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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 llvm-gcc4</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 the low level virtual machine. It contains an
86 assembler, disassembler, bitcode analyzer and bitcode optimizer. It
87 also contains basic regression tests that can be used to test the LLVM
88 tools and the GCC front end.</p>
90 <p>The second piece is the GCC front end. This component provides a version of
91 GCC that compiles C and C++ code into LLVM bitcode. Currently, the GCC front
92 end uses the GCC parser to convert code to LLVM. Once
93 compiled into LLVM bitcode, a program can be manipulated with the LLVM tools
94 from the LLVM suite.</p>
97 There is a third, optional piece called Test Suite. It is a suite of programs
98 with a testing harness that can be used to further test LLVM's functionality
104 <!-- *********************************************************************** -->
106 <a name="quickstart">Getting Started Quickly (A Summary)</a>
108 <!-- *********************************************************************** -->
112 <p>Here's the short story for getting up and running quickly with LLVM:</p>
115 <li>Read the documentation.</li>
116 <li>Read the documentation.</li>
117 <li>Remember that you were warned twice about reading the documentation.</li>
118 <li>Install the llvm-gcc-4.2 front end if you intend to compile C or C++
119 (see <a href="#installcf">Install the GCC Front End</a> for details):
121 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt></li>
122 <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf -</tt></li>
123 <li><tt><i>install-binutils-binary-from-MinGW</i></tt> (Windows only)</li>
124 <li>Note: If the binary extension is "<tt>.bz</tt>" use <tt>bunzip2</tt> instead of <tt>gunzip</tt>.</li>
125 <li>Note: On Windows, use <a href="http://www.7-zip.org/">7-Zip</a> or a similar archiving tool.</li>
126 <li>Add <tt>llvm-gcc</tt>'s "<tt>bin</tt>" directory to your <tt>PATH</tt> environment variable.</li>
129 <li>Get the LLVM Source Code
131 <li>With the distributed files (or use <a href="#checkout">SVN</a>):
133 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
134 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
139 <li><b>[Optional]</b> Get the Test Suite Source Code
141 <li>With the distributed files (or use <a href="#checkout">SVN</a>):
143 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
144 <li><tt>cd llvm/projects</tt>
145 <li><tt>gunzip --stdout llvm-test-<i>version</i>.tar.gz | tar -xvf -</tt>
146 <li><tt>mv llvm-test-<i>version</i> test-suite</tt>
152 <li>Configure the LLVM Build Environment
154 <li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
155 <li><tt><i>/path/to/llvm/</i>configure [options]</tt><br>
159 <li><tt>--prefix=<i>directory</i></tt>
160 <p>Specify for <i>directory</i> the full pathname of where you
161 want the LLVM tools and libraries to be installed (default
162 <tt>/usr/local</tt>).</p></li>
163 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
164 <p>Optionally, specify for <i>directory</i> the full pathname of the
165 C/C++ front end installation to use with this LLVM configuration. If
166 not specified, the PATH will be searched. This is only needed if you
167 want to run test-suite or do some special kinds of LLVM builds.</p></li>
168 <li><tt>--enable-spec2000=<i>directory</i></tt>
169 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
170 benchmarks should be available in
171 <tt><i>directory</i></tt>.</p></li>
175 <li>Build the LLVM Suite:
177 <li><tt>gmake -k |& tee gnumake.out
178 # this is csh or tcsh syntax</tt></li>
179 <li>If you get an "internal compiler error (ICE)" or test failures, see
180 <a href="#brokengcc">below</a>.</li>
185 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
186 detailed information on configuring and compiling LLVM. See <a
187 href="#environment">Setting Up Your Environment</a> for tips that simplify
188 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
189 Layout</a> to learn about the layout of the source code tree.</p>
193 <!-- *********************************************************************** -->
195 <a name="requirements">Requirements</a>
197 <!-- *********************************************************************** -->
201 <p>Before you begin to use the LLVM system, review the requirements given below.
202 This may save you some trouble by knowing ahead of time what hardware and
203 software you will need.</p>
205 <!-- ======================================================================= -->
207 <a name="hardware">Hardware</a>
212 <p>LLVM is known to work on the following platforms:</p>
214 <table cellpadding="3" summary="Known LLVM platforms">
222 <td>x86<sup><a href="#pf_1">1</a></sup></td>
227 <td>x86<sup><a href="#pf_1">1</a></sup></td>
237 <td>V9 (Ultrasparc)</td>
242 <td>x86<sup><a href="#pf_1">1</a></sup></td>
251 <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
256 <td>MacOS X<sup><a href="#pf_2">2</a>,<a href="#pf_9">9</a></sup></td>
261 <td>Cygwin/Win32</td>
262 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a>,
263 <a href="#pf_11">11</a></sup></td>
264 <td>GCC 3.4.X, binutils 2.20</td>
268 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,
269 <a href="#pf_8">8</a>, <a href="#pf_10">10</a>,
270 <a href="#pf_11">11</a></sup></td>
271 <td>GCC 3.4.X, binutils 2.20</td>
275 <p>LLVM has partial support for the following platforms:</p>
277 <table summary="LLVM partial platform support">
285 <td>x86<sup><a href="#pf_1">1</a></sup></td>
286 <td>Visual Studio 2005 SP1 or higher<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
288 <td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
293 <td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
299 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
304 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
305 <td>Itanium (IA-64)</td>
309 <td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
310 <td>Itanium (IA-64)</td>
316 <td>mingw-w64's GCC-4.5.x<sup><a href="#pf_12">12</a></sup></td>
322 <div class="doc_notes">
324 <li><a name="pf_1">Code generation supported for Pentium processors and
326 <li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
327 <li><a name="pf_3">No native code generation</a></li>
328 <li><a name="pf_4">Build is not complete: one or more tools do not link or function</a></li>
329 <li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
330 <li><a name="pf_6">The port is done using the MSYS shell.</a></li>
331 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
332 <li><a name="pf_8">Binutils 2.20 or later is required to build the assembler
333 generated by LLVM properly.</a></li>
334 <li><a name="pf_9">XCode 2.5 and gcc 4.0.1</a> (Apple Build 5370) will trip
335 internal LLVM assert messages when compiled for Release at optimization
336 levels greater than 0 (i.e., <i>"-O1"</i> and higher).
337 Add <i>OPTIMIZE_OPTION="-O0"</i> to the build command line
338 if compiling for LLVM Release or bootstrapping the LLVM toolchain.</li>
339 <li><a name="pf_10">For MSYS/MinGW on Windows, be sure to install the MSYS
340 version of the perl package, and be sure it appears in your path
341 before any Windows-based versions such as Strawberry Perl and
342 ActivePerl, as these have Windows-specifics that will cause the
343 build to fail.</a></li>
344 <li><a name="pf_11">To use LLVM modules on Win32-based system,
345 you may configure LLVM with <i>"--enable-shared"</i>.</a></li>
346 <li><a name="pf_12">To compile SPU backend, you need to add
347 <tt>"LDFLAGS=-Wl,--stack,16777216"</tt> to configure.</a></li>
351 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
352 mode, depending on the system (it is so large because of all the debugging
353 information and the fact that the libraries are statically linked into multiple
354 tools). If you do not need many of the tools and you are space-conscious, you
355 can pass <tt>ONLY_TOOLS="tools you need"</tt> to make. The Release build
356 requires considerably less space.</p>
358 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
359 guaranteed to do so. If compilation is successful, the LLVM utilities should be
360 able to assemble, disassemble, analyze, and optimize LLVM bitcode. Code
361 generation should work as well, although the generated native code may not work
362 on your platform.</p>
364 <p>The GCC front end is not very portable at the moment. If you want to get it
365 to work on another platform, you can download a copy of the source and <a
366 href="GCCFEBuildInstrs.html">try to compile it</a> on your platform.</p>
370 <!-- ======================================================================= -->
372 <a name="software">Software</a>
375 <p>Compiling LLVM requires that you have several software packages
376 installed. The table below lists those required packages. The Package column
377 is the usual name for the software package that LLVM depends on. The Version
378 column provides "known to work" versions of the package. The Notes column
379 describes how LLVM uses the package and provides other details.</p>
380 <table summary="Packages required to compile LLVM">
381 <tr><th>Package</th><th>Version</th><th>Notes</th></tr>
384 <td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
385 <td>3.79, 3.79.1</td>
386 <td>Makefile/build processor</td>
390 <td><a href="http://gcc.gnu.org/">GCC</a></td>
392 <td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
396 <td><a href="http://www.gnu.org/software/texinfo/">TeXinfo</a></td>
398 <td>For building the CFE</td>
402 <td><a href="http://subversion.tigris.org/project_packages.html">SVN</a></td>
404 <td>Subversion access to LLVM<sup><a href="#sf2">2</a></sup></td>
409 Are DejaGnu and expect obsolete?
410 Shall we mention Python? -->
413 <td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
415 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
419 <td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
421 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
425 <td><a href="http://expect.nist.gov/">expect</a></td>
427 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
431 <td><a href="http://www.perl.com/download.csp">perl</a></td>
433 <td>Nightly tester, utilities</td>
437 <td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
439 <td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
443 <td><a href="http://www.gnu.org/software/autoconf/">GNU Autoconf</a></td>
445 <td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
449 <td><a href="http://www.gnu.org/software/automake/">GNU Automake</a></td>
451 <td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
455 <td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
457 <td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
463 <div class="doc_notes">
465 <li><a name="sf1">Only the C and C++ languages are needed so there's no
466 need to build the other languages for LLVM's purposes.</a> See
467 <a href="#brokengcc">below</a> for specific version info.</li>
468 <li><a name="sf2">You only need Subversion if you intend to build from the
469 latest LLVM sources. If you're working from a release distribution, you
470 don't need Subversion.</a></li>
471 <li><a name="sf3">Only needed if you want to run the automated test
472 suite in the <tt>llvm/test</tt> directory.</a></li>
473 <li><a name="sf4">If you want to make changes to the configure scripts,
474 you will need GNU autoconf (2.60), and consequently, GNU M4 (version 1.4
475 or higher). You will also need automake (1.9.6). We only use aclocal
476 from that package.</a></li>
480 <p>Additionally, your compilation host is expected to have the usual
481 plethora of Unix utilities. Specifically:</p>
483 <li><b>ar</b> - archive library builder</li>
484 <li><b>bzip2*</b> - bzip2 command for distribution generation</li>
485 <li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
486 <li><b>chmod</b> - change permissions on a file</li>
487 <li><b>cat</b> - output concatenation utility</li>
488 <li><b>cp</b> - copy files</li>
489 <li><b>date</b> - print the current date/time </li>
490 <li><b>echo</b> - print to standard output</li>
491 <li><b>egrep</b> - extended regular expression search utility</li>
492 <li><b>find</b> - find files/dirs in a file system</li>
493 <li><b>grep</b> - regular expression search utility</li>
494 <li><b>gzip*</b> - gzip command for distribution generation</li>
495 <li><b>gunzip*</b> - gunzip command for distribution checking</li>
496 <li><b>install</b> - install directories/files </li>
497 <li><b>mkdir</b> - create a directory</li>
498 <li><b>mv</b> - move (rename) files</li>
499 <li><b>ranlib</b> - symbol table builder for archive libraries</li>
500 <li><b>rm</b> - remove (delete) files and directories</li>
501 <li><b>sed</b> - stream editor for transforming output</li>
502 <li><b>sh</b> - Bourne shell for make build scripts</li>
503 <li><b>tar</b> - tape archive for distribution generation</li>
504 <li><b>test</b> - test things in file system</li>
505 <li><b>unzip*</b> - unzip command for distribution checking</li>
506 <li><b>zip*</b> - zip command for distribution generation</li>
510 <!-- ======================================================================= -->
512 <a name="brokengcc">Broken versions of GCC and other tools</a>
517 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
518 bugs in the compiler. In particular, several versions of GCC crash when trying
519 to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang.
520 Other versions of GCC will probably work as well. GCC versions listed
521 here are known to not work. If you are using one of these versions, please try
522 to upgrade your GCC to something more recent. If you run into a problem with a
523 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
524 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
525 of GCC you are using.
528 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
529 problems in the STL that effectively prevent it from compiling LLVM.
532 <p><b>GCC 3.2.2 and 3.2.3</b>: These versions of GCC fails to compile LLVM with
533 a bogus template error. This was fixed in later GCCs.</p>
535 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
536 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
537 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
539 <p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
540 Cygwin does not work. Please <a href="GCCFEBuildInstrs.html#cygwin">upgrade
541 to a newer version</a> if possible.</p>
542 <p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
543 possibly others) does not compile LLVM correctly (it appears that exception
544 handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
545 to a newer version of GCC.</p>
546 <p><b>GCC 3.4.0 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
547 code generator, causing an infinite loop in the llvm-gcc build when built
548 with optimizations enabled (i.e. a release build).</p>
549 <p><b>GCC 3.4.2 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
550 code generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0)
551 correctly compiles LLVM at -O2. A work around is to build release LLVM
552 builds with "make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ..."</p>
553 <p><b>GCC 3.4.x on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1056">
554 miscompiles portions of LLVM</a>.</p>
555 <p><b>GCC 3.4.4 (CodeSourcery ARM 2005q3-2)</b>: this compiler miscompiles LLVM
556 when building with optimizations enabled. It appears to work with
557 "<tt>make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1</tt>" or build a debug
559 <p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
561 <p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
562 default with ENABLE_OPTIMIZED=1. To work around this, build with
563 "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
564 <p><b>GCC 4.1.1</b>: GCC fails to build LLVM with template concept check errors
565 compiling some files. At the time of this writing, GCC mainline (4.2)
566 did not share the problem.</p>
567 <p><b>GCC 4.1.1 on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1063">
568 miscompiles portions of LLVM</a> when compiling llvm itself into 64-bit
569 code. LLVM will appear to mostly work but will be buggy, e.g. failing
570 portions of its testsuite.</p>
571 <p><b>GCC 4.1.2 on OpenSUSE</b>: Seg faults during libstdc++ build and on x86_64
572 platforms compiling md5.c gets a mangled constant.</p>
573 <p><b>GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian</b>: Appears
574 to miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining
575 about symbols remaining in the table on destruction.</p>
576 <p><b>GCC 4.1.2 20071124 (Red Hat 4.1.2-42)</b>: Suffers from the same symptoms
577 as the previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).</p>
578 <p><b>Cygwin GCC 4.3.2 20080827 (beta) 2</b>:
579 Users <a href="http://llvm.org/PR4145">reported</a> various problems related
580 with link errors when using this GCC version.</p>
581 <p><b>Debian GCC 4.3.2 on X86</b>: Crashes building some files in LLVM 2.6.</p>
582 <p><b>GCC 4.3.3 (Debian 4.3.3-10) on ARM</b>: Miscompiles parts of LLVM 2.6
583 when optimizations are turned on. The symptom is an infinite loop in
584 FoldingSetImpl::RemoveNode while running the code generator.</p>
585 <p><b>GCC 4.3.5 and GCC 4.4.5 on ARM</b>: These can miscompile <tt>value >>
586 1</tt> even at -O0. A test failure in <tt>test/Assembler/alignstack.ll</tt> is
587 one symptom of the problem.
588 <p><b>GNU ld 2.16.X</b>. Some 2.16.X versions of the ld linker will produce very
589 long warning messages complaining that some ".gnu.linkonce.t.*" symbol was
590 defined in a discarded section. You can safely ignore these messages as they are
591 erroneous and the linkage is correct. These messages disappear using ld
594 <p><b>GNU binutils 2.17</b>: Binutils 2.17 contains <a
595 href="http://sourceware.org/bugzilla/show_bug.cgi?id=3111">a bug</a> which
596 causes huge link times (minutes instead of seconds) when building LLVM. We
597 recommend upgrading to a newer version (2.17.50.0.4 or later).</p>
599 <p><b>GNU Binutils 2.19.1 Gold</b>: This version of Gold contained
600 <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=9836">a bug</a>
601 which causes intermittent failures when building LLVM with position independent
602 code. The symptom is an error about cyclic dependencies. We recommend
603 upgrading to a newer version of Gold.</p>
609 <!-- *********************************************************************** -->
611 <a name="starting">Getting Started with LLVM</a>
613 <!-- *********************************************************************** -->
617 <p>The remainder of this guide is meant to get you up and running with
618 LLVM and to give you some basic information about the LLVM environment.</p>
620 <p>The later sections of this guide describe the <a
621 href="#layout">general layout</a> of the the LLVM source tree, a <a
622 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
623 href="#links">links</a> to find more information about LLVM or to get
626 <!-- ======================================================================= -->
628 <a name="terminology">Terminology and Notation</a>
633 <p>Throughout this manual, the following names are used to denote paths
634 specific to the local system and working environment. <i>These are not
635 environment variables you need to set but just strings used in the rest
636 of this document below</i>. In any of the examples below, simply replace
637 each of these names with the appropriate pathname on your local system.
638 All these paths are absolute:</p>
643 This is the top level directory of the LLVM source tree.
648 This is the top level directory of the LLVM object tree (i.e. the
649 tree where object files and compiled programs will be placed. It
650 can be the same as SRC_ROOT).
655 This is where the LLVM GCC Front End is installed.
657 For the pre-built GCC front end binaries, the LLVMGCCDIR is
658 <tt>llvm-gcc/<i>platform</i>/llvm-gcc</tt>.
663 <!-- ======================================================================= -->
665 <a name="environment">Setting Up Your Environment</a>
671 In order to compile and use LLVM, you may need to set some environment
675 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bitcode/libs</tt></dt>
676 <dd>[Optional] This environment variable helps LLVM linking tools find the
677 locations of your bitcode libraries. It is provided only as a
678 convenience since you can specify the paths using the -L options of the
679 tools and the C/C++ front-end will automatically use the bitcode files
681 <tt>lib</tt> directory.</dd>
686 <!-- ======================================================================= -->
688 <a name="unpack">Unpacking the LLVM Archives</a>
694 If you have the LLVM distribution, you will need to unpack it before you
695 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
696 suite and the LLVM GCC front end compiled for your platform. There is an
697 additional test suite that is optional. Each file is a TAR archive that is
698 compressed with the gzip program.
701 <p>The files are as follows, with <em>x.y</em> marking the version number:
703 <dt><tt>llvm-x.y.tar.gz</tt></dt>
704 <dd>Source release for the LLVM libraries and tools.<br></dd>
706 <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
707 <dd>Source release for the LLVM test-suite.</dd>
709 <dt><tt>llvm-gcc-4.2-x.y.source.tar.gz</tt></dt>
710 <dd>Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
711 directory for build instructions.<br></dd>
713 <dt><tt>llvm-gcc-4.2-x.y-platform.tar.gz</tt></dt>
714 <dd>Binary release of the llvm-gcc-4.2 front end for a specific platform.<br></dd>
720 <!-- ======================================================================= -->
722 <a name="checkout">Checkout LLVM from Subversion</a>
727 <p>If you have access to our Subversion repository, you can get a fresh copy of
728 the entire source code. All you need to do is check it out from Subversion as
732 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
733 <li>Read-Only: <tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
734 <li>Read-Write:<tt>svn co https://user@llvm.org/svn/llvm-project/llvm/trunk
739 <p>This will create an '<tt>llvm</tt>' directory in the current
740 directory and fully populate it with the LLVM source code, Makefiles,
741 test directories, and local copies of documentation files.</p>
743 <p>If you want to get a specific release (as opposed to the most recent
744 revision), you can checkout it from the '<tt>tags</tt>' directory (instead of
745 '<tt>trunk</tt>'). The following releases are located in the following
746 subdirectories of the '<tt>tags</tt>' directory:</p>
749 <li>Release 2.9: <b>RELEASE_29/final</b></li>
750 <li>Release 2.8: <b>RELEASE_28</b></li>
751 <li>Release 2.7: <b>RELEASE_27</b></li>
752 <li>Release 2.6: <b>RELEASE_26</b></li>
753 <li>Release 2.5: <b>RELEASE_25</b></li>
754 <li>Release 2.4: <b>RELEASE_24</b></li>
755 <li>Release 2.3: <b>RELEASE_23</b></li>
756 <li>Release 2.2: <b>RELEASE_22</b></li>
757 <li>Release 2.1: <b>RELEASE_21</b></li>
758 <li>Release 2.0: <b>RELEASE_20</b></li>
759 <li>Release 1.9: <b>RELEASE_19</b></li>
760 <li>Release 1.8: <b>RELEASE_18</b></li>
761 <li>Release 1.7: <b>RELEASE_17</b></li>
762 <li>Release 1.6: <b>RELEASE_16</b></li>
763 <li>Release 1.5: <b>RELEASE_15</b></li>
764 <li>Release 1.4: <b>RELEASE_14</b></li>
765 <li>Release 1.3: <b>RELEASE_13</b></li>
766 <li>Release 1.2: <b>RELEASE_12</b></li>
767 <li>Release 1.1: <b>RELEASE_11</b></li>
768 <li>Release 1.0: <b>RELEASE_1</b></li>
771 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
772 you get it from the Subversion repository:</p>
774 <div class="doc_code">
777 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
781 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
782 configured by the LLVM configure script as well as automatically updated when
783 you run <tt>svn update</tt>.</p>
785 <p>If you would like to get the GCC front end source code, you can also get it
786 and build it yourself. Please follow <a href="GCCFEBuildInstrs.html">these
787 instructions</a> to successfully get and build the LLVM GCC front-end.</p>
791 <!-- ======================================================================= -->
793 <a name="git_mirror">GIT mirror</a>
798 <p>GIT mirrors are available for a number of LLVM subprojects. These mirrors
799 sync automatically with each Subversion commit and contain all necessary
800 git-svn marks (so, you can recreate git-svn metadata locally). Note that right
801 now mirrors reflect only <tt>trunk</tt> for each project. You can do the
802 read-only GIT clone of LLVM via:</p>
804 <pre class="doc_code">
805 git clone http://llvm.org/git/llvm.git
808 <p>If you want to check out clang too, run:</p>
810 <pre class="doc_code">
811 git clone http://llvm.org/git/llvm.git
813 git clone http://llvm.org/git/clang.git
817 Since the upstream repository is in Subversion, you should use
818 <tt>"git pull --rebase"</tt>
819 instead of <tt>"git pull"</tt> to avoid generating a non-linear
820 history in your clone.
821 To configure <tt>"git pull"</tt> to pass <tt>--rebase</tt> by default
822 on the master branch, run the following command:
825 <pre class="doc_code">
826 git config branch.master.rebase true
829 <h4>Sending patches with Git</h4>
832 Please read <a href="DeveloperPolicy.html#patches">Developer Policy</a>, too.
836 Assume <tt>master</tt> points the upstream and <tt>mybranch</tt> points your
837 working branch, and <tt>mybranch</tt> is rebased onto <tt>master</tt>.
838 At first you may check sanity of whitespaces:
841 <pre class="doc_code">
842 git diff --check master..mybranch
846 The easiest way to generate a patch is as below:
849 <pre class="doc_code">
850 git diff master..mybranch > /path/to/mybranch.diff
854 It is a little different from svn-generated diff. git-diff-generated diff has
855 prefixes like <tt>a/</tt> and <tt>b/</tt>. Don't worry, most developers might
856 know it could be accepted with <tt>patch -p1 -N</tt>.
860 But you may generate patchset with git-format-patch. It generates
861 by-each-commit patchset. To generate patch files to attach to your article:
864 <pre class="doc_code">
865 git format-patch --no-attach master..mybranch -o /path/to/your/patchset
869 If you would like to send patches directly, you may use git-send-email or
870 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
873 <pre class="doc_code">
874 git format-patch --attach master..mybranch --stdout | git imap-send
878 Then, your .git/config should have [imap] sections.
881 <pre class="doc_code">
883 host = imaps://imap.gmail.com
884 user = <em>your.gmail.account</em>@gmail.com
885 pass = <em>himitsu!</em>
889 folder = "[Gmail]/Drafts"
890 ; example for Japanese, "Modified UTF-7" encoded.
891 folder = "[Gmail]/&Tgtm+DBN-"
896 <h4>For developers to work with git-svn</h4>
899 <p>To set up clone from which you can submit code using
900 <tt>git-svn</tt>, run:</p>
902 <pre class="doc_code">
903 git clone http://llvm.org/git/llvm.git
905 git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
906 git config svn-remote.svn.fetch :refs/remotes/origin/master
907 git svn rebase -l # -l avoids fetching ahead of the git mirror.
909 # If you have clang too:
911 git clone http://llvm.org/git/clang.git
913 git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
914 git config svn-remote.svn.fetch :refs/remotes/origin/master
918 <p>To update this clone without generating git-svn tags that conflict
919 with the upstream git repo, run:</p>
921 <pre class="doc_code">
922 git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
926 git checkout master &&
930 <p>This leaves your working directories on their master branches, so
931 you'll need to <tt>checkout</tt> each working branch individually and
932 <tt>rebase</tt> it on top of its parent branch. (Note: This script is
933 intended for relative newbies to git. If you have more experience,
934 you can likely improve on it.)</p>
936 <p>The git-svn metadata can get out of sync after you mess around with
937 branches and <code>dcommit</code>. When that happens, <code>git svn
938 dcommit</code> stops working, complaining about files with uncommitted
939 changes. The fix is to rebuild the metadata:</p>
941 <pre class="doc_code">
950 <!-- ======================================================================= -->
952 <a name="installcf">Install the GCC Front End</a>
957 <p>Before configuring and compiling the LLVM suite (or if you want to use just the LLVM
958 GCC front end) you can optionally extract the front end from the binary distribution.
959 It is used for running the LLVM test-suite and for compiling C/C++ programs. Note that
960 you can optionally <a href="GCCFEBuildInstrs.html">build llvm-gcc yourself</a> after building the
961 main LLVM repository.</p>
963 <p>To install the GCC front end, do the following (on Windows, use an archival tool
964 like <a href="http://www.7-zip.org/">7-zip</a> that understands gzipped tars):</p>
967 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
968 <li><tt>gunzip --stdout llvm-gcc-4.2-<i>version</i>-<i>platform</i>.tar.gz | tar -xvf
972 <p>Once the binary is uncompressed, if you're using a *nix-based system, add a symlink for
973 <tt>llvm-gcc</tt> and <tt>llvm-g++</tt> to some directory in your path. If you're using a
974 Windows-based system, add the <tt>bin</tt> subdirectory of your front end installation directory
975 to your <tt>PATH</tt> environment variable. For example, if you uncompressed the binary to
976 <tt>c:\llvm-gcc</tt>, add <tt>c:\llvm-gcc\bin</tt> to your <tt>PATH</tt>.</p>
978 <p>If you now want to build LLVM from source, when you configure LLVM, it will
979 automatically detect <tt>llvm-gcc</tt>'s presence (if it is in your path) enabling its
980 use in test-suite. Note that you can always build or install <tt>llvm-gcc</tt> at any
981 point after building the main LLVM repository: just reconfigure llvm and
982 test-suite will pick it up.
985 <p>As a convenience for Windows users, the front end binaries for MinGW/x86 include
986 versions of the required w32api and mingw-runtime binaries. The last remaining step for
987 Windows users is to simply uncompress the binary binutils package from
988 <a href="http://mingw.org/">MinGW</a> into your front end installation directory. While the
989 front end installation steps are not quite the same as a typical manual MinGW installation,
990 they should be similar enough to those who have previously installed MinGW on Windows systems.</p>
992 <p>To install binutils on Windows:</p>
995 <li><tt><i>download GNU Binutils from <a href="http://sourceforge.net/projects/mingw/files/">MinGW Downloads</a></i></tt></li>
996 <li><tt>cd <i>where-you-uncompressed-the-front-end</i></tt></li>
997 <li><tt><i>uncompress archived binutils directories (not the tar file) into the current directory</i></tt></li>
1000 <p>The binary versions of the LLVM GCC front end may not suit all of your needs. For
1001 example, the binary distribution may include an old version of a system header
1002 file, not "fix" a header file that needs to be fixed for GCC, or it may be linked with
1003 libraries not available on your system. In cases like these, you may want to try
1004 <a href="GCCFEBuildInstrs.html">building the GCC front end from source</a>. Thankfully,
1005 this is much easier now than it was in the past.</p>
1007 <p>We also do not currently support updating of the GCC front end by manually overlaying
1008 newer versions of the w32api and mingw-runtime binary packages that may become available
1009 from MinGW. At this time, it's best to think of the MinGW LLVM GCC front end binary as
1010 a self-contained convenience package that requires Windows users to simply download and
1011 uncompress the GNU Binutils binary package from the MinGW project.</p>
1013 <p>Regardless of your platform, if you discover that installing the LLVM GCC front end
1014 binaries is not as easy as previously described, or you would like to suggest improvements,
1015 please let us know how you would like to see things improved by dropping us a note on our
1016 <a href="http://llvm.org/docs/#maillist">mailing list</a>.</p>
1020 <!-- ======================================================================= -->
1022 <a name="config">Local LLVM Configuration</a>
1027 <p>Once checked out from the Subversion repository, the LLVM suite source
1029 configured via the <tt>configure</tt> script. This script sets variables in the
1030 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
1031 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
1032 the Makefiles needed to begin building LLVM.</p>
1034 <p>The following environment variables are used by the <tt>configure</tt>
1035 script to configure the build system:</p>
1037 <table summary="LLVM configure script environment variables">
1038 <tr><th>Variable</th><th>Purpose</th></tr>
1041 <td>Tells <tt>configure</tt> which C compiler to use. By default,
1042 <tt>configure</tt> will look for the first GCC C compiler in
1043 <tt>PATH</tt>. Use this variable to override
1044 <tt>configure</tt>'s default behavior.</td>
1048 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
1049 <tt>configure</tt> will look for the first GCC C++ compiler in
1050 <tt>PATH</tt>. Use this variable to override
1051 <tt>configure</tt>'s default behavior.</td>
1055 <p>The following options can be used to set or enable LLVM specific options:</p>
1058 <dt><i>--with-llvmgccdir</i></dt>
1059 <dd>Path to the LLVM C/C++ FrontEnd to be used with this LLVM configuration.
1060 The value of this option should specify the full pathname of the C/C++ Front
1061 End to be used. If this option is not provided, the PATH will be searched for
1062 a program named <i>llvm-gcc</i> and the C/C++ FrontEnd install directory will
1063 be inferred from the path found. If the option is not given, and no llvm-gcc
1064 can be found in the path then a warning will be produced by
1065 <tt>configure</tt> indicating this situation. LLVM may still be built with
1066 the <tt>tools-only</tt> target but attempting to build the runtime libraries
1067 will fail as these libraries require llvm-gcc and llvm-g++. See
1068 <a href="#installcf">Install the GCC Front End</a> for details on installing
1069 the C/C++ Front End. See
1070 <a href="GCCFEBuildInstrs.html">Bootstrapping the LLVM C/C++ Front-End</a>
1071 for details on building the C/C++ Front End.</dd>
1072 <dt><i>--with-tclinclude</i></dt>
1073 <dd>Path to the tcl include directory under which <tt>tclsh</tt> can be
1074 found. Use this if you have multiple tcl installations on your machine and you
1075 want to use a specific one (8.x) for LLVM. LLVM only uses tcl for running the
1076 dejagnu based test suite in <tt>llvm/test</tt>. If you don't specify this
1077 option, the LLVM configure script will search for the tcl 8.4 and 8.3
1081 <dt><i>--enable-optimized</i></dt>
1083 Enables optimized compilation (debugging symbols are removed
1084 and GCC optimization flags are enabled). Note that this is the default
1085 setting if you are using the LLVM distribution. The default behavior
1086 of an Subversion checkout is to use an unoptimized build (also known as a
1090 <dt><i>--enable-debug-runtime</i></dt>
1092 Enables debug symbols in the runtime libraries. The default is to strip
1093 debug symbols from the runtime libraries.
1095 <dt><i>--enable-jit</i></dt>
1097 Compile the Just In Time (JIT) compiler functionality. This is not
1099 on all platforms. The default is dependent on platform, so it is best
1100 to explicitly enable it if you want it.
1103 <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
1104 <dd>Controls which targets will be built and linked into llc. The default
1105 value for <tt>target_options</tt> is "all" which builds and links all
1106 available targets. The value "host-only" can be specified to build only a
1107 native compiler (no cross-compiler targets available). The "native" target is
1108 selected as the target of the build host. You can also specify a comma
1109 separated list of target names that you want available in llc. The target
1110 names use all lower case. The current set of targets is: <br>
1111 <tt>alpha, ia64, powerpc, skeleton, sparc, x86</tt>.
1113 <dt><i>--enable-doxygen</i></dt>
1114 <dd>Look for the doxygen program and enable construction of doxygen based
1115 documentation from the source code. This is disabled by default because
1116 generating the documentation can take a long time and producess 100s of
1117 megabytes of output.</dd>
1118 <dt><i>--with-udis86</i></dt>
1119 <dd>LLVM can use external disassembler library for various purposes (now it's
1120 used only for examining code produced by JIT). This option will enable usage
1121 of <a href="http://udis86.sourceforge.net/">udis86</a> x86 (both 32 and 64
1122 bits) disassembler library.</dd>
1125 <p>To configure LLVM, follow these steps:</p>
1128 <li><p>Change directory into the object root directory:</p>
1130 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1132 <li><p>Run the <tt>configure</tt> script located in the LLVM source
1135 <div class="doc_code">
1136 <pre>% <i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</pre>
1142 <!-- ======================================================================= -->
1144 <a name="compile">Compiling the LLVM Suite Source Code</a>
1149 <p>Once you have configured LLVM, you can build it. There are three types of
1155 These builds are the default when one is using an Subversion checkout and
1156 types <tt>gmake</tt> (unless the <tt>--enable-optimized</tt> option was
1157 used during configuration). The build system will compile the tools and
1158 libraries with debugging information. To get a Debug Build using the
1159 LLVM distribution the <tt>--disable-optimized</tt> option must be passed
1160 to <tt>configure</tt>.
1163 <dt>Release (Optimized) Builds
1165 These builds are enabled with the <tt>--enable-optimized</tt> option to
1166 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
1167 <tt>gmake</tt> command line. For these builds, the build system will
1168 compile the tools and libraries with GCC optimizations enabled and strip
1169 debugging information from the libraries and executables it generates.
1170 Note that Release Builds are default when using an LLVM distribution.
1175 These builds are for use with profiling. They compile profiling
1176 information into the code for use with programs like <tt>gprof</tt>.
1177 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
1178 on the <tt>gmake</tt> command line.
1181 <p>Once you have LLVM configured, you can build it by entering the
1182 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
1184 <div class="doc_code"><pre>% gmake</pre></div>
1186 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
1187 are using a version of GCC that is known not to compile LLVM.</p>
1190 If you have multiple processors in your machine, you may wish to use some of
1191 the parallel build options provided by GNU Make. For example, you could use the
1194 <div class="doc_code"><pre>% gmake -j2</pre></div>
1196 <p>There are several special targets which are useful when working with the LLVM
1200 <dt><tt>gmake clean</tt>
1202 Removes all files generated by the build. This includes object files,
1203 generated C/C++ files, libraries, and executables.
1206 <dt><tt>gmake dist-clean</tt>
1208 Removes everything that <tt>gmake clean</tt> does, but also removes files
1209 generated by <tt>configure</tt>. It attempts to return the source tree to the
1210 original state in which it was shipped.
1213 <dt><tt>gmake install</tt>
1215 Installs LLVM header files, libraries, tools, and documentation in a
1217 under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
1218 defaults to <tt>/usr/local</tt>.
1221 <dt><tt>gmake -C runtime install-bytecode</tt>
1223 Assuming you built LLVM into $OBJDIR, when this command is run, it will
1224 install bitcode libraries into the GCC front end's bitcode library
1225 directory. If you need to update your bitcode libraries,
1226 this is the target to use once you've built them.
1230 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
1231 details on these <tt>make</tt> targets and descriptions of other targets
1234 <p>It is also possible to override default values from <tt>configure</tt> by
1235 declaring variables on the command line. The following are some examples:</p>
1238 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
1240 Perform a Release (Optimized) build.
1243 <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
1245 Perform a Release (Optimized) build without assertions enabled.
1248 <dt><tt>gmake ENABLE_OPTIMIZED=0</tt>
1250 Perform a Debug build.
1253 <dt><tt>gmake ENABLE_PROFILING=1</tt>
1255 Perform a Profiling build.
1258 <dt><tt>gmake VERBOSE=1</tt>
1260 Print what <tt>gmake</tt> is doing on standard output.
1263 <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
1264 <dd>Ask each tool invoked by the makefiles to print out what it is doing on
1265 the standard output. This also implies <tt>VERBOSE=1</tt>.
1269 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
1270 it and any subdirectories that it contains. Entering any directory inside the
1271 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
1272 that directory that is out of date.</p>
1276 <!-- ======================================================================= -->
1278 <a name="cross-compile">Cross-Compiling LLVM</a>
1282 <p>It is possible to cross-compile LLVM itself. That is, you can create LLVM
1283 executables and libraries to be hosted on a platform different from the
1284 platform where they are build (a Canadian Cross build). To configure a
1285 cross-compile, supply the configure script with <tt>--build</tt> and
1286 <tt>--host</tt> options that are different. The values of these options must
1287 be legal target triples that your GCC compiler supports.</p>
1289 <p>The result of such a build is executables that are not runnable on
1290 on the build host (--build option) but can be executed on the compile host
1291 (--host option).</p>
1294 <!-- ======================================================================= -->
1296 <a name="objfiles">The Location of LLVM Object Files</a>
1301 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1302 several LLVM builds. Hence, it is possible to build LLVM for several different
1303 platforms or configurations using the same source tree.</p>
1305 <p>This is accomplished in the typical autoconf manner:</p>
1308 <li><p>Change directory to where the LLVM object files should live:</p>
1310 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1312 <li><p>Run the <tt>configure</tt> script found in the LLVM source
1315 <div class="doc_code"><pre>% <i>SRC_ROOT</i>/configure</pre></div></li>
1318 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1319 named after the build type:</p>
1322 <dt>Debug Builds with assertions enabled (the default)
1326 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/bin</tt>
1328 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/lib</tt>
1336 <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1338 <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1346 <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1348 <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1354 <!-- ======================================================================= -->
1356 <a name="optionalconfig">Optional Configuration Items</a>
1362 If you're running on a Linux system that supports the "<a
1363 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
1364 module, and you have root access on the system, you can set your system up to
1365 execute LLVM bitcode files directly. To do this, use commands like this (the
1366 first command may not be required if you are already using the module):</p>
1368 <div class="doc_code">
1370 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1371 $ echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1372 $ chmod u+x hello.bc (if needed)
1378 This allows you to execute LLVM bitcode files directly. On Debian, you
1379 can also use this command instead of the 'echo' command above:
1382 <div class="doc_code">
1384 $ sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1392 <!-- *********************************************************************** -->
1394 <a name="layout">Program Layout</a>
1396 <!-- *********************************************************************** -->
1400 <p>One useful source of information about the LLVM source base is the LLVM <a
1401 href="http://www.doxygen.org/">doxygen</a> documentation available at <tt><a
1402 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1403 The following is a brief introduction to code layout:</p>
1405 <!-- ======================================================================= -->
1407 <a name="examples"><tt>llvm/examples</tt></a>
1411 <p>This directory contains some simple examples of how to use the LLVM IR and
1415 <!-- ======================================================================= -->
1417 <a name="include"><tt>llvm/include</tt></a>
1422 <p>This directory contains public header files exported from the LLVM
1423 library. The three main subdirectories of this directory are:</p>
1426 <dt><tt><b>llvm/include/llvm</b></tt></dt>
1427 <dd>This directory contains all of the LLVM specific header files. This
1428 directory also has subdirectories for different portions of LLVM:
1429 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1432 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1433 <dd>This directory contains generic support libraries that are provided with
1434 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1435 and a Command Line option processing library store their header files here.
1438 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1439 <dd>This directory contains header files configured by the <tt>configure</tt>
1440 script. They wrap "standard" UNIX and C header files. Source code can
1441 include these header files which automatically take care of the conditional
1442 #includes that the <tt>configure</tt> script generates.</dd>
1446 <!-- ======================================================================= -->
1448 <a name="lib"><tt>llvm/lib</tt></a>
1453 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1454 almost all code exists in libraries, making it very easy to share code among the
1455 different <a href="#tools">tools</a>.</p>
1458 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1459 <dd> This directory holds the core LLVM source files that implement core
1460 classes like Instruction and BasicBlock.</dd>
1462 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1463 <dd>This directory holds the source code for the LLVM assembly language parser
1466 <dt><tt><b>llvm/lib/BitCode/</b></tt></dt>
1467 <dd>This directory holds code for reading and write LLVM bitcode.</dd>
1469 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1470 different program analyses, such as Dominator Information, Call Graphs,
1471 Induction Variables, Interval Identification, Natural Loop Identification,
1474 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1475 <dd> This directory contains the source code for the LLVM to LLVM program
1476 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1477 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1478 Elimination, and many others.</dd>
1480 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1481 <dd> This directory contains files that describe various target architectures
1482 for code generation. For example, the <tt>llvm/lib/Target/X86</tt>
1483 directory holds the X86 machine description while
1484 <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter.</dd>
1486 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1487 <dd> This directory contains the major parts of the code generator: Instruction
1488 Selector, Instruction Scheduling, and Register Allocation.</dd>
1490 <dt><tt><b>llvm/lib/MC/</b></tt></dt>
1491 <dd>(FIXME: T.B.D.)</dd>
1493 <!--FIXME: obsoleted -->
1494 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1495 <dd> This directory contains the source level debugger library that makes
1496 it possible to instrument LLVM programs so that a debugger could identify
1497 source code locations at which the program is executing.</dd>
1499 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1500 <dd> This directory contains libraries for executing LLVM bitcode directly
1501 at runtime in both interpreted and JIT compiled fashions.</dd>
1503 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1504 <dd> This directory contains the source code that corresponds to the header
1505 files located in <tt>llvm/include/ADT/</tt>
1506 and <tt>llvm/include/Support/</tt>.</dd>
1511 <!-- ======================================================================= -->
1513 <a name="projects"><tt>llvm/projects</tt></a>
1517 <p>This directory contains projects that are not strictly part of LLVM but are
1518 shipped with LLVM. This is also the directory where you should create your own
1519 LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1520 to set up your own project.</p>
1523 <!-- ======================================================================= -->
1525 <a name="runtime"><tt>llvm/runtime</tt></a>
1530 <p>This directory contains libraries which are compiled into LLVM bitcode and
1531 used when linking programs with the GCC front end. Most of these libraries are
1532 skeleton versions of real libraries; for example, libc is a stripped down
1533 version of glibc.</p>
1535 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1540 <!-- ======================================================================= -->
1542 <a name="test"><tt>llvm/test</tt></a>
1546 <p>This directory contains feature and regression tests and other basic sanity
1547 checks on the LLVM infrastructure. These are intended to run quickly and cover
1548 a lot of territory without being exhaustive.</p>
1551 <!-- ======================================================================= -->
1553 <a name="test-suite"><tt>test-suite</tt></a>
1557 <p>This is not a directory in the normal llvm module; it is a separate
1559 module that must be checked out (usually to <tt>projects/test-suite</tt>).
1561 module contains a comprehensive correctness, performance, and benchmarking
1563 suite for LLVM. It is a separate Subversion module because not every LLVM
1565 interested in downloading or building such a comprehensive test suite. For
1566 further details on this test suite, please see the
1567 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1570 <!-- ======================================================================= -->
1572 <a name="tools"><tt>llvm/tools</tt></a>
1577 <p>The <b>tools</b> directory contains the executables built out of the
1578 libraries above, which form the main part of the user interface. You can
1579 always get help for a tool by typing <tt>tool_name -help</tt>. The
1580 following is a brief introduction to the most important tools. More detailed
1581 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1585 <dt><tt><b>bugpoint</b></tt></dt>
1586 <dd><tt>bugpoint</tt> is used to debug
1587 optimization passes or code generation backends by narrowing down the
1588 given test case to the minimum number of passes and/or instructions that
1589 still cause a problem, whether it is a crash or miscompilation. See <a
1590 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1591 on using <tt>bugpoint</tt>.</dd>
1593 <dt><tt><b>llvm-ar</b></tt></dt>
1594 <dd>The archiver produces an archive containing
1595 the given LLVM bitcode files, optionally with an index for faster
1598 <dt><tt><b>llvm-as</b></tt></dt>
1599 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1602 <dt><tt><b>llvm-dis</b></tt></dt>
1603 <dd>The disassembler transforms the LLVM bitcode to human readable
1606 <dt><tt><b>llvm-ld</b></tt></dt>
1607 <dd><tt>llvm-ld</tt> is a general purpose and extensible linker for LLVM.
1608 It performs standard link time optimizations and allows optimization
1609 modules to be loaded and run so that language specific optimizations can
1610 be applied at link time.</dd>
1612 <dt><tt><b>llvm-link</b></tt></dt>
1613 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1614 a single program.</dd>
1616 <dt><tt><b>lli</b></tt></dt>
1617 <dd><tt>lli</tt> is the LLVM interpreter, which
1618 can directly execute LLVM bitcode (although very slowly...). For architectures
1619 that support it (currently x86, Sparc, and PowerPC), by default, <tt>lli</tt>
1620 will function as a Just-In-Time compiler (if the functionality was compiled
1621 in), and will execute the code <i>much</i> faster than the interpreter.</dd>
1623 <dt><tt><b>llc</b></tt></dt>
1624 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1625 translates LLVM bitcode to a native code assembly file or to C code (with
1626 the -march=c option).</dd>
1628 <dt><tt><b>llvm-gcc</b></tt></dt>
1629 <dd><tt>llvm-gcc</tt> is a GCC-based C frontend that has been retargeted to
1630 use LLVM as its backend instead of GCC's RTL backend. It can also emit LLVM
1631 bitcode or assembly (with the <tt>-emit-llvm</tt> option) instead of the
1632 usual machine code output. It works just like any other GCC compiler,
1633 taking the typical <tt>-c, -S, -E, -o</tt> options that are typically used.
1634 Additionally, the the source code for <tt>llvm-gcc</tt> is available as a
1635 separate Subversion module.</dd>
1637 <dt><tt><b>opt</b></tt></dt>
1638 <dd><tt>opt</tt> reads LLVM bitcode, applies a series of LLVM to LLVM
1639 transformations (which are specified on the command line), and then outputs
1640 the resultant bitcode. The '<tt>opt -help</tt>' command is a good way to
1641 get a list of the program transformations available in LLVM.<br>
1642 <dd><tt>opt</tt> can also be used to run a specific analysis on an input
1643 LLVM bitcode file and print out the results. It is primarily useful for
1644 debugging analyses, or familiarizing yourself with what an analysis does.</dd>
1648 <!-- ======================================================================= -->
1650 <a name="utils"><tt>llvm/utils</tt></a>
1655 <p>This directory contains utilities for working with LLVM source code, and some
1656 of the utilities are actually required as part of the build process because they
1657 are code generators for parts of LLVM infrastructure.</p>
1660 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1661 that finds differences between code that LLC generates and code that LLI
1662 generates. This is a useful tool if you are debugging one of them,
1663 assuming that the other generates correct output. For the full user
1664 manual, run <tt>`perldoc codegen-diff'</tt>.<br><br>
1666 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1667 syntax-highlighting files which will work with Emacs and XEmacs editors,
1668 providing syntax highlighting support for LLVM assembly files and TableGen
1669 description files. For information on how to use the syntax files, consult
1670 the <tt>README</tt> file in that directory.<br><br>
1672 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1673 and outputs all non-generated source files, which is useful if one wishes
1674 to do a lot of development across directories and does not want to
1675 individually find each file. One way to use it is to run, for example:
1676 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1679 <dt><tt><b>llvmgrep</b></tt></dt>
1680 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1681 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1682 line. This is a very efficient way of searching the source base for a
1683 particular regular expression.</dd>
1685 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1686 files in the current directory and then compiles and links the tool that
1687 is the first argument. For example, assuming you are in the directory
1688 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1689 simply running <tt>makellvm llc</tt> will make a build of the current
1690 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1691 causing a re-linking of LLC.<br><br>
1693 <dt><tt><b>NewNightlyTest.pl</b></tt> and
1694 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1695 cron script to generate nightly status reports of the functionality of
1696 tools, and the results can be seen by following the appropriate link on
1697 the <a href="http://llvm.org/">LLVM homepage</a>.<br><br>
1699 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1700 the tool used to generate register descriptions, instruction set
1701 descriptions, and even assemblers from common TableGen description
1704 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1705 syntax-highlighting files which will work with the VIM editor, providing
1706 syntax highlighting support for LLVM assembly files and TableGen
1707 description files. For information on how to use the syntax files, consult
1708 the <tt>README</tt> file in that directory.<br><br>
1716 <!-- *********************************************************************** -->
1718 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1720 <!-- *********************************************************************** -->
1723 <p>This section gives an example of using LLVM. llvm-gcc3 is now obsolete,
1724 so we only include instructions for llvm-gcc4.
1727 <p><b>Note:</b> The <i>gcc4</i> frontend's invocation is <b><i>considerably different</i></b>
1728 from the previous <i>gcc3</i> frontend. In particular, the <i>gcc4</i> frontend <b><i>does not</i></b>
1729 create bitcode by default: <i>gcc4</i> produces native code. As the example below illustrates,
1730 the '--emit-llvm' flag is needed to produce LLVM bitcode output. For <i>makefiles</i> and
1731 <i>configure</i> scripts, the CFLAGS variable needs '--emit-llvm' to produce bitcode
1734 <!-- ======================================================================= -->
1736 <a name="tutorial4">Example with llvm-gcc4</a>
1742 <li><p>First, create a simple C file, name it 'hello.c':</p>
1744 <div class="doc_code">
1746 #include <stdio.h>
1749 printf("hello world\n");
1754 <li><p>Next, compile the C file into a native executable:</p>
1756 <div class="doc_code"><pre>% llvm-gcc hello.c -o hello</pre></div>
1758 <p>Note that llvm-gcc works just like GCC by default. The standard -S and
1759 -c arguments work as usual (producing a native .s or .o file,
1760 respectively).</p></li>
1762 <li><p>Next, compile the C file into a LLVM bitcode file:</p>
1764 <div class="doc_code">
1765 <pre>% llvm-gcc -O3 -emit-llvm hello.c -c -o hello.bc</pre></div>
1767 <p>The -emit-llvm option can be used with the -S or -c options to emit an
1768 LLVM ".ll" or ".bc" file (respectively) for the code. This allows you
1769 to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
1770 the bitcode file.</p>
1772 <p>Unlike llvm-gcc3, llvm-gcc4 correctly responds to -O[0123] arguments.
1775 <li><p>Run the program in both forms. To run the program, use:</p>
1777 <div class="doc_code"><pre>% ./hello</pre></div>
1781 <div class="doc_code"><pre>% lli hello.bc</pre></div>
1783 <p>The second examples shows how to invoke the LLVM JIT, <a
1784 href="CommandGuide/html/lli.html">lli</a>.</p></li>
1786 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1789 <div class="doc_code">
1790 <pre>llvm-dis < hello.bc | less</pre>
1793 <li><p>Compile the program to native assembly using the LLC code
1796 <div class="doc_code"><pre>% llc hello.bc -o hello.s</pre></div></li>
1798 <li><p>Assemble the native assembly language file into a program:</p>
1800 <div class="doc_code">
1802 <b>Solaris:</b> % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native
1804 <b>Others:</b> % gcc hello.s -o hello.native
1808 <li><p>Execute the native code program:</p>
1810 <div class="doc_code"><pre>% ./hello.native</pre></div>
1812 <p>Note that using llvm-gcc to compile directly to native code (i.e. when
1813 the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
1822 <!-- *********************************************************************** -->
1824 <a name="problems">Common Problems</a>
1826 <!-- *********************************************************************** -->
1830 <p>If you are having problems building or using LLVM, or if you have any other
1831 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1832 Asked Questions</a> page.</p>
1836 <!-- *********************************************************************** -->
1838 <a name="links">Links</a>
1840 <!-- *********************************************************************** -->
1844 <p>This document is just an <b>introduction</b> on how to use LLVM to do
1845 some simple things... there are many more interesting and complicated things
1846 that you can do that aren't documented here (but we'll gladly accept a patch
1847 if you want to write something up!). For more information about LLVM, check
1851 <li><a href="http://llvm.org/">LLVM homepage</a></li>
1852 <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1853 <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1854 that Uses LLVM</a></li>
1859 <!-- *********************************************************************** -->
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1868 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1869 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1870 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
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