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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>
21 <li><a href="#brokengcc">Broken versions of GCC</a>
24 <li><a href="#starting">Getting Started with LLVM</a>
26 <li><a href="#terminology">Terminology and Notation</a>
27 <li><a href="#environment">Setting Up Your Environment</a>
28 <li><a href="#unpack">Unpacking the LLVM Archives</a>
29 <li><a href="#checkout">Checkout LLVM from CVS</a>
30 <li><a href="#installcf">Install the GCC Front End</a>
31 <li><a href="#config">Local LLVM Configuration</a>
32 <li><a href="#compile">Compiling the LLVM Suite Source Code</a>
33 <li><a href="#objfiles">The Location of LLVM Object Files</a>
34 <li><a href="#optionalconfig">Optional Configuration Items</a>
37 <li><a href="#layout">Program layout</a>
39 <li><a href="#cvsdir"><tt>CVS</tt> directories</a>
40 <li><a href="#include"><tt>llvm/include</tt></a>
41 <li><a href="#lib"><tt>llvm/lib</tt></a>
42 <li><a href="#runtime"><tt>llvm/runtime</tt></a>
43 <li><a href="#test"><tt>llvm/test</tt></a>
44 <li><a href="#llvmtest"><tt>llvm-test</tt></a>
45 <li><a href="#tools"><tt>llvm/tools</tt></a>
46 <li><a href="#utils"><tt>llvm/utils</tt></a>
49 <li><a href="#tutorial">An Example Using the LLVM Tool Chain</a>
50 <li><a href="#problems">Common Problems</a>
51 <li><a href="#links">Links</a>
54 <div class="doc_author">
56 <a href="mailto:criswell@uiuc.edu">John Criswell</a>,
57 <a href="mailto:sabre@nondot.org">Chris Lattner</a>,
58 <a href="http://misha.brukman.net">Misha Brukman</a>,
59 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>, and
60 <a href="mailto:gshi1@uiuc.edu">Guochun Shi</a>.
65 <!-- *********************************************************************** -->
66 <div class="doc_section">
67 <a name="overview"><b>Overview</b></a>
69 <!-- *********************************************************************** -->
71 <div class="doc_text">
73 <p>Welcome to LLVM! In order to get started, you first need to know some
74 basic information.</p>
76 <p>First, LLVM comes in two pieces. The first piece is the LLVM suite. This
77 contains all of the tools, libraries, and header files needed to use the low
78 level virtual machine. It contains an assembler, disassembler, bytecode
79 analyzer, and bytecode optimizer. It also contains a test suite that can be
80 used to test the LLVM tools and the GCC front end.</p>
82 <p>The second piece is the GCC front end. This component provides a version of
83 GCC that compiles C and C++ code into LLVM bytecode. Currently, the GCC front
84 end is a modified version of GCC 3.4 (we track the GCC 3.4 development). Once
85 compiled into LLVM bytecode, a program can be manipulated with the LLVM tools
86 from the LLVM suite.</p>
90 <!-- *********************************************************************** -->
91 <div class="doc_section">
92 <a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a>
94 <!-- *********************************************************************** -->
96 <div class="doc_text">
98 <p>Here's the short story for getting up and running quickly with LLVM:</p>
101 <li>Read the documentation.</li>
102 <li>Read the documentation.</li>
103 <li>Remember that you were warned twice about reading the documentation.</li>
104 <li>Install the GCC front end:
106 <li><tt>cd <i>where-you-want-the-C-front-end-to-live</i></tt>
107 <li><tt>gunzip --stdout cfrontend.<i>platform</i>.tar.gz | tar -xvf -</tt>
108 <li><b>Sparc and MacOS X Only:</b><br>
109 <tt>cd cfrontend/<i>platform</i><br>
113 <li>Get the Source Code
115 <li>With the distributed files:
117 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
118 <li><tt>gunzip --stdout llvm-<i>version</i>.tar.gz | tar -xvf -</tt>
122 <li>With anonymous CVS access (or use a <a href="#mirror">mirror</a>):
124 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt></li>
126 :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt></li>
127 <li>Hit the return key when prompted for the password.
128 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm
130 <li><tt>cd llvm</tt></li>
134 <li>Configure the LLVM Build Environment
136 <li>Change directory to where you want to store the LLVM object
137 files and run <tt>configure</tt> to configure the Makefiles and
138 header files for the default platform. Useful options include:
140 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
141 <p>Specify the full pathname of where the LLVM GCC frontend is
143 <li><tt>--enable-spec2000=<i>directory</i></tt>
144 <p>Enable the SPEC2000 benchmarks for testing. The SPEC2000
145 benchmarks should be available in
146 <tt><i>directory</i></tt>.</p></li>
150 <li>Build the LLVM Suite:
152 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.</li>
153 <li><tt>gmake -k |& tee gnumake.out
154 # this is csh or tcsh syntax</tt></li>
155 <li>If you get an "internal compiler error (ICE)" see <a href="#brokengcc">below</a>.</li>
160 <p>Consult the <a href="#starting">Getting Started with LLVM</a> section for
161 detailed information on configuring and compiling LLVM. See <a
162 href="#environment">Setting Up Your Environment</a> for tips that simplify
163 working with the GCC front end and LLVM tools. Go to <a href="#layout">Program
164 Layout</a> to learn about the layout of the source code tree.</p>
168 <!-- *********************************************************************** -->
169 <div class="doc_section">
170 <a name="requirements"><b>Requirements</b></a>
172 <!-- *********************************************************************** -->
174 <div class="doc_text">
176 <p>Before you begin to use the LLVM system, review the requirements given below.
177 This may save you some trouble by knowing ahead of time what hardware and
178 software you will need.</p>
182 <!-- ======================================================================= -->
183 <div class="doc_subsection">
184 <a name="hardware"><b>Hardware</b></a>
187 <div class="doc_text">
189 <p>LLVM is known to work on the following platforms:</p>
193 <li>Linux on x86 (Pentium and above)
195 <li>Approximately 2.6 GB of Free Disk Space
197 <li>Source code: 57 MB</li>
198 <li>Object code: 2.5 GB</li>
199 <li>GCC front end: 30 MB</li>
204 <li>Solaris on SparcV9 (Ultrasparc)
206 <li>Approximately 2.6 GB of Free Disk Space
208 <li>Source code: 57 MB</li>
209 <li>Object code: 2.5 GB</li>
210 <li>GCC front end: 46 MB</li>
215 <li>FreeBSD on x86 (Pentium and above)
217 <li>Approximately 1 GB of Free Disk Space
219 <li>Source code: 57 MB</li>
220 <li>Object code: 850 MB</li>
221 <li>GCC front end: 40 MB</li>
226 <li>MacOS X on PowerPC
228 <li>Experimental support for static native code generation
229 <li>Approximately 1.6 GB of Free Disk Space
231 <li>Source code: 57 MB</li>
232 <li>Object code: 1.5 GB</li>
233 <li>GCC front end: 36 MB</li>
240 <li><div class="doc_warning">No native code generation</div>
241 <li>Approximately 2 GB of Free Disk Space
243 <li>Source code: 92 MB</li>
244 <li>Object code: 2.8 GB</li>
245 <li>GCC front end: 123 MB</li>
252 <p>The LLVM suite <i>may</i> compile on other platforms, but it is not
253 guaranteed to do so. If compilation is successful, the LLVM utilities should be
254 able to assemble, disassemble, analyze, and optimize LLVM bytecode. Code
255 generation should work as well, although the generated native code may not work
256 on your platform.</p>
258 <p>The GCC front end is not very portable at the moment. If you want to get it
259 to work on another platform, you can download a copy of the source and <a
260 href="CFEBuildInstrs.html">try to compile it</a> on your platform.</p>
264 <!-- ======================================================================= -->
265 <div class="doc_subsection">
266 <a name="software"><b>Software</b></a>
269 <div class="doc_text">
271 <p>Compiling LLVM requires that you have several software packages
275 <li><a href="http://gcc.gnu.org">GCC 3.x with C and C++ language
276 support</a> (See <a href="#brokengcc">below</a> for specific version info)</li>
278 <li><a href="http://savannah.gnu.org/projects/make">GNU Make</a></li>
280 <li><a href="http://www.gnu.org/software/flex">Flex</a></li>
282 <li><a href="http://www.gnu.org/software/bison/bison.html">Bison</a></li>
285 <p>There are some additional tools that you may want to have when working with
289 <li><A href="http://www.gnu.org/software/automake">GNU Automake</A></li>
290 <li><A href="http://www.gnu.org/software/autoconf">GNU Autoconf</A></li>
291 <li><A href="http://savannah.gnu.org/projects/m4">GNU M4</A>
293 <p>If you want to make changes to the configure scripts, you will need GNU
294 autoconf (2.57 or higher), and consequently, GNU M4 (version 1.4 or
295 higher). You will also need automake. Any old version of
296 automake from 1.4p5 on should work; we only use aclocal from that
299 <li><A href="http://www.codesourcery.com/qm/qmtest">QMTest 2.0.3</A></li>
300 <li><A href="http://www.python.org">Python</A>
303 These are needed to use the LLVM test suite. Please note that newer
304 versions of QMTest may not work with the LLVM test suite. QMTest 2.0.3
305 can be retrieved from the QMTest CVS repository using the following
308 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository login</tt>
310 <li>When prompted, use <tt>anoncvs</tt> as the password.
312 <li><tt>cvs -d :pserver:anoncvs@cvs.codesourcery.com:/home/qm/Repository co -r release-2-0-3 qm</tt>
320 <!-- ======================================================================= -->
321 <div class="doc_subsection">
322 <a name="brokengcc">Broken versions of GCC</a>
325 <div class="doc_text">
327 <p>LLVM is very demanding of the host C++ compiler, and as such tends to expose
328 bugs in the compiler. In particular, several versions of GCC crash when trying
329 to compile LLVM. We routinely use GCC 3.3.3 and GCC 3.4.0 and have had success
330 with them. Other versions of GCC will probably work as well. GCC versions listed
331 here are known to not work. If you are using one of these versions, please try
332 to upgrade your GCC to something more recent. If you run into a problem with a
333 version of GCC not listed here, please <a href="mailto:llvmdev@cs.uiuc.edu">let
334 us know</a>. Please use the "<tt>gcc -v</tt>" command to find out which version
335 of GCC you are using.
338 <p><b>GCC versions prior to 3.0</b>: GCC 2.96.x and before had several
339 problems in the STL that effectively prevent it from compiling LLVM.
342 <p><b>GCC 3.3.2</b>: This version of GCC suffered from a <a
343 href="http://gcc.gnu.org/PR13392">serious bug</a> which causes it to crash in
344 the "<tt>convert_from_eh_region_ranges_1</tt>" GCC function.</p>
350 <!-- *********************************************************************** -->
351 <div class="doc_section">
352 <a name="starting"><b>Getting Started with LLVM</b></a>
354 <!-- *********************************************************************** -->
356 <div class="doc_text">
358 <p>The remainder of this guide is meant to get you up and running with
359 LLVM and to give you some basic information about the LLVM environment.</p>
361 <p>The later sections of this guide describe the <a
362 href="#layout">general layout</a> of the the LLVM source tree, a <a
363 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
364 href="#links">links</a> to find more information about LLVM or to get
368 <!-- ======================================================================= -->
369 <div class="doc_subsection">
370 <a name="terminology">Terminology and Notation</a>
373 <div class="doc_text">
375 <p>Throughout this manual, the following names are used to denote paths
376 specific to the local system and working environment. <i>These are not
377 environment variables you need to set but just strings used in the rest
378 of this document below</i>. In any of the examples below, simply replace
379 each of these names with the appropriate pathname on your local system.
380 All these paths are absolute:</p>
385 This is the top level directory of the LLVM source tree.
390 This is the top level directory of the LLVM object tree (i.e. the
391 tree where object files and compiled programs will be placed. It
392 can be the same as SRC_ROOT).
397 This is the where the LLVM GCC Front End is installed.
399 For the pre-built GCC front end binaries, the LLVMGCCDIR is
400 <tt>cfrontend/<i>platform</i>/llvm-gcc</tt>.
405 <!-- ======================================================================= -->
406 <div class="doc_subsection">
407 <a name="environment">Setting Up Your Environment</a>
410 <div class="doc_text">
413 In order to compile and use LLVM, you will need to set some environment
414 variables. There are also some shell aliases which you may find useful.
415 You can set these on the command line, or better yet, set them in your
416 <tt>.cshrc</tt> or <tt>.profile</tt>.
419 <dt><tt>LLVM_LIB_SEARCH_PATH</tt>=<tt><i>LLVMGCCDIR</i>/bytecode-libs</tt>
421 This environment variable helps the LLVM GCC front end find bytecode
422 libraries that it will need for compilation.
425 <dt>alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/gcc</tt>
426 <dt>alias llvmg++ <i>LLVMGCCDIR</i><tt>/bin/g++</tt>
428 This alias allows you to use the LLVM C and C++ front ends without putting
429 them in your <tt>PATH</tt> or typing in their complete pathnames.
434 <!-- ======================================================================= -->
435 <div class="doc_subsection">
436 <a name="unpack">Unpacking the LLVM Archives</a>
439 <div class="doc_text">
442 If you have the LLVM distribution, you will need to unpack it before you
443 can begin to compile it. LLVM is distributed as a set of two files: the LLVM
444 suite and the LLVM GCC front end compiled for your platform. Each
445 file is a TAR archive that is compressed with the gzip program.
448 <p> The files are as follows:
451 <dd>This is the source code to the LLVM suite.
454 <dt>cfrontend-1.3.sparc-sun-solaris2.8.tar.gz
455 <dd>This is the binary release of the GCC front end for Solaris/Sparc.
458 <dt>cfrontend-1.3.i686-redhat-linux-gnu.tar.gz
459 <dd>This is the binary release of the GCC front end for Linux/x86.
462 <dt>cfrontend-1.3.i386-unknown-freebsd5.1.tar.gz
463 <dd>This is the binary release of the GCC front end for FreeBSD/x86.
466 <dt>cfrontend-1.3.powerpc-apple-darwin7.0.0.tar.gz
467 <dd>This is the binary release of the GCC front end for MacOS X/PPC.
472 <!-- ======================================================================= -->
473 <div class="doc_subsection">
474 <a name="checkout">Checkout LLVM from CVS</a>
477 <div class="doc_text">
479 <p>If you have access to our CVS repository, you can get a fresh copy of
480 the entire source code. All you need to do is check it out from CVS as
484 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
485 <li><tt>cvs -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm login</tt>
486 <li>Hit the return key when prompted for the password.
487 <li><tt>cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co
491 <p>This will create an '<tt>llvm</tt>' directory in the current
492 directory and fully populate it with the LLVM source code, Makefiles,
493 test directories, and local copies of documentation files.</p>
495 <p>If you want to get a specific release (as opposed to the most recent
496 revision), you can specify a label. The following releases have the following
500 <li>Release 1.3: <b>RELEASE_13</b></li>
501 <li>Release 1.2: <b>RELEASE_12</b></li>
502 <li>Release 1.1: <b>RELEASE_11</b></li>
503 <li>Release 1.0: <b>RELEASE_1</b></li>
506 <p>If you would like to get the GCC front end source code, you can also get it
507 from the CVS repository:</p>
510 cvs -z3 -d :pserver:anon@llvm-cvs.cs.uiuc.edu:/var/cvs/llvm co llvm-gcc
513 <p>Please note that you must follow <a href="CFEBuildInstrs.html">these
514 instructions</a> to successfully build the LLVM C front-end.</p>
518 <!-- ======================================================================= -->
519 <div class="doc_subsubsection">
520 <a name="mirrors">LLVM CVS Mirrors</a>
523 <div class="doc_text">
525 <p>If the main CVS server is overloaded or inaccessible, you can try one of
526 these user-hosted mirrors:</p>
529 <li><a href="http://llvm.x10sys.com/">Mirror hosted by eXtensible Systems
534 <!-- ======================================================================= -->
535 <div class="doc_subsection">
536 <a name="installcf">Install the GCC Front End</a>
539 <div class="doc_text">
541 <p>Before configuring and compiling the LLVM suite, you need to extract the LLVM
542 GCC front end from the binary distribution. It is used for building the
543 bytecode libraries later used by the GCC front end for linking programs, and its
544 location must be specified when the LLVM suite is configured.</p>
546 <p>To install the GCC front end, do the following:</p>
549 <li><tt>cd <i>where-you-want-the-front-end-to-live</i></tt></li>
550 <li><tt>gunzip --stdout cfrontend-<i>version</i>.<i>platform</i>.tar.gz | tar -xvf
554 <p>If you are using Solaris/Sparc or MacOS X/PPC, you will need to fix the
557 <p><tt>cd cfrontend/<i>platform</i><br>
558 ./fixheaders</tt></p>
560 <p>The binary versions of the GCC front end may not suit all of your needs. For
561 example, the binary distribution may include an old version of a system header
562 file, not "fix" a header file that needs to be fixed for GCC, or it may be
563 linked with libraries not available on your system.</p>
565 <p>In cases like these, you may want to try <a
566 href="CFEBuildInstrs.html">building the GCC front end from source.</a> This is
567 not for the faint of heart, so be forewarned.</p>
571 <!-- ======================================================================= -->
572 <div class="doc_subsection">
573 <a name="config">Local LLVM Configuration</a>
576 <div class="doc_text">
578 <p>Once checked out from the CVS repository, the LLVM suite source code must be
579 configured via the <tt>configure</tt> script. This script sets variables in
580 <tt>llvm/Makefile.config</tt> and <tt>llvm/include/Config/config.h</tt>. It
581 also populates <i>OBJ_ROOT</i> with the Makefiles needed to begin building
584 <p>The following environment variables are used by the <tt>configure</tt>
585 script to configure the build system:</p>
588 <tr><th>Variable</th><th>Purpose</th></tr>
591 <td>Tells <tt>configure</tt> which C compiler to use. By default,
592 <tt>configure</tt> will look for the first GCC C compiler in
593 <tt>PATH</tt>. Use this variable to override
594 <tt>configure</tt>'s default behavior.</td>
598 <td>Tells <tt>configure</tt> which C++ compiler to use. By default,
599 <tt>configure</tt> will look for the first GCC C++ compiler in
600 <tt>PATH</tt>. Use this variable to override
601 <tt>configure</tt>'s default behavior.</td>
605 <p>The following options can be used to set or enable LLVM specific options:</p>
608 <dt><i>--with-llvmgccdir=LLVMGCCDIR</i>
610 Path to the location where the LLVM GCC front end binaries and
611 associated libraries were installed. This must be specified as an
614 <dt><i>--enable-optimized</i>
616 Enables optimized compilation by default (debugging symbols are removed
617 and GCC optimization flags are enabled). The default is to use an
618 unoptimized build (also known as a debug build).
620 <dt><i>--enable-jit</i>
622 Compile the Just In Time (JIT) compiler functionality. This is not
624 on all platforms. The default is dependent on platform, so it is best
625 to explicitly enable it if you want it.
627 <dt><i>--enable-spec2000</i>
628 <dt><i>--enable-spec2000=<<tt>directory</tt>></i>
630 Enable the use of SPEC2000 when testing LLVM. This is disabled by default
631 (unless <tt>configure</tt> finds SPEC2000 installed). By specifying
632 <tt>directory</tt>, you can tell configure where to find the SPEC2000
633 benchmarks. If <tt>directory</tt> is left unspecified, <tt>configure</tt>
634 uses the default value
635 <tt>/home/vadve/shared/benchmarks/speccpu2000/benchspec</tt>.
637 <dt><i>--enable-spec95</i>
638 <dt><i>--enable-spec95=<<tt>directory</tt>></i>
640 Enable the use of SPEC95 when testing LLVM. It is similar to the
641 <i>--enable-spec2000</i> option.
643 <dt><i>--enable-povray</i>
644 <dt><i>--enable-povray=<<tt>directory</tt>></i>
646 Enable the use of Povray as an external test. Versions of Povray written
647 in C should work. This option is similar to the <i>--enable-spec2000</i>
651 <p>To configure LLVM, follow these steps:</p>
654 <li>Change directory into the object root directory:
656 <tt>cd <i>OBJ_ROOT</i></tt>
659 <li>Run the <tt>configure</tt> script located in the LLVM source tree:
661 <tt><i>SRC_ROOT</i>/configure</tt>
665 <p>In addition to running <tt>configure</tt>, you must set the
666 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
667 This environment variable is used to locate "system" libraries like
668 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set to
669 the absolute path of the <tt>bytecode-libs</tt> subdirectory of the GCC front
670 end, or <i>LLVMGCCDIR</i>/<tt>bytecode-libs</tt>. For example, one might set
671 <tt>LLVM_LIB_SEARCH_PATH</tt> to
672 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the x86
673 version of the GCC front end on our research machines.</p>
677 <!-- ======================================================================= -->
678 <div class="doc_subsection">
679 <a name="compile">Compiling the LLVM Suite Source Code</a>
682 <div class="doc_text">
684 <p>Once you have configured LLVM, you can build it. There are three types of
690 These builds are the default when one types <tt>gmake</tt> (unless the
691 <tt>--enable-optimized</tt> option was used during configuration). The
692 build system will compile the tools and libraries with debugging
696 <dt>Release (Optimized) Builds
698 These builds are enabled with the <tt>--enable-optimized</tt> option to
699 <tt>configure</tt> or by specifying <tt>ENABLE_OPTIMIZED=1</tt> on the
700 <tt>gmake</tt> command line. For these builds, the build system will
701 compile the tools and libraries with GCC optimizations enabled and strip
702 debugging information from the libraries and executables it generates.
707 These builds are for use with profiling. They compile profiling
708 information into the code for use with programs like <tt>gprof</tt>.
709 Profile builds must be started by specifying <tt>ENABLE_PROFILING=1</tt>
710 on the <tt>gmake</tt> command line.
713 <p>Once you have LLVM configured, you can build it by entering the
714 <i>OBJ_ROOT</i> directory and issuing the following command:</p>
716 <p><tt>gmake</tt></p>
718 <p>If the build fails, please <a href="#brokengcc">check here</a> to see if you
719 are using a known broken version of GCC to compile LLVM with.</p>
722 If you have multiple processors in your machine, you may wish to use some of
723 the parallel build options provided by GNU Make. For example, you could use the
726 <p><tt>gmake -j2</tt></p>
728 <p>There are several special targets which are useful when working with the LLVM
732 <dt><tt>gmake clean</tt>
734 Removes all files generated by the build. This includes object files,
735 generated C/C++ files, libraries, and executables.
738 <dt><tt>gmake distclean</tt>
740 Removes everything that <tt>gmake clean</tt> does, but also removes files
741 generated by <tt>configure</tt>. It attempts to return the source tree to the
742 original state in which it was shipped.
745 <dt><tt>gmake install</tt>
747 Installs LLVM libraries and tools in a heirarchy under $PREFIX, specified with
748 <tt>./configure --prefix=[dir]</tt>, defaults to <tt>/usr/local</tt>.
751 <dt><tt>gmake install-bytecode</tt>
753 Assuming you built LLVM into $OBJDIR, when this command is run in
754 $OBJDIR/runtime, it will install bytecode libraries into the GCC front end's
755 bytecode library directory. If you need to update your bytecode libraries,
756 this is the target to use once you've built them.
760 <p>It is also possible to override default values from <tt>configure</tt> by
761 declaring variables on the command line. The following are some examples:</p>
764 <dt><tt>gmake ENABLE_OPTIMIZED=1</tt>
766 Perform a Release (Optimized) build.
769 <dt><tt>gmake ENABLE_PROFILING=1</tt>
771 Perform a Profiling build.
774 <dt><tt>gmake VERBOSE=1</tt>
776 Print what <tt>gmake</tt> is doing on standard output.
780 <p>Every directory in the LLVM object tree includes a <tt>Makefile</tt> to build
781 it and any subdirectories that it contains. Entering any directory inside the
782 LLVM object tree and typing <tt>gmake</tt> should rebuild anything in or below
783 that directory that is out of date.</p>
787 <!-- ======================================================================= -->
788 <div class="doc_subsection">
789 <a name="objfiles">The Location of LLVM Object Files</a>
792 <div class="doc_text">
794 <p>The LLVM build system is capable of sharing a single LLVM source tree among
795 several LLVM builds. Hence, it is possible to build LLVM for several different
796 platforms or configurations using the same source tree.</p>
798 <p>This is accomplished in the typical autoconf manner:</p>
801 <li><p>Change directory to where the LLVM object files should live:</p>
803 <p><tt>cd <i>OBJ_ROOT</i></tt></p></li>
805 <li><p>Run the <tt>configure</tt> script found in the LLVM source
808 <p><tt><i>SRC_ROOT</i>/configure</tt></p></li>
811 <p>The LLVM build will place files underneath <i>OBJ_ROOT</i> in directories
812 named after the build type:</p>
819 <dd><tt><i>OBJ_ROOT</i>/tools/Debug</tt>
821 <dd><tt><i>OBJ_ROOT</i>/lib/Debug</tt>
829 <dd><tt><i>OBJ_ROOT</i>/tools/Release</tt>
831 <dd><tt><i>OBJ_ROOT</i>/lib/Release</tt>
839 <dd><tt><i>OBJ_ROOT</i>/tools/Profile</tt>
841 <dd><tt><i>OBJ_ROOT</i>/lib/Profile</tt>
847 <!-- ======================================================================= -->
848 <div class="doc_subsection">
849 <a name="optionalconfig">Optional Configuration Items</a>
852 <div class="doc_text">
855 If you're running on a linux system that supports the "<a
856 href="http://www.tat.physik.uni-tuebingen.de/~rguenth/linux/binfmt_misc.html">binfmt_misc</a>"
857 module, and you have root access on the system, you can set your system up to
858 execute LLVM bytecode files directly. To do this, use commands like this (the
859 first command may not be required if you are already using the module):</p>
862 $ mount -t binfmt_misc none /proc/sys/fs/binfmt_misc
863 $ echo ':llvm:M::llvm::/path/to/lli:' > /proc/sys/fs/binfmt_misc/register
864 $ chmod u+x hello.bc (if needed)
869 This allows you to execute LLVM bytecode files directly. Thanks to Jack
870 Cummings for pointing this out!
876 <!-- *********************************************************************** -->
877 <div class="doc_section">
878 <a name="layout"><b>Program Layout</b></a>
880 <!-- *********************************************************************** -->
882 <div class="doc_text">
884 <p>One useful source of information about the LLVM source base is the LLVM <a
885 href="http://www.doxygen.org">doxygen</a> documentation available at <tt><a
886 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>.
887 The following is a brief introduction to code layout:</p>
891 <!-- ======================================================================= -->
892 <div class="doc_subsection"><a name="cvsdir"><tt>CVS</tt> directories</a></div>
894 <div class="doc_text">
896 <p>Every directory checked out of CVS will contain a <tt>CVS</tt> directory; for
897 the most part these can just be ignored.</p>
901 <!-- ======================================================================= -->
902 <div class="doc_subsection"><a name="include"><tt>llvm/include</tt></a></div>
904 <div class="doc_text">
906 <p>This directory contains public header files exported from the LLVM
907 library. The three main subdirectories of this directory are:</p>
910 <dt><tt><b>llvm/include/llvm</b></tt></dt>
911 <dd>This directory contains all of the LLVM specific header files. This
912 directory also has subdirectories for different portions of LLVM:
913 <tt>Analysis</tt>, <tt>CodeGen</tt>, <tt>Target</tt>, <tt>Transforms</tt>,
916 <dt><tt><b>llvm/include/llvm/Support</b></tt></dt>
917 <dd>This directory contains generic support libraries that are provided with
918 LLVM but not necessarily specific to LLVM. For example, some C++ STL utilities
919 and a Command Line option processing library store their header files here.
922 <dt><tt><b>llvm/include/llvm/Config</b></tt></dt>
923 <dd>This directory contains header files configured by the <tt>configure</tt>
924 script. They wrap "standard" UNIX and C header files. Source code can
925 include these header files which automatically take care of the conditional
926 #includes that the <tt>configure</tt> script generates.</dd>
930 <!-- ======================================================================= -->
931 <div class="doc_subsection"><a name="lib"><tt>llvm/lib</tt></a></div>
933 <div class="doc_text">
935 <p>This directory contains most of the source files of the LLVM system. In LLVM,
936 almost all code exists in libraries, making it very easy to share code among the
937 different <a href="#tools">tools</a>.</p>
940 <dt><tt><b>llvm/lib/VMCore/</b></tt></dt>
941 <dd> This directory holds the core LLVM source files that implement core
942 classes like Instruction and BasicBlock.</dd>
944 <dt><tt><b>llvm/lib/AsmParser/</b></tt></dt>
945 <dd>This directory holds the source code for the LLVM assembly language parser
948 <dt><tt><b>llvm/lib/ByteCode/</b></tt></dt>
949 <dd>This directory holds code for reading and write LLVM bytecode.</dd>
951 <dt><tt><b>llvm/lib/Analysis/</b></tt><dd>This directory contains a variety of
952 different program analyses, such as Dominator Information, Call Graphs,
953 Induction Variables, Interval Identification, Natural Loop Identification,
956 <dt><tt><b>llvm/lib/Transforms/</b></tt></dt>
957 <dd> This directory contains the source code for the LLVM to LLVM program
958 transformations, such as Aggressive Dead Code Elimination, Sparse Conditional
959 Constant Propagation, Inlining, Loop Invariant Code Motion, Dead Global
960 Elimination, and many others.</dd>
962 <dt><tt><b>llvm/lib/Target/</b></tt></dt>
963 <dd> This directory contains files that describe various target architectures
964 for code generation. For example, the <tt>llvm/lib/Target/SparcV9</tt>
965 directory holds the Sparc machine description while
966 <tt>llvm/lib/Target/CBackend</tt> implements the LLVM-to-C converter</dd>
968 <dt><tt><b>llvm/lib/CodeGen/</b></tt></dt>
969 <dd> This directory contains the major parts of the code generator: Instruction
970 Selector, Instruction Scheduling, and Register Allocation.</dd>
972 <dt><tt><b>llvm/lib/Debugger/</b></tt></dt>
973 <dd> This directory contains the source level debugger library that makes
974 it possible to instrument LLVM programs so that a debugger could identify
975 source code locations at which the program is executing.</dd>
977 <dt><tt><b>llvm/lib/ExecutionEngine/</b></tt></dt>
978 <dd> This directory contains libraries for executing LLVM bytecode directly
979 at runtime in both interpreted and JIT compiled fashions.</dd>
981 <dt><tt><b>llvm/lib/Support/</b></tt></dt>
982 <dd> This directory contains the source code that corresponds to the header
983 files located in <tt>llvm/include/Support/</tt>.</dd>
985 <dt><tt><b>llvm/lib/System/</b></tt></dt>
986 <dd>This directory contains the operating system abstraction layer that
987 shields LLVM from platform-specific coding.</dd>
992 <!-- ======================================================================= -->
993 <div class="doc_subsection"><a name="runtime"><tt>llvm/runtime</tt></a></div>
994 <div class="doc_text">
996 <p>This directory contains libraries which are compiled into LLVM bytecode and
997 used when linking programs with the GCC front end. Most of these libraries are
998 skeleton versions of real libraries; for example, libc is a stripped down
999 version of glibc.</p>
1001 <p>Unlike the rest of the LLVM suite, this directory needs the LLVM GCC front
1006 <!-- ======================================================================= -->
1007 <div class="doc_subsection"><a name="test"><tt>llvm/test</tt></a></div>
1008 <div class="doc_text">
1009 <p>This directory contains feature and regression tests and other basic sanity
1010 checks on the LLVM infrastructure. These are intended to run quickly and cover
1011 a lot of territory without being exhaustive.</p>
1014 <!-- ======================================================================= -->
1015 <div class="doc_subsection"><a name="llvmtest"><tt>llvm-test</tt></a></div>
1016 <div class="doc_text">
1017 <p>This is not a directory in the normal llvm module, it is a separate CVS
1018 module that must be checked out (usually to <tt>test/projects</tt>). This
1019 module contains a comprehensive correctness, performance and benchmarking test
1020 suite for LLVM. It is a separate CVS module because not every LLVM user is
1021 interested in downloading or building such a comprehensive test. For further
1022 details on this test suite, please see the
1023 <a href="TestingGuide.html">Testing Guide</a> document.</p>
1026 <!-- ======================================================================= -->
1027 <div class="doc_subsection"><a name="tools"><tt>llvm/tools</tt></a></div>
1028 <div class="doc_text">
1030 <p>The <b>tools</b> directory contains the executables built out of the
1031 libraries above, which form the main part of the user interface. You can
1032 always get help for a tool by typing <tt>tool_name --help</tt>. The
1033 following is a brief introduction to the most important tools:</p>
1036 <dt><tt><b>analyze</b></tt></dt>
1037 <dd><tt>analyze</tt> is used to run a specific
1038 analysis on an input LLVM bytecode file and print out the results. It is
1039 primarily useful for debugging analyses, or familiarizing yourself with
1040 what an analysis does.</dd>
1042 <dt><tt><b>bugpoint</b></tt></dt>
1043 <dd><tt>bugpoint</tt> is used to debug
1044 optimization passes or code generation backends by narrowing down the
1045 given test case to the minimum number of passes and/or instructions that
1046 still cause a problem, whether it is a crash or miscompilation. See <a
1047 href="HowToSubmitABug.html">HowToSubmitABug.html</a> for more information
1048 on using <tt>bugpoint</tt>.</dd>
1050 <dt><tt><b>llvmc</b></tt></dt>
1051 <dd>The LLVM Compiler Driver. This program can
1052 be configured to utilize both LLVM and non-LLVM compilation tools to enable
1053 pre-processing, translation, optimization, assembly, and linking of programs
1054 all from one command line. <tt>llvmc</tt> also takes care of processing the
1055 dependent libraries found in bytecode. This reduces the need to get the
1056 traditional <tt>-l<name></tt> options right on the command line.</dd>
1058 <dt><tt><b>llvm-ar</b></tt></dt>
1059 <dd>The archiver produces an archive containing
1060 the given LLVM bytecode files, optionally with an index for faster
1063 <dt><tt><b>llvm-as</b></tt></dt>
1064 <dd>The assembler transforms the human readable LLVM assembly to LLVM
1067 <dt><tt><b>llvm-dis</b></tt></dt>
1068 <dd>The disassembler transforms the LLVM bytecode to human readable
1071 <dt><tt><b>llvm-link</b></tt></dt>
1072 <dd><tt>llvm-link</tt>, not surprisingly, links multiple LLVM modules into
1073 a single program.</dd>
1075 <dt><tt><b>lli</b></tt></dt>
1076 <dd><tt>lli</tt> is the LLVM interpreter, which
1077 can directly execute LLVM bytecode (although very slowly...). In addition
1078 to a simple interpreter, <tt>lli</tt> also has a tracing mode (entered by
1079 specifying <tt>-trace</tt> on the command line). Finally, for
1080 architectures that support it (currently only x86 and Sparc), by default,
1081 <tt>lli</tt> will function as a Just-In-Time compiler (if the
1082 functionality was compiled in), and will execute the code <i>much</i>
1083 faster than the interpreter.</dd>
1085 <dt><tt><b>llc</b></tt></dt>
1086 <dd> <tt>llc</tt> is the LLVM backend compiler, which
1087 translates LLVM bytecode to a SPARC or x86 assembly file, or to C code (with
1088 the -march=c option).</dd>
1090 <dt><tt><b>llvmgcc</b></tt></dt>
1091 <dd><tt>llvmgcc</tt> is a GCC-based C frontend
1092 that has been retargeted to emit LLVM code as the machine code output. It
1093 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
1094 -o</tt> options that are typically used. The source code for the
1095 <tt>llvmgcc</tt> tool is currently not included in the LLVM CVS tree
1096 because it is quite large and not very interesting.
1099 <dt><tt><b>gccas</b></tt></dt>
1100 <dd>This tool is invoked by the <tt>llvmgcc</tt> frontend as the
1101 "assembler" part of the compiler. This tool actually assembles LLVM
1102 assembly to LLVM bytecode, performs a variety of optimizations, and
1103 outputs LLVM bytecode. Thus when you invoke
1104 <tt>llvmgcc -c x.c -o x.o</tt>, you are causing <tt>gccas</tt> to be
1105 run, which writes the <tt>x.o</tt> file (which is an LLVM bytecode file
1106 that can be disassembled or manipulated just like any other bytecode
1107 file). The command line interface to <tt>gccas</tt> is designed to be
1108 as close as possible to the <b>system</b> `<tt>as</tt>' utility so that
1109 the gcc frontend itself did not have to be modified to interface to
1110 a "weird" assembler.</dd>
1112 <dt><tt><b>gccld</b></tt></dt>
1113 <dd><tt>gccld</tt> links together several LLVM bytecode files into one
1114 bytecode file and does some optimization. It is the linker invoked by
1115 the GCC frontend when multiple .o files need to be linked together.
1116 Like <tt>gccas</tt>, the command line interface of <tt>gccld</tt> is
1117 designed to match the system linker, to aid interfacing with the GCC
1123 <dt><tt><b>opt</b></tt></dt>
1124 <dd><tt>opt</tt> reads LLVM bytecode, applies a
1125 series of LLVM to LLVM transformations (which are specified on the command
1126 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
1127 command is a good way to get a list of the program transformations
1128 available in LLVM.</dd>
1132 <!-- ======================================================================= -->
1133 <div class="doc_subsection"><a name="utils"><tt>llvm/utils</tt></a></div>
1134 <div class="doc_text">
1136 <p>This directory contains utilities for working with LLVM source code, and some
1137 of the utilities are actually required as part of the build process because they
1138 are code generators for parts of LLVM infrastructure.</p>
1141 <dt><tt><b>Burg/</b></tt> <dd><tt>Burg</tt> is an instruction selector
1142 generator -- it builds trees on which it then performs pattern-matching to
1143 select instructions according to the patterns the user has specified. Burg
1144 is currently used in the Sparc V9 backend.<p>
1146 <dt><tt><b>codegen-diff</b></tt> <dd><tt>codegen-diff</tt> is a script
1147 that finds differences between code that LLC generates and code that LLI
1148 generates. This is a useful tool if you are debugging one of them,
1149 assuming that the other generates correct output. For the full user
1150 manual, run <tt>`perldoc codegen-diff'</tt>.<p>
1152 <dt><tt><b>cvsupdate</b></tt> <dd><tt>cvsupdate</tt> is a script that will
1153 update your CVS tree, but produce a much cleaner and more organized output
1154 than simply running <tt>`cvs -z3 up -dP'</tt> will. For example, it will group
1155 together all the new and updated files and modified files in separate
1156 sections, so you can see at a glance what has changed. If you are at the
1157 top of your LLVM CVS tree, running <tt>utils/cvsupdate</tt> is the
1158 preferred way of updating the tree.<p>
1160 <dt><tt><b>emacs/</b></tt> <dd>The <tt>emacs</tt> directory contains
1161 syntax-highlighting files which will work with Emacs and XEmacs editors,
1162 providing syntax highlighting support for LLVM assembly files and TableGen
1163 description files. For information on how to use the syntax files, consult
1164 the <tt>README</tt> file in that directory.<p>
1166 <dt><tt><b>getsrcs.sh</b></tt> <dd>The <tt>getsrcs.sh</tt> script finds
1167 and outputs all non-generated source files, which is useful if one wishes
1168 to do a lot of development across directories and does not want to
1169 individually find each file. One way to use it is to run, for example:
1170 <tt>xemacs `utils/getsources.sh`</tt> from the top of your LLVM source
1173 <dt><tt><b>llvmgrep</b></tt></dt>
1174 <dd>This little tool performs an "egrep -H -n" on each source file in LLVM and
1175 passes to it a regular expression provided on <tt>llvmgrep</tt>'s command
1176 line. This is a very efficient way of searching the source base for a
1177 particular regular expression.</dd>
1179 <dt><tt><b>makellvm</b></tt> <dd>The <tt>makellvm</tt> script compiles all
1180 files in the current directory and then compiles and links the tool that
1181 is the first argument. For example, assuming you are in the directory
1182 <tt>llvm/lib/Target/Sparc</tt>, if <tt>makellvm</tt> is in your path,
1183 simply running <tt>makellvm llc</tt> will make a build of the current
1184 directory, switch to directory <tt>llvm/tools/llc</tt> and build it,
1185 causing a re-linking of LLC.<p>
1187 <dt><tt><b>NightlyTest.pl</b></tt> and
1188 <tt><b>NightlyTestTemplate.html</b></tt> <dd>These files are used in a
1189 cron script to generate nightly status reports of the functionality of
1190 tools, and the results can be seen by following the appropriate link on
1191 the <a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a>.<p>
1193 <dt><tt><b>TableGen/</b></tt> <dd>The <tt>TableGen</tt> directory contains
1194 the tool used to generate register descriptions, instruction set
1195 descriptions, and even assemblers from common TableGen description
1198 <dt><tt><b>vim/</b></tt> <dd>The <tt>vim</tt> directory contains
1199 syntax-highlighting files which will work with the VIM editor, providing
1200 syntax highlighting support for LLVM assembly files and TableGen
1201 description files. For information on how to use the syntax files, consult
1202 the <tt>README</tt> file in that directory.<p>
1208 <!-- *********************************************************************** -->
1209 <div class="doc_section">
1210 <a name="tutorial">An Example Using the LLVM Tool Chain</a>
1212 <!-- *********************************************************************** -->
1214 <div class="doc_text">
1217 <li>First, create a simple C file, name it 'hello.c':
1219 #include <stdio.h>
1221 printf("hello world\n");
1226 <li><p>Next, compile the C file into a LLVM bytecode file:</p>
1227 <p><tt>% llvmgcc hello.c -o hello</tt></p>
1229 <p>Note that you should have already built the tools and they have to be
1230 in your path, at least <tt>gccas</tt> and <tt>gccld</tt>.</p>
1232 <p>This will create two result files: <tt>hello</tt> and
1233 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
1234 corresponds the the compiled program and the library facilities that it
1235 required. <tt>hello</tt> is a simple shell script that runs the bytecode
1236 file with <tt>lli</tt>, making the result directly executable. Note that
1237 all LLVM optimizations are enabled by default, so there is no need for a
1238 "-O3" switch.</p></li>
1240 <li><p>Run the program. To make sure the program ran, execute one of the
1241 following commands:</p>
1243 <p><tt>% ./hello</tt></p>
1247 <p><tt>% lli hello.bc</tt></p></li>
1249 <li><p>Use the <tt>llvm-dis</tt> utility to take a look at the LLVM assembly
1252 <p><tt>% llvm-dis < hello.bc | less</tt><p></li>
1254 <li><p>Compile the program to native assembly using the LLC code
1257 <p><tt>% llc hello.bc -o hello.s</tt></p>
1259 <li><p>Assemble the native assembly language file into a program:</p>
1261 <p><b>Solaris:</b><tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.native</tt></p>
1262 <p><b>Others:</b><tt>% gcc hello.s -o hello.native</tt></p>
1264 <li><p>Execute the native code program:</p>
1266 <p><tt>% ./hello.native</tt></p></li>
1272 <!-- *********************************************************************** -->
1273 <div class="doc_section">
1274 <a name="problems">Common Problems</a>
1276 <!-- *********************************************************************** -->
1278 <div class="doc_text">
1280 <p>If you are having problems building or using LLVM, or if you have any other
1281 general questions about LLVM, please consult the <a href="FAQ.html">Frequently
1282 Asked Questions</a> page.</p>
1286 <!-- *********************************************************************** -->
1287 <div class="doc_section">
1288 <a name="links">Links</a>
1290 <!-- *********************************************************************** -->
1292 <div class="doc_text">
1294 <p>This document is just an <b>introduction</b> to how to use LLVM to do
1295 some simple things... there are many more interesting and complicated things
1296 that you can do that aren't documented here (but we'll gladly accept a patch
1297 if you want to write something up!). For more information about LLVM, check
1301 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
1302 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
1303 <li><a href="http://llvm.cs.uiuc.edu/docs/Projects.html">Starting a Project
1304 that Uses LLVM</a></li>
1309 <!-- *********************************************************************** -->
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1318 <a href="mailto:sabre@nondot.org">Chris Lattner</a><br>
1319 <a href="http://llvm.x10sys.com/rspencer/">Reid Spencer</a><br>
1320 <a href="http://llvm.cs.uiuc.edu">The LLVM Compiler Infrastructure</a><br>
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