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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 the full pathname of where the LLVM GCC frontend is
134 <li><tt>--enable-spec2000=<i>directory</i></tt>
135 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
136 benchmarks should be available in
137 <tt><i>directory</i></tt>.</p></li>
141 <li>Build the LLVM Suite:
143 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.
144 <li><tt>gmake -k |& tee gnumake.out
145 # this is csh or tcsh syntax</tt>
150 <p>Consult the <a href="starting">Getting Started with LLVM</a> section for
151 detailed information on configuring and compiling LLVM. See <a
152 href="#environment">Setting Up Your Environment</a> for tips that simplify
153 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
154 Layout</a> to learn about the layout of the source code tree.</p>
158 <!-- *********************************************************************** -->
159 <div class="doc_section">
160 <a name="requirements"><b>Requirements</b></a>
162 <!-- *********************************************************************** -->
164 <div class="doc_text">
166 <p>Before you begin to use the LLVM system, review the requirements given below.
167 This may save you some trouble by knowing ahead of time what hardware and
168 software you will need.</p>
172 <!-- ======================================================================= -->
173 <div class="doc_subsection">
174 <a name="hardware"><b>Hardware</b></a>
177 <div class="doc_text">
179 <p>LLVM is known to work on the following platforms:</p>
183 <li>Linux on x86 (Pentium and above)
185 <li>Approximately 918 MB of Free Disk Space
187 <li>Source code: 28 MB</li>
188 <li>Object code: 850 MB</li>
189 <li>GCC front end: 40 MB</li>
194 <li>Solaris on SparcV9 (Ultrasparc)
196 <li>Approximately 1.52 GB of Free Disk Space
198 <li>Source code: 28 MB</li>
199 <li>Object code: 1470 MB</li>
200 <li>GCC front end: 50 MB</li>
205 <li>FreeBSD on x86 (Pentium and above)
207 <li>Approximately 918 MB of Free Disk Space
209 <li>Source code: 28 MB</li>
210 <li>Object code: 850 MB</li>
211 <li>GCC front end: 40 MB</li>
216 <li>MacOS X on PowerPC
218 <li>No native code generation
219 <li>Approximately 1.20 GB of Free Disk Space
221 <li>Source code: 28 MB</li>
222 <li>Object code: 1160 MB</li>
223 <li>GCC front end: 40 MB</li>
230 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
231 guaranteed to do so. If compilation is successful, the LLVM utilities should be
232 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
233 generation should work as well, although the generated native code may not work
234 on your platform.</p>
236 <p>The GCC front end is not very portable at the moment. If you want to get it
237 to work on another platform, you can download a copy of the source and try to
238 compile it on your platform.</p>
242 <!-- ======================================================================= -->
243 <div class="doc_subsection">
244 <a name="software"><b>Software</b></a>
247 <div class="doc_text">
249 <p>Compiling LLVM requires that you have several software packages
253 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
256 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
258 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
260 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
263 <p>There are some additional tools that you may want to have when working with
267 <li><A href="http://www.gnu.org/software/automake">GNU Automake</A></li>
268 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A></li>
269 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
271 <p>If you want to make changes to the configure scripts, you will need GNU
272 autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
273 higher). You will also need automake. Any old version of
274 automake from 1.4p5 on should work; we only use aclocal from that
277 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest</A></li>
278 <li><A href="http://www.python.org">Python</A>
280 <p>These are needed to use the LLVM test suite.</p></li>
284 <p>The remainder of this guide is meant to get you up and running with
285 LLVM and to give you some basic information about the LLVM environment.
286 A <a href="#starting">complete guide to installation</a> is provided in the
289 <p>The later sections of this guide describe the <a
290 href="#layout">general layout</a> of the the LLVM source tree, a <a
291 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
292 href="#links">links</a> to find more information about LLVM or to get
297 <!-- *********************************************************************** -->
298 <div class="doc_section">
299 <a name="starting"><b>Getting Started with LLVM</b></a>
301 <!-- *********************************************************************** -->
303 <!-- ======================================================================= -->
304 <div class="doc_subsection">
305 <a name="terminology">Terminology and Notation</a>
308 <div class="doc_text">
310 <p>Throughout this manual, the following names are used to denote paths
311 specific to the local system and working environment. <i>These are not
312 environment variables you need to set but just strings used in the rest
313 of this document below</i>. In any of the examples below, simply replace
314 each of these names with the appropriate pathname on your local system.
315 All these paths are absolute:</p>
320 This is the top level directory of the LLVM source tree.
325 This is the top level directory of the LLVM object tree (i.e. the
326 tree where object files and compiled programs will be placed. It
327 can be the same as SRC_ROOT).
332 This is the where the LLVM GCC Front End is installed.
334 For the pre-built GCC front end binaries, the LLVMGCCDIR is
335 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
340 <!-- ======================================================================= -->
341 <div class="doc_subsection">
342 <a name="environment">Setting Up Your Environment</a>
345 <div class="doc_text">
348 In order to compile and use LLVM, you will need to set some environment
349 variables. There are also some shell aliases which you may find useful.
350 You can set these on the command line, or better yet, set them in your
351 <tt>.cshrc</tt> or <tt>.profile</tt>.
354 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
356 This environment variable helps the LLVM GCC front end find bytecode
357 libraries that it will need for compilation.
360 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
361 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
363 This alias allows you to use the LLVM C and C++ front ends without putting
364 them in your <tt>PATH</tt> or typing in their complete pathnames.
369 <!-- ======================================================================= -->
370 <div class="doc_subsection">
371 <a name="unpack">Unpacking the LLVM Archives</a>
374 <div class="doc_text">
377 If you have the LLVM distribution, you will need to unpack it before you
378 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
379 suite and the LLVM GCC front end compiled for your platform. Each
380 file is a TAR archive that is compressed with the gzip program.
383 <p> The files are as follows:
386 <dd>This is the source code to the LLVM suite.
389 <dt>cfrontend-1.1.sparc-sun-solaris2.8.tar.gz
390 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
393 <dt>cfrontend-1.1.i686-redhat-linux-gnu.tar.gz
394 <dd>This is the binary release of the GCC front end for Linux/x86.
397 <dt>cfrontend-1.1.i386-unknown-freebsd5.1.tar.gz
398 <dd>This is the binary release of the GCC front end for FreeBSD/x86.
401 <dt>cfrontend-1.1.powerpc-apple-darwin7.0.0.tar.gz
402 <dd>This is the binary release of the GCC front end for MacOS X/PPC.
407 <!-- ======================================================================= -->
408 <div class="doc_subsection">
409 <a name="checkout">Checkout LLVM from CVS</a>
412 <div class="doc_text">
414 <p>If you have access to our CVS repository, you can get a fresh copy of
415 the entire source code. All you need to do is check it out from CVS as
419 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
420 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
421 <li>Hit the return key when prompted for the password.
422 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
426 <p>This will create an '<tt>llvm</tt>' directory in the current
427 directory and fully populate it with the LLVM source code, Makefiles,
428 test directories, and local copies of documentation files.</p>
430 <p>If you want to get a specific release (as opposed to the most recent
431 revision), you can specify a label. The following releases have the following
436 Release 1.1: <b>RELEASE_11</b>
440 Release 1.0: <b>RELEASE_1</b>
444 <p>Note that the GCC front end is not included in the CVS repository. You
445 should have downloaded the binary distribution for your platform.</p>
449 <!-- ======================================================================= -->
450 <div class="doc_subsection">
451 <a name="installcf">Install the GCC Front End</a>
454 <div class="doc_text">
456 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
457 GCC front end from the binary distribution. It is used for building the
458 bytecode libraries later used by the GCC front end for linking programs, and its
459 location must be specified when the LLVM suite is configured.</p>
461 <p>To install the GCC front end, do the following:</p>
464 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
465 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
469 <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
472 <p><tt>cd cfrontend/sparc<br>
473 ./fixheaders</tt></p>
475 <p>The binary versions of the GCC front end may not suit all of your needs. For
476 example, the binary distribution may include an old version of a system header
477 file, not "fix" a header file that needs to be fixed for GCC, or it may be
478 linked with libraries not available on your system.</p>
480 <p>In cases like these, you may want to try <a
481 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
482 not for the faint of heart, so be forewarned.</p>
486 <!-- ======================================================================= -->
487 <div class="doc_subsection">
488 <a name="config">Local LLVM Configuration</a>
491 <div class="doc_text">
493 <p>Once checked out from the CVS repository, the LLVM suite source code must be
494 configured via the <tt>configure</tt> script. This script sets variables in
495 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
496 also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
499 <p>The following environment variables are used by the <tt>configure</tt>
500 script to configure the build system:</p>
510 <td>Tells <tt>configure</tt> which C compiler to use. By default,
511 <tt>configure</tt> will look for the first GCC C compiler in
512 <tt>PATH</tt>. Use this variable to override
513 <tt>configure</tt>'s default behavior.</td>
518 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
519 <tt>configure</tt> will look for the first GCC C++ compiler in
520 <tt>PATH</tt>. Use this variable to override
521 <tt>configure</tt>'s default behavior.</td>
525 <p>The following options can be used to set or enable LLVM specific options:</p>
528 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
530 Path to the location where the LLVM C front end binaries and
531 associated libraries were installed. This must be specified as an
534 <dt><i>--enable-optimized</i>
536 Enables optimized compilation by default (debugging symbols are removed
537 and GCC optimization flags are enabled). The default is to use an
538 unoptimized build (also known as a debug build).
540 <dt><i>--enable-jit</i>
542 Compile the Just In Time (JIT) compiler functionality. This is not
544 on all platforms. The default is dependent on platform, so it is best
545 to explicitly enable it if you want it.
547 <dt><i>--enable-spec2000</i>
548 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
550 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
551 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
552 <tt>directory</tt>, you can tell configure where to find the SPEC2000
553 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
554 uses the default value
555 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
558 <p>To configure LLVM, follow these steps:</p>
561 <li>Change directory into the object root directory:
563 <tt>cd <i>OBJ_ROOT</i></tt>
566 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
568 <tt><i>SRC_ROOT</i>/configure</tt>
572 <p>In addition to running <tt>configure</tt>, you must set the
573 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
574 This environment variable is used to locate "system" libraries like
575 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
576 the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
577 end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
578 <tt>LLVM_LIB_SEARCH_PATH</tt> to
579 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
580 version of the GCC front end on our research machines.</p>
584 <!-- ======================================================================= -->
585 <div class="doc_subsection">
586 <a name="compile">Compiling the LLVM Suite Source Code</a>
589 <div class="doc_text">
591 <p>Once you have configured LLVM, you can build it. There are three types of
597 These builds are the default when one types <tt>gmake</tt> (unless the
598 <tt>--enable-optimized</tt> option was used during configuration). The
599 build system will compile the tools and libraries with debugging
603 <dt>Release (Optimized) Builds
605 These builds are enabled with the <tt>--enable-optimized</tt> option to
606 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
607 <tt>gmake</tt> command line. For these builds, the build system will
608 compile the tools and libraries with GCC optimizations enabled and strip
609 debugging information from the libraries and executables it generates.
614 These builds are for use with profiling. They compile profiling
615 information into the code for use with programs like <tt>gprof</tt>.
616 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
617 on the <tt>gmake</tt> command line.
620 <p>Once you have LLVM configured, you can build it by entering the
621 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
623 <p><tt>gmake</tt></p>
625 <p>If you have multiple processors in your machine, you may wish to use some of
626 the parallel build options provided by GNU Make. For example, you could use the
629 <p><tt>gmake -j2</tt></p>
631 <p>There are several special targets which are useful when working with the LLVM
635 <dt><tt>gmake clean</tt>
637 Removes all files generated by the build. This includes object files,
638 generated C/C++ files, libraries, and executables.
641 <dt><tt>gmake distclean</tt>
643 Removes everything that <tt>gmake clean</tt> does, but also removes
644 files generated by <tt>configure</tt>. It attempts to return the
645 source tree to the original state in which it was shipped.
648 <dt><tt>gmake install</tt>
650 Installs LLVM files into the proper location. For the most part,
651 this does nothing, but it does install bytecode libraries into the
652 GCC front end's bytecode library directory. If you need to update
653 your bytecode libraries, this is the target to use once you've built
658 <p>It is also possible to override default values from <tt>configure</tt> by
659 declaring variables on the command line. The following are some examples:</p>
662 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
664 Perform a Release (Optimized) build.
667 <dt><tt>gmake ENABLE_PROFILING=1</tt>
669 Perform a Profiling build.
672 <dt><tt>gmake VERBOSE=1</tt>
674 Print what <tt>gmake</tt> is doing on standard output.
678 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
679 it and any subdirectories that it contains. Entering any directory inside the
680 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
681 that directory that is out of date.</p>
685 <!-- ======================================================================= -->
686 <div class="doc_subsection">
687 <a name="objfiles">The Location of LLVM Object Files</a>
690 <div class="doc_text">
692 <p>The LLVM build system is capable of sharing a single LLVM source tree among
693 several LLVM builds. Hence, it is possible to build LLVM for several different
694 platforms or configurations using the same source tree.</p>
696 <p>This is accomplished in the typical autoconf manner:</p>
699 <li><p>Change directory to where the LLVM object files should live:</p>
701 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
703 <li><p>Run the <tt>configure</tt> script found in the LLVM source
706 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
709 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
710 named after the build type:</p>
717 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
719 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
727 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
729 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
737 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
739 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
745 <!-- *********************************************************************** -->
746 <div class="doc_section">
747 <a name="layout"><b>Program Layout</b></a>
749 <!-- *********************************************************************** -->
751 <div class="doc_text">
753 <p>One useful source of information about the LLVM source base is the LLVM <a
754 href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a
755 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
756 The following is a brief introduction to code layout:</p>
760 <!-- ======================================================================= -->
761 <div class="doc_subsection">
762 <a name="cvsdir"><tt>CVS</tt> directories</a>
765 <div class="doc_text">
767 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
768 the most part these can just be ignored.</p>
772 <!-- ======================================================================= -->
773 <div class="doc_subsection">
774 <a name="include"><tt>llvm/include</tt></a>
777 <div class="doc_text">
779 <p>This directory contains public header files exported from the LLVM
780 library. The three main subdirectories of this directory are:</p>
783 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
784 specific header files. This directory also has subdirectories for
785 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
786 <tt>Target</tt>, <tt>Transforms</tt>, etc...</li>
788 <li><tt>llvm/include/Support</tt> - This directory contains generic
789 support libraries that are independent of LLVM, but are used by LLVM.
790 For example, some C++ STL utilities and a Command Line option processing
791 library store their header files here.</li>
793 <li><tt>llvm/include/Config</tt> - This directory contains header files
794 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
795 and C header files. Source code can include these header files which
796 automatically take care of the conditional #includes that the
797 <tt>configure</tt> script generates.</li>
802 <!-- ======================================================================= -->
803 <div class="doc_subsection">
804 <a name="lib"><tt>llvm/lib</tt></a>
807 <div class="doc_text">
809 <p>This directory contains most of the source files of the LLVM system. In LLVM,
810 almost all code exists in libraries, making it very easy to share code among the
811 different <a href="#tools">tools</a>.</p>
814 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
815 source files that implement core classes like Instruction and BasicBlock.
817 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
818 for the LLVM assembly language parser library.
820 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
821 and write LLVM bytecode.
823 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
826 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
827 different program analyses, such as Dominator Information, Call Graphs,
828 Induction Variables, Interval Identification, Natural Loop Identification,
831 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
832 code for the LLVM to LLVM program transformations, such as Aggressive Dead
833 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
834 Invariant Code Motion, Dead Global Elimination, and many others...
836 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
837 describe various target architectures for code generation. For example,
838 the llvm/lib/Target/Sparc directory holds the Sparc machine
841 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
842 of the code generator: Instruction Selector, Instruction Scheduling, and
845 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
846 that corresponds to the header files located in
847 <tt>llvm/include/Support/</tt>.
852 <!-- ======================================================================= -->
853 <div class="doc_subsection">
854 <a name="runtime"><tt>llvm/runtime</tt></a>
857 <div class="doc_text">
859 <p>This directory contains libraries which are compiled into LLVM bytecode and
860 used when linking programs with the GCC front end. Most of these libraries are
861 skeleton versions of real libraries; for example, libc is a stripped down
862 version of glibc.</p>
864 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
869 <!-- ======================================================================= -->
870 <div class="doc_subsection">
871 <a name="test"><tt>llvm/test</tt></a>
874 <div class="doc_text">
876 <p>This directory contains regression tests and source code that is used to test
877 the LLVM infrastructure.</p>
881 <!-- ======================================================================= -->
882 <div class="doc_subsection">
883 <a name="tools"><tt>llvm/tools</tt></a>
886 <div class="doc_text">
888 <p>The <b>tools</b> directory contains the executables built out of the
889 libraries above, which form the main part of the user interface. You can
890 always get help for a tool by typing <tt>tool_name --help</tt>. The
891 following is a brief introduction to the most important tools.</p>
894 <dt><tt><b>analyze</b></tt> <dd><tt>analyze</tt> is used to run a specific
895 analysis on an input LLVM bytecode file and print out the results. It is
896 primarily useful for debugging analyses, or familiarizing yourself with
897 what an analysis does.<p>
899 <dt><tt><b>bugpoint</b></tt> <dd><tt>bugpoint</tt> is used to debug
900 optimization passes or code generation backends by narrowing down the
901 given test case to the minimum number of passes and/or instructions that
902 still cause a problem, whether it is a crash or miscompilation. See <a
903 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
904 on using <tt>bugpoint</tt>.<p>
906 <dt><tt><b>llvm-ar</b></tt> <dd>The archiver produces an archive containing
907 the given LLVM bytecode files, optionally with an index for faster
910 <dt><tt><b>llvm-as</b></tt> <dd>The assembler transforms the human readable
911 LLVM assembly to LLVM bytecode.<p>
913 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
914 bytecode to human readable LLVM assembly.<p>
916 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
917 links multiple LLVM modules into a single program.<p>
919 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
920 can directly execute LLVM bytecode (although very slowly...). In addition
921 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
922 specifying <tt>-trace</tt> on the command line). Finally, for
923 architectures that support it (currently only x86 and Sparc), by default,
924 <tt>lli</tt> will function as a Just-In-Time compiler (if the
925 functionality was compiled in), and will execute the code <i>much</i>
926 faster than the interpreter.<p>
928 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler, which
929 translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
930 the -march=c option).<p>
932 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
933 that has been retargeted to emit LLVM code as the machine code output. It
934 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
935 -o</tt> options that are typically used. The source code for the
936 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
937 because it is quite large and not very interesting.<p>
941 <dt><tt><b>gccas</b></tt> <dd>This tool is invoked by the
942 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
943 tool actually assembles LLVM assembly to LLVM bytecode,
944 performs a variety of optimizations, and outputs LLVM bytecode. Thus
945 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
946 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
947 an LLVM bytecode file that can be disassembled or manipulated just like
948 any other bytecode file). The command line interface to <tt>gccas</tt>
949 is designed to be as close as possible to the <b>system</b>
950 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
951 modified to interface to a "weird" assembler.<p>
953 <dt><tt><b>gccld</b></tt> <dd><tt>gccld</tt> links together several LLVM
954 bytecode files into one bytecode file and does some optimization. It is
955 the linker invoked by the GCC frontend when multiple .o files need to be
956 linked together. Like <tt>gccas</tt>, the command line interface of
957 <tt>gccld</tt> is designed to match the system linker, to aid
958 interfacing with the GCC frontend.</dl><p>
961 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
962 series of LLVM to LLVM transformations (which are specified on the command
963 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
964 command is a good way to get a list of the program transformations
971 <!-- ======================================================================= -->
972 <div class="doc_subsection">
973 <a name="utils"><tt>llvm/utils</tt></a>
976 <div class="doc_text">
978 <p>This directory contains utilities for working with LLVM source code, and some
979 of the utilities are actually required as part of the build process because they
980 are code generators for parts of LLVM infrastructure.</p>
983 <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
984 generator -- it builds trees on which it then performs pattern-matching to
985 select instructions according to the patterns the user has specified. Burg
986 is currently used in the Sparc V9 backend.<p>
988 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
989 that finds differences between code that LLC generates and code that LLI
990 generates. This is a useful tool if you are debugging one of them,
991 assuming that the other generates correct output. For the full user
992 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
994 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
995 update your CVS tree, but produce a much cleaner and more organized output
996 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
997 together all the new and updated files and modified files in separate
998 sections, so you can see at a glance what has changed. If you are at the
999 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1000 preferred way of updating the tree.<p>
1002 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1003 syntax-highlighting files which will work with Emacs and XEmacs editors,
1004 providing syntax highlighting support for LLVM assembly files and TableGen
1005 description files. For information on how to use the syntax files, consult
1006 the <tt>README</tt> file in that directory.<p>
1008 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1009 and outputs all non-generated source files, which is useful if one wishes
1010 to do a lot of development across directories and does not want to
1011 individually find each file. One way to use it is to run, for example:
1012 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1015 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1016 files in the current directory and then compiles and links the tool that
1017 is the first argument. For example, assuming you are in the directory
1018 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1019 simply running <tt>makellvm llc</tt> will make a build of the current
1020 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1021 causing a re-linking of LLC.<p>
1023 <dt><tt><b>NightlyTest.pl</b></tt> and
1024 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1025 cron script to generate nightly status reports of the functionality of
1026 tools, and the results can be seen by following the appropriate link on
1027 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
1029 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1030 the tool used to generate register descriptions, instruction set
1031 descriptions, and even assemblers from common TableGen description
1034 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1035 syntax-highlighting files which will work with the VIM editor, providing
1036 syntax highlighting support for LLVM assembly files and TableGen
1037 description files. For information on how to use the syntax files, consult
1038 the <tt>README</tt> file in that directory.<p>
1044 <!-- *********************************************************************** -->
1045 <div class="doc_section">
1046 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1048 <!-- *********************************************************************** -->
1050 <div class="doc_text">
1053 <li>First, create a simple C file, name it 'hello.c':
1055 #include <stdio.h>
1057 printf("hello world\n");
1062 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1063 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1065 <p>This will create two result files: <tt>hello</tt> and
1066 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1067 corresponds the the compiled program and the library facilities that it
1068 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1069 file with <tt>lli</tt>, making the result directly executable.</p></li>
1071 <li><p>Run the program. To make sure the program ran, execute one of the
1072 following commands:</p>
1074 <p><tt>% ./hello</tt></p>
1078 <p><tt>% lli hello.bc</tt></p></li>
1080 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1083 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1085 <li><p>Compile the program to native Sparc assembly using the code
1086 generator (assuming you are currently on a Sparc system):</p>
1088 <p><tt>% llc hello.bc -o hello.s</tt></p>
1090 <li><p>Assemble the native sparc assemble file into a program:</p>
1092 <p><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt></p>
1094 <li><p>Execute the native sparc program:</p>
1096 <p><tt>% ./hello.sparc</tt></p></li>
1102 <!-- *********************************************************************** -->
1103 <div class="doc_section">
1104 <a name="problems">Common Problems</a>
1106 <!-- *********************************************************************** -->
1108 <div class="doc_text">
1110 <p>If you are having problems building or using LLVM, or if you have any other
1111 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1112 Asked Questions</a> page.</p>
1116 <!-- *********************************************************************** -->
1117 <div class="doc_section">
1118 <a name="links">Links</a>
1120 <!-- *********************************************************************** -->
1122 <div class="doc_text">
1124 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1125 some simple things... there are many more interesting and complicated things
1126 that you can do that aren't documented here (but we'll gladly accept a patch
1127 if you want to write something up!). For more information about LLVM, check
1131 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1132 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1133 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1134 that Uses LLVM</a></li>
1139 <!-- *********************************************************************** -->
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1148 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1149 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
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