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12 Getting Started with the LLVM System
16 <li><a href="#overview">Overview</a>
17 <li><a href="#quickstart">Getting Started Quickly (A Summary)</a>
18 <li><a href="#requirements">Requirements</a>
20 <li><a href="#hardware">Hardware</a></li>
21 <li><a href="#software">Software</a></li>
22 <li><a href="#brokengcc">Broken versions of GCC and other tools</a></li>
25 <li><a href="#starting">Getting Started with LLVM</a>
27 <li><a href="#terminology">Terminology and Notation</a></li>
28 <li><a href="#environment">Setting Up Your Environment</a></li>
29 <li><a href="#unpack">Unpacking the LLVM Archives</a></li>
30 <li><a href="#checkout">Checkout LLVM from Subversion</a></li>
31 <li><a href="#git_mirror">LLVM GIT mirror</a></li>
32 <li><a href="#installcf">Install the GCC Front End</a></li>
33 <li><a href="#config">Local LLVM Configuration</a></li>
34 <li><a href="#compile">Compiling the LLVM Suite Source Code</a></li>
35 <li><a href="#cross-compile">Cross-Compiling LLVM</a></li>
36 <li><a href="#objfiles">The Location of LLVM Object Files</a></li>
37 <li><a href="#optionalconfig">Optional Configuration Items</a></li>
40 <li><a href="#layout">Program layout</a>
42 <li><a href="#examples"><tt>llvm/examples</tt></a></li>
43 <li><a href="#include"><tt>llvm/include</tt></a></li>
44 <li><a href="#lib"><tt>llvm/lib</tt></a></li>
45 <li><a href="#projects"><tt>llvm/projects</tt></a></li>
46 <li><a href="#runtime"><tt>llvm/runtime</tt></a></li>
47 <li><a href="#test"><tt>llvm/test</tt></a></li>
48 <li><a href="#test-suite"><tt>test-suite</tt></a></li>
49 <li><a href="#tools"><tt>llvm/tools</tt></a></li>
50 <li><a href="#utils"><tt>llvm/utils</tt></a></li>
53 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
55 <li><a href="#tutorial4">Example with Clang</a></li>
57 <li><a href="#problems">Common Problems</a>
58 <li><a href="#links">Links</a>
61 <div class="doc_author">
63 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
64 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
65 <a href="http://misha.brukman.net/">Misha Brukman</a>,
66 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
67 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
72 <!-- *********************************************************************** -->
74 <a name="overview">Overview</a>
76 <!-- *********************************************************************** -->
80 <p>Welcome to LLVM! In order to get started, you first need to know some
81 basic information.</p>
83 <p>First, LLVM comes in three pieces. The first piece is the LLVM
84 suite. This contains all of the tools, libraries, and header files
85 needed to use LLVM. It contains an assembler, disassembler, bitcode
86 analyzer and bitcode optimizer. It also contains basic regression tests that
87 can be used to test the LLVM tools and the Clang front end.</p>
89 <p>The second piece is the <a href="http://clang.llvm.org/">Clang</a> front end.
90 This component compiles C, C++, Objective C, and Objective C++ code into LLVM
91 bitcode. Once compiled into LLVM bitcode, a program can be manipulated with the
92 LLVM tools from the LLVM suite.
96 There is a third, optional piece called Test Suite. It is a suite of programs
97 with a testing harness that can be used to further test LLVM's functionality
103 <!-- *********************************************************************** -->
105 <a name="quickstart">Getting Started Quickly (A Summary)</a>
107 <!-- *********************************************************************** -->
111 <p>The LLVM Getting Started documentation may be out of date. So, the Clang
112 <a href="http://clang.llvm.org/get_started.html">Getting Started</a> page might
113 also be a good place to start.</p>
115 <p>Here's the short story for getting up and running quickly with LLVM:</p>
118 <li>Read the documentation.</li>
119 <li>Read the documentation.</li>
120 <li>Remember that you were warned twice about reading the documentation.</li>
124 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
125 <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
131 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
132 <li><tt>cd llvm/tools</tt>
133 <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
137 <li>Checkout Compiler-RT:
139 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
140 <li><tt>cd llvm/projects</tt>
141 <li><tt>svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk
142 compiler-rt</tt></li>
146 <li>Get the Test Suite Source Code <b>[Optional]</b>
148 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
149 <li><tt>cd llvm/projects</tt>
150 <li><tt>svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite</tt></li>
154 <li>Configure and build LLVM and Clang:
156 <li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
157 <li><tt>mkdir build</tt> (for building without polluting the source dir)</li>
158 <li><tt>cd build</tt></li>
159 <li><tt>../llvm/configure [options]</tt></li>
163 <li><tt>--prefix=<i>directory</i></tt> -
164 Specify for <i>directory</i> the full pathname of where you
165 want the LLVM tools and libraries to be installed (default
166 <tt>/usr/local</tt>).</li>
170 <li><tt>--enable-optimized</tt> -
171 Compile with optimizations enabled (default is NO).</li>
175 <li><tt>--enable-assertions</tt> -
176 Compile with assertion checks enabled (default is YES).</li>
179 <li><tt>make [-j]</tt> - The -j specifies the number of jobs (commands) to
180 run simultaneously. This builds both LLVM and Clang for Debug+Asserts mode.
181 The --enabled-optimized configure option is used to specify a Release build.</li>
182 <li><tt>make check-all</tt> -
183 This run the regression tests to ensure everything is in working order.</li>
184 <li><tt>make update</tt> -
185 This command is used to update all the svn repositories at once, rather then
186 having to <tt>cd</tt> into the individual repositories and running
187 <tt>svn update</tt>.</li>
188 <li>It is also possible to use CMake instead of the makefiles. With CMake
189 it is also possible to generate project files for several IDEs: Eclipse
190 CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.</li>
191 <li>If you get an "internal compiler error (ICE)" or test failures, see
192 <a href="#brokengcc">below</a>.</li>
200 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
201 detailed information on configuring and compiling LLVM. See <a
202 href="#environment">Setting Up Your Environment</a> for tips that simplify
203 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
204 Layout</a> to learn about the layout of the source code tree.</p>
208 <!-- *********************************************************************** -->
210 <a name="requirements">Requirements</a>
212 <!-- *********************************************************************** -->
216 <p>Before you begin to use the LLVM system, review the requirements given below.
217 This may save you some trouble by knowing ahead of time what hardware and
218 software you will need.</p>
220 <!-- ======================================================================= -->
222 <a name="hardware">Hardware</a>
227 <p>LLVM is known to work on the following platforms:</p>
229 <table cellpadding="3" summary="Known LLVM platforms">
237 <td>x86<sup><a href="#pf_1">1</a></sup></td>
242 <td>x86<sup><a href="#pf_1">1</a></sup></td>
252 <td>V9 (Ultrasparc)</td>
257 <td>x86<sup><a href="#pf_1">1</a></sup></td>
266 <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
271 <td>MacOS X<sup><a href="#pf_2">2</a>,<a href="#pf_9">9</a></sup></td>
276 <td>Cygwin/Win32</td>
277 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a>,
278 <a href="#pf_11">11</a></sup></td>
279 <td>GCC 3.4.X, binutils 2.20</td>
283 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,
284 <a href="#pf_8">8</a>, <a href="#pf_10">10</a>,
285 <a href="#pf_11">11</a></sup></td>
286 <td>GCC 3.4.X, binutils 2.20</td>
290 <p>LLVM has partial support for the following platforms:</p>
292 <table summary="LLVM partial platform support">
300 <td>x86<sup><a href="#pf_1">1</a></sup></td>
301 <td>Visual Studio 2008 or higher<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
303 <td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
308 <td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
314 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
319 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
320 <td>Itanium (IA-64)</td>
324 <td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
325 <td>Itanium (IA-64)</td>
331 <td>mingw-w64's GCC-4.5.x<sup><a href="#pf_12">12</a></sup></td>
337 <div class="doc_notes">
339 <li><a name="pf_1">Code generation supported for Pentium processors and
341 <li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
342 <li><a name="pf_3">No native code generation</a></li>
343 <li><a name="pf_4">Build is not complete: one or more tools do not link or function</a></li>
344 <li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
345 <li><a name="pf_6">The port is done using the MSYS shell.</a></li>
346 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
347 <li><a name="pf_8">Binutils 2.20 or later is required to build the assembler
348 generated by LLVM properly.</a></li>
349 <li><a name="pf_9">XCode 2.5 and gcc 4.0.1</a> (Apple Build 5370) will trip
350 internal LLVM assert messages when compiled for Release at optimization
351 levels greater than 0 (i.e., <i>"-O1"</i> and higher).
352 Add <i>OPTIMIZE_OPTION="-O0"</i> to the build command line
353 if compiling for LLVM Release or bootstrapping the LLVM toolchain.</li>
354 <li><a name="pf_10">For MSYS/MinGW on Windows, be sure to install the MSYS
355 version of the perl package, and be sure it appears in your path
356 before any Windows-based versions such as Strawberry Perl and
357 ActivePerl, as these have Windows-specifics that will cause the
358 build to fail.</a></li>
359 <li><a name="pf_11">To use LLVM modules on Win32-based system,
360 you may configure LLVM with <i>"--enable-shared"</i>.</a></li>
361 <li><a name="pf_12">To compile SPU backend, you need to add
362 <tt>"LDFLAGS=-Wl,--stack,16777216"</tt> to configure.</a></li>
366 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
367 mode, depending on the system (it is so large because of all the debugging
368 information and the fact that the libraries are statically linked into multiple
369 tools). If you do not need many of the tools and you are space-conscious, you
370 can pass <tt>ONLY_TOOLS="tools you need"</tt> to make. The Release build
371 requires considerably less space.</p>
373 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
374 guaranteed to do so. If compilation is successful, the LLVM utilities should be
375 able to assemble, disassemble, analyze, and optimize LLVM bitcode. Code
376 generation should work as well, although the generated native code may not work
377 on your platform.</p>
379 <p>The GCC front end is not very portable at the moment. If you want to get it
380 to work on another platform, you can download a copy of the source and <a
381 href="GCCFEBuildInstrs.html">try to compile it</a> on your platform.</p>
385 <!-- ======================================================================= -->
387 <a name="software">Software</a>
390 <p>Compiling LLVM requires that you have several software packages
391 installed. The table below lists those required packages. The Package column
392 is the usual name for the software package that LLVM depends on. The Version
393 column provides "known to work" versions of the package. The Notes column
394 describes how LLVM uses the package and provides other details.</p>
395 <table summary="Packages required to compile LLVM">
396 <tr><th>Package</th><th>Version</th><th>Notes</th></tr>
399 <td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
400 <td>3.79, 3.79.1</td>
401 <td>Makefile/build processor</td>
405 <td><a href="http://gcc.gnu.org/">GCC</a></td>
407 <td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
411 <td><a href="http://www.gnu.org/software/texinfo/">TeXinfo</a></td>
413 <td>For building the CFE</td>
417 <td><a href="http://subversion.tigris.org/project_packages.html">SVN</a></td>
419 <td>Subversion access to LLVM<sup><a href="#sf2">2</a></sup></td>
424 Are DejaGnu and expect obsolete?
425 Shall we mention Python? -->
428 <td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
430 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
434 <td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
436 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
440 <td><a href="http://expect.nist.gov/">expect</a></td>
442 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
446 <td><a href="http://www.perl.com/download.csp">perl</a></td>
452 <td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
454 <td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
458 <td><a href="http://www.gnu.org/software/autoconf/">GNU Autoconf</a></td>
460 <td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
464 <td><a href="http://www.gnu.org/software/automake/">GNU Automake</a></td>
466 <td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
470 <td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
472 <td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
478 <div class="doc_notes">
480 <li><a name="sf1">Only the C and C++ languages are needed so there's no
481 need to build the other languages for LLVM's purposes.</a> See
482 <a href="#brokengcc">below</a> for specific version info.</li>
483 <li><a name="sf2">You only need Subversion if you intend to build from the
484 latest LLVM sources. If you're working from a release distribution, you
485 don't need Subversion.</a></li>
486 <li><a name="sf3">Only needed if you want to run the automated test
487 suite in the <tt>llvm/test</tt> directory.</a></li>
488 <li><a name="sf4">If you want to make changes to the configure scripts,
489 you will need GNU autoconf (2.60), and consequently, GNU M4 (version 1.4
490 or higher). You will also need automake (1.9.6). We only use aclocal
491 from that package.</a></li>
495 <p>Additionally, your compilation host is expected to have the usual
496 plethora of Unix utilities. Specifically:</p>
498 <li><b>ar</b> - archive library builder</li>
499 <li><b>bzip2*</b> - bzip2 command for distribution generation</li>
500 <li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
501 <li><b>chmod</b> - change permissions on a file</li>
502 <li><b>cat</b> - output concatenation utility</li>
503 <li><b>cp</b> - copy files</li>
504 <li><b>date</b> - print the current date/time </li>
505 <li><b>echo</b> - print to standard output</li>
506 <li><b>egrep</b> - extended regular expression search utility</li>
507 <li><b>find</b> - find files/dirs in a file system</li>
508 <li><b>grep</b> - regular expression search utility</li>
509 <li><b>gzip*</b> - gzip command for distribution generation</li>
510 <li><b>gunzip*</b> - gunzip command for distribution checking</li>
511 <li><b>install</b> - install directories/files </li>
512 <li><b>mkdir</b> - create a directory</li>
513 <li><b>mv</b> - move (rename) files</li>
514 <li><b>ranlib</b> - symbol table builder for archive libraries</li>
515 <li><b>rm</b> - remove (delete) files and directories</li>
516 <li><b>sed</b> - stream editor for transforming output</li>
517 <li><b>sh</b> - Bourne shell for make build scripts</li>
518 <li><b>tar</b> - tape archive for distribution generation</li>
519 <li><b>test</b> - test things in file system</li>
520 <li><b>unzip*</b> - unzip command for distribution checking</li>
521 <li><b>zip*</b> - zip command for distribution generation</li>
525 <!-- ======================================================================= -->
527 <a name="brokengcc">Broken versions of GCC and other tools</a>
532 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
533 bugs in the compiler. In particular, several versions of GCC crash when trying
534 to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang.
535 Other versions of GCC will probably work as well. GCC versions listed
536 here are known to not work. If you are using one of these versions, please try
537 to upgrade your GCC to something more recent. If you run into a problem with a
538 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
539 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
540 of GCC you are using.
543 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
544 problems in the STL that effectively prevent it from compiling LLVM.
547 <p><b>GCC 3.2.2 and 3.2.3</b>: These versions of GCC fails to compile LLVM with
548 a bogus template error. This was fixed in later GCCs.</p>
550 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
551 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
552 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
554 <p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
555 Cygwin does not work. Please <a href="GCCFEBuildInstrs.html#cygwin">upgrade
556 to a newer version</a> if possible.</p>
557 <p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
558 possibly others) does not compile LLVM correctly (it appears that exception
559 handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
560 to a newer version of GCC.</p>
561 <p><b>GCC 3.4.0 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
562 code generator, causing an infinite loop in the llvm-gcc build when built
563 with optimizations enabled (i.e. a release build).</p>
564 <p><b>GCC 3.4.2 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
565 code generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0)
566 correctly compiles LLVM at -O2. A work around is to build release LLVM
567 builds with "make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ..."</p>
568 <p><b>GCC 3.4.x on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1056">
569 miscompiles portions of LLVM</a>.</p>
570 <p><b>GCC 3.4.4 (CodeSourcery ARM 2005q3-2)</b>: this compiler miscompiles LLVM
571 when building with optimizations enabled. It appears to work with
572 "<tt>make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1</tt>" or build a debug
574 <p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
576 <p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
577 default with ENABLE_OPTIMIZED=1. To work around this, build with
578 "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
579 <p><b>GCC 4.1.1</b>: GCC fails to build LLVM with template concept check errors
580 compiling some files. At the time of this writing, GCC mainline (4.2)
581 did not share the problem.</p>
582 <p><b>GCC 4.1.1 on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1063">
583 miscompiles portions of LLVM</a> when compiling llvm itself into 64-bit
584 code. LLVM will appear to mostly work but will be buggy, e.g. failing
585 portions of its testsuite.</p>
586 <p><b>GCC 4.1.2 on OpenSUSE</b>: Seg faults during libstdc++ build and on x86_64
587 platforms compiling md5.c gets a mangled constant.</p>
588 <p><b>GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian</b>: Appears
589 to miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining
590 about symbols remaining in the table on destruction.</p>
591 <p><b>GCC 4.1.2 20071124 (Red Hat 4.1.2-42)</b>: Suffers from the same symptoms
592 as the previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).</p>
593 <p><b>Cygwin GCC 4.3.2 20080827 (beta) 2</b>:
594 Users <a href="http://llvm.org/PR4145">reported</a> various problems related
595 with link errors when using this GCC version.</p>
596 <p><b>Debian GCC 4.3.2 on X86</b>: Crashes building some files in LLVM 2.6.</p>
597 <p><b>GCC 4.3.3 (Debian 4.3.3-10) on ARM</b>: Miscompiles parts of LLVM 2.6
598 when optimizations are turned on. The symptom is an infinite loop in
599 FoldingSetImpl::RemoveNode while running the code generator.</p>
600 <p><b>GCC 4.3.5 and GCC 4.4.5 on ARM</b>: These can miscompile <tt>value >>
601 1</tt> even at -O0. A test failure in <tt>test/Assembler/alignstack.ll</tt> is
602 one symptom of the problem.
603 <p><b>GNU ld 2.16.X</b>. Some 2.16.X versions of the ld linker will produce very
604 long warning messages complaining that some ".gnu.linkonce.t.*" symbol was
605 defined in a discarded section. You can safely ignore these messages as they are
606 erroneous and the linkage is correct. These messages disappear using ld
609 <p><b>GNU binutils 2.17</b>: Binutils 2.17 contains <a
610 href="http://sourceware.org/bugzilla/show_bug.cgi?id=3111">a bug</a> which
611 causes huge link times (minutes instead of seconds) when building LLVM. We
612 recommend upgrading to a newer version (2.17.50.0.4 or later).</p>
614 <p><b>GNU Binutils 2.19.1 Gold</b>: This version of Gold contained
615 <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=9836">a bug</a>
616 which causes intermittent failures when building LLVM with position independent
617 code. The symptom is an error about cyclic dependencies. We recommend
618 upgrading to a newer version of Gold.</p>
624 <!-- *********************************************************************** -->
626 <a name="starting">Getting Started with LLVM</a>
628 <!-- *********************************************************************** -->
632 <p>The remainder of this guide is meant to get you up and running with
633 LLVM and to give you some basic information about the LLVM environment.</p>
635 <p>The later sections of this guide describe the <a
636 href="#layout">general layout</a> of the the LLVM source tree, a <a
637 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
638 href="#links">links</a> to find more information about LLVM or to get
641 <!-- ======================================================================= -->
643 <a name="terminology">Terminology and Notation</a>
648 <p>Throughout this manual, the following names are used to denote paths
649 specific to the local system and working environment. <i>These are not
650 environment variables you need to set but just strings used in the rest
651 of this document below</i>. In any of the examples below, simply replace
652 each of these names with the appropriate pathname on your local system.
653 All these paths are absolute:</p>
658 This is the top level directory of the LLVM source tree.
663 This is the top level directory of the LLVM object tree (i.e. the
664 tree where object files and compiled programs will be placed. It
665 can be the same as SRC_ROOT).
670 This is where the LLVM GCC Front End is installed.
672 For the pre-built GCC front end binaries, the LLVMGCCDIR is
673 <tt>llvm-gcc/<i>platform</i>/llvm-gcc</tt>.
678 <!-- ======================================================================= -->
680 <a name="environment">Setting Up Your Environment</a>
686 In order to compile and use LLVM, you may need to set some environment
690 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bitcode/libs</tt></dt>
691 <dd>[Optional] This environment variable helps LLVM linking tools find the
692 locations of your bitcode libraries. It is provided only as a
693 convenience since you can specify the paths using the -L options of the
694 tools and the C/C++ front-end will automatically use the bitcode files
696 <tt>lib</tt> directory.</dd>
701 <!-- ======================================================================= -->
703 <a name="unpack">Unpacking the LLVM Archives</a>
709 If you have the LLVM distribution, you will need to unpack it before you
710 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
711 suite and the LLVM GCC front end compiled for your platform. There is an
712 additional test suite that is optional. Each file is a TAR archive that is
713 compressed with the gzip program.
716 <p>The files are as follows, with <em>x.y</em> marking the version number:
718 <dt><tt>llvm-x.y.tar.gz</tt></dt>
719 <dd>Source release for the LLVM libraries and tools.<br></dd>
721 <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
722 <dd>Source release for the LLVM test-suite.</dd>
724 <dt><tt>llvm-gcc-4.2-x.y.source.tar.gz</tt></dt>
725 <dd>Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
726 directory for build instructions.<br></dd>
728 <dt><tt>llvm-gcc-4.2-x.y-platform.tar.gz</tt></dt>
729 <dd>Binary release of the llvm-gcc-4.2 front end for a specific platform.<br></dd>
735 <!-- ======================================================================= -->
737 <a name="checkout">Checkout LLVM from Subversion</a>
742 <p>If you have access to our Subversion repository, you can get a fresh copy of
743 the entire source code. All you need to do is check it out from Subversion as
747 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
748 <li>Read-Only: <tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
749 <li>Read-Write:<tt>svn co https://user@llvm.org/svn/llvm-project/llvm/trunk
754 <p>This will create an '<tt>llvm</tt>' directory in the current
755 directory and fully populate it with the LLVM source code, Makefiles,
756 test directories, and local copies of documentation files.</p>
758 <p>If you want to get a specific release (as opposed to the most recent
759 revision), you can checkout it from the '<tt>tags</tt>' directory (instead of
760 '<tt>trunk</tt>'). The following releases are located in the following
761 subdirectories of the '<tt>tags</tt>' directory:</p>
764 <li>Release 2.9: <b>RELEASE_29/final</b></li>
765 <li>Release 2.8: <b>RELEASE_28</b></li>
766 <li>Release 2.7: <b>RELEASE_27</b></li>
767 <li>Release 2.6: <b>RELEASE_26</b></li>
768 <li>Release 2.5: <b>RELEASE_25</b></li>
769 <li>Release 2.4: <b>RELEASE_24</b></li>
770 <li>Release 2.3: <b>RELEASE_23</b></li>
771 <li>Release 2.2: <b>RELEASE_22</b></li>
772 <li>Release 2.1: <b>RELEASE_21</b></li>
773 <li>Release 2.0: <b>RELEASE_20</b></li>
774 <li>Release 1.9: <b>RELEASE_19</b></li>
775 <li>Release 1.8: <b>RELEASE_18</b></li>
776 <li>Release 1.7: <b>RELEASE_17</b></li>
777 <li>Release 1.6: <b>RELEASE_16</b></li>
778 <li>Release 1.5: <b>RELEASE_15</b></li>
779 <li>Release 1.4: <b>RELEASE_14</b></li>
780 <li>Release 1.3: <b>RELEASE_13</b></li>
781 <li>Release 1.2: <b>RELEASE_12</b></li>
782 <li>Release 1.1: <b>RELEASE_11</b></li>
783 <li>Release 1.0: <b>RELEASE_1</b></li>
786 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
787 you get it from the Subversion repository:</p>
789 <div class="doc_code">
792 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
796 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
797 configured by the LLVM configure script as well as automatically updated when
798 you run <tt>svn update</tt>.</p>
800 <p>If you would like to get the GCC front end source code, you can also get it
801 and build it yourself. Please follow <a href="GCCFEBuildInstrs.html">these
802 instructions</a> to successfully get and build the LLVM GCC front-end.</p>
806 <!-- ======================================================================= -->
808 <a name="git_mirror">GIT mirror</a>
813 <p>GIT mirrors are available for a number of LLVM subprojects. These mirrors
814 sync automatically with each Subversion commit and contain all necessary
815 git-svn marks (so, you can recreate git-svn metadata locally). Note that right
816 now mirrors reflect only <tt>trunk</tt> for each project. You can do the
817 read-only GIT clone of LLVM via:</p>
819 <pre class="doc_code">
820 git clone http://llvm.org/git/llvm.git
823 <p>If you want to check out clang too, run:</p>
825 <pre class="doc_code">
826 git clone http://llvm.org/git/llvm.git
828 git clone http://llvm.org/git/clang.git
832 Since the upstream repository is in Subversion, you should use
833 <tt>"git pull --rebase"</tt>
834 instead of <tt>"git pull"</tt> to avoid generating a non-linear
835 history in your clone.
836 To configure <tt>"git pull"</tt> to pass <tt>--rebase</tt> by default
837 on the master branch, run the following command:
840 <pre class="doc_code">
841 git config branch.master.rebase true
844 <h4>Sending patches with Git</h4>
847 Please read <a href="DeveloperPolicy.html#patches">Developer Policy</a>, too.
851 Assume <tt>master</tt> points the upstream and <tt>mybranch</tt> points your
852 working branch, and <tt>mybranch</tt> is rebased onto <tt>master</tt>.
853 At first you may check sanity of whitespaces:
856 <pre class="doc_code">
857 git diff --check master..mybranch
861 The easiest way to generate a patch is as below:
864 <pre class="doc_code">
865 git diff master..mybranch > /path/to/mybranch.diff
869 It is a little different from svn-generated diff. git-diff-generated diff has
870 prefixes like <tt>a/</tt> and <tt>b/</tt>. Don't worry, most developers might
871 know it could be accepted with <tt>patch -p1 -N</tt>.
875 But you may generate patchset with git-format-patch. It generates
876 by-each-commit patchset. To generate patch files to attach to your article:
879 <pre class="doc_code">
880 git format-patch --no-attach master..mybranch -o /path/to/your/patchset
884 If you would like to send patches directly, you may use git-send-email or
885 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
888 <pre class="doc_code">
889 git format-patch --attach master..mybranch --stdout | git imap-send
893 Then, your .git/config should have [imap] sections.
896 <pre class="doc_code">
898 host = imaps://imap.gmail.com
899 user = <em>your.gmail.account</em>@gmail.com
900 pass = <em>himitsu!</em>
904 folder = "[Gmail]/Drafts"
905 ; example for Japanese, "Modified UTF-7" encoded.
906 folder = "[Gmail]/&Tgtm+DBN-"
907 ; example for Traditional Chinese
908 folder = "[Gmail]/&g0l6Pw-"
913 <h4>For developers to work with git-svn</h4>
916 <p>To set up clone from which you can submit code using
917 <tt>git-svn</tt>, run:</p>
919 <pre class="doc_code">
920 git clone http://llvm.org/git/llvm.git
922 git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
923 git config svn-remote.svn.fetch :refs/remotes/origin/master
924 git svn rebase -l # -l avoids fetching ahead of the git mirror.
926 # If you have clang too:
928 git clone http://llvm.org/git/clang.git
930 git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
931 git config svn-remote.svn.fetch :refs/remotes/origin/master
935 <p>To update this clone without generating git-svn tags that conflict
936 with the upstream git repo, run:</p>
938 <pre class="doc_code">
939 git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
943 git checkout master &&
947 <p>This leaves your working directories on their master branches, so
948 you'll need to <tt>checkout</tt> each working branch individually and
949 <tt>rebase</tt> it on top of its parent branch. (Note: This script is
950 intended for relative newbies to git. If you have more experience,
951 you can likely improve on it.)</p>
953 <p>The git-svn metadata can get out of sync after you mess around with
954 branches and <code>dcommit</code>. When that happens, <code>git svn
955 dcommit</code> stops working, complaining about files with uncommitted
956 changes. The fix is to rebuild the metadata:</p>
958 <pre class="doc_code">
967 <!-- ======================================================================= -->
969 <a name="installcf">Install the GCC Front End</a>
974 <p>Before configuring and compiling the LLVM suite (or if you want to use just the LLVM
975 GCC front end) you can optionally extract the front end from the binary distribution.
976 It is used for running the LLVM test-suite and for compiling C/C++ programs. Note that
977 you can optionally <a href="GCCFEBuildInstrs.html">build llvm-gcc yourself</a> after building the
978 main LLVM repository.</p>
980 <p>To install the GCC front end, do the following (on Windows, use an archival tool
981 like <a href="http://www.7-zip.org/">7-zip</a> that understands gzipped tars):</p>
984 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
985 <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf
989 <p>Once the binary is uncompressed, if you're using a *nix-based system, add a symlink for
990 <tt>llvm-gcc</tt> and <tt>llvm-g++</tt> to some directory in your path. If you're using a
991 Windows-based system, add the <tt>bin</tt> subdirectory of your front end installation directory
992 to your <tt>PATH</tt> environment variable. For example, if you uncompressed the binary to
993 <tt>c:\llvm-gcc</tt>, add <tt>c:\llvm-gcc\bin</tt> to your <tt>PATH</tt>.</p>
995 <p>If you now want to build LLVM from source, when you configure LLVM, it will
996 automatically detect <tt>llvm-gcc</tt>'s presence (if it is in your path) enabling its
997 use in test-suite. Note that you can always build or install <tt>llvm-gcc</tt> at any
998 point after building the main LLVM repository: just reconfigure llvm and
999 test-suite will pick it up.
1002 <p>As a convenience for Windows users, the front end binaries for MinGW/x86 include
1003 versions of the required w32api and mingw-runtime binaries. The last remaining step for
1004 Windows users is to simply uncompress the binary binutils package from
1005 <a href="http://mingw.org/">MinGW</a> into your front end installation directory. While the
1006 front end installation steps are not quite the same as a typical manual MinGW installation,
1007 they should be similar enough to those who have previously installed MinGW on Windows systems.</p>
1009 <p>To install binutils on Windows:</p>
1012 <li><tt><i>download GNU Binutils from <a href="http://sourceforge.net/projects/mingw/files/">MinGW Downloads</a></i></tt></li>
1013 <li><tt>cd <i>where-you-uncompressed-the-front-end</i></tt></li>
1014 <li><tt><i>uncompress archived binutils directories (not the tar file) into the current directory</i></tt></li>
1017 <p>The binary versions of the LLVM GCC front end may not suit all of your needs. For
1018 example, the binary distribution may include an old version of a system header
1019 file, not "fix" a header file that needs to be fixed for GCC, or it may be linked with
1020 libraries not available on your system. In cases like these, you may want to try
1021 <a href="GCCFEBuildInstrs.html">building the GCC front end from source</a>. Thankfully,
1022 this is much easier now than it was in the past.</p>
1024 <p>We also do not currently support updating of the GCC front end by manually overlaying
1025 newer versions of the w32api and mingw-runtime binary packages that may become available
1026 from MinGW. At this time, it's best to think of the MinGW LLVM GCC front end binary as
1027 a self-contained convenience package that requires Windows users to simply download and
1028 uncompress the GNU Binutils binary package from the MinGW project.</p>
1030 <p>Regardless of your platform, if you discover that installing the LLVM GCC front end
1031 binaries is not as easy as previously described, or you would like to suggest improvements,
1032 please let us know how you would like to see things improved by dropping us a note on our
1033 <a href="http://llvm.org/docs/#maillist">mailing list</a>.</p>
1037 <!-- ======================================================================= -->
1039 <a name="config">Local LLVM Configuration</a>
1044 <p>Once checked out from the Subversion repository, the LLVM suite source
1046 configured via the <tt>configure</tt> script. This script sets variables in the
1047 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
1048 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
1049 the Makefiles needed to begin building LLVM.</p>
1051 <p>The following environment variables are used by the <tt>configure</tt>
1052 script to configure the build system:</p>
1054 <table summary="LLVM configure script environment variables">
1055 <tr><th>Variable</th><th>Purpose</th></tr>
1058 <td>Tells <tt>configure</tt> which C compiler to use. By default,
1059 <tt>configure</tt> will look for the first GCC C compiler in
1060 <tt>PATH</tt>. Use this variable to override
1061 <tt>configure</tt>'s default behavior.</td>
1065 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
1066 <tt>configure</tt> will look for the first GCC C++ compiler in
1067 <tt>PATH</tt>. Use this variable to override
1068 <tt>configure</tt>'s default behavior.</td>
1072 <p>The following options can be used to set or enable LLVM specific options:</p>
1075 <dt><i>--with-llvmgccdir</i></dt>
1076 <dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
1077 The value of this option should specify the full pathname of the C/C++ Front
1078 End to be used. If this option is not provided, the PATH will be searched for
1079 a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
1080 be inferred from the path found. If the option is not given, and no llvm-gcc
1081 can be found in the path then a warning will be produced by
1082 <tt>configure</tt> indicating this situation. LLVM may still be built with
1083 the <tt>tools-only</tt> target but attempting to build the runtime libraries
1084 will fail as these libraries require llvm-gcc and llvm-g++. See
1085 <a href="#installcf">Install the GCC Front End</a> for details on installing
1086 the C/C++ Front End. See
1087 <a href="GCCFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
1088 for details on building the C/C++ Front End.</dd>
1089 <dt><i>--with-tclinclude</i></dt>
1090 <dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
1091 found. Use this if you have multiple tcl installations on your machine and you
1092 want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
1093 dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
1094 option, the LLVM configure script will search for the tcl 8.4 and 8.3
1098 <dt><i>--enable-optimized</i></dt>
1100 Enables optimized compilation (debugging symbols are removed
1101 and GCC optimization flags are enabled). Note that this is the default
1102 setting if you are using the LLVM distribution. The default behavior
1103 of an Subversion checkout is to use an unoptimized build (also known as a
1107 <dt><i>--enable-debug-runtime</i></dt>
1109 Enables debug symbols in the runtime libraries. The default is to strip
1110 debug symbols from the runtime libraries.
1112 <dt><i>--enable-jit</i></dt>
1114 Compile the Just In Time (JIT) compiler functionality. This is not
1116 on all platforms. The default is dependent on platform, so it is best
1117 to explicitly enable it if you want it.
1120 <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
1121 <dd>Controls which targets will be built and linked into llc. The default
1122 value for <tt>target_options</tt> is "all" which builds and links all
1123 available targets. The value "host-only" can be specified to build only a
1124 native compiler (no cross-compiler targets available). The "native" target is
1125 selected as the target of the build host. You can also specify a comma
1126 separated list of target names that you want available in llc. The target
1127 names use all lower case. The current set of targets is: <br>
1128 <tt>arm, cbe, cpp, hexagon, mblaze, mips, mipsel, msp430, powerpc, ptx, sparc, spu, x86, x86_64, xcore</tt>.
1130 <dt><i>--enable-doxygen</i></dt>
1131 <dd>Look for the doxygen program and enable construction of doxygen based
1132 documentation from the source code. This is disabled by default because
1133 generating the documentation can take a long time and producess 100s of
1134 megabytes of output.</dd>
1135 <dt><i>--with-udis86</i></dt>
1136 <dd>LLVM can use external disassembler library for various purposes (now it's
1137 used only for examining code produced by JIT). This option will enable usage
1138 of <a href="http://udis86.sourceforge.net/">udis86</a> x86 (both 32 and 64
1139 bits) disassembler library.</dd>
1142 <p>To configure LLVM, follow these steps:</p>
1145 <li><p>Change directory into the object root directory:</p>
1147 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1149 <li><p>Run the <tt>configure</tt> script located in the LLVM source
1152 <div class="doc_code">
1153 <pre>% <i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</pre>
1159 <!-- ======================================================================= -->
1161 <a name="compile">Compiling the LLVM Suite Source Code</a>
1166 <p>Once you have configured LLVM, you can build it. There are three types of
1172 These builds are the default when one is using an Subversion checkout and
1173 types <tt>gmake</tt> (unless the <tt>--enable-optimized</tt> option was
1174 used during configuration). The build system will compile the tools and
1175 libraries with debugging information. To get a Debug Build using the
1176 LLVM distribution the <tt>--disable-optimized</tt> option must be passed
1177 to <tt>configure</tt>.
1180 <dt>Release (Optimized) Builds
1182 These builds are enabled with the <tt>--enable-optimized</tt> option to
1183 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
1184 <tt>gmake</tt> command line. For these builds, the build system will
1185 compile the tools and libraries with GCC optimizations enabled and strip
1186 debugging information from the libraries and executables it generates.
1187 Note that Release Builds are default when using an LLVM distribution.
1192 These builds are for use with profiling. They compile profiling
1193 information into the code for use with programs like <tt>gprof</tt>.
1194 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
1195 on the <tt>gmake</tt> command line.
1198 <p>Once you have LLVM configured, you can build it by entering the
1199 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
1201 <div class="doc_code"><pre>% gmake</pre></div>
1203 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
1204 are using a version of GCC that is known not to compile LLVM.</p>
1207 If you have multiple processors in your machine, you may wish to use some of
1208 the parallel build options provided by GNU Make. For example, you could use the
1211 <div class="doc_code"><pre>% gmake -j2</pre></div>
1213 <p>There are several special targets which are useful when working with the LLVM
1217 <dt><tt>gmake clean</tt>
1219 Removes all files generated by the build. This includes object files,
1220 generated C/C++ files, libraries, and executables.
1223 <dt><tt>gmake dist-clean</tt>
1225 Removes everything that <tt>gmake clean</tt> does, but also removes files
1226 generated by <tt>configure</tt>. It attempts to return the source tree to the
1227 original state in which it was shipped.
1230 <dt><tt>gmake install</tt>
1232 Installs LLVM header files, libraries, tools, and documentation in a
1234 under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
1235 defaults to <tt>/usr/local</tt>.
1238 <dt><tt>gmake -C runtime install-bytecode</tt>
1240 Assuming you built LLVM into $OBJDIR, when this command is run, it will
1241 install bitcode libraries into the GCC front end's bitcode library
1242 directory. If you need to update your bitcode libraries,
1243 this is the target to use once you've built them.
1247 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
1248 details on these <tt>make</tt> targets and descriptions of other targets
1251 <p>It is also possible to override default values from <tt>configure</tt> by
1252 declaring variables on the command line. The following are some examples:</p>
1255 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
1257 Perform a Release (Optimized) build.
1260 <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
1262 Perform a Release (Optimized) build without assertions enabled.
1265 <dt><tt>gmake ENABLE_OPTIMIZED=0</tt>
1267 Perform a Debug build.
1270 <dt><tt>gmake ENABLE_PROFILING=1</tt>
1272 Perform a Profiling build.
1275 <dt><tt>gmake VERBOSE=1</tt>
1277 Print what <tt>gmake</tt> is doing on standard output.
1280 <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
1281 <dd>Ask each tool invoked by the makefiles to print out what it is doing on
1282 the standard output. This also implies <tt>VERBOSE=1</tt>.
1286 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
1287 it and any subdirectories that it contains. Entering any directory inside the
1288 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
1289 that directory that is out of date.</p>
1293 <!-- ======================================================================= -->
1295 <a name="cross-compile">Cross-Compiling LLVM</a>
1299 <p>It is possible to cross-compile LLVM itself. That is, you can create LLVM
1300 executables and libraries to be hosted on a platform different from the
1301 platform where they are build (a Canadian Cross build). To configure a
1302 cross-compile, supply the configure script with <tt>--build</tt> and
1303 <tt>--host</tt> options that are different. The values of these options must
1304 be legal target triples that your GCC compiler supports.</p>
1306 <p>The result of such a build is executables that are not runnable on
1307 on the build host (--build option) but can be executed on the compile host
1308 (--host option).</p>
1311 <!-- ======================================================================= -->
1313 <a name="objfiles">The Location of LLVM Object Files</a>
1318 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1319 several LLVM builds. Hence, it is possible to build LLVM for several different
1320 platforms or configurations using the same source tree.</p>
1322 <p>This is accomplished in the typical autoconf manner:</p>
1325 <li><p>Change directory to where the LLVM object files should live:</p>
1327 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1329 <li><p>Run the <tt>configure</tt> script found in the LLVM source
1332 <div class="doc_code"><pre>% <i>SRC_ROOT</i>/configure</pre></div></li>
1335 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1336 named after the build type:</p>
1339 <dt>Debug Builds with assertions enabled (the default)
1343 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/bin</tt>
1345 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/lib</tt>
1353 <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1355 <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1363 <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1365 <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1371 <!-- ======================================================================= -->
1373 <a name="optionalconfig">Optional Configuration Items</a>
1379 If you're running on a Linux system that supports the "<a
1380 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
1381 module, and you have root access on the system, you can set your system up to
1382 execute LLVM bitcode files directly. To do this, use commands like this (the
1383 first command may not be required if you are already using the module):</p>
1385 <div class="doc_code">
1387 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1388 $ echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1389 $ chmod u+x hello.bc (if needed)
1395 This allows you to execute LLVM bitcode files directly. On Debian, you
1396 can also use this command instead of the 'echo' command above:
1399 <div class="doc_code">
1401 $ sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1409 <!-- *********************************************************************** -->
1411 <a name="layout">Program Layout</a>
1413 <!-- *********************************************************************** -->
1417 <p>One useful source of information about the LLVM source base is the LLVM <a
1418 href="http://www.doxygen.org/">doxygen</a> documentation available at <tt><a
1419 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1420 The following is a brief introduction to code layout:</p>
1422 <!-- ======================================================================= -->
1424 <a name="examples"><tt>llvm/examples</tt></a>
1428 <p>This directory contains some simple examples of how to use the LLVM IR and
1432 <!-- ======================================================================= -->
1434 <a name="include"><tt>llvm/include</tt></a>
1439 <p>This directory contains public header files exported from the LLVM
1440 library. The three main subdirectories of this directory are:</p>
1443 <dt><tt><b>llvm/include/llvm</b></tt></dt>
1444 <dd>This directory contains all of the LLVM specific header files. This
1445 directory also has subdirectories for different portions of LLVM:
1446 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1449 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1450 <dd>This directory contains generic support libraries that are provided with
1451 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1452 and a Command Line option processing library store their header files here.
1455 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1456 <dd>This directory contains header files configured by the <tt>configure</tt>
1457 script. They wrap "standard" UNIX and C header files. Source code can
1458 include these header files which automatically take care of the conditional
1459 #includes that the <tt>configure</tt> script generates.</dd>
1463 <!-- ======================================================================= -->
1465 <a name="lib"><tt>llvm/lib</tt></a>
1470 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1471 almost all code exists in libraries, making it very easy to share code among the
1472 different <a href="#tools">tools</a>.</p>
1475 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1476 <dd> This directory holds the core LLVM source files that implement core
1477 classes like Instruction and BasicBlock.</dd>
1479 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1480 <dd>This directory holds the source code for the LLVM assembly language parser
1483 <dt><tt><b>llvm/lib/BitCode/</b></tt></dt>
1484 <dd>This directory holds code for reading and write LLVM bitcode.</dd>
1486 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1487 different program analyses, such as Dominator Information, Call Graphs,
1488 Induction Variables, Interval Identification, Natural Loop Identification,
1491 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1492 <dd> This directory contains the source code for the LLVM to LLVM program
1493 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1494 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1495 Elimination, and many others.</dd>
1497 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1498 <dd> This directory contains files that describe various target architectures
1499 for code generation. For example, the <tt>llvm/lib/Target/X86</tt>
1500 directory holds the X86 machine description while
1501 <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
1503 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1504 <dd> This directory contains the major parts of the code generator: Instruction
1505 Selector, Instruction Scheduling, and Register Allocation.</dd>
1507 <dt><tt><b>llvm/lib/MC/</b></tt></dt>
1508 <dd>(FIXME: T.B.D.)</dd>
1510 <!--FIXME: obsoleted -->
1511 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1512 <dd> This directory contains the source level debugger library that makes
1513 it possible to instrument LLVM programs so that a debugger could identify
1514 source code locations at which the program is executing.</dd>
1516 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1517 <dd> This directory contains libraries for executing LLVM bitcode directly
1518 at runtime in both interpreted and JIT compiled fashions.</dd>
1520 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1521 <dd> This directory contains the source code that corresponds to the header
1522 files located in <tt>llvm/include/ADT/</tt>
1523 and <tt>llvm/include/Support/</tt>.</dd>
1528 <!-- ======================================================================= -->
1530 <a name="projects"><tt>llvm/projects</tt></a>
1534 <p>This directory contains projects that are not strictly part of LLVM but are
1535 shipped with LLVM. This is also the directory where you should create your own
1536 LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1537 to set up your own project.</p>
1540 <!-- ======================================================================= -->
1542 <a name="runtime"><tt>llvm/runtime</tt></a>
1547 <p>This directory contains libraries which are compiled into LLVM bitcode and
1548 used when linking programs with the GCC front end. Most of these libraries are
1549 skeleton versions of real libraries; for example, libc is a stripped down
1550 version of glibc.</p>
1552 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1557 <!-- ======================================================================= -->
1559 <a name="test"><tt>llvm/test</tt></a>
1563 <p>This directory contains feature and regression tests and other basic sanity
1564 checks on the LLVM infrastructure. These are intended to run quickly and cover
1565 a lot of territory without being exhaustive.</p>
1568 <!-- ======================================================================= -->
1570 <a name="test-suite"><tt>test-suite</tt></a>
1574 <p>This is not a directory in the normal llvm module; it is a separate
1576 module that must be checked out (usually to <tt>projects/test-suite</tt>).
1578 module contains a comprehensive correctness, performance, and benchmarking
1580 suite for LLVM. It is a separate Subversion module because not every LLVM
1582 interested in downloading or building such a comprehensive test suite. For
1583 further details on this test suite, please see the
1584 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1587 <!-- ======================================================================= -->
1589 <a name="tools"><tt>llvm/tools</tt></a>
1594 <p>The <b>tools</b> directory contains the executables built out of the
1595 libraries above, which form the main part of the user interface. You can
1596 always get help for a tool by typing <tt>tool_name -help</tt>. The
1597 following is a brief introduction to the most important tools. More detailed
1598 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1602 <dt><tt><b>bugpoint</b></tt></dt>
1603 <dd><tt>bugpoint</tt> is used to debug
1604 optimization passes or code generation backends by narrowing down the
1605 given test case to the minimum number of passes and/or instructions that
1606 still cause a problem, whether it is a crash or miscompilation. See <a
1607 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1608 on using <tt>bugpoint</tt>.</dd>
1610 <dt><tt><b>llvm-ar</b></tt></dt>
1611 <dd>The archiver produces an archive containing
1612 the given LLVM bitcode files, optionally with an index for faster
1615 <dt><tt><b>llvm-as</b></tt></dt>
1616 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1619 <dt><tt><b>llvm-dis</b></tt></dt>
1620 <dd>The disassembler transforms the LLVM bitcode to human readable
1623 <dt><tt><b>llvm-ld</b></tt></dt>
1624 <dd><tt>llvm-ld</tt> is a general purpose and extensible linker for LLVM.
1625 It performs standard link time optimizations and allows optimization
1626 modules to be loaded and run so that language specific optimizations can
1627 be applied at link time.</dd>
1629 <dt><tt><b>llvm-link</b></tt></dt>
1630 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1631 a single program.</dd>
1633 <dt><tt><b>lli</b></tt></dt>
1634 <dd><tt>lli</tt> is the LLVM interpreter, which
1635 can directly execute LLVM bitcode (although very slowly...). For architectures
1636 that support it (currently x86, Sparc, and PowerPC), by default, <tt>lli</tt>
1637 will function as a Just-In-Time compiler (if the functionality was compiled
1638 in), and will execute the code <i>much</i> faster than the interpreter.</dd>
1640 <dt><tt><b>llc</b></tt></dt>
1641 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1642 translates LLVM bitcode to a native code assembly file or to C code (with
1643 the -march=c option).</dd>
1645 <dt><tt><b>llvm-gcc</b></tt></dt>
1646 <dd><tt>llvm-gcc</tt> is a GCC-based C frontend that has been retargeted to
1647 use LLVM as its backend instead of GCC's RTL backend. It can also emit LLVM
1648 bitcode or assembly (with the <tt>-emit-llvm</tt> option) instead of the
1649 usual machine code output. It works just like any other GCC compiler,
1650 taking the typical <tt>-c, -S, -E, -o</tt> options that are typically used.
1651 Additionally, the the source code for <tt>llvm-gcc</tt> is available as a
1652 separate Subversion module.</dd>
1654 <dt><tt><b>opt</b></tt></dt>
1655 <dd><tt>opt</tt> reads LLVM bitcode, applies a series of LLVM to LLVM
1656 transformations (which are specified on the command line), and then outputs
1657 the resultant bitcode. The '<tt>opt -help</tt>' command is a good way to
1658 get a list of the program transformations available in LLVM.<br>
1659 <dd><tt>opt</tt> can also be used to run a specific analysis on an input
1660 LLVM bitcode file and print out the results. It is primarily useful for
1661 debugging analyses, or familiarizing yourself with what an analysis does.</dd>
1665 <!-- ======================================================================= -->
1667 <a name="utils"><tt>llvm/utils</tt></a>
1672 <p>This directory contains utilities for working with LLVM source code, and some
1673 of the utilities are actually required as part of the build process because they
1674 are code generators for parts of LLVM infrastructure.</p>
1677 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1678 that finds differences between code that LLC generates and code that LLI
1679 generates. This is a useful tool if you are debugging one of them,
1680 assuming that the other generates correct output. For the full user
1681 manual, run <tt>`perldoc codegen-diff'</tt>.<br><br>
1683 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1684 syntax-highlighting files which will work with Emacs and XEmacs editors,
1685 providing syntax highlighting support for LLVM assembly files and TableGen
1686 description files. For information on how to use the syntax files, consult
1687 the <tt>README</tt> file in that directory.<br><br>
1689 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1690 and outputs all non-generated source files, which is useful if one wishes
1691 to do a lot of development across directories and does not want to
1692 individually find each file. One way to use it is to run, for example:
1693 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1696 <dt><tt><b>llvmgrep</b></tt></dt>
1697 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1698 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1699 line. This is a very efficient way of searching the source base for a
1700 particular regular expression.</dd>
1702 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1703 files in the current directory and then compiles and links the tool that
1704 is the first argument. For example, assuming you are in the directory
1705 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1706 simply running <tt>makellvm llc</tt> will make a build of the current
1707 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1708 causing a re-linking of LLC.<br><br>
1710 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1711 the tool used to generate register descriptions, instruction set
1712 descriptions, and even assemblers from common TableGen description
1715 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1716 syntax-highlighting files which will work with the VIM editor, providing
1717 syntax highlighting support for LLVM assembly files and TableGen
1718 description files. For information on how to use the syntax files, consult
1719 the <tt>README</tt> file in that directory.<br><br>
1727 <!-- *********************************************************************** -->
1729 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1731 <!-- *********************************************************************** -->
1734 <p>This section gives an example of using LLVM with the Clang front end.</p>
1736 <!-- ======================================================================= -->
1738 <a name="tutorial4">Example with clang</a>
1744 <li><p>First, create a simple C file, name it 'hello.c':</p>
1746 <div class="doc_code">
1748 #include <stdio.h>
1751 printf("hello world\n");
1756 <li><p>Next, compile the C file into a native executable:</p>
1758 <div class="doc_code"><pre>% clang hello.c -o hello</pre></div>
1760 <p>Note that clang works just like GCC by default. The standard -S and
1761 -c arguments work as usual (producing a native .s or .o file,
1762 respectively).</p></li>
1764 <li><p>Next, compile the C file into a LLVM bitcode file:</p>
1766 <div class="doc_code">
1767 <pre>% clang -O3 -emit-llvm hello.c -c -o hello.bc</pre></div>
1769 <p>The -emit-llvm option can be used with the -S or -c options to emit an
1770 LLVM ".ll" or ".bc" file (respectively) for the code. This allows you
1771 to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
1772 the bitcode file.</p></li>
1774 <li><p>Run the program in both forms. To run the program, use:</p>
1776 <div class="doc_code"><pre>% ./hello</pre></div>
1780 <div class="doc_code"><pre>% lli hello.bc</pre></div>
1782 <p>The second examples shows how to invoke the LLVM JIT, <a
1783 href="CommandGuide/html/lli.html">lli</a>.</p></li>
1785 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1788 <div class="doc_code">
1789 <pre>llvm-dis < hello.bc | less</pre>
1792 <li><p>Compile the program to native assembly using the LLC code
1795 <div class="doc_code"><pre>% llc hello.bc -o hello.s</pre></div></li>
1797 <li><p>Assemble the native assembly language file into a program:</p>
1799 <div class="doc_code">
1801 <b>Solaris:</b> % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native
1803 <b>Others:</b> % gcc hello.s -o hello.native
1807 <li><p>Execute the native code program:</p>
1809 <div class="doc_code"><pre>% ./hello.native</pre></div>
1811 <p>Note that using clang to compile directly to native code (i.e. when
1812 the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
1821 <!-- *********************************************************************** -->
1823 <a name="problems">Common Problems</a>
1825 <!-- *********************************************************************** -->
1829 <p>If you are having problems building or using LLVM, or if you have any other
1830 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1831 Asked Questions</a> page.</p>
1835 <!-- *********************************************************************** -->
1837 <a name="links">Links</a>
1839 <!-- *********************************************************************** -->
1843 <p>This document is just an <b>introduction</b> on how to use LLVM to do
1844 some simple things... there are many more interesting and complicated things
1845 that you can do that aren't documented here (but we'll gladly accept a patch
1846 if you want to write something up!). For more information about LLVM, check
1850 <li><a href="http://llvm.org/">LLVM homepage</a></li>
1851 <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1852 <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1853 that Uses LLVM</a></li>
1858 <!-- *********************************************************************** -->
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1867 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1868 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1869 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
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