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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 and MacOS X Only:</b><br>
100 <tt>cd cfrontend/<i>platform</i><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-<i>version</i>.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>
194 <li>Solaris on SparcV9 (Ultrasparc)
196 <li>Approximately 1.52 GB of Free Disk Space
198 <li>Source code: 28 MB</li>
199 <li>Object code: 1470 MB</li>
200 <li>GCC front end: 50 MB</li>
205 <li>FreeBSD on x86 (Pentium and above)
207 <li>Approximately 918 MB of Free Disk Space
209 <li>Source code: 28 MB</li>
210 <li>Object code: 850 MB</li>
211 <li>GCC front end: 40 MB</li>
216 <li>MacOS X on PowerPC
218 <li>No native code generation
219 <li>Approximately 1.20 GB of Free Disk Space
221 <li>Source code: 28 MB</li>
222 <li>Object code: 1160 MB</li>
223 <li>GCC front end: 40 MB</li>
230 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
231 guaranteed to do so. If compilation is successful, the LLVM utilities should be
232 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
233 generation should work as well, although the generated native code may not work
234 on your platform.</p>
236 <p>The GCC front end is not very portable at the moment. If you want to get it
237 to work on another platform, you can download a copy of the source and try to
238 compile it on your platform.</p>
242 <!-- ======================================================================= -->
243 <div class="doc_subsection">
244 <a name="software"><b>Software</b></a>
247 <div class="doc_text">
249 <p>Compiling LLVM requires that you have several software packages
253 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
256 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
258 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
260 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
263 <p>There are some additional tools that you may want to have when working with
267 <li><A href="http://www.gnu.org/software/automake">GNU Automake</A></li>
268 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A></li>
269 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
271 <p>If you want to make changes to the configure scripts, you will need GNU
272 autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
273 higher). You will also need automake. Any old version of
274 automake from 1.4p5 on should work; we only use aclocal from that
277 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest</A></li>
278 <li><A href="http://www.python.org">Python</A>
280 <p>These are needed to use the LLVM test suite.</p></li>
284 <p>The remainder of this guide is meant to get you up and running with
285 LLVM and to give you some basic information about the LLVM environment.
286 A <a href="#starting">complete guide to installation</a> is provided in the
289 <p>The later sections of this guide describe the <a
290 href="#layout">general layout</a> of the the LLVM source tree, a <a
291 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
292 href="#links">links</a> to find more information about LLVM or to get
297 <!-- *********************************************************************** -->
298 <div class="doc_section">
299 <a name="starting"><b>Getting Started with LLVM</b></a>
301 <!-- *********************************************************************** -->
303 <!-- ======================================================================= -->
304 <div class="doc_subsection">
305 <a name="terminology">Terminology and Notation</a>
308 <div class="doc_text">
310 <p>Throughout this manual, the following names are used to denote paths
311 specific to the local system and working environment. <i>These are not
312 environment variables you need to set but just strings used in the rest
313 of this document below</i>. In any of the examples below, simply replace
314 each of these names with the appropriate pathname on your local system.
315 All these paths are absolute:</p>
320 This is the top level directory of the LLVM source tree.
325 This is the top level directory of the LLVM object tree (i.e. the
326 tree where object files and compiled programs will be placed. It
327 can be the same as SRC_ROOT).
332 This is the where the LLVM GCC Front End is installed.
334 For the pre-built GCC front end binaries, the LLVMGCCDIR is
335 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
340 <!-- ======================================================================= -->
341 <div class="doc_subsection">
342 <a name="environment">Setting Up Your Environment</a>
345 <div class="doc_text">
348 In order to compile and use LLVM, you will need to set some environment
349 variables. There are also some shell aliases which you may find useful.
350 You can set these on the command line, or better yet, set them in your
351 <tt>.cshrc</tt> or <tt>.profile</tt>.
354 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
356 This environment variable helps the LLVM GCC front end find bytecode
357 libraries that it will need for compilation.
360 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
361 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
363 This alias allows you to use the LLVM C and C++ front ends without putting
364 them in your <tt>PATH</tt> or typing in their complete pathnames.
369 <!-- ======================================================================= -->
370 <div class="doc_subsection">
371 <a name="unpack">Unpacking the LLVM Archives</a>
374 <div class="doc_text">
377 If you have the LLVM distribution, you will need to unpack it before you
378 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
379 suite and the LLVM GCC front end compiled for your platform. Each
380 file is a TAR archive that is compressed with the gzip program.
383 <p> The files are as follows:
386 <dd>This is the source code to the LLVM suite.
389 <dt>cfrontend-1.2.sparc-sun-solaris2.8.tar.gz
390 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
393 <dt>cfrontend-1.2.i686-redhat-linux-gnu.tar.gz
394 <dd>This is the binary release of the GCC front end for Linux/x86.
397 <dt>cfrontend-1.2.i386-unknown-freebsd5.1.tar.gz
398 <dd>This is the binary release of the GCC front end for FreeBSD/x86.
401 <dt>cfrontend-1.2.powerpc-apple-darwin7.0.0.tar.gz
402 <dd>This is the binary release of the GCC front end for MacOS X/PPC.
407 <!-- ======================================================================= -->
408 <div class="doc_subsection">
409 <a name="checkout">Checkout LLVM from CVS</a>
412 <div class="doc_text">
414 <p>If you have access to our CVS repository, you can get a fresh copy of
415 the entire source code. All you need to do is check it out from CVS as
419 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
420 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
421 <li>Hit the return key when prompted for the password.
422 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
426 <p>This will create an '<tt>llvm</tt>' directory in the current
427 directory and fully populate it with the LLVM source code, Makefiles,
428 test directories, and local copies of documentation files.</p>
430 <p>If you want to get a specific release (as opposed to the most recent
431 revision), you can specify a label. The following releases have the following
436 Release 1.2: <b>RELEASE_12</b>
440 Release 1.1: <b>RELEASE_11</b>
444 Release 1.0: <b>RELEASE_1</b>
449 If you would like to get the GCC front end source code, you can also get it
450 from the CVS repository:
452 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
459 <!-- ======================================================================= -->
460 <div class="doc_subsection">
461 <a name="installcf">Install the GCC Front End</a>
464 <div class="doc_text">
466 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
467 GCC front end from the binary distribution. It is used for building the
468 bytecode libraries later used by the GCC front end for linking programs, and its
469 location must be specified when the LLVM suite is configured.</p>
471 <p>To install the GCC front end, do the following:</p>
474 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
475 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
479 <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
482 <p><tt>cd cfrontend/<i>platform</i><br>
483 ./fixheaders</tt></p>
485 <p>The binary versions of the GCC front end may not suit all of your needs. For
486 example, the binary distribution may include an old version of a system header
487 file, not "fix" a header file that needs to be fixed for GCC, or it may be
488 linked with libraries not available on your system.</p>
490 <p>In cases like these, you may want to try <a
491 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
492 not for the faint of heart, so be forewarned.</p>
496 <!-- ======================================================================= -->
497 <div class="doc_subsection">
498 <a name="config">Local LLVM Configuration</a>
501 <div class="doc_text">
503 <p>Once checked out from the CVS repository, the LLVM suite source code must be
504 configured via the <tt>configure</tt> script. This script sets variables in
505 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
506 also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
509 <p>The following environment variables are used by the <tt>configure</tt>
510 script to configure the build system:</p>
520 <td>Tells <tt>configure</tt> which C compiler to use. By default,
521 <tt>configure</tt> will look for the first GCC C compiler in
522 <tt>PATH</tt>. Use this variable to override
523 <tt>configure</tt>'s default behavior.</td>
528 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
529 <tt>configure</tt> will look for the first GCC C++ compiler in
530 <tt>PATH</tt>. Use this variable to override
531 <tt>configure</tt>'s default behavior.</td>
535 <p>The following options can be used to set or enable LLVM specific options:</p>
538 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
540 Path to the location where the LLVM GCC front end binaries and
541 associated libraries were installed. This must be specified as an
544 <dt><i>--enable-optimized</i>
546 Enables optimized compilation by default (debugging symbols are removed
547 and GCC optimization flags are enabled). The default is to use an
548 unoptimized build (also known as a debug build).
550 <dt><i>--enable-jit</i>
552 Compile the Just In Time (JIT) compiler functionality. This is not
554 on all platforms. The default is dependent on platform, so it is best
555 to explicitly enable it if you want it.
557 <dt><i>--enable-spec2000</i>
558 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
560 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
561 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
562 <tt>directory</tt>, you can tell configure where to find the SPEC2000
563 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
564 uses the default value
565 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
567 <dt><i>--enable-spec95</i>
568 <dt><i>--enable-spec95=<<tt>directory</tt>></i>
570 Enable the use of SPEC95 when testing LLVM. It is similar to the
571 <i>--enable-spec2000</i> option.
573 <dt><i>--enable-povray</i>
574 <dt><i>--enable-povray=<<tt>directory</tt>></i>
576 Enable the use of Povray as an external test. Versions of Povray written
577 in C should work. This option is similar to the <i>--enable-spec2000</i>
581 <p>To configure LLVM, follow these steps:</p>
584 <li>Change directory into the object root directory:
586 <tt>cd <i>OBJ_ROOT</i></tt>
589 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
591 <tt><i>SRC_ROOT</i>/configure</tt>
595 <p>In addition to running <tt>configure</tt>, you must set the
596 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
597 This environment variable is used to locate "system" libraries like
598 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
599 the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
600 end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
601 <tt>LLVM_LIB_SEARCH_PATH</tt> to
602 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
603 version of the GCC front end on our research machines.</p>
607 <!-- ======================================================================= -->
608 <div class="doc_subsection">
609 <a name="compile">Compiling the LLVM Suite Source Code</a>
612 <div class="doc_text">
614 <p>Once you have configured LLVM, you can build it. There are three types of
620 These builds are the default when one types <tt>gmake</tt> (unless the
621 <tt>--enable-optimized</tt> option was used during configuration). The
622 build system will compile the tools and libraries with debugging
626 <dt>Release (Optimized) Builds
628 These builds are enabled with the <tt>--enable-optimized</tt> option to
629 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
630 <tt>gmake</tt> command line. For these builds, the build system will
631 compile the tools and libraries with GCC optimizations enabled and strip
632 debugging information from the libraries and executables it generates.
637 These builds are for use with profiling. They compile profiling
638 information into the code for use with programs like <tt>gprof</tt>.
639 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
640 on the <tt>gmake</tt> command line.
643 <p>Once you have LLVM configured, you can build it by entering the
644 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
646 <p><tt>gmake</tt></p>
648 <p>If you have multiple processors in your machine, you may wish to use some of
649 the parallel build options provided by GNU Make. For example, you could use the
652 <p><tt>gmake -j2</tt></p>
654 <p>There are several special targets which are useful when working with the LLVM
658 <dt><tt>gmake clean</tt>
660 Removes all files generated by the build. This includes object files,
661 generated C/C++ files, libraries, and executables.
664 <dt><tt>gmake distclean</tt>
666 Removes everything that <tt>gmake clean</tt> does, but also removes
667 files generated by <tt>configure</tt>. It attempts to return the
668 source tree to the original state in which it was shipped.
671 <dt><tt>gmake install</tt>
673 Installs LLVM files into the proper location. For the most part,
674 this does nothing, but it does install bytecode libraries into the
675 GCC front end's bytecode library directory. If you need to update
676 your bytecode libraries, this is the target to use once you've built
681 <p>It is also possible to override default values from <tt>configure</tt> by
682 declaring variables on the command line. The following are some examples:</p>
685 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
687 Perform a Release (Optimized) build.
690 <dt><tt>gmake ENABLE_PROFILING=1</tt>
692 Perform a Profiling build.
695 <dt><tt>gmake VERBOSE=1</tt>
697 Print what <tt>gmake</tt> is doing on standard output.
701 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
702 it and any subdirectories that it contains. Entering any directory inside the
703 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
704 that directory that is out of date.</p>
708 <!-- ======================================================================= -->
709 <div class="doc_subsection">
710 <a name="objfiles">The Location of LLVM Object Files</a>
713 <div class="doc_text">
715 <p>The LLVM build system is capable of sharing a single LLVM source tree among
716 several LLVM builds. Hence, it is possible to build LLVM for several different
717 platforms or configurations using the same source tree.</p>
719 <p>This is accomplished in the typical autoconf manner:</p>
722 <li><p>Change directory to where the LLVM object files should live:</p>
724 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
726 <li><p>Run the <tt>configure</tt> script found in the LLVM source
729 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
732 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
733 named after the build type:</p>
740 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
742 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
750 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
752 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
760 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
762 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
768 <!-- *********************************************************************** -->
769 <div class="doc_section">
770 <a name="layout"><b>Program Layout</b></a>
772 <!-- *********************************************************************** -->
774 <div class="doc_text">
776 <p>One useful source of information about the LLVM source base is the LLVM <a
777 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
778 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
779 The following is a brief introduction to code layout:</p>
783 <!-- ======================================================================= -->
784 <div class="doc_subsection">
785 <a name="cvsdir"><tt>CVS</tt> directories</a>
788 <div class="doc_text">
790 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
791 the most part these can just be ignored.</p>
795 <!-- ======================================================================= -->
796 <div class="doc_subsection">
797 <a name="include"><tt>llvm/include</tt></a>
800 <div class="doc_text">
802 <p>This directory contains public header files exported from the LLVM
803 library. The three main subdirectories of this directory are:</p>
806 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
807 specific header files. This directory also has subdirectories for
808 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
809 <tt>Target</tt>, <tt>Transforms</tt>, etc...</li>
811 <li><tt>llvm/include/Support</tt> - This directory contains generic
812 support libraries that are independent of LLVM, but are used by LLVM.
813 For example, some C++ STL utilities and a Command Line option processing
814 library store their header files here.</li>
816 <li><tt>llvm/include/Config</tt> - This directory contains header files
817 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
818 and C header files. Source code can include these header files which
819 automatically take care of the conditional #includes that the
820 <tt>configure</tt> script generates.</li>
825 <!-- ======================================================================= -->
826 <div class="doc_subsection">
827 <a name="lib"><tt>llvm/lib</tt></a>
830 <div class="doc_text">
832 <p>This directory contains most of the source files of the LLVM system. In LLVM,
833 almost all code exists in libraries, making it very easy to share code among the
834 different <a href="#tools">tools</a>.</p>
837 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
838 source files that implement core classes like Instruction and BasicBlock.
840 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
841 for the LLVM assembly language parser library.
843 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
844 and write LLVM bytecode.
846 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
849 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
850 different program analyses, such as Dominator Information, Call Graphs,
851 Induction Variables, Interval Identification, Natural Loop Identification,
854 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
855 code for the LLVM to LLVM program transformations, such as Aggressive Dead
856 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
857 Invariant Code Motion, Dead Global Elimination, and many others...
859 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
860 describe various target architectures for code generation. For example,
861 the llvm/lib/Target/Sparc directory holds the Sparc machine
864 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
865 of the code generator: Instruction Selector, Instruction Scheduling, and
868 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
869 that corresponds to the header files located in
870 <tt>llvm/include/Support/</tt>.
875 <!-- ======================================================================= -->
876 <div class="doc_subsection">
877 <a name="runtime"><tt>llvm/runtime</tt></a>
880 <div class="doc_text">
882 <p>This directory contains libraries which are compiled into LLVM bytecode and
883 used when linking programs with the GCC front end. Most of these libraries are
884 skeleton versions of real libraries; for example, libc is a stripped down
885 version of glibc.</p>
887 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
892 <!-- ======================================================================= -->
893 <div class="doc_subsection">
894 <a name="test"><tt>llvm/test</tt></a>
897 <div class="doc_text">
899 <p>This directory contains regression tests and source code that is used to test
900 the LLVM infrastructure.</p>
904 <!-- ======================================================================= -->
905 <div class="doc_subsection">
906 <a name="tools"><tt>llvm/tools</tt></a>
909 <div class="doc_text">
911 <p>The <b>tools</b> directory contains the executables built out of the
912 libraries above, which form the main part of the user interface. You can
913 always get help for a tool by typing <tt>tool_name --help</tt>. The
914 following is a brief introduction to the most important tools:</p>
917 <dt><tt><b>analyze</b></tt> <dd><tt>analyze</tt> is used to run a specific
918 analysis on an input LLVM bytecode file and print out the results. It is
919 primarily useful for debugging analyses, or familiarizing yourself with
920 what an analysis does.<p>
922 <dt><tt><b>bugpoint</b></tt> <dd><tt>bugpoint</tt> is used to debug
923 optimization passes or code generation backends by narrowing down the
924 given test case to the minimum number of passes and/or instructions that
925 still cause a problem, whether it is a crash or miscompilation. See <a
926 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
927 on using <tt>bugpoint</tt>.<p>
929 <dt><tt><b>llvm-ar</b></tt> <dd>The archiver produces an archive containing
930 the given LLVM bytecode files, optionally with an index for faster
933 <dt><tt><b>llvm-as</b></tt> <dd>The assembler transforms the human readable
934 LLVM assembly to LLVM bytecode.<p>
936 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
937 bytecode to human readable LLVM assembly.<p>
939 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
940 links multiple LLVM modules into a single program.<p>
942 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
943 can directly execute LLVM bytecode (although very slowly...). In addition
944 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
945 specifying <tt>-trace</tt> on the command line). Finally, for
946 architectures that support it (currently only x86 and Sparc), by default,
947 <tt>lli</tt> will function as a Just-In-Time compiler (if the
948 functionality was compiled in), and will execute the code <i>much</i>
949 faster than the interpreter.<p>
951 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler, which
952 translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
953 the -march=c option).<p>
955 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
956 that has been retargeted to emit LLVM code as the machine code output. It
957 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
958 -o</tt> options that are typically used. The source code for the
959 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
960 because it is quite large and not very interesting.<p>
964 <dt><tt><b>gccas</b></tt> <dd>This tool is invoked by the
965 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
966 tool actually assembles LLVM assembly to LLVM bytecode,
967 performs a variety of optimizations, and outputs LLVM bytecode. Thus
968 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
969 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
970 an LLVM bytecode file that can be disassembled or manipulated just like
971 any other bytecode file). The command line interface to <tt>gccas</tt>
972 is designed to be as close as possible to the <b>system</b>
973 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
974 modified to interface to a "weird" assembler.<p>
976 <dt><tt><b>gccld</b></tt> <dd><tt>gccld</tt> links together several LLVM
977 bytecode files into one bytecode file and does some optimization. It is
978 the linker invoked by the GCC frontend when multiple .o files need to be
979 linked together. Like <tt>gccas</tt>, the command line interface of
980 <tt>gccld</tt> is designed to match the system linker, to aid
981 interfacing with the GCC frontend.</dl><p>
984 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
985 series of LLVM to LLVM transformations (which are specified on the command
986 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
987 command is a good way to get a list of the program transformations
994 <!-- ======================================================================= -->
995 <div class="doc_subsection">
996 <a name="utils"><tt>llvm/utils</tt></a>
999 <div class="doc_text">
1001 <p>This directory contains utilities for working with LLVM source code, and some
1002 of the utilities are actually required as part of the build process because they
1003 are code generators for parts of LLVM infrastructure.</p>
1006 <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
1007 generator -- it builds trees on which it then performs pattern-matching to
1008 select instructions according to the patterns the user has specified. Burg
1009 is currently used in the Sparc V9 backend.<p>
1011 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1012 that finds differences between code that LLC generates and code that LLI
1013 generates. This is a useful tool if you are debugging one of them,
1014 assuming that the other generates correct output. For the full user
1015 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
1017 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1018 update your CVS tree, but produce a much cleaner and more organized output
1019 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1020 together all the new and updated files and modified files in separate
1021 sections, so you can see at a glance what has changed. If you are at the
1022 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1023 preferred way of updating the tree.<p>
1025 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1026 syntax-highlighting files which will work with Emacs and XEmacs editors,
1027 providing syntax highlighting support for LLVM assembly files and TableGen
1028 description files. For information on how to use the syntax files, consult
1029 the <tt>README</tt> file in that directory.<p>
1031 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1032 and outputs all non-generated source files, which is useful if one wishes
1033 to do a lot of development across directories and does not want to
1034 individually find each file. One way to use it is to run, for example:
1035 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1038 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1039 files in the current directory and then compiles and links the tool that
1040 is the first argument. For example, assuming you are in the directory
1041 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1042 simply running <tt>makellvm llc</tt> will make a build of the current
1043 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1044 causing a re-linking of LLC.<p>
1046 <dt><tt><b>NightlyTest.pl</b></tt> and
1047 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1048 cron script to generate nightly status reports of the functionality of
1049 tools, and the results can be seen by following the appropriate link on
1050 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
1052 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1053 the tool used to generate register descriptions, instruction set
1054 descriptions, and even assemblers from common TableGen description
1057 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1058 syntax-highlighting files which will work with the VIM editor, providing
1059 syntax highlighting support for LLVM assembly files and TableGen
1060 description files. For information on how to use the syntax files, consult
1061 the <tt>README</tt> file in that directory.<p>
1067 <!-- *********************************************************************** -->
1068 <div class="doc_section">
1069 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1071 <!-- *********************************************************************** -->
1073 <div class="doc_text">
1076 <li>First, create a simple C file, name it 'hello.c':
1078 #include <stdio.h>
1080 printf("hello world\n");
1085 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1086 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1088 <p>This will create two result files: <tt>hello</tt> and
1089 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1090 corresponds the the compiled program and the library facilities that it
1091 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1092 file with <tt>lli</tt>, making the result directly executable.</p></li>
1094 <li><p>Run the program. To make sure the program ran, execute one of the
1095 following commands:</p>
1097 <p><tt>% ./hello</tt></p>
1101 <p><tt>% lli hello.bc</tt></p></li>
1103 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1106 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1108 <li><p>Compile the program to native Sparc assembly using the code
1109 generator (assuming you are currently on a Sparc system):</p>
1111 <p><tt>% llc hello.bc -o hello.s</tt></p>
1113 <li><p>Assemble the native sparc assemble file into a program:</p>
1115 <p><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt></p>
1117 <li><p>Execute the native sparc program:</p>
1119 <p><tt>% ./hello.sparc</tt></p></li>
1125 <!-- *********************************************************************** -->
1126 <div class="doc_section">
1127 <a name="problems">Common Problems</a>
1129 <!-- *********************************************************************** -->
1131 <div class="doc_text">
1133 <p>If you are having problems building or using LLVM, or if you have any other
1134 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1135 Asked Questions</a> page.</p>
1139 <!-- *********************************************************************** -->
1140 <div class="doc_section">
1141 <a name="links">Links</a>
1143 <!-- *********************************************************************** -->
1145 <div class="doc_text">
1147 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1148 some simple things... there are many more interesting and complicated things
1149 that you can do that aren't documented here (but we'll gladly accept a patch
1150 if you want to write something up!). For more information about LLVM, check
1154 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1155 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1156 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1157 that Uses LLVM</a></li>
1162 <!-- *********************************************************************** -->
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1171 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1172 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
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