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10 <div class="doc_title">
11 Getting Started with the LLVM System
15 <li><a href="#overview">Overview</a>
16 <li><a href="#quickstart">Getting Started Quickly (A Summary)</a>
17 <li><a href="#requirements">Requirements</a>
19 <li><a href="#hardware">Hardware</a>
20 <li><a href="#software">Software</a>
21 <li><a href="#brokengcc">Broken versions of GCC</a>
24 <li><a href="#starting">Getting Started with LLVM</a>
26 <li><a href="#terminology">Terminology and Notation</a>
27 <li><a href="#environment">Setting Up Your Environment</a>
28 <li><a href="#unpack">Unpacking the LLVM Archives</a>
29 <li><a href="#checkout">Checkout LLVM from CVS</a>
30 <li><a href="#installcf">Install the GCC Front End</a>
31 <li><a href="#config">Local LLVM Configuration</a>
32 <li><a href="#compile">Compiling the LLVM Suite Source Code</a>
33 <li><a href="#objfiles">The Location of LLVM Object Files</a>
34 <li><a href="#optionalconfig">Optional Configuration Items</a>
37 <li><a href="#layout">Program layout</a>
39 <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
40 <li><a href="#include"><tt>llvm/include</tt></a>
41 <li><a href="#lib"><tt>llvm/lib</tt></a>
42 <li><a href="#runtime"><tt>llvm/runtime</tt></a>
43 <li><a href="#test"><tt>llvm/test</tt></a>
44 <li><a href="#llvmtest"><tt>llvm-test</tt></a>
45 <li><a href="#tools"><tt>llvm/tools</tt></a>
46 <li><a href="#utils"><tt>llvm/utils</tt></a>
49 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
50 <li><a href="#problems">Common Problems</a>
51 <li><a href="#links">Links</a>
54 <div class="doc_author">
56 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
57 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
58 <a href="http://misha.brukman.net">Misha Brukman</a>,
59 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
60 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
65 <!-- *********************************************************************** -->
66 <div class="doc_section">
67 <a name="overview"><b>Overview</b></a>
69 <!-- *********************************************************************** -->
71 <div class="doc_text">
73 <p>Welcome to LLVM! In order to get started, you first need to know some
74 basic information.</p>
76 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
77 contains all of the tools, libraries, and header files needed to use the low
78 level virtual machine. It contains an assembler, disassembler, bytecode
79 analyzer, and bytecode optimizer. It also contains a test suite that can be
80 used to test the LLVM tools and the GCC front end.</p>
82 <p>The second piece is the GCC front end. This component provides a version of
83 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
84 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
85 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
86 from the LLVM suite.</p>
90 <!-- *********************************************************************** -->
91 <div class="doc_section">
92 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
94 <!-- *********************************************************************** -->
96 <div class="doc_text">
98 <p>Here's the short story for getting up and running quickly with LLVM:</p>
101 <li>Read the documentation.</li>
102 <li>Read the documentation.</li>
103 <li>Remember that you were warned twice about reading the documentation.</li>
104 <li>Install the GCC front end:
106 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
107 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
108 <li><b>Sparc and MacOS X Only:</b><br>
109 <tt>cd cfrontend/<i>platform</i><br>
113 <li>Get the Source Code
115 <li>With the distributed files:
117 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
118 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
122 <li>With anonymous CVS access (or use a <a href="#mirror">mirror</a>):
124 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
126 :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt></li>
127 <li>Hit the return key when prompted for the password.
128 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm
130 <li><tt>cd llvm</tt></li>
134 <li>Configure the LLVM Build Environment
136 <li>Change directory to where you want to store the LLVM object
137 files and run <tt>configure</tt> to configure the Makefiles and
138 header files for the default platform. Useful options include:
140 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
141 <p>Specify the full pathname of where the LLVM GCC frontend is
143 <li><tt>--enable-spec2000=<i>directory</i></tt>
144 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
145 benchmarks should be available in
146 <tt><i>directory</i></tt>.</p></li>
150 <li>Build the LLVM Suite:
152 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.</li>
153 <li><tt>gmake -k |& tee gnumake.out
154 # this is csh or tcsh syntax</tt></li>
155 <li>If you get an "internal compiler error (ICE)" see <a href="#brokengcc">below</a>.</li>
160 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
161 detailed information on configuring and compiling LLVM. See <a
162 href="#environment">Setting Up Your Environment</a> for tips that simplify
163 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
164 Layout</a> to learn about the layout of the source code tree.</p>
168 <!-- *********************************************************************** -->
169 <div class="doc_section">
170 <a name="requirements"><b>Requirements</b></a>
172 <!-- *********************************************************************** -->
174 <div class="doc_text">
176 <p>Before you begin to use the LLVM system, review the requirements given below.
177 This may save you some trouble by knowing ahead of time what hardware and
178 software you will need.</p>
182 <!-- ======================================================================= -->
183 <div class="doc_subsection">
184 <a name="hardware"><b>Hardware</b></a>
187 <div class="doc_text">
189 <p>LLVM is known to work on the following platforms:</p>
191 <table cellpadding="3">
197 <th>GCC front end</th>
202 <td>x86<sup>1</sup></td>
210 <td>V9 (Ultrasparc)</td>
218 <td>x86<sup>1</sup></td>
225 <td>MacOS X<sup>2</sup></td>
233 <td>AIX<sup>3</sup></td>
241 <td>Linux<sup>3</sup></td>
252 <sup>1</sup> Code generation supported for Pentium processors and up<br>
253 <sup>2</sup> Code generation supported for 32-bit ABI only<br>
254 <sup>3</sup> No native code generation<br>
257 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
258 guaranteed to do so. If compilation is successful, the LLVM utilities should be
259 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
260 generation should work as well, although the generated native code may not work
261 on your platform.</p>
263 <p>The GCC front end is not very portable at the moment. If you want to get it
264 to work on another platform, you can download a copy of the source and <a
265 href="CFEBuildInstrs.html">try to compile it</a> on your platform.</p>
269 <!-- ======================================================================= -->
270 <div class="doc_subsection">
271 <a name="software"><b>Software</b></a>
274 <div class="doc_text">
276 <p>Compiling LLVM requires that you have several software packages
280 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
281 support</a> (See <a href="#brokengcc">below</a> for specific version info)</li>
283 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
285 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
287 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
290 <p>There are some additional tools that you may want to have when working with
294 <li><A href="http://www.gnu.org/software/automake">GNU Automake</A></li>
295 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A></li>
296 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
298 <p>If you want to make changes to the configure scripts, you will need GNU
299 autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
300 higher). You will also need automake. Any old version of
301 automake from 1.4p5 on should work; we only use aclocal from that
304 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest 2.0.3</A></li>
305 <li><A href="http://www.python.org">Python</A>
308 These are needed to use the LLVM test suite. Please note that newer
309 versions of QMTest may not work with the LLVM test suite. QMTest 2.0.3
310 can be retrieved from the QMTest CVS repository using the following
313 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository login</tt>
315 <li>When prompted, use <tt>anoncvs</tt> as the password.
317 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository co -r release-2-0-3 qm</tt>
325 <!-- ======================================================================= -->
326 <div class="doc_subsection">
327 <a name="brokengcc">Broken versions of GCC</a>
330 <div class="doc_text">
332 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
333 bugs in the compiler. In particular, several versions of GCC crash when trying
334 to compile LLVM. We routinely use GCC 3.3.3 and GCC 3.4.0 and have had success
335 with them. Other versions of GCC will probably work as well. GCC versions listed
336 here are known to not work. If you are using one of these versions, please try
337 to upgrade your GCC to something more recent. If you run into a problem with a
338 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
339 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
340 of GCC you are using.
343 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
344 problems in the STL that effectively prevent it from compiling LLVM.
347 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
348 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
349 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
355 <!-- *********************************************************************** -->
356 <div class="doc_section">
357 <a name="starting"><b>Getting Started with LLVM</b></a>
359 <!-- *********************************************************************** -->
361 <div class="doc_text">
363 <p>The remainder of this guide is meant to get you up and running with
364 LLVM and to give you some basic information about the LLVM environment.</p>
366 <p>The later sections of this guide describe the <a
367 href="#layout">general layout</a> of the the LLVM source tree, a <a
368 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
369 href="#links">links</a> to find more information about LLVM or to get
373 <!-- ======================================================================= -->
374 <div class="doc_subsection">
375 <a name="terminology">Terminology and Notation</a>
378 <div class="doc_text">
380 <p>Throughout this manual, the following names are used to denote paths
381 specific to the local system and working environment. <i>These are not
382 environment variables you need to set but just strings used in the rest
383 of this document below</i>. In any of the examples below, simply replace
384 each of these names with the appropriate pathname on your local system.
385 All these paths are absolute:</p>
390 This is the top level directory of the LLVM source tree.
395 This is the top level directory of the LLVM object tree (i.e. the
396 tree where object files and compiled programs will be placed. It
397 can be the same as SRC_ROOT).
402 This is the where the LLVM GCC Front End is installed.
404 For the pre-built GCC front end binaries, the LLVMGCCDIR is
405 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
410 <!-- ======================================================================= -->
411 <div class="doc_subsection">
412 <a name="environment">Setting Up Your Environment</a>
415 <div class="doc_text">
418 In order to compile and use LLVM, you will need to set some environment
419 variables. There are also some shell aliases which you may find useful.
420 You can set these on the command line, or better yet, set them in your
421 <tt>.cshrc</tt> or <tt>.profile</tt>.
424 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
426 This environment variable helps the LLVM GCC front end find bytecode
427 libraries that it will need for compilation.
430 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
431 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
433 This alias allows you to use the LLVM C and C++ front ends without putting
434 them in your <tt>PATH</tt> or typing in their complete pathnames.
439 <!-- ======================================================================= -->
440 <div class="doc_subsection">
441 <a name="unpack">Unpacking the LLVM Archives</a>
444 <div class="doc_text">
447 If you have the LLVM distribution, you will need to unpack it before you
448 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
449 suite and the LLVM GCC front end compiled for your platform. Each
450 file is a TAR archive that is compressed with the gzip program.
453 <p> The files are as follows:
456 <dd>This is the source code to the LLVM suite.
459 <dt>cfrontend-1.3.sparc-sun-solaris2.8.tar.gz
460 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
463 <dt>cfrontend-1.3.i686-redhat-linux-gnu.tar.gz
464 <dd>This is the binary release of the GCC front end for Linux/x86.
467 <dt>cfrontend-1.3.i386-unknown-freebsd5.1.tar.gz
468 <dd>This is the binary release of the GCC front end for FreeBSD/x86.
471 <dt>cfrontend-1.3.powerpc-apple-darwin7.0.0.tar.gz
472 <dd>This is the binary release of the GCC front end for MacOS X/PPC.
477 <!-- ======================================================================= -->
478 <div class="doc_subsection">
479 <a name="checkout">Checkout LLVM from CVS</a>
482 <div class="doc_text">
484 <p>If you have access to our CVS repository, you can get a fresh copy of
485 the entire source code. All you need to do is check it out from CVS as
489 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
490 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
491 <li>Hit the return key when prompted for the password.
492 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
496 <p>This will create an '<tt>llvm</tt>' directory in the current
497 directory and fully populate it with the LLVM source code, Makefiles,
498 test directories, and local copies of documentation files.</p>
500 <p>If you want to get a specific release (as opposed to the most recent
501 revision), you can specify a label. The following releases have the following
505 <li>Release 1.3: <b>RELEASE_13</b></li>
506 <li>Release 1.2: <b>RELEASE_12</b></li>
507 <li>Release 1.1: <b>RELEASE_11</b></li>
508 <li>Release 1.0: <b>RELEASE_1</b></li>
511 <p>If you would like to get the GCC front end source code, you can also get it
512 from the CVS repository:</p>
515 cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-gcc
518 <p>Please note that you must follow <a href="CFEBuildInstrs.html">these
519 instructions</a> to successfully build the LLVM C front-end.</p>
523 <!-- ======================================================================= -->
524 <div class="doc_subsubsection">
525 <a name="mirrors">LLVM CVS Mirrors</a>
528 <div class="doc_text">
530 <p>If the main CVS server is overloaded or inaccessible, you can try one of
531 these user-hosted mirrors:</p>
534 <li><a href="http://llvm.x10sys.com/">Mirror hosted by eXtensible Systems
539 <!-- ======================================================================= -->
540 <div class="doc_subsection">
541 <a name="installcf">Install the GCC Front End</a>
544 <div class="doc_text">
546 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
547 GCC front end from the binary distribution. It is used for building the
548 bytecode libraries later used by the GCC front end for linking programs, and its
549 location must be specified when the LLVM suite is configured.</p>
551 <p>To install the GCC front end, do the following:</p>
554 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
555 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
559 <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
562 <p><tt>cd cfrontend/<i>platform</i><br>
563 ./fixheaders</tt></p>
565 <p>The binary versions of the GCC front end may not suit all of your needs. For
566 example, the binary distribution may include an old version of a system header
567 file, not "fix" a header file that needs to be fixed for GCC, or it may be
568 linked with libraries not available on your system.</p>
570 <p>In cases like these, you may want to try <a
571 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
572 not for the faint of heart, so be forewarned.</p>
576 <!-- ======================================================================= -->
577 <div class="doc_subsection">
578 <a name="config">Local LLVM Configuration</a>
581 <div class="doc_text">
583 <p>Once checked out from the CVS repository, the LLVM suite source code must be
584 configured via the <tt>configure</tt> script. This script sets variables in
585 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
586 also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
589 <p>The following environment variables are used by the <tt>configure</tt>
590 script to configure the build system:</p>
593 <tr><th>Variable</th><th>Purpose</th></tr>
596 <td>Tells <tt>configure</tt> which C compiler to use. By default,
597 <tt>configure</tt> will look for the first GCC C compiler in
598 <tt>PATH</tt>. Use this variable to override
599 <tt>configure</tt>'s default behavior.</td>
603 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
604 <tt>configure</tt> will look for the first GCC C++ compiler in
605 <tt>PATH</tt>. Use this variable to override
606 <tt>configure</tt>'s default behavior.</td>
610 <p>The following options can be used to set or enable LLVM specific options:</p>
613 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
615 Path to the location where the LLVM GCC front end binaries and
616 associated libraries were installed. This must be specified as an
619 <dt><i>--enable-optimized</i>
621 Enables optimized compilation by default (debugging symbols are removed
622 and GCC optimization flags are enabled). The default is to use an
623 unoptimized build (also known as a debug build).
625 <dt><i>--enable-jit</i>
627 Compile the Just In Time (JIT) compiler functionality. This is not
629 on all platforms. The default is dependent on platform, so it is best
630 to explicitly enable it if you want it.
632 <dt><i>--enable-spec2000</i>
633 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
635 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
636 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
637 <tt>directory</tt>, you can tell configure where to find the SPEC2000
638 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
639 uses the default value
640 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
642 <dt><i>--enable-spec95</i>
643 <dt><i>--enable-spec95=<<tt>directory</tt>></i>
645 Enable the use of SPEC95 when testing LLVM. It is similar to the
646 <i>--enable-spec2000</i> option.
648 <dt><i>--enable-povray</i>
649 <dt><i>--enable-povray=<<tt>directory</tt>></i>
651 Enable the use of Povray as an external test. Versions of Povray written
652 in C should work. This option is similar to the <i>--enable-spec2000</i>
656 <p>To configure LLVM, follow these steps:</p>
659 <li>Change directory into the object root directory:
661 <tt>cd <i>OBJ_ROOT</i></tt>
664 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
666 <tt><i>SRC_ROOT</i>/configure</tt>
670 <p>In addition to running <tt>configure</tt>, you must set the
671 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
672 This environment variable is used to locate "system" libraries like
673 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
674 the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
675 end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
676 <tt>LLVM_LIB_SEARCH_PATH</tt> to
677 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
678 version of the GCC front end on our research machines.</p>
682 <!-- ======================================================================= -->
683 <div class="doc_subsection">
684 <a name="compile">Compiling the LLVM Suite Source Code</a>
687 <div class="doc_text">
689 <p>Once you have configured LLVM, you can build it. There are three types of
695 These builds are the default when one types <tt>gmake</tt> (unless the
696 <tt>--enable-optimized</tt> option was used during configuration). The
697 build system will compile the tools and libraries with debugging
701 <dt>Release (Optimized) Builds
703 These builds are enabled with the <tt>--enable-optimized</tt> option to
704 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
705 <tt>gmake</tt> command line. For these builds, the build system will
706 compile the tools and libraries with GCC optimizations enabled and strip
707 debugging information from the libraries and executables it generates.
712 These builds are for use with profiling. They compile profiling
713 information into the code for use with programs like <tt>gprof</tt>.
714 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
715 on the <tt>gmake</tt> command line.
718 <p>Once you have LLVM configured, you can build it by entering the
719 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
721 <p><tt>gmake</tt></p>
723 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
724 are using a known broken version of GCC to compile LLVM with.</p>
727 If you have multiple processors in your machine, you may wish to use some of
728 the parallel build options provided by GNU Make. For example, you could use the
731 <p><tt>gmake -j2</tt></p>
733 <p>There are several special targets which are useful when working with the LLVM
737 <dt><tt>gmake clean</tt>
739 Removes all files generated by the build. This includes object files,
740 generated C/C++ files, libraries, and executables.
743 <dt><tt>gmake distclean</tt>
745 Removes everything that <tt>gmake clean</tt> does, but also removes files
746 generated by <tt>configure</tt>. It attempts to return the source tree to the
747 original state in which it was shipped.
750 <dt><tt>gmake install</tt>
752 Installs LLVM libraries and tools in a heirarchy under $PREFIX, specified with
753 <tt>./configure --prefix=[dir]</tt>, defaults to <tt>/usr/local</tt>.
756 <dt><tt>gmake -C runtime install</tt>
758 Assuming you built LLVM into $OBJDIR, when this command is run, it will
759 install bytecode libraries into the GCC front end's bytecode library
760 directory. If you need to update your bytecode libraries,
761 this is the target to use once you've built them.
765 <p>It is also possible to override default values from <tt>configure</tt> by
766 declaring variables on the command line. The following are some examples:</p>
769 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
771 Perform a Release (Optimized) build.
774 <dt><tt>gmake ENABLE_PROFILING=1</tt>
776 Perform a Profiling build.
779 <dt><tt>gmake VERBOSE=1</tt>
781 Print what <tt>gmake</tt> is doing on standard output.
785 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
786 it and any subdirectories that it contains. Entering any directory inside the
787 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
788 that directory that is out of date.</p>
792 <!-- ======================================================================= -->
793 <div class="doc_subsection">
794 <a name="objfiles">The Location of LLVM Object Files</a>
797 <div class="doc_text">
799 <p>The LLVM build system is capable of sharing a single LLVM source tree among
800 several LLVM builds. Hence, it is possible to build LLVM for several different
801 platforms or configurations using the same source tree.</p>
803 <p>This is accomplished in the typical autoconf manner:</p>
806 <li><p>Change directory to where the LLVM object files should live:</p>
808 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
810 <li><p>Run the <tt>configure</tt> script found in the LLVM source
813 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
816 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
817 named after the build type:</p>
824 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
826 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
834 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
836 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
844 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
846 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
852 <!-- ======================================================================= -->
853 <div class="doc_subsection">
854 <a name="optionalconfig">Optional Configuration Items</a>
857 <div class="doc_text">
860 If you're running on a linux system that supports the "<a
861 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
862 module, and you have root access on the system, you can set your system up to
863 execute LLVM bytecode files directly. To do this, use commands like this (the
864 first command may not be required if you are already using the module):</p>
867 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
868 $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
869 $ chmod u+x hello.bc (if needed)
874 This allows you to execute LLVM bytecode files directly. Thanks to Jack
875 Cummings for pointing this out!
881 <!-- *********************************************************************** -->
882 <div class="doc_section">
883 <a name="layout"><b>Program Layout</b></a>
885 <!-- *********************************************************************** -->
887 <div class="doc_text">
889 <p>One useful source of information about the LLVM source base is the LLVM <a
890 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
891 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
892 The following is a brief introduction to code layout:</p>
896 <!-- ======================================================================= -->
897 <div class="doc_subsection"><a name="cvsdir"><tt>CVS</tt> directories</a></div>
899 <div class="doc_text">
901 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
902 the most part these can just be ignored.</p>
906 <!-- ======================================================================= -->
907 <div class="doc_subsection"><a name="include"><tt>llvm/include</tt></a></div>
909 <div class="doc_text">
911 <p>This directory contains public header files exported from the LLVM
912 library. The three main subdirectories of this directory are:</p>
915 <dt><tt><b>llvm/include/llvm</b></tt></dt>
916 <dd>This directory contains all of the LLVM specific header files. This
917 directory also has subdirectories for different portions of LLVM:
918 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
921 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
922 <dd>This directory contains generic support libraries that are provided with
923 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
924 and a Command Line option processing library store their header files here.
927 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
928 <dd>This directory contains header files configured by the <tt>configure</tt>
929 script. They wrap "standard" UNIX and C header files. Source code can
930 include these header files which automatically take care of the conditional
931 #includes that the <tt>configure</tt> script generates.</dd>
935 <!-- ======================================================================= -->
936 <div class="doc_subsection"><a name="lib"><tt>llvm/lib</tt></a></div>
938 <div class="doc_text">
940 <p>This directory contains most of the source files of the LLVM system. In LLVM,
941 almost all code exists in libraries, making it very easy to share code among the
942 different <a href="#tools">tools</a>.</p>
945 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
946 <dd> This directory holds the core LLVM source files that implement core
947 classes like Instruction and BasicBlock.</dd>
949 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
950 <dd>This directory holds the source code for the LLVM assembly language parser
953 <dt><tt><b>llvm/lib/ByteCode/</b></tt></dt>
954 <dd>This directory holds code for reading and write LLVM bytecode.</dd>
956 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
957 different program analyses, such as Dominator Information, Call Graphs,
958 Induction Variables, Interval Identification, Natural Loop Identification,
961 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
962 <dd> This directory contains the source code for the LLVM to LLVM program
963 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
964 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
965 Elimination, and many others.</dd>
967 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
968 <dd> This directory contains files that describe various target architectures
969 for code generation. For example, the <tt>llvm/lib/Target/SparcV9</tt>
970 directory holds the Sparc machine description while
971 <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter</dd>
973 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
974 <dd> This directory contains the major parts of the code generator: Instruction
975 Selector, Instruction Scheduling, and Register Allocation.</dd>
977 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
978 <dd> This directory contains the source level debugger library that makes
979 it possible to instrument LLVM programs so that a debugger could identify
980 source code locations at which the program is executing.</dd>
982 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
983 <dd> This directory contains libraries for executing LLVM bytecode directly
984 at runtime in both interpreted and JIT compiled fashions.</dd>
986 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
987 <dd> This directory contains the source code that corresponds to the header
988 files located in <tt>llvm/include/Support/</tt>.</dd>
990 <dt><tt><b>llvm/lib/System/</b></tt></dt>
991 <dd>This directory contains the operating system abstraction layer that
992 shields LLVM from platform-specific coding.</dd>
997 <!-- ======================================================================= -->
998 <div class="doc_subsection"><a name="runtime"><tt>llvm/runtime</tt></a></div>
999 <div class="doc_text">
1001 <p>This directory contains libraries which are compiled into LLVM bytecode and
1002 used when linking programs with the GCC front end. Most of these libraries are
1003 skeleton versions of real libraries; for example, libc is a stripped down
1004 version of glibc.</p>
1006 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1011 <!-- ======================================================================= -->
1012 <div class="doc_subsection"><a name="test"><tt>llvm/test</tt></a></div>
1013 <div class="doc_text">
1014 <p>This directory contains feature and regression tests and other basic sanity
1015 checks on the LLVM infrastructure. These are intended to run quickly and cover
1016 a lot of territory without being exhaustive.</p>
1019 <!-- ======================================================================= -->
1020 <div class="doc_subsection"><a name="llvmtest"><tt>llvm-test</tt></a></div>
1021 <div class="doc_text">
1022 <p>This is not a directory in the normal llvm module, it is a separate CVS
1023 module that must be checked out (usually to <tt>test/projects</tt>). This
1024 module contains a comprehensive correctness, performance and benchmarking test
1025 suite for LLVM. It is a separate CVS module because not every LLVM user is
1026 interested in downloading or building such a comprehensive test. For further
1027 details on this test suite, please see the
1028 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1031 <!-- ======================================================================= -->
1032 <div class="doc_subsection"><a name="tools"><tt>llvm/tools</tt></a></div>
1033 <div class="doc_text">
1035 <p>The <b>tools</b> directory contains the executables built out of the
1036 libraries above, which form the main part of the user interface. You can
1037 always get help for a tool by typing <tt>tool_name --help</tt>. The
1038 following is a brief introduction to the most important tools:</p>
1041 <dt><tt><b>analyze</b></tt></dt>
1042 <dd><tt>analyze</tt> is used to run a specific
1043 analysis on an input LLVM bytecode file and print out the results. It is
1044 primarily useful for debugging analyses, or familiarizing yourself with
1045 what an analysis does.</dd>
1047 <dt><tt><b>bugpoint</b></tt></dt>
1048 <dd><tt>bugpoint</tt> is used to debug
1049 optimization passes or code generation backends by narrowing down the
1050 given test case to the minimum number of passes and/or instructions that
1051 still cause a problem, whether it is a crash or miscompilation. See <a
1052 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1053 on using <tt>bugpoint</tt>.</dd>
1055 <dt><tt><b>llvmc</b></tt></dt>
1056 <dd>The LLVM Compiler Driver. This program can
1057 be configured to utilize both LLVM and non-LLVM compilation tools to enable
1058 pre-processing, translation, optimization, assembly, and linking of programs
1059 all from one command line. <tt>llvmc</tt> also takes care of processing the
1060 dependent libraries found in bytecode. This reduces the need to get the
1061 traditional <tt>-l<name></tt> options right on the command line.</dd>
1063 <dt><tt><b>llvm-ar</b></tt></dt>
1064 <dd>The archiver produces an archive containing
1065 the given LLVM bytecode files, optionally with an index for faster
1068 <dt><tt><b>llvm-as</b></tt></dt>
1069 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1072 <dt><tt><b>llvm-dis</b></tt></dt>
1073 <dd>The disassembler transforms the LLVM bytecode to human readable
1076 <dt><tt><b>llvm-link</b></tt></dt>
1077 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1078 a single program.</dd>
1080 <dt><tt><b>lli</b></tt></dt>
1081 <dd><tt>lli</tt> is the LLVM interpreter, which
1082 can directly execute LLVM bytecode (although very slowly...). In addition
1083 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
1084 specifying <tt>-trace</tt> on the command line). Finally, for
1085 architectures that support it (currently only x86 and Sparc), by default,
1086 <tt>lli</tt> will function as a Just-In-Time compiler (if the
1087 functionality was compiled in), and will execute the code <i>much</i>
1088 faster than the interpreter.</dd>
1090 <dt><tt><b>llc</b></tt></dt>
1091 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1092 translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
1093 the -march=c option).</dd>
1095 <dt><tt><b>llvmgcc</b></tt></dt>
1096 <dd><tt>llvmgcc</tt> is a GCC-based C frontend
1097 that has been retargeted to emit LLVM code as the machine code output. It
1098 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
1099 -o</tt> options that are typically used. The source code for the
1100 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
1101 because it is quite large and not very interesting.
1104 <dt><tt><b>gccas</b></tt></dt>
1105 <dd>This tool is invoked by the <tt>llvmgcc</tt> frontend as the
1106 "assembler" part of the compiler. This tool actually assembles LLVM
1107 assembly to LLVM bytecode, performs a variety of optimizations, and
1108 outputs LLVM bytecode. Thus when you invoke
1109 <tt>llvmgcc -c x.c -o x.o</tt>, you are causing <tt>gccas</tt> to be
1110 run, which writes the <tt>x.o</tt> file (which is an LLVM bytecode file
1111 that can be disassembled or manipulated just like any other bytecode
1112 file). The command line interface to <tt>gccas</tt> is designed to be
1113 as close as possible to the <b>system</b> `<tt>as</tt>' utility so that
1114 the gcc frontend itself did not have to be modified to interface to
1115 a "weird" assembler.</dd>
1117 <dt><tt><b>gccld</b></tt></dt>
1118 <dd><tt>gccld</tt> links together several LLVM bytecode files into one
1119 bytecode file and does some optimization. It is the linker invoked by
1120 the GCC frontend when multiple .o files need to be linked together.
1121 Like <tt>gccas</tt>, the command line interface of <tt>gccld</tt> is
1122 designed to match the system linker, to aid interfacing with the GCC
1128 <dt><tt><b>opt</b></tt></dt>
1129 <dd><tt>opt</tt> reads LLVM bytecode, applies a
1130 series of LLVM to LLVM transformations (which are specified on the command
1131 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
1132 command is a good way to get a list of the program transformations
1133 available in LLVM.</dd>
1137 <!-- ======================================================================= -->
1138 <div class="doc_subsection"><a name="utils"><tt>llvm/utils</tt></a></div>
1139 <div class="doc_text">
1141 <p>This directory contains utilities for working with LLVM source code, and some
1142 of the utilities are actually required as part of the build process because they
1143 are code generators for parts of LLVM infrastructure.</p>
1146 <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
1147 generator -- it builds trees on which it then performs pattern-matching to
1148 select instructions according to the patterns the user has specified. Burg
1149 is currently used in the Sparc V9 backend.<p>
1151 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1152 that finds differences between code that LLC generates and code that LLI
1153 generates. This is a useful tool if you are debugging one of them,
1154 assuming that the other generates correct output. For the full user
1155 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
1157 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1158 update your CVS tree, but produce a much cleaner and more organized output
1159 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1160 together all the new and updated files and modified files in separate
1161 sections, so you can see at a glance what has changed. If you are at the
1162 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1163 preferred way of updating the tree.<p>
1165 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1166 syntax-highlighting files which will work with Emacs and XEmacs editors,
1167 providing syntax highlighting support for LLVM assembly files and TableGen
1168 description files. For information on how to use the syntax files, consult
1169 the <tt>README</tt> file in that directory.<p>
1171 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1172 and outputs all non-generated source files, which is useful if one wishes
1173 to do a lot of development across directories and does not want to
1174 individually find each file. One way to use it is to run, for example:
1175 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1178 <dt><tt><b>llvmgrep</b></tt></dt>
1179 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1180 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1181 line. This is a very efficient way of searching the source base for a
1182 particular regular expression.</dd>
1184 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1185 files in the current directory and then compiles and links the tool that
1186 is the first argument. For example, assuming you are in the directory
1187 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1188 simply running <tt>makellvm llc</tt> will make a build of the current
1189 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1190 causing a re-linking of LLC.<p>
1192 <dt><tt><b>NightlyTest.pl</b></tt> and
1193 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1194 cron script to generate nightly status reports of the functionality of
1195 tools, and the results can be seen by following the appropriate link on
1196 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
1198 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1199 the tool used to generate register descriptions, instruction set
1200 descriptions, and even assemblers from common TableGen description
1203 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1204 syntax-highlighting files which will work with the VIM editor, providing
1205 syntax highlighting support for LLVM assembly files and TableGen
1206 description files. For information on how to use the syntax files, consult
1207 the <tt>README</tt> file in that directory.<p>
1213 <!-- *********************************************************************** -->
1214 <div class="doc_section">
1215 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1217 <!-- *********************************************************************** -->
1219 <div class="doc_text">
1222 <li>First, create a simple C file, name it 'hello.c':
1224 #include <stdio.h>
1226 printf("hello world\n");
1231 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1232 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1234 <p>Note that you should have already built the tools and they have to be
1235 in your path, at least <tt>gccas</tt> and <tt>gccld</tt>.</p>
1237 <p>This will create two result files: <tt>hello</tt> and
1238 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1239 corresponds the the compiled program and the library facilities that it
1240 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1241 file with <tt>lli</tt>, making the result directly executable. Note that
1242 all LLVM optimizations are enabled by default, so there is no need for a
1243 "-O3" switch.</p></li>
1245 <li><p>Run the program. To make sure the program ran, execute one of the
1246 following commands:</p>
1248 <p><tt>% ./hello</tt></p>
1252 <p><tt>% lli hello.bc</tt></p></li>
1254 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1257 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1259 <li><p>Compile the program to native assembly using the LLC code
1262 <p><tt>% llc hello.bc -o hello.s</tt></p>
1264 <li><p>Assemble the native assembly language file into a program:</p>
1266 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1267 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1269 <li><p>Execute the native code program:</p>
1271 <p><tt>% ./hello.native</tt></p></li>
1277 <!-- *********************************************************************** -->
1278 <div class="doc_section">
1279 <a name="problems">Common Problems</a>
1281 <!-- *********************************************************************** -->
1283 <div class="doc_text">
1285 <p>If you are having problems building or using LLVM, or if you have any other
1286 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1287 Asked Questions</a> page.</p>
1291 <!-- *********************************************************************** -->
1292 <div class="doc_section">
1293 <a name="links">Links</a>
1295 <!-- *********************************************************************** -->
1297 <div class="doc_text">
1299 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1300 some simple things... there are many more interesting and complicated things
1301 that you can do that aren't documented here (but we'll gladly accept a patch
1302 if you want to write something up!). For more information about LLVM, check
1306 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1307 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1308 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1309 that Uses LLVM</a></li>
1314 <!-- *********************************************************************** -->
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1323 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1324 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1325 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
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