1 ====================================
2 Getting Started with the LLVM System
3 ====================================
11 Welcome to LLVM! In order to get started, you first need to know some basic
14 First, LLVM comes in three pieces. The first piece is the LLVM suite. This
15 contains all of the tools, libraries, and header files needed to use LLVM. It
16 contains an assembler, disassembler, bitcode analyzer and bitcode optimizer. It
17 also contains basic regression tests that can be used to test the LLVM tools and
20 The second piece is the `Clang <http://clang.llvm.org/>`_ front end. This
21 component compiles C, C++, Objective C, and Objective C++ code into LLVM
22 bitcode. Once compiled into LLVM bitcode, a program can be manipulated with the
23 LLVM tools from the LLVM suite.
25 There is a third, optional piece called Test Suite. It is a suite of programs
26 with a testing harness that can be used to further test LLVM's functionality
29 Getting Started Quickly (A Summary)
30 ===================================
32 The LLVM Getting Started documentation may be out of date. So, the `Clang
33 Getting Started <http://clang.llvm.org/get_started.html>`_ page might also be a
36 Here's the short story for getting up and running quickly with LLVM:
38 #. Read the documentation.
39 #. Read the documentation.
40 #. Remember that you were warned twice about reading the documentation.
43 * ``cd where-you-want-llvm-to-live``
44 * ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
48 * ``cd where-you-want-llvm-to-live``
50 * ``svn co http://llvm.org/svn/llvm-project/cfe/trunk clang``
52 #. Checkout Compiler-RT:
54 * ``cd where-you-want-llvm-to-live``
55 * ``cd llvm/projects``
56 * ``svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk compiler-rt``
58 #. Get the Test Suite Source Code **[Optional]**
60 * ``cd where-you-want-llvm-to-live``
61 * ``cd llvm/projects``
62 * ``svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite``
64 #. Configure and build LLVM and Clang:
66 * ``cd where-you-want-to-build-llvm``
67 * ``mkdir build`` (for building without polluting the source dir)
69 * ``../llvm/configure [options]``
72 * ``--prefix=directory`` --- Specify for *directory* the full pathname of
73 where you want the LLVM tools and libraries to be installed (default
76 * ``--enable-optimized`` --- Compile with optimizations enabled (default
79 * ``--enable-assertions`` --- Compile with assertion checks enabled
82 * ``make [-j]`` --- The ``-j`` specifies the number of jobs (commands) to run
83 simultaneously. This builds both LLVM and Clang for Debug+Asserts mode.
84 The ``--enable-optimized`` configure option is used to specify a Release
87 * ``make check-all`` --- This run the regression tests to ensure everything
90 * ``make update`` --- This command is used to update all the svn repositories
91 at once, rather then having to ``cd`` into the individual repositories and
92 running ``svn update``.
94 * It is also possible to use CMake instead of the makefiles. With CMake it is
95 possible to generate project files for several IDEs: Xcode, Eclipse CDT4,
96 CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.
98 * If you get an "internal compiler error (ICE)" or test failures, see
101 Consult the `Getting Started with LLVM`_ section for detailed information on
102 configuring and compiling LLVM. See `Setting Up Your Environment`_ for tips
103 that simplify working with the Clang front end and LLVM tools. Go to `Program
104 Layout`_ to learn about the layout of the source code tree.
109 Before you begin to use the LLVM system, review the requirements given below.
110 This may save you some trouble by knowing ahead of time what hardware and
111 software you will need.
116 LLVM is known to work on the following host platforms:
118 ================== ===================== =============
120 ================== ===================== =============
121 AuroraUX x86\ :sup:`1` GCC
122 Linux x86\ :sup:`1` GCC, Clang
123 Linux amd64 GCC, Clang
124 Linux ARM\ :sup:`4` GCC, Clang
125 Linux PowerPC GCC, Clang
126 Solaris V9 (Ultrasparc) GCC
127 FreeBSD x86\ :sup:`1` GCC, Clang
128 FreeBSD amd64 GCC, Clang
129 MacOS X\ :sup:`2` PowerPC GCC
130 MacOS X x86 GCC, Clang
131 Cygwin/Win32 x86\ :sup:`1, 3` GCC
132 Windows x86\ :sup:`1` Visual Studio
133 Windows x64 x86-64 Visual Studio
134 ================== ===================== =============
138 #. Code generation supported for Pentium processors and up
139 #. Code generation supported for 32-bit ABI only
140 #. To use LLVM modules on Win32-based system, you may configure LLVM
141 with ``--enable-shared``.
142 #. MCJIT not working well pre-v7, old JIT engine not supported any more.
144 Note that you will need about 1-3 GB of space for a full LLVM build in Debug
145 mode, depending on the system (it is so large because of all the debugging
146 information and the fact that the libraries are statically linked into multiple
147 tools). If you do not need many of the tools and you are space-conscious, you
148 can pass ``ONLY_TOOLS="tools you need"`` to make. The Release build requires
149 considerably less space.
151 The LLVM suite *may* compile on other platforms, but it is not guaranteed to do
152 so. If compilation is successful, the LLVM utilities should be able to
153 assemble, disassemble, analyze, and optimize LLVM bitcode. Code generation
154 should work as well, although the generated native code may not work on your
160 Compiling LLVM requires that you have several software packages installed. The
161 table below lists those required packages. The Package column is the usual name
162 for the software package that LLVM depends on. The Version column provides
163 "known to work" versions of the package. The Notes column describes how LLVM
164 uses the package and provides other details.
166 =========================================================== ============ ==========================================
167 Package Version Notes
168 =========================================================== ============ ==========================================
169 `GNU Make <http://savannah.gnu.org/projects/make>`_ 3.79, 3.79.1 Makefile/build processor
170 `GCC <http://gcc.gnu.org/>`_ 3.4.2 C/C++ compiler\ :sup:`1`
171 `TeXinfo <http://www.gnu.org/software/texinfo/>`_ 4.5 For building the CFE
172 `SVN <http://subversion.tigris.org/project_packages.html>`_ >=1.3 Subversion access to LLVM\ :sup:`2`
173 `python <http://www.python.org/>`_ >=2.5 Automated test suite\ :sup:`3`
174 `GNU M4 <http://savannah.gnu.org/projects/m4>`_ 1.4 Macro processor for configuration\ :sup:`4`
175 `GNU Autoconf <http://www.gnu.org/software/autoconf/>`_ 2.60 Configuration script builder\ :sup:`4`
176 `GNU Automake <http://www.gnu.org/software/automake/>`_ 1.9.6 aclocal macro generator\ :sup:`4`
177 `libtool <http://savannah.gnu.org/projects/libtool>`_ 1.5.22 Shared library manager\ :sup:`4`
178 `zlib <http://zlib.net>`_ >=1.2.3.4 Compression library\ :sup:`5`
179 =========================================================== ============ ==========================================
183 #. Only the C and C++ languages are needed so there's no need to build the
184 other languages for LLVM's purposes. See `below` for specific version
186 #. You only need Subversion if you intend to build from the latest LLVM
187 sources. If you're working from a release distribution, you don't need
189 #. Only needed if you want to run the automated test suite in the
190 ``llvm/test`` directory.
191 #. If you want to make changes to the configure scripts, you will need GNU
192 autoconf (2.60), and consequently, GNU M4 (version 1.4 or higher). You
193 will also need automake (1.9.6). We only use aclocal from that package.
194 #. Optional, adds compression/uncompression capabilities to selected LLVM
197 Additionally, your compilation host is expected to have the usual plethora of
198 Unix utilities. Specifically:
200 * **ar** --- archive library builder
201 * **bzip2** --- bzip2 command for distribution generation
202 * **bunzip2** --- bunzip2 command for distribution checking
203 * **chmod** --- change permissions on a file
204 * **cat** --- output concatenation utility
205 * **cp** --- copy files
206 * **date** --- print the current date/time
207 * **echo** --- print to standard output
208 * **egrep** --- extended regular expression search utility
209 * **find** --- find files/dirs in a file system
210 * **grep** --- regular expression search utility
211 * **gzip** --- gzip command for distribution generation
212 * **gunzip** --- gunzip command for distribution checking
213 * **install** --- install directories/files
214 * **mkdir** --- create a directory
215 * **mv** --- move (rename) files
216 * **ranlib** --- symbol table builder for archive libraries
217 * **rm** --- remove (delete) files and directories
218 * **sed** --- stream editor for transforming output
219 * **sh** --- Bourne shell for make build scripts
220 * **tar** --- tape archive for distribution generation
221 * **test** --- test things in file system
222 * **unzip** --- unzip command for distribution checking
223 * **zip** --- zip command for distribution generation
228 Broken versions of GCC and other tools
229 --------------------------------------
231 LLVM is very demanding of the host C++ compiler, and as such tends to expose
232 bugs in the compiler. In particular, several versions of GCC crash when trying
233 to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang. Other
234 versions of GCC will probably work as well. GCC versions listed here are known
235 to not work. If you are using one of these versions, please try to upgrade your
236 GCC to something more recent. If you run into a problem with a version of GCC
237 not listed here, please `let us know <mailto:llvmdev@cs.uiuc.edu>`_. Please use
238 the "``gcc -v``" command to find out which version of GCC you are using.
240 **GCC versions prior to 3.0**: GCC 2.96.x and before had several problems in the
241 STL that effectively prevent it from compiling LLVM.
243 **GCC 3.2.2 and 3.2.3**: These versions of GCC fails to compile LLVM with a
244 bogus template error. This was fixed in later GCCs.
246 **GCC 3.3.2**: This version of GCC suffered from a `serious bug
247 <http://gcc.gnu.org/PR13392>`_ which causes it to crash in the
248 "``convert_from_eh_region_ranges_1``" GCC function.
250 **Cygwin GCC 3.3.3**: The version of GCC 3.3.3 commonly shipped with Cygwin does
253 **SuSE GCC 3.3.3**: The version of GCC 3.3.3 shipped with SuSE 9.1 (and possibly
254 others) does not compile LLVM correctly (it appears that exception handling is
255 broken in some cases). Please download the FSF 3.3.3 or upgrade to a newer
258 **GCC 3.4.0 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
259 generator, causing an infinite loop in the llvm-gcc build when built with
260 optimizations enabled (i.e. a release build).
262 **GCC 3.4.2 on linux/x86 (32-bit)**: GCC miscompiles portions of the code
263 generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0) correctly
264 compiles LLVM at -O2. A work around is to build release LLVM builds with
265 "``make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ...``"
267 **GCC 3.4.x on X86-64/amd64**: GCC `miscompiles portions of LLVM
268 <http://llvm.org/PR1056>`__.
270 **GCC 3.4.4 (CodeSourcery ARM 2005q3-2)**: this compiler miscompiles LLVM when
271 building with optimizations enabled. It appears to work with "``make
272 ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1``" or build a debug build.
274 **IA-64 GCC 4.0.0**: The IA-64 version of GCC 4.0.0 is known to miscompile LLVM.
276 **Apple Xcode 2.3**: GCC crashes when compiling LLVM at -O3 (which is the
277 default with ENABLE_OPTIMIZED=1. To work around this, build with
278 "``ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2``".
280 **GCC 4.1.1**: GCC fails to build LLVM with template concept check errors
281 compiling some files. At the time of this writing, GCC mainline (4.2) did not
284 **GCC 4.1.1 on X86-64/amd64**: GCC `miscompiles portions of LLVM
285 <http://llvm.org/PR1063>`__ when compiling llvm itself into 64-bit code. LLVM
286 will appear to mostly work but will be buggy, e.g. failing portions of its
289 **GCC 4.1.2 on OpenSUSE**: Seg faults during libstdc++ build and on x86_64
290 platforms compiling md5.c gets a mangled constant.
292 **GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian**: Appears to
293 miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining about
294 symbols remaining in the table on destruction.
296 **GCC 4.1.2 20071124 (Red Hat 4.1.2-42)**: Suffers from the same symptoms as the
297 previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).
299 **Cygwin GCC 4.3.2 20080827 (beta) 2**: Users `reported
300 <http://llvm.org/PR4145>`_ various problems related with link errors when using
303 **Debian GCC 4.3.2 on X86**: Crashes building some files in LLVM 2.6.
305 **GCC 4.3.3 (Debian 4.3.3-10) on ARM**: Miscompiles parts of LLVM 2.6 when
306 optimizations are turned on. The symptom is an infinite loop in
307 ``FoldingSetImpl::RemoveNode`` while running the code generator.
309 **SUSE 11 GCC 4.3.4**: Miscompiles LLVM, causing crashes in ValueHandle logic.
311 **GCC 4.3.5 and GCC 4.4.5 on ARM**: These can miscompile ``value >> 1`` even at
312 ``-O0``. A test failure in ``test/Assembler/alignstack.ll`` is one symptom of
315 **GCC 4.6.3 on ARM**: Miscompiles ``llvm-readobj`` at ``-O3``. A test failure
316 in ``test/Object/readobj-shared-object.test`` is one symptom of the problem.
318 **GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long
319 warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was
320 defined in a discarded section. You can safely ignore these messages as they are
321 erroneous and the linkage is correct. These messages disappear using ld 2.17.
323 **GNU binutils 2.17**: Binutils 2.17 contains `a bug
324 <http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link
325 times (minutes instead of seconds) when building LLVM. We recommend upgrading
326 to a newer version (2.17.50.0.4 or later).
328 **GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug
329 <http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes
330 intermittent failures when building LLVM with position independent code. The
331 symptom is an error about cyclic dependencies. We recommend upgrading to a
332 newer version of Gold.
334 **Clang 3.0 with libstdc++ 4.7.x**: a few Linux distributions (Ubuntu 12.10,
335 Fedora 17) have both Clang 3.0 and libstdc++ 4.7 in their repositories. Clang
336 3.0 does not implement a few builtins that are used in this library. We
337 recommend using the system GCC to compile LLVM and Clang in this case.
339 **Clang 3.0 on Mageia 2**. There's a packaging issue: Clang can not find at
340 least some (``cxxabi.h``) libstdc++ headers.
342 **Clang in C++11 mode and libstdc++ 4.7.2**. This version of libstdc++
343 contained `a bug <http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53841>`__ which
344 causes Clang to refuse to compile condition_variable header file. At the time
345 of writing, this breaks LLD build.
347 .. _Getting Started with LLVM:
349 Getting Started with LLVM
350 =========================
352 The remainder of this guide is meant to get you up and running with LLVM and to
353 give you some basic information about the LLVM environment.
355 The later sections of this guide describe the `general layout`_ of the LLVM
356 source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find
357 more information about LLVM or to get help via e-mail.
359 Terminology and Notation
360 ------------------------
362 Throughout this manual, the following names are used to denote paths specific to
363 the local system and working environment. *These are not environment variables
364 you need to set but just strings used in the rest of this document below*. In
365 any of the examples below, simply replace each of these names with the
366 appropriate pathname on your local system. All these paths are absolute:
370 This is the top level directory of the LLVM source tree.
374 This is the top level directory of the LLVM object tree (i.e. the tree where
375 object files and compiled programs will be placed. It can be the same as
378 .. _Setting Up Your Environment:
380 Setting Up Your Environment
381 ---------------------------
383 In order to compile and use LLVM, you may need to set some environment
386 ``LLVM_LIB_SEARCH_PATH=/path/to/your/bitcode/libs``
388 [Optional] This environment variable helps LLVM linking tools find the
389 locations of your bitcode libraries. It is provided only as a convenience
390 since you can specify the paths using the -L options of the tools and the
391 C/C++ front-end will automatically use the bitcode files installed in its
394 Unpacking the LLVM Archives
395 ---------------------------
397 If you have the LLVM distribution, you will need to unpack it before you can
398 begin to compile it. LLVM is distributed as a set of two files: the LLVM suite
399 and the LLVM GCC front end compiled for your platform. There is an additional
400 test suite that is optional. Each file is a TAR archive that is compressed with
403 The files are as follows, with *x.y* marking the version number:
407 Source release for the LLVM libraries and tools.
409 ``llvm-test-x.y.tar.gz``
411 Source release for the LLVM test-suite.
415 Checkout LLVM from Subversion
416 -----------------------------
418 If you have access to our Subversion repository, you can get a fresh copy of the
419 entire source code. All you need to do is check it out from Subversion as
422 * ``cd where-you-want-llvm-to-live``
423 * Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm``
424 * Read-Write:``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm``
426 This will create an '``llvm``' directory in the current directory and fully
427 populate it with the LLVM source code, Makefiles, test directories, and local
428 copies of documentation files.
430 If you want to get a specific release (as opposed to the most recent revision),
431 you can checkout it from the '``tags``' directory (instead of '``trunk``'). The
432 following releases are located in the following subdirectories of the '``tags``'
435 * Release 3.3: **RELEASE_33/final**
436 * Release 3.2: **RELEASE_32/final**
437 * Release 3.1: **RELEASE_31/final**
438 * Release 3.0: **RELEASE_30/final**
439 * Release 2.9: **RELEASE_29/final**
440 * Release 2.8: **RELEASE_28**
441 * Release 2.7: **RELEASE_27**
442 * Release 2.6: **RELEASE_26**
443 * Release 2.5: **RELEASE_25**
444 * Release 2.4: **RELEASE_24**
445 * Release 2.3: **RELEASE_23**
446 * Release 2.2: **RELEASE_22**
447 * Release 2.1: **RELEASE_21**
448 * Release 2.0: **RELEASE_20**
449 * Release 1.9: **RELEASE_19**
450 * Release 1.8: **RELEASE_18**
451 * Release 1.7: **RELEASE_17**
452 * Release 1.6: **RELEASE_16**
453 * Release 1.5: **RELEASE_15**
454 * Release 1.4: **RELEASE_14**
455 * Release 1.3: **RELEASE_13**
456 * Release 1.2: **RELEASE_12**
457 * Release 1.1: **RELEASE_11**
458 * Release 1.0: **RELEASE_1**
460 If you would like to get the LLVM test suite (a separate package as of 1.4), you
461 get it from the Subversion repository:
463 .. code-block:: console
466 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
468 By placing it in the ``llvm/projects``, it will be automatically configured by
469 the LLVM configure script as well as automatically updated when you run ``svn
475 Git mirrors are available for a number of LLVM subprojects. These mirrors sync
476 automatically with each Subversion commit and contain all necessary git-svn
477 marks (so, you can recreate git-svn metadata locally). Note that right now
478 mirrors reflect only ``trunk`` for each project. You can do the read-only Git
481 .. code-block:: console
483 % git clone http://llvm.org/git/llvm.git
485 If you want to check out clang too, run:
487 .. code-block:: console
490 % git clone http://llvm.org/git/clang.git
492 If you want to check out compiler-rt too, run:
494 .. code-block:: console
497 % git clone http://llvm.org/git/compiler-rt.git
499 If you want to check out the Test Suite Source Code (optional), run:
501 .. code-block:: console
504 % git clone http://llvm.org/git/test-suite.git
506 Since the upstream repository is in Subversion, you should use ``git
507 pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history
508 in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the
509 master branch, run the following command:
511 .. code-block:: console
513 % git config branch.master.rebase true
515 Sending patches with Git
516 ^^^^^^^^^^^^^^^^^^^^^^^^
518 Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too.
520 Assume ``master`` points the upstream and ``mybranch`` points your working
521 branch, and ``mybranch`` is rebased onto ``master``. At first you may check
522 sanity of whitespaces:
524 .. code-block:: console
526 % git diff --check master..mybranch
528 The easiest way to generate a patch is as below:
530 .. code-block:: console
532 % git diff master..mybranch > /path/to/mybranch.diff
534 It is a little different from svn-generated diff. git-diff-generated diff has
535 prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it
536 could be accepted with ``patch -p1 -N``.
538 But you may generate patchset with git-format-patch. It generates by-each-commit
539 patchset. To generate patch files to attach to your article:
541 .. code-block:: console
543 % git format-patch --no-attach master..mybranch -o /path/to/your/patchset
545 If you would like to send patches directly, you may use git-send-email or
546 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
548 .. code-block:: console
550 % git format-patch --attach master..mybranch --stdout | git imap-send
552 Then, your .git/config should have [imap] sections.
557 host = imaps://imap.gmail.com
558 user = your.gmail.account@gmail.com
563 folder = "[Gmail]/Drafts"
564 ; example for Japanese, "Modified UTF-7" encoded.
565 folder = "[Gmail]/&Tgtm+DBN-"
566 ; example for Traditional Chinese
567 folder = "[Gmail]/&g0l6Pw-"
569 For developers to work with git-svn
570 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
572 To set up clone from which you can submit code using ``git-svn``, run:
574 .. code-block:: console
576 % git clone http://llvm.org/git/llvm.git
578 % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
579 % git config svn-remote.svn.fetch :refs/remotes/origin/master
580 % git svn rebase -l # -l avoids fetching ahead of the git mirror.
582 # If you have clang too:
584 % git clone http://llvm.org/git/clang.git
586 % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
587 % git config svn-remote.svn.fetch :refs/remotes/origin/master
590 Likewise for compiler-rt and test-suite.
592 To update this clone without generating git-svn tags that conflict with the
593 upstream Git repo, run:
595 .. code-block:: console
597 % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
598 % git checkout master
601 git checkout master &&
604 Likewise for compiler-rt and test-suite.
606 This leaves your working directories on their master branches, so you'll need to
607 ``checkout`` each working branch individually and ``rebase`` it on top of its
610 For those who wish to be able to update an llvm repo/revert patches easily using
611 git-svn, please look in the directory for the scripts ``git-svnup`` and
614 To perform the aforementioned update steps go into your source directory and
615 just type ``git-svnup`` or ``git svnup`` and everything will just work.
617 If one wishes to revert a commit with git-svn, but do not want the git hash to
618 escape into the commit message, one can use the script ``git-svnrevert`` or
619 ``git svnrevert`` which will take in the git hash for the commit you want to
620 revert, look up the appropriate svn revision, and output a message where all
621 references to the git hash have been replaced with the svn revision.
623 To commit back changes via git-svn, use ``git svn dcommit``:
625 .. code-block:: console
629 Note that git-svn will create one SVN commit for each Git commit you have pending,
630 so squash and edit each commit before executing ``dcommit`` to make sure they all
631 conform to the coding standards and the developers' policy.
633 On success, ``dcommit`` will rebase against the HEAD of SVN, so to avoid conflict,
634 please make sure your current branch is up-to-date (via fetch/rebase) before
637 The git-svn metadata can get out of sync after you mess around with branches and
638 ``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining
639 about files with uncommitted changes. The fix is to rebuild the metadata:
641 .. code-block:: console
646 Please, refer to the Git-SVN manual (``man git-svn``) for more information.
648 Local LLVM Configuration
649 ------------------------
651 Once checked out from the Subversion repository, the LLVM suite source code must
652 be configured via the ``configure`` script. This script sets variables in the
653 various ``*.in`` files, most notably ``llvm/Makefile.config`` and
654 ``llvm/include/Config/config.h``. It also populates *OBJ_ROOT* with the
655 Makefiles needed to begin building LLVM.
657 The following environment variables are used by the ``configure`` script to
658 configure the build system:
660 +------------+-----------------------------------------------------------+
661 | Variable | Purpose |
662 +============+===========================================================+
663 | CC | Tells ``configure`` which C compiler to use. By default, |
664 | | ``configure`` will check ``PATH`` for ``clang`` and GCC C |
665 | | compilers (in this order). Use this variable to override |
666 | | ``configure``\'s default behavior. |
667 +------------+-----------------------------------------------------------+
668 | CXX | Tells ``configure`` which C++ compiler to use. By |
669 | | default, ``configure`` will check ``PATH`` for |
670 | | ``clang++`` and GCC C++ compilers (in this order). Use |
671 | | this variable to override ``configure``'s default |
673 +------------+-----------------------------------------------------------+
675 The following options can be used to set or enable LLVM specific options:
677 ``--enable-optimized``
679 Enables optimized compilation (debugging symbols are removed and GCC
680 optimization flags are enabled). Note that this is the default setting if you
681 are using the LLVM distribution. The default behavior of an Subversion
682 checkout is to use an unoptimized build (also known as a debug build).
684 ``--enable-debug-runtime``
686 Enables debug symbols in the runtime libraries. The default is to strip debug
687 symbols from the runtime libraries.
691 Compile the Just In Time (JIT) compiler functionality. This is not available
692 on all platforms. The default is dependent on platform, so it is best to
693 explicitly enable it if you want it.
695 ``--enable-targets=target-option``
697 Controls which targets will be built and linked into llc. The default value
698 for ``target_options`` is "all" which builds and links all available targets.
699 The value "host-only" can be specified to build only a native compiler (no
700 cross-compiler targets available). The "native" target is selected as the
701 target of the build host. You can also specify a comma separated list of
702 target names that you want available in llc. The target names use all lower
703 case. The current set of targets is:
705 ``arm, cpp, hexagon, mips, mipsel, msp430, powerpc, ptx, sparc, spu,
706 systemz, x86, x86_64, xcore``.
710 Look for the doxygen program and enable construction of doxygen based
711 documentation from the source code. This is disabled by default because
712 generating the documentation can take a long time and producess 100s of
717 LLVM can use external disassembler library for various purposes (now it's used
718 only for examining code produced by JIT). This option will enable usage of
719 `udis86 <http://udis86.sourceforge.net/>`_ x86 (both 32 and 64 bits)
720 disassembler library.
722 To configure LLVM, follow these steps:
724 #. Change directory into the object root directory:
726 .. code-block:: console
730 #. Run the ``configure`` script located in the LLVM source tree:
732 .. code-block:: console
734 % SRC_ROOT/configure --prefix=/install/path [other options]
736 Compiling the LLVM Suite Source Code
737 ------------------------------------
739 Once you have configured LLVM, you can build it. There are three types of
744 These builds are the default when one is using an Subversion checkout and
745 types ``gmake`` (unless the ``--enable-optimized`` option was used during
746 configuration). The build system will compile the tools and libraries with
747 debugging information. To get a Debug Build using the LLVM distribution the
748 ``--disable-optimized`` option must be passed to ``configure``.
750 Release (Optimized) Builds
752 These builds are enabled with the ``--enable-optimized`` option to
753 ``configure`` or by specifying ``ENABLE_OPTIMIZED=1`` on the ``gmake`` command
754 line. For these builds, the build system will compile the tools and libraries
755 with GCC optimizations enabled and strip debugging information from the
756 libraries and executables it generates. Note that Release Builds are default
757 when using an LLVM distribution.
761 These builds are for use with profiling. They compile profiling information
762 into the code for use with programs like ``gprof``. Profile builds must be
763 started by specifying ``ENABLE_PROFILING=1`` on the ``gmake`` command line.
765 Once you have LLVM configured, you can build it by entering the *OBJ_ROOT*
766 directory and issuing the following command:
768 .. code-block:: console
772 If the build fails, please `check here`_ to see if you are using a version of
773 GCC that is known not to compile LLVM.
775 If you have multiple processors in your machine, you may wish to use some of the
776 parallel build options provided by GNU Make. For example, you could use the
779 .. code-block:: console
783 There are several special targets which are useful when working with the LLVM
788 Removes all files generated by the build. This includes object files,
789 generated C/C++ files, libraries, and executables.
793 Removes everything that ``gmake clean`` does, but also removes files generated
794 by ``configure``. It attempts to return the source tree to the original state
795 in which it was shipped.
799 Installs LLVM header files, libraries, tools, and documentation in a hierarchy
800 under ``$PREFIX``, specified with ``./configure --prefix=[dir]``, which
801 defaults to ``/usr/local``.
803 ``gmake -C runtime install-bytecode``
805 Assuming you built LLVM into $OBJDIR, when this command is run, it will
806 install bitcode libraries into the GCC front end's bitcode library directory.
807 If you need to update your bitcode libraries, this is the target to use once
810 Please see the `Makefile Guide <MakefileGuide.html>`_ for further details on
811 these ``make`` targets and descriptions of other targets available.
813 It is also possible to override default values from ``configure`` by declaring
814 variables on the command line. The following are some examples:
816 ``gmake ENABLE_OPTIMIZED=1``
818 Perform a Release (Optimized) build.
820 ``gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1``
822 Perform a Release (Optimized) build without assertions enabled.
824 ``gmake ENABLE_OPTIMIZED=0``
826 Perform a Debug build.
828 ``gmake ENABLE_PROFILING=1``
830 Perform a Profiling build.
834 Print what ``gmake`` is doing on standard output.
836 ``gmake TOOL_VERBOSE=1``
838 Ask each tool invoked by the makefiles to print out what it is doing on
839 the standard output. This also implies ``VERBOSE=1``.
841 Every directory in the LLVM object tree includes a ``Makefile`` to build it and
842 any subdirectories that it contains. Entering any directory inside the LLVM
843 object tree and typing ``gmake`` should rebuild anything in or below that
844 directory that is out of date.
846 This does not apply to building the documentation.
847 LLVM's (non-Doxygen) documentation is produced with the
848 `Sphinx <http://sphinx-doc.org/>`_ documentation generation system.
849 There are some HTML documents that have not yet been converted to the new
850 system (which uses the easy-to-read and easy-to-write
851 `reStructuredText <http://sphinx-doc.org/rest.html>`_ plaintext markup
853 The generated documentation is built in the ``SRC_ROOT/docs`` directory using
855 For instructions on how to install Sphinx, see
856 `Sphinx Introduction for LLVM Developers
857 <http://lld.llvm.org/sphinx_intro.html>`_.
858 After following the instructions there for installing Sphinx, build the LLVM
859 HTML documentation by doing the following:
861 .. code-block:: console
864 $ make -f Makefile.sphinx
866 This creates a ``_build/html`` sub-directory with all of the HTML files, not
867 just the generated ones.
868 This directory corresponds to ``llvm.org/docs``.
869 For example, ``_build/html/SphinxQuickstartTemplate.html`` corresponds to
870 ``llvm.org/docs/SphinxQuickstartTemplate.html``.
871 The :doc:`SphinxQuickstartTemplate` is useful when creating a new document.
876 It is possible to cross-compile LLVM itself. That is, you can create LLVM
877 executables and libraries to be hosted on a platform different from the platform
878 where they are built (a Canadian Cross build). To configure a cross-compile,
879 supply the configure script with ``--build`` and ``--host`` options that are
880 different. The values of these options must be legal target triples that your
881 GCC compiler supports.
883 The result of such a build is executables that are not runnable on on the build
884 host (--build option) but can be executed on the compile host (--host option).
886 Check :doc:`HowToCrossCompileLLVM` and `Clang docs on how to cross-compile in general
887 <http://clang.llvm.org/docs/CrossCompilation.html>`_ for more information
888 about cross-compiling.
890 The Location of LLVM Object Files
891 ---------------------------------
893 The LLVM build system is capable of sharing a single LLVM source tree among
894 several LLVM builds. Hence, it is possible to build LLVM for several different
895 platforms or configurations using the same source tree.
897 This is accomplished in the typical autoconf manner:
899 * Change directory to where the LLVM object files should live:
901 .. code-block:: console
905 * Run the ``configure`` script found in the LLVM source directory:
907 .. code-block:: console
911 The LLVM build will place files underneath *OBJ_ROOT* in directories named after
914 Debug Builds with assertions enabled (the default)
918 ``OBJ_ROOT/Debug+Asserts/bin``
922 ``OBJ_ROOT/Debug+Asserts/lib``
928 ``OBJ_ROOT/Release/bin``
932 ``OBJ_ROOT/Release/lib``
938 ``OBJ_ROOT/Profile/bin``
942 ``OBJ_ROOT/Profile/lib``
944 Optional Configuration Items
945 ----------------------------
947 If you're running on a Linux system that supports the `binfmt_misc
948 <http://en.wikipedia.org/wiki/binfmt_misc>`_
949 module, and you have root access on the system, you can set your system up to
950 execute LLVM bitcode files directly. To do this, use commands like this (the
951 first command may not be required if you are already using the module):
953 .. code-block:: console
955 % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
956 % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
957 % chmod u+x hello.bc (if needed)
960 This allows you to execute LLVM bitcode files directly. On Debian, you can also
961 use this command instead of the 'echo' command above:
963 .. code-block:: console
965 % sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
973 One useful source of information about the LLVM source base is the LLVM `doxygen
974 <http://www.doxygen.org/>`_ documentation available at
975 `<http://llvm.org/doxygen/>`_. The following is a brief introduction to code
981 This directory contains some simple examples of how to use the LLVM IR and JIT.
986 This directory contains public header files exported from the LLVM library. The
987 three main subdirectories of this directory are:
989 ``llvm/include/llvm``
991 This directory contains all of the LLVM specific header files. This directory
992 also has subdirectories for different portions of LLVM: ``Analysis``,
993 ``CodeGen``, ``Target``, ``Transforms``, etc...
995 ``llvm/include/llvm/Support``
997 This directory contains generic support libraries that are provided with LLVM
998 but not necessarily specific to LLVM. For example, some C++ STL utilities and
999 a Command Line option processing library store their header files here.
1001 ``llvm/include/llvm/Config``
1003 This directory contains header files configured by the ``configure`` script.
1004 They wrap "standard" UNIX and C header files. Source code can include these
1005 header files which automatically take care of the conditional #includes that
1006 the ``configure`` script generates.
1011 This directory contains most of the source files of the LLVM system. In LLVM,
1012 almost all code exists in libraries, making it very easy to share code among the
1015 ``llvm/lib/VMCore/``
1017 This directory holds the core LLVM source files that implement core classes
1018 like Instruction and BasicBlock.
1020 ``llvm/lib/AsmParser/``
1022 This directory holds the source code for the LLVM assembly language parser
1025 ``llvm/lib/Bitcode/``
1027 This directory holds code for reading and write LLVM bitcode.
1029 ``llvm/lib/Analysis/``
1031 This directory contains a variety of different program analyses, such as
1032 Dominator Information, Call Graphs, Induction Variables, Interval
1033 Identification, Natural Loop Identification, etc.
1035 ``llvm/lib/Transforms/``
1037 This directory contains the source code for the LLVM to LLVM program
1038 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1039 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1040 Elimination, and many others.
1042 ``llvm/lib/Target/``
1044 This directory contains files that describe various target architectures for
1045 code generation. For example, the ``llvm/lib/Target/X86`` directory holds the
1046 X86 machine description while ``llvm/lib/Target/ARM`` implements the ARM
1049 ``llvm/lib/CodeGen/``
1051 This directory contains the major parts of the code generator: Instruction
1052 Selector, Instruction Scheduling, and Register Allocation.
1058 ``llvm/lib/Debugger/``
1060 This directory contains the source level debugger library that makes it
1061 possible to instrument LLVM programs so that a debugger could identify source
1062 code locations at which the program is executing.
1064 ``llvm/lib/ExecutionEngine/``
1066 This directory contains libraries for executing LLVM bitcode directly at
1067 runtime in both interpreted and JIT compiled fashions.
1069 ``llvm/lib/Support/``
1071 This directory contains the source code that corresponds to the header files
1072 located in ``llvm/include/ADT/`` and ``llvm/include/Support/``.
1077 This directory contains projects that are not strictly part of LLVM but are
1078 shipped with LLVM. This is also the directory where you should create your own
1079 LLVM-based projects. See ``llvm/projects/sample`` for an example of how to set
1080 up your own project.
1085 This directory contains libraries which are compiled into LLVM bitcode and used
1086 when linking programs with the Clang front end. Most of these libraries are
1087 skeleton versions of real libraries; for example, libc is a stripped down
1090 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
1096 This directory contains feature and regression tests and other basic sanity
1097 checks on the LLVM infrastructure. These are intended to run quickly and cover a
1098 lot of territory without being exhaustive.
1103 This is not a directory in the normal llvm module; it is a separate Subversion
1104 module that must be checked out (usually to ``projects/test-suite``). This
1105 module contains a comprehensive correctness, performance, and benchmarking test
1106 suite for LLVM. It is a separate Subversion module because not every LLVM user
1107 is interested in downloading or building such a comprehensive test suite. For
1108 further details on this test suite, please see the :doc:`Testing Guide
1109 <TestingGuide>` document.
1116 The **tools** directory contains the executables built out of the libraries
1117 above, which form the main part of the user interface. You can always get help
1118 for a tool by typing ``tool_name -help``. The following is a brief introduction
1119 to the most important tools. More detailed information is in
1120 the `Command Guide <CommandGuide/index.html>`_.
1124 ``bugpoint`` is used to debug optimization passes or code generation backends
1125 by narrowing down the given test case to the minimum number of passes and/or
1126 instructions that still cause a problem, whether it is a crash or
1127 miscompilation. See `<HowToSubmitABug.html>`_ for more information on using
1132 The archiver produces an archive containing the given LLVM bitcode files,
1133 optionally with an index for faster lookup.
1137 The assembler transforms the human readable LLVM assembly to LLVM bitcode.
1141 The disassembler transforms the LLVM bitcode to human readable LLVM assembly.
1145 ``llvm-link``, not surprisingly, links multiple LLVM modules into a single
1150 ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode
1151 (although very slowly...). For architectures that support it (currently x86,
1152 Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time
1153 compiler (if the functionality was compiled in), and will execute the code
1154 *much* faster than the interpreter.
1158 ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a
1159 native code assembly file or to C code (with the ``-march=c`` option).
1163 ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations
1164 (which are specified on the command line), and then outputs the resultant
1165 bitcode. The '``opt -help``' command is a good way to get a list of the
1166 program transformations available in LLVM.
1168 ``opt`` can also be used to run a specific analysis on an input LLVM bitcode
1169 file and print out the results. It is primarily useful for debugging
1170 analyses, or familiarizing yourself with what an analysis does.
1175 This directory contains utilities for working with LLVM source code, and some of
1176 the utilities are actually required as part of the build process because they
1177 are code generators for parts of LLVM infrastructure.
1182 ``codegen-diff`` is a script that finds differences between code that LLC
1183 generates and code that LLI generates. This is a useful tool if you are
1184 debugging one of them, assuming that the other generates correct output. For
1185 the full user manual, run ```perldoc codegen-diff'``.
1189 The ``emacs`` directory contains syntax-highlighting files which will work
1190 with Emacs and XEmacs editors, providing syntax highlighting support for LLVM
1191 assembly files and TableGen description files. For information on how to use
1192 the syntax files, consult the ``README`` file in that directory.
1196 The ``getsrcs.sh`` script finds and outputs all non-generated source files,
1197 which is useful if one wishes to do a lot of development across directories
1198 and does not want to individually find each file. One way to use it is to run,
1199 for example: ``xemacs `utils/getsources.sh``` from the top of your LLVM source
1204 This little tool performs an ``egrep -H -n`` on each source file in LLVM and
1205 passes to it a regular expression provided on ``llvmgrep``'s command
1206 line. This is a very efficient way of searching the source base for a
1207 particular regular expression.
1211 The ``makellvm`` script compiles all files in the current directory and then
1212 compiles and links the tool that is the first argument. For example, assuming
1213 you are in the directory ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your
1214 path, simply running ``makellvm llc`` will make a build of the current
1215 directory, switch to directory ``llvm/tools/llc`` and build it, causing a
1220 The ``TableGen`` directory contains the tool used to generate register
1221 descriptions, instruction set descriptions, and even assemblers from common
1222 TableGen description files.
1226 The ``vim`` directory contains syntax-highlighting files which will work with
1227 the VIM editor, providing syntax highlighting support for LLVM assembly files
1228 and TableGen description files. For information on how to use the syntax
1229 files, consult the ``README`` file in that directory.
1233 An Example Using the LLVM Tool Chain
1234 ====================================
1236 This section gives an example of using LLVM with the Clang front end.
1241 #. First, create a simple C file, name it 'hello.c':
1248 printf("hello world\n");
1252 #. Next, compile the C file into a native executable:
1254 .. code-block:: console
1256 % clang hello.c -o hello
1260 Clang works just like GCC by default. The standard -S and -c arguments
1261 work as usual (producing a native .s or .o file, respectively).
1263 #. Next, compile the C file into an LLVM bitcode file:
1265 .. code-block:: console
1267 % clang -O3 -emit-llvm hello.c -c -o hello.bc
1269 The -emit-llvm option can be used with the -S or -c options to emit an LLVM
1270 ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use
1271 the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file.
1273 #. Run the program in both forms. To run the program, use:
1275 .. code-block:: console
1281 .. code-block:: console
1285 The second examples shows how to invoke the LLVM JIT, :doc:`lli
1286 <CommandGuide/lli>`.
1288 #. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code:
1290 .. code-block:: console
1292 % llvm-dis < hello.bc | less
1294 #. Compile the program to native assembly using the LLC code generator:
1296 .. code-block:: console
1298 % llc hello.bc -o hello.s
1300 #. Assemble the native assembly language file into a program:
1302 .. code-block:: console
1304 % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris
1306 % gcc hello.s -o hello.native # On others
1308 #. Execute the native code program:
1310 .. code-block:: console
1314 Note that using clang to compile directly to native code (i.e. when the
1315 ``-emit-llvm`` option is not present) does steps 6/7/8 for you.
1320 If you are having problems building or using LLVM, or if you have any other
1321 general questions about LLVM, please consult the `Frequently Asked
1322 Questions <FAQ.html>`_ page.
1329 This document is just an **introduction** on how to use LLVM to do some simple
1330 things... there are many more interesting and complicated things that you can do
1331 that aren't documented here (but we'll gladly accept a patch if you want to
1332 write something up!). For more information about LLVM, check out:
1334 * `LLVM Homepage <http://llvm.org/>`_
1335 * `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_
1336 * `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_