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10 <div class="doc_title">
11 Getting Started with the LLVM System
15 <li><a href="#overview">Overview</a>
16 <li><a href="#quickstart">Getting Started Quickly (A Summary)</a>
17 <li><a href="#requirements">Requirements</a>
19 <li><a href="#hardware">Hardware</a>
20 <li><a href="#software">Software</a>
23 <li><a href="#starting">Getting Started with LLVM</a>
25 <li><a href="#terminology">Terminology and Notation</a>
26 <li><a href="#environment">Setting Up Your Environment</a>
27 <li><a href="#unpack">Unpacking the LLVM Archives</a>
28 <li><a href="#checkout">Checkout LLVM from CVS</a>
29 <li><a href="#installcf">Install the GCC Front End</a>
30 <li><a href="#config">Local LLVM Configuration</a>
31 <li><a href="#compile">Compiling the LLVM Suite Source Code</a>
32 <li><a href="#objfiles">The Location of LLVM Object Files</a>
35 <li><a href="#layout">Program layout</a>
37 <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
38 <li><a href="#include"><tt>llvm/include</tt></a>
39 <li><a href="#lib"><tt>llvm/lib</tt></a>
40 <li><a href="#runtime"><tt>llvm/runtime</tt></a>
41 <li><a href="#test"><tt>llvm/test</tt></a>
42 <li><a href="#tools"><tt>llvm/tools</tt></a>
43 <li><a href="#utils"><tt>llvm/utils</tt></a>
46 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
47 <li><a href="#problems">Common Problems</a>
48 <li><a href="#links">Links</a>
52 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>,
53 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
54 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
55 <a href="http://misha.brukman.net">Misha Brukman</a>, and
56 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>.</p>
59 <!-- *********************************************************************** -->
60 <div class="doc_section">
61 <a name="overview"><b>Overview</b></a>
63 <!-- *********************************************************************** -->
65 <div class="doc_text">
67 <p>Welcome to LLVM! In order to get started, you first need to know some
68 basic information.</p>
70 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
71 contains all of the tools, libraries, and header files needed to use the low
72 level virtual machine. It contains an assembler, disassembler, bytecode
73 analyzer, and bytecode optimizer. It also contains a test suite that can be
74 used to test the LLVM tools and the GCC front end.</p>
76 <p>The second piece is the GCC front end. This component provides a version of
77 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
78 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
79 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
80 from the LLVM suite.</p>
84 <!-- *********************************************************************** -->
85 <div class="doc_section">
86 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
88 <!-- *********************************************************************** -->
90 <div class="doc_text">
92 <p>Here's the short story for getting up and running quickly with LLVM:</p>
95 <li>Install the GCC front end:
97 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
98 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
99 <li><b>Sparc Only:</b><br>
100 <tt>cd cfrontend/sparc<br>
104 <li>Get the Source Code
106 <li>With the distributed files:
108 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
109 <li><tt>gunzip --stdout llvm.tar.gz | tar -xvf -</tt>
113 <li>With anonymous CVS access:
115 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
117 :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt></li>
118 <li>Hit the return key when prompted for the password.
119 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm
121 <li><tt>cd llvm</tt></li>
125 <li>Configure the LLVM Build Environment
127 <li>Change directory to where you want to store the LLVM object
128 files and run <tt>configure</tt> to configure the Makefiles and
129 header files for the default platform. Useful options include:
131 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
132 <p>Specify where the LLVM GCC frontend is installed.</p></li>
133 <li><tt>--enable-spec2000=<i>directory</i></tt>
134 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
135 benchmarks should be available in
136 <tt><i>directory</i></tt>.</p></li>
140 <li>Build the LLVM Suite:
142 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.
143 <li><tt>gmake -k |& tee gnumake.out
144 # this is csh or tcsh syntax</tt>
149 <p>Consult the <a href="starting">Getting Started with LLVM</a> section for
150 detailed information on configuring and compiling LLVM. See <a
151 href="#environment">Setting Up Your Environment</a> for tips that simplify
152 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
153 Layout</a> to learn about the layout of the source code tree.</p>
157 <!-- *********************************************************************** -->
158 <div class="doc_section">
159 <a name="requirements"><b>Requirements</b></a>
161 <!-- *********************************************************************** -->
163 <div class="doc_text">
165 <p>Before you begin to use the LLVM system, review the requirements given below.
166 This may save you some trouble by knowing ahead of time what hardware and
167 software you will need.</p>
171 <!-- ======================================================================= -->
172 <div class="doc_subsection">
173 <a name="hardware"><b>Hardware</b></a>
176 <div class="doc_text">
178 <p>LLVM is known to work on the following platforms:</p>
182 <li>Linux on x86 (Pentium and above)
184 <li>Approximately 760 MB of Free Disk Space
186 <li>Source code: 30 MB</li>
187 <li>Object code: 670 MB</li>
188 <li>GCC front end: 60 MB</li>
192 <li>Solaris on SparcV9 (Ultrasparc)
194 <li>Approximately 1.24 GB of Free Disk Space
196 <li>Source code: 30 MB</li>
197 <li>Object code: 1000 MB</li>
198 <li>GCC front end: 210 MB</li>
204 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
205 guaranteed to do so. If compilation is successful, the LLVM utilities should be
206 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
207 generation should work as well, although the generated native code may not work
208 on your platform.</p>
210 <p>The GCC front end is not very portable at the moment. If you want to get it
211 to work on another platform, you can download a copy of the source and try to
212 compile it on your platform.</p>
216 <!-- ======================================================================= -->
217 <div class="doc_subsection">
218 <a name="software"><b>Software</b></a>
221 <div class="doc_text">
223 <p>Compiling LLVM requires that you have several software packages
227 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
230 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
232 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
234 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
237 <p>There are some additional tools that you may want to have when working with
241 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A>
242 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
244 <p>If you want to make changes to the configure scripts, you will need GNU
245 autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
248 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest</A></li>
249 <li><A href="http://www.python.org">Python</A>
251 <p>These are needed to use the LLVM test suite.</p></li>
256 <p>The remainder of this guide is meant to get you up and running with
257 LLVM and to give you some basic information about the LLVM environment.
258 A <a href="#starting">complete guide to installation</a> is provided in the
261 <p>The later sections of this guide describe the <a
262 href="#layout">general layout</a> of the the LLVM source tree, a <a
263 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
264 href="#links">links</a> to find more information about LLVM or to get
269 <!-- *********************************************************************** -->
270 <div class="doc_section">
271 <a name="starting"><b>Getting Started with LLVM</b></a>
273 <!-- *********************************************************************** -->
275 <!-- ======================================================================= -->
276 <div class="doc_subsection">
277 <a name="terminology">Terminology and Notation</a>
280 <div class="doc_text">
282 <p>Throughout this manual, the following names are used to denote paths
283 specific to the local system and working environment. <i>These are not
284 environment variables you need to set but just strings used in the rest
285 of this document below</i>. In any of the examples below, simply replace
286 each of these names with the appropriate pathname on your local system.
287 All these paths are absolute:</p>
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>.
312 <!-- ======================================================================= -->
313 <div class="doc_subsection">
314 <a name="environment">Setting Up Your Environment</a>
317 <div class="doc_text">
320 In order to compile and use LLVM, you will need to set some environment
321 variables. There are also some shell aliases which you may find useful.
322 You can set these on the command line, or better yet, set them in your
323 <tt>.cshrc</tt> or <tt>.profile</tt>.
326 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
328 This environment variable helps the LLVM GCC front end find bytecode
329 libraries that it will need for compilation.
332 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
333 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
335 This alias allows you to use the LLVM C and C++ front ends without putting
336 them in your <tt>PATH</tt> or typing in their complete pathnames.
341 <!-- ======================================================================= -->
342 <div class="doc_subsection">
343 <a name="unpack">Unpacking the LLVM Archives</a></h3>
346 <div class="doc_text">
349 If you have the LLVM distribution, you will need to unpack it before you
350 can begin to compile it. LLVM is distributed as a set of three files. Each
351 file is a TAR archive that is compressed with the gzip program.
354 <p> The three files are as follows:
357 <dd>This is the source code to the LLVM suite.
360 <dt>cfrontend.sparc.tar.gz
361 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
364 <dt>cfrontend.x86.tar.gz
365 <dd>This is the binary release of the GCC front end for Linux/x86.
370 <!-- ======================================================================= -->
371 <div class="doc_subsection">
372 <a name="checkout">Checkout LLVM from CVS</a></h3>
375 <div class="doc_text">
377 <p>If you have access to our CVS repository, you can get a fresh copy of
378 the entire source code. All you need to do is check it out from CVS as
382 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
383 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
384 <li>Hit the return key when prompted for the password.
385 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
389 <p>This will create an '<tt>llvm</tt>' directory in the current
390 directory and fully populate it with the LLVM source code, Makefiles,
391 test directories, and local copies of documentation files.</p>
393 <p>Note that the GCC front end is not included in the CVS repository. You
394 should have downloaded the binary distribution for your platform.</p>
398 <!-- ======================================================================= -->
399 <div class="doc_subsection">
400 <a name="installcf">Install the GCC Front End</a></h3>
403 <div class="doc_text">
405 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
406 GCC front end from the binary distribution. It is used for building the
407 bytecode libraries later used by the GCC front end for linking programs, and its
408 location must be specified when the LLVM suite is configured.</p>
410 <p>To install the GCC front end, do the following:</p>
413 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
414 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf
418 <p>If you are on a Sparc/Solaris machine, you will need to fix the header
421 <p><tt>cd cfrontend/sparc<br>
422 ./fixheaders</tt></p>
424 <p>The binary versions of the GCC front end may not suit all of your needs. For
425 example, the binary distribution may include an old version of a system header
426 file, not "fix" a header file that needs to be fixed for GCC, or it may be
427 linked with libraries not available on your system.</p>
429 <p>In cases like these, you may want to try <a
430 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
431 not for the faint of heart, so be forewarned.</p>
435 <!-- ======================================================================= -->
436 <div class="doc_subsection">
437 <a name="config">Local LLVM Configuration</a>
440 <div class="doc_text">
442 <p>Once checked out from the CVS repository, the LLVM suite source code must be
443 configured via the <tt>configure</tt> script. This script sets variables in
444 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
445 also populates <i>OBJ_ROOT</i> with the Makefiles needed to build LLVM.</p>
447 <p>The following environment variables are used by the <tt>configure</tt>
448 script to configure the build system:</p>
458 <td>Tells <tt>configure</tt> which C compiler to use. By default,
459 <tt>configure</tt> will look for the first GCC C compiler in
460 <tt>PATH</tt>. Use this variable to override
461 <tt>configure</tt>'s default behavior.</td>
466 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
467 <tt>configure</tt> will look for the first GCC C++ compiler in
468 <tt>PATH</tt>. Use this variable to override
469 <tt>configure</tt>'s default behavior.</td>
473 <p>The following options can be used to set or enable LLVM specific options:</p>
476 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
478 Path to the location where the LLVM C front end binaries and
479 associated libraries will be installed.
481 <dt><i>--enable-optimized</i>
483 Enables optimized compilation by default (debugging symbols are removed
484 and GCC optimization flags are enabled). The default is to use an
485 unoptimized build (also known as a debug build).
487 <dt><i>--enable-jit</i>
489 Compile the Just In Time (JIT) functionality. This is not available
490 on all platforms. The default is dependent on platform, so it is best
491 to explicitly enable it if you want it.
493 <dt><i>--enable-spec2000</i>
494 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
496 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
497 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
498 <tt>directory</tt>, you can tell configure where to find the SPEC2000
499 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
500 uses the default value
501 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
504 <p>To configure LLVM, follow these steps:</p>
507 <li>Change directory into the object root directory:
509 <tt>cd <i>OBJ_ROOT</i></tt>
512 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
514 <tt><i>SRC_ROOT</i>/configure</tt>
518 <p>In addition to running <tt>configure</tt>, you must set the
519 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
520 This environment variable is used to locate "system" libraries like
521 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
522 the absolute path for the bytecode-libs subdirectory of the GCC front end
523 install, or <i>LLVMGCCDIR</i>/bytecode-libs. For example, one might set
524 <tt>LLVM_LIB_SEARCH_PATH</tt> to
525 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the X86
526 version of the GCC front end on our research machines.</p>
530 <!-- ======================================================================= -->
531 <div class="doc_subsection">
532 <a name="compile">Compiling the LLVM Suite Source Code</a>
535 <div class="doc_text">
537 <p>Once you have configured LLVM, you can build it. There are three types of
543 These builds are the default when one types <tt>gmake</tt> (unless the
544 <tt>--enable-optimized</tt> option was used during configuration). The
545 build system will compile the tools and libraries with debugging
549 <dt>Release (Optimized) Builds
551 These builds are enabled with the <tt>--enable-optimized</tt> option to
552 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
553 <tt>gmake</tt> command line. For these builds, the build system will
554 compile the tools and libraries with GCC optimizations enabled and strip
555 debugging information from the libraries and executables it generates.
560 These builds are for use with profiling. They compile profiling
561 information into the code for use with programs like <tt>gprof</tt>.
562 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
563 on the <tt>gmake</tt> command line.
566 <p>Once you have LLVM configured, you can build it by entering the
567 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
569 <p><tt>gmake</tt></p>
571 <p>If you have multiple processors in your machine, you may wish to use some of
572 the parallel build options provided by GNU Make. For example, you could use the
575 <p><tt>gmake -j2</tt></p>
577 <p>There are several special targets which are useful when working with the LLVM
581 <dt><tt>gmake clean</tt>
583 Removes all files generated by the build. This includes object files,
584 generated C/C++ files, libraries, and executables.
587 <dt><tt>gmake distclean</tt>
589 Removes everything that <tt>gmake clean</tt> does, but also removes
590 files generated by <tt>configure</tt>. It attempts to return the
591 source tree to the original state in which it was shipped.
594 <dt><tt>gmake install</tt>
596 Installs LLVM files into the proper location. For the most part,
597 this does nothing, but it does install bytecode libraries into the
598 GCC front end's bytecode library directory. If you need to update
599 your bytecode libraries, this is the target to use once you've built
604 <p>It is also possible to override default values from <tt>configure</tt> by
605 declaring variables on the command line. The following are some examples:</p>
608 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
610 Perform a Release (Optimized) build.
613 <dt><tt>gmake ENABLE_PROFILING=1</tt>
615 Perform a Profiling build.
618 <dt><tt>gmake VERBOSE=1</tt>
620 Print what <tt>gmake</tt> is doing on standard output.
624 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
625 it and any subdirectories that it contains. Entering any directory inside the
626 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
627 that directory that is out of date.</p>
631 <!-- ======================================================================= -->
632 <div class="doc_subsection">
633 <a name="objfiles">The Location of LLVM Object Files</a>
636 <div class="doc_text">
638 <p>The LLVM build system is capable of sharing a single LLVM source tree among
639 several LLVM builds. Hence, it is possible to build LLVM for several different
640 platforms or configurations using the same source tree.</p>
642 <p>This is accomplished in the typical autoconf manner:</p>
645 <li><p>Change directory to where the LLVM object files should live:</p>
647 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
649 <li><p>Run the <tt>configure</tt> script found in the LLVM source
652 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
655 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
656 named after the build type:</p>
663 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
665 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
673 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
675 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
683 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
685 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
691 <!-- *********************************************************************** -->
692 <div class="doc_section">
693 <a name="layout"><b>Program Layout</b></a>
695 <!-- *********************************************************************** -->
697 <div class="doc_text">
699 <p>One useful source of information about the LLVM source base is the LLVM <a
700 href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a
701 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
702 The following is a brief introduction to code layout:</p>
706 <!-- ======================================================================= -->
707 <div class="doc_subsection">
708 <a name="cvsdir"><tt>CVS</tt> directories</a>
711 <div class="doc_text">
713 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
714 the most part these can just be ignored.</p>
718 <!-- ======================================================================= -->
719 <div class="doc_subsection">
720 <a name="include"><tt>llvm/include</tt></a>
723 <div class="doc_text">
725 <p>This directory contains public header files exported from the LLVM
726 library. The three main subdirectories of this directory are:</p>
729 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
730 specific header files. This directory also has subdirectories for
731 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
732 <tt>Target</tt>, <tt>Transforms</tt>, etc...</li>
734 <li><tt>llvm/include/Support</tt> - This directory contains generic
735 support libraries that are independent of LLVM, but are used by LLVM.
736 For example, some C++ STL utilities and a Command Line option processing
737 library store their header files here.</li>
739 <li><tt>llvm/include/Config</tt> - This directory contains header files
740 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
741 and C header files. Source code can include these header files which
742 automatically take care of the conditional #includes that the
743 <tt>configure</tt> script generates.</li>
748 <!-- ======================================================================= -->
749 <div class="doc_subsection">
750 <a name="lib"><tt>llvm/lib</tt></a>
753 <div class="doc_text">
755 <p>This directory contains most of the source files of the LLVM system. In LLVM,
756 almost all code exists in libraries, making it very easy to share code among the
757 different <a href="#tools">tools</a>.</p>
760 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
761 source files that implement core classes like Instruction and BasicBlock.
763 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
764 for the LLVM assembly language parser library.
766 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
767 and write LLVM bytecode.
769 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
772 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
773 different program analyses, such as Dominator Information, Call Graphs,
774 Induction Variables, Interval Identification, Natural Loop Identification,
777 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
778 code for the LLVM to LLVM program transformations, such as Aggressive Dead
779 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
780 Invariant Code Motion, Dead Global Elimination, and many others...
782 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
783 describe various target architectures for code generation. For example,
784 the llvm/lib/Target/Sparc directory holds the Sparc machine
787 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
788 of the code generator: Instruction Selector, Instruction Scheduling, and
791 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
792 that corresponds to the header files located in
793 <tt>llvm/include/Support/</tt>.
798 <!-- ======================================================================= -->
799 <div class="doc_subsection">
800 <a name="runtime"><tt>llvm/runtime</tt></a>
803 <div class="doc_text">
805 <p>This directory contains libraries which are compiled into LLVM bytecode and
806 used when linking programs with the GCC front end. Most of these libraries are
807 skeleton versions of real libraries; for example, libc is a stripped down
808 version of glibc.</p>
810 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
815 <!-- ======================================================================= -->
816 <div class="doc_subsection">
817 <a name="test"><tt>llvm/test</tt></a>
820 <div class="doc_text">
822 <p>This directory contains regression tests and source code that is used to test
823 the LLVM infrastructure.</p>
827 <!-- ======================================================================= -->
828 <div class="doc_subsection">
829 <a name="tools"><tt>llvm/tools</tt></a>
832 <div class="doc_text">
834 <p>The <b>tools</b> directory contains the executables built out of the
835 libraries above, which form the main part of the user interface. You can
836 always get help for a tool by typing <tt>tool_name --help</tt>. The
837 following is a brief introduction to the most important tools.</p>
842 <dt><tt><b>analyze</b></tt><dd> <tt>analyze</tt> is used to run a specific
843 analysis on an input LLVM bytecode file and print out the results. It is
844 primarily useful for debugging analyses, or familiarizing yourself with
845 what an analysis does.<p>
847 <dt><tt><b>bugpoint</b></tt><dd> <tt>bugpoint</tt> is used to debug
848 optimization passes or code generation backends by narrowing down the
849 given test case to the minimum number of passes and/or instructions that
850 still cause a problem, whether it is a crash or miscompilation. See <a
851 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
852 on using <tt>bugpoint</tt>.<p>
854 <dt><tt><b>llvm-ar</b></tt><dd>The archiver produces an archive containing
855 the given LLVM bytecode files, optionally with an index for faster
858 <dt><tt><b>llvm-as</b></tt><dd>The assembler transforms the human readable
859 LLVM assembly to LLVM bytecode.<p>
861 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
862 bytecode to human readable LLVM assembly. Additionally, it can convert
863 LLVM bytecode to C, which is enabled with the <tt>-c</tt> option.<p>
865 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
866 links multiple LLVM modules into a single program.<p>
868 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
869 can directly execute LLVM bytecode (although very slowly...). In addition
870 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
871 specifying <tt>-trace</tt> on the command line). Finally, for
872 architectures that support it (currently only x86 and Sparc), by default,
873 <tt>lli</tt> will function as a Just-In-Time compiler (if the
874 functionality was compiled in), and will execute the code <i>much</i>
875 faster than the interpreter.<p>
877 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler,
878 which translates LLVM bytecode to a SPARC or x86 assembly file.<p>
880 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
881 that has been retargeted to emit LLVM code as the machine code output. It
882 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
883 -o</tt> options that are typically used. The source code for the
884 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
885 because it is quite large and not very interesting.<p>
888 <dt><tt><b>gccas</b></tt><dd> This tool is invoked by the
889 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
890 tool actually assembles LLVM assembly to LLVM bytecode,
891 performs a variety of optimizations, and outputs LLVM bytecode. Thus
892 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
893 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
894 an LLVM bytecode file that can be disassembled or manipulated just like
895 any other bytecode file). The command line interface to <tt>gccas</tt>
896 is designed to be as close as possible to the <b>system</b>
897 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
898 modified to interface to a "weird" assembler.<p>
900 <dt><tt><b>gccld</b></tt><dd> <tt>gccld</tt> links together several LLVM
901 bytecode files into one bytecode file and does some optimization. It is
902 the linker invoked by the GCC frontend when multiple .o files need to be
903 linked together. Like <tt>gccas</tt>, the command line interface of
904 <tt>gccld</tt> is designed to match the system linker, to aid
905 interfacing with the GCC frontend.<p>
908 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
909 series of LLVM to LLVM transformations (which are specified on the command
910 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
911 command is a good way to get a list of the program transformations
912 available in LLVM.<p>
918 <!-- ======================================================================= -->
919 <div class="doc_subsection">
920 <a name="utils"><tt>llvm/utils</tt></a>
923 <div class="doc_text">
925 <p>This directory contains utilities for working with LLVM source code, and some
926 of the utilities are actually required as part of the build process because they
927 are code generators for parts of LLVM infrastructure.</p>
930 <td><tt><b>Burg/</b></tt><dd> <tt>Burg</tt> is an instruction selector
931 generator -- it builds trees on which it then performs pattern-matching to
932 select instructions according to the patterns the user has specified. Burg
933 is currently used in the Sparc V9 backend.<p>
935 <dt><tt><b>codegen-diff</b></tt><dd> <tt>codegen-diff</tt> is a script
936 that finds differences between code that LLC generates and code that LLI
937 generates. This is a useful tool if you are debugging one of them,
938 assuming that the other generates correct output. For the full user
939 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
941 <dt><tt><b>cvsupdate</b></tt><dd> <tt>cvsupdate</tt> is a script that will
942 update your CVS tree, but produce a much cleaner and more organized output
943 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
944 together all the new and updated files and modified files in separate
945 sections, so you can see at a glance what has changed. If you are at the
946 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
947 preferred way of updating the tree.<p>
949 <dt><tt><b>emacs/</b></tt><dd> The <tt>emacs</tt> directory contains
950 syntax-highlighting files which will work with Emacs and XEmacs editors,
951 providing syntax highlighting support for LLVM assembly files and TableGen
952 description files. For information on how to use the syntax files, consult
953 the <tt>README</tt> file in that directory.<p>
955 <dt><tt><b>getsrcs.sh</b></tt><dd> The <tt>getsrcs.sh</tt> script finds
956 and outputs all non-generated source files, which is useful if one wishes
957 to do a lot of development across directories and does not want to
958 individually find each file. One way to use it is to run, for example:
959 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
962 <dt><tt><b>makellvm</b></tt><dd> The <tt>makellvm</tt> script compiles all
963 files in the current directory and then compiles and links the tool that
964 is the first argument. For example, assuming you are in the directory
965 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
966 simply running <tt>makellvm llc</tt> will make a build of the current
967 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
968 causing a re-linking of LLC.<p>
970 <dt><tt><b>NightlyTest.pl</b></tt> and
971 <tt><b>NightlyTestTemplate.html</b></tt><dd> These files are used in a
972 cron script to generate nightly status reports of the functionality of
973 tools, and the results can be seen by following the appropriate link on
974 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
976 <dt><tt><b>TableGen/</b></tt><dd> The <tt>TableGen</tt> directory contains
977 the tool used to generate register descriptions, instruction set
978 descriptions, and even assemblers from common TableGen description
981 <dt><tt><b>vim/</b></tt><dd> The <tt>vim</tt> directory contains
982 syntax-highlighting files which will work with the VIM editor, providing
983 syntax highlighting support for LLVM assembly files and TableGen
984 description files. For information on how to use the syntax files, consult
985 the <tt>README</tt> file in that directory.<p>
991 <!-- *********************************************************************** -->
992 <div class="doc_section">
993 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
995 <!-- *********************************************************************** -->
997 <div class="doc_text">
1000 <li>First, create a simple C file, name it 'hello.c':
1002 #include <stdio.h>
1004 printf("hello world\n");
1009 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1010 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1012 <p>This will create two result files: <tt>hello</tt> and
1013 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1014 corresponds the the compiled program and the library facilities that it
1015 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1016 file with <tt>lli</tt>, making the result directly executable.</p></li>
1018 <li><p>Run the program. To make sure the program ran, execute one of the
1019 following commands:</p>
1021 <p><tt>% ./hello</tt></p>
1025 <p><tt>% lli hello.bc</tt></p></li>
1027 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1030 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1032 <li><p>Compile the program to native Sparc assembly using the code
1033 generator (assuming you are currently on a Sparc system):</p>
1035 <p><tt>% llc hello.bc -o hello.s</tt></p>
1037 <li><p>Assemble the native sparc assemble file into a program:</p>
1039 <p><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt></p>
1041 <li><p>Execute the native sparc program:</p>
1043 <p><tt>% ./hello.sparc</tt></p></li>
1049 <!-- *********************************************************************** -->
1050 <div class="doc_section">
1051 <a name="problems">Common Problems</a>
1053 <!-- *********************************************************************** -->
1055 <div class="doc_text">
1057 <p>If you are having problems building or using LLVM, or if you have any other
1058 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1059 Asked Questions</a> page.</p>
1063 <!-- *********************************************************************** -->
1064 <div class="doc_section">
1065 <a name="links">Links</a>
1067 <!-- *********************************************************************** -->
1069 <div class="doc_text">
1071 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1072 some simple things... there are many more interesting and complicated things
1073 that you can do that aren't documented here (but we'll gladly accept a patch
1074 if you want to write something up!). For more information about LLVM, check
1078 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1079 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1080 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1081 that Uses LLVM</a></li>
1086 <!-- *********************************************************************** -->
1089 <div class="doc_footer">
1090 <address><a href="mailto:sabre@nondot.org">Chris Lattner</a></address>
1091 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a>
1093 Last modified: $Date$