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>Find the path to the CVS repository containing LLVM (we'll
111 call this <i>CVSROOTDIR</i>).
112 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
113 <li><tt>cvs -d <i>CVSROOTDIR</i> checkout 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 path for the CVS repository containing the LLVM source
286 code. Ask the person responsible for your local LLVM installation to
292 This is the top level directory of the LLVM source tree.
297 This is the top level directory of the LLVM object tree (i.e. the
298 tree where object files and compiled programs will be placed. It
299 can be the same as SRC_ROOT).
304 This is the where the LLVM GCC Front End is installed.
306 For the pre-built GCC front end binaries, the LLVMGCCDIR is
307 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
310 <!------------------------------------------------------------------------->
311 <h3><a name="environment">Setting Up Your Environment</a></h3>
312 <!------------------------------------------------------------------------->
315 In order to compile and use LLVM, you will need to set some environment
316 variables. There are also some shell aliases which you may find useful.
317 You can set these on the command line, or better yet, set them in your
318 <tt>.cshrc</tt> or <tt>.profile</tt>.
321 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/llvm-gcc/bytecode-libs</tt>
323 This environment variable helps the LLVM GCC front end find bytecode
324 libraries that it will need for compilation.
327 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/llvm-gcc/bin/gcc</tt>
328 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/llvm-gcc/bin/g++</tt>
330 This alias allows you to use the LLVM C and C++ front ends without putting
331 them in your <tt>PATH</tt> or typing in their complete pathnames.
334 <!------------------------------------------------------------------------->
335 <h3><a name="unpack">Unpacking the LLVM Archives</a></h3>
336 <!------------------------------------------------------------------------->
339 If you have the LLVM distribution, you will need to unpack it before you
340 can begin to compile it. LLVM is distributed as a set of three files. Each
341 file is a TAR archive that is compressed with the gzip program.
344 <p> The three files are as follows:
347 <dd>This is the source code to the LLVM suite.
350 <dt>cfrontend.sparc.tar.gz
351 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
354 <dt>cfrontend.x86.tar.gz
355 <dd>This is the binary release of the GCC front end for Linux/x86.
358 <!------------------------------------------------------------------------->
359 <h3><a name="checkout">Checkout LLVM from CVS</a></h3>
360 <!------------------------------------------------------------------------->
362 <p>If you have access to our CVS repository, you can get a fresh copy of
363 the entire source code. All you need to do is check it out from CVS as
366 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
367 <li><tt>cvs -d <i>CVSROOTDIR</i> checkout llvm</tt></p>
370 <p>This will create an '<tt>llvm</tt>' directory in the current
371 directory and fully populate it with the LLVM source code, Makefiles,
372 test directories, and local copies of documentation files.</p>
375 Note that the GCC front end is not included in the CVS repository. You
376 should have downloaded the binary distribution for your platform.
379 <!------------------------------------------------------------------------->
380 <h3><a name="installcf">Install the GCC Front End</a></h3>
381 <!------------------------------------------------------------------------->
384 Before configuring and compiling the LLVM suite, you need to extract the
385 LLVM GCC front end from the binary distribution. It is used for building the
386 bytecode libraries later used by the GCC front end for linking programs, and
387 its location must be specified when the LLVM suite is configured.
391 To install the GCC front end, do the following:
393 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt>
394 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf
398 <!------------------------------------------------------------------------->
399 <h3><a name="config">Local LLVM Configuration</a></h3>
400 <!------------------------------------------------------------------------->
402 <p>Once checked out from the CVS repository, the LLVM suite source code
403 must be configured via the <tt>configure</tt> script. This script sets
404 variables in <tt>llvm/Makefile.config</tt> and
405 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i> with
406 the Makefiles needed to build LLVM.
409 The following environment variables are used by the <tt>configure</tt>
410 script to configure the build system:
424 Tells <tt>configure</tt> which C compiler to use. By default,
425 <tt>configure</tt> will look for the first GCC C compiler in
426 <tt>PATH</tt>. Use this variable to override
427 <tt>configure</tt>'s default behavior.
434 Tells <tt>configure</tt> which C++ compiler to use. By default,
435 <tt>configure</tt> will look for the first GCC C++ compiler in
436 <tt>PATH</tt>. Use this variable to override
437 <tt>configure</tt>'s default behavior.
443 The following options can be used to set or enable LLVM specific options:
447 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
449 Path to the location where the LLVM C front end binaries and
450 associated libraries will be installed.
452 <dt><i>--enable-optimized</i>
454 Enables optimized compilation by default (debugging symbols are removed
455 and GCC optimization flags are enabled). The default is to use an
456 unoptimized build (also known as a debug build).
458 <dt><i>--enable-jit</i>
460 Compile the Just In Time (JIT) functionality. This is not available
461 on all platforms. The default is dependent on platform, so it is best
462 to explicitly enable it if you want it.
464 <dt><i>--enable-spec2000</i>
465 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
467 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
468 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
469 <tt>directory</tt>, you can tell configure where to find the SPEC2000
470 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
471 uses the default value
472 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
476 To configure LLVM, follow these steps:
478 <li>Change directory into the object root directory:
480 <tt>cd <i>OBJ_ROOT</i></tt>
483 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
485 <tt><i>SRC_ROOT</i>/configure</tt>
490 In addition to running <tt>configure</tt>, you must set the
491 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
492 This environment variable is used to locate "system" libraries like
493 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set
494 to the absolute path for the bytecode-libs subdirectory of the GCC front end
495 install, or <i>LLVMGCCDIR</i>/llvm-gcc/bytecode-libs. For example, one might
496 set <tt>LLVM_LIB_SEARCH_PATH</tt> to
497 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the X86
498 version of the GCC front end on our research machines.<p>
500 <!------------------------------------------------------------------------->
501 <h3><a name="compile">Compiling the LLVM Suite Source Code</a></h3>
502 <!------------------------------------------------------------------------->
504 Once you have configured LLVM, you can build it. There are three types of
510 These builds are the default when one types <tt>gmake</tt> (unless the
511 <tt>--enable-optimized</tt> option was used during configuration). The
512 build system will compile the tools and libraries with debugging
516 <dt>Release (Optimized) Builds
518 These builds are enabled with the <tt>--enable-optimized</tt> option to
519 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
520 <tt>gmake</tt> command line. For these builds, the build system will
521 compile the tools and libraries with GCC optimizations enabled and strip
522 debugging information from the libraries and executables it generates.
527 These builds are for use with profiling. They compile profiling
528 information into the code for use with programs like <tt>gprof</tt>.
529 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
530 on the <tt>gmake</tt> command line.
533 Once you have LLVM configured, you can build it by entering the
534 <i>OBJ_ROOT</i> directory and issuing the following command:
539 If you have multiple processors in your machine, you may wish to use some
540 of the parallel build options provided by GNU Make. For example, you could
548 There are several special targets which are useful when working with the LLVM
552 <dt><tt>gmake clean</tt>
554 Removes all files generated by the build. This includes object files,
555 generated C/C++ files, libraries, and executables.
558 <dt><tt>gmake distclean</tt>
560 Removes everything that <tt>gmake clean</tt> does, but also removes
561 files generated by <tt>configure</tt>. It attempts to return the
562 source tree to the original state in which it was shipped.
565 <dt><tt>gmake install</tt>
567 Installs LLVM files into the proper location. For the most part,
568 this does nothing, but it does install bytecode libraries into the
569 GCC front end's bytecode library directory. If you need to update
570 your bytecode libraries, this is the target to use once you've built
576 It is also possible to override default values from <tt>configure</tt> by
577 declaring variables on the command line. The following are some examples:
580 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
582 Perform a Release (Optimized) build.
585 <dt><tt>gmake ENABLE_PROFILING=1</tt>
587 Perform a Profiling build.
590 <dt><tt>gmake VERBOSE=1</tt>
592 Print what <tt>gmake</tt> is doing on standard output.
596 Every directory in the LLVM object tree includes a <tt>Makefile</tt> to
597 build it and any subdirectories that it contains. Entering any directory
598 inside the LLVM object tree and typing <tt>gmake</tt> should rebuild
599 anything in or below that directory that is out of date.
601 <!------------------------------------------------------------------------->
602 <h3><a name="objfiles">The Location of LLVM Object Files</a></h3>
603 <!------------------------------------------------------------------------->
606 The LLVM build system is capable of sharing a single LLVM source tree among
607 several LLVM builds. Hence, it is possible to build LLVM for several
608 different platforms or configurations using the same source tree.
610 This is accomplished in the typical autoconf manner:
612 <li>Change directory to where the LLVM object files should live:
614 <tt>cd <i>OBJ_ROOT</i></tt>
616 <li>Run the <tt>configure</tt> script found in the LLVM source directory:
618 <tt><i>SRC_ROOT</i>/configure</tt>
622 The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
623 named after the build type:
631 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
633 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
641 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
643 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
651 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
653 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
657 <!--=====================================================================-->
659 <h2><a name="layout"><b>Program Layout</b></a></h2>
662 <!--=====================================================================-->
665 One useful source of information about the LLVM source base is the LLVM <a
666 href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a
667 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
668 The following is a brief introduction to code layout:
671 <!------------------------------------------------------------------------->
672 <h3><a name="cvsdir"><tt>CVS</tt> directories</a></h3>
673 <!------------------------------------------------------------------------->
675 Every directory checked out of CVS will contain a <tt>CVS</tt> directory;
676 for the most part these can just be ignored.
679 <!------------------------------------------------------------------------->
680 <h3><a name="include"><tt>llvm/include</tt></a></h3>
681 <!------------------------------------------------------------------------->
683 This directory contains public header files exported from the LLVM
684 library. The three main subdirectories of this directory are:<p>
687 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
688 specific header files. This directory also has subdirectories for
689 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
690 <tt>Target</tt>, <tt>Transforms</tt>, etc...
692 <li><tt>llvm/include/Support</tt> - This directory contains generic
693 support libraries that are independent of LLVM, but are used by LLVM.
694 For example, some C++ STL utilities and a Command Line option processing
695 library store their header files here.
697 <li><tt>llvm/include/Config</tt> - This directory contains header files
698 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
699 and C header files. Source code can include these header files which
700 automatically take care of the conditional #includes that the
701 <tt>configure</tt> script generates.
704 <!------------------------------------------------------------------------->
705 <h3><a name="lib"><tt>llvm/lib</tt></a></h3>
706 <!------------------------------------------------------------------------->
708 This directory contains most of the source files of the LLVM system. In
710 code exists in libraries, making it very easy to share code among the
711 different <a href="#tools">tools</a>.<p>
714 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
715 source files that implement core classes like Instruction and BasicBlock.
717 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
718 for the LLVM assembly language parser library.
720 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
721 and write LLVM bytecode.
723 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
726 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
727 different program analyses, such as Dominator Information, Call Graphs,
728 Induction Variables, Interval Identification, Natural Loop Identification,
731 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
732 code for the LLVM to LLVM program transformations, such as Aggressive Dead
733 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
734 Invariant Code Motion, Dead Global Elimination, and many others...
736 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
737 describe various target architectures for code generation. For example,
738 the llvm/lib/Target/Sparc directory holds the Sparc machine
741 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
742 of the code generator: Instruction Selector, Instruction Scheduling, and
745 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
746 that corresponds to the header files located in
747 <tt>llvm/include/Support/</tt>.
750 <!------------------------------------------------------------------------->
751 <h3><a name="runtime"><tt>llvm/runtime</tt></a></h3>
752 <!------------------------------------------------------------------------->
755 This directory contains libraries which are compiled into LLVM bytecode and
756 used when linking programs with the GCC front end. Most of these libraries
757 are skeleton versions of real libraries; for example, libc is a stripped down
762 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
766 <!------------------------------------------------------------------------->
767 <h3><a name="test"><tt>llvm/test</tt></a></h3>
768 <!------------------------------------------------------------------------->
770 <p>This directory contains regression tests and source code that is used to
771 test the LLVM infrastructure.
774 <!------------------------------------------------------------------------->
775 <h3><a name="tools"><tt>llvm/tools</tt></a></h3>
776 <!------------------------------------------------------------------------->
778 <p>The <b>tools</b> directory contains the executables built out of the
779 libraries above, which form the main part of the user interface. You can
780 always get help for a tool by typing <tt>tool_name --help</tt>. The
781 following is a brief introduction to the most important tools.</p>
786 <dt><tt><b>analyze</b></tt><dd> <tt>analyze</tt> is used to run a specific
787 analysis on an input LLVM bytecode file and print out the results. It is
788 primarily useful for debugging analyses, or familiarizing yourself with
789 what an analysis does.<p>
791 <dt><tt><b>bugpoint</b></tt><dd> <tt>bugpoint</tt> is used to debug
792 optimization passes or code generation backends by narrowing down the
793 given test case to the minimum number of passes and/or instructions that
794 still cause a problem, whether it is a crash or miscompilation. See <a
795 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
796 on using <tt>bugpoint</tt>.<p>
798 <dt><tt><b>llvm-ar</b></tt><dd>The archiver produces an archive containing
799 the given LLVM bytecode files, optionally with an index for faster
802 <dt><tt><b>llvm-as</b></tt><dd>The assembler transforms the human readable
803 LLVM assembly to LLVM bytecode.<p>
805 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
806 bytecode to human readable LLVM assembly. Additionally, it can convert
807 LLVM bytecode to C, which is enabled with the <tt>-c</tt> option.<p>
809 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
810 links multiple LLVM modules into a single program.<p>
812 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
813 can directly execute LLVM bytecode (although very slowly...). In addition
814 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
815 specifying <tt>-trace</tt> on the command line). Finally, for
816 architectures that support it (currently only x86 and Sparc), by default,
817 <tt>lli</tt> will function as a Just-In-Time compiler (if the
818 functionality was compiled in), and will execute the code <i>much</i>
819 faster than the interpreter.<p>
821 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler,
822 which translates LLVM bytecode to a SPARC or x86 assembly file.<p>
824 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
825 that has been retargeted to emit LLVM code as the machine code output. It
826 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
827 -o</tt> options that are typically used. The source code for the
828 <tt>llvmgcc</tt> tool is currently not included in the LLVM cvs tree
829 because it is quite large and not very interesting.<p>
832 <dt><tt><b>gccas</b></tt><dd> This tool is invoked by the
833 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
834 tool actually assembles LLVM assembly to LLVM bytecode,
835 performs a variety of optimizations, and outputs LLVM bytecode. Thus
836 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
837 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
838 an LLVM bytecode file that can be disassembled or manipulated just like
839 any other bytecode file). The command line interface to <tt>gccas</tt>
840 is designed to be as close as possible to the <b>system</b>
841 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
842 modified to interface to a "weird" assembler.<p>
844 <dt><tt><b>gccld</b></tt><dd> <tt>gccld</tt> links together several LLVM
845 bytecode files into one bytecode file and does some optimization. It is
846 the linker invoked by the GCC frontend when multiple .o files need to be
847 linked together. Like <tt>gccas</tt>, the command line interface of
848 <tt>gccld</tt> is designed to match the system linker, to aid
849 interfacing with the GCC frontend.<p>
852 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
853 series of LLVM to LLVM transformations (which are specified on the command
854 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
855 command is a good way to get a list of the program transformations
856 available in LLVM.<p>
860 <!------------------------------------------------------------------------->
861 <h3><a name="utils"><tt>llvm/utils</tt></a></h3>
862 <!------------------------------------------------------------------------->
864 This directory contains utilities for working with LLVM source code, and some
865 of the utilities are actually required as part of the build process because
866 they are code generators for parts of LLVM infrastructure.
869 <td><tt><b>Burg/</b></tt><dd> <tt>Burg</tt> is an instruction selector
870 generator -- it builds trees on which it then performs pattern-matching to
871 select instructions according to the patterns the user has specified. Burg
872 is currently used in the Sparc V9 backend.<p>
874 <dt><tt><b>codegen-diff</b></tt><dd> <tt>codegen-diff</tt> is a script
875 that finds differences between code that LLC generates and code that LLI
876 generates. This is a useful tool if you are debugging one of them,
877 assuming that the other generates correct output. For the full user
878 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
880 <dt><tt><b>cvsupdate</b></tt><dd> <tt>cvsupdate</tt> is a script that will
881 update your CVS tree, but produce a much cleaner and more organized output
882 than simply running <tt>`cvs up -dP'</tt> will. For example, it will group
883 together all the new and updated files and modified files in separate
884 sections, so you can see at a glance what has changed. If you are at the
885 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
886 preferred way of updating the tree.<p>
888 <dt><tt><b>emacs/</b></tt><dd> The <tt>emacs</tt> directory contains
889 syntax-highlighting files which will work with Emacs and XEmacs editors,
890 providing syntax highlighting support for LLVM assembly files and TableGen
891 description files. For information on how to use the syntax files, consult
892 the <tt>README</tt> file in that directory.<p>
894 <dt><tt><b>getsrcs.sh</b></tt><dd> The <tt>getsrcs.sh</tt> script finds
895 and outputs all non-generated source files, which is useful if one wishes
896 to do a lot of development across directories and does not want to
897 individually find each file. One way to use it is to run, for example:
898 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
901 <dt><tt><b>makellvm</b></tt><dd> The <tt>makellvm</tt> script compiles all
902 files in the current directory and then compiles and links the tool that
903 is the first argument. For example, assuming you are in the directory
904 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
905 simply running <tt>makellvm llc</tt> will make a build of the current
906 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
907 causing a re-linking of LLC.<p>
909 <dt><tt><b>NightlyTest.pl</b></tt> and
910 <tt><b>NightlyTestTemplate.html</b></tt><dd> These files are used in a
911 cron script to generate nightly status reports of the functionality of
912 tools, and the results can be seen by following the appropriate link on
913 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
915 <dt><tt><b>TableGen/</b></tt><dd> The <tt>TableGen</tt> directory contains
916 the tool used to generate register descriptions, instruction set
917 descriptions, and even assemblers from common TableGen description
920 <dt><tt><b>vim/</b></tt><dd> The <tt>vim</tt> directory contains
921 syntax-highlighting files which will work with the VIM editor, providing
922 syntax highlighting support for LLVM assembly files and TableGen
923 description files. For information on how to use the syntax files, consult
924 the <tt>README</tt> file in that directory.<p>
928 <!--=====================================================================-->
930 <center><a name="tutorial">An Example Using the LLVM Tool Chain</center>
933 <!--=====================================================================-->
936 <li>First, create a simple C file, name it 'hello.c':
938 #include <stdio.h>
940 printf("hello world\n");
945 <li>Next, compile the C file into a LLVM bytecode file:<p>
947 <tt>% llvmgcc hello.c -o hello</tt><p>
949 This will create two result files: <tt>hello</tt> and
950 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
951 corresponds the the compiled program and the library facilities that it
952 required. <tt>hello</tt> is a simple shell script that runs the bytecode
953 file with <tt>lli</tt>, making the result directly executable.<p>
955 <li>Run the program. To make sure the program ran, execute one of the
956 following commands:<p>
958 <tt>% ./hello</tt><p>
962 <tt>% lli hello.bc</tt><p>
964 <li>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
967 <tt>% llvm-dis < hello.bc | less</tt><p>
969 <li>Compile the program to native Sparc assembly using the code
970 generator (assuming you are currently on a Sparc system):<p>
972 <tt>% llc hello.bc -o hello.s</tt><p>
974 <li>Assemble the native sparc assemble file into a program:<p>
976 <tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt><p>
978 <li>Execute the native sparc program:<p>
980 <tt>% ./hello.sparc</tt><p>
985 <!--=====================================================================-->
987 <center><a name="problems">Common Problems</a></center>
990 <!--=====================================================================-->
992 If you are having problems building or using LLVM, or if you have any other
993 general questions about LLVM, please consult the
994 <a href="FAQ.html">Frequently Asked Questions</a> page.
996 <!--=====================================================================-->
997 <h2><center><a name="links">Links</a></center></h2>
999 <!--=====================================================================-->
1001 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1002 some simple things... there are many more interesting and complicated things
1003 that you can do that aren't documented here (but we'll gladly accept a patch
1004 if you want to write something up!). For more information about LLVM, check
1008 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1009 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1010 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project that Uses LLVM</a></li>
1015 If you have any questions or run into any snags (or you have any
1016 additions...), please send an email to
1017 <a href="mailto:sabre@nondot.org">Chris Lattner</a>.</p>
1019 <!-- Created: Mon Jul 1 02:29:02 CDT 2002 -->
1020 <!-- hhmts start -->
1021 Last modified: Mon Aug 11 13:52:22 CDT 2003