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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>
23 <li><a href="#starting">Getting Started with LLVM</a>
25 <li><a href="#terminology">Terminology and Notation</a>
26 <li><a href="#environment">Setting Up Your Environment</a>
27 <li><a href="#unpack">Unpacking the LLVM Archives</a>
28 <li><a href="#checkout">Checkout LLVM from CVS</a>
29 <li><a href="#installcf">Install the GCC Front End</a>
30 <li><a href="#config">Local LLVM Configuration</a>
31 <li><a href="#compile">Compiling the LLVM Suite Source Code</a>
32 <li><a href="#objfiles">The Location of LLVM Object Files</a>
33 <li><a href="#optionalconfig">Optional Configuration Items</a>
36 <li><a href="#layout">Program layout</a>
38 <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
39 <li><a href="#include"><tt>llvm/include</tt></a>
40 <li><a href="#lib"><tt>llvm/lib</tt></a>
41 <li><a href="#runtime"><tt>llvm/runtime</tt></a>
42 <li><a href="#test"><tt>llvm/test</tt></a>
43 <li><a href="#tools"><tt>llvm/tools</tt></a>
44 <li><a href="#utils"><tt>llvm/utils</tt></a>
47 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
48 <li><a href="#problems">Common Problems</a>
49 <li><a href="#links">Links</a>
52 <div class="doc_author">
54 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
55 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
56 <a href="http://misha.brukman.net">Misha Brukman</a>,
57 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
58 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
63 <!-- *********************************************************************** -->
64 <div class="doc_section">
65 <a name="overview"><b>Overview</b></a>
67 <!-- *********************************************************************** -->
69 <div class="doc_text">
71 <p>Welcome to LLVM! In order to get started, you first need to know some
72 basic information.</p>
74 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
75 contains all of the tools, libraries, and header files needed to use the low
76 level virtual machine. It contains an assembler, disassembler, bytecode
77 analyzer, and bytecode optimizer. It also contains a test suite that can be
78 used to test the LLVM tools and the GCC front end.</p>
80 <p>The second piece is the GCC front end. This component provides a version of
81 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
82 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
83 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
84 from the LLVM suite.</p>
88 <!-- *********************************************************************** -->
89 <div class="doc_section">
90 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
92 <!-- *********************************************************************** -->
94 <div class="doc_text">
96 <p>Here's the short story for getting up and running quickly with LLVM:</p>
99 <li>Install the GCC front end:
101 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
102 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
103 <li><b>Sparc and MacOS X Only:</b><br>
104 <tt>cd cfrontend/<i>platform</i><br>
108 <li>Get the Source Code
110 <li>With the distributed files:
112 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
113 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
117 <li>With anonymous CVS access (or use a <a href="#mirror">mirror</a>):
119 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
121 :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt></li>
122 <li>Hit the return key when prompted for the password.
123 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm
125 <li><tt>cd llvm</tt></li>
129 <li>Configure the LLVM Build Environment
131 <li>Change directory to where you want to store the LLVM object
132 files and run <tt>configure</tt> to configure the Makefiles and
133 header files for the default platform. Useful options include:
135 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
136 <p>Specify the full pathname of where the LLVM GCC frontend is
138 <li><tt>--enable-spec2000=<i>directory</i></tt>
139 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
140 benchmarks should be available in
141 <tt><i>directory</i></tt>.</p></li>
145 <li>Build the LLVM Suite:
147 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.
148 <li><tt>gmake -k |& tee gnumake.out
149 # this is csh or tcsh syntax</tt>
154 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
155 detailed information on configuring and compiling LLVM. See <a
156 href="#environment">Setting Up Your Environment</a> for tips that simplify
157 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
158 Layout</a> to learn about the layout of the source code tree.</p>
162 <!-- *********************************************************************** -->
163 <div class="doc_section">
164 <a name="requirements"><b>Requirements</b></a>
166 <!-- *********************************************************************** -->
168 <div class="doc_text">
170 <p>Before you begin to use the LLVM system, review the requirements given below.
171 This may save you some trouble by knowing ahead of time what hardware and
172 software you will need.</p>
176 <!-- ======================================================================= -->
177 <div class="doc_subsection">
178 <a name="hardware"><b>Hardware</b></a>
181 <div class="doc_text">
183 <p>LLVM is known to work on the following platforms:</p>
187 <li>Linux on x86 (Pentium and above)
189 <li>Approximately 1.02 GB of Free Disk Space
191 <li>Source code: 45 MB</li>
192 <li>Object code: 956 MB</li>
193 <li>GCC front end: 40 MB</li>
198 <li>Solaris on SparcV9 (Ultrasparc)
200 <li>Approximately 1.75 GB of Free Disk Space
202 <li>Source code: 45 MB</li>
203 <li>Object code: 1705 MB</li>
204 <li>GCC front end: 50 MB</li>
209 <li>FreeBSD on x86 (Pentium and above)
211 <li>Approximately 935 MB of Free Disk Space
213 <li>Source code: 45 MB</li>
214 <li>Object code: 850 MB</li>
215 <li>GCC front end: 40 MB</li>
220 <li>MacOS X on PowerPC
222 <li>No native code generation
223 <li>Approximately 1.25 GB of Free Disk Space
225 <li>Source code: 45 MB</li>
226 <li>Object code: 1160 MB</li>
227 <li>GCC front end: 40 MB</li>
234 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
235 guaranteed to do so. If compilation is successful, the LLVM utilities should be
236 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
237 generation should work as well, although the generated native code may not work
238 on your platform.</p>
240 <p>The GCC front end is not very portable at the moment. If you want to get it
241 to work on another platform, you can download a copy of the source and try to
242 compile it on your platform.</p>
246 <!-- ======================================================================= -->
247 <div class="doc_subsection">
248 <a name="software"><b>Software</b></a>
251 <div class="doc_text">
253 <p>Compiling LLVM requires that you have several software packages
257 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
260 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
262 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
264 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
267 <p>There are some additional tools that you may want to have when working with
271 <li><A href="http://www.gnu.org/software/automake">GNU Automake</A></li>
272 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A></li>
273 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
275 <p>If you want to make changes to the configure scripts, you will need GNU
276 autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
277 higher). You will also need automake. Any old version of
278 automake from 1.4p5 on should work; we only use aclocal from that
281 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest 2.0.3</A></li>
282 <li><A href="http://www.python.org">Python</A>
285 These are needed to use the LLVM test suite. Please note that newer
286 versions of QMTest may not work with the LLVM test suite. QMTest 2.0.3
287 can be retrieved from the QMTest CVS repository using the following
290 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository login</tt>
292 <li>When prompted, use <tt>anoncvs</tt> as the password.
294 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository co -r release-2-0-3 qm</tt>
301 <p>The remainder of this guide is meant to get you up and running with
302 LLVM and to give you some basic information about the LLVM environment.
303 A <a href="#starting">complete guide to installation</a> is provided in the
306 <p>The later sections of this guide describe the <a
307 href="#layout">general layout</a> of the the LLVM source tree, a <a
308 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
309 href="#links">links</a> to find more information about LLVM or to get
314 <!-- *********************************************************************** -->
315 <div class="doc_section">
316 <a name="starting"><b>Getting Started with LLVM</b></a>
318 <!-- *********************************************************************** -->
320 <!-- ======================================================================= -->
321 <div class="doc_subsection">
322 <a name="terminology">Terminology and Notation</a>
325 <div class="doc_text">
327 <p>Throughout this manual, the following names are used to denote paths
328 specific to the local system and working environment. <i>These are not
329 environment variables you need to set but just strings used in the rest
330 of this document below</i>. In any of the examples below, simply replace
331 each of these names with the appropriate pathname on your local system.
332 All these paths are absolute:</p>
337 This is the top level directory of the LLVM source tree.
342 This is the top level directory of the LLVM object tree (i.e. the
343 tree where object files and compiled programs will be placed. It
344 can be the same as SRC_ROOT).
349 This is the where the LLVM GCC Front End is installed.
351 For the pre-built GCC front end binaries, the LLVMGCCDIR is
352 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
357 <!-- ======================================================================= -->
358 <div class="doc_subsection">
359 <a name="environment">Setting Up Your Environment</a>
362 <div class="doc_text">
365 In order to compile and use LLVM, you will need to set some environment
366 variables. There are also some shell aliases which you may find useful.
367 You can set these on the command line, or better yet, set them in your
368 <tt>.cshrc</tt> or <tt>.profile</tt>.
371 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
373 This environment variable helps the LLVM GCC front end find bytecode
374 libraries that it will need for compilation.
377 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
378 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
380 This alias allows you to use the LLVM C and C++ front ends without putting
381 them in your <tt>PATH</tt> or typing in their complete pathnames.
386 <!-- ======================================================================= -->
387 <div class="doc_subsection">
388 <a name="unpack">Unpacking the LLVM Archives</a>
391 <div class="doc_text">
394 If you have the LLVM distribution, you will need to unpack it before you
395 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
396 suite and the LLVM GCC front end compiled for your platform. Each
397 file is a TAR archive that is compressed with the gzip program.
400 <p> The files are as follows:
403 <dd>This is the source code to the LLVM suite.
406 <dt>cfrontend-1.2.sparc-sun-solaris2.8.tar.gz
407 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
410 <dt>cfrontend-1.2.i686-redhat-linux-gnu.tar.gz
411 <dd>This is the binary release of the GCC front end for Linux/x86.
414 <dt>cfrontend-1.2.i386-unknown-freebsd5.1.tar.gz
415 <dd>This is the binary release of the GCC front end for FreeBSD/x86.
418 <dt>cfrontend-1.2.powerpc-apple-darwin7.0.0.tar.gz
419 <dd>This is the binary release of the GCC front end for MacOS X/PPC.
424 <!-- ======================================================================= -->
425 <div class="doc_subsection">
426 <a name="checkout">Checkout LLVM from CVS</a>
429 <div class="doc_text">
431 <p>If you have access to our CVS repository, you can get a fresh copy of
432 the entire source code. All you need to do is check it out from CVS as
436 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
437 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
438 <li>Hit the return key when prompted for the password.
439 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
443 <p>This will create an '<tt>llvm</tt>' directory in the current
444 directory and fully populate it with the LLVM source code, Makefiles,
445 test directories, and local copies of documentation files.</p>
447 <p>If you want to get a specific release (as opposed to the most recent
448 revision), you can specify a label. The following releases have the following
452 <li>Release 1.2: <b>RELEASE_12</b></li>
453 <li>Release 1.1: <b>RELEASE_11</b></li>
454 <li>Release 1.0: <b>RELEASE_1</b></li>
457 <p>If you would like to get the GCC front end source code, you can also get it
458 from the CVS repository:</p>
461 cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-gcc
464 <p>Please note that you must follow <a href="CFEBuildInstrs.html">these
465 instructions</a> to successfully build the LLVM C front-end.</p>
469 <!-- ======================================================================= -->
470 <div class="doc_subsubsection">
471 <a name="mirrors">LLVM CVS Mirrors</a>
474 <div class="doc_text">
476 <p>If the main CVS server is overloaded or inaccessible, you can try one of
477 these user-hosted mirrors:</p>
480 <li><a href="http://llvm.x10sys.com/">Mirror hosted by eXtensible Systems
485 <!-- ======================================================================= -->
486 <div class="doc_subsection">
487 <a name="installcf">Install the GCC Front End</a>
490 <div class="doc_text">
492 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
493 GCC front end from the binary distribution. It is used for building the
494 bytecode libraries later used by the GCC front end for linking programs, and its
495 location must be specified when the LLVM suite is configured.</p>
497 <p>To install the GCC front end, do the following:</p>
500 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
501 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
505 <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
508 <p><tt>cd cfrontend/<i>platform</i><br>
509 ./fixheaders</tt></p>
511 <p>The binary versions of the GCC front end may not suit all of your needs. For
512 example, the binary distribution may include an old version of a system header
513 file, not "fix" a header file that needs to be fixed for GCC, or it may be
514 linked with libraries not available on your system.</p>
516 <p>In cases like these, you may want to try <a
517 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
518 not for the faint of heart, so be forewarned.</p>
522 <!-- ======================================================================= -->
523 <div class="doc_subsection">
524 <a name="config">Local LLVM Configuration</a>
527 <div class="doc_text">
529 <p>Once checked out from the CVS repository, the LLVM suite source code must be
530 configured via the <tt>configure</tt> script. This script sets variables in
531 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
532 also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
535 <p>The following environment variables are used by the <tt>configure</tt>
536 script to configure the build system:</p>
546 <td>Tells <tt>configure</tt> which C compiler to use. By default,
547 <tt>configure</tt> will look for the first GCC C compiler in
548 <tt>PATH</tt>. Use this variable to override
549 <tt>configure</tt>'s default behavior.</td>
554 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
555 <tt>configure</tt> will look for the first GCC C++ compiler in
556 <tt>PATH</tt>. Use this variable to override
557 <tt>configure</tt>'s default behavior.</td>
561 <p>The following options can be used to set or enable LLVM specific options:</p>
564 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
566 Path to the location where the LLVM GCC front end binaries and
567 associated libraries were installed. This must be specified as an
570 <dt><i>--enable-optimized</i>
572 Enables optimized compilation by default (debugging symbols are removed
573 and GCC optimization flags are enabled). The default is to use an
574 unoptimized build (also known as a debug build).
576 <dt><i>--enable-jit</i>
578 Compile the Just In Time (JIT) compiler functionality. This is not
580 on all platforms. The default is dependent on platform, so it is best
581 to explicitly enable it if you want it.
583 <dt><i>--enable-spec2000</i>
584 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
586 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
587 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
588 <tt>directory</tt>, you can tell configure where to find the SPEC2000
589 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
590 uses the default value
591 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
593 <dt><i>--enable-spec95</i>
594 <dt><i>--enable-spec95=<<tt>directory</tt>></i>
596 Enable the use of SPEC95 when testing LLVM. It is similar to the
597 <i>--enable-spec2000</i> option.
599 <dt><i>--enable-povray</i>
600 <dt><i>--enable-povray=<<tt>directory</tt>></i>
602 Enable the use of Povray as an external test. Versions of Povray written
603 in C should work. This option is similar to the <i>--enable-spec2000</i>
607 <p>To configure LLVM, follow these steps:</p>
610 <li>Change directory into the object root directory:
612 <tt>cd <i>OBJ_ROOT</i></tt>
615 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
617 <tt><i>SRC_ROOT</i>/configure</tt>
621 <p>In addition to running <tt>configure</tt>, you must set the
622 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
623 This environment variable is used to locate "system" libraries like
624 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
625 the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
626 end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
627 <tt>LLVM_LIB_SEARCH_PATH</tt> to
628 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
629 version of the GCC front end on our research machines.</p>
633 <!-- ======================================================================= -->
634 <div class="doc_subsection">
635 <a name="compile">Compiling the LLVM Suite Source Code</a>
638 <div class="doc_text">
640 <p>Once you have configured LLVM, you can build it. There are three types of
646 These builds are the default when one types <tt>gmake</tt> (unless the
647 <tt>--enable-optimized</tt> option was used during configuration). The
648 build system will compile the tools and libraries with debugging
652 <dt>Release (Optimized) Builds
654 These builds are enabled with the <tt>--enable-optimized</tt> option to
655 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
656 <tt>gmake</tt> command line. For these builds, the build system will
657 compile the tools and libraries with GCC optimizations enabled and strip
658 debugging information from the libraries and executables it generates.
663 These builds are for use with profiling. They compile profiling
664 information into the code for use with programs like <tt>gprof</tt>.
665 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
666 on the <tt>gmake</tt> command line.
669 <p>Once you have LLVM configured, you can build it by entering the
670 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
672 <p><tt>gmake</tt></p>
674 <p>If you have multiple processors in your machine, you may wish to use some of
675 the parallel build options provided by GNU Make. For example, you could use the
678 <p><tt>gmake -j2</tt></p>
680 <p>There are several special targets which are useful when working with the LLVM
684 <dt><tt>gmake clean</tt>
686 Removes all files generated by the build. This includes object files,
687 generated C/C++ files, libraries, and executables.
690 <dt><tt>gmake distclean</tt>
692 Removes everything that <tt>gmake clean</tt> does, but also removes
693 files generated by <tt>configure</tt>. It attempts to return the
694 source tree to the original state in which it was shipped.
697 <dt><tt>gmake install</tt>
699 Installs LLVM files into the proper location. For the most part,
700 this does nothing, but it does install bytecode libraries into the
701 GCC front end's bytecode library directory. If you need to update
702 your bytecode libraries, this is the target to use once you've built
707 <p>It is also possible to override default values from <tt>configure</tt> by
708 declaring variables on the command line. The following are some examples:</p>
711 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
713 Perform a Release (Optimized) build.
716 <dt><tt>gmake ENABLE_PROFILING=1</tt>
718 Perform a Profiling build.
721 <dt><tt>gmake VERBOSE=1</tt>
723 Print what <tt>gmake</tt> is doing on standard output.
727 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
728 it and any subdirectories that it contains. Entering any directory inside the
729 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
730 that directory that is out of date.</p>
734 <!-- ======================================================================= -->
735 <div class="doc_subsection">
736 <a name="objfiles">The Location of LLVM Object Files</a>
739 <div class="doc_text">
741 <p>The LLVM build system is capable of sharing a single LLVM source tree among
742 several LLVM builds. Hence, it is possible to build LLVM for several different
743 platforms or configurations using the same source tree.</p>
745 <p>This is accomplished in the typical autoconf manner:</p>
748 <li><p>Change directory to where the LLVM object files should live:</p>
750 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
752 <li><p>Run the <tt>configure</tt> script found in the LLVM source
755 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
758 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
759 named after the build type:</p>
766 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
768 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
776 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
778 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
786 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
788 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
794 <!-- ======================================================================= -->
795 <div class="doc_subsection">
796 <a name="optionalconfig">Optional Configuration Items</a>
799 <div class="doc_text">
802 If you're running on a linux system that supports the "<a
803 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
804 module, and you have root access on the system, you can set your system up to
805 execute LLVM bytecode files directly. To do this, use commands like this (the
806 first command may not be required if you are already using the module):</p>
809 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
810 $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
811 $ chmod u+x hello.bc (if needed)
816 This allows you to execute LLVM bytecode files directly. Thanks to Jack
817 Cummings for pointing this out!
823 <!-- *********************************************************************** -->
824 <div class="doc_section">
825 <a name="layout"><b>Program Layout</b></a>
827 <!-- *********************************************************************** -->
829 <div class="doc_text">
831 <p>One useful source of information about the LLVM source base is the LLVM <a
832 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
833 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
834 The following is a brief introduction to code layout:</p>
838 <!-- ======================================================================= -->
839 <div class="doc_subsection">
840 <a name="cvsdir"><tt>CVS</tt> directories</a>
843 <div class="doc_text">
845 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
846 the most part these can just be ignored.</p>
850 <!-- ======================================================================= -->
851 <div class="doc_subsection">
852 <a name="include"><tt>llvm/include</tt></a>
855 <div class="doc_text">
857 <p>This directory contains public header files exported from the LLVM
858 library. The three main subdirectories of this directory are:</p>
861 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
862 specific header files. This directory also has subdirectories for
863 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
864 <tt>Target</tt>, <tt>Transforms</tt>, etc...</li>
866 <li><tt>llvm/include/Support</tt> - This directory contains generic
867 support libraries that are independent of LLVM, but are used by LLVM.
868 For example, some C++ STL utilities and a Command Line option processing
869 library store their header files here.</li>
871 <li><tt>llvm/include/Config</tt> - This directory contains header files
872 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
873 and C header files. Source code can include these header files which
874 automatically take care of the conditional #includes that the
875 <tt>configure</tt> script generates.</li>
880 <!-- ======================================================================= -->
881 <div class="doc_subsection">
882 <a name="lib"><tt>llvm/lib</tt></a>
885 <div class="doc_text">
887 <p>This directory contains most of the source files of the LLVM system. In LLVM,
888 almost all code exists in libraries, making it very easy to share code among the
889 different <a href="#tools">tools</a>.</p>
892 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
893 source files that implement core classes like Instruction and BasicBlock.
895 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
896 for the LLVM assembly language parser library.
898 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
899 and write LLVM bytecode.
901 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
904 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
905 different program analyses, such as Dominator Information, Call Graphs,
906 Induction Variables, Interval Identification, Natural Loop Identification,
909 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
910 code for the LLVM to LLVM program transformations, such as Aggressive Dead
911 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
912 Invariant Code Motion, Dead Global Elimination, and many others...
914 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
915 describe various target architectures for code generation. For example,
916 the llvm/lib/Target/SparcV9 directory holds the Sparc machine
919 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
920 of the code generator: Instruction Selector, Instruction Scheduling, and
923 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
924 that corresponds to the header files located in
925 <tt>llvm/include/Support/</tt>.
930 <!-- ======================================================================= -->
931 <div class="doc_subsection">
932 <a name="runtime"><tt>llvm/runtime</tt></a>
935 <div class="doc_text">
937 <p>This directory contains libraries which are compiled into LLVM bytecode and
938 used when linking programs with the GCC front end. Most of these libraries are
939 skeleton versions of real libraries; for example, libc is a stripped down
940 version of glibc.</p>
942 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
947 <!-- ======================================================================= -->
948 <div class="doc_subsection">
949 <a name="test"><tt>llvm/test</tt></a>
952 <div class="doc_text">
954 <p>This directory contains regression tests and source code that is used to test
955 the LLVM infrastructure.</p>
959 <!-- ======================================================================= -->
960 <div class="doc_subsection">
961 <a name="tools"><tt>llvm/tools</tt></a>
964 <div class="doc_text">
966 <p>The <b>tools</b> directory contains the executables built out of the
967 libraries above, which form the main part of the user interface. You can
968 always get help for a tool by typing <tt>tool_name --help</tt>. The
969 following is a brief introduction to the most important tools:</p>
972 <dt><tt><b>analyze</b></tt> <dd><tt>analyze</tt> is used to run a specific
973 analysis on an input LLVM bytecode file and print out the results. It is
974 primarily useful for debugging analyses, or familiarizing yourself with
975 what an analysis does.<p>
977 <dt><tt><b>bugpoint</b></tt> <dd><tt>bugpoint</tt> is used to debug
978 optimization passes or code generation backends by narrowing down the
979 given test case to the minimum number of passes and/or instructions that
980 still cause a problem, whether it is a crash or miscompilation. See <a
981 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
982 on using <tt>bugpoint</tt>.<p>
984 <dt><tt><b>llvm-ar</b></tt> <dd>The archiver produces an archive containing
985 the given LLVM bytecode files, optionally with an index for faster
988 <dt><tt><b>llvm-as</b></tt> <dd>The assembler transforms the human readable
989 LLVM assembly to LLVM bytecode.<p>
991 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
992 bytecode to human readable LLVM assembly.<p>
994 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
995 links multiple LLVM modules into a single program.<p>
997 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
998 can directly execute LLVM bytecode (although very slowly...). In addition
999 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
1000 specifying <tt>-trace</tt> on the command line). Finally, for
1001 architectures that support it (currently only x86 and Sparc), by default,
1002 <tt>lli</tt> will function as a Just-In-Time compiler (if the
1003 functionality was compiled in), and will execute the code <i>much</i>
1004 faster than the interpreter.<p>
1006 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler, which
1007 translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
1008 the -march=c option).<p>
1010 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
1011 that has been retargeted to emit LLVM code as the machine code output. It
1012 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
1013 -o</tt> options that are typically used. The source code for the
1014 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
1015 because it is quite large and not very interesting.<p>
1019 <dt><tt><b>gccas</b></tt> <dd>This tool is invoked by the
1020 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
1021 tool actually assembles LLVM assembly to LLVM bytecode,
1022 performs a variety of optimizations, and outputs LLVM bytecode. Thus
1023 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
1024 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
1025 an LLVM bytecode file that can be disassembled or manipulated just like
1026 any other bytecode file). The command line interface to <tt>gccas</tt>
1027 is designed to be as close as possible to the <b>system</b>
1028 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
1029 modified to interface to a "weird" assembler.<p>
1031 <dt><tt><b>gccld</b></tt> <dd><tt>gccld</tt> links together several LLVM
1032 bytecode files into one bytecode file and does some optimization. It is
1033 the linker invoked by the GCC frontend when multiple .o files need to be
1034 linked together. Like <tt>gccas</tt>, the command line interface of
1035 <tt>gccld</tt> is designed to match the system linker, to aid
1036 interfacing with the GCC frontend.</dl><p>
1039 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
1040 series of LLVM to LLVM transformations (which are specified on the command
1041 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
1042 command is a good way to get a list of the program transformations
1049 <!-- ======================================================================= -->
1050 <div class="doc_subsection">
1051 <a name="utils"><tt>llvm/utils</tt></a>
1054 <div class="doc_text">
1056 <p>This directory contains utilities for working with LLVM source code, and some
1057 of the utilities are actually required as part of the build process because they
1058 are code generators for parts of LLVM infrastructure.</p>
1061 <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
1062 generator -- it builds trees on which it then performs pattern-matching to
1063 select instructions according to the patterns the user has specified. Burg
1064 is currently used in the Sparc V9 backend.<p>
1066 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1067 that finds differences between code that LLC generates and code that LLI
1068 generates. This is a useful tool if you are debugging one of them,
1069 assuming that the other generates correct output. For the full user
1070 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
1072 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1073 update your CVS tree, but produce a much cleaner and more organized output
1074 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1075 together all the new and updated files and modified files in separate
1076 sections, so you can see at a glance what has changed. If you are at the
1077 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1078 preferred way of updating the tree.<p>
1080 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1081 syntax-highlighting files which will work with Emacs and XEmacs editors,
1082 providing syntax highlighting support for LLVM assembly files and TableGen
1083 description files. For information on how to use the syntax files, consult
1084 the <tt>README</tt> file in that directory.<p>
1086 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1087 and outputs all non-generated source files, which is useful if one wishes
1088 to do a lot of development across directories and does not want to
1089 individually find each file. One way to use it is to run, for example:
1090 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1093 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1094 files in the current directory and then compiles and links the tool that
1095 is the first argument. For example, assuming you are in the directory
1096 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1097 simply running <tt>makellvm llc</tt> will make a build of the current
1098 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1099 causing a re-linking of LLC.<p>
1101 <dt><tt><b>NightlyTest.pl</b></tt> and
1102 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1103 cron script to generate nightly status reports of the functionality of
1104 tools, and the results can be seen by following the appropriate link on
1105 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
1107 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1108 the tool used to generate register descriptions, instruction set
1109 descriptions, and even assemblers from common TableGen description
1112 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1113 syntax-highlighting files which will work with the VIM editor, providing
1114 syntax highlighting support for LLVM assembly files and TableGen
1115 description files. For information on how to use the syntax files, consult
1116 the <tt>README</tt> file in that directory.<p>
1122 <!-- *********************************************************************** -->
1123 <div class="doc_section">
1124 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1126 <!-- *********************************************************************** -->
1128 <div class="doc_text">
1131 <li>First, create a simple C file, name it 'hello.c':
1133 #include <stdio.h>
1135 printf("hello world\n");
1140 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1141 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1143 <p>Note that you should have already built the tools and they have to be
1144 in your path, at least <tt>gccas</tt> and <tt>gccld</tt>.</p>
1146 <p>This will create two result files: <tt>hello</tt> and
1147 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1148 corresponds the the compiled program and the library facilities that it
1149 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1150 file with <tt>lli</tt>, making the result directly executable. Note that
1151 all LLVM optimizations are enabled by default, so there is no need for a
1152 "-O3" switch.</p></li>
1154 <li><p>Run the program. To make sure the program ran, execute one of the
1155 following commands:</p>
1157 <p><tt>% ./hello</tt></p>
1161 <p><tt>% lli hello.bc</tt></p></li>
1163 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1166 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1168 <li><p>Compile the program to native assembly using the LLC code
1171 <p><tt>% llc hello.bc -o hello.s</tt></p>
1173 <li><p>Assemble the native assembly language file into a program:</p>
1175 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1176 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1178 <li><p>Execute the native code program:</p>
1180 <p><tt>% ./hello.native</tt></p></li>
1186 <!-- *********************************************************************** -->
1187 <div class="doc_section">
1188 <a name="problems">Common Problems</a>
1190 <!-- *********************************************************************** -->
1192 <div class="doc_text">
1194 <p>If you are having problems building or using LLVM, or if you have any other
1195 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1196 Asked Questions</a> page.</p>
1200 <!-- *********************************************************************** -->
1201 <div class="doc_section">
1202 <a name="links">Links</a>
1204 <!-- *********************************************************************** -->
1206 <div class="doc_text">
1208 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1209 some simple things... there are many more interesting and complicated things
1210 that you can do that aren't documented here (but we'll gladly accept a patch
1211 if you want to write something up!). For more information about LLVM, check
1215 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1216 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1217 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1218 that Uses LLVM</a></li>
1223 <!-- *********************************************************************** -->
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1232 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1233 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
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