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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="#tools"><tt>llvm/tools</tt></a>
45 <li><a href="#utils"><tt>llvm/utils</tt></a>
48 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
49 <li><a href="#problems">Common Problems</a>
50 <li><a href="#links">Links</a>
53 <div class="doc_author">
55 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
56 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
57 <a href="http://misha.brukman.net">Misha Brukman</a>,
58 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
59 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
64 <!-- *********************************************************************** -->
65 <div class="doc_section">
66 <a name="overview"><b>Overview</b></a>
68 <!-- *********************************************************************** -->
70 <div class="doc_text">
72 <p>Welcome to LLVM! In order to get started, you first need to know some
73 basic information.</p>
75 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
76 contains all of the tools, libraries, and header files needed to use the low
77 level virtual machine. It contains an assembler, disassembler, bytecode
78 analyzer, and bytecode optimizer. It also contains a test suite that can be
79 used to test the LLVM tools and the GCC front end.</p>
81 <p>The second piece is the GCC front end. This component provides a version of
82 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
83 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
84 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
85 from the LLVM suite.</p>
89 <!-- *********************************************************************** -->
90 <div class="doc_section">
91 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
93 <!-- *********************************************************************** -->
95 <div class="doc_text">
97 <p>Here's the short story for getting up and running quickly with LLVM:</p>
100 <li>Install the GCC front end:
102 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
103 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
104 <li><b>Sparc and MacOS X Only:</b><br>
105 <tt>cd cfrontend/<i>platform</i><br>
109 <li>Get the Source Code
111 <li>With the distributed files:
113 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
114 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
118 <li>With anonymous CVS access (or use a <a href="#mirror">mirror</a>):
120 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
122 :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt></li>
123 <li>Hit the return key when prompted for the password.
124 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm
126 <li><tt>cd llvm</tt></li>
130 <li>Configure the LLVM Build Environment
132 <li>Change directory to where you want to store the LLVM object
133 files and run <tt>configure</tt> to configure the Makefiles and
134 header files for the default platform. Useful options include:
136 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
137 <p>Specify the full pathname of where the LLVM GCC frontend is
139 <li><tt>--enable-spec2000=<i>directory</i></tt>
140 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
141 benchmarks should be available in
142 <tt><i>directory</i></tt>.</p></li>
146 <li>Build the LLVM Suite:
148 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.</li>
149 <li><tt>gmake -k |& tee gnumake.out
150 # this is csh or tcsh syntax</tt></li>
151 <li>If you get an "internal compiler error (ICE)" see <a href="#brokengcc">below</a>.</li>
156 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
157 detailed information on configuring and compiling LLVM. See <a
158 href="#environment">Setting Up Your Environment</a> for tips that simplify
159 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
160 Layout</a> to learn about the layout of the source code tree.</p>
164 <!-- *********************************************************************** -->
165 <div class="doc_section">
166 <a name="requirements"><b>Requirements</b></a>
168 <!-- *********************************************************************** -->
170 <div class="doc_text">
172 <p>Before you begin to use the LLVM system, review the requirements given below.
173 This may save you some trouble by knowing ahead of time what hardware and
174 software you will need.</p>
178 <!-- ======================================================================= -->
179 <div class="doc_subsection">
180 <a name="hardware"><b>Hardware</b></a>
183 <div class="doc_text">
185 <p>LLVM is known to work on the following platforms:</p>
189 <li>Linux on x86 (Pentium and above)
191 <li>Approximately 1.02 GB of Free Disk Space
193 <li>Source code: 45 MB</li>
194 <li>Object code: 956 MB</li>
195 <li>GCC front end: 40 MB</li>
200 <li>Solaris on SparcV9 (Ultrasparc)
202 <li>Approximately 1.75 GB of Free Disk Space
204 <li>Source code: 45 MB</li>
205 <li>Object code: 1705 MB</li>
206 <li>GCC front end: 50 MB</li>
211 <li>FreeBSD on x86 (Pentium and above)
213 <li>Approximately 935 MB of Free Disk Space
215 <li>Source code: 45 MB</li>
216 <li>Object code: 850 MB</li>
217 <li>GCC front end: 40 MB</li>
222 <li>MacOS X on PowerPC
224 <li>No native code generation
225 <li>Approximately 1.25 GB of Free Disk Space
227 <li>Source code: 45 MB</li>
228 <li>Object code: 1160 MB</li>
229 <li>GCC front end: 40 MB</li>
236 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
237 guaranteed to do so. If compilation is successful, the LLVM utilities should be
238 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
239 generation should work as well, although the generated native code may not work
240 on your platform.</p>
242 <p>The GCC front end is not very portable at the moment. If you want to get it
243 to work on another platform, you can download a copy of the source and <a href="CFEBuildInstrs.html">try to compile it</a> on your platform.</p>
247 <!-- ======================================================================= -->
248 <div class="doc_subsection">
249 <a name="software"><b>Software</b></a>
252 <div class="doc_text">
254 <p>Compiling LLVM requires that you have several software packages
258 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
259 support</a> (See <a href="#brokengcc">below</a> for specific version info)</li>
261 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
263 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
265 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
268 <p>There are some additional tools that you may want to have when working with
272 <li><A href="http://www.gnu.org/software/automake">GNU Automake</A></li>
273 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A></li>
274 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
276 <p>If you want to make changes to the configure scripts, you will need GNU
277 autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
278 higher). You will also need automake. Any old version of
279 automake from 1.4p5 on should work; we only use aclocal from that
282 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest 2.0.3</A></li>
283 <li><A href="http://www.python.org">Python</A>
286 These are needed to use the LLVM test suite. Please note that newer
287 versions of QMTest may not work with the LLVM test suite. QMTest 2.0.3
288 can be retrieved from the QMTest CVS repository using the following
291 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository login</tt>
293 <li>When prompted, use <tt>anoncvs</tt> as the password.
295 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository co -r release-2-0-3 qm</tt>
303 <!-- ======================================================================= -->
304 <div class="doc_subsection">
305 <a name="brokengcc">Broken versions of GCC</a>
308 <div class="doc_text">
310 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
311 bugs in the compiler. In particular, several versions of GCC crash when trying
312 to compile LLVM. We routinely use GCC 3.3.3 and GCC 3.4.0 and have had success
313 with them. Other versions of GCC will probably work as well. GCC versions listed
314 here are known to not work. If you are using one of these versions, please try
315 to upgrade your GCC to something more recent. If you run into a problem with a
316 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
317 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
318 of GCC you are using.
321 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
322 problems in the STL that effectively prevent it from compiling LLVM.
325 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
326 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
327 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
333 <!-- *********************************************************************** -->
334 <div class="doc_section">
335 <a name="starting"><b>Getting Started with LLVM</b></a>
337 <!-- *********************************************************************** -->
339 <div class="doc_text">
341 <p>The remainder of this guide is meant to get you up and running with
342 LLVM and to give you some basic information about the LLVM environment.</p>
344 <p>The later sections of this guide describe the <a
345 href="#layout">general layout</a> of the the LLVM source tree, a <a
346 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
347 href="#links">links</a> to find more information about LLVM or to get
351 <!-- ======================================================================= -->
352 <div class="doc_subsection">
353 <a name="terminology">Terminology and Notation</a>
356 <div class="doc_text">
358 <p>Throughout this manual, the following names are used to denote paths
359 specific to the local system and working environment. <i>These are not
360 environment variables you need to set but just strings used in the rest
361 of this document below</i>. In any of the examples below, simply replace
362 each of these names with the appropriate pathname on your local system.
363 All these paths are absolute:</p>
368 This is the top level directory of the LLVM source tree.
373 This is the top level directory of the LLVM object tree (i.e. the
374 tree where object files and compiled programs will be placed. It
375 can be the same as SRC_ROOT).
380 This is the where the LLVM GCC Front End is installed.
382 For the pre-built GCC front end binaries, the LLVMGCCDIR is
383 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
388 <!-- ======================================================================= -->
389 <div class="doc_subsection">
390 <a name="environment">Setting Up Your Environment</a>
393 <div class="doc_text">
396 In order to compile and use LLVM, you will need to set some environment
397 variables. There are also some shell aliases which you may find useful.
398 You can set these on the command line, or better yet, set them in your
399 <tt>.cshrc</tt> or <tt>.profile</tt>.
402 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
404 This environment variable helps the LLVM GCC front end find bytecode
405 libraries that it will need for compilation.
408 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
409 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
411 This alias allows you to use the LLVM C and C++ front ends without putting
412 them in your <tt>PATH</tt> or typing in their complete pathnames.
417 <!-- ======================================================================= -->
418 <div class="doc_subsection">
419 <a name="unpack">Unpacking the LLVM Archives</a>
422 <div class="doc_text">
425 If you have the LLVM distribution, you will need to unpack it before you
426 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
427 suite and the LLVM GCC front end compiled for your platform. Each
428 file is a TAR archive that is compressed with the gzip program.
431 <p> The files are as follows:
434 <dd>This is the source code to the LLVM suite.
437 <dt>cfrontend-1.2.sparc-sun-solaris2.8.tar.gz
438 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
441 <dt>cfrontend-1.2.i686-redhat-linux-gnu.tar.gz
442 <dd>This is the binary release of the GCC front end for Linux/x86.
445 <dt>cfrontend-1.2.i386-unknown-freebsd5.1.tar.gz
446 <dd>This is the binary release of the GCC front end for FreeBSD/x86.
449 <dt>cfrontend-1.2.powerpc-apple-darwin7.0.0.tar.gz
450 <dd>This is the binary release of the GCC front end for MacOS X/PPC.
455 <!-- ======================================================================= -->
456 <div class="doc_subsection">
457 <a name="checkout">Checkout LLVM from CVS</a>
460 <div class="doc_text">
462 <p>If you have access to our CVS repository, you can get a fresh copy of
463 the entire source code. All you need to do is check it out from CVS as
467 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
468 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
469 <li>Hit the return key when prompted for the password.
470 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
474 <p>This will create an '<tt>llvm</tt>' directory in the current
475 directory and fully populate it with the LLVM source code, Makefiles,
476 test directories, and local copies of documentation files.</p>
478 <p>If you want to get a specific release (as opposed to the most recent
479 revision), you can specify a label. The following releases have the following
483 <li>Release 1.2: <b>RELEASE_12</b></li>
484 <li>Release 1.1: <b>RELEASE_11</b></li>
485 <li>Release 1.0: <b>RELEASE_1</b></li>
488 <p>If you would like to get the GCC front end source code, you can also get it
489 from the CVS repository:</p>
492 cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-gcc
495 <p>Please note that you must follow <a href="CFEBuildInstrs.html">these
496 instructions</a> to successfully build the LLVM C front-end.</p>
500 <!-- ======================================================================= -->
501 <div class="doc_subsubsection">
502 <a name="mirrors">LLVM CVS Mirrors</a>
505 <div class="doc_text">
507 <p>If the main CVS server is overloaded or inaccessible, you can try one of
508 these user-hosted mirrors:</p>
511 <li><a href="http://llvm.x10sys.com/">Mirror hosted by eXtensible Systems
516 <!-- ======================================================================= -->
517 <div class="doc_subsection">
518 <a name="installcf">Install the GCC Front End</a>
521 <div class="doc_text">
523 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
524 GCC front end from the binary distribution. It is used for building the
525 bytecode libraries later used by the GCC front end for linking programs, and its
526 location must be specified when the LLVM suite is configured.</p>
528 <p>To install the GCC front end, do the following:</p>
531 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
532 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
536 <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
539 <p><tt>cd cfrontend/<i>platform</i><br>
540 ./fixheaders</tt></p>
542 <p>The binary versions of the GCC front end may not suit all of your needs. For
543 example, the binary distribution may include an old version of a system header
544 file, not "fix" a header file that needs to be fixed for GCC, or it may be
545 linked with libraries not available on your system.</p>
547 <p>In cases like these, you may want to try <a
548 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
549 not for the faint of heart, so be forewarned.</p>
553 <!-- ======================================================================= -->
554 <div class="doc_subsection">
555 <a name="config">Local LLVM Configuration</a>
558 <div class="doc_text">
560 <p>Once checked out from the CVS repository, the LLVM suite source code must be
561 configured via the <tt>configure</tt> script. This script sets variables in
562 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
563 also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
566 <p>The following environment variables are used by the <tt>configure</tt>
567 script to configure the build system:</p>
577 <td>Tells <tt>configure</tt> which C compiler to use. By default,
578 <tt>configure</tt> will look for the first GCC C compiler in
579 <tt>PATH</tt>. Use this variable to override
580 <tt>configure</tt>'s default behavior.</td>
585 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
586 <tt>configure</tt> will look for the first GCC C++ compiler in
587 <tt>PATH</tt>. Use this variable to override
588 <tt>configure</tt>'s default behavior.</td>
592 <p>The following options can be used to set or enable LLVM specific options:</p>
595 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
597 Path to the location where the LLVM GCC front end binaries and
598 associated libraries were installed. This must be specified as an
601 <dt><i>--enable-optimized</i>
603 Enables optimized compilation by default (debugging symbols are removed
604 and GCC optimization flags are enabled). The default is to use an
605 unoptimized build (also known as a debug build).
607 <dt><i>--enable-jit</i>
609 Compile the Just In Time (JIT) compiler functionality. This is not
611 on all platforms. The default is dependent on platform, so it is best
612 to explicitly enable it if you want it.
614 <dt><i>--enable-spec2000</i>
615 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
617 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
618 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
619 <tt>directory</tt>, you can tell configure where to find the SPEC2000
620 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
621 uses the default value
622 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
624 <dt><i>--enable-spec95</i>
625 <dt><i>--enable-spec95=<<tt>directory</tt>></i>
627 Enable the use of SPEC95 when testing LLVM. It is similar to the
628 <i>--enable-spec2000</i> option.
630 <dt><i>--enable-povray</i>
631 <dt><i>--enable-povray=<<tt>directory</tt>></i>
633 Enable the use of Povray as an external test. Versions of Povray written
634 in C should work. This option is similar to the <i>--enable-spec2000</i>
638 <p>To configure LLVM, follow these steps:</p>
641 <li>Change directory into the object root directory:
643 <tt>cd <i>OBJ_ROOT</i></tt>
646 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
648 <tt><i>SRC_ROOT</i>/configure</tt>
652 <p>In addition to running <tt>configure</tt>, you must set the
653 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
654 This environment variable is used to locate "system" libraries like
655 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
656 the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
657 end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
658 <tt>LLVM_LIB_SEARCH_PATH</tt> to
659 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
660 version of the GCC front end on our research machines.</p>
664 <!-- ======================================================================= -->
665 <div class="doc_subsection">
666 <a name="compile">Compiling the LLVM Suite Source Code</a>
669 <div class="doc_text">
671 <p>Once you have configured LLVM, you can build it. There are three types of
677 These builds are the default when one types <tt>gmake</tt> (unless the
678 <tt>--enable-optimized</tt> option was used during configuration). The
679 build system will compile the tools and libraries with debugging
683 <dt>Release (Optimized) Builds
685 These builds are enabled with the <tt>--enable-optimized</tt> option to
686 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
687 <tt>gmake</tt> command line. For these builds, the build system will
688 compile the tools and libraries with GCC optimizations enabled and strip
689 debugging information from the libraries and executables it generates.
694 These builds are for use with profiling. They compile profiling
695 information into the code for use with programs like <tt>gprof</tt>.
696 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
697 on the <tt>gmake</tt> command line.
700 <p>Once you have LLVM configured, you can build it by entering the
701 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
703 <p><tt>gmake</tt></p>
705 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
706 are using a known broken version of GCC to compile LLVM with.</p>
709 If you have multiple processors in your machine, you may wish to use some of
710 the parallel build options provided by GNU Make. For example, you could use the
713 <p><tt>gmake -j2</tt></p>
715 <p>There are several special targets which are useful when working with the LLVM
719 <dt><tt>gmake clean</tt>
721 Removes all files generated by the build. This includes object files,
722 generated C/C++ files, libraries, and executables.
725 <dt><tt>gmake distclean</tt>
727 Removes everything that <tt>gmake clean</tt> does, but also removes
728 files generated by <tt>configure</tt>. It attempts to return the
729 source tree to the original state in which it was shipped.
732 <dt><tt>gmake install</tt>
734 Installs LLVM files into the proper location. For the most part,
735 this does nothing, but it does install bytecode libraries into the
736 GCC front end's bytecode library directory. If you need to update
737 your bytecode libraries, this is the target to use once you've built
742 <p>It is also possible to override default values from <tt>configure</tt> by
743 declaring variables on the command line. The following are some examples:</p>
746 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
748 Perform a Release (Optimized) build.
751 <dt><tt>gmake ENABLE_PROFILING=1</tt>
753 Perform a Profiling build.
756 <dt><tt>gmake VERBOSE=1</tt>
758 Print what <tt>gmake</tt> is doing on standard output.
762 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
763 it and any subdirectories that it contains. Entering any directory inside the
764 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
765 that directory that is out of date.</p>
769 <!-- ======================================================================= -->
770 <div class="doc_subsection">
771 <a name="objfiles">The Location of LLVM Object Files</a>
774 <div class="doc_text">
776 <p>The LLVM build system is capable of sharing a single LLVM source tree among
777 several LLVM builds. Hence, it is possible to build LLVM for several different
778 platforms or configurations using the same source tree.</p>
780 <p>This is accomplished in the typical autoconf manner:</p>
783 <li><p>Change directory to where the LLVM object files should live:</p>
785 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
787 <li><p>Run the <tt>configure</tt> script found in the LLVM source
790 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
793 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
794 named after the build type:</p>
801 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
803 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
811 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
813 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
821 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
823 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
829 <!-- ======================================================================= -->
830 <div class="doc_subsection">
831 <a name="optionalconfig">Optional Configuration Items</a>
834 <div class="doc_text">
837 If you're running on a linux system that supports the "<a
838 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
839 module, and you have root access on the system, you can set your system up to
840 execute LLVM bytecode files directly. To do this, use commands like this (the
841 first command may not be required if you are already using the module):</p>
844 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
845 $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
846 $ chmod u+x hello.bc (if needed)
851 This allows you to execute LLVM bytecode files directly. Thanks to Jack
852 Cummings for pointing this out!
858 <!-- *********************************************************************** -->
859 <div class="doc_section">
860 <a name="layout"><b>Program Layout</b></a>
862 <!-- *********************************************************************** -->
864 <div class="doc_text">
866 <p>One useful source of information about the LLVM source base is the LLVM <a
867 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
868 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
869 The following is a brief introduction to code layout:</p>
873 <!-- ======================================================================= -->
874 <div class="doc_subsection">
875 <a name="cvsdir"><tt>CVS</tt> directories</a>
878 <div class="doc_text">
880 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
881 the most part these can just be ignored.</p>
885 <!-- ======================================================================= -->
886 <div class="doc_subsection">
887 <a name="include"><tt>llvm/include</tt></a>
890 <div class="doc_text">
892 <p>This directory contains public header files exported from the LLVM
893 library. The three main subdirectories of this directory are:</p>
896 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
897 specific header files. This directory also has subdirectories for
898 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
899 <tt>Target</tt>, <tt>Transforms</tt>, etc...</li>
901 <li><tt>llvm/include/Support</tt> - This directory contains generic
902 support libraries that are independent of LLVM, but are used by LLVM.
903 For example, some C++ STL utilities and a Command Line option processing
904 library store their header files here.</li>
906 <li><tt>llvm/include/Config</tt> - This directory contains header files
907 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
908 and C header files. Source code can include these header files which
909 automatically take care of the conditional #includes that the
910 <tt>configure</tt> script generates.</li>
915 <!-- ======================================================================= -->
916 <div class="doc_subsection">
917 <a name="lib"><tt>llvm/lib</tt></a>
920 <div class="doc_text">
922 <p>This directory contains most of the source files of the LLVM system. In LLVM,
923 almost all code exists in libraries, making it very easy to share code among the
924 different <a href="#tools">tools</a>.</p>
927 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
928 source files that implement core classes like Instruction and BasicBlock.
930 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
931 for the LLVM assembly language parser library.
933 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
934 and write LLVM bytecode.
936 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
939 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
940 different program analyses, such as Dominator Information, Call Graphs,
941 Induction Variables, Interval Identification, Natural Loop Identification,
944 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
945 code for the LLVM to LLVM program transformations, such as Aggressive Dead
946 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
947 Invariant Code Motion, Dead Global Elimination, and many others...
949 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
950 describe various target architectures for code generation. For example,
951 the llvm/lib/Target/SparcV9 directory holds the Sparc machine
954 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
955 of the code generator: Instruction Selector, Instruction Scheduling, and
958 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
959 that corresponds to the header files located in
960 <tt>llvm/include/Support/</tt>.
965 <!-- ======================================================================= -->
966 <div class="doc_subsection">
967 <a name="runtime"><tt>llvm/runtime</tt></a>
970 <div class="doc_text">
972 <p>This directory contains libraries which are compiled into LLVM bytecode and
973 used when linking programs with the GCC front end. Most of these libraries are
974 skeleton versions of real libraries; for example, libc is a stripped down
975 version of glibc.</p>
977 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
982 <!-- ======================================================================= -->
983 <div class="doc_subsection">
984 <a name="test"><tt>llvm/test</tt></a>
987 <div class="doc_text">
989 <p>This directory contains regression tests and source code that is used to test
990 the LLVM infrastructure.</p>
994 <!-- ======================================================================= -->
995 <div class="doc_subsection">
996 <a name="tools"><tt>llvm/tools</tt></a>
999 <div class="doc_text">
1001 <p>The <b>tools</b> directory contains the executables built out of the
1002 libraries above, which form the main part of the user interface. You can
1003 always get help for a tool by typing <tt>tool_name --help</tt>. The
1004 following is a brief introduction to the most important tools:</p>
1007 <dt><tt><b>analyze</b></tt> <dd><tt>analyze</tt> is used to run a specific
1008 analysis on an input LLVM bytecode file and print out the results. It is
1009 primarily useful for debugging analyses, or familiarizing yourself with
1010 what an analysis does.<p>
1012 <dt><tt><b>bugpoint</b></tt> <dd><tt>bugpoint</tt> is used to debug
1013 optimization passes or code generation backends by narrowing down the
1014 given test case to the minimum number of passes and/or instructions that
1015 still cause a problem, whether it is a crash or miscompilation. See <a
1016 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1017 on using <tt>bugpoint</tt>.<p>
1019 <dt><tt><b>llvm-ar</b></tt> <dd>The archiver produces an archive containing
1020 the given LLVM bytecode files, optionally with an index for faster
1023 <dt><tt><b>llvm-as</b></tt> <dd>The assembler transforms the human readable
1024 LLVM assembly to LLVM bytecode.<p>
1026 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
1027 bytecode to human readable LLVM assembly.<p>
1029 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
1030 links multiple LLVM modules into a single program.<p>
1032 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
1033 can directly execute LLVM bytecode (although very slowly...). In addition
1034 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
1035 specifying <tt>-trace</tt> on the command line). Finally, for
1036 architectures that support it (currently only x86 and Sparc), by default,
1037 <tt>lli</tt> will function as a Just-In-Time compiler (if the
1038 functionality was compiled in), and will execute the code <i>much</i>
1039 faster than the interpreter.<p>
1041 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler, which
1042 translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
1043 the -march=c option).<p>
1045 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
1046 that has been retargeted to emit LLVM code as the machine code output. It
1047 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
1048 -o</tt> options that are typically used. The source code for the
1049 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
1050 because it is quite large and not very interesting.<p>
1054 <dt><tt><b>gccas</b></tt> <dd>This tool is invoked by the
1055 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
1056 tool actually assembles LLVM assembly to LLVM bytecode,
1057 performs a variety of optimizations, and outputs LLVM bytecode. Thus
1058 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
1059 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
1060 an LLVM bytecode file that can be disassembled or manipulated just like
1061 any other bytecode file). The command line interface to <tt>gccas</tt>
1062 is designed to be as close as possible to the <b>system</b>
1063 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
1064 modified to interface to a "weird" assembler.<p>
1066 <dt><tt><b>gccld</b></tt> <dd><tt>gccld</tt> links together several LLVM
1067 bytecode files into one bytecode file and does some optimization. It is
1068 the linker invoked by the GCC frontend when multiple .o files need to be
1069 linked together. Like <tt>gccas</tt>, the command line interface of
1070 <tt>gccld</tt> is designed to match the system linker, to aid
1071 interfacing with the GCC frontend.</dl><p>
1074 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
1075 series of LLVM to LLVM transformations (which are specified on the command
1076 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
1077 command is a good way to get a list of the program transformations
1084 <!-- ======================================================================= -->
1085 <div class="doc_subsection">
1086 <a name="utils"><tt>llvm/utils</tt></a>
1089 <div class="doc_text">
1091 <p>This directory contains utilities for working with LLVM source code, and some
1092 of the utilities are actually required as part of the build process because they
1093 are code generators for parts of LLVM infrastructure.</p>
1096 <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
1097 generator -- it builds trees on which it then performs pattern-matching to
1098 select instructions according to the patterns the user has specified. Burg
1099 is currently used in the Sparc V9 backend.<p>
1101 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1102 that finds differences between code that LLC generates and code that LLI
1103 generates. This is a useful tool if you are debugging one of them,
1104 assuming that the other generates correct output. For the full user
1105 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
1107 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1108 update your CVS tree, but produce a much cleaner and more organized output
1109 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1110 together all the new and updated files and modified files in separate
1111 sections, so you can see at a glance what has changed. If you are at the
1112 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1113 preferred way of updating the tree.<p>
1115 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1116 syntax-highlighting files which will work with Emacs and XEmacs editors,
1117 providing syntax highlighting support for LLVM assembly files and TableGen
1118 description files. For information on how to use the syntax files, consult
1119 the <tt>README</tt> file in that directory.<p>
1121 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1122 and outputs all non-generated source files, which is useful if one wishes
1123 to do a lot of development across directories and does not want to
1124 individually find each file. One way to use it is to run, for example:
1125 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1128 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1129 files in the current directory and then compiles and links the tool that
1130 is the first argument. For example, assuming you are in the directory
1131 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1132 simply running <tt>makellvm llc</tt> will make a build of the current
1133 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1134 causing a re-linking of LLC.<p>
1136 <dt><tt><b>NightlyTest.pl</b></tt> and
1137 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1138 cron script to generate nightly status reports of the functionality of
1139 tools, and the results can be seen by following the appropriate link on
1140 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
1142 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1143 the tool used to generate register descriptions, instruction set
1144 descriptions, and even assemblers from common TableGen description
1147 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1148 syntax-highlighting files which will work with the VIM editor, providing
1149 syntax highlighting support for LLVM assembly files and TableGen
1150 description files. For information on how to use the syntax files, consult
1151 the <tt>README</tt> file in that directory.<p>
1157 <!-- *********************************************************************** -->
1158 <div class="doc_section">
1159 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1161 <!-- *********************************************************************** -->
1163 <div class="doc_text">
1166 <li>First, create a simple C file, name it 'hello.c':
1168 #include <stdio.h>
1170 printf("hello world\n");
1175 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1176 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1178 <p>Note that you should have already built the tools and they have to be
1179 in your path, at least <tt>gccas</tt> and <tt>gccld</tt>.</p>
1181 <p>This will create two result files: <tt>hello</tt> and
1182 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1183 corresponds the the compiled program and the library facilities that it
1184 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1185 file with <tt>lli</tt>, making the result directly executable. Note that
1186 all LLVM optimizations are enabled by default, so there is no need for a
1187 "-O3" switch.</p></li>
1189 <li><p>Run the program. To make sure the program ran, execute one of the
1190 following commands:</p>
1192 <p><tt>% ./hello</tt></p>
1196 <p><tt>% lli hello.bc</tt></p></li>
1198 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1201 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1203 <li><p>Compile the program to native assembly using the LLC code
1206 <p><tt>% llc hello.bc -o hello.s</tt></p>
1208 <li><p>Assemble the native assembly language file into a program:</p>
1210 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1211 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1213 <li><p>Execute the native code program:</p>
1215 <p><tt>% ./hello.native</tt></p></li>
1221 <!-- *********************************************************************** -->
1222 <div class="doc_section">
1223 <a name="problems">Common Problems</a>
1225 <!-- *********************************************************************** -->
1227 <div class="doc_text">
1229 <p>If you are having problems building or using LLVM, or if you have any other
1230 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1231 Asked Questions</a> page.</p>
1235 <!-- *********************************************************************** -->
1236 <div class="doc_section">
1237 <a name="links">Links</a>
1239 <!-- *********************************************************************** -->
1241 <div class="doc_text">
1243 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1244 some simple things... there are many more interesting and complicated things
1245 that you can do that aren't documented here (but we'll gladly accept a patch
1246 if you want to write something up!). For more information about LLVM, check
1250 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1251 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1252 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1253 that Uses LLVM</a></li>
1258 <!-- *********************************************************************** -->
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1267 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1268 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
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