1==================================== 2Getting Started with the LLVM System 3==================================== 4 5.. contents:: 6 :local: 7 8Overview 9======== 10 11Welcome to LLVM! In order to get started, you first need to know some basic 12information. 13 14First, LLVM comes in three pieces. The first piece is the LLVM suite. This 15contains all of the tools, libraries, and header files needed to use LLVM. It 16contains an assembler, disassembler, bitcode analyzer and bitcode optimizer. It 17also contains basic regression tests that can be used to test the LLVM tools and 18the Clang front end. 19 20The second piece is the `Clang <http://clang.llvm.org/>`_ front end. This 21component compiles C, C++, Objective C, and Objective C++ code into LLVM 22bitcode. Once compiled into LLVM bitcode, a program can be manipulated with the 23LLVM tools from the LLVM suite. 24 25There is a third, optional piece called Test Suite. It is a suite of programs 26with a testing harness that can be used to further test LLVM's functionality 27and performance. 28 29Getting Started Quickly (A Summary) 30=================================== 31 32The LLVM Getting Started documentation may be out of date. So, the `Clang 33Getting Started <http://clang.llvm.org/get_started.html>`_ page might also be a 34good place to start. 35 36Here's the short story for getting up and running quickly with LLVM: 37 38#. Read the documentation. 39#. Read the documentation. 40#. Remember that you were warned twice about reading the documentation. 41 42 * In particular, the *relative paths specified are important*. 43 44#. Checkout LLVM: 45 46 * ``cd where-you-want-llvm-to-live`` 47 * ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm`` 48 49#. Checkout Clang: 50 51 * ``cd where-you-want-llvm-to-live`` 52 * ``cd llvm/tools`` 53 * ``svn co http://llvm.org/svn/llvm-project/cfe/trunk clang`` 54 55#. Checkout Extra Clang Tools **[Optional]**: 56 57 * ``cd where-you-want-llvm-to-live`` 58 * ``cd llvm/tools/clang/tools`` 59 * ``svn co http://llvm.org/svn/llvm-project/clang-tools-extra/trunk extra`` 60 61#. Checkout LLD linker **[Optional]**: 62 63 * ``cd where-you-want-llvm-to-live`` 64 * ``cd llvm/tools`` 65 * ``svn co http://llvm.org/svn/llvm-project/lld/trunk lld`` 66 67#. Checkout Polly Loop Optimizer **[Optional]**: 68 69 * ``cd where-you-want-llvm-to-live`` 70 * ``cd llvm/tools`` 71 * ``svn co http://llvm.org/svn/llvm-project/polly/trunk polly`` 72 73#. Checkout Compiler-RT (required to build the sanitizers) **[Optional]**: 74 75 * ``cd where-you-want-llvm-to-live`` 76 * ``cd llvm/projects`` 77 * ``svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk compiler-rt`` 78 79#. Checkout Libomp (required for OpenMP support) **[Optional]**: 80 81 * ``cd where-you-want-llvm-to-live`` 82 * ``cd llvm/projects`` 83 * ``svn co http://llvm.org/svn/llvm-project/openmp/trunk openmp`` 84 85#. Checkout libcxx and libcxxabi **[Optional]**: 86 87 * ``cd where-you-want-llvm-to-live`` 88 * ``cd llvm/projects`` 89 * ``svn co http://llvm.org/svn/llvm-project/libcxx/trunk libcxx`` 90 * ``svn co http://llvm.org/svn/llvm-project/libcxxabi/trunk libcxxabi`` 91 92#. Get the Test Suite Source Code **[Optional]** 93 94 * ``cd where-you-want-llvm-to-live`` 95 * ``cd llvm/projects`` 96 * ``svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite`` 97 98#. Configure and build LLVM and Clang: 99 100 *Warning:* Make sure you've checked out *all of* the source code 101 before trying to configure with cmake. cmake does not pickup newly 102 added source directories in incremental builds. 103 104 The build uses `CMake <CMake.html>`_. LLVM requires CMake 3.4.3 to build. It 105 is generally recommended to use a recent CMake, especially if you're 106 generating Ninja build files. This is because the CMake project is constantly 107 improving the quality of the generators, and the Ninja generator gets a lot 108 of attention. 109 110 * ``cd where you want to build llvm`` 111 * ``mkdir build`` 112 * ``cd build`` 113 * ``cmake -G <generator> [options] <path to llvm sources>`` 114 115 Some common generators are: 116 117 * ``Unix Makefiles`` --- for generating make-compatible parallel makefiles. 118 * ``Ninja`` --- for generating `Ninja <https://ninja-build.org>`_ 119 build files. Most llvm developers use Ninja. 120 * ``Visual Studio`` --- for generating Visual Studio projects and 121 solutions. 122 * ``Xcode`` --- for generating Xcode projects. 123 124 Some Common options: 125 126 * ``-DCMAKE_INSTALL_PREFIX=directory`` --- Specify for *directory* the full 127 pathname of where you want the LLVM tools and libraries to be installed 128 (default ``/usr/local``). 129 130 * ``-DCMAKE_BUILD_TYPE=type`` --- Valid options for *type* are Debug, 131 Release, RelWithDebInfo, and MinSizeRel. Default is Debug. 132 133 * ``-DLLVM_ENABLE_ASSERTIONS=On`` --- Compile with assertion checks enabled 134 (default is Yes for Debug builds, No for all other build types). 135 136 * Run your build tool of choice! 137 138 * The default target (i.e. ``make``) will build all of LLVM 139 140 * The ``check-all`` target (i.e. ``make check-all``) will run the 141 regression tests to ensure everything is in working order. 142 143 * CMake will generate build targets for each tool and library, and most 144 LLVM sub-projects generate their own ``check-<project>`` target. 145 146 * Running a serial build will be *slow*. Make sure you run a 147 parallel build; for ``make``, use ``make -j``. 148 149 * For more information see `CMake <CMake.html>`_ 150 151 * If you get an "internal compiler error (ICE)" or test failures, see 152 `below`_. 153 154Consult the `Getting Started with LLVM`_ section for detailed information on 155configuring and compiling LLVM. Go to `Directory Layout`_ to learn about the 156layout of the source code tree. 157 158Requirements 159============ 160 161Before you begin to use the LLVM system, review the requirements given below. 162This may save you some trouble by knowing ahead of time what hardware and 163software you will need. 164 165Hardware 166-------- 167 168LLVM is known to work on the following host platforms: 169 170================== ===================== ============= 171OS Arch Compilers 172================== ===================== ============= 173Linux x86\ :sup:`1` GCC, Clang 174Linux amd64 GCC, Clang 175Linux ARM\ :sup:`4` GCC, Clang 176Linux PowerPC GCC, Clang 177Solaris V9 (Ultrasparc) GCC 178FreeBSD x86\ :sup:`1` GCC, Clang 179FreeBSD amd64 GCC, Clang 180NetBSD x86\ :sup:`1` GCC, Clang 181NetBSD amd64 GCC, Clang 182MacOS X\ :sup:`2` PowerPC GCC 183MacOS X x86 GCC, Clang 184Cygwin/Win32 x86\ :sup:`1, 3` GCC 185Windows x86\ :sup:`1` Visual Studio 186Windows x64 x86-64 Visual Studio 187================== ===================== ============= 188 189.. note:: 190 191 #. Code generation supported for Pentium processors and up 192 #. Code generation supported for 32-bit ABI only 193 #. To use LLVM modules on Win32-based system, you may configure LLVM 194 with ``-DBUILD_SHARED_LIBS=On``. 195 #. MCJIT not working well pre-v7, old JIT engine not supported any more. 196 197Note that Debug builds require a lot of time and disk space. An LLVM-only build 198will need about 1-3 GB of space. A full build of LLVM and Clang will need around 19915-20 GB of disk space. The exact space requirements will vary by system. (It 200is so large because of all the debugging information and the fact that the 201libraries are statically linked into multiple tools). 202 203If you are space-constrained, you can build only selected tools or only 204selected targets. The Release build requires considerably less space. 205 206The LLVM suite *may* compile on other platforms, but it is not guaranteed to do 207so. If compilation is successful, the LLVM utilities should be able to 208assemble, disassemble, analyze, and optimize LLVM bitcode. Code generation 209should work as well, although the generated native code may not work on your 210platform. 211 212Software 213-------- 214 215Compiling LLVM requires that you have several software packages installed. The 216table below lists those required packages. The Package column is the usual name 217for the software package that LLVM depends on. The Version column provides 218"known to work" versions of the package. The Notes column describes how LLVM 219uses the package and provides other details. 220 221=========================================================== ============ ========================================== 222Package Version Notes 223=========================================================== ============ ========================================== 224`GNU Make <http://savannah.gnu.org/projects/make>`_ 3.79, 3.79.1 Makefile/build processor 225`GCC <http://gcc.gnu.org/>`_ >=4.8.0 C/C++ compiler\ :sup:`1` 226`python <http://www.python.org/>`_ >=2.7 Automated test suite\ :sup:`2` 227`zlib <http://zlib.net>`_ >=1.2.3.4 Compression library\ :sup:`3` 228=========================================================== ============ ========================================== 229 230.. note:: 231 232 #. Only the C and C++ languages are needed so there's no need to build the 233 other languages for LLVM's purposes. See `below` for specific version 234 info. 235 #. Only needed if you want to run the automated test suite in the 236 ``llvm/test`` directory. 237 #. Optional, adds compression / uncompression capabilities to selected LLVM 238 tools. 239 240Additionally, your compilation host is expected to have the usual plethora of 241Unix utilities. Specifically: 242 243* **ar** --- archive library builder 244* **bzip2** --- bzip2 command for distribution generation 245* **bunzip2** --- bunzip2 command for distribution checking 246* **chmod** --- change permissions on a file 247* **cat** --- output concatenation utility 248* **cp** --- copy files 249* **date** --- print the current date/time 250* **echo** --- print to standard output 251* **egrep** --- extended regular expression search utility 252* **find** --- find files/dirs in a file system 253* **grep** --- regular expression search utility 254* **gzip** --- gzip command for distribution generation 255* **gunzip** --- gunzip command for distribution checking 256* **install** --- install directories/files 257* **mkdir** --- create a directory 258* **mv** --- move (rename) files 259* **ranlib** --- symbol table builder for archive libraries 260* **rm** --- remove (delete) files and directories 261* **sed** --- stream editor for transforming output 262* **sh** --- Bourne shell for make build scripts 263* **tar** --- tape archive for distribution generation 264* **test** --- test things in file system 265* **unzip** --- unzip command for distribution checking 266* **zip** --- zip command for distribution generation 267 268.. _below: 269.. _check here: 270 271Host C++ Toolchain, both Compiler and Standard Library 272------------------------------------------------------ 273 274LLVM is very demanding of the host C++ compiler, and as such tends to expose 275bugs in the compiler. We are also planning to follow improvements and 276developments in the C++ language and library reasonably closely. As such, we 277require a modern host C++ toolchain, both compiler and standard library, in 278order to build LLVM. 279 280For the most popular host toolchains we check for specific minimum versions in 281our build systems: 282 283* Clang 3.1 284* GCC 4.8 285* Visual Studio 2015 (Update 3) 286 287Anything older than these toolchains *may* work, but will require forcing the 288build system with a special option and is not really a supported host platform. 289Also note that older versions of these compilers have often crashed or 290miscompiled LLVM. 291 292For less widely used host toolchains such as ICC or xlC, be aware that a very 293recent version may be required to support all of the C++ features used in LLVM. 294 295We track certain versions of software that are *known* to fail when used as 296part of the host toolchain. These even include linkers at times. 297 298**GNU ld 2.16.X**. Some 2.16.X versions of the ld linker will produce very long 299warning messages complaining that some "``.gnu.linkonce.t.*``" symbol was 300defined in a discarded section. You can safely ignore these messages as they are 301erroneous and the linkage is correct. These messages disappear using ld 2.17. 302 303**GNU binutils 2.17**: Binutils 2.17 contains `a bug 304<http://sourceware.org/bugzilla/show_bug.cgi?id=3111>`__ which causes huge link 305times (minutes instead of seconds) when building LLVM. We recommend upgrading 306to a newer version (2.17.50.0.4 or later). 307 308**GNU Binutils 2.19.1 Gold**: This version of Gold contained `a bug 309<http://sourceware.org/bugzilla/show_bug.cgi?id=9836>`__ which causes 310intermittent failures when building LLVM with position independent code. The 311symptom is an error about cyclic dependencies. We recommend upgrading to a 312newer version of Gold. 313 314Getting a Modern Host C++ Toolchain 315^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 316 317This section mostly applies to Linux and older BSDs. On Mac OS X, you should 318have a sufficiently modern Xcode, or you will likely need to upgrade until you 319do. Windows does not have a "system compiler", so you must install either Visual 320Studio 2015 or a recent version of mingw64. FreeBSD 10.0 and newer have a modern 321Clang as the system compiler. 322 323However, some Linux distributions and some other or older BSDs sometimes have 324extremely old versions of GCC. These steps attempt to help you upgrade you 325compiler even on such a system. However, if at all possible, we encourage you 326to use a recent version of a distribution with a modern system compiler that 327meets these requirements. Note that it is tempting to install a prior 328version of Clang and libc++ to be the host compiler, however libc++ was not 329well tested or set up to build on Linux until relatively recently. As 330a consequence, this guide suggests just using libstdc++ and a modern GCC as the 331initial host in a bootstrap, and then using Clang (and potentially libc++). 332 333The first step is to get a recent GCC toolchain installed. The most common 334distribution on which users have struggled with the version requirements is 335Ubuntu Precise, 12.04 LTS. For this distribution, one easy option is to install 336the `toolchain testing PPA`_ and use it to install a modern GCC. There is 337a really nice discussions of this on the `ask ubuntu stack exchange`_. However, 338not all users can use PPAs and there are many other distributions, so it may be 339necessary (or just useful, if you're here you *are* doing compiler development 340after all) to build and install GCC from source. It is also quite easy to do 341these days. 342 343.. _toolchain testing PPA: 344 https://launchpad.net/~ubuntu-toolchain-r/+archive/test 345.. _ask ubuntu stack exchange: 346 http://askubuntu.com/questions/271388/how-to-install-gcc-4-8-in-ubuntu-12-04-from-the-terminal 347 348Easy steps for installing GCC 4.8.2: 349 350.. code-block:: console 351 352 % wget https://ftp.gnu.org/gnu/gcc/gcc-4.8.2/gcc-4.8.2.tar.bz2 353 % wget https://ftp.gnu.org/gnu/gcc/gcc-4.8.2/gcc-4.8.2.tar.bz2.sig 354 % wget https://ftp.gnu.org/gnu/gnu-keyring.gpg 355 % signature_invalid=`gpg --verify --no-default-keyring --keyring ./gnu-keyring.gpg gcc-4.8.2.tar.bz2.sig` 356 % if [ $signature_invalid ]; then echo "Invalid signature" ; exit 1 ; fi 357 % tar -xvjf gcc-4.8.2.tar.bz2 358 % cd gcc-4.8.2 359 % ./contrib/download_prerequisites 360 % cd .. 361 % mkdir gcc-4.8.2-build 362 % cd gcc-4.8.2-build 363 % $PWD/../gcc-4.8.2/configure --prefix=$HOME/toolchains --enable-languages=c,c++ 364 % make -j$(nproc) 365 % make install 366 367For more details, check out the excellent `GCC wiki entry`_, where I got most 368of this information from. 369 370.. _GCC wiki entry: 371 http://gcc.gnu.org/wiki/InstallingGCC 372 373Once you have a GCC toolchain, configure your build of LLVM to use the new 374toolchain for your host compiler and C++ standard library. Because the new 375version of libstdc++ is not on the system library search path, you need to pass 376extra linker flags so that it can be found at link time (``-L``) and at runtime 377(``-rpath``). If you are using CMake, this invocation should produce working 378binaries: 379 380.. code-block:: console 381 382 % mkdir build 383 % cd build 384 % CC=$HOME/toolchains/bin/gcc CXX=$HOME/toolchains/bin/g++ \ 385 cmake .. -DCMAKE_CXX_LINK_FLAGS="-Wl,-rpath,$HOME/toolchains/lib64 -L$HOME/toolchains/lib64" 386 387If you fail to set rpath, most LLVM binaries will fail on startup with a message 388from the loader similar to ``libstdc++.so.6: version `GLIBCXX_3.4.20' not 389found``. This means you need to tweak the -rpath linker flag. 390 391When you build Clang, you will need to give *it* access to modern C++11 392standard library in order to use it as your new host in part of a bootstrap. 393There are two easy ways to do this, either build (and install) libc++ along 394with Clang and then use it with the ``-stdlib=libc++`` compile and link flag, 395or install Clang into the same prefix (``$HOME/toolchains`` above) as GCC. 396Clang will look within its own prefix for libstdc++ and use it if found. You 397can also add an explicit prefix for Clang to look in for a GCC toolchain with 398the ``--gcc-toolchain=/opt/my/gcc/prefix`` flag, passing it to both compile and 399link commands when using your just-built-Clang to bootstrap. 400 401.. _Getting Started with LLVM: 402 403Getting Started with LLVM 404========================= 405 406The remainder of this guide is meant to get you up and running with LLVM and to 407give you some basic information about the LLVM environment. 408 409The later sections of this guide describe the `general layout`_ of the LLVM 410source tree, a `simple example`_ using the LLVM tool chain, and `links`_ to find 411more information about LLVM or to get help via e-mail. 412 413Terminology and Notation 414------------------------ 415 416Throughout this manual, the following names are used to denote paths specific to 417the local system and working environment. *These are not environment variables 418you need to set but just strings used in the rest of this document below*. In 419any of the examples below, simply replace each of these names with the 420appropriate pathname on your local system. All these paths are absolute: 421 422``SRC_ROOT`` 423 424 This is the top level directory of the LLVM source tree. 425 426``OBJ_ROOT`` 427 428 This is the top level directory of the LLVM object tree (i.e. the tree where 429 object files and compiled programs will be placed. It can be the same as 430 SRC_ROOT). 431 432Unpacking the LLVM Archives 433--------------------------- 434 435If you have the LLVM distribution, you will need to unpack it before you can 436begin to compile it. LLVM is distributed as a set of two files: the LLVM suite 437and the LLVM GCC front end compiled for your platform. There is an additional 438test suite that is optional. Each file is a TAR archive that is compressed with 439the gzip program. 440 441The files are as follows, with *x.y* marking the version number: 442 443``llvm-x.y.tar.gz`` 444 445 Source release for the LLVM libraries and tools. 446 447``llvm-test-x.y.tar.gz`` 448 449 Source release for the LLVM test-suite. 450 451.. _checkout: 452 453Checkout LLVM from Subversion 454----------------------------- 455 456If you have access to our Subversion repository, you can get a fresh copy of the 457entire source code. All you need to do is check it out from Subversion as 458follows: 459 460* ``cd where-you-want-llvm-to-live`` 461* Read-Only: ``svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm`` 462* Read-Write: ``svn co https://user@llvm.org/svn/llvm-project/llvm/trunk llvm`` 463 464This will create an '``llvm``' directory in the current directory and fully 465populate it with the LLVM source code, Makefiles, test directories, and local 466copies of documentation files. 467 468If you want to get a specific release (as opposed to the most recent revision), 469you can check it out from the '``tags``' directory (instead of '``trunk``'). The 470following releases are located in the following subdirectories of the '``tags``' 471directory: 472 473* Release 3.5.0 and later: **RELEASE_350/final** and so on 474* Release 2.9 through 3.4: **RELEASE_29/final** and so on 475* Release 1.1 through 2.8: **RELEASE_11** and so on 476* Release 1.0: **RELEASE_1** 477 478If you would like to get the LLVM test suite (a separate package as of 1.4), you 479get it from the Subversion repository: 480 481.. code-block:: console 482 483 % cd llvm/projects 484 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite 485 486By placing it in the ``llvm/projects``, it will be automatically configured by 487the LLVM cmake configuration. 488 489Git Mirror 490---------- 491 492Git mirrors are available for a number of LLVM subprojects. These mirrors sync 493automatically with each Subversion commit and contain all necessary git-svn 494marks (so, you can recreate git-svn metadata locally). Note that right now 495mirrors reflect only ``trunk`` for each project. 496 497.. note:: 498 499 On Windows, first you will want to do ``git config --global core.autocrlf 500 false`` before you clone. This goes a long way toward ensuring that 501 line-endings will be handled correctly (the LLVM project mostly uses Linux 502 line-endings). 503 504You can do the read-only Git clone of LLVM via: 505 506.. code-block:: console 507 508 % git clone https://git.llvm.org/git/llvm.git/ 509 510If you want to check out clang too, run: 511 512.. code-block:: console 513 514 % cd llvm/tools 515 % git clone https://git.llvm.org/git/clang.git/ 516 517If you want to check out compiler-rt (required to build the sanitizers), run: 518 519.. code-block:: console 520 521 % cd llvm/projects 522 % git clone https://git.llvm.org/git/compiler-rt.git/ 523 524If you want to check out libomp (required for OpenMP support), run: 525 526.. code-block:: console 527 528 % cd llvm/projects 529 % git clone https://git.llvm.org/git/openmp.git/ 530 531If you want to check out libcxx and libcxxabi (optional), run: 532 533.. code-block:: console 534 535 % cd llvm/projects 536 % git clone https://git.llvm.org/git/libcxx.git/ 537 % git clone https://git.llvm.org/git/libcxxabi.git/ 538 539If you want to check out the Test Suite Source Code (optional), run: 540 541.. code-block:: console 542 543 % cd llvm/projects 544 % git clone https://git.llvm.org/git/test-suite.git/ 545 546Since the upstream repository is in Subversion, you should use ``git 547pull --rebase`` instead of ``git pull`` to avoid generating a non-linear history 548in your clone. To configure ``git pull`` to pass ``--rebase`` by default on the 549master branch, run the following command: 550 551.. code-block:: console 552 553 % git config branch.master.rebase true 554 555Sending patches with Git 556^^^^^^^^^^^^^^^^^^^^^^^^ 557 558Please read `Developer Policy <DeveloperPolicy.html#one-off-patches>`_, too. 559 560Assume ``master`` points the upstream and ``mybranch`` points your working 561branch, and ``mybranch`` is rebased onto ``master``. At first you may check 562sanity of whitespaces: 563 564.. code-block:: console 565 566 % git diff --check master..mybranch 567 568The easiest way to generate a patch is as below: 569 570.. code-block:: console 571 572 % git diff master..mybranch > /path/to/mybranch.diff 573 574It is a little different from svn-generated diff. git-diff-generated diff has 575prefixes like ``a/`` and ``b/``. Don't worry, most developers might know it 576could be accepted with ``patch -p1 -N``. 577 578But you may generate patchset with git-format-patch. It generates by-each-commit 579patchset. To generate patch files to attach to your article: 580 581.. code-block:: console 582 583 % git format-patch --no-attach master..mybranch -o /path/to/your/patchset 584 585If you would like to send patches directly, you may use git-send-email or 586git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts]. 587 588.. code-block:: console 589 590 % git format-patch --attach master..mybranch --stdout | git imap-send 591 592Then, your .git/config should have [imap] sections. 593 594.. code-block:: ini 595 596 [imap] 597 host = imaps://imap.gmail.com 598 user = your.gmail.account@gmail.com 599 pass = himitsu! 600 port = 993 601 sslverify = false 602 ; in English 603 folder = "[Gmail]/Drafts" 604 ; example for Japanese, "Modified UTF-7" encoded. 605 folder = "[Gmail]/&Tgtm+DBN-" 606 ; example for Traditional Chinese 607 folder = "[Gmail]/&g0l6Pw-" 608 609.. _developers-work-with-git-svn: 610 611For developers to work with git-svn 612^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 613 614To set up clone from which you can submit code using ``git-svn``, run: 615 616.. code-block:: console 617 618 % git clone https://git.llvm.org/git/llvm.git/ 619 % cd llvm 620 % git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username> 621 % git config svn-remote.svn.fetch :refs/remotes/origin/master 622 % git svn rebase -l # -l avoids fetching ahead of the git mirror. 623 624 # If you have clang too: 625 % cd tools 626 % git clone https://git.llvm.org/git/clang.git/ 627 % cd clang 628 % git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username> 629 % git config svn-remote.svn.fetch :refs/remotes/origin/master 630 % git svn rebase -l 631 632Likewise for compiler-rt, libomp and test-suite. 633 634To update this clone without generating git-svn tags that conflict with the 635upstream Git repo, run: 636 637.. code-block:: console 638 639 % git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees. 640 % git checkout master 641 % git svn rebase -l 642 % (cd tools/clang && 643 git checkout master && 644 git svn rebase -l) 645 646Likewise for compiler-rt, libomp and test-suite. 647 648This leaves your working directories on their master branches, so you'll need to 649``checkout`` each working branch individually and ``rebase`` it on top of its 650parent branch. 651 652For those who wish to be able to update an llvm repo/revert patches easily using 653git-svn, please look in the directory for the scripts ``git-svnup`` and 654``git-svnrevert``. 655 656To perform the aforementioned update steps go into your source directory and 657just type ``git-svnup`` or ``git svnup`` and everything will just work. 658 659If one wishes to revert a commit with git-svn, but do not want the git hash to 660escape into the commit message, one can use the script ``git-svnrevert`` or 661``git svnrevert`` which will take in the git hash for the commit you want to 662revert, look up the appropriate svn revision, and output a message where all 663references to the git hash have been replaced with the svn revision. 664 665To commit back changes via git-svn, use ``git svn dcommit``: 666 667.. code-block:: console 668 669 % git svn dcommit 670 671Note that git-svn will create one SVN commit for each Git commit you have pending, 672so squash and edit each commit before executing ``dcommit`` to make sure they all 673conform to the coding standards and the developers' policy. 674 675On success, ``dcommit`` will rebase against the HEAD of SVN, so to avoid conflict, 676please make sure your current branch is up-to-date (via fetch/rebase) before 677proceeding. 678 679The git-svn metadata can get out of sync after you mess around with branches and 680``dcommit``. When that happens, ``git svn dcommit`` stops working, complaining 681about files with uncommitted changes. The fix is to rebuild the metadata: 682 683.. code-block:: console 684 685 % rm -rf .git/svn 686 % git svn rebase -l 687 688Please, refer to the Git-SVN manual (``man git-svn``) for more information. 689 690For developers to work with a git monorepo 691^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 692 693.. note:: 694 695 This set-up is using an unofficial mirror hosted on GitHub, use with caution. 696 697To set up a clone of all the llvm projects using a unified repository: 698 699.. code-block:: console 700 701 % export TOP_LEVEL_DIR=`pwd` 702 % git clone https://github.com/llvm-project/llvm-project-20170507/ llvm-project 703 % cd llvm-project 704 % git config branch.master.rebase true 705 706You can configure various build directory from this clone, starting with a build 707of LLVM alone: 708 709.. code-block:: console 710 711 % cd $TOP_LEVEL_DIR 712 % mkdir llvm-build && cd llvm-build 713 % cmake -GNinja ../llvm-project/llvm 714 715Or lldb: 716 717.. code-block:: console 718 719 % cd $TOP_LEVEL_DIR 720 % mkdir lldb-build && cd lldb-build 721 % cmake -GNinja ../llvm-project/llvm -DLLVM_ENABLE_PROJECTS=lldb 722 723Or a combination of multiple projects: 724 725.. code-block:: console 726 727 % cd $TOP_LEVEL_DIR 728 % mkdir clang-build && cd clang-build 729 % cmake -GNinja ../llvm-project/llvm -DLLVM_ENABLE_PROJECTS="clang;libcxx;libcxxabi" 730 731A helper script is provided in ``llvm/utils/git-svn/git-llvm``. After you add it 732to your path, you can push committed changes upstream with ``git llvm push``. 733 734.. code-block:: console 735 736 % export PATH=$PATH:$TOP_LEVEL_DIR/llvm-project/llvm/utils/git-svn/ 737 % git llvm push 738 739While this is using SVN under the hood, it does not require any interaction from 740you with git-svn. 741After a few minutes, ``git pull`` should get back the changes as they were 742committed. Note that a current limitation is that ``git`` does not directly 743record file rename, and thus it is propagated to SVN as a combination of 744delete-add instead of a file rename. 745 746The SVN revision of each monorepo commit can be found in the commit notes. git 747does not fetch notes by default. The following commands will fetch the notes and 748configure git to fetch future notes. Use ``git notes show $commit`` to look up 749the SVN revision of a git commit. The notes show up ``git log``, and searching 750the log is currently the recommended way to look up the git commit for a given 751SVN revision. 752 753.. code-block:: console 754 755 % git config --add remote.origin.fetch +refs/notes/commits:refs/notes/commits 756 % git fetch 757 758If you are using `arc` to interact with Phabricator, you need to manually put it 759at the root of the checkout: 760 761.. code-block:: console 762 763 % cd $TOP_LEVEL_DIR 764 % cp llvm/.arcconfig ./ 765 % mkdir -p .git/info/ 766 % echo .arcconfig >> .git/info/exclude 767 768 769Local LLVM Configuration 770------------------------ 771 772Once checked out from the Subversion repository, the LLVM suite source code must 773be configured before being built. This process uses CMake. 774Unlinke the normal ``configure`` script, CMake 775generates the build files in whatever format you request as well as various 776``*.inc`` files, and ``llvm/include/Config/config.h``. 777 778Variables are passed to ``cmake`` on the command line using the format 779``-D<variable name>=<value>``. The following variables are some common options 780used by people developing LLVM. 781 782+-------------------------+----------------------------------------------------+ 783| Variable | Purpose | 784+=========================+====================================================+ 785| CMAKE_C_COMPILER | Tells ``cmake`` which C compiler to use. By | 786| | default, this will be /usr/bin/cc. | 787+-------------------------+----------------------------------------------------+ 788| CMAKE_CXX_COMPILER | Tells ``cmake`` which C++ compiler to use. By | 789| | default, this will be /usr/bin/c++. | 790+-------------------------+----------------------------------------------------+ 791| CMAKE_BUILD_TYPE | Tells ``cmake`` what type of build you are trying | 792| | to generate files for. Valid options are Debug, | 793| | Release, RelWithDebInfo, and MinSizeRel. Default | 794| | is Debug. | 795+-------------------------+----------------------------------------------------+ 796| CMAKE_INSTALL_PREFIX | Specifies the install directory to target when | 797| | running the install action of the build files. | 798+-------------------------+----------------------------------------------------+ 799| LLVM_TARGETS_TO_BUILD | A semicolon delimited list controlling which | 800| | targets will be built and linked into llc. This is | 801| | equivalent to the ``--enable-targets`` option in | 802| | the configure script. The default list is defined | 803| | as ``LLVM_ALL_TARGETS``, and can be set to include | 804| | out-of-tree targets. The default value includes: | 805| | ``AArch64, AMDGPU, ARM, BPF, Hexagon, Mips, | 806| | MSP430, NVPTX, PowerPC, Sparc, SystemZ, X86, | 807| | XCore``. | 808+-------------------------+----------------------------------------------------+ 809| LLVM_ENABLE_DOXYGEN | Build doxygen-based documentation from the source | 810| | code This is disabled by default because it is | 811| | slow and generates a lot of output. | 812+-------------------------+----------------------------------------------------+ 813| LLVM_ENABLE_SPHINX | Build sphinx-based documentation from the source | 814| | code. This is disabled by default because it is | 815| | slow and generates a lot of output. Sphinx version | 816| | 1.5 or later recommended. | 817+-------------------------+----------------------------------------------------+ 818| LLVM_BUILD_LLVM_DYLIB | Generate libLLVM.so. This library contains a | 819| | default set of LLVM components that can be | 820| | overridden with ``LLVM_DYLIB_COMPONENTS``. The | 821| | default contains most of LLVM and is defined in | 822| | ``tools/llvm-shlib/CMakelists.txt``. | 823+-------------------------+----------------------------------------------------+ 824| LLVM_OPTIMIZED_TABLEGEN | Builds a release tablegen that gets used during | 825| | the LLVM build. This can dramatically speed up | 826| | debug builds. | 827+-------------------------+----------------------------------------------------+ 828 829To configure LLVM, follow these steps: 830 831#. Change directory into the object root directory: 832 833 .. code-block:: console 834 835 % cd OBJ_ROOT 836 837#. Run the ``cmake``: 838 839 .. code-block:: console 840 841 % cmake -G "Unix Makefiles" -DCMAKE_INSTALL_PREFIX=/install/path 842 [other options] SRC_ROOT 843 844Compiling the LLVM Suite Source Code 845------------------------------------ 846 847Unlike with autotools, with CMake your build type is defined at configuration. 848If you want to change your build type, you can re-run cmake with the following 849invocation: 850 851 .. code-block:: console 852 853 % cmake -G "Unix Makefiles" -DCMAKE_BUILD_TYPE=type SRC_ROOT 854 855Between runs, CMake preserves the values set for all options. CMake has the 856following build types defined: 857 858Debug 859 860 These builds are the default. The build system will compile the tools and 861 libraries unoptimized, with debugging information, and asserts enabled. 862 863Release 864 865 For these builds, the build system will compile the tools and libraries 866 with optimizations enabled and not generate debug info. CMakes default 867 optimization level is -O3. This can be configured by setting the 868 ``CMAKE_CXX_FLAGS_RELEASE`` variable on the CMake command line. 869 870RelWithDebInfo 871 872 These builds are useful when debugging. They generate optimized binaries with 873 debug information. CMakes default optimization level is -O2. This can be 874 configured by setting the ``CMAKE_CXX_FLAGS_RELWITHDEBINFO`` variable on the 875 CMake command line. 876 877Once you have LLVM configured, you can build it by entering the *OBJ_ROOT* 878directory and issuing the following command: 879 880.. code-block:: console 881 882 % make 883 884If the build fails, please `check here`_ to see if you are using a version of 885GCC that is known not to compile LLVM. 886 887If you have multiple processors in your machine, you may wish to use some of the 888parallel build options provided by GNU Make. For example, you could use the 889command: 890 891.. code-block:: console 892 893 % make -j2 894 895There are several special targets which are useful when working with the LLVM 896source code: 897 898``make clean`` 899 900 Removes all files generated by the build. This includes object files, 901 generated C/C++ files, libraries, and executables. 902 903``make install`` 904 905 Installs LLVM header files, libraries, tools, and documentation in a hierarchy 906 under ``$PREFIX``, specified with ``CMAKE_INSTALL_PREFIX``, which 907 defaults to ``/usr/local``. 908 909``make docs-llvm-html`` 910 911 If configured with ``-DLLVM_ENABLE_SPHINX=On``, this will generate a directory 912 at ``OBJ_ROOT/docs/html`` which contains the HTML formatted documentation. 913 914Cross-Compiling LLVM 915-------------------- 916 917It is possible to cross-compile LLVM itself. That is, you can create LLVM 918executables and libraries to be hosted on a platform different from the platform 919where they are built (a Canadian Cross build). To generate build files for 920cross-compiling CMake provides a variable ``CMAKE_TOOLCHAIN_FILE`` which can 921define compiler flags and variables used during the CMake test operations. 922 923The result of such a build is executables that are not runnable on the build 924host but can be executed on the target. As an example the following CMake 925invocation can generate build files targeting iOS. This will work on Mac OS X 926with the latest Xcode: 927 928.. code-block:: console 929 930 % cmake -G "Ninja" -DCMAKE_OSX_ARCHITECTURES="armv7;armv7s;arm64" 931 -DCMAKE_TOOLCHAIN_FILE=<PATH_TO_LLVM>/cmake/platforms/iOS.cmake 932 -DCMAKE_BUILD_TYPE=Release -DLLVM_BUILD_RUNTIME=Off -DLLVM_INCLUDE_TESTS=Off 933 -DLLVM_INCLUDE_EXAMPLES=Off -DLLVM_ENABLE_BACKTRACES=Off [options] 934 <PATH_TO_LLVM> 935 936Note: There are some additional flags that need to be passed when building for 937iOS due to limitations in the iOS SDK. 938 939Check :doc:`HowToCrossCompileLLVM` and `Clang docs on how to cross-compile in general 940<http://clang.llvm.org/docs/CrossCompilation.html>`_ for more information 941about cross-compiling. 942 943The Location of LLVM Object Files 944--------------------------------- 945 946The LLVM build system is capable of sharing a single LLVM source tree among 947several LLVM builds. Hence, it is possible to build LLVM for several different 948platforms or configurations using the same source tree. 949 950* Change directory to where the LLVM object files should live: 951 952 .. code-block:: console 953 954 % cd OBJ_ROOT 955 956* Run ``cmake``: 957 958 .. code-block:: console 959 960 % cmake -G "Unix Makefiles" SRC_ROOT 961 962The LLVM build will create a structure underneath *OBJ_ROOT* that matches the 963LLVM source tree. At each level where source files are present in the source 964tree there will be a corresponding ``CMakeFiles`` directory in the *OBJ_ROOT*. 965Underneath that directory there is another directory with a name ending in 966``.dir`` under which you'll find object files for each source. 967 968For example: 969 970 .. code-block:: console 971 972 % cd llvm_build_dir 973 % find lib/Support/ -name APFloat* 974 lib/Support/CMakeFiles/LLVMSupport.dir/APFloat.cpp.o 975 976Optional Configuration Items 977---------------------------- 978 979If you're running on a Linux system that supports the `binfmt_misc 980<http://en.wikipedia.org/wiki/binfmt_misc>`_ 981module, and you have root access on the system, you can set your system up to 982execute LLVM bitcode files directly. To do this, use commands like this (the 983first command may not be required if you are already using the module): 984 985.. code-block:: console 986 987 % mount -t binfmt_misc none /proc/sys/fs/binfmt_misc 988 % echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register 989 % chmod u+x hello.bc (if needed) 990 % ./hello.bc 991 992This allows you to execute LLVM bitcode files directly. On Debian, you can also 993use this command instead of the 'echo' command above: 994 995.. code-block:: console 996 997 % sudo update-binfmts --install llvm /path/to/lli --magic 'BC' 998 999.. _Program Layout: 1000.. _general layout: 1001 1002Directory Layout 1003================ 1004 1005One useful source of information about the LLVM source base is the LLVM `doxygen 1006<http://www.doxygen.org/>`_ documentation available at 1007`<http://llvm.org/doxygen/>`_. The following is a brief introduction to code 1008layout: 1009 1010``llvm/examples`` 1011----------------- 1012 1013Simple examples using the LLVM IR and JIT. 1014 1015``llvm/include`` 1016---------------- 1017 1018Public header files exported from the LLVM library. The three main subdirectories: 1019 1020``llvm/include/llvm`` 1021 1022 All LLVM-specific header files, and subdirectories for different portions of 1023 LLVM: ``Analysis``, ``CodeGen``, ``Target``, ``Transforms``, etc... 1024 1025``llvm/include/llvm/Support`` 1026 1027 Generic support libraries provided with LLVM but not necessarily specific to 1028 LLVM. For example, some C++ STL utilities and a Command Line option processing 1029 library store header files here. 1030 1031``llvm/include/llvm/Config`` 1032 1033 Header files configured by the ``configure`` script. 1034 They wrap "standard" UNIX and C header files. Source code can include these 1035 header files which automatically take care of the conditional #includes that 1036 the ``configure`` script generates. 1037 1038``llvm/lib`` 1039------------ 1040 1041Most source files are here. By putting code in libraries, LLVM makes it easy to 1042share code among the `tools`_. 1043 1044``llvm/lib/IR/`` 1045 1046 Core LLVM source files that implement core classes like Instruction and 1047 BasicBlock. 1048 1049``llvm/lib/AsmParser/`` 1050 1051 Source code for the LLVM assembly language parser library. 1052 1053``llvm/lib/Bitcode/`` 1054 1055 Code for reading and writing bitcode. 1056 1057``llvm/lib/Analysis/`` 1058 1059 A variety of program analyses, such as Call Graphs, Induction Variables, 1060 Natural Loop Identification, etc. 1061 1062``llvm/lib/Transforms/`` 1063 1064 IR-to-IR program transformations, such as Aggressive Dead Code Elimination, 1065 Sparse Conditional Constant Propagation, Inlining, Loop Invariant Code Motion, 1066 Dead Global Elimination, and many others. 1067 1068``llvm/lib/Target/`` 1069 1070 Files describing target architectures for code generation. For example, 1071 ``llvm/lib/Target/X86`` holds the X86 machine description. 1072 1073``llvm/lib/CodeGen/`` 1074 1075 The major parts of the code generator: Instruction Selector, Instruction 1076 Scheduling, and Register Allocation. 1077 1078``llvm/lib/MC/`` 1079 1080 (FIXME: T.B.D.) ....? 1081 1082``llvm/lib/ExecutionEngine/`` 1083 1084 Libraries for directly executing bitcode at runtime in interpreted and 1085 JIT-compiled scenarios. 1086 1087``llvm/lib/Support/`` 1088 1089 Source code that corresponding to the header files in ``llvm/include/ADT/`` 1090 and ``llvm/include/Support/``. 1091 1092``llvm/projects`` 1093----------------- 1094 1095Projects not strictly part of LLVM but shipped with LLVM. This is also the 1096directory for creating your own LLVM-based projects which leverage the LLVM 1097build system. 1098 1099``llvm/test`` 1100------------- 1101 1102Feature and regression tests and other sanity checks on LLVM infrastructure. These 1103are intended to run quickly and cover a lot of territory without being exhaustive. 1104 1105``test-suite`` 1106-------------- 1107 1108A comprehensive correctness, performance, and benchmarking test suite for LLVM. 1109Comes in a separate Subversion module because not every LLVM user is interested 1110in such a comprehensive suite. For details see the :doc:`Testing Guide 1111<TestingGuide>` document. 1112 1113.. _tools: 1114 1115``llvm/tools`` 1116-------------- 1117 1118Executables built out of the libraries 1119above, which form the main part of the user interface. You can always get help 1120for a tool by typing ``tool_name -help``. The following is a brief introduction 1121to the most important tools. More detailed information is in 1122the `Command Guide <CommandGuide/index.html>`_. 1123 1124``bugpoint`` 1125 1126 ``bugpoint`` is used to debug optimization passes or code generation backends 1127 by narrowing down the given test case to the minimum number of passes and/or 1128 instructions that still cause a problem, whether it is a crash or 1129 miscompilation. See `<HowToSubmitABug.html>`_ for more information on using 1130 ``bugpoint``. 1131 1132``llvm-ar`` 1133 1134 The archiver produces an archive containing the given LLVM bitcode files, 1135 optionally with an index for faster lookup. 1136 1137``llvm-as`` 1138 1139 The assembler transforms the human readable LLVM assembly to LLVM bitcode. 1140 1141``llvm-dis`` 1142 1143 The disassembler transforms the LLVM bitcode to human readable LLVM assembly. 1144 1145``llvm-link`` 1146 1147 ``llvm-link``, not surprisingly, links multiple LLVM modules into a single 1148 program. 1149 1150``lli`` 1151 1152 ``lli`` is the LLVM interpreter, which can directly execute LLVM bitcode 1153 (although very slowly...). For architectures that support it (currently x86, 1154 Sparc, and PowerPC), by default, ``lli`` will function as a Just-In-Time 1155 compiler (if the functionality was compiled in), and will execute the code 1156 *much* faster than the interpreter. 1157 1158``llc`` 1159 1160 ``llc`` is the LLVM backend compiler, which translates LLVM bitcode to a 1161 native code assembly file. 1162 1163``opt`` 1164 1165 ``opt`` reads LLVM bitcode, applies a series of LLVM to LLVM transformations 1166 (which are specified on the command line), and outputs the resultant 1167 bitcode. '``opt -help``' is a good way to get a list of the 1168 program transformations available in LLVM. 1169 1170 ``opt`` can also run a specific analysis on an input LLVM bitcode 1171 file and print the results. Primarily useful for debugging 1172 analyses, or familiarizing yourself with what an analysis does. 1173 1174``llvm/utils`` 1175-------------- 1176 1177Utilities for working with LLVM source code; some are part of the build process 1178because they are code generators for parts of the infrastructure. 1179 1180 1181``codegen-diff`` 1182 1183 ``codegen-diff`` finds differences between code that LLC 1184 generates and code that LLI generates. This is useful if you are 1185 debugging one of them, assuming that the other generates correct output. For 1186 the full user manual, run ```perldoc codegen-diff'``. 1187 1188``emacs/`` 1189 1190 Emacs and XEmacs syntax highlighting for LLVM assembly files and TableGen 1191 description files. See the ``README`` for information on using them. 1192 1193``getsrcs.sh`` 1194 1195 Finds and outputs all non-generated source files, 1196 useful if one wishes to do a lot of development across directories 1197 and does not want to find each file. One way to use it is to run, 1198 for example: ``xemacs `utils/getsources.sh``` from the top of the LLVM source 1199 tree. 1200 1201``llvmgrep`` 1202 1203 Performs an ``egrep -H -n`` on each source file in LLVM and 1204 passes to it a regular expression provided on ``llvmgrep``'s command 1205 line. This is an efficient way of searching the source base for a 1206 particular regular expression. 1207 1208``makellvm`` 1209 1210 Compiles all files in the current directory, then 1211 compiles and links the tool that is the first argument. For example, assuming 1212 you are in ``llvm/lib/Target/Sparc``, if ``makellvm`` is in your 1213 path, running ``makellvm llc`` will make a build of the current 1214 directory, switch to directory ``llvm/tools/llc`` and build it, causing a 1215 re-linking of LLC. 1216 1217``TableGen/`` 1218 1219 Contains the tool used to generate register 1220 descriptions, instruction set descriptions, and even assemblers from common 1221 TableGen description files. 1222 1223``vim/`` 1224 1225 vim syntax-highlighting for LLVM assembly files 1226 and TableGen description files. See the ``README`` for how to use them. 1227 1228.. _simple example: 1229 1230An Example Using the LLVM Tool Chain 1231==================================== 1232 1233This section gives an example of using LLVM with the Clang front end. 1234 1235Example with clang 1236------------------ 1237 1238#. First, create a simple C file, name it 'hello.c': 1239 1240 .. code-block:: c 1241 1242 #include <stdio.h> 1243 1244 int main() { 1245 printf("hello world\n"); 1246 return 0; 1247 } 1248 1249#. Next, compile the C file into a native executable: 1250 1251 .. code-block:: console 1252 1253 % clang hello.c -o hello 1254 1255 .. note:: 1256 1257 Clang works just like GCC by default. The standard -S and -c arguments 1258 work as usual (producing a native .s or .o file, respectively). 1259 1260#. Next, compile the C file into an LLVM bitcode file: 1261 1262 .. code-block:: console 1263 1264 % clang -O3 -emit-llvm hello.c -c -o hello.bc 1265 1266 The -emit-llvm option can be used with the -S or -c options to emit an LLVM 1267 ``.ll`` or ``.bc`` file (respectively) for the code. This allows you to use 1268 the `standard LLVM tools <CommandGuide/index.html>`_ on the bitcode file. 1269 1270#. Run the program in both forms. To run the program, use: 1271 1272 .. code-block:: console 1273 1274 % ./hello 1275 1276 and 1277 1278 .. code-block:: console 1279 1280 % lli hello.bc 1281 1282 The second examples shows how to invoke the LLVM JIT, :doc:`lli 1283 <CommandGuide/lli>`. 1284 1285#. Use the ``llvm-dis`` utility to take a look at the LLVM assembly code: 1286 1287 .. code-block:: console 1288 1289 % llvm-dis < hello.bc | less 1290 1291#. Compile the program to native assembly using the LLC code generator: 1292 1293 .. code-block:: console 1294 1295 % llc hello.bc -o hello.s 1296 1297#. Assemble the native assembly language file into a program: 1298 1299 .. code-block:: console 1300 1301 % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native # On Solaris 1302 1303 % gcc hello.s -o hello.native # On others 1304 1305#. Execute the native code program: 1306 1307 .. code-block:: console 1308 1309 % ./hello.native 1310 1311 Note that using clang to compile directly to native code (i.e. when the 1312 ``-emit-llvm`` option is not present) does steps 6/7/8 for you. 1313 1314Common Problems 1315=============== 1316 1317If you are having problems building or using LLVM, or if you have any other 1318general questions about LLVM, please consult the `Frequently Asked 1319Questions <FAQ.html>`_ page. 1320 1321.. _links: 1322 1323Links 1324===== 1325 1326This document is just an **introduction** on how to use LLVM to do some simple 1327things... there are many more interesting and complicated things that you can do 1328that aren't documented here (but we'll gladly accept a patch if you want to 1329write something up!). For more information about LLVM, check out: 1330 1331* `LLVM Homepage <http://llvm.org/>`_ 1332* `LLVM Doxygen Tree <http://llvm.org/doxygen/>`_ 1333* `Starting a Project that Uses LLVM <http://llvm.org/docs/Projects.html>`_ 1334