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
93 <li><b>Sparc Only:</b><br>
95 cd cfrontend/sparc<br>
102 <li>Get the Source Code
104 <li>With the distributed files:
106 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
107 <li><tt>gunzip --stdout llvm.tar.gz | tar -xvf -</tt>
113 <li>With anonymous CVS access:
115 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
116 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
117 <li>Hit the return key when prompted for the password.
118 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm</tt>
126 <li>Configure the LLVM Build Environment
128 <li>Change directory to where you want to store the LLVM object
129 files and run <tt>configure</tt> to configure the Makefiles and
130 header files for the default platform.
131 Useful options include:
133 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
135 Specify where the LLVM GCC frontend is installed.
138 <li><tt>--enable-spec2000=<i>directory</i></tt>
140 Enable the SPEC2000 benchmarks for testing. The SPEC2000
141 benchmarks should be available in <tt><i>directory</i></tt>.
147 <li>Build the LLVM Suite
149 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.
150 <li><tt>gmake -k |& tee gnumake.out
151 # this is csh or tcsh syntax</tt>
159 Consult the <a href="starting">Getting Started with LLVM</a> section for
160 detailed information on configuring and compiling LLVM. See
161 <a href="#environment">Setting Up Your Environment</a> for tips that
162 simplify working with the GCC front end and LLVM tools. Go to
163 <a href="#layout">Program Layout</a> to learn about the layout of the
166 <!--=====================================================================-->
168 <h2><a name="requirements"><b>Requirements</b></a></h2>
171 <!--=====================================================================-->
173 Before you begin to use the LLVM system, review the requirements given
174 below. This may save you some trouble by knowing ahead of time what
175 hardware and software you will need.
177 <!--=====================================================================-->
178 <h3><a name="hardware"><b>Hardware</b></a></h3>
179 <!--=====================================================================-->
180 LLVM is known to work on the following platforms:
182 <li> Linux on x86 (Pentium and above)
184 <li> Approximately 760 MB of Free Disk Space
186 <li>Source code: 30 MB
187 <li>Object code: 670 MB
188 <li>GCC front end: 60 MB
194 <li> Solaris on SparcV9 (Ultrasparc)
196 <li> Approximately 1.24 GB of Free Disk Space
198 <li>Source code: 30 MB
199 <li>Object code: 1000 MB
200 <li>GCC front end: 210 MB
205 The LLVM suite <i>may</i> compile on other platforms, but it is not
206 guaranteed to do so. If compilation is successful, the LLVM utilities
207 should be able to assemble, disassemble, analyze, and optimize LLVM
208 bytecode. Code generation should work as well, although the generated
209 native code may not work on your platform.
211 The GCC front end is not very portable at the moment. If you want to get
212 it to work on another platform, you can download a copy of the source
213 and try to compile it on your platform.
216 <!--=====================================================================-->
217 <h3><a name="software"><b>Software</b></a></h3>
218 <!--=====================================================================-->
221 Compiling LLVM requires that you have several software packages installed:
225 <a href="http://gcc.gnu.org">GCC 3.x with C and C++ language support</a>
228 <a href="http://savannah.gnu.org/projects/make">GNU Make</a>
231 <a href="http://www.gnu.org/software/flex">Flex</a>
234 <a href="http://www.gnu.org/software/bison/bison.html">Bison</a>
238 There are some additional tools that you may want to have when working with
243 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A>
244 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
246 If you want to make changes to the configure scripts, you will need
247 GNU autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4
251 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest</A>
252 <li><A href="http://www.python.org">Python</A>
254 These are needed to use the LLVM test suite.
258 <p>The remainder of this guide is meant to get you up and running with
259 LLVM and to give you some basic information about the LLVM environment.
260 A <a href="#starting">complete guide to installation</a> is provided in the
263 <p>The later sections of this guide describe the <a
264 href="#layout">general layout</a> of the the LLVM source tree, a <a
265 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
266 href="#links">links</a> to find more information about LLVM or to get
269 <!--=====================================================================-->
271 <h2><a name="starting"><b>Getting Started with LLVM</b></a></h2>
274 <!--=====================================================================-->
276 <!------------------------------------------------------------------------->
277 <h3><a name="terminology">Terminology and Notation</a></h3>
278 <!------------------------------------------------------------------------->
280 <p>Throughout this manual, the following names are used to denote paths
281 specific to the local system and working environment. <i>These are not
282 environment variables you need to set but just strings used in the rest
283 of this document below</i>. In any of the examples below, simply replace
284 each of these names with the appropriate pathname on your local system.
285 All these paths are absolute:</p>
289 This is the top level directory of the LLVM source tree.
294 This is the top level directory of the LLVM object tree (i.e. the
295 tree where object files and compiled programs will be placed. It
296 can be the same as SRC_ROOT).
301 This is the where the LLVM GCC Front End is installed.
303 For the pre-built GCC front end binaries, the LLVMGCCDIR is
304 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
307 <!------------------------------------------------------------------------->
308 <h3><a name="environment">Setting Up Your Environment</a></h3>
309 <!------------------------------------------------------------------------->
312 In order to compile and use LLVM, you will need to set some environment
313 variables. There are also some shell aliases which you may find useful.
314 You can set these on the command line, or better yet, set them in your
315 <tt>.cshrc</tt> or <tt>.profile</tt>.
318 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
320 This environment variable helps the LLVM GCC front end find bytecode
321 libraries that it will need for compilation.
324 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
325 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
327 This alias allows you to use the LLVM C and C++ front ends without putting
328 them in your <tt>PATH</tt> or typing in their complete pathnames.
331 <!------------------------------------------------------------------------->
332 <h3><a name="unpack">Unpacking the LLVM Archives</a></h3>
333 <!------------------------------------------------------------------------->
336 If you have the LLVM distribution, you will need to unpack it before you
337 can begin to compile it. LLVM is distributed as a set of three files. Each
338 file is a TAR archive that is compressed with the gzip program.
341 <p> The three files are as follows:
344 <dd>This is the source code to the LLVM suite.
347 <dt>cfrontend.sparc.tar.gz
348 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
351 <dt>cfrontend.x86.tar.gz
352 <dd>This is the binary release of the GCC front end for Linux/x86.
355 <!------------------------------------------------------------------------->
356 <h3><a name="checkout">Checkout LLVM from CVS</a></h3>
357 <!------------------------------------------------------------------------->
359 <p>If you have access to our CVS repository, you can get a fresh copy of
360 the entire source code. All you need to do is check it out from CVS as
363 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
364 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
365 <li>Hit the return key when prompted for the password.
366 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm</tt>
369 <p>This will create an '<tt>llvm</tt>' directory in the current
370 directory and fully populate it with the LLVM source code, Makefiles,
371 test directories, and local copies of documentation files.</p>
374 Note that the GCC front end is not included in the CVS repository. You
375 should have downloaded the binary distribution for your platform.
378 <!------------------------------------------------------------------------->
379 <h3><a name="installcf">Install the GCC Front End</a></h3>
380 <!------------------------------------------------------------------------->
383 Before configuring and compiling the LLVM suite, you need to extract the
384 LLVM GCC front end from the binary distribution. It is used for building
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 If you are on a Sparc/Solaris machine, you will need to fix the header
410 The binary versions of the GCC front end may not suit all of your needs.
411 For example, the binary distribution may include an old version of a system
412 header file, not "fix" a header file that needs to be fixed for GCC, or it
413 may be linked with libraries not available on your system.
417 In cases like these, you may want to try
418 <a href="CFEBuildInstrs.html">building the GCC front end from source.</a>
419 This is not for the faint of heart, so be forewarned.
421 <!------------------------------------------------------------------------->
422 <h3><a name="config">Local LLVM Configuration</a></h3>
423 <!------------------------------------------------------------------------->
425 <p>Once checked out from the CVS repository, the LLVM suite source code
426 must be configured via the <tt>configure</tt> script. This script sets
427 variables in <tt>llvm/Makefile.config</tt> and
428 <tt>llvm/include/Config/config.h</tt>. It also populates <i>OBJ_ROOT</i>
429 with the Makefiles needed to build LLVM.
432 The following environment variables are used by the <tt>configure</tt>
433 script to configure the build system:
447 Tells <tt>configure</tt> which C compiler to use. By default,
448 <tt>configure</tt> will look for the first GCC C compiler in
449 <tt>PATH</tt>. Use this variable to override
450 <tt>configure</tt>'s default behavior.
457 Tells <tt>configure</tt> which C++ compiler to use. By default,
458 <tt>configure</tt> will look for the first GCC C++ compiler in
459 <tt>PATH</tt>. Use this variable to override
460 <tt>configure</tt>'s default behavior.
466 The following options can be used to set or enable LLVM specific options:
470 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
472 Path to the location where the LLVM C front end binaries and
473 associated libraries will be installed.
475 <dt><i>--enable-optimized</i>
477 Enables optimized compilation by default (debugging symbols are removed
478 and GCC optimization flags are enabled). The default is to use an
479 unoptimized build (also known as a debug build).
481 <dt><i>--enable-jit</i>
483 Compile the Just In Time (JIT) functionality. This is not available
484 on all platforms. The default is dependent on platform, so it is best
485 to explicitly enable it if you want it.
487 <dt><i>--enable-spec2000</i>
488 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
490 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
491 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
492 <tt>directory</tt>, you can tell configure where to find the SPEC2000
493 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
494 uses the default value
495 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
499 To configure LLVM, follow these steps:
501 <li>Change directory into the object root directory:
503 <tt>cd <i>OBJ_ROOT</i></tt>
506 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
508 <tt><i>SRC_ROOT</i>/configure</tt>
513 In addition to running <tt>configure</tt>, you must set the
514 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
515 This environment variable is used to locate "system" libraries like
516 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set
517 to the absolute path for the bytecode-libs subdirectory of the GCC front end
518 install, or <i>LLVMGCCDIR</i>/bytecode-libs. For example, one might
519 set <tt>LLVM_LIB_SEARCH_PATH</tt> to
520 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the X86
521 version of the GCC front end on our research machines.<p>
523 <!------------------------------------------------------------------------->
524 <h3><a name="compile">Compiling the LLVM Suite Source Code</a></h3>
525 <!------------------------------------------------------------------------->
527 Once you have configured LLVM, you can build it. There are three types of
533 These builds are the default when one types <tt>gmake</tt> (unless the
534 <tt>--enable-optimized</tt> option was used during configuration). The
535 build system will compile the tools and libraries with debugging
539 <dt>Release (Optimized) Builds
541 These builds are enabled with the <tt>--enable-optimized</tt> option to
542 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
543 <tt>gmake</tt> command line. For these builds, the build system will
544 compile the tools and libraries with GCC optimizations enabled and strip
545 debugging information from the libraries and executables it generates.
550 These builds are for use with profiling. They compile profiling
551 information into the code for use with programs like <tt>gprof</tt>.
552 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
553 on the <tt>gmake</tt> command line.
556 Once you have LLVM configured, you can build it by entering the
557 <i>OBJ_ROOT</i> directory and issuing the following command:
562 If you have multiple processors in your machine, you may wish to use some
563 of the parallel build options provided by GNU Make. For example, you could
571 There are several special targets which are useful when working with the LLVM
575 <dt><tt>gmake clean</tt>
577 Removes all files generated by the build. This includes object files,
578 generated C/C++ files, libraries, and executables.
581 <dt><tt>gmake distclean</tt>
583 Removes everything that <tt>gmake clean</tt> does, but also removes
584 files generated by <tt>configure</tt>. It attempts to return the
585 source tree to the original state in which it was shipped.
588 <dt><tt>gmake install</tt>
590 Installs LLVM files into the proper location. For the most part,
591 this does nothing, but it does install bytecode libraries into the
592 GCC front end's bytecode library directory. If you need to update
593 your bytecode libraries, this is the target to use once you've built
599 It is also possible to override default values from <tt>configure</tt> by
600 declaring variables on the command line. The following are some examples:
603 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
605 Perform a Release (Optimized) build.
608 <dt><tt>gmake ENABLE_PROFILING=1</tt>
610 Perform a Profiling build.
613 <dt><tt>gmake VERBOSE=1</tt>
615 Print what <tt>gmake</tt> is doing on standard output.
619 Every directory in the LLVM object tree includes a <tt>Makefile</tt> to
620 build it and any subdirectories that it contains. Entering any directory
621 inside the LLVM object tree and typing <tt>gmake</tt> should rebuild
622 anything in or below that directory that is out of date.
624 <!------------------------------------------------------------------------->
625 <h3><a name="objfiles">The Location of LLVM Object Files</a></h3>
626 <!------------------------------------------------------------------------->
629 The LLVM build system is capable of sharing a single LLVM source tree among
630 several LLVM builds. Hence, it is possible to build LLVM for several
631 different platforms or configurations using the same source tree.
633 This is accomplished in the typical autoconf manner:
635 <li>Change directory to where the LLVM object files should live:
637 <tt>cd <i>OBJ_ROOT</i></tt>
639 <li>Run the <tt>configure</tt> script found in the LLVM source directory:
641 <tt><i>SRC_ROOT</i>/configure</tt>
645 The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
646 named after the build type:
654 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
656 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
664 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
666 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
674 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
676 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
680 <!--=====================================================================-->
682 <h2><a name="layout"><b>Program Layout</b></a></h2>
685 <!--=====================================================================-->
688 One useful source of information about the LLVM source base is the LLVM <a
689 href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a
690 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
691 The following is a brief introduction to code layout:
694 <!------------------------------------------------------------------------->
695 <h3><a name="cvsdir"><tt>CVS</tt> directories</a></h3>
696 <!------------------------------------------------------------------------->
698 Every directory checked out of CVS will contain a <tt>CVS</tt> directory;
699 for the most part these can just be ignored.
702 <!------------------------------------------------------------------------->
703 <h3><a name="include"><tt>llvm/include</tt></a></h3>
704 <!------------------------------------------------------------------------->
706 This directory contains public header files exported from the LLVM
707 library. The three main subdirectories of this directory are:<p>
710 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
711 specific header files. This directory also has subdirectories for
712 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
713 <tt>Target</tt>, <tt>Transforms</tt>, etc...
715 <li><tt>llvm/include/Support</tt> - This directory contains generic
716 support libraries that are independent of LLVM, but are used by LLVM.
717 For example, some C++ STL utilities and a Command Line option processing
718 library store their header files here.
720 <li><tt>llvm/include/Config</tt> - This directory contains header files
721 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
722 and C header files. Source code can include these header files which
723 automatically take care of the conditional #includes that the
724 <tt>configure</tt> script generates.
727 <!------------------------------------------------------------------------->
728 <h3><a name="lib"><tt>llvm/lib</tt></a></h3>
729 <!------------------------------------------------------------------------->
731 This directory contains most of the source files of the LLVM system. In
733 code exists in libraries, making it very easy to share code among the
734 different <a href="#tools">tools</a>.<p>
737 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
738 source files that implement core classes like Instruction and BasicBlock.
740 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
741 for the LLVM assembly language parser library.
743 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
744 and write LLVM bytecode.
746 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
749 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
750 different program analyses, such as Dominator Information, Call Graphs,
751 Induction Variables, Interval Identification, Natural Loop Identification,
754 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
755 code for the LLVM to LLVM program transformations, such as Aggressive Dead
756 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
757 Invariant Code Motion, Dead Global Elimination, and many others...
759 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
760 describe various target architectures for code generation. For example,
761 the llvm/lib/Target/Sparc directory holds the Sparc machine
764 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
765 of the code generator: Instruction Selector, Instruction Scheduling, and
768 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
769 that corresponds to the header files located in
770 <tt>llvm/include/Support/</tt>.
773 <!------------------------------------------------------------------------->
774 <h3><a name="runtime"><tt>llvm/runtime</tt></a></h3>
775 <!------------------------------------------------------------------------->
778 This directory contains libraries which are compiled into LLVM bytecode and
779 used when linking programs with the GCC front end. Most of these libraries
780 are skeleton versions of real libraries; for example, libc is a stripped down
785 Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front end
789 <!------------------------------------------------------------------------->
790 <h3><a name="test"><tt>llvm/test</tt></a></h3>
791 <!------------------------------------------------------------------------->
793 <p>This directory contains regression tests and source code that is used to
794 test the LLVM infrastructure.
797 <!------------------------------------------------------------------------->
798 <h3><a name="tools"><tt>llvm/tools</tt></a></h3>
799 <!------------------------------------------------------------------------->
801 <p>The <b>tools</b> directory contains the executables built out of the
802 libraries above, which form the main part of the user interface. You can
803 always get help for a tool by typing <tt>tool_name --help</tt>. The
804 following is a brief introduction to the most important tools.</p>
809 <dt><tt><b>analyze</b></tt><dd> <tt>analyze</tt> is used to run a specific
810 analysis on an input LLVM bytecode file and print out the results. It is
811 primarily useful for debugging analyses, or familiarizing yourself with
812 what an analysis does.<p>
814 <dt><tt><b>bugpoint</b></tt><dd> <tt>bugpoint</tt> is used to debug
815 optimization passes or code generation backends by narrowing down the
816 given test case to the minimum number of passes and/or instructions that
817 still cause a problem, whether it is a crash or miscompilation. See <a
818 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
819 on using <tt>bugpoint</tt>.<p>
821 <dt><tt><b>llvm-ar</b></tt><dd>The archiver produces an archive containing
822 the given LLVM bytecode files, optionally with an index for faster
825 <dt><tt><b>llvm-as</b></tt><dd>The assembler transforms the human readable
826 LLVM assembly to LLVM bytecode.<p>
828 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
829 bytecode to human readable LLVM assembly. Additionally, it can convert
830 LLVM bytecode to C, which is enabled with the <tt>-c</tt> option.<p>
832 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
833 links multiple LLVM modules into a single program.<p>
835 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
836 can directly execute LLVM bytecode (although very slowly...). In addition
837 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
838 specifying <tt>-trace</tt> on the command line). Finally, for
839 architectures that support it (currently only x86 and Sparc), by default,
840 <tt>lli</tt> will function as a Just-In-Time compiler (if the
841 functionality was compiled in), and will execute the code <i>much</i>
842 faster than the interpreter.<p>
844 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler,
845 which translates LLVM bytecode to a SPARC or x86 assembly file.<p>
847 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
848 that has been retargeted to emit LLVM code as the machine code output. It
849 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
850 -o</tt> options that are typically used. The source code for the
851 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
852 because it is quite large and not very interesting.<p>
855 <dt><tt><b>gccas</b></tt><dd> This tool is invoked by the
856 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
857 tool actually assembles LLVM assembly to LLVM bytecode,
858 performs a variety of optimizations, and outputs LLVM bytecode. Thus
859 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
860 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
861 an LLVM bytecode file that can be disassembled or manipulated just like
862 any other bytecode file). The command line interface to <tt>gccas</tt>
863 is designed to be as close as possible to the <b>system</b>
864 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
865 modified to interface to a "weird" assembler.<p>
867 <dt><tt><b>gccld</b></tt><dd> <tt>gccld</tt> links together several LLVM
868 bytecode files into one bytecode file and does some optimization. It is
869 the linker invoked by the GCC frontend when multiple .o files need to be
870 linked together. Like <tt>gccas</tt>, the command line interface of
871 <tt>gccld</tt> is designed to match the system linker, to aid
872 interfacing with the GCC frontend.<p>
875 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
876 series of LLVM to LLVM transformations (which are specified on the command
877 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
878 command is a good way to get a list of the program transformations
879 available in LLVM.<p>
883 <!------------------------------------------------------------------------->
884 <h3><a name="utils"><tt>llvm/utils</tt></a></h3>
885 <!------------------------------------------------------------------------->
887 This directory contains utilities for working with LLVM source code, and some
888 of the utilities are actually required as part of the build process because
889 they are code generators for parts of LLVM infrastructure.
892 <td><tt><b>Burg/</b></tt><dd> <tt>Burg</tt> is an instruction selector
893 generator -- it builds trees on which it then performs pattern-matching to
894 select instructions according to the patterns the user has specified. Burg
895 is currently used in the Sparc V9 backend.<p>
897 <dt><tt><b>codegen-diff</b></tt><dd> <tt>codegen-diff</tt> is a script
898 that finds differences between code that LLC generates and code that LLI
899 generates. This is a useful tool if you are debugging one of them,
900 assuming that the other generates correct output. For the full user
901 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
903 <dt><tt><b>cvsupdate</b></tt><dd> <tt>cvsupdate</tt> is a script that will
904 update your CVS tree, but produce a much cleaner and more organized output
905 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
906 together all the new and updated files and modified files in separate
907 sections, so you can see at a glance what has changed. If you are at the
908 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
909 preferred way of updating the tree.<p>
911 <dt><tt><b>emacs/</b></tt><dd> The <tt>emacs</tt> directory contains
912 syntax-highlighting files which will work with Emacs and XEmacs editors,
913 providing syntax highlighting support for LLVM assembly files and TableGen
914 description files. For information on how to use the syntax files, consult
915 the <tt>README</tt> file in that directory.<p>
917 <dt><tt><b>getsrcs.sh</b></tt><dd> The <tt>getsrcs.sh</tt> script finds
918 and outputs all non-generated source files, which is useful if one wishes
919 to do a lot of development across directories and does not want to
920 individually find each file. One way to use it is to run, for example:
921 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
924 <dt><tt><b>makellvm</b></tt><dd> The <tt>makellvm</tt> script compiles all
925 files in the current directory and then compiles and links the tool that
926 is the first argument. For example, assuming you are in the directory
927 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
928 simply running <tt>makellvm llc</tt> will make a build of the current
929 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
930 causing a re-linking of LLC.<p>
932 <dt><tt><b>NightlyTest.pl</b></tt> and
933 <tt><b>NightlyTestTemplate.html</b></tt><dd> These files are used in a
934 cron script to generate nightly status reports of the functionality of
935 tools, and the results can be seen by following the appropriate link on
936 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
938 <dt><tt><b>TableGen/</b></tt><dd> The <tt>TableGen</tt> directory contains
939 the tool used to generate register descriptions, instruction set
940 descriptions, and even assemblers from common TableGen description
943 <dt><tt><b>vim/</b></tt><dd> The <tt>vim</tt> directory contains
944 syntax-highlighting files which will work with the VIM editor, providing
945 syntax highlighting support for LLVM assembly files and TableGen
946 description files. For information on how to use the syntax files, consult
947 the <tt>README</tt> file in that directory.<p>
951 <!--=====================================================================-->
953 <center><a name="tutorial">An Example Using the LLVM Tool Chain</center>
956 <!--=====================================================================-->
959 <li>First, create a simple C file, name it 'hello.c':
961 #include <stdio.h>
963 printf("hello world\n");
968 <li>Next, compile the C file into a LLVM bytecode file:<p>
970 <tt>% llvmgcc hello.c -o hello</tt><p>
972 This will create two result files: <tt>hello</tt> and
973 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
974 corresponds the the compiled program and the library facilities that it
975 required. <tt>hello</tt> is a simple shell script that runs the bytecode
976 file with <tt>lli</tt>, making the result directly executable.<p>
978 <li>Run the program. To make sure the program ran, execute one of the
979 following commands:<p>
981 <tt>% ./hello</tt><p>
985 <tt>% lli hello.bc</tt><p>
987 <li>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
990 <tt>% llvm-dis < hello.bc | less</tt><p>
992 <li>Compile the program to native Sparc assembly using the code
993 generator (assuming you are currently on a Sparc system):<p>
995 <tt>% llc hello.bc -o hello.s</tt><p>
997 <li>Assemble the native sparc assemble file into a program:<p>
999 <tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt><p>
1001 <li>Execute the native sparc program:<p>
1003 <tt>% ./hello.sparc</tt><p>
1008 <!--=====================================================================-->
1010 <center><a name="problems">Common Problems</a></center>
1013 <!--=====================================================================-->
1015 If you are having problems building or using LLVM, or if you have any other
1016 general questions about LLVM, please consult the
1017 <a href="FAQ.html">Frequently Asked Questions</a> page.
1019 <!--=====================================================================-->
1020 <h2><center><a name="links">Links</a></center></h2>
1022 <!--=====================================================================-->
1024 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1025 some simple things... there are many more interesting and complicated things
1026 that you can do that aren't documented here (but we'll gladly accept a patch
1027 if you want to write something up!). For more information about LLVM, check
1031 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1032 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1033 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project that Uses LLVM</a></li>
1038 If you have any questions or run into any snags (or you have any
1039 additions...), please send an email to
1040 <a href="mailto:sabre@nondot.org">Chris Lattner</a>.</p>
1041 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
1044 <!-- Created: Mon Jul 1 02:29:02 CDT 2002 -->
1045 <!-- hhmts start -->
1046 Last modified: Thu Nov 6 14:50:33 CST 2003