-4.2-x.y.source.tar.gz``
458 Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
459 directory for build instructions.
461 ``llvm-gcc-4.2-x.y-platform.tar.gz``
463 Binary release of the llvm-gcc-4.2 front end for a specific platform.
465 Checkout LLVM from Subversion
466 -----------------------------
468 If you have access to our Subversion repository, you can get a fresh copy of the
469 entire source code. All you need to do is check it out from Subversion as
472 * ``cd where-you-want-llvm-to-live``
473 * Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
474 * Read-Write:``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
476 This will create an '``llvm``' directory in the current directory and fully
477 populate it with the LLVM source code, Makefiles, test directories, and local
478 copies of documentation files.
480 If you want to get a specific release (as opposed to the most recent revision),
481 you can checkout it from the '``tags``' directory (instead of '``trunk``'). The
482 following releases are located in the following subdirectories of the '``tags``'
485 * Release 3.1: **RELEASE_31/final**
486 * Release 3.0: **RELEASE_30/final**
487 * Release 2.9: **RELEASE_29/final**
488 * Release 2.8: **RELEASE_28**
489 * Release 2.7: **RELEASE_27**
490 * Release 2.6: **RELEASE_26**
491 * Release 2.5: **RELEASE_25**
492 * Release 2.4: **RELEASE_24**
493 * Release 2.3: **RELEASE_23**
494 * Release 2.2: **RELEASE_22**
495 * Release 2.1: **RELEASE_21**
496 * Release 2.0: **RELEASE_20**
497 * Release 1.9: **RELEASE_19**
498 * Release 1.8: **RELEASE_18**
499 * Release 1.7: **RELEASE_17**
500 * Release 1.6: **RELEASE_16**
501 * Release 1.5: **RELEASE_15**
502 * Release 1.4: **RELEASE_14**
503 * Release 1.3: **RELEASE_13**
504 * Release 1.2: **RELEASE_12**
505 * Release 1.1: **RELEASE_11**
506 * Release 1.0: **RELEASE_1**
508 If you would like to get the LLVM test suite (a separate package as of 1.4), you
509 get it from the Subversion repository:
511 .. code-block:: console
514 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
516 By placing it in the ``llvm/projects``, it will be automatically configured by
517 the LLVM configure script as well as automatically updated when you run ``svn
523 GIT mirrors are available for a number of LLVM subprojects. These mirrors sync
524 automatically with each Subversion commit and contain all necessary git-svn
525 marks (so, you can recreate git-svn metadata locally). Note that right now
526 mirrors reflect only ``trunk`` for each project. You can do the read-only GIT
529 .. code-block:: console
531 % git clone http://llvm.org/git/llvm.git
533 If you want to check out clang too, run:
535 .. code-block:: console
537 % git clone http://llvm.org/git/llvm.git
539 % git clone http://llvm.org/git/clang.git
541 Since the upstream repository is in Subversion, you should use ``git
542 pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
543 in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the
544 master branch, run the following command:
546 .. code-block:: console
548 % git config branch.master.rebase true
550 Sending patches with Git
551 ^^^^^^^^^^^^^^^^^^^^^^^^
553 Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
555 Assume ``master`` points the upstream and ``mybranch`` points your working
556 branch, and ``mybranch`` is rebased onto ``master``. At first you may check
557 sanity of whitespaces:
559 .. code-block:: console
561 % git diff --check master..mybranch
563 The easiest way to generate a patch is as below:
565 .. code-block:: console
567 % git diff master..mybranch > /path/to/mybranch.diff
569 It is a little different from svn-generated diff. git-diff-generated diff has
570 prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
571 could be accepted with ``patch -p1 -N``.
573 But you may generate patchset with git-format-patch. It generates by-each-commit
574 patchset. To generate patch files to attach to your article:
576 .. code-block:: console
578 % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
580 If you would like to send patches directly, you may use git-send-email or
581 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
583 .. code-block:: console
585 % git format-patch --attach master..mybranch --stdout | git imap-send
587 Then, your .git/config should have [imap] sections.
592 host = imaps://imap.gmail.com
593 user = your.gmail.account@gmail.com
598 folder = "[Gmail]/Drafts"
599 ; example for Japanese, "Modified UTF-7" encoded.
600 folder = "[Gmail]/&Tgtm+DBN-"
601 ; example for Traditional Chinese
602 folder = "[Gmail]/&g0l6Pw-"
604 For developers to work with git-svn
605 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
607 To set up clone from which you can submit code using ``git-svn``, run:
609 .. code-block:: console
611 % git clone http://llvm.org/git/llvm.git
613 % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
614 % git config svn-remote.svn.fetch :refs/remotes/origin/master
615 % git svn rebase -l # -l avoids fetching ahead of the git mirror.
617 # If you have clang too:
619 % git clone http://llvm.org/git/clang.git
621 % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
622 % git config svn-remote.svn.fetch :refs/remotes/origin/master
625 To update this clone without generating git-svn tags that conflict with the
626 upstream git repo, run:
628 .. code-block:: console
630 % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
631 % git checkout master
634 git checkout master &&
637 This leaves your working directories on their master branches, so you'll need to
638 ``checkout`` each working branch individually and ``rebase`` it on top of its
639 parent branch. (Note: This script is intended for relative newbies to git. If
640 you have more experience, you can likely improve on it.)
642 The git-svn metadata can get out of sync after you mess around with branches and
643 ``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
644 about files with uncommitted changes. The fix is to rebuild the metadata:
646 .. code-block:: console
651 Local LLVM Configuration
652 ------------------------
654 Once checked out from the Subversion repository, the LLVM suite source code must
655 be configured via the ``configure`` script. This script sets variables in the
656 various ``*.in`` files, most notably ``llvm/Makefile.config`` and
657 ``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the
658 Makefiles needed to begin building LLVM.
660 The following environment variables are used by the ``configure`` script to
661 configure the build system:
663 +------------+-----------------------------------------------------------+
664 | Variable | Purpose |
665 +============+===========================================================+
666 | CC | Tells ``configure`` which C compiler to use. By default, |
667 | | ``configure`` will look for the first GCC C compiler in |
668 | | ``PATH``. Use this variable to override ``configure``\'s |
669 | | default behavior. |
670 +------------+-----------------------------------------------------------+
671 | CXX | Tells ``configure`` which C++ compiler to use. By |
672 | | default, ``configure`` will look for the first GCC C++ |
673 | | compiler in ``PATH``. Use this variable to override |
674 | | ``configure``'s default behavior. |
675 +------------+-----------------------------------------------------------+
677 The following options can be used to set or enable LLVM specific options:
679 ``--enable-optimized``
681 Enables optimized compilation (debugging symbols are removed and GCC
682 optimization flags are enabled). Note that this is the default setting if you
683 are using the LLVM distribution. The default behavior of an Subversion
684 checkout is to use an unoptimized build (also known as a debug build).
686 ``--enable-debug-runtime``
688 Enables debug symbols in the runtime libraries. The default is to strip debug
689 symbols from the runtime libraries.
693 Compile the Just In Time (JIT) compiler functionality. This is not available
694 on all platforms. The default is dependent on platform, so it is best to
695 explicitly enable it if you want it.
697 ``--enable-targets=target-option``
699 Controls which targets will be built and linked into llc. The default value
700 for ``target_options`` is "all" which builds and links all available targets.
701 The value "host-only" can be specified to build only a native compiler (no
702 cross-compiler targets available). The "native" target is selected as the
703 target of the build host. You can also specify a comma separated list of
704 target names that you want available in llc. The target names use all lower
705 case. The current set of targets is:
707 ``arm, cpp, hexagon, mblaze, mips, mipsel, msp430, powerpc, ptx, sparc, spu,
708 x86, x86_64, xcore``.
712 Look for the doxygen program and enable construction of doxygen based
713 documentation from the source code. This is disabled by default because
714 generating the documentation can take a long time and producess 100s of
719 LLVM can use external disassembler library for various purposes (now it's used
720 only for examining code produced by JIT). This option will enable usage of
721 `udis86 <http://udis86.sourceforge.net/>`_ x86 (both 32 and 64 bits)
722 disassembler library.
724 To configure LLVM, follow these steps:
726 #. Change directory into the object root directory:
728 .. code-block:: console
732 #. Run the ``configure`` script located in the LLVM source tree:
734 .. code-block:: console
736 % SRC_ROOT/configure --prefix=/install/path [other options]
738 Compiling the LLVM Suite Source Code
739 ------------------------------------
741 Once you have configured LLVM, you can build it. There are three types of
746 These builds are the default when one is using an Subversion checkout and
747 types ``gmake`` (unless the ``--enable-optimized`` option was used during
748 configuration). The build system will compile the tools and libraries with
749 debugging information. To get a Debug Build using the LLVM distribution the
750 ``--disable-optimized`` option must be passed to ``configure``.
752 Release (Optimized) Builds
754 These builds are enabled with the ``--enable-optimized`` option to
755 ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
756 line. For these builds, the build system will compile the tools and libraries
757 with GCC optimizations enabled and strip debugging information from the
758 libraries and executables it generates. Note that Release Builds are default
759 when using an LLVM distribution.
763 These builds are for use with profiling. They compile profiling information
764 into the code for use with programs like ``gprof``. Profile builds must be
765 started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
767 Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
768 directory and issuing the following command:
770 .. code-block:: console
774 If the build fails, please `check here`_ to see if you are using a version of
775 GCC that is known not to compile LLVM.
777 If you have multiple processors in your machine, you may wish to use some of the
778 parallel build options provided by GNU Make. For example, you could use the
781 .. code-block:: console
785 There are several special targets which are useful when working with the LLVM
790 Removes all files generated by the build. This includes object files,
791 generated C/C++ files, libraries, and executables.
795 Removes everything that ``gmake clean`` does, but also removes files generated
796 by ``configure``. It attempts to return the source tree to the original state
797 in which it was shipped.
801 Installs LLVM header files, libraries, tools, and documentation in a hierarchy
802 under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
803 defaults to ``/usr/local``.
805 ``gmake -C runtime install-bytecode``
807 Assuming you built LLVM into $OBJDIR, when this command is run, it will
808 install bitcode libraries into the GCC front end's bitcode library directory.
809 If you need to update your bitcode libraries, this is the target to use once
812 Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
813 these ``make`` targets and descriptions of other targets available.
815 It is also possible to override default values from ``configure`` by declaring
816 variables on the command line. The following are some examples:
818 ``gmake ENABLE_OPTIMIZED=1``
820 Perform a Release (Optimized) build.
822 ``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
824 Perform a Release (Optimized) build without assertions enabled.
826 ``gmake ENABLE_OPTIMIZED=0``
828 Perform a Debug build.
830 ``gmake ENABLE_PROFILING=1``
832 Perform a Profiling build.
836 Print what ``gmake`` is doing on standard output.
838 ``gmake TOOL_VERBOSE=1``
840 Ask each tool invoked by the makefiles to print out what it is doing on
841 the standard output. This also implies ``VERBOSE=1``.
843 Every directory in the LLVM object tree includes a ``Makefile`` to build it and
844 any subdirectories that it contains. Entering any directory inside the LLVM
845 object tree and typing ``gmake`` should rebuild anything in or below that
846 directory that is out of date.
848 This does not apply to building the documentation.
849 LLVM's (non-Doxygen) documentation is produced with the
850 `Sphinx <http://sphinx-doc.org/>`_ documentation generation system.
851 There are some HTML documents that have not yet been converted to the new
852 system (which uses the easy-to-read and easy-to-write
853 `reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup
855 The generated documentation is built in the ``SRC_ROOT/docs`` directory using
857 For instructions on how to install Sphinx, see
858 `Sphinx Introduction for LLVM Developers
859 <http://lld.llvm.org/sphinx_intro.html>`_.
860 After following the instructions there for installing Sphinx, build the LLVM
861 HTML documentation by doing the following:
863 .. code-block:: console
866 $ make -f Makefile.sphinx
868 This creates a ``_build/html`` sub-directory with all of the HTML files, not
869 just the generated ones.
870 This directory corresponds to ``llvm.org/docs``.
871 For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to
872 ``llvm.org/docs/SphinxQuickstartTemplate.html``.
873 The :doc:`SphinxQuickstartTemplate` is useful when creating a new document.
878 It is possible to cross-compile LLVM itself. That is, you can create LLVM
879 executables and libraries to be hosted on a platform different from the platform
880 where they are built (a Canadian Cross build). To configure a cross-compile,
881 supply the configure script with ``--build`` and ``--host`` options that are
882 different. The values of these options must be legal target triples that your
883 GCC compiler supports.
885 The result of such a build is executables that are not runnable on on the build
886 host (--build option) but can be executed on the compile host (--host option).
888 The Location of LLVM Object Files
889 ---------------------------------
891 The LLVM build system is capable of sharing a single LLVM source tree among
892 several LLVM builds. Hence, it is possible to build LLVM for several different
893 platforms or configurations using the same source tree.
895 This is accomplished in the typical autoconf manner:
897 * Change directory to where the LLVM object files should live:
899 .. code-block:: console
903 * Run the ``configure`` script found in the LLVM source directory:
905 .. code-block:: console
909 The LLVM build will place files underneath *OBJ_ROOT* in directories named after
912 Debug Builds with assertions enabled (the default)
916 ``OBJ_ROOT/Debug+Asserts/bin``
920 ``OBJ_ROOT/Debug+Asserts/lib``
926 ``OBJ_ROOT/Release/bin``
930 ``OBJ_ROOT/Release/lib``
936 ``OBJ_ROOT/Profile/bin``
940 ``OBJ_ROOT/Profile/lib``
942 Optional Configuration Items
943 ----------------------------
945 If you're running on a Linux system that supports the `binfmt_misc
946 <http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html>`_
947 module, and you have root access on the system, you can set your system up to
948 execute LLVM bitcode files directly. To do this, use commands like this (the
949 first command may not be required if you are already using the module):
951 .. code-block:: console
953 % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
954 % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
955 % chmod u+x hello.bc (if needed)
958 This allows you to execute LLVM bitcode files directly. On Debian, you can also
959 use this command instead of the 'echo' command above:
961 .. code-block:: console
963 % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
971 One useful source of information about the LLVM source base is the LLVM `doxygen
972 <http://www.doxygen.org/>`_ documentation available at
973 `<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
979 This directory contains some simple examples of how to use the LLVM IR and JIT.
984 This directory contains public header files exported from the LLVM library. The
985 three main subdirectories of this directory are:
987 ``llvm/include/llvm``
989 This directory contains all of the LLVM specific header files. This directory
990 also has subdirectories for different portions of LLVM: ``Analysis``,
991 ``CodeGen``, ``Target``, ``Transforms``, etc...
993 ``llvm/include/llvm/Support``
995 This directory contains generic support libraries that are provided with LLVM
996 but not necessarily specific to LLVM. For example, some C++ STL utilities and
997 a Command Line option processing library store their header files here.
999 ``llvm/include/llvm/Config``
1001 This directory contains header files configured by the ``configure`` script.
1002 They wrap "standard" UNIX and C header files. Source code can include these
1003 header files which automatically take care of the conditional #includes that
1004 the ``configure`` script generates.
1009 This directory contains most of the source files of the LLVM system. In LLVM,
1010 almost all code exists in libraries, making it very easy to share code among the
1013 ``llvm/lib/VMCore/``
1015 This directory holds the core LLVM source files that implement core classes
1016 like Instruction and BasicBlock.
1018 ``llvm/lib/AsmParser/``
1020 This directory holds the source code for the LLVM assembly language parser
1023 ``llvm/lib/BitCode/``
1025 This directory holds code for reading and write LLVM bitcode.
1027 ``llvm/lib/Analysis/``
1029 This directory contains a variety of different program analyses, such as
1030 Dominator Information, Call Graphs, Induction Variables, Interval
1031 Identification, Natural Loop Identification, etc.
1033 ``llvm/lib/Transforms/``
1035 This directory contains the source code for the LLVM to LLVM program
1036 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1037 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1038 Elimination, and many others.
1040 ``llvm/lib/Target/``
1042 This directory contains files that describe various target architectures for
1043 code generation. For example, the ``llvm/lib/Target/X86`` directory holds the
1044 X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
1047 ``llvm/lib/CodeGen/``
1049 This directory contains the major parts of the code generator: Instruction
1050 Selector, Instruction Scheduling, and Register Allocation.
1056 ``llvm/lib/Debugger/``
1058 This directory contains the source level debugger library that makes it
1059 possible to instrument LLVM programs so that a debugger could identify source
1060 code locations at which the program is executing.
1062 ``llvm/lib/ExecutionEngine/``
1064 This directory contains libraries for executing LLVM bitcode directly at
1065 runtime in both interpreted and JIT compiled fashions.
1067 ``llvm/lib/Support/``
1069 This directory contains the source code that corresponds to the header files
1070 located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
1075 This directory contains projects that are not strictly part of LLVM but are
1076 shipped with LLVM. This is also the directory where you should create your own
1077 LLVM-based projects. See ``llvm/projects/sample`` for an example of how to set
1078 up your own project.
1083 This directory contains libraries which are compiled into LLVM bitcode and used
1084 when linking programs with the Clang front end. Most of these libraries are
1085 skeleton versions of real libraries; for example, libc is a stripped down
1088 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
1094 This directory contains feature and regression tests and other basic sanity
1095 checks on the LLVM infrastructure. These are intended to run quickly and cover a
1096 lot of territory without being exhaustive.
1101 This is not a directory in the normal llvm module; it is a separate Subversion
1102 module that must be checked out (usually to ``projects/test-suite``). This
1103 module contains a comprehensive correctness, performance, and benchmarking test
1104 suite for LLVM. It is a separate Subversion module because not every LLVM user
1105 is interested in downloading or building such a comprehensive test suite. For
1106 further details on this test suite, please see the :doc:`Testing Guide
1107 <TestingGuide>` document.
1114 The **tools** directory contains the executables built out of the libraries
1115 above, which form the main part of the user interface. You can always get help
1116 for a tool by typing ``tool_name -help``. The following is a brief introduction
1117 to the most important tools. More detailed information is in
1118 the `Command Guide <CommandGuide/index.html>`_.
1122 ``bugpoint`` is used to debug optimization passes or code generation backends
1123 by narrowing down the given test case to the minimum number of passes and/or
1124 instructions that still cause a problem, whether it is a crash or
1125 miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
1130 The archiver produces an archive containing the given LLVM bitcode files,
1131 optionally with an index for faster lookup.
1135 The assembler transforms the human readable LLVM assembly to LLVM bitcode.
1139 The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
1143 ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
1148 ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
1149 (although very slowly...). For architectures that support it (currently x86,
1150 Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
1151 compiler (if the functionality was compiled in), and will execute the code
1152 *much* faster than the interpreter.
1156 ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
1157 native code assembly file or to C code (with the ``-march=c`` option).
1161 ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
1162 (which are specified on the command line), and then outputs the resultant
1163 bitcode. The '``opt -help``' command is a good way to get a list of the
1164 program transformations available in LLVM.
1166 ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
1167 file and print out the results. It is primarily useful for debugging
1168 analyses, or familiarizing yourself with what an analysis does.
1173 This directory contains utilities for working with LLVM source code, and some of
1174 the utilities are actually required as part of the build process because they
1175 are code generators for parts of LLVM infrastructure.
1180 ``codegen-diff`` is a script that finds differences between code that LLC
1181 generates and code that LLI generates. This is a useful tool if you are
1182 debugging one of them, assuming that the other generates correct output. For
1183 the full user manual, run ```perldoc codegen-diff'``.
1187 The ``emacs`` directory contains syntax-highlighting files which will work
1188 with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
1189 assembly files and TableGen description files. For information on how to use
1190 the syntax files, consult the ``README`` file in that directory.
1194 The ``getsrcs.sh`` script finds and outputs all non-generated source files,
1195 which is useful if one wishes to do a lot of development across directories
1196 and does not want to individually find each file. One way to use it is to run,
1197 for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
1202 This little tool performs an ``egrep -H -n`` on each source file in LLVM and
1203 passes to it a regular expression provided on ``llvmgrep``'s command
1204 line. This is a very efficient way of searching the source base for a
1205 particular regular expression.
1209 The ``makellvm`` script compiles all files in the current directory and then
1210 compiles and links the tool that is the first argument. For example, assuming
1211 you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
1212 path, simply running ``makellvm llc`` will make a build of the current
1213 directory, switch to directory ``llvm/tools/llc`` and build it, causing a
1218 The ``TableGen`` directory contains the tool used to generate register
1219 descriptions, instruction set descriptions, and even assemblers from common
1220 TableGen description files.
1224 The ``vim`` directory contains syntax-highlighting files which will work with
1225 the VIM editor, providing syntax highlighting support for LLVM assembly files
1226 and TableGen description files. For information on how to use the syntax
1227 files, consult the ``README`` file in that directory.
1231 An Example Using the LLVM Tool Chain
1232 ====================================
1234 This section gives an example of using LLVM with the Clang front end.
1239 #. First, create a simple C file, name it 'hello.c':
1246 printf("hello world\n");
1250 #. Next, compile the C file into a native executable:
1252 .. code-block:: console
1254 % clang hello.c -o hello
1258 Clang works just like GCC by default. The standard -S and -c arguments
1259 work as usual (producing a native .s or .o file, respectively).
1261 #. Next, compile the C file into a LLVM bitcode file:
1263 .. code-block:: console
1265 % clang -O3 -emit-llvm hello.c -c -o hello.bc
1267 The -emit-llvm option can be used with the -S or -c options to emit an LLVM
1268 ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
1269 the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
1271 #. Run the program in both forms. To run the program, use:
1273 .. code-block:: console
1279 .. code-block:: console
1283 The second examples shows how to invoke the LLVM JIT, :doc:`lli
1284 <CommandGuide/lli>`.
1286 #. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
1288 .. code-block:: console
1290 % llvm-dis < hello.bc | less
1292 #. Compile the program to native assembly using the LLC code generator:
1294 .. code-block:: console
1296 % llc hello.bc -o hello.s
1298 #. Assemble the native assembly language file into a program:
1300 .. code-block:: console
1302 % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
1304 % gcc hello.s -o hello.native # On others
1306 #. Execute the native code program:
1308 .. code-block:: console
1312 Note that using clang to compile directly to native code (i.e. when the
1313 ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
1318 If you are having problems building or using LLVM, or if you have any other
1319 general questions about LLVM, please consult the `Frequently Asked
1320 Questions <FAQ.html>`_ page.
1327 This document is just an **introduction** on how to use LLVM to do some simple
1328 things... there are many more interesting and complicated things that you can do
1329 that aren't documented here (but we'll gladly accept a patch if you want to
1330 write something up!). For more information about LLVM, check out:
1332 * `LLVM Homepage <http://llvm.org/>`_
1333 * `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
1334 * `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_