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John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]3 <head>
4 <title>Getting Started with LLVM System</title>
5 </head>
6
7 <body bgcolor=white>
8 <center><h1>Getting Started with the LLVM System<br><font size=3>By: <a
9 href="mailto:gshi1@uiuc.edu">Guochun Shi</a>,
John Criswelldd899fa2003-06-30 22:20:46 +0000[diff] [blame]10 <a href="mailto:sabre@nondot.org">Chris Lattner,</a>
11 <a href="mailto:criswell@uiuc.edu">John Criswell,</a> and
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]12 <a href="http://www.cs.uiuc.edu/~vadve">Vikram Adve</a>
13 </font></h1></center>
14
15 <!--=====================================================================-->
16 <h2><a name="Contents">Contents</a></h2>
17 <!--=====================================================================-->
18
19 <ul>
20 <li><a href="#overview">Overview</a>
21 <li><a href="#starting">Getting started with LLVM</a>
22 <ol>
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]23 <li><a href="#requirements">Requirements</a>
24 <ol>
25 <li><a href="#hardware">Hardware</a>
26 <li><a href="#software">Software</a>
27 </ol>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]28 <li><a href="#quickstart">Getting started quickly (a summary)</a>
29 <li><a href="#checkout">Checkout LLVM from CVS</a>
30 <li><a href="#terminology">Terminology and Notation</tt></a>
31 <li><a href="#objfiles">The location for object files</tt></a>
32 <li><a href="#config">Local Configuration Options</tt></a>
33 <li><a href="#environment">Setting up your environment</a>
34 <li><a href="#compile">Compiling the source code</a>
35 </ol>
36 <li><a href="#layout">Program layout</a>
37 <ol>
38 <li><a href="#cvsdir">CVS directories</a>
39 <li><a href="#dd"><tt>Depend</tt>, <tt>Debug</tt>, &amp;
40 <tt>Release</tt> directories</a></li>
41 <li><a href="#include"><tt>llvm/include</tt></a>
42 <li><a href="#lib"><tt>llvm/lib</tt></a>
43 <li><a href="#test"><tt>llvm/test</tt></a>
44 <li><a href="#tools"><tt>llvm/tools</tt></a>
45 </ol>
46 <li><a href="#tutorial">An example using the LLVM tool chain</a>
47 <li><a href="#links">Links</a>
48 </ul>
49
50
51 <!--=====================================================================-->
52 <center>
53 <h2><a name="overview"><b>Overview</b></a></h2>
54 </center>
55 <!--=====================================================================-->
56
57 <p>The <a href"starting">next section</a> of this guide is meant to get
58 you up and running with LLVM and to give you some basic information about
59 the LLVM environment. The <a href"#quickstart">first subsection</a> gives
60 a short summary for those who are already familiar with the system and
61 want to get started as quickly as possible.
62
63 <p>The later sections of this guide describe the <a
64 href"#layout">general layout</a> of the the LLVM source-tree, a <a
65 href="#tutorial">simple example</a> using the LLVM tool chain, and <a
66 href="#links">links</a> to find more information about LLVM or to get
67 help via e-mail.
68
69 <!--=====================================================================-->
70 <center>
71 <h2><a name="starting"><b>Getting Started</b></a></h2>
72 </center>
73 <!--=====================================================================-->
74
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]75 <!--=====================================================================-->
76 <h3><a name="requirements"><b>Requirements</b></a></h3>
77 <!--=====================================================================-->
78
79 <!--=====================================================================-->
80 <h4><a name="hardware"><b>Hardware</b></a></h4>
81 <!--=====================================================================-->
82 LLVM is known to work on the following platforms:
83 <ul>
84 <li> Linux on x86
85 <ul>
86 <li> Approximately 700 MB of Free Disk Space
87 <ul>
88 <li>Source code: 30 MB
89 <li>Object code: 670 MB
90 </ul>
91 </ul>
92 <li> Solaris on Sparc
93 <ul>
94 <li> Approximately 1.03 GB of Free Disk Space
95 <ul>
96 <li>Source code: 30 MB
97 <li>Object code: 1000 MB
98 </ul>
99 </ul>
100 </ul>
101
102 LLVM may compile on other platforms. While the LLVM utilities should work,
103 they will only generate Sparc or x86 machine code.
104
105 <!--=====================================================================-->
106 <h4><a name="software"><b>Software</b></a></h4>
107 <!--=====================================================================-->
108 <p>
109 Compiling LLVM requires that you have several different software packages
110 installed:
111
112 <ul>
113 <li> GCC
114 <p>
115 The GNU Compiler Collection must be installed with C and C++ language
116 support. GCC 3.x is supported, although some effort has been made to
117 support GCC 2.96.
118 </p>
119
120 <p>
121 Note that we currently do not support any other C++ compiler.
122 </p>
123
124 <li> GNU Make
125 <p>
126 The LLVM build system relies upon GNU Make extensions. Therefore, you
127 will need GNU Make (sometimes known as gmake) to build LLVM.
128 </p>
129
130 <li> Flex and Bison
131 <p>
132 The LLVM source code is built using flex and bison. You will not be
133 able to configure and compile LLVM without them.
134 </p>
135 </ul>
136
137 <p>
138 There are some additional tools that you may want to have when working with
139 LLVM:
140 </p>
141
142 <ul>
143 <li> GNU Autoconf and GNU M4
144 <p>
145 If you want to make changes to the autoconf scripts which configure LLVM
146 for compilation, you will need GNU autoconf, and consequently, GNU M4.
147 LLVM was built with autoconf 2.53, so that release and any later
148 release should work.
149 </p>
150 </ul>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]151
152 <!--=====================================================================-->
153 <h3><a name="quickstart"><b>Getting Started Quickly (A Summary)</b></a></h3>
154 <!--=====================================================================-->
155
156 Here's the short story for getting up and running quickly with LLVM:
Chris Lattner96768ea2003-02-14 04:22:13 +0000[diff] [blame]157 <ol>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]158 <li>Find the path to the CVS repository containing LLVM (we'll call this <i>CVSROOTDIR</i>).
159 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
160 <li><tt>cvs -d <i>CVSROOTDIR</i> checkout llvm</tt>
161 <li><tt>cd llvm</tt>
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]162 <li>Run <tt>configure</tt> to configure the Makefiles and header files.
163 Useful options include:
164 <ul>
165 <li><tt>--with-objroot=<i>directory</i></tt>
166 <br>
167 Specifiy where object files should be placed during the build.
168
169 <li><tt>--with-llvmgccdir=<i>directory</i></tt>
170 <br>
171 Specifiy where the LLVM C frontend has been installed.
172 </ul>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]173 <li>Set your LLVM_LIB_SEARCH_PATH environment variable.
174 <li><tt>gmake -k |& tee gnumake.out
175 &nbsp;&nbsp;&nbsp;# this is csh or tcsh syntax</tt>
Chris Lattner96768ea2003-02-14 04:22:13 +0000[diff] [blame]176 </ol>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]177
178 <p>See <a href="#environment">Setting up your environment</a> on tips to
179 simplify working with the LLVM front-end and compiled tools. See the
180 other sub-sections below for other useful details in working with LLVM,
181 or go straight to <a href="#layout">Program Layout</a> to learn about the
182 layout of the source code tree.
183
184 <!------------------------------------------------------------------------->
185 <h3><a name="terminology">Terminology and Notation</a></h3>
186 <!------------------------------------------------------------------------->
187
188 <p>Throughout this manual, the following names are used to denote paths
189 specific to the local system and working environment. <i>These are not
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]190 environment variables you need to set but just strings used in the rest
191 of this document below</i>. In any of the examples below, simply replace
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]192 each of these names with the appropriate pathname on your local system.
Chris Lattner1db872d2002-09-06 16:26:13 +0000[diff] [blame]193 All these paths are absolute:</p>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]194 <ul>
195 </ul>
196
197 <!------------------------------------------------------------------------->
198 <h3><a name="checkout">Checkout LLVM from CVS</a></h3>
199 <!------------------------------------------------------------------------->
200
201 <p>Before checking out the source code, you will need to know the path to
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]202 the CVS repository containing the LLVM source code (we'll call this
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]203 <i>CVSROOTDIR</i> below). Ask the person responsible for your local LLVM
204 installation to give you this path.
205
206 <p>To get a fresh copy of the entire source code, all you
207 need to do is check it out from CVS as follows:
208 <ul>
209 <li><tt>cd <i>where-you-want-llvm-to-live</i></tt>
210 <li><tt>cvs -d <i>CVSROOTDIR</i> checkout llvm</tt></p>
211 </ul>
212
213 <p>This will create an '<tt>llvm</tt>' directory in the current
214 directory and fully populate it with the LLVM source code, Makefiles,
215 test directories, and local copies of documentation files.</p>
216
217 <!------------------------------------------------------------------------->
218 <h3><a name="config">Local Configuration Options</a></h3>
219 <!------------------------------------------------------------------------->
220
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]221 <p>Once checked out from the CVS repository, options and pathnames specific
222 to an installation of LLVM can be set via the <tt>configure</tt> script.
223 This script sets variables in <tt>llvm/Makefile.config</tt> and
224 <tt>llvm/include/Config/config.h</tt>.
225
226 <p>
227 The following environment variables are used by <tt>configure</tt> to
228 configure Makefile.config:
229 </p>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]230
231 <ul>
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]232 <p><li><i>CXX</i> = Pathname of the C++ compiler to use.
233 <p><li><i>CC</i> = Pathname of the C compiler to use.
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]234 </ul>
235
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]236 The following options can be used to set or enable LLVM specific options:
237
238 <ul>
239 <p><li><i>--with-objroot=LLVM_OBJ_ROOT</i> =
240 Path to the directory where
241 object files, libraries, and executables should be placed.
242 (See the Section on <a href=#objfiles>
243 The location for LLVM object files</a>
244 for more information.)
245 <p><li><i>--with-llvmgccdir=LLVMGCCDIR</i> =
246 Path to the location of the LLVM front-end
247 binaries and associated libraries.
248 <p><li><i>--enable-optimized</i> =
249 Enables optimized compilation (debugging symbols are removed and GCC
250 optimization flags are enabled).
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]251 <p><li><i>--enable-jit</i> =
252 Compile the Just In Time (JIT) functionality. This is not available
253 on all platforms.
254 </ul>
255
256 In addition to running <tt>configure</tt>, you must set the
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]257 <tt>LLVM_LIB_SEARCH_PATH</tt> environment variable in your startup scripts.
258 This environment variable is used to locate "system" libraries like
259 "<tt>-lc</tt>" and "<tt>-lm</tt>" when linking. This variable should be set
260 to the absolute path for the bytecode-libs subdirectory of the C front-end
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]261 install. For example, one might set <tt>LLVM_LIB_SEARCH_PATH</tt> to
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]262 <tt>/home/vadve/lattner/local/x86/llvm-gcc/bytecode-libs</tt> for the X86
263 version of the C front-end on our research machines.<p>
264
265 <!------------------------------------------------------------------------->
266 <h3><a name="objfiles">The location for LLVM object files</a></h3>
267 <!------------------------------------------------------------------------->
268
269 <p>The LLVM make system sends most output files generated during the build
270 into the directory defined by the variable OBJ_ROOT in
271 <tt>llvm/Makefile.config</tt>. This can be either just your normal LLVM
272 source tree or some other directory writable by you. You may wish to put
273 object files on a different filesystem either to keep them from being backed
274 up or to speed up local builds.
275
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]276 <p>If you wish to place output files into a separate directory, use the
277 <tt>--with-objroot=<i>directory</i></tt> option of <tt>configure</tt> to
278 set the top level directory of where the object files will go. Otherwise,
279 leave this option unspecified, and <tt>configure</tt> will place files
280 within the LLVM source tree.
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]281
282 <!------------------------------------------------------------------------->
283 <h3><a name="environment">Setting up your environment</a></h3>
284 <!------------------------------------------------------------------------->
285
286 <i>NOTE: This step is optional but will set up your environment so you
287 can use the compiled LLVM tools with as little hassle as
288 possible.</i>)
289
290 <p>Add the following lines to your <tt>.cshrc</tt> (or the corresponding
291 lines to your <tt>.profile</tt> if you use a bourne shell derivative).
292
293 <pre>
294 # Make the C front end easy to use...
295 alias llvmgcc <i>LLVMGCCDIR</i><tt>/bin/llvm-gcc</tt>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]296
297 # Make the LLVM tools easy to use...
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]298 setenv PATH <i>OBJ_ROOT</i>/llvm/tools/Debug:${PATH}
299 </pre>
300 The <tt>llvmgcc</tt> alias is useful because the C compiler is not
301 included in the CVS tree you just checked out.
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]302
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]303 <p>The other <a href="#tools">LLVM tools</a> are part of the LLVM
304 source base and built when compiling LLVM. They will be built into the
305 <tt><i>OBJ_ROOT</i>/tools/Debug</tt> directory.</p>
306
307 <!------------------------------------------------------------------------->
308 <h3><a name="compile">Compiling the source code</a></h3>
309 <!------------------------------------------------------------------------->
310
311 <p>Every directory in the LLVM source tree includes a <tt>Makefile</tt> to
312 build it and any subdirectories that it contains. These makefiles require
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]313 that you use GNU Make (sometimes called <tt>gmake</tt>) instead of
314 <tt>make</tt> to
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]315 build them, but can
316 otherwise be used freely. To build the entire LLVM system, just enter the
317 top level <tt>llvm</tt> directory and type <tt>gmake</tt>. A few minutes
318 later you will hopefully have a freshly compiled toolchain waiting for you
319 in <tt><i>OBJ_ROOT</i>/llvm/tools/Debug</tt>. If you want to look at the
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]320 libraries that
321 were compiled, look in <tt><i>OBJ_ROOT</i>/llvm/lib/Debug</tt>.</p>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]322
323 If you get an error about a <tt>/localhome</tt> directory, follow the
324 instructions in the section about <a href="#environment">Setting Up Your
325 Environment.</a>
326
327
328
329 <!--=====================================================================-->
330 <center>
331 <h2><a name="layout"><b>Program Layout</b></a></h2>
332 </center>
333 <!--=====================================================================-->
334
335 <p>One useful source of infomation about the LLVM sourcebase is the LLVM <a
336 href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a
337 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>. The
338 following is a brief introduction to code layout:</p>
339
340
341 <!------------------------------------------------------------------------->
342 <h3><a name="cvsdir"><tt>CVS</tt> directories</a></h3>
343 <!------------------------------------------------------------------------->
344
345 Every directory checked out of CVS will contain a <tt>CVS</tt> directory;
346 for the most part these can just be ignored.
347
348
349 <!------------------------------------------------------------------------->
350 <h3><a name="ddr"><tt>Depend</tt>, <tt>Debug</tt>, &amp; <tt>Release</tt>
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]351 directories</a></h3>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]352 <!------------------------------------------------------------------------->
353
354 If you are building with the "<tt>OBJ_ROOT=.</tt>" option enabled in the
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]355 <tt>Makefile.config</tt> file (i.e. you did not specify
356 <tt>--with-objroot</tt> when you ran <tt>configure</tt>), most source
357 directories will contain two
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]358 directories, <tt>Depend</tt> and <tt>Debug</tt>. The <tt>Depend</tt>
359 directory contains automatically generated dependance files which are used
360 during compilation to make sure that source files get rebuilt if a header
361 file they use is modified. The <tt>Debug</tt> directory holds the object
362 files, library files, and executables that are used for building a debug
363 enabled build. The <tt>Release</tt> directory is created to hold the same
364 files when the <tt>ENABLE_OPTIMIZED=1</tt> flag is passed to <tt>gmake</tt>,
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]365 causing an optimized build to be performed.<p>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]366
367
368 <!------------------------------------------------------------------------->
369 <h3><a name="include"><tt>llvm/include</tt></a></h3>
370 <!------------------------------------------------------------------------->
371
372 This directory contains public header files exported from the LLVM
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]373 library. The three main subdirectories of this directory are:<p>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]374
John Criswell8df90e02003-06-11 20:46:40 +0000[diff] [blame]375 <ol>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]376 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
377 specific header files. This directory also has subdirectories for
378 different portions of LLVM: <tt>Analysis</tt>, <tt>CodeGen</tt>,
379 <tt>Reoptimizer</tt>, <tt>Target</tt>, <tt>Transforms</tt>, etc...
380
381 <li><tt>llvm/include/Support</tt> - This directory contains generic
382 support libraries that are independant of LLVM, but are used by LLVM.
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]383 For example, some C++ STL utilities and a Command Line option processing
384 library.
385
386 <li><tt>llvm/include/Config</tt> - This directory contains header files
387 configured by the <tt>configure</tt> script. They wrap "standard" UNIX
388 and C header files. Source code can include these header files which
389 automatically take care of the conditional #includes that the configure
390 script generates.
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]391 </ol>
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]392
393 <!------------------------------------------------------------------------->
394 <h3><a name="lib"><tt>llvm/lib</tt></a></h3>
395 <!------------------------------------------------------------------------->
396
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]397 This directory contains most of the source files of the LLVM system. In
398 LLVM almost all
399 code exists in libraries, making it very easy to share code among the
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]400 different <a href="#tools">tools</a>.<p>
401
402 <dl compact>
403 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
404 source files that implement core classes like Instruction and BasicBlock.
405
406 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
407 for the LLVM assembly language parser library.
408
409 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
410 and write LLVM bytecode.
411
412 <dt><tt>llvm/lib/CWriter/</tt><dd> This directory implements the LLVM to C
413 converter.
414
415 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
416 different program analyses, such as Dominator Information, Call Graphs,
417 Induction Variables, Interval Identification, Natural Loop Identification,
418 etc...
419
420 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
421 code for the LLVM to LLVM program transformations, such as Aggressive Dead
422 Code Elimination, Sparse Conditional Constant Propagation, Inlining, Loop
423 Invarient Code Motion, Dead Global Elimination, Pool Allocation, and many
424 others...
425
426 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
427 describe various target architectures for code generation. For example,
428 the llvm/lib/Target/Sparc directory holds the Sparc machine
429 description.<br>
430
431 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
432 of the code generator: Instruction Selector, Instruction Scheduling, and
433 Register Allocation.
434
435 <dt><tt>llvm/lib/Reoptimizer/</tt><dd> This directory holds code related
436 to the runtime reoptimizer framework that is currently under development.
437
438 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
439 that corresponds to the header files located in
440 <tt>llvm/include/Support/</tt>.
441 </dl>
442
443 <!------------------------------------------------------------------------->
444 <h3><a name="test"><tt>llvm/test</tt></a></h3>
445 <!------------------------------------------------------------------------->
446
447 <p>This directory contains regression tests and source code that is used to
448 test the LLVM infrastructure...</p>
449
450 <!------------------------------------------------------------------------->
451 <h3><a name="tools"><tt>llvm/tools</tt></a></h3>
452 <!------------------------------------------------------------------------->
453
454 <p>The <b>tools</b> directory contains the executables built out of the
455 libraries above, which form the main part of the user interface. You can
456 always get help for a tool by typing <tt>tool_name --help</tt>. The
457 following is a brief introduction to the most important tools.</p>
458
459 <dl compact>
460 <dt><tt><b>as</b></tt><dd>The assembler transforms the human readable
461 LLVM assembly to LLVM bytecode.<p>
462
463 <dt><tt><b>dis</b></tt><dd>The disassembler transforms the LLVM bytecode
464 to human readable LLVM assembly. Additionally it can convert LLVM
465 bytecode to C, which is enabled with the <tt>-c</tt> option.<p>
466
467 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
468 can directly execute LLVM bytecode (although very slowly...). In addition
469 to a simple intepreter, <tt>lli</tt> is also has debugger and tracing
470 modes (entered by specifying <tt>-debug</tt> or <tt>-trace</tt> on the
471 command line, respectively).<p>
472
473 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler,
474 which translates LLVM bytecode to a SPARC assembly file.<p>
475
476 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC based C frontend
477 that has been retargeted to emit LLVM code as the machine code output. It
478 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
479 -o</tt> options that are typically used. The source code for the
480 <tt>llvmgcc</tt> tool is currently not included in the LLVM cvs tree
481 because it is quite large and not very interesting.<p>
482
483 <ol>
484 <dt><tt><b>gccas</b></tt><dd> This tool is invoked by the
485 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
486 tool actually assembles LLVM assembly to LLVM bytecode,
John Criswell7a73b802003-06-30 21:59:07 +0000[diff] [blame]487 performs a variety of optimizations,
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]488 and outputs LLVM bytecode. Thus when you invoke <tt>llvmgcc -c x.c -o
489 x.o</tt>, you are causing <tt>gccas</tt> to be run, which writes the
490 <tt>x.o</tt> file (which is an LLVM bytecode file that can be
491 disassembled or manipulated just like any other bytecode file). The
492 command line interface to <tt>gccas</tt> is designed to be as close as
493 possible to the <b>system</b> '<tt>as</tt>' utility so that the gcc
494 frontend itself did not have to be modified to interface to a "wierd"
495 assembler.<p>
496
497 <dt><tt><b>gccld</b></tt><dd> <tt>gccld</tt> links together several LLVM
498 bytecode files into one bytecode file and does some optimization. It is
499 the linker invoked by the gcc frontend when multiple .o files need to be
500 linked together. Like <tt>gccas</tt> the command line interface of
501 <tt>gccld</tt> is designed to match the system linker, to aid
502 interfacing with the GCC frontend.<p>
503 </ol>
504
505 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads LLVM bytecode, applies a
506 series of LLVM to LLVM transformations (which are specified on the command
507 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
508 command is a good way to get a list of the program transformations
509 available in LLVM.<p>
510
511
512 <dt><tt><b>analyze</b></tt><dd> <tt>analyze</tt> is used to run a specific
513 analysis on an input LLVM bytecode file and print out the results. It is
514 primarily useful for debugging analyses, or familiarizing yourself with
515 what an analysis does.<p>
516
517 </dl>
518
519 <!--=====================================================================-->
520 <h2><a name="tutorial">An example using the LLVM tool chain</h2>
521 <!--=====================================================================-->
522
523 <ol>
524 <li>First, create a simple C file, name it 'hello.c':
525 <pre>
526 #include &lt;stdio.h&gt;
527 int main() {
528 printf("hello world\n");
529 return 0;
530 }
531 </pre>
532
533 <li>Next, compile the C file into a LLVM bytecode file:<p>
534
535 <tt>% llvmgcc hello.c -o hello</tt><p>
536
537 This will create two result files: <tt>hello</tt> and
538 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
539 corresponds the the compiled program and the library facilities that it
540 required. <tt>hello</tt> is a simple shell script that runs the bytecode
541 file with <tt>lli</tt>, making the result directly executable.<p>
542
543 <li>Run the program. To make sure the program ran, execute one of the
544 following commands:<p>
John Criswell8df90e02003-06-11 20:46:40 +0000[diff] [blame]545
John Criswell85ed3612003-06-12 19:34:44 +0000[diff] [blame]546 <tt>% ./hello</tt><p>
547
548 or<p>
549
550 <tt>% lli hello.bc</tt><p>
551
552 <li>Use the <tt>dis</tt> utility to take a look at the LLVM assembly
553 code:<p>
554
555 <tt>% dis < hello.bc | less</tt><p>
556
557 <li>Compile the program to native Sparc assembly using the code
558 generator:<p>
559
560 <tt>% llc hello.bc -o hello.s</tt><p>
561
562 <li>Assemble the native sparc assemble file into a program:<p>
563
564 <tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt><p>
565
566 <li>Execute the native sparc program:<p>
567
568 <tt>% ./hello.sparc</tt><p>
569
570 </ol>
571
572
573 <!--=====================================================================-->
574 <h2><a name="links">Links</a></h2>
575 <!--=====================================================================-->
576
577 <p>This document is just an <b>introduction</b> to how to use LLVM to do
578 some simple things... there are many more interesting and complicated things
579 that you can do that aren't documented here (but we'll gladly accept a patch
580 if you want to write something up!). For more information about LLVM, check
581 out:</p>
582
583 <ul>
584 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
585 <li><a href="http://llvm.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
586 </ul>
587
588 <hr>
589
590 If you have any questions or run into any snags (or you have any
591 additions...), please send an email to
592 <a href="mailto:sabre@nondot.org">Chris Lattner</a>.</p>
593
594 <!-- Created: Mon Jul 1 02:29:02 CDT 2002 -->
595 <!-- hhmts start -->
596Last modified: Tue Jun 3 22:06:43 CDT 2003
597<!-- hhmts end -->
598 </body>
Guochun Shif4688a82002-07-17 23:05:56 +0000[diff] [blame]599</html>