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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="#config">Local LLVM Configuration</a></li>
33 <li><a href="#compile">Compiling the LLVM Suite Source Code</a></li>
34 <li><a href="#cross-compile">Cross-Compiling LLVM</a></li>
35 <li><a href="#objfiles">The Location of LLVM Object Files</a></li>
36 <li><a href="#optionalconfig">Optional Configuration Items</a></li>
39 <li><a href="#layout">Program layout</a>
41 <li><a href="#examples"><tt>llvm/examples</tt></a></li>
42 <li><a href="#include"><tt>llvm/include</tt></a></li>
43 <li><a href="#lib"><tt>llvm/lib</tt></a></li>
44 <li><a href="#projects"><tt>llvm/projects</tt></a></li>
45 <li><a href="#runtime"><tt>llvm/runtime</tt></a></li>
46 <li><a href="#test"><tt>llvm/test</tt></a></li>
47 <li><a href="#test-suite"><tt>test-suite</tt></a></li>
48 <li><a href="#tools"><tt>llvm/tools</tt></a></li>
49 <li><a href="#utils"><tt>llvm/utils</tt></a></li>
52 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
54 <li><a href="#tutorial4">Example with Clang</a></li>
56 <li><a href="#problems">Common Problems</a>
57 <li><a href="#links">Links</a>
60 <div class="doc_author">
62 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
63 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
64 <a href="http://misha.brukman.net/">Misha Brukman</a>,
65 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
66 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
71 <!-- *********************************************************************** -->
73 <a name="overview">Overview</a>
75 <!-- *********************************************************************** -->
79 <p>Welcome to LLVM! In order to get started, you first need to know some
80 basic information.</p>
82 <p>First, LLVM comes in three pieces. The first piece is the LLVM
83 suite. This contains all of the tools, libraries, and header files
84 needed to use LLVM. It contains an assembler, disassembler, bitcode
85 analyzer and bitcode optimizer. It also contains basic regression tests that
86 can be used to test the LLVM tools and the Clang front end.</p>
88 <p>The second piece is the <a href="http://clang.llvm.org/">Clang</a> front end.
89 This component compiles C, C++, Objective C, and Objective C++ code into LLVM
90 bitcode. Once compiled into LLVM bitcode, a program can be manipulated with the
91 LLVM tools from the LLVM suite.
95 There is a third, optional piece called Test Suite. It is a suite of programs
96 with a testing harness that can be used to further test LLVM's functionality
102 <!-- *********************************************************************** -->
104 <a name="quickstart">Getting Started Quickly (A Summary)</a>
106 <!-- *********************************************************************** -->
110 <p>The LLVM Getting Started documentation may be out of date. So, the Clang
111 <a href="http://clang.llvm.org/get_started.html">Getting Started</a> page might
112 also be a good place to start.</p>
114 <p>Here's the short story for getting up and running quickly with LLVM:</p>
117 <li>Read the documentation.</li>
118 <li>Read the documentation.</li>
119 <li>Remember that you were warned twice about reading the documentation.</li>
123 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
124 <li><tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
130 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
131 <li><tt>cd llvm/tools</tt>
132 <li><tt>svn co http://llvm.org/svn/llvm-project/cfe/trunk clang</tt></li>
136 <li>Checkout Compiler-RT:
138 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
139 <li><tt>cd llvm/projects</tt>
140 <li><tt>svn co http://llvm.org/svn/llvm-project/compiler-rt/trunk
141 compiler-rt</tt></li>
145 <li>Get the Test Suite Source Code <b>[Optional]</b>
147 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
148 <li><tt>cd llvm/projects</tt>
149 <li><tt>svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite</tt></li>
153 <li>Configure and build LLVM and Clang:
155 <li><tt>cd <i>where-you-want-to-build-llvm</i></tt></li>
156 <li><tt>mkdir build</tt> (for building without polluting the source dir)</li>
157 <li><tt>cd build</tt></li>
158 <li><tt>../llvm/configure [options]</tt>
159 <br>Some common options:
162 <li><tt>--prefix=<i>directory</i></tt> -
163 Specify for <i>directory</i> the full pathname of where you
164 want the LLVM tools and libraries to be installed (default
165 <tt>/usr/local</tt>).</li>
169 <li><tt>--enable-optimized</tt> -
170 Compile with optimizations enabled (default is NO).</li>
174 <li><tt>--enable-assertions</tt> -
175 Compile with assertion checks enabled (default is YES).</li>
178 <li><tt>make [-j]</tt> - The -j specifies the number of jobs (commands) to
179 run simultaneously. This builds both LLVM and Clang for Debug+Asserts mode.
180 The --enabled-optimized configure option is used to specify a Release build.</li>
181 <li><tt>make check-all</tt> -
182 This run the regression tests to ensure everything is in working order.</li>
183 <li><tt>make update</tt> -
184 This command is used to update all the svn repositories at once, rather then
185 having to <tt>cd</tt> into the individual repositories and running
186 <tt>svn update</tt>.</li>
187 <li>It is also possible to use CMake instead of the makefiles. With CMake
188 it is also possible to generate project files for several IDEs: Eclipse
189 CDT4, CodeBlocks, Qt-Creator (use the CodeBlocks generator), KDevelop3.</li>
190 <li>If you get an "internal compiler error (ICE)" or test failures, see
191 <a href="#brokengcc">below</a>.</li>
198 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
199 detailed information on configuring and compiling LLVM. See <a
200 href="#environment">Setting Up Your Environment</a> for tips that simplify
201 working with the Clang front end and LLVM tools. Go to <a href="#layout">Program
202 Layout</a> to learn about the layout of the source code tree.</p>
206 <!-- *********************************************************************** -->
208 <a name="requirements">Requirements</a>
210 <!-- *********************************************************************** -->
214 <p>Before you begin to use the LLVM system, review the requirements given below.
215 This may save you some trouble by knowing ahead of time what hardware and
216 software you will need.</p>
218 <!-- ======================================================================= -->
220 <a name="hardware">Hardware</a>
225 <p>LLVM is known to work on the following platforms:</p>
227 <table cellpadding="3" summary="Known LLVM platforms">
235 <td>x86<sup><a href="#pf_1">1</a></sup></td>
240 <td>x86<sup><a href="#pf_1">1</a></sup></td>
250 <td>V9 (Ultrasparc)</td>
255 <td>x86<sup><a href="#pf_1">1</a></sup></td>
264 <td>MacOS X<sup><a href="#pf_2">2</a></sup></td>
269 <td>MacOS X<sup><a href="#pf_2">2</a>,<a href="#pf_9">9</a></sup></td>
274 <td>Cygwin/Win32</td>
275 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_8">8</a>,
276 <a href="#pf_11">11</a></sup></td>
277 <td>GCC 3.4.X, binutils 2.20</td>
281 <td>x86<sup><a href="#pf_1">1</a>,<a href="#pf_6">6</a>,
282 <a href="#pf_8">8</a>, <a href="#pf_10">10</a>,
283 <a href="#pf_11">11</a></sup></td>
284 <td>GCC 3.4.X, binutils 2.20</td>
288 <p>LLVM has partial support for the following platforms:</p>
290 <table summary="LLVM partial platform support">
298 <td>x86<sup><a href="#pf_1">1</a></sup></td>
299 <td>Visual Studio 2008 or higher<sup><a href="#pf_4">4</a>,<a href="#pf_5">5</a></sup></td>
301 <td>AIX<sup><a href="#pf_3">3</a>,<a href="#pf_4">4</a></sup></td>
306 <td>Linux<sup><a href="#pf_3">3</a>,<a href="#pf_5">5</a></sup></td>
312 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
317 <td>Linux<sup><a href="#pf_7">7</a></sup></td>
318 <td>Itanium (IA-64)</td>
322 <td>HP-UX<sup><a href="#pf_7">7</a></sup></td>
323 <td>Itanium (IA-64)</td>
329 <td>mingw-w64's GCC-4.5.x<sup><a href="#pf_12">12</a></sup></td>
335 <div class="doc_notes">
337 <li><a name="pf_1">Code generation supported for Pentium processors and
339 <li><a name="pf_2">Code generation supported for 32-bit ABI only</a></li>
340 <li><a name="pf_3">No native code generation</a></li>
341 <li><a name="pf_4">Build is not complete: one or more tools do not link or function</a></li>
342 <li><a name="pf_5">The GCC-based C/C++ frontend does not build</a></li>
343 <li><a name="pf_6">The port is done using the MSYS shell.</a></li>
344 <li><a name="pf_7">Native code generation exists but is not complete.</a></li>
345 <li><a name="pf_8">Binutils 2.20 or later is required to build the assembler
346 generated by LLVM properly.</a></li>
347 <li><a name="pf_9">Xcode 2.5 and gcc 4.0.1</a> (Apple Build 5370) will trip
348 internal LLVM assert messages when compiled for Release at optimization
349 levels greater than 0 (i.e., <i>"-O1"</i> and higher).
350 Add <i>OPTIMIZE_OPTION="-O0"</i> to the build command line
351 if compiling for LLVM Release or bootstrapping the LLVM toolchain.</li>
352 <li><a name="pf_10">For MSYS/MinGW on Windows, be sure to install the MSYS
353 version of the perl package, and be sure it appears in your path
354 before any Windows-based versions such as Strawberry Perl and
355 ActivePerl, as these have Windows-specifics that will cause the
356 build to fail.</a></li>
357 <li><a name="pf_11">To use LLVM modules on Win32-based system,
358 you may configure LLVM with <i>"--enable-shared"</i>.</a></li>
359 <li><a name="pf_12">To compile SPU backend, you need to add
360 <tt>"LDFLAGS=-Wl,--stack,16777216"</tt> to configure.</a></li>
364 <p>Note that you will need about 1-3 GB of space for a full LLVM build in Debug
365 mode, depending on the system (it is so large because of all the debugging
366 information and the fact that the libraries are statically linked into multiple
367 tools). If you do not need many of the tools and you are space-conscious, you
368 can pass <tt>ONLY_TOOLS="tools you need"</tt> to make. The Release build
369 requires considerably less space.</p>
371 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
372 guaranteed to do so. If compilation is successful, the LLVM utilities should be
373 able to assemble, disassemble, analyze, and optimize LLVM bitcode. Code
374 generation should work as well, although the generated native code may not work
375 on your platform.</p>
379 <!-- ======================================================================= -->
381 <a name="software">Software</a>
384 <p>Compiling LLVM requires that you have several software packages
385 installed. The table below lists those required packages. The Package column
386 is the usual name for the software package that LLVM depends on. The Version
387 column provides "known to work" versions of the package. The Notes column
388 describes how LLVM uses the package and provides other details.</p>
389 <table summary="Packages required to compile LLVM">
390 <tr><th>Package</th><th>Version</th><th>Notes</th></tr>
393 <td><a href="http://savannah.gnu.org/projects/make">GNU Make</a></td>
394 <td>3.79, 3.79.1</td>
395 <td>Makefile/build processor</td>
399 <td><a href="http://gcc.gnu.org/">GCC</a></td>
401 <td>C/C++ compiler<sup><a href="#sf1">1</a></sup></td>
405 <td><a href="http://www.gnu.org/software/texinfo/">TeXinfo</a></td>
407 <td>For building the CFE</td>
411 <td><a href="http://subversion.tigris.org/project_packages.html">SVN</a></td>
413 <td>Subversion access to LLVM<sup><a href="#sf2">2</a></sup></td>
418 Are DejaGnu and expect obsolete?
419 Shall we mention Python? -->
422 <td><a href="http://savannah.gnu.org/projects/dejagnu">DejaGnu</a></td>
424 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
428 <td><a href="http://www.tcl.tk/software/tcltk/">tcl</a></td>
430 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
434 <td><a href="http://expect.nist.gov/">expect</a></td>
436 <td>Automated test suite<sup><a href="#sf3">3</a></sup></td>
440 <td><a href="http://www.perl.com/download.csp">perl</a></td>
446 <td><a href="http://savannah.gnu.org/projects/m4">GNU M4</a>
448 <td>Macro processor for configuration<sup><a href="#sf4">4</a></sup></td>
452 <td><a href="http://www.gnu.org/software/autoconf/">GNU Autoconf</a></td>
454 <td>Configuration script builder<sup><a href="#sf4">4</a></sup></td>
458 <td><a href="http://www.gnu.org/software/automake/">GNU Automake</a></td>
460 <td>aclocal macro generator<sup><a href="#sf4">4</a></sup></td>
464 <td><a href="http://savannah.gnu.org/projects/libtool">libtool</a></td>
466 <td>Shared library manager<sup><a href="#sf4">4</a></sup></td>
472 <div class="doc_notes">
474 <li><a name="sf1">Only the C and C++ languages are needed so there's no
475 need to build the other languages for LLVM's purposes.</a> See
476 <a href="#brokengcc">below</a> for specific version info.</li>
477 <li><a name="sf2">You only need Subversion if you intend to build from the
478 latest LLVM sources. If you're working from a release distribution, you
479 don't need Subversion.</a></li>
480 <li><a name="sf3">Only needed if you want to run the automated test
481 suite in the <tt>llvm/test</tt> directory.</a></li>
482 <li><a name="sf4">If you want to make changes to the configure scripts,
483 you will need GNU autoconf (2.60), and consequently, GNU M4 (version 1.4
484 or higher). You will also need automake (1.9.6). We only use aclocal
485 from that package.</a></li>
489 <p>Additionally, your compilation host is expected to have the usual
490 plethora of Unix utilities. Specifically:</p>
492 <li><b>ar</b> - archive library builder</li>
493 <li><b>bzip2*</b> - bzip2 command for distribution generation</li>
494 <li><b>bunzip2*</b> - bunzip2 command for distribution checking</li>
495 <li><b>chmod</b> - change permissions on a file</li>
496 <li><b>cat</b> - output concatenation utility</li>
497 <li><b>cp</b> - copy files</li>
498 <li><b>date</b> - print the current date/time </li>
499 <li><b>echo</b> - print to standard output</li>
500 <li><b>egrep</b> - extended regular expression search utility</li>
501 <li><b>find</b> - find files/dirs in a file system</li>
502 <li><b>grep</b> - regular expression search utility</li>
503 <li><b>gzip*</b> - gzip command for distribution generation</li>
504 <li><b>gunzip*</b> - gunzip command for distribution checking</li>
505 <li><b>install</b> - install directories/files </li>
506 <li><b>mkdir</b> - create a directory</li>
507 <li><b>mv</b> - move (rename) files</li>
508 <li><b>ranlib</b> - symbol table builder for archive libraries</li>
509 <li><b>rm</b> - remove (delete) files and directories</li>
510 <li><b>sed</b> - stream editor for transforming output</li>
511 <li><b>sh</b> - Bourne shell for make build scripts</li>
512 <li><b>tar</b> - tape archive for distribution generation</li>
513 <li><b>test</b> - test things in file system</li>
514 <li><b>unzip*</b> - unzip command for distribution checking</li>
515 <li><b>zip*</b> - zip command for distribution generation</li>
519 <!-- ======================================================================= -->
521 <a name="brokengcc">Broken versions of GCC and other tools</a>
526 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
527 bugs in the compiler. In particular, several versions of GCC crash when trying
528 to compile LLVM. We routinely use GCC 4.2 (and higher) or Clang.
529 Other versions of GCC will probably work as well. GCC versions listed
530 here are known to not work. If you are using one of these versions, please try
531 to upgrade your GCC to something more recent. If you run into a problem with a
532 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
533 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
534 of GCC you are using.
537 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
538 problems in the STL that effectively prevent it from compiling LLVM.
541 <p><b>GCC 3.2.2 and 3.2.3</b>: These versions of GCC fails to compile LLVM with
542 a bogus template error. This was fixed in later GCCs.</p>
544 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
545 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
546 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
548 <p><b>Cygwin GCC 3.3.3</b>: The version of GCC 3.3.3 commonly shipped with
549 Cygwin does not work.</p>
550 <p><b>SuSE GCC 3.3.3</b>: The version of GCC 3.3.3 shipped with SuSE 9.1 (and
551 possibly others) does not compile LLVM correctly (it appears that exception
552 handling is broken in some cases). Please download the FSF 3.3.3 or upgrade
553 to a newer version of GCC.</p>
554 <p><b>GCC 3.4.0 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
555 code generator, causing an infinite loop in the llvm-gcc build when built
556 with optimizations enabled (i.e. a release build).</p>
557 <p><b>GCC 3.4.2 on linux/x86 (32-bit)</b>: GCC miscompiles portions of the
558 code generator at -O3, as with 3.4.0. However gcc 3.4.2 (unlike 3.4.0)
559 correctly compiles LLVM at -O2. A work around is to build release LLVM
560 builds with "make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2 ..."</p>
561 <p><b>GCC 3.4.x on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1056">
562 miscompiles portions of LLVM</a>.</p>
563 <p><b>GCC 3.4.4 (CodeSourcery ARM 2005q3-2)</b>: this compiler miscompiles LLVM
564 when building with optimizations enabled. It appears to work with
565 "<tt>make ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O1</tt>" or build a debug
567 <p><b>IA-64 GCC 4.0.0</b>: The IA-64 version of GCC 4.0.0 is known to
569 <p><b>Apple Xcode 2.3</b>: GCC crashes when compiling LLVM at -O3 (which is the
570 default with ENABLE_OPTIMIZED=1. To work around this, build with
571 "ENABLE_OPTIMIZED=1 OPTIMIZE_OPTION=-O2".</p>
572 <p><b>GCC 4.1.1</b>: GCC fails to build LLVM with template concept check errors
573 compiling some files. At the time of this writing, GCC mainline (4.2)
574 did not share the problem.</p>
575 <p><b>GCC 4.1.1 on X86-64/amd64</b>: GCC <a href="http://llvm.org/PR1063">
576 miscompiles portions of LLVM</a> when compiling llvm itself into 64-bit
577 code. LLVM will appear to mostly work but will be buggy, e.g. failing
578 portions of its testsuite.</p>
579 <p><b>GCC 4.1.2 on OpenSUSE</b>: Seg faults during libstdc++ build and on x86_64
580 platforms compiling md5.c gets a mangled constant.</p>
581 <p><b>GCC 4.1.2 (20061115 (prerelease) (Debian 4.1.1-21)) on Debian</b>: Appears
582 to miscompile parts of LLVM 2.4. One symptom is ValueSymbolTable complaining
583 about symbols remaining in the table on destruction.</p>
584 <p><b>GCC 4.1.2 20071124 (Red Hat 4.1.2-42)</b>: Suffers from the same symptoms
585 as the previous one. It appears to work with ENABLE_OPTIMIZED=0 (the default).</p>
586 <p><b>Cygwin GCC 4.3.2 20080827 (beta) 2</b>:
587 Users <a href="http://llvm.org/PR4145">reported</a> various problems related
588 with link errors when using this GCC version.</p>
589 <p><b>Debian GCC 4.3.2 on X86</b>: Crashes building some files in LLVM 2.6.</p>
590 <p><b>GCC 4.3.3 (Debian 4.3.3-10) on ARM</b>: Miscompiles parts of LLVM 2.6
591 when optimizations are turned on. The symptom is an infinite loop in
592 FoldingSetImpl::RemoveNode while running the code generator.</p>
593 <p><b>SUSE 11 GCC 4.3.4</b>: Miscompiles LLVM, causing crashes in ValueHandle logic.</p>
594 <p><b>GCC 4.3.5 and GCC 4.4.5 on ARM</b>: These can miscompile <tt>value >>
595 1</tt> even at -O0. A test failure in <tt>test/Assembler/alignstack.ll</tt> is
596 one symptom of the problem.
597 <p><b>GNU ld 2.16.X</b>. Some 2.16.X versions of the ld linker will produce very
598 long warning messages complaining that some ".gnu.linkonce.t.*" symbol was
599 defined in a discarded section. You can safely ignore these messages as they are
600 erroneous and the linkage is correct. These messages disappear using ld
603 <p><b>GNU binutils 2.17</b>: Binutils 2.17 contains <a
604 href="http://sourceware.org/bugzilla/show_bug.cgi?id=3111">a bug</a> which
605 causes huge link times (minutes instead of seconds) when building LLVM. We
606 recommend upgrading to a newer version (2.17.50.0.4 or later).</p>
608 <p><b>GNU Binutils 2.19.1 Gold</b>: This version of Gold contained
609 <a href="http://sourceware.org/bugzilla/show_bug.cgi?id=9836">a bug</a>
610 which causes intermittent failures when building LLVM with position independent
611 code. The symptom is an error about cyclic dependencies. We recommend
612 upgrading to a newer version of Gold.</p>
618 <!-- *********************************************************************** -->
620 <a name="starting">Getting Started with LLVM</a>
622 <!-- *********************************************************************** -->
626 <p>The remainder of this guide is meant to get you up and running with
627 LLVM and to give you some basic information about the LLVM environment.</p>
629 <p>The later sections of this guide describe the <a
630 href="#layout">general layout</a> of the the LLVM source tree, a <a
631 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
632 href="#links">links</a> to find more information about LLVM or to get
635 <!-- ======================================================================= -->
637 <a name="terminology">Terminology and Notation</a>
642 <p>Throughout this manual, the following names are used to denote paths
643 specific to the local system and working environment. <i>These are not
644 environment variables you need to set but just strings used in the rest
645 of this document below</i>. In any of the examples below, simply replace
646 each of these names with the appropriate pathname on your local system.
647 All these paths are absolute:</p>
652 This is the top level directory of the LLVM source tree.
657 This is the top level directory of the LLVM object tree (i.e. the
658 tree where object files and compiled programs will be placed. It
659 can be the same as SRC_ROOT).
666 <!-- ======================================================================= -->
668 <a name="environment">Setting Up Your Environment</a>
674 In order to compile and use LLVM, you may need to set some environment
678 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt>/path/to/your/bitcode/libs</tt></dt>
679 <dd>[Optional] This environment variable helps LLVM linking tools find the
680 locations of your bitcode libraries. It is provided only as a
681 convenience since you can specify the paths using the -L options of the
682 tools and the C/C++ front-end will automatically use the bitcode files
684 <tt>lib</tt> directory.</dd>
689 <!-- ======================================================================= -->
691 <a name="unpack">Unpacking the LLVM Archives</a>
697 If you have the LLVM distribution, you will need to unpack it before you
698 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
699 suite and the LLVM GCC front end compiled for your platform. There is an
700 additional test suite that is optional. Each file is a TAR archive that is
701 compressed with the gzip program.
704 <p>The files are as follows, with <em>x.y</em> marking the version number:
706 <dt><tt>llvm-x.y.tar.gz</tt></dt>
707 <dd>Source release for the LLVM libraries and tools.<br></dd>
709 <dt><tt>llvm-test-x.y.tar.gz</tt></dt>
710 <dd>Source release for the LLVM test-suite.</dd>
712 <dt><tt>llvm-gcc-4.2-x.y.source.tar.gz</tt></dt>
713 <dd>Source release of the llvm-gcc-4.2 front end. See README.LLVM in the root
714 directory for build instructions.<br></dd>
716 <dt><tt>llvm-gcc-4.2-x.y-platform.tar.gz</tt></dt>
717 <dd>Binary release of the llvm-gcc-4.2 front end for a specific platform.<br></dd>
723 <!-- ======================================================================= -->
725 <a name="checkout">Checkout LLVM from Subversion</a>
730 <p>If you have access to our Subversion repository, you can get a fresh copy of
731 the entire source code. All you need to do is check it out from Subversion as
735 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
736 <li>Read-Only: <tt>svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm</tt></li>
737 <li>Read-Write:<tt>svn co https://user@llvm.org/svn/llvm-project/llvm/trunk
742 <p>This will create an '<tt>llvm</tt>' directory in the current
743 directory and fully populate it with the LLVM source code, Makefiles,
744 test directories, and local copies of documentation files.</p>
746 <p>If you want to get a specific release (as opposed to the most recent
747 revision), you can checkout it from the '<tt>tags</tt>' directory (instead of
748 '<tt>trunk</tt>'). The following releases are located in the following
749 subdirectories of the '<tt>tags</tt>' directory:</p>
752 <li>Release 3.1: <b>RELEASE_31/final</b></li>
753 <li>Release 3.0: <b>RELEASE_30/final</b></li>
754 <li>Release 2.9: <b>RELEASE_29/final</b></li>
755 <li>Release 2.8: <b>RELEASE_28</b></li>
756 <li>Release 2.7: <b>RELEASE_27</b></li>
757 <li>Release 2.6: <b>RELEASE_26</b></li>
758 <li>Release 2.5: <b>RELEASE_25</b></li>
759 <li>Release 2.4: <b>RELEASE_24</b></li>
760 <li>Release 2.3: <b>RELEASE_23</b></li>
761 <li>Release 2.2: <b>RELEASE_22</b></li>
762 <li>Release 2.1: <b>RELEASE_21</b></li>
763 <li>Release 2.0: <b>RELEASE_20</b></li>
764 <li>Release 1.9: <b>RELEASE_19</b></li>
765 <li>Release 1.8: <b>RELEASE_18</b></li>
766 <li>Release 1.7: <b>RELEASE_17</b></li>
767 <li>Release 1.6: <b>RELEASE_16</b></li>
768 <li>Release 1.5: <b>RELEASE_15</b></li>
769 <li>Release 1.4: <b>RELEASE_14</b></li>
770 <li>Release 1.3: <b>RELEASE_13</b></li>
771 <li>Release 1.2: <b>RELEASE_12</b></li>
772 <li>Release 1.1: <b>RELEASE_11</b></li>
773 <li>Release 1.0: <b>RELEASE_1</b></li>
776 <p>If you would like to get the LLVM test suite (a separate package as of 1.4),
777 you get it from the Subversion repository:</p>
779 <div class="doc_code">
782 % svn co http://llvm.org/svn/llvm-project/test-suite/trunk test-suite
786 <p>By placing it in the <tt>llvm/projects</tt>, it will be automatically
787 configured by the LLVM configure script as well as automatically updated when
788 you run <tt>svn update</tt>.</p>
792 <!-- ======================================================================= -->
794 <a name="git_mirror">GIT mirror</a>
799 <p>GIT mirrors are available for a number of LLVM subprojects. These mirrors
800 sync automatically with each Subversion commit and contain all necessary
801 git-svn marks (so, you can recreate git-svn metadata locally). Note that right
802 now mirrors reflect only <tt>trunk</tt> for each project. You can do the
803 read-only GIT clone of LLVM via:</p>
805 <pre class="doc_code">
806 git clone http://llvm.org/git/llvm.git
809 <p>If you want to check out clang too, run:</p>
811 <pre class="doc_code">
812 git clone http://llvm.org/git/llvm.git
814 git clone http://llvm.org/git/clang.git
818 Since the upstream repository is in Subversion, you should use
819 <tt>"git pull --rebase"</tt>
820 instead of <tt>"git pull"</tt> to avoid generating a non-linear
821 history in your clone.
822 To configure <tt>"git pull"</tt> to pass <tt>--rebase</tt> by default
823 on the master branch, run the following command:
826 <pre class="doc_code">
827 git config branch.master.rebase true
830 <h4>Sending patches with Git</h4>
833 Please read <a href="DeveloperPolicy.html#patches">Developer Policy</a>, too.
837 Assume <tt>master</tt> points the upstream and <tt>mybranch</tt> points your
838 working branch, and <tt>mybranch</tt> is rebased onto <tt>master</tt>.
839 At first you may check sanity of whitespaces:
842 <pre class="doc_code">
843 git diff --check master..mybranch
847 The easiest way to generate a patch is as below:
850 <pre class="doc_code">
851 git diff master..mybranch > /path/to/mybranch.diff
855 It is a little different from svn-generated diff. git-diff-generated diff has
856 prefixes like <tt>a/</tt> and <tt>b/</tt>. Don't worry, most developers might
857 know it could be accepted with <tt>patch -p1 -N</tt>.
861 But you may generate patchset with git-format-patch. It generates
862 by-each-commit patchset. To generate patch files to attach to your article:
865 <pre class="doc_code">
866 git format-patch --no-attach master..mybranch -o /path/to/your/patchset
870 If you would like to send patches directly, you may use git-send-email or
871 git-imap-send. Here is an example to generate the patchset in Gmail's [Drafts].
874 <pre class="doc_code">
875 git format-patch --attach master..mybranch --stdout | git imap-send
879 Then, your .git/config should have [imap] sections.
882 <pre class="doc_code">
884 host = imaps://imap.gmail.com
885 user = <em>your.gmail.account</em>@gmail.com
886 pass = <em>himitsu!</em>
890 folder = "[Gmail]/Drafts"
891 ; example for Japanese, "Modified UTF-7" encoded.
892 folder = "[Gmail]/&Tgtm+DBN-"
893 ; example for Traditional Chinese
894 folder = "[Gmail]/&g0l6Pw-"
899 <h4>For developers to work with git-svn</h4>
902 <p>To set up clone from which you can submit code using
903 <tt>git-svn</tt>, run:</p>
905 <pre class="doc_code">
906 git clone http://llvm.org/git/llvm.git
908 git svn init https://llvm.org/svn/llvm-project/llvm/trunk --username=<username>
909 git config svn-remote.svn.fetch :refs/remotes/origin/master
910 git svn rebase -l # -l avoids fetching ahead of the git mirror.
912 # If you have clang too:
914 git clone http://llvm.org/git/clang.git
916 git svn init https://llvm.org/svn/llvm-project/cfe/trunk --username=<username>
917 git config svn-remote.svn.fetch :refs/remotes/origin/master
921 <p>To update this clone without generating git-svn tags that conflict
922 with the upstream git repo, run:</p>
924 <pre class="doc_code">
925 git fetch && (cd tools/clang && git fetch) # Get matching revisions of both trees.
929 git checkout master &&
933 <p>This leaves your working directories on their master branches, so
934 you'll need to <tt>checkout</tt> each working branch individually and
935 <tt>rebase</tt> it on top of its parent branch. (Note: This script is
936 intended for relative newbies to git. If you have more experience,
937 you can likely improve on it.)</p>
939 <p>The git-svn metadata can get out of sync after you mess around with
940 branches and <code>dcommit</code>. When that happens, <code>git svn
941 dcommit</code> stops working, complaining about files with uncommitted
942 changes. The fix is to rebuild the metadata:</p>
944 <pre class="doc_code">
953 <!-- ======================================================================= -->
955 <a name="config">Local LLVM Configuration</a>
960 <p>Once checked out from the Subversion repository, the LLVM suite source
962 configured via the <tt>configure</tt> script. This script sets variables in the
963 various <tt>*.in</tt> files, most notably <tt>llvm/Makefile.config</tt> and
964 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
965 the Makefiles needed to begin building LLVM.</p>
967 <p>The following environment variables are used by the <tt>configure</tt>
968 script to configure the build system:</p>
970 <table summary="LLVM configure script environment variables">
971 <tr><th>Variable</th><th>Purpose</th></tr>
974 <td>Tells <tt>configure</tt> which C compiler to use. By default,
975 <tt>configure</tt> will look for the first GCC C compiler in
976 <tt>PATH</tt>. Use this variable to override
977 <tt>configure</tt>'s default behavior.</td>
981 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
982 <tt>configure</tt> will look for the first GCC C++ compiler in
983 <tt>PATH</tt>. Use this variable to override
984 <tt>configure</tt>'s default behavior.</td>
988 <p>The following options can be used to set or enable LLVM specific options:</p>
991 <dt><i>--enable-optimized</i></dt>
993 Enables optimized compilation (debugging symbols are removed
994 and GCC optimization flags are enabled). Note that this is the default
995 setting if you are using the LLVM distribution. The default behavior
996 of an Subversion checkout is to use an unoptimized build (also known as a
1000 <dt><i>--enable-debug-runtime</i></dt>
1002 Enables debug symbols in the runtime libraries. The default is to strip
1003 debug symbols from the runtime libraries.
1005 <dt><i>--enable-jit</i></dt>
1007 Compile the Just In Time (JIT) compiler functionality. This is not
1009 on all platforms. The default is dependent on platform, so it is best
1010 to explicitly enable it if you want it.
1013 <dt><i>--enable-targets=</i><tt>target-option</tt></dt>
1014 <dd>Controls which targets will be built and linked into llc. The default
1015 value for <tt>target_options</tt> is "all" which builds and links all
1016 available targets. The value "host-only" can be specified to build only a
1017 native compiler (no cross-compiler targets available). The "native" target is
1018 selected as the target of the build host. You can also specify a comma
1019 separated list of target names that you want available in llc. The target
1020 names use all lower case. The current set of targets is: <br>
1021 <tt>arm, cpp, hexagon, mblaze, mips, mipsel, msp430, powerpc, ptx, sparc, spu, x86, x86_64, xcore</tt>.
1023 <dt><i>--enable-doxygen</i></dt>
1024 <dd>Look for the doxygen program and enable construction of doxygen based
1025 documentation from the source code. This is disabled by default because
1026 generating the documentation can take a long time and producess 100s of
1027 megabytes of output.</dd>
1028 <dt><i>--with-udis86</i></dt>
1029 <dd>LLVM can use external disassembler library for various purposes (now it's
1030 used only for examining code produced by JIT). This option will enable usage
1031 of <a href="http://udis86.sourceforge.net/">udis86</a> x86 (both 32 and 64
1032 bits) disassembler library.</dd>
1035 <p>To configure LLVM, follow these steps:</p>
1038 <li><p>Change directory into the object root directory:</p>
1040 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1042 <li><p>Run the <tt>configure</tt> script located in the LLVM source
1045 <div class="doc_code">
1046 <pre>% <i>SRC_ROOT</i>/configure --prefix=/install/path [other options]</pre>
1052 <!-- ======================================================================= -->
1054 <a name="compile">Compiling the LLVM Suite Source Code</a>
1059 <p>Once you have configured LLVM, you can build it. There are three types of
1065 These builds are the default when one is using an Subversion checkout and
1066 types <tt>gmake</tt> (unless the <tt>--enable-optimized</tt> option was
1067 used during configuration). The build system will compile the tools and
1068 libraries with debugging information. To get a Debug Build using the
1069 LLVM distribution the <tt>--disable-optimized</tt> option must be passed
1070 to <tt>configure</tt>.
1073 <dt>Release (Optimized) Builds
1075 These builds are enabled with the <tt>--enable-optimized</tt> option to
1076 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
1077 <tt>gmake</tt> command line. For these builds, the build system will
1078 compile the tools and libraries with GCC optimizations enabled and strip
1079 debugging information from the libraries and executables it generates.
1080 Note that Release Builds are default when using an LLVM distribution.
1085 These builds are for use with profiling. They compile profiling
1086 information into the code for use with programs like <tt>gprof</tt>.
1087 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
1088 on the <tt>gmake</tt> command line.
1091 <p>Once you have LLVM configured, you can build it by entering the
1092 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
1094 <div class="doc_code"><pre>% gmake</pre></div>
1096 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
1097 are using a version of GCC that is known not to compile LLVM.</p>
1100 If you have multiple processors in your machine, you may wish to use some of
1101 the parallel build options provided by GNU Make. For example, you could use the
1104 <div class="doc_code"><pre>% gmake -j2</pre></div>
1106 <p>There are several special targets which are useful when working with the LLVM
1110 <dt><tt>gmake clean</tt>
1112 Removes all files generated by the build. This includes object files,
1113 generated C/C++ files, libraries, and executables.
1116 <dt><tt>gmake dist-clean</tt>
1118 Removes everything that <tt>gmake clean</tt> does, but also removes files
1119 generated by <tt>configure</tt>. It attempts to return the source tree to the
1120 original state in which it was shipped.
1123 <dt><tt>gmake install</tt>
1125 Installs LLVM header files, libraries, tools, and documentation in a
1127 under $PREFIX, specified with <tt>./configure --prefix=[dir]</tt>, which
1128 defaults to <tt>/usr/local</tt>.
1131 <dt><tt>gmake -C runtime install-bytecode</tt>
1133 Assuming you built LLVM into $OBJDIR, when this command is run, it will
1134 install bitcode libraries into the GCC front end's bitcode library
1135 directory. If you need to update your bitcode libraries,
1136 this is the target to use once you've built them.
1140 <p>Please see the <a href="MakefileGuide.html">Makefile Guide</a> for further
1141 details on these <tt>make</tt> targets and descriptions of other targets
1144 <p>It is also possible to override default values from <tt>configure</tt> by
1145 declaring variables on the command line. The following are some examples:</p>
1148 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
1150 Perform a Release (Optimized) build.
1153 <dt><tt>gmake ENABLE_OPTIMIZED=1 DISABLE_ASSERTIONS=1</tt>
1155 Perform a Release (Optimized) build without assertions enabled.
1158 <dt><tt>gmake ENABLE_OPTIMIZED=0</tt>
1160 Perform a Debug build.
1163 <dt><tt>gmake ENABLE_PROFILING=1</tt>
1165 Perform a Profiling build.
1168 <dt><tt>gmake VERBOSE=1</tt>
1170 Print what <tt>gmake</tt> is doing on standard output.
1173 <dt><tt>gmake TOOL_VERBOSE=1</tt></dt>
1174 <dd>Ask each tool invoked by the makefiles to print out what it is doing on
1175 the standard output. This also implies <tt>VERBOSE=1</tt>.
1179 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
1180 it and any subdirectories that it contains. Entering any directory inside the
1181 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
1182 that directory that is out of date.</p>
1186 <!-- ======================================================================= -->
1188 <a name="cross-compile">Cross-Compiling LLVM</a>
1192 <p>It is possible to cross-compile LLVM itself. That is, you can create LLVM
1193 executables and libraries to be hosted on a platform different from the
1194 platform where they are build (a Canadian Cross build). To configure a
1195 cross-compile, supply the configure script with <tt>--build</tt> and
1196 <tt>--host</tt> options that are different. The values of these options must
1197 be legal target triples that your GCC compiler supports.</p>
1199 <p>The result of such a build is executables that are not runnable on
1200 on the build host (--build option) but can be executed on the compile host
1201 (--host option).</p>
1204 <!-- ======================================================================= -->
1206 <a name="objfiles">The Location of LLVM Object Files</a>
1211 <p>The LLVM build system is capable of sharing a single LLVM source tree among
1212 several LLVM builds. Hence, it is possible to build LLVM for several different
1213 platforms or configurations using the same source tree.</p>
1215 <p>This is accomplished in the typical autoconf manner:</p>
1218 <li><p>Change directory to where the LLVM object files should live:</p>
1220 <div class="doc_code"><pre>% cd <i>OBJ_ROOT</i></pre></div></li>
1222 <li><p>Run the <tt>configure</tt> script found in the LLVM source
1225 <div class="doc_code"><pre>% <i>SRC_ROOT</i>/configure</pre></div></li>
1228 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
1229 named after the build type:</p>
1232 <dt>Debug Builds with assertions enabled (the default)
1236 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/bin</tt>
1238 <dd><tt><i>OBJ_ROOT</i>/Debug+Asserts/lib</tt>
1246 <dd><tt><i>OBJ_ROOT</i>/Release/bin</tt>
1248 <dd><tt><i>OBJ_ROOT</i>/Release/lib</tt>
1256 <dd><tt><i>OBJ_ROOT</i>/Profile/bin</tt>
1258 <dd><tt><i>OBJ_ROOT</i>/Profile/lib</tt>
1264 <!-- ======================================================================= -->
1266 <a name="optionalconfig">Optional Configuration Items</a>
1272 If you're running on a Linux system that supports the "<a
1273 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
1274 module, and you have root access on the system, you can set your system up to
1275 execute LLVM bitcode files directly. To do this, use commands like this (the
1276 first command may not be required if you are already using the module):</p>
1278 <div class="doc_code">
1280 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
1281 $ echo ':llvm:M::BC::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
1282 $ chmod u+x hello.bc (if needed)
1288 This allows you to execute LLVM bitcode files directly. On Debian, you
1289 can also use this command instead of the 'echo' command above:
1292 <div class="doc_code">
1294 $ sudo update-binfmts --install llvm /path/to/lli --magic 'BC'
1302 <!-- *********************************************************************** -->
1304 <a name="layout">Program Layout</a>
1306 <!-- *********************************************************************** -->
1310 <p>One useful source of information about the LLVM source base is the LLVM <a
1311 href="http://www.doxygen.org/">doxygen</a> documentation available at <tt><a
1312 href="http://llvm.org/doxygen/">http://llvm.org/doxygen/</a></tt>.
1313 The following is a brief introduction to code layout:</p>
1315 <!-- ======================================================================= -->
1317 <a name="examples"><tt>llvm/examples</tt></a>
1321 <p>This directory contains some simple examples of how to use the LLVM IR and
1325 <!-- ======================================================================= -->
1327 <a name="include"><tt>llvm/include</tt></a>
1332 <p>This directory contains public header files exported from the LLVM
1333 library. The three main subdirectories of this directory are:</p>
1336 <dt><tt><b>llvm/include/llvm</b></tt></dt>
1337 <dd>This directory contains all of the LLVM specific header files. This
1338 directory also has subdirectories for different portions of LLVM:
1339 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
1342 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
1343 <dd>This directory contains generic support libraries that are provided with
1344 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
1345 and a Command Line option processing library store their header files here.
1348 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
1349 <dd>This directory contains header files configured by the <tt>configure</tt>
1350 script. They wrap "standard" UNIX and C header files. Source code can
1351 include these header files which automatically take care of the conditional
1352 #includes that the <tt>configure</tt> script generates.</dd>
1356 <!-- ======================================================================= -->
1358 <a name="lib"><tt>llvm/lib</tt></a>
1363 <p>This directory contains most of the source files of the LLVM system. In LLVM,
1364 almost all code exists in libraries, making it very easy to share code among the
1365 different <a href="#tools">tools</a>.</p>
1368 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
1369 <dd> This directory holds the core LLVM source files that implement core
1370 classes like Instruction and BasicBlock.</dd>
1372 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
1373 <dd>This directory holds the source code for the LLVM assembly language parser
1376 <dt><tt><b>llvm/lib/BitCode/</b></tt></dt>
1377 <dd>This directory holds code for reading and write LLVM bitcode.</dd>
1379 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
1380 different program analyses, such as Dominator Information, Call Graphs,
1381 Induction Variables, Interval Identification, Natural Loop Identification,
1384 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
1385 <dd> This directory contains the source code for the LLVM to LLVM program
1386 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
1387 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
1388 Elimination, and many others.</dd>
1390 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
1391 <dd> This directory contains files that describe various target architectures
1392 for code generation. For example, the <tt>llvm/lib/Target/X86</tt>
1393 directory holds the X86 machine description while
1394 <tt>llvm/lib/Target/ARM</tt> implements the ARM backend.</dd>
1396 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
1397 <dd> This directory contains the major parts of the code generator: Instruction
1398 Selector, Instruction Scheduling, and Register Allocation.</dd>
1400 <dt><tt><b>llvm/lib/MC/</b></tt></dt>
1401 <dd>(FIXME: T.B.D.)</dd>
1403 <!--FIXME: obsoleted -->
1404 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
1405 <dd> This directory contains the source level debugger library that makes
1406 it possible to instrument LLVM programs so that a debugger could identify
1407 source code locations at which the program is executing.</dd>
1409 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
1410 <dd> This directory contains libraries for executing LLVM bitcode directly
1411 at runtime in both interpreted and JIT compiled fashions.</dd>
1413 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
1414 <dd> This directory contains the source code that corresponds to the header
1415 files located in <tt>llvm/include/ADT/</tt>
1416 and <tt>llvm/include/Support/</tt>.</dd>
1421 <!-- ======================================================================= -->
1423 <a name="projects"><tt>llvm/projects</tt></a>
1427 <p>This directory contains projects that are not strictly part of LLVM but are
1428 shipped with LLVM. This is also the directory where you should create your own
1429 LLVM-based projects. See <tt>llvm/projects/sample</tt> for an example of how
1430 to set up your own project.</p>
1433 <!-- ======================================================================= -->
1435 <a name="runtime"><tt>llvm/runtime</tt></a>
1440 <p>This directory contains libraries which are compiled into LLVM bitcode and
1441 used when linking programs with the Clang front end. Most of these libraries are
1442 skeleton versions of real libraries; for example, libc is a stripped down
1443 version of glibc.</p>
1445 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1450 <!-- ======================================================================= -->
1452 <a name="test"><tt>llvm/test</tt></a>
1456 <p>This directory contains feature and regression tests and other basic sanity
1457 checks on the LLVM infrastructure. These are intended to run quickly and cover
1458 a lot of territory without being exhaustive.</p>
1461 <!-- ======================================================================= -->
1463 <a name="test-suite"><tt>test-suite</tt></a>
1467 <p>This is not a directory in the normal llvm module; it is a separate
1469 module that must be checked out (usually to <tt>projects/test-suite</tt>).
1471 module contains a comprehensive correctness, performance, and benchmarking
1473 suite for LLVM. It is a separate Subversion module because not every LLVM
1475 interested in downloading or building such a comprehensive test suite. For
1476 further details on this test suite, please see the
1477 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1480 <!-- ======================================================================= -->
1482 <a name="tools"><tt>llvm/tools</tt></a>
1487 <p>The <b>tools</b> directory contains the executables built out of the
1488 libraries above, which form the main part of the user interface. You can
1489 always get help for a tool by typing <tt>tool_name -help</tt>. The
1490 following is a brief introduction to the most important tools. More detailed
1491 information is in the <a href="CommandGuide/index.html">Command Guide</a>.</p>
1495 <dt><tt><b>bugpoint</b></tt></dt>
1496 <dd><tt>bugpoint</tt> is used to debug
1497 optimization passes or code generation backends by narrowing down the
1498 given test case to the minimum number of passes and/or instructions that
1499 still cause a problem, whether it is a crash or miscompilation. See <a
1500 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1501 on using <tt>bugpoint</tt>.</dd>
1503 <dt><tt><b>llvm-ar</b></tt></dt>
1504 <dd>The archiver produces an archive containing
1505 the given LLVM bitcode files, optionally with an index for faster
1508 <dt><tt><b>llvm-as</b></tt></dt>
1509 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1512 <dt><tt><b>llvm-dis</b></tt></dt>
1513 <dd>The disassembler transforms the LLVM bitcode to human readable
1516 <dt><tt><b>llvm-link</b></tt></dt>
1517 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1518 a single program.</dd>
1520 <dt><tt><b>lli</b></tt></dt>
1521 <dd><tt>lli</tt> is the LLVM interpreter, which
1522 can directly execute LLVM bitcode (although very slowly...). For architectures
1523 that support it (currently x86, Sparc, and PowerPC), by default, <tt>lli</tt>
1524 will function as a Just-In-Time compiler (if the functionality was compiled
1525 in), and will execute the code <i>much</i> faster than the interpreter.</dd>
1527 <dt><tt><b>llc</b></tt></dt>
1528 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1529 translates LLVM bitcode to a native code assembly file or to C code (with
1530 the -march=c option).</dd>
1532 <dt><tt><b>llvm-gcc</b></tt></dt>
1533 <dd><tt>llvm-gcc</tt> is a GCC-based C frontend that has been retargeted to
1534 use LLVM as its backend instead of GCC's RTL backend. It can also emit LLVM
1535 bitcode or assembly (with the <tt>-emit-llvm</tt> option) instead of the
1536 usual machine code output. It works just like any other GCC compiler,
1537 taking the typical <tt>-c, -S, -E, -o</tt> options that are typically used.
1538 Additionally, the the source code for <tt>llvm-gcc</tt> is available as a
1539 separate Subversion module.</dd>
1541 <dt><tt><b>opt</b></tt></dt>
1542 <dd><tt>opt</tt> reads LLVM bitcode, applies a series of LLVM to LLVM
1543 transformations (which are specified on the command line), and then outputs
1544 the resultant bitcode. The '<tt>opt -help</tt>' command is a good way to
1545 get a list of the program transformations available in LLVM.<br>
1546 <dd><tt>opt</tt> can also be used to run a specific analysis on an input
1547 LLVM bitcode file and print out the results. It is primarily useful for
1548 debugging analyses, or familiarizing yourself with what an analysis does.</dd>
1552 <!-- ======================================================================= -->
1554 <a name="utils"><tt>llvm/utils</tt></a>
1559 <p>This directory contains utilities for working with LLVM source code, and some
1560 of the utilities are actually required as part of the build process because they
1561 are code generators for parts of LLVM infrastructure.</p>
1564 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1565 that finds differences between code that LLC generates and code that LLI
1566 generates. This is a useful tool if you are debugging one of them,
1567 assuming that the other generates correct output. For the full user
1568 manual, run <tt>`perldoc codegen-diff'</tt>.<br><br>
1570 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1571 syntax-highlighting files which will work with Emacs and XEmacs editors,
1572 providing syntax highlighting support for LLVM assembly files and TableGen
1573 description files. For information on how to use the syntax files, consult
1574 the <tt>README</tt> file in that directory.<br><br>
1576 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1577 and outputs all non-generated source files, which is useful if one wishes
1578 to do a lot of development across directories and does not want to
1579 individually find each file. One way to use it is to run, for example:
1580 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1583 <dt><tt><b>llvmgrep</b></tt></dt>
1584 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1585 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1586 line. This is a very efficient way of searching the source base for a
1587 particular regular expression.</dd>
1589 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1590 files in the current directory and then compiles and links the tool that
1591 is the first argument. For example, assuming you are in the directory
1592 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1593 simply running <tt>makellvm llc</tt> will make a build of the current
1594 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1595 causing a re-linking of LLC.<br><br>
1597 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1598 the tool used to generate register descriptions, instruction set
1599 descriptions, and even assemblers from common TableGen description
1602 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1603 syntax-highlighting files which will work with the VIM editor, providing
1604 syntax highlighting support for LLVM assembly files and TableGen
1605 description files. For information on how to use the syntax files, consult
1606 the <tt>README</tt> file in that directory.<br><br>
1614 <!-- *********************************************************************** -->
1616 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1618 <!-- *********************************************************************** -->
1621 <p>This section gives an example of using LLVM with the Clang front end.</p>
1623 <!-- ======================================================================= -->
1625 <a name="tutorial4">Example with clang</a>
1631 <li><p>First, create a simple C file, name it 'hello.c':</p>
1633 <div class="doc_code">
1635 #include <stdio.h>
1638 printf("hello world\n");
1643 <li><p>Next, compile the C file into a native executable:</p>
1645 <div class="doc_code"><pre>% clang hello.c -o hello</pre></div>
1647 <p>Note that clang works just like GCC by default. The standard -S and
1648 -c arguments work as usual (producing a native .s or .o file,
1649 respectively).</p></li>
1651 <li><p>Next, compile the C file into a LLVM bitcode file:</p>
1653 <div class="doc_code">
1654 <pre>% clang -O3 -emit-llvm hello.c -c -o hello.bc</pre></div>
1656 <p>The -emit-llvm option can be used with the -S or -c options to emit an
1657 LLVM ".ll" or ".bc" file (respectively) for the code. This allows you
1658 to use the <a href="CommandGuide/index.html">standard LLVM tools</a> on
1659 the bitcode file.</p></li>
1661 <li><p>Run the program in both forms. To run the program, use:</p>
1663 <div class="doc_code"><pre>% ./hello</pre></div>
1667 <div class="doc_code"><pre>% lli hello.bc</pre></div>
1669 <p>The second examples shows how to invoke the LLVM JIT, <a
1670 href="CommandGuide/html/lli.html">lli</a>.</p></li>
1672 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1675 <div class="doc_code">
1676 <pre>llvm-dis < hello.bc | less</pre>
1679 <li><p>Compile the program to native assembly using the LLC code
1682 <div class="doc_code"><pre>% llc hello.bc -o hello.s</pre></div></li>
1684 <li><p>Assemble the native assembly language file into a program:</p>
1686 <div class="doc_code">
1688 <b>Solaris:</b> % /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native
1690 <b>Others:</b> % gcc hello.s -o hello.native
1694 <li><p>Execute the native code program:</p>
1696 <div class="doc_code"><pre>% ./hello.native</pre></div>
1698 <p>Note that using clang to compile directly to native code (i.e. when
1699 the -emit-llvm option is not present) does steps 6/7/8 for you.</p>
1708 <!-- *********************************************************************** -->
1710 <a name="problems">Common Problems</a>
1712 <!-- *********************************************************************** -->
1716 <p>If you are having problems building or using LLVM, or if you have any other
1717 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1718 Asked Questions</a> page.</p>
1722 <!-- *********************************************************************** -->
1724 <a name="links">Links</a>
1726 <!-- *********************************************************************** -->
1730 <p>This document is just an <b>introduction</b> on how to use LLVM to do
1731 some simple things... there are many more interesting and complicated things
1732 that you can do that aren't documented here (but we'll gladly accept a patch
1733 if you want to write something up!). For more information about LLVM, check
1737 <li><a href="http://llvm.org/">LLVM homepage</a></li>
1738 <li><a href="http://llvm.org/doxygen/">LLVM doxygen tree</a></li>
1739 <li><a href="http://llvm.org/docs/Projects.html">Starting a Project
1740 that Uses LLVM</a></li>
1745 <!-- *********************************************************************** -->
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1754 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1755 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1756 <a href="http://llvm.org/">The LLVM Compiler Infrastructure</a><br>
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