1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
4 <title>Getting Started with LLVM System</title>
8 <center><h1>Getting Started with the LLVM System<br><font size=3>By: <a
9 href="mailto:gshi1@uiuc.edu">Guochun Shi</a>,
10 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
11 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
12 <a href="http://misha.brukman.net">Misha Brukman</a>, and
13 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>
16 <!--=====================================================================-->
17 <h2><a name="Contents">Contents</a></h2>
18 <!--=====================================================================-->
21 <li><a href="#overview">Overview</a>
22 <li><a href="#quickstart">Getting Started Quickly (A Summary)</a>
23 <li><a href="#requirements">Requirements</a>
25 <li><a href="#hardware">Hardware</a>
26 <li><a href="#software">Software</a>
29 <li><a href="#starting">Getting Started with LLVM</a>
31 <li><a href="#terminology">Terminology and Notation</tt></a>
32 <li><a href="#environment">Setting Up Your Environment</a>
33 <li><a href="#unpack">Unpacking the LLVM Archives</a>
34 <li><a href="#checkout">Checkout LLVM from CVS</a>
35 <li><a href="#installcf">Install the GCC Front End</a>
36 <li><a href="#config">Local LLVM Configuration</tt></a>
37 <li><a href="#compile">Compiling the LLVM Suite Source Code</a>
38 <li><a href="#objfiles">The Location of LLVM Object Files</tt></a>
40 <li><a href="#layout">Program layout</a>
42 <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
43 <li><a href="#include"><tt>llvm/include</tt></a>
44 <li><a href="#lib"><tt>llvm/lib</tt></a>
45 <li><a href="#runtime"><tt>llvm/runtime</tt></a>
46 <li><a href="#test"><tt>llvm/test</tt></a>
47 <li><a href="#tools"><tt>llvm/tools</tt></a>
48 <li><a href="#utils"><tt>llvm/utils</tt></a>
50 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
51 <li><a href="#problems">Common Problems</a>
52 <li><a href="#links">Links</a>
56 <!--=====================================================================-->
58 <h2><a name="overview"><b>Overview</b></a></h2>
61 <!--=====================================================================-->
63 Welcome to LLVM! In order to get started, you first need to know some
67 First, LLVM comes in two pieces. The first piece is the LLVM suite. This
68 contains all of the tools, libraries, and header files needed to use the
69 low level virtual machine. It contains an assembler, disassembler,
70 bytecode analyzer, and bytecode optimizer. It also contains a test suite
71 that can be used to test the LLVM tools and the GCC front end.
73 The second piece is the GCC front end. This component provides a version
74 of GCC that compiles C and C++ code into LLVM bytecode. Currently, the
75 GCC front end is a modified version of GCC 3.4 (we track the GCC 3.4
76 development). Once compiled into LLVM bytecode, a program can be
77 manipulated with the LLVM tools from the LLVM suite.
79 <!--=====================================================================-->
81 <h2><a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a></h2>
84 <!--=====================================================================-->
86 Here's the short story for getting up and running quickly with LLVM:
88 <li>Install the GCC front end:
90 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
91 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf
97 <li>Get the Source Code
99 <li>With the distributed files:
101 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
102 <li><tt>gunzip --stdout llvm.tar.gz | tar -xvf -</tt>
108 <li>With anonymous CVS access:
110 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
111 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
112 <li>Hit the return key when prompted for the password.
113 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm</tt>
121 <li>Configure the LLVM Build Environment
123 <li>Change directory to where you want to store the LLVM object
124 files and run <tt>configure</tt> to configure the Makefiles and
125 header files for the default platform.
126 Useful options include:
128 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
130 Specify where the LLVM GCC frontend is installed.
133 <li><tt>--enable-spec2000=<i>directory</i></tt>
135 Enable the SPEC2000 benchmarks for testing. The SPEC2000
136 benchmarks should be available in <tt><i>directory</i></tt>.
142 <li>Build the LLVM Suite
144 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.
145 <li><tt>gmake -k |& tee gnumake.out
146 # this is csh or tcsh syntax</tt>
154 Consult the <a href="starting">Getting Started with LLVM</a> section for
155 detailed information on configuring and compiling LLVM. See
156 <a href="#environment">Setting Up Your Environment</a> for tips that
157 simplify working with the GCC front end and LLVM tools. Go to
158 <a href="#layout">Program Layout</a> to learn about the layout of the
161 <!--=====================================================================-->
163 <h2><a name="requirements"><b>Requirements</b></a></h2>
166 <!--=====================================================================-->
168 Before you begin to use the LLVM system, review the requirements given
169 below. This may save you some trouble by knowing ahead of time what
170 hardware and software you will need.
172 <!--=====================================================================-->
173 <h3><a name="hardware"><b>Hardware</b></a></h3>
174 <!--=====================================================================-->
175 LLVM is known to work on the following platforms:
177 <li> Linux on x86 (Pentium and above)
179 <li> Approximately 760 MB of Free Disk Space
181 <li>Source code: 30 MB
182 <li>Object code: 670 MB
183 <li>GCC front end: 60 MB
189 <li> Solaris on SparcV9 (Ultrasparc)
191 <li> Approximately 1.24 GB of Free Disk Space
193 <li>Source code: 30 MB
194 <li>Object code: 1000 MB
195 <li>GCC front end: 210 MB
200 The LLVM suite <i>may</i> compile on other platforms, but it is not
201 guaranteed to do so. If compilation is successful, the LLVM utilities
202 should be able to assemble, disassemble, analyze, and optimize LLVM
203 bytecode. Code generation should work as well, although the generated
204 native code may not work on your platform.
206 The GCC front end is not very portable at the moment. If you want to get
207 it to work on another platform, you can always request
208 <a href="mailto:llvm-request@zion.cs.uiuc.edu">a copy of the source</a>
209 and try to compile it on your platform.
212 <!--=====================================================================-->
213 <h3><a name="software"><b>Software</b></a></h3>
214 <!--=====================================================================-->
217 Compiling LLVM requires that you have several software packages installed:
221 <a href="http://gcc.gnu.org">GCC 3.x with C and C++ language support</a>
224 <a href="http://savannah.gnu.org/projects/make">GNU Make</a>
227 <a href="http://www.gnu.org/software/flex">Flex</a>
230 <a href="http://www.gnu.org/software/bison/bison.html">Bison</a>
234 There are some additional tools that you may want to have when working with
239 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A>
240 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
242 If you want to make changes to the configure scripts, you will need
243 GNU autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4
247 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest</A>
248 <li><A href="http://www.python.org">Python</A>
250 These are needed to use the LLVM test suite.
254 <p>The remainder of this guide is meant to get you up and running with
255 LLVM and to give you some basic information about the LLVM environment.
256 A <a href="#starting">complete guide to installation</a> is provided in the
259 <p>The later sections of this guide describe the <a
260 href="#layout">general layout</a> of the the LLVM source tree, a <a
261 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
262 href="#links">links</a> to find more information about LLVM or to get
265 <!--=====================================================================-->
267 <h2><a name="starting"><b>Getting Started with LLVM</b></a></h2>
270 <!--=====================================================================-->
272 <!------------------------------------------------------------------------->
273 <h3><a name="terminology">Terminology and Notation</a></h3>
274 <!------------------------------------------------------------------------->
276 <p>Throughout this manual, the following names are used to denote paths
277 specific to the local system and working environment. <i>These are not
278 environment variables you need to set but just strings used in the rest
279 of this document below</i>. In any of the examples below, simply replace
280 each of these names with the appropriate pathname on your local system.
281 All these paths are absolute:</p>
285 This is the top level directory of the LLVM source tree.
290 This is the top level directory of the LLVM object tree (i.e. the
291 tree where object files and compiled programs will be placed. It
292 can be the same as SRC_ROOT).
297 This is the where the LLVM GCC Front End is installed.
299 For the pre-built GCC front end binaries, the LLVMGCCDIR is
300 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
303 <!------------------------------------------------------------------------->
304 <h3><a name="environment">Setting Up Your Environment</a></h3>
305 <!------------------------------------------------------------------------->
308 In order to compile and use LLVM, you will need to set some environment
309 variables. There are also some shell aliases which you may find useful.
310 You can set these on the command line, or better yet, set them in your
311 <tt>.cshrc</tt> or <tt>.profile</tt>.
314 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/llvm-gcc/bytecode-libs</tt>
316 This environment variable helps the LLVM GCC front end find bytecode
317 libraries that it will need for compilation.
320 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/llvm-gcc/bin/gcc</tt>
321 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/llvm-gcc/bin/g++</tt>
323 This alias allows you to use the LLVM C and C++ front ends without putting
324 them in your <tt>PATH</tt> or typing in their complete pathnames.
327 <!------------------------------------------------------------------------->
328 <h3><a name="unpack">Unpacking the LLVM Archives</a></h3>
329 <!------------------------------------------------------------------------->
332 If you have the LLVM distribution, you will need to unpack it before you
333 can begin to compile it. LLVM is distributed as a set of three files. Each
334 file is a TAR archive that is compressed with the gzip program.
337 <p> The three files are as follows:
340 <dd>This is the source code to the LLVM suite.
343 <dt>cfrontend.sparc.tar.gz
344 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
347 <dt>cfrontend.x86.tar.gz
348 <dd>This is the binary release of the GCC front end for Linux/x86.
351 <!------------------------------------------------------------------------->
352 <h3><a name="checkout">Checkout LLVM from CVS</a></h3>
353 <!------------------------------------------------------------------------->
355 <p>If you have access to our CVS repository, you can get a fresh copy of
356 the entire source code. All you need to do is check it out from CVS as
359 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
360 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
361 <li>Hit the return key when prompted for the password.
362 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm</tt>
365 <p>This will create an '<tt>llvm</tt>' directory in the current
366 directory and fully populate it with the LLVM source code, Makefiles,
367 test directories, and local copies of documentation files.</p>
370 Note that the GCC front end is not included in the CVS repository. You
371 should have downloaded the binary distribution for your platform.
374 <!------------------------------------------------------------------------->
375 <h3><a name="installcf">Install the GCC Front End</a></h3>
376 <!------------------------------------------------------------------------->
379 Before configuring and compiling the LLVM suite, you need to extract the
380 LLVM GCC front end from the binary distribution. It is used for building the
381 bytecode libraries later used by the GCC front end for linking programs, and
382 its location must be specified when the LLVM suite is configured.
386 To install the GCC front end, do the following:
388 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt>
389 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf
393 <!------------------------------------------------------------------------->
394 <h3><a name="config">Local LLVM Configuration</a></h3>
395 <!------------------------------------------------------------------------->
397 <p>Once checked out from the CVS repository, the LLVM suite source code
398 must be configured via the <tt>configure</tt> script. This script sets
399 variables in <tt>llvm/Makefile.config</tt> and
400 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i>
401 with the Makefiles needed to build LLVM.
404 The following environment variables are used by the <tt>configure</tt>
405 script to configure the build system:
419 Tells <tt>configure</tt> which C compiler to use. By default,
420 <tt>configure</tt> will look for the first GCC C compiler in
421 <tt>PATH</tt>. Use this variable to override
422 <tt>configure</tt>'s default behavior.
429 Tells <tt>configure</tt> which C++ compiler to use. By default,
430 <tt>configure</tt> will look for the first GCC C++ compiler in
431 <tt>PATH</tt>. Use this variable to override
432 <tt>configure</tt>'s default behavior.
438 The following options can be used to set or enable LLVM specific options:
442 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
444 Path to the location where the LLVM C front end binaries and
445 associated libraries will be installed.
447 <dt><i>--enable-optimized</i>
449 Enables optimized compilation by default (debugging symbols are removed
450 and GCC optimization flags are enabled). The default is to use an
451 unoptimized build (also known as a debug build).
453 <dt><i>--enable-jit</i>
455 Compile the Just In Time (JIT) functionality. This is not available
456 on all platforms. The default is dependent on platform, so it is best
457 to explicitly enable it if you want it.
459 <dt><i>--enable-spec2000</i>
460 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
462 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
463 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
464 <tt>directory</tt>, you can tell configure where to find the SPEC2000
465 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
466 uses the default value
467 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
471 To configure LLVM, follow these steps:
473 <li>Change directory into the object root directory:
475 <tt>cd <i>OBJ_ROOT</i></tt>
478 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
480 <tt><i>SRC_ROOT</i>/configure</tt>
485 In addition to running <tt>configure</tt>, you must set the
486 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
487 This environment variable is used to locate "system" libraries like
488 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set
489 to the absolute path for the bytecode-libs subdirectory of the GCC front end
490 install, or <i>LLVMGCCDIR</i>/llvm-gcc/bytecode-libs. For example, one might
491 set <tt>LLVM_LIB_SEARCH_PATH</tt> to
492 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the X86
493 version of the GCC front end on our research machines.<p>
495 <!------------------------------------------------------------------------->
496 <h3><a name="compile">Compiling the LLVM Suite Source Code</a></h3>
497 <!------------------------------------------------------------------------->
499 Once you have configured LLVM, you can build it. There are three types of
505 These builds are the default when one types <tt>gmake</tt> (unless the
506 <tt>--enable-optimized</tt> option was used during configuration). The
507 build system will compile the tools and libraries with debugging
511 <dt>Release (Optimized) Builds
513 These builds are enabled with the <tt>--enable-optimized</tt> option to
514 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
515 <tt>gmake</tt> command line. For these builds, the build system will
516 compile the tools and libraries with GCC optimizations enabled and strip
517 debugging information from the libraries and executables it generates.
522 These builds are for use with profiling. They compile profiling
523 information into the code for use with programs like <tt>gprof</tt>.
524 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
525 on the <tt>gmake</tt> command line.
528 Once you have LLVM configured, you can build it by entering the
529 <i>OBJ_ROOT</i> directory and issuing the following command:
534 If you have multiple processors in your machine, you may wish to use some
535 of the parallel build options provided by GNU Make. For example, you could
543 There are several special targets which are useful when working with the LLVM
547 <dt><tt>gmake clean</tt>
549 Removes all files generated by the build. This includes object files,
550 generated C/C++ files, libraries, and executables.
553 <dt><tt>gmake distclean</tt>
555 Removes everything that <tt>gmake clean</tt> does, but also removes
556 files generated by <tt>configure</tt>. It attempts to return the
557 source tree to the original state in which it was shipped.
560 <dt><tt>gmake install</tt>
562 Installs LLVM files into the proper location. For the most part,
563 this does nothing, but it does install bytecode libraries into the
564 GCC front end's bytecode library directory. If you need to update
565 your bytecode libraries, this is the target to use once you've built
571 It is also possible to override default values from <tt>configure</tt> by
572 declaring variables on the command line. The following are some examples:
575 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
577 Perform a Release (Optimized) build.
580 <dt><tt>gmake ENABLE_PROFILING=1</tt>
582 Perform a Profiling build.
585 <dt><tt>gmake VERBOSE=1</tt>
587 Print what <tt>gmake</tt> is doing on standard output.
591 Every directory in the LLVM object tree includes a <tt>Makefile</tt> to
592 build it and any subdirectories that it contains. Entering any directory
593 inside the LLVM object tree and typing <tt>gmake</tt> should rebuild
594 anything in or below that directory that is out of date.
596 <!------------------------------------------------------------------------->
597 <h3><a name="objfiles">The Location of LLVM Object Files</a></h3>
598 <!------------------------------------------------------------------------->
601 The LLVM build system is capable of sharing a single LLVM source tree among
602 several LLVM builds. Hence, it is possible to build LLVM for several
603 different platforms or configurations using the same source tree.
605 This is accomplished in the typical autoconf manner:
607 <li>Change directory to where the LLVM object files should live:
609 <tt>cd <i>OBJ_ROOT</i></tt>
611 <li>Run the <tt>configure</tt> script found in the LLVM source directory:
613 <tt><i>SRC_ROOT</i>/configure</tt>
617 The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
618 named after the build type:
626 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
628 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
636 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
638 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
646 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
648 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
652 <!--=====================================================================-->
654 <h2><a name="layout"><b>Program Layout</b></a></h2>
657 <!--=====================================================================-->
660 One useful source of information about the LLVM source base is the LLVM <a
661 href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a
662 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
663 The following is a brief introduction to code layout:
666 <!------------------------------------------------------------------------->
667 <h3><a name="cvsdir"><tt>CVS</tt> directories</a></h3>
668 <!------------------------------------------------------------------------->
670 Every directory checked out of CVS will contain a <tt>CVS</tt> directory;
671 for the most part these can just be ignored.
674 <!------------------------------------------------------------------------->
675 <h3><a name="include"><tt>llvm/include</tt></a></h3>
676 <!------------------------------------------------------------------------->
678 This directory contains public header files exported from the LLVM
679 library. The three main subdirectories of this directory are:<p>
682 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
683 specific header files. This directory also has subdirectories for
684 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
685 <tt>Target</tt>, <tt>Transforms</tt>, etc...
687 <li><tt>llvm/include/Support</tt> - This directory contains generic
688 support libraries that are independent of LLVM, but are used by LLVM.
689 For example, some C++ STL utilities and a Command Line option processing
690 library store their header files here.
692 <li><tt>llvm/include/Config</tt> - This directory contains header files
693 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
694 and C header files. Source code can include these header files which
695 automatically take care of the conditional #includes that the
696 <tt>configure</tt> script generates.
699 <!------------------------------------------------------------------------->
700 <h3><a name="lib"><tt>llvm/lib</tt></a></h3>
701 <!------------------------------------------------------------------------->
703 This directory contains most of the source files of the LLVM system. In
705 code exists in libraries, making it very easy to share code among the
706 different <a href="#tools">tools</a>.<p>
709 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
710 source files that implement core classes like Instruction and BasicBlock.
712 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
713 for the LLVM assembly language parser library.
715 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
716 and write LLVM bytecode.
718 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
721 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
722 different program analyses, such as Dominator Information, Call Graphs,
723 Induction Variables, Interval Identification, Natural Loop Identification,
726 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
727 code for the LLVM to LLVM program transformations, such as Aggressive Dead
728 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
729 Invariant Code Motion, Dead Global Elimination, and many others...
731 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
732 describe various target architectures for code generation. For example,
733 the llvm/lib/Target/Sparc directory holds the Sparc machine
736 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
737 of the code generator: Instruction Selector, Instruction Scheduling, and
740 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
741 that corresponds to the header files located in
742 <tt>llvm/include/Support/</tt>.
745 <!------------------------------------------------------------------------->
746 <h3><a name="runtime"><tt>llvm/runtime</tt></a></h3>
747 <!------------------------------------------------------------------------->
750 This directory contains libraries which are compiled into LLVM bytecode and
751 used when linking programs with the GCC front end. Most of these libraries
752 are skeleton versions of real libraries; for example, libc is a stripped down
757 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
761 <!------------------------------------------------------------------------->
762 <h3><a name="test"><tt>llvm/test</tt></a></h3>
763 <!------------------------------------------------------------------------->
765 <p>This directory contains regression tests and source code that is used to
766 test the LLVM infrastructure.
769 <!------------------------------------------------------------------------->
770 <h3><a name="tools"><tt>llvm/tools</tt></a></h3>
771 <!------------------------------------------------------------------------->
773 <p>The <b>tools</b> directory contains the executables built out of the
774 libraries above, which form the main part of the user interface. You can
775 always get help for a tool by typing <tt>tool_name --help</tt>. The
776 following is a brief introduction to the most important tools.</p>
781 <dt><tt><b>analyze</b></tt><dd> <tt>analyze</tt> is used to run a specific
782 analysis on an input LLVM bytecode file and print out the results. It is
783 primarily useful for debugging analyses, or familiarizing yourself with
784 what an analysis does.<p>
786 <dt><tt><b>bugpoint</b></tt><dd> <tt>bugpoint</tt> is used to debug
787 optimization passes or code generation backends by narrowing down the
788 given test case to the minimum number of passes and/or instructions that
789 still cause a problem, whether it is a crash or miscompilation. See <a
790 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
791 on using <tt>bugpoint</tt>.<p>
793 <dt><tt><b>llvm-ar</b></tt><dd>The archiver produces an archive containing
794 the given LLVM bytecode files, optionally with an index for faster
797 <dt><tt><b>llvm-as</b></tt><dd>The assembler transforms the human readable
798 LLVM assembly to LLVM bytecode.<p>
800 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
801 bytecode to human readable LLVM assembly. Additionally, it can convert
802 LLVM bytecode to C, which is enabled with the <tt>-c</tt> option.<p>
804 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
805 links multiple LLVM modules into a single program.<p>
807 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
808 can directly execute LLVM bytecode (although very slowly...). In addition
809 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
810 specifying <tt>-trace</tt> on the command line). Finally, for
811 architectures that support it (currently only x86 and Sparc), by default,
812 <tt>lli</tt> will function as a Just-In-Time compiler (if the
813 functionality was compiled in), and will execute the code <i>much</i>
814 faster than the interpreter.<p>
816 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler,
817 which translates LLVM bytecode to a SPARC or x86 assembly file.<p>
819 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
820 that has been retargeted to emit LLVM code as the machine code output. It
821 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
822 -o</tt> options that are typically used. The source code for the
823 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
824 because it is quite large and not very interesting.<p>
827 <dt><tt><b>gccas</b></tt><dd> This tool is invoked by the
828 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
829 tool actually assembles LLVM assembly to LLVM bytecode,
830 performs a variety of optimizations, and outputs LLVM bytecode. Thus
831 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
832 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
833 an LLVM bytecode file that can be disassembled or manipulated just like
834 any other bytecode file). The command line interface to <tt>gccas</tt>
835 is designed to be as close as possible to the <b>system</b>
836 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
837 modified to interface to a "weird" assembler.<p>
839 <dt><tt><b>gccld</b></tt><dd> <tt>gccld</tt> links together several LLVM
840 bytecode files into one bytecode file and does some optimization. It is
841 the linker invoked by the GCC frontend when multiple .o files need to be
842 linked together. Like <tt>gccas</tt>, the command line interface of
843 <tt>gccld</tt> is designed to match the system linker, to aid
844 interfacing with the GCC frontend.<p>
847 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
848 series of LLVM to LLVM transformations (which are specified on the command
849 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
850 command is a good way to get a list of the program transformations
851 available in LLVM.<p>
855 <!------------------------------------------------------------------------->
856 <h3><a name="utils"><tt>llvm/utils</tt></a></h3>
857 <!------------------------------------------------------------------------->
859 This directory contains utilities for working with LLVM source code, and some
860 of the utilities are actually required as part of the build process because
861 they are code generators for parts of LLVM infrastructure.
864 <td><tt><b>Burg/</b></tt><dd> <tt>Burg</tt> is an instruction selector
865 generator -- it builds trees on which it then performs pattern-matching to
866 select instructions according to the patterns the user has specified. Burg
867 is currently used in the Sparc V9 backend.<p>
869 <dt><tt><b>codegen-diff</b></tt><dd> <tt>codegen-diff</tt> is a script
870 that finds differences between code that LLC generates and code that LLI
871 generates. This is a useful tool if you are debugging one of them,
872 assuming that the other generates correct output. For the full user
873 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
875 <dt><tt><b>cvsupdate</b></tt><dd> <tt>cvsupdate</tt> is a script that will
876 update your CVS tree, but produce a much cleaner and more organized output
877 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
878 together all the new and updated files and modified files in separate
879 sections, so you can see at a glance what has changed. If you are at the
880 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
881 preferred way of updating the tree.<p>
883 <dt><tt><b>emacs/</b></tt><dd> The <tt>emacs</tt> directory contains
884 syntax-highlighting files which will work with Emacs and XEmacs editors,
885 providing syntax highlighting support for LLVM assembly files and TableGen
886 description files. For information on how to use the syntax files, consult
887 the <tt>README</tt> file in that directory.<p>
889 <dt><tt><b>getsrcs.sh</b></tt><dd> The <tt>getsrcs.sh</tt> script finds
890 and outputs all non-generated source files, which is useful if one wishes
891 to do a lot of development across directories and does not want to
892 individually find each file. One way to use it is to run, for example:
893 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
896 <dt><tt><b>makellvm</b></tt><dd> The <tt>makellvm</tt> script compiles all
897 files in the current directory and then compiles and links the tool that
898 is the first argument. For example, assuming you are in the directory
899 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
900 simply running <tt>makellvm llc</tt> will make a build of the current
901 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
902 causing a re-linking of LLC.<p>
904 <dt><tt><b>NightlyTest.pl</b></tt> and
905 <tt><b>NightlyTestTemplate.html</b></tt><dd> These files are used in a
906 cron script to generate nightly status reports of the functionality of
907 tools, and the results can be seen by following the appropriate link on
908 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
910 <dt><tt><b>TableGen/</b></tt><dd> The <tt>TableGen</tt> directory contains
911 the tool used to generate register descriptions, instruction set
912 descriptions, and even assemblers from common TableGen description
915 <dt><tt><b>vim/</b></tt><dd> The <tt>vim</tt> directory contains
916 syntax-highlighting files which will work with the VIM editor, providing
917 syntax highlighting support for LLVM assembly files and TableGen
918 description files. For information on how to use the syntax files, consult
919 the <tt>README</tt> file in that directory.<p>
923 <!--=====================================================================-->
925 <center><a name="tutorial">An Example Using the LLVM Tool Chain</center>
928 <!--=====================================================================-->
931 <li>First, create a simple C file, name it 'hello.c':
933 #include <stdio.h>
935 printf("hello world\n");
940 <li>Next, compile the C file into a LLVM bytecode file:<p>
942 <tt>% llvmgcc hello.c -o hello</tt><p>
944 This will create two result files: <tt>hello</tt> and
945 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
946 corresponds the the compiled program and the library facilities that it
947 required. <tt>hello</tt> is a simple shell script that runs the bytecode
948 file with <tt>lli</tt>, making the result directly executable.<p>
950 <li>Run the program. To make sure the program ran, execute one of the
951 following commands:<p>
953 <tt>% ./hello</tt><p>
957 <tt>% lli hello.bc</tt><p>
959 <li>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
962 <tt>% llvm-dis < hello.bc | less</tt><p>
964 <li>Compile the program to native Sparc assembly using the code
965 generator (assuming you are currently on a Sparc system):<p>
967 <tt>% llc hello.bc -o hello.s</tt><p>
969 <li>Assemble the native sparc assemble file into a program:<p>
971 <tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt><p>
973 <li>Execute the native sparc program:<p>
975 <tt>% ./hello.sparc</tt><p>
980 <!--=====================================================================-->
982 <center><a name="problems">Common Problems</a></center>
985 <!--=====================================================================-->
987 If you are having problems building or using LLVM, or if you have any other
988 general questions about LLVM, please consult the
989 <a href="FAQ.html">Frequently Asked Questions</a> page.
991 <!--=====================================================================-->
992 <h2><center><a name="links">Links</a></center></h2>
994 <!--=====================================================================-->
996 <p>This document is just an <b>introduction</b> to how to use LLVM to do
997 some simple things... there are many more interesting and complicated things
998 that you can do that aren't documented here (but we'll gladly accept a patch
999 if you want to write something up!). For more information about LLVM, check
1003 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1004 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1005 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project that Uses LLVM</a></li>
1010 If you have any questions or run into any snags (or you have any
1011 additions...), please send an email to
1012 <a href="mailto:sabre@nondot.org">Chris Lattner</a>.</p>
1014 <!-- Created: Mon Jul 1 02:29:02 CDT 2002 -->
1015 <!-- hhmts start -->
1016 Last modified: Mon Aug 11 13:52:22 CDT 2003