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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>
35 <li><a href="#layout">Program layout</a>
37 <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
38 <li><a href="#include"><tt>llvm/include</tt></a>
39 <li><a href="#lib"><tt>llvm/lib</tt></a>
40 <li><a href="#runtime"><tt>llvm/runtime</tt></a>
41 <li><a href="#test"><tt>llvm/test</tt></a>
42 <li><a href="#tools"><tt>llvm/tools</tt></a>
43 <li><a href="#utils"><tt>llvm/utils</tt></a>
46 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
47 <li><a href="#problems">Common Problems</a>
48 <li><a href="#links">Links</a>
52 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>,
53 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
54 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
55 <a href="http://misha.brukman.net">Misha Brukman</a>, and
56 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>.</p>
59 <!-- *********************************************************************** -->
60 <div class="doc_section">
61 <a name="overview"><b>Overview</b></a>
63 <!-- *********************************************************************** -->
65 <div class="doc_text">
67 <p>Welcome to LLVM! In order to get started, you first need to know some
68 basic information.</p>
70 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
71 contains all of the tools, libraries, and header files needed to use the low
72 level virtual machine. It contains an assembler, disassembler, bytecode
73 analyzer, and bytecode optimizer. It also contains a test suite that can be
74 used to test the LLVM tools and the GCC front end.</p>
76 <p>The second piece is the GCC front end. This component provides a version of
77 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
78 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
79 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
80 from the LLVM suite.</p>
84 <!-- *********************************************************************** -->
85 <div class="doc_section">
86 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
88 <!-- *********************************************************************** -->
90 <div class="doc_text">
92 <p>Here's the short story for getting up and running quickly with LLVM:</p>
95 <li>Install the GCC front end:
97 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
98 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
99 <li><b>Sparc Only:</b><br>
100 <tt>cd cfrontend/sparc<br>
104 <li>Get the Source Code
106 <li>With the distributed files:
108 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
109 <li><tt>gunzip --stdout llvm.tar.gz | tar -xvf -</tt>
113 <li>With anonymous CVS access:
115 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
117 :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt></li>
118 <li>Hit the return key when prompted for the password.
119 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm
121 <li><tt>cd llvm</tt></li>
125 <li>Configure the LLVM Build Environment
127 <li>Change directory to where you want to store the LLVM object
128 files and run <tt>configure</tt> to configure the Makefiles and
129 header files for the default platform. Useful options include:
131 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
132 <p>Specify the full pathname of where the LLVM GCC frontend is
134 <li><tt>--enable-spec2000=<i>directory</i></tt>
135 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
136 benchmarks should be available in
137 <tt><i>directory</i></tt>.</p></li>
141 <li>Build the LLVM Suite:
143 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.
144 <li><tt>gmake -k |& tee gnumake.out
145 # this is csh or tcsh syntax</tt>
150 <p>Consult the <a href="starting">Getting Started with LLVM</a> section for
151 detailed information on configuring and compiling LLVM. See <a
152 href="#environment">Setting Up Your Environment</a> for tips that simplify
153 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
154 Layout</a> to learn about the layout of the source code tree.</p>
158 <!-- *********************************************************************** -->
159 <div class="doc_section">
160 <a name="requirements"><b>Requirements</b></a>
162 <!-- *********************************************************************** -->
164 <div class="doc_text">
166 <p>Before you begin to use the LLVM system, review the requirements given below.
167 This may save you some trouble by knowing ahead of time what hardware and
168 software you will need.</p>
172 <!-- ======================================================================= -->
173 <div class="doc_subsection">
174 <a name="hardware"><b>Hardware</b></a>
177 <div class="doc_text">
179 <p>LLVM is known to work on the following platforms:</p>
183 <li>Linux on x86 (Pentium and above)
185 <li>Approximately 918 MB of Free Disk Space
187 <li>Source code: 28 MB</li>
188 <li>Object code: 850 MB</li>
189 <li>GCC front end: 40 MB</li>
196 <li>Solaris on SparcV9 (Ultrasparc)
198 <li>Approximately 1.52 GB of Free Disk Space
200 <li>Source code: 28 MB</li>
201 <li>Object code: 1470 MB</li>
202 <li>GCC front end: 50 MB</li>
209 <li>FreeBSD on x86 (Pentium and above)
211 <li>Approximately 918 MB of Free Disk Space
213 <li>Source code: 28 MB</li>
214 <li>Object code: 850 MB</li>
215 <li>GCC front end: 40 MB</li>
222 <li>MacOS X on PowerPC
224 <li>No native code generation
225 <li>Approximately 1.20 GB of Free Disk Space
227 <li>Source code: 28 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 try to
244 compile it on your platform.</p>
248 <!-- ======================================================================= -->
249 <div class="doc_subsection">
250 <a name="software"><b>Software</b></a>
253 <div class="doc_text">
255 <p>Compiling LLVM requires that you have several software packages
259 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
262 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
264 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
266 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
269 <p>There are some additional tools that you may want to have when working with
273 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A>
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
280 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest</A></li>
281 <li><A href="http://www.python.org">Python</A>
283 <p>These are needed to use the LLVM test suite.</p></li>
287 <p>The remainder of this guide is meant to get you up and running with
288 LLVM and to give you some basic information about the LLVM environment.
289 A <a href="#starting">complete guide to installation</a> is provided in the
292 <p>The later sections of this guide describe the <a
293 href="#layout">general layout</a> of the the LLVM source tree, a <a
294 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
295 href="#links">links</a> to find more information about LLVM or to get
300 <!-- *********************************************************************** -->
301 <div class="doc_section">
302 <a name="starting"><b>Getting Started with LLVM</b></a>
304 <!-- *********************************************************************** -->
306 <!-- ======================================================================= -->
307 <div class="doc_subsection">
308 <a name="terminology">Terminology and Notation</a>
311 <div class="doc_text">
313 <p>Throughout this manual, the following names are used to denote paths
314 specific to the local system and working environment. <i>These are not
315 environment variables you need to set but just strings used in the rest
316 of this document below</i>. In any of the examples below, simply replace
317 each of these names with the appropriate pathname on your local system.
318 All these paths are absolute:</p>
323 This is the top level directory of the LLVM source tree.
328 This is the top level directory of the LLVM object tree (i.e. the
329 tree where object files and compiled programs will be placed. It
330 can be the same as SRC_ROOT).
335 This is the where the LLVM GCC Front End is installed.
337 For the pre-built GCC front end binaries, the LLVMGCCDIR is
338 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
343 <!-- ======================================================================= -->
344 <div class="doc_subsection">
345 <a name="environment">Setting Up Your Environment</a>
348 <div class="doc_text">
351 In order to compile and use LLVM, you will need to set some environment
352 variables. There are also some shell aliases which you may find useful.
353 You can set these on the command line, or better yet, set them in your
354 <tt>.cshrc</tt> or <tt>.profile</tt>.
357 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
359 This environment variable helps the LLVM GCC front end find bytecode
360 libraries that it will need for compilation.
363 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
364 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
366 This alias allows you to use the LLVM C and C++ front ends without putting
367 them in your <tt>PATH</tt> or typing in their complete pathnames.
372 <!-- ======================================================================= -->
373 <div class="doc_subsection">
374 <a name="unpack">Unpacking the LLVM Archives</a></h3>
377 <div class="doc_text">
380 If you have the LLVM distribution, you will need to unpack it before you
381 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
382 suite and the LLVM GCC front end compiled for your platform. Each
383 file is a TAR archive that is compressed with the gzip program.
386 <p> The files are as follows:
389 <dd>This is the source code to the LLVM suite.
392 <dt>cfrontend-1.1.sparc-sun-solaris2.8.tar.gz
393 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
396 <dt>cfrontend-1.1.i686-redhat-linux-gnu.tar.gz
397 <dd>This is the binary release of the GCC front end for Linux/x86.
400 <dt>cfrontend-1.1.i386-unknown-freebsd5.1.tar.gz
401 <dd>This is the binary release of the GCC front end for FreeBSD/x86.
404 <dt>cfrontend-1.1.powerpc-apple-darwin7.0.0.tar.gz
405 <dd>This is the binary release of the GCC front end for MacOS X/PPC.
410 <!-- ======================================================================= -->
411 <div class="doc_subsection">
412 <a name="checkout">Checkout LLVM from CVS</a></h3>
415 <div class="doc_text">
417 <p>If you have access to our CVS repository, you can get a fresh copy of
418 the entire source code. All you need to do is check it out from CVS as
422 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
423 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
424 <li>Hit the return key when prompted for the password.
425 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
429 <p>This will create an '<tt>llvm</tt>' directory in the current
430 directory and fully populate it with the LLVM source code, Makefiles,
431 test directories, and local copies of documentation files.</p>
434 If you want to get a specific release (as opposed to the most recent revision),
435 you can specify a label. The following releases have the following label:
438 Release 1.1: <b>RELEASE_11</b>
442 Release 1.0: <b>RELEASE_1</b>
447 <p>Note that the GCC front end is not included in the CVS repository. You
448 should have downloaded the binary distribution for your platform.</p>
452 <!-- ======================================================================= -->
453 <div class="doc_subsection">
454 <a name="installcf">Install the GCC Front End</a></h3>
457 <div class="doc_text">
459 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
460 GCC front end from the binary distribution. It is used for building the
461 bytecode libraries later used by the GCC front end for linking programs, and its
462 location must be specified when the LLVM suite is configured.</p>
464 <p>To install the GCC front end, do the following:</p>
467 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
468 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
472 <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
475 <p><tt>cd cfrontend/sparc<br>
476 ./fixheaders</tt></p>
478 <p>The binary versions of the GCC front end may not suit all of your needs. For
479 example, the binary distribution may include an old version of a system header
480 file, not "fix" a header file that needs to be fixed for GCC, or it may be
481 linked with libraries not available on your system.</p>
483 <p>In cases like these, you may want to try <a
484 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
485 not for the faint of heart, so be forewarned.</p>
489 <!-- ======================================================================= -->
490 <div class="doc_subsection">
491 <a name="config">Local LLVM Configuration</a>
494 <div class="doc_text">
496 <p>Once checked out from the CVS repository, the LLVM suite source code must be
497 configured via the <tt>configure</tt> script. This script sets variables in
498 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
499 also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
502 <p>The following environment variables are used by the <tt>configure</tt>
503 script to configure the build system:</p>
513 <td>Tells <tt>configure</tt> which C compiler to use. By default,
514 <tt>configure</tt> will look for the first GCC C compiler in
515 <tt>PATH</tt>. Use this variable to override
516 <tt>configure</tt>'s default behavior.</td>
521 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
522 <tt>configure</tt> will look for the first GCC C++ compiler in
523 <tt>PATH</tt>. Use this variable to override
524 <tt>configure</tt>'s default behavior.</td>
528 <p>The following options can be used to set or enable LLVM specific options:</p>
531 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
533 Path to the location where the LLVM C front end binaries and
534 associated libraries were installed. This must be specified as an
537 <dt><i>--enable-optimized</i>
539 Enables optimized compilation by default (debugging symbols are removed
540 and GCC optimization flags are enabled). The default is to use an
541 unoptimized build (also known as a debug build).
543 <dt><i>--enable-jit</i>
545 Compile the Just In Time (JIT) compiler functionality. This is not
547 on all platforms. The default is dependent on platform, so it is best
548 to explicitly enable it if you want it.
550 <dt><i>--enable-spec2000</i>
551 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
553 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
554 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
555 <tt>directory</tt>, you can tell configure where to find the SPEC2000
556 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
557 uses the default value
558 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
561 <p>To configure LLVM, follow these steps:</p>
564 <li>Change directory into the object root directory:
566 <tt>cd <i>OBJ_ROOT</i></tt>
569 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
571 <tt><i>SRC_ROOT</i>/configure</tt>
575 <p>In addition to running <tt>configure</tt>, you must set the
576 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
577 This environment variable is used to locate "system" libraries like
578 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
579 the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
580 end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
581 <tt>LLVM_LIB_SEARCH_PATH</tt> to
582 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
583 version of the GCC front end on our research machines.</p>
587 <!-- ======================================================================= -->
588 <div class="doc_subsection">
589 <a name="compile">Compiling the LLVM Suite Source Code</a>
592 <div class="doc_text">
594 <p>Once you have configured LLVM, you can build it. There are three types of
600 These builds are the default when one types <tt>gmake</tt> (unless the
601 <tt>--enable-optimized</tt> option was used during configuration). The
602 build system will compile the tools and libraries with debugging
606 <dt>Release (Optimized) Builds
608 These builds are enabled with the <tt>--enable-optimized</tt> option to
609 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
610 <tt>gmake</tt> command line. For these builds, the build system will
611 compile the tools and libraries with GCC optimizations enabled and strip
612 debugging information from the libraries and executables it generates.
617 These builds are for use with profiling. They compile profiling
618 information into the code for use with programs like <tt>gprof</tt>.
619 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
620 on the <tt>gmake</tt> command line.
623 <p>Once you have LLVM configured, you can build it by entering the
624 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
626 <p><tt>gmake</tt></p>
628 <p>If you have multiple processors in your machine, you may wish to use some of
629 the parallel build options provided by GNU Make. For example, you could use the
632 <p><tt>gmake -j2</tt></p>
634 <p>There are several special targets which are useful when working with the LLVM
638 <dt><tt>gmake clean</tt>
640 Removes all files generated by the build. This includes object files,
641 generated C/C++ files, libraries, and executables.
644 <dt><tt>gmake distclean</tt>
646 Removes everything that <tt>gmake clean</tt> does, but also removes
647 files generated by <tt>configure</tt>. It attempts to return the
648 source tree to the original state in which it was shipped.
651 <dt><tt>gmake install</tt>
653 Installs LLVM files into the proper location. For the most part,
654 this does nothing, but it does install bytecode libraries into the
655 GCC front end's bytecode library directory. If you need to update
656 your bytecode libraries, this is the target to use once you've built
661 <p>It is also possible to override default values from <tt>configure</tt> by
662 declaring variables on the command line. The following are some examples:</p>
665 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
667 Perform a Release (Optimized) build.
670 <dt><tt>gmake ENABLE_PROFILING=1</tt>
672 Perform a Profiling build.
675 <dt><tt>gmake VERBOSE=1</tt>
677 Print what <tt>gmake</tt> is doing on standard output.
681 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
682 it and any subdirectories that it contains. Entering any directory inside the
683 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
684 that directory that is out of date.</p>
688 <!-- ======================================================================= -->
689 <div class="doc_subsection">
690 <a name="objfiles">The Location of LLVM Object Files</a>
693 <div class="doc_text">
695 <p>The LLVM build system is capable of sharing a single LLVM source tree among
696 several LLVM builds. Hence, it is possible to build LLVM for several different
697 platforms or configurations using the same source tree.</p>
699 <p>This is accomplished in the typical autoconf manner:</p>
702 <li><p>Change directory to where the LLVM object files should live:</p>
704 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
706 <li><p>Run the <tt>configure</tt> script found in the LLVM source
709 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
712 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
713 named after the build type:</p>
720 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
722 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
730 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
732 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
740 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
742 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
748 <!-- *********************************************************************** -->
749 <div class="doc_section">
750 <a name="layout"><b>Program Layout</b></a>
752 <!-- *********************************************************************** -->
754 <div class="doc_text">
756 <p>One useful source of information about the LLVM source base is the LLVM <a
757 href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a
758 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
759 The following is a brief introduction to code layout:</p>
763 <!-- ======================================================================= -->
764 <div class="doc_subsection">
765 <a name="cvsdir"><tt>CVS</tt> directories</a>
768 <div class="doc_text">
770 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
771 the most part these can just be ignored.</p>
775 <!-- ======================================================================= -->
776 <div class="doc_subsection">
777 <a name="include"><tt>llvm/include</tt></a>
780 <div class="doc_text">
782 <p>This directory contains public header files exported from the LLVM
783 library. The three main subdirectories of this directory are:</p>
786 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
787 specific header files. This directory also has subdirectories for
788 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
789 <tt>Target</tt>, <tt>Transforms</tt>, etc...</li>
791 <li><tt>llvm/include/Support</tt> - This directory contains generic
792 support libraries that are independent of LLVM, but are used by LLVM.
793 For example, some C++ STL utilities and a Command Line option processing
794 library store their header files here.</li>
796 <li><tt>llvm/include/Config</tt> - This directory contains header files
797 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
798 and C header files. Source code can include these header files which
799 automatically take care of the conditional #includes that the
800 <tt>configure</tt> script generates.</li>
805 <!-- ======================================================================= -->
806 <div class="doc_subsection">
807 <a name="lib"><tt>llvm/lib</tt></a>
810 <div class="doc_text">
812 <p>This directory contains most of the source files of the LLVM system. In LLVM,
813 almost all code exists in libraries, making it very easy to share code among the
814 different <a href="#tools">tools</a>.</p>
817 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
818 source files that implement core classes like Instruction and BasicBlock.
820 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
821 for the LLVM assembly language parser library.
823 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
824 and write LLVM bytecode.
826 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
829 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
830 different program analyses, such as Dominator Information, Call Graphs,
831 Induction Variables, Interval Identification, Natural Loop Identification,
834 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
835 code for the LLVM to LLVM program transformations, such as Aggressive Dead
836 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
837 Invariant Code Motion, Dead Global Elimination, and many others...
839 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
840 describe various target architectures for code generation. For example,
841 the llvm/lib/Target/Sparc directory holds the Sparc machine
844 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
845 of the code generator: Instruction Selector, Instruction Scheduling, and
848 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
849 that corresponds to the header files located in
850 <tt>llvm/include/Support/</tt>.
855 <!-- ======================================================================= -->
856 <div class="doc_subsection">
857 <a name="runtime"><tt>llvm/runtime</tt></a>
860 <div class="doc_text">
862 <p>This directory contains libraries which are compiled into LLVM bytecode and
863 used when linking programs with the GCC front end. Most of these libraries are
864 skeleton versions of real libraries; for example, libc is a stripped down
865 version of glibc.</p>
867 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
872 <!-- ======================================================================= -->
873 <div class="doc_subsection">
874 <a name="test"><tt>llvm/test</tt></a>
877 <div class="doc_text">
879 <p>This directory contains regression tests and source code that is used to test
880 the LLVM infrastructure.</p>
884 <!-- ======================================================================= -->
885 <div class="doc_subsection">
886 <a name="tools"><tt>llvm/tools</tt></a>
889 <div class="doc_text">
891 <p>The <b>tools</b> directory contains the executables built out of the
892 libraries above, which form the main part of the user interface. You can
893 always get help for a tool by typing <tt>tool_name --help</tt>. The
894 following is a brief introduction to the most important tools.</p>
899 <dt><tt><b>analyze</b></tt><dd> <tt>analyze</tt> is used to run a specific
900 analysis on an input LLVM bytecode file and print out the results. It is
901 primarily useful for debugging analyses, or familiarizing yourself with
902 what an analysis does.<p>
904 <dt><tt><b>bugpoint</b></tt><dd> <tt>bugpoint</tt> is used to debug
905 optimization passes or code generation backends by narrowing down the
906 given test case to the minimum number of passes and/or instructions that
907 still cause a problem, whether it is a crash or miscompilation. See <a
908 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
909 on using <tt>bugpoint</tt>.<p>
911 <dt><tt><b>llvm-ar</b></tt><dd>The archiver produces an archive containing
912 the given LLVM bytecode files, optionally with an index for faster
915 <dt><tt><b>llvm-as</b></tt><dd>The assembler transforms the human readable
916 LLVM assembly to LLVM bytecode.<p>
918 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
919 bytecode to human readable LLVM assembly. Additionally, it can convert
920 LLVM bytecode to C, which is enabled with the <tt>-c</tt> option.<p>
922 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
923 links multiple LLVM modules into a single program.<p>
925 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
926 can directly execute LLVM bytecode (although very slowly...). In addition
927 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
928 specifying <tt>-trace</tt> on the command line). Finally, for
929 architectures that support it (currently only x86 and Sparc), by default,
930 <tt>lli</tt> will function as a Just-In-Time compiler (if the
931 functionality was compiled in), and will execute the code <i>much</i>
932 faster than the interpreter.<p>
934 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler,
935 which translates LLVM bytecode to a SPARC or x86 assembly file.<p>
937 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
938 that has been retargeted to emit LLVM code as the machine code output. It
939 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
940 -o</tt> options that are typically used. The source code for the
941 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
942 because it is quite large and not very interesting.<p>
945 <dt><tt><b>gccas</b></tt><dd> This tool is invoked by the
946 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
947 tool actually assembles LLVM assembly to LLVM bytecode,
948 performs a variety of optimizations, and outputs LLVM bytecode. Thus
949 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
950 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
951 an LLVM bytecode file that can be disassembled or manipulated just like
952 any other bytecode file). The command line interface to <tt>gccas</tt>
953 is designed to be as close as possible to the <b>system</b>
954 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
955 modified to interface to a "weird" assembler.<p>
957 <dt><tt><b>gccld</b></tt><dd> <tt>gccld</tt> links together several LLVM
958 bytecode files into one bytecode file and does some optimization. It is
959 the linker invoked by the GCC frontend when multiple .o files need to be
960 linked together. Like <tt>gccas</tt>, the command line interface of
961 <tt>gccld</tt> is designed to match the system linker, to aid
962 interfacing with the GCC frontend.<p>
965 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
966 series of LLVM to LLVM transformations (which are specified on the command
967 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
968 command is a good way to get a list of the program transformations
969 available in LLVM.<p>
975 <!-- ======================================================================= -->
976 <div class="doc_subsection">
977 <a name="utils"><tt>llvm/utils</tt></a>
980 <div class="doc_text">
982 <p>This directory contains utilities for working with LLVM source code, and some
983 of the utilities are actually required as part of the build process because they
984 are code generators for parts of LLVM infrastructure.</p>
987 <td><tt><b>Burg/</b></tt><dd> <tt>Burg</tt> is an instruction selector
988 generator -- it builds trees on which it then performs pattern-matching to
989 select instructions according to the patterns the user has specified. Burg
990 is currently used in the Sparc V9 backend.<p>
992 <dt><tt><b>codegen-diff</b></tt><dd> <tt>codegen-diff</tt> is a script
993 that finds differences between code that LLC generates and code that LLI
994 generates. This is a useful tool if you are debugging one of them,
995 assuming that the other generates correct output. For the full user
996 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
998 <dt><tt><b>cvsupdate</b></tt><dd> <tt>cvsupdate</tt> is a script that will
999 update your CVS tree, but produce a much cleaner and more organized output
1000 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1001 together all the new and updated files and modified files in separate
1002 sections, so you can see at a glance what has changed. If you are at the
1003 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1004 preferred way of updating the tree.<p>
1006 <dt><tt><b>emacs/</b></tt><dd> The <tt>emacs</tt> directory contains
1007 syntax-highlighting files which will work with Emacs and XEmacs editors,
1008 providing syntax highlighting support for LLVM assembly files and TableGen
1009 description files. For information on how to use the syntax files, consult
1010 the <tt>README</tt> file in that directory.<p>
1012 <dt><tt><b>getsrcs.sh</b></tt><dd> The <tt>getsrcs.sh</tt> script finds
1013 and outputs all non-generated source files, which is useful if one wishes
1014 to do a lot of development across directories and does not want to
1015 individually find each file. One way to use it is to run, for example:
1016 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1019 <dt><tt><b>makellvm</b></tt><dd> The <tt>makellvm</tt> script compiles all
1020 files in the current directory and then compiles and links the tool that
1021 is the first argument. For example, assuming you are in the directory
1022 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1023 simply running <tt>makellvm llc</tt> will make a build of the current
1024 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1025 causing a re-linking of LLC.<p>
1027 <dt><tt><b>NightlyTest.pl</b></tt> and
1028 <tt><b>NightlyTestTemplate.html</b></tt><dd> These files are used in a
1029 cron script to generate nightly status reports of the functionality of
1030 tools, and the results can be seen by following the appropriate link on
1031 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
1033 <dt><tt><b>TableGen/</b></tt><dd> The <tt>TableGen</tt> directory contains
1034 the tool used to generate register descriptions, instruction set
1035 descriptions, and even assemblers from common TableGen description
1038 <dt><tt><b>vim/</b></tt><dd> The <tt>vim</tt> directory contains
1039 syntax-highlighting files which will work with the VIM editor, providing
1040 syntax highlighting support for LLVM assembly files and TableGen
1041 description files. For information on how to use the syntax files, consult
1042 the <tt>README</tt> file in that directory.<p>
1048 <!-- *********************************************************************** -->
1049 <div class="doc_section">
1050 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1052 <!-- *********************************************************************** -->
1054 <div class="doc_text">
1057 <li>First, create a simple C file, name it 'hello.c':
1059 #include <stdio.h>
1061 printf("hello world\n");
1066 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1067 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1069 <p>This will create two result files: <tt>hello</tt> and
1070 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1071 corresponds the the compiled program and the library facilities that it
1072 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1073 file with <tt>lli</tt>, making the result directly executable.</p></li>
1075 <li><p>Run the program. To make sure the program ran, execute one of the
1076 following commands:</p>
1078 <p><tt>% ./hello</tt></p>
1082 <p><tt>% lli hello.bc</tt></p></li>
1084 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1087 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1089 <li><p>Compile the program to native Sparc assembly using the code
1090 generator (assuming you are currently on a Sparc system):</p>
1092 <p><tt>% llc hello.bc -o hello.s</tt></p>
1094 <li><p>Assemble the native sparc assemble file into a program:</p>
1096 <p><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt></p>
1098 <li><p>Execute the native sparc program:</p>
1100 <p><tt>% ./hello.sparc</tt></p></li>
1106 <!-- *********************************************************************** -->
1107 <div class="doc_section">
1108 <a name="problems">Common Problems</a>
1110 <!-- *********************************************************************** -->
1112 <div class="doc_text">
1114 <p>If you are having problems building or using LLVM, or if you have any other
1115 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1116 Asked Questions</a> page.</p>
1120 <!-- *********************************************************************** -->
1121 <div class="doc_section">
1122 <a name="links">Links</a>
1124 <!-- *********************************************************************** -->
1126 <div class="doc_text">
1128 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1129 some simple things... there are many more interesting and complicated things
1130 that you can do that aren't documented here (but we'll gladly accept a patch
1131 if you want to write something up!). For more information about LLVM, check
1135 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1136 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1137 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1138 that Uses LLVM</a></li>
1143 <!-- *********************************************************************** -->
1147 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1148 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
1149 Last modified: $Date$