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3 <head>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]4 <title>Getting Started with LLVM System</title>
Guochun Shif4688a82002-07-17 23:05:56 +0000[diff] [blame]5 </head>
6
Chris Lattner945de2d2002-07-24 19:59:33 +0000[diff] [blame]7 <body bgcolor=white>
8 <h1>Getting Started with the LLVM System<br><font size=3>By: <a
9 href="mailto:gshi1@uiuc.edu">Guochun Shi</a> and <a
10 href="mailto:sabre@nondot.org">Chris Lattner</a></font></h1>
11
Guochun Shif4688a82002-07-17 23:05:56 +0000[diff] [blame]12 <ul>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]13 <li><a href="#quickstart">Getting started with LLVM</a>
14 <ol>
15 <li><a href="#cvs">Checkout LLVM from CVS</a>
Chris Lattnercefbd322002-08-13 21:10:30 +0000[diff] [blame]16 <li><a href="#shared">Access to <tt>/shared</tt></a>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]17 <li><a href="#environment">Set up your environment</a>
18 <li><a href="#compile">Compiling the Source Code</a>
19 </ol>
Guochun Shif4688a82002-07-17 23:05:56 +0000[diff] [blame]20 <li><a href="#layout">Program layout</a>
21 <ol>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]22 <li><a href="#cvsdir">CVS directories</a>
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]23 <li><a href="#dd"><tt>Depend</tt>, <tt>Debug</tt>, &amp;
24 <tt>Release</tt> directories</a></li>
25 <li><a href="#include"><tt>llvm/include</tt></a>
26 <li><a href="#lib"><tt>llvm/lib</tt></a>
27 <li><a href="#test"><tt>llvm/test</tt></a>
28 <li><a href="#tools"><tt>llvm/tools</tt></a>
Guochun Shif4688a82002-07-17 23:05:56 +0000[diff] [blame]29 </ol>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]30 <li><a href="#tutorial">An example using the LLVM tool chain</a>
Guochun Shif4688a82002-07-17 23:05:56 +0000[diff] [blame]31 <li><a href="#links">Links</a>
32 </ul>
Guochun Shif4688a82002-07-17 23:05:56 +0000[diff] [blame]33
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]34
35
36 <!--=====================================================================-->
37 <h2><a name="quickstart">Getting Started with LLVM</a></h2>
38 <!--=====================================================================-->
39
40 <p>This guide is meant to get you up and running with LLVM as quickly as
41 possible. Once you get the basic system running you can choose an area to
42 dive into and learn more about. If you get stuck or something is missing
43 from this document, please email <a
44 href="mailto:sabre@nondot.org">Chris</a>.</p>
45
46
47 <!------------------------------------------------------------------------->
48 <h3><a name="tools">Checkout LLVM from CVS</a></h3>
49 <!------------------------------------------------------------------------->
50
51 <p>First step is to get the actual source code. To do this, all you need to
52 do is check it out from CVS. From your home directory, just enter:</p>
53
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]54 <p><tt>cvs -d /home/vadve/vadve/Research/DynOpt/CVSRepository checkout
55 llvm</tt></p>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]56
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]57 <p>This will create an '<tt>llvm</tt>' directory in your home directory and
58 fully populate it with the source code for LLVM.</p>
Chris Lattnercefbd322002-08-13 21:10:30 +0000[diff] [blame]59
60
61 <!------------------------------------------------------------------------->
62 <h3><a name="shared">Access to <tt>/shared</tt></a></h3>
63 <!------------------------------------------------------------------------->
64
65 By default, LLVM is configured to send all compiled files into the
66 <tt>/shared/[yourloginname]/</tt> directory. The idea is that this
67 directory is local to the machine you're working on, so the huge libraries
68 and <tt>.o</tt> files you will be compiling will not have to be sent over
69 NFS. If you are in a situation where this setup is correct, you don't have
70 to do anything. If you don't have a <tt>/shared</tt> directory, you will
71 have to make a couple of modifications to your setup.<p>
72
73 The first modification is that you need to enable the "<tt>BUILD_ROOT =
74 .</tt> line in the top level <tt>Makefile.common</tt>. This will instruct
75 LLVM to build into the current directory tree instead of
76 <tt>/shared</tt>.<p>
77
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]78
79 <!------------------------------------------------------------------------->
80 <h3><a name="tools">Set up your environment</a></h3>
81 <!------------------------------------------------------------------------->
82
83 <p>Now that you have the source code available, you should set up your
84 environment to be able to use the LLVM tools (once compiled) with as little
85 hassle as possible. To do this, we recommend that you add the following
86 lines to your <tt>.cshrc</tt> (or the corresponding lines to your
87 <tt>.profile</tt> if you use a bourne shell derivative):
88
89 <pre>
90 # Make the C frontend easy to use...
91 alias llvmgcc /home/vadve/lattner/cvs/gcc_install/bin/gcc
92
93 # Make the LLVM tools easy to use...
Chris Lattnercefbd322002-08-13 21:10:30 +0000[diff] [blame]94 setenv PATH /shared/[yourloginname]/llvm/tools/Debug:${PATH}
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]95 </pre>
96
97 <p>The C compiler is not included in the CVS tree you just checked out, so
98 we just point to the cannonical location, and access it with the
99 <tt>llvmgcc</tt> command. The rest of the <a href="#tools">LLVM tools</a>
Chris Lattnercefbd322002-08-13 21:10:30 +0000[diff] [blame]100 will be built into the <tt>llvm/tools/Debug</tt> directory. If you do not
101 have access to <tt>/shared</tt>, use this line instead:</p>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]102
Chris Lattnercefbd322002-08-13 21:10:30 +0000[diff] [blame]103 <pre>
104 setenv PATH ~/llvm/tools/Debug:${PATH}
105 </pre>
106
107 Adding these two lines to your path will make it much easier to use the LLVM
108 tools.</p>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]109
110
111 <!------------------------------------------------------------------------->
112 <h3><a name="compile">Compiling the Source Code</a></h3>
113 <!------------------------------------------------------------------------->
114
115 <p>Every directory in the LLVM source tree includes a Makefile to build it,
116 and any subdirectories that it contains. These makefiles require that you
117 use <tt>gmake</tt>, instead of <tt>make</tt> to build them, but can
118 otherwise be used freely. To build the entire LLVM system, just enter the
119 top level <tt>llvm</tt> directory and type <tt>gmake</tt>. A few minutes
120 later you will hopefully have a freshly compiled toolchain waiting for you
121 in <tt>llvm/tools/Debug</tt>. If you want to look at the libraries that
122 were compiled, look in <tt>llvm/lib/Debug</tt>.</p>
123
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]124 <p>By default, the LLVM build process sends all temporary (<tt>.o</tt>,
125 <tt>.so</tt>, <tt>.a</tt>) files into a <tt>/shared/[your login
126 name]/...</tt> directory, which is supposed to be on a disk local to the
127 current machine. If you get an error talking about a <tt>/shared</tt>
Chris Lattnercefbd322002-08-13 21:10:30 +0000[diff] [blame]128 directory, follow the instructions in the <a href="#shared">section about
129 <tt>/shared</tt></a>.<p>
130
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]131
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]132
133 <!--=====================================================================-->
134 <h2><a name="layout">Program Layout</a></h2>
135 <!--=====================================================================-->
136
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]137 <p>One useful source of infomation about the LLVM sourcebase is the LLVM <a
138 href="http://www.doxygen.org">doxygen</a> documentation, available at <tt><a
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]139 href="http://llvm.cs.uiuc.edu/doxygen/">http://llvm.cs.uiuc.edu/doxygen/</a></tt>. The
140 following is a brief introduction to code layout:</p>
141
142
143 <!------------------------------------------------------------------------->
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]144 <h3><a name="cvsdir"><tt>CVS</tt> directories</a></h3>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]145 <!------------------------------------------------------------------------->
146
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]147 Every directory checked out of CVS will contain a <tt>CVS</tt> directory,
148 for the most part these can just be ignored.
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]149
150
151 <!------------------------------------------------------------------------->
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]152 <h3><a name="ddr"><tt>Depend</tt>, <tt>Debug</tt>, &amp; <tt>Release</tt>
153 directories</a></h3>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]154 <!------------------------------------------------------------------------->
155
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]156 If you are building with the "<tt>BUILD_ROOT=.</tt>" option enabled in the
157 <tt>Makefile.common</tt> file, most source directories will contain two
158 directories, <tt>Depend</tt> and <tt>Debug</tt>. The <tt>Depend</tt>
159 directory contains automatically generated dependance files which are used
160 during compilation to make sure that source files get rebuilt if a header
161 file they use is modified. The <tt>Debug</tt> directory holds the object
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]162 files, library files and executables that are used for building a debug
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]163 enabled build. The <tt>Release</tt> directory is created to hold the same
164 files when the <tt>ENABLE_OPTIMIZED=1</tt> flag is passed to <tt>gmake</tt>,
165 causing an optimized built to be performed.<p>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]166
167
168 <!------------------------------------------------------------------------->
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]169 <h3><a name="include"><tt>llvm/include</tt></a></h3>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]170 <!------------------------------------------------------------------------->
171
172 This directory contains public header files exported from the LLVM
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]173 library. The two main subdirectories of this directory are:<p>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]174
175 <ol>
176 <li><tt>llvm/include/llvm</tt> - This directory contains all of the LLVM
177 specific header files. This directory also has subdirectories for
178 different portions of llvm: <tt>Analysis</tt>, <tt>CodeGen</tt>,
179 <tt>Reoptimizer</tt>, <tt>Target</tt>, <tt>Transforms</tt>, etc...
180
181 <li><tt>llvm/include/Support</tt> - This directory contains generic
182 support libraries that are independant of LLVM, but are used by LLVM.
183 For example, some C++ STL utilities and a Command Line option processing
184 library.
185 </ol>
186
187 <!------------------------------------------------------------------------->
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]188 <h3><a name="lib"><tt>llvm/lib</tt></a></h3>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]189 <!------------------------------------------------------------------------->
190
191 This directory contains most source files of LLVM system. In LLVM almost all
192 code exists in libraries, making it very easy to share code among the
193 different <a href="#tools">tools</a>.<p>
194
195 <dl compact>
196 <dt><tt>llvm/lib/VMCore/</tt><dd> This directory holds the core LLVM
197 source files that implement core classes like Instruction and BasicBlock.
198
199 <dt><tt>llvm/lib/AsmParser/</tt><dd> This directory holds the source code
200 for the LLVM assembly language parser library.
201
202 <dt><tt>llvm/lib/ByteCode/</tt><dd> This directory holds code for reading
203 and write LLVM bytecode.
204
205 <dt><tt>llvm/lib/CWrite/</tt><dd> This directory implements the LLVM to C
206 converter.
207
208 <dt><tt>llvm/lib/Analysis/</tt><dd> This directory contains a variety of
209 different program analyses, such as Dominator Information, Call Graphs,
210 Induction Variables, Interval Identification, Natural Loop Identification,
211 etc...
212
213 <dt><tt>llvm/lib/Transforms/</tt><dd> This directory contains the source
214 code for the LLVM to LLVM program transformations, such as Aggressive Dead
215 Code Elimination, Sparse Conditional Constant Propogation, Inlining, Loop
216 Invarient Code Motion, Dead Global Elimination, Pool Allocation, and many
217 others...
218
219 <dt><tt>llvm/lib/Target/</tt><dd> This directory contains files that
220 describe various target architectures for code generation. For example,
221 the llvm/lib/Target/Sparc directory holds the Sparc machine
222 description.<br>
223
224 <dt><tt>llvm/lib/CodeGen/</tt><dd> This directory contains the major parts
225 of the code generator: Instruction Selector, Instruction Scheduling, and
226 Register Allocation.
227
228 <dt><tt>llvm/lib/Reoptimizer/</tt><dd> This directory holds code related
229 to the runtime reoptimizer framework that is currently under development.
230
231 <dt><tt>llvm/lib/Support/</tt><dd> This directory contains the source code
232 that corresponds to the header files located in
233 <tt>llvm/include/Support/</tt>.
234 </dl>
235
236 <!------------------------------------------------------------------------->
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]237 <h3><a name="test"><tt>llvm/test</tt></a></h3>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]238 <!------------------------------------------------------------------------->
239
240 <p>This directory contains regression tests and source code that is used to
241 test the LLVM infrastructure...</p>
242
243 <!------------------------------------------------------------------------->
Chris Lattner44ac6592002-08-09 16:14:56 +0000[diff] [blame]244 <h3><a name="tools"><tt>llvm/tools</tt></a></h3>
Chris Lattner7fe7f812002-07-24 19:51:14 +0000[diff] [blame]245 <!------------------------------------------------------------------------->
246
247 <p>The <b>tools</b> directory contains the executables built out of the
248 libraries above, which form the main part of the user interface. You can
249 always get help for a tool by typing <tt>tool_name --help</tt>. The
250 following is a brief introduction to the most important tools.</p>
251
252 <dl compact>
253 <dt><tt><b>as</b></tt><dd>The assembler transforms the human readable
254 llvm assembly to llvm bytecode.<p>
255
256 <dt><tt><b>dis</b></tt><dd>The disassembler transforms the llvm bytecode
257 to human readable llvm assembly. Additionally it can convert LLVM
258 bytecode to C, which is enabled with the <tt>-c</tt> option.<p>
259
260 <dt><tt><b>lli</b></tt><dd> <tt>lli</tt> is the LLVM interpreter, which
261 can directly execute LLVM bytecode (although very slowly...). In addition
262 to a simple intepreter, <tt>lli</tt> is also has debugger and tracing
263 modes (entered by specifying <tt>-debug</tt> or <tt>-trace</tt> on the
264 command line, respectively).<p>
265
266 <dt><tt><b>llc</b></tt><dd> <tt>llc</tt> is the LLVM backend compiler,
267 which translates LLVM bytecode to a SPARC assembly file.<p>
268
269 <dt><tt><b>llvmgcc</b></tt><dd> <tt>llvmgcc</tt> is a GCC based C frontend
270 that has been retargeted to emit LLVM code as the machine code output. It
271 works just like any other GCC compiler, taking the typical <tt>-c, -S, -E,
272 -o</tt> options that are typically used. The source code for the
273 <tt>llvmgcc</tt> tool is currently not included in the LLVM cvs tree
274 because it is quite large and not very interesting.<p>
275
276 <ol>
277 <dt><tt><b>gccas</b></tt><dd> This took is invoked by the
278 <tt>llvmgcc</tt> frontend as the "assembler" part of the compiler. This
279 tool actually assembles its input, performs a variety of optimizations,
280 and outputs LLVM bytecode. Thus when you invoke <tt>llvmgcc -c x.c -o
281 x.o</tt>, you are causing <tt>gccas</tt> to be run, which writes the
282 <tt>x.o</tt> file (which is an LLVM bytecode file that can be
283 disassembled or manipulated just like any other bytecode file). The
284 command line interface to <tt>gccas</tt> is designed to be as close as
285 possible to the <b>system</b> <tt>as</tt> utility so that the gcc
286 frontend itself did not have to be modified to interface to a "wierd"
287 assembler.<p>
288
289 <dt><tt><b>gccld</b></tt><dd> <tt>gccld</tt> links together several llvm
290 bytecode files into one bytecode file and does some optimization. It is
291 the linker invoked by the gcc frontend when multiple .o files need to be
292 linked together. Like <tt>gccas</tt> the command line interface of
293 <tt>gccld</tt> is designed to match the system linker, to aid
294 interfacing with the GCC frontend.<p>
295 </ol>
296
297 <dt><tt><b>opt</b></tt><dd> <tt>opt</tt> reads llvm bytecode, applies a
298 series of LLVM to LLVM transformations (which are specified on the command
299 line), and then outputs the resultant bytecode. The '<tt>opt --help</tt>'
300 command is a good way to get a list of the program transformations
301 available in LLVM.<p>
302
303
304 <dt><tt><b>analyze</b></tt><dd> <tt>analyze</tt> is used to run a specific
305 analysis on an input LLVM bytecode file and print out the results. It is
306 primarily useful for debugging analyses, or familiarizing yourself with
307 what an analysis does.<p>
308
309 </dl>
310
311 <!--=====================================================================-->
312 <h2><a name="tutorial">An example using the LLVM tool chain</h2>
313 <!--=====================================================================-->
314
315 <ol>
316 <li>First, create a simple C file, name it 'hello.c':
317 <pre>
318 #include &lt;stdio.h&gt;
319 int main() {
320 printf("hello world\n");
321 return 0;
322 }
323 </pre>
324
325 <li>Next, compile the C file into a LLVM bytecode file:<p>
326
327 <tt>% llvmgcc hello.c -o hello</tt><p>
328
329 This will create two result files: <tt>hello</tt> and
330 <tt>hello.bc</tt>. The <tt>hello.bc</tt> is the LLVM bytecode that
331 corresponds the the compiled program and the library facilities that it
332 required. <tt>hello</tt> is a simple shell script that runs the bytecode
333 file with <tt>lli</tt>, making the result directly executable.<p>
334
335 <li>Run the program. To make sure the program ran, execute one of the
336 following commands:<p>
337
338 <tt>% ./hello</tt><p>
339
340 or<p>
341
342 <tt>% lli hello.bc</tt><p>
343
344 <li>Use the <tt>dis</tt> utility to take a look at the LLVM assembly
345 code:<p>
346
347 <tt>% dis < hello.bc | less</tt><p>
348
349 <li>Compile the program to native Sparc assembly using the code
350 generator:<p>
351
352 <tt>% llc hello.bc -o hello.s</tt><p>
353
354 <li>Assemble the native sparc assemble file into a program:<p>
355
356 <tt>% /opt/SUNWspro/bin/cc -xarch=v9 hello.s -o hello.sparc</tt><p>
357
358 <li>Execute the native sparc program:<p>
359
360 <tt>% ./hello.sparc</tt><p>
361
362 </ol>
363
364
365 <!--=====================================================================-->
366 <h2><a name="links">Links</a></h2>
367 <!--=====================================================================-->
368
369 <p>This document is just an <b>introduction</b> to how to use LLVM to do
370 some simple things... there are many more interesting and complicated things
371 that you can do that aren't documented here (but we'll gladly accept a patch
372 if you want to write something up!). For more information about LLVM, check
373 out:</p>
374
375 <ul>
376 <li><a href="http://llvm.cs.uiuc.edu/">LLVM homepage</a></li>
377 <li><a href="http://tank.cs.uiuc.edu/doxygen/">LLVM doxygen tree</a></li>
378 </ul>
379
380 <hr>
381
382 If you have any questions or run into any snags (or you have any
383 additions...), please send an email to <a
384 href="mailto:sabre@nondot.org">Chris Lattner</a> or <a
385 href="mailto:gshi1@uiuc.edu">Guochun Shi</a>. <p>
386
Guochun Shif4688a82002-07-17 23:05:56 +0000[diff] [blame]387 <!-- Created: Mon Jul 1 02:29:02 CDT 2002 -->
388 <!-- hhmts start -->
Chris Lattnercefbd322002-08-13 21:10:30 +0000[diff] [blame]389Last modified: Tue Aug 13 16:09:25 CDT 2002
Guochun Shif4688a82002-07-17 23:05:56 +0000[diff] [blame]390<!-- hhmts end -->
391 </body>
392</html>