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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>
33 <li><a href="#optionalconfig">Optional Configuration Items</a>
36 <li><a href="#layout">Program layout</a>
38 <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
39 <li><a href="#include"><tt>llvm/include</tt></a>
40 <li><a href="#lib"><tt>llvm/lib</tt></a>
41 <li><a href="#runtime"><tt>llvm/runtime</tt></a>
42 <li><a href="#test"><tt>llvm/test</tt></a>
43 <li><a href="#tools"><tt>llvm/tools</tt></a>
44 <li><a href="#utils"><tt>llvm/utils</tt></a>
47 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
48 <li><a href="#problems">Common Problems</a>
49 <li><a href="#links">Links</a>
53 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
54 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
55 <a href="http://misha.brukman.net">Misha Brukman</a>,
56 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
57 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.</p>
60 <!-- *********************************************************************** -->
61 <div class="doc_section">
62 <a name="overview"><b>Overview</b></a>
64 <!-- *********************************************************************** -->
66 <div class="doc_text">
68 <p>Welcome to LLVM! In order to get started, you first need to know some
69 basic information.</p>
71 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
72 contains all of the tools, libraries, and header files needed to use the low
73 level virtual machine. It contains an assembler, disassembler, bytecode
74 analyzer, and bytecode optimizer. It also contains a test suite that can be
75 used to test the LLVM tools and the GCC front end.</p>
77 <p>The second piece is the GCC front end. This component provides a version of
78 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
79 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
80 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
81 from the LLVM suite.</p>
85 <!-- *********************************************************************** -->
86 <div class="doc_section">
87 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
89 <!-- *********************************************************************** -->
91 <div class="doc_text">
93 <p>Here's the short story for getting up and running quickly with LLVM:</p>
96 <li>Install the GCC front end:
98 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
99 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
100 <li><b>Sparc and MacOS X Only:</b><br>
101 <tt>cd cfrontend/<i>platform</i><br>
105 <li>Get the Source Code
107 <li>With the distributed files:
109 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
110 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
114 <li>With anonymous CVS access:
116 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
118 :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt></li>
119 <li>Hit the return key when prompted for the password.
120 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm
122 <li><tt>cd llvm</tt></li>
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. Useful options include:
132 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
133 <p>Specify the full pathname of where the LLVM GCC frontend is
135 <li><tt>--enable-spec2000=<i>directory</i></tt>
136 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
137 benchmarks should be available in
138 <tt><i>directory</i></tt>.</p></li>
142 <li>Build the LLVM Suite:
144 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.
145 <li><tt>gmake -k |& tee gnumake.out
146 # this is csh or tcsh syntax</tt>
151 <p>Consult the <a href="starting">Getting Started with LLVM</a> section for
152 detailed information on configuring and compiling LLVM. See <a
153 href="#environment">Setting Up Your Environment</a> for tips that simplify
154 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
155 Layout</a> to learn about the layout of the source code tree.</p>
159 <!-- *********************************************************************** -->
160 <div class="doc_section">
161 <a name="requirements"><b>Requirements</b></a>
163 <!-- *********************************************************************** -->
165 <div class="doc_text">
167 <p>Before you begin to use the LLVM system, review the requirements given below.
168 This may save you some trouble by knowing ahead of time what hardware and
169 software you will need.</p>
173 <!-- ======================================================================= -->
174 <div class="doc_subsection">
175 <a name="hardware"><b>Hardware</b></a>
178 <div class="doc_text">
180 <p>LLVM is known to work on the following platforms:</p>
184 <li>Linux on x86 (Pentium and above)
186 <li>Approximately 1.02 GB of Free Disk Space
188 <li>Source code: 45 MB</li>
189 <li>Object code: 956 MB</li>
190 <li>GCC front end: 40 MB</li>
195 <li>Solaris on SparcV9 (Ultrasparc)
197 <li>Approximately 1.75 GB of Free Disk Space
199 <li>Source code: 45 MB</li>
200 <li>Object code: 1705 MB</li>
201 <li>GCC front end: 50 MB</li>
206 <li>FreeBSD on x86 (Pentium and above)
208 <li>Approximately 935 MB of Free Disk Space
210 <li>Source code: 45 MB</li>
211 <li>Object code: 850 MB</li>
212 <li>GCC front end: 40 MB</li>
217 <li>MacOS X on PowerPC
219 <li>No native code generation
220 <li>Approximately 1.25 GB of Free Disk Space
222 <li>Source code: 45 MB</li>
223 <li>Object code: 1160 MB</li>
224 <li>GCC front end: 40 MB</li>
231 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
232 guaranteed to do so. If compilation is successful, the LLVM utilities should be
233 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
234 generation should work as well, although the generated native code may not work
235 on your platform.</p>
237 <p>The GCC front end is not very portable at the moment. If you want to get it
238 to work on another platform, you can download a copy of the source and try to
239 compile it on your platform.</p>
243 <!-- ======================================================================= -->
244 <div class="doc_subsection">
245 <a name="software"><b>Software</b></a>
248 <div class="doc_text">
250 <p>Compiling LLVM requires that you have several software packages
254 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
257 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
259 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
261 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
264 <p>There are some additional tools that you may want to have when working with
268 <li><A href="http://www.gnu.org/software/automake">GNU Automake</A></li>
269 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A></li>
270 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
272 <p>If you want to make changes to the configure scripts, you will need GNU
273 autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
274 higher). You will also need automake. Any old version of
275 automake from 1.4p5 on should work; we only use aclocal from that
278 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest 2.0.3</A></li>
279 <li><A href="http://www.python.org">Python</A>
282 These are needed to use the LLVM test suite. Please note that newer
283 versions of QMTest may not work with the LLVM test suite. QMTest 2.0.3
284 can be retrieved from the QMTest CVS repository using the following
287 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository login</tt>
289 <li>When prompted, use <tt>anoncvs</tt> as the password.
291 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository co -r release-2-0-3 qm</tt>
298 <p>The remainder of this guide is meant to get you up and running with
299 LLVM and to give you some basic information about the LLVM environment.
300 A <a href="#starting">complete guide to installation</a> is provided in the
303 <p>The later sections of this guide describe the <a
304 href="#layout">general layout</a> of the the LLVM source tree, a <a
305 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
306 href="#links">links</a> to find more information about LLVM or to get
311 <!-- *********************************************************************** -->
312 <div class="doc_section">
313 <a name="starting"><b>Getting Started with LLVM</b></a>
315 <!-- *********************************************************************** -->
317 <!-- ======================================================================= -->
318 <div class="doc_subsection">
319 <a name="terminology">Terminology and Notation</a>
322 <div class="doc_text">
324 <p>Throughout this manual, the following names are used to denote paths
325 specific to the local system and working environment. <i>These are not
326 environment variables you need to set but just strings used in the rest
327 of this document below</i>. In any of the examples below, simply replace
328 each of these names with the appropriate pathname on your local system.
329 All these paths are absolute:</p>
334 This is the top level directory of the LLVM source tree.
339 This is the top level directory of the LLVM object tree (i.e. the
340 tree where object files and compiled programs will be placed. It
341 can be the same as SRC_ROOT).
346 This is the where the LLVM GCC Front End is installed.
348 For the pre-built GCC front end binaries, the LLVMGCCDIR is
349 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
354 <!-- ======================================================================= -->
355 <div class="doc_subsection">
356 <a name="environment">Setting Up Your Environment</a>
359 <div class="doc_text">
362 In order to compile and use LLVM, you will need to set some environment
363 variables. There are also some shell aliases which you may find useful.
364 You can set these on the command line, or better yet, set them in your
365 <tt>.cshrc</tt> or <tt>.profile</tt>.
368 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
370 This environment variable helps the LLVM GCC front end find bytecode
371 libraries that it will need for compilation.
374 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
375 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
377 This alias allows you to use the LLVM C and C++ front ends without putting
378 them in your <tt>PATH</tt> or typing in their complete pathnames.
383 <!-- ======================================================================= -->
384 <div class="doc_subsection">
385 <a name="unpack">Unpacking the LLVM Archives</a>
388 <div class="doc_text">
391 If you have the LLVM distribution, you will need to unpack it before you
392 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
393 suite and the LLVM GCC front end compiled for your platform. Each
394 file is a TAR archive that is compressed with the gzip program.
397 <p> The files are as follows:
400 <dd>This is the source code to the LLVM suite.
403 <dt>cfrontend-1.2.sparc-sun-solaris2.8.tar.gz
404 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
407 <dt>cfrontend-1.2.i686-redhat-linux-gnu.tar.gz
408 <dd>This is the binary release of the GCC front end for Linux/x86.
411 <dt>cfrontend-1.2.i386-unknown-freebsd5.1.tar.gz
412 <dd>This is the binary release of the GCC front end for FreeBSD/x86.
415 <dt>cfrontend-1.2.powerpc-apple-darwin7.0.0.tar.gz
416 <dd>This is the binary release of the GCC front end for MacOS X/PPC.
421 <!-- ======================================================================= -->
422 <div class="doc_subsection">
423 <a name="checkout">Checkout LLVM from CVS</a>
426 <div class="doc_text">
428 <p>If you have access to our CVS repository, you can get a fresh copy of
429 the entire source code. All you need to do is check it out from CVS as
433 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
434 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
435 <li>Hit the return key when prompted for the password.
436 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
440 <p>This will create an '<tt>llvm</tt>' directory in the current
441 directory and fully populate it with the LLVM source code, Makefiles,
442 test directories, and local copies of documentation files.</p>
444 <p>If you want to get a specific release (as opposed to the most recent
445 revision), you can specify a label. The following releases have the following
450 Release 1.2: <b>RELEASE_12</b>
454 Release 1.1: <b>RELEASE_11</b>
458 Release 1.0: <b>RELEASE_1</b>
463 If you would like to get the GCC front end source code, you can also get it
464 from the CVS repository:
466 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
473 <!-- ======================================================================= -->
474 <div class="doc_subsection">
475 <a name="installcf">Install the GCC Front End</a>
478 <div class="doc_text">
480 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
481 GCC front end from the binary distribution. It is used for building the
482 bytecode libraries later used by the GCC front end for linking programs, and its
483 location must be specified when the LLVM suite is configured.</p>
485 <p>To install the GCC front end, do the following:</p>
488 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
489 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
493 <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
496 <p><tt>cd cfrontend/<i>platform</i><br>
497 ./fixheaders</tt></p>
499 <p>The binary versions of the GCC front end may not suit all of your needs. For
500 example, the binary distribution may include an old version of a system header
501 file, not "fix" a header file that needs to be fixed for GCC, or it may be
502 linked with libraries not available on your system.</p>
504 <p>In cases like these, you may want to try <a
505 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
506 not for the faint of heart, so be forewarned.</p>
510 <!-- ======================================================================= -->
511 <div class="doc_subsection">
512 <a name="config">Local LLVM Configuration</a>
515 <div class="doc_text">
517 <p>Once checked out from the CVS repository, the LLVM suite source code must be
518 configured via the <tt>configure</tt> script. This script sets variables in
519 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
520 also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
523 <p>The following environment variables are used by the <tt>configure</tt>
524 script to configure the build system:</p>
534 <td>Tells <tt>configure</tt> which C compiler to use. By default,
535 <tt>configure</tt> will look for the first GCC C compiler in
536 <tt>PATH</tt>. Use this variable to override
537 <tt>configure</tt>'s default behavior.</td>
542 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
543 <tt>configure</tt> will look for the first GCC C++ compiler in
544 <tt>PATH</tt>. Use this variable to override
545 <tt>configure</tt>'s default behavior.</td>
549 <p>The following options can be used to set or enable LLVM specific options:</p>
552 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
554 Path to the location where the LLVM GCC front end binaries and
555 associated libraries were installed. This must be specified as an
558 <dt><i>--enable-optimized</i>
560 Enables optimized compilation by default (debugging symbols are removed
561 and GCC optimization flags are enabled). The default is to use an
562 unoptimized build (also known as a debug build).
564 <dt><i>--enable-jit</i>
566 Compile the Just In Time (JIT) compiler functionality. This is not
568 on all platforms. The default is dependent on platform, so it is best
569 to explicitly enable it if you want it.
571 <dt><i>--enable-spec2000</i>
572 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
574 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
575 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
576 <tt>directory</tt>, you can tell configure where to find the SPEC2000
577 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
578 uses the default value
579 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
581 <dt><i>--enable-spec95</i>
582 <dt><i>--enable-spec95=<<tt>directory</tt>></i>
584 Enable the use of SPEC95 when testing LLVM. It is similar to the
585 <i>--enable-spec2000</i> option.
587 <dt><i>--enable-povray</i>
588 <dt><i>--enable-povray=<<tt>directory</tt>></i>
590 Enable the use of Povray as an external test. Versions of Povray written
591 in C should work. This option is similar to the <i>--enable-spec2000</i>
595 <p>To configure LLVM, follow these steps:</p>
598 <li>Change directory into the object root directory:
600 <tt>cd <i>OBJ_ROOT</i></tt>
603 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
605 <tt><i>SRC_ROOT</i>/configure</tt>
609 <p>In addition to running <tt>configure</tt>, you must set the
610 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
611 This environment variable is used to locate "system" libraries like
612 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
613 the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
614 end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
615 <tt>LLVM_LIB_SEARCH_PATH</tt> to
616 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
617 version of the GCC front end on our research machines.</p>
621 <!-- ======================================================================= -->
622 <div class="doc_subsection">
623 <a name="compile">Compiling the LLVM Suite Source Code</a>
626 <div class="doc_text">
628 <p>Once you have configured LLVM, you can build it. There are three types of
634 These builds are the default when one types <tt>gmake</tt> (unless the
635 <tt>--enable-optimized</tt> option was used during configuration). The
636 build system will compile the tools and libraries with debugging
640 <dt>Release (Optimized) Builds
642 These builds are enabled with the <tt>--enable-optimized</tt> option to
643 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
644 <tt>gmake</tt> command line. For these builds, the build system will
645 compile the tools and libraries with GCC optimizations enabled and strip
646 debugging information from the libraries and executables it generates.
651 These builds are for use with profiling. They compile profiling
652 information into the code for use with programs like <tt>gprof</tt>.
653 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
654 on the <tt>gmake</tt> command line.
657 <p>Once you have LLVM configured, you can build it by entering the
658 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
660 <p><tt>gmake</tt></p>
662 <p>If you have multiple processors in your machine, you may wish to use some of
663 the parallel build options provided by GNU Make. For example, you could use the
666 <p><tt>gmake -j2</tt></p>
668 <p>There are several special targets which are useful when working with the LLVM
672 <dt><tt>gmake clean</tt>
674 Removes all files generated by the build. This includes object files,
675 generated C/C++ files, libraries, and executables.
678 <dt><tt>gmake distclean</tt>
680 Removes everything that <tt>gmake clean</tt> does, but also removes
681 files generated by <tt>configure</tt>. It attempts to return the
682 source tree to the original state in which it was shipped.
685 <dt><tt>gmake install</tt>
687 Installs LLVM files into the proper location. For the most part,
688 this does nothing, but it does install bytecode libraries into the
689 GCC front end's bytecode library directory. If you need to update
690 your bytecode libraries, this is the target to use once you've built
695 <p>It is also possible to override default values from <tt>configure</tt> by
696 declaring variables on the command line. The following are some examples:</p>
699 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
701 Perform a Release (Optimized) build.
704 <dt><tt>gmake ENABLE_PROFILING=1</tt>
706 Perform a Profiling build.
709 <dt><tt>gmake VERBOSE=1</tt>
711 Print what <tt>gmake</tt> is doing on standard output.
715 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
716 it and any subdirectories that it contains. Entering any directory inside the
717 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
718 that directory that is out of date.</p>
722 <!-- ======================================================================= -->
723 <div class="doc_subsection">
724 <a name="objfiles">The Location of LLVM Object Files</a>
727 <div class="doc_text">
729 <p>The LLVM build system is capable of sharing a single LLVM source tree among
730 several LLVM builds. Hence, it is possible to build LLVM for several different
731 platforms or configurations using the same source tree.</p>
733 <p>This is accomplished in the typical autoconf manner:</p>
736 <li><p>Change directory to where the LLVM object files should live:</p>
738 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
740 <li><p>Run the <tt>configure</tt> script found in the LLVM source
743 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
746 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
747 named after the build type:</p>
754 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
756 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
764 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
766 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
774 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
776 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
782 <!-- ======================================================================= -->
783 <div class="doc_subsection">
784 <a name="optionalconfig">Optional Configuration Items</a>
787 <div class="doc_text">
790 If you're running on a linux system that supports the "<a
791 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
792 module, and you have root access on the system, you can set your system up to
793 execute LLVM bytecode files directly. To do this, use commands like this (the
794 first command may not be required if you are already using the module):</p>
797 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
798 $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
799 $ chmod u+x hello.bc (if needed)
804 This allows you to execute LLVM bytecode files directly. Thanks to Jack
805 Cummings for pointing this out!
811 <!-- *********************************************************************** -->
812 <div class="doc_section">
813 <a name="layout"><b>Program Layout</b></a>
815 <!-- *********************************************************************** -->
817 <div class="doc_text">
819 <p>One useful source of information about the LLVM source base is the LLVM <a
820 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
821 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
822 The following is a brief introduction to code layout:</p>
826 <!-- ======================================================================= -->
827 <div class="doc_subsection">
828 <a name="cvsdir"><tt>CVS</tt> directories</a>
831 <div class="doc_text">
833 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
834 the most part these can just be ignored.</p>
838 <!-- ======================================================================= -->
839 <div class="doc_subsection">
840 <a name="include"><tt>llvm/include</tt></a>
843 <div class="doc_text">
845 <p>This directory contains public header files exported from the LLVM
846 library. The three main subdirectories of this directory are:</p>
849 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
850 specific header files. This directory also has subdirectories for
851 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
852 <tt>Target</tt>, <tt>Transforms</tt>, etc...</li>
854 <li><tt>llvm/include/Support</tt> - This directory contains generic
855 support libraries that are independent of LLVM, but are used by LLVM.
856 For example, some C++ STL utilities and a Command Line option processing
857 library store their header files here.</li>
859 <li><tt>llvm/include/Config</tt> - This directory contains header files
860 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
861 and C header files. Source code can include these header files which
862 automatically take care of the conditional #includes that the
863 <tt>configure</tt> script generates.</li>
868 <!-- ======================================================================= -->
869 <div class="doc_subsection">
870 <a name="lib"><tt>llvm/lib</tt></a>
873 <div class="doc_text">
875 <p>This directory contains most of the source files of the LLVM system. In LLVM,
876 almost all code exists in libraries, making it very easy to share code among the
877 different <a href="#tools">tools</a>.</p>
880 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
881 source files that implement core classes like Instruction and BasicBlock.
883 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
884 for the LLVM assembly language parser library.
886 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
887 and write LLVM bytecode.
889 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
892 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
893 different program analyses, such as Dominator Information, Call Graphs,
894 Induction Variables, Interval Identification, Natural Loop Identification,
897 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
898 code for the LLVM to LLVM program transformations, such as Aggressive Dead
899 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
900 Invariant Code Motion, Dead Global Elimination, and many others...
902 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
903 describe various target architectures for code generation. For example,
904 the llvm/lib/Target/SparcV9 directory holds the Sparc machine
907 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
908 of the code generator: Instruction Selector, Instruction Scheduling, and
911 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
912 that corresponds to the header files located in
913 <tt>llvm/include/Support/</tt>.
918 <!-- ======================================================================= -->
919 <div class="doc_subsection">
920 <a name="runtime"><tt>llvm/runtime</tt></a>
923 <div class="doc_text">
925 <p>This directory contains libraries which are compiled into LLVM bytecode and
926 used when linking programs with the GCC front end. Most of these libraries are
927 skeleton versions of real libraries; for example, libc is a stripped down
928 version of glibc.</p>
930 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
935 <!-- ======================================================================= -->
936 <div class="doc_subsection">
937 <a name="test"><tt>llvm/test</tt></a>
940 <div class="doc_text">
942 <p>This directory contains regression tests and source code that is used to test
943 the LLVM infrastructure.</p>
947 <!-- ======================================================================= -->
948 <div class="doc_subsection">
949 <a name="tools"><tt>llvm/tools</tt></a>
952 <div class="doc_text">
954 <p>The <b>tools</b> directory contains the executables built out of the
955 libraries above, which form the main part of the user interface. You can
956 always get help for a tool by typing <tt>tool_name --help</tt>. The
957 following is a brief introduction to the most important tools:</p>
960 <dt><tt><b>analyze</b></tt> <dd><tt>analyze</tt> is used to run a specific
961 analysis on an input LLVM bytecode file and print out the results. It is
962 primarily useful for debugging analyses, or familiarizing yourself with
963 what an analysis does.<p>
965 <dt><tt><b>bugpoint</b></tt> <dd><tt>bugpoint</tt> is used to debug
966 optimization passes or code generation backends by narrowing down the
967 given test case to the minimum number of passes and/or instructions that
968 still cause a problem, whether it is a crash or miscompilation. See <a
969 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
970 on using <tt>bugpoint</tt>.<p>
972 <dt><tt><b>llvm-ar</b></tt> <dd>The archiver produces an archive containing
973 the given LLVM bytecode files, optionally with an index for faster
976 <dt><tt><b>llvm-as</b></tt> <dd>The assembler transforms the human readable
977 LLVM assembly to LLVM bytecode.<p>
979 <dt><tt><b>llvm-dis</b></tt><dd>The disassembler transforms the LLVM
980 bytecode to human readable LLVM assembly.<p>
982 <dt><tt><b>llvm-link</b></tt><dd> <tt>llvm-link</tt>, not surprisingly,
983 links multiple LLVM modules into a single program.<p>
985 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
986 can directly execute LLVM bytecode (although very slowly...). In addition
987 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
988 specifying <tt>-trace</tt> on the command line). Finally, for
989 architectures that support it (currently only x86 and Sparc), by default,
990 <tt>lli</tt> will function as a Just-In-Time compiler (if the
991 functionality was compiled in), and will execute the code <i>much</i>
992 faster than the interpreter.<p>
994 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler, which
995 translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
996 the -march=c option).<p>
998 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC-based C frontend
999 that has been retargeted to emit LLVM code as the machine code output. It
1000 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
1001 -o</tt> options that are typically used. The source code for the
1002 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
1003 because it is quite large and not very interesting.<p>
1007 <dt><tt><b>gccas</b></tt> <dd>This tool is invoked by the
1008 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
1009 tool actually assembles LLVM assembly to LLVM bytecode,
1010 performs a variety of optimizations, and outputs LLVM bytecode. Thus
1011 when you invoke <tt>llvmgcc -c x.c -o x.o</tt>, you are causing
1012 <tt>gccas</tt> to be run, which writes the <tt>x.o</tt> file (which is
1013 an LLVM bytecode file that can be disassembled or manipulated just like
1014 any other bytecode file). The command line interface to <tt>gccas</tt>
1015 is designed to be as close as possible to the <b>system</b>
1016 `<tt>as</tt>' utility so that the gcc frontend itself did not have to be
1017 modified to interface to a "weird" assembler.<p>
1019 <dt><tt><b>gccld</b></tt> <dd><tt>gccld</tt> links together several LLVM
1020 bytecode files into one bytecode file and does some optimization. It is
1021 the linker invoked by the GCC frontend when multiple .o files need to be
1022 linked together. Like <tt>gccas</tt>, the command line interface of
1023 <tt>gccld</tt> is designed to match the system linker, to aid
1024 interfacing with the GCC frontend.</dl><p>
1027 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
1028 series of LLVM to LLVM transformations (which are specified on the command
1029 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
1030 command is a good way to get a list of the program transformations
1037 <!-- ======================================================================= -->
1038 <div class="doc_subsection">
1039 <a name="utils"><tt>llvm/utils</tt></a>
1042 <div class="doc_text">
1044 <p>This directory contains utilities for working with LLVM source code, and some
1045 of the utilities are actually required as part of the build process because they
1046 are code generators for parts of LLVM infrastructure.</p>
1049 <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
1050 generator -- it builds trees on which it then performs pattern-matching to
1051 select instructions according to the patterns the user has specified. Burg
1052 is currently used in the Sparc V9 backend.<p>
1054 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1055 that finds differences between code that LLC generates and code that LLI
1056 generates. This is a useful tool if you are debugging one of them,
1057 assuming that the other generates correct output. For the full user
1058 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
1060 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1061 update your CVS tree, but produce a much cleaner and more organized output
1062 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1063 together all the new and updated files and modified files in separate
1064 sections, so you can see at a glance what has changed. If you are at the
1065 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1066 preferred way of updating the tree.<p>
1068 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1069 syntax-highlighting files which will work with Emacs and XEmacs editors,
1070 providing syntax highlighting support for LLVM assembly files and TableGen
1071 description files. For information on how to use the syntax files, consult
1072 the <tt>README</tt> file in that directory.<p>
1074 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1075 and outputs all non-generated source files, which is useful if one wishes
1076 to do a lot of development across directories and does not want to
1077 individually find each file. One way to use it is to run, for example:
1078 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1081 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1082 files in the current directory and then compiles and links the tool that
1083 is the first argument. For example, assuming you are in the directory
1084 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1085 simply running <tt>makellvm llc</tt> will make a build of the current
1086 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1087 causing a re-linking of LLC.<p>
1089 <dt><tt><b>NightlyTest.pl</b></tt> and
1090 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1091 cron script to generate nightly status reports of the functionality of
1092 tools, and the results can be seen by following the appropriate link on
1093 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
1095 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1096 the tool used to generate register descriptions, instruction set
1097 descriptions, and even assemblers from common TableGen description
1100 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1101 syntax-highlighting files which will work with the VIM editor, providing
1102 syntax highlighting support for LLVM assembly files and TableGen
1103 description files. For information on how to use the syntax files, consult
1104 the <tt>README</tt> file in that directory.<p>
1110 <!-- *********************************************************************** -->
1111 <div class="doc_section">
1112 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1114 <!-- *********************************************************************** -->
1116 <div class="doc_text">
1119 <li>First, create a simple C file, name it 'hello.c':
1121 #include <stdio.h>
1123 printf("hello world\n");
1128 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1129 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1131 <p>This will create two result files: <tt>hello</tt> and
1132 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1133 corresponds the the compiled program and the library facilities that it
1134 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1135 file with <tt>lli</tt>, making the result directly executable.</p></li>
1137 <li><p>Run the program. To make sure the program ran, execute one of the
1138 following commands:</p>
1140 <p><tt>% ./hello</tt></p>
1144 <p><tt>% lli hello.bc</tt></p></li>
1146 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1149 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1151 <li><p>Compile the program to native Sparc assembly using the code
1152 generator (assuming you are currently on a Sparc system):</p>
1154 <p><tt>% llc hello.bc -o hello.s</tt></p>
1156 <li><p>Assemble the native sparc assemble file into a program:</p>
1158 <p><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt></p>
1160 <li><p>Execute the native sparc program:</p>
1162 <p><tt>% ./hello.sparc</tt></p></li>
1168 <!-- *********************************************************************** -->
1169 <div class="doc_section">
1170 <a name="problems">Common Problems</a>
1172 <!-- *********************************************************************** -->
1174 <div class="doc_text">
1176 <p>If you are having problems building or using LLVM, or if you have any other
1177 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1178 Asked Questions</a> page.</p>
1182 <!-- *********************************************************************** -->
1183 <div class="doc_section">
1184 <a name="links">Links</a>
1186 <!-- *********************************************************************** -->
1188 <div class="doc_text">
1190 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1191 some simple things... there are many more interesting and complicated things
1192 that you can do that aren't documented here (but we'll gladly accept a patch
1193 if you want to write something up!). For more information about LLVM, check
1197 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1198 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1199 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1200 that Uses LLVM</a></li>
1205 <!-- *********************************************************************** -->
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1215 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
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